Raspberry Supplementation Improves Insulin Signaling and Promotes Brown-Like Adipocyte Development in White Adipose Tissue of Obese Mice.

SCOPE: Excessive lipid accumulation in white adipose tissue (WAT) leads to chronic inflammation and metabolic dysfunction. Raspberry (RB) contains high amount of polyphenols and dietary fibers. The objective of the study is to evaluate the effects of RB supplementation on WAT morphology, inflammation, and insulin signaling in high fat diet (HFD)-induced obese mice, and further explore the underlying mechanisms.

METHODS AND RESULTS: C57BL/6J mice are fed with a control diet or a HFD supplemented with 0 or 5% freeze dried RB for 12 weeks. RB supplementation decreases WAT hypertrophy induced by HFD and suppresses pro-inflammatory cytokines expression and macrophage infiltration in WAT. Meanwhile, RB addition improves insulin sensitivity of HFD-mice. Additionally, RB supplementation drives the browning of WAT (beige adipogenesis), which is associated with elevated PGC-1α and FNDC5/irisin contents. Consistently, the content of beige adipocyte markers including UCP1, PRDM16, Cytochrome C, Cidea, and Elvol3 is enhanced in HFD-mice, which are correlated with increased AMPK phosphorylation and Sirt1 protein contents.

CONCLUSION: Dietary RB attenuated adipocyte hypertrophy and inflammation of WAT in HFD-mice and improves insulin sensitivity and beige adipogenesis, which is associated with increased FNDC5/irisin content and activation of AMPK/Sirt1 pathway. RB supplementation provides a promising strategy to prevent diet-induced obesity.