Abstract
Thiamine diphosphate (TDP) and magnesium are co-factors for key enzymes in human intermediary metabolism. However, their role in the systemic inflammatory response (SIR) is not clear. Therefore, the aim of the present study was to examine the relation between acute changes in the SIR and thiamine and magnesium dependent enzyme activity in patients undergoing elective knee arthroplasty (a standard reproducible surgical injury in apparently healthy individuals). Patients (n = 35) who underwent elective total knee arthroplasty had venous blood samples collected pre- and post-operatively for 3 days, for measurement of whole blood TDP, serum and erythrocyte magnesium, erythrocyte transketolase activity (ETKA), lactate dehydrogenase (LDH), glucose and lactate concentrations. Pre-operatively, TDP concentrations, erythrocyte magnesium concentrations, ETKA and plasma glucose were within normal limits for all patients. In contrast, 5 patients (14%) had low serum magnesium concentrations (< 0.75 mmol/L). On post-operative day1, both TDP concentrations (p < 0.001) and basal ETKA (p < 0.05) increased and serum magnesium concentrations decreased (p < 0.001). Erythrocyte magnesium concentrations correlated with serum magnesium concentrations (rs = 0.338, p < 0.05) and remained constant during SIR. Post-operatively 14 patients (40%) had low serum magnesium concentrations. On day1 serum magnesium concentrations were directly associated with LDH (p < 0.05), WCC (p < 0.05) and neutrophils (p < 0.01). Whole blood TDP and basal ETKA increased while serum magnesium concentrations decreased, indicating increased requirement for thiamine and magnesium dependent enzyme activity during SIR. Therefore, thiamine and magnesium represent potentially modifiable therapeutic targets that may modulate the host inflammatory response. Erythrocyte magnesium concentrations are likely to be reliable measures of status, whereas serum magnesium concentrations and whole blood TDP may not.ClinicalTrials.gov: NCT03554668.
Highlights
Thiamine diphosphate (TDP) and magnesium are co-factors for key enzymes in human intermediary metabolism
It is of interest that thiamine requires magnesium for conversion to its active form, thiamine diphosphate (TDP)[15], and TDP requires magnesium to act as a co-factor for thiamine dependent e nzymes[5]
Prior to surgery whole blood TDP and erythrocyte transketolase activity (ETKA) were classified above the lower reference interval for all patients (Fig. 1) and this relationship remained similar during the post-operative systemic inflammatory response (Fig. 2)
Summary
Thiamine diphosphate (TDP) and magnesium are co-factors for key enzymes in human intermediary metabolism. Their role in the systemic inflammatory response (SIR) is not clear. Patients (n = 35) who underwent elective total knee arthroplasty had venous blood samples collected preand post-operatively for 3 days, for measurement of whole blood TDP, serum and erythrocyte magnesium, erythrocyte transketolase activity (ETKA), lactate dehydrogenase (LDH), glucose and lactate concentrations. On post-operative day[1], both TDP concentrations (p < 0.001) and basal ETKA (p < 0.05) increased and serum magnesium concentrations decreased (p < 0.001). Whole blood TDP and basal ETKA increased while serum magnesium concentrations decreased, indicating increased requirement for thiamine and magnesium dependent enzyme activity during SIR. Accurate quantification of total body magnesium is challenging, as magnesium is predominantly located within intra-cellular compartments, while circulating serum magnesium is approximately 30% bound to proteins (mainly albumin) and it is reported that free measurable magnesium may be perturbed by the inflammatory response[18]
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