SPINAL-CORD OF THE RAT CONTAINS MORE LIPOPROTEIN-LIPASE THAN OTHER BRAIN-REGIONS

Lipoprotein lipase (LPL) is important for the delivery of triglyceride fatty acids (TGFA) to a variety of tissues. We have used measurements of heparin-releasable LPL activity, immunohistochemistry, in situ hybridization, and Northern analysis to more fully characterize the location of LPL within the entire central nervous system (CNS) of the rat. Surprisingly, the levels of LPL activity and mRNA in the caudal spinal cord were 5- to 10-times higher than those found in any other area of the brain, levels similar to those found in adipose tissue or skeletal muscle. A number of cell types including neurons in the hippocampus, Purkinje cells of the cerebellum, and cells deep within the cortex were identified as sources of LPL mRNA. LPL protein was found within many vascular structures throughout the CNS, and within Purkinje cells. The strongest immunostaining was around nerve rootlets associated with the caudal spinal cord. Feeding studies were carried out with [C-14] oleic acid to see whether CNS LPL functioned in the uptake of TGFA. These studies demonstrated uptake of chylomicron triglyceride fatty acids throughout the CNS. The localization of LPL within these structures suggests that the uptake of triglyceride fatty acids is an integral part of normal lipid metabolism of the central nervous system and may be important in regulating feeding behavior and/or maintaining normal neuronal function.