Effects of aging and food restriction on the antioxidant enzyme activity of rat livers

Effects of alternate-day fasting and time-restricted feeding in obese middle-aged female rats

OBJECTIVES

Obesity is a multifactorial condition associated with metabolic alterations that can be aggravated during female aging. Calorie restriction via intermittent fasting (IF) diets may reduce body weight and therefore have the potential to decrease obesity and associated comorbidities, such as insulin resistance. This study investigated the effects of two IF protocols, alternate-day fasting (ADF) and time-restricted feeding (TRF) in middle-aged obese female rats.

METHODS

Wistar rats (age 15 mo) were fed with standard chow or high-fat diet for 8 wk and then separated into the following groups (n = 5-8 each) for another 8 wk: control (received standard chow), obese (received high-fat diet), obese + ADF (24-h fasting protocol), and obese + TRF (14 h daily).

RESULTS

At the end of the study, both IF protocols were able to reduce body weight and body mass index compared with the obese group. However, no changes were observed in adiposity and glucose homeostasis. We also found an increase in total leukocytes, lymphocytes, and monocytes in the TRF group and a higher number of platelets in the ADF group. Blood lipid profiles, including triglycerides and high-density lipoprotein, as well as liver stress responses, such as heat shock protein 70 and malondialdehyde, were not changed by IF.

CONCLUSIONS

Although ADF and TRF protocols resulted in a reduction of body weight and body mass index, these dietary interventions did not promote health benefits, such as reducing blood lipid profile, adiposity, and insulin resistance. In addition, ADF and TRF increased inflammatory biomarkers, which may increase the risk of obesity-associated comorbidities.

Dietary Restriction and Oxidative Stress: Friends or Enemies?

Significance: It is well established that lifestyle and dietary habits have a tremendous impact on life span, the rate of aging, and the onset/progression of age-related diseases. Specifically, dietary restriction (DR) and other healthy dietary patterns are usually accompanied by physical activity and differ from Western diet that is rich in fat and sugars. Moreover, as the generation of reactive oxidative species is the major causative factor of aging, while DR could modify the level of oxidative stress, it has been proposed that DR increases both survival and longevity. Recent Advances: Despite the documented links between DR, aging, and oxidative stress, many issues remain to be addressed. For instance, the free radical theory of aging is under "re-evaluation," while DR as a golden standard for prolonging life span and ameliorating the effects of aging is also under debate. Critical Issues: This review article pays special attention to highlight the link between DR and oxidative stress in both aging and age-related diseases. We discuss in particular DR's capability to counteract the consequences of oxidative stress and the molecular mechanisms involved in these processes. Future Directions: Although DR is undoubtedly beneficial, several considerations must be taken into account when designing the best dietary intervention. Use of intermittent fasting, daily food reduction, or DR mimetics? Future research should unravel the pros and cons of all these processes. Antioxid. Redox Signal. 34, 421-438.

Stereological study and analysis of oxidative stress during renal aging in rats

PURPOSE

To evaluate renal histological changes by stereology and morphometry and analyze the main markers of oxidative stress in rats undergoing natural aging.

METHODS

Seventy two Wistar rats were divided into six groups of 12 rats each, which were euthanized at 3, 6, 9, 12, 18, and 24 months of age. Right kidney was stereologically and morphometrically analyzed to calculate the volumetric density (Vv[glom]), numerical density (Nv[glom]) and glomerular volume (Vol[glom]). Left kidney was used to determine the levels of nonprotein thiols, lipid peroxidation, and protein carbonylation, as well as the activities of superoxide-dismutase and catalase enzymes.

RESULTS

Both Vv[glom] and Nv[glom] values showed gradual decreases between groups. Activity of superoxide-dismutase was elevated at 24 months of age, and the levels of nonprotein thiols were higher in older animals. Greater catalase activity and protein carbonylation were observed in animals between 6 and 12 months of age but lessened in older rats. Lipid peroxidation decreased in the older groups.

CONCLUSIONS

Morphometric and stereological analyses revealed a gradual decrease in the volume and density of renal glomeruli during aging, as well as kidney atrophy. These findings related to oxidative stress clarify many changes occurring in kidney tissues during senescence in rats.

Age-Related Changes in Antioxidative Enzyme Capacity in Tongue of Fischer 344 Rats

Objectives

Antioxidative enzyme efficiency changes in some organs with age. However, no study has been conducted on age-related antioxidant enzyme changes in tongue. In the present study, the authors investigated the activities of four antioxidative enzymes and their protein expressions in the tongues of young and old Fischer 344 rats.

Methods

Age-dependent changes in the enzyme activities of total superoxide dismutase (SOD), Mn-SOD, Cu/Zn-SOD, catalase (CAT), and glutathione peroxidase (GPx) were determined using chemical kits, and the protein expressions levels of these enzymes by Western blotting. The study was conducted using rats aged 7 months (the young group, n=8) and 22 months (the old group, n=8).

Results

Total SOD, Cu/Zn-SOD, and GPx activities in the tongues of old rats were lower than in young rats, and similarly, corresponding protein expressions were downregulated in old rats. On the other hand, although the protein expressions of Mn-SOD and CAT were lower in old rats, their enzyme activities were not.

Conclusion

The results of this study provide a possible mechanism for the tongue aging process, as in old Fischer 344 rats the antioxidant defense system was diminished with respect to enzyme activity levels and protein abundances.

Nutritional Status as the Key Modulator of Antioxidant Responses Induced by High Environmental Ammonia and Salinity Stress in European Sea Bass (Dicentrarchus labrax)

Salinity fluctuation is one of the main factors affecting the overall fitness of marine fish. In addition, water borne ammonia may occur simultaneously with salinity stress. Additionally, under such stressful circumstances, fish may encounter food deprivation. The physiological and ion-osmo regulatory adaptive capacities to cope with all these stressors alone or in combination are extensively addressed in fish. To date, studies revealing the modulation of antioxidant potential as compensatory response to multiple stressors are rather lacking. Therefore, the present work evaluated the individual and combined effects of salinity challenge, ammonia toxicity and nutritional status on oxidative stress and antioxidant status in a marine teleost, European sea bass (Dicentrarchus labrax). Fish were acclimated to normal seawater (32 ppt), to brackish water (20 ppt and 10 ppt) and to hypo-saline water (2.5 ppt). Following acclimation to different salinities for two weeks, fish were exposed to high environmental ammonia (HEA, 20 mg/L representing 50% of 96h LC₅₀ value for ammonia) for 12 h, 48 h, 84 h and 180 h, and were either fed (2% body weight) or fasted (unfed for 7 days prior to HEA exposure). Results show that in response to decreasing salinities, oxidative stress indices such as xanthine oxidase activity, levels of hydrogen peroxide (H₂O₂) and lipid peroxidation (malondialdehyde, MDA) increased in the hepatic tissue of fasted fish but remained unaffected in fed fish. HEA exposure at normal salinity (32 ppt) and at reduced salinities (20 ppt and 10 ppt) increased ammonia accumulation significantly (84 h–180 h) in both feeding regimes which was associated with an increment of H₂O₂ and MDA contents. Unlike in fasted fish, H₂O₂ and MDA levels in fed fish were restored to control levels (84 h–180 h); with a concomitant increase in superoxide dismutase (SOD), catalase (CAT), components of the glutathione redox cycle (reduced glutathione, glutathione peroxidase and glutathione reductase), ascorbate peroxidase (APX) activity and reduced ascorbate (ASC) content. On the contrary, fasted fish could not activate many of these protective systems and rely mainly on CAT and ASC dependent pathways as antioxidative sentinels. The present findings exemplify that in fed fish single factors and a combination of HEA exposure and reduced seawater salinities (upto 10 ppt) were insufficient to cause oxidative damage due to the highly competent antioxidant system compared to fasted fish. However, the impact of HEA exposure at a hypo-saline environment (2.5 ppt) also defied antioxidant defence system in fed fish, suggesting this combined factor is beyond the tolerance range for both feeding groups. Overall, our results indicate that the oxidative stress mediated by the experimental conditions were exacerbated during starvation, and also suggest that feed deprivation particularly at reduced seawater salinities can instigate fish more susceptible to ammonia toxicity.

Oxidative stress and genotoxicity of the ionic liquid 1-octyl-3-methylimidazolium bromide in zebrafish (Danio rerio)

Ionic liquids (ILs) have a great reputation due to their negligible volatility, designability, good stability, and ability to be recycled. They are considered to be "green" solvents and have great promise in many fields. In recent years, the toxicities of ILs have garnered increasing attention as reported by a number of studies. However, previous studies have primarily focused on their lethal toxicities, and data were limited on their toxic effects at nonlethal doses. We performed a study on the toxic effects of 1-octyl-3-methylimidazolium bromide ([Omim]Br) on zebrafish. During a 28-day period, male and female zebrafish were separately exposed to sequential concentrations (0, 5, 10, 20, and 40 mg/L) of [Omim]Br. Fishes were sampled after 7, 14, 21, and 28 days of exposure, and reactive oxygen species (ROS) levels, activities of antioxidant enzymes (superoxide dismutase and catalase), lipid peroxidation (LPO), and DNA damage in fish livers were measured. ROS, LPO, and DNA damage were all induced by the ionic liquid, and antioxidant enzyme activities increased at the beginning and then decreased. These phenomena demonstrate that [Omim]Br can induce oxidative stress and DNA damage in zebrafish.

The effects of pre-weaning undernutrition on the expression levels of free radical deactivating enzymes in the mouse brain

A mild degree of undernutrition brought about by restricting the amount of food in the diet is known to alter the life span of an animal. It has been hypothesised that this may be related to the effects of undernutrition on an animals anti-oxidant defense system. We have therefore, used real-time PCR (rt-PCR) techniques to determine the levels of mRNA expression for manganese superoxide dismutase (MnSOD), copper/zinc superoxide dismutase (Cu/ZnSOD), glutathione peroxidase 1 (GPx 1) and catalase in the brains of Quackenbush mice undernourished from conception until 21-post-natal days of age. It was found that 21- and 61-day-old undernourished mice had a deficit in the expression of Cu/ZnSOD in both the cerebellum and forebrain regions compared to age-matched controls. The expression of MnSOD was found to be greater in the cerebellum, but not the forebrain region, of 21-day-old undernourished mice. There were no significant differences in the expression of GPx 1 and catalase between control and undernourished or previously undernourished mice. Our results confirm that undernutrition during the early life of a mouse may disrupt some of the enzymes involved in the anti-oxidant defense systems.

Responses of the antioxidant system in QGY-7701 cells to the cytotoxicity and apoptosis induced by 1-octyl-3-methylimidazolium chloride

This study aims to evaluate the cytotoxicity and responses of the cellular antioxidant system of 1-octyl-3-methylimidazolium chloride ([C8 mim][Cl]) on human hepatocarcinoma QGY-7701 cells. The results show that [C8 mim][Cl] can inhibit QGY-7701 cell growth and decrease their viabilities in a dose-dependent manner. The results also reveal that [C8 mim][Cl] exposure can induce apoptosis in the [C8 mim][Cl]-treated QGY-7701 cells. In addition, the results of biochemical assays show that [C8 mim][Cl] exposure causes overproduction of reactive oxygen species (ROS), inhibits superoxide dismutase (SOD) and catalase (CAT) activities, decreases reduced glutathione (GSH) content, and increases the cellular malondialdehyde (MDA) level. These results suggest that ROS-mediated oxidative stress may be responsible for the apoptosis induced by [C8 mim][Cl] in QGY-7701 cells.

Effect of modest caloric restriction on oxidative stress in women, a randomized trial

Objectives

It is not established to what extent caloric intake must be reduced to lower oxidative stress in humans. The aim of this study was to determine the effect of short-term, moderate caloric restriction on markers of oxidative stress and inflammation in overweight and obese premenopausal women.

Materials/Methods

Randomized trial comparison of 25% caloric restriction (CR) or control diet in 40 overweight or obese women (body mass index 32±5.8 kg/m²) observed for 28 days and followed for the next 90 days. Weight, anthropometry, validated markers of oxidative stress (F₂-isoprostane) and inflammation (C-reactive protein), adipokines, hormones, lipids, interleukins, and blood pressure were assessed at baseline, during the intervention, and at follow-up.

Results

Baseline median F₂-isoprostane concentration (57.0, IQR = 40.5–79.5) in the CR group was 1.75-fold above average range for normal weight women (32.5 pg/ml). After starting of the caloric restriction diet, F₂-isoprostane levels fell rapidly in the CR group, reaching statistical difference from the control group by day 5 (median 33.5, IQR = 26.0–48.0, P<0.001) and remained suppressed while continuing on the caloric restriction diet. Three months after resuming a habitual diet, concentrations of F₂-isoprostane returned to baseline elevated levels in ∼80% of the women.

Conclusions

Oxidative stress can be rapidly reduced and sustained through a modest reduction in caloric intake suggesting potential health benefits in overweight and obese women.

Trial Registration

Clinicaltrials.gov NCT00808275

The effect of caloric restriction and glycemic load on measures of oxidative stress and antioxidants in humans: results from the CALERIE Trial of Human Caloric Restriction

Decreasing oxidative stress and increasing antioxidant defense has been hypothesized as one mechanism by which caloric restriction (CR) increases longevity in animals. A total of 46 moderately overweight volunteers (BMI: 25-30 kg/m2), ages 20-42 yr were randomized to either high glycemic (HG) or low glycemic (LG) dietary load CR regimen at either 10% (n=12) or 30% (n=34) of basal caloric intake. All food was provided to participants for 6 mo. Overall, after controlling for CR levels and dietary regimen for 6 mo, plasma glutathione peroxidase activity increased (p=0.04) and plasma protein carbonyl levels decreased (p=0.02) and a non-significant decrease in plasma 8-epi-prostaglandin F2α level was observed (p=0.09). No significant change was observed in other plasma antioxidants such as superoxide dismutase and catalase. These findings indicate that short term CR (10% or 30%) in moderately overweight subjects modulates some but not all measures of antioxidant defense and oxidative stress.

Effect of every-other-day fasting on spontaneous chromosomal damage in rat's bone-marrow cells

Dietary restriction in experimental rodents, either by calorie restriction (CR) or by every-other-day fasting (EODF), was shown to protect against cancer and increase lifespan. One of the suggested hypotheses to explain the beneficial effects of dietary restriction is that the diet stabilizes the integrity of the genetic information. The effects of EODF on the spontaneous frequency of sister chromatid exchanges (SCE) and chromosomal aberrations (CA) were examined in bone-marrow cells of 3-mo-old Wistar male rats. After 12 wk of EODF diet, significant reduction in the frequency of SCE and total number of CA was observed. Data indicate a protective effect of EODF diet against spontaneous mutations in rats.

Acute effects of 1-octyl-3-methylimidazolium bromide ionic liquid on the antioxidant enzyme system of mouse liver

The effects of acute exposure of intraperitoneal injection of aqueous 1-octyl-3-methylimidazolium bromide on the antioxidant enzymes and lipid peroxidation of the treated mouse liver were investigated in the present paper. Thirty mice were treated with 17.9 (0.5 median lethal dose, LD(50)) and 35.7 mg/kg (1 LD(50)) of the ionic liquid or saline solution by intraperitoneal injection for 10h. Significant increase in hepatosomatic index and decrease in liver protein content were found in 1 LD(50) group. No statistically significant change was observed in the activity of superoxide dismutase in both treated groups compared to the control group. In the case of catalase activity, the decrease was recorded only at dose of 1 LD(50). As for the activity of glutathione peroxidase, increase in 0.5 LD(50) group while significant decrease at dose of 1 LD(50) was noted. There was an increase in the activity of glutathione-S-transferase in these two treated groups in comparison to the control. However, no effect on the level of lipid peroxidation was found in the treated groups. These results showed that the acute exposure of aqueous ionic liquid could cause damage to mouse, leading to antioxidant responses in livers of the treated mice.

DNA damage, cellular senescence and organismal ageing: causal or correlative?

Cellular senescence has long been used as a cellular model for understanding mechanisms underlying the ageing process. Compelling evidence obtained in recent years demonstrate that DNA damage is a common mediator for both replicative senescence, which is triggered by telomere shortening, and premature cellular senescence induced by various stressors such as oncogenic stress and oxidative stress. Extensive observations suggest that DNA damage accumulates with age and that this may be due to an increase in production of reactive oxygen species (ROS) and a decline in DNA repair capacity with age. Mutation or disrupted expression of genes that increase DNA damage often result in premature ageing. In contrast, interventions that enhance resistance to oxidative stress and attenuate DNA damage contribute towards longevity. This evidence suggests that genomic instability plays a causative role in the ageing process. However, conflicting findings exist which indicate that ROS production and oxidative damage levels of macromolecules including DNA do not always correlate with lifespan in model animals. Here we review the recent advances in addressing the role of DNA damage in cellular senescence and organismal ageing.

Proteomics analysis of hypothalamic response to energy restriction in dairy cows

The hypothalamus is the central regulatory unit that balances a number of body functions including metabolic rate, hunger, and satiety signals. Hypothalamic neurons monitor and respond to alterations of circulating nutrients and hormones that reflect the peripheral energy status. These extracellular signals are integrated within the cell at the ATP:AMP ratio and at the level of ROS, triggering gene expression associated with glucose and lipid metabolism. In order to identify new molecular factors potentially associated with the control of energy homeostasis, metabolic adaptation, and regulation of feed intake, hypothalami from ad libitum fed and energy restricted cows were characterized using 2-DE and MALDI-TOF-MS. Among 189 different protein spots identified, nine proteins were found to be differentially expressed between groups. Beside the 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase, stress-induced phosphoprotein-1, heat shock protein 70 kDa-protein-5, dihydropyrimidinase-related protein-2, [Cu-Zn]-superoxide dismutase, ubiquitin carboxy-terminal hydrolase-L1, and inorganic pyrophosphatase were found to be up-regulated, whereas glyceraldehyde 3-phosphate dehydrogenase and aconitase-2 were down-regulated in the restricted group. In conclusion, differentially expressed proteins are related to energy and nucleotide metabolism and cellular stress under conditions of dietary energy deficiency. These proteins may be new candidate molecules that are potentially involved in signaling for maintaining energy homeostasis.

Effects of Taurine in Cellular Responses to Oxidative Stress in Young and Middle-Aged Rat Liver

Aging is related with an increased cellular level of lipid peroxides and reactive oxygen species (ROS). The useful effects of taurine as an antioxidant in biological systems have been attributed to its capability to stabilize biomembranes, to scavenge ROS, and to decrease the peroxidation of unsaturated membrane lipids. The aim of the present study was to investigate the effects of taurine on malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GPx), thioredoxin reductase (TR), and endothelial nitric oxide synthase (eNOS) in young and middle-aged rat liver. There was not a significant difference in liver MDA levels between the control groups of young and middle-aged rats (P > 0.05). However, liver GSH levels, and GPx and TR activities between the control groups of young and middle-aged rats were significantly different (P < 0.05). Liver MDA level was significantly lower in the taurine group of middle-aged rats (P < 0.05). Liver GSH levels, and GPx and TR activities were significantly increased in the taurine group of middle-aged rats when compared to the control group (P < 0.05). Liver MDA level was significantly lower in the taurine group of young rats than the ones in the control group (P < 0.05). Liver TR activity was significantly increased in the taurine group of young rats when compared to the control group (P < 0.05). Liver GPx activity was not statistically different between the taurine and the control groups in young rats (P > 0.05). Liver GSH levels were not different between the young taurine and the control groups (P > 0.05). Immunohistochemical studies exhibited no change in eNOS activity after taurine injection in young rats. However, in middle-aged rats, taurine lowered the eNOS reactivity to the same level found in young rats. These results suggested that exogenous taurine might play a role in aging by means of its reducing effects on free radical levels in parallel to an increase in the antioxidant capacity.

Long-term calorie restriction reduces proton leak and hydrogen peroxide production in liver mitochondria

Calorie restriction (CR) without malnutrition increases maximal life span in diverse species. It has been proposed that reduction in energy expenditure and reactive oxygen species (ROS) production could be a mechanism for life span extension with CR. As a step toward testing this theory, mitochondrial proton leak, H2O2 production, and markers of oxidative stress were measured in liver from FBNF1 rats fed control or 40% CR diets for 12 or 18 mo. CR was initiated at 6 mo of age. Proton leak kinetics curves, generated from simultaneous measures of oxygen consumption and membrane potential, indicated a decrease in proton leak after 18 mo of CR, while only a trend toward a proton leak decrease was observed after 12 mo. Significant shifts in phosphorylation and substrate oxidation curves also occurred with CR; however, these changes occurred in concert with the proton leak changes. Metabolic control analysis indicated no difference in the overall pattern of control of the oxidative phosphorylation system between control and CR animals. At 12 mo, no significant differences were observed between groups for H2O2 production or markers of oxidative stress. However, at 18 mo, protein carbonyl content was lower in CR animals, as was H2O2 production when mitochondria were respiring on either succinate alone or pyruvate plus malate in the presence of rotenone. These results indicate that long-term CR lowers mitochondrial proton leak and H2O2 production, and this is consistent with the idea that CR may act by decreasing energy expenditure and ROS production.

Effect of reactive oxygen species on the metabolism of tryptophan in rat brain: influence of age

In an earlier study, oxidation of tryptophan hydroxylase was implicated as its affinity was decreased with aging in rat brain. To establish any potential link between its oxidative damage and aging, we have determined the activities of antioxidant enzymes in midbrain, pons and medulla of 2, 12 and 24 month old Fisher 344 BNF1 rats. The results obtained suggest that the activities of antioxidant enzymes varied considerably with age and brain regions studied. Activities of Cu/Zn superoxide dismutase and glutathione peroxidase were found to increase from 2 to 12 months and then decrease in 24 month old rats. However catalase activity decreased consistently with the age. A parallel increase in the carbonyl content was observed in these brain regions indicating the oxidation of proteins. Reactive oxygen species when included in the incubation mixture decreased the activity of tryptophan hydroxylase in a concentration dependent manner. The loss of tryptophan hydroxylase activity induced by hydrogen peroxide and superoxide anion was prevented by catalase. However superoxide dismutase did not provide such protection. Sulfhydryl agents, cysteine, glutathione and dithiothreitol partially prevented the loss of activity. These studies suggest an involvement of reactive oxygen species for sulfhydryl oxidation of tryptophan hydroxylase in aging.

Proton leak and hydrogen peroxide production in liver mitochondria from energy-restricted rats

Energy restriction (ER), without malnutrition, is the only environmental intervention that consistently increases maximum life span in laboratory rodents. One theory proposes that a reduction in energy expenditure and reactive oxygen species production is the mechanism responsible for this action of ER. To further test this theory, proton leak, H2O2 production, lipid peroxidation, and protein carbonyls were measured in mitochondria from FBNF1 rats fed either a control or 40% ER diet (onset at 6 mo of age). Liver mitochondria were isolated at 7 and 12 mo of age. Liver weight decreased 25 and 36% at 1 and 6 mo of ER, respectively (P < 0.05). ER resulted in an increase (P < 0.05) in percent total polyunsaturates, n-6 polyunsaturates, and total unsaturates (6 mo only) in mitochondrial lipids. These changes, however, were not associated with significant alterations in mitochondrial function. State 4 respiration and membrane potential were not different (P > 0.05) between groups at either assessment period. Similarly, proton leak kinetics were not different between control and ER animals. Top-down metabolic control analysis and its extension, elasticity analysis, were used at the 6-mo assessment and revealed no difference in control of the oxidative phosphorylation system between control and ER rats. H2O2 production with either succinate or pyruvate/malate substrates was also not different (P > 0.05) between groups at either time point. In conclusion, ER did not alter proton leak or H2O2 production at this age or stage of restriction in liver.

Effect of food deprivation on oxidative stress biomarkers in fish (Sparus aurata)

Oxidative stress in fish (Sparus aurata) as a consequence of food restriction and fasting, has been studied. Four groups of fish were maintained for 46 days under different conditions of food supplementation: a control group with no food restriction (ratio of food/fish of 2% w/w), two groups of animals with restricted food supplement (1 and 0.5%) and a fasting group (no meal addition). Finally, all the fish were provided with food at the same ratio as the control group for the last 7 days. Sampling and weighing of fish were carried out every week and their livers were used for the analysis of known biomarkers of oxidative stress. Malondialdehyde and oxidized glutathione levels increased at the third week in fish with partial or total food deprivation, but these levels returned to normal values when the fish readapted to the control conditions. Antioxidant enzymes were also analyzed and significant increases in superoxide dismutase (SOD), glutathione reductase and glutathione peroxidase activities were found in parallel with food restriction; however catalase activity decreased in fasting fish. New SOD isoforms were detected by isoelectrofocusing in fish under food restriction at the second week, which disappeared when starved fish returned to the control conditions. These new SOD isoforms were detected before the appearance of other usual oxidative stress biomarkers.

Food restriction attenuates blood lipid peroxidation in carbon tetrachloride-intoxicated rats

OBJECTIVE

We investigated whether food restriction offers protection against the toxicity of carbon tetrachloride (CCl(4)) and, if so, at what percentage of restriction.

METHODS

The effects of food restriction (75% and 50% of food intake) and food restriction followed by CCl(4) treatment on lipid peroxidation and antioxidant enzymes were studied in female Wistar rats. A single dose of CCl(4) (3 mL/kg of body weight, subcutaneous) was administered at the end of the 30-d feeding period.

RESULTS

The magnitude of increase in lipid peroxidation was less after CCl(4) treatment in food-restricted animals than in animals fed ad libitum (control), whereas alanine transaminase, aspartate transaminase, and alkaline phosphatase activities in plasma were enhanced due to CCl(4) treatment. The magnitude of increase in the marker enzymes was less in food-restricted animals than in control animals. Erythrocytes from food-restricted rats were more resistant to hydrogen peroxide-induced peroxidation than were those from control rats. The activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione-S-transferase were higher in food-restricted animals.

CONCLUSIONS

The present results suggested that food restriction can minimize drug-related increases in peroxidation and protect the system against drug toxicity, presumably by induction of antioxidant potential.

Age-related changes in protein oxidation and proteolysis in mammalian cells

Reactive oxygen species generated as by-products of oxidative metabolism, or from environmental sources, frequently damage cellular macromolecules. Proteins are recognized as major targets of oxidative modification, and the accumulation of oxidized proteins is a characteristic feature of aging cells. An increase in the amount of oxidized proteins has been reported in many experimental aging models, as measured by the level of intracellular protein carbonyls or dityrosine, or by the accumulation of protein-containing pigments such as lipofuscin and ceroid bodies. In younger individuals, moderately oxidized soluble cell proteins appear to be selectively recognized and rapidly degraded by the proteasome. An age-related accumulation of oxidized proteins could, therefore, be a result of declining activity of the proteasome. Previous research to investigate the notion of an age-related decline in the content and/or activity of the proteasome has generated contradictory results. The latest evidence, including our own recent findings, indicates that proteasome activity does, indeed, decline during aging as the enzyme complex is progressively inhibited by oxidized and cross-linked protein aggregates. We propose that cellular aging involves both an increase in (mitochondrial) oxidant production and a progressive decline in proteasome activity. Eventually so much proteasome is inactivated that oxidized proteins begin to accumulate rapidly and contribute to cellular dysfunction and senescence.

Calorie restriction and age-related oxidative stress

Calorie restriction (CR) in mammals has been recognized as the best characterized and most reproducible strategy for extending maximum survival, retarding physiological aging, and delaying the onset of age-related pathologic conditions in mammals. The overwhelming majority of studies using CR have used short-lived rodent species, although current work using rhesus and squirrel monkeys will determine whether this paradigm is also relevant to manipulating the rate of primate aging. The mechanism by which restricted calorie intake modifies the rate of aging and pathology has been the subject of much controversy, although an attenuation in the lifetime accumulation of oxidative damage appears to be a central feature. Although the majority of studies have focused on the ability of cells from calorie-restricted animals to scavenge free radicals to explain the slower accrual of oxidative damage with age, it is not established that CR has a consistent effect to upregulate the activity of these enzymes in all tissues. A major effect of calorie-restricted feeding now appears to be on the rate of production or leak of free radicals from the mitochondria. The details of the adaptation and the signaling pathway that induces this effect are currently unknown.