ClC-3 deficiency protects preadipocytes against apoptosis induced by palmitate in vitro and in type 2 diabetes mice

Palmitate, a common saturated free fatty acid (FFA), has been demonstrated to induce preadipocyte apoptosis in the absence of adipogenic stimuli, suggesting that preadipocytes may be prone to apoptosis under adipogenic insufficient conditions, like type 2 diabetes mellitus (T2DM). ClC-3, encoding Cl(-) channel or Cl(-)/H(+) antiporter, is critical for cell fate choices of proliferation versus apoptosis under diseased conditions. However, it is unknown whether ClC-3 is related with preadipocyte apoptosis induced by palmitate or T2DM. Palmitate, but not oleate, induced apoptosis and increase in ClC-3 protein expression and endoplasmic reticulum (ER) stress in 3T3-L1 preadipocyte. ClC-3 specific siRNA attenuated palmitate-induced apoptosis and increased protein levels of Grp78, ATF4, CHOP and phosphorylation of JNK1/2, whereas had no effects on increased phospho-PERK and phospho-eIF2α protein expression. Moreover, the enhanced apoptosis was shown in preadipocytes from high-sucrose/fat, low-dose STZ induced T2DM mouse model with hyperglycemia, hyperlipidemia (elevated serum TG and FFA levels) and insulin resistance. ClC-3 knockout significantly attenuated preadipocyte apoptosis and the above metabolic disorders in T2DM mice. These data demonstrated that ClC-3 deficiency prevent preadipocytes against palmitate-induced apoptosis via suppressing ER stress, and also suggested that ClC-3 may play a role in regulating cellular apoptosis and disorders of glucose and lipid metabolism during T2DM.