Scrotal ultrasonographic findings in obese infertile patients and their correlations to semen and hormonal profile

Sperm DNA damage: The possible link between obesity and male infertility, an update of the current literature

Obesity prevalence worldwide is increasing significantly. Whilst maternal obesity has clear detrimental impacts on fertility, pregnancy and foetal outcomes, more recently there has been an increasing focus on the role of paternal obesity in human fertility. Recent meta-analyses have indicated that obesity in men negatively affects basic sperm parameters such as sperm count, concentration and motility, increases the incidence of infertility and reduces the chances of conception. Sperm DNA damage, typically characterised by DNA strand breaks and oxidation of DNA nucleotides, is a specialised marker of sperm quality that has been independently associated with recurrent miscarriage, reduced assisted reproduction success and increased mutational loads in subsequent offspring. Whilst, there are still conflicting data in humans as to the association of obesity in men with sperm DNA damage, evidence from rodent models is clear, indicating that male obesity increases sperm DNA damage. Human data are often conflicting because of the large heterogeneity amongst studies, the use of body mass index as the indicator of obesity and the methods used for detection of sperm DNA damage. Furthermore, comorbidities of obesity (i.e., heat stress, adipokines, insulin resistance, changes in lipids, hypogonadism and obstructive sleep apnoea) are also independently associated with increased sperm DNA damage that is not always modified in men with obesity, and as such may provide a causative link to the discrepancies amongst human studies. In this review, we provide an update on the literature regarding the associations between obesity in men and fertility, basic sperm parameters and sperm DNA damage. We further discuss potential reasons for the discrepancies in the literature and outline possible direct and indirect mechanisms of increased sperm DNA damage resulting from obesity. Finally, we summarise intergenerational obesity through the paternal linage and how sperm DNA damage may contribute to the transmission.

Association of diabetes and obesity with sperm parameters and testosterone levels: a meta-analysis

BACKGROUND

The present study performed two distinct meta-analyses with common outcomes (sperm parameters); one was performed in obese individuals (and non-obese controls) and the other in diabetic individuals (and non-diabetic controls).

METHODS

PubMed, Embase, The Cochrane library, Web of Science, Scopus databases were searched to collect clinical studies related to the effects of obesity and diabetes on male sperm from inception to on 1st February 2021. Statistical meta-analyses were performed using the RevMan 5.4 software. Stata16 software was used to detect publication bias. The methodological quality of the included studies was assessed with the Ottawa-Newcastle scale using a star-based system.

RESULTS

A total of 44 studies were finally included in the present study, which enrolled 20,367 obese patients and 1386 patients with diabetes. The meta-analysis results showed that both obesity and diabetes were associated with reduced semen volume (obese versus non-obese controls: mean difference (MD) = - 0.25, 95% CI = (- 0.33, - 0.16), p < 0.001; diabetes versus non-diabetic controls: MD = - 0.45, 95% CI = (- 0.63, - 0.27), p < 0.001), reduced sperm count (obese versus non-obese controls: MD = - 23.84, 95% CI = (- 30.36, - 17.33), p < 0.001; diabetes versus non-diabetic controls: MD = - 13.12, 95% CI = (- 18.43, - 7.82), p < 0.001), reduced sperm concentration (obese versus non-obese controls: MD = - 7.26, 95% CI = (- 10.07, - 4.46), p < 0.001; diabetes versus non-diabetic controls: MD = - 11.73, 95% CI = (- 21.44, - 2.01), p = 0.02), reduced progressive motility (obese versus non-obese controls: MD = - 5.68, 95% CI = (- 8.79, - 2.56), p < 0.001; diabetes versus non-diabetic controls: MD = - 14.37, 95% CI = (- 21.79, - 6.96), p = 0.001), and decreased testosterone levels (obese versus non-obese controls: MD = - 1.11, 95% CI = (- 1.92, - 0.30), p = 0.007; diabetes versus non-diabetic controls: MD = - 0.37, 95% CI = (- 0.63, - 0.12), p = 0.004).

CONCLUSIONS

Current evidence suggests that obesity and diabetes negatively affect sperm parameters in men and are associated with low testosterone levels. Due to the limitation of the number and quality of included studies, the above conclusions need to be verified by more high-quality studies.