Distinct Dose-Dependent Association of Free Fatty Acids with Diabetes Development in Nonalcoholic Fatty Liver Disease Patients

BACKGROUND: Excessive delivery of free fatty acids (FFAs) to the liver promotes steatosis and insulin resistance (IR), with IR defined as reduced glucose uptake, glycogen synthesis and anti-lipolysis stimulated by normal insulin levels. Whether the associations between FFAs and diabetes development differ between patients with and without nonalcoholic fatty liver disease (NAFLD) remains unclear. METHODS: Consecutive subjects (2,220 NAFLD subjects and 1,790 non-NAFLD subjects according to ultrasound imaging) were enrolled from the First Affiliated Hospital of Sun Yat-sen University between 2009 and 2019. The homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. RESULTS: There was an approximate J-shaped relationship between FFA levels and HOMA-IR in the NAFLD group. Higher FFA concentration quartiles were associated with higher risks of IR (odds ratio [OR], 9.24; 95% confidence interval [CI], 6.43 to 13.36), prediabetes (OR, 10.48; 95% CI, 5.66 to 19.39), and type 2 diabetes mellitus (T2DM; OR, 19.43; 95% CI, 12.75 to 29.81) in the NAFLD group but not in the non-NAFLD group. The cut-off points for the FFA levels increased in a stepwise manner in discriminating IR, prediabetes and T2DM (573, 697, and 715 μmol/L) in the NAFLD group but not in non-NAFLD individuals. CONCLUSION: A distinct dose-dependent relationship of FFA levels was found with IR, prediabetes and T2DM in NAFLD patients. Screening serum FFA levels in NAFLD patients would be valuable in preventing diabetes development.