SIRT1 haplo-insufficiency results in reduced cortical bone thickness, increased porosity and decreased estrogen receptor alpha in bone in adult 129/Sv female mice

New Perspectives on Postmenopausal Osteoporosis: Mechanisms and Potential Therapeutic Strategies of Sirtuins and Oxidative Stress

Estrogen levels are the core factor influencing postmenopausal osteoporosis (PMOP). Estrogen can affect the progression of PMOP by regulating bone metabolism, influencing major signaling pathways related to bone metabolism, and modulating immune responses. When estrogen levels decline, the activity of Sirtuins (SIRTs) is reduced. SIRTs are enzymes that function as NAD+-dependent deacetylases. SIRTs can modulate osteocyte function, sustain mitochondrial homeostasis, and modulate relevant signaling pathways, thereby improving bone metabolic imbalances, reducing bone resorption, and promoting bone formation. In PMOP, SIRT1, SIRT3, and SIRT6 are primarily affected. Oxidative stress (OS) is a crucial factor in PMOP, as it generates excessive reactive oxygen species (ROS) that exacerbate PMOP. There is a certain interplay between SIRTs and OS. The reduced activity of SIRTs leads to intensified OS and the excessive accumulation of ROS. In return, ROS suppresses the AMPK signaling pathway and the synthesis of NAD+, which consequently diminishes the function of SIRTs. Natural SIRT activators and natural antioxidants, which are characterized by high safety, convenience, and minimal side effects, represent a potential therapeutic strategy for PMOP. This study aims to investigate the mechanisms of SIRTs and OS in PMOP and summarize potential therapeutic strategies to assist in the improvement of PMOP.

SIRT1 and exercise-induced bone metabolism: a regulatory nexus

Regular exercise positively influences bone health, enhances bone density and strength, and reduces the risk of osteoporosis. Silent information regulator of transcription 1 (SIRT1) is a deacetylase that plays a pivotal role in the regulation of various biological processes. In this review, we explore the role of SIRT1 in modulating bone metabolism in response to exercise. SIRT1 regulates crucial cellular processes, including inflammation, aging, autophagy, and oxidative stress, in bone cells such as bone marrow mesenchymal stem cells, osteoblasts, and osteoclasts, in response to exercise-induced stimuli. Notably, exercise influences bone metabolism by modulating muscle metabolism and neurotransmitters, with SIRT1 acting as a key mediator. A comprehensive understanding of SIRT1's regulatory mechanisms will facilitate a deeper exploration of the principles underlying exercise-induced improvements in bone metabolism, ultimately providing novel insights into the treatment of bone metabolic disorders.

Association between ESR1 and COL1A1 gene polymorphisms and skeletal fluorosis in Tibetan, Kazakh, Mongolian and Russian populations, China

BACKGROUND

Skeletal fluorosis is a chronic metabolic bone disease caused by excessive accumulation of fluoride in the bones. Previous studies have found that when the intake of tea fluoride is similar, the prevalence of skeletal fluorosis varies greatly among different ethnic groups, which may be related to different genetic backgrounds. Single nucleotide polymorphisms (SNPs) of estrogen receptor 1 (ESR1) and collagen type 1 α1 (COL1A1) were strongly associated with bone metabolism as well as bone growth and development, but their association with the risk of skeletal fluorosis has not been reported.

PURPOSE

To explore the incidence of skeletal fluorosis in different nationalities in the endemic fluorosis area of brick-tea type. To study the relationship between 4 SNPS of ESR1 and COL1A1 gene and skeletal fluorosis.

METHODS

A cross-sectional study was conducted in Inner Mongolia, Qinghai and Xinjiang. By including exclusion criteria, a total of 989 people were included in the study, demographic data were collected, and physical examinations and laboratory biochemical tests were performed. The X-ray of the participants were diagnosed according to the diagnostic criteria of Chinese endemic skeletal fluorosis (WS192-2008). Fluoride levels in tea or urine were measured using fluoride ion electrodes. SNP was evaluated using Sequenom-MassARRAY system.

RESULT

The prevalence of skeletal fluorosis varies among different nationalities. Binary logistic regression found that carried the ESR1 Rs9340799 G allele played a protective role in brick-tea-type fluorosis (OR = 0.673[95% CI, 0.495,0.914]). Russians carried the COL1A1 Rs1800012 T allele had a significantly higher risk of developing skeletal fluorosis (OR = 6.370 [95% CI, 1.413,28.715]). When stratified by sex, carriage of the T allele in COL1A1 Rs1800012 significantly increased the risk of developing skeletal fluorosis in Russian men. At the same time, changes in tea fluoride intake and older age can affect the effect of genetic background differences on the risk of skeletal fluorosis.

CONCLUSION

Our data suggested that there may be a genetic component to the risk of skeletal fluorosis in participants of different ethnicities and that this difference could modified by tea fluoride intake, sex or age.

Role of sirtuins in obesity and osteoporosis: molecular mechanisms and therapeutic targets

The prevalence of obesity and osteoporosis (OP) represents a significant public health concern on a global scale. A substantial body of evidence indicates that there is a complex relationship between obesity and OP, with a correlation between the occurrence of OP and obesity. In recent years, sirtuins have emerged as a prominent area of interest in the fields of aging and endocrine metabolism. Among the various research avenues exploring the potential of sirtuins, the effects of these proteins on obesity and OP have garnered significant attention from numerous researchers. Sirtuins regulate energy balance and lipid balance, which in turn inhibit the process of adipogenesis. Additionally, sirtuins regulate the balance between osteogenic and osteoblastic activity, which protects against the development of OP. However, no study has yet provided a comprehensive discussion of the relationship between the three: sirtuins, obesity, and OP. This paper will therefore describe the relationship between sirtuins and obesity, the relationship between sirtuins and OP, and a discussion focusing on the possibility of treating OP caused by obesity by targeting sirtuins. This will be based on the common influences on the occurrence of obesity and OP (such as mesenchymal stem cells, gut microbiota, and insulin). Finally, the potential of SIRT1, an important member of sirtuins, in polyphenolic natural products for the treatment of obesity and OP will be presented. This will contribute to a better understanding of the interactions between sirtuins and obesity and bone, which will facilitate the development of new therapeutic strategies for obesity and OP in the future.

Role of SIRT1-mediated synaptic plasticity and neurogenesis: Sex-differences in antidepressant-like efficacy of catalpol

BACKGROUND

Catalpol, an important compound found in Rehmannia glutinosa (a plant with high nutritional and antidepressant medicinal value), exhibits various biological activities and has the ability to penetrate the blood-brain barrier. Our recent studies revealed a gender difference in the antidepressant activity of Rehmannia glutinosa with females showing better responses than males. Catalpol is likely the key compound responsible for this gender-specific difference, which caters to current clinical observations that the severity and impact of depression are approximately two to three times higher in females than in males. However, the sex-specific mechanism of catalpol's antidepressant effects remains unclear.

PURPOSE AND METHODS

Our recent molecular network predictions suggest that the gender-specific antidepressant properties of catalpol primarily involve the regulation of SIRT1-mediated synaptic plasticity and neurogenesis. Building on this, the present study used a well-established chronic unpredictable mild stress model of depression in mice to confirm the sex-specific antidepressant characteristics of catalpol over time and intensity. Furthermore, using SIRT1 inhibitors and activators, behavioral tests, hematoxylin & eosin, Nissl, and Golgi staining, western blotting, immunofluorescence, and real-time PCR, we evaluated the key indicators of depressive behavior, synaptic plasticity, and neurogenesis before and after SIRT1 intervention to comprehensively assess whether the sex-specific antidepressant mechanism of catalpol indeed involves SIRT1-mediated synaptic plasticity and neurogenesis.

RESULTS

The gender-dependent antidepressant effects of catalpol are characterized by a faster onset and stronger effects in females compared to males, with females showing stronger regulation of SIRT1-mediated synaptic plasticity and neurogenesis. Activation of SIRT1 preserved the gender differences in catalpol's effects on depressive behavior, hippocampal synaptic plasticity (including neuronal consolidation, neuronal density, dendritic spines, and PSD95 and SYP gene and protein expression), and neurogenesis (including enhancement of GAP43 and MAP2 expression, activation of c-myc, cyclinD1, Ngn2, and NeuroD1 mRNA levels, and upregulation of the Wnt3a/β-catenin/GSK-3β pathway), while inhibition of SIRT1 abolished these gender differences in the effects of catalpol.

CONCLUSIONS

Catalpol exhibits higher antidepressant activity in female mice compared to male mice, and the mechanism underlying this gender difference in antidepressant effects may depend on catalpol's higher sensitivity in improving hippocampal SIRT1-mediated synaptic plasticity and neurogenesis in females. The novelty of this study lies in its first-time revelation of the gender-specific phenotypes, targets, and molecular mechanisms of the antidepressant effects of catalpol.

Sirtuins mediate mitochondrial quality control mechanisms: a novel therapeutic target for osteoporosis

Mitochondria plays a role in cell differentiation and apoptosis processes. Maintaining mitochondrial function is critical, and this involves various aspects of mitochondrial quality control such as protein homeostasis, biogenesis, dynamics, and mitophagy. Osteoporosis, a metabolic bone disorder, primarily arises from two factors: the dysregulation between lipogenic and osteogenic differentiation of aging bone marrow mesenchymal stem cells, and the imbalance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption. Mitochondrial quality control has the potential to mitigate or even reverse the effects. Among the Sirtuin family, consisting of seven Sirtuins (SIRT1-7), SIRT1-SIRT6 play a crucial role in maintaining mitochondrial quality control. Additionally, SIRT1, SIRT3, SIRT6, and SIRT7 are directly involved in normal bone development and homeostasis by modulating bone cells. However, the precise mechanism by which these Sirtuins exert their effects remains unclear. This article reviews the impact of various aspects of mitochondrial quality control on osteoporosis, focusing on how SIRT1, SIRT3, and SIRT6 can improve osteoporosis by regulating mitochondrial protein homeostasis, biogenesis, and mitophagy. Furthermore, we provide an overview of the current state of clinical and preclinical drugs that can activate Sirtuins to improve osteoporosis. Specific Sirtuin-activating compounds are effective, but further studies are needed. The findings of this study may offer valuable insights for future research on osteoporosis and the development of clinical prevention and therapeutic target strategies.