Mechanistic links between gut microbial community dynamics, microbial functions and metabolic health

Figure 3 Hypothesised triggers and drivers in diet-induced dysbiosis. Progression from homeostasis to clinical manifestation of metabolic dysfunction may emerge from shifts in microbe-associated molecular patterns (MAMPs; green) and metabolites (blue), initiated by long-term consumption of diets with reduced amount of dietary fibre but high saturated fat. A: Reduction in the availability of fermenting substrates in conjunction with excess secretion of anti-bacterial bile acids can alter the competition dynamics of commensal organisms and pathobionts. Consequent depletion of polysaccharide A and butyrate promotes immune dysfunction by altering the balance of regulatory T cells (T_Reg) and helper T cells (T_Helper); B and C: Shifts in microbial products contribute to the impairment of gut barrier function and the leakage of MAMPs; D: Dietary factors, microbial signals and host responses act in concert to drive inflammation, which provides a positive feedback pathway in favour of chronic disease development.