Spexin protects cardiomyocytes from hypoxia-induced metabolic and mitochondrial dysfunction

Spexin inhibits excessive autophagy-induced ferroptosis to alleviate doxorubicin-induced cardiotoxicity by upregulating Beclin 1

BACKGROUND AND PURPOSE

Doxorubicin is widely used in the treatment of malignant tumours, but doxorubicin-induced cardiotoxicity severely limits its clinical application. Spexin is a neuropeptide that acts as a novel biomarker in cardiovascular disease. However, the effects of spexin on doxorubicin-induced cardiotoxicity is unclear.

EXPERIMENTAL APPROACH

We established a model of doxorubicin-induced cardiotoxicity both in vivo and in vitro. Levels of cardiac damage in mice was assessed through cardiac function assessment, determination of serum cardiac troponin T and CKMB levels and histological examination. CCK8 and PI staining were used to assess the doxorubicin-induced toxicity in cultures of cardiomyocytes in vitro. Ferroptosis was assessed using FerroOrange staining, determination of MDA and 4-HNE content and ferroptosis-associated proteins SLC7A11 and GPX4. Mitochondrial membrane potential and lipid peroxidation levels were measured using TMRE and C11-BODIPY 581/591 probes, respectively. Myocardial autophagy was assessed by expression of P62 and Beclin1.

KEY RESULTS

Spexin treatment improved heart function of mice with doxorubicin-induced cardiotoxicity, and attenuated doxorubicin-induced cardiotoxicity by decreasing iron accumulation, abnormal lipid metabolism and inhibiting ferroptosis. Interestingly, doxorubicin caused excessive autophagy in cardiomyocyte in culture, which could be alleviated by treatment with spexin. Knockdown of Beclin 1 eliminated the protective effects of spexin in mice with DIC.

CONCLUSION AND IMPLICATIONS

Spexin ameliorated doxorubicin-induced cardiotoxicity by inhibiting excessive autophagy-induced ferroptosis, suggesting that spexin could be a drug candidate against doxorubicin-induced cardiotoxicity. Beclin 1 might be critical in mediating the protective effect of spexin against doxorubicin-induced cardiotoxicity.

Systemic and tissue-specific spexin response to acute treadmill exercise in rats

Spexin (SPX) is a 14-amino-acid peptide that plays an important role in the regulation of metabolism and energy homeostasis. It is well known that a variety of bioactive molecules released into the circulation by organs and tissues in response to acute and chronic exercise, known as exerkines, mediate the benefits of exercise by improving metabolic health. However, it is unclear whether acute exercise affects SPX levels in the circulation and peripheral tissues. This study aimed to determine whether acute treadmill exercise induces plasma SPX levels, as well as mRNA expression and immunostaining of SPX in skeletal muscle, adipose tissue, and liver. Male Sprague Dawley rats were divided into sedentary and acute exercise groups. Plasma, soleus (SOL), extensor digitorum longus (EDL), adipose tissue, and liver samples were collected at six time points (0, 1, 3, 6, 12, and 24 h) following 60 min of acute treadmill exercise at a speed of 25 m/min and 0 % grade. Acute exercise increased plasma SPX levels and induced mRNA expression of Spx in the SOL, EDL, and liver. Immunohistochemical analysis demonstrated that acute exercise led to a decrease in SPX immunostaining in the liver. Taken together, these findings suggest that SPX increases in response to acute exercise as a potential exerkine candidate, and the liver may be one of the sources of acute exercise-induced plasma SPX levels in rats. However, a comprehensive analysis is needed to fully elucidate the systemic response of SPX to acute exercise, as well as the tissue from which SPX is secreted.

Evaluating the therapeutic effect of vitamin D and nerolidol on lung injury due to experimental myocardial infarction: The potential role of asprosin and spexin

Injury to internal organs caused by myocardial infarction (MI), although often neglected, is a very serious condition which damages internal organs especially the lungs. Changes in microcirculation can begin with acute lung injury and result in severe respiratory failure. The aim of this study was to create new approaches that will explain the pathophysiology and treatment of the disease by examining the therapeutic effects of vitamin D (VITD) and Nerolidol (NRD) on the injuries of the lungs caused by MI, and their relationship with asprosin / spexin proteins.

METHODS

Six groups of seven experimental animals each were constituted. Control, VITD (only 50 IU/day during the experiment), NRD (only 100 mg/kg/day during the experiment), MI (200 mg/kg isoproterenol was administered to rats as a single dose subcutaneously), MI+VITD (200 mg/kg isoproterenol +50 IU/day) and MI+NRD (200 mg/kg isoproterenol +100 mg/kg/day) were the six (6) groups constituted. Tissues were analyzed using histopathological and immunohistochemical methods, whereas serum samples were analyzed using ELISA method.

RESULTS

The result of the histopathological study for the MI group showed an observed increase in inflammatory cells, congestion, interalveolar septal thickening, erythrocyteloaded macrophages and fibrosis in the lung tissues. The treatment groups however recorded significant differences with regards to these parameters. In the immunohistochemical analysis, expressions of asprosin and spexin were observed in the smooth muscle structures and interalveolar areas of the vessels and bronchioles of the lung, as well as the bronchiole epithelium. There was no significant difference between the groups in terms of asprosin and spexin expression in the bronchiol epithelium. When immunohistochemical and serum ELISA results were examined, it was observed that asprosin levels increased significantly in the lung tissues of the MI group compared to the control group, decreased significantly in the treatment groups treated with Vitamin D and NRD after MI. While spexin decreased significantly in the MI group compared to the control group, it increased significantly in the MI+VİTD group, but did not change in the MI+NRD group.

CONCLUSION

It was observed that serious injuries occurred in the lungs due to myocardial infarction and that, VITD and NRD treatments had a curative effect on those injuries. It was also observed that Asprosin and Speksin proteins can have effect on mechanisms of both injury and therapy of the lung. Furthermore, the curative effects of VITD are dependent on the expression of asprosin and spexin; whereas the observation indicated that nerolidol could be effective through asprosin-dependent mechanisms and specisin by independent mechanisms.

Puerarin ameliorates non-alcoholic fatty liver disease by inhibiting lipid metabolism through FMO5

Introduction: Pueraria lobata is traditionally used in China for treatment of non-alcoholic fatty liver disease (NAFLD). Puerarin, a functional drug extracted from Pueraria lobata, features a pharmacological activity. The present study aims to investigate the effect of puerarin intervention on NAFLD. Methods: We established an NAFLD mouse model using a high-fat diet with 60% fat and evaluated the impact of puerarin intervention. Results and discussion: Our results demonstrate that puerarin intervention significantly ameliorates lipid accumulation and protects the liver from high-fat-induced damage while reducing oxidative stress levels in the liver. Furthermore, puerarin intervention significantly downregulates the transcription levels of acetyl-CoA carboxylase (ACC1) in the liver. It also upregulates the transcription levels of carnitine palmitoyltransferase 1 (CPT1), peroxisome proliferator-activated receptor alpha (PPARα), and peroxisome proliferators-activated receptor γ coactivator alpha (PGC1α), which are related to oxidation. Furthermore, we demonstrated that flavin-containing monooxygenase (FMO5) was involved in the protective effect of puerarin against NFALD. In conclusion, the present study demonstrated the beneficial effect of puerarin on NAFLD and showed that puerarin could prevent liver injury and lipid accumulation caused by NAFLD via activating FMO5. These findings provide a new theoretical basis for applying puerarin as a therapeutic agent for NAFLD.

Spexin Diminishes Atrial Fibrillation Vulnerability by Acting on Galanin Receptor 2

BACKGROUND

G protein-coupled receptors play a critical role in atrial fibrillation (AF). Spexin is a novel ligand of galanin receptors (GALRs). In this study, we investigated the regulation of spexin and GALRs on AF and the underlying mechanisms.

METHODS

Global spexin knockout (SPX-KO) and cardiomyocyte-specific GALRs knockout (GALR-cKO) mice underwent burst pacing electrical stimulation. Optical mapping was used to determine atrial conduction velocity and action potential duration. Atrial myocyte action potential duration and inward rectifying K+ current (IK1) were recorded using whole-cell patch clamps. Isolated cardiomyocytes were stained with Fluo-3/AM dye, and intracellular Ca2+ handling was examined by CCD camera. A mouse model of AF was established by Ang-II (angiotensin II) infusion.

RESULTS

Spexin plasma levels in patients with AF were lower than those in subjects without AF, and knockout of spexin increased AF susceptibility in mice. In the atrium of SPX-KO mice, potassium inwardly rectifying channel subfamily J member 2 (KCNJ2) and sarcolipin (SLN) were upregulated; meanwhile, IK1 current was increased and Ca2+ handling was impaired in isolated atrial myocytes of SPX-KO mice. GALR2-cKO mice, but not GALR1-cKO and GALR3-cKO mice, had a higher incidence of AF, which was associated with higher IK1 current and intracellular Ca2+ overload. The phosphorylation level of CREB (cyclic AMP responsive element binding protein 1) was upregulated in atrial tissues of SPX-KO and GALR2-cKO mice. Chromatin immunoprecipitation confirmed the recruitment of p-CREB to the proximal promoter regions of KCNJ2 and SLN. Finally, spexin treatment suppressed CREB signaling, decreased IK1 current and decreased intracellular Ca2+ overload, which thus reduced the inducibility of AF in Ang-II-infused mice.

CONCLUSIONS

Spexin reduces atrial fibrillation susceptibility by inhibiting CREB phosphorylation and thus downregulating KCNJ2 and SLN transcription by GALR2 receptor. The spexin/GALR2/CREB signaling pathway represents a novel therapeutic avenue in the development of agents against atrial fibrillation.

Spexin acts as a novel glucose-lowering factor in grass carp (Ctenopharyngodon idella)

At present, the physiological roles of various hormones in fish glucose metabolism have been elucidated. Spexin, a 14-amino acids polypeptide, is highly conserved in many species and has functions such as reducing body weight and improving insulin resistance. In this paper, the open reading frame (ORF) of spx21 in grass carp (Ctenopharyngodon idella) was cloned, and the tissue distribution of spx1 and spx2, their direct and indirect regulatory effects on glucose metabolism of grass carp were investigated. The ORF of spx2 gene in grass carp was 279 bp in length. Moreover, spx1 was highly expressed in the adipose tissue, while spx2 was highly expressed in the brain. In vitro, SPX1 and SPX2 showed opposite effects on the glycolytic pathway in the primary hepatocytes. In vivo, intraperitoneal injection of SPX1 and SPX2 significantly reduced serum glucose levels and increased hepatopancreas glycogen contents. Meanwhile, SPX1 and SPX2 promoted the expression of key genes of glycolysis (pk) and glycogen synthesis (gys) in the hepatopancreas at 3 h post injection. As for indirect effects, 1000 nM SPX1 and SPX2 significantly increased insulin-mediated liver type phosphofructokinase (pfkla) mRNA expression and enhanced the inhibitory effects of insulin on glucose-6-phosphatase (g6pase), phosphoenolpyruvate carboxykinase (pepck), glycogen phosphorylase L (pygl) mRNA expression. Our results show that SPX1 and SPX2 have similar indirect effects on the regulation of glucose metabolism that enhance insulin activity, but they exhibit opposite roles in terms of direct effects.

Spexin ameliorated obesity-related metabolic disorders through promoting white adipose browning mediated by JAK2-STAT3 pathway

BACKGROUND

Spexin, a 14 amino acid peptide, has been reported to regulate obesity and its associated complications. However, little is known about the underlying molecular mechanism. Therefore, this study aimed to investigate the effects of spexin on obesity and explore the detailed molecular mechanisms in vivo and in vitro.

METHODS

Male C57BL/6J mice were fed a high-fat diet (HFD) for 12 weeks to induce obesity, and mice fed a standard fat diet were used as controls. Then, these mice were treated with SPX or Vehicle by intraperitoneal injection for an additional 12 weeks, respectively. The metabolic profile, fat-browning specific markers and mitochondrial contents were detected. In vitro, 3T3-L1 cells were used to investigate the molecular mechanisms.

RESULTS

After 12 weeks of treatment, SPX significantly decreased body weight, serum lipid levels, and improved insulin sensitivity in HFD-induced obese mice. Moreover, SPX was found to promote oxygen consumption in HFD mice, and it increased mitochondrial content as well as the expression of brown-specific markers in white adipose tissue (WAT) of HFD mice. These results were consistent with the increase in mitochondrial content and the expression of brown-specific markers in 3T3-L1 mature adipocytes. Of note, the spexin-mediated beneficial pro-browning actions were abolished by the JAK2/STAT3 pathway antagonists in mature 3T3-L1 cells.

CONCLUSIONS

These data indicate that spexin ameliorates obesity-induced metabolic disorders by improving WAT browning via activation of the JAK2/STAT3 signaling pathway. Therefore, SPX may serve as a new therapeutic candidate for treating obesity.

Spexin alleviates hypertension, hyperuricaemia, dyslipidemia and insulin resistance in high fructose diet induced metabolic syndrome in rats via enhancing PPAR-ɣ and AMPK and inhibiting IL-6 and TNF-α

Spexin is a novel peptide implicated in obesity and energy homeostasis. The objective of the current study was to evaluate the effect of spexin on blood pressure, insulin resistance, and dyslipidemia in rats with metabolic syndrome (MS) induced by high-fructose diet (HFD) and the possible underlying mechanism. Forty adult male rats were randomly assigned into four equal groups; Control, Spexin, HFD and HFD + spexin. Induction of the MS with HFD was associated with increased body mass index, elevated blood pressure, blood glucose, insulin, uric acid, advanced glycation end products and insulin resistance, interlekin-6, tumour necrosis factor-alpha together with dyslipidemia, low-serum spexin, peroxisome proliferator-activated receptors-gamma (PPAR-ɣ) and adenosine monophosphate-activated protein kinase (AMPK). Spexin attenuated MS-induced deleterious effects which can be attributed to activation of PPAR-ɣ and AMPK as well as inhibiting inflammation. These findings indicate that spexin could be a beneficial complementary agent for metabolic syndrome treatment.

Cord Blood Spexin Level in Mothers with Obesity-Forecast of Future Obesity?

Spexin (SPX) is a peptide that plays an important role in the regulation of food intake and body weight (BW) by the effect on carbohydrate-lipid metabolism. However, the role of SPX in fetal life, in children, and in adolescent metabolism is limited. Therefore, we decided to check whether obesity affects the concentration of SPX in the mother's peripheral blood (MB) and umbilical cord blood (UCB). Using MB and UCB sera on the day of delivery obtained from 48 women (24 non-obese and 24 obese) and commercially available Elisa kits and colorimetric assays, we determined changes in SPX and the relationship between SPX concentration and other metabolic and anthropometric markers (body weight and BMI) on the day of delivery and in children at the age of 36 months. We found lower concentrations of SPX in MB (p < 0.05) and UCB (p < 0.01) derived from obese women (BMI > 30) and a moderate linear correlation (r = 0.4429; p < 0.01) between SPX concentrations in MB and UCB. We also noted that the concentration of SPX is not correlated with the child's body weight on the day of birth (r = -0.0128). However, there is a relationship between SPX at birth and body weight at 3 years of age (r = -0.3219; p < 0.05). Based on the obtained results, it can be assumed that spexin is one of the factors modulating the child's metabolism already in the fetal period and can be considered a potential marker of future predisposition to obesity. However, confirmation of this thesis requires additional research.

Spexin level in acute myocardial infarction in the emergency department

Background

We aimed to determine the serum spexin level in patients with acute myocardial infarction (AMI) admitted to the emergency department.

Methods

A total of 100 patients with AMI (50 with ST-segment elevation myocardial infarction (STEMI) and 50 with non-ST-segment elevation myocardial infarction (NSTEMI)) and 50 control group patients with non-cardiac chest pain were included in the study. A detailed anamnesis was taken, a physical examination was performed, and 12-lead electrocardiograms and venous blood samples were taken at the time of admission. Spexin levels were measured via enzyme-linked immunosorbent assay.

Results

Serum spexin levels were significantly lower in the AMI group than in the non-cardiac chest pain group (p<0.001). There was no significant difference in serum spexin levels between STEMI and NSTEMI patients (p=0.83). In receiver operating curve analysis, we detected 58% sensitivity, 76% specificity, 82.9% positive predictive value, and 47.5% negative predictive value with an optimal cutoff value of 532 pg/mL for the diagnosis of AMI.

Conclusions

In this study, serum spexin levels were significantly lower in AMI patients compared to patients with non-cardiac chest pain. The decrease in spexin levels suggests that it has the potential to be used as a diagnostic marker in AMI patients.

Eleutheroside E from pre-treatment of Acanthopanax senticosus (Rupr.etMaxim.) Harms ameliorates high-altitude-induced heart injury by regulating NLRP3 inflammasome-mediated pyroptosis via NLRP3/caspase-1 pathway

Eleutheroside E, a major natural bioactive compound in Acanthopanax senticosus (Rupr.etMaxim.) Harms, possesses anti-oxidative, anti-fatigue, anti-inflammatory, anti-bacterial and immunoregulatory effects. High-altitude hypobaric hypoxia affects blood flow and oxygen utilisation, resulting in severe heart injury that cannot be reversed, thereby eventually causing or exacerbating high-altitude heart disease and heart failure. The purpose of this study was to determine the cardioprotective effects of eleutheroside E against high-altitude-induced heart injury (HAHI), and to study the mechanisms by which this happens. A hypobaric hypoxia chamber was used in the study to simulate hypobaric hypoxia at the high altitude of 6000 m. 42 male rats were randomly assigned to 6 equal groups and pre-treated with saline, eleutheroside E 100 mg/kg, eleutheroside E 50 mg/kg, or nigericin 4 mg/kg. Eleutheroside E exhibited significant dose-dependent effects on a rat model of HAHI by suppressing inflammation and pyroptosis. Eleutheroside E downregulated the expressions of brain natriuretic peptide (BNP), creatine kinase isoenzymes (CK-MB) and lactic dehydrogenase (LDH). Moreover, The ECG also showed eleutheroside E improved the changes in QT interval, corrected QT interval, QRS interval and heart rate. Eleutheroside E remarkably suppressed the expressions of NLRP3/caspase-1-related proteins and pro-inflammatory factors in heart tissue of the model rats. Nigericin, known as an agonist of NLRP3 inflammasome-mediated pyroptosis, reversed the effects of eleutheroside E. Eleutheroside E prevented HAHI and inhibited inflammation and pyroptosis via the NLRP3/caspase-1 signalling pathway. Taken together, eleutheroside E is a prospective, effective, safe and inexpensive agent that can be used to treat HAHI.

Protective Effect of N-Acetylcysteine Against Aluminum-Induced Kidney Tissue Damage in Rats

Aluminum (AL) is an important nephrotoxic agent with a high daily exposure rate and property of accumulation in tissues. This study aimed to investigate the potential protective efficacy of N-acetylcysteine (NAC) against AL exposure-induced nephrotoxicity in rats. Twenty-eight rats were randomly divided into 4 groups as control, N-acetylcysteine group (NC), AL, and AL + NC, with an equal number of rats in each group (n = 7). No application was made to the control group. A total of 150 mg/kg/day NAC was administered to the NC group and 30 mg/kg/day AL was administered to the AL group intraperitoneally (i.p.). The AL + NC group received 30 mg/kg/day AL and 150 mg/kg/day NAC i.p. Biochemical parameters in blood serum and histopathological changes in kidney tissue, oxidative stress parameters, spexin (SPX), and apoptotic protein levels were examined after 15 days. Histopathological changes, biochemical parameters, oxidative stress parameters, and apoptotic protein levels were significantly irregular in the AL group compared to the control group. Moreover, SPX levels increased in the AL group. However, NAC treatment regulated AL exposure-related changes in the AL + NC group. NAC treatment may have a prophylactic effect against nephrotoxicity due to AL exposure. SPX may play a role in AL-induced nephrotoxicity.

The role of spexin in energy metabolism

Spexin, also identified as neuropeptide Q (NPQ), is a 14 amino acid peptide discovered by bioinformatic methods. It has a conserved structure in many species and is widely expressed in the central nervous system and peripheral tissues. It has an associated receptor, galanin receptor 2/3 (GALR2/3). Mature spexin peptides can exert various functions by activating GALR2/3, such as inhibiting food intake, inhibiting lipid absorption, reducing body weight, and improving insulin resistance. Spexin is expressed in the adrenal gland, pancreas, visceral fat, and thyroid, with the highest expression in the adrenal gland, followed by the pancreas. Physiologically, spexin and insulin interact in pancreatic islets. Spexin may be one of the regulators of endocrine function in the pancreas. Spexin is a possible indicator of insulin resistance and it has a variety of functional properties, here we review its role in energy metabolism.

Adipose-Muscle crosstalk in age-related metabolic disorders: The emerging roles of adipo-myokines

Obesity and type 2 diabetes account for a considerable proportion of the global burden of age-related metabolic diseases. In age-related metabolic diseases, tissue crosstalk and metabolic regulation have been primarily linked to endocrine processes. Skeletal muscle and adipose tissue are endocrine organs that release myokines and adipokines into the bloodstream, respectively. These cytokines regulate metabolic responses in a variety of tissues, including skeletal muscle and adipose tissue. However, the intricate mechanisms underlying adipose-muscle crosstalk in age-related metabolic diseases are not fully understood. Recent exciting evidence suggests that myokines act to control adipose tissue functions, including lipolysis, browning, and inflammation, whereas adipokines mediate the beneficial actions of adipose tissue in the muscle, such as glucose uptake and metabolism. In this review, we assess the mechanisms of adipose-muscle crosstalk in age-related disorders and propose that the adipokines adiponectin and spexin, as well as the myokines irisin and interleukin-6 (IL-6), are crucial for maintaining the body's metabolic balance in age-related metabolic disorders. In addition, these changes of adipose-muscle crosstalk in response to exercise or dietary flavonoid consumption are part of the mechanisms of both functions in the remission of age-related metabolic disorders. A better understanding of the intricate relationships between adipose tissue and skeletal muscle could lead to more potent therapeutic approaches to prolong life and prevent age-related metabolic diseases.

Exercise training rescues adipose tissue spexin expression and secretion in diet-induced obese mice

Exercise training improves obesity-induced metabolic diseases through regulation of adipokines. Previous studies have shown that adipocyte-spexin participates in metabolic diseases such as obesity and diabetes via the modulation of energy homeostasis and insulin resistance. The objective of this research was to investigate the effects of swimming exercise on the levels of adipocyte-spexin and the underlying mechanisms. The normal chow diet (NC)-fed and high-fat diet (HFD)-fed mice were divided into exercise or sedentary groups. The expression and secretion of spexin in adipose tissue were assessed by quantitative real-time PCR and ELISA. The present findings uncovered the effect of exercise-induced spexin expression in the adipose tissue of obese mice. Besides, chronic exercise-induced upregulation of adipose spexin may be mediated by COUP-TF2 and KLF9. In addition, constant-moderate intensity exercise increased the levels of GLUT4, SIRT1 and PGC-1α in the skeletal muscles of mice. These results suggest that spexin is a potential mediator for exercise to ameliorate obesity-induced insulin resistance, namely, the beneficial effect of exercise on insulin sensitivity is at least partly mediated by spexin. Thus, exercise restores spexin production and release, which increases insulin sensitivity and maintains metabolic balance in the adipose tissues of HFD-induced obese mice.

Epididymal white adipose tissue promotes angiotensin II-induced cardiac fibrosis in an exosome-dependent manner

Cardiac fibrosis is a process characterized by extracellular matrix accumulation leading to myocardial dysfunction. Angiotensin II (Ang II) has been shown to play an important role in the pathogenesis of cardiac fibrosis. However, the underlying mechanisms are not well established. Dysfunction of adipose tissue has been shown to promote remote organ injury, but its role in Ang II-induced cardiac remodeling is still unclear. In this study, we demonstrated that epididymal white adipose tissue (eWAT) promoted Ang II-induced cardiac fibrosis and subsequent cardiac dysfunction in an exosome-dependent manner. Both eWAT removal and administration of an inhibitor of exosome biogenesis strongly attenuated Ang II-induced abnormalities. Moreover, exosomes isolated from Ang II-stimulated adipocytes promoted cardiac fibroblasts (CFs) activity. A mechanistic study identified that the miR-23a-3p level was significantly increased in exosomes derived from Ang II-challenged adipocytes and serum exosomes from Ang II-infused mice. Importantly, tail vein injection of ago-miR-23a-3p caused cardiac fibrosis and dysfunction, while antago-miR-23a-3p inhibited Ang II-induced cardiac fibrosis. Bioinformatics analysis and further validation experiments revealed that RAP1 is a direct downstream target of miR-23a-3p, and overexpression of RAP1 reversed the profibrotic effect of miR-23a-3p. Taken together, these findings elucidated the role of eWAT in Ang II-induced myocardial fibrosis and indicated that adipocyte-derived exosomes mediate pathologic communication between dysfunctional adipose tissue and the heart by transporting miR-23a-3p into CFs, transforming fibroblasts into myofibroblasts and promoting excessive collagen deposition by targeting RAP1. Prevention of abnormal adipocyte exosome production, inhibition of miR-23a-3p biogenesis, and treatment with a miR-23a-3p antagonist are novel strategies for treating cardiac fibrosis.

Treatment with spexin mitigates diet-induced hepatic steatosis in vivo and in vitro through activation of galanin receptor 2

It was reported that spexin as an adipocyte-secreted protein could regulate obesity and insulin resistance. However, the specific metabolic contribution of spexin to fatty liver remains incompletely understood. Herein, we investigated the effects of spexin on hepatosteatosis and explored the underlying molecular mechanisms. HFD-fed mice were injected with spexin and/or GALR2 antagonist M871, while PA-induced HepG2 cells were treated with spexin in the absence or presence of M871 for 12 h, respectively. Gene expression in liver tissues and hepatocytes was assessed by qRT-PCR and western blotting, respectively. The results showed that body weight, visceral fat content, liver lipid droplet formation, hepatic intracellular triglyceride, and serum triglyceride were reduced in spexin-treated mice. Furthermore, spexin increased the expression of hepatic CPT1A, PPARα, SIRT1, KLF9, PGC-1α and PEPCK in vivo and in vitro. Additionally, spexin treatment improved glucose tolerance and insulin sensitivity in mice fed the HFD. Interestingly, these spexin-mediated beneficial effects were abolished by the GALR2 antagonist M871 in mice fed HFD and PA-induced HepG2 cells, suggesting that spexin mitigated HFD-induced hepatic steatosis by activating the GALR2, thereby increasing CPT1A, PPARα, SIRT1, KLF9, PGC-1α and PEPCK expression. Taken together, these data suggest that spexin ameliorates NAFLD by improving lipolysis and fatty acid oxidation via activation of GALR2 signaling.

Mechanisms for Bile Acids CDCA- and DCA-Stimulated Hepatic Spexin Expression

Spexin (SPX) is a novel peptide involved in glucose and lipid metabolism and suppresses hepatic total bile acid levels by inhibiting hepatic cholesterol 7α-hydroxylase 1 expression. As important mediators for glycolysis/gluconeogenesis and lipid metabolism, the effects of bile acids on SPX expression is yet to be understood. By using SMMC7721 and BEL-7402 cell lines, we screened the effects of bile acids and found that chenodeoxycholic acid (CDCA) and deoxycholic acid (DCA) can stimulate SPX gene transcription. Both CDCA and DCA were able to stimulate SPX mRNA expression in the liver but not colon and ileum in mice. In SMMC7721 and BEL-7402 cells, CDCA- and DCA-induced SPX promoter activity was mimicked by bile acid receptor FXR and TGR5 activation and suppressed by FXR and TGR5 silencing. Adenylate cyclase (AC)/cyclic adenosine monophosphate (cAMP) activators significantly increased SPX promoter activity whereas the inhibitors for AC/CAMP/protein kinase A (PKA) and mitogen-activated protein kinases (MAPK) pathway attenuated CDCA- and DCA-induced SPX transcription. Thus, CDCA and DCA stimulate SPX expression at the hepatic level through FXR and TGR5 mediated AC/cAMP/PKA and MAPK cascades.

Emerging central and peripheral actions of spexin in feeding behavior, leptin resistance and obesity

Consumption of a high calorie diet with irregular eating and sedentary behavior habits is typical of the current suboptimal lifestyle, contributing to the development of metabolic diseases such as obesity and type 2 diabetes mellitus. Most notably, the disorder of adipokine secretion in visceral adiposity is a major contributor to metabolic diseases with advancing age. In this regard, spexin and leptin are established as anorexigenic adipokines that can modulate adipogenesis and glucose metabolism by suppressing food intake or increasing energy expenditure, respectively. Emerging evidence points out that spexin levels are lower in the serum and adipose tissue of patients with obesity and/or insulin resistance, whereas circulating levels of leptin are higher in obesity and comorbidities. In turn, spexin and leptin pharmacologically induce beneficial effects on the brain's modulation of food intake and energy expenditure. On the other hand, endocrine crosstalk via spexin and leptin has also been reported in patients suffering from obesity and diabetes. Spexin plays a crucial role in the regulation of leptin secretion and leptin resistance. It should therefore be taken into account that studying the role of spexin in leptin regulation will help us combat the pathologies of obesity caused by leptin resistance.

Impact of spexin on metabolic diseases and inflammation: An updated minireview

Spexin (SPX) is a 14 amino acid length peptide hormone which was discovered using bioinformatic tools. It is extensively expressed in central and peripheral tissues and secreted into circulation in response to metabolic stress. Recent studies revealed that SPX acts as a multifunctional peptide in various metabolic processes such as body weight, food intake, energy balance, glucose and lipid metabolism, lipid storage, salt-water balance, and arterial blood pressure. Endogenous SPX is sensitive to metabolic changes, and circulating levels of SPX have been shown to be reduced in chronic diseases such as obesity, diabetes, and insulin resistance. Moreover, in fish and rodent models, systemic SPX treatment has positive effects on metabolism including reduced food intake, fat mass, lipid accumulation, and inflammation, improved insulin sensitivity, energy expenditure, and organ functions which are underlying mechanisms in diseases. Taken together, these findings suggest that SPX is a potential drug target for the development of new pharmacological strategies to cure metabolic diseases. This review focuses on metabolo-protective properties of SPX and discusses novel insights into the biology and mechanism of SPX in the pathogenesis of diabetes, obesity, non-alcoholic fatty liver disease, metabolic syndrome, polycystic ovary syndrome, cardiovascular diseases, and kidney diseases, which are considerable global health problems.

Spexin ameliorates skeletal muscle insulin resistance through activation of GAL2 receptor

Skeletal muscle is a principal tissue involved in energy expenditure and glucose metabolism. Although the results of our and other studies show that spexin could decrease food intake and obesity, the specific metabolic effect of spexin on glucose metabolism of skeletal muscle is still unclear. The aim of this study is to investigate whether spexin might mitigate obesity-induced insulin resistance in skeletal muscles and to explore its underlying mechanisms. The high fat diet-fed mice were treated with 50 μg/kg/d spexin for 21 consecutive days, and the differentiated myotubes of L6 were treated with spexin (200, 400, 800 nM) in the absence or presence of M871 (800 nM) for 12 h respectively. Besides, the galanin type 2 (GAL2) receptor knockdown myotubes were treated with 800 nM spexin for 12 h in this study. The present findings showed that spexin reversed hyperglycemia and glucose intolerance as well as insulin intolerance and insulin resistance in the mice fed with high fat diet. Furthermore, spexin markedly augmented the peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) expression and deacetylation, and further triggered glucose transporter 4 (GLUT4) expression and trafficking in myotubes through p38 mitogen-activated protein kinase (P38MAPK) and protein kinase B (AKT) activation. More importantly, the elevation of glucose consumption related genes by spexin were abolished by GAL2 receptor antagonist or silencing of GAL2 receptor in myotubes. In conclusion, our findings provide a novel insight that spexin can protect against insulin resistance and increase glucose consumption in skeletal muscles mainly through activation of GAL2/GLUT4 signal pathway. Spexin might therefore be a novel therapeutic target for hyperglycemia and insulin resistance in clinic.

Adipose tissue spexin in physical exercise and age-associated diseases

It is known that a strong association exists between a suboptimal lifestyle (physical inactivity and sedentary behavior and/or high calorie diet) and increased propensity of developing age-associated diseases, such as obesity and T2DM. Physical exercise can alleviate obesity-induced insulin resistance and T2DM, however, the precise mechanism for this outcome is not fully understood. The endocrine disorder of adipose tissue in obesity plays a critical role in the development of insulin resistance. In this regard, spexin has been recently described as an adipokine that plays an important role in the pathophysiology of obesity-induced insulin resistance and T2DM. In obese states, expression of adipose tissue spexin is reduced, inducing the adipose tissue and skeletal muscle more susceptible to insulin resistance. Emerging evidences point out that exercise can increase spexin expression. In return, spexin could exert the exercise-protective roles to ameliorate insulin resistance, suggesting that spexin is a potential mediator for exercise to ameliorate obesity-induced insulin resistance and T2DM, namely, the beneficial effect of exercise on insulin sensitivity is at least partly mediated by spexin. This review summarizes our and others' recent studies regarding the effects of obesity on adipose tissue spexin induction, along with the potential effect of exercise on this response in obese context, and provides a new insight into the multivariate relationship among exercise, spexin and T2DM. It should be therefore taken into account that a combination of spexin and exercise training is an effective therapeutic strategy for age-associated diseases.

Serum spexin differed in newly diagnosed type 2 diabetes patients according to body mass index and increased with the improvement of metabolic status

OBJECTIVE

The aim of this study was to explore serum spexin levels in newly diagnosed type 2 diabetes mellitus (T2DM) patients with different body mass indexes (BMIs) and to investigate the changes of spexin after improvement of metabolic indicators.

METHODS

A total of 323 newly diagnosed T2DM patients from national Metabolic Management Center (MMC) in Shanghai General Hospital were recruited. T2DM patients were categorized into three groups: diabetes with obesity group (DM-OB group, BMI≥28 kg/m², n=89), diabetes with overweight group (DM-OV group, 24≤BMI<28 kg/m², n=161), and diabetes with normal weight group (DM-NW group, 18≤BMI<24 kg/m², n=73). In addition, 41 volunteers with normal glucose tolerance (NGT) were used as controls. Spexin and metabolic parameters were compared at baseline, and changes after MMC follow-up in 100 DM patients were investigated.

RESULTS

In the DM-OB group, the level of spexin was significantly lower than that in the DM-OV group and the DM-NW group (P < 0.01). Spexin was significantly negatively related to body mass index (BMI, β=-0.214, P<0.001), waist circumference (β=-0.249, P<0.001), visceral fat area (VFA, β=-0.214, P<0.001), and subcutaneous fat area (SFA, β=-0.265, P<0.001) after adjustment for age and sex. Among all the metabolic indicators, the decline in BMI in the DM-OB group was the most obvious among those in the three groups (-3.7 ± 0.8 kg/m² vs. -0.9 ± 0.3 kg/m² vs. 0.7 ± 0.6 kg/m², P<0.01) after one year of MMC standardized management. The serum spexin level in the DM-OB group increased the most (1.00 ± 0.10 ng/mL vs. 0.49 ± 0.06 ng/mL in DM-OV group and 0.58 ± 0.09 ng/mL in DM-NW group, P < 0.001).

CONCLUSIONS

Serum spexin differed in newly diagnosed T2DM patients according to BMI and was lowest in the DM-OB group. With the improvement of metabolic indicators, especially the decline in BMI, serum spexin increased significantly after MMC management.

Spexin Promotes the Proliferation and Differentiation of C2C12 Cells In Vitro—The Effect of Exercise on SPX and SPX Receptor Expression in Skeletal Muscle In Vivo

SPX (spexin) and its receptors GalR2 and GalR3 (galanin receptor subtype 2 and galanin receptor subtype 3) play an important role in the regulation of lipid and carbohydrate metabolism in human and animal fat tissue. However, little is still known about the role of this peptide in the metabolism of muscle. The aim of this study was to determine the impact of SPX on the metabolism, proliferation and differentiation of the skeletal muscle cell line C2C12. Moreover, we determined the effect of exercise on the SPX transduction pathway in mice skeletal muscle. We found that increased SPX, acting via GalR2 and GalR3 receptors, and ERK1/2 phosphorylation stimulated the proliferation of C2C12 cells (p < 0.01). We also noted that SPX stimulated the differentiation of C2C12 by increasing mRNA and protein levels of differentiation markers Myh, myogenin and MyoD (p < 0.01). SPX consequently promoted myoblast fusion into the myotubule (p < 0.01). Moreover, we found that, in the first stage (after 2 days) of myocyte differentiation, GalR2 and GalR3 were involved, whereas in the last stage (day six), the effect of SPX was mediated by the GalR3 isoform. We also noted that exercise stimulated SPX and GalR2 expression in mice skeletal muscle as well as an increase in SPX concentration in blood serum. These new insights may contribute to a better understanding of the role of SPX in the metabolism of skeletal muscle.

Novel insights on the role of spexin as a biomarker of obesity and related cardiometabolic disease

Spexin (SPX) is a 14-amino acid neuropeptide, discovered recently using bioinformatic techniques. It is encoded by the Ch12:orf39 gene that is widely expressed in different body tissues/organs across species, and secreted into systemic circulation. Recent reports have highlighted a potentially important regulatory role of SPX in obesity and related comorbidities. SPX is also ubiquitously expressed in human tissues, including white adipose tissue. The circulating concentration of SPX is significantly lower in individuals with obesity compared to normal weight counterparts. SPX's role in obesity appears to be related to various factors, such as the regulation of energy expenditure, appetite, and eating behaviors, increasing locomotion, and inhibiting long-chain fatty acid uptake into adipocytes. Recent reports have also suggested SPX's relationship with novel biomarkers of cardiovascular disease (CVD) and glucose metabolism and evoked the potential role of SPX as a key biomarker/player in the early loss of cardiometabolic health and development of CVD and diabetes later in life. Data on age-related changes in SPX and SPX's response to various interventions are also emerging. The current review focuses on the role of SPX in obesity and related comorbidities across the life span, and its response to interventions in these conditions. It is expected that this article will provide new ideas for future research on SPX and its metabolic regulation, particularly related to cardiometabolic diseases.

Adropin and spexin hormones regulate the systemic inflammation in adenine-induced chronic kidney failure in rat

Chronic kidney disease is one of the major global health problems. Chronic renal failure is stimulated by many cytokines and chemokines. Adropin and spexin (SPX) are peptides hormones. These peptides could affect inflammatory conditions, but this is unclear. Due to the limited information, we planned to investigate the impact of adropin and SPX hormones on systemic inflammation in adenine induced chronic kidney failure rat model. Chronic kidney failure was induced by administering adenine hemisulfate. Renal functions were measured by an autoanalyzer. Granulocyte colony-stimulating factor (G-CSF), interferon-gamma (IFN-γ), interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-10, IL-12, IL-13, IL-17A, tumor necrosis factor-alpha, Eotaxin, growth-regulated oncogene-alpha, IP-10, monocyte chemoattractant protein (MCP)-1, MCP-3, macrophage inflammatory protein (MIP)-1α, MIP-2, and RANTES levels were determined by Luminex. We observed an increase in 24-h urine volume and serum creatinine. Blood urea nitrogen (BUN) and urine protein levels were also significantly higher in the chronic kidney failure (CKF) group. Urine protein and 24-h urine volume were reduced with adropin and SPX treatments. Furthermore, G-CSF, IFN-γ, IL-4, IL-5, IL-10, IL-12, IL-17A, and GRO-α significantly increased by CKF induction; however, these cytokines and chemokines significantly decreased by adropin treatment in the CKF group. Furthermore, adropin increased IP-10, MCP-1, MIP-1α, and MIP-2 levels. In addition, SPX treatment had a more limited effect, decreasing only G-CSF, IFN-γ, and IL-5 levels. The combined adropin + SPX treatment significantly reduced G-CSF, IFN-γ, IL-4, IL-5, IL-12, and IL-17A. Furthermore, IP-10, MCP-1, MCP-3, and MIP-2 were significantly increased by these combined treatments. Our findings indicate that renal functions and inflammatory response were modulated by adropin and SPX peptides. These peptides may have protective effects on systemic inflammation and renal failure progression.

Inflammatory response and matrix metalloproteinases in chronic kidney failure: Modulation by adropin and spexin

Chronic kidney disease is a major global public health problem. The peptide hormones adropin and spexin modulate many physiological functions such as energy balance and glucose, lipid and protein metabolism. However, it is unclear whether these peptides may exert effects on renal damage, tissue remodeling, and inflammatory conditions. In view of the limited information, we aimed to investigate the effect of adropin and spexin on matrix metalloproteinase and inflammatory response genes a rat model of adenine-induced chronic kidney failure. Chronic kidney failure was induced in rats by administering adenine hemisulfate. Renal function was determined in an autoanalyzer. Histopathological modifications were assessed by H&E staining. mRNA expression levels of ALOX 15, COX 1, COX 2, IL-1β, IL-10, IL-17A, IL-18 IL-21, IL-33, KIM-1, MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, MMP-13, NGAL, TGFβ1, TIMP-1, and TNFα in kidney tissue were measured by qPCR. Our results showed an increase of 24-h urine volume, serum creatinine, BUN, and urine protein levels in group with adenine-induced CKF. Adropin and spexin treatments decreased urine protein and 24-h urine volume. Renal damage, TIMP-1, IL-33, and MMP-2 increased after CKF induction, while COX 1, MMP-9, and MMP-13 levels were significantly reduced. Furthermore, KIM-1, TIMP-1, IL-33, and MMP-2 were downregulated by spexin treatment. Renal damage, NGAL, TIMP-1 IL-17A, IL-33, MMP-2, and MMP-3 decreased after adropin treatment, while MMP-13 levels were upregulated. Treatment with adropin+spexin decreased KIM-1, NGAL, TIMP-1, IL-1β, IL-17A, IL-18, IL-33, ALOX 15, COX 1, COX 2, TGFβ1, TNFα, MMP-2, MMP-3, and MMP-7, but increased MMP-13 levels. Our findings revealed that inflammatory response and MMP genes were modulated by adropin and spexin. These peptides may have protective effects on inflammation and chronic kidney damage progression.

Obesity and diabetes are major risk factors for epicardial adipose tissue inflammation

BACKGROUND

Epicardial adipose tissue (EAT) directly overlies the myocardium, with changes in its morphology and volume associated with myriad cardiovascular and metabolic diseases. However, EAT’s immune structure and cellular characterization remain incompletely described. We aimed to define the immune phenotype of EAT in humans and compare such profiles across lean, obese, and diabetic patients.

METHODS

We recruited 152 patients undergoing open-chest coronary artery bypass grafting (CABG), valve repair/replacement (VR) surgery, or combined CABG/VR. Patients’ clinical and biochemical data and EAT, subcutaneous adipose tissue (SAT), and preoperative blood samples were collected. Immune cell profiling was evaluated by flow cytometry and complemented by gene expression studies of immune mediators. Bulk RNA-Seq was performed in EAT across metabolic profiles to assess whole-transcriptome changes observed in lean, obese, and diabetic groups.

RESULTS

Flow cytometry analysis demonstrated EAT was highly enriched in adaptive immune (T and B) cells. Although overweight/obese and diabetic patients had similar EAT cellular profiles to lean control patients, the EAT exhibited significantly (P ≤ 0.01) raised expression of immune mediators, including IL-1, IL-6, TNF-α, and IFN-γ. These changes were not observed in SAT or blood. Neither underlying coronary artery disease nor the presence of hypertension significantly altered the immune profiles observed. Bulk RNA-Seq demonstrated significant alterations in metabolic and inflammatory pathways in the EAT of overweight/obese patients compared with lean controls.

CONCLUSION

Adaptive immune cells are the predominant immune cell constituent in human EAT and SAT. The presence of underlying cardiometabolic conditions, specifically obesity and diabetes, rather than cardiac disease phenotype appears to alter the inflammatory profile of EAT. Obese states markedly alter EAT metabolic and inflammatory signaling genes, underlining the impact of obesity on the EAT transcriptome profile.

FUNDING

Barts Charity MGU0413, Abbott, Medical Research Council MR/T008059/1, and British Heart Foundation FS/13/49/30421 and PG/16/79/32419.

Circulating spexins in children with obesity: relation to cardiometabolic risk

BACKGROUND/OBJECTIVES

The role of spexin (SPX) in energy metabolism, endocrinal homeostasis, and vasculopathy is emerging. However, scarce data are available about its role in childhood obesity and obesity-related vasculopathy. Hence, we aimed to assess the level of SPX in obese and normal-weight children, and to correlate it with aortic distensibility (AD) and aortic stiffness index (ASI).

SUBJECTS/METHODS

Forty obese children were compared to 40 matched normal-weighed children. Weight, height, and body mass index (BMI) z score and mean blood pressure (Bl-Pr) percentile on three different occasions were obtained. SPX, fasting triglycerides, cholesterol, low-density (LDL), high-density lipoproteins (HDL), and insulin were measured with calculation of the homeostatic model assessment insulin resistance (HOMA-IR). Internal aortic diameter was measured with calculation of AD, strain (AS), and ASI.

RESULTS

Children with obesity had significantly lower SPX (P = 0.004), HDL (P < 0.001), and AD (P < 0.001) and higher systolic Bl-Pr (P < 0.001), diastolic Bl-Pr (P < 0.001), LDL (P = 0.011), HOMA-IR (P < 0.001), and ASI (P < 0.001). Significant negative correlation was found between SPX and BMI z score (r = -0.646, P < 0.001), systolic Bl-Pr (r = -0.641, P < 0.001), diastolic Bl-Pr (r = -0.427, P < 0.001), HOMA-IR (r = -0.349, P = 0.028), and ASI (r = -0.389, P = 0.013), while significant positive correlation was found between SPX and AS (P < 0.001, r = 0.633) and AD (P < 0.001, r = 0.612). However, no significant correlation was found between SPX and age (r = -0.01, P = 0.953), TG (r = 0.048, P = 0.767), total cholesterol (r = -0.023, P = 0.887), LDL (r = -0.299, P = 0.061), and HDL (r = 0.193, P = 0.232).

CONCLUSIONS

Children with obesity had significantly lower SPX than controls. SPX was correlated with BMI, Bl-Pr, HOMA-IR, and vasculopathy in children with obesity independent of their age and lipid profile. Further studies should explore the pathomechanism of SPX and its potential role in the management of obesity and obesity-related cardiometabolic risk.

Normobaric oxygen therapy attenuates hyperglycolysis in ischemic stroke

Normobaric oxygen therapy has gained attention as a simple and convenient means of achieving neuroprotection against the pathogenic cascade initiated by acute ischemic stroke. The mechanisms underlying the neuroprotective efficacy of normobaric oxygen therapy, however, have not been fully elucidated. It is hypothesized that cerebral hyperglycolysis is involved in the neuroprotection of normobaric oxygen therapy against ischemic stroke. In this study, Sprague-Dawley rats were subjected to either 2-hour middle cerebral artery occlusion followed by 3- or 24-hour reperfusion or to a permanent middle cerebral artery occlusion event. At 2 hours after the onset of ischemia, all rats received either 95% oxygen normobaric oxygen therapy for 3 hours or room air. Compared with room air, normobaric oxygen therapy significantly reduced the infarct volume, neurological deficits, and reactive oxygen species and increased the production of adenosine triphosphate in ischemic rats. These changes were associated with reduced transcriptional and translational levels of the hyperglycolytic enzymes glucose transporter 1 and 3, phosphofructokinase 1, and lactate dehydrogenase. In addition, normobaric oxygen therapy significantly reduced adenosine monophosphate-activated protein kinase mRNA expression and phosphorylated adenosine monophosphate-activated protein kinase protein expression. These findings suggest that normobaric oxygen therapy can reduce hyperglycolysis through modulating the adenosine monophosphate-activated protein kinase signaling pathway and alleviating oxidative injury, thereby exhibiting neuroprotective effects in ischemic stroke. This study was approved by the Institutional Animal Investigation Committee of Capital Medical University (approval No. AEEI-2018-033) on August 13, 2018.

Spexin-expressing neurons in the magnocellular nuclei of the human hypothalamus

Neuropeptides are involved in numerous brain activities being responsible for a wide spectrum of higher mental functions. The purpose of this concise, structural and qualitative investigation was to map the possible immunoreactivity of the novel neuropeptide spexin (SPX) within the human magnocellular hypothalamus. SPX is a newly identified peptide, a natural ligand for the galanin receptors (GALR) 2/3, with no molecular structure similarities to currently known regulatory factors. SPX seems to have multiple physiological functions, with an involvement in reproduction and food-intake regulation recently revealed in animal studies. For the first time we describe SPX expressing neurons in the supraoptic (SON) and paraventricular (PVN) nuclei of the human hypothalamus using immunohistochemical and fluorescent methods, key regions involved in the mechanisms of osmotic homeostasis, energy expenditure, consummatory behaviour, reproductive processes, social recognition and stress responses. The vast majority of neurons located in both examined neurosecretory nuclei show abundant SPX expression and this may indirectly implicate a potential contribution of SPX signalling to the hypothalamic physiology in the human brain.