bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Epinephrine on Pancreatic β-cell and α-Cell Function in Patients With NIDDM
Authors: Ortiz-Alonso Francisco J , Herman William H , Zobel Donna L , Perry Timothy J , Smith Merry J , Halter Jeffrey B
Published: September 2013

The purposes of this study were to determine whether patients with non-insulin-dependent diabetes mellitus (NIDDM) have an enhanced glycemic response to epinephrine (EPI) and to quantitate the effect of physiological elevations of EPI on pancreatic islet function in these patients. The increment of plasma glucose (PG) in response to 45 min of EPI infusion (mean plasma EPI 2490 pM) was more than twofold greater in nine NIDDM patients than in 20 nondiabetic control subjects (mean ± SE ΔPG 3.9 ± 0.3 vs. 1.7 ± 0.1 mM, P < 0.0001). The effects of EPI on β-cell and α-cell function were compared in nine NIDDM patients and 9 age- and weight-matched control subjects during infusions of saline or two doses of EPI on separate days (mean plasma EPI 270, 1120, and 2490 pM). On each day, the acute insulin response (AIR) and acute glucagon response (AGR) to 5 g i.v. arginine were measured at three matched steady-state PG levels (means of 9, 14, and 29 mM). β-cell sensitivity to glucose (slope of glucose potentiation) and β-cell secretory capacity, or AIRmax (AIR at the highest clamped PG level), were calculated. In control subjects, EPI inhibited the AIR at PG concentrations of 9 and 14 mM (both P < 0.05) but had no effect on the AIRmax, resulting in a rightward shift of the curve relating the AIR and PG and a decrease in the slope of glucose potentiation (P < 0.01). In contrast in NIDDM patients, EPI inhibited the AIR at all PG levels, including the AIRmax (all P < 0.05). EPI enhanced the AGR at all PG levels in control subjects but had no consistent effect on the AGR in patients with NIDDM. Multiple linear regression analysis demonstrated that, in both groupos, the AIR was significantly influenced by varying PG and EPI levels, together explaining >50% of the variation of AIR. These studies indicate that 1) the hyperglycemic effect of EPI is increased in patients with NIDDM, 2) EPI decreases β-cell sensitivity to glucose in control subjects and may also decrease maximal β-cell secretory capacity in NIDDM, and 3) EPI has no consistent effect on α-cell function in NIDDM. These findings suggest that the stress of intercurrent illness may induce a greater derangement of glycemic control in NIDDM patients than in nondiabetic humans, due in part to the failure of hyperglycemia to adequately compensate for the inhibitory effect of EPI on β-cell function.
Pituitary Response to Growth Hormone–Releasing Hormone in IDDM: Abnormal Responses to Insulin and Hyperglycemia
Authors: Press Martin , Caprio Sonia , Tamborlane William V , Bhushan Rhajat , Thorner Michael , Vale Wylie , Rivier Jean , Sherwin Robert S
Published: September 2013

In poorly controlled insulin-dependent diabetes mellitus (IDDM), hyperglycemia fails to inhibit the pituitary response to growth hormone–releasing factor (GRF). To evaluate whether this derangement is reversed by a simultaneous elevation of circulating insulin, 0.3 μg/kg i.v. GRF 1–40 was administered to nine poorly controlled IDDM subjects (HbA1 > 11.1%) with and without concomitant infusion of insulin. In the absence of insulin, the poorly controlled IDDM subjects demonstrated a growth hormone response to GRF similar to that of nondiabetic subjects, despite marked hyperglycemia (∼ 16.8 mM). When insulin was infused into these same patients (insulin clamp) to produce combined hyperinsulinemia (528 ± 90 pM) and hyperglycemia (16.5 ± 1.98 mM), the GRF-induced growth hormone rise was markedly exaggerated (65 ± 11 vs. 20 ± 4 μg/L without insulin infusion, P < 0.001). This enhancement of GRF-stimulated growth hormone release by insulin was strikingly attenuated (22 ± 7 μg/L) in five well-controlled diabetic subjects studied under conditions of similar hyperinsulinemia (486 ± 84 pM) and hyperglycemia (16.41 ± 0.95 mM). In contrast, in nondiabetic subjects, acute hyperinsulinemia reduced the growth hormone response to GRF. We conclude that the failure of hyperglycemia to block the pituitary response to GRF in poorly controlled diabetes is not attributable to the lack of a coincident increase in circulating insulin. The paradoxical stimulatory effect of insulin on GRF-induced growth hormone release may contribute to the high spontaneous growth hormone levels characteristically seen in poorly controlled insulin-treated patients, and its attenuation after intensive insulin therapy may contribute to the reversal of growth hormone hypersecretion in well-controlled diabetic patients.
Effect of Mg2+ on Na+-Dependent Inositol Transport: Role for Mg2+ in Etiology of Diabetic Complications
Authors: Grafton Gillian , Bunce Christopher M , Sheppard Michael C , Brown Geoffrey , Baxter Michael A
Published: September 2013

Diabetes mellitus is associated with a significant reduction in the serum concentration of Mg2+. Several studies have suggested that hypomagnesemia may be implicated in the etiology of diabetic complications; however, no mechanism has been proposed. This study demonstrates that Mg2+ is a positive effector of inositol transport and is capable of promoting a 2.5-fold increase in the affinity of the transporter for inositol. Analysis of the kinetics of inositol transport shows that, at physiological concentrations of inositol, the reductions in Mg2+ concentrations that occur in diabetic patients would result in a significant decline in the rate of inositol transport (1.5- to 2-fold). We suggest that hypomagnesemia may be linked to the development of diabetic complications via reduction in the rate of inositol transport and subsequent intracellular inositol depletion. This assertion allows hypomagnesemia and the polyol theory to be unified into one mechanistic model for the development of diabetic complications.
Dysfunction of Insulin Mediator Protein Kinase FA in Lymphocytes of Patients with NIDDM
Authors: Yang Shiaw-Der , Hwang Hong-So , Ha Tak-Lam , Lai Yein-Gei , Jean Yue-Jen
Published: September 2013

Patients with non-insulin-dependent diabetes mellitus (NIDDM) had an impaired capability to activate exogenous ATP · Mg-dependent protein phosphatase in lymphocytes compared with nondiabetic subjects. More importantly, the impaired protein phosphatase activation in the lymphocytes of patients with NIDDM could be consistently and completely restored to normal by exogenous pure protein kinase FA (the activating factor of ATP.Mg-dependentprotein phosphatase), indicating that the molecular mechanism for the impaired protein phosphatase activation in patients with NIDDM is due to a functional loss of kinase FA. By contrast, both NIDDM patients and nondiabetic subjects had similar levels of total cell proteins and spontaneously active protein phosphatase activity in their lymphocytes, indicating that the dysfunction of kinase FA in patients with NIDDM is very specific. Statistical analysis further revealed that the lymphocytes isolated from 21 nondiabetic subjects contained high levels of FA activity (148 ± 22 mU/mg cell protein), whereas, the lymphocytes of 21 patients with NIDDM contained low levels of FA activity (50 ± 22 mU/mg), indicating statistically significant differences in FA activity between diabetic patients and nondiabetic subjects. This is the first report providing initial evidence that patients with NIDDM may statistically have a common impairment in the protein phosphatase activation in their lymphocytes and that the molecular mechanism for this defect is due to a biochemical dysfunction of protein kinase FA, a biological mediator for both insulin and epidermal growth factor.
Identification of Genetic Markers Flanking the Locus for Maturity-Onset Diabetes of the Young on Human Chromosome 20
Authors: Bowden Donald W , Gravius Thomas C , Akots Gita , Fajans Stefan S
Published: September 2013

A systematic search for genetic linkage with maturity-onset diabetes of the young (MODY) as expressed in the R.-W. pedigree has been carried out. Evidence for linkage was found with restriction-fragment—length polymorphism loci that map to human chromosome 20. Two-point linkage analysis with CRI-L1214 (D20S16) and MODY gave a log of the odds (lod) score of 4.16 at Θ = 0.08. Multipoint linkage analysis with nine restriction-fragment–length polymorphism loci resulted in a lod score of 4.81 withthe MODY locus in an ∼20-cM region bounded by D20S16 and D20S14-D20S18. Examination of the pattern of MODY segregation suggests that additional factors, possibly geneticcould be involved in the age of onset of the disease.
Prevention of Adoptive Transfer in BB Rats by Prophylactic Insulin Treatment
Authors: Bertrand Sylvie , Paepe Monique De , Vigeant Claire , Yale Jean-François
Published: September 2013

Prophylactic insulin can prevent diabetes in the BB rat. We evaluated its use to prevent adoptive transfer of diabetes by activated splenocytes. Con A-activated spleen cells from acutely diabetic BB rats were divided into two equal aliquots and injected intravenously in paired diabetes-prone BB rat litter mates. At the time of cell injection, subcutaneous insulin injections (15 U · kg−1 · day−1) were started in one of each pair (n = 21) of littermates, and the control litter mates (n = 21) were injected with saline. The incidence of diabetes, observed 35 days after cell injection, was 95% in control rats compared with 29% in insulin-treated rats (P < 0.05). To confirm the absence of diabetes, insulin was stopped in all nondiabetic insulin-treated rats at 63 days of age. An OGTT was performed at 65 days of age: 4 rats were glucose intolerant. All rats received comparable numbers of Con A-activated splenocytes. At the time the rats were killed, 3 insulin-treated rats had a completely normal morphology and a normal glucose tolerance. All control rats had insulitis whether they were diabetic or not. No significant difference in any mononuclear subset was observed in relation to insulin treatment. We conclude that prophylactic insulin can prevent adoptive transfer of diabetes in the BB rat without inducing changes in the mononuclear cell subsets.
Influence of Glycemic Control on Interaction of Very-Low- and Low-Density Lipoproteins Isolated From Type I Diabetic Patients With Human Monocyte-Derived Macrophages
Authors: Klein Richard L , Wohltmann Hulda J , Lopes-Virella Maria F
Published: September 2013

The VLDL and LDL fractions were isolated from 29 patients with type 1 diabetes at the time of admission to the hospital to restore glycemic control and again at discharge. These lipoprotein fractions were incubated with human monocyte-derived macrophages, and the rates of macrophage CE synthesis were determined. The rates of CE synthesis in human macrophages were significantly greater (P < 0.005) when incubated with VLDL isolated from type I diabetic patients before compared with after glycemic control was attained and averaged 1.84 ± 0.52 and 1.09 ± 0.27 nmol (1.20 ± 0.34 and 0.71 ± 0.18 μg) [14C]cholesteryl oleate synthesized mg cell protein−1 · 20 h−1 respectively. In contrast, when LDL isolated from the same patient during the same period was incubated with human macrophages, the rates of cellular cholesteryl ester synthesis did not differ significantly and averaged 4.23 ± 1.26 and 3.91 ± 0.96 nmol (2.75 ± 0.82 and 2.55 ± 0.63 μg) [14C]cholesteryl oleate synthesized · mg−1 cell protein · 20 h−1, respectively. There was a significant increase in the total cholesterol content of VLDL isolated before glycemic control compared with that isolated after glycemic control was attained (P < 0.05) resulting from a significant increase in the FC and CE (P < 0.05) contents of these VLDL particles. There was a significant decrease in the ratio of FC to PL in VLDL, but not LDL, isolated after glycemic control (P < 0.05).

The percentage of apoE in VLDL was significantly decreased (P < 0.05) after glycemic control was attained. In LDL isolated after glycemic control was achieved, a significant decrease (P < 0.005) in the percentage of triglycerides was observed. In addition, there was a significant decrease (P < 0.0001) in the extent of glycation of LDL isolated after glycemic control. These studies suggest that during periods of poor glycemic control, the composition of VLDL isolated from type 1 diabetic patients is altered. These modified VLDLs stimulate CE synthesis rates in human macrophages and, thus, may contribute to the increased prevalence of atherosclerosis in diabetic patients.
Relationship Between Decrements in Glucose Level and Metabolic Response to Hypoglycemia in Absence of Counterregulatory Hormones in the Conscious Dog
Authors: Connolly Cynthia C , Adkins-Marshall Bess A , Neal Doss W , Pugh William , Jaspan Jonathan B , Cherrington Alan D
Published: September 2013

To determine the relationship between decreases in glucose and metabolic regulation in the absence of counterregulatory hormones, we infused overnight-fasted, conscious, adrenalectomized dogs (lacking cortisol and EPI) with somatostatin (to eliminate glucagon and growth hormone) and intraportal insulin (30 pmol · kg−1 · min−1), creating arterial insulin levels of ∼2000 pM. Glucose was infused during one 120-min period, two 90-min periods, and one 45-min period to establish levels of 5.9 ± 0.1, 3.4 ± 0.1, 2.5 ± 0.1, and 1.7 ± 0.1 mM, respectively. NE levels were 1.24 ± 0.23, 1.85 ± 0.27, 2.04 ± 0.26, and 2.50 ± 0.20 nM, respectively. During the euglycemic control period, the liver took up glucose (7.5 ± 1.9 μmol · kg−1 · min−1), but hypoglycemia triggered successively greater rates of net hepatic glucose output (3.0 ± 0.7, 4.6 ± 0.9, and 6.9 ± 1.4 μmol · kg−1 · min−1). Total gluconeogenic precursor uptake by the liver increased with hypoglycemia. Intrahepatic gluconeogenic efficiency rose progressively (by 106 ± 42,199 ± 56, and 268 ± 55%). Both glycerol and NEFA levels rose, indicating lipolysis was enhanced. Net hepatic NEFA uptake and ketone production increased proportionally, but the ketone level rose only with severe hypoglycemia. In conclusion, despite marked hyperinsulinemia and the absence of glucagon, EPI, and cortisol, we observed that lipolysis and glucose and ketone production increase in response to decreases in glucose. This suggests that neural and/or autoregulatory mechanisms can play a role in combating hypoglycemia.
Forebrain Ischemia in Diabetic and Nondiabetic BB Rats Studied With 31P Magnetic Resonance Spectroscopy
Authors: Sutherland Garnette R , Peeling James , Sutherland Eric , Tyson Randy , Dai Fulin , Kozlowski Piotr , Saunders John K
Published: September 2013

In spontaneously diabetic BB rats, the effect of chronically maintained blood glucose levels on the degree of energy failure and brain pH change during an ischemic insult, and on subsequent recovery after reperfusion, was studied with in vivo 31P magnetic resonance spectroscopy. Short duration forebrain ischemia (10-min carotid occlusion plus hypotension of 50 mmHg) was induced in diabetic and nondiabetic male BB rats whose blood glucose levels were maintained with insulin. Spectra were obtained in 1-min blocks before, during, and for 1 h after ischemia. Before ischemia, hypoglycemic (blood glucose <3 mM) diabetic rats had an increased PI peak intensity, with no significant pH change, compared with other groups. During ischemia, the rate and extent of hydrolysis of high-energy phosphate metabolites (as measured by an increase in PI) decreased, and the severity of tissue acidosis increased as preischemia blood glucose concentration increased. Among hyperglycemic BB rats, similar ischemia-induced changes were found for subgroups with blood glucose levels of 13.7 ± 1.2 and 20.3 ± 0.6 mM, in keeping with the known decrease in hexose binding sites associated with chronic hyperglycemia. Decline in PCr level during ischemia was not significantly different between groups. With reperfusion, both PI and pH values rapidly returned to preischemia values. PCr levels, however, did not recover in hyperglycemic diabetic animals, with the degree of residual impairment dependent on the preischemia glucose level. Results suggest that optimal management of diabetes may lessen the degree of injury within the ischemic penumbra in diabetic patients who suffer a stroke.
Hyperglycemia Markedly Enhances Skeletal Muscle Glycogen Synthase Activity in Diabetic, But Not in Normal Conscious Rats
Authors: Farrace Stefano , Rossetti Luciano
Published: September 2013

Both hyperinsulinemia and hyperglycemia stimulate skeletal muscle glucose uptake. However, the intracellular metabolic fate of the phosphorylated glucose may be different when the prevalent stimulus for glucose uptake is hyperinsulinemia or hyperglycemia. To define the impact of hyperglycemia on the intracellular glucose disposal, we studied control and diabetic conscious rats under four experimental conditions: 1) basal insulin and basal glucose; 2) basal insulin and high glucose; 3) high insulin and basal glucose; and 4) high insulin and high glucose. Under both basal insulin (130 pM) and high insulin (2500 pM), hyperglycemia (15 mM) increased glucose uptake and muscle and liver glycogen synthesis similarly in control and diabetic rats. Hyperglycemia resulted in a more significant decline in the muscle G-6-P concentration in diabetic rats than in control rats, suggesting activation of intracellular glucose metabolism. The diabetic skeletal muscle glycogen synthase was severely resistant to insulin stimulation compared with control (FV0.1 = 0.31 ± 0.04 vs. 0.49 ± 0.03; Km = 0.19 ± 0.05 vs. 0.10 ± 0.01 mM; P < 0.01), but it was markedly responsive to glucose stimulation under both basal (FV0.1 = 0.38 ± 0.03 vs. 0.21 ± 0.03; Km = 0.10 ± 0.01 vs. 6.35 ± 0.08 mM) and high insulin (FV0.1 = 0.65 ± 0.07 vs. 0.31 ± 0.04; Km = 0.11 ± 0.02 vs. 0.19 ± 0.05 mM). By contrast, in control rats, hyperglycemia did not exert any stimulatory effect on skeletal muscle glycogen synthase. Thus, some metabolic alteration associated with the diabetic state renders the skeletal muscle glycogen synthase selectively responsive to glucose stimulation. This may represent a compensatory mechanism for the severe impairment in insulin's activation of this enzyme in diabetes.
Differential Tissue Regulation of Insulinlike Growth Factor Binding Proteins in Experimental Diabetes Mellitus in the Rat
Authors: Gelato Marie C , Alexander Daniela , Marsh Kenneth
Published: September 2013

The expression and regulation of IGF-I is tissue-specific in diabetes mellitus in the rat. These studies were designed to examine if similar tissue specificity exists for IGF-BPs in the diabetic milieu. Diabetes mellitus was induced by a single i.p. injection of STZ (100 mg/kg body weight). Rats were treated with either vehicle—Insulin, vanadate, or phlorizin for 7–14 days. Tissues were analyzed for IGF-BPs by ligand blotting and by affinity cross-linking and immunoprecipitation. In liver tissue from nondiabetic control rats, multiple forms of IGF-BPs were noted, ranging from 48,000 to 25,000 Mr. In diabetic rat liver tissue, the 25,000-Mr form was unchanged, whereas the higher Mr forms (48,000–42,000 Mr) were decreased, and the 30,000-Afr form was increased. Insulin therapy of diabetic rats decreased all forms to below control levels. In the kidney tissue of control rats, faint IGF-BP bands were seen at 30,000 and 25,000 Mr In diabetic rat kidney tissue, the 30,000-Afr form again was increased (as in liver) and restored to control levels with insulin therapy. In contrast, only a 30,000-Afr band was seen in control pituitary tissue, which was slightly increased in the diabetic rats and also was decreased below control levels by insulin. In hypothalamus and cerebral cortex tissue, bands at 30,000 and 25,000 Mr were noted, and neither was altered by diabetes or insulin treatment. Treatment of diabetic rats with vanadate and phlorizin resulted in comparable blood glucose levels, which were only slightly higher than those achieved with insulin therapy. However, although tissue IGF-BPs from vanadate-treated rats were similar to those with insulin therapy, phlorizin was without effect. Immunoprecipitation demonstrated that IGF-BP-1 and IGF-BPs were increased in the livers and kidneys of diabetic animals (presumably represented by the 30,000-Afr band on ligand blotting). In pituitary, hypothalamus, and cerebral cortex tissue, IGF-BPs was the predominant species of BP identified. Although the diabetic state caused increases in BPs in pituitary, no changes were noted in the cerebral cortex and hypothalamus. Therefore, these data suggest that the IGF-BPs in peripheral and neural tissues are differentially regulated by insulin and glucose.
Induction of Resistance to Endothelin-1's Biochemical Actions by Elevated Glucose Levels in Retinal Pericytes
Authors: Rubia Guadalupe De La , Oliver F Javier , Inoguchi Toyoshi , King George L
Published: September 2013

Because retinal pericytes have contractile properties and are affected by diabetes, we have studied the responsiveness of pericytes to ET-1, a potent vasoconstrictor, in the presence of various concentrations of glucose. Cultured calf retinal pericytes were exposed to glucose levels of 5.5 or 25 mM for up to 8 days. Radioreceptor studies that used [125I]ET-1 showed that pericytes contained high-affinity binding sites with Kd of 3 × 10−10 M, and these binding affinities were unaffected by glucose concentration. Receptor number appears to be elevated, but this increase was NS. Responsiveness of pericytes to ET-1 was studied with respect to stimulation of DAG and IP3 levels and PKC activities. In contrast to receptor binding, exposure to 25 mM glucose for >6 days blunted pericyte responsiveness to ET-1. The time course of ET-1 stimulation as measured by [3H]glycerol labeling, and IP3 level showed a 98% increase in [3H]DAG at 10 min and a fourfold increase for IP3, respectively. Cells exposed to 25 mM glucose only had a 32% increase for DAG, and no increase for IP3 was observed. Dose-response studies on the stimulation of [3H]DAG increase showed the range of ET-1's effect to be between 10−9 and 10−7 M. At maximum, cells exposed to 5.5 mM glucose had a 70% increase versus only a 30% increase in those exposed to 25 mM glucose. Similarly, ET-1 only increased the total DAG levels in pericytes exposed to 5.5 mM glucose by 41%. PKC activity also was measured because DAG is one of its cellular activators. In cells exposed to 5 mM glucose, ET-1 increased PKC-specific activity in the membraneous pool after 30 min by twoto fourfold without changes in the cytosol. In those cells exposed to 25 mM glucose, no increase in the membranous PKC activity was noted. These findings show that exposure of pericytes to elevated levels of glucose can cause resistance to some of ET-1's biochemical actions at the postreceptor sites. Possibly, the loss of pericyte function as observed in early diabetic retinopathy could be attributable to the developed resistance to ET-1 in the retinal microvessels.
Intermittent Hypoglycemia Impairs Glucose Counterregulation
Authors: Widom Barbara , Simonson Donald C
Published: September 2013

IDDM patients who maintain strict glycemic control have impaired counterregulatory hormone and symptomatic responses to hypoglycemia. To test the hypothesis that intermittent exposure to hypoglycemia plays an etiological role in these defective responses, we produced 4 consecutive daily episodes of hypoglycemia in 10 healthy, nondiabetic volunteers by using the insulin clamp technique. Fasting (5.3 ± 0.1 vs. 5.4 ± 0.1 mM) and nadir (2.3 ± 0.1 vs. 2.4 ± 0.1 mM) glucose levels achieved during insulin infusion did not differ on study days 1 and 4. In contrast, the glucose levels required to stimulate an increase in EPI (2.8 vs. 3.1 mM), glucagon (2.8 vs. 3.2 mM), cortisol (2.4 vs. 2.9 mM), GH (2.6 vs. 3.0 mM), and autonomic hypoglycemic symptoms (2.2 vs. 2.5 mM) were all significantly lower on study day 4 versus study day 1 (P < 0.005–0.05). Basal levels of EPI and cortisol, but not glucagon, GH, or NE also were reduced on the final study day. We conclude that intermittent hypoglycemia can result in attenuation of the hormonal and symptomatic responses to insulin-induced hypoglycemia and may contribute to the defective counterregulatory responses in patients with well-controlled IDDM.
Lack of Feedback Inhibition of Insulin Secretion in Denervated Human Pancreas
Authors: Luzi Livio , Battezzati Alberto , Perseghin Gianluca , Bianchi Elda , Vergani Sandro , Secchi Antonio , Rocca Ennio La , Staudacher Carlo , Spotti Donatella , Ferrari Giovanni , Carlo Valerio Dl , Pozza Guido
Published: September 2013

In this study, pancreas transplantation is used as a clinical model of pancreas denervation in humans. To assess the role of innervation on the feedback autoinhibition of insulin secretion, we studied four groups of subjects—group 1: 16 patients with combined pancreas and kidney transplantation (plasma glucose = 5.1 mM, HbA1c = 6.4%, creatinine = 86 mM); group 2: 8 patients with chronic uveitis on the same immunosuppressive therapy as transplanted patients (12 mg/day prednisone, 5 mg · kg−1 · day−1 CsA); group 3: 4 uremic, nondiabetic patients in chronic hemodialysis; group 4: 7 normal, nondiabetic control subjects. The following means were used to study the groups: 1) a two-step hyperinsulinemic euglycemic clamp (insulin infusion rate = 1 mil and 5 mil · kg−1 · min−1); and 2) a 0.3 mil · kg−1 · min−1 hypoglycemic clamp (steady-state plasma glucose = 3.1 mM). Basal plasma-free IRI (84 ± 6, 42 ± 12, 72 ± 12, and 30 ± 6 pM in groups 1, 2, 3, and 4, respectively), basal C-peptide (0.79 ± 0.05, 0.66 ± 0.05, 3.04 ± 0.20, and 0.59 ± 0.06 nM in groups 1, 2, 3, and 4, respectively), and glucagon (105 ±13, 69 ± 4,171 ±10, and 71 ± 5 pg/ml in groups 1, 2, 3, and 4, respectively) were increased in groups 1 and 3 with respect to groups 2 and 4 (P < 0.01). During euglycemic hyperinsulinemia, plasma C-peptide decreased by 45, 20, and 44% in groups 2, 3, and 4, respectively, but showed no significant change from the basal in patients with transplanted pancreases. During insulin-induced hypoglycemia, C-peptide concentration was suppressed by 80 and 85% in groups 2 and 4, respectively, but only by 57 and 40% in groups 1 and 3, respectively; glucagon response was blunted in patients with transplanted pancreases in all groups. In conclusion, these results support the hypothesis that feedback inhibition of insulin secretion is mediated by neural control in humans. The partial restoration of inhibition of insulin secretion during hypoglycemia presumably is attributable to catecholamine release, or to exposure of the β-cell to low glucose concentration.
Sib-Pair Analysis of Adenosine Deaminase Locus in NIDDM
Authors: Baroni Marco G , Alcolado Juan C , Needham Edward W A , Pozzilli Paolo , Stocks Joseph , Galton David J
Published: September 2013

Recently, linkage between the ADA gene locus and MODY, a subtype of NIDDM, has been reported. The possibility that the region of chromosome 20q containing the ADA locus also may play a role in susceptibility to NIDDM needs to be investigated. Therefore, we examined the linkage between the ADA locus and NIDDM in affected siblings of 50 European white diabetic pedigrees—21 Italian and 29 British. Departure from independent segregation of the disease and an Alu VpA polymorphism within the 5' flanking region of the ADA locus was tested in the affected sib-pairs with the APM statistical method. After DNA amplification by the PCR and PAGE, five alleles were identified in the ALU VpA tract at the ADA locus in the two populations. Allele frequencies did not differ significantly between the two populations (X2 = 2.426, P > 0.05 [NS]). Analysis of the 50 diabetic sib sets, and independently of the Italian and British groups of affected sib pairs, revealed no segregation distortion between the marker locus and NIDDM. We conclude that mutations within or around the ADA locus are unlikely to play a major role in the etiology of NIDDM.
Linkage Analysis of GLUT1 (HepG2) and GLUT2 (Liver/Islet) Genes in Familial NIDDM
Authors: Elbein Steven C , Hoffman Michael D , Matsutani Akira , Permutt M Alan
Published: September 2013

Familial NIDDM probably results from combined inherited defects of insulin secretion and action. Members of the facilitative glucose transporter family are strong candidates for both defects, and RFLPs for both GLUT1 (erythrocyte) and GLUT2 (liver/islet) genes have been associated with NIDDM in some populations. To test the hypothesis that GLUT1 and GLUT2 mutations contribute to the inherited predisposition to NIDDM, we examined linkage of these loci with NIDDM in 18 large Utah white pedigrees (two and three generation) ascertained for >2 NIDDM siblings. We used two RFLPs detected with Xba1 and Stu1 for the GLUT1 transporter. For the GLUT2 (liver/β-cell) transporter gene, we used an RFLP detected with EcoR1 and a highly polymorphic (6-allele) dinucleotide (microsatellite) repeat. Analysis was performed with the MLINK program of the LINKAGE package. We tested four models for each locus: dominant and recessive, with IGT alternately considered as unknown affection status, or affected if IGT was diagnosed <45 yr of age and unknown if >45 yr. Disease gene frequencies were chosen to give approximate disease prevalence in American whites (q = 0.03, dominant; q = 0.25, recessive). Linkage of GLUT1 and NIDDM was strongly and significantly rejected under all models, with total (pooled) LOD scores of −5.7 to −8.9, indicating >500,000:1 odds against linkage. Pooled LOD scores were significantly negative (<−2.0, or 100:1 odds against linkage) to a recombination fraction of >5%. No heterogeneity was apparent. Analysis of GLUT2 gave similar results, with LOD scores of <−4.0 under each model, indicating at least 10,000:1 odds against linkage. Again, linkage was excluded within a 5% recombination fraction. Two pedigrees had individual LOD scores of >0.8 under some models, which may have suggested heterogeneity. Formal testing did not support the presence of a linked subgroup for either gene, however. These data fail to support a role for either GLUT1 or GLUT2 genes in the genetic predisposition to NIDDM. However, mutations of either or both genes may be present in rare pedigrees, in other racial groups, or as minor contributors in a polygenic disease.
HLA and Insulin-Dependent Diabetes. A protective perspective
Authors: Sheehy Michael J
Published: September 2013

This article presents a model for the HLA effect in insulin-dependent diabetes mellitus (IDDM) that is almost the mirror image of a model suggested by Nepom. In the Nepom model, the products of certain HLA alleles are associated with IDDM because they bind and present a specific peptide or peptides so as to induce an immune response to pancreatic β-cells; certain other alleles can protect against IDDM if they compete strongly for binding of the diabetogenic peptide. My model focuses instead on the failure of the immune system to maintain tolerance to pancreatic β-cells. I suggest that the HLA alleles negatively associated with IDDM (e.g., DR2 and DQw1) produce products with high affinity for certain β-cell peptide or peptides needed to establish and maintain tolerance to β-cells, whereas the alleles that are common in IDDM (e.g., DR3, DR4, and DQw8) produce products that have low affinity for the tolerogenic peptide or peptides or that bind the peptide or peptides in the wrong orientation or configuration for establishing tolerance. I also discuss the multiplicity of HLA loci, alleles, and amino acids contributing to IDDM and the fact that the associations of specific loci, alleles, and even genotypes with IDDM depend not only on their intrinsic properties but also on various population parameters.
Effects of Streptozocin-Induced Diabetes and Food Restriction on Quantities and Source of T4 and T3 in Rat Tissues
Authors: Schröder-van der Elst Janny P , van der Heide Daan
Published: September 2013

Diabetes mellitus and fasting are both associated with low plasma thyroid hormone concentrations and loss of body weight. To discriminate between the separate effects of energy shortage and insulin, we studied control rats, diabetic rats (DM), DM rats treated with insulin (DMI), and rats after modified fasting (MF1 and MF2; 70 and 30% of normal daily food intake, respectively). In double-isotopic equilibrium experiments, we determined the tissue thyroxine (T4) and triiodothyronine (T3) concentrations and the contribution of local T4-to-T3 conversion to total T3 in rat tissues; thyroidal T4 and T3 secretion and extrathyroidal T3 production were calculated. In DM and DMI rats, plasma T4 and T3 decreased; in MF1 and MF2 rats, only plasma T4 decreased. Thyroidal T4 secretion decreased, whereas that of T3 remained normal. The decrease in tissue T4 in MF and DM rats paralleled the decrease in plasma T4. Although plasma T3 did not differ in DM and DMI rats, total T3 concentrations in all tissues were not the same due to changed uptake of T3 from plasma and local T4-to-T3 conversion; these changes were not found in several tissues of MF1 and MF2 rats. Our results suggest that the decrease in tissue T4 during diabetes mellitus is due to the decrease in plasma T4 caused by the decreased thyroidal secretion, possibly due to intracellular energy shortage. The changes in tissue T3 during diabetes mellitus are only partly attributable to the same phenomenon; in several tissues, the decrease in T3 seems more related to the lack of insulin.
Insulin-Stimulated Glucose Transport in Circulating Mononuclear Cells From Nondiabetic and IDDM Subjects
Authors: Daneman Denis , Zinman Bernard , Elliott M Esther , Bilan Philip J , Klip Amira
Published: September 2013

The objectives of this study were 1) to evaluate glucose transport and its regulation by insulin in easily accessible human cells, 2) to investigate the glucose transporter isoforms involved, and 3) to establish whether a defect in glucose transport is associated with peripheral insulin resistance, which is common in insulin-dependent diabetes mellitus (IDDM) patients. We measured 2-deoxyglucose (2-DG) uptake in circulating mononuclear cells from 23 nondiabetic adults, 16 adults with IDDM, and 10 children with IDDM. Circulating mononuclear cells were separated from whole blood by Ficoll gradients and incubated with ± 1 nM insulin. 2-DG uptake was measured after incubation with [3H]2-DG and cell separation through corn oil-phthalate. Cytochalasin B-inhibitable 2-DG uptake (basal and insulin stimulated) was higher in control than in IDDM subjects (P < 0.001). Insulin significantly increased 2-DG uptake or 3-O-methylglucose uptake in both groups. Basal and insulin-stimulated 2-DG uptake was similar for adults and children with IDDM and did not correlate with age or body mass index in any group or disease duration, insulin dosage, or HbA1c in IDDM. In separated monocytes and lymphocytes, 2-DG uptake increased in response to insulin only in the monocyte population. Insulin dose-response curves indicated maximal stimulation of hexose uptake at 1–2 nM insulin for both control and diabetic subjects and demonstrated a significant decrease in maximal insulin response in the latter. Immunoblotting with specific antibodies revealed that circulating mononuclear cells and separated monocytes express the GLUT1 but not the GLUT4 isoform of the glucose transporter. The immunoreactive GLUT1 content was not significantly different in monocytes from diabetic than from control adults. We conclude that 1) basal hexose uptake is significantly lower in circulating mononuclear cells from IDDM than control subjects; 2) insulin significantly increases 2-DG uptake in circulating mononuclear cells from both groups, but the absolute insulin-stimulated hexose uptake is lower in the IDDM than the control subjects; 3) the insulin response is likely mediated by GLUT1 transporters in the monocyte subpopulation; and 4) maximal insulin response is subnormal in the IDDM group, but this is not linked to a decrease in GLUT1 transporter content.
Effects of Insulin Treatment on Lipoprotein Composition and Function in Patients With IDDM
Authors: Bagdade John D , Dunn Fredrick L
Published: September 2013

Normolipidemic patients of both sexes with insulin-dependent diabetes mellitus have the same pervasive changes in lipoprotein surface and core lipid composition. The disproportionate increase observed in their lipoprotein free (unesterified) cholesterol relative to the predominant surface phospholipid lecithin (phosphatidycholine) is reflected by elevation of the FC-L ratio in their whole plasma, VLDL, HDL2, and HDL3. As a possible consequence of this qualitative disturbance, cholesteryl ester transfer is pathologically increased and the mass of cholesteryl ester transferred from HDL to VLDL+LDL is significantly greater in IDDM patients than in control subjects at 1, 2, and 4 hr (P < 0.001). Consistent with accelerated CET in vivo, the TG-CE core lipid ratio was decreased in VLDL from six subjects (IDDM 9.5 ± 0.8 vs. control 12.9 ± 3.4; P < 0.01) and increased in their HDL (diabetic 0.55 ± 0.11 vs. control 0.42 ± 0.04: P < 0.025). These abnormalities in lipoprotein composition and CET do not correlate with glycemic control and persist after intensive management with s.c. insulin. They may be related to the peripheral hyperinsulinemia that is an unavoidable consequence of conventional s.c. insulin administration because preliminary studies indicate that these disturbances in lipoprotein composition and function are reversed when systemic insulin levels are lowered and insulin is delivered into the portal circulation from an i.p. catheter connected to an implanted programmable s.c. insulin pump.
Nonenzymatic Glycosylation of Macromolecules: Prospects of Pharmacologic Modulation
Authors: Brownlee Michael
Published: September 2013

Diabetes increases the risk of developing atherosclerotic arterial disease significantly. Although elevated glycohemoglobin was shown to be an independent risk factor in older women in the Framingham Heart Study, the relationship between hyperglycemia and macrovascular disease is complicated by the many other factors that influence atherogenesis in nondiabetic people. Studies in vitro suggest that chronic hyperglycemia may accelerate the atherogenic process through excessive glycation of various components of the arterial wall. These data are reviewed critically, and the biochemistry and pharmacological potential of the glycation-inhibitor aminoguanidine is discussed.
Minimally Modified Lipoproteins in Diabetes
Authors: Berliner JA , Territo M , Navab M , Andalibi A , Parhami F , Liao F , Kim J , Estworthy S , Lusis AJ , Fogelman AM
Published: September 2013

Studies from several laboratories suggest that oxidized LDL may play an important role in atherogenesis. Our group previously showed that treatment of aortic endothelial cells with low levels of MM-LDL caused increased expression of MCP-1, M-CSF, tissue factor, and a monocyte-binding protein. In these studies MM-LDL was produced by storage of native LDL. We now show that cocultures of endothelial and smooth muscle cells can also produce MM-LDL from native LDL. This production of MM-LDL by cells is prevented by preincubating the LDL with probucol or vitamin E. However, addition of antioxidants to MM-LDL did not block its action. In past studies we also showed that endothelial cells exhibit differential sensitivity to the effects of MM-LDL. We report herein that in resistant cells there is no elevation of catalase, glutathione peroxidase, or copper-zinc-dependent SOD. However, maganese-dependent SOD is elevated in resistant cells. Ways in which MM-LDL production may be elevated in poorly controlled diabetics subjects are discussed.
Lipoprotein-lmmune Complexes and Diabetic Vascular Complications
Authors: Gisinger Christoph , Lopes-Virella Maria F
Published: September 2013

In earlier studies, we showed that incubation of HMM with LDL IC led to cellular CE accumulation and to the transformation of macrophages into foam cells. This study demonstrates that the stimulation of macrophages with RBC-LDL-IC also increases the uptake of native LDL, most likely because of an increased LDL receptor number, as shown by Scatchard plot analysis (x-axis intercept 1267 vs. 352 ng LDL/mg protein in control cells). To determine whether the increase in LDL-receptor activity was secondary to a decrease in the macrophage free (nonassociated) cholesterol content, we measured the T-UC and the UC associated with intracellular intact LDL and demonstrated that 50% of the T-UC is associated with intact LDL. UC not associated with LDL (free cholesterol) was lower in LDL-IC-stimulated cells than in control cells. These results suggest that UC associated with nondegraded intracellular LDL is nonregulatory, a conclusion that was also supported by finding increased sterol synthesis (192.8 ± 22.9 pmol/mg protein vs. 94.8 ±11.8) in RBC-LDL-IC-stimulated macrophages. In conclusion, the uptake of RBC-LDL-IC by macrophages led to increased intracellular accumulation of CE and UC, to a decrease in the cell regulatory pool of free cholesterol, and to an increase in LDL-receptor activity.
Renal Functional Reserve in the Early Stage of Experimental Diabetes
Authors: Nicola Luca De , Blantz Roland C , Gabbai Francis B
Published: September 2013

The role of renal functional reserve (RFR; increase in plasma flow and glomerular filtration rate in response to protein loading) as an indicator of increased glomerular hydrostatic pressure and flow was evaluated in recent-onset poorly controlled diabetic rats. Streptozocin-induced diabetic (STZ-D) rats were studied with micropuncture (MP) technique after 10–15 days of diabetes (daily blood glucose level 15.3–18 mmol). We also studied STZ-D rats treated with the converting-enzyme inhibitor (CEI) enalapril or the angiotensin II (ANG II) receptor antagonist DuP 753 (DuP) for 3 days before MP. Nondiabetic rats (NOR) served as controls. Glomerular hemodynamics and proximal tubular reabsorption were measured in the control period and during intravenous glycine infusion. In NOR rats, glycine increased single-nephron plasma flow (SNPF) and single-nephron glomerular filtration rate (SNGFR). Although STZ-D rats did not exhibit hyperfiltration, SNGFR and SNPF were not modified by glycine, defining loss of RFR. CEI rats responded to glycine with an increase in SNGFR due to a rise in SNPF and a rise in the ultrafiltration coefficient. Interestingly, loss of RFR in STZ-D rats was associated with a decrease in absolute proximal reabsorption. The decrease in absolute proximal reabsorption was corrected by both CEI and DuP, although glomerular vasodilation was restored only in the CEI group. In conclusion, at the early stage of diabetes mellitus, loss of RFR does not detect hyperfiltration, but rather the presence of a tubular alteration probably dependent on ANG II. The CEI enalapril but not DuP restored RFR in diabetic rats, suggesting that other ANG II-independent effects of CEI are important in restoring a normal response to glycine.
Glomerular Abnormalities in Long-Term Experimental Diabetes: Role of Hemodynamic and Nonhemodynamic Factors and Effects of Antihypertensive Therapy
Authors: Fujihara Clarice K , Padilha Regina M , Zatz Roberto
Published: September 2013

To evaluate the role of glomerular hypertension, glomerular hypertrophy, glomerular lipid deposition, and plasma cholesterol levels in diabetic glomerulopathy, Munich-Wistar rats received streptozocin and daily insulin injections and were assigned to one of three groups: untreated diabetic (DMC), hydralazine-treated diabetic (DMH), and enalapril-treated diabetic (DME). Age-matched control rats were also studied. At 6–10 wk of diabetes, DMC rats showed marked elevations of glomerular pressure and glomerular filtration rate as well as slight glomerular enlargement and cholesterol elevation. DMH and DME rats exhibited arterial hypotension but no change in cholesterol or glomerular volume. Glomerular pressure was normalized by enalapril but not by hydralazine treatment. Additional rats were followed up to 12 mo of diabetes. Slight hypertension was seen in DMC rats, whereas sustained hypotension occurred in DMH and DME rats. Progressive albuminuria occurred in DMC and DMH but not in DME rats. At 12 mo, glomerular hypertension persisted in DMC and DMH rats but was still absent in DME rats. Cholesterol was elevated in DMC and slightly lower in DMH and DME rats. Glomeruli were equally enlarged in the diabetic groups. Glomerular sclerotic lesions and lipid deposits appeared in DMC and DMH but not in DME rats. These findings are consistent with the notion that glomerular hypertension may promote glomerular injury in experimental diabetes. Glomerular lipid deposition may also participate in this process, although a causal relationship was not demonstrated. Glomerular hypertrophy and cholesterol were unrelated to glomerular injury, although they may have exacerbated hemodynamically mediated damage.
Multiple TCR Vβ Usage by Infiltrates of Young NOD Mouse Islets of Langerhans: A Polymerase Chain Reaction Analysis
Authors: Waters Simon H , O'Neil John J , Melican David T , Appel Michael C
Published: September 2013

Because a restricted repertoire of T-cell receptor (TCR) Vβp gene expression has been reported in other autoimmune diseases, the possibility of similarly restricted Vα gene expression by T-cell infiltrates of NOD mouse islets was examined. With isolated islets from 4- to 12-wk-old NOD mice, a prospective polymerase chain reaction analysis with 18 Vβ-specific oligonucleotide primers was performed on the noncloned and unexpanded islet-infiltrating T cells. The methodology used permitted the detection of a minimum of 50 T cells. In contrast to the restricted TCR Vβ gene usage reported for other autoimmune diseases, infiltrates of even the youngest mice were characterized by expression of multiple Vβ gene segments.
Genetic and Environmental Determinants of Type II Diabetes in Mexico City and San Antonio
Authors: Stern Michael P , Gonzalez Clicerio , Mitchell Braxton D , Villalpando Enrique , Haffner Steven M , Hazuda Hazuda P
Published: September 2013

To study genetic and environmental determinants of non-insulin-dependent (type II) diabetes, we compared a random sample of 35- to 64-yr-old Mexican-American men and women living in several low-income barrio neighborhoods of San Antonio to similarly aged Mexicans living in a low-income colonia of Mexico City (Colonia Liberales). A total of 1138 Mexican Americans, representing 64.3% of the original sample, and 646 Mexicans, representing 69.2% of the original sample, participated in the survey. Diabetes was diagnosed using World Health Organization criteria. Genetic susceptibility to type II diabetes was inferred from the percentage of Native American genetic admixture as estimated from skin reflectance measurements. The prevalence of diabetes was 36% higher among San Antonio Mexican Americans than among Mexicans in Mexico City; this difference was highly statistically significant (age- and sex-adjusted prevalence ratio 1.36, P = 0.006). This excess was observed despite the fact that genetic susceptibility, as inferred from the admixture estimates, was similar in the two cities. On the other hand, Mexicans were somewhat leaner as measured by body mass index and skin folds. Mexican women consumed fewer total calories than Mexican-American women, but there was no difference in the caloric intake of men. Mexico City residents ate less fat (18–19% of total calories vs. 31–32% in San Antonio, P < 0.001), more carbohydrate (64–65 vs. 49%, P < 0.001), and performed more physical activity than San Antonio Mexican Americans. Mexicans appeared to consume more refined sugar than Mexican Americans. Mexicans had lower total cholesterol but higher triglyceride and fasting insulin concentrations than Mexican Americans (all P < 0.002). The latter two observations are compatible with the hypothesis that the high-carbohydrate diet in Mexico City stimulated carbohydrate-induced hypertriglyceridemia, which was not offset by the greater degree of physical activity and leanness of Mexicans compared with Mexican Americans. The results of this study suggest that environmental factors can override genetic susceptibility in the expression of the type II diabetes trait.