bluuebunny/crossref_metadata_2025 huggingface dataset:
Downregulation of Fibronectin Overexpression Reduces Basement Membrane Thickening and Vascular Lesions in Retinas of Galactose-Fed Rats
Authors: Roy Sayon , Sato Tsuyoshi , Paryani Gulabray , Kao Richard
Published: March 2007

Overexpression of extracellular matrix (ECM) components is closely associated with the development of vascular basement membrane (BM) thickening, a histological hallmark of diabetic microangiopathy. To determine whether BM thickening of retinal capillaries could be prevented by down regulating synthesis of fibronectin, an ECM component, we used antisense oligos targeted against translation initiation site of the fibronectin transcript in galactose-fed rat, an animal model of diabetic retinopathy. After 2 months of galactose-feeding, intravitreal administration of 3 μmol/l antisense fibronectin oligos was initiated at monthly intervals for 3 months. The antisense strategy significantly reduced fibronectin mRNA and protein level in the retinas of treated eyes compared with untreated eyes of galactose-fed rats (130 ± 16 vs. 179 ± 18% of control, P < 0.01, and 144 ± 28 vs. 204 ± 22% of control, respectively, r = 0.9) and resulted in partial reduction of retinal capillary BM width (123 ± 16 vs. 201 ± 12 nm, P < 0.03). In eyes treated with antisense fibronectin oligos, ∼35% reduction in both pericyte loss and acellular retinal capillaries was observed (P < 0.04 and P < 0.03, respectively). Glycohemoglobin level was consistently elevated in the treated (6.9 ± 0.6%) and untreated (6.5 ± 0.7%) galactose-fed rats compared with control rats (4.5 ± 0.8%). Overall, these results indicate that downregulation of fibronectin synthesis reduces BM thickening in retinal capillaries with beneficial effect to retinal lesions. The antisense fibronectin oligos may provide a useful approach for reducing vascular lesions in diabetic retinopathy. The thickened vascular BM may be a potential therapeutic target for preventing retinal lesions in diabetic retinopathy.
The Peroxisome Proliferator-Activated Receptor-γ2 Gene Polymorphism (Pro12Ala) Beneficially Influences Insulin Resistance and Its Tracking From Childhood to Adulthood
Authors: Li Shengxu , Chen Wei , Srinivasan Sathanur R. , Boerwinkle Eric , Berenson Gerald S.
Published: March 2007

The peroxisome proliferator-activated receptor (PPAR)-γ2 gene polymorphism Pro12Ala has been associated with increased insulin sensitivity in some but not all studies. Little is known about its effect on the tracking of insulin resistance status over time. These aspects were examined in a community-based sample of 686 white young adults, aged 20–38 years, and 426 white children, aged 4–17 years, and a subsample of a cohort (n = 362) who participated both as children and adults, with an average follow-up period of 13.4 years. Insulin resistance was measured by the homeostasis model assessment of insulin resistance (HOMA-IR) using fasting insulin and glucose. The frequency of the variant Ala12 allele was 0.104 in whites vs. 0.017 in blacks. After adjusting for sex, age, and BMI, adult subjects with the genotype Pro/Pro, Pro/Ala, and Ala/Ala, respectively, showed significant decreasing trends in fasting insulin (11.7, 10.3, and 8.8 μU/ml; P = 0.002) and HOMA-IR (2.4, 2.1, and 1.7; P = 0.006). Similar but nonsignificant trends were noted in childhood. A significant genotype-BMI interaction effect on insulin (P = 0.020), glucose (P = 0.007), and HOMA-IR (P = 0.001) was found in adulthood, with carriers versus noncarriers showing attenuated association with BMI. The genotype-BMI interaction effect on these variables tended to be similar in childhood. With respect to tracking over time, of individuals in the top age- and sex-specific quartile of HOMA-IR in childhood, 48.7% (38/78) of noncarriers vs. 16.7% (2/12) of the carriers (P = 0.035) remained in the same quartile in adulthood. A similar trend was observed for insulin (2/13 vs. 35/77, P = 0.037). In conclusion, the Pro12Ala polymorphism of the PPAR-γ2 gene beneficially influences insulin resistance and its tracking from childhood to adulthood. Further, the Ala12 allele attenuates the adverse association between adiposity and insulin resistance measures.
Genetic Variation in the Small Heterodimer Partner Gene and Young-Onset Type 2 Diabetes, Obesity, and Birth Weight in U.K. Subjects
Authors: Mitchell Simon M.S. , Weedon Michael N. , Owen Katharine R. , Shields Beverley , Wilkins-Wall Beverley , Walker Mark , McCarthy Mark I. , Frayling Timothy M. , Hattersley Andrew T.
Published: March 2007

The orphan receptor small heterodimer partner (SHP, NR0B2) modulates the transcription activity of the MODY1 gene HNF4a. Mutations in SHP were found in 7% of Japanese obese young-onset type 2 diabetic patients and were associated with moderate obesity and increased birth weight. We investigated SHP in 1927 U.K. subjects, examining relationships with type 2 diabetes, obesity, and birth weight. Sequencing of the coding region of SHP in 122 obese, young-onset type 2 diabetic patients detected the polymorphism G171A. The polymorphism was not associated with diabetes in case control or familial association studies. The A allele (frequency 0.07) was not associated with obesity in type 2 diabetic subjects (n = 348), their parents (n = 272), or young nondiabetic adults (n = 925). However, the rare (<1%) AA homozygotes had a raised BMI in each cohort; this was significant when all cohorts were combined (Z score = 0.67 AA vs. −0.05 G/x, P = 0.02). There was no association with corrected birth weight in 382 normal babies, but the only AA baby was 4,069 g. Our study suggests that genetic variation in SHP is unlikely to be common in the predisposition to diabetes, obesity, or increased birth weight in U.K. Caucasians.
Linkage for BMI at 3q27 Region Confirmed in an African-American Population
Authors: Luke Amy , Wu Xiaodong , Zhu Xiaofeng , Kan Donghui , Su Yan , Cooper Richard
Published: March 2007

Significant and suggestive linkage for BMI on 3q27 has been reported by several groups, including our own study in African Americans. To further establish the linkage evidence on 3q27, we recruited an independent African-American sample comprising 545 individuals in 128 families. We genotyped 15 short tandem-repeat markers evenly spaced in the 112 cM region around the peak on 3q27 identified in our earlier study. Multipoint linkage analysis by GENEHUNTER2 gave the maximum logarithm of odds (LOD) score 2.4 at map position 188 cM in this sample. When we combined the two samples, linkage evidence was increased to a maximum LOD score (MLS) of 4.3 (point-wise P = 4.34 × 10−6) at 188 cM, with a 7 cM 1-LOD-drop interval around the peak. The multiple replications of linkage evidence in the region on 3q27 strongly confirm its potential importance as a candidate region in the search for obesity-related genes.
Contribution of Variants in the Small Heterodimer Partner Gene to Birthweight, Adiposity, and Insulin Levels
Authors: Hung Chiao-Chien Connie , Farooqi I. Sadaf , Ong Ken , Luan Jian’an , Keogh Julia M. , Pembrey Marcus , Yeo Giles S.H. , Dunger David , Wareham Nicholas J. , O’ Rahilly Stephen
Published: March 2007

Loss of function mutations in the small heterodimer partner (SHP) gene have been reported to cause obesity and increased birth weight. We examined the relation between genetic variation in SHP and birth weight, adiposity, and insulin levels in three independent populations. The coding regions and 562 bases of the SHP promoter were screened for mutations in 329 subjects with severe early-onset obesity. Two novel missense mutations, R34G and R36C, were identified; these were not found in control subjects and did not cosegregate with obesity in family studies. Two common polymorphisms, G171A and −195CTGAdel, were found in 12 and 16% of subjects, respectively. Within the obese cohort, G171A and −195CTGAdel carriers had higher and lower birth weights, respectively, than wild-type subjects, the rare homozygotes for G171A being particularly large at birth. In a U.K. population-based cohort of 1,079 children, the 171A allele was associated with higher BMI (P < 0.05) and waist circumference (P = 0.001). Children carrying the G171A variant had higher 30-min insulin responses to a glucose load (P = 0.03). In conclusion, although mutations in SHP are not a common cause of severe human obesity, genetic variation in the SHP locus may influence birth weight and have effects on BMI, possibly through effects on insulin secretion.
Reduced Activation of Phosphatidylinositol-3 Kinase and Increased Serine 636 Phosphorylation of Insulin Receptor Substrate-1 in Primary Culture of Skeletal Muscle Cells From Patients With Type 2 Diabetes
Authors: Bouzakri Karim , Roques Marina , Gual Philippe , Espinosa Sophie , Guebre-Egziabher Fitsum , Riou Jean-Paul , Laville Martine , Le Marchand-Brustel Yannick , Tanti Jean-François , Vidal Hubert
Published: March 2007

To understand better the defects in the proximal steps of insulin signaling during type 2 diabetes, we used differentiated human skeletal muscle cells in primary culture. When compared with cells from control subjects, myotubes established from patients with type 2 diabetes presented the same defects as those previously evidenced in vivo in muscle biopsies, including defective stimulation of phosphatidylinositol (PI) 3-kinase activity, decreased association of PI 3-kinase with insulin receptor substrate (IRS)-1 and reduced IRS-1 tyrosine phosphorylation during insulin stimulation. In contrast to IRS-1, the signaling through IRS-2 was not altered. Investigating the causes of the reduced tyrosine phosphorylation of IRS-1, we found a more than twofold increase in the basal phosphorylation of IRS-1 on serine 636 in myotubes from patients with diabetes. Concomitantly, there was a higher basal mitogen-activated protein kinase (MAPK) activity in these cells, and inhibition of the MAPKs with PD98059 strongly reduced the level of serine 636 phosphorylation. These results suggest that IRS-1 phosphorylation on serine 636 might be involved in the reduced phosphorylation of IRS-1 on tyrosine and in the subsequent alteration of insulin-induced PI 3-kinase activation. Moreover, increased MAPK activity seems to play a role in the phosphorylation of IRS-1 on serine residue in human muscle cells.
Leptin Activation of Corticosterone Production in Hepatocytes May Contribute to the Reversal of Obesity and Hyperglycemia in Leptin-Deficient ob/ob Mice
Authors: Liu Yanjun , Nakagawa Yuichi , Wang Ying , Li Renshan , Li Xiaojun , Ohzeki Takehiko , Friedman Theodore C.
Published: March 2007

Glucocorticoids have been implicated as pathophysiological mediators of obesity and insulin resistance and are regulated by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). This enzyme regenerates active corticosterone from inactive 11-keto forms. To assess the role of 11β-HSD1-mediated synthesis of active corticosterone in leptin-related obesity and diabetes, we examined the peripheral effect of leptin on 11β-HSD1 activity and gene expression in vivo and in vitro in hepatocytes from ob/ob mice and in liver of streptozotocin (STZ)-treated ob/ob mice. We observed an inverse relationship between hepatic 11β-HSD1 expression and body weight in ob/ob mice and lean littermates. Leptin treatment of ob/ob mice markedly increased hepatic 11β-HSD1 activity and mRNA expression. This induction of 11β-HSD1 expression corresponded to reduced levels of circulating corticosterone and weight loss in ob/ob mice treated with leptin, indicating that impaired hepatic 11β-HSD1 expression may contribute to the pathogenesis of obesity in ob/ob mice. In addition, leptin treatment of STZ-treated ob/ob mice caused marked increases in hepatic 11β-HSD1 levels associated with decreased body weight and a significant reduction in hyperglycemia due to pancreatic β-cell damage. Addition of leptin to ob/ob mouse primary hepatocytes led to a dose-dependent increase in 11β-HSD1 mRNA expression. In contrast, leptin did not influence 11β-HSD1 expression in primary hepatocytes from db/db mice, indicating that leptin regulation of 11β-HSD1 expression is probably mediated by the functional leptin receptor. Thus, leptin appears to be an important metabolic signal that directly activates intrahepatic corticosterone production. These findings suggest that the liver-specific interaction of leptin with 11β-HSD1 is involved in the development of obesity and insulin resistance in ob/ob mice.
Circadian Variation in the Onset of Myocardial Infarction
Authors: Rana Jamal S. , Mukamal Kenneth J. , Morgan James P. , Muller James E. , Mittleman Murray A.
Published: March 2007

There are conflicting reports regarding circadian variation in the onset of acute myocardial infarction (MI) among patients with diabetes. We therefore, studied the circadian pattern of the incidence of acute MI in patients (n = 3,882) who were enrolled in the Onset Study stratified by the presence, type, and duration of diabetes. The Onset Study was conducted at 64 U.S. medical centers between August 1989 and September 1996. We used harmonic regression model to evaluate the circadian variation of MI symptom onset in patients with and without diabetes. Subgroup analysis was performed according to the presence, type, and duration of diabetes by the χ2 test (dividing the day into four 6-h intervals). Patients without diabetes exhibited a prominent morning peak in the incidence of acute MI symptom onset (P < 0.001). In contrast, patients with type 1 diabetes and type 2 diabetes ≥5 years had a marked attenuation of the morning peak. Patients who had type 2 diabetes diagnosed within the previous 5 years had a pattern of onset of acute MI similar to patients without diabetes. Patients with type 1 diabetes and those with type 2 diabetes ≥5 years have an attenuation of the morning peak in acute MI. Inconsistency in observation of such an effect in patients with diabetes in the past may well have been due to difference in the duration of diabetes and thus the variable extent of underlying autonomic dysfunction.
Alternative Splicing of NHE-1 Mediates Na-Li Countertransport and Associates With Activity Rate
Authors: Zerbini Gianpaolo , Maestroni Anna , Breviario Diego , Mangili Ruggero , Casari Giorgio
Published: March 2007

Sodium-lithium countertransport (SLC) is an ouabain-insensitive exchange of Na for Li found in the erythrocyte membrane of several mammalian species. Although increased SLC activity is presently the most consistent intermediate phenotype of essential hypertension and diabetic nephropathy in humans, the gene responsible for this membrane transport has not been identified. Because of functional similarities, SLC was suggested to represent an in vitro mode of operation of the Na-H exchanger (NHE). This hypothesis, however, has been long hampered by the total insensitivity of SLC to amiloride, which is an intrinsic inhibitor of the first isoform of NHE, the only NHE isoform detected in human erythrocytes. We describe here the identification in human reticulocytes and erythrocytes of an alternative splicing of NHE lacking the amiloride binding site. Transfection experiments with this spliced variant restore amiloride-insensitive, phloretin-sensitive SLC activity. Expression of both regular and spliced transcripts of NHE is increased in subjects with high SLC activity. Altogether, these findings, by extending to NHE the characteristics of inheritance and predictivity previously attributed to SLC, eventually restore the candidacy of NHE isoform 1 as a gene involved in the pathogenesis of essential hypertension and diabetic nephropathy.
Impact of Genetic Background on Development of Hyperinsulinemia and Diabetes in Insulin Receptor/Insulin Receptor Substrate-1 Double Heterozygous Mice
Authors: Kulkarni Rohit N. , Almind Katrine , Goren H. Joseph , Winnay Jonathon N. , Ueki Kohjiro , Okada Terumasa , Kahn C. Ronald
Published: March 2007

Type 2 diabetes is a complex disease in which genetic and environmental factors interact to produce alterations in insulin action and insulin secretion, leading to hyperglycemia. To evaluate the influence of genetic background on development of diabetes in a genetically susceptible host, we generated mice that are double heterozygous (DH) for knockout of the insulin receptor and insulin receptor substrate-1 on three genetic backgrounds (C57BL/6 [B6], 129Sv, and DBA). Although DH mice on all backgrounds showed insulin resistance, their phenotypes were dramatically different. B6 DH mice exhibited marked hyperinsulinemia and massive islet hyperplasia and developed early hyperglycemia, with 85% overtly diabetic by 6 months. By contrast, 129Sv DH mice showed mild hyperinsulinemia and minimal islet hyperplasia, and < 2% developed diabetes. DBA mice had slower development of hyperglycemia, intermediate insulin levels, and evidence of islet degeneration, with 64% developing diabetes. Thus, mice carrying the same genetic defects on different backgrounds exhibited the full spectrum of abnormalities observed in humans with type 2 diabetes, which allowed for identification of potential loci that promote development of the diabetic phenotype.
Magnetic Resonance-Defined Periportal Steatosis Following Intraportal Islet Transplantation
Authors: Markmann James F. , Rosen Mark , Siegelman Evan S. , Soulen Michael C. , Deng Shaoping , Barker Clyde F. , Naji Ali
Published: March 2007

There is growing interest in more widespread application of isolated islet transplantation for the treatment of type 1 diabetes; however, the sequelae of long-term islet residence within the liver are unknown. We report herein a consequence of intraportal islet transplantation, specifically the development of periportal hepatic steatosis apparently induced by the local secretion of insulin within the liver.
Transcriptional Program of the Endocrine Pancreas in Mice and Humans
Authors: Kaestner Klaus H. , Lee Catherine S. , Scearce L. Marie , Brestelli John E. , Arsenlis Athanasios , Le Phillip Phuc , Lantz Kristen A. , Crabtree Jonathan , Pizarro Angel , Mazzarelli Joan , Pinney Deborah , Fischer Steve , Manduchi Elisabetta , Stoeckert Christian J. , Gradwohl Gerard , Clifton Sandra W. , Brown Juliana R. , Inoue Hiroshi , Cras-Méneur Corentin , Permutt M. Alan
Published: March 2007

The Endocrine Pancreas Consortium was formed in late 1999 to derive and sequence cDNA libraries enriched for rare transcripts expressed in the mammalian endocrine pancreas. Over the past 3 years, the Consortium has generated 20 cDNA libraries from mouse and human pancreatic tissues and deposited >150,000 sequences into the public expressed sequence tag databases. A special effort was made to enrich for cDNAs from the endocrine pancreas by constructing libraries from isolated islets. In addition, we constructed a library in which fetal pancreas from Neurogenin 3 null mice, which consists of only exocrine and duct cells, was subtracted from fetal wild-type pancreas to enrich for the transcripts from the endocrine compartment. Sequence analysis showed that these clones cluster into 9,464 assembly groups (approximating unique transcripts) for the mouse and 13,910 for the human sequences. Of these, >4,300 were unique to Consortium libraries. We have assembled a core clone set containing one cDNA for each assembly group for the mouse and have constructed the corresponding microarray, termed “PancChip 4.0,” which contains >9,000 nonredundant elements. We show that this PancChip is highly enriched for genes expressed in the endocrine pancreas. The mouse and human clone sets and corresponding arrays will be important resources for diabetes research.
Duodenal Leptin Stimulates Cholecystokinin Secretion
Authors: Guilmeau Sandra , Buyse Marion , Tsocas Annick , Laigneau Jean Pierre , Bado André
Published: March 2007

Some of the actions of leptin depend on cholecystokinin (CCK). However, it is unknown whether leptin modulates the release of CCK. Here, we demonstrate in vitro that leptin induces the phosphorylation of extracellular signal–related kinase (ERK)-1/2 proteins and increases CCK release (EC50 = 0.23 nmol/l) in CCK-secreting STC-1 cells. We showed that rat duodenal juice contains leptin that circulates free and bound to macromolecules, suggesting that leptin has a lumenal action on the intestine. In vivo in the rat, duodenal infusion of leptin increased plasma CCK at levels comparable to those induced by feeding. Moreover, meal-induced increases in plasma CCK were markedly reduced in obese fa/fa rats, whereas the mobilization of the gastric leptin pool was similar in lean and obese Zucker rats. The release of CCK by leptin presumably generates a positive feedback loop. Indeed, the blockade of CCK receptors reversed the meal reduction of the stomach leptin pool and the meal-increased plasma insulin, consistent with the previous concept of an entero-insular axis. Collectively, these data support a novel mode of action of leptin where leptin and CCK may potentiate their own effects by cross-stimulating their secretion. The impairment of this leptin-CCK loop may have pathological implications related to obesity and diabetes.
Increased Islet Volume but Unchanged Islet Number in ob/ob Mice
Authors: Bock Troels , Pakkenberg Bente , Buschard Karsten
Published: March 2007

It is important for our understanding of the pancreatic islets to study whether new islets are able to form in the intact pancreas. We developed a new method to determine the total number and the mean volume of the pancreatic islets, and we used this method to study the expansion of the islet mass in ob/ob mice (n = 8), using ob/+ mice (n = 8) as controls. The total islet volume was increased by a factor of 3.6 in ob/ob mice compared with ob/+ mice, whereas, importantly, the total number of islets did not differ among ob/ob mice and ob/+ mice (3,193 ± 160 islets in ob/ob mice vs. 3,184 ± 142 islets in ob/+ mice, P = 0.97). The coefficient of variation in the volume distribution of islets was equal in the two groups, showing that in ob/ob mice, the existing islets expand their volume by the same proportion, without a net formation of new islets. We suggest that the pancreatic islets should be considered as anatomically such complex structures that islet neogenesis does not spontaneously occur in an intact pancreas. Cells within the existing islets are presumably the most important sources for islet cell hyperplasia during expansion of the total islet mass.
Young-Onset Type 2 Diabetes Families Are the Major Contributors to Genetic Loci in the Diabetes UK Warren 2 Genome Scan and Identify Putative Novel Loci on Chromosomes 8q21, 21q22, and 22q11
Authors: Frayling Timothy M. , Wiltshire Steven , Hitman Graham A. , Walker Mark , Levy Jonathan C. , Sampson Mike , Groves Christopher J. , Menzel Stephan , McCarthy Mark I. , Hattersley Andrew T.
Published: March 2007

A young onset of type 2 diabetes is likely to result, in part, from greater genetic susceptibility. Young-onset families may therefore represent a group in which genes are more easily detectable by linkage. To test this hypothesis, we conducted age at diagnosis (AAD) stratified linkage analyses in the Diabetes UK Warren 2 sibpairs. In the previously published unstratified analysis, evidence for linkage (logarithm of odds [LOD] >1.18) was found at seven loci. The LOD scores at these seven loci were higher in the 245 families with AAD <55 years (L55) compared with the 328 families with AAD >55 years (G55). Five of these seven loci (1q24-25, 5q13, 8p21-22, 8q24.2, and 10q23.2) had LOD scores >1.18 in the L55 subset but only one (8p21-22) did in the G55 subset. Two additional loci (8q21.13 and 21q22.2) showed evidence for linkage in the L55 subset alone. Another locus (22q11) showed evidence for linkage in a subset of families with AAD <45 years. Using a locus-counting approach, the L55 subset had significantly more loci (P ∼0.01) than expected under the null hypothesis of no linkage across the LOD score range 0.59–3.0. In contrast, the G55 subset contained no more susceptibility loci than that expected by chance. In conclusion, young-onset families provide both disproportionate evidence for linkage to known loci and evidence for additional novel loci. Our data confirm our hypothesis that families segregating young-onset type 2 diabetes represent a more powerful resource for defining susceptibility genes by linkage.
A Functional Variant in the Peroxisome Proliferator-Activated Receptor γ2 Promoter Is Associated With Predictors of Obesity and Type 2 Diabetes in Pima Indians
Authors: Muller Yunhua Li , Bogardus Clifton , Beamer Brock A. , Shuldiner Alan R. , Baier Leslie J.
Published: March 2007

Peroxisome proliferator-activated receptor γ (PPARγ)-2 is a member of the nuclear hormone receptor superfamily that is expressed predominantly in adipocytes and is thought to have a role in energy homeostasis, adipogenesis, and insulin sensitivity. A functional single nucleotide polymorphism (SNP) that predicts a proline to alanine substitution (Pro12Ala) within the coding region of this gene has previously been associated with obesity and type 2 diabetes in several populations. In this study, we identified several novel SNPs in the promoter region of PPARγ2 and genotyped them, along with the previously identified Pro12Ala SNP. In 241 nondiabetic Pima subjects, the Pro12Ala was associated with whole-body insulin action (P = 0.05), hepatic insulin action (P = 0.03), and fasting plasma insulin concentrations (P = 0.01). One of the promoter SNPs positioned within a putative E2 box was in high linkage disequilibrium (|D′| = 0.98) with the Pro12Ala. This promoter SNP was similarly associated with whole-body insulin action (P = 0.04) and hepatic insulin action (P = 0.05), but not fasting plasma insulin concentrations. Functional studies in transfected 3T3-L1 cells demonstrated that this single base substitution in the putative E2 box significantly altered transcriptional activity from a luciferase reporter construct. These data indicate that this promoter SNP, via its effect on PPARγ2 expression, may also have functional consequences on PPARγ2-activated pathways, and perhaps both the promoter SNP and the Pro12Ala contribute to PPARγ2-related phenotypes.
Promoter Polymorphisms of the TNF-α (G-308A) and IL-6 (C-174G) Genes Predict the Conversion From Impaired Glucose Tolerance to Type 2 Diabetes
Authors: Kubaszek Agata , Pihlajamäki Jussi , Komarovski Vladislav , Lindi Virpi , Lindström Jaana , Eriksson Johan , Valle Timo T. , Hämäläinen Helena , Ilanne-Parikka Pirjo , Keinänen-Kiukaanniemi Sirkka , Tuomilehto Jaakko , Uusitupa Matti , Laakso Markku
Published: March 2007

High levels of cytokines are risk factors for type 2 diabetes. Therefore, we investigated whether the promoter polymorphisms of the tumor necrosis factor-α (TNF-α; G-308A) and interleukin 6 (IL-6; C-174G) genes predict the conversion from impaired glucose tolerance (IGT) to type 2 diabetes in the Finnish Diabetes Prevention Study. Altogether, 490 overweight subjects with IGT whose DNA was available were randomly divided into one of the two treatment assignments: the control group and the intensive, individualized diet and exercise intervention group. The −308A allele of the TNF-α gene was associated with an approximate twofold higher risk for type 2 diabetes compared with the G-308G genotype (odds ratio 1.80, 95% CI 1.05–3.09; P = 0.034). Subjects with both the A allele of the TNF-α gene and the C-174C genotype of the IL-6 gene had a 2.2-fold (CI 1.02–4.85, P = 0.045) higher risk of developing type 2 diabetes than subjects without the risk genotypes. We conclude that the −308A allele of the promoter polymorphism (G-308A) of the TNF-α gene is a predictor for the conversion from IGT to type 2 diabetes. Furthermore, this polymorphism seems to have a gene-gene interaction with the C-174C genotype of the IL-6 gene.
Effect of Training on Muscle Triacylglycerol and Structural Lipids
Authors: Helge Jørn W. , Dela Flemming
Published: March 2007

We studied whether endurance training impacts insulin sensitivity by affecting the structural and storage lipids in humans. Eight male subjects participated (age 25 ± 1 years, height 178 ± 3 cm, weight 76 ± 4 kg [mean ± SE]). Single-leg training was performed for 30 min/day for 4 weeks at ∼70% of single-leg maximal oxygen uptake. After 8, 14, and 30 days, a two-step hyperinsulinemic-euglycemic glucose clamp, combined with catheterization of an artery and both femoral veins, was performed. In addition, a muscle biopsy was obtained from vastus lateralis of both legs. Maximal oxygen uptake increased by 7% in the trained leg (T), and training workload increased (P < 0.05) from 79 ± 12 to 160 ± 15 W. At day 8, glucose uptake was higher (P < 0.01) in the trained (0.8 ± 0.2, 6.0 ± 0.8, 13.4 ± 1.2 mg · min−1 · kg−1 leg wt) than the untrained leg (0.5 ± 0.2, 3.7 ± 0.6, 10.5 ± 1.5 mg · min−1 · kg−1 leg wt) at basal and the two succeeding clamp steps, respectively. After day 8, training did not further increase leg glucose uptake. Individual muscle triacylglycerol fatty acid composition and total triacylglycerol content were not significantly affected by training and thus showed no relation to leg glucose uptake. Individual muscle phospholipid fatty acids were not affected by training, but the content of phospholipid polyunsaturated fatty acids was higher (P < 0.06) after 30 than 8 days in T. Furthermore, after 30 days of training, the sum of phospholipid long-chain polyunsaturates was correlated to leg glucose uptake (r = 0.574, P < 0.04). Endurance training did not influence muscle triacylglycerol content or total triacylglycerol fatty acid composition. In contrast, training induced a minor increase in the content of phospholipid fatty acid membrane polyunsaturates, which may indicate that membrane lipids may have a role in the training-induced increase in insulin sensitivity.
Interaction of Insulin and Prior Exercise in Control of Hepatic Metabolism of a Glucose Load
Authors: Pencek R. Richard , James Freyja , Lacy D. Brooks , Jabbour Kareem , Williams Phillip E. , Fueger Patrick T. , Wasserman David H.
Published: March 2007

To determine if prior exercise enhances insulin-stimulated extraction of glucose by the liver, chronically catheterized dogs were submitted to 150 min of treadmill exercise or rest. After exercise or rest, dogs received portal glucose (18 μmol · kg−1 · min−1), peripheral somatostatin, and basal portal glucagon infusions from t = 0 to 150 min. A peripheral glucose infusion was used to clamp arterial blood glucose at 8.3 mmol/l. Insulin was infused into the portal vein to create either basal levels or mild hyperinsulinemia. Prior exercise did not increase whole-body glucose disposal in the presence of basal insulin (25.5 ± 1.5 vs. 20.3 ± 1.7 μmol · kg−1 · min−1), but resulted in a marked enhancement in the presence of elevated insulin (97.2 ± 15.1 vs. 64.4 ± 7.4 μmol · kg−1 · min−1). Prior exercise also increased net hepatic glucose uptake in the presence of both basal insulin (7.5 ± 1.2 vs. 2.9 ± 2.4 μmol · kg−1 · min−1) and elevated insulin (22.0 ± 3.5 vs. 11.5 ± 1.8 μmol · kg−1 · min−1). Likewise, net hepatic glucose fractional extraction was increased by prior exercise with both basal insulin (0.04 ± 0.01 vs. 0.01 ± 0.01 μmol · kg−1 · min−1) and elevated insulin (0.10 ± 0.01 vs. 0.05 ± 0.01). Hepatic glycogen synthesis was increased by elevated insulin, but was not enhanced by prior exercise. Although the increase in glucose extraction after exercise could be ascribed to increased insulin action, the increase in hepatic glycogen synthesis was independent of it.
Endothelial Differentiation Gene Receptors in Pancreatic Islets and INS-1 Cells
Authors: Laychock Suzanne G. , Tian Yingrao , Sessanna Shawn M.
Published: March 2007

The endothelial differentiation gene (EDG) receptors are a class of G protein-coupled receptors. EDG-1, -3, -5, -6, and -8 bind the bioactive lipid sphingosine-1-phosphate (SPP) as the primary signaling ligand. EDG-2, -4, and -7 bind the ligand lysophosphatidic acid. EDG-1, -2, -3, -5, -6, and -7, but not -8, mRNAs were expressed in isolated rat pancreatic islets, whereas INS-1 insulinoma cells expressed only EDG-1, -2, -3, and -5 mRNAs. EDG-4 mRNA was expressed in mouse islets. EDG-1 mRNA but not EDG-3 mRNA was rapidly induced relative to 18S rRNA after stimulation of isolated islets with phorbol 12-myristate 13-acetate (PMA) or cholecystokinin-8S for 2 h. The protein kinase C inhibitor GF 109203X blocked the EDG-1 induction by PMA. Similarly, in islets stimulated for 2 h with 17 mmol/l glucose, the relative EDG-1 mRNA levels increased almost twofold compared with levels in control islets at 5.5 mmol/l glucose. In contrast, after 11 mmol/l glucose stimulation for 7 days, the relative levels of rat islet EDG-1 mRNA were significantly reduced to 54% below that of islets cultured at 5.5 mmol/l glucose. There was no change in relative EDG-3 mRNA levels. Stimulation of EDG receptors in islets and INS-1 cells with SPP inhibited glucagon-like peptide 1 (GLP-1)-stimulated cAMP production and insulin secretion in a concentration-dependent manner. Pertussis toxin antagonized the SPP effects on insulin release. Thus, EDG receptors are expressed in pancreatic islet β-cells and Gi seems to mediate the inhibition by SPP of adenylyl cyclase and cAMP formation and inhibition of the stimulation of insulin secretion by GLP-1.
Characterization of Endocrine Progenitor Cells and Critical Factors for Their Differentiation in Human Adult Pancreatic Cell Culture
Authors: Gao Ru , Ustinov Jarkko , Pulkkinen Mari-Anne , Lundin Karolina , Korsgren Olle , Otonkoski Timo
Published: March 2007

We have reproduced a previously described method for the in vitro generation of endocrine cells in adult human pancreatic tissue culture. The aim of this study was to characterize the nature of pancreatic progenitor cells and to identify the factors necessary for their differentiation in this model. During monolayer expansion, two types of cells proliferated sequentially; first cytokeratin 19 (CK19)-positive ductal epithelial cells and then nestin-positive fibroblastoid cells. After the bromodeoxyuridine-labeled cells were traced in differentiated islet buds, some of the proliferating ductal cells had differentiated into endocrine cells, whereas nestin-positive cells could not give rise to endocrine tissue. Serum-free culture was found to be an absolute requirement for the endocrine differentiation to occur. Also, overlay of the cells with Matrigel was essential, whereas nicotinamide had a potentiating effect. The in vitro–generated islet buds released insulin in response to glucose nearly as efficiently as native islets. When transplanted under the kidney capsule of nude mice, only one of five grafts demonstrated further growth with foci of both endocrine and exocrine differentiation. Our results support the previous notion that pancreatic progenitor cells represent a subpopulation of ductal epithelial cells. No evidence was found for the development of endocrine cells from nestin-positive stem cells.
Pancreatic β-Cell Lipotoxicity Induced by Overexpression of Hormone-Sensitive Lipase
Authors: Sörhede Winzell Maria , Svensson Håkan , Enerbäck Sven , Ravnskjaer Kim , Mandrup Susanne , Esser Victoria , Arner Peter , Alves-Guerra Marie-Clotilde , Miroux Bruno , Sundler Frank , Ahrén Bo , Holm Cecilia
Published: March 2007

Lipid perturbations associated with triglyceride overstorage in β-cells impair insulin secretion, a process termed lipotoxicity. To assess the role of hormone-sensitive lipase, which is expressed and enzymatically active in β-cells, in the development of lipotoxicity, we generated transgenic mice overexpressing hormone-sensitive lipase specifically in β-cells. Transgenic mice developed glucose intolerance and severely blunted glucose-stimulated insulin secretion when challenged with a high-fat diet. As expected, both lipase activity and forskolin-stimulated lipolysis was increased in transgenic compared with wild-type islets. This was reflected in significantly lower triglycerides levels in transgenic compared with wild-type islets in mice receiving the high-fat diet, whereas no difference in islet triglycerides was found between the two genotypes under low-fat diet conditions. Our results highlight the importance of mobilization of the islet triglyceride pool in the development of β-cell lipotoxicity. We propose that hormone-sensitive lipase is involved in mediating β-cell lipotoxicity by providing ligands for peroxisome proliferator-activated receptors and other lipid-activated transcription factors, which in turn alter the expression of critical genes. One such gene might be uncoupling protein-2, which was found to be upregulated in transgenic islets, a change that was accompanied by decreased ATP levels.
Vascular Endothelial Function and Blood Pressure Homeostasis in Mice Overexpressing IGF Binding Protein-1
Authors: Wheatcroft Stephen B. , Kearney Mark T. , Shah Ajay M. , Grieve David J. , Williams Ian L. , Miell John P. , Crossey Paul A.
Published: March 2007

IGFs and their binding proteins (IGFBPs) play a significant role in metabolic regulation, and there is growing evidence that they also exert important vascular effects. IGFBP-1 contributes to glucose counterregulation, and observational studies demonstrate an inverse association between circulating IGFBP-1 levels and cardiovascular risk factors. Furthermore, IGFBP-1 levels are lower in subjects with overt macrovascular disease. We therefore hypothesized that IGFBP-1 exerts potentially beneficial effects, either directly or indirectly, on blood pressure regulation and vascular function. We tested this hypothesis using a unique transgenic mouse, which overexpresses human IGFBP-1, and explored the effect of this protein on metabolic, blood pressure, and vascular homeostasis. IGFBP-1-overexpressing mice exhibited postprandial hyperinsulinemia with preservation of glucocompetence and insulin sensitivity. Blood pressure was unchanged in the fasting state but was significantly lower in transgenic mice after a carbohydrate load. Aortic rings from IGFBP-1-overexpressing mice were hypocontractile in response to vasoconstrictors, and relaxation responses were unimpaired. Basal nitric oxide production was increased and endothelial nitric oxide synthase mRNA expression upregulated in aortae of these mice. Our data suggest that IGFBP-1 plays an important and potentially beneficial role in regulating metabolic and vascular homeostasis.
Production of Nε-(Carboxymethyl)Lysine Is Impaired in Mice Deficient in NADPH Oxidase
Authors: Anderson Melissa M. , Heinecke Jay W.
Published: March 2007

Advanced glycation end products (AGEs) derived from glucose are implicated in the pathogenesis of diabetic vascular disease. However, many lines of evidence suggest that other pathways also promote AGE formation. One potential mechanism involves oxidants produced by the NADPH oxidase of neutrophils, monocytes, and macrophages. In vitro studies have demonstrated that glycolaldehyde, a product of serine oxidation, reacts with proteins to form Nε-(carboxymethyl)lysine (CML), a chemically well-characterized AGE. We used mice deficient in phagocyte NADPH oxidase (gp91-phox−/−) to explore the role of oxidants in AGE production in isolated neutrophils and intact animals. Activated neutrophils harvested from wild-type mice generated CML on ribonuclease A (RNase A), a model protein, by a pathway that required l-serine. CML formation by gp91-phox−/− neutrophils was impaired, suggesting that oxidants produced by phagocyte NADPH oxidase contribute to the cellular formation of AGEs. To determine whether these observations are physiologically relevant, we used isotope-dilution gas chromatography/mass spectrometry to quantify levels of protein-bound CML in mice suffering from acute peritoneal inflammation. Phagocytes from the gp91-phox−/− mice contained much lower levels of CML than those from the wild-type mice. Therefore, oxidants generated by phagocyte NADPH oxidase may play a role in AGE formation in vivo by a glucose-independent pathway.
Differential Influences of Peroxisome Proliferator–Activated Receptorsγ and -α on Food Intake and Energy Homeostasis
Authors: Larsen Philip J. , Jensen Per Bo , Sørensen Rikke V. , Larsen Leif Kongskov , Vrang Niels , Wulff Erik M. , Wassermann Karsten
Published: March 2007

Chronic treatment with compounds activating peroxisome proliferator–activated receptor (PPAR)γ and -α influences body energy stores, but the underlying mechanisms are only partially known. In a chronic-dosing study, equiefficacious antihyperglycemic doses of the PPARγ agonist pioglitazone and PPARα/γ dual activator ragaglitazar were administered to obesity-prone male rats. The PPARα agonist fenofibrate had no effect on insulin sensitivity. Pioglitazone transiently increased and fenofibrate transiently decreased food intake, whereas ragaglitazar had no impact on feeding. As a result, body adiposity increased in pioglitazone-treated rats and decreased in fenofibrate-treated rats. PPARγ compounds markedly increased feed efficiency, whereas PPARα agonist treatment decreased feed efficiency. In fenofibrate-treated rats, plasma acetoacetate was significantly elevated. Plasma levels of this potentially anorectic ketone body were unaffected in pioglitazone- and ragaglitazar-treated rats. High-fat feeding markedly increased visceral fat pads, and this was prevented by pioglitazone and ragaglitazar treatment. Pioglitazone treatment enlarged subcutaneous adiposity in high-fat–fed rats. In conclusion, PPARγ activation increases both food intake and feed efficiency, resulting in net accumulation of subcutaneous body fat. The impact of PPARγ activation on feeding and feed efficiency appears to be partially independent because the PPARα component of ragaglitazar completely counteracts the orexigenic actions of PPARγ activation without marked impact on feed efficiency.
Peripheral, But Not Central, Administration of Adiponectin Reduces Visceral Adiposity and Upregulates the Expression of Uncoupling Protein in Agouti Yellow (Ay/a) Obese Mice
Authors: Masaki Takayuki , Chiba Seiichi , Yasuda Tohru , Tsubone Tetsuo , Kakuma Tetsuya , Shimomura Iichiro , Funahashi Tohru , Matsuzawa Yuji , Yoshimatsu Hironobu
Published: March 2007

To examine the peripheral and central roles of adiponectin in energy intake and expenditure, we investigated the effects of adiponectin on food intake, adiposity, sympathetic nerve activity (SNA), and mRNA expressions of uncoupling protein (UCP) in the brown adipose tissue (BAT), white adipose tissue (WAT) and skeletal muscle in agouti yellow (Ay/a) obese mice. Intraperitoneal administration of adiponectin (1.5 mg/kg for 7 days) attenuated body weight gain and reduced visceral adiposity in Ay/a obese mice compared with PBS-treated controls. In addition, adiponectin treatment increased the expression of UCP1 mRNA in BAT, UCP2 mRNA in WAT, and UCP3 mRNA in skeletal muscle compared with PBS-treated Ay/a controls. Acute peripheral administration of adiponectin (1.5 mg/kg, one injection) also increased SNA in the BAT accompanied by an increase in rectal temperature. Finally, these above responses as well as expression of c-Fos–like immunohistochemistry in the hypothalamus were not induced by central application of adiponectin (0–15 μg/kg). Taken together, adiponectin effectively regulated visceral adiposity, SNA, and UCP mRNA expression peripherally, suggesting that this substance can be used as a therapeutic tool, administered peripherally, in the treatment of visceral obesity and related metabolic disorders.
Immunologic Activity in the Small Intestinal Mucosa of Pediatric Patients With Type 1 Diabetes
Authors: Westerholm-Ormio Mia , Vaarala Outi , Pihkala Päivi , Ilonen Jorma , Savilahti Erkki
Published: March 2007

Involvement of gut immune system has been implicated in the pathogenesis of type 1 diabetes. However, few studies have been performed on the gut mucosa from patients with type 1 diabetes. Thus, we characterized the stage of immune activation in jejunal biopsy samples from 31 children with type 1 diabetes by immunohistochemistry, in situ hybridization, and RT-PCR. We found enhanced expressions of HLA-DR, HLA-DP, and intercellular adhesion molecule-1 by immunohistochemistry even on structurally normal intestine of patients with type 1 diabetes and no signs of celiac disease. In addition, the densities of IL-1α- and IL-4-positive cells detected by immunohistochemistry and IL-4 mRNA-expressing cells evaluated by in situ hybridization were increased in the lamina propria in patients with type 1 diabetes and normal mucosa. Instead, the densities of IL-2, γ-interferon (IFN-γ), and tumor necrosis factor α-positive cells, the density of IFN-γ mRNA positive cells, and the amounts of IFN-γ mRNA detected by RT-PCR correlated with the degree of celiac disease in patients with type 1 diabetes. Our study supports the hypothesis that a link exists between the gut immune system and type 1 diabetes.
Pancreatic-Derived Factor (FAM3B), a Novel Islet Cytokine, Induces Apoptosis of Insulin-Secreting β-Cells
Authors: Cao Xiaopei , Gao Zhiyong , Robert Claudia E. , Greene Scott , Xu Gang , Xu Weizhen , Bell Ewan , Campbell Don , Zhu Yuan , Young Robert , Trucco Matteo , Markmann James F. , Naji Ali , Wolf Bryan A.
Published: March 2007

PANDER (PANcreatic DERived factor, FAM3B), a newly discovered secreted cytokine, is specifically expressed at high levels in the islets of Langerhans of the endocrine pancreas. To evaluate the role of PANDER in β-cell function, we investigated the effects of PANDER on rat, mouse, and human pancreatic islets; the β-TC3 cell line; and the α-TC cell line. PANDER protein was present in α- and β-cells of pancreatic islets, insulin-secreting β-TC3 cells, and glucagon-secreting α-TC cells. PANDER induced islet cell death in rat and human islets. Culture of β-TC3 cells with recombinant PANDER had a dose-dependent inhibitory effect on cell viability. This effect was also time-dependent. PANDER caused apoptosis of β-cells as assessed by electron microscopy, annexin V fluorescent staining, and flow-cytometric terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. PANDER did not affect cytosolic Ca2+ levels or nitric oxide levels. However, PANDER activated caspase-3. Hence, PANDER may have a role in the process of pancreatic β-cell apoptosis.
An Insulin-Degrading Enzyme Inhibitor Decreases Amylin Degradation, Increases Amylin-Induced Cytotoxicity, and Increases Amyloid Formation in Insulinoma Cell Cultures
Authors: Bennett Robert G. , Hamel Frederick G. , Duckworth William C.
Published: March 2007

Amylin (islet amyloid polypeptide) is the chief component of the islet amyloid found in type 2 diabetes, and amylin fibril precursors may be cytotoxic to pancreatic β-cells. Little is known about the prevention of amylin aggregation. We investigated the role of insulin-degrading enzyme (IDE) in amylin degradation, amyloid deposition, and cytotoxicity in RIN-m5F insulinoma cells. Human 125I-labeled amylin degradation was inhibited by 46 and 65% with the addition of 100 nmol/l human amylin or insulin, respectively. 125I-labeled insulin degradation was inhibited with 100 nmol/l human amylin, rat amylin, and insulin (by 50, 50, and 73%, respectively). The IDE inhibitor bacitracin inhibited amylin degradation by 78% and insulin degradation by 100%. Amyloid staining by Congo red fluorescence was detectable at 100 nmol/l amylin and was pronounced at 1,000 nmol/l amylin treatment for 48 h. Bacitracin treatment markedly increased staining at all amylin concentrations. Bacitracin with amylin caused a dramatic decrease in cell viability compared with amylin alone (68 and 25%, respectively, at 10 nmol/l amylin). In summary, RIN-m5F cells degraded both amylin and insulin through a common proteolytic pathway. IDE inhibition by bacitracin impaired amylin degradation, increased amyloid formation, and increased amylin-induced cytotoxicity, suggesting a role for IDE in amylin clearance and the prevention of amylin aggregation.