Comparison of the islet cell antibody pattern of monoclonal glutamic acid decarboxylase antibodies recognizing linear and conformational epitopes

Morphology of pancreatic islets: a time course of pre-diabetes in Zucker fatty rats

The Zucker fatty rat (fa/fa; ZR) is considered as a model for pre-diabetes, as characterised by a genetic defect in the leptin receptor, which results in hyperphagia, insulin resistance, hyperinsulinaemia, hyperlipoproteinaemia, and obesity. These animals become glucose intolerant but do not develop type 2 diabetes. As a consequence of increased adiposity and insulin resistance, the endocrine pancreas of ZR undergoes adaptive and compensatory changes. Measurements of the time course of the pathological changes by the histological analysis of the pancreatic islet in combination with metabolic parameters are an effective way to reveal disease progression. A loss in glucose tolerance occurs in ZR by 10 weeks of age and progressively worsens by 19 weeks of age. This process is accompanied by impaired islet histology, changes of beta-cell mass, and impaired islet function. The early expression of insulin resistance and glucose intolerance in ZR results in morphological and functional changes of pancreatic islets despite their capability to maintain normoglycaemia.

Sensitive monoclonal antibody-based sandwich ELISA for determination of the diabetes-associated autoantigen glutamic acid decarboxylase GAD65

Although various methods for the detection of autoantibodies against glutamic acid decarboxylase (GAD65-AAb) are known, no sensitive method for the quantification of GAD65 as autoantigen is available. We describe a sandwich ELISA based on monoclonal GAD65 antibodies (Mc-GAD65-Ab) of different epitope specificities to quantify GAD65 in pancreatic islets and in different organ/cell extracts and during the preparation of GAD from brain extracts. GAD65 was captured via solid phase coated Mc-GAD65-Ab and detected via a second biotin-labelled Mc-GAD65-Ab recognizing a NH2-terminal epitope of the molecule. The detection limit was estimated to be 0.03 ng GAD65/ml using alkaline phosphatase (AP)-conjugated streptavidin. GAD65 contents in islets of neonatal BB/OK rats and Lewis rats amounted to 37.4 and 43.7 pg/islet, respectively. Furthermore, GAD65 was quantified in brain extracts of pig (55.1 ng/mg protein), mouse (39.5 ng/mg), rat (243.8 ng/mg) and pig cerebellum (514.8 ng/mg) and in different organ extracts of Lewis rat.