Cl- channels regulate lipid droplet formation via Rab8a expression during adipocyte differentiation

Several studies have shown that Cl^- channels regulate the differentiation of some cell types. Thus, we investigated the role of Cl^- channels on adipocyte differentiation using adipose tissue-derived stem cells (ASCs) and Cl^- channel blocker. We induced rabbit ASCs into adipocytes using Cl^- channel blocker. The expression levels of adipocyte markers were no significant difference between the cells treated with a Cl^- channel blocker NPPB and untreated cells. However, when the cells were treated with NPPB, lipid droplets (LDs) sizes decreased compared with the untreated control. Interestingly, the expression levels of Rab8a, which is known as a regulator of LD fusion, were also decreased in the cells treated with NPPB. Other Cl^- channel blockers, DIDS and IAA-94, also inhibited large LDs formation and Rab8a expression. These results demonstrate that Cl^- channels do not regulate the adipocyte differentiation, but do regulate the LDs formation via Rab8a expression.Abbreviations: ASCs: adipose tissue-derived stem cells; LDs: lipid droplets; RUNX2: runt-related transcription factor 2; CFTR: cystic fibrosis transmembrane conductance regulator; TG: triacylglycerol; FA: fatty acid; GLUT4: glucose transporter type 4; ER: endoplasmic reticulum; ADRP: adipose differentiation-related protein; TIP47: tail-interacting protein of 47 kD; HSL: hormone sensitive lipase; PBS: phosphate-buffered saline; DMEM: Dulbecco's modified Eagle Medium; FBS: fetal bovine serum; SMA: smooth muscle actin; FAS: fatty acid synthase; ZONAB: ZO-1 associated nucleic acid binding protein; PPAR-γ: peroxisome proliferator-activated receptor-γ; C/EBPα: CCAAT/enhancer binding protein α; CE: cholesteryl ester; V-ATPase: vacuolar H⁺ ATPase.