Bifidobacterium adolescentis attenuates brown adipose tissue whitening and improves metabolic markers in high-fat diet-induced obese rats.

PURPOSE: Activation of brown adipose tissue (BAT) has emerged as a promising strategy for combating obesity due to its thermogenic capacity. However, chronic high-fat diet (HFD) exposure impairs BAT function and promotes a "whitening" phenotype characterized by lipid droplet enlargement and reduced thermogenic activity. Bifidobacterium adolescentis (B. adolescentis) has been reported to improve lipid metabolism and energy balance. This study investigated whether B. adolescentis supplementation attenuates HFD-induced BAT whitening, evaluated at transcriptional and histological levels, and examined its association with thermogenic and lipolytic gene expression.

METHODS

Twenty-four six-weeks-old male Sprague-Dawley rats were allocated into four groups for 16 weeks: control (standard chow diet), HFD, HFD-B. adolescentis-8 W (4 × 10¹⁰ CFU/day from week 8 to week 16), and HFD-B. adolescentis-16 W (4 × 10¹⁰ CFU/day for 16 weeks). Probiotic supplementation was administered via drinking water. Metabolic parameters, serum lipid profile, BAT histomorphmetery assessed by hematoxylin and eosin staining, and mRNA expression of thermogenesis- and lipolysis-related genes (Ucp1, Prdm16, Pgc-1α, Sirt1, Ampk, Atgl, and Hsl) were evaluated.

RESULTS

B. adolescentis supplementation significantly attenuated HFD-induced weight gain and improved serum lipid parameters. These effects were accompanied by increased mRNA expression of Sirt1, Ampk, and key thermogenic and lipolytic genes in BAT. Histological analysis revealed partial preservation of multilocular adipocyte morphology and reduced cytoplasmic hypertrophy compared with the HFD group.

CONCLUSION

B. adolescentis supplementation mitigated HFD-induced metabolic disturbances and attenuated BAT whitening. These effects were associated with the upregulation of thermogenesis- and lipolysis-related genes, including Sirt1 and Ampk. Further mechanistic studies are required to determine whether these molecular changes play a causal role in mediating the protective effects of this probiotic.