Lesson on obesity and anatomy of adipose tissue: new models of study in the era of clinical and translational research

Implications of obesity-mediated cellular dysfunction and adipocytokine signaling pathways in the pathogenesis of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage degradation, bone sclerosis, and chronic low-grade inflammation. Aging and injury play key roles in OA pathogenesis by triggering the release of proinflammatory factors from adipose tissue and other sources. Obesity and aging impair the function of endoplasmic reticulum (ER) chaperones, leading to ER stress, protein misfolding, and cellular apoptosis. Obesity also induces mitochondrial dysfunction in OA through oxidative stress and disrupts mitochondrial dynamics, exacerbating chondrocyte damage. These factors contribute to inflammation, matrix imbalance, and chondrocyte apoptosis. Adipocytes, the primary source of adipokines, release inflammatory mediators that affect joint cells. Several adipocytokines have a central role in the regulation of many aspects of inflammation. Adiponectin and leptin are the two most abundant adipocytokines that are strongly associated with OA progression. This literature review suggests that adipokines activate many signaling pathways to exert downstream effects and play significant roles in obesity-induced OA. Understanding this rapidly growing family of mainly adipocyte-derived mediators and obesity-mediated cellular dysfunction may be important in the development of new therapies for obesity-associated OA management.

Adropin-Driven Browning: Targeting M2 Macrophages to Combat PCOS

Polycystic ovary syndrome (PCOS) is a common endocrine disorder in women of reproductive age, associated with chronic low-grade inflammation and metabolic disorders. The exact pathogenesis of PCOS remains unclear. Adropin, a secreted protein encoded by the energy homeostasis gene (Enho), has immunometabolic regulatory functions. In the present study, the serum levels of adropin were significantly lower (P < 0.001) in PCOS mice than controls, and adropin deficiency exacerbated the obesity and inflammatory phenotypes in letrozole (LTZ)-induced PCOS mice. In vitro experiments, it has shown that adropin mediated the phenotypic change of RAW264.7 macrophages to M2 through upregulation of heme oxygenase-1 (HO-1), and then adropin-treated macrophage-conditioned medium (Adr-CM) induced browning of fully differentiated 3T3-L1 adipocytes. Finally, vivo experiments by injecting adropin into PCOS model mice showed that adropin treatment significantly reduced body weight, and promoted macrophage M2 anti-inflammatory phenotypic transformation and browning of white adipose tissue. In summary, the present study reveals a novel mechanism by which adropin indirectly promotes adipose tissue browning by regulating macrophage polarisation, which provides a new perspective and experimental basis for the therapeutic strategy of PCOS and its related metabolic disorders.