Effects of phentermine and phenformin on biomarkers of aging in rats

BACKGROUND: Caloric restriction (CR) is the only treatment known to substantially prolong both average and maximal life span in experimental animals. Interventions that mimic certain effects of CR could be potential anti-aging treatments in humans. Drugs which reduce appetite (anorexiants) represent one class of candidate treatments. Agents that reduce the glucose utilization by the organism could also represent another class of candidate CR mimetics. OBJECTIVE: In our study, we addressed the following questions: (1) Does treatment with an anorexiant reduce caloric intake and body weight of experimental animals comparable to that caused by CR? (2) Does treatment with an antidiabetic agent influence caloric intake and body weight? (3) Does treatment with any of these drugs affect metabolic parameters of an organism in the way similar to that observed with CR? Methods: One hundred and twenty 6-month-old female Wistar-derived LIO rats were randomly subdivided into four groups and exposed to: (1) ad libitum feeding with placebo (controls); (2) the antidiabetic drug phenformin (2 mg/kg); (3) the anorectic drug phentermine (1 mg/kg), and (4) the same amount of food as the group with the least food intake during the previous week (pair-fed controls). Food and water intake, body weight, and rectal temperature were measured weekly during 16 weeks. At the end of the 16th week of the experiment, serum levels of glucose, total beta-lipoprotein and pre-beta-lipoprotein fractions, cholesterol, triglycerides, insulin, total triiodothyronine, and free thyroxine were estimated. The contents of diene conjugates and Schiff's bases, total antioxidant activity, the activities of Cu/Zn superoxide dismutase, glutathione S-transferase, and glutathione peroxidase, and the generation of reactive oxygen species (ROS) were studied in brain and liver homogenates and in the serum. RESULTS: The controls exposed to pair feeding had a significantly reduced food consumption (about 20%) as compared with the ad libitum fed controls and thus exhibited a moderate CR. Treatment with phentermine reduced the caloric intake by about 12% as compared with the ad libitum fed controls. Body weight and water intake in this group were only slightly decreased (by about 2 and 5%, respectively) as compared with the controls. The mean rectal temperature in the phentermine group (38 degrees C) was significantly higher than in the ad libitum fed (37.8 degrees C) and pair-fed (37.6 degrees C) controls. Treatment with phentermine also resulted in significantly reduced ROS levels in all tissues studied, while the highest ROS production was found in ad libitum (blood serum) and pair-fed (brain) controls. Treatment with phenformin did not significantly influence food and water consumption, body weight, and temperature when compared with the ad libitum fed controls. Rats treated with this antidiabetic drug showed intermediate values of ROS generation. Differences among the groups in total antioxidant activity were not obvious. CONCLUSIONS: Treatment with phentermine reduces caloric intake slightly less than is commonly observed in CR studies. CR due to forcibly reduced feeding and CR due to substance-suppressed appetite appear to act through different metabolic mechanisms and thus may affect aging and longevity in different ways.     

Short-term caloric restriction improves ischemic tolerance independent of opening of ATP-sensitive K+ channels in both young and aged hearts

Ischemic tolerance decreases with aging and the cardioprotective effect of ischemic preconditioning (IPC) is impaired in aged animals. Although lifelong caloric restriction (CR) profoundly affects the physiological and pathophysiological modifications induced by aging and markedly increases life span in several species, it is unclear whether short-term CR affects ischemic tolerance and IPC in aged hearts. Six-month-old (Y) and 24-month-old (O) Fischer 344 male rats were randomly divided into two groups; AL rats were fed ad libitum, whereas CR rats were fed 90% of the caloric intake of AL for 2 weeks followed by 65% of the caloric intake for 2 weeks. Isolated perfused hearts were subjected to 25 min of ischemia followed by 30 min of reperfusion with or without IPC. The recovery of LV function after reperfusion improved with IPC in ALY but not in ALO. CR improved the recovery of LV function in both CRY and CRO but the cardioprotective effect of IPC was not additive to that of CR. Neither 5-hydroxydecanoate nor glibenclamide abrogated the protective effect of CR in either CRY or CRO. The recovery of myocardial high-energy phosphates after reperfusion was better with CR in both generations. There was no difference in myocardial expression levels of AMP-activated kinase (AMPK) but AMPK-alpha phosphorylated at Thr172 increased with CR in both Y and O. In conclusion, short-term CR improves myocardial ischemic tolerance independent of the opening of KATP channels in both Y and O. CR-induced cardioprotection is associated with an increase in activated AMPK.     

短期能量限制对正常大鼠胰岛素敏感性的影响

目的探讨短期能量限制（CR）对正常大鼠胰岛素敏感性的影响及其机制。方法将24只F344/NSIc系雄性大鼠随机分为对照组（AL组）和能量限制组（CR组）各12只。AL组自由摄入食物及水,CR组限制食物摄入（不禁水）8周（饲料总摄入量为对照组的64%）。采用高胰岛素—正常血糖钳夹试验测定两组葡萄糖输注率（GIR）判断其胰岛素敏感性（GIR越高,胰岛素敏感性越高）;比较两组体质量增加及内脏脂肪重量;Western blot法检测骨骼肌葡萄糖转运体4（Glu T4）、蛋白激酶B底物蛋白160（AS160）及磷酸化AS160（p-AS160）蛋白表达。结果CR组GIR明显高于对照组,体质量及内脏脂肪重量明显低于对照组;两组Glu T4、AS160及p-AS160蛋白表达无显著差异。结论短期CR可提高大鼠正常状态下的胰岛素敏感性,其机制可能与AS160上游的胰岛素信号转导蛋白有关。     

Calorie restriction and rapamycin inhibit MMTV-Wnt-1 mammary tumor growth in a mouse model of postmenopausal obesity

Obesity is an established risk and progression factor for postmenopausal breast cancer. Interventions to decrease caloric intake and/or increase energy expenditure beneficially impact tumor progression in normoweight humans and animal models. However, despite the increasingly high global prevalence of obesity, the effects and underlying mechanisms of these energy balance modulating interventions are poorly characterized in obese individuals. The goal of this study was to better characterize the mechanism(s) responsible for the link between energy balance and breast cancer progression in the postmenopausal obesity context. We compared the effects of calorie restriction (CR), treadmill exercise (EX), and mammalian target of rapamycin (mTOR inhibitor) treatment on body composition, serum biomarkers, cellular signaling, and mammary tumor growth in obese mice. Ovariectomized C57BL/6 mice were administered a diet-induced obesity regimen for 8 weeks, then randomized into three treatment groups: control (semipurified diet fed ad libitum, maintained the obese state); 30% CR (isonutrient relative to control except 30% reduction in carbohydrate calories); and EX (control diet fed ad libitum plus treadmill exercise). Mice were implanted with syngeneic MMTV-Wnt-1 mammary tumor cells at week 12. Rapamycin treatment (5 mg/kg every 48 h) started at week 14. Tumors were excised at week 18. CR and rapamycin (but not EX) significantly reduced final tumor weight compared to control. In follow-up analysis, constitutive activation of mTOR ablated the inhibitory effects of CR on Wnt-1 mammary tumor growth. We conclude that mTOR inhibition may be a pharmacologic strategy to mimic the anticancer effects of CR and break the obesity-breast cancer progression link.     

Effect of a caloric restriction regimen on the angiogenic capacity of aorta and on the expression of endothelin-1 during ageing

Ageing is accompanied by impaired angiogenesis, as well as by a deficient expression of several angiogenic growth factors and the alteration of endothelial functions. Caloric restriction (CR) is the only intervention that can extend lifespan and retard age-related-decline functions in mammals by reducing the rate of ageing and the progression of the associated diseases. Herein, we have investigated the effects of ageing and of a caloric restriction regimen (mild or severe) on the angiogenic response and on the expression of endothelin-1 (ET-1) in the aorta of male 3-, 12- or 24-month-old Sprague-Dawley rats fed ad libitum (AL), fed ad libitum and fasted 1 day a week (mild CR) or fasted every other in alternate days (severe CR). Our findings, using the rat aorta ring assay, show that the angiogenic capacity of aorta decreases with ageing in the oldest rats only. Furthermore, caloric restriction counteracts the age-related changes caloric restrictions actually give raise to a similar recovery. Interestingly, the mRNA ET-1 levels as well as ET-1 expression in aorta sprouting decreases both in middle and in aged animals. Mild and severe caloric restriction regimens prevents ET-1 changes.     

Adjusted and unadjusted energy usage rates both determine body fat and plasma leptin in male Fischer 344 rats.

Previous studies of the relationship between plasma leptin and energy usage have yielded contradictory findings. The present study was therefore conducted to clearly distinguish and measure the energy usage rate and the energy usage rate adjusted for a surrogate of metabolically active tissue mass. We investigated the simultaneous relationships between these two measures of energy usage, leptin, and body fat in 21-month-old adult male Fischer 344 rats on three different long-term dietary regimens: (1) continuous ad libitum feeding (Ad-lib); (2) ad libitum feeding until early adulthood, and then continuous 60% caloric restriction (CR); and (3) ad libitum feeding until early adulthood, then 60% caloric restriction until 16 months, and then ad libitum feeding for 5 months (CR/Ad-lib). Two versions of the daily usage rate were measured: daily dietary caloric intake (DCI), and daily energy expenditure (EE) based on indirect calorimetry. Two versions of the metabolically active tissue mass were also measured: fat-free mass (FFM), and the sum of the weight of the heart, brain, liver, and kidneys. Energy usage rates were adjusted for these measures of metabolically active tissue mass to yield measures of the energy metabolic rate. Correlation, regression, and path analyses showed that both the energy usage rate and adjusted energy usage rate played important independent roles in determining body fat and plasma leptin, but only after multivariate techniques were used to account for the simultaneous interactions between variables. Increases in the energy usage rate were associated with increases in body fat and the adjusted energy usage rate. Increases in the adjusted energy usage rate were associated with decreases in body fat and plasma leptin. These findings suggest that differences in subjects adjusted energy usage rate could explain some of the apparently contradictory findings concerning the relationship between energy usage and plasma leptin in previously published studies. In conclusion, this appears to be the first study to clearly separate and quantify the effects of the energy usage rate and adjusted energy usage rate on body fat and plasma leptin. The findings suggest that under conditions of long-term stable body weight, both of these measures of energy usage play independent simultaneous roles in determining body fat and plasma leptin.     

Life-long caloric restriction does not alter the severity of age-related osteoarthritis

Chronic adipose tissue inflammation and its associated adipokines have been linked to the development of osteoarthritis (OA). It has been shown that caloric restriction may decrease body mass index and adiposity. The objectives of this study were to investigate the effect of lifelong caloric restriction on bone morphology, joint inflammation, and spontaneously occurring OA development in aged mice. C57BL/NIA mice were fed either a calorie-restricted (CR) or ad libitum (AL) diet starting at 14 weeks of age. All mice were sacrificed at 24 months of age. Adipose tissue and knee joints were then harvested. Bone parameters of the joints were analyzed by micro-CT. OA and joint synovitis were determined using histology and semiquantitative analysis. Lifelong caloric restriction did not alter the severity of OA development in C57BL/NIA aged mice, and there was no difference in the total joint Mankin score between CR and AL groups (p = 0.99). Mice also exhibited similar levels of synovitis (p = 0.54). The bone mineral density of the femur and the tibia was comparable between the groups with a small increase in cancellous bone volume fraction in the lateral femoral condyle of the CR group compared with the AL group. Lifelong caloric restriction did not alter the incidence of OA or joint synovitis in C57BL/NIA mice, indicating that a reduction of caloric intake alone was not sufficient to prevent spontaneous age-related OA. Nonetheless, early initiation of CR continued throughout a life span did not negatively impact bone structural properties.     

Influence of age and caloric restriction on expression of hepatic genes for xenobiotic and oxygen metabolizing enzymes in the mouse

The influence of age and life-span-prolonging caloric restriction on the expression of hepatic genes for xenobiotic and activated oxygen metabolism was investigated in female C3B10RF1 mice, a long-lived hybrid strain. Animals were fed either ad libitum, or diets reduced 20% or 52% in total calories but approximately unchanged in total protein, vitamins, and minerals. Cytochrome P1- and P3-450 (cyp1A1 and cyp1A2, respectively) mRNA levels decreased approximately 40% between age 4-5 months (young) and 30-31 months (old) in ad libitum fed animals (p less than or equal to .05). Caloric restriction eliminated this decrease. Manganese-superoxide dismutase mRNA decreased significantly in old ad libitum fed mice, and caloric restriction eliminated this decrease. No change in manganese-superoxide dismutase activity was detected, probably due to its low level and the large variability inherent in the assay. Catalase mRNA increased with age, but was not affected by diet. Catalase activity increased significantly with caloric restriction in young and old mice, in the absence of an increase in catalase mRNA, suggesting translational or posttranslational effects. CuZn-superoxide dismutase, glutathione peroxidase and epoxide hydrolase mRNA, and the ratio of ribosomal to total mRNA did not change with age or diet.     

Lifelong caloric restriction and interleukin-6 secretion from adipose tissue: effects on physical performance decline in aged rats

We investigated whether caloric restriction (CR) improves physical performance in a rodent model of aging, and whether this effect is accompanied with a decrease in visceral adipose tissue production of proinflammatory cytokines. Body composition, standardized physical performance measures, as well as in vitro visceral adipose tissue cytokine secretion and circulating levels of an inflammatory marker were cross-sectionally assessed in ad libitum (AL)-fed and lifelong CR Fischer 344 x Brown Norway male rats aged 18, 24, and 29 months. Fat to lean mass ratio increased and physical performance declined with age in the AL rats. Compared to AL rats, CR rats had lower fat mass, fat to lean ratio, adipose tissue secretion of interleukin-6, and circulating levels of C-reactive protein, and higher physical performance scores. Therefore, CR may be an effective intervention for improving functional status into advanced age and is perhaps mediated via a reduction in adipose tissue-generated proinflammatory cytokine production.     

Effects of caloric restriction or augmentation in adult rats: longevity and lesion biomarkers of aging

Caloric restriction (CR) initiated in young rodents has been thoroughly documented to enhance longevity, but its efficacy when introduced at older ages has not been well investigated. Cohorts of 18- and 26-month-old male F344 x BN F1 hybrid rats were fed either: 1) NIH-31 meal (C); 2) vitamin and mineral fortified NIH-31 meal (R); or 3) vitamin and mineral fortified NIH-31 meal supplemented with corn oil and sweetened condensed milk (S). The C control rats were fed ad libitum, R rats were restricted to 32% of the caloric intake of the controls, and S rats were allowed to consume not more than 8% more calories than C rats. After 6 weeks, the average weights were significantly different between all diet and age groups. Although calorie manipulation altered body weight, no significant effect of the dietary intervention on longevity was found. The average lesion burden, including tumor burden and prevalence of nearly all commonly occurring lesions, were comparable between the groups. Thus, the manipulation of weight at ages beyond middle age has a much less profound impact than similar interventions during growth and maturation in rats.     

Nutritional influences on aging of Fischer 344 rats: I. Physical, metabolic, and longevity characteristics

The aims of this research were (a) to compare food restriction initiated in adult life of male Fischer 344 rats with that limited to early life or involving most of the life span on physical, metabolic, and longevity characteristics and (b) to study a similar level of protein restriction without caloric restriction on these characteristics. Food restriction (60% of the ad libitum intake) initiated at 6 months of age markedly increased life span as did a similar restriction started at 6 weeks of age, but food restriction limited to early life (6 weeks to 6 months of age) and protein restriction caused only a small increase in longevity. Food restriction does not act by reducing the intake of calories or other nutrient per gram of body mass, a finding not in accord with classic views. A progressive decrease in spontaneous locomotive activity with age occurred in ad libitum fed but not restricted rats.     

Cellular adaptation contributes to calorie restriction-induced preservation of skeletal muscle in aged rhesus monkeys

We have previously shown that a 30% reduced calorie intake diet delayed the onset of muscle mass loss in adult monkeys between ~16 and ~22 years of age and prevented multiple cellular phenotypes of aging. In the present study we show the impact of long term (~17 years) calorie restriction (CR) on muscle aging in very old monkeys (27-33 yrs) compared to age-matched Control monkeys fed ad libitum, and describe these data in the context of the whole longitudinal study. Muscle mass was preserved in very old calorie restricted (CR) monkeys compared to age-matched Controls. Immunohistochemical analysis revealed an age-associated increase in the proportion of Type I fibers in the VL from Control animals that was prevented with CR. The cross sectional area (CSA) of Type II fibers was reduced in old CR animals compared to earlier time points (16-22 years of age); however, the total loss in CSA was only 15% in CR animals compared to 36% in old Controls at ~27 years of age. Atrophy was not detected in Type I fibers from either group. Notably, Type I fiber CSA was ~1.6 fold greater in VL from CR animals compared to Control animals at ~27 years of age. The frequency of VL muscle fibers with defects in mitochondrial electron transport system enzymes (ETS(ab)), the absence of cytochrome c oxidase and hyper-reactive succinate dehydrogenase, were identical between Control and CR. We describe changes in ETS(ab) fiber CSA and determined that CR fibers respond differently to the challenge of mitochondrial deficiency. Fiber counts of intact rectus femoris muscles revealed that muscle fiber density was preserved in old CR animals. We suggest that muscle fibers from CR animals are better poised to endure and adapt to changes in muscle mass than those of Control animals.     

Bioenergetics in the aging Fischer 344 rat: effects of exercise and food restriction

The capacity for energy production was evaluated in male, Fischer 344 rats as they advanced from adulthood through senescence. At 10 months of age, the animals were divided into three groups: sedentary, fed ad libitum (S); exercised by treadmill running, fed ad libitum (E); and sedentary, caloric restricted by alternate day feeding (R). Activities of selected enzymes, ADP-stimulated respiration and levels of cytochromes, were determined in homogenates of liver and gastrocnemius muscle prepared from young controls (10-month old S) and 18-, 24-, and 30-month old animals. In liver, age-linked decrements were found in the activities of 3-hydroxyacyl-CoA dehydrogenase (S, E, and R) and citrate synthase (S), and in cytochrome c content (S and E), whereas substrate-catalysed oxidations were unaffected. In the gastrocnemius muscle (S, E, and R), respiration, activities of enzymes of the Krebs cycle and glycolysis, and cytochrome content were decreased after the age of 18 months. Oxidative capacity was increased in muscle through exercise (about 40%) and in liver by food restriction (about 20%). Body and soleus muscle mass declined similarly in all groups (about 14% from 30 to 18 months of age), whereas the loss of weight in the gastrocnemius muscle was much greater (34%). The data indicate that energy metabolism in the senescent animal is competent to meet its needs and age-related declines in energy metabolism are secondary to the aging process.     

Influence of age and long-term dietary restriction on plasma insulin-like growth factor-1 (IGF-1), IGF-1 gene expression, and IGF-1 binding proteins.

The purpose of these studies was to determine more accurately the relationship between IGF-1 and life span, and to determine whether moderate dietary caloric restriction alters the age-related changes in IGF-1. Studies included an assessment of plasma IGF-1, hepatic IGF-1 mRNA, and plasma IGF-1 binding proteins (IGF-1-BP). Rats (6, 12, 22, and 28 months of age) were fed ad libitum or maintained on a diet 60% of ad libitum. In ad libitum fed animals, plasma IGF-1 decreased by 20% between 6 and 28 months of age. Similar age-related declines were observed in dietary restricted animals but levels were generally 14-25% lower at each age group. IGF-1 mRNA levels demonstrated similar decreases with age in ad libitum fed animals, but in dietary restricted animals, levels plateaued at 22 and 28 months. IGF-1 binding protein analysis revealed 3 bands at approximate molecular weights of 40k, 30k, and 24k. All bands demonstrated a decrease in relative IGF-1-BP concentration with age, as well as a decrease in the 40k and 30k binding proteins after dietary restriction. These results indicate that (a) aging in ad libitum fed animals is associated with decreases in plasma IGF-1, IGF-1-BP, and IGF-1 mRNA levels; and (b) long-term dietary restriction decreases plasma IGF-1 and IGF-1-BP levels in each age group although the age-associated decreases in IGF-1 mRNA levels are prevented by dietary restriction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased hepatic apoptosis during short-term caloric restriction is not associated with an enhancement in caspase levels

Long-term caloric restriction extends lifespan, probably through a reduction in radical production and attenuation of oxidative stress. In addition, caloric restriction is associated with a reduction and incidence in tumor pathology, probably, in part, via an enhanced rate of apoptosis. We examined whether short-term (2-month) caloric restriction (40% reduction compared to ad libitum controls) increased hepatic apoptosis and if this was associated by an enhancement in various proteolytic caspase (-3, -7, -9, -12) levels and/or a decrease in two potential inhibitors of apoptosis (the x-linked inhibitor of apoptosis protein XIAP and heat shock protein 70). Short-term caloric restriction resulted in a significant decline, compared to ad libitum controls, in both body mass (30%) and liver mass (46%). While hepatic apoptosis (DNA fragmentation) was significantly higher in the caloric restricted rats, this was not associated with any increase in caspase (-3, -7, -9, -12) levels in the liver. Indeed, the levels of caspase-3, -7 and -12 were significantly lower in the caloric restricted group compared to the ad libitum controls and no differences were observed between groups in either XIAP or HSP70 levels. These findings suggest that enhanced hepatic apoptosis observed after 2-months of caloric restriction is not a result of elevated caspase levels at this time, thereby suggesting that an alternative, caspase-independent pathway may be involved.     

Effects of life-long caloric restriction and voluntary exercise on age-related changes in levels of catecholamine biosynthetic enzymes and angiotensin II receptors in the rat adrenal medulla and hypothalamus

We examined if life-long mild caloric restriction (CR) alone or with voluntary exercise prevents the age-related changes in catecholamine biosynthetic enzyme levels in the adrenal medulla and hypothalamus. Ten-week-old Fisher-344 rats were assigned to: sedentary; sedentary+8% CR; or 8% CR+wheel running. Rats were euthanized at 6 or 24 months of age. Tyrosine hydroxylase (TH) mRNA expression was 4.4-fold higher in the adrenal medullae and 60% lower in the hypothalamus of old sedentary rats compared to young (p<0.01). Life-long CR reduced the age-related increase in adrenomedullary TH by 50% (p<0.05), and completely reversed the changes in hypothalamic TH. Voluntary exercise, however, had no additional effect over CR. Since angiotensin II is involved in the regulation of catecholamine biosynthesis, we examined the expressions of angiotensin II receptor subtypes in the adrenal medulla. AT(1) protein levels were 2.8-fold higher in the old animals compared to young (p<0.01), and while AT(1) levels were unaffected by CR alone, CR+wheel running decreased AT(1) levels by 50% (p<0.01). AT(2) levels did not change with age, however CR+wheel running increased its level by 42% (p<0.05). These data indicate that a small decrease in daily food intake can avert age-related changes in catecholamine biosynthetic enzyme levels in the adrenal medulla and hypothalamus, possibly through affecting angiotensin II signaling.     

Caloric restriction protects mitochondrial function with aging in skeletal and cardiac muscles

In skeletal muscles and heart in vitro complex IV activity is lower in young adult caloric restricted (CR) animals despite normal aerobic function in situ and in vivo. On the other hand, whereas markers of oxidative capacity decline 25% to 46% between 8 and 10 months and 35 months in ad libitum fed (AL) animals, in most muscles there is no decline in CR across the same absolute age (35 mo old) or relative age (35% survival rate) span and PGC-1alpha gene expression in gastrocnemius muscle declines more slowly with aging. The present results show that CR largely prevents the age-associated decline in mitochondrial function in heart and skeletal muscles, and suggest that this is secondary to a better-maintained drive on mitochondrial biogenesis.     

Effects of caloric restriction and growth hormone resistance on the expression level of peroxisome proliferator-activated receptors superfamily in liver of normal and long-lived growth hormone receptor/binding protein knockout mice

Growth hormone receptor/binding protein knockout (GHR-KO) mice live approximately 40% longer than their normal siblings do. These mice have dramatically reduced plasma levels of insulin-like growth factor 1 (IGF1) and enhanced insulin sensitivity. We examined the expression level of peroxisome proliferator-activated receptors (PPARs) and retinoid X receptors family genes in the livers of normal and GHR-KO mice fed ad libitum or subjected to long-term 30% caloric restriction (CR). The levels of PPARgamma and PPARalpha messenger RNA and proteins and the levels of retinoid X receptors messenger RNA were elevated in long-lived GHR-KO mice as compared to normal mice with no major effect of CR in either genotype. These findings suggest that enhanced insulin sensitivity of GHR-KO mice may be related to the altered actions of PPARs family members in the liver. The results also indicate that CR may increase insulin sensitivity through a different mechanism.     

Peripheral lymphocyte 8-OHdG levels correlate with age-associated increase of tissue oxidative DNA damage in Sprague-Dawley rats. Protective effects of caloric restriction

8-hydroxy-deoxyguanosine adducts (8-OHdG), indices of oxidative DNA damage, were measured by immunohystochemistry with diaminobenzidine detection in the brain, skeletal muscle, heart, liver, tenuum mucosa and lymphocytes from young (4 months) and aged (24 months) Sprague-Dawley rats fed ad libitum or held on two different caloric restriction diets (alternate day ad libitum feeding or daily feeding with 40% reduced calories). In the absence of caloric restriction the levels of oxidative DNA damage increased as a function of age in all tissues examined, with a maximum approximately 3-fold increase being detected in the peripheral lymphocytes and the heart and a minimum approximately 2-fold increase being detected in the liver and brain tissues. Caloric restriction regimens effectively reduced age-dependent increase of oxidative DNA damage in all tissues examined; in particular, the brain and small intestine did not exhibit any age-related increase of oxidative DNA damage. We propose that the levels of 8-OHdG in peripheral lymphocytes may serve a biochemical index of age-related whole organism oxidative DNA damage. Immunohistochemistry might be exploited as a rapid and simple techniques for measuring lymphocytes oxidative DNA damage in large scale studies.