DIETARY-REGULATION OF THE VERY-LOW-DENSITY LIPOPROTEIN RECEPTOR IN MOUSE HEART AND FAT

The very low density lipoprotein (VLDL) receptor is a member of the LD L receptor family. As opposed to the LDL receptor, the VLDL receptor i s expressed primarily in muscle and adipose tissue. Although the VLDL receptor is capable of binding lipoproteins, its functional role is st ill unclear. Previous studies found that VLDL receptor expression is u naffected by fasting in the rat. The current studies examined whether VLDL receptor expression is altered with fasting in the mouse. Balb/c mice were fasted for periods up to 48 hours, killed, hearts and epidid ymal fat obtained, and total membranes prepared. To detect the VLDL re ceptor a portion of the rat VLDL receptor was expressed as a bacterial fusion protein, purified and used to immunize rabbits. The antibodies raised specifically recognized intact VLDL receptor. When cardiac mem branes were immunoblotted, VLDL receptor expression increased progress ively with fasting, doubling at 36 hours. In contrast, VLDL receptor e xpression decreased progressively with fasting in membranes from epidi dymal fat, being reduced 70% by 48 hours. Thus, VLDL receptor expressi on appears to be regulated in mouse heart and fat by nutritional pertu rbation, supporting a potential role for the VLDL receptor in the deli very of triglycerides/fatty acids as fuel.