Insulin secretion and insulin sensitivity are normal in non-diabetic subjects from maternal inheritance diabetes and deafness families.

BACKGROUND: The pathophysiological mechanism of diabetes mellitus in the presence of the 3243 A-G tRNALEU(UR) mitochondrial DNA mutation is thought to result from deficient insulin secretion. However, few subjects with normal glucose tolerance have been studied to determine the sequence of events resulting in the development of diabetes mellitus. AIM: To determine whether abnormalities of insulin sensitivity, insulin secretion or glucose effectiveness are present in non-diabetic subjects with the 3243 A-G tRNALEU(UUR) mitochondrial DNA mutation. METHODS: Twelve non-diabetic subjects with the mutation were compared with 12 controls, matched for age and anthropometric parameters, using both oral and intravenous glucose tolerance tests, the latter with Minimal Model analysis. RESULTS: Following an oral glucose load we found significantly higher blood glucose levels at 90 min and 120 min and significantly higher insulin levels at 120 min and 180 min in non-diabetic subjects with the mutation but no difference in the insulinogenic indices at 30 min and 180 min. From the intravenous glucose tolerance test there was no difference in overall glucose tolerance, insulin sensitivity, first- or second-phase insulin secretion, proinsulin secretion or glucose effectiveness. Insulin-independent glucose disposal was increased in subjects with lower insulin sensitivity and declined with increasing age in subjects with the mutation but not in controls. CONCLUSIONS: While there appear to be subtle defects of glucose handling in non-diabetic subjects with the 3243 mutation, these could not be explained by differences in insulin sensitivity or secretion.     

Insulin sensitivity,insulin secretion and glucose effectiveness in diabetic and non-diabetic cirrhotic patients

Summary In cirrhotic patients with normal fasting glucose levels both insulin insensitivity and a blunted early insulin response to oral glucose are important determinants of the degree of intolerance to oral glucose. It is not known whether the ability of hyperglycaemia per se to enhance glucose disposal (glucose effectiveness) is also impaired. It is also unclear whether overt diabetes is due to (1) more marked insulin insensitivity; (2) impaired insulin secretion; (3) reduced glucose effectiveness; or (4) a combination of these mechanisms. We used the minimal model to analyse the results of a 3-h intravenous glucose tolerance test to assess glucose effectiveness, insulin sensitivity and insulin responses in 12 non-diabetic cirrhotic patients, 8 diabetic cirrhotic patients and 10 normal control subjects. Fasting blood glucose levels were 4.8±0.2, 7.5±0.6 and 4.7±0.1 mmol/l, respectively. Fasting insulin and C-peptide levels were higher in both cirrhotic patient groups compared with control subjects. The glucose clearance between 6 and 19 min after i.v. glucose was lower in both cirrhotic groups (non-diabetic, 1.56±0.14, diabetic, 0.76±0.06, control subjects, 2.49±0.16 min^–1%, both p<0.001 vs control subjects). Serum insulin peaked at 3 and 23 min in the non-diabetic cirrhotic patients and control subjects; both peaks were higher in the non-diabetic cirrhotic patients and showed a delayed return to basal levels. In the diabetic cirrhotic patients, the first phase insulin and C-peptide response to i.v. glucose was absent; their early (22–27 min) incremental insulin response to i. v. tolbutamide was however similar to that of control subjects but 43% lower than in the non-diabetic cirrhotic patients (p<0.05). Insulin sensitivity was markedly reduced in both cirrhotic groups (non-diabetic, 1.11±0.24×10^–4, diabetic, 0.33±0.53×10^–4, control subjects, 4.37±0.53×10^–4 min^–1 per mU·l^–1, both p<0.001 vs controls). Glucose effectiveness was normal in the non-diabetic cirrhotic patients but 29% lower in the diabetic group. It would appear that overt diabetes develops in those cirrhotic patients who in addition to insulin insensitivity have a marked impairment of insulin secretion. An associated reduction in glucose effectiveness may be a contributory factor.     

Hepatocyte nuclear factor-1 alpha gene inactivation: cosegregation between liver adenomatosis and diabetes phenotypes in two maturity-onset diabetes of the young (MODY)3 families

Heterozygous germline mutations of the hepatocyte nuclear factor (HNF)-1 alpha are associated with maturity-onset diabetes of the young (MODY)3. Recently, the biallelic inactivation of the HNF-1 alpha gene was reported in liver adenomas. We show the occurrence of liver adenomatosis in six MODY3-affected patients from two unrelated and large families. Liver adenomatosis was characterized by the presence of numerous adenomas within a normal hepatic parenchyma. The HNF-1 alpha hot-spot germline mutation P291fs was identified in the two probands and in 16 relatives from the two families. The six patients affected by liver adenomatosis and diabetes exhibited the mutation. The analysis of liver-cell tumors from two affected patients evidenced the biallelic inactivation of HNF-1 alpha. The familial screening confirmed the clinical heterogeneity of the liver phenotype, from silent liver adenomatosis to fatal hemorrhage. These observations warrant the systematic screening for liver adenomatosis in MODY3 families to prevent its potentially deadly complications. Moreover, such screening may help to determine if a particular mutational spectrum of HNF-1 alpha is associated with liver adenomatosis and to establish its prevalence in this frequent form of diabetes in the young adult.     

Counterregulatory responses to hypoglycemia in patients with maturity-onset diabetes of the young caused by HNF-1alpha gene mutations (MODY3)

Mutations of HNF-1alpha lead to severe beta cell dysfunction, resulting in decreased glucose-induced insulin secretion. HNF-1alpha is also expressed in liver, kidney and pancreatic alpha cells, but the functional consequences of HNF-1alpha mutations in these organs remain unknown. We therefore assessed the counterregulatory responses to hypoglycemia in six patients with HNF-1alpha mutations (MODY3), five patients with non-insulin-dependent diabetes mellitus (NIDDM) and in nine healthy controls. Plasma glucagon concentrations and endogenous glucose production were measured every 15 min during a hyperinsulinemic clamp with progressive hypoglycemia. Plasma glucagon concentrations were similar at basal glycemia (73+/-6, 69+/-5 and 69+/-7 ng/l) and reached peak values of 88+/-9, 88+/-11 and 89+/-7 ng/l at a glycemia of 3.6 mmol/l in MODY3 patients, patients with NIDDM and controls respectively (NS). Suppression of endogenous glucose production by insulin was blunted in MODY3 patients (3.3+/-1.2 micromol/kg per min) and in patients with NIDDM (4.4+/-0.6 micromol/kg per min) compared with controls (1.7+/-0.5 micromol/kg per min, P<0.05 compared with both MODY3 patients and patients with NIDDM). During hypoglycemia, endogenous glucose production increased to 8.6+/-2.1, 8.8+/-0.7 and 7.0+/-1.0 micromol/kg per min in MODY3 patients, patients with NIDDM and controls respectively (all NS). These data indicate that mutations of HNF-1alpha in MODY3 do not result in a decreased glucagon secretion or alterations of glucose production during hypoglycemia.     

Insulin secretion, insulin sensitivity and diabetes in black children.

Historically, type 2 diabetes has been considered rare in the pediatric population. However, over the last decade, there has been a disturbing upswing in the rate of non-type 1 diabetes in the pediatric age group, particularly adolescents, with a greater proportion of Black children being affected. In this review, the following questions will be addressed: (1) what are the clinical characteristics of youth-onset atypical diabetes, (2) how common is it, (3) what are the risk factors, and (4) how should it be treated?     

Low plasma insulin-like growth factor-1 levels are associated with reduced insulin sensitivity and increased insulin secretion in nondiabetic subjects

Background and aimWeight gain is associated with a decline in insulin sensitivity and a compensatory increase in insulin secretion. IGF-1 is a plausible candidate to explain these divergent phenomena. In this cross-sectional study, we analyzed the relationship between IGF-1 levels, insulin sensitivity and secretion in 110 nondiabetic subjects with a wide range of BMI to verify this hypothesis.Methods and resultsSubjects underwent OGTT, IVGTT and euglycemic-hyperinsulinemic clamp. HOMA-beta, IVGTT-derived and OGTT-derived indexes for first-phase and second-phase insulin secretion were higher in obese as compared with overweight and normal-weight groups, while glucose disposal was lower. IGF-1 levels were negatively correlated with IVGTT-derived and OGTT-derived indexes first-phase and second-phase insulin secretion, and positively correlated with glucose disposal. These correlations were no longer significant after adjustment for BMI.In a multivariate analysis, the variables associated with glucose disposal were IGF-1, age, triglycerides, and 2-h post-load glucose accounting for 23.4% of its variation. When BMI was entered into the model, the variables associated with glucose disposal were triglycerides, 2-h post-load glucose and BMI accounting for 27.2% of variation. In a multivariate analysis, the only variable associated with IVGTT-derived first-phase and second-phase insulin secretion was IGF-1 accounting for 10.4% and 15.1% of variation, respectively. When BMI was entered into the model, it became the only variable associated with both first-phase and second-phase insulin secretion accounting for 25.7% and 37.6% of variation, respectively.ConclusionThese data suggest that progressive reduction in IGF-1 levels may be involved in obesity-related changes in both insulin sensitivity and secretion.     

Insulin secretion and insulin sensitivity in diabetic subgroups: studies in the prediabetic and diabetic state

Aims/hypothesis. To evaluate insulin sensitivity and insulin secretion in prediabetic and diabetic subjects with mutations in MODY1 (HNF-4α) and MODY3 (HNF-1α) genes, in subjects with GAD antibodies, latent autoimmune diabetes in adults and in subjects with the common form of Type II (non-insulin-dependent) diabetes mellitus. Methods. Insulin secretion was measured as the incremental 30-min insulin (I30) and insulin glucose ratio (I:G30) during OGTT whereas insulin sensitivity was measured as the insulin sensitivity index during OGTT in 131 carriers of MODY mutations [NGT = 38, IFG/IGT = 21, diabetes mellitus (DM) = 72], in 293 subjects with GADA (NGT = 47, IFG/IGT = 29, DM = 217) and in 2961 subjects with a family history of the common form of Type II diabetes but without MODY mutations or GADA (NGT = 1360, IFG/IGT = 857, DM = 744). A subgroup of the subjects underwent a euglycaemic clamp (n = 210) and intravenous glucose tolerance test (n = 337) for the estimation of insulin sensitivity and first-phase insulin secretion. Results. Non-diabetic subjects with MODY mutations had pronounced impaired insulin secretion (I30, I:G30) compared with the two other groups (p = 0.005). Normal or non-diabetic glucose tolerance was maintained by enhanced insulin sensitivity compared with the other two groups (p < 0.05 and p < 0.005). In contrast to patients with Type II diabetes and with adult latent autoimmune diabetes, MODY patients showed only a modest deterioration in insulin sensitivity at onset of diabetes. The 2-h glucose values inversely correlated with insulin sensitivity in subjects with GADA (r = –0.447, p < 0.001) and subjects from Type II diabetic families (r = –0.426, p < 0.001), whereas no such relation was observed in subjects with MODY mutations (r = 0.151, p = NS). There were no statistically significant differences in insulin secretion or insulin sensitivity between subjects with GADA or subjects with a family history of Type II diabetes, either at the NGT or the IFG/IGT stage. Conclusion/interpretation. Glucose-tolerant carriers of MODY mutations are characterised by a severe impairment in insulin secretion. Enhanced insulin sensitivity is the most likely explanation for the normal glucose tolerance. Whereas subjects with positive GADA or Type II diabetes have impaired insulin sensitivity with increasing glucose concentrations, MODY mutation carriers seem to be protected from the effect of glucose toxicity. [Diabetologia (2000) 43: 1476–1483] Received: 23 March 2000 and in revised form: 29 August 2000     

Conditional expression of hepatocyte nuclear factor-1beta, the maturity-onset diabetes of the young-5 gene product, influences the viability and functional competence of pancreatic beta-cells

Mutations in the gene encoding hepatocyte nuclear factor (HNF)1beta result in maturity-onset diabetes of the young-(MODY)5, by impairing insulin secretory responses and, possibly, by reducing beta-cell mass. The functional role of HNF1beta in normal beta-cells is poorly understood; therefore, in the present study, wild-type (WT) HNF1beta, or one of two naturally occurring MODY5 mutations (an activating mutation, P328L329del, or a dominant-negative form, A263insGG) were conditionally expressed in the pancreatic beta-cell line, insulin-1 (INS-1), and the functional consequences examined. Surprisingly, overexpression of the dominant-negative mutant did not modify any of the functional properties of the cells studied (including insulin secretion, cell growth and viability). By contrast, expression of WT HNF1beta was associated with a time- and dose-dependent inhibition of INS-1 cell proliferation and a marked increase in apoptosis. Induction of WT HNF1beta also inhibited the insulin secretory response to nutrient stimuli, membrane depolarisation or activation of protein kinases A and C and this correlated with a significant decrease in pancrease-duodenum homeobox-1 protein levels. The attenuation of insulin secretion was, however, dissociated from the inhibition of proliferation and loss of viability, since expression of the P328L329del mutant led to a reduced rate of cell proliferation, but failed to induce apoptosis or to alter insulin secretion. Taken together, the present results suggest that mature rodent beta-cells are sensitive to increased expression of WT HNF1beta and they imply that the levels of this protein are tightly regulated to maintain secretory competence and cell viability.     

上海地区肥胖糖调节受损者的胰岛素敏感性和1相胰岛素分泌功能研究

目的研究上海地区肥胖的糖调节受损(IGR)者胰岛素敏感性和胰岛β细胞1相胰岛素分泌功能。方法共有129例受试者[非肥胖正常对照38名,IGR包括单独糖耐量受损(IGT)64例,单独空腹血糖受损(IFG)8例,IFG+IGT 19例]接受了口服75g葡萄糖耐量试验和胰岛素改良的减少样本数(n =12)的Bergman微小模型技术结合频繁采血的静脉葡萄糖耐量试验(FSIGTT)。胰岛素抵抗由FSIGTT中胰岛素敏感性指数(S1)加以评估,而FSIGTT中对葡萄糖急性胰岛素分泌反应(AIRg)则用以评价胰岛β细胞分泌功能。处理指数(DI=AIRg×S1)用于评价AIRg是否代偿机体的胰岛素抵抗。结果(1)与正常对照组相比,3组IGR患者之S1明显降低(均P<0．01),3组差异无统计学意义;(2)AIRg在正常组和IGT组之间差异无统计学意义,但均大于IFG和IFG+IGT组,差异有统计学意义(P<0．05或JP<0．01)。IFG +IGT组的AIRg值显著低于IGT组(P<0．01);(3)与正常组相比,DI指数在3组IGR显著降低(P< 0．01),但在IGR组间差异无统计学意义;(4)S1与空腹胰岛素、体重指数、血清尿酸呈显著负相关(校正r2 =0．568,P<0．01);而AIRg与2h胰岛素显著正相关,与空腹血糖、2h血糖和年龄负相关(校正r2=0．402, P<0．01)。结论上海地区肥胖的初诊IGR患者(包括单独IGT、单独IFG和IFG+IGT患者)存在着程度近似的胰岛素抵抗;急性相胰岛素分泌功能在校正胰岛素抵抗影响因素后IGT患者尚属正常,在IFG和IFG+IGT患者已明显降低,且3组的β细胞代偿功能均为一致性失代偿。     

Determinants of insulin secretion and sensitivity in bangladeshi type 2 diabetic subjects

Background: The relative contribution of insulin secretion and sensitivity in the development of type 2 diabetes mellitus (T2DM) vary from population to population due to the heterogeneous nature of the disease. The study was undertaken to evaluate the insulin secretory capacity and sensitivity in a Bangladeshi type 2 diabetic population and to explore the association of some of the anthropometric (BMI, WHR, MBP) and biochemical factors (glucose, lipids, HbA(1c)) known to modulate B-cell function and insulin action. Methods: Ninety three T2DM and 70 age-matched control subjects were studied for their fasting glucose, lipids, HbA(1c) (by HPLC) and C-peptide (by ELISA). Insulin secretion (HOMA B) and insulin sensitivity (HOMA S) were calculated by homeostasis model assessment (HOMA). Results: Both insulin secretion and sensitivity were significantly reduced in diabetic as compared to control subjects (HOMA B%, geometric M +/- SD, 34.67 +/- 1.73 vs 104.71 +/- 1.34, p < 0.001; HOMA S%, 67.60 +/- 1.69 vs 85.11 +/- 1.54, p < 0.01). However, the discriminant function coefficient for HOMA B (1.142) was about 1.5 times higher than that for HOMA S (0.731). In T2DM, HOMA B had positive correlation with BMI (r = 0.362, p < 0.001) and inverse correlation with plasma glucose (r = - 0.701, p < 0.001) and HbA1c (r = - 0.612, p < 0.001). HOMA S was inversely correlated to BMI (r = - 0.274, p < 0.01), WHR (r = - 0.252, p < 0.05), plasma total cholesterol (r = - 0.240, p < 0.05) and triglycerides (r = 0.301, p < 0.01). Conclusions: Both insulin secretory dysfunction and insulin resistance are present in Bangladeshi T2DM subjects, but B-cell dysfunction seems to be the predominant defect. BMI, plasma glucose and insulin are the major determinants of insulin secretory capacity; and generalized as well as central obesity, plasma glucose, total cholesterol, triglycerides and insulin are among the major determinants of insulin sensitivity in this population.     

Impaired maximum microvascular hyperaemia in patients with MODY 3 (hepatocyte nuclear factor-1alpha gene mutations).

AIMS: Functional abnormalities of blood flow and capillary pressure may be involved in the pathogenesis of diabetic microangiopathy. Important differences in microvascular behaviour are observed between Type 1 and Type 2 diabetes mellitus, raising the possibility that the pathogenesis of microangiopathy may differ between these. MODY3 patients have hyperglycaemia as a result of genetic defect of beta-cell function rather than increased insulin resistance and are susceptible to microvascular complications and offer an opportunity to examine microvascular behaviour in this setting. METHODS: The maximum microvascular hyperaemic response to local heating of the skin was studied in 12 MODY3 patients and age and sex-matched control subjects using laser Doppler fluximetry. RESULTS: Maximum hyperaemia was reduced in MODY3 patients (median 1.17 (range 0.88-1.92)V vs. 1.70 (1.07-2.19)V normal control subjects; P=0.03) and thus was negatively associated with duration of diabetes (r(s)=-0.79; P = 0.002). CONCLUSIONS: The results suggest that the duration of diabetes is a determinant of impaired microvascular hyperaemia in MODY3 patients. The pattern of vasodilatory impairment is similar to that observed in Type 1 diabetes mellitus and differs from that seen in Type 2 diabetes. This provides support for the concept that beta cell dysfunction and insulin resistance may have differing effects on microvascular behaviour.     

Insulin supplement in type 2 diabetic patients with secondary failure to oral agents ameliorates hepatic and peripheral insulin sensitivity but not insulin secretion

In order to investigate the mechanism of amelioration of metabolic abnormalities with supplementary doses of insulin, islet B-cell function and insulin sensitivity were measured in 10 patients with Type 2 diabetes in secondary failure to oral agents. A small dose of ultralente insulin (0.26 +/- 0.07 U kg-ideal-body-weight-1) was added in the morning before breakfast. After 3 months insulin therapy and progressive improvement of metabolic control (HbA1 from 10.5 +/- 0.4 to 9.0 +/- 0.3% at the end of insulin treatment, p less than 0.001), basal C-peptide and incremental area during an oral glucose tolerance test were unchanged. In vivo peripheral insulin sensitivity (euglycaemic clamp with insulin infusion of 40, 160, and 600 mU m-2 min-1, respectively) was significantly improved (glucose requirement: to 4.7 +/- 1.0 from 3.0 +/- 0.6 mg kg-1 min-1, p less than 0.05 at first insulin level; to 10.8 +/- 0.5 from 9.3 +/- 0.7 mg kg-1 min-1, p less than 0.01 at second level; to 13.3 +/- 0.6 from 11.8 +/- 0.8 mg kg-1 min-1, p less than 0.025 at third level). Basal hepatic glucose production was also significantly reduced (from 4.3 +/- 0.4 to 3.3 +/- 0.3 mg kg-1 min-1, p less than 0.05), and residual glucose production further suppressed after insulin supplement (from 1.1 +/- 0.4 to 0.3 +/- 0.2 mg kg-1 min-1 after 120 min at 100 mU l-1 plasma insulin, p less than 0.05). Specific insulin binding to mononuclear leucocytes was unchanged (from 3.1 +/- 0.3 to 3.5 +/- 0.3%, NS).     

Insulin secretion, insulin sensitivity and hepatic insulin extraction in primary hyperparathyroidism before and after surgery

OBJECTIVE: Primary hyperparathyroidism (pHPT) is associated with hypertension, hyperinsulinaemia, and insulin resistance. The present study investigated the causes of these metabolic disturbances by quantifying insulin sensitivity and glucose effectiveness, and by assessing the time course of beta-cell insulin secretion and hepatic insulin extraction, during a dynamic condition such as after an intravenous glucose load. In addition, we evaluated the possible link between metabolic disorders and high blood pressure. SUBJECTS: We studied 16 patients with pHPT, before and 12 weeks after parathyroidectomy; eight of these patients were re-evaluated one year after surgery. The control group consisted of 18 healthy volunteers. DESIGN AND MEASUREMENTS: All subjects underwent an oral and a frequently sampled intravenous glucose tolerance test. The data from the intravenous glucose tolerance test were analysed by means of the minimal model technique which yields relevant parameters to comprehend the metabolic status of the single individual. RESULTS: The glucose intolerance condition was characterized by a severely impaired insulin sensitivity in pHPT (3.2 +/- 0.5 vs 9.5 +/- 1.5 x 10(4)/min/(microU/ml) of control subjects; P < 0.001), as well as by a reduced glucose effectiveness, (0.02 +/- 0.002 vs 0.03 +/- 0.003/min of control subjects; P < 0.04). Total insulin secretion during the 4 hours of the test was almost twofold elevated in comparison to the control subjects (32795 +/- 4769 vs 16864 +/- 1850 pM, P < 0.004) and its basal component significantly correlated with the high blood pressure. Hepatic extraction of insulin was significantly increased in pHPT (85 +/- 2 vs 76 +/- 2%, P < 0.03), possibly as a compensatory mechanism of hypersecretion, which however did not prevent peripheral hyperinsulinaemia in pHPT. Patients with pHPT were divided into two subgroups with normal and impaired glucose tolerance. The patients with impaired glucose tolerance had a significant reduction of first phase insulin response, although their basal and stimulated insulin levels were higher. Tissue insulin sensitivity and glucose effectiveness did not significantly differ between the two subgroups. After surgery, all the biochemical parameters (former hypercalcaemia, hypophosphataemia, elevated parathormone levels) were normalized, insulin sensitivity significantly improved (6 +/- 1 x 10(4)/min/(microU/ml), P < 0.001), whereas glucose effectiveness remained completely unchanged. Basal and stimulated insulin responses were insignificantly lowered after surgery, and hepatic extraction did not change either. CONCLUSIONS: Patients with pHPT exhibited decreased insulin sensitivity and insulin hypersecretion. The latter is only partially ameliorated by increased hepatic insulin extraction. After surgery, although the biochemical abnormalities were fully reversible, the metabolic changes improved only partially.     

Insulin secretion, peripheral insulin sensitivity and insulin-receptor binding in subjects with different degrees of obesity

OBJECTIVES: The aim of the present study was to investigate insulin secretion, insulin-receptor binding and peripheral insulin sensitivity in subjects with different degrees of obesity. METHODS: 36 obese subjects with normal glucose tolerance and different degrees of obesity and 40 healthy normal-weight subjects participated in the study. Peripheral insulin sensitivity was measured by using the euglycaemic hyperinsulinaemic clamp technique, and insulin-receptor binding-on circulating mononuclear blood cells. Insulin secretion was studied during intravenous tolbutamide test. RESULTS: The subjects with I degree of obesity demonstrated a significant decrease in the number of total (p<0.0001) and high-affinity (p<0.01) insulin receptors per cell, as well as significantly higher insulin receptor affinity (p<0.01) as compared to the normal-weight subjects. The subjects with II degree of obesity also demonstrated a significant decrease in the number of total (p<0.0001) and high-affinity receptors (p<0.001) per cell as well as an increase (p<0.001) in insulin-receptor affinity as compared to the controls. The significantly decreased receptor number in the subjects with I and II degree of obesity was accompanied by an increase in insulin receptor affinity; thus their insulin-receptor binding being maintained similar to the controls. The subjects with III degree obesity presented a significant decrease (p<0.0001) in the number of both the total and high-affinity insulin receptors as well as a reduction in insulin receptor affinity as compared to the controls. Therefore the percentage of specifically bound insulin was significantly lower (p<0.01) as compared to that of the control group. Insulin resistance in the obese subjects is associated with secondary hyperinsulinaemia, which is present in subjects with I and II degree of obesity; while in severely obese subjects exhaustion of beta-cell secretory capacity is observed. CONCLUSION: We consider that III degree of obesity appears to be a risk factor for type 2 diabetes mellitus as the alterations in insulin sensitivity, insulin-receptor binding and beta-cell secretion are quite similar to the reported in diabetic patients.     

Enhanced hepatic insulin sensitivity,but peripheral insulin resistance in patients with Type 1 (insulin-dependent) diabetes

Summary Sensitivity to insulin in vivo was studied in 8 normal weight C-peptide negative Type 1 (insulin-dependent) diabetic patients (age 23±1 years, diabetes duration 6±2 years), and in 8 age, weight and sex matched healthy subjects, using the euglycaemic clamp and 3-³H-glucose tracer technique. Prior to the study diabetic patients were maintained normoglycaemic overnight by a glucose controlled insulin infusion. Sequential infusions of insulin in 3 periods of 2 h resulted in mean steady state insulin levels of 12±2 versus 11±1, 18±2 versus 18±2 and 28±3 versus 24±2 U/ml in diabetic patients and control subjects. Corresponding glucose utilization rates were 2.4±0.2 versus 2.4±0.1, 2.4±0.2 versus 3.0±0.3 and 2.9±0.3 versus 4.6±O.6 mg·kg^–1·min^–1, p<0.02. Portal insulin values in the three periods were calculated to 12±2 versus 25±3, 18±2 versus 32±3 and 28±3 versus 37±3 U/ml in the diabetic patients and control subjects using peripheral insulin and C-peptide concentrations and assuming a portal to peripheral insulin concentration gradient of 1 in diabetic patients and of 2.4 in control subjects. Corresponding glucose production rates were 2.5±0.2 versus 2.4±0.1, 1.6±0.1 versus 0.9±0.2 and 0.7±0.1 versus 0.4±0.2 mg·kg^–1·min^–1. Using this approach the insulin dose-response curve for the peripheral glucose utilization was right-ward shifted, while the dose-response curve for the hepatic glucose production as a function of portal insulin levels was left-ward shifted. We conclude that in vivo insulin action is increased in the liver but decreased in peripheral tissues in insulin treated Type 1 diabetic patients. Presumably these oppositely directed changes in insulin action are acquired defects, secondary to the present mode of peripheral insulin treatment.