bluuebunny/crossref_metadata_2025 huggingface dataset:
Gene Expression of GLUT4 in Skeletal Muscle From Insulin-Resistant Patients With Obesity, IGT, GDM, and NIDDM
Authors: Garvey W Timothy , Maianu Lidia , Hancock Jerry A , Golichowski Alan M , Baron Alain
Published: September 2013

In obesity, impaired glucose tolerance (IGT), non-insulin-dependent diabetes mellitus (NIDDM), and gestational diabetes mellitus (GDM), defects in glucose transport system activity, contribute to insulin resistance in target tissues. In adipocytes from obese and NIDDM patients, we found that pretranslational suppression of the insulin-responsive GLUT4 glucose transporter isoform is a major cause of cellular insulin resistance; however, whether this process is operative in skeletal muscle is not clear. To address this issue, we performed percutaneous biopsies of the vastus lateralis in lean and obese control subjects and in obese patients with IGT and NIDDM and open biopsies of the rectus abdominis at cesarian section in lean and obese gravidas and gravidas with GDM. GLUT4 was measured in total postnuclear membrane fractions from both muscles by immunoblot analyses. The maximally insulin-stimulated rate of in vivo glucose disposal, assessed with euglycemic glucose clamps, decreased 26% in obesity and 74% in NIDDM, reflecting diminished glucose uptake by muscle. However, in vastus lateralis, relative amounts of GLUT4 per milligram membrane protein were similar (NS) among lean (1.0 ± 0.2) and obese (1.5 ± 0.3) subjects and patients with IGT (1.4 ± 0.2) and NIDDM (1.2 ± 0.2). GLUT4 content was also unchanged when levels were normalized per wet weight, per total protein, and per DNA as an index of cell number. Levels of GLUT4 mRNA were similarly not affected by obesity, IGT, or NIDDM whether normalized per RNA or for the amount of an unrelated constitutive mRNA species. Because muscle fibers (types I and II) exhibit different capacities for insulin-mediated glucose uptake, we tested whether a change in fiber composition could cause insulin resistance without altering overall levels of GLUT4. However, we found that quantities of fiber-specific isoenzymes (phopholamban and types I and II Ca2+-ATPase) were similar in all subject groups. In rectus abdominis, GLUT4 content was similar in the lean, obese, and GDM gravidas whether normalized per milligram membrane protein (relative levels were 1.0 ± 0.2, 1.3 ± 0.1, and 1.0 ± 0.2, respectively) or per wet weight, total protein, and DNA. We conclude that in human disease states characterized by insulin resistance, i.e., obesity, IGT, NIDDM, and GDM, GLUT4 gene expression is normal in vastus lateralis or rectus abdominis. To the extent that these muscles are representative of total muscle mass, insulin resistance in skeletal muscle may involve impaired GLUT4 function or translocation and not transporter depletion as observed in adipose tissue.
Beneficial Effect of Intravenous Bolus of Corticotropin-Releasing Factor on Glucose Intolerance of Genetically Obese (fa/fa) Rats
Authors: Rohner-Jeanrenaud Françoise , Jeanrenaud Bernard
Published: September 2013

The effect of an ovine corticotropin-releasing factor (oCRF) bolus administered intravenously at the onset of glucose ingestion during oral glucose tolerance tests (OGTTs) was evaluated in conscious lean (FA/FA) and genetically obese (fa/fa) rats. When the amount of oCRF was purposely small to not stimulate the hypothalamo-pituitary-adrenal (HPA) axis, it normalized the glucose intolerance of genetically obese rats as tested during OGTTs and decreased their insulin output, whereas it had no effect in lean rats. In obese rats, plasma xylose levels measured after the ingestion of a xylose load were unaltered by the intravenous oCRF bolus, indicating that the beneficial effect of oCRF on glucose intolerance of fa/fa rats was unlikely to be dependent on glucose absorption. When the intravenous bolus of oCRF was doubled at the onset of OGTTs, it stimulated the HPA axis and produced a worsening of glucose intolerance in obese rats together with an increase in their insulin response. Again, it had no effect in lean rats. The abnormal intravenous glucose tolerance of obese rats was unaffected by the administration of an oCRF bolus: This is in keeping with previous data showing that bypassing the oral cavity fails to elicit several sensory reflexes that markedly influence subsequent glucose clearance. It has been suggested that obese rats may have deficient oropharyngeal reflexes that could be reactivated by the oCRF bolus, thereby being responsible for the normalization of their impaired OGTT, which lies in the hepatic glucose production process.
Atrial Natriuretic Peptide and Prostacyclin Synergistically Mediate Hyperfiltration and Hyperperfusion of Diabetic Rats
Authors: Perico Norberto , Benigni Ariela , Gabanelli Maurizio , Piccinelli Antonella , Ròg Marek , De Riva Carlo , Remuzzi Giuseppe
Published: September 2013

The relative contribution of atrial natriuretic peptide (ANP) and vasodilatory prostaglandins to hyperfiltration in Wistar rats with experimental diabetes was studied 6–8 wk after streptozocin injection. Plasma levels of immunoreactive ANP were significantly higher (P < 0.01) in hyperglycemic diabetic (72.9 ± 11.7 pg/ml) than in normoglycemic diabetic (44.8 ± 8.6 pg/ml) or nondiabetic (40.0 ± 6.8 pg/ml) rats. Blocking endogenous ANP by specific ANP-antiserum infusion reduced significantly (P < 0.01) glomerular filtration rate (GFR) and renal plasma flow (RPF) of hyperglycemic rats compared with preinfusion values (1.23 ± 0.06–1.02 ± 0.04; 2.87 ± 0.25–2.40 ± 0.10 ml · min−1 · 100 g−1, respectively). However, correction of hyperfiltration and hyperperfusion was only partial (nondiabetic rats GFR 0.85 ± 0.07; RPF 2.27 ± 0.13 ml · min−1 · 100 g−1). Because diabetic rats with hyperglycemia also had an increased urinary excretion of prostacyclin metabolite 6-keto–prostaglandin F1α (220.6 ± 62.8 ng/24 h) compared with nondiabetic rats (51.2 ± 2.7 ng/24 h), we wondered whether excessive prostacyclin formation contributed to hyperfiltration and hyperperfusion in this setting. Indomethacin infusion partially reduced GFR (1.25 ± 0.07 to 1.06 ± 0.07 ml · min−1 · 100 g−1 P < 0.05) and RPF (2.85 ± 0.11 to 2.46 ± 0.12 ml · min−1 · 100 g−1 P < 0.01) in diabetic rats. The combined infusion of ANP antiserum and indomethacin normalized GFR and RPF in diabetic rats with hyperglycemia (1.27 ± 0.05 to 0.88 ± 0.05 and 2.84 ± 0.10 to 2.22 ± 0.06 ml · min−1 · 100 g−1, respectively; P < 0.01). This study documents that in experimental diabetic rats with hyperglycemia, increased ANP and prostacyclin act synergistically in mediating the increased GFR and RPF.
Mechanisms of Hyperglycemia-Induced Insulin Resistance in Whole Body and Skeletal Muscle of Type I Diabetic Patients
Authors: Vuorinen-Markkola Helena , Koivisto Veikko A , Yki-Jarvinen Hannele
Published: September 2013

To examine the mechanisms of hyperglycemia-induced insulin resistance, eight insulin-dependent (type I) diabetic men were studied twice, after 24 h of hyperglycemia (mean blood glucose 20.0 ± 0.3 mM, i.v. glucose) and after 24 h of normoglycemia (7.1 ± 0.4 mM, saline) while receiving identical diets and insulin doses. Whole-body and forearm glucose uptake were determined during a 300-min insulin infusion (serum free insulin 359 ± 22 and 373 ± 29 pM, after hyper- and normoglycemia, respectively). Muscle biopsies were taken before and at the end of the 300-min insulin infusion. Plasma glucose levels were maintained constant during the 300-min period by keeping glucose for 150 min at 16.7 ± 0.1 mM after 24-h hyperglycemia and increasing it to 16.5 ± 0.1 mM after normoglycemia and by allowing it thereafter to decrease in both studies to normoglycemia. During the normoglycemic period (240–300 min), total glucose uptake (25.0 ± 2.8 vs. 33.8 ± 3.9 μmol·kg−1 body wt·min−1 P < 0.05) was 26% lower, forearm glucose uptake (11 ± 4 vs. 18 ± 3 μmol.kg−1 forearm.min−1 P < 0.05) was 35% lower, and nonoxidative glucose disposal (8.9 ± 2.2 vs. 19.4 ± 3.3 μmol.kg−1 body wt−1min−1, P < 0.01) was 54% lower after 24 h of hyper- and normoglycemia, respectively. Glucose oxidation rates were similar. Basal muscle glycogen content was similar after 24 h of hyperglycemia (234 ± 23 mmol/kg dry muscle) and normoglycemia (238 ± 22 mmol/kg dry muscle). Insulin increased muscle glycogen to 273 ± 22 mmol/kg dry muscle after 24 h of hyperglycemia and to 296 ± 33 mmol/kg dry muscle after normoglycemia (P < 0.05 vs. 0 min for both). Muscle ATP, free glucose, glucose-6-phosphate, and fructose-6-phosphate concentrations were similar after both 24-h treatment periods and did not change in response to insulin. We conclude that a marked decrease in whole-body, muscle, and nonoxidative glucose disposal can be induced by hyperglycemia alone.
Glomerular Structure in IDDM Women With Low Glomerular Filtration Rate and Normal Urinary Albumin Excretion
Authors: Lane Pascale H , Steffes Michael W , Mauer S Michael
Published: September 2013

Eight women with insulin-dependent diabetes mellitus (IDDM) with low creatinine clearance rate (CCR) and normal urinary albumin excretion (UAE) were compared with three other groups of diabetic women: 19 with normal creatinine clearance rate (CCR) and UAE, 7 with normal CCR and microalbuminuria, and 7 with low CCR and microalbuminuria. The four groups were similar in age, duration of diabetes, HbA1, incidence of urinary tract infection, prevalence of bladder neuropathy, and urinary urea nitrogen excretion rate. The prevalence of hypertension was similar among the groups, although mean arterial pressure was higher in the low CCR and microalbuminuria group. Renal area index was lower in the low CCR and normal UAE groups than in the other groups of diabetic patients, but was not different from normal. Morphometric measures of mesangial expansion and estimates of arteriolar hyalinosis and global glomerulosclerosis were increased to a similar degree in the low CCR and normal UAE, normal CCR and microalbuminuria, and low CCR and microalbuminuria groups compared with the group without abnormalities of renal function. Therefore, it is likely that diabetic glomerulopathy is, at least in part, responsible for the loss of glomerular filtration rate seen in the low CCR and normal UAE patients. Thus, the definition of incipient nephropathy may have to be expanded beyond the concept of microalbuminuria if longitudinal study of such patients reveals an increased risk of the subsequent development of overt nephropathy. Finally, screening for diabetic kidney disease among IDDM patients should include determination of glomerular filtration rate and measurement of UAE and blood pressure, especially among women.
Ionic, Electrical, and Secretory Effects of Inhibitors of Arachidonic Acid Metabolism in Mouse Pancreatic β-Cells
Authors: Drews Gisela , Garrino Maria-Grazia , Henquin Jean-Claude
Published: September 2013

Mouse islets were used to study the effects of inhibitors of cyclooxygenase and lipoxygenase pathways on insulin release, ionic fluxes, and β-cell membrane potential. The cyclooxygenase inhibitors, Na-salicylate and Na-acetylsalicylate, potentiated glucose-induced insulin release, despite a decrease in Ca influx evidenced by inhibition of the Ca-dependent electrical activity in β-cells and 45Ca efflux from islets perifused with a medium containing Ca. This paradox can probably be explained by a mobilization of intracellular Ca (acceleration of 45Ca efflux in the absence of Ca) with subsequent activation of K+ channels (acceleration of 86Rb efflux) and repolarization of the membrane. These effects of salicylate could not be ascribed to a change in intracellular pH because they were not mimicked by 2-Cl-benzoate, which has a similar pK as salicylate but increased insulin release by stimulating Ca influx in β-cells. Among the other cyclooxygenase inhibitors tested, indomethacin caused a slight potentiation of insulin release accompanied by marginal increases in 45Ca efflux and electrical activity, whereas flurbiprofen and ibuprofen were ineffective. Among the lipoxygenase inhibitors, compound BW 755c reversibly decreased glucose-induced insulin release by inhibiting Ca influx in β-cells, but nordihydroguaiaretic acid had no effect. Inhibitors of arachidonic acid metabolism have effects on ionic fluxes and β-cell membrane potential, which may explain some of the changes in insulin release they produce.
Prospective Analysis of The Insulin-Resistance Syndrome (Syndrome X)
Authors: Haffner Steven M , Valdez Rodolfo A , Hazuda Helen P , Mitchell Braxton D , Morales Philip A , Stern Michael P
Published: September 2013

Many studies have shown that hyperinsulinemia and/or insulin resistance are related to various metabolic and physiological disorders including hypertension, dyslipidemia, and non-insulin-dependent diabetes mellitus. This syndrome has been termed Syndrome X. An important limitation of previous studies has been that they all have been cross sectional, and thus the presence of insulin resistance could be a consequence of the underlying metabolic disorders rather than its cause. We examined the relationship of fasting insulin concentration (as an indicator of insulin resistance) to the incidence of multiple metabolic abnormalities in the 8-yr follow-up of the cohort enrolled in the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease in Mexican Americans and non-Hispanic whites. In univariate analyses, fasting insulin was related to the incidence of the following conditions: hypertension, decreased high-density lipoprotein cholesterol concentration, increased triglyceride concentration, and non-insulin-dependent diabetes mellitus. Hyperinsulinemia was not related to increased low-density lipoprotein or total cholesterol concentration. In multivariate analyses, after adjustment for obesity and body fat distribution, fasting insulin continued to be significantly related to the incidence of decreased high-density lipoprotein cholesterol and increased triglyceride concentrations and to the incidence of non-insulin-dependent diabetes mellitus. Baseline insulin concentrations were higher in subjects who subsequently developed multiple metabolic disorders. These results were not attributable to differences in baseline obesity and were similar in Mexican Americans and non-Hispanic whites. These results support the existence of a metabolic syndrome and the relationship of that syndrome to multiple metabolic disorders by showing that elevations of insulin concentration precede the development of numerous metabolic disorders.
Diurnal Variation in Glucose Tolerance: Cyclic Suppression of Insulin Action and Insulin Secretion in Normal-Weight, But Not Obese, Subjects
Authors: Lee Amy , Ader Marilyn , Bray George A , Bergman Richard N
Published: September 2013

The relative roles of insulin sensitivity, insulin secretion, and glucose effectiveness to the diurnal rhythm of glucose tolerance were examined in normal-weight (n = 12) and obese (n = 11) subjects. Two frequently sampled intravenous glucose tolerance tests were performed in each subject at 0800 on one occasion and 1800 on a separate day. Tests were preceded by identical fasts of 10–12 h. In nonobese subjects, glucose tolerance, expressed as the 10- to 16-min KG value (KGS), was much reduced in the evening (AM 2.98 ± 0.45, PM 1.86 ± 0.33 min−1 P < 0.002). In the obese subjects, tolerance was lower in the morning than normal-weight subjects (2.19 ± 0.31 min−1), but unlike in nonobese subjects, tolerance was not significantly reduced during the day (1.90 ± 0.18 min−1 P > 0.40). The reduction in glucose tolerance in the normal-weight subjects was caused by diminished insulin sensitivity (parameter S1, AM 15.4 ± 2.9, PM 10.2 ± 1.9 × 10−5 min−1/pM, P < 0.01) and reduced β-cell responsivity to glucose. The evening decrease in the latter was reflected both in first-phase plasma insulin (AM 2466 ± 441, PM 1825 ± 381 pM/10 min, P < 0.05) and the potentiation slope (AM 462 ± 68, PM 267 ± 35 pM/mM, P < 0.01). In contrast, consistent with no diurnal variation in glucose tolerance, obese subjects exhibited no decline in insulin sensitivity in the evening (AM 3.6 ± 0.7, PM 4.9 ± 1.0 × 10−5 min−1/pM). A marginally significant decline in (β-cell responsiveness was observed in the obese group (potentiation slope AM 388 ± 78, PM 233 ± 58 pM/mM, P < 0.05). Glucose tolerance is maintained when the pancreas adequately compensates for prevailing insulin resistance, a relationship described by the disposition index (SI, × Φ1). This product decreased 46% in nonobese subjects from morning to evening (P < 0.05), reflecting the inability of the pancreas to overcome prevailing insulin resistance, and resulting in evening glucose intolerance. No diurnal decline in the disposition index was observed in obese subjects. The diurnal rhythms in insulin sensitivity and secretion in nonobese subjects are not consistent with known rhythms in growth hormone or cortisol, but could be due to the effects of a putative diurnal rhythm of sympathetic activity, which would suppress both insulin sensitivity and secretion in the evening. The absence of a rhythm in the obese could reflect an autonomic or hormonal dysfunction that may be related to body-weight regulation.
Visceral Obesity in Men: Associations With Glucose Tolerance, Plasma Insulin, and Lipoprotein Levels
Authors: Pouliot Marie-Christine , Després Jean-Pierre , Nadeau André , Moorjani Sital , Prud'Homme Denis , Lupien Paul J , Tremblay Angelo , Bouchard Claude
Published: September 2013

The relations of regional adipose tissue (AT) distribution measured by computed tomography (CT) to plasma insulin-glucose homeostasis and lipoprotein-lipid levels were studied in 58 obese and 29 lean control men. In the group of obese men, the visceral AT area measured by CT was positively correlated with fasting plasma triglyceride and insulin levels and with glucose and insulin areas under the curves measured during a 75-g oral glucose tolerance test. Visceral AT area was also negatively associated with plasma high-density lipoprotein (HDL) and HDL2 cholesterol levels. The relative accumulation of abdominal fat, estimated by the ratio of abdominal to femoral AT areas obtained by CT, was also a significant correlate of indices of carbohydrate metabolism and was the best univariate correlate of plasma lipoprotein levels. No significant associations were observed between the visceral AT area, the ratio of abdominal to femoral AT areas, and indices of carbohydrate and lipoprotein metabolism in the group of lean men. On the other hand, the subcutaneous abdominal AT area was a significant correlate of the glucose area under the curve in both groups of men, but this association was not independent from the percentage of total body fat. No relationship was observed between the femoral AT area and indices of carbohydrate metabolism in either lean or obese groups. In obese men, however, the femoral AT area was negatively correlated with plasma triglyceride concentration and positively correlated with plasma HDL and HDL2 cholesterol levels. Comparison between two subgroups of equally obese men showing either low or high levels of visceral AT and a group of lean men generally revealed that only obese men with high levels of visceral AT showed significant metabolic alterations compared with lean men. These results demonstrate that the amount of visceral AT and the ratio of abdominal to femoral AT measured by CT are important correlates of the alterations in carbohydrate and lipoprotein metabolism observed in obese men. In addition, our results suggest that obesity is required to observe significant associations between body fat distribution measured by CT and metabolic variables. Finally, we suggest that, in men, a high accumulation of femoral fat may be protective against the adverse effects of obesity, particularly abdominal obesity, on plasma lipoprotein levels.
Familial Clustering of Insulin Sensitivity
Authors: Martin Blaise C , Warram James H , Rosner Bernard , Rich Stephen S , Soeldner J Stuart , Krolewski Andrzej S
Published: September 2013

This study's objective was to determine whether there is familial clustering of insulin sensitivity (SI) or insulin-independent glucose uptake (SG), which would be evidence that they are genetically determined traits. Outpatients had a 3-h intravenous glucose tolerance test. Nondiabetic individuals (n = 183), ranging in age from 16 to 60 yr, were from 105 families that had 2 parents with non-insulin-dependent diabetes mellitus. Of these families, 62 contributed 1 offspring, 21 contributed 2, 13 contributed 3, 6 contributed 4, and 2 and 1 contributed 5 and 6, respectively. The minimal model of glucose disposal and the glucose and insulin values from the intravenous glucose tolerance tests were used to estimate SI and SG. The intraclass correlation coefficient was used to compare the within-family variability of SI and SG with the respective between-family distributions. The intraclass correlation coefficients were 0.26 (P = 0.008) for SI and 0.081 (P = 0.45) for SG. SI and SG were uncorrelated (r = −0.059, P = 0.42). The intraclass correlation of SI could not be explained by familial clustering of fasting insulin or ideal body weight. Finally, the 10 families with the lowest values of SI had a significantly higher within-sibship variability of SI than the other 33 families (P < 0.001, F test). SI but not SG showed familial clustering, which is consistent with a polygenic determinant of SI. In addition, a large within-family variability of SI in some families is compatible with a major gene effect with a dominant mode of inheritance. Thus, defects in genes affecting SI are plausible candidates for determinants of familial clustering of non-insulin-dependent diabetes mellitus.
Stimulation by Proinsulin of Expression of Plasminogen Activator Inhibitor Type-I in Endothelial Cells
Authors: Schneider David J , Nordt Thomas K , Sobel Burton E
Published: September 2013

In patients with non-insulin-dependent diabetes mellitus, concentrations in plasma of insulin and its precursors, proinsulin and split proinsulin, are increased. Because increased concentrations of plasminogen activator inhibitor type-1 (PAI-1) occur also, we hypothesized that proinsulin and split proinsulin may augment endothelial cell PAI-1 expression, thereby potentially attenuating endogenous fibrinolysis and accelerating atherosclerosis. Proinsulin increased PAI-1 activity in conditioned media of endothelial cells as did split proinsulin, paralleled by increased expression of PAI-1 mRNA. These effects of proinsulin were not dependent on its conversion to insulin nor on its interactions with the insulin receptor. The proinsulin stimulation of PAI-1 expression was not attenuated by either anti-insulin receptor antibodies or a 100-fold excess of insulin. Furthermore, proinsulin-mediated increases in PAI-1 expression were not inhibited by a 500-fold excess of insulinlike growth factor I. In addition, inhibition of tyrosine kinase, which mediates many of the diverse effects of insulin and insulinlike growth factor I, did not attenuate the effect of proinsulin. These results indicate that proinsulin augments PAI-1 expression, potentially contributing to vasculopathy in patients with non-insulin-dependent diabetes mellitus.
Poly I:C Accelerates Development of Diabetes Mellitus in Diabetes-Prone BB Rat
Authors: Ewel Cynthia H , Sobel Douglas O , Zeligs Barbara J , Bellanti Joseph A
Published: September 2013

We developed a new experimental model of accelerated diabetes mellitus in the genetically susceptible diabetes-prone BB rat with the administration of the IFN-α inducer poly I:C. With this model, there was both an increased incidence and accelerated onset of insulin-dependent-diabetes in poly I:C–treated animals compared with saline-treated controls. All twelve rats administered poly I:C (5 μg/gm body weight 3 times/wk) developed diabetes by 57 days of age (100%) compared with 1 of 27 (3.7%) saline-treated controls. Furthermore, the development of diabetes was accelerated in the poly I:C–treated group (mean age ± SE at onset 52.8 ± 0.58 days) compared with saline-treated controls (89.3 ± 2.4 days, P < 0.01). Additionally, poly I:C–treated rats had higher mean serum IFN-α levels than saline-treated rats at weeks 2 and 3 of treatment (210 vs. 27 and 183 vs. 25 U/ml, respectively, P < 0.001). Poly I:C treatment of 5 Wistar rats, the parental strain, which is not susceptible to diabetes, did not result in insulitis, diabetes, or hyperglycemia. The histopathologic findings of insulitis and decreased immunoreactive islet insulin in poly I:C–accelerated diabetic BB rats and in BB rats with spontaneous diabetes suggest a similar pathophysiology.
Does Nitric Oxide Mediate Autoimmune Destruction of β-Cells?: Possible Therapeutic Interventions in IDDM
Authors: Corbett John A , McDaniel Michael L
Published: September 2013

Cytokines have been implicated as immunological effector molecules that induce dysfunction and destruction of the pancreatic β-cell. The mechanisms of cytokine action on the β-cell are unknown; however, nitric oxide, resulting from cytokine-induced expression of nitric oxide synthase, has been implicated as the cellular effector molecule mediating β-cell dysfunction. Nitric oxide is a free radical that targets intracellular iron-containing enzymes, which results in the loss of their function. The cytokine IL-1β induces the formation of nitric oxide in isolated rat islets and the insulinoma cell line, Rin-m5F. NMMA and NAME, both inhibitors of nitric oxide synthase, completely protect islets from the deleterious effects of IL-1β. These inhibitors are competitive in nature and inhibit both the cytokine-inducible and constitutive isoforms of nitric oxide synthase with nearly identical kinetics. This may preclude their use as therapeutic agents because of increases in blood pressure which result from the inhibition of constitutive nitric oxide synthase activity. Aminoguanidine, an inhibitor of nonenzymatic glycosylation of cellular and extracellular constituents associated with diabetic complications, recently has been reported to inhibit nitric oxide synthase. Aminoguanidine is ∼40-fold more effective in inhibiting the inducible isoform of nitric oxide synthase, suggesting that aminoguanidine or analogues may serve as potential therapeutic agents to block diseases associated with nitric oxide production by the inducible isoform of nitric oxide synthase. In vivo administration of TNF IL-1 has been shown to induce antidiabetogenic effects in the NOD mouse. This anti-diabetogenic effect of cytokines appears to conflict with evidence suggesting that cytokines mediate β-cell dysfunction. The role of nitric oxide in both cytokine-mediated β-cell dysfunction, and the antidiabetogenic effects of cytokines, as well as the potential therapeutic use of aminoguanidine, are evaluated in this study.
Free Radical Activity and Hemostatic Factors in NIDDM Patients With and Without Microalbuminuria
Authors: Collier Andrew , Rumley Ann , Rumley Alan G , Paterson John R , Leach John P , Lowe Gordon D O , Small Michael
Published: September 2013

In non-insulin-dependent diabetes mellitus (NIDDM) patients, microalbuminuria predicts early mortality, predominantly from cardiovascular disease. Increased free radical activity and abnormalities in hemostasis have been implicated in the development of vascular disease. Therefore, we measured markers of free radical activity (nonperoxide-conjugated diene isomer of linoleic acid [PL-9,11-LA′] and lipid peroxides expressed as malondialdehyde [MDA]) along with the hemostatic variables: fibrinogen, von Willebrand factor (vWf), plasminogen activator inhibitor (PAI-1), tissue plasminogen activator (t-PA), and plasmin activity (Bβ15–42) in 24 NIDDM patients (12 patients with microalbuminuria and 12 without microalbuminuria) and in 12 age-matched control subjects. There were no differences in linoleic acid (PL-9,12-LA) concentrations between the three groups. PL-9,11-LA′ was elevated in the microalbuminuric patients compared with control subjects (P < 0.05), but there was no difference between the two diabetic groups. MDA was elevated in the microalbuminuric diabetic patients compared with those patients without microalbuminuria (P < 0.05) and control subjects (P < 0.001). MDA was also increased in the patients without microalbuminuria compared with control subjects (P < 0.01). Except for Bβ15–42, all the hemostatic variables were increased (P < 0.05) in the diabetic patients compared with control subjects. The microalbuminuric diabetic patients had further increases in vWf (P < 0.03) and t-PA (P < 0.03) compared with patients with microalbuminuria. Our study suggests that there is an increase in free radical activity and abnormalities in hemostatic variables favoring a hypercoagulable state in NIDDM, especially in those with microalbuminuria. These changes may contribute to vascular disease, which is particularly prevalent in NIDDM patients with microalbuminuria.
Susceptibility to IDDM in a Chinese Population: Role of HLA Class II Alleles
Authors: Penny Michelle A , Jenkins David , Mijovic Catherine H , Jacobs Karen H , Cavan David A , Yeung Vincent T F , Cockram Clive S , Hawkins Brian R , Fletcher Jeremy A , Barnett Anthony H
Published: September 2013

MHC associations with IDDM in a Chinese population were studied to investigate genetic susceptibility to the disorder. The frequency of HLA-DR3 was significantly higher in the diabetic patients (19/49 [38.7%] vs. control subjects, 11/105 [10.5%], Pc < 1.3 × 10−3, RR = 5.3 [CI 2.3–12.1]), whereas DR4 was not (11/49 [22.4%] vs. 28/105 [26.7%], NS). The frequency of DR3/4 heterozygosity was higher in the diabetic patients (6/49 [12.2%] vs. control subjects, 0/105 [0%], P = 1.7 × 10−3, RR = 31.5 [CI 3.8–263.6]). The frequency of DR3/9 heterozygosity also was higher in the diabetic patients (6/49 [12.2%] vs. control subjects, 2/105 [1.9%], P = 0.03, RR = 6.2 [CI 3.0–12.7]). No significant associations were noted between DQB1 alleles and IDDM. Among DR4-positive subjects, the frequency of DQB1 allele DQB1*0302 was higher in the diabetic patients (10*11 [90.0%] vs. control subjects, 12/24 [50%], Pc < 0.05, RR = 7.0 [CI 1.3–38.0]), and the frequency of DQB1*0401 was significantly lower in the diabetic patients (2/11 [18.2%] vs. control subjects, 16/24 [66.7%], Pc = 0.04, RR = 0.1 [CI 0.02–0.46]). No DR4 subtype was associated significantly with IDDM. The frequency of DQA1*0501, a DQA1 allele, was higher in diabetic patients (22/41 [53.7%] vs. control subjects, 20/95 [21.1%], Pc < 3 × 10−3, RR = 4.3 [CI 2.0–9.3]). The frequency of DQA1*0301, which has been associated consistently with IDDM in other ethnic groups, was not significantly higher in the diabetic patients in this study (27/41 [65.9%] vs. control subjects, 53/95 [55.8%], NS). The frequency of the DR4 haplotype DRB1*0405-DQA1*0301-DQB1*0401 was lower among DR4- positive diabetic patients (2/10 [20%] vs. DR4-positive control subjects, 12/21 [57.1%], NS), in direct contrast with Japanese populations. These results suggest that if DQB1 and DQA1 alleles determine IDDM susceptibility, other MHC factors must modify their effect.
Studies on Autoimmunity for T-Cell-Mediated β-Cell Destruction: Distinct Difference in β-Cell Destruction Between CD4+ and CD8+ T-Cell Clones Derived From Lymphocytes Infiltrating the Islets of NOD Mice
Authors: Nagata Masao , Yoon Ji-Won
Published: September 2013

Six CD4+ and three CD8+ islet-reactive T-cell clones were established from lymphocytes infiltrating the pancreatic islets of NOD mice. Two of six CD4+ T-cell clones responded to NOD islet cells only, not to spleen cells. The remaining four clones responded to both islet cells and spleen cells from NOD mice, but not to cells from other strains of mice, including SJL, C3H, C57BL/6, and DBA/2 mice. None of the CD4+ T-cell clones had a cytotoxic effect on the cultured islet cells. On the other hand, all of the CD8+ T-cell clones showed both a proliferative response and a cytotoxic effect on the islet cells, with the restriction of MHC class I H-2Db. Electron microscopic studies revealed that islet-specific CD4+ T-cells attached closely to islet cells but did not destroy them. In contrast, CD8+ T-cell clones showed pseudopodialike protrusions into β-cells, but not α- or δ-cells, leading to selective destruction of β-cells. CD8+ CTLs could not be isolated from islets of NOD mice < 10 wk of age, even if the islets showed lymphocytic infiltration, whereas CD4+ T-cells could be isolated from islets of these younger NOD mice. On the basis of these observations, we concluded that CD4+ and CD8+ T-cells interact differently with β-cells at different stages in T-cell–mediated β-cell destruction. CD4+ T-cells may secrete cytokines, which in turn activate effector cell populations, whereas CD8+ T-cells may act as a final effector directly involved in β-cell destruction.
A New Method for Quantification of Islets by Measurement of Zinc Content
Authors: Jindal Rahul M , Taylor Richard P , Gray Derek W R , Esmeraldo Ronaldo , Morris Peter J
Published: September 2013

The ability to quantify the yield of pancreatic islet tissue after isolation is important for interlaboratory comparisons and for the assessment of islet yield prior to clinical transplantation. Because pancreatic islets contain a much higher concentration of zinc than other tissues, we investigated the analysis of zinc as a measure of islet tissue yield. Rat islets of standard diameter 250 μm were handpicked into samples containing 10–80 islets. The zinc content was measured by EAAS and showed a linear correlation with islet number. A zinc binding fluorescent dye, TSQ, was investigated as a way of simplifying the zinc measurement for routine use. Samples of 10–80 islets of 250 μm were sonicated in 3 ml zinc-free water, 0.18 fimol TSQ was added, and the TSQ-zinc fluorescence was measured at 480 nm. A linear correlation was observed. Exocrine contamination up to 50% barely affected the results. Islet zinc content also was shown to be correlated linearly with islet number for freshly isolated human islets. Measurement of zinc by TSQ fluorescence is a rapid, cheap, and objective measure of islet tissue content.
Altered Regulation of Renin Secretion by Insulinlike Growth Factors and Angiotensin II in Diabetic Rats
Authors: Jost-Vu Elke , Horton Richard , Antonipillai Indra
Published: September 2013

The etiology of the low renin state in DM is not clear. To assess the role of certain growth and regulatory factors in this process, we studied the effects of insulin, IGF-I, and IGF-II on the renin-angiotensin system in normal and 8-wk STZ-induced diabetic rats. Renin secretion was studied both in static incubations and by perifusion of rat renal cortical slices. In diabetic rats, both plasma renin activity (0.65 ±1.6 vs. 4.0 ±1.2 ng ANG I · ml−1 · h−1) and tissue renin concentrations (27 ± 5 vs. 51 ± 8 ng ANG I · mg tissue−1 · h−1) were reduced. Insulin (0.1–1.0 mu/ml) and IGF-I (10−9 to 4 × 10−9 M) stimulated renin secretion in normal tissue (control, 95 ± 3%; insulin [0.5 mu/ml], 134 ± 7%; IGF-I «4 × 10−9 M], 149 ± 7%). IGF-I stimulated renin secretion in perifusions as early as 30 min, whereas IGF-II had no effect. However, in diabetic renal tissue, neither insulin (0.1–1.0 mu/ml) nor IGF-I (10−9 to 4 × 10−9 M) had an effect on renin. This lack of effect was overcome by adding up to 100-fold higher concentrations of these growth factors. ANG II (10−10M–10−8 M) had an exaggerated inhibitory effect on renin secretion in diabetic tissue. This study suggests that the low renin state in DM may be explained by the enhanced inhibitory effect of ANG II and the resistance to the secretogogue actions of insulin and IGF-I.
Insulin Treatment, Endogenous Insulin Concentration, and ECG Abnormalities in Diabetic Pima Indians: Cross-Sectional and Prospective Analyses
Authors: Liu Quan Zhi , Knowler William C , Nelson Robert G , Saad Mohammed F , Charles Marie A , Liebow Irving M , Bennett Peter H , Pettitt David J
Published: September 2013

The prevalence and incidence of CHD, defined by ECG abnormalities according to the Tecumseh criteria for Minnesota Codes, were determined in Pima Indians >25 yr of age. In a cross-sectional analysis, the age-sex-adjusted prevalence (± SE) of ECG abnormalities was higher in 1454 NIDDM patients (6.86 ± 0.65%) than in 1696 nondiabetic subjects (3.23 ± 0.63%; prevalence rate ratio = 2.12; 95% Cl 1.39–3.25). In a prospective analysis, the age-sex-adjusted incidence (± SE) of ECG abnormalities was higher in 824 NIDDM patients (12.77 ±1.67) than in 935 nondiabetic subjects (5.93 ± 1.43 cases/1000 person-yr; incidence rate ratio = 2.15; 95% Cl 1.26–3.69). The prevalence of ECG abnormalities in insulin-treated NIDDM patients was significantly higher than in NIDDM patients not treated with insulin (age-sex-adjusted OR = 2.83; 95% Cl 1.84–4.33); and this association persisted when adjusted for other factors such as sBP, BMI, duration of diabetes, serum cholesterol concentration, and oral hypoglycemic agents (OR = 2.12; 95% Cl 1.34–3.37). In the prospective analysis, the incidence of ECG abnormalities in NIDDM patients treated with insulin was higher than in those NIDDM patients not treated with insulin, but, when controlled for age, sex, duration of diabetes, and oral hypoglycemic agents in a proportional-hazards model, the relationship with insulin treatment was not statistically significant (incidence rate ratio = 1.36; 95% Cl 0.80–2.31). This suggests that insulin treatment may be a marker of more severe diabetes, and that factors associated with clinical indications for insulin treatment, rather than insulin treatment per se, are related causally to CHD. On the other hand, endogenous fasting and 2-h postload serum insulin concentrations were not associated with ECG abnormalities among 761 NIDDM patients not treated with insulin nor among 1226 nondiabetic subjects. Furthermore, in the prospective study, neither endogenous fasting nor 2-h postload serum insulin was associated with the subsequent development of ECG abnormalities in NIDDM patients or nondiabetic subjects.
Total Body Fat Content and Fat Topography Are Associated Differently With In Vivo Glucose Metabolism in Nonobese and Obese Nondiabetic Women
Authors: Bonora Enzo , Prato Stefano Del , Bonadonna Riccardo C , Gulli Giovanni , Solini Anna , shank Myron L , Ghiatas Abraham A , Lancaster Jack L , Kilcoyne Raphael F , Alyassin Abdalmajeid M , DeFronzo Ralph A
Published: September 2013

In this study, total body fat content and fat topography were related to glucose metabolism in the basal and nsulin-stimulated states in 18 nonobese and 18 obesepremenopausal nondiabetic women. All subjects received a euglycemic insulin (20 mil · min−1 · m2) clamp study in combination with [3-3H]-D-glucose infusion and indirect calorimetry to quantitate total body glucose uptake, glucose oxidation, and nonoxidative glucose disposal. Total body fat content was determined with tritiated water, whereas body fat distribution was estimated from the WHR, the STR, and the VSR (measured by magnetic resonance imaging). In the postabsorptive state, total body glucose utilization, glucose oxidation, and nonoxidative glucose disposal rates were similar in nonobese and obese women, whereas during the insulin clamp all three metabolic parameters were reduced significantly in the obese group. In nonobese women, total body fat content was related inversely to both total and nonoxidative glucose disposal during the insulin clamp, whereas no relationship was found between glucose metabolism (total, oxidative, and nonoxidative) and WHR, STR, or VSR. In contrast, in obese women, no relationship was observed between total body fat content and any measure of insulin-mediated glucose metabolism. However, both WHR and VSR were related inversely to total, oxidative, and nonoxidative glucose disposal rates during the insulin clamp. These results suggest that total body fat content and body fat topography are associated differently with insulin-mediated glucose metabolism in nonobese and obese women. In the nonobese women, total body fat mass appears to be a primary determinant of tissue sensitivity to insulin, whereas in obese women, body fat topography exerts a more dominant effect.
Abnormal Agonist-Stimulated Cardiac Parasympathetic Acetylcholine Release in Streptozocin-Induced Diabetes
Authors: Uccioli Luigi , Magnani Paolo , Tilli Pietro , Cotroneo Patrizia , Manto Andrea , Greco Aldo Virgilio , Sima Anders A F , Greene Douglas A , Menzinger Guido , Ghirlanda Giovanni
Published: September 2013

We examined the effect of three distinct depolarizing conditions on [3H]ACh release from cardiac postganglionic parasympathetic neurons in age-matched controls and insulin-treated STZ-induced diabetic rats to determine whether alterations in neurotransmitter release were present in the diabetic group. The effect of TTX, which exerts a use- and voltage-dependent block of sodium channels, was examined on the release of ACh stimulated by SRIF14 (preferentially acts at the cell body). We also studied the effect of STZ-induced diabetes on [3H]ACh release by the relatively site-specific depolarizing agent VT (preferentially acts at the axon) and high potassium (non-site-specific). Basal, SRIF14-(10−7 M), VT-(1CT4 M), and K+ (100 mM)-stimulated [3H]ACh release was similar in control and STZ-induced diabetic animals. However, in STZ-induced diabetic but not control rats, SRIF14-induced [3H]ACh release was resistant to TTX (2 × 107 M). In addition, the response to submaximal K+ (25 mM) stimulation was greater in STZ-induced diabetic compared with control animals. Treatment with insulin corrected these abnormalities. These data indicate that in the acute STZ-induced diabetic rat, SRIF14-, VT-, and high K+-evoked release of ACH is not impaired, which suggests that the mechanisms associated with ACh storage and release in postganglionic cardiac parasympathetic neurons are not affected in this model. However, the TTX insensitivity and the increase in ACh release in response to submaximal K+ stimulation inSTZ-induced diabetes are consistent with a positive shift in the resting membrane potential in postganglionic cardiac parasympathetic axons similar to that reported in peripheral somatic nerve axons in experimental diabetes.
Insulin Secretion, myo-Inositol Transport, and Na+-K+-ATPase in Glucose-Desensitized Rat Islets
Authors: Xia Menghang , Laychock Suzanne G
Published: September 2013

Glucose-induced insulin secretion is desensitized during long-term exposure of pancreatic islet beta-cells to elevated glucose levels. This study characterizes an in vitro model of glucose-induced desensitization in cultured isolated islets of the rat. Insulin secretion in desensitized islets cultured with 11 mM glucose for 4–7 days was progressively reduced compared with the normal freshly isolated (fresh) islets. When desensitized islets were returned to a basal concentration of glucose (5.5 mM) for up to 2 h, the glucose sensitivity of insulin secretion was restored to normal (recovered islets). Carbachol and L-arginine also reversed the effects of desensitization. However, basal insulin release was elevated in desensitized and recovered islets. Sodium-dependent myo-inositol uptake was reduced during desensitization by up to 49% within 4 days. myo-Inositol uptake was restored to normal in a time-dependent manner during recovery of islets at 5.5 mM glucose. The recovery of myo-inositol uptake paralleled that of insulin release. The apparent transport constant for myo-inositol uptake was significantly increased during desensitization, whereas the maximum uptake was not changed. myo-Inositol supplementation (35 or 250 µM) during islet culture did not alter myo-inositol uptake or insulin secretion in desensitized islets. Na+)-K+)-ATPase activity, but not 5′-nucleotidase activity, in desensitized islets was also inhibited by 65 and 47% when compared with fresh islet and recovered islet Na+)-K+-ATPase activity, respectively. Thus, cultured islets represent an appropriate model to study biochemical parameters associated with the onset and reversibility of glucose desensitization of insulin secretion. associated with the onset and reversibility of glucose desensitization of insulin secretion. Alterations in Na+-K+-ATPase activity and coupled myo-inositol uptake during desensitization may contribute to the defective pattern of insulin release in this model.
Measurement by Microdialysis of the Insulin Concentration in Subcutaneous Interstitial Fluid: Importance of the Endothelial Barrier for Insulin
Authors: Jansson Per-Anders E , Fowelin Jesper P , Von Schenck Henning P , Smith Ulf P , Lönnroth Peter N
Published: September 2013

To evaluate the interstitial insulin and inulin concentrations, 20-min microdialysis samples from the abdominal subcutaneous tissue were obtained by using two 45-mm polypropylene dialyzing tubes (o.d. ∼ 0.5 mm, pore size 0.2 micron) during a euglycemic hyperinsulinemic (120 mU · m−2 · min−1) clamp (n = 9) or during a constant inulin infusion (n = 5). After in situ calibration of the microdialysis catheters during steady-state conditions, interstitial and plasma insulin concentrations were estimated to 654 ± 102 and 1176 ± 66 pM, respectively, i.e., a 44% difference (P < 0.001). A doubling of the insulin infusion rate (240 mU · m−2 · m−1), leading to supraphysiological plasma insulin levels, raised the interstitial insulin concentrations markedly slower (∼20 min) than in plasma. Moreover, at steady state the concentration difference in the two compartments prevailed even during the high insulin infusion rate (55% difference, P < 0.01). In contrast, the interstitial inulin levels were similar to the plasma concentrations in subjects given a constant inulin infusion. Thus, the data suggest the presence of an endothelial barrier for insulin in the subcutaneous tissue. This barrier, in combination with tissue clearance of insulin, leads to lower insulin levels and altered kinetics with a slower rise in the interstitial fluid compared with plasma.
Diabetic Neuropathy 3 Years After Successful Pancreas and Kidney Transplantation
Authors: Müller-Felber Wolfgang , Landgraf Rüdiger , Scheuer Ralf , Wagner Stefan , Reimers Carl Detlev , Nusser Johann , Abendroth Deitmar , Illner Wolf-Dieter , Land Walter
Published: September 2013

Twenty-seven patients with successful transplantation and a control group of 14 patients with early rejection of the pancreas graft but functioning kidney graft were examined in a prospective study for 3 yr. Before transplantation, all patients had long-standing type I diabetes with advanced secondary complications, including end-stage diabetic nephropathy. After transplantation in the patients of both groups, kidney function was almost normal. Mean HbA1 levels were normal in the group with pancreas graft survival. In the control group, HbA1 levels were, on average, 1.5% higher compared with the group with pancreas survival (P = 0.00005). After 3 yr, the patients with functioning pancreas graft showed fewer symptoms (mean difference 1.0 in a symptom score ranging from 0 to 16, P = 0.004) compared with the control group. No statistically significant difference between both groups concerning clinical signs of polyneuropathy could be observed. In the pancreas and kidney transplantation group, peroneal and median nerve conduction velocities increased 7.2 m/s (P < 0.01) and 3.5 m/s (P < 0.05), respectively, whereas no increase was registered in the control group. The change of median and sural sensory nerve conduction velocities, peroneal and median compound muscle action potentials, and sural and median sensory action potentials was insignificant. In conclusion, although the improvement of clinical symptoms and neurophysiological signs of polyneuropathy was modest in the pancreas and kidney transplantation group, our data suggest that successful pancreas transplantation is able not only to halt the progression of diabetic polyneuropathy but also to improve it to some extent even at a far advanced stage.