The presented study is the first comprehensive prospective study that evaluates the main and additional sperm parameters, the seminal composition, including markers of accessory sex glands, leptin, inorganic ions, pro-inflammatory cytokines in overweight / obese males. It has been confirmed that a BMI increase adversely affects the above-mentioned parameters and, accordingly, negatively affects the male fertility potential.
The animal models were used as the second direction of the presented work to confirm existing or clarify contradictory observations obtained during human studies. The experimental part included 30 sexually mature white non-linear male rats with a body weight of 250–300 g. All animals were randomly divided into 3 groups (10 males in each). The control group (CG) received a standard chow; the first experimental animal's group was on a high-fat diet (HFD) – the standard feed was supplemented with lard to achieve 45% of daily caloric intake by fat; the second experimental group consumed a diet with a high fat and sugar (HFHSD) – 40% of kсal of fats and 46% of carbohydrates.
It was demonstrated that after 7 weeks of feeding a high-fat high-sugar diet, the visceral fat index significantly increased by 40% (p < 0.05), confirming significant metabolic changes in this group and, accordingly, a more effective application of HFHSD for modeling adiposity in rats. The proposed high-calorie diets did not cause significant changes in such indicators as body weight gain, Lee index, and gonadosomatic index (p > 0.05).
It was confirmed that high-calorie nutrition during 7 weeks caused typical signs of dyslipidemia – the concentration of total cholesterol in the HFD rat's blood plasma increased by 24.5% (p = 0.035), in the HFHSD group – by 29.8% (p = 0.035); the atherogenic coefficient was higher by 1.8–2.1 times (р < 0.05); and the low-density lipoprotein fraction increased by 2.1 times (p = 0.025). No significant difference was found in blood plasma glucose levels between groups (p > 0.05). The mean leptin concentration before the start of the experiment did not differ between the groups and was 0.4–0.44 ng/ml (p = 0.05), and a slight increase of leptin levels was observed in all groups after 7 weeks of feeding diets: in the HFD by 9.0%, in the HFHSD – by 14% from the initial data (p < 0.05).
The analysis of epididymal suspension showed that sperm motility worsened in the experimental groups: it was 13% lower in the HFD group, and 18% lower in the HFHSD group compared to the CG (p < 0.05). The total number of isolated spermatozoa and viability did not show a significant difference between the groups (p > 0.05).
In the presented work, for the first time in Ukraine, the mitochondrial functional state of intact spermatozoa is described against the background of diet-induced obesity. The basal respiration rate of spermatozoa was 0.040 ± 0.013 nM/O2/10 million cells/min among HFHSD animals and was almost twice as high as in CG (p = 0.015). The maximal mitochondrial oxygen consumption, which is a measure of the response cells’ ability to increase energy demand, was 30% higher in this group of rats (p = 0.04); decreasing of the mitochondria reserve respiratory capacity (spare respiratory capacity) was registered, but no statistically significant difference between the groups was found (p > 0.05).
It was shown that the optimal concentration of the protonophore for achieving the maximum respiration of intact sperm cells was 0.5 μM/l FCCP. It has been confirmed the oxygen consumption measurement is a fairly sensitive marker of the mitochondrial functional state. The obtained results complement scientific data in the field of sperm bioenergetics under physiological conditions / impact of various external factors, and expand the understanding of the influence of excessive adiposity on the male fertility potential.
