Reproductive Profile of Neuronal Androgen Receptor Knockout Female Mice With a Low Dose of DHT

Hyperandrogenism and polycystic ovarian syndrome result from the imbalance or increase of androgen levels in females. Androgen receptor (AR) mediates the effects of androgens, and this study examines whether neuronal AR plays a role in reproduction under normal and increased androgen conditions in female mice. The neuron-specific AR knockout (KO) mouse (SynARKO) was generated from a female mouse (synapsin promoter driven Cre) and a male mouse (Ar fl/y). Puberty onset and the levels of reproductive hormones such as LH, FSH, testosterone, and estradiol were comparable between the control and the SynARKO mice. There were no differences in cyclicity and fertility between the control and SynARKO mice, with similar impairment in both groups on DHT treatment. Neuronal AR KO, as in this SynARKO mouse model, did not alleviate the infertility associated with DHT treatment. These studies suggest that neuronal AR KO neither altered reproductive function under physiological androgen levels, nor restored fertility under hyperandrogenic conditions.

Neuronal AR Regulates Glucose Homeostasis and Energy Expenditure in Lean Female Mice With Androgen Excess

Hyperandrogenemia and polycystic ovary syndrome are a result of the imbalance of androgen levels in females. Androgen receptor (Ar) mediates the effect of androgen, and this study examines how neuronal Ar in the central nervous system mediates metabolism under normal and increased androgen conditions in female mice. The neuron-specific ARKO mouse (SynARKO) was created from female (Ar fl/wt; synapsin promoter driven Cre) and male (Ar fl/y) mice. A glucose tolerance test revealed impaired glucose tolerance that was partially alleviated in the SynARKO-dihydrotestosterone (DHT) mice compared with Con-DHT mice after 4 months of DHT treatment. Heat production and food intake was higher in Con-DHT mice than in Con-veh mice; these effects were not altered between SynARKO-veh and SynARKO-DHT mice, indicating that excess androgens may partially alter calorie intake and energy expenditure in females via the neuronal Ar. The pAkt/Akt activity was higher in the hypothalamus in Con-DHT mice than in Con-veh mice, and this effect was attenuated in SynARKO-DHT mice. Western blot studies show that markers of inflammation and microglia activation, such as NF-kB p-65 and IBA1, increased in the hypothalamus of Con-DHT mice compared with Con-veh. These studies suggest that neuronal Ar mediates the metabolic impacts of androgen excess in females.

Androgen-induced insulin resistance is ameliorated by deletion of hepatic androgen receptor in females

Androgen excess is one of the most common endocrine disorders of reproductive-aged women, affecting up to 20% of this population. Women with elevated androgens often exhibit hyperinsulinemia and insulin resistance. The mechanisms of how elevated androgens affect metabolic function are not clear. Hyperandrogenemia in a dihydrotestosterone (DHT)-treated female mouse model induces whole body insulin resistance possibly through activation of the hepatic androgen receptor (AR). We investigated the role of hepatocyte AR in hyperandrogenemia-induced metabolic dysfunction by using several approaches to delete hepatic AR via animal-, cell-, and clinical-based methodologies. We conditionally disrupted hepatocyte AR in female mice developmentally (LivARKO) or acutely by tail vein injection of an adeno-associated virus with a liver-specific promoter for Cre expression in AR^fl/fl mice (adLivARKO). We observed normal metabolic function in littermate female Control (AR^fl/fl ) and LivARKO (AR^fl/fl ; Cre^+/- ) mice. Following chronic DHT treatment, female Control mice treated with DHT (Con-DHT) developed impaired glucose tolerance, pyruvate tolerance, and insulin tolerance, not observed in LivARKO mice treated with DHT (LivARKO-DHT). Furthermore, during an euglycemic hyperinsulinemic clamp, the glucose infusion rate was improved in LivARKO-DHT mice compared to Con-DHT mice. Liver from LivARKO, and primary hepatocytes derived from LivARKO, and adLivARKO mice were protected from DHT-induced insulin resistance and increased gluconeogenesis. These data support a paradigm in which elevated androgens in females disrupt metabolic function via hepatic AR and insulin sensitivity was restored by deletion of hepatic AR.

Metabolic Dyslipidemia and Cardiovascular Outcomes in Type 2 Diabetes Mellitus: Findings From the Look AHEAD Study

Background

Metabolic dyslipidemia (high triglyceride) and low high‐density lipoprotein cholesterol (HDL‐C) is highly prevalent in type 2 diabetes mellitus (T2DM). The extent to which diabetes mellitus–related abnormalities in the triglyceride–HDL‐C profile associates with cardiovascular disease (CVD) risk is incompletely understood. We evaluated the associations of triglyceride and HDL‐C status with CVD outcomes in individuals with T2DM.

Methods and Results

We analyzed data from 4199 overweight/obese adults with T2DM free of CVD with available data on triglyceride and HDL‐C at baseline (2001–2004) in the Look AHEAD (Action for Health in Diabetes) study. We used Cox proportional models to estimate hazard ratios (HRs) and 95% CIs of: (1) composite CVD outcome (myocardial infarction, stroke, hospitalization for angina, and/or death from cardiovascular causes); (2) coronary artery disease events; and (3) cerebrovascular accidents (stroke). Of the 4199 participants, 62% (n=2600) were women, with a mean age of 58 years (SD, 7), and 40% (n=1659) had metabolic dyslipidemia at baseline. Over a median follow‐up of 9.5 years (interquartile range, 8.7–10.3), 500 participants experienced the composite CVD outcome, 396 experienced coronary artery disease events, and 100 experienced stroke. Low HDL‐C was associated with higher hazards of the composite CVD outcome (HR, 1.36; 95% CI, 1.12–1.64 [P=0.002]) and coronary artery disease events (HR, 1.46; 95% CI, 1.18–1.81 [P=0.001]) but not stroke (HR, 1.38; 95% CI, 0.90–2.11 [P=0.140]). Compared with patients with normal triglyceride and normal HDL, participants with metabolic dyslipidemia had higher risks of the composite CVD outcome (HR, 1.30; 95% CI, 1.03–1.63 [P=0.025]) and coronary artery disease events (HR, 1.48; 95% CI, 1.14–1.93 [P=0.003]) but not stroke (HR, 1.23; 95% CI, 0.74–2.05 [P=0.420]).

Conclusions

In a large sample of overweight/obese individuals with T2DM, metabolic dyslipidemia was associated with higher risks of CVD outcomes. Our findings highlight the necessity to account for metabolic dyslipidemia in CVD risk stratification among patients with T2DM.

Registration

URL: https://www.lookaheadtrial.org; Unique identifier: NCT00017953.

Increased mTOR activity and metabolic efficiency in mouse and human cells containing the African-centric tumor-predisposing p53 variant Pro47Ser

The Pro47Ser variant of p53 (S47) exists in African-descent populations and is associated with increased cancer risk in humans and mice. Due to impaired repression of the cystine importer Slc7a11, S47 cells show increased glutathione (GSH) accumulation compared to cells with wild -type p53. We show that mice containing the S47 variant display increased mTOR activity and oxidative metabolism, as well as larger size, improved metabolic efficiency, and signs of superior fitness. Mechanistically, we show that mTOR and its positive regulator Rheb display increased association in S47 cells; this is due to an altered redox state of GAPDH in S47 cells that inhibits its ability to bind and sequester Rheb. Compounds that decrease glutathione normalize GAPDH-Rheb complexes and mTOR activity in S47 cells. This study reveals a novel layer of regulation of mTOR by p53, and raises the possibility that this variant may have been selected for in early Africa.

Gonadotrope androgen receptor mediates pituitary responsiveness to hormones and androgen-induced subfertility

Many women with hyperandrogenemia suffer from irregular menses and infertility. However, it is unknown whether androgens directly affect reproduction. Since animal models of hyperandrogenemia-induced infertility are associated with obesity, which may impact reproductive function, we have created a lean mouse model of elevated androgen using implantation of low dose dihydrotestosterone (DHT) pellets to separate the effects of elevated androgen from obesity. The hypothalamic-pituitary-gonadal axis controls reproduction. While we have demonstrated that androgen impairs ovarian function, androgen could also disrupt neuroendocrine function at the level of brain and/or pituitary to cause infertility. To understand how elevated androgens might act on pituitary gonadotropes to influence reproductive function, female mice with disruption of the androgen receptor (Ar) gene specifically in pituitary gonadotropes (PitARKO) were produced. DHT treated control mice with intact pituitary Ar (Con-DHT) exhibit disrupted estrous cyclicity and fertility with reduced pituitary responsiveness to GnRH at the level of both calcium signaling and LH secretion. These effects were ameliorated in DHT treated PitARKO mice. Calcium signaling controls GnRH regulation of LH vesicle exotocysis. Our data implicated upregulation of GEM (a voltage-dependent calcium channel inhibitor) in the pituitary as a potential mechanism for androgen's pathological effects. These results demonstrate that gonadotrope AR, as an extra-ovarian regulator, plays an important role in reproductive pathophysiology.

SUN-110 The Role Of RasD2 In Metabolism And Obesity

RasD2 encodes for a small GTP-binding protein that was initially identified and studied for its highly enriched expression in the striatum, where its expression is regulated by thyroid hormone and dopamine. Subsequently RasD2 has been shown to also be expressed in other tissues, including pancreatic islets, kidney, and heart. Microarray analysis comparing gene expression of islets from C57BL/6J mice fed a high-fat diet (HFD) vs regular chow found that RasD2 expression was increased in islets of mice fed a HFD, and RasD2 expression has been shown to increase in response to various insulin secretagogues, like imidazoline and sulfonylurea. However the downstream effects of these changes in RasD2 expression have never been fully elucidated. The aim of this project is to more fully characterize the role of RasD2 in metabolism. C57BL/6J mice with deletion of RasD2 were fed HFD (45% kcal fat) or regular chow and compared to their WT littermates. Glucose homeostasis was assessed with intraperitoneal glucose tolerance test and body composition was measured using ¹H-Magnetic Resonance Spectroscopy. When fed a regular diet, RasD2 KO mice had slightly lower body weight, but had similar body composition and no significant change in glucose tolerance when compared to WT littermates. When fed HFD, RasD2 KO and WT mice both gained a similar amount of body weight and developed glucose intolerance, but KO mice had less fat, and a higher proportion of lean mass. Using QPCR and western blot, we showed that RasD2 is expressed in adipose tissue, and that RasD2 expression increases in 3T3-L1 cells during differentiate into adipocytes. These data suggest a role for RasD2 in regulates energy homeostasis and/or adipogenesis, which may prove to be an attractive target in the battle against obesity. Ongoing studies will elucidate a more detailed mechanism.

Pancreatic islet neuropeptide Y overexpression has minimal effect on islet morphology and β-cell adaptation to high-fat diet

Neuropeptide Y (NPY) is highly expressed in the hypothalamus, where it regulates feeding and energy homeostasis. Interestingly, NPY and its receptors are also expressed in peripheral tissues with roles in metabolism, including pancreatic islets. In islets, NPY is known to suppress insulin secretion acutely. In addition, the role of NPY in β-cell de-differentiation has been postulated recently. Therefore, we studied transgenic mice expressing NPY under rat insulin promoter (TG) to determine the effects of chronic up-regulation of NPY on islet morphology and function. NPY levels were 25 times higher in islets of TG mice compared with wild-type (WT) littermates, whereas no differences in NPY expression were noted in the brains of TG and WT mice. Islet NPY secretion was 2.3-fold higher in TG compared with WT mice. There were no significant changes in body weight, glucose tolerance, or insulin sensitivity in TG mice fed regular rodent diet or high-fat diet (HF). Islet β-cell area was comparable between TG and WT mice both on regular rodent and HF diets, indicating that NPY overexpression is insufficient to alter β-cell maturation or the compensatory increase of β-cell area on HF. One abnormality noted was that the glucose-stimulated insulin secretion in islets isolated from TG was reduced compared with those from WT mice on HF diet. Overall, an increase in islet NPY level has little impact on islet function and is insufficient to affect glucose homeostasis in mice.

Adiponectin complexes in human cerebrospinal fluid: distinct complex distribution from serum

AIMS/HYPOTHESIS

Adiponectin is an adipocyte-derived secretory factor that is specifically produced in adipocytes. It exerts effects on energy homeostasis via peripheral and central mechanisms. However, it is not clear whether adiponectin crosses the blood-brain barrier in humans. In serum, adiponectin circulates in several different complexes, each of which has distinct functions. Here, we wanted to test whether adiponectin can be found in human cerebrospinal fluid (CSF) and whether specific adiponectin complexes are enriched in CSF compared with peripheral serum samples. We also wanted to establish whether there is a sex-related difference with regard to the distribution of adiponectin oligomers in CSF.

MATERIALS AND METHODS

We studied 22 subjects (11 men, 11 women) in this study. Their average BMI was 28.0+/-4.7 kg/m2; average age was 70+/-7 years.

RESULTS

Analysis of total adiponectin revealed that adiponectin protein is present in human CSF at approximately 0.1% of serum concentration. The distribution of adiponectin oligomers differs considerably in CSF from that of serum within matched samples from the same patients. Only the adiponectin trimeric and low-molecular-mass hexameric complexes are found in CSF, with a bias towards the trimeric form in most patients. Male subjects have a higher CSF:serum ratio of total adiponectin (p<0.05; n=20) and have slightly higher trimer levels in serum and CSF than female subjects.

CONCLUSIONS/INTERPRETATION

We conclude that the adiponectin trimer is the predominant oligomer in human CSF.

Transgenic expression of syndecan-1 uncovers a physiological control of feeding behavior by syndecan-3

Transgenic expression in the hypothalamus of syndecan-1, a cell surface heparan sulfate proteoglycan (HSPG) and modulator of ligand-receptor encounters, produces mice with hyperphagia and maturity-onset obesity resembling mice with reduced action of alpha melanocyte stimulating hormone (alphaMSH). Via their HS chains, syndecans potentiate the action of agouti-related protein and agouti signaling protein, endogenous inhibitors of alphaMSH. In wild-type mice, syndecan-3, the predominantly neural syndecan, is expressed in hypothalamic regions that control energy balance. Food deprivation increases hypothalamic syndecan-3 levels several-fold. Syndecan-3 null mice, otherwise apparently normal, respond to food deprivation with markedly reduced reflex hyperphagia. We propose that oscillation of hypothalamic syndecan-3 levels physiologically modulates feeding behavior.

Type I corticosteroid receptor-like immunoreactivity in the rat salivary glands and distal colon: modulation by corticosteroids

A 167 amino acid fragment of the N-terminal domain of the human type I corticosteroid (mineralocorticoid) receptor was fused to the glutathione S-transferase gene using the Gex expression plasmid and the fusion protein used to raise the monospecific polyclonal antibody, MINREC4. Immunostaining experiments showed that MINREC4 specifically bound type I receptor in the distal tubule of the kidney, the ductal elements of the salivary glands and the epithelium of the distal colon in the rat. Adrenalectomy abolished staining in the parotid and colon, and reduced immunoreactivity in the submandibular gland. Administration of corticosterone or aldosterone resulted in partial restoration of immunostaining in the parotid, and a complete restoration of staining to intact levels in the submandibular gland and colon. These results suggest that adrenocorticoid binding to the type I receptor may result in tissue specific conformational changes in the binding protein and that the MINREC4 antibody may be used to study the effects.

Type I corticosteroid receptor-like immunoreactivity in the rat CNS: distribution and regulation by corticosteroids

Previous maps of Type I corticosteroid receptor binding in the rat central nervous system (CNS) revealed a restricted distribution of the receptor in limbic regions, hypothalamus, and circumventricular organs. More recent studies have shown a more widespread expression of the receptor, with high levels of Type I receptor mRNA in limbic, motor, and sensory systems. We have used two antisera against peptide sequences derived from the cDNA of the human Type I corticosteroid receptor to map the regional distribution and corticosteroid regulation of the intracellular location of Type I corticosteroid receptor-like immunoreactivity (Type I-ir) in the rat CNS. Neurons showing Type I-ir were observed at all levels of the CNS. Highest densities of immunoreactive neurons were observed in limbic regions, isocortex, and some thalamic nuclei. Motor, sensory, and visceral systems often showed moderate densities of immunoreactive neurons. Type I-ir glia were observed in some fiber systems, e.g., corpus callosum, medial lemniscus, cerebral peduncles, spinal trigeminal tract, and funiculi of the spinal cord. In the majority of neurons and in glia, Type I-ir showed a diffusely nuclear and cytoplasmic location. Long-term adrenalectomy reduced immunoreactivity in most neurons and glia. Neuronal Type I-ir was localized mainly in the cytoplasm after long-term adrenalectomy. Nuclear immunoreactivity was retained in some neurons in the globus pallidus, motor trigeminal nucleus, and laminae 8 and 9 of the spinal cord. Acute treatment with corticosterone or aldosterone restored neuronal and glial Type I-ir to densities below that seen in intact rats.

Postnatal development of corticosteroid receptor immunoreactivity in the rat hippocampus

Postnatal changes in corticosteroid receptor immunoreactivity in the rat hippocampus were examined using an antiserum against a fusion protein containing an N-terminal peptide of the Type I receptor, and a monoclonal antibody against the rat liver Type II-receptor. Age-related regional differences were observed. In the pyramidal cell layer of Ammon's horn, and granule cell layer of the dentate gyrus (DG), the percentage of Type I receptor immunoreactive (Type I-ir) and Type II receptor immunoreactive (Type II-ir) cells was high perinatally, declined sharply by postnatal day 10 (P10), and showed a variable increase to adult levels subsequently. The pyramidal cells of CA1-CA2, subiculum and DG showed a selective increase in Type II-ir in late postnatal life into adulthood, while most other regions showed higher Type I-ir in both early and late postnatal life, suggesting different roles for these receptors during development. Type II-ir was predominantly nuclear in most neurons, except for a transient appearance of cytoplasmic Type II-ir in neurons of the stratum oriens and molecular layers of Ammon's horn and dentate gyrus of P20-P30. Type I-ir was diffusely nuclear and cytoplasmic at all developmental ages. This is suggestive of differential genomic and extragenomic roles for these receptors during postnatal development of the hippocampus.