Nonhuman primates contribute unique understanding to anovulatory infertility in women

The Use of Non-Human Primates in Biological and Medical Research: Evidence Submitted by FRAME to the Academy of Medical Sciences/Medical Research Council/Royal Society/Wellcome Trust Working Group

The Academy of Medical Sciences, the Medical Research Council, the Royal Society and the Wellcome Trust are undertaking a study into the use of non-human primates in biological and medical research. An independent working group of scientific experts, led by Sir David Weatherall, aims to produce a report summarising the findings of this study, early in 2006. The trends in primate research, and the nature and effects of recent and proposed changes in the global use of non-human primates in research, will be investigated. The associated ethical, welfare and regulatory issues, and the role and impact of the Three Rs principles of refinement, reduction and replacement will also be reviewed. As part of this study, a call for evidence was made. The evidence submitted by FRAME emphasised that the use of non-human primates for fundamental research or for regulatory testing still fails to take into account the fact that, although non-human primates are anatomically and physiologically similar to humans, they are not necessarily relevant models for studies on human disease or human physiology. FRAME continues to believe that we have a duty to ensure that these animals are not used without overwhelming evidence that they are the only suitable and relevant models for use in work of undeniable significance.

Higher offspring mortality with short interbirth intervals in free-ranging rhesus macaques

Short birth intervals have long been linked to adverse child outcomes in humans. However, it remains unclear the extent to which the birth interval has a direct influence on offspring mortality, independent of the confounding effects of modern environments and human sociocultural practices on reproductive behavior. Outside of humans, the relationship between birth intervals and offspring mortality has been rarely tested, leaving an open question of how much the findings from humans imply evolutionarily conserved mechanisms. Here, using ∼9,000 birth records from ∼1,400 free-ranging rhesus macaque mothers, we show that short birth intervals preceding or succeeding the birth of an offspring are both associated with higher offspring mortality, after controlling for heterogeneity across mothers and birth cohorts. We clarify that the mortality risk of a short birth interval to an offspring is contingent on the survival of its older or younger sibling, the condition that reduces maternal resources for investment in the offspring. This finding suggests that life-history tradeoffs between offspring quantity (a short birth interval) and quality (offspring survival) form an evolutionary force shaping variation in birth intervals. Consistent with the well-known observation made in humans, we also found a nonlinear relationship between the preceding interbirth interval and infant mortality. The overall congruence with the findings from the human literature indicates a robust relationship between birth intervals and offspring mortality.

Long-term effects of repeated superovulation on the uterus and mammary gland in rhesus monkeys

PURPOSE

The aim of this study is to evaluate the effect of repeated controlled ovarian hyperstimulation (COH) on the structure and function of the uterus and mammary gland.

METHODS

Three adult female rhesus monkeys were superovulated up to four times, and three spontaneously ovulating monkeys were used as controls. After a 5-year period, the uterus and mammary gland tissue samples were collected for examination of their structure and function. Further, the expression of certain tumor markers was examined to assess the cancer risk for each organ.

RESULTS

Expression of Wnt7a (associated with the functional/developmental status of the uterus) was significantly decreased in the uterus of superovulated monkeys, and decreased expression of proliferation marker PCNA was found in uterine cells. Meanwhile, abnormal Golgi-derived secretory vesicles with an irregular shape were observed in the mammary glands of the superovulated monkeys, and decreased PCNA expression together with increased expression of caspase-3 (an apoptosis marker) was indicated in the mammary cells. The expression of tumor molecular markers of the uterus and mammary gland was not significantly different between the two groups.

CONCLUSIONS

Repeated COH affects the expression of the uterine development-related gene several years later, and uterine cells exhibited a low proliferation status. The ultrastructure of the mammary gland epithelial cells was abnormal, and the cells exhibited both low proliferation and high apoptosis status. Cancer risk for these organs was not observed. Given that primates are the closest relatives of humans, the results obtained from this study provide more intuitive information for optimization of clinical COH.

Cellular and Animal Studies: Insights into Pathophysiology and Therapy of PCOS

Basic science studies have advanced our understanding of the role of key enzymes in the steroidogenesis pathway and those that affect the pathophysiology of PCOS. Studies with ovarian theca cells taken from women with PCOS have demonstrated increased androgen production due to increased CYP17A1 and HSD3B2 enzyme activities. Furthermore, overexpression of DENND1A variant 2 in normal theca cells resulted in a PCOS phenotype with increased androgen production. Notably, cellular steroidogenesis models have facilitated the understanding of the mechanistic effects of pharmacotherapies, including insulin sensitizers (e.g., pioglitazone and metformin) used for the treatment of insulin resistance in PCOS, on androgen production. In addition, animal models of PCOS have provided a critical platform to study the effects of therapeutic agents in a manner closer to the physiological state. Indeed, recent breakthroughs have demonstrated that natural derivatives such as the dietary medium-chain fatty acid decanoic acid (DA) can restore estrous cyclicity and lower androgen levels in an animal model of PCOS, thus laying the platform for novel therapeutic developments in PCOS. This chapter reviews the current understanding on the pathways modulating androgen biosynthesis, and the cellular and animal models that form the basis for preclinical research in PCOS, and sets the stage for clinical research.

Polycystic ovary syndrome

Polycystic ovary syndrome (PCOS), a heterogeneous and chronic condition, today affects about 5% of women of reproductive age. PCOS is strongly associated with states of insulin resistance and hyperinsulinemia. Risk factors include genetics, metabolic profiles, and the in utero environment. Long-term consequences of PCOS include metabolic complications such as diabetes, obesity, and cardiovascular disease. Dysregulation of insulin action is closely linked to the pathogenesis of PCOS. However, whether insulin resistance is the causative factor in the development of PCOS remains to be ascertained. Moreover, the mechanism by which insulin resistance may lead to reproductive dysfunction requires further elucidation.

Nonhuman primates and other animal models in diabetes research

Animal models are important for determining the pathogenesis of and potential treatments for obesity and diabetes. Nonhuman primates (NHPs) are particularly useful for studying these disorders. As in humans, type 2 diabetes mellitus is the most common form of diabetes in NHPs and occurs more often in older obese animals, with a metabolic progression from insulin resistance (IR) and impaired glucose tolerance to overt diabetes. Histopathologic changes in pancreatic islets are also similar to those seen in humans with diabetes. Initially, there is islet hyperplasia with abundant insulin production to compensate for IR, followed by insufficient insulin production with replacement of islets with islet-associated amyloid. Diabetic NHPs also have adverse changes in plasma lipid and lipoprotein concentrations, biomarkers of obesity, inflammation, and oxidative stress, and protein glycation that contribute to the numerous complications of the disease. Furthermore, sex hormones, pregnancy, and environmental factors (e.g., diet and stress) affect IR and can also contribute to diabetes progression in NHPs. Additionally, due to their similar clinical and pathologic characteristics, NHPs have been used in many pharmacological studies to assess new therapeutic agents. For these reasons, NHPs are particularly valuable animal models of obesity and diabetes for studying disease pathogenesis, risk factors, comorbidities, and therapeutic interventions.

Fetal, infant, adolescent and adult phenotypes of polycystic ovary syndrome in prenatally androgenized female rhesus monkeys

Old World monkeys provide naturally occurring and experimentally induced phenotypes closely resembling the highly prevalent polycystic ovary syndrome (PCOS) in women. In particular, experimentally induced fetal androgen excess in female rhesus monkeys produces a comprehensive adult PCOS-like phenotype that includes both reproductive and metabolic dysfunction found in PCOS women. Such a reliable experimental approach enables the use of the prenatally androgenized (PA) female rhesus monkey model to (1) examine fetal, infant and adolescent antecedents of adult pathophysiology, gaining valuable insight into early phenotypic expression of PCOS, and (2) to understand adult pathophysiology from a mechanistic perspective. Elevated circulating luteinizing hormone (LH) levels are the earliest indication of reproductive dysfunction in late gestation nonhuman primate fetuses and infants exposed to androgen excess during early (late first to second trimester) gestation. Such early gestation-exposed PA infants also are hyperandrogenic, with both LH hypersecretion and hyperandrogenism persisting in early gestation-exposed PA adults. Similarly, subtle metabolic abnormalities appearing in young nonhuman primate infants and adolescents precede the abdominal adiposity, hyperliplidemia and increased incidence of type 2 diabetes that characterize early gestation-exposed PA adults. These new insights into the developmental origins of PCOS, and progression of the pathophysiology from infancy to adulthood, provide opportunities for clinical intervention to ameliorate the PCOS phenotype thus providing a preventive health-care approach to PCOS-related abnormalities. For example, PCOS-like traits in PA monkeys, as in PCOS women, can improve with better insulin-glucose homeostasis, suggesting that lifestyle interventions preventing increased adiposity in adolescent daughters of PCOS mothers also may reduce their risk of acquiring many PCOS-related metabolic abnormalities in adulthood.

Polycystic Ovary Syndrome, Obesity and Reproductive Implications

Polycystic ovary syndrome (PCOS) is one of the most common causes of female infertility, affecting 5–10% of women of reproductive age. The syndrome is characterized by anovulation, hyperandrogenism and polycystic ovaries. Furthermore, PCOS is associated with insulin resistance and obesity, which is present in approximately 50% of women with PCOS. Reproductive function in women with PCOS is strongly dependent on bodyweight and metabolic status. Obesity is associated with an increased risk of infertility and may also have a negative influence on pregnancy outcome. Considering the worldwide epidemic of obesity, clinical problems relating to PCOS may worsen and increase in frequency. Lifestyle interventions resulting in weight loss comprise the most successful strategy to improve symptoms of PCOS. However, many patients fail to lose weight or may quickly regain weight. It is an important challenge to develop effective lifestyle programs and adjuvant pharmacologic treatments in order to improve reproductive and metabolic health among women with PCOS.

Species Comparison of the Role of p38 MAP Kinase in the Female Reproductive System

The p38 mitogen-activated protein kinases (MAPKs) are members of discrete signal transduction pathways that have significant regulatory roles in a variety of biological processes, depending on the cell, tissue and organ type. p38 MAPKs are involved in inflammation, cell growth and differentiation and cell cycle. In the female reproductive system, p38 MAPKs are known to regulate various aspects of the reproductive process such as mammalian estrous and menstrual cycles as well as early pregnancy and parturition. p38 MAPKs have also been implicated in alterations and pathologies observed in the female reproductive system. Therefore, pharmacologic modulation of p38 MAPKs, and inter-connected signaling pathways (e.g., estrogen receptor signaling, c-fos, c-jun), may influence reproductive physiology and function. This article provides a critical, comparative review of available data on the roles of p38 MAPKs in the mammalian female reproductive system and in reproductive pathophysiology in humans and preclinical species. We first introduce fundamental differences and similarities of the mammalian female reproductive system that should be considered by toxicologists and toxicologic pathologists when assessing the effects of new pharmacologic agents on the female reproductive system. We then explore in detail the known roles for p38 MAPKs and related molecules in female reproduction. This foundation is then extended to pathological conditions in which p38 MAPKs are thought to play an integral role.

Ovarian dysfunction and the premenopausal origins of coronary heart disease

OBJECTIVE

The menopausal loss of cyclic ovarian function is believed to contribute to coronary heart disease (CHD). However, ovarian function varies substantially throughout the premenopausal years, with disruptions in hormonal activity ranging from mild to profound. Here we propose our "precocious acceleration" hypothesis, which holds that to the extent cyclic ovarian function affords protection against CHD, even mild ovulatory abnormalities in young women will accelerate development of this disease.

DESIGN

Data relating to the expression and incidence of premenopausal ovarian dysfunction in women and its relationship to CHD are reviewed. Also reviewed are the results from experiments conducted with socially housed cynomolgus monkeys (Macaca fascicularis), focused on the causes, occurrence, and pathobiological sequelae of premenopausal ovarian dysfunction. The implications of the foregoing material for understanding the health of peri- and postmenopausal women are then considered.

RESULTS

Epidemiological and clinical studies indicate that common premenopausal reproductive abnormalities (manifested along a continuum from mild subclinical alterations to complete suppression) are associated with increased risk of CHD. This increased risk is probably mediated by different pathways, depending on whether the reproductive deficits relate to hypoestrogenemia (functional hypothalamic anovulatory syndrome) or hyperandrogenemia (polycystic ovary syndrome). Furthermore, although clinically obvious expressions of these syndromes affect perhaps 10% of premenopausal women, evidence suggests that a much larger number may experience subclinical dysfunction capable of increasing CHD risk.

CONCLUSIONS

Epidemiological data and systematic studies in nonhuman primates provide initial support for the precocious acceleration hypothesis, suggesting that efforts to protect the health of postmenopausal women would best begin during the premenopausal years.

Effect of pre-freezing conditions on semen cryopreservation in rhesus monkeys

Although sperm cryopreservation has been studied in at least 17 non-human primate species, systematic factor optimization for any single species is lacking. Gene banking of non-human primate sperm is still in its infancy. The objective of the present study was to initiate a systematic approach to optimize the process of sperm cryopreservation for rhesus macaques, specifically, factors related to pre-freezing conditions (e.g., straw freezing position, sperm concentration, sperm washing, equilibration methods, and equilibration time periods). Straw position had no effect on post-thaw motility (P=0.193). Sperm concentration was tested in a range from 5 x 10(6)mL(-1) to 5 x 10(8)mL(-1); post-thaw motility of sperm samples frozen at 5 x 10(7)cell mL(-1) (51.0+/-10.6%; mean+/-S.D.) and 5 x 10(8)cell mL(-1) (48.1+/-7.3%) were higher than samples frozen at 5 x 10(6)cells mL(-1) (33.0+/-12.0%, P=0.003). Comparison of motility immediately after thawing between samples with (51.2+/-6.2%) and without washing (53.9+/-6.8%) revealed no differences (P>0.05). However, washing improved sperm forward progression within 1h after thawing, whereas unwashed sperm retained higher post-thaw motility and progression during extended incubation (4h) after thawing (P<0.05). Equilibration methods (with or without pre-cooling) made no difference on post-thaw motility (P>0.05), and the most effective equilibration time was the duration required for samples to acclimate to 4 degrees C prior to freezing. Evaluation and optimization of these pre-freezing conditions will help to minimize sources of injury, maximize survival, and contribute to the development of an optimized cryopreservation protocol for rhesus macaque sperm.

Isolating with physical restraint low status female monkeys during luteal phase might make an appropriate premenstrual depression syndrome model

BACKGROUND

Rhesus monkeys (Macaca mulatta) have a close phylogenetic relationship to humans, and have a similar 28-day menstrual cycle with similar hormonal fluctuations. In this study, we attempt to establish the premenstrual depression syndrome of rhesus monkey (M. mulatta) models by isolation with physical restraint of low social status young female monkeys during their luteal phase.

METHODS

Low social status young female rhesus monkeys (M. mulatta) were isolated with physical restraint during their luteal phase by using a specifically designed isolating-cage. During the entire menses cycle, serum levels of 5-hydroxytrypamine, noradrenalin and adrenalin were detected by capillary zone electrophoresis, and the changes in the serum levels of progesterone, estradiol and prolactin were investigated by radioimmunoassay. At the same time, the pharmaceutical interference effect of Jingqianshu granule, a traditional Chinese medicine specifically used to cure premenstrual depression patients, was tested using this premenstrual depression syndrome monkey model.

RESULTS

After being immured in two consecutive menstrual cycles, monkeys presented depressive symptoms during the premenstrual phase of three consecutive menstrual cycles. The serum contents of the three kinds of monoamine neurotransmitters in depressive monkeys were significantly higher than the normal ones. The serum levels of progesterone and prolactin increased obviously, and a marked change in the pattern of progesterone secretion could be observed. Moreover, the premenstrual depressive symptoms of model group monkeys could not only be cured by Jingqianshu granule, but the higher serum levels of prolactin and monoamine neurotransmitters in these monkeys could be reduced by this herbal medicine. These data were well in line with clinical observations of women with premenstrual depression syndrome.

CONCLUSION

Our results in this study for the first time indicate that isolation with physical restraint of low status young female monkeys during their luteal phase makes an appropriate premenstrual depression syndrome model. This model might potentially facilitate studies on the etiology of premenstrual depression syndrome and the development of better methods for the therapy of this disease.

Polycystic ovary syndrome and its developmental origins

The prenatal testosterone (T)-treated adult female rhesus monkey is one animal model of polycystic ovary syndrome (PCOS) in women, with early prenatal T excess programming a permanent PCOS-like phenotype characterized by luteinizing hormone (LH) hypersecretion from reduced hypothalamic sensitivity to steroid negative feedback and relative insulin excess from increased abdominal adiposity. These combined reproductive and metabolic abnormalities are associated with ovarian hyperandrogenism and follicular arrest in adulthood, as well as premature follicle differentiation and impaired embryo development during gonadotropin therapy for in vitro fertilization (IVF). A second animal model for PCOS, the prenatal T-treated sheep also is characterized by LH hypersecretion from reduced hypothalamic sensitivity to steroid negative feedback, persistent follicles and insulin resistance, but also is associated with intrauterine growth retardation and compensatory growth after birth. The ability of prenatal T excess in both species to alter the developmental trajectory of multiple organ systems in utero provides evidence that the hormonal environment of intrauterine life programs target tissue differentiation, raising the possibility that T excess in human fetal development promotes PCOS in adulthood. Such a hypothesis must include data from clinical studies of PCOS women to clarify the homology between these PCOS-like animal models and PCOS per se in reproductive and metabolic function. Future studies should develop new clinical strategies that improve pregnancy outcome and minimize pregnancy loss in women with disorders of insulin action, including PCOS, obesity and diabetes mellitus as well as minimize transgenerational susceptibility to adult PCOS and its metabolic derangements in male close relatives.

Gonadotrophin-releasing hormone (GnRH) release in marmosets II: pulsatile release of GnRH and pituitary gonadotrophin in adult females

Unlike other mammals, including rodents, Old World primates and humans, common marmosets and probably all other New World primates synthesise and release chorionic gonadotrophin (CG), and not luteinising hormone (LH) from pituitary gonadotrophs. However, little is known about the physiological dynamics of gonadotrophin-releasing hormone (GnRH)-regulated CG release from gonadotrophs and whether such CG release has pulsatile release characteristics similar to those of LH in other mammalian species. Consequently, we performed a series of in vivo and in vitro studies in ovariectomised laboratory rats and female marmosets to compare GnRH-induced pituitary LH and CG release characteristics, respectively. Exogenous GnRH stimulated a slower onset of release of marmoset pituitary CG, both in vivo and in vitro, and induced an approximately 400% greater increase in the duration of marmoset pituitary CG release compared to that for rat LH. Not surprisingly, hypothalamic pulsatile release of GnRH in vivo was not obviously concordant with endogenous episodic changes in circulating levels of CG in marmosets, in contrast to the clear concordance observed between in vivo GnRH and LH release previously demonstrated in rats and other mammals. Pituitary CG release in marmosets thus demonstrates considerable divergence from the timely hypothalamic GnRH-regulated LH release in other female mammals, implying potentially different physiological dynamics in gonadotrophin regulation of marmoset ovarian function.

Effects of rhFSH dose on ovarian follicular response, oocyte recovery and embryo development in rhesus monkeys

The objective was to study the effects of dose of recombinant human follicular stimulating hormone (rhFSH) for ovarian stimulation in rhesus monkeys. Nineteen pubertal and 109 adult female rhesus monkeys were given 37.5, 18, or 9 IU of rhFSH twice-daily for 8 days (total of 600, 300, or 150 IU of rhFSH per cycle, respectively; designated Regimens 1, 2 and 3). Ovarian responses were assessed with ultrasonography, serum concentrations of E2 and FSH, and by in vitro developmental potential (following IVF) of retrieved oocytes. Regimen 1 had more monkeys with very large follicles (diameter>8 mm) than Regimen 2 (P<0.05), which impaired development potential. However, there were no differences between Regimens 1 and 2 in oocyte recovery, whereas Regimen 3 did not elicit superovulation. The developmental potential of embryos obtained from Regimen 2 was higher than that of Regimen 1, as determined by culture to the blastocyst stage in vitro (proportion of blastocysts relative to collected MII oocytes was 55.8% versus 36.8% in pubertal and 63.8% versus 44.2% in adult monkeys; P<0.05 for each), and the results of embryo transfer from Regimen 2 were acceptable. In conclusion, we inferred that the optimal rhFSH dose for ovarian stimulation in rhesus monkeys was a total of 300 IU; this dose should be efficacious for ovarian stimulation as the quality or recovered oocytes was higher and the risk of overstimulation was reduced.

Differential requirements for hematopoietic commitment between human and rhesus embryonic stem cells

Progress toward clinical application of ESC-derived hematopoietic cellular transplantation will require rigorous evaluation in a large animal allogeneic model. However, in contrast to human ESCs (hESCs), efforts to induce conclusive hematopoietic differentiation from rhesus macaque ESCs (rESCs) have been unsuccessful. Characterizing these poorly understood functional differences will facilitate progress in this area and likely clarify the critical steps involved in the hematopoietic differentiation of ESCs. To accomplish this goal, we compared the hematopoietic differentiation of hESCs with that of rESCs in both EB culture and stroma coculture. Initially, undifferentiated rESCs and hESCs were adapted to growth on Matrigel without a change in their phenotype or karyotype. Subsequent differentiation of rESCs in OP9 stroma led to the development of CD34(+)CD45(-) cells that gave rise to endothelial cell networks in methylcellulose culture. In the same conditions, hESCs exhibited convincing hematopoietic differentiation. In cytokine-supplemented EB culture, rESCs demonstrated improved hematopoietic differentiation with higher levels of CD34(+) and detectable levels of CD45(+) cells. However, these levels remained dramatically lower than those for hESCs in identical culture conditions. Subsequent plating of cytokine-supplemented rhesus EBs in methylcellulose culture led to the formation of mixed colonies of erythroid, myeloid, and endothelial cells, confirming the existence of bipotential hematoendothelial progenitors in the cytokine-supplemented EB cultures. Evaluation of four different rESC lines confirmed the validity of these disparities. Although rESCs have the potential for hematopoietic differentiation, they exhibit a pause at the hemangioblast stage of hematopoietic development in culture conditions developed for hESCs.

Assessment of circadian rhythms throughout the menstrual cycle of female rhesus monkeys

Reproductive cyclicity has a significant influence on the regulation of circadian rhythms in rodents. Studies have suggested that there are changes in body temperature rhythms between the follicular and luteal phases in human females. This study examined the effects of menstrual cyclicity on physiological and behavioral circadian rhythms in female rhesus monkeys (Macaca mulatta), an acknowledged biomedical model. Seven unrestrained subjects were implanted with a biotelemetry transmitter to measure body temperature and heart rate and an accelerometer was used to measure physical activity. Water was available ad libitum and drinking was measured via an electronic circuit attached to a water lixit. A video-based task system, the Psychomotor Test System, provided environmental enrichment and delivered a pelletized diet. Mean, phase, and amplitude of each rhythm were calculated. Estrogen and progesterone conjugates were assayed and quantified from daily urine samples to identify follicular and luteal phases of the menstrual cycle. Average circadian variables were then compared between these phases. Heart rate was significantly (P< or =0.05) delayed in the luteal phase. Albeit non-significant, analysis showed a trend toward decreased circadian amplitude of body temperature in the luteal phase.

Genetic and environmental origins of obesity relevant to reproduction

Obesity has a negative impact on reproductive health, particularly in women with polycystic ovarian syndrome (PCOS). Obesity itself is the product of both genetic and environmental influences, although the current 'epidemic' of obesity is largely related to changes in diet and lifestyle. Single gene defects leading to obesity and disordered reproductive function are rare but can are informative about metabolic pathways involved in appetite regulation. There is good evidence that PCOS has an important genetic background, which probably involves the interaction of several genes. The phenotype of PCOS and its impact on reproductive function is profoundly affected by obesity, which, in turn has both genetic and environmental influences. Understanding the genetic basis of PCOS is important but improvements in diet and lifestyle are the best means of improving reproductive function.

Androgen excess fetal programming of female reproduction: a developmental aetiology for polycystic ovary syndrome?

The aetiology of polycystic ovary syndrome (PCOS) remains unknown. This familial syndrome is prevalent among reproductive-aged women and its inheritance indicates a dominant regulatory gene with incomplete penetrance. However, promising candidate genes have proven unreliable as markers for the PCOS phenotype. This lack of genetic linkage may represent both extreme heterogeneity of PCOS and difficulty in establishing a universally accepted PCOS diagnosis. Nevertheless, hyperandrogenism is one of the most consistently expressed PCOS traits. Animal models that mimic fetal androgen excess may thus provide unique insight into the origins of the PCOS syndrome. Many female mammals exposed to androgen excess in utero or during early post-natal life typically show masculinized and defeminized behaviour, ovulatory dysfunction and virilized genitalia, although behavioural and ovulatory dysfunction can coexist without virilized genitalia based upon the timing of androgen excess. One animal model shows particular relevance to PCOS: the prenatally androgenized female rhesus monkey. Females exposed to androgen excess early in gestation exhibit hyperandrogenism, oligomenorrhoea and enlarged, polyfollicular ovaries, in addition to LH hypersecretion, impaired embryo development, insulin resistance accompanying abdominal obesity, impaired insulin response to glucose and hyperlipidaemia. Female monkeys exposed to androgen excess late in gestation mimic these programmed changes, except for LH and insulin secretion defects. In utero androgen excess may thus variably perturb multiple organ system programming and thereby provide a single, fetal origin for a heterogeneous adult syndrome.

Role of the nonhuman primate for research related to women's health

This overview of the current status of medical problems that affect women is related to current studies on pathophysiology and therapeutic interventions using nonhuman primates to demonstrate the utility of the primate model for the study of disease processes in women. The current medical literature on women's health is compared with the literature on nonhuman primate research. The findings reviewed in the articles of ILAR Journal Volume 45 Issue 2 of 2004 are evaluated in the context of the scope and problems associated with disease entities in women. Nonhuman primate research with known information regarding women's disease is discussed, and the utility of the animal model for the study of human disease is highlighted, based on its significant relevance due to similarities of nonhuman primate and human subjects' physiology, metabolism, and responses to therapeutic interventions. Additional advantages of the animal model include the ability to control the experimental environment and the capacity to perform chronic study procedures. These findings allow us to utilize the nonhuman primate as the most relevant model in the animal world for the study of human disease processes.

Sex hormones, insulin sensitivity, and diabetes mellitus

Sex differences and the role of gonadal hormones in modulating insulin sensitivity and glucose tolerance are of increasing interest and importance because of the increasing prevalence of type 2 diabetes mellitus and the metabolic abnormalities associated with aging. Body composition is closely associated with insulin sensitivity, and increased body fat, particularly in the visceral compartment, is a risk factor for developing type 2 diabetes mellitus. Sex differences in body composition and/or insulin sensitivity are evident in humans throughout the lifespan. Ovarian hormones influence insulin sensitivity across the menstrual cycle, during pregnancy, and in the menopausal transition. Similarly, estrogens and progestins used for contraception and hormone replacement therapy affect glucoregulation. Nonhuman primates and humans have similar life histories and reproductive characteristics. As a result, nonhuman primates provide a valuable model for investigating factors related to insulin sensitivity. Studies of nonhuman primates have contributed significantly to our understanding of sex differences and the influence of sex steroids in this context. This brief review surveys present knowledge of the sex differences in body composition, insulin sensitivity, and risk for development of type 2 diabetes mellitus derived from studies in humans and nonhuman primates. The influences of endogenous and exogenous gonadal steroids are emphasized.

Usefulness of the Monkey Model to Investigate the Role of Soy in Postmenopausal Women's Health

Some of the important health issues for postmenopausal women include cardiovascular disease, osteoporosis, breast cancer, and relief of menopausal symptoms. Ovariectomized cynomolgus monkeys (Macaca fascicularis) have many strengths as models for research in this area including a close phylogenetic relationship to humans, similarities in lipid/lipoprotein metabolism and coronary artery anatomy, similar skeletal anatomical and morphological characteristics, mammary glands with similar pathophysiological characteristics, and a 28-day menstrual cycle with similar hormonal fluctuations. Monkeys (macaques) also experience declining ovarian function and irregular menstrual cycles (natural menopause) when they approach 24 to 29 yr of age. However, because of their very short life span after natural menopause, ovariectomized macaques are used to model postmenopausal women. The cynomolgus monkey model has been useful in defining the potential cardiovascular benefits of soy foods and soy supplements; however, it remains unclear whether the observations are generalizable to all women or only to those who, like cynomolgus monkeys, convert the soy isoflavone daidzein to the metabolite equol. Particularly important has been the use of the cynomolgus monkey model to understand the effects of soy on breast health. There is evidence from a cynomolgus monkey trial to suggest that soy/soy phytoestrogens have no estrogen agonist effects for breast. Finally, soy/soy phytoestrogens do not appear to be an adequate alternative to postmenopausal hormone therapy. Nevertheless, important attributes of soy have been identified, and it may have potential as a complementary component to hormone therapy.