bluuebunny/crossref_metadata_2025 huggingface dataset:
Glucose Potentiation of Arginine-Induced Insulin Secretion is Impaired in Subjects With a Glucokinase Glu256Lys Mutation
Authors: Wajngot Alexandre , Alvarsson Michael , Glaser Anna , Efendic Suad , Luthman Holger , Grill Valdemar
Published: September 2013

Insulin and glucagon release and insulin sensitivity were investigated in patients with glucokinase deficiency. Five subjects with a missense mutation (Glu256Lys) were studied. They were compared with six healthy subjects with low insulin response but normal glucose tolerance. Insulin and glucagon levels were measured at blood glucose 7.1 ± 0.1 mmol/l and at 10.9 ± 0.2 mmol/l with or without arginine (5 g i.v.). Insulin sensitivity was assessed as the ratio between infused glucose and the insulin level (M:I) during hyperglycemic clamps. Glu256Lys subjects were nonobese and had fasting blood glucose 6.7 ± 0.1 mmol/l (P < 0.001 vs. control group). Insulin release was reduced in response to 11 mmol/l glucose (61% of control group, P < 0.05) as well as to arginine in the presence of 11 mmol/l glucose (54% of control group, P < 0.01). Also, the slope of potentiation, i.e., the enhancement of arginine-induced release as a function of prevailing glucose concentration, was reduced (delta insulin/delta glucose, 47% of control group, P < 0.05). As for glucagon release, the response to arginine was not inhibited normally by glucose, resulting in threefold higher levels at 11 mmol/l glucose versus control subjects. Insulin sensitivity, assessed as M:I, was significantly (P < 0.05) reduced (55% of control group). Glucokinase deficiency thus affects not only insulin responses to glucose per se but also glucose potentiation of responses to non-nutrient secretagogues. Abnormalities in glucagon release and insulin sensitivity coexist with attenuated insulin responses in glucokinase-deficient subjects.
Parental Origin of Diabetes-Associated HLA Types in Sibling Pairs With Type I Diabetes
Authors: Bain Stephen C , Rowe Bethan R , Barnett Anthony H , Todd John A
Published: September 2013

Genetic susceptibility to type I diabetes is partly determined by genes located in the human leukocyte antigen (HLA) region on chromosome 6. It has been claimed that the transmission of HLA-encoded susceptibility is influenced by parental sex. Fathers are reported to transmit HLA-DR4 haplotypes more frequently to their diabetic offspring than mothers. More recently, it has been suggested that the presence of HLA-DR4 in a mother may influence susceptibility in her offspring, even when it is not inherited. We have analyzed 172 multiplex diabetic pedigrees from the U.K. and find no evidence to support an important effect of parental sex on the inheritance of HLA-encoded susceptibility. Examination of a further 110 pedigrees from the U.S. supports this finding. These results have important implications for strategies involving genetic screening for type I diabetes.
ApoA-IV Polymorphism Associated With Myocardial Infarction in Obese NIDDM Patients: The San Luis Valley Diabetes Study
Authors: Rewers Marian , Kamboh M Ilyas , Hoag Sharon , Shetterly Susan M , Ferrell Robert E , Hamman Richard F
Published: September 2013

Non-insulin-dependent diabetes mellitus (NIDDM) confers myocardial infarction (MI) risk unexplained by known factors. In 356 NIDDM patients and 1,087 people with normal glucose tolerance, we investigated the association between MI risk and polymorphism at codon 360 in the apolipoprotein A-IV (apoA-IV) gene. During 1984–1992, MI was diagnosed in 84 diabetic and in 106 nondiabetic people. The risk of MI did not differ by apoA-IV phenotype in nondiabetic people; however, in NIDDM patients, those with the apoA-IV 1–2 phenotype had 2.8 (95% confidence interval: 1.4–5.6) higher MI risk than those with the 1–1 phenotype, adjusting for age, gender, ethnicity, hypertension, smoking, body mass index, fat centrality, and low-density lipoprotein and high-density lipoprotein cholesterol. The risk of MI was particularly high in obese NIDDM patients with the apoA-IV 1–2 phenotype: 5.1 (2.4–11.2) times that in obese apoA-IV 1–1 NIDDM patients and 7.7 (3.6–16.7) times that in lean nondiabetic people. The effect of apoA-IV 1–2 did not appear to be a part of the insulin-resistance syndrome nor was it dependent on diabetes duration or control. One half of the excess MI risk in the diabetic population studied was explained by the apoA-IV 1–2 phenotype. These results indicate that ∼ 17% of NIDDM patients have a high MI risk apoA-IV phenotype that is particularly deleterious in obese patients.
Immunization With the Larger Isoform of Mouse Glutamic Acid Decarboxylase (GAD67) Prevents Autoimmune Diabetes in NOD Mice
Authors: Elliott John F , Qin Hui-Yu , Bhatti Siinita , Smith Dean K , Singh Raj Kumari , Dillon Tom , Lauzon Jana , Singh Bhagirath
Published: September 2013

The 65-kDa isoform of glutamic acid decarboxylase (GAD65) has been implicated in autoimmune diabetes in NOD mice, but the role of the 67-kDa GAD isoform (GAD67) is less clear. We found that immunization of 4-week-old NOD mice with purified recombinant mouse GAD67 prevented or significantly delayed the onset of diabetes. To further explore this phenomenon, we characterized anti-GAD67 immune responses in naive and GAD-immunized NOD mice. Anti-GAD67 antibodies titers were relatively low in naive mice at all ages, but a single immunization with GAD67 at 4 weeks induced high titers of anti-GAD antibodies by 6 weeks of age. In both 4-week-old and diabetic NOD mice, there were significant endogenous T-cell proliferative responses against purified recombinant mouse GAD67. These T-cell proliferative responses were blocked by anti-I-ANOD and anti-CD4 antibodies. To characterize the anti-GAD T-cell responses in the NOD mice, we established T-cell lines and T-cell clones which recognized GAD67, and we used recombinant subfragments of GAD to localize the predominant T-cell epitopes in GAD67. T-cells from naive NOD mice proliferated in response to all GAD subfragments, whereas T-cells from diabetic mice responded primarily to the COOH-terminal 83 amino acids of GAD67. These results suggest that GAD67 is an autoantigen in IDDM and immunization of prediabetic NOD mice with GAD67 can prevent the onset of diabetes.
Diazoxide Causes Recovery of β-Cell Glucose Responsiveness in 90% Pancreatectomized Diabetic Rats
Authors: Leahy Jack L , Bumbalo Lisa M , Chen Chuan
Published: September 2013

Chronic hyperglycemia causes near-total disappearance of glucose-induced insulin secretion. The etiology has been suggested to be a nonsustainable stimulation of insulin release that causes β-cells to become unresponsive to glucose through an undefined mechanism. We used an inhibitor of insulin secretion, diazoxide, to test this hypothesis in 90% pancreatectomized (Px) rats. Px rats were given 5 days of diazoxide (30 mg/kg orally twice a day) or tap water starting on postoperative day 8, 15, or 22. In vitro pancreas perfusions were conducted 36 h posttreatment (2, 3, or 4 weeks after surgery) using a protocol of 15 min of 16.7 mM glucose followed by 15 min of 16.7 mM glucose plus 10 mM arginine. In 2-week Px rats, insulin responses to 16.7 mM glucose and to glucose/arginine were both appropriate for the reduced β-cell mass, i.e., no defect in β-cell glucose responsiveness had yet occurred. Diazoxide had no affect on insulin release at this time. Between 2 and 3 weeks after pancreatectomy, insulin output to 16.7 mM glucose fell 75%, and that to glucose/arginine fell 50%. Diazoxide given at this time partially blocked the fall in glucose-induced insulin secretion and totally prevented that with arginine. The increased insulin secretion caused by diazoxide was accompanied by 1) lower nonfasting plasma glucose values, 2) improved glucose tolerance after oral glucose load, and 3) a 50% increase in pancreatic insulin content. Our results support the concept that excessive insulin secretion is a major cause of the hyperglycemia-induced loss of β-cell glucose responsiveness. A leading candidate for the mechanism of this effect is depleted pancreatic insulin stores. Overstimulation of insulin secretion provides a new target for pharmacological therapy aimed at reducing glucose intolerance in non-insulin-dependent diabetes mellitus.
Regulation of Insulin-Like Growth Factor–Binding Protein-1 in Rat Serum
Authors: Lewitt Moirá S , Saunders Heather , Phyual Jenny L , Baxter Robert C
Published: September 2013

Previous studies support a role for insulin-like growth factor–binding protein-1 (IGFBP-1) in modulating insulin-like growth factor (IGF) availability for glucose homeostasis. We have developed a radioimmunoassay (RIA) for rat IGFBP-1 (rIGFBP-1) and have examined the regulation of circulating levels by nutritional and hormonal status. Rabbit antisera were raised against pure rIGFBP-1, and an assay was established with a sensitivity of 50 pg. In the rat, serum IGFBP-1 concentrations decrease with increasing developmental age. They were highest in fetal rat serum, exceeding 4 mg/L, and decreased to <0.1 mg/L in adult animals. Serum rIGFBP-1 levels increased during fasting, 6-fold after 24 h and 18-fold after 48 h, and were suppressed to levels identical to ad libitum–fed control rats within 2 h of refeeding. Fasting levels were >2-fold higher in female than male animals. IGFBP-1 concentrations were suppressed by >50% in two rat models of insulin resistance. Levels increased in STZ-induced (streptozotocin) diabetes and were suppressed to normal with insulin treatment. Exercise stimulated rIGFBP-1 concentrations in fasting animals. On immunoblotting after SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis), rIGFBP-1 in serum appeared as a doublet with molecular masses at 31 and 33 kD. The components of this doublet did not vary across the range of experimental conditions. These observations indicate that the pattern of regulation of rIGFBP-1 is similar to that seen in previous studies of human IGFBP-1, with age, sex, and nutritional status being important regulators. The availability of appropriate rat models and a sensitive ria will allow additional study of the regulatory mechanisms and the physiologucal role of IGFBP-1.
Suppression of Gluconeogenesis After a 3-Day Fast Does Not Deplete Liver Glycogen in Patients With NIDDM
Authors: Clore John N , Blackard William G
Published: September 2013

To determine the effect of inhibition of gluconeogenesis on liver glycogen stores in patients with non-insulin-dependent diabetes mellitus (NIDDM) after a 3-day fast, 10% ethanol (EtOH) was administered intravenously to nine obese patients with NIDDM and six obese nondiabetic subjects. Rates of glucose appearance (3-[3H]glucose) and [U-14C]alanine incorporation into glucose (alanine gluconeogenesis [Ala-GNG]) were determined before and during EtOH administration, and residual glycogen stores were assessed by the incremental glucose response to glucagon (glucoseAUC). Hepatic glucose output (HGO) was closely correlated with plasma glucose levels (r = 0.71, P < 0.001) after the 3-day fast and was significantly greater in the diabetic compared with the nondiabetic subjects (13.8 ± 1.4 vs. 7.6 ± 0.6 μmol · kg−1 FFM · min−1 P < 0.01). During the 120-min EtOH infusion, Ala-GNG fell by more than 50% in both groups and did not increase after intravenous glucagon administration. HGO fell modestly in both the diabetic and nondiabetic subjects during the first 30 min of EtOH infusion and stabilized thereafter. In contrast to Ala-GNG, HGO increased significantly after intravenous glucagon administration in both the diabetic and nondiabetic subjects, but the increase was significantly greater in the patients with NIDDM (P < 0.01). The glucose area under the curve in response to glucagon (glucoseAUC) was lower in the presence of EtOH than in its absence (14.9 ± 7 vs. 68 ± 15.6 mM/min, P < 0.01) in the obese nondiabetic subjects, which suggests a decrease in liver glycogen stores. In contrast, EtOH infusion did not alter the glucoseAUC in obese diabetic subjects compared with saline control studies (134.7 ± 17.8 vs. 102.6 ± 20 mM/min, NS). The persistent increase in glucoseAUC suggests that glycogen stores are not depleted by EtOH-induced suppression of gluconeogenesis in patients with NIDDM after a 3-day fast.
An Upstream Element From the Human Insulin Receptor Gene Promoter Contains Binding Sites for C/EBPβ and NF-1
Authors: Webster Nicolas J G , Kong Yan , Cameron Katherine E , Resnik Jamie L
Published: September 2013

We have shown previously that a 500-bp region of the human insulin receptor promoter (−0.3 to −1.8 kb) was able to stimulate transcription from a heterologous thymidine kinase promoter in HepG2 hepatoma cells but not in HeLa fibroblasts. Footprint analysis localized the transcription factor binding sites to a 36-bp region at −1420. In this paper, we analyze the factors that recognize this element and show that it contains binding sites for the CAAT/enhancer binding protein C/EBP and nuclear factor 1 (NF-1). In addition we show that both C/EBPα and the C/EBPβ can transactivate the human insulin receptor promoter in a dose-dependent manner.
Evidence for Effects of Insulin on Sensory Processing in Humans
Authors: Kern Werner , Schlosser Christopher , Kerner Wolfgang , Pietrowsky Reinhard , Born Jan , Fehm Horst L
Published: September 2013

Systemic insulin passes the blood-brain barrier and insulin receptors have been detected in various brain regions. Yet, the biological significance of insulin acting on the brain remains rather unclear. Reports of different awareness of hypoglycemic symptoms during hypoglycemia induced by human insulin (HI) and porcine insulin (PI) suggest a modulatory influence of insulin on sensory processing. In a double-blind, within-subject, crossover comparison, we recorded visual-evoked potentials (VEP) in 30 healthy men during euglycemia and after 20 or 50 min of constant hypoglycemia of 2.66 mM (47.9 mg/dl) induced by HI and PI. Blood glucose and serum insulin levels were identical in both sessions. Hypoglycemia reduced amplitudes of the VEP components P1 and N2 and increased latencies of N1, P1, and N2. However, hypoglycemia-induced changes in VEP amplitudes and latencies were significantly stronger during PI and HI infusion: P1-N2 difference amplitude decreased from (mean ± SE) 11.9 ± 0.9 to 10.7 ± 0.8 μV during HI and from 12.4 ± 0.9 to 8.7 ± 0.7 μV during PI infusion (P < 0.002). P1 latency increased from 112.0 ± 3.2 to 118.8 ± 3.2 ms during HI and from 114.0 ± 3.3 to 126.3 ± 4.6 ms during PI infusion (P < 0.05). Differences between the effects of the insulins were consistently apparent after 20 min of hypoglycemia, which indicates a short-term action of the hormone. The results add to those of a foregoing study demonstrating differential effects of HI- and PI-induced hypoglycemia on auditory evoked potentials. The changes in sensory processing during hypoglycemia, depending on the type of insulin, suggest a direct modulation of these brain functions by insulin.
Fibrinogen Plasma Levels as a Marker of Thrombin Activation in Diabetes
Authors: Ceriello Antonio , Taboga Claudio , Giacomello Roberta , Falleti Edmondo , Stasio Gianni De , Motz Enrico , Lizzio Sebastiano , Gonano Fabio , Bartoli Ettore
Published: September 2013

This study attempted to verify the existence of a correlation between fibrinogen, a major cardiovascular risk factor in diabetes, and indexes of thrombin generation and action, prothrombin fragment 1 + 2 (F1 + 2), and D-dimer (D-D), in a group of diabetic subjects compared with a matched control group. Forty insulin-dependent diabetes mellitus patients and 30 matched healthy control subjects participated in this study. The subjects were tested for the following parameters: fibrinogen, prothrombin F1 + 2, D-D, fasting glycemia, and HbA1c. In addition, 5 diabetic subjects who maintained stable fibrinogen plasma levels > 300 mg/dl for at least 6 months before the study were treated with 12,500 U/day subcutaneous heparin for 7 days. Diabetic subjects showed increased levels of fibrinogen, prothrombin F1 + 2, and D-D plasma levels. Simple linear regression analysis detected a positive correlation between fibrinogen and prothrombin F1 + 2, D-D, and glycosylated HbA1c. In the five diabetic subjects treated with heparin fibrinogen, prothrombin F1 + 2 and D-D levels decreased at the end of the treatment. All these parameters returned to baseline after 7 days of washout. These data indicate that fibrinogen plasma levels are correlated to parameters of thrombin activation in plasma in diabetic patients and suggest that high fibrinogen plasma levels might be a risk marker for cardiovascular disease in diabetes because it is an expression of an existing thrombophilia.
Splanchnic Insulin Dynamics and Secretion Pulsatilities in Abdominal Obesity
Authors: Sonnenberg Gabriele E , Hoffman Raymond G , Mueller Robert A , Kissebah Ahmed H
Published: September 2013

Insulin secretion, clearance dynamics, and their relationship to peripheral plasma insulin and glucose levels were monitored during three 12-h periods of overnight rest, intake of three meals, and continuous enteral feeding of mixed nutrients. The low-frequency ultradian and the high-frequency insulin secretion pulsatility characteristics during the steady-states of overnight rest and continuous enteral feeding were also examined. In abdominally obese subjects, the insulin secretion rate was consistently higher than normal by 2.3-fold. Peripheral plasma insulin levels were increased by 3.4-fold during the overnight period and by 4- to 5-fold during the two fed states. Endogenous insulin clearance was significantly reduced during feeding. Both low- and high-frequency insulin secretory pulsatilities were detected in the abdominally obese subjects. Pulse periods were within the normal range. Pulse maxima, nadirs, and absolute amplitudes were increased concomitant with the increase in insulin secretion. Ultradian relative pulse amplitudes, however, were blunted. A significantly higher pulse-to-pulse variability was observed in the abdominally obese subjects compared with normal subjects. Furthermore, a significantly higher level of interindividual variability in the nutrient-stimulated insulin secretion and in the ultradian pulse characteristics was observed. Thus in abdominal obesity, the increase in pancreatic insulin output is limited and the secretory pulsatilities are aberrant, suggesting a defect in the insulin secretory process. Diminished insulin clearance contributes to the degree of peripheral hyperinsulinemia compensating for the insulin resistance characteristic of this form of obesity.
Diminished Insulin Secretory Reserve in Diabetic Pancreas Transplant and Nondiabetic Kidney Transplant Recipients
Authors: Teuscher Adrian U , Seaquist Elizabeth R , Robertson R Paul
Published: September 2013

Although both kidney and pancreas transplantation can restore renal and pancreatic endocrine functions, the accompanying immunosuppression may cause diminished glucose tolerance in some individuals. Therefore, we determined to what extent pancreas transplantation itself and the triple immunosuppressive therapy used in pancreas transplant recipients have adverse effects on insulin secretory reserve. β-cell secretory reserve was assessed by the method of glucose potentiation of arginine-induced insulin secretion in 25 normoglycemic pancreas recipients, 12 nondiabetic kidney recipients using the same immunosuppressive therapy, 3 psoriasis patients treated long term with cyclosporine, 5 arthritis patients treated long term with prednisone, and their respective sex-, age-, and body mass index-matched control subjects. Levels of fasting glucose, HbA1c, and glucose disappearance rates were normal in all subjects. During the glucose potentiation study, pancreas recipients had significantly less insulin secretion than control subjects (maximal acute response [ARmax] = 1,083 ± 93% vs. 3,938 ± 355%, P < 0.001). Insulin responses were also decreased in kidney recipients (ARmax = 2,296 ± 290%) vs. control subjects (4,691 ± 554%, P = 0.001) and in psoriasis patients treated with cyclosporine (ARmax = 2,153 ± 390%) vs. control subjects (3,962 ± 88%, P = 0.011), but not as extreme as that seen in pancreas recipients. No abnormalities were observed in arthritis patients treated with steroids. We conclude that normoglycemic pancreas and kidney transplant recipients receiving triple immunosuppressive therapy have diminished β-cell secretory reserve. Because this defect was present in psoriasis patients treated long term with cyclosporine, but not in arthritis patients treated long term with prednisone, this adverse effect was probably caused in part by cyclosporine.
Hyperglycemia Suppresses the Adrenal Medullary: Response to Hypoxemia
Authors: Cohen Wayne R , Deutsch Joan
Published: September 2013

An in vivo microdialysis technique was used to study adrenal medullary function in 6 euglycemic and 6 hyperglycemic anesthetized Sprague-Dawley rats exposed to hypoxia. After stabilization of an adrenal dialysis probe, dialyzable adrenal epinephrine and norepinephrine were measured in response to 15 min of 7.8% oxygen breathing in both groups. In euglycemic rats, hypoxia increased epinephrine and norepinephrine by 650 and 320% above baseline, respectively. During hyperglycemia, (mean plasma glucose level 30.0 mM) epinephrine and norepinephrine rose only 119 and 104%, respectively. The catecholamine increase in the hyperglycemic rats was significantly attenuated in comparison to euglycemic controls (epinephrine, P = 0.0232; norepinephrine, P = 0.0079). These data demonstrate that acute hyperglycemia has the capacity to suppress the normal adrenal medullary response to hypoxemia.
Diabetic Teratogenesis: In Vitro Evidence for a Multifactorial Etiology With Little Contribution From Glucose Per Se
Authors: Buchanan Thomas A , Denno Kelly M , Sipos George F , Sadler Thomas W
Published: September 2013

To determine the extent to which elevated glucose and 3-hydroxybutyrate (3OHB) concentrations contribute to the embryotoxic properties of diabetic serum, we tested the effects of serum from untreated or acutely insulin-treated diabetic rats on the development of mouse embryos during neurulation in vitro. Male Sprague-Dawley rats (n = 143) with streptozocin-induced diabetes for 1 week received infusions of insulin (n = 105) or saline (n = 38) for up to 120 min. The insulin-infused animals were exsanguinated when serum glucose concentrations fell to between 5.6 and 8.3 mM. Saline-infused animals were exsanguinated after a similar duration of infusion. Serum samples were tested for embryotoxic effects on 3–6 somite mouse embryos cultured in vitro for 24 h. Of embryos cultured in serum from untreated diabetic animals (glucose: 24 ± 1 mM; 3OHB: 2.0 ± 0.3 mM), 36% (31 of 87) exhibited gross malformations, mostly of the neural tube. Only 16% (10 of 62) of embryos grown in serum from acutely insulin-treated animals (glucose: 7.4 ± 0.2 mM; 3OHB: 0.20 ± 0.06 mM) were malformed. This rate that was < half the rate caused by exposure to diabetic serum (P < 0.01), but a rate that remained much > the rate associated with culture in normal serum (0% in this study; < 2% historically). In vitro addition of glucose to serum from insulin-treated animals to re-establish hyperglycemia in the diabetic range (25 mM) resulted in a 17% (12 of 70) malformation rate, nearly identical to the 16% rate caused by normoglycemic serum from insulin-treated animals. Addition of D-3OHB to approximate the highest concentration encountered in untreated diabetic serum (∼4 mM) increased the malformation rate to 29% (21 of 73 embryos; P = 0.08 vs. unmodified serum from insulin-treated animals). Addition of glucose (to ∼25 mM) and 3OHB (to ∼4 mM) resulted in a 23% malformation rate, which was not significantly different from the rate caused by unmodified serum from the insulintreated group. These findings demonstrate that factors other than glucose and 3OHB account for much of the teratogenic potential of diabetic serum in this in vitro culture system. Moreover, the data suggest that glucose perse is not a major cause of the embryotoxicity of diabetic serum in this system, whereas 3OHB may account for some of the toxic effects.
Pancreas Transplantation in Diabetic Humans Normalizes Hepatic Glucose Production During Hypoglycemia
Authors: Barrou Zina , Seaquist Elizabeth R , Robertson R Paul
Published: September 2013

Although successful pancreas transplantation in humans with type I diabetes mellitus restores glucose-induced insulin secretion, provides freedom from insulin treatment, and normalizes fasting glucose levels, much less is known about its effects on counterregulation of hypoglycemia. To determine whether pancreas transplantation normalizes glucagon secretion and hepatic glucose production (HGP) during hypoglycemia, we performed hyperinsulinemic hypoglycemic clamps in successful recipients of pancreas allografts. Recipients were found to have glucagon secretory responses during hypoglycemia that were similar to those of control subjects (incremental glucagon response: recipients, 147 ± 34 ng/L; control subjects, 161 ± 43 ng/L, NS) but were significantly higher than those of matched subjects with type I diabetes (23 ± 9 ng/L, P < 0.01). HGP rates at the end of 120 min of hypoglycemia were also significantly higher in recipients and control subjects than in subjects with diabetes (pancreas recipients, 1.92 ± 0.33 mg.kg−1 · min−1; control subjects, 2.05 ± 0.18 mg.kg−1 · min−1; subjects with type I diabetes, 0.58 ± 0.12 mg.kg−1 · min−1). A comparison with a third group of nondiabetic kidney transplant recipients demonstrated that the beneficial effects on glucose counterregulation were a result of pancreas transplantation and not the associated immunosuppressive therapy. We conclude that pancreas transplantation restores hypoglycemia-induced glucagon secretion and HGP, thereby allowing for normalization of glucose recovery from hypoglycemia.
GAD Antibody Negative NIDDM in Adult Black Subjects with Diabetic Ketoacidosis and Increased Frequency of Human Leukocyte Antigen DR3 and DR4: Flatbush Diabetes
Authors: Banerji Mary Ann , Chaiken Rochelle L , Huey Howard , Tuomi Tiinamaija , Norin Allen J , Mackay Ian R , Rowley Merrill J , Zimmet Paul Z , Lebovitz Harold E
Published: September 2013

The objective of this study is to understand the metabolic and immunologic basis of diabetes in adult blacks with diabetic ketoacidosis (DKA). Twenty-one black adults presenting with DKA ([mean ± SD] blood pH = 7.18 ± 0.09, plasma glucose = 693 ± 208 mg/dl, and positive serum ketones) had a subsequent clinical course of non-insulin-dependent diabetes mellitus (NIDDM). Human leukocyte antigens (HLAs) DR and DQ and antibodies to glutamic acid decarboxylase (GAD) and islet cell cytoplasmic proteins (ICP) were measured to assess autoimmunity. Insulin action was evaluated by the euglycemic insulin clamp, and insulin secretion was measured by C-peptide responses to oral glucose. Ketoacidosis was treated with insulin. Two subjects had a precipitating illness; four had a history of NIDDM. At the time of study, subjects' glycemic control was good (HbA1c = 5.7 ± 1.6%). Nine subjects were treated with insulin, and 12 were on either sulfonylurea treatment or diet alone. Men (n = 12) were younger than women (n = 9) (40.8 ± 9.8 and 51.1 ± 6.3 years of age, respectively, P < 0.05) but similar in body mass index (27.8 ± 2.7 and 29.98 ± 4.1 kg/m2, respectively). Antibodies to GAD and ICP were absent. All but one subject was insulin resistant compared with normal subjects (glucose disposal 3.56 ± 0.04 vs. 6.86 ± 0.02 mg.kg−1 · min−1), and insulin secretion was lower. HLA DR3 and DR4 frequency was higher than in nondiabetic black control subjects (65 vs. 30%, P < 0.012).(ABSTRACT TRUNCATED AT 250 WORDS)
The Effect of Aminoguanidine and Tolrestat on Glucose Toxicity in Bovine Retinal Capillary Pericytes
Authors: Chibber Rakesh , Molinatti Pia A , Wong John S K , Mirlees Don , Kohner Eva M
Published: September 2013

Cultured bovine retinal capillary pericytes (BRP) were used to investigate the effect of an aldose reductase inhibitor, tolrestat, and an inhibitor of advanced glycation end products (AGE) formation, aminoguanidine, on glucose toxicity. Glucose at high concentration reduced the replicative activity of pericytes in a dose-dependent manner. Tolrestat completely inhibited the production of sorbitol in cells exposed to a high concentration of glucose but failed to protect the cells from glucose toxicity. These results suggest that sorbitol accumulation in cells is probably not the major mechanism for glucose toxicity. In contrast, the addition of aminoguanidine at 10 mM concentration to the culture media protected pericytes from glucose toxicity. The degree of protected pericytes from glucose toxicity. The degree of protection was dose-dependent and evident at aminoguanidine concentration as low as 1 mM. The drug was only slightly toxic to BRP but induced morphological changes in pericytes with the loss of cellular processes and decreased cell spreading. This may suggest some action of aminoguanidine on the pericyte cytoskeleton. High concentration of glucose significantly increased the level of early glycation but not fluorescent AGE formation on BRP proteins. This was inhibited by the addition of aminoguanidine suggesting that glycation of cellular/membrane proteins and other mechanisms may play an important role in the toxic action of high glucose levels in cultured pericytes.
Reversibility of Diabetes- and Diuresis-Induced Alterations in Rat Bladder Dome Muscarinic Receptors
Authors: Fukomoto Yuji , Yoshida Masaki , Weiss Robert M , Latifpour Jamshid
Published: September 2013

Previous studies from our laboratory demonstrated that 8 weeks of streptozocin (STZ)-induced diabetes and sucrose-fed diuresis resulted in increases in the density of muscarinic receptors in rat bladder dome and that early insulin treatment (started 3 days after the onset of diabetes) prevented the diabetes-induced upregulation (J Pharmacol Exp Ther 248:81–88, 1989; Diabetes 40: 1150–1156, 1991; J Urol 147:760–763, 1992). To determine whether diabetes- and diuresis-induced alterations in muscarinic receptors in rat bladder dome are reversible, we administered insulin (beginning 8 weeks after the onset of diabetes) or removed sucrose from drinking water of diuretic rats (beginning 8 weeks after the onset of diuresis). Five groups of rats were maintained for 16 weeks: 1) STZ-induced diabetic rats (65 mg/kg intravenously); 2) insulin-treated diabetic rats (5–8 U/day insulin subcutaneously beginning 8 weeks after the onset of diabetes); 3) sucrose-fed diuretic rats (5% sucrose in drinking water throughout 16 weeks); 4) sucrose-removed rats (sucrose withdrawn from drinking water after 8 weeks of the sucrose-induced diuretic state); and 5) age-matched control rats. Radioligand receptor binding experiments with [3H]quinuclidinyl benzilate showed an increase in the density of muscarinic receptors in bladder dome of diabetic and sucrose-fed rats compared with age-matched control rats. Removing the 5% sucrose from the drinking water of diuretic rats reversed the increased water intake and urine output, decreased the bladder hypertrophy that accompanied the diuretic state, and corrected the upregulation of the muscarinic receptors. Late insulin treatment also improved (to a lesser extent than removing the sucrose) the bladder enlargement, polydipsia, polyuria, and the muscarinic receptor upregulation in diabetic rats. Pharmacological evaluation indicated that the induction of diabetes did not affect muscarinic subtype specificity but did result in an alteration in muscarinic receptor-G protein coupling in rat bladder dome.
Effects of Hyperglycemia on In Vivo Adipose Tissue Metabolism Studied With Microdialysis in IDDM Subjects
Authors: van der Merwe Teré M , Eklund Lars , Jansson Per-Anders E , Lönnroth Peter N
Published: September 2013

The effect of hyperglycemia on in vivo adipose tissue metabolism was studied with microdialysis in seven lean patients with insulin-dependent diabetes mellitus (IDDM) receiving a constant infusion of insulin (36 pmol·m−2 · min−1). Glucose was infused in a randomized fashion to maintain either a lower glucose level (6.6 ± 0.3 mM, mean ± SE) or hyperglycemia (11.8 ± 0.8 mM) for 3 h. For insulin concentrations of 84 ± 12 and 96 ± 12 pM, hyperglycemia (11.8 ± 0.8 mM) did not alter the plasma glycerol or lactate levels significantly but resulted in a significant (P < 0.0001) increase in plasma free fatty acid levels (0.49 ± 0.13 vs. 0.32 ± 0.08 mM). Plasma catecholamine levels were unchanged during hyperglycemia. Interstitial glycerol concentrations, measured in abdominal subcutaneous adipose tissue as an index of lipolysis, were not significantly influenced by hyperglycemia when compared with concentrations at the lower glucose level (92 ± 30 vs. 106 ± 18 µM). Moreover, hyperglycemia did not change abdominal adipose interstitial lactate levels significantly (1,248 ± 174 vs. 1,351 ± 159 microM during euglycemia). It may be concluded that hyperglycemia has no independent antilipolytic effect in IDDM subjects. Furthermore, in these patients, hyperglycemia gives no further lactate production in the subcutaneous adipose tissue in the presence of low physiological insulin levels.
Alterations in Immunoreactive Proinsulin and Insulin Clearance Induced by Weight Loss in NIDDM
Authors: Polonsky Kenneth S , Gumbiner Barry , Ostrega Diane , Griver Kay , Tager Howard , Henry Robert R
Published: September 2013

Subjects with overt non-insulin-dependent diabetes mellitus (NIDDM) were studied in comparison to obese nondiabetic control subjects and patients with subclinical diabetes. Pancreatic insulin secretion rates were measured by deconvolution of peripheral C-peptide over a 24-h period while subjects consumed an isocaloric mixed diet. Subjects were then placed on caloric restriction for at least 6 weeks, during which time body weight fell by at least 10%. Refeeding with solid mixed meals was then resumed for at least 2 weeks until isocaloric intake was attained, and then the meal profiles were repeated. Before weight loss, insulin, C-peptide, and insulin secretion rates were significantly higher in subjects with subclinical diabetes than in the other two groups. Proinsulin concentrations were significantly greater in the two diabetic groups than in control subjects, but, when expressed as a percentage of the total insulin immunoreactivity, the differences were significant only in the group with overt diabetes. Weight loss because of hypocaloric feeding resulted in a significant increase in the rate of clearance of endogenously secreted insulin but did not affect the clearance of C-peptide. In obese subjects and those with subclinical diabetes, weight loss was associated with a reduction in insulin secretion rates, presumably as a result of improvements in insulin sensitivity. In patients with overt diabetes and hyperglycemia, weight loss improved β-cell responsiveness to glucose and was associated with an increase in insulin clearance and a reduction in proinsulin immunoreactivity. contribution of proinsulin to total insulin immunoreactivity, measurement of total insulin-like immunoreactivity alone may provide misleading information in comparing β-cell function before and after weight loss in patients with insulin resistance, glucose intolerance, and diabetes.
Proximal Enhancer of the Human Insulin Receptor Gene Binds the Transcription Factor Sp1
Authors: Chen Hui , Walker Gillian E , Taylor Simeon I , McKeon Catherine
Published: September 2013

The insulin receptor is a growth regulator present on the surface of most cells that transmits a mitogenic signal in response to insulin. Thus, the gene for the insulin receptor is constitutively expressed at low levels in all cells. We characterize a constitutive enhancer element that is present in the proximal promoter of the human insulin receptor gene. We have localized the enhancer to a 26–base-pair (26-bp) sequence from –528 to –503. When this sequence is inserted into the proximal promoter, a three- to fourfold increase in promoter activity is observed, and when two copies are inserted, a five- to sixfold increase is seen. Electrophoretic mobility shift analysis demonstrates that nuclear factors binding to this sequence are found in many different cell types. At least two proteins with different specificities bind within this 26-bp sequence. The identity of the predominant binding protein is Sp1, because an oligonucleotide composed of an Sp1 consensus binding sequence can compete for several of the DNA-protein complexes. In addition, we demonstrate that purified Sp1 can bind to the 26-bp oligonucleotide and that this complex comigrates with a DNA-protein complex formed with a HeLa nuclear extract. Finally, an antibody to human Sp1 protein is able to bind to the enhancer DNA/HeLa protein complex and supershift this complex. These findings suggest that this sequence corresponds to a general element that may contribute to the ubiquitous expression of the human insulin receptor gene.
Reduced Na+ -K+ -ATPase Activity and Plasma Lysophosphatidylcholine Concentrations in Diabetic Patients
Authors: Rabini Rosa A , Galassi Roberto , Fumelli Paolo , Dousset Nicole , Solera Marie L , Valdiguie Pierre , Curatola Giovanna , Ferretti Gianna , Taus Marina , Mazzanti Laura
Published: September 2013

A fraction from normal human plasma inhibiting Na+ -K+ ATPase has been recently identified as lysophosphatidylcholine (LPC). The aim of this study was to investigate the existence of a relationship between the activity of the cellular membrane Na+ -K− -ATPase and plasma LPC in human diabetes. We studied 10 patients with insulin-dependent-diabetes mellitus (IDDM), 14 patients with non-insulin-dependent diabetes mellitus (NIDDM), and 10 sex- and age-matched control subjects. Plasma LPC concentrations were increased in both IDDM and NIDDM patients compared with control subjects. Na+ -K+ -ATPase activity was reduced in both groups of patients in erythrocyte and platelet membranes. There was a significant correlation between the concentrations of plasma LPC and Na+ -K+ -ATPase activity in both erythrocyte and platelet membranes (P < 0.01). To investigate the effect of LPC on the enzyme, Na+ -K+ -ATPase activity was determined in erythrocyte membranes obtained from six healthy subjects after in vitro incubation with increasing concentrations of LPC (1–10 microM). Enzymatic activity was significantly reduced by in vitro LPC at a concentration of 2.5 microM, with a further decrease at 5 microM. These data suggest that the decrease in Na+ -K+ -ATPase activity in diabetes might be due to increased LPC concentrations.
Isolation of the Human LIM/Homeodomain Gene Islet-1 and Identification of a Simple Sequence Repeat 1
Authors: Tanizawa Yukio , Riggs Andrew C , Dagogo-Jack Samuel , Vaxillaire Martine , Froguel Philippe , Liu Li , Donis-Keller Helen , Permutt M Alan
Published: September 2013

The islet-1 (Isl-1) gene encodes a protein that binds to the enhancer region of the insulin gene. Isl-1 is a member of the LIM/homeodomain family of transcription factors. Because insulin deficiency, either relative or absolute, is a cardinal feature of non-insulin-dependent diabetes mellitus (NIDDM), this study addressed the question of whether mutations in genes that regulate insulin production could be involved. Rat Isl-1 was the first insulin enhancer binding protein to be isolated, and, in this study, the rat gene was used to isolate a partial human islet Isl-1 cDNA and subsequently to isolate genomic clones. A simple sequence repeat was found in the Isl-1 gene, and polymerase chain reaction amplification of this region of genomic DNA revealed 12 alleles in St. Louis African-Americans (het = 0.87), 14 alleles in black Nigerians (het = 0.89), 8 alleles in Japanese (het = 0.69), and 8 alleles in Caucasians (het = 0.81). Genetic linkage analysis uniquely placed Isl-1 on chromosome 5q (D5S395[12.8 cM]Isl-1 [11.6 cM]D5S407). The simple sequence repeat polymorphism at the Isl-1 locus was used to evaluate mutations in this gene as a possible contributor to the pathogenesis of NIDDM. Allelic frequencies did not differ between patients with NIDDM (n = 165) and nondiabetic control subjects (n = 163) in two black populations (St. Louis African-Americans and Nigerians). Linkage analyses in 15 nonglucokinase maturity-onset diabetes of the young pedigrees indicated that linkage could be rejected (LOD score < −3.0) over a distance of 15 cM.(ABSTRACT TRUNCATED AT 250 WORDS)
Insulin Sensitivity in Cystic Fibrosis
Authors: Moran Aantoinette , Pyzdrowski Kathryn L , Weinreb Jane , Kahn Barbara B , Smith Stephen A , Adams Karwyn S , Seaquist Elizabeth R
Published: September 2013

Cystic fibrosis (CF) patients demonstrate a spectrum of pancreatic β-cell abnormalities. Those with no exocrine insufficiency (NEXO) have normal insulin secretion. Exocrine-insufficient CF patients with overt diabetes (EXO-IT) have impaired insulin secretion and fasting hyperglycemia. Exocrine-insufficient patients without diabetes (EXO) have impaired insulin secretion but maintain normoglycemia. We postulated that EXO individuals compensate for insulin deficiency by increasing insulin sensitivity and investigated glucose utilization in CF. To examine hepatic and peripheral insulin sensitivity, euglycemic-hyperinsulinemic clamp studies were performed by using the hot GINF isotope dilution technique. Insulin was sequentially infused at 0.25, 1.0, and 10.0 mU · kg−1 · min−1. Glucose-mediated glucose uptake (GMGU) was assessed on another day with hyperglycemic clamp studies, during which insulin and somatostatin were infused to hold insulin-mediated glucose uptake constant between the two clamp studies. Skeletal muscle GLUT4 levels were assessed in EXO and control patients with Western blotting. Three patterns of peripheral and hepatic insulin sensitivity were seen that were related to the degree of pancreatic β-cell dysfunction. NEXO individuals had normal peripheral and hepatic insulin sensitivity. EXO individuals had enhanced peripheral insulin sensitivity that was not associated with a change in skeletal muscle glucose transporter abundance compared with control patients; paradoxically, EXO subjects demonstrated hepatic insulin resistance. EXO-IT had peripheral and hepatic insulin resistance. GMGU was diminished in both EXO and EXO-IT subjects. The unique combination of increased hepatic glucose production and increased peripheral glucose utilization seen in EXO may be a metabolic adaptation to increased peripheral energy needs. Increased glucose utilization is not attributable to a change in skeletal muscle GLUT4 or glycogen levels. Insulin resistance in CF patients with overt diabetes may be related to severe hyperglycemia secondary to impairment of insulin secretion.
Endothelial-Dependent Vascular Effects of Insulin and Insulin-Like Growth Factor I in the Perfused Rat Mesenteric Artery and Aortic Ring
Authors: Wu Hui-Yuan , Jeng Young Y , Yue Chung-jun , Chyu Kuang-Yuh , Hsueh Willa A , Chan Timothy M
Published: September 2013

Insulin and insulin-like growth factor I (IGF-I) exhibit vasoactivity. To examine the role of the endothelium in mediating the vascular responses to insulin and IGF-I, we exposed both isolated intact rat mesenteric arteries and rat aortic rings to these growth factors in the presence and absence of endothelium. Perfusion of rat mesenteric arteries with insulin, IGF-I, or IGF-II resulted in the potentiation of arginine vasopressin (AVP)-induced vasoconstriction. Of these growth factors, IGF-I was the most potent, with a significant effect at 0.6 nM and maximal effects at 6.0 nM, followed by IGF-II and insulin. Endothelial denudation or addition of cycloheximide prevented the growth-factor effects. Tissue cGMP levels in the mesenteric artery were minimally affected by growth factors. Insulin and IGF-I vascular effects were not inhibited by BQ123, an endothelin (ET) antagonist that blocked ET-1 enhancement of AVP response. Perfusion of mesenteric arteries with IGF-I for 1 h did not alter vessel ET-1 or ET-1 mRNA contents. Addition of indomethacin markedly inhibited the IGF-I effect on AVP contraction. Thus, the mesenteric vascular effect of insulin and IGF-I is not associated with ET-1 release but appears to link to an increased release of an endothelial-derived contracting factor or the decreased production of an endothelial-derived relaxing factor from the cyclooxygenase pathway. In contrast to their action in the mesenteric artery, insulin (exceeding 100 nM) and IGF-I (1–30 nM) attenuated AVP- and norepinephrine-induced contraction in rat aortic rings. Endothelial-denudation abolished this effect. L-Ng monomethyl arginine markedly reduced insulin and IGF-I responses in the aortic rings, suggesting involvement of endothelial nitric oxide production. Furthermore, IGF-I moderately increased tissue cGMP levels in the rings. These results suggest that the vascular effects of insulin and IGF-I are vessel-specific and mediated by the endothelium, possibly via IGF-I receptors.
Aldose Reductase Catalysis and Crystallography: Insights From Recent Advances in Enzyme Structure and Function
Authors: Petrash J Mark , Tarle Ivan , Wilson David K , Quiocho Florante A
Published: September 2013

Enhanced metabolism of glucose via the polyol pathway may play an important role in the pathogenesis of diabetic retinopathy, neuropathy, and nephropathy. Aldose reductase catalyzes the NADPH-dependent conversion of glucose to sorbitol, the first step in the polyol pathway. Interruption of the polyol pathway by inhibition of aldose reductase holds considerable promise as a therapeutic measure to prevent or delay the onset and severity of these late complications of diabetes. Dramatic advances in our understanding of the molecular biology, enzymology, and three-dimensional structure of aldose reductase have occurred in recent years, providing new and challenging insights into the enzyme's catalytic mechanism. Recent developments in structure determination of aldose reductase and the implications for evaluation and development of aldose reductase inhibitors are summarized.
Identification of Glutamic Acid Decarboxylase Autoantibody Heterogeneity and Epitope Regions in Type I Diabetes
Authors: Ujihara Noriko , Daw Kendra , Gianani Roberto , Boel Esper , Yu Liping , Powers Alvin C
Published: September 2013

Glutamic acid decarboxylase (GAD) is an autoantigen of the islet cell antibodies (ICAs) present in type I diabetes. GAD autoantibodies are also found in patients with stiffman syndrome and in certain ICA-positive individuals who rarely develop diabetes on long-term follow-up. This latter subset of ICA has been termed restricted or beta-cell-specific ICA because the antibodies react with only the beta-cells of the islet. By immunoprecipitation of recombinant GAD65 and GAD67 protein and protein fragments, 83% of sera from individuals with new-onset diabetes or prediabetes (n = 30) had GAD65 autoantibodies, but only 26% had GAD67 autoantibodies. In contrast, all restricted ICA sera (n = 6) had both GAD65 and GAD67 autoantibodies. In both types of sera, the binding of GAD67 autoantibodies could be blocked by preincubation of the serum with GAD65 and GAD67, but the binding of GAD65 autoantibodies could not be blocked by preincubation with GAD67. The titer of GAD65 autoantibodies was much higher in the restricted ICA sera (titer > 1:1,000) than in the sera from individuals with new-onset diabetes or prediabetes (titer < 1:100) and was reflected by the greater amount of GAD65 protein immunoprecipitated by restricted ICA sera (2.61 ± 1.39 U) compared with sera from individuals with new-onset diabetes (0.51 ± 0.34 U). The restricted ICA sera immunoprecipitated equimolar amounts of GAD65 protein fragments, suggesting a non-conformational or linear epitope; epitope mapping localized the major epitope region to amino acids 361–442 and a second minor epitope region to amino acids 1–195. For the monoclonal antibody GAD6, the GAD65 epitope region localized to amino acids 529–585. In contrast, the sera from individuals with new-onset diabetes or prediabetes immunoprecipitated equal amounts of full-length GAD65 protein and a GAD65 fragment containing amino acids 188–585, but did not immunoprecipitate smaller GAD65 protein fragments, which suggests an epitope(s) dependent on protein conformation. These results suggest that subsets of GAD autoantibodies exist and indicate a heterogeneity in the immune response to GAD.