Circulating neuregulin 4 levels are inversely associated with subclinical cardiovascular disease in obese adults

The journey towards physiology and pathology: Tracing the path of neuregulin 4

Neuregulin 4 (Nrg4), an epidermal growth factor (EGF) family member, can bind to and activate the ErbB4 receptor tyrosine kinase. Nrg4 has five different isoforms by alternative splicing and performs a wide variety of functions. Nrg4 is involved in a spectrum of physiological processes including neurobiogenesis, lipid metabolism, glucose metabolism, thermogenesis, and angiogenesis. In pathological processes, Nrg4 inhibits inflammatory factor levels and suppresses apoptosis in inflammatory diseases. In addition, Nrg4 could ameliorate obesity, insulin resistance, and cardiovascular diseases. Furthermore, Nrg4 improves non-alcoholic fatty liver disease (NAFLD) by promoting autophagy, improving lipid metabolism, and inhibiting cell death of hepatocytes. Besides, Nrg4 is closely related to the development of cancer, hyperthyroidism, and some other diseases. Therefore, elucidation of the functional role and mechanisms of Nrg4 will provide a clearer view of the therapeutic potential and possible risks of Nrg4.

Study of neuregulin-4 levels in newly diagnosed type 2 diabetes mellitus

Background

Neuregulin-4 is a recently recognized adipokine acting as ligands to tyrosine kinases receptor of the Erb B family. This adipose tissue augmented endocrine factor participates in the modulation of lipid and glucose metabolism and energy homeostasis. This novel adipokine is associated with insulin resistance, dyslipidemia, obesity, oxidative stress, and inflammation.

Objective

The study aimed to compare plasma levels of neuregulin-4 in newly diagnosed type 2 diabetes mellitus as compared to matched controls and to correlate with glycemic and lipid parameters.

Materials and Methods

100 newly diagnosed T2DM patients and 100 age, sex, and BMI-matched controls after fulfilling all exclusion and inclusion criteria were included in the study. Fasting and postprandial blood glucose levels, glycated hemoglobin (HbA1c), and fasting plasma insulin levels were measured in both cases and controls. HOMA-IR values in both groups were calculated using fasting glucose and insulin levels.

Results

Mean levels of plasma neuregulin-4(pg/mL) in newly diagnosed T2DM were 7949.76 ± 949.76) pg/ml, which was significantly lower as compared to 9143 ±949.76) pg/ml in the control group (P-value <.0001). In the present study, a significant negative correlation was seen between plasma neuregulin-4 (pg/mL) with fasting blood sugar, postprandial blood sugar, HbA1C, and HOMA-IR with a correlation coefficient of -0.303, -0.416, -0.433, and -0.514, respectively. Moreover, a significant positive correlation was seen between plasma neuregulin-4 (pg/mL) with HDL with a correlation coefficient of 0.216. A significant negative correlation was seen between plasma neuregulin-4 (pg/mL) and LDL, with a correlation coefficient -0.208.

Conclusion

Neuregulin levels are significantly lower in diabetics as compared to controls. There levels correlated inversely with HbA1C and HOMA IR.

The relationship of circulating neuregulin 4 and irisin, and traditional and novel cardiometabolic risk factors with the risk and severity of coronary artery disease

BACKGROUND AND AIMS

Neuregulin 4 (NRG4) and irisin are adipokines that have been suggested to be associated with cardiometabolic risk factors and coronary artery disease (CAD), but the data are inconclusive. This study aimed to investigate the relationship between circulating NRG4 and irisin and cardiometabolic risk factors with CAD risk and severity.

METHODS AND RESULTS

In this cross-sectional study, the presence of CAD and the severity of stenosis (gensini score) were documented based on coronary angiography in 166 adults. Circulating NRG4 and irisin, glucose homeostasis markers, hs-CRP, lipid profiles, blood pressure, and anthropometric measurements were assessed as well. Age (p = 0.005), sex (p = 0.008), SBP (p = 0.033), DBP (p = 0.04), MAP (p = 0.018), FBG (p = 0.012), insulin (p = 0.039) and HOMA-IR (p = 0.01) were significantly associated with odds of having CAD. The final logistic regression model showed that age, sex, HOMA-IR, and MAP were the most important determinants of having CAD. There were no significant associations between circulating irisin and NRG4 with odds of having CAD. The final general linear model showed that being men (β = 17.303, 95% CI: 7.086-27.52, P = 0.001), age (Aβ = 0.712, 95% CI: 0.21-1.214, P = 0.006), HOMA-IR (Aβ = 2.168, 95% CI: 0.256 to 4.079, P = 0.027), and NRG4 level (β = 1.836, 95% CI: 0.119-3.553, P = 0.036) were directly associated with higher gensini score. Participants with the three-vessel disease had a mean increase of about 5 units in circulating irisin compared to those with no clinical CAD (β = 5.221, 95% CI: 0.454-9.987, p = 0.032).

CONCLUSIONS

This study showed that the adipokines NRG4 and Irisin might be associated with the severity of coronary stenosis.

Implications of the Serum Concentrations of Neuregulin-4 (Nrg4) in Patients with Coronary Artery Disease: A Case-Control Study

Background

Neuregulin-4 (Nrg4), a novel brown fat-enriched factor, has been reported to play a crucial role in developing metabolic disorders. The current case-control study aimed to investigate the association between serum Nrg4 and coronary artery disease (CAD).

Methods

This study enrolled 43 patients with CAD and 43 subjects with normal coronary arteries diagnosed by coronary angiography. Anthropometric and biochemical parameters were measured and recorded. The serum Nrg4 level was determined using the enzyme-linked immunosorbent assay. The relationships between circulating Nrg4 and CAD and other clinical parameters were analyzed. A receiver operating characteristic analysis was applied to assess the utility of Nrg4 in identifying CAD.

Results

The study population comprised 86 patients, including 64 men (74.4%), at a mean age of 57.83±6.01 years. Patients with CAD had significantly lower serum Nrg4 than the control group (P<0.001). The serum Nrg4 level was negatively correlated with anthropometric variables, including the body mass index, waist circumference, and the waist-to-hip ratio, fasting blood glucose, and the triglyceride-glucose index (P<0.05). In multivariable-adjusted regression analysis, the odds of CAD decreased by 46% per 1 SD elevation in the serum Nrg4 level (OR, 0.54; 95% CI, 0.40 to 0.73; P<0.001) after controlling for potential confounders. Nrg4 showed a significantly high area under the curve value (AUC, 0.85; 95% CI, 0.75 to 0.94) with 81.4% sensitivity and 95.3% specificity to identify CAD.

Conclusion

Generally, the serum level of Nrg4 declines in patients with CAD, which might be an independent risk factor for CAD.

Correlation of asprosin and Nrg-4 with type 2 diabetes Mellitus Complicated with Coronary Heart Disease and the Diagnostic Value

PURPOSE

Asprosin is a newly discovered adipose factor secreted by white fat, which is involved in glucose metabolism and inflammation. Neuregulin-4 (Nrg-4) is a new adipose factor released from brown adipose tissue and is considered to play an important role in metabolism. This study aims to explore the association between serum Asprosin, Nrg-4 level and coronary heart disease(CHD) in patients with type 2 diabetes mellitus(T2DM) and the diagnostic value.

PATIENTS AND METHODS

157 patients with T2DM were enrolled from Affiliated Hospital of Chengde Medical University between December 2020 to July 2021. These patients were divided into T2DM without CHD group (T2DM-0, n = 80) and T2DM with CHD (T2DM-CHD, n = 77). Serum Asprosin and Nrg-4 expression was detected by enzyme-linked immunosorbent assay, and the correlations between Asprosin or Nrg-4 and clinical and biochemical indicators were analyzed. A receiver operating characteristics curve analysis and area under the curve (AUC) were used to evaluate diagnostic accuracy.

RESULTS

Serum Asprosin level of the T2DM-CHD group were significantly higher and Nrg-4 level significantly lower than those of the T2DM-0 group.Spearman correlation analysis showed that serum Asprosin levels were significantly positively correlated with diabetes course,history of hypertension, fasting plasma glucose(FPG), glycosylated hemoglobin A1c(HbA1C), triglycerides(TG),triglyceride glucose index(TyG index) and urea, and negatively correlated with ALT (all p < 0.05). Nrg-4 was negatively correlated with history of hypertension, body mass index(BMI), FPG, HbA1C, TG, and TyG indexes (all p < 0.05), and positively correlated with high-density lipoprotein cholesterol(HDL-C)(p < 0.05).Logistic regression analysis showed that after adjusting potential confounders, Asprosin was a risk factor for diabetes mellitus, Nrg-4 was a protective factor.The AUC of Asprosin for diagnosing T2DM-CHD was 0.671 (95% confidence interval [CI] 0.584-0.759), and the AUC of the Nrg4 index for diagnosing T2DM-CHD was 0.772 (95% CI 0.700-0.844). The AUC of Asprosin and Nrg-4 for the combined diagnosis of T2DM-CHD was 0.796 (95% CI 0.726-0.864).

CONCLUSION

Asprosin and Nrg-4 may be novel diagnostic biomarkers for T2DM with CHD, as they effectively improved the diagnostic accuracy for T2DM-CHD.

Neuregulin 4 as a novel adipokine in energy metabolism

Adipose tissue has been shown to play a key role in energy metabolism and it has been shown to regulate metabolic homeostasis through the secretion of adipokines. Neuregulin 4 (Nrg4), a novel adipokine secreted mainly by brown adipose tissue (BAT), has recently been characterized as having an important effect on the regulation of energy homeostasis and glucolipid metabolism. Nrg4 can modulate BAT-related thermogenesis by increasing sympathetic innervation of adipose tissue and therefore has potential metabolic benefits. Nrg4 improves metabolic dysregulation in various metabolic diseases such as insulin resistance, obesity, non-alcoholic fatty liver disease, and diabetes through several mechanisms such as anti-inflammation, autophagy regulation, pro-angiogenesis, and lipid metabolism normalization. However, inconsistent findings are found regarding the effects of Nrg4 on metabolic diseases in clinical settings, and this heterogeneity needs to be further clarified by future studies. The potential metabolic protective effect of Nrg4 suggests that it may be a promising endocrine therapeutic target.

Circulating galectin-3 levels are inversely associated with subclinical cardiovascular disease in obese adults

BACKGROUND

Galectin-3 is a new cytokine that is mainly secreted by activated macrophages. It is involved in apoptosis, inflammation and may play a role in the development of cardiovascular disease (CVD). However, there is little information about the association between circulating galectin-3 and subclinical atherosclerosis in humans.

METHODS AND RESULTS

We measured serum galectin-3 in 483 obese adult subjects (aged 40 years and over) who had the measurement of carotid intima-media thickness (CIMT) recruited from the community. Adults with lower levels of circulating galectin-3 had increased CIMT (p < 0.05). In multivariable linear regression analyses, circulating galectin-3 was independently associated with CIMT. The risks of increased CIMT were significantly decreased by 65.1% (OR (95% CI): 0.349 (0.165-0.739)), adjusting for possible confounding factors. Notably, individuals in the lowest quartile of serum galectin-3 were 1.80 times (p < 0.05) more likely to have increased CIMT than those in the highest quartile in multivariable logistic regression analyses; however, such associations with circulating galectin-3 were not noted for carotid plague.

CONCLUSIONS

These findings propose that circulating galectin-3 concentrations are inversely associated with increased CIMT in obese adults, which may be a potential biomarker of CVD.

Beiging of perivascular adipose tissue regulates its inflammation and vascular remodeling

Although inflammation plays critical roles in the development of atherosclerosis, its regulatory mechanisms remain incompletely understood. Perivascular adipose tissue (PVAT) has been reported to undergo inflammatory changes in response to vascular injury. Here, we show that vascular injury induces the beiging (brown adipose tissue-like phenotype change) of PVAT, which fine-tunes inflammatory response and thus vascular remodeling as a protective mechanism. In a mouse model of endovascular injury, macrophages accumulate in PVAT, causing beiging phenotype change. Inhibition of PVAT beiging by genetically silencing PRDM16, a key regulator to beiging, exacerbates inflammation and vascular remodeling following injury. Conversely, activation of PVAT beiging attenuates inflammation and pathological vascular remodeling. Single-cell RNA sequencing reveals that beige adipocytes abundantly express neuregulin 4 (Nrg4) which critically regulate alternative macrophage activation. Importantly, significant beiging is observed in the diseased aortic PVAT in patients with acute aortic dissection. Taken together, vascular injury induces the beiging of adjacent PVAT with macrophage accumulation, where NRG4 secreted from the beige PVAT facilitates alternative activation of macrophages, leading to the resolution of vascular inflammation. Our study demonstrates the pivotal roles of PVAT in vascular inflammation and remodeling and will open a new avenue for treating atherosclerosis.

Perivascular adipose tissue (PVAT) has been reported to undergo inflammatory changes in response to vascular injury. Here, the authors show that vascular injury induces the beiging (brown adipose tissue-like phenotype change) of PVAT, which fine-tunes inflammatory response as a protective mechanism.

Neuregulin 4 suppresses NASH-HCC development by restraining tumor-prone liver microenvironment

The mammalian liver comprises heterogeneous cell types within its tissue microenvironment that undergo pathophysiological reprogramming in disease states, such as non-alcoholic steatohepatitis (NASH). Patients with NASH are at an increased risk for the development of hepatocellular carcinoma (HCC). However, the molecular and cellular nature of liver microenvironment remodeling that links NASH to liver carcinogenesis remains obscure. Here, we show that diet-induced NASH is characterized by the induction of tumor-associated macrophage (TAM)-like macrophages and exhaustion of cytotoxic CD8+ T cells in the liver. The adipocyte-derived endocrine factor Neuregulin 4 (NRG4) serves as a hormonal checkpoint that restrains this pathological reprogramming during NASH. NRG4 deficiency exacerbated the induction of tumor-prone liver immune microenvironment and NASH-related HCC, whereas transgenic NRG4 overexpression elicited protective effects in mice. In a therapeutic setting, recombinant NRG4-Fc fusion protein exhibited remarkable potency in suppressing HCC and prolonged survival in the treated mice. These findings pave the way for therapeutic intervention of liver cancer by targeting the NRG4 hormonal checkpoint.

Neuregulin 4 (NRG4) - the hormone with clinical significance in gestational diabetes mellitus

This study aimed at determining the association between serum neuregulin 4 (NRG4) and insulin in gestational diabetes mellitus (GDM) and their correlation with other metabolic parameters. A cross-sectional study was conducted from June 2018 to February 2019 at Ziauddin University, Karachi. Pregnant women (n = 80), at 24-28 weeks of gestation, were recruited. Demographic data, anthropometric measurements and antenatal history were recorded. The fasting blood was drawn for testing fasting blood sugar (FBS), NRG4, insulin and lipid profile. The subjects were evaluated for glucose challenge test after 50 g glucose ingestion. NRG4 levels (1.00 ± 0.15) were found significantly high (p < .04) in healthy group compared to GDM (0.95 ± 0.11). In GDM females, high levels for FBS (p < .02) and cholesterol (p < .03) were observed. Homeostatic model assessment of insulin resistance (HOMA-IR) had direct weak association with NRG4, inverse relationship with cholesterol and LDL but significant association (p < .05) with insulin. Significantly high NRG4 in healthy females suggests its potential role in regulating insulin sensitivity. Impact StatementWhat is already known on this subject? Neuregulin 4 (NGR4) is a batokine which plays a potential role in regulating insulin sensitivity, maintaining energy and metabolic homeostasis. Due to its role in lipid and glucose homeostasis, some studies report its role in gestational diabetes mellitus (GDM) but the results were controversial.What do the results of this study add? The study showed that NGR4 levels were significantly low in GDM subjects. Other metabolic factors especially insulin and homeostatic model assessment of insulin resistance (HOMA-IR) were found associated significantly (p < .05) with NGR4.What are the implications of these findings for clinical practice and/or further research? NGR4 can be a potential biomarker for gestational diabetes. Nevertheless, in order to confirm these findings, further studies, with bigger sample size are required to further ascertain the prospects of NRG4 as a potential biomarker for gestational diabetes.

Circulating adipsin is associated with asymptomatic carotid atherosclerosis in obese adults

Background

Adipsin has been identified as a secreted adipokine that plays a critical pathogenic role in metabolic disorders. However, it is not clear regarding the association of circulating adipsin with cardiovascular disease (CVD). This study will explore the association between circulating adipsin and asymptomatic carotid atherosclerosis in Chinese obese adults.

Methods

A total of 483 obese adult subjects (aged 40 years or older) were enrolled in this study. Serum adipsin concentrations and carotid intima-media thickness (CIMT) were measured to determine these associations.

Results

Individuals with increased CIMT and asymptomatic carotid atherosclerosis had lower levels of circulating adipsin than controls (both p < 0.05). The prevalence of asymptomatic carotid atherosclerosis was significantly higher in subjects with lower levels of serum adipsin than those with higher values (42.5% vs. 36.7%, p < 0.05). Notably, subjects in the lowest quartile of serum adipsin were 1.94 times (p = 0.059) more likely to have increased CIMT and 2.91 times (p = 0.03) more likely to have asymptomatic carotid atherosclerosis than those in the highest quartile in multivariable logistic regression analyses, adjusting for age, gender, current smoking, alcohol consumption, physical activity, BMI, systolic BP, fasting glucose, total cholesterol, HDL-c, and HOMA-IR. However, such associations with circulating adipsin were not noted for atherosclerotic plaque.

Conclusions

These findings suggest that circulating adipsin concentrations are a potential marker of risks of increased CIMT and asymptomatic carotid atherosclerosis in obese Chinese adults.

Adiposity Measurements and Metabolic Syndrome Are Linked Through Circulating Neuregulin 4 and Adipsin Levels in Obese Adults

Background

Adiposity and adipokines are associated with metabolic disorders, but little is known regarding that whether adiposity measurements link metabolic syndrome (MetS) through circulating neuregulin 4 (Nrg4) and adipsin levels.

Materials and Methods

A total of 1212 subjects with a waist circumference greater than 90 cm for men or 80 cm for women were enrolled from a Chinese community. Circulating Nrg4 and adipsin levels were measured using commercial kits. Mediation analyses of circulating Nrg4 and adipsin were performed in the study using linear and logistic regression.

Results

Subjects with MetS had higher waist circumference, visceral fat level, and circulating adipsin level, and lower levels of circulating Nrg4 and muscle mass to visceral fat (MVF) ratio (all P < 0.05). In multivariable logistic regression analyses, after adjusting for confounding variables, per standard deviation (SD) increase in waist circumference and visceral fat level were significantly associated with increased odds of MetS [OR (95% CI), 1.42 (1.22–1.64); 2.20 (1.62–2.99); respectively]; and per SD reduction in MVF ratio was significantly associated with reduced odds of MetS [OR (95% CI), 0.65 (0.55–0.77)]. In the mediation analyses, both circulating Nrg4 and adipsin levels mediated the association between waist circumference (8.31% and 18.35%, respectively), visceral fat level (7.50% and 9.98%, respectively), and MVF ratio (5.80% and 9.86%, respectively) and MetS after adjustments.

Conclusion

These findings indicate that adiposity measurements and MetS are linked through circulating Nrg4 and adipsin levels in obese adults, suggesting that circulating Nrg4 and adipsin levels might be potential predictors for management of MetS.

Neuregulins: protective and reparative growth factors in multiple forms of cardiovascular disease

Neuregulins (NRGs) are protein ligands that act through ErbB receptor tyrosine kinases to regulate tissue morphogenesis, plasticity, and adaptive responses to physiologic needs in multiple tissues, including the heart and circulatory system. The role of NRG/ErbB signaling in cardiovascular biology, and how it responds to physiologic and pathologic stresses is a rapidly evolving field. While initial concepts focused on the role that NRG may play in regulating cardiac myocyte responses, including cell survival, growth, adaptation to stress, and proliferation, emerging data support a broader role for NRGs in the regulation of metabolism, inflammation, and fibrosis in response to injury. The constellation of effects modulated by NRGs may account for the findings that two distinct forms of recombinant NRG-1 have beneficial effects on cardiac function in humans with systolic heart failure. NRG-4 has recently emerged as an adipokine with similar potential to regulate cardiovascular responses to inflammation and injury. Beyond systolic heart failure, NRGs appear to have beneficial effects in diastolic heart failure, prevention of atherosclerosis, preventing adverse effects on diabetes on the heart and vasculature, including atherosclerosis, as well as the cardiac dysfunction associated with sepsis. Collectively, this literature supports the further examination of how this developmentally critical signaling system functions and how it might be leveraged to treat cardiovascular disease.

The Effect of Omega-3 Fatty Acid Supplementation on Serum Adipocytokines, Lipid Profile and Biochemical Markers of Inflammation in Recreational Runners

BACKGROUND

The study aimed to evaluate the effects of a 3-week ω-3 PUFA supplementation on serum adipocytokines (i.e., adiponectin, leptin), neuregulin-4 (NRG4) and erythrocyte omega-3 (ω-3) fatty acid content, as well as the blood antioxidant defense capacity in non-elite endurance runners.

METHODS

Twenty-four runners were randomized into two groups: the supplemented group, who received omega free fatty acids extract containing 142 mg of EPA, 267 mg of DHA, 12 mg of vitamin E and 5 µg of vitamin D, each administrated at a dose of six capsules twice a day for three weeks, or the placebo group. Venous blood samples were withdrawn at the start and at the end of the study protocols to estimate serum biochemical variables.

RESULTS

A significantly higher ω-3 index and lower AA/EPA ratio was observed after ω-3 PUFA compared to pre-supplementation levels (p < 0.001 and p < 0.001, respectively). An increase in baseline adiponectin and NRG4 levels, as well as a decrease of leptin concentration and lipid profile improvement, were observed in subjects after a ω-3 PUFA diet. The increased ω-3 index had a significant effect on TNFα levels and a serum marker of antioxidant defense.

CONCLUSIONS

The ω-3 PUFA extract with added vitamin E and D supplementation may have a positive effect on the function of the adipocyte tissue, as well as the ability to prevent cardiovascular complications in athletes.

Clinical importance of neuregulin-4 and its receptor ErbB4 in periodontal disease pathogenesis

OBJECTIVE

The aim of this clinical trial was to evaluate the levels of Neuregulin-4 (Nrg4), Erb-b2 receptor tyrosine kinase 4 (ErbB4), interleukin (IL)-6, IL-10, nitric oxide synthase (NOS)-2, and arginase (Arg)-1 in periodontal health and disease.

MATERIALS AND METHODS

This study includes systemically healthy 20 periodontally healthy (H), 20 gingivitis (G), 20 stage II periodontitis (P1), and 20 stage III periodontitis (P2) subjects. Periodontal clinical measurements and samples of gingival crevicular fluid (GCF) and serum were obtained at baseline and 4 weeks after non-surgical periodontal treatment (NSPT). Enzyme-linked immunosorbent assay (ELISA) was used to determine ErbB4, Nrg4, IL-6, IL-10, NOS2, and Arg1 levels in all samples.

RESULTS

GCF ErbB4 and Nrg4 total amounts and IL-6/IL-10 ratio were significantly higher in G, P1, and P2 groups than H group. Serum NOS2 levels were significantly lower, whereas serum Arg1 levels were higher in H group than the others. The GCF levels of ErbB4 and Nrg4 were significantly decreased after NSPT in G, P1, and P2 groups. Additionally, the GCF levels of ErbB4 and Nrg4 were positively correlated with all clinical parameters and IL-6/IL-10 ratio.

CONCLUSIONS

Nrg4 and its receptor ErbB4 might have crucial roles in the pathogenesis of periodontal disease. These results should be verified with future prospective studies to further clarify the exact role of those biomarkers.

Differences in Neuregulin 4 Expression in Children: Effects of Fat Depots and Obese Status

PURPOSE

To observe the expression of Nrg4, uncoupling protein-1 (UCP1), tumor necrosis factor α (TNFα), CD31, VE-cadherin/CDH5 and vascular endothelial growth factor A (VEGF-A) mRNA in abdominal subcutaneous (SC), omental (OM) adipose tissue in children with relation to anthropometric parameters. Further to verify the effect of inflammatory mediators on Nrg4 and UCP1 mRNA expression in adipocytes.

METHODS

Paired SC and OM adipose tissues were obtained from 58 children. In vitro, the adipocytes isolated from primary inguinal adipose tissue of mice were treated with TNFα (50 ng/ml) for 12-48 h. mRNA levels of Nrg4, UCP1 and TNFα were determined by real-time PCR.

RESULTS

Nrg4, UCP1, VEGF-A and CDH5 mRNA levels in SC were significantly higher than those in OM adipose tissue and the mRNA level of TNFα showed the opposite result. Moreover, Nrg4 and UCP1 mRNA in SC were significantly lower in overweight children compared to normal weight children. Nrg4 in SC and OM was negatively associated with BMISDS, WHtR. CDH55 mRNA in OM was negatively associated with WHR. VEGF-A was positively correlated with Nrg4 in SC. In vitro, Nrg4 and UCP1 mRNA levels in adipocytes were dose- and time-dependently decreased under TNFα treatment.

CONCLUSIONS

Nrg4, UCP1, VEGF-A and CDH5 mRNA expression in adipose tissues display a depot-specific pattern. Nrg4 mRNA levels in adipose tissue are decreased with obesity and associated with WAT browning and angiogenesis. TNFα may be involved in the regulation of Nrg4 level in adipose tissue, which may be one of the causes of the down-regulation of Nrg4 expression in obesity with chronic inflammatory response.

Neuregulin, an Effector on Mitochondria Metabolism That Preserves Insulin Sensitivity

Various external factors modulate the metabolic efficiency of mitochondria. This review focuses on the impact of the growth factor neuregulin and its ErbB receptors on mitochondria and their relationship with several physiopathological alterations. Neuregulin is involved in the differentiation of heart, skeletal muscle, and the neuronal system, among others; and its deficiency is deleterious for the health. Information gathered over the last two decades suggests that neuregulin plays a key role in regulating the mitochondrial oxidative machinery, which sustains cell survival and insulin sensitivity.

Regulation of Energy Metabolism by Receptor Tyrosine Kinase Ligands

Metabolic diseases, such as diabetes, obesity, and fatty liver disease, have now reached epidemic proportions. Receptor tyrosine kinases (RTKs) are a family of cell surface receptors responding to growth factors, hormones, and cytokines to mediate a diverse set of fundamental cellular and metabolic signaling pathways. These ligands signal by endocrine, paracrine, or autocrine means in peripheral organs and in the central nervous system to control cellular and tissue-specific metabolic processes. Interestingly, the expression of many RTKs and their ligands are controlled by changes in metabolic demand, for example, during starvation, feeding, or obesity. In addition, studies of RTKs and their ligands in regulating energy homeostasis have revealed unexpected diversity in the mechanisms of action and their specific metabolic functions. Our current understanding of the molecular, biochemical and genetic control of energy homeostasis by the endocrine RTK ligands insulin, FGF21 and FGF19 are now relatively well understood. In addition to these classical endocrine signals, non-endocrine ligands can govern local energy regulation, and the intriguing crosstalk between the RTK family and the TGFβ receptor family demonstrates a signaling network that diversifies metabolic process between tissues. Thus, there is a need to increase our molecular and mechanistic understanding of signal diversification of RTK actions in metabolic disease. Here we review the known and emerging molecular mechanisms of RTK signaling that regulate systemic glucose and lipid metabolism, as well as highlighting unexpected roles of non-classical RTK ligands that crosstalk with other receptor pathways.

Clinical significance of serum concentrations of neuregulin-4, in acute coronary syndrome

Acute coronary syndrome (ACS) is closely associated with an increased risk of death. Nrg4, a novel adipocytokine, has negative correlations with indicators of metabolic syndrome. Here, we investigated whether circulating Nrg4 associates with the prevalence of ACS. In this case-control study, a total of 257 subjects (144 patients with ACS and 56 patients diagnosed with stable angina pectoris (SAP)) compared to 57 healthy controls. Serum Nrg4 and hs-CRP concentrations were determined by ELISA. The associations of circulating Nrg4 with other clinical parameters were also analyzed. Serum levels of Nrg4 were lower in patients compared to the control subjects (0.7 ± 0.53 ng/mL versus 1.1 ± 0.9 ng/mL, P = 0.018). There was a significant association between higher Nrg4 level and lower risk of ACS (OR = 0.15; 95%CI = 0.02–0.9; P = 0.046), but not with SAP. This association was independent of potential confounders including traditional cardiovascular risk factors. The distribution of patients with no, 1, 2 and 3 vessel stenosis was significantly different in Nrg4 quartiles. Patients in the lower quartile of Nrg4 were more likely to experience 3 vessel diseases. Serum levels of Nrg4 correlated negatively with HDL-cholesterol in ACS patients. Decreased serum levels of Nrg4 might be an independent risk factor for ACS.

Is Neuregulin-4 a predictive marker of microvascular complications in type 2 diabetes mellitus?

BACKGROUND AND AIMS

Neuregulin-4 (Nrg-4) is a new adipokine released from brown adipose tissue. It plays pivotal role in regulating systemic energy balance, glucose and lipid metabolism and in reducing chronic inflammation. We aimed to investigate the relation between diabetic microvascular complications (DMC) and serum (Nrg-4) levels in patients with type 2 diabetes mellitus.

METHODS

Patients with type 2 diabetes mellitus were divided into DMC and diabetic patients without microvascular complications (non-DMC). Nrg-4 levels of the patients were compared.

RESULTS

Fifty and 29 patients enrolled to the DMC and non-DMC groups, respectively. Nrg-4 was 1.23 (0.02-5.1) ng/mL and 2.5 (0.21-6.01) ng/mL in DMC and in non-DMC groups, respectively (P < .001). In patients with DMC, FPG was 189.5 (89-446) mg/ dL, whereas it was 128 (95-278) mg/dL in non-DMC diabetic patients (P < .001). HbA1c was also significantly higher in the DMC group than in the non-DMC group (P < .001). Negative correlation was found between Nrg-4 and FPG (r = -0.231, P = .03), HBA1c (r = -0.312, P = .003) and microalbuminuria (r = -0.277, P = .009). Logistic regression analysis showed a 1-unit decrease in Nrg-4 to increase the presence of DMC by 1.9 times. The best cut-off value of Nrg-4 was 1.56 ng/mL with 82.1% sensitivity and 64% specificity, in predicting DMC.

CONCLUSION

In patients with diabetes, Nrg-4 levels may be a good predictor of early detection of one or more DMC, as microvascular dysfunction in an organ system is considered to be an initial onset of subclinical systemic damage.

A systematic review of the association of neuregulin 4, a brown fat-enriched secreted factor, with obesity and related metabolic disturbances

Neuregulin 4 (Nrg4), a novel brown fat-enriched hormone, plays a key role in the modulation of glucose and lipid metabolism and energy balance. Recent data have demonstrated that the expression of Nrg4 is substantially down-regulated in mouse and human obesity, making its regulatory aspect intriguing. Because of the close relationship between Nrg4, obesity, and associated metabolic diseases, this systematic review aimed to assess the association of Nrg4 with obesity and related metabolic disturbances, emphasizing its possible mechanisms of action in these disorders. We searched PubMed/Medline, ScienceDirect, Scopus, EMBASE, ProQuest, and Google Scholar up until June 2019. The evidence reviewed here indicates that Nrg4 may contribute to the prevention of obesity and related metabolic complications by elevating brown adipose tissue activity, increasing the expression of thermogenic markers, decreasing the expression of lipogenic/adipogenic genes, exacerbating white adipose tissue browning, increasing the number of brite/beige adipocytes, promoting hepatic fat oxidation and ketogenesis, inducing neurite outgrowth, enhancing blood vessels in adipose tissue, increasing the circulatory levels of healthy adipokines, and improving glucose homeostasis. Thus, Nrg4 appears to be a novel therapeutic strategy for the treatment of obesity and associated metabolic complications. However, prospective cohort studies are warranted to confirm these outcomes.

Changes of circulating neuregulin 4 and its relationship with 25-hydroxy vitamin D and other diabetic vascular complications in patients with diabetic peripheral neuropathy

BACKGROUND

Neuregulin 4 (Nrg4) is a novel neurotrophic adipokine associated with the development of diabetic peripheral neuropathy (DPN), however, the pathological mechanism remains poorly understood. The purpose of our study was to investigate the association of circulating Nrg4 with DPN and 25-hydroxy vitamin D [25(OH)D], a multifunctional secosteroid hormone that regulates other neurotrophic factors and adipokines gene expression, and other diabetic vascular complications.

METHODS

Circulating Nrg4 levels were measured with an ELISA kit in 164 newly diagnosed type 2 diabetes mellitus (nT2DM) patients. The relationship between circulating Nrg4 and DPN and other parameters was analyzed.

RESULTS

Circulating Nrg4 levels were significantly lower in nT2DM patients with DPN than those without, and subjects in the highest quartile of circulating Nrg4 had significantly lower vibration perception threshold (VPT), the prevalence of DPN, the proportion of persons with VPT > 25 V, and significantly higher circulating 25(OH)D (all P < 0.01). Moreover, circulating Nrg4 was positively and independently associated with 25(OH)D, and was negatively with VPT (P < 0.01 or P < 0.05), but showed no associations with the prevalence of peripheral arterial disease, diabetic nephropathy, and diabetic retinopathy (all P > 0.05). Additionally,the prevalence of DPN and risk of DPN development were progressively decreased with increasing circulating Nrg4 quartiles, independently of potential confounding factors.

CONCLUSIONS

These data demonstrate that decreased levels of circulating Nrg4 might lead to the development of DPN through its close interaction with circulating 25(OH)D not with other diabetic vascular complications. Further prospective studies are needed to identify our findings in these populations.

Association between circulating neuregulin4 levels and diabetes mellitus: A meta-analysis of observational studies

INTRODUCTION

Neuregulin 4 (Nrg4) was proven as a brown fat-enriched secreted factor that can regulate glucose and lipid metabolism. However, the association between circulating Nrg4 levels and diabetes mellitus (DM) in human remains unclear. We conducted a meta-analysis to investigate association of circulating Nrg4 with DM.

METHODS

Observational studies comparing circulating Nrg4 levels in diabetes patients and health controls were included. Circulating Nrg4, correlation coefficients of clinical indices and circulating Nrg4 were pooled by meta-analysis.

RESULTS

Seven studies were included. The pooled results indicated there were no significant difference in the circulating Nrg4 between diabetes patients and controls (SMD = 0.18, 95%CI = -0.06 to 0.42, P = 0.143). However, diabetes patients had higher circulating Nrg4 than their controls in cross-sectional studies (SMD = 0.55, 95%CI = 0.36 to 0.73, P<0.001). None of the renal function and metabolic syndrome markers were correlated with circulating Nrg4, whereas the HbA1c and BMI were positively correlated (rs = 0.09, 95%CI = 0.03 to 0.16, P = 0.005; rs = 0.20, 95%CI = 0.07 to 0.34, P = 0.003; respectively).

CONCLUSION

Our findings suggested circulating Nrg4 may play a role in in the development of DM in cross-sectional studies and circulating Nrg4 might be associated with imbalance in glucose metabolism and obesity.

New Insights into Adipokines as Potential Biomarkers for Type-2 Diabetes Mellitus

A large number of studies have been focused on investigating serum biomarkers associated with risk or diagnosis of type-2 diabetes mellitus. In the last decade, promising studies have shown that circulating levels of adipokines could be used as a relevant biomarker for diabetes mellitus progression as well as therapeutic future targets. Here, we discuss the possible use of recently described adipokines, including apelin, omentin-1, resistin, FGF-21, neuregulin-4 and visfatin, as early biomarkers for diabetes. In addition, we also include recent findings of other well known adipokines such as leptin and adiponectin. In conclusion, further studies are needed to clarify the pathophysiological significance and clinical value of these biological factors as potential biomarkers in type-2 diabetes and related dysfunctions.

Elevated serum neuregulin 4 levels in patients with hyperthyroidism

OBJECTIVE

Recent studies have shown that neuregulin 4 (Nrg4), a member of the epidermal growth factor (EGF) family of extracellular ligands, plays an important role in the prevention of obesity, insulin resistance and nonalcoholic fatty liver disease (NAFLD). Considering that thyroid hormone (TH) has profound effects on whole-body energy metabolism, we speculate that circulating Nrg4 levels might be altered in patients with hyperthyroidism.

DESIGN AND METHODS

A total of 129 hyperthyroid patients and 100 healthy subjects were recruited. Of them, 39 hyperthyroid patients received thionamide treatment for 3 months until euthyroidism. Serum Nrg4 levels were determined using the ELISA method. To further confirm the relationship between TH and Nrg4, C57BL/6 mice were treated with T3 and quantitative real-time PCR was performed to detect Nrg4 gene expression.

RESULTS

Serum Nrg4 levels were significantly elevated in hyperthyroid patients as compared with normal controls (3.84 ± 1.63 vs 2.21 ± 1.04 ng/mL, P < 0.001). After achieving euthyroidism by thionamide treatment, serum Nrg4 levels dropped markedly from 3.57 ± 1.26 to 1.94 ± 0.72 ng/ml (P < 0.001). After adjustment for potential confounders, serum Nrg4 levels were independently associated with hyperthyroidism. The upregulation of Nrg4 expression in the livers and white adipose tissues by T3 was further confirmed by animal and cell culture experiments.

CONCLUSIONS

Serum Nrg4 levels were increased in patients with hyperthyroidism. The liver and white adipose tissue might be primary sources contributing to elevated serum Nrg4 concentrations.

Decreased serum neuregulin 4 levels associated with non-alcoholic fatty liver disease in children with obesity

Neuregulin 4 (Nrg4), a newly identified adipokine secreted by brown adipose tissue, is hypothesised to play a crucial role in metabolism. The present study aimed to evaluate the association between serum Nrg4 levels and non-alcoholic fatty liver disease (NAFLD) in children with obesity in China. A total of 123 children with obesity were included in this study. Anthropometric and biochemical parameters were measured in all subjects. NAFLD was diagnosed using ultrasonography. The serum levels of Nrg4, leptin and adiponectin were measured by enzyme-linked immunosorbent assay. NAFLD was identified in 58 children with obesity (47.2%). Serum Nrg4 levels were significantly lower in the NAFLD group (2.24 [1.20, 3.22] ng/mL) than in the control group (5.50 [2.45, 10.85] ng/mL) (p < 0.001). Serum Nrg4 levels were negatively correlated with most of the anthropometric and biochemical parameters (p < 0.05) but were positively correlated with high-density lipoprotein cholesterol (p < 0.05). In multiple stepwise regression analyses, serum Nrg4 levels were independently related with WHtR (β = -2.009, p = 0.048) and homeostasis model assessment of insulin resistance (β = -0.524, p = 0.005). Furthermore, a multivariable logistic regression analysis of NAFLD prediction by Nrg4 revealed an odds ratio of 0.129 (95% confidence interval: 0.028-0.587, p < 0.01). The receiver operating characteristic curve analysis of the diagnostic value of using serum Nrg4 levels to differentiate NAFLD in children with obesity showed that the area under the curve was 0.723; the cutoff for serum Nrg4 levels to have diagnostic value for predicting NAFLD in children with obesity was 3.39 ng/mL. Elevated Nrg4 is associated with a decreased risk of NAFLD in children with obesity.

Proteomic Profiles in Advanced Age-Related Macular Degeneration Using an Aptamer-Based Proteomic Technology

Purpose

To explore top-ranked plasma proteins related to neovascular age-related macular degeneration (AMD) and geographic atrophy (GA), and explore pathways related to neovascular AMD and GA.

Methods

We conducted a pilot study of patients with neovascular AMD (n = 10), GA (n = 10), and age-matched cataract controls (n = 10) who were recruited into an AMD registry. We measured 4001 proteins in ethylenediaminetetraacetic acid plasma samples using an aptamer-based proteomic technology. Relative concentrations of each of 4001 proteins were log (base 2) transformed and compared between cases of neovascular AMD and GA versus controls using linear regression. Pathway analysis was conducted using pathways downloaded from Reactome.

Results

In this pilot study, higher levels of vinculin and lower levels of CD177 were found in patients with neovascular AMD compared with controls. Neuregulin-4 was higher and soluble intercellular adhesion molecule-1 was lower in patients with GA compared with controls. For neovascular AMD, cargo trafficking to the periciliary membrane, fibroblast growth factor receptor 3b ligand binding and activation, and vascular endothelial growth factor–related pathways were in the top ranked pathways. The top-ranked pathways for GA included several related to ErbB4 signaling.

Conclusions

We found different proteins and different pathways associated with neovascular AMD and GA. Vinculin and some of the top-ranked pathways have been previously associated with AMD, whereas others have not been described.

Translational Relevance

Biomarkers identified in plasma likely reflect systemic alterations in protein expression and may improve our understanding of the mechanisms leading to AMD.

Association of Circulating Neuregulin-4 with Presence and Severity of Coronary Artery Disease

Neuregulin-4 (Nrg4) is a newly discovered adipokine that is synthesized in many tissues and plays an important role in modulating systemic energy metabolism and in the development of metabolic disorders. However, little is known about the relationship between Nrg4 and coronary artery disease (CAD). In this study, we investigated the association between Nrg4 and the presence and severity of CAD.We enrolled 73 patients diagnosed by coronary angiography (CAG) as having CAD and 32 controls. The CAD group was divided into two subgroups according to their SYNTAX score. Plasma levels of Nrg4 were measured in all participants and compared among different groups. The relationship between Nrg4 and CAD was analyzed. Receiver operating characteristic (ROC) analysis was conducted to evaluate the usefulness Nrg4 in assessing the presence and severity of CAD.Nrg4 levels were negatively associated with the SYNTAX score (r = -0.401, P = 0.000). The patients with a higher SYNTAX score had significantly lower Nrg4 levels as compared with the low SYNTAX score subgroup and the controls (P < 0.05). The Nrg4 levels of the low SYNTAX score subgroup were much lower than controls (P < 0.05). Furthermore, an association between Nrg4 and CAD (odds ratio, 0.279; 95% confidence interval, 0.088-0.882) was observed. Nrg4 had 43.8% sensitivity and 96.9% specificity for identifying CAD, and 73.1% sensitivity and 87.3% specificity for identifying patients who had severe coronary artery lesions.Nrg4 levels were found to be inversely associated with the presence and severity of CAD.

Clinical significance of neuregulin 4 (NRG4) in gestational diabetes mellitus

OBJECTIVE

Gestational diabetes mellitus (GDM) is defined as glucose intolerance detected during pregnancy. GDM is increasing worldwide and is associated with adverse maternal and fetal outcomes. Neuregulin 4 (NGR4) is epidermal growth factor like signaling molecule. It plays an important role in cell to cell communication furthermore recent studies indicate that NRG4 may work as a novel adipokine with a possible role in maintaining energy and metabolic homeostasis. The aim of the present study was to assess serum NRG4 levels along with several metabolic parameters in patients diagnosed with gestational diabetic mellitus.

MATERIALS AND METHODS

In this prospective cross-sectional study, the study group was composed of 63 women with GDM and 64 healthy pregnant women matched for age, body mass index (BMI) and gestational age. Blood samples were collected at the 24-28th gestational weeks. Serum NRG4, total cholesterol, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), triglycerides, glucose levels during 75-gr OGTT, fasting insulin, glycosylated hemoglobin A1c (HbA1c), alanine aminotransferase (ALT) and creatinine levels were measured. Homeostasis model assessment of insulin resistance (HOMA-IR) values were calculated.

RESULTS

Serum NRG4 values were significantly elevated in the GDM group compared to the control group (p < .001). Multivariate linear regression analyzes revealed that BMI (β = 0.910, p < .001), glucose 2-h OGTT (β = 0.866, p < .001) and HOMA-IR (β = 0.222, p < .001) independently and positively predicted NRG4 levels.

CONCLUSIONS

Serum NRG4 levels were associated with metabolic parameters of GDM. The present study can be considered to be a guide for future studies to clarify the pathophysiology of NGR4 in GDM patients.

Epigenetic Programming of Synthesis, Release, and/or Receptor Expression of Common Mediators Participating in the Risk/Resilience for Comorbid Stress-Related Disorders and Coronary Artery Disease

Corticotrophin releasing factor, vasopressin, oxytocin, natriuretic hormones, angiotensin, neuregulins, some purinergic substances, and some cytokines contribute to the long-term modulation and restructuring of cardiovascular regulation networks and, at the same time, have relevance in situations of comorbid abnormal stress responses. The synthesis, release, and receptor expression of these mediators seem to be under epigenetic control since early stages of life, possibly underlying the comorbidity to coronary artery disease (CAD) and stress-related disorders (SRD). The exposure to environmental conditions, such as stress, during critical periods in early life may cause epigenetic programming modifying the development of pathways that lead to stable and long-lasting alterations in the functioning of these mediators during adulthood, determining the risk of or resilience to CAD and SRD. However, in contrast to genetic information, epigenetic marks may be dynamically altered throughout the lifespan. Therefore, epigenetics may be reprogrammed if the individual accepts the challenge to undertake changes in their lifestyle. Alternatively, epigenetics may remain fixed and/or even be inherited in the next generation. In this paper, we analyze some of the common neuroendocrine functions of these mediators in CAD and SRD and summarize the evidence indicating that they are under early programming to put forward the theoretical hypothesis that the comorbidity of these diseases might be epigenetically programmed and modified over the lifespan of the individual.

Plasma Neuregulin 4 Levels Are Associated with Metabolic Syndrome in Patients Newly Diagnosed with Type 2 Diabetes Mellitus

Neuregulin 4 (Nrg4) has been proposed to play a role in the pathogeneses of obesity, insulin resistance, and dyslipidemia. However, information about the link between Nrg4 and metabolic syndrome (MetS) is scarce, especially in patients with newly diagnosed type 2 diabetes mellitus (nT2DM). This study aimed at investigating whether Nrg4 is associated with MetS in nT2DM patients. A total of 311 patients with nT2DM were recruited. Plasma Nrg4 concentration was determined by ELISA. Plasma Nrg4 concentration was lower in nT2DM patients with MetS than in nT2DM patients without MetS (P = 0.001). Nrg4 concentration showed negative correlations with most of the analyzed indicators of MetS. MetS was less prevalent among subjects in the highest quartile of plasma Nrg4 concentration than among those in the lowest quartile (P < 0.01). Age- and sex-adjusted plasma Nrg4 concentrations were positively correlated with concentrations of high-density lipoprotein cholesterol (HDL-C) and apolipoprotein A (both P < 0.05) and negatively correlated with triglyceride, high-sensitivity C-reactive protein (hs-CRP), and gamma-glutamyltransferase concentrations, neutrophil count, and white blood cell (WBC) count (all P < 0.05). In multivariate analysis, Nrg4 was independently associated with hs-CRP level, WBC count, and HDL-C level (P = 0.001 or P < 0.05). Multiple logistic regression analysis of MetS prediction by Nrg4 revealed an odds ratio of 0.560 (95% CI: 0.374-0.837; P < 0.01). Decreased plasma Nrg4 levels, which may be associated with augmented oxidative stress, inflammation, and dyslipidemia, might be involved in the development of MetS in nT2DM patients.

NRG1-Fc improves metabolic health via dual hepatic and central action

Neuregulins (NRGs) are emerging as an important family of signaling ligands that regulate glucose and lipid homeostasis. NRG1 lowers blood glucose levels in obese mice, whereas the brown fat-enriched secreted factor NRG4 protects mice from high-fat diet-induced insulin resistance and hepatic steatosis. However, the therapeutic potential of NRGs remains elusive, given the poor plasma half-life of the native ligands. Here, we engineered a fusion protein using human NRG1 and the Fc domain of human IgG1 (NRG1-Fc) that exhibited extended half-life in circulation and improved potency in receptor signaling. We evaluated its efficacy in improving metabolic parameters and dissected the mechanisms of action. NRG1-Fc treatment triggered potent AKT activation in the liver, lowered blood glucose, improved insulin sensitivity, and suppressed food intake in obese mice. NRG1-Fc acted as a potent secretagogue for the metabolic hormone FGF21; however, the latter was largely dispensable for its metabolic effects. NRG1-Fc directly targeted the hypothalamic POMC neurons to promote membrane depolarization and increase firing rate. Together, NRG1-Fc exhibits improved pharmacokinetic properties and exerts metabolic benefits through dual inhibition of hepatic gluconeogenesis and caloric intake.

Decreased plasma neuregulin 4 concentration is associated with increased high-sensitivity C-reactive protein in newly diagnosed type 2 diabetes mellitus patients: a cross-sectional study

AIMS

Inflammation has been reported to be involved in the pathogenesis of atherosclerosis. This principal objective of this study was to investigate if the secretion of neuregulin 4 (Nrg4), a soluble protein associated with metabolic syndrome and subclinical cardiovascular disease, is correlated with the inflammation marker high-sensitivity C-reactive protein (hs-CRP) in patients with newly diagnosed type 2 diabetes mellitus (nT2DM).

METHODS

A study group of 311 nT2DM patients was divided into three subgroups based on hs-CRP tertiles. Multiple linear regression was conducted to explore the association between plasma Nrg4 and hs-CRP levels.

RESULTS

The nT2DM patients with the highest hs-CRP levels (>2.46 mg/L) exhibited higher atherogenic coefficients and atherogenic index of plasma (AIP) levels, but lower levels of plasma Nrg4, as compared to those with the lowest hs-CRP levels (<0.63 mg/L). Plasma Nrg4 levels were inversely associated with white blood cell count, hs-CRP, and AIP and positively associated with high-density lipoprotein cholesterol (HDL-C), before and after adjustment for age, gender, body mass index (BMI), and body fat percentage (P < 0.01 or P < 0.05). hs-CRP was the factor most strongly associated with plasma Nrg4 levels.

CONCLUSIONS

These results indicate that lower plasma Nrg4 levels may be associated with elevated hs-CRP in nT2DM patients. It generates the hypothesis that decreased levels of Nrg4 may trigger the development of atherosclerosis through its proinflammatory effects. These findings need to be confirmed by further prospective studies.

BACE1-Dependent Neuregulin-1 Signaling: An Implication for Schizophrenia

Schizophrenia is a chronic psychiatric disorder with a lifetime prevalence of about 1% in the general population. Recent studies have shown that Neuregulin-1 (Nrg1) is a candidate gene for schizophrenia. At least 15 alternative splicing of NRG1 isoforms all contain an extracellular epidermal growth factor (EGF)-like domain, which is sufficient for Nrg1 biological activity including the formation of myelin sheaths and the regulation of synaptic plasticity. It is known that Nrg1 can be cleaved by β-secretase (BACE1) and the resulting N-terminal fragment (Nrg1-ntf) binds to receptor tyrosine kinase ErbB4, which activates Nrg1/ErbB4 signaling. While changes in Nrg1 expression levels in schizophrenia still remain controversial, understanding the BACE1-cleaved Nrg1-ntf and Nrg1/ErbB4 signaling in schizophrenia neuropathogenesis is essential and important. In this review paper, we included three major parts: (1) Nrg1 structure and cleavage pattern by BACE1; (2) BACE1-dependent Nrg1 cleavage associated with schizophrenia in human studies; and (3) Animal studies of Nrg1 and BACE1 mutations with behavioral observations. Our review will provide a better understanding of Nrg1 in schizophrenia and a potential strategy for using BACE1 cleavage of Nrg1 as a unique biomarker for diagnosis, as well as a new therapeutic target, of schizophrenia.