Insulin-resistant Diabetic Patients Research Articles

Investigation of the clinical outcomes of long-term vitamin D supplementation in Egyptian Type 2 Diabetes Mellitus patients

Background: Diabetes mellitus (DM) is a group of metabolic disorders Characterized by chronic hyperglycaemic condition resulting from defects in insulin secretion, insulin action or both. Type2 Diabetes Mellitus (T2DM) is the predominant form of diabetes and represent 90% of all cases of DM. Studies show that vitamin D (VD) has an important role in modifying the risk of T2DM, especially among insulin resistant diabetic patients. Recently a novel association between insulin resistance and vitamin D deficiency has been proposed. Aim: In the current research we investigate the association between hypovitaminosis D and T2DM. Also we will study the effect of vitamin D supplementation on glycemic status, oxidative stress status and inflammatory markers in T2DM patients. Methods and patients: forty T2DM patients with hypovitaminosis D were assessed for glycemic, inflammatory and antioxidants parameters. After 6 months of VD supplementation for the intervention group of patients (n=20), there was significant improvement in VD level, Homeostatic model assessment of insulin resistance (HOMA - IR), Fasting blood glucose (FBG), glycated haemoglobin (HbAIC), serum insulin, interleukin 6 (IL-6), tumor necrosis factor -α (TNF-α), total antioxidant capacity (TAC) and malondialdehyde (MDA). Conclusion: Vitamin D supplementation has a promising effect on the treatment of Type 2 Diabetes as there is a significant improvement in glycemic , inflammatory and oxidative parameters in Type 2 Diabetes mellitus patients

206-OR: Generation of Induced Pluripotent Stem Cells Derived from a Patient with PIK3R1 Mutation and Analysis of Defects in Insulin Action in Hepatocytes Differentiated from These Cells

Background: A protocol of differentiation form induced pluripotent stem cells (iPSCs) to hepatocytes has been previously reported, and such iPSCs-derived hepatocytes possessed morphological and biochemical characteristics similar to authentic hepatocytes. It is however unknown whether iPSCs-derived hepatocytes normally respond to metabolic regulatory hormones including insulin. Mutations in the gene for p85α subunit of PI3K (PIK3R1), an essential element of insulin action, give rise to severe insulin resistance in human. Such cases are very rare, and only ∼30 families with PIK3R1 mutations have been reported as of today. Methods and Results: We established a protocol of differentiation from iPSCs to hepatocytes that respond to insulin. In hepatocytes differentiated from iPSCs derived from healthy subject with this protocol, phosphorylation of AKT and the expression of the lipogenic genes FASN as well as SREBF1c were induced by insulin. Furthermore, the expression of the gluconeogenic gene G6PC was upregulated by a combination of cAMP and dexamethasone, which was markedly impaired by the addition of insulin. We then generated iPSCs from a severe insulin resistant diabetic patient with the PIK3R1 c.1945C>T mutation, a hot-spot mutation in this gene. Insulin-induced gene expression along with phosphorylation of AKT was impaired in hepatocytes differentiated from the patient-derived iPSCs. We also repaired the mutation of PIK3R1 in the patient-derived iPSCs by the CRISPR/Cas9 genome editing. Insulin responsiveness was recovered in hepatocytes differentiated from the resultant iPSCs in which the mutation was repaired. Conclusion: We established a differentiation protocol of hepatocytes in which insulin’s metabolic actions can be evaluated. The usefulness of this protocol was validated with the use of iPSCs derived from a severe insulin-resistant patient with PIK3R1 mutation. Disclosure T. Hamaguchi: None. Y. Hirota: Other Relationship; Self; Sanofi. T. Takeuchi: None. M. Koyanagi-Aoi: None. T. Aoi: None. W. Ogawa: Research Support; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharma GmbH & Co.KG, Eli Lilly Japan K.K., Kowa Company, Ltd., Nippon Boehringer Ingelheim Co. Ltd., Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd. Other Relationship; Self; Sumitomo Dainippon Pharma Co., Ltd., Takeda Pharmaceutical Company Limited.

2195-PUB: Use of U500 Insulin in External Pump for Insulin-Resistant Diabetic Patients: A French Experience

Use of large insulin doses is more frequent in diabetes due to an increase in the prevalence of severe obesity worlwide. Insulin-associated treatments such as metformin or GLP-1 receptor agonists (GLP-1RA) can help and use of insulin concentrated at 500 IU/ml (U500) has been associated with an improve in glycemic control in previous studies including severe insulin resistant patients. We report our experience of U500 in subjects with high HbA1c despite insulin pump therapy (CSII) combined or not with metformin and/or GLP-1RA. Eighteen T2D and 3 T1D were studied (13M and 8F), age: 59.5 ± 9.6 years, diabetes duration : 18.8 ± 9.8 years. Eight subjects used metformin and 7 used GLP-1RA (5 used metformin and GLP-1RA). Treatment with U500 was carried out during a 5-day hospitalization. Metformin and/or GLP-1RA were continued or not during the follow-up according to the decision of the patient’s diabetologist. Mean duration of follow-up was 9 months. A decrease in HbA1c was found (initial vs. final) : 9.4 ± 1.2% vs. 8.5 ± 1.3% (p =0.05). No change was found for weight : 123.9 ± 26.4 kg vs. 121.0 ± 30.3 kg (NS), BMI : 41.5 ± 7.2 kg/m2 vs. 40.2 ± 7.3kg/m2 (NS), daily total insulin needs (U100 equivalent) : 198.4 ± 70.5 IU vs. 228 ± 121 IU (NS), basal needs : 81.8 ± 29.2 IU vs. 87 ± 36 IU (NS) and prandial needs : 116.5 ± 61.3 IU vs. 143 ± 110 IU (NS). No changes were found for lipidic parameters as total cholesterol (TC) : 1.85 ± 1.10 g/l vs. 1.80 ± 0.92 g/l (NS), HDL-C : 0.36 ± 0.08 g/l vs. 0.31 ± 0.06 g/l (NS), LDL-C : 0.83 ± 0.32 g/l vs. 0.71 ± 0.30 g/l (NS) and TG : 3.98 ± 7.56 g/l vs. 3.4 ± 5.3 g/l (NS). No change in use of metformine and/or GLP-1RA and no side effect were found during the follow-up. Conclusion: In our practice, use of U500 in insulin-resistant patients treated with CSII is well tolerated and is associated with a decrease in HbA1c despite no change in weight or daily insulin needs. Evolution of glycemic variability (including TIR and hypoglycemias) using continuous glucose monitoring is currently being analyzed. Disclosure Y. Oualit: None. D. Pâris: Board Member; Self; Novo Nordisk Inc. Consultant; Self; Eli Lilly and Company, Sanofi-Aventis. L. Kessler: Consultant; Self; Lilly Diabetes, Medtronic, Novartis Pharma K.K., Novo Nordisk A/S, Vertex Pharmaceuticals. T. Bahougne: None. N. Jeandidier: Consultant; Self; Sanofi-Aventis. Research Support; Self; Lilly Diabetes. L. Meyer: Board Member; Self; Abbott, Lilly Diabetes, Novo Nordisk A/S.

Cardiovascular responses to sugary drinks in humans: galactose presents milder cardiac effects than glucose or fructose.

There is increasing interest into the potentially beneficial effects of galactose for obesity and type 2 diabetes management as it is a low-glycemic sugar reported to increase satiety and fat mobilization. However, fructose is also a low-glycemic sugar but with greater blood pressure elevation effects than after glucose ingestion. Therefore, we investigated here the extent to which the ingestion of galactose, compared to glucose and fructose, impacts upon haemodynamics and blood pressure. In a randomized cross-over study design, 9 overnight-fasted young men attended 3 separate morning sessions during which continuous cardiovascular monitoring was performed at rest for at least 30min before and 120min after ingestion of 500mL of water containing 60g of either glucose, fructose or galactose. These measurements included beat-to-beat systolic and diastolic blood pressure, heart rate deduced by electrocardiography, and stroke volume derived by impedance cardiography; these measurements were used to calculate cardiac output and total peripheral resistance. Ingestion of galactose, like glucose, led to significantly lesser increases in systolic, diastolic and mean blood pressure than fructose ingestion (p<0.05). Furthermore, the increase in cardiac output and reduction in total peripheral resistance observed after ingestion of glucose were markedly lower after galactose ingestion (p<0.01). Galactose thus presents the interesting characteristics of a low-glycemic sugar with mild cardiovascular effects. Further studies are warranted to confirm the clinical relevance of the milder cardiovascular effects of galactose than other sugars for insulin resistant obese and/or diabetic patients with cardiac insufficiency.

The Relationship between Type 2 Diabetes and Total Ghrelin Level in a Population Sample in the United Arab Emirates

There is a debate about the relation between ghrelin and insulin. Many researchers have found low ghrelin level in diabetic patients while others claim that no correlation between them. Thus further investigations are needed to clarify the precise role of ghrelin in the development and/ or treatment of diabetes. To date and up to our knowledge, this is the first study to be conducted on Emirati people in the United Arab Emirates (UAE) to explore the relationship between ghrelin concentration and type 2 diabetes. This research aimed for better understanding about the role of ghrelin hormone in the pathogenesis process of diabetes disease, in an attempt to help patients who find it difficult to control their diabetes by studying the relation between serum total ghrelin levels; insulin and insulin resistance in patients with type 2 diabetes mellitus in the UAE and relate them to the glycemic condition. A cross sectional study was conducted at Rashid Centre for Diabetes and Research (RCDR) in Ajman, UAE. Thirty patients were selected from the outpatient clinic at RCDR and fifteen healthy controls were included in this study. The Blood sample was collected from each participant and analyzed for HbA1c, insulin, glucose and total ghrelin level. Ghrelin level was measured using the enzyme-linked immunosorbent assay (ELISA) technique. The results of this study showed that mean ghrelin level was low in both insulin-resistant and noninsulin resistant diabetic patients as compared to the control group. In conclusion, low ghrelin level is associated with poor diabetes control and bad prognosis parameters in type 2 diabetic patients.

Lack of consistency between two commercial ELISAs and against an in-house ELISA for the detection of CD36 in human plasma

CD36 is a widely expressed cell surface receptor, that among other ligands binds lipoproteins, and its function has been implicated in many of the complications belonging to the metabolic syndrome. We have previously identified a circulating form of CD36 and established an in-house ELISA assay for measurement of CD36 in plasma. Plasma CD36 was elevated in insulin resistant obese and diabetic patients, and in patients with unstable atherosclerotic plaques. The objective of this study was to compare two new commercial CD36 ELISA assays and our in-house ELISA assay. CD36 was measured in 30 plasma samples from 10 individuals by the in-house and the two commercial assays (Cusabio Biotech and Adipobioscience). Our results demonstrate that there is an absolute incongruity between the three assays. The incongruity could not be explained by different pre-analytical procedures in assay protocols. The lack of correlation indicates that measurement of CD36 levels in plasma is not trivial. The two commercial assays are not appropriate for CD36 detection in plasma and it seems unlikely that the established pathophysiological association with elevated plasma CD36 can be reproduced.

Insulin-resistant conditions: A favorable milieu for aggressive drug-resistant malignancies.

Insulin-resistant conditions: A favorable milieu for aggressive drug-resistant malignancies.

Successful Management of Extremely Insulin-Resistant Obese Diabetic Patient with Insulin Glargine, U-500 Regular Insulin and Pramlintide

Treating diabetes in obese patients is extremely challenging. Recently, physician’s use of U-500 regular insulin has increased to treat diabetes in this population. Here we report the use of the combination – insulin glargine, U-500 regular insulin and pramlintide to successfully manage type 2 diabetes in an extremely obese patient with a BMI of 54, A1C of 10.6 and a C-peptide level of 3.5 that indicated insulin resistance. With use of this combination of three drugs we were able to reduce the total number of drugs needed to manage patient’s diabetes from five to three, thereby also improving the likelihood of compliance.

Extreme Insulin Resistance: Indications and Approaches to the Use of U-500 Insulin in Type 2 Diabetes Mellitus

The use of U-500 insulin in the management of highly insulin resistant diabetic patients is growing. There are a number of reports that have noted the effects of U-500 insulin using multiple daily injections or continuous subcutaneous insulin infusion on hemoglobin A(1c), weight, and total daily insulin dosage. The effect of U-500 insulin use on glycemic control, changes in body weight, total daily insulin dosage, incidence of hypoglycemia, and effect on lipid levels and blood pressure as well as patient satisfaction and quality of life will be reviewed. In addition, this article will delineate algorithms of U-500 use, compare multiple daily injections or continuous subcutaneous insulin infusion, and discuss U-500 insulin pharmacokinetics.

Pre‐operative carbohydrate loading may be used in type 2 diabetes patients

Post-operative insulin resistance and hyperglycaemia are associated with an impaired outcome after surgery. Pre-operative oral carbohydrate loading (CHO) reduces post-operative insulin resistance with a reduced risk of hyperglycaemia during post-operative nutrition. Insulin-resistant diabetic patients have not been given CHO because the effects on pre-operative glycaemia and gastric emptying are unknown. Twenty-five patients (45-73 years) with type 2 diabetes [glycated haemoglobin (HbA1c) 6.2 +/- 0.2%, mean +/- SEM] and 10 healthy control subjects (45-72 years) were studied. A carbohydrate-rich drink (400 ml, 12.5%) was given with paracetamol 1.5 g for determination of gastric emptying. Peak glucose was higher in diabetic patients than in healthy subjects (13.4 +/- 0.5 vs. 7.6 +/- 0.5 mM; P<0.01) and occurred later after intake (60 vs. 30 min; P<0.01). Glucose concentrations were back to baseline at 180 vs. 120 min in diabetic patients and healthy subjects, respectively (P<0.01). At 120 min, 10.9 +/- 0.7% and 13.3 +/- 1.2% of paracetamol remained in the stomach in diabetic patients and healthy, subjects respectively. Gastric half-emptying time (T50) occurred at 49.8 +/- 2.2 min in diabetics and at 58.6 +/- 3.7 min in healthy subjects (P<0.05). Neither peak glucose, glucose at 180 min, gastric T50, nor retention at 120 min differed between insulin (HbA1c 6.8 +/- 0.7%)- and non-insulin-treated (HbA1c 5.6 +/- 0.4%) patients. Type 2 diabetic patients showed no signs of delayed gastric emptying, suggesting that a carbohydrate-rich drink may be safely administrated 180 min before anaesthesia without risk of hyperglycaemia or aspiration pre-operatively.

Ocular Disorders Secondary to Systemic Disease and the Potential Role of Carnitines

L-carnitine has a wide-ranging role in several physiological processes, but perhaps most significantly in long-chain fatty acid oxidation in the mitochondrial matrix. Osmolytic (or osmoprotective) properties have also been suggested for the compound. Importantly, the ability of L-carnitine to improve insulin sensitivity in insulin-resistant diabetic patients may, together with the agent's antioxidant and antiapoptotic activity, provide some degree of protection against the progression of diabetic retinopathy. L-carnitine may also protect against the deleterious effects of ocular ischaemic syndrome, and, indeed, acetyl-L-carnitine has been shown to significantly improve retinal damage and visual acuity in patients with monolateral or bilateral retinal artery occlusion. The antioxidant, antiapoptotic and osmolytic properties of L-carnitine also suggest that this agent may have valuable clinical utility in neurotrophic keratopathy and bullous keratopathy. Thus, further detailed investigation of the important clinical potential of L-carnitine in various ocular conditions (e.g. diabetic retinopathy, ocular ischaemic syndrome, neurotrophic keratopathy and bullous keratopathy) that occur secondary to systemic diseases is now clearly warranted.

Thiazolidinediones: A novel class of drugs for the prevention of diabetic nephropathy?

Diabetic nephropathy is the leading cause of end-stage renal disease. Novel preventive measures for diabetic renal complications are urgently needed. Miyazaki et al. report that rosiglitazone, a thiazolidinedione insulin sensitizer and a potent peroxisome proliferator-activated receptor gamma agonist, not only effectively improves glycemic control but also halts progression of albuminuria in type 2 diabetic patients with early-stage diabetic nephropathy. These findings could offer a new prevention of diabetic nephropathy in insulin-resistant diabetic patients.

Identification of a novel class of dithiolethiones that prevent hepatic insulin resistance via the adenosine monophosphate-activated protein kinase-p70 ribosomal S6 kinase-1 pathway

Several established liver diseases of various causes are highly associated with hepatic insulin resistance, which is characterized by the desensitization of target cells to insulin. Peripheral insulin resistance is observed in most patients who have cirrhosis. Conversely, insulin-resistant diabetic patients are at increased risk for developing liver disease. Current therapeutic interventions in insulin resistance are limited and therefore likely to be advanced by new tailor-made drugs. Oltipraz, a prototype dithiolthione, inhibits transforming growth factor beta1 and has the ability to regenerate cirrhotic liver. We investigated the effects of oltipraz and synthetic dithiolthiones on hepatic insulin resistance and the molecular basis of action. Oltipraz and other dithiolethione compounds were tested on tumor necrosis factor alpha (TNF-alpha)-induced insulin resistance and glucose homeostasis in vitro and in vivo via immunoblotting, plasmid transfection, kinase analysis, and functional assays. Oltipraz treatment inhibited the ability of TNF-alpha to activate p70 ribosomal S6 kinase-1 (S6K1) downstream of mammalian target of rapamycin, thus preventing insulin receptor substrate-1 serine phosphorylation and protecting insulin signals. Moreover, oltipraz activated AMP-activated protein kinase (AMPK), whose inhibition by a dominant negative mutant abolished S6K1 inhibition and protected insulin signaling, indicating that AMPK activation leads to S6K1 inhibition. In hepatocyte-derived cell lines, oltipraz inhibited glucose production. Oltipraz prevented hepatic insulin resistance in C57BL/6 mice challenged with endotoxin (or TNF-alpha), leptin-deficient mice, and mice fed a high-fat diet. Synthetic dithiolethiones comparably inhibited insulin resistance. Our findings led to the identification of dithiolethione compounds that prevent insulin resistance through a mechanism involving AMPK-mediated S6K1 inhibition and thereby sensitize hepatic insulin response.

Dyslipidaemia in type 2 diabetes: a panel discussion

Dyslipidaemia in type 2 diabetes: a panel discussion

Leptin Induces Mitochondrial Superoxide Production and Monocyte Chemoattractant Protein-1 Expression in Aortic Endothelial Cells by Increasing Fatty Acid Oxidation via Protein Kinase A

Leptin, a circulating hormone secreted mainly from adipose tissues, is involved in the control of body weight. The plasma concentrations are correlated with body mass index, and are reported to be high in patients with insulin resistance, which is one of the major risk factors for cardiovascular disease. However, the direct effect of leptin on vascular wall cells is not fully understood. In this study, we investigated the effects of leptin on reactive oxygen species (ROS) generation and expression of monocyte chemoattractant protein-1 (MCP-1) in bovine aortic endothelial cells (BAEC). We found that leptin increases ROS generation in BAEC in a dose-dependent manner and that its effects are additive with those of glucose. Rotenone, thenoyltrifluoroacetone (TTFA), carbonyl cyanide m-chlorophenylhydrazone (CCCP), Mn(III)tetrakis (4-benzoic acid) porphyrin (MnTBAP), uncoupling protein-1 (UCP1) HVJ-liposomes, or manganese superoxide dismutase (MnSOD) HVJ-liposomes completely prevented the effect of leptin, suggesting that ROS arise from mitochondrial electron transport. Leptin increased fatty acid oxidation by stimulating the activity of carnitine palmitoyltransferase-1 (CPT-1) and inhibiting that of acetyl-CoA carboxylase (ACC), pace-setting enzymes for fatty acid oxidation and synthesis, respectively. Leptin-induced ROS generation, CPT-1 activation, ACC inhibition, and MCP-1 overproduction were found to be completely prevented by either genistein, a tyrosine kinase inhibitor, H-89, a protein kinase A (PKA) inhibitor, or tetradecylglycidate, a CPT-1 inhibitor. Leptin activated PKA, and the effects of leptin were inhibited by the cAMP antagonist Rp-cAMPS. These results suggest that leptin induces ROS generation by increasing fatty acid oxidation via PKA activation, which may play an important role in the progression of atherosclerosis in insulin-resistant obese diabetic patients.

Troglitazone: antihyperglycemic activity and potential role in the treatment of type 2 diabetes.

Insulin resistance is a major component of type 2 diabetes; therefore, an insulin sensitizer agent like the thiazolidinedione compound troglitazone is considered a very promising drug. Troglitazone exerts an antihyperglycemic activity in a dose-dependent manner between 200 and 600 mg/day in type 2 diabetic patients treated with diet alone, sulfonylureas, or insulin. Additive antihyperglycemic effect may also be obtained by combining troglitazone and metformin. The antihyperglycemic effect of troglitazone as monotherapy is rather modest (reduction of HbA1c by 0.5-1.0%), but it appears to be somewhat greater when it is combined with other antidiabetic drugs. No double-blind studies have directly compared the activity of troglitazone with that of sulfonylureas or metformin. Troglitazone has been shown to exert additional beneficial effects on serum lipid profile and arterial blood pressure. It may be considered as a valuable alternative in insulin-resistant (obese and hyperinsulinemic) diabetic patients who appear to be the best responders to the drug. However, the efficacy of troglitazone is challenged by its safety profile, and the risk of hepatotoxicity still remains a major concern in clinical practice.

L-Carnitine Improves Glucose Disposal in Type 2 Diabetic Patients

Objective: Aim of the present study is to evaluate the effects of L-carnitine on insulin-mediated glucose uptake and oxidation in type II diabetic patients and compare the results with those in healthy controls.Design: Fifteen type II diabetic patients and 20 healthy volunteers underwent a short-term (2 hours) euglycemic hyperinsulinemic clamp with simultaneous constant infusion of L-carnitine (0.28 μmole/kg bw/minute) or saline solution. Respiratory gas exchange was measured by an open-circuit ventilated hood system. Plasma glucose, insulin, non-esterified fatty acids (NEFA) and lactate levels were analyzed. Nitrogen urinary excretion was calculated to evaluate protein oxidation.Results: Whole body glucose uptake was significantly (p<0.001) higher with L-carnitine than with saline solution in the two groups investigated (48.66±4.73 without carnitine and 52.75±5.19 μmoles/kgffm/minute with carnitine in healthy controls, and 35.90±5.00 vs. 38.90±5.16 μmoles/kgffm/minute in diabetic patients). Glucose oxidation significantly increased only in the diabetic group (17.61±3.33 vs. 16.45±2.95 μmoles/kgffm/minute, p<0.001). On the contrary, glucose storage increased in both groups (controls: 26.36±3.25 vs. 22.79±3.46 μmoles/kgffm/minute, p<0.001; diabetics: 21.28±3.18 vs. 19.66±3.04 μmoles/kgffm/minute, p<0.001). In type II diabetic patients, plasma lactate significantly decreased during L-carnitine infusion compared to saline, going from the basal period to the end-clamp period (0.028±0.0191 without carnitine and 0.0759±0.0329 with carnitine, p<0.0003).Conclusions: L-carnitine constant infusion improves insulin sensitivity in insulin resistant diabetic patients; a significant effect on whole body insulin-mediated glucose uptake is also observed in normal subjects. In diabetics, glucose, taken up by the tissues, appears to be promptly utilized as fuel since glucose oxidation is increased during L-carnitine administration. The significantly reduced plasma levels of lactate suggest that this effect might be exerted through the activation of pyruvate dehydrogenase, whose activity is depressed in the insulin resistant status.

Regulation of mesangial cell ion channels by insulin and angiotensin II. Possible role in diabetic glomerular hyperfiltration.

We used patch clamp methodology to investigate how glomerular mesangial cells (GMC) depolarize, thus stimulating voltage-dependent Ca2+ channels and GMC contraction. In rat GMC cultures grown in 100 mU/ml insulin, 12% of cell-attached patches contained a Ca(2+)-dependent, 4-picosiemens Cl- channel. Basal NPo (number of channels times open probability) was < 0.1 at resting membrane potential. Acute application of 1-100 nM angiotensin II (AII) or 0.25 microM thapsigargin (to release [Ca2+]i stores) increased NPo. In GMC grown without insulin, Cl- channels were rare (4%) and unresponsive to AII or thapsigargin in cell-attached patches, and less sensitive to [Ca2+]i in excised patches. GMC also contained 27-pS nonselective cation channels (NSCC) stimulated by AII, thapsigargin, or [Ca2+]i, but again only when insulin was present. In GMC grown without insulin, 15 min of insulin exposure increased NPo (insulin > or = 100 microU/ml) and restored AII and [Ca2+]i responsiveness (insulin > or = 1 microU/ml) to both Cl- and NSCC. GMC AII receptor binding studies showed a Bmax (binding sites) of 2.44 +/- 0.58 fmol/mg protein and a Kd (binding dissociation constant) of 3.02 +/- 2.01 nM in the absence of insulin. Bmax increased by 86% and Kd was unchanged after chronic (days) insulin exposure. In contrast, neither Kd nor Bmax was significantly affected by acute (15-min) exposure. Therefore, we concluded that: (a) rat GMC cultures contain Ca(2+)-dependent Cl- and NSCC, both stimulated by AII. (b) Cl- efflux and cation influx, respectively, would promote GMC depolarization, leading to voltage-dependent Ca2+ channel activation and GMC contraction. (c) Responsiveness of Cl- and NSCC to AII is dependent on insulin exposure; AII receptor density increases with chronic, but not acute insulin, and channel sensitivity to [Ca2+]i increases with both acute and chronic insulin. (d) Decreased GMC contractility may contribute to the glomerular hyperfiltration seen in insulinopenic or insulin-resistant diabetic patients.

Defect in insulin action on expression of the muscle/adipose tissue glucose transporter gene in skeletal muscle of type 1 diabetic patients.

Recently several members of the glucose transporter family have been identified by molecular cloning techniques. We determined the effect of a 4-h insulin infusion on the expression of the muscle/adipose tissue (GLUT-4) glucose transporter mRNA and protein in 14 insulin-treated type 1 diabetic patients and 15 matched nondiabetic subjects. GLUT-4 mRNA and protein concentrations were determined in muscle biopsies taken before and at the end of the insulin infusion during maintenance of normoglycemia. In response to insulin, muscle GLUT-4 mRNA increased in the nondiabetic subjects from 24 +/- 3 to 36 +/- 4 pg/microgram RNA (P less than 0.001) but remained unchanged in the insulin-resistant diabetic patients (24 +/- 2 vs. 26 +/- 2 pg/microgram RNA, before vs. after insulin). The glucose transporter protein concentrations were similar in the basal state and decreased by 21 +/- 7% (P less than 0.02) in the normal subjects but remained unchanged in the diabetic patients. The increase of the GLUT-4 mRNA and the decrease in the GLUT-4 protein correlated with the rate of glucose uptake [correlation coefficient (r) = -0.55, P less than 0.01, and r = -0.44, P less than 0.05, respectively]. We conclude that the insulin response of both the GLUT-4 glucose transporter mRNA and protein are absent in skeletal muscle of insulin-resistant type 1 diabetic patients. Thus, impaired insulin regulation of glucose transporter gene expression can be one of the underlying mechanisms of insulin resistance in type 1 diabetes.

Affinity of IgG-insulin antibodies to human (recombinant DNA) insulin and porcine insulin in insulin-treated diabetic individuals with and without insulin resistance.

The affinity of human (recombinant DNA) insulin and porcine insulin to preformed IgG-insulin antibodies of insulin-treated diabetic individuals was studied in 29 insulin-treated diabetic patients. The binding of 125I-human insulin and 125I-porcine insulin with antibodies was similar in the group of patients without insulin resistance (N = 25). The sera of insulin-resistant diabetic patients (N = 4), containing very high IgG-insulin immunoglobulins, showed a significantly lower affinity for human insulin compared with porcine insulin (P less than 0.01). All four patients with insulin-antibody-mediated insulin resistance were positive for HLA-DR4, but negative for -DR3, supporting the concept of an immunogenetically transferred anti-insulin immune response in insulin-treated diabetic individuals. Based on the reduced binding of human insulin to IgG-antibodies of very high titers in patients with insulin resistance, a potential therapeutic advantage of human insulin therapy can be expected in such infrequent cases of immunologic insulin resistance.