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

Neuregulin-4 protects cardiomyocytes against high-glucose-induced ferroptosis via the AMPK/NRF2 signalling pathway

BACKGROUND

High glucose levels are key factors and key contributors to several cardiovascular diseases associated with cardiomyocyte injury. Ferroptosis, which was identified in recent years, is a mode of cell death caused by the iron-mediated accumulation of lipid peroxides. Neuregulin-4 (Nrg4) is an adipokine that has protective effects against metabolic disorders and insulin resistance. Our previous study revealed that Nrg4 has a protective effect against diabetic myocardial injury, and the aim of this study was to investigate whether Nrg4 could attenuate the occurrence of high glucose-induced ferroptosis in cardiomyocytes.

METHODS

We constructed an in vivo diabetic myocardial injury model in which primary cardiomyocytes were cultured in vitro and treated with Nrg4. Changes in ferroptosis-related protein levels and ferroptosis-related indices in cardiomyocytes were observed. In addition, we performed back-validation and explored signalling pathways that regulate ferroptosis in primary cardiomyocytes.

RESULTS

Nrg4 attenuated cardiomyocyte ferroptosis both in vivo and in vitro. Additionally, the AMPK/NRF2 signalling pathway was activated during this process, and when the AMPK/NRF2 pathway was inhibited, the beneficial effects of Nrg4 were attenuated.

CONCLUSION

Nrg4 antagonizes high glucose-induced ferroptosis in cardiomyocytes via the AMPK/NRF2 signalling pathway.

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.

Neuregulin 4 mediates the metabolic benefits of mild cold exposure by promoting beige fat thermogenesis

Interorgan crosstalk via secreted hormones and metabolites is a fundamental aspect of mammalian metabolic physiology. Beyond the highly specialized endocrine cells, peripheral tissues are emerging as an important source of metabolic hormones that influence energy and nutrient metabolism and contribute to disease pathogenesis. Neuregulin 4 (Nrg4) is a fat-derived hormone that protects mice from nonalcoholic steatohepatitis (NASH) and NASH-associated liver cancer by shaping hepatic lipid metabolism and the liver immune microenvironment. Despite its enriched expression in brown fat, whether NRG4 plays a role in thermogenic response and mediates the metabolic benefits of cold exposure are areas that remain unexplored. Here we show that Nrg4 expression in inguinal white adipose tissue (iWAT) is highly responsive to chronic cold exposure. Nrg4 deficiency impairs beige fat induction and renders mice more susceptible to diet-induced metabolic disorders under mild cold conditions. Using mice with adipocyte and hepatocyte-specific Nrg4 deletion, we reveal that adipose tissue-derived NRG4, but not hepatic NRG4, is essential for beige fat induction following cold acclimation. Furthermore, treatment with recombinant NRG4-Fc fusion protein promotes beige fat induction in iWAT and improves metabolic health in mice with diet-induced obesity. These findings highlight a critical role of NRG4 in mediating beige fat induction and preserving metabolic health under mild cold conditions.

Relationship between chronic obstructive pulmonary disease and adiponectin concentrations: An updated meta-analysis and single-cell RNA sequencing

BACKGROUND

Adipose tissue, being an organ of the endocrine system, can influence the severity of chronic obstructive pulmonary disease (COPD). Even though several inflammatory markers can potentially significantly influence lung function, the precise function of adipokines, like adiponectin, in COPD is still disputed. To analyze the association of COPD with adiponectin concentrations, a meta-analysis of the most recent literature and single-cell sequencing data were conducted.

METHODS

Studies in Embase, PubMed, Cochrane Library, and Web of Science were browsed to obtain relevant data, which were then assessed with the aid of R 4.1.3 and STATA 11.0 software. Standardized mean differences and correlation coefficients aided the analysis of effect values. Moreover, a single-cell sequencing GSE136831 dataset was retrieved to ascertain the mRNA expression of adiponectin gene (ADIPOQ) in the lung tissue of COPD patients to confirm the difference in the expression of adiponectin between the case and control groups.

RESULTS

This meta-analysis comprised 18 publications involving 24 studies. The overall combined data established the concentration of plasma/serum adiponectin as significantly higher in patients with COPD compared to healthy subjects. Subgroup analyses based on disease status, specimen type, ethnicity, study design method, measurement method, and age of COPD patients demonstrated that all patients with COPD had elevated levels of adiponectin compared to healthy controls. When subgroup analysis was performed for gender alone, the results depicted that male COPD patients had significantly higher adiponectin than healthy males, while female patients of COPD had elevated adiponectin compared to healthy females. Furthermore, it was found that plasma/serum adiponectin appeared to be positively correlated with tumor necrosis factor-α, and it was negatively correlated with FEV1% and FEV1/FVC. The results of single-cell sequencing data suggested that ADIPOQ mRNA was mainly expressed in alveolar epithelial cells, and the level of ADIPOQ mRNA was higher in lung tissues of patients with COPD than in lung tissues of healthy subjects.

CONCLUSION

This meta-analysis suggests that the levels of plasma/serum adiponectin are significantly elevated in patients with COPD versus controls. Tumor necrosis factor-α, FEV1/FVC, and FEV1% may all be associated with the concentrations of adiponectin.

Comparison of ocular surface assessment outcomes between healthy controls and patients with obstructive sleep apnea-hypopnea syndrome: a meta-analysis of the literature

Objective: This meta-analysis aims to determine whether ocular surface alterations are associated with disease severity in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). Methods: The protocol for this systematic review and meta-analysis was registered in PROSPERO. We conducted the search in six electronic databases (China National Knowledge Infrastructure, EMBASE, Cochrane Library, Web of Science, Wanfang, and PubMed) from since the construction of the databases to 30 December 2022. The standard mean difference (SMD) and correlation coefficients are reported as measures of the effect size in the presence of retrieved data. In addition, the random effects model or fixed effects model was used in a combined analysis. Stata 11.0 and R 3.6.1 were used for statistical analyses of the data. Results: A total of 15 studies satisfied the inclusion criteria for this study. The prevalence of floppy eyelid syndrome (FES) and dry eye syndrome in patients with obstructive sleep apnea-hypopnea syndrome was 40 and 48%, respectively. In addition, the Schirmer 1 value and tear break-up time (TBUT) were remarkably reduced in patients with OSAHS when compared to that of the controls. The ocular surface disease index (OSDI) scores, Oxford corneal staining scores, and the rates of loss in the meibomian glands were elevated in patients with obstructive sleep apnea-hypopnea syndrome when compared to that of the controls, especially those with severe disease. Moreover, the Schirmer 1 value and tear break-up time exhibited a negative correlation with the apnea-hypopnea index (AHI), and the OSDI showed a positive association with the apnea-hypopnea index. Conclusion: Patients with OSAHS had a greater prevalence of FES than the healthy controls. They also showed lower Schirmer 1 value and tear break-up time but had a higher OSDI, Oxford corneal staining scores, and rates of loss in the meibomian glands than the healthy controls. Clinical Trial Registration: (https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=392527).

Evaluation of Nrg4 and thiol/disulfide homeostasis in patients with GDM

BACKGROUND

In this study, we aimed to evaluate the role of neuregulin4 (Nrg4) in the etiopathogenesis of gestational diabetes mellitus (GDM) and thiol/disulfide homeostasis as an indicator of oxidative stress.

METHODS

This prospective, case-control study included 34 women with diabetes and 34 healthy pregnant women who applied between January 2017 and January 2020. Levels of native and total thiol, disulfide and Nrg4 were measured in both diabetes mellitus and healthy pregnant groups.

RESULTS

When compared to the control group, the serum neuregulin4 levels in the diabetes group were considerably lower (3.22 ± 2.16 vs. 4.55 ± 0.96, p < 0.001). Native thiol (292.67 ± 43.65 vs. 366.40 ± 51.28; p < 0.001), total thiol (388.60 ± 46.60 vs. 414.52 ± 54.19; p < 0.001) levels and native thiol/total thiol ratio (75.51 ± 8.95 vs. 88.35 ± 3.54; p < 0.001) were lower in diabetes group compared to control group. Disulfide level (47.96 ± 19.52 vs. 24.06 ± 7.69) and disulfide/native thiol (17.13 ± 8.03, vs. 6.67 ± 2.30) and disulfide/total thiol (12.24 ± 4.47 vs. 5.82 ± 1.77) ratios were higher in diabetes group (all p < 0.001).

CONCLUSIONS

We suggested that decreased Nrg4 level and impaired oxidative stress parameters may be related with the increased risk of diabetes. However, we did not found a correlation between the Nrg4 and oxidative stress parameters.

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.

Serum neuregulin 4 is negatively correlated with insulin sensitivity in humans and impairs mitochondrial respiration in HepG2 cells

Neuregulin 4 (NRG4) has been described to improve metabolic disturbances linked to obesity status in rodent models. The findings in humans are controversial. We aimed to investigate circulating NRG4 in association with insulin action in humans and the possible mechanisms involved. Insulin sensitivity (euglycemic hyperinsulinemic clamp) and serum NRG4 concentration (ELISA) were analysed in subjects with a wide range of adiposity (n = 89). In vitro experiments with human HepG2 cell line were also performed. Serum NRG4 was negatively correlated with insulin sensitivity (r = −0.25, p = 0.02) and positively with the inflammatory marker high-sensitivity C reative protein (hsCRP). In fact, multivariant linear regression analyses showed that insulin sensitivity contributed to BMI-, age-, sex-, and hsCRP-adjusted 7.2% of the variance in serum NRG4 (p = 0.01). No significant associations were found with adiposity measures (BMI, waist circumference or fat mass), plasma lipids (HDL-, LDL-cholesterol, or fasting triglycerides) or markers of liver injury. Cultured hepatocyte HepG2 treated with human recombinant NRG4 had an impact on hepatocyte metabolism, leading to decreased gluconeogenic- and mitochondrial biogenesis-related gene expression, and reduced mitochondrial respiration, without effects on expression of lipid metabolism-related genes. Similar but more pronounced effects were found after neuregulin 1 administration. In conclusion, sustained higher serum levels of neuregulin-4, observed in insulin resistant patients may have deleterious effects on metabolic and mitochondrial function in hepatocytes. However, findings from in vitro experiments should be confirmed in human primary hepatocytes.

Evaluating Serum Neuregulin 4 as a Noninvasive Biomarker in Patients with Non-alcoholic Fatty Liver Disease

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) spectrum ranges from simple hepatic steatosis to non-alcoholic steatohepatitis. Considering the restrictions of liver biopsy, various serological biomarkers have recently emerged for non-invasive diagnosis of NAFLD. AIM: This study aimed to evaluate the association between serum neuregulin 4 (Nrg4) and NAFLD and the use of serum Nrg4 as a noninvasive marker for diagnosis of NAFLD. METHODS: Sixty-three Egyptian NAFLD patients and 63 controls were enrolled and subjected to detailed history taking, thorough clinical examination including anthropometric measures (body mass index [BMI] and waist circumference). Laboratory investigations included complete blood count, lipid profile (total cholesterol, low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein-cholesterol [HDL-C], triglycerides), serum albumin, transaminases, bilirubin levels, hepatitis markers (anti-HCV antibodies and hepatitis B surface antigen), anti-nuclear antibodies and anti-smooth muscle antibody. Measurement of serum Nrg4 by ELISA and non-invasive NAFLD scores such as NAFLD fibrosis score and FIB4 score were applied to all patients. RESULTS: There was a statistically significant difference between cases and controls regarding the BMI, waist circumference, hemoglobin level, total leukocytic count, total cholesterol, LDL-C, HDL-C, and serum triglycerides levels. Nrg4 was significantly decreased in NAFLD patients as compared to controls. Moreover, Nrg4, total cholesterol, and LDL-C levels were statistically significant independent predictors of NAFLD. No significant differences were observed between Nrg4 level and the variable stages of hepatic fibrosis by NAFLD fibrosis score. CONCLUSION: Decreased serum Nrg4 level is frequent in NAFLD patients and is an independent predictor of NAFLD, suggesting that Nrg4 might have a potential role in prevention and treatment of NAFLD.

The correlation of serum/plasma IGF-1 concentrations with obstructive sleep apnea hypopnea syndrome: A meta-analysis and meta-regression

BACKGROUND

Obstructive sleep apnea hypopnea syndrome (OSAHS) is a common disease that has serious cardiovascular and metabolic effects. Insulin-like growth factor 1 (IGF-1) levels are reportedly reduced in patients with OSAHS; however, this is still a matter of debate. Therefore, we investigated the association between serum/plasma IGF-1 levels and OSAHS in this meta-analysis.

METHODS

Wan Fang, Excerpta Medica dataBASE, Web of Science, China National Knowledge Infrastructure, VIP, PubMed, and other databases were searched for materials published in any language before April 2, 2022. Two researchers analyzed the studies for quality according to the Newcastle-Ottawa Scale. The acquired data were analyzed using Stata 11.0 and R 3.6.1 software. The effect size was estimated and calculated using standard mean differences and correlation coefficients. Moreover, a combined analysis was conducted using either a random- or fixed-effects model.

RESULTS

Ultimately, 34 studies met our inclusion criteria. Our findings revealed that the plasma/serum IGF-1 concentrations in patients with OSAHS was significantly reduced compared with those in healthy subjects. Subgroup analyses were performed according to OSAHS severity, ethnicity, age, body mass index, specimen testing method, and study design. The outcomes suggested that nearly all subgroups of patients with OSAHS had reduced serum IGF-1 levels. Disease severity and differences in ethnicity were identified as possible influencing factors of serum IGF-1 levels in patients with OSAHS in the meta-regression analysis, and no other factors were found to alter plasma/serum IGF-1 concentrations. Moreover, plasma/serum IGF-1 concentrations were negatively correlated with apnea-hypopnea index and oxygen desaturation index scores and positively associated with minimum oxygen saturation.

CONCLUSION

Serum/plasma IGF-1 concentrations in patients with OSAHS were greatly reduced compared with those of patients in the control group, and were negatively correlated with apnea-hypopnea index and oxygen desaturation index scores and positively correlated with minimum oxygen saturation.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022322738.

Laryngopharyngeal Reflux in Obstructive Sleep Apnea-Hypopnea Syndrome: An Updated Meta-Analysis

Laryngopharyngeal reflux (LPR) is a common disorder in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS). This meta-analysis was carried out to evaluate the LPR prevalence in individuals with OSAHS and to analyze the correlation of LPR positivity with the clinical features of patients with OSAHS. A detailed review of the English and Chinese literature on the occurrence of LPR in patients with OSAHS was performed by employing online search tools such as PubMed, EMBASE, Web of Science, VIP, CNKI, WanFang, etc. Two researchers analyzed the studies for quality according to the STROBE standard checklist. The acquired data were analyzed using Stata 11.0 and R 3.6.1 software. The effect size was estimated and calculated using weighted mean difference (WMD) and correlation coefficients. Moreover, a combined analysis was performed by employing either a random- or fixed-effects model. Ultimately, 27 studies met our inclusion criteria. Our study revealed that the LPR prevalence in OSAHS patients was 49%. We carried out subgroup analyses as per OSAHS severity, ethnicity, and body mass index (BMI). The results suggested that the probability of LPR in European and American patients with OSAHS was higher, and the prevalence of LPR was higher in obese individuals and patients with severe OSAHS. Moreover, apnea-hypopnea index (AHI) and BMI were higher in LPR-positive OSAHS patients than in LPR-negative OSAHS patients, but no significant variation in age was observed in the two groups. Moreover, the reflux symptom index (RSI) scores and the reflux finding score (RFS) exhibited a positive correlation with AHI. The current literature shows a higher incidence of LPR in individuals with OSAHS (49%). The severity of AHI in individuals with OSAHS is associated with the presence of LPR. Patients with OSAHS accompanied by LPR showed higher BMI and AHI as compared to those patients with LPR-negative OSAHS.

Adipokines in metabolic and reproductive functions in birds: An overview of current knowns and unknowns

Adipose tissue is now recognized as an active endocrine organ, which synthesizes and secretes numerous peptides factors called adipokines. In mammals, they exert pleiotropic effects affecting energy metabolism but also fertility. In mammals, secretion of adipokines is altered in adipose tissue dysfunctions and may participate to obesity-associated disorders. Thus, adipokines are promising candidates both for novel pharmacological treatment strategies and as diagnostic tools. As compared to mammals, birds exhibit several unique physiological features, which make them an interesting model for comparative studies on endocrine control of metabolism and adiposity and reproductive functions. Some adipokines such as leptin and visfatin may have different roles in avian species as compared to mammals. In addition, some of them found in mammals such as CCL2 (chemokine ligand 2), resistin, omentin and FGF21 (Fibroblast Growth factor 21) have not yet been mapped to the chicken genome model and among its annotated gene models. This brief review aims to summarize data (structure, metabolic and reproductive roles and molecular mechanisms involved) related to main avian adipokines (leptin, adiponectin, visfatin, and chemerin) and we will briefly discuss the adipokines that are still lacking in avian species.

Is there a role for neuregulin 4 in human nonalcoholic fatty liver disease?

BACKGROUND

Neuregulin 4 (Nrg4), a novel adipokine enriched in brown adipose tissue has been observed to negatively regulate de novo hepatic lipogenesis and limit nonalcoholic fatty liver disease (NAFLD) progression to nonalcoholic steatohepatitis (NASH) in rodents. However, the role of Nrg4 in human NAFLD remains unclear to date. We analysed Nrg4 plasma levels and its association with liver disease severity together with the transcriptional profile of the Nrg4 pathway in liver and visceral adipose tissue (VAT) of NAFLD patients.

METHODS

Plasma Nrg4 levels were measured in 65 NAFLD patients and 43 healthy controls (HC). Hepatic steatosis and fibrosis were diagnosed and quantified with chemical shift MRI and transient elastography respectively. Furthermore, blood lipid levels, HOMA-IR and systemic pro-inflammatory cytokines (TNF-α, IL-6 and IFN-γ) were analysed. Microarray analyses to assess differences in the Nrg4 and its receptor family ErbB pathway in liver and VAT from an independent patient group with biopsy proven NAFL (simple steatosis) (n = 4), NASH (n = 5) and normal liver (n = 6) were performed.

RESULTS

Plasma Nrg4 levels were not significantly different between NAFLD patients and HC (p = 0.622). Furthermore, plasma Nrg4 levels did not correlate with the hepatic fat fraction (r = -0.028, p = 0.829) and were not significantly different between NAFLD patients with or without hepatic fibrosis (p = 0.087). Finally, the expression profile of 82 genes related to the Nrg4-ErbB pathway in liver and VAT was not significantly different between NAFL, NASH or obese controls.

CONCLUSION

Our study does not support a role for Nrg4 in the pathophysiology of human NAFLD.