bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of Two Missense Mutations in the GIP Receptor Gene: A Functional Study and Association Analysis with NIDDM: No Evidence of Association with Japanese NIDDM Subjects
Authors: Kubota Akira , Yamada Yuichiro , Hayami Tadao , Yasuda Koichiro , Someya Yoshimichi , Ihara Yu , Kagimoto Shinji , Watanabe Rie , Taminato Tomohiko , Tsuda Kinsuke , Seino Yutaka
Published: September 2013

Gastric inhibitory polypeptide (GIP) potently stimulates insulin secretion from pancreatic islets in the presence of glucose as an incretin. Because the insulinotropic effect of GIP is reduced in NIDDM, it should be clarified whether defects in the GIP receptor gene contribute to the impaired insulin secretion in NIDDM. Using genomic DNA samples from Japanese NIDDM and non-NIDDM subjects, we have investigated the entire coding region of the GIP receptor gene by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP). We have identified two missense mutations, Gly198→Cys (Gly198Cys) in exon 7 and Glu354→Gln (Glu354Gln) in exon 12. Investigation of the function of GIP receptor with either of these mutations reveals a half-maximal stimulation value of GIP-induced cAMP response in Chinese hamster ovary cells expressing the GIP receptor with Gly198Cys of 6.3 ± 1.2 × 10−10 mol/l (n = 3), which was considerably higher than that of the normal GIP receptor, 9.4 ± 3.8 × 10−12 mol/l GIP (n = 3), whereas that of the GIP receptor with Glu354Gln was not significantly different from that of the normal GIP receptor. To assess the possible role of the GIP receptor gene in genetic susceptibility to NIDDM, we have examined the allelic frequencies of Gly198Cys and Glu354Gln in NIDDM and control subjects. Association studies show no relationship between NIDDM and either of the two mutations.
Effects of Chronically Elevated Glucose Levels on the Functional Properties of Rat Pancreatic β-Cells
Authors: Ling Zhidong , Kiekens Rita , Mahler Tania , Schuit Frans C , Pipeleers-Marichal Miriam , Sener Abdullah , Klöppel Gunther , Malaisse Willy J , Pipeleers Daniel G
Published: September 2013

This study examines the effects of chronically elevated glucose levels on the survival and function of purified rat β-cells. Prolonged exposure (9 days) of β-cell aggregates to 20 mmol/l glucose did not lead to cell losses, but reduced the amount of insulin secreted in response to glucose. This decrease was not caused by cellular desensitization but resulted from the lower cellular insulin content after a prolonged imbalance between stimulated rates of insulin synthesis and release. Virtually all β-cells exhibited a state of metabolic and biosynthetic activation, which was maintained for at least 2 h in glucose-depleted media. Their rates of protein and insulin synthesis were amplified by glucose, reaching (half-) maximal stimulation at lower glucose concentrations (2 and 5 mmol/l, respectively) than control cells cultured at 10 mmol/l glucose (5 and 10 mmol/l, respectively). As for insulin release, the net glucose effect on insulin synthesis was markedly reduced as compared with that in control cells. This was also the case after culture at 6 mmol/l glucose. In the latter condition, the lower glucose-inducible activities were caused by cellular desensitization, with 50% of the β-cells unresponsive to glucose and the other 50% responding with a lower sensitivity (half-maximal stimulation at 7 mmol/l glucose). Comparison of β-cells cultured at the three glucose concentrations indicated that prolonged exposure to elevated glucose levels increases the number of degranulated cells, of cells with a high proportion of immature insulin granules, and of cells with glycogen deposition-morphologic features previously described in conditions of hyperglycemia. It is concluded that chronic exposure (9 days) of rat β-cells to elevated glucose levels induces a prolonged state of β-cell activation and glucose hypersensitivity rather than a glucotoxicity or glucose desensitization. This shift in the functional state of the β-cell population is responsible for a reduced insulin release in response to glucose, as observed in other conditions of prolonged exposure to high glucose levels.
Mechanisms of Sulfonylurea's Stimulation of Insulin Secretion In Vivo: Selective Amplification of Insulin Secretory Burst Mass
Authors: Pørksen Niels K , Munn Stephen R , Steers Jeffery L , Schmitz Ole , Veldhuis Johannes D , Butler Peter C
Published: September 2013

Although sulfonylureas enhance insulin secretion, it is unknown whether these hypoglycemic chemicals stimulate insulin secretion through the augmentation of the pulsatile or basal modes of insulin release. Enhanced pulsatile insulin could occur in turn through amplification of the burst mass or an increase in burst frequency. To address the mechanism of sulfonylurea action, we employed a recently validated canine model with a portal vein sampling catheter and flow probe to measure pulsatile insulin secretion in vivo directly in response to tolbutamide infusion or ingestion. After a 16-h fast, seven dogs were studied in the postabsorptive basal state and during a tolbutamide (0.2 mg/min) infusion when their plasma glucose concentrations were clamped at euglycemia. Insulin concentrations in the carotid artery (basal vs. tolbutamide, 85 ± 12 vs. 325 ± 66 pmol/l; P < 0.01) and portal vein (basal vs. tolbutamide, 345 ± 55 vs. 1,288 ± 230 pmol/l; P < 0.01) increased during tolbutamide infusion, but the portal vein plasma flow did not change. Increased plasma insulin concentrations were achieved by a fourfold increase in the total insulin secretion rate (2.3 ± 0.2 to 9.4 ± 1.9 pmol · kg−1 · min−1; basal vs. tolbutamide, P < 0.01). The augmented total insulin secretion was achieved mechanistically via a marked and selective increase in the insulin secretory burst mass (basal vs. tolbutamide, 266 ± 64 vs. 817 ± 144 pmol/pulse; P < 0.01), with no change in portal-vein insulin pulse frequency (basal vs. tolbutamide, 10.1 ± 0.6 vs. 11.1 ± 0.8 pulses/h; P = 0.3). Oral (250 mg) tolbutamide also magnified the endogenous insulin secretion rate by the preferential amplification of the secretory pulse mass (basal vs. tolbutamide, 167 ± 37 vs. 362 ± 50 pmol/pulse; P < 0.01). Neither the infusion nor the ingestion of tolbutamide changed the calculated clearance rates of endogenously secreted insulin. We conclude that sulfonylurea (tolbutamide) induced insulin secretion in vivo is achieved by the highly selective amplification of insulin secretory burst mass with no change in basal insulin release or the frequency of the β-cell-network pacemaker.
In the Absence of Counterregulatory Hormones, the Increase in Hepatic Glucose Production During Insulin-Induced Hypoglycemia in the Dog Is Initiated in the Liver Rather Than the Brain
Authors: Connolly Cynthia C , Myers Sharon R , Neal Doss W , Hastings Jon R , Cherrington Alan D
Published: September 2013

We have previously demonstrated that the liver can release glucose in response to insulin-induced hypoglycemia, despite the absence of glucagon, epinephrine, cortisol, and growth hormone. The aim of this study was to determine whether this is activated by liver or brain hypoglycemia. We assessed the response to insulin-induced hypoglycemia in the absence of counterregulatory hormones in overnight-fasted conscious adrenalectomized dogs that were given somatostatin and intraportal insulin (30 pmol · kg−1 · min−1) for 360 min. Glucose was infused to maintain euglycemia for 3 h and then to allow limited peripheral hypoglycemia for the next 3 h. During peripheral hypoglycemia, five dogs received glucose via both carotid and vertebral arteries to maintain cerebral euglycemia (H-EU group) concurrently with peripheral hypoglycemia, while six dogs received saline in these vessels to allow simultaneous cerebral and peripheral hypoglycemia (H-HY group). Throughout the study, arterial insulin was 1,675 ± 295 and 1,440 ± 310 pmol/l in the H-HY and H-EU groups, respectively. Glucose fell from 6.2 ± 0.3 to 2.1 ± 0.0 mmol/l and from 5.8 ± 0.3 to 1.9 ± 0.1 mmol/l in the last hour in the H-HY and H-EU groups, respectively (P < 0.05 for both). Norepinephrine rose from 1.12 ± 0.35 to 2.44 ± 0.69 nmol/l and from 1.09 ± 0.07 to 1.74 ± 0.16 nmol/l in the last hour in the H-HY and H-EU groups, respectively (P < 0.05 for both; no difference between groups). Glucagon, epinephrine, and cortisol were below the limits of detection. The liver switched from uptake to output of glucose during peripheral hypoglycemia in both the H-HY (–7.1 ± 2.1 to 5.4 ± 3.1 μmol · kg−1 · min−1) and H-EU (–7.9 ± 3.5 to 3.4 ± 1.7 μmol · kg−1 · min−1) groups (P < 0.05 for both; no difference between groups). Alanine levels and net hepatic alanine uptake fell similarly in both groups. There were increases (P < 0.05) in glycerol (12 ± 3 to 258 ± 47 μmol/l) and nonesterified fatty acid (194 ± 10 to 540 ± 80 micromol/l) levels and in total ketone production (0.4 ± 0.1 to 1.1 ± 0.2 μmol · kg−1 · min−1) in the H-HY group, but these parameters did not change in the H-EU group. These data clearly indicate that the lipolytic and hepatic responses to hypoglycemia are driven by differential sensing mechanisms. Thus, during insulin-induced hypoglycemia, when counterregulatory hormones are absent, liver hypoglycemia triggers the increase in hepatic glucose production, whereas cerebral hypoglycemia causes the increases in lipolysis and ketogenesis.
The Roles of Catecholamines in Glucoregulation in Intense Exercise as Defined by the Islet Cell Clamp Technique
Authors: Sigal Ronald J , Fisher Simon , Halter Jeffrey B , Vranic Mladen , Marliss Errol B
Published: September 2013

Exercise at > 85% VO2max causes the greatest known physiological increases in glucose production rates (Ra). To define the relative roles of catecholamine versus glucagon/insulin responses in stimulating Ra, normal subjects in the postabsorptive state exercised at 87 ± 2% VO2max during an islet cell clamp (IC): intravenous octreotide (somatostatin analog), 30 ng s· kg−1 · min−1; glucagon, 0.8 ng · kg−1 · min−1; growth hormone, 10 ng · kg−1 · min−1; and insulin adjusted to achieve euglycemia, then constant 56 ± 7 min before exercise. Seven control subjects exercised without an IC. In four subjects (IC-1) with hormone infusions held constant during exercise, plasma insulin rose 76% and glucagon 35%, perhaps because of altered hemodynamics. In seven subjects (IC-2), hormone infusions were decreased stepwise during exercise and returned stepwise to initial rates during early recovery. Ra increased sixfold in control and both IC groups. Plasma norepinephrine and epinephrine likewise increased > 12-fold with no differences among groups; both catecholamines correlated closely with Ra. Because mixed venous blood plasma insulin declined and glucagon did not change in control subjects, the glucagon-to-insulin ratio increased from 0.20 to 0.26 (P = 0.02). In IC subjects, plasma insulin increased and glucagon was either constant (IC-2) or increased < insulin, resulting in nonsignificant declines in the immunoreactive glucose-to-immunoreactive insulin ratio. Although a rise in insulin would have been expected to attenuate the Ra increment, this effect was overridden. The strong correlations of Ra with catecholamines and the similar Ra responses despite divergent glucagon-to-insulin responses are consistent with the primacy of catecholamines in regulation of Ra in intense exercise.
An Approach for Identifying Simple Sequence Repeat DNA Polymorphisms Near Cloned cDNAs and Genes: Linkage Studies of the Islet Amyloid Polypeptide/Amylin and Liver Glycogen Synthase Genes and NIDDM
Authors: Gambino Vita , Menzel Stephan , Trabb Jeffrey B , Xiang Kun-San , Lindner Tom , Louït Aymeric , Chen Eric , Mereu Laurie E , Furuta Hiroto , Iwasaki Naoko , Kawamura Makiko , Omori Yasue , Rietzsch Hannes , Schulze Jan , Schröder Hans-Egbert , Concannon Patrick , Hanis Craig L , Spielman Richard S , Yamagata Kazuya , Cox Nancy J , Bell Graeme I
Published: September 2013

Genetic factors contribute to the development of NIDDM, and genes involved in regulating pancreatic β-cell function and insulin's effects on glucose metabolism are good candidates for being NIDDM susceptibility loci. However, testing candidate genes for linkage to NIDDM depends on the identification of highly informative DNA polymorphisms in or near the candidate locus. Here we describe an approach for identifying highly polymorphic markers near candidate genes that utilizes the emerging physical map of the human genome. A sequence-tagged site from the candidate gene is used to screen the Centre d'Etude du Polymorphisme Humain megabase-insert yeast artificial chromosome library, which contains information on the physical localization of >3,000 genetically mapped simple sequence repeat DNA polymorphisms. Thus, identification of a yeast artificial chromosome containing the candidate locus will in many instances also identify a physically linked simple sequence repeat DNA polymorphism that can be used as a marker for the candidate gene in linkage studies. We have used this approach to identify a marker for the islet amyloid polypeptide gene on chromosome 12. The physical mapping of this gene to a yeast artificial chromosome showed that it was in the same yeast artificial chromosome as the gene encoding liver glycogen synthase, another possible NIDDM susceptibility gene. Affected sib pair studies using a simple sequence repeat DNA polymorphism physically linked to the islet amyloid polypeptide and liver glycogen synthase genes showed no evidence for linkage with NIDDM, indicating that they are not major genes contributing to NIDDM susceptibility.
Transgenic Mouse and Gene Therapy
Authors: Harada Kenji , Shimano Hitoshi , Ishibashi Shun , Yamada Nobuhiro
Published: September 2013

In the transgenic mouse, a specific gene can be transduced or deleted to study its function and relation to human diseases. Recently, various lines of transgenic mice that overexpress or lack a specific gene have been established and are available to study the pathophysiology of human diseases, including atherosclerosis, diabetes, and hyperlipidemia. We have established transgenic mouse lines with an integrated rat apolipoprotein (apo) E gene under control of the metallothionein promoter. Overexpression of apoE in the liver reduced plasma cholesterol and triglyceride levels and prevented dietinduced hypercholesterolemia. Another transgenic model with overexpression of apoE under control of the H2 Ld promoter in the arterial wall was established. In this model, the formation of fatty streak lesions was markedly inhibited, suggesting that apoE has antiatherogenic actions. Finally, we discuss gene therapy, which will be an important therapeutic approach to correct genetic abnormalities found in metabolic diseases.
Diabetes and Cardiovascular Disease in a Prospective Population Survey in Japan: The Hisayama Study
Authors: Fujishima Masatoshi , Kiyohara Yutaka , Kato Isao , Ohmura Takao , Iwamoto Hiromitsu , Nakayama Keizo , Ohmori Susumu , Yoshitake Taketo
Published: September 2013

To elucidate the effect of glucose intolerance on cardiovascular disease in the current Japanese population, we performed a 75-g oral glucose tolerance test in 2,427 Hisayama residents aged 40–79 years in 1988, who were free from a previous history of stroke or myocardial infarction, and followed them prospectively for 5 years. The prevalence of diabetes (NIDDM) among men was 13% and that of impaired glucose tolerance (IGT) was 20%; the corresponding values for women were 9 and 19%, respectively. The age- and sex-adjusted incidence of cerebral infarction (6.5 per 1,000 person-years, P 0.01) and coronary heart disease (5.0 per 1,000 person-years, P 0.05) was significantly higher in subjects with NIDDM than in those with normal glucose tolerance (1.9 and 1.6 per 1,000 person-years, respectively). In addition, subjects with IGT and NIDDM had a higher risk of cardiovascular disease including stroke and coronary heart disease than did those with normal glucose tolerance after adjustment for age and sex, namely the relative risk for IGT was 1.9 (95% CI 1.2–3.2), and the relative risk for NIDDM was 3.0 (95% CI 1.8–5.2). These associations remained significant even after controlling for six other risk factors including hypertension in multivariate analysis. Our data suggest that NIDDM is a significant risk factor for both cerebral infarction and coronary heart disease and also that IGT itself is a risk factor for cardiovascular disease in the general Japanese population today.
Cytokines, Modified Lipoproteins, and Arteriosclerosis in Diabetes
Authors: Lopes-Virella Maria F , Virella Gabriel
Published: September 2013

Modified lipoproteins, particularly different forms of oxidized LDL (ox-LDL), have been reported to elicit humoral immune responses both in experimental animals and humans. In diabetes, glycation and oxidation processes coexist and lead to the formation of glycoxidation products. Ox-LDL has been demonstrated in atheromatous lesions, anti-ox-LDL antibodies have been detected in circulation and in atheromatous plaques, and immune complexes (ICs) formed with LDL and anti-LDL (LDL-IC) have been isolated from the serum of patients with manifestations of atherosclerosis. In addition, in vitro formed LDL-ICs and ICs isolated from patients have been demonstrated to cause intracellular accumulation of cholesteryl esters (CEs) in human macrophages and fibroblasts. The accumulation of CEs in macrophages exposed to LDL-ICs is unique to this type of IC and is associated with paradoxical overexpression of LDL receptor and with increased synthesis and release of interleukin Iβ and tumor necrosis factor (TNF) α. The overexpression of LDL receptors is higher in LDL-IC-stimulated macrophages that release markedly high amounts of TNF-α than in macrophages that release low amounts of TNF-α into the medium. The release of cytokines in the subendothelial space may have a significant role in promoting the interaction of endothelial cells with mononuclear cells, causing endothelial cell damage directly or indirectly, and also in inducing smooth muscle cell proliferation. Thus, in view of the above data, it can be concluded that humoral autoimmunity may play a significant role in the pathogen-esis of atherosclerosis in diabetes.
The Role of Insulin Resistance in Korean Patients With Coronary Atherosclerosis
Authors: Huh Kap Bum , Lee Hyun Chul , Cho Seung Yun , Lee Jong Ho , Song Young Duk
Published: September 2013

To determine whether dietary modification improves insulin resistance and coronary atherosclerosis, we randomly assigned 14 Korean patients to an experimental group (low-fat, low-cholesterol diet, high polyunsaturated/saturated fatty acid ratio, and calorie restriction) or to a control group (no dietary change). Coronary artery lesions were analyzed by quantitative coronary angiography, and postglucose insulin responses were measured. At baseline, there were no significant differences in body weight, BMI, waist-to-hip ratio (WHR), and plasma lipid and insulin levels between the two groups. After completion of the 1-year diet program, the experimental group showed significant reductions in body weight (66.0 ± 3.2 to 61.6 ± 3.8 kg [means ± SE], <0.01) and WHR (0.96 ± 0.01 to 0.93 ± 0.01, P < 0.05). Total cholesterol (5.45 ± 0.45 to 4.50 ± 0.44 mmol/l, P < 0.05), LDL cholesterol (3.71 ± 0.36 to 2.98 ± 0.37 mmol/l, P < 0.05), and triglyceride (1.91 ± 0.28 to 1.29±0.17 mmol/l, P < 0.05) were also significantly reduced in the experimental group. The mean insulin response during an oral glucose tolerance test was also significantly decreased (258.6 ± 26.4 to 181.8 ± 6.6 mmol/1, P < 0.05). In contrast, there were no significant changes in these parameters in the control group. When only coronary artery lesions >50% stenosed were analyzed, the average percentage diameter stenosis regressed from 63.2 to 56.8% in the experimental group. However, there were no significant changes in the control group. Our trial suggests that decreases in body weight and WHR and an improvement in insulin resistance with a low-fat, low-cholesterol diet and caloric restriction may reduce risk factors and reverse coronary atherosclerotic lesions in 1 year.
Insulin Suppresses Endothelial Secretion of C-Type Natriuretic Peptide, A Novel Endothelium-Derived Relaxing Peptide
Authors: Igaki Toshio , Itoh Hiroshi , Suga Shin-ichi , Komatsu Yasato , Ogawa Yoshihiro , Doi Kentaro , Yoshimasa Takaaki , Nakao Kazuwa
Published: September 2013

We have previously reported that C-type natriuretic peptide (CNP), the third member of the natriuretic peptide family, is produced in vascular endothelial cells (ECs) and acts as an endothelium-derived relaxing peptide. We further demonstrated the detection of the gene transcripts of CNP and atrial natriuretic peptide (ANP) B receptor, a specific receptor for CNP, in human blood vessels. We thus propose the existence of a vascular natriuretic peptide system (NPS). CNP secretion was also demonstrated to be stimulated by various growth factors and cytokines. To clarify the significance of vascular NPS in proliferative vascular complications associated with diabetes, hypertension, or atherosclerosis, in the present study we examined the effect of insulin on CNP secretion from cultured ECs. Insulin at a concentration in the physiological range (10−10−10−7 mol/1) potently suppressed CNP secretion, whereas insulin at the same concentration did not suppress endothelin (ET) secretion from EC. IGF-I had no significant effect on CNP secretion. Insulin, therefore, can be a potent inhibitor of CNP secretion through the activation of insulin receptor. Since CNP has been shown to be a potent inhibitor of vascular smooth muscle cell proliferation, the present study suggests the possibility that attenuated activity of vascular NPS is associated with hyperinsulinemia, which might result in proliferative vascular lesions.
A Fatty Acid—Induced Decrease in Pyruvate Dehydrogenase Activity Is an Important Determinant of β-Cell Dysfunction in the Obese Diabetic db/db Mouse
Authors: Zhou Yun-Ping , Berggren Per-Olof , Grill Valdemar
Published: September 2013

We studied the effects of fatty acid oxidation on insulin secretion of db/db mice and underlying molecular mechanisms of these effects. At 2–3 months of age, db/db mice were markedly obese, hyperglycemic, and hyperinsulinemic. Serum free fatty acid (FFA) levels were increased in 2-month-old (1.5 ± 0.1 vs. 1.1 ± 0.1 mmol/l, P < 0.05) and 3-month-old (1.9 ± 0.1 vs. 1.2 ± 0.1 mmol/l, P < 0.01) mice compared with the age and sex-matched db/+ mice serving as controls. Glucose-induced insulin release from db/db islets was markedly decreased compared with that from db/+ islets and was specifically ameliorated (by 54% in 2-month-old and 38% in 3-month-old mice) by exposure to a carnitine palmitoyltransferase I inhibitor, etomoxir (1 μmol/l). Etomoxir failed to affect the insulin response to α-ketoisocaproate. The effect of etomoxir on glucose-induced insulin release was lost after culturing db/db islets in RPMI medium containing 22 mmol/l glucose but no fatty acid. Culture of db/+ islets with 0.125 mmol/l palmitate led to a decrease in glucose-induced insulin secretion, which was partially reversible by etomoxir. Both islet glucose oxidation and the ratio of glucose oxidation to utilization were decreased in db/db islets. Etomoxir significantly enhanced glucose oxidation by 60% and also the ratio of oxidation to glucose utilization (from 27 ± 2.5 to 37 ±3.0%, P < 0.05). Pyruvate dehydrogenase (PDH) activity was decreased in islets of db/db mice (75 ±4.2 vs. 91 ± 2.9 nU/ng DNA, P < 0.01), whereas PDH kinase activity was increased (rate of PDH inactivation −0.25 ± 0.02 vs. −0.11 ± 0.02/min, P < 0.01). These abnormalities were partly but not wholly reversed by a 2-h preexposure to etomoxir. In conclusion, elevated FFA levels in the db/db mouse diminish glucose-induced insulin secretion by a glucose–fatty acid cycle in which fatty acid oxidation inhibits glucose oxidation by decreasing PDH activity and increasing PDH kinase activities.
Association of HLA-DPB1*0301 With IDDM in Mexican-Americans
Authors: Erlich Henry A , Rotter Jerome I , Chang Julie D , Shaw Sylvia J , Raffel Leslie J , Klitz William , Bugawan Teodorica L , Zeidler Adina
Published: September 2013

Susceptibility to IDDM has been associated with specific alleles at the HLA class II loci in a variety of human populations. Previous studies among Mexican-Americans, a group ancestrally derived from Native Americans and Hispanic whites, showed that the DR4 haplotypes (DRB1*0405-DQB1*0302 and DRB1*0402-DQB1*0302) and the DR3 haplotype (DRB1*0301-DQB1*0201) were increased among patients and suggested a role for both DR and DQ alleles in susceptibility and resistance. Based on the analysis of 42 Mexican-American IDDM families and ethnically matched control subjects by polymerase chain reaction/sequence-specific oligonucleotide probe typing, we report an association of IDDM with the DPB1 allele, *0301 (relative risk = 6.6; P = 0.0012) in this population. The analysis of linkage disequilibrium patterns in this population indicates that the observed increased frequency in DPB1*0301 among patients cannot be attributed simply to linkage disequilibrium with high-risk DR-DQ haplotypes. These data suggest that in addition to alleles at the DRB1 and DQB1 loci, polymorphism at the DPB1 locus may also influence IDDM risk.
Oral Vanadyl Sulfate Improves Insulin Sensitivity in NIDDM but Not in Obese Nondiabetic Subjects
Authors: Halberstam Meyer , Cohen Neil , Shlimovich Pavel , Rossetti Luciano , Shamoon Harry
Published: September 2013

We compared the effects of oral vanadyl sulfate (100 mg/day) in moderately obese NIDDM and nondiabetic subjects. Three-hour euglycemic-hyperinsulinemic (insulin infusion 30 mU · m−2 · min−1) clamps were performed after 2 weeks of placebo and 3 weeks of vanadyl sulfate treatment in six nondiabetic control subjects (age 37 ± 3 years; BMI 29.5 ± 2.4 kg/m2) and seven NIDDM subjects (age 53 ± 2 years; BMI 28.7 ±1.8 kg/m2). Glucose turnover ([3-3H]glucose), glycolysis from plasma glucose, glycogen synthesis, and whole-body carbohydrate and lipid oxidation were evaluated. Decreases in fasting plasma glucose (by ∼1.7 mmol/l) and HbAlc (both P < 0.05) were observed in NIDDM subjects during treatment; plasma glucose was unchanged in control subjects. In the latter, the glucose infusion rate (GIR) required to maintain euglycemia (40.1 ± 5.7 and 38.1 ± 4.8 μmol · kg fat-free mass [FFM]−1 · min−1) and glucose disposal (Rd) (41.7 ± 5.7 and 38.9 ±4.7 μmol · kg FFM−1 · min−1) were similar during placebo and vanadyl sulfate administration, respectively. Hepatic glucose output (HGO) was completely suppressed in both studies. In contrast, in NIDDM subjects, vanadyl sulfate increased GIR ∼82% (17.3 ± 4.7 to 30.9 ± 2.7 μmol · kg FFM−1 · min−1, P < 0.05); this improvement in insulin sensitivity was due to both augmented stimulation of Rd (26.0 ±4.0 vs. 33.6 ± 2.22 μmol · kg FFM−1 · min−1, P < 0.05) and enhanced suppression of HGO (7.7 ± 3.1 vs. 1.3 ± 0.9 μmol · kg FFM−1 · min−1, P < 0.05). Increased insulin-stimulated glycogen synthesis accounted for >80% of the increased Rd with vanadyl sulfate (P < 0.005), but plasma glucose flux via glycolysis was unchanged. In NIDDM subjects, vanadyl sulfate was also associated with greater suppression of plasma free fatty acids (FFAs) (P < 0.01) and lipid oxidation (P < 0.05) during clamps. The reduction in HGO and increase in Rd were both highly correlated with the decline in plasma FFA concentrations during the clamp period (P < 0.001). In conclusion, small oral doses of vanadyl sulfate do not alter insulin sensitivity in nondiabetic subjects, but it does improve both hepatic and skeletal muscle insulin sensitivity in NIDDM subjects in part by enhancing insulin's inhibitory effect on lipolysis. These data suggest that vanadyl sulfate may improve a defect in insulin signaling specific to NIDDM.
Increased Urea Synthesis in Insulin-Dependent Diabetic Dogs Maintained Normoglycemic: Effect of Portal Insulin Administration and Food Protein Content
Authors: Freyse E-J , Rebrin K , Schneider T , Petrzika M , Fischer U
Published: September 2013

In IDDM, the gluconeogenic turnover of amino acids is increased even if glycemia is well controlled and may be restored to normal by means of prehepatic insulin substitution. Therefore, the present study was designed 1) to investigate the influence of route of insulin administration (portal versus peripheral) on the urea production rate, which is considered to measure amino acid catabolism, and 2) to elucidate the impact of different food-protein intake. Paired studies were conducted in chronic insulin-dependent diabetic dogs maintained normoglycemic. Diabetic animals and nondiabetic controls were fed either a high-protein diet (46% of energy intake provided by proteins; study 1) or a low-protein carbohydrate-supplemented diet (20% of energy intake provided by protein; study 2) for 2 days, and flux rates of glucose and urea were measured using isotope dilution techniques. In both studies, the diabetic animals were maintained normoglycemic by glucose-controlled insulin infusion delivered either systemically or portally. In study 1 versus study 2, the animals showed lower α-amino nitrogen levels and concentrations of gluconeogenic amino acids, predominantly alanine. There were no significant differences in plasma glucose and glucose turnover between the experimental groups on either systemic or portal insulin infusion versus controls; however, peripheral insulin levels were higher for diabetic animals maintained with systemic versus portal insulin delivery (P < 0.05). No significant differences in glucagon, lactate, pyruvate, nonesterified fatty acids, or β-hydroxybutyrate were observed. Urea production was significantly higher in study 1 compared with study 2: 7.48 ± 0.83 vs. 5.97 ± 0.59 μmol · kg−1 · min−1 (normal dogs); 12.97 ± 1.86 vs. 5.54 ± 0.60 μmol · kg−1 · min−1 (diabetic dogs on portal insulin); 16.11 ± 2.59 vs. 6.82 ± 0.70 μmol · kg−1 · min−1 (diabetic dogs on systemic insulin infusion); P < 0.05 for all. The diabetic dogs maintained normoglycemic with systemic insulin infusions had significantly higher rates of urea synthesis than those with portal insulin infusion (P < 0.05). It is concluded that in IDDM, even if normoglycemia is managed, there is significantly increased amino acid catabolism with posthepatic systemic insulin treatment. This increased catabolic rate is more pronounced during high-protein nourishment.
Expression of Insulin Receptor mRNA and Insulin Receptor Substrate 1 in Pancreatic Islet β-Cells
Authors: Harbeck Mark C , Louie Diane C , Howland Jennie , Wolf Bryan A , Rothenberg Paul L
Published: September 2013

The expression of insulin receptor mRNA was examined in rat pancreatic islet cells by single-cell reverse transcriptase (RT)–polymerase chain reaction (PCR). Single cells from disaggregated islets were individually isolated in a microcapillary pipet, and the β-cells were identified by amplification of the mRNA for insulin. We found that in single β-cells, the mRNA for the insulin receptor was also expressed. The fraction of single islet cells expressing both insulin receptor and insulin mRNAs corresponds closely to the fraction of β-cells in the disaggregated islet cell preparation. These results indicate that normal β-cells have the potential to express authentic insulin receptors. Immunohistochemical analysis was insufficiently sensitive for assaying insulin receptor protein; however, insulin receptor substrate 1 (IRS-1) was readily immunolocalized in islet β-cells. Since IRS-1 links several cell surface receptors, including those for insulin and IGF-I, to distal signal transduction pathways, our observations indicate that hormonal regulation of islet β-cells potentially involves the same signal transduction pathway that mediates insulin and growth factor signaling in peripheral insulin target tissue cell types.
Expression of Transporter Associated With Antigen Processing–1 in the Endocrine Cells of Human Pancreatic Islets: Effect of Cytokines and Evidence of Hyperexpression in IDDM
Authors: Vives-Pi Marta , Armengol Maria , Alcalde Laura , Costa Manuela , Somoza Nuria , Vargas Francesca , Jaraquemada Dolores , Pujol-Borrell Ricardo
Published: September 2013

A possible role of transporter associated with antigen processing (TAP)-l in the pathogenesis of IDDM has been investigated by examining the level of TAP-1 expression in the islets of IDDM pancreas and by studying in vitro the effect of interferon (IFN)-γ, IFN-α, and tumor necrosis factor-α in TAP-1 expression by cultured islet cells. A remarkable hyperexpression of TAP-1 has been found in the endocrine cells (β and non-β) of IDDM islets, which constitutes first evidence of hyperexpression of this molecule in the target organ of an autoimmune disease. TAP-1 hyperexpression correlated clearly with HLA class I hyperexpression but only very partially with HLA class II ectopic expression. IFN-γ and IFN-α, both cytokines putatively implicated in IDDM pathogenesis, were capable of inducing TAP-1 protein (as assessed by immunofluorescence flow cytometry) and message (by Northern blot analysis and reverse transcription polymerase chain reaction). These findings suggest that under the influence of cytokines (most probably IFN-α) β-cells may express in their surface a high density of HLA class I–peptide complexes that may facilitate their recognition and lysis by low-affinity CD8+ T-cells.
VLDL Triglyceride Kinetics in Wistar Fatty Rats, An Animal Model of NIDDM: Effects of Dietary Fructose Alone or in Combination With Pioglitazone
Authors: Kazumi Tsutomu , Hirano Tsutomu , Odaka Hiroyuki , Ebara Tetsu , Amano Nobuyuki , Hozumi Toshiki , Ishida Yoshihiko , Yoshino Gen
Published: September 2013

The effects of dietary fructose alone or in combination with a new oral agent, pioglitazone, on VLDL-triglyceride (TG) turnover were studied in genetically obese Wistar fatty rats characterized by hyperinsulinemia (7,488 ± 954 pmol/l), hyperglycemia (22.5 ± 1.4 mmol/l), and hypertriglyceridemia (4.39 ± 0.54 mmol/l). They had an increased hepatic TG production (16.2 ± 0.1 μmol/min; lean rats, 5.4 ± 0.3 μmol/min) as well as a longer half-life of VLDL-TG from lean donors (8.8 ± 1.4 min, lean recipients; 2.3 ± 0.9 min). In addition, in lean recipients, the half-life of VLDL-TG from fatty donors was longer than that from lean donors (4.80 ± 0.56 vs. 3.14 ± 0.23 min). Although feeding fructose into fatty rats did not change plasma glucose and insulin levels, it produced a twofold increase in TG levels (8.74 ± 1.15 mmol/l). This was associated with a 1.7-fold increase in TG production to 27.5 ± 1.2 μmol/min, while no significant change was found in the half-life of lean VLDL-TG in fructose-fed fatty recipients (10.9 ± 2.4 min) or in that of VLDL-TG from fructose-fed fatty donors in lean recipients (4.46 ± 0.76 min). Daily administration of pioglitazone (3 mg/kg body weight) in fructose-fed fatty rats ameliorated glycemia and triglyceridemia to the level of lean rats (8.1 ± 0.7 and 1.18 ± 0.05 mmol/l, respectively) and insulinemia to a lesser extent (2,712 ± 78 pmol/l). A fall in TG levels was associated with improvement of an impairment in the ability of fructose-fed fatty rats to remove lean VLDL-TG (half-life: 2.6 ± 0.6 min). Pioglitazone, however, produced no change in TG production (25.9 ± 2.7 μmol/min), the half-life of VLDL-TG from fructose-fed fatty donors in lean recipients (4.17 ± 0.38 min), or the activity of lipoprotein lipase and hepatic lipase in postheparin plasma. We conclude that in Wistar fatty rats 1) hypertriglyceridemia is attributed to TG overproduction and impaired TG catabolism, and the latter is due to changes in both VLDL, such that they are less able to be removed, and changes in the nature of Wistar fatty rats, such that they are less able to remove VLDL-TG; 2) fructose further increases hepatic TG production with a resultant deterioration in hypertriglyceridemia; 3) pioglitazone normalizes TG levels by altering the physiology of the Wistar fatty rats in a manner that increases their ability to remove VLDL-TG from the circulation.
Human Prohormone Convertase 3 Gene: Exon-Intron Organization and Molecular Scanning for Mutations in Japanese Subjects With NIDDM
Authors: Ohagi Shinya , Sakaguchi Hidenobu , Sanke Tokio , Tatsuta Hitomi , Hanabusa Tadashi , Nanjo Kishio
Published: September 2013

Proinsulin is converted to insulin by the concerted action of two sequence-specific subtilisin-like proteases termed prohormone convertase 2 (PC2) and prohormone convertase 3 (PC3). PC3 is a type I proinsulin-processing enzyme that initiates the sequential processing of proinsulin to insulin by cleaving the proinsulin molecule on the COOH-terminal side of the dibasic peptide, Arg31-Arg32, joining the B-chain and C-peptide. Thus, PC3 plays a key role in regulating insulin biosynthesis. Expressions of insulin and PC3, but not PC2, are coordinately regulated by glucose, consistent with the important role of PC3 in regulating proinsulin processing. NIDDM is associated with increased secretion of proinsulin and proinsulin-like molecules, suggesting that mutations in the PC3 gene may be involved in the development of this disorder. To examine this hypothesis, we have isolated and characterized the human PC3 gene and screened it for mutations in a group of Japanese subjects with NIDDM. The PC3 gene consists of 14 exons spanning more than 35 kb. The exon-intron organization of PC2 and PC3 genes are conserved, consistent with a common evolutionary origin for the prohormone convertase gene family. Single-strand conformational analysis and nucleotide sequencing of the entire coding region of the PC3 gene in 102 Japanese subjects with NIDDM revealed missense mutations in exons 2 (Arg/Gln53) and 14 (Gln/Glu638), neither of which was associated with NIDDM in this population. These data suggest that genetic variation in the PC3 gene is unlikely to be a major contributor to NIDDM susceptibility in Japanese.
Impact of Recent Antecedent Hypoglycemia on Hypoglycemic Cognitive Dysfunction in Nondiabetic Humans
Authors: Hvidberg Annemarie , Fanelli Carmine G , Hershey Tamara , Terkamp Christoph , Craft Suzanne , Cryer Philip E
Published: September 2013

To test the hypothesis that glycemic thresholds for hypoglycemic cognitive dysfunction, like those for neuroendocrine responses to and symptoms of hypoglycemia, shift to lower plasma glucose concentrations after recent antecedent hypoglycemia, 16 healthy young adult subjects (7 women and 9 men) were studied on two separate occasions in random sequence, once with hyperinsulinemic hypoglycemia (2.6 ± 0.1 mmol/l, 47 ± 1 mg/dl) and once with otherwise identical hyperinsulinemic euglycemia (4.8 ± 0.1 mmol/l, 86 ± 5 mg/dl) between 1430 and 1630. Neuroendocrine, symptomatic, and cognitive responses to hyperinsulinemic stepped hypoglycemic (4.7, 4.2, 3.6, 3.0, 2.8, 2.5, and 2.2 mmol/l; 85, 75, 65, 55, 50, 45, and 40 mg/dl) clamps were quantitated the following morning on both occasions. Cognitive function tests included measures of information processing (Serial Addition), attention (Stroop Arrow Word), pattern recognition and memory (Delayed Non-Match to Sample), and declarative memory (Paragraph Recall). As expected, plasma glucagon (P = 0.0094), epinephrine (P = 0.0063), and pancreatic polypeptide (P = 0.0046) responses to stepped hypoglycemia were reduced significantly, and symptomatic responses tended to be reduced after afternoon hypoglycemia. Performance on the cognitive function tests deteriorated (P < 0.0001) during stepped hypoglycemic clamps, but there were no significant overall effects of antecedent hypoglycemia on hypoglycemic cognitive dysfunction. Although deterioration was reduced (P < 0.05) from the 2.8 mmol/l (50 mg/dl) to the 2.5 mmol/l (45 mg/dl) steps on the Serial Addition and Delayed Non-Match to Sample tasks after afternoon hypoglycemia, comparable differences were not found on the Stroop Arrow Word or Paragraph Recall tasks. Thus, glycemic thresholds for hypoglycemic cognitive dysfunction, unlike those for neuroendocrine responses to and symptoms of hypoglycemia, do not seem to shift to substantially lower plasma glucose concentrations after recent antecedent hypoglycemia in nondiabetic humans.
Evidence for a Major Role for Glucagon in Regulation of Plasma Glucose in Conscious, Nondiabetic, and Alloxan-Induced Diabetic Rabbits
Authors: Brand Christian L , Jørgensen Peer N , Svendsen Ivan , Hoist Jens J
Published: September 2013

Effects of glucagon immunoneutralization on plasma glucose, insulin, and glucagon were studied 2–4 h after intravenous injection of a high-affinity, monoclonal glucagon antibody into normal as well as moderately and severely alloxan (ALX)-induced diabetic rabbits (n = 5–7). A monoclonal trinitrophenyl antibody was used in control studies. Endogenous glucagon was completely neutralized as evidenced by undetectable levels of free glucagon and high plasma glucagon-binding capacities. In postabsorbtive normal rabbits, glucagon neutralization decreased plasma glucose by 2.2 ± 0.3 mmol/l, and the resulting plasma levels of insulin and glucagon (indirectly measured) were 8 ± 3 and 640 ± 129% of baseline, respectively. However, when euglycemia was maintained by means of glucose infusion (steady-state plasma glucose and glucose infusion rate: 6.6 ± 0.1 mmol/l and 3.0 ± 0.4 mg · kg−1 · min−1), both plasma insulin and glucagon remained unaltered. Thus, the glucose infusion rate accurately reflects glucagon's contribution to postabsorbtive glucose production. In both moderately and severely diabetic rabbits, immunoneutralization of glucagon decreased plasma glucose by ∼8 mmol/l, leading to euglycemia (7.3 ± 1.1 mmol/l) and reduced hyperinsulinemia (41 ± 9% of baseline) in the former and to partial restoration of euglycemia (12.7 ± 1.8 mmol/l) and unchanged insulin levels in the latter group of diabetic rabbits (P < 0.05 vs. controls in all studies). No significant changes were observed in control studies. In conclusion, glucagon is an important regulator of postabsorbtive glucose production in normal rabbits and plays an important role in the maintenance of hyperglycemia in ALX-induced diabetic rabbits.
Salt Restriction Reduces Hyperfiltration, Renal Enlargement, and Albuminuria in Experimental Diabetes
Authors: Allen Terri J , Waldron Matthew J , Casley David , Jerums George , Cooper Mark E
Published: September 2013

The effects of dietary salt restriction on the renin angiotensin system, glomerular filtration rate (GFR), renal size, and albuminuria were assessed in streptozotocin diabetic rats. Two series of experiments were performed: one short-term with severe salt restriction and the second long-term with moderate salt restriction. The first studied the effect of a very-low-salt diet for 4 weeks on GFR, renal size, and plasma angiotensin II concentration in diabetic and control rats. Diabetic and control male Sprague-Dawley rats received either a very-low-salt (0.005% NaCl) or a normal-salt (0.4% NaCl) diet. Diabetes was associated with a 49% increase in GFR, a 34% increase in kidney weight, and an 85% reduction in plasma angiotensin II when compared with control rats (P < 0.001). Sodium restriction in diabetic rats reduced GFR, restored plasma angiotensin II to control values, and retarded kidney growth when compared with diabetic rats receiving a normal sodium diet. GFR correlated negatively with plasma angiotensin II (r = −0.65, P < 0.001) and positively with kidney weight (r = 0.66, P < 0.001). In the second experiment, serial measurements of albuminuria and GFR were performed in control, diabetic, and saltrestricted (0.05% NaCl) control and diabetic rats over 24 weeks. Albuminuria showed a continuous rise in the diabetic rats when compared with control rats. Salt restriction attenuated the increase in albuminuria over the whole study period as well as reducing blood pressure and kidney weight in the diabetic rats. In conclusion, sodium restriction was associated with a lower GFR and kidney weight after 4 weeks and reduced levels of albuminuria, kidney weight, and blood pressure after 24 weeks in diabetic rats. Salt restriction may have an important role in the prevention and treatment of diabetic nephropathy.
Effect of Granulocyte-Colony Stimulating Factor on Generation of Oxygen-Derived Free Radicals and Myeloperoxidase Activity in Neutrophils From Poorly Controlled NIDDM Patients
Authors: Sato Noriyuki , Kashima Koji , Tanaka Yoshito , Shimizu Hiroyuki , Mori Masatomo
Published: September 2013

To evaluate whether granulocyte-colony stimulating factor (G-CSF) improves an impaired production of oxygen-derived free radicals by neutrophils from poorly controlled NIDDM patients, we studied the effect of G-CSF on myeloperoxidase (MPO) activity and chemiluminescence amplified by a Cypridina luciferin analog (CLA-DCL), which is dependent on O−2 generation, and luminol (L-DCL), which is dependent on OCl− generation, in response to formyl-methonylleucyl- phenylalanine. Both CLA-DCL and L-DCL by neutrophils from the diabetic group (n = 15, HbA1c >10%) were significantly decreased (26 and 37%, respectively: P < 0.01) compared with the age-matched normal control group (n = 15), and L-DCL was more sensitive to this inhibition than CLA-DCL (P > 0.05). In both control and diabetic neutrophils, G-CSF significantly enhanced both CLA-DCL (175% in control and 156% in diabetic) and L-DCL (283% in control and 346% in diabetic). In diabetic neutrophils, the enhancing effect of G-CSF on L-DCL was more sensitive than on CLA-DCL (P = 0.001). There was a positive correlation between HbAlc and the enhancing effect of G-CSF on L-DCL in diabetic patients (P > 0.05), but not on CLA-DCL. MPO activity was also decreased in the diabetic group (63%, P > 0.05) , and G-CSF improved this impaired MPO activity (184%, P > 0.01). Furthermore, there was a positive correlation between HbA1c and the improving effect of G-CSF on MPO activity (P > 0.05). Because bacterial infection still accounts for an important cause of morbidity and mortality in diabetic patients, these data suggest that G-CSF may be useful as a drug to prevent the aggravation of bacterial infection by improving neutrophil function, especially through H2O2-MPO-OCl− mechanism, in poorly controlled diabetic patients.
Cow's Milk–Free Diet Does Not Prevent Diabetes in NOD Mice
Authors: Paxson Jessica A , Weber Jennifer G , Kulczycki Anthony
Published: September 2013

Early dietary exposure to cow's milk proteins has been proposed as an important environmental factor in the development of IDDM both in humans and in diabetes-prone rodents. To examine the significance of cow's milk protein in IDDM, 120 NOD mice were maintained, starting from conception until sacrifice, on one of four diets: standard PMI Picolab Rodent Diet 20, a milk-free modification of the standard Picolab diet, a milk-free diet incorporating 0.036% bovine serum albumin (BSA), and a milk-free diet including 0.036% bovine IgG (BGG). The cumulative IDDM incidence at 7 months for these mice in a specific pathogen-free environment on the respective diets was 78, 93, 93, and 67% for females, and 17, 54, 17, and 0% for males. The ages of diabetes onset and insulitis scores were similar for mice on each diet. The unexpectedly lower incidence of IDDM in mice on the milk-free diet that included BGG raises the possibility this cow's milk protein might possibly have some protective effect against the development of IDDM in NOD mice. Our main finding was that the standard, milk-free, and BSA-containing diets resulted in comparable incidences of IDDM in NOD mice, demonstrating that neither cow's milk whey proteins in general nor BSA in particular are significantly important as etiologic dietary agents in IDDM in NOD mice.