Effect of resveratrol and lipoic acid on sirtuin-regulated expression of metabolic genes in bovine liver and muscle slice cultures.

Sirtuins (Sirt) are NAD-dependent deacetylases that are activated by the antioxidants resveratrol (RSV) and lipoic acid (LA). The objective of this study was to determine in bovine liver and muscle slice cultures the effect of RSV and LA treatment on the expresssion of Sirt1, Sirt3, peroxisome proliferator-activated receptor γ coactivator 1α (PPARGC1A), and the forkhead box O transcription factors FoxO1 and FoxO3 as well as other factors involved in glucose and lipid metabolism and related to Sirt activity. Tissue slices from crossbred bulls were treated during 60 min with 40 or 80 µ RSV and 30, 100, 300, or 1,000 µ LA under restricted conditions (Krebs-Ringer buffer without nutrients) and fed conditions (2.5 m propionate in combination with 1 n glucagon) for liver slices or with 0.01 µ epinephrine for muscle slices. Quantitative real-time PCR was used to analyze the expression of the mRNA for the genes studied and western blot analysis for the expression of the protein for Sirt1. Our results show that the expression of the mRNA for Sirt1 was enhanced by RSV in liver under restriction ( ≤ 0.0112) and by LA in muscle, more under restriction ( ≤ 0.0121) than after epinephrine administration ( < 0.0001). Sirt3 is affected in a dose-dependent manner by both compounds in both tissues and under both metabolic conditions ( ≤ 0.0452). The expression of the protein for Sirt1 was increased by LA in both tissues under restricted conditions ( = 0.0026 and = 0.0201, respectively) but in liver also in fed conditions ( = 0.0016). Genes involved in the antioxidant response were upregulated in both tissues. These results indicate that bovine Sirt respond differently to RSV and LA stimulation than monogastric Sirt do and that gluconeogenesis in ruminants is not related to Sirt to the same degree as in monogastric species. However, these results provide information about the possible role of Sirt in ruminant metabolism.

Potential role of sirtuins in livestock production.

Sirtuins are NAD(+)-dependent histone and protein deacetylases, which have been studied during the last decade with a focus on their role in lifespan extension and age-related diseases under normal and calorie-restricted or pathological conditions. However, sirtuins also have the ability to regulate energy homeostasis as they can sense the metabolic state of the cell through the NAD(+)/NADH ratio; hence, changes in the diet can modify the expression of these enzymes. Dietary manipulations are a common practice currently being used in livestock production with favorable results, probably due in part to the enhanced activity of sirtuins. Nevertheless, sirtuin expression in livestock species has not been a research target. For these reasons, the goal of this review is to awaken interest in these enzymes for future detailed characterization in livestock species by presenting a general introduction to what sirtuins are, how they work and what is known about their role in livestock.

Bovine sirtuins: initial characterization and expression of sirtuins 1 and 3 in liver, muscle, and adipose tissue.

Sirtuins, the mammalian homologs of the silent information regulator 2 gene of Saccharomyces cerevisiae, are members of the NAD(+)-dependent family of histone deacetylases. In vertebrates, 7 sirtuins have been described, with different cellular localizations and target proteins. Glucose and lipid metabolism are among the processes regulated by these enzymes. In ruminants, gluconeogenesis is the main biochemical pathway by which glucose is obtained. Because sirtuins in bovines have not been studied, the aim of this work was to obtain sequences coding for the 7 sirtuins and determine the expression patterns of sirtuin1 (Sirt1) and sirtuin3 (Sirt3) in the liver, muscle, and adipose tissue of calves and bulls. Using PCR amplification, we obtained sirtuin gene sequences and reported them to the National Center for Biotechnology Information GenBank. Characteristic sequence motifs corresponding to the sirtuin catalytic core domain were found, including the active and zinc-binding sites. Relative expression patterns of Sirt1 and Sirt3 in liver, muscle, and adipose tissue were quantified by real-time PCR, normalizing to the geometric mean of the housekeeping genes cyclophilin A and ß-actin. Expression of Sirt1 was less in liver and muscle, whereas it was greater in adipose tissue of adult animals, with statistical differences (P=0.0071) only in the latter. In the case of Sirt3, expression was greater in all 3 adult tissues, but statistical differences were found only in liver (P=0.0141) and muscle (P=0.0017). The greatest expression was observed in liver for Sirt1 and in muscle for Sirt3, whereas the least expression was in muscle for Sirt1 and in adipose tissue for Sirt3. In other species, sirtuin expression (both Sirt1 and Sirt3) in liver is reported to be the greatest among these 3 tissues, a pattern different from what we measured. These differences in expression can be associated with metabolic differences between nonruminant and ruminant species. However, further research on the relationship between bovine sirtuins and ruminant metabolism is required for a better understanding of these fields.