Fish oil-diet benefits may be mediated by gut microbes

 

Caesar et al. reveal how saturated lipids in lard affect gut microbial composition to promote obesity and WAT inflammation via TLR signaling and CCL2; in contrast, mice fed a fish-oil diet enriched in polyunsaturated fatty acids are protected. Transfer of microbiota from fish-oil-fed mice dampens lard-induced inflammation. Diets rich in fish oil versus diets rich in lard (e.g., bacon) produce very different bacteria in the guts of mice, reports a study published August 27 in Cell Metabolism. The researchers transferred these microbes into other mice to see how they affected health. The results suggest that gut bacteria share some of the responsibility for the beneficial effects of fish oil and the harmful effects of lard. In particular, mice that received transplants of gut microbes associated with a fish oil diet were protected against diet-induced weight gain and inflammation compared with mice transplanted with gut microbes associated with a lard diet. This demonstrates that gut microbes are an independent factor aggravating inflammation associated with diet-induced obesity and gives hope that a probiotic might help counteract a "greasy" diet. "We wanted to determine whether gut microbes directly contribute to the metabolic differences associated with diets rich in healthy and unhealthy fats," says first study author Robert Caesar of the University of Gothenburg. Even though the study was done in mice, "our goal is to identify interventions for optimizing metabolic health in humans." Caesar, working in the lab of senior study author Fredrik Bäckhed, began by feeding either lard or fish oil to mice for 11 weeks and monitoring signs of metabolic health. While the consumption of lard promoted the growth of bacteria called Bilophila, which have been linked to gut inflammation, the fish oil diet increased the abundance of bacteria called Akkermansia muciniphila, known to reduce weight gain and improve glucose metabolism in mice. "We were surprised that the lard and the fish oil diet, despite having the same energy content and the same amount of dietary fiber--which is the primary energy source for the gut bacteria--resulted in fundamentally different gut microbiota communities and that the microbiota per se had such large effects on health," Caesar says. In the next set of experiments, Caesar conducted "fecal transplants" to test whether fish oil-diet microbes could improve the health of mice fed only lard and vice versa. The results provide additional evidence that gut microbe communities can both determine and recover health problems caused by poor diet. "Our paper supports previous reports indicating the bacteria Akkermansia muciniphila is a promoter of a healthy phenotype," Bäckhed says. "However, further investigations will be needed to determine if this bacteria can be used as probiotic strain and, in that case, how it should be combined with diet to optimize health outcomes." Story Source: The above post is reprinted from materials provided by Cell Press. Note: Materials may be edited for content and length. Journal Reference: Caesar et al. Crosstalk between Gut Microbiota and Dietary Lipids Aggravates WAT Inflammation through TLR Signaling. Cell Metabolism, 2015 DOI: 10.1016/j.cmet.2015.07.026 Cell Press. "Fish oil-diet benefits may be mediated by gut microbes." ScienceDaily. ScienceDaily, 27 August 2015. www.sciencedaily.com/releases/2015/08/150827130139.htm

Body weight heavily influenced by gut microbes: Genes shape body weight by affecting gut microbes

 

By studying pairs of twins at King's Department of Twin Research, researchers identified a specific, little known bacterial family that is highly heritable and more common in individuals with low body weight. This microbe also protected against weight gain when transplanted into mice.

The results, published today in the journal Cell, could pave the way for personalised probiotic therapies that are optimised to reduce the risk of obesity-related diseases based on an individual's genetic make-up.

Previous research has linked both genetic variation and the composition of gut microbes to metabolic disease and obesity. Despite these shared effects, the relationship between human genetic variation and the diversity of gut microbes was presumed to be negligible.

In the study, funded by National Institutes of Health (NIH), researchers sequenced the genes of microbes found in more than 1,000 fecal samples from 416 pairs of twins. The abundances of specific types of microbes were found to be more similar in identical twins, who share 100 per cent of their genes, than in non-identical twins, who share on average only half of the genes that vary between people. These findings demonstrate that genes influence the composition of gut microbes.

The type of bacteria whose abundance was most heavily influenced by host genetics was a recently identified family called 'Christensenellaceae'. Members of this health-promoting bacterial family were more abundant in individuals with a low body weight than in obese individuals. Moreover, mice that were treated with this microbe gained less weight than untreated mice, suggesting that increasing the amounts of this microbe may help to prevent or reduce obesity.

Professor Tim Spector, Head of the Department of Twin Research and Genetic Epidemiology at King's College London, said: 'Our findings show that specific groups of microbes living in our gut could be protective against obesity -- and that their abundance is influenced by our genes. The human microbiome represents an exciting new target for dietary changes and treatments aimed at combating obesity.

'Twins have been incredibly valuable in uncovering these links -- but we now want to promote the use of microbiome testing more widely in the UK through the British Gut Project. This is a crowd-sourcing experiment that allows anyone with an interest in their diet and health to have their personal microbes tested genetically using a simple postal kit and a small donation via our website (www.britishgut.org). We want thousands to join up so we can continue to make major discoveries about the links between our gut and our health.'

Ruth Ley, Associate Professor at Cornell University in the United States, said: 'Up until now, variation in the abundances of gut microbes has been explained by diet, the environment, lifestyle, and health. This is the first study to firmly establish that certain types of gut microbes are heritable -- that their variation across a population is in part due to host genotype variation, not just environmental influences. These results will also help us find new predictors of disease and aid prevention.'