Abstract
Obesity is frequently accompanied with chronic inflammation over the whole body and is always associated with symptoms that include those arising from metabolic and vascular alterations. On the other hand, the chronic inflammatory status in the male genital tract may directly impair spermatogenesis and is even associated with male subfertility. However, it is still unclear if the chronic inflammation induced by obesity damages spermatogenesis in the male genital tract. To address this question, we used a high fat diet (HFD) induced obese mouse model and recruited obese patients from the clinic. We detected increased levels of tumor necrosis factor (TNF-α), interleukin-6 (IL-6), and NOD-like receptor family pyrin domain containing-3 (NLRP3) in genital tract tissues including testis, epididymis, seminal vesicle, prostate, and serum from obese mice. Meanwhile, the levels of immunoglobulin G (IgG) and corticosterone were significantly higher than those in the control group in serum. Moreover, signal factors regulated by TNF-α, i.e., p38, nuclear factor-κB (NF-κB), Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and their phosphorylated status, and inflammasome protein NLRP3 were expressed at higher levels in the testis. For overweight and obese male patients, the increased levels of TNF-α and IL-6 were also observed in their seminal plasma. Furthermore, there was a positive correlation between the TNF-α and IL-6 levels and BMI whereas they were inversely correlated with the sperm concentration and motility. In conclusion, impairment of male fertility may stem from a chronic inflammatory status in the male genital tract of obese individuals.
Highlights
Obesity is a global health problem and the prevalence of obesity has risen substantially in the past three decades
To confirm that chronic inflammation existed in the genital tract of overweight and obese males, 272 semen samples from normal weight, overweight and obese human males were collected and analyzed
The male obese mouse model induced by high-fat diet can develop a remarkable impairment of sperm function, including reduced sperm motility, decreased acrosome reaction and fertility rate, and abnormal sperm morphology (Fan et al, 2015)
Summary
Obesity is a global health problem and the prevalence of obesity has risen substantially in the past three decades. Obesity is a metabolic disease resulting from behavior and heritable causes It is associated with a number of chronic states including metabolic syndrome, hyperlipidemia, type-2 diabetes, cancer, cardiovascular disease, and infertility (An et al, 2017). Besides these associations between obesity and disease, studies over the past years indicate there are important signaling pathways connecting this metabolic syndrome with the immune system (Tilg and Moschen, 2006). One of the sources of these mediators may be dysfunctional adipocytes (Esser et al, 2014)
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