Effect of Lipid Restriction on Mitochondrial Free Radical Production and Oxidative DNA Damage

Abstract

Many studies have shown that caloric restriction (40%) decreases mitochondrial reactive oxygen species (ROS) generation in rodents. Moreover, we have recently found that 7 weeks of 40% protein restriction without strong caloric restriction also decreases ROS production in rat liver. This is interesting since it has been reported that protein restriction can also extend longevity in rodents. In the present study we have investigated the possible role of dietary lipids in the effects of caloric restriction on mitochondrial oxidative stress. Using semipurified diets, the ingestion of lipids in male Wistar rats was decreased by 40% below controls, while the other dietary components were ingested at exactly the same level as in animals fed ad libitum. After 7 weeks of treatment the liver mitochondria of lipid-restricted animals showed significant increases in oxygen consumption with complex I-linked substrates (pyruvate/malate and glutamate/malate). Neither mitochondrial H(2)O(2) production nor oxidative damage to mitochondrial or nuclear DNA was modified in lipid-restricted animals. Oxidative damage to mitochondrial DNA was one order of magnitude higher than that of nuclear DNA in both dietary groups. These results deny a role for lipids and reinforce the possible role of dietary proteins as being responsible for the decrease in mitochondrial ROS production and DNA damage in caloric restriction.

Effect of 8.5% and 25% caloric restriction on mitochondrial free radical production and oxidative stress in rat liver

“…However, the results of the present investigation rule out this possibility since it was found that 8.5% CR does not modify mitochondrial ROS generation. Thus, the present results, together with the previous ones concerning 40% CR (Gredilla et al 2001;Gredilla and Barja 2005), 40% protein restriction (Sanz et al 2004), 40% carbohydrate restriction (Sanz et al 2006a), and 40% lipid restriction (Sanz et al 2006b) demonstrate that the lower dietary intake of the proteins themselves is responsible for the decrease in mitochondrial ROS generation and oxidative damage to mtDNA that is observed during 40% CR.…”

“…*(P < 0.05), **(P < 0.01), ***(P < 0.001) Biogerontology (2007) 8: 555-566 561 On the other hand, the lack of effect of 8.5% CR is important concerning the final identification of the dietary factor responsible for the well know decrease in mitochondrial ROS production in 40% CR. In previous studies we have found that both 40% CR (Gredilla et al 2001) and 40% protein restriction (Sanz et al 2004) decrease mitochondrial ROS production at complex I and oxidative damage to mtDNA in rat liver, whereas neither carbohydrate (Sanz et al 2006a) nor lipid restriction (Sanz et al 2006b) brought about these changes. This strongly suggested that restriction of the proteins themselves was responsible for this CR effect.…”

“…Thus, before ruling out a causal role for the calories, it is necessary to check whether 8.5% CR affects or not mitochondrial ROS production and oxidative stress. Analogously, the decreased carbohydrate intake during the carbohydrate restriction experiment (Sanz et al 2006a) unavoidably led to 25% CR, and in the case of lipid restriction (Sanz et al 2006b) the degree of CR was only 7%. Since only the carbohydrate restriction experiment lead to substantially different and much higher restriction of calories, 25% CR was also selected as the second level of calorie restriction in the present investigation.…”

“…Looking for the dietary factor responsible for the decreases in mitochondrial ROS production and oxidative stress, we have separately studied the effects of 40% protein restriction (Sanz et al 2004), 40% carbohydrate restriction (Sanz et al 2006a) and 40% lipid restriction (Sanz et al 2006b), without changing the amounts of the rest of dietary components, in male Wistar rats. The outcome of these studies was that neither 40% carbohydrate nor 40% lipid restriction modified mitochondrial ROS generation and oxidative stress, whereas 40% protein restriction did decrease those parameters in a very similar way to that observed in 40% CR, and the decrease in ROS generation during protein restriction specifically occurred, like in CR, at complex I.…”

Pharmacological Approaches to Improve Ageing

“…Particularly, protein restriction, PR, where a percentage of calories derived from protein is replaced by fat or carbohydrate, has been investigated in rodents and decreases in mitochondrial reactive oxygen species production and DNA and protein oxidative modifications have been reported , which could explain the increase in lifespan previously reported for PR (Leto et al, 1976). Similar effects were obtained with reduction of the amino acid methionine , but they could not be replicated by restricting lipid intake alone (Sanz et al, 2006a) or carbohydrate intake alone (Sanz et al, 2006b). IF, a regimen of either alternate day fasting or fasting for a day after 2 days of feeding, both increases lifespan and delays or prevents some age-related diseases (reviewed in Mattson & Wan, 2005).…”