Asprosin in umbilical cord of newborns and maternal blood of gestational diabetes, preeclampsia, severe preeclampsia, intrauterine growth retardation and macrosemic fetus

Adipokines in pregnancy

Reproductive success consists of a sequential events chronology, starting with the ovum fertilization, implantation of the embryo, placentation, and cellular processes like proliferation, apoptosis, angiogenesis, endocrinology, or metabolic changes, which taken together finally conduct the birth of healthy offspring. Currently, many factors are known that affect the regulation and proper maintenance of pregnancy in humans, domestic animals, or rodents. Among the determinants of reproductive success should be distinguished: the maternal microenvironment, genes, and proteins as well as numerous pregnancy hormones that regulate the most important processes and ensure organism homeostasis. It is well known that white adipose tissue, as the largest endocrine gland in our body, participates in the synthesis and secretion of numerous hormones belonging to the adipokine family, which also may regulate the course of pregnancy. Unfortunately, overweight and obesity lead to the expansion of adipose tissue in the body, and its excess in both women and animals contributes to changes in the synthesis and release of adipokines, which in turn translates into dramatic changes during pregnancy, including those taking place in the organ that is crucial for the proper progress of pregnancy, i.e. the placenta. In this chapter, we are summarizing the current knowledge about levels of adipokines and their role in the placenta, taking into account the physiological and pathological conditions of pregnancy, e.g. gestational diabetes mellitus, preeclampsia, or intrauterine growth restriction in humans, domestic animals, and rodents.

In Silico and In Vitro Mapping of Receptor-Type Protein Tyrosine Phosphatase Receptor Type D in Health and Disease: Implications for Asprosin Signalling in Endometrial Cancer and Neuroblastoma

BACKGROUND

Protein Tyrosine Phosphatase Receptor Type D (PTPRD) is involved in the regulation of cell growth, differentiation, and oncogenic transformation, as well as in brain development. PTPRD also mediates the effects of asprosin, which is a glucogenic hormone/adipokine derived following the cleavage of the C-terminal of fibrillin 1. Since the asprosin circulating levels are elevated in certain cancers, research is now focused on the potential role of this adipokine and its receptors in cancer. As such, in this study, we investigated the expression of PTPRD in endometrial cancer (EC) and the placenta, as well as in glioblastoma (GBM).

METHODS

An array of in silico tools, in vitro models, tissue microarrays (TMAs), and liquid biopsies were employed to determine the gene and protein expression of PTPRD in healthy tissues/organs and in patients with EC and GBM.

RESULTS

PTPRD exhibits high expression in the occipital lobe, parietal lobe, globus pallidus, ventral thalamus, and white matter, whereas in the human placenta, it is primarily localised around the tertiary villi. PTPRD is significantly upregulated at the mRNA and protein levels in patients with EC and GBM compared to healthy controls. In patients with EC, PTPRD is significantly downregulated with obesity, whilst it is also expressed in the peripheral leukocytes. The EC TMAs revealed abundant PTPRD expression in both low- and high-grade tumours. Asprosin treatment upregulated the expression of PTPRD only in syncytialised placental cells.

CONCLUSIONS

Our data indicate that PTPRD may have potential as a biomarker for malignancies such as EC and GBM, further implicating asprosin as a potential metabolic regulator in these cancers. Future studies are needed to explore the potential molecular mechanisms/signalling pathways that link PTPRD and asprosin in cancer.

Asprosin, a novel glucogenic adipokine implicated in type 2 diabetes mellitus

Asprosin, encoded by penultimate two exons (exon 65 and exon 66) of the gene Fibrillin 1 (FBN1), has been recently discovered to be a novel hormone secreted by white adipose tissues during fasting. The glucose metabolism disorders are often accompanied by increased asprosin level. Previous research suggests that asprosin may contribute to the development of diabetes by regulating glucose homeostasis, appetite, insulin secretion, and insulin sensitivity. In this review, we summarize the recent findings from studies on asprosin and its association with Type 2 diabetes mellitus, and discusses its mechanisms from various aspects, so as to provide clinical diagnosis and treatment ideas for T2DM.

Association Between Plasma Asprosin Levels and Gestational Diabetes Mellitus

Purpose

This study sought to investigate whether asprosin can be used in the diagnosis of GDM or for diagnostic purposes in high-risk pregnancies, along with a review of other parameters that may be associated with serum asprosin levels.

Patients and Methods

The study investigated the association between gestational diabetes mellitus (GDM) and asprosin levels. A total of 93 participants; 30 patients with GDM, 33 healthy pregnant women with normal glucose tolerance (NGT), and 30 healthy non-diabetic women (control group) at the Endocrinology and Metabolic Diseases outpatient clinic of a tertiary care university hospital were enrolled in the study. Patients with GDM and NGT were examined in terms of GDM between the 24th and 28th week of pregnancy (2nd trimester). Patient data were collected during routine examinations, and asprosin levels were measured using the ELISA method. All participants underwent testing for measurements of serum hemoglobin, insulin, C-peptide, fasting plasma glucose, and glycated hemoglobin (HbA1c) levels following a fasting period of at least eight hours.

Results

Asprosin levels were higher in pregnant women with NGT and with GDM versus controls (Control-NGT asprosin, p = 0.001; Control-GDM asprosin, p = 0.001). Pregnant women with GDM had higher asprosin levels than those with NGT (p = 0.001). In detecting GDM in pregnant women, an asprosin cutoff value of >31.709 ng/mL yielded a sensitivity of 93.3%, specificity of 90.9%, positive predictive value of 90.3%, and negative predictive value of 93.75% (p < 0.001).

Conclusion

Serum asprosin levels can potentially be used as a marker in the diagnosis of GDM.

Betatrophin, elabela, asprosin, glucagon and subfatin peptides in breast tissue, blood and milk in gestational diabetes

We investigated the presence of asprosin (ASP), betatrophin, elabela (ELA), glucagon and subfatin (SUB) in the milk of mothers with gestational diabetes mellitus (GDM) and compared their levels with blood levels. We also investigated whether these peptides are synthesized by the breast. We investigated 12 volunteer mothers with GDM and 14 pregnant non-GDM control mothers. The peptides were measured using ELISA and their tissue localization was determined using immunohistochemistry. Breast milk contains ASP, betatrophin, ELA, glucagon and SUB. The amount of the peptides ranged from highest to the lowest in colostrum, transitional milk and mature milk. The amount of peptides in the milk was greater than for blood. The peptides, except for ELA, were increased in milk and blood by GDM. Betatrophin and ELA are synthesized in the connective tissue of the breast. ASP, glucagon and SUB are synthesized in the alveolar tissue of the breast. These peptides in breast milk may contribute to the development of the gastrointestinal tract of newborns and infants.

Asprosin in health and disease, a new glucose sensor with central and peripheral metabolic effects

Adipose tissue malfunction leads to altered adipokine secretion which might consequently contribute to an array of metabolic diseases spectrum including obesity, diabetes mellitus, and cardiovascular disorders. Asprosin is a novel diabetogenic adipokine classified as a caudamin hormone protein. This adipokine is released from white adipose tissue during fasting and elicits glucogenic and orexigenic effects. Although white adipose tissue is the dominant source for this multitask adipokine, other tissues also may produce asprosin such as salivary glands, pancreatic B-cells, and cartilage. Significantly, plasma asprosin levels link to glucose metabolism, lipid profile, insulin resistance (IR), and β-cell function. Indeed, asprosin exhibits a potent role in the metabolic process, induces hepatic glucose production, and influences appetite behavior. Clinical and preclinical research showed dysregulated levels of circulating asprosin in several metabolic diseases including obesity, type 2 diabetes mellitus (T2DM), polycystic ovarian syndrome (PCOS), non-alcoholic fatty liver (NAFLD), and several types of cancer. This review provides a comprehensive overview of the asprosin role in the etiology and pathophysiological manifestations of these conditions. Asprosin could be a promising candidate for both novel pharmacological treatment strategies and diagnostic tools, although developing a better understanding of its function and signaling pathways is still needed.

Fibrillin-1 and asprosin, novel players in metabolic syndrome

Fibrillin-1 is a major component of the extracellular microfibrils, where it interacts with other extracellular matrix proteins to provide elasticity to connective tissues, and regulates the bioavailability of TGFβ family members. A peptide consisting of the C-terminal 140 amino acids of fibrillin-1 has recently been identified as a glucogenic hormone, secreted from adipose tissue during fasting and targeting the liver to release glucose. This fragment, called asprosin, also signals in the hypothalamus to stimulate appetite. Asprosin levels are correlated with many of the pathologies indicative of metabolic syndrome, including insulin resistance and obesity. Previous studies and reviews have addressed the therapeutic potential of asprosin as a target in obesity, diabetes and related conditions without considering mechanisms underlying the relationship between generation of asprosin and expression of the much larger fibrillin-1 protein. Profibrillin-1 undergoes obligatory cleavage at the cell surface as part of its assembly into microfibrils, producing the asprosin peptide as well as mature fibrillin-1. Patterns of FBN1 mRNA expression are inconsistent with the necessity for regulated release of asprosin. The asprosin peptide may be protected from degradation in adipose tissue. We present evidence for an alternative possibility, that asprosin mRNA is generated independently from an internal promoter within the 3' end of the FBN1 gene, which would allow for regulation independent of fibrillin-synthesis and is more economical of cellular resources. The discovery of asprosin opened exciting possibilities for treatment of metabolic syndrome related conditions, but there is much to be understood before such therapies could be introduced into the clinic.

Differential Regulation of Genes by the Glucogenic Hormone Asprosin in Ovarian Cancer

Background: Ovarian cancer (OvCa) is one of the most lethal forms of gynaecological malignancy. Altered energy metabolism and increased aerobic glycolysis in OvCa are hallmarks that demand attention. The glucogenic hormone asprosin is often dysregulated in metabolic disorders such as insulin resistance, diabetes (type 2 and gestational), and preeclampsia. Despite association with metabolic disorders, its role in energy metabolism within the tumour microenvironment is yet to be explored. Here, we study the role of asprosin in OvCa using transcriptomics and expand on functional studies with clinical samples. Methods: RNA sequencing, functional gene enrichment analysis, Western blotting and ImageStream. Results: Following treatment with 100 nM of asprosin, the serous OvCa cell line, SKOV-3, displayed 160 and 173 gene regulatory changes, at 4 and 12 h respectively, when compared with control samples (p < 0.05 and Log2FC > 1). In addition to energy metabolism and glucose-related pathways, asprosin was shown to alter pathways associated with cell communication, TGF-β signalling, and cell proliferation. Moreover, asprosin was shown to induce phosphorylation of ERK1/2 in the same in vitro model. Using liquid biopsies, we also report for novel expression of asprosin’s predicted receptors OR4M1 and TLR4 in cancer-associated circulating cells; with significant reduction seen between pre-chemotherapy and end of first line chemotherapy, in addition to patients under maintenance with bevacizumab +/− olaparib for OR4M1. Conclusions: In relation to OvCa, asprosin appears to regulate numerous signalling pathways in-vitro. The prognostic potential of OR4M1 in liquid biopsies should also be explored further.

The Effects of Asprosin on Exercise-Intervention in Metabolic Diseases

Fibrillin is the major constituent of extracellular microfibrils, which are distributed throughout connective tissues. Asprosin is derived from the C-terminal region of the FBN1 gene, which encodes profibrillin that undergoes cleavage by furin protein. In response to fasting with low dietary glucose, asprosin is released as a secreted factor from white adipose tissue, and is transported to the liver for the mediation of glucose release into the blood circulation. Through binding to OLFR734, an olfactory G-protein-coupled receptor in liver cells, asprosin induces a glucogenic effect to regulate glucose homeostasis. Bioinformatics analyses revealed that the FBN1 gene is abundantly expressed in human skeletal muscle-derived mesoangioblasts, osteoblast-like cells, and mesenchymal stem cells, indicating that the musculoskeletal system might play a role in the regulation of asprosin expression. Interestingly, recent studies suggest that asprosin is regulated by exercise. This timely review discusses the role of asprosin in metabolism, its receptor signalling, as well as the exercise regulation of asprosin. Collectively, asprosin may have a vital regulatory effect on the improvement of metabolic disorders such as diabetes mellitus and obesity via exercise.

Protein tyrosine phosphatase receptor δ serves as the orexigenic asprosin receptor

Asprosin is a fasting-induced glucogenic and centrally acting orexigenic hormone. The olfactory receptor Olfr734 is known to be the hepatic receptor for asprosin that mediates its effects on glucose production, but the receptor for asprosin's orexigenic function has been unclear. Here, we have identified protein tyrosine phosphatase receptor δ (Ptprd) as the orexigenic receptor for asprosin. Asprosin functions as a high-affinity Ptprd ligand in hypothalamic AgRP neurons, regulating the activity of this circuit in a cell-autonomous manner. Genetic ablation of Ptprd results in a strong loss of appetite, leanness, and an inability to respond to the orexigenic effects of asprosin. Ablation of Ptprd specifically in AgRP neurons causes resistance to diet-induced obesity. Introduction of the soluble Ptprd ligand-binding domain in the circulation of mice suppresses appetite and blood glucose levels by sequestering plasma asprosin. Identification of Ptprd as the orexigenic asprosin receptor creates a new avenue for the development of anti-obesity therapeutics.

Correlation of metabolic characteristics with maternal, fetal and placental asprosin in human pregnancy

OBJECTIVE

Asprosin is a recently discovered hormone associated with obesity and diabetes mellitus. Little is known about asprosin's role during pregnancy, but a contribution of asprosin to pregnancy complications resulting from maternal obesity and gestational diabetes mellitus (GDM) is conceivable. We assessed the potential effects of obesity, GDM and other clinical parameters on maternal and fetal umbilical plasma asprosin concentrations and placental asprosin expression.

DESIGN

The Cologne-Placenta Cohort Study comprises 247 female patients, from whom blood and placentas were collected at the University Hospital Cologne.

METHODS

We studied the maternal and fetal umbilical plasma and placentas of pregnant women with an elective, primary section. Sandwich ELISA measurements of maternal and fetal umbilical plasma and immunohistochemical stainings of placental tissue were performed to determine the asprosin levels. Also, the relation between asprosin levels and clinical blood parameters was studied.

RESULTS

There was a strong correlation between the maternal and fetal plasma asprosin levels and both increased with GDM in normal-weight and obese women. Asprosin immunoreactivity was measured in cultivated placental cells and placental tissue. BMI and GDM were not but pre-pregnancy exercise and smoking were correlated with maternal and/or fetal asprosin levels. Placental asprosin levels were associated with maternal but not with fetal plasma asprosin levels and with BMI but not with GDM. Placental asprosin was related to maternal insulin levels and increased upon insulin treatment in GDM patients.

CONCLUSIONS

Asprosin could potentially act as a biomarker and contribute to the clinical manifestation of pregnancy complications associated with maternal obesity.

Sensitive asprosin detection in clinical samples reveals serum/saliva correlation and indicates cartilage as source for serum asprosin

The C-terminal pro-fibrillin-1 propeptide asprosin is described as white adipose tissue derived hormone that stimulates rapid hepatic glucose release and activates hunger-promoting hypothalamic neurons. Numerous studies proposed correlations of asprosin levels with clinical parameters. However, the enormous variability of reported serum and plasma asprosin levels illustrates the need for sensitive and reliable detection methods in clinical samples. Here we report on newly developed biochemical methods for asprosin concentration and detection in several body fluids including serum, plasma, saliva, breast milk, and urine. Since we found that glycosylation impacts human asprosin detection we analyzed its glycosylation profile. Employing a new sandwich ELISA revealed that serum and saliva asprosin correlate strongly, depend on biological sex, and feeding status. To investigate the contribution of connective tissue-derived asprosin to serum levels we screened two cohorts with described cartilage turnover. Serum asprosin correlated with COMP, a marker for cartilage degradation upon running exercise and after total hip replacement surgery. This together with our finding that asprosin is produced by primary human chondrocytes and expressed in human cartilage suggests a contribution of cartilage to serum asprosin. Furthermore, we determined asprosin levels in breast milk, and urine, for the first time, and propose saliva asprosin as an accessible clinical marker for future studies.

Sex-Specific Effects of Maternal and Post-Weaning High-Fat Diet on Adipose Tissue Remodeling and Asprosin Expression in Mice Offspring

SCOPE

Perinatal high-fat diet (HFD) increases risk of metabolic disorders in offspring. Adipose tissue remodeling is associated with metabolic syndrome. The current study characterizes the profile of maternal HFD-induced changes in adipose tissue remodeling and adipokines expression in mice offspring.

METHODS AND RESULTS

Female C57BL/6 mice are fed with CHOW or HFD for 2 weeks before mating, throughout gestation and lactation. At weaning, pups are randomly fed with CHOW or HFD, resulting in eight groups according to sex and maternal diet: Male CHOW-CHOW (MCC), Male CHOW-HFD (MCH), Male HFD-CHOW (MHC), Male HFD-HFD (MHH), Female CHOW-CHOW (FCC), Female CHOW-HFD (FCH), Female HFD-CHOW (FHC), and Female HFD-HFD (FHH). Increased body weight, impaired glucose tolerance, increased adipose tissue mass and hypertrophy, and decreased circulating asprosin level are only observed in male offspring exposure to maternal HFD. Serum asprosin level negatively correlates with fasting blood glucose, serum cholesterol (CHO), and high-density lipoprotein (HDL) levels, while positively correlates with serum low-density lipoprotein (LDL) and glutamate-oxaloacetate transaminase (GOT) levels in male offspring. A combination of genetic and biochemical analyses of adipokines shows the depot- and sex-specific changes in response to maternal and/or post-weaning HFD.

CONCLUSION

This study's results reveal the differential metabolic changes in response to maternal and/or post-weaning HFD in male and female offspring. The effect of maternal HFD on metabolic phonotype is more obvious in male offspring, supporting the notion that males are more susceptible to HFD-induced metabolic disorders.

Serum levels of Asprosin in patients diagnosed with coronary artery disease (CAD): a case-control study

Background

Coronary artery disease (CAD) is considered as a multi-faceted chronic inflammatory disease involving reduced blood supply to the myocardium as a result of accumulating lipids in the atrial walls. Visceral adiposity with disrupted release of adipokines play a key role in its pathogenesis. Asprosin is a newly identified fasting-induced glucogenic adipokine that has been related with metabolic disorders such as type II diabetes mellitus and polycystic ovary syndrome. The preset study sought to assess circulating asprosin in context of CAD.

Methods

In this study, serum levels of asprosin were determined in 88 CAD patients and 88 non-CAD healthy controls. Serum IL-6, TNF-α, asprosin and adiponectin were assessed using ELISA kits.

Results: Serum asprosin was found to be higher in CAD patients when compared to non-CAD subjects (7.84 ± 2.08 versus 5.02 ± 1.29 μg/mL, p <  0.001). Similarly, serum TNF-α, and IL-6 elevated in CAD group significantly (p <  0.001). However, circulating adiponectin diminished in CAD group when compared with non-CAD subjects (p < 0.001). Moreover, serum asprosin levels directly correlated with BMI, FBG, HOMA-IR, TG and TC. Logistic regression analyses showed that asprosin levels were associated with increased risk of developing CAD (odds ratio: 3.01, 95% CI: 2.16, 4.20 and p < 0.001), after adjusting for potential confounders (age, sex and BMI).

Conclusions

The present study findings suggested a possible relation of serum asprosin with the pathogenesis of CAD, in particular through insulin resistance and dyslipidemia.

Asprosin, a novel pleiotropic adipokine implicated in fasting and obesity-related cardio-metabolic disease: Comprehensive review of preclinical and clinical evidence

White adipose tissue is a dynamic endocrine organ that releases an array of adipokines, which play a key role in regulating metabolic homeostasis and multiple other physiological processes. An altered adipokine secretion profile from adipose tissue depots frequently characterizes obesity and related cardio-metabolic diseases. Asprosin is a recently discovered adipokine that is released in response to fasting. Following secretion, asprosin acts - via an olfactory G-protein coupled receptor and potentially via other unknown receptor(s) - on hepatocytes and agouti-related peptide-expressing neurons in the central nervous system to stimulate glucose secretion and promote appetite, respectively. A growing body of both in vitro and in vivo studies have shown asprosin to exert a number of effects on different metabolic tissues. Indeed, asprosin can attenuate insulin signalling and promote insulin resistance in skeletal muscle by increasing inflammation and endoplasmic reticulum stress. Interestingly, asprosin may also play a protective role in cardiomyocytes that are exposed to hypoxic conditions. Moreover, clinical studies have reported elevated circulating asprosin levels in obesity, type 2 diabetes and other obesity-related cardio-metabolic diseases, with significant associations to clinically relevant parameters. Understanding the spectrum of the effects of this novel adipokine is essential in order to determine its physiologic role and its significance as a potential therapeutic target and/or a biomarker of cardio-metabolic disease. The present review offers a comprehensive overview of the published literature on asprosin, including both clinical and preclinical studies, focusing on its role in metabolism and cardio-metabolic disease.

Asprosin-neutralizing antibodies as a treatment for metabolic syndrome

Background

Recently, we discovered a new glucogenic and centrally acting orexigenic hormone - asprosin. Asprosin is elevated in metabolic syndrome (MS) patients, and its genetic loss results in reduced appetite, leanness, and blood glucose burden, leading to protection from MS.

Methods

We generated three independent monoclonal antibodies (mAbs) that recognize unique asprosin epitopes and investigated their preclinical efficacy and tolerability in the treatment of MS.

Results

Anti-asprosin mAbs from three distinct species lowered appetite and body weight, and reduced blood glucose in a dose-dependent and epitope-agnostic fashion in three independent MS mouse models, with an IC50 of ~1.5 mg/kg. The mAbs displayed a half-life of over 3days in vivo, with equilibrium dissociation-constants in picomolar to low nanomolar range.

Conclusions

We demonstrate that anti-asprosin mAbs are dual-effect pharmacologic therapy that targets two key pillars of MS - over-nutrition and hyperglycemia. This evidence paves the way for further development towards an investigational new drug application and subsequent human trials for treatment of MS, a defining physical ailment of our time.

Funding

DK118290 and DK125403 (R01; National Institute of Diabetes and Digestive and Kidney Diseases), DK102529 (K08; National Institute of Diabetes and Digestive and Kidney Diseases), Caroline Wiess Law Scholarship (Baylor College of Medicine, Harrington Investigatorship Harrington Discovery Institute at University Hospitals, Cleveland); Chao Physician Scientist Award (Baylor College of Medicine); RP150551 and RP190561 (Cancer Prevention and Research Institute of Texas [CPRIT]).

Asprosin-A Fasting-Induced, Glucogenic, and Orexigenic Adipokine as a New Promising Player. Will It Be a New Factor in the Treatment of Obesity, Diabetes, or Infertility? A Review of the Literature

Asprosin is a recently discovered protein released during fasting conditions mainly by adipocytes from white adipose tissue. As a glucogenic peptide, it stimulates the release of glucose from hepatic cells by binding to the OLFR734 receptor and leading to the activation of the G protein-cAMP-PKA pathway. As it crosses the blood–brain barrier, it also acts as an orexigenic peptide that stimulates food intake through activation of AgRP neurons in the hypothalamus; thus, asprosin participates in maintaining the body’s energy homeostasis. Moreover, studies have shown that asprosin levels are pathologically elevated in obesity and related diseases. However, the administration of anti-asprosin antibodies can both normalize its concentration and reduce food intake in obese mice, which makes it an interesting factor to combat obesity and related diseases. Current research also draws attention to the relationship between asprosin and fertility, especially in men. Asprosin improves age- and obesity-related decrease in fertility potential by improving sperm motility. It should also be mentioned that plasma asprosin levels can be differentially modulated by physical activity; intense anaerobic exercise increases asprosin level, while aerobic exercise decreases it. However, further research is necessary to confirm the exact mechanisms of asprosin activity and its potential as a therapeutic target.

A state of the art review on the novel mediator asprosin in the metabolic syndrome

Metabolic syndrome is a complex and heterogeneous pathology characterized by a cluster of biochemical, clinical, and metabolic factors that came together in raising the risk of cardiovascular diseases, type 2 diabetes mellitus, and all-cause mortality. Some of these features are well defined in this syndrome like: obesity, inflammation, hypertension, insulin resistance, atherosclerotic dyslipidemias, endothelial dysfunction, and inflammation. This circuit is intermediated by a complex network of hormones, cytokines, transcription factors, and adipokines, among others. Some like leptin, adiponectin, Plasminogen activator inhibitor-1, interleukin-6, Tumor necrosis factor, and their influence on the metabolic syndrome are well described in the literature and new players are described continuously. One novel player was described in 2016 by Romere et al as a fasting-induced glycogenic protein hormone named asprosin. In order to perform a state-of-the-art, nonsystematic review of asprosin, a study of the available literature was carried out in the main database (Pubmed) and the results were studied and correlated to better understand the mechanism of action of this hormone. Asprosin is not only associated with the metabolic syndrome features like glucose and lipid metabolism, insulin resistance, obesity and inflammation but also in other pathologies metabolic syndrome related like diabetic retinopathy, polycystic ovary syndrome and anorexia nervosa. A limited number of pathways were already unveiled although much more research is needed to better understand the therapeutical potential of asprosin in the metabolic syndrome.

Fibrillin-1 and fibrillin-1-derived asprosin in adipose tissue function and metabolic disorders

The extracellular matrix microenvironment of adipose tissue is of critical importance for the differentiation, remodeling and function of adipocytes. Fibrillin-1 is one of the main components of microfibrils and a key player in this process. Furin processing of profibrillin-1 results in mature fibrillin-1 and releases the C-terminal propeptide as a circulating hunger hormone, asprosin. Mutations in the fibrillin-1 gene lead to adipose tissue dysfunction and causes Marfan syndrome, marfanoid progeroid lipodystrophy syndrome, and neonatal progeroid syndrome. Increased TGF-β signaling, altered mechanical properties and impaired adipogenesis are potential causes of adipose tissue dysfunction, mediated through deficient microfibrils. Circulating asprosin on the other hand is secreted primarily by white adipose tissue under fasting conditions and in obesity. It increases hepatic glucose production and drives insulin secretion and appetite stimulation through inter-organ cross talk. This review discusses the metabolic consequences of fibrillin-1 and fibrillin-1-derived asprosin in pathological conditions. Understanding the dynamic role of fibrillin-1 in the adipose tissue milieu and of circulating asprosin in the body can provide novel mechanistic insights into how fibrillin-1 may contribute to metabolic syndrome. This could lead to new management regimens of patients with metabolic disease.

Energy Regulation Mechanism and Therapeutic Potential of Asprosin

Genetic studies of patients with neonatal progeroid syndrome led to the discovery of the novel fasting-induced, glucogenic, and orexigenic hormone named asprosin, the C-terminal cleavage product of profibrillin. Upon secretion, asprosin travels to the liver, where it exerts a glucogenic effect through OR4M1, an olfactory G-protein-coupled receptor. It also crosses the blood-brain barrier to stimulate appetite-modulating neurons in the arcuate nucleus of the hypothalamus, exerting an orexigenic effect via an as yet unidentified receptor. Specifically, it stimulates appetite by activating orexigenic AgRP neurons and inhibiting anorexigenic POMC neurons. Studies have also focused on the therapeutic potential of inhibiting asprosin for treatment of obesity and type 2 diabetes, both of which are characterized by high levels of circulating asprosin. It has been shown that anti-asprosin monoclonal antibodies reduce blood glucose, appetite, and body weight, validating asprosin as a therapeutic target. Current work aims to uncover key features of the asprosin biology such as the identification of its neuronal receptor, identification of the secretion mechanism from adipose tissue, and development of anti-asprosin monoclonal antibodies as diabetes and obesity therapies.

Asprosin: A Novel Player in Metabolic Diseases

Asprosin, a novel glucogenic adipokine, is encoded by two exons (exon 65 and exon 66) of the gene Fibrillin 1 (FBN1) and mainly synthesized and released by white adipose tissue during fasting. Asprosin plays a complex role in the central nervous system (CNS), peripheral tissues, and organs. It is involved in appetite, glucose metabolism, insulin resistance (IR), cell apoptosis, etc. In this review, we will summarize the newly discovered roles of asprosin in metabolic diseases including diabetes, obesity, polycystic ovarian syndrome (PCOS), and cardiovascular disease (CVD), which may contribute to future clinical diagnosis and treatment.