GASTRIC-INHIBITORY POLYPEPTIDE (GIP) RESPONSES IN TYPE-2 DIABETES USING 3 DIFFERENT ANTIBODIES

Contradictory reports of gastric inhibitory polypeptide (GIP) response s in diabetes have been published by different workers using different radioimmunoassay systems. The present study was undertaken to assess GIP responses in type 2 diabetes using three antibodies (S100, GP01 an d GP24). Seven untreated diabetics and seven healthy control subjects had a standard 50 g oral glucose tolerance test. An alcohol extract of plasma of each sample was assayed using these three different antibod ies. Using S100, GIP responses in the diabetic group were significantl y lower at 30' (P<0.025) and at 120' (P<0.01) and the integrated incre mental GIP responses also were significantly lower in the diabetic gro up (P<0.025). Using GP01, GIP responses in the diabetic group were sig nificantly lower only at 120' (P<0.05) but there was no significant di fference in the integrated incremental GIP responses. Using GP24, ther e was no significant difference between the diabetic and control group s at any time intervals or in the integrated incremental responses. Ho wever, three to sixfold higher levels of GIP were recorded when using GP24 as compared with the other two antibody systems which gave simila r absolute values. Structurally abnormal variable cross-reacting 5000 dalton (5 kDa) and 8 kDa GIP forms or still unidentified structurally GIP related peptides associated with type 2 diabetes might be responsi ble for these conflicting results.