Aged Rats Research Articles

Early life consumption of a "processed" diet high in advanced glycation end products impairs memory function and alters the gut microbiome in rats

Recent evidence indicates that “ultra-processed” foods constitute ~65% of total energy intake among children in the U.S. The impacts of excessive processed food consumption during development are poorly understood, in part because there are neither clear definitions of, nor a robust classification system accounting for, the complexity of food processing variables and how they interrelate in final food products. Heat treatment, a common form of food processing, can induce the chemical Maillard reaction and lead to foods rich in advanced glycation end products (AGEs). The neurocognitive implications of high levels of AGE consumption, particularly during early life, are unknown. Here, we used a rat model to evaluate the effects of adolescent consumption of a heat-treated diet high in AGEs on cognition and the gut microbiome in adulthood. In a series of studies, rats received either an otherwise healthy AGE-rich diet (AGE rats; AIN-93G diet heated at 160ºC for 60min) or a non-AGE-rich diet (CTL rats; AIN-93G diet without heat treatment) during adolescence (postnatal days 26-60). Metabolic, behavioral, and gut microbiome assessments were performed in adulthood. Results revealed that AGE rats exhibited hippocampal (HPC)-dependent memory deficits relative to CTL rats in the absence of altered body weight, body composition, glucose tolerance, and behavioral measures of anxiety. Administering a drug to break down AGEs (alagebrium; 1mg/kg/day) concomitantly with the heat-treated diet prevented memory impairments, supporting a causal role of AGEs in early life diet-induced HPC dysfunction. Microbiome sequencing analyses revealed that AGE rats had substantially reduced abundance of the bacterial genus Lactococcus relative to controls, and Lactococcus abundance was strongly correlated with memory performance. Administration of Lactococcus lactis by oral gavage (109 colony forming units/day) from PN 26-40 during exposure to the heat-treated diet rescued the AGE diet-induced memory impairments. Collective findings from this work identify a connection between a specific food processing variable (i.e., increased dietary AGEs through heat treatment), the gut microbiome, and impaired neurocognition. This work was supported by the National Institute of Diabetes and Digestive and Kidney Diseases under grant DK123423 (awarded to SEK and AAF); the National Institute on Aging through a Postdoctoral Ruth L. Kirschstein National Research Service Award under grant F32AG077932 (awarded to AMRH); and a National Science Foundation Graduate Research Fellowship (awarded to LT). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Investigating the Effect of Rapamycin on Impaired Proteostasis in Aged Skeletal Muscle After Disuse Atrophy

Older individuals undergo loss of muscle mass and strength, which can be compounded during bed rest and extended hospital stays. Adult and aged individuals lose muscle mass at similar rates during periods of disuse; however, only aged skeletal muscle fails to fully recover once activity resumes. Current efforts to facilitate skeletal muscle recovery are aimed at increasing myofibrillar protein synthesis by stimulating mTORC1(mammalian target of rapamycin complex 1), a major regulator of protein synthesis. However, we showed that skeletal muscle in aged rats already has higher rates of myofibrillar protein synthesis and mTORC1 activity than adult rats. We also showed that aged skeletal muscle has an accumulation of insoluble ubiquitinated proteins compared to adult muscle, indicating impaired proteostasis and possibly impaired autophagy degradation. We hypothesized that mTORC1 inhibition via rapamycin administration would reduce protein synthesis and the accumulation of p62 aggregates, facilitating recovery in aged skeletal muscle after disuse. Methods: Adult (10 months) and old (26 months) OKC HET rats were hindlimb unloaded (HU) for 14-days to induce atrophy, followed by subsequent 14 days of reloading (RE) through normal ambulation. Animals were fed either a control or rapamycin-supplemented (42 ppm) diet. To determine bulk protein synthesis, rats were labeled with deuterium oxide (D2O) during weight bearing (WB), HU, and RE, (n=4-6 per time point per group). Finally, to assess the presence of autophagy related protein aggregates we immuno stained for Sequestosome 1/p62, an autophagy cargo receptor protein. Results: Our data showed that myofibrillar protein synthesis rates were elevated in the old muscle compared to the adult ( k = 0.029 1/day ±0.002 vs. 0.039 1/day ±0.002, p<0.0001), and that protein synthesis rates were lower in the old rapamycin cohort (k = 1/day ±0.002 vs. 1/day ±0.003, p<0.0001). Furthermore, p62 puncta was three-fold more abundant (p<0.01) in aged skeletal muscle, compared to the adult muscle. Although the sample size is small, when comparing p62 puncta in the old rapamycin group to the old controls, there was no difference between the cohorts. Conclusion: We show that mTORC1 inhibition reduces protein synthesis in aged skeletal muscle. We also show that aged muscle has more p62 aggregates compared to adult skeletal muscle, indicating that autophagy related targets are not being degraded effciently with age. Further analyses will assess the effects of mTORC1 inhibition on other proteostatic mechanisms in atrophied skeletal muscle of aged rats. NIA Training Grant: 5T32AG052363-04VA I01 BX005592 APS SURF. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Mitochondrial Fragmentation Increases with Aging in Rats

The diaphragm muscle (DIAm) is the major pump muscle for breathing. Neural control of the DIAm involves recruitment of phrenic motor neurons (PhMNs) comprising motor units that vary in their mechanical and fatigue properties. Smaller PhMNs innervating fatigue resistant DIAm fibers are highly active being recruited during breathing, while larger PhMNs are infrequently recruited during more forceful expulsive behaviors. Previously, we found that to support their higher activity levels, smaller PhMNs have higher mitochondrial volume density and are less fragmented compared to larger PhMNs. With aging, larger PhMNs are more vulnerable and ~30% are lost, and those surviving display greater mitochondrial fragmentation. We also found that older rats exhibit elevated levels of the proinflammatory cytokine tumor necrosis factor alpha (TNFa), which in other tissue has been linked to mitochondrial fragmentation via activation of the IRE1a S724-mediated endoplasmic reticulum (ER) stress pathway. Accordingly, we hypothesized that in 24-month-old rats, increased TNFa levels activate the pIRE1aS724-mediated ER stress pathway, leading to XBP1s splicing, which transcriptionally increases expression of cyclin-dependent kinases (CDK1 and CDK5) that mediate phosphorylation of DRP1 at Serine 616 (pDRP1S616), and ultimately mitochondrial fragmentation. We found that serum TNFa levels increased ~3.5 fold in 24-month rats compared to 6-month rats. Consistent with elevated TNFa, we found increased pIRE1aS724 and XBP1s splicing in the cervical ventral horn of 24-month rats. In retrogradely labeled PhMNs, we found XBP1s was localized to the nucleus, consistent with transcriptional activation of gene expression. Bioinformatic analysis and ChIP assay confirmed XBP1s binding to the CDK1 and CDK5 promoter regions in rat cervical ventral horn. Both CDK1 and CDK5 mRNA and protein were elevated in the cervical ventral of 24-month rats. In aged rats, pDRP1S616 phosphorylation increased with a corresponding increase in mitochondrial fragmentation. Our results support our hypothesis that chronic inflammation (elevated TNFa levels) in older rats activate the pIRE1aS724-mediated ER stress pathway, leading to XBP1s splicing, which transcriptionally targets CDK1 and CDK5 expression mediating pDRP1S616 phosphorylation and mitochondrial fragmentation. Research Supported by NIH R01 grant AG44615. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

High-fat diet induces sarcopenic obesity in natural aging rats through the gut–trimethylamine N-oxide–muscle axis

IntroductionThe lack of suitable animal models for sarcopenic obesity (SO) limits in-depth research into the disease. Emerging studies have demonstrated that gut dysbiosis is involved in the development of SO. As the importance of microbial metabolites is starting to unveil, it is necessary to comprehend the specific metabolites associated with gut microbiota and SO. ObjectivesWe aimed to investigate whether high-fat diet (HFD) causes SO in natural aging animal models and specific microbial metabolites that are involved in linking HFD and SO. MethodsYoung rats received HFD or control diet for 80 weeks, and obesity-related metabolic disorders and sarcopenia were measured. 16S rRNA sequencing and non-targeted and targeted metabolomics methods were used to detect fecal gut microbiota and serum metabolites. Gut barrier function was evaluated by intestinal barrier integrity and intestinal permeability. Trimethylamine N-oxide (TMAO) treatment was further conducted for verification. ResultsHFD resulted in body weight gain, dyslipidemia, impaired glucose tolerance, insulin resistance, and systemic inflammation in natural aging rats. HFD also caused decreases in muscle mass, strength, function, and fiber cross-sectional area and increase in muscle fatty infiltration in natural aging rats. 16S rRNA sequencing and nontargeted and targeted metabolomics analysis indicated that HFD contributed to gut dysbiosis, mainly characterized by increases in deleterious bacteria and TMAO. HFD destroyed intestinal barrier integrity and increased intestinal permeability, as evaluated by reducing levels of colonic mucin-2, tight junction proteins, goblet cells and elevating serum level of fluorescein isothiocyanate-dextran 4. Correlation analysis showed a positive association between TMAO and SO. In addition, TMAO treatment aggravated the development of SO in HFD-fed aged rats through regulating the ROS-AKT/mTOR signaling pathway. ConclusionHFD leads to SO in natural aging rats, partially through the gut–microbiota–TMAO–muscle axis.

Estrogen deficiency in rats alters the expression and localization of redox proteins in the bone and bone marrow

Imbalances in bone formation/bone resorption ratio can occur under diverse conditions and diseases leading to an alteration of bone mineral density and strength. One of the most dramatic changes altering bone’s microarchitecture occurs under estrogen deficient conditions in humans and in other mammals. For instance, estrogen deficiency during menopause in women induces the formation and accumulation of reactive oxygen species (ROS) and a dysregulation of redox signaling. The bone and bone marrow are especially susceptible to the effects of oxidative stress and ROS. In tissues like the bone, cells are equipped with important defense systems to maintain homeostasis and to survive. Redox proteins of the thioredoxin family represent the most important protective system in cells that act against ROS and repair their intracellular effects. Redox proteins of the thioredoxin family comprise thioredoxins (Trxs), glutaredoxins (Grxs), and peroxiredoxins (Prxs). From all these protein classes, Prxs are the only ones that work as classical ROS scavengers being able to reduce hydrogen peroxide (H2O2), peroxynitrites and organic peroxides. Prxs are localized in different cellular compartments such as mitochondria (Prx3), cytosol and nucleus (Prx1 and Prx2), endoplasmic reticulum (Prx4), and peroxisomes (Prx5). We hypothesized that changes in estrogen levels may alter the expression and localization of Prxs in the bone and bone marrow. In this study, we analyzed the cellular localization and expression patterns of Prxs in the bone and bone marrow of rats as well as the effects of estrogens on their expression levels. We compared sham, ovariectomized, as well as ovariectomized/estrogen-replaced female rats of the same age. Western blot and immunohistochemistry revealed that all peroxiredoxins were abundantly expressed in different cell types of the bone and bone marrow such as osteocytes, chondrocytes, osteoclasts, bone lining cells, osteoblasts, and hematopoietic precursor cells. After ovariectomy, redox protein levels were significantly reduced in most cell types of the bone and bone marrow compartment. In addition to this, estrogen deficient animals showed increased levels of Prx1 in bone marrow supernatant suggesting a major redox dysregulation in this compartment. Estrogen replacement restored the levels of most redox proteins in the bone and bone marrow compartment and reduced the amount of extracellular Prx1. Based on these results, we conclude that estrogen deficiency negatively affects the ability of bone and bone marrow cells to maintain redox proteins at physiological levels. These results also reveal the widespread effects that are mediated by estrogen affecting different protein systems and tissues in the body. This work was funded by a Seed Discovery Grant (grant #3670920201102 to JG) from Long Island University. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Characterization of cardiac fibrosis in older lean vs. obese male ZSF1 rats

The ZSF1 rat is a novel strain produced by crossing a ZDF (Zucker diabetic fatty) female and SHHF (Spontaneously Hypertensive Heart Failure) male rat. Offspring of this hybrid have two phenotypes: healthy lean or obese prone to diabetes and heart failure. The metabolic syndrome and hypertension displayed by the obese ZSF1 rat mimics that seen in individuals who are predisposed to heart failure with preserved ejection fraction (HFpEF). Historically, HFpEF is a diffcult disease to accurately model with rodents and the ZSF1 rat is a promising model for the spontaneous progression to HFpEF. In recent studies, the oldest age at which ZSF1 rats were studied was 32 weeks and these obese rats displayed diastolic dysfunction, cardiac fibrosis, and hypertrophy. Since the prevalence of HFpEF increases with advanced age, the aim of the current study is to evaluate the extent of fibrosis in older ZSF1 rats (40-42 weeks) and determine whether this age group is more appropriate for the study of fibrotic cardiac remodeling related to HFpEF. We hypothesize that left ventricular (LV) fibrosis and collagen gene expression will be increased in obese compared to lean counterparts. Furthermore, we expect that the extent of fibrosis in this age group will exceed that reported in 32-week-old rats; thus, providing an improved model for the study of fibrotic heart disease. Lean and obese male ZSF1 rats (n=8/group) were aged to 40-42 weeks. Rats were anesthetized with a ketamine/xylazine cocktail and cardiac function was evaluated by invasive hemodynamics. The heart was removed, and the LV was trimmed and weighed. A mid-myocardial section from the LV was fixed and embedded in paraffn for histology. Remaining LV tissue was frozen for extraction of RNA and protein for biochemical analysis. LV collagen was assessed by Sirius red stain and collagen I ( Col1a1) and III ( Col3a1) gene expression were assessed by RTqPCR. With no significant difference in heart rate, obese ZSF1 rats had higher LV developed pressure compared to lean (191.1 vs. 122.0 mmHg, p<0.05) and increased maximum and minimum dP/dT (p<0.05). Obese ZSF1 rats exhibited cardiac hypertrophy as measured by LV weight normalized to tibial length (30.21 vs. 23.61 mg/mm, p<0.05, n=7/group) and increased fibrosis (Sirius red) compared to lean counterparts. Furthermore, the fibrosis in obese ZSF1 rats was concentrated in the endocardial and perivascular regions, and qualitatively more than previously published in the 32-week-old ZSF1. Preliminarily, obese ZSF1 rats exhibit a 3.5-fold increase in Col1a1 (p=0.02) and a 19-fold increase in C ol3a1 (p=0.06) gene expression compared to lean (n=3/group). Interestingly, not only is this a larger increase than that reported in 32-week-old old ZSF1s, but the relative increase in Col3a1 vs. Col1a1 is larger. Taken together, these data suggest a progression of cardiac fibrosis beyond what has been reported in the 32-week-old ZSF1 rats. Use of aged ZSF1 rats may be valuable for the study of fibrogenic mediators in HFpEF for the elucidation of therapeutic agents to reduce or reverse cardiac fibrosis. Future studies will include female rats to evaluate sex-specific progression of fibrosis. North Carolina Biotechnology Center Flash Grant (JH) and ECU REDE startup program (AG). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Mammalian target of rapamycin mediates expression and activity of ADAM 17 in diabetic kidney disease

Purpose: Previous data have illustrated a role for the matrix metalloprotease A Disintegrin And Metalloprotease 17 (ADAM17), known to cleave growth factors and cytokines, in renal cell injury in diabetes. The goal of this study was to identify upstream regulators of ADAM17 in the cascade of events contributing to extracellular matrix accumulation in diabetic nephropathy. Rationale: Diabetic kidney disease is a serious complication faced by type 1 and type 2 diabetic patients alike. Albuminuria and extracellular matrix accumulation are prominent features of the disease and this accumulation of extracellular matrix is a contributing factor to renal fibrosis and decline in renal function. The mechanisms involved in the pathogenesis of diabetic kidney disease have not been completely identified. Methodology: Age and weight-matched Sprague Dawley rats were obtained from Harlan Laboratories (Indianapolis, IN). Type 1 diabetes was induced through tail vein injection of streptozotocin. After rats were determined to be diabetic by blood glucose measurement, rapamycin treatments were administered intraperitoneally for two months. Both kidneys were removed and frozen in liquid nitrogen for microscopy and experimental analyses or formalin fixed for morphometric imaging at the experimental endpoint. Kidney cortex homogenates were used for western blot analyses and enzymatic activity assays. Findings: Using the mTOR complex 1 inhibitor rapamycin, it was determined that increased ADAM17 enzymatic activity and ADAM17 protein expression is dependent on mTORC1 in streptozotocin-induced type 1 diabetic rats. Inhibition of mTORC1 with rapamycin abrogated the increase in collagen IV α 2 protein expression observed in diabetic rat cortex. Additionally, this study is the first to provide evidence that mTOR complex 1 activates ADAM17 contributing to extracellular matrix accumulation in diabetic nephropathy. Studies are continuing looking at the molecular mechanisms involved in mTOR activation of ADAM17 resulting in downstream effects in cultured human proximal tubular epithelial cells. Research reported in this poster was supported by the University of the Incarnate Word Offce of Research and Graduate Studies. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effects of potassium supplementation and deficiency on the progression of salt-sensitive hypertension

While the physiological effects of sodium on blood pressure are well established, many of the effects of potassium remain unclear. Prior work found that increased potassium intake decreases blood pressure and risk of cardiovascular disease, improves vasodilation, has reno-protective effects, and can stimulate natriuresis. In this study, we examined how different sodium/potassium ratios affect the development of salt-sensitive hypertension, specifically examining changes in the kidney and the renin angiotensin aldosterone system (RAAS). We hypothesized that blood pressure would directly correlate to the Na+/K+ ratio and that there would be compensatory changes in RAAS and in expression of renal potassium channels, particularly inwardly rectifying potassium (Kir) channels. At 9 weeks of age, male and female Dahl SS rats were placed on a high salt (4% NaCl) diet for 5 weeks with normal potassium (NK, 0.36% K+), high potassium (HK, 1.41% K+), or potassium depleted (DK, <0.0001% K+) diet. After 5 weeks of dietary intervention, DK animals were hypokalemic, and HK animals had significantly increased plasma potassium. Potassium supplementation attenuated the development of salt-sensitive hypertension in male rats fed the HK diet compared to NK; the DK group did not develop hypertension. Potassium supplementation did not attenuate blood pressure in female rats, who also had a higher mortality rate on the DK diet. Heart rates were unchanged in both male and female HK groups but were significantly lower in the DK groups of both sexes. After 5 weeks of diet, the total body weights of DK rats were significantly lower. The 2 kidney/total body weight ratios were not different between the HK and NK groups, but the kidneys of the DK group were significantly larger, likely due to their smaller body weights. Medullary protein casts in DK rats of both sexes were decreased but no renoprotective effects were observed in the HK group. Western blot analysis of renal potassium channels demonstrated no changes in the expression of ROMK, significantly increased Kir5.1 in DK males and females, and a significant increase in Kir4.1 and the alpha-subunit of the Na+/K+-ATPase in DK males. We analyzed RAAS metabolites from plasma samples collected at the endpoint: Ang I (1-10), Ang IV (3-8), and Ang (1-5) were significantly decreased in DK males and females, Ang II (1-8) and Ang III (2-8) were significantly reduced in DK males, and aldosterone was significantly increased in HK males and females. These results provide a comprehensive assessment of how various potassium diets affect the development of salt-sensitive hypertension in both males and females, which will provide a solid foundation for future mechanistic studies. R01DK129227, I01 BX004024, R35HL135749. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Effect of Combined Exercise on the Expression of FoxO and Atrogin Pathway Genes in the Gastrocnemius and Soleus Muscles of Elderly Rats

The Effect of Combined Exercise on the Expression of FoxO and Atrogin Pathway Genes in the Gastrocnemius and Soleus Muscles of Elderly Rats

Effects of Short-, Medium-, and Long-Term Treatment Using Photobiomodulation Therapy Combined with Static Magnetic Field in Aging Rats.

(1) Background: We investigated the detrimental and protective effects of short-, medium, and long-term treatment with different doses of photobiomodulation therapy combined with static magnetic field (PBMT-sMF) during the aging process. (2) Methods: Rats were treated for 15, 30, and 60 weeks with 1, 3, 10, and 30 J of PBMT-sMF or a placebo control. In addition, eight young rats were not subjected to any procedure or treatment and were euthanized at six weeks old. Skin, muscle, bone, kidney, liver, and blood samples were analyzed. (3) Results: No differences between the groups in the morphology of the skin, muscle, and bone was observed. Glutamic pyruvic transaminase levels were increased in the placebo group after 30 and 60 weeks. Glutamic oxaloacetic transaminase levels were also increased in the placebo group after 30 weeks. An increase in creatinine in the PBMT-sMF 3, 10, and 30 J groups compared with that in the young control group was observed. No significant difference in urea levels between the groups was noted. Vascular endothelial growth factor increased in the PBMT-sMF 10 and 30 J groups after 15 weeks of treatment and in the PBMT-sMF 3 J after 60 weeks. Finally, vascular endothelial growth factor decreased in the PBMT-sMF 30 J group after 30 weeks of treatment. (4) Conclusions: PBMT-sMF did not have detrimental effects on the skin, muscle, bone, kidney, or liver after short-, medium-, and long-term treatments in aging rats. In addition, PBMT-sMF may have protective effects on the muscle tissue in aging rats after short- and long-term treatment.

Curcumin attenuates brain aging by reducing apoptosis and oxidative stress.

Brain aging is a physiological event, and oxidative stress and apoptosis are involved in the natural aging process of the brain. Curcumin is a natural antioxidant with potent anti-aging and neuroprotective properties. Therefore, we investigated the protective effects of curcumin on brain apoptosis and oxidative stress, brain-derived neurotrophic factor (BDNF), and vascular endothelial growth factor (VEGF) in aged rats. Old female Wistar rats were randomly divided into three groups (n = 7); as follows: (1) control; (2); saline and (3) curcumin (received 30mg/kg of curcumin, 5 days/week for 8 weeks, intraperitoneally). Our results indicated that treatment with curcumin in aged rats attenuates brain lipid peroxidation, which was accompanied by a significant increase in the BDNF, VEGF, superoxide dismutase (SOD) activity, and anti-apoptotic protein BCl-2. No significant change in brain anti-apoptotic Bax protein levels was observed after curcumin treatment. The study indicates that curcumin could alleviate brain aging which may be due to attenuating oxidative stress, inhibiting apoptosis, and up-regulating SOD activity, which in turn enhances VEGF and BDNF. Therefore, curcumin has potential therapeutic value in the treatment of neurological apoptosis, neurogenesis, and angiogenesis changes caused by brain aging.

The Energy Required to Synthesize Lean and Adipose Tissue in Rats.

Although the energy stored in lean tissue (LT) and adipose tissue (AT) is well known, the energy required to synthesize these tissues is less clear. While elucidating the energy required for AT synthesis may not be so important, the elucidation of the energy required for LT synthesis is important for individuals who aim to increase their skeletal muscle. Theoretically the energy at the point at which ΔLT/Δbody weight (BW) reaches 100% on a regression curve, which indicates the relationship between ΔLT/ΔBW and the energy used to accumulate body tissue, is considered to be the energy expended to synthesize LT. We therefore investigated the relationship using rats. Rats of different ages, and rats in exercised or sedentary states were used because their ΔLT/ΔBW was expected to be different. ΔLT/ΔBW was higher in the 4-wk-old group than in the 8-wk-old group and higher in the exercise group than in the sedentary group. We found a positive correlation between ΔLT/ΔBW and the energy expended to synthesize tissues that accumulated in the body. This energy was lower in the 8-wk-old group, which had a lower ΔLT/ΔBW in comparison to the 4-wk-old group, but was not affected by exercise. The regression curve revealed that the energy expended to synthesize LT was 2.9 kcal/g, while that expended to synthesize AT was 1.1 kcal/g. Therefore, combined with the energy accumulated to the tissues, the energy required to accumulate LT is approximately 4.0 kcal/g, while that required to accumulate AT is approximately 8.5 kcal/g.

Comparing the efficacy of concomitant treatment of resistance exercise and creatine monohydrate versus multiple individual therapies in age related sarcopenia

Aging-related sarcopenia is a degenerative loss of strength and skeletal muscle mass that impairs quality of life. Evaluating NUDT3 gene and myogenin expression as new diagnostic tools in sarcopenia. Also, comparing the concomitant treatment of resistance exercise (EX) and creatine monohydrate (CrM) versus single therapy by EX, coenzyme Q10 (CoQ10), and CrM using aged rats. Sixty male rats were equally divided into groups. The control group, aging group, EX-treated group, the CoQ10 group were administered (500 mg/kg) of CoQ10, the CrM group supplied (0.3 mg/kg of CrM), and a group of CrM concomitant with resistance exercise. Serum lipid profiles, certain antioxidant markers, electromyography (EMG), nudix hydrolase 3 (NUDT3) expression, creatine kinase (CK), and sarcopenic index markers were measured after 12 weeks. The gastrocnemius muscle was stained with hematoxylin–eosin (H&E) and myogenin. The EX-CrM combination showed significant improvement in serum lipid profile, antioxidant markers, EMG, NUDT3 gene, myogenin expression, CK, and sarcopenic index markers from other groups. The NUDT3 gene and myogenin expression have proven efficient as diagnostic tools for sarcopenia. Concomitant treatment of CrM and EX is preferable to individual therapy because it reduces inflammation, improves the lipid serum profile, promotes muscle regeneration, and thus has the potential to improve sarcopenia.

Low-fat cheese ameliorates glucose intolerance and normalizes insulin secretion in a rat model of type 2 diabetes by promoting β-cell recovery.

We aimed to determine if cheese could reduce glucose intolerance in aged rats with overt type 2 diabetes (T2D). Male Sprague-Dawley rats treated with high-fat diet (HFD) and streptozotocin (STZ) to elicit T2D were hyperglycemic. One week after STZ injection, low-fat (LOW) or regular-fat (REG) cheese was provided for 5 weeks and compared with T2D and low-fat diet reference (REF) groups. Food intake and weight gain were similar in all groups. Oral glucose tolerance tests revealed glucose intolerance in T2D rats that was partially ameliorated by LOW but not REG. Insulin secretion during the oral glucose tolerance test was impaired in T2D and REG at 10min (p<0.05) but the iAUC was highly variable in all groups and statistical differences were not detected (p>0.05). β-cell mass and pancreatic insulin content in T2D and REG were 50% lower than REF (p<0.05), whereas LOW was not significantly different. Although isolated islets from all groups responded to glucose, the absolute amount of insulin secreted by T2D and REG was markedly reduced compared with REF, while LOW islets had relatively normal secretion. In conclusion, LOW but not REG cheese enhanced β-cell recovery from HFD/STZ treatment that led to amelioration of glucose tolerance within 5 weeks.

Diet-induced and age-related changes in rats: the impact of N-stearoylethanolamine intake on plasma lipoproteins, adiponectin, and adipocyte cholesterol-phospholipid composition

Adiponectin is secreted by adipose tissue, associated with lipoprotein (LP) metabolism, down-regulated­ in insulin resistance states, and reduced in individuals suffering from obesity and cardiovascular diseases. Phospholipids and cholesterol are the main components of cell membranes and play a critical role in storage and secretory adipocyte functions. N-stearoylethanolamine (NSE) is a minor lipid affecting cell membrane lipids’ composition. Our study aimed to investigate plasma levels of adiponectin and cholesterol of low- and high-density LP (LDL and HDL) and adipocyte cholesterol-phospholipid (Chol-PL) composition of different age rats with high-fat diet (HFD)-induced obesity and insulin resistance and their changes under NSE administration. Our study demonstrated that chronic dietary fat overloading leads to obesity accompanied by impairment of glucose tolerance, a manifestation of dyslipidemia, and changes in plasma adiponectin levels in rats from two age groups (10-month-old and and 24-month-old). Prolonged HFD led to a reduction in plasma adiponectin levels and the growth of adipocyte cholesterol content in rats of different ages. A significant increase in plasma LDL-Chol level and main adipocyte PLs (phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, and lysophosphatidylcholine) was observed in younger rats, whereas not detected in elder animals after dietary fats overloading. The decrease in the content of anionic phospholipids (phosphatidylinositol + phosphatidylserine) was also detected in 10-month-old HFD rats compared to the control animals. NSE administration positively affected the normalization of adiponectin levels in both age HFD groups. It significantly impacted the reduction of LDL-Chol levels and the growth of HDL-Chol concentration in the blood plasma of 10-month-old rats as well as PL-composition of young HFD rats and anionic PL restoring in 24-month-old rats. The positive effect on investigated parameters makes NSE a prospective agent for treating diet-induced and age-related metabolic disorders threatening cardiovascular diseases. Keywords: adiponectin, adipose tissue, aging, cholesterol, dyslipidemia, lipoproteins, N-stearoylethanolamine, phospholipids

L-arginine, inosine and meldonium effect on the vascular wall reactivity of adult rats

Changes in the structure, metabolism and cardiovascular system function that develop during ageing are the basis for the circulatory pathology occurrence in old age. Currently, cardiovascular system diseases are one of the main causes of mortality in almost all developed countries. Therefore, searching for new drugs to correct the metabolism and functions of organs and systems whose activity is disrupted during ageing is an urgent problem. The article presents the study influence results of the synthesis precursor of endothelial relaxing factor - NO (ERF-NO) L-arginine, the purine nucleoside inosine and the β-oxidation inhibitor of fatty acids meldonium on the vascular wall reactivity of adult rats. When used separately, these drugs have been shown to cause slight relaxation of the thoracic aorta isolated segments in adult animals. When L-arginine, inosine and meldonium are used together, there is no summation of their pharmacological effect on blood vessels, however, some vasodilator effect potentiation is observed. The acetylcholine (Ach) vasodilator effect was significantly more than the vasodilator effect of the studied composition (L-arginine + inosine + meldonium), conventionally called Melarginine. It should be noted that, although the vasodilator Ach effect was significant, it was short-term, and the vasodilator effect of the studied combination (Melarginine) was long-lasting. A pronounced vasodilator response to Ach indicates the preservation of the endothelium in adult rats. Therefore, with intact endothelium in adult animals, Melarginine does not cause significant vascular relaxation. In aged rats, which typically exhibit endothelial damage, the effect of Melarginine may be more significant compared to adults. This will be the subject of our further study. Still, Melarginine has a small but long-lasting vasodilatory effect in adult rats, which also helps regulate vascular tone. _________________________________________________________________________________________ Keywords: vessel reactivity; endothelial dysfunction; L-arginine; inosine; meldonium; Melarginine

Investigating the Effect of Resistance-Aerobic Training on the Absorption and Resorption Biomarkers of Bone Tissue in Young, Adult and Elderly Male Rats

Introduction: Exercise training is likely to be a non-pharmacological intervention to improve bone health in children and the elderly. The aim of this study was to investigate the effect of resistance-aerobic training on RUX2, CTX, RANKL and ALP biomarkers in rats of different ages. Methods: In the present experimental study, 30 male Wistar rats were obtained from Instituto Pasteur of Iran and were divided into three groups according to their age: immature (2 weeks old), mature (6 weeks old) and elderly (96 weeks old). In each age group, the mice were randomly divided into two training (n=5) and control (n=5) groups. Six weeks of combined training included three sessions of aerobic training and three sessions of resistance training per week. Extracting genes by PCR method was used. One-way analysis of variance and Tukey's post hoc test and SPSS16 software were used. The significance level P≥0.05 was considered. Results: One-way analysis of variance showed that resistance-aerobic training has had a significant effect on RUNX2, RANKL and ALP variables of rats in different age groups (P &lt; 0.05). This significance was not observed in CTX variable (P &gt; 0.05). On the other hand, the results of Tukey's RUNX2 test were significantly different between the adult training and elderly training groups (p=‌0.019) as well as between the elderly control groups (p = 0.01) and adult training (p = 0.002). Regarding the RANKL variable, it showed that there was a significant difference only between the adult exercise group and the elderly control group (p = 0.01). Conclusion: Resistance-endurance training probably increases absorption and reabsorption biomarkers such as RUX2, RANKL and ALP in immature, mature and elderly male rats.

Sex-specific cardiovascular remodeling leads to a divergent sex-dependent development of heart failure in aged hypertensive rats

IntroductionThe prevalence of heart failure with preserved ejection fraction (HFpEF) is continuously rising and predominantly affects older women often hypertensive and/or obese or diabetic. Indeed, there is evidence on sex differences in the development of HF. Hence, we studied cardiovascular performance dependent on sex and age as well as pathomechanisms on a cellular and molecular level.MethodsWe studied 15-week- and 1-year-old female and male hypertensive transgenic rats carrying the mouse Ren-2 renin gene (TG) and compared them to wild-type (WT) controls at the same age. We tracked blood pressure and cardiac function via echocardiography. After sacrificing the 1-year survivors we studied vascular smooth muscle and endothelial function. Isolated single skinned cardiomyocytes were used to determine passive stiffness and Ca2+-dependent force. In addition, Western blots were applied to analyse the phosphorylation status of sarcomeric regulatory proteins, titin and of protein kinases AMPK, PKG, CaMKII as well as their expression. Protein kinase activity assays were used to measure activities of CaMKII, PKG and angiotensin-converting enzyme (ACE).ResultsTG male rats showed significantly higher mortality at 1 year than females or WT male rats. Left ventricular (LV) ejection fraction was specifically reduced in male, but not in female TG rats, while LV diastolic dysfunction was evident in both TG sexes, but LV hypertrophy, increased LV ACE activity, and reduced AMPK activity as evident from AMPK hypophosphorylation were specific to male rats. Sex differences were also observed in vascular and cardiomyocyte function showing different response to acetylcholine and Ca2+-sensitivity of force production, respectively cardiomyocyte functional changes were associated with altered phosphorylation states of cardiac myosin binding protein C and cardiac troponin I phosphorylation in TG males only. Cardiomyocyte passive stiffness was increased in TG animals. On a molecular level titin phosphorylation pattern was altered, though alterations were sex-specific. Thus, also the reduction of PKG expression and activity was more pronounced in TG females. However, cardiomyocyte passive stiffness was restored by PKG and CaMKII treatments in both TG sexes.ConclusionHere we demonstrated divergent sex-specific cardiovascular adaptation to the over-activation of the renin-angiotensin system in the rat. Higher mortality of male TG rats in contrast to female TG rats was observed as well as reduced LV systolic function, whereas females mainly developed HFpEF. Though both sexes developed increased myocardial stiffness to which an impaired titin function contributes to a sex-specific molecular mechanism. The functional derangements of titin are due to a sex-specific divergent regulation of PKG and CaMKII systems.

Sex, age, and species differences of perfluorooctanoic acid modeled by flow- versus permeability-limited physiologically-based pharmacokinetic models

This study aimed to investigate sex, age, and species differences of perfluorooctanoic acid (PFOA) using physiologically-based pharmacokinetic (PBPK) models in rats and humans. PBPK models were generally developed as either flow- or permeability-limited models. The flow-limited model is cost-effective and allows for human PK prediction through simple allometric scaling, while the permeability-limited model can incorporate detailed information on the disposition process through in vitro-in vivo extrapolation (IVIVE). PFOA was administered via oral or intravenous administration with 5 mg/kg in male and female rats of different ages and the data was used to develop the PBPK models. Our results showed that both models successfully captured sex differences in rats, while only the flow-limited model with male rats and the permeability-limited model with both male and female rats provided comparable predictions in the human clinical study. More than the flow-limited model, the permeability-limited model effectively explained sex differences in rats and species differences through IVIVE. Additionally, the ontogeny-based mechanistic description of PFOA disposition enabled the interpretation of age- and sex-dependent pharmacokinetics. Although the flow-limited PBPK model lacked mechanistic interpretability compared to the permeability-limited model, it demonstrated reliable human prediction through simple allometric scaling. In conclusion, the permeability PBPK model could interpret age, sex, and species differences and it could improve the accuracy of human prediction.

Coenzyme Q10 and exercise training reinstate middle cerebral artery occlusion-induced behavioral deficits and hippocampal long-term potentiation suppression in aging rats.

Patients experience post-stroke cognitive impairment during aging. To date, no specific treatment solution has been reported for this disorder. The purpose of this study was to evaluate the effects of exercise training and coenzyme Q10 supplementation on middle cerebral artery occlusion (MCAO) induced behavioral impairment, long-term potentiation inhibition and cerebral infarction size in aging rats. Fifty aging male rats underwent MCAO surgery and were randomly distributed in to the following groups: 1-Sham, 2- control, 3- Coenzyme Q10, 4- Exercise training and 5- Exercise training with Q10 supplementation (Ex + Q10). Aerobic training groups were allowed to run on a treadmill for 12 weeks. Q10 (50mg/kg) was administered intragastrically by gavage. Morris water maze, shuttle box and elevated plus maze tests were used to evaluate cognitive function. The population spike (PS) amplitude and slope of excitatory postsynaptic potentials (EPSP) in the dentate gyrus area were recorded as a result of perforant pathway electrical stimulation. Our study showed that Q10 and aerobic training alone ameliorate spatial memory in the acquisition phase, but have no effect on spatial memory in the retention phase. Q10 and exercise training synergistically promoted spatial memory in the retention phase. Q10 and exercise training separately and simultaneously mitigated cerebral ischemia-induced passive avoidance memory impairment in acquisition and retention phases. The EPSP did not differ between the groups, but exercise training and Q10 ameliorate the PS amplitude in hippocampal responses to perforant path stimulation. Exercising and Q10 simultaneously reduced the cerebral infarction volume. Collectively, the findings of the present study imply that 12 weeks of aerobic training and Q10 supplementation alone can simultaneously reverse cerebral ischemia induced neurobehavioral deficits via amelioration of synaptic plasticity and a reduction in cerebral infarction volume in senescent rats.