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Differential hexosamine biosynthetic pathway gene expression with type 2 diabetes

View Article: PubMed Central - PubMed

ABSTRACT

The hexosamine biosynthetic pathway (HBP) culminates in the attachment of O-linked β-N-acetylglucosamine (O-GlcNAc) onto serine/threonine residues of target proteins. The HBP is regulated by several modulators, i.e. O-linked β-N-acetylglucosaminyl transferase (OGT) and β-N-acetylglucosaminidase (OGA) catalyze the addition and removal of O-GlcNAc moieties, respectively; while flux is controlled by the rate-limiting enzyme glutamine:fructose-6-phosphate amidotransferase (GFPT), transcribed by two genes, GFPT1 and GFPT2. Since increased HBP flux is glucose-responsive and linked to insulin resistance/type 2 diabetes onset, we hypothesized that diabetic individuals exhibit differential expression of HBP regulatory genes. Volunteers (n = 60; n = 20 Mixed Ancestry, n = 40 Caucasian) were recruited from Stellenbosch and Paarl (Western Cape, South Africa) and classified as control, pre- or diabetic according to fasting plasma glucose and HbA1c levels, respectively. RNA was purified from leukocytes isolated from collected blood samples and OGT, OGA, GFPT1 and GFPT2 expressions determined by quantitative real-time PCR. The data reveal lower OGA expression in diabetic individuals (P < 0.01), while pre- and diabetic subjects displayed attenuated OGT expression vs. controls (P < 0.01 and P < 0.001, respectively). Moreover, GFPT2 expression decreased in pre- and diabetic Caucasians vs. controls (P < 0.05 and P < 0.01, respectively). We also found ethnic differences, i.e. Mixed Ancestry individuals exhibited a 2.4-fold increase in GFPT2 expression vs. Caucasians, despite diagnosis (P < 0.01). Gene expression of HBP regulators differs between diabetic and non-diabetic individuals, together with distinct ethnic-specific gene profiles. Thus differential HBP gene regulation may offer diagnostic utility and provide candidate susceptibility genes for different ethnic groupings.

No MeSH data available.


Related in: MedlinePlus

Reduced OGA gene expression in diabetic individuals. Decreased OGA/GUSB gene expression in diabetic vs. pre-diabetic (#P < 0.05), and control subjects (**P < 0.01) (n = 44) (HbA1c characterization). B. Lower OGA/ACTB expression in diabetic vs. control (*P < 0.05; $$P < 0.01), and pre-diabetic individuals (#P < 0.05) (n = 43) (HbA1c characterization). C. Attenuated OGA/RPL37A expression in diabetic vs. control individuals (*P < 0.05) (n = 35) (HbA1c characterization). D. Lower OGA/GUSB gene expression in diabetic subjects vs. pre-diabetic ($P < 0.05) and control subjects (*P < 0.05; ##P < 0.01) (n = 47) (blood glucose characterization). E. Decreased OGA/ACTB levels in diabetic vs. control (*P < 0.05; $$P < 0.01), and pre-diabetic vs. control subjects (#P < 0.05) (n = 43) (blood glucose characterization). F. No statistically significant differences in OGA/RPL37A expression between study groups (n = 46) (blood glucose characterization). Data are expressed as the mean ± SEM. Values are expressed as a relative percentage to controls (100%).
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f0005: Reduced OGA gene expression in diabetic individuals. Decreased OGA/GUSB gene expression in diabetic vs. pre-diabetic (#P < 0.05), and control subjects (**P < 0.01) (n = 44) (HbA1c characterization). B. Lower OGA/ACTB expression in diabetic vs. control (*P < 0.05; $$P < 0.01), and pre-diabetic individuals (#P < 0.05) (n = 43) (HbA1c characterization). C. Attenuated OGA/RPL37A expression in diabetic vs. control individuals (*P < 0.05) (n = 35) (HbA1c characterization). D. Lower OGA/GUSB gene expression in diabetic subjects vs. pre-diabetic ($P < 0.05) and control subjects (*P < 0.05; ##P < 0.01) (n = 47) (blood glucose characterization). E. Decreased OGA/ACTB levels in diabetic vs. control (*P < 0.05; $$P < 0.01), and pre-diabetic vs. control subjects (#P < 0.05) (n = 43) (blood glucose characterization). F. No statistically significant differences in OGA/RPL37A expression between study groups (n = 46) (blood glucose characterization). Data are expressed as the mean ± SEM. Values are expressed as a relative percentage to controls (100%).

Mentions: We initially evaluated OGA mRNA expression levels in pre-diabetic and diabetic individuals compared to control subjects. When analyzing the data according to HbA1c levels, diabetic individuals displayed a 35.6 ± 6.3% decrease in OGA expression vs. control subjects (Fig. 1A). This difference was also statistically significant when compared to the pre-diabetic group. We confirmed these findings by normalizing the data to two additional reference genes, ACTB (Fig. 1B) and RPL37A (Fig. 1C). A similar pattern emerged when study participants were categorized according to fasting blood glucose levels, i.e. OGA expression was reduced by 33 ± 7.8% and 24.3 ± 9.8% vs. control and pre-diabetic subjects, respectively (Fig. 1D). The findings were corroborated by normalizing to ACTB (Fig. 1E) and RPL37A (Fig. 1F). Although normalizing to three separate reference genes and different characterizations yielded varying degrees of sensitivity, the same fundamental trend was observed: decreased OGA expression in diabetic individuals compared to control and pre-diabetic individuals.


Differential hexosamine biosynthetic pathway gene expression with type 2 diabetes
Reduced OGA gene expression in diabetic individuals. Decreased OGA/GUSB gene expression in diabetic vs. pre-diabetic (#P < 0.05), and control subjects (**P < 0.01) (n = 44) (HbA1c characterization). B. Lower OGA/ACTB expression in diabetic vs. control (*P < 0.05; $$P < 0.01), and pre-diabetic individuals (#P < 0.05) (n = 43) (HbA1c characterization). C. Attenuated OGA/RPL37A expression in diabetic vs. control individuals (*P < 0.05) (n = 35) (HbA1c characterization). D. Lower OGA/GUSB gene expression in diabetic subjects vs. pre-diabetic ($P < 0.05) and control subjects (*P < 0.05; ##P < 0.01) (n = 47) (blood glucose characterization). E. Decreased OGA/ACTB levels in diabetic vs. control (*P < 0.05; $$P < 0.01), and pre-diabetic vs. control subjects (#P < 0.05) (n = 43) (blood glucose characterization). F. No statistically significant differences in OGA/RPL37A expression between study groups (n = 46) (blood glucose characterization). Data are expressed as the mean ± SEM. Values are expressed as a relative percentage to controls (100%).
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f0005: Reduced OGA gene expression in diabetic individuals. Decreased OGA/GUSB gene expression in diabetic vs. pre-diabetic (#P < 0.05), and control subjects (**P < 0.01) (n = 44) (HbA1c characterization). B. Lower OGA/ACTB expression in diabetic vs. control (*P < 0.05; $$P < 0.01), and pre-diabetic individuals (#P < 0.05) (n = 43) (HbA1c characterization). C. Attenuated OGA/RPL37A expression in diabetic vs. control individuals (*P < 0.05) (n = 35) (HbA1c characterization). D. Lower OGA/GUSB gene expression in diabetic subjects vs. pre-diabetic ($P < 0.05) and control subjects (*P < 0.05; ##P < 0.01) (n = 47) (blood glucose characterization). E. Decreased OGA/ACTB levels in diabetic vs. control (*P < 0.05; $$P < 0.01), and pre-diabetic vs. control subjects (#P < 0.05) (n = 43) (blood glucose characterization). F. No statistically significant differences in OGA/RPL37A expression between study groups (n = 46) (blood glucose characterization). Data are expressed as the mean ± SEM. Values are expressed as a relative percentage to controls (100%).
Mentions: We initially evaluated OGA mRNA expression levels in pre-diabetic and diabetic individuals compared to control subjects. When analyzing the data according to HbA1c levels, diabetic individuals displayed a 35.6 ± 6.3% decrease in OGA expression vs. control subjects (Fig. 1A). This difference was also statistically significant when compared to the pre-diabetic group. We confirmed these findings by normalizing the data to two additional reference genes, ACTB (Fig. 1B) and RPL37A (Fig. 1C). A similar pattern emerged when study participants were categorized according to fasting blood glucose levels, i.e. OGA expression was reduced by 33 ± 7.8% and 24.3 ± 9.8% vs. control and pre-diabetic subjects, respectively (Fig. 1D). The findings were corroborated by normalizing to ACTB (Fig. 1E) and RPL37A (Fig. 1F). Although normalizing to three separate reference genes and different characterizations yielded varying degrees of sensitivity, the same fundamental trend was observed: decreased OGA expression in diabetic individuals compared to control and pre-diabetic individuals.

View Article: PubMed Central - PubMed

ABSTRACT

The hexosamine biosynthetic pathway (HBP) culminates in the attachment of O-linked &beta;-N-acetylglucosamine (O-GlcNAc) onto serine/threonine residues of target proteins. The HBP is regulated by several modulators, i.e. O-linked &beta;-N-acetylglucosaminyl transferase (OGT) and &beta;-N-acetylglucosaminidase (OGA) catalyze the addition and removal of O-GlcNAc moieties, respectively; while flux is controlled by the rate-limiting enzyme glutamine:fructose-6-phosphate amidotransferase (GFPT), transcribed by two genes, GFPT1 and GFPT2. Since increased HBP flux is glucose-responsive and linked to insulin resistance/type 2 diabetes onset, we hypothesized that diabetic individuals exhibit differential expression of HBP regulatory genes. Volunteers (n&nbsp;=&nbsp;60; n&nbsp;=&nbsp;20 Mixed Ancestry, n&nbsp;=&nbsp;40 Caucasian) were recruited from Stellenbosch and Paarl (Western Cape, South Africa) and classified as control, pre- or diabetic according to fasting plasma glucose and HbA1c levels, respectively. RNA was purified from leukocytes isolated from collected blood samples and OGT, OGA, GFPT1 and GFPT2 expressions determined by quantitative real-time PCR. The data reveal lower OGA expression in diabetic individuals (P&nbsp;&lt;&nbsp;0.01), while pre- and diabetic subjects displayed attenuated OGT expression vs. controls (P&nbsp;&lt;&nbsp;0.01 and P&nbsp;&lt;&nbsp;0.001, respectively). Moreover, GFPT2 expression decreased in pre- and diabetic Caucasians vs. controls (P&nbsp;&lt;&nbsp;0.05 and P&nbsp;&lt;&nbsp;0.01, respectively). We also found ethnic differences, i.e. Mixed Ancestry individuals exhibited a 2.4-fold increase in GFPT2 expression vs. Caucasians, despite diagnosis (P&nbsp;&lt;&nbsp;0.01). Gene expression of HBP regulators differs between diabetic and non-diabetic individuals, together with distinct ethnic-specific gene profiles. Thus differential HBP gene regulation may offer diagnostic utility and provide candidate susceptibility genes for different ethnic groupings.

No MeSH data available.


Related in: MedlinePlus