bluuebunny/crossref_metadata_2025 huggingface dataset:
Transcriptional Control of Apolipoprotein A-I Gene Expression in Diabetes
Authors: Mooradian Arshag D. , Haas Michael J. , Wong Norman C.W.
Published: March 2007

Cardiovascular disease continues to be the leading cause of mortality in diabetes. One of the factors contributing to the increased risk is the high prevalence rate of low plasma concentrations of HDL cholesterol. Multiple potential mechanisms account for the cardioprotective effects of HDL and its main protein apolipoprotein (apo) A-I. The reduced plasma concentrations of HDL could be the result of increased fractional clearance of HDL and reduced expression of apo A-I. In animal models of diabetes and in cell cultures treated with high concentrations of glucose, apo A-I expression is reduced. In this review we will discuss the alterations in transcriptional control of apo A-I in diabetes. The role of select nutritional and hormonal alterations commonly found in diabetes will be reviewed. Specifically, we will review the literature on the effect of hyperglycemia, hypoinsulinemia, and ketoacidosis, as well as the role of various mediators of insulin resistance, such as fatty acids, cytokines, and prostanoids, on apo A-I promoter activity. Identifying the mechanisms that modulate apo A-I gene expression will aid in the new development of therapeutic agents that increase plasma apo A-I and HDL concentrations.
Stimulation of Hepatocyte Glucose Metabolism by Novel Small Molecule Glucokinase Activators
Authors: Brocklehurst Katy J. , Payne Victoria A. , Davies Rick A. , Carroll Debra , Vertigan Helen L. , Wightman Heather J. , Aiston Susan , Waddell Ian D. , Leighton Brendan , Coghlan Matthew P. , Agius Loranne
Published: March 2007

Glucokinase (GK) has a major role in the control of blood glucose homeostasis and is a strong potential target for the pharmacological treatment of type 2 diabetes. We report here the mechanism of action of two novel and potent direct activators of GK: 6-[(3-isobutoxy-5-isopropoxybenzoyl)amino]nicotinic acid(GKA1) and 5-({3-isopropoxy-5-[2-(3-thienyl)ethoxy]benzoyl}amino)-1,3,4-thiadiazole-2-carboxylic acid(GKA2), which increase the affinity of GK for glucose by 4- and 11-fold, respectively. GKA1 increased the affinity of GK for the competitive inhibitor mannoheptulose but did not affect the affinity for the inhibitors palmitoyl-CoA and the endogenous 68-kDa regulator (GK regulatory protein [GKRP]), which bind to allosteric sites or to N-acetylglucosamine, which binds to the catalytic site. In hepatocytes, GKA1 and GKA2 stimulated glucose phosphorylation, glycolysis, and glycogen synthesis to a similar extent as sorbitol, a precursor of fructose 1-phosphate, which indirectly activates GK through promoting its dissociation from GKRP. Consistent with their effects on isolated GK, these compounds also increased the affinity of hepatocyte metabolism for glucose. GKA1 and GKA2 caused translocation of GK from the nucleus to the cytoplasm. This effect was additive with the effect of sorbitol and is best explained by a “glucose-like” effect of the GK activators in translocating GK to the cytoplasm. In conclusion, GK activators are potential antihyperglycemic agents for the treatment of type 2 diabetes through the stimulation of hepatic glucose metabolism by a mechanism independent of GKRP.
Expression of Voltage-Gated Potassium Channels in Human and Rhesus Pancreatic Islets
Authors: Yan Lizhen , Figueroa David J. , Austin Christopher P. , Liu Yuan , Bugianesi Randal M. , Slaughter Robert S. , Kaczorowski Gregory J. , Kohler Martin G.
Published: March 2007

Voltage-gated potassium channels (Kv channels) are involved in repolarization of excitable cells. In pancreatic β-cells, prolongation of the action potential by block of delayed rectifier potassium channels would be expected to increase intracellular free calcium and to promote insulin release in a glucose-dependent manner. However, the specific Kv channel subtypes responsible for repolarization in β-cells, most importantly in humans, are not completely resolved. In this study, we have investigated the expression of 26 subtypes from Kv subfamilies in human islet mRNA. The results of the RT-PCR analysis were extended by in situ hybridization and/or immunohistochemical analysis on sections from human or Rhesus pancreas. Cell-specific markers were used to show that Kv2.1, Kv3.2, Kv6.2, and Kv9.3 are expressed in β-cells, that Kv3.1 and Kv6.1 are expressed in α-cells, and that Kv2.2 is expressed in δ-cells. This study suggests that more than one Kv channel subtype might contribute to the β-cell delayed rectifier current and that this current could be formed by heterotetramers of active and silent subunits.
No Evidence for Significant Transdifferentiation of Bone Marrow Into Pancreatic β-Cells In Vivo
Authors: Lechner Andreas , Yang Yong-Guang , Blacken Robyn A. , Wang Lan , Nolan Anna L. , Habener Joel F.
Published: March 2007

Several recent studies have suggested that the adult bone marrow harbors cells that can differentiate into tissues from all three germ layers. Other reports have contradicted these findings or attributed them to cell fusion. In this study, we investigated whether bone marrow−derived cells contribute to the renewal of adult pancreatic endocrine cells, in particular insulin-producing β-cells, in vivo. To address this issue, we studied mice transplanted with green fluorescent protein (GFP)−positive, sex-mismatched bone marrow. We also extended our studies to pancreatic injury models (partial pancreatectomy and streptozotocin administration). All animals showed stable full donor chimerism in the peripheral blood and microscopic analysis at 4–6 weeks and 3 months after transplantation, indicating that the GFP+ and Y chromosome−positive donor bone marrow contributed substantially to blood, lymphatic, and interstitial cells in the pancreas. However, after examining >100,000 β-cells, we found only 2 β-cells positive for GFP, both of which were in control animals without pancreatic injury. Thus our study results did not support the concept that bone marrow contributes significantly to adult pancreatic β-cell renewal.
Consequences on β-Cell Function and Reserve After Long-Term Pancreas Transplantation
Authors: Robertson R. Paul
Published: March 2007

β-Cell replacement in diabetes using pancreatic islets or β-cell surrogates is a research area undergoing intense scrutiny. Once this approach is demonstrated to be reproducibly successful, the next major issue will be the length of time that success will be sustained. Whole and segmental pancreas transplants are now successful for up to two decades. Study of these grafts can provide insight into and predictions about β-cell function and reserve when islet transplantation becomes a routine. The studies described herein investigated 102 human whole and segmental transplant recipients and control subjects to address the following five questions. 1) Is the usual reciprocal relationship between the acute insulin response to intravenous glucose (AIRgluc) and the level of fasting plasma glucose (FPG) maintained in pancreas transplant recipients? 2) Do recipients who have no AIRgluc have an acute insulin response to intravenous arginine (AIRarg)? 3) Do recipients of whole pancreata from cadaveric donors have twice the amount of insulin secretory reserve as that found in recipients of 50% segmental grafts from living, related donors? 4) What clinically accessible measure of insulin secretion best correlates with glucose potentiation of arginine-induced insulin secretion (GPAIS)? 5) Do successful pancreas transplant recipients evince time-dependent declines in β-cell function and glycemic regulation when studied long term and longitudinally? The results demonstrate that 1) the normal relationship between AIRgluc and fasting glucose levels is maintained despite systemic venous drainage of allografts and consequent hyperinsulinemia; 2) AIRgluc and AIRarg decrease in parallel as fasting glucose levels rise, although AIRarg is still present after AIRgluc disappears; 3) AIRarg and AIRgluc are strongly predictive of β-cell mass; 4) AIRarg and AIRgluc are strongly predictive of insulin secretory reserve; and 5) transplant recipients who have successfully maintained normoglycemia for an average of 10 years and up to 22 years nonetheless experience time-related declines in β-cell function.
Magnetic Resonance Imaging of the Brain in Diabetes
Authors: Schmidt Reinhold , Launer Lenore J. , Nilsson Lars-Göran , Pajak Andrzej , Sans Susanna , Berger Klaus , Breteler Monique M. , de Ridder Maria , Dufouil Carole , Fuhrer Rebecca , Giampaoli Simona , Hofman Albert ,   for the CASCADE Consortium
Published: March 2007

Diabetic patients are at increased risk for stroke, but little is known about the presence of other brain lesions. We studied the association of magnetic resonance imaging–detected brain lesions to diabetes in 1,252 individuals aged 65–75 years who were randomly selected from eight European population registries or defined working populations. All scans were centrally read for brain abnormalities, including infarcts, white matter lesions, and atrophy. We used a three-point scale to rate periventricular white matter lesions, and the volume of subcortical lesions was calculated according to their number and size. Subjective grading of cortical atrophy by lobe and summation of the lobar grades resulted in a total cortical atrophy score. The mean of three linear measurements of the ventricular diameter relative to the intracranial cavity defined the severity of subcortical atrophy. After adjustment for possible confounders, diabetes was associated with cortical brain atrophy but not with any focal brain lesions or subcortical atrophy. There was a strong interaction of diabetes and hypertension, such that the association between diabetes and cortical atrophy existed only in hypertensive but not in normotensive participants. Cognitive and pathological data are needed to determine the clinical significance of these findings as well as to understand the mechanisms underlying these associations.
Attenuation of Renal Injury in db/db Mice Overexpressing Superoxide Dismutase
Authors: DeRubertis Frederick R. , Craven Patricia A. , Melhem Mona F. , Salah Eman M.
Published: March 2007

The effects of overexpression of Cu2+/Zn2+ superoxide dismutase-1 (SOD-1) on indexes of renal injury were compared in 5-month-old nontransgenic (NTg) db/db mice and db/db mice hemizygous for the human SOD-1 transgene (SOD-Tg). Both diabetic groups exhibited similar hyperglycemia and weight gain. However, in NTg-db/db mice, albuminuria, glomerular accumulation of immunoreactive transforming growth factor-β, collagen α1(IV), nitrotyrosine, and mesangial matrix were all significantly increased compared with either nondiabetic mice or SOD-Tg-db/db. SOD-1 activity and reduced glutathione levels were higher, whereas malondialdehyde content was lower, in the renal cortex of SOD-Tg-db/db compared with NTg-db/db mice, consistent with a renal antioxidant effect in the transgenic mice. Inulin clearance (CIN) and urinary excretion of guanosine 3′,5′-cyclic monophosphate (UcGMP) were increased in SOD-Tg-db/db mice compared with corresponding values in nondiabetic mice or NTg-db/db mice. CIN and UcGMP were suppressed by Nω-nitro-l-arginine methyl ester in SOD-Tg-db/db but not in NTg-db/db mice, implying nitric oxide (NO) dependence of these increases and enhanced renal NO bioactivity in SOD-Tg-db/db. Studies of NO-responsive cGMP in isolated glomeruli supported greater quenching of NO in glomeruli from NTg-db/db compared with SOD-Tg-db/db mice. Evidence of increased NO responsiveness and the suppression of glomerular nitrotyrosine may both reflect reduced NO-superoxide interaction in SOD-Tg-db/db mice. The results implicate superoxide in the pathogenesis of diabetic nephropathy.
Potential Contributory Role of H-Ras, a Small G-Protein, in the Development of Retinopathy in Diabetic Rats
Authors: Kowluru Renu A. , Kowluru Anjaneyulu , Chakrabarti Subrata , Khan Zia
Published: March 2007

Hyperglycemia is thought to be the underlying factor in the development of diabetic retinopathy, but the mechanisms involved remain partially understood. Diabetes increases oxidative stress, and reactive oxygen species affect the interactions between a small-molecular- weight G-protein, H-Ras, and several of its effector proteins. The purpose of this study was to examine the regulatory role of H-Ras in glucose-induced apoptosis of retinal endothelial cells. The expressions of H-Ras and its effector protein (Raf-1) were compared in the retina obtained from diabetic rats (2–8 months’ duration) and age-matched normal rats and in retinal endothelial cells exposed to high-glucose medium. The effect of inhibition of H-Ras function on glucose-induced capillary cell death and the potential involvement of oxidative stress in diabetes-induced activation of H-Ras were also determined. The expressions of H-Ras and Raf-1 were increased in the retina in diabetes, and antioxidant therapy prevented diabetes-induced increased protein and mRNA expressions. The inhibitors of Ras farnesylation inhibited glucose-induced nitric oxides and apoptosis in isolated retinal endothelial cells. Thus, the results suggest that functional activation of H-Ras might be one of the signaling steps involved in glucose-induced capillary cell apoptosis and supports the role of H-Ras in the development of retinopathy in diabetes.
An Obesity-Related Locus in Chromosome Region 12q23-24
Authors: Li Wei-Dong , Dong Chuanhui , Li Ding , Zhao Hongyu , Price R. Arlen
Published: March 2007

Obesity is a growing health problem in the U.S. As a complex trait, obesity involves multiple genes and gene-gene and gene-environment interactions that contribute to its pathogenesis. Here we report significant linkage from a scan of a large sample segregating extreme obesity and normal weight. We have used 382 microsatellite markers in 1,297 individuals from 260 European-American families. We conducted nonparametric linkage (NPL) analyses for dichotomous BMI (using BMI ≥27, ≥30, ≥35, and ≥40 kg/m2) using Genehunter. We also analyzed quantitative traits (BMI, percentage of fat, and waist circumference) by the family regression method using Merlin_regress. We found evidence for linkage on chromosome 12 (125 cM, D12S2070, logarithm of odds [LOD] 3.79, P = 0.00001 for percentage of fat; LOD 2.98, P = 0.0001 for BMI; and LOD 2.86, P = 0.00014 for waist circumference) by family regression analyses. Adding three additional markers to the intervals flanking the chromosome 12 peak yielded an LOD score of 4.08 (P = 0.00001) for percentage of fat at 116 cM and LOD scores of 3.57 (P = 0.00003) and 3.05 (P = 0.00009) for BMI and waist circumference, respectively, at 125 cM. We also obtained other suggestive linkages on chromosomes 2, 3, 7, 8, 9, 12, 13, and 21. Our results suggest multiple loci that could influence obesity, particularly a locus in chromosome region 12q23-24.
Genetic Variants in Human Sterol Regulatory Element Binding Protein-1c in Syndromes of Severe Insulin Resistance and Type 2 Diabetes
Authors: Laudes Matthias , Barroso Inês , Luan Jian’an , Soos Maria A. , Yeo Giles , Meirhaeghe Aline , Logie Lisa , Vidal-Puig Antonio , Schafer Alan J. , Wareham Nick J. , O’Rahilly Stephen
Published: March 2007

The transcription factor sterol regulatory element binding protein (SREBP)-1c is intimately involved in the regulation of lipid and glucose metabolism. To investigate whether mutations in this gene might contribute to insulin resistance, we screened the exons encoding the aminoterminal transcriptional activation domain in a cohort of 85 unrelated human subjects with severe insulin resistance. Two missense mutations (P87L and P416A) were found in single affected patients but not in 47 control subjects. However, these variants were indistinguishable from the wild-type in their ability to bind DNA or to transactivate an SREBP-1 responsive promoter construct. We also identified a common intronic single nucleotide polymorphism (C/T) located between exon 18c and 19c. In a case-control study of 517 U.K. Caucasian case subjects and 517 age- and sex-matched control subjects, the T-allele at this locus was significantly associated with type 2 diabetes in men (odds ratio = 1.42 [1.11–1.82], P = 0.005) but not women. In a separate population-based study of 1,100 Caucasians, carriers of the T-allele showed significantly higher levels of total and LDL cholesterol (P < 0.05) compared with wild-type individuals. In summary, we have conducted the first study of the SREBP-1c gene as a candidate for human insulin resistance. Although the rare mutations identified were functionally silent in the assays used, we obtained some evidence, which requires conformation in other populations, that a common variant in the SREBP-1c gene might influence diabetes risk and plasma cholesterol level.
Evidence From a Large U.K. Family Collection That Genes Influencing Age of Onset of Type 2 Diabetes Map to Chromosome 12p and to the MODY3/NIDDM2 Locus on 12q24
Authors: Wiltshire Steven , Frayling Timothy M. , Groves Christopher J. , Levy Jonathan C. , Hitman Graham A. , Sampson Mike , Walker Mark , Menzel Stephan , Hattersley Andrew T. , Cardon Lon R. , McCarthy Mark I.
Published: March 2007

Additional information on genetic susceptibility effects relevant to type 2 diabetes pathogenesis can be extracted from existing genome scans by extending examination to related phenotypes such as age at disease onset. In this study, we report the reanalysis of data from 573 U.K. sibships ascertained for multiplex type 2 diabetes, using age at onset (assessed by the proxy measure of age at diagnosis) as the phenotype of interest. Genome-wide evidence for linkage to age at diagnosis was evaluated using both variance components and Haseman-Elston (HECOM) regression approaches, with extensive simulations to derive empirical significance values. There was broad agreement across analyses with six regions of interest (logarithm of odds [LOD] ≥1.18) identified on chromosomes 1qter, 4p15–4q12, 5p15, 12p13–12q13, 12q24, and 14q12–14q21. The strongest empirically “suggestive” evidence for linkage comes from regions on chromosome 12. The first region (12p13–12q13), peaking at D12S310 (variance components LOD [LODVC] = 2.08, empirical pointwise P = 0.0007; HECOM LOD [LODhecom] = 2.58, P = 0.0010) seems to be novel. The second (12q24) peaking between D12S324 and D12S1659 (LODVC = 1.87, P = 0.0016; LODhecom = 1.93, P = 0.0027) overlaps a region showing substantial prior evidence for diabetes linkage. These data provide additional evidence that genes mapping to these chromosomal regions are involved in the susceptibility to, and/or development of, type 2 diabetes.
Interaction of 6-Phosphofructo-2-Kinase/Fructose-2,6-Bisphosphatase (PFK-2/FBPase-2) With Glucokinase Activates Glucose Phosphorylation and Glucose Metabolism in Insulin-Producing Cells
Authors: Massa Laura , Baltrusch Simone , Okar David A. , Lange Alex J. , Lenzen Sigurd , Tiedge Markus
Published: March 2007

The bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2) was recently identified as a new intracellular binding partner for glucokinase (GK). Therefore, we studied the importance of this interaction for the activity status of GK and glucose metabolism in insulin-producing cells by overexpression of the rat liver and pancreatic islet isoforms of PFK-2/FBPase-2. PFK-2/FBPase-2 overexpression in RINm5F-GK cells significantly increased the GK activity by 78% in cells expressing the islet isoform, by 130% in cells expressing the liver isoform, and by 116% in cells expressing a cAMP-insensitive liver S32A/H258A double mutant isoform. Only in cells overexpressing the wild-type liver PFK-2/FBPase-2 isoform was the increase of GK activity abolished by forskolin, apparently due to the regulatory site for phosphorylation by a cAMP-dependent protein kinase. In cells overexpressing any isoform of the PFK-2/FBPase-2, the increase of the GK enzyme activity was antagonized by treatment with anti–FBPase-2 antibody. Increasing the glucose concentration from 2 to 10 mmol/l had a significant stimulatory effect on the GK activity in RINm5F-GK cells overexpressing any isoform of PFK-2/FBPase-2. The interaction of GK with PFK-2/FBPase-2 takes place at glucose concentrations that are physiologically relevant for the activation of GK and the regulation of glucose-induced insulin secretion. This new mechanism of posttranslational GK regulation may also represent a new site for pharmacotherapeutic intervention in type 2 diabetes treatment.
Regulated Expression of pdx-1 Promotes In Vitro Differentiation of Insulin-Producing Cells From Embryonic Stem Cells
Authors: Miyazaki Satsuki , Yamato Eiji , Miyazaki Jun-ichi
Published: March 2007

Embryonic stem (ES) cells can differentiate into many cell types. Recent reports have shown that ES cells can differentiate into insulin-producing cells. However, the differentiation is not efficient enough to produce insulin-secreting cells for future therapeutic use. Pdx-1, a homeodomain-containing transcription factor, is a crucial regulator for pancreatic development. We established an ES cell line in which exogenous pdx-1 expression was precisely regulated by the Tet-off system integrated into the ROSA26 locus. Using this cell line, we examined the effect of pdx-1 expression during in vitro differentiation via embryoid body formation. The results showed that pdx-1 expression clearly enhanced the expression of the insulin 2, somatostatin, Kir6.2, glucokinase, neurogenin3, p48, Pax6, PC2, and HNF6 genes in the resulting differentiated cells. Immunohistochemical examination also revealed that insulin was highly produced in most of the differentiated ES cells. Thus, exogenous expression of pdx-1 should provide a promising approach for efficiently producing insulin-secreting cells from human ES cells for future therapeutic use in diabetic patients.
Diabetic Patients Without Vascular Complications Display Enhanced Basal Platelet Activation and Decreased Antioxidant Status
Authors: Véricel Evelyne , Januel Caroline , Carreras Martine , Moulin Philippe , Lagarde Michel
Published: March 2007

Vascular complications are the leading causes of morbidity and mortality in diabetic patients. The contribution of platelets to thromboembolic complications is well documented, but their involvement in the initiation of the atherosclerotic process is of rising interest. Thus, the aim of the present study was to evaluate basal arachidonic acid metabolism in relation to the redox status of platelets in both type 1 and type 2 diabetic patients, in the absence of vascular complications, as compared with respective control subjects. For the first time, we show that basal thromboxane B2, the stable catabolite of thromboxane A2, significantly increased in resting platelets from both type 1 and type 2 diabetic patients (58 and 88%, respectively), whereas platelet malondialdehyde level was only higher in platelets from type 2 diabetic subjects (67%). On the other hand, both vitamin E levels and cytosolic glutathione peroxidase activities were significantly lower in platelets from diabetic patients as compared with respective control subjects. We conclude that platelet hyperactivation was detectable in well-controlled diabetic patients without complications. This abnormality was associated with increased oxidative stress and impaired antioxidant defense in particular in type 2 diabetic patients. These alterations contribute to the increased risk for occurrence of vascular diseases in such patients.
Thiazolidinediones, Like Metformin, Inhibit Respiratory Complex I
Authors: Brunmair Barbara , Staniek Katrin , Gras Florian , Scharf Nicole , Althaym Aleksandra , Clara Renate , Roden Michael , Gnaiger Erich , Nohl Hans , Waldhäusl Werner , Fürnsinn Clemens
Published: March 2007

Metformin and thiazolidinediones (TZDs) are believed to exert their antidiabetic effects via different mechanisms. As evidence suggests that both impair cell respiration in vitro, this study compared their effects on mitochondrial functions. The activity of complex I of the respiratory chain, which is known to be affected by metformin, was measured in tissue homogenates that contained disrupted mitochondria. In homogenates of skeletal muscle, metformin and TZDs reduced the activity of complex I (30 mmol/l metformin, −15 ± 2%; 100 μmol/l rosiglitazone, −54 ± 7; and 100 μmol/l pioglitazone, −12 ± 4; P < 0.05 each). Inhibition of complex I was confirmed by reduced state 3 respiration of isolated mitochondria consuming glutamate + malate as substrates for complex I (30 mmol/l metformin, −77 ± 1%; 100 μmol/l rosiglitazone, −24 ± 4; and 100 μmol/l pioglitazone, −18 ± 5; P < 0.05 each), whereas respiration with succinate feeding into complex II was unaffected. In line with inhibition of complex I, 24-h exposure of isolated rat soleus muscle to metformin or TZDs reduced cell respiration and increased anaerobic glycolysis (glucose oxidation: 270 μmol/l metformin, −30 ± 9%; 9 μmol/l rosiglitazone, −25 ± 8; and 9 μmol/l pioglitazone, −45 ± 3; lactate release: 270 μmol/l metformin, +84 ± 12; 9 μmol/l rosiglitazone, +38 ± 6; and 9 μmol/l pioglitazone, +64 ± 11; P < 0.05 each). As both metformin and TZDs inhibit complex I activity and cell respiration in vitro, similar mitochondrial actions could contribute to their antidiabetic effects.
Transforming Growth Factor-β1 Production Is Correlated With Genetically Determined ACE Expression in Congenic Rats
Authors: Pueyo Maria E. , Challah Mireille , Gauguier Dominique , Louedec Liliane , Philippe Monique , Gaertner Roger , Marre Michel , Michel Jean-Baptiste , Jacob Marie-Paule
Published: March 2007

Genetic background appears to modulate the development of diabetic vascular complications. In particular, polymorphisms in the ACE gene have been associated with diabetic nephropathy and, in some studies, macrovascular complications. However, the links between ACE gene polymorphism and factors implicated in diabetes complications remain unknown. The aim of this study was to determine whether the ACE genotype could modify factors, such as transforming growth factor (TGF)-β1, involved in the complications of diabetes. For this purpose, congenic rats (L.BNAce10), differing from the LOU strain in only a small segment of chromosome 10 containing the ACE locus, were generated. These congenic rats have plasma ACE levels twice as high as the donor strain. Diabetes was induced in rats of both strains, and its effects on ACE and TGF-β1 expressions were evaluated in lungs and kidneys. In lung, the main source of ACE production, ACE mRNA levels and activity were higher in L.BNAce10 rats than in LOU rats. Diabetes increased ACE lung expression in rats of both strains in a similar manner. TGF-β1 expression was also higher in lungs of L.BNAce10 compared with LOU rats and was also increased by diabetes. Furthermore, a strong correlation was found between TGF-β1 and ACE expressions. In renal arterioles, ACE and TGF-β mRNA expressions were higher in L.BNAce10 rats than LOU rats (both diabetic and nondiabetic). In these vessels, there was also a correlation between ACE and TGF-β1 expressions. Urine TGF-β1 concentration depended on the genotype and was further increased by diabetes. These results show that TGF-β1 expression is correlated with ACE expression and suggest that this growth factor could be a link between ACE gene polymorphism and diabetic vascular complications.
Maternal-Fetal Interactions and Birth Order Influence Insulin Variable Number of Tandem Repeats Allele Class Associations with Head Size at Birth and Childhood Weight Gain
Authors: Ong Ken K. , Petry Clive J. , Barratt Bryan J. , Ring Susan , Cordell Heather J. , Wingate Diane L. ,   the Avon Longitudinal Study of Pregnancy and Childhood Study Team, Pembrey Marcus E. , Todd John A. , Dunger David B.
Published: March 2007

Polymorphism of the insulin gene (INS) variable number of tandem repeats (VNTR; class I or class III alleles) locus has been associated with adult diseases and with birth size. Therefore, this variant is a potential contributory factor to the reported fetal origins of adult disease. In the population-based Avon Longitudinal Study of Pregnancy and Childhood birth cohort, we have confirmed in the present study the association between the INS VNTR III/III genotype and larger head circumference at birth (odds ratio [OR] 1.92, 95% CI 1.23–3.07; P = 0.004) and identified an association with higher cord blood IGF-II levels (P = 0.05 to 0.0001). The genotype association with head circumference was influenced by maternal parity (birth order): the III/III OR for larger head circumference was stronger in second and subsequent pregnancies (OR 5.0, 95% CI 2.2–11.5; P = 0.00003) than in first pregnancies (1.2, 0.6–2.2; P = 0.8; interaction with birth order, P = 0.02). During childhood, the III/III genotype remained associated with larger head circumference (P = 0.004) and was also associated with greater BMI (P = 0.03), waist circumference (P = 0.03), and higher fasting insulin levels in girls (P = 0.02). In addition, there were interactions between INS VNTR genotype and early postnatal weight gain in determining childhood BMI (P = 0.001 for interaction), weight (P = 0.005), and waist circumference (P = 0.0005), such that in the ∼25% of children (n = 286) with rapid early postnatal weight gain, class III genotype–negative children among this group gained weight more rapidly. Our results indicate that complex prenatal and postnatal gene–maternal/fetal interactions influence size at birth and childhood risk factors for adult disease.
Association Between Variation in the Actin-Binding Gene Caldesmon and Diabetic Nephropathy in Type 1 Diabetes
Authors: Conway Bryan R. , Maxwell A. Peter , Savage David A. , Patterson Chris C. , Doran Peter P. , Murphy Madeline , Brady Hugh R. , Fogarty Damian G.
Published: March 2007

Dysfunction of the actin cytoskeleton is a key event in the pathogenesis of diabetic nephropathy. We previously reported that certain cytoskeletal genes are upregulated in mesangial cells exposed to a high extracellular glucose concentration. One such gene, caldesmon, lies on chromosome 7q35, a region linked to nephropathy in family studies, making it a candidate susceptibility gene for diabetic nephropathy. We screened all exons, untranslated regions, and a 5-kb region upstream of the gene for variation using denaturing high-performance liquid chromatography technology. An A>G single nucleotide polymorphism (SNP) at position −579 in the promoter region was associated with nephropathy in a case-control study using 393 type 1 diabetic patients from Northern Ireland (odds ratio [OR] 1.38, 95% CI 1.02–1.86, P = 0.03). A similar trend was found in an independent sample from a second center. When the sample groups were combined (n = 606), the association between the −579G allele and nephropathy remained significant (OR 1.35, 1.07–1.70, P = 0.01). The haplotype structure in the surrounding 7-kb region was determined. No single haplotype was more strongly associated with nephropathy than the −579A>G SNP. These results suggest a role for the caldesmon gene in susceptibility to diabetic nephropathy in type 1 diabetes.
Ciliary Neurotrophic Factor and Leptin Induce Distinct Patterns of Immediate Early Gene Expression in the Brain
Authors: Kelly Joseph F. , Elias Carol F. , Lee Charlotte E. , Ahima Rexford S. , Seeley Randy J. , Bjørbæk Christian , Oka Takakazu , Saper Clifford B. , Flier Jeffrey S. , Elmquist Joel K.
Published: March 2007

Ciliary neurotrophic factor (CNTF) and leptin decrease food intake and body weight. Lipopolysaccharide (LPS) is a potent exogenous pyrogen and produces anorexia via cytokine production. CNTF-, leptin-, and LPS-induced cytokines all act on type I cytokine receptors. However, it is not known if these cytokines engage similar central nervous system (CNS) pathways to exert their effects. To assess mechanisms by which these cytokines act, we examined the patterns of immediate early gene expression (SOCS-3, c-fos, and tis-11) in the brain following intravenous administration. CNTF and LPS induced gene expression in circumventricular organs; ependymal cells of the ventricles, meninges, and choroid plexus; and the arcuate nucleus of the hypothalamus. CNTF administration also induced fever and cyclooxygenase-2 mRNA expression. In contrast, we found no evidence of leptin-induced inflammation. CNTF and leptin are being assessed as potential therapeutic antiobesity agents, and both potently reduce food intake. Our findings support the hypothesis that CNTF and leptin engage distinct CNS sites and CNTF possesses inflammatory properties distinct from leptin.
Relationship to Insulin Resistance of the Adult Treatment Panel III Diagnostic Criteria for Identification of the Metabolic Syndrome
Authors: Cheal Karen L. , Abbasi Fahim , Lamendola Cindy , McLaughlin Tracey , Reaven Gerald M. , Ford Earl S.
Published: March 2007

The Adult Treatment Panel III (ATP III) has published criteria for diagnosing the metabolic syndrome, a cluster of closely related abnormalities related to insulin resistance that increase cardiovascular disease risk. The present analysis was performed to evaluate the ability of these criteria to identify insulin-resistant individuals. The population consisted of 443 healthy volunteers, with measurements of BMI, blood pressure, fasting plasma glucose, triglycerides, HDL cholesterol concentrations, and steady-state plasma glucose (SSPG) concentration. Insulin resistance was defined as being in the top tertile of SSPG concentrations. Of the population, 20% satisfied ATP III criteria for the metabolic syndrome. Although insulin resistance and the presence of the metabolic syndrome were significantly associated (P < 0.001), the sensitivity and positive predictive value equaled 46% (69 of 149) and 76% (69 of 91), respectively. Being overweight, with high triglycerides, low HDL cholesterol, or elevated blood pressure, most often resulted in a diagnosis of the metabolic syndrome. Thus, the ATP III criteria do not provide a sensitive approach to identifying insulin-resistant individuals. The individual components vary both in terms of their utility in making a diagnosis of the metabolic syndrome and their relationship to insulin resistance, with the obesity and lipid criteria being most useful.
Exercise and Myocyte Enhancer Factor 2 Regulation in Human Skeletal Muscle
Authors: McGee Sean L. , Hargreaves Mark
Published: March 2007

Overexpression of GLUT4 in skeletal muscle enhances whole-body insulin action. Exercise increases GLUT4 gene and protein expression, and a binding site for the myocyte enhancer factor 2 (MEF-2) is required on the GLUT4 promoter for this response. However, the molecular mechanisms involved remain elusive. In various cell systems, MEF-2 regulation is a balance between transcriptional repression by histone deacetylases (HDACs) and transcriptional activation by the nuclear factor of activated T-cells (NFAT), peroxisome proliferator-activated receptor-γ coactivator 1 (PGC-1), and the p38 mitogen-activated protein kinase. The purpose of this study was to determine if these same mechanisms regulate MEF-2 in contracting human skeletal muscle. Seven subjects performed 60 min of cycling at ∼70% of Vo2peak. After exercise, HDAC5 was dissociated from MEF-2 and exported from the nucleus, whereas nuclear PGC-1 was associated with MEF-2. Exercise increased total and nuclear p38 phosphorylation and association with MEF-2, without changes in total or nuclear p38 protein abundance. This result was associated with p38 sequence-specific phosphorylation of MEF-2 and an increase in GLUT4 mRNA. Finally, we found no role for NFAT in MEF-2 regulation. From these data, it appears that HDAC5, PGC-1, and p38 regulate MEF-2 and could be potential targets for modulating GLUT4 expression.
Relationship Between Insulin Sensitivity and Sphingomyelin Signaling Pathway in Human Skeletal Muscle
Authors: Straczkowski Marek , Kowalska Irina , Nikolajuk Agnieszka , Dzienis-Straczkowska Stella , Kinalska Ida , Baranowski Marcin , Zendzian-Piotrowska Malgorzata , Brzezinska Zofia , Gorski Jan
Published: March 2007

In vitro studies revealed that insulin resistance might be associated with the intracellular formation of ceramide, the second messenger in the sphingomyelin signaling pathway. The aim of the present study was to examine the content and composition of fatty acids in ceramide and sphingomyelin in human muscle and to evaluate their relationships with insulin sensitivity. The study was conducted on 27 male subjects with normal glucose tolerance. Euglycemic-hyperinsulinemic clamps and biopsies of vastus lateralis muscle were performed. In 10 subjects, additional biopsies were taken after a 4-h clamp and after a clamp with concurrent Intralipid/heparin infusion. We identified 13 ceramides and sphingomyelins according to fatty acid residues. Insulin sensitivity was related to total ceramide content (r = −0.49, P = 0.01) and to ceramide consisting of palmitic (r = −0.48, P = 0.011), palmitoleic (r = −0.45, P = 0.019), mirystic (r = −0.42, P = 0.028), and nervonic acid (r = −0.39, P = 0.047). Hyperinsulinemia did not affect estimated muscle parameters. Intralipid/heparin infusion resulted in a 24.73% decrease in insulin sensitivity (P = 0.007) and a 47.81% increase in ceramide content (P = 0.005). These changes were significantly related to each other (r = −0.64, P = 0.046). A relationship with the decrease in insulin sensitivity was also observed for ceramides consisting of palmitic (r = −0.68, P = 0.03) and linoleic (r = −0.66, P = 0.038) acid. Our data indicate that the sphingomyelin signaling pathway in muscle might be an important factor determining the development of insulin resistance in humans.
Third Ventricular Alloxan Reversibly Impairs Glucose Counterregulatory Responses
Authors: Sanders Nicole M. , Dunn-Meynell Ambrose A. , Levin Barry E.
Published: March 2007

Glucokinase (GK) is hypothesized to be the critical glucosensor of pancreatic β-cells and hypothalamic glucosensing neurons. To understand the role of GK in glucoprivic counterregulatory responses, we injected alloxan, a GK inhibitor and toxin, into the third ventricle (3v) to target nearby GK-expressing neurons. Four and 6 days after 3v, but not 4v, alloxan injection, alloxan-treated rats ate only 30% and their blood glucose area under the curve was only 28% of saline controls’ after systemic 2-deoxy-d-glucose. In addition, their hyperglycemic response to hindbrain glucoprivation induced with 5-thio-glucose was impaired, whereas fasting blood glucose levels and food intake after an overnight fast were elevated. These impaired responses were associated with the destruction of 3v tanycytes, reduced glial fibrillary acidic protein-immunoreactivity surrounding the 3v, neuronal swelling, and decreased arcuate nucleus neuropeptide Y (NPY) mRNA. Nevertheless, hypothalamic GK mRNA was significantly elevated. Two weeks after alloxan injection, 3v tanycyte destruction was reversed along with restoration of feeding and hyperglycemic responses to both systemic and hindbrain glucoprivation. At this time there were significant decreases in GK, NPY, and proopiomelanocortin mRNA. Thus, neural substrates near and around the 3v affected by alloxan may be critically involved in the expression of these glucoprivic responses.
Role of Caveolin-1 in the Modulation of Lipolysis and Lipid Droplet Formation
Authors: Cohen Alex W. , Razani Babak , Schubert William , Williams Terence M. , Wang Xiao Bo , Iyengar Puneeth , Brasaemle Dawn L. , Scherer Philipp E. , Lisanti Michael P.
Published: March 2007

Recently, it was shown that caveolin-1 can be redirected from the cell surface to intracellular lipid droplets in a variety of cell types. Here, we directly address the role of caveolin-1 in lipid droplet formation and breakdown, showing that caveolin-1 null mice exhibit markedly attenuated lipolytic activity. Mechanistically, although the activity of protein kinase A (PKA) was greatly increased in caveolin-1 null adipocytes, the phosphorylation of perilipin was dramatically reduced, indicating that caveolin-1 may facilitate the PKA-mediated phosphorylation of perilipin. In support of this hypothesis, coimmunoprecipitation experiments revealed that treatment with a β3-adrenergic receptor agonist resulted in ligand-induced complex formation between perilipin, caveolin-1, and the catalytic subunit of PKA in wild-type but not in caveolin-1 null fat pads. We also show that caveolin-1 expression is important for efficient lipid droplet formation because caveolin-1 null embryonic fibroblasts stably transfected with perilipin accumulated ∼4.5-fold less lipid than perilipin-transfected wild-type cells. Finally, high-pressure freeze-substitution electron microscopy of adipose tissue revealed dramatic perturbations in the architecture of the “lipid droplet cortex” (the interface between the lipid droplet surface and the cytoplasm) in caveolin-1 null perigonadal adipocytes. Taken together, our data provide the first molecular genetic evidence that caveolin-1 plays a critical functional and structural role in the modulation of both lipid droplet biogenesis and metabolism in vivo.
Interleukin-4 but not Interleukin-10 Protects Against Spontaneous and Recurrent Type 1 Diabetes by Activated CD1d-Restricted Invariant Natural Killer T-Cells
Authors: Mi Qing-Sheng , Ly Dalam , Zucker Peter , McGarry Megan , Delovitch Terry L.
Published: March 2007

In nonobese diabetic (NOD) mice, a deficiency in the number and function of invariant natural killer T-cells (iNKT cells) contributes to the onset of type 1 diabetes. The activation of CD1d-restricted iNKT cells by α-galactosylceramide (α-GalCer) corrects these deficiencies and protects against spontaneous and recurrent type 1 diabetes. Although interleukin (IL)-4 and IL-10 have been implicated in α-GalCer–induced protection from type 1 diabetes, a precise role for these cytokines in iNKT cell regulation of susceptibility to type 1 diabetes has not been identified. Here we use NOD.IL-4–/– and NOD.IL-10–/– knockout mice to further evaluate the roles of IL-4 and IL-10 in α-GalCer–induced protection from type 1 diabetes. We found that IL-4 but not IL-10 expression mediates protection against spontaneous type 1 diabetes, recurrent type 1 diabetes, and prolonged syngeneic islet graft function. Increased transforming growth factor-β gene expression in pancreatic lymph nodes may be involved in α-GalCer–mediated protection in NOD.IL-10–/– knockout mice. Unlike the requirement of IL-7 and IL-15 to maintain iNKT cell homeostasis, IL-4 and IL-10 are not required for α-GalCer–induced iNKT cell expansion and/or survival. Our data identify an important role for IL-4 in the protection against type 1 diabetes by activated iNKT cells, and these findings have important implications for cytokine-based therapy of type 1 diabetes and islet transplantation.
Investigation of the Human ANP Gene in Type 1 Diabetic Nephropathy
Authors: Roussel Ronan , Trégouët David-Alexandre , Hadjadj Samy , Jeunemaı̂tre Xavier , Marre Michel
Published: March 2007

The atrial natriuretic peptide gene (PND) is a candidate gene for diabetic nephropathy. We systematically analyzed five nonsynonymous PND polymorphisms and tested the association of genotype and haplotype distributions with diabetic nephropathy in a cross-sectional study and a 6-year follow-up study (489 and 301 type 1 diabetic patients, respectively). For this purpose, a new maximum-likelihood method dealing with haplotype-based association analysis for survival data was developed. None of the genotypes or haplotypes were associated with the disease in the case-control study. In the follow-up study, C708T and T2238C showed a weak association with disease progression, but T2238C was strongly associated with progression in poorly controlled subjects (mean HbA1c during follow-up was more than the median value [8.5%]; log-rank [TC or CC versus TT], P = 0.007; adjusted hazard ratio, TC or CC versus TT, 2.28, 95% CI 1.10–4.74; P = 0.027). The raw effect of the 2238C allele (hazard risk ratio 1.93, 95% CI 1.15–3.24; P = 0.012) was further confirmed by the haplotype analysis, suggesting that the 2238C allele of PND may affect the course of nephropathy in inadequately controlled type 1 diabetic patients.
Advanced Glycation End Products Modulate the Maturation and Function of Peripheral Blood Dendritic Cells
Authors: Price Claire L. , Sharp Patrick S. , North Margaret E. , Rainbow Sandra J. , Knight Stella C.
Published: March 2007

Advanced glycation end products (AGEs), a complex and heterogeneous group of posttranslational modifications of proteins in vivo, have been widely studied for their involvement in diabetic complications; these complications are largely vascular and accompanied by inflammation. Because dendritic cells (DCs) initiate and modulate inflammatory responses, we hypothesized that AGEs might exert immunomodulatory effects via antigen-presenting DCs. To test this hypothesis, we investigated effects of the AGE peptide, compared with the naked peptide, on maturation, costimulatory molecule expression, and function of DCs in peripheral blood. From flow cytometry, we found a dose-dependent inhibition in CD83 expression on DCs exposed for 2.5 h to each of two synthetic AGE peptides. A similar culture for 24 h additionally produced an inhibition of CD80 expression, whereas exposure to AGEs for 3 days induced a large increase in DC numbers and a concomitant loss of monocyte/macrophages. Exposure of DCs to AGEs resulted in a dose-dependent loss in their capacity to stimulate primary proliferation of allogeneic T-cells. We conclude that AGEs promote development of DCs but that these DCs fail to express maturation markers and lose the capacity to stimulate primary T-cell responses. Effects of AGEs on DCs could be instrumental in the immunological changes associated with diabetes.
Changes in the Dimeric State of Neuronal Nitric Oxide Synthase Affect the Kinetics of Secretagogue-Induced Insulin Response
Authors: Lajoix Anne-Dominique , Pugnière Martine , Roquet Françoise , Mani Jean-Claude , Dietz Samuel , Linck Nathalie , Faurie Fleur , Ribes Gérard , Petit Pierre , Gross René
Published: March 2007

We previously showed that pancreatic β-cells express a neuronal isoform of nitric oxide synthase (nNOS) that controls insulin secretion by exerting two enzymatic activities: nitric oxide (NO) production and cytochrome c reductase activity. We now bring evidence that two inhibitors of nNOS, N-ω-nitro-l-arginine methyl ester (l-NAME) and 7-nitroindazole (7-NI), increase glucose-induced insulin secretion but affect β-cell function differently. In the presence of l-NAME, insulin response is monophasic, whereas 7-NI preserves the normal biphasic secretory pattern. In addition, the alterations of β-cell functional response induced by the inhibitors also differ by their sensitivity to a substitutive treatment with sodium nitroprusside, a chemical NO donor. These differences are probably related to the nature of the two inhibitors. Indeed, using low-temperature SDS-PAGE and real-time analysis of nNOS dimerization by surface plasmon resonance, we could show that 7-NI, which competes with arginine and tetrahydrobiopterin (BH4), an essential cofactor for nNOS dimer formation, inhibits dimerization of the enzyme, whereas the substrate-based inhibitor l-NAME stabilizes the homodimeric state of nNOS. The latter effect could be reproduced by the two endogenous inhibitors of NOS, N-ω-methyl-l-arginine and asymmetric dimethylarginine, and resulted interestingly in a reduced ability of the protein inhibitor of nNOS (PIN) to dissociate nNOS dimers. We conclude that intracellular factors able to induce abnormalities in the nNOS monomer/dimer equilibrium could lead to pancreatic β-cell dysfunction.