Effects of nutrients and hormones on transcriptional and post‐transcriptional regulation of fatty acid synthase in rat liver

Abstract

The effects of nutrients and hormones on transcriptional and post‐transcriptional regulation of fatty acid synthase in rat liver were investigated following cDNA cloning. When fasted rats were fed a carbohydrate/protein diet, the transcriptional rate was greatly increased even in 1 h. The transcriptional rate, mRNA concentration and enzyme induction reached maximum levels in 4 h, 8–16 h and 48 h, respectively. Although dietary carbohydrate increased each level more than protein did, both carbohydrate and protein were required to reach a high level. Corn oil feeding markedly decreased the transcriptional rate. In diabetic rats, the transcriptional rate, mRNA concentration and enzyme induction were very low in comparison with the normal. By treating the diabetic rats with insulin, however, the transcriptional rate was increased 5‐fold in 1 h and 15‐fold in 6 h, preceding a great increase in the mRNA and enzyme levels. On the other hand, fructose feeding or triiodothyronine treatment of diabetic rats abundantly increased the mRNA concentration and somewhat increased the transcriptional rate. Thus, it is suggested that insulin mainly stimulates the transcription of the fatty acid synthase gene, whereas triiodothyronine and fructose mainly increase the mRNA stability.

Characterization of rat liver malonyl-CoA decarboxylase and the study of its role in regulating fatty acid metabolism

“…Since many enzymes that control lipid metabolism are altered in diabetes [25], we have studied MCD in two models that represent both Type I and Type II (insulin-resistant) diabetes. In 6-weekold streptozotocin-diabetic rats, many of the hepatic enzymes involved in the regulation of lipid metabolism are suppressed [17,[26][27][28]. In these insulin-deficient animals, blood glucose levels and fatty acid levels rise [21], which was confirmed by our results (Table 2).…”

Insulin‐ and polyunsaturated fatty acid‐responsive region(s) of rat ATP citrate‐lyase gene promoter

“…The cDNAs were labeled by a multiprimer DNA labeling system kit (Amersham, Buckinghamshire, UK) using [ot-a2p]dCTP. To measure the mRNA concentration of the enzyme, the total RNA (20 l.tg) was denatured with formaldehyde at 65°C for 15 min, spotted on nylon filter, and then radiated with UV light for 5 min, The filter was prehybridized and then hybridized as described previously [17]. Relative densities of the hybridization signals were determined by scanning the autoradiograms at 525 nm and normalized to the values of the 18S rRNA.…”

Nutritional and Hormonal Regulation of Uncoupling Protein Gene Expression in Rat Adipocytes

“…To measure the mRNA levels, the total RNA (10-30 g) was denatured with formamide, spotted on a nylon filter and then hybridized with 32 P-labeled cDNA as described previously ( 20 ). The relative densities of hybridization signals were determined by scanning the autoradiograms at 525 nm and normalized by the values of the 18S rRNA.…”

“…Total cellular RNA from adipocytes was isolated by the method of acid guanidium thiocyanate-phenol-chloroform extraction ( 19 ). Dot blot hybridization of total cellular RNA was performed as described previously ( 20 ). UCP-1, -2, and -3 cDNA fragments spanning nucleotides ϩ 100 to ϩ 865, ϩ 100 to ϩ 871 and ϩ 100 to ϩ 868, respectively, were cloned from rat adipose tissue by reverse transcription and polymerase chain reaction amplification according to Ref.…”