Testosterone and atherosclerosis

Genetics and Pathophysiological Mechanisms of Lipoprotein(a)-Associated Cardiovascular Risk

Elevated lipoprotein(a) is a genetically transmitted codominant trait that is an independent risk driver for cardiovascular disease. Lipoprotein(a) concentration is heavily influenced by genetic factors, including LPA kringle IV-2 domain size, single-nucleotide polymorphisms, and interleukin-1 genotypes. Apolipoprotein(a) is encoded by the LPA gene and contains 10 subtypes with a variable number of copies of kringle -2, resulting in >40 different apolipoprotein(a) isoform sizes. Genetic loci beyond LPA, such as APOE and APOH, have been shown to impact lipoprotein(a) levels. Lipoprotein(a) concentrations are generally 5% to 10% higher in women than men, and there is up to a 3-fold difference in median lipoprotein(a) concentrations between racial and ethnic populations. Nongenetic factors, including menopause, diet, and renal function, may also impact lipoprotein(a) concentration. Lipoprotein(a) levels are also influenced by inflammation since the LPA promoter contains an interleukin-6 response element; interleukin-6 released during the inflammatory response results in transient increases in plasma lipoprotein(a) levels. Screening can identify elevated lipoprotein(a) levels and facilitate intensive risk factor management. Several investigational, RNA-targeted agents have shown promising lipoprotein(a)-lowering effects in clinical studies, and large-scale lipoprotein(a) testing will be fundamental to identifying eligible patients should these agents become available. Lipoprotein(a) testing requires routine, nonfasting blood draws, making it convenient for patients. Herein, we discuss the genetic determinants of lipoprotein(a) levels, explore the pathophysiological mechanisms underlying the association between lipoprotein(a) and cardiovascular disease, and provide practical guidance for lipoprotein(a) testing.

Low testosterone levels relate to poorer cognitive function in women in an APOE-ε4-dependant manner

BACKGROUND

Past research suggests that low testosterone levels relate to poorer cognitive function and higher Alzheimer's disease (AD) risk; however, these findings are inconsistent and are mostly derived from male samples, despite similar age-related testosterone decline in females. Both animal and human studies demonstrate that testosterone's effects on brain health may be moderated by apolipoprotein E ε4 allele (APOE-ε4) carrier status, which may explain some previous inconsistencies. We examined how testosterone relates to cognitive function in older women versus men across healthy aging and the AD continuum and the moderating role of APOE-ε4 genotype.

METHODS

Five hundred and sixty one participants aged 55-90 (155 cognitively normal (CN), 294 mild cognitive impairment (MCI), 112 AD dementia) from the Alzheimer's Disease Neuroimaging Initiative (ADNI), who had baseline cognitive and plasma testosterone data, as measured by the Rules Based Medicine Human DiscoveryMAP Panel were included. There were 213 females and 348 males (self-reported sex assigned at birth), and 52% of the overall sample were APOE-ε4 carriers. We tested the relationship of plasma testosterone levels and its interaction with APOE-ε4 status on clinical diagnostic group (CN vs. MCI vs. AD), global, and domain-specific cognitive performance using ANOVAs and linear regression models in sex-stratified samples. Cognitive domains included verbal memory, executive function, processing speed, and language.

RESULTS

We did not observe a significant difference in testosterone levels between clinical diagnostic groups in either sex, regrardless of APOE-ε4 status. Across clinical diagnostic group, we found a significant testosterone by APOE-ε4 interaction in females, such that lower testosterone levels related to worse global cognition, processing speed, and verbal memory in APOE-ε4 carriers only. We did not find that testosterone, nor its interaction with APOE-ε4, related to cognitive outcomes in males.

CONCLUSIONS

Findings suggest that low testosterone levels in older female APOE-ε4 carriers across the aging-MCI-AD continuum may have deleterious, domain-specific effects on cognitive performance. Although future studies including additional sex hormones and longitudinal cognitive trajectories are needed, our results highlight the importance of including both sexes and considering APOE-ε4 carrier status when examining testosterone's role in cognitive health.

The effect of testosterone level on metabolic syndrome: a cross-sectional study

BACKGROUND

Metabolic syndrome (MS) may reduce circulating testosterone and, at the same time, low testosterone levels may lead to MS. Thus, identifying problems regarding sex hormones and examining their effects on the pathogenesis of MS is important to prevent serious complications of the condition, such as diabetes or cardiovascular diseases.

AIMS

This study aimed to investigate the correlations between MS-related parameters and androgen levels.

METHODS

A total of 108 males [median age 48.5 years (min/max = 21/77 years)] were included in the study. Blood pressure and anthropometric measurements (body mass index, waist circumference, hip circumference, thigh circumference, neck circumference, and length of index and ring finger) were performed. Biochemical analysis was assessed. Additionally, total testosterone, free testosterone, and sex hormone binding globulin levels were investigated.

RESULTS

Weak negative correlations were observed between testosterone levels and several anthropometric measures/glucose metabolisms (p < 0.05). The highest correlation was between total testosterone levels and body mass index (rho= -0.390, p < 0.001) CONCLUSION: According to our results, controlling weight, one of the preventable risk factors, can have a positive effect on testosterone levels and, therefore, on the cardiovascular system through different mechanisms.

Parameter study on characteristic pulse diagram of polycystic ovary syndrome based on logistic regression analysis

This study aimed to explore the parameters of the independent predictive characteristic pulse diagram of polycystic ovary syndrome (PCOS) by analysing the pulse characteristics between healthy women and the PCOS group. A total of 278 women were recruited for this study. Pulse wave parameters were collected by the pulse spectrum analyser. The single-factor analysis of the pulse diagram parameters was used to identify significant indicators, and the logistic regression analysis was carried out on the above indicators with statistical differences to obtain independent predictors. According to the single-factor and multi-factor analyses, h₁, h₅, h₃/h₁, t, t₁ and t₅ were independent predictors of PCOS diagnosis. The results showed that PCOS patients had a faster heart rate, decreased left ventricular systolic function and decreased aortic compliance compared to healthy individuals. These findings suggested that the characteristic pulse parameters screened out are valuable for the diagnosis of PCOS.IMPACT STATEMENTWhat is already known on this subject? Polycystic ovary syndrome (PCOS) is a common gynecological reproductive endocrine and metabolic disease, which is significant for screening and early intervention in the disease. However, due to the lack of pulse's diagnostic evidence of PCOS, there is still an unknown area in the research on the correlation between PCOS and pulse diagram parameters.What do the results of this study add? This study fills the gap between the research on PCOS and pulse wave. The study also shows that the pulse characteristic parameters h₁, h₅, h₃/h₁, t, t₁, and t₅ are independent predictors of PCOS, suggesting that the patients have a higher heart rate, lower ventricular systolic function, and aortic compliance than healthy individuals.What are the implications of these findings for clinical practice and/or further research? Prominent risk factors for pulse parameters associated with the occurrence of PCOS facilitate early screening and diagnosis of the disease. The objectification of pulse diagnosis helps to establish a health management model, which can be used for the accurate assessment and treatment of PCOS by traditional Chinese medicine (TCM). It provides a clinical reference for the study of pulse diagnosis objectification.

Gender-Specific Coagulation Profiles of Peripheral and Portal Blood May Help to Differentiate Malignant from Benign Pancreatic Tumour-Pilot Study

Objective: Pancreatic adenocarcinoma (PDAC) and mass forming chronic pancreatitis (CP) can be easily misdiagnosed due to their resemblances in clinical, radiological, and biochemical criteria. In our previous study, we reported a very high concentration of D-Dimers in portal blood in patients with pancreatic cancer which may help to differentiate malignant from benign pancreatic tumours. In this study, we aim to describe other portal and peripheral coagulation profiles of PDAC in comparison to CP patients, as well to test the hypothesis; thus, it is possible to distinguish pancreatic malignancy and benign tumour based on these parameters. Methods: We included retrospectively 115 patients with the absence of venous thromboembolism (VTE), qualified to surgical treatment due to pancreatic tumours, both PDAC and CP. Patients underwent surgery in General and Transplant Surgery Unit of Medical University of Lodz between December 2011 and February 2014. Patients with distant metastases diagnosed before or during the surgery were excluded. The coagulation profile, which includes fibrinogen, activated partial thromboplastin time (aPTT), prothrombin time (PT), and thrombin time (TT), was determined in blood samples from the portal and peripheral vein taken intraoperatively. Results: The fibrinogen level was higher and the aPTT index shortened in the peripheral and portal blood of the PDAC group, which reflects the well-known link between PDAC and general hypercoagulability. Furthermore, these effects are sex-specific. The mean age in the CP group was lower than in the PDAC group (54.63 ± 12.37 vs. 63.77 ± 3.23, p < 0.001) and correlated with the fibrinogen distribution in male patients with CP (portal r = 0.34; p = 0.07; peripheral r = 0.39; p = 0.04). We calculated sex-specific logistic regression models (male: peripheral aPTT and age, AUC: 0.795, female: portal fibrinogen and age, AUC: 0.805), both maintaining the good discrimination properties after V-fold cross validation (0.759, 0.742). Conclusions: Our study shows that the differences between coagulation profiles in PDAC and CP patients not only seems to be a reflection of gender-specific biological features, but also helps to discriminate between them. The main goal of the study was to explore the biology of pancreatic cancer and lay a solid base for further investigations of PDAC biomarkers. This paper is the first to describe the detailed coagulation profile in portal blood in patients with pancreatic solid tumors. At present, the clinical application of our results is not clear; however, we hope that it may improve our understanding of this complex disease.

Glucocorticoids and Risk of Venous Thromboembolism in Asthma Patients Aged 20-59 Years in the United Kingdom's CPRD 1995-2015

BACKGROUND

Glucocorticoids, the class of steroids used in management of asthma, have been observed to be associated with adverse events such as increased coagulation and inhibition of fibrinolysis. This study evaluated the risk of VTE in relation to the use of glucocorticoids in patients with asthma.

METHODS

We conducted a nested case-control study among patients aged 20-59 years with asthma who received at least one glucocorticoid prescription during 1995-2015 in the UK-based Clinical Practice Research Datalink GOLD. We used descriptive analyses and conditional logistic regression to evaluate the risk of VTE associated with glucocorticoid use.

RESULTS

The adjusted ORs (aORs) (95% CI) for VTE in patients exposed to glucocorticoids were 1.9 (1.6-2.3), 1.4 (1.1-1.8), and 1.2 (0.9-1.5) for current, recent, and past glucocorticoid users, respectively, compared to the unexposed. The aORs (95% CI) for VTE in patients exposed to systemic glucocorticoid and inhaled glucocorticoids, compared to the unexposed, were 3.5 (2.7-4.5) and 1.5 (1.3-1.8), respectively.

CONCLUSION

Current and systemic glucocorticoid use was associated with a dose-response increased risk of incident idiopathic VTE.

Cardiovascular and Cerebrovascular Safety of Testosterone Replacement Therapy Among Aging Men with Low Testosterone Levels: A Cohort Study

PURPOSE

We assessed the risk of ischemic stroke, transient ischemic attack, and myocardial infarction associated with testosterone replacement therapy (TRT) among aging men with low testosterone levels.

METHODS

Using the UK Clinical Practice Research Datalink, we formed a cohort of men aged 45 years or older with low testosterone levels and no evidence of hypogonadotropic or testicular disease, between 1995 and 2017. Hazard ratios (HRs) and 95% confidence intervals (CIs) of a composite of ischemic stroke/transient ischemic attack and myocardial infarction were estimated using time-dependent Cox proportional hazards models, comparing current use of TRT with nonuse.

RESULTS

The cohort included 15,401 men. During 71,541 person-years of follow-up, 850 patients experienced an ischemic stroke/transient ischemic attack/myocardial infarction (crude incidence rate 1.19 [95% confidence interval (CI), 1.11-1.27] per 100 persons per year). Compared with nonuse, current use of TRT was associated with an increased risk of the composite outcome (HR 1.21; 95% CI, 1.00-1.46). This risk was highest in the first 6 months to 2 years of continuous TRT use (HR 1.35; 95% CI, 1.01-1.79), as well as among men aged 45-59 years (HR 1.44; 95% CI, 1.07-1.92).

CONCLUSIONS

TRT may increase the risk of cardiovascular events in aging men with low testosterone levels, particularly in the first 2 years of use. In the absence of identifiable causes of hypogonadism, TRT should be initiated with caution among aging men with low testosterone levels.

Metabolic and genetic profiling of young adults with and without a family history of premature coronary heart disease (MAGNETIC). Study design and methodology

INTRODUCTION

First-degree relatives of individuals with premature coronary artery disease (CAD) are at increased risk of CAD. The research hypothesis of this project assumes that there are differences in the metabolic profiles between individuals with and without a positive family history (FH) of premature CAD.

MATERIAL AND METHODS

The study group will comprise healthy patients (n = 500) aged 18-35 years with a FH of premature CAD, and the control group (n = 500) will consist of healthy subjects without a FH of premature CAD. Blood tests assessing the lipid profile will be carried out. Patients will respond to a questionnaire regarding FH and dietary habits. Measurement of carotid intima media thickness will be performed. Analysis of single-nucleotide polymorphisms (SNPs) associated with premature CAD will be carried out for every patient. Metabolomic profiling will be performed using a high-sensitivity Bruker AVANCE II 600 MHz NMR spectroscope.

RESULTS

The results of this study will include a comparison of metabolic profiles assessed by 1H-NMR spectroscopy in the study and control groups and the results of analyses of the relationship between the metabolic profiles and genetic risk score calculated based on evaluated SNPs associated with premature CAD.

CONCLUSIONS

This study will deepen our knowledge of the aetiopathogenesis of atherosclerosis by identifying metabolic patterns associated with a positive FH of premature CAD. Obtaining a detailed FH will enable adjustments for major risk factors of premature CAD in the proband's first-degree relatives. This research project also provides a chance to discover new biomarkers associated with the risk of premature CAD.

Addition of Estradiol to Cross-Sex Testosterone Therapy Reduces Atherosclerosis Plaque Formation in Female ApoE-/- Mice

The contributions of estradiol and testosterone to atherosclerotic lesion progression are not entirely understood. Cross-sex hormone therapy (XHT) for transgender individuals dramatically alters estrogen and testosterone levels and consequently could have widespread consequences for cardiovascular health. Yet, no preclinical research has assessed atherosclerosis risk after XHT. We examined the effects of testosterone XHT after ovariectomy on atherosclerosis plaque formation in female mice and evaluated whether adding low-dose estradiol to cross-sex testosterone treatments after ovariectomy reduced lesion formation. Six-week-old female ApoE-/- C57BL/6 mice underwent ovariectomy and began treatments with testosterone, estradiol, testosterone with low-dose estradiol, or vehicle alone until euthanized at 23 weeks of age. Atherosclerosis lesion progression was measured by Oil Red O stain and confirmed histologically. We found reduced atherosclerosis in the estradiol- and combined testosterone/estradiol-treated mice compared with those treated with testosterone or vehicle only in the whole aorta (-75%), aortic arch (-80%), and thoracic aorta (-80%). Plaque size was similarly reduced in the aortic sinus. These reductions in lesion size after combined testosterone/estradiol treatment were comparable to those obtained with estrogen alone. Testosterone/estradiol combined therapy resulted in less atherosclerosis plaque formation than either vehicle or testosterone alone after ovariectomy. Testosterone/estradiol therapy was comparable to estradiol replacement alone, whereas mice treated with testosterone only fared no better than untreated controls after ovariectomy. Adding low-dose estrogen to cross-sex testosterone therapy after oophorectomy could improve cardiovascular outcomes for transgender patients. Additionally, these results contribute to understanding of the effects of estrogen and testosterone on atherosclerosis progression.

Between mind and heart: Sex-based cognitive bias in cardiovascular disease treatment

Given that both men and women experience cardiovascular disease (CVD), a common misconception is that they have similar risk factors and clinical presentation, receive comparable treatment, and have equivalent clinical outcomes; in reality differences are observed between men and women for each of these endpoints. Moreover, these differences occur as a function of both gender and sex. A review of the literature reveals widespread bias in the selection of research subjects based on these factors, in addition to implicit patient and provider biases that impede the access of women to recommended primary and secondary CVD management. In this perspective, we identify strategies to eliminate such biases and improve women's access to CVD treatments to ensure their care is consistent with current guidelines.

2-Chloro-4-[[(1R,2R)-2-hydroxy-2-methyl-cyclopentyl]amino]-3-methyl-benzonitrile: A Transdermal Selective Androgen Receptor Modulator (SARM) for Muscle Atrophy

A transdermal SARM has a potential to have therapeutic benefit through anabolic activity in muscle while sparing undesired effects of benign prostate hyperplasia (BPH) and liver-mediated decrease in HDL-C. 2-Chloro-4-[(2-hydroxy-2-methyl-cyclopentyl)amino]-3-methyl-benzonitrile 6 showed the desired muscle and prostate effects in a preclinical ORX rat model. Compound 6 had minimal effect on HDL-C levels in cynomolgus monkeys and showed human cadaver skin permeability, thus making it an effective tool for proof-of-concept studies in a clinical setting.

Androgen Modulates Functions of Endothelial Progenitor Cells through Activated Egr1 Signaling

Researches show that androgens have important effects on migration of endothelial cells and endothelial protection in coronary heart disease. Endothelial progenitor cells (EPCs) as a progenitor cell type that can differentiate into endothelial cells, have a critical role in angiogenesis and endothelial protection. The relationship between androgen and the functions of EPCs has animated much interest and controversy. In this study, we investigated the angiogenic and migratory functions of EPCs after treatment by dihydrotestosterone (DHT) and the molecular mechanisms as well. We found that DHT treatment enhanced the incorporation of EPCs into tubular structures formed by HUVECs and the migratory activity of EPCs in the transwell assay dose dependently. Moreover, microarray analysis was performed to explore how DHT changes the gene expression profiles of EPCs. We found 346 differentially expressed genes in androgen-treated EPCs. Angiogenesis-related genes like Egr-1, Vcan, Efnb2, and Cdk2ap1 were identified to be regulated upon DHT treatment. Furthermore, the enhanced angiogenic and migratory abilities of EPCs after DHT treatment were inhibited by Egr1-siRNA transfection. In conclusion, our findings suggest that DHT markedly enhances the vessel forming ability and migration capacity of EPCs. Egr1 signaling may be a possible pathway in this process.

New therapy via targeting androgen receptor in monocytes/macrophages to battle atherosclerosis

The male sex has a higher risk to develop coronary artery diseases, including atherosclerosis. The androgen receptor (AR) is expressed in several atherosclerosis-associated cell types, including monocytes/macrophages, endothelial cells (ECs), and smooth muscle cells (SMCs), but its pathophysiological role in each cell type during the development of atherosclerotic lesions remains unclear. Using the Cre-loxP system, we selectively knocked out AR in these 3 cell types and the resultant AR knockout (ARKO) mice, monocyte/macrophage ARKO, EC-ARKO, and SMC-ARKO, were then crossed with the low-density lipoprotein receptor (LDLR) deficient (LDLR(-/-)) mice to develop monocyte/macrophage ARKO-LDLR(-/-), EC-ARKO-LDLR(-/-), and SMC-ARKO-LDLR(-/-) mice for the study of atherosclerosis. The results showed that the monocyte/macrophage ARKO-LDLR(-/-) mice had reduced atherosclerosis compared with the wild-type-LDLR(-/-) control mice. However, no significant difference was detected in EC-ARKO-LDLR(-/-) and SMC-ARKO-LDLR(-/-) mice compared with wild-type-LDLR(-/-) mice, suggesting that the AR in monocytes/macrophages, and not in ECs and SMCs, plays a major role to promote atherosclerosis. Molecular mechanism dissection suggested that AR in monocytes/macrophages upregulated the tumor necrosis factor-α, integrin β2, and lectin-type oxidized LDL receptor 1 molecules that are involved in 3 major inflammation-related processes in atherosclerosis, including monocytes/macrophages migration and adhesion to human umbilical vein ECs, and subsequent foam cell formation. Targeting AR via the AR degradation enhancer, ASC-J9, in wild-type-LDLR(-/-) mice showed similar effects as seen in monocyte/macrophage ARKO-LDLR(-/-) mice with little influence on lipid profile. In conclusion, the AR in monocytes/macrophages plays key roles in atherosclerosis and targeting AR with ASC-J9 may represent a new potential therapeutic approach to battle atherosclerosis.

Effects of varying doses of testosterone on atherogenic markers in healthy younger and older men

Whether exogenous testosterone is proatherogenic remains controversial. We assessed the effects of graded doses of testosterone on serum markers of oxidative stress, chemotaxis, adhesion, and inflammation in healthy younger and older men. In a double-blind, randomized trial, 121 eugonadal men ( n = 61, 18–35 years of age and n = 60, 60–75 years of age) were randomized to one of five groups to receive weekly injections of 25, 50, 125, 300, or 600 mg of testosterone enanthate for 20 wk, respectively, along with a long-acting gonadotropin-releasing hormone (GnRH) agonist. Energy and protein intakes were standardized and no resistance training was allowed. We measured plasma levels of the atherogenic biomarkers monocyte chemotactic protein-1 (MCP-1), soluble intracellular adhesion molecule-1 (sICAM-1), 8-isoprostane-PGF2α (8-iso-PGF2α), and high-sensitivity C-reactive protein (hs-CRP) before and after the intervention. Administration of increasing doses of testosterone led to reduction in total 8-iso-PGF2α in the younger (p-trendYounger = 0.01), but not older (p-trendOlder = 0.79) men. No significant linear associations were observed between testosterone dose and MCP-1, sICAM-1, or hs-CRP (all p-trend >0.20). In apparently healthy men, over a wide dose range, testosterone did not adversely affect atherogenic biomarkers. Long-term studies with larger sample sizes are warranted to determine whether testosterone supplementation affects atherosclerosis progression and cardiovascular risk.

Untrained young men have dysfunctional HDL compared with strength-trained men irrespective of body weight status

We examined the impact of strength fitness and body weight on the redox properties of high-density lipoprotein (HDL) and associations with indices of vascular and metabolic health. Ninety young men were categorized into three groups: 1) overweight untrained (OU; n = 30; BMI 30.7 ± 2.1 kg/m(2)); 2) overweight trained [OT; n = 30; BMI 29.0 ± 1.9; ≥4 d/wk resistance training (RT)]; and 3) lean trained (LT; n = 30; BMI 23.7 ± 1.4; ≥4 d/wk RT). Using a novel assay on the basis of the HDL-mediated rate of oxidation of dihydrorhodamine (DOR), we determined the functional (redox) properties of HDL and examined correlations between DOR and indices of vascular and metabolic health in the cohort. DOR was significantly lower in both trained groups compared with the untrained group (LT, 1.04 ± 0.49; OT, 1.39 ± 0.57; OU, 1.80 ± 0.74; LT vs. OU P < 0.00001; OT vs. OU P = 0.02), however, DOR in the OT group was not significantly different from that of the LT group. DOR was negatively associated with HDL-cholesterol (R = -0.64), relative strength (R = -0.42), sex hormone-binding globulin (R = -0.42), and testosterone (R = -0.35) (all P ≤ 0.001); whereas DOR was positively associated with triglycerides (R = 0.39, P = 0.002), oxidized low-density lipoprotein (R = 0.32), body mass index (R = 0.43), total mass (R = 0.35), total fat mass (R = 0.42), waist circumference (R = 0.45), and trunk fat mass (R = 0.42) (all P ≤ 0.001). Chronic RT is associated with improved HDL redox activity. This may contribute to the beneficial effects of RT on reducing cardiovascular disease risk, irrespective of body weight status.

Risks and benefits of testosterone therapy in older men

In young men (defined as age<50 years) with classic hypogonadism caused by known diseases of the hypothalamus, pituitary or testes, testosterone replacement therapy induces a number of beneficial effects, for example, the development of secondary sex characteristics, improvement and maintenance of sexual function, and increases in skeletal muscle mass and BMD. Moreover, testosterone treatment in this patient population is associated with a low frequency of adverse events. Circulating testosterone levels decline progressively with age, starting in the second and third decade of life, owing to defects at all levels of the hypothalamic-pituitary-testicular axis. In cohort studies, testosterone levels are associated weakly but consistently with muscle mass, strength, physical function, anaemia, BMD and bone quality, visceral adiposity, and with the risk of diabetes mellitus, coronary artery disease, falls, fractures and mortality. However, the clinical benefits and long-term risks of testosterone therapy--especially prostate-related and cardiovascular-related adverse events--have not been adequately assessed in large, randomized clinical trials involving older men (defined as age>65 years) with androgen deficiency. Therefore, a general policy of testosterone replacement in all older men with age-related decline in testosterone levels is not justified.

Dihydrotestosterone regulating apolipoprotein M expression mediates via protein kinase C in HepG2 cells

Background

Administration of androgens decreases plasma concentrations of high-density lipid cholesterol (HDL-C). However, the mechanisms by which androgens mediate lipid metabolism remain unknown. This present study used HepG2 cell cultures and ovariectomized C57BL/6 J mice to determine whether apolipoprotein M (ApoM), a constituent of HDL, was affected by dihydrotestosterone (DHT).

Methods

HepG2 cells were cultured in the presence of either DHT, agonist of protein kinase C (PKC), phorbol-12-myristate-13-acetate (PMA), blocker of androgen receptor flutamide together with different concentrations of DHT, or DHT together with staurosporine at different concentrations for 24 hrs. Ovariectomized C57BL/6 J mice were treated with DHT or vehicle for 7d or 14d and the levels of plasma ApoM and livers ApoM mRNA were measured. The mRNA levels of ApoM, ApoAI were determined by real-time RT-PCR. ApoM and ApoAI were determined by western blotting analysis.

Results

Addition of DHT to cell culture medium selectively down-regulated ApoM mRNA expression and ApoM secretion in a dose-dependent manner. At 10 nM DHT, the ApoM mRNA levels were about 20% lower than in untreated cells and about 40% lower at 1000 nM DHT than in the control cells. The secretion of ApoM into the medium was reduced to a similar extent. The inhibitory effect of DHT on ApoM secretion was not blocked by the classical androgen receptor blocker flutamide but by an antagonist of PKC, Staurosporine. Agonist of PKC, PMA, also reduced ApoM. At 0.5 μM PMA, the ApoM mRNA levels and the secretion of ApoM into the medium were about 30% lower than in the control cells. The mRNA expression levels and secretion of another HDL-associated apolipoprotein AI (ApoAI) were not affected by DHT. The levels of plasma ApoM and liver ApoM mRNA of DHT-treated C57BL/6 J mice were lower than those of vehicle-treated mice.

Conclusions

DHT directly and selectively down-regulated the level of ApoM mRNA and the secretion of ApoM by protein kinase C but independently of the classical androgen receptor.

A novel mouse model of Alzheimer's disease with chronic estrogen deficiency leads to glial cell activation and hypertrophy

The role of estrogens in Alzheimer's disease (AD) involving β-amyloid (Aβ) generation and plaque formation was mostly tested in ovariectomized mice with or without APP mutations. The aim of the present study was to explore the abnormalities of neural cells in a novel mouse model of AD with chronic estrogen deficiency. These chimeric mice exhibit a total FSH-R knockout (FORKO) and carry two transgenes, one expressing the β-amyloid precursor protein (APPsw, Swedish mutation) and the other expressing presenilin-1 lacking exon 9 (PS1Δ9). The most prominent changes in the cerebral cortex and hippocampus of these hypoestrogenic mice were marked hypertrophy of both cortical neurons and astrocytes and an increased number of activated microglia. There were no significant differences in the number of Aβ plaques although they appeared less compacted and larger than those in APPsw/PS1Δ9 control mice. Similar glia abnormalities were obtained in wild-type primary cortical neural cultures treated with letrozole, an aromatase inhibitor. The concordance of results from APPsw/PS1Δ9 mice with or without FSH-R deletion and those with letrozole treatment in vitro (with and without Aβ treatment) of primary cortical/hippocampal cultures suggests the usefulness of these models to explore molecular mechanisms involved in microglia and astrocyte activation in hypoestrogenic states in the central nervous system.

Gender differences in the cardiovascular effects of sex hormones

Over the last decade, compelling evidence supports the idea that the different impact of cardiovascular disease (CVD) and the differences in vascular biology in men and women may be, at least in part, related to the cardiovascular and metabolic effects of sex steroid hormones. Indeed, androgens and oestrogens influence a multitude of vascular biological processes and their cardiovascular effects are multifaceted. While in women the effects of androgens mainly depend upon oestrogens' levels and, ultimately, upon the estradiol/testosterone ratio, the effects of androgens in men mostly relate to their aromatization into oestrogens. Oestrogens exert potential beneficial effects on the cardiovascular system in both sexes. In women, the effect of oestrogens, alone or in association with progestins, has been widely investigated, but data obtained from older patient populations have lead the medical community and the general public to misleading conclusions. Growing evidence supports the 'timing hypothesis', which suggests that oestrogen/hormone replacement therapy may increase CVD risk if started late after menopause, but produce beneficial cardiovascular effects in younger postmenopausal women. Because in men adequate interventional studies with testosterone are lacking, specific investigations should be performed.

Low testosterone levels predict all-cause mortality and cardiovascular events in women: a prospective cohort study in German primary care patients

OBJECTIVE

Although associations between testosterone and cardiovascular (CV) morbidity in women have been proposed, no large prospective study has evaluated potential associations between testosterone and mortality in women. The objective was to determine whether baseline testosterone levels in women are associated with future overall or CV morbidity and mortality.

DESIGN

Prospective cohort study with a 4.5-year follow-up period.

METHODS

From a representative sample of German primary care practices, 2914 female patients between 18 and 75 years were analyzed for the main outcome measures: CV risk factors, CV diseases, and all-cause mortality.

RESULTS

At baseline, the study population was aged 57.96±14.37 years with a mean body mass index of 26.71±5.17 kg/m(2). No predictive value of total testosterone for incident CV risk factors or CV diseases was observed in logistic regressions. Patients with total testosterone levels in the lowest quintile Q1, however, had a higher risk to die of any cause or to develop a CV event within the follow-up period compared to patients in the collapsed quintiles Q2-Q5 in crude and adjusted Cox regression models (all-cause mortality: Q2-Q5 versus Q1: crude hazard ratios (HR) 0.49, 95% confidence interval (CI) 0.33-0.74; adjusted HR 0.62, 95% CI 0.42-0.939; CV events: Q2-Q5 versus Q1: crude HR 0.54, 95% CI 0.38-0.77; adjusted HR 0.68, 95% CI 0.48-0.97). Kaplan-Meier curves revealed similar data.

CONCLUSIONS

Low baseline testosterone in women is associated with increased all-cause mortality and incident CV events independent of traditional risk factors.

Cardiac and vascular changes in elderly atherosclerotic mice: the influence of gender

Background

Although advanced age is considered a risk factor for several diseases, the impact of gender on age-associated cardiovascular diseases, such as atherosclerotic processes and valvular diseases, remains not completely clarified. The present study was designed to assess aortic valve morphology and function and vascular damage in elderly using the apolipoprotein E knockout (ApoE KO) mouse. Our hypothesis was that advanced age-related cardiovascular changes are aggravated in atherosclerotic male mice.

Methods

The grade (0 to 4) of aortic regurgitation was evaluated through angiography. In addition, vascular lipid deposition and senescence were evaluated through histochemical analyses in aged male and female ApoE KO mice, and the results were compared to wild-type C57BL/6J (C57) mice.

Results

Aortic regurgitation was observed in 92% of the male ApoE KO mice and 100% of the male C57 mice. Comparatively, in age-matched female ApoE KO and C57 mice, aortic regurgitation was observed in a proportion of 58% and 53%, respectively. Histological analysis of the aorta showed an outward (positive) remodeling in ApoE KO mice (female: 1.86 ± 0.15; male: 1.89 ± 0.68) using C57 groups as reference values. Histochemical evaluation of the aorta showed lipid deposition and vascular senescence only in the ApoE KO group, which were more pronounced in male mice.

Conclusion

The data show that male gender contributes to the progression of aortic regurgitation and that hypercholesterolemia and male gender additively contribute to the occurrence of lipid deposition and vascular senescence in elderly mice.

Endogenous testosterone and mortality in male hemodialysis patients: is it the result of aging?

BACKGROUND AND OBJECTIVES

Low serum testosterone levels in hemodialysis (HD) patients have recently been associated with cardiovascular risk factors and increased mortality. To confirm this observation, we investigated the predictive role of serum total testosterone levels on mortality in a large group of male HD patients from Turkey.

DESIGN, SETTINGS, PARTICIPANTS, & MEASUREMENTS

A total of 420 prevalent male HD patients were sampled in March 2005 and followed up for all-cause mortality. Serum total testosterone levels were measured by ELISA at baseline and studied in relation to mortality and cardiovascular risk profile.

RESULTS

Mean testosterone level was 8.69 ± 4.10 (0.17 to 27.40) nmol/L. A large proportion of patients (66%) had testosterone deficiency (<10 nmol/L). In univariate analysis, serum testosterone levels were positively correlated with creatinine and inversely correlated with age, body mass index, and lipid parameters. During an average follow-up of 32 months, 104 (24.8%) patients died. The overall survival rate was significantly lower in patients within the low testosterone tertile (<6.8 nmol/L) compared with those within the high tertile (>10.1 nmol/L; 64 versus 81%; P = 0.004). A 1-nmol/L increase in serum testosterone level was associated with a 7% decrease in overall mortality (hazard ratio 0.93; 95% confidence interval 0.89 to 0.98; P = 0.01); however, this association was dependent on age and other risk factors in adjusted Cox regression analyses.

CONCLUSIONS

Testosterone deficiency is common in male HD patients. Although testosterone levels, per se, predicted mortality in this population, this association was largely dependent on age.

Down-regulation of murine testicular 17β-HSD3 and hepatic CYP1A2 enzymes by a bovine testes extract

Purpose

We investigated the effects of a bovine testes extract (BTE), which was developed as an alternative product for andropausal men, on expression of testicular enzymes responsible for sex hormone synthesis genes and a carcinogen activation related gene.

Methods

Expression of testicular CYP1A2, CYP11A1, CYP17, 3β-HSD, and 17β-HSD3 mRNAs as well as hepatic CYP1A2 mRNA were semi-quantitatively determined by RT-PCR. In addition, expression of hepatic CYP1A2 protein and methoxyresorufin O-demethylase activity were carried out.

Results

Bovine testes extract did not alter the testicular expression of CYP11A1, CYP17, and 3β-HSD mRNAs, while that of CYP11A1 was significantly down-regulated by testosterone. Interestingly, administration of BTE for 3 weeks significantly suppressed testicular 17β-HSD3 and hepatic CYP1A2 mRNA. Correspondingly, methoxyresorufin O-demethylase (MROD) activity and expression of hepatic CYP1A2 protein were significantly decreased.

Conclusions

These findings strongly suggested considering risks versus benefits and raised concerns regarding the use of BTE as an alternative medication or health supplement in andropausal men due to its potential for suppressing expression of both 17β-HSD3 and CYP1A2 mRNAs, testicular enzymes responsible for sex hormone gene synthesis.

The effects of endogenous and exogenous androgens on cardiovascular disease risk factors and progression

Cardiovascular disease incidence rates have long been known to significantly differ between the two sexes. Estrogens alone fail to explain this phenomenon, bringing an increasing amount of attention to the role of androgens. Contrary to what was initially hypothesized, androgens seem to have an overall cardioprotective effect, especially in men. Recent studies and published data continue to support this notion displaying a consistent inverse correlation with atherosclerosis progression and cardiovascular disease both in regressive and prospective study models. Clinical studies have also revealed what seems to be a differential androgenic effect on various cardiovascular risk factors between men and women. Further insight indicates that in order to avoid confusion it may be also preferable to separately examine the effects of endogenous androgen levels from exogenous testosterone administration, as well as discern the differential results of low to normal and supraphysiological administration doses. This review summarizes old and recent data according to the above distinctions, in an attempt to further our understanding of the role of androgens in cardiovascular disease.

Sex-related differences in the associations between hyperleptinemia, insulin resistance and dysfibrinolysis

The adipocyte-derived hormone leptin is associated with insulin resistance and reduced fibrinolytic status--or dysfibrinolysis--in humans. As leptin associates differentially to the development of cardiovascular disease and diabetes in men and women, we hypothesized that leptin and insulin sensitivity are related to dysfibrinolysis in a sex-dependent manner. Thirty-two men and 40 women were recruited from the Monitoring of trends and determinants in Cardiovascular disease (MONICA) population sample, representing the highest and lowest quartiles of fasting insulin levels. Lipids, fibrinolytic status [plasminogen activator inhibitor 1 (PAI-1) activity, tissue plasminogen activator (tPA) mass and activity, and tPA-PAI complex], leptin, testosterone and sex-hormone-binding globulin were measured. Insulin sensitivity was estimated using the euglycaemic clamp technique. Body composition was determined by bioimpedance. Determinants for circulating levels of fibrinolytic factors were explored in a multivariate linear regression analysis. Levels of fibrinolytic variables and estimated insulin sensitivity did not differ between men and women. Leptin was independently associated with reduced fibrinolytic status (high PAI-1 activity, low tPA activity, high tPA mass, and high tPA-PAI complex) in men (P < 0.001-0.002). In women, fat mass and/or insulin sensitivity were related to these factors (P < 0.001-0.03), and leptin only to reduced tPA activity (P = 0.002). Hyperleptinemia, dysfibrinolysis, insulin sensitivity and androgenicity associate differentially in men and women.

Polymorphisms of steroid 5-alpha-reductase type I (SRD5A1) gene are associated to peripheral arterial disease

Although animal studies support the hypothesis that androgenic biological actions may affect experimental atherosclerosis progression, evidence for a relationship between androgen effects and peripheral arterial disease (PAD), a common clinical form of atherosclerosis, is weak or contradictory. Testosterone, the main androgen hormone, is converted in a 5alpha-reduced form by enzymatic activities in the target cells and some specific actions are mediated by such metabolites. Steroid 5-alpha reductase isoenzymes (SRD5A1 and SRD5A2) catalyze the conversion to the bioactive potent androgen dihydrotestosterone and other reduced metabolites and represent relevant regulators of local hormonal actions. In the present study we tested for the association of selected single nucleotide polymorphisms (SNP) of SRD5A1 and SRD5A2 with symptomatic PAD patients. Two different SNP in the SRD5A1 were significantly associated which the PAD phenotype (p<0.03, odds ratio 1.73), while no association was found between PAD phenotypes and SRD5A2. Since the examined SRDA1 gene variant was previously associated with a low enzymatic activity, we suggest that a decreased local enzymatic conversion of testosterone may contribute to PAD genetic susceptibility.

Hydrogen sulphide is involved in testosterone vascular effect

BACKGROUND

Testosterone (T) induces a rapid relaxation in vascular tissues of different species due to a nongenomic effect of this steroid on vessels. Different mechanisms have been proposed to explain T-induced vasodilatation but the effective mechanism(s) and the mediators involved are still a matter of debate.

OBJECTIVES

We have evaluated if H(2)S pathway is involved in T vascular effects.

DESIGN AND SETTING

Male Wistar rats were sacrificed and thoracic aorta was rapidly dissected and cleaned from fat and connective tissue. Rings of 2-3 mm length were cut and placed in organ baths filled with oxygenated Krebs solution at 37 degrees C and mounted to isometric force transducers. H(2)S determination was performed on thoracic aortic rings incubated with T or vehicle and in presence of inhibitors. H2S concentration was calculated against a calibration curve of NaHS (3-250 microM). Results were expressed as nmoles/mg protein.

MEASUREMENTS

Vascular reactivity was evaluated by using isometric transducers. H(2)S determination was performed by using a cystathionine beta-synthetase (CBS) and cystathionine gamma lyase (CSE) activity assay. CSE and CBS protein levels were assessed by Western blot analysis. Statistical analysis was performed by using two-way ANOVA and unpaired Student's t-test where appropriate.

RESULTS

T significantly increased conversion of L-cysteine to H(2)S. This effect was significantly reduced by PGG and BCA, two specific inhibitors of CSE. T (10 nM-10 microM) induced a concentration-dependent vasodilatation of rat aortic rings in vitro that was significantly and concentration-dependent inhibited by PGG, BCA, and glybenclamide. Incubation of aorta with T up to 1 h did not change CBS/CSE expression, suggesting that T modulates enzymatic activity.

CONCLUSIONS

Here we demonstrate that T vasodilator effect involves H(2)S, a novel gaseous mediator. T modulates H(2)S levels by increasing the enzymatic conversion of L-cysteine to H(2)S.

Gene expression analyses in cynomolgus monkeys provides mechanistic insight into high-density lipoprotein-cholesterol reduction by androgens in primates

Androgens increase muscle mass, decrease fat mass, and reduce high-density lipoprotein cholesterol (HDL), but the relationship between body composition, lipoprotein metabolism, and androgens has not been explained. Here we treated ovariectomized cynomolgus monkeys with 5alpha-dihydrotestosterone (DHT) or vehicle for 14 d and measured lipoprotein and triglycerides. Nuclear magnetic resonance analysis revealed that DHT dose-dependently reduced the cholesterol content of large HDL particles and decreased mean HDL particle size (P < 0.01) and also tended to lower low-density lipoprotein cholesterol without altering other lipoprotein particles. Liver and visceral fat biopsies taken before and after DHT treatment for 1 or 14 d were analyzed by genome-wide microarrays. In liver, DHT did not alter the expression of most genes involved in cholesterol synthesis or uptake but rapidly increased small heterodimer partner (SHP) RNA, along with concomitant repression of CYP7A1, a target of SHP transcriptional repression and the rate-limiting enzyme in bile acid synthesis. DHT regulation of SHP and CYP7A1 also occurs in rats, indicating a conserved mechanism. In adipose tissue, pathway analyses suggested coordinate regulation of adipogenesis, tissue remodeling, and lipid homeostasis. Genes encoding IGF-I and beta-catenin were induced, as were extracellular matrix, cell adhesion, and cytoskeletal components, whereas there was consistent down-regulation of genes involved in triacylglycerol metabolism. Interestingly, cholesterol ester transfer protein RNA was induced rapidly in monkey adipose tissue, whereas its inhibitor apolipoprotein CI was repressed. These data provide insight into the androgenic regulation of lipoprotein homeostasis and suggest that changes in adipose lipoprotein metabolism could contribute to HDL cholesterol reduction.

Cellular SR-BI and ABCA1-mediated cholesterol efflux are gender-specific in healthy subjects

We evaluated the impact of gender differences in both the quantitative and qualitative features of HDL subspecies on cellular free cholesterol efflux through the scavenger receptor class B type I (SR-BI), ABCA1, and ABCG1 pathways. For that purpose, healthy subjects (30 men and 26 women) matched for age, body mass index, triglyceride, apolipoprotein A-I, and high density lipoprotein-cholesterol (HDL-C) levels were recruited. We observed a significant increase (+14%; P < 0.03) in the capacity of whole sera from women to mediate cellular free cholesterol efflux via the SR-BI-dependent pathway compared with sera from men. Such enhanced efflux capacity resulted from a significant increase in plasma levels of large cholesteryl ester-rich HDL2 particles (+20%; P < 0.04) as well as from an enhanced capacity (+14%; P < 0.03) of these particles to mediate cellular free cholesterol efflux via SR-BI. By contrast, plasma from men displayed an enhanced free cholesterol efflux capacity (+31%; P < 0.001) via the ABCA1 transporter pathway compared with that from women, which resulted from a 2.4-fold increase in the plasma level of prebeta particles (P < 0.008). Moreover, in women, SR-BI-mediated cellular free cholesterol efflux was significantly correlated with plasma HDL-C (r = 0.72, P < 0.0001), whereas this relationship was not observed in men. In conclusion, HDL-C level may not represent the absolute indicator of the efficiency of the initial step of the reverse cholesterol transport.

Long-term danazol prophylaxis does not lead to increased carotid intima-media thickness in hereditary angioedema patients

BACKGROUND

Hereditary angioedema (HAE) is characterized by episodic edematous attacks due to the deficiency of the C1-inhibitor (C1-INH). Recently, we have described that the long-term use of danazol affects lipid metabolism, resulting in decreased high-density lipoprotein (HDL) and increased low-density lipoprotein (LDL) cholesterol levels, which might lead to accelerated, early atherosclerosis. Our aim in the present study was to investigate the impact of danazol treatment on the risk of atherosclerosis in HAE patients.

METHODS

The prevalence of vascular disease, as well as carotid intima-media thickness (IMT)--an objective marker of atherosclerosis--was determined in 32 HAE patients undergoing danazol prophylaxis, and compared to 25 HAE patients without danazol treatment, as well as to 20 healthy controls. Distinct atherosclerosis risk profiles were determined in addition.

RESULTS

HAE patients with danazol prophylaxis had higher body mass index (p=0.0055 and 0.0020), creatinine (p=0.0001 and 0.0130), alanine aminotransferase (p=0.0298 and 0.0457), LDL (p=0.0060 and <0.0001) and decreased HDL (p<0.0001 and <0.0001) levels compared to both control groups. The prevalence of vascular diseases did not differ in the two patient groups. No significant differences were observed in mean (0.43 (0.37-0.50)mm vs. 0.40 (0.35-0.49)mm, p=0.5465) carotid IMT values, when comparing patients with or without long-term danazol prophylaxis.

CONCLUSIONS

Thickening of IMT due to danazol use was not observed in HAE patients. We hypothesize that the functional deficiency of C1-INH might confer protection against atherosclerosis in these patients.

The sudden and unexpected death of a female-to-male transsexual patient

A 32-year-old woman, who was intramuscularly injected with testosterone enanthate (125 mg) once or twice a month over a two-year period for female-to-male transsexualism, died suddenly. A forensic autopsy was performed to investigate the cause of death. Concentric cardiac hypertrophy was macroscopically observed. In the left and right coronary arteries, atherosclerosis was generally observed within the endothelium. In particular, there was severe stenosis (>90%) at the start of the left descending branch. In the myocardium, both coagulation necrosis and contraction band necrosis were microscopically observed. Moreover, myocardial fibrosis and myocardial calcification were diffusely detected, respectively. The cause of death was diagnosed as ischemic heart disease due to coronary stenosis. There is some debate as to whether cross-hormone replacement is related to the occurrence of coronary artery disease or not, however, it is possible that the development of ischemic heart disease was aggravated by the administration of testosterone enanthate in the current case.

Expanding the therapeutic use of androgens via selective androgen receptor modulators (SARMs)

Selective androgen receptor modulators (SARMs) are a novel class of androgen receptor (AR) ligands that might change the future of androgen therapy dramatically. With improved pharmacokinetic characteristics and tissue-selective pharmacological activities, SARMs are expected to greatly extend the clinical applications of androgens to osteoporosis, muscle wasting, male contraception and diseases of the prostate. Mechanistic studies with currently available SARMs will help to define the contributions of differential tissue distribution, tissue-specific expression of 5alpha-reductase, ligand-specific regulation of gene expression and AR interactions with tissue-specific coactivators to their observed tissue selectivity, and lead to even greater expansion of selective anabolic therapies.

Influence of methyltestosterone postmenopausal therapy on plasma lipids, inflammatory factors, glucose metabolism and visceral fat: a randomized study

BACKGROUND

There has been a growing interest in treating postmenopausal women with androgens. However, hyperandrogenemia in females has been associated with increased risk of cardiovascular disease.

OBJECTIVE

We aimed to assess the effects of androgen replacement on cardiovascular risk factors.

DESIGN

Thirty-seven postmenopausal women aged 42-62 years that had undergone hysterectomy were prospectively enrolled in a double-blind protocol to receive, for 12 months, percutaneous estradiol (E2) (1 mg/day) combined with either methyltestosterone (MT) (1.25 mg/day) or placebo.

METHODS

Along with treatment, we evaluated serum E2, testosterone, sex hormone-binding globulin (SHBG), free androgen index, lipids, fibrinogen, and C-reactive protein; glucose tolerance; insulin resistance; blood pressure; body-mass index; and visceral and subcutaneous abdominal fat mass as assessed by computed tomography.

RESULTS

A significant reduction in SHBG (P < 0.001) and increase in free testosterone index (P < 0.05; Repeated measures analysis of variance) were seen in the MT group. Total cholesterol, triglycerides, fibrinogen, and systolic and diastolic blood pressure were significantly lowered to a similar extent by both regimens, but high-density lipoprotein cholesterol decreased only in the androgen group. MT-treated women showed a modest rise in body weight and gained visceral fat mass relative to the other group (P < 0.05), but there were no significant detrimental effects on fasting insulin levels and insulin resistance.

CONCLUSION

This study suggests that the combination of low-dose oral MT and percutaneous E2, for 1 year, does not result in expressive increase of cardiovascular risk factors. This regimen can be recommended for symptomatic postmenopausal women, although it seems prudent to perform baseline and follow-up lipid profile and assessment of body composition, especially in those at high risk of cardiovascular disease.

Insuficiência androgênica na mulher e potenciais riscos da reposição terapêutica

Na mulher, os androgênios decrescem lenta e progressivamente a partir da quarta década e por toda a vida. O declínio dos androgênios pode gerar um estado de deficiência que se manifesta insidiosamente por diminuição da função sexual, bem estar e energia, alterações na composição corporal e perda de massa óssea. Se há história de ooforectomia bilateral, pan-hipopituitarismo, supressão da androgênese adrenal e/ou os níveis séricos de testosterona biodisponível se encontram reduzidos, é provável que estes sinais e sintomas sejam aliviados pela administração criteriosa de androgênios, cuja prática tem se difundido. Nas doses atualmente preconizadas, parece que os benefícios sobre massa óssea, sexualidade e qualidade de vida são alcançados sem importantes efeitos colaterais de virilização. Entretanto, trabalhos bem controlados são necessários para validar a hipótese de que a administração terapêutica de androgênios em mulheres não tem, a longo prazo, repercussões significativas na incidência sobre câncer de mama ou conseqüências metabólicas indesejáveis.

The M16 mouse: an outbred animal model of early onset polygenic obesity and diabesity

OBJECTIVE

To characterize the phenotypic consequences of long-term selective breeding for rapid weight gain, with an emphasis on obesity and obesity-induced diabetes (diabesity).

RESEARCH METHODS AND PROCEDURES

M16 is the result of long-term selection for 3- to 6-week weight gain from an ICR base population. Experiment 1 characterized males from both lines for body weights (3, 6, and 8 weeks), feed (4 to 8 weeks) and H(2)O (6 to 8 weeks) consumption, and heat loss, body composition, and levels of several plasma proteins at 8 weeks of age. Experiment 2 characterized differences between lines for both sexes at three ages (6, 8, and 16 weeks) and fed two diets (high and normal fat). Body weight, composition, blood glucose, and plasma insulin and leptin levels were evaluated after an 8-hour fast.

RESULTS

At all ages measured, M16 mice were heavier, fatter, hyperphagic, hyperinsulinemic, and hyperleptinemic relative to ICR. M16 males and females were hyperglycemic relative to ICR, with 56% and 22% higher fasted blood glucose levels at 8 weeks of age.

DISCUSSION

M16 mice represent an outbred animal model to facilitate gene discovery and pathway regulation controlling early onset polygenic obesity and type 2 diabetic phenotypes. Phenotypes prevalent in the M16 model, with obesity and diabesity exhibited at a young age, closely mirror current trends in human populations.