G. M. Nardelli

In search of predictive markers of remission from insulin dependence in type 1 diabetes: a preliminary report

We studied 18 newly diagnosed diabetic patients (8 males and 10 females, aged 18-26 years, within 10-120 days from the onset of symptoms) who were submitted for 15 days to intensive insulin therapy performed via subcutaneous insulin infusion (CSII). We investigated some metabolic and immunological parameters in order to identify a possible marker to predict the selection of patients potentially more responsive to CSII treatment for the remission of type 1 diabetes. In accordance with the International Diabetes Immunology Group we considered clinical remission as being the withdrawal of insulin therapy for at least 3 months. In order to assess beta-cell function a fasting and post-prandial serum C-peptide, blood glucose and HbA1c were performed on all patients before, and 3 days after, the discontinuation of CSII. Islet cell antibodies were determined in all sera by indirect immunofluorescence. Analysis of T-lymphocyte subpopulations was carried out before starting the therapy. The following monoclonal antibodies were used: CD4, CD8, CD57, CD25, HLA-DR. The levels of C3 and C4 and serum IgG, IgA and IgM were also evaluated. After CSII, 11 of 18 patients showed remission. At the beginning of the study we observed no major difference in metabolic parameters between the two groups. Interestingly, the patients who exhibited remission presented a statistically higher percentage of positive cells for CD57, HLA-DR and CD25 surface antigens, significantly lower C4 levels and CD4/CD8 ratio and significantly higher IgG levels compared with patients who did not show any remission.(ABSTRACT TRUNCATED AT 250 WORDS)

Somatomedin-C (Sm-C). Study in diabetic patients with and without retinopathy

SummaryIn the present study we evaluated somatomedin-C (Sm-C) plasma levels in diabetic patients, with and without retinopathy. One hundred and thirty four diabetic patients (65 type I and 69 type II) and 90 controls, strictly matched for age and sex, were enrolled in the study. Ophthalmoscopy and fluorescein angiography allowed to distinguish: 49 patients without retinopathy, 45 patients with background retinopathy, and 40 with proliferative retinopathy. Growth hormone (GH) and Sm-C plasma levels were measured using a pool of 20–24 blood samples over 24h. Sm-C levels in type I (0.62±0.11 U/ml) and type II (0.56±0.09 U/ml) patients were significantly decreased (p<0.01) when compared to controls (0.89±0.30 U/ml). The mean daily secretion of GH was significantly (p<0.01) greater in diabetic patients (7.8±2.6 ng/ml) than in controls (4.1±1.5 ng/ml), but no correlation was found between Sm-C and GH (r=0.15; p=n.s.). Our findings did not show any correlation between Sm-C plasma levels and either the existence of retinopathy, regardless of the degree of microvascular damage, or duration of the disease, or degree of metabolic control, as evaluated by HbA1c.

Extreme insulin resistance due to anti-insulin receptor antibodies: a direct demonstration of autoantibody secretion by peripheral lymphocytes

A 59-year-old woman with systemic lupus erythematosus was found to have marked hyperglycemia, extreme insulin resistance and abnormally high plasma immunoreactive insulin. Her circulating erythrocytes displayed a dramatic decrease of 125I-labeled insulin binding. Both the whole serum and purified IgG fraction strongly inhibited the binding of radiolabeled insulin to control erythrocytes. These results suggested, although indirectly, the existence of antibodies to insulin receptors in the serum of the patient. To directly investigate this issue, we used an enzyme-linked solid-phase immunoassay which allows the detection and enumeration of lymphocytes secreting antibodies towards insulin receptors. Peroxidase-conjugated anti-human immunoglobulin is used to reveal the binding of antibodies to insulin receptor-coated dishes. We demonstrated that the patients mononuclear cells, when briefly incubated in Petri dishes with partially purified insulin receptor, were able to secrete immunoglobulins of G class specifically directed to the antigen. Moreover, only a fraction of the whole population of anti-insulin receptor antibodies was directed towards the insulin binding region of the receptor, seemingly corresponding to the auto-antibodies detected with conventional binding-inhibition assay.

PLASMATIC LEVELS OF FIBRONECTIN IN DIABETICS WITH AND WITHOUT RETINOPATHY. CORRELATION WITH SOME HORMONAL AND METABOLIC PARAMETERS

SummaryFibronectin is a high molecular weight alpha-2-glycoprotein. Its peculiar role in the structure of connective tissue, together with its wide involvement in coagulative dynamics, justified the increasing interest for fibronectin in the pathogenesis of diabetic disease and its vascular sequelae. In the present work, we evaluated the levels of plasma fibronectin (PF) in diabetics with and without retinopathy, and studied the possible correlation between the glycoprotein and some hormonal and metabolic parameters, expression of glycometabolic balance. We examined 26 type I and 24 type II diabetics, further divided into retinopathics and not retinopathics, and 43 normal subjects. We did not find any significant difference in PF levels either between normals and diabetics, or between type I and type II patients, or between retinopathics and not retinopathics. PF was significantly correlated to age, both in normals and in diabetics. Diabetic patients showed a significant positive correlation of PF to total cholesterol (r=0.56; p<0.05) and triglycerides (r=0.36; p<0.05). This seems to suggest, although indirectly, the existence of a relationship between the levels of PF and the degree of large vessel involvement. No significant correlation was found with HbA1c, β-OH, AcAc, lactate, pyruvate, C-peptide, total and free insulin or GH. We further indicated an inverse correlation between PF and plasma glucagon (IRG). Very low levels of PF are commonly associated with high IRG plasma values during acute energy deprivation such as prolonged fasting and ketoacidotic coma. Therefore, PF levels might represent an index of latent to overt energy depletion.

Duration of residual B-cell function in maturity-onset diabetes.

SummaryIn order to evaluate factors influencing the duration of residual B-cell function in maturityonset diabetics we investigated 104 patients (age 60±11 years) with a mean duration of disease of 11.3±8.7 years by measuring fasting C-peptide (FCP) and fasting blood glucose levels (FBG), C-peptide increment after a standardized breakfast and both mean diurnal plasma glucose (MBG) and mean diurnal C-peptide levels (MCP). C-peptide levels were found to be reciprocally dependent on both the age at onset (positively) and, conversely, on the duration of diabetes (y=0.75+0.026x1−0.049x2; R=0.52, t1=2.76, t2=−4.08). In particular, the present B-cell secretory capacity appears to be lower the younger the patients were at onset, thus suggesting that inherent impairment of B-cell capacity may play a crucial role in determining age at onset of type II diabetes and thus the duration of their residual B-cell function. Moreover, by analyzing separately the data from patients treated with insulin and oral agents respectively, we found that the influence of the duration of the disease on the rate on B-cell exhaustion is unrelated to the mode of treatment even though B-cell capacity at onset appears to be more severely reduced in insulin-treated subjects who, apart from anything else, were younger at onset. In addition, no significant difference was found in FCP levels between patients showing MBG values above or below 160 mg/dl (1.76±0.66vs 1.57±0.68 ng/ml), whereas MCP values were lower in patients with MBG above 160 mg/dl (2.14±0.92vs 2.55±0.88 ng/ml; p<0.05) who, on the other hand, showed significant reduction in the C-peptide response to breakfast. These data suggest that prolonged metabolic derangement may impair the physiological response of B-cells and eventually lead, via B-cell overstimulation, or via a gap between synthesis and release of insulin, or through other as yet poorly understood mechanisms, to earlier insulin dependence in maturity-onset diabetic patients.

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

SummaryOptimal 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 ≤ 120 and 180 mg/dl, respectively, HbAlc ≤ 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 non-remitters (NR) than in remitters (R): 0.36–0.64vs 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 ± 0.37vs 0.22 ± 0.16 ng/ml, p<0.001). Finally, blood distribution of T, B, T4 and T8 lymphocyte subsets was measured in all patients, both before and after CSII. The T4/T8 ratio was found to be significantly increased in NR group patients (3.19 ± 0.45vs 2.41 ± 0.23, p<0.005). The immunologic pattern did not show any significant modification after ten days of optimized control by CSII. In conclusion, immunologic background and residual B-cell function may be associated with a different susceptibility to remission from insulin therapy in newly diagnosed young adult diabetics.