Effect of estradiol and progesterone treatment on carbohydrate metabolizing enzymes in tissues of aging female rats

Influence of menstrual cycle on muscle glycogen utilization during high-intensity intermittent exercise until exhaustion in healthy women

The present study investigated the effects of the menstrual cycle on muscle glycogen and circulating substrates during high-intensity intermittent exercise until exhaustion in healthy women who habitually exercised. In total, 11 women with regular menstrual cycles completed three tests, which comprised the early follicular phase (E-FP), late follicular phase (L-FP), and luteal phase (LP) of the menstrual cycle. High-intensity intermittent exercise until exhaustion was performed on each test day. Evaluation of muscle glycogen concentration by ¹³C-magnetic resonance spectroscopy and measurement of estradiol, progesterone, blood glucose, lactate, free fatty acids (FFA), and insulin concentrations were conducted before exercise (Pre) and immediately after exercise (Post). Muscle glycogen concentrations from thigh muscles at Pre and Post were not significantly different between menstrual cycle phases (P = 0.57). Muscle glycogen decreases by exercise were significantly greater in L-FP (59.0 ± 12.4 mM) than in E-FP (48.3 ± 14.4 mM, P < 0.05). Nonetheless, blood glucose, blood lactate, serum FFA, serum insulin concentrations, and exercise time until exhaustion in E-FP, L-FP, and LP were similar. The study results suggest that although exercise time does not change according to the menstrual cycle, the menstrual cycle influences muscle glycogen utilization during high-intensity intermittent exercise until exhaustion in women with habitual exercise activity. Novelty: This study compared changes in muscle glycogen concentration across the menstrual cycle during high-intensity intermittent exercise until exhaustion using ¹³C-magnetic resonance spectroscopy. Our results highlight the influence of the menstrual cycle on muscle glycogen during high-intensity intermittent exercise in healthy women.

Neuroimmunomodulation by estrogen in health and disease

Systemic homeostasis is maintained by the robust bidirectional regulation of the neuroendocrine-immune network by the active involvement of neural, endocrine and immune mediators. Throughout female reproductive life, gonadal hormones undergo cyclic variations and mediate concomitant modulations of the neuroendocrine-immune network. Dysregulation of the neuroendocrine-immune network occurs during aging as a cumulative effect of declining neural, endocrine and immune functions and loss of compensatory mechanisms including antioxidant enzymes, growth factors and co-factors. This leads to disruption of homeostasis and sets the stage for the development of female-specific age-associated diseases such as autoimmunity, osteoporosis, cardiovascular diseases and hormone-dependent cancers. Ovarian hormones especially estrogen, play a key role in the maintenance of health and homeostasis by modulating the nervous, endocrine and immune functions and thereby altering neuroendocrine-immune homeostasis. Immunologically estrogen's role in the modulation of Th1/Th2 immune functions and contributing to pro-inflammatory conditions and autoimmunity has been widely studied. Centrally, hypothalamic and pituitary hormones influence gonadal hormone secretion in murine models during onset of estrous cycles and are implicated in reproductive aging-associated acyclicity. Loss of estrogen affects neuronal plasticity and the ensuing decline in cognitive functions during reproductive aging in females implicates estrogen in the incidence and progression of neurodegenerative diseases. Peripherally, sympathetic noradrenergic (NA) innervations of lymphoid organs and the presence of both adrenergic (AR) and estrogen receptors (ER) on lymphocytes poise estrogen as a potent neuroimmunomodulator during health and disease. Cyclic variations in estrogen levels throughout reproductive life, perimenopausal surge in estrogen levels followed by its precipitous decline, concomitant with decline in central hypothalamic catecholaminergic activity, peripheral sympathetic NA innervation and associated immunosuppression present an interesting study to explore female-specific age-associated diseases in a new light.

Estrogen-induced neuroprotective and anti-inflammatory effects are dependent on the brain areas of middle-aged female rats

BACKGROUND

Reproductive aging in females is characterized by fluctuations and precipitous decline in estrogen levels, which may lead to reduction in cognitive function and age-associated neurodegenerative disorders. The nature of estrogen-mediated neuronal plasticity is unknown during reproductive aging. We hypothesize that estrogen treatment of early middle-aged ovariectomized rats may exert specific effects in the brain by modulating signaling pathways regulating metabolic enzymes, inflammatory markers, antioxidant status, cholinergic function and survival signals.

PURPOSE

To investigate the mechanisms of estrogen-induced effects on neuroprotection and neuroinflammation through the involvement of intracellular signaling pathways in brain areas of ovariectomized (OVX) middle-aged (MA) female rats.

METHODS

Ovariectomized early MA female Sprague-Dawley rats (n=8/group) were implanted with 17β-estradiol (E2) 30-day release pellets (0.6μg and 300μg). At the end of the treatment period, frontal cortex (FC), striatum (STR), medial basal hypothalamus (MBH), and hippocampus (HP) were isolated and examined for the expression of tyrosine hydroxylase (p-TH), nerve growth factor (NGF), p-NF-κB (p50 and p65)and p-ERK, p-CREB, p-Akt, and activities of cholinesterases and antioxidant enzymes, key regulatory enzymes of metabolic pathways, and nitric oxide production.

RESULTS

E2 enhanced p-TH expression in FC and HP, reduced NGF expression in HP, and suppressed p-NF-κB expression in FC and STR. It also increased the expression of molecular markers (p-ERK, p-CREB and p-Akt), and nitric oxide production in various brain areas, while differentially regulating the activities of metabolic enzymes and cholinesterases.

CONCLUSION

Estrogen modulates the neural and inflammatory factors, and intracellular markers depending on the brain areas that may influence differential remodeling of neuronal circuitry which can be used to develop therapeutic strategies in cognitive impairment and neurodegenerative disorders in aging.

Early decline in glucose transport and metabolism precedes shift to ketogenic system in female aging and Alzheimer's mouse brain: implication for bioenergetic intervention

We previously demonstrated that mitochondrial bioenergetic deficits in the female brain accompanied reproductive senescence and was accompanied by a shift from an aerobic glycolytic to a ketogenic phenotype. Herein, we investigated the relationship between systems of fuel supply, transport and mitochondrial metabolic enzyme expression/activity during aging (3–15 months) in the hippocampus of nontransgenic (nonTg) background and 3xTgAD female mice. Results indicate that during female brain aging, both nonTg and 3xTgAD brains undergo significant decline in glucose transport, as detected by FDG-microPET, between 6–9 months of age just prior to the transition into reproductive senescence. The deficit in brain metabolism was sustained thereafter. Decline in glucose transport coincided with significant decline in neuronal glucose transporter expression and hexokinase activity with a concomitant rise in phosphorylated/inactivated pyruvate dehydrogenase. Lactate utilization declined in parallel to the decline in glucose transport suggesting lactate did not serve as an alternative fuel. An adaptive response in the nonTg hippocampus was a shift to transport and utilization of ketone bodies as an alternative fuel. In the 3xTgAD brain, utilization of ketone bodies as an alternative fuel was evident at the earliest age investigated and declined thereafter. The 3xTgAD adaptive response was to substantially increase monocarboxylate transporters in neurons while decreasing their expression at the BBB and in astrocytes. Collectively, these data indicate that the earliest change in the metabolic system of the aging female brain is the decline in neuronal glucose transport and metabolism followed by decline in mitochondrial function. The adaptive shift to the ketogenic system as an alternative fuel coincided with decline in mitochondrial function. Translationally, these data provide insights into the earliest events in bioenergetic aging of the female brain and provide potential targets for preventing shifts to less efficient bioenergetic fuels and transition to the ketogenic phenotype of the Alzheimer's brain.

The estrogen receptor-α is required and sufficient to maintain physiological glucose uptake in the mouse heart

Estrogens attenuate cardiac hypertrophy and increase cardiac contractility via their cognate estrogen receptors (ERs) ERα and ERβ. Because female sex hormones enhance global glucose use and because myocardial function and mass are tightly linked to cardiac glucose metabolism, we tested the hypothesis that expression and activation of the ERα might be required and sufficient to maintain physiological cardiac glucose uptake in the murine heart. Cardiac glucose uptake quantified in vivo by 18F-fluorodeoxyglucose positron emission tomography was strongly impaired in ovariectomized compared with gonadal intact female C57BL/6JO mice. The selective ERα agonist 16α-LE2 and the nonselective ERα and ERβ agonist 17β-estradiol completely restored cardiac glucose uptake in ovariectomized mice. Cardiac 18F-fluorodeoxyglucose uptake was strongly decreased in female ERα knockout mice compared with wild-type littermates. Analysis of cardiac mRNA accumulation by quantitative RT-PCR revealed an upregulation of genes involved in glycolisis and tricarboxylic acid cycle by ERα treatment. In conclusion, systemic activation of ERα is sufficient, and its expression is required to maintain physiological glucose uptake in the murine heart, which is likely to contribute to known cardioprotective estrogen effects.

The gonadal hormone regulates the plasma lactate levels in type 2 diabetes treated with and without metformin

OBJECTIVE

Our previous study showed there was a gender difference in plasma lactate concentrations in subjects with type 2 diabetes. This study investigated the effect of sex hormone levels on plasma lactic acid (LA) levels in type 2 diabetes with and without metformin therapy.

SUBJECTS AND METHODS

Fasting whole blood specimens of 392 type 2 diabetes patients treated with metformin (n=199) or not (n=193) were collected. LA was measured with an enzyme-electrode assay. Levels of sex hormones, including testosterone (T) and estradiol (E(2)), were measured with a chemiluminescence microparticle immunoassay. Spearman's or Pearson's correlation and logistic regression analysis were performed for the factors associated with LA.

RESULTS

The LA level in the metformin group was significantly higher than that in the non-metformin group (1.26±0.43 vs. 1.14±0.49 mmol/L, P<0.001), and LA levels of females were significantly higher than those of males (P<0.001). LA concentrations were positively correlated with E(2) level but negatively correlated with metformin and T levels (P<0.01). The logistic regression analysis showed that gender, creatinine, E(2), metformin, and T were independent factors influencing lactate levels. Analysis of subgroups demonstrated that the LA concentrations increased with the elevation of E(2) level (P<0.05) but decreased with the rising of T level (P<0.05).

CONCLUSIONS

Sex hormones play an important role on regulating plasma lactate levels in diabetes patients treated with metformin. E(2) up-regulates but T tend to down-regulate lactate levels.

Estradiol modulates membrane-linked ATPases, antioxidant enzymes, membrane fluidity, lipid peroxidation, and lipofuscin in aged rat liver

Free radical production and oxidative stress are known to increase in liver during aging, and may contribute to the oxidative damage. These changes increase during menopausal condition in females when the level of estradiol is decreased. The objective of this study was to observe the changes in activities of membrane linked ATPases (Na⁺K⁺ ATPase, Ca²⁺ ATPase), antioxidant enzymes (superoxide dismutase, glutathione-S-transferase), lipid peroxidation levels, lipofuscin content and membrane fluidity occurring in livers of female rats of 3, 12 and 24 months age groups, and to see whether these changes are restored to 3 months control levels rats after exogenous administration of 17-β-estradiol (E2). The aged rats (12 and 24 months) were given subcutaneous injection of E2 (0.1 μg/g body weight) daily for one month. The results obtained in the present work revealed that normal aging was associated with significant decrease in the activities of membrane linked ATPases, antioxidant enzymes, membrane fluidity and an increase in lipid peroxidation and lipofuscin content in livers of aging female rats. The present study showed that E2 treatment reversed the changes to normal levels. E2 treatment may be beneficial in preventing some of the age related changes in the liver by increasing antioxidant defenses.

Protective effects of 17β estradiol on altered age related neuronal parameters in female rat brain

Biological aging is a fundamental process observed in almost all living beings. During aging the brain experiences structural, molecular, and functional alterations. Aging in females and males is considered as the end of natural protection against age related diseases like osteoporosis, coronary heart disease, diabetes, Alzheimer's and Parkinson's disease. These changes increase during menopausal condition in females when the level of estradiol is decreased. The aim of the present study was to investigate the anti-aging and protective potential of 17β estradiol (E2) treatment on activities of membrane linked ATPases (Na⁺K⁺ ATPase, Ca²⁺ATPase), antioxidant enzymes (superoxide dismutases, glutathione-S-transferases), intrasynaptosomal calcium levels, membrane fluidity and neurolipofuscin in the brain of aging female rats of 3 months (young), 12 months (adult) and 24 months (old) age groups, and to see whether these changes are restored to normal levels after exogenous administration of E2 (0.1 μg/g body weight for one month).The results obtained in the present work revealed that normal aging was associated with significant decrease in the activities of membrane linked ATPases, antioxidant enzymes and an increase in neurolipofuscin, intrasynaptosomal calcium levels in brain of aging female rats. The present study showed that E2 treatment reversed the changes to near normal levels. E2 treatment appears to be beneficial in preventing some of the age related changes in the brain, an important anti-aging effect of the hormone.

Physiological and biochemical effects of 17β estradiol in aging female rat brain

Aging in females and males is considered as the end of natural protection against age related diseases like osteoporosis, coronary heart disease, diabetes, Alzheimer's disease and Parkinson's disease. These changes increase during menopausal condition in females when the level of estradiol is decreased. The objective of this study was to observe the changes in activities of monoamine oxidase, glucose transporter-4 levels, membrane fluidity, lipid peroxidation levels and lipofuscin accumulation occurring in brains of female rats of 3 months (young), 12 months (adult) and 24 months (old) age groups, and to see whether these changes are restored to normal levels after exogenous administration of estradiol (0.1 μg/g body weight for 1 month). The results obtained in the present work revealed that normal aging was associated with significant increases in the activity of monoamine oxidase, lipid peroxidation levels and lipofuscin accumulation in the brains of aging female rats, and a decrease in glucose transporter-4 level and membrane fluidity. Our data showed that estradiol treatment significantly decreased monoamine oxidase activity, lipid peroxidation and lipofuscin accumulation in brain regions of aging rats, and a reversal of glucose transporter-4 levels and membrane fluidity was achieved, therefore it can be concluded from the present findings that estradiol's beneficial effects seemed to arise from its antilipofuscin, antioxidant and antilipidperoxidative effects, implying an overall anti-aging action. The results of this study will be useful for pharmacological modification of the aging process and applying new strategies for control of age related disorders.

Myelin pathogenesis and functional deficits following SCI are age-associated

Most spinal cord injuries (SCI) occur in young adults. In the past few decades however, the average age at time of SCI and the percentage of injuries in persons over the age of 60 have increased. Studies have shown that there is an age-associated delay in the rate of remyelination following toxin-induced demyelination of the spinal cord, suggesting that there may be an age-associated difference in regenerative efficiency. Here we examine for the first time locomotor recovery, bladder recovery, and myelin pathology in young (3 months), aged (12 months), and geriatric (24 months) female rats following contusion SCI. Our assessments indicate that aged and geriatric rats have a delayed rate of locomotor recovery following contusion SCI as compared to young rats. Additionally, aged and geriatric rats have significantly slower bladder recovery as compared to young rats. Examination of myelin pathology reveals that aged and geriatric rats have significantly greater area of pathology and amount of demyelination, as well as significantly less remyelination as compared to young rats following contusion SCI. These data are the first to indicate that there is an age-associated decline in the rate and extent of both locomotor and bladder recovery following contusion SCI, and that age adversely affects the degree of general pathology, demyelination, and remyelination that accompanies contusion SCI.

Impact of female sex hormones on liver tissue lactic acidosis during ischemia

BACKGROUND

Lower liver transplant success is observed when the donor is female. Intracellular acidosis during ischemia is proposed to contribute to the injury sustained by the transplanted organ and its role in livers obtained from nonheartbeating donors is unclear. Research has shown that livers of female rats develop a greater degree of intracellular acidosis during ischemia than males. This work explores the role of sex hormones in mediating this sex difference.

METHODS

Subgroups of neutered female rats were given 17 beta-estradiol (E), progesterone (P), or combination (E+P). To compare the effects of female sex hormones in males, subgroups of intact and castrated males received 17 beta-estradiol. In vivo and ischemic liver biopsies were taken and analyzed for lactate and H.

RESULTS

Although there was no effect of hormone therapy on baseline metabolic parameters, during ischemia compared to neutered females, livers from E females significantly (P<0.01) increased lactate by 56% and H+ by 71%, while E+P significantly increased only lactate (39%; P<0.05). Livers from neutered males given 17 beta-estradiol showed significantly greater (P<0.001) accumulation of lactate (80%) and H+ (79%). This was even shown in intact males, where despite a blunted response, 17 beta-estradiol, significantly (P<0.05) increased lactate by 39% and H+ by 25%.

CONCLUSION

This study illustrates the mechanisms for the sex difference in the liver's metabolic response to ischemia are estrogen mediated, which is seen even in the presence of male hormones, thus offering one explanation for the lower liver transplant success when the donor is female.

Effect of hormone replacement therapy in normalizing age related neuronal markers in different age groups of naturally menopausal rats

Aging of the normal brain is accompanied by changes in its structure, function, and metabolism. There are significant gender differences in aging brain. Most of these changes increase during menopausal condition in females when the level of estradiol and progesterone are decreased. The objective of this study was to determine the effect of estradiol and progesterone (separate as well as combined) hormones in neuronal tissues from naturally menopausal rats of different age groups. Results show decreased activity of Acetylcholine esterase (AChE) whereas the level of lipid peroxidation increased with age, and after the hormone treatments both AChE activity and level of lipid peroxidation returned to control values. The deposition of lipofuscin, a pigment that accumulated intraneuronally in brain and other tissues and is considered a marker of aging, was increased with aging and the hormone treatment decreased this deposition. The present study clearly shows reduction in risk factors associated with aging in the murine model system by hormone treatments, namely estrogen and progesterone by increasing the activity of acetylcholine esterase and decreasing the levels of lipid peroxidation and lipofuscin deposition in different parts of aging brain. This study suggests that hormone replacement therapy may either reduce or delay the onset of age related diseases like Alzheimer's, Parkinson's and other neurological disorders.

Chronic estradiol and progesterone treatment in conscious dogs: effects on insulin sensitivity and response to hypoglycemia

We evaluated the effect of chronic (3 wk) subcutaneous treatment with progesterone and estradiol (PE; producing serum levels observed in the 3rd trimester of pregnancy) or placebo (C) on hepatic and whole body insulin sensitivity and response to hypoglycemia in conscious, overnight-fasted nonpregnant female dogs, using tracer and arteriovenous difference techniques. Insulin was infused peripherally for 3 h at 1.8 mU x kg(-1) x min(-1). Glucose was allowed to fall to 3 mM (Hypo) or maintained at 6 mM (Eugly) by peripheral glucose infusion. Insulin concentrations were significantly higher in Eugly-PE (n = 7) and Hypo-PE (n = 7) than in Eugly-C (n = 6) and Hypo-C groups (n = 7), but there were no significant differences in hepatic insulin extraction. Concentrations of glucagon, cortisol, epinephrine, and norepinephrine did not differ significantly between Eugly groups or between Hypo groups. Whole body glucose disposal, adjusted for the differences in insulin between groups, was 35% higher in Eugly-C vs. Eugly-PE groups (P < 0.05). Eugly-C and Eugly-PE groups exhibited similar rates of net hepatic glucose uptake, but the rate of glucose appearance was greater in Eugly-PE in the last hour (P < 0.05). Net hepatic glucose output was greater (P < 0.05) in Hypo-PE than in Hypo-C groups, and the glucose infusion rate required to maintain equivalent hypoglycemia was less (P < 0.05). The rate of gluconeogenic flux did not differ between Hypo groups. Chronic progesterone and estradiol exposure caused whole body (primarily skeletal muscle) insulin resistance and enhanced the liver's response to hypoglycemia without altering counterregulatory hormone concentrations.

Estradiol and progesterone treatments change the lipid profile in naturally menopausal rats from different age groups

The effect of estradiol and progesterone therapy in serum and liver on the lipid profile of naturally menopausal albino rats of the Wistar strain of different age groups (12,18 and 24 months) have been measured and compared with the age matched groups. Three months old rats were used as young controls. The aged rats were administered subcutaneous injection of 17-beta-estradiol (0.1 microg/g body weight), progesterone (2.5 microg/g body weight) and similar concentrations of both in combined treatment for 1 month and the level of triglycerides (TG), total lipids (TL), total cholesterol (TC), high density lipoprotein (HDL), low density lipoprotein (LDL) and very low density lipoprotein (VLDL) were measured in serum and liver of 3, 12, 18 and 24 months old control as well as treated groups. The results show that TG, HDL, VLDL levels were increased significantly by 71%, 155%, 54%, respectively in liver of 24 months old rats by combination treatment when compared with age matched control animals. The levels of TL, TC and LDL were decreased by 20%, 31%, and 30%, respectively in serum of 12 months old rats in combination treatment group. The effect was more significant in 12 and 24 months old female rats with administration of estrogen and combined (EP) treatments. The results indirectly suggest that hormone replacement therapy (HRT) can reduce the risk of cardiovascular disease (CVD) thereby playing a cardio-protective role by restoring lipid and hormone levels to the similar levels as found in young female animals.