Aged Female Wistar Rats Research Articles

PS-B02-15: LIGHT POLLUTION, OBESITY, AND HYPERTENSION- “LIFESTYLE” RISK FACTORS ASSOCIATED WITH AN INCREASED RISK OF MALIGNANT ARRHYTHMIAS. ANTIARRHYTHMIC EFFECT OF OMACOR.

Objective: Light pollution disrupts circadian rhythms that may promote obesity and hypertension, but their association with the susceptibility to malignant cardiac arrhythmias is not well known. We examined whether continuous light as well as a high sucrose diet affect rat heart gene transcripts, miRNAs, or protein expression and hence arrhythmogenesis. In parallel, the benefit of omega-3 (Omacor) supplementation was assessed. Design and method: In the first experiment, male and female spontaneously hypertensive (SHR) and normotensive Wistar (WR) rats were housed in 12 h/12 h light/dark cycles or exposed to continuous light at 300 lux for 6 weeks. In the second experiment, aged female WR rats were fed with 30% sucrose for 8 weeks. In both experiments half of the rats were supplemented with Omacor (200 mg /100 g b.w). Susceptibility to electrically-inducible ventricular fibrillation (VF) was assessed in perfused heart. Results: Rats exposed to continuous light or fed by sucrose were more vulnerable to develop VF. There was a down-regulation of myocardial connexin-43 (Cx43) along with an increased pro-inflammatory NF-kB and iNOS transcripts and decreased sarcoplasmic reticulum Ca2+ ATPase transcripts in response to continuous light. Omacor treatment increased the electrical threshold for VF induction associated with attenuation of pro-arrhythmic alterations in myocardial Cx43, NF-kB and iNOS. Sucrose fed rats exhibited suppression of Cx43 and PKC epsilon signaling, along with upregulation of myocardial PKC delta and miR-30a that is involved in fibrosis. Myocardial miR-1 expression levels involved in the regulation of Cx43 were not affected by the sucrose diet nor Omacor treatment. Antiarrhythmic effects of Omacor supplementation have been shown by attenuation of Cx43, PKC, and miR-30a myocardial abnormalities. Conclusions: Findings suggest that light pollution and sucrose diet jeopardize myocardial Cx43-mediated electrical communication, thereby increase susceptibility of the heart to malignant arrhythmias. Adverse effects were alleviated by treatment with Omacor, supporting its potential benefit and the relevance of monitoring the omega-3 index in at-risk human populations. This research was supported by VEGA 2/0002/20, 2/0158/19, APVV 21-0410, 18-0548, 19-0317, EU ITMS 26230120009

17β-Estradiol improves insulin signalling and insulin resistance in the aged female hearts: Role of inflammatory and anti-inflammatory cytokines

Aging effects in energy balance in all tissues and organs, including the cardiovascular. The risk of cardiovascular disease is drastically higher in postmenopausal women than in premenopausal women. Estrogen plays an important role in the cardiac function and body's metabolism. The aim of this study was to determine whether 17β-estradiol (E2) has beneficial effects on insulin resistance and some key stages of the insulin signalling pathway in the aged hearts. Young and aged female Wistar rats were ovariectomized and were randomly divided into three groups: young (YS) and aged (AS) sham, young (YV) and aged (AV) vehicle, and young (YE2) and aged (AE2) E2 treatment groups. E2 (1 mg/kg) was administrated every four days for four weeks. Results showed that ovariectomy increased fasting blood glucose, insulin, and HOMAIR in young, while none of these parameters was affected in aged animals. On the other hand, aging itself increased these variables. Furthermore, E2 therapy alleviated these changes in both young and aged animals. Moreover, aging also decreased the p-IRS1, p-Akt level, and translocation of GLUT4 to the plasma membrane. E2 reduced the negative impact of menopause and aging on insulin sensitivity by favoring increase in the level of IL-10 and decrease in the levels of TNF-α and IL-1β. Our results indicated that the heart response to E2 depended on age, and E2 increased insulin sensitivity in the heart of both young and aged animals by altering inflammatory conditions. Determining the exact mechanism of this action is suggested in future studies.

Myotendinous junction plasticity in aged ovariectomized rats submitted to aquatic training.

The study aims to describe the tissue plasticity of MTJ through the morphological analysis of MTJ soleus in ovariectomized aged female Wistar rats submitted to aquatic training. Forty aged Wistar rats, 1 year and 2 months of age, were divided into four groups: sedentary (S), trained (T), ovariectomized (O), and trained/ovariectomized (OT). Employing the transmission electron microscopy, the ultrastructural and morphometric elements were revealed. In the S group, changes in morphological characteristics as a consequence of the aging process were seen, demonstrated by the conical shape of the muscle cell extremity, a large area with collagen deposit, and misalignment of sarcomeres in series. The T group presented ample adjustments when revealed the organization of MTJ, through the increase of the contact area and greater lengths of sarcoplasmatic invaginations and evaginations. The O group revealed extensive tissue disorganization with muscle atrophy, reduction of MTJ contact area, and consequently, changes in sarcoplasmatic invaginations and evaginations. The OT group demonstrated extensive remodeling with restructuring MTJ through the increase of tissue contact area, extensive organization, parallel arrangement, and increased length of sarcoplasmatic invaginations and evaginations. The distal sarcomeres presented higher lengths compared to the proximal sarcomeres in both the groups. We conclude that aquatic training was effective in the organization and structural remodeling of the myotendinous interface of ovariectomized aged rats. There was a greater area of contact, and consequently, greater resistance in the myotendinous interface promoting a lower predisposition to injuries.

Effects of estradiol and genistein on the insulin signaling pathway in the cerebral cortex of aged female rats

Menopause leads to a decrease in estrogen production that increases central insulin resistance, contributing to the development of neurodegenerative diseases. We have evaluated the influence of aging and estradiol or genistein treatments on some key stages of the insulin signaling pathway in the cerebral cortex. Young and aged female Wistar rats were ovariectomized and treated acutely with 17β-estradiol (1.4μg/kg body weight), two doses of genistein (10 or 40mg/kg body weight), or vehicle. The cortical expression of several key insulin signaling pathway components was analyzed by western blotting. Our results showed an age-related deterioration in the interactions between the regulatory subunit of phosphatidylinositol 3-kinase (p85α) and the activated form of insulin receptor substrate 1 (p-IRS1tyr612), as well as between p85α and the 46kDa isoform of the estrogen receptor α (ERα46). Moreover, aging also decreased the translocation of glucose transporter-4 (GLUT4) to the plasma membrane. 17β-Estradiol but not genistein reduced the negative impact of aging on central insulin sensitivity by favoring this GLUT4 translocation, and therefore could be neuroprotective against the associated neurodegenerative diseases. However, protein kinase B (Akt) activation by genistein suggests that other possible mechanisms are involved in the neuroprotective effects of this phytoestrogen during the aging process.

17β-Estradiol and genistein acute treatments improve some cerebral cortex homeostasis aspects deteriorated by aging in female rats

Aging is associated with decreased insulin sensitivity and impaired cerebral glucose homeostasis. These changes increase neural sensitivity to metabolic damage contributing to cognitive decline, being the decrease in plasma estrogen following menopause one of the main factors involved in aged females. Phytoestrogens as genistein are structurally similar to 17β-estradiol, bind to estrogen receptors, and can evoke both estrogenic and anti-estrogenic effects. Estrogens and phytoestrogens have neuroprotective potential, but the physiological mechanisms are not fully understood. Young and aged female Wistar rats were ovariectomized and treated acutely with 17β-estradiol (1.4μg/kg body weight), genistein (10 or 40mg/kg body weight), or vehicle. Cortical expression of glucose transporter-3 (GLUT-3) and -4 (GLUT-4), cytochrome c oxidase (CO), estrogen receptor-α (ERα) and -β (ERβ) was measured by Western blotting. There was an age-related decline in GLUT-4, CO and ERβ levels. Both drugs, estradiol and genistein, were able to reverse GLUT-3 downregulation in the cortex following late ovariectomy. However, genistein was the only treatment able to restore completely GLUT-4 levels in aged rats. In contrast, estradiol was more potent than genistein at increasing CO, a marker of cerebral oxidative metabolism. As regards ER levels, estradiol increased the ERα67 quantity diminished by late ovariectomy, while genistein did the same with the other ERα isoform, ERα46, highlighting drug-specific differences in expression changes for both isoforms. On the other hand, no treatment-related differences were found regarding ERβ levels. Therefore, genistein like estradiol could be suitable treatments against cortical metabolic dysfunction caused by aging. These treatments may hold promise as neuroprotective strategies against diabetes and age-related neurodegenerative diseases.

Changes in kynurenine pathway metabolism in the brain, liver and kidney of aged female Wistar rats

The kynurenine pathway of tryptophan catabolism plays an important role in several biological systems affected by aging. We quantified tryptophan and its metabolites kynurenine (KYN), kynurenine acid (KYNA), picolinic acid (PIC) and quinolinic acid (QUIN), and activity of the kynurenine pathway enzymes indoleamine 2,3-dioxygenase (IDO), tryptophan 2,3-dioxygenase (TDO) and quinolinic acid phosphoribosyltransferase (QPRTase), in the brain, liver and kidney of young, middle-aged and old female Wistar rats. Tryptophan levels and TDO activity decreased in all tissues with age. In contrast, brain IDO activity increased with age, while liver and kidney IDO activity decreased with age. The levels of KYN, KYNA, QUIN and PIC in brain all increased with age, while the levels of KYN in the liver and kidney showed a tendency to decrease. The levels of KYNA in the liver did not change, but the levels of KYNA in the kidney increased. The levels of PIC and QUIN increased significantly in the liver but showed a tendency to decrease in the kidney. QPRTase activity in both brain and liver decreased with age but was elevated in the kidney in middle-aged (12-month-old) rats. These age-associated changes in tryptophan metabolism have the potential to impact upon major biological processes, including lymphocyte function, pyridine (NAD(P)(H)) synthesis and N-methyl-d-aspartate (NMDA)-mediated synaptic transmission, and may therefore contribute to several degenerative changes of the elderly.

Conjugated equine estrogens reverse the effects of aging on central and peripheral allopregnanolone and beta-endorphin levels in female rats

Objective To compare β-endorphin and allopregnanolone levels and their response to a 2-week oral estrogen treatment with conjugated equine estrogens (CEE) in young ovariectomized (ovx) and in healthy aged female rats. Design Prospective study. Setting Animal laboratory in an academic environment. Animal(s) Twenty-four young ovx and 24 healthy aged female Wistar rats were treated with CEE. Three 8-rat control groups (cycling, ovx, and aged rats) were also included. Intervention(s) Treated rats underwent 14-day oral treatment with three doses of CEE: 0.1 mg/kg/day, 0.5 mg/kg/day, and 2 mg/kg/day. Main outcome measure(s) Cerebral and peripheral β-endorphin and allopregnanolone levels. Result(s) Beta-endorphin levels were lower in aged vs. cycling and ovx control rats. In brain and serum allopregnanolone levels were lower in aged vs. cycling control rats, whereas in the adrenals they were higher in aged vs. cycling animals. In the hypothalamus and anterior pituitary allopregnanolone levels were lower in ovx vs. aged animals. In both ovx and aged animals, CEE treatment reverted the effects of ovariectomy and aging, in a dose-dependent manner. Conclusion(s) Aging is associated with a decrease in cerebral and peripheral β-endorphin and allopregnanolone. In hypoestrogenic rats, CEE treatment restores allopregnanolone and β-endorphin content; this indicates a role for these compounds as neuroendocrine mediators of the effects of estrogens.