Spexin as an indicator of beneficial effects of exercise in human obesity and diabetes

The Investigation of Kisspeptin, Spexin and Galanin in Euthyroid Women with Hashimoto's Thyroiditis

OBJECTIVE

The hallmarks of Hashimoto's thyroiditis (HT) include the destruction of thyroid cells by leading to insulin resistance (IR), hypothyroidism, and metabolic abnormalities. Kisspeptin, spexin, and galanin control appetite and body weight (BW) to regulate metabolisms. Here, we sought to determine if galanin, kisspeptin, and spexin are linked to the pathophysiology of HT in euthyroid female individuals.

METHODS

Forty-five women with HT and 45 healthy control women of the same age participated in the current study. The enzyme-linked immunosorbent assay (ELISA) method was used to measure the serum levels of galanin, spexin, and kisspeptin.

RESULTS

In comparison to the controls, HT patients had significantly higher levels of kisspeptin (p < 0.01), galanin (p < 0.01), anti-thyroid peroxidase (anti-TPO) (p < 0.001), anti-thyroglobulin (anti-Tg) (p < 0.001), and body mass index (BMI) (p < 0.05). The two groups were comparable in terms of spexin, free triiodothyronine-3 (fT3), fT4, thyroid-stimulating hormone (TSH) levels, and homeostatic model assessment for insulin resistance (HOMA-IR). Galanin and kisspeptin were seen to have a positive correlation (p < 0.01; r = 0.786).

CONCLUSIONS

Euthyroid women with HT were found to have higher levels of kisspeptin and galanin. These results imply that kisspeptin and galanin may be linked to the pathogenesis of hypothyroidism, and as a result, we believe that these markers may be beneficial in the early detection and treatment of HT patients.

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.

Enhancing cardiometabolic health: unveiling the synergistic effects of high-intensity interval training with spirulina supplementation on selected adipokines, insulin resistance, and anthropometric indices in obese males

This study investigated the combined effects of 12 weeks of high-intensity interval training (HIIT) and spirulina supplementation on adipokine levels, insulin resistance, anthropometric indices, and cardiorespiratory fitness in 44 obese males (aged 25-40 years). The participants were randomly assigned to one of four groups: control (CG), supplement (SG), training (TG), or training plus supplement (TSG). The intervention involved daily administration of either spirulina or a placebo and HIIT three times a week for the training groups. Anthropometric indices, HOMA-IR, VO2peak, and circulating adipokines (asprosin and lipocalin2, omentin-1, irisin, and spexin) were measured before and after the 12-week intervention. Post-intervention analysis indicated differences between the CG and the three interventional groups for body weight, fat-free mass (FFM), percent body fat (%BF), HOMA-IR, and adipokine levels (p < 0.05). TG and SG participants had increased VO2peak (p < 0.05). Spirulina supplementation with HIIT increased VO2peak, omentin-1, irisin, and spexin, while causing decreases in lipocalin-2 and asprosin levels and improvements in body composition (weight, %fat), BMI, and HOMA-IR. Notably, the combination of spirulina and HIIT produced more significant changes in circulating adipokines and cardiometabolic health in obese males compared to either supplementation or HIIT alone (p < 0.05). These findings highlight the synergistic benefits of combining spirulina supplementation with HIIT, showcasing their potential in improving various health parameters and addressing obesity-related concerns in a comprehensive manner.

Spexin may induce mitochondrial biogenesis in white and brown adipocytes via the hypothalamus-pituitary-thyroid (HPT) axis

AIM

The present study aimed to investigate the effect of the intracerebroventricular (icv) administration of spexin on the hypothalamus-pituitary-thyroid (HPT) axis (TRH, TSH, T4 and T3 hormones) and energy expenditure (PGC-1α and UCP1 genes) in white adipose (WAT) and brown adipose tissues (BAT) in rats. Furthermore, the study aimed to determine the effects of spexin on food-water consumption and body weight of rats.

MATERIAL AND METHOD

The study was conducted with 40 male rats that were divided into 4 groups: Control, Sham, Spexin 30 and Spexin 100 (n = 10). Spexin (1 μl/hour) was administered to rats other than those in the control group for 7 days with osmotic minipumps intracerebroventricularly, artificial cerebrospinal fluid (vehicle) was administered to the Sham group, and 30 nMol and 100 nMol spexin was infused to the Spexin 30 and Spexin 100 groups, respectively. Food-water consumption and body weight of the rats were monitored during the experiments. After the seven-day infusion, the rats were decapitated and serum TSH, fT4 and fT3 levels were determined with ELISA on rat blood samples. Also, TRH gene expression levels from the hypothalamus tissues and PGC-1α and UCP1 expression levels from WAT and BAT were determined by real-time PCR.

FINDINGS

It was determined that icv spexin infusion reduced daily food consumption and body weight without leading to a significant change in water consumption (p < 0.05). Icv spexin infusion significantly decreased serum TSH, and increased fT4 and fT3 levels when compared to control and sham groups (p < 0.05). Moreover, icv spexin infusion increased the TRH expressions in the hypothalamus tissues and PGC-1α UCP1 in the WAT and BAT (p < 0.05).

CONCLUSION

Icv Spexin infusion may have effects on food consumption and body weight as well as, thyroid hormones and energy metabolism.

Immunoexpression of Spexin in Selected Segments of the Bovine (Bos taurus taurus) Gastrointestinal Tract

In the expansive domain of neuropeptide investigation, spexin (SPX) has emerged as a captivating subject, exerting a significant impact on diverse physiological processes. Initially identified in mice, SPX's distribution transcends various organs, suggesting its potential regulatory roles. Despite extensive research in smaller species, a notable gap exists in our comprehension of SPX in larger mammals, particularly ruminants. Our study meticulously explores the immunolocalization of SPX within the gastrointestinal organs of bovines, with a specific focus on the abomasum, jejunum, and colon. Tissue samples from Holstein-Friesian cattle underwent careful processing, and gene mRNA expression levels, particularly GALR2 and SPX, were assessed. Intriguingly, our findings revealed that GALR2 expression was highest in the jejunum, signifying a potentially critical role in this digestive segment. Immunohistochemistry further unveiled distinct patterns of SPX immunoreactivity in each examined region-abomasum, jejunum, and colon-highlighting nuanced, region-specific responses. Notably, the abomasum and jejunum predominantly exhibited positive immunoreactivity in the submucosal plexus, while the colon, in contrast, demonstrated a higher degree of immunoreactivity in myenteric plexus neurons. Our investigation, grounded in the hypothesis of ubiquitous SPX distribution in ruminants, delves deeper into the intricate role of SPX within the enteric nervous system. This study meticulously explores the spatial distribution of SPX within the myenteric and submucosal plexuses, integral components of the enteric nervous system. These findings significantly enhance our understanding of SPX's potential roles in gastrointestinal regulation in bovines, providing a unique perspective on larger mammals and enriching our comprehension of this intriguing neuropeptide's significance in various physiological processes.

Unravelling the anti-inflammatory and antioxidant effects of standardized green and black caffeinated coffee, tea, and their mixtures in an obese male rat model: Insights from biochemical, metabolomic, and histopathological analyses

Obesity is one of the major metabolic syndrome risk factors upon which altered metabolic pathways follow. This study aimed to discern altered metabolic pathways associated with obesity and to pinpoint metabolite biomarkers in serum of obese rats fed on high fructose diet using metabolomics. Further, the effect of standardized green versus black caffeinated aqueous extracts (tea and coffee) in controlling obesity and its comorbidities through monitoring relevant serum biomarkers viz. Leptin, adiponectin, spexin, malondialdehyde, total antioxidant capacity. Liver tissue oxidative stress (catalase, super oxide dismutase and glutathione) and inflammation (IL-1β and IL-6) markers were assessed for green coffee and its mixture with green tea. Results revealed improvement of all parameters upon treatments with more prominence for those treated with green caffeinated extract (coffee and tea) especially in mixture. Upon comparing with obese rat group, the green mixture of coffee and tea exhibited anti-hyperlipidemic action through lowering serum triglycerides by 35.0% and elevating high density lipoprotein by 71.0%. Black tea was likewise effective in lowering serum cholesterol and low density lipoprotein by 28.0 and 50.6%, respectively. GC-MS- based metabolomics of rat serum led to the identification of 34 metabolites with obese rat serum enriched in fatty acids (oleamide).

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.

Circulating spexin levels are influenced by the glycemic status and correlated with pancreatic β-cell function in Chinese subjects

AIMS

Spexin plays a role in regulating glucose metabolism. This study investigated the spexin levels in different glycemic status and its association with insulin secretion in humans.

METHODS

A total of 462 subjects were recruited in this study, including 52 healthy subjects, 106 first-degree relatives (FDRs) of type 2 diabetes mellitus (T2DM), 115 impaired glucose regulation (IGR), 80 newly diagnosed T2DM, and 106 established T2DM. Serum spexin was measured using ELISA. The homeostasis model assessment of insulin resistance (HOMA2-IR) and β-cell function (HOMA2-β), and Stumvoll index estimating first- and second-phase insulin secretion were calculated.

RESULTS

Spexin levels were higher in FDRs [235.53 pg/ml (185.28, 293.95)] and IGR [239.79 pg/ml (191.52, 301.69)], comparable in newly diagnosed T2DM [224.68 pg/ml (187.37, 279.74)], and lower in established T2DM [100.11 pg/ml (78.50, 137.34)], compared with healthy subjects [200.23 pg/ml (160.32, 275.65)]. Spexin levels were negatively correlated with fasting plasma glucose (FPG) (r =  - 0.355, P < 0.001), hemoglobin A1C (HbA1c) (r =  - 0.379, P < 0.001), and HOMA2-IR (r =  -  0.225, P < 0.001), and positively correlated with HOMA2-β (r = 0.245, P < 0.001) after adjusting for age, sex, and BMI. Multivariate linear regression analysis showed that established T2DM and HOMA2-β were independently associated with serum spexin levels.

CONCLUSIONS

Serum spexin levels represented as a bell-shaped curve along the glycemic continuum and is closely related with insulin secretion in humans.

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.

Does exercise during a ketogenic diet effectively alter appetite sensation, appetite-regulating hormones, and body composition?

Exercise and diet are two essential interventions in weight control. The purpose of this study was to compare the effectiveness of two exercise training types during a ketogenic diet (KD) on appetite sensation, appetite-regulating hormones, and body composition in overweight or obese man. Thirty-six men, overweight or with obesity, voluntarily participated in this study. The participants were randomly assigned into three groups, including KD (n = 12), aerobic training during KD (AT-KD) (n = 12), and resistance training during KD (RT-KD) (n = 12) groups. The participants followed a low-carbohydrate diet for 6 weeks. Exercise training programs consisted of three sessions per week over 6 weeks. Appetite sensation was analyzed using a visual analogue scale (VAS) in fasting and postprandial states. The Enzyme-Linked Immunosorbent Assay (ELISA) method analyzed appetite-regulating hormones, including spexin, leptin, and acylated ghrelin, in a fasting state. Body composition was measured using bioelectrical impedance analysis (BIA). Furthermore, the ketosis state was monitored by measuring urinary ketones weekly. The results indicated that in both AT-KD and RT-KD groups, spexin and acylated ghrelin increased while leptin decreased without any between-group differences. Hunger and prospective food consumption (PFC) declined while satiety and fullness increased in all groups. The AT-KD group experienced a significant decrease in hunger and PFC, while fullness increased compared with the KD group. Fat mass, weight, and body mass index (BMI) decreased in all groups. Lean body mass increased in the RT-KD group (+2.66 kg) compared with both AT-KD and KD groups (-1.71 and -1.33 kg, respectively). This study demonstrated that AT-KD and RT-KD effectively altered appetite-regulating hormones and suppressed appetite sensation. In addition, both interventions had a favorable effect on weight loss and body fat reduction, with a more pronounced effect of RT-KD on maintaining lean body mass in overweight or obese men.

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.

Circulating Spexin Is Associated with Body Mass Index and Fat Mass but Not with Physical Activity and Psychological Parameters in Women across a Broad Body Weight Spectrum

Spexin (SPX) is a novel, widely expressed peptide, with anorexigenic effects demonstrated in animal models and negatively correlated with body mass index (BMI) in humans. It increases locomotor activity in rodents and is elevated in human plasma following exercise. Studies have also shown an effect of stress and anxiety on SPX’s expression in different brain structures in animals. The relationships between plasma SPX and physical activity, body composition, and patient-reported outcomes such as perceived stress, depressiveness, anxiety, and eating behaviors are unknown and were examined in this study over a wide BMI range. A total of 219 female (n = 68 with anorexia nervosa; n = 79 with obesity; n = 72 with normal weight) inpatients were enrolled. Perceived stress (PSQ 20), anxiety (GAD 7), depressiveness (PHQ 9), and eating disorder pathology (EDI 2), as well as BMI, bioimpedance analysis, and accelerometry, were measured cross-sectionally at the beginning of treatment and correlated with plasma SPX levels (measured by ELISA) obtained at the same time. Plasma SPX levels were negatively associated with BMI (r = −0.149, p = 0.027) and body fat mass (r = −0.149, p = 0.04), but did not correlate with perceived stress, anxiety, depressiveness, eating behavior, energy expenditure, and physical activity (p > 0.05). The results replicate the negative correlation of SPX with BMI and fat mass, but do not support the hypothesis that peripheral SPX plays a role in the regulation of stress, depressiveness, anxiety, eating behavior, or physical activity.

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.

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.

Blood and aqueous humor phoenixin, endocan and spexin in patients with diabetes mellitus and cataract with and without diabetic retinopathy

Peptide phoenixin (PNX), endocan (EDC), and spexin (SPX) are associated with diabetes. Therefore, the purpose of this study was to investigate the levels of PNX, EDC and SPX in the blood and aqueous humor (AH) of patient with type 2 diabetes with and without DRP and cataract. 30 type 2 diabetes patients with cataract (DM + C), 30 DRP patient with cataract (DRP + C), 30 non-diabetic patient with only cataract and 30 control participants were enrolled into this study. PNX, EDC, and SPX were measured in blood and AH by ELISA. In patients with DRP + C, the levels of PNX and EDC were significantly higher in both AH and blood samples compared with the group of patients without DRP + C (<0.05). Also, in patients with DM + C, the levels of PNX and EDC were higher in both AH and blood samples compared with the group of patients without DM + C. However, in patients with DRP + C, the levels of SPX were significantly lower in both AH and blood samples compared with the group of patients without DRP + C (<0.05). Also, in patients with DM + C, the levels of SPX were also lower in both AH and blood samples compared with the group of patients without DM + C. These findings suggest that increased PNX, EDC, and decreased SPX amounts in blood and AH of DM + C and DRP + C groups when compared with control and cataract groups show that they might have a role in the pathophysiology of DM + C, especially in the DRP + C.

Recent Advances in the Treatment of Insulin Resistance Targeting Molecular and Metabolic Pathways: Fighting a Losing Battle?

Diabetes Mellitus (DM) is amongst the most notable causes of years of life lost worldwide and its prevalence increases perpetually. The disease is characterized as multisystemic dysfunctions attributed to hyperglycemia resulting directly from insulin resistance (IR), inadequate insulin secretion, or enormous glucagon secretion. Insulin is a highly anabolic peptide hormone that regulates blood glucose levels by hastening cellular glucose uptake as well as controlling carbohydrate, protein, and lipid metabolism. In the course of Type 2 Diabetes Mellitus (T2DM), which accounts for nearly 90% of all cases of diabetes, the insulin response is inadequate, and this condition is defined as Insulin Resistance. IR sequela include, but are not limited to, hyperglycemia, cardiovascular system impairment, chronic inflammation, disbalance in oxidative stress status, and metabolic syndrome occurrence. Despite the substantial progress in understanding the molecular and metabolic pathways accounting for injurious effects of IR towards multiple body organs, IR still is recognized as a ferocious enigma. The number of widely available therapeutic approaches is growing, however, the demand for precise, safe, and effective therapy is also increasing. A literature search was carried out using the MEDLINE/PubMed, Google Scholar, SCOPUS and Clinical Trials Registry databases with a combination of keywords and MeSH terms, and papers published from February 2021 to March 2022 were selected as recently published papers. This review paper aims to provide critical, concise, but comprehensive insights into the advances in the treatment of IR that were achieved in the last months.

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.

Circulating levels of urocortin neuropeptides are impaired in children with overweight

OBJECTIVE

The corticotropin-releasing factor neuropeptides (corticotropin-releasing hormone [CRH] and urocortin [UCN]-1,2,3) and spexin contribute to the regulation of energy balance and inhibit food intake in mammals. However, the status of these neuropeptides in children with overweight has yet to be elucidated. This study investigated the effect of increased body weight on the circulating levels of these neuropeptides.

METHODS

A total of 120 children with a mean age of 12 years were enrolled in the study. Blood samples were collected to assess the circulating levels of neuropeptides and were correlated with various anthropometric, clinical, and metabolic markers.

RESULTS

Plasma levels of UCNs were altered in children with overweight but less so in those with obesity. Furthermore, the expression pattern of UCN1 was opposite to that of UCN2 and UCN3, which suggests a compensatory effect. However, no significant effect of overweight and obesity was observed on CRH and spexin levels. Finally, UCN3 independently associated with circulating zinc-alpha-2-glycoprotein and UCN2 levels, whereas UCN1 was strongly predicted by TNFα levels.

CONCLUSIONS

Significant changes in neuropeptide levels were primarily observed in children with overweight and were attenuated with increased obesity. This suggests the presence of a compensatory mechanism for neuropeptides to curb the progression of obesity.

Urocortin Neuropeptide Levels Are Impaired in the PBMCs of Overweight Children

The corticotropin-releasing hormone (CRH) and urocortins (UCNs) have been implicated in energy homeostasis and the cellular stress response. However, the expression of these neuropeptides in children remains unclear. Therefore, we determined the impact of obesity on their expression in 40 children who were normal weight, overweight, and had obesity. Peripheral blood mononuclear cells (PBMCs) and plasma were used to assess the expression of neuropeptides. THP1 cells were treated with 25 mM glucose and 200 µM palmitate, and gene expression was measured by real-time polymerase chain reaction (RT-PCR). Transcript levels of neuropeptides were decreased in PBMCs from children with increased body mass index as indicated by a significant decrease in UCN1, UCN3, and CRH mRNA in overweight and obese children. UCN3 mRNA expression was strongly correlated with UCN1, UCN2, and CRH. Exposure of THP1 cells to palmitate or a combination of high glucose and palmitate for 24 h increased CRH, UCN2, and UCN3 mRNA expression with concomitant increased levels of inflammatory and endoplasmic reticulum stress markers, suggesting a crosstalk between these neuropeptides and the cellular stress response. The differential impairment of the transcript levels of CRH and UCNs in PBMCs from overweight and obese children highlights their involvement in obesity-related metabolic and cellular stress.

Spexin and Galanin in Metabolic Functions and Social Behaviors With a Focus on Non-Mammalian Vertebrates

Spexin (SPX) and galanin (GAL) are two neuropeptides that are phylogenetically related and have descended from a common ancestral gene. Considerable attention has been given to these two multifunctional neuropeptides because they share GAL receptors 1,2, and 3. Since GAL and SPX-synthesizing neurons have been detected in several brain areas, therefore, it can be speculated that SPX and GAL are involved in various neurophysiological functions. Several studies have shown the functions of these two neuropeptides in energy regulation, reproduction, and response to stress. SPX acts as a satiety factor to suppress food intake, while GAL has the opposite effect as an orexigenic factor. There is evidence that SPX acts as an inhibitor of reproductive functions by suppressing gonadotropin release, while GAL modulates the activity of gonadotropin-releasing hormone (GnRH) neurons in the brain and gonadotropic cells in the pituitary. SPX and GAL are responsive to stress. Furthermore, SPX can act as an anxiolytic factor, while GAL exerts anti-depressant and pro-depressive effects depending on the receptor it binds. This review describes evidence supporting the central roles of SPX and GAL neuropeptides in energy balance, reproduction, stress, and social behaviors, with a particular focus on non-mammalian vertebrate systems.

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.

The Neuropeptide Spexin Promotes the Osteoblast Differentiation of MC3T3-E1 Cells via the MEK/ERK Pathway and Bone Regeneration in a Mouse Calvarial Defect Model

BACKGROUND

The neural regulation of bone regeneration has emerged recently. Spexin (SPX) is a novel neuropeptide and regulates multiple biological functions. However, the effects of SPX on osteogenic differentiation need to be further investigated. Therefore, the aim of this study is to investigate the effects of SPX on osteogenic differentiation, possible underlying mechanisms, and bone regeneration.

METHODS

In this study, MC3T3-E1 cells were treated with various concentrations of SPX. Cell proliferation, osteogenic differentiation marker expressions, alkaline phosphatase (ALP) activity, and mineralization were evaluated using the CCK-8 assay, reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR), ALP staining, and alizarin red S staining, respectively. To determine the underlying molecular mechanism of SPX, the phosphorylation levels of signaling molecules were examined via western blot analysis. Moreover, in vivo bone regeneration by SPX (0.5 and 1 µg/µl) was evaluated in a calvarial defect model. New bone formation was analyzed using micro-computed tomography (micro-CT) and histology.

RESULTS

The results indicated that cell proliferation was not affected by SPX. However, SPX significantly increased ALP activity, mineralization, and the expression of genes for osteogenic differentiation markers, including runt-related transcription factor 2 (Runx2), Alp, collagen alpha-1(I) chain (Col1a1), osteocalcin (Oc), and bone sialoprotein (Bsp). In contrast, SPX downregulated the expression of ectonucleotide pyrophosphatase/phosphodiesterase 1 (Enpp1). Moreover, SPX upregulated phosphorylated mitogen-activated protein kinase kinase (MEK1/2) and extracellular signal-regulated kinase (ERK1/2). In vivo studies, micro-CT and histologic analysis revealed that SPX markedly increased a new bone formation.

CONCLUSION

Overall, these results demonstrated that SPX stimulated osteogenic differentiation in vitro and increased in vivo bone regeneration via the MEK/ERK pathway.

The Association of Serum Circulating Neuropeptide Q and Chemerin Levels with Cardiometabolic Risk Factors among Patients with Metabolic Syndrome

The potential involvement of neuropeptide Q (NPQ) and chemerin (CHEM) in metabolic disorders is yet to be fully elucidated. The aim of this study was to evaluate serum concentrations of NPQ and CHEM and to establish their relationship with cardiometabolic risk factors among individuals with metabolic syndrome. A total of 66 patients with metabolic syndrome (MetS) and 83 healthy volunteers (non-MetS) underwent biochemical, blood pressure, and anthropometric measurements. The concentration of NPQ in the MetS group was significantly lower (0.47 (0.34 ; 0.54) vs. 0.52 (0.43 ; 0.60) ng/mL, p = 0.015) than in non-MetS, while there were no differences in CHEM level. In the entire study population, we observed several negative correlations between NPQ concentration and waist-hip ratio (WHR), visceral adipose tissue, diastolic blood pressure (DBP), triglycerides (TG) along with a positive correlation with high-density lipoprotein (HDL), total muscle mass, and CHEM. Moreover, a negative correlation was observed in the MetS group between NPQ and glycemia. CHEM showed no significant correlations with cardiometabolic risk factors in the study population. In a multiple regression model, the total muscle mass proved to be an independent factor determining NPQ concentration in the population (p < 0.00000001, R²_adj = 28.6%). NPQ seems to protect against metabolic disorders correlated with obesity. Thus, it is worth considering NPQ level as a candidate protective biomarker of metabolic syndrome complications.

Spexin: Its role, regulation, and therapeutic potential in the hypothalamus

Spexin is the most recently discovered member of the galanin/kisspeptin/spexin family of peptides. This 14-amino acid peptide is highly conserved and is implicated in homeostatic functions including, but not limited to, metabolism, energy homeostasis, and reproduction. Spexin is expressed by neurons in the hypothalamus, which coordinate energy homeostasis and reproduction. Critically, levels of spexin appear to be altered in disorders related to energy homeostasis and reproduction, such as obesity, diabetes, and polycystic ovarian syndrome. In this review, we discuss the evidence for the involvement of spexin in the hypothalamic control of energy homeostasis and reproduction. The anorexigenic properties of spexin have been attributed to its effects on the energy-regulating neuropeptide Y/agouti-related peptide neurons and proopiomelanocortin neurons. While the role of spexin in reproduction remains unclear, there is evidence that gonadotropin-releasing hormone expressing neurons may produce and respond to spexin. Furthermore, we discuss the disorders and concomitant treatments, which have been reported to alter spexin expression, as well as the underlying signaling mechanisms that may be involved. Finally, we discuss the biochemical basis of spexin, its interaction with its cognate receptors, and how this information can be adapted to develop therapeutics for disorders related to the alteration of energy homeostasis and reproduction.

Effect of Exercise Training on Spexin Level, Appetite, Lipid Accumulation Product, Visceral Adiposity Index, and Body Composition in Adults With Type 2 Diabetes

ObjectiveTo compare the effects of resistance and aerobic training (RT and AT) on spexin (SPX), appetite, lipid accumulation product (LAP), visceral adiposity index (VAI), and body composition in type 2 diabetes mellitus (T2DM) patients. Materials and Methods: Thirty-six T2DM men were randomized to receive RT (n = 12), AT (n = 12), or to act as a non-exercise control (CON, n = 12) 3 days a week for 12 weeks. Results: SPX was increased after both RT and AT (66.2% and 46.5%, respectively). VAI, LAP, and homeostasis model assessment-insulin resistance (HOMA-IR) were reduced in both groups, while quantitative insulin sensitivity check index (Quicki) and McAuley's indexes were increased following both interventions. However, the increases of both hunger and PFC in the RT group were greater than those of the AT. Moreover, the improvement of upper-body strength (41% vs. 10.3%) and lower-body strength (42.2% vs. 20.5%) in the RT group was greater than those of the AT. Conclusion: Our investigation shows that regardless of the modes of the regimen, a 12-week exercise intervention with RT and AT can effectively induce a significant improvement in SPX levels, appetite, LAP, VAI, and body composition in adults with T2DM.

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.

Short-term changes and correlations of plasma spexin, kisspeptin, and galanin levels after laparoscopic sleeve gastrectomy

PURPOSE

To determine the circulating levels of spexin, kisspeptin, galanin, and the correlations between these peptides after laparoscopic sleeve gastrectomy (LSG).

METHODS

The plasma levels of the spexin, kisspeptin, and galanin and metabolic parameters (body mass index, weight loss, % excess weight loss, body fat, fasting glucose, HbA1C, and cholesterol levels) were measured (baseline, 1 month, and 3 months) and correlated in thirty adult individuals with obesity (22 female and 8 male) after LSG.

RESULTS

The body mass index (BMI), body fat, fasting glucose, total and low-density lipoprotein cholesterol decreased, while high-density lipoprotein cholesterol and % EWL (excess weight loss) increased at 3 months after surgery. The plasma spexin levels increased at 3 months, kisspeptin levels increased at 1 month and stabilized afterward, and galanin levels decreased at 3 months after LSG. Significant correlations were found between metabolic parameters with spexin, kisspeptin, and galanin. In addition, spexin and kisspeptin were negatively correlated with galanin, while spexin was positively correlated with kisspeptin.

CONCLUSIONS

The biochemical data reveal evidence that LSG causes an increase in the levels of spexin, and kisspeptin and a decrease in galanin levels. Our findings, therefore, suggest a possible interaction between these novel peptides, which have potential roles in obesity and glucose metabolism.