Differential hexosamine biosynthetic pathway gene expression with type 2 diabetes

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.

Transcriptomic analyses reveal rhythmic and CLOCK-driven pathways in human skeletal muscle

“…Phospholipase PLD1 ( Teng et al, 2015 ), involved in intracellular membrane trafficking and maintenance of glucose homeostasis in human skeletal muscle ( Huang et al, 2005 ) was rhythmically expressed in vivo and in vitro. Moreover, oscillatory genes in both datasets included NAMPT , KLF11, and GFPT2 , the latter controlling the flux of glucose into the hexosamine pathway, tightly linked to hyperglycemia and insulin resistance ( Coomer and Essop, 2014 ). The expression of NAMPT , a key regulator of NAD + synthesis and muscle maintenance ( Frederick et al, 2016 ), was previously shown to be regulated by CLOCK and BMAL1 in complex with SIRT1 ( Ramsey et al, 2009 ; Garten et al, 2015 ).…”

Damaging effects of hyperglycemia on cardiovascular function: spotlight on glucose metabolic pathways

“…At present, very few clinical studies exist to demonstrate a causal link between HBP activation and high glucose-induced complications in diabetic individuals. Studies from our laboratory recently showed increased HBP activation and O-GlcNAc levels in leukocytes of individuals with diabetes and prediabetes (272) and decreased ␤-N-acetylglucosaminidase gene expression with type 2 diabetes (64). Moreover, other researchers have found that individuals with type 2 diabetes displayed an association of glutamine:fructose-6-phosphate amidotransferase mRNA levels and enzyme activity with postprandial hyperglycemia and oxidative stress (274).…”

Effects of Rich-Polyphenols Extract of Dendrobium loddigesii on Anti-Diabetic, Anti-Inflammatory, Anti-Oxidant, and Gut Microbiota Modulation in db/db Mice

“…Oxidative stress was considered as a unifying mechanism of diabetic and its complications [3]. Diabetes can lead to abnormal metabolism of energy, carbohydrates, fat and protein [4,5,6]; high glucose and free fatty acids levels can stimulate oxidative stress, increase the expression of inflammatory factors and lead to insulin resistance [7]. IL-6 and TNF-α, as major inflammatory factors, participate in the development of T2DM; the increasing expression of TNF-α and IL-6 can cause pathological injury and diabetes complications [8,9].…”