In this study, we explored the mechanisms by which the angiotensin converting enzyme inhibitor (ACEI), enalapril, and the Ang II receptor blocker (ARB), losartan suppress oxidative stress and NF-κB activation-induced inflammatory responses in aged rat kidney. The experimentations were carried out utilizing aged (24-month-old) Brown Norway x Fischer 344 (F1) male rats which were randomized into 3 groups and administered enalapril (40 mg/kg), losartan (30 mg/kg) or placebo for 6 months (daily p.o.). The level of reactive species (RS), peroxynitrite (ONOO−), GSH/GSSG and lipid peroxidation were measured. The activity of the pro-inflammatory transcription factor NF-κB, and gene expression of proteins in upstream signaling cascades were measured by electro-mobility shift assay (EMSA) and Western blotting. Enalapril and losartan differentially attenuated redox imbalance and the redox-sensitive transcription factor, NF-κB pathway. Furthermore, stimulation of the NF-κB activation pathway by phosphorylation of p65 was attenuated by both compounds. Moreover, mediation of phosphorylation of p65 by phosphorylation of IκB kinase αβ (IKKαβ) and mitogen- and stress-activated protein kinase-1 (MSK1), were also inhibited by enalapril and losartan. Finally, both compounds also lowered expression of NF-κB-dependent inflammatory genes, such as cyclooxygenase-2 (COX-2),) and inducible NO synthase (iNOS). Only losartan lowered levels of 5-lipoxygenase (5-LOX). These findings indicate that enalapril and losartan differentially suppress inflammatory responses via inhibition of oxidative stress-induced NF-κB activation in aged rat kidney.
The primary purpose of the present set of studies was to provide a direct comparison of the effects of the angiotensin-converting enzyme inhibitor enalapril and the angiotensin receptor blocker losartan on body composition, physical performance, and muscle quality when administered late in life to aged rats. Overall, enalapril treatment consistently attenuated age-related increases in adiposity relative to both placebo and losartan. The maximal effect was achieved after 3 months of treatment (between 24 and 27 months of age), at a dose of 40 mg/kg and was observed in the absence of any changes in physical activity, body temperature, or food intake. In addition, the reduction in fat mass was not due to changes in pathology given that enalapril attenuated age-related increases in tumor development relative to placebo- and losartan-treated animals. Both enalapril and losartan attenuated age-related decreases in grip strength, suggesting that changes in body composition appear dissociated from improvements in physical function and may reflect a differential impact of enalapril and losartan on muscle quality. To link changes in adiposity to improvements in skeletal muscle quality, we performed gene array analyses to generate hypotheses regarding cell signaling pathways altered with enalapril treatment. Based on these results, our primary follow-up pathway was mitochondria-mediated apoptosis of myocytes. Relative to losartan- and placebo-treated rats, only enalapril decreased DNA fragmentation and caspase-dependent apoptotic signaling. These data suggest that attenuation of the severity of skeletal muscle apoptosis promoted by enalapril may represent a distinct mechanism through which this compound improves muscle strength/quality.
Age-related adiposity; Body composition; Sarcopenia; Renin–angiotensin system; Physical function; Muscle quality
This study investigated the metabolic changes with age in the Fischer 344 × Brown Norway rat and its suitability as an animal model of postmaturational insulin resistance. Specifically, we determined whether an age-associated decrease in glucose disposal is associated with diminished whole body insulin responsiveness and/or a decrease in glucose transporter (GLUT-4) protein and mRNA content in medial gastrocnemius muscle of male Fischer 344 × Brown Norway rats of ages 8, 18, and 28 months. Fasting plasma glucose was unchanged with age. There was a significant age effect on visceral adiposity, fasting plasma insulin levels, insulin responsiveness, and GLUT-4 protein content. Insulin responsiveness and GLUT-4 protein were lower in the 18-month-old rats than in the 8-month-old rats. The findings of age-associated increases in visceral adiposity and insulin resistance, and decreases in GLUT-4 in the Fisher 344 × Brown Norway rat, suggest that this rat strain may be an appropriate model for studying the effects of aging on glucose homeostasis.
Calorie restriction (CR; ~60% of ad libitum, AL intake) has been associated with substantial alterations in body composition and insulin sensitivity. Recently, several proteins that are secreted by nontraditional endocrine tissues, including skeletal muscle and other tissues, have been discovered to modulate energy metabolism, body composition, and insulin sensitivity. The aim of this study was to characterize the influence of CR by rats on plasma levels of six of these newly recognized metabolic hormones (BDNF, FGF21, IL-1β, myonectin, myostatin, and irisin). Body composition of 9-month old male Fischer-344/Brown Norway rats (AL and CR groups) was determined by nuclear magnetic resonance. Blood sampled from the carotid artery of unanesthetized rats was used to measure concentrations of glucose and plasma proteins. As expected, CR versus AL rats had significantly altered body composition (reduced percent fat mass, increased percent lean mass) and significantly improved insulin sensitivity (based on the homeostasis model assessment-estimated insulin resistance index). Also consistent with previous reports, CR compared to AL rats had significantly greater plasma levels of adiponectin and corticosterone. However, there were no significant diet-related differences in plasma levels of BDNF, FGF21, IL-1β, myonectin, myostatin, or irisin. In conclusion, these results indicate that alterations in plasma concentration of these six secreted proteins are not essential for the CR-related improvement in insulin sensitivity in rats.
Myonectin; Myostatin; FGF21; Irisin; Insulin resistance; Dietary restriction; Adiponectin; FNDC5
Identification of biological mediators in sarcopenia is pertinent to the development of targeted interventions to alleviate this condition. Iron is recognized as a potent pro-oxidant and a catalyst for the formation of reactive oxygen species in biological systems. It is well accepted that iron accumulates with senescence in several organs, but little is known about iron accumulation in muscle and how it may affect muscle function. In addition, it is unclear if interventions which reduced age-related loss of muscle quality, such as calorie restriction, impact iron accumulation. We investigated non-heme iron concentration, oxidative stress to nucleic acids in gastrocnemius muscle and key indices of sarcopenia (muscle mass and grip strength) in male Fischer 344 X Brown Norway rats fed ad libitum (AL) or a calorie restricted diet (60% of ad libitum food intake starting at 4 months of age) at 8, 18, 29 and 37 months of age. Total non-heme iron levels in the gastrocnemius muscle of AL rats increased progressively with age. Between 29 and 37 months of age, the non-heme iron concentration increased by approximately 200% in AL-fed rats. Most importantly, the levels of oxidized RNA in gastrocnemius muscle of AL rats were significantly increased as well. The striking age-associated increase in non-heme iron and oxidized RNA levels and decrease in sarcopenia indices were all attenuated in the calorie restriction (CR) rats. These findings strongly suggest that the age-related iron accumulation in muscle contributes to increased oxidative damage and sarcopenia, and that CR effectively attenuates these negative effects.
Age-related tongue weakness may contribute to swallowing deficits in the elderly. One contributing factor may be an alteration in muscle fiber type properties with aging. However, it is not clear how muscle fiber types within the aged tongue may vary from those found in young adults, or how fiber types may vary across the anteroposterior axis of the extrinsic tongue muscles. We examined myosin heavy chain (MHC) composition of anterior, medial, and posterior sections of the genioglossus muscle (GG) in 10 old male Fischer 344/Brown Norway rats and compared findings to previously reported data from young adult male rats. Significant differences (p< .01) between young adult and old rats were found in the distribution of MHC isoforms along the anteroposterior axis of the muscle. In the anterior, medial, and posterior regions, there was a significantly smaller proportion of type IIb MHC in the old rat GG muscles, while the proportion of type IIx MHC was significantly greater. In the medial region, the proportion of type I MHC was found to be significantly greater in the old rats. Thus, we found a shift to more slowly contracting muscle fibers in the aged rat tongue.
Tongue; Dysphagia; Myosin heavy chain; Aging; Deglutition; Deglutition Disorders
In this study, we tested the hypothesis that, in the male Fischer 344 × Brown Norway (F344xBN) rat, aging would be associated with an increase in sympathetic nervous system activity and a decrease in skeletal muscle β-adrenergic-receptor (β-AR) density and function. Radioligand-binding studies using [125I]iodocyanopindolol were done to evaluate β-AR density (Bmax) and antagonist-binding affinity in gastrocnemius and cardiac muscle from 6-, 18-, and 28-mo-old male F344xBN rats. β-AR function was measured as adenylyl cyclase (AC) activity stimulated by the β-AR agonist isoproterenol (Iso, 10−4 M). Basal arterial plasma norepinephrine (pNE) concentrations were higher in the 28-than in the 6- and 18-mo-old rats. Bmax was greatest and Iso-stimulated AC activity was unchanged in gastrocnemius muscle of the 28-mo-old age group. In contrast, there was an age-associated decrease in Bmax and Iso-stimulated AC activity in cardiac muscle. In conclusion, there was an age-associated increase in pNE concentrations in male F344xBN rats, suggesting an increase in sympathetic nervous system activity. In addition, there was an age-associated increase in skeletal muscle β-AR density, whereas in skeletal muscle β-AR-stimulated AC activity remained unchanged with age.
adenylyl cyclase; catecholamines; sympathetic nervous system; isoproterenol; forskolin
Decreased cognitive performance reduces independence and quality of life for aging individuals. Healthy brain aging does not involve significant neuronal loss, but little is known about the effects of aging at synaptic terminals. Age-related cognitive decline likely reflects the manifestation of dysregulated synaptic function and ineffective neurotransmission. In this study, hippocampal synaptosomes were enriched from Young-adult (3 months), Adult (12 months), and Aged (26 months) Fischer 344 × Brown Norway rats, and quantitative alterations in the synaptoproteome were examined by 2-DIGE and MS/MS. Bioinformatic analysis of differentially expressed proteins identified a significant effect of aging on a network of neurotransmission-regulating proteins. Specifically, altered expression of DNM1, HPCA, PSD95, SNAP25, STX1, SYN1, SYN2, SYP, and VAMP2 was confirmed by immunoblotting. 14-3-3 isoforms identified in the proteomic analysis were also confirmed due to their implication in the regulation of the synaptic vesicle cycle and neurotransmission modulation. The findings of this study demonstrate a coordinated downregulation of neurotransmission-regulating proteins that suggests an age-based deterioration of hippocampal neurotransmission occurring between adulthood and advanced age. Altered synaptic protein expression may decrease stimulus-induced neurotransmission and vesicle replenishment during prolonged or intense stimulation, which are necessary for learning and the formation and perseverance of memory.
aging; proteomic; hippocampus; synapse; SNARE; neurotransmission
Caloric restriction (CR) attenuates aging-related degenerative processes throughout the body. It is less clear, however, whether CR has a similar effect in the brain, particularly in the hippocampus, an area important for learning and memory processes that often are compromised in aging. In order to evaluate the effect of CR on synapses across lifespan, we quantified synapses stereologically in the middle molecular layer of the dentate gyrus (DG) of young, middle aged, and old Fischer 344 X Brown Norway rats fed ad libitum (AL) or a CR diet from 4 months of age. The results indicate that synapses are maintained across lifespan in both AL and CR rats. In light of this stability, we addressed whether aging and CR influence neurotransmitter receptor levels by measuring subunits of NMDA (NR1, NR2A, and NR2B) and AMPA (GluR1, GluR2) receptors in the DG of a second cohort of AL and CR rats across lifespan. The results reveal that the NR1 and GluR1 subunits decline with age in AL, but not CR rats. The absence of an aging-related decline in these subunits in CR rats, however, does not arise from increased levels in old CR rats. Instead, it is due to subunit decreases in young CR rats to levels that are sustained in CR rats throughout lifespan, but that are reached in AL rats only in old age.
We measured the loss of cardiac mitochondrial function related to aging in males of three rat strains presenting with different longevity and aging phenotypes: the Fischer 344 (F344), the Brown Norway (BN), and the hybrid F344×BN. The F344 rat has a short life span and a ∼45% decrease in coupled mitochondrial oxidation in the cardiac permeabilized fibers from the old rats compared with the young rats. Citrate synthase activity in the permeabilized fibers (mitochondrial content) did not change significantly with aging. The BN live longer compared with the F344 and have a 15%–18% loss of mitochondrial respiration in the aged rats compared with the young rats. The differences are not significant. In hybrids, more resistant to aging than are the BN and the F344, mitochondrial function is preserved during aging. The difference in longevity of the different strains is correlated with mitochondrial dysfunction in the heart, suggesting the importance of mitochondria in cardiac aging.
Aging; Mitochondrial; Oxidative phosphorylation; Rat; Strains
Hyperactivity of the hypothalamo-pituitary-adrenocortical (HPA) axis is linked with age-related decrements in cognition and neuronal survival. However, the nature and extent of age-related HPA axis deficits varies considerably across and indeed, within strains. The current study was designed to assess variance in HPA axis function using two rodent models commonly used in aging studies: Fischer 344 (F344) and F344/Brown-Norway F1 hybrid rats (F344/BN). We examined both basal and stress-induced ACTH and corticosterone (CORT) release in two stress contexts thought to differ in intensity: novel environment (‘mild’) and restraint (‘intense’). Variability of the data was tested with a modification of the Brown-Forsythe test of homoscedasticity. The results indicated that F344 rats exhibit greater peak HPA responses. Furthermore, in most cases variability was increased in aged rats relative to young and middle-aged rats of the same strain, indicative of the emergence of individual differences in stress responsivity amongst older rats. The results suggest that these older rat strains may be useful models to further assess individual differences in neuroendocrine aging.
aging; stress; HPA; ACTH; corticosterone; homoscedasticity
Because of differences in muscle architecture and biomechanics, the purpose of this study was to determine whether muscle contractile properties of rat hindlimb and tongue were differentially affected by aging.
Deep peroneal and hypoglossal nerves were stimulated in 6 young and 7 old Fischer 344-Brown Norway rats to allow recording of muscle contractile properties of tongue and extensor digitorum longus (EDL) muscle in the hindlimb. In the same animals, the following measurements were made: (a) twitch contraction time (CT; in milliseconds), (b) half decay time (HDT; in milliseconds), (c) maximum twitch force (in grams), (d) tetanic force, and (e) fatigue index determined from repetitive stimulation of the muscles.
No significant differences were observed in young versus old groups in retrusive tongue forces, whereas a significant (p < .05) decrement in EDL tetanic forces was found in old rats. Slower CT in old rats was observed only in the tongue. Old and young groups were not significantly different in fatigue index or HDT for tongue or EDL.
Old animals generated equivalent maximum tongue forces with stimulation, but they were slower in achieving these forces than young animals. Limb and cranial muscles were not affected equally by aging. As such, information derived from limb muscle studies may not easily generalize to the cranial motor system.
aging; tongue; extensor digitorum longus; muscle contraction
Mitochondria-mediated apoptosis represents a central process driving age-related muscle loss. However, the temporal relation between mitochondrial apoptotic signaling and sarcopenia as well as the regulation of release of pro-apoptotic factors from the mitochondria has not been elucidated. In this study, we investigated mitochondrial apoptotic signaling in skeletal muscle of rats across a wide age range. We also investigated whether mitochondrial-driven apoptosis was accompanied by changes in the expression of Bcl-2 proteins and components of the mitochondrial permeability transition pore (mPTP). Analyses were performed on gastrocnemius muscle of 8-, 18-, 29- and 37- month-old male Fischer344×Brown Norway rats (9 per group). Muscle weight declined progressively with advancing age, concomitant with increased apoptotic DNA fragmentation. Cytosolic and nuclear levels of apoptosis inducing factor (AIF) and endonuclease G (EndoG) increased in old and senescent animals. In contrast, cytosolic levels of cytochrome c were unchanged with age. Mitochondrial Bcl-2, Bax and Bid increased dramatically in 37-month-old rats, with no changes in the Bax/Bcl-2 ratio in any of the age groups. Finally, expression of cyclophilin D was enhanced at very old age. Our findings indicate that the mitochondrial caspase-independent apoptotic pathway may play a more prominent role in skeletal muscle loss than caspase-mediated apoptosis.
sarcopenia; apoptosis; permeability transition pore; AIF; endonuclease G
Despite advances in treatment, age-related cardiac dysfunction still remains a leading cause of cardiovascular death. Recent data have suggested that increases in cardiomyocyte apoptosis may be involved in the pathological remodeling of heart. Here, we examine the effects of aging on cardiomyocyte apoptosis in 6-, 30-, and 36-month-old Fischer344xBrown Norway F1 hybrid rats (F344XBN). Compared with 6-month hearts, aged hearts exhibited increased TdT-mediated dUTP nick end labeling–positive nuclei, caspase-3 activation, caspase-dependent cleavage of α-fodrin and diminished phosphorylation of protein kinase B/Akt (Thr 308). These age-dependent increases in cardiomyocyte apoptosis were associated with alterations in the composition of the cardiac dystrophin glycoprotein complex and elevated cytoplasmic IgG and albumin immunoreactivity. Immunohistochemical analysis confirmed these data and demonstrated qualitative differences in localization of dystrophin–glycoprotein complex (DGC) molecules with aging. Taken together, these data suggest that aging-related increases in cardiac apoptotic activity model may be due, at least in part, to age-associated changes in DGC structure.
Aging; Cardiac declines with age; Dystroglycan; Apoptosis; Cellular senescence
TNF-α-mediated apoptosis is enhanced in aged rodent muscles, suggesting that this pathway may be involved in sarcopenia. Interleukin-15 (IL-15), a muscle-derived anabolic cytokine, mitigates muscle wasting and apoptosis in cachectic rats. This effect is thought to occur through inhibition of TNF-α-triggered apoptosis. We investigated IL-15 signaling and the TNF-α-mediated pathway of apoptosis in the gastrocnemius muscle of Fischer344×Brown Norway rats across the ages of 8, 18, 29 and 37 months, in relation to life-long calorie restriction (CR, 40% calorie intake reduction). Aging caused loss of muscle mass and increased apoptotic DNA fragmentation, which were mitigated by CR. Protein levels of IL-15 and mRNA abundance of IL-15 receptor α-chain decreased in senescent ad libitum (AL) fed rats, but were maintained in CR rodents. Elevations of TNF-α, TNF-receptor 1, cleaved caspase-8 and -3 were observed at advanced age in AL rats. These changes were prevented or mitigated by CR. Our results indicate that aging is associated with decreased IL-15 signaling in rat gastrocnemius muscle, which may contribute to sarcopenia partly through enhanced TNF-α-mediated apoptosis. Preservation of IL-15 signaling by CR may therefore represent a further mechanism contributing to the anti-aging effect of this dietary intervention in skeletal muscle.
sarcopenia; interleukin-15; tumor necrosis factor-α; calorie restriction; apoptosis
Muscle atrophy with aging or disuse is associated with deregulated iron homeostasis and increased oxidative stress likely inflicting damage to nucleic acids. Therefore, we investigated RNA and DNA oxidation, and iron homeostasis in gastrocnemius muscles. Disuse atrophy was induced in 6- and 32-month old male Fischer 344/Brown Norway rats by 14 days of hind limb suspension (HS). We show that RNA, but not DNA, oxidative damage increased 85% with age and 36% with HS in aged muscle. Additionally, non-heme iron levels increased 233% with aging and 83% with HS at old age, while staining for free iron was strongest in the smallest fibers. Simultaneously, the mRNA abundance of transferrin receptor-1 decreased by 80% with age and 48% with HS for young animals, while that of the hepcidin regulator hemojuvelin decreased 37% with age, but increased about 44% with disuse, indicating a dysregulation of iron homeostasis favoring increased intracellular free iron in atrophied muscles. RNA and DNA concentrations increased with age and were negatively correlated with muscle mass, whereas protein concentrations decreased with aging, indicating a preferential loss of protein compared to nucleic acids. Furthermore, xanthine oxidase activity increased with age, but not with HS, while mRNA abundance of the Y box-binding protein-1, which has been suggested to bind oxidized RNA, did not change with age or HS. These results suggest that RNA oxidation, possibly mediated by increased non-heme iron, might contribute to muscle atrophy due to disuse particularly in aged muscle.
gastrocnemius; hemojuvelin (HJV); RNA oxidation; sarcopenia; transferrin receptor 1 (TfR1); Y box binding protein 1 (YB-1); xanthine oxidase (XOD)
The purpose of this study was to ascertain the effect of aging on muscle contractile properties associated with tongue protrusion in a rat model. Fischer 344/Brown Norway hybrid rats, ten young (9 months old) and ten old (32 months old), were used to measure protrusive contractile properties. Results showed a significant reduction in tetanic forces in the old animals. The following measures of muscle contraction were not different between age groups: mean twitch contraction force, twitch contraction time, twitch contraction half-decay time, and a calculated measure of fatigability. In conclusion, aging influenced protrusive tongue muscle contractions in a rat model such that tetanic forces were reduced. The reduction of tetanus force may parallel findings in human subjects relative to isometric tongue force generation and may be associated with age-related disorders of swallowing.
Dysphagia; Tongue force; Aging; Deglutition; Deglutition disorders
Aging, which is an independent risk factor for heart disease, alters body fat mass and its function. Epicardial fat plays an important physiological and pathophysiological role on cardiac structure and function. This study investigated if aging altered the abundance of epicardial (EF) and abdominal fat (AF) derived mediators in a sex dependent manner in female and male Fischer 344 × Brown Norway hybrid (FBN) rats. EF and AF were obtained from 48 female and male, young (6 months), aged (26/30 months) and very aged (30/36 months) FBN rats. Adipose derived anti-inflammatory and pro-inflammatory mediators were measured using ELISA, adipokine array and real-time qPCR. No dramatic changes in circulating lipids other than a higher triglyceride and high density lipoprotein in aged females and a significantly increased circulating adiponectin (p< 0.005) in aged rats were observed. Real time PCR results showed that compared to 6mo old female rats, the aged (26mo) and very aged (30mo) rats had significantly lower levels of EF genes: adiponectin (p<0.005), PPARγ (p<0.01, 0.005), IL-6 (p<0.01) and PAI-1 (p<0.01, 0.01), respectively, but not in AF. In contrast, the male rats exhibited an increase in IL-6 in EF (p< 0.005) but a decrease in adiponectin and PPARγ in AF with aging. These changes might be attributed to differences in adipocyte make-up or macrophage infiltration. In conclusion, aging had a more profound impact on EF derived mediators in female rather than male rats, which might help explain the increased risk to cardiovascular disease seen in older women.
Aging; adipose tissue; gender; obesity
We tested the hypotheses that: 1) long-term facilitation (LTF) following acute intermittent hypoxia (AIH) varies among three inbred rat strains: Fischer 344 (F344), Brown Norway (BN) and Lewis rats, and 2) ventral cervical spinal levels of genes important for phrenic LTF (pLTF) vary in association with pLTF magnitude. Lewis and F344, but not BN rats exhibited significant increases in phrenic and hypoglossal burst amplitude 60 min post-AIH that were significantly greater than control experiments without AIH, indicating strain differences in phrenic (98%, 56% and 20%, respectively) and hypoglossal LTF (66%, 77% and 5%, respectively). Ventral spinal 5-HT2A receptor mRNA and protein levels were higher in F344 and Lewis versus BN, suggesting that higher 5-HT2A receptor levels are associated with greater pLTF. More complex relationships were found for 5-HT7, BDNF and TrkB mRNA. BN had higher 5-HT7 and TrkB mRNA versus F344; BN and Lewis had higher BDNF mRNA levels versus F344. Genetic variations in serotonergic function may underlie strain differences in AIH-induced pLTF.
We examined the effect of 28 days of overload on mammalian target of rapamycin (mTOR) and extracellular signal–regulated kinase (ERK) signaling in young adult (Y; 6-month old) and aged (O; 30-month old) Fischer 344 × Brown Norway rats subjected to bilateral synergist ablation (SA) of two thirds of the gastrocnemius muscle or sham surgery (CON). Although plantaris (PLA) muscle hypertrophy was attenuated by aging, mTOR phosphorylation was 44% and 35% greater in Y SA and O SA compared with CON (p = .038). Ribosomal protein S6 phosphorylation was 114% and 24% higher in Y SA and O SA compared with CON (p = .009). Eukaryotic initiation factor 2Bϵ phosphorylation was 33% and 9% higher in Y SA and O SA compared with CON (p = .04). Translational signaling in young adult and aged plantaris muscle is equally responsive to chronic overload.
mTOR; Muscle hypertrophy; Muscle overload; Aging
Aging is associated with increases in body mass and fat mass (FM), whereas fat-free mass (FFM) either decreases or remains unchanged. The purpose of this study was to determine whether dual-energy X-ray absorptiometry (DXA) accurately detects age-associated changes in male Fischer 344 × Brown–Norway rats ages 8, 18, and 28 months. Eviscerated animal carcasses were first examined via the Lunar DPX-IQ DXA (small animal software version 1.0; HiRes (0.6 × 1.2 mm) medium mode). Eviscerated carcasses were then weighed, autoclaved, homogenized, and fat isolated from aliquots of homogenate via methanol/chloroform extraction. In both chemical (CHEM) and DXA analysis, carcass mass (CM), FM, and % fat were significantly higher (P < 0.0001) in the 18 and 28 versus 8-month-old rats. CHEM showed greater FFM in the 18 versus 8 months-old rats but not the 28 months-old animals. DXA was unable to detect the age-associated changes in FFM. Regression analysis showed a strong correlation between CHEM and DXA methods for CM (r = 0.98, P < 0.0001) and FM (r = 0.97, P < 0.0001), but less strong for FFM (r = 0.59, P = 0.0002). In conclusion, compared to CHEM, DXA consistently overestimated CM and FM across the age groups by 9% and 77%, respectively, and underestimated FFM by 5%.
Lean body mass; Fat free mass; Fat mass; Dual-energy x-ray absorptiometry
Fractionated whole brain irradiation (WBI) is used to treat primary brain tumors and brain metastases, but also is associated with late-delayed cognitive impairment. Previously, impaired performance was demonstrated in Fischer 344 x Brown Norway (F344xBN) rats on a hippocampal-dependent learning and memory test 12 months after fractionated WBI at middle age (1). The present study investigated whether there also is an affect on hippocampal neuron number or volume in that animal model.
Methods and Materials
Twelve month-old F344xBN male rats were divided into WBI and control (CON) groups (n=6/group). Anesthetized WBI rats received 45 Gy of 137Cs γ rays delivered as nine 5 Gy fractions twice per week for 4.5 weeks. CON rats were anesthetized, but not irradiated. Twelve months following WBI completion, all rats were anesthetized, perfused with paraformaldehyde, and hippocampal sections were immunostained with the neuron-specific antibody, NeuN. Using unbiased stereology, total neuron number and the volume of the neuronal and neuropil layers were determined in the dentate gyrus (DG), CA3, and CA1 subregions of hippocampus.
No differences in tissue integrity or neuron distribution were observed between the WBI and CON groups. Moreover, quantitative analys is demonstrated that neither total neuron number nor the volume of neuronal or neuropil layers differed between the two groups for any subregion.
Impairment on a hippocampal-dependent learning and memory test occurs one year following fractionated WBI at middle-age. The same WBI regimen, however, does not lead to a loss of neurons or a reduction in the volume of hippocampus.
fractionated WBI; middle-age; hippocampus; neuron number; Fischer 344 x Brown Norway rats
Aging is associated with oxidative damage and an imbalance in redox signaling in a variety of tissues, yet little is known about the extent of age-induced oxidative stress in the sympathoadrenal system. Lifelong caloric restriction has been shown to lower levels of oxidative stress and slow the aging process. Therefore, the aims of this study were two-fold: 1) to investigate the effect of aging on oxidative stress in the adrenal medulla and hypothalamus and 2) determine if lifelong 40% caloric restriction (CR) reverses the adverse effects of age-induced oxidative stress in the sympathetic adrenomedullary system. Adult (18 months) and very old (38 months) male Fischer 344 x Brown Norway rats were divided into ad libitum or 40% CR groups and parameters of oxidative stress were analyzed in the adrenal medulla and the hypothalamus. A significant age-dependent increase in lipid peroxidation (+20%, P<0.05) and tyrosine nitration (+111%, P<0.001) were observed in the adrenal medulla while age resulted in a reduction in the protein expression of key antioxidant enzymes, CuZnSOD (−27%, P<0.01) and catalase (−27%, P<0.05) in the hypothalamus. Lifelong CR completely prevented the age-induced increase in lipid peroxidation in the adrenal medulla and restored the age-related decline in antioxidant enzymes in the hypothalamus. These data indicate that aging results in a significant increase in oxidative stress in the sympathoadrenal system. Importantly, lifelong CR restored the age-related changes in oxidative stress in the adrenal medulla and hypothalamus. Caloric restriction could be a potential non-pharmacological intervention to prevent increased oxidative stress in the sympathetic adrenomedullary system with age.
aging; caloric restriction; oxidative stress; antioxidant enzymes; adrenal medulla; hypothalamus
Available studies indicate that both genetic background and aging influence collateral growth capacity, but it is not known how their combination affects collateral growth. We evaluated collateral growth induced by ileal artery ligation in Fischer 344 (F344), Brown Norway (BN), and the first generation hybrid of F344 × BN (F1) rats available for aging research from the National Institute on Aging. Collateral growth was determined by paired diameter measurements in anesthetized rats immediately and 7 days postligation. In 3-mo-old rats, significant collateral growth occurred only in BN (35% ± 11%, P < 0.001). The endothelial cell number in arterial cross sections was also determined, since this precedes shear-mediated luminal expansion. When compared with the same animal controls, the intimal cell number was increased only in BN rats (92% ± 21%, P < 0.001). The increase in intimal cell number and the degree of collateral luminal expansion in BN rats was not affected by age from 3 to 24 mo. Immunohistochemical studies demonstrated that intimal cell proliferation was much greater in the collaterals of BN than of F1 rats. The remarkable difference between these three strains of rats used in aging research and the lack of an age-related impairment in the BN rats are novel observations. These rat strains mimic clinical observations of interindividual variation in collateral growth capacity and the impact of age on arteriogenesis and should be useful models to investigate the molecular mechanisms responsible for such differences.
strain dependent; endothelial proliferation; macrophage recruitment
Altering dopamine synaptic transmission can affect both cranial and limb sensorimotor function, but often to a different degree of severity. We hypothesized that haloperidol has dose-dependent but differential effects on lingual forces, lingual movement rates, and limb movement initiation. We measured average and maximal lingual force, tongue press rate and cataleptic descent time in 9 Fischer 344/Brown Norway rats in varied doses of haloperidol. Decreases in lingual force and temporal parameters and increases in cataleptic descent time were related to haloperidol dose. However, they were related to a different degree as the relationships were strong between average force and tongue press rate, moderate between maximal force and tongue press rate, moderate between average force and cataleptic descent time, and weak between maximal force and cataleptic descent time. Elucidating the relationships between the cranial and limb sensorimotor systems in the context of altered dopamine synaptic transmission may assist in developing therapies for conditions such as Parkinson's disease.
tongue; haloperidol; dopamine; rat