ABSTRACT Adipose omeostasishomoeostasis is maintained through the precise coordination of lipogenesis, lipolysis, and adipocyte differentiation, with microenvironmental components dynamically regulating lipid metabolism. Even though the classical cAMP-PKA pathway has been well-characterized for its function in lipid metabolism by phosphorylating transcription factors and lipolytic enzymes, little is known about how it collaborates with elements of the adipose tissue microenvironment, such as immune cells and the vascular endothelium, especially in pathological situations like obesity. EPAC, a newly discovered cAMP effector, has shown new signalingsignallingsignalling signalling pathways in the immune and cardiovascular systems by activating small G proteins. However, there are important understanding gaps regarding its roles in adipose metabolism, namely adipocyte development, microenvironmental interaction, and the pathophysiology of metabolic diseases. By bringing together disparate studies on PKA and EPAC, this review provides the first comprehensive synthesis of the cAMP-PKA/EPAC dual signaling signalling signallingcins signalling network, filling in knowledge gaps. The reciprocal regulation between this signaling signalling signalling signalling network and the adipose microenvironment establishes a novel ‘signaling-microenvironment-systemic metabolism’ framework for understanding metabolic disorders, including obesity, diabetes, and hepatic steatosis. Pharmacological modulation of the PKA/EPAC signalingsignalling signalling signalling pathways may therefore represent a viable therapeutic approach for restoring adipose tissue homeostasis homoeostasis.

ABSTRACT Different adipose tissues (AT) have been described, including subcutaneous and visceral tissues (SCAT and VAT). They display different morphological structures, physiological and metabolic functions. Imaging adipocytes in the whole AT was not feasible because of the large adipocyte sizes and the lipid-full content of the droplets that increased the refractive index. Tissue clearing is then required mainly through a delipidation step, which induces also a tissue shrinkage. Our aim was to image in 3D freshly extracted adipocytes and compare them to those within their tissues. Trout ATs were stained with 5DTAF (extracellular matrix) and Nile Red (lipids). After clearing with Histodenz, 3D images were obtained using a confocal microscope, and adipocytes were segmented and measured. In situ, major differences in adipocyte size and shape were observed between the VAT and SCAT. Ex situ, only the size mattered because all cells were round outside their tissues. This method can be applied to other species, such as mice. In situ, adipocyte sphericity was even higher in the SCAT from a Swiss and a C57Bl6. This approach demonstrates that 3D adipocyte imaging with lipid labeling enables accurate morphological characterization, provides insights into depot-specific structural features, and supports optimization of cell isolation protocols

ABSTRACT Obesity is a major global health issue. This study aimed to elucidate its molecular mechanisms by analysing the expression of lncRNAs, miRNAs, and mRNAs in visceral adipose tissue. Through integrated transcriptome sequencing and bioinformatics analysis of obese and normal groups, we observed 118, 92 and 227 differentially expressed lncRNAs, miRNAs and mRNAs, respectively. Functional enrichment analysis revealed these genes were primarily involved in immune response and inflammation-related pathways. A competing endogenous RNA (ceRNA) network was constructed, identifying key interactions among five target genes, including SDC4. Validation confirmed SDC4 was significantly upregulated in obese subjects, and this expression level positively correlated with body mass index and triglyceride. These findings suggest that SDC4 offers the possibility of being a therapeutic target for obesity.

ABSTRACT Background Neuregulin 4 (Nrg4) is a brown adipose tissue-derived adipokine that greatly affects systemic metabolism and improves metabolic derangements. Although abnormal circulating levels of Nrg4 are common in obesity, it remains elusive whether low or elevated levels of this batokine are associated with the onset of metabolic diseases. Aim To assess Nrg4 levels and its role as a feasible biomarker to predict the severity of obesity, gestational diabetes mellitus (GDM), type 2 diabetes mellitus (T2DM), non-alcoholic fatty liver disease (NAFLD), and cardiovascular diseases (CVD). Methods A search for relevant studies was performed systematically using prominent search engines, including PubMed, Google Scholar, and Embase, by following PRISMA guidelines. Results Ample clinical evidence reported low serum/plasma levels of Nrg4 in obesity and these were inversely proportional to the indices of metabolic syndrome, including body mass index, waist circumference, triglycerides, fasting plasma glucose, and homoeostatic model assessment for insulin resistance as well as high-sensitivity C-reactive protein. Low circulating Nrg4 levels may aid in the prediction of morbid obesity, and subsequent GDM, T2DM, NAFLD, and CVD. Conclusion Current clinical evidence emphasizes that the circulating levels of Nrg4 are decreased in morbid obesity, and it also highlights that Nrg4 May serve as a potential prognostic biomarker for obesity-related metabolic diseases.

ABSTRACT A Disintegrin And Metalloproteinase domain-containing protein 10 (ADAM10), is involved in several metabolic and inflammatory pathways. We speculated that ADAM10 plays a modulatory role in adipose tissue inflammation and metabolism. To this end, we studied adipose tissue-specific ADAM10 knock-out mice (aKO). While young, regular chow diet-fed aKO mice showed increased insulin sensitivity, following prolonged (33 weeks) high-fat diet (HFD) exposure, aKO mice developed obesity and insulin resistance. Compared to controls, aKO mice showed less inflammatory adipokine profile despite the significant increase in adiposity. In brown adipose tissue, aKO mice on HFD had changes in CD8+ T cell populations indicating a lesser inflammatory pattern. Following HFD, both aKO and control littermates demonstrated decreased adipose tissue pro-inflammatory macrophages, and increased anti-inflammatory accumulation, without differences between the genotypes. Collectively, our observations indicate that selective deletion of ADAM10 in adipocytes results in a mitigated inflammatory response, leading to increased insulin sensitivity in young mice fed with regular diet. This state of insulin sensitivity, following prolonged HFD, facilitates energy storage resulting in increased fat accumulation which ultimately leads to the development of a phenotype of obesity and insulin resistance. In conclusion, the data indicate that ADAM10 has a modulatory effect of inflammation and whole-body energy metabolism.

ABSTRACT Background Platinum is a commonly used drug for ovarian cancer (OvCa) treatment, but drug resistance limits its clinical application. This study intended to delineate the effects of adipocytes on platinum resistance in OvCa. Methods OvCa cells were maintained in the adipocyte-conditioned medium. Cell viability and apoptosis were detected by CCK-8 and flow cytometry, separately. Proliferation and apoptosis-related protein expression were assayed by western blot. The IC50 values of cisplatin and carboplatin were determined using CCK-8. IGF1 secretion and expression were assayed via ELISA and western blot, respectively. A xenograft model was established, and pathological changes were detected by H&E staining. Proliferation and apoptosis-associated protein expression was assessed via IHC. Results Adipocytes promoted the viability and repressed cell apoptosis in OvCa, as well as enhancing platinum resistance, while the addition of IGF-1 R inhibitor reversed the effects of adipocytes on proliferation, apoptosis, and drug resistance of OvCa cells. Treatment with different concentrations of Ojeok-san (OJS) inhibited the adipocyte-induced platinum resistance in OvCa cells by suppressing IGF1. The combined treatment of OJS and cisplatin significantly inhibited tumour growth in vivo with good mouse tolerance. Conclusion In summary, OJS inhibited OvCa proliferation and platinum resistance by suppressing adipocyte paracrine IGF1 secretion.

ABSTRACT Mitochondria are essential for generating cellular energy and are significant in the pathogenesis of obesity. Human visceral and subcutaneous preadipocytes (HPA-v and HPA-s) were cultured into mature adipocytes. Intracellular triglyceride (TG) content was assessed using oil-red O staining and tissue triglyceride determination. Mitochondrial membrane potential (MMP) and reactiveoxygen species (ROS) levels were measured with fluorescent indicators. Gene and protein expression related to mitochondrial biogenesis were analyzed by real-time quantitative PCR and Western blotting. Morphological changes were observed via electron microscopy. Results show that PDBSN significantly increased MMP while decreasing TG and ROS levels. The transcription and protein levelsof PGC1-α and MTFA were upregulated, and mitochondrial fusion and fission markers (MFN1, MFN2, NRF1, DRP1) were elevated. Additionally, PDBSN enhanced maximumrespiratory capacity and reduced ROS. These findings suggest that PDBSN improves mitochondrial function, providing insights for obesity treatment and metabolic disease management.

ABSTRACT Brown adipocytes were proposed to reverse metabolic conditions such as obesity and diabetes, which make them potential for therapeutic applications. Brown adipocytes and browning process are capable of thermogenesis, the uncoupling metabolism which allows them to promote balanced energy expenditure, a fundamental mechanism for improving metabolic disorders. Thermogenesis process is not only performed by the thermogenin UCPs within the mitochondria, but instead, is globally regulated within brown and browning adipose tissues, which induces signalling molecules that can be sent to nearby and distant tissues to generate systemic effects on metabolism. This review highlights thermogenesis and describes the crosstalk between different organelles within browning and brown adipocytes, as well as their interorgan axes to regulate whole body metabolism. Finally, browning and thermogenesis activation will also be discussed in terms of physiological conditions, in which, we propose that thermogenesis and functional activities of brown adipocytes should be considered individually in future clinical application.

ABSTRACT Adipokines are proteins secreted by adipose tissue to regulate glucolipid metabolism and play vital roles in our body. Different adipokines have more than one endocrine function and be divided into several different categories according to their functions, including adipokines involved in glucolipid metabolism, the inflammatory response, insulin action, activation of brown adipose tissue (BAT) and appetite regulation. Multiple adipokines interact with each other to regulate metabolic processes. Based on the recent progress of adipokine research, this article discusses the role and mechanism of various adipokines in glucolipid metabolism, which may provide new ideas for understanding the pathogenesis and improving the treatment of various metabolic diseases.

ABSTRACT The capacity of adipose stem/progenitor cells (ASCs) to undergo self-renewal and differentiation is crucial for adipose tissue homoeostasis, regeneration and expansion. However, the heterogeneous ASC populations of the adipose lineage constituting adipose tissue are not precisely known. In the present study, we demonstrate that cell surface expression of dipeptidyl peptidase-4 (DPP4)/cluster of differentiation 26 (CD26) subdivides the DLK1−/CD34+/CD45−/CD31− ASC pool of human white adipose tissues (WATs) into two large populations. Ex vivo, DPP4+ ASCs possess higher self-renewal and proliferation capacity and lesser adipocyte differentiation potential than DDP4− ASCs. The knock-down of DPP4 in ASC leads to significantly reduced proliferation and self-renewal capacity, while adipogenic differentiation is increased. Ectopic overexpression of DPP4 strongly inhibits adipogenesis. Moreover, in whole mount stainings of human subcutaneous (s)WAT, we detect DPP4 in CD34+ ASC located in the vascular stroma surrounding small blood vessels and in mature adipocytes. We conclude that DPP4 is a functional marker for an abundant ASC population in human WAT with high proliferation and self-renewal potential and low adipogenic differentiation capacity.