Aspectos nutricionales y medioambientales relacionados con parámetros reproductivos en varones jóvenes

Resum

NTRODUCTION In recent decades, numerous studies have indicated a decline in sperm concentration. The factors involved are multifactorial, but the most important are changes in lifestyle, such as the shift from the traditional Mediterranean diet to a more Western diet, or exposure to certain endocrine disruptors (ED). The Western dietary pattern is characterized by an increased consumption of ultra-processed foods, including sugar-sweetened beverages, which add up to 400 kcal per day to our daily diet. The relationship between sugar-sweetened beverages and male reproductive function in humans is poorly described in the literature. On the other hand, EDs are environmental chemicals that can mimic natural hormones. Exposure to these toxicants is thought to be ubiquitous and unintentional. Some of these compounds may have estrogenic or antiandrogenic effects. This group includes bisphenol A (BPA), found in polycarbonate plastics and food packaging; benzophenone (BP), an ultraviolet (UV) filter widely used in sunscreens; and parabens, versatile antimicrobial preservatives added to personal care products and foods to extend their shelf life. OBJECTIVES To evaluate the associations between sugar-sweetened beverage consumption and urinary concentrations of BPA, parabens, and BP-type UV filters and semen quality, levels of reproductive hormones, and sperm DNA fragmentation index in healthy young men. MATERIAL AND METHODS Observational cross-sectional study in university men (aged 18 to 23 years) from the Region of Murcia between 2010 and 2011. To study seminal quality and reproductive hormones, a total of 209 patients were included, while for sperm DNA defragmentation, a total of 158 patients from the same cohort were analyzed. On the same day as the physical evaluation, participants provided urine, semen and blood samples, and completed questionnaires about their lifestyle habits. BPA, BP-type UV filters and parabens were measured in urine samples using liquid-liquid dispersive microextraction techniques and then analyzed by high-performance liquid chromatography coupled to tandem mass spectrometry. Semen quality was assessed using the WHO Criteria, 2010 and included the following parameters: sperm volume, concentration, total sperm count, motility and morphology. In addition, serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), total and free testosterone (T), estradiol (E2) and inhibin B were determined. DNA fragmentation analysis was performed using the sperm chromatin dispersion test (SCD). The sperm fragmentation index (SFI) was defined as the percentage of sperm with fragmented DNA divided by the total number of sperm analyzed. Multiple linear regression analyses, crude and adjusted for important covariates, were used to evaluate possible associations between sugar-sweetened beverage intake, different environmental chemical compounds and semen parameters, as well as hormone levels and sperm fragmentation. Bayesian kernel machine regression (BKMR) models were also used to evaluate the mixture effect on sperm DNA fragmentation. RESULTS Males in the highest quartile of sugar-sweetened beverage intake had a higher percentage of morphologically normal sperm (37.4% [6.1, 68.3]) (p-trend = 0.047) and higher estradiol levels (9.5% [3.5, 22.5] (p-trend = 0.047) than those in the first quartile. On the other hand, no association was found between urinary BPA concentrations and SFI in the total group. However, in the subgroup of men with SFI > 30%, significant positive associations were observed across quartiles (p-trend=0.02) and with continuous BPA levels [β = 0.055; 95%CI: (0.002, 0.108)]. Finally, analyzing ED mixtures, it was observed that increased urinary 4-OHBP concentration proved to be the factor contributing most to the negative association between urinary ED concentrations and SFI, being -5.5 % [95 % CI: -10.7, -0.3] for those in the 50th percentile, and -5.4 % [95 % CI: -10.8, -0.1] for those in the 75th percentile. No significant associations were observed between other ED and SFI. CONCLUSIONS Our results suggest that sperm morphology and estradiol levels may be associated with sugar-sweetened beverage consumption. Similarly, our results suggest that there is a positive association between urinary BPA concentrations and SFI. Similarly, the results of mixtures analyses showed a statistically significant negative association between urinary 4-OHBP levels and the SFI. However, the observed effects are likely to be small and of uncertain clinical significance. Further studies are needed to confirm these results and to draw conclusions in other male populations.