c-peptide and beta-Thalassemia

To analyze the secretion of the insulin precursor proinsulin in patients with beta-thalassemia and its possible relation to iron overload.. We assessed fasting proinsulin, insulin, C-peptide and glucose levels from 34 patients with beta-thalassemia and 33 healthy controls. The correlation to age, body mass index, hepatic iron concentration, serum ferritin and serum AST was analyzed.. Fasting proinsulin (p < 0.002) and proinsulin-to-insulin ratio (p < 0.02) were significantly increased in patients with thalassemia irrespective of the degree of glucose tolerance. They correlated positively to serum ferritin, liver iron, patient age and serum AST (all p < 0.05).. Disproportionately elevated proinsulin levels in thalassemic patients indicate early beta-cell dysfunction due to siderosis. An additional biological significance of hyperproinsulinemia and its possible ability to predict long-term iron toxicity in these patients remain to be clarified.

Topics: Adolescent; Adult; beta-Thalassemia; Blood Glucose; C-Peptide; Child; Child, Preschool; Diabetes Complications; Diabetes Mellitus; Enzyme-Linked Immunosorbent Assay; Fasting; Female; Glucose Tolerance Test; Humans; Insulin; Iron; Iron Overload; Liver; Male; Proinsulin; Radioimmunoassay

To assess insulin sensitivity and secretion in the fasting state in regularly transfused patients with beta-thalassaemia major with normal glucose response during an oral glucose tolerance test and to estimate its possible relation to iron overload.. We measured fasting glucose, insulin and C-peptide levels in 24 patients with beta-thalassaemia major and 18 control subjects matched for age and body mass index. Insulin sensitivity and insulin release index were calculated according to the homeostasis model assessment (HOMA). Correlations with age, body mass index and serum ferritin were also calculated.. Fasting glucose levels in patients were increased compared with control subjects (5.5 +/- 0.12 vs. 4.7 +/- 0.13 mmol/l, mean +/- SEM, P < 0.001). Pancreatic B-cell insulin secretion in the fasting state (estimated by SC(HOMA)) was lower in thalassaemic patients (SC(HOMA) 88.5 +/- 11.11 vs. 184.3 +/- 23.72 in control subjects, P < 0.001). Patients were then divided into those with impaired (IFG) and normal (NFG) fasting glucose. SC(HOMA) was higher in the patients with NFG compared with those with IFG patients (110.6 +/- 17.63 vs. 66.3 +/- 10.88, respectively, P < 0.05) but estimated insulin sensitivity (ISI(HOMA)) was similar. Plasma values of C-peptide correlated positively with ferritin (r = 0.42, P = 0.04) and SC(HOMA) (r = 0.45, P = 0.02) and negatively with ISI(HOMA) (r = -0.43, P = 0.03).. These results support the concept that impaired B-cell function, as reflected by a reduction in the insulin secretion index, is present in beta-thalassaemic patients with normoglycaemia before changes in oral glucose tolerance tests are apparent.

Topics: Adult; beta-Thalassemia; Blood Glucose; C-Peptide; Case-Control Studies; Diabetes Mellitus; Female; Glucose Tolerance Test; Homeostasis; Humans; Insulin; Insulin Secretion; Male; Models, Biological

Type 1 diabetes mellitus (DM) is a frequent complication in patients with beta-thalassemia. It is believed to be due to the damage inflicted by iron overload of the pancreatic beta cells. Liver disorders and genetic influences seem to be additional predisposing factors.. To study the prevalence of diabetes and impaired glucose tolerance (IGT) in transfusion-dependent Egyptian beta-thalassemic patients and to evaluate the possible role of genotyping in the pathogenesis of diabetes associated with beta-thalassemia.. A total of 56 transfusion-dependent beta-thalassemic patients aged 10-31 (mean age=15.9 +/- 5.7 yr), 32 males and 24 females, including 48 thalassemia major and eight thalassemia intermedia; compared to 15 age- and sex-matched controls. All were subjected to history and examination, laboratory investigations: complete blood count (CBC), serum ferritin, liver function tests, hepatitis B and C markers, fasting blood glucose, oral glucose tolerance test (OGTT) and fasting C-peptide. Genotyping for 16 mutations was assessed in thalassemic patients with abnormal glucose tolerance.. The prevalence of diabetes was 10.4% (5 of 48) and IGT was 14.6% (7 of 48) among thalassemia major, whereas, none of thalassemia intermedia had abnormal glucose tolerance. Fasting C-peptide was lower in beta-thalassemic patients compared to controls (p <0.001); the level was significantly higher in patients complicated by diabetes or IGT compared with other thalassemic patients (p <0.001). Chronic hepatitis C was detected in all patients (100%) with abnormal glucose tolerance. Genotyping showed that IVS II nt 745 was detected in 77.7% of cases with abnormal glucose tolerance.. Abnormal glucose tolerance is common in multiply transfused beta-thalassemia major patients, which could be attributed to progressive and early loss of beta-cell mass, along with persistent insulin resistance. Chronic hepatitis C may play a role in the development of abnormal glucose tolerance. An association between diabetes and genotyping IVS II nt 745 was found. Patients with this particular genotype are advised to check their blood glucose every 6 months to detect early occurrence of diabetes.

Topics: Adolescent; Adult; beta-Thalassemia; Blood Transfusion; C-Peptide; Child; Diabetes Mellitus; Egypt; Female; Genotype; Glucose Intolerance; Hepatitis C, Chronic; Humans; Male

This study investigated the effects of the alpha-glucosidase inhibitor, acarbose, on glycemic control and insulin secretion in thalassemic patients with impaired glucose tolerance. The safety and tolerability of the drug were also evaluated. Nine patients (4 men and 5 women, aged 20-34 years) with beta-thalassemia major received a standardized nutritional test load prior to and following 3 months treatment with acarbose 100 mg t.i.d. Blood glucose, insulin and C-peptide levels were measured at 0, 60, 90 and 120 min post-loading. Plasma glucose levels after 3 months of acarbose treatment tended to be slightly lower than pre-treatment levels. Although fasting serum insulin and plasma C-peptide levels were unchanged after acarbose therapy, postprandial serum levels of both hormones were markedly reduced (by 24-47% and 19-32%, respectively, at 60-120 min post-loading). Body mass index, liver enzymes and serum lipids were unaltered following acarbose treatment. Gastrointestinal disturbances were mild and tended to decrease during the course of acarbose therapy. Acarbose is a well-tolerated agent for the management of thalassemic patients with glucose intolerance and normal or increased insulin secretion. It is possible that acarbose may prevent or delay progression from impaired glucose homeostasis to frank insulin-dependent diabetes mellitus.

Topics: Acarbose; Adult; beta-Thalassemia; Blood Glucose; Body Mass Index; C-Peptide; Enzyme Inhibitors; Female; Food; Gastrointestinal Diseases; Glycoside Hydrolase Inhibitors; Homeostasis; Humans; Insulin; Kinetics; Lipids; Liver; Male; Pilot Projects

Topics: Adolescent; Adult; beta-Thalassemia; Blood Glucose; C-Peptide; Child; Child, Preschool; Fasting; Glucose Intolerance; Humans; Infant; Insulin; Insulin Resistance; Insulin Secretion; Kinetics; Proinsulin

To better understand the pathophysiology of glucose intolerance secondary to iron overload in patients with thalassemia major, we performed tolbutamide-modified frequently sampled iv glucose tolerance tests (FSIGTs) in 10 thalassemic patients (6 males and 4 females; 21.7 +/- 1.2 yr old; body mass index, 19.7 +/- 0.6 kg/m2) and 10 healthy controls (5 males and 5 females; 22.4 +/- 1.3 yr; body mass index, 20.6 +/- 0.5 kg/m2). Insulin secretion and action were quantified by application of the minimal model of glucose kinetics and the combined model of insulin and C-peptide kinetics to the FSIGT data. The insulin sensitivity index was significantly lower in thalassemia patients [72 +/- 12 min-1(nmol/mL)] compared to controls [158 +/- 21 min-1(nmol/mL); P = 0.0026]. The integrated insulin response during the FSIGT was significantly greater in thalassemia patients than in controls after tolbutamide injection (P = 0.042). The difference in insulin levels was apparently due to reduced hepatic insulin extraction in thalassemia (78 +/- 2% vs. 68 +/- 3%; P = 0.0251). Seven of the 10 thalassemia patients were studied prospectively at 6-month intervals for 6-12 months. Repeated measures analysis of variance indicated that across a 6-month interval, there was a decrease in the total integrated insulin response (P = 0.002), with no change in insulin sensitivity (P = 0.86). In conclusion, patients with thalassemia major have significant insulin resistance, which may be compensated for by an elevated circulating insulin level. The elevated insulin level in response to tolbutamide appears to be due to reduced hepatic extraction of insulin and not to an enhanced insulin secretory response. Over time, patients with thalassemia experience a reduction in their circulating insulin levels. Persistent insulin resistance along with a progressive reduction in circulating insulin levels may lead to glucose intolerance and diabetes mellitus, which have a high prevalence in patients with thalassemia major.

Topics: Adolescent; Adult; Analysis of Variance; beta-Thalassemia; C-Peptide; Fasting; Female; Ferritins; Glucose; Glucose Tolerance Test; Half-Life; Humans; Insulin; Insulin Secretion; Male; Pancreas; Prospective Studies; Time Factors