Effect of reduction of plasma triglycerides with gemfibrozil on high-density-lipoprotein-cholesterol concentrations

The aim of this study was to test the hypothesis that the plasma triglyceride (TG) concentration must be reduced below approximately 0.85-1.13 mmol l-1 (75-100 mg/dl-1) in order to achieve a substantial increase in plasma high-density-lipoprotein-cholesterol (HDL-C) levels. The study design consisted of a non-randomized clinical trial, which was conducted at an out-patient clinic at a university-affiliated VA Medical Center. The participants consisted of 55 ambulatory middle-aged men with a baseline fasting HDL-C concentration of less than or equal to 1.17 mmol l-1 (45 mg dl-1) and baseline TG in the range 1.13-5.6 mmol l-1 (100-500 mg dl-1). Subjects were treated with gemfibrozil, 600 mg twice a day for 3 months. Fasting plasma HDL-C, TG, low density lipoprotein-cholesterol, and total cholesterol were measured at 1-month intervals for 3 months. Subjects were divided into three groups on the basis of TG level achieved on therapy: Group I (n = 14), TG less than 0.85 mmol l-1 (75 mg dl-1); Group II (n = 20), TG 0.86-1.41 mmol l-1 (76-125 mg dl-1); Group III (n = 21), TG greater than 1.41 mmol l-1 (125 mg dl-1). The mean increase in HDL-C in Group I was 0.20 mmol l-1 (7.8 mg dl-1), a significantly (P = 0.0067) greater increase than was observed in the other two groups. There was no correlation between the magnitude of change in TG and the magnitude of change in HDL-C concentration in the group as a whole (Pearson's correlation coefficient, r = -0.06, P = 0.6). In conclusion, the increase in HDL-C levels observed with gemfibrozil therapy is associated with the absolute level of TG achieved by therapy. Substantial increases in HDL-C concentration might not be expected to occur consistently unless TG levels are reduced to values that are considered below the usually cited 'normal' range.