Diurnal rhythms and effects of fasting and refeeding on rat adipose
tissue lipoprotein lipase.
Berg, Martin, Gunilla Olivecrona, and Thomas Olivecrona.
Department of Medical Biochemistry and Biophysics, Ume University,
S-901 87 UME, SWEDEN
APStracts 3:0176E, 1996.
The activity of lipoprotein lipase (LPL) in adipose tissue is
modulated by changes in the nutritional status. We have measured LPL
activity, mass and mRNA levels in rat adipose tissue during normal
feeding cycles, during short- and long-term fasting, and during re
-feeding after fasting. LPL activity displayed a diurnal rhythm. The
activity was highest during the night and early morning, decreased to
a minimum during the early afternoon and then increased again. These
changes corresponded to the feeding pattern. The increases/decreases
resulted from changes in LPL synthetic rate compounded by post
-translational mechanisms. During short-term fasting, LPL specific
activity decreased to less than 30% of control. The specific activity
was restored within 4 hours by re-feeding. On longer fasting, LPL
mRNA decreased. This became significant from 36 hours. On re-feeding
it took 12 hours to restore the mRNA levels, whereas tissue LPL
activity and mass could not be fully restored by 36 hours of re
-feeding. These data shows that LPL activity during short-term fasting
is regulated post-transcriptionally, which allows for quick up
-regulation after re-feeding. On longer fasting, other mechanisms
affecting LPL transcription and synthesis come into play and up
-regulation after re-feeding is slowed down.
Received 8 May 1996; accepted in final form 31 July 1996.
APS Manuscript Number E225-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996