Our gut microbiota has recently emerged as a potential target for tackling obesity and related metabolic disorders. Prebiotics and probiotics have been the most closely studied interventions for lessening the metabolic complications of obesity.
However, a wide range of factors can determine if individuals will respond or not to a gut microbiota-targeted intervention. For example, habitual fiber intake and baseline gut microbiota have been shown to largely influence gut microbiota response to diet.
A new small study in mice and people with obesity shows that baseline fecal microbiota composition may influence the metabolic response to inulin supplementation, adding to mounting evidence showing gut microbiota’s role in variable responses towards diet.
Julie Rodriguez and colleagues inoculated the baseline fecal microbiota from four people with obesity to antibiotic-pretreated mice, which were subsequently fed with a high-fat diet and supplemented with inulin. Mice colonized with the fecal microbiota from the obese individuals showed different responses to inulin depending on their gut microbiota.
Inulin regulated changes differently in adipose tissue, liver and skeletal muscle in mice. While inulin had no effect in mice receiving fecal microbiota from donors 2 and 3, the two other mice groups receiving microbiota from donors 1 and 4 showed a metabolic improvement, especially in donor 1.
Although inulin did not alter the overall gut microbiota composition, the inter-individual variability observed in metabolic outcomes was accompanied by specific changes at the phylum, family and genera level in recipient mice, depending on the donor. Indeed, Barnesiella, Bilophila, Butyricimonas, Victivallis, Clostridium XIVa, Akkermansia, Raoultella and Blautia all correlated with decreased adiposity and hepatic steatosis, while inulin increased Roseburia species in all recipient mice.
To explore the extent to which gut bacteria were sensitive to metabolic improvements driven by inulin, the authors undertook a close study of a human cohort of patients with obesity who were treated with inulin. That cohort included the four donors used for the murine fecal microbiota transplantation.
Supplementing the cohort with 16g/day of inulin for 3 months led to metabolic and microbiota changes similar to mice in donors 1, 2 and 3. Although gut microbiota richness was similar between participants with unchanged body mass index (BMI) when compared with those with decreased BMI, responders showed an increase in Bifidobacterium species and Butyricicoccus and a decrease in Collinsella, Barnesiella, Akkermansia and Bilophila.
On the whole, these findings show that certain subsets of gut bacteria may mediate the metabolic effects of the well known prebiotic inulin in both mice and individuals with obesity. Gut microbiome research has highlighted that applying a one-size-fits all diet is not an accurate approach, as not all people respond the same way to food. The interactions between diet and our gut microbiome are personalized and this study reveals how relevant the preintervention characteristics of the gut microbiota are in driving metabolic improvements in obese patients treated with inulin. Similarly, it has been shown in healthy adults that following a high dietary fiber diet determines those who will benefit from an inulin-type fructan prebiotic.
The authors acknowledged in the paper that “These findings support that characterizing the gut microbiota prior to nutritional intervention with prebiotics is important to increase the positive outcome in the context of obesity and metabolic disorders.”
Rodriguez J, Hiel S, Neyrinck AM, et al. Discovery of the gut microbial signature driving the efficacy of prebiotic intervention in obese patients. Gut. 2020; doi: 10.1136/gutjnl-2019-319726.