bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrate Retention in Riparian Ground Water at Natural and Elevated Nitrate Levels in North Central Minnesota
Authors: Duff John H. , Jackman Alan P. , Triska Frank J. , Sheibley Richard W. , Avanzino Ronald J.
Published: January 2007

The relationship between local ground water flows and NO3− transport to the channel was examined in three well transects from a natural, wooded riparian zone adjacent to the Shingobee River, MN. The hillslope ground water originated as recharge from intermittently grazed pasture up slope of the site. In the hillslope transect perpendicular to the stream, ground water NO3− concentrations decreased from ∼3 mg N L−1 beneath the ridge (80 m from the channel) to 0.01 to 1.0 mg N L−1 at wells 1 to 3 m from the channel. The Cl− concentrations and NO3/Cl ratios decreased toward the channel indicating NO3− dilution and biotic retention. In the bankside well transect parallel to the stream, two distinct ground water environments were observed: an alluvial environment upstream of a relict beaver dam influenced by stream water and a hillslope environment downstream of the relict beaver dam. Nitrate was elevated to levels representative of agricultural runoff in a third well transect located ∼5 m from the stream to assess the effectiveness of the riparian zone as a NO3− sink. Subsurface NO3− injections revealed transport of up to 15 mg N L−1 was nearly conservative in the alluvial riparian environment. Addition of glucose stimulated dissolved oxygen uptake and promoted NO3− retention under both background and elevated NO3− levels in summer and winter. Disappearance of added NO3− was followed by transient NO2− formation and, in the presence of C2H2, by N2O formation, demonstrating potential denitrification. Under current land use, most NO3− associated with local ground water is biotically retained or diluted before reaching the channel. However, elevating NO3− levels through agricultural cultivation would likely result in increased NO3− transport to the channel.
Quantifying Constraints Imposed by Calcium and Iron on Bacterial Reduction of Uranium(VI)
Authors: Stewart Brandy D. , Neiss Jim , Fendorf Scott
Published: January 2007

Uranium is a redox active contaminant of concern to both human health and ecological preservation. In anaerobic soils and sediments, the more mobile, oxidized form of uranium (UO22+ and associated species) may be reduced by dissimilatory metal‐reducing bacteria. Despite rapid reduction in controlled, experimental systems, various factors within soils or sediments may limit biological reduction of U(VI), inclusive of competing electron acceptors and alterations in uranyl speciation. Here we elucidate the impact of U(VI) speciation on the extent and rate of reduction, and we examine the impact of Fe(III) (hydr)oxides (ferrihydrite, goethite, and hematite) varying in free energies of formation. Observed pseudo first‐order rate coefficients for U(VI) reduction vary from 12 ± 0.60 × 10−3 h−1 (0 mM Ca in the presence of goethite) to 2.0 ± 0.10 × 10−3 h−1 (0.8 mM Ca in the presence of hematite). Nevertheless, dissolved Ca (at concentrations from 0.2 to 0.8 mM) decreases the extent of U(VI) reduction by ∼25% after 528 h relative to rates without Ca present. Imparting an important criterion on uranium reduction, goethite and hematite decrease the dissolved concentration of calcium through adsorption and thus tend to diminish the effect of calcium on uranium reduction. Ferrihydrite, in contrast, acts as a competitive electron acceptor and thus, like Ca, decreases uranium reduction. However, while ferrihydrite decreases U(VI) in solutions without Ca, with increasing Ca concentrations U(VI) reduction is enhanced in the presence of ferrihydrite (relative to its absence)—U(VI) reduction, in fact, becomes almost independent of Ca concentration. The quantitative framework described herein helps to predict the fate and transport of uranium within anaerobic environments.
Phosphorus Transport Pathways to Streams in Tile‐Drained Agricultural Watersheds
Authors: Gentry L. E. , David M. B. , Royer T. V. , Mitchell C. A. , Starks K. M.
Published: January 2007

Agriculture is a major nonpoint source of phosphorus (P) in the Midwest, but how surface runoff and tile drainage interact to affect temporal concentrations and fluxes of both dissolved and particulate P remains unclear. Our objective was to determine the dominant form of P in streams (dissolved or particulate) and identify the mode of transport of this P from fields to streams in tile‐drained agricultural watersheds. We measured dissolved reactive P (DRP) and total P (TP) concentrations and loads in stream and tile water in the upper reaches of three watersheds in east‐central Illinois (Embarras River, Lake Fork of the Kaskaskia River, and Big Ditch of the Sangamon River). For all 16 water year by watershed combinations examined, annual flow‐weighted mean TP concentrations were >0.1 mg L−1, and seven water year by watershed combinations exceeded 0.2 mg L−1 Concentrations of DRP and particulate P (PP) increased with stream discharge; however, particulate P was the dominant form during overland runoff events, which greatly affected annual TP loads. Concentrations of DRP and PP in tiles increased with discharge, indicating tiles were a source of P to streams. Across watersheds, the greatest DRP concentrations (as high as 1.25 mg L−1) were associated with a precipitation event that followed widespread application of P fertilizer on frozen soils. Although eliminating this practice would reduce the potential for overland runoff of P, soil erosion and tile drainage would continue to be important transport pathways of P to streams in east‐central Illinois.
Seasonality of Selected Surface Water Constituents in the Indian River Lagoon, Florida
Authors: Qian Y. , Migliaccio K. W. , Wan Y. , Li Y. C. , Chin D.
Published: January 2007

Seasonality is often the major exogenous effect that must be compensated for or removed to discern trends in water quality. Our objective was to provide a methodological example of trend analysis using water quality data with seasonality. Selected water quality constituents from 1979 to 2004 at three monitoring stations in southern Florida were evaluated for seasonality. The seasonal patterns of flow‐weighted and log‐transformed concentrations were identified by applying side‐by‐side boxplots and the Wilcoxon signed‐rank test (p < 0.05). Seasonal and annual trends were determined by trend analysis (Seasonal Kendall or Tobit procedure) using the U.S. Geological Survey (USGS) Estimate TREND (ESTREND) program. Major water quality indicators (specific conductivity, turbidity, color, and chloride), except for turbidity at Station C24S49, exhibited significant seasonal patterns. Almost all nutrient species (NO2–N, NH4–N, total Kjeldahl N, PO4–P, and total P) had an identical seasonal pattern of concentrations significantly greater in the wet than in the dry season. Some water quality constituents were observed to exhibit significant annual or seasonal trends. In some cases, the overall annual trend was insignificant while opposing trends were present in different seasons. By evaluating seasonal trends separately from all data, constituents can be assessed providing a more accurate interpretation of water quality trends.
Nitrogen and Phosphorus Budgets in Experimental Grasslands of Variable Diversity
Authors: Oelmann Yvonne , Kreutziger Yvonne , Temperton Vicky M. , Buchmann Nina , Roscher Christiane , Schumacher Jens , Schulze Ernst‐Detlef , Weisser Wolfgang W. , Wilcke Wolfgang
Published: January 2007

Previous research has shown that plant diversity influences N and P cycles. However, the effect of plant diversity on complete ecosystem N and P budgets has not yet been assessed. For 20 plots of artificially established grassland mixtures differing in plant diversity, we determined N and P inputs by bulk and dry deposition and N and P losses by mowing (and subsequent removal of the biomass) and leaching from April 2003 to March 2004. Total deposition of N and P was 2.3 ± 0.1 and 0.2 ± 0.01 g m−2 yr−1, respectively. Mowing was the main N and P loss. The net N and P budgets were negative (–6.3 ± 1.1 g N and –1.9 ± 0.2 g P m−2 yr−1). For N, this included a conservative estimate of atmospheric N2 fixation. Nitrogen losses as N2O were expected to be small at our study site (<0.05 g m−2 yr−1). Legumes increased the removal of N with the harvest and decreased leaching of NH4–N and dissolved organic nitrogen (DON) from the canopy. Reduced roughness of grass‐containing mixtures decreased dry deposition of N and P. Total dissolved P and NO3–N leaching from the canopy increased in the presence of grasses attributable to the decreased N and P demand of grass‐containing mixtures. Species richness did not have an effect on any of the studied fluxes. Our results demonstrate that the N and P fluxes in managed grassland are modified by the presence or absence of particular functional plant groups and are mainly driven by the management.
Factors Influencing the Concentration of Volatile Fatty Acids, Ammonia, and Other Nutrients in Stored Liquid Pig Manure
Authors: Conn Kenneth L. , Topp Edward , Lazarovits George
Published: January 2007

In order to minimize odor and manage nutrients in liquid pig manure we need to be able to predict what operational practices most influence the concentrations of volatile fatty acids (VFAs), ammonium nitrogen (NH4+–N), and other nutrients present in the manure. To determine this, we collected manure from 15 pig operations in southwestern Ontario in the fall of 2001 and 2002 and spring of 2002 and 2003. The manure was stored in concrete tanks at all operations. Manure from finishing pigs had the highest concentration of VFAs, NH4+–N, and other nutrients, followed by manure from mixed operations, and then manure from sow operations. The average concentration of total VFAs and NH4+–N in finishing pig manure was 166 mM compared with 36 and 99 mM, respectively, in sow manure. Total N, P, and K were 2.3, 2.5, and 1.7 times greater, respectively, in finishing pig compared with sow manure. There was no seasonal or year to year variation in amount. The diet of the pigs, use of feed additives or antibiotics, location of tanks, and whether the tanks were covered or mixed were not significant factors contributing to the difference in manure chemistry. The main reason for the differences between the three types of manure was manure dilution. The average dry matter content of finishing pig manure was 4.5 times that of sow manure. This was due to larger density of pigs in finishing compared with sow operations, less manure storage capacity per pig for finishing compared with sow operations, and more wash water being used for sow operations.
Prairie and Turf Buffer Strips for Controlling Runoff from Paved Surfaces
Authors: Steinke K. , Stier J. C. , Kussow W. R. , Thompson A.
Published: January 2007

Eutrophication of surface waters due to nonpoint source pollution from urban environments has raised awareness of the need to decrease runoff from roads and other impervious surfaces. These concerns have led to precautionary P application restrictions on turf and requirements for vegetative buffer strips. The impacts of two plant communities and three impervious/pervious surface ratios were assessed on runoff water quality and quantity. A mixed forb/grass prairie and a Kentucky bluegrass (Poa pratensis L.) blend were seeded and runoff was monitored and analyzed for total volume, total P, soluble P, soluble organic P, bioavailable P, total suspended solids, and total organic suspended solids. Mean annual runoff volumes, all types of mean annual P nutrient losses, and sediment loads were not significantly affected by treatments because over 80% of runoff occurred during frozen soil conditions. Total P losses from prairie and turf were similar, averaging 1.96 and 2.12 kg ha−1 yr−1, respectively. Vegetation appeared to be a likely contributor of nutrients, particularly from prairie during winter dormancy. When runoff occurred during non‐frozen soil conditions turf allowed significantly (P ≤ 0.10) lower runoff volumes compared with prairie vegetation and the 1:2 and 1:4 impervious/pervious surface ratios had less runoff than the 1:1 ratio (P ≤ 0.05). In climates where the majority of runoff occurs during frozen ground conditions, vegetative buffers strips alone are unlikely to dramatically reduce runoff and nutrient loading into surface waters. Regardless of vegetation type or size, natural nutrient biogeochemical cycling will cause nutrient loss in surface runoff waters, and these values may represent baseline thresholds below which values cannot be obtained.
Application Methods Affect Phosphorus‐Induced Lead Immobilization from a Contaminated Soil
Authors: Yoon Joon Ki , Cao Xinde , Ma Lena Q.
Published: January 2007

Phosphate rock (PR) and phosphoric acid (PA) are an effective combination of P sources for immobilizing Pb in contaminated soils. This column experiment examined the effectiveness of different application methods on Pb immobilization in a contaminated soil. Phosphate was applied at a P/Pb molar ratio of 4 with half as PR and half PA. While PR was mixed with the soil or placed as a layer, aqueous PA was applied from the top of the column as one or two applications. After 4 wk of incubation, total and soluble Pb and P, TCLP‐Pb (toxicity characteristic leaching procedure) and PBET‐Pb (physiologically‐based extraction test) in the P‐treated soil were determined. Phosphate addition effectively reduced leachable Pb to below the EPA drinking water standard of 15 μg L−1 in all treatments. Mixing both PA and PR with the soil was the most effective method in Pb immobilization, reducing TCLP‐Pb by up to 95% and PBET‐Pb by 25 to 42%. Application of PR as a layer in the soil column was the most effective in reducing Pb migration (by 73–79%) and minimizing soil acidification and P entrophication, potential drawbacks of PA. Applying PA in two applications was less effective than one application. Mixing PR and PA with the soil plus placing PR as a layer can be employed for effective remediation of Pb‐contaminated soils, reducing Pb leachability, bioavailability, and mobility while minimizing soil acidification and P entrophication.
What Aspect of Dietary Modification in Broilers Controls Litter Water‐Soluble Phosphorus
Authors: Leytem A. B. , Plumstead P. W. , Maguire R. O. , Kwanyuen P. , Brake J.
Published: January 2007

Environmental concerns about phosphorus (P) losses from animal agriculture have led to interest in dietary strategies to reduce the concentration and solubility of P in manures and litters. To address the effects of dietary available phosphorus (AvP), calcium (Ca), and phytase on P excretion in broilers, 18 dietary treatments were applied in a randomized complete block design to each of four replicate pens of 28 broilers from 18 to 42 d of age. Treatments consisted of three levels of AvP (3.5, 3.0, and 2.5 g kg−1) combined with three levels of Ca (8.0, 6.9, and 5.7 g kg−1) and two levels of phytase (0 and 600 phytase units [FTU]). Phytase was added at the expense of 1.0 g kg−1 P from dicalcium phosphate. Fresh litter was collected from pens when the broilers were 41 d of age and analyzed for total P, soluble P, and phytate P as well as P composition by 31P nuclear magnetic resonance (NMR) spectroscopy. Results indicated that the inclusion of phytase at the expense of inorganic P or reductions in AvP decreased litter total P by 28 to 43%. Litter water‐soluble P (WSP) decreased by up to 73% with an increasing dietary Ca/AvP ratio, irrespective of phytase addition. The ratio of WSP/total P in litter decreased as the dietary Ca/AvP ratio increased and was greater in the phytase‐amended diets. This study indicated that while feeding reduced AvP diets with phytase decreased litter total P, the ratio of Ca/AvP in the diet was primarily responsible for effects on WSP. This is important from an environmental perspective as the amount of WSP in litter could be related to potential for off‐site P losses following land application of litter.
Topical Administration of Nepafenac Inhibits Diabetes-Induced Retinal Microvascular Disease and Underlying Abnormalities of Retinal Metabolism and Physiology
Authors: Kern Timothy S. , Miller Casey M. , Du Yunpeng , Zheng Ling , Mohr Susanne , Ball Sherry L. , Kim M. , Jamison Jeffrey A. , Bingaman David P.
Published: January 2007

Pharmacologic treatment of diabetic retinopathy via eyedrops could have advantages but has not been successful to date. We explored the effect of topical Nepafenac, an anti-inflammatory drug known to reach the retina when administered via eyedrops, on the development of early stages of diabetic retinopathy and on metabolic and physiologic abnormalities that contribute to the retinal disease. Streptozotocin-induced diabetic rats were assigned to three groups (0.3% Nepafenac eyedrops, vehicle eyedrops, and untreated control) for comparison to age-matched nondiabetic control animals. Eyedrops were administered in both eyes four times per day for 2 and 9 months. At 2 months of diabetes, insulin-deficient diabetic control rats exhibited significant increases in retinal prostaglandin E2, superoxide, vascular endothelial growth factor (VEGF), nitric oxide (NO), cyclooxygenase-2, and leukostasis within retinal microvessels. All of these abnormalities except NO and VEGF were significantly inhibited by Nepafenac. At 9 months of diabetes, a significant increase in the number of transferase-mediated dUTP nick-end labeling–positive capillary cells, acellular capillaries, and pericyte ghosts were measured in control diabetic rats versus nondiabetic controls, and topical Nepafenac significantly inhibited all of these abnormalities (all P < 0.05). Diabetes-induced activation of caspase-3 and -6 in retina was partially inhibited by Nepafenac (all P < 0.05). Oscillatory potential latency was the only abnormality of retinal function reproducibly detected in these diabetic animals, and Nepafenac significantly inhibited this defect (P < 0.05). Nepafenac did not have a significant effect on diabetes-induced loss of cells in the ganglion cell layer or in corneal protease activity. Topical ocular administration of Nepafenac achieved sufficient drug delivery to the retina and diabetes-induced alterations in retinal vascular metabolism, function, and morphology were inhibited. In contrast, little or no effect was observed on diabetes-induced alterations in retinal ganglion cell survival. Local inhibition of inflammatory pathways in the eye offers a novel therapeutic approach toward inhibiting the development of lesions of diabetic retinopathy.
Alterations of Adenine Nucleotide Metabolism and Function of Blood Platelets in Patients With Diabetes
Authors: Michno Anna , Bielarczyk Hanna , Pawełczyk Tadeusz , Jankowska-Kulawy Agnieszka , Klimaszewska Joanna , Szutowicz Andrzej
Published: January 2007

Increased activity of blood platelets contributes to vascular complications in patients with diabetes. The aim of this work was to investigate whether persisting hyperglycemia in diabetic patients generates excessive accumulation of ATP/ADP, which may underlie platelet hyperactivity. Platelet ATP and ADP levels, thiobarbituric acid–reactive species synthesis, and aggregation of platelets from patients with diabetes were 18–82% higher than in platelets from healthy participants. In patients with diabetes, platelet stimulation with thrombin caused about two times greater release of ATP and ADP than in the healthy group while decreasing intraplatelet nucleotide content to similar levels in both groups. This indicates that the increased content of adenylate nucleotides in the releasable pool in the platelets of diabetic patients does not affect their level in metabolic cytoplasmic/mitochondrial compartments. Significant correlations between platelet ATP levels and plasma fructosamine, as well as between platelet ATP/ADP and platelet activities, have been found in diabetic patients. In conclusion, chronic hyperglycemia-evoked elevations of ATP/ADP levels and release from blood platelets of patients with diabetes may be important factors underlying platelet hyperactivity in the course of the disease.
Identification of the Amyloid-Degrading Enzyme Neprilysin in Mouse Islets and Potential Role in Islet Amyloidogenesis
Authors: Zraika Sakeneh , Hull Rebecca L. , Udayasankar Jayalakshmi , Clark Anne , Utzschneider Kristina M. , Tong Jenny , Gerchman Fernando , Kahn Steven E.
Published: January 2007

Islet amyloid contributes to loss of β-cell mass and function in type 2 diabetes. It is poorly understood how the building block of amyloid, islet amyloid polypeptide (IAPP), misfolds and accumulates within the islet to contribute to cellular dysfunction. We sought to determine whether neprilysin, an amyloid-degrading enzyme, is present in islets and plays a role in the accumulation of amyloid fibrils. Human IAPP (hIAPP) transgenic mice, a model of islet amyloid in which primarily male mice develop amyloid by 12 months of age, were studied at 10 weeks and 6 months of age, enabling investigation of islet changes before and during early amyloidogenesis. Neprilysin was present in islets, including β-cells, and islet neprilysin mRNA and activity were found to decline with age in nontransgenic mice as well as in hIAPP transgenic female mice. In contrast, neprilysin mRNA and activity did not decrease in amyloid-prone hIAPP transgenic male mice at 6 months compared with nontransgenic mice and female hIAPP transgenic mice. Islet amyloid was detected in 43% of the 6-month-old hIAPP transgenic male mice only, suggesting the sustained elevation of islet neprilysin in these mice was a compensatory mechanism aimed at preventing amyloid accumulation. In keeping with amyloid formation, the proportion of insulin-positive area to islet area was significantly reduced in 6-month-old hIAPP transgenic male mice, which also displayed mild fasting hyperglycemia compared with age-matched transgenic female and nontransgenic mice. Together, these findings demonstrate that neprilysin is a factor associated with islet amyloid accumulation and subsequent deterioration of β-cell function in hIAPP transgenic male mice.
IGF-Binding Protein-2 Protects Against the Development of Obesity and Insulin Resistance
Authors: Wheatcroft Stephen B. , Kearney Mark T. , Shah Ajay M. , Ezzat Vivienne A. , Miell John R. , Modo Michael , Williams Stephen C.R. , Cawthorn Will P. , Medina-Gomez Gema , Vidal-Puig Antonio , Sethi Jaswinder K. , Crossey Paul A.
Published: January 2007

Proliferation of adipocyte precursors and their differentiation into mature adipocytes contributes to the development of obesity in mammals. IGF-I is a potent mitogen and important stimulus for adipocyte differentiation. The biological actions of IGFs are closely regulated by a family of IGF-binding proteins (IGFBPs), which exert predominantly inhibitory effects. IGFBP-2 is the principal binding protein secreted by differentiating white preadipocytes, suggesting a potential role in the development of obesity. We have generated transgenic mice overexpressing human IGFBP-2 under the control of its native promoter, and we show that overexpression of IGFBP-2 is associated with reduced susceptibility to obesity and improved insulin sensitivity. Whereas wild-type littermates developed glucose intolerance and increased blood pressure with aging, mice overexpressing IGFBP-2 were protected. Furthermore, when fed a high-fat/high-energy diet, IGFBP-2–overexpressing mice were resistant to the development of obesity and insulin resistance. This lean phenotype was associated with decreased leptin levels, increased glucose sensitivity, and lower blood pressure compared with wild-type animals consuming similar amounts of high-fat diet. Our in vitro data suggest a direct effect of IGFBP-2 preventing adipogenesis as indicated by the ability of recombinant IGFBP-2 to impair 3T3-L1 differentiation. These findings suggest an important, novel role for IGFBP-2 in obesity prevention.
Linkage and Association Analyses of Type 2 Diabetes/Impaired Glucose Metabolism and Adiponectin Serum Levels in Japanese Americans From Hawaii
Authors: Kovac Ilija P. , Havlik Richard J. , Foley Daniel , Peila Rita , Hernandez Dena , Wavrant-De Vrièze Fabienne , Singleton Andrew , Egan Josephine , Taub Dennis , Rodriguez Beatriz , Masaki Kamal , Curb J. David , Fujimoto Wilfred Y. , Wilson Alexander F.
Published: January 2007

Type 2 diabetes is a common disorder associated with obesity. Lower plasma levels of adiponectin were associated with type 2 diabetes. Candidate regions on chromosomes 1 (∼70 cM) and 14 (∼30 cM) were evaluated for replication of suggestive linkage results for type 2 diabetes/impaired glucose homeostasis in an independent sample of Japanese Americans. Replication of independent linkage evidence for serum levels of adiponectin on chromosome 14 was also evaluated. We investigated 529 subjects from 175 sibships who were originally part of the Honolulu Heart Program. Analyses included nonparametric linkage and association using SAGE (Statistical Analysis for Genetic Epidemiology) and FBAT (family-based test of association) programs and Monte Carlo simulation of Fisher’s exact test in SAS. For type 2 diabetes/impaired glucose metabolism, nominal linkage evidence (P < 0.02) followed-up by genotypic association (P = 0.016) was found with marker D14S297 at 31.8 cM; linkage analyses using only diabetes phenotype were also nominally significant at this marker (P < 0.02). Nominal evidence for genotypic association to adiponectin serum level phenotype (P = 0.04) was found with the marker D14S1032 at 23.2 cM. The present study was limited by relatively small sample size. Nevertheless, these results corroborate earlier studies, suggesting that further research is warranted in the candidate region ∼30 cM on chromosome 14.
Tumor Necrosis Factor-α Induces Intestinal Insulin Resistance and Stimulates the Overproduction of Intestinal Apolipoprotein B48-Containing Lipoproteins
Authors: Qin Bolin , Qiu Wei , Avramoglu Rita Kohen , Adeli Khosrow
Published: January 2007

There is growing evidence suggesting intestinal insulin resistance and overproduction of apolipoprotein (apo) B48–containing chylomicrons in insulin-resistant states. In the current study, we investigated the potential role of the inflammatory cytokine tumor necrosis factor-α (TNF-α) in the development of insulin resistance and aberrant lipoprotein metabolism in the small intestine in a Syrian golden hamster model. TNF-α infusion decreased whole-body insulin sensitivity, based on in vivo euglycemic clamp studies in chow-fed hamsters. Analysis of intestinal tissue in TNF-α–treated hamsters indicated impaired phosphorylation of insulin receptor-β, insulin receptor substrate-1, Akt, and Shc and increased phosphorylation of p38, extracellular signal–related kinase-1/2, and Jun NH2-terminal kinase. TNF-α infusion also increased intestinal production of total apoB48, triglyceride-rich lipoprotein apoB48, and serum triglyceride levels in both fasting and postprandial (fat load) states. The effects of TNF-α on plasma apoB48 levels could be blocked by the p38 inhibitor SB203580. Ex vivo experiments using freshly isolated enterocytes also showed TNF-α–induced p38 phosphorylation and intestinal apoB48 overproduction, effects that could be blocked by SB203580. Interestingly, TNF-α increased the mRNA and protein mass of intestinal microsomal triglyceride transfer protein without altering apoB mRNA levels. Enterocytes were found to have detectable levels of both TNF-α receptor types (p55 and p75), and antibodies against either of the two TNF-α receptors partially blocked the stimulatory effect of TNF-α on apoB48 production and p38 phosphorylation. In summary, these data suggest that intestinal insulin resistance can be induced in hamsters by TNF-α infusion, and it is accompanied by intestinal overproduction of apoB48-containing lipoproteins. TNF-α–induced stimulation of intestinal lipoprotein production appears to be mediated via TNF-α receptors and the p38 mitogen-activated protein kinase pathway.
Impact of Type 2 Diabetes on Nitric Oxide and Adrenergic Modulation of Myocardial Perfusion
Authors: Madsen Mette M. , Søndergaard Hanne M. , Bøttcher Morten , Buus Niels H. , Schmitz Ole , Bøtker Hans E. , Nielsen Torsten T.
Published: January 2007

Type 2 diabetic patients are characterized by a reduced adenosine-induced hyperemic myocardial perfusion, which may contribute to their increased cardiovascular morbidity. We hypothesized that the reduced hyperemia can be explained by functional changes in endothelial or autonomic nervous regulation. In 12 type 2 diabetic patients without signs of ischemic heart disease and 14 age-matched control subjects, myocardial perfusion was measured at rest, during adenosine, and during adenosine and α-receptor blockade (phentolamine) using positron emission tomography on two separate days: 1) with, and 2) without nitric oxide (NO) inhibition with NG-nitro-l-arginine methyl ester. Myocardial perfusion during adenosine was lower in type 2 diabetic patients compared with control subjects (P = 0.05). No significant effect of NO inhibition on myocardial perfusion during adenosine was found in any of the groups. In control subjects, α-receptor blockade increased hyperemic myocardial vascular resistance during NO inhibition, whereas no effect was observed in type 2 diabetic patients. At rest, a significant correlation was observed between rate-pressure product and myocardial perfusion in control subjects. NO inhibition and type 2 diabetes abolished this correlation. Endothelial and cardiac autonomic nerve function seems to play only a minimal role in the reduced hyperemic myocardial perfusion in type 2 diabetic patients. However, the linear correlation between resting perfusion and cardiac work appears to be abolished in type 2 diabetes and during NO synthase inhibition.
Melanin Concentrating Hormone Is a Novel Regulator of Islet Function and Growth
Authors: Pissios Pavlos , Ozcan Umut , Kokkotou Efi , Okada Terumasa , Liew Chong Wee , Liu Siming , Peters Jennifer N. , Dahlgren Gabriella , Karamchandani Jason , Kudva Yogish C. , Kurpad Amarnath J. , Kennedy Robert T. , Maratos-Flier Eleftheria , Kulkarni Rohit N.
Published: January 2007

Melanin concentrating hormone (MCH) is a hypothalamic neuropeptide known to play a critical role in energy balance. We have previously reported that overexpression of MCH is associated with mild obesity. In addition, mice have substantial hyperinsulinemia and islet hyperplasia that is out of proportion with their degree of obesity. In this study, we further explored the role of MCH in the endocrine pancreas. Both MCH and MCHR1 are expressed in mouse and human islets and in clonal β-cell lines as assessed using quantitative real-time PCR and immunohistochemistry. Mice lacking MCH (MCH-KO) on either a C57Bl/6 or 129Sv genetic background showed a significant reduction in β-cell mass and complemented our earlier observation of increased β-cell mass in MCH-overexpressing mice. Furthermore, the compensatory islet hyperplasia secondary to a high-fat diet, which was evident in wild-type controls, was attenuated in MCH-KO. Interestingly, MCH enhanced insulin secretion in human and mouse islets and rodent β-cell lines in a dose-dependent manner. Real-time PCR analyses of islet RNA derived from MCH-KO revealed altered expression of islet-enriched genes such as glucagon, forkhead homeobox A2, hepatocyte nuclear factor (HNF)4α, and HNF1α. Together, these data provide novel evidence for an autocrine role for MCH in the regulation of β-cell mass dynamics and in islet secretory function and suggest that MCH is part of a hypothalamic-islet (pancreatic) axis.
Salicylate-Based Anti-Inflammatory Drugs Inhibit the Early Lesion of Diabetic Retinopathy
Authors: Zheng Ling , Howell Scott J. , Hatala Denise A. , Huang Kun , Kern Timothy S.
Published: January 2007

It has been previously reported that aspirin inhibited the development of diabetic retinopathy in diabetic animals, raising the possibility that anti-inflammatory drugs may have beneficial effects on diabetic retinopathy. To further explore this, we compared effects of oral consumption of three different salicylate-based drugs (aspirin, sodium salicylate, and sulfasalazine) on the development of early stages of diabetic retinopathy in rats. These three drugs differ in their ability to inhibit cyclooxygenase but share an ability to inhibit nuclear factor-κB (NF-κB). Diabetes of 9–10 months duration significantly increased the number of TUNEL (transferase-mediated dUTP nick-end labeling)-positive capillary cells and acellular (degenerate) capillaries in the retinal vasculature, and all three salicylate-based drugs inhibited this cell death and formation of acellular capillaries without altering the severity of hyperglycemia. In short-term diabetes (2–4 months), all three salicylates inhibited the diabetes-induced loss of neuronal cells from the ganglion cell layer. Oral aspirin (as a representative of the salicylate family) inhibited diabetes-induced increase in NF-κB DNA-binding affinity in electrophoretic mobility shift assay and transcription factor array in nuclear extract isolated from whole retina. All three salicylates inhibited the diabetes-induced translocation of p50 (a subunit of NF-κB) into nuclei of retinal vascular endothelial cells of the isolated retinal vasculature, as well as of p50 and p65 into nuclei of cells in the ganglion cell layer and inner nuclear layer on whole-retinal sections. Sulfasalazine (also as a representative of the salicylates) inhibited the diabetes-induced upregulation of several inflammatory gene products, which are regulated by NF-κB, including vascular cell adhesion molecule, intracellular adhesion molecule-1, inducible nitric oxide synthase, and cyclooxygenase-2 in whole-retinal lysate. Salicylates, in doses administrated in our experiments, inhibited NF-κB and perhaps other transcription factors in the retina, were well tolerated, and offered new tools to investigate and inhibit the development of diabetic retinopathy.
Ceramide- and Oxidant-Induced Insulin Resistance Involve Loss of Insulin-Dependent Rac-Activation and Actin Remodeling in Muscle Cells
Authors: JeBailey Lellean , Wanono Oshrit , Niu Wenyan , Roessler Jessica , Rudich Assaf , Klip Amira
Published: January 2007

In muscle cells, insulin elicits recruitment of the glucose transporter GLUT4 to the plasma membrane. This process engages sequential signaling from insulin receptor substrate (IRS)-1 to phosphatidylinositol (PI) 3-kinase and the serine/threonine kinase Akt. GLUT4 translocation also requires an Akt-independent but PI 3-kinase–and Rac-dependent remodeling of filamentous actin. Although IRS-1 phosphorylation is often reduced in insulin-resistant states in vivo, several conditions eliciting insulin resistance in cell culture spare this early step. Here, we show that insulin-dependent Rac activation and its consequent actin remodeling were abolished upon exposure of L6 myotubes beginning at doses of C2-ceramide or oxidant-producing glucose oxidase as low as 12.5 μmol/l and 12.5 mU/ml, respectively. At 25 μmol/l and 25 mU/ml, glucose oxidase and C2-ceramide markedly reduced GLUT4 translocation and glucose uptake and lowered Akt phosphorylation on Ser473 and Thr308, yet they affected neither IRS-1 tyrosine phosphorylation nor its association with p85 and PI 3-kinase activity. Small interfering RNA–dependent Rac1 knockdown prevented actin remodeling and GLUT4 translocation but spared Akt phosphorylation, suggesting that Rac and actin remodeling do not contribute to overall Akt activation. We propose that ceramide and oxidative stress can each affect two independent arms of insulin signaling to GLUT4 at distinct steps, Rac–GTP loading and Akt phosphorylation.
Pancreatic Lipomatosis Is a Structural Marker in Nondiabetic Children With Mutations in Carboxyl-Ester Lipase
Authors: Ræder Helge , Haldorsen Ingfrid S. , Ersland Lars , Grüner Renate , Taxt Torfinn , Søvik Oddmund , Molven Anders , Njølstad Pål R.
Published: January 2007

Both pancreatic volume reduction and lipomatosis have been observed in subjects with diabetes. The underlying molecular and pathological mechanisms are, however, poorly known, and it has been speculated that both features are secondary to diabetes. We have recently described pancreatic atrophy and lipomatosis in diabetic subjects of two Norwegian families with a novel syndrome of diabetes and exocrine pancreatic dysfunction caused by heterozygous carboxyl-ester lipase (CEL) mutations. To explore the early pathological events in this syndrome, we performed radiological examinations of the pancreas in nondiabetic mutation carriers with signs of exocrine dysfunction. In a case series study at a tertiary hospital, we evaluated 11 nondiabetic and mutation-positive children with fecal elastase deficiency and 11 age- and sex-matched control subjects using ultrasound and magnetic resonance imaging (MRI) to estimate pancreatic fat content. The pancreata of nondiabetic mutation carriers exhibited increased reflectivity on ultrasound and had MRI findings indicative of lipomatosis. Apparently, carriers of heterozygous CEL mutations accumulate fat in their pancreas before the anticipated development of diabetes. Our findings suggest that lipomatosis of the pancreas reflects early events involved in the pathogenesis of diabetes and exocrine pancreatic dysfunction syndrome.
P2 Promoter Variants of the Hepatocyte Nuclear Factor 4α Gene Are Associated With Type 2 Diabetes in Mexican Americans
Authors: Lehman Donna M. , Richardson Dawn K. , Jenkinson Chris P. , Hunt Kelly J. , Dyer Thomas D. , Leach Robin J. , Arya Rector , Abboud Hanna E. , Blangero John , Duggirala Ravindranath , Stern Michael P.
Published: January 2007

Common and rare variants of the hepatocyte nuclear factor 4α (HNF4A) gene have been associated with type 2 diabetes and related traits in several populations suggesting the involvement of this transcription factor in diabetes pathogenesis. Single nucleotide polymorphisms (SNPs) within a large haplotype block surrounding the alternate P2 promoter, located ∼45 kb upstream from the coding region, have been investigated in several populations of varying ethnicity with inconsistent results. Additionally, SNPs located within the P1 promoter and coding region have also been inconsistently associated with type 2 diabetes. Characterization of variation across this gene region in Mexican-American populations has not been reported. We therefore examined polymorphisms across the HNF4A gene in a cohort of Mexican-American pedigrees and assessed their association with type 2 diabetes. We observed evidence for association of SNPs in the P2 promoter region with type 2 diabetes (P = 0.003) and its age at diagnosis (P = 0.003). The risk allele frequency (53%) was intermediate to that reported in Caucasian populations (20–27%) and Pima Indians (83%). No other SNPs were associated with either trait. These results support the possibility that a variant in the P2 promoter region of HNF4A, or variants in linkage disequilibrium within this region, contributes to susceptibility to type 2 diabetes in many ethnic populations including Mexican Americans.
Deletion of Protein Kinase C-β Isoform In Vivo Reduces Renal Hypertrophy but Not Albuminuria in the Streptozotocin-Induced Diabetic Mouse Model
Authors: Meier Matthias , Park Joon-Keun , Overheu Daniel , Kirsch Torsten , Lindschau Carsten , Gueler Faikah , Leitges Michael , Menne Jan , Haller Hermann
Published: January 2007

The protein kinase C (PKC)-β isoform has been implicated to play a pivotal role in the development of diabetic kidney disease. We tested this hypothesis by inducing diabetic nephropathy in PKC-β–deficient (PKC-β−/−) mice. We studied nondiabetic and streptozotocin-induced diabetic PKC-β−/− mice compared with appropriate 129/SV wild-type mice. After 8 weeks of diabetes, the high-glucose–induced renal and glomerular hypertrophy, as well as the increased expression of extracellular matrix proteins such as collagen and fibronectin, was reduced in PKC-β−/− mice. Furthermore, the high-glucose–induced expression of the profibrotic cytokine transforming growth factor (TGF)-β1 and connective tissue growth factor were significantly diminished in the diabetic PKC-β−/− mice compared with diabetic wild-type mice, suggesting a role of the PKC-β isoform in the regulation of renal hypertrophy. Notably, increased urinary albumin-to-creatinine ratio persisted in the diabetic PKC-β−/− mice. The loss of the basement membrane proteoglycan perlecan and the podocyte protein nephrin in the diabetic state was not prevented in the PKC-β−/− mice as previously demonstrated in the nonalbuminuric diabetic PKC-α−/− mice. In summary, the differential effects of PKC-β deficiency on diabetes-induced renal hypertrophy and albuminuria suggest that PKC-β contributes to high-glucose–induced TGF-β1 expression and renal fibrosis, whereas perlecan, as well as nephrin, expression and albuminuria is regulated by other signaling pathways.
A Possible Role for the PPARG Pro12Ala Polymorphism in Preterm Birth
Authors: Meirhaeghe Aline , Boreham Colin A.G. , Murray Liam J. , Richard Florence , Smith George Davey , Young Ian S. , Amouyel Philippe
Published: January 2007

The links between preterm birth, low birth weight, and adult vascular/metabolic morbidity remain unclear. Genetic susceptibility of babies related to these three conditions might contribute to this long-term association. We tested whether the Pro12Ala polymorphism of the peroxisome proliferator–activated receptor γ (PPARG) gene could play a role in birth weight and duration of gestation. We genotyped two independent cross-sectional studies from Northern Ireland (n = 382 and 620). In combined populations, the PPARG Ala12 allele was associated (P = 0.03) with lower birth weight, primarily caused by shorter gestational duration (P = 0.04). The frequency of Ala12 allele carriers was higher (P = 0.027) in the group of individuals born before term (35%, n = 60) than in the group of individuals born at term (22%, n = 942). The odds ratios (95% CI) of preterm birth for Ala12 allele carriers were 1.9 (1.1–3.4), P = 0.022, and 4.2 (1.9–9.7), P = 0.0006 (adjusted for sex, maternal age, and study), when considering 37 or 35 weeks of pregnancy as a threshold for preterm birth, respectively. Interestingly, the same allele was also associated with a moderate decreased risk of miscarriages in mothers. In conclusion, the PPARG Pro12Ala polymorphism might represent a genetic susceptibility factor for preterm birth and constitute a link between preterm birth and metabolic diseases later in life.
PTPN22 R620W Functional Variant in Type 1 Diabetes and Autoimmunity Related Traits
Authors: Chelala Claude , Duchatelet Sabine , Joffret Marie-Line , Bergholdt Regine , Dubois-Laforgue Danièle , Ghandil Pegah , Pociot Flemming , Caillat-Zucman Sophie , Timsit José , Julier Cécile
Published: January 2007

The PTPN22 gene, encoding the lymphoid-specific protein tyrosine phosphatase, a negative regulator in the T-cell activation and development, has been associated with the susceptibility to several autoimmune diseases, including type 1 diabetes. Based on combined case-control and family-based association studies, we replicated the finding of an association of the PTPN22 C1858T (R620W) functional variant with type 1 diabetes, which was independent from the susceptibility status at the insulin gene and at HLA-DR (DR3/4 compared with others). The risk contributed by the 1858T allele was increased in patients with a family history of other autoimmune diseases, further supporting a general role for this variant on autoimmunity. In addition, we found evidence for an association of 1858T allele with the presence of GAD autoantibodies (GADA), which was restricted to patients with long disease duration (>10 years, P < 0.001). This may help define a subgroup of patients with long-term persistence of GADA. The risk conferred by 1858T allele on GAD positivity was additive, and our meta-analysis also supported an additive rather than dominant effect of this variant on type 1 diabetes, similar to previous reports on rheumatoid arthritis and systemic lupus erythematosus.
Tag Polymorphisms at the A20 (TNFAIP3) Locus Are Associated With Lower Gene Expression and Increased Risk of Coronary Artery Disease in Type 2 Diabetes
Authors: Boonyasrisawat Watip , Eberle Delphine , Bacci Simonetta , Zhang Yuan-Yuan , Nolan David , Gervino Ernest V. , Johnstone Michael T. , Trischitta Vincenzo , Shoelson Steven E. , Doria Alessandro
Published: January 2007

A20 or tumor necrosis factor (TNF)-induced protein 3 (TNFAIP3) is a negative regulator of nuclear factor-κB (NF-κB). We have investigated whether polymorphisms in this gene are associated with increased atherosclerosis in diabetic patients. Five tag single nucleotide polymorphisms (SNPs) were typed in 479 type 2 diabetic patients from Boston, including 239 coronary artery disease (CAD)-positive case subjects and 240 CAD-negative control subjects. Two tag SNPs (rs5029930 and rs610604) were independently associated with CAD; adjusted odds ratios (ORs) for minor allele carriers were 2.3 (95% CI 1.4–3.8, P = 0.001) and 2.0 (1.3–2.9, P = 0.0008), respectively. The association with rs610604 was dependent on glycemic control, with ORs of 3.9 among subjects with A1C ≤7.0% and 1.2 for those with A1C >7.0% (P for interaction = 0.015). A similar interaction pattern was found among 231 CAD-positive and 332 CAD-negative type 2 diabetic patients from Italy (OR 2.2, P = 0.05 vs. OR 0.9, P = 0.63 in the low vs. high A1C strata, P for interaction = 0.05). Quantitative RT-PCR in blood mononuclear cells from 83 nondiabetic subjects showed that rs610604 and rs5029930 minor allele homozygotes have 30–45% lower levels of A20 mRNA than major allele homozygotes, and heterozygotes have intermediate levels (P = 0.04 and 0.028, respectively). These findings point to variability in the A20/TNFAIP3 gene as a modulator of CAD risk in type 2 diabetes. This effect is mediated by allelic differences in A20 expression.
Protein–Tyrosine Phosphatase 1B–Deficient Myocytes Show Increased Insulin Sensitivity and Protection Against Tumor Necrosis Factor-α–Induced Insulin Resistance
Authors: Nieto-Vazquez Iria , Fernández-Veledo Sonia , de Alvaro Cristina , Rondinone Cristina M. , Valverde Angela M. , Lorenzo Margarita
Published: January 2007

Protein–tyrosine phosphatase (PTP)1B is a negative regulator of insulin signaling and a therapeutic target for type 2 diabetes. In this study, we have assessed the role of PTP1B in the insulin sensitivity of skeletal muscle under physiological and insulin-resistant conditions. Immortalized myocytes have been generated from PTP1B-deficient and wild-type neonatal mice. PTP1B−/− myocytes showed enhanced insulin-dependent activation of insulin receptor autophosphorylation and downstream signaling (tyrosine phosphorylation of insulin receptor substrate [IRS]-1 and IRS-2, activation of phosphatidylinositol 3-kinase, and serine phosphorylation of AKT), compared with wild-type cells. Accordingly, PTP1B−/− myocytes displayed higher insulin-dependent stimulation of glucose uptake and GLUT4 translocation to the plasma membrane than wild-type cells. Treatment with tumor necrosis factor-α (TNF-α) induced insulin resistance on glucose uptake, impaired insulin signaling, and increased PTP1B activity in wild-type cells. Conversely, the lack of PTP1B confers protection against insulin resistance by TNF-α in myocyte cell lines and in adult male mice. Wild-type mice treated with TNF-α developed a pronounced hyperglycemia along the glucose tolerance test, accompanied by an impaired insulin signaling and increased PTP1B activity in muscle. However, mice lacking PTP1B maintained a rapid clearance of glucose and insulin sensitivity and displayed normal muscle insulin signaling regardless the presence of TNF-α.