Synthesis and regulation of lipoprotein lipase in the hippocampus

Lipoprotein lipase (LPL) expression was determined in adult rat hippocampus and compared to enzyme expression in other brain regions. Hippocampus LPL mRNA levels were at least 2.5-fold higher than those detected in the cerebral cortex, cerebellum, and remaining brain regions. Enzyme mass and activity levels in the hippocampus were also increased to a similar degree. De novo synthesis of LPL in the hippocampus was confirmed by [35S]methionine-labeling of the tissue and identification of a 57 kDa protein obtained by immunoprecipitation. Addition of an excess amount of bovine LPL completely prevented the immunoprecipitation of this protein. The effect of nutritional modulations on brain LPL activity was determined after a 12-h fast. While no significant changes were observed in other regions of the brain, hippocampus LPL activity in fasted rats increased by 60% compared to the fed control group. Simultaneously, fasting reduced adipose LPL activity by 60%. Intraperitoneal injection of ACTH over a 5-day period had no effect on hippocampus LPL activity, while adipose LPL levels increased 2.3-fold and heart LPL levels decreased 1.4-fold. We conclude that LPL is synthesized, active and regulated in a tissue-specific manner in the adult rat hippocampus.