Abnormal Non Esterified Fatty Acid Suppression After a Mixed Meal Test in Patients With Partial Lipodystrophy

Abstract

Elevated levels of non-esterified fatty acids (NEFA) have been observed in individuals with several clinical scenarios of insulin resistance, such as in diabetes mellitus and lipodystrophy. Insulin is a well-known stimulator of de novo lipogenesis. Despite the reduction of adipose tissue mass, paradoxically elevated circulating NEFA concentrations have been observed in patients with different lipodystrophy syndromes. Aiming to understand the behavior of NEFA in lipodystrophy versus common Type 2 diabetes mellitus during feeding, we compared NEFA kinetics during a mixed meal test in patients with partial lipodystrophy (PL) and Type 2 diabetes mellitus (DM). We reviewed data from 17 PL patients (13F/4M, ages 12–64) matched by gender and BMI to 20 DM patients (13F/7M, ages 24–72). All patients were evaluated during fasting state and then underwent a mixed meal test (MMT). Blood samples were collected before (fasting) and at 30, 60, 90, 120, and 180 minutes post-meal to measure glucose, insulin, non-esterified free fatty acids (NEFA), and triglyceride levels. Adipose tissue insulin resistance (ADIPO-IR) and homeostatic model of insulin resistance (HOMA-IR) were calculated from the fasting measurements, and the area under the curve (AUC) and maximum percentage of change from baseline were calculated from the MMT data. Fasting insulin and triglyceride (Tg) levels were lower in the DM group compared to the PL group (Insulin: 24.4±13.7 vs. 68.0±67.2 pmol/L, p=0.003 and Tg: 168.0±107.7 vs. 1378.3±1927.3 mg/dL, p<0.001). HOMA-IR was significantly higher in the PL group compared to the DM group (6.0±2.1 vs. 3.3±1.5, p=0.005), as well as ADIPO-IR (297.0±241.1 vs. 115.3±80.1, p=0.03). NEFA, glucose and triglyceride AUC were significantly higher in the PL group compared to the DM group. Patients with PL had higher glucose and triglyceride levels throughout the MMT at all-time points. Interestingly, NEFA levels were similar in both groups at baseline, but the PL group suppressed NEFA less than DM group (54.9±13.3% vs. 69.2±11.1%, p=0.002) despite higher insulin levels. Additionally, we divided the PL group according to the presence of a pathogenic variant in the lamin A gene (n=8) versus those without mutations in this gene (n=9), but there were no notable differences among these subgroups with respect to NEFA levels at baseline or during the meal. These findings support the need to better understand and address the origins of abnormal NEFA kinetics and adipose tissue insulin resistance in PL patients.