bluuebunny/crossref_metadata_2025_split huggingface dataset:
High-Fat Diet–Induced Neuropathy of Pre-Diabetes and Obesity
Authors: Obrosova Irina G. , Ilnytska Olga , Lyzogubov Valeriy V. , Pavlov Ivan A. , Mashtalir Nazar , Nadler Jerry L. , Drel Viktor R. 
Published: September 2007

OBJECTIVE—Subjects with dietary obesity and pre-diabetes have an increased risk for developing both nerve conduction slowing and small sensory fiber neuropathy. Animal models of this type of neuropathy have not been described. This study evaluated neuropathic changes and their amenability to dietary and pharmacological interventions in mice fed a high-fat diet (HFD), a model of pre-diabetes and alimentary obesity.
RESEARCH DESIGN AND METHODS—Female C57BL6/J mice were fed normal diets or HFDs for 16 weeks.
RESULTS—HFD-fed mice developed obesity, increased plasma FFA and insulin concentrations, and impaired glucose tolerance. They also had motor and sensory nerve conduction deficits, tactile allodynia, and thermal hypoalgesia in the absence of intraepidermal nerve fiber loss or axonal atrophy. Despite the absence of overt hyperglycemia, the mice displayed augmented sorbitol pathway activity in the peripheral nerve, as well as 4-hydroxynonenal adduct nitrotyrosine and poly(ADP-ribose) accumulation and 12/15-lipoxygenase overexpression in peripheral nerve and dorsal root ganglion neurons. A 6-week feeding with normal chow after 16 weeks on HFD alleviated tactile allodynia and essentially corrected thermal hypoalgesia and sensory nerve conduction deficit without affecting motor nerve conduction slowing. Normal chow containing the aldose reductase inhibitor fidarestat (16 mg · kg−1· day −1) corrected all functional changes of HFD-induced neuropathy.
CONCLUSIONS—Similar to human subjects with pre-diabetes and obesity, HFD-fed mice develop peripheral nerve functional, but not structural, abnormalities and, therefore, are a suitable model for evaluating dietary and pharmacological approaches to halt progression and reverse diabetic neuropathy at the earliest stage of the disease.
Essential Role for Signal Transducer and Activator of Transcription-1 in Pancreatic β-Cell Death and Autoimmune Type 1 Diabetes of Nonobese Diabetic Mice
Authors: Kim Sunshin , Kim Hun Sik , Chung Kun Wook , Oh Seung Hoon , Yun Jong Won , Im Sin-Hyeog , Lee Moon-Kyu , Kim Kwang-Won , Lee Myung-Shik 
Published: September 2007

OBJECTIVE—We have reported important roles for signal transducer and activator of transcription-1 (STAT1) in pancreatic β-cell death by cytokines in vitro. However, in vivo evidence supporting the role for STAT1 in natural type 1 diabetes has not been reported. We studied whether STAT1 plays an important role in the development of natural type 1 diabetes.RESEARCH DESIGN AND METHODS—We produced nonobese diabetic (NOD)/STAT1−/− mice by backcrossing and studied the in vivo role of STAT1 in β-cell death and type 1 diabetes.RESULTS— STAT1 −/− islet cells were resistant to death by interferon (IFN)-γ/tumor necrosis factor (TNF)-α or IFN-γ/interleukin (IL)-1β combination. Cytochrome c translocation by IFN-γ/TNF-α was abrogated in STAT1−/− islet cells. The induction of X-linked inhibitor of apoptosis protein by TNF-α was inhibited by IFN-γ in STAT1+/− islet cells but not in STAT1−/− islet cells. Inducible nitric oxide (NO) synthase induction and NO production by IFN-γ/IL-1β were impaired in STAT1−/− islet cells. Strikingly, diabetes and insulitis were completely abrogated in NOD/STAT1−/− mice. Development of diabetes after CD4+ diabetogenic T-cell transfer was inhibited in those mice. STAT1−/− neonatal pancreata were not destroyed when grafted into diabetic NOD/BDC2.5 mice that developed CD4+ T-cell–dependent islet cell death. In NOD/STAT1−/− mice, autoreactive T-cell priming was not impaired, but Th1 differentiation was impaired. A janus kinase (JAK) 2 inhibitor upstream of STAT1 attenuated islet cell death by IFN-γ/TNF-α or IFN-γ/IL-1β and delayed diabetes onset in NOD/BDC2.5-SCID mice.CONCLUSIONS—These data demonstrate a critical role for STAT1 in β-cell death, T-cell immunoregulation, and type 1 diabetes in vivo and suggest potential therapeutic values of STAT1 or JAK inhibitors in the treatment/prevention of type 1 diabetes.
The Transcriptional Coactivator Peroxisome Proliferator–Activated Receptor (PPAR)γ Coactivator-1α and the Nuclear Receptor PPARα Control the Expression of Glycerol Kinase and Metabolism Genes Independently of PPARγ Activation in Human White Adipocytes
Authors: Mazzucotelli Anne , Viguerie Nathalie , Tiraby Claire , Annicotte Jean-Sébastien , Mairal Aline , Klimcakova Eva , Lepin Emmanuelle , Delmar Paul , Dejean Sébastien , Tavernier Geneviève , Lefort Corinne , Hidalgo Juan , Pineau Thierry , Fajas Lluis , Clément Karine , Langin Dominique 
Published: September 2007

OBJECTIVE—The purpose of this work was to determine the pattern of genes regulated by peroxisome proliferator–activated receptor (PPAR) γ coactivator 1α (PGC-1α) in human adipocytes and the involvement of PPARα and PPARγ in PGC-1α transcriptional action.
RESEARCH DESIGN AND METHODS—Primary cultures of human adipocytes were transduced with a PGC-1α adenovirus and treated with PPARγ and PPARα agonists. Variation in gene expression was assessed using pangenomic microarrays and quantitative RT-PCR. To investigate glycerol kinase (GyK), a target of PGC-1α, we measured enzymatic activity and glycerol incorporation into triglycerides. In vivo studies were performed on wild-type and PPARα−/− mice. The GyK promoter was studied using chromatin immunoprecipitation and promoter reporter gene assays.
RESULTS—Among the large number of genes regulated by PGC-1α independently of PPARγ, new targets involved in metabolism included the gene encoding GyK. The induction of GyK by PGC-1α was observed at the levels of mRNA, enzymatic activity, and glycerol incorporation into triglycerides. PPARα was also upregulated by PGC-1α. Its activation led to an increase in GyK expression and activity. PPARα was shown to bind and activate the GyK promoter. Experiments in mice confirmed the role of PGC-1α and PPARα in the regulation of GyK in vivo.
CONCLUSIONS—This work uncovers novel pathways regulated by PGC-1α and reveals that PPARα controls gene expression in human white adipocytes. The induction of GyK by PGC-1α and PPARα may promote a futile cycle of triglyceride hydrolysis and fatty acid reesterification.
Farnesoid X Receptor Modulates Renal Lipid Metabolism, Fibrosis, and Diabetic Nephropathy
Authors: Jiang Tao , Wang Xiaoxin X. , Scherzer Pnina , Wilson Paul , Tallman James , Takahashi Hideaki , Li Jinping , Iwahashi Mieko , Sutherland Eileen , Arend Lois , Levi Moshe 
Published: September 2007

OBJECTIVE—Recent studies indicate an important role for nuclear receptors in regulating lipid and carbohydrate metabolism, fibrosis, and inflammation. Farnesoid X receptor (FXR) is a member of the nuclear hormone receptor superfamily. FXR is highly expressed in the liver, intestine, adrenal gland, and kidney. The primary bile acids are the highest affinity endogenous ligands for FXR. The effects of FXR agonists in diabetic kidney disease, the main cause of end-stage renal disease, however, have not been determined.
RESEARCH DESIGN AND METHODS—To identify the effect of FXR activation in modulation of diabetic nephropathy, we treated 1) C57BL/6J mice on low-fat diet or high-fat diet with FXR agonists (GW4064 or cholic acid) for 1 week; 2) C57BLKS/J-db/db mice and their lean mates with GW4064 for 1 week; and 3) C57BL/6J-db/db mice and their lean mates with cholic acid for 12 weeks.
RESULTS—We found that FXR agonists modulate renal sterol regulatory element–binding protein-1 (SREBP-1) expression and lipid metabolism and renal expression of profibrotic growth factors, proinflammatory cytokines, and oxidative stress enzymes and decrease glomerulosclerosis, tubulointerstitial fibrosis, and proteinuria. In renal mesangial cells, overexpression of FXR or treatment with GW4064 also inhibited SREBP-1c and other lipogenic genes, transforming growth factor-β, and interleukin-6, suggesting a direct role of FXR in modulating renal lipid metabolism and modulation of fibrosis and inflammation.
CONCLUSIONS—These results therefore indicate a new and important role for FXR in the kidney and provide new therapeutic avenues for the treatment of diabetic nephropathy.
The Adipokine Lipocalin 2 Is Regulated by Obesity and Promotes Insulin Resistance
Authors: Yan Qing-Wu , Yang Qin , Mody Nimesh , Graham Timothy E. , Hsu Chung-Hsin , Xu Zhao , Houstis Nicholas E. , Kahn Barbara B. , Rosen Evan D. 
Published: September 2007

OBJECTIVE—We identified lipocalin 2 (Lcn2) as a gene induced by dexamethasone and tumor necrosis factor-α in cultured adipocytes. The purpose of this study was to determine how expression of Lcn2 is regulated in fat cells and to ascertain whether Lcn2 could be involved in metabolic dysregulation associated with obesity.
RESEARCH DESIGN AND METHODS—We examined Lcn2 expression in murine tissues and in 3T3-L1 adipocytes in the presence and absence of various stimuli. We used quantitative Western blotting to observe Lcn2 serum levels in lean and obese mouse models. To assess effects on insulin action, we used retroviral delivery of short hairpin RNA to reduce Lcn2 levels in 3T3-L1 adipocytes.
RESULTS— Lcn2 is highly expressed by fat cells in vivo and in vitro. Expression of Lcn2 is elevated by agents that promote insulin resistance and is reduced by thiazolidinediones. The expression of Lcn2 is induced during 3T3-L1 adipogenesis in a CCAAT/enhancer-binding protein–dependent manner. Lcn2 serum levels are elevated in multiple rodent models of obesity, and forced reduction of Lcn2 in 3T3-L1 adipocytes improves insulin action. Exogenous Lcn2 promotes insulin resistance in cultured hepatocytes.
CONCLUSIONS— Lcn2 is an adipokine with potential importance in insulin resistance associated with obesity.
Variants of the Transcription Factor 7-Like 2 (TCF7L2) Gene Are Associated With Type 2 Diabetes in an African-American Population Enriched for Nephropathy
Authors: Sale Michèle M. , Smith Shelly G. , Mychaleckyj Josyf C. , Keene Keith L. , Langefeld Carl D. , Leak Tennille S. , Hicks Pamela J. , Bowden Donald W. , Rich Stephen S. , Freedman Barry I. 
Published: September 2007

OBJECTIVE—Recently, variants in the TCF7L2 gene have been reported to be associated with type 2 diabetes across multiple Europid populations, but only one small sample of African-American type 2 diabetic patients has been examined. Our objective was to investigate the importance of TCF7L2 in a larger African-American case-control population.
RESEARCH DESIGN AND METHODS—We investigated single nucleotide polymorphisms (SNPs) in six known type 2 diabetes genes in 577 African-American case subjects with type 2 diabetes enriched for nephropathy and 596 African-American control subjects. Additionally, we genotyped 70 ancestry-informative markers (AIMs) to apply adjustments for differences in ancestral proportions.
RESULTS—The most significant associations were observed with TCF7L2 intron 3 SNPs rs7903146 (additive P = 4.10 × 10−6, odds ratio [OR] 1.51; admixture-adjusted Pa = 3.77 × 10−6) and rs7901695 (P = 0.001, OR 1.30; Pa = 0.003). The 2-SNP haplotype containing these SNPs was also associated with type 2 diabetes (P = 3 × 10−5). Modest associations were also seen with TCF7L2 intron 4 SNPs rs7895340, rs11196205, and rs12255372 (0.01 &lt; P &lt; 0.05; 0.03 &lt; Pa &lt; 0.08), as well as with ATP-sensitive inwardly rectifying potassium channel subunit Kir6.2 (KCNJ11) and hepatocyte nuclear factor 4-α (HNF4A) SNPs (0.01 &lt; P &lt; 0.05; 0.01 &lt; Pa &lt; 0.41). No significant associations were detected with genotyped calpain 10 (CAPN10), peroxisome proliferator–activated receptor γ (PPARG), and transcription factor 1 (TCF1) SNPs.
CONCLUSIONS—This study indicates that variants in the TCF7L2 gene significantly contribute to diabetes susceptibility in African-American populations.
Glucose Ingestion Fails to Inhibit Hypothalamic Neuronal Activity in Patients With Type 2 Diabetes
Authors: Vidarsdottir Solrun , Smeets Paul A.M. , Eichelsheim Diane L. , van Osch Matthias J.P. , Viergever Max A. , Romijn Johannes A. , van der Grond Jeroen , Pijl Hanno 
Published: September 2007

OBJECTIVE—The hypothalamus plays a critical role in the regulation of energy balance and fuel flux. Glucose ingestion inhibits hypothalamic neuronal activity in healthy humans. We hypothesized that hypothalamic neuronal activity in response to an oral glucose load would be altered in patients with type 2 diabetes.
RESEARCH DESIGN AND METHODS—In this randomized, single blind, case-control study, 7 type 2 diabetic men (BMI 27.9 ± 2.0 kg/m2) and 10 age-matched healthy men (BMI 26.1 ± 3.2 kg/m2) were scanned twice for 38 min on separate days using functional magnetic resonance imaging. After 8 min, they ingested either a glucose solution (75 g in 300 ml water) or water (300 ml).
RESULTS—Glucose ingestion resulted in a prolonged significant blood oxygen level–dependent signal decrease in the upper and lower hypothalamus in healthy subjects but not in diabetic patients.
CONCLUSIONS—Glucose ingestion fails to inhibit hypothalamic neuronal activity in patients with type 2 diabetes. Failure of neural circuits to properly adapt to nutrient ingestion may contribute to metabolic imbalance in type 2 diabetic patients.
Effect of Insulin Deprivation on Muscle Mitochondrial ATP Production and Gene Transcript Levels in Type 1 Diabetic Subjects
Authors: Karakelides Helen , Asmann Yan W. , Bigelow Maureen L. , Short Kevin R. , Dhatariya Ketan , Coenen-Schimke Jill , Kahl Jane , Mukhopadhyay Debabrata , Nair K. Sreekumaran 
Published: September 2007

OBJECTIVE—Muscle mitochondrial dysfunction occurs in many insulin-resistant states, such as type 2 diabetes, prompting a hypothesis that mitochondrial dysfunction may cause insulin resistance. We determined the impact of insulin deficiency on muscle mitochondrial ATP production by temporarily depriving type 1 diabetic patients of insulin treatment.
RESEARCH DESIGN AND METHODS—We withdrew insulin for 8.6 ± 0.6 h in nine C-peptide–negative type 1 diabetic subjects and measured muscle mitochondrial ATP production and gene transcript levels (gene array and real-time quantitative PCR) and compared with insulin-treated state. We also measured oxygen consumption (indirect calorimetry); plasma levels of glucagon, bicarbonate, and other substrates; and urinary nitrogen.
RESULTS—Withdrawal of insulin resulted in increased plasma glucose, branched chain amino acids, nonesterified fatty acids, β-hydroxybutyrate, and urinary nitrogen but no change in bicarbonate. Insulin deprivation decreased muscle mitochondrial ATP production rate (MAPR) despite an increase in whole-body oxygen consumption and altered expression of many muscle mitochondrial gene transcripts. Transcript levels of genes involved in oxidative phosphorylation were decreased, whereas those involved in vascular endothelial growth factor (VEGF) signaling, inflammation, cytoskeleton signaling, and integrin signaling pathways were increased.
CONCLUSIONS—Insulin deficiency and associated metabolic changes reduce muscle MAPR and expression of oxidative phosphorylation genes in type 1 diabetes despite an increase in whole-body oxygen consumption. Increase in transcript levels of genes involved in VEGF, inflammation, cytoskeleton, and integrin signaling pathways suggest that vascular factors and cell proliferation that may interact with mitochondrial changes occurred.
Association Study of the Genetic Polymorphisms of the Transcription Factor 7-Like 2 (TCF7L2) Gene and Type 2 Diabetes in the Chinese Population
Authors: Chang Yi-Cheng , Chang Tien-Jyun , Jiang Yi-Der , Kuo Shan-Shan , Lee Kuan-Ching , Chiu Ken C. , Chuang Lee-Ming 
Published: September 2007

OBJECTIVE—Genetic polymorphisms of the transcription factor 7-like 2 (TCF7L2) gene is one of the few validated genetic variants with large effects on the risk of type 2 diabetes in the populations of European ancestry. In this study, we aimed to explore the effect of the TCF7L2 polymorphisms in a Han Chinese population.
RESEARCH DESIGN AND METHODS—We genotyped 20 single nucleotide polymorphisms (SNPs) across the TCF7L2 gene in 1,520 unrelated subjects from a Han Chinese population in Taiwan. The associations of SNPs and haplotypes with type 2 diabetes and linkage disequilibrium (LD) structure of the TCF7L2 gene were analyzed.
RESULTS—The previously reported SNPs rs7903146 T- and rs12255372 T-alleles of the TCF7L2 gene were rare and were not associated with type 2 diabetes in a Chinese population, which may attribute to the low frequencies of these two SNPs. SNP rs290487 located in an LD block close to the 3′ end of the gene was associated with type 2 diabetes (allele-specific P = 0.0021; permuted P = 0.03). The odds ratio was 1.36 for the CT genotype (95% CI 1.08−1.71; P = 0.0063) and 1.51 for the CC genotype (1.10 −2.07; P = 0.0085) compared with the TT genotype, corresponding to a population attributable risk fraction of 18.7%. The haplotypes composed of rs290487 were also significantly associated with type 2 diabetes (global P = 0.012).
CONCLUSIONS—We identified a novel risk-conferring genetic variant of TCF7L2 for type 2 diabetes in a Chinese population. Our data suggested that the TCF7L2 genetic polymorphisms are major determinants for risk of type 2 diabetes in the Chinese population.
Meal Fatty Acid Uptake in Visceral Fat in Women
Authors: Votruba Susanne B. , Mattison Rebecca S. , Dumesic Daniel A. , Koutsari Christina , Jensen Michael D. 
Published: September 2007

OBJECTIVE—Differential meal fat uptake into adipose tissue depots may be a determinant of body fat distribution.
RESEARCH DESIGN AND METHODS—We used the meal fat tracer/adipose tissue biopsy approach to compare the effects of meal fat content on the fat uptake into visceral and upper and lower body subcutaneous fat depots in 21 premenopausal women. [3H]triolein was used to trace the fate of fatty acids from a normal-fat or high-fat meal.
RESULTS—The proportion of dietary fat uptake into the three depots did not differ between meals; visceral fat accounted for only ∼5% of meal fat disposal irrespective of visceral fat mass. For the women consuming the normal-fat meal, the uptake of meal fatty acid into femoral fat (milligrams meal fat per gram lipid) increased as a function of leg fat mass (r = 0.68, P &lt; 0.05), which we interpret as increased efficiency of uptake. The opposite pattern was seen in omental fat with the normal-fat meal and in all depots after the high-fat meal. For both meals, ∼40% of meal fat was oxidized (3H2O production) after 24 h.
CONCLUSIONS—We conclude that greater thigh adipose tissue in women is associated with greater efficiency of meal fat storage under conditions of energy balance, whereas the opposite is seen with visceral fat. These findings imply that different mechanisms may regulate fatty acid uptake in different depots, which may in turn impact on body fat distribution.
Protein Kinase C-ζ Activation Markedly Enhances β-Cell Proliferation
Authors: Vasavada Rupangi C. , Wang Lin , Fujinaka Yuichi , Takane Karen K. , Rosa Taylor C. , Mellado-Gil Jose M.D. , Friedman Peter A. , Garcia-Ocaña Adolfo 
Published: September 2007

OBJECTIVE— Diabetes results from a deficiency of functional β-cells. Previous studies have identified hepatocyte growth factor (HGF) and parathyroid hormone–related protein (PTHrP) as two potent β-cell mitogens. The objective of this study is to determine 1) whether HGF and PTHrP have additive/synergistic effects on β-cell growth and proliferation; 2) the signaling pathways through which these growth factors mediate β-cell mitogenesis; and 3) whether activation of this/these signaling pathway(s) enhances human β-cell replication.
RESEARCH DESIGN AND METHODS— We generated and phenotypically analyzed doubly transgenic mice overexpressing PTHrP and HGF in the β-cell. INS-1 and primary mouse and human islet cells were used to identify mitogenic signaling pathways activated by HGF and/or PTHrP.
RESULTS— Combined overexpression of HGF and PTHrP in the β-cell of doubly transgenic mice did not result in additive/synergistic effects on β-cell growth and proliferation, suggesting potential cross-talk between signaling pathways activated by both growth factors. Examination of these signaling pathways in INS-1 cells revealed atypical protein kinase C (PKC) as a novel intracellular target activated by both HGF and PTHrP in β-cells. Knockdown of PKCζ, but not PKCι/λ, expression using specific small-interfering RNAs blocked growth factor–induced INS-1 cell proliferation. Furthermore, adenovirus-mediated delivery of kinase-dead PKCζ completely inhibited β-cell proliferation in primary islet cells overexpressing PTHrP and/or HGF. Finally, adenovirus-mediated delivery of constitutively active PKCζ in mouse and human primary islet cells significantly enhanced β-cell proliferation.
CONCLUSIONS— PKCζ is essential for PTHrP- and HGF-induced β-cell proliferation. PKCζ activation could be useful in therapeutic strategies for expanding β-cell mass in vitro and in vivo.
Mitochondrial Energetics in the Heart in Obesity-Related Diabetes
Authors: Boudina Sihem , Sena Sandra , Theobald Heather , Sheng Xiaoming , Wright Jordan J. , Hu Xia Xuan , Aziz Salwa , Johnson Josie I. , Bugger Heiko , Zaha Vlad G. , Abel E. Dale 
Published: September 2007

OBJECTIVE—In obesity and diabetes, myocardial fatty acid utilization and myocardial oxygen consumption (MVo2) are increased, and cardiac efficiency is reduced. Mitochondrial uncoupling has been proposed to contribute to these metabolic abnormalities but has not been directly demonstrated.
RESEARCH DESIGN AND METHODS—Oxygen consumption and cardiac function were determined in db/db hearts perfused with glucose or glucose and palmitate. Mitochondrial function was determined in saponin-permeabilized fibers and proton leak kinetics and H2O2 generation determined in isolated mitochondria.
RESULTS— db/db hearts exhibited reduced cardiac function and increased MVo2. Mitochondrial reactive oxygen species (ROS) generation and lipid and protein peroxidation products were increased. Mitochondrial proliferation was increased in db/db hearts, oxidative phosphorylation capacity was impaired, but H2O2 production was increased. Mitochondria from db/db mice exhibited fatty acid–induced mitochondrial uncoupling that is inhibitable by GDP, suggesting that these changes are mediated by uncoupling proteins (UCPs). Mitochondrial uncoupling was not associated with an increase in UCP content, but fatty acid oxidation genes and expression of electron transfer flavoproteins were increased, whereas the content of the F1 α-subunit of ATP synthase was reduced.
CONCLUSIONS—These data demonstrate that mitochondrial uncoupling in the heart in obesity and diabetes is mediated by activation of UCPs independently of changes in expression levels. This likely occurs on the basis of increased delivery of reducing equivalents from β-oxidation to the electron transport chain, which coupled with decreased oxidative phosphorylation capacity increases ROS production and lipid peroxidation.