Low Hepatic Fat and Stearoyl-CoA Desaturase Activity Contribute to Paradoxically Normal Triglyceride-Rich Lipoproteins in Insulin Resistant Black Women—The Federal Women Study

Abstract

In black women, triglycerides (TG) are paradoxically normal in the presence of insulin resistance (IR). This TG paradox while partially explained by low visceral fat, might be further clarified by delineating the association of triglyceride rich lipoprotein (TRLP) subclasses with hepatic fat, IR and stearoyl-CoA enzyme activity (SCD-116, a marker of de novo lipogenesis). We hypothesized that fasting TRLP, hepatic fat and SCD-116 activity would be lower in black vs. white women. In 122 federally employed women without diabetes, we compared fasting TRLP number and size (measured with NMR) in 73 black (58 African American and 15 African immigrant) and 49 white; age 44±10 (mean±SD), range 24- 62y; BMI 30.0±5.6, range 20.3-45.2 kg/m2. Hepatic and visceral fat were measured by proton MRS. RBC fatty acid profiles were measured by gas chromatography (mol %) and used to estimate SCD-116 (16:1n-7/to 16:0). Total, large, medium and small TRLPs, visceral fat, SCD-116 were similar in blacks and lower than in whites before and after adjustment for age and body fat (P<0.001). Blacks had lower SI (2.28 (1.52) vs. 2.74 (2.81), median(IQR) P=0.05, and hepatic fat (0.7 (1.1) vs. 1.2 (2.1), P=0.03. SCD-116 correlated with hepatic fat (r=0.34, P<0.01). Habitual physical activity, dietary fatty acid profiles were similar (P>0.1). In multivariate linear models, age, SCD-116, body fat, visceral fat and SI, but not race or liver fat, were independently associated with total TRLP (adjR2=0.44, P<0.01). Medium and large TRLP number was independently predicted by visceral fat and SCD-116 activity (adjR2=0.37, P<0.01); race was the only predictor for small TRLPs (adjR2=0.14, P<0.01). Therefore, lower hepatic fat and SCD-116 maybe important contributors to the paradoxically normal fasting TRLP in insulin resistant black women. Disclosure S.T. Chung: None. M. Galvan-De La Cruz: None. S. Bernstein: None. A. Onuzuruike: None. N.R. Matthan: None. R. Ouwerkerk: None. L. Mabundo: None. M.L. Sampson: None. A.B. Courville: None. A.M. Gharib: None. A.H. Lichtenstein: None. A. Remaley: None. A.E. Sumner: None.