Modulatory effects of ghrelin on sperm quality alterations induced by a fructose-enriched diet

Abstract

The objectives of this study were: 1) to evaluate the effects of a fructose enriched diet (FED) on rat sperm quality, epididymal function (i.e. oxidative stress and alpha-glucosidase expression) and testosterone concentrations; 2) to determine if the administration of ghrelin (Ghrl), reverses the effects induced by FED. After validating the protocol as an inductor of metabolic syndrome like-symptoms, adult male rats were assigned to one of the following treatments for 8 weeks: FED = 10% fructose enriched in water (v/v); FED + Ghrl = fructose enriched diet plus Ghrl (6 nmol/animal/day, s.c.) from week 6-8; or C = water without fructose (n = 5-10 animals/group). FED significantly decreased sperm concentration and motile sperm count/ml vs C (FED: 19.0 ± 1.6 × 10⁶sperm/ml and 834.6 ± 137.0, respectively vs C: 25.8 ± 2.8 × 10⁶ and 1300.4 ± 202.4, respectively; p < 0.05); ghrelin injection reversed this negative effect (23.5 ± 1.6 × 10⁶sperm/ml and 1381.7 ± 71.3 respectively). FED resulted in hypogonadism, but Ghrl could not normalize testosterone concentrations (C: 1.4 ± 0.1 ng/ml vs FED: 0.8 ± 0.2 ng/ml and FED + Ghrl: 0.6 ± 0.2 ng/ml; p < 0.05). Ghrelin did not reverse metabolic abnormalities secondary to FED. FED did not alter epididymal expression of antioxidants enzymes (superoxido-dismutase, catalase and glutathione peroxidases -Gpx-). Nevertheless, FED + Ghrl significantly increased the expression of Gpx3 (FED + Ghrl: 3.47 ± 0.48 vs FED: 0.69 ± 0.28 and C: 1.00 ± 0.14; p < 0.05). The expression of neutral alpha-glucosidase, which is a marker of epididymal function, did not differ between treatments. In conclusion, the administration of Ghrl modulated the negative effects of FED on sperm quality, possibly by an epididymal increase in Gpx3 expression. However, Ghrl could not neither normalize the metabolism of FED animals, nor reverse hypogonadism.

Keywords: Cell biology; Developmental biology; Diet; Endocrinology; Epididymis; Glutathione peroxidase; Metabolic syndrome; Molecular biology; Neutral alpha-glucosidase; Oxidative stress.

Fig. 1

Body weight evolution of male rats treated for 8 weeks with a fructose enriched diet (FED; 10% fructose v/v in drinking water). A subgroup of FED animals received ghrelin (s.c., 6 nmol/animal/day) for the last two weeks of treatment (FED + Ghrl, i.e. from day 42–56). FED and C (control animals) were injected s.c., during this last two weeks of treatment, with isotonic solution (ghrelin vehicle).Values are expressed as Mean±SDM. Number of animals/treatment: C = 7; FED = 10; FED + Ghrl = 5. An increase in food intake independently of treatment was seen in male rats: days 1 vs 7 vs 14 vs 21 and 28 vs 35 vs 42, 49 and 56 (p < 0.05).