glucose tolerance tests

outline the process

• fasted overnight

• control blood sample is taken

• given a bolus of glucose at a defined dose per kg of bodyweight

• blood samples are colleced at intervals over a period of 120-240 minutes

• enzymatic assay is used to measure the amount of glucose in each sample

• a set of known glucose concentration standards are assayed at the same time as the clinical samples to enable interpolation of the clinical samples

• glucose oxidase method is used: series of known standards add to microtiter plate. the assay mixture containing the enzyme glucose oxidase, chromogen and peroxidase is added to all samples in the microtiter plate and the assay is allowed to develop.

• enzymatic reaction occurs and a pink colour develop due to the chromogen and the intestity of colour change is proportional to amount of glucose in the sample

• a spectrophotometer is used to measure the absorbance of the pink colour at a particular wavelength

growth hormone

• suppresses the action of insulin on peripheral tissues leading to decreased glucose uptake and increased hepatic glucose production

• hyperinsulinemia

cortisol

• decrease in insulin sensitivity and induce insulin resistance

• increase blood sugar levels

catecholamines

• inhibit insulin secretion

• decrease insulin sensitivity

• promote hyperglycemia

antibodies

• bind to insulin and neutralise it preventing it from binding to receptors

• hyperglycemia

diacylglycerol

• impairs insulin sigalling by inhibiting insulin receptor substrate

alpha-2-glycoprotein

• binds to insulin receptor and inhibits its tyrosine kinase activity

• enhances basal glucose uptake in apidocytes by increasing expression of GLUT 4

fructosamine

• when glucose levels are elevated glucose molecules permanently bind to proteins eg albumin in the blood through glycation to form glycated proteins