Manuel J. Jayo

Bone mass in female cynomolgus macaques: a cross-sectional and longitudinal study by age.

A cross-sectional study by age was designed to evaluate and describe the bone mineral content (BMC, g) and density (BMD, g/cm2) in a population of female cynomolgus macaques (Macaca fascicularis). Dual-energy X-ray absorptiometry was used to measure, in segments L2-L4 of the lumbar spine, the BMC (BMCs), BMD (BMDs), length, and total-body BMC (BMCTB) in 171 female monkeys ranging in age between 3.7 and 22.0 years. The animals were divided into three age groups: (1) young (<6.5 years, n=51); (2) adult (>6.5 years and <10.5 years, n=63); and (3) mature (>10.5 years, n=57). Young animals had a significantly lower (P<0.05) body weight and shorter trunk length than adult or mature animals. Young animals also had significantly less (P<0.05) BMCS, BMDS, and BMCTB than adult or mature animals, and had significantly shorter (P<0.05) lumbar spine vertebral segments than the other two groups. Longitudinally, 63 animals had repeated lumbar spine scans to examine changes over time. Young animals showed a positive and significant change (P<0.05) in BMCS and BMDS through time, whereas these parameters did not change in adult animals, and mature animals had a trend towards bone loss through time. Densitometric results suggested that peak bone mass in the lumbar spine was achieved by 9 years of age. Radiographic and dental criteria were developed to identify animals that had reached peak bone mass, and the combined radiographic and dental scoring system reliably identified animals 9 years and older. Female cynomolgus macaques 9 years old or older are recommended for investigations of bone remodeling and associated conditions, such as osteoporosis.

The effects of hormone replacement therapy on carbohydrate metabolism and cardiovascular risk factors in surgically postmenopausal cynomolgus monkeys

Controversy exists regarding the effects of estrogen and estrogen/progestin replacement therapies on glucose tolerance and insulin resistance. Also unknown are whether changes in glucose tolerance and insulin resistance with hormone therapy affect arterial glycation and atherosclerosis. We studied ovariectomized female monkeys fed a lipid-lowering diet and given either no hormone replacement therapy (n = 25) or conjugated equine estrogens (CEE) alone (n = 22) or combined with medroxyprogesterone acetate ([MPA] n = 21) for 30 months. Monkeys receiving combined hormone replacement had significantly higher fasting glucose and insulin levels and higher insulin responses to a glucose challenge compared with controls or those given estrogen alone. Monkeys given estrogen-only therapy had lower body weights, lower measures of abdominal adiposity, and decreased serum androgen concentrations. However, due to the effective dietary lipid decrease, there was no additional effect of hormone treatment on atherosclerosis. Also, there was no correlation between either arterial glycation or insulin levels and atherosclerosis extent. Thus, although there were adverse effects of combined hormone replacement therapy on carbohydrate metabolism, we were unable to determine whether these effects altered the extent of atherosclerosis.

Oral contraceptive treatment inhibits the normal acquisition of bone mineral in skeletally immature young adult female monkeys

The purpose of the present study was to determine the effects of oral contraceptive therapy on bone density and serum markers of bone metabolism in a prospective, longitudinal study of young adult female cynomolgus monkeys. Two hundred and seven intact cynomolgus monkeys were randomized to two groups, and fed an atherogenic diet containing either no drug (Control) or a triphasic oral contraceptive regimen (Contraceptive). Measurements of bone density were carried out by dual-energy X-ray absorptiometry at 10-month intervals (0, 10, and 20 months) and serum bone biomarkers were determined at 5-month intervals over the 20-month time course. No significant differences in these variables were observed prior to treatment. Both groups of animals gained bone mineral during the study, indicating that peak bone mass had not been reached at baseline. Contraceptive-treated animals gained less spinal (lumbar vertebrae 2–4) bone mineral content and density and less whole-body bone mineral content than Controls over the course of the study. Significant depressive effects of contraceptive treatment on gains in BMC and BMD were observed during each 10-month interval of the study. Bone metabolism was inhibited in the Contraceptive group, as reflected by marked reductions (∼ 40%) in serum osteocalcin and alkaline phosphatase levels along with moderate reductions in serum acid phosphatase and calcium. The results suggest that triphasic oral contraceptive treatment of young adult female monkeys that have not reached peak bone mass inhibits net bone accretion and/or growth by reducing bone metabolism. Thus, prolonged continuous oral contraceptive use in skeletally immature females may lead to a lower peak bone mass — an effect which could increase the risk of fractures in later life.

Accuracy and precision of lumbar bone mineral content by dual-energy X-ray absorptiometry in live female monkeys

SummaryDual-energy X-ray absorptiometry (DXA) was used to determine thein vivo bone mineral content (BMC) of lumbar vertebrae in 20 feral adult female cynomolgus macaques (Macaca fascicularis). The ash weight of the third lumbar vertebra (L3) was compared to the measured L3BMC of thein vivo DXA analyses. Correlation between the estimated L3BMC by DXA and the actual ash weight was significant (r=0.965,P<0.01); however, DXA methodology underestimated ash weight on the average of 6.2%. Correlation was significant between two sequentialin vivo DXA scans (r=0.988,P<0.001). Noninvasivein vivo DXA was a fast, precise, and effective method for measuring the lumbar BMC in female cynomolgus macaques.

Effects of oestrogens and progestogens on coronary atherosclerosis and osteoporosis of monkeys.

We have used the cynomolgus macaque as a model for the study of the effects of endogenous and exogenous sex steroid hormones on atherosclerosis and osteoporosis. As in human beings, premenopausal female cynomolgus macaques develop much less extensive coronary artery atherosclerosis than their male counterparts. Furthermore, surgical menopause results in a more atherogenic plasma lipoprotein pattern and an approximate doubling of atherosclerosis extent. Frequent pregnancy, a hyperoestrogenic state, results in an approximate 50% reduction in atherosclerosis extent. Physiological replacement with 17 beta-oestradiol alone or in combination with progesterone prevents the increase in coronary artery atherosclerosis extent associated with ovariectomy. This effect is independent of plasma lipoprotein concentrations and appears to be accounted for, at least in part, by an inhibitory effect of oestrogen replacement therapy on the uptake and degradation of LDL by the artery wall. Also, as in human beings, treatment with certain types of combination oral contraceptives results in marked decreases in plasma HDL-C concentration. Nonetheless, coronary artery atherosclerosis extent is reduced in monkeys by oral contraceptive treatment, and this effect is most pronounced among animals at highest risk due to theoretically adverse plasma lipoprotein profiles. It appears that, as with oestrogen replacement therapy, this effect can be accounted for, at least in part, by an inhibition of the uptake and degradation of low density lipoprotein by the artery wall. The monkey also appears to be a good model for studies of postmenopausal bone loss. As in women, surgical menopause results in significant diminution of bone mineral density and bone mineral content. Also, serum biomarkers of bone turnover (total alkaline phosphatase, acid phosphatase, tartrate-resistant acid phosphatase and osteocalcin) are increased in surgically postmenopausal monkeys, indicating increased bone turnover resulting from the surgical menopause. These increases in bone loss and indices of bone turnover were prevented by physiological oestrogen replacement therapy. Cynomolgus monkeys seem to be exceptionally useful models for studies of the effects of sex steroid hormones on atherosclerosis and osteoporosis, two major public health problems in postmenopausal women.

Effects on bone of oral hormone replacement therapy initiated 2 years after ovariectomy in young adult monkeys

The purpose of this study was to determine the effects of oral estrogen replacement therapy with conjugated equine estrogens (CEE), alone or in combination with continuous medroxyprogesterone acetate (MPA), on lumbar spine bone mineral content (BMC) and density (BMD) and on serum chemistries in ovariectomized cynomolgus monkeys when therapy is initiated following a 2 year hypoestrogenic period. Study design was done in the form of a randomized, placebo-controlled, nonhuman primate paraclinical trial. Monkeys were subjects in an experiment designed to study the effects of a lipid-lowering diet combined with hormone replacement therapy on atherosclerosis. Initially, they were ovariectomized and fed a high-fat diet for 24 months. They were then were allocated to three treatment groups by stratified randomization and were fed a diet containing reduced dietary fat for an additional 28 months. Treatment groups consisted of: (1) an untreated group (ovx, n = 24); (2) a CEE-treated group (CEE, n = 19); and (3) a CEE plus continuous MPA group (CEE + MPA, n = 20). Lumbar spine BMC and BMD values were measured by dual-energy x-ray absorptiometry at baseline and 4, 10, 16, 22, and 28 months of treatment. Serum chemistries were relevant to bone metabolism at 22 and 28 months. Rates of gain in BMC and BMD were greater (p < 0.05) in hormone-supplemented animals (groups 2 and 3) than in untreated ovx animals during the first 16 months of treatment, resulting in increased BMC and BMD measurements in these groups. Serum markers of bone metabolism were significantly lower (p < 0.05) in the hormone-treated groups (groups 2 and 3) compared with ovx animals after 22 and 28 months of treatment, indicating reductions in bone turnover rate. Oral estrogen replacement with CEE at doses similar to those taken by women leads to significantly increased BMC and BMD in monkeys, even when therapy is begun 2 years after ovariectomy. Most of the increase occurred during the first 16 months of treatment. The addition of MPA to the CEE regimen provided no additional benefit.