PubMed Health⌕ Search

Biomedical subjects

C Leeuwenburgh

Publications and source records attributed to C Leeuwenburgh.

At least 19 recordsLinked to original sources
PubMed2006

Tissue-specific effect of age and caloric restriction diet on mitochondrial DNA content.

The effect of age and caloric-restriction (CR) diet on mitochondrial DNA (mtDNA) content in different rat tissues was investigated. A decrease of the mtDNA content occurs with aging in liver and soleus muscle, whereas there is no age-related significant change of mtDNA content in brain. CR fully reverses the age-dependent loss of mtDNA in liver and soleus, whereas it results in a significant increase of mtDNA amount above the value of aged ad libitum fed rats in brain. These results further support the tissue-specific effect of CR, likely because of the different dependence of tissues on external nutrient uptake.

Age Factors↗
PubMed2005

Mitochondrial DNA mutations, oxidative stress, and apoptosis in mammalian aging.

Mutations in mitochondrial DNA (mtDNA) accumulate in tissues of mammalian species and have been hypothesized to contribute to aging. We show that mice expressing a proofreading-deficient version of the mitochondrial DNA polymerase g (POLG) accumulate mtDNA mutations and display features of accelerated aging. Accumulation of mtDNA mutations was not associated with increased markers of oxidative stress or a defect in cellular proliferation, but was correlated with the induction of apoptotic markers, particularly in tissues characterized by rapid cellular turnover. The levels of apoptotic markers were also found to increase during aging in normal mice. Thus, accumulation of mtDNA mutations that promote apoptosis may be a central mechanism driving mammalian aging.

Aging↗
PubMed2004

Ageing and subcellular distribution of mitochondria: role of mitochondrial DNA deletions and energy production.

The rapid growing population of elderly illustrates the importance of understanding the mechanisms responsible for ageing and the detrimental effects on health associated with increasing age. One of the primary mechanisms may be because of the accumulation of mtDNA damage and oxidative damage with age. Previous studies have examined this correlation in post-mitotic tissues such as skeletal muscle, heart and brain with decreased mitochondrial function, such as enzymatic activities of the electron transport chain and ATP production. However, regional differences in the subcellular location of mitochondria exist and most studies have failed to differentiate the effects of these two autonomous fractions, the subsarcolemmal and intermyofibrillar populations. Hence, while future research attempts to explain the mechanisms responsible for ageing in the mitochondrion, it should also take into account the independent pathways of these two distinctly different populations.

Adenosine Triphosphate↗
PubMed2004

Measurement of the 4,834-bp mitochondrial DNA deletion level in aging rat liver and brain subjected or not to caloric restriction diet.

Several studies have demonstrated an age-related accumulation of the amount of a specific 4834-bp mitochondrial DNA (mtDNA) deletion in different tissues of rat (liver, brain, and skeletal muscle). We investigated the influence of a caloric restriction diet (CR) on a selected age-associated marker of mtDNA damage, as the 4834-bp deletion, using quantitative real-time PCR. The mtDNA deleted level has been determined with respect to the mitochondrial D-loop level, using specific primers and TaqMan probes for each target. In liver we found an age-related increase of the deletion level (twofold) that was reversed and brought back to the adult level by a CR diet. On the contrary, in the brain the age-related increase of the deletion level (eightfold) was not affected by CR at all. The different effect of the CR on the deletion level in liver and brain might be a further element supporting the tissue-specificity of the aging process.

Aging↗
PubMed2002

Effects of aging and caloric restriction on mitochondrial energy production in gastrocnemius muscle and heart.

Mitochondria are chronically exposed to reactive oxygen intermediates. As a result, various tissues, including skeletal muscle and heart, are characterized by an age-associated increase in reactive oxidant-induced mitochondrial DNA (mtDNA) damage. It has been postulated that these alterations may result in a decline in the content and rate of production of ATP, which may affect tissue function, contribute to the aging process, and lead to several disease states. We show that with age, ATP content and production decreased by approximately 50% in isolated rat mitochondria from the gastrocnemius muscle; however, no decline was observed in heart mitochondria. The decline observed in skeletal muscle may be a factor in the process of sarcopenia, which increases in incidence with advancing age. Lifelong caloric restriction, which prolongs maximum life span in animals, did not attenuate the age-related decline in ATP content or rate of production in skeletal muscle and had no effect on the heart. 8-Oxo-7,8-dihydro-2'-deoxyguanosine in skeletal muscle mtDNA was unaffected by aging but decreased 30% with caloric restriction, suggesting that the mechanisms that decrease oxidative stress in these tissues with caloric restriction are independent from ATP availability. The generation of reactive oxygen species, as indicated by H2O2 production in isolated mitochondria, did not change significantly with age in skeletal muscle or in the heart. Caloric restriction tended to reduce the levels of H2O2 production in the muscle but not in the heart. These data are the first to show that an age-associated decline in ATP content and rate of ATP production is tissue specific, in that it occurs in skeletal muscle but not heart, and that mitochondrial ATP production was unaltered by caloric restriction in both tissues.

Adenosine Triphosphate↗
PubMed2001

Supplementation with vitamin C and N-acetyl-cysteine increases oxidative stress in humans after an acute muscle injury induced by eccentric exercise.

There has been no investigation to determine if the widely used over-the-counter, water-soluble antioxidants vitamin C and N-acetyl-cysteine (NAC) could act as pro-oxidants in humans during inflammatory conditions. We induced an acute-phase inflammatory response by an eccentric arm muscle injury. The inflammation was characterized by edema, swelling, pain, and increases in plasma inflammatory indicators, myeloperoxidase and interleukin-6. Immediately following the injury, subjects consumed a placebo or vitamin C (12.5 mg/kg body weight) and NAC (10 mg/kg body weight) for 7 d. The resulting muscle injury caused increased levels of serum bleomycin-detectable iron and the amount of iron was higher in the vitamin C and NAC group. The concentrations of lactate dehydrogenase (LDH), creatine kinase (CK), and myoglobin were significantly elevated 2, 3, and 4 d postinjury and returned to baseline levels by day 7. In addition, LDH and CK activities were elevated to a greater extent in the vitamin C and NAC group. Levels of markers for oxidative stress (lipid hydroperoxides and 8-iso prostaglandin F2alpha; 8-Iso-PGF2alpha) and antioxidant enzyme activities were also elevated post-injury. The subjects receiving vitamin C and NAC had higher levels of lipid hydroperoxides and 8-Iso-PGF2alpha 2 d after the exercise. This acute human inflammatory model strongly suggests that vitamin C and NAC supplementation immediately post-injury, transiently increases tissue damage and oxidative stress.

Acetylcysteine↗
PubMed2001

Reactive carbonyl formation by oxidative and non-oxidative pathways.

The spectrophotometric protein carbonyl assay is used as an indicator of protein damage by free radical reactions in vitro and in a variety of pathologies. We investigated model proteins and a variety of oxidative and non-oxidative reactions, as well as what effects hemoglobin, myoglobin, and cytochrome c might have on levels of protein carbonyls. We show that oxidative as well as non-oxidative mechanisms introduce carbonyl groups into proteins, providing a moiety for quantification with 2,4-dinitrophenylhydrazine (DNPH). Bovine serum albumin exposed to oxidative scenarios, such as hypochlorous acid, peroxynitrite, and metal-catalyzed oxidation exhibited variable, but increased levels of carbonyls. Other non-oxidative modification systems, in which proteins are incubated with various aldehydes, such as malondialdehyde, acrolein, glycolaldehyde, and glyoxal also generated significant amounts of carbonyls. Furthermore, purified myoglobin, hemoglobin, and cytochrome c show high absorbance at the same wavelengths as DNPH. The high levels observed are due to the innate absorbance of hemoglobin, myoglobin, and cytochrome c near the assay spectra of DNPH. These studies show that carbonyl content could be due to oxidative as well as non-oxidative mechanisms and that heme-containing compounds may effect carbonyl quantification.

Aldehydes↗
PubMed2001

Aged rat hearts are not more susceptible to ischemia-reperfusion injury in vivo: role of glutathione.

The current study tested the hypothesis that ischemia-reperfusion (I-R) can cause more severe myocardial dysfunction and oxidative damage in senescent rats than young adult rats. Male Fischer 344 rats at the age of 6 (adult) and 24 (old) months were subjected to an open-chest heart surgery and randomly assigned to one of the following treatments: ischemia only (I), with the occlusion of the main descending branch of the left coronary artery (LCA) for 30 min; I-R, with the release of LCA occlusion for 20 min; or sham (S) operation. Heart mechanical performance was monitored using a fluid-filled catheter inserted in the right carotid artery and advanced to the left ventricle. Ischemia caused similar reductions of left ventricle systolic pressure (LVSP) and contractility (+/-dP/dt) in adult and aged hearts. After I-R, adult hearts regained 82% (P<0.05) of the pre-ischemic LVSP, whereas the aged hearts regained 91% (P>0.05) of LVSP. There was no significant difference in the reduction of +/-dP/dt with I-R between adult and aged hearts. Old rats had lower pre-ischemic heart rate than adult rats, however, I-R caused no reduction of heart rate, and a smaller reduction of pressure-rate double product in the aged rats (10%, P>0.05) than the adult rats (23%, P<0.01). Aged rats demonstrated greater myocardial and plasma glutathione (GSH) concentrations prior to surgery, and maintained higher GSH levels and GSH:glutathione disulfide (GSSG) ratio with I-R. Aged hearts also had higher GSH peroxidase, GSH reductase and GSH sulfur-transferase activities than adult hearts, while I-R induced lipid peroxidation was similar. It is concluded that senescent hearts with intact circulatory and neural inputs are not more susceptible to I-R injury than adult hearts during myocardial I-R, partly because they have a greater GSH antioxidant protection.

Aging↗
PubMed2001

Apoptosis and aging: role of the mitochondria.

Apoptosis research is a rapidly developing area, but the role of apoptosis is still unclear and controversial. For example, several studies document a significant loss of cardiac and skeletal myocytes during normal aging, possibly by apoptotic mechanisms. This loss in cells may be directly mediated by mitochondrial dysfunction caused by chronic exposure to oxidants and increased activation of mitochondrial permeability transition pores. This review will discuss apoptosis in the context of normal aging of T cells, cardiac myocytes, skeletal muscle, and brain cortex. Particular attention is paid to the role of the mitochondria, because they have been implicated as a major control center regulating apoptosis. Mitochondrial oxidative stress and a decline in mitochondrial energy production in vitro often leads to activation of apoptotic pathways, but whether this occurs in vivo is unclear.

Aging↗
PubMed2001

Apoptosis and exercise.

This brief review will discuss an exciting new area in exercise science, namely the role of apoptosis or programmed cell death in exercise. Apoptotic cell death differs morphologically and biochemically from necrotic cell death, although both appear to occur after exercise. Accelerated apoptosis has been documented to occur in a variety of disease states, such as AIDS and Alzheimer's disease, as well as in the aging heart. In striking contrast, failure to activate this genetically regulated cell death may result in cancer and certain viral infections. We will discuss factors that may activate apoptosis during and after exercise and the importance of cell turnover after exercise. We will also discuss differences in apoptosis between lymphocyte and skeletal muscle cells. We speculate that exercise-induced apoptosis is a normal regulatory process that serves to remove certain damaged cells without a pronounced inflammatory response, thus ensuring optimal body function.

Apoptosis↗
PubMed2001

A hydroxyl radical-like species oxidizes cynomolgus monkey artery wall proteins in early diabetic vascular disease.

Recent evidence argues strongly that the marked increase in risk for atherosclerotic heart disease seen in diabetics cannot be explained by a generalized increase in oxidative stress. Here, we used streptozotocin to induce hyperglycemia in cynomolgus monkeys for 6 months and tested whether high glucose levels promote localized oxidative damage to artery wall proteins. We focused on three potential agents of oxidative damage: hydroxyl radical, tyrosyl radical, and reactive nitrogen species. To determine which pathways operate in vivo, we quantified four stable end products of these reactants -- ortho-tyrosine, meta-tyrosine, o,o'-dityrosine, and 3-nitrotyrosine -- in aortic proteins. Levels of ortho-tyrosine, meta-tyrosine, and o,o'-dityrosine, but not of 3-nitrotyrosine, were significantly higher in aortic tissue of hyperglycemic animals. Of the oxidative agents we tested, only hydroxyl radical mimicked this pattern of oxidized amino acids. Moreover, tissue levels of ortho-tyrosine and meta-tyrosine correlated strongly with serum levels of glycated hemoglobin, a measure of glycemic control. We conclude that short-term hyperglycemia in primates promotes oxidation of artery wall proteins by a species that resembles hydroxyl radical. Our observations suggest that glycoxidation reactions in the arterial microenvironment contribute to early diabetic vascular disease, raising the possibility that antioxidant therapies might interrupt this process.

Animals↗
PubMed2001

Oxidative stress and antioxidants in exercise.

Increased aerobic metabolism during exercise is a potential source of oxidative stress. In muscle, mitochondria are one important source of reactive intermediates that include superoxide (O2*-), hydrogen peroxide (H2O2), and possibly hydroxyl radical (HO*). The recent discovery that mitochondria may generate nitric oxide (NO*) also has implications for oxidant production and mitochondrial function. In this review, we critically examine the concept that production of reactive intermediates increases during exercise. Because the health benefits of regular exercise are well-documented, we also examine adaptations to exercise that may decrease oxidative stress. These include increased antioxidant defenses, reduced basal production of oxidants, and reduction of radical leak during oxidative phosphorylation.

Adaptation, Physiological↗
PubMed2000

Increased oxidative stress in kwashiorkor.

To test the hypothesis that kwashiorkor is associated with increased oxidative stress, urinary concentrations of 2 oxidized amino acids, o,o '-dityrosine and ortho -tyrosine, were measured by gas chromatography-mass spectrometry. Children with kwashiorkor, with or without infection, had a 3- to 7-fold increase in urinary o,o '-dityrosine and a 1.5- to 2-fold increase in ortho -tyrosine when compared with well-nourished children. This observation raises the possibility that oxidative damage to proteins and other biologic targets plays a role in the clinical manifestations of kwashiorkor.

Child, Preschool↗
PubMed1999

Long-term ascorbic acid administration reverses endothelial vasomotor dysfunction in patients with coronary artery disease.

BACKGROUND: Loss of endothelium-derived nitric oxide (EDNO) contributes to the clinical expression of coronary artery disease (CAD). Increased oxidative stress has been linked to impaired endothelial vasomotor function in atherosclerosis, and recent studies demonstrated that short-term ascorbic acid treatment improves endothelial function. METHODS AND RESULTS: In a randomized, double-blind, placebo-controlled study, we examined the effects of single-dose (2 g PO) and long-term (500 mg/d) ascorbic acid treatment on EDNO-dependent flow-mediated dilation of the brachial artery in patients with angiographically established CAD. Flow-mediated dilation was examined by high-resolution vascular ultrasound at baseline, 2 hours after the single dose, and 30 days after long-term treatment in 46 patients with CAD. Flow-mediated dilation improved from 6.6+/-3.5% to 10.1+/-5.2% after single-dose treatment, and the effect was sustained after long-term treatment (9. 0+/-3.7%), whereas flow-mediated dilation was 8.6+/-4.7% at baseline and remained unchanged after single-dose (7.8+/-4.4%) and long-term (7.9+/-4.5%) treatment with placebo (P=0.005 by repeated-measures ANOVA). Plasma ascorbic acid concentrations increased from 41.4+/-12. 9 to 115.9+/-34.2 micromol/L after single-dose treatment and to 95. 0+/-36.1 micromol/L after long-term treatment (P<0.001). CONCLUSIONS: In patients with CAD, long-term ascorbic acid treatment has a sustained beneficial effect on EDNO action. Because endothelial dysfunction may contribute to the pathogenesis of cardiovascular events, this study indicates that ascorbic acid treatment may benefit patients with CAD.

Adult↗
PubMed1999

Hydroxyl radical generation during exercise increases mitochondrial protein oxidation and levels of urinary dityrosine.

Isolated mitochondria are well-established sources of oxidants in vitro. There is little direct evidence that mitochondria promote oxidative stress in vivo, however. Model system studies demonstrate that ortho-tyrosine, meta-tyrosine, and o,o'-dityrosine increase in proteins oxidized by hydroxyl radical. To determine whether mitochondria generate oxidants in vivo, we used isotope dilution gas chromatography mass spectrometry to quantify levels of these markers in the heart muscle of control and exercised rats. Exercise led to a 50% increase in ortho-tyrosine, metatyrosine, and o,o'-dityrosine in the mitochondrial proteins but not cytosolic proteins of heart muscle. This increase was transient, and levels returned to normal when exercised animals were allowed to rest. There also was a transient increase in the level of o,o'-dityrosine in the urine of exercised rats. This relationship between mitochondrial and urine levels of o,o'-dityrosine suggests that urine assays of this oxidized amino acid may serve as noninvasive measures of oxidative stress. These observations also provide direct evidence that heart muscle mitochondria produce an intermediate resembling the hydroxyl radical that promotes protein oxidation in vivo.

Animals↗
PubMed1999

Exercise training-induced alterations in skeletal muscle antioxidant capacity: a brief review.

Cellular oxidants include a variety of reactive oxygen, nitrogen, and chlorinating species. It is well established that the increase in metabolic rate in skeletal muscle during contractile activity results in an increased production of oxidants. Failure to remove these oxidants during exercise can result in significant oxidative damage of cellular biomolecules. Fortunately, regular endurance exercise results in adaptations in the skeletal muscle antioxidant capacity, which protects myocytes against the deleterious effects of oxidants and prevents extensive cellular damage. This review discusses the effects of chronic exercise on the up-regulation of both antioxidant enzymes and the glutathione antioxidant defense system. Primary antioxidant enzymes superoxide dismutase, glutathione peroxidase, and catalase will be discussed as well as glutathione, which is an important nonenzymatic antioxidant. Growing evidence indicates that exercise training results in an elevation in the activities of both superoxide dismutase and glutathione peroxidase along with increased cellular concentrations of glutathione in skeletal muscles. It seems plausible that increased cellular concentrations of these antioxidants will reduce the risk of cellular injury, improve performance, and delay muscle fatigue.

Antioxidants↗
PubMed1999

Oxidized amino acids in the urine of aging rats: potential markers for assessing oxidative stress in vivo.

Oxidative damage of proteins has been implicated in disease and aging. In vitro studies demonstrate that two unnatural amino acids, o,o'-dityrosine and o-tyrosine, are stable markers of protein oxidation. We have investigated the possibility that assaying these compounds in urine could provide a noninvasive way to determine levels of protein oxidation in vivo. Isotope dilution gas chromatography-mass spectrometry was used to quantify levels of o,o'-dityrosine and o-tyrosine in skeletal muscle and urine of aging rats subjected to two interventions: 1) dietary antioxidant supplementation and 2) exercise training. In both sedentary rats and exercise-trained rats, antioxidant therapy reduced levels of protein-bound o,o'-dityrosine in skeletal muscle. In contrast, antioxidant therapy or exercise training minimally affected o-tyrosine levels in this tissue. Levels of the oxidized amino acids in urine samples mirrored those of skeletal muscle proteins. Quantification of the levels of oxidized amino acids in urine may thus serve as a noninvasive measure of oxidative stress in vivo because they change in parallel with levels of protein-bound oxidized amino acids in skeletal muscle.

Adaptation, Physiological↗