High-Fat Diet–Induced Adipocyte Cell Death Occurs Through a Cyclophilin D Intrinsic Signaling Pathway Independent of Adipose Tissue Inflammation

Abstract

OBJECTIVE Previous studies have demonstrated that mice fed a high-fat diet (HFD) develop insulin resistance with proinflammatory macrophage infiltration into white adipose tissue. Concomitantly, adipocytes undergo programmed cell death with the loss of the adipocyte-specific lipid droplet protein perilipin, and the dead/dying adipocytes are surrounded by macrophages that are organized into crown-like structures. This study investigated whether adipocyte cell death provides the driving signal for macrophage inflammation or if inflammation induces adipocyte cell death. RESEARCH DESIGN AND METHODS Two knockout mouse models were used: granulocyte/monocyte-colony stimulating factor (GM-CSF)–null mice that are protected against HFD-induced adipose tissue inflammation and cyclophilin D (CyP-D)–null mice that are protected against adipocyte cell death. Mice were fed for 4–14 weeks with a 60% HFD, and different markers of cell death and inflammation were analyzed. RESULTS HFD induced a normal extent of adipocyte cell death in GM-CSF–null mice, despite a marked reduction in adipose tissue inflammation. Similarly, depletion of macrophages by clodronate treatment prevented HFD-induced adipose tissue inflammation without any affect on adipocyte cell death. However, CyP-D deficiency strongly protected adipocytes from HFD-induced cell death, without affecting adipose tissue inflammation. CONCLUSIONS These data demonstrate that HFD-induced adipocyte cell death is an intrinsic cellular response that is CyP-D dependent but is independent of macrophage infiltration/activation.