Impact of moderate calorie restriction on testicular morphology and endocrine function in adult rhesus macaques (Macaca mulatta). Sitzmann BD, Brown DI, Garyfallou VT, Kohama SG, Mattison JA, Ingram DK, Roth GS, Ottinger MA, Urbanski HF. Age (Dordr). 2014 Feb;36(1):183-97.
We previously reported that moderate calorie restriction (CR) has minimal impact on testicular gene expression in young adult rhesus macaques, and no obvious negative impact on semen quality or plasma testosterone levels. We now extend these findings by examining the influence of CR on various aspects of the reproductive axis of older males, including 24-h circulating testosterone levels, testicular gene expression, and testicular morphology. Young adult and old adult male rhesus macaques were subjected to either 30 % CR for 5-7 years, or were fed a standard control diet. Analysis of the 24-h plasma testosterone profiles revealed a significant age-associated decline, but no evidence for CR-induced suppression in either the young or old males. Similarly, expression profiling of key genes associated with testosterone biosynthesis and Leydig cell maintenance showed no significant CR-induced changes in either the young or old animals. The only evidence for CR-associated negative effects on the testis was detected in the old animals at the histological level; when old CR animals were compared with their age-matched controls, there was a modest decrease in seminiferous tubule diameter and epithelium height, with a concomitant increase in the number of depleted germ cell lines. Reassuringly, data from this study and our previous study suggest that moderate CR does not negatively impact 24-h plasma testosterone profiles or testicular gene expression. Although there appear to be some minor CR-induced effects on testicular morphology in old animals, it is unclear if these would significantly compromise fertility.
Select quotes from the study:
“Testosterone decline, especially during aging, can result in weakening muscle function, bone density and alteration of other physiological parameters related to overall aging (Bremner et al. 1983; Feldman et al. 2002; Harman et al. 2001; Moffat et al. 2002; Sitzmann et al.2008). Also of importance is the neurological impact of T loss. Some studies have reported that men with Alzheimer’s disease (AD) have significantly lower T levels than aged men without AD (Moffat et al. 2002; Rosario et al. 2006). Significantly, T depletion appears to occur well before clinical and pathological diagnosis of AD, suggesting that low T levels may contribute to AD pathogenesis rather than results from it (Rosario et al. 2006).”
“Surprisingly, maximum circulating T levels were significantly higher in old CR males than in their age-matched controls. Whether this apparent increase is physiologically significant is unclear, but when considered together with our previous finding that CR enhanced the daily minimum T levels in young males, it may be indicative of a subtle improvement of physiological efficiency elicited by moderate CR.”
“Moreover, findings in the old adults may be an indication that CR can contribute to the maintenance of elevated T levels during old age, which would be of great physiological benefit.”
“The most important finding, however, is that moderate CR does not suppress T production or disrupt the 24-h pattern of T in the circulation; if anything, it may even enhance circulating T levels. Consequently, CR is unlikely to negatively impact androgen-mediated nonreproductive functions, and may exert additional beneficial effects.”
I was in my office talking about my recent blog topic of calorie restriction reducing muscle loss and sarcopenia with aging and how it was the opposite of what I would have expected. One of my patients asked why. I was unsure, saying most of the papers I looked showed an overall reduction in cell death, and muscle cells are among those cells, and this appears to explain at least part of it, though the mechanisms are still not understood. Then someone said something about calories and testosterone, and I said given the results on muscle mass, calorie restriction might also increase/preserve testosterone levels with age. Within minutes I was on pubmed combining key words of calorie restriction and testosterone and this was the first paper I got printed.
The researchers found that calorie restriction (30%) for 5-7 years did not negatively affect testosterone levels but actually increased mean plasma testosterone levels 20.7% in young adult male monkeys (beginning at the peripubertal period of 4 years 11 months) and 26.7% in older ones (age not given). Also interesting to me is that the terminal body weight at death of the older calorie restricted monkeys was slightly more in the control group (6.69 vs 6.27 kg), but the calorie restricted monkeys were lighter in the younger group (9.19 vs 10.72 kg) perhaps reflecting some combination of increased muscle/decreased fat that one might expect with increased testosterone levels as found in the other study.
As a physical therapist, findings like this sound like they could have considerable positive impact on my patients’ lives. I’m still not sure how to ideally implement it in the lives of people. For example 30% reduction compared to what? I’ll keep reading the research and see what I find, but in the meantime it makes for interesting conversation in the gym.
Thanks for reading my blog. If you have any questions or comments (even hostile ones) please don’t hesitate to ask/share. If you’re reading one of my older blogs, perhaps unrelated to neck or back pain, and it helps you, please remember Spinal Flow Yoga for you or someone you know in the future.
Chad Reilly is a Physical Therapist, obtaining his Master’s in Physical Therapy from Northern Arizona University. He graduated Summa Cum Laude with a B.S. Exercise Science also from NAU. He is a Certified Strength and Conditioning Specialist, and holds a USA Weightlifting Club Coach Certification as well as a NASM Personal Training Certificate. Chad completed his Yoga Teacher Training at Sampoorna Yoga in Goa, India.