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.     

Reduced glycogen synthase activity in skeletal muscle from obese patients with and without Type 2 (non-insulin-dependent) diabetes mellitus

Summary In order to evaluate the importance of a defect in insulin mediated non-oxidative glucose metabolism and glycogen synthase activity in skeletal muscles in obese subjects with and without Type 2 (non-insulin-dependent) diabetes mellitus we studied: 10 lean and 10 obese control subjects and 12 obese diabetic patients using the euglycaemic hyperinsulinaemic clamp technique (basal, 20 mU · (m²)^–1 · min^–1, 80mU·(m²)^–1·min^–1) in combination with indirect calorimetry. Muscle biopsies were taken from m. vastus lateralis at each insulin level. We found that non-oxidative glucose metabolism could be stimulated by insulin in all three groups (p<0.01). The values obtained at the highest insulin levels (around 140 U/ml) were lower in both obese groups compared to the lean control subjects (118±21, 185±31, 249±14 mg·(m²)^–1·min^–1 (p< 0.01)). Insulin stimulation of the glycogen synthase activity at a glucose-6-phosphate concentration of 0.1 mmol/l was absent in both obese groups, while activities increased significantly in the lean control subjects (19.6±4.2% to 45.6±6.8%, p< 0.01). Glycogen synthase activities at the highest insulin concentrations only differed significantly between lean control subjects and obese diabetic patients (45±7% and 31±5%, p< 0.05). We conclude that insulin resistance in peripheral tissues in obese subjects with and without Type 2 diabetes may be partly explained by a reduced insulin mediated non-oxidative glucose metabolism and that this abnormality might be due to an absent insulin stimulation of glycogen synthase in skeletal muscles. This enzyme defect is correlated to obesity itself.     

Both acute and chronic near-normoglycaemia are required to improve insulin resistance in Type 1 (insulin-dependent) diabetes mellitus

Summary To determine the impact of both short- and longterm near-normoglycaemia on insulin resistance in Type 1 (insulin-dependent) diabetes hepatic glucose production (mg · kg^–1 · min^–1) and peripheral glucose utilisation (M-value, mg · kg^–1 · min^–1) were estimated during an euglycaemic hyperinsulinaemic clamp (10 mU · kg · min) in patients with either good (HbA_1c<5.8%, groups A and B) or poor (HbA_1c>7.5%, groups C and D) long-term metabolic control (time > 12 months) and in healthy subjects (HbA_1c: 5.08±0.20%; n=8). To this end blood glucose was stabilized at 6.7 mmol/l by overnight (t=12 h) i.v. regular insulin in groups (n=8 each) A (HbA_1c: 5.49±0.46%) and C (HbA_1c: 8.83±1.20%),while groups B (HbA_1c:5.55±0.19%) andD (HbA_1c: 8.51±1.09%) were kept overnight on long-acting insulin without feed-back control of blood glucose before euglycaemic clamping. Thereby, pre-equilibration of blood glucose at 6.7 mmol/l was shown to normalize basal hepatic glucose production (A: 2.27±0.48; C 2.50±0.57 mg · kg^–1 · min^–1) despite different HbA_1c values, whereas basal hepatic glucose production stayed elevated in groups B (3.09±0.38 mg · kg^–1 · min^–1) and D (3.21±0.58 mg · kg^–1 · min^–1) with poor actual glycaemia (B: 10.9±4.6; D: 12.1±4.6 mmol/l). To restitute peripheral glucose utilisation close to normal (healthy subjects: 13.99±2.13; A: 12.12±2.67; B: 8.72±3.0; C: 10.27±1.69; D: 7.10±2.31 mg · kg^–1 · min^–1; healthy subjects vs A: NS; healthy subjects vs B, C, D: p<0.05) both long-term (HbA_1c<5.8%) and acute nearnormoglycaemia by 12-h i. v. insulin pre-treatment were required (group A). We conclude that good long-term glucose control per se is unable to normalize hepatic and peripheral glucose metabolism in Type 1 diabetic patients unless actual near-normoglycaemia is provided consistently, e.g. by i.v. overnight infusion of regular insulin.     

Impaired insulin action in newly diagnosed type 1 (insulin-dependent) diabetes mellitus

Summary Hepatic and peripheral insulin sensitivity were investigated in five newly diagnosed Type 1 (insulin-dependent) diabetic subjects before and after 1 week of twice daily insulin therapy. Eight weight-matched control subjects were also studied. Hepatic glucose production and glucose utilization were measured basally and during two sequential 2-h insulin (25 and 40 mU· kg^–1· h^–1)/glucose infusion periods. In the untreated hyperglycaemic diabetic patients hepatic glucose production was 16.3±2.6, 8.1±1.1 and 3.6±2.8|mol· kg^–1· min^–1 respectively for each of the three periods (mean±SEM), and fell with treatment to 12.5±1.4, 0.5±0.5 and 0.5±0.5 mol· kg^–1· min^–1. Hepatic glucose production for normal subjects was 13.4±0.7, 2.3±0.8 and <0.1 mol-kg^–1· min^–1. Glucose utilization was 12.7±1.4,18.2±0.7 and 22.1±3.4mol· kg^–1· min^–1 before treatment in the diabetic subjects, and 11.8±1.7, 20.9±3.3 and 30.1±3.6 after treatment. These values compare with those in the euglycaemic control subjects (13.4±0.7, 18.7±1.6 and 36.3±2.7 mol · kg^–1· min^–1). The pre-treatment metabolic clearance rate of glucose in all diabetic studies with insulin levels >30mU/l was 2.6 ±0.4 and rose to 3.9 ±0.5 ml· kg^–1· min^–1 following insulin therapy. This was significantly lower than in the control subjects (6.7±0.8 ml· kg^–1 · min^–1; p<0.005). Basal nonesterified fatty acid levels were high in the untreated, but normal in the treated diabetic subjects, and fell in response to insulin infusion. Basal -hydroxybutyrate levels were high in both diabetic groups, but also fell in response to insulin infusion. Erythrocyte insulin receptor binding was normal in the untreated diabetic subjects, and was not changed by treatment. Therefore, treatment of newly diagnosed Type 1 diabetic subjects with insulin reverses the hepatic insensitivity to insulin. In contrast, treatment only partially improves peripheral glucose disposal. Since erythrocyte insulin receptor binding is normal, it is likely that a post-receptor defect in peripheral glucose metabolism exists in Type 1 diabetic patients despite insulin therapy and good diabetic control for a period of 1 week.     

The course and determinants of insulin action in Type 1 (insulin-dependent) diabetes mellitus

Summary The course and determinants of insulin action were investigated in 8 newly diagnosed Type 1 (insulin-dependent) diabetic patients, who were studied every 3 months for one year, and in three groups of 8 patients each with 5, 10 and 20 years diabetes, studied once. Fifteen healthy subjects matched for age, sex and body weight served as control subjects. Dose-response curves were constructed using sequential euglycaemic (5.0 mmol/l) clamps (insulin infusion rates: 0.5, 1.0, 2.0 and 5.0 mU·kg^–1·min^–1 in periods of 2h). After 1/2 month of insulin treatment, insulin responsiveness was normal, but sensitivity was decreased (ED₅₀ 70±7 mU/l (SEM) vs 54±4mU/l in control subjects, p<0.05). After 6 months, insulin sensitivity was improved (ED₅₀ 57±4 mU/l, p<0.01 vs 1/2 month and not significant (NS) vs control subjects); but after 9 and 12 months, it was reduced again, similarly to 0.5 month. Insulin responsiveness remained normal at all time-points. In the three groups of patients with longstanding diabetes, impaired insulin sensitivity with normal responsiveness was noted also (ED₅₀ 73±9 mU/l, p<0.02 vs control subjects). At 6, 9 and 12 months, glycaemic control (HbA₁) and insulin dose were inverse correlates for insulin action; in patients with longstanding disease, this was noted for HbA₁ and body weight, in control subjects for body weight. In conclusion, decreased insulin sensitivity re-develops in Type 1 diabetes within the first year following an initial improvement. Presumably, hyperglycaemia plays a role in the pathogenesis of this recurrence.     

Hepatic and peripheral insulin resistance: A common feature of Type 2 (non-insulin-dependent) and Type 1 (insulin-dependent) diabetes mellitus

Summary Hepatic glucose production (³H-glucose technique) and insulin-mediated glucose uptake (insulin clamp technique) were measured in 38 Type 2 (non-insulin-dependent) and 11 Type 1 (insulin-dependent) diabetic patients. Fasting plasma glucose concentration was 8.3 ± 0.5 mmol/l in the former, and 9.6 ± 1.3 mmol/1 in the latter group; the respective fasting plasma insulin levels were 19 ± 2 mU/l (p < 0.005 versus 13 ± 1 mU/l in 33 age-matched control subjects), and 9 ± 1 mU/l (p < 0.01 versus 14 ± 1 mU/l in 36 younger control subjects). In the fasting state, hepatic glucose production was slightly increased (15%, 0.1 > p > 0.05) in the Type 2 diabetic patients and markedly elevated (65%, p < 0.001) in the Type 1 patients compared with their respective control groups. In both groups of diabetic subjects, the rates of hepatic glucose production were inappropriately high for the prevailing plasma glucose and insulin levels, indicating the presence of hepatic resistance to insulin. Basal plasma glucose clearance was also significantly reduced in both the Type 2 (34%) and the Type 1 (14%) diabetic subjects. The fasting plasma glucose concentration correlated directly with hepatic glucose production, and inversely with plasma glucose clearance. During the insulin clamp, plasma insulin was maintained at approximately 100 mU/l in all groups, while plasma glucose was maintained constant at the respective fasting levels. Total glucose uptake was reduced in both the Type 2 (4.57 ± 0.31 versus 6.39 ± 0.25 mg · min^–1 · kg^–1 in the control subjects, p < 0.01) and the Type 1 (4.77 ± 0.48 versus 7.03 ± 0.22 mg · min^–1 · kg^–1, p < 0.01) diabetic patients. Insulin-stimulated glucose clearance was reduced to a similar extent in Type 2 (54%) and Type 1 (61%) diabetic subjects, and correlated directly with fasting glucose clearance. These results show that insulin resistance is a common feature of both types of diabetes and can be demonstrated in the basal as well as the insulin-stimlated state. Both hepatic and peripheral resistance to the action of insulin contribute to diabetic hyperglycaemia.     

Insulin resistance in Type 1 (insulin-dependent) diabetes: dependence on plasma insulin concentration

Summary Sensitivity to insulin in vivo was studied in six Type 1 diabetic patients without residual insulin secretion and without clinical insulin resistance, and in eight non-diabetic subjects, using the euglycaemic insulin clamp technique. Insulin was infused for four periods of 2 h sequentially at 0.5, 1.0, 2.0 and 5.0 mU · kg^-1 · min^-1; for each insulin infusion period the steady-state plasma free insulin levels were comparable in the diabetic and non-diabetic subjects. The mean ±SEM plasma glucose concentration was 4.9±0.03 mmol/l in the diabetic subjects (coefficient of variation of plasma glucose values: 5.7±0.7%) and 4.6±0.01 mmol/l in the control subjects (coefficient of variation: 5.1±0.6%). Insulin-mediated glucose disposal was lower in the diabetic than in the non-diabetic subjects at the two lower insulin infusion rates (mean±SEM = 2.03±0.27 versus 4.8±0.64 mg · kg^-1 · min^-1 at the first insulin infusion rate, p<0.01, and 5.59±0.59 versus 8.36±0.61 mg · kg^-1 · min^-1 at the second insulin infusion rate, p<0.01). However, insulin-induced glucose uptake did not differ significantly between the two groups at the third and fourth rates of insulin infusion. These results show that impaired insulin sensitivity in Type 1 diabetes is dependent on insulin concentration.     

In vivo insulin action and muscle glycogen synthase activity in Type 2 (non-insulin-dependent) diabetes mellitus: effects of diet treatment

Summary Insulin resistant glucose metabolism is a key element in the pathogenesis of Type 2 (non-insulin-dependent) diabetes mellitus. Insulin resistance may be of both primary (genetic) and secondary (metabolic) origin. Before and after diet-induced improvement of glycaemic control seven obese patients with newly-diagnosed Type 2 diabetes were studied with the euglycaemic clamp technique in combination with indirect calorimetry and forearm glucose balance. Muscle biopsies were obtained in the basal state and again after 3 h of hyperinsulinaemia (200 mU/l) for studies of insulin receptor and glycogen synthase activities. Similar studies were performed in seven matched control subjects. Insulin-stimulated glucose utilization improved from 110±11 to 183±23 mg·m^–2·min^–1 (p<0.03); control subjects: 219+23 mg·m^–2·min^–1 (p=NS, vs post-diet Type 2 diabetes). Nonoxidative glucose disposal increased from 74±17 to 138+19 mg·m^–2·min^–1 (p<0.03), control subjects: 159±22 mg· m^–2·m^–1 (p=NS, vs post-diet Type 2 diabetic patients). Forearm blood glucose uptake during hyperinsulinaemia increased from 1.58±0.54 to 3.35±0.23 mol·l^–1·min^–1 (p<0.05), control subjects: 2.99±0.86 mol·l^–1·min^–1 (p=NS, vs post-diet Type 2 diabetes). After diet therapy the increase in insulin sensitivity correlated with reductions in fasting plasma glucose levels (r=0.97, p<0.001), reductions in serum fructosamine (r=0.77, p<0.05), and weight loss (r=0.78, p<0.05). Values of muscle glycogen synthase sensitivity to glucose 6-phosphate (A_0.5 for glucose 6-phosphate) were similar in the basal state. However, insulin stimulation of glycogen synthase was more pronounced after diet treatment (A_0.5: 0.43±0.06 (before) vs 0.30±0.04 mmol/l (after); p<0.03; control subjects: 0.22±0.03 mmol/l). Muscle insulin receptor binding and kinase activity were similar before and after diet treatment and comparable to values in the control group. The data suggest that impaired insulin stimulation of in vivo glucose turn-over and muscle glycogen synthase activity tend to be restored during successful diet treatment of patients with Type 2 diabetes.     

The relationship of acute insulin sensitivity to the progression of vascular disease in long-term Type 1 (insulin-dependent) diabetes mellitus

Summary In 51 individuals with Type 1 (insulin-dependent) diabetes mellitus initially of more than 15 years' duration, the acute hypoglycaemic effect of intravenous insulin (0.11 IU/ kg) was related to outcome over 18 years. This acute insulin sensitivity, or glucose assimilation index, was reproducible over the period of study.At 18-year follow-up, initial low glucose assimilation index (<0.082 mmol·1^–1· min^–1 was significantly (p<0.01) associated with death from vascular disease. Low glucose assimilation index was similarly significantly (p<0.01) associated with progression of atherosclerotic disease, but not with microangiopathy alone. Hypertension (systolic blood pressure > 150mmHg and/or diastolic blood pressure > 95 mmHg) was the only other parameter significantly (p<0.01) related to outcome, but this relationship was no longer significant once glucose assimilation index had been taken into account. A linear logistic analysis confirmed that acute insulin sensitivity was independently associated with outcome. Neither initial clinical control of diabetes nor glycosylated haemoglobin level in the 26 survivors was related to vascular prognosis.     

Optimization of basal insulin delivery in Type 1 diabetes: a retrospective study on the use of continuous subcutaneous insulin infusion and insulin glargine.

AIMS: To compare the effects on glycaemic control after using continuous subcutaneous insulin infusion (CSII) or insulin glargine. METHODS: Data were obtained from 17 diabetes outpatient clinics in Sweden, employing the same diabetes data management system. Type 1 diabetic patients using multiple dose injections were included prior to starting on either CSII (n = 563) or glargine (n = 513). The median duration of therapy was 25 months for CSII and 6 months for glargine. The comparison between the treatment modalities was carried out by multiple regression analysis and logistic regression analysis in an attempt at reducing the influence of confounding factors. RESULTS: The mean HbA1c decrease was 0.59 +/- 1.19% for CSII and 0.20 +/- 1.07% for glargine (P < 0.001, when assessed by logistic regression). An additional 0.1% lower HbA1c would be expected if glargine had been optimized with basal insulin 40-60% of the daily dose. The more pronounced effect of CSII was achieved with a lower daily dosage of insulin. In a multiple regression analysis with a change of HbA1c as the dependent variable, the following variables were significant: choice of treatment (P < 0.001), HbA1c prior to treatment (P < 0.001) and BMI prior to treatment (P < 0.01). CONCLUSION: Both regimes improved metabolic control, but CSII resulted in significantly higher reduction in HbA1c than after insulin glargine treatment, particularly in those individuals who had higher levels of HbA1c at baseline.     

Nocturnal spikes of growth hormone secretion cause the dawn phenomenon in Type 1 (insulin-dependent) diabetes mellitus by decreasing hepatic (and extrahepatic) sensitivity to insulin in the absence of insulin waning

Summary The aim of the present studies was to test the hypothesis that the dawn phenomenon in Type 1 (insulin-de-pendent) diabetes mellitus is due to a decrease in insulin sensitivity caused by nocturnal spikes of growth hormone. Twelve subjects with Type 1 diabetes were studied on two different occasions, from 24.00 to 02.00 hours, and from 06.00 to 08.00 hours with the euglycaemic clamp technique at two plasma free insulin levels (25 mU/l,n=7; 80 mU/l,n=5). To eliminate the confounding factor of insulin waning of previous Biostator studies, prior to clamp experiments the diabetic subjects were infused with i.v. insulin by means of a syringe pump according to their minute-to-minute insulin requirements. Insulin sensitivity decreased at dawn as compared to the early night hours (30% increase in the rate of hepatic glucose production, 25% decrease in the rate of peripheral glucose utilisation). Plasma insulin clearance did not change overnight. In seven Type 1 diabetic subjects, suppression of nocturnal spikes of growth hormone secretion by somatostatin during basal glucagon and growth hormone replacement resulted in complete abolition of the increased rate of hepatic glucose production at dawn. Replacement of nocturnal spikes of growth hormone faithfully reproduced the increase in hepatic glucose production at dawn of the control study. It is concluded that the dawn phenomenon in Type 1 diabetes mellitus examined during optimal insulin replacement, first, is due solely to a decrease in insulin sensitivity and not to an increase in insulin clearance; second, that the decrease in insulin sensitivity at dawn takes place both in the liver and peripheral tissues; third, that the decrease in hepatic (and most likely extrahepatic) insulin sensitivity at dawn is caused by nocturnal spikes of growth hormone secretion.     

胰岛素泵治疗儿童1型糖尿病疗效观察

目的 观察胰岛素泵持续皮下输注短效胰岛素(CSII)对儿童1型糖尿病(T1DM)的治疗效果。方法 ①胰岛素泵持续皮下输注CSII治疗6例传统胰岛素治疗(CIT)血糖控制不满意的TDM患儿。并比较其用泵前后空腹血糖(FBG)、餐后2小时血糖(2hPBG)、糖化血红蛋白(HbAk)、胰岛素(INS)用量、胆固醇(CH)及甘油三酯(FG)的变化；②治疗组用泵后上述代谢指标与33例正常对照组比较。结果 ①治疗组用泵后FBG、2hPBG、HbAk、INS用量、TG均较用泵前显著降低；用泵后INS用量减少16％；用泵后患儿依从性增高。②治疗组用泵后FBG、CH及TG均较正常对照组无差异，2hPBG、HbAk仍显著高于正常对照，但均达到强化治疗目的。结论 ①CSII治疗儿童TDM可显著改善其代谢指标，使血糖和血脂降至正常和接近正常。②CSII治疗儿童通过改善HbAk及血脂TDM，可延缓其慢性并发症的发生。     

Metformin increases insulin sensitivity and basal glucose clearance in Type 2 (non-insulin dependent) diabetes mellitus

Abstract The effects of metformin on glycaemia, insulin and c-peptide levels, hepatic glucose production and insulin sensitivity (using the euglycaemic, hyperinsulinaemic clamp) were evaluated at fortnightly intervals in 9 Type 2 diabetic patients using a stepwise dosing protocol: Stage 1 - no metformin for four weeks; stage 2 - metformin 500mg mane; stage 3 - metformin 500mg thrice daily; stage 4 – metformin 1000mg thrice daily. Results are expressed as Mean ± SEM. Fasting blood glucose decreased from basal values (9.7 ±1.0 mmol/L) by 13% at stage 2, 34% at stage 3 and 41% at stage 4 (p<0.02 vs basal for all stages; p<0.02 stage 2 vs stage 3). Post-prandial glycaemia was significantly improved only with metformin 3000mg/day (p<0.05). Fasting, meal-stimulated and total insulin and c-peptide levels showed no change. Hepatic glucose output did not change significantly with metformin. Insulin sensitivity, measured as total glucose utilisation during hyperinsulinaemia, increased from stage 1 (10.3 ± 2.1 μmoL/kg/min) by 23% at stage 3 (p < 0.05) and by 29% at stage 4 (p < 0.02). Basal metabolic clearance of glucose increased compared to stage 1 (1.69 ±0.16 mL/kg/min) by 30% at stage 2, 53% at stage 3 and 44% at stage 4 (all p <0.02). This study demonstrates that improved efficiency of glucose utilisation, both basally and under conditions of euglycaemic hyperinsulinaemia, is the basis of metformin's antihyperglycaemic action.     

Predictors of insulin sensitivity in Type 2 diabetes mellitus.

AIMS: To identify the independent predictors of insulin sensitivity in Type 2 diabetes, and to establish whether isolated Type 2 diabetes (i.e. diabetes without overweight, dyslipidaemia and hypertension) is a condition of insulin resistance. METHODS: We examined 45 patients with non-insulin-treated Type 2 diabetes undergoing a 4-h euglycaemic hyperinsulinaemic clamp (20 mU/m2 per min) combined with 3H-3-D-glucose and 14C-U-glucose infusions and indirect calorimetry. We also examined 1366 patients with non-insulin-treated Type 2 diabetes randomly selected among those attending the Diabetes Clinic and in whom insulin resistance was estimated by Homeostasis Model Assessment (HOMA-IR). RESULTS: In the 45 patients undergoing glucose clamp studies, insulin-mediated total glucose disposal (TGD) was independently and negatively associated with systolic blood pressure (standardized beta coefficient = -0.407, P = 0.003), plasma triglycerides (beta= -0.355, P = 0.007), and HbA1c (beta= -0.350, P = 0.008). The overall variability of TGD explained by these variables was 53%. Overweight diabetic subjects with central fat distribution, hypertension, hypertriglyceridaemia and poor glycometabolic control had insulin-mediated TGD values markedly lower than their lean counterparts without hypertension, with normal triglycerides, and with good glycometabolic control (16 +/- 5 vs. 31 +/- 10 micromol/min per kg lean body mass, P < 0.01). Nevertheless, the latter still were markedly insulin-resistant when compared with sex- and age-matched non-diabetic control subjects (31 +/- 10 vs. 54 +/- 13 micromol/min per kg lean body mass, P < 0.01). In the 1366 Type 2 diabetic patients of the epidemiological study, HOMA-IR value was independently associated with HbA1c (beta = 0.283, P < 0.0001), plasma triglycerides (beta = 0.246, P < 0.0001), body mass index (beta = 0.139, P < 0.001), waist girth (beta = 0.124, P < 0.001) and hypertension (beta = 0.066, P = 0.006). CONCLUSION: Overweight, central fat distribution, dyslipidaemia, hypertension and poor glycometabolic control are strong independent predictors of insulin resistance in Type 2 diabetes. However, reduced insulin sensitivity can be found even when Type 2 diabetes is isolated and well controlled.     

Expression of glycogen synthase and phosphofructokinase in muscle from Type 1 (insulin-dependent) diabetic patients before and after intensive insulin treatment

Summary The aim of the present study was to determine whether short-term appropriate insulinization of Type 1 (insulin-dependent) diabetic patients in longterm poor glycaemic control (HbA_1C>9.5%) was associated with an adaptive regulation of the activity and gene expression of key proteins in muscle glycogen storage and glycolysis: glycogen synthase and phosphofructokinase, respectively. In nine diabetic patients biopsies of quadriceps muscle were taken before and 24-h after intensified insulin therapy and compared to findings in eight control subjects. Subcutaneous injections of rapid acting insulin were given at 3-h intervals to improve glycaemic control in diabetic patients (fasting plasma glucose decreased from 20.8±0.8 to 8.7±0.8 mmol/l whereas fasting serum insulin increased from 59±8 to 173±3 pmol/l). Before intensified insulin therapy, analysis of muscle biopsies from diabetic patients showed a normal total glycogen synthase ctivity but a 48% decrease (p=0.006) in glycogen synthase fractional velocity (0.1 mmol/l glucose 6-phosphate) (FV_0.1) and a 45% increase (p=0.01) in the half-maximal activation constant of glycogen synthase (A_0.5). The activity of phosphofructokinase and the specific mRNA and immunoreactive protein levels of both glycogen synthase and phosphofructokinase were similar in the two groups. The 2.8-fold increase in serum insulin levels and the halving of the plasma glucose level for at least 15 h were associated with a normalization of glycogen synthase fractional activity (FV_0.1) and of the half-maximal activation constant (A_0.5) whereas the enzyme activity of phosphofructokinase and the mRNA and protein levels of both glycogen synthase and phosphofructokinase remained normal. In conclusion: 1) Reduced allosterical activation of glycogen synthase in muscle of Type 1 diabetic patients in poor metabolic control occurs in the presence of normal total activity as well as normal immunoreactive protein mass and mRNA level of glycogen synthase. 2) Changes in serum insulin within the physiological range play no role in the short-term regulation of glycogen synthase mRNA and protein abundance in muscle from Type 1 diabetic patients.     

Decreased hepatic glucagon responses in Type 1 (insulin-dependent) diabetes mellitus

Summary The effect of glucagon infusion on hepatic glucose production during euglycaemia was evaluated in seven Type 1 (insulin-dependent) diabetic patients and in ten control subjects. In the diabetic subjects normoglycaemia was maintained during the night preceding the study by a variable intravenous insulin and glucose infusion. During the study endogenous insulin secretion was suppressed by somatostatin (450 g/h) and replaced by insulin infusion (0.15 mU·kg^–1·min^–1). ³H-glucose was infused for isotopic determination of glucose turnover. Plasma glucose was clamped at 5 mmol/1 for 2 h 30 min and glucagon (1.5 ng· kg^–1·min^–1) was then infused for the following 3 h. Hepatic glucose production and glucose utilisation were measured during the first, second and third hour of the glucagon infusion. Basal hepatic glucose production (just prior to glucagon infusion) was similar in diabetic (1.2±0.3 mg·kg^–1·min^–1) and control (1.6±0.1 mg·kg^–1·min^–1) subjects. In diabetic patients hepatic glucose production rose slowly to 2.1±0.5 mg·kg^–1·min^–1 during the first hours of glucagon infusion and stabilized at this level (2.4±0.5 mg·kg^–1·min^–1) in the third hour. In control subjects hepatic glucose production increased sharply to higher levels than in the diabetic subjects (3.4±0.3 mg·kg^–1·min^–1) during the first and second hour of glucagon infusion (p<0.05) and then gradually fell (2.9±0.4 mg·kg^–1·min^–1) during the third hour. In conclusion, when stimulated with glucagon at a physiologic plasma concentration diabetic patients had 1) an overall reduced hepatic glucose production response and 2) an abnormal sluggish response pattern. These abnormalities may imply inappropriate counter-regulation following a hypoglycaemic episode.     

Pathogenesis of Type 2 (non-insulin-dependent) diabetes mellitus: candidates for a signal transmitter defect causing insulin resistance of the skeletal muscle

Summary Insulin resistance of skeletal muscle, liver and fat combined with an abnormality of insulin secretion characterizes Type 2 (non-insulin-dependent) diabetes mellitus. There is increasing evidence that the insulin resistance of the skeletal muscle plays a key role early in the development of Type 2 diabetes. As a consequence recent research efforts have focussed on the characterization of insulin signal transduction elements in the muscle which are candidates for a localization of a defect causing insulin resistance i.e. the insulin receptor, phosphatases related to insulin action, glycogen synthase and the glucose transporters. In this review we attempt to summarize present knowledge about abnormalities of these systems in skeletal muscle of Type 2 diabetic and pre-diabetic individuals. We try to classify abnormalities as secondary events or as candidates for putative primary molecular defects which might initiate the development of insulin resistance as early as in the pre-diabetic state.     

Altered islet Beta-cell function before the onset of Type 1 (insulin-dependent) diabetes mellitus

Summary To define the glucose to insulin dose-response relationship before the onset of diabetes, we studied 22 nondiabetic co-twins of patients with Type 1 (insulin-dependent) diabetes mellitus and nine control subjects. All had intravenous glucose tests at 0.02, 0.1 and 0.5 g/kg and were followedup prospectively for at least 6 years. Seven twins developed diabetes a mean of 7 months later; the remaining 15 are now unlikely to develop diabetes. The seven pre-diabetic twins had higher fasting insulin levels than control subjects (4.2±2.0 vs 1.8±1.8 nmol/l; p<0.05); but lower glucose clearance (1.0±0.5 vs 1.9±0.7 %/min; p<0.05), first phase insulin response at 0.5 g/kg (21.1±23.2 vs 143±50 nmol/l; p<0.0001), and total insulin responses at 0.1 g/kg (p<0.05) and 0.5 g/kg (p<0.00005). Using a curve-fitting programme, the normal glucose to insulin relationship was lost in prediabetic twins who had lower coefficient of determination (R²) than control subjects (p<0.01). In contrast, 15 low-risk twins and their nine control subjects had similar fasting glucose and insulin levels, glucose clearance, R² and insulin secretory responses to different glucose loads. The positive predictive values of subnormal R² and subnormal first phase insulin response were 67 % and 58 % respectively. These observations demonstrate an altered glucose to insulin dose-response relationship and loss of maximum insulin secretory response to glucose before the onset of Type 1 diabetes.