bluuebunny/crossref_metadata_2025 huggingface dataset:
Occurrence, Predictors, and Clinical Significance of Autonomic Neuropathy in NIDDM: Ten-Year Follow-Up From the Diagnosis
Authors: Töyry Jari P , Niskanen Leo K , Mäntysaari Matti J , Länsimies Esko A , Uusitupa Matti IJ
Published: September 2013

Little is known about the occurrence and predictive factors of autonomic neuropathy and its relationship to cardiovascular mortality in NIDDM patients, and no long-term follow-up studies including nondiabetic control subjects are available. A total of 133 patients with newly diagnosed NIDDM (70 men) and 144 control subjects (62 men) were examined at baseline and after 5 and 10 years of follow-up. Deep-breathing tests (baseline, 5-year, and 10-year) and active orthostatic tests (5- and 10-year) were performed. Criteria for autonomic neuropathy were parasympathetic (expiration-to-inspiration ratio ≤1.10), sympathetic (systolic blood pressure decrease ≥30 mmHg in the orthostatic test), and combined autonomic neuropathy (parasympathetic with sympathetic neuropathy). The frequency of parasympathetic neuropathy (NIDDM patients versus control subjects) was 4.9 vs. 2.2% (P = 0.224) at baseline, 19.6 vs. 8.5% (P = 0.017) at 5 years, and 65.0 vs. 28.0% (P < 0.001) at 10 years of follow-up. The frequency of sympathetic neuropathy was 6.8 vs. 5.6% (P = 0.709) at 5 years and 24.4 vs. 9.0% (P = 0.003) at 10 years of follow-up. These figures for combined autonomic neuropathy were 2.1 vs. 1.8% (P = 0.869) at 5 years and 15.2 vs. 4.2% (P = 0.007) at 10 years of follow-up. NIDDM patients with parasympathetic neuropathy at the 10-year examination showed worse glycemic control and higher insulin values than those without parasympathetic neuropathy. Furthermore, in our subjects, women were more prone to have parasympathetic neuropathy than men. Parasympathetic neuropathy at baseline was more frequent in those who died from a cardiovascular cause than those who did not (13 vs. 3%, P = 0.045). Similarly, sympathetic autonomic nervous dysfunction at the 5-year examination predicted the 10-year cardiovascular mortality. In conclusion, the frequency of autonomic neuropathy in NIDDM patients increases sharply with time. The development of autonomic neuropathy is connected with poor glycemic control. Interestingly, a high insulin level seems to have a predictive role in the development of parasympathetic autonomic neuropathy irrespective of obesity and glycemia.
Effect of Cross-Linking on Matrix Permeability: A Model for AGE-Modified Basement Membranes
Authors: Boyd-White Judy , Williams James C
Published: September 2013

There is much evidence that basement membranes, such as in the renal glomerulus, act as macromolecular sieves, restricting the passage of proteins. Cross-linking of matrix proteins, as occurs because of advanced glycosylation end products (AGEs) in diabetes, may have an effect on the sieving properties of the basement membrane. To test this hypothesis, Matrigel, a basement membrane-like matrix, was cross-linked with glycolaldehyde and control and cross-linked matrices compared. Control matrices allowed less bovine serum albumin to pass through than did cross-linked matrices, with sieving coefficients (SCs) of 0.38 ± 0.02 and 0.52 ± 0.02, respectively (P < 0.0005). The control matrices also allowed less cross-linked albumin through than did the cross-linked matrices: 0.13 ± 0.01 vs. 0.17 ± 0.02 (P < 0.002). The SCs of a series of fluorescein isothiocyanate dextrans (four sizes, Mr 16,000–168,000) were lower for the control matrix than for the cross-linked matrix (P < 0.03). In addition, the SC for glycated albumin (incubated with glucose-6-phosphate) was higher than that of normal albumin for both the control (P < 0.04) and cross-linked matrices (P < 0.001). These data indicate that cross-linking of the matrix increases permeability to macromolecules. Analysis of the data using fiber-matrix theory suggests that the mean fiber radius was increased in the cross-linked matrix. The data also indicate that glycated albumin filters through the matrices more easily than does normal albumin. In relation to the situation seen in vivo, it is possible that glycation of circulating proteins and AGE modification of glomerular basement membrane proteins may both contribute to the proteinuria seen in diabetes.
QTc Duration is Associated With Levels of Insulin and Glucose Tolerance: The Zutphen Elderly Study
Authors: Dekker Jacqueline M , Feskens Edith JM , Schouten Evert G , Klootwijk Peter , Pool Jan , Kromhout Daan
Published: September 2013

Prolongation of heart rate-adjusted QT length (corrected QT interval [QTc]) is associated with elevated risk of coronary heart disease and sudden death. This may have to do with autonomic cardiac control. Because insulin is known to stimulate sympathetic activity, we studied the association of insulin level and glucose tolerance with QTc. In 1990, 383 elderly men 70–89 years of age without previous myocardial infarctions or known diabetes had a 12-lead electrocardiogram recorded and glucose tolerance determined in the frame of an ongoing follow-up study. QTc was significantly associated with fasting glucose, insulin, and C-peptide and glucose levels 60 and 120 min after an oral glucose load. For fasting C-peptide and the area under the glucose curve (AUGC), this association could not be explained by the concomitant occurrence of other risk factors of coronary heart disease. Furthermore, fasting C-peptide and the AUGC were independently additive predictors of QTc duration. The difference in QTc between men in the extreme quintiles of both variables was 22 ms. QTc prolongation seems to be part of the insulin resistance syndrome. The association may be explained by increased sympathetic activity induced by high insulin levels. An additional explanation could be an effect of high insulin, impaired glucose utilization, or both on membrane activity of myocardial cells.
The Clinical Features and Treatment of Arteriosclerosis Obliterane With Diabetes
Authors: Tsushima Nobuko , Matsuo Hiroshi , Hayashi Tokio , Homma Satoshi
Published: September 2013

The objective of this study was to clarify the differences, if any, in the clinical features between diabetic and nondiabetic patients with arteriosclerosis obliterane (ASO) and to select the optimal treatment for diabetic patients with ASO. The 171 patients with ASO studied were classified into nondiabetic and diabetic groups. Each group was subdivided into an intermittent claudication (1C) group and ulcer and necrosis (ULC) group. The frequency of complications with cardiac and cerebral vascular diseases and risk factors of arteriosclerosis were analyzed. Ankle and brachial blood pressure and ankle/brachial pressure index (API) were measured, and blood rheological parameters of filterability using Nuclepore filter membrane and viscosity of whole blood and plasma were measured. Three indexes of walking distance were measured by our ASO-Treadmill protocol to evaluate qualitatively the effect of treatment. There were 95 diabetic patients with ASO and 76 nondiabetic patients. Of the nondiabetic patients, 81 had 1C and 14 had ULC, and of the diabetic patients, 63 had 1C and 13 had ULC. The diabetic group showed more frequent complications with coronary heart disease (56.5 vs. 25.6%), but the two groups showed the same frequency of cerebrovascular diseases (30%). The diabetic ULC subgroup showed higher fasting plasma glucose than the diabetic 1C subgroup. The API of the ULC subgroup was significantly lower than that of the 1C subgroup in the nondiabetic patients, whereas that of the ULC subgroup was not significantly lower than that of the 1C subgroup in the diabetic patients. Stenotic lesions of arteriography in both the nondiabetic and diabetic ULC subgroups demonstrated a tendency toward multisegmental and belowknee lesions compared with the two 1C subgroups. For blood rheology-related factors, the diabetic ASO subgroup demonstrated a significantly elevated fibrinogen level compared with the normal control value, for patients of average age. After walking exercise treatment, a significant increase in the walking distance was obtained. After treatment with Cilostazol, prostaglandin I2 analog, and LDL apheresis, the rheological indexes were significantly improved, while the API did not change. We conclude that therapeutic improvement of blood rheological properties would be effective for prolongation and improvement of the quality of life for diabetic patients with ASO.
Vitamin E Normalizes Diacylglycerol—Protein Kinase C Activation Induced by Hyperglycemia in Rat Vascular Tissues
Authors: Kunisaki Makoto , Fumio Umeda , Nawata Hajime , King George L
Published: September 2013

Hyperglycemia, a major cause of vascular complications in diabetes, has been shown to activate the diacylglycerol (DAG)-protein kinase C (PKC) pathway in vascular tissues. We have found that D-α-tocopherol (vitamin E) treatment reversed the adverse effects of hyperglycemia both in vitro and in vivo. In aortic smooth muscle cells (ASMCs), the PKC specific activity from the membranous fraction and total DAG were increased by 31 ± 4% (P < 0.05) and 50 ± 7% (P < 0.05), respectively, when the glucose levels were changed from 5.5 to 22 mmol/1. D-α-tocopherol prevented the glucose-stimulated increases in DAG level and PKC activity as well as the amount of PKC βII isoform in ASMCs cultured with elevated glucose levels. Comparing streptozotocin-induced diabetic rats after 2 weeks of disease to controls, specific membranous PKC activities and total DAG levels were increased in aorta (162%, P < 0.05; 60%, P < 0.05). Intraperitoneal injection of D-α-tocopherol (40 mg/kg) every other day resulted in a significant decrease of the elevated membranous PKC specific activity and total DAG levels in parallel with a significant increase of D-α-tocopherol content in the aorta. These findings suggested that D-α-tocopherol can prevent the activation of PKC in the vascular cells and aorta induced by hyperglycemia by normalizing the elevated levels of DAG.
Involvement of Glycation and Oxidative Stress in Diabetic Macroangiopathy
Authors: Taniguchi Naoyuki , Kaneto Hideaki , Asahi Michio , Takahashi Motoko , Wenyi Che , Higashiyama Shigeki , Fujii Junichi , Suzuki Keiichiro , Kayanoki Yoshiro
Published: September 2013

Under diabetic conditions, the Maillard reaction facilitates the production of reactive oxygen species, and the activity of antioxidant enzymes such as Cu,Zn-superoxide dismutase is decreased, resulting in a remarkable increase of oxidative stress. The oxidative stress attacks DNA, lipids, and proteins and is also thought to be involved in the pathogenesis of diabetic complications, including the progression of macroangiopathy. Proliferation of smooth muscle cells (SMCs) is known to be associated with progression of macroangiopathy and is modulated by several growth factors. At least three mi-togens for SMCs, platelet-derived growth factor (PDGF), flbroblast growth factor, and heparin-binding epidermal growth factor-like growth factor (HB-EGF), are known to be produced by SMCs themselves and are considered to be the most potent growth factors in the progression of macroangiopathy as seen in diabetes. HB-EGF, but not PDGF, is regulated at the transcriptional level by 3-de-oxyglucosone (3-DG), a major and highly reactive intermediate in the glycation reaction. The induction seems to be triggered by the increase of reactive oxygen species produced by 3-DG. Taken together, glycation reactions under diabetic conditions may be highly associated with the pathogenesis of diabetic macroangiopathy by enhancing the gene expression of HB-EGF.
Intensive Insulin Therapy in Type II Diabetes: Rationale and Collaborative Clinical Trial Results
Authors: Colwell John A
Published: September 2013

The rationale for intensive insulin therapy and results from major clinical trials in diabetes are reviewed. The Diabetes Control and Complications Trial (DCCT) has shown that intensive insulin therapy will prevent or delay the onset of retinopathy, nephropathy, and neuropathy in type I diabetes. The University Group Diabetes Program (UGDP) and the U.K. Prospective Diabetes Study (UKPDS) have addressed the issue of insulin versus oral agent or diet therapy in people with recently diagnosed type II diabetes. The UGDP showed that effective glycemie control could be achieved with intensive insulin therapy, but no effect on vascular end points was seen. Early data from the UKPDS also suggest that intensive insulin therapy may be more effective in lowering HbA1c toward normal than oral agents or diet. A pressing clinical problem is the question of the use of intensive insulin therapy in type II diabetic individuals who remain hyperglycemie despite pharmacological therapy. A Veterans Affairs Cooperative Study explored the feasibility of using intensive insulin therapy in 153 male type II diabetic patients with these characteristics. A 2% lowering of HbA1c was seen, with no increase in weight gain or in hypoglycemia. However, 40 of 153 patients (26.1%) had cardiovascular events during the 27-month trial; no difference in cardiovascular event rates was seen between the two treatment groups. A long-term multicenter collaborative trial is needed to assess the benefltcrisk ratio of intensive insulin therapy for type II diabetic patients in whom pharmacological therapy failed to provide glycemie management.
Diabetic Macroangiopathy and Atherosclerosis
Authors: Andresen Jens L , Rasmussen Lars M , Ledet Thomas
Published: September 2013

In the present study, we have compared and analyzed published data related to the pathogenesis of the large vessel disease in diabetes. The prevailing opinion appears to be that diabetes accelerates the mechanism that leads to development of classical atherosclerosis. However, as an alternative, we have amassed data that point to the presence of a diabetic macroangiopathy. This phenomenon comprises a constellation of nonatherosclerotic large vessel abnormalities. Today, we know that accumulation of periodic acid-Schiff (PAS)-positive material, as laminin, fibronectin, and type IV collagen, occurs together with hyaluronic acid and various types of connective tissue and calcium deposition. All these changes occur independent of the presence of atherosclerosis in the large vessels of diabetic patients. It seems to us that these observations emphasize that the concept of a specific diabetic macroangiopathy is a more fruitful working hypothesis than the usual theory of a link between atherosclerosis and diabetes. It provides a causal relationship (although the mechanism is unknown) between such changes and the abnormal metabolism in diabetes and a background for research strategy and tactics, aiming finally at the possibility of prevention and/or treatment of this common and dangerous disease.
Plasma Free Fatty Acids Decrease Insulin-Stimulated Skeletal Muscle Glucose Uptake by Suppressing Glycolysis in Conscious Rats
Authors: Kim Jason K , Wi Jae K , Youn Jang H
Published: September 2013

The effects of elevated plasma free fatty acid (FFA) levels on insulin-stimulated whole-body and skeletal muscle glucose transport, glucose uptake, glycolysis, and glycogen synthesis were studied in conscious rats during hyperinsulinemic-euglycemic clamps with (n = 26) or without (n = 23) Intralipid and heparin infusion. Whole-body and skeletal muscle glucose uptake, glycolysis, and glycogen synthesis were estimated using d-[3-3H]glucose and 2-[14C]deoxyglucose (study 1), and glucose transport activity was assessed by analyzing plasma kinetics of l-[14C]glucose and 3-O-[3H]-methylglucose (study 2). Plasma FFA levels decreased during the clamps without intralipid but increased above basal during the clamps with Intralipid infusion (P < 0.01 for both). Elevated plasma FFA levels decreased insulin-stimulated whole-body glucose uptake by ∼ 15% and ∼ 20% during physiological and maximal insulin clamps, respectively (P < 0.01). Similarly, insulin-stimulated glucose uptake was also decreased in individual skeletal muscles with Intralipid infusion (P < 0.05). The most profound effect of elevated plasma FFA levels was a 30–50% suppression of insulin-stimulated glycolysis in whole body and individual skeletal muscles in both clamps. In contrast, physiological insulin-stimulated glycogen synthesis was increased with elevated plasma FFA levels in whole body and individual skeletal muscles (P < 0.05). Glucose-6-phosphate (G-6-P) levels were increased in soleus and extensor digitorum longus (EDL) muscles with Intralipid infusion in both clamps (P < 0.05). Intralipid infusion did not alter the time profiles of plasma l-glucose and 3-O-methylglucose after an intravenous injection during maximal insulin clamps, and compartmental analysis indicated no significant effect of elevated FFA levels on glucose transport activity in insulin-sensitive tissues (P > 0.05). Thus, elevated plasma FFA decreased insulin-stimulated glucose uptake in skeletal muscle by suppressing glycolysis and increasing G-6-P levels. These findings suggest that the classic glucose-fatty acid cycle was the predominant mechanism underlying the inhibitory effect of FFA on skeletal muscle glucose uptake.
High Glucose Induces Antioxidant Enzymes in Human Endothelial Cells in Culture: Evidence Linking Hyperglycemia and Oxidative Stress
Authors: Ceriello Antonio , Russo Patrizia dello , Amstad Paul , Cerutti Peter
Published: September 2013

It has been suggested that oxidative stress may play an important role in the pathogenesis of diabetic complications. Hyperglycemia may cause increased production of free radicals, and evidence supports a prominent role for these reactive molecules as mediators of endothelial cell dysfunction in diabetes. It has been demonstrated that active oxygen species induce antioxidant enzyme expression in some tissues, and this phenomenon is considered proof of an existing oxygen-dependent toxicity. In this study, human endothelial cells from umbilical vein, immortalized human endothelial cells, and immortalized human endothelial cells transfected to express high glutathione peroxidase levels were grown in normal and high-glucose conditions. High glucose delayed replication after 7 and 14 days of culture of human endothelial cells, both from umbilical vein and immortalized, while transfected cells were not affected. The activity and the mRNA expression of the antioxidant enzymes CuZn-superoxide-dismutase, Mn-superoxide-dismutase, catalase, and glutathione peroxidase were evaluated after 2, 7, and 14 days of culture. High glucose at days 7 and 14 induced an overexpression of CuZn-superoxide-dismutase, catalase, and glutathione peroxidase in both human endothelial cells from umbilical vein and immortalized human endothelial cells, while in transfected cells it did not. This study demonstrates that high glucose induces an increase in antioxidant enzyme levels in human endothelial cells, suggesting that elevated glucose levels may produce an oxidative stress in the cells.
Enhanced Expression of Platelet-Derived Growth Factor-β Receptor by High Glucose Involvement of Platelet-Derived Growth Factor in Diabetic Angiopathy
Authors: Inaba Toshimori , Ishibashi Shun , Gotoda Takanari , Kawamura Masako , Morino Noritsugu , Nojima Yoshihisa , Kawakami Masanobu , Yazaki Yoshio , Yamada Nobuhiro
Published: September 2013

Coronary heart disease is a major complication of diabetic subjects, and platelet-derived growth factor (PDGF) has been implicated in the development of atherosclerosis. We investigated the effects of high glucose on expression of PDGF-β receptor. In a binding assay with 125I-labeled PDGF-BB homodimer, high concentrations of glucose increased high-affinity binding of PDGF-BB on human monocyte-derived macrophages and rabbit aortic medial smooth muscle cells. Northern blot analysis confirmed the enhanced effect of glucose on expression of PDGF-β receptor mRNA in human monocyte-derived macrophages. The protein kinase C inhibitor, staurosporin, completely suppressed an increase in PDGF-BB binding by high glucose, and high glucose significantly activated protein kinase C. These results indicated that PDGF-β receptor expression was enhanced by high glucose through the activation of protein kinase C. Furthermore, we observed similar effects of high glucose on both PDGF-β receptor expression and protein kinase C activation in rat mesangial cells and human capillary endothelial cells. Our results suggest that stimulation of the PDGF system is significantly involved in the development not only of diabetic atherosclerosis but also of microangiopathy.
Hematocrit and Risk of NIDDM
Authors: Wannamethee S Goya , Perry Ivan J , Shaper A Gerald
Published: September 2013

There is limited evidence that raised hematocrit levels may be associated with insulin resistance, which links cardiovascular disease with NIDDM. The association between hematocrit level at screening and the subsequent development of physician-diagnosed NIDDM during 12.8 years of follow-up was examined in a prospective study of 7,735 middle-aged men drawn at random from general practice in 24 British towns. With the exclusion of men with missing hematocrit data and men with diabetes at screening, data were available for 7,193 men, in whom there were 187 new cases of NIDDM during follow-up. The risk of NIDDM increased significantly with increasing hematocrit levels. There was more than a fourfold increase in relative risk (RR) of diabetes among men with a hematocrit of ≥48% relative to those with a hematocrit <42%, adjusted for age and BMI (RR 4.5; 95% CI 2.5–6.3). On further adjustment for predictors of NIDDM with which hematocrit is correlated, there remained a strong linear association with the risk of diabetes. There was a nearly fourfold increased risk of NIDDM in the highest relative to the lowest hematocrit group in the fully adjusted proportional hazard model (RR 3.6; 95% CI 1.7–7.6). The strong positive association between hematocrit level and risk of diabetes was seen even after exclusion of men with preexisting ischemic heart disease. The findings suggest that a raised hematocrit level, which is a major determinant of whole blood viscosity, should be added to the cluster of risk factors that link NIDDM with atheromatous, vascular disease.
Diabetes Increases Sciatic Nerve Susceptibility to Endothelin-Induced Ischemia
Authors: Zochodne Douglas W , Cheng Chu , Sun Hong
Published: September 2013

Endothelin-1 (ET) is a potent vasoconstrictor of vasa nervorum, the vascular supply of peripheral nerve trunks, that may, through elevated circulating levels, promote microangiopathy in human diabetes patients. In previous work, we observed that sciatic nerve trunks of rats exposed to epineurial ET developed transient dose-dependent endoneurial ischemia that might be associated with reversible motor conduction block. In the present study, we explored the possibility that ET ischemia might selectively damage axons of diabetic nerve trunks. We exposed the sciatic nerves of rats with streptozotocin-induced diabetes of 6–8 weeks duration and age-matched nondiabetic controls to supramaximal vasoconstrictive concentrations of epineurial ET and studied serial regional erythrocyte flux (laser Doppler flowmeter) and sciatic tibial motor conduction for up to 14 days. In diabetic rats, but not controls, ET ischemia damaged a large proportion of sciatic axons, predicted in each instance by focal motor conduction block across the site of ET application and eventual loss of distal motor nerve excitability. Histological studies confirmed the presence of severe axonal degeneration in diabetic sciatic nerves exposed to ET. Part of the susceptibility to ET in diabetes was accounted for by more intense and prolonged vasoconstriction. Diabetic nerves are selectively susceptible to ET-mediated ischemia.
Metabolic Impairment Precedes Insulin Resistance in Skeletal Muscle During High-Fat Feeding in Rats
Authors: Kim Jason K , Wi Jae K , Youn Jang H
Published: September 2013

To examine whether impairment of intracellular glucose metabolism precedes insulin resistance, we determined the time courses of changes in insulin-stimulated glucose uptake, glycolysis, and glycogen synthesis during high-fat feeding in rats. Animals were fed with a high-fat (66.5%) diet ad libitum for 0, 2, 4, 7, or 14 days (n = 10–11 in each group) after 5 days of a low-fat (12.5%) diet. Submaximal and maximal insulin-stimulated glucose fluxes were estimated in whole body and individual skeletal muscles using the glucose clamp technique combined with D-[3-3H]glucose infusion and 2-[1-14C]deoxyglucose injection. Both submaximal and maximal insulin-stimulated glucose uptake in whole body decreased gradually with high-fat feeding. However, the decreases were minimal and not statistically significant during the initial few days (i.e., 2 and 4 days) of high-fat feeding (P > 0.05). In contrast, insulin-stimulated whole-body glycolysis (both maximal and submaximal) significantly decreased by ∼30% with 2 days of high-fat feeding and remained suppressed thereafter (P < 0.05). Similar patterns of changes in insulin-stimulated glucose uptake and glycolysis were also observed in skeletal muscle. Insulin-stimulated glycogen synthesis and glucose-6-phosphate (G-6-P) concentrations in skeletal muscle increased significantly during the initial few days of high-fat feeding and gradually returned to control levels by day 14, suggesting that increased G-6-P concentrations were responsible for increased glycogen synthesis. Thus, suppression of insulin-stimulated glycolysis and a compensatory increase in glycogen synthesis (presumably arising from the glucose-fatty acid cycle) preceded decreases in insulin-stimulated glucose uptake in skeletal muscle during high-fat feeding. These findings suggest that the insulin resistance may develop as a secondary response to impaired intracellular glucose metabolism.
The Role of Cell Adhesion Molecules in the Development of IDDM: Implications for Pathogenesis and Therapy
Authors: Yang Xiao-Dong , Michie Sara A , Roland Tisch , Weissman Irving , McDevitt Hugh O
Published: September 2013

IDDM is a chronic inflammatory disease in which there is autoimmune-mediated organ-specific destruction of the insulin-producing β-cells in the pancreatic islets of Langerhans. The migration of autoreactive lymphocytes and other leukocytes from the bloodstream into the target organ is of clear importance in the etiology of many organ-specific autoimmune/inflammatory disorders, including IDDM. In IDDM, this migration results in lymphocytic invasion of the islets (formation of insulitis) and subsequent destruction of β-cells. Migration of lymphocytes from the bloodstream into tissues is a complex process involving sequential adhesion and activation events. This migration is controlled in part by selective expression and functional regulation of cell adhesion molecules (CAMs) on the surface of lymphocytes and vascular endothelial cells or in the extracellular matrix. Understanding the mechanisms that regulate lymphocyte migration to the pancreatic islets will lead to further understanding of the pathogenesis of IDDM. In this article, we summarize the recent advances regarding the function of CAMs in the development of IDDM in animal models and in humans and discuss the potential for developing CAM-based therapies for IDDM.
Associations of Fasting Blood Glucose With Cholesterol Absorption and Synthesis in Nondiabetic Middle-Aged Men
Authors: Strandberg Timo E , Salomaa Veikko , Venhanen Hannu , Miettinen Tatu A
Published: September 2013

NIDDM and the metabolic syndrome are characterized by a low serum HDL cholesterol content and a high triglyceride level, whereas total and LDL cholesterol concentrations are not necessarily elevated. Variable results have been reported on cholesterol absorption, elimination, and synthesis in NIDDM, but no studies are available on subjects within the normal range of blood glucose. From serum samples collected in 1985 from 203 nondiabetic men aged 51–66 years, we examined lipids, cholesterol precursors (reflecting cholesterol synthesis), and plant sterols and cholestanol (reflecting cholesterol absorption) in relation to fasting blood glucose. The findings prompted us (in 1993) to further examine 11 men from the highest and lowest glucose thirds of 203 nondiabetic men by additional dietary, serum, and fecal analyses for absorption, elimination, and synthesis of cholesterol and insulin sensitivity. In 1985, blood glucose was significantly related to LDL apolipoprotein B (P = 0.05) but not to LDL cholesterol (P = 0.19). Significantly higher serum lathosterol and desmosterol-to-cholesterol proportions and lower plant sterol and cholestanol proportions in the highest rather than the lowest glucose thirds suggested that the subjects with high normal blood glucose had decreased absorption and enhanced synthesis of cholesterol. In 1993, men with the lowest glucose versus those with the highest glucose had a lower waist-to-hip ratio, plasma HbA1c, fasting and postload insulin and glucose values, and a higher insulin sensitivity index. In agreement with the 1985 noncholesterol sterol data, direct analyses of cholesterol metabolism showed further higher cholesterol absorption efficiency (P = 0.03) and serum plant sterol and cholestanol proportions (P < 0.001). Despite a slightly lower dietary cholesterol intake, cholesterol synthesis (P = 0.02) and serum lathosterol (P < 0.01) and desmosterol (P < 0.01) proportions were lowest in men with the lowest glucose third. We conclude that noncholesterol sterols in serum exhibits a long-lasting correlation with blood glucose level in a nondiabetic male population. Low intestinal absorption and high synthesis of cholesterol characterize men with high normal blood glucose. Differences in cholesterol metabolism could be due to underlying insulin effects associated with obesity-like fat distribution and may thus imply novel aspects in the metabolic interrelation between insulin and cholesterol in humans.
Isolation, Characterization, and Chromosomal Mapping of the Human Insulin Promoter Factor 1 (IPF-1) Gene
Authors: Inoue Hiroshi , Yukio Tanizawa , Ueda Kohei , Kuwano Akira , Liu Li , Donis-keller Helen , Permutt M Alan
Published: September 2013

Insulin promoter factor 1 (IPF-1) is a homeodomaincontaining protein that is thought to be a key regulator of pancreatic islet development and insulin gene transcription in β-cells. This report describes the isolation and characterization of the human IPF-1 gene. The coding region, which showed 83% nucleotide identity with the mouse IPF-1 gene, was encoded by two exons that extended over a 5-kb region of human genome. The deduced human IPF-1 protein contained 283 amino acids, 1 amino acid less than the mouse IPF-1 protein. The homeodomain region of IPF-1 was encoded by the second exon, and it was highly conserved among species. The human IPF-1 gene was mapped to chromosome 13ql2(12.1) by fluorescent in situ hybridization (FISH) analysis. A simple sequence repeat polymorphism (ipflCA2) was identified in the genomic clone. Polymerase chain reaction (PCR) amplification of this repeat region revealed two alleles (heterozygosity = 0.32). This simple sequence repeat polymorphism, and thus the IPF-1 gene, was incorporated into the human linkage map by genotyping reference Human Polymorphism Study Center (CEPH) pedigrees. Multipoint analysis with the CEPH genotype database placed the gene with equal likelihood between two marker intervals: D13S292—cdx3GA1 and cdx3GA1—D13S289 on chromosome 13, consistent with the results of FISH analysis. Two-point linkage analysis inferred that the most likely location for ipflCA2 was at θ = 0 from cdx3GA1 locus. The exon-intron boundaries of the IPF-1 gene were sequenced, and primers were synthesized to search the homeodomain region for potential variants in patients with NIDDM. By single-strand conformational polymorphism analysis, no variants were found within this region in 61 Japanese patients, which could contribute to the pathogenesis of NIDDM. The isolation of the human IPF-1 gene, along with characterization of its genomic structure and chromosomal mapping, will now permit the assessment of the role of this gene in the pathogenesis of NIDDM in various populations.
Differential Responsiveness to Interferon-α in β-Cells and Non-β-Cells
Authors: Bonnevie-Nielsen V , Buschard K , Dyrberg T
Published: September 2013

Interferon-α (IFN-α) is important in the innate immune defense, particularly in viral infections. IFN-α induces 2ʹ,5ʹA synthetase, the products of which, 2ʹ,5ʹ-oligoadenine nucleotides, activate mRNA degrading enzymes. IFN-α is the first detectable cytokine in the insulitis lesion seen in recent-onset IDDM, and insulin promoter directed expression of IFN-α in transgenic mice leads to development of IDDM. Here, we demonstrate that IFN-α induces 2ʹ,5ʹA synthetase activity only in insulin-producing βTC3 cells and in isolated single rat β-cells but not in αTC3 cells or in isolated rat non-β-cells. The increased responsiveness of β-cells but not non-β-cells to IFN-α with the ensuing activation of the mRNA-degrading 2ʹ,5ʹA synthetase system suggests why only the β-cells are destroyed in the diabetogenic process.
Leptin Concentrations in Diabetic and Nondiabetic Mexican-Americans
Authors: Haffner Steven M , Stern Michael P , Miettinen Heikki , Wei Ming , Gingerich Ronald L
Published: September 2013

Leptin, the product of the OB gene, is increased in obese individuals, suggesting resistance to its effect. We questioned whether subjects with NIDDM have an altered regulation of serum leptin levels. We used a radioimmunoassay to measure serum leptin levels in three groups from the San Antonio Heart Study: 1) 50 Mexican-Americans with NIDDM; 2) 50 nondiabetic Mexican-Americans matched by age and sex to the diabetic Mexican-Americans; and 3) 50 nondiabetic Mexican-Americans matched by age, sex, and BMI to the diabetic Mexican-Americans. Leptin concentrations did not differ significantly by diabetic status. Leptin concentrations were significantly correlated with BMI in all groups (NIDDM women: r = 0.637; nondiabetic women: r = 0.772; NIDDM men: r = 0.849; and nondiabetic men: r = 0.686; all P < 0.001). Leptin levels were higher in women than in men regardless of diabetic status. We concluded that the leptin concentrations were not different in diabetic and nondiabetic subjects and that the association of leptin with obesity was similar in diabetic and nondiabetic subjects.
K+ Channels: Generating Excitement in Pancreatic β-Cells
Authors: Dukes Iain D , Philipson Louis H
Published: September 2013

K+ channels play a key role in cellular physiology by regulating the efflux of K+ ions. They are the most diverse group of ion channel proteins; more than 30 K+ channel genes have been characterized. Regulated by ATP, voltage, and calcium, multiple K+ channels coexist in the P-cell to regulate membrane potential, cell excitability, and insulin secretion. Recent developments at the molecular level have greatly expanded our understanding of P-cell K+ channel structure and function, especially in regard to the ATP-sensitive K+ channel, the target for sulfonylurea drugs. Mutations in K+ channel genes underlie diseases as diverse as persistent hyperinsulinemia of infancy, cardiac long QT syndrome, cerebellar degeneration, and certain ataxias. These discoveries have identified new pharmacological targets for possible therapeutic intervention in the treatment of diabetes.
Wortmannin Inhibits Insulin Secretion in Pancreatic Islets and β-TC3 Cells Independent of Its Inhibition of Phosphatidylinositol 3-Kinase
Authors: Gao Zhi-yong , Konrad Robert J , Collins Heather , Matschinsky Franz M , Rothenberg Paul L , Wolf Bryan A
Published: September 2013

Glucose is the primary stimulus for insulin secretion by pancreatic β-cells, and it triggers membrane depolarization and influx of extracellular Ca2+. Cholinergic agonists amplify insulin release by several pathways, including activation of phospholipase C, which hydrolyzes membrane polyphosphoinositides. A novel phospholipid, phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3[, a product of phosphatidylinositol 3-kinase (PI 3-kinase), has recently been found in various cell types. We demonstrate by immunoblotting that PI 3-kinase is present in both cytosolic and membrane fractions of insulin-secreting β-TC3 cells and in rat islets. The catalytic activity of PI 3-kinase in immunoprecipitates of islets and β-TC3 cells was measured by the production of radioactive phosphatidylinositol 3-monophosphate from phosphatidylinositol (Ptdlns) in the presence of [γ-32P[ATP. Wortmannin, a fungal metabolite, dose dependency inhibited PI 3-kinase activity of both islets and P-TC3 cells, with an IC50 of 1 nmol/l and a maximally effective concentration of 100 nmol/l, when it was added directly to the kinase assay. However, if intact islets were incubated with wortmannin and PI 3-kinase subsequently was determined in islet immunoprecipitates, ∼50% inhibition of PI 3-kinase activity (but no inhibition of glucose- and carbachol-stimulated insulin secretion) from intact islets was obtained at wortmannin concentrations of 100 µmol/l. Wortmannin, at higher concentrations (1 and 10 µmol/l), inhibited glucose- and carbachol-induced insulin secretion of intact rat islets by 58 and 92%, respectively. Wortmannin had no effect on the basal insulin release from rat islets. A similar dose curve of inhibition of glucose- and carbachol-induced insulin secretion by wortmannin was obtained when β-TC3 cells were used. Cellu-lar metabolism was not changed by any wortmannin concentrations tested (0.01–10 µmol/l). Both basal cytosolic [Ca2+]1 and carbamyl choline-induced increases of [Ca2+]1 were unaffected by wortmannin in the presence of 2.5 mmol/l Ca2+, while Ca2+ mobilization from intracellular stores was partially decreased by wortmannin. Together, these data suggest that wortmannin at concentrations that inhibit PI 3-kinase does not affect insulin secretion. PI 3-kinase is unlikely to have a major role in insulin secretion induced by glucose and carbachol.Diabetes 45:854–862, 1996
Glucose-6-Phosphatase mRNA and Activity Are Increased to the Same Extent in Kidney and Liver of Diabetic Rats
Authors: Mithieux Gilles , Vidal Hubert , Zitoun Carine , Bruni Nathalie , Daniele Nathalie , Minassian Carol
Published: September 2013

Using Northern blot with a specific glucose-6-phosphatase (Glc6Pase) cDNA probe and enzymatic activity determination, we studied the effect of streptozotocininduced diabetes on Glc6Pase in rat gluconeogenic tissues. The Glc6Pase mRNA abundance was increased four to five times in both the liver and kidney of diabetic rats. This was correlated with a concomitant 130% increase in Glc6Pase catalytic subunit in both tissues. The elevated level of Glc6Pase mRNA was significantly corrected in both the liver and kidney of diabetic rats after a 12-h insulin treatment. We also studied Glc6Pase mRNA and activity in gluconeogenic tissues during the fed-fasted and fasted-refed transitions in normal rats. In the liver, the abundance of Glc6Pase mRNA was sharply increased about four times after 24 or 48 h of fasting. In the kidney, the Glc6Pase mRNA level was gradually increased some three and five times after 24 and 48 h of fasting, respectively. The increase of Glc6Pase mRNA in both organs was matched with a doubling of the activity of Glc6Pase catalytic subunit: rapid in the liver and gradual in the kidney. The liver Glc6Pase mRNA abundance in 48-h fasted rats was acutely and importantly decreased upon refeeding. The kidney Glc6Pase mRNA level was also significantly lowered under these conditions, albeit less rapidly. These data demonstrate that efficient control of Glc6Pase takes place in both gluconeogenic organs at the pretranslational level and suggest that insulin might play an important role in this control. In addition, using reverse transcription-polymerase chain reaction and Northern blot, we report that Glc6Pase mRNA is not detectable in several other tissues previously assumed to express the enzyme.
Activation of β3 Adrenergic Receptors Suppresses Leptin Expression and Mediates a Leptin-Independent Inhibition of Food Intake in Mice
Authors: Mantzoros Christos S , Frederich Robert C , Flier Jeffrey S , Qu Daqing , Susulic Vedrana S , Lowell Bradford B , Maratos-Flier Eleftheria
Published: September 2013

To examine potential interactions between leptin and the β3 adrenergic system in the regulation of food intake, we determined the effects of treatment with a selective β3 adrenergic receptor (AR) agonist (CL 316,243 [1 mgfleg]) on body weight, food intake, and leptin expression. Studies were carried out in C57B1/6J and FVB male control mice as well as in mice with targeted disruption of the β3 AR gene. These findings were correlated with measurement of the expression in hypothalamus of neuropeptide Y (NPY) and melanin concentrating hormone (MCH), two neuropeptides that may be involved in the central regulation of food intake. Treatment with CL 316,243 (1 mg/kg) for 12 or 24 h decreased leptin mRNA abundance and circulating levels to 20% of baseline in normal animals. No effect of the CL 316,243 compound was seen in mice with targeted disruption of the β3 AR gene. Despite the falling leptin levels, β3 agonist administration acutely suppressed food intake. Finally, the induced suppression of food intake and leptin levels occurred despite unchanged or increased hypothalamic expression of the orexigenic neuropeptides NPY and MCH. Thus, β3 AR agonists via β3 ARs suppress leptin levels acutely and simultaneously suppress food intake via a mechanism that operates downstream of leptin and two of its putative central targets.
Roles of Glucose Transport and Glucose Phosphorylation in Muscle Insulin Resistance of NIDDM
Authors: Bonadonna Riccardo C , Bonora Enzo , Prato Stefano Del , Saccomani Maria Pia , Cobelli Claudio , Natali Andrea , Frascerra Silvia , Pecori Neda , Ferrannini Eleuterio , Bier Dennis , DeFronzo Ralph A , Gulli Giovanni
Published: September 2013

Insulin resistance for glucose metabolism in skeletal muscle is a key feature in NIDDM. The quantitative role of the cellular effectors of glucose metabolism in determining this insulin resistance is still imperfectly known. We assessed transmembrane glucose transport and intraceUular glucose phosphorylation in vivo in skeletal muscle in nonobese NIDDM patients. We performed euglycemic insulin clamp studies in combination with the forearm balance technique (brachial artery and deep forearm vein catheterization) in five nonobese NIDDM patients and seven age- and weight-matched control subjects (study 1). d-Mannitol (a nontransportable molecule), 3-O-[14C]methyl-d-glucose (transportable, but not metabolizable) and d[3–3H]glucose (transportable and metabolizable) were simultaneously injected into the brachial artery, and the washout curves were measured in the deep venous effluent blood. In vivo rates of transmembrane transport and intracellular phosphorylation of d-glucose in forearm muscle were determined by analyzing the washout curves with the aid of a multicompartmental model of glucose kinetics in forearm tissues. At similar steady-state concentrations of plasma insulin (∼500 pmol/l) and glucose (∼5.0 mmol/l), the rates of transmembrane influx (34.3 ± 9.1 vs. 58.5 ± 6.5 μmol · min-1 μ kg-1 P < 0.05) and intracellular phosphorylation (5.4 ± 1.6 vs. 38.8 ± 5.1 μmol μ min-1 · kg-1 P < 0.01) in skeletal muscle were markedly lower in the NIDDM patients than in the control subjects. In the NIDDM patients (study 2), the insulin clamp was repeated at hyperglycemia (∼13 mmol/l) trying to match the rates of transmembrane glucose influx measured during the clamp in the controls. The rate of transmembrane glucose influx (62 ± 15 μmol · min-1 · kg-1) in the NIDDM patients was similar to the control subjects, but the rate of intracellular glucose phosphorylation (16.6 ± 7.5 μmol · min-1 · kg-1), although threefold higher than in the patients during study 1 (P < 0.05), was still ∼60% lower than in the control subjects (P < 0.05). These data suggest that when assessed in vivo, both transmembrane transport and intracellular phosphorylation of glucose are refractory to insulin action and add to each other in determining insulin resistance in skeletal muscle of NIDDM patients. It will be of interest to compare the present results with the in vivo quantitation of the initial rate of muscle glucose transport when methodology to perform this measurement becomes available.
Glucose-Dependent Interleukin 6 and Tumor Necrosis Factor Production by Human Peripheral Blood Monocytes In Vitro
Authors: Morohoshi Masaharu , Fujisawa Kazuhiko , Uchimuraa Isao , Numano Fujio
Published: September 2013

To clarify the mechanisms that cause elevation of plasma fibrinogen levels in diabetes, we first examined the effect of hyperglycemia on the production of interleukin 6 (IL-6) and tumor necrosis factor (TNF) by cultured human peripheral blood monocytes. Monocyte-enriched fractions isolated from 20 healthy volunteers were incubated with 11 mmol/l glucose, 33 mmoM glucose, or mannitol as an osmolar control for 6 or 24 h. After 6 h of incubation, IL-6 and TNF-α mRNA levels were analyzed by reverse transcription and polymerase chain reaction. In addition, after 24 h of incubation, IL-6 and TNF-α immunoreactivity in the culture medium was measured by enzyme-linked immunoassay. Both IL-6 and TNF-α mRNA levels and immunoreactivity were significantly increased by treatment with 33 mmol/l glucose compared with treatment with 11 mmol/l glucose or 11 mmol/l glucose with 22 mmol/l mannitol. In addition, preincubation of the cells with an anti-TNF monoclonal antibody (mAb) blocked the stimulatory effect of 33 mmol/l glucose on IL-6 synthesis and secretion. Second, we examined the ability of conditioned media from human peripheral blood monocytes to stimulate β-fibrinogen mRNA synthesis in HepG2 cells. The conditioned medium from monocytes treated with 33 mmol/l glucose increased β-fibrinogen mRNA levels. The results of this study demonstrate that hyperglycemia stimulated IL-6 and TNF synthesis and secretion by human peripheral monocytes in vitro and that the IL-6 response to hyperglycemia may be mediated by TNF. Furthermore, hyperglycemia may increase fibrinogen levels through stimulation of peripheral monocytes. These results suggest that hyperglycemia may cause hyperfibrinogenemia in diabetic patients through an IL-6-dependent and TNF-dependent mechanism.