How do fasting blood fats and a marker of dietary-fat transport differ between female distance runners and sedentary women?

Details

The abstract begins with reports that endurance-type exercise is associated with less atherogenic plasma lipid and lipoprotein profiles. Previous studies had found lower plasma triglycerides and VLDL, and higher HDL, in endurance-trained people than in sedentary people.

This study aimed to evaluate the effect of endurance-type exercise on the metabolism of exogenous lipoproteins, using apolipoprotein (apo) B-48 as a marker. It was a comparative study of 19 fasting female distance runners (R) and 23 similarly aged sedentary control women (S), measuring plasma lipids, lipoproteins, apolipoproteins, and VLDL-apo B subspecies.

Lipoproteins were separated by sequential ultracentrifugation. Apolipoproteins were measured by single radial immunodiffusion. Apo B subspecies in VLDL (density d<1.006 g/ml) were analyzed by SDS–3.5% polyacrylamide gel electrophoresis. After staining, protein bands were evaluated with a densitometer and their peak areas were measured. The apo B-48 ratio was calculated as the percentage of apo B-48 in total apo B.

Fasting plasma concentrations are listed below in the order sedentary controls versus runners, in mg/dl, as mean±SE: • Triglycerides (TG): 78.5±7.1 versus 66.7±4.4. • Cholesterol (Ch): 164.4±5.9 versus 189.5±5.6 (p<0.005). • HDL-Ch: 69.0±3.5 versus 83.8±3.9 (p<0.01). • Apo A-I: 160.9±5.0 versus 183.3±5.2 (p<0.005). • Apo B: 94.6±3.2 versus 101.5±2.7. • Apo C-II: 3.2±0.2 versus 3.3±0.2. • Apo C-III: 7.8±0.4 versus 8.6±0.4. • Apo E: 3.5±0.1 versus 4.6±0.3 (p<0.005). Plasma cholesterol, HDL-Ch, apo A-I, and apo E were significantly higher in runners than in sedentary controls. Within the lipoprotein fractions, runners had lower VLDL and higher HDL concentrations; the higher HDL was primarily attributable to increased HDL2.

The VLDL apo B-48 ratio was significantly lower in runners, at 2.86±0.39%, than in sedentary controls, at 4.6±0.54% (p<0.05). An age-related rise in the apo B-48 ratio was observed in sedentary controls. This increase was not observed in runners. Among runners, the apo B-48 ratio showed a tendency toward a positive correlation with VLDL-TG concentrations. A significant negative correlation was also observed between the apo B-48 ratio and HDL2-Ch concentrations.

The authors interpreted these data as indicating that endurance-type exercise decreases exogenous lipoproteins, most likely through increased lipoprotein lipase (LPL) activity. They noted that some studies have suggested chylomicron remnants may contribute to atherogenesis. They speculated that endurance-type exercise favorably affects exogenous lipoprotein metabolism.