Didier Maugendre

Acute insulin response to intravenous glucose, glucagon and arginine in some subjects at risk for type 1 (insulin-dependent) diabetes mellitus

SummaryThe relationships between first-phase insulin secretion to i.v. glucagon and i.v. arginine were studied in 19 healthy adult volunteers (Group I) and in 21 subjects at risk for Type 1 (insulin-dependent) diabetes mellitus with either a “normal” (n=11; Group II a) or a “low” insulin response to i.v. glucose (n=10; Group II b). Groups I and II a displayed similar insulin responses to the three secretagogues. In contrast, Group II b demonstrated lower insulin responses to both glucagon and arginine than control subjects (p}<0.007 and (p}<0.04 respectively) orthan “normo-responders” to glucose (#x007D;<0.007 and p<0.04 respectively). In Group II b however, arginine-stimulated insulin release was increased compared to the response to glucose (p}<0.006), while glucagon and glucose led to non-statistically different responses. Five “low-responders” developed Type 1 diabetes. As a group, they displayed lower responses to glucagon and to arginine than subjects who up to now have not developed the disease (p<0.05 and p<0.0003 respectively). In the subjects who progressed to diabetes, the responses to glucose and glucagon were similarly blunted. In the “low-responders” who have not developed the disease, no statistical difference could be detected between mean responses to glucagon and glucose, but four out of these five subjects had a glucagon-stimulated response within the control range and higher than their corresponding response to glucose. Arginine led to a higher stimulation than glucose, in subgroups that either progressed to diabetes (p<0.006) or did not (p<0.002). Finally, “low-responders” who did not develop diabetes displayed similar responses to both glucagon and arginine than “normo-responders” to glucose. A progressive decrease of arginine-stimulated insulin response may be a later event during pre-Type 1 diabetes than a blunted response to glucose, while a loss of glucagon-stimulated insulin release may be intermediate. Diminished response to all secretagogues may offer better prediction than a “low” response to glucose alone.

Differential β-cell response to glucose, glucagon, and arginine during progression to type I (insulin-dependent) diabetes mellitus

Acute insulin responses to glucose (AIRG), glucagon (AIRGln), and arginine (AIRArg) were evaluated prospectively in nine subjects positive for islet-cell antibodies (ICAs) who later progressed to type I diabetes or impaired glucose tolerance (IGT) (progressors), 64 ICA-positive subjects at risk who did not develop type I diabetes, 365 ICA-negative relatives of diabetic patients who also remained free of the disease, and 89 control subjects. Seven progressors already had a low AIRG at entry into the study, and the other two became low responders 3 to 9 months before diabetes or IGT, with a progressive decline of AIRG over serial intravenous (IV) glucose tolerance tests. At entry into the study, the group of progressors displayed lower AIRG, AIRGln, and AIRArg than the other three groups (P < .001). However, AIRArg was less altered than AIRG. During the course of the prediabetic phase, there was a progressive decline in AIRG and AIRGln analyzed as a function either of time (P < .006) or of basal glycemia (P < .05), ie, two different ways of estimating worsening of the disease process. Conversely, there was no significant decrease in AIRArg with time or with increasing basal glycemia, so that AIRArg was not totally blunted in these prediabetic subjects even a few months before the onset of diabetes. The persistence of a substantial response to arginine, ie, higher than the fifth control percentile, even at a late stage, was confirmed in five of nine diabetic patients tested either at onset of the disease or during non-insulin-receiving remission. Whereas AIRG deteriorates during prediabetes, AIRArg appears to be less altered with time and increased basal glycemia, remaining substantial even at the onset of the disease. This reinforces the supposition that the prediabetic state may be associated with a glucose-specific β-cell functional abnormality in addition to a decreasing β-cell mass.

Combined analysis of islet cell antibodies which cross-react with mouse pancreas, antibodies to the Mr 64,000 islet protein, and antibodies to glutamate decarboxylase in subjects at risk for IDDM

SummaryWith regard to progression to diabetes, ICA cross-reactive with mouse pancreas, antibodies to the Mr 64,000 islet antigen (64K), antibodies immunotrap-ping brain GAD activity, and IAA were analysed in 53 ICA-positive first-degree relatives of IDDM patients and 18 ICA-positive schoolchildren without a family history of diabetes. Sera from 29 (55 %) relatives did not bind to mouse pancreas, whereas 24 (45 %) displayed cross-species reaction. ICA titres on human and mouse pancreas were weakly correlated in the overall population (p >0.05) but more strongly (p >0.01) in only those subjects who displayed antibodies on tissues from both species. GAD and 64K antibodies were detected in 31 % and 35 % of relatives. In schoolchildren, the frequencies of cross-species reactive ICA (22%), GAD antibodies (6%), 64K antibodies (22%), and IAA (6%), were lower (p > 0.05) than in relatives. A strong correlation (p > 0.0001) was observed between GAD and 64K antibodies. GAD or 64K antibodies were strongly correlated with ICA on human pancreas (p > 0.0001) but poorly with ICA on mouse pancreas (p = 0.05). After pre-incubation of sera with brain ho-mogenate, ICA titres were unaffected on mouse pancreas but reduced on human pancreas. ICA-positive subjects who displayed neither cross-species reactive ICA nor GAD or 64K antibodies were more frequent (p > 0.05) among schoolchildren than relatives, whereas subjects who displayed all antibody specificities were more numerous (p > 0.04) in relatives. All relatives with ICA binding only to human pancreas, as well as all schoolchildren, permanently displayed an AIRG higher than the first control percentile and remained non-diabetic. Five of ten relatives with cross-species reactive ICA, GAD and 64K antibodies at the same time displayed acute insulin response to glucose which fell below the first control percentile and developed the disease. The cross-species heterogeneity of ICA was thus confirmed in a large series of relatives and revealed in the general population. Detection of cross-species reactive ICA, GAD antibodies, or 64K antibodies enhances the prognostic significance after conventional ICA screening. The combination of these antibodies is more indicative of diabetes development than any antibody alone. Correlations between tests and absorption experiments indicate that GAD 64 is an ICA antigen on human but not on mouse pancreas, and that ICA which recognize GAD 64K coexist with others which react with mouse pancreas but not with GAD. A third ICA subset might have been revealed by high-titred ICA without either cross-species reactivity or GAD or 64K antibodies. This latter state was more frequent in the general population than in relatives and might typify an early immune response which may or may not progress.

Class II MHC antigen induction on rat insulinoma (RINm5F) and colon carcinoma (TS) cells by co-culture with diabetic and normal xenogenic lymphocytes

Two MHC Class II-negative rat epithelial cell lines (RINm5F beta-cells and TS colic cells) were co-cultured with xenogenic lymphocytes from Type I diabetic patients or from low-dose streptozotocin (SZ) diabetic mice. MHC Class II antigens (Ag) were easily induced on both cell lines in such co-culture conditions, representing an experimental approach to insulitis. Our data indicate that: (1) lymphocytes from diabetic patients or from SZ mice were more efficient than lymphocytes from healthy controls in inducing Class II Ag on RIN cells. Lymphocytes from patients with autoimmune thyroid diseases were also more efficient than control lymphocytes, indicating that the ability to induce Class II may be related to the activation of lymphocytes rather than being diabetes-specific. (2) Rat colon carcinoma cells (TS) were also induced to express high levels of Class II Ag upon co-culture with SZ or control mouse lymphocytes. (3) Class II+ RIN cells were observed after 24 h of co-culture; their number increased after 48 and 72 h. The number of class II+ RIN increased proportionally to the number of lymphocytes in the culture. (4) Induction of Class II Ag was obtained by cell-free supernatants of mouse lymphocytes/RIN co-cultures and was inhibited by cyclosporine A, suggesting that Class II induction in this model is mediated by lymphokines. (5) Depletion experiments indicate that both monocytes and lymphocytes play a role in this Class II induction.