Blood trihalomethane concentrations in relation to sperm mitochondrial DNA copy number and telomere length among 958 healthy men.

BACKGROUND: In animal and human studies, exposure to trihalomethanes (THMs) has been associated with reduced semen quality. However, the underlying mechanisms remain poorly understood. OBJECTIVE: To investigate the associations of blood THM concentrations with sperm mitochondrial DNA copy number (mtDNAcn) and telomere length (TL) among healthy men. METHODS: We recruited 958 men who volunteered as potential sperm donors. A single blood sample was collected from each participant at recruitment and measured for chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM) concentrations. Within a 90-day follow-up, the last semen sample provided by each participant was quantified for sperm mtDNAcn and TL. We used multivariable linear regression models to assess the associations between blood THM concentrations and sperm mtDNAcn and TL. We also performed stratified analyses according to the time intervals between baseline blood THM determinations and semen collection (i.e., 0-9, 10-14, 15-69, or >69 days) to explore potential windows of susceptibility. RESULTS: After adjusting for potential confounders, we found inverse associations between quartiles (or categories) of blood TBM, brominated THM (Br-THM, the sum of BDCM, DBCM, and TBM), and total THM (TTHM, the sum of all four THMs) concentrations and sperm mtDNAcn (all P for trend≤0.03). Besides, we found inverse associations between quartiles of blood TCM, Br-THM, chlorinated THM (Cl-THM, the sum of TCM, BDCM, and DBCM), and TTHM concentrations and sperm TL (all P for trend<0.10). Stratified analyses showed stronger associations between Br-THM concentrations and sperm mtDNAcn determined 15-69 days since baseline exposure determinations, and between blood TCM and TTHM concentrations and sperm TL determined >69 days since baseline exposure determinations. CONCLUSION: Exposure to THMs may be associated with sperm mitochondrial and telomeric dysfunction.

[Levels of serum reproductive hormones and metabolic syndrome in adult males].

OBJECTIVE: To investigate the prevalence of metabolic syndrome (MS) and its relationship with reproductive hormones in adult males in China. METHODS: Using the cluster and stratified sampling methods, we conducted an investigation among 3 600 adult males aged over 20 years in Hebei, Shaanxi and Jiangsu provinces. We obtained their reproductive hormone levels, biochemical indicators and basic body indexes and compared them between the two groups of subjects. RESULTS: A total of 3 332 valid serum samples were collected, which revealed a prevalence rate of MS of 38.5% in the adult males. Compared with the non-MS subjects, the MS males showed a significantly higher free testosterone index (FTI, 0.39 ± 0.15 vs 0.45 ± 0.19, P < 0.01) but lower levels of total testosterone (TT, ï¼»16.35 ± 4.78ï¼½ vs ï¼»13.37 ± 4.23ï¼½ nmo/L, P < 0.01) and sex hormone-binding globulin (SHBG, ï¼»47.13 ± 20.50ï¼½ vs ï¼»33.32 ± 14.91ï¼½ nmol/L, P < 0.01) and testosterone secretion index (TSI, 3.64 ± 1.92 vs 3.14 ± 1.80, P < 0.01). There were no statistically significant differences between the two groups in the levels of calculated free testosterone (cFT) and LH (P > 0.05). Spearman rank correlation analysis showed that the levels of serum TT and SHBG were correlated with all the indicators of MS (P < 0.01) except systolic blood pressure (SBP), while that of cFT only with the levels of high-density lipoprotein (HDL), fasting blood glucose (FBG) and SBP (P < 0.01). After adjusted for age, smoking, drinking, and body mass index (BMI), all the MS indicators were significantly associated with the SHBG level (P < 0.01), but not high blood pressure with the serum TT level (P > 0.05). After adjusted for the age, smoking, drinking, BMI and TT, the serum SHBG level was the main independent risk factor for MS (OR: 0.965, 95% CI: 0.958－0.973, P < 0.01). CONCLUSIONS: The level of serum cFT is not correlated with while that of SHBG is the main independent risk factor for metabolic syndrome in adult males in China.