Advertisements
Feeds:
Posts
Comments

Posts Tagged ‘Thoracic diaphragm’


Stanford Study Finds miRNA-320a a Broad Regulator of Glycolysis, Potential Drug Target

 Reporter: Aviva Lev-Ari, PhD, RN

A study by Stanford researchers has found that microRNA-320a appears to regulate glycolysis in response to oxidative stress in several biological systems, including lung cancer and wasting of disused muscle.

The Stanford team was initially interested in better understanding the wasting of diaphragm muscles due to mechanical ventilation, but expanded its study to look at lung cancer and an experimental in vitro model of oxidative stress, as well as the similarity of pathogenic glycolytic pathways across these biological systems.

The group profiled miRNA and protein expression in samples from human diaphragm muscles under mechanical ventilation to identify miRNAs associated with the glycolytic rate-limiting enzyme phosphofructokinase, or PFKm, without which glycolysis is reduced.

The group initially identified 28 miRNAs that were significantly downregulated and three that were upregulated in the ventilated human diaphragm samples. Using predictive software, the group pinpointed miR-320a as being potentially involved in the regulation PFKm.

To validate miR-320a, the researchers looked at all three experimental systems — samples of diaphragm tissue, lung cancer, and an in vitro cell model under oxidative stress. In all three, miR-320a was down-regulated in the samples versus the control.

The group also confirmed that miR-320a influences PFKm in each system, and further demonstrated that miR-320a knockdown increased lactate levels in vitro; and thathigher miR-320a levels reduced lactate levels in in vivo mouse experiments.

The group wrote that the study shows for the first time that glycolytic activity “is increased in diaphragm tissue that is noncontractile as a result of full mechanical ventilator support.” The results also confirmed that glycolysis up-regulation, or the Warburg effect, is present in lung adenocarcinoma, and that both otherwise divergent disorders are in fact linked by the influence of miR-320a.

The finding has implications for cancer treatment, as well as more effective treatment for dysfunctional diaphragm muscles following breathing support using a ventilator, according to the team, which published the study online in the FASEB Journal earlier this month.

Glycolysis is the process of converting sugar into energy, and is implicated in the growth of some cancers through a process called the Warburg effect. To the Stanford team, the Warburg effect seen in lung adenocarcinoma “appears to closely mimic” that of dysfunctional human diaphragm tissue after mechanical ventilation therapy, a condition called ventilator-induced diaphragm dysfunction, or VIDD.

The Stanford researchers claim that their study shows that these very divergent biological systems share the same glycolysis regulatory apparatus involving miR-320a, which the authors believe they are the first to identify.

Additionally, “miR-320 regulation of glycolysis may represent a general mechanism underlying other clinical diseases that are associated with changes in energy supply,” the researchers wrote, such as cardiac ischemia, to insulin resistance.

In cancer specifically, down-regulation of miR-320a has been previously reported in a number of malignancies, the group reported. Coupled with the fact that the Warburg effect is thought to be important in many cancers, and the results of the group’s study in adenocarcinoma, this suggests that miR-320a “may be directly related” to the development of cancer, and that the associated glycolysis may be a potential drug target.

FASEB J. 2012 Jul 5. [Epub ahead of print]

Oxidative stress-responsive microRNA-320 regulates glycolysis in diverse biological systems.

Tang HLee MSharpe OSalamone LNoonan EJHoang CDLevine SRobinson WHShrager JB.

Source

*Division of Thoracic Surgery, Department of Cardiothoracic Surgery.

Abstract

Glycolysis is the initial step of glucose catabolism and is up-regulated in cancer cells (the Warburg Effect). Such shifts toward a glycolytic phenotype have not been explored widely in other biological systems, and the molecular mechanisms underlying the shifts remain unknown. With proteomics, we observed increased glycolysis in disused human diaphragm muscle. In disused muscle, lung cancer, and H(2)O(2)-treated myotubes, we show up-regulation of the rate-limiting glycolytic enzyme muscle-type phosphofructokinase (PFKm, >2 fold, P<0.05) and accumulation of lactate (>150%, P<0.05). Using microRNA profiling, we identify miR-320a as a regulator of PFKm expression. Reduced miR-320a levels (to ∼50% of control, P<0.05) are associated with the increased PFKm in each of these diverse systems. Manipulation of miR-320a levels both in vitro and in vivo alters PFKm and lactate levels in the expected directions. Further, miR-320a appears to regulate oxidative stress-induced PFKm expression, and reduced miR-320a allows greater induction of glycolysis in response to H(2)O(2) treatment. We show that this microRNA-mediated regulation occurs through PFKm’s 3′ untranslated region and that Ets proteins are involved in the regulation of PFKm via miR-320a. These findings suggest that oxidative stress-responsive microRNA-320a may regulate glycolysis broadly within nature.-Tang, H., Lee, M., Sharpe, O., Salamone, L., Noonan, E. J., Hoang, C. D., Levine, S., Robinson, W. H., Shrager, J. B. Oxidative stress-responsive microRNA-320 regulates glycolysis in diverse biological systems.

Advertisements

Read Full Post »