Age-related increase in the expression of 11ß-hydroxysteroid dehydrogenase type 1 in the hippocampus of male rhesus macaques.

Introduction: The hippocampus is especially susceptible to age-associated neuronal pathologies, and there is concern that the age-associated rise in cortisol secretion from the adrenal gland may contribute to their etiology. Furthermore, because 11ß-hydroxysteroid dehydrogenase type 1 (HSD11B1) catalyzes the reduction of cortisone to the active hormone cortisol, it is plausible that an increase in the expression of this enzyme enhances the deleterious impact of cortisol in the hippocampus and contributes to the neuronal pathologies that underlie cognitive decline in the elderly. Methods: Rhesus macaques were used as a translational animal model of human aging, to examine age-related changes in gene and protein expressions of (HSD11B1/HSD11B1) in the hippocampus, a region of the brain that plays a crucial role in learning and memory. Results: Older animals showed significantly (p < 0.01) higher base-line cortisol levels in the circulation. In addition, they showed significantly (p < 0.05) higher hippocampal expression of HSD11B1 but not NR3C1 and NR3C2 (i.e., two receptor-encoding genes through which cortisol exerts its physiological actions). A similar age-related significant (p < 0.05) increase in the expression of the HSD11B1 was revealed at the protein level by western blot analysis. Discussion: The data suggest that an age-related increase in the expression of hippocampal HSD11B1 is likely to raise cortisol concentrations in this cognitive brain area, and thereby contribute to the etiology of neuropathologies that ultimately lead to neuronal loss and dementia. Targeting this enzyme pharmacologically may help to reduce the negative impact of elevated cortisol concentrations within glucocorticoid-sensitive brain areas and thereby afford neuronal protection.

Acute responses of stevia and d-tagatose intake on metabolic parameters and appetite/satiety in insulin resistance.

OBJECTIVE: To examine the effects of d-tagatose or stevia preloads on carbohydrate metabolism markers after an oral glucose load, as well as subjective and objective appetite in women with insulin resistance (IR). RESEARCH DESIGN AND METHODS: Randomized controlled crossover study. Women with IR without T2DM (n = 33; aged 23.4 ± 3.8; BMI 28.1 ± 3.4 kg × m-2) underwent three oral glucose loads (3 h each) on three different days. Ten min before oral glucose load, volunteers consumed a preload of 60 mL water (control), 60 mL water with stevia (15.3 mg), or d-tagatose (5000 mg). Serum glucose and C-peptide were evaluated at -10, 30-, 60-, 90-, 120-, and 180-min. Subjective appetite was determined with a visual analog scale. Food intake was measured at ad libitum buffet after 180 min. RESULTS: C-peptide iAUC was significantly higher for stevia (median (IQR): 1033 (711-1293) ng × min × L-1) vs. d-tagatose (794 (366-1134) ng × min × L-1; P = 0.001) or control (730 (516-1078) ng × min × L-1; P = 0.012). At 30- and 60-min serum glucose was higher for stevia vs other conditions (P < 0.01). Volunteers reported greater satiety for stevia and d-tagatose vs. control at 60 min and greater desire to eat for stevia vs. control at 120- min (all P < 0.05). Objective appetite did not vary by condition (P = 0.06). CONCLUSIONS: Our findings suggest that these NNS are not inert. Stevia intake produced an acute response on C-peptide release while increased serum glucose at earlier times. It is possible that NNS affects subjective but not objective appetite. This trial is registered at clinicaltrials.gov as NCT04327245. CLINICAL TRIAL REGISTRY: NCT04327245.

Lack of effect of short-term DHEA supplementation on the perimenopausal ovary†.

Dehydroepiandrosterone (DHEA) hormonal supplementation can improve oocyte quality in women with diminished ovarian function. However, it is unclear whether DHEA supplementation can also enhance ovarian function during the perimenopause (i.e., when the number of follicles in the ovary has undergone a marked reduction). To address this question, we examined the impact of 2.5-months of daily 5-mg oral DHEA supplementation on the number of ovarian follicles and the concentration of anti-Müllerian hormone (AMH) in perimenopausal rhesus macaques. Like women, these long-lived nonhuman primates have ~ 28-day menstrual cycles and eventually undergo menopause. They also show similar age-related neuroendocrine changes, including a marked decrease in circulating concentrations of DHEA and DHEA sulfate (DHEAS). Our experimental design involved the following three groups of animals (N = 6 per group): Young adult (mean age = 11.6 years), Old control (mean age = 23.1 years), and Old DHEA-treated (mean age = 23.5 years). Histological examination of the ovaries revealed a significant age-related decrease in the mean number of primordial follicles despite DHEA supplementation. Moreover, AMH concentrations within the ovaries and circulation, assessed by Western analysis and ELISA, respectively, showed significant age-related decreases that were not attenuated by DHEA supplementation. Taken together, these results fail to show a clear effect of short-term physiological DHEA supplementation on the perimenopausal ovary. However, they do not exclude the possibility that alternative DHEA supplementation paradigms (e.g., involving an earlier start date, longer duration and using pharmacological doses) may extend reproductive potential during aging.

Gene expression profiling of the SCN in young and old rhesus macaques.

In mammals, the suprachiasmatic nucleus (SCN) is the location of a master circadian pacemaker. It receives photic signals from the environment via the retinal hypothalamic tract, which play a key role in synchronizing the body's endogenously generated circadian rhythms with the 24-h rhythm of the environment. Therefore, it is plausible that age-related changes within the SCN contribute to the etiology of perturbed activity-rest cycles that become prevalent in humans during aging. To test this hypothesis, we used gene arrays and quantitative RT-PCR to profile age-related gene expression changes within the SCN of male rhesus macaques - a pragmatic translational animal model of human aging, which similarly displays an age-related attenuation of daytime activity levels. As expected, the SCN showed high expression of arginine vasopressin, vasoactive intestinal polypeptide, calbindin and nuclear receptor subfamily 1, group D, member 1 (NR1D1) (also known as reverse strand of ERBA (REV-ERBα), both at the mRNA and protein level. However, no obvious difference was detected between the SCNs of young (7-12 years) and old animals (21-26 years), in terms of the expression of core clock genes or genes associated with SCN signaling and neurotransmission. These data demonstrate the resilience of the primate SCN to normal aging, at least at the transcriptional level and, at least in males, suggest that age-related disruption of activity-rest cycles in humans may instead stem from changes within other components of the circadian system, such as desynchronization of subordinate oscillators in other parts of the body.

Locomotor activity and the expression of orexin A and orexin B in aged female rhesus macaques.

Reduced activity has been linked to age-associated physiological changes but the underlying root cause is unclear. The goal of the present study was to compare the orexin neuronal system of old (23-29 years) female rhesus macaques with either active or sedentary 24-hour locomotor activity patterns. Using immunohistochemistry, we counted the number of orexin A and orexin B neurons in the lateral hypothalamic area of each animal. Overall, we observed no difference in the distribution pattern or number of either orexin A or orexin B immune-positive neurons between animals in the 2 groups. Thus, reduced activity in the elderly is unlikely to stem from a loss of orexin neuronal perikarya in the lateral hypothalamic area. This, however, does not rule out the possibility that the reduced activity stems from reduced orexin neuronal projections to arousal centers of the brain, such as the locus coeruleus, or from attenuated release of orexin.