Consistent with thesereports, dietary supplementation with vitamin E (483 mg daily for8 weeks) has produced a 20% increase in testosterone synthesis inhealthy men . A re-evaluation of the Health Professionals Follow-Up Studydata after an additional 8 years of observation initially reportedthat compared to the effects of the consumption of less than 90mg of vitamin C daily, the daily consumption of 1000 mg or moresignificantly increased the relative risk of forming a kidney stone by41% . In a short, 6-day study, the consumption of2000 mg of supplemental vitamin C by individuals with histories of prior kidney stone formation produced a significant increase in theurinary excretion of oxalate, a putative biomarker of urolithogenicrisk . Ascorbate, the dominant form of vitamin C in humans ,contains 2 enolic hydrogen atoms that provide electrons that areavailable for nonenzymatic transfer to biological oxidants and provide the basis for the antioxidant properties of vitamin C. In a double-blind, randomized, placebocontrolledstudy, healthy men with initially "desirable" resting plasmafree testosterone concentrations and participating in a prescribedexercise regimen added 600 mg of phosphatidylserine to their dailydiets for 10 days . Phosphatidylserine also stimulatesthe isomerase activity of HSD3B2 in the testes, increasing testosteronesynthesis through the alternate "Δ4" pathway (pregnenolone →progesterone → androstenedione → testosterone) 247,255,256. Phosphatidylserine-dependent activation ofAkt is followed by Akt activation of protein kinase C , whichparticipates in signaling pathways that culminate in testosteronesynthesis through the primary "Δ5" pathway (pregnenolone→ 17α-hydroxypregnenolone → dehydroepiandrosterone →androstenedione → testosterone). Testosteroneanabolism in men is proportional to the plasma concentration ofpituitary-derived luteinizing hormone (LH) and is triggered bybinding of LH to its plasma membrane receptors on Leydig cells ofthe testes and subsequent activation of intracellular signaling cascades that increase the conversion of adenosine monophosphate(AMP) to cyclic AMP (cAMP) and initiate the de novo synthesis oftestosterone . The biochemistry of testosterone synthesis within the Leydigcells of the human testes is well characterized 3,4. The biochemistry of testosterone synthesis within the Leydig cells of thehuman testes is well characterized. Sodium fluoride, a substance widely present in drinking water and food, can influence testosterone production by altering oxidative stress levels in the testes (8). This study underscores the importance of comprehensive antioxidant approaches, particularly lifestyle OBS, in male testosterone deficiency. Moreover, red blood cell resistance to free radicals is also positively correlated with survival in this species (Alonso-Alvarez et al. 2006), suggesting that the fitness cost of testosterone-induced increase in oxidative stress might be substantial. Staining with H2DCFDA to check ROS generation revealed a left shift of the histogram in 100-nmol l−1 testosterone-treated cells (a, c). ROS reduction was found in cells treated with epitestosterone ranging from 50 nmol l−1 to 500 µmol l−1, especially in 100 nmol l−1, 500 nmol l−1 and 1 µmol l−1. Reduced ROS generation was found in 50 and 100 nmol l−1 (PP−1 testosterone-treated TM3 cells (Figure 2b). In c and d, time-dependent declines in ROS production and lipid peroxidation were shown in testosterone-treated cells. However, a time-dependent enhancement of ROS generation was found in the cells treated with 10-µmol l−1 epitestosterone (data not shown). (b) Cells were incubated with 100-nmol l−1 testosterone at 37 °C for various time periods, and then the cell viability was determined. For time-related studies, testosterone was administered at a dose of 100 nmol l−1 for 6, 8, 12, 24, 36 and 48 h. For testosterone supplementation studies, testosterone (Organon, Oss, The Netherlands) was administered at the doses of 10, 50, 100, 500, 1000 and 2000 nmol l−1. It was proposed that decreases in testosterone levels with aging may reflect reactive oxygen species (ROS) elevation and further disruption of the ability of Leydig cells to produce testosterone.6, 7 Testosterone levels notably decline with aging;3, 4 however, a recent report showed no correlation between androgen receptor (AR) polymorphism and the serum concentrations of total and free testosterone in elderly men.5 The mechanism by which aged Leydig cells lose their steroidogenic function remains unclear. This study was financially supported by the Shin Kong Wu Ho-Su Memorial Hospital (SKH-TMU-93-43). TIH and SHK participated in the design and concept formation of this study. Although further investigations of the mechanism governing the differential effects of testosterone treatment are needed, our in vitro results provide the first clues for further animal and clinical tests and shed light on testosterone replacement therapy. Clinically, the proper application of testosterone replacement therapy is of great concern. As for ROS generation, the epitestosterone showed similar effect to testosterone.
