Plasma aspirin esterase and associated plasma esterases in old age and frailty

Abstract

The elderly form a physiological heterogeneous group. This thesis is concerned with the activity of plasma aspirin esterase and several other plasma esterases in the fit, community-dwelling and frail hospitalized elderly. I, Several studies have produced evidence to suggest that drug metabolism is altered in the frail elderly and some of this work has centred around the plasma esterases. Kinetic analysis of plasma from young people, and fit and frail elderly people showed that the reduced plasma aspirin esterase in the latter group was most likely due to a reduced amount of cholinesterase enzyme (a reduced maximal activity) rather than that of a compromised affinity of the enzyme (increased Km). Purification of whole plasma achieved the removal of 97% of the albumin component of plasma aspirin esterase. Subsequent kinetic analysis confirmed that there was no change in the Km value of plasma aspirin esterase in the three groups as a result of isolating the cholinesterase enzyme. Following this, it was postulated that the reduced activity of several plasma esterases in the frail elderly may be due to their often poor nutritional status. A group of frail elderly people were randomised and half received a supplemented hospital diet. Plasma aspirin esterase, cholinesterase, paraoxonase, phenylacetate esterase, red blood cell intracellular esterase and red blood cell acetylcholinesterase in addition to anthropometric measurements were measured at 0,4 and 8 weeks of the study period. The control group did not gain weight whereas the group who received a supplemented diet gained an average 1.3Kg (non-significant). The post study weight and TSF measurements between the fed and control groups differed signifcantly at p<0.05. There were no significant changes in any of the esterases at 8 weeks however plasma cholinesterase did show a significant increase in activity at 4 week (p < 0.05) and plasma paraoxonase showed a trend towards an improved activity.