Although obvious effects of obesity on female reproduction and oocytes are emerging, the effects on male fertility and sperm quality are less clear with studies reporting conflicting results. We hypothesize that male obesity affects sperm function and physiology probably as a result of elevated oxidative stress in spermatozoa and therefore elevated levels of sperm DNA damage and loss of function. Six-week-old C57/Bl6 male mice (n = 36) were randomly allocated to two groups: group 1 (n = 18) received a control diet, whereas group 2 (n = 18) received a high-fat diet (HFD). At the completion of a 9-week period, mice were sacrificed and spermatozoa were obtained. Sperm motility, concentration, intracellular reactive oxygen species (ROS) production and sperm DNA damage were measured. The ability of the sperm to undergo capacitation, acrosome reaction, sperm binding and ability to fertilize an oocyte were also assessed. The percentage of motile spermatozoa was decreased in the HFD group compared with controls (36 ± 2% vs. 44 ± 4%; p < 0.05). Intracellular ROS was elevated (692 ± 83 vs. 409 ± 22 units; p < 0.01) in the HFD group compared with controls. Sperm DNA damage was also increased (1.64 ± 0.6% vs. 0.17 ± 0.06%; p < 0.05) in the HFD group compared with the control group. Furthermore, the percentage of non-capacitated sperm was significantly lower compared with controls (12.34% vs. 21.06%; p < 0.01). The number of sperm bound to each oocyte was significantly lower (41.14 ± 2.5 vs. 58.39 ± 2.4; p < 0.01) in the HFD group compared with that in controls and resulted in significantly lower fertilization rates (25.9% vs. 43.9%; p < 0.01). This report provides evidence that obesity may induce oxidative stress and sperm DNA damage as well as decreased fertilizing ability. This is important as DNA damage in the sperm as a result of oxidative stress has been linked to poor reproductive outcomes.
Palmer NO, Bakos HW, Owens JA, Setchell BP, Lane M. Diet and exercise in an obese mouse fed a high-fat diet improve metabolic health and reverse perturbed sperm function. Am J Physiol Endocrinol Metab 302: E768 -E780, 2012. First published January 17, 2012; doi:10.1152/ajpendo.00401.2011.-Male obesity is associated with reduced sperm motility and morphology and increased sperm DNA damage and oxidative stress; however, the reversibility of these phenotypes has never been studied. Therefore, the aim of this study was to assess the reversibility of obesity and its associated sperm physiology and function in mice in response to weight loss through diet and exercise. C57BL6 male mice (n ϭ 40) were fed either a control diet (CD; 6% fat) or a high-fat diet (HFD; 21% fat) for 10 wk before allocation to either diet and/or swimming exercise interventions for 8 wk. Diet alone reduced adiposity (1.6-fold) and serum cholesterol levels (1.7-fold, P Ͻ 0.05), while exercise alone did not alter these, but exercise plus diet also improved glucose tolerance (1.3-fold, P Ͻ 0.05). Diet and/or exercise improved sperm motility (1.2-fold) and morphology (1.1-fold, P Ͻ 0.05), and reduced sperm DNA damage (1.5-fold), reactive oxygen species (1.1-fold), and mitochondrial membrane potential (1.2-fold, P Ͻ 0.05) and increased sperm binding (1.4-fold) (P Ͻ 0.05). Sperm parameters were highly correlated with measures of glycemia, insulin action, and serum cholesterol (all P Ͻ 0.05) regardless of adiposity or intervention, suggesting a link between systemic metabolic status and sperm function. This is the first study to show that the abnormal sperm physiology resulting from obesity can be reversed through diet and exercise, even in the presence of ongoing obesity, suggesting that diet and lifestyle interventions could be a combined approach to target subfertility in overweight and obese men. lifestyle interventions; fertility and metabolism OBESITY IS A GLOBAL HEALTH PROBLEM that is reaching epidemic proportions, with 1.6 billion adults classified as overweight and 400 million adults classified as obese worldwide (60). Consequently, the rates of male obesity in reproductive age men has nearly tripled since the 1970s (33). Recent studies in both humans and other species shows that male obesity impairs male reproductive potential, affecting both the molecular and physical structure of sperm (1,10,16,20,21,34,35,38,45,47,50,63,75,79) and the health of the developing fetus and subsequent offspring (9,24,42,55,59).Although fertility is not always impaired in obese men, almost 80% of men that present to fertility clinics are classified as either overweight or obese, suggestive of an interaction between obesity and sperm function (9). There is a negative impact of male obesity on standard semen parameters, including motility, count, and hormone abundance, such as testosterone and inhibin B (1,5,16,18,21,22,32,35,37,45,47,52,62,69,85). Further studies have reported reduced pregnancy success and live birth outcomes after IVF treatment in overweight and...
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