Association Study of Sirtuin 1 Polymorphisms with Bone Mineral Density and Body Mass Index

Gene polymorphisms of SIRT1 in patients with rheumatoid arthritis

AIM

Previous studies have shown that silent information regulator 1 (SIRT1) expression is elevated in rheumatoid arthritis (RA) patients. However, whether gene polymorphisms in SIRT1 gene associated with RA in a Chinese Han population remains to be discussed.

METHOD

In this case-control study, 529 RA patients and 700 healthy controls were selected, and association of 11 SIRT1 gene polymorphisms (rs12415800, rs3740051, rs932658, rs3740053, rs7895833, rs10509291, rs33957861, rs7069102, rs2273773, rs3818292, rs1467568) with RA susceptibility was evaluated.

RESULTS

Frequency of GA+GG genotype of rs3740051 in RA patients was significantly lower than that in healthy controls (P = .037). Frequencies of GC and GC+GG genotypes of rs7069102 were significantly lower than those in healthy controls (P = .036, P = .047). Frequencies of GA and GA+GG genotypes of rs1467568 were lower in RA patients as compared to those in healthy controls (P = .011, P = .013). For rs2273773, RA patients who carried the T allele had higher number of tender joints than patients who carried the C allele (P = .033). Other polymorphisms did not associate with RA risk.

CONCLUSION

The findings suggest that rs3740051, rs7069102 and rs1467568 variants in SIRT1 gene are related to RA susceptibility in a Chinese Han population.

Role of histone deacetylases in bone development and skeletal disorders

Bone cells must constantly respond to hormonal and mechanical cues to change gene expression programs. Of the myriad of epigenomic mechanisms used by cells to dynamically alter cell type-specific gene expression, histone acetylation and deacetylation has received intense focus over the past two decades. Histone deacetylases (HDACs) represent a large family of proteins with a conserved deacetylase domain first described to deacetylate lysine residues on histone tails. It is now appreciated that multiple classes of HDACs exist, some of which are clearly misnamed in that acetylated lysine residues on histone tails is not the major function of their deacetylase domain. Here, we will review the roles of proteins bearing deacetylase domains in bone cells, focusing on current genetic evidence for each individual HDAC gene. While class I HDACs are nuclear proteins whose primary role is to deacetylate histones, class IIa and class III HDACs serve other important cellular functions. Detailed knowledge of the roles of individual HDACs in bone development and remodeling will set the stage for future efforts to specifically target individual HDAC family members in the treatment of skeletal diseases such as osteoporosis.

Investigation of SIRT1 gene variants in HIV-associated lipodystrophy and metabolic syndrome

HIV-infected individuals on chronic use of highly active antiretroviral therapy (HAART) are more likely to develop adipose tissue and metabolic disorders, such as lipodystrophy (LD) and metabolic syndrome (MetS). The development of these phenotypes is known to be multifactorial. Thus, variants in genes implicated in adipogenesis and lipid metabolism may increase susceptibility to LD and MetS. Sirtuin 1 (SIRT1) may influence the outcome of these disturbances due to its role in the regulation of transcription factors involved in energy regulation. Therefore, we genotyped four polymorphisms located in SIRT1 (rs2273773 T>C, rs12413112 G>A, rs7895833 A>G, rs12049646 T>C) in 832 HIV-infected patients receiving HAART by real-time polymerase chain reaction. The prevalence of LD was 55.8% and MetS was 35.3%. Lipoatrophy was the most prevalent subtype in all samples (38.0%) and showed significant difference between white and non-white individuals (P = 0.002). None of the genetic variants investigated in SIRT1 was associated with LD and MetS. White individuals and those in longer time of HAART use were more likely to develop LD. We concluded that these SIRT1 polymorphisms are not predictive factors to the development of lipodystrophy and metabolic syndrome in HIV-infected individuals from Brazil.

Association of SIRT-1 Gene Polymorphism and Vitamin D Level in Egyptian Patients With Rheumatoid Arthritis

Background

We investigated SIRT-1 genetic variant and its association with vitamin D level in Egyptian patients with rheumatoid arthritis (RA).

Methods

Seventy Egyptian subjects were enrolled in our study and divided into two groups: RA group (n = 50 patients) and healthy control group (n = 20 subjects). Five milliliter blood sample was withdrawn from each subject followed by laboratory investigation and DNA extraction for SIRT-1 gene polymorphism assessment (rs7895833 A>G, rs7069102 C>G and rs2273773 C>T) and vitamin D level expression.

Results

There was statistically significant difference between rheumatoid cases and controls with regard to vitamin D level with 88% of cases showing insufficient vitamin D versus all controls showing sufficient level. SIRT-1 different SNPs rs2273773, rs7895833and rs7069102 genotype frequencies were statistically significant in RA compared to control group (P = 0.001). There was no statistically significant difference between different genotypes of rs2273773, rs7895833 and rs7069102 with regard to vitamin D level.

Conclusion

We concluded that there is a strong association between SIRT-1 polymorphism genotyping and RA. Vitamin D level was insufficient in Egyptian patients with RA.

Effects of self-reported calorie restriction on correlations between SIRT1 polymorphisms and body mass index and long-term weight change

SIRT1 acts as a cellular sensor to detect energy availability and modulates fat and glucose metabolism. This study assessed the effects of self-reported calorie restriction (CR) and exercise on correlations between SIRT1 polymorphisms and body mass index (BMI) and long-term weight change. This cross-sectional study enrolled 4023 subjects aged 35-69years (1847 men and 2176 women) selected from participants in the Japan Multi-Institutional Collaborative Cohort Study. This study was based on a self-administered questionnaire. No significant correlations between SIRT1 polymorphisms and BMI or long-term weight change were found in either the CR or the active groups. In the no-CR group, women with the rs1467568 G allele had a higher BMI than women without (p=0.02). Moreover, women with the rs7895833 A or rs1467568 G allele gained more weight from the age of 20years than women without these alleles (p=0.03 for rs7895833 and p=0.003 for rs1467568). In addition, the odds ratios (95% confidence intervals) of these alleles for overweight (BMI >27.5kg/m²) were significantly high in the no-CR women group (1.78 (1.06-2.99) for rs7895833 and 1.88 (1.13-3.15) for rs1467568) but not in the CR group. The results of this study suggest that CR might override the genetic contributions of the SIRT1 rs7895833 A and rs1467568 G alleles to BMI and long-term weight change.

Reduced Sirtuin1 expression at the femoral neck in women who sustained an osteoporotic hip fracture

To investigate the role of Sirtuin1 in osteoporosis, Sirtuin1 was determined at the femoral neck in female patients undergoing hip operation for fractured hip or osteoarthritis. Reduced Sirtuin1 was found in osteoporotic patients. Pharmacologic activation of Sirtuin1 reduced sclerostin, an inhibitor of bone formation. Activation of Sirtuin1 may be a new direction to generate therapies for osteoporosis.

INTRODUCTION

The aim of the study are to investigate the role of Sirtuin1 (Sirt1), an anti-aging factor and a player in age-associated diseases, in osteoporotic hip fractures, and test the hypothesis that Sirt1 is a negative regulator of sclerostin, a bone formation inhibitor, in human femoral bone marrow mesenchymal cells (BM-MSCs).

METHODS

Sirt1 and sclerostin were determined by western blot in bone samples obtained intra-operatively from the inferior medial cortex of the femoral neck (calcar region) in female patients undergoing partial hip replacement for fractured neck of femur (N = 10) or hip replacement for osteoarthritis (N = 8) (mean ± SD age 81 ± 8.1 vs. 68 ± 9.3 years; BMI 26.2 ± 3.6 vs. 25.9 ± 7.1 kg/m(2) in osteoporotic and osteoarthritis patients). Calcar thickness and femoral bone mineral density (BMD) were determined preoperatively by X-ray using a digital TraumaCad(™) software and DEXA. Femoral BM-MSCs were collected intra-operatively and treated with SRT3025, a Sirt1 activator. Sclerostin and dentin matrix acidic phosphoprotein (DMP1) were determined by western blot and messenger RNA (mRNA) expression of Lef1 and DMP1 was evaluated by quantitative real-time PCR.

RESULTS

Osteoporotic (OP) patients had reduced cortical thickness, femoral neck, and total hip BMD compared to osteoarthritis (OA) patients. Calcar Sirt1 expression was significantly reduced, while sclerostin was markedly increased in OP compared to OA patients. Sirt1 and sclersotin expressions were inversely correlated (r = -0.49, P = 0.047). SRT3025 administration down-regulated sclerostin and up-regulated DMP1 protein level and increased LEF1 and DMP1 mRNA expressions in OP patient-derived BM-MSCs.

CONCLUSIONS

Reduced femoral neck Sirt1 may play a role in osteoporotic hip fractures in part via influencing local sclerostin expression. The therapeutic potential of Sirt1 activation in osteoporosis warrants further investigation.

In Search of New Therapeutic Targets in Obesity Treatment: Sirtuins

Most of the available non-invasive medical therapies for obesity are non-efficient in a long-term evaluation; therefore there is a constant need for new methods of treatment. Research on calorie restriction has led to the discovery of sirtuins (silent information regulators, SIRTs), enzymes regulating different cellular pathways that may constitute potential targets in the treatment of obesity. This review paper presents the role of SIRTs in the regulation of glucose and lipid metabolism as well as in the differentiation of adipocytes. How disturbances of SIRTs’ expression and activity may lead to the development of obesity and related complications is discussed. A special emphasis is placed on polymorphisms in genes encoding SIRTs and their possible association with susceptibility to obesity and metabolic complications, as well as on data regarding altered expression of SIRTs in human obesity. Finally, the therapeutic potential of SIRTs-targeted strategies in the treatment of obesity and related disorders is discussed.

Polymorphism in the SIRT1 gene and parameters of metabolic syndrome in a sample of the adult Brazilian population

ABSTRACT Objective: To evaluate whether the single nucleotide polymorphism rs7895833 (A/G) of the gene SIRT1 is associated with metabolic syndrome criteria in a sample of Brazilian adults. Methods: Serum samples and oral mucosal cells were collected from 243 subjects aged 30 to 70 years. Biochemical, hormonal, and anthropometric data were obtained. The single nucleotide polymorphism rs7895833 (A/G) was analyzed by polymerase chain reaction using the amplification refractory mutation system. Results: Among the 243 study subjects, 100 (41.15%) were classified as non-metabolic syndrome and 143 (58.85%), as metabolic syndrome. The frequency of the single nucleotide polymorphism rs7895833 (A/G) did not differ between the groups. However, 111 patients (45.67%) were overweight (body mass index: 25-29.9 kg/m2). Blood glucose, total cholesterol, triglycerides, very low density lipoprotein, low density lipoprotein, waist and hip circumferences, and blood pressure were higher in the metabolic syndrome group than in the non-metabolic syndrome group. Free thyroxine 4, grown hormone, and insulin levels were within the normal range. The metabolic conditions of the patients with metabolic syndrome indicate biochemical, anthropometric, and hormonal changes characteristic of overweight and obesity. Conclusion: The SIRT1 polymorphism rs7895833 (A/G) is not associated with the metabolic syndrome in the adult Brazilian population.

A remarkable age-related increase in SIRT1 protein expression against oxidative stress in elderly: SIRT1 gene variants and longevity in human

Aging is defined as the accumulation of progressive organ dysfunction. Controlling the rate of aging by clarifying the complex pathways has a significant clinical importance. Nowadays, sirtuins have become famous molecules for slowing aging and decreasing age-related disorders. In the present study, we analyzed the SIRT1 gene polymorphisms (rs7895833 A>G, rs7069102 C>G and rs2273773 C>T) and its relation with levels of SIRT1, eNOS, PON-1, cholesterol, TAS, TOS, and OSI to demonstrate the association between genetic variation in SIRT1 and phenotype at different ages in humans. We observed a significant increase in the SIRT1 level in older people and found a significant positive correlation between SIRT1 level and age in the overall studied population. The oldest people carrying AG genotypes for rs7895833 have the highest SIRT1 level suggesting an association between rs7895833 SNP and lifespan longevity. Older people have lower PON-1 levels than those of adults and children which may explain the high levels of SIRT1 protein as a compensatory mechanism for oxidative stress in the elderly. The eNOS protein level was significantly decreased in older people as compared to adults. There was no significant difference in the eNOS level between older people and children. The current study is the first to demonstrate age-related changes in SIRT1 levels in humans and it is important for a much better molecular understanding of the role of the longevity gene SIRT1 and its protein product in aging. It is also the first study presenting the association between SIRT1 expression in older people and rs7895833 in SIRT1 gene.

Sirtuin gene polymorphisms are associated with chronic obstructive pulmonary disease in patients in Muğla province

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is an irreversible progressive chronic inflammatory disease that causes shortness of breath in consequence of a decrease in pulmonary functions. The pulmonary inflammatory pathogenesis is multifactorial. We have too little up-to-date information about the relation between COPD and genetics. In our study, the relation with the SIRT1 gene's mononucleotide polymorphisms (SNP) rs7895833, rs7069102 and rs2273773 was analyzed through various laboratory data.

MATERIAL AND METHODS

One hundred COPD patients from the archive records of the Chest Diseases Department of Muğla Sitki Kocman University Medical Faculty were included in the study. A control group was constituted from 100 healthy individuals who live in the same geographical region. The SIRT1 genotypes for these patients were determined using polymerase chain reaction (PCR) and confronting two-pair primers (CTPP) methods. The SIRT1 gene polymorphisms rs7895833, rs7069102 and rs2273773 were analyzed. GG, AG, AA genotypes and G and A alleles of rs7895833, TT, TC, CC genotypes and T and C alleles of rs2273773, and CC, CG, GG genotypes and C and G alleles of rs7069102 were examined. The data in both groups were compared.

CONCLUSIONS

A significant difference between GG, AG and AA genotypes of rs7895833 was found. Especially, the AG genotype was observed more in the group with COPD, with a significant difference. A significant difference between TT, TC and CC genotypes of rs2273773 was found. There was a significant difference between two groups with regards to C and G alleles of rs7069102. A significant difference was not found between the groups with regards to G and A alleles of rs7895833. A difference was not found for both groups between T and C alleles of rs2273773. It shows that these polymorphisms of the SIRT1 gene may be associated with COPD.

SIRT1 gene polymorphisms are associated with growth traits in Nanyang cattle

Growth is under complex genetic control and uncovering the molecular mechanisms how the genes and polymorphisms affect economic growth traits, are important for successful marker-assisted selection and more efficient management strategies in commercial cattle populations. SIRT1 is a NAD(+)-dependent deacetylase that belongs to the class III histone deacetylases. It plays an important role in numerous fundamental cellular processes including gene silencing, DNA repair, and metabolic regulation. In addition, SIRT1 acts as an inhibitor of adipogenesis and has been associated with body weight regulation. The objective of the present study was to identify single nucleotide polymorphisms (SNPs) of bovine SIRT1 using 1255 animals representing the five main Chinese breeds and to determine if these SNPs are associated with economically important traits in Nanyang cattle. The approach consisted of resequencing SIRT1 using a panel of DNA from unrelated animals of five different breeds and the process revealed five novel SNPs. SNPs g.17324T>C and g.17491G>A exhibited a high degree of linkage disequilibrium in all tested breeds. Seven major haplotypes accounting for 91.2% of the alleles were observed and the haplotype 'GCCGA' was the most common haplotype in NY, QC, LX and JX breeds. An association analysis was performed between the five SNPs and six performance traits. SNP g.-274C>G was demonstrated to have a strong effect on 24-months-old body weight and g.17379A>G polymorphism was related to 6 and 12-months-old body weight in NY population, although these effects did not remained significant after the Bonferroni correction. Our results provide evidence that polymorphisms in SIRT1 are associated with growth efficiency traits, and may be used for marker-assisted selection and management in feedlot cattle.

A novel c.-274C>G polymorphism in bovine SIRT1 gene contributes to diminished promoter activity and is associated with increased body size

SIRT1, a mammalian homologue for yeast silent information regulator 2 (SIR2), is a NAD(+) -dependent deacetylase that belongs to the class III histone deacetylases. It plays an important role in diverse cellular processes, including stress resistance, mitochondrial function, suppression of inflammation and DNA repair. In this study, we screened and identified a novel polymorphism (c.-274C>G) in the SIRT1 promoter region. In silico prediction reveals that this SNP is in the core of cell cycle-dependent element (CDE)-binding motif. Interestingly, the G allele abolished a CDE-binding site, which suggested its functional significance. In the luciferase assay system, we found that the G allele-containing construct displayed a strikingly lower promoter activity compared with the C allele, which may downregulate SIRT1 expression levels. Additionally, we observed a significant association between the c.-274C>G polymorphism and growth traits in Nanyang cattle, suggesting that anomalous transcription factor-based repression of SIRT1 may increase bovine fat mass and body size.

Seven sirtuins for seven deadly diseases of aging

Sirtuins are a class of NAD(+)-dependent deacetylases having beneficial health effects. This extensive review describes the numerous intracellular actions of the seven mammalian sirtuins, their protein targets, intracellular localization, the pathways they modulate, and their role in common diseases of aging. Selective pharmacological targeting of sirtuins is of current interest in helping to alleviate global disease burden. Since all sirtuins are activated by NAD(+), strategies that boost NAD(+) in cells are of interest. While most is known about SIRT1, the functions of the six other sirtuins are now emerging. Best known is the involvement of sirtuins in helping cells adapt energy output to match energy requirements. SIRT1 and some of the other sirtuins enhance fat metabolism and modulate mitochondrial respiration to optimize energy harvesting. The AMP kinase/SIRT1-PGC-1α-PPAR axis and mitochondrial sirtuins appear pivotal to maintaining mitochondrial function. Downregulation with aging explains much of the pathophysiology that accumulates with aging. Posttranslational modifications of sirtuins and their substrates affect specificity. Although SIRT1 activation seems not to affect life span, activation of some of the other sirtuins might. Since sirtuins are crucial to pathways that counter the decline in health that accompanies aging, pharmacological agents that boost sirtuin activity have clinical potential in treatment of diabetes, cardiovascular disease, dementia, osteoporosis, arthritis, and other conditions. In cancer, however, SIRT1 inhibitors could have therapeutic value. Nutraceuticals such as resveratrol have a multiplicity of actions besides sirtuin activation. Their net health benefit and relative safety may have originated from the ability of animals to survive environmental changes by utilizing these stress resistance chemicals in the diet during evolution. Each sirtuin forms a key hub to the intracellular pathways affected.