ANGPTL8 (Betatrophin) is Expressed in Visceral Adipose Tissue and Relates to Human Hepatic Steatosis in Two Independent Clinical Collectives

Angiopoietin-like protein 8 (ANGPTL8)/betatrophin expression in visceral adipose tissue and associations with circulating fatty acid profile have not yet been investigated. Forty subjects were included in a cross-sectional study, 57 in a dietary weight reduction intervention. Circulating Angiopoietin-like protein 8/betatrophin was measured in all subjects. Liver and adipose tissue were sampled and plasma fatty acids and tissue Angiopoietin-like protein 8/betatrophin expression were evaluated in the cross-sectional study. In the intervention study oral glucose testing and liver magnetic resonance scanning at baseline and after 6 months were performed. Angiopoietin- like protein 8/betatrophin mRNA was increased in visceral compared to subcutaneous adipose tissue (p < 0.001). Circulating ANGPTL8/betatrophin correlated with liver steatosis (r = 0.42, p = 0.047), triacylglycerols (r = 0.34, p = 0.046), saturated (r = 0.43, p = 0.022), monounsaturated (r = 0.51, p = 0.007), and polyunsaturated fatty acids (r = -0.53, p = 0.004). In the intervention study, baseline Angiopoietin-like protein 8/betatrophin correlated with age (r = 0.32, p = 0.010) and triacylglycerols (r = 0.30, p = 0.02) and was increased with hepatic steatosis (p = 0.033). Weight loss reduced liver fat by 45 % and circulating Angiopoietin-like protein 8/betatrophin by 11 % (288 +/- 17 vs. 258 +/- 17 pg/ml; p = 0.015). Angiopoietin- like protein 8/betatrophin is related to liver steatosis, while visceral adipose tissue represents an additional site of expression in humans.