The Ratio of Unsaturated to Saturated Fatty Acids is a Distinguishing Feature of NAFLD in Subjects With Metabolic Disease
Authors: Falcone John N , Hurd Maurice A , Kumar Sonal , Yeung Michele , Newberry Carolyn , So Marie Yanielle , Dakin Gregory , Bellorin-Marin Omar , Afaneh Cheguevara , Hudgins Lisa , Peña Jessica , Goncalves Marcus D 
Published: May 2021

Abstract
Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent chronic liver disease affecting at least a quarter of the world’s population. NAFLD is commonly associated with other metabolic conditions such as insulin resistance, type 2 diabetes, obesity, and dyslipidemia. Given the liver’s prominent role in regulating glucose and lipid homeostasis, we hypothesized that subjects with NAFLD have a distinct profile of blood analytes. This investigation examines the association between NAFLD and circulating markers of glucose and lipid metabolism in order to identify a NAFLD-specific metabolite panel that can be used as a predictive biomarker in future studies.
We are performing a cross-sectional study in 500 subjects to identify genetic and hormonal factors that correlate with the presence of NAFLD. This abstract reports a preliminary analysis of the results from the first 45 subjects enrolled. Fasting blood samples were collected from 31 subjects with NAFLD and 14 subjects with other metabolic diseases (‘Other’) and without radiologic evidence of NAFLD. The following analytes were measured: serum alanine aminotransferase (ALT), total cholesterol, direct-LDL, HDL, triglycerides, ApoB, small dense LDL-C (sdLDL), VLDL, Lp(a), cholesterol absorption/production markers (beta-sitosterol, campesterol, lathosterol, and desmosterol), glucose, insulin, hemoglobin A1C, adiponectin, hs-CRP, and fatty acids (saturated and unsaturated). Homeostasis model assessment of insulin resistance (HOMA-IR) was calculated from glucose and insulin levels, and fatty acids were batched together by structural similarity and reported as indices. The groups were compared using multiple t-tests or the Kolmogorov-Smirnov test when data were non-parametric.
The NAFLD group had a mean age 48.4 ± 12.9 yrs and BMI 32.9 ± 6.6 kg/m2. These participants were 61% female and 58% had dyslipidemia, 25% pre-diabetes, and 25% type 2 diabetes. The Other group had a mean age 49.9 ± 12.9 yrs and BMI 39.1 ± 15.6 kg/m2. They were 64% female and 57% had dyslipidemia, 14% pre-diabetes, and 21% type 2 diabetes. ALT was higher in the NAFLD group (55 ± 40 vs 27 ± 22 IU/L, P&lt;0.001). Intriguingly, the saturated fatty acid index was elevated in the NAFLD group (32.5 ± 1.9 vs 30.1 ± 2.2 %, P&lt;0.05), and the omega-6 fatty acid index was elevated in the Other group (42.9 ± 3.7 vs 38.5 ± 4.7 %, P&lt;0.05). These changes led to an unsaturated/saturated fatty acid ratio that was significantly lower in the NAFLD group (2.0 ± 0.1 vs 2.3 ± 0.2, P&lt;0.01). There were no other significant differences in the blood metabolites and hormones.
In this small sample comparing subjects with metabolic disease with and without NAFLD, levels of ALT and the ratio of circulating unsaturated/saturated fatty acids are distinguishing features of NAFLD. These may be helpful measures to identify subjects with metabolic disease that require further evaluation for NAFLD.