bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlations of In Vivo β-Cell Function Tests With β-Cell Mass and Pancreatic Insulin Content in Streptozocin-Administered Baboons
Authors: McCulloch David K , Koerker Donna J , Kahn Steven E , Bonner-Weir Susan , Palmer Jerry P
Published: September 2013

In vivo β-cell function tests are used increasingly in humans during the preclinical phase of insulin-dependent diabetes mellitus (IDDM), but the severity of the β-cell loss responsible for the abnormalities seen in these tests is unknown. We have measured several physiological β-cell function tests—fasting plasma glucose, glucose disappearance constant, fasting insulin, acute insulin responses to arginine (AIRarginine) and glucose (AIRglucose), and glucose potentiation of AIRarginine (∆ AIRarginine/∆G) and two direct objective measurements (pancreatic insulin content [PIC] and quantitative β-cell mass)—in adolescent male baboons (Papio anubis/cyanocephalus). We have correlated in vivo measurements obtained within 3 days after the animals were killed with in vitro estimates of PIC and β-cell mass in 15 animals, (2 nondiabetic requiring insulin treatment and 13 after varying doses of streptozocin to induce degrees of β-cell damage ranging from normoglycemia to severe hyperglycemia). There was a strong linear correlation between β-cell mass and PIC (r = 0.79, P < 0.001). Physiological measures of β-cell function were significantly correlated with both PIC and β-cell mass. The correlations between physiological measures and β-cell mass were linear and intercepted the β-cell mass axis at 0.15–0.2 g, suggesting that in vivo measures of β-cell function approach 0 when there is still ∼40–50% of the β-cell mass detectable histologically. With PIC, the linear correlations intercepted the axes close to 0. These findings provide considerable validity to the measurements of β-cell function used in preclinical IDDM in humans. Our data suggest that such physiological measurements give an accurate valid reflection of changes in β-cell mass and pancreatic insulin content.
Oxidation of Spectrin and Deformability Defects in Diabetic Erythrocytes
Authors: Schwartz Robert S , Madsen John W , Rybicki Anne C , Nagel Ronald L
Published: September 2013

We reasoned that de novo oxidative damage, as a result of increased protein glycosylation, could participate in the mechanisms whereby diabetic erythrocytes acquire membrane abnormalities. To examine this hypothesis, the extent of erythrocyte membrane protein glycosylation and the oxidative status of spectrin, the major component of the erythrocyte membrane skeleton, were examined. Labeling erythrocyte membranes with [3H]borohydride, which labels glucose residues bound to proteins, revealed that several proteins were heavily glycosylated compared with nondiabetic erythrocyte membranes. In particular, the proteins β-spectrin, ankyrin, and protein 4.2 were the most glycosylated. Although sodium dodecyl sulfate–polyacrylamide gel electrophoresis of diabetic erythrocyte membranes did not reveal any quantitative or qualitative abnormalities in spectrin or other membrane proteins, examination of spectrin oxidative status by amino acid analysis and with cis-dichlorodiammineplatinum(II) (cDDP), a chemical probe specific for protein methionine and cysteine residues, demonstrated that the diabetic spectrin was oxidatively damaged: spectrin from diabetic subjects contained 35% less methionine (P < 0.002), 15% less histidine (P < 0.006), and a twofold increase in cysteic acid (P < 0.001) compared with normal spectrin. Diabetic spectrin bound 32% less cDDP than normal spectrin (P < 0.001); the lowest cDDP binding was observed with spectrin from insulin-dependent diabetic subjects. The extent of cDDP binding to diabetic spectrin correlated moderately and inversely with glycosylated hemoglobin (GHb) levels (n = 12, r = −0.727). Erythrocyte deformability, measured by ektacytometry, was decreased between 5 and 23% of control measurements (average of ∼10%) in 21 of 32 diabetic subjects surveyed. Diabetic subjects with decreased erythrocyte deformability also had higher GHb levels than diabetic subjects with normal erythrocyte deformability (P < 0.01). Although there was only a modest inverse correlation between these two parameters (n = 28, r = −0.566), the fact that 61% of the diabetic subjects studied exhibited both decreased deformability and increased GHb levels suggests that deformability abnormalities may become apparent once a threshold GHb level is reached. We conclude that spectrin in diabetic erythrocytes is oxidatively damaged. Protein glycosylation may be responsible for oxidative damage, although other factors in addition to or in concert with protein glycosylation may also be involved. Oxidation of spectrin may participate in the mechanisms resulting in diabetic erythrocyte deformability abnormalities.
Amelioration of Nerve Na+-K+-ATPase Activity Independently of myo-Inositol Level by PGE1 Analogue OP-1206 · α-CD in Streptozocin-Induced Diabetic Rats
Authors: Sonobe Masanobu , Yasuda Hitoshi , Hisanaga Takashi , Maeda Kengo , Yamashita Makio , Kawabata Toru , Kikkawa Ryuichi , Taniguchi Yuzo , Shigeta Yukio
Published: September 2013

An oral prostaglandin E1 (PGE1) analogue, OP-1206 · α-CD, was given to rats with streptozocin (STZ)-induced diabetes to examine the therapeutic effects of OP-1206 on short-term and long-term diabetic neuropathy and its action mechanism with special reference to nerve Na+-K+-ATPase activity. In the short-term experiment, OP-1206 was administered daily to diabetic rats in 3- and 30-mg/kg doses for 4 wk from the day of STZ injection. In the long-term study, 10 μg/kg OP-1206 was also given daily for 8 wk from 7 mo after induction of diabetes. The compound improved decreased sciatic motor nerve conduction velocity in both short-term and long-term diabetic rats. The nerve Na+-K+-ATPase activity of diabetic rats, reduced by 40% compared with controls, was reversed to the level of controls in both experiments, whereas weight loss and hyperglycemia were unchanged, and neither nerve sorbitol accumulation nor myo-inositol depletion was corrected. In a morphometric analysis of myelinated nerve fibers (MNFs) in long-term diabetes, the mean diameter of the largest 10% of MNFs was significantly reduced in untreated diabetic compared with control rats, but OP-1206 completely reversed this reduction. The results suggest that OP-1206 ameliorates a decrease in nerve Na+-K+-ATPase activity without any effect on nerve myo-inositol level and that the compound may be not only a potent therapeutic agent for the treatment of diabetic neuropathy but also a useful research tool to investigate the mechanism of nerve Na+-K+-ATPase activity regulation.
Possible Genetic Defects in Regulation of Glycosaminoglycans in Patients With Diabetic Nephropathy
Authors: Deckert Torsten , Horowitz Irena M , Kofoed-Enevoldsen Allan , Kjellén Lena , Deckert Marja , Lykkelund Claus , Burcharth Flemming
Published: September 2013

The hypothesis of genetic defects in glycosaminoglycan (GAG) regulation among patients with insulin-dependent diabetes mellitus (IDDM) and nephropathy was assessed by studies in tissue cultures of fibroblasts obtained from 7 patients with normal urinary albumin excretion, 11 patients with diabetic nephropathy, and 6 nondiabetic control subjects. The incorporation of [3H] glucosamine and [35S] sulfate into hyaluronic acid (HA), chondroitin sulfate and dermatan sulfate (CS + DS), and heparan sulfate (HS) was measured in cells, matrix, and medium and related to micrograms of tissue protein. Large interindividual variations were seen in all three groups, and the incorporation of [3H] glucosamine into HA, CS + DS, and HS and [35S] sulfate into CS + DS and HS were not significantly different between the three groups. However, the fractional incorporation of [3H]glucosamine into HS was significantly reduced in diabetic patients with nephropathy compared with control subjects. This was the case not only when related to the total amount of GAGs (P = 0.014) but also when related to HA (P = 0.014). No significant difference was seen between control subjects and normoalbuminuric diabetic patients. The degree of N-sulfation of HS was not significantly different between the experimental groups. The results suggest that patients with diabetic nephropathy may suffer from deficiencies of coordinate regulation in the biosynthesis of GAG in fibroblasts, which may lead to a reduced density of HS in the extracellular matrix. If these changes reflect alterations in the biosynthesis of GAG from endothelial, myomedial, and mesangial cells, this observation may be relevant for the pathogenesis of severe diabetic complications.
Exhibition of Specific Alterations in Activities and mRNA Levels of Rat Islet Glycolytic and Mitochondrial Enzymes in Three Different in Vitro Model Systems for Attenuated Insulin Release
Authors: Svensson Carina , Welsh Nils , Krawetz Stephen A , Welsh Michael
Published: September 2013

We studied the possible relationships between the functional status of the β-cell and activities or mRNA contents of enzymes involved in the catabolism of glucose. Three different in vitro models with attenuated insulin response were used: rat islets cultured at a low glucose concentration, rat islets incubated in vitro with streptozocin, and fetal rat islets. The fetal and streptozocin-administered islets were compared with adult islets cultured in RPMI-1640 containing 11 mM glucose, and the effects of the in vitro glucose concentrations (3.3, 11, and 28 mM) were assessed on adult islets only. Cellular mRNA levels for the mitochondrial DNA-encoded cytochrome b and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were determined by Northern-blot analysis. Enzymatic activities of high-Km (glucokinase) and low-Km (hexokinase) glucose-phosphorylating enzymes and succinate–cytochrome c reductase were also determined. Islets cultured at 3.3 mM glucose displayed a decreased activity of glucokinase compared with islets cultured at 28 mM glucose (23.3 ± 12%), whereas there was no difference in hexokinase activity or the level of GAPDH mRNA. The activity of succinate–cytochrome c reductase was similar in islets cultured at the different glucose concentrations. The level of cytochrome b mRNA increased at 28 mM glucose compared with islets cultured at 11 mM glucose (140 ± 14%). Islets incubated with streptozocin and subsequently cultured for 7 days at 11 mM glucose exhibited a decreased level of cytochrome b mRNA (65 ± 5%) and no differences in the activities of glucokinase, hexokinase, succinate–cytochrome c reductase, or the level of GAPDH mRNA. Fetal islets displayed increased activity of hexokinase (570 ± 130%) and succinate–cytochrome c reductase (185 ± 42%) and a decreased level of cytochrome b mRNA (62 ± 11%) in comparison with adult islets cultured at similar conditions. No differences of glucokinase activity or the level of GAPDH mRNA were detected in these islets. The results suggest that the degree of expression of certain genes coding for enzymes in the oxidative metabolism of glucose may influence the ability of the α-cell to synthesize and secrete insulin.
Prevention of Inhibitory Effect of Free Fatty Acids on Insulin Binding and Action in Isolated Rat Hepatocytes by Etomoxir
Authors: Svedberg Jan , Björntorp Per , Lönnroth Peter , Smith Ulf
Published: September 2013

We recently demonstrated a marked inhibitory effect of high physiological concentrations of free fatty acids (FFAs) on insulin binding, degradation, and action in isolated rat hepatocytes. To elucidate the mechanism, male rats were treated for 3 days with saline (control) or etomoxir (ethyl 2-[6-(p-chlorophenoxy)hexyl]-glycidate), a prodrug, which in vivo is converted to a specific competitive inhibitor of carnitine palmitoyltransferase, and thus, lipid oxidation. Oleic acid (0.4 mM) reduced both 125I-labeled insulin binding and insulin-stimulated [14C]aminoisobutyric acid transport ∼40% in cells from control animals. However, this FFA concentration was without effect in cells from etomoxir-treated animals. Etomoxir increased EC50 for the inhibitory effect of oleic acid on insulin binding ∼ threefold. The data indicate that the mitochondrial oxidation of fatty acids may be important for their inhibitory effect on insulin binding and action in isolated rat hepatocytes.
Increased Plasma Apolipoprotein(a) Levels in IDDM Patients With Microalbuminuria
Authors: Jenkins Alicia J , Steele Jenkins S , Janus Edward D , Best James D
Published: September 2013

Patients with insulin-dependent diabetes mellitus (IDDM) have a significantly increased risk of macrovascular disease, particularly if they have persistent proteinuria. To determine whether altered levels of apolipoprotein(a) [apo(a)], the plasminogenlike glycoprotein of the potentially atherogenic lipoprotein(a); contribute to the increased risk of atherosclerosis, apo(a) levels were measured in 107 patients with IDDM and compared with nondiabetic control subjects and male elective coronary artery graft patients. Apo(a) levels were increased in diabetic patients with microalbuminuria (geometric mean 245 U/L, 95% confidence interval [CI] 142–427, n = 30) and albuminuria (mean 196 U/L, 95% CI 97–397, n = 18) with levels comparable to patients with coronary artery disease (mean 193 U/L, 95% CI 126–298, n = 40), which were higher than in the control group (mean 107 U/L, 95% CI 85–134, n = 140; P = 0.016). Apo(a) levels in diabetic patients without microalbuminuria (mean 86 U/L, 95% CI 63–116, n = 59) were comparable with the control population and less than in those with microalbuminuria (P < 0.001) and albuminuria (P = 0.014). The elevated apo(a) levels found in patients with IDDM and increased urinary albumin loss may contribute to their heightened risk of macrovascular disease.
Characterization of Endocrine-Rich Monolayers of Human Fetal Pancreas That Display Reduced Immunogenicity
Authors: Simpson A M , Tuch B E , Vincent P C
Published: September 2013

Fibroblast-free insulin-secreting monolayers of human fetal pancreas (14–20 wk of gestation) were formed by plating isletlike cell clusters (ICCs) obtained from partially digested pancreases on plates coated with bovine corneal matrix. Human fetal pancreatic cells, freshly digested with collagen, displayed a 17-fold response to human peripheral blood lymphocytes (HPBLs) in mixed-lymphocyte culture. After 14 days in culture, monolayers derived from ICCs exhibited a smaller, twofold response to HPBLs. By comparison, in monolayers produced from single-cell suspensions, fibroblast overgrowth remained a problem. The endocrine component of the monolayers was 65 ± 13 and 43 ± 8%, respectively, with the number of β-cells being 51 and 9%. Cells from both monolayers displayed increased insulin release when exposed to 10 mM theophylline, 10 mM Ca2+, and 0.6–1.3 microM 12-O-tetradecanoylphorbol-13-acetate but not to 20 mM glucose. Monolayers derived from ICCs synthesized DNA, proinsulin, and protein. This study showed that it is possible to establish an endocrine-rich monolayer of human fetal pancreas that has greatly reduced immunogenicity. The existence of residual activity to HPBLs suggests some additional form of immunosuppression is required to prevent rejection of this tissue when grafted into diabetic patients. Subculturing and cryopreservation may also be needed to achieve adequate numbers of β-cells for clinical transplantation.
Expression of Functional Human Epstein-Barr Virus/C3d Receptor ([CR2] CD21) on Insulinoma Cell Line: Induction of Tumor Rejection but Not Diabetes in Syngeneic Rats
Authors: Carel Jean-Claude , Holers V Michael , Chick William L , Littman Dan , Lacy Paul E
Published: September 2013

We stably expressed human complement receptor 2 ([CR2] CD21 C3d/Epstein-Barr virus [EBV] receptor) on the rat insulinoma cell line RINm5F with a recombinant retroviral vector. CR2-expressing RINm5F cells secreted 78–33% less insulin than parental cells or cells transduced with an antisense vector and could be infected with high-titer EBV. We tested whether human CR2 expression on RINm5F cells would affect tumorigenesis after transplantation to syngeneic New England Deaconess Hospital rats. Non-CR2–expressing antisense-transduced RINm5F cells rapidly grew tumors and caused hypoglycemia, hyperinsulinemia, and the death of the animals after 15.7 ± 0.7 days. CR2-expressing RINm5F cells were infiltrated by mononuclear cells at an early stage and eventually caused noninfiltrated tumors and the death of the animals after 33.0 ± 0.4 days. These tumors were CR2− and are believed to have arisen from a minor CR2− population of tumor cells. The pancreatic islets were histologically normal at all time points. We conclude that expression of a xenoantigen on a rat insulinoma cell line induces an immune response in syngeneic rats but does not result in breakage of tolerance to parental or revertant cells.
Insulin and Glucose Levels and Prevalence of Glucose Intolerance in Pedigrees With Multiple Diabetic Siblings
Authors: Elbein Steven C , Maxwell Teresa M , Schumacher Mary Catherine
Published: September 2013

Hyperinsulinemia may be an early inherited marker for a defect in insulin action that subsequently results in glucose intolerance and non-insulin-dependent diabetes mellitus (NIDDM). To examine the role of hyperinsulinemia in individuals at high genetic risk for NIDDM and determine the prevalence of impaired glucose tolerance (IGT) and newly diagnosed diabetes in members of NIDDM pedigrees, we studied 310 members of 16 pedigrees ascertained for ≥2 NIDDM siblings. Nondiabetic members of all pedigrees were examined by 75-g oral glucose tolerance test with fasting and 1-h insulin levels. Participants had height and weight recorded. Spouses of pedigree members (n = 88) served as control subjects. The spouse control subjects were older and slightly more obese than the undiagnosed pedigree members. The prevalence of IGT was 14.8% in spouses and 7.7% in pedigree members, and NIDDM was present in 11.3% of spouses and 2.3% of previously undiagnosed pedigree members. However, neither spouses nor pedigree members differed significantly from published age-specific prevalence rates for IGT or newly diagnosed NIDDM. Insulin and glucose levels were examined in pedigree members with normal glucose tolerance (NGT). Fasting insulin levels were not significantly different between spouses and NGT pedigree members. However, after adjustment for age, weight (body mass index), and sex, NGT pedigree members had higher 1-h insulin levels and higher fasting and 1-h glucose levels than spouses. These differences were also evident when pedigree members with at least 1 affected (NIDDM or IGT) parent were compared with spouses with no family history of diabetes. However, when NGT pedigrees were compared by the number of parents affected, those individuals with 1 or 2 affected parents tended to have lower fasting and 1-h postglucose insulin levels and higher plasma glucose levels at 1 and 2 h than individuals with 2 unaffected parents. Although we found no evidence that younger individuals at risk for NIDDM have an increased prevalence of IGT or NIDDM by World Health Organization criteria, we did find relative hyperinsulinemia and hyperglycemia in members of pedigrees with a strong family history of NIDDM. However, within such pedigrees, offspring of affected parents tend to be hypoinsulinemic compared with their cousins with no affected parents. These findings suggest that, although hyperinsulinemia and insulin resistance characterize NIDDM pedigree members compared with control subjects, within NIDDM pedigrees, defective (β-cell function may also determine the risk of developing NIDDM.
Nutrition and Somatomedin: XXVII. Total and Free IGF-I and IGF Binding Proteins in Rats With Streptozocin-Induced Diabetes
Authors: Graubert Michael D , Goldstein Steven , Phillips Lawerence S
Published: September 2013

Impaired growth in diabetic humans occurs despite increased growth hormone and normal insulinlike growth factor I (IGF-I). Because IGF-I circulates complexed to binding proteins (BPs), we asked whether diabetes-related changes in IGF BPs could be associated with alterations in free unbound IGF-I—presumably the active form. Rats were given streptozocin (STZ) in increasing doses to produce graded severity of diabetes. IGF BP-1 and BP-3 were measured by ligand blotting, total IGF-I was determined by radioimmunoassay after separation from BPs by isocratic high-performance liquid chromatography (HPLC) at pH 3.9, and free IGF-I was estimated operationally as immunoreactivity with molecular weight equal to native IGF-I after HPLC at pH 7. Animals given 36 mg/kg STZ exhibited a glucose level of 9.74 mM and impaired weight gain, with little alteration in IGF BPs or total or free IGF-I. In contrast, animals given 72 mg/kg STZ (glucose level 24.64 mM and weight loss) had insignificant changes in total IGF-I and BP-3 but a 300% increase in BP-1 and a 50% fall in free IGF-I (both P < 0.005). With 144 and 288 mg/kg STZ, animals had further metabolic decompensation and weight loss, with progressive fall in BP-3 and rise in BP-1; total and free IGF-I fell to 10–20% of control (both P < 0.001). High-STZ animals (288 mg/kg) given high doses of protamine zinc insulin (PZI; 10 U/100 g body wt) gained weight and had subnormal glucose, whereas animals given low doses (3 U/100 g body wt PZI) were modestly hyperglycemic and gained less weight. Although both high- and low-dose insulin raised total IGF-I to 70–90% of normal, free IGF-I was fully restored with high-dose insulin but raised to only 38% of control with low-dose insulin (P < 0.001); animals given low-dose insulin had BP-1 levels threefold higher than animals given high-dose insulin (P < 0.05). Across all groups, free IGF-I was inversely correlated with levels of BP-1 (r = –0.79, P < 0.001). We conclude that free IGF-I is more sensitive to metabolic status than total IGF-I; levels of free IGF-I appear to reflect underlying alterations in IGF BPs. Decreased free IGF-I may contribute to impaired growth in diabetes mellitus.
Inducement of Antibody That Mimics Insulin Action on Insulin Receptor by Insulin Autoantibody Directed at Determinant at Asparagine Site on Human Insulin B Chain
Authors: Uchigata Yasuko , Takayama-Hasumi Sumiko , Kawanishi Koichi , Hirata Yukimasa
Published: September 2013

We previously showed that purified human IgG1 insulin autoantibody (IAA) from the serum of male patient T.H. with insulin autoimmune syndrome is directed at a determinant at the asparagine site on the human insulin B chain. An anti-idiotypic antibody (anti-TH) that inhibited TH-IAA binding to human insulin was obtained by immunizing BALB/c mice with TH-IAA. Anti-TH bound to viable IM-9 cells and the purified insulin receptor from IM-9 cells. Anti-TH binding to IM-9 cells and the insulin receptor was inhibited by TH-IAA but not by human IgG. Moreover, incubation of HepG2 cells with anti-TH had an inhibitory effect on insulin binding to HepG2 cells. Anti-TH, like insulin, stimulated amino acid uptake in HepG2 cells. These findings indicate that the conformation of TH-IAA idiotope is a mirror image of the determinant on the insulin B chain, the binding site for TH-IAA on anti-TH is also related to the insulin binding site on the insulin receptor, and anti-TH mimics insulin action on the insulin receptor.
Relative Hypersecretion of Proinsulin in Rat Model of NIDDM
Authors: Leahy Jack L , Halban Phillipe A , Weir Gordon C
Published: September 2013

The plasma ratio of proinsulin to insulin is raised in individuals with non-insulin-dependent diabetes mellitus (NIDDM). Increased secretion of proinsulin relative to insulin is thought to be the cause, although differential changes in clearance have not been ruled out. This study was conducted in a rat model of NIDDM, 90% pancreatectomized (Px) rats, to investigate the pathophysiology of this observation. Proinsulin storage and secretion were assessed with high-performance liquid chromatography separation of the insulins and the proinsulins, followed by quantification of the peaks by insulin radioimmunoassay. In Px rats, the relative proportion of proinsulin in pancreas extracts was twice that of control (sham-operated) rats (15.6 ± 1.4 vs. 8.3 ± 1.4%, P < 0.01). Samples obtained from the portal vein during in vitro pancreas perfusion also had an elevated proinsulin fraction (Px, 10.3 ± 3.0; sham, 3.0 ± 0.6%; P < 0.006). In summary, 90% Px rats share many pathophysiological features with NIDDM, including loss of normal proinsulin homeostasis. Our results suggest that chronic hyperglycemia causes an intrinsic change in β-cells that is characterized by the increased storage and secretion of proinsulin.
Effect of Diabetes on Fast Response to Norepinephrine in Rat Aorta
Authors: Rinaldi Gustavo J , Cingolani Horacio E
Published: September 2013

The fast and slow components of the mechanical response to 1 μM norepinephrine (NE) were measured in aortic rings isolated from eight spontaneously diabetic rats, six streptozocin-induced diabetic (STZ-D) rats, six STZ-D rats treated with 2.5 U insulin/day during the 4 days before being killed, and six age- and sex-matched control rats. The total contraction to NE (i.e., the sum of fast and slow components) was similar in the four groups: spontaneously diabetic, 16.53 ± 1.72 mN; STZ-D, 15.68 ± 1.41 mN; insulin-treated, 16.17 ± 2.05 mN; and control, 15.27 ± 0.96 mN (NS). The fast component, measured graphically in a total contraction in 1.35 mM Ca, was greater in spontaneously diabetic (12.61 ± 1.07 mN, P < 0.05) and STZ-D (12.25 ± 0.89 mN, P < 0.05) rats compared with control (9.14 ± 0.74 mN) or insulin-treated (8.58 ± 1.23 mN) rats. The same increase of the fast component was detectable after 3 min of incubation in Ca-free medium + 2 mM EGTA (control 6.54 ± 0.47 mN, spontaneously diabetic 9.07 ± 0.76 mN, P < 0.05; STZ-D 8.82 ± 0.72 mN, P < 0.05), and it was also abolished by insulin treatment (insulin-treated 6.29 ± 0.36 mN). We conclude that the diabetic state increases the fast component of NE-induced contraction either in the absence or presence of Ca in the medium. This suggests that such an increase depends on a larger release of Ca from intracellular stores.
Sequence of Human Galanin and Its Inhibition of Glucose-Stimulated Insulin Secretion From RIN Cells
Authors: McKnight Gary L , Karlsen Allan E , Kowalyk Stephan , Mathewes Shannon L , Sheppard Paul O , O'Hara Patrick J , Taborsky Gerald J
Published: September 2013

Human progalanin cDNA was cloned with polymerase chain reaction techniques. The cDNA sequence predicts that the human form of galanin has a substitution of the glycine residue found at position 30 in other species and thus is likely to retain this residue during posttranslational processing and not be amidated at the COOH terminus. Furthermore, the cDNA sequence predicts three additional amino acid substitutions compared with known galanins. Human galanin was synthesized, and its bioactivity was compared with porcine and rat galanin based on inhibition of insulin release from a glucose-responsive rat insulinoma (RIN) cell line. Human galanin inhibited glucose-stimulated insulin secretion in adose-dependent manner in RIN cells. Human, porcine, and rat galanin exhibited similar activity with ED50 <1 nM.
Na+/H+ Antiport Activity and Cell Growth in Cultured Skin Fibroblasts of IDDM Patients With Nephropathy
Authors: Trevisan Roberto , Li Lai K , Messent Jeanne , Tariq Taimur , Earle Kenneth , Walker James D , Viberti Giancarlo
Published: September 2013

IDDM patients with incipient and overt nephropathy have been found to exhibit an overactivity of RBC sodium-lithium countertransport. To explore the physiological relevance of this finding, we measured the activity of Na+/H+ antiport in serially passaged cultured skin fibroblasts from IDDM patients with and without nephropathy and from normal, nondiabetic control subjects. Na+/H+ antiport activity (measured as the rate of amiloride-sensitive Na+ influx at pH1 = 6.4, extracellular pH = 8.0, and [Na+] = 1 mM) was elevated significantly in IDDM patients with nephropathy compared with IDDM patients without nephropathy and nondiabetic control subjects (13.35 ± 3.8 vs. 8.54 ± 2.0 vs. 7.33 ± 2.3 nmol Na+ · mg protein−1 · min−1; P < 0.006 and P < 0.001, respectively). A kinetic analysis of Na+/H+ antiport activity showed that the raised activity in IDDM patients with nephropathy was caused by an increased Vmax for extracellular Na+. Km values were similar in the three groups. pH-stimulated amiloride-sensitive Na+ influx also was higher under baseline conditions and after serum stimulation in cells from IDDM patients with nephropathy. pHI values were significantly higher, both during active proliferation and after 10-min exposure to serum, in cells from IDDM patients with nephropathy, compared with IDDM patients without nephropathy and nondiabetic control subjects. Serum-stimulated incorporation of [3H]thymidine into DNA was greater in IDDM patients with nephropathy than in the other two groups (35.7 ± 18.9- vs. 17.4 ± 7.5- vs. 11.9 ± 8.7-fold stimulation above baseline; P < 0.01 for both). These data from cultured skin fibroblasts suggest that intrinsic abnormalities in cell function, independent of the metabolic disturbances of diabetes, are characteristic of IDDM patients who develop nephropathy.
Lp(a) Concentrations in NIDDM
Authors: Haffner Steven M , Morales Philip A , Stern Michael P , Gruber M Katherine
Published: September 2013

NIDDM patients have a two- to fourfold increased risk of CHD relative to nondiabetic subjects. This excess risk is explained only partially by increased levels of standard risk factors. We compared the plasma concentrations of Lp(a) in NIDDM patients (n = 260) and nondiabetic subjects (n = 336) who participated in a population-based study (San Antonio Heart Study). Lp(a) was measured using a monoclonal anti-Lp(a) antibody. NIDDM patients and nondiabetic subjects had similar Lp(a) concentrations for both men (13.6 ± 1.5 vs. 16.1 ± 1.4 mg/dl) and women (12.6 ± 0.8 vs. 15.9 ± 1.3 mg/dl) (P = 0.361). Duration of diabetes and level of fasting glycemia were not significantly related to Lp(a) concentrations. Lp(a) levels were significantly higher in patients who had higher total and LDL cholesterol levels. We conclude that in a large population-based study, Lp(a) levels are not increased in NIDDM patients.
Glucokinase and NIDDM: A Candidate Gene That Paid Off
Authors: Permutt M Alan , Chiu Ken C , Tanizawa Yukio
Published: September 2013

Glucokinase, the major enzyme that phosphorylates glucose upon entry into liver and islet β-cells, has been considered a prime candidate for inherited defects predisposing to NIDDM. Now that the human gene has been isolated, this question has been addressed directly. Polymorphic markers flanking the gene were identified. These markers (microsatellites) are composed of variable numbers of dinucleotide repeats that vary in size, resulting in different alleles. Variably sized alleles can be typed rapidly from genomic DNA of individuals by the PCR. Studies of inheritance of glucokinase genes have revealed significant linkage in families with early-onset NIDDM, or MODY, and mutations have been identified within the coding region of the gene in some families. These studies are extremely encouraging, as they indicate that genes can be identified even in this heterogeneous genetic disorder. This study considers the phenotypes that result from glucokinase defects and the relationship of MODY to NIDDM, and it estimates the role of glucokinase defects in NIDDM in general.
β-Cell Antigen–Specific Lysis of Macrophages by CD4 T-Cell Clones From Newly Diagnosed IDDM Patient: A Putative Mechanism of T-Cell–Mediated Autoimmune Islet Cell Destruction
Authors: Roep Bart O , Kallan Aram A , Devries René R P
Published: September 2013

Immunophenotyping of the early lesion in the pancreatic islets of Langerhans demonstrates a predominance of CD4+ lymphocytes, which may be preceded by an increase in islet macrophages. This observation implies that both types of cells may be involved in autoimmune-mediated β-cell destruction leading to IDDM. In an attempt to attribute a role to β-cell antigen-specific CD4-expressing T-cell clones recently isolated from a newly diagnosed IDDM patient, we investigated whether such CD4 T-cells may be pathogenic in an in vitro cytotoxicity assay with HLA-DR-matched antigen-presenting macrophages as target. We report herein that, indeed, β-cell antigen-specific CD4+ T-cells are capable of lysing macrophages in an antigen-specific fashion. This cytotoxicity is HLA-DR restricted, T-cell receptor complex mediated, and CD4 dependent. These observations imply that both helper T-cells and macrophages may be involved in the disease process via interaction between T-cells and macrophages pulsed with β-cell antigen.
Islet Amyloid Polypeptide/Amylin in Pancreatic β-Cell Line Derived From Transgenic Mouse Insulinoma
Authors: Kanatsuka Azuma , Makino Hideichi , Yamaguchi Takahide , Ohsawa Haruhiko , Tokuyama Yoshiharu , Saitoh Takeo , Yamamura Ken-Ichi , Miyazaki Jun-Ichi , Yoshida Sho
Published: September 2013

We examined the production and secretion of IAPP in a β-cell line, MIN6, which is derived from an insulinoma obtained by targeted expression of the SV40 T-antigen gene in a transgenic mouse. RNA blot analysis revealed an abundance of IAPP and insulin II mRNA in the cells, findings comparable with those in the pancreas of a normal mouse. The presence of IAPP and insulin was confirmed immunohistochemically and by RIA. Analysis of the reverse-phase HPLC identified IAPP in cells with authentic mouse IAPP. Raising the glucose concentration from 5.6 to 25 mM failed to induce increments in IAPP and insulin II mRNAs. The cells secrete IAPP and insulin for short- and long-term incubations in response to concentration of glucose in the medium. These features resemble those of islet cells from normal animals. This β-cell line will aid in analyzing the regulation of IAPP gene expression and the mechanisms of IAPP biosynthesis and secretion.
Linkage Analysis of Glucokinase Gene With NIDDM in Caucasian Pedigrees
Authors: Cook Joanne T E , Hattersley Andrew T , Christopher Pau , Bown Edwin , Barrow Beryl , Patel Pushpa , Shaw J Andrew G , Cookson William O C M , Permutt M Alan , Turner Robert C
Published: September 2013

NIDDM has a strong genetic component, as evidenced by the high level of concordance between identical twins. The nature of the genetic predisposition has remained largely unknown. Recently, the glucokinase gene locus on chromosome 7p has been shown to be linked to a subtype of NIDDM known as MODY in French and British pedigrees, and glucokinase mutations have been identified. To study the relationship between the glucokinase gene and NIDDM, we performed a linkage analysis in 12 Caucasian pedigrees ascertained through a proband with classical NIDDM. The LINKAGE program was used under four models, including autosomal dominant and recessive, with individuals with glucose intolerance counted as either affected or of unknown status. Linkage was significantly rejected with the dominant models (LOD scores −4.65, −4.25), and was unlikely with the recessive model when glucose intolerance was considered as affected (LOD score −1.38). These findings suggest that mutations in or near the glucokinase gene are unlikely to be the major cause of the inherited predisposition to NIDDM in Caucasian pedigrees, but do not exclude a role for this locus wit a polygenic model, or a major role in some pedigrees.
Pathogenic Factors Responsible for Glucose Intolerance in Patients With NIDDM
Authors: Taniguchi Ataru , Nakai Yoshikatsu , Fukushima Mitsuo , Kawamura Hitomi , Imura Hiroo , Nagata Itaru , Tokuyama Kumpei
Published: September 2013

To define the pathogenic factors responsible for glucose intolerance in NIDDM, we estimated insulin secretory capacity, SI, and SG in 11 healthy, nondiabetic subjects and 9 NIDDM patients who had no SI impairment. All subjects studied were nonobese and normotensive. Each underwent a 75-g OGTT and a modified FSIGT: glucose was administered (300 mg/kg body weight), and insulin was infused (20 mU/kg over 5 min) from 20 to 25 min after the administration of glucose. SI and SG were estimated by Bergman's minimal-model method. The insulin response to oral glucose was significantly lower in NIDDM patients than in normal control subjects. First-phase insulin secretion expressed as the integrated area of plasma insulin above the basal level during the first 20 min was much smaller in NIDDM subjects (214 ±112 pM · min) than in control subjects (4643 ± 885 pM · min, P < 0.01). S, was not statistically different in normal control subjects (1.27 ± 0.18 × 10−4 min−1 · pM−1) versus diabetic patients (1.62 ± 0.33 × 10−4 min−1 · pM−1). However, SG was significantly lower in diabetic subjects (1.11 ± 0.17 × 10−2 min−1) than in control subjects (2.35 ± 0.26 × 10−2 min−1 P < 0.01). These results suggest that impaired insulin secretion and decreased SG are the factors responsible for glucose intolerance of Japanese NIDDM patients with normal insulin sensitivity. Because SI and SG are the factors responsible for glucose intolerance of NIDDM patients with insulin resistance, it is conceivable that decreased SG is common in NIDDM patients regardless of their SI index.
Reevaluation of Autoantibodies to Islet Cell Membrane in IDDM: Failure to Detect Islet Cell Surface Antibodies Using Human Islet Cells as Substrate
Authors: Vives Marta , Somoza Nuria , Soldevila Gloria , Gomis Ramon , Lucas Anna , Sanmarti Anna , Pujol-Borrell Ricardo
Published: September 2013

Since their demonstration in 1975, ICSAs have been proposed as serological markers and pathogenic elements in IDDM. ICSAs are detected in the sera of most newly diagnosed IDDM patients by indirect IFL that uses viable preparations of rat islet or insulinoma cells as substrate, but they also can be detected by using human insulinoma or fetal islet cells. We have tried to demonstrate ICSAs in the sera of 31 newly diagnosed diabetic patients, including 6 positive samples on human fetal islet cells, which used their natural target for the first time: normal human islet cells. In spite of using different types of preparations of these cells (i.e., freshly dispersed cell suspensions, monolayer cultures, or dispersed islets after culture), ICSAs could not be detected by IFL under the UV microscope, nor by flow cytometry. In contrast, 9 of 29 of the sera gave a positive staining on the RIN rat insulinoma cells. In an attempt to establish whether the putative ICSA autoantigen is present in the surface of human islet cells in the diabetic pancreas, the insulitis microenvironment was emulated by exposing the islets to three types of stress: 1) cytokines (IFN-γ and TNF-α); 2) heat shock; and 3) hyperglycemia. However, diabetic sera failed again to recognize membrane antigens on the islet cells after either of these treatments. Neither were islet cells from a newly diagnosed diabetic patient stained by its autologous serum (ICA titer >80 JDF U). These results suggest that ICSA autoantigen is not expressed in the membrane of human islet cells and therefore raises doubts about their proposed pathogenic role.
Influence of STZ-Induced Diabetes on Zero-Stress States of Rat Pulmonary and Systemic Arteries
Authors: Liu Shu Qian , Fung Yuan-Cheng
Published: September 2013

Zero-stress states of the main pulmonary arteries and aorta and small systemic arteries were determined in 22 nondiabetic and 29 streptozocin (STZ)-induced diabetic rats. The zero-stress state of each vessel was obtained by cutting the vessel transversely into a series of short rings, then cutting each ring radially, which caused the ring to spring open into a sector. Each sector can be characterized by its opening angle. The opening angle has strong regional dependence. In some regions of rat arteries, the opening angle can be >360°. Rats were studied 5, 10, 20, 30, and 40 days after an injection of 75 mg/kg body wt i.v. STZ. During diabetes development, the opening angles in general increased and reached a plateau in ∼30 days. The maximum change of opening angle over normal lies in the range of 18–105°, depending on location. The pulmonary arteries were affected by diabetes as much as the systemic arteries. The course of change of the opening angle during diabetogenesis was different from those of the serum glucose level and blood pressure. Blood pressure in carotid, external iliac, and pulmonary arteries did not change significantly in diabetogenesis. To clarify the physiological meaning of the opening angle, we measured the circumferential strain in the blood vessel wall in homeostatic condition and the residual strain at the no-load state, with both strains referred to the zero-stress state. We calculated the corresponding stresses in the vessel wall. The circumferential stress in the vessel wall was greatly increased by diabetes; great errors will result if the opening angle is ignored.
Exaggerated Sensitivity to NE-Induced Vasoconstriction in IDDM Patients With Microalbuminuria: Possible Etiology and Diagnostic Implications
Authors: Bodmer Charles W , Patrick Alan W , How Tien V , Williams Gareth
Published: September 2013

Increased urinary albumin excretion rate (AER) in the microalbuminuric phase of diabetic nephropathy has been attributed to intraglomerular hypertension. This could be caused by constriction of efferent glomerular arterioles, which carry α-adrenoceptors. We tested the hypothesis that insulin-dependent diabetes mellitus (IDDM) patients with microalbuminuria are hypersensitive to vasoconstriction induced by norepinephrine (NE). We studied 15 IDDM patients with microalbuminuria (AER 32–295 mg/24 h), 13 IDDM patients with normal AER (5–24 mg/24 h), and 9 nondiabetic subjects (AER 8–22 mg/24 h). All were normotensive. NE-induced vasoconstriction was measured in dorsal hand veins, which carry α-receptors similar to those of glomerular efferent arterioles. Vein diameter was measured with a linear displacement probe during a stepped NE infusion (1–32 ng/min) into the vein, and venoconstriction was expressed as a percentage of the maximum passively distended venous diameter. Microalbuminuric IDDM patients exhibited significantly greater vasoconstriction (P < 0.005) at all NE infusion rates than both other groups. The NE infusion rate producing 50% of maximal venoconstriction (ED50) in the microalbuminuric IDDM group (median 1.1 ng/min, range 0.2–25.2 ng/min) was significantly less than in both the normoalbuminuric IDDM group (median 12.5 ng/min, range 4.9–40.5 ng/min, P = 0.00007) and the nondiabetic group (median 17.7 ng/min, range 5.9–42.2 ng/min, P = 0.0003). Dose-response curves and ED50 did not differ significantly between normalbuminuric IDDM and nondiabetic groups. IDDM patients with microalbuminuria are hypersensitive to NE-induced vasoconstriction. Such an abnormality in efferent glomerular arterioles could contribute to albuminuria and, if affecting the systemic resistance vessels, to the hypertension that coexists with later phases of nephropathy. This test may help identify at an early stage IDDM patients at risk of developing nephropathy.
Risk Factors for Coronary Heart Disease in Diabetes Mellitus
Authors: Jarrett RJ
Published: September 2013

A review of the putative risk factors associated with the development of coronary heart disease in diabetes is presented. Emphasis is given to the effect of nephropathy (persistent proteinuria) and hypertension on cardiovascular mortality in IDDM. Risk factors associated with CHD in NIDDM are also reviewed. Finally, possible reasons to explain the increased incidence of CHD associated with proteinuria in IDDM patients, including lipoprotein abnormalities, increased fibrinogen levels, increased platelet adhesiveness, and altered hemostatic variables, are discussed.
Plasma Lipid and Lipoprotein Disorders in IDDM
Authors: Dunn Fredrick L
Published: September 2013

Abnormal lipoprotein metabolism contributes to the increased risk of premature atherosclerosis in people with insulin-dependent (type I) diabetes. Although hypertriglyceridemia is common in those with untreated IDDM, treatment with conventional insulin therapy usually restores fasting lipoprotein profiles to nondiabetic levels. Intensive insulin therapy improves glycemie control and lipoprotein concentrations, but does not ameliorate the changes in lipoprotein composition described in people with IDDM. Some of these persistent changes in lipoprotein composition have been attributed to peripheral hyperinsulinemia associated with s.c. insulin therapy. The recent availability of implantable insulin-infusion pumps for treatment of IDDM has allowed the study of the effect of i.p. insulin delivery on lipoprotein metabolism, i.p. insulin therapy is capable of maintaining near normal plasma glucose levels while reducing the peripheral hyperinsulinemia. Although results have been contradictory, studies of i.p. insulin therapy may eventually help to determine whether some of the observed changes in lipoprotein metabolism and composition in people with IDDM are due to the peripheral hyperinsulinemia associated with s.c. insulin therapy.
Identification of ApoB-Containing Lipoprotein Families in NIDDM
Authors: Alaupovic Peter , Bard Jean-Marie , Tavella Marcelo , Shafer David
Published: September 2013

The purpose of this study was to determine the concentrations and composition of apoB-containing lipoprotein families in whole plasma and major lipoprotein density classes of a selected group of Native Americans from northeastern Oklahoma with non-insulin-dependent diabetes mellitus. The measurement of lipoprotein density classes showed that the total lipoprotein mass of very-low-density lipoproteins was significantly higher and that of high-density lipoproteins significantly lower in diabetic patients than nondiabetic control subjects regardless of their plasma triglyceride levels. The VLDLs were enriched with TG, free cholesterol, and apolipoproteins C-III and E. HDLs were enriched with TG but depleted of apoC-III and apoE. There was no change in the levels of TG-enriched low-density lipoproteins. Fractionation of VLDL by sequential immunoprecipitation with antisera to apoE and apoC-III established that increased concentrations of this density class in diabetic patients are due to elevated levels of TG-rich lipoprotein LP-B:C and lipoprotein LP-B:C:E. The levels of LP-B:C particles were increased more than the levels of LP-B:C:E particles. The LDLs were characterized by a slight increase in TG-enriched lipoprotein B and no change in the levels of LP-B:C and LP-B:C:E. There was no difference between diabetic patients with or without vascular disease in the levels of LP-B and LP-B:C:E. However, patients with vascular disease had higher concentrations of LP-B:C particles in VLDL and whole plasma than patients without vascular disease. In conclusion, the most characteristic abnormalities of lipid transport in people with NIDDM are increased levels of TG-rich LP-B:C and LP-B:C:E particles of modified chemical composition and decreased concentrations of apoA-l-containing lipoproteins of modified chemical composition. These abnormalities seem to be present in most diabetic patients regardless of their plasma TG levels. It appears that diabetic patients with vascular disease have higher levels of LP-B:C particles and higher LP-B:C-LP-B:C:E ratios than diabetic patients without vascular disease. The metabolic behavior and atherogenic potential of LP-B:C and other TG-rich apoB-containing lipoproteins remain to be ascertained in future studies.