Enaocrinol. Japon. 1980, S. R. No.1, 127-133 Parallel Dysfunctions of Pancreatic A, B and PP Cells in Insulin Dependent Diabetes KYOHEI NONAKA, HIROYUKITOYOSHIMA, TOSHIAKIHANAFUSA AND SEIICHIROTARUI The Second Department of Internal Medicine, Osaka University Medical School, Fukushima-ku Osaka 553, Japan Synopsis To test the possibility that insulitis might play an etiological role in the pathogenesis of insulin dependent diabetes, functions of 3 kinds of islet constituting cells (A, B and PP cells) were estimated by quantifying secretory responses of glucagon-, C- peptide-and pancreatic polypeptide-producing cells to hyperglycemia and hypoglycemia. In insulin dependent diabetes, all 3 hormonal respo:ses were severely impaired to the same extent. On the other hand, 3 islet cell functions were uniformly but less severly impaired in insulin independent diabetics without a diabetic family history. These results suggest that A, B and PP cells of islet of Langerhans are evenly de- stroyed in parallel fashion at least in insulin dependent diabetes and in some insulin independent diabetes, suggesting insulitis as a possible cause of these types of diabetes. Recently insulitis has been recognized to play a certain role in the etiology of Materials and Methods insulin dependent diabetes mellitus. Insulitis occurs as the result of a direct attack on B- 9 insulin dependent and 20 insulin independent diabetics participated in the present study. Of 20 in- cells by viruses such as coxsackie B4(Coleman sulin independent diabetics, 10 were without a family et al., 1973, Yoon et al., 1979) and ence- history of diabetes and 10 with it. Insulin dependent phalomyocarditis virus (Craighead and Mc- diabetes was defined as diabetes of juvenile onset, Lane, 1968) or as the result of a subsequent ketosis prone or uncontrollable without using in- autoimmune mechanism (Irvine, 1977). The sulin. 0.5 g per kg of body weight of glucose was given intravenously to induce hyperglycemia. C- islet cell damage caused by these agents peptide immunoreactivity (CPR) in response to hy- is not limited to any particular cell type perglycemia was regarded as a measure of islet B of 4 islet constituting cells (Bottazzo et al., cell function. After 30 min of glucose administra- tion, 0.2-0.4 U per kg of body weight of purified 1974). Therefore, glucagon producing (A), regular insulin, monocomponent actrapid insulin, insulin producing (B) and pancreatic poly- was injected intravenously to induce hypoglycemia. peptide producing (PP) cells are possibly Immunoreactive glucagon (IRG) and pancreatic all damaged to the same extent. We tried polypeptide (HPP) in response to hypoglycemia were assayed as measures of islet A and PP cell func- to see if these changes could be observed tions. The radioimmunoassay of IRG was de- by quantifying these cell functions in insulin scribed elsewhere (Nonaka and Foa 1969). HPP dependent and insulin independent diabetics was measured by the double antibody method using of our outpatient clinic. highly purified human pancreatic polypeptide for standard and bovine pancreatic polypeptide for iodi- nation, both of which were generous gifts from Dr. R. E. Chance (Lilly Research Laboratories). CPR Endocrinol. Japon. 128 NONAKA et al. December 1980 was assayed by using a kit from Daiichi Isotope Laboratory. Plasma glucose was measured by the glucose oxidase method with Beckman's Glucose Analyzer. Results 1. Changes of plasma glucose to glucose and insulin administration In normal controls shown in the shadow of the upper panel of Fig. 1, the mean plasma glucose concentration increased from the basal level of 96•}3 (mean•}S.E.) mg/dl at 0 min to a peak of 368•}7 mg/d/ at 2 min after glucose administration, then decreased gradually. After insulin injection, the plasma glucose level continued to decline and reached a nadir of 30•}2 mg/dl at 60 min, then increased gradually toward normo- glycemia. In diabetics, the mean plasma glu- cose of insulin dependent and independent diabetics increased from the basal level of 141•}9 mg/dl to 391•}17 mg/dl at 2 min in response to intravenous glucose, then de- creased much more slowly than in controls until 30 min. After insulin injection, plasma Fig. 1. Top panel: Mcan•}S.E. of plasma glucose (PG) in response to hyper- and hypoglycemic glucose of diabetics declined as fast as in stimuli in insulin dependent (•œ-•œ) and inde- controls to a nadir of 43•}3 mg/dl at 120 pendent (•›- - -•›) diabetics. Hatchei.shadow rep- min. Due to the fact that initial levels of resent mean•}S.D. of normals. Middle panel: Mean•}S.E. of CPR. Lines and shadow are the plasma glucose in diabetics vary markedly same as in the top panel. Large circles represent from one case to another, the time needed significant changes over basal level. Bottom panel: to reach hypoglycemia differs also from one Mean•}S.E. of IRG. Lines, shadow and large patient to another. All diabetics in the pre- circles are the same as in the middle panel. As- sent study showed hypoglycemic signs and terisk indicate significant differences between two symptoms at various times from 90 to 150 groups of diabetes (*p<0.05, **p<0.025, ***p< 0.01). min, with average glasma glucose of 35•} 2 mg/dl. In insulin independent diabetics the 2. Plasma CPR responses (middle panel plasma CPR gradually increased from the of Fig. 1) basal level of 1.6•}0.1 ng/ml to a blunt Plasma CPR in normals increased from peak of 2.4•}0.2 ng/m/ at 30 min, then the basal level of 1.4•}0.2 ng/m/ to a peak decreased slowly. In insulin dependent of 4.2•}0.3 ng/m/ at 2 min, than decreased diabetics, the basal CPR level was as low gradually, remaining elevated for next 60 as 0.6•}0.2 ng/ml, which is significantly min. After 90 min it fell to less than the basal lower than the normal level, and was not level and decreased gradually in response increased significantly by the glucose load. to hypoglycemia until the end of the test. As shown in Fig. 1, CPR levels in two types S. R. No.1 PARALLEL DYSFUNCTIONS OF ISLET HORMONES IN IDDM 129 of 133•}28 pg/ml at 120 min. On the other hand, in insulin dependent diabetics, IRG response to hyperglycemia was poor and there was hardly any response to hypo- glycemia. 4. HPP responses (Fig. 2) In normal controls (In Fig. 2, represented by the shaded area at the bottom) plasma HPP tended to decline in response to hyper- glycemia from a basal level of 54•}17 pg/ml to a minimum of 34•}5 pg/m/ at 10 min after the injection of glucose (Fig. 2) In response to hypoglycemia, plasma HPP rose steeply from a level of 57•}27 mg/ml at 60 min, when the nadir of plasma glucose was achieved, to a peak level of 1320•}200 pg/ ml at 75 min, and then was gradually re- duced toward the end of the test. As shown in the bottom panel of Fig. 2, HPP increments of two types of diabetes behaved quite differently in response to hypoglycemia. Namely, a significantly lower response to hypoglycemia was observed in Fig. 2. Top panel: Changes of plasma glucose insulin dependent diabetics than in insulin (mean•}S.E.) to glucose and insulin. Lines and shadow represent the same as Fig. 1. Lower panal: independent diabetics at 105 and 120 min Increment of plasma HPP level (mean•}S.E.) over (p<0.05), in spite of the fact that the dura- basal value. tion of hypoglycemia was rather longer in the insulin dependent group. of diabetes differed markedly and signifi To quantify a substantial HPP response cantly at any time except at 150 min. to hypoglycemia, we introduced an "HPP- area" index in individual subject. The "HPP- 3. Plasma IRG responses (bottom panel of area" was defined as the area under the Fig. 1) curve of plasma HPP from the blood sam- In normal controls, as shown in the pling time when plasma glucose first fell shadow at the bottom of the Fig. 1, the to less than 40 mg/dl to the time 30 min mean basal plasma IRG was 55•}11 pg/ml. later. This index was regarded as the It was not changed by the glucose load. substantial response of HPP to hypoglycemia. After insulin administration, however, it The results obtained with this procedure increased to 93•}30 pg/ml at 60 min and are given in Fig. 3. The "HPP-area" in dia- reached a peak of 177•}39 pg/ml at 75 min, betics (15370•}3270 pg•min/ml) was signi- remaining at that level until the end of the ficantly lower than that in normals (28490 test. The plasma IRG of insulin indepen- ±4630pg・min/ml, p<0.05). Among dia- dent diabetics decreased from the basal value betes, the "Hpp-area" in insulin independent of 76•}12 pg/ml to significantly lower diabetics (21630•}4720 pg•Emin/ml) was not levels at 20, 50, 60 and 75 min after glucose significantly different from that in normals, injection, then increased gradually to a peak and the HPP-area in insulin dependent Endocrinol. Japan. 130 NONAKA et al. December 1980 response over basal level (4CPR) to hyper- glycemia as a measure of B cell function and maximal IRG respone over basal level (△IRG) to hypoglycemia such as that of A cell function. As shown in the right panel of Fig. 4, CPR response in insulin dependent diabetes was reduced to about one tenth that of normals and that in insulin independent diabetes to one third.