The Effect of FOXC2-AS1 on White Adipocyte Browning and the Possible Regulatory Mechanism

Molecular targets for management of diabetes: Remodelling of white adipose to brown adipose tissue

Diabetes mellitus is a disorder characterised metabolic dysfunction that results in elevated glucose level in the bloodstream. Diabetes is of two types, type1 and type 2 diabetes. Obesity is considered as one of the major reasons intended for incidence of diabetes hence it turns out to be essential to study about the adipose tissue which is responsible for fat storage in body. Adipose tissues play significant role in maintaining the balance between energy stabilization and homeostasis. The three forms of adipose tissue are - White adipose tissue (WAT), Brown adipose tissue (BAT) and Beige adipose tissue (intermediate form). The amount of BAT gets reduced, and WAT starts to increase with the age. WAT when exposed to certain stimuli gets converted to BAT by the help of certain transcriptional regulators. The browning of WAT has been a matter of study to treat the metabolic disorders and to initiate the expenditure of energy. The three main regulators responsible for the browning of WAT are PRDM16, PPARγ and PGC-1α via various cellular and molecular mechanism. Presented review article includes the detailed elaborative aspect of genes and proteins involved in conversion of WAT to BAT.

Pulling the trigger: Noncoding RNAs in white adipose tissue browning

White adipose tissue (WAT) serves as the primary site for energy storage and endocrine regulation in mammals, while brown adipose tissue (BAT) is specialized for thermogenesis and energy expenditure. The conversion of white adipocytes to brown-like fat cells, known as browning, has emerged as a promising therapeutic strategy for reversing obesity and its associated co-morbidities. Noncoding RNAs (ncRNAs) are a class of transcripts that do not encode proteins but exert regulatory functions on gene expression at various levels. Recent studies have shed light on the involvement of ncRNAs in adipose tissue development, differentiation, and function. In this review, we aim to summarize the current understanding of ncRNAs in adipose biology, with a focus on their role and intricate mechanisms in WAT browning. Also, we discuss the potential applications and challenges of ncRNA-based therapies for overweight and its metabolic disorders, so as to combat the obesity epidemic in the future.

A Novel LncRNA MSTRG.310246.1 Promotes Differentiation and Thermogenesis in Goat Brown Adipocytes

Brown adipose tissue (BAT) plays a critical role in maintaining the body temperature in newborn lamb due to its unique non-shivering thermogenesis. Previous studies have found that BAT thermogenesis is regulated by several long non-coding RNAs (lncRNAs). Here, we identified a novel lncRNA, MSTRG.310246.1, which was enriched in BAT. MSTRG.310246.1 was localized in both the nuclear and cytoplasmic compartments. In addition, MSTRG.310246.1 expression was upregulated during brown adipocyte differentiation. Overexpression of MSTRG.310246.1 increased the differentiation and thermogenesis of goat brown adipocytes. On the contrary, the knockdown of MSTRG.310246.1 inhibited the differentiation and thermogenesis of goat brown adipocytes. However, MSTRG.310246.1 had no effect on goat white adipocyte differentiation and thermogenesis. Our results show that MSTRG.310246.1 is a BAT-enriched LncRNA that improves the differentiation and thermogenesis of goat brown adipocytes.

Epigenetic regulation in metabolic diseases: mechanisms and advances in clinical study

Epigenetics regulates gene expression and has been confirmed to play a critical role in a variety of metabolic diseases, such as diabetes, obesity, non-alcoholic fatty liver disease (NAFLD), osteoporosis, gout, hyperthyroidism, hypothyroidism and others. The term 'epigenetics' was firstly proposed in 1942 and with the development of technologies, the exploration of epigenetics has made great progresses. There are four main epigenetic mechanisms, including DNA methylation, histone modification, chromatin remodelling, and noncoding RNA (ncRNA), which exert different effects on metabolic diseases. Genetic and non-genetic factors, including ageing, diet, and exercise, interact with epigenetics and jointly affect the formation of a phenotype. Understanding epigenetics could be applied to diagnosing and treating metabolic diseases in the clinic, including epigenetic biomarkers, epigenetic drugs, and epigenetic editing. In this review, we introduce the brief history of epigenetics as well as the milestone events since the proposal of the term 'epigenetics'. Moreover, we summarise the research methods of epigenetics and introduce four main general mechanisms of epigenetic modulation. Furthermore, we summarise epigenetic mechanisms in metabolic diseases and introduce the interaction between epigenetics and genetic or non-genetic factors. Finally, we introduce the clinical trials and applications of epigenetics in metabolic diseases.

Potential Involvement of LncRNAs in Cardiometabolic Diseases

Characterized by cardiovascular disease and diabetes, cardiometabolic diseases are a major cause of mortality around the world. As such, there is an urgent need to understand the pathogenesis of cardiometabolic diseases. Increasing evidence suggests that most of the mammalian genome are transcribed as RNA, but only a few percent of them encode for proteins. All of the RNAs that do not encode for proteins are collectively called non-protein-coding RNAs (ncRNAs). Among these ncRNAs, long ncRNAs (lncRNAs) are considered as missing keys to understand the pathogeneses of various diseases, including cardiometabolic diseases. Given the increased interest in lncRNAs, in this study, we will summarize the latest trend in the lncRNA research from the perspective of cardiometabolism and disease by focusing on the major risk factors of cardiometabolic diseases: obesity, cholesterol, diabetes, and hypertension. Because genetic inheritance is unavoidable in cardiometabolic diseases, we paid special attention to the genetic factors of lncRNAs that may influence cardiometabolic diseases.

Identification of thermogenesis-related lncRNAs in small extracellular vesicles derived from adipose tissue

Background

Brown adipose tissue (BAT) is considered as a primary location of adaptive thermogenesis and the thermogenic activities of brown adipocytes are also connected to generating heat and counteracting obesity. Recent studies revealed that BAT could secrete certain batokines-like factors especially small extracellular vesicles (sEVs), which contributed to the systemic consequences of BAT activities. As a newly emerging class of mediators, some long non-coding RNAs (lncRNAs) have exhibited metabolic regulatory effects in adipocyte development. However, besides the well-studied lncRNAs, the lncRNAs carried by sEVs derived from brown adipose tissue (sEV-BAT) have not been identified yet. 

Results

In this study, we demonstrated that sEV-BAT could induce beige adipocyte differentiation both in ASCs and 3T3-L1 cells, while sEV-WAT had no corresponding effects. The lncRNA microarray assay on sEV-WAT and sEV-BAT revealed a total of 563 types of known lncRNAs were identified to be differentially expressed, among which 232 lncRNAs were upregulated and 331 lncRNAs were downregulated in sEV-BAT. Three novel candidates (AK029592, humanlincRNA1030 and ENSMUST00000152284) were selected for further validation. LncRNA–mRNA network analysis revealed candidate lncRNAs were largely embedded in cellular metabolic pathways. During adipogenic and thermogenic phenotype differentiation in ASCs and 3T3-L1 cells, only the expressions of AK029592 were upregulated. The three lncRNAs were all relatively enriched in brown adipose tissues and brown adipocytes. In different adipocytes, sEV and adipose tissue, the expression of AK029592 and ENSMUST00000152284 were remarkably decreased in obese mice compared to lean mice, while obesity state could not change the expression of humanlincRNA1030.

Conclusion

Collectively, our profiling study provided a comprehensive catalog for the study of lncRNAs specifically carried by sEV-BAT and indicated the potential regulatory role of certain sEV-BAT lncRNAs in thermogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08883-0.

CircRNA-mediated regulation of brown adipose tissue adipogenesis

Adipose tissue represents a candidate target for the treatment of metabolic illnesses, such as obesity. Brown adipose tissue (BAT), an important heat source within the body, promotes metabolic health through fat consumption. Therefore, the induction of white fat browning may improve lipid metabolism. Currently, the specific roles of circRNA in BAT and white adipose tissue (WAT) remain elusive. Herein, we conducted circRNA expression profiling of mouse BAT and WAT using RNA-seq. We identified a total of 12,183 circRNAs, including 165 upregulated and 79 downregulated circRNAs between BAT and WAT. Differentially expressed (DE) circRNAs were associated with the mitochondrion, mitochondrial part, mitochondrial inner membrane, mitochondrial envelope, therefore, these circRNAs may affect the thermogenesis and lipid metabolism of BAT. Moreover, DE circRNAs were enriched in browning- and thermogenesis-related pathways, including AMPK and HIF-1 signaling. In addition, a novel circRNA, circOgdh, was found to be highly expressed in BAT, formed by back-splicing of the third and fourth exons of the Ogdh gene, and exhibited higher stability than linear Ogdh. circOgdh was mainly distributed in the cytoplasm and could sponge miR-34a-5p, upregulating the expression of Atgl, a key lipolysis gene, which enhanced brown adipocyte lipolysis and suppressed lipid droplet accumulation. Our findings offer in-depth knowledge of the modulatory functions of circRNAs in BAT adipogenesis.

Role of lncRNAs into Mesenchymal Stromal Cell Differentiation

Currently, findings support that 75% of the human genome is actively transcribed, but only 2% is translated into a protein, according to databases such as ENCODE (Encyclopedia of DNA Elements) [1]. The development of high-throughput sequencing technologies, computational methods for genome assembly and biological models have led to the realization of the importance of the previously unconsidered non-coding fraction of the genome. Along with this, noncoding RNAs have been shown to be epigenetic, transcriptional and post-transcriptional regulators in a large number of cellular processes [2]. Within the group of non-coding RNAs, lncRNAs represent a fascinating field of study, given the functional versatility in their mode of action on their molecular targets. In recent years, there has been an interest in learning about lncRNAs in MSC differentiation. The aim of this review is to address the signaling mechanisms where lncRNAs are involved, emphasizing their role in either stimulating or inhibiting the transition to differentiated cell. Specifically, the main types of MSC differentiation are discussed: myogenesis, osteogenesis, adipogenesis and chondrogenesis. The description of increasingly new lncRNAs reinforces their role as players in the well-studied field of MSC differentiation, allowing a step towards a better understanding of their biology and their potential application in the clinic.

Long Noncoding RNAs: Novel Important Players in Adipocyte Lipid Metabolism and Derivative Diseases

Obesity, a global public health issue, is characterized by excessive adiposity and is strongly related to some chronic diseases including cardiovascular diseases and diabetes. Extra energy intake-induced adipogenesis involves various transcription factors and long noncoding RNAs (lncRNAs) that control lipogenic mRNA expression. Currently, lncRNAs draw much attention for their contribution to adipogenesis and adipose tissue function. Increasing evidence also manifests the pivotal role of lncRNAs in modulating white, brown, and beige adipose tissue development and affecting the progression of the diseases induced by adipose dysfunction. The aim of this review is to summarize the roles of lncRNAs in adipose tissue development and obesity-caused diseases to provide novel drug targets for the treatment of obesity and metabolic diseases.