Insulin resistance and dyslipidemia are both considered to be risk factors for metabolic syndrome. Low levels of IGF1 are associated with insulin resistance. Elevation of low-density lipoprotein cholesterol (LDL-C) concomitant with depression of high-density lipoprotein cholesterol (HDL-C) increase the risk of obesity and type 2 diabetes mellitus (T2DM). Liver secretes IGF1 and catabolizes cholesterol regulated by the rate-limiting enzyme of bile acid synthesis from cholesterol 7α-hydroxylase (CYP7A1). NO-1886, a chemically synthesized lipoprotein lipase activator, suppresses diet-induced insulin resistance with the improvement of HDL-C. The goal of the present study is to evaluate whether NO-1886 upregulates IGF1 and CYP7A1 to benefit glucose and cholesterol metabolism. By using human hepatoma cell lines (HepG2 cells) as an in vitro model, we found that NO-1886 promoted IGF1 secretion and CYP7A1 expression through the activation of signal transducer and activator of transcription 5 (STAT5). Pretreatment of cells with AG 490, the inhibitor of STAT pathway, completely abolished NO-1886-induced IGF1 secretion and CYP7A1 expression. Studies performed in Chinese Bama minipigs pointed out an augmentation of plasma IGF1 elicited by a single dose administration of NO-1886. Long-term supplementation with NO-1886 recovered hyperinsulinemia and low plasma levels of IGF1 suppressed LDL-C and facilitated reverse cholesterol transport by decreasing hepatic cholesterol accumulation through increasing CYP7A1 expression in high-fat/high-sucrose/high-cholesterol diet minipigs. These findings indicate that NO-1886 upregulates IGF1 secretion and CYP7A1 expression to improve insulin resistance and hepatic cholesterol accumulation, which may represent an alternative therapeutic avenue of NO-1886 for T2DM and metabolic syndrome.
Qinkai Li, Weidong Yin, Manbo Cai, Yi Liu, Hongjie Hou, Qingyun Shen, Chi Zhang, Junxia Xiao, Xiaobo Hu, Qishisan Wu, Makoto Funaki and Yutaka Nakaya
Zhe-Zhen Liao, Xiao-Yan Qi, Yadi Wang, Jiao-Yang Li, Qian-Qian Gu, Can Hu, Yin Hu, Heng Sun, Li Ran, Jing Yang, Jiang Hua Liu and Xinhua Xiao
Remodeling of energy-storing white fat into energy-consuming beige fat has led to a promising new approach to alleviate adiposity. Several studies have shown adipokines can induce white adipose tissues (WAT) beiging through autocrine or paracrine actions. Betatrophin, a novel adipokine, has been linked to energy expenditure and lipolysis but not clearly clarified. Here, we using high-fat diet induced obesity to determine how betatrophin modulate beiging and adiposity. We found that betatrophin-knockdown mice displayed less white fat mass and decreased plasma TG and NEFA levels. Consistently, inhibition of betatrophin leads to the phenotype change of adipocytes characterized by increased mitochondria contents, beige adipocytes and mitochondrial biogenesis-specific markers both in vivo and in vitro. Notably, blocking AMP-activated protein kinase (AMPK) signaling pathway is able to abolish enhanced beige-like characteristics in betatrophin-knockdown adipocytes. Collectively, down-regulation of betatrophin induces beiging in white adipocytes through activation of AMPK signaling pathway. These processes suggest betatrophin as a latent therapeutic target for obesity.