Protocol for the measurement of human brain transketolase activity

Thiamine (vitamin B1) as thiamine diphosphate (or thiamine pyrophosphate) is a cofactor for enzymes involved in energy metabolism and is essential for brain function. Reliable biomarkers of thiamine status and function are necessary to understand thiamine's role in health and disease and provide mechanistic insights and to determine the efficacy of pharmacological interventions of thiamine analogues. The activity of the thiamine-dependent transketolase enzyme in erythrocytes is the established functional marker of whole-body thiamine status. In this chapter, we describe the analogous method optimized for the determination of transketolase activity in brain tissue and the calculation of the brain transketolase 'activity coefficient'. Provided are full method details for the preparation of brain material and instructions to perform the assay in 96-well plates using a microplate spectrophotometer. We provide details of suitable quality control materials and tips for troubleshooting. Instructions are also provided for the calculation of absolute basal transketolase activity. These protocols provide standardization for the determination of transketolase activity in human post mortem brain samples or from animal experiments and will be useful for researchers interested in the role of thiamine in brain-related conditions. Such protocols are essential to harmonize methods between laboratories for the benefit of comparisons between studies.