bluuebunny/crossref_metadata_2025 huggingface dataset:
Lipid Infusion Impairs Physiologic Insulin-Mediated Capillary Recruitment and Muscle Glucose Uptake In Vivo
Authors: Clerk Lucy H. , Rattigan Stephen , Clark Michael G.
Published: March 2007

Infusion of triglycerides and heparin causes insulin resistance in muscle. Because the vascular actions of insulin, particularly capillary recruitment, may contribute to the increase in glucose uptake by skeletal muscle, we investigated the effects of Intralipid/heparin infusion on the hemodynamic actions of insulin during clamp conditions. Saline or 10% Intralipid/heparin (33 U/ml) was infused into anesthetized rats at 20 μl/min for 6 h. At 4 h into the saline infusion, a 2-h hyperinsulinemic (3 mU · min−1 · kg−1)-euglycemic clamp was conducted (Ins group). At 4 h into the lipid infusion, a 2-h saline control (Lip group) or 2-h hyperinsulinemic-euglycemic clamp (Lip + Ins group) was conducted. Arterial blood pressure, heart rate, femoral blood flow (FBF), hindleg vascular resistance, glucose infusion rate (GIR), hindleg glucose uptake (HGU), and muscle 2-deoxyglucose uptake (R′g) were measured. Capillary recruitment, as measured by metabolism of infused 1-methylxanthine (1-MX), was also assessed. When compared with either Lip or Lip + Ins, Ins had no effect on arterial blood pressure, heart rate, FBF, or vascular resistance but increased GIR, HGU, and R′g of soleus, plantaris, extensor digitorum longus, and gastrocnemius red muscles and hindlimb 1-MX metabolism. GIR, HGU, and R′g of soleus, plantaris, gastrocnemius red, and the combined muscles and 1-MX metabolism were less in Lip + Ins than in Ins rats. HGU correlated closely with hindleg capillary recruitment (r = 0.86, P < 0.001) but not total hindleg blood flow. In conclusion, acute elevation of plasma free fatty acids blocks insulin-mediated glucose uptake and capillary recruitment.
Increased Urinary Albumin Excretion, Endothelial Dysfunction, and Chronic Low-Grade Inflammation in Type 2 Diabetes
Authors: Stehouwer Coen D.A. , Gall Mari-Anne , Twisk Jos W.R. , Knudsen Elisabeth , Emeis Jef J. , Parving Hans-Henrik
Published: March 2007

In 328 type 2 diabetic patients followed for 9.0 years (mean), we investigated whether endothelial dysfunction and chronic inflammation (estimated from plasma markers) can explain the association between (micro)albuminuria and mortality. Of the patients, 113 died. Mortality was increased in patients with baseline microalbuminuria or macroalbuminuria (odds ratios as compared with normoalbuminuria, 1.78 [P < 0.05] and 2.86 [P < 0.01]) and in patients with soluble vascular cell adhesion molecule 1 in the third tertile and C-reactive protein in the second and third tertiles (odds ratios as compared with the first tertile, 2.05 [ P < 0.01], and 1.80 [P < 0.05] and 2.92 [ P < 0.01]). These associations were mutually independent. The mean yearly change in urinary albumin excretion was 9.4%; in von Willebrand factor, 8.1%; in tissue-type plasminogen activator, 2.8%; in soluble vascular cell adhesion molecule 1, 5.2%; in soluble E-selectin, −2.3%; in C-reactive protein, 3.8%; and in fibrinogen, 2.3%. The longitudinal development of urinary albumin excretion was significantly and independently determined by baseline levels of and the longitudinal development of BMI, systolic blood pressure, serum creatinine, glycated hemoglobin and plasma von Willebrand factor (baseline only), soluble E-selectin (baseline only), tissue-type plasminogen activator, C-reactive protein, and fibrinogen. The longitudinal developments of markers of endothelial function and inflammation were interrelated. In type 2 diabetes, increased urinary albumin excretion, endothelial dysfunction, and chronic inflammation are interrelated processes that develop in parallel, progress with time, and are strongly and independently associated with risk of death.
Caspase Activation in Retinas of Diabetic and Galactosemic Mice and Diabetic Patients
Authors: Mohr Susanne , Xi Xia , Tang Jie , Kern Timothy S.
Published: March 2007

Apoptosis of retinal capillary cells begins early in diabetes and likely contributes to the capillary obliteration that is an important feature of diabetic retinopathy. Caspases are proteolytic enzymes that are closely involved in the induction and execution phases of apoptosis, but their role in the development of diabetic retinopathy has not been studied previously. Our study focused on the measurement of activities of multiple caspases in retinas of mice at different durations of diabetes. Several caspases (including caspases-1, -2, -6, -8, and -9) were activated as early as 2 months of diabetes. The caspases activity pattern changed with increasing duration of disease, suggesting a slowly developing caspases cascade. Activities of executioner caspases (e.g., cas-6 and -3) became elevated after longer duration of diabetes, and the induction of cas-3 activity was associated with the duration of diabetes at which capillary cells begin to show evidence of undergoing apoptosis. Retinas from patients with type 2 diabetes likewise showed a significant increase in activities of cas-1, -3, -4, and -6. For comparison, retinal caspases were also measured in experimental galactosemia, another model that develops a diabetic-like retinopathy. The pattern of caspases activation differed between diabetes and galactosemia, but cas-1 activity became elevated soon after elevation of blood hexose concentration in both. Caspases offer new therapeutic targets to test the role of apoptosis in the development of diabetic retinopathy.
Difference in Ischemic Regulation of Vascular Endothelial Growth Factor and Pigment Epithelium--Derived Factor in Brown Norway and Sprague Dawley Rats Contributing to Different Susceptibilities to Retinal Neovascularization
Authors: Gao Guoquan , Li Yan , Fant James , Crosson Craig E. , Becerra S. Patricia , Ma Jian-xing
Published: March 2007

The present study compared susceptibilities of Sprague Dawley (SD) and Brown Norway (BN) rats with ischemia-induced retinal neovascularization. An exposure to constant hyperoxia followed by normoxia induced significant retinal neovascularization in BN rats but not in SD rats, as demonstrated by fluorescein retinal angiography, measurement of avascular area, and count of preretinal vascular cells. These results indicate a rat strain difference in susceptibility to retinal neovascularization. To understand the molecular basis responsible for the strain difference, we have measured the levels of pigment epithelium-derived factor (PEDF), an angiogenic inhibitor, and vascular endothelial growth factor (VEGF), a major angiogenic stimulator in the retina. The hyperoxia-treated BN rats showed a significant reduction in retinal PEDF, but they showed a substantial increase of VEGF at both the protein and RNA levels, resulting in an increased VEGF-to-PEDF ratio. Hyperoxia-treated SD rats showed changes in PEDF and VEGF levels that were less in magnitude and of shorter duration than in BN rats. In age-matched normal BN and SD rats, however, there was no detectable difference in the basal VEGF-to-PEDF ratio between the strains. These observations support the idea that different regulation of angiogenic inhibitors and stimulators under ischemia are responsible for the differences in susceptibility to ischemia-induced retinal neovascularization in SD and BN rats.
Abnormalities of Glucose Metabolism in Patients With Early Renal Failure
Authors: Sechi Leonardo A. , Catena Cristiana , Zingaro Laura , Melis Alessandra , De Marchi Sergio
Published: March 2007

Abnormalities of glucose metabolism and hyperinsulinemia have been demonstrated in patients with end-stage renal disease and may contribute to the development of atherosclerotic complications in these patients. In the present study, we investigated the stage of renal failure in which abnormalities of glucose metabolism develop and whether these abnormalities were associated with an increased prevalence of cardiovascular events in patients with early renal failure. In 321 untreated essential hypertensive patients, we assessed renal function by measuring 24-h creatinine clearance, urinary protein excretion, and microalbuminuria; we assessed cardiovascular status by clinical and laboratory tests; and we measured plasma glucose, insulin, and C-peptide levels at fasting and after a 75-g oral glucose load. To evaluate insulin sensitivity, a hyperinsulinemic-euglycemic clamp was performed in a subgroup of 104 patients. Patients with creatinine clearance <30 ml · min−1 · 1.73 m−2, severe hypertension, BMI <30 kg/m2, and diabetes or family history of diabetes were excluded. Hypertensive patients were found to be hyperinsulinemic when compared with 92 matched normotensive subjects. Early renal failure (creatinine clearance <90 ml · min−1 · 1.73 m−2) caused by hypertensive nephrosclerosis was detected in 116 of 321 patients. Analysis of patients with varying degrees of renal function impairment demonstrated increased plasma glucose and insulin response to oral glucose load, decreased fasting glucose-to-insulin ratio, and reduced sensitivity to insulin only in those patients with creatinine clearance <50 ml · min−1 · 1.73 m−2. Parameters of glucose metabolism were not correlated with creatinine clearance and microalbuminuria. Prevalence of atherosclerotic cardiovascular events was significantly related to reduction of creatinine clearance, but parameters of glucose metabolism were comparable in patients with and without evidence of atherosclerotic damage. Thus, in patients with hypertensive nephrosclerosis and early impairment of glomerular filtration, alterations of glucose metabolism become evident only when creatinine clearance is <50 ml · min−1 · 1.73 m−2 and are not related to microalbuminuria and cardiovascular complications.
The Second Activating Glucokinase Mutation (A456V)
Authors: Christesen Henrik B.T. , Jacobsen Bendt B. , Odili Stella , Buettger Carol , Cuesta-Munoz Antonio , Hansen Torben , Brusgaard Klaus , Massa Ornella , Magnuson Mark A. , Shiota Chiyo , Matschinsky Franz M. , Barbetti Fabrizio
Published: March 2007

In this study, a second case of hyperinsulinemic hypoglycemia due to activation of glucokinase is reported. The 14-year-old proband had a history of neonatal hypoglycemia, treated with diazoxide. He was admitted with coma and convulsions due to nonketotic hypoglycemia. His BMI was 34 kg/m2, and his fasting blood glucose ranged from 2.1 to 2.7 mmol/l, associated with inappropriately high serum levels of insulin, C-peptide, and proinsulin. An oral glucose tolerance test (OGTT) showed exaggerated responses of these peptides followed by profound hypoglycemia. Treatment with diazoxide and chlorothiazide was effective. His mother never had clinical hypoglycemic symptoms, even though her fasting blood glucose ranged from 2.9 to 3.5 mmol/l. Increases in serum insulin, C-peptide, and proinsulin in response to an OGTT suggested a lower threshold for glucose-stimulated insulin release (GSIR). Screening for mutations in candidate genes revealed a heterozygous glucokinase mutation in exon 10, substituting valine for alanine at codon 456 (A456V) in the proband and his mother. The purified recombinant glutathionyl S-transferase fusion protein of the A456V glucokinase revealed a decreased glucose S0.5 (the concentration of glucose needed to achieve the half-maximal rate of phosphorylation) from 8.04 (wild-type) to 2.53 mmol/l. The mutant’s Hill coefficient was decreased, and its maximal specific activity kcat was increased. Mathematical modeling predicted a markedly lowered GSIR threshold of 1.5 mmol/l. The theoretical and practical implications are manifold and significant.
Molecular Analysis of Berardinelli-Seip Congenital Lipodystrophy in Oman
Authors: Heathcote Kirsten , Rajab Anna , Magré Jocelyne , Syrris Petros , Besti Mehran , Patton Michael , Délépine Marc , Lathrop Mark , Capeau Jacqueline , Jeffery Steve
Published: March 2007

Congenital generalized lipodystrophy (CGL) is a rare disorder characterized by the absence of body fat and insulin resistance and accompanied by other features, including acanthosis nigricans, organomegaly, hyperandrogenism, and diabetes. We have examined case subjects from 11 families in Oman with CGL. All subjects were the progeny of consanguineous marriages; therefore, a homozygosity mapping strategy was used to investigate the reported loci, 11q13 and 9q34. Three subjects could be linked to 11q13, and mutations were found within the seipin gene. An additional eight subjects were linked to 9q34, but the locus was in a 9-cM interval with no known microsatellites, so further fine mapping was not possible. However, two sibships (four subjects) did not map to either locus, raising the possibility of more than two lipodystrophy loci within the Oman population.
Indinavir Induces Acute and Reversible Peripheral Insulin Resistance in Rats
Authors: Hruz Paul W. , Murata Haruhiko , Qiu Haijun , Mueckler Mike
Published: March 2007

The use of HIV protease inhibitors (PIs) has been associated with several metabolic changes, including lipodystrophy, hyperlipidemia, and insulin resistance. The etiology of these adverse effects remains unknown. PIs have recently been found to cause acute and reversible inhibition of GLUT4 activity in vitro. To determine the acute in vivo effects of indinavir on whole-body glucose homeostasis, glucose tolerance tests were performed on PI-naïve Wistar rats immediately after a single intravenous dose of indinavir. Glucose and insulin levels were significantly elevated in indinavir-treated versus control rats (P < 0.05) during the initial 30 min of the glucose tolerance test. Under euglycemic- hyperinsulinemic clamp conditions, indinavir treatment acutely reduced the glucose infusion rate required to maintain euglycemia by 18 and 49% at indinavir concentrations of 14 and 27 μmol/l, respectively. Muscle 2-deoxyglucose uptake was similarly reduced under these conditions. Restoration of insulin sensitivity was observed within 4 h after stopping the indinavir infusion. Indinavir did not alter the suppression of hepatic glucose output under hyperinsulinemic conditions. These data demonstrate that indinavir causes acute and reversible changes in whole-body glucose homeostasis in rats and support the contribution of GLUT4 inhibition to the development of insulin resistance in patients treated with PIs.
Pulsatile Insulin Release From Islets Isolated From Three Subjects With Type 2 Diabetes
Authors: Lin Jian-Man , Fabregat Marta E. , Gomis Ramon , Bergsten Peter
Published: March 2007

Plasma insulin in healthy subjects shows regular oscillations, which are important for the hypoglycemic action of the hormone. In individuals with type 2 diabetes, these regular variations are altered, which has been implicated in the development of insulin resistance and hyperglycemia. The origin of the change is unknown, but derangement of the islet secretory pattern has been suggested as a contributing cause. In the present study, we show the dynamics of insulin release from individually perifused islets isolated from three subjects with type 2 diabetes. Insulin release at 3 mmol/l glucose was 10.5 ± 4.5 pmol · g−1 · s−1 and pulsatile (0.26 ± 0.05 min−1). In islets from one subject, 11 mmol/l glucose transiently increased insulin release by augmentation of the insulin pulses without affecting the frequency. Addition of 1 mmol/l tolbutamide did not increase insulin release. In islets from the remaining subjects, insulin release was not affected by 11 mmol/l glucose. Tolbutamide transiently increased insulin release in islets from one subject. Insulin release from four normal subjects at 3 mmol/l glucose was 4.3 ± 0.8 pmol · g−1 · s−1 and pulsatile (0.23 ± 0.03 min−1). At 11 mmol/l glucose, insulin release increased in islets from all subjects. Tolbutamide further increased insulin release in islets from two subjects. It is concluded that islets from the three individuals with type 2 diabetes release insulin in pulses. The impaired secretory response to glucose may be related to impaired metabolism before mitochondrial degradation of the sugar.
The Ryanodine Receptor Calcium Channel of β-Cells
Authors: Islam Md. Shahidul
Published: March 2007

The list of Ca2+ channels involved in stimulus-secretion coupling in β-cells is increasing. In this respect the roles of the voltage-gated Ca2+ channels and IP3 receptors are well accepted. There is a lack of consensus about the significance of a third group of Ca2+ channels called ryanodine (RY) receptors. These are large conduits located on Ca2+ storage organelle. Ca2+ gates these channels in a concentration- and time-dependent manner. Activation of these channels by Ca2+ leads to fast release of Ca2+ from the stores, a process called Ca2+-induced Ca2+ release (CICR). A substantial body of evidence confirms that β-cells have RY receptors. CICR by RY receptors amplifies Ca2+ signals. Some properties of RY receptors ensure that this amplification process is engaged in a context-dependent manner. Several endogenous molecules and processes that modulate RY receptors determine the appropriate context. Among these are several glycolytic intermediates, long-chain acyl CoA, ATP, cAMP, cADPR, NO, and high luminal Ca2+ concentration, and all of these have been shown to sensitize RY receptors to the trigger action of Ca2+. RY receptors, thus, detect co-incident signals and integrate them. These Ca2+ channels are targets for the action of cAMP-linked incretin hormones that stimulate glucose-dependent insulin secretion. In β-cells some RY receptors are located on the secretory vesicles. Thus, despite their low abundance, RY receptors are emerging as distinct players in β-cell function by virtue of their large conductance, strategic locations, and their ability to amplify Ca2+ signals in a context-dependent manner.
Tumor Necrosis Factor-α Suppresses Adipocyte-Specific Genes and Activates Expression of Preadipocyte Genes in 3T3-L1 Adipocytes
Authors: Ruan Hong , Hacohen Nir , Golub Todd R. , Van Parijs Luk , Lodish Harvey F.
Published: March 2007

Tumor necrosis factor-α (TNF-α) is a contributing cause of the insulin resistance seen in obesity and obesity-linked type 2 diabetes, but the mechanism(s) by which TNF-α induces insulin resistance is not understood. By using 3T3-L1 adipocytes and oligonucleotide microarrays, we identified 142 known genes reproducibly upregulated by at least threefold after 4 h and/or 24 h of TNF-α treatment, and 78 known genes downregulated by at least twofold after 24 h of TNF-α incubation. TNF-α-induced genes include transcription factors implicated in preadipocyte gene expression or NF-κB activation, cytokines and cytokine-induced proteins, growth factors, enzymes, and signaling molecules. Importantly, a number of adipocyte-abundant genes, including GLUT4, hormone sensitive lipase, long-chain fatty acyl-CoA synthase, adipocyte complement-related protein of 30 kDa, and transcription factors CCAAT/enhancer binding protein-α, receptor retinoid X receptor-α, and peroxisome profilerator-activated receptor γ were significantly downregulated by TNF-α treatment. Correspondingly, 24-h exposure of 3T3-L1 adipocytes to TNF-α resulted in reduced protein levels of GLUT4 and several insulin signaling proteins, including the insulin receptor, insulin receptor substrate 1 (IRS-1), and protein kinase B (AKT). Nuclear factor-κB (NF-κB) was activated within 15 min of TNF-α addition. 3T3-L1 adipocytes expressing IκBα-DN, a nondegradable NF-κB inhibitor, exhibited normal morphology, global gene expression, and insulin responses. However, absence of NF-κB activation abolished suppression of >98% of the genes normally suppressed by TNF-α and induction of 60–70% of the genes normally induced by TNF-α. Moreover, extensive cell death occurred in IκBα-DN-expressing adipocytes after 2 h of TNF-α treatment. Thus the changes in adipocyte gene expression induced by TNF-α could lead to insulin resistance. Further, NF-κB is an obligatory mediator of most of these TNF-α responses.
Effects of Acute and Chronic Administration of the Melanocortin Agonist MTII in Mice With Diet-Induced Obesity
Authors: Pierroz Dominique D. , Ziotopoulou Mary , Ungsunan Linda , Moschos Stergios , Flier Jeffrey S. , Mantzoros Christos S.
Published: March 2007

High-fat diet-induced obesity (DIO) in rodents is associated with hyperleptinemia and resistance to leptin, but the response to agents acting downstream of leptin receptors remains unknown. We assessed the response of mice with DIO to treatment with MTII, an α-melanocyte-stimulating hormone analog. MTII delivered four times daily by intraperitoneal injection to C57BL/6J mice produced a dose-responsive effect on food intake, body weight, leptin, corticosterone, insulin, and free fatty acids. In DIO mice, administration of MTII 100 μg q.i.d. i.p. markedly suppressed feeding during the first 4 days of treatment, with food intake returning to control levels at day 5. Progressive weight loss also occurred over the first 4 days, after which weight plateaued at a level below control. After 8 days of treatment, MTII-treated DIO mice had major suppression of both leptin and insulin levels. Central administration of MTII for 4 days (10 nmol/day) in DIO mice significantly suppressed food intake, induced weight loss, and increased energy expenditure. These results indicate that 1) MTII administration to DIO mice causes suppression of food intake and body weight loss, and decreased food intake is primarily responsible for weight loss; 2) peripheral MTII improves insulin resistance in DIO mice; 3) “tachyphylaxis” to the effect of chronic MTII treatment on food intake occurs; and 4) at least some of the effects of MTII are exerted centrally. In conclusion, treatment with a melanocortin agonist is a promising therapeutic approach to DIO and associated insulin resistance.
A 1α,25-Dihydroxyvitamin D3 Analog Enhances Regulatory T-Cells and Arrests Autoimmune Diabetes in NOD Mice
Authors: Gregori Silvia , Giarratana Nadia , Smiroldo Simona , Uskokovic Milan , Adorini Luciano
Published: March 2007

Type 1 diabetes is a chronic progressive autoimmune disease characterized by mononuclear cell infiltration, dominated by interleukin-12 (IL-12)-dependent Th1 cells, of the pancreatic islets, with subsequent destruction of insulin-producing β-cells. Here, we demonstrate that treatment of adult nonobese diabetic (NOD) mice with an analog of 1α,25-dihydroxyvitamin D3, an immunomodulatory agent preventing dendritic cell maturation, decreases lipopolysaccharide-induced IL-12 and γ-interferon production, arrests Th1 cell infiltration and progression of insulitis, and inhibits diabetes development at nonhypercalcemic doses. Arrest of disease progression is accompanied by an enhanced frequency in the pancreatic lymph nodes of CD4+CD25+ regulatory T-cells that are able to inhibit the T-cell response to the pancreatic autoantigen insulinoma-associated protein 2 and to significantly delay disease transfer by pathogenic CD4+CD25− cells. Thus, a short treatment of adult NOD mice with an analog of 1,25-dihydroxyvitamin D3 inhibits IL-12 production, blocks pancreatic infiltration of Th1 cells, enhances CD4+CD25+ regulatory cells, and arrests the progression of type 1 diabetes, suggesting its possible application in the treatment of human autoimmune diabetes.
Limited Impact of Vigorous Exercise on Defenses Against Hypoglycemia
Authors: McGregor Veronica P. , Greiwe Jeffrey S. , Banarer Salomon , Cryer Philip E.
Published: March 2007

Hypoglycemia-associated autonomic failure (HAAF)—reduced autonomic (including adrenomedullary epinephrine) and symptomatic responses to hypoglycemia caused by recent antecedent hypoglycemia—plays a key role in the pathogenesis of defective glucose counterregulation and hypoglycemia unawareness and thus iatrogenic hypoglycemia in type 1 diabetes. On the basis of the findings that cortisol infusion mimics and deficient or inhibited cortisol secretion minimizes this phenomenon, it has been suggested that the cortisol response to antecedent hypoglycemia mediates HAAF. We tested the hypothesis that any stimulus that releases cortisol, such as exercise, reduces autonomic and symptomatic responses to subsequent hypoglycemia. Thirteen healthy young adults (four women) were studied on three occasions in random sequence: 1) cycle exercise (∼70% peak oxygen consumption) from 0830 to 0930 h and from 1200 to 1300 h on day 1 and hyperinsulinemic (2.0 mU · kg−1 · min−1) stepped hypoglycemic (85, 75, 65, 55, and 45 mg/dl) clamps on day 2, 2) rest on day 1 and identical hypoglycemic clamps on day 2, and 3) hyperinsulinemic-euglycemic clamps. Exercise raised plasma cortisol concentrations to 16.9 ± 1.9 (0930 h) and 16.6 ± 1.6 μg/dl (1300 h) on day 1. Compared with rest on day 1, exercise on day 1 was associated with reduced epinephrine (P = 0.0113) responses—but not norepinephrine (P = 0.6270), neurogenic symptom (P = 0.6470), pancreatic polypeptide (P = 0.0629), or glucagon (P = 0.0436, but higher) responses—to hypoglycemia on day 2. However, the effect was small. (The final day 2 hypoglycemia epinephrine values were 765 ± 106 pg/ml after rest on day 1 and 550 ± 94 pg/ml after exercise on day 1 compared with 30 ± 6 pg/ml during euglycemia.) These data are consistent with the hypothesis that the cortisol response to hypoglycemia mediates in part the reduced epinephrine response to subsequent hypoglycemia, one key component of HAAF in type 1 diabetes. However, the small effect suggests that an additional factor or factors may well be involved. These data do not support the hypothesis that the cortisol response to hypoglycemia mediates the reduced neurogenic symptom response to subsequent hypoglycemia, another key component of HAAF in type 1 diabetes.
Rosiglitazone, a Peroxisome Proliferator-Activated Receptor-γ, Inhibits the Jun NH2-Terminal Kinase/Activating Protein 1 Pathway and Protects the Heart From Ischemia/Reperfusion Injury
Authors: Khandoudi Nassirah , Delerive Philippe , Berrebi-Bertrand Isabelle , Buckingham Robin E. , Staels Bart , Bril Antoine
Published: March 2007

This study was conducted to evaluate whether treatment of normal and diabetic rat hearts with rosiglitazone, a high-affinity ligand of the peroxisome proliferator-activated receptor-γ (PPAR-γ) used for the treatment of type 2 diabetes, improves postischemic functional recovery. The effects of acute rosiglitazone administration were investigated using working hearts isolated from normal rat or rats diabetic for 4 weeks after streptozotocin (STZ) injection. Hearts were subjected to 30 min of normothermic, zero-flow ischemia followed by 30-min reperfusion. Rosiglitazone (1 μmol/l) administered before ischemia had no effect on cardiac function during baseline perfusion, but it significantly improved aortic flow during reperfusion in both normal and diabetic hearts. In a chronic protocol in which rosiglitazone was given by daily gavage (10 μmol/kg body wt) immediately after STZ injection, rosiglitazone also prevented postischemic injury and significantly improved functional recovery. Using Western immunoblotting, it was demonstrated that the acute cardioprotective effect of rosiglitazone is associated with an inhibition of Jun NH2-terminal kinase phosphorylation in both normal and diabetic rat hearts. Furthermore, rosiglitazone also inhibited activating protein-1 DNA-binding activity. These data, demonstrating that rosiglitazone limits postischemic injury in isolated hearts, suggest an important function for PPAR-γ in the heart.
The 807T Allele in α2 Integrin Is Protective Against Atherosclerotic Arterial Wall Thickening and the Occurrence of Plaque in Patients With Type 2 Diabetes
Authors: Maeno Takaaki , Koyama Hidenori , Tahara Hideki , Komatsu Miyoko , Emoto Masanori , Shoji Tetsuo , Inaba Masaaki , Miki Takami , Okuno Yasuhisa , Nishizawa Yoshiki
Published: March 2007

Polymorphism of α2 integrin (C807T) is shown to be associated with an increased incidence of thrombotic cardiovascular events. However, it is not clear whether this polymorphism is associated with atherosclerotic arterial wall thickening. In this study, we examined the association of C807T polymorphism with arterial wall thickness in 265 control subjects and 272 patients with type 2 diabetes. In all subjects, intima-media thickness of the right carotid artery in the 807TT group (0.649 ± 0.028 mm [SE]) was significantly (P = 0.0228, Scheffe’s F test) less than in the 807CC group (0.767 ± 0.033). This effect of polymorphism is gene dose dependent (P = 0.0227, ANOVA). The similar association was also observed in patients with diabetes but not in control subjects. Multiple regression analysis in all subjects revealed that the T allele was inversely (β = −0.095, P = 0.021) associated with intima-media thickness independent of age, HbA1c, and HDL cholesterol. Finally, an inverse relation between the occurrence of carotid plaque and the T allele was observed in patients with diabetes with an adjusted odds ratio of 0.487 (P = 0.031) in multiple logistic regression analyses. These results suggest that the number of 807T alleles in α2 integrin is protective against atherosclerotic arterial wall thickening and the occurrence of plaque in patients with type 2 diabetes.
Mechanisms of Amelioration of Glucose-Induced Endothelial Dysfunction Following Inhibition of Protein Kinase C In Vivo
Authors: Booth Gregory , Stalker Timothy J. , Lefer Allan M. , Scalia Rosario
Published: March 2007

Inhibition of protein kinase C (PKC) activity has been shown to improve the endothelial dysfunction associated with hyperglycemia and diabetes. The mechanisms by which inhibition of PKC activity ameliorates endothelial dysfunction in diabetes are not well understood. We investigated the relationship between PKC inhibition and leukocyte-endothelium interaction in the microcirculation of the rat mesentery exposed to 25 mmol/l d-glucose for 12 h. d-Glucose significantly increased leukocyte rolling and adherence in mesenteric postcapillary venules. This proinflammatory action of d-glucose was inhibited by superfusion of the mesentery with 30 nmol/l bisindolylmaleimide-I, a potent, selective PKC inhibitor (P < 0.01 vs. glucose alone after 90 min of superfusion). Immunohistochemical localization of the cell adhesion molecules P-selectin and intercellular adhesion molecule (ICAM)-1 on the endothelial cell surface was increased by 25 mmol/l d-glucose (P < 0.001 vs. control tissue from rats injected with saline), which was significantly reduced by bisindolylmaleimide-I (P < 0.001 vs. glucose alone). In addition, we studied adhesion of isolated neutrophils to rat superior mesenteric artery (SMA) vascular segments stimulated with 25 mmol/l d-glucose for 4 h in vitro. Pretreatment of the SMA vascular segments with either superoxide dismutase enzyme (100 units/ml) or bisindolylmaleimide-I (30 nmol/l) equally inhibited the increased neutrophil adherence to SMA endothelium in response to glucose. These data demonstrate that inhibition of PKC activity reduces leukocyte-endothelium interactions by suppressing surface expression of endothelial cell adhesion molecules in response to increased oxidative stress. These results provide a novel mechanism by which inhibition of PKC activity improves endothelial cell function in hyperglycemia and diabetes.
The Early Natural History of Nephropathy in Type 1 Diabetes
Authors: Mauer Michael , Drummond Keith ,   for the International Diabetic Nephropathy Study Group
Published: March 2007

This report describes the design and baseline demographic and clinical data in the study of the early natural history of diabetic nephropathy (DN) in type 1 diabetes carried out by the International Diabetic Nephropathy Study Group. The study enrolled 243 patients ages 10–40 years (16.8 ± 6.0, mean ± SD) with type 1 diabetes for 2–20 years (8.0 ± 4.2) at centers in the United States (Minneapolis), Canada (Montreal), and France (Paris). At baseline, all patients were normotensive, none had reduced glomerular filtration rate (GFR), and all but eight were normoalbuminuric (NA). All patients had baseline renal biopsies. During the study, patients will have multiple measurements of blood pressure (BP), renal function, albumin excretion rate (AER), glycemia, and other variables, with repeat renal biopsies planned at 5 years after baseline. The 31.3% of the approached patients who agreed to participate were similar in age, diabetes duration, HbA1c, AER, and sex to those refusing participation. Age, diabetes duration, HbA1c, and AER were similar among the three centers, but systolic BP, GFR, renal plasma flow (RPF), and filtration fraction were lower in the Paris center. The 153 patients with hyperfiltration (GFR >130 ml · min−1 · 1.73 m−2) had greater RPF than those with normal GFR. The eight microalbuminuric patients tended to have longer duration of diabetes but were otherwise similar to the NA patients. The role of these and other variables in determining the development rate of the early lesions of DN over the 5 years between biopsies is the central issue under study.
Effect of the (C825T) Gβ3 Polymorphism on Adrenoceptor-Mediated Lipolysis in Human Fat Cells
Authors: Rydén Mikael , Faulds Gary , Hoffstedt Johan , Wennlund Anders , Arner Peter
Published: March 2007

A common Gβ3 gene polymorphism (C825T) influences G protein receptor-mediated signal transduction. We investigated whether this polymorphism influences lipolysis in isolated subcutaneous fat cells from 114 healthy obese subjects. The Gβ3 protein content was markedly decreased in adipocytes of TT carriers, but the alternatively spliced short form of Gβ3 previously shown in platelets of 825T carriers was not detected. Fat cells of TT carriers showed a significant 10-fold decrease in the half-maximum effective concentration of agonists selective for lipolytic β1- and β2-adrenoceptors as well as for the antilipolytic α2A-adrenoceptor. In TT carriers, maximum β-adrenoceptor agonist-stimulated lipolysis was decreased, but the maximum antilipolytic effect of α2-adrenoceptors was less marked. Norepinephrine induced adipocyte lipolysis and circulating fasting levels of free fatty acids and glycerol were reduced by half in TT carriers. The polymorphism did not influence the adipocyte content of α2A-adrenoceptors, β2-adrenoceptors, Gαi, or Gαs. In conclusion, the C825T variant of Gβ3 influences lipolysis. Adipocytes of TT carriers have a lower Gβ3 protein content and a decreased function of native Gs- as well as Gi-coupled adrenoceptors, which reduces the lipolytic effect of catecholamines. These data differ from those obtained in other cell systems that have shown increased expression of an alternative spliced Gβ3 variant and enhanced G protein signaling in 825T carriers, indicating that the polymorphism has cell type-specific effects that may be of importance for type 2 diabetes and other insulin-resistant conditions.
Contribution of Known and Unknown Susceptibility Genes to Early-Onset Diabetes in Scandinavia
Authors: Lindgren Cecilia M. , Widén Elisabeth , Tuomi Tiinamaija , Li Haiyan , Almgren Peter , Kanninen Timo , Melander Olle , Weng Jianping , Lehto Markku , Groop Leif C.
Published: March 2007

In an attempt to identify novel susceptibility genes predisposing to early-onset diabetes (EOD), we performed a genome-wide scan using 433 markers in 222 individuals (119 with diabetes) from 29 Scandinavian families with ≥2 members with onset of diabetes ≤45 years. The highest nonparametric linkage (NPL) score, 2.7 (P < 0.01), was observed on chromosome 1p (D1S473/D1S438). Six other regions on chromosomes 3p, 7q, 11q, 18q, 20q, and 21q showed a nominal P value <0.05. Of the EOD subjects in these 29 families, 20% were GAD antibody positive and 68% displayed type 1 diabetes HLA risk alleles (DQB*02 or 0302). Mutations in maturity-onset diabetes of the young (MODY) 1–5 genes and the A3243G mitochondrial DNA mutation were detected by single-strand conformation polymorphism and direct sequencing. To increase homogeneity, we analyzed a subsample of five families with autosomal dominant inheritance of EOD (greater than or equal to two members with age at diagnosis ≤35 years). The highest NPL scores were found on chromosome 1p (D1S438–D1S1665; NPL 3.0; P < 0.01) and 16q (D16S419; NPL 2.9; P < 0.01). After exclusion of three families with MODY1, MODY3, and mitochondrial mutations, the highest NPL scores were observed on chromosomes 1p (D1S438; NPL 2.6; P < 0.01), 3p (D3S1620; NPL 2.2; P < 0.03), 5q (D5S1465; NPL 2.1; P < 0.03), 7q (D7S820; NPL 2.0; P < 0.03), 18q (D18S535; NPL 1.9; P < 0.04), 20q (D20S195; NPL 2.5; P < 0.02), and 21q (D21S1446; NPL 2.2; P < 0.03). We conclude that considerable heterogeneity exists in Scandinavian subjects with EOD; 24% had MODY or maternally inherited diabetes and deafness, and ∼60% were GAD antibody positive or had type 1 diabetes-associated HLA genotypes. Our data also point at putative chromosomal regions, which could harbor novel genes that contribute to EOD.
Haplotype Combinations of Calpain 10 Gene Polymorphisms Associate With Increased Risk of Impaired Glucose Tolerance and Type 2 Diabetes in South Indians
Authors: Cassell Paul G. , Jackson Alan E. , North Bernard V. , Evans Julie C. , Syndercombe-Court Denise , Phillips Chris , Ramachandran Ambady , Snehalatha Chamukuttan , Gelding Susan V. , Vijayaravaghan Shanti , Curtis David , Hitman Graham A.
Published: March 2007

Haplotype combination 112/121 and its intrinsic variants (UCSNP43, -19, and -63) identified within the calpain 10 gene are associated with increased risk of type 2 diabetes in Mexican-Americans. We evaluated whether this haplotype combination and its constituent haplotypes and variants contribute to increased susceptibility to impaired fasting glucose (IFG)/impaired glucose tolerance (IGT) and type 2 diabetes in a South Indian population. Two study groups were used: 95 families ascertained through a proband with type 2 diabetes and 468 subjects recruited as part of an urban survey (69.1% with normal glucose tolerance, 12.8% with IFG/IGT, and 18.2% with type 2 diabetes). The four-locus haplotype combination 1112/1121 (UCSNP44, -43, -19, and -63) in South Indians conferred both a 10.7-fold increased risk for IFG/IGT (P = 0.001) and a 5.78- to 6.52-fold increased risk for type 2 diabetes in the two study groups (families P = 0.025, urban survey P = 0.015). A combination of the 1112 haplotype with the 1221 haplotype also appeared to increase risk for both IFG/IGT and type 2 diabetes. Contrary to what might be expected, quantitative trait analysis in the families found that transmission of the disease-related 1121 and 1112 haplotypes was associated with a reduced hip size and lower waist-to-hip ratio, respectively. This study supports the paradigm that specific haplotype combinations of calpain 10 variants increase risk of both IFG/IGT and type 2 diabetes. However, the relative infrequency of the “at-risk” combinations in the South Indian population suggests that calpain 10 is not a common determinant of susceptibility to type 2 diabetes.
5′ Flanking Variants of Resistin Are Associated With Obesity
Authors: Engert James C. , Vohl Marie-Claude , Williams Scott M. , Lepage Pierre , Loredo-Osti J C. , Faith Janet , Doré Carole , Renaud Yannick , Burtt Noël P. , Villeneuve Amélie , Hirschhorn Joel N. , Altshuler David , Groop Leif C. , Després Jean-Pierre , Gaudet Daniel , Hudson Thomas J.
Published: March 2007

Diabetes and obesity have long been known to be related. The recently characterized adipocyte hormone resistin (also called FIZZ3/ADSF) has been implicated as a molecular link between impaired glucose tolerance (IGT) and obesity in mice. A search for sequence variants at the human resistin locus identified nine single-nucleotide polymorphisms (SNPs) but no coding variants. An investigation into the association of these SNPs with diabetes and obesity revealed two 5′ flanking variants (g.-537 and g.-420), in strong linkage disequilibrium, that are associated with BMI. In nondiabetic individuals from the Quebec City area and the Saguenay-Lac-St-Jean region of Quebec, the g.-537 mutation (allelic frequency = 0.04) was significantly associated with an increase in BMI (P = 0.03 and P = 0.01, respectively). When the data from these two populations were combined and adjusted for age and sex, both the g.-537 (odds ratio [OR] 2.72, 95% CI 1.28–5.81) and the g.-420 variants (1.58, 1.06–2.35) were associated with an increased risk for a BMI ≥30 kg/m2. In contrast, in case/control and family-based study populations from Scandinavia, we saw no effect on BMI with either of these promoter variants. No association was seen with diabetes in any of the population samples.
A Common Polymorphism in the 5′-Untranslated Region of the VEGF Gene Is Associated With Diabetic Retinopathy in Type 2 Diabetes
Authors: Awata Takuya , Inoue Kiyoaki , Kurihara Susumu , Ohkubo Tomoko , Watanabe Masaki , Inukai Kouichi , Inoue Ikuo , Katayama Shigehiro
Published: March 2007

Vascular endothelial growth factor (VEGF), a major mediator of vascular permeability and angiogenesis, may play a pivotal role in mediating the development and progression of diabetic retinopathy. In the present study, we examined the genetic variations of the VEGF gene to assess its possible relation to diabetic retinopathy in type 2 diabetic patients. Among seven common polymorphisms in the promoter region, 5′-untranslated region (UTR) and 3′UTR of the VEGF gene, genotype distribution of the C(−634)G polymorphism differed significantly (P = 0.011) between patients with (n = 150) and without (n = 118) retinopathy, and the C allele was significantly increased in patients with retinopathy compared with those without retinopathy (P = 0.0037). The odds ratio (OR) for the CC genotype of C(−634)G to the GG genotype was 3.20 (95% CI 1.45–7.05, P = 0.0046). The −634C allele was significantly increased in patients with nonproliferative diabetic retinopathy (non-PDR) (P = 0.0026) and was insignificantly increased in patients with proliferative diabetic retinopathy (PDR) (P = 0.081) compared with patients without retinopathy, although frequencies of the allele did not differ significantly between the non-PDR and PDR groups. Logistic regression analysis revealed that the C(−634)G polymorphism was strongly associated with an increased risk of retinopathy (P = 0.0018). Furthermore, VEGF serum levels were significantly higher in healthy subjects with the CC genotype of the C(−634)G polymorphism than in those with the other genotypes. These data suggest that the C(−634)G polymorphism in the 5′UTR of the VEGF gene is a novel genetic risk factor for diabetic retinopathy.
Positional Candidate Gene Analysis of Lim Domain Homeobox Gene (Isl-1) on Chromosome 5q11-q13 in a French Morbidly Obese Population Suggests Indication for Association With Type 2 Diabetes
Authors: Barat-Houari Mouna , Clément Karine , Vatin Vincent , Dina Christian , Bonhomme Geneviève , Vasseur Francis , Guy-Grand Bernard , Froguel Philippe
Published: March 2007

The Lim domain homeobox gene (Isl-1) is a positional candidate gene for obesity that maps on chromosome 5q11-q13, a locus linked to BMI and leptin levels in French Caucasians. Isl-1 might be involved in body weight regulation and glucose homeostasis via the activation of proglucagon gene expression, which encodes for glucagon and glucagon-like peptides. By mutation screening of 72 obese subjects, we identified three single-nucleotide polymorphisms (SNPs) in the Isl1 gene. The allele frequencies in the morbidly obese group did not differ from that of the control group. In the obese group, the −47G allele was associated with a decreased risk of type 2 diabetes (odds ratio 0.41, P = 0.019). The AG bearers displayed a higher maximal BMI than the AA bearers in the whole obese group (P = 0.026) as well as in the type 2 diabetic obese subgroup (P = 0.014). In obese families, this allele was not preferentially transmitted from heterozygous parents to their obese siblings, indicating that Isl-1 does not contribute to the linkage with obesity on 5cen-q. However, in French Caucasian morbidly obese subjects, the Isl1-47A→G SNP may modulate the risk for type 2 diabetes and may increase body weight in diabetic morbidly obese subjects.
Genetic Studies of Late Diabetic Complications
Authors: Rogus John J. , Warram James H. , Krolewski Andrzej S.
Published: March 2007

Genes play a role in many processes underlying late diabetic complications, but efforts to identify genetic variants have produced disappointing and contradictory results. Here, we evaluate whether the study designs and analytic methods commonly being used are optimal for finding susceptibility genes for diabetic complications. We do so by generating plausible genetic models and assessing the performance of case-control and family-based trio study designs. What emerges as a key determinant of success is duration of diabetes. This perspective focuses on duration of diabetes before complication onset and its influence on the ability to detect major and minor gene effects. It does not delve into the distinct effect of duration after complication onset, which can enrich case subjects with genotypes conferring survival advantage. We use clinically diagnosed nephropathy in type 1 diabetes to show how ignoring duration can result in considerable power loss in both case-control and family-based trio designs. We further show how, under certain circumstances, disregard for duration information can paradoxically lead to implicating nonrisk alleles as causative. Our results indicate that problems can be minimized by selecting case subjects with short diabetes duration and, to a lesser extent, control subjects with long duration or, perhaps, by adjusting for duration during analysis.
Diabetes Impairs Hypothalamo-Pituitary-Adrenal (HPA) Responses to Hypoglycemia, and Insulin Treatment Normalizes HPA but not Epinephrine Responses
Authors: Chan Owen , Chan Stephen , Inouye Karen , Shum Kathy , Matthews Stephen G. , Vranic Mladen
Published: March 2007

We recently established that in addition to plasma adrenocorticotrophic hormone (ACTH) and corticosterone, hypothalamic corticotrophin-releasing hormone (CRH) mRNA and hippocampal type 1 glucocorticoid receptor (GR1) mRNA were also upregulated in uncontrolled streptozotocin-induced diabetes. In the current study, control, diabetic, and insulin-treated diabetic rats underwent a hyperinsulinemic-hypoglycemic glucose clamp to evaluate central mechanisms of hypothalamo-pituitary-adrenal (HPA) and counterregulatory responses to insulin-induced hypoglycemia. Increases in plasma ACTH, corticosterone, and epinephrine were significantly lower in diabetic rats versus controls. Insulin treatment restored ACTH and corticosterone but not epinephrine responses to hypoglycemia in diabetic rats. Glucagon and norepinephrine responses to hypoglycemia were not affected by diabetes or insulin treatment. In response to hypoglycemia, hypothalamic CRH mRNA and pituitary proopiomelanocortin mRNA expression increased in control and insulin-treated but not in untreated diabetic rats. Arginine vasopressin mRNA was unaltered by hypoglycemia in all groups. Interestingly, hypoglycemia decreased hippocampal GR1 mRNA expression in control and insulin-treated diabetic rats but not in diabetic rats. In contrast, type 2 glucocortoid receptor (GR2) mRNA was not altered by hypoglycemia. In conclusion, despite increased basal HPA activity, HPA responses to hypoglycemia were markedly reduced in uncontrolled diabetes. We speculate that the defect in CRH response could be related to the defective GR1 response. It is intriguing that insulin treatment restored the HPA response to hypoglycemia but, surprisingly, not the deficient epinephrine response. This is important because during severe hypoglycemia, epinephrine is an important counterregulatory hormone.