J. S. Soeldner

Slow glucose removal rate and hyperinsulinemia precede the development of type II diabetes in the offspring of diabetic parents.

OBJECTIVE To determine whether insulin resistance or insulin deficiency is primary in the pathogenesis of type II diabetes. DESIGN Cohort analytic study of persons with normal glucose tolerance but with a high risk for developing type II diabetes (average follow-up time, 13 years). SETTING Outpatients had an intravenous glucose tolerance test and were contacted periodically to ascertain diagnoses of diabetes. PARTICIPANTS One hundred and fifty-five normal offspring, ranging in age from 16 to 60 years, of two parents with type II diabetes and 186 normal control subjects in the same age range who had no family history of diabetes. MEASUREMENTS AND MAIN RESULTS Two phenotypic characteristics distinguished the offspring of diabetic parents from control subjects. They had slower glucose removal rates (Kg) (P less than 0.01) and higher insulin levels (fasting and during the second phase of insulin response to intravenous glucose; P less than 0.0001) than did control subjects, even after adjustment for differences in obesity. Sixteen percent of the offspring developed type II diabetes. Mean Kg at baseline was 1.7%/min among offspring who subsequently developed diabetes, 2.2%/min among offspring who remained nondiabetic, and 2.3%/min among control subjects. Corresponding means for first-phase insulin were 498, 354, and 373 pM, respectively, whereas second-phase insulin means were 329, 117, and 87 pM, respectively. In multivariate analysis, low Kg and high serum insulin levels independently increased the risk for developing diabetes among the offspring of diabetic parents. CONCLUSIONS One to two decades before type II diabetes is diagnosed, reduced glucose clearance is already present. This reduced clearance is accompanied by compensatory hyperinsulinemia, not hypoinsulinemia, suggesting that the primary defect is in peripheral tissue response to insulin and glucose, not in the pancreatic beta cell.

A rapid method for the determination of glycosylated hemoglobins using high pressure liquid chromatography

Hemoglobin (Hb) Alc is a minor component of Hb found in normal individuals but elevated two or threefold in patients with diabetes mellitus. Limited studies have suggested that the level of Hb Alc is proportional to the integrated concentration of glucose over time. Thus it could serve as an index of hyperglycemia. Its measurement may enable a more objective approach to assessing whether or not the control of hyperglycemia can be correlated with the severity of complications of diabetes. Large scale clinicab studies of Hb Alc have not been undertaken for lack of a rapid assay system. This article describes a method of high pressure liquid chromatography (HPLC) which enables the isolation of Hb Alc in 27 min using only 12 microgram of Hb (100 microliter of blood) and a second method for the isolation of total fast Hb components (also elevated in diabetes) in 11 min. Using the first method, a total of 36 assays were performed on the blood of a single normal volunteer over a one month period. the mean level of Hb Alc was 4.95 +/- 0.12% (SD) +/- 0.02% (SEM), while the coefficient of variation (C.V.) was 2.4%. The mean Hb Alc & b level was 1.65 +/- 0.06% +/- 0.01% (C.V. = 3.6%). Values for Hb Alc in 10 normal individuals were 5.06 (mean) +/- 0.32% (SD) +/- 0.01% (SEM). Hb Alc values in 15 patients with diabetes mellitus ranged from 6.8 to 20.0%. The second method was designed to assay Hb Ala, Hb Alb, and Hb Alc as a single peak and yielded results identical to the sum of these components as determined by the first method ( r = 0.98; p less than 0.001).

Hypertension: The Major Risk Factor in Juvenile-onset Insulin-dependent Diabetics

The prevalence of hypertension in various age groups of diabetics and its role as a risk factor in juvenileonset insulin-dependent diabetics followed for 40 yr after diagnosis was evaluated. The results show clearly that hypertension is more prevalent in diabetics of any age after age 24 yr than in the general population. In this type of diabetes, although death due to renal disease occurs earlier than that due to coronary heart disease, both causes of death are significantly related to hypertension. Those patients with an onset of diabetes 13 yr of age or younger can expect to live longer following the diagnosis of diabetes mellitus than those with an onset after 13 yr of age, perhaps because hypertension appears at about the same age in both groups. Case/control analysis of the data shows that survivors have significantly less hypertension than those dying of renal or cardiac disease. Furthermore, the close temporal relationship between the onset of hypertension and the onset of proteinuria in patients with either renal or coronary deaths suggests that the hypertension in these patients is renal in origin. Two other risk factors, smoking and serum lipids, were evaluated in this population. From the data thus far accumulated, neither smoking nor lipids appear to influence mortality significantly. We conclude that hypertension is the major additive risk factor for mortality in juvenile-onset insulin-dependent diabetics.

Pre-Type I Diabetes: Linear Loss of Beta Cell Response to Intravenous Glucose

Twenty-one intravenous (i.v.) glucose tolerance tests were performed on nine subjects before the onset of overt type I diabetes mellitus. Islet cell antibodies (6 of 9 subjects) and elevated levels of la-positive T-lymphocytes (3 of 3 subjects studied) were detected during the prediabetic period. Elevations of fasting blood glucose and peak glucose during oral glucose tolerance tests were not observed until the year before onset of clinically overt diabetes. During the prediabetic period, there was a progressive loss of early-phase insulin release to i. v. glucose (rate of decline, 20–40 μU/ml insulin release/yr; correlation coefficient, 0.9).

Life-Table Analysis of Progression to Diabetes of Anti-Insulin Autoantibody-Positive Relatives of Individuals With Type I Diabetes

Cytoplasmic islet cell antibody–negative (ICA−; <20 Juvenile Diabetes Foundation units, n = 1670) and ICA+ (n = 42) first-degree relatives of type I (insulindependent) diabetic individuals were studied for competitive insulin autoantibodies (ClAAs) with a radioassay. Overall, 3.7% of first-degree relatives (64 of 1712) were CIAA+. Of ICA− relatives, 2.7% (45 of 1670) exceeded the upper limit of our normal CIAA range (>39 nU/ml), and 45% (19 of 42) of ICA+ relatives exceeded this normal range. Follow-up serums for repeat CIAA determination have been obtained from 16 of the nondiabetic CIAA/ICA individuals (time between samples, 0.4–5.8 yr). Fourteen of these 16 (87%) CIAA/ICA relatives were found to still be positive on follow-up, and 2 of the relatives who were positive on the first determination were negative on their follow-up test. With a mean follow-up of ∼2 yr, 4 of 45 (9%) of the CIAA+/ICA-relatives, 5 of 23 (22%) of the ICA/CIAA-relatives, and 12 of 19 (63%) of the CIAA+/ICA+ relatives developed diabetes. Life-table analysis indicated that, overall, 53% of CIAA+ relatives become diabetic after 5 yr of follow-up versus 65% of ICA+ relatives. Also by life-table analysis, the predicted risk after 5 yr of follow-up for progression to diabetes is 17% for CIAA+/ICA− relatives, 42% for ICA+/CIAA− relatives, and 77% for CIAA/ICA+ relatives. The highest rate of progression to diabetes was found in ICA+ relatives with CIAA levels >150 nU/ml (100% projected to be diabetic within 5 yr, P < .008 vs. ICA/CIAA relatives).

Acute Postchallenge Hyperinsulinemia Predicts Weight Gain: A Prospective Study

The relationships of insulin secretion and insulin action to body weight are incompletely understood. Obesity is associated with reduced sensitivity to insulin and high fasting and postprandial serum insulin levels. However, it is unknown whether insulin secretion rises to compensate for insulin resistance or high insulin secretion promotes body weight gain and the development of insulin resistance. To shed light on this question, we examined weight gain over an interval of 16.7 ± 3.9 years (mean ± SD) in 107 glucose-tolerant offspring (48 men, 59 women) of two parents with NIDDM. The offspring had a baseline intravenous glucose tolerance test, at which time they were aged 32.9 ± 9.7 years, and only those who did not develop diabetes during the follow-up period were included. We estimated insulin sensitivity with the insulin sensitivity index from Bergmans minimal model of glucose disposal and acute insulin secretion from the incremental area under the insulin curve in the first 10 min of the intravenous glucose tolerance test. Weight-gain rate (g/year) was defined as the regression slope of each subjects body weight over time. High acute insulin secretion, young age, and low baseline percent ideal body weight (IBW) were each associated with a high rate of weight gain. After adjustment for differences in age and IBW, statistically significant effects of insulin sensitivity (P = 0.05) as well as acute insulin secretion (P = 0.001) were obtained. To estimate the effects of acute insulin secretion and insulin sensitivity on the average rate of weight gain (adjusting for age and IBW), the study group was stratified into four subgroups by dividing it at the medians of these two variables. Among those with low acute insulin secretion, weight-gain rate was the same regardless of whether insulin sensitivity was low or high (176 and 152 g/year, respectively). Among those with high acute insulin secretion, mean weight-gain rate was still rather low in those with low insulin sensitivity (271 g/year), but it was quite high in those with high insulin sensitivity (672 g/year; significantly higher than in all other subgroups). Therefore a high first-phase insulin response to intravenous glucose is a risk factor for long-term weight gain, and this effect is particularly manifested in insulin-sensitive individuals.

Prognostically significant heterogeneity of cytoplasmic islet cell antibodies in relatives of patients with type I diabetes.

A significant proportion of relatives of patients with insulin-dependent (type I) diabetes with high titers of cytoplasmic islet cell autoantibodies (ICAs) do not progress to overt diabetes with up to 8 yr of follow-up. This may reflect that follow-up of such relatives has not been long enough to observe diabetes, that despite expression of identical ICAs, some relatives will not progress to diabetes; or that there is heterogeneity in what is identified as ICA. We identified a subset of ICA that was restricted in its species (not reacting with mouse islets) and cell-type reactivity within islets (β-cell specific). Only one of eight relatives whose sera had the restricted pattern of reactivity progressed to overt diabetes, and on sequential evaluation, all but the one relative who progressed to diabetes have maintained normal first-phase insulin secretion to intravenous glucose. In contrast, by life-table analysis, 70% of relatives expressing nonrestricted ICA became diabetic within 5 yr of follow-up (1 of 8 vs. 16 of 25 diabetic at last follow-up, P < 0.02). Moreover, preliminary data suggest a significant association of the human leukocyte antigen DQB1*0602 allele of DR2 haplotypes with the restricted ICA pattern (4 of 5 DQB1*0602 restricted vs. 0 nonrestricted ICA, P = 0.006). We propose that expression of a genetically determined restricted ICA pattern confers a markedly lower risk for progression to diabetes. Our studies suggest that relatives with restricted ICA may comprise most ICA+ relatives who do not develop diabetes or abnormal first-phase insulin secretion on follow-up of >5 yr and that expression of such autoantibodies may be associated with the ‘protective’ DQB1*0602 allele.

Acquired Defect in Interleukin-2 Production in Patients with Type I Diabetes Mellitus

Deficient production of interleukin-2 has been reported in Type I diabetes, but its cause has not been elucidated. We therefore measured interleukin-2 production in 27 patients with Type I diabetes, 20 patients with Type II diabetes (6 requiring insulin), 5 monozygotic twin pairs discordant for Type I diabetes, and 10 nondiabetic persons with islet-cell antibodies. Interleukin-2 production was decreased in patients with Type I diabetes as compared with controls (35.8 +/- 2.5 vs. 61.6 +/- 4.6 percent, P less than 0.001). Interleukin-2 production did not differ between patients with Type II diabetes and controls, regardless of whether the patients used insulin. Twins with Type I diabetes had decreased interleukin-2 production as compared with normal controls (33.2 +/- 5.4 vs. 61.6 +/- 4.6 percent, P less than 0.001) and with their nondiabetic twins (33.2 +/- 5.4 vs. 54.5 +/- 3.4 percent, P less than 0.005). Interleukin-2 production in nondiabetic twins and in nondiabetic persons with islet-cell antibodies was normal. There was no correlation between glycosylated hemoglobin levels and interleukin-2 production in any diabetic group. We conclude that patients with Type I diabetes have an acquired defect in interleukin-2 production, whereas patients with Type II diabetes do not, and that this defect is not correlated with an ongoing autoimmune process, with hyperglycemia, or with insulin administration or oral hypoglycemic therapy. Thus, the defect appears to be related to marked beta-cell destruction, although not to the metabolic consequences thereof or the responsible autoimmune process.

Reproducibility and Comparative Analysis of Repeated Intravenous and Oral Glucose Tolerance Tests

We have developed a methodology for measuring the reproducibility of the oral glucose tolerance test (OGTT) and the intravenous glucose tolerance test (IVGTT) in normal subjects and in offspring of conjugal diabetic parents. Both groups of subjects revealed more striking correlations of several parameters of blood glucose and insulin secretion between two IVGTTs than between two OGTTs. Employing arbitrary criteria, we calculated a “reproducibility index” as a quantitative measure of blood glucose variability in each subject. No significant difference was found in the reproducibility of OGTT versus IVGTT, nor in normals versus the offspring. Only about 50 per cent of the tests in normals and in the offspring could be considered to be “reproducible.” The offspring revealed greater correlations of several parameters, particularly insulin secretion, between the two IVGTTs and between the two OGTTs as compared with the normal group. However, the blood glucose variations tended to be considerably greater in the offspring from one to the other test.

Differential Sensitivity to β-Cell Secretagogues in “Early,” Type I Diabetes Mellitus

The insulin secretory response to various β-cell secretagogues was studied in four children (ages 11,11, 12, and 10 yr) in “early” stages or remission of type I diabetes mellitus. One child was an anti-islet antibody positive monozygotic twin of a type I diabetic subject, two children had impaired glucose tolerance and elevated levels of la-positive T-cells, and the fourth was in remission (off insulin) of type I diabetes 6 mo after immunotherapy. The peak first-phase (0–10 min) insulin increment after intravenous (i.v.) glucose was negligible in each patient, whereas the peak responses to i.v. glucagon, tolbutamide, arginine, and oral glucose ranged between 10% and 43% of median responses in normal control subjects. The rank order of response to a variety of secretagogues was remarkably similar in all four subjects: i.v. arginine > i.v. glucagon > oral glucose > i.v. tolbutamide > i.v. glucose. These studies indicate that a “functional” β-cell defect, namely a complete loss of response to i.v. glucose and a partial loss to other secretagogues, exists in type I diabetic patients before complete β-cell destruction. This alteration in β-cell responsiveness probably underlies our prior observation of slowly progressive loss of i.v.-glucose-induced insulin release in islet cell antibody-positive siblings of type I diabetic subjects.