Varietal Differences in Kidney Beans Modulate Gut Microbiota and Inflammation During High-Fat Diet-Induced Obesity in Male Mice.

Background

Obesity-associated inflammation arises from adipose dysfunction and intestinal disturbances, including altered microbiota and short-chain fatty acid (SCFA) metabolism. Beans (Phaseolus vulgaris) are rich in non-digestible carbohydrates and polyphenols, but whether kidney bean varieties differing in seed coat colour exert distinct effects on inflammation in obesity remains unclear.

Objective

To determine whether supplementation of an obesogenic high-fat (HF) diet with white or dark red kidney beans modulates gut microbiota, SCFAs, and intestinal, systemic, and neuroinflammatory outcomes.

Methods

Male C57Bl/6N mice (n = 12/group) were fed a basal diet (BD; modified AIN-93G), an HF diet (60% kcal from fat), or an HF diet supplemented with 15% cooked white (HF + WK) or dark red kidney beans (HF + DK) for nine weeks. Outcomes included cecal microbiota composition, predicted KEGG pathways with taxon contributors mapped with BURRITO (a tool for linking predicted microbial functions to contributing taxa), and SCFA-related pathways; cecal and fecal SCFA concentrations; colon histomorphometry and expression of gut barrier junction and inflammatory genes; serum cytokines and adipose hormones; and hippocampal inflammatory and barrier genes.

Results

Mice consuming bean-supplemented HF diets had higher microbial diversity, enrichment of SCFA-producing taxa (Prevotella, Lactobacillus, Muribaculaceae), and lower obesity-associated genera versus HF alone (Mucispirillum, rc4-4). Bean diets elevated cecal acetate and butyrate concentrations, which aligned with increases in predicted acetate kinase in both bean groups versus HF and BD, and butyrate kinase in HF + DK versus BD. Bean supplementation attenuated HF-induced reduction of goblet cells and systemic interleukin (IL)-10. The HF + DK group had lower colonic tumour necrosis factor (TNF)-α and partially attenuated hippocampal IL-6. SCFAs were inversely associated with systemic and neuroinflammatory markers in HF + DK mice.

Conclusions

Kidney bean supplementation mitigated HF diet-induced intestinal, systemic, and neuroinflammatory disturbances in male mice, with microbiota and SCFA modulation. Further, dark red beans exerted stronger anti-inflammatory effects, highlighting the role of seed coat colour in bean-mediated obesity outcomes.