bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Effects of High and Low Carbohydrate Diets on Plasma Lipoproteins and Insulin Sensitivity in Patients With Mild NIDDM
Authors: Garg Abhimanyu , Grundy Scott M , Unger Roger H
Published: September 2013

Previous studies indicate that diets rich in digestible carbohydrates improve glucose tolerance in nondiabetic individuals, but may worsen glycemic control in NIDDM patients with moderately severe hyperglycemia. The effects of such high-carbohydrate diets on glucose metabolism in patients with mild NIDDM have not been studied adequately. This study compares responses to an isocaloric high-carbohydrate diet (60% of total energy from carbohydrates) and a low-carbohydrate diet (35% of total energy from carbohydrates) in 8 men with mild NIDDM. Both diets were low in saturated fatty acids, whereas the low-carbohydrate diet was rich in monounsaturated fatty acids. The two diets were matched for dietary fiber content (25 g/day). All patients were randomly assigned to receive first one and then the other diet, each for a period of 21 days, in a metabolic ward. Compared with the low-carbohydrate diet, the high-carbohydrate diet caused a 27.5% increase in plasma triglycerides and a similar increase in VLDL-cholesterol levels; it also reduced levels of HDL cholesterol by 11%. Plasma glucose and insulin responses to identical standard breakfast meals were studied on days 4 and 21 of each period, and these did not differ significantly between the two diets. At the end of each period, a euglycemic hyperinsulinemic glucose clamp study with simultaneous infusion of [3-3H]glucose revealed no significant changes in hepatic insulin sensitivity; and peripheral insulin-mediated glucose disposal remained unchanged (14.7 ± 1.4 vs. 16.5 ± 2.3 μM · kg−1 · min−1 on the high-carbohydrate and low-carbohydrate diets, respectively). We conclude that in patients with mild NIDDM, high-carbohydrate diets do not improve glycemic control nor insulin sensitivity, and they raise plasma triglyceride and VLDL-cholesterol concentrations and reduce HDL-cholesterol levels, which may not be desirable.
Heterogeneity of Messenger RNA That Encodes the Rat Insulin Receptor Is Limited to the Domain of Exon 11: Analysis by RNA Heteroduplex Mapping, Amplification of cDNA, and In Vitro Translation
Authors: Goldstein Barry J , Dudley Alana L
Published: September 2013

Structural isoforms of the insulin receptor that occur in various tissues have been postulated to be involved in certain actions of insulin in target cells. To determine whether these insulin-receptor subtypes are caused by alterations in the receptor primary structure, we used RNA heteroduplex mapping and amplification of cDNA to detect variation in the coding region of insulin-receptor mRNA from 5 rat tissues. A complete series of overlapping antisense [32P]RNA probes was prepared from plasmids containing segments of a full-length rat insulin-receptor cDNA, and probes were hybridized individually in solution with polyadenylated RNA from rat brain, kidney, liver, skeletal muscle, and spleen. After ribonuclease digestion, probe fragments were analyzed by denaturing gel electrophoresis. Tissue-specific cleavage of the mRNA:RNA probe heteroduplex, attributable to sequence mismatch, was detected only for a single probe covering the distal α-subunit, as expected for the known alternative splicing of rat insulin-receptor mRNA in this region. No evidence for additional heterogeneity of the receptor mRNA coding region was observed in the 5 tissues studied either by RNA heteroduplex mapping or, in some areas, by regional amplification of insulin-receptor cDNA. Cell-free translation of size-fractionated polyadenylated RNA was used to further demonstrate that each of the major insulin-receptor mRNA size classes in rat liver contained both forms of the alternatively spliced mRNA transcripts and produced two insulin-proreceptor polypeptides. These results suggest that heterogeneity of the insulin-receptor mRNA coding region affecting the receptor primary structure is limited to the distal α-subunit near the subunit cleavage site. Many of the reported structural isoforms of the mature insulin receptor are therefore likely to occur by specific posttranslational processing events that may influence the transmission of the insulin signal in various tissues.
Inverse Relationship Between Serum Lp(a) Levels and First-Phase Insulin Secretion
Authors: Sidhu Mandeep , Crook David , Godsland Ian F , Walton Christopher , Wynn Victor , Oliver Michael F
Published: September 2013

Relationships between serum Lp(a) levels and insulin metabolism were investigated in 147 healthy nonobese men attending an executive health-screening program. Each subject received an IVGTT with measurement of plasma levels of glucose, insulin, and C-peptide. An inverse relationship was seen with the first-phase plasma insulin response when subjects were stratified into quartile ranges of the serum Lp(a) distribution. This relationship was supported by mathematical modeling analyses of these data, which revealed an inverse relationship between serum Lp(a) levels and first-phase pancreatic insulin secretion and plasma Insulin responsiveness to glucose.
Insulin Secretory Profiles and C-Peptide Clearance Kinetics at 6 Months and 2 Years After Kidney-Pancreas Transplantation
Authors: Blackman John D , Polonsky Kenneth S , Jaspan Jonathan B , Sturis Jeppe , Cauter Eve Van , Thistlethwaite J Richard
Published: September 2013

Glucose, insulin secretion, and insulin secretory pulses were measured by deconvolution of peripheral C-peptide concentrations in 10 IDDM recipients of a combined kidney-pancreas allograft 6 mo post-transplantation and were compared with 10 matched nondiabetic control subjects. Seven of the 10 recipients were restudied 2 yr post-transplantation. To control for immunosuppressive therapy, 6 patients with a kidney allograft also were studied. Pancreatic insulin secretion rates were evaluated over a 24-h period with three mixed meals. Six months post-transplantation, fasting (5.3 ± 0.1 vs. 5.3 ± 0.1 mM), average 24-h (6.0 ± 0.1 vs. 5.7 ± 0.1 mM), and meal-related (6.1 ± 0.3 vs. 5.8 ± 0.2 mM) plasma glucose levels were not different in control subjects and recipients, respectively. Total 24-h insulin secretion rates were similar between the two groups (150 ± 15 vs. 182 ± 24 nmol · m−2 · 24 h−1). However, post-transplantation, the relationship between basal and meal-stimulated insulin secretion was altered with increased basal insulin secretion (52.2 ± 6.4 vs. 97.4 ± 12.5 pmol · m−2 · min−1 P < 0.004) and reduced meal-related secretion. The proportion of total 24-h insulin secretion comprised by basal secretion was 44 ± 4% in the control subjects vs. 73 ± 5% in recipients. The number of ultradian oscillations of insulin secretion identified in each 24-h period by pulse analysis was similar in control subjects and recipients (11.9 ± 0.9 vs. 10.4 ± 0.5 oscillations/24 h). Two years post-transplantation, the glucose profiles and oscillatory insulin secretory patterns remained intact. Basal insulin secretion was 76 ± 11 pmol · m−2 · min−1 and 24-h insulin secretion was 167 ± nmol m−2 24 h−1. Six kidney-transplant recipients studied showed that 47 ± 3% of 24-h insulin secretion was basal secretion. This finding supported the idea that altered meal secretory patterns observed in the kidney-pancreas recipients were not the result of immunosuppressive therapy. After combined kidney-pancreas transplantation 1) plasma glucose profiles remain normal 2 yr post-transplantation, 2) clearance of C-peptide is reduced, 3) basal insulin secretion is increased but meal responses are reduced, and 4) the normal oscillatory pattern of insulin secretion persists.
Recombinant Glutamic Acid Decarboxylase (Representing the Single Isoform Expressed in Human Islets) Detects IDDM-Associated 64,000-Mr Autoantibodies
Authors: Karlsen Allan E , Hagopian William A , Petersen Jacob S , Boel Esper , Dyrberg Thomas , Grubin Catherine E , Michelsen Birgitte K , Madsen Ole D , Lernmark Åke
Published: September 2013

GAD is an autoantigen in IDDM. Molecular cloning and specific antibodies allowed us to demonstrate that only the lower Mr GAD64 isoform is expressed in human islets, in contrast to human brain, rat islets, and rat brain, all of which express both GAD64 and GAD67. Expression of the human islet GAD64 isoform in COS-7 and BHK cells resulted in an enzymatically active rGAD64, which is immunoreactive with diabetic sera comparable with that of the islet 64,000-Mr autoantigen. Immunoprecipitation analyses showed that 21/28 (75%) IDDM sera had rGAD64 antibodies compared with only 1/59 (1.7%) of the healthy control sera. In immunoblot analyses, an SMS serum—but only 1/10 randomly selected IDDM sera—recognized the blotted rGAD64 without relation to immunoprecipitation titers. In conclusion, only the GAD64 isoform is expressed in human islets, in contrast to rat islets, which also express the GAD67 isoform. The immunological properties of human rGAD64 are comparable with the native 64,000-Mr islet autoantigen, allowing further studies of the immunopathogenesis of IDDM.
G-Proteins and Hormonal Inhibition of Insulin Secretion From HIT-T15 Cells and Isolated Rat Islets
Authors: Seaquist Elizabeth R , Neal Andrea Robertson , Shoger Kirk D , Walseth Timothy F , Robertson R Paul
Published: September 2013

G-proteins are important mediators of hormonal inhibition of insulin secretion. To characterize the pertussis toxin–sensitive substrates present in HIT cell membranes, we performed immunoblots with specific antisera and found evidence for the presence of GIα1, GIα2, GIα3, and three forms of GOoα. We observed that pertussis toxin–sensitive substrates mediate all of the effects of SRIF, and a major portion of the effects of EPI, on insulin secretion from rat islets during static incubations. These results agree with our previously reported studies examining phasic glucose-induced insulin secretion from HIT cells. To ascertain whether inhibition of adenylate cyclase, presumably involving coupling of the catalytic subunit to GI, may be a common mechanism for both hormones, we studied the effects of 8-bromo-cyclic AMP and found that this agent partially prevented the inhibitory effects of both hormones. We also observed that the inhibitory effects of SRIF and EPI on insulin were nonadditive, that both hormones were additive to nickel chloride during inhibition of insulin release, and that they noncompetitively inhibited glipizide-induced insulin secretion through pertussis toxin-sensitive mechanisms. Together, these results suggest that both hormones exert their effects on insulin secretion at multiple G- protein -regulated sites including adenylate cyclase and sites distal to the glipizide-binding site on the KATP channel.
Glycation of Albumin, Not Glomerular Basement Membrane, Alters Permeability in an In Vitro Model
Authors: Daniels Barbara S , Hauser Elizabeth B
Published: September 2013

The effects of glycation of either albumin, a plasma protein, or GBM were examined in an in vitro model of GBM permeability. Albumin was incubated with glucose in vitro, and nonglycated and glycated albumin were separated by affinity chromatography. Rat GBM was glycated either in vivo after the induction of diabetes or in vitro after incubation with 25 mM glucose. 150 μg of GBM was consolidated in an ultrafiltration cell, and albumin permeability across the GBM filter was assessed at an applied pressure (50 mmHg) selected to approximate glomerular capillary pressure in vivo. The sieving coefficient of glycated albumin was greater than the sieving coefficient of nonglycated albumin (0.25 ± 0.03 vs. 0.10 ± 0.02; P < 0.05). GBM glycated in vivo in diabetic rats exhibited native albumin and water permeability that was indistinguishable from that for GBM from control rats. Similarly, GBM glycated in vitro by incubation with 25 mM glucose exhibited water and albumin permeability identical to that for GBM incubated in buffer. Thus, the glycation of albumin, but not of GBM, leads to enhanced permeability in an in vitro GBM filtration system. Increased permeability of glycated albumin may contribute to albuminuria and/or renal injury in states of increased circulating glycated albumin such as diabetes and experimental galactosemia.
Effects of Acute and Chronic Counterregulatory Hormone Infusions on Glucose Tolerance and Insulin Sensitivity in Diabetic Dogs
Authors: Sleeman Mark W , Christopher Michael J , Martin Iva K , Ward Glenn M , Alford Frank P , Best James D
Published: September 2013

The effects of elevated EPI and CORT levels on KG, SI and SG were studied in dogs with alloxan-induced diabetes. Conscious dogs received SAL, EPI 20 ng μ kg−1 · min−1 for 30 min (short EPI) or 72 h (long EPI), or CORT 200 μg · kg−1 · min−1 for 60 min (short CORT) or 72 h (long CORT) before assessment of glucose metabolism by rapid sampling for glucose and insulin levels after 300 mg/kg i.v. glucose and exogenous insulin infusion designed to simulate the normal secretory pattern. With EPI infusion, KQ fell acutely from 2.9 ± 0.4 to 2.0 ± 0.2%/min (SAL vs. short EPI, P < 0.05), but rose to 3.4 ± 0.4%/min during long EPI. Minimal-model analysis of the glucose response with the insulin data as input showed that S1 decreased acutely from 4.7 ± 1.8 to 2.5 ± 0.6 × 10−5 min−1/pM (SAL vs. short EPI, P < 0.05), but rose to 4.5 ± 2.5 × 10−1 min−1/pM during long EPI. The effects of EPI on SG paralleled the results for KG and S1, with acute decline from 3.9 ± 0.4 to 2.1 ± 0.4 × 10−2 min−1 (SAL vs. short EPI, P < 0.05) and recovery to 3.3 ± 0.3 × 10−2 min−1 during long EPI. During CORT infusion, Kg tended to fall (SAL 2.9 ± 0.4 vs. short CORT 2.5 ± 0.5 vs. long CORT 2.2 ± 0.5%/min). This decline was related to a fall of S1 (SAL 4.7 ±1.8 vs. short CORT 2.7 ± 1.8 vs. long CORT 1.2 ± 0.7 × 10−1 min−1/pM, P < 0.05 long CORT vs. SAL), whereas SG levels were similar for the three groups. These results indicate that, in the absence of any compensatory change of insulin secretion, adaptation to the metabolic effects of long-term hormone elevation occurs for EPI but not CORT, which has a sustained effect on S1. Therefore, CORT may be more important than EPI as a contributor to long-term stress-induced hyperglycemia in people with type I diabetes.
1,25-Dihydroxyvitamin D3 Prevents Insulitis in NOD Mice
Authors: Mathieu Chantal , Laureys Jos , Sobis Halina , Vandeputte Michel , Waer Mark , Bouillon Roger
Published: September 2013

The active form of vitamin D, 1,25(OH)2D3, can prevent various forms of experimentally induced autoimmune disorders. The aim of this study was to confirm these findings in NOD mice that spontaneously develop an autoimmune type of diabetes mellitus. Therefore, the effect of a long-term 1,25(OH)2D3 treatment on the incidence of insulitis, the histological lesion preceding diabetes, was studied. Forty-three NOD mice were treated with 1,25(OH)2D3 (5 μg/kg) i.p. every other day from age 21 days on, when no insulitis was present yet. At day 100,16 control mice receiving the treatment vehicle (arachis oil) had an incidence of insulitis of 75%, whereas only 41% of the 1,25(OH)2D3-treated animals developed insulitis (P < 0.025). Calcemia, determined 24 h after the last 1,25(OH)2D3 injection was 2.5 ± 0.3 mM, which was higher than in control animals (2.3 ± 0.1 mM), but was well tolerated. Cellular immunity, as assessed with the mixed lymphocyte reaction performed at day 100, was not impaired significantly. This study demonstrates that long-term treatment with high doses of 1,25(OH)2D3 is able to decrease the incidence of insulitis in spontaneous autoimmune diabetes without major side effects.
Lactate Production and Pyruvate Dehydrogenase Activity in Fat and Skeletal Muscle From Diabetic Rats
Authors: Mondon Carl E , Jones Ian R , Azhar Salman , Hollenbeck Clarie B , Reaven Gerald M
Published: September 2013

This study was initiated to explore the possibility that an increase in the supply of gluconeogenic precursors contributes to the overproduction of glucose by the liver in NIDDM patients. To address this issue, a form of experimental NIDDM was produced in rats by injecting a low dose (38 mg/kg) of STZ and comparing lactate and alanine production and PDH activity in skeletal muscle and isolated adipocytes from normal and diabetic rats. Skeletal muscle lactate production was measured by using a hindlimb perfusion technique and was significantly greater (P < 0.01) in the diabetic rats compared with two groups of control rats: one perfused at normal glucose levels and the other perfused at glucose concentrations comparable with those observed in diabetic rats. Alanine production by hindlimb from diabetic rats was 46% greater than hindlimbs from control rats perfused at normal glucose levels (P < 0.01) but was not significantly greater than control rats perfused at diabetic glucose levels. The percentage of glucose converted to lactate by muscle from both control groups was 4–5%, significantly lower than the 18% conversion rate observed in diabetic animals (P < 0.001). An increase in the ratio of lactate produced/glucose transport by isolated adipocytes from diabetic rats also was observed when measured in both the basal state (0.65 ± 0.12 vs. 0.15 ± 0.03, P < 0.01) and in the presence of maximal amounts of insulin (0.15 ± 0.02 vs. 0.04 ± 0.01, P < 0.02). Total PDH activity in fat and muscle was similar in both groups of animals, but PDH present in the active form was significantly reduced in the diabetic compared with the normal rats in fat (39 ± 6 vs. 58 ± 5%, P < 0.05) and in muscle (11 ± 5 vs. 47 ± 10%, P < 0.01). In conclusion, low-dose STZ-induced diabetes in rats is characterized by reduced PDH activity and increased lactate production in skeletal muscle and adipose tissue, changes that, in the presence of insulin deficiency, could contribute to enhanced HGP.
Glucose Transporters of Rat Peripheral Nerve: Differential Expression of GLUT1 Gene by Schwann Cells and Perineurial Cells In Vivo and In Vitro
Authors: Muona Päivi , Sollberg Stephan , Peltonen Juha , Uitto Jouni
Published: September 2013

Expression of GLUTs in rat peripheral nerve was first studied at the mRNA level with Northern transfer analysis with cDNAs specific for GLUT1, GLUT2, GLUT3, and GLUT4. GLUT1 mRNA was the only GLUT mRNA detectable in rat sciatic nerve. In situ hybridization localized this mRNA to the perineurium and to some endo- and epineurial capillaries. Indirect immunofluorescence stainings demonstrated that GLUT1 protein epitopes were concentrated primarily in the perineurium and endoneurial capillaries. Also, some Schwann cells, a few epineurial capillaries, and medium-sized blood vessels showed a faintly positive immunoreaction. All cell types present in primary cultures initiated from rat sciatic nerve (perineurial cells, Schwann cells, and fibroblasts) expressed GLUT1 protein in vitro. Thus, Schwann cells, which expressed GLUT1 only occasionally at a low level in vivo, have the potential to express GLUT1 at a markedly higher level under cell culture conditions. Incubation of the cultures in 25 mM D-glucose for 7 days caused a 39% reduction in the amount of immunodetectable GLUT1 protein, and a marked (34%) decrease of GLUT1 mRNA compared with cultures incubated in 5.5 mM D-glucose. Interestingly, the reduction of [3H]-2-DG uptake in the same cultures exceeded 70%, suggesting that the reduced amount of GLUT1 protein alone did not explain the marked reduction in glucose uptake in these cultures. Immunostaining of the cell cultures suggested that perineurial cells were the main target for the glucose-induced decrease of GLUT1 protein.
Effects of STZ-Induced Diabetes and Fasting on Insulin Receptor mRNA Expression and Insulin Receptor Gene Transcription in Rat Liver
Authors: Tozzo Effie , Desbuquois Bernard
Published: September 2013

Insulinopenic states in rodents are known to cause an increase in the number of hepatic insulin receptors. To determine if this change is related to an abnormality in insulin receptor gene expression, insulin receptor binding, insulin receptor mRNA levels, and insulin receptor gene transcription rates have been measured in livers from rats rendered hypoinsulinemic by STZ administration (65 mg/kg) or fasting. In the two groups of experimental rats, insulin binding to liver plasma membranes was increased (∼40 and 25%, respectively) relative to control, normoinsulinemic animals. Northern blot analysis of either total or poly (A)+ RNA from livers of hypo- and normoinsulinemic rats revealed two major insulin receptor mRNA species of 9.5 and 7.5 kbs. In hypoinsulinemic rats, insulin receptor mRNA levels were increased ≤10-fold, with similar effects on the two mRNA species. The effects of STZ administration and fasting on insulin receptor binding and insulin receptor mRNA levels were fully reversed by insulin treatment or refeeding, respectively. Injection of ACT D, an inhibitor of gene transcription, decreased insulin receptor mRNA levels by >80% in control and diabetic rats and suppressed the overexpression of mRNA seen in diabetic rats. In vitro nuclear transcription assays showed that the rate of transcription of the insulin receptor gene was increased 2-fold in STZ-induced diabetic rats and fasted rats relative to control animals. Taken together, these results suggest that the upregulation of the insulin receptor induced by chronic insulinopenia results, at least in part, from an increase in insulin receptor gene transcription.
Elevated Levels of Circulating Adhesion Molecules in IDDM Patients and in Subjects at Risk for IDDM
Authors: Lampeter Eberhard R , Kishimoto Takashi K , Rothlein Robert , Mainolfi Elizabeth A , Bertrams Jorg , Kolb Hubert , Martin Stephan
Published: September 2013

Serum levels of recently discovered circulating forms of adhesion molecules, ICAM-1 and L-selectin, were found to be elevated in IDDM patients and in subjects at risk for developing IDDM compared with 100 normal, nondiabetic blood donors. Both adhesion molecules were determined by sandwich ELISA. Serum concentrations of either clCAM-1 or cL-selectin were >2SD of normal mean in 10 of 14 recent-onset IDDM patients (P < 0.05). Serum levels of clCAM-1 and cL-selectin did not correlate. In first-degree relatives, elevated adhesion molecule levels were observed in the 6 ICA+ individuals and in the ICA− individuals all (n = 14) with a genetic risk of IDDM (sharing HLA-DR3 and/or -DR4− with the diabetic relative) but not in the HLA-DR3− and/or -DR4− relatives (n = 13). We conclude that elevated clCAM-1 and cL-selectin levels occur independently of ICA status and probably reflect ongoing immune processes in recent-onset IDDM patients and first-degree relatives at risk for IDDM.
Effect of Vitamin C on Glycosylation of Proteins
Authors: Davie Sarah J , Gould Barry J , Yudkin John S
Published: September 2013

Twelve nondiabetic subjects consumed 1 g/day vitamin C for 3 mo. A fasting blood sample was taken at the start of the study and at the end of each month for the measurement of plasma and intraerythrocyte glucose, vitamin C, glycosylated hemoglobin (affinity chromatography and electrophoresis), and glycosylated albumin (affinity chromatography). Although there were no significant changes in fasting glycemia, glycosylated hemoglobin (affinity chromatography) decreased 18%, from 6.18 ± 0.48% (mean ± SD) at the start to 5.05 ± 0.50% (P < 0.0001) after 3 mo, whereas, HbA1 measured by electrophoresis increased 16%, from 6.17 ± 0.61 to 7.16 ± 0.59% (P < 0.0001) in this period. Glycosylated albumin decreased 33%, from 1.56 ± 0.24 to 1.04 ± 1.01% (P < 0.0001) after 3 mo. This discrepancy between glycosylated hemoglobin measured by electrophoresis and affinity chromatography was due to methodological differences between the two techniques, with affinity chromatography measuring “true” glycosylated hemoglobin. The greater decrease found with glycosylated albumin was probably due to the different distribution of vitamin C between plasma and within the erythrocyte, levels after 1 mo of supplementation being 109 ± 19 and 59 ± 9 μM, respectively (P < 0.001). This indicates that administration of oral vitamin C may inhibit the glycosylation of proteins in vivo by a competitive mechanism.
Cloning and Expression of IDDM-Specific Human Autoantigens
Authors: Rabin Daniel U , Pleasic Susan M , Palmer-Crocker Rebecca , Shapiro Jeffrey A
Published: September 2013

A DNA cloning approach was taken to identify islet cell protein antigens that are recognized specifically by insulin-dependent diabetes mellitus (IDDM) sera. A human islet cDNA library was generated and screened with diabetic sera. In this article, identification of two clones is described. Proteins expressed by these λ phages appeared to react specifically with newly diagnosed diabetic sera. Islet cell antibody 12 (ICA12) was tested by Western blotting. ICA512 was not reactive with sera in the Western format but was specifically immunoprecipitated by diabetic sera from an Escherichia coli extract.
Changes in Blood Coagulation, Platelet Function, and Plasminogen-Plasmin System in Diabetes
Authors: Kwaan Hau C
Published: September 2013

The increased risk of thromboembolism in people with diabetes mellitus is in part due to changes in the hemostatic mechanism including abnormal platelet function leading to platelet activation, increase in several coagulation factors, decrease in natural anticoagulants, and impaired fibrinolytic activity. Both microangiopathy and atherosclerosis in people with diabetes will enhance the thrombotic potential of these abnormal hemostatic changes. The recent recognition of a role of the components of the plasminogenplasmin system in many biologic functions at the cellular level has led to studies showing that the angiopathic complications of diabetes may also be caused by impaired plasminogen activator function.
Maillard Reaction-Mediated Molecular Damage to Extracellular Matrix and Other Tissue Proteins in Diabetes, Aging, and Uremia
Authors: Monnier Vincent M , Sell David R , Nagaraj Ramanakoppa H , Miyata Satoshi , Grandhee Sunitha , Odetti Patrizio , Ibrahim Said A
Published: September 2013

Recent progress in structure elucidation of products of the advanced Maillard reaction now allows probing specifically for the role of this reaction in the pathogenesis of age- and diabetes-related complications. Pyrraline is a glucose-derived advanced glycation end product against which polyclonal and monoclonal antibodies have been raised. Immunohistochemical localization studies revealed that pyrraline is found predominantly in the sclerosed extracellular matrix of glomerular and arteriolar renal tissues from both diabetic and aged nondiabetic individuals. Pentosidine and carboxymethyllysine are Maillard end products derived from both glucose and ascorbate. In addition, pentosidine can be formed from several other sugars under oxidative conditions, and in vitro studies suggest that a common intermediate involving a pentose is a necessary precursor molecule. The highest levels of these advanced Maillard products are generally found in the extracellular matrix, but these products are also present in lens proteins and in proteins with a fast turnover such as plasma proteins. Diabetes, and especially uremia, greatly catalyzes pentosidine formation. Both conditions are characterized by accelerated cataractogenesis, atherosclerosis, and neuropathy, suggesting that molecular damage by advanced Maillard reaction products may be a common mechanism in their development.
Role of Oxygen in Cross-Linking and Chemical Modification of Collagen by Glucose
Authors: Fu Min-Xin , Knecht Kevin J , Thorpe Suzanne R , Baynes John W
Published: September 2013

The role of oxygen in chemical modification and cross-linking of rat tail collagen by glucose was studied at physiological pH and temperature in vitro. Cross-linking of collagen under air depended on glucose concentration, but was inhibited under antioxidative conditions (nitrogen atmosphere with transition metal chelators). The cross-linking reaction under air depended on phosphate buffer concentration, but this effect was eliminated by addition of chelators, identifying trace metal ions in the buffer as catalysts of oxidative cross-linking reaction. Antioxidative conditions had no effect on glycation, that is, formation of fructose lysine, but inhibited formation of the glycoxidation products Ne-(carboxymethyl)lysine and pentosidine as well as the development of fluorescence in glycated collagen. Glycation itself decreased during continued incubation of the collagen without glucose; however, cross-linking and concentrations of glycoxidation products and fluorescence in collagen were not reversible under either oxidative or antioxidative conditions. These observations are consistent with recent studies in vivo on the reversibility of collagen glycation, the irreversibility of formation of glycoxidation products and fluorescence, and the strong correlations between glycoxidation products and fluorescence in collagen (1). These results indicate that oxidation reactions play a critical role in the extended chemical modification and cross-linking of collagen by glucose and suggest that measurement of glycoxidation products should be useful for assessing cumulative chemical modification of collagen by glucose in vivo.
Structural and Functional Changes of Laminin and Type IV Collagen After Nonenzymatic Glycation
Authors: Charonis Aristidis S , Tsilibary Effie C
Published: September 2013

Laminin and type IV collagen are two major basement membrane glycoproteins; they are large multidomain macromolecules that are involved in two types of functions. First, they provide the structural framework of all basement membranes, and second, they interact with cell-surface molecules and are key to adhesion, spreading, and proliferation of cells. We summarize experimental evidence that nonenzymatic glucosylation of these two macromolecules in vitro alters their structure, their ability to polymerize, and their ability to promote cell adhesion. Additional studies are needed to document these changes in situ and therefore extend these conclusions to intact basement membranes.
Role of Cytokines in Inducing Hyperlipidemia
Authors: Feingold Kenneth R , Grunfeld Carl
Published: September 2013

Plasma lipid levels are elevated in people with diabetes, and a direct relationship can be demonstrated between indices of diabetic control and plasma lipid levels. Many observations suggest that diabetes may be associated with enhanced cytokine production, raising the possibility that some of the metabolic abnormalities associated with diabetes may be due to or exacerbated by cytokine overproduction. Tumor necrosis factor induces a rapid increase in serum triglyceride levels caused by an increase in VLDL of normal composition. Although in vitro studies showed that TNF decreases adipose tissue lipoprotein lipase activity, recent studies with intact animals demonstrated that TNF increases serum triglyceride levels by stimulating hepatic lipid secretion, not by affecting clearance. The increase in hepatic VLDL triglyceride secretion induced by TNF is due to both the stimulation of hepatic de novo fatty acid synthesis and an increase in lipolysis. Other cytokines including IL-1, IL-6, and α-interferon increase hepatic de novo fatty acid synthesis. Similarly, cytokines such as IL-1 and α-, β-, and γ-interferon also increase lipolysis. Thus, a variety of cytokines acting at different receptors can affect multiple processes that can alter lipid metabolism and increase serum lipid levels. These cytokine-induced increases in serum lipoprotein levels may be a beneficial response for the host. Studies show that lipoproteins, including VLDL, bind endotoxin and can protect against the toxic effects of endotoxin. Moreover, lipoproteins bind a variety of viruses, reducing their infectivity. Lipoproteins also bind urate crystals, which reduces the inflammatory response induced by these crystals. Thus, it can be postulated that lipoproteins are part of a nonspecific immune response stimulated by cytokines, the hormones of the immune systems, that can decrease the toxicity of harmful biological and chemical agents. Although these changes may have benefit under some circumstances, the overproduction of cytokines in people with diabetes could lead to inappropriate metabolic effects, including hyperlipidemia, that in the long run could have adverse consequences, such as accelerated atherosclerosis.
Iatrogenic Hypoglycemia as a Cause of Hypoglycemia-Associated Autonomic Failure in IDDM: A Vicious Cycle
Authors: Cryer Philip E
Published: September 2013

Three hypoglycemia-associated clinical syndromes in people with insulin-dependent diabetes mellitus (IDDM)—defective glucose counterregulation, hypoglycemia unawareness, and elevated glycemic thresholds for symptoms and activation of counterregulatory systems during effective intensive therapy—have much in common. They segregate together, are associated with increased frequency of severe iatrogenic hypoglycemia, and share several pathophysiological features, including reduced autonomic nervous system responses to a given degree of hypoglycemia. In the setting of reduced glucagon responses, the reduced adrenomedullary epinephrine responses play a key role in the pathogenesis of iatrogenic hypoglycemia in affected patients. Thus, these syndromes are examples of hypoglycemia-associated autonomic failure in IDDM, a disorder distinct from classical diabetic autonomic neuropathy. The pathogenesis of hypoglycemiaassociated autonomic failure is not known, need not be the same in all three syndromes, and could be multifactorial even in a given syndrome. The recent finding that short-term antecedent hypoglycemia results in reduced symptomatic and autonomic (including adrenomedullary) responses to subsequent hypoglycemia in nondiabetic humans leads logically to the following hypothesis concerning one potential pathogenetic mechanism: recent antecedent iatrogenic hypoglycemia is a major cause of hypoglycemiaassociated autonomic failure in IDDM, and hypoglycemia-associated autonomic failure, by reducing both symptoms of and defenses against developing hypoglycemia, results in recurrent severe hypoglycemia, thus creating a vicious cycle. If this hypothesis is confirmed, it will suggest strategies to reduce the frequency of iatrogenic hypoglycemia in people with IDDM.
Differential Effect of Aspirin on Platelet Aggregation in IDDM
Authors: Mori Trevor A , Vandongen Robert , Douglas Andrea J , McCulloch Ross K , Burke Valerie
Published: September 2013

Diabetes mellitus is associated with a high incidence of cardiovascular diseases not directly attributable to hyperlipidemia, smoking, or hypertension, but which in part may be explained by an enhanced tendency to thrombosis due to increased platelet activity. The aim of this study was to evaluate platelet function and compare the effectiveness of the antiplatelet drug aspirin on platelet aggregation in diabetic and nondiabetic subjects. Platelet aggregation and composition were examined in 20 male Insulin-dependent diabetes mellitus (IDDM) patients and 20 nondiabetic control subjects matched for age and body mass Index. All were normotensive with serum total cholesterol <6.5 mM. Although within the clinically acceptable normal range, blood pressure was significantly higher in diabetic patients (130/75 mmHg) than in control subjects (123/70 mmHg) (P < 0.05). Serum thromboxane B2 and ex vivo aggregation of platelets In response to two doses of the agonists collagen and platelet-activating factor (PAF) were similar to nondiabetic subjects. However, after taking 100 mg/day aspirin for 5 days, platelet aggregation to collagen was reduced by 76% in control subjects compared to 56% in IDDM patients (P < 0.001). Aspirin treatment also reduced the slope of the aggregation curve and increased the lag time (the period between the addition of collagen and the start of irreversible aggregation) significantly more in control than In diabetic platelets. This difference in platelet aggregation could not be attributed to differences in platelet serotonin or thromboxane A2 secretion, the latter being almost completely suppressed by aspirin in each group. Platelet aggregation to PAF was similar in both groups and was not affected by aspirin. IDDM patients had a significantly higher percentage of linoleic acid but lower percentage of ω-3 fatty acids in plasma and platelet phospholipids. The phospholipid-cholesterol ratio and membrane fluidity were not altered in diabetic platelets. These results suggest that platelets from IDDM patients are resistant to the effect of aspirin by mechanisms independent of both the cyclooxygenase and PAF pathways of aggregation.
Cold Storage of Rat Pancreas Before Purification of Islet β-Cells
Authors: Korbutt Gregory S , Pipeleers Daniel G
Published: September 2013

Allotransplantations in rats have demonstrated that aggregates of purified islet endocrine cells are less immunogenic than isolated islets. If purified islet cells are to be tested in humans, their preparation should be feasible from cold-preserved organs. We compared the yield in purified β-cells from freshly harvested rat pancreases with that from cold-stored organs. After 24 h of preservation in Collins' solution or in University of Wisconsin (UW) solution, the number of purified β-cells per pancreas was 40% lower (P < 0.05) thanthat obtained from nonpreserved controls. Addition of 5 mM benzamidine/4% bovine serum albumin to Collins' solution resulted in similar recoveries as with freshly harvested organs; this addition did not increase the yield from UW solution-stored organs. When compared to preparations from fresh pancreases, islets and islet cells isolated from pancreases preserved in Collins' solution-bovine serum albumin-benzamidine were comparable in structural integrity, viability in culture, secretory responsiveness in vitro, and capability of correcting hyperglycemia in streptozocin-induced diabetic rats. We conclude that addition of benzamidine to Collins' preservation solution allows purification of islet β-cells from 24-h- preserved rat pancreases in the same yield and quality as from freshly harvested organs. These results indicate that cold-preserved pancreases can be used for the preparation of purified islet cell grafts.
Black-White Contrasts In Insulin Levels During Pubertal Development: The Bogalusa Heart Study
Authors: Svec Frank , Nastasi Kent , Hilton Charles , Bao Weihang , Srinivasan Santhanur R , Berenson Gerald S
Published: September 2013

Three hundred and seventy-seven children and adolescents aged 5–17 yr from the biracial (black-white) community of Bogalusa, Louisiana, were evaluated for Tanner stage of sexual development, plasma glucose, and insulin levels during an oral glucose tolerance test. Children of the two races were of similar age, weight, and height at each Tanner stage. Overall insulin response was compared by measuring the area under the insulin curve from the glucose tolerance test. Blacks, especially black females, had significantly higher insulin responses than their white counterparts. The insulin-glucose ratio at the initial t = 0 min baseline did not vary with race or sex throughout the Tanner stages. However, the 30 min postglucose data revealed clear differences between the races with blacks showing a higher insulin-glucose ratio. Ratios increased throughout puberty for both blacks and whites, boys and girls. The trends of racial contrasts seemed to be discernible even at the earliest stage of development. It is concluded that there is a clear difference between blacks and whites in insulin response to a glucose load early in childhood. These findings lead to the hypothesis that the greater prevalence of non-insulindependent diabetes mellitus seen in adult blacks, especially females, may be an expression of a difference in insulin secretion and related insulin resistance in early childhood.
Development of Proliferative Retinopathy in NIDDM: A Follow-up Study of American Indians in Oklahoma
Authors: Lee Elisa T , Lee Vivian S , Lu Min , Russell Dana
Published: September 2013

To determine the incidence of and risk factors for the development of proliferative diabetic retinopathy (PDR) in Oklahoma Indians, we performed a cohort follow-up study of 927 Indians who underwent detailed eye examinations between 1972 and 1980. The mean age of participants was 52 yr with a duration of diabetes of 6.9 yr at baseline. At follow-up, 513 (55.3%) were alive, 407 (43.9%) were deceased, and 7 (0.8%) could not be traced. After a mean follow-up time of 12.7 yr, the overall incidence of PDR among those who survived and who underwent follow-up ophthalmic examinations (354 participants) was 18.6%; 45% of those with background retinopathy at baseline developed PDR. Significant independent predictors of PDR, determined by muKivariate analysis, were fasting plasma glucose level, duration of diabetes, plasma cholesterol, systolic blood pressure, and therapeutic regimen. A fasting plasma glucose level >11.1 mM (200 mg/dl) increased the risk of retinopathy to 3.6 times that for a level <7.8 mM (140 mg/dl); 74% of those who had background retinopathy and a baseline fasting glucose >11.1 mM (200 mg/dl) developed PDR. Over half of all participants with plasma cholesterol levels >7.8 mM (300 mg/dl) developed PDR in the follow-up interval. Elevated systolic blood pressure was a particularly significant risk factor for those with a long duration of diabetes. Proliferative retinopathy poses a serious health threat to Oklahoma Indians and represents a cause of visual impairment that may be preventable by early diagnosis of PDR and intervention with photocoagulation therapy. Determining whether glycemic and hypertensive control reduces the risk of PDR requires controlled clinical trials.
Dose Effect of Cis- and Trans-Encoded HLA-DQαβ Heterodimers in IDDM Susceptibility
Authors: Khalil Iman , Deschamps Ingeborg , Lepage Virginia , Al-Daccak Reem , Degos Laurent , Hors Jacques
Published: September 2013

Insulin-dependent diabetes mellitus (IDDM) in whites is strongly associated with particular HLA-DQαβ heterodimers composed of a DQα chain with anrginine at residue 52 (Arg52+) combined to a DQβ chain lacking an aspartic acid at residue 57 (Asp57−. With the aim of confirming this association, clarifying which heterodimers account for the highest risk of IDDM and explaining the excess risk of DR3-DQw2/DR4-DQw8,115 unrelated white IDDM patients and 108 unrelated healthy nondiabetic control subjects were studied. With polymerase chain reaction and sequence-specific oligonucleotide probes, both patients and control subjects were typed for their HLA-DQA1 and DQB1 alleles and their DQA1-DQB1 haplotype and genotype frequencies were compared. Four major findings emerged from our analysis. 1) Arg52+ DQα/Asp57− Dβp heterodimers, formed in cis and/r in trans, are strongly associated with susceptibility to IDDM; 97% of patients and 46% of control subjects had at least one such susceptibility heterodimer (relative risk [RR] 32, confidence interval [Cl] 14.25–71.86, P < 10−. 2) The degree of disease susceptibility depends on the number of such DQ heterodimers that a subject can express according to his or her DQA1-DQB1 genotype. The highest RR was observed in patients with four susceptibility DQ heterodimers (RR 41, Cl 17.05–95.9). 3) Only part of the susceptibility DQ heterodimers were significantly increased in patients, conferring IDDM susceptibility of different strength. The strongest association was with the DQA1*0501-DQB1*0302 combination formed in trans position (RR 35.2, Cl 12.88–96.78, P < 10−7). 4) The simultaneous expression of four different susceptibility heterodimers explains the highest risk of DR3-DQw2/DR4-DQw8 heterozygotes. In conclusion, there is a dose effect of cis- and trans-encoded HLA-DQαβ heterodimers in IDDM susceptibility influenced by the diversity of these molecules.
Major Gene Effect for Insulin Levels in Familial NIDDM Pedigrees
Authors: Schumacher Mary C , Hasstedt Sandra J , Hunt Steven C , Williams Roger R , Elbein Steven C
Published: September 2013

Insulin resistance and hyperinsulinemia are familial traits that may precede and predict the onset of non-insulin-dependent diabetes mellitus (NIDDM). In some populations, the distribution of fasting insulin levels and measures of in vivo insulin action suggest the effects of a single major gene. We previously noted hyperinsulinemia among unaffected members of 16 large white pedigrees ascertained through two or more NIDDM siblings. To examine the hypothesis that insulin levels are determined by a single major genetic locus, we used segregation analysis to examine fasting insulin levels in 206 family members and 65 spouses who had normal glucose tolerance tests by World Health Organization criteria. Segregation analysis supported a major locus determining fasting insulin levels and segregating as an autosomal recessive allele with a frequency of 0.25. Thus, homozygotes represented 6.25% of the population, and homozygosity for the hyperinsulinemia allele elevated the mean fasting insulin level from 70.3 to 211.1 pM (11.7–35.2 μU/ml). The analysis apportioned the variance in fasting insulin as 33.1% due to the major autosomal locus, 11.4% due to polygenic inheritance, and 55.5% due to unmeasured effects. Homozygotes for the recessive allele had higher 1-h insulin levels than all others (911.7 vs. 427.2 pM [152.0 vs. 71.2 μU/ml]). We also found evidence for a major locus determining 1-h-stimulated insulin levels, with codominant inheritance as the most likely pattern in inheritance. The causal relationship between these findings and NIDDM has not been determined, and segregation of direct measures of insulin action remains to be demonstrated. However, we have found evidence for a major gene locus that may contribute to the observed familial aggregation of impaired insulin action in relatives of NIDDM individuals and the inherited predisposition to NIDDM.