Larry H Bernstein, MD, FCAP, Reviewer and Curator
Researchers Solve a Mystery about Type 2 Diabetes Drug
AB SCIEX TripleTOF® and QTRAP® technologies support breakthrough medical study.
Published: Friday, November 22, 2013
Researchers from St. Vincent’s Institute of Medical Research in Melbourne, Australia, in collaboration with researchers at McMaster University in Canada, are reportedly the first to discover how the type 2 diabetes drug metformin actually works, providing a molecular understanding that could lead to the development of more effective therapies. Mass spectrometry technologies from AB SCIEX played a critical role in the analysis that led to this breakthrough finding. The research is published in this month’s issue of the journal Nature Medicine.
Doctors have known for decades that metformin helps treat type 2 diabetes. However, questions had lingered for more than 50 years whether this drug, which is available as a generic drug,
- worked to lower blood glucose in patients by directly working on the glucose.
People with type 2 diabetes have high blood sugar levels and have trouble converting sugar in their blood into energy because of low levels of insulin. For treating this condition, metformin is considered the most widely prescribed anti-diabetic drug in the world.
Until now, no one had been able to explain adequately how this drug lowers blood sugar. According to this new study, the drug works by reducing harmful fat in the liver. People who take metformin reportedly often have a fatty liver, which is frequently caused by obesity.
“Fat is likely a key trigger for pre-diabetes in humans,” said Professor Bruce Kemp, PhD, the Head of Protein Chemistry and Metabolism at St. Vincent’s Institute of Medical Research. “Our study indicates that
- metformin doesn’t directly reduce sugar metabolism, as previously suspected, but instead
- reduces fat in the liver, which in turn allows insulin to work effectively.”
The breakthrough in pinning down how the drug functions began with the researchers making
- genetic mutations to the genes of two enzymes, ACC1 and ACC2,
in mice, so they could no longer be controlled. What happened next surprised the researchers:
- the mice didn’t get fat as expected,
but Associate Professor Gregory Steinberg, PhD at McMaster University noticed that
- the mice had fatty livers and a pre-diabetic condition.
Then the researchers put the mice on
- a high fat diet and they became fat, while metformin
- did not lower the blood sugar levels of the mutant mice.
The findings are expected to help researchers better directly target the condition, which affects over 100 million people around the world, according to published reports. It is also believed that with the mystery of metformin solved, the application of the drug could go beyond just diabetes and potentially be used to treat other medical conditions.
“AB SCIEX mass spectrometry solutions help researchers explore big questions and conduct breakthrough studies, such as this remarkable type 2 diabetes study,” said Rainer Blair, President of AB SCIEX. “In order to understand disease at the molecular level, researchers need the sensitive detection and reproducible quantitation provided by AB SCIEX tools. We enable the research community to solve biological mysteries and rethink the possibilities to transform health.”
For the research conducted by the Australian and Canadian researchers, the analysis at the molecular level was optimized on AB SCIEX instrumentation, including the AB SCIEX TripleTOF® 5600 and the AB SCIEX QTRAP® 5500 system.
The TripleTOF system, with its high-speed, high-quality MS/MS capabilities,
- was used for the discovery of key proteins and phosphopeptides.
The QTRAP system, with its high sensitivity MRM (multiple reaction monitoring) capabilities,
- was used for quantitation of metabolites, including nucleotides and malonyl-CoA.
Bardoxolone Methyl in Type 2 Diabetes and Stage 4 Chronic Kidney Disease
D de Zeeuw, T Akizawa, P Audhya, GL Bakris, M Chin, ….,and GM Chertow, for the BEACON Trial Investigators
November 9, 2013 http://dx.doi.org/10.1056/NEJMoa1306033
Type 2 diabetes mellitus is the most important cause of progressive chronic kidney disease in the developed and developing worlds. Various therapeutic approaches to slow progression, including
- restriction of dietary protein,
- glycemic control, and
- control of hypertension,
have yielded mixed results.1-3 Several randomized clinical trials have shown that
- inhibitors of the renin–angiotensin–aldosterone system significantly reduce the risk of progression,4-6 although
- the residual risk remains high.7
None of the new agents tested during the past decade have proved effective in late-stage clinical trials.8-12
Oxidative stress and impaired antioxidant capacity intensify
- with the progression of chronic kidney disease.13
In animals with chronic kidney disease,
- oxidative stress and inflammation
- are associated with impaired activity of the nuclear 1 factor (erythroid-derived 2)–related factor 2 (Nrf2) transcription factor.
The synthetic triterpenoid bardoxolone methyl and its analogues are the most potent known activators of the Nrf2 pathway. Studies involving humans,14 including persons with type 2 diabetes mellitus and stage 3b or 4 chronic kidney disease, have shown that
- bardoxolone methyl can reduce the serum creatinine concentration for up to 52 weeks.15
We designed the Bardoxolone Methyl Evaluation in Patients with Chronic Kidney Disease and Type 2 Diabetes Mellitus: the Occurrence of Renal Events (BEACON) trial to test the hypothesis that
- treatment with bardoxolone methyl reduces the risk of end-stage renal disease (ESRD) or death from cardiovascular causes
among patients with type 2 diabetes mellitus and stage 4 chronic kidney disease.
Methods
Study Design and Oversight
The BEACON trial was a phase 3, randomized, double-blind, parallel-group, international, multicenter trial of
- once-daily administration of bardoxolone methyl (at a dose of 20 mg in an amorphous spray-dried dispersion formulation), as compared with placebo.
Participants were receiving background conventional therapy that included
- inhibitors of the renin–angiotensin–aldosterone system,
- insulin or other hypoglycemic agents, and, when appropriate,
- other cardiovascular medications.
The trial design and the characteristics of the trial participants at baseline have been described previously.16,17
Reata Pharmaceuticals sponsored the trial. The trial was jointly designed by employees of the sponsor and the academic investigators who were members of the steering committee. The steering committee, which was led by the academic investigators and included members who were employees of the sponsor, supervised the trial design and operation. An independent data and safety monitoring committee reviewed interim safety data every 90 days or on an ad hoc basis on request. The sponsor collected the trial data and transferred them to independent statisticians at Statistics Collaborative. The sponsor also contracted a second independent statistical group (Axio Research) to support the independent data and safety monitoring committee. The trial protocol was approved by the institutional review board at each participating study site. The protocol and amendments are available with the full text of this article at NEJM.org. The steering committee takes full responsibility for the integrity of the data and the interpretation of the trial results and for the fidelity of the study to the protocol. The first and last authors wrote the first draft of the manuscript. All the members of the steering committee made the decision to submit the manuscript for publication.
Study Population
Briefly, we included adults with
- type 2 diabetes mellitus and
- an estimated glomerular filtration rate (GFR) of 15 to <30 ml per minute per 1.73 m2 BSA.
- Persons with poor glycemic control,
- uncontrolled hypertension, or
- a recent cardiovascular event (≤12 weeks before randomization) or
- New York Heart Association class III or IV heart failure were excluded.
Additional inclusion and exclusion criteria are listed in Table S1 in the Supplementary Appendix, available at NEJM.org. All the patients provided written informed consent.
Randomization and Intervention
Randomization was stratified according to study site with the use of variable-sized blocks. The steering committee, sponsor, investigators, and trial participants were unaware of the group assignments. After randomization,
- patients received either bardoxolone methyl or placebo.
The prescription of all other medications was at the discretion of treating physicians, who were encouraged to adhere to published clinical-practice guidelines. Patients underwent event ascertainment and laboratory testing according to the study schema shown in Figure S1 in the Supplementary Appendix. Ambulatory blood-pressure monitoring was performed in a substudy that included 174 patients (8%).
The statistical analysis plan defined the study period as the number of days from randomization to a common study-termination date. In the case of patients who were still receiving the study drug on the termination date, data on vital events were collected for an additional 30 days.
Outcomes
The primary composite outcome was ESRD or death from cardiovascular causes. We defined ESRD as
- the need for maintenance dialysis for 12 weeks or more or kidney transplantation.
If a patient died before undergoing dialysis for 12 weeks, the independent events-adjudication committee adjudicated whether the need for dialysis represented ESRD or acute renal failure. Patients who declined dialysis and who subsequently died were categorized as having had ESRD. All ESRD events were adjudicated. Death from cardiovascular causes was defined as death due to either cardiovascular or unknown causes.
The trial had three prespecified secondary outcomes —
- first, the change in estimated GFR as calculated with the use of the four-variable Modification of Diet in Renal Disease study equation, with serum creatinine levels calibrated to an isotope-dilution standard for mass spectrometry;
- second, hospitalization for heart failure or death due to heart failure; and
- third, a composite outcome of nonfatal myocardial infarction, nonfatal stroke, hospitalization for heart failure, or death from cardiovascular causes.
The events-adjudication committee, whose members were unaware of the study assignments, evaluated whether
- ESRD events,
- cardiovascular events,
- neurologic events, and
- deaths
met the prespecified criteria for primary and secondary outcomes (described in detail in the Supplementary Appendix).
Statistical Analysis
We calculated that we needed to enroll 2000 patients on the basis of the following assumptions:
- a two-sided type I error rate of 5%, an event rate of 24% for the primary composite outcome in the placebo group during the first 2 years of the study,
- a hazard ratio of 0.68 (bardoxolone methyl vs. placebo) for the primary composite outcome,
- discontinuation of the study drug by 13.5% of the patients in the bardoxolone methyl group each year, and
- a 2.5% annual loss to follow-up in each group.
Under these assumptions, if 300 patients had a primary composite outcome, the statistical power would be 85%.
We collected and analyzed all outcome data in accordance with the intention-to-treat principle. We calculated Kaplan–Meier product-limit estimates of
- the cumulative incidence of the primary composite outcome.
We computed hazard ratios and 95% confidence intervals with the use of Cox proportional-hazards regression models with adjustment for
- the baseline estimated GFR and urinary albumin-to-creatinine ratio.
We performed analogous analyses for secondary time-to-event outcomes. Given the abundance of early adverse events, we also report discrete cumulative incidences at 4 weeks and 52 weeks.
For longitudinal analyses of estimated GFR, we performed mixed-effects regression analyses using
- study group,
- time,
- the interaction of study group with time,
- estimated GFR at baseline,
- the interaction of baseline estimated GFR with time, and
- urinary albumin-to-creatinine ratio as covariates, and
- we compared the means between the bardoxolone methyl group and the placebo group.
We adopted similar approaches when examining the effects of treatment on other continuous measures assessed at multiple visits. Since the between-group difference in the primary composite outcome was not significant,
secondary and other outcomes with P values of less than 0.05 were considered to be nominally significant.
Statistical analyses were performed with the use of SAS software, version 9.3 (SAS Institute). Additional details of the statistical analysis are provided in the Supplementary Appendix.
Results
Patients
From June 2011 through September 2012, a total of 2185 patients underwent randomization, including 1545 (71%) in the United States, 334 (15%) in the European Union, 133 (6%) in Australia, 87 (4%) in Canada, 46 (2%) in Israel, and 40 (2%) in Mexico. Figure S2 in the Supplementary Appendix shows the disposition of the study participants.
As shown in Table 1Table 1Baseline Characteristics of the Patients in the Intention-to-Treat Population., the patients were diverse with respect to age, sex, race or ethnic group, and region of origin;
- diabetic retinopathy and neuropathy were common conditions among the patients,
- as was overt cardiovascular disease.
See Table S2 in the Supplementary Appendix for a more detailed description of the characteristics of the patients at baseline; Figure S3 in the Supplementary Appendix shows the distribution of baseline estimated GFR and urinary albumin-to-creatinine ratio.
Drug Exposure
The median duration of exposure to the study drug was 7 months (interquartile range, 3 to 11) among patients randomly assigned to bardoxolone methyl and
- 8 months (interquartile range, 5 to 11) among those randomly assigned to placebo.
Figure S4 in the Supplementary Appendix shows the time to discontinuation of the study drug. Table S3 in the Supplementary Appendix shows the reasons that patients discontinued the study drug and the reasons that patients discontinued the study.
- The median duration of follow-up was 9 months in both groups.
Outcomes
Primary Composite Outcome
A total of 69 of 1088 patients (6%) randomly assigned to bardoxolone methyl and 69 of 1097 (6%) randomly assigned to placebo had a primary composite outcome (hazard ratio in the bardoxolone methyl group vs. the placebo group, 0.98; 95% confidence interval [CI], 0.70 to 1.37; P=0.92) (Figure 1AFigure 1Kaplan–Meier Plots of the Time to the First Event of the Primary Outcome and Its Components.).
- Death from cardiovascular causes occurred in 27 patients randomly assigned to bardoxolone methyl and in 19 randomly assigned to placebo (hazard ratio, 1.44; 95% CI, 0.80 to 2.59; P=0.23) (Figure 1B).
- ESRD developed in 43 patients randomly assigned to bardoxolone methyl and in 51 randomly assigned to placebo (hazard ratio, 0.82; 95% CI, 0.55 to 1.24; P=0.35) (Figure 1C).
One patient in each group died from cardiovascular causes after the development of ESRD. The mean (±SD) estimated GFR
- before the development of ESRD was 18.1±8.3 ml per minute per 1.73 m^2 in the bardoxolone methyl group and
- 14.9±4.0 ml per minute per 1.73 m2 in the placebo group.
Secondary Outcomes
During the study period, 96 patients in the bardoxolone methyl group had heart-failure events (93 patients with at least one hospitalization due to heart failure and 3 patients who died from heart failure without hospitalization),
- as compared with 55 in the placebo group (55 patients with at least one hospitalization due to heart failure and
- no patients who died from heart failure without hospitalization) (hazard ratio, 1.83; 95% CI, 1.32 to 2.55; P<0.001) (Figure 2AFigure 2Kaplan–Meier Plots of the Time to the First Event of the Discrete Secondary Outcomes.).
A total of 139 patients in the bardoxolone methyl group, as compared with 86 in the placebo group, had
- a composite outcome event of nonfatal myocardial infarction, nonfatal stroke, hospitalization for heart failure, or death from cardiovascular causes (hazard ratio, 1.71; 95% CI, 1.31 to 2.24; P<0.001) (Figure 2B).
Incidences of Composite Outcomes and Rates of Death from Any Cause
The cumulative incidences of the primary composite outcome and of the two secondary composite outcomes at 4 weeks and at 52 weeks are shown in Table S4 in the Supplementary Appendix. The rates of death from any cause are shown in Figure S5 in the Supplementary Appendix. From the time of randomization to the end of follow-up, 75 patients died: 44 patients in the bardoxolone methyl group and 31 in the placebo group (hazard ratio, 1.47; 95% CI, 0.93 to 2.32; P=0.10). The causes of death are listed in Table S5 in the Supplementary Appendix.
Estimated GFR
Patients randomly assigned to placebo had a significant mean decline in the estimated GFR from the baseline value (−0.9 ml per minute per 1.73 m2; 95% CI, −1.2 to −0.5), whereas those randomly assigned to bardoxolone methyl had a significant mean increase from the baseline value (5.5 ml per minute per 1.73 m2; 95% CI, 5.2 to 5.9). The difference between the two groups was 6.4 ml per minute per 1.73 m2 (95% CI, 5.9 to 6.9; P<0.001) (Figure 3AFigure 3Estimated Glomerular Filtration Rate (GFR), Body Weight, and Urinary Albumin-to-Creatinine Ratio.).
Physiological Variables
Physiological variables are shown in Table S6 in the Supplementary Appendix. The mean body weight remained stable in the placebo group
- but declined steadily and substantially in the bardoxolone methyl group (Figure 3B).
There was a significantly smaller decrease from baseline in mean systolic blood pressure in the bardoxolone methyl group than in the placebo group (between-group difference, 1.5 mm Hg [95% CI, 0.5 to 2.5]), and
- the mean diastolic blood pressure increased from baseline in the bardoxolone methyl group whereas it decreased in the placebo group (between-group difference, 2.1 mm Hg [95% CI, 1.6 to 2.6]).
Blood-pressure results from the substudy in which ambulatory blood-pressure monitoring was performed were similar in direction but were more pronounced (between-group difference of 7.9 mm Hg [95% CI, 3.8 to 12.0] in systolic blood pressure and 3.2 mm Hg [95% CI, 1.3 to 5.2] in diastolic blood pressure).
- Heart rate also increased significantly in the bardoxolone methyl group, as compared with the placebo group (between-group difference, 3.8 beats per minute; 95% CI, 3.2 to 4.4).
Other Laboratory Variables
Data on laboratory variables are shown in Table S7 in the Supplementary Appendix.
- The urinary albumin-to-creatinine ratio increased significantly in the bardoxolone methyl group, as compared with the placebo group (Figure 3C).
- Serum magnesium, albumin, hemoglobin, and glycated hemoglobin levels decreased significantly in the bardoxolone methyl group, as compared with the placebo group.
- The level of B-type natriuretic peptide increased significantly by week 24 in the bardoxolone methyl group, as compared with the placebo group.
Adverse Events
The rates of serious adverse events are summarized in Table 2Table 2Most Commonly Reported Serious Adverse Events in the Intention-to-Treat Population. Serious adverse events occurred more frequently in the bardoxolone methyl group than in the placebo group (717 events in 363 patients vs. 557 events in 295 patients). There were 11 neoplastic events in the bardoxolone methyl group and 10 in placebo group. The most commonly reported adverse events are summarized in Table S8 in the Supplementary Appendix.
Discussion
The current trial was designed to determine whether bardoxolone methyl, an activator of the cytoprotective Nrf2 pathway, would reduce the risk of ESRD
- among patients with type 2 diabetes mellitus and stage 4 chronic kidney disease
- who were receiving guideline-based conventional therapy.
The trial was terminated early because of safety concerns, driven primarily by an increase in cardiovascular events in the bardoxolone methyl group. Bardoxolone methyl did not lower the risk of ESRD or of death from cardiovascular causes, although too few events occurred during the trial to reliably determine the true effect of the drug on the primary composite outcome.
Given the truncated duration of the trial and the number of adjudicated events (46% of the events planned), and assuming no change in any of the original assumptions, we estimated the conditional power of the trial to be less than 40%. Although patients treated with bardoxolone methyl had a significant increase in the estimated GFR, as compared with those who received placebo,
- there was a significantly higher incidence of heart failure and of the composite outcome of nonfatal myocardial infarction, nonfatal stroke, hospitalization for heart failure, or death from cardiovascular causes in the bardoxolone methyl group.
- There were numerically more deaths from any cause among patients treated with bardoxolone methyl than among those in the placebo group.
Bardoxolone methyl is among the first orally available antioxidant Nrf2 activators. A small previous study showed that bardoxolone methyl
- reduced inflammation and oxidative stress13 and
- induced a decline in the serum creatinine level.
In the 52-Week Bardoxolone Methyl Treatment: Renal Function in CKD/Type 2 Diabetes (BEAM) trial,15 227 patients with type 2 diabetes mellitus and an estimated GFR of 20 to 45 ml per minute per 1.73 m2
- had a significant increase in the estimated GFR (mean change, 8.2 to 11.4 ml per minute per 1.73 m2, depending on the dose group)
- that was sustained over the entire trial period.
Muscle spasms and hypomagnesemia were the most common adverse events;
- there was no increase in the rate of heart failure or other cardiovascular events.
The current trial was designed to determine whether the change in estimated GFR that we anticipated on the basis of the results of the BEAM trial would translate into a slower progression toward ESRD. Although in the current trial ESRD developed in fewer patients in the bardoxolone methyl group than in the placebo group, the early termination of the trial precludes conclusion of the effect on ESRD events.
The mechanism linking bardoxolone methyl to heart failure is unknown. Since an excess in heart-failure events was unanticipated, echocardiography was not performed routinely before randomization. Although weight declined significantly in the bardoxolone methyl group, we were unable to determine whether there was loss of body fat, intracellular (skeletal muscle) water, or extracellular (interstitial) water.
The fall in serum albumin and hemoglobin levels may reflect hemodilution caused by fluid retention.
Bardoxolone methyl also increased blood pressure.
An increase in preload due to volume expansion and an increase in afterload (as reflected by increased blood pressure),
- coupled with an increase in heart rate,
- constitute a potentially potent combination of factors that are likely to precipitate heart failure in an at-risk population.
The rise in the level of B-type natriuretic peptide with bardoxolone methyl
- is consistent with an increase in left ventricular wall stress owing to one or more of these mediators or to unrecognized factors such as
- impaired diastolic filling of the left ventricle.
After recognizing the initial increase in heart-failure events, the independent data and safety monitoring committee tried to identify
- clinical characteristics that were associated with patients who were at elevated risk for heart failure
- after the initiation of bardoxolone methyl therapy (with the possibility of modifying eligibility criteria or otherwise altering the trial),
but the committee was unable to do so. Other, noncardiovascular adverse events were also observed more frequently among patients exposed to bardoxolone methyl than among those who received placebo. Whether the effects of Nrf2 activation, or one or more counterregulatory responses, rendered this particular population vulnerable, is unknown. Zoja et al.18 found an increase in albuminuria and blood pressure along with weight loss in Zucker diabetic fatty rats treated with an analogue of bardoxolone methyl; these effects were not observed in other studies in Zucker diabetic fatty rats or other rodent models or in 1-year toxicologic studies in monkeys.19-21
Why were these adverse effects identified in the current trial and not in the BEAM trial?
- First, the number of patient-months of drug exposure in the current trial was roughly 10 times that in the BEAM trial.
- Second, the population in the present trial had more severe chronic kidney disease than did the population in the BEAM trial.
Observational studies have shown significantly higher rates of death and cardiovascular events, including heart failure,
- among patients with stage 4 chronic kidney disease than among patients with stage 3 chronic kidney disease.22
Finally, our trial used an amorphous spray-dried dispersion formulation of bardoxolone methyl at a fixed dose rather than at an adjusted dose. We chose the 20-mg dose and the specific formulation used in the BEACON trial
- on the basis of four phase 2 studies of chronic kidney disease (three studies used the crystalline formulation, and one used the amorphous formulation),
- a crossover pharmacokinetics study involving humans that used both formulations, and
- several studies in animals that used both formulations (Meyer C: personal communication),
to provide an activity and safety profile that was similar to that observed with 75 mg of the crystalline formulation, which was one of the dose levels tested in the BEAM trial.
In conclusion, among patients with type 2 diabetes mellitus and stage 4 chronic kidney disease, bardoxolone methyl did not reduce the risk of the primary composite outcome of ESRD or death from cardiovascular causes. Significantly increased risks of heart failure and of the composite cardiovascular outcome (nonfatal myocardial infarction, nonfatal stroke, hospitalization for heart failure, or death from cardiovascular causes) prompted termination of the trial.
Alto, CA 93034, or at gchertow@stanford.edu.
Investigators in the Bardoxolone Methyl Evaluation in Patients with Chronic Kidney Disease and Type 2 Diabetes Mellitus: the Occurrence of Renal Events (BEACON) trial are listed in the Supplementary Appendix, available at NEJM.org.
Table 1. Baseline Characteristics of the Patients in the Intention-to-Treat Population.
Fig 1. Kaplan–Meier Plots of the Time to the First Event of the Primary Outcome and Its Components.
Fig 2. Kaplan–Meier Plots of the Time to the First Event of the Discrete Secondary Outcomes
Fig 3. Estimated Glomerular Filtration Rate (GFR), Body Weight, and Urinary Albumin-to-Creatinine Ratio
Table 2 Most Commonly Reported Serious Adverse Events in the Intention-to-Treat Population
References
1 Klahr S, Levey AS, Beck GJ, et al. The effects of dietary protein restriction and blood-pressure control on the progression of chronic renal disease. N Engl J Med 1994;330:877-884
2 The ADVANCE Collaborative Group. Intensive blood glucose control and vascular outcomes in patients with type 2 diabetes. N Engl J Med 2008;358:2560-2572
3 Parving HH, Andersen AR, Smidt UM, Svendsen PA. Early aggressive antihypertensive treatment reduces rate of decline in kidney function in diabetic nephropathy. Lancet 1983;1:1175-1179
4 Brenner BM, Cooper ME, de Zeeuw D, et al. Effects of losartan on renal and cardiovascular outcomes in patients with type 2 diabetes and nephropathy. N Engl J Med 2001;345:861-869
5 Lewis EJ, Hunsicker LG, Clarke WR, et al. Renoprotective effect of the angiotensin-receptor antagonist irbesartan in patients with nephropathy due to type 2 diabetes. N Engl J Med 2001;345:851-860
6 Parving HH, Lehnert H, Brochner-Mortensen J, Gomis R, Andersen S, Arner P. The effect of irbesartan on the development of diabetic nephropathy in patients with type 2 diabetes. N Engl J Med 2001;345:870-878
7 Heerspink HJ, de Zeeuw D. The kidney in type 2 diabetes therapy. Rev Diabet Stud 2011;8:392-402
8 Pfeffer MA, Burdmann EA, Chen CY, et al. A trial of darbepoetin alfa in type 2 diabetes and chronic kidney disease. N Engl J Med 2009;361:2019-2032
9 Parving HH, Brenner BM, McMurray JJ, et al. Cardiorenal end points in a trial of aliskiren for type 2 diabetes. N Engl J Med 2012;367:2204-2213
10 Packham DK, Wolfe R, Reutens AT, et al. Sulodexide fails to demonstrate renoprotection in overt type 2 diabetic nephropathy. J Am Soc Nephrol 2012;23:123-130
Combined Angiotensin Inhibition for the Treatment of Diabetic Nephropathy
Linda F. Fried, M.D., M.P.H., Nicholas Emanuele, M.D., Jane H. Zhang, Ph.D., Mary Brophy, M.D., Todd A. Conner, Pharm.D., William Duckworth, M.D., David J. Leehey, M.D., Peter A. McCullough, M.D., M.P.H., Theresa O’Connor, Ph.D., Paul M. Palevsky, M.D., Robert F. Reilly, M.D., Stephen L. Seliger, M.D., Stuart R. Warren, J.D., Pharm.D., Suzanne Watnick, M.D., Peter Peduzzi, Ph.D., and Peter Guarino, M.P.H., Ph.D. for the VA NEPHRON-D Investigators
N Engl J Med 2013; 369:1892-1903November 14, 2013DOI: 10.1056/NEJMoa1303154
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Background
Combination therapy with angiotensin-converting–enzyme (ACE) inhibitors and angiotensin-receptor blockers (ARBs) decreases proteinuria; however, its safety and effect on the progression of kidney disease are uncertain.
Methods
We provided losartan (at a dose of 100 mg per day) to patients with type 2 diabetes, a urinary albumin-to-creatinine ratio (with albumin measured in milligrams and creatinine measured in grams) of at least 300, and an estimated glomerular filtration rate (GFR) of 30.0 to 89.9 ml per minute per 1.73 m2 of body-surface area and then randomly assigned them to receive lisinopril (at a dose of 10 to 40 mg per day) or placebo. The primary end point was the first occurrence of a change in the estimated GFR (a decline of ≥30 ml per minute per 1.73 m2 if the initial estimated GFR was ≥60 ml per minute per 1.73 m2 or a decline of ≥50% if the initial estimated GFR was <60 ml per minute per 1.73 m2), end-stage renal disease (ESRD), or death. The secondary renal end point was the first occurrence of a decline in the estimated GFR or ESRD. Safety outcomes included mortality, hyperkalemia, and acute kidney injury.
Results
The study was stopped early owing to safety concerns. Among 1448 randomly assigned patients with a median follow-up of 2.2 years, there were 152 primary end-point events in the monotherapy group and 132 in the combination-therapy group (hazard ratio with combination therapy, 0.88; 95% confidence interval [CI], 0.70 to 1.12; P=0.30). A trend toward a benefit from combination therapy with respect to the secondary end point (hazard ratio, 0.78; 95% CI, 0.58 to 1.05; P=0.10) decreased with time (P=0.02 for nonproportionality). There was no benefit with respect to mortality (hazard ratio for death, 1.04; 95% CI, 0.73 to 1.49; P=0.75) or cardiovascular events. Combination therapy increased the risk of hyperkalemia (6.3 events per 100 person-years, vs. 2.6 events per 100 person-years with monotherapy; P<0.001) and acute kidney injury (12.2 vs. 6.7 events per 100 person-years, P<0.001).
Conclusions
Combination therapy with an ACE inhibitor and an ARB was associated with an increased risk of adverse events among patients with diabetic nephropathy. (Funded by the Cooperative Studies Program of the Department of Veterans Affairs Office of Research and Development; VA NEPHRON-D ClinicalTrials.gov number, NCT00555217.)
A complete list of investigators in the Veterans Affairs Nephropathy in Diabetes (VA NEPHRON-D) study is provided in the Supplementary Appendix, available at NEJM.org.
Figure 1 Kaplan–Meier Plot of Cumulative Probabilities of the Primary and Secondary End Points and Death.
Figure 2 Kaplan–Meier Plot of Cumulative Probabilities of Acute Kidney Injury and Hyperkalemia
The End of Dual Therapy with Renin–Angiotensin–Aldosterone System Blockade?
Nov 14, 2013 de Zeeuw D. (Editorial)
N Engl J Med 2013; 369:1960-1962
Treatment aimed at multiple risk factors and specific markers such as glucose level, blood pressure, body weight, cholesterol levels, and albuminuria has been the main focus to slow cardiovascular and renal risk among patients with diabetes. Among the agents used, those that interrupt the renin–angiotensin–aldosterone system (RAAS) have shown protection that extends beyond decreasing blood pressure. In part, these additional effects may be explained by a decrease in albuminuria.1 Therefore, angiotensin-converting–enzyme (ACE) inhibitors and angiotensin II–receptor blockers (ARBs) have become first-choice drugs in patients with diabetes. Despite some success, the residual cardiovascular and renal risk among patients with diabetes remains
Diabetes: Mouse Studies Point to Kinase as Treatment Target
Published: Nov 24, 2013
By Kristina Fiore, Staff Writer, MedPage Today
Targeting a pathway that plays a major role in both hepatic glucose production and insulin sensitivity may eventually help treat type 2 diabetes, researchers reported.
In a series of experiments in mice, researchers found that inhibition of the kinase CaMKII — or even some of its downstream components — lowered blood glucose and insulin levels, Ira Tabas, MD, PhD, of Columbia University Medical Center in New York City, and colleagues reported online in Cell Metabolism.
The pathway is activated by glucagon signaling in the liver, and appears to have roles in both insulin resistance as well as hepatic glucose production in the liver.
In an earlier study, Tabas and colleagues showed that inhibiting the CaMKII pathway lowered hepatic glucose production by suppressing p38-mediated FoxO1 nuclear localization.
In the current study, they found CaMKII inhibition suppresses levels of the pseudo-kinase TRB3 to improve Akt-phosphorylation, thereby improving insulin sensitivity.
Thus this single pathway targets “two cardinal features of type 2 diabetes — hyperglycemia and defective insulin signaling,” the researchers wrote.
“When we realized we had one common pathway that was responsible for these two disparate processes that, in essence, comprises all of type 2 diabetes, we though it would be an ideal target for new drug therapy,” Tabas told MedPage Today.
Tabas and colleagues conducted several experiments to evaluate the CaMKII pathway.
In one experiment in obese mice, they found that
- no matter how CaMKII was knocked out, it led to lower blood glucose levels and lower fasting plasma insulin levels in response to a glucose challenge.
The improvements also occurred
- when they knocked out downstream processes, including p38 and MAPK-activating protein kinase 2 (MK2).
“Thus liver p38 and MK2, like CaMKII, play an important role in the development of hyperglycemia and hyperinsulinemia in obese mice,” they wrote.
In further analyses, the researchers discovered
- deleting or inhibiting any of these three elements ultimately improved insulin-induced Akt-phosphorylation in obese mice —
- an important part of improving insulin sensitivity.
And unlike the effects on hepatic glucose production, these changes didn’t occur through effects on FoxO1.
Instead, inhibiting the CaMKII pathway suppressed levels of the pseudo-kinase TRB3, which likely occurred because of suppression of ATF4 —
- all of which led to an increase in Akt-phosphorylation and insulin sensitivity.
Indeed, when mice were made to overexpress TRB3, the improvement in phosphorylation disappeared, “indicating that
- the suppression of TRB3 by CaMKII deficiency is causally important in the improvement in insulin signaling,” they wrote.
As a result, there “appear to be two separate CaMKII pathways,
- one involved in CaMKII-p38-FoxO1 dependent hepatic glucose production, and
- the other involved in defective insulin-induced p-Akt,” they wrote.
The findings suggest the possibility of a drug that can target both hyperglycemia and insulin resistance in type 2 diabetes, they said.
Association Between a Genetic Variant Related to Glutamic Acid Metabolism and Coronary Heart Disease in Individuals With Type 2 Diabetes
Lu Qi; Qibin Qi; S Prudente; C Mendonca; F Andreozzi; et al.
JAMA. 2013;310(8):821-828. http://dx.doi.org/10.1001/jama.2013.276305.
Importance
Diabetes is associated with an elevated risk of coronary heart disease (CHD). Previous studies have suggested that the genetic factors predisposing to excess cardiovascular risk may be different in diabetic and nondiabetic individuals.
Objective
To identify genetic determinants of CHD that are specific to patients with diabetes.
Design, Setting, and Participants
We studied 5 independent sets of CHD cases and CHD-negative controls from the Nurses’ Health Study (enrolled in 1976 and followed up through 2008), Health Professionals Follow-up Study (enrolled in 1986 and followed up through 2008), Joslin Heart Study (enrolled in 2001-2008), Gargano Heart Study (enrolled in 2001-2008), and Catanzaro Study (enrolled in 2004-2010). Included were a total of 1517 CHD cases and 2671 CHD-negative controls, all with type 2 diabetes. Results in diabetic patients were compared with those in 737 nondiabetic CHD cases and 1637 nondiabetic CHD-negative controls from the Nurses’ Health Study and Health Professionals Follow-up Study cohorts. Exposures included 2 543 016 common genetic variants occurring throughout the genome.
Main Outcomes and Measures
Coronary heart disease—defined as fatal or nonfatal myocardial infarction, coronary artery bypass grafting, percutaneous transluminal coronary angioplasty, or angiographic evidence of significant stenosis of the coronary arteries.
Results
A variant on chromosome 1q25 (rs10911021) was consistently associated with CHD risk among diabetic participants,
- with risk allele frequencies of 0.733 in cases vs 0.679 in controls (odds ratio, 1.36 [95% CI, 1.22-1.51]; P = 2 × 10−8).
No association between this variant and CHD was detected among nondiabetic participants, with risk allele frequencies of 0.697 in cases vs 0.696 in controls (odds ratio, 0.99 [95% CI, 0.87-1.13]; P = .89),
- consistent with a significant gene × diabetes interaction on CHD risk (P = 2 × 10−4).
Compared with protective allele homozygotes, rs10911021 risk allele
- homozygotes were characterized by a 32% decrease in the expression of the neighboring glutamate-ammonia ligase (GLUL) gene in human endothelial cells (P = .0048).
- A decreased ratio between plasma levels of γ-glutamyl cycle intermediates pyroglutamic and glutamic acid was also shown in risk allele homozygotes (P = .029).
Conclusion and Relevance
A single-nucleotide polymorphism (rs10911021) was identified that was significantly associated with CHD among persons with diabetes but not in those without diabetes and was functionally related to glutamic acid metabolism, suggesting a mechanistic link.
Adipocyte Heme Oxygenase-1 Induction Attenuates Metabolic Syndrome In Both Male And Female Obese Mice
Angela Burgess1,2, Ming Li2, Luca Vanella1, Dong Hyun Kim1, Rita Rezzani4, et al.
1Department of Physiology and Pharmacology, University of Toledo, Toledo, OH 43614
2Department of Pharmacology, New York Medical College, Valhalla, NY 10595
3Department of Medicine, New York Medical College, Valhalla, NY 10595
4Department of Biomedical Sciences and Biotechnology, University of Brescia, Brescia, Italy
5Department of Pediatrics and Center for Applied Genomics, Charles University, Prague, Czech Republic
6The Rockefeller University, New York, New York 10065
Hypertension. 2010 December ; 56(6): 1124–1130. http://dx.doi.org/10.1161/HYPERTENSIONAHA.110.151423
Abstract
Increases in visceral fat are associated with
- increased inflammation,
- dyslipidemia,
- insulin resistance,
- glucose intolerance and
- vascular dysfunction.
We examined the effect of the potent heme oxygenase (HO)-1 inducer, cobalt protoporphyrin (CoPP), on regulation of adiposity and glucose levels in both female and male obese mice. Both lean and obese mice were administered CoPP intraperitoneally, (3mg/kg/once a week) for 6 weeks. Serum levels of
- adiponectin,
- TNFα,
- IL-1β and
- IL-6, and
- HO-1,
- PPARγ,
- pAKT, and
- pMPK protein expression
were measured in adipocytes and vascular tissue . While female obese mice continued to gain weight at a rate similar to controls, induction of HO-1 slowed the rate of weight gain in male obese mice. HO-1 induction led to lowered blood pressure
levels in obese males and females mice similar to that of lean male and female mice.
HO-1 induction also produced a significant decrease in the plasma levels of IL-6, TNF-α, IL-1β and fasting glucose of obese females compared to untreated female obese mice. HO-1 induction
- increased the number and
- decreased the size of adipocytes of obese animals.
HO-1 induction increased adiponectin, pAKT, pAMPK, and PPARγ levels in adipocyte of obese animals. Induction of HO-1, in adipocytes was associated with
- an increase in adiponectin and
- a reduction in inflammatory cytokines.
These findings offer the possibility of treating not only hypertension, but also other detrimental metabolic consequences of obesity
- including insulin resistance and dyslipidemia in obese populations
- by induction of HO-1 in adipocytes.
Introduction
Moderate to severe obesity is associated with increased risk for cardiovascular complications and insulin resistance in humans1, 2 and animals3, 4. Cardiovascular risk is specifically associated with increased intra-abdominal fat. Women in their reproductive years have a higher BMI than males, which largely reflects increased overall subcutaneous adipose tissue or “gynoid” obesity, this is not associated with increased cardiovascular risk5. However, due to increases in visceral fat with aging, after the age of 60 the fat distribution in females more closely resembles that in males6. Increased androgen levels also often occur after the menopausal transition. These changes in visceral fat content and androgen levels correlate with both central obesity and insulin resistance and are an important determinant of cardiovascular risk7.
Heme oxygenase (HO) catalyzes the breakdown of heme, a potentially harmful pro-oxidant, into its products biliverdin and carbon monoxide, with a concomitant release of iron (reviewed in8). While HO-2 is expressed constitutively, HO-1 is inducible in response to oxidative stress and its induction has been reported to normalize vascular and renal function9–11. Further, induction of HO-1 slows weight gain, decreases levels of TNF-α and IL-6 and increases serum levels of adiponectin in obese rats and obese diabetic mice4, 9, 12.
The association observed between HO-1 and adiponectin has led to the proposal of the existence of a cytoprotective HO-1/adiponectin axis4, 13. Previously, L’Abbate et al,14 have shown that induction of HO-1 is associated with a parallel increase in the serum levels of adiponectin, which has well-documented
- insulin-sensitizing,
- antiapoptotic,
- antioxidative and
- anti-inflammatory properties.
Adiponectin is an abundant protein secreted from adipocytes. Once secreted, it mediates its actions by binding to a set of receptors, such as
- adipoR1 and adipoR2, and also
- through induction of AMPK signaling pathways15, 16.
In addition, increases in adiponectin play a protective role against TNF mediated endothelial activation17.
In this study, we evaluated the effect of CoPP, a potent inducer of HO-1,
- on visceral and subcutaneous fat distribution in both female and male obese mice.
We show for the first time a resistance to weight reduction upon administration of CoPP in female obese mice but
- a significant decrease in inflammatory cytokines.
Despite continued obesity,
- CoPP normalized blood pressure levels,
- decreased circulating cytokines, and
- increased insulin sensitivity in obese females.
CoPP treatment of obese mice
- increased the number and
- reduced the size of adipocytes.
CoPP treatment of both male and female obese mice reversed the reduction in adiponectin levels seen in obesity. This study suggests that in spite of continued obesity,
- HO-1 induction in female obese mice serves a protective role against obesity associated metabolic consequences via expansion of healthy smaller insulin-sensitive adipocytes.
Results
Effect of induction of HO-1 on body weight, appearance, and fat content of female and male obese mice. Previously, we have shown CoPP treatment results in the prevention of weight gain in several male models of obesity including obese and db/db mice and Zucker fat rats4, 12. We extended our studies to examine the effect of CoPP on weight gain in female obese mice. CoPP-treatment prevented weight gain in male obese mice when compared to age-matched male controls (Figure S1). The revention of body weight gain was accompanied by a
reduction in visceral fat in male obese mice. However, female obese mice administered CoPP did not lose weight but continued to gain weight at the same rate as untreated female obese mice (Figure S1). This was in spite of food intake being comparable between the two
groups. CoPP administration decreased subcutaneous fat content in both obese males and females (p<0.05; p<0.05, respectively). CoPP produced a decrease (p<0.05) in visceral fat in male but not in female obese mice when compared to untreated obese mice (Figure S1D).
We examined adipocyte size by haematoxilin-eosin staining in both lean, obese and CoPP treated obese female mice (Figure 1A, upper panel). CoPP treatment resulted in a decrease in adipocyte size (p<0.05) compared to untreated obese animals (Figure 1A, lower left panel). We then examined the number of adipocytes in lean, obese and CoPP-treated obese female mice. The number of adipocytes (mean±SE) in lean, obese and CoPP-treated obese animals was 40.83±3.50, 18.33±1.80 and 32.00±1.67 respectively indicating that CoPP treatment of obese mice increased the number of adipocytes to levels similar to those in lean animals (Figure 1A, lower right panel). Similar results were seen in male animals.
The induction of HO-1 was associated with a reduction in blood pressure (BP). Systolic blood pressure in obese female mice was 142 ± 6.5 mm Hg compared to obese-CoPP treated, 109 ± 8.1 mm Hg, p<0.05. The value in obese female mice treated with CoPP is similar to the blood pressure seen in lean female mice (110 ± 9.6 mm Hg). The systolic blood pressure in obese male mice was 144± 4.5 mm Hg compared to obese-CoPP treated, 104 ± 3.6 mm Hg, p<0.05.
We further examined whether CoPP affects HO-1 expression in adipocyte using immunohistochemistry and western blot analysis. Immunostaining showed increased levels of HO-1 (green staining), located on the surface of adipocytes, after CoPP treatment (p<0.05), compared with female obese mice, Figure 1B. As seen in Figure 1C, HO-1 and
HO-2 levels in adipocyte isolated from lean, untreated female obese mice or female obese mice treated with CoPP. Densitometry analysis showed that HO-1 was increased
significantly in female obese mice treated with CoPP, compared to non-treated female obese mice, p<0.05, which is in agreement with immunohistochemistry results. This pattern of HO expression in obesity occurs in other tissues, including aortas, kidneys and hearts of male obese mice4, 13.
Effect of CoPP on HO-1 expression and HO activity in female and male obese mice
HO-1 protein levels were increased by CoPP treatments in liver and renal tissues similar to that seen in adipocytes. Western blot analysis showed significant differences (p<0.05) in the ratio of HO-1 to actin in renal of male and female obese and lean mice (Figure S 2A). Obesity decreasd HO-1 levels in both sexes when compared to age matched lean animals.
In addition, HO-1 levels were significantly (p<0.05) lower in obese females compared to obese males (Figure S 2A). This reflects a less active HO system in both male and female
obese animals compared to age matched lean controls. Next, we compared the effect of CoPP on male and female HO-1 gene expression in adipocytes. CoPP increased HO-1
expression in both male and female obese animals compared to untreated obese animals (Figure S 2B, p<0.001 and p<0.001, respectively). Similar results of HO-1 expression were seen in liver tissues (Result not shown).
Effect of CoPP on cytokine levels in female and male obese mice
CoPP administration resulted in a significnt increase in the levels of plasma adiponectin in both female (p<0.001) and male obese (p<0.001) mice (Figure 2A). Untreated female obese animals exhibited a significant (p<0.05) increase in plasma IL-6 levels when compared to age-matched male obese mice (Figure 2B). CoPP decreased plasma IL-6 levels in both female and male obese mice (p<0.05A )p<0.01, respectively) when compared to untreated obese miec. Similar results were observed with plasma TNF-α and IL-1β levels (Figure 2C and 2D). These results indicate that though female obese mice exhibited elevated serum levels of inflammatory cytokines compared to male obese mice, CoPP acts with equal efficacy in both female and male obese animals in reducing inflammation while simultaneously increasing serum adiponectin levels (Figure 2).
Effect of CoPP on blood glucose and LDL levels in female and male obese mice
Fasting glucose levels were determined after the development of insulin resistance. CoPP produced a decrease in glucose levels in both fasting female (p<0.05) and male (p<0.001) obese mice when compared to untreated obese control animals (Figure 3A). CoPP reduced LDL levels in both male (p<0.01) and female (p<0.05) obese mice when compared to untreated obese controls (Figure 3B). Treatment with SnMP, increased LDL levels. In separate experiments two weeks apart, glucose levels and insulin sensitivity were determined after development of insulin resistance (Fig. 4A and B). Blood glucose levels in female obese mice were elevated (p<0.01) 30 min after glucose administration and remained elevated. In CoPP-treated female obese mice produced a decrease in glucose but not in the vehicle-treated female obese mice (p<0.01).
Effect of Obesity on Protein Expression Levels of pAKT, pAMPK, and PPARγ levels in female and male obese mice
Western blot analysis of adipocytes harvested from fat tissues,showed significant differences in basal protein expression levels of pAKT and pAMPK in untreated female obese mice compared to untreated obese male mice. pAMPK levels were higher in obese females compared to obese males (Figure 5A, p< 0.05). This was also the case for pAKT protein levels, where increased levels of pAKT were seen in obese females compared to obese males (Figure 5B, p<0.05). CoPP treatment increased pAMPK and pAKT levels in bothe obese females and obese males. In addition, CoPP administration increased PPARγ levels, in both male (p<0.001) and female (p<0.05) obese mice (Figures 5C).
Discussion
In the current study, we show for the first time that induction of HO-1 regulates adiposity in both male and female animals via an increase in adipocyte HO-1 protein levels. A second novel finding is that induction of HO-1 was associated not only with a decrease in adipocyte cell size but with an increase in adipocyte cell number. Further, induction of HO-1 affects visceral and subcutaneous fat distribution and metabolic function in male obese mice differently than in female obese mice. Despite continued obesity, upregulation of HO-1 induced major improvements in the metabolic profile of female obese mice exhibiting symptoms of Type 2 diabetes including: high plasma levels of proinflammatory cytokines, hyperglycemia, dyslipidemia, and low adiponectin levels. CoPP treatment resulted in increased serum adiponectin levels and decreased blood pressure. Adiponectin is exclusively secreted from adipose tissue, and its expression is higher in subcutaneous rather than invisceral adipose tissue. Increased adiponectin levels reduce adipocyte size and increase adipocyte number12, resulting in smaller, more insulin sensitive adipocytes. Adiponectin has recently attracted much attention because it has insulin-sensitizing properties that enhance fatty acid oxidation, liver insulin action, and glucose uptake and positively affect serum trglyceride levels18–21. Levels of circulating adiponectin are inversely correlated with plasma levels of oxidized LDL in patients with Type 2 diabetes and coronary artery disease, which suggests that low adiponectin levels are associated with an increased oxidative state in the arterial wall22. Thus, increases in adiponectin mediated by upregulation of HO-1 may account for improved insulin sensitivity and reduced levels of LDL and inflammatory cytokines (TNF-α, IL-1β, and IL-6 levels) in both male and female mice.
Females continued to gain weight in spite of the metabolic improvements. One plausible explanation for this anomaly is the direct effects of HO-1 on adiponectin mediating clonal expansion of pre-adipocytes. This supports the concept that expansion of adipogenesis leads to an increased number of adipocytes of smaller cell size; smaller adipocytes are considered to be healthy, insulin sensitive adipocyte cells that are capable of producing adiponectin23. This hypothesis is supported by the increase in the number of smaller adipocytes seen in
CoPP-treated female obese animals without affecting weight gain when compared to female obese animals. Similar results for the presence were seen in males indicating that this effect is not sex specific.
Upregulation of HO-1 was also associated with increased levels of adipocyte pAKT, and pAMPK and PPARγ levels. Previous studies have indicated that insulin resistance and impaired PI3K/pAKT signaling can lead to the of endothelial dysfunction24. In the current study, increased HO-1 expression was associated with increases in both AKT and AMPK phosphorylation; these actions may protect renal arterioles from insulin mediated endothelial damage. By this mechanism, increased levels of HO-1 limit oxidative stress and facilitate activation of an adiponectin-pAMPK-pAKT pathway and increased insulin sensitivity. Induction of adiponectin and activation of the pAMPK-AKT pathway has been shown to provide vascular protection25, 26. A reduction in AMPK and AKT levels may also explain why inhibition of HO activity in CoPP-treated obese mice increased inflammatory cytokine levels while decreasing adiponectin. The action of CoPP in increasing pAKT, pAMPK and PPARγ is associated with improved glucose tolerance and decreased insulin resistant.
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