SIRT1

The sirtuin family comprises seven NAD+-dependent deacetylases which control the overall health of organisms through the regulation of pleiotropic metabolic pathways. Sirtuins are important modulators of adipose tissue metabolism and their expression is higher in lean than obese subjects. At present, the role of sirtuins in adipose-derived stem cells has not been investigated yet. Therefore, in this study, we evaluated the expression of the complete panel of sirtuins in adipose-derived stem cells isolated from both subcutaneous and visceral fat of non-obese and obese subjects. We aimed at investigating the influence of obesity on sirtuins’ levels, their role in obesity-associated inflammation, and the relationship with the peroxisome proliferator-activated receptor delta, which also plays functions in adipose tissue metabolism. The mRNA levels in the four types of adipose-derived stem cells were evaluated by quantitative polymerase chain reaction, in untreated cells and also after 8 h of hypoxia exposure. Correlations among sirtuins’ expression and clinical and molecular parameters were also analyzed. We found that sirtuin1–6 exhibited significant higher mRNA expression in visceral adipose-derived stem cells compared to subcutaneous adipose-derived stem cells of non-obese subjects. Sirtuin1–6 levels were markedly reduced in visceral adipose-derived stem cells of obese patients. Sirtuins’ expression in visceral adipose-derived stem cells correlated negatively with body mass index and C-reactive protein and positively with peroxisome proliferator-activated receptor delta. Finally, only in the visceral adipose-derived stem cells of obese patients hypoxia-induced mRNA expression of all of the sirtuins. Our results highlight that sirtuins’ levels in adipose-derived stem cells are consistent with protective effects against visceral obesity and inflammation, and suggest a transcriptional mechanism through which acute hypoxia up-regulates sirtuins in the visceral adipose-derived stem cells of obese patients.

Background: Hepatic steatosis is among the most common causes of chronic liver diseases, although established effective treatments are not evident.  Previous studies reported that Kurozu improved hypercholesterolemia and carbohydrate metabolism. However, the effect of Kurozu on the incidence of hepatic steatosis is not clear.
Objective: The effect of Kurozu on the onset of hepatic steatosis by administering a high-fat diet (HFD) for 110 weeks was evaluated in C57BL/6J mice.
Methods: HFD treatment for 110 weeks accelerated the onset of hepatic steatosis more than a standard diet, whereas concentrated Kurozu (CK) supplementation ameliorated the effect of an HFD feeding. The effect of supplementation with resveratrol in an HFD on the onset of hepatic steatosis was also evaluated. To elucidate the mechanism of the effect of Kurozu on the expression of lipid metabolism genes, acute treatment for 10 days with Kurozu was also examined.
Results: Supplementation with resveratrol in HFD-fed mice did not ameliorate hepatic steatosis. Body weights were significantly lower in the CK + HFD and Resveratrol + HFD groups than in the control HFD group in middle age. No significant differences in all-cause mortality were observed following supplementation with CK or resveratrol. CK and resveratrol supplements significantly inhibited decreases in dehydroepiandrosterone sulphate serum levels at postnatal week 120. CK and resveratrol supplements did not affect the survival of mice. The ingestion of Kurozu for 10 days significantly elevated the expression levels of Sirt1, Pgc-1α, Lpin1, and Igfbp1 in the liver.
Conclusion: These results suggest that ingesting CK may delay the onset of hepatic steatosis HFD feeding causes.

Adult neurogenesis plays increasingly recognized roles in brain homeostasis and repair and is profoundly affected by energy balance and nutrients. We found that the expression of Hes-1 (hairy and enhancer of split 1) is modulated in neural stem and
progenitor cells (NSCs) by extracellular glucose through the coordinated action of CREB (cyclic AMP responsive element binding protein) and Sirt-1 (Sirtuin 1), two cellular nutrient sensors. Excess glucose reduced CREB-activated Hes-1 expression
and results in impaired cell proliferation. CREB-deficient NSCs expanded poorly in vitro and did not respond to glucose availability. Elevated glucose also promoted Sirt-1-dependent repression of the Hes-1 promoter. Conversely, in low glucose, CREB replaced Sirt-1 on the chromatin associated with the Hes-1 promoter enhancing Hes-1 expression and cell proliferation. Thus, the glucose-regulated antagonism between CREB and Sirt-1 for Hes-1 transcription participates in the metabolic regulation of neurogenesis.

Background and objectives: Sirtuin-1 (SIRT1) is a conserved a NAD +-dependent protein deacetylase essential for cellular metabolism and defence against oxidative stress and endothelial dysfunction. This study aimed to compare effects of 8 weeks of aerobic and combined training on serum level of SIRT1 and PGC1-α in coronary artery bypass graft patients. Methods: In this semi-experimental study, 45 non-active men (mean age 47.4 ± 3.3 years) who had undergone coronary artery bypass graft surgery were randomly divided into three groups: aerobic training, combined resistance and aerobic training and control. Trainings were performed at 80% of maximum heart rate, three sessions a week for 8 weeks. Blood samples were collected 24 hours before the first exercise session and 48 hours after the last training session. T-test and one-way analysis of variance were used for assessment of within-group and between-group differences, respectively. P-values less than 0.05 were considered as statistically significant. Results: The 8-week aerobic and combined training increased serum levels of SIRT1 and PGC-1α compared with the control group, and significantly decreased the weight of subjects (p=0.001). There was no significant difference in serum levels of SIRT1 and PGC-1α between the two training groups (P≥0.05). Conclusion: Both combined and aerobic training significantly improve the SIRT1 and PGC-1α levels in coronary artery bypass graft patients.

Aims: To determine the effects and underlying molecular mechanisms of caloric restriction (CR) in C57BL/6 mice. Methods: Thirty-six 6-week-old male C57BL/6 mice were assigned to a normal control group (NC, n = 12), a high energy group (HE, n = 12), and a CR group (n = 12), and received a normal diet, a high-calorie diet, or a calorie-restricted diet, respectively, for 44 weeks. Body weight and serum glucose concentration were regularly recorded, and animals were sacrificed and hippocampus tissues were collected for immunohis-tochemistry (n = 6 per group), western blotting (n = 3 per group) and real-time polymerase chain reaction (n = 3 per group) analysis at the end of the 44-week experimental period. Immunohistochemistry, western blotting and real-time polymerase chain reaction were used to detect changes in hippocampal proteins may be involved in the SIRT1/mTOR pathways. Results: Body weight and serum glucose over the 44 weeks in animals from the CR group were lower than those of HE group. The number of SIRT1-immunoreactive cells in the CR group was significantly higher than in the NC and HE groups, and SIRT1 mRNA expression in the CR group was significantly higher than that in the HE group, but there was no difference in SIRT1 protein expression among the three groups. mTOR and S6K1 protein activation and mTOR and S6K1 mRNA were significantly lower in the CR group than in the NC group. Conclusions: Our findings suggest that a CR diet could lead to activation of SIRT1 and suppression of mTOR and S6K1 activation in C57BL/6 mice. We have shown that the SIRT1/mTOR signaling pathways may be involved in the neuroprotective effect of CR.

Pancreatic cancer (PC), the fourth leading cause of cancer-related deaths, is characterized by high aggressiveness and resistance to chemotherapy. Pancreatic carcinogenesis is kept going by derangement of essential cell processes, such as proliferation, apoptosis, metabolism and autophagy, characterized by rhythmic variations with 24-h periodicity driven by the biological clock. We assessed the expression of the circadian genes ARNLT, ARNLT2, CLOCK, PER1, PER2, PER3, CRY1, CRY2 and the starvation-activated histone/protein deacetylase SIRT1 in 34 matched tumor and non-tumor tissue specimens of PC patients, and evaluated in PC derived cell lines if the modulation of SIRT1 expression through starvation could influence the temporal pattern of expression of the circadian genes. We found a significant down-regulation of ARNLT (p = 0.015), CRY1 (p = 0.013), CRY2 (p = 0.001), PER1 (p < 0.0001), PER2 (p < 0.001), PER3 (p = 0.001) and SIRT1 (p = 0.017) in PC specimens. PER3 and CRY2 expression levels were lower in patients with jaundice at diagnosis ( < 0.05). Having adjusted for age, adjuvant therapy and tumor stage, we evidenced that patients with higher PER2 and lower SIRT1 expression levels showed lower mortality (p = 0.028). Levels and temporal patterns of expression of many circadian genes and SIRT1 significantly changed upon serum starvation in vitro, with differences among four different PC cell lines examined (BXPC3, CFPAC, MIA-PaCa-2 and PANC-1). Serum deprivation induced changes of the overall mean level of the wave and amplitude, lengthened or shortened the cycle time and phase-advanced or phase-delayed the rhythmic oscillation depending on the gene and the PC cell line examined. In conclusion, a severe deregulation of expression of SIRT1 and circadian genes was evidenced in the cancer specimens of PC patients, and starvation influenced gene expression in PC cell lines, suggesting that the altered interplay between SIRT1 and the core circadian proteins could represent a crucial player in the process of pancreatic carcinogenesis.

Background and Objectives: Cardiac rehabilitation improves functional capacity of post-coronary artery bypass grafting (CABG) patients. Therefore, the aim of this study was to evaluate effects of eight weeks of cardiac rehabilitation on serum levels of sirutin1 (SIRT1) and functional capacity of post-CABG patients. Methods: Forty-five non-active men (mean age: 47.4 ± 3.3 years, duration of disease: 150 ± 69.12 months) were randomly divided into three equal groups: aerobic exercise, combined (resistance and aerobic) exercise and control. The subjects performed trainings at 60-75% of maximum heart rate, three sessions a week for eight weeks. Blood samples were collected 24 hours before the first exercise session and 48 hours after the last exercise session. Data were analyzed with SPSS 16.0 using one-way ANOVA and the Tukey post hoc test. P-values less than 0.05 were considered statistically significant. Results: Aerobic and combined exercise increased serum SIRT1 levels and functional capacity. There was no significant decrease in body mass index (P=0.06). The SIRT1 level did not differ significantly between the two exercise groups after the intervention (P=0.91). There were significant difference between the study groups in terms of the travelled distance (P<0.034). Conclusion: Both combined and aerobic exercise can increase serum levels of SIRT1, reduce body mass index and improve functional capacity in CABG patients.

Diabetic nephropathy is a leading cause of end-stage renal failure. Approximately
20-40% patients with diabetes mellitus will develop nephropathy with a significant proportion
requiring regular dialysis or kidney transplantation. The International Diabetes Federation
estimates that 366 million people had diabetes worldwide in 2011 and 552 million people will
have this disease by 2030.1 The increasing incidence of diabetes elevates diabetic nephropathy
to one of the most important current public health issues, representing a significant burden on
the health system.2 Despite current interventional strategies being intensively implemented,
the number of patients with diabetes requiring renal replacement therapy for end-stage renal
disease is growing.3 Current treatments of diabetic nephropathy slow its progression,3 so the
optimal therapeutic strategy to arrest or reverse the nephropathy is needed urgently. As multiple
risk factors and their interactions promote the development of diabetic nephropathy, targeting
a single factor may be ineffective in the treatment of this disease; thus, optimal treatments by
targeting multiple factors need to be developed to arrest or reverse the diabetic nephropathy.

Sirt1/AMPK and Akt/mTOR axes regulate cellular energy homeostasis and metabolism. Sodium butyrate (NaB) is a product of healthy gut microbiota and a histone deacetylase inhibitor. Recent studies have shown that NaB activates the intracellular pathways involving key metabolic regulator molecules. However, the effect of NaB on Sirt1/AMPK and Akt/mTOR axes is not reported. We compared genetic expression of Sirt1, AMPK, Akt, and mTOR in adipose tissue from mice treated with NaB versus placebo. Four groups of mice (n=27) mice were administered oral NaB, intraperitoneal (i.p) NaB, oral placebo or i.p placebo for 16 days. RNA was isolated from the epididymal fat pads and relative genetic expression of AMPK, Sirt1, mTOR and Akt was measured using real time PCR. Oral NaB group showed decreased genetic expression of AMPK (0.04 fold, p<0.001), mTOR (0.30 fold, p=0.04), Akt (0.29 fold, p=0.67) and Sirt1 (0.83 fold, p=0.18). In the I/P group AMPK (2.26 fold, p=0.33), Akt (1.3 fold, p=0.59) and Sirt1 (1.69, p=0.45) were increased while mTOR was unchanged (0.99 fold, p=0.81). Our study for the first time reports on change in genetic expression of Sirt1/AMPK and Akt/mTOR axes in adipose tissue of mice given oral and intraperitoneal NaB treatment.

SIRT1 (silent information regulator two protein) is a type III protein deacetylase that regulates a variety of important metabolic and physiologic processes including stress resistance, metabolism, apoptosis and energy balance. It reverses cholesterol transport and reduces risk for development of atherosclerosis and cardiovascular disease. The following review highlights the potential role of SIRT1 on cardiovascular biology and function.

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 β-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.

Lin28 is a small RNA-binding protein that plays an important role in regulating developmental timing, stem cell reprogramming, and oncogenesis. However, the significance of the effect of post-translational modifications on Lin28 activity is not fully understood. In this study, we demonstrated that PCAF directly interacted with and acetylated Lin28. We also showed that the acetylation of Lin28 can be specifically reversed by the deacetylase SIRT1. These findings suggest that the PCAF/SIRT1 balance plays an important role in regulating Lin28 activity. Furthermore, we found that the cold shock domain of Lin28 is the major target of PCAF-mediated acetylation, which leads to a severe reduction in the Lin28 protein levels and an increase in the level of mature let-7a. This study provides the first demonstration that post-translational modification regulates Lin28 activity during let-7a biogenesis and sheds light on the regulation of Lin28 in ES cells and carcinogenesis.