SIRT1 transgenic mice show phenotypes resembling calorie restriction

Sirtuins and the circadian clock interplay in cardioprotection: focus on sirtuin 1

Chronic disruption of circadian rhythms which include intricate molecular transcription-translation feedback loops of evolutionarily conserved clock genes has serious health consequences and negatively affects cardiovascular physiology. Sirtuins (SIRTs) are nuclear, cytoplasmic and mitochondrial histone deacetylases that influence the circadian clock with clock-controlled oscillatory protein, NAMPT, and its metabolite NAD+. Sirtuins are linked to the multi-organ protective role of melatonin, particularly in acute kidney injury and in cardiovascular diseases, where melatonin, via upregulation of SIRT1 expression, inhibits the apoptotic pathway. This review focuses on SIRT1, an NAD+-dependent class III histone deacetylase which counterbalances the intrinsic histone acetyltransferase activity of one of the clock genes, CLOCK. SIRT1 is involved in the development of cardiomyocytes, regulation of voltage-gated cardiac sodium ion channels via deacetylation, prevention of atherosclerotic plaque formation in the cardiovascular system, protection against oxidative damage and anti-thrombotic actions. Overall, SIRT1 has a see-saw effect on cardioprotection, with low levels being cardioprotective and higher levels leading to cardiac hypertrophy.

Developmental programming: intrauterine caloric restriction promotes upregulation of mitochondrial sirtuin with mild effects on oxidative parameters in the ovaries and testes of offspring

According to the developmental origins of health and disease (DOHaD) hypothesis, changes in the maternal environment are known to reprogram the metabolic response of offspring. Known for its redox modulation, caloric restriction extends the lifespan of some species, which contributes to diminished cellular damage. Little is known about the effects of gestational caloric restriction, in terms of antioxidant parameters and molecular mechanisms of action, on the reproductive organs of offspring. This study assessed the effects of moderate (20%) caloric restriction on redox status parameters, molecular expression of sirtuin (SIRT) 1 and SIRT3 and histopathological markers in the ovaries and testes of adult rats that were subjected to gestational caloric restriction. Although enzyme activity was increased, ovaries from female pups contained high levels of oxidants, whereas testes from male pups had decreased antioxidant enzyme defences, as evidenced by diminished glyoxalase I activity and reduced glutathione content. Expression of SIRT3, a deacetylase enzyme related to cellular bioenergetics, was increased in both ovaries and testes. Previous studies have suggested that, in ovaries, diminished antioxidant metabolism can lead to premature ovarian failure. Unfortunately, there is little information regarding the redox profile in the testis. This study is the first to assess the redox network in both ovaries and testes, suggesting that, although intrauterine caloric restriction improves molecular mechanisms, it has a negative effect on the antioxidant network and redox status of reproductive organs of young adult rats.

Current mechanisms of primordial follicle activation and new strategies for fertility preservation

Premature ovarian insufficiency (POI) is characterized by symptoms caused by ovarian dysfunction in patients aged <40 years. It is associated with a shortened reproductive lifespan. The only effective treatment for patients who are eager to become pregnant is IVF/Embryo Transfer (ET) using oocytes donated by young women. However, the use of the technique is constrained by the limited supply of oocytes and ethical issues. Some patients with POI still have some residual follicles in the ovarian cortex, which are not regulated by gonadotropin. These follicles are dormant. Therefore, activating dormant primordial follicles (PFs) to obtain high-quality oocytes for assisted reproductive technology may bring new hope for patients with POI. Therefore, this study aimed to explore the factors related to PF activation, such as the intercellular signaling network, the internal microenvironment of the ovary and the environment of the organism. In addition, we discussed new strategies for fertility preservation, such as in vitro activation and stem cell transplantation.

Renoprotective effects of estrogen on acute kidney injury: the role of SIRT1

Acute kidney injury (AKI) is a common syndrome associated with high morbidity and mortality, despite progress in medical care. Many studies have shown that there are sex differences and different role of sex hormones particularly estrogens in kidney injury. In this regard, the incidence and rate of progression of kidney diseases are higher in men compared with women. These observations suggest that female sex hormone may be renoprotective. Silent information regulator 2 homolog 1 (SIRT1) is a histone deacetylase, which is implicated in multiple biologic processes in several organisms. In the kidneys, SIRT1 inhibits renal cell apoptosis, inflammation, and fibrosis. Studies have reported a link between SIRT1 and estrogen. In addition, SIRT1 regulates ERα expression and inhibition of SIRT1 activity suppresses ERα expression. This effect leads to inhibition of estrogen-responsive gene expression. In this text, we review the role of SIRT1 in mediating the protective effects of estrogen in the onset and progression of AKI.

Vitamin K2 Alleviates Insulin Resistance in Skeletal Muscle by Improving Mitochondrial Function Via SIRT1 Signaling

Aims: High-fat diet (HFD)-induced insulin resistance (IR) impairs skeletal muscle mitochondrial biogenesis and functions, adversely affecting human health and lifespan. Vitamin K2 (VK2) has a beneficial role in improving insulin sensitivity and glucose metabolism. However, the underlying molecular mechanisms of VK2 on insulin sensitivity have not been well established. We investigated VK2's modulation of mitochondrial function to protect against IR in mice and cell models. Results: VK2 supplementation could effectively ameliorate the development of IR by improving mitochondrial function in both HFD-fed mice and palmitate acid-exposed cells. We revealed for the first time that HFD-caused mitochondrial dysfunction could be reversed by VK2 treatment. VK2 enhanced the mitochondrial function by improving mitochondrial respiratory capacity, increasing mitochondrial biogenesis and the enzymatic activities of mitochondrial complexes through SIRT1 signaling. The benefits of VK2 were abrogated in C₂C₁₂ transfected with SIRT1 siRNA but not in C₂C₁₂ transfected with AMPK siRNA. VK2 and SRT1720, a specific agonist of SIRT1, had the same effect on improving mitochondrial function via SIRT1 signaling. Thus, SIRT1 is required for VK2 improvement in skeletal muscle. Further, the beneficial effects of both VK2 and geranylgeraniol contribute to inhibited IR in skeletal muscle via SIRT1. Innovation and Conclusion: These studies demonstrated a previously undiscovered mechanism by which VK2 alleviates IR in skeletal muscle by improving mitochondrial function via SIRT1. Naturally occurring VK2 prevents IR by improving mitochondrial function through SIRT1 signaling. These results could provide a foundation to identify new VK2-based preventive and therapeutic strategies for IR.

Resveratrol's Anti-Cancer Effects through the Modulation of Tumor Glucose Metabolism

Simple Summary

The prevention and treatment of cancer is an ongoing medical challenge. In the context of personalized medicine, the well-studied polyphenol resveratrol could complement classical tumor therapy. It may affect key processes such as inflammation, angiogenesis, proliferation, metastasis, glucose metabolism, and apoptosis in various cancers because resveratrol acts as a multi-targeting agent by modulating multiple signal transduction pathways. This review article focuses on resveratrol’s ability to modify tumor glucose metabolism and its associated therapeutic capacity. Resveratrol reduces glucose uptake and glycolysis by affecting Glut1, PFK1, HIF-1α, ROS, PDH, and the CamKKB/AMPK pathway. It also inhibits cell growth, invasion, and proliferation by targeting NF-kB, Sirt1, Sirt3, LDH, PI-3K, mTOR, PKM2, R5P, G6PD, TKT, talin, and PGAM. In addition, resveratrol induces apoptosis by targeting integrin, p53, LDH, and FAK. In conclusion, resveratrol has many potentials to intervene in tumor processes if bioavailability can be increased and this natural compound can be used selectively.

Abstract

Tumor cells develop several metabolic reprogramming strategies, such as increased glucose uptake and utilization via aerobic glycolysis and fermentation of glucose to lactate; these lead to a low pH environment in which the cancer cells thrive and evade apoptosis. These characteristics of tumor cells are known as the Warburg effect. Adaptive metabolic alterations in cancer cells can be attributed to mutations in key metabolic enzymes and transcription factors. The features of the Warburg phenotype may serve as promising markers for the early detection and treatment of tumors. Besides, the glycolytic process of tumors is reversible and could represent a therapeutic target. So-called mono-target therapies are often unsafe and ineffective, and have a high prevalence of recurrence. Their success is hindered by the ability of tumor cells to simultaneously develop multiple chemoresistance pathways. Therefore, agents that modify several cellular targets, such as energy restriction to target tumor cells specifically, have therapeutic potential. Resveratrol, a natural active polyphenol found in grapes and red wine and used in many traditional medicines, is known for its ability to target multiple components of signaling pathways in tumors, leading to the suppression of cell proliferation, activation of apoptosis, and regression in tumor growth. Here, we describe current knowledge on the various mechanisms by which resveratrol modulates glucose metabolism, its potential as an imitator of caloric restriction, and its therapeutic capacity in tumors.

The Regulatory Effect of SIRT1 on Extracellular Microenvironment Remodeling

The sirtuins family is well known by its unique nicotinamide adenine dinucleotide (NAD⁺)-dependent deacetylase function. The most-investigated member of the family, Sirtuin 1 (SIRT1), accounts for deacetylating a broad range of transcription factors and coregulators, such as p53, the Forkhead box O (FOXO), and so on. It serves as a pivotal regulator in various intracellular biological processes, including energy metabolism, DNA damage response, genome stability maintenance and tumorigenesis. Although the most attention has been focused on its intracellular functions, the regulatory effect on extracellular microenvironment remodeling of SIRT1 has been recognized by researchers recently. SIRT1 can regulate cell secretion process and participate in glucose metabolism, neuroendocrine function, inflammation and tumorigenesis. Here, we review the advances in the understanding of SIRT1 on remodeling the extracellular microenvironment, which may provide new ideas for pathogenesis investigation and guidance for clinical treatment.

From Obesity to Hippocampal Neurodegeneration: Pathogenesis and Non-Pharmacological Interventions

High-caloric diet and physical inactivity predispose individuals to obesity and diabetes, which are risk factors of hippocampal neurodegeneration and cognitive deficits. Along with the adipose-hippocampus crosstalk, chronically inflamed adipose tissue secretes inflammatory cytokine could trigger neuroinflammatory responses in the hippocampus, and in turn, impairs hippocampal neuroplasticity under obese and diabetic conditions. Hence, caloric restriction and physical exercise are critical non-pharmacological interventions to halt the pathogenesis from obesity to hippocampal neurodegeneration. In response to physical exercise, peripheral organs, including the adipose tissue, skeletal muscles, and liver, can secret numerous exerkines, which bring beneficial effects to metabolic and brain health. In this review, we summarized how chronic inflammation in adipose tissue could trigger neuroinflammation and hippocampal impairment, which potentially contribute to cognitive deficits in obese and diabetic conditions. We also discussed the potential mechanisms underlying the neurotrophic and neuroprotective effects of caloric restriction and physical exercise by counteracting neuroinflammation, plasticity deficits, and cognitive impairments. This review provides timely insights into how chronic metabolic disorders, like obesity, could impair brain health and cognitive functions in later life.

SIRTI and cortisol in unexplained infertile females; a cross sectional study, in Karachi Pakistan

OBJECTIVE

To explore a disparity in anti-oxidants (SIRT1) and pro-oxidants (cortisol) levels as a plausible cause of unexplained infertility in females.

METHODOLOGY

It was a cross sectional study in which 342 females with unexplained infertility were recruited from ACIMC outpatient clinic: 135 infertile cases and 207 fertile controls. Biochemical estimation of serum cortisol and SIRT1 was performed using Enzyme Linked Immuno Sorbent Assay. Statistical comparisons were performed using Student-t test and Mann-Whitney U test. Associations between circulating hormone levels and infertility were determined using Spearman's rank correlation. Associations were considered significant where value of p was less than 0.05.

RESULTS

The stress hormones profile of case and control demonstrated that the antioxidant SIRT1 was significantly lower in infertile females when compared with the fertile (p =< 0.001) while (the oxidant) Cortisol showed a contrast of results with higher values of in infertile females when compared with fertile counterparts (p =< 0.01). There was a strong negative association observed between SIRT1 and cortisol serum level (r = 0.244, p < 0.001).

CONCLUSION

Chronic stress causes oxidative stress that is depicted by a decrease in antioxidant levels in infertile females.

The Potential of Resveratrol to Act as a Caloric Restriction Mimetic Appears to Be Limited: Insights from Studies in Mice

Caloric restriction (CR) has been shown repeatedly to prolong the lifespan in laboratory animals, with its benefits dependent on molecular targets forming part of the nutrient signaling network, including the NAD-dependent deacetylase silent mating type information regulation 2 homologue 1 (SIRT1). It has been hypothesized that the stilbene resveratrol (RSV) may counteract age- and obesity-related diseases similarly to CR. In yeast and worms, RSV-promoted longevity also depended on SIRT1. While it remains unclear whether RSV can prolong lifespans in mammals, some studies in rodents supplemented with RSV have reported lowered body weight (BW) and fat mass, improved insulin sensitivity, lowered cholesterol levels, increased fitness, and mitochondrial biogenesis. Molecular mechanisms possibly leading to such changes include altered gene transcription and activation of SIRT1, AMP-activated kinase (AMPK), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A). However, some mouse models did not benefit from RSV treatment to the same extent as others. We conducted a literature search on PubMed (15 April, 2020) for trials directly comparing RSV application to CR feeding in mice. In most studies retrieved by this systematic PubMed search, mice supplemented with RSV did not show significant reductions of BW, glucose, or insulin. Moreover, in some of these studies, RSV and CR treatments affected molecular targets differently and/or findings on RSV and CR impacts varied between trials. We discuss those RSV-induced changes in gene transcription hypothesized to partly counteract age-related alterations. Although there may be a moderate effect of RSV supplementation on parameters such as insulin sensitivity toward a more CR-like profile in mice, data are inconsistent. Likewise, RSV supplementation trials in humans report controversial findings. While we consider that RSV may, under certain circumstances, moderately mimic some aspects of CR, current evidence does not fully support its use to prevent or treat age- or obesity-related diseases.

Corylin reduces obesity and insulin resistance and promotes adipose tissue browning through SIRT-1 and β3-AR activation

Brown adipose tissue (BAT) activation or beige adipocytes in white adipocytes (WAT) (browning) is a novel strategy against obesity. Corylin, a flavonoid compound extract from Psoralea corylifolia L., has been shown to exert anti-inflammatory, anticancer, and anti-atherosclerotic effects and ameliorate hyperlipidemia and insulin resistance. However, the therapeutic effect of corylin on obesity remains unknown. The objective of this study was to evaluate the effect of corylin on browning or obesity. Here, we report that corylin induced browning by elevating the expression levels of beige- or browning-specific marker genes, including cited1, hoxc9, pgc1α, prdm16, and ucp1, in 3T3-L1 adipocytes, WAT and BAT. Moreover, corylin also strikingly reduced body weight and fat accumulation and increased insulin sensitivity, mitochondrial biogenesis, and β-oxidation in HFD- and DIO-treated mice. The browning and lipolysis effects of corylin were abolished by sirtuin 1 (SIRT1) inhibitor (EX527) and β3-adrenergic receptor (β3-AR) antagonist (L-748,337) treatment. The possible molecular mechanism of corylin on the browning and lipolysis of adipocytes is through SIRT1- or β3-AR-dependent pathways. The study suggested that corylin exerts anti-obesity effects through the browning of white adipocytes, activating of BAT and promoting of lipid metabolism. Therefore, corylin may be a helpful therapeutic candidate for treating obesity.

Potential Anti-Aging Substances Derived from Seaweeds

Aging is a major risk factor for many chronic diseases, such as cancer, cardiovascular disease, and diabetes. The exact mechanisms underlying the aging process are not fully elucidated. However, a growing body of evidence suggests that several pathways, such as sirtuin, AMP-activated protein kinase, insulin-like growth factor, autophagy, and nuclear factor erythroid 2-related factor 2 play critical roles in regulating aging. Furthermore, genetic or dietary interventions of these pathways can extend lifespan by delaying the aging process. Seaweeds are a food source rich in many nutrients, including fibers, polyunsaturated fatty acids, vitamins, minerals, and other bioactive compounds. The health benefits of seaweeds include, but are not limited to, antioxidant, anti-inflammatory, and anti-obese activities. Interestingly, a body of studies shows that some seaweed-derived extracts or isolated compounds, can modulate these aging-regulating pathways or even extend lifespans of various animal models. However, few such studies have been conducted on higher animals or even humans. In this review, we focused on potential anti-aging bioactive substances in seaweeds that have been studied in cells and animals mainly based on their anti-aging cellular and molecular mechanisms.

Blood SIRT1 Shows a Coherent Association with Leptin and Adiponectin in Relation to the Degree and Distribution of Adiposity: A Study in Obesity, Normal Weight and Anorexia Nervosa

Sirtuin 1 (SIRT1) is a sensor of cell energy availability, and with leptin and adiponectin, it regulates metabolic homeostasis. Widely studied in tissues, SIRT1 is under evaluation as a plasmatic marker. We aimed at assessing whether circulating SIRT1 behaves consistently with leptin and adiponectin in conditions of deficiency, excess or normal fat content. Eighty subjects were evaluated: 27 with anorexia nervosa (AN), 26 normal-weight and 27 with obesity. Bloodstream SIRT1, leptin and adiponectin (ELISA), total and trunk fat mass (FM) %, abdominal visceral adipose tissue, liver steatosis and epicardial fat thickness (EFT) were assessed. For each fat store, the coefficient of determination (R²) was used to evaluate the prediction capability of SIRT1, leptin and adiponectin. Plasma SIRT1 and adiponectin coherently decreased with the increase of FM, while the opposite occurred with leptin. Mean levels of each analyte were different between groups (p < 0.005). A significant association between plasma variables and FM depots was observed. SIRT1 showed a good predictive strength for FM, particularly in the obesity group, where the best R² was recorded for EFT (R² = 0.7). Blood SIRT1, adiponectin and leptin behave coherently with FM and there is synchrony between them. The association of SIRT1 with FM is substantially superimposable to that of adiponectin and leptin. Given its homeostatic roles, SIRT1 may deserve to be considered as a plasma clinical/biochemical parameter of adiposity and metabolic health.

Moderate SIRT1 overexpression protects against brown adipose tissue inflammation

OBJECTIVE

Metainflammation is a chronic low-grade inflammatory state induced by obesity and associated comorbidities, including peripheral insulin resistance. Brown adipose tissue (BAT), a therapeutic target against obesity, is an insulin target tissue sensitive to inflammation. Therefore, it is necessary to find strategies to protect BAT against the effects of inflammation in energy balance. In this study, we explored the impact of moderate sirtuin 1 (SIRT1) overexpression on insulin sensitivity and β-adrenergic responses in BAT and brown adipocytes (BA) under pro-inflammatory conditions.

METHODS

The effect of inflammation on BAT functionality was studied in obese db/db mice and lean wild-type (WT) mice or mice with moderate overexpression of SIRT1 (SIRT1^Tg+) injected with a low dose of bacterial lipopolysaccharide (LPS) to mimic endotoxemia. We also conducted studies on differentiated BA (BA-WT and BA-SIRT1^Tg+) exposed to a macrophage-derived pro-inflammatory conditioned medium (CM) to evaluate the protection of SIRT1 overexpression in insulin signaling and glucose uptake, mitochondrial respiration, fatty acid oxidation (FAO), and norepinephrine (NE)-mediated-modulation of uncoupling protein-1 (UCP-1) expression.

RESULTS

BAT from the db/db mice was susceptible to metabolic inflammation manifested by the activation of pro-inflammatory signaling cascades, increased pro-inflammatory gene expression, tissue-specific insulin resistance, and reduced UCP-1 expression. Impairment of insulin and noradrenergic responses were also found in the lean WT mice upon LPS injection. In contrast, BAT from the mice with moderate overexpression of SIRT1 (SIRT1^Tg+) was protected against LPS-induced activation of pro-inflammatory signaling, insulin resistance, and defective thermogenic-related responses upon cold exposure. Importantly, the decline in triiodothyronine (T₃) levels in the circulation and intra-BAT after exposure of the WT mice to LPS and cold was markedly attenuated in the SIRT1^Tg+ mice. In vitro BA experiments in the two genotypes revealed that upon differentiation with a T₃-enriched medium and subsequent exposure to a macrophage-derived pro-inflammatory CM, only BA-SIRT1^Tg+ fully recovered insulin and noradrenergic responses.

CONCLUSIONS

This study has ascertained the benefit of the moderate overexpression of SIRT1 to confer protection against defective insulin and β-adrenergic responses caused by BAT inflammation. Our results have potential therapeutic value in combinatorial therapies for BAT-specific thyromimetics and SIRT1 activators to combat metainflammation in this tissue.

Parental SIRT1 Overexpression Attenuate Metabolic Disorders Due to Maternal High-Fat Feeding

Maternal obesity can contribute to the development of obesity and related metabolic disorders in progeny. Sirtuin (SIRT)1, an essential regulator of metabolism and stress responses, has recently emerged as an important modifying factor of developmental programming. In this study, to elucidate the effects of parental SIRT1 overexpression on offspring mechanism, four experimental groups were included: (1) Chow-fed wild-type (WT)-dam × Chow-fed WT-sire; (2) High-fat diet (HFD)-fed WT-dam × Chow-fed WT-sire; (3) HFD-fed hemizygous SIRT1-transgenic (Tg)-dam × Chow-fed WT-sire; and (4) HFD-fed WT dam × Chow-fed Tg-sire. Our results indicate that Tg breeders had lower body weight and fat mass compared to WT counterparts and gave birth to WT offspring with reductions in body weight, adiposity and hyperlipidaemia compared to those born of WT parents. Maternal SIRT1 overexpression also reversed glucose intolerance, and normalised abnormal fat morphology and the expression of dysregulated lipid metabolism markers, including SIRT1. Despite having persistent hepatic steatosis, offspring born to Tg parents showed an improved balance of hepatic glucose/lipid metabolic markers, as well as reduced levels of inflammatory markers and TGF-β/Smad3 fibrotic signalling. Collectively, the data suggest that parental SIRT1 overexpression can ameliorate adverse metabolic programming effects by maternal obesity.

Cancer diets for cancer patients: Lessons from mouse studies and new insights from the study of fatty acid metabolism in tumors

Specific diets for cancer patients have the potential to offer an adjuvant modality to conventional anticancer therapy. If the concept of starving cancer cells from nutrients to inhibit tumor growth is quite simple, the translation into the clinics is not straightforward. Several diets have been described including the Calorie-restricted diet based on a reduction in carbohydrate intake and the Ketogenic diet wherein the low carbohydrate content is compensated by a high fat intake. As for other diets that deviate from normal composition only by one or two amino acids, these diets most often revealed a reduction in tumor growth in mice, in particular when associated with chemo- or radiotherapy. By contrast, in cancer patients, the interest of these diets is almost exclusively supported by case reports precluding any conclusions on their real capacity to influence disease outcome. In parallel, the field of tumor lipid metabolism has emerged in the last decade offering a better understanding of how fatty acids are captured, synthesized or stored as lipid droplets in cancers. Fatty acids participate to cancer cell survival in the hypoxic and acidic tumor microenvironment and also support proliferation and invasiveness. Interestingly, while such addiction for fatty acids may account for cancer progression associated with high fat diet, it could also represent an Achilles heel for tumors. In particular n-3 polyunsaturated fatty acids represent a class of lipids that can exert potent cytotoxic effects in tumors and therefore represent an attractive diet supplementation to improve cancer patient outcomes.

Effects of timed food availability on reproduction and metabolism in zebra finches: Molecular insights into homeostatic adaptation to food-restriction in diurnal vertebrates

Food availability affects metabolism and reproduction in higher vertebrates including birds. This study tested the idea of adaptive homeostasis to time-restricted feeding (TRF) in diurnal zebra finches by using multiple (behavioral, physiological and molecular) assays. Adult birds were subjected for 1 week or 3 weeks to food restriction for 4 h in the evening (hour 8-12) of the 12 h light-on period, with controls on ad lib feeding. Birds on TRF showed enhanced exploratory behavior and plasma triglycerides levels, but did not show differences from ad lib birds in the overall food intake, body mass, and plasma corticosterone and thyroxine levels. As compared to ad lib feeding, testis size and circulation testosterone were reduced after first but not after third week of TRF. The concomitant change in the mRNA expression of metabolic and reproductive genes was also found after week 1 of TRF. Particularly, TRF birds showed increased expression of genes coding for gonadotropin releasing hormone (GnRH) in hypothalamus, and for receptors of androgen (AR) and estrogen (ER-alpha) in both hypothalamus and testes. However, genes coding for the deiodinases (Dio2, Dio3) and gonadotropin inhibiting hormone (GnIH) showed no difference between feeding conditions in both hypothalamus and testes. Further, increased Sirt1, Fgf10 and Ppar-alpha, and decreased Egr1 expression in the liver suggested TRF-effects on the overall metabolism. Importantly, TRF-effects on gene expressions by week 1 seemed alleviated to a considerable extent by week 3. These results on TRF-induced reproductive and metabolic effects suggest homeostatic adaptation to food-restriction in diurnal vertebrates.

SIRT1/FOXO3a axis plays an important role in the prevention of mandibular bone loss induced by 1,25(OH)2D deficiency

It has been reported that 1,25 dihydroxyvitamin D [1,25(OH)2D] deficiency leads to the loss of mandibular bone, however the mechanism is unclear. We investigated whether the Sirt1/FOXO3a signaling pathway is involved in this process. Using a 1,25(OH)2D deficiency model induced by genetic deletion in mice of 25-hydroxyvitamin D-1α hydroxylase [1α(OH)ase-/- mice]. We first documented a sharp reduction of expression levels of Sirt1 in the 1α(OH)ase-/- mice in vivo. Next, we demonstrated dose-dependent upregulation of Sirt1 by treatment with exogenous 1,25(OH)2D3in vitro. We then identified a functional VDR binding site in the Sirt1 promoter. By crossing Prx1-Sirt1 transgenic mice with 1α(OH)ase-/- mice we demonstrated that the overexpression of Sirt1 in mesenchymal stem cells (MSCs) greatly improved the 1α(OH)ase-/- mandibular bone loss phenotype by increasing osteoblastic bone formation and reducing osteoclastic bone resorption. In mechanistic studies, we showed, in 1α(OH)ase-/- mice, decreases of Sirt1 and FoxO3a, an increase in oxidative stress as reflected by a reduction of the antioxidant enzymes peroxiredoxin1 (Prdx1), SOD1 and SOD2 expression, and an increase of markers for osteocyte senescence and senescence associated secretory phenotypes (SASP), including β-galactosidase (β-gal), p16, p53 and p21. The targeted overexpression of Sirt1 in the 1α(OH)ase-/- mice restored the expression levels of these molecules. Finally, we demonstrated that a Sirt1 agonist can upregulate FOXO3a activity by increasing deacetylation and nuclear translocation. Overall, results from this study support the concept that targeted increases in Sirt1/FOXO3a signaling levels can greatly improve the bone loss caused by 1,25(OH)2D deficiency.

Peroxisome Proliferator-Activated Receptors and Caloric Restriction-Common Pathways Affecting Metabolism, Health, and Longevity

Caloric restriction (CR) is a traditional but scientifically verified approach to promoting health and increasing lifespan. CR exerts its effects through multiple molecular pathways that trigger major metabolic adaptations. It influences key nutrient and energy-sensing pathways including mammalian target of rapamycin, Sirtuin 1, AMP-activated protein kinase, and insulin signaling, ultimately resulting in reductions in basic metabolic rate, inflammation, and oxidative stress, as well as increased autophagy and mitochondrial efficiency. CR shares multiple overlapping pathways with peroxisome proliferator-activated receptors (PPARs), particularly in energy metabolism and inflammation. Consequently, several lines of evidence suggest that PPARs might be indispensable for beneficial outcomes related to CR. In this review, we present the available evidence for the interconnection between CR and PPARs, highlighting their shared pathways and analyzing their interaction. We also discuss the possible contributions of PPARs to the effects of CR on whole organism outcomes.

Sirtuin 1 deficiency decreases bone mass and increases bone marrow adiposity in a mouse model of chronic energy deficiency

Sirtuin of type 1 (Sirt1), a class III HDAC, is known to be involved in the regulation of differentiation of skeletal stem cells (SSCs) into osteoblasts and adipocytes. In caloric restriction, it has been shown that the expression and activity of Sirt1 is a tissue-dependent regulation. However, at present, no study has focused on the link between Sirt1, bone marrow adiposity (BMA) and osteoporosis related to anorexia nervosa (AN). Thus, the aims of this work were to (i) determine BMA and bone changes in a mouse model replicating the phenotypes of AN (separation-based anorexia model (SBA)); (ii) determine the expression of Sirt1 in bone marrow stromal cells (BMSCs) extracted from these mice and identify their differentiation capacities; (iii) study the effects of pharmacological activation and inhibition of Sirt1 on the osteoblastogenesis and adipogenesis of these cells and (iiii) delineate the molecular mechanism by which Sirt1 could regulate osteogenesis in an SBA model. Our results demonstrated that SBA protocol induces an increase in BMA and alteration of bone architecture. In addition, BMSCs from restricted mice present a down-regulation of Sirt1 which is accompanied by an increase in adipogenesis at expense of osteogenesis. After a 10-day organotypic culture, tibias from SBA mice displayed low levels of Sirt1 mRNA which are restored by resveratrol treatment. Interestingly, this recovery of Sirt1 levels also returned the BMA, BV/TV and Tb.Th in cultured tibias from SBA mice to normal levels. In contrast of down-regulation of Sirt1 expression induced by sirtinol treatment, stimulation of Sirt1 expression by resveratrol lead to a decrease in adipogenesis and increase in osteogenesis. Finally, to investigate the molecular mechanisms by which Sirt1 could regulate osteogenesis in the SBA model, the acetylation levels of Runx2 and Foxo1 transcription factors were determined. Our data show that this chronic energy deficiency in female mice causes a decrease in BMSC activity, resulting in critical changes to Runx2 and Foxo1 acetylation levels and thus to their activity. Altogether, these data suggest that Sirt1 could be considered as a potential therapeutic target in osteoporosis related to AN.

Lifelong SIRT-1 overexpression attenuates large artery stiffening with advancing age

Advanced age is accompanied by aortic stiffening that is associated with decreased vascular expression of sirtuin-1 (SIRT-1). Interventions that increase SIRT-1 expression also lower age-related aortic stiffness. Therefore, we sought to determine if lifelong SIRT-1 overexpression would attenuate age-related aortic stiffening. Aortic pulse wave velocity (PWV) was assessed from 3-24 months in SIRT-1 transgenic overexpressing (SIRTTG) and wild-type (WT) mice. To determine the role of aortic structural changes on aortic stiffening, histological assessment of aortic wall characteristics was performed. Across the age range (3-24 mo), PWV was 8-17% lower in SIRTTG vs. WT (P<0.05). Moreover, the slope of age-related aortic stiffening was lower in SIRTTG vs. WT (2.1±0.2 vs. 3.8±0.3 cm/sec/mo, respectively). Aortic elastin decreased with advancing age in WT (P<0.05 old vs. young WT), but was maintained in SIRTTG mice (P>0.05). There was an age-related increase in aortic collagen, advanced glycation end products, and calcification in WT (P<0.05 old vs. young WT). However, this did not occur in SIRTTG (P>0.05). These findings indicate that lifelong SIRT-1 overexpression attenuates age-related aortic stiffening. These functional data are complemented by histological assessment, demonstrating that the deleterious changes to the aortic wall that normally occur with advancing age are prevented in SIRTTG mice.

The Peroxisome Proliferator-Activated Receptor-Gamma Coactivator-1α-Heme Oxygenase 1 Axis, a Powerful Antioxidative Pathway with Potential to Attenuate Diabetic Cardiomyopathy

Significance: From studies of diabetic animal models, the downregulation of peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α)-heme oxygenase 1 (HO-1) axis appears to be a crucial event in the development of obesity and diabetic cardiomyopathy (DCM). In this review, we discuss the role of metabolic and biochemical stressors in the rodent and human pathophysiology of DCM. A crucial contributor for many cardiac pathologies is excessive production of reactive oxygen species (ROS) pathologies, which lead to extensive cellular damage by impairing mitochondrial function and directly oxidizing DNA, proteins, and lipid membranes. We discuss the role of ROS production and inflammatory pathways with multiple contributing and confounding factors leading to DCM. Recent Advances: The relevant biochemical pathways that are critical to a therapeutic approach to treat DCM, specifically caloric restriction and its relation to the PGC-1α-HO-1 axis in the attenuation of DCM, are elucidated. Critical Issues: The increased prevalence of diabetes mellitus type 2, a major contributor to unique cardiomyopathy characterized by cardiomyocyte hypertrophy with no effective clinical treatment. This review highlights the role of mitochondrial dysfunction in the development of DCM and potential oxidative targets to attenuate oxidative stress and attenuate DCM. Future Directions: Targeting the PGC-1α-HO-1 axis is a promising approach to ameliorate DCM through improvement in mitochondrial function and antioxidant defenses. A pharmacological inducer to activate PGC-1α and HO-1 described in this review may be a promising therapeutic approach in the clinical setting.

The Role of Vascular Aging in Atherosclerotic Plaque Development and Vulnerability

BACKGROUND

The ongoing demographical shift is leading to an unprecedented aging of the population. As a consequence, the prevalence of age-related diseases, such as atherosclerosis and its thrombotic complications is set to increase in the near future. Endothelial dysfunction and vascular stiffening characterize arterial aging and set the stage for the development of cardiovascular diseases. Atherosclerotic plaques evolve over time, the extent to which these changes might affect their stability and predispose to sudden complications remains to be determined. Recent advances in imaging technology will allow for longitudinal prospective studies following the progression of plaque burden aimed at better characterizing changes over time associated with plaque stability or rupture. Oxidative stress and inflammation, firmly established driving forces of age-related CV dysfunction, also play an important role in atherosclerotic plaque destabilization and rupture. Several genes involved in lifespan determination are known regulator of redox cellular balance and pre-clinical evidence underlines their pathophysiological roles in age-related cardiovascular dysfunction and atherosclerosis.

OBJECTIVE

The aim of this narrative review is to examine the impact of aging on arterial function and atherosclerotic plaque development. Furthermore, we report how molecular mechanisms of vascular aging might regulate age-related plaque modifications and how this may help to identify novel therapeutic targets to attenuate the increased risk of CV disease in elderly people.

Therapeutic potential of nicotinamide adenine dinucleotide (NAD)

Nicotinamide adenine nucleotide (NAD) is a small ubiquitous hydrophilic cofactor that participates in several aspects of cellular metabolism. As a coenzyme it has an essential role in the regulation of energetic metabolism, but it is also a cosubstrate for enzymes that regulate fundamental biological processes such as transcriptional regulation, signaling and DNA repairing among others. The fluctuation and oxidative state of NAD levels regulate the activity of these enzymes, which is translated into marked effects on cellular function. While alterations in NAD homeostasis are a common feature of different conditions and age-associated diseases, in general, increased NAD levels have been associated with beneficial health effects. Due to its therapeutic potential, the interest in this molecule has been renewed, and the regulation of NAD metabolism has become an attractive target for drug discovery. In fact, different approaches to replenish or increase NAD levels have been tested, including enhancement of biosynthesis and inhibition of NAD breakdown. Despite further research is needed, this review provides an overview and update on NAD metabolism, including the therapeutic potential of its regulation, as well as pharmacokinetics, safety, precautions and formulation challenges of NAD supplementation.

Spatiotemporal gating of SIRT1 functions by O-GlcNAcylation is essential for liver metabolic switching and prevents hyperglycemia

Inefficient physiological transitions are known to cause metabolic disorders. Therefore, investigating mechanisms that constitute molecular switches in a central metabolic organ like the liver becomes crucial. Specifically, upstream mechanisms that control temporal engagement of transcription factors, which are essential to mediate physiological fed-fast-refed transitions are less understood. SIRT1, a NAD⁺-dependent deacetylase, is pivotal in regulating hepatic gene expression and has emerged as a key therapeutic target. Despite this, if/how nutrient inputs regulate SIRT1 interactions, stability, and therefore downstream functions are still unknown. Here, we establish nutrient-dependent O-GlcNAcylation of SIRT1, within its N-terminal domain, as a crucial determinant of hepatic functions. Our findings demonstrate that during a fasted-to-refed transition, glycosylation of SIRT1 modulates its interactions with various transcription factors and a nodal cytosolic kinase involved in insulin signaling. Moreover, sustained glycosylation in the fed state causes nuclear exclusion and cytosolic ubiquitin-mediated degradation of SIRT1. This mechanism exerts spatiotemporal control over SIRT1 functions by constituting a previously unknown molecular relay. Of note, loss of SIRT1 glycosylation discomposed these interactions resulting in aberrant gene expression, mitochondrial dysfunctions, and enhanced hepatic gluconeogenesis. Expression of nonglycosylatable SIRT1 in the liver abrogated metabolic flexibility, resulting in systemic insulin resistance, hyperglycemia, and hepatic inflammation, highlighting the physiological costs associated with its overactivation. Conversely, our study also reveals that hyperglycosylation of SIRT1 is associated with aging and high-fat-induced obesity. Thus, we establish that nutrient-dependent glycosylation of SIRT1 is essential to gate its functions and maintain physiological fitness.

Age and sex as confounding factors in the relationship between cardiac mitochondrial function and type 2 diabetes in the Nile Grass rat

Our study revisits the role of cardiac mitochondrial adjustments during the progression of type 2 diabetes mellitus (T2DM), while considering age and sex as potential confounding factors. We used the Nile Grass rats (NRs) as the animal model. After weaning, animals were fed either a Standard Rodent Chow Diet (SRCD group) or a Mazuri Chinchilla Diet (MCD group) consisting of high-fiber and low-fat content. Both males and females in the SRCD group, exhibited increased body mass, body mass index, and plasma insulin compared to the MCD group animals. However, the females were able to preserve their fasting blood glucose throughout the age range on both diets, while the males showed significant hyperglycemia starting at 6 months in the SRCD group. In the males, a higher citrate synthase activity-a marker of mitochondrial content-was measured at 2 months in the SRCD compared to the MCD group, and this was followed by a decline with age in the SRCD group only. In contrast, females preserved their mitochondrial content throughout the age range. In the males exclusively, the complex IV capacity expressed independently of mitochondrial content varied with age in a diet-specific pattern; the capacity was elevated at 2 months in the SRCD group, and at 6 months in the MCD group. In addition, females, but not males, were able to adjust their capacity to oxidize long-chain fatty acid in accordance with the fat content of the diet. Our results show clear sexual dimorphism in the variation of mitochondrial content and oxidative phosphorylation capacity with diet and age. The SRCD not only leads to T2DM but also exacerbates age-related cardiac mitochondrial defects. These observations, specific to male NRs, might reflect deleterious dietary-induced changes on their metabolism making them more prone to the cardiovascular consequences of aging and T2DM.

An insulin-inducible transcription factor, SHARP-1, represses transcription of the SIRT1 longevity gene

The rat enhancer of split- and hairy-related protein (SHARP)-1 genes encode insulin-inducible transcriptional repressors. A longevity gene, sirtuin 1 (SIRT1) encodes protein deacetylase. These play an important role in regulating hepatic glucose metabolism. In this study, to evaluate a correlation with these gene expressions, we examined whether SIRT1 effects on expression of the SHARP-1 gene by a treatment with a SIRT1 inhibitor or activator in rat H4IIE hepatoma cells. Whereas the SIRT1 inhibitor increased the level of SHARP-1 mRNA, the SIRT1 activator decreased it. Next, whether SHARP-1 effect on the transcriptional activity of the human SIRT1 gene using luciferase reporter assays was determined. Promoter activity of the SIRT1 gene was specifically repressed by SHARP-1. Further reporter analysis using 5'- deleted or mutated constructs revealed that an E box sequence (5'-CACGTG-3') of the SIRT1 gene promoter was required for the inhibitory effect of SHARP-1. Thus, we conclude that expressions between the SHARP-1 and the SIRT1 genes show a negative correlation and that SHARP-1 represses transcription of the SIRT1 gene.

The ageing epigenome and its rejuvenation

Ageing is characterized by the functional decline of tissues and organs and the increased risk of ageing-associated disorders. Several 'rejuvenating' interventions have been proposed to delay ageing and the onset of age-associated decline and disease to extend healthspan and lifespan. These interventions include metabolic manipulation, partial reprogramming, heterochronic parabiosis, pharmaceutical administration and senescent cell ablation. As the ageing process is associated with altered epigenetic mechanisms of gene regulation, such as DNA methylation, histone modification and chromatin remodelling, and non-coding RNAs, the manipulation of these mechanisms is central to the effectiveness of age-delaying interventions. This Review discusses the epigenetic changes that occur during ageing and the rapidly increasing knowledge of how these epigenetic mechanisms have an effect on healthspan and lifespan extension, and outlines questions to guide future research on interventions to rejuvenate the epigenome and delay ageing processes.

Long-term caloric restriction activates the myocardial SIRT1/AMPK/PGC-1α pathway in C57BL/6J male mice

Background

Caloric restriction (CR) can help in improving heart function. There is as yet no consensus on the mechanism of the effect of CR. Silent mating-type information regulation 1 (SIRT1), adenosine monophosphate-activated protein kinase (AMPK), and mTOR are key players in metabolic stress management. We aimed to explore the effect of CR on the myocardial SIRT1/AMPK/mTOR pathway in mice.

Methods

Thirty-six 6-week-old male C57BL/6J mice were randomly divided into three groups: normal control group (NC group, n = 12), high-energy group (HE group, n = 12) and CR group (n = 12) according to different diets. After 11 months, western blot was used to examine proteins such as p-AMPK, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), SIRT1, and p-mTOR, whereas real-time PCR was used to examine the expression of AMPK, PGC-1α, and SIRT1 transcripts.

Results

Compared to the HE group, the CR group displayed increased expression of myocardial p-AMPK protein, SIRT1 protein and mRNA, and PGC-1a mRNA. However, no difference was observed in the expression of p-mTOR protein and mTOR mRNA in the myocardium among the three groups.

Conclusions

CR improves the SIRT1/AMPK/PGC-1α pathway in mice myocardium with no effect on the mTOR pathway.

Two novel SIRT1 activators, SCIC2 and SCIC2.1, enhance SIRT1-mediated effects in stress response and senescence

SIRT1, a NAD⁺-dependent deacetylase, is the most well-studied member of class III histone deacetylases. Due to its wide range of activities and substrate targets, this enzyme has emerged as a major regulator of different physiological processes. However, SIRT1-mediated alterations are also implicated in the pathogenesis of several conditions, including metabolic and neurodegenerative disorders, and cancer. Current evidence highlights the potential role of SIRT1 as an attractive therapeutic target for disease prevention and treatment strategies, thus propelling the development of new pharmacological agents. By high-throughput screening of a large library of compounds, we identified SCIC2 as an effective SIRT1 activator. This small molecule showed enzymatic activity of 135.8% at 10 μM, an AC₅₀ value of 50 ± 1.8 µM, and bound SIRT1 with a K_D of 26.4 ± 0.6 μM. In order to potentiate its SIRT1-activating ability, SCIC2 was subjected to modelling studies, leading to the identification of a more potent derivative, SCIC2.1. SCIC2.1 displayed higher SIRT1 activity (175%; AC₅₀ = 36.83 ± 2.23 µM), stronger binding to SIRT1, and greater cell permeability than SCIC2. At cellular level, both molecules did not alter the cell cycle progression of cancer cells and normal cells, and were able to strengthen SIRT1-mediated effects in stress response. Finally, SCIC2 and SCIC2.1 attenuated induction of senescence by reducing senescence-associated β-galactosidase activity. Our findings warrant further investigation of these two novel SIRT1 activators in in vivo and human studies.

Metabolic Reprogramming and Signaling to Chromatin Modifications in Tumorigenesis

Cellular proliferation relies on a high energetic status, replenished through nutrient intake, that leads to the production of biosynthetic material. A communication between the energetic levels and the control of gene expression is essential to engage in cell division. Multiple nutrient and metabolic sensing mechanisms in cells control transcriptional responses through cell signaling cascades that activate specific transcription factors associated with a concomitant regulation of the chromatin state. In addition to this canonical axis, gene expression could be directly influenced by the fluctuation of specific key intermediary metabolites of central metabolic pathways which are also donors or cofactors of histone and DNA modifications. This alternative axis represents a more direct connection between nutrients and the epigenome function. Cancer cells are highly energetically demanding to sustain proliferation. To reach their energetic demands, cancer cells rewire metabolic pathways. Recent discoveries show that perturbations of metabolic pathways in cancer cells have a direct impact on the epigenome. In this chapter, the interaction between metabolic driven changes of transcriptional programs in the context of tumorigenesis will be discussed.

Lipid Droplet-Derived Monounsaturated Fatty Acids Traffic via PLIN5 to Allosterically Activate SIRT1

Lipid droplets (LDs) provide a reservoir for triacylglycerol storage and are a central hub for fatty acid trafficking and signaling in cells. Lipolysis promotes mitochondrial biogenesis and oxidative metabolism via a SIRT1/PGC-1α/PPARα-dependent pathway through an unknown mechanism. Herein, we identify that monounsaturated fatty acids (MUFAs) allosterically activate SIRT1 toward select peptide-substrates such as PGC-1α. MUFAs enhance PGC-1α/PPARα signaling and promote oxidative metabolism in cells and animal models in a SIRT1-dependent manner. Moreover, we characterize the LD protein perilipin 5 (PLIN5), which is known to enhance mitochondrial biogenesis and function, to be a fatty-acid-binding protein that preferentially binds LD-derived monounsaturated fatty acids and traffics them to the nucleus following cAMP/PKA-mediated lipolytic stimulation. Thus, these studies identify the first-known endogenous allosteric modulators of SIRT1 and characterize a LD-nuclear signaling axis that underlies the known metabolic benefits of MUFAs and PLIN5.

New Insights for Cellular and Molecular Mechanisms of Aging and Aging-Related Diseases: Herbal Medicine as Potential Therapeutic Approach

Aging is a progressive disease affecting around 900 million people worldwide, and in recent years, the mechanism of aging and aging-related diseases has been well studied. Treatments for aging-related diseases have also made progress. For the long-term treatment of aging-related diseases, herbal medicine is particularly suitable for drug discovery. In this review, we discuss cellular and molecular mechanisms of aging and aging-related diseases, including oxidative stress, inflammatory response, autophagy and exosome interactions, mitochondrial injury, and telomerase damage, and summarize commonly used herbals and compounds concerned with the development of aging-related diseases, including Ginkgo biloba, ginseng, Panax notoginseng, Radix astragali, Lycium barbarum, Rhodiola rosea, Angelica sinensis, Ligusticum chuanxiong, resveratrol, curcumin, and flavonoids. We also summarize key randomized controlled trials of herbal medicine for aging-related diseases during the past ten years. Adverse reactions of herbs were also described. It is expected to provide new insights for slowing aging and treating aging-related diseases with herbal medicine.

Protective effect of ganoderic acid against the streptozotocin induced diabetes, inflammation, hyperlipidemia and microbiota imbalance in diabetic rats

Diabetes mellitus (DM) is a metabolic disorder with numerous symptoms categorized via serves hyperglycemia effect along with altered fat, protein and carbohydrate metabolism mainly resultant from defects in insulin action/secretion or both. The aim of the current experimental study was to comfort the neuroprotective effect of ganoderic acid against the streptozotocin (STZ)-induced type I diabetes mellitus in mice and explore the underlying mechanism. Differentiation of 3T3-L1 preadipocytes effect; hepatic and glucose consumption effect of ganoderic acid was estimated on HepG2 cell lines and peroxisome proliferator-activated receptor (PPAR). FFA content was estimated in adipose and hepatic tissues. Ganoderic acid induced the 3T3-L1 preadipocytes differentiation. The mRNA expression of PPAR was increased in the high glucose-treated group in HepG2 and ganoderic acid treatment down-regulated the mRNA expression of PPAR. Ganoderic acid exhibited the inhibitory effect of α-glucosidase and α-amylase. Ganoderic acid demonstrated the reduced blood glucose and increase insulin level and also reduced the free fatty in hepatic and adipose tissue. Histopathological study showed the enhancement of β-cells in ganoderic acid-treated mice. Finally, their prebiotic effects on gut microbiota were illustrated via enhancing the population of diabetes resistant bacteria and also reducing the quantity of diabetes sensitive bacteria. Ganoderic acid attenuated STZ induced T1DM in mice via inflammatory pathways.

The Role of Signaling Pathways of Inflammation and Oxidative Stress in Development of Senescence and Aging Phenotypes in Cardiovascular Disease

The ASK1-signalosome→p38 MAPK and SAPK/JNK signaling networks promote senescence (in vitro) and aging (in vivo, animal models and human cohorts) in response to oxidative stress and inflammation. These networks contribute to the promotion of age-associated cardiovascular diseases of oxidative stress and inflammation. Furthermore, their inhibition delays the onset of these cardiovascular diseases as well as senescence and aging. In this review we focus on whether the (a) ASK1-signalosome, a major center of distribution of reactive oxygen species (ROS)-mediated stress signals, plays a role in the promotion of cardiovascular diseases of oxidative stress and inflammation; (b) The ASK1-signalosome links ROS signals generated by dysfunctional mitochondrial electron transport chain complexes to the p38 MAPK stress response pathway; (c) the pathway contributes to the sensitivity and vulnerability of aged tissues to diseases of oxidative stress; and (d) the importance of inhibitors of these pathways to the development of cardioprotection and pharmaceutical interventions. We propose that the ASK1-signalosome regulates the progression of cardiovascular diseases. The resultant attenuation of the physiological characteristics of cardiomyopathies and aging by inhibition of the ASK1-signalosome network lends support to this conclusion. Importantly the ROS-mediated activation of the ASK1-signalosome p38 MAPK pathway suggests it is a major center of dissemination of the ROS signals that promote senescence, aging and cardiovascular diseases. Pharmacological intervention is, therefore, feasible through the continued identification of potent, non-toxic small molecule inhibitors of either ASK1 or p38 MAPK activity. This is a fruitful future approach to the attenuation of physiological aspects of mammalian cardiomyopathies and aging.

Partially Hydrolyzed Guar Gum Attenuates d-Galactose-Induced Oxidative Stress and Restores Gut Microbiota in Rats

Partially hydrolyzed guar gum (PHGG) has received considerable attention for its various bioactive functions. The injection of d-galactose can cause aging-related injury which is usually resulted from oxidative stress on tissues and cells. In this study, d-galactose (200 mg/kg/day) was injected into rats, and the protective effects of PHGG (500, 1000, and 1500 mg/kg/day) against oxidative damages, as well as its probiotic functions, were analyzed. The results showed that PHGG treatment at a concentration of 1500 mg/kg/day greatly reduced the levels of lactic acid, nitric oxide, inducible nitric oxide synthase, advanced glycation end products, and increased the telomerase activity, by 7.60%, 9.25%, 12.28%, 14.58%, and 9.01%, respectively. Moreover, PHGG significantly elevated the activities of antioxidant enzymes and decreased the content of malondialdehyde in rat serum and brain. The oxidative damage was also significantly alleviated in the liver and hippocampus and the expressions of brain-derived neurotrophic factor and choline acetyltransferase also increased. Furthermore, PHGG treatment could significantly regulated the expression of sirtuin 1, forkhead box O1, and tumor protein p53 in the hippocampus. It also increased the levels of organic acids and improved the composition of intestinal microbiota. These findings demonstrated that PHGG treatment could effectively alleviate the oxidative damage and dysbacteriosis.

Sirtuins and NAD+ in the Development and Treatment of Metabolic and Cardiovascular Diseases

The sirtuin family of nicotinamide adenine dinucleotide-dependent deacylases (SIRT1-7) are thought to be responsible, in large part, for the cardiometabolic benefits of lean diets and exercise and when upregulated can delay key aspects of aging. SIRT1, for example, protects against a decline in vascular endothelial function, metabolic syndrome, ischemia-reperfusion injury, obesity, and cardiomyopathy, and SIRT3 is protective against dyslipidemia and ischemia-reperfusion injury. With increasing age, however, nicotinamide adenine dinucleotide levels and sirtuin activity steadily decrease, and the decline is further exacerbated by obesity and sedentary lifestyles. Activation of sirtuins or nicotinamide adenine dinucleotide repletion induces angiogenesis, insulin sensitivity, and other health benefits in a wide range of age-related cardiovascular and metabolic disease models. Human clinical trials testing agents that activate SIRT1 or boost nicotinamide adenine dinucleotide levels are in progress and show promise in their ability to improve the health of cardiovascular and metabolic disease patients.

SIRT1 in the Development and Treatment of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Current treatment options for inoperable HCCs have decreased therapeutic efficacy and are associated with systemic toxicity and chemoresistance. Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide–dependent enzyme that is frequently overexpressed in HCC, where it promotes tumorigenicity, metastasis, and chemoresistance. SIRT1 also maintains the tumorigenic and self-renewal proprieties of liver cancer stem cells. Multiple tumor-suppressive microRNAs (miRNAs) are downregulated in HCC and, as a consequence, permit SIRT1-induced tumorigenicity. However, either directly targeting SIRT1, combining conventional chemotherapy with SIRT1 inhibitors, or upregulating tumor-suppressive miRNAs may improve therapeutic efficacy and patient outcomes. Here, we present the interaction between SIRT1, miRNAs, and liver cancer stem cells and discuss the consequences of their interplay for the development and treatment of HCC.

Nicotinamide and NAFLD: Is There Nothing New Under the Sun?

Nicotinamide adenine dinucleotide (NAD) has a critical role in cellular metabolism and energy homeostasis. Its importance has been established early with the discovery of NAD's therapeutic role for pellagra. This review addresses some of the recent findings on NAD physiopathology and their effects on nonalcoholic fatty liver disease (NAFLD) pathogenesis, which need to be considered in the search for a better therapeutic approach. Reduced NAD concentrations contribute to the dysmetabolic imbalance and consequently to the pathogenesis of NAFLD. In this perspective, the dietary supplementation or the pharmacological modulation of NAD levels appear to be an attractive strategy. These reviewed studies open the doors to growing interest in NAD metabolism for NAFLD diagnosis, prevention, and treatment. Future rigorous clinical studies in humans will be necessary to validate these preliminary but promising results.

Toward a unified theory of aging and regeneration

Growing evidence supports the antagonistic pleiotropy theory of mammalian aging. Accordingly, changes in gene expression following the pluripotency transition, and subsequent transitions such as the embryonic–fetal transition, while providing tumor suppressive and antiviral survival benefits also result in a loss of regenerative potential leading to age-related fibrosis and degenerative diseases. However, reprogramming somatic cells to pluripotency demonstrates the possibility of restoring telomerase and embryonic regeneration pathways and thus reversing the age-related decline in regenerative capacity. A unified model of aging and loss of regenerative potential is emerging that may ultimately be translated into new therapeutic approaches for establishing induced tissue regeneration and modulation of the embryo-onco phenotype of cancer.

High Fructose Intake and Adipogenesis

In modern societies, high fructose intake from sugar-sweetened beverages has contributed to obesity development. In the diet, sucrose and high fructose corn syrup are the main sources of fructose and can be metabolized in the intestine and transported into the systemic circulation. The liver can metabolize around 70% of fructose intake, while the remaining is metabolized by other tissues. Several tissues including adipose tissue express the main fructose transporter GLUT5. In vivo, chronic fructose intake promotes white adipose tissue accumulation through activating adipogenesis. In vitro experiments have also demonstrated that fructose alone induces adipogenesis by several mechanisms, including (1) triglycerides and very-low-density lipoprotein (VLDL) production by fructose metabolism, (2) the stimulation of glucocorticoid activation by increasing 11β-HSD1 activity, and (3) the promotion of reactive oxygen species (ROS) production through uric acid, NOX and XOR expression, mTORC1 signaling and Ang II induction. Moreover, it has been observed that fructose induces adipogenesis through increased ACE2 expression, which promotes high Ang-(1-7) levels, and through the inhibition of the thermogenic program by regulating Sirt1 and UCP1. Finally, microRNAs may also be involved in regulating adipogenesis in high fructose intake conditions. In this paper, we propose further directions for research in fructose participation in adipogenesis.

Sirt1 Promotes Osteogenic Differentiation and Increases Alveolar Bone Mass via Bmi1 Activation in Mice

Sirtuin 1 (Sirt1), a protein deacetylase, is a novel target for bone metabolism. To investigate whether overexpression of Sirt1 in mandibular mesenchymal stem cells (M-MSCs) increased alveolar bone mass in vivo, we generated Sirt1 transgenic mice (Sirt1^TG ), with Sirt1 gene expression driven by the Prx1 gene, which represents the mesenchymal lineage. Our results demonstrated that overexpression of Sirt1 in M-MSCs increased the alveolar bone volume in 1-month-old, 9-month-old, and 18-month-old Sirt1^TG mice compared with age-matched wild-type (WT) mice, and in ovariectomized Sirt1^TG mice compared with ovariectomized WT mice by stimulating M-MSC differentiation into osteoblasts. Treatment with resveratrol, a Sirt1 activator, increased Sirt1 binding with Bmi1 and reduced Bmi1 acetylation in a dose-dependent manner demonstrated in M-MSC cultures. Both treatment with resveratrol in M-MSC cultures and overexpressed Sirt1 in M-MSCs ex vivo cultures increased nuclear translocation of Bmi1. Furthermore, we demonstrated that deletion of Bmi1 blocked the increased alveolar bone volume in Sirt1^TG mice. The Sirt1 activator resveratrol inhibited human MSC senescence and promoted their differentiation into osteoblasts, which were associated with upregulating the expression levels of Sirt1 and nuclear translocation of Bmi1. The present results suggested that Sirt1 promotes MSC proliferation and osteogenic differentiation, inhibits MSC senescence to increase alveolar bone volume by promoting the deacetylation and nuclear translocation of Bmi1. Thus, our study elucidated the mechanism by which Sirt1 increases alveolar bone mass, and these findings are important for the clinical application of the Sirt1 activator resveratrol for the promotion of alveolar bone formation and prevention of alveolar bone loss. © 2019 American Society for Bone and Mineral Research.

Metformin-induced autophagy and irisin improves INS-1 cell function and survival in high-glucose environment via AMPK/SIRT1/PGC-1α signal pathway

In order to explore the protective function of metformin on pancreatic β cells to alleviate insulin resistance and underlying mechanisms, INS-1 cells were cultured into normal control (N), high glucose (H), high glucose and metformin (H + Met), high glucose and chloroquine (H + CQ), and high glucose and Ex527 (H + Ex527) groups, respectively. Upon 24-hr cultivation, the proliferation and glucose-stimulated insulin secretion (GSIS) of INS-1 cells were determined, and the expression of irisin and other proteins associated with AMPK/SIRT1/PGC-1α signal pathway, autophagy, and apoptosis was evaluated. Compared with the N group, the cells from the H group revealed lower proliferation, GSIS, and expression of irisin and proteins associated with AMPK/SIRT1/PGC-1α signal pathway and autophagy, but higher expression of proteins associated with apoptosis; in contrast, metformin could significantly rescue lower cell proliferation, GSIS, and expression of proteins associated with AMPK/SIRT1/PGC-1α signal pathway and autophagy, as well as irisin, and suppress apoptosis in high-glucose environment. Meanwhile, autophagy inhibitor CQ and SIRT1 inhibitor Ex527 can block above functions of metformin. Therefore, metformin can promote INS-1 cell proliferation, enhance GSIS, and suppress apoptosis by activating AMPK/SIRT1/PGC-1α signal pathway, up-regulating irisin expression, and inducing autophagy in INS-1 cells in high-glucose environment.

Hepatic arginase 2 (Arg2) is sufficient to convey the therapeutic metabolic effects of fasting

Caloric restriction and intermittent fasting are emerging therapeutic strategies against obesity, insulin resistance and their complications. However, the effectors that drive this response are not completely defined. Here we identify arginase 2 (Arg2) as a fasting-induced hepatocyte factor that protects against hepatic and peripheral fat accumulation, hepatic inflammatory responses, and insulin and glucose intolerance in obese murine models. Arg2 is upregulated in fasting conditions and upon treatment with the hepatocyte glucose transporter inhibitor trehalose. Hepatocyte-specific Arg2 overexpression enhances basal thermogenesis, and protects from weight gain, insulin resistance, glucose intolerance, hepatic steatosis and hepatic inflammation in diabetic mouse models. Arg2 suppresses expression of the regulator of G-protein signalling (RGS) 16, and genetic RGS16 reconstitution reverses the effects of Arg2 overexpression. We conclude that hepatocyte Arg2 is a critical effector of the hepatic glucose fasting response and define a therapeutic target to mitigate the complications of obesity and non-alcoholic fatty liver disease.

Fasting is known for its beneficial effects on obesity and diabetes-related health complications. Here Zhang et al. show that fasting induces expression of arginase-2 (Arg2) in the liver, and that hepatic Arg2, by suppressing the expression of the regulator of G-protein signalling 16, recapitulates the positive effects of fasting in obesity and diabetes.

Aldosterone Modulates the Mechanistic Target of Rapamycin Signaling in Male Mice

Both mechanistic target of rapamycin (mTOR) pathway and aldosterone are implicated in the development of cardiovascular and renal disease. However, the interaction between aldosterone and the mTOR pathway is unknown. We hypothesized the following: that (i) increased aldosterone will modulate the activity of the mTORC1 and mTORC2 molecular pathways in the heart and kidney; (ii) a physiologic increase in aldosterone will affect these pathways differently than a pathophysiologic one; and (iii) the changes in the mTOR level/activity will differ between the heart and kidney. In both kidney and heart tissues, phosphorylation of mTOR is significantly decreased when aldosterone levels are physiologically increased (by dietary sodium restriction), followed by a decrease in phosphorylated p70S6K1 in cardiac, but not renal, tissue. Sirtuin 1, an epigenetic modulator, is decreased in the heart but increased in the kidney. Conversely, pathophysiologic aldosterone levels (an infusion for 3 weeks) had divergent effects on phosphorylated mTOR and the downstream substrates of mTORC1 and mTORC2 in cardiac and renal tissues. Increased aldosterone levels significantly alter mTOR activity in the heart and kidney. In the kidney, substantial differences were noted if the increase was produced physiologically vs pathophysiologically, suggesting that mTOR activity, in part, may mediate aldosterone-induced renal damage. Thus, modulating mTOR activity may reduce aldosterone-dependent renal damage similar to mineralocorticoid receptor blockade but potentially with less adverse side effects.

Pharmacologic or genetic activation of SIRT1 attenuates the fat-induced decrease in beta-cell function in vivo

Background

There is evidence that sirtuin 1 (SIRT1), a key regulator of nutrient metabolism, increases β-cell secretory function. Excess circulating fat, as seen in obesity, has been shown to decrease β-cell function, an effect that may involve decreased SIRT1 activity. Consequently, SIRT1 activation may increase β-cell function in conditions of elevated plasma-free fatty acid levels. Here we attempted to attenuate the lipid-induced decrease in β-cell function in vivo using pharmacological and genetic models of SIRT1 activation.

Methods

Our pharmacologic model involved 48 h intravenous infusion of Wistar rats with either saline or oleate with or without the SIRT1 activator resveratrol. Additionally, we used β-cell-specific SIRT1 overexpressing (BESTO) mice and wild-type littermates infused for 48 h intravenously with either saline or oleate. In both models, the infusion period was followed by assessment of β-cell function using the hyperglycemic clamp method.

Results

Lipid infusion resulted in a significant decrease in β-cell function as expected in both rats (p < 0.05) and mice (p < 0.001). Both models of SIRT1 activation, which did not alter β-cell function in the absence of fat, resulted in partial protection from the fat-induced decrease in β-cell function (NS vs. control).

Conclusion

These results suggest that SIRT1 is a therapeutic target in decreased β-cell function specifically induced by fat.

Drugs targeting SIRT1, a new generation of therapeutics for osteoporosis and other bone related disorders?

With an aging population and limited treatment options, osteoporosis currently represents a significant public health challenge. Recent animal studies indicate that longevity-associated SIRT1 may serve as an attractive pharmacological target for the treatment of osteoporosis and other bone related disorders. Pre-clinical studies demonstrate that mice treated with SIRT1 agonists show protection against age-related, post-menopausal, and disuse models of osteoporosis. Conversely, SIRT1 knockout models display low bone mass phenotypes associated with increased bone resorption and decreased bone formation. This review summarizes recent animal and human experimental data showing that pharmacological activation of SIRT1 may act in a manner that current treatments do not, namely by treating the imbalance in bone remodeling that is the root cause of osteoporosis and other bone disorders.

Improved mass spectrometry-based activity assay reveals oxidative and metabolic stress as sirtuin-1 regulators

Sirtuin-1 (SirT1) catalyzes NAD⁺-dependent protein lysine deacetylation and is a critical regulator of energy and lipid metabolism, mitochondrial biogenesis, apoptosis, and senescence. Activation of SirT1 mitigates metabolic perturbations associated with diabetes and obesity. Pharmacologic molecules, cellular redox, and nutritional states can regulate SirT1 activity.

Technical barriers against measuring endogenous SirT1 activity have limited characterization of SirT1 in disease and its activation by small molecules. Herein, we developed a relative quantitative mass spectrometry-based technique for measuring endogenous SirT1 activity (RAMSSAY/RelAtive Mass Spectrometry Sirt1 Activity assaY) in cell and tissue homogenates using a biotin-labeled, acetylated p53-derived peptide as a substrate.

We demonstrate that oxidative and metabolic stress diminish SirT1 activity in the hepatic cell line HepG2. Moreover, pharmacologic molecules including nicotinamide and EX-527 attenuate SirT1 activity; purported activators of SirT1, the polyphenol S17834, the polyphenol resveratrol, or the non-polyphenolic Sirtris compound SRT1720, failed to activate endogenous SirT1 significantly. Furthermore, we provide evidence that feeding a high fat high sucrose diet (HFHS) to mice inhibits endogenous SirT1 activity in mouse liver.

In summary, we introduce a robust, specific and sensitive mass spectrometry-based assay for detecting and quantifying endogenous SirT1 activity using a biotin-labeled peptide in cell and tissue lysates. With this assay, we determine how pharmacologic molecules and metabolic and oxidative stress regulate endogenous SirT1 activity. The assay may also be adapted for other sirtuin isoforms.

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Fast, sensitive, and specific MALDI-TOF based sirtuin-1 activity assay applicable to cell and tissue lysates.

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Oxidative and metabolic stress inhibit Sirtuin-1 deacetylase activity.

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Purported activators of SirT1failed to significantly activate endogenous SirT1.

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The activity assay is adaptable to other sirtuin isoforms using specific synthetic peptides and assay conditions.

SIRT1 knock-in mice preserve ovarian reserve resembling caloric restriction

Previous studies have proposed that caloric restriction (CR) regulates many cell functions and prolongs the lifespan of an organism. Our previous studies proposed that CR also prevents follicular activation and preserves the ovarian reserve in mice by activating SIRT1. To test if SIRT1 preserves the ovarian reserve and prolongs the ovarian longevity, we generated SIRT1 knock-in mice that can overexpress SIRT1 in oocytes of the mouse. Ovaries of the mice at ages 35 days and 15 months were collected, and the follicular development and follicular reserve were examined. The vaginal opening and onset of estrus of transgenic female mice (both the homozygous and heterozygous for SIRT1 overexpression) were later than that of wild-type mice. Both the homozygous and heterozygous SIRT1-overexpressing mice had a larger and stronger reproductive capacity than wild-type mice. Moreover, 35-day-old and 15-month-old homozygous and heterozygous SIRT1-overexpressing mice also had a higher mean number and percentage of healthy follicles, fewer atretic follicles than wild-type mice, and the mean number and percentage of primordial follicles in both the homozygous and heterozygous SIRT1-overexpressing mice were higher than wild-type mice at the same age. However, the phenotypes of heterozygous and homozygous transgenic mice came no difference. Immunohistochemistry showed increased expression of SIRT1 and FOXO3a, and decreased expression of mTOR in both the homozygous and heterozygous SIRT1-overexpressing mice compared with wild-type mice. Thus, oocyte-specific SIRT1-overexpressing mice continuously activate FOXO3a and suppress mTOR and have a larger reproductive capacity, larger follicle reserve and longer ovarian lifespan.