Cysteine dietary supplementation reverses the decrease in mitochondrial ROS production at complex I induced by methionine restriction.

It has been described that dietary cysteine reverses many of the beneficial changes induced by methionine restriction in aging rodents. In this investigation male Wistar rats were subjected to diets low in methionine, supplemented with cysteine, or simultaneously low in methionine and supplemented with cysteine. The results obtained in liver showed that cysteine supplementation reverses the decrease in mitochondrial ROS generation induced by methionine restriction at complex I. Methionine restriction also decreased various markers of oxidative and non-oxidative stress on mitochondrial proteins which were not reversed by cysteine. Instead, cysteine supplementation also lowered protein damage in association with decreases in mTOR activation. The results of the present study add the decrease in mitochondrial ROS production to the various beneficial changes induced by methionine restriction that are reversed by cysteine dietary supplementation.

Protein modification by advanced Maillard adducts can be modulated by dietary polyunsaturated fatty acids.

Advanced Maillard adducts, such as N epsilon-(carboxymethyl)lysine and N epsilon-(carboxyethyl)lysine, can be formed efficiently in vitro from both peroxidation of polyunsaturated fatty acids and glycolysis intermediates. In an attempt to differentiate the in vivo influence of the two pathways in these modifications, Wistar rats were chronically fed with specially designed diets rich in saturated or unsaturated fats. The degree of fatty acid unsaturation of all analysed organs (liver, kidney, brain) was altered by these dietary stresses. Protein glycoxidative and lipoxidative modifications were measured by GC/MS. In accordance with fatty acid profiles, concentrations of N epsilon-(malondialdehyde)lysine in these tissues were significantly increased in animals fed the unsaturated fat diet. In contrast, N epsilon-(carboxymethyl)lysine and N epsilon-(carboxyethyl)lysine concentrations were strongly dependent on the tissue analysed; although the unsaturated fat diet increased their levels significantly in brain, levels were unchanged in kidney and decreased in liver. These later results could be interpreted on the basis that polyunsaturated fatty acids decrease the expression of several glycolytic enzymes in liver. Globally, these data suggest that tissue-specific metabolic characteristics play a key role in the degree of cellular protein modification by Maillard reactions, e.g. by modulation of the concentration of glycolysis intermediates or via specific defensive systems in these organs.

Correlation of fatty acid unsaturation of the major liver mitochondrial phospholipid classes in mammals to their maximum life span potential.

Free radical damage is considered a determinant factor in the rate of aging. Unsaturated fatty acids are the tissue macromolecules that are most sensitive to oxidative damage. Therefore, the presence of low proportions of fatty acid unsaturation is expected in the tissues of long-lived animals. Accordingly, the fatty acid compositions of the major liver mitochondrial phospholipid classes from eight mammals, ranging in maximum life span potential (MLSP) from 3.5 to 46 yr, show that the total number of double bonds is inversely correlated with MLSP in both phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn) (r = 0.757, P < 0.03, and r = 0.862, P < 0.006, respectively), but not in cardiolipin (P = 0.323). This is due not to a low content of unsaturated fatty acids in long-lived animals, but mainly to a redistribution between kinds of fatty acids on PtdCho and PtdEtn, shifting from arachidonic (r = 0.911, P < 0.002, and r = 0.681, P = 0.05, respectively), docosahexaenoic (r = 0.931 and r = 0.965, P < 0.0001, respectively) and palmitic (r = 0.944 and r = 0.974, P < 0.0001, respectively) acids to linoleic acid (r = 0.942, P < 0.0001, for PtdCho; and r = 0.957, P < 0.0001, for PtdEtn). For cardiolipin, only arachidonic acid showed a significantly inverse correlation with MLSP (r = 0.904, P < 0.002). This pattern strongly suggests the presence of a species-specific desaturation pathway and deacylation-reacylation cycle in determining the mitochondrial membrane composition, maintaining a low degree of fatty acid unsaturation in long-lived animals.

Effect of dietary vitamin E levels on fatty acid profiles and nonenzymatic lipid peroxidation in the guinea pig liver.

Guinea pigs were fed for five weeks with three diets containing different levels of vitamin E: LOW (but nondeficient, 15 mg of vitamin E/kg diet), MEDIUM (150 mg/kg diet), and HIGH (1,500 mg/kg diet). Dietary vitamin E supplementation did not change oxidative stress indicators in the hydrophilic compartment but increased liver alpha-tocopherol in a dose-dependent way and strongly decreased sensitivity to nonenzymatic in vitro liver lipid peroxidation. This last effect was already observed in group MEDIUM, and no further decrease in in vitro lipid peroxidation occurred from group MEDIUM to group HIGH. The protective effect of vitamin E against in vitro lipid peroxidation was observed even though an optimum dietary concentration of vitamin C for this animal model was present in the three different vitamin E diets. Both HIGH and LOW vitamin E decreased percentage fatty acid unsaturation in all phospholipid fractions from membrane origin in relation to group MEDIUM. The results, together with previous information, show that both vitamin E and vitamin C at intermediate concentrations are needed for optimal protection against lipid peroxidation and loss of fatty acid unsaturation even in normal nonstressful conditions. These protective concentrations are higher than those needed to avoid deficiency syndromes.

Dietary vitamin C decreases endogenous protein oxidative damage, malondialdehyde, and lipid peroxidation and maintains fatty acid unsaturation in the guinea pig liver.

Guinea pigs were fed during 5 weeks with three different levels of vitamin C in the diet: 33 (marginal deficiency), 660, or 13,200 mg of vitamin C per kg of diet. The group fed 660 mg of vitamin C/kg of diet showed strongly reduced levels of protein carbonyls (46% decrease), malondialdehyde (HPLC; 72% decrease), and in vitro production of TBARS (both stimulated with ascorbate-Fe2+ and with NADPH-ADP-Fe2+; 68% and 71% decrease), increased glutathione reductase activity, and increased vitamin C content (48 times higher) in the liver in relation to the group fed 33 mg/kg. The treatment with 660 mg of vitamin C/kg did not decrease any of the antioxidant defenses studied: superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, GSH, vitamin E, or uric acid. Further supplementation with 13,200 mg vitamin C/kg also reduced protein and lipid peroxidation, but decreased hepatic glutathione reductase and uric acid and resulted in a lower body weight of the animals. Both low (33 mg/kg) and very high (13,200 mg/kg) levels of vitamin C decreased body weight, glutathione reductase, and unsaturation of fatty acids in membrane lipids. The results show that a diet supplying an amount of vitamin C 40 times higher than the minimum daily requirement to avoid scurvy increases the global antioxidant capacity and is of protective value against endogenous lipid and protein oxidation in the liver under normal nonstressful conditions.