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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.

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VAD diet partially recovered the impaired insulin-regulated gene expression in ZF primary rat hepatocytes.ZL and ZF rats were fed either a VAS or VAD diet for 8 weeks. Primary hepatocytes were isolated from rats in ad libitum. Cells 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), and Srebp-1c (C). The data were expressed as fold induction. The gene transcript levels from the no treatment group (0 nM insulin, no RA) for both ZL and ZF were arbitrarily set to 1. The numbers of hepatocyte isolation are presented in parenthesis. All p<0.05; for (A), a<b<c, d<e<f, g<h<i, j<k<l, m<o, p<r/s/t, q<s/t, r<t, x<y; for (B), a′>b′>c′, d′>e′>f′, g′>h′>i, j′>k′>l′, m′>n′, o′>q′/r′, p′>r′, s′>t′>u′, v′>x′/y′, w′>y′; for (C), a″<b″<c″, d″<e″<f″, h″<i″<j″, k″<m″, n″<p″, q″<s″, using one-way ANOVA. * or # for comparing ZL and ZF at corresponding treatments using Student's t-test, respectively.
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pone-0100868-g002: VAD diet partially recovered the impaired insulin-regulated gene expression in ZF primary rat hepatocytes.ZL and ZF rats were fed either a VAS or VAD diet for 8 weeks. Primary hepatocytes were isolated from rats in ad libitum. Cells 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), and Srebp-1c (C). The data were expressed as fold induction. The gene transcript levels from the no treatment group (0 nM insulin, no RA) for both ZL and ZF were arbitrarily set to 1. The numbers of hepatocyte isolation are presented in parenthesis. All p<0.05; for (A), a<b<c, d<e<f, g<h<i, j<k<l, m<o, p<r/s/t, q<s/t, r<t, x<y; for (B), a′>b′>c′, d′>e′>f′, g′>h′>i, j′>k′>l′, m′>n′, o′>q′/r′, p′>r′, s′>t′>u′, v′>x′/y′, w′>y′; for (C), a″<b″<c″, d″<e″<f″, h″<i″<j″, k″<m″, n″<p″, q″<s″, using one-way ANOVA. * or # for comparing ZL and ZF at corresponding treatments using Student's t-test, respectively.

Mentions: VA deficiency reduced food intake, body mass, plasma insulin and triglyceride levels in Zucker rats [9]. Hence, it may attenuate the impairment of the insulin-regulated gene expression in ZF rat hepatocytes. Figure 2A (left panel) showed that, in both VAD and VAS ZL primary hepatocytes, insulin dose-dependently induced the Gck expression (first and second column clusters), and RA synergized with insulin to induce its expression (third and fourth column clusters). The fold inductions of Gck expression by insulin (marked by *) or by RA + insulin (marked by #) in the VAS ZL hepatocytes were significantly higher than that in VAD ZL hepatocytes at the corresponding insulin concentrations. In comparison, the insulin-induced Gck expression was impaired in both VAD and VAS ZF hepatocytes regardless of RA (Figure 2A, right panel).


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)

VAD diet partially recovered the impaired insulin-regulated gene expression in ZF primary rat hepatocytes.ZL and ZF rats were fed either a VAS or VAD diet for 8 weeks. Primary hepatocytes were isolated from rats in ad libitum. Cells 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), and Srebp-1c (C). The data were expressed as fold induction. The gene transcript levels from the no treatment group (0 nM insulin, no RA) for both ZL and ZF were arbitrarily set to 1. The numbers of hepatocyte isolation are presented in parenthesis. All p<0.05; for (A), a<b<c, d<e<f, g<h<i, j<k<l, m<o, p<r/s/t, q<s/t, r<t, x<y; for (B), a′>b′>c′, d′>e′>f′, g′>h′>i, j′>k′>l′, m′>n′, o′>q′/r′, p′>r′, s′>t′>u′, v′>x′/y′, w′>y′; for (C), a″<b″<c″, d″<e″<f″, h″<i″<j″, k″<m″, n″<p″, q″<s″, using one-way ANOVA. * or # for comparing ZL and ZF at corresponding treatments using Student's t-test, respectively.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4126667&req=5

pone-0100868-g002: VAD diet partially recovered the impaired insulin-regulated gene expression in ZF primary rat hepatocytes.ZL and ZF rats were fed either a VAS or VAD diet for 8 weeks. Primary hepatocytes were isolated from rats in ad libitum. Cells 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), and Srebp-1c (C). The data were expressed as fold induction. The gene transcript levels from the no treatment group (0 nM insulin, no RA) for both ZL and ZF were arbitrarily set to 1. The numbers of hepatocyte isolation are presented in parenthesis. All p<0.05; for (A), a<b<c, d<e<f, g<h<i, j<k<l, m<o, p<r/s/t, q<s/t, r<t, x<y; for (B), a′>b′>c′, d′>e′>f′, g′>h′>i, j′>k′>l′, m′>n′, o′>q′/r′, p′>r′, s′>t′>u′, v′>x′/y′, w′>y′; for (C), a″<b″<c″, d″<e″<f″, h″<i″<j″, k″<m″, n″<p″, q″<s″, using one-way ANOVA. * or # for comparing ZL and ZF at corresponding treatments using Student's t-test, respectively.
Mentions: VA deficiency reduced food intake, body mass, plasma insulin and triglyceride levels in Zucker rats [9]. Hence, it may attenuate the impairment of the insulin-regulated gene expression in ZF rat hepatocytes. Figure 2A (left panel) showed that, in both VAD and VAS ZL primary hepatocytes, insulin dose-dependently induced the Gck expression (first and second column clusters), and RA synergized with insulin to induce its expression (third and fourth column clusters). The fold inductions of Gck expression by insulin (marked by *) or by RA + insulin (marked by #) in the VAS ZL hepatocytes were significantly higher than that in VAD ZL hepatocytes at the corresponding insulin concentrations. In comparison, the insulin-induced Gck expression was impaired in both VAD and VAS ZF hepatocytes regardless of RA (Figure 2A, right panel).

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