bluuebunny/crossref_metadata_2025 huggingface dataset:
Higher Offspring Birth Weight Predicts the Metabolic Syndrome in Mothers but Not Fathers 8 Years After Delivery
Authors: Yajnik Chittaranjan S. , Joglekar Charu V. , Pandit Anand N. , Bavdekar Ashish R. , Bapat Swati A. , Bhave Sheila A. , Leary Samantha D. , Fall Caroline H.D.
Published: March 2007

In Europid populations, low birth weight of offspring predicts insulin resistance in the mother and cardiovascular disease in both parents. We investigated the association between birth weight of offspring and obesity and cardiovascular risk in the parents of 477 8-year-old children born at the King Edward Memorial Hospital, Pune, India. Eight years after the birth of the child, mothers (33 years of age, n = 459) of heavier babies were taller and more obese (BMI, fat mass, and waist circumference, all P < 0.001) than mothers of lighter babies. Increasing offspring birth weight predicted higher homeostasis model assessment for insulin resistance (P < 0.01) and metabolic syndrome in mothers (P < 0.001) (adjusted for offspring sex and birth order, maternal age, and socioeconomic status) but not hyperglycemia. Fathers (39 years of age, n = 398) of heavier babies were taller and heavier, independent of maternal size (P < 0.01, both), but were not more insulin resistant. Unlike other reports, lower offspring birth weight did not predict insulin resistance in fathers. Thus, urban Indian parents have a higher risk of being obese 8 years after delivery of a heavier child. Mothers but not fathers of heavier babies also have a higher risk of being insulin resistant and developing the metabolic syndrome. Our findings highlight the need for a better understanding of the relation between fetal growth and future health before contemplating public health interventions to improve fetal growth.
Protein Kinase Cβ Selective Inhibitor LY333531 Attenuates Diabetic Hyperalgesia Through Ameliorating cGMP Level of Dorsal Root Ganglion Neurons
Authors: Kim Hyoh , Sasaki Teiji , Maeda Kengo , Koya Daisuke , Kashiwagi Atsunori , Yasuda Hitoshi
Published: March 2007

Streptozocin (STZ)-induced diabetic rats show hyperalgesia that is partially attributed to altered protein kinase C (PKC) activity. Both attenuated neuronal nitric oxide synthase (nNOS)-cGMP system and tetrodotoxin-resistant (TTX-R) Na channels in dorsal root ganglion neurons may be involved in diabetic hyperalgesia. We examined whether PKCβ inhibition ameliorates diabetic hyperalgesia and, if so, whether the effect is obtained through action on neurons by testing nociceptive threshold in normal and STZ-induced diabetic rats treated with or without PKCβ-selective inhibitor LY333531 (LY) and by assessing the implication of LY in either nNOS-cGMP system or TTX-R Na channels of isolated dorsal root ganglion neurons. The decreased nociceptive threshold in diabetic rats was improved either after 4 weeks of LY treatment or with a single intradermal injection into the footpads. The treatment of LY for 6 weeks significantly decreased p-PKCβ and ameliorated a decrease in cGMP content in dorsal root ganglia of diabetic rats. The latter effect was confirmed in ex vivo condition. The treatment with NO donor for 4 weeks also normalized both diabetic hyperalgesia and decreased cGMP content in dorsal root ganglions. The expressions of nNOS and TTX-R Na channels were not changed with LY treatment. These results suggest that LY is effective for treating diabetic hyperalgesia through ameliorating the decrease in the nNOS-cGMP system.
Prevention of Incipient Diabetic Nephropathy by High-Dose Thiamine and Benfotiamine
Authors: Babaei-Jadidi Roya , Karachalias Nikolaos , Ahmed Naila , Battah Sinan , Thornalley Paul J.
Published: March 2007

Accumulation of triosephosphates arising from high cytosolic glucose concentrations in hyperglycemia is the trigger for biochemical dysfunction leading to the development of diabetic nephropathy—a common complication of diabetes associated with a high risk of cardiovascular disease and mortality. Here we report that stimulation of the reductive pentosephosphate pathway by high-dose therapy with thiamine and the thiamine monophosphate derivative benfotiamine countered the accumulation of triosephosphates in experimental diabetes and inhibited the development of incipient nephropathy. High-dose thiamine and benfotiamine therapy increased transketolase expression in renal glomeruli, increased the conversion of triosephosphates to ribose-5-phosphate, and strongly inhibited the development of microalbuminuria. This was associated with decreased activation of protein kinase C and decreased protein glycation and oxidative stress—three major pathways of biochemical dysfunction in hyperglycemia. Benfotiamine also inhibited diabetes-induced hyperfiltration. This was achieved without change in elevated plasma glucose concentration and glycated hemoglobin in the diabetic state. High-dose thiamine and benfotiamine therapy is a potential novel strategy for the prevention of clinical diabetic nephropathy.
Insulin Prevents Depolarization of the Mitochondrial Inner Membrane in Sensory Neurons of Type 1 Diabetic Rats in the Presence of Sustained Hyperglycemia
Authors: Huang Tze-Jen , Price Sally A. , Chilton Lucy , Calcutt Nigel A. , Tomlinson David R. , Verkhratsky Alex , Fernyhough Paul
Published: March 2007

Mitochondrial dysfunction has been proposed as a mediator of neurodegeneration in diabetes complications. The aim of this study was to determine whether deficits in insulin-dependent neurotrophic support contributed to depolarization of the mitochondrial membrane in sensory neurons of streptozocin (STZ)-induced diabetic rats. Whole cell fluorescent video imaging using rhodamine 123 (R123) was used to monitor mitochondrial inner membrane potential (Δψm). Treatment of cultured dorsal root ganglia (DRG) sensory neurons from normal adult rats for up to 1 day with 50 mmol/l glucose had no effect; however, 1.0 nmol/l insulin increased Δψm by 100% (P < 0.05). To determine the role of insulin in vivo, STZ-induced diabetic animals were treated with background insulin and the Δψm of DRG sensory neurons was analyzed. Insulin therapy in STZ-induced diabetic rats had no effect on raised glycated hemoglobin or sciatic nerve polyol levels, confirming that hyperglycemia was unaffected. However, insulin treatment significantly normalized diabetes-induced deficits in sensory and motor nerve conduction velocity (P < 0.05). In acutely isolated DRG sensory neurons from insulin-treated STZ animals, the diabetes-related depolarization of the Δψm was corrected (P < 0.05). The results demonstrate that loss of insulin-dependent neurotrophic support may contribute to mitochondrial membrane depolarization in sensory neurons in diabetic neuropathy.
Minimal Model-Based Insulin Sensitivity Has Greater Heritability and a Different Genetic Basis Than Homeostasis Model Assessment or Fasting Insulin
Authors: Bergman Richard N. , Zaccaro Daniel J. , Watanabe Richard M. , Haffner Steven M. , Saad Mohammed F. , Norris Jill M. , Wagenknecht Lynne E. , Hokanson James E. , Rotter Jerome I. , Rich Steven S.
Published: March 2007

Insulin resistance is an important risk factor for development of type 2 diabetes as well as other chronic conditions, including hypertension, cardiovascular disease, and colon cancer. To find genes for insulin resistance it is necessary to assess insulin action in large populations. We have previously measured insulin action in a large cohort of subjects (Insulin Resistance and Atherosclerosis Study [IRAS] Family Study) using the minimal model approach. In this study, we compare sensitivity from the minimal model (insulin sensitivity index [SI]) with the measure of insulin resistance emanating from the homeostasis model assessment (HOMA) approach. The former measure emerges from the glycemic response to endogenous and exogenous insulin; the latter is based solely on fasting measures of glucose and insulin. A total of 112 pedigrees were represented, including 1,362 individuals with full phenotypic assessment. Heritability of SI was significantly greater than that for HOMA (0.310 vs. 0.163) and for fasting insulin (0.171), adjusted for age, sex, ethnicity, and BMI. In addition, correlation between SI and either HOMA or fasting insulin was only ∼50% accounted for by genetic factors, with the remainder accounted for by environment. Thus SI, a direct measure of insulin sensitivity, is determined more by genetic factors rather than measures such as HOMA, which reflect fasting insulin.
Effect of Exercise Intensity on Skeletal Muscle AMPK Signaling in Humans
Authors: Chen Zhi-Ping , Stephens Terry J. , Murthy Sid , Canny Benedict J. , Hargreaves Mark , Witters Lee A. , Kemp Bruce E. , McConell Glenn K.
Published: March 2007

The effect of exercise intensity on skeletal muscle AMP-activated protein kinase (AMPK) signaling and substrate metabolism was examined in eight men cycling for 20 min at each of three sequential intensities: low (40 ± 2% Vo2 peak), medium (59 ± 1% Vo2 peak), and high (79 ± 1% Vo2 peak). Muscle free AMP/ATP ratio only increased at the two higher exercise intensities (P < 0.05). AMPK α1 (1.5-fold) and AMPK α2 (5-fold) activities increased from low to medium intensity, with AMPK α2 activity increasing further from medium to high intensity. The upstream AMPK kinase activity was substantial at rest and only increased 50% with exercise, indicating that, initially, signaling through AMPK did not require AMPK kinase posttranslational modification. Acetyl-CoA carboxylase (ACC)-β phosphorylation was sensitive to exercise, increasing threefold from rest to low intensity, whereas neuronal NO synthase (nNOS)μ phosphorylation was only observed at the higher exercise intensities. Glucose disappearance (tracer) did not increase from rest to low intensity, but increased sequentially from low to medium to high intensity. Calculated fat oxidation increased from rest to low intensity in parallel with ACCβ phosphorylation, then declined during high intensity. These results indicate that ACCβ phosphorylation is especially sensitive to exercise and tightly coupled to AMPK signaling and that AMPK activation does not depend on AMPK kinase activation during exercise.
Higher Insulin Concentrations Are Required to Suppress Gluconeogenesis Than Glycogenolysis in Nondiabetic Humans
Authors: Adkins Aron , Basu Rita , Persson Mai , Dicke Betty , Shah Pankaj , Vella Adrian , Schwenk W. Frederick , Rizza Robert
Published: March 2007

To determine the mechanism(s) by which insulin inhibits endogenous glucose production (EGP) in nondiabetic humans, insulin was infused at rates of 0.25, 0.375, or 0.5 mU · kg−1 · min−1 and glucose was clamped at ∼5.5 mmol/l. EGP, gluconeogenesis, and uridine-diphosphoglucose (UDP)-glucose flux were measured using [3-3H]glucose, deuterated water, and the acetaminophen glucuronide methods, respectively. An increase in insulin from ∼75 to ∼100 to ∼150 pmol/l (∼12.5 to ∼17 to ∼25 μU/ml) resulted in progressive (ANOVA; P < 0.02) suppression of EGP (13.1 ± 1.3 vs. 11.7 ± 1.03 vs. 6.4 ± 2.15 μmol · kg−1 · min−1) that was entirely due to a progressive decrease (ANOVA; P < 0.05) in the contribution of glycogenolysis to EGP (4.7 ± 1.7 vs. 3.4 ± 1.2 vs. –2.1 ± 1.3 μmol · kg−1 · min−1). In contrast, both the contribution of gluconeogenesis to EGP (8.4 ± 1.0 vs. 8.3 ± 1.1 vs. 8.5 ± 1.3 μmol · kg−1 · min−1) and UDP-glucose flux (5.0 ± 0.4 vs. 5.0 ± 0.3 vs. 4.0 ± 0.5 μmol · kg−1 · min−1) remained unchanged. The contribution of the direct (extracellular) pathway to UDP-glucose flux was minimal and constant during all insulin infusions. We conclude that higher insulin concentrations are required to suppress the contribution of gluconeogenesis of EGP than are required to suppress the contribution of glycogenolysis to EGP in healthy nondiabetic humans. Since suppression of glycogenolysis occurred without a decrease in UDP-glucose flux, this implies that insulin inhibits EGP, at least in part, by directing glucose-6-phosphate into glycogen rather than through the glucose-6-phosphatase pathway.
Hyperphagic Effects of Brainstem Ghrelin Administration
Authors: Faulconbridge Lucy F. , Cummings David E. , Kaplan Joel M. , Grill Harvey J.
Published: March 2007

The role of ghrelin in feeding control has been addressed from a largely hypothalamic perspective, with little attention directed at ingestive consequences of stimulation of the peptide’s receptor, the growth hormone secretagogue receptor (GHS-R), in the caudal brainstem. Here, we demonstrate a hyperphagic response to stimulation of GHS-R in the caudal brainstem. Ghrelin (150 pmol) delivered to the third and fourth ventricles significantly and comparably increased cumulative food intake, with maximal response ∼3 h after injection. The meal patterning effects underlying this hyperphagia were also similar for the two placements (i.e., significant reduction in the time between injection and first-meal onset, an increase in the number of meals taken shortly after the injection, and a trend toward an increase in the average size of the first meals that approached but did not achieve statistical significance). In a separate experiment, ghrelin microinjected unilaterally into the dorsal vagal complex (DVC) significantly increased food intake measured 1.5 and 3 h after treatment. The response was obtained with a 10-pmol dose, establishing the DVC as a site of action with at least comparable sensitivity to that reported for the arcuate nucleus. Taken together, the results affirm a caudal brainstem site of action and recommend further investigation into multisite interactions underlying the modulation of ingestive behavior by ghrelin.
The Hepatic Vagus Mediates Fat-Induced Inhibition of Diabetic Hyperphagia
Authors: la Fleur Susanne E. , Ji Hong , Manalo Sotara L. , Friedman Mark I. , Dallman Mary F.
Published: March 2007

Diabetic rats both overeat high-carbohydrate diet and have altered hypothalamic neuropeptide Y (NPY) and corticotropin-releasing factor (CRF). In contrast, a high-fat diet reduces caloric intake of diabetics to normal, reflected by normal hypothalamic NPY and CRF content. How the brain senses these changes in diet is unknown. To date, no hormonal changes explain these diet-induced changes in caloric intake. We tested whether the common branch of the hepatic vagus mediates the fat signal. We presented fat in two ways. First, diabetic and vehicle-treated rats were offered a cup of lard in addition to their normal high-carbohydrate diet. Second, we switched diabetic rats from high-carbohydrate diet to high-fat diet, without choice. In streptozotocin-treated rats, both methods resulted in fat-induced inhibition of caloric intake and normalization of hypothalamic neuropeptides to nondiabetic levels. Strikingly, common branch hepatic vagotomy (unlike gastroduodenal vagotomy) entirely blocked these fat-induced changes. Although a shift in hepatic energy status did not explain the lard-induced changes in diabetic rats, the data suggested that common hepatic branch vagotomy does not interfere with hepatic energy status. Furthermore, common branch hepatic vagotomy without diabetes induced indexes of obesity. Abnormal function of the hepatic vagus, as occurs in diabetic neuropathy, may contribute to diabetic obesity.
Peroxisome Proliferator-Activated Receptor (PPAR)-α Activation Prevents Diabetes in OLETF Rats
Authors: Koh Eun Hee , Kim Min-Seon , Park Joong-Yeol , Kim Hyun Sik , Youn Ji-Young , Park Hye-Sun , Youn Jang Hyun , Lee Ki-Up
Published: March 2007

Lipid accumulation in nonadipose tissues is closely related to the development of type 2 diabetes in obese subjects. We examined the potential preventive effect of peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ stimulation on the development of diabetes in obese diabetes-prone OLETF rats. Chronic administration of a PPAR-α agonist (0.5% [wt/wt] fenofibrate) or a PPAR-γ agonist (3 mg · kg−1 · day−1 rosiglitazone) completely prevented the development of glycosuria. Pancreatic islets from untreated OLETF rats underwent sequential hypertrophy and atrophy, which was completely prevented by chronic fenofibrate treatment. In contrast, rosiglitazone treatment did not affect islet hypertrophy at earlier stages but prevented β-cell atrophy at later stages. Fenofibrate treatment decreased body weight and visceral fat, whereas rosiglitazone treatment increased body weight. Despite the opposite effects on adiposity, both drugs were equally effective in improving insulin actions in skeletal muscle. Furthermore, both drugs significantly decreased the triglyceride content in the soleus muscle and pancreatic islets. The present study demonstrates that the PPAR-α agonist fenofibrate prevents the development of diabetes in OLETF rats by reducing adiposity, improving peripheral insulin action, and exerting beneficial effects on pancreatic β-cells.
S100B-RAGE-Mediated Augmentation of Angiotensin II-Induced Activation of JAK2 in Vascular Smooth Muscle Cells Is Dependent on PLD2
Authors: Shaw Sean S. , Schmidt Ann Marie , Banes Amy K. , Wang Xiaodan , Stern David M. , Marrero Mario B.
Published: March 2007

Angiotensin II (Ang II), a vasoactive peptide that is also considered a growth factor, has been implicated in both normal and diabetic cellular proliferation. We recently found that activation of janus kinase 2 (JAK2) is essential for the Ang II–induced proliferation of vascular smooth muscle cells (VSMCs) and that high glucose augments Ang II–induced proliferation of VSMCs by increasing signal transduction through activation of JAK2. Here, we demonstrate that S100B, a ligand for the receptor of advanced glycation end products (RAGEs), augmented both Ang II–induced tyrosine phosphorylation of JAK2 and cell proliferation in VSMCs in a receptor-dependent manner. We also found that S100B-RAGE interaction triggered intracellular generation of reactive oxygen species (ROS), VSMC proliferation, and JAK2 tyrosine phosphorylation via activation of phospholipase D (PLD)2. These results provide direct evidence for linkages between PLD2, ROS production, and S100B-RAGE–induced enhancement of Ang II–induced cell proliferation and activation of JAK2 in VSMCs.
IL-1 Receptor Deficiency Slows Progression to Diabetes in the NOD Mouse
Authors: Thomas Helen E. , Irawaty Windy , Darwiche Rima , Brodnicki Thomas C. , Santamaria Pere , Allison Janette , Kay Thomas W.H.
Published: March 2007

Proinflammatory cytokines are believed to be important in pancreatic β-cell destruction in the development of type 1 diabetes. They act by upregulation of genes including Fas and inducible nitric oxide synthase (iNOS), which have both been shown to lead to β-cell death in vitro. We used mice deficient in the interleukin (IL)-1 receptor (IL-1R) to assess the contribution of IL-1 to different models of diabetes. IL-1R-deficient islets were protected from the damaging effects of tumor necrosis factor (TNF) and interferon (IFN)-γ in vitro, and β-cell expression of iNOS was reduced, suggesting that IL-1 mediates the induction of iNOS by TNF and IFN-γ. IL-1 action was not required for induction of class I major histocompatibility complex or Fas by TNF and IFN-γ. IL-1R-deficient nonobese diabetic (NOD) mice developed diabetes significantly slower than wild-type mice. IL-1R deficiency did not affect diabetes in 8.3 TCR transgenic NOD mice but prolonged the time to diabetes in BDC2.5 TCR transgenic NOD mice. We conclude that IL-1R deficiency slows progression to diabetes in NOD mice but on its own does not prevent diabetes.
Inhibition of Lipase Activity and Lipolysis in Rat Islets Reduces Insulin Secretion
Authors: Mulder Hindrik , Yang Shumin , Winzell Maria Sörhede , Holm Cecilia , Ahrén Bo
Published: March 2007

Lipids may serve as coupling factors in KATP-independent glucose sensing in β-cells. We have previously demonstrated that β-cells harbor lipase activities, one of which is the hormone-sensitive lipase. Whether β-cell lipases are critical for glucose-stimulated insulin secretion (GSIS) by providing lipid-derived signals from endogenous lipids is unknown. Therefore, using a lipase inhibitor (orlistat), we examined whether lipase inhibition reduces insulin secretion. Islet lipolysis stimulated by glucose and diglyceride lipase activity was abolished by orlistat. Incubation of rat islets with orlistat dose dependently inhibited GSIS; this inhibition was reversed by 1 mmol/l palmitate, suggesting that orlistat acts via impaired formation of an acylglyceride-derived coupling signal. Orlistat inhibited the potentiating effect of forskolin on GSIS, an effect proposed to be due to activation of a lipase. In perifused islets, orlistat attenuated mainly the second phase of insulin secretion. Because the rise in islet ATP/ADP levels in response to glucose and oxidation of the sugar were unaffected by orlistat whereas the second phase of insulin secretion was reduced, it seems likely that a lipid coupling factor involved in KATP-independent glucose sensing has been perturbed. Thus, β-cell lipase activity is involved in GSIS, emphasizing the important role of β-cell lipid metabolism for insulin secretion.
Gene and Protein Kinase Expression Profiling of Reactive Oxygen Species-Associated Lipotoxicity in the Pancreatic β-Cell Line MIN6
Authors: Wang Xiaolin , Li Hui , De Leo Domenica , Guo Wanbei , Koshkin Vasilij , Fantus I. George , Giacca Adria , Chan Catherine B. , Der Sandy , Wheeler Michael B.
Published: March 2007

Oligonucleotide microarrays were used to define oleic acid (OA)-regulated gene expression and proteomic technology to screen protein kinases in MIN6 insulinoma cells. The effects of oxidative stress caused by OA and potential protective effects of N-acetyl-l-cysteine (NAC), a scavenger of reactive oxygen species (ROS), on global gene expression and β-cell function were investigated. Long-term exposure of MIN6 cells to OA led to a threefold increase in basal insulin secretion, a 50% decrease in insulin content, an inhibition of glucose-stimulated insulin secretion (GSIS), and a twofold increase in the level of ROS. The addition of NAC normalized both the OA-induced insulin content and ROS elevation, but it failed to restore GSIS. Microarray studies and subsequent quantitative PCR analysis showed that OA consistently regulated the expression of 45 genes involved in metabolism, cell growth, signal transduction, transcription, and protein processing. The addition of NAC largely normalized the expression of the OA-regulated genes involved in cell growth and differentiation but not other functions. A protein kinase screen showed that OA regulated the expression and/or phosphorylation levels of kinases involved in stress-response mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and cell cycle control pathways. Importantly, these findings indicate that chronic OA exposure can impair β-cell function through ROS-dependent and -independent mechanisms.
Long-Term Renal Effects of a Neutralizing RAGE Antibody in Obese Type 2 Diabetic Mice
Authors: Flyvbjerg Allan , Denner Larry , Schrijvers Bieke F. , Tilton Ronald G. , Mogensen Trine H. , Paludan Søren R. , Rasch Ruth
Published: March 2007

Advanced glycation end products (AGEs) have been implicated in the pathogenesis of diabetic kidney disease. The actions of AGEs are mediated both through a non–receptor-mediated pathway and through specific receptors for AGE (RAGEs). To explore a specific role for RAGE in renal changes in type 2 diabetes, we examined the renal effects of a neutralizing murine RAGE antibody in db/db mice, a model of obese type 2 diabetes. One group of db/db mice was treated for 2 months with the RAGE antibody, and another db/db group was treated for the same period with an irrelevant IgG. Two groups of nondiabetic db/+ mice were treated with either RAGE antibody or isotype-matched IgG for 2 months. Placebo-treated db/db mice showed a pronounced increase in kidney weight, glomerular volume, basement membrane thickness (BMT), total mesangial volume, urinary albumin excretion (UAE), and creatinine clearance compared with nondiabetic controls. In RAGE antibody–treated db/db mice, the increase in kidney weight, glomerular volume, mesangial volume, and UAE was reduced, whereas the increase in creatinine clearance and BMT was fully normalized. Notably, these effects in db/db mice were seen without impact on body weight, blood glucose, insulin levels, or food consumption. In conclusion, RAGE is an important pathogenetic factor in the renal changes in an animal model of type 2 diabetes.
Genome-Wide Search for Type 2 Diabetes/Impaired Glucose Homeostasis Susceptibility Genes in the Chinese
Authors: Xiang Kunsan , Wang Yanqing , Zheng Taishan , Jia Weiping , Li Jie , Chen Lei , Shen Kunxue , Wu Songhua , Lin Xin , Zhang Guodong , Wang Congrong , Wang Suijun , Lu Huijuan , Fang Qichen , Shi Yi , Zhang Rong , Xu Jing , Weng Qin
Published: March 2007

This genome-wide search for susceptibility genes to type 2 diabetes/impaired glucose homeostasis (IGH) was performed on a relatively homogenous Chinese sample with a total number of 257 pedigrees and 385 affected sibpairs. Two regions showed significant linkage to type 2 diabetes/IGH in the Chinese. The region showing linkage to type 2 diabetes/IGH from the entire sample group analysis was located on chromosome 6q21-q23 (128.93 cM, 1-LOD [logarithm of odds] support interval between 124 and 142 cM, according to the Marshfield genetic map), with a maximum likelihood score of 6.23, a nonparametric linkage (all) score of 4.48, and empirical P value <0.001. With a subanalysis based on 101 affected sibpairs with age at diagnosis of type 2 diabetes/IGH <40 years, we detected significant evidence for linkage to chromosome 1q21-q24 (192.1 cM, 1-LOD support interval between 182 and 197 cM), with a maximum likelihood score of 8.91, a nonparametric linkage (all) score of 5.70, and empirical P value <0.001. No interaction was observed between these two regions. Our independent replication of the region on chromosome 1q that has been shown to be linked significantly to type 2 diabetes/IGH in Chinese supports the notion that gene(s) in this region may be universally important in the development of human type 2 diabetes.
Distinguishing Covariation From Causation in Diabetes
Authors: Lan Hong , Rabaglia Mary E. , Schueler Kathryn L. , Mata Christine , Yandell Brian S. , Attie Alan D.
Published: March 2007

Protein disulfide isomerase (Pdi) is reported to be an insulin-regulated gene whose expression level is increased in the livers of rats with streptozotocin-induced diabetes. We found that Pdi mRNA is ∼20-fold more abundant in the diabetes-susceptible BTBR mouse strain relative to the diabetes-resistant C56BL/6 (B6) strain. A genetic analysis was carried out to determine whether there is a causal relationship between elevated Pdi expression and diabetes phenotype in BTBR-ob/ob mice. We mapped Pdi mRNA abundance as a quantitative trait in 108 (B6 × BTBR)F2-ob/ob mice segregating for diabetes. We detected a single linkage at the telomeric end of chromosome 11, where the Pdi gene itself resides (logarithm of odds score >30.0). No linkage was detected for the Pdi mRNA trait in the regions where we have previously identified quantitative trait loci for diabetes traits. Sequencing of the Pdi promoter and cDNA revealed several single nucleotide polymorphisms between these two mouse strains. We conclude that in our experimental model, elevated Pdi expression is cis regulated and is not linked to diabetes susceptibility. Genetic analysis is a powerful tool for distinguishing covariation from causation in expression array studies of disease traits.
Identification of Major Quantitative Trait Loci Controlling Body Weight Variation in ob/ob Mice
Authors: Stoehr Jonathan P. , Byers Jessica E. , Clee Susanne M. , Lan Hong , Boronenkov Igor V. , Schueler Kathryn L. , Yandell Brian S. , Attie Alan D.
Published: March 2007

The adipocyte hormone leptin constitutes an important component of the regulation of energy homeostasis; leptin-deficient animals, such as obese mice, are strikingly overweight. The seemingly uninhibited weight gain in obese mice belies the fact that control of energy homeostasis remains under precise, heritably modifiable control. Herein, we report large, heritable differences in body weight and food intake between BTBR-ob/ob and B6-ob/ob mice. We have identified two loci, called modifier of obese (Moo1 and Moo2), that explain the majority of the heritable variance in (BTBR × B6) F2-ob/ob mice. Using interval-specific congenic mouse lines, we mapped Moo1 to an 8-Mb segment of chromosome 2 and demonstrated that Moo1 exerts its effects primarily by regulating total fat mass. Although null alleles of leptin are rare, the majority of overweight adults are leptin resistant, suggesting that leptin-independent pathways, such as those studied here, are important regulators of energy homeostasis. Thus, the identification of these loci may provide important new insights into the pathogenesis of human obesity.
PKCα Is Activated But Not Required During Glucose-Induced Insulin Secretion From Rat Pancreatic Islets
Authors: Carpenter Lee , Mitchell Christopher J. , Xu Zheng Z. , Poronnik Philip , Both Gerald W. , Biden Trevor J.
Published: March 2007

The role of protein kinase C (PKC) in glucose-stimulated insulin secretion (GSIS) is controversial. Using recombinant adenoviruses for overexpression of PKCα and PKCδ, in both wild-type (WT) and kinase-dead (KD) forms, we here demonstrate that activation of these two PKCs is neither necessary nor sufficient for GSIS from batch-incubated, rat pancreatic islets. In contrast, responses to the pharmacologic activator 12-O-tetradecanoylphorbol-13-acetate (TPA) were reciprocally modulated by overexpression of the PKCαWT or PKCαKD but not the corresponding PKCδ adenoviruses. The kinetics of the secretory response to glucose (monitored by perifusion) were not altered in either cultured islets overexpressing PKCαKD or freshly isolated islets stimulated in the presence of the conventional PKC (cPKC) inhibitor Go6976. However, the latter did inhibit the secretory response to TPA. Using phosphorylation state-specific antisera for consensus PKC phosphorylation sites, we also showed that (compared with TPA) glucose causes only a modest and transient functional activation of PKC (maximal at 2–5 min). However, glucose did promote a prolonged (15 min) phosphorylation of PKC substrates in the presence of the phosphatase inhibitor okadaic acid. Overall, the results demonstrate that glucose does stimulate PKCα in pancreatic islets but that this makes little overall contribution to GSIS.
Stimulation of Lipolysis by Tumor Necrosis Factor-α in 3T3-L1 Adipocytes Is Glucose Dependent
Authors: Green Allan , Rumberger John M. , Stuart Charles A. , Ruhoff Mary S.
Published: March 2007

Tumor necrosis factor-α (TNF-α) and hyperglycemia both impair insulin sensitivity in vivo. This may be secondary to stimulation of adipose tissue lipolysis and consequent increased circulating free fatty acids (FFAs). Here we report that neither TNF-α nor glucose alone has a pronounced effect on lipolysis in 3T3-L1 adipocytes. However, the combination of TNF-α plus glucose markedly stimulates lipolysis. Glucose does not affect the ability of isoproterenol to stimulate lipolysis. Alternative substrates such as acetate, pyruvate, and lactate do not allow the TNF-α effect. Mannose was almost as effective as glucose; fructose was marginally effective, but galactose was ineffective. The effectiveness of the sugars corresponded with production of lactate, i.e., the cells readily produced lactate from glucose or mannose, slightly from fructose, and not at all from galactose. The ability of TNF-α to phosphorylate extracellular signal-regulated kinase 1 (ERK1) and ERK2 and to downregulate perilipin (which has been implicated in the lipolytic effect of TNF-α) was not affected by glucose. We conclude that the lipolytic action of TNF-α is influenced by glucose in 3T3-L1 adipocytes. The findings suggest that glucose metabolism is required for the lipolytic response to TNF-α but not for early signaling events. These findings suggest novel mechanisms by which TNF-α and hyperglycemia raise FFA levels and induce insulin resistance.
Responsiveness to Peripherally Administered Melanocortins in Lean and Obese Mice
Authors: Blüher Susann , Ziotopoulou Mary , Bullen John W. , Moschos Stergios J. , Ungsunan Linda , Kokkotou Efi , Maratos-Flier Eleftheria , Mantzoros Christos S.
Published: March 2007

To elucidate mechanisms of melanocortin action, we investigated the effects of a melanocortin receptor agonist (melanotetan II [MTII]) in lean C57BL/6J and obese (DIO, ob/ob, UCP1-DTA) mice. MTII administration (100 μg q.i.d. i.p.) for 24 h results in similar weight loss but a more pronounced decrease of food intake in DIO mice. After 4 and 8 days of MTII treatment, however, the reduction in both food intake and body weight is more pronounced in DIO mice than in lean mice. MTII administration for 24 h prevents food deprivation-induced alterations in hypothalamic neuropeptide Y (NPY) and liver adiponectin receptor 1 and adiponectin receptor 2 mRNA expression, but does not alter hypothalamic mRNA expression of melanocortin 4 receptor or adiponectin serum and mRNA expression levels. NPY and agouti gene-related protein (AgRP) mRNA expression after 8 days of MTII is increased to levels comparable to pair-fed mice. In summary, 1) MTII is an effective treatment for obesity and related metabolic defects in leptin-resistant (DIO, UCP1-DTA) and leptin-sensitive (ob/ob) mouse models of obesity; 2) the effects of MTII on food intake and body weight are more pronounced in DIO mice than in lean mice; 3) the tachyphylactic effect after prolonged MTII administration appears to be, at least in part, caused by a compensatory upregulation of NPY and AgRP mRNA levels, whereas decreasing leptin levels may play a very minor role in mediating tachyphylaxis; and 4) alterations in adiponectin receptor mRNA expression after fasting or MTII treatment may contribute to altered insulin sensitivity and needs to be studied further.
Recruitment of Bone Marrow-Derived Endothelial Cells to Sites of Pancreatic β-Cell Injury
Authors: Mathews Vikram , Hanson Piia T. , Ford Eric , Fujita Jun , Polonsky Kenneth S. , Graubert Timothy A.
Published: March 2007

Endothelial progenitor cells (EPCs) are detectable in the blood and bone marrow throughout life. These cells contribute to new blood vessel formation (neovascularization) in physiological states such as wound healing and in pathological states such as tumor angiogenesis. We hypothesized that bone marrow-derived EPCs could play a role in the response to pancreatic islet cell injury. We used a murine model of experimentally induced β-cell injury followed by transplantation with genetically marked bone marrow cells. Bone marrow-derived cells were detectable throughout the pancreas after transplantation. Whereas the total number of bone marrow-derived cells in the pancreas decreased over time, the frequency of endothelial cells (of both donor and recipient origin) increased after transplantation in the animals in which β-cell injury had been induced. There was no evidence in this model that bone marrow-derived cells differentiated into insulin-expressing cells. This study provides evidence that bone marrow-derived EPCs are recruited to the pancreas in response to islet injury. EPC-mediated neovascularization of the pancreas could in principle be exploited to facilitate the recovery of non-terminally injured β-cells or to improve the survival and/or function of islet allografts.
Transferrin and Iron Contribute to the Lipolytic Effect of Serum in Isolated Adipocytes
Authors: Rumberger John M. , Peters Theodore , Burrington Christine , Green Allan
Published: March 2007

Previous reports have demonstrated that normal serum can increase the rate of adipocyte lipolysis in vitro. However, the nature of the lipolytic activity has remained obscure. We have investigated the lipolytic activity of human serum using isolated rat adipocytes. Human serum resulted in a dose-dependent stimulation of lipolysis (glycerol release) in adipocytes, with a half-maximal effective dose of 0.05% serum and with maximal stimulation with 1% serum. The effect of serum on glycerol release was rapid (within 30 min), and the effect was reversible. Partial purification of this lipolytic activity using gel filtration and ion-exchange chromatography demonstrates that a protein of ∼80 kDa contributes to the lipolytic activity. Human transferrin mimicked the activity of partially purified serum, resulting in a maximal 50% increase in basal lipolysis. In addition, ferrous sulfate heptahydrate induced a biphasic increase in the rate of lipolysis, with a maximal increase of 50% at ∼0.6 μg/ml iron. Inhibitors of protein kinase A (H89) and mitogen-activated protein kinase (PD98059) did not block the effect of serum on lipolysis, whereas the free radical scavenger N-acetyl-l-cysteine completely inhibited the effect. These findings suggest that the stimulatory effect of serum on lipolysis is in part mediated by iron, probably through a prooxidant mechanism.
Regulation of Growth Hormone Secretagogue Receptor Gene Expression in the Arcuate Nuclei of the Rat by Leptin and Ghrelin
Authors: Nogueiras Ruben , Tovar Sulay , Mitchell Sharon E. , Rayner D. Vernon , Archer Zoe A. , Dieguez Carlos , Williams Lynda M.
Published: March 2007

The anorexigenic and orexigenic hormones leptin and ghrelin act in opposition to one another. When leptin signaling is reduced, as in the Zucker fatty rat, or when circulating ghrelin is increased during fasting, the effect of ghrelin becomes more dominant, indicating an influence of both hormones on ghrelin action. This effect could be mediated via the level of expression of ghrelin receptor (growth hormone secretagogue receptor [GHS-R]). For testing this, GHS-R expression was measured using in situ hybridization in Zucker fatty versus lean rats; in fed versus fasted (48 h) rats, treated with either ghrelin or leptin; and in GH-deficient, dwarf versus control rats. In the arcuate nuclei of the Zucker fatty rat and in fasted rats, GHS-R expression is significantly increased. A single leptin intracerebroventricular injection attenuated the fasting-induced increase in GHS-R but had no effect in fed rats 2 h after injection, whereas leptin infusion for 24 h or longer significantly decreased GHS-R expression in fed rats. Ghrelin significantly increased GHS-R expression but not in dwarf rats. These results show that the level of GHS-R expression in the ARC is reduced by leptin and increased by ghrelin and that the effect of ghrelin may be GH dependent.
Elevated C-Reactive Protein Levels in the Development of Type 1 Diabetes
Authors: Chase H. Peter , Cooper Sonia , Osberg Iris , Stene Lars C. , Barriga Katherine , Norris Jill , Eisenbarth George S. , Rewers Marian
Published: March 2007

Elevated C-reactive protein (CRP) levels have previously been described before the onset of type 2 diabetes and gestational diabetes. We hypothesized that inflammation, as reflected by elevated CRP levels, can help predict development of islet autoimmunity or type 1 diabetes. Children at risk for type 1 diabetes and followed in the Diabetes Autoimmunity Study of the Young (DAISY) had blood samples drawn and frozen serum saved at various intervals after birth. CRP was measured using a high-sensitivity sandwich enzyme immunoassay. Islet autoantibodies (IAs) were measured using biochemical immunoassays. Elevations in CRP concentrations were significantly more frequent (P < 0.01) in children who later developed type 1 diabetes (8 of 16 children) than in children negative for IAs at their last testing (3 of 26). Children with one or more positive IA were more likely to have elevated CRP concentrations (15 of 36) than IA-negative children (3 of 26; P < 0.01). The finding of elevated CRP levels in infants and young children before the onset of type 1 diabetes adds to the evidence that the disease is an immunoinflammatory disorder. The elevated CRP levels may provide an additional marker for risk of progression to type 1 diabetes.
Artifactual Insulin Release From Differentiated Embryonic Stem Cells
Authors: Hansson Mattias , Tonning Anna , Frandsen Ulrik , Petri Andreas , Rajagopal Jayaraj , Englund Mikael C.O. , Heller R. Scott , Håkansson Joakim , Fleckner Jan , Sköld Helen Nilsson , Melton Douglas , Semb Henrik , Serup Palle
Published: March 2007

Several recent reports claim the generation of insulin-producing cells from embryonic stem cells via the differentiation of progenitors that express nestin. Here, we investigate further the properties of these insulin-containing cells. We find that although differentiated cells contain immunoreactive insulin, they do not contain proinsulin-derived C-peptide. Furthermore, we find variable insulin release from these cells upon glucose addition, but C-peptide release is never detected. In addition, many of the insulin-immunoreactive cells are undergoing apoptosis or necrosis. We further show that cells cultured in the presence of a phosphoinositide 3-kinase inhibitor, which previously was reported to facilitate the differentiation of insulin+ cells, are not C-peptide immunoreactive but take up fluorescein isothiocyanate–labeled insulin from the culture medium. Together, these data suggest that nestin+ progenitor cells give rise to a population of cells that contain insulin, not as a result of biosynthesis but from the uptake of exogenous insulin. We conclude that C-peptide biosynthesis and secretion should be demonstrated to claim insulin production from embryonic stem cell progeny.
Preserved Glucoregulation but Attenuation of the Vascular Actions of Insulin in Mice Heterozygous for Knockout of the Insulin Receptor
Authors: Wheatcroft Stephen B. , Shah Ajay M. , Li Jian-Mei , Duncan Edward , Noronha Brian T. , Crossey Paul A. , Kearney Mark T.
Published: March 2007

Type 2 diabetes is preceded by years of insulin resistance and is characterized by reduced bioavailability of the antiatherosclerotic signaling molecule nitric oxide (NO) and premature atherosclerosis. The relationship between resistance to the glucoregulatory actions of insulin and its effects on the vasculature (in particular NO-dependent responses) is poorly characterized. We studied this relationship in mice heterozygous for knockout of the insulin receptor (IRKO), which have a mild perturbation of insulin signaling. Male heterozygous IRKO mice aged 8–12 weeks were compared with age- and sex-matched littermates. IRKO mice had fasting blood glucose, insulin, free fatty acid, and triglyceride levels similar to those of wild-type mice. Intraperitoneal glucose and insulin tolerance tests were also similar in the two groups. Insulin levels in response to a glucose load were approximately twofold higher in IRKO compared with wild-type mice (1.08 ± 0.11 vs. 0.62 ± 0.13 ng/ml; P = 0.004). Despite this mild metabolic phenotype, IRKO mice had increased systolic blood pressure (124 ± 4 vs. 110 ± 3 mmHg; P = 0.01). Basal NO bioactivity, assessed from the increase in tension of phenylephrine preconstricted aortic rings in response to the NO synthase inhibitor NG-monomethyl-l-arginine, was reduced in IRKO (61 ± 14 vs. 152 ± 30%; P = 0.005). Insulin-mediated NO release in aorta, assessed as the reduction in phenylephrine constrictor response after insulin preincubation, was lost in IRKO mice (5 ± 8% change vs. 66 ± 9% reduction in wild-type; P = 0.03). Insulin-stimulated aortic endothelial NO synthase phosphorylation was also significantly blunted in IRKO mice (P < 0.05). These data demonstrate that insulin-stimulated NO responses in the vasculature are exquisitely sensitive to changes in insulin-signaling pathways in contrast to the glucoregulatory actions of insulin. These findings underscore the importance of early intervention in insulin-resistant states, where glucose homeostasis may be normal but substantial abnormalities of the vascular effects of insulin may already be present.
Selective Loss of Calcitonin Gene-Related Peptide-Expressing Primary Sensory Neurons of the A-Cell Phenotype in Early Experimental Diabetes
Authors: Jiang Yun , Nyengaard Jens Randel , Zhang Jin Song , Jakobsen Johannes
Published: March 2007

To evaluate the possible role of neuropeptide immunoreactive primary sensory neurons on the development of nociceptive dysfunction in diabetes, the absolute numbers of immunoreactive substance P and calcitonin gene–related peptide (CGRP) dorsal root ganglion (DRG) cell bodies were estimated in diabetic and nondiabetic BALB/C (p75+/+) and p75 receptor knockout (p75−/−) mice with unilateral sciatic nerve crush. The total numbers of immunoreactive substance P A-cells, substance P B-cells, CGRP A-cells, and CGRP B-cells in L5DRG were estimated using semithick consecutive sections and the optical fractionator. After 4 weeks of streptozotocin-induced diabetes, the number of immunoreactive CGRP A-cells was reduced from 692 ± 122 to 489 ± 125 (P = 0.004) in p75+/+ mice on the noncrushed side. In p75−/− mice, there was no such effect of diabetes on the immunoreactive CGRP A-cell number. In p75+/+ and p75−/− mice, there was no effect of diabetes on the immunoreactive CGRP B-cell number, nor was there any effect of diabetes on the immunoreactive substance P B-cell number. Sciatic nerve crush was associated with a substantial loss of L5DRG B-cells in diabetic and nondiabetic p75+/+ mice and with substantial loss of immunoreactive substance P cells in diabetic p75+/+ mice. In diabetic and nondiabetic p75−/− mice, there was no crush effect on neuropeptide expression. It is concluded that experimental diabetes in the mouse is associated with loss of immunoreactive CGRP primary sensory neurons of the A-cell phenotype, that this loss could play a role for the touch-evoked nociception in the model, and that the neuronal immunoreactive CGRP abnormality possibly is mediated by activation of the p75 neurotrophin receptor.
Genetic Evidence for Discordance Between Obesity- and Diabetes-Related Traits in the LGXSM Recombinant Inbred Mouse Strains
Authors: Cheverud James M. , Ehrich Thomas H. , Kenney Jane P. , Pletscher L. Susan , Semenkovich Clay F.
Published: March 2007

Obesity and its comorbidities, particularly type 2 diabetes, have become serious public health problems over the past few decades. Although the current pandemic is largely caused by societal environmental changes in diet, variation in response to these changes have, in part, a genetic basis. Here we address the genetic basis for both obesity- and diabetes-related traits themselves and dietary fat responses for these traits in a set of recombinant inbred mouse strains formed from the cross of LG/J with SM/J (LGXSM lines) fed a standard low-fat (15% calories from fat) or high-fat (42% calories from fat) diet. We found substantial genetic variation for most of the traits studied. Weight at time of death, liver weight, and weight of the reproductive fat pad had especially high heritabilities, whereas heart weight and serum levels of free fatty acids and triglycerides had low heritabilities. Genetic correlations were very high among fat pad weights and serum leptin, indicating shared genetic variation between fat levels and hormonal appetite control. These obesity traits were moderately correlated with adult growth, liver weight, and serum insulin and cholesterol levels. A majority of traits also displayed genetic variation in response to a high-fat diet, especially the weight of the reproductive and renal fat pads as well as the liver. Genetic correlations in dietary response followed a pattern similar to that found for the traits themselves. Several strains manifested discordant responses for obesity, glucose, and insulin, consistent with the presence of genotypes protective for diabetes in the presence of obesity. These recombinant inbred strains represent potentially valuable new models for dissecting the complex physiological relationships among obesity and diabetes.