Sestrins in Physiological Stress Responses

Maternal serum interleukin-1β, FoxO1 and Sestrin2 levels in predicting preterm delivery

The study aimed to investigate whether serum IL-1β, FoxO1and Sesn2 concentrations differed between threatened preterm labor (TPL) and uncomplicated pregnancies. This study was conducted on 54 women with TPL pregnancies and 26 healthy pregnant women. The TPL group was further divided into two subgroups according to the gestational age at delivery. Patients who gave birth within 48-72 hours after the hospitalization were referred to as preterm delivery (PD) and those who gave birth at ≥37 weeks were referred to as term delivery (TD). Maternal levels of serum IL-1β, FoxO1 and Sesn2 were measured with the use of enzyme-linked immunosorbent assay kits. The mean maternal serum IL-1β and FoxO1 of PD were significantly higher than TD (p<.000*) and the control group (p < .000*). The mean maternal serum IL-1β, FoxO1 level of TD was significantly higher than the control group (p<.000*). The mean maternal serum Sesn2 levels of TD and the control group were significantly higher than the preterm group (p<.000*). The mean maternal serum Sesn2 level of the control group was significantly higher than the TD group (p <.000*). A negative correlation was found between serum concentration of serum IL-1β, and FoxO1 with the gestational week of delivery (r= -0.722, p< .000*for, IL-1β; r = -0.625, p < .000* for FoxO1). A positive correlation was found between the serum concentration of serum Sesn2 with the gestational week of delivery (r = 0.507, p<.000* for sesn2). High serum IL-1β, FoxO1 levels, and low Sesn2 levels may have the potential to be used as biomarkers for the differentiation of PD and TD.

Sestrin2 in POMC neurons modulates energy balance and obesity related metabolic disorders via mTOR signaling

Sestrin2 is a highly conserved protein that can be induced under various stress conditions. Researches have revealed that the signaling pathway of the mammalian target of rapamycin (mTOR) is essential in modulating both glucose and lipid metabolism. However, the precise involvement of Sestrin2 in the hypothalamus, particularly in pro-opiomelanocortin (POMC) neurons, in control of energy homeostasis remains uncertain. In this study, we aimed to investigate the functional role of Sestrin2 in hypothalamic POMC neurons in regulation of energy balance, as well as revealing the underlying mechanisms. Therefore, cre-dependent AAV virus encoding or silencing Sestrin2 was injected into the hypothalamic ARC of pomc-cre transgenic mice. The results demonstrated that Sestrin2 overexpression in POMC neurons ameliorated high-fat diet (HFD)-induced obesity and increased energy expenditure. Conversely, Sestrin2 deficiency in POMC neurons predisposed mice to HFD induced obesity. Additionally, the thermogenesis of brown adipose tissue and lipolysis of inguinal white adipose tissue were both enhanced by the increased sympathetic nerve innervation in Sestrin2 overexpressed mice. Further exploration revealed that Sestrin2 overexpression inhibited the mTOR signaling pathway in hypothalamic POMC neurons, which may account for the alleviation of systematic metabolic disturbance induced by HFD in these mice. Collectively, our findings demonstrate that Sestrin2 in POMC neurons plays a pivotal role in maintaining energy balance in a context of HFD-induced obesity by inhibiting the mTOR pathway, providing new insights into how hypothalamic neurons respond to nutritional signals to protect against obesity-associated metabolic dysfunction.

Interventions of sestrin proteins: Insights to clinical therapy

Sestrin proteins, conserved family proteins which mainly induced by ROS, DNA damage, inflammation, and other injuries. Growing evidences proved sestrin proteins exert protective functions in cardiovascular diseases, chronic degenerative osteoarthritis, musculoskeletal diseases, aging and others, sestrin proteins exhibit an anti-inflammatory response, improving metabolism and other valuable character. However, there is no comprehensive and detailed summary and literature research on the intervention methods of sestrin proteins at present. As the advance of research during last several years, exercise training and other interventions are considered to be the potential methods to up-regulate expression level of protein. In view of the physiological function of this protein, a review of the main studies on regulating the expression level of this protein can provide a novel approach for the clinical treatment and scientific research. In present study, all related researches about interventions and potential mechanisms were reviewed and the mainstream methodologies were described.

Sestrin2 and Sestrin3 protect spermatogenesis against heat-induced meiotic defects†

Heat stress induces testicular oxidative stress, impairs spermatogenesis, and increases the risk of male infertility. Recent studies have highlighted the antioxidative properties of the Sestrins family in reducing cellular oxidative damage. However, the role of Sestrins (Sestrin1, 2, and 3) in the testicular response to heat stress remains unclear. Here, we found that Sestrin2 and 3 were highly expressed in the testis relative to Sestrin1. Then, the Sestrin2-/- and Sestrin3-/- mice were generated by CRISPR/Cas9 to investigate the role of them on spermatogenesis after heat stress. Our data showed that Sestrin2-/- and Sestrin3-/- mice testes exhibited more severe damage manifested by exacerbated loss of germ cells and higher levels of oxidative stress as compared to wild-type counterparts after heat stress. Notably, Sestrin2-/- and Sestrin3-/- mice underwent a remarkable increase in heat-induced spermatocyte apoptosis than that of controls. Furthermore, the transcriptome landscape of spermatocytes and chromosome spreading showed that loss of Sestrin2 and Sestrin3 exacerbated meiotic failure by compromising DNA double-strand breaks repair after heat stress. Taken together, our work demonstrated a critical protective function of Sestrin2 and Sestrin3 in mitigating the impairments of spermatogenesis against heat stress.

Antioxidant and anti-ageing effects of oleuropein aglycone in canine skeletal muscle cells

Reactive oxygen species (ROS) are normally produced in skeletal muscle. However, an imbalance in their regulatory systems can lead to their accumulation and ultimately to oxidative stress, which is one of the causes of the ageing process. Companion dogs share the same environment and lifestyle as humans, making them an excellent comparative model for the study of ageing, as well as they constitute a growing market for bioactive molecules that improve the quality of life of pets. The anti-ageing properties of oleuropein aglycone (OLE), a bioactive compound from olive leaves known for its antioxidant properties, were investigated in Myok9 canine muscle cell model. After incubation with OLE, senescence was induced in the canine cellular model by hydrogen peroxide (H2O2). Analyses were performed on cells after seven days of differentiation. The oxidative stress induced by H2O2 treatment on differentiated canine muscle cells led to a significant increase in ROS formation, which was reduced by OLE pretreatment alone or in combination with H2O2 by about 34% and 32%, respectively. Cells treated with H2O2 showed a 48% increase the area of senescent cells stained by SA-β-gal, while OLE significantly reduced the coloured area by 52%. OLE, alone or in combination with H2O2, showed a significant antioxidant activity, possibly through autophagy activation, as indicated by the expression of autophagic markers.

Lysine specific demethylase 1 inhibits sodium arsenite activation of HSCs by regulating SESN2/AMPK/ULK1 signaling pathway activity

Lysine specific demethylase 1 (LSD1) is a histone demethylase that specifically catalyzes the demethylation of histone H3K4 (H3K4me1/2) and regulates gene expression. In addition, it can mediate the process of autophagy through its demethylase activity. Sestrin2 (SESN2) is a stress-induced protein and a positive regulator of autophagy. In NaAsO2-induced mouse fibrotic livers and activated hepatic stellate cells (HSCs), LSD1 expression is decreased, SESN2 expression is increased, and autophagy levels are also increased. Overexpression of LSD1 and silencing of SESN2 decreased the level of autophagy and attenuated the activation of HSCs induced by NaAsO2. LSD1 promoted SESN2 gene transcription by increasing H3K4me1/2 in the SESN2 promoter region. 3-methyladenine (3-MA) and chloroquine were used to inhibit autophagy of HSCs, and the degree of activation was also alleviated. Taken together, LSD1 positively regulates SESN2 by increasing H3K4me1/2 enrichment in the SESN2 promoter region, which in turn increases the level of autophagy and promotes the activation of HSCs. Our results may provide new evidence for the importance of LSD1 in the process of autophagy and activation of HSCs induced by arsenic poisoning. Increasing the expression and activity of LSD1 is expected to be an effective way to reverse the autophagy and activation of HSCs induced by arsenic poisoning.

Redox signaling and skeletal muscle adaptation during aerobic exercise

Redox regulation is a fundamental physiological phenomenon related to oxygen-dependent metabolism, and skeletal muscle is mainly regarded as a primary site for oxidative phosphorylation. Several studies have revealed the importance of reactive oxygen and nitrogen species (RONS) in the signaling process relating to muscle adaptation during exercise. To date, improving knowledge of redox signaling in modulating exercise adaptation has been the subject of comprehensive work and scientific inquiry. The primary aim of this review is to elucidate the molecular and biochemical pathways aligned to RONS as activators of skeletal muscle adaptation and to further identify the interconnecting mechanisms controlling redox balance. We also discuss the RONS-mediated pathways during the muscle adaptive process, including mitochondrial biogenesis, muscle remodeling, vascular angiogenesis, neuron regeneration, and the role of exogenous antioxidants.

Sestrin2 reduces ferroptosis via the Keap1/Nrf2 signaling pathway after intestinal ischemia-reperfusion

Sestrins are metabolic regulators that respond to stress by reducing the levels of reactive oxygen species (ROS) and inhibiting the activity of target of rapamycin complex 1 (mTORC1). Previous research has demonstrated that Sestrin2 mitigates ischemia-reperfusion (IR) injury in the heart, liver, and kidneys. However, its specific role in intestinal ischemia-reperfusion (IIR) injury remains unclear. To elucidate the role of Sestrin2 in IIR injury, we conducted an experimental study using a C57BL/6J mouse model of IIR. We noticed an increase in the levels of Sestrin2 expression and indicators associated with ferroptosis. Our study revealed that manipulating Sestrin2 expression in Caco-2 cells through overexpression or knockdown resulted in a corresponding decrease or increase, respectively, in ferroptosis levels. Furthermore, our investigation revealed that Sestrin2 alleviated ferroptosis caused by IIR injury through the activation of the Keap1/Nrf2 signal pathway. This finding highlights the potential of Sestrin2 as a therapeutic target for alleviating IIR injury. These findings indicated that the modulation of Sestrin2 could be a promising strategy for managing prolonged IIR injury.

Sestrin1, 2, and 3 are dispensable for female fertility in mice

BACKGROUND

Sestrins have been implicated in regulating aging in various organs through multiple pathways. However, their roles in ovarian aging remain unrevealed.

METHODS

Female Sestrin1-/-, Sestrin2-/-, and Sestrin3-/- mice were generated using the CRISPR-Cas9 system. Body weights, little sizes, ovarian weights, estrous cyclicity, and follicle number in female mice were observed. ELISA was utilized to measure serum anti-Müllerian hormone (AMH) levels. Real time PCR, western blot, immunofluorescence, and Masson trichrome staining were employed for assessment of aging-related change.

RESULTS

The deletion of Sestrin 1, 2, or 3 had no discernible impact on body weights,or serum AMH levels in female mice at the age of 12 months. And there were no discernible differences in litter sizes or estrous cyclicity which were assessed at the age of 8 months. At the age of 12 months, no significant differences were observed in ovarian weights or follicle numbers among the knockout mice. Consistently, the extent of fibrosis within the ovaries remained comparable across all experimental groups at this age. Additionally, autophagy, apoptosis, DNA damage, and inflammation within the ovaries were also found to be comparable to those in wild-type mice of the same age.

CONCLUSIONS

The loss of Sestrin 1, 2, or 3 does not exert a noticeable influence on ovarian function during the aging process. Sestrin1, 2, and 3 are not essential for female fertility in mice.

Orientin alleviates ox-LDL-induced oxidative stress, inflammation and apoptosis in human vascular endothelial cells by regulating Sestrin 1 (SESN1)-mediated autophagy

Endothelial cells are a crucial component of the vessel-tissue wall and exert an important role in atherosclerosis (AS). To explore the role of Orientin in AS, human vascular endothelial cells (HUVECs) were induced by oxidized low-density lipoprotein (ox-LDL) to simulate the vascular endothelial injury during AS. Cell viability was detected by CCK-8 assay. Oxidative stress and inflammation related markers were measured using kits, RT-qPCR or western blot. Besides, cell apoptosis was assessed with TUNEL staining and cell autophagy was evaluated by LC3 immunofluorescent staining. Additionally, western blot was utilized to evaluate the expression of Sestrin 1 (SESN1) and proteins in AMPK/mTOR signaling. Afterwards, SESN1 was silenced to determine the expression of autophagy-related proteins. The further application of autophagy inhibitor 3-methyladenine (3-MA) was used to clarify the regulatory mechanism of Orientin on autophagy. Results showed that the decreased viability of HUVECs caused by ox-LDL induction was elevated by Orientin. Oxidative stress and inflammation were also attenuated after Orientin addition in HUVECs under ox-LDL condition. Moreover, Orientin suppressed apoptosis and induced autophagy of HUVECs stimulated by ox-LDL, accompanied by enhanced level of phospho (p)-AMPK and declined level of p-mTOR. Interestingly, SESN1 level was elevated by Orientin, and SESN1 depletion alleviated autophagy and reduced p-AMPK expression but enhanced p-mTOR expression. The further experiments indicated that SESN1 silencing or 3-MA addition reversed the inhibitory effects of Orientin on the oxidative stress, inflammation and apoptosis of HUVECs. Collectively, Orientin could induce autophagy by activating SESN1 expression, thereby regulating AMPK/mTOR signaling in ox-LDL-induced HUVECs.

Modulation of Leucine Sensors to Mitigate Antipsychotics-Induced Metabolic Syndrome: A New Vista

Second-generation antipsychotics (SGAs) are currently the mainstay in the pharmacotherapy of some psychiatric disorders, which have improved the quality of life of millions of patients globally. A broad spectrum of activity and diminished liabilities of extrapyramidal side effects have made SGAs better alternatives compared to first-generation antipsychotics. Nevertheless, they display a complex profile of activity by affecting an array of biological targets and, as a result, are associated with a constellation of metabolic abnormalities such as hyperglycemia, dyslipidemia, weight gain, and cardiovascular problems. The SGAs-induced metabolic syndrome's exact mechanism has remained nebulous, but some evidence points the finger at mTOR signaling. In this viewpoint, we propose potential strategies to prevent or alleviate the SGA-induced metabolic adverse effects by modulating the activity of the leucine sensors, Sestrins.

Exploring In Vivo Models of Musculoskeletal Frailty: A Comprehensive Systematic Review

Musculoskeletal frailty-a common and debilitating condition linked to aging and chronic diseases-presents a major public health issue. In vivo models have become a key tool for researchers as they investigate the condition's underlying mechanisms and develop effective interventions. This systematic review examines the current body of research on in vivo models of musculoskeletal frailty, without any time constraints. To achieve this aim, we utilized three electronic databases and incorporated a total of 11 studies. Our investigation delves into varied animal models that simulate specific features of musculoskeletal frailty, including muscle loss, bone density reduction, and functional decline. Furthermore, we examine the translational prospects of these models in augmenting our comprehension of musculoskeletal frailty and streamlining the production of groundbreaking therapeutic approaches. This review provides significant insights and guidance for healthcare researchers and practitioners who aim to combat musculoskeletal frailty, ultimately enhancing the quality of life for older adults and individuals affected by this condition.

Resistance exercise alleviates dexamethasone-induced muscle atrophy via Sestrin2/MSTN pathway in C57BL/6J mice

AIM

It has long been recognized that resistance exercise can substantially increase skeletal muscle mass and strength, but whether it can protect against glucocorticoid-induced muscle atrophy and its potential mechanism is yet to be determined. This study aimed to investigate the protective effects of resistance exercise in dexamethasone-induced muscle atrophy and elucidate the possible function of exercise-induced protein Sestrin2 in this process.

METHODS

Eight-week-old male C57BL/6J mice carried out the incremental mouse ladder exercise for 11 weeks. Two weeks before the end of the intervention, mice were daily intraperitoneally injected with dexamethasone. Body composition, muscle mass, and exercise performance were examined to evaluate muscle atrophy. In vitro, C2C12 cells were used for RT-qPCR, Western Blot, and immunofluorescence experiments to elucidate the potential mechanism.

RESULTS

Our results showed that long-term resistance exercise is an effective intervention for dexamethasone-induced muscle atrophy. We also found that Sestrin2 plays a vital role in dexamethasone-induced muscle atrophy. In both animal (P = .0006) and cell models (P = .0266), dexamethasone intervention significantly reduced the protein expression of Sestrin2, which was increased (P = .0112) by resistance exercise. Inversely, overexpression of Sestrin2 improved (P < .0001) dexamethasone-induced myotube cell atrophy by reducing the activation of the ubiquitin-proteasome pathway via inhibiting Forkhead box O3 (FoxO3a) and myostatin (MSTN)/small mother against decapentaplegic (Smad) signaling pathways.

CONCLUSION

Taken together, our results indicated that Sestrin2 may serve as an effective molecule that mimics the protective effect of resistance exercise on dexamethasone-induced muscle atrophy.

Counteracting Immunosenescence-Which Therapeutic Strategies Are Promising?

Aging attenuates the overall responsiveness of the immune system to eradicate pathogens. The increased production of pro-inflammatory cytokines by innate immune cells under basal conditions, termed inflammaging, contributes to impaired innate immune responsiveness towards pathogen-mediated stimulation and limits antigen-presenting activity. Adaptive immune responses are attenuated as well due to lowered numbers of naïve lymphocytes and their impaired responsiveness towards antigen-specific stimulation. Additionally, the numbers of immunoregulatory cell types, comprising regulatory T cells and myeloid-derived suppressor cells, that inhibit the activity of innate and adaptive immune cells are elevated. This review aims to summarize our knowledge on the cellular and molecular causes of immunosenescence while also taking into account senescence effects that constitute immune evasion mechanisms in the case of chronic viral infections and cancer. For tumor therapy numerous nanoformulated drugs have been developed to overcome poor solubility of compounds and to enable cell-directed delivery in order to restore immune functions, e.g., by addressing dysregulated signaling pathways. Further, nanovaccines which efficiently address antigen-presenting cells to mount sustained anti-tumor immune responses have been clinically evaluated. Further, senolytics that selectively deplete senescent cells are being tested in a number of clinical trials. Here we discuss the potential use of such drugs to improve anti-aging therapy.

Exercise ameliorates chronic inflammatory response induced by high-fat diet via Sestrin2 in an Nrf2-dependent manner

Chronic inflammation is a major contributor to the development of metabolic disorders and is commonly seen in studies of diet-induced obesity in humans and rodents. Exercise has been shown to have anti-inflammatory properties, though the exact mechanisms are still not fully understood. Sestrins and Nrf2 are of interest to researchers as they are known to protect against inflammation and oxidative stress. In this study, we aim to explore the interconnection between Sestrin2 (SESN2) and Nrf2 and their roles in exercise benefits on chronic inflammation. Our data showed that SESN2 knockout aggravated the abnormalities of body weight, fat mass, and serum lipid that were induced by a high-fat diet (HFD), and a concomitant increase of TNF-α, IL-1β and IL-6 in both serum and skeletal muscle. Notably, exercise was found to reverse these changes, and SESN2 was found to be necessary for exercise to reduce the inflammatory response in skeletal muscles, though not in serum. Immunoprecipitation and bioinformatics prediction experiments further revealed that SESN2 directly binds to Nrf2, indicating a protein-protein interaction between the two. Furthermore, our data demonstrated that SESN2 protein is necessary for exercise-induced effects on Nrf2 pathway in HFD-fed mice, and Nrf2 protein is necessary to enable SESN2 to reduce the inflammation caused by palmitic acid (PA)+ oleic acid (OA) treatment in vitro. Our findings indicate that exercise mitigates chronic inflammation induced by HFD through SESN2 in an Nrf2-dependent manner. Our study reveals a novel molecular mechanism whereby the SESN2/Nrf2 pathway mediates the positive impact of exercise on chronic inflammation.

Muscular Sestrins: Roles in Exercise Physiology and Stress Resistance

Sestrins are a family of stress-inducible proteins that are critical for stress adaptation and the maintenance of metabolic homeostasis. High expression of Sestrins is observed in skeletal and cardiac muscle tissues, suggesting their significance in the physiological homeostasis of these organs. Furthermore, expression of Sestrins is dynamically controlled in the tissues, based on the level of physical activity and the presence or absence of stress insults. Genetic studies in model organisms have shown that muscular Sestrin expression is critical for metabolic homeostasis, exercise adaptation, stress resistance, and repair and may mediate the beneficial effects of some available therapeutics. The current minireview summarizes and discusses recent findings that shed light on the role of Sestrins in regulating muscle physiology and homeostasis.

Sestrin2 prevents neonatal incision pain and re-incision enhanced hyperalgesia in adult rats

BACKGROUND

Improving the methods for recognizing pain is important for infants admitted to the neonatal intensive care unit. Sestrin2 is a novel stress-inducible protein with a neuroprotective role that functions as a molecular mediator of hormesis. Nevertheless, the role of sestrin2 in the pain process is still unclear. The following study examined the role of sestrin2 on mechanical hypersensitivity after pups incision, as well as enhanced pain hyperalgesia after adulthood re-incision in rats.

METHODS

The experiment was divided into two parts: (1) studying the effect of sestrin2 in the neonatal incision; (2) studying the priming effect in adulthood re-incision. An animal model was established in seven-day-old rat pups with a right hind paw incision. Pups were intrathecally administrated rh-sestrin2 (exogenous sestrin2). Paw withdrawal threshold testing was performed to assay mechanical allodynia; tissue was analyzed in ex vivo using Western blot and immunofluorescence. SB203580 was further used to inhibit microglial function and evaluate the sex-dependent effect in adulthood.

RESULTS

Sestrin2 expression increased transitorily in the spinal dorsal horn in pups after incision. Administration of rh-sestrin2 improved pups' mechanical hypersensitivity by regulating the AMPK/ERK pathway and alleviated re-incision-induced enhanced hyperalgesia in male and female adult rats. After administration of SB203580 in pups, the mechanical hyperalgesia following re-incision in adult rats was prevented in males but not females; however, the protective effect of SB203580 in males was counteracted by silencing sestrin2.

CONCLUSIONS

These data suggest that sestrin2 prevents neonatal incision pain and re-incision enhanced hyperalgesia in adult rats. Moreover, microglia inhibition affects enhanced hyperalgesia only in adult males, which may be regulated through the sestrin2 mechanism. To sum up, these sestrin2 data may be a potential common molecular target for treating re-incision hyperalgesia in different sexes.

A cross-talk between sestrins, chronic inflammation and cellular senescence governs the development of age-associated sarcopenia and obesity

The rapid increase in both the lifespan and proportion of older adults is accompanied by the unprecedented rise in age-associated chronic diseases, including sarcopenia and obesity. Aging is also manifested by increased susceptibility to multiple endogenous and exogenous stresses enabling such chronic conditions to develop. Among the main physiological regulators of cellular adaption to various stress stimuli, such as DNA damage, hypoxia, and oxidative stress, are sestrins (Sesns), a family of three evolutionarily conserved proteins, Sesn1, 2, and 3. Age-associated sarcopenia and obesity are characterized by two key processes: (i) accumulation of senescent cells in the skeletal muscle and adipose tissue and (ii) creation of a systemic, chronic, low-grade inflammation (SCLGI). Presumably, failed SCLGI resolution governs the development of these chronic conditions. Noteworthy, Sesns activate senolytics, which are agents that selectively eliminate senescent cells, as well as specialized pro-resolving mediators, which are factors that physiologically provide inflammation resolution. Sesns reveal clear beneficial effects in pre-clinical models of sarcopenia and obesity. Based on these observations, we propose a novel treatment strategy for age-associated sarcopenia and obesity, complementary to the conventional therapeutic modalities: Sesn activation, SCLGI resolution, and senescent cell elimination.

Sertoli cell adaptation to glucose deprivation: Potential role of AMPK in the regulation of lipid metabolism

Sertoli cells (SCs) provide an adequate environment for germ cell development. SCs possess unique features that meet germ cells' metabolic demands: they produce lactate from glucose, which is delivered as energy substrate to germ cells. SCs store fatty acids (FAs) as triacylglycerols (TAGs) in lipid droplets (LDs) and can oxidize FAs to sustain their own energetic demands. They also produce ketone bodies from FAs. It has been shown that exposure of SCs to metabolic stresses, such as glucose deprivation, triggers specific adaptive responses that sustain cell survival and preserve lactate supply to germ cells. The aim of the present study was to investigate whether there are modifications in rat SCs lipid metabolism, including LD content, FA oxidation, and ketone bodies production, as part of their adaptive response to glucose deprivation. The present study was performed in 20-day-old rat SCs cultures. We determined LD content by Oil Red O staining, FA oxidation by measuring the release of ³ H₂ O from [³ H] palmitate, TAGs and 3-hydroxybutyrate levels by spectrophotometric methods, and mRNA levels by RT-qPCR. Results show that the absence of glucose in SC culture medium entails: (1) a decrease in LD content and TAGs levels that is accompanied by decreased perilipin 1 mRNA levels, (2) an increase in FA oxidation that is in part mediated by AMP kinase (AMPK) activation and (3) a decrease in 3-hydroxybutyrate production. Additionally, we studied whether sestrins (SESN1, 2 and 3), proteins involved in the cellular response to stress, are regulated in glucose deprivation conditions. We show that there is an increase in SESN2 mRNA levels in deprived conditions. In conclusion, glucose deprivation affects SC lipid metabolism promoting FA mobilization from LDs to be used as energy source.

Polysaccharides from Bletilla striata protect against mercury-induced gastrointestinal toxicology in adult Drosophila melanogaster via modulation of sestrin

Oxidative stress was one of the major causes of heavy metal-induced toxicity in organisms. The polysaccharide from Bletilla striata (Orchidaceae) (BSP) has been recently recognized as a novel player in the management of oxidative stress response in organisms. Here, we took the midgut of adult Drosophila melanogaster (Diptera: Drosophilidae) (D. melanogaster), a functional equivalent to the mammalian intestine and stomach, as a model to evaluate the protective effects of BSP (50 μg/mL) on mercuric chloride-induced gastrointestinal toxicology in insects. As a result, BSP exposure significantly improved the survival rates and climbing ability of adult flies exposed to mercury. Further study demonstrated that BSP significantly alleviated the mercury-induced oxidative injury to midgut epithelium, at least partly, through increasing antioxidant enzyme activity (glutathione-S-transferase and superoxide dismutase), decreasing reactive oxidative species production, inhibiting cell death, restoring intestinal epithelial barrier and regulating intestinal stem cell-mediated tissue regeneration. Additionally, sestrin, an oxidative-stress gene, was required in mediating the protection of BSP against mercury-induced oxidative damage to midgut. This study suggested that BSP has great potential for future application in the treatment and prevention of heavy metal-induced gastrointestinal adversities in mammals.

Nelumbinis Stamen Ameliorates Chronic Restraint Stress-Induced Muscle Dysfunction and Fatigue in Mice by Decreasing Serum Corticosterone Levels and Activating Sestrin2

Nelumbo nucifera Gaertn. is an important aquatic vegetable, and its dried stamen (Nelumbinis stamen, NS) is a valuable nutraceutical usually used as a herbal tea. Here, we used ultrahigh-performance liquid chromatography (UPLC)-quadrupole time-of-flight mass spectrometry and high-performance liquid chromatography (HPLC) to chemically profile NS and quantify their main constituent flavonoids, respectively. In total, 44 components were identified, including organic acids, flavonoids, monoterpene glycosides, and fatty acids. Experimental mice were induced with fatigue by exposure to chronic restraint stress (CRS) for 8 h daily for 15 days and then treated with an aqueous extract of NS (0.5 and 1 g/kg) via gavage. NS significantly mitigated CRS-induced skeletal muscle dysfunction and fatigue in mice possibly by lowering serum corticosterone levels and restoring Sestrin2 expression in the gastrocnemius to regulate metabolism, preserve mitochondrial homeostasis, and promote antioxidant capacity. These results demonstrate that NS can be used as a nutraceutical or supplement for controlling stress-induced muscle dysfunction and fatigue.

Simultaneous loss of TSC1 and DEPDC5 in skeletal and cardiac muscles produces early-onset myopathy and cardiac dysfunction associated with oxidative damage and SQSTM1/p62 accumulation

By promoting anabolism, MTORC1 is critical for muscle growth and maintenance. However, genetic MTORC1 upregulation promotes muscle aging and produces age-associated myopathy. Whether MTORC1 activation is sufficient to produce myopathy or indirectly promotes it by accelerating tissue aging is elusive. Here we examined the effects of muscular MTORC1 hyperactivation, produced by simultaneous depletion of TSC1 and DEPDC5 (CKM-TD). CKM-TD mice produced myopathy, associated with loss of skeletal muscle mass and force, as well as cardiac failure and bradypnea. These pathologies were manifested at eight weeks of age, leading to a highly penetrant fatality at around twelve weeks of age. Transcriptome analysis indicated that genes mediating proteasomal and macroautophagic/autophagic pathways were highly upregulated in CKM-TD skeletal muscle, in addition to inflammation, oxidative stress, and DNA damage signaling pathways. In CKM-TD muscle, autophagosome levels were increased, and the AMPK and ULK1 pathways were activated; in addition, autophagy induction was not completely blocked in CKM-TD myotubes. Despite the upregulation of autolysosomal markers, CKM-TD myofibers exhibited accumulation of autophagy substrates, such as SQSTM1/p62 and ubiquitinated proteins, suggesting that the autophagic activities were insufficient. Administration of a superoxide scavenger, tempol, normalized most of these molecular pathologies and subsequently restored muscle histology and force generation. However, CKM-TD autophagy alterations were not normalized by rapamycin or tempol, suggesting that they may involve non-canonical targets other than MTORC1. These results collectively indicate that the concomitant muscle deficiency of TSC1 and DEPDC5 can produce early-onset myopathy through accumulation of oxidative stress, which dysregulates myocellular homeostasis.Abbreviations: AMPK: AMP-activated protein kinase; CKM: creatine kinase, M-type; COX: cytochrome oxidase; DEPDC5: DEP domain containing 5, GATOR1 subcomplex subunit; DHE: dihydroethidium; EDL: extensor digitorum longus; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; GAP: GTPase-activating protein; GTN: gastrocnemius; MTORC1: mechanistic target of rapamycin kinase complex 1; PLA: plantaris; QUAD: quadriceps; RPS6KB/S6K: ribosomal protein S6 kinase beta; SDH: succinate dehydrogenase; SOL: soleus; SQSTM1: sequestosome 1; TA: tibialis anterior; TSC1: TSC complex subunit 1; ULK1: unc-51 like autophagy activating kinase 1.

Circulating Sestrins and Force Velocity Profiling in Older Adults with Type 2 Diabetes

ABSTRACTType 2 diabetes mellitus (T2DM) in old age affects the musculoskeletal system causing loss of muscle mass, strength, and physical function. Stress-inducible proteins named sestrins are potential novel biomarkers of muscle function due to their ability to suppress oxidative stress and prevent muscle degeneration. Our aim was to determine the association between different force-velocity (F-V) profiles with body composition, physical performance, and glucose control in older adults with T2DM. We also intended to determine the potential utility of sestrin 1 (Sesn1) and 2 (Sesn2) as biomarkers of physical functionality. Fifty-nine participants (69-79 years) were classified in 3 groups according to their F-V profile based on the leg press exercise: nondeficit (N_DEF= 40.7%), force deficit (F_DEF= 28.8%), and velocity deficit (V_DEF= 30.5%). Both V_DEF and F_DEF groups showed lower muscle power than N_DEF (Cohen's d 0.87 and 0.75 for effect size, respectively). Serum Sesn2 levels, maximal dynamic strength, arms and legs fat-free mass were reduced in F_DEF compared to the N_DEF group (p < 0.05), whereas glycated hemoglobin (HbA1c) and fasting glucose levels were similar among groups. ROC analysis revealed the distinction between the N_DEF and F_DEF group based on Sesn2 concentrations (<0.72 ng/mL), suggesting their potential use as functional biomarkers for early intervention through exercise. Older adults with T2DM show different F-V profiles, related to low levels of Sesn2, impaired body composition and physical performance, and may be taken into consideration to target exercise training in this specific population.

Endosomal v-ATPase as a Sensor Determining Myocardial Substrate Preference

The heart is a metabolically flexible omnivore that can utilize a variety of substrates for energy provision. To fulfill cardiac energy requirements, the healthy adult heart mainly uses long-chain fatty acids and glucose in a balanced manner, but when exposed to physiological or pathological stimuli, it can switch its substrate preference to alternative substrates such as amino acids (AAs) and ketone bodies. Using the failing heart as an example, upon stress, the fatty acid/glucose substrate balance is upset, resulting in an over-reliance on either fatty acids or glucose. A chronic fuel shift towards a single type of substrate is linked with cardiac dysfunction. Re-balancing myocardial substrate preference is suggested as an effective strategy to rescue the failing heart. In the last decade, we revealed that vacuolar-type H⁺-ATPase (v-ATPase) functions as a key regulator of myocardial substrate preference and, therefore, as a novel potential treatment approach for the failing heart. Fatty acids, glucose, and AAs selectively influence the assembly state of v-ATPase resulting in modulation of its proton-pumping activity. In this review, we summarize these novel insights on v-ATPase as an integrator of nutritional information. We also describe its exploitation as a therapeutic target with focus on supplementation of AA as a nutraceutical approach to fight lipid-induced insulin resistance and contractile dysfunction of the heart.

SESN1 attenuates the Ox‑LDL‑induced inflammation, apoptosis and endothelial‑mesenchymal transition of human umbilical vein endothelial cells by regulating AMPK/SIRT1/LOX1 signaling

Endothelial cells are an important component of the heart and vasculature and form a crucial link between the cardiovascular system and the immune system. Sestrin 1 (SESN1) has an important role in atherosclerosis by inhibiting NOD-like receptor family pyrin domain containing 3 inflammasome activation. However, whether SESN1 is involved in human umbilical vein endothelial cell (HUVEC) injury caused by atherosclerosis has remained to be elucidated. The present study aimed to investigate the functions of SESN1 in the inflammatory response, apoptosis and endothelial-mesenchymal transition (EndMT) of HUVECs following stimulation with oxidized low-density lipoprotein (Ox-LDL). SESN1 expression at the mRNA and protein levels was detected using reverse transcription-quantitative PCR (RT-qPCR) and western blot analysis. Following SESN1 overexpression in Ox-LDL-stimulated HUVECs, cell viability was determined using a Cell Counting Kit-8 assay. Terminal deoxynucleotidyl transferase-mediated nick-end labeling staining was employed to detect cell apoptosis and western blot analysis was used to determine the levels of apoptosis-related proteins. RT-qPCR, ELISA and western blot were utilized to determine the levels of inflammatory factors. Immunofluorescence staining, RT-qPCR and western blot analysis were employed to assess the EndMT of Ox-LDL-stimulated HUVECs. The results revealed that SESN1 exhibited a low expression in HUVECs following Ox-LDL stimulation. SESN1 overexpression suppressed inflammation, apoptosis and EndMT in Ox-LDL-induced HUVECs. In addition, SESN1 stimulated adenosine monophosphate-activated protein kinase catalytic subunit α1/sirtuin 1 signaling to suppress Ox-LDL receptor-1 expression. An AMPK and SIRT1 inhibitor reversed the effects of SESN1 overexpression on the inflammatory response, apoptosis and EndMT of HUVECs exposed to Ox-LDL. Taken together, the present study demonstrated that SENS1 exerts a suppressive effect on Ox-LDL-induced inflammation, apoptosis and EndMT of HUVECs, suggesting that SENS1 may be used as a novel biomarker for endothelial injury-related disorders.

SESN3 Inhibited SMAD3 to Relieve Its Suppression for MiR-124, Thus Regulating Pre-Adipocyte Adipogenesis

Sestrin-3, together with the other two members Sestrin-1 and Sestrin-2, belongs to the Sestrin family. The Sestrin protein family has been demonstrated to be involved in antioxidative, metabolic homeostasis, and even the development of nonalcoholic steatohepatitis (NASH). However, the adipogenic regulatory role of SESN3 in adipogenesis still needs to be further explored. In this study, we demonstrated SESN3 inhibited porcine pre-adipocyte proliferation, thus suppressing its adipogenesis. Meanwhile, SESN3 has been demonstrated to inhibit Smad3 thus protecting against NASH. Further, for our previous study, we found mmu-miR-124 involved in 3T3-L1 cell adipogenesis regulation. In this study, we also identified that ssc-miR-124 inhibited porcine pre-adipocyte proliferation, thus suppressing its adipogenesis, and the SMAD3 was an inhibitor of ssc-miR-124 by binding to its promoter. Furthermore, the ssc-miR-124 targeted porcine C/EBPα and GR and thus inhibited pre-adipocyte adipogenesis. In conclusion, SESN3 inhibited SMAD3, thus improving ssc-miR124, and then suppressed C/EBPα and GR to regulate pre-adipocytes adipogenesis.

Sestrin2 induction contributes to anti-inflammatory responses and cell survival by globular adiponectin in macrophages

Adiponectin, an adipose tissue-derived hormone, exhibits a modulatory effect on cell death/survival and possesses potent anti-inflammatory properties. However, the underlying molecular mechanisms remain elusive. Sestrin2, a stress-inducible metabolic protein, has shown cytoprotective and inflammation-modulatory effects under stressful conditions. In this study, we examined the role of sestrin2 signaling in the modulation of cell survival and inflammatory responses by globular adiponectin (gAcrp) in macrophages. We observed that gAcrp induced a significant increase in sestrin2 expression in both RAW 264.7 murine macrophages and primary murine macrophages. Notably, gAcrp treatment markedly increased expression of hypoxia inducible factor-1 α (HIF-1α) and gene silencing of HIF-1α blocked sestrin2 induction by gAcrp. In addition, pretreatment with a pharmacological inhibitor of ERK or PI3K abrogated both sestrin2 and HIF-1α expression by gAcrp, indicating that ERK/PI3K-mediated HIF-1α signaling pathway plays a critical role in sestrin2 induction by gAcrp. Furthermore, sestrin2 induction is implicated in autophagy activation, and knockdown of sestrin2 prevented enhanced cell viability by gAcrp. Moreover, gene silencing of sestrin2 caused restoration of gAcrp-induced expression of anti-inflammatory genes in a gene-selective manner. Taken together, these results indicate that sestrin2 induction critically contributes to cell survival and anti-inflammatory responses by gAcrp in macrophages.

Sestrin2 Regulates Osteoclastogenesis via the p62-TRAF6 Interaction

The receptor activator of nuclear factor-kappa B ligand (RANKL) mediates osteoclast differentiation and functions by inducing Ca²⁺ oscillations, activating mitogen-activated protein kinases (MAPKs), and activating nuclear factor of activated T-cells type c1 (NFATc1) via the RANK and tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) interaction. Reactive oxygen species (ROS) also plays an important role during osteoclastogenesis and Sestrin2, an antioxidant, maintains cellular homeostasis upon stress injury via regulation of ROS, autophagy, and inflammation. However, the role of Sestrin2 in osteoclastogenesis remains unknown. In this study, we investigated the role of Sestrin2 in the RANKL-RANK-TRAF6 signaling pathway during osteoclast differentiation. Deletion of Sestrin2 (Sesn2) increased bone mass and reduced the number of multinucleated osteoclasts on bone surfaces. RANKL-induced osteoclast differentiation and function decreased in Sesn2 knockout (KO) bone marrow-derived monocytes/macrophages (BMMs) due to inhibition of NFATc1 expression, but osteoblastogenesis was not affected. mRNA expression of RANKL-induced specific osteoclastogenic genes and MAPK protein expression were lower in Sesn2 KO BMMs than wild-type (WT) BMMs after RANKL treatment. However, the Sesn2 deletion did not affect ROS generation or intracellular Ca²⁺ oscillations during osteoclastogenesis. In contrast, the interaction between TRAF6 and p62 was reduced during osteoclasts differentiation in Sesn2 KO BMMs. The reduction in the TRAF6/p62 interaction and TRAP activity in osteoclastogenesis in Sesn2 KO BMMs was recovered to the WT level upon expression of Flag-Sesn2 in Sesn2 KO BMMs. These results suggest that Sestrin2 has a novel role in bone homeostasis and osteoclasts differentiation through regulation of NFATc1 and the TRAF6/p62 interaction.

Sestrin2 as a Potential Target for Regulating Metabolic-Related Diseases

Sestrin2 is a highly conserved protein that can be induced under a variety of stress conditions, including DNA damage, oxidative stress, endoplasmic reticulum (ER) stress, and metabolic stress. Numerous studies have shown that the AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway has a crucial role in the regulation of metabolism. Sestrin2 regulates metabolism via a number of pathways, including activation of AMPK, inhibition of the mTOR complex 1 (mTORC1), activation of mTOR complex 2 (mTORC2), inhibition of ER stress, and promotion of autophagy. Therefore, modulation of Sestrin2 activity may provide a potential therapeutic target for the prevention of metabolic diseases such as insulin resistance, diabetes, obesity, non-alcoholic fatty liver disease, and myocardial ischemia/reperfusion injury. In this review, we examined the regulatory relationship between Sestrin2 and the AMPK/mTOR signaling pathway and the effects of Sestrin2 on energy metabolism.