Among other health problems, obesity can cause chronic inflammation in various tissues from fat cell production of inflammatory signaling proteins. A team led by researchers from Shanghai Jiao Tong University now connect this obesity-induced inflammation to problems in male fertility through studies in mice and men.
The team compared the level of inflammatory markers in the genital tracts of normal male mice and those fed a high-fat diet to become obese. The testes of obese mice underwent changes in structure and sex hormone expression. There was a decreased level of testosterone, which helps maintain the protective blood-testes barrier.
Inflammatory proteins that normally circulate in the blood were accordingly found elevated in the tissues of the genital tract, including the testes, epididymis, seminal vesicle, and prostate. Among these proteins were those previously shown to affect sperm function and production.
The team then looked at human semen samples provided by 272 donors. Of these, 82 individuals had healthy weight, 150 were overweight and 40 were obese. Increased levels of inflammatory proteins were found in the overweight and obese samples, with the protein levels positively correlating with the donors’ BMI. Sperm concentration and motility, important indicators of fertility, were also significantly decreased in the overweight and obese samples. As expected, these indicators inversely correlated with BMI.
The study, published recently in Frontiers in Physiology conclude that “impairment of male fertility may stem from a chronic inflammatory status in the male genital tract of obese individuals.” The findings not only provide insight into mechanisms linking obesity and fertility, but can also lead to new therapeutic avenues of enhancing male fertility, including targeting inflammation in the male genital tract.
"Obesity is a serious problem in modern society and both obesity and male infertility rates continue to increase," says senior author Zhide Ding. "Reducing BMI is important in improving male fertility."
Image: SEM micrograph of human sperm cells. Image courtesy of Wikimedia commons.