A recent study lent insight into the role of the microbiota in both diet-related and genetic obesity in humans.
This Chinese study, led by Prof. Liping Zhao, Prof. Aihua Yin, and Prof. Huiru Tang, involved 17 children with Prader-Willi syndrome (PWS) — the most common genetic cause of morbid obesity in children — and 21 with simple (diet-induced) obesity.
The children received an intensive dietary intervention in a hospital setting. The diet, aimed at changing the gut microbiota, included a high intake of whole grains, traditional Chinese medicinal foods and prebiotics.
Post-intervention, both groups showed reduced weight, better behavioural control of food cravings, improved measurements of metabolic health, and less systemic inflammation. The gut microbiota — analyzed to the strain level — also showed structural changes: beneficial bacteria such as bifidobacteria increased, and proinflammatory toxin producers decreased.
Urine profiling showed that the intervention diet induced overall changes in the host ‘metabotype‘ — reducing, for example, the detrimental metabolites trimethylamine N-oxide and indoxyl sulfate.
When bacterial changes were correlated with changes in urine metabolites, researchers identified specific bacterial genomes that use dietary components to produce toxic metabolites relevant to obesity. They say that these toxin-producing bacteria could become targets for obesity therapies in the future.
Furthermore, the microbial community from before and after intervention was transplanted into germ-free mice. Indeed, the pre-intervention gut microbiota induced higher inflammation and larger adipocytes in mice compared with the post-intervention microbiota from the same patient.
The researchers concluded that dysbiosis of the gut microbiota contributes significantly to both simple obesity and genetic obesity in children. They also say their detailed analysis of the microbiota changes that occur support the hypothesis that gut microbiota ecosystems function somewhat like rainforest ecosystems, where different species work together in functional groups (‘guilds’) that together adapt to environmental perturbations.
Zhang C, et al. (2015) Dietary Modulation of Gut Microbiota Contributes to Alleviation of Both Genetic and Simple Obesity in Children. EBioMedicine DOI: http://dx.doi.org/10.1016/j.ebiom.2015.07.007