bluuebunny/crossref_metadata_2025 huggingface dataset:
Higher Glycemic Thresholds for Symptoms During β-Adrenergic Blockade in IDDM
Authors: Hirsch Irl B , Boyle Patrick J , Craft Suzanne , Cryer Philip E
Published: September 2013

We tested the hypotheses that nonselective β-adrenergic blockade does not cause absolute hypoglycemia unawareness but shifts the glycemic thresholds for symptoms to lower plasma glucose concentrations and that neither neuroglycopenic symptoms nor cognitive impairments during hypoglycemia are altered by β-adrenergic blockade. To do so, we applied the euglycemic and stepped hypoglycemic clamp techniques to patients with moderately controlled insulin-dependent diabetes mellitus (IDDM) in the absence (n = 8) and presence (n = 9) of the nonselective β-adrenergic antagonist propranolol. Compared with the corresponding euglycemic clamps, total symptom scores first increased at the 4.4-mM plasma glucose step (a higher level than that of 2.8 mM in nondiabetic subjects studied previously) in the absence of propranolol. β-adrenergic blockade did not produce absolute hypoglycemia unawareness. Indeed, at the frankly hypoglycemic step of 2.8 mM, total symptom scores tended to be higher in the presence than in the absence of propranolol. This was largely the result of greater (P < 0.01) perception of diaphoresis. However, symptom scores did not increase until the 3.3-mM plasma glucose step during β-adrenergic blockade. The perception of hunger, and perhaps that of tremulousness, was reduced by propranolol at the higher glucose steps. Neuroglycopenic symptoms were not reduced by propranolol. The cognitive function of memory, but not that of attention, was impaired, also starting at the 4.4-mM glucose step. This was not impaired further by propranolol. Thus, we formed the following conclusions. 1) Nonselective β-adrenergic blockade does not cause absolute hypoglycemia unawareness but shifts the glycemic thresholds for symptoms to lower plasma glucose concentrations in patients with IDDM. 2) β-adrenergic blockade does not reduce neuroglycopenic symptoms, and it does not further impair cognitive function during hypoglycemia in IDDM patients.
High Incidence of Thyroiditis and Anti-Thyroid Autoantibodies in NOD Mice
Authors: Bernard Nicole F , Ertug Fatma , Margolese Howard
Published: September 2013

NOD mice develop spontaneous insulin-dependent diabetes mellitus (IDDM) associated with infiltration of pancreatic islets with mononuclear cells. Islet infiltration results in autoimmune destruction of insulin-secreting β-cells. Because in humans and BB rats diabetes is often associated with autoimmune thyroid disease (ATD), the NOD mouse model was examined for evidence of thyroiditis and serum antibodies reactive with mouse thyroid membrane antigens (MTMAs). The incidence of thyroiditis was 77% in mice > 180 days old, 67% in mice 61–180 days old, 72% in mice 31–60 days old, 74% in mice 21–30 days old, 78% in mice 11–20 days old, and 90% in mice ≤10 days old. NOD mice ≤30 days old had less-severe thyroiditis than animals > 180 days old. There was no significant different in severity of thyroiditis between any of the other age-groups tested. The incidence of thyroiditis was not increased in diabetic compared with nondiabetic animals, nor was an association found between thyroiditis and sex. The high incidence of thyroiditis in the ≤30-day-old age-group indicates that infiltration of lymphocytes into the thyroid can precede initiation of insulitis in this model. Although both thyroiditis and insulitis in NOD mice began early (by the 1st and 2nd mo of life, respectively), no significant association between infiltration of these two organs was noted in individual mice. Circulating antibodies to MTMA were demonstrated in 35% of NOD mice. Anti-MTMA antibodies were found significantly more frequently in NOD mice with thyroiditis than in those without mononuclear cell infiltration. Antibodies of this specificity precede the onset of diabetes and are likely to be secondary to mononuclear cell–mediated thyroid cell damage, although this has not been proven. The NOD mouse, in addition to being an excellent animal model for IDDM, can also be studied as a model for ATD. In addition NOD mice may be useful for exploring the underlying cause of the association between diabetes and ATD.
Evidence That Two Naturally Occurring Human Insulin Receptor α-Subunit Variants Are Immunologically Distinct
Authors: Sesti Giorgio , Adelaide Marini Maria , Montemurro Antonio , Condorelli Luigi , Borboni Patrizia , Haring Hans-Ulrich , Ullrich Axel , Goldfine Ira D , De Pirro Roberto , Lauro Renato
Published: September 2013

The IgG from a patient (Italy 2 [I-2]) with hypoglycemia, due to autoantibodies to the insulin receptor, was purified on protein A Sepharose into two fractions that were tested in various human tissues and cells. The IgG fraction that bound protein A (absorbed IgG [IgGa]) nearly completely inhibited the binding of 125I-labeled insulin to various cells or tissues (placenta, IM-9, adipocytes, HEp-2-larynx cells, Epstein-Barr virus lymphocytes) but not >50% of 125I-labeled insulin binding to human liver membranes. Conversely, both the IgG fraction from this patient, which did not bind protein A (flow-through IgG [IgGb]), and the IgGa fraction from a second similar patient (Italy 1 [I-1]) almost completely inhibited the binding of 125I-labeled insulin to liver membranes. The IgGa fraction from patient I-2 did not change receptor affinity because 50% inhibition of 125I-labeled insulin binding was not affected by either the presence or absence of these IgG fractions. Furthermore, liver binding data were not due to cross-reaction of 125I-labeled insulin to the insulinlike growth factor I receptor, and treatment of liver membranes with neuraminidase did not alter the inhibitory effect of the IgGa fraction from patient I-2 on 125I-labeled insulin binding to liver. Binding inhibition experiments performed with cells transfected with and overexpressing the −12 (human insulin receptor [HIR]-A) or the +12 (HIR-B) variant of HIR revealed that the IgGa fraction from patient I-2 inhibited 125I-labeled insulin binding to the HIR-A receptor but not to the HIR-B receptor. The data reported herein demonstrate that the two naturally occurring insulin-receptor variants are immunologically distinct and indicate that the HIR-B variant is predominantly expressed in liver compared with other human tissues.
Effect of Angiotensin-Converting Enzyme Inhibition on Renal Function and Albuminuria in Normotensive Type I Diabetic Patients
Authors: Wiegmann Thomas B , Herron Kristine G , Chonko Arnold M , MacDougall Margaret L , Moore Wayne V
Published: September 2013

Normotensive patients with insulin-dependent (type l) diabetes mellitus (n = 18) were given 25 mg captopril (b.i.d.) and placebo for 3 mo in a randomized double-blind crossover study. Patients had normal renal function, and none had retinopathy. Albuminuria was <20 μg/min in 12 patients and between 20 and 200 μg/min in the other 6. Patients were examined at the end of the placebo and captopril phases. Captopril caused little reduction in blood pressure obtainedby 24-h ambulatory monitoring (systolic 126.0 ± 2.7 to 123.9 ± 2.4 mmHg, P< 0.08; diastolic 74.2 ± 1.9 to 72.1 ± 1.9 mmHg, P < 0.09). Captopril lowered glomerular filtration rate from 99.5 ± 7.7 to 71.0 ± 5.5 ml · min−1 · 1.73 m−2(P < 0.01), whereas renal plasma flow (443.9 ± 15.2 ml.min−1. 1.73 m−2) remained unchanged. Filtration fraction was reduced from 22.4 ± 1.4 to 17.4 ± 1.4% (P < 0.01). Urinary albumin excretion was reduced from 59.1 ± 0.15 to 27.7 ± 13.9 μg/min (P < 0.1). Reduction was relatedto the extent of initial albuminuria (r = 0.997, P < 0.001), a relationship that remained significant after logarithmic transformation (r = 0.540, P < 0.02). Dextran clearance was used to determine glomerular capillary function. Angiotensin inhibition caused reduction in effective glomerular pore size and also reduced flow via the nondiscriminatory shunt. Angiotensin inhibition in normotensive patients with type I diabetes was well tolerated. Reduction in albuminuria is mediated by a combination of hemodynamic changes and alterations in glomerular capillary function.
Expression of GLUT1 and GLUT2 Glucose Transporter Isoforms in Rat Islets of Langerhans and Their Regulation by Glucose
Authors: Yasuda Koichiro , Yamada Yuichiro , Inagaki Nobuya , Yano Hideki , Okamoto Yoshimasa , Tsuji Kazuo , Fukumoto Hirofumi , Imura Hiroo , Seino Susumu , Seino Yutaka
Published: September 2013

Previous studies revealed that rat islets express the GLUT2-liver facilitative glucose transporter isoform, a glucose carrier with a low affinity for glucose but a high capacity for glucose transport. These studies indicated the presence of a second glucose transporter in rat islets; however, they did not indicate to which of the five known facilitative glucose transporters it corresponded. In this study, we isolated RNA from rat islets of Langerhans and confirmed the presence of GLUT2 mRNA. In addition, we present dataindicating that the second isoform expressed in islets is the GLUT1-erythrocyte isoform.The effect of culturing islets in 5.5, 8.3, or 11.1 mM glucose on the levels of GLUT1 and GLUT2 mRNA also was examined. The levels of GLUT1 and GLUT2 mRNA were two- and threefold higher, respectively, in islets cultured for 24 h in 11.1 mM glucose compared with those incubated in the presence of 5.5 mM glucose. Therefore, the previously observed increase in GLUT2 mRNA levels in the islets of rats made hyperglycemic by chronic infusion of glucose can be mimicked in vitro, implying that glucose regulates GLUT2 mRNA expression.
Insulin Is Required for the Liver to Respond to Intraportal Glucose Delivery in the Conscious Dog
Authors: Pagliassotti Michael J , Moore Mary C , Neal Doss W , Cherrington Alan D
Published: September 2013

To determine whether insulin is essential for the augmented hepatic glucose uptake observed in the presence of intraportal glucose delivery, SRIF was used to induce acute insulin deficiency in 5 conscious dogs, and glucose was infused into the portal vein or a peripheral vein in two sequential, randomized periods. Insulin and C-peptide levels were below the limits of detection after SRIF infusion, and the load of glucose presented to the liver was approximately doubled and equivalent during the portal and peripheral periods. Net hepatic glucose output was 2.9 ± 0.9 and 2.1 ± 1.1 μmol · kg−1 · min−1 during portal and peripheral glucose delivery, respectively. In an additional set of protocols, pancreatectomized dogs were used to investigate the effects of prolonged insulin deficiency (n = 5) and acute insulin replacement (n = 4) on the hepatic response to intraportal glucose delivery. In the prolonged insulin deficiency protocol, SRIF was used to lower glucagon and thereby reduce circulating glucose levels, and glucose was infused into the portal or peripheral circulations in two sequential, randomized periods. As with acute insulin deficiency, net hepatic glucose output was still evident and similar (3.6 ± 1.1 and 4.2 ± 1.3 μmol · kg−1 · min−1) during portal and peripheral glucose delivery, respectively. When the pancreatectomized dogs were restudied using a similar protocol, but one in which insulin was replaced (4X-basal), and the glucose load to the liver was matched to that which occurred in the prolonged insulin deficiency protocol, net hepatic glucose uptake was 23.6 ± 6.1 μmol · kg−1 · min−1 during portal glucose delivery but only 10.3 ± 3.5 μmol · kg−1 · min−1 during peripheral glucose delivery. These results suggest that the induction of net hepatic glucose uptake and the augmented hepatic response to intraportal glucose delivery require the presence of insulin.
Evidence for Distinctive and Intrinsic Defects in Insulin Action in Polycystic Ovary Syndrome
Authors: Dunaif Andrea , Segal Karen R , Shelley Donna R , Green Georgette , Dobrjansky Areta , Licholai Teresa
Published: September 2013

Women with PCO have a unique but poorly characterized disorder of insulin action. Obese (n = 16) and nonobese (n = 14) PCO women and age- and weight-matched normal, nondiabetic ovulatory women (obese, n = 15; nonobese, n = 17) had insulin action determined in vivo with sequential multiple insulin dose euglycemic clamps and in isolated abdominal adipocytes to clarify the mechanisms of insulin resistance. PCO resulted in significant increases in the ED50 insulin for glucose utilization in vivo (P < 0.001) and in adipocytes (P < 0.01), without significant changes in adipocyte insulin-binding sites. PCO also resulted in significant decreases in maximal insulin-stimulated rates of glucose utilization in vivo (P < 0.01) and in adipocytes (P < 0.01). Obesity resulted in smaller decreases in insulin sensitivity than PCO (ED50 insulin, P < 0.001 in vivo and P < 0.05 in adipocytes), but greater decreases in insulin responsiveness (Vmax P < 0.001 in vivo and in adipocytes). The ED50 insulin for suppression of HGP was increased only in obese PCO women (P < 0.001), and the interactions between PCO and obesity on this parameter were statistically significant. No significant correlations between androgen or estrogen levels and adipocyte insulin binding or action were found. Because insulin binding was not changed, we conclude that the major lesion causing insulin resistance in PCO is a striking decrease in insulin sensitivity secondary to a defect in the insulin receptor and/or postreceptor signal transduction. PCO also is associated with modest but significant decreases in glucose transport. These defects in insulin action appear to represent intrinsic abnormalities that are independent of obesity, metabolic derangements, body fat topography, and sex hormone levels. Conversely, changes in hepatic insulin sensitivity appear to be acquired with obesity.
Recovery of Glucose-Induced Insulin Secretion in a Rat Model of NIDDM Is Not Accompanied by Return of the B-Cell GLUT2 Glucose Transporter
Authors: Chen Chuan , Thorens Bernard , Bonner-Weir Susan , Weir Gordon C , Leahy John L
Published: September 2013

The NSTZ rat model combines loss of glucose-induced insulin secretion with a reduced amount of the high Km B-cell glucose transporter, GLUT2. The purpose of this study was to determine whether the restoration of glucose-induced insulin secretion was paralleled by an increase of GLUT2. Rats injected at 2 days of age with 90 mg/kg STZ were studied at 8–13 wk of age. Insulin secretion was assessed in the isolated perfused pancreas with 16.7 mM glucose preceded by 40 min of 0 or 5.5 mM glucose. In control rats, 16.7 mM glucose caused the same large biphasic insulin response whether preceded by 0 or 5.5 mM glucose. In NSTZ rats, after 5.5 mM glucose, 16.7 mM glucose elicited virtually no rise in insulin release. In contrast, after 0 mM glucose, a large insulin response to the glucose challenge occurred that was equal to that of the control groups when the differences in B-cell mass were taken into account. However, the dose-response curve for glucose-induced insulin secretion was shifted to the left, and no second phase of insulin secretion was observed. GLUT2 was assessed after the perfusions by indirect immunofluorescence with anti-GLUT2 antisera. Both control groups showed homogenous staining in all B-cells. NSTZ rats perfused with 5.5 mM glucose had a marked diminution in GLUT2 staining. We observed no increase in GLUT2 staining in the NSTZ rats perfused with 0 mM glucose. In summary, our results show: 1) the recovered glucose responsiveness in NSTZ rats after perfusion with 0 mM glucose appears in the presence of a reduced level of GLUT2; 2) the recovered glucose-induced insulin secretion is abnormal in that the glucose dose-response curve is shifted to lower glucose concentrations and a blunted second phase occurs. These results suggest that several steps are altered in the glucose signaling pathway of glucose unresponsive B-cells from NSTZ rats, and that a reduction of GLUT2 level may be only a partial cause of the secretory defects of diabetic B-cells.
Human Small Intestine Facilitative Fructose/Glucose Transporter (GLUT5) Is Also Present in Insulin-Responsive Tissues and Brain: Investigation of Biochemical Characteristics and Translocation
Authors: Shepherd Peter R , Gibbs E Michael , Wesslau Christian , Gould Gwyn W , Kahn Barbara B
Published: September 2013

A recent study by C.F. Burant et al. (13) demonstrates that GLUT5 is a high-affinity fructose transporter with a much lower capacity to transport glucose. To characterize the potential role of GLUT5 in fructose and glucose transport in insulin-sensitive tissues, we investigated the distribution and insulin-stimulated translocation of the GLUTS protein in human tissues by immunoblotting with an antibody to the COOH-terminus of the human GLUTS sequence. GLUTS was detected in postnuclear membranes from the small intestine, kidney, heart, four different skeletal muscle groups, and the brain, and in plasma membranes from adipocytes. Cytochalasin-B photolabeled a 53,000-Mr protein in small intestine membranes that was immunoprecipitated by the GLUT5 antibody; labeling was inhibited by D- but not L-glucose. N-glycanase treatment resulted in a band of 45,000 Mr in all tissues. Plasma membranes were prepared from isolated adipocytes from 5 nonobese and 4 obese subjects. Incubation of adipocytes from either group with 7 nM insulin did not recruit GLUT5 to the plasma membrane, in spite of a 54% insulin-stimulated increase in GLUT4 in nonobese subjects. Thus, GLUT5 appears to be a constitutive sugar transporter that is expressed in many tissues. Further studies are needed to define its overall contribution to fructose and glucose transport in insulin-responsive tissues and brain.
Mutated Insulin Receptor Val996 Reduces Insulin-Dependent Generation of Inositol Glycan and Diacylglycerol
Authors: Suzuki Susumu , Taneda Yoshinobu , Hirai Satoshi , Yamamoto-Honda Ritsuko , Toyota Takayoshi
Published: September 2013

We evaluated whether insulin-receptor tyrosine kinase activity is required for activation of PDH, insulin-induced hydrolysis of PIG and generation of IG and 1,2-DAG. For the analysis, we used stable-transfected CHO cell lines expressing wild-type human insulin receptor (CHO-wt cells) or the mutant receptor (Val996) that lacks tyrosine kinase activity (CHO-mut cells) (1,2). Insulin stimulated PDH activity in three CHO cell lines in a dose-dependent manner. Half-maximal concentrations of insulin to activate PDH was 7 × 10−11 M in the CHO-wt cells, 10−9 M in the parental cells, and 8 × 10−9 M in the CHO-mut cells. Insulin stimulated hydrolysis of PIG and generation of IG and DAG in three CHO cell lines in a dose-dependent manner. Half-maximal concentrations of insulin to induce generation of IG was 8 × 10−11 M in the CHO-wt cells, 109 M in the parental CHO cells, and 10−8 M in the CHO-mut cells. ED50 for the stimulation of DAG generation was 7 × 10−11 M in the CHO-wt cells, 10−9 M in the parental cells, and 10−8 M in the CHO-mut cells. It is concluded that insulin-dependent PDH activation, PIG hydrolysis, and IG and DAG generation are mediated by the wild-type but not by the mutated insulin receptor of Val996. This study suggests that tyrosine kinase activity of the insulin receptor might be a prerequisite for insulin-stimulated generation of IG and DAG.
Features of Insulin-Resistance Syndrome in Men From French Caribbean Islands: The Telecom Study
Authors: Fontbonne Annick , Papoz Laure , Eschwege Eveline , Roger Marc , Saint-Paul Michel , Simon Dominique
Published: September 2013

The prevalence of diabetes is known to be high in the West Indies, whereas CVD seems relatively rare. This apparently contradicts the existence of the insulin-resistance syndrome, a cluster of metabolic abnormalities supposedly favoring both diabetes and cardiovascular complications. To address the question of whether this contradiction could be accounted for by specific features of this syndrome, we compared 1505 Caucasian and 181 Afro-Caribbean men, all participants in the French Telecom Study. The Afro-Caribbeans were of the same age and had the same BMI as the Caucasians; they also had significantly higher subscapular skin-fold thickness and fasting insulin level, but similar BP and blood glucose level, and significantly lower plasma triglyceride level. Thus, although some features of the insulin-resistance syndrome were present (central adiposity and high insulin levels), none of the associated metabolic abnormalities were present. However, within the Afro-Caribbean group, subjects with plasma insulin concentrations above the median (>52 pM) had higher mean BP and glucose and triglyceride levels compared with subjects with insulin concentrations ≤52 pM (P < 0.001). After adjustment for age and BMI, these differences, though smaller, still were statistically significant. These findings confirm that higher insulin concentrations are associated with higher levels of potentially atherogenic and diabetogenic metabolic parameters. However, depending on ethnic origin, the mean levels of these parameters seem to be different, with the consequence that, even if they are elevated with increasing insulin levels, they may not reach values high enough to determine a substantial risk of disease.
Spontaneous Long-Term Hyperglycemic Rat With Diabetic Complications: Otsuka Long-Evans Tokushima Fatty (OLETF) Strain
Authors: Kawano Kazuya , Hirashima Tsukasa , Mori Shigehito , Saitoh Yuichi , Kurosumi Masao , Natori Takashi
Published: September 2013

A spontaneously diabetic rat with polyuria, polydipsia, and mild obesity was discovered in 1984 in an outbred colony of Long-Evans rats, which had been purchased from Charles River Canada (St. Constant, Quebec, Canada) in 1982. A strain of rats developed from this rat by selective breeding has since been maintained at the Tokushima Research Institute (Otsuka Pharmaceutical, Tokushima, Japan) and named OLETF. The characteristic features of OLETF rats are 1) late onset of hyperglycemia (after 18 wk of age); 2) a chronic course of disease; 3) mild obesity; 4) inheritance by males; 5) hyperplastic foci of pancreatic islets; and 6) renal complication (nodular lesions). Histologically, the changes of pancreatic islets can be classified into three stages: 7) an early stage (6–20 wk of age) of cellular infiltration and degeneration; 2) a hyperplastic stage (20–40 wk of age); and 3) a final stage (at >40 wk of age). These clinical and pathological features of disease in OLETF rats resemble those of human NIDDM.
Phosphoribosyl Pyrophosphate Formation in the Rat Adrenal Gland in Relation to Adrenal Growth in Experimental Diabetes
Authors: Kunjara Sirilaksana , Sochor Milena , Ahmed Salah , Greenbaum A Leslie , McLean Patricia
Published: September 2013

Adrenal growth occurs in experimental diabetes, and evidence exists for increased adrenal function. The concentration of PPRibP has been examined in the rat adrenal gland at various times after induction of diabetes with STZ, in view of the key role it plays in the synthesis of Purs and Pyrs. The PPRibP level was exceptionally high in the adrenal gland and increased faster than the rate of growth during the initial rapid growth phase—the first 7 days after STZ was given; PPRibP synthetase showed a parallel increase. Formation of R5P via the oxidative and nonoxidative segments of the PPP also was measured. The oxidative enzymes, G-6-PD and 6-PGD, increased in parallel with growth during the early phase, but showed a more marked rise during the secondary, slower, growth phase seen 6 wk after STZ was given, when this may be associated with the known sustained rise in plasma corticosteroids. The nonoxidative enzymes of the PPP, an alternate route for the production of pPPRibp, showed smaller changes. The specifically high adrenal concentration of PPRibP may be related to the high Km for PPRibP (250 μM) of the first enzyme of the de novo pathway of Pur synthesis, as such synthesis may be required in the rat to replace the net loss of ATP associated with catecholamine secretion. Factors controlling PPRibP synthetase and their potential relative importance in the adrenal gland have been considered.
Characterization of Glucose-Induced In Situ Protein Kinase C Activity in Cultured Vascular Smooth Muscle Cells
Authors: Williams Bryan , Schrier Robert W
Published: September 2013

The VSMC is an important target for the injurious effects of hyperglycemia in vivo. PKC plays a key role in the regulation of VSMC contraction and growth. This study examines whether elevated extracellular glucose concentrations (10–30 mM [180–540 mg/dl]) activate PKC in cultured rat VSMCs in vitro. A new, rapid, and highly specific assay was used to determine in situ PKC activity in digitonin-permeabilized VSMCs. PKC activity in VSMCs responded rapidly to variations in extracellular glucose concentrations. PKC was activated significantly within 10 min of exposure to D-glucose (20 mM) versus glucose (5 mM). Moreover, with continued exposure to D-glucose (20 mM), PKC activation was sustained for up to 48 h. Reducing D-glucose concentrations to 5 mM restored PKC activity to control values within 1 h. PKC activation was also glucose-concentration dependent. A threshold of only 15 mM (270 mg/dl) was required to significantly and maximally activate PKC in VSMC. PKC was not activated in the presence of osmotic control media that contained either elevated mannrtol or L-glucose concentrations. In marked contrast to the sustained PKC activation induced by D-glucose in VSMCs, the normal physiological PKC response to the pressor hormones, All and AVP, was short-lived and returned to base line within minutes. Sustained PKC activation in the presence of elevated D-glucose concentrations in vitro could disturb the normal physiological regulation of VSMC function and growth and thereby may contribute to the apparent vasotoxicity of hyperglycemia in vivo.
ECM Gene Expression and Its Modulation by Insulin in Diabetic Rats
Authors: Fukui Mitsumine , Nakamura Tsukasa , Ebihara Isao , Shirato Isao , Tomino Yasuhiko , Koide Hikaru
Published: September 2013

The steady-state levels of mRNA encoding for the α1(IV) collagen chain, laminin B1 and B2 chains, basement membrane HSPG, and α1(I) and a1(III) collagen chains were examined in rat glomeruli at 4, 12, and 24 wk after injection of STZ. The mRNA levels for the α1(IV) collagen chain, laminin B1 and B2 chains, and α1 (I) and α1(I) and α1(III) collagen chains increased significantly with age in the STZ-induced diabetic rats before morphological thickening of basement membrane occurred. In contrast, the mRNA levels for HSPG decreased markedly 4 wk after STZ injection and then increased with age compared with those for control rats. The mRNA levels for these ECM components showed a continuous decline with age in controls. Treating the diabetic rats with insulin for 4 wk ameliorated the abnormally regulated ECM gene expression in the glomeruli. These data suggest that the abnormal regulation of ECM gene expression in the glomeruli may contribute to the expansion of mesangial matrix and basement membrane thickening in diabetic rats, and that hyperglycemia may play a role in the abnormal ECM gene expression.
Role of Cytosolic Ca2+ in Impaired Sensitivity to Glucose of Rat Pancreatic Islets Exposed to High Glucose In Vitro
Authors: Okamoto Yoshimasa , Ishida Hitoshi , Taminato Tomohiko , Tsuji Kazuo , Kurose Takeshi , Tsuura Yoshiyuki , Kato Seika , Imura Hiroo , Seino Yutaka
Published: September 2013

Sustained exposure to high concentrations of glucose selectively impairs the ability of pancreatic islets to secrete insulin in acute glucose stimulation. In order to evaluate the interrelationship between impaired insulin secretion and the dynamics of the cytosolic free Ca2+ level ([Ca2+]i), we have investigated the effect of high glucose exposure on both [Ca2+]i dynamics in single rat β-cells and insulin release from rat pancreatic islets. Islets cultured at a high glucose concentration (16.7 mM) for 24 h showed significant reductions of the 16.7 mM GSIR compared with islets cultured at a normal glucose concentration (5.5 mM) (3.38 ± 0.24 vs. 4.26 ± 0.34%, respectively, P < 0.05). The capacity of glucose to raise the [Ca2+]i level also was significantly reduced in the β-cells maintained for 24 h at 16.7 mM glucose (P < 0.001). An additional culture in the medium with 5.5 mM glucose for 16 h restored both the GSIR and the [Ca2+]i response of islets cultured at high glucose. On the other hand, insulin release and [Ca2+]i rise in response to 20 mM L-Arg were well preserved. These observations confirm that exposure of pancreatic β-cells to high glucose concentrations induces a selective reduction of the GSIR and, further, shows that this impaired response is reversibly restored by an additional culture with normal glucose. We also suggest that the inability of glucose to provoke a [Ca2+]i rise, which is observed in the β-cells exposed to high glucose, may be responsible for the selective impairment of the GSIR.
The Metabolic Profile of NIDDM Is Fully Established in Glucose-Tolerant Offspring of Two Mexican-American NIDDM Parents
Authors: Gulli Giovanni , Ferrannini Eleuterio , Stern Michael , Haffner Steven , DeFronzo Ralph A
Published: September 2013

NIDDM patients with overt fasting hyperglycemia are characterized by multiple defects involving both Insulin secretion and insulin action. At this point of the natural history of NIDDM, however, it is difficult to establish which defects are primary and which are acquired secondary to insulinopenia and chronic hyperglycemia. To address this question, we have studied the glucose-tolerant offspring (probands) of two Mexican-American NIDDM parents. Such individuals are at high risk for developing NIDDM later in life. The probands are characterized by hyperinsulinemia in the fasting state and in response to both oral and Intravenous glucose. Insulin-mediated glucose disposal (insulin clamp technique), measured at two physiological levels of hyperinsulinemia (∼240 and 450 pM [∼40 and 75 μU/ml]), was reduced by 43 and 33%, respectively. During both the low- and high-dose insulin clamp steps, impaired nonoxidative glucose disposal, which primarily represents glycogen synthesis, was the major defect responsible for the Insulin resistance. During the lower dose insulin clamp step only, a small decrease in glucose oxidation was observed. No defect in suppression of HGP by insulin was demonstrable. The ability of insulin to inhibit lipid oxidation (measured by indirect calorimetry) and plasma FFA concentration was impaired at both levels of hyperinsulinemia. These results indicate that the glucose-tolerant offspring of two NIDDM parents are characterized by hyperinsulinemia and manifest all of the metabolic abnormalities that characterize the fully established diabetic state, including insulin resistance, a major impairment in nonoxidative glucose disposal, a quantitatively less important defect in glucose oxidation, and a diminished insulin-mediated suppression of lipid oxidation and plasma FFA concentration.
CD8 T Cells Are Not Required for Islet Destruction Induced by a CD4+ Islet-Specific T-Cell Clone
Authors: Bradley Brenda J , Haskins Kathryn , Rosa Francisco G La , Lafferty Kevin J
Published: September 2013

A panel of CD4+ T-cell clones has been isolated from the spleen and lymph nodes of diabetic NOD mice. These clones have been shown to be islet-specific both in vivo and in vitro. One of the clones, BDC-6.9, initiates extensive damage to islet tissue when placed adjacent to an NOD islet graft that has been used to reverse diabetes in (CBA × NOD)F1 recipients or when injected intraperitonealiy into such animals. In this study, we show that BDC-6.9 T cells can initiate islet destruction in the absence of detectable CD8 T cells either in the periphery or in the lesion that develops after the transfer of the cloned islet-reactive T cells.
Reinnervation of Syngeneic Mouse Pancreatic Islets Transplanted Into Renal Subcapsular Space
Authors: Korsgren Olle , Andersson Arne , Jansson Leif , Sundler Frank
Published: September 2013

A syngeneic transplantation of 150 islets into the subcapsular renal space was performed on normoglycemic or alloxan-induced diabetic male C57BL/6 mice. Six, 8, 14, or 20–21 wk after transplantation, the graft-bearing kidney was removed and processed for microscopical examinations with indirect immunofluorescence for neuropeptides and tyrosine hydroxylase, and with acetylcholinesterase staining to visualize nerve fibers within the graft. Six weeks after implantation, only a few scattered nerve fibers were observed within the grafts. A progressive increase in the number of nerves was observed until 14 wk after transplantation, after which, a stable level was reached. Alloxan-induced diabetic mice showed quantitatively and qualitatively similar reinnervation to normoglycemic mice 20 wk after transplantation. The findings demonstrate the presence of sympathetic nerve fibers (containing tyrosine hydroxylase and neuropeptide Y), mainly accompanying ingrowing blood vessels; parasympathetic nerve fibers (containing acetylcholinesterase and vasoactive intestinal peptide), possibly reaching the graft from the adjacent renal capsule; and afferent nerve fibers (containing substance P and calcitonin gene-related peptide), which were less numerous. The data suggest that transplanted islets become reinnervated by ingrowth of nerve fibers from the implantation organ and that several types of nerves are present.
Alterations in Cardiac Parasympathetic Indices in STZ-Induced Diabetic Rats
Authors: Lund Donald D , Subieta Alberto R , Pardini Benet J , Chang Kyoung SK
Published: September 2013

Autonomic neuropathy involving parasympathetic innervation is a complication of diabetes mellitus. Biochemical and morphological indices of the parasympathetic innervation of the heart were investigated in rats after diabetes mellitus was induced with streptozocin (STZ). Choline acetyltransferase (CAT) activity was used as a biochemical marker for parasympathetic innervation. Total CAT activity within the hearts of diabetic rats was unchanged after 1 and 2 wk of diabetes and was significantly reduced after 4, 8, and 12 wk. Morphological changes within the cardiac portion of the parasympathetic innervation were assessed at 8 wk when CAT activity was decreased. In diabetic rats, there was a reduction in both cardiac ganglion cell size and number. In contrast, in insulin-treated STZ-induced diabetic rats, ganglion cells were similar in size and number to those in a control group given 3-O-methylglucose to prevent induction of diabetes mellitus by STZ. Thus, diabetes mellitus is associated with alterations in cardiac parasympathetic innervation in rats, and supplemental insulin protects against these changes. These alterations may contribute to impaired parasympathetic neural control of the heart in diabetes mellitus.
Subcellular Localization of GLUT4 in Nonstimulated and Insulin-Stimulated Soleus Muscle of Rat
Authors: Bornemann Aantje , Ploug Thorkil , Schmalbruch Henning
Published: September 2013

Soleus muscles of fed rats were fixed by vascular perfusion with paraformaldehyde; individual fibers were teased and immunostained with a polyclonal antibody against the COOH-terminal of GLUT4. The binding sites were visualized by a horseradish peroxidase–coupled secondary antibody and diaminobenzidine. The fibers were embedded in epoxy resin and studied by electron microscopy. Strong immunoreactivity was found in subsarcolemmal clusters of vesicles and cisternae, Golgilike structures, and triadic junctions. Clusters of vesicles between myofibrils were occasionally stained. The plasma membrane was unlabeled. However, the plasma membrane was labeled when the rats had been injected with insulin (40 U/kg body wt) 15 min before perfusion fixation. In non–insulin-injected rats, the plasma membrane might show spotty staining close to clusters of intensely labeled subsarcolemmal vesicles. This may have been due to diffusion but may also indicate that there are domains of GLUT4 in the plasma membrane of nonstimulated fibers or that the endogenous insulin activity to some extent had translocated GLUT4 from the intracellular pool into the plasma membrane. Coated vesicles that were also labeled were found adjacent to subsarcolemmal vesicles and cisternae; it is possible that coated vesicles play a role during insulin- or contraction-induced translocation of GLUT4 between subsarcolemmal pool and plasma membrane. It has been proposed that glucose uptake into skeletal muscle fibers takes place across the t-tubule membrane rather than across the plasma membrane. This would explain the presence of GLUT4 at triadic junctions. Alternatively, we suggest that GLUT4 in t-tubules represents a second intracellular pool.
Tissue-Specific Regulation of Basic Fibroblast Growth Factor mRNA Levels by Diabetes
Authors: Karpen Charles W , Spanheimer Robert G , Randolph Anna L , Lowe William L
Published: September 2013

Because basic fibroblast growth factor (bFGF) is recognized as an angiogenic factor and diabetes is characterized by multiple vascular complications, including diabetic microangiopathy, we examined the regulation of tissue bFGF mRNA levels by diabetes. Diabetes was induced in male Sprague-Dawley rats by injection of 125 mg/kg body wt i.v. streptozocin (STZ), with intensive insulin therapy initiated in half of the diabetic rats. Rats were killed 96 h postinjection of STZ. Tissue bFGF and insulinlike growth factor I (IGF-I) mRNA levels were measured simultaneously with a solution hybridization–RNase protection assay. bFGF mRNA levels increased from 1.7- to 2.7-fold in eye, heart, lung, and brain from diabetic compared with buffer-injected control rats. In skeletal muscle, bFGF mRNA levels decreased to 23% of control levels, whereas bFGF mRNA levels were unchanged in kidneys from diabetic versus control rats. Changes in tissue bFGF mRNA levels were partially reversed by insulin treatment in all tissues. In contrast, IGF-I mRNA levels were significantly decreased from 15 to 50% of control levels in all tissues studied except those in brain, which decreased to only 85% of control levels. These data demonstrate that bFGF mRNA levels are altered by diabetes in a tissue-specific fashion and are consistent with the hypothesis that increased production of bFGF may contribute to the development of diabetic microangiopathy in some tissues.
Risk Factors for Coronary Heart Disease in Diabetic and Nondiabetic Native Americans: The Strong Heart Study
Authors: Howard Barbara V , Welty Thomas K , Fabsitz Richard R , Cowan Linda D , Oopik Arvo J , Le Ngoc-Anh , Yeh Jeunliang , Savage Peter J , Lee Elisa T
Published: September 2013

The Strong Heart Study is a study of cardiovascular disease and its risk factors among diabetic and nondiabetic Native Americans. The study includes 12 tribes in Arizona, Oklahoma, and North and South Dakota. Phase I, initiated in October 1988, included a mortality survey to determine CVD death rates in individuals 35–74 yr old between 1984 and 1988, and a medical record review to determine rates of myocardial infarction and stroke for individuals ages 45–74 during the same time. In addition, a physical examination was performed on persons 45–74 yr old to measure the prevalence of cardiovascular and peripheral vascular diseases and known and suspected risk factors, in Phase II, CVD mortality and morbidity rates will be determined in the examined cohort by surveillance. CVD risk factors, changes in risk factors over time, and the relationship between risk factors and CVD incidence will be assessed longitudinally. This study provides data on the relative importance of cardiovascular risk factors in nondiabetic and diabetic Native Americans and will provide insight into possible variations in the quantitative or qualitative importance of CVD risk factors among diverse population groups.
Lipoprotein Oxidation and Lipoprotein-lnduced Cell Injury in Diabetes
Authors: Chisolm Guy M , Irwin Kimberly C , Penn Marc S
Published: September 2013

There is ample evidence that oxidized lipoproteines exist in vivo, not only in atherosclerotic lesions, but also associated with some experimental models of diabetes. Whether the lipoprotein oxidation is an eplphenomenon of other atherogenic or diabetogenic agents or processes or whether it is causally related to lesion formation in atherosclerosis or other forms of tissue damage in people with diabetes is unresolved. Intense Interest in testing these ideas derives from in vitro observations of the ways in which oxidized lipoproteines interact with cells that are unlike the Interactions with native lipoproteins. Many of these altered Interactions suggest known features of atherosclerotic lesions, and recent data show that antioxidant treatment reduces the progression of vascular lesions. There are reasons to believe that hyperglycemia may worsen lipid and lipoprotein oxidation. If this observation is the case in vivo, and If it is ultimately proved that lipoprotein oxidation facilltates lesion development, these events may help explain the accelerated atherosclerosis suffered by diabetic patients. The multiple pathways for which there is evidence that hyperglycemia may contribute to oxldative events—for example, by enhancing free radical production in stimulated inflammatory cells or by forming glycation products that can propagate free radical events—suggest avenues for further research and may ultimately indicate points for intervention in the various manifestations of the disease.
Lipoprotein Glycation and Its Metabolic Consequences
Authors: Lyons Timothy J
Published: September 2013

In people with diabetes, glycation of apolipoproteins correlates with other indices of recent glycemic control, including HbA1. For several reasons, increased glycation of apolipoproteins may play a role in the accelerated development of atherosclerosis in diabetic patients. Recognition of glycated LDL by the classical LDL receptor is impaired, whereas its uptake by human monocyte-macrophages is enhanced. These alterations may contribute to hyperlipidemia and accelerated foam-cell formation, respectively. Glycation of LDL also enhances its capacity to stimulate platelet aggregation. The uptake of VLDL from diabetic patients by human monocytemacrophages is enhanced. This enhancement may be due, at least in part, to increased glycation of its lipoproteins. Glycation of HDL impairs its recognition by cells and reduces its effectiveness in reverse cholesterol transport. Glycation of apolipoproteins may also generate free radicals, increasing oxidative damage to the apolipoproteins themselves, the lipids in the particle core, and any neighboring macromolecules. This effect may be most significant in extravasated lipoproteins. In these, increased glycation promotes covalent binding to vascular structural proteins, and oxidative reactions may cause direct damage to the vessel wall. Glycoxidation, or browning, of sequestered lipoproteins may further enhance their atherogenicity. Finally, glycated or glycoxidized lipoproteins may be immunogenic, and lipoprotein-immune complexes are potent stimulators of foam-cell formation.
Immune Mechanisms of Atherosclerosis in Diabetes Mellitus
Authors: Lopes-Virella Maria F , Virella Gabriel
Published: September 2013

It was recently proposed that the increased levels of modified lipoproteins in diabetic patients may be responsible for the accelerated development of macrovascular complications associated with the disease. Modified lipoproteins are believed to induce the transformation of macrophages into foam cells and, in some cases, to induce endothelial cell damage. In addition, modified lipoproteins trigger an immune response leading to the formation of antibodies and then to the formation of LDL-containing immune complexes. In this review, we summarize the evidence linking LDL glycation and oxidation with intracellular accumulation of cholesterol esters and foam-cell formation, and we discuss their potential for inducing an autoimmune response and the formation of lipoprotein-containing immune complexes. The formation of LDL-ICs seems particularly significant, because these ICs are avidly taken up by macrophages through their Fc receptors and induce not only massive intracellular accumulation of CE but also a paradoxical increase in LDL-receptor expression. Our experimental data suggest that the uptake of LDL-IC is facilitated by RBC adsorption, in agreement with the role of RBC in the adsorption of circulating IC and their delivery to phagocytic cells. In addition, macrophages are activated when ingesting LDL-IC and release IL-1β and TNF-α, which can contribute to the initiation and progression of an atheromatous lesion by several mechanisms. Although it is difficult to envisage how LDL-IC could initiate an endothelial lesion, it is easy to speculate about their role as cofactors in the initiation and progression of the atherosclerotic process.
Chylomicron and Chylomicron Remnant Metabolism in STZ-Induced Diabetic Rats
Authors: Staprans Ilona , Pan Xian-Mang , Rapp Joseph H , Feingold Kenneth R
Published: September 2013

The small intestine is an important source of plasma lipoproteins in various diabetic animal models. This increase in intestinally derived lipids originate from diet and/or primary lipid synthesis, and these lipids are transported to the plasma as chylomicrons (CM).The understanding of the metabolism of these triglyceride-rich particles has assumed considerable importance. When [14C]cholesterol and [3H]triglyceridelabeled normal CM were injected into rats, we found no difference in either the initial plasma clearance or in the hepatic uptake between control and diabetic rats. However, the clearance rate and hepatic uptake were dependent on the triglyceride concentration administered. Both the initial clearance and hepatic uptake in control and diabetic rats slowed to a similar extent with increasing triglyceride dose demonstrating the influence of the size of the endogenous triglyceride pool on the metabolic rate of CM. No difference was found in the clearance of CM remnants between control and diabetic rats when examined both in vivo and in liver perfusion experiments. Furthermore, with affinity chromatography, we found that the increase in serum triglycerides levels in diabetic rats was due to triglyceride-rich very-low-density lipoproteins and/or CM and not to the accumulation of remnants, which supports the observation that remnant clearance is not impaired. Despite the absence of alterations in bulk CM metabolism, we observed an increase in CM–CM remnant binding to the endothelium in hearts of diabetic rats. Both the increased delivery to the liver and the increased binding of CM–CM remnants to endothelial surfaces could contribute to the increased risk of atherosclerosis in diabetes.