Thomas C. Register

Medroxyprogesterone Acetate Antagonizes Inhibitory Effects of Conjugated Equine Estrogens on Coronary Artery Atherosclerosis

Although estrogen replacement therapy is associated with reduced risk of coronary heart disease and reduced extent of coronary artery atherosclerosis, the effects of combined (estrogen plus progestin) hormone-replacement therapy are uncertain. Some observational data indicate that users of combined hormone replacement consisting of continuously administered oral conjugated equine estrogens (CEE) and oral sequentially administered (7 to 14 days per month) medroxyprogesterone acetate (MPA) experience a reduction in risk similar to that of users of CEE alone. However, the effects of combined, continuously administered CEE plus MPA (a prescribing pattern that has gained favor) on the risk of coronary heart disease or atherosclerosis are not known. We studied the effects of CEE (monkey equivalent of 0.625 mg/d) and MPA (monkey equivalent of 2.5 mg/d), administered separately or in combination, on the extent of coronary artery atherosclerosis (average plaque size) in surgically postmenopausal cynomolgus monkeys fed atherogenic diets and treated with these hormones for 30 months. Treatment with CEE alone resulted in atherosclerosis extent that was reduced 72% relative to untreated (estrogen-deficient) controls (P < .004). Atherosclerosis extent in animals treated with CEE plus MPA or MPA alone did not differ from that of untreated controls. Although treatment had marked effects on plasma lipoprotein patterns, statistical adjustment for variation in plasma lipoproteins did not alter the between-group relationships in atherosclerotic plaque size, suggesting that these factors do not explain substantially the atheroprotective effect of estrogen or the MPA-associated antagonism. Although the mechanism(s) remains unclear, we conclude that oral CEE inhibits the initiation and progression of coronary artery atherosclerosis and that continuously administered oral MPA antagonizes this atheroprotective effect.

Adiponectin as a novel determinant of bone mineral density and visceral fat

Growing evidence suggests that positive associations between fat mass (FM) and bone mineral density (BMD) are mediated by not only biomechanical but also biochemical factors. Adiponectin is a novel adipocyte-derived hormone that regulates energy homeostasis and has anti-inflammatory and anti-atherogenic effects. Unlike other adipokines such as leptin, adiponectin levels decrease in obesity and type 2 diabetes. The purpose of our study was to investigate associations of serum adiponectin with BMD (DXA and QCT), FM (DXA and QCT), and serum leptin and soluble leptin receptor levels in 38 women and 42 men (age 39-81, BMI 17-55, 86% with type 2 diabetes). After adjusting for age, gender, race, smoking, and diabetes status, serum adiponectin was inversely associated with areal BMD (r = -0.20 to -0.3, all P < 0.01), volumetric BMD (r = -0.35 to -0.44, all P < 0.01), and visceral fat volume (r = -0.30, P < 0.01). These associations remained significant after adjusting for whole body fat mass. The associations of adiponectin with subcutaneous fat volume, whole body FM, and serum leptin level were not significant (all P > 0.1). These data suggest that adiponectin may play a role in the protective effects of visceral fat on BMD.

Regression of Atherosclerosis in Female Monkeys

The objective of this study was to determine the structural and functional changes that occur in the artery wall in response to plasma lipid lowering and hormone replacement in surgically postmenopausal monkeys with established coronary artery atherosclerosis. Eighty-eight surgically postmenopausal cynomolgus monkeys were fed an atherogenic diet for 24 months and were then allocated into 4 groups: group 1 (n = 20), a baseline necropsy group; group 2 (n = 25), a lipid-lowering diet only; group 3 (n = 22), lipid lowering plus conjugated equine estrogen treatment equivalent to 0.625 mg/d for a woman; and group 4 (n = 21), lipid lowering plus conjugated equine estrogen and medroxyprogesterone acetate treatment (equivalent to 2.5 mg/d for a woman). Treatment was for 30 months. Histomorphometric analysis of perfusion-fixed coronary arteries revealed that plaque size did not change significantly in any of the groups compared with group 1 (P > .20). Plasma lipid lowering permitted coronary artery remodeling to occur (coronary artery and lumen size doubled compared with group 1) (P < .05); however, hormone therapy did not augment remodeling. Quantitative angiographic analysis of coronary artery reactivity revealed that lipid lowering improved dilator responses to acetylcholine by 22 +/- 4% (P = .01) but not to nitroglycerin (P = .23). Hormone replacement did not further affect vascular reactivity to the agonists tested (P > .4), but addition of medroxyprogesterone acetate diminished the beneficial effects of conjugated estrogens on coronary flow reserve (P = .03). In summary, the major arterial sequelae of lipid lowering in female monkeys were artery and lumen enlargement and improved reactivity of large epicardial coronary arteries. Addition of hormone replacement to the dietary modification did not further augment these improvements, except for the dilator capacity of the coronary microcirculation.

Hepatic steatosis and subclinical cardiovascular disease in a cohort enriched for type 2 diabetes: the Diabetes Heart Study.

OBJECTIVES:To explore mechanisms whereby hepatic steatosis may be associated with cardiovascular risk, we investigated cross-sectional relationships between hepatic steatosis, regional fat accumulation, inflammatory biomarkers, and subclinical measures of atherosclerosis in the Diabetes Heart Study.METHODS:The Diabetes Heart Study is a family study of sibling pairs concordant for type 2 diabetes. A subset of 623 randomly selected participants was evaluated for hepatic steatosis, defined as a liver:spleen attenuation ratio of <1.0 by computed tomography. We quantified visceral fat, subcutaneous fat, coronary, aortic, and carotid artery calcium by computed tomography; and carotid atherosclerosis by ultrasound. Associations between the liver:spleen attenuation ratio and these factors were expressed as Spearman correlations.RESULTS:After adjustment for age, race, gender, body mass index, and diabetes status, the liver:spleen attenuation ratio correlated with visceral fat (r = −0.22, P < 0.0001) and subcutaneous fat (r = −0.13, P = 0.031). Hepatic steatosis was associated with lower high-density lipoprotein (r = 0.21, P < 0.0001), higher triglycerides (r = −0.25, P < 0.0001), higher C-reactive protein (r = −0.095, P = 0.004), and lower serum adiponectin (r = 0.34, P < 0.0001). There were no significant associations between the liver:spleen attenuation ratio and coronary, aortic, or carotid calcium, or carotid intimal thickness.CONCLUSIONS:This suggests that hepatic steatosis is less likely a direct mediator of cardiovascular disease and may best be described as an epiphenomenon. The strong correlations between pro-atherogenic biomarkers, visceral fat, and elements of the metabolic syndrome suggest that hepatic steatosis reflects more than general adiposity, but represents a systemic, inflammatory, pro-atherogenic adipose state.

Coronary artery and cultured aortic smooth muscle cells express mRNA for both the classical estrogen receptor and the newly described estrogen receptor beta

Estrogens exhibit potent anti-atherogenic effects through mechanisms which may involve direct effects on the artery. The existence of the classical estrogen receptor (ERalpha) in vascular tissues has been established. Recently a new estrogen receptor (ERbeta) has been discovered which represents a distinct gene product with homology to the classical ERalpha. The purpose of the present study was to determine if ERbeta mRNA is expressed in vascular tissues of female and male primates. Oligonucleotide primers were developed for the specific RT-PCR amplification of ERalpha or ERbeta mRNA. RT-PCR products of the appropriate size for ERalpha and for ERbeta were observed after amplification of RNA isolated from coronary arteries of both male and female cynomolgus monkeys. Similar results were obtained from cultured aortic smooth muscle cells and from monkey reproductive tissues such as ovary and uterus. The relative expression of ERbeta to ERalpha mRNA was greatest in ovary, on the same order of magnitude in monkey vascular tissues and uterus, while the human breast cancer cell line MCF-7 exhibited a very low level of ERbeta relative to ERalpha. Sequence analysis of isolated RT-PCR products showed >95% similarity between the monkey and the published human sequences for both ERalpha and ERbeta. These findings suggest that estrogen may influence vascular gene expression not only through classical ERalpha but also through the newly described ERbeta. These findings also demonstrate the potential for targeting of these receptors in males for prevention or treatment of heart disease.

Functional estrogen receptors in adult articular cartilage: estrogen replacement therapy increases chondrocyte synthesis of proteoglycans and insulin-like growth factor binding protein 2.

OBJECTIVE Epidemiologic studies suggest a protective effect of estrogen replacement therapy (ERT) against the development of knee and hip osteoarthritis, but a potential mechanism for this effect is not known. The present study was done to determine if functional estrogen receptors (ERs) are present in adult articular cartilage and to determine if ERT in vivo affects the production of insulin-like growth factor binding proteins (IGFBPs). METHODS Reverse transcription-polymerase chain reaction, immunoblotting, and immunohistochemistry were used to measure messenger RNA (mRNA) and protein for ERs in adult monkey articular cartilage. Cultured chondrocytes transfected with a reporter construct containing the estrogen response element (ERE/luciferase) were stimulated with estrogen in vitro to determine functional activity of the ERs. IGFBP production was measured by ligand and immunoblotting of conditioned media of cells cultured from control and estrogen-treated surgically menopausal monkeys. Proteoglycan (PG) synthesis was estimated by measurement of 35SO4 incorporation. RESULTS ERa and ERbeta mRNA were present in adult monkey articular cartilage, and ER protein was demonstrated by immunoblotting and immunohistochemistry. Estrogen treatment in vitro of cells transfected with the ERE/luciferase construct resulted in a 2.87-fold increase (P = 0.0163) in reporter production over that of untreated cells. Compared with untreated controls, IGFBP-2 production was significantly increased (P < 0.008) in conditioned media of chondrocytes cultured from monkeys that had received ERT in vivo. Increased IGFBP-2 in these cultures was associated with a 1.41-fold increase (P = 0.02) in the level of sulfate incorporation. CONCLUSION Transcriptionally functional ER are present in adult articular cartilage, and ERT increases the production of IGFBP-2 and the synthesis of PGs by chondrocytes from surgically menopausal monkeys. These results indicate that estrogen can have a direct effect on adult articular cartilage.

Effect of Voluntary Weight Loss on Bone Mineral Density in Older Overweight Women

OBJECTIVES: To examine the effect of diet and exercise‐induced weight loss on bone mineral density in overweight postmenopausal women

Epinephrine Protects Cancer Cells from Apoptosis via Activation of cAMP-dependent Protein Kinase and BAD Phosphorylation

The stress hormone epinephrine is known to elicit multiple systemic effects that include changes in cardiovascular parameters and immune responses. However, information about its direct action on cancer cells is limited. Here we provide evidence that epinephrine reduces sensitivity of cancer cells to apoptosis through interaction with β2-adrenergic receptors. The antiapoptotic mechanism of epinephrine primarily involves phosphorylation and inactivation of the proapoptotic protein BAD by cAMP-dependent protein kinase. Moreover, BAD phosphorylation was observed at epinephrine concentrations found after acute and chronic psychosocial stress. Antiapoptotic signaling by epinephrine could be one of the mechanisms by which stress promotes tumorigenesis and decreases the efficacy of anti-cancer therapies.

Social stress-associated depression in adult female cynomolgus monkeys (Macaca fascicularis).

This paper describes a behavior pattern in adult female cynomolgus monkeys that has several behavioral and physiological characteristics in common with human depression including reduced body fat, low levels of activity, high heart rate, hypothalamic-pituitary-adrenal (HPA) axis disturbances, and increased mortality. Under certain circumstances, this depressive behavior appears more common in socially stressed subordinate, than dominant, females. This is the first animal model of social stress-related depression in females and the first primate model of adult depression. It is important to have a female animal model of depression because women are more likely to experience a clinically significant depression than men, and depression in women is often associated with changes in reproductive system function. This model is particularly useful because these monkeys have menstrual cycles that are similar to those of women, and those that exhibit depressive behavior have relatively low levels of ovarian steroids. These monkeys may be a useful model of reproductive system-associated mood disorders in females.

Behavioral stress accelerates prostate cancer development in mice

Prostate cancer patients have increased levels of stress and anxiety. Conversely, men who take beta blockers, which interfere with signaling from the stress hormones adrenaline and noradrenaline, have a lower incidence of prostate cancer; however, the mechanisms underlying stress-prostate cancer interactions are unknown. Here, we report that stress promotes prostate carcinogenesis in mice in an adrenaline-dependent manner. Behavioral stress inhibited apoptosis and delayed prostate tumor involution both in phosphatase and tensin homolog-deficient (PTEN-deficient) prostate cancer xenografts treated with PI3K inhibitor and in prostate tumors of mice with prostate-restricted expression of c-MYC (Hi-Myc mice) subjected to androgen ablation therapy with bicalutamide. Additionally, stress accelerated prostate cancer development in Hi-Myc mice. The effects of stress were prevented by treatment with the selective β2-adrenergic receptor (ADRB2) antagonist ICI118,551 or by inducible expression of PKA inhibitor (PKI) or of BCL2-associated death promoter (BAD) with a mutated PKA phosphorylation site (BADS112A) in xenograft tumors. Effects of stress were also blocked in Hi-Myc mice expressing phosphorylation-deficient BAD (BAD3SA). These results demonstrate interactions between prostate tumors and the psychosocial environment mediated by activation of an adrenaline/ADRB2/PKA/BAD antiapoptotic signaling pathway. Our findings could be used to identify prostate cancer patients who could benefit from stress reduction or from pharmacological inhibition of stress-induced signaling.