bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Trial of N-Acetyl-Cysteine, Taurine, and Oxerutin on Skin and Kidney Damage in Long-Term Experimental Diabetes
Authors: Odetti Patrizio , Pesce Carlo , Traverso Nicola , Menini Stefano , Maineri Elena Pesce , Cosso Luana , Valentini Sabina , Patriarca Stefania , Cottalasso Damiano , Marinari Umberto M. , Pronzato Maria Adelaide
Published: March 2007

This study analyzes the effect of chronic treatment with different antioxidants (N-acetyl-cysteine [NAC], taurine, a combination of NAC and taurine, and oxerutin) on long-term experimental diabetes induced by streptozotocin in rats. Glycoxidative damage was evaluated in the skin; glomerular structural changes were studied with morphometry and immunohistochemistry. Oxerutin treatment and the combined NAC plus taurine treatment resulted in reduced accumulation of collagen-linked fluorescence in skin in comparison with untreated diabetic rats. All treatments except taurine reduced glomerular accumulation of Nε-(carboxymethyl)lysine and protected against the increase in glomerular volume typical of diabetes; furthermore, the apoptosis rate was significantly decreased and the glomerular cell density was better preserved. Glycoxidative markers in the skin turned out to be good indicators of the glomerular condition. The findings that emerged from our study support the hypothesis that glomerular damage in diabetes can be prevented or at least attenuated by supplementation with specific antioxidants. Treatment with oxerutin and combined treatment with NAC plus taurine gave the most encouraging results, whereas the results of taurine-only treatment were either negligible or negative and therefore suggest caution in the use of this molecule in single-drug treatment courses.
The E23K Variant of Kir6.2 Associates With Impaired Post-OGTT Serum Insulin Response and Increased Risk of Type 2 Diabetes
Authors: Nielsen Eva-Maria D. , Hansen Lars , Carstensen Bendix , Echwald Søren M. , Drivsholm Thomas , Glümer Charlotte , Thorsteinsson Birger , Borch-Johnsen Knut , Hansen Torben , Pedersen Oluf
Published: March 2007

The E23K polymorphism of the pancreatic β-cell ATP-sensitive K+ (KATP) channel subunit Kir6.2 (KCNJ11) is associated with type 2 diabetes in whites, and a recent in vitro study of the E23K variant suggests that the association to diabetes might be explained by a slight inhibition of serum insulin release. In a study comprising 519 unrelated glucose-tolerant subjects, we addressed the question as to whether the E23K variant was related to reduced serum insulin release during an oral glucose tolerance test (OGTT). Furthermore, the polymorphism was examined in a case-control study comprising 803 type 2 diabetic patients and 862 glucose-tolerant control subjects. The E23K variant was associated with significant reductions in the insulinogenic index (P = 0.022) and serum insulin levels under the response curve during an OGTT (0–120 min) (P = 0.014) as well as with an increase in BMI (P = 0.013). In the present study, the association of the E23K polymorphism with type 2 diabetes was not significant (P = 0.26). However, the K23K genotype significantly associated with type 2 diabetes in a meta-analysis of white case and control subjects (n = 2,824, odds ratio [OR] 1.49, P = 0.00022). In conclusion, the widespread E23K polymorphism may have a diabetogenic effect by impairing glucose-induced insulin release and increasing BMI.
Disruption of the Striated Muscle Glycogen Targeting Subunit PPP1R3A of Protein Phosphatase 1 Leads to Increased Weight Gain, Fat Deposition, and Development of Insulin Resistance
Authors: Delibegovic Mirela , Armstrong Christopher G. , Dobbie Lorraine , Watt Peter W. , Smith Andrew J.H. , Cohen Patricia T.W.
Published: March 2007

Disruption of the PPP1R3A gene encoding the glycogen targeting subunit (GM/RGL) of protein phosphatase 1 (PP1) causes substantial lowering of the glycogen synthase activity and a 10-fold decrease in the glycogen levels in skeletal muscle. Homozygous GM−/− mice show increased weight gain after 3 months of age and become obese, weighing ∼20% more than their wild-type (WT) littermates after 12 months of age. Glucose tolerance is impaired in 11-month-old GM−/− mice, and their skeletal muscle is insulin-resistant at ≥12 months of age. The massive abdominal and other fat depositions observed at this age are likely to be a consequence of impaired blood glucose utilization in skeletal muscle. PP1-GM activity, assayed after specific immunoadsorption, was absent from GM−/− mice and stimulated in the hind limb muscles of WT mice by intravenous infusion of insulin. PP1-R5/PTG, another glycogen targeted form of PP1, was not significantly stimulated by insulin in the skeletal muscle of WT mice but showed compensatory stimulation by insulin in GM−/− mice. Our results suggest that dysfunction of PP1-GM may contribute to the pathophysiology of human type 2 diabetes.
Enhanced Basal Activation of Mitogen-Activated Protein Kinases in Adipocytes From Type 2 Diabetes
Authors: Carlson Christian J. , Koterski Sandra , Sciotti Richard J. , Poccard German Braillard , Rondinone Cristina M.
Published: March 2007

Serine and threonine kinases may contribute to insulin resistance and the development of type 2 diabetes. To test the potential for members of the mitogen-activated protein (MAP) kinase family to contribute to type 2 diabetes, we examined basal and insulin-stimulated Erk 1/2, JNK, and p38 phosphorylation in adipocytes isolated from healthy and type 2 diabetic individuals. Maximal insulin stimulation increased the phosphorylation of Erk 1/2 and JNK in healthy control subjects but not type 2 diabetic patients. Insulin stimulation did not increase p38 phosphorylation in either healthy control subjects or type 2 diabetic patients. In type 2 diabetic adipocytes, the basal phosphorylation status of these MAP kinases was significantly elevated and was associated with decreased IRS-1 and GLUT4 in these fat cells. To determine whether MAP kinases were involved in the downregulation of IRS-1 and GLUT4 protein levels, selective inhibitors were used to inhibit these MAP kinases in 3T3-L1 adipocytes treated chronically with insulin. Inhibition of Erk 1/2, JNK, or p38 had no effect on insulin-stimulated reduction of IRS-1 protein levels. However, inhibition of the p38 pathway prevented the insulin-stimulated decrease in GLUT4 protein levels. In summary, type 2 diabetes is associated with an increased basal activation of the MAP kinase family. Furthermore, upregulation of the p38 pathway might contribute to the loss of GLUT4 expression observed in adipose tissue from type 2 diabetic patients.
Local Lactate Perfusion of the Ventromedial Hypothalamus Suppresses Hypoglycemic Counterregulation
Authors: Borg Monica A. , Tamborlane William V. , Shulman Gerald I. , Sherwin Robert S.
Published: March 2007

We have previously reported that a glucosensor integrating hormonal responses to hypoglycemia is located in the ventromedial hypothalamus (VMH) and that local VMH glucose perfusion blocks counterregulatory hormone responses. To determine whether the by-product of glucose metabolism, lactate, can function within the VMH as an alternative for glucose, we delivered lactate locally to the VMH, during systemic hypoglycemia. For this purpose, we combined bilateral VMH microdialysis perfusion (metabolically active l-lactate or its nonmetabolizable d-isomer) with a euglycemic-hypoglycemic clamp in conscious chronically catheterized Sprague-Dawley rats. Local VMH perfusion with l-lactate decreased counterregulatory hormone responses to hypoglycemia by 80–85% as compared with the nonmetabolizable d-lactate control. Moreover, hormonal suppression with l-lactate was accompanied by an approximate fourfold increase in the amount of exogenous glucose infused to maintain a stable hypoglycemic plateau (P < 0.05). In conclusion, the glucose-sensing mechanism in the VMH responds to lactate and, thus, is not specific for glucose. This implies that the VMH may act as a fuel sensor rather than as a glucose sensor.
Modulation of Circulating and Adipose Tissue Adiponectin Levels by Antidiabetic Therapy
Authors: Phillips Susan A. , Ciaraldi Theodore P. , Kong Alice P.S. , Bandukwala Rahil , Aroda Vanita , Carter Leslie , Baxi Sunita , Mudaliar Sunder R. , Henry Robert R.
Published: March 2007

The relationship between insulin action and control of the adipocyte-derived factor adiponectin was studied in age- and weight-matched obese individuals with type 2 diabetes failing sulfonylurea therapy. After initial metabolic characterization, subjects were randomized to troglitazone or metformin treatment groups; all subjects received glyburide (10 mg BID) as well. Treatment was continued for 3 months. The extent of glycemic control after treatment was similar in both groups. However, the increase in maximal insulin-stimulated glucose disposal rate was greater following troglitazone therapy (+44%) compared with metformin treatment (+20%). Troglitazone treatment increased serum adiponectin levels nearly threefold. There was no change in serum adiponectin with metformin treatment. A positive correlation was found between increases in whole-body glucose disposal rates and serum adiponectin levels after troglitazone; no such relationship was seen with metformin. The adiponectin protein content of subcutaneous abdominal adipocytes was increased following troglitazone treatment and unchanged after metformin. Adiponectin release from adipocytes was also augmented with troglitazone treatment. Adiponectin was present in adipocytes and plasma in several multimeric forms; a trimer was the major form secreted from adipocytes. These results indicate that increases in adiponectin content and secretion are associated with improved insulin action but are not directly related to glycemic control. Modulation of adipocyte function, including upregulation of adiponectin synthesis and secretion, may be an important mechanism by which thiazolidinediones influence insulin action.
Effects of Identical Weight Loss on Body Composition and Features of Insulin Resistance in Obese Women With High and Low Liver Fat Content
Authors: Tiikkainen Mirja , Bergholm Robert , Vehkavaara Satu , Rissanen Aila , Häkkinen Anna-Maija , Tamminen Marjo , Teramo Kari , Yki-Järvinen Hannele
Published: March 2007

Our objective was to determine how 8% weight loss influences subcutaneous, intra-abdominal, and liver fat (LFAT), as well as features of insulin resistance, in obese women with high versus low LFAT. A total of 23 women with previous gestational diabetes were divided into groups of high (9.4 ± 1.4%) and low (3.3 ± 0.4%) LFAT based on their median LFAT (5%) measured with proton spectroscopy. Both groups were similar with respect to age, BMI, and intra-abdominal and subcutaneous fat. Before weight loss, women with high LFAT had higher fasting serum insulin and triglyceride concentrations than women with low LFAT. At baseline, LFAT correlated with the percent of fat (r = 0.44, P < 0.05) and saturated fat (r = 0.45, P < 0.05) of total caloric intake but not intra-abdominal or subcutaneous fat or fasting serum free fatty acids. Weight loss was similar between the groups (high LFAT −7.4 ± 0.2 vs. low LFAT −7.7 ± 0.3 kg). LFAT decreased from 9.4 ± 1.4 to 4.8 ± 0.7% (P < 0.001) in women with high LFAT and from 3.3 ± 0.4 to 2.0 ± 0.2% (P < 0.001) in women with low LFAT. The absolute decrease in LFAT was significantly higher in women with high than low LFAT (−4.6 ± 1.0 vs. −1.3 ± 0.3%, P < 0.005). The decrease in LFAT was closely correlated with baseline LFAT (r = −0.85, P < 0.001) but not with changes in the volumes of intra-abdominal or subcutaneous fat depots, which decreased similarly in both groups. LFAT appears to be related to the amount of fat in the diet rather than the size of endogenous fat depots in obese women. Women with initially high LFAT lost more LFAT by similar weight loss than those with low LFAT, although both groups lost similar amounts of subcutaneous and intra-abdominal fat. These data suggest that LFAT is regulated by factors other than intra-abdominal and subcutaneous fat. Therefore, LFAT does not appear to simply reflect the size of endogenous fat stores.
Role of H1-Calponin in Pancreatic AR42J Cell Differentiation Into Insulin-Producing Cells
Authors: Morioka Tomoaki , Koyama Hidenori , Yamamura Hisako , Tanaka Shinji , Fukumoto Shinya , Emoto Masanori , Mizuguchi Hiroyuki , Hayakawa Takao , Kojima Itaru , Takahashi Katsuhito , Nishizawa Yoshiki
Published: March 2007

Basic or h1-calponin is a smooth muscle–specific, actin-binding protein that is involved in the regulation of smooth muscle contractile activity. We found in this study the expression of mRNA and protein for h1-calponin in AR42J-B13 cells, which is a useful model for investigating islet β-cell differentiation from pancreatic common precursor cells. Following treatment of AR42J cells with activin A and hepatocyte growth factor, the protein levels of h1-calponin decreased in a time-dependent manner during the course of the cell differentiation. When h1-calponin was continuously overexpressed by utilizing recombinant adenovirus-mediated gene transfer, the percentage of cell differentiation in h1-calponin overexpressing cells was markedly suppressed as compared with that in the cells without overexpression (6.7 ± 2.5 vs. 28.6 ± 3.2%, P < 0.001, Student’s t test). Finally, overexpression of h1-calponin (65.6 ± 3.4), or that lacking actin-binding domain (55.9 ± 3.4%), significantly (P < 0.001) suppressed the activin A–stimulated transcriptional activity of activin responsive element (ARE), whereas calponin homology-domain disruption mutant did not (100.6 ± 1.9%). These results suggest that regulation of h1-calponin is involved in the regulation of differentiation of AR42J cells into insulin-producing cells at least partly through modulating ARE transcriptional activity.
Enhanced Recombinant Adeno-Associated Virus-Mediated Vascular Endothelial Growth Factor Expression in the Adult Mouse Retina
Authors: Rakoczy P. Elizabeth , Brankov Meliha , Fonceca Angela , Zaknich Tammy , Rae Ben C. , Lai Chooi-May
Published: March 2007

Diabetic retinopathy, one of the most serious complications of long-term diabetes, could clinically be divided into two stages: 1) background retinopathy that does not cause visual impairment and 2) proliferative retinopathy, which is a potentially blinding condition. This study aims to investigate the correlation between enhancement of vascular endothelial growth factor (VEGF) expression and neovascular changes. A binary recombinant adeno-associated virus construct producing green fluorescent protein (GFP) and VEGF under the control of the human cytomegalovirus promoter, recombinant adeno-associated virus (rAAV).VEGF.GFP, was produced and injected into the subretinal space of C57BL mice. GFP expression was tracked by fluorescence fundus photography, and VEGF expression was confirmed by immunohistochemistry and enzyme-linked immunoassay. Neovascular changes were monitored by fluorescein angiography and histology and by quantifying the number of inner retinal vessels. GFP expression was found in 100% of injected eyes, and vascular changes were detected in 9 of 10 rAAV.VEGF.GFP-injected eyes. Of these, four demonstrated microaneurysms and five showed moderate to severe leakage. There was a statistically significant increase in blood vessel number in the inner nuclear layer (P < 0.03) and dilatation of retinal veins (P ≤ 0.05). This work has demonstrated that the development of different stages of diabetic retinopathy is closely correlated with an increased VEGF level in the retina.
Semicarbazide-Sensitive Amine Oxidase/Vascular Adhesion Protein-1 Activity Exerts an Antidiabetic Action in Goto-Kakizaki Rats
Authors: Abella Anna , Marti Luc , Camps Marta , Claret Marc , Fernández-Alvarez J. , Gomis Ramon , Gumà Anna , Viguerie Nathalie , Carpéné Christian , Palacín Manuel , Testar Xavier , Zorzano Antonio
Published: March 2007

In this study we have explored whether the bifunctional protein semicarbazide-sensitive amine oxidase (SSAO)/vascular adhesion protein-1 (VAP-1) represents a novel target for type 2 diabetes. To this end, Goto-Kakizaki (GK) diabetic rats were treated with the SSAO substrate benzylamine and with low ineffective doses of vanadate previously shown to have antidiabetic effects in streptozotocin-induced diabetic rats. The administration of benzylamine in combination with vanadate in type 2 diabetic rats acutely stimulated glucose tolerance, and the chronic treatment normalized hyperglycemia, stimulated glucose transport in adipocytes, and reversed muscle insulin resistance. Acute in vivo administration of benzylamine and vanadate stimulated skeletal muscle glucose transport, an effect that was also observed in incubated muscle preparations coincubated with adipose tissue explants or with human recombinant SSAO. Acute administration of benzylamine/vanadate also ameliorated insulin secretion in diabetic GK rats, and this effect was also observed in incubated pancreatic islets. In keeping with these observations, we also demonstrate that pancreatic islets express SSAO/VAP-1. As far as mechanisms of action, we have found that benzylamine/vanadate causes enhanced tyrosine phosphorylation of proteins and reduced protein tyrosine phosphatase activity in adipocytes. In addition, incubation of human recombinant SSAO, benzylamine, and vanadate generates peroxovanadium compounds in vitro. Based on these data, we propose that benzylamine/vanadate administration generates peroxovanadium locally in pancreatic islets, which stimulates insulin secretion and also produces peroxovanadium in adipose tissue, activating glucose metabolism in adipocytes and in neighboring muscle. This opens the possibility of using the SSAO/VAP-1 activity as a local generator of protein tyrosine phosphatase inhibitors in antidiabetic therapy.
Diabetes Can Alter the Signal Transduction Pathways in the Lens of Rats
Authors: Zatechka D. Steven , Kador Peter F. , Garcia-Castiñeiras Sixto , Lou Marjorie F.
Published: March 2007

Diabetes is known to affect cataract formation by means of osmotic stress induced by activated aldose reductase in the sorbitol pathway. In addition, alterations in the bioavailability of numerous extralenticular growth factors has been reported and shown to result in various consequences. We have found that the basic fibroblast growth factor (bFGF) accumulates in the vitreous humor of 3- and 8-week diabetic rats. Consequently, the associating signal transduction cascades were severely disrupted, including upregulated phosphorylation of extracellular signal-regulated kinase (ERK) and the common stress-associated mitogen-activated protein kinases p38 and SAPK/JNK. Conversely, under diabetic condition, we observed a dramatic inhibition of phosphatidylinositol-3 kinase activity in lenses obtained from the same animal. Rats treated with the aldose reductase inhibitor AL01576 for the duration of the diabetic condition showed that the diabetes-induced lenticular signaling alterations were normalized, comparable to controls. However, treatment of AL01576 in vitro was ineffective at normalizing the altered constituents in extracted diabetic vitreous after the onset of diabetes. The effect of AL01576 in the high galactose-induced cataract model in vitro was also examined. Administration of AL01576 to lens organ culture normalized the aberrant signaling effects and morphological characteristics associated with in vitro sugar cataract formation. In conclusion, our findings demonstrate diabetes-associated alterations in the lens signal transduction parameters and the effectiveness of AL01576 at normalizing such alterations. The causes for these alterations can be attributed to elevated vitreal bFGF in conjunction with osmotic stress and associated attenuation in redox status of the lens.
Nephrin Expression Is Reduced in Human Diabetic Nephropathy
Authors: Doublier Sophie , Salvidio Gennaro , Lupia Enrico , Ruotsalainen Vesa , Verzola Daniela , Deferrari Giacomo , Camussi Giovanni
Published: March 2007

We studied the distribution of nephrin in renal biopsies from 17 patients with diabetes and nephrotic syndrome (7 type 1 and 10 type 2 diabetes), 6 patients with diabetes and microalbuminuria (1 type 1 and 5 type 2 diabetes), and 10 normal subjects. Nephrin expression was semiquantitatively evaluated by measuring immunofluorescence intensity by digital image analysis. We found an extensive reduction of nephrin staining in both type 1 (67 ± 9%; P < 0.001) and type 2 (65 ± 10%; P < 0.001) diabetic patients with diabetes and nephrotic syndrome when compared with control subjects. The pattern of staining shifted from punctate/linear distribution to granular. In patients with microalbuminuria, the staining pattern of nephrin also showed granular distribution and reduction intensity of 69% in the patient with type 1 diabetes and of 62 ± 4% (P < 0.001) in the patients with type 2 diabetes. In vitro studies on human cultured podocytes demonstrated that glycated albumin and angiotensin II reduced nephrin expression. Glycated albumin inhibited nephrin synthesis through the engagement of receptor for advanced glycation end products, whereas angiotensin II acted on cytoskeleton redistribution, inducing the shedding of nephrin. This study indicates that the alteration in nephrin expression is an early event in proteinuric patients with diabetes and suggests that glycated albumin and angiotensin II contribute to nephrin downregulation.
Is Podocyte Injury Relevant in Diabetic Nephropathy?
Authors: Dalla Vestra Michele , Masiero Alessandra , Roiter Anna Maria , Saller Alois , Crepaldi Gaetano , Fioretto Paola
Published: March 2007

Podocyte structural changes have been suggested to be involved in the pathogenesis of albuminuria in diabetes. We evaluated podocytes density, number, and structure in 67 white patients with type 2 diabetes: 21 normoalbuminuric (NA), 23 microalbuminuric (MA), and 23 proteinuric (P). Kidney function and biopsy studies were performed; 20 kidney donors served as control subjects. Electron microscopic morphometric analysis was used to estimate numerical density of podocytes per glomerulus [Nv(epi/glom)], filtration slit length density per glomerulus (FSLv/glom), and foot process width (FPW). The number of podocytes per glomerulus (Epi N/glom) was obtained by multiplying Nv(epi/glom) by mean glomerular volume. Nv(epi/glom) was significantly decreased in all type 2 diabetic groups compared with control subjects and was lower in MA and P than in NA (P < 0.0001, ANOVA). Epi N/glom was lower in MA and P patients compared with control subjects (P < 0.002, ANOVA); however, there were no significant differences among the type 2 diabetic groups. In addition, MA and P had decreased FSLv/glom and increased FPW compared with NA (P < 0.005 for both, ANOVA). The albumin excretion rate was inversely related to Nv(epi/glom) and FSLv/glom and directly to FPW (P < 0.0005 for all), whereas there was no correlation with Epi N/glom. In conclusion, changes in podocyte structure and density occur since the early stages of diabetic nephropathy and might contribute to increasing albuminuria in type 2 diabetic patients. These findings also suggest that in white type 2 diabetic patients, the density of podocytes may be functionally more relevant than the absolute number.
Evaluation of Autofluorescent Property of Hemoglobin-Advanced Glycation End Product as a Long-Term Glycemic Index of Diabetes
Authors: Gopalkrishnapillai Bijukumar , Nadanathangam Vigneshwaran , Karmakar Nivedita , Anand Sneh , Misra Anoop
Published: March 2007

Current methods for measuring long-term glycemia in patients with diabetes are HbA1c and advanced glycation end products (AGEs), which are estimated by phenyl boronate affinity chromatography and competitive enzyme-linked immunosorbent assay, respectively. In this study, we hypothesize that the intrinsic fluorescence property of hemoglobin-AGE (Hb-AGE) may be a simple, accurate, and therefore better index for long-term glycemic status due to its highly specific nature and longer half-life. To establish this contention, in vitro and in vivo experiments were carried out. The former was performed by incubating commercially available hemoglobin with 5 and 20 mmol/l glucose and the latter through experimentally induced (streptozotocin) diabetes in an animal model (male Wistar rats) to identify the new fluorophore formed due to the nonenzymatic glycosylation of hemoglobin. An adduct exhibiting fluorescence at 308/345 nm of excitation/emission wavelengths has been identified and its time-dependent formation established. Under in vitro conditions, the first appearance of the new fluorophore was noticed only after a period of 2 months, whereas under in vivo conditions, it increased significantly after 2 months of hyperglycemia. Consistent with the observations, studies on patients with type 2 diabetes demonstrated an elevated level of this new fluorescent adduct in patients with persisting high levels of plasma glucose for >2 months. Based on the results obtained, Hb-AGE appears to be an efficient fluorescence-based biosensing molecule for the long-term monitoring of glycemic control in diabetes.
Differential Activation Mechanisms of Erk-1/2 and p70S6K by Glucose in Pancreatic β-Cells
Authors: Briaud Isabelle , Lingohr Melissa K. , Dickson Lorna M. , Wrede Christian E. , Rhodes Christopher J.
Published: March 2007

Glucose can activate the mitogen-activated kinases, Erk-1/2, and the ribosomal-S6 kinase, p70S6K, in β-cells, contributing to an increase in mitogenesis. However, the signaling mechanism by which glucose induces Erk-1/2 and p70S6K phosphorylation activation is undefined. Increased glucose metabolism increases [Ca2+]i and [cAMP], and it was investigated if these secondary signals were linked to glucose-induced Erk-1/2 and p70S6K activation in pancreatic β-cells. Blocking Ca2+ influx with verapamil, or inhibiting protein kinase A (PKA) with H89, prevented glucose-induced Erk-1/2 phosphorylation. Increasing cAMP levels by GLP-1 potentiated glucose-induced Erk-1/2 phosphorylation via PKA activation. Elevation of [Ca2+]i by glyburide potentiated Erk-1/2 phosphorylation, which was also inhibited by H89, suggesting increased [Ca2+]i preceded PKA for glucose-induced Erk-1/2 activation. Adenoviral-mediated expression of dominant negative Ras in INS-1 cells decreased IGF-1-induced Erk-1/2 phosphorylation but had no effect on that by glucose. Collectively, our study indicates that a glucose-induced rise in [Ca2+]i leads to cAMP-induced activation of PKA that acts downstream of Ras and upstream of the MAP/Erk kinase, MEK, to mediate Erk-1/2 phosphorylation via phosphorylation activation of Raf-1. In contrast, glucose-induced p70S6K activation, in the same β-cells, was mediated by a distinct signaling pathway independent of Ca2+/cAMP, most likely via mTOR-kinase acting as an “ATP-sensor.”
Restoration of Euglycemia and Normal Acute Insulin Response to Glucose in Obese Subjects With Type 2 Diabetes Following Bariatric Surgery
Authors: Polyzogopoulou Eftihia V. , Kalfarentzos Fotios , Vagenakis Apostolos G. , Alexandrides Theodore K.
Published: March 2007

Insulin resistance and loss of glucose-stimulated acute insulin response (AIR) are the two major and earliest defects in the course of type 2 diabetes. We investigated whether weight loss after bariatric surgery in patients with morbid obesity and type 2 diabetes could restore euglycemia and normal AIR to an intravenous glucose tolerance test (IVGTT). We studied 25 morbidly obese patients—12 with type 2 diabetes, 5 with impaired glucose tolerance, and 8 with normal glucose tolerance (NGT)—before and after a biliopancreatic diversion (BPD) with Roux-en-Y gastric bypass (RYGBP). Twelve individuals with normal BMI served as control subjects. Twelve months after surgery, in the diabetes group, BMI decreased from 53.2 ± 2.0 to 29.2 ± 1.7 kg/m2, fasting glucose decreased from 9.5 ± 0.83 to 4.5 ± 0.13 mmol/l, and fasting insulin decreased from 168.4 ± 25.9 to 37.7 ± 4.4 pmol/l (mean ± SE; P < 0.001). AIR, the mean of insulin concentration at 2, 3, and 5 min over basal in the IVGTT, increased by 770 and 935% at 3 and 12 months after surgery, respectively (from 24.0 ± 22.7 to 209 ± 43.4 and 248 ± 33.1 pmol/l, respectively; P < 0,001). Conversely, in the NGT group, the AIR decreased by 40.5% (from 660 ± 60 to 393 ± 93 pmol/l; P = 0.027) 12 months after surgery. BPD with RYGBP performed in morbidly obese patients with type 2 diabetes leads to significant weight loss, euglycemia, and normal insulin sensitivity; but most importantly, it restores a normal β-cell AIR to glucose and a normal relationship of AIR to insulin sensitivity. This is the first study to demonstrate that the lost glucose-induced AIR in patients with type 2 diabetes of mild or moderate severity is a reversible abnormality.
Adenovirus Early Region 3 Antiapoptotic 10.4K, 14.5K, and 14.7K Genes Decrease the Incidence of Autoimmune Diabetes in NOD Mice
Authors: Pierce Melissa A. , Chapman Harold D. , Post Cristina M. , Svetlanov Anton , Efrat Shimon , Horwitz Marshall , Serreze David V.
Published: March 2007

Genes in the early region 3 (E3) of the adenovirus genome allow the virus to evade host immune responses by interfering with major histocompatibility (MHC) class I-mediated antigen presentation and tumor necrosis factor-α (TNF-α)- or Fas-induced apoptosis of infected cells. Autoimmune type 1 diabetes (T1D) is inhibited in NOD mice transgenically expressing all E3 genes under control of a rat insulin promoter (RIPE3/NOD). For dissecting the protective mechanisms afforded by various E3 genes, they were subdivided into RIP-driven transgene constructs. Strong T1D protection mediated at the β-cell level characterized DL704/NOD mice lacking the E3 gp19K gene suppressing MHC class I expression but retaining the 10.4K, 14.5K, and 14.7K genes inhibiting Fas- or TNF-α-induced apoptosis and TNF-α-induced NF-kB activation. Much weaker protection characterized DL309/NOD mice expressing the gp19K but not the 10.4K, 14.5K, and 14.7K genes. While RIPE3/NOD splenocytes had an unexpected decrease in ability to adoptively transfer T1D, splenocytes from both the DL704 and DL309 stocks efficiently did so. These findings indicate that all E3 genes must be expressed to inhibit the diabetogenic potential of NOD immune cells. They also demonstrate that the antiapoptotic E3 genes most effectively protect pancreatic β-cells from diabetogenic immune responses.
Analysis of Insulin-Producing Cells During In Vitro Differentiation From Feeder-Free Embryonic Stem Cells
Authors: Moritoh Yusuke , Yamato Eiji , Yasui Yumiko , Miyazaki Satsuki , Miyazaki Jun-ichi
Published: March 2007

Embryonic stem (ES) cells can differentiate into many cell types and are expected to be useful for tissue engineering. Recent reports have shown that ES cells can differentiate into insulin-producing cells in response to the transient expression of the pdx-1 gene, after the removal of feeder cells. To investigate the lineage of insulin-producing cells and their in vitro differentiation, we introduced the βgeo gene, encoding a β-galactosidase-neomycin phosphotransferase fusion protein under the control of the mouse insulin 2 promoter, into ES cells that had been adapted to feeder-free culture, and analyzed insulin gene expression during their in vitro differentiation. We also examined the expression of transcription factors that are related to the differentiation of the pancreas. X-gal staining analysis revealed β-galactosidase-positive cells on the surface and in the center of the embryoid body that proliferated during differentiation. Glucose-responsive insulin-producing cells, derived from our feeder-free ES cells, expressed insulin 2, pdx-1, Pax4, and Isl1 and also the glucagon, somatostatin, and PP genes. Moreover, the genes encoding p48, amylase, and carboxypeptidase A were also expressed. These results suggest that ES cells can differentiate not only into endocrine cells but also into exocrine cells of the pancreas, without the initiation of pdx-1 expression.
Intra-Islet Somatostatin Regulates Glucagon Release via Type 2 Somatostatin Receptors in Rats
Authors: Cejvan Kenan , Coy David H. , Efendic Suad
Published: March 2007

Exogenously administered somatostatin (SST) inhibits secretion of insulin and glucagon. Furthermore, it is hypothesized that islet SST regulates glucagon secretion by a local action. A number of studies utilizing SST antibodies have been performed to test this hypothesis, and their results have been conflicting. Five subtypes of SST receptor (SSTR1–5) mediate the effect of SST on target cells. In rodents, SST inhibits the release of glucagon, but not that of insulin, via SSTR2. A novel SSTR2-selective antagonist, DC-41-33, was synthesized recently. We have investigated the effects of this antagonist on arginine-stimulated glucagon and insulin release in batch incubations of isolated rat islets, perifused isolated rat islets, and isolated perfused rat pancreas. In batch incubations at 3.3 mmol/l glucose, DC-41-33 increased glucagon release in a dose-dependent manner. At the maximum dose tested (2 μmol/l), DC-41-33 enhanced the glucagon response by 4.3- to 5-fold. Similarly, this compound increased arginine-induced glucagon release in perifused islets at 3.3 mmol/l glucose (2.8-fold) and perfused pancreas at 3.3 and 5.5 mmol/l glucose (2.5- and 2.3-fold, respectively). In the two latter experimental systems, DC-41-33 had no significant effect on insulin release. In conclusion, our results strongly support the hypothesis that islet SST inhibits glucagon secretion via a local action.
Circulating Adiponectin Levels Are Reduced in Nonobese but Insulin-Resistant First-Degree Relatives of Type 2 Diabetic Patients
Authors: Pellmé F. , Smith U. , Funahashi T. , Matsuzawa Y. , Brekke H. , Wiklund O. , Taskinen M.-R. , Jansson P.-A.
Published: March 2007

Adiponectin, one of the most abundant gene transcript proteins in human fat cells, has been shown to improve insulin action and is also suggested to exert antiatherogenic effects. We measured circulating adiponectin levels and risk factors for atherosclerosis in 45 healthy first-degree relatives of type 2 diabetic subjects (FDR) as well as 40 healthy control subjects (CON) without a known family history of diabetes. Insulin sensitivity (Si) was studied with the minimal model, and measurements of adiponectin, metabolic variables, inflammatory markers, and endothelial injury markers, as well as lipoprotein concentrations, were performed. FDR were insulin resistant (3.3 ± 2.4 vs. 4.5 ± 2.6 × 10−4 × min−1 per μU/ml [mean ± SD], P < 0.01), and their circulating plasma adiponectin levels (6.6 ± 1.8 vs. 8.1 ± 3.0 μg/ml, P < 0.03) were decreased. After adjustments for age in FDR, adiponectin levels were negatively correlated with fasting proinsulin (r −0.64, P < 0.001), plasminogen activator inhibitor (PAI)-1 activity (r −0.56, P < 0.001), fasting insulin (r −0.55, P < 0.001), and acute insulin response (r −0.40, P < 0.05); they were positively related to HDL cholesterol (r 0.48, P < 0.01) and Si (r 0.41, P < 0.01). Furthermore, when adjusted for age, waist, and Si, adiponectin was associated with HDL cholesterol and proinsulin, which explained 51% of the variation in adiponectin in multiple regression analyses in that group. In conclusion, circulating plasma adiponectin levels were decreased in nonobese but insulin-resistant FDR and, in addition, related to several facets of the insulin resistance syndrome (IRS). Thus, hypoadiponectinemia may be an important component of the association between cardiovascular disease and IRS.
A Low-Iron-Available, Polyphenol-Enriched, Carbohydrate-Restricted Diet to Slow Progression of Diabetic Nephropathy
Authors: Facchini Francesco S. , Saylor Kami L.
Published: March 2007

Diabetic nephropathy has become the leading cause of uremia. Several lines of evidence suggest dietary factors other than protein intake have a substantial role in the progression of diabetic nephropathy to end-stage renal disease. The present investigation was initiated to evaluate whether a carbohydrate-restricted, low-iron-available, polyphenol-enriched (CR-LIPE) diet may delay and improve the outcome of diabetic nephropathy to a greater extent than standard protein restriction. To this aim, 191 diabetic patients, all with type 2 diabetes, were randomized to either CR-LIPE or standard protein restriction and the following outcomes monitored: doubling of serum creatinine, cumulative incidence of end-stage renal disease, and all cause mortality. Over a mean follow-up interval of 3.9 ± 1.8 years, serum creatinine concentration doubled in 19 patients on CR-LIPE (21%) and in 31 control subjects (39%) (P < 0.01). Renal replacement therapy or death occurred in 18 patients on CR-LIPE (20%) and in 31 control subjects (39%) (P < 0.01). These differences were independent from follow-up interval, sex, mean arterial blood pressure, HbA1c, initial renal dysfunction, and angiotensin system inhibitor use. In conclusion, CR-LIPE was 40–50% more effective than standard protein restriction in improving renal and overall survival rates.
Plasma Prekallikrein
Authors: Jaffa Ayad A. , Durazo-Arvizu Ramon , Zheng Deyi , Lackland Daniel T. , Srikanth Sujata , Garvey W. Timothy , Schmaier Alvin H. ,   the DCCT/EDIC Study Group
Published: March 2007

The relevance and significance of the plasma kallikrein/kinin system as a risk factor for the development of vascular complications in diabetic patients was explored in a cross-sectional study. We measured the circulating levels of plasma prekallikrein (PK) activity, factor XII, and high−molecular weight kininogen in the plasma of 636 type 1 diabetic patients from the Diabetes Control and Complications Trial/Epidemiology and Diabetes Intervention and Complications Study cohort. The findings demonstrated that type 1 diabetic patients with blood pressure ≥140/90 mmHg have increased PK levels compared with type 1 diabetic patients with blood pressure <140/90 (1.53 ± 0.07 vs. 1.27 ± 0.02 units/ml; P < 0.0001). Regression analysis also determined that plasma PK levels positively and significantly correlated with diastolic (DBP) and systolic blood pressures (SBP) as continuous variables (r = 0.17 and 0.18, respectively; P < 0.0001). In multivariate regression analysis, the semipartial r2 value for PK was 2.93% for SBP and 2.92% for DBP (P < 0.0001). A positive correlation between plasma PK levels and the urinary albumin excretion rate (AER) was also observed (r = 0.16, P < 0.0001). In categorical analysis, patients with macroalbuminuria had a significantly higher level of plasma PK than normoalbuminuric patients (1.45 ± 0.08 vs. 1.27 ± 0.02 units/ml; P < 0.01), whereas microalbuminuric patients had an intermediate PK value (1.38 ± 0.05 units/ml; P = NS). Among patients in the microalbuminuric subgroup, we observed a positive and independent correlation between PK and AER in univariate and multivariate regression analysis (r = 0.27, P < 0.03; n = 63). We concluded that in type 1 diabetes, 1) PK levels are elevated in association with increased blood pressure; 2) PK levels are independently correlated with AER and are categorically elevated in patients with macroalbuminuria; and 3) although the positive correlation between PK and AER within the subgroups of patients with microalbuminuria suggest that PK could be a marker for progressive nephropathy, longitudinal studies will be necessary to address this issue.
Diabetic LDL Triggers Apoptosis in Vascular Endothelial Cells
Authors: Artwohl Michaela , Graier Wolfgang F. , Roden Michael , Bischof Martin , Freudenthaler Angelika , Waldhäusl Werner , Baumgartner-Parzer Sabina M.
Published: March 2007

This study compares the effects of LDL glycated either in vitro (LDLiv) or in vivo in diabetic patients (LDLD) on apoptosis, proliferation, and associated protein expression in cultured human umbilical vein endothelial cells. At 100 mg/l, both LDL species considerably increase apoptosis (LDLiv 63%, LDLD 40%; P < 0.05) compared with intraindividual nonglycated LDL subfractions. Considering its lower degree of glycation (LDLD 5–10%, LDLiv 42%), LDLD’s relative proapoptotic activity is 2.7-fold greater than that of LDLiv. Glycated LDL-induced apoptosis is associated with increased expression of apoptosis promotors (LDLiv: bak 88%, CPP-32 49%; LDLD: bak 18%, CPP-32 11%; P < 0.05) and is attenuated by caspase inhibitors. Glycated LDL’s antiproliferative activity (LDLiv −34%, LDLD −9%; P < 0.01) relates to reduction (P < 0.05) of cyclin D3 (LDLiv −27%, LDLD −24%) and of hypo- (LDLiv −22%, LDLD −19%) and hyperphosphorylated (LDLiv −53%, LDLD −22%) retinoblastoma protein and is paralleled by reduced expression of endothelial nitric oxide synthase (LDLiv −30%, LDLD −23%). In response to lipoprotein lipase, LDLD more markedly triggers endothelial apoptosis (27.1-fold) compared with LDLiv, suggesting that LDLD owns a higher potential for endothelial cell damage than LDLiv. The observed behavior of LDLD versus LDLiv could be of clinical importance and well relate to differences in structure and cellular uptake of LDLD compared with LDLiv.
Endothelial Nitric Oxide Synthase Polymorphisms Are Associated With Type 2 Diabetes and the Insulin Resistance Syndrome
Authors: Monti Lucilla D. , Barlassina Cristina , Citterio Lorena , Galluccio Elena , Berzuini Carlo , Setola Emanuela , Valsecchi Gianpietro , Lucotti Pietro , Pozza Guido , Bernardinelli Luisa , Casari Giorgio , Piatti PierMarco
Published: March 2007

Endothelial nitric oxide synthase (eNOS) variants were previously demonstrated in cardiovascular disease. To evaluate whether eNOS gene variants are associated with insulin resistance and type 2 diabetes, we evaluated polymorphisms in Exon7 (E298D), intron 18 (IVS18 + 27A→C), and intron 23 (IVS23 + 10G→T) in 159 type 2 diabetic patients without macrovascular complications and in 207 healthy control subjects. Samples for all hormonal and metabolic variables were obtained after an overnight fast. The D298 and IVS18 + 27C alleles, but not the IVS23 + 10G→T variant, were significantly more frequent in type 2 diabetic patients than in control subjects. The two- and three-loci haplotype analysis showed that there is a statistically significant association between the eNOS variants and type 2 diabetes. No significant differences were observed in the clinical characteristics of type 2 diabetic patients according to genotypes (except for visceral obesity [waist-to-hip ratio], which was significantly more present in D298 homozygotes). Healthy control subjects homozygous for both D298 and IVS18 + 27C presented higher insulin, C-peptide, and nitric oxide levels, as well as higher HOMA (homeostasis model assessment) values than the double wild-type homozygotes, with values superimposable on those found in type 2 diabetic patients. In conclusion, we described a significant association between eNOS gene polymorphisms and type 2 diabetes, suggesting a new genetic susceptibility factor for hyperinsulinemia, insulin resistance, and type 2 diabetes.
A Common Polymorphism in the Promoter of UCP2 Contributes to the Variation in Insulin Secretion in Glucose-Tolerant Subjects
Authors: Sesti Giorgio , Cardellini Marina , Marini Maria Adelaide , Frontoni Simona , D’Adamo Monica , Del Guerra Silvia , Lauro Davide , De Nicolais Pierluigi , Sbraccia Paolo , Del Prato Stefano , Gambardella Sergio , Federici Massimo , Marchetti Piero , Lauro Renato
Published: March 2007

It was reported that the common −866G/A polymorphism in the promoter of the human uncoupling protein-2 (UCP2) gene, which enhances its trascriptional activity, is associated with increased mRNA levels in human adipocytes and reduced risk of obesity. Studies in knockout mice and β-cells indicate that UCP2 may play a role in β-cell function. In this study, we addressed the question of whether the common −866G/A polymorphism in UCP2 gene contributes to the variation of insulin secretion in humans by genotyping 301 nondiabetic subjects who underwent an oral glucose tolerance test. Glucose-stimulated insulin secretion estimated by several indexes of β-cell function was significantly lower in carriers of the −866A/A genotype compared with −866A/G or −866G/G according to the dosage of the A allele (P = 0.002–0.05). To investigate directly whether the UCP2 −866G/A polymorphism affects human islet function, pancreatic islets isolated from two −866G/G homozygous, seven −866G/A heterozygous, and one −866A/A homozygous nondiabetic donors were studied. Islets from −866A/A homozygous had lower insulin secretion in response to glucose stimulation as compared with −866G/G and −866G/A carriers. These results indicate that the common −866G/A polymorphism in the UCP2 gene may contribute to the biological variation of insulin secretion in humans.
Association of Polymorphisms in GPR10, the Gene Encoding the Prolactin-Releasing Peptide Receptor With Blood Pressure, but not Obesity, in a U.K. Caucasian Population
Authors: Bhattacharyya Sumit , Luan Jian’an , Challis Benjamin , Schmitz Catherine , Clarkson Paul , Franks Paul W. , Middelberg Rita , Keogh Julia , Farooqi I. Sadaf , Montague Carl , Brennand John , Wareham Nicholas J. , O’Rahilly Stephen
Published: March 2007

Prolactin-releasing peptide (PrRP) and its G-protein-coupled receptor, GPR10, have been implicated in the central control of appetite and blood pressure. To determine whether mutations in these genes might contribute to morbid obesity, we screened both genes in 94 subjects with severe early-onset obesity. Four rare silent variants in PrRP and eight polymorphisms in GPR10 were found, two of which (V283I and P305L) altered amino acid sequence but were also found in U.K. Caucasian control subjects. Cells expressing the P305L variant receptor generated less intracellular calcium in response to PrRP than cells expressing the wild-type receptor. To examine whether genetic variation of the GPR10 locus might be associated with phenotypes relevant to obesity and/or blood pressure, the most common noncoding (G-62A) and coding (C914T [P305L]) polymorphisms were typed in 1,084 U.K. Caucasians. While no association was found with BMI, carriers of the P305L allelic variant had significantly lower systolic (123.95 vs. 128.55 mmHg, P < 0.05) and diastolic (74.90 vs. 78.20 mmHg, P < 0.01) blood pressure than wild-type subjects. In conclusion, we have conducted the first genetic study of GPR10 and its ligand PrRP in relation to metabolic phenotypes and have identified an association between GPR10 polymorphisms and diastolic and systolic blood pressure. The alteration in signaling properties of the receptor produced by P305L may provide a functional basis for this association.
Glucose 6-Phosphate Regulates Hepatic Glycogenolysis Through Inactivation of Phosphorylase
Authors: Aiston Susan , Andersen Birgitte , Agius Loranne
Published: March 2007

High glucose concentration suppresses hepatic glycogenolysis by allosteric inhibition and dephosphorylation (inactivation) of phosphorylase-a. The latter effect is attributed to a direct effect of glucose on the conformation of phosphorylase-a. Although glucose-6-phosphate (G6P), like glucose, stimulates dephosphorylation of phosphorylase-a by phosphorylase phosphatase, its physiological role in regulating glycogenolysis in intact hepatocytes has not been tested. We show in this study that metabolic conditions associated with an increase in G6P, including glucokinase overexpression and incubation with octanoate or dihydroxyacetone, cause inactivation of phosphorylase. The latter conditions also inhibit glycogenolysis. The activity of phosphorylase-a correlated inversely with the G6P concentration within the physiological range. The inhibition of glycogenolysis and inactivation of phosphorylase-a caused by 10 mmol/l glucose can be at least in part counteracted by inhibition of glucokinase with 5-thioglucose, which lowers G6P. In conclusion, metabolic conditions that alter the hepatic G6P content affect glycogen metabolism not only through regulation of glycogen synthase but also through regulation of the activation state of phosphorylase. Dysregulation of G6P in diabetes by changes in activity of glucokinase or glucose 6-phosphatase may be a contributing factor to impaired suppression of glycogenolysis by hyperglycemia.