The human gut microbiota and glucose metabolism: a scoping review of key bacteria and the potential role of SCFAs

Abstract

The gut microbiota plays a fundamental role in human nutrition and metabolism and may have direct implications for type 2 diabetes and associated pre-conditions. An improved understanding of relationships between human gut microbiota and glucose metabolism could lead to novel opportunities for type 2 diabetes prevention, but human observational studies reporting on such findings have not been extensively reviewed. Here, we review the literature on associations between gut microbiota and markers and stages of glucose dysregulation and insulin resistance in healthy adults and in adults with metabolic disease and risk factors. We present the current evidence for identified key bacteria and their potential roles in glucose metabolism independently of overweight, obesity and metabolic drugs. We provide support for short-chain fatty acids (SCFA) mediating such effects and discuss the role of diet and gut microbiota x diet derived metabolites. From 5983 initially identified PubMed records, 45 original studies were eligible and reviewed. Alpha diversity and 45 bacterial taxa were associated with selected outcomes. Six taxa were most frequently associated with glucose metabolism: Akkermansia muciniphila, Bifidobacterium longum, Clostridium leptum group, Faecalibacterium prausnitzii and Faecalibacterium (inversely associated) and Dorea (directly associated). For Dorea and A. muciniphila, associations were independent of metabolic drugs and body measures. For A. muciniphila and F. prausnitzii, limited evidence supported SCFA-mediation of potential effects on glucose metabolism. We conclude that observational studies applying metagenomics sequencing to identify species-level relationships are warranted, as are studies accounting for confounding factors and investigating SCFA and postprandial glucose metabolism. Such advances in the field will, together with mechanistic and prospective studies and investigations into diet-gut microbiota interactions, have the potential to bring critical insight into roles of gut microbiota and microbial metabolites in human glucose metabolism and to contribute towards the development of novel prevention strategies for type 2 diabetes, including precision nutrition.

Association of gut microbiota and glucose metabolism in children with disparate degrees of adiposity

“…Studies have confirmed that Bifidobacterium is an important probiotic, which plays an important role in improving obesity and related metabolic indicators 30 . The abundance of B. longum was frequently found to be lower with elevated glucose and INS levels 31 . Therefore, we speculated that B. longum may play a certain compensatory role in glucose metabolism in children with severe obesity in this study.…”

“…30 The abundance of B. longum was frequently found to be lower with elevated glucose and INS levels. 31 Therefore, we speculated that B. longum may play a certain compensatory role in glucose metabolism in children with severe obesity in this study.…”

Probiotic Potential and Safety Assessment of Type Strains of Weissella and Periweissella Species

“…Since not all the starch introduced in the diet is hydrolyzed by human enzymes, being partially available as an energy source for the gut microbiota ( 36 ), glucosidases might be of utmost importance for probiotics, allowing them to be competitive in the human gastrointestinal ( 37 ) and genitourinary ( 38 ) tracts. In addition, the starch fermentation by gut microbiota, including probiotics, produces as beneficial products the short-chain fatty acids (SCFAs) which are documented to have a relevant role in healthy aging and exploit anti-inflammatory and antiproliferative effects ( 39 , 40 ).…”

Selenium-enrichedBifidobacterium longumDD98 relieves irritable bowel syndrome induced by chronic unpredictable mild stress in mice

“…, Christensenellaceae , Actinobacteria , and Verrucomicrobia , were also proven to be beneficial to humans and were associated with the production of SCFAs. 113–115 Thus, administration of Se- B. longum DD98 showed a generally positive effect on the gut-brain axis.…”