Limits...
Vitamin A and feeding statuses modulate the insulin-regulated gene expression in Zucker lean and fatty primary rat hepatocytes.

Chen W, Howell ML, Li Y, Li R, Chen G - PLoS ONE (2014)

Bottom Line: Unattended hepatic insulin resistance predisposes individuals to dyslipidemia, type 2 diabetes and many other metabolic complications.To examine the effects of vitamin A (VA), total energy intake and feeding conditions on the insulin-regulated gene expression in primary hepatocytes of Zucker lean (ZL) and fatty (ZF) rats, we analyze the expression levels of hepatic model genes in response to the treatments of insulin and retinoic acid (RA).These results demonstrate that VA and feeding statuses modulate the hepatic insulin sensitivity at the gene expression level.

View Article: PubMed Central - PubMed

Affiliation: Department of Nutrition, University of Tennessee at Knoxville, Knoxville, Tennessee, United States of America.

ABSTRACT
Unattended hepatic insulin resistance predisposes individuals to dyslipidemia, type 2 diabetes and many other metabolic complications. The mechanism of hepatic insulin resistance at the gene expression level remains unrevealed. To examine the effects of vitamin A (VA), total energy intake and feeding conditions on the insulin-regulated gene expression in primary hepatocytes of Zucker lean (ZL) and fatty (ZF) rats, we analyze the expression levels of hepatic model genes in response to the treatments of insulin and retinoic acid (RA). We report that the insulin- and RA-regulated glucokinase, sterol regulatory element-binding protein-1c and cytosolic form of phosphoenolpyruvate carboxykinase expressions are impaired in hepatocytes of ZF rats fed chow or a VA sufficient (VAS) diet ad libitum. The impairments are partially corrected when ZF rats are fed a VA deficient (VAD) diet ad libitum or pair-fed a VAS diet to the intake of their VAD counterparts in non-fasting conditions. Interestingly in the pair-fed ZL and ZF rats, transient overeating on the last day of pair-feeding regimen changes the expression levels of some VA catabolic genes, and impairs the insulin- and RA-regulated gene expression in hepatocytes. These results demonstrate that VA and feeding statuses modulate the hepatic insulin sensitivity at the gene expression level.

Show MeSH

Related in: MedlinePlus

Impaired insulin-regulated gene expression in primary hepatocytes of ZF rats fed chow ad libitum.ZL and ZF rats were fed standard chow for eight weeks before primary hepatocytes were harvested. The primary hepatocytes were incubated in medium A with increasing concentrations of insulin (0 nM to 100 nM) in the absence or presence of RA (5 µM) for 6 hours. Total RNA was extracted, synthesized into cDNA, and then subjected to real-time PCR analysis for the expression levels of Gck (A), Pck1 (B), Srebp-1c (C), and Pklr (D). The expression level of each gene transcript in ZL or ZF hepatocytes treated with vehicle control was arbitrarily set to 1. The data were expressed as fold induction. The numbers of hepatocyte isolation are presented in parenthesis. All p<0.05; for (A), a′<b′<c′, a<b<c, d′<e′, d<e; for (B), f′>g′>h′, f>g>h, i′>j′, i>k; for (C), l′<m′<n′, m<o, p′<q′, r<s using one-way ANOVA; * or # for comparing ZL or ZF at corresponding treatments using Student's t-test, respectively.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4126667&req=5

pone-0100868-g001: Impaired insulin-regulated gene expression in primary hepatocytes of ZF rats fed chow ad libitum.ZL and ZF rats were fed standard chow for eight weeks before primary hepatocytes were harvested. The primary hepatocytes were incubated in medium A with increasing concentrations of insulin (0 nM to 100 nM) in the absence or presence of RA (5 µM) for 6 hours. Total RNA was extracted, synthesized into cDNA, and then subjected to real-time PCR analysis for the expression levels of Gck (A), Pck1 (B), Srebp-1c (C), and Pklr (D). The expression level of each gene transcript in ZL or ZF hepatocytes treated with vehicle control was arbitrarily set to 1. The data were expressed as fold induction. The numbers of hepatocyte isolation are presented in parenthesis. All p<0.05; for (A), a′<b′<c′, a<b<c, d′<e′, d<e; for (B), f′>g′>h′, f>g>h, i′>j′, i>k; for (C), l′<m′<n′, m<o, p′<q′, r<s using one-way ANOVA; * or # for comparing ZL or ZF at corresponding treatments using Student's t-test, respectively.

Mentions: We compared the insulin-regulated gene expression in primary hepatocytes from ZL and ZF rats fed chow ad libitum. Insulin dose-dependently induced the Gck and Srebp-1c expressions (Figure 1A and 1C), and suppressed the Pck1 expression (Figure 1B) in ZL hepatocytes. RA (5 µM) synergized with insulin to induce the Gck and Srebp-1c expressions (Figure 1A and 1C). The elevated Pck1 level in the presence of RA was still lowered by insulin at 1 nM or higher (Figure 1B). Comparably in ZF hepatocytes, the fold inductions of Gck expression by insulin (marked by *) and RA + insulin (marked by #) at the corresponding concentrations were significantly lower than that in ZL hepatocytes (Figure 1A). The inductions of Srebp-1c by insulin (0.1 to 100 nM) and RA + insulin (0.1 to 100 nM) were abolished in ZF hepatocytes (Figure 1C). Additionally, the insulin-mediated suppression of Pck1 was less profound in ZF hepatocytes compared with that in ZL hepatocytes (Figure 1B, marked by * and #, and Figure S1 in File S1). Furthermore, the expressions of liver type pyruvate kinase gene (Pklr) in primary hepatocytes from either ZL or ZF rats were not affected by insulin and RA treatments (Figure 1D). These data confirmed our previous observations [9] and demonstrated the hepatic insulin resistance at the gene expression level in ZF rats fed chow ad libitum.


Vitamin A and feeding statuses modulate the insulin-regulated gene expression in Zucker lean and fatty primary rat hepatocytes.

Chen W, Howell ML, Li Y, Li R, Chen G - PLoS ONE (2014)

Impaired insulin-regulated gene expression in primary hepatocytes of ZF rats fed chow ad libitum.ZL and ZF rats were fed standard chow for eight weeks before primary hepatocytes were harvested. The primary hepatocytes were incubated in medium A with increasing concentrations of insulin (0 nM to 100 nM) in the absence or presence of RA (5 µM) for 6 hours. Total RNA was extracted, synthesized into cDNA, and then subjected to real-time PCR analysis for the expression levels of Gck (A), Pck1 (B), Srebp-1c (C), and Pklr (D). The expression level of each gene transcript in ZL or ZF hepatocytes treated with vehicle control was arbitrarily set to 1. The data were expressed as fold induction. The numbers of hepatocyte isolation are presented in parenthesis. All p<0.05; for (A), a′<b′<c′, a<b<c, d′<e′, d<e; for (B), f′>g′>h′, f>g>h, i′>j′, i>k; for (C), l′<m′<n′, m<o, p′<q′, r<s using one-way ANOVA; * or # for comparing ZL or ZF at corresponding treatments using Student's t-test, respectively.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126667&req=5

pone-0100868-g001: Impaired insulin-regulated gene expression in primary hepatocytes of ZF rats fed chow ad libitum.ZL and ZF rats were fed standard chow for eight weeks before primary hepatocytes were harvested. The primary hepatocytes were incubated in medium A with increasing concentrations of insulin (0 nM to 100 nM) in the absence or presence of RA (5 µM) for 6 hours. Total RNA was extracted, synthesized into cDNA, and then subjected to real-time PCR analysis for the expression levels of Gck (A), Pck1 (B), Srebp-1c (C), and Pklr (D). The expression level of each gene transcript in ZL or ZF hepatocytes treated with vehicle control was arbitrarily set to 1. The data were expressed as fold induction. The numbers of hepatocyte isolation are presented in parenthesis. All p<0.05; for (A), a′<b′<c′, a<b<c, d′<e′, d<e; for (B), f′>g′>h′, f>g>h, i′>j′, i>k; for (C), l′<m′<n′, m<o, p′<q′, r<s using one-way ANOVA; * or # for comparing ZL or ZF at corresponding treatments using Student's t-test, respectively.
Mentions: We compared the insulin-regulated gene expression in primary hepatocytes from ZL and ZF rats fed chow ad libitum. Insulin dose-dependently induced the Gck and Srebp-1c expressions (Figure 1A and 1C), and suppressed the Pck1 expression (Figure 1B) in ZL hepatocytes. RA (5 µM) synergized with insulin to induce the Gck and Srebp-1c expressions (Figure 1A and 1C). The elevated Pck1 level in the presence of RA was still lowered by insulin at 1 nM or higher (Figure 1B). Comparably in ZF hepatocytes, the fold inductions of Gck expression by insulin (marked by *) and RA + insulin (marked by #) at the corresponding concentrations were significantly lower than that in ZL hepatocytes (Figure 1A). The inductions of Srebp-1c by insulin (0.1 to 100 nM) and RA + insulin (0.1 to 100 nM) were abolished in ZF hepatocytes (Figure 1C). Additionally, the insulin-mediated suppression of Pck1 was less profound in ZF hepatocytes compared with that in ZL hepatocytes (Figure 1B, marked by * and #, and Figure S1 in File S1). Furthermore, the expressions of liver type pyruvate kinase gene (Pklr) in primary hepatocytes from either ZL or ZF rats were not affected by insulin and RA treatments (Figure 1D). These data confirmed our previous observations [9] and demonstrated the hepatic insulin resistance at the gene expression level in ZF rats fed chow ad libitum.

Bottom Line: Unattended hepatic insulin resistance predisposes individuals to dyslipidemia, type 2 diabetes and many other metabolic complications.To examine the effects of vitamin A (VA), total energy intake and feeding conditions on the insulin-regulated gene expression in primary hepatocytes of Zucker lean (ZL) and fatty (ZF) rats, we analyze the expression levels of hepatic model genes in response to the treatments of insulin and retinoic acid (RA).These results demonstrate that VA and feeding statuses modulate the hepatic insulin sensitivity at the gene expression level.

View Article: PubMed Central - PubMed

Affiliation: Department of Nutrition, University of Tennessee at Knoxville, Knoxville, Tennessee, United States of America.

ABSTRACT
Unattended hepatic insulin resistance predisposes individuals to dyslipidemia, type 2 diabetes and many other metabolic complications. The mechanism of hepatic insulin resistance at the gene expression level remains unrevealed. To examine the effects of vitamin A (VA), total energy intake and feeding conditions on the insulin-regulated gene expression in primary hepatocytes of Zucker lean (ZL) and fatty (ZF) rats, we analyze the expression levels of hepatic model genes in response to the treatments of insulin and retinoic acid (RA). We report that the insulin- and RA-regulated glucokinase, sterol regulatory element-binding protein-1c and cytosolic form of phosphoenolpyruvate carboxykinase expressions are impaired in hepatocytes of ZF rats fed chow or a VA sufficient (VAS) diet ad libitum. The impairments are partially corrected when ZF rats are fed a VA deficient (VAD) diet ad libitum or pair-fed a VAS diet to the intake of their VAD counterparts in non-fasting conditions. Interestingly in the pair-fed ZL and ZF rats, transient overeating on the last day of pair-feeding regimen changes the expression levels of some VA catabolic genes, and impairs the insulin- and RA-regulated gene expression in hepatocytes. These results demonstrate that VA and feeding statuses modulate the hepatic insulin sensitivity at the gene expression level.

Show MeSH
Related in: MedlinePlus