Hypoglycemic effect of dietary fibers from Moringa oleifera leaves: In vitro and in vivo studies.

Moringa leaf is traditionally regarded as a natural antagonistic diabetic herb in many countries. This study aimed to investigate the potential hypoglycemic activity of Moringa dietary fibers (MDFs) with different particle sizes in vitro and in vivo and reveal the related mechanisms. Among MDFs, MDF200 exhibited the highest glucose adsorption and diffusion retarding capacities and the most effective inhibition of digestive enzyme activities in vitro. All MDF interventions ameliorated insulin resistance and tissue damage, alleviated oxidative stress and dyslipidemia in high-fat diet and streptozotocin induced type 2 diabetes mice in vivo. MDF interventions, especially MDF80 and MDF200, remarkably promoted the diversity of cecum flora and the abundance of beneficial intestinal bacteria (Ileibacterium, Bifidobacterium), while inhibited the harmful bacteria (Clostridium_sensu_stricto_1). The ratio of Firmicutes/Bacteroidetes was significantly reduced by MDF40 and MDF80 interventions. MDF80 promoted fecal acetic acid, butyric acid and total short-chain fatty acids (SCFAs), while MDF40 promoted fecal propionic acid. All MDF interventions remarkably promoted the secretion of glucagon-like peptide-1 (GLP-1) and stimulated higher G protein-coupled receptor 43 (GPR43) protein expression in liver. Larger MDF activated phosphorylation of AMPK and Erk, while smaller MDF stimulated GLP-1, more PI3K and phosphorylation of Akt protein expression. These results revealed that MDFs ameliorated T2DM through modulating microbiota-SCFAs receptor (GPR43)/AMPK signaling pathways and stimulating GLP-1 secretion and activated liver PI3K/Akt signaling pathways. This study offers an effective case for MDFs as a potential dietary intervention or adjuvant treatment for type 2 diabetes and the application of Moringa leaf as a functional food material.