Urinary 8-hydroxy-2''-deoxyguanosine as a biological marker of in vivo oxidative DNA damage.

DNA is subject to constant oxidative damage from endogenous oxidants. The oxidized DNA is continuously repaired and the oxidized bases are excreted in the urine. A simple routine analytical procedure is described for urinary 8-hydroxy-2'-deoxyguanosine, an oxidative DNA damage adduct, as an indicator of oxidative damage in humans and rodents. This adduct was purified from human urine and characterized. The described assay employs a series of solid-phase extraction steps that separate 8-hydroxy-2'-deoxyguanosine from other urinary constituents, followed by analysis by gradient reversed-phase HPLC coupled to a dual-electrode high-efficiency electrochemical detection system. Analysis of urine from three species by this method indicates that mice excrete approximately 3.3-fold more 8-hydroxy-2'-deoxyguanosine than humans (582 vs. 178 residues per cell per day), a result that supports the proposal that oxidative damage to DNA increases in proportion to species-specific basal metabolic rates.     

Oxidative damage to DNA: relation to species metabolic rate and life span.

Oxidative damage to DNA is caused by reactive by-products of normal metabolism, as well as by radiation. Oxidized DNA bases excised by DNA repair enzymes and excreted in urine were measured in four different species to determine the relation between specific metabolic rate (ml of O2 consumed per gram of body weight per hr) and oxidative DNA damage. An average of 6.04 nmol of thymine glycol per kg/day and 2.58 nmol of thymidine glycol per kg/day were found in mouse urine and 1.12 nmol of thymine glycol per kg/day and 0.95 nmol of thymidine glycol per kg/day were found in monkey urine. On a body weight basis, mice excrete 18 times more thymine glycol plus thymidine glycol than do humans, and monkeys excrete 4 times more thymine glycol plus thymidine glycol than do humans. When results among mice, rats, monkeys, and humans are compared, specific metabolic rate correlates highly with oxidative DNA damage. These findings are consistent with the theory that free radical-induced DNA damage may play a central role in the aging process.     

Assay of excised oxidative DNA lesions: isolation of 8-oxoguanine and its nucleoside derivatives from biological fluids with a monoclonal antibody column.

An immunoaffinity column is described that facilitates the analysis of oxidative damage products of DNA and RNA in urine, blood plasma, and medium isolated from cultures of Escherichia coli. In intact animals, lesions (adducts) excised from DNA are transported from the cell through the circulation and excreted in urine. In bacteria, DNA adducts are excreted directly into the medium. In either case, the adducts can be assayed as a measure of oxidative damage to DNA. A monoclonal antibody that recognizes 8-oxo-7,8-dihydro-2'-deoxyguanosine (oxo8dG;8-hydroxy-2'-deoxyguanosine), a bio-marker of oxidative damage to DNA, has been isolated, and its substrate binding properties have been characterized. The relative binding affinities of this monoclonal antibody for oxo8dG, unmodified nucleosides, or derivatives of Gua made it suitable for the preparation of immunoaffinity columns that greatly facilitate the isolation of oxo8dG, 8-oxo-7,8-dihydroguanine, and 8-oxo-7,8-dihydroguanosine from various biological fluids. Quantitative analysis of these adducts in urine of rats fed a nucleic acid-free diet and in the medium from cultures of E. coli suggests that oxo8-7,8-dihydroguanine is the principal repair product from oxo8-dG in DNA of both eukaryotes and prokaryotes. The results support our previous estimate of about 10(5) oxidative lesions to DNA being formed and excised in an average rat cell per day.     

Thymine glycol and thymidine glycol in human and rat urine: a possible assay for oxidative DNA damage.

Thymine glycol is a DNA damage product of ionizing radiation and other oxidative mutagens. In an attempt to find a noninvasive assay for oxidative DNA damage in individuals, we have developed an HPLC assay for free thymine glycol and thymidine glycol in urine. Our results indicate that humans excrete about 32 nmol of the two glycols per day. Rats, which have a higher specific metabolic rate and a shorter life span, excrete about 15 times more thymine glycol plus thymidine glycol per kg of body weight than do humans. We present evidence that thymine glycol and thymidine glycol are likely to be derived from repair of oxidized DNA, rather than from alternative sources such as the diet or bacterial flora. This noninvasive assay of DNA oxidation products may allow the direct testing of current theories which relate oxidative metabolism to the processes of aging and cancer in man.     

In vivo oxidative metabolism of a major peroxidation-derived DNA adduct, M1dG

3-(2-Deoxy-beta-D-erythro-pentofuranosyl)pyrimido[1,2-alpha]purin-10(3H)-one (M1dG) is a DNA adduct arising from the reaction of 2-deoxyguanosine with the lipid peroxidation product, malondialdehyde, or the DNA peroxidation product, base propenal. M1dG is mutagenic in bacteria and mammalian cells and is present in the genomic DNA of healthy human beings. It is also detectable, albeit at low levels, in the urine of healthy individuals, which may make it a useful biomarker of DNA damage linked to oxidative stress. We investigated the possibility that the low urinary levels of M1dG reflect metabolic conversion to derivatives. M1dG was rapidly removed from plasma (t(1/2) = 10 min) after i.v. administration to rats. A single urinary metabolite was detected that was identified as 6-oxo-M1dG by MS, NMR spectroscopy, and independent chemical synthesis. 6-Oxo-M1dG was generated in vitro by incubation of M1dG with rat liver cytosols, and studies with inhibitors suggested that xanthine oxidase and aldehyde oxidase are involved in the oxidative metabolism. M1dG also was metabolized by three separate human liver cytosol preparations, indicating 6-oxo-M1dG is a likely metabolite in humans. This represents a report of the oxidative metabolism of an endogenous DNA adduct and raises the possibility that other endogenous DNA adducts are metabolized by oxidative pathways. 6-Oxo-M1dG may be a useful biomarker of endogenous DNA damage associated with inflammation, oxidative stress, and certain types of cancer chemotherapy.     

Effect of specific activation of γ‐aminobutyric acid receptor in vivo on oxidative stress‐induced damage after extended hepatectomy

Aim: γ‐Aminobutyric acid (GABA) is a multifunctional molecule with various physiological effects throughout the body. The regulation of GABA receptor (GABAR) plays a key role in reducing the damage mediated by oxidative stress (OS). Extended hepatectomy causes fatal OS‐induced injury in the liver remnant. We aimed to investigate the effect of a GABAR agonist in extended hepatectomy. Methods: Saline or a GABAR agonist (43.56 nmol/g bodyweight of muscimol) was administrated intravenously at 4 h preoperatively. C57BL/6 mice were divided into three groups: laparotomy only, 90% hepatectomy with saline and 90% hepatectomy with a GABAR agonist. Liver samples were obtained at 6 h after surgery. Results: Survival curves were prolonged by the GABAR agonist. Histopathological findings and biochemical profiles showed that the GABAR agonist reduced liver damage. Immunohistological assessment demonstrated that the GABAR agonist prevented apoptotic induction. As shown by 4‐hydroxynonenal, which reflects OS‐induced damage, 90% hepatectomy caused OS and the GABAR agonist reduced OS. We measured ataxia‐telangiectasia mutated kinase (ATM), H2AX, Akt and free radical scavenging enzymes because they may be affected by GABAR regulation, and found that Akt was greatly decreased after 90% hepatectomy, but it recovered with the GABAR agonist. Conclusion: GABAR is activated by a specific agonist in the liver in vivo. This activation reduces OS‐mediated damage after extended hepatectomy in vivo, and the mechanism via an Akt‐dependent pathway may be a key.     

Oxidative damage to DNA during aging: 8-hydroxy-2''-deoxyguanosine in rat organ DNA and urine.

Oxidative damage to DNA is shown to be extensive and could be a major cause of the physiological changes associated with aging and the degenerative diseases related to aging such as cancer. The oxidized nucleoside, 8-hydroxy-2'-deoxyguanosine (oh8dG), one of the approximately 20 known oxidative DNA damage products, has been measured in DNA isolated from various organs of Fischer 344 rats of different ages. oh8dG was present in the DNA isolated from all the organs studied: liver, brain, kidney, intestine, and testes. Steady-state levels of oh8dG ranged from 8 to 73 residues per 10(6) deoxyguanosine residues or 0.2-2.0 x 10(5) residues per cell. Levels of oh8dG in DNA increased with age in liver, kidney, and intestine but remained unchanged in brain and testes. The urinary excretion of oh8dG, which presumably reflects its repair from DNA by nuclease activity, decreased with age from 481 to 165 pmol per kg of body weight per day for urine obtained from 2-month- and 25-month-old rats, respectively. 8-Hydroxyguanine, the proposed repair product of a glycosylase activity, was also assayed in the urine. We estimate approximately 9 x 10(4) oxidative hits to DNA per cell per day in the rat. The results suggest that the age-dependent accumulation of oh8dG residues observed in DNA from liver, kidney, and intestine is principally due to the slow loss of DNA nuclease activity; however, an increase in the rate of oxidative DNA damage cannot be ruled out.     

Interleukin-6 inhibits oxidative injury and necrosis after extreme liver resection

Extreme hepatectomy or resection of more than 80% of liver mass often leads to liver failure and death and is a major limitation to therapeutic liver resection for patients with liver tumors. We sought to define the mechanisms leading to liver failure and to determine the utility of interleukin-6 (IL-6) administration to improve outcomes. Mice were injected with Chinese hamster ovary cells expressing human IL-6 or no recombinant protein, or were administered recombinant IL-6 or carrier by osmotic mini-pump. Mice were then subjected to 70% or 87% hepatectomy. Light and electron microscopy of liver sections after 87% hepatectomy showed ballooning hepatocytes, vacuolar changes, and mitochondrial abruption, with absence of anoikic nuclei. No significant activation of executor caspases or DNA laddering was observed, although a dramatic decrease in cellular adenosine triphosphate (ATP) stores was measured, suggesting cell death was by a necrotic pathway involving mitochondrial dysfunction. A large increase in protein oxidation was observed, indicative of significant oxidative stress. IL-6 treatment before 87% hepatectomy resulted in less biochemical and histological evidence of liver injury as well as earlier proliferating chain nuclear antigen (PCNA) expression and accelerated recovery of liver mass. IL-6 pretreatment induced the antioxidative injury proteins, ref-1 and GPX1, decreased protein oxidation, vacuolar changes and leakage of mitochondrial products, improved ATP stores, and maintained cellular ultrastructure after 87% hepatectomy. CONCLUSION: Massive oxidative injury and mitochondrial dysfunction occurs in the liver after extreme hepatectomy. IL-6 improves recovery and survival from extreme liver resection by enhancing pro-growth pathways, reducing oxidative stress, and maintaining mitochondrial function.     

Overexpression of thioredoxin-1 reduces oxidative stress in the placenta of transgenic mice and promotes fetal growth via glucose metabolism

Oxidative stress occurs where there is an imbalance between the production and scavenging of free radicals. Pregnancy per se is a state of oxidative stress due to the increased metabolic activity of placental mitochondria and reduced scavenging ability of antioxidant systems. Overproduction of reactive oxygen species may be associated with impaired fetal growth. However, the physiological influence of antioxidant systems on fetal growth is not well understood. In this study we assessed the effects of antioxidant systems on fetal growth using human thioredoxin (hTRX)-1 overexpressing transgenic (Tg) mice. Tg or C57BL/6 [wild-type (WT)] male mice were mated with WT female mice, and dams were killed to obtain the fetuses and placentas on gestational d 15. Tg fetuses were significantly heavier than WT fetuses, whereas placental weight did not differ significantly between the two groups. Immunohistochemically, hTRX-1 was localized to the nuclei of labyrinthine trophoblasts in Tg mice. In addition, placental expression of 8-hydroxy-2'-deoxyguanosine, which reflects DNA damage caused by oxidative stress, was reduced in Tg mice compared with WT mice. Placental expression of glucose transporter-1 mRNA and protein was significantly higher in Tg mice than WT mice, whereas no significant differences were observed for glucose transporter-3, IGF, and IGF-binding protein mRNA expression. These results suggest that placental and/or systemic antioxidant systems can influence fetal growth. In particular, increased hTRX-1 activity and the resulting modified placental redox state may play an important role in fetal growth by increasing the availability of glucose.     

Overexpression of thioredoxin prevents acute hepatitis caused by thioacetamide or lipopolysaccharide in mice

Thioredoxin (Trx) is a small redox-active protein with antioxidant and antiapoptotic effects. Trx transgenic (Tg) mice are more resistant to cerebral infarction and survive longer than wild-type (WT) C57BL/6 mice. The aim of the present study was to investigate the protective role of Trx in acute hepatitis models. The expression of endogenous Trx was decreased in thioacetamide (TAA)-induced acute hepatitis. TAA (100 microg/g) was injected intraperitoneally in WT and Tg mice. Survival rate after TAA injection was higher in Tg mice than in WT mice. The level of oxidative stress was significantly less in Tg mice than in WT mice, as shown by the protein carbonylation assay and lipid peroxidation assay. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL)-positive cells were less in Tg mice than in WT mice, which was consistent with DNA laddering assay. Caspase-3 and caspase-9 activities and cytochrome c release were significantly inhibited in Tg mice compared with those in WT mice. In addition, lipopolysaccharide (LPS) plus d-galactosamine (GalN), or anti-Fas antibody (Jo2) were injected. Survival rate after LPS plus GalN injection was much higher in Tg mice than in WT mice. In contrast, there was no difference in survival rate after Jo2 injection between WT and Tg mice. In conclusion, transgene of Trx attenuated TAA- or LPS-induced acute lethal hepatitis. In addition to an antioxidant effect, Trx has the potential to protect acute liver injury via an antiapoptotic effect, which mainly inhibits mitochondria-mediated apoptosis signaling.     

Oxidative stress and extracellular matrices after hepatectomy and liver transplantation in rats简

AIM: To investigate oxidative stress (OS)-mediated damage and the behavior of extracellular matrices in various rat models because shear stress with portal hypertension and cold ischemia/warm reperfusion injury trigger the liver regeneration cascade after surgery. These injuries also cause fatal liver damage.METHODS: Rats were divided into four groups according to the surgery performed: control; hepatectomy with 40% liver remnant (60% hepatectomy); orthotopic liver transplantation (OLT) with whole liver graft (100% OLT); and split OLT (SOLT) with 40% graft (40% SOLT). Survival was evaluated. Blood and liver samples were collected at 6 h after surgery. Biochemical and histopathological examinations were performed. OS-induced damage, 4-hydroxynonenal, ataxia-telangiectasia mutated kinase, histone H2AX, phosphatidylinositol 3-kinase (PI3K) and Akt were evaluated by western blotting. Behavior of extracellular matrices, matrix metalloproteinase (MMP)-9, MMP-2, tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 were also evaluated by western blotting and zymography.RESULTS: Although 100% OLT survived, 60% hepatectomy and 40% SOLT showed poor survival. Histopathological, immunohistological, biochemical and protein assays revealed that 60% hepatectomy, 100% OLT and 40% SOLT showed liver damage. PI3K and Akt were decreased in 60% hepatectomy and 40% SOLT. For protein expression, 40% SOLT showed differences in MMP-9, MMP-2 and TIMP-2. TIMP-1 showed differences in 60% hepatectomy and 40% SOLT. For protein activity, MMP-9 demonstrated significant differences in 60% hepatectomy, 100% OLT and 40% SOLT.CONCLUSION: Under conditions with an insufficient liver remnant, prevention of OS-induced damage via the Akt/PI3K pathway may be key to improve the postoperative course. MMP-9 may be also a therapeutic target after surgery.     

Oxidative stress and extracellular matrices after hepatectomy and liver transplantation in rats

AIM:To investigate oxidative stress(OS)-mediated damage and the behavior of extracellular matrices in various rat models because shear stress with portal hypertension and cold ischemia/warm reperfusion injury trigger the liver regeneration cascade after surgery. These injuries also cause fatal liver damage.METHODS: Rats were divided into four groups according to the surgery performed: control; hepatectomy with 40% liver remnant(60% hepatectomy); orthotopic liver transplantation(OLT) with whole liver graft(100% OLT); and split OLT(SOLT) with 40% graft(40% SOLT). Survival was evaluated. Blood and liver samples were collected at 6 h after surgery. Biochemical and histopathological examinations were performed. OSinduced damage, 4-hydroxynonenal, ataxia-telangiectasia mutated kinase, histone H2AX, phosphatidylinositol 3-kinase(PI3K) and Akt were evaluated by western blotting. Behavior of extracellular matrices, matrix metalloproteinase(MMP)-9, MMP-2, tissue inhibitor of metalloproteinase(TIMP)-1 and TIMP-2 were also evaluated by western blotting and zymography. RESULTS: Although 100% OLT survived, 60% hepatectomy and 40% SOLT showed poor survival. Histopathological, immunohistological, biochemical and protein assays revealed that 60% hepatectomy, 100% OLT and 40% SOLT showed liver damage. PI3K and Akt were decreased in 60% hepatectomy and 40% SOLT. For protein expression, 40% SOLT showed differences in MMP-9, MMP-2 and TIMP-2. TIMP-1 showed differences in 60% hepatectomy and 40% SOLT. For protein activity, MMP-9 demonstrated significant differences in 60% hepatectomy, 100% OLT and 40% SOLT. CONCLUSION: Under conditions with an insufficient liver remnant, prevention of OS-induced damage via the Akt/PI3K pathway may be key to improve the postoperative course. MMP-9 may be also a therapeutic target after surgery.     

Thioredoxin 1 overexpression extends mainly the earlier part of life span in mice

We examined the effects of increased levels of thioredoxin 1 (Trx1) on resistance to oxidative stress and aging in transgenic mice overexpressing Trx1 [Tg(TRX1)(+/0)]. The Tg(TRX1)(+/0) mice showed significantly higher Trx1 protein levels in all the tissues examined compared with the wild-type littermates. Oxidative damage to proteins and levels of lipid peroxidation were significantly lower in the livers of Tg(TRX1)(+/0) mice compared with wild-type littermates. The survival study demonstrated that male Tg(TRX1)(+/0) mice significantly extended the earlier part of life span compared with wild-type littermates, but no significant life extension was observed in females. Neither male nor female Tg(TRX1)(+/0) mice showed changes in maximum life span. Our findings suggested that the increased levels of Trx1 in the Tg(TRX1)(+/0) mice were correlated to increased resistance to oxidative stress, which could be beneficial in the earlier part of life span but not the maximum life span in the C57BL/6 mice.     

The mitochondrial theory of aging: Insight from transgenic and knockout mouse models

A substantial body of evidence has accumulated over the past 35 years in support of a role for oxidative damage to the mitochondrial respiratory chain and mitochondrial DNA in the determination of mammalian lifespan. The goal of this review is to provide a concise summary of recent studies using transgenic and knockout mouse models with altered expression of mitochondrial antioxidant enzymes (MnSOD (Sod2Tg and Sod2^+/−), thioredoxin 2 (Trx2^+/−), mitochondrial targeted catalase (mCAT) and mutant mice models that have been genetically manipulated to increase mitochondrial deletions or mutations (Polγ^D257A/D257A mutant mice) to examine the role of mitochondrial oxidative stress in aging. The majority of studies using these strategies do not support a clear role for mitochondrial oxidative stress or a vicious cycle of oxidative damage in the determination of lifespan in mice and furthermore do not support the free radical theory of aging. However, several key questions remain to be addressed and clearly more studies are required to fully understand the role of mitochondria in age-related disease and aging.     

Oxidative DNA damage in diabetes mellitus: its association with diabetic complications

Aims/hypothesis. Augmented oxidative stress induced by hyperglycaemia possibly contributes to the pathogenesis of diabetic complications. Oxidative stress is known to increase the conversion of deoxyguanosine to 8-oxo, 2 ′-deoxyguanosine in DNA. To investigate the possible contribution of oxidative DNA damage to the pathogenesis of diabetic complications, we measured the content of 8-oxo, 2 ′-deoxyguanosine in the urine and the blood mononuclear cells of Type II (non-insulin-dependent) diabetic patients. Methods. We studied 53 Type II diabetic patients and 39 age-matched healthy control subjects. We assayed 8-oxo, 2 ′-deoxyguanosine by HPLC-electrochemical detection method. Results. The content of 8-oxo, 2 ′-deoxyguanosine in the urine and the mononuclear cells of the Type II diabetic patients was much higher than that of the control subjects. Urinary 8-oxo, 2 ′-deoxyguanosine excretion and the 8-oxo, 2 ′-deoxyguanosine content in the mononuclear cells from the diabetic patients with complications were higher than those from the diabetic patients without complications. Urinary excretion of 8-oxo, 2 ′-deoxyguanosine was significantly correlated with the 8-oxo, 2 ′-deoxyguanosine content in the mononuclear cells. The 8-oxo, 2 ′-deoxyguanosine content in the urine and mononuclear cells was correlated with the haemoglobin A_{1 c} value. Conclusion/interpretation. This is the first report of a direct association between oxidative DNA damage and the complications of diabetes. The augmented oxidative DNA damage in diabetes is speculated to contribute to the pathogenesis of diabetic complications. [Diabetologia (1999) 42: 995–998] Received: 5 January 1999 and in revised form: 18 March 1999     

Effect of coronary angiography on oxidative DNA damage observed in circulating lymphocytes

Endogenous oxidative DNA damage is caused by multiple endogenous and exogenous factors. It is not completely known whether coronary angiography has an effect on DNA damage. The aim of this study was to investigate whether coronary angiography causes oxidative DNA damage. Fifty-four patients who underwent elective coronary angiography for diagnostic purpose were enrolled to the study. For each subject, the frequency of oxidative DNA damage was analyzed by using the comet assay, which is a sensitive biomarker of DNA damage, before and after diagnostic procedures. A highly significant increase of DNA damage mean score was observed in all patients after the coronary angiography procedure (p < 0.001). No significant associations were found between the change in oxidative DNA damage and dose of contrast media and radiation exposure time. A significant correlation was observed between the change of DNA damage and age, hyperlipidemia, hypertension, smoking, Gensini score index, and vitamin B(12) (r = 0.496, p< 0.001 ; r = 0.416, p = 0.002; r = 0.284, p = 0.038; r = 0.275, p = 0.044; r = 0.742, p < 0.001; r = -0.347, p = 0.048, respectively). The change of oxidative DNA damage was higher in patients with 3-vessel disease compared with 2-vessel disease, 1-vessel disease, and normal coronary arteries (99.6 +/-8.4, 62.0 +/-2.0, 43.2 +/-8.4, 21.6 +/-11.6 respectively; ANOVA p < 0.001). Multiple linear regression analysis showed that age and Gensini score index were independent predictors of the change of DNA damage (beta = 0.425, p = 0.003, beta = 0.684, p = 0.001 respectively). Our findings demonstrate that increased oxidative DNA damage in undergoing coronary angiography might be dependent on the severity of coronary artery disease and age, rather than on contrast media and radiation exposure time.     

Mitochondrial glutathione content determines the rate of liver regeneration after partial hepatectomy in eu- and hypothyroid rats

BACKGROUND/AIMS: Mitochondrial glutathione has been postulated to affect mitochondrial function and liver regeneration. METHODS: Mitochondrial respiration, total and oxidized glutathione, and liver regeneration were assessed after partial hepatectomy in glutathione-depleted and in hypothyroid rats with/without supplementation of glutathione ester. RESULTS: Mitochondrial, cytosolic and circulating glutathione levels were lower in glutathione-depleted rats. Hepatectomy was followed by significant changes of intra- and extracellular glutathione and of mitochondrial respiration. In glutathione-deficient rats, the recovery of mitochondrial function and the liver regeneration were delayed. Administration of glutathione ester partially corrected the fall of cytosolic and mitochondrial glutathione following hepatectomy, reduced mitochondrial oxidative damage, and accelerated the restoration of mitochondrial respiration and the rate of liver regeneration. In hypothyroid rats, intracellular glutathione homeostasis and mitochondrial respiration were impaired already at baseline; slower regeneration and mitochondrial oxidative alterations were observed after hepatectomy. Glutathione ester ameliorated the regenerative response in hypothyroid rats by providing higher concentrations of cytosolic and mitochondrial glutathione. CONCLUSIONS: Glutathione depletion and hypothyroidism affect the mitochondrial function during liver regeneration. Liver regenerates more slowly in glutathione-depleted and in hypothyroid rats. The earlier restoration of mitochondrial function and the higher rate of proliferation in glutathione ester treated rats suggest that the maintenance of intracellular glutathione facilitates liver regeneration.     

Long-term effects of caloric restriction or exercise on DNA and RNA oxidation levels in white blood cells and urine in humans

Excessive adiposity is associated with increased oxidative stress and accelerated aging. Weight loss induced by negative energy balance reduces markers of oxidation in experimental animals and humans. The long-term effects of weight loss induced by calorie restriction or increased energy expenditure induced by exercise on measures of oxidative stress and damage have not been studied in humans. The objective of the present study was to compare the effects of 20% caloric restriction or 20% exercise alone over 1 year on oxidative damage to DNA and RNA, as assessed through white blood cell and urine analyses. Eighteen men and women aged 50 to 60 years with a body mass index (BMI) between 23.5 to 29.9 kg/m(2) were assigned to one of two conditions--20% CR (n = 9) or 20% EX (n = 9)--which was designed to produce an identical energy deficit through increased energy expenditure. Compared to baseline, both interventions significantly reduced oxidative damage to both DNA (48.5% and 49.6% reduction for the CR and EX groups, respectively) and RNA (35.7% and 52.1% reduction for the CR and EX groups, respectively) measured in white blood cells. However, urinary levels of DNA and RNA oxidation products did not differ from baseline values following either 12-month intervention program. Data from the present study provide evidence that negative energy balances induced through either CR or EX result in substantial and similar improvements in markers of DNA and RNA damage to white blood cells, potentially by reducing systemic oxidative stress.     

Modulation of age-associated oxidative DNA damage in rat brain cerebral cortex, striatum and hippocampus by L-carnitine

The free radical theory of cell aging may have significant relevance in the pathogenesis of a number of age-related neurological disorders. A large body of experimental evidence supports the existence of a relationship between genomic instability, DNA damage and aging. The age-associated accumulation of oxidative DNA damage is well documented in central nervous system. The decline of mitochondrial respiratory function and loss of normal cellular homeostasis as consequences of excessive accumulation of endogenous oxidative damages to DNA have long been indicated in the aging process. In the present study, age-associated alterations in the content of DNA and accumulation of oxidative DNA damage products such as 8-OHdG and DNA protein cross-links are mainly focused. In parallel, we have also investigated the salubrious effect of l-carnitine against oxidative DNA damage as it possesses energy and antioxidant improving properties. Our results thus reveal that L-carnitine has inhibiting effect on the accumulation of age-related oxidative DNA damage in various brain regions, viz. cerebral cortex, striatum and hippocampus.