bluuebunny/crossref_metadata_2025 huggingface dataset:
Cardiac and Glycemic Benefits of Troglitazone Treatment in NIDDM
Authors: Ghazzi Mahmoud N , Perez Julio E , Antonucci Tammy K , Driscoll Joseph H , Huang Saling M , Faja Barbara W ,   The Troglitazone Study Group, Whitcomb Randall W
Published: September 2013

Troglitazone is a thiazolidinedione under development for the treatment of NIDDM and potentially other insulin-resistant disease states. Treatment with troglitazone is associated with an improvement in hyperglycemia, hyperinsulinemia, and insulin-mediated glucose disposal. No significant side effects have been observed in humans. Because of reported cardiac changes in animals treated with drugs of this class, this multicenter 48-week study was conducted to evaluate whether NIDDM patients treated with troglitazone develop any cardiac mass increase or functional impairment. A total of 154 NIDDM patients were randomized to receive troglitazone 800 mg q.d. or glyburide titrated to achieve glycemic control (≤20 mg b.i.d. or q.d.). Twodimensional echocardiography and pulsed Doppler were used to measure left ventricular mass index (LVMI), cardiac index (CI), and stroke volume index (SVI). All echocardiograms were performed at each center (baseline, 12, 24, 36, and 48 weeks), recorded on videotape, and forwarded to a blinded central echocardiographic interpreter for analysis. The results showed that LVMI of patients treated with troglitazone was not statistically or clinically different from baseline after 24 or 48 weeks. Statistically significant increases in SVI and CI and a statistically significant decrease in diastolic pressure and estimated peripheral resistance were observed in troglitazone-treated patients. These results were not sex-specific. Glycemic benefits of troglitazone treatment were observed as evidenced by long-term improvement of HbA1c and C-peptide levels. Furthermore, triglycerides were significantly lower, and HDL was significantly higher at weeks 24 and 48. In conclusion, NIDDM patients treated with troglitazone do not show any cardiac mass increase or cardiac function impairment. Conversely, patients on troglitazone benefited from enhanced cardiac output and stroke volume, possibly as a result of decreased peripheral resistance. Treatment with troglitazone appears to have a favorable impact on known cardiovascular risk factors and could potentially lower cardiovascular morbidity in NIDDM patients.
Muscle Rad Expression and Human Metabolism: Potential Role of the Novel Ras-Related GTPase in Energy Expenditure and Body Composition
Authors: Garvey W Timothy , Maianu Lidia , Kennedy Adele , Wallace Penny , Ganaway Elizabeth , Hamacher Lawrence L , Yarnall David P , Lenhard James M , Burns Daniel K
Published: September 2013

Ras associated with diabetes (Rad), a new ras-related GTPase, was recently identified by subtractive cloning as an mRNA in skeletal muscle that is overexpressed in NIDDM. To better understand its metabolic significance, we measured skeletal muscle Rad expression in well-characterized insulin sensitive (IS) and insulin resistant (IR) subjects with normal glucose tolerance and in untreated NIDDM patients. We found no differences in expression of Rad mRNA levels among IS, IR, and NIDDM groups using a ribonuclease protection assay (0.22 ± 0.06, 0.13 ± 0.01, and 0.16 ± 0.02 relative units, respectively; NS) and no differences in Rad protein expression using a specific anti-peptide Rad antibody (1.05 ± 0.18, 1.14 ± 0.08, and 1.08 ± 0.21 units/mg protein, respectively; NS). However, Rad protein levels were positively correlated with BMI (r = 0.43, P = 0.03) and percentage body fat (r = 0.55, P < 0.005), two independent measures of obesity, and negatively correlated with resting metabolic rate (r = 0.49, P = 0.01). In multiple regression analyses, percentage body fat and resting metabolic rate independently accounted for 30 and 10% of individual variability in muscle Rad protein expression. In conclusion, Rad expression in skeletal muscle is not altered as a function of insulin resistance or NIDDM in humans. However, these data, for the first time, implicate a role for Rad in regulating body composition and energy expenditure and provide a framework for studies designed to elucidate Rad's cellular functions.
Amino Acid Polymorphisms in the ATP-Regulatable Inward Rectifier Kir6.2 and Their Relationships to Glucose- and Tolbutamide-Induced Insulin Secretion, the Insulin Sensitivity Index, and NIDDM
Authors: Hansen Lars , Echwald Søren M , Hansen Torben , Urhammer Søren A , Clausen Jesper O , Pedersen Oluf
Published: September 2013

Kir6.2 is an inwardly rectifying potassium channel that is expressed in pancreatic (β-cells and cardiac and skeletal muscle. Expressed together with the highaffinity sulphonylurea receptor, it reconstitutes a sulphonylurea- and also ATP-sensitive potassium channel resembling the native (β-cell channel. The objective of this study was to search for mutations in the Kir6.2 gene that might be associated with NIDDM or related to altered insulin secretion, insulin action, or glucose metabolism in healthy subjects. Using polymerase chain reaction–single-strand conformation polymorphism analysis (PCR-SSCP) on genomic DNA from 69 Danish NIDDM patients and 66 matched control subjects, we report the finding of three missense polymorphisms in otherwise conserved codons and three silent polymorphisms in the gene encoding Kir6.2: codon 23 (GAG/AAG), Glu→Lys; codon 190 (GCT/GCC), Ala→Ala; codon 267 (CTC/CTG), Leu→Leu; codon 270 (CTG/GTG), Leu→Val; codon 337 (ATC/GTC), Ile→Val; codon 381 (AAG/AAA), Lys→Lys. The codon 23 and codon 337 amino acid polymorphisms were always coupled. The allelic frequencies of the polymorphisms were similar in NIDDM patients and control subjects. The amino acid polymorphisms were not associated with altered insulin secretion after intravenous glucose or tolbutamide injections or with altered glucose effectiveness in a phenotype study of 346 young healthy subjects. However, carriers of the maximal load of amino acid variants, the compound homozygous codon 23/337 and heterozygous codon 270, had on average a 62% higher insulin sensitivity index (P = 0.006), compared with noncarriers. We conclude that a combination of common Kir6.2 amino acid variants may contribute to the genetic background behind the large variation of the insulin sensitivity index in the general population.
Trehalose: A Cryoprotectant That Enhances Recovery and Preserves Function of Human Pancreatic Islets After Long-Term Storage
Authors: Beattie Gillian M , Crowe John H , Lopez Ana D , Cirulli Vincenzo , Ricordi Camillo , Hayek Alberto
Published: September 2013

The scarcity of available tissue for transplantation in diabetes and the need for multiple donors make it mandatory to use an optimal cryopreservation method that allows maximal recovery and preservation of β-cell function. We have developed a method to cryopreserve islets with excellent survival of endocrine cells. Current methods use DMSO as cryoprotectant. Our method involves introducing both DMSO and the disaccharide trehalose into the cells during cooling. Uptake and release of trehalose occurred during the thermotropic lipid-phase transition measured in pancreatic endocrine cells between 5° and 9°C, using [14C]trehalose. Recovery of adult islets after cryopreservation with 300 mmol/l trehalose was 92 vs. 58% using DMSO alone. In vitro function, in terms of insulin content and release in response to secretagogues, was indistinguishable from fresh islets. Grafts from islets cryopreserved with trehalose contained 14-fold more insulin than grafts from islets cryopreserved without trehalose. Results with human fetal islet-like cell clusters (ICCs) were more pronounced: recovery from cryopreservation was 94%, compared with 42% without trehalose. Complete functionality of fetal cells was also restored; tritiated thymidine incorporation and insulin content and release were similar to fresh tissue. After transplantation in nude mice, there was a 15-fold increase in insulin content of grafts from ICCs cryopreserved with trehalose compared with ICCs cryopreserved without trehalose. Thus, the addition of trehalose to cryopreservation protocols leads to previously unobtainable survival rates of human pancreatic endocrine tissue.
Protein Kinase A-Dependent Stimulation of Exocytosis in Mouse Pancreatic β-Cells by Glucose-Dependent Insulinotropic Polypeptide
Authors: Ding Wei-Guang , Gromada Jesper
Published: September 2013

The mechanisms by which glucose-dependent insulinotropic polypeptide (GIP) stimulates insulin secretion were investigated by measurements of whole-cell Ca2+ currents, the cytoplasmic Ca2+ concentration, and cell capacitance as an indicator of exocytosis in individual mouse pancreatic β-cells maintained in short-term culture. GIP produced a 4.2-fold potentiation of depolarization-induced exocytosis. This stimulation of exocytosis was not associated with a change in the whole-cell Ca2+-current, and there was only a small increase (30%) in the cytoplasmic Ca2+ concentration [intercellular free Ca2+([Ca2+]i)]. The stimulatory effect of GIP on exocytosis was blocked by pretreatment with the specific protein kinase A (PKA) inhibitor Rp-8-BrcAMPS. Glucagon-like peptide-I(7–36) amide (GLP-I) stimulated exocytosis (90%) in the presence of a maximal GIP concentration (100 nmol/1). Replacement of GLP-I with forskolin produced a similar stimulatory action on exocytosis. These effects of GLP-I and forskolin in the presence of GIP did not involve a change in the whole-cell Ca2+-current or [Ca2+]i. GIP was ineffective in the presence of both forskolin and the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX). Under the same experimental conditions, the protein kinase C (PKC)-activating phorbol ester 4-phorbol 12-myristate 13-acetate (PMA) stimulated exocytosis (60%). Collectively, our data indicate that the insulinotropic hormone GIP stimulates insulin secretion from pancreatic β-cells, through the cAMP/PKA signaling pathway, by interacting with the secretory machinery at a level distal to an elevation in [Ca2+]i.
Diagnostic Heterogeneity of Diabetes in Lean Young Adults: Classification Based on Immunological and Genetic Parameters
Authors: Dussoix Philippe , Vaxillaire Martine , Iynedjian Patrick B , Tiercy Jean-Marie , Ruiz Juan , Spinas Giatgen A , Berger Willy , Zahnd Gaston , Froguel Philippe , Philippe Jacques
Published: September 2013

The aim of our study was to investigate the relative prevalence of the different forms of diabetes in young adults and their respective clinical characteristics. Included were 51 nonobese patients (BMI < 27 kg/m2) with diabetes diagnosed before age 40, excluding typical IDDM. Each patient was subjected to screening for glucokinase gene (MODY2) and mitochondrial DNA (at nucleotide 3243) mutations, to HLA class II genotyping, and screening for the presence of islet cell antibodies (ICAs) and anti-GAD antibodies. Informative families were analyzed for linkage of diabetes to chromosome 12q (MODY3). Based on clinical criteria, patients were subdivided into MODY (n = 19) and non-MODY (n = 32). In the MODY group, we identified three patients with MODY2, one with the 3243 mitochondrial mutation, and another with autoimmune diabetes. One of the five MODY families available for linkage study was shown to have MODY3. In the non-MODY group, we found five patients with autoimmune diabetes and one with MODY2. No clinical parameter was helpful to classify patients in one of these subclasses of diabetes; however, the glucagon-stimulated C-peptide was useful to discriminate between MODY2 patients and the others. In conclusion, young and lean non-insulin-dependent diabetic patients constitute a very heterogeneous group, although they present similar clinical characteristics. The clinical distinction of MODY and non-MODY patients allows correct classification in, at most, 75% of the patients and thus is not sufficient to predict clinical course. However, immunological and genetic parameters allowed us to classify only 25% of the patients in specific diagnostic classes.
Hypertension as a Risk Factor for Diabetic Neuropathy: A Prospective Study
Authors: Forrest Kimberly Y-Z , Maser Raelene E , Pambianco Georgia , Becker Dorothy J , Orchard Trevor J
Published: September 2013

The pathogeneses of diabetic neuropathy is still unclear. This study prospectively investigated the risk factors for distal symmetrical polyneuropathy (DSP) in a cohort of childhood-onset IDDM patients. Subjects from the Epidemiology of Diabetes Complications (EDC) Study were clinically examined at baseline and then biennially. DSP was diagnosed by a combination of clinical criteria, symptoms and signs (Diabetes Control and Complications Trial [DCCT] exam), and quantitative sensory threshold (QST). Among the 463 (70.4%) subjects who were free of DSP at baseline, 453 (97.8%) participated in at least one biennial reexamination during the first 6 years of follow-up and were included in the current analysis. A total of 68 (15.0%) subjects developed DSP in 6 years, giving a cumulative probability of 0.29. The Cox proportional hazards model shows that longer IDDM duration, hypertension, poor glycemic control, height, and smoking were all independent predictors of the incidence of DSP (all P < 0.0001, except for smoking for which P = 0.03). Hypertension showed the greatest impact on the development of DSP for individuals with either short or long IDDM duration. This study confirms some risk factors for DSP found in crosssectional studies and suggests a strong relationship between hypertension and DSP. The results indicate that in addition to good glycemic control, avoidance of smoking and good blood pressure control may be helpful in preventing or delaying the onset of DSP in IDDM patients.
Nitric Oxide Inhibition of Transforming Growth Factor-β and Collagen Synthesis in Mesangial Cells
Authors: Craven Patricia A , Studer Rebecca K , Felder Jill , Phillips Stephen , DeRubertis Frederick R
Published: September 2013

Culture of mesangial cells (MCs) in 5.6 vs. 30.0 mmol/1 glucose for 3 weeks induced a sustained increase in protein kinase C (PKC) activity, transforming growth factor (TGF)-β1 mRNA, bioactive TGF-β, and collagen synthesis. Nitric oxide (NO), generated exogenously by the NO donor S-nitroso-N-acetyl, D,L-penicillamine (SNAP) or endogenously after the exposure of MC to interleukin-1β (IL-1β), suppressed bioactive TGF-β in MCs cultured in 5.6 or 30.0 mmol/1 glucose and suppressed or abolished increases in TGF-β1 mRNA and collagen synthesis induced by high concentrations of glucose or phorbol 12,13-dibutyrate without altering values obtained with normal glucose concentrations. SNAP had a transient suppressive effect on PKC activity, which may explain at least in part some of the actions of SNAP. The selective inhibitor of PKC, bisindolylmaleimide (GFX), mimicked NO action. The ability of SNAP and IL-lβ to suppress TGF-β and collagen synthesis was not mediated by cGMP, since the cGMP analog, 8-Br-PET-cGMP, did not mimic NO action and an antagonist of cGMP-dependent protein kinase, Rp-8-pCPT-cGMPs, did not prevent the inhibitory actions of SNAP. N-ω-L-arginine methyl ester (NMMA) increased TGF-β in glomerular capillary endothelial cells (GCECs) and stimulated collagen synthesis by MC in a co-culture with GCECs. Captopril inhibited TGF-β and collagen synthesis and increased cGMP in co-cultures of GCECs and MCs. These effects of captopril were abolished by NMMA, implying mediation by NO. Thus, endogenous NO produced by GCECs may modulate TGF-β production by both GCECs and MCs and act to suppress matrix protein synthesis by MCs.
Genetic Studies of the Sulfonylurea Receptor Gene Locus in NIDDM and in Morbid Obesity Among French Caucasians
Authors: Hani El Habib , Clément Karine , Velho Gilberto , Vionnet Nathalie , Hager Jörg , Philippi Anne , Dina Christian , Inoue Hiroshi , Permutt M Alan , Basdevant Arnaud , North Michael , Demenais Florence , Guy-Grand Bernard , Froguel Philippe
Published: September 2013

The sulfonylurea receptor (SUR) is a key component in glucose-stimulated insulin secretion. Obesity and NIDDM are frequently associated and share some metabolic abnormalities, suggesting that they might also share some susceptibility genes. Thus, the SUR encoding gene is a plausible candidate for a primary pancreatic β-cell defect and thus for hyperglycemia and weight gain. Through association and linkage studies, we have investigated the potential role of the SUR gene in families with NIDDM and in two independent sets of morbidly obese families. The exon 22 T-allele at codon 761 was more common in patients with NIDDM (7.7%) and morbid obesity (7.8%) than in control subjects (1.8%, P = 0.030 and P = 0.023, respectively). This variant was associated with morbid obesity (odds ratio 3.71, P = 0.017) and NIDDM (odds ratio 2.20, P = 0.04; association dependent on BMI). Although the frequencies for intron 24 variant were similar in all groups, morbidly obese patients homozygous for the c-allele had a more deleterious form of obesity. Sib-pair linkage studies with NIDDM in French Caucasian families gave no evidence for linkage to the SUR locus. However, in one set of the obese families, we found an indication for linkage with a SUR-linked microsatellite marker (D11S419, P = 0.0032). We conclude that in Caucasians, the SUR locus may contribute to the genetic susceptibility to NIDDM and obesity.
Predictors of Progression From Impaired Glucose Tolerance to NIDDM: An Analysis of Six Prospective Studies
Authors: Edelstein Sharon L , Knowler William C , Bain Raymond P , Andres Reubin , Barrett-Connor Elizabeth L , Dowse Gary K , Haffher Steven M , Pettitt David J , Sorkin John D , Muller Denis C , Collins Veronica R , Hamman Richard F
Published: September 2013

Risk factors associated with the progression from impaired glucose tolerance (IGT) to NIDDM were examined in data from six prospective studies. IGT and NIDDM were defined in all studies by World Health Organization (WHO) criteria, and baseline risk factors were measured at the time of first recognition of IGT. The studies varied in size from 177 to 693 participants with IGT, and included men and women followed from 2 to 27 years after the recognition of IGT. Across the six studies, the incidence rate of NIDDM was 57.2/1,000 person-years and ranged from 35.8/1,000 to 87.3/1,000 person-years. Although baseline measures of fasting and 2-h postchallenge glucose levels were both positively associated with NIDDM incidence, incidence rates were sharply higher for those in the top quartile of fasting plasma glucose levels, but increased linearly with increasing 2-h postchallenge glucose quartiles. Incidence rates were higher among the Hispanic, Mexican-American, Pima, and Nauruan populations than among Caucasians. The effect of baseline age on NIDDM incidence rates differed among the studies; the rates did not increase or rose only slightly with increasing baseline age in three of the studies and formed an inverted U in three studies. In all studies, estimates of obesity (including BMI, waist-to-hip ratio, and waist circumference) were positively associated with NIDDM incidence. BMI was associated with NIDDM incidence independently of fasting and 2-h post challenge glucose levels in the combined analysis of all six studies and in three cohorts separately, but not in the three studies with the highest NIDDM incidence rates. Sex and family history of diabetes were generally not related to NIDDM progression. This analysis indicates that persons with IGT are at high risk and that further refinement of risk can be made by other simple measurements. The ability to identify persons at high risk of NIDDM should facilitate clinical trials in diabetes prevention.
The Ala54Thr Polymorphism of the Fatty Acid Binding Protein 2 Gene Does Not Influence Insulin Sensitivity in Finnish Nondiabetic and NIDDM Subjects
Authors: Rissanen Johanna , Pihlajamäki Jussi , Heikkinen Sami , Kekäläinen Päivi , Kuusisto Johanna , Laakso Markku
Published: September 2013

Insulin resistance and hyperinsulinemia are major predictors of NIDDM. Since several studies have demonstrated that heredity plays a significant role in the development of insulin resistance (1), defects in genes that regulate insulin action could potentially contribute to the risk of NIDDM. A locus on chromosome 4q has been shown to be linked with fasting insulin levels (2), 2-h insulin levels (3,4), and insulin action (2) in Pima Indians and Mexican-Americans, suggesting that the fatty acid binding protein 2 (FABP2) gene is a promising candidate gene for insulin resistance and NIDDM.
Glucocorticoids as Counterregulatory Hormones of Leptin: Toward an Understanding of Leptin Resistance
Authors: Zakrzewska K E , Cusin I , Sainsbury A , Rohner-Jeanrenaud F , Jeanrenaud B
Published: September 2013

The product of the ob gene, leptin, is a hormone secreted by adipose tissue that acts in the hypothalamus to regulate the size of the body fat depot. Its central administration has been shown to decrease food intake and body weight, while favoring energy dissipation. As glucocorticoids are known to play a permissive role in the establishment and maintenance of obesity syndromes in rodents, it was hypothesized that they do so by restraining the effect of leptin. Leptin injected intracerebroventricularly as a bolus of 3 μg in normal rats induced modest reductions in body weight and food intake. In marked contrast, the same dose of leptin had very potent and long-lasting effects in decreasing both body weight and food intake when administered to adrenalectomized rats. Further, glucocorticoid supplementation of adrenalectomized rats dose-dependently inhibited these potent effects of leptin. These data suggest that glucocorticoids play a key inhibitory role in the action of leptin. Under normal conditions, this inhibitory influence of glucocorticoids may prevent lasting hypophagia. In obesity with degrees of hypercorticism, it may contribute to “leptin resistance,” whose etiology is still little understood.
Contribution of Autonomic Neuropathy to Reduced Plasma Adrenaline Responses to Hypoglycemia in IDDM: Evidence for a Nonselective Defect
Authors: Bottini Paolo , Boschetti Enrico , Pampanelli Simone , Ciofetta Marco , Sindaco Paola Del , Scionti Luciano , Brunetti Paolo , Bolli Geremia B
Published: September 2013

To determine the contribution of clinically overt diabetic autonomic neuropathy (DAN) to reduced plasma adrenaline responses to hypoglycemia in IDDM and to establish its selectivity for hypoglycemia, we studied 17 IDDM patients (7 without DAN [DAN−] and 10 with DAN [DAN+]), of whom 5 had and 5 did not have postural hypotension (DAN+PH+ and DAN+PH−, respectively), and 8 nondiabetic subjects on 2 different occasions, i.e., clamped hypoglycemia (steps from 5.0 to 2.2 mmol/l plasma glucose) and 30-min steady-state exercise at 55% VO2max. Recent antecedent hypoglycemia was meticulously prevented before the studies to exclude hypoglycemia as a cause of reduced responses of adrenaline to hypoglycemia. In DAN− patients, maximal responses of adrenaline to hypoglycemia were reduced (2.44 ± 0.58 nmol/l vs. 4.9 ± 0.54 nmol/l in nondiabetic patients) (P < 0.05). In DAN+, adrenaline responses initiated at a lower plasma glucose and were lower than in DAN− (DAN+PH−, 1.06 ± 0.38 nmol/l; DAN+PH+, 0.84 ± 0.27 nmol/l; P < 0.001, but NS between PH− and PH+). In response to exercise, adrenaline increased less in DAN− (0.89 ±0.11 nmol/l) patients than in nondiabetic subjects (1.19 ± 0.14 nmol/l; NS) and only to 0.36 ± 0.07 nmol/l in DAN+PH− and 0.23 ± 0.09 nmol/l in DAN+PH+ (P < 0.001 vs. DAN− and nondiabetic subjects). These results were confirmed when nondiabetic and DAN− subjects repeated the exercise at 60 watts (35 and 41% of Vo2max, respectively), i.e., at the same absolute workload of DAN+ patients. Thus, DAN (both PH+ and PH−) contributes to reduced responses of adrenaline to hypoglycemia independently of recent antecedent hypoglycemia. The adrenaline defect in DAN is not selective for hypoglycemia.
Effect of Insulin on Systemic and Renal Handling of Albumin in Nondiabetic and NIDDM Subjects
Authors: Catalano Carlo , Muscelli Elsa , Galvan Alfredo Quiñones , Baldi Simona , Masoni Antonio , Gibb Ian , Torffvit Ole , Seghieri Giuseppe , Ferrannini Ele
Published: September 2013

Insulin resistance and hyperinsulinemia cluster with microalbuminuria in both diabetic and nondiabetic subjects, but the mechanism underlying this association is unknown. To test the hypothesis that insulin influences protein permeability, we measured the albumin transcapillary escape rate (TER) by the 131I-labeled albumin technique in 12 healthy volunteers and 12 normoalbuminuric NIDDM patients (fasting plasma glucose, 10.9 ± 1.3 mmol/l) during 4 h of isoglycemia with high (1.1 mU · min−1 · kg−1) or, on a different day, low (0.1 mU · min−1 · kg−1) insulin infusion. In both patients and control subjects, high insulin was associated with a 7% decrease in blood volume (P = 6.006) and a 6% decrease in diastolic blood pressure (P < 0.02), these two changes being related to one another (r = 0.56, P < 0.01). Basal albumin TER was similar in patients (8.4 ± 0.5% · h−1) and control subjects (7.7 ± 0.7% · h−1) and was not significantly changed by high insulin in either group (patients vs. control subjects, 7.3 ± 0.9 vs. 6.2 ± 0.4% · h−1; NS vs. low insulin). In contrast, high insulin increased renal albumin excretion (from 3.6 ± 0.8 to 5.4 ± 1.1 μg/min, P < 0.01) and clearance rate (0.09 ± 0.02 to 0.13 ± 0.03 μl/min, P < 0.001) in patients but not in control subjects. To localize the effect of insulin along the nephron, we measured the urinary excretion of N-acetyl-β-D-glucosaminidase (β-NAG), released by the proximal tubule; retinol-binding protein (RBP), reabsorbed by the proximal tubule; and Tamm-Horsfall protein (THP) and epidermal growth factor (EGF), both secreted by the distal tubule. For both β-NAG and RBP, but not EGF or THP, insulin enhanced urinary excretion (diabetics vs. controls: β-NAG, 0.48 vs. −0.15 μU/min [P = 0.03]; RBP, 78 vs. −32 ng/min [P = 0.05]). In conclusion, physiological hyperinsulinemia does not affect systemic albumin permeability in healthy subjects or normoalbuminuric NIDDM patients. In contrast, in NIDDM patients, but not in healthy subjects, insulin increases the urinary excretion of albumin and protein markers of proximal tubular function. The significance of this finding for the pathogenesis of diabetic nephropathy remains to be established.
Leptin Is Present in Human Cord Blood
Authors: Sivan Eyal , Lin W Michael , Homko Carol J , Reece E Albert , Boden Guenther
Published: September 2013

It has recently been reported that the ob gene receptor was expressed on human and murine hematopoietic stem cells and that the ob gene product leptin stimulated hemato- and lymphopoiesis at the stem cell level. These findings suggest a role for leptin in hemato- and lymphopoiesis during fetal development. There is at present no evidence, however, that leptin is synthesized and released by the fetus. To investigate this possibility, we have measured plasma leptin concentrations in the cord blood of 78 newborn infants. We found that leptin was present in all 78 infants in concentrations comparable with those found in adults (0.6–55.7 ng/ml). Overall, plasma leptin concentrations in the cord blood of infants correlated with birth weight (r = 0.74, P < 0.001). These observations show that leptin is synthesized and released by fetal fat cells. In addition, they are compatible with the concept that leptin may play a role in human fetal hematopoiesis.
Increased Prevalence of Mitochondrial DNA Deletions in Skeletal Muscle of Older Individuals With Impaired Glucose Tolerance: Possible Marker of Glycemic Stress
Authors: Liang Ping , Hughes Virginia , Fukagawa Naomi K
Published: September 2013

To determine the relationship between mitochondrial DNA (mtDNA) mutations and age-related impaired glucose tolerance (IGT), mtDNA from skeletal muscle of 19 volunteers, ages 55–75 years, with either IGT or diabetes and 17 age- and sex-matched control subjects was analyzed using a long-extension polymerase chain reaction (PCR) combined with a quantitative PCR. We found the common 4,977-bp deletion in 84% of the IGT/diabetes group compared with only 41% in the control group (P < 0.02). Multiple other deletions of different sizes were identified in 13 out of 19 IGT/diabetes patients (68%) compared with 2 out of 17 control subjects (12%) (P < 0.002). Because of the heterogeneity and variation in the mutations identified, we propose that these mtDNA mutations were the result rather than the cause of IGT. The increase in type and frequency of mtDNA deletions in diabetes and IGT patients may be related to oxidative damage by oxygen free radicals. These may be produced in greater amounts as a result of hyperglycemia or may be more abundant because of an abnormality in the scavenging of free radicals by antioxidants.
Metabolic Defects in Lean Nondiabetic Offspring of NIDDM Parents: A Cross-Sectional Study
Authors: Perseghin Gianluca , Ghosh Soumitra , Gerow Karynn , Shulman Gerald I
Published: September 2013

First-degree relatives of NIDDM patients have an ∼40% lifetime risk of developing diabetes, and insulin resistance is the best predictor. However, insulin resistance is altered by many other factors, including age, diet, exercise, and medications. To investigate the metabolic and endocrine alterations associated with insulin resistance when all the above confounding factors are excluded, we examined the first phase of insulin secretion and insulin sensitivity in 49 white normoglycemic (4.99 ± 0.51 vs. 4.95 ± 0.41 mmol/l) nonexercising lean (BMI, 24 ± 3 vs. 23 ± 2 kg/m2; 105 ± 3 vs. 104 ± 3% of ideal body weight) offspring of NIDDM patients. These subjects were compared with 29 matched healthy control subjects by means of an intravenous glucose bolus (0.3 g/kg body wt), immediately followed by a euglycemic-hyperinsulinemic (∼420 μmol/l) clamp, along with lipid and amino acid profiles. The offspring showed fasting hyperinsulinemia (40.6 ± 15.8 vs. 30.9 ± 13.6 μmol/l; P = 0.005) and higher free fatty acid (FFA) levels (582 ± 189 vs. 470 ± 140 μmol/l; P = 0.007), whereas triglycerides, total cholesterol, and HDL and LDL cholesterol levels were comparable with those of control subjects. Alanine (320 ± 70 vs. 361 ± 73 μmol/l; P = 0.017), serine (P = 0.05), and glutamine and glycine (P = 0.02) were lower in the offspring than in the control subjects, whereas branched-chain amino acids (343 ± 54 vs. 357 ± 54 μmol/l; P = 0.28) were not different. Insulin sensitivity was lower (4.86 ± 1.65 vs. 6.17 ± 1.56 mg · kg−1 · min−1; P = 0.001), and an inverse correlation with fasting FFAs in the offspring (adjusted R2 = 0.21, P = 0.0005), but not in control subjects (adjusted R2 = 0.03, P = 0.368), was found. Because insulin sensitivity in the offspring appeared to be a mixture of three distributions, they were subdivided into three subgroups: very low, low, and normal insulin sensitivity (20, 47, and 33%, respectively). The same alterations in amino acid and FFA metabolism were observed in the very low and low subgroups but not in the normal subgroup. The first phase of insulin secretion appeared to compensate significantly for insulin resistance in the low subgroup versus the normal subgroup and controls, but was inappropriately low in the subgroup with very low insulin sensitivity considering its degree of insulin resistance. In conclusion, lean insulin-resistant offspring of NIDDM parents showed 1) trimodal distribution of insulin sensitivity, 2) high fasting plasma FFA concentrations, 3) an inverse correlation between insulin sensitivity and FFA concentration, 4) low plasma gluconeogenic amino acid concentrations, and 5) defective insulin secretion when related to insulin sensitivity in the subgroup of very resistant offspring. These results suggest that, in this white population, insulin sensitivity may be determined by a single major gene and that alterations in FFA metabolism may play a role in the pathogenesis of NIDDM.
Evidence of Increased Systemic Glucose Production and Gluconeogenesis in an Early Stage of NIDDM
Authors: Perriello Gabriele , Pampanelli Simone , Del Sindaco Paola , Lalli Carlo , Ciofetta Marco , Volpi Elena , Santeusanio Fausto , Brunetti Paolo , Bolli Geremia B
Published: September 2013

To assess the mechanisms of fasting hyperglycemia in NIDDM patients with mild elevation of fasting plasma glucose (FPG) compared with NIDDM patients with overt hyperglycemia, we studied 29 patients with NIDDM, who were divided in two groups according to their fasting plasma glucose (<7.8 and ≥7.8 mmol/l for groups A and B, respectively), and 16 control subjects who were matched with NIDDM patients for age, sex, and body mass index. All subjects were infused with ]3-3H]glucose between 10:00 P.M. and 10:00 A.M. during overnight fasting to determine glucose fluxes. In 27 subjects (17 diabetic and 10 control), ]U-14C]alanine was simultaneously infused between 4:00 A.M. and 10:00 A.M. to measure gluconeogenesis (GNG) from alanine. Arterialized- venous plasma samples were collected every 30 min for measurement of glucose fluxes, GNG, and glucoregulatory hormones. In group A, plasma glucose, rate of systemic glucose production (SGP), and GNG were greater than in control subjects (7.2 ± 0.2 vs. 4.9 ± 0.1 mmol/l, 10.9 ± 0.2 vs. 9.5 ± 0.3 μmol · kg−1 · min−1, and 0.58 ± 0.04 vs. 0.37 ± 0.02 μmol · kg−1 · min−1, respectively, for group A and control subjects; mean value 8:00 A.M.-10:00 A.M., all P < 0.05). Both increased SGP and GNG correlated with plasma glucose in all subjects (r = 0.77 and r = 0.75, respectively, P < 0.005). Plasma counterregulatory hormones did not differ in NIDDM patients compared to control subjects. The present studies demonstrate that SGP and GNG are increased in NIDDM patients without overt fasting hyperglycemia.Thus these metabolic abnormalities primarily contribute to early development of overnight and fasting hyperglycemia in NIDDM.
D-Glucose Stimulates Mesangial Cell GLUT1 Expression and Basal and IGF-I–Sensitive Glucose Uptake in Rat Mesangial Cells: Implications for Diabetic Nephropathy
Authors: Heilig Charles W , Liu Yanan , England Rebecca L , Freytag Svend O , Gilbert Jeffery D , Heilig Kathleen O , Zhu Min , Concepcion Luis A , Brosius Frank C
Published: September 2013

The complications of diabetes arise in part from abnormally high cellular glucose uptake and metabolism. To determine whether altered glucose transporter expression may be involved in the pathogenesis of diabetic nephropathy, we investigated the effects of elevated extracellular glucose concentrations on facilitative glucose transporter (GLUT) expression in rat mesangial cells. GLUT1 was the only transporter isoform detected. Cells exposed to 20 mmol/1 glucose medium for 3 days demonstrated increases in GLUT1 mRNA (134%, P < 0.002), GLUT1 protein (68%, P < 0.02), and Vmax (50%, P < 0.05) for uptake of the glucose analog ]3H]2-deoxyglucose (3H2-DOG), when compared to cells chronically adapted to physiologic glucose concentrations (8 mmol/1). The increase in GLUT1 protein was sustained at 3 months, the latest time point tested (77% above control, P < 0.01). In contrast, hypertonic mannitol had no effect on GLUT1 protein levels. Insulin-like growth factor I (IGF-I; 30 ng/ml) increased the uptake of 3H2-DOG by 28% in 8 mmol/1 glucose-treated cells (P < 0.05) and by 75% in cells switched to 20 mmol/1 glucose for 3 days (P < 0.005). These increases in 3H2-DOG uptake occurred despite a lack of effect of IGF-I on GLUT1 protein levels (P > 0.5 vs. control). Therefore, hyperglycemia and IGF-I treatment both lead to increases in mesangial cell glucose uptake, and hyperglycemia induces increased GLUT1 expression, which can directly lead to the pathological changes of diabetic nephropathy. The effects of high glucose and of IGF-I to stimulate 3H2-DOG uptake also appear to be additive.
Vitamin E Decreases the Occurrence of Malformations in the Offspring of Diabetic Rats
Authors: Simán C Martin , Eriksson Ulf J
Published: September 2013

An association between excess oxygen radical activity and disturbed embryogenesis in diabetic pregnancy has been suggested. In the present study, the protective capacity of vitamin E with different treatment regimens was investigated in early and late pregnancy of streptozotocin-induced diabetic rats. Daily gavaging of 0.2 g/kg or 0.8 g/kg of vitamin E exerted moderate protective effects. In contrast, treatment with a diet enriched with 2% (wt/wt) of vitamin E, yielding an approximate daily dosage of 2 g/kg of vitamin E, clearly restored both embryonic and fetal morphology. Highperformance liquid chromatography measurement showed that maternal diabetes decreased embryonic content of vitamin E. When pregnant diabetic animals were supplemented with vitamin E, increased concentrations of the vitamin were found in maternal, embryonic, and fetal tissues. Thus, despite marked accumulation of vitamin E in maternal tissues, the compound apparently reached the conceptus. Thiobarbituric acid reactive substances (TBARS) were estimated as a measure of lipid peroxidation, and no changes were observed in maternal tissue, embryonic tissue, placenta, and fetal brain in the untreated diabetic group. In contrast, a fivefold increase of TBARS was found in fetal liver, a rise that was reduced with vitamin E treatment of the diabetic pregnant rats and completely normalized with 2% vitamin E in the diet. Congenital malformations caused by experimental diabetes can be prevented by antioxidants in vivo. These findings further corroborate the notion that an imbalance in the metabolism of free oxygen radicals is involved in the embryonic maldevelopment of diabetic pregnancy, and suggest a direction for prophylactic treatment in the future.
B-Cells Are Required for the Initiation of Insulitis and Sialitis in Nonobese Diabetic Mice
Authors: Noorchashm Hooman , Noorchashm Negin , Kern Joshua , Rostami Susan Y , Barker Clyde F , Naji Ali
Published: September 2013

Nonobese diabetic (NOD) mice spontaneously develop an acute onset of hyperglycemia reminiscent of human type I diabetes. The disease is the end result of a mononuclear cell infiltration of pancreatic islets (insulitis), culminating in the selective destruction of islet β-Cells by autoreactive T-cells. NOD mice also exhibit defects in B-cell tolerance as manifested by the presence of autoantibodies against islet cell autoantigens. Based on the potential ability of B-cells to act as antigen presenting cells, we hypothesized that autoreactive B-cells of NOD mice may be necessary for the activation of islet reactive CD4+ T-cells. In the present study, we utilized an anti–μ antibody to induce in vivo depletion of B-cells and found that B-cell depletion completely abrogates the development of insulitis and sialitis in NOD mice. In contrast, control IgG-treated NOD mice developed insulitis and sialitis by 5 weeks of age. Additionally, the discontinuation of anti–μ chain antibody treatment led to the full restoration of the B-cellpool and the reappearance of insulitis and sialitis. Thus, we conclude that B-cells are a requisite cell population for the genesis of the inflammatory lesions of the islets of Langerhans. This finding suggests that autoreactive B-cells may act as the antigen presenting cells necessary for the initial activation of β-cell-reactive CD4+ T-cells implicated in the pathogenesis of autoimmune diabetes.
Islet Capillary Blood Pressure Increase Mediated by Hyperglycemia in NIDDM GK Rats
Authors: Carlsson Per-Ola , Jansson Leif , Östenson Claes-Gören , Källskog Örjan
Published: September 2013

This study was performed to measure pancreatic islet capillary pressure under basal conditions and after an acute glucose stimulation of insulin release in normal rats. In addition, the islet capillary pressure was estimated in GK rats, an animal model of NIDDM. Hydrostatic pressure in single pancreatic islet capillaries was determined in vivo by direct measurement using the micropuncture technique. The pancreatic islets were visualized by injection of neutral red. This intravital staining had no effect on islet function, whole pancreatic and islet blood flow, and capillary blood pressure in the exocrine pancreas. Islet capillary blood pressure in normoglycemic Wistar F rats was estimated at 3.1 ± 0.3 mmHg (n = 15). Administration of D-glucose (1g/kg) doubled this value, whereas no effect was seen after injection of an equimolar dose of the non-metabolizable glucose-derivative 3-O-methyl glucose. In GK rats, basal islet capillary blood pressure was increased (5.7 ± 0.4 mmHg; n = 10; P < 0.001) when compared with the control Wistar F rats. Reduction of blood glucose levels in GK rats with phlorizin treatment showed this increased basal islet capillary pressure in GK rats to be glucose dependent and reversible. In the present study, we have for the first time shown that both acute and chronic hyperglycemia augment islet capillary pressure. The effects of a chronically increased islet capillary pressure on long-term islet function remain to be determined.
Fatty Acids Mediate the Acute Extrahepatic Effects of Insulin on Hepatic Glucose Production in Humans
Authors: Lewis Gary F , Vranic Mladen , Harley Patricia , Giacca Adria
Published: September 2013

We have shown previously in humans that insulin partly suppresses hepatic glucose production (HGP) by an extrahepatic (indirect) mechanism. In the present study, we investigated the role of free fatty acids (FFAs) in mediating the extrahepatic effects of insulin in humans and determined the extent to which insulin can regulate HGP by a non–FFA-mediated effect. Sixteen healthy men received an intravenous tolbutamide infusion for 3 h, and pancreatic insulin secretion was calculated by deconvolution of peripheral C-peptide levels. On a subsequent occasion, equimolar exogenous insulin was infused by peripheral vein. In both studies, glucose was clamped at euglycemia. We have previously validated this method and shown no independent insulin-like activity of tolbutamide. During the clamp, 9 of the 16 subjects received a low dose of heparin and Intralipid to prevent the insulin-induced suppression of FFAs, while 7 subjects received a high dose of heparin and Intralipid to raise FFAs ∼2.5-fold. In both the highand low-dose groups, peripheral insulin was higher and calculated portal insulin lower with peripheral versus portal insulin delivery. In the low-dose group, HGP decreased by 68.3 ±2.1% with portal insulin delivery and 64.7 ± 3.7% with peripheral insulin delivery (NS). In the high-dose group, HGP decreased by 58.0 ± 4.5% with portal insulin and 48.3 ± 5.0% with peripheral insulin (P < 0.05). Four individuals who participated in the high-dose group underwent an additional peripheral insulin study in which the same dose of exogenous insulin was infused as in the high-dose group but in the absence of heparin and Intralipid. During this latter study, FFA levels declined by ∼90% during hyperinsulinemia, and HGP was suppressed by 71.8 ± 5.6%, which was a much greater suppression (P < 0.01) than when FFA levels were raised in these subjects during the equivalent rate insulin infusion. In summary, the previously observed greater suppression of HGP with equimolar peripheral versus portal insulin is eliminated or reversed, depending on plasma FFA levels, if FFAs are prevented from decreasing, suggesting an important role of FFAs in mediating the extrahepatic effects of insulin on HGP. However, the effect of FFA clamping is relatively small with a significant degree of suppression of HGP (by ∼50%), which remains evenwhen FFAs are elevated above basal levels, suggesting that in the physiological range FFAs only partially influence the suppression of HGP in humans. This suggests that other mechanisms, most likely hepatic, dominate the acute insulin-induced suppression of glucose production.
Long-Term Effect of Lisinopril and Atenolol on Kidney Function in Hypertensive NIDDM Subjects With Diabetic Nephropathy
Authors: Nielsen Flemming S , Rossing Peter , Gall Mari-Anne , Skøtt Peter , Smidt Ulla M , Parving Hans-Henrik
Published: September 2013

The aim of our study was to evaluate whether inhibition of ACE (lisinopril 10–20 mg/day) can reduce the rate of decline in kidney function more than reducing blood pressure with conventional antihypertensive treatment (atenolol 50–100 mg/day), usually in combination with a diuretic. We performed a prospective, randomized, parallel study for 42 months, double blind for the first 12 months and single blind thereafter. Forty-three (21 lisinopril and 22 atenolol) hypertensive NIDDM patients with diabetic nephropathy were enrolled. Data from 36 patients (17 lisinopril and 19 atenolol, 60 ± 7 years of age, 27 men) who completed at least 12 months of the study period are presented. At baseline, the two groups were comparable: glomerular filtration rate (51Cr-EDTA plasma clearance) was 75 ± 6 and 74 ± 8 ml · min−1 · 1.73 m−2, mean 24-h ambulatory blood pressure (A&D TM2420) was 110 ± 3 and 114 ± 2 mmHg, and 24-h urinary albumin excretion rate was 961 (range 331–5,727) and 1,578 (476–5,806) mg/24 h in the lisinopril and atenolol groups, respectively. The mean follow-up time was similar, 37 and 35 months in the lisinopril and atenolol groups, respectively. Mean ambulatory blood pressure was equally reduced in the two groups, 12 ± 2 and 10 ± 2 mmHg in the lisinopril and atenolol groups, respectively. Glomerular filtration rate declined in a biphasic manner with a faster initial (0 to 6 months) change of 1.25 ± 0.49 and 0.81 ± 0.29 ml · min−1 · month−1 followed by a slower sustained decline (6 to 42 months) of 0.59 ± 0.10 and 0.54 ± 0.13 ml · min−1 · month−1 in the lisinopril and atenolol groups, respectively. No significant differences were observed in either initial or sustained decline in glomerular filtration rate between the two groups. Urinary albumin excretion was reduced (% reduction of baseline) more in the lisinopril than in the atenolol group, at 55 (95% CI 29–72) and 15% (−13 to 34), respectively (P = 0.01). In conclusion, the relentless decline in kidney function characteristically found in hypertensive NIDDM patients with diabetic nephropathy can be reduced equally effectively by two antihypertensive treatments, the β-blocker atenolol and the ACE inhibitor lisinopril.
Evidence for a Novel Peripheral Action of Leptin as a Metabolic Signal to the Adrenal Gland: Leptin Inhibits Cortisol Release Directly
Authors: Bornstein Stefan R , Uhlmann Katja , Haidan Andrea , Ehrhart-Bornstein Monika , Scherbaum Werner A
Published: September 2013

The crucial role of glucocorticoids in obesity and insulin resistance and the actions of the OB protein leptin on the hypothalamic-pituitary-adrenal (HPA) axis suggest that there is an important interaction of leptin with the glucocorticoid system. Therefore, we designed a study to test the effect of leptin directly on adrenocortical steroidogenesis. Primary cultures of bovine adrenocortical cells were incubated with increasing concentrations (10–1,000 ng/ml) of recombinant mouse leptin for 24 h, and the effects of leptin on basal and ACTH-stimulated cortisol secretion were determined. The accumulation of P450 17α mRNA following incubation with ACTH (10 nmol/1) and leptin (10–1,000 ng/ml) was analyzed by Northern blot. Adrenocortical cells were characterized by immunohistochemical staining for 17α-hydroxyprogesterone. Leptin (10–1,000 ng/ml) inhibited basal and ACTHstimulated cortisol release. At a concentration that occurs in obese individuals in vivo (100 ng/ml), it reduced basal cortisol secretion to 52.7 ± 37% (mean ± SE). The rise in cortisol secretion following maximal ACTH stimulation (10 nmol/1) was blunted to 55.2 ± 27%. At more physiological concentrations of ACTH (0.1 nmol/1), the inhibition of cortisol release by coincubation with low doses of leptin (10 ng/ml) was even more pronounced, leading to a reduction to 32.8% (1,248 ± 134 vs. 410 ± 157 nmol/1). Addition of OB protein (10–1,000 ng/ml) led to a dose-dependent reduction of ACTH-stimulated cytochrome P450 17α mRNA accumulation (from 80 to 45%), suggesting that leptin regulates adrenal steroidogenesis at the transcriptional level. These data clearly demonstrate that leptin inhibits cortisol production in adrenocortical cells and therefore appears to be a metabolic signal that directly acts on the adrenal gland.