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Archive for the ‘Gut Microbiome and Obesity’ Category


Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

The bacterial makeup of human milk is influenced by the mode of breastfeeding, according to a new study. Although previously considered sterile, breast milk is now known to contain a low abundance of bacteria. While the complexities of how maternal microbiota influence the infant microbiota are still unknown, this complex community of bacteria in breast milk may help to establish the infant gut microbiota. Disruptions in this process could alter the infant microbiota, causing predisposition to chronic diseases such as allergies, asthma, and obesity. While it’s unclear how the breast milk microbiome develops, there are two theories describing its origins. One theory speculates that it originates in the maternal mammary gland, while the other theory suggests that it is due to retrograde inoculation by the infant’s oral microbiome.

 

To address this gap in knowledge scientists carried out bacterial gene sequencing on milk samples from 393 healthy mothers three to four months after giving birth. They used this information to examine how the milk microbiota composition is affected by maternal factors, early life events, breastfeeding practices, and other milk components. Among the many factors analyzed, the mode of breastfeeding (with or without a pump) was the only consistent factor directly associated with the milk microbiota composition. Specifically, indirect breastfeeding was associated with a higher abundance of potential opportunistic pathogens, such as Stenotrophomonas and Pseudomonadaceae. By contrast, direct breastfeeding without a pump was associated with microbes typically found in the mouth, as well as higher overall bacterial richness and diversity. Taken together, the findings suggest that direct breastfeeding facilitates the acquisition of oral microbiota from infants, whereas indirect breastfeeding leads to enrichment with environmental (pump-associated) bacteria.

 

The researchers argued that this study supports the theory that the breast milk microbiome is due to retrograde inoculation. Their findings indicate that the act of pumping and contact with the infant oral microbiome influences the milk microbiome, though they noted more research is needed. In future studies, the researchers will further explore the composition and function of the milk microbiota. In addition to bacteria, they will profile fungi in the milk samples. They also plan to investigate how the milk microbiota influences both the gut microbiota of infants and infant development and health. Specifically, their projects will examine the association of milk microbiota with infant growth, asthma, and allergies. This work could have important implications for microbiota-based strategies for early-life prevention of chronic conditions.

 

References:

 

https://www.genomeweb.com/sequencing/human-breast-milk-microbiome-affected-mode-feeding#.XIOH0igzZPY

 

http://childstudy.ca/2019/02/13/breastmilk-microbiome-linked-to-method-of-feeding/

 

https://gizmodo.com/pumping-breast-milk-changes-its-microbiome-1832568169

 

https://www.sciencedaily.com/releases/2019/02/190213124445.htm

 

https://www.cell.com/cell-host-microbe/fulltext/S1931-3128(19)30049-6

 

https://www.unicef.org.uk/babyfriendly/news-and-research/baby-friendly-research/infant-health-research/epigenetics-microbiome-research/

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Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

The relationship between gut microbial metabolism and mental health is one of the most intriguing and controversial topics in microbiome research. Bidirectional microbiota–gut–brain communication has mostly been explored in animal models, with human research lagging behind. Large-scale metagenomics studies could facilitate the translational process, but their interpretation is hampered by a lack of dedicated reference databases and tools to study the microbial neuroactive potential.

 

Out of all the many ways, the teeming ecosystem of microbes in a person’s gut and other tissues might affect health. But, its potential influences on the brain may be the most provocative for research. Several studies in mice had indicated that gut microbes can affect behavior, and small scale studies on human beings suggested this microbial repertoire is altered in depression. Studies by two large European groups have found that several species of gut bacteria are missing in people with depression. The researchers can’t say whether the absence is a cause or an effect of the illness, but they showed that many gut bacteria could make substances that affect the nerve cell function—and maybe the mood.

 

Butyrate-producing Faecalibacterium and Coprococcus bacteria were consistently associated with higher quality of life indicators. Together with DialisterCoprococcus spp. was also depleted in depression, even after correcting for the confounding effects of antidepressants. Two kinds of microbes, Coprococcus and Dialister, were missing from the microbiomes of the depressed subjects, but not from those with a high quality of life. The researchers also found the depressed people had an increase in bacteria implicated in Crohn disease, suggesting inflammation may be at fault.

 

Looking for something that could link microbes to mood, researchers compiled a list of 56 substances important for proper functioning of nervous system that gut microbes either produce or break down. They found, for example, that Coprococcus seems to have a pathway related to dopamine, a key brain signal involved in depression, although they have no evidence how this might protect against depression. The same microbe also makes an anti-inflammatory substance called butyrate, and increased inflammation is implicated in depression.

 

Still, it is very much unclear that how microbial compounds made in the gut might influence the brain. One possible channel is the vagus nerve, which links the gut and brain. Resolving the microbiome-brain connection might lead to novel therapies. Some physicians and companies are already exploring typical probiotics, oral bacterial supplements, for depression, although they don’t normally include the missing gut microbes identified in the new study.

 

References:

 

https://www.sciencemag.org/news/2019/02/evidence-mounts-gut-bacteria-can-influence-mood-prevent-depression?utm_source=Nature+Briefing

 

https://www.nature.com/articles/s41564-018-0337-x

 

https://www.ncbi.nlm.nih.gov/pubmed/22968153

 

https://www.ncbi.nlm.nih.gov/pubmed/24888394

 

https://www.ncbi.nlm.nih.gov/pubmed/27067014

 

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Benefits of Fiber in Diet

Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

UPDATED on 1/15/2019

This is How Much Daily Fiber to Eat for Better Health – More appears better in meta-analysis — as in more than 30 g/day

by Ashley Lyles, Staff Writer, MedPage Today

In the systematic review, observational data showed a 15% to 30% decline in cardiovascular-related death, all-cause mortality, and incidence of stroke, coronary heart disease, type 2 diabetes, and colorectal cancer among people who consumed the most dietary fiber compared to those consuming the lowest amounts.

Whole grain intake yielded similar findings.

Risk reduction associated with a range of critical outcomes was greatest when daily intake of dietary fibre was between 25 g and 29 g. Dose-response curves suggested that higher intakes of dietary fibre could confer even greater benefit to protect against cardiovascular diseases, type 2 diabetes, and colorectal and breast cancer.

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(18)31809-9.pdf

Eating more dietary fiber was linked with lower risk of disease and death, a meta-analysis showed.

According to observational studies, risk was reduced most for a range of critical outcomes from all-cause mortality to stroke when daily fiber consumption was between 25 grams and 29 grams, reported Jim Mann, PhD, of University of Otago in Dunedin, New Zealand, and colleagues in The Lancet.

By upping daily intake to 30 grams or more, people had even greater prevention of certain conditions: colorectal and breast cancer, type 2 diabetes, and cardiovascular diseases, according to dose-response curves the authors created.

Quantitative guidelines relating to dietary fiber have not been available, the researchers said. With the GRADE method, they determined that there was moderate and low-to-moderate certainty of evidence for the benefits of dietary fiber consumption and whole grain consumption, respectively.

Included in the systematic review were 58 clinical trials and 185 prospective studies for a total of 4,635 adult participants with 135 million person-years of information (one trial in children was included, but analyzed separately from adults). Trials and prospective studies assessing weight loss, supplement use, and participants with a chronic disease were excluded.

 

Food is digested by bathing in enzymes that break down its molecules. Those molecular fragments then pass through the gut wall and are absorbed in our intestines. But our bodies make a limited range of enzymes, so that we cannot break down many of the tough compounds in plants. The term “dietary fiber” refers to those indigestible molecules. These dietary fibers are indigestible only to us. The gut is coated with a layer of mucus, on which sits a carpet of hundreds of species of bacteria, part of the human microbiome. Some of these microbes carry the enzymes needed to break down various kinds of dietary fibers.

 

Scientists at the University of Gothenburg in Sweden are running experiments that are yielding some important new clues about fiber’s role in human health. Their research indicates that fiber doesn’t deliver many of its benefits directly to our bodies. Instead, the fiber we eat feeds billions of bacteria in our guts. Keeping them happy means our intestines and immune systems remain in good working order. The scientists have recently reported that the microbes are involved in the benefits obtained from the fruits-and-vegetables diet. Research proved that low fiber diet decreases the gut bacteria population by tenfold.

 

Along with changes to the microbiome there were also rapid changes observed in the experimental mice. Their intestines got smaller, and its mucus layer thinner. As a result, bacteria wound up much closer to the intestinal wall, and that encroachment triggered an immune reaction. After a few days on the low-fiber diet, mouse intestines developed chronic inflammation. After a few weeks, they started putting on fat and developing higher blood sugar levels. Inflammation can help fight infections, but if it becomes chronic, it can harm our bodies. Among other things, chronic inflammation may interfere with how the body uses the calories in food, storing more of it as fat rather than burning it for energy.

 

In a way fiber benefits human health is by giving, indirectly, another source of food. When bacteria finished harvesting the energy in the dietary fiber, they cast off the fragments as waste. That waste — in the form of short-chain fatty acids — is absorbed by intestinal cells, which use it as fuel. But the gut’s microbes do more than just make energy. They also send messages. Intestinal cells rely on chemical signals from the bacteria to work properly. The cells respond to the signals by multiplying and making a healthy supply of mucus. They also release bacteria-killing molecules. By generating these responses, gut bacteria help to maintain a peaceful coexistence with the immune system. They rest on the gut’s mucus layer at a safe distance from the intestinal wall. Any bacteria that wind up too close get wiped out by antimicrobial poisons.

 

A diet of fiber-rich foods, such as fruits and vegetables, reduces the risk of developing diabetes, heart disease and arthritis. Eating more fiber seems to lower people’s mortality rate, whatever be the cause. Researchers hope that they will learn more about how fiber influences the microbiome to use it as a way to treat disorders. Lowering inflammation with fiber may also help in the treatment of immune disorders such as inflammatory bowel disease. Fiber may also help reverse obesity. They found that fiber supplements helped obese people to lose weight. It’s possible that each type of fiber feeds a particular set of bacteria, which send their own important signals to our bodies.

 

References:

 

https://www.nytimes.com/2018/01/01/science/food-fiber-microbiome-inflammation.html

 

 

https://www.ncbi.nlm.nih.gov/pubmed/29276171

 

https://www.ncbi.nlm.nih.gov/pubmed/29276170

 

https://www.ncbi.nlm.nih.gov/pubmed/29486139

 

https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/fiber/art-20043983

 

https://nutritiouslife.com/eat-empowered/high-fiber-diet/

 

http://www.eatingwell.com/article/287742/10-amazing-health-benefits-of-eating-more-fiber/

 

http://www.cookinglight.com/eating-smart/nutrition-101/what-is-a-high-fiber-diet

 

https://www.helpguide.org/articles/healthy-eating/high-fiber-foods.htm

 

https://www.gicare.com/diets/high-fiber-diet/

 

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Reporter and Curator: Dr. Sudipta Saha, Ph.D.

 

The trillions of microbes in the human gut are known to aid the body in synthesizing key vitamins and other nutrients. But this new study suggests that things can sometimes be more adversarial.

 

Choline is a key nutrient in a range of metabolic processes, as well as the production of cell membranes. Researchers identified a strain of choline-metabolizing E. coli that, when transplanted into the guts of germ-free mice, consumed enough of the nutrient to create a choline deficiency in them, even when the animals consumed a choline-rich diet.

 

This new study indicate that choline-utilizing bacteria compete with the host for this nutrient, significantly impacting plasma and hepatic levels of methyl-donor metabolites and recapitulating biochemical signatures of choline deficiency. Mice harboring high levels of choline-consuming bacteria showed increased susceptibility to metabolic disease in the context of a high-fat diet.

 

DNA methylation is essential for normal development and has been linked to everything from aging to carcinogenesis. This study showed changes in DNA methylation across multiple tissues, not just in adult mice with a choline-consuming gut microbiota, but also in the pups of those animals while they developed in utero.

 

Bacterially induced reduction of methyl-donor availability influenced global DNA methylation patterns in both adult mice and their offspring and engendered behavioral alterations. This study reveal an underappreciated effect of bacterial choline metabolism on host metabolism, epigenetics, and behavior.

 

The choline-deficient mice with choline-consuming gut microbes also showed much higher rates of infanticide, and exhibited signs of anxiety, with some mice over-grooming themselves and their cage-mates, sometimes to the point of baldness.

 

Tests have also shown as many as 65 percent of healthy individuals carry genes that encode for the enzyme that metabolizes choline in their gut microbiomes. This work suggests that interpersonal differences in microbial metabolism should be considered when determining optimal nutrient intake requirements.

 

References:

 

https://news.harvard.edu/gazette/story/2017/11/harvard-research-suggests-microbial-menace/

 

http://www.cell.com/cell-host-microbe/fulltext/S1931-3128(17)30304-9

 

https://www.ncbi.nlm.nih.gov/pubmed/23151509

 

https://www.ncbi.nlm.nih.gov/pubmed/25677519

 

http://mbio.asm.org/content/6/2/e02481-14

 

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Functional Analysis of the Microbiome for Development of Potential Therapeutic Approaches to Weight Regain

Reporter: Aviva Lev-Ari, PhD, RN

 

Transplanting fecal microbes to prevent recurring obesity

Finally, the researchers used these insights to develop new treatments for recurrent obesity. They implanted formerly obese mice with gut microbes from mice that had never been obese. This fecal microbiome transplantation erased the “memory” of obesity in these mice when they were re-exposed to a high-calorie diet, preventing excessive recurrent obesity.

Gut Microbes Contribute to Recurrent ‘Yo-Yo’ Obesity, Study Shows

By Einat Paz-Frankel, NoCamels December 18, 2016

Researchers at Israel’s Weizmann Institute of Science have shown in mice that intestinal microbes – collectively termed the gut microbiome – play an unexpectedly important role in exacerbated post-dieting weight gain, and that this common phenomenon may in the future be prevented or treated by altering the composition or function of the microbiome.

“We’ve shown in obese mice that following successful dieting and weight loss, the microbiome retains a ‘memory’ of previous obesity,” Elinav said in a statement. “This persistent microbiome accelerated the regaining of weight when the mice were put back on a high-calorie diet or ate regular food in excessive amounts.”

http://nocamels.com/2016/12/gut-microbes-recurrent-obesity-diet/

 

Original Research

Persistent microbiome alterations modulate the rate of post-dieting weight regain

Nature (2016) doi:10.1038/nature20796

Corrected online

28 November 2016

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Abstract

In tackling the obesity pandemic, significant efforts are devoted to the development of effective weight reduction strategies, yet many dieting individuals fail to maintain a long-term weight reduction, and instead undergo excessive weight regain cycles. The mechanisms driving recurrent post-dieting obesity remain largely elusive. Here, we identify an intestinal microbiome signature that persists after successful dieting of obese mice, which contributes to faster weight regain and metabolic aberrations upon re-exposure to obesity-promoting conditions and transmits the accelerated weight regain phenotype upon inter-animal transfer. We develop a machine-learning algorithm that enables personalized microbiome-based prediction of the extent of post-dieting weight regain. Additionally, we find that the microbiome contributes to diminished post-dieting flavonoid levels and reduced energy expenditure, and demonstrate that flavonoid-based ‘post-biotic’ intervention ameliorates excessive secondary weight gain. Together, our data highlight a possible microbiome contribution to accelerated post-dieting weight regain, and suggest that microbiome-targeting approaches may help to diagnose and treat this common disorder.

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