Limits...
Increased systemic glucose tolerance with increased muscle glucose uptake in transgenic mice overexpressing RXRγ in skeletal muscle.

Sugita S, Kamei Y, Akaike F, Suganami T, Kanai S, Hattori M, Manabe Y, Fujii N, Takai-Igarashi T, Tadaishi M, Oka J, Aburatani H, Yamada T, Katagiri H, Kakehi S, Tamura Y, Kubo H, Nishida K, Miura S, Ezaki O, Ogawa Y - PLoS ONE (2011)

Bottom Line: Combination of RXRγ and PPARδ resulted in an increase in Glut1-Luc activity in skeletal muscle in vivo.These results show the importance of skeletal muscle gene regulation in systemic glucose metabolism.Increasing RXRγ expression may be a novel therapeutic strategy against type 2 diabetes.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.

ABSTRACT

Background: Retinoid X receptor (RXR) γ is a nuclear receptor-type transcription factor expressed mostly in skeletal muscle, and regulated by nutritional conditions. Previously, we established transgenic mice overexpressing RXRγ in skeletal muscle (RXRγ mice), which showed lower blood glucose than the control mice. Here we investigated their glucose metabolism.

Methodology/principal findings: RXRγ mice were subjected to glucose and insulin tolerance tests, and glucose transporter expression levels, hyperinsulinemic-euglycemic clamp and glucose uptake were analyzed. Microarray and bioinformatics analyses were done. The glucose tolerance test revealed higher glucose disposal in RXRγ mice than in control mice, but insulin tolerance test revealed no difference in the insulin-induced hypoglycemic response. In the hyperinsulinemic-euglycemic clamp study, the basal glucose disposal rate was higher in RXRγ mice than in control mice, indicating an insulin-independent increase in glucose uptake. There was no difference in the rate of glucose infusion needed to maintain euglycemia (glucose infusion rate) between the RXRγ and control mice, which is consistent with the result of the insulin tolerance test. Skeletal muscle from RXRγ mice showed increased Glut1 expression, with increased glucose uptake, in an insulin-independent manner. Moreover, we performed in vivo luciferase reporter analysis using Glut1 promoter (Glut1-Luc). Combination of RXRγ and PPARδ resulted in an increase in Glut1-Luc activity in skeletal muscle in vivo. Microarray data showed that RXRγ overexpression increased a diverse set of genes, including glucose metabolism genes, whose promoter contained putative PPAR-binding motifs.

Conclusions/significance: Systemic glucose metabolism was increased in transgenic mice overexpressing RXRγ. The enhanced glucose tolerance in RXRγ mice may be mediated at least in part by increased Glut1 in skeletal muscle. These results show the importance of skeletal muscle gene regulation in systemic glucose metabolism. Increasing RXRγ expression may be a novel therapeutic strategy against type 2 diabetes.

Show MeSH

Related in: MedlinePlus

Levels of ‘glucose metabolic process’ gene expression in                            the skeletal muscle of RXRγ mice.Representative gene expressions of ‘glucose metabolic process                            genes’ analyzed by microarray and GO analysis (Table 5) were                            examined by quantitative real-time PCR. The value for wild-type                            (littermates of line 4-3) mice was set at 100, and relative values are                            shown. Mice were females of 4 months of age. The number of animals was 6                            for both control (open bars) and RXRγ (filled bars) mice. These                            samples were also used in microarray analysis (Dataset                                S1). * P<0.05 and **                                P<0.01 compared with respective control. N. S.,                            not significant.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3105070&req=5

pone-0020467-g005: Levels of ‘glucose metabolic process’ gene expression in the skeletal muscle of RXRγ mice.Representative gene expressions of ‘glucose metabolic process genes’ analyzed by microarray and GO analysis (Table 5) were examined by quantitative real-time PCR. The value for wild-type (littermates of line 4-3) mice was set at 100, and relative values are shown. Mice were females of 4 months of age. The number of animals was 6 for both control (open bars) and RXRγ (filled bars) mice. These samples were also used in microarray analysis (Dataset S1). * P<0.05 and ** P<0.01 compared with respective control. N. S., not significant.

Mentions: In order to gain insight into the gene expression change in RXRγ mice, we performed microarray analysis. As shown in Dataset S1, 738 genes were up-regulated in the analysis. As expected, Glut1 expression was increased in the microarray data. Also, SREBP1c expression, which we previously reported [9], was increased in the microarray data. Using the data, we performed GO analysis to determine if genes, up-regulated in RXRγ mice, are associated with particular biological processes. Our GO analysis revealed genes with increased expression in the RXRγ mice in various categories (Table 4), including ‘glucose metabolic process’ genes and ‘fatty acid biosynthetic process’ genes, which indicated that overexpression of RXRγ affects the expression of many genes. The up-regulated genes categorized as glucose metabolism genes in GO term are listed in Table 5. Among them, we confirmed enhanced gene expression by quantitative real time PCR (Fig. 5), supporting the microarray data reliable. Moreover, we calculated the ratio of putative transcription factor binding motifs in glucose metabolism genes, which were up-regulated in RXRγ mice. In the sample, several motifs showed statistical significance (Table 6) (P<0.05), including PPAR responsive elements. These data suggest that glucose metabolism genes up-regulated in RXRγ mice are possible target genes of the RXRγ and PPAR heterodimer.


Increased systemic glucose tolerance with increased muscle glucose uptake in transgenic mice overexpressing RXRγ in skeletal muscle.

Sugita S, Kamei Y, Akaike F, Suganami T, Kanai S, Hattori M, Manabe Y, Fujii N, Takai-Igarashi T, Tadaishi M, Oka J, Aburatani H, Yamada T, Katagiri H, Kakehi S, Tamura Y, Kubo H, Nishida K, Miura S, Ezaki O, Ogawa Y - PLoS ONE (2011)

Levels of ‘glucose metabolic process’ gene expression in                            the skeletal muscle of RXRγ mice.Representative gene expressions of ‘glucose metabolic process                            genes’ analyzed by microarray and GO analysis (Table 5) were                            examined by quantitative real-time PCR. The value for wild-type                            (littermates of line 4-3) mice was set at 100, and relative values are                            shown. Mice were females of 4 months of age. The number of animals was 6                            for both control (open bars) and RXRγ (filled bars) mice. These                            samples were also used in microarray analysis (Dataset                                S1). * P<0.05 and **                                P<0.01 compared with respective control. N. S.,                            not significant.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105070&req=5

pone-0020467-g005: Levels of ‘glucose metabolic process’ gene expression in the skeletal muscle of RXRγ mice.Representative gene expressions of ‘glucose metabolic process genes’ analyzed by microarray and GO analysis (Table 5) were examined by quantitative real-time PCR. The value for wild-type (littermates of line 4-3) mice was set at 100, and relative values are shown. Mice were females of 4 months of age. The number of animals was 6 for both control (open bars) and RXRγ (filled bars) mice. These samples were also used in microarray analysis (Dataset S1). * P<0.05 and ** P<0.01 compared with respective control. N. S., not significant.
Mentions: In order to gain insight into the gene expression change in RXRγ mice, we performed microarray analysis. As shown in Dataset S1, 738 genes were up-regulated in the analysis. As expected, Glut1 expression was increased in the microarray data. Also, SREBP1c expression, which we previously reported [9], was increased in the microarray data. Using the data, we performed GO analysis to determine if genes, up-regulated in RXRγ mice, are associated with particular biological processes. Our GO analysis revealed genes with increased expression in the RXRγ mice in various categories (Table 4), including ‘glucose metabolic process’ genes and ‘fatty acid biosynthetic process’ genes, which indicated that overexpression of RXRγ affects the expression of many genes. The up-regulated genes categorized as glucose metabolism genes in GO term are listed in Table 5. Among them, we confirmed enhanced gene expression by quantitative real time PCR (Fig. 5), supporting the microarray data reliable. Moreover, we calculated the ratio of putative transcription factor binding motifs in glucose metabolism genes, which were up-regulated in RXRγ mice. In the sample, several motifs showed statistical significance (Table 6) (P<0.05), including PPAR responsive elements. These data suggest that glucose metabolism genes up-regulated in RXRγ mice are possible target genes of the RXRγ and PPAR heterodimer.

Bottom Line: Combination of RXRγ and PPARδ resulted in an increase in Glut1-Luc activity in skeletal muscle in vivo.These results show the importance of skeletal muscle gene regulation in systemic glucose metabolism.Increasing RXRγ expression may be a novel therapeutic strategy against type 2 diabetes.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Medicine and Metabolism, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.

ABSTRACT

Background: Retinoid X receptor (RXR) γ is a nuclear receptor-type transcription factor expressed mostly in skeletal muscle, and regulated by nutritional conditions. Previously, we established transgenic mice overexpressing RXRγ in skeletal muscle (RXRγ mice), which showed lower blood glucose than the control mice. Here we investigated their glucose metabolism.

Methodology/principal findings: RXRγ mice were subjected to glucose and insulin tolerance tests, and glucose transporter expression levels, hyperinsulinemic-euglycemic clamp and glucose uptake were analyzed. Microarray and bioinformatics analyses were done. The glucose tolerance test revealed higher glucose disposal in RXRγ mice than in control mice, but insulin tolerance test revealed no difference in the insulin-induced hypoglycemic response. In the hyperinsulinemic-euglycemic clamp study, the basal glucose disposal rate was higher in RXRγ mice than in control mice, indicating an insulin-independent increase in glucose uptake. There was no difference in the rate of glucose infusion needed to maintain euglycemia (glucose infusion rate) between the RXRγ and control mice, which is consistent with the result of the insulin tolerance test. Skeletal muscle from RXRγ mice showed increased Glut1 expression, with increased glucose uptake, in an insulin-independent manner. Moreover, we performed in vivo luciferase reporter analysis using Glut1 promoter (Glut1-Luc). Combination of RXRγ and PPARδ resulted in an increase in Glut1-Luc activity in skeletal muscle in vivo. Microarray data showed that RXRγ overexpression increased a diverse set of genes, including glucose metabolism genes, whose promoter contained putative PPAR-binding motifs.

Conclusions/significance: Systemic glucose metabolism was increased in transgenic mice overexpressing RXRγ. The enhanced glucose tolerance in RXRγ mice may be mediated at least in part by increased Glut1 in skeletal muscle. These results show the importance of skeletal muscle gene regulation in systemic glucose metabolism. Increasing RXRγ expression may be a novel therapeutic strategy against type 2 diabetes.

Show MeSH
Related in: MedlinePlus