Cardiovascular and Metabolic Consequences of Testosterone Supplements in Young and Old Male Spontaneously Hypertensive Rats: Implications for Testosterone Supplements in Men

Chronic intermittent hypoxia-induced hypertension: the impact of sex hormones

Obstructive sleep apnea, a common form of sleep-disordered breathing, is characterized by intermittent cessations of breathing that reduce blood oxygen levels and contribute to the development of hypertension. Hypertension is a major complication of obstructive sleep apnea that elevates the risk of end-organ damage. Premenopausal women have a lower prevalence of obstructive sleep apnea and cardiovascular disease than men and postmenopausal women, suggesting that sex hormones play a role in the pathophysiology of sleep apnea-related hypertension. The lack of protection in men and postmenopausal women implicates estrogen and progesterone as protective agents but testosterone as a permissive agent in sleep apnea-induced hypertension. A better understanding of how sex hormones contribute to the pathophysiology of sleep apnea-induced hypertension is important for future research and possible hormone-based interventions. The effect of sex on the pathophysiology of sleep apnea and associated intermittent hypoxia-induced hypertension is of important consideration in the screening, diagnosis, and treatment of the disease and its cardiovascular complications. This review summarizes our current understanding of the impact of sex hormones on blood pressure regulation in sleep apnea with a focus on sex differences.

Testosterone modulates vasodilation in mesenteric arteries of hypertensive rats

AIMS

To evaluate the effects of testosterone on endothelium-dependent vasodilation and oxidative stress in mesenteric resistance arteries.

MAIN METHODS

Spontaneously hypertensive rats (SHR), aged 8 to 10 weeks, were divided into four groups: intact (SHAM), intact treated with testosterone (TTO; 3 mg/kg/day) via subcutaneous route (s.c.), intact treated with testosterone and anastrozole [aromatase enzyme inhibitor (TTO + ANA; 0.1 mg/kg/day, s.c.)] and intact treated with testosterone and finasteride [5 α-reductase enzyme inhibitor (TTO + FIN; 5 mg/kg/day, s.c.)] for four weeks. Concentration-response curves to acetylcholine (ACh, 0.1 nmol/L - 10 μmol/L) were obtained in mesenteric resistance arteries previously contracted with phenylephrine (PE, 3 μmol/L), before and after the use of selective inhibitors. Reactive oxygen species (ROS) levels were assessed in the vessels and the endothelium analyzed by scanning electron microscopy.

KEY FINDINGS

TTO group showed a lower participation of nitric oxide (NO), increased oxidative stress, and participation of prostanoids and endothelium-dependent hyperpolarization (EDH), possibly to maintain the vasodilator response. Lower participation of NO and prostanoids, combined to an increased participation of EDH, were observed in the TTO + ANA group, in addition to higher levels of ROS and altered endothelial morphology. The vasodilation to ACh was impaired in TTO + FIN, along increased participation of NO, reduction of prostanoids, and greater EDH-dependent vasodilation.

SIGNIFICANCE

Testosterone contributes to endothelial vasodilation by enhancing EDH through an increased participation of epoxyeicosatrienoic acids. While the decrease in NO appears to involve the participation of dihydrotestosterone, 17 β-estradiol seems to stimulate the action of the NO pathway and prostanoids.

Probiotics Bifidobacterium lactis M8 and Lactobacillus rhamnosus M9 prevent high blood pressure via modulating the gut microbiota composition and host metabolic products

IMPORTANCE

Elevated blood pressure affects 40% of the adult population, which accounts for high cardiovascular disease risk and further high mortality yearly. The global understanding of the gut microbiome for hypertension may provide important insights into the prevention. Bifidobacterium lactis M8 and Lactobacillus rhamnosus M9 originated from human breast milk, were able to decrease blood pressure, and modified metabolites in a high fructose-induced elevated blood pressure mouse model. Moreover, we found there was a close relationship between unexplored gut microbes and elevated blood pressure. Also, subsequently, the cross-link was explored among gut microbes, metabolites, and some metabolic pathways in gut microbial environment through introducing novel prediction methodology and bioinformatic analysis. It allowed us to hypothesize that probiotics can prevent elevated blood pressure via gut microbiota and related metabolism.Thus, utilization of dietary strategies (such as probiotics) to maintain the blood pressure level is of crucial importance.

Sex differences in preclinical models of hypertension

Hypertension remains the primary contributor in the development of cardiovascular disease which is rapidly increasing worldwide. High blood pressure affects men and women differently and understanding these sex differences is the ultimate unmet need for researchers in this field. Due to the inherent differences in hypertension prevalence, control and outcomes between men and women, novel research needs to be carried out to tackle these disparities and improve targeted treatment. Animal models of hypertension have provided valuable insights into the sexual dimorphism of blood pressure mechanisms. The availability of genetic and non-genetic hypertensive strains allows the opportunity to study diverse environmental and genetic factors that affect blood pressure, therefore presenting a valuable tool for researchers. Sex differences are present before birth and throughout life, which presents a challenge for the study of disease development in humans, but these complexities can be resolved with the use of in vivo models that display similarities to human disease. The aim of the present review is to provide an overview of the different available animal models of hypertension that present sexual dimorphisms and to discuss their relevance to humans.

The role of sex and gender in hypertension

Hypertension (HTN) is a critical primary modifiable risk factor for the development of cardiovascular diseases, with recognized sex-based differences. While sex refers to one's biological genetic makeup and attributes, gender encompasses the individual's psycho-socio-cultural characteristics, including their environment and living conditions. The impact of each gendered variable may differ amongst men and women with respect to HTN. Applying a sex and gender-based lenses to inform our understanding of HTN has the potential to unveil important contributors of HTN-related cardiovascular outcomes. For instance, increased life stressors, work related anxiety and depression, typically have more pronounced effect on women than men with HTN. The impact of social surrounding including marital status and social support on HTN also differs amongst men and women. While married men are less likely to have higher blood pressure, single women, and those who never married are less likely to have HTN. Additionally, the beneficial role of social support is more pronounced in more historically marginalized cultural groups compared to majority. Finally, socioeconomic status, including education level and income have a linear and inverse relationship in blood pressure control in more resource-rich countries. The aim of this review is to summarize how sex and gender interact in shaping the clinical course of HTN demonstrating the importance of both sex and gender in HTN risk and its treatment. Hence, when investigating the role of gendered factors in HTN it is imperative to consider cultural, and social settings. In this narrative we found that employment and education play a significant role in manifestation and control of HTN particularly in women.

Sex differences in the renin-angiotensin-aldosterone system and its roles in hypertension, cardiovascular, and kidney diseases

Cardiovascular disease is a pathology that exhibits well-researched biological sex differences, making it possible for physicians to tailor preventative and therapeutic approaches for various diseases. Hypertension, which is defined as blood pressure greater than 130/80 mmHg, is the primary risk factor for developing coronary artery disease, stroke, and renal failure. Approximately 48% of American men and 43% of American women suffer from hypertension. Epidemiological data suggests that during reproductive years, women have much lower rates of hypertension than men. However, this protective effect disappears after the onset of menopause. Treatment-resistant hypertension affects approximately 10.3 million US adults and is unable to be controlled even after implementing ≥3 antihypertensives with complementary mechanisms. This indicates that other mechanisms responsible for modulating blood pressure are still unclear. Understanding the differences in genetic and hormonal mechanisms that lead to hypertension would allow for sex-specific treatment and an opportunity to improve patient outcomes. Therefore, this invited review will review and discuss recent advances in studying the sex-specific physiological mechanisms that affect the renin-angiotensin system and contribute to blood pressure control. It will also discuss research on sex differences in hypertension management, treatment, and outcomes.

Does Patient-Applied Testosterone Replacement Therapy Pose Risk for Blood Pressure Elevation? Circadian Medicine Perspectives

We reviewed medication package inserts, US Food and Drug Administration (FDA) reports, and journal publications concerning the 10 nonbiosimilar patient-applied (PA) testosterone (T) replacement therapies (TRTs) for intraday serum T patterning and blood pressure (BP) effects. Blood T concentration is circadian rhythmic in young adult eugonadal males, being highest around awakening and lowest before bedtime. T level and 24 h variation are blunted in primary and secondary hypogonadism. Utilized as recommended, most PA-TRTs achieve nonphysiologic T 24 h patterning. Only Androderm^® , an evening PA transdermal patch, closely replicates the normal T circadian rhythmicity. Accurate determination of risk for BP elevation and hypertension (HTN) by PA-TRTs is difficult due to limitations of office BP measurements (OBPM) and suboptimal methods and endpoints of ambulatory BP monitoring (ABPM). OBPM is subject to "White Coat" pressor effect resulting in unrepresentative BP values plus masked normotension and masked HTN, causing misclassification of approximately 45% of trial participants, both before and during treatment. Change in guideline-recommended diagnostic thresholds over time causes misclassification of an additional approximately 15% of participants. ABPM is improperly incorporated into TRT safety trials. It is done for 24 h rather than preferred 48 h; BP is oversampled during wakefulness, biasing derived 24 h mean values; 24 h mean systolic and diastolic BP (SBP, DBP) are inappropriate primary outcomes, because of not being best predictors of risk for major acute cardiovascular events (MACE); "daytime" and "nighttime" BP means referenced to clock time are reported rather than biologically relevant wake-time and sleep-time BP means; most importantly, asleep SBP mean and dipping, strongest predictors of MACE, are disregarded. © 2022 American Physiological Society. Compr Physiol 12: 1-20, 2022.

Emerging Roles for G Protein-Coupled Estrogen Receptor 1 in Cardio-Renal Health: Implications for Aging

Cardiovascular (CV) and renal diseases are increasingly prevalent in the United States and globally. CV-related mortality is the leading cause of death in the United States, while renal-related mortality is the 8th. Despite advanced therapeutics, both diseases persist, warranting continued exploration of disease mechanisms to develop novel therapeutics and advance clinical outcomes for cardio-renal health. CV and renal diseases increase with age, and there are sex differences evident in both the prevalence and progression of CV and renal disease. These age and sex differences seen in cardio-renal health implicate sex hormones as potentially important regulators to be studied. One such regulator is G protein-coupled estrogen receptor 1 (GPER1). GPER1 has been implicated in estrogen signaling and is expressed in a variety of tissues including the heart, vasculature, and kidney. GPER1 has been shown to be protective against CV and renal diseases in different experimental animal models. GPER1 actions involve multiple signaling pathways: interaction with aldosterone and endothelin-1 signaling, stimulation of the release of nitric oxide, and reduction in oxidative stress, inflammation, and immune infiltration. This review will discuss the current literature regarding GPER1 and cardio-renal health, particularly in the context of aging. Improving our understanding of GPER1-evoked mechanisms may reveal novel therapeutics aimed at improving cardio-renal health and clinical outcomes in the elderly.

Sex Differences in the Prevalence, Outcomes and Management of Hypertension

PURPOSE OF REVIEW

To review recent data on sex differences in the prevalence, outcomes and management of hypertension.

RECENT FINDINGS

Although hypertension is overall more common in males, females experience a much sharper incline in blood pressure from the third decade of life and consequently the prevalence of hypertension accelerates comparatively with age. Mechanisms responsible for these blood pressure trajectories may include the sustained vascular influence of hypertensive disorders of pregnancy, interactions between the renin-angiotensin-aldosterone system and sex hormones or even psychosocial gendered factors such as socioeconomic deprivation. Moreover, the impact of hypertension is not uniform and females are at higher risk of developing a multitude of adverse cardiovascular outcomes at lower blood pressure thresholds. Blood pressure is a sexually dimorphic trait and although significant differences exist in the prevalence, pathophysiology and outcomes of hypertension in males and females, limited data exist to support sex-specific blood pressure targets.

Sex steroids receptors, hypertension, and vascular ageing

Sex hormone receptors are expressed throughout the vasculature and play an important role in the modulation of blood pressure in health and disease. The functions of these receptors may be important in the understanding of sexual dimorphism observed in the pathophysiology of both hypertension and vascular ageing. The interconnectivity of these factors can be exemplified in postmenopausal females, who with age and estrogen deprivation, surpass males with regard to hypertension prevalence, despite experiencing significantly less disease burden in their estrogen replete youth. Estrogen and androgen receptors mediate their actions via direct genomic effects or rapid non-genomic signaling, involving a host of mediators. The expression and subtype composition of these receptors changes through the lifespan in response to age, disease and hormonal exposure. These factors may promote sex steroid receptor-mediated alterations to the Renin-Angiotensin-Aldosterone System (RAAS), and increases in oxidative stress and inflammation, thereby contributing to the development of hypertension and vascular injury with age.

Testosterone attenuates hypoxia-induced hypertension by affecting NRF1-mediated transcriptional regulation of ET-1 and ACE

Hypertension induced by hypoxia at high altitude is one of the typical symptoms of high-altitude reactions (HARs). Emerging evidence indicates that endothelial abnormalities, including increases in angiotensin-2 (Ang-2) and endothelin-1 (ET-1), are closely associated with hypertension. Thus, low blood oxygen-induced endothelial dysfunction through acceleration of Ang-2 and ET-1 synthesis may alleviate HARs. In this study, we investigated the effects of hypoxia on rat blood pressure (BP) and endothelial injury. We found that BP increased by 10 mmHg after treatment with 10% O₂ (~5500 m above sea level) for 24 h. Consistently, serum Ang-2 and ET-1 levels were increased along with decreases in NO levels. In endothelial cells, angiotensin-1-converting enzyme (ACE) and ET-1 expression levels were upregulated. Interestingly, nuclear respiratory factor 1 (NRF1) levels were also upregulated, consistent with the changes in ACE and ET-1 levels. We further demonstrated that NRF1 transcriptionally activated ACE and ET-1 by directly binding to their promoter regions, suggesting that the endothelial cell dysfunction induced by hypoxia was due to NRF1-dependent upregulation of ACE and ET-1. Surprisingly, testosterone supplementation showed significant protective effects on BP, while castration induced even higher BPs in rats exposed to hypoxia. We further showed that physiological testosterone repressed NRF1 expression in vivo and in vitro and thereby reduced Ang-2 and ET-1 levels, which was dependent on hypoxia. In summary, we have identified that physiological testosterone protects against hypoxia-induced hypertension through inhibition of NRF1, which transcriptionally regulates ACE and ET-1 expression.

Effects of the oral testosterone undecanoate Kyzatrex™ on ambulatory blood pressure in hypogonadal men

Testosterone replacement therapies have been shown to increase blood pressure (BP) in hypogonadal men. We studied the effects of a new formulation of testosterone undecanoate (Kyzatrex™) on ambulatory blood pressure (ABP) and heart rate, in 155 men with hypogonadism (mean age, 50.5 years, 76.8% white, 36.1% on antihypertensive therapy). The ABP, heart rate and clinical assessments were obtained at baseline and following 120 and 180 days of therapy. Mean changes from baseline in 24‐h ambulatory systolic BP of 1.7 mmHg (95% CI, 0.3, 3.1) at day 120 and 1.8 mmHg (95% CI, 0.3, 3.2) at day 180 were observed post‐treatment. For those men on antihypertensive drug therapy, increases in mean 24‐h systolic BP were greater than those not taking antihypertensive drugs (3.4 vs 0.7 mmHg at day 120 and 3.1 vs 1.0 mmHg at day 180, respectively). Changes from baseline in 24‐h diastolic BP and heart rate at day 120 were smaller (<1 mmHg and <1 beat/min, respectively). There were no relationships observed between testosterone concentration or hemoglobin levels with ABP. Multivariable analyses showed that baseline ambulatory BP and antihypertensive therapy were significantly correlated with BP changes. These data demonstrate small increases in ambulatory BP following 120 days on this oral testosterone undecanoate with no further changes at 180 days. Changes in ambulatory BP were minimal in patients not taking antihypertensive therapy.

Protective effects of ginseng stem-leaf saponins on D-galactose-induced reproductive injury in male mice

Panax ginseng is a perennial plant in the Araliaceae family. In this study, we investigated the protective effects of ginseng stem-leaf saponins (GSLS) isolated from P. ginseng against D-galactose-induced reproductive function decline, oxidative stress, and inflammatory response. Reproductive injuries were induced in mice via the subcutaneous injection of D-galactose (300 mg/kg) for six weeks. The mice were then treated with GSLS by intragastric administration. GSLS inhibited markers of oxidative stress and inflammatory cytokines induced by D-galactose in serum, liver and kidney, whereas GSLS increased the activities of antioxidant enzymes. Compared to the mice treated only with D-galactose, GSLS treatment significantly increased the average path velocity, straight line velocity, curvilinear velocity, and amplitude of the lateral head displacement of mouse sperm. Meanwhile, GSLS significantly increased the testosterone level and reduced the cortisol, FSH, and LH levels. Histopathological examination revealed alterations in the number and the arrangement of spermatogenic cells in the seminiferous tubules of the mice in the GSLS group. GSLS treatment suppressed MAPKs pathway activation in testes. These results suggest that GSLS can attenuate D-galactose-induced oxidative stress and inflammatory response in serum, liver and kidney, and ameliorate reproductive damage by inhibiting MAPKs signaling pathway.

Systemic effects of the hormonal treatment of male hypogonadism with preliminary indications for the management of COVID-19 patients

Male hypogonadism, defined as an inadequate production of testosterone (T), is associated with a greater morbidity and mortality. Epidemiological studies identified T deficiency as a risk factor for cardiovascular disease. Also, low serum T levels impact on glucose homeostasis through a worse glucose uptake, utilization, and disposal, and the general negative impact on metabolism. The aim of this review is to provide a comprehensive and updated overview of the effects of T replacement therapy on metabolic and cardiovascular systems and prostate tissue in patients with hypogonadism, including molecular mechanisms through which T exerts its actions. Furthermore, recent findings on novel coronavirus disease (COVID-19) epidemiology have shown a greater mortality in male compared with female patients and a role of T in promoting the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infection of the host cells has been demonstrated. Hence, the secondary aim of this review is to provide preliminary indications on the management in patients with COVID-19.

Study on the Antihypertensive Mechanism of Astragalus membranaceus and Salvia miltiorrhiza Based on Intestinal Flora-Host Metabolism

Our previous studies have shown that the combination of Astragalus membranaceus and Salvia miltiorrhiza (HD) had a good antihypertensive effect, but its potential mechanism remained unclear. This study aimed to investigate the role of intestinal flora and serum metabolism induced by HD against hypertension. 16 spontaneous hypertensive rats (SHRs) were divided into HD group (5.9 g/kg) and model group (M) (normal saline), with eight Wistar-Kyoto (WKY) rats as control group (W) (normal saline). Rats were fed by gavage once a day for 28 days. The changes of intestinal flora and serum metabolism were analyzed by 16S rDNA sequencing and LC-MS/MS assay. HD decreased blood pressure steadily, improved the structure and composition of imbalance flora in SHRs, increased the abundance and diversity of flora, and decreased flora Firmicutes to Bacteroidetes (F/B) ratio. Rumen bacterium NK4A214, Clostridium sp. MC 40 increased remarkably in M group. Akkermansia, Akkermansia muciniphila, and Lactobacillus intestinalis increased significantly in HD group, which were functionally related to the significant increase of Lachnoclostridium, Faecalibaculum, and Lactobacillus reuteri in W group, which were all probiotics producing butyric acid, lactic acid, and regulating inflammation and other antihypertensive related factors. HD also changed the serum metabolic pattern of SHRs. 16 potential biomarkers related to inflammation, vasodilation, steroid hormones, oxidative stress, and etc. changed significantly, mainly enriched in arachidonic acid metabolism, tryptophan metabolism, steroid hormone biosynthesis, and glutathione metabolism. The correlation analysis demonstrated that the dominant genius and species in three groups were highly correlated with steroid hormone biosynthesis, arachidonic acid metabolism, tryptophan metabolism, and vitamin B6 metabolism. Our research indicated that HD had a good antihypertensive effect, which may be driven by the protective intestinal flora and beneficial metabolites induced by it, and the metabolites were closely related to the changes of intestinal flora. It provided new insights for the antihypertensive mechanism of HD.

Paradoxical effect of testosterone supplementation therapy on cardiac ischemia/reperfusion injury in aged rats

Aging is followed by numerous physiological limitations that reduce health span, particularly cardiovascular and metabolic disorders. Testosterone supplementation therapy (TST) has been widely used in the treatment of aging dysfunctions in either adult or aged patients, although recent evidence have suggested that the incidence of myocardial infarction might be increased in elderly patients. So far, though, the effects of TST in the progression of cardiac ischemia/reperfusion (IR) injury in aged hearts remain unclear. Male aged (23-24 months old) and adult (6 months old) Wistar rats were treated with placebo (Old + Placebo n = 5 / Adult + Placebo n = 5) or TST (Old + TST n = 7 / Adult + TST n = 5) for 30 days. After euthanasia, artificially-perfused isolated rat hearts were submitted to IR. Cardiac expression levels of genes encoding α and β myosin heavy chain (MHC), ryanodine receptor (RyR), brain-natriuretic peptide (BNP), sarcoplasmic reticulum Ca2+ ATPase 2a (SERCA2a), glucose-regulated protein 78 kDa (GRP78), eukaryotic initiation factor 2α (eIF2α), C/EBP-homologous protein (CHOP), caspase 3 and B cell lymphoma 2 (Bcl-2) were accessed by qRT-PCR. Protein levels of CHOP, p-Akt, and p-glycogen synthase kinase 3β (p-GSK-3β) were measured by Western Blot. Compared to placebo-treated aged rats, Old + TST group exhibited increased heart weight and up-regulation of αMHC mRNA expression levels, whereas βMHC mRNA expression (p < 0.05). During reperfusion, left ventricular developed pressure, dP/dt+, dP/dt-, and cardiac contractile function index were increased in Old + TST rat hearts (p < 0.05), whereas infarct size was increased (p < 0.05) in comparison with Old + Placebo group. p-Akt levels of Old + TST rat hearts were decreased when compared to Old + Placebo group. Conversely, TST did not promote significant effects in adult rat hearts. Taken together, these findings suggest that myocardial stunning and infarct size of aged hearts were distinctly affected by TST.

Testosterone plays a permissive role in angiotensin II-induced hypertension and cardiac hypertrophy in male rats

Sex hormones contribute to sex differences in blood pressure. Inappropriate activation of the renin-angiotensin system is involved in vascular dysfunction and hypertension. This study evaluated the role of androgens (testosterone) in angiotensin II (Ang II)-induced increase in blood pressure, vascular reactivity, and cardiac hypertrophy. Eight-week-old male Wistar rats underwent sham operation, castration, or castration with testosterone replacement. After 12 weeks of chronic changes in androgen status, Ang II (120 ng/kg per minute) or saline was infused for 28 days via subcutaneous miniosmotic pump, and changes in blood pressure was measured. Vascular reactivity and Ang II receptor levels were examined in mesenteric arteries. Heart weight, cardiac ANP mRNA levels, and fibrosis were also assessed. Ang II infusion increased arterial pressure in intact males. The Ang II-induced increase in hypertensive response was prevented in castrated males. Testosterone replacement in castrated males restored Ang II-induced hypertensive responses. Castration reduced vascular AT1R/AT2R ratio, an effect that was reversed by testosterone replacement. Ang II-induced hypertension was associated with increased contractile response of mesenteric arteries to Ang II and phenylephrine in intact and testosterone-replaced castrated males; these increases were prevented in castrated males. Ang II infusion induced increased left ventricle-to-body weight ratio and ANP mRNA expression, indicators of left ventricular hypertrophy, and fibrosis in intact and testosterone-replaced castrated males, and castration prevented the increase in these parameters caused by Ang II. This study demonstrates that testosterone plays a permissive role in development and maintenance of Ang II-induced vascular dysfunction, hypertension, and cardiac hypertrophy.

A new approach to study the sex differences in adipose tissue

Obesity is one of the most invaliding and preventable diseases in the United States. Growing evidence suggests that there are sex differences in obesity in human and experimental animals. However, the specific mechanisms of this disease are unknown. Consequently, there is any particular treatment according to the sex/gender at this time. During the last decade, we observe a rise in the study of adipocyte and the possible mechanisms involved in the different roles of the fat. Furthermore, the effect of sex steroids on the adipocyte is one of the fields that need elucidation. Supporting evidence suggests that sex steroids play an essential role not only in the fat distribution, but also, in its metabolism, proliferation, and function. Thus, using in vitro and in vivo studies will contribute to our fight against this critical health public problem encompassing both sexes. In the present review, we discuss some of the recent advances in the adipocytes and the effect of the sex steroids on the adipose tissue. Also, we propose a new alternative to study the role of sex steroids on adipocyte biology through human adipose-derived stem cells.

DHEA Treatment Effects on Redox Environment in Skeletal Muscle of Young and Aged Healthy Rats

BACKGROUND

Dehydroepiandrosterone (DHEA) is an important precursor of active steroid hormone, produced abundantly by the adrenal cortex with an age-dependent pattern.

OBJECTIVE

We investigated whether chronic DHEA administration impacts on redox status and on Akt protein activation in skeletal muscle during the aging process (3 and 24 months-old rats).

METHODS

Rats received one weekly dose/5 weeks of DHEA (10 mg/kg) or vehicle. Gastrocnemius muscle was removed to evaluate glutathione system, hydrogen peroxide, antioxidant enzymes, and expression of Akt kinase protein.

RESULTS

In the 3-months-old rats DHEA induced an increase in hydrogen peroxide when compared both to its control (276%) and the 24-months-old DHEA group (485%). Moreover, in the 24- months-old rats DHEA caused an increase in GSSG (41 and 28%), a decrease in reduced-GSH (55 and 51%), and a more oxidized redox status (reduction in GSH/GSSG ratio, 47 and 65 %) when compared to 3-month-old DHEA and to 24-months-old control groups, respectively. Both older groups had increased G6PDH (2.7 fold) and GST (1.7 fold) activities when compared to younger groups, independently of any DHEA treatment. However, there was no modulation of Akt protein (phosphorylated/total isoform).

CONCLUSION

The results show that chronic DHEA administration to 3 and 24-months-old rats may not present positive effects regarding the redox environment in skeletal muscle without modulation of pro-survival Akt kinase. Due to the large-scale self-administration of DHEA as an "anti-aging" dietary supplement, it is crucial to investigate its molecular mechanisms over oxidative stressinduced related diseases.