Docosahexaenoic acid supplementation-increased oxidative damage in bone marrow DNA in aged rats and its relation to antioxidant vitamins

Molecular Interactions between Dietary Lipids and Bone Tissue during Aging

Age-related bone disorders such as osteoporosis or osteoarthritis are a major public health problem due to the functional disability for millions of people worldwide. Furthermore, fractures are associated with a higher degree of morbidity and mortality in the long term, which generates greater financial and health costs. As the world population becomes older, the incidence of this type of disease increases and this effect seems notably greater in those countries that present a more westernized lifestyle. Thus, increased efforts are directed toward reducing risks that need to focus not only on the prevention of bone diseases, but also on the treatment of persons already afflicted. Evidence is accumulating that dietary lipids play an important role in bone health which results relevant to develop effective interventions for prevent bone diseases or alterations, especially in the elderly segment of the population. This review focuses on evidence about the effects of dietary lipids on bone health and describes possible mechanisms to explain how lipids act on bone metabolism during aging. Little work, however, has been accomplished in humans, so this is a challenge for future research.

Nucleotide excision repair deficiency increases levels of acrolein-derived cyclic DNA adduct and sensitizes cells to apoptosis induced by docosahexaenoic acid and acrolein

The acrolein derived cyclic 1,N(2)-propanodeoxyguanosine adduct (Acr-dG), formed primarily from ω-3 polyunsaturated fatty acids such as docosahexaenoic acid (DHA) under oxidative conditions, while proven to be mutagenic, is potentially involved in DHA-induced apoptosis. The latter may contribute to the chemopreventive effects of DHA. Previous studies have shown that the levels of Acr-dG are correlated with apoptosis induction in HT29 cells treated with DHA. Because Acr-dG is shown to be repaired by the nucleotide excision repair (NER) pathway, to further investigate the role of Acr-dG in apoptosis, in this study, NER-deficient XPA and its isogenic NER-proficient XAN1 cells were treated with DHA. The Acr-dG levels and apoptosis were sharply increased in XPA cells, but not in XAN1 cells when treated with 125μM of DHA. Because DHA can induce formation of various DNA damage, to specifically investigate the role of Acr-dG in apoptosis induction, we treated XPA knockdown HCT116+ch3 cells with acrolein. The levels of both Acr-dG and apoptosis induction increased significantly in the XPA knockdown cells. These results clearly demonstrate that NER deficiency induces higher levels of Acr-dG in cells treated with DHA or acrolein and sensitizes cells to undergo apoptosis in a correlative manner. Collectively, these results support that Acr-dG, a ubiquitously formed mutagenic oxidative DNA adduct, plays a role in DHA-induced apoptosis and suggest that it could serve as a biomarker for the cancer preventive effects of DHA.

From alga to omega; have we reached peak (fish) oil?

SummaryWhile the Inuit diet was highly cardio-protective and consuming oily fish within a Western diet is to a lesser degree, the case for purified fish oil supplements is less convincing. Purification of fish oil removes lipophilic polyphenols which likely contribute to the health benefits of oily fish; leaving the ω3 highly unsaturated fatty acids exposed and prone to conferring oxidative and inflammatory stress. The authors believe that due to such issues as dietary shift, it may now be inadvisable to prescribe or sell purified ω3 highly unsaturated fatty acids supplements, unless the appropriate co-factors are included.

PUFAs in serum cholesterol ester and oxidative DNA damage in Japanese men and women

BACKGROUND

PUFAs are susceptible to lipid peroxidation and play a role in inflammation, both of which can induce oxidative stress. However, the relation of PUFA to oxidative DNA damage in humans is elusive.

OBJECTIVE

We examined the association between concentrations of circulatory PUFAs and urinary 8-oxo-7,8-dihydroguanine (8-oxoGua) in Japanese men and women.

DESIGN

The subjects were 495 participants (290 men and 205 women) in a cross-sectional study in 2 municipal offices in Japan. Serum cholesterol ester (CE) and phospholipid fatty acid composition were measured by gas-liquid chromatography. Urinary 8-oxoGua concentrations were measured by HPLC, and 8-oxoGua values for each tertile of PUFA after adjustment for covariates were calculated by multiple regression.

RESULTS

Urinary 8-oxoGua concentrations increased with increasing concentrations of n-3 (omega-3) PUFAs, EPA, and DHA in serum CE (P-trend = 0.001, 0.01, and 0.009, respectively), whereas they decreased with increasing concentrations of n-6 PUFAs and linoleic acid (P-trend = 0.02 and 0.051, respectively).

CONCLUSION

Oxidative DNA damage may be greater with higher concentrations of long-chain n-3 PUFAs but lower with higher concentrations of n-6 (omega-6) PUFAs.

Plasma phosphatidylcholine concentrations of polyunsaturated fatty acids are differentially associated with hip bone mineral density and hip fracture in older adults: the Framingham Osteoporosis Study

Polyunsaturated fatty acids (PUFAs) may influence bone health. The objective of this work was to examine associations between plasma phosphatidylcholine (PC) PUFA concentrations and hip measures: (1) femoral neck bone mineral density (FN-BMD) (n = 765); (2) 4-year change in FN-BMD (n = 556); and (3) hip fracture risk (n = 765) over 17-year follow-up among older adults in the Framingham Osteoporosis Study. BMD measures were regressed on quintile of plasma PC PUFAs (docosahexaenoic acid [DHA], linoleic acid [LA], and arachidonic acid [AA]), adjusted for covariates. Hazard ratios (HR) and 95% confidence interval (CI) for hip fracture were estimated by quintile of plasma PC PUFAs, adjusted for covariates. Higher concentrations of PC DHA were associated with loss of FN-BMD over 4 years in women (p-trend = 0.04), but was protective in men in the uppermost quintile compared to men grouped in the lower four quintiles, in post hoc analysis (p = 0.01). PC LA concentrations were inversely associated with baseline FN-BMD in women (p-trend = 0.02), and increased hip fracture risk in women and men (p-trend = 0.05), but body mass index (BMI) adjustment attenuated these associations (p-trend = 0.12 and p-trend = 0.14, respectively). A trend toward a protective association was observed between PC AA and baseline FN-BMD in men (p-trend = 0.06). Women and men with the highest PC AA concentrations had 51% lower hip fracture risk than those with the lowest (HR = 0.49, 95% CI = 0.24-1.00). Opposing effects of PC DHA on FN-BMD loss observed in women and men need further clarification. Bone loss associated with PC LA may be confounded by BMI. High PC AA concentrations may be associated with reduced hip fracture risk.

EPA but not DHA appears to be responsible for the efficacy of omega-3 long chain polyunsaturated fatty acid supplementation in depression: evidence from a meta-analysis of randomized controlled trials

BACKGROUND

Epidemiologic and case-control data suggest that increased dietary intake of omega-3 long-chain polyunsaturated fatty acids (omega3 LC-PUFAs) may be of benefit in depression. However, the results of randomized controlled trials are mixed and controversy exists as to whether either eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) or both are responsible for the reported benefits.

OBJECTIVE

The aim of the current study was to provide an updated meta-analysis of all double-blind, placebo-controlled, randomized controlled trials examining the effect of omega3 LC-PUFA supplementation in which depressive symptoms were a reported outcome. The study also aimed to specifically test the differential effectiveness of EPA versus DHA through meta-regression and subgroup analyses.

DESIGN

Studies were selected using the PubMed database on the basis of the following criteria: (1) randomized design; (2) placebo controlled; (3) use of an omega3 LC-PUFA preparation containing DHA, EPA, or both where the relative amounts of each fatty acid could be quantified; and (4) reporting sufficient statistics on scores of a recognizable measure of depressive symptoms.

RESULTS

Two hundred forty-one studies were identified, of which 28 met the above inclusion criteria and were therefore included in the subsequent meta-analysis. Using a random effects model, overall standardized mean depression scores were reduced in response to omega3 LC-PUFA supplementation as compared with placebo (standardized mean difference = -0.291, 95% CI = -0.463 to -0.120, z = -3.327, p = 0.001). However, significant heterogeneity and evidence of publication bias were present. Meta-regression studies showed a significant effect of higher levels of baseline depression and lower supplement DHAEPA ratio on therapeutic efficacy. Subgroup analyses showed significant effects for: (1) diagnostic category (bipolar disorder and major depression showing significant improvement with omega3 LC-PUFA supplementation versus mild-to-moderate depression, chronic fatigue and non-clinical populations not showing significant improvement); (2) therapeutic as opposed to preventive intervention; (3) adjunctive treatment as opposed to monotherapy; and (4) supplement type. Symptoms of depression were not significantly reduced in 3 studies using pure DHA (standardized mean difference 0.001, 95% CI -0.330 to 0.332, z = 0.004, p = 0.997) or in 4 studies using supplements containing greater than 50% DHA (standardized mean difference = 0.141, 95% CI = -0.195 to 0.477, z = 0.821, p = 0.417). In contrast, symptoms of depression were significantly reduced in 13 studies using supplements containing greater than 50% EPA (standardized mean difference = -0.446, 95% CI = -0.753 to -0.138, z = -2.843, p = 0.005) and in 8 studies using pure ethyl-EPA (standardized mean difference = -0.396, 95% CI = -0.650 to -0.141, z = -3.051, p = 0.002). However, further meta-regression studies showed significant inverse associations between efficacy and study methodological quality, study sample size, and duration, thus limiting the confidence of these findings.

CONCLUSIONS

The current meta-analysis provides evidence that EPA may be more efficacious than DHA in treating depression. However, owing to the identified limitations of the included studies, larger, well-designed, randomized controlled trials of sufficient duration are needed to confirm these findings.

Oxidative stress and DNA damage in older adults that do exercises regularly

OBJECTIVES

Free radicals may damage lipids, proteins and DNA, which may lead to critical diseases in the aging. This work evaluated levels of malondialdehyde (MDA), glutathione peroxidase (GPx) and DNA damage by comet assay (SCGE) in older adults that do exercises regularly.

DESIGN AND METHODS

110 females, aged 66.3+/-8 years were divided into sedentary (n=54), walking (n=36) and muscle building (n=20) groups. Levels of MDA, GPx and SCGE were measured in venous blood before and after exercise.

RESULTS

MDA levels were higher (P<0.005) and GPx levels were lower (P<0.005) in active groups than in sedentary group. SCGE index after physical activity was greater than at baseline (muscle building: P=0.004; walking: P=0.002).

CONCLUSIONS

Exercise reduces the diseases risk, but may promote the production of free radicals. It remains unclear whether cell adaptations responsible for health benefits are associated with such events. However we may suggest the existence of a different biochemical pattern for older adults that do exercise regularly.

Formation of Nepsilon-(succinyl)lysine in vivo: a novel marker for docosahexaenoic acid-derived protein modification

Free radical-catalyzed peroxidation of docosahexaenoic acid (DHA, C22:6/omega-3) generates various lipid peroxidation products that covalently modify biomolecules such as proteins. Under a free radical-generating system, DHA significantly modified lysine residues in bovine serum albumin. Upon incubation of oxidized DHA with an amino-compound pyridoxamine or a lysine-containing peptide, N-propanoyl and N-succinyl adducts were determined to be the major modification products. The hydroperoxide levels in the oxidized DHA closely reflected the formation of the N(epsilon)-(succinyl)lysine (SUL) upon reaction with the peptide, indicating that the hydroperoxides of DHA represent a potential pathway for the formation of SUL. To detect the DHA-derived protein modification in vivo, we developed a monoclonal antibody (mAb2B12) specific to SUL and found that the antibody specifically reacts with the SUL moiety. The formation of SUL was then immunochemically demonstrated in the liver of mice fed with DHA followed by intraperitoneal injection of carbon tetrachloride (CCl(4)), a hepatic lipid peroxidation model. Immunoreactive materials with mAb2B12 were observed in the DHA + CCl(4) group, but were not significant in the control, DHA-alone, and CCl(4)-alone groups. These data suggest that the formation of DHA-derived adducts such as SUL may be implicated in the oxidative damage observed in DHA-enriched tissues.

Lipid Peroxidation and the Thiobarbituric Acid Assay: Standardization of the Assay When Using Saturated and Unsaturated Fatty Acids

Saturated fatty acids are less vulnerable to lipid peroxidation than their unsaturated counterparts. In this investigation, individual fatty acids of the C(16), C(18) and (20) families were subjected to the thiobarbituric (TBA) assay. These fatty acids were chosen based on their degree of saturation and configuration of double bonds. Interestingly, an assay threshold was reached where increasing the fatty acid concentration resulted in no additional decrease in the TBARS concentrations. Therefore, the linear range of TBARS inhibition was determined for fatty acids in the C(16) and C(20) families. The rate of TBARS inhibition was greater for the saturated than for unsaturated fatty acids, as measured from the slope of the linear range. These findings demonstrate the need to standardize the TBARS assay using multiple fatty acid concentrations when using this assay for measuring in vitro lipid peroxidation.

Modification of the longevity-related degree of fatty acid unsaturation modulates oxidative damage to proteins and mitochondrial DNA in liver and brain

Previous studies have shown that tissue fatty acid unsaturation correlates inversely with maximum longevity. However, it is unclear if this is related to the effects of fatty acid unsaturation only on lipids, or also on proteins and DNA, specially on mitochondrial DNA (mtDNA) oxidative damage. In this investigation the degree of fatty acid unsaturation of liver and brain was successfully manipulated in Wistar rats by chronic feeding with specially designed semipurified diets rich in saturated or unsaturated fats. The brain, an organ of special relevance for aging, was most profoundly affected by the increase in fatty acid unsaturation, and showed significant increases in malondialdehyde (MDA)-lysine, aminoadipic semialdehyde (a protein carbonyl), N(epsilon)-(carboxymethyl)lysine, and N(epsilon)-(carboxyethyl)lysine in proteins, as well as in 8-oxo,7,8-dihydro-2'-deoxyguanosine (8-oxodG) in mtDNA without changes in nuclear DNA (nDNA). In the liver 8-oxodG was also increased in mtDNA and not in nDNA. These DNA results are consistent with the presence of a high density of mitochondrial inner membranes (rich in lipids and in reactive oxygen species generation capacity) near mtDNA but not near nDNA. Among the protein markers analyzed, MDA-lysine was most consistent and responsive to fatty acid unsaturation, since it increased in both organs and showed the highest increase. These results, together with previous data from our laboratories, show that increasing the degree of fatty unsaturation of postmitotic tissues in vivo can raise not only lipid but also protein and mtDNA oxidative damage. This is mechanistically relevant in relation to the constitutively low tissue fatty acid unsaturation of long-lived animals.

Protective effect of supplementation of fish oil with high n-3 polyunsaturated fatty acids against oxidative stress-induced DNA damage of rat liver in vivo

The present study was undertaken to know the effect of supplementation of fish oil with high n-3 polyunsaturated fatty acids (PUFA) on oxidative stress-induced DNA damage of rat liver in vivo. Male Wistar rats were fed a diet containing fish oil or safflower oil with high n-6 PUFA at 50 g/kg of diet and an equal amount of vitamin E at 59 mg/kg of diet for 6 weeks. Livers of rats fed fish oil were rich in n-3 PUFA, whereas those of rats fed safflower oil were rich in n-6 PUFA. Ferric nitrilotriacetate was intraperitoneally injected to induce oxidative stress. The degree of lipid peroxidation of the liver was assessed by the levels of phospholipid hydroperoxides and thiobarbituric acid-reactive substances (TBARS), and the degree of oxidative DNA damage was assessed by comet type characterization in alkaline single-cell gel electrophoresis and 8-hydroxy-2'-deoxyguanosine levels. The levels of TBARS of the livers of the fish oil diet group increased to a greater extent than those of the safflower oil diet group, whereas the levels of the hydroperoxides of the livers of both diet groups increased to a similar extent. The vitamin E level of livers of the fish oil diet group was remarkably decreased. The degree of DNA damage of both diet groups was increased, but the increased level of the fish oil diet group was remarkably lower than that of the safflower oil diet group. The above results indicate that fish oil supplementation does not enhance but appears to protect against oxidative stress-induced DNA damage and suggest that lipid peroxidation does not enhance but lowers the DNA damage.

Suppression of free radical-induced DNA strand breaks by linoleic acid and low density lipoprotein in vitro

The results of the present study have shown that unoxidized linoleic acid (LA) and low density lipoprotein (LDL) suppressed free radical-induced supercoiled plasmid DNA strand breaks. Unoxidized LA suppressed DNA strand breaks induced by free radicals generated from hydrogen peroxide/Fe(II) ion, 2'-azobis(2-amidinopropane)hydrochloride (AAPH), and 4-(hydroxymethyl)benzene diazonium salt. Thiobarbituric acid reactive substances (TBARS) of LA were increased on treatment with the radical generators. The intensities of the electron spin resonance (ESR) signals of the spin adducts of the radicals were reduced by unoxidized LA. Although LA hydroperoxide caused DNA strand breaks as has already been shown, its strand breaking activity was observed only at the higher concentrations. Unoxidized LDL inhibited ascorbic acid/Cu(II) ion-, ascorbic acid/Fe(II) ion-, peroxynitrite- and AAPH-induced DNA strand breaks. The TBARS of LDL were increased by treatment with the agents. LDL oxidized with Cu(II) ion did not cause DNA strand breaks. The results indicate that the potency of the free radicals to cause DNA strand breaks was attenuated by the fatty acid and the lipoprotein through lipid peroxidation.

Dietary CLA and DHA modify skin properties in mice

This study investigated the influence of PUFA on the properties of mouse skin. Mice (3 wk old) were given free access to oils high in linoleic acid, CLA, or DHA for 4 wk. At the end of the experiment, their skins were compared by both biochemical and histological methods. No significant differences in lipid and collagen contents were detected among treatments, although the FA composition in the skin was altered depending upon the FA composition of the supplemented oils. Electron microscopy revealed that the subcutaneous tissue layers in the CLA and DHA groups were significantly thinner than that in the high linoleic acid group, whereas no differences in the thickness of dermis layers were observed among the three groups. These results suggest that skin properties in mice are readily modified by dietary FA sources within 4 wk of dietary oil supplementation.

Effects of dietary fats on bone health in advanced age

Evidence is accumulating that dietary lipids play an important role in bone health. Most of the data supporting the effects of lipids on bones have been collected in young adult and/or developing animals. Based upon this work, mechanisms have been proposed to explain how lipids act to enhance or inhibit bone resorption and deposition. Little work, however, has been done in older models. Since osteoporosis primarily afflicts the elderly, such work is needed in order to determine if mechanisms relevant to the young differ in advanced age, and to develop effective interventions for this especially vulnerable segment of the population. This article reviews evidence that dietary lipids are important to bone health in older individuals, and describes possible mechanisms that may be of particular relevance to the elderly. Specifically, studies supporting the influence of dietary lipids on calcium excretion, growth hormone secretion, fatty acid metabolism, and osteoblast formation are reviewed.

Blood 8-hydroxy-2'-deoxyguanosine is associated with erythropoietin resistance in haemodialysis patients

BACKGROUND

8-Hydroxy-2'-deoxyguanosine (8-OHdG), a product of oxidized DNA, is increased in haemodialysis (HD) patients, but the clinical relevance of enhanced 8-OHdG production in these patients remains unknown.

METHODS

We cross-sectionally measured serum 8-OHdG in 73 patients on maintenance HD (age 68+/-2 years, time on HD 85+/-11 months, male/female=42/31), and examined the relationship between blood 8-OHdG and the severity of renal anaemia and the weekly dosage of recombinant human erythropoietin (rHuEPO).

RESULTS

There was a significant increase in serum 8-OHdG in HD patients compared with normal subjects. Serum 8-OHdG was positively correlated with the patients' age (r=0.231, P<0.05) but not with the duration of HD. Serum 8-OHdG was significantly higher in diabetic subjects than in non-diabetic subjects (P<0.05). Serum 8-OHdG had a significant inverse correlation with haemoglobin (Hb) (r=-0.526, P<0.01) but a positive correlation with the rHuEPO dose (r=0.443, P<0.01) and the ratio of the weekly rHuEPO dose divided by Hb (r=0.487, P<0.01). Serum 8-OHdG was not correlated with inflammatory and nutritional parameters.

CONCLUSIONS

These findings suggest that the elevation of circulating 8-OHdG may be associated, at least in part, with rHuEPO resistance in HD patients.

Decreased plasma and tissue levels of vitamin C in a rat model of aging: implications for antioxidative defense

Aging is an independent risk factor for the development of cardiovascular and many other diseases. The aging process is known to be associated with increased oxidative stress, possibly related to an age-inherent loss of antioxidant capacity. Vitamin C is a major naturally occurring antioxidant. Thus, we investigated its role in a rat model of aging. Vitamin C in plasma and tissues as well as malondialdehyde in the heart were measured in young (6 months old) and old (27-30 months old) F1 (F344 x BN) healthy male rats fed a normal diet. In old rats, vitamin C plasma levels were found to be decreased (p<0.02) as compared with young animals. Furthermore, there was a tissue-specific distribution: in the heart, liver, kidney, lungs, and skeletal muscle, vitamin C decreased with age (p<0.005 to p<0.05), while no significant differences could be observed in the aortic wall and in the brain. Organs of the digestive tract rather showed an increase of vitamin C levels with age. Oxidative stress, determined representatively in the heart by measuring malondialdehyde tissue levels, exhibited an age-dependent increase (p<0.05). A distinct pattern of specific tissue distribution of vitamin C suggests a differential age-associated regulation. As vitamin C decreased concomitantly to an increase in cardiac lipid peroxidation, its supplementation may be useful to prevent age-related oxidative stress and tissue aging.