Animal & Avian Sciences Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2741

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Effects of Aging and Moderate Calorie Restriction on the Reproductive Axis of the Male Rhesus Macaque (Macaca mulatta)
(2007-04-25) Sitzmann, Brandon Dale; Ottinger, Mary Ann; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Calorie restriction (CR) has been established as the only non-genetic method of altering longevity and attenuating biological changes associated with aging. This nutritional paradigm has been effective in nematodes, flies, rodents, dogs and possibly non-human primates. Its long history notwithstanding, little is known regarding the exact mechanism(s) of CR action or its potential impact on the hypothalamic-pituitary-gonadal (HPG) axis. The objectives of this project were to: 1) analyze neuroendocrine changes to the HPG axis that occur with aging and 2) evaluate the effects of moderate CR on reproductive function in male rhesus macaques. Pituitary gene expression profiling, semi-quantitative RT-PCR (sqRT-PCR) and immunohistochemistry showed circadian clock mechanism components present in three age categories of macaques, demonstrated age differences in expression for Per2, indicated differential expression of Per2 and Bmal1 at opposing time points and revealed daily rhythmic expression of REV-ERBα protein. These data indicate the ability of the macaque pituitary to express core-clock genes, their protein products, and to do so in a 24-hour rhythm. Young Adult CON and CR pituitary gene expression profiles detected potential differential expression in <150 probesets. A decline in>TSHR and CGA was detected in CR macaques as measured by sqRT-PCR. Other genes investigated showed no diet-induced changes. Young Adult CON and CR testicular gene expression profiles detected potential differential expression in <300 probesets although mRNA expression was not altered based on sqRT-PCR and real-time RT-PCR. Age-related>and/or diet-induced changes in HSD17β3, INSL3, CSNK1E and CGA were observed in a separate experiment with CGA in Old Adult CR subjects returning to youthful levels. Semen samples were collected from Young Adult CON and CR macaques. Normal spermiogram measures, ZP-binding, AR assay and SCSA^® were conducted and indicated no differences between CON and CR-treated animals. Both groups exhibited similar daily testosterone profiles with no differences in mean or maximum levels; however, daily minimum testosterone levels were lower in CON animals. It appears that moderate CR had limited impact on neuroendocrine or reproductive function in male rhesus macaques based on our selected endpoints. Thus, advantageous CR health benefits can be achieved without obvious negative consequences to the HPG axis.
Effects of Moderate Calorie Restriction on Ovarian Function and Decline in Rhesus Monkeys
(2006-04-27) Wu, Julie Mei-Fen; Ottinger, Mary Ann; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Calorie restriction (CR) has long been heralded as the only proven nutritional intervention for life extension. Recent data demonstrated that moderate CR also extended reproductive lifespan in female rats. The objectives of this project were to: 1) analyze general hormonal changes that occur with aging and menopause and 2) evaluate the effects (whether beneficial or detrimental) of moderate (30%) CR on ovarian function and decline in rhesus monkeys (Macaca mulatta). Hormone analyses demonstrated elevated FSH and reduced INHB in Old monkeys, prior to menstrual cycle irregularity and alterations in E2 or P4. Our data are the first demonstration of this hormonal event occurring in monkeys. Furthermore, moderate CR did not impair normal ovarian function or aging. Evaluation of three clinically available tests: day 3 FSH, the Clomiphene Citrate Challenge Test (CCCT) and the Exogenous FSH Ovarian Reserve Test (EFORT), demonstrated that CCCT is efficacious in monkeys, especially with the use of E2 and INHB. As such, CCCT is the most cost effective and best predictor of ovarian response. Responses were similar between CON and CR. Oocytes from old short-term CON and CR monkeys were collected and fertilized with spermatozoa collected from normal males. Interestingly, CR appears to prolong ovarian responsiveness to exogenous gonadotropins and improve embryonic development in vitro in old female rhesus monkeys. Microarray analysis of gene expression was conducted in luteinizing granulosa cells. A subset of responsive genes were identified that will require validation by via real time polymerase chain reaction (RT-PCR). These data will provide insight into potential mechanisms of direct action of CR on the ovary. Therefore, the results of this study have provided evidence for the utility of the rhesus monkey as a model for human menopause. Additionally, moderate CR did not impair normal reproductive function or decline. We also confirmed the efficacy of the CCCT in rhesus monkeys and recommend its use as a diagnostic tool. Finally, CR improved ovarian response to exogenous gonadotropins and has beneficial effects on oocyte quality and subsequent embryo development.