The androgen receptor confers protection against diet-induced atherosclerosis, obesity, and dyslipidemia in female mice.

Androgens have important cardiometabolic actions in males, but their metabolic role in females is unclear. To determine the physiologic androgen receptor (AR)-dependent actions of androgens on atherogenesis in female mice, we generated female AR-knockout (ARKO) mice on an atherosclerosis-prone apolipoprotein E (apoE)-deficient background. After 8 weeks on a high-fat diet, but not on a normal chow diet, atherosclerosis in aorta was increased in ARKO females (+59% vs. control apoE-deficient mice with intact AR gene). They also displayed increased body weight (+18%), body fat percentage (+62%), and hepatic triglyceride levels, reduced insulin sensitivity, and a marked atherogenic dyslipidemia (serum cholesterol, +52%). Differences in atherosclerosis, body weight, and lipid levels between ARKO and control mice were abolished in mice that were ovariectomized before puberty, consistent with a protective action of ovarian androgens mediated via the AR. Furthermore, the AR agonist dihydrotestosterone reduced atherosclerosis (-41%; thoracic aorta), subcutaneous fat mass (-44%), and cholesterol levels (-35%) in ovariectomized mice, reduced hepatocyte lipid accumulation in hepatoma cells in vitro, and regulated mRNA expression of hepatic genes pivotal for lipid homeostasis. In conclusion, we demonstrate that the AR protects against diet-induced atherosclerosis in female mice and propose that this is mediated by modulation of body composition and lipid metabolism.

Androgen receptor-dependent and independent atheroprotection by testosterone in male mice.

The atheroprotective effect of testosterone is thought to require aromatization of testosterone to estradiol, but no study has adequately addressed the role of the androgen receptor (AR), the major pathway for the physiological effects of testosterone. We used AR knockout (ARKO) mice on apolipoprotein E-deficient background to study the role of the AR in testosterone atheroprotection in male mice. Because ARKO mice are testosterone deficient, we sham operated or orchiectomized (Orx) the mice before puberty, and Orx mice were supplemented with placebo or a physiological testosterone dose. From 8 to 16 wk of age, the mice consumed a high-fat diet. In the aortic root, ARKO mice showed increased atherosclerotic lesion area (+80%, P < 0.05). Compared with placebo, testosterone reduced lesion area both in Orx wild-type (WT) mice (by 50%, P < 0.001) and ARKO mice (by 24%, P < 0.05). However, lesion area was larger in testosterone-supplemented ARKO compared with testosterone-supplemented WT mice (+57%, P < 0.05). In WT mice, testosterone reduced the presence of a necrotic core in the plaque (80% among placebo-treated vs. 12% among testosterone-treated mice; P < 0.05), whereas there was no significant effect in ARKO mice (P = 0.20). In conclusion, ARKO mice on apolipoprotein E-deficient background display accelerated atherosclerosis. Testosterone treatment reduced atherosclerosis in both WT and ARKO mice. However, the effect on lesion area and complexity was more pronounced in WT than in ARKO mice, and lesion area was larger in ARKO mice even after testosterone supplementation. These results are consistent with an AR-dependent as well as an AR-independent component of testosterone atheroprotection in male mice.

A single early postnatal estradiol injection affects morphology and gene expression of the ovary and parametrial adipose tissue in adult female rats.

Events during early life can affect reproductive and metabolic functions in adulthood. We evaluated the programming effects of a single early postnatal estradiol injection (within 3h after birth) in female rats. We assessed ovarian and parametrial adipose tissue morphology, evaluated gene expression related to follicular development and adipose tissue metabolism, and developed a non-invasive volumetric estimation of parametrial adipose tissue by magnetic resonance imaging. Estradiol reduced ovarian weight, increased antral follicle size and number of atretic antral follicles, and decreased theca interna thickness in atretic antral follicles. Adult estradiol-injected rats also had malformed vaginal openings and lacked corpora lutea, confirming anovulation. Estradiol markedly reduced parametrial adipose tissue mass. Adipocyte size was unchanged, suggesting reduced adipocyte number. Parametrial adipose tissue lipoprotein lipase activity was increased. In ovaries, estradiol increased mRNA expression of adiponectin, complement component 3, estrogen receptor α, and glucose transporter 3 and 4; in parametrial adipose tissue, expression of complement component 3 was increased, expression of estrogen receptor α was decreased, and expression of leptin, lipoprotein lipase, and hormone-sensitive lipase was unaffected. These findings suggest that early postnatal estradiol exposure of female rats result in long-lasting effects on the ovary and parametrial adipose tissue at adult age.

Early postnatal oestradiol exposure causes insulin resistance and signs of inflammation in circulation and skeletal muscle.

Early postnatal events can predispose to metabolic and endocrine disease in adulthood. In this study, we evaluated the programming effects of a single early postnatal oestradiol injection on insulin sensitivity in adult female rats. We also assessed the expression of genes involved in inflammation and glucose metabolism in skeletal muscle and adipose tissue and analysed circulating inflammation markers as possible mediators of insulin resistance. Neonatal oestradiol exposure reduced insulin sensitivity and increased plasma levels of monocyte chemoattractant protein-1 (MCP-1) and soluble intercellular adhesion molecule-1. In skeletal muscle, oestradiol increased the expression of genes encoding complement component 3 (C3), Mcp-1, retinol binding protein-4 (Rbp4) and transforming growth factor beta1 (Tgfbeta1). C3 and MCP-1 are both related to insulin resistance, and C3, MCP-1 and TGFbeta1 are also involved in inflammation. Expression of genes encoding glucose transporter-4 (Glut 4), carnitine-palmitoyl transferase 1b (Cpt1b), peroxisome proliferator-activated receptor delta (Ppard) and uncoupling protein 3 (Ucp3), which are connected to glucose uptake, lipid oxidation, and energy uncoupling, was down regulated. Expression of several inflammatory genes in skeletal muscle correlated negatively with whole-body insulin sensitivity. In s.c. inguinal adipose tissue, expression of Tgfbeta1, Ppard and C3 was decreased, while expression of Rbp4 and Cpt1b was increased. Inguinal adipose tissue weight was increased but adipocyte size was unaltered, suggesting an increased number of adipocytes. We suggest that early neonatal oestrogen exposure may reduce insulin sensitivity by inducing chronic, low-grade systemic and skeletal muscle inflammation and disturbances of glucose and lipid metabolism in skeletal muscle in adulthood.

Hyperinsulinemic rats are normotensive but sensitized to angiotensin II.

The effect of insulin on blood pressure (BP) is debated, and an involvement of an activated renin-angiotensin aldosterone system (RAAS) has been suggested. We studied the effect of chronic insulin infusion on telemetry BP and assessed sympathetic activity and dependence of the RAAS. Female Sprague-Dawley rats received insulin (2 units/day, INS group, n = 12) or insulin combined with losartan (30 mg.kg(-1).day(-1), INS+LOS group, n = 10), the angiotensin II receptor antagonist, for 6 wk. Losartan-treated (LOS group, n = 10) and untreated rats served as controls (n = 11). We used telemetry to measure BP and heart rate (HR), and acute ganglion blockade and air-jet stress to investigate possible control of BP by the sympathetic nervous system. In addition, we used myograph technique to study vascular function ex vivo. The INS and INS+LOS groups developed euglycemic hyperinsulinemia. Insulin did not affect BP but increased HR (27 beats/min on average). Ganglion blockade reduced mean arterial pressure (MAP) similarly in all groups. Air-jet stress did not increase sympathetic reactivity but rather revealed possible blunting of the stress response in hyperinsulinemia. Chronic losartan markedly reduced 24-h-MAP in the INS+LOS group (-38 +/- 1 mmHg P < 0.001) compared with the LOS group (-18 +/- 1 mmHg, P

Postnatal testosterone exposure results in insulin resistance, enlarged mesenteric adipocytes, and an atherogenic lipid profile in adult female rats: comparisons with estradiol and dihydrotestosterone.

Postnatal events contribute to features of the metabolic syndrome in adulthood. In this study, postnatally administered testosterone reduced insulin sensitivity and increased the mesenteric fat depot, the size of mesenteric adipocytes, serum levels of total cholesterol, low-density lipoprotein cholesterol, and triglycerides, and the atherogenic index in adult female rats. To assess the involvement of estrogen and androgen receptors in these programming effects, we compared testosterone-exposed rats to rats exposed to estradiol or dihydrotestosterone (DHT). Estradiol-treated rats had lower insulin sensitivity than testosterone-treated rats and, like those rats, had enlarged mesenteric adipocytes and increased triglyceride levels. DHT also reduced insulin sensitivity but did not mimic the other metabolic effects of testosterone. All treated rats were probably anovulatory, but only those treated with testosterone had reduced testosterone levels. This study confirms our previous finding that postnatal administration of testosterone reduces insulin sensitivity in adult female rats and shows that this effect is accompanied by unfavorable changes in mesenteric fat tissue and in serum lipid levels. The findings in the estradiol and DHT groups suggest that estrogen receptors exert stronger metabolic programming effects than androgen receptors. Thus, insults such as sex hormone exposure in early life may have long-lasting effects, thereby creating a predisposition to disturbances in insulin sensitivity, adipose tissue, and lipid profile in adulthood.

Maternal taurine supplementation in the late pregnant rat stimulates postnatal growth and induces obesity and insulin resistance in adult offspring.

An adequate supply of taurine during fetal life is important for normal beta-cell development and insulin action. An altered availability of taurine may programme glucose metabolism in utero and result in type 2 diabetes in adult age. We examined whether maternal taurine supplementation in late pregnant rats affects postnatal growth, adult body composition, insulin sensitivity and endogenous insulin secretion in intrauterine growth restricted (IUGR) and normal offspring. Uterine artery ligation or sham operations were performed on gestational day (GD) 19. Taurine supplementation was given to half of the dams from GD 18 until term, resulting in four groups of offspring: sham (n = 22), sham/taurine (n = 22), IUGR (n = 22) and IUGR/taurine (n = 24). The offspring were studied at 12 weeks of age. In offspring with normal birth weight, fetal taurine supplementation markedly stimulated postnatal growth. In sham/taurine females, fat depots, plasma free fatty acid and leptin concentrations were increased, and insulin sensitivity was reduced. Insulin sensitivity was unaltered in IUGR and IUGR/taurine offspring. However, whereas IUGR offspring showed little catch-up growth, 50% of IUGR/taurine animals displayed complete catch-up at 12 weeks of age, and these animals had increased fat depots and reduced insulin sensitivity. In conclusion, taurine supplementation in late gestation resulted in accelerated postnatal growth, which was associated with adult obesity and insulin resistance in both IUGR and normal offspring. This effect was particularly evident in females. These data suggest that fetal taurine availability is an important determinant for postnatal growth, insulin sensitivity and fat accumulation.

Prenatal exposure to interleukin-6 results in hypertension and alterations in the renin-angiotensin system of the rat.

Cytokines are emerging as important in developmental processes. They may induce alterations in normal gene expression patterns, activate angiotensinogen transcription, or alter expression of the renin-angiotensin system (RAS). To determine whether prenatal exposure to interleukin-6 (IL-6) influences gene expression of the intrarenal RAS and contributes to renal dysfunction and hypertension in adulthood, we exposed female rats to IL-6 early (EIL-6 females) and late (LIL-6 females) in pregnancy and analysed blood pressure in the offspring at 5-20 weeks of age. Renal fluid and electrolyte excretion was assessed in clearance experiments, mRNA expression by real-time PCR, and protein levels by Western blot. Systolic pressure was increased at 5 weeks in IL-6 females and at 11 weeks in males. Circulatory RAS levels were increased in all IL-6 females, but angiotensin-1-converting enzyme (ACE) activity was increased only in LIL-6 females. LIL-6 males and IL-6 females showed decreased urinary flow rate and urinary sodium and potassium excretion. Dopamine excretion was decreased IL-6 females. In adult renal cortex, renin expression was increased in all IL-6 females, but angiotensinogen mRNA was increased only in LIL-6 females; AT(1) receptor (AT(1)-R) mRNA and protein levels were increased in LIL-6 females, whereas AT(2) receptor (AT(2)-R) levels were decreased in LIL-6 females and EIL-6 males. In adult renal medulla, AT(1)-R protein levels were increased in LIL-6 females, and AT(2)-R mRNA and protein levels were decreased in EIL-6 males and LIL-6 females. Prenatal IL-6 exposure may cause hypertension by altering the renal and circulatory RAS and renal fluid and electrolyte excretion, especially in females.