Erythrocyte transketolase activation

Activation of apotransketolase in erythrocyte lysate by thiamin diphosphate added in vitro has become the most widely used and accepted index of thiamin nutritional status. Apotransketolase is unstable both in vivo and in vitro therefore, problems may arise in the interpretation of results, especially if samples have been stored for any appreciable time. An activation coefficient 1. 25 is 

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These various reports stress the need to supplement parenteral nutrition with thiamine-containing vitamins unless there is adequate dietary intake, and to monitor serum thiamine and erythrocyte transketolase activity so that supplementary thiamine can be given in good time, if necessary intravenously (45). Giving thiamine will not rectify the various disorders if hepatic function is severely disturbed, because then thiamine is not phosphorylated and hence remains physiologically inactive. 

Baines M, Davies G. The evaluation of erythrocyte thiamin diphosphate as an indicator of thiamin status in man, and its comparison with erythrocyte transketolase activity measurements. Ann Clin Biochem 1988 25 (Pt 6) 698-705. 

Puxty JA, Haskew AE, Ratcliffe JG, McMurray J. Changes in erythrocyte transketolase activity and the thiamine pyrophosphate effect during storage of blood. Ann Clin Biochem 1985 22 (Pt 4) 423-7. 

Talwar D, Davidson H, Cooney J, St JO Reilly D. Vitamin B(l) status assessed by direct measurement of thiamin pyrophosphate in erythrocytes or whole blood by HPLC comparison with erythrocyte transketolase activation assay. Clin Chem 2000 46 704-10. 

Thiamine deficiency can be assessed by measuring blood levels. Increased blood levels of pyruvate and lactate suggest thiamine deficiency. Measurement of erythrocyte transketolase activity, which requires TPP as a coenzyme, confirms the deficiency. 

Thiamine deficiency is most frequently assessed by assaying erythrocyte transketolase activity in the presence and absence of added TPP. If the red blood cells have sufficient thiamine, the transketolase will be fully saturated with TPP, and no increase in activity will be observed when TPP is added to the assay system. An increase in transketolase activity indicates that the patient is thiamine deficient. 

ETK AC = Erythrocyte Transketolase Activity Coefficient TDP = thiamine diphosphate N.S. = not specified MTD = moderate thiamine deficiency TD = thiamine... 

Erythrocyte transketolase activity was the classic method to assess thiamine status. Two samples of blood are incubated with excess substrate for the pentose phosphate pathway to one is also added excess thiamine diphosphate while the other serves as the control. The amount of substrate remaining and product formed are quantified, and any enhancement in activity resulting from the added thiamine diphosphate indicates that the sample was originally deficient in thiamine to some extent. 

Warnock, L.G., Prudhomme, C.R., and Wagner, C., 1978. The determination of thiamin pyrophosphate in blood and other tissues, and its correlation with erythrocyte transketolase activity. The Journal of Nutrition. 108 421-427. 

Erythrocyte transketolase activity was found to be lowered in different groups of TD patients (Herve et al. 1995 Khounnorath et al. 2011) (Table 33.2). However, post mortem brains of alcoholics who died without symptoms of Wernicke s encephalopathy (WE) revealed 20-35% reductions in the activities of all TDP-dependent enzymes in various brain regions (Lavoie and Butterworth 1995). This means that some degree of TD-induced reductions in oxidative metabolism may be tolerated. In fact, individual sensitivity to TDP deficits may be modified by coexisting clinical conditions such as alcoholism, renal insufficiency, dialysis programmes, aging, diabetes, cardiovascular complications, and voluntary or socio-economically dependent dietary habits (Tables 33.1 and 33.2). 

ETK, erythrocyte transketolase activity TDP, thiamine diphosphate ETK-A-TDP, activation... 

There are laboratory tests that might serve as markers of early stages of thiamine deficits. These include erythrocyte transketolase activity, blood TDP or serum y-glutamyl transferase, which in combination with questionnaire anamnesis, may facilitate early diagnosis to impose easy and efficient treatment with thiamine. 

Herve, C., Beyne, P., Letteron, Ph., and Delacoux E., 1995. Comparison of erythrocyte transketolase activity with thiamine phosphate ester levels in chronic alcoholic patients. Clinica Chimica Acta. 234 91-100. 

Pietrzak, L, and Baczyk, K., 2001. Erythrocyte transketolase activity and guanidine compounds in hemodialysis patients. Kidney International. 59(Suppl. 78) S97-S101. 

Thiamine pyrophosphate is required as a cofactor for transketolase activity. Decreased erythrocyte transketolase activity is therefore found in thiamine deficiency and activity is increased by the addition of thiamine pyrophosphate to the assay system. 

In general, the recommended allowances are based (1) on assessments of the effects of varying levels of dietary thiamin on the occurrence of clinical signs of deficiency, (2) on the excretion of thiamin or its metabolites, and (3) on erythrocyte transketolase activity. Most studies have been conducted on subjects fed diets with ratios of carbohydrate and fatsimilar to those commonly consumed in the United States. There is evidence that dietary fat spares thiamin to some extent... 

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