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

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 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.

Systems biology approach identifies key genes and related pathways in childhood obesity

BACKGROUND

Childhood obesity is triggered by a complex interplay of environmental, genetic, and epigenetic factors; however, the molecular mechanisms behind this disease are not completely elucidated. Thus, the aim of this study was to investigate molecular mechanisms involved in childhood obesity by implementing a systems biology approach.

METHODS

Experimentally validated and computationally predicted genes related to childhood obesity were downloaded from DisGeNET database. A protein-protein interaction (PPI) network was constructed using the STRING database and analyzed at Cytoscape web-tool. Hub-bottleneck genes and functional clusters were identified through CytoHubba and MCODE plugins, respectively. Functional enrichment analyses were performed based on Gene Ontology terms and KEGG Pathways.

RESULTS

The DisGeNET search retrieved 191 childhood obesity-related genes. The resulting PPI network contained 12 hub-bottleneck genes (INS, LEP, STAT3, POMC, ALB, TNF, BDNF, CAT, GCG, PPARG, VEGFA, and ADIPOQ) and 4 functional clusters, with cluster 1 showing the highest interaction score. Genes at this cluster were enriched at inflammation, carbohydrate, and lipid metabolism pathways. With exception of POMC, all hub-bottleneck genes were found in cluster 1, which contains highly connected genes that possibly play key roles in obesity-related pathways.

CONCLUSIONS

Our systems biology approach revealed a set of highly interconnected genes associated with childhood obesity, providing comprehensive information regarding genetic and molecular factors involved in the pathogenesis of this disease.