Diurnal changes in intestinal apolipoprotein A-IV and its relation to food intake and corticosterone in rats.
To further investigate the role of intestinal aplipoprotein A-IV (apo A-IV) in the management of daily food intake, we examined the diurnal patterns in apo A-IV gene and protein expression in freely feeding (FF) and food-restricted (FR; food provided 4 h daily for 4 wk) rats that were killed at 3-h intervals throughout the 24-h diurnal cycle. In FF rats, the intestinal apo A-IV mRNA and protein levels showed a circadian rhythm concomitant with the feeding pattern. The daily pattern of fluctuation of apo A-IV, however, was altered in FR rats, which had a marked increase in intestinal apo A-IV levels during the 4-h feeding period of light phase. In both FF and FR rats, increased plasma corticosterone (Cort) levels temporally coincided with the increasing phase of intestinal apo A-IV mRNA and protein expression. Depletion of Cort by adrenalectomy abolished the diurnal rhythm by decreasing the apo A-IV expression during the dark period but did not change the feeding rhythm. Exposure of adrenalectomized rats to consistent Cort level (50-mg continuous release Cort pellet) resulted in fixed apo A-IV levels throughout the day. These results indicate that intestinal apo A-IV exhibits a diurnal rhythm, which can be regulated by endogenous Cort independently of the light-dark cue. The fact that intestinal apo A-IV levels were consistent with the food intake during the normal diurnal cycle as well as during the cycle of 4-h feeding each day suggests that intestinal apo A-IV is involved in the regulation of daily food intake.
Shen
Ling
L
Dept. of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45237-0507, USA.
Ma
Li-yun
LY
Qin
Xiao-fa
XF
Jandacek
Ronald
R
Sakai
Randall
R
Liu
Min
M
D000818:Animals; D000975:Antioxidants / Q000032:analysis* / Q000494:pharmacology*; D001054:Apolipoproteins A / Q000032:analysis* / Q000494:pharmacology*; D002940:Circadian Rhythm; D003345:Corticosterone / Q000494:pharmacology; D005247:Feeding Behavior / Q000502:physiology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
D000975:Antioxidants; D001054:Apolipoproteins A; C022205:apolipoprotein A-IV; D003345:Corticosterone