Flaxseed Oil Alleviates Chronic HFD-Induced Insulin Resistance through Remodeling Lipid Homeostasis in Obese Adipose Tissue

Emerging evidence suggests that higher circulating long-chain n-3 polyunsaturated fatty acids (n-3PUFA) levels were intimately associated with lower prevalence of obesity and insulin resistance. However, the understanding of bioactivity and potential mechanism of a-linolenic acid-rich flaxseed oil (ALA-FO) against insulin resistance was still limited. This study evaluated the effect of FO on high-fat diet (HFD)-induced insulin resistance in C57BL/6J mice focused on adipose tissue lipolysis. Mice after HFD feeding for 16 weeks (60% fat-derived calories) exhibited systemic insulin resistance, which was greatly attenuated by medium dose of FO (M-FO), paralleling with differential accumulation of ALA and its n-3 derivatives across serum lipid fractions. Moreover, M-FO was sufficient to effectively block the metabolic activation of adipose tissue macrophages (ATMs), thereby improving adipose tissue insulin signaling. Importantly, suppression of hypoxia-inducible factors HIF-l alpha and HIF-2 alpha were involved in FO-mediated modulation of adipose tissue lipolysis, accompanied by specific reconstitution of n-3PUFA within adipose tissue lipid fractions.