Abstract
Male endurance athletes have been reported to have lower testosterone concentrations than their sedentary counterparts, which may have detrimental health effects including increased risk of musculoskeletal injury and fertility complications secondary to decreased sex hormone production. Cholesterol supplementation has been reported to increase serum sex hormones. PURPOSE: The purpose of this study was to investigate whether a treadmill endurance exercise program would cause exercise-induced reproductive dysfunction in male rats and assess the impact of increased dietary cholesterol on sex hormone levels. METHODS: Male Sprague-Dawley Rats (n=20) were randomly assigned to a control group (C) or an exercise training group (EX) that performed treadmill running 40 min/day, 6 days/wk for a duration of 12 wks. At study midpoint (wk 6), rats were randomized to receive either a High-Cholesterol (HC) Diet (n=10) or remain on standard purified diet (n=10). Fasting blood samples were collected at baseline, wk 6, and wk 12. Serum testosterone (T) and leptin were measured via ELISA. Serum lipids (TC, HDL, LDL, TG) were measured via clinical chemistry analyzer. Body weight (BW) and voluntary food intake (EI) were measured weekly. RESULTS: At end of wk 6, EX had significantly lower BW (494.3+34.7g versus 565.3+47.9g, p=0.001), mean daily EI (77.5+3.5 kcal versus 91.6+5.2 kcal, p<0.001), and serum leptin (90.8+40.1 pg/mL versus 635.7+225.6 pg/mL, p=0.001) in comparison to C. No difference was observed between EX and C in serum T (12.7+6.0 ng/mL versus 12.9+5.8 ng/mL). At end of wk 12, exercise groups (EX and EX+HC) had significantly lower BW (539.4+40.6g versus 645.1+60.7g, p<0.001), mean daily EI (81.7+2.9 kcal versus 87.8+1.9 kcal, p<0.01), and serum leptin (132.8+110.1 pg/mL versus 519.2+300.8 pg/mL, p=0.001) in comparison to C and C+HC. HC diet did not have significant impact upon serum T in comparison to standard diet (3.8+3.4 ng/mL versus 4.9+2.4 ng/mL). CONCLUSIONS: Despite low energy availability, exercise-induced reproductive changes may not occur in training programs <12 weeks. Lower EI observed in exercise groups despite higher energy expenditure may indicate that low energy availability in endurance-trained individuals may be inadvertent. Supported by American Egg Board Graduate Fellowship Research Grant
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