Richness of human gut microbiome correlates with metabolic markers | Nature

We are facing a global metabolic health crisis provoked by an obesity epidemic. Here we report the human gut microbial composition in a population sample of 123 non-obese and 169 obese Danish individuals. We find two groups of individuals that differ by the number of gut microbial genes and thus gut bacterial richness. They contain known and previously unknown bacterial species at different proportions; individuals with a low bacterial richness (23% of the population) are characterized by more marked overall adiposity, insulin resistance and dyslipidaemia and a more pronounced inflammatory phenotype when compared with high bacterial richness individuals. The obese individuals among the lower bacterial richness group also gain more weight over time. Only a few bacterial species are sufficient to distinguish between individuals with high and low bacterial richness, and even between lean and obese participants. Our classifications based on variation in the gut microbiome identify subsets of individuals in the general white adult population who may be at increased risk of progressing to adiposity-associated co-morbidities. Analysis of the gut microbial gene composition in obese and non-obese individuals shows marked differences in bacterial richness between the two groups, with individuals with low richness exhibiting increased adiposity, insulin resistance, dyslipidaemia and inflammation; only a few bacterial marker species are needed to distinguish between individuals with high and low bacterial richness, providing potential for future diagnostic tools. Obesity is a risk factor for cardiovascular disease, diabetes, osteoporosis and other conditions including some cancers. Other influences must be at work to determine which, if any, metabolic diseases obese individuals will suffer, and two papers in this issue of Nature look at the role one of these factors, the richness of the gut microbiome. Le Chatelier et al. analysed the gut microbial gene composition in non-obese and obese individuals and found marked differences in gene and species richness. Individuals with low richness exhibited increased adiposity, insulin resistance, dyslipidaemia and inflammation. Obese individuals with low microbial richness tended to gain more body weight than those with high microbial richness. The authors also demonstrate that analysis of just a few bacterial marker species was sufficient to distinguish between high and low bacterial richness. Cotillard et al. monitored gut microbe profiles during diet-induced weight loss and weight stabilization interventions in obese or overweight individuals. They report that increased consumption of high-fibre foods, such as fruit and vegetables, leads to an increase in bacterial richness and improves some clinical symptoms associated with obesity. This finding supports previous work linking diet to the composition of gut microbe populations, and suggests that a permanent change might be achieved by appropriate diet....