Developmental and nutritional regulation of the messenger RNAs for fatty acid synthase, malic enzyme and albumin in the livers of embryonic and newly-hatched chicks

Abstract

The mRNAs for fatty acid synthase and malic enzyme were almost undetectable in total RNA extracted from the livers of 16-day old chick embryos. Both mRNAs increased in abundance between the 16th day of incubation and the day of hatching. In neonates, fatty acid synthase mRNA level was dependent on nutritional status, increasing slowly if the chicks were starved and rapidly if they were fed. The abundance of malic enzyme mRNA decreased in starved neonatal chicks and increased in fed ones. When neonates were first fed and then starved, starvation caused a large decrease in the abundance of both mRNAs. Conversely, feeding, after a period of starvation, resulted in a substantial increase in both mRNAs. The relative abundances of fatty acid synthase and malic enzyme mRNAs correlated positively with relative rates of enzyme synthesis. Thus, nutritional and hormonal regulation of the synthesis of these two 'lipogenic' enzymes is exerted primarily at a pre-translational level. The abundance of albumin mRNA decreased significantly between the 16th day of incubation and the day of hatching but did not change thereafter in fed or starved chicks. The relative stability of albumin mRNA levels after hatching attests to the selectivity of the nutritional regulation of fatty acid synthase and malic enzyme mRNAs. The decrease in albumin mRNA which occurred between 16 days of incubation and hatching contrasts with the increase in albumin mRNA sequences which occurred during late gestation in the fetal rat (20). High levels of albumin in the chick embryo may be related to the lack of an analogue of mammalian alpha-fetoprotein in birds.

The isolation and characterization of a mutant allele at a new X-linked locus,mex, affecting NADP+-dependent enzymes inDrosophila melanogaster

“…This precludes the possibility of substantial posttranslational modifications resulting from the action of the mex + product. This is consistent with observations in chicks and rats on the nutritional and hormonal regulation of ME, where the regulation appears to exert its influence at the pretranslational level (Magnuson and Nikodem, 1983;Morris et aL, 1984).…”

“…In chicks, regulation of mRNA levels throughout development and during nutritional manipulation controls the relative rates of ME synthesis with decreased abundance in starved neonatal chicks and increased in fed organisms (Morris et al, 1984). Similarly, supplementation of Drosophila melanogaster diet with lipid decreased the concentration of NADP +-dependent enzyme molecules capable of generating NADPH for lipogenesis (Geer et al, 1976).…”

Clinicochemical follow-up of broiler rearing — A five-week study

“…A highly similar pattern has been described in turkey poults by Szabó et al (2005), comparing the post-hatch state to the entire rearing phase of 20 weeks. The relatively low plasma albumin level in the immediate post-hatch period is also supported by the results of Morris et al (1984), who reported a strong decrease for albumin mRNA in the chicken embryo just before hatching. The subsequent quick increase of albumin concentration (during the 1st week) and the relatively balanced globulin levels finally led to a quite steady ratio of these compounds.…”

Hepatic regulation of fatty acid synthase by insulin and T3: evidence for T3genomic and nongenomic actions

“…In the liver, the activity of FAS, like most lipogenic enzymes (95), is regulated through nutrients and hormones. Starvation causes a decrease in the activity of the enzyme, and refeeding restores it (3,67). A similar effect of refeeding is also observed on the mRNA expression level and stability, as well as on the transcription (3,41,48,52,66).…”