No abstract

To gain insight into the antiaging mechanisms of caloric restriction (CR), mitochondria from liver tissue of male Brown Norway rats were used to study the effects of CR and insulin on mitochondrial reactive oxygen species production and bioenergetics. As assessed by hydrogen peroxide measurement, CR resulted in a decrease in the production rate of reactive oxygen species. This decrease was attributed to a decrease in protonmotive force in mitochondria from the CR animals. The decrease in protonmotive force resulted from an increase in proton leak activity and a concomitant decrease in substrate oxidation activity. Each of these effects of CR was reversed by subjecting CR animals to 2 wk of insulin treatment. To achieve continuous and stable insulin delivery, animals were placed under temporary halothane anesthesia and miniosmotic pumps were implanted subcutaneously. To gain further insight into how CR and insulin exerted its effects on mitochondrial bioenergetics, the effects of CR and insulin were quantified using modular metabolic control analysis. This analysis revealed that the effects of CR were transmitted through different reaction branches of the bioenergetic system, and insulin reversed the effects of CR by acting through the same branches. These results provide a plausible mechanism by which mitochondrial reactive oxygen species production is lowered by CR and a complete description of the effects of CR on mitochondrial bioenergetics. They also indicate that these changes may be due to lowered insulin concentrations and altered insulin signaling in the CR animal.

Brain aging frequently underlies cognitive decline and is a major risk factor for neurodegenerative conditions. The exact molecular mechanisms underlying brain aging, however, remain unknown. Whole transcriptome sequencing provides unparalleled depth and sensitivity in gene expression profiling. It also allows non-coding RNA and splice variant detection/comparison across phenotypes. Using RNA-seq to sequence the cerebral cortex transcriptome in 6-, 12- and 28-month-old rats, age-related changes were studied. Protein-coding genes related to MHC II presentation and serotonin biosynthesis were differentially expressed (DE) in aging. Relative to protein-coding genes, more non-coding genes were DE over the three age-groups. RNA-seq quantifies not only levels of whole genes but also of their individual transcripts. Over the three age-groups, 136 transcripts were DE, 37 of which were so-called dark matter transcripts that do not map to known exons. Fourteen of these transcripts were identified as novel putative long non-coding RNAs. Evidence of isoform switching and changes in usage were found. Promoter and coding sequence usage were also altered, hinting of possible changes to mitochondrial transport within neurons. Therefore, in addition to changes in the expression of protein-coding genes, changes in transcript expression, isoform usage, and non-coding RNAs occur with age. This study demonstrates dynamic changes in RNA with age at various genomic levels, which may reflect changes in regulation of transcriptional networks and provides non-coding RNA gene candidates for further studies.Electronic supplementary materialThe online version of this article (doi:10.1007/s11357-012-9410-1) contains supplementary material, which is available to authorized users.

Chronic dietary restriction such that the body weight of CFY Sprague-Dawley female rats was 50% that of animals fed ad libitum resulted in enhanced longevity (LD 50 of 1090 days compared to 704 days). All the experimental females had reached puberty by 227 days and 80% were able to conceive and wean young at 510 days, an age beyond that at which the control rats had ceased to breed (450 days). Some (25%) of the experimental rats were able to breed at over 800 days of age.