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Title:The identification and characterization of two murine genes regulated by the level of dietary fat
Author(s):Swartz, Deborah Ann
Doctoral Committee Chair(s):Erdman, John W.
Department / Program:Nutritional Sciences
Discipline:Nutritional Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Biology, Molecular
Health Sciences, Nutrition
Abstract:We have investigated the influence of the level of dietary fat on hepatic stearoyl CoA desaturase 1 (Scd1) and Low Fat Mammary 1 (Lfm1) expression and describe the structural organization of the Lfm1 gene. Scd1 and Lfm1 were isolated from a cDNA library constructed from mammary gland tissue of BALB/c mice fed a low fat diet (Elliott et al. 1993. Biochim. Biophys. Res. Comm. 190: 167-174). Northern hybridization analyses of hepatic total RNA from BALB/c mice fed diets containing 0, 5, 10, 15 or 20% corn oil showed a significant dose-dependent decrease in Scd1 mRNA abundance. Increasing the concentrations of dietary fat from 0-5% to 10, 15 or 20% significantly ($P<$ 0.05) decreased Scd1 mRNA by 50%, 75%, and 82%, respectively. The time course of Scd1 mRNA induction and the effects of fasting and refeeding on its abundance were examined in BALB/c mice fed diets containing 3, 10 or 20% corn oil. Hepatic Scd1 mRNA expression decreased after 12 h of fasting but increased 4-fold 6 h after refeeding in the 3% fat group compared to the 20% fat group. The abundance of Scd1 mRNA was also determined in response to type and amount of dietary fat in two inbred strains of mice with different susceptibilities to disease. Scd1 mRNA expression significantly ($P<$ 0.05) decreased in BALB/c mice fed diets containing 20% corn or coconut oil compared to those fed 4% of these fats in otherwise identical diets. C57BL/6 mice, which are more susceptible to atherosclerosis and type II diabetes compared to BALB/c mice, showed a significant ($P<$ 0.05) decrease in Scd1 mRNA abundance when fed diets containing 20% corn oil compared to 4% corn oil. In contrast, the level of Scd1 mRNA abundance remained unchanged by 4 and 20% coconut oil.
Northern analysis determining the abundance of hepatic Lfm1 mRNA as a function of the level of dietary fat in BALB/c mice did not show a significant dietary fat effect. However, a trend of decreasing $Lfm1/\beta$-actin ratio with increasing level of dietary fat (0-20% fat) was observed. The effects of fasting and refeeding on Lfm1 mRNA expression was examined in BALB/c mice fed diets containing 3 or 20% corn oil. The $Lfm1/\beta$-actin ratio was significantly ($P<$ 0.005) lower (33%) in the 20% fat group compared to the 3% fat group during ad libitum feeding. After 12 h of fasting the $Lfm1/\beta$-actin ratio was significantly ($P<$ 0.005) higher (76%) in mice previously fed the 20% fat diet than in those fed the 3% fat. No significant differences were observed after the mice were refed their respective diets for 2h. To begin analyses of the mechanisms involved in the dietary regulation of Lfm1 we cloned and analyzed genomic copies of Lfm1. Four Lfm1 genes, including 2 pseudogenes, were isolated and characterized suggesting that Lfm1 belongs to a small gene family. (Abstract shortened by UMI.)
Issue Date:1995
Rights Information:Copyright 1995 Swartz, Deborah Ann
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9624505
OCLC Identifier:(UMI)AAI9624505

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