Exploring the Gut Microbiota: Key Insights Into Its Role in Obesity, Metabolic Syndrome, and Type 2 Diabetes

Abstract

The gut microbiota (GM), comprising trillions of microorganisms in the gastrointestinal tract, is a key player in the development of obesity and related metabolic disorders, such as type 2 diabetes (T2D), metabolic syndrome (MS), and cardiovascular diseases. This mini-review delves into the intricate roles and mechanisms of the GM in these conditions, offering insights into potential therapeutic strategies targeting the microbiota. The review elucidates the diversity and development of the human GM, highlighting its pivotal functions in host physiology, including nutrient absorption, immune regulation, and energy metabolism. Studies show that GM dysbiosis is linked to increased energy extraction, altered metabolic pathways, and inflammation, contributing to obesity, MS, and T2D. The interplay between dietary habits and GM composition is explored, underscoring the influence of diet on microbial diversity and metabolic functions. Additionally, the review addresses the impact of common medications and therapeutic interventions like fecal microbiota transplantation on GM composition. The evidence so far advocates for further research to delineate the therapeutic potential of GM modulation in mitigating obesity and metabolic diseases, emphasizing the necessity of clinical trials to establish effective and sustainable treatment protocols.

Keywords: gut microbiome; gut microbiota; metabolic syndrome; obesity; type 2 diabetes.

Figure 1.

Gut microbiota and host metabolism: the gut microbiome plays a crucial role in the metabolism of dietary components. Undigested carbohydrates, proteins, and fats from the diet reach the colon and serve as substrates for bacterial fermentation. Gut bacteria possess a diverse array of enzymes that break down complex dietary components into metabolites like SCF, gases, and other bioactive compounds. These microbial metabolites can influence host energy balance, appetite regulation, and metabolic processes. For instance, SCF produced from fiber fermentation can modulate host energy harvest, satiety hormones, and glucose homeostasis. Additionally, the gut microbiome is involved in the metabolism of polyphenols, bile acids, and vitamins, further impacting host metabolism and health. Abbreviations: GLP-1, glucagon-like peptide 1; GPCR, G protein coupled receptor; PYY, peptide YY; SCF, short-chain fatty acid; TGR-5, Takeda growth factor receptor 5.

Figure 2.

Mechanisms linking GM dysbiosis to obesity and metabolic syndrome: GM dysbiosis contributes to the development and progression of obesity and related metabolic abnormalities by influencing energy extraction from the diet, intestinal permeability, gut inflammation, proinflammatory markers, insulin sensitivity, circadian rhythm, sympathetic nervous system, and immune system. Abbreviations: GM, gut microbiota; LPS, lipopolysaccharide; SCF, short-chain fatty acid; SNS, sympathetic nervous system; TMA, trimethylamine; TMAO, trimethylamine oxide.

Figure 3.

Factors influencing gut microbiota and potential therapeutic targets: this figure depicts the wide range of external and host factors and characteristics intrinsic to microbiota that affect the gut microbiota, as well as the potential areas for therapeutic targeting.