Relation between sodium–lithium countertransport and hypertriglyceridemia in type V hyperlipidemia

Sodium–lithium countertransport (SLC) kinetics were measured in 30 patients with type V hyperlipidemia, 30 patients with type IIB hyperlipidemia on similar treatment, and 30 age- and sex-matched healthy controls. Clinical and laboratory data including basic anthropometry and blood pressure were obtained and blood was taken for detailed lipid biochemistry, glucose, insulin, and leptin measurements. Patients with type V hyperlipidemia were normotensive but more obese than controls, had elevated triglycerides, very low-density lipoprotein, glucose, and insulin; and reduced HDL cholesterol compared with type IIb controls. The median SLC activity (0.23 v 0.21 mmol Li +/L RBC/h) and median maximal velocity (0.33 v 0.31 mmol Li +/L RBC/h) were increased, but not significantly, compared to controls. In patients with type V hyperlipidemia SLC maximal velocity correlated with log triglycerides (r 2 = 0.853; P < .001) and log very low-density lipoprotein (VLDL) triglycerides (r 2 = 0.947; P < .001). Sodium–lithium countertransport maximal velocity correlated weakly with the homeostasis model assessment index of insulin resistance (r 2 = 0.224; P = .06). The sodium affinity of the transporter did not differ between the groups and was independent of any of clinical or biochemical parameter studied. We conclude that VLDL triglyceride is strongly correlated with SLC maximal velocity and activity in patients with type V hyperlipidemia.