C-peptide secretion during the remission phase of juvenile diabetes

Characterisation of the endocrine pancreas in type 1 diabetes: islet size is maintained but islet number is markedly reduced

Insulin deficiency in type 1 diabetes (T1D) is generally considered a consequence of immune‐mediated specific beta‐cell loss. Since healthy pancreatic islets consist of ~65% beta cells, this would lead to reduced islet size, while the number of islets per pancreas volume (islet density) would not be affected. In this study, we compared the islet density, size, and size distribution in biopsies from subjects with recent‐onset or long‐standing T1D, with that in matched non‐diabetic subjects. The results presented show preserved islet size and islet size distribution, but a marked reduction in islet density in subjects with recent onset T1D compared with non‐diabetic subjects. No further reduction in islet density occurred with increased disease duration. Insulin‐negative islets in T1D subjects were dominated by glucagon‐positive cells that often had lost the alpha‐cell transcription factor ARX while instead expressing PDX1, normally only expressed in beta cells within the islets. Based on our findings, we propose that failure to establish a sufficient islet number to reach the beta‐cell mass needed to cope with episodes of increased insulin demand contributes to T1D susceptibility. Exhaustion induced by relative lack of beta cells could then potentially drive beta‐cell dedifferentiation to alpha‐cells, explaining the preserved islet size observed in T1D compared to controls.

Aetiology of type 1 diabetes: Physiological growth in children affects disease progression

The prevailing view is that type 1 diabetes (T1D) develops as a consequence of a severe decline in β-cell mass resulting from T-cell-mediated autoimmunity; however, progression from islet autoantibody seroconversion to overt diabetes and finally to total loss of C-peptide production occurs in most affected individuals only slowly over many years or even decades. This slow disease progression should be viewed in relation to the total β-cell mass of only 0.2 to 1.5 g in adults without diabetes. Focal lesions of acute pancreatitis with accumulation of leukocytes, often located around the ducts, are frequently observed in people with recent-onset T1D, and most patients display extensive periductal fibrosis, the end stage of inflammation. An injurious inflammatory adverse event, occurring within the periductal area, may have negative implications for islet neogenesis, dependent on stem cells residing within or adjacent to the ductal epithelium. This could in part prevent the 30-fold increase in β-cell mass that would normally occur during the first 20 years of life. This increase occurs in order to maintain glucose metabolism during the physiological increases in insulin production that are required to balance the 20-fold increase in body weight during childhood and increased insulin resistance during puberty. Failure to expand β-cell mass during childhood would lead to clinically overt T1D and could help to explain the apparently more aggressive form of T1D occurring in growing children when compared with that observed in affected adults.

Remission in diabetic children in Riyadh

Few data are available about temporary remission in insulin dependent mellitus in Riyadh. Thirty-seven out of 115 (32.1%) diabetic children diagnosed over five and a half years (1985 to mid-1990) in Suleimania Children's Hospital were retrospectively studied. Partial temporary remission rate was 30.4% (35/115). Total temporary remission rate was 1.7% (2/115), lasting 18 months in a seven-year-old patient. The partial remission rate was higher in children above five years of age (36.9%), in children of unrelated parents (34.3%) and in female patients (51.4%). Of these, 64.8% were Saudi. Fifty-four percent of these patients presentd at onset without diabetic ketoacidosis and mean duration of symptoms before diagnosis was short (9.2 days). Mean time of occurrence was five weeks and mean duration of remission was nine weeks. Mean initial insulin dose was 1.35 unit/kg/day, while mean dose during the remission was 0.34 unit/kg/day. Mean glycosylated hemoglobin at onset was 12.3% and 7.4% during remission. Mean C-peptide level improved markedly from 0.16 nmol/L at onset to 0.29 nmol/L during remission and rose to 0.61 nmol/L following glucagon intravenous injection demonstrating the temporary recovery of pancreatic B-cell function. Finally, our low figures of remission (32.1%) are probably related to the young age distribution at onset in our series and perhaps to a different pattern of severity of insulin dependent diabetes mellitus in our community.

Remission from insulin dependence induced by continuous subcutaneous insulin infusion (CSII) in type I, newly diagnosed diabetics: role of some hormonal and immunologic factors

Optimal and early control of recent onset, type I diabetes by intensive insulin therapy has been reported to allow insulin withdrawal in about two thirds of subjects treated. We used continuous s.c. insulin infusion (CSII) in the attempt to induce a temporary remission of insulin dependence in 18 newly diagnosed young adult diabetics. After 10 days of optimized glycometabolic control, insulin infusion was stopped and patients were switched to glibenclamide (15 mg/die) plus metformin (1 g/die). Diabetics were considered in remission of insulin dependence when their metabolic control fulfilled the following criteria for at least 3 months: absence of glycosuria, pre- and post-prandial blood glucose less than or equal to 120 and 180 mg/dl, respectively, HbA1c less than or equal to 7%. Insulin therapy could be discontinued for periods of over three months in 11 subjects (61%) and for as long as 18 months in one case. Insulin requirement during CSII was slightly higher in nonremitters (NR) than in remitters (R): 0.36-0.64 vs 0.26-0.41 U/kg/die. After 24 months from CSII, R still showed lower insulin requirement (0.35-0.42 U/kg/die) than NR (0.55-0.75 U/kg/die). Further, the role of some hormonal and immunologic factors was investigated. Plasma C-peptide and glucagon were measured, fasting and 2h after each meal, both on admission and immediately after CSII, when patients were switched to oral therapy. No difference in hormone levels could be detected on admission, whereas, after CSII, mean post-prandial increase of C-peptide over basal was significantly higher in R than in NR (1.18 +/- 0.37 vs 0.22 +/- 0.16 ng/ml, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Reversal of insulin resistance in type 1 diabetes following initiation of insulin treatment

The biological action and pharmacokinetics of insulin were assessed in nine type 1 (insulin-dependent) diabetic patients before and after 3 months conventional insulin treatment, and in seven age and weight-matched non-diabetic controls, by means of the euglycaemic insulin clamp technique. The mean (+/- S.E.) metabolic clearance rate of insulin, when infused at 1 mU/kg/min, was similar in untreated and treated diabetic patients and in controls (22.7 +/- 2.0, 19.3 +/- 3.8, and 22.9 +/- 3.3 ml/kg/min) but, when infused at 6 mU/kg/min, was greater (p less than 0.01 and less than 0.01) in untreated patients (18.0 +/- 2.5 ml/kg/min) than in treated patients (11.5 +/- 1.4 ml/kg/min) and controls (12.7 +/- 1.3 ml/kg/min). Insulin-mediated glucose disposal was reduced (p less than 0.01 and less than 0.01) at insulin infusion rates 1 and 6 mU/kg/min in untreated patients (18.5 +/- 1.9 and 33.8 +/- 4.5 mumol/kg/min) when compared with controls (35.8 +/- 3.4 and 62.0 +/- 4.7 mumol/kg/min) and was improved (p less than 0.01 and less than 0.01) following insulin treatment (36.1 +/- 4.6 and 64.8 +/- 4.2 mumol/kg/min). Daily insulin requirement fell by 33% following 3 months insulin treatment with improvement in mean HbA1 from 16.3 +/- 0.7 to 8.2 +/- 0.4%, but without significant increase in endogenous insulin secretion. The 'honeymoon phenomenon', which has traditionally been attributed exclusively to resurrection of endogenous insulin release, may also be related to normalization of insulin action following institution of insulin treatment.

Sustained initial remission induced by intensive insulin treatment in type I diabetes. Possible role of the genetic background

A remission defined by the possibility of temporarily discontinuing insulin therapy while blood glucose remains normal is not infrequently observed after intensive insulin therapy in newly diagnosed acute type I diabetes in the South of France. In order to analyze possible factors of such a remission, 47 newly diagnosed ketotic diabetics under 35 years of age and of Caucasian origin were enrolled in a prospective study. They were given continuous s.c. insulin infusion for two weeks and oral agents were introduced on day 8. In 16 patients insulin could not be withdrawn. In 31 insulin was stopped for more than 3 months (mean 12.3, range 3-35) while blood glucose remained below 6 mmol/l fasting (mean 5.3) and 7.8 post-prandial (mean 5.1) and glycosylated Hb below 8.5% (mean 6). At presentation, diabetics who later went into remission and those who did not, showed no difference in age (22.3 vs 23.1 years), sex ratio, apparent duration of symptoms (1.4 vs 1.6 months), glycosylated hemoglobin (12.0 vs 13.1%) and basal or post-prandial C-peptide values or presence of islet cell antibodies. No differences were observed in the frequency of DR3 and DR4 antigens in the two groups but diabetics who developed a remission bore the A 19.2 antigen (9/31 vs 1/16) and the B18 one (11/31 vs 1/16) more frequently, A 19.2 and B18 being associated in 7 cases of this group. This increased frequency in the remission group of HLA antigens, more often observed in diabetics of Mediterranean origin, suggests that differences in the genetic background may be associated with a difference in the evolution of the disease.

Beta-cell function recovery is not the only factor responsible for remission in type I diabetics: evaluation of C-peptide secretion in diabetic children after first metabolic recompensation and at partial remission phase

In 9 newly diagnosed type I diabetic children the residual beta-cell secretory capacity was examined after stimulation with oral glucose load, glucagon and iv glucose plus arginine hydrochloride administration shortly after diagnosis and in the partial remission phase. A significant C-peptide secretion induced by these substances except by iv glucose was found at both investigation times. Whereas beta-cell function did only slightly increase from the initial testing to the measurements in the partial remission, beta-cell sensitivity increased significantly (p less than 0.05). The data suggest that "partial remission" referred to C-peptide secretion starts very early after insulin treatment and that other factors, possibly a decrease of peripheral insulin resistance, are involved in the improved metabolic control in partial remission phase.

The effect of glucose, tolbutamide, and arginine on C-peptide release during remission in type I diabetes mellitus

The insulin secretory capacity was examined in diabetic children at the time of partial clinical remission during which their condition could be managed with low insulin therapy (less than 0.5 U insulin/kg body weight) and no urinary glucose excretion. The extent of the residual beta cell function in 26 children was assessed either by an i.v. arginine test, a combined i.v. glucose-i.v. arginine test, a combined i.v. tolbutamide-i.v. arginine test, or a combined oral glucose-i.v. arginine test determining the C-peptide response by calculating the area under the curve above baseline levels. Two of the children were tested repeatedly. Under the above conditions i.v. glucose and i.v. tolbutamide did not release C-peptide in diabetic children. In contrast, C-peptide secretion during arginine infusion following i.v. glucose or i.v. tolbutamide was significantly enhanced compared to the C-peptide secretion observed during arginine infusion alone. The C-peptide response to oral glucose was sluggish with no effect on the following arginine infusion. The results indicate that during remission in juvenile onset diabetes i.v. glucose and i.v. tolbutamide without themselves being an appropriate signal for C-peptide release amplify the response to a subsequent arginine infusion under appropriate conditions.

Insulinopenia in impaired glucose tolerance preservation of insulin response to I.V. arginine and tolbutamide

Immunoreactive insulin (IRI) response to successive i.v. injections of glucose (0.3 g/kg), arginine (5 g) and tolbutamide (20 mg/kg) was measured in 11 non-obese patients with mild glucose intolerance and 11 control subjects. In 3 of the patients the IRI response to i.v. arginine and subsequent i.v. glucose was also measured. The mean peak IRI level following glucose was grossly diminished in the patients compared to controls but peak IRI levels following arginine and tolbutamide were similar in the two groups. Administering arginine prior to glucose in the 3 patients tested resulted in a lowering of the IRI response to arginine but no increase in the IRI response to glucose. The decreased IRI response to i.v. glucose associated with an adequate response to i.v. arginine and tolbutamide in these patients suggests a failure of the B-cell sensor mechanism for glucose and may provide a physiological explanation for the recognized value of restricting carbohydrate relative to protein in the treatment of this condition. Any defect in the sensor mechanism for arginine appears quantitatively much less severe than that to glucose.

Future management of diabetes mellitus

A review of therapies for diabetes mellitus reveals little that is new for the diabetic today. Also, there is little evidence that progression of diabetic complications can be slowed or halted with currently available therapeutic modalities that are acceptable to patients and can be applied in an everyday clinical setting. Few new drugs are likely to be ready for marketing in the immediate future, and most of the pharmacologic approaches that are now under study do not address the basic problem of lost sensitivity of the beta cell to endogenous glucose. In the longer term, it is likely that an oral insulin, allowing more convenient management of diabetes, will be available, as well as several new drug classes that may offer therapy adjunctive to insulin. As more is learned of the cellular physiology of the islet cell and the pathology of diabetes mellitus, some additional therapeutic breakthrough may occur. It is highly likely that an implantable or portable infusion system, either of the closed- or open-loop type, will be available when technologic problems are overcome. Islet cell transplantation may provide a definitive treatment for diabetes. At the very least, the questions should be resolved relating to careful physiologic control of the metabolic aberrations of diabetes mellitus. Unfortunately, because of the relatively slow evolution of diabetic vascular pathology, it will be several decades before current studies can provide the answers. If present hypotheses are confirmed, future therapeutic approaches can be more clearly defined; if the hypotheses must be rejected, the therapeutic dilemmas will remain.

Hemoglobin A1c (HbA1c) in children with long standing and newly diagnosed diabetes mellitus

In 35 children with long-standing diabetes mellitus, a significant correlation was found between the hemoglobin A1c (HbA1c)--and the 24-hour urinary glucose excretion. By contrast, 11 newly diagnosed diabetic children had grossly elevated HbA1c-concentrations, but no correlations could be established between the levels of HbA1c and the duration of symptoms, blood glucose, glycosuria, ketonuria and the acid--base status. However, HbA1c and C-peptide were significantly correlated. The elevated HbA1c-concentrations decreased towards normal in all of these 11 children after 2--3 months following adequate therapy. The results suggest that the determination of HbA1c may serve as a valuable metabolic control index in children with long-standing diabetes mellitus, but adds little information in newly diagnosed patients. For the individual diabetic child during the early treatment period, HbA1c may be the index of choice for adequacy of metabolic control.