Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.2 (PDK1)
 2,238 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activity of pyruvate dehydrogenase (PDH) is reduced in diabetic patients. Phosphorylation of the PDH E1alpha subunit by PDH kinase contributes to the suppression of PDH activity. PDH requires thiamine as a coenzyme. We investigated the exact mechanism of diabetes-induced PDH inhibition, and the effect of thiamine in both in vivo and in vitro experiments. Treatment of rats with thiamine significantly, although partially, recovered streptozotocin (STZ)-induced reductions in mitochondrial PDH activity. Nevertheless, we found that PDH E1alpha phosphorylation in the thiamine-treated STZ group was perfectly diminished to the same level as that in the control group. STZ treatment significantly caused enhancements of the expression of O-glycosylated protein in the rat hearts, which was decreased by thiamine repletion. Next, the rat cardiac fibroblasts (RCFs) were cultured in the presence of high glucose levels. Thiamine dramatically recovered high glucose-induced PDH inhibition. High glucose loads did not alter the phosphorylated PDH E1alpha. PDH inhibition in RCFs was not accompanied by an increase in the PDH E1alpha phosphorylation. The O-glycosylated protein was markedly increased in RCFs exposed to high glucose, which was inhibited by thiamine. These results suggest that thiamine ameliorates diabetes-induced PDH inhibition by suppressing the increased expression of the O-glycosylated protein. The O-glycosylation of PDH E1alpha may be involved in the regulation of the PDH activity.
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PMID:Thiamine ameliorates diabetes-induced inhibition of pyruvate dehydrogenase (PDH) in rat heart mitochondria: investigating the discrepancy between PDH activity and PDH E1alpha phosphorylation in cardiac fibroblasts exposed to high glucose. 2064 37

Malignant cells frequently demonstrate an oncogenic-driven reliance on glycolytic metabolism to support their highly proliferative nature. Overexpression of pyruvate dehydrogenase kinase (PDK) may promote this unique metabolic signature of tumor cells by inhibiting mitochondrial function. PDKs function to phosphorylate and inhibit pyruvate dehydrogenase (PDH) activity. Silencing of PDK expression has previously been shown to restore mitochondrial function and reduce tumor cell proliferation. High dose Vitamin B1, or thiamine, possesses antitumor properties related to its capacity to reduce PDH phosphorylation and promote its enzymatic activity, presumably through PDK inhibition. Though a promising nutraceutical approach for cancer therapy, thiamine's low bioavailability may limit clinical effectiveness. Here, we have demonstrated exploiting the commercially available lipophilic thiamine analogs sulbutiamine and benfotiamine increases thiamine's anti-cancer effect in vitro. Determined by crystal violet proliferation assays, both sulbutiamine and benfotiamine reduced thiamine's millimolar IC50 value to micromolar equivalents. HPLC analysis revealed that sulbutiamine and benfotiamine significantly increased intracellular thiamine and TPP concentrations in vitro, corresponding with reduced levels of PDH phosphorylation. Through an ex vitro kinase screen, thiamine's activated cofactor form thiamine pyrophosphate (TPP) was found to inhibit the function of multiple PDK isoforms. Attempts to maximize intracellular TPP by exploiting thiamine homeostasis gene expression resulted in enhanced apoptosis in tumor cells. Based on our in vitro evaluations, we conclude that TPP serves as the active species mediating thiamine's inhibitory effect on tumor cell proliferation. Pharmacologic administration of benfotiamine, but not sulbutiamine, reduced tumor growth in a subcutaneous xenograft mouse model. It remains unclear if benfotiamine's effects in vivo are associated with PDK inhibition or through an alternative mechanism of action. Future work will aim to define the action of lipophilic thiamine mimetics in vivo in order to translate their clinical usefulness as anticancer strategies.
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PMID:Thiamine mimetics sulbutiamine and benfotiamine as a nutraceutical approach to anticancer therapy. 3181 Jan 15