Diurnal changes in intestinal apolipoprotein A-IV and its relation to food intake and corticosterone in rats

Abstract

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 pettern. 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.

Circadian Regulation of Intestinal Lipid Absorption by Apolipoprotein AIV Involves Forkhead Transcription Factors A2 and O1 and Microsomal Triglyceride Transfer Protein

“…Lipids-ApoAIV expression shows diurnal variations (13,38,39). Consistent with these studies, apoAIV mRNA levels were low in the daytime and high at night in wild-type mice (Fig.…”

“…Another feature of apoAIV that is pertinent to lipid absorption is its circadian expression (13,38,39). Serum apoAIV exhibits circadian rhythms.…”

Diurnal Regulation of Microsomal Triglyceride Transfer Protein and Plasma Lipid Levels

“…Here we show that MTP and apoB show diurnal variations. Shen et al (60) have reported that apoAIV protein and mRNA levels were high in the dark compared with those present in the day. Thus, it appears that at least three genes involved in lipoprotein assembly and secretion are coordinately regulated, and we propose that lipoprotein assembly and secretion exhibit circadian variations in the liver and intestine.…”

The −256T>C Polymorphism in the Apolipoprotein A-II Gene Promoter Is Associated with Body Mass Index and Food Intake in the Genetics of Lipid Lowering Drugs and Diet Network Study

“…Although the authors did not mention APOA2 as a potential candidate gene in explaining such results, the APOA2 gene is in this locus. Despite the scarcity of previous data supporting a role of APOA2 in regulating food intake, copious experimental evidence demonstrates a pivotal role of another apolipoprotein, APOA4, as a satiety signal (20,21,39,40 ). Fujimoto et al (39 ) were the first to report that APOA4 is (16,18 ).…”