Delayed clearance of triglyceride-rich lipoproteins in young, healthy obese subjects

Abstract

Obesity is associated with the metabolic syndrome. The aims were, first, to study the postprandial triglyceride clearance in young, healthy obese subjects and, second, to investigate if fasting triglycerides can predict delayed postprandial triglyceride clearance. Eighteen apparently healthy, obese subjects with no clinical signs of metabolic disturbances participated. Controls were age- and sex-matched, healthy, normal weight subjects. Subclinical markers of metabolic disturbances were assessed by measuring postprandial triglycerides in serum and in chylomicrons by oral fat tolerance test. Postprandial triglyceride clearance for 8 h was assessed indirectly as removal of the lipid from serum during the oral fat tolerance test. Insulin resistance was measured by the homeostasis model assessment of insulin resistance (HOMA-IR). Twelve (66%) of the apparently healthy obese individuals had insulin resistance measured by HOMA-IR. There was a delayed clearance of serum triglycerides and chylomicron triglycerides at 6 h when compared with the control group, while, at 8 h, the differences were only detected for the chylomicron triglyceride clearance. Triglyceride response was significantly greater in the obese subjects. Fasting triglycerides in upper normal level predicted a delayed postprandial triglyceride clearance and insulin resistance. In young, apparently healthy obese subjects early metabolic disturbances including insulin resistance and delayed postprandial triglyceride clearance can be detected. Fasting serum triglyceride in upper normal level predicted delayed postprandial triglyceride clearance and insulin resistance.

Keywords: Chylomicrons; fasting triglycerides; insulin resistance; metabolic healthy obese.

Figure 1

Oral fat tolerance test in apparently healthy, obese and normal weight subjects at study baseline. Upper part shows total serum triglycerides (SE‐TG) and lower part shows chylomicron triglycerides (CM‐TG). At 0 h, the subject ingested a standard meal. Asterisks denote significant difference (repeated measure analysis of variance [RM‐ANOVA]: interaction time × group; post hoc comparison, Bonferroni correction). Dagger denotes a significant difference in grand mean (RM‐ANOVA, between subjects). Double dagger denotes significant difference in triglyceride clearance at 6 or 8 h (Wilcoxon). Triangles represent obese subjects; circles represent normal weight subjects. Values are estimated marginal means (95% confidence interval).

Figure 2

Total serum triglycerides (SE‐TG) in oral fat tolerance test in normal weight and apparently healthy, obese subjects. Estimated marginal means (standard error of the mean, SEM) of the observed interaction between weight group, fasting triglyceride group and time is plotted. Triangles represent obese subjects; circles represent normal weight subjects. Solid lines indicate fasting triglyceride level >1.02 mmol L⁻¹; dashed lines indicate fasting triglyceride level ≤1.02 mmol L⁻¹. Asterisks indicate significant contrast. Values are estimated marginal means (95% confidence interval).

Figure 3

Indirect total serum triglycerides (SE‐TG) clearance at 6 h vs. insulin sensitivity (whole body insulin sensitivity index, WBISI; a) and insulin resistance (insulin resistance by the homeostasis model assessment, HOMA‐IR; b). Normal weight subjects are shown as squares, obese subjects as circles. Linear regression line is based on all subjects. Dashed lines indicate 95% confidence interval for prediction.