FIG. 7.

Inhibition of caspase-3 facilitates a striking increase in triglyceride accumulation in d-100 hearts. Plasma collected at termination was evaluated for triglyceride (A) and NEFA (B) using diagnostic kits. Oil Red O staining of representative cardiac sections showing lipid accumulation is described in C (left panel). Bar = 100 μm. Representative electron micrograph of hearts from different groups is depicted in C (right panel). Bar = 500 nm. Black arrow head, lipid-like vacuoles. Cardiac triglyceride was extracted with organic solvent and determined using high-performance liquid chromatography (D). Plasma membranes were isolated and used for identification of CD36 (E). Palmitate oxidation in myocytes isolated from the different groups was assessed by measuring ¹⁴CO₂ (F). Results are the means ± SE of 3–5 rats in each group. *Significantly different from control subjects; +significantly different from all other groups; #significantly different from untreated d-100, P < 0.05. A graphic representation of caspase-3 control of cardiac metabolism is described in G. After severe hypoinsulinemia, a decrease in full-length PKD requires both activation of caspase-3 together with loss of the binding protein 14-3-3ζ. Proteolysis of PKD is unable to transfer cardiac LPL to the vascular lumen. The caspase inhibitor, Z-DEVD, effectively lowers caspase-3 activity in d-100 hearts, prevents PKD cleavage, and increases LPL vesicle formation and translocation to the coronary lumen. This increase in luminal LPL is associated with a decline in circulating triglyceride but a striking cardiac triglyceride accumulation. AU, arbitrary unit; TG, triglyceride; Casp3, caspase-3. (A high-quality color digital representation of this figure is available in the online issue.)