SEMINAR: Jaime Navarro

Speaker: Jaime Navarro
Obesity, Diabetes and Comorbidities Lab.
Centro de Investigación Príncipe Felipe

Role of Pla2g6 in adipocyte differentiation and function

Abstract: Obesity is a major risk factor for metabolic and cardiovascular complications. While most research focuses on why individuals with obesity develop comorbidities, our study investigates the opposite phenomenon: why some individuals remain metabolically resilient despite excess adiposity. One of the most widely accepted explanations for adipose tissue dysfunction is the adipose tissue expandability hypothesis. During adipogenesis, alterations in progenitor cells can restrict their proliferative capacity (hyperplasia), leading instead to adipocyte hypertrophy, a process that promotes chronic inflammation and insulin resistance. To understand mechanisms that uncouple excess adiposity from metabolic dysfunction, we investigated the role of Pla2g6, a candidate gene identified in a genome-wide cross-phenotype meta-analysis of adiposity–cardiometabolic trait pairs, in adipocyte differentiation and function. Pla2g6 encodes a phospholipase involved in the Land’s cycle of membrane phospholipid remodelling. In vitro, Pla2g6 expression increased during 3T3-L1 adipocyte differentiation. CRISPR-Cas9–mediated Pla2g6 knockout (KO) resulted in impaired proliferation, altered cell morphology, and defective adipogenesis, accompanied by reduced lipid accumulation and decreased expression of adipogenic and lipogenic genes. Lipidomic profiling revealed altered phospholipid remodelling in Pla2g6-KO cells, including the accumulation of PUFA-enriched glycerophospholipids, which resulted in increased membrane fluidity during adipogenesis. Global RNA-seq analysis (LRT) revealed three major clusters of differentially expressed genes in Pla2g6-KO versus control cells, related to cell cycle regulation and mitosis, extracellular matrix (ECM) remodelling, cell migration, and lipid metabolism. Flow cytometry and cyclin expression analyses confirmed a marked reduction in mitotic capacity during mitotic clonal expansion (MCE), a key phase of adipogenesis, suggesting a potential mechanism underlying differentiation defects. Matrisome proteomic analysis of Pla2g6-KO cells revealed an immature ECM, reflecting a pre-adipocyte state, with downregulation of key mature ECM proteins at days 6-9 of differentiation. Notably, PLA2G6 also localises to mitochondria, prompting us to examine its role in mitochondrial biology; Pla2g6-KO cells showed a higher number of mitochondria, more elongated and with increased metabolic activity. Lastly, the treatment with Pparγ agonist Rosiglitazone partially rescued adipogenesis on Pla2g6-KO cells but induced a hypertrophic phenotype, increasing significantly the expression of adipogenic markers in the Pla2g6-KO cells vs control ones. Altogether, our research provides a novel role for Pla2g6 in adipose tissue expansion and further characterisation is needed to understand its precise function.