bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuroadaptive Changes in NMDAR1 Gene Expression after Extinction of Cocaine Self‐Administration
Authors: CRESPO JOSÉ A. , OLIVA JOSÉ M. , GHASEMZADEH M. BEHNAM , KALIVAS PETER W. , AMBROSIO E.
Published: July 2010

Abstract:The aim of the present work was to study the time course effects in levels of mRNA encodingN‐methyl‐d‐aspartate receptor subunit 1 (NMDAR1) after long‐term cocaine self‐administration (1 mg/kg/ injection) and its extinction using a yoked‐box procedure. NMDAR1 content was measured by quantitativein situhybridization histochemistry in prefrontal cortex, caudate‐putamen, nucleus accumbens, olfactory tubercle, and piriform cortex immediately after cessation of the last session of cocaine self‐administration (Day 0) and 1, 5, and 10 days after the extinction period. The results show that long‐term cocaine self‐administration and its extinction alter NMDAR1 gene expression in these forebrain regions, and that the changes depend upon the brain region examined and the type of cocaine administration (contingent, noncontingent, and saline). Compared to saline and noncontingent cocaine administration, contingent cocaine produced an up‐regulation in NMDAR1 gene expression on Day 0 in all the brain regions analyzed. NMDAR1 levels of contingent animals decreased progressively in the absence of cocaine, and the decrement persisted 10 days after the extinction of cocaine self‐administration behavior in all the forebrain areas, with the exception of olfactory tubercle. In contrast, noncontingent cocaine administration did not produce any change in NMDAR1 gene expression on Day 0, and extinction resulted in an increase of NMDAR1 mRNA content on Days 1 and 5 and returned to control (saline) values on Day 10. These results suggest that an interaction between environmental stimuli and the pharmacological action of cocaine during drug self‐administration and its extinction may represent an important factor in the regulation of cocaine effects on NMDAR1 gene expression.
Estrogen, Anti‐Estrogen, and Gender
Authors: DLUZEN DEAN E. , McDERMOTT JANET L.
Published: July 2010

Abstract:In Part 1 of this report, we review data on the effects of estrogen (E), the anti‐E tamoxifen (TMX), and testosterone (T) on methamphetamine (METH)‐induced neurotoxicity in female and male CD‐1 mice. Treatment of gonadectomized females with a physiological regimen of E significantly diminished the amount of striatal dopamine (DA) depletion to METH compared with non‐E‐treated mice. If these E‐treated mice received coadministered TMX, the neuroprotective effects of E were abolished. However, TMX administration to either intact female or male mice appeared to exhibit a neuroprotective effect. Whereas E administration one week before METH treatment serves as a neuroprotectant, reversing the treatment order (METH→one week→E) failed to indicate any neurorestorative effects for E. This striatal DA‐preserving effect of E was gender specific, because males receiving an identical treatment of E followed by METH failed to show any evidence of neuroprotection, nor did the predominantly male gonadal steroid hormone T afford any neuroprotection in gonadectomized male or female mice. In the second part of the report, we direct our attention toward examining some of the means by which E can exert this neuroprotective effect. The findings that gonadectomized female, but not intact male, mice treated with E show a significant reduction in body temperature can contribute to the gender‐specific METH neuroprotection. E also diminishes the initial amounts of DA evoked by METH, as observed when E is co‐infused with METH into superfused striatal tissue fragments of gonadectomized female and male mice. By contrast, T tends to increase METH‐evoked DA responses. Finally, differences in mRNA levels were obtained between male and female mice treated with METH. Intact female mice tend to show greater levels of striatal glial fibrillary acidic protein and decreased levels of plasminogen activator inhibitor‐1 compared with males. Each of these factors, combined with our previous findings that E can inhibit DA transporter function, represent significant events contributing to E/gender‐dependent effects on METH neurotoxicity.
Adaptation to Repeated Cocaine Administration in Rats
Authors: BINIENDA ZBIGNIEW K. , PEREIRA FREDERICO , ALPER KENNETH , SLIKKER WILLIAM , ALI SYED F.
Published: July 2010

Abstract:Quantitative electroencephalogram (EEG) studies in cocaine‐dependent human patients show deficits in slow‐wave brain activity, reflected in diminished EEG power in the delta and theta frequency bands. In the present study, electrophysiological measures were monitored in 10 nonanesthetized, adult male Sprague‐Dawley rats via bipolar, epidural electrodes implanted over the somatosensory cortex. Control electrocorticograms (ECoG) were recorded twice within a two‐week interval to establish a baseline. Rats were subsequently injected daily with cocaine HCl at 15 mg/kg, i.p., for two weeks. The ECoG was recorded during a 1‐h session one day after the last injection. Total concentrations of dopamine (DA) and its metabolites were assayed in caudate nucleus (CN) and frontal cortex (FC) using HPLC/EC. Compared with controls, marked increases in DA concentrations were observed in both regions. The DA turnover decreased significantly. The power spectra, obtained by use of a fast Fourier transformation, revealed a significant decrease in slow‐wave delta frequency bands following repeated exposure to cocaine. These data are consistent with reported findings in humans that repeated exposures to cocaine result in a decrease in slow‐wave brain activity. Further studies are necessary to establish whether regional alterations in blood flow and metabolic activity may underlie such observations.
Effects of Acute Toxic Doses of Psychostimulants on Extracellular Levels of Excitatory Amino Acids and Taurine in Rats
Authors: ANDERZHANOVA E. , RAYEVSKY K. S. , SARANSAARI P. , RIITAMAA E. , OJA S. S.
Published: July 2010

Abstract:We used microdialysis to study how acute toxic doses ofd‐amphetamine and sydnocarb [3‐(β‐phenylisopropyl)‐N‐phenylcarbamoylsydnonimine], an original Russian psychostimulant, affect extracellular levels of glutamate, aspartate, and taurine in the neostriatum of halothane‐anesthetized male Sprague‐Dawley rats. The administration ofd‐amphetamine (5.0 mg/kg × 4 ip) caused gradual fivefold increases in the extracellular glutamate and taurine levels and moderate increases in the extracellular aspartate level. Sydnocarb administration (23.8 mg/kg × 4 ip, a dose equimolar to 5.0 mg/kgd‐amphetamine) elicited a marked increase in the extracellular aspartate level and a small increase in the extracellular level of glutamate. The extracellular taurine level increased only after the last (fourth) injection. We conclude that a massive increase in extracellular taurine reflects hyperactivation of glutamatergic neurotransmission elicited by acute toxic dose ofd‐amphetamine. Sydnocarb seems to be less neurotoxic thand‐amphetamine, because it elicits lesser changes in the extracellular levels of glutamate and taurine.
Calpain Upregulation and Neuron Death in Spinal Cord of MPTP‐Induced Parkinsonism in Mice
Authors: CHERA BHISHAM , SCHAECHER KURT E. , ROCCHINI ANNE , IMAM SYED Z. , RAY SWAPAN K. , ALI SYED F. , BANIK NAREN L.
Published: July 2010

Abstract:Parkinson's disease (PD) is a neurodegenerative disorder resulting in slowness, tremors, and imbalance. Treatment of mice with 1‐methyl‐4‐phenyl‐1,2,3,6 tetrahydropyridine (MPTP) is one of several models used to mimic PD in humans. Administration of MPTP leads to the production of 1‐methyl‐4‐phenyl‐2,3 dihydropyridinium (MPP+). MPP+is taken up by dopaminergic neurons, causing mitochondrial dysfunction and cell death. Because calpain is involved in neuronal cell death and mitochondrial dysfunction, we examined the level of calpain in neurons in the substantia nigra (SN) and hippocampus of MPTP‐treated C57BL/6 mice. Because of the interconnections between spinal cord and upper central nervous system neurons, we examined morphology, calpain activity, and calpain expression in neurons by double immunofluorescence using calpain and neuron marker (NeuN) antibodies. In controls, calpain expression was low in SN, hippocampus, and spinal cord NeuN+cells, and the NeuN stain was concentrated around the nucleus. In mice sacrificed 24 h after administration of three 20 mg/kg doses of MPTP, calpain expression was slightly increased in SN and hippocampal neurons and moderately increased in spinal cord neurons. In these animals, the NeuN stain was less concentrated around the nuclear membrane. One week after MPTP treatment, calpain content in NeuN+cells was greatly increased in SN, hippocampus, and spinal cord. Morphologically, SN and spinal cord neurons, treated for one week, were necrotic with a granular cytoplasmic NeuN content. Also, MPTP treatment upregulated calpain activity and mRNA level in spinal cord. These data suggest that following MPTP treatment, calpain causes neuronal death in SN as well as in spinal cord.
Increased Sensitivity in Dopamine D2‐like Brain Receptors from 2,4‐Dichlorophenoxyacetic Acid (2,4‐D)‐Exposed and Amphetamine‐Challenged Rats
Authors: BORTOLOZZI ANALÍA , DUFFARD RICARDO , ANTONELLI MARTA , DE DUFFARD ANA MARÍA EVANGELISTA
Published: July 2010

Abstract: To determine whether the dopamine D2 receptor plays a crucial role in chemically acquired sensitivity to drugs of abuse like amphetamine (AMPH) after an exposure to aryloxoalkanoic compounds, we examined in the present work the impact of AMPH (10 mg/kg, i.p.) on the dopaminergic D2‐like receptors. Rats were exposed to 2,4‐D 70 mg/kg/day from gestation day (GD) 16 to postnatal day (PND) 23. After weaning, the pups were assigned to one of the two subgroups: T1 (fed with untreated diet until PND 90) and T2 (maintained with 2,4‐D diet until PND 90). After that, an acute challenge with AMPH was administered to each animal. Rats were sacrificed at 0, 5, 24, 72, and 168 h after AMPH, and membranes of striatum (CPu), prefrontal cortex (PfC), hippocampus (H), and cerebellum (Ce) were obtained. Binding studies employing [3H]nemonapride showed that AMPH caused an increase in DA D2‐like receptors of all brain areas between 5 and 24 h after the treatment, with a reduction to the basal levels one week later. The AMPH challenge to (T1 and T2) 2,4‐D‐exposed rats showed an alteration on receptor density depending on brain area and on sex, more than on the 2,4‐D exposure time. This D2‐like receptor density increase could explain the exacerbated behaviors of the 2,4‐D‐exposed and amphetamine‐challenged animals, as previously observed by us. The withdrawal of 2,4‐D did not produce a real reversion to basal levels of D2‐like receptors, indicating that herbicide exposure during the preweanling period caused a sensitization and a stable DA D2‐like receptor increase that was elicited when the system was challenged with this dopaminergic drug.
Serotonergic Neurotoxicity of MDMA (Ecstasy) in the Developing Rat Brain
Authors: MEYER JERROLD S. , ALI SYED F.
Published: July 2010

Abstract:The abused drug 3,4‐methylenedioxymethamphetamine (MDMA) damages fine serotonergic fibers and nerve terminals in adult organisms; however, developing animals seem less susceptible to this effect. One proposed hypothesis is that neonates are less sensitive to MDMA neurotoxicity because they fail to show drug‐induced hyperthermia. We tested this hypothesis by producing hyperthermia in neonatal rats for 2 hours after each of twice‐daily MDMA (10 mg/kg sc) or saline injections given over the period from postnatal day (PD) 1 to 4. Other drug‐treated and control litters were maintained at normothermic temperatures after injection. Differential core body temperatures were achieved by placing pups (without the dam) in humidified, thermostatically controlled incubators. Temperatures were monitored with a thermocouple probe at 30‐minute intervals. Pups subsequently remained undisturbed until sacrifice at PD 25 and PD 60 for assessment of serotonergic damage by measuring 5‐HT transporter (SERT) binding in the hippocampus and neocortex as well as 5‐HT and 5‐HIAA concentrations (PD 25 only). Neonatal MDMA exposure led to significant reductions in both SERT binding and 5‐HT levels in the hippocampus at PD 25, independent of body temperature during treatment. Hippocampal SERT binding increased between PD 25 and PD 60 in both the MDMA and saline groups, but the MDMA‐related deficit remained unchanged. Interestingly, the neocortex showed no effect of MDMA at PD 25, but SERT binding was significantly reduced at PD 60. Thus, MDMA can exert serotonergic neurotoxicity in developing animals in the absence of elevated body temperature. Hippocampal serotonergic innervation is damaged early, whereas neocortical effects emerge at a later time. Furthermore, the tendency for serotonergic recovery may be less after neonatal MDMA exposure than exposure of adult animals.
Cell‐Mediated Immune Response in MDMA Users After Repeated Dose Administration
Authors: PACIFICI R. , ZUCCARO P. , FARRÉ M. , PICHINI S. , DI CARLO S. , ROSET P. N. , PALMI I. , ORTUÑO J. , MENOYO E. , SEGURA J. , DE LA TORRE R.
Published: July 2010

Abstract:Acute administration of 3,4‐methylenedioxymethamphetamine (MDMA, “ecstasy”) produces time‐dependent immune dysfunction in humans. Recreational use of MDMA generally includes repeated drug consumption, often in association with other drugs, such as alcohol and cannabis. In the laboratory setting, repeated MDMA administration to healthy MDMA consumers produced a time‐dependent immune dysfunction similar to that observed with the ingestion of a single dose, and the first of the two administrations paralleled the time‐course of MDMA‐induced cortisol stimulation kinetics and MDMA plasma concentrations. A significant decrease in CD4 T‐helper cells with simultaneous increase in natural killer (NK) cell and a decrease in functional responsiveness of lymphocytes to mitogenic stimulation was observed. Response to the second dose was either long‐lasting compared with the first dose or disproportionate and did not show any parallelism with cortisol and MDMA plasma concentrations. This circumstance extended the critical period during which immunocompetence is highly impaired as a result of MDMA use. Accumulation of MDMA in the body of a poor metabolizer induced higher immunomodulatory effects with statistically significant differences in NK cell function compared with extensive metabolizers. When basal values of lymphocyte subsets were examined in a population of recreational MDMA users participating in different clinical trials, alterations in several immunological parameters were observed. The absolute number of lymphocytes, in particular T lymphocytes and CD4 T‐helper cell subsets, showed a trend toward reduced values, although cell counts were within normal limits. By contrast, NK cells in MDMA consumers were reduced to one‐third of those from healthy persons. A statistically significant decrease in affected immune parameters was recorded during a 2‐year observation period in a subgroup of recreational MDMA users. These permanent alterations in immunologic homeostasis may result in impairment of general health and subsequent increased susceptibility to infection and immune‐related disorders.
Nitric Oxide Production and Nitric Oxide Synthase Expression in Platelets from Heroin Abusers before and after Ultrarapid Detoxification
Authors: BATISTA ANA , MACEDO TICE , TAVARES PAULA , RIBEIRO CARLOS FONTES , RELVAS JOÃO , GOMES PIEDADE , RAMALHEIRA CARLOS , BOTTO ISABEL , VALE LUISA , FERREIRA LUÍS , GÜETE ORLANDO , RUIZ GUADALUPE
Published: July 2010

Abstract:Prolonged heroin abuse has been associated with neurotoxicity. Thus, the involvement of nitric oxide (NO) in heroin‐induced dopaminergic neurotoxicity could be a reasonable explanation for heroin‐induced changes in brain. Enzymatically derived NO has been implicated in numerous physiological and pathological processes in the brain. Whereas during development NO participates in growing and maturation processes, excess NO production in the adult in response to inflammation, injury, or trauma, participates in both cell death and repair. The expression and activity of the inducible isoform of NO synthase (iNOS) play a pivotal role in sustained and elevated NO release. Recent evidence suggests that neurons can respond to proinflammatory stimuli and take part in brain inflammation. The effect of heroin abuse on platelet NO production and on expression of iNOS in drug addicts submitted to an ultrarapid detoxification was studied. The NO production was estimated from the nitrite concentration, and nitric oxide synthase was determined by Western blotting analysis. Results showed no difference in nitrite content of resting platelets between heroin abuser and control groups. However, after platelet stimulation, heroin abusers showed significantly lower nitrite values. The Western blotting analysis reinforced these results. After ultrarapid detoxification, platelet nitrite production in heroin abusers showed no differences compared to control subjects. Our results suggest that heroin consumption decreases the iNOS synthase expression and platelet NO production. Detoxification treatment restores these changes.
Recombinant μ‐δ Receptor as a Marker of Opiate Abuse
Authors: DAMBINOVA SVETLANA A. , IZYKENOVA GALINA A.
Published: July 2010

Abstract:The brain is particularly vulnerable to drugs of abuse changing the neuroreceptor functions. Opiates interact and overstimulate heterogeneous opioid receptors leading to their desensitization, internalization, and activation of recombinant opioid receptor. The molecular properties of rat and human brain recombinant μ‐δ receptor were compared with those of purified μ‐ and δ‐receptors. cDNA coding the unique fragment of recombinant μ‐δ receptor was isolated and sequenced. We hypothesized that recombinant μ‐δ receptor may be a hallmark of opiate abuse. Peptide fragments of the μ‐ (MOR), δ‐ (DOR), and recombinant μ‐δ‐ (MDOR) receptors were used as antigens to assess the presence of autoantibodies in the blood of rats that self‐administered heroin and cocaine, as well as drug abusers. Significant steady elevation of MDOR autoantibodies were measured in sera of rats that self‐administered heroin compared to that for cocaine and vehicle animals. The appearance and increased level of MDOR autoantibodies in opiate abusers correlated with severity of the disorder and duration of drug exposure.
PPARγ, an X‐ceptor for Xs
Authors: KOUTNIKOVA HANA , AUWERX JOHAN
Published: July 2010

Abstract: Evidence from both human genetic studies and characterization of peroxisome proliferator‐activated receptor gamma (PPARγ) knockout mice suggested that the prime function of PPARγ is fat formation and that its role in insulin sensitization might be secondary to this function. The thrifty function of PPARγ was most likely evolutionary beneficial, but might in “times of plenty” contribute to the pathogenesis of disorders, such as obesity, insulin resistance, type 2 diabetes, and hyperlipidemia, often commonly referred to as “syndrome X”. This role of PPARγ in these diseases also questions the eventual therapeutic benefits of pure PPARγ activation, which is associated with an increase in adipose tissue mass. We characterized a new chemical class of PPARγ agonists, that is, FMOC‐l‐leucine (FLL). FLL induces a different conformation of PPARγ relative to classical PPARγ ligands. Mass spectrometry indicates that two molecules of FLL bind to a single PPARγ molecule, making its mode of receptor interaction distinctive. FLL recruits a different set of coactivators and activates PPARγ with a lower potency, but a similar maximal efficacy, relative to known PPARγ ligands. In contrast, FLL is a more effective insulin sensitizer than current PPARγ agonists, an effect potentially linked to its weak adipogenic activity. These data make a strong point for potential therapeutic benefits of PPARγ modulation rather than activation.
Adiposity and the Development of Diabetes in Mouse Genetic Models
Authors: KOZAK LESLIE P. , ROSSMEISL MARTIN
Published: July 2010

Abstract: While it is certain from the analysis of transgenic models of lipodystrophy that a critical mass of adipose tissue is necessary to prevent the development of diabetes, the reasons why diabetes develops in one obese individual and not in another need to be further investigated. This is also one of the major questions associated with the current obesity epidemic and the development of the metabolic syndrome. The severe lipodystrophic models do not really address this big problem. In this presentation, we point out that models exist among inbred strains of mice that can contribute towards finding answers to the diabetes found in the metabolic syndrome. The differences responsible for the phenotypic variations are undoubtedly multifactorial and involve many genes, but there are powerful genetic resources to investigate these problems.
Transgenic Mice Overexpressing the Rate‐Limiting Enzyme for Hexosamine Synthesis in Skeletal Muscle or Adipose Tissue Exhibit Total Body Insulin Resistance
Authors: COOKSEY ROBERT C. , McCLAIN DONALD A.
Published: July 2010

Abstract: High concentrations of glucose induce insulin resistance and impair insulin secretion in a manner that mirrors type 2 diabetes, a phenomenon known as glucose toxicity. High concentrations of hexosamines mimic these effects, leading to the hypothesis that cells use hexosamine flux as a glucose‐ and satiety‐sensing pathway. Overexpression of the rate‐limiting enzyme for hexosamine synthesis (glutamine:fructose‐6‐phosphate amidotransferase, GFA) in muscle and fat results in insulin resistance and hyperleptinemia. GFA overexpression targeted to liver results in hyperlipidemia and to the beta cell in increased insulin secretion. Thus, excess hexosamine flux leads to a coordinated response whereby fuel is shunted toward long‐term storage, mirroring the “thrifty phenotype”. The results suggest a mechanism by which chronic overnutrition leads to the phenotype of type 2 diabetes.
Insulin Action in Skeletal Muscle
Authors: IDRIS ISKANDAR , GRAY SAMUEL , DONNELLY RICHARD
Published: July 2010

Abstract: Protein kinase C (PKC) is a family of multifunctional isozymes that plays an important role in the regulation of intracellular insulin signal transduction in various insulin‐sensitive tissues. This article highlights current understanding on the mechanism of PKC‐induced insulin resistance in skeletal muscle, a major target site for insulin‐mediated glucose disposal. Initial, apparently contradictory findings on the role of PKC on insulin action can be explained on the basis that certain PKC isoforms (e.g., ‐ζ and ‐λ) have been identified as downstream targets of PI3‐kinase activation, while DAG‐sensitive PKCs (e.g., ‐θ and ‐ε) have negative regulatory effects on insulin signaling. Hence, pharmacological therapies targeting specific PKC isoforms could enhance insulin action and improve glycemic control in patients with impaired glucose tolerance and overt diabetes.
Muscle Long‐Chain Acyl CoA Esters and Insulin Resistance
Authors: COONEY G. J. , THOMPSON A. L. , FURLER S. M. , YE J. , KRAEGEN E. W.
Published: July 2010

Abstract: A common observation in animal models and in humans is that accumulation of muscle triglyceride is associated with the development of insulin resistance. In animals, this is true of genetic models of obesity and nutritional models of insulin resistance generated by high‐fat feeding, infusion of lipid, or infusion of glucose. Although there is a strong link between the accumulation of triglycerides (TG) in muscle and insulin resistance, it is unlikely that TG are directly involved in the generation of muscle insulin resistance. There are now other plausible mechanistic links between muscle lipid metabolites and insulin resistance, in addition to the classic substrate competition proposed by Randle's glucose‐fatty acid cycle. The first step in fatty acid metabolism (oxidation or storage) is activation to the long‐chain fatty acyl CoA (LCACoA). This review covers the evidence suggesting that cytosolic accumulation of this active form of lipid in muscle can lead to impaired insulin signaling, impaired enzyme activity, and insulin resistance, either directly or by conversion to other lipid intermediates that alter the activity of key kinases and phosphatases. Actions of fatty acids to bind specific nuclear transcription factors provide another mechanism whereby different lipids could influence metabolism.
Regulation of Fat Metabolism in Skeletal Muscle
Authors: JEUKENDRUP ASKER E.
Published: July 2010

Abstract: Regulation of carbohydrate and fat utilization by skeletal muscle at rest and during exercise has been the subject of investigation since the early 1960s when Randle et al. proposed the so‐called glucose‐fatty acid cycle to explain the reciprocal relationship between carbohydrate and fat metabolism. The suggested mechanisms were based on the premise that an increase in fatty acid (FA) availability would result in increased fat metabolism and inhibition of carbohydrate metabolism. Briefly, accumulation of acetyl‐CoA would result in inhibition of pyruvate dehydrogenase (PDH), accumulation of citrate would inhibit phosphofructokinase (PFK), and accumulation of glucose‐6‐phosphate (G6P) would reduce hexokinase (HK) activity. Ultimately, this would inhibit carbohydrate metabolism with increasing availability and oxidation of FA. Although there is some evidence for the existence of the glucose‐FA cycle at rest and during low‐intensity exercise, it cannot explain substrate use at moderate to high exercise intensities. More recently, evidence has accumulated that increases in glycolytic flux may decrease fat metabolism. Potential sites of regulation are the transport of FA into the sarcoplasma, lipolysis of intramuscular triacylglycerol (IMTG) by hormone‐sensitive lipase (HSL), and transport of FA across the mitochondrial membrane. There are several potential regulators of fat oxidation: first, malonyl‐CoA concentration, which is formed from acetyl‐CoA, catalyzed by the enzyme acetyl‐CoA carboxylase (ACC), which in turn will inhibit carnitine palmitoyl transferase I (CPT I). Another possible mechanism is accumulation of acetyl‐CoA that will result in acetylation of the carnitine pool, reducing the free carnitine concentration. This could theoretically reduce FA transport into the mitochondria. There is also some recent evidence that CPT I is inhibited by small reductions in pH that might be observed during exercise at high intensities. It is also possible that FA entry into the sarcolemma is regulated by translocation of FAT/CD36 in a similar manner to glucose transport by GLUT‐4. Studies suggest that the regulatory mechanisms may be different at rest and during exercise and may change as the exercise intensity increases. Regulation of skeletal muscle fat metabolism is clearly multifactorial, and different mechanisms may dominate in different conditions.
Is a Pro12Ala Polymorphism of the PPARγ2 Gene Related to Obesity and Type 2 Diabetes Mellitus in the Czech Population?
Authors: ŠRÁMKOVÁ DANIELA , KUNEŠOVÁ MARIE , HAINER VOJTECH , HILL MARTIN , VCELÁK JOSEF , BENDLOVÁ BELA
Published: July 2010

Abstract: The peroxisome proliferator‐activated receptors (PPARs) are members of the nuclear hormone receptor subfamily of transcription factors. PPARγ2 plays a key role in regulation of adipocyte differentiation and energy homeostasis. Recent studies provide evidence that the Pro12Ala polymorphism is linked to obesity and type 2 diabetes mellitus, but the results are controversial and depend on ethnicity. The aim of this study was to determine allele frequencies and to study the influence of the polymorphism on biochemical and anthropometric parameters in a Czech healthy adult population, in type 2 diabetics, and in a group of obese women. Results: The frequency of the Pro12Ala PPARγ2 gene polymorphism in Czech probands is similar to other central European populations. Frequency of the Pro12Ala substitution tends to be higher in obese women and diabetics compared with controls. The fasting insulin levels in the 12Ala carriers were significantly lower within the group of diabetics even after adjustment for age, BMI, and the length of diabetes duration. In obese women, higher WHR was found in subjects with the 12Ala allele. Conclusions: This study indicates that the substitution Pro12Ala is not associated with a decreased obesity or diabetes risk in the Czech population. However, the present data show that fasting insulin concentrations are lower in diabetics with the 12Ala allele than in those without it. This finding provides evidence that the polymorphism may influence glucose homeostasis.
Fatty Acid Regulation of Gene Expression
Authors: CLARKE STEVEN D. , GASPERIKOVA DANIELA , NELSON CAROLANNE , LAPILLONNE ALEXANDRE , HEIRD WILLIAM C.
Published: July 2010

Abstract:The development of obesity and associated insulin resistance involves a multitude of gene products, including proteins involved in lipid synthesis and oxidation, thermogenesis, and cell differentiation. The genes encoding these proteins are in essence the blueprints that we have inherited from our parents. However, what determines the way in which blueprints are interpreted is largely dictated by a collection of environmental factors. The nutrients we consume are among the most influential of these environmental factors. During the early stages of evolutionary development, nutrients functioned as primitive hormonal signals that allowed the early organisms to turn on pathways of synthesis or storage during periods of nutrient deprivation or excess. As single‐cell organisms evolved into complex life forms, nutrients continued to be environmental factors that interacted with hormonal signals to govern the expression of genes encoding proteins involved in energy metabolism, cell differentiation, and cell growth. Nutrients govern the tissue content and activity of different proteins by functioning as regulators of gene transcription, nuclear RNA processing, mRNA degradation, and mRNA translation, as well as functioning as posttranslational modifiers of proteins. One dietary constituent that has a strong influence on cell differentiation, growth, and metabolism is fat. The fatty acid component of dietary lipid not only influences hormonal signaling events by modifying membrane lipid composition, but fatty acids have a very strong direct influence on the molecular events that govern gene expression. In this review, we discuss the influence that (n‐9), (n‐6), and (n‐3) fatty acids exert on gene expression in the liver and skeletal muscle and the impact this has on intra‐ and interorgan partitioning of metabolic fuels.
The Responses of Serum and Adipose Fatty Acids to a One‐Year Weight Reduction Regimen in Female Obese Monozygotic Twins
Authors: KUNEŠOVÁ M. , PHINNEY S. , HAINER V. , TVRZICKÁ E. , ŠTICH V. , PARÍZKOVÁ J. , ŽÁK A. , STUNKARD A.
Published: July 2010

Abstract: We have reported strong intrapair resemblances (IPRs) in serum phosphatidylcholine (PC) fatty acid composition within adult monozygotic twins living apart. This study assessed the contribution of genetic factors to changes in serum and adipose tissue fatty acids resulting from weight loss and followed by a subsequent year of weight maintenance. Eleven pairs of female obese monozygotic twins (age: 38.9 ± 1.8; BMI: 32.5 ± 0.9) were recruited for the study. Fasting serum and adipose tissue were obtained after 1 week of inpatient stabilization, after 1 month of inpatient very‐low‐calorie diet (VLCD), and again after 1 year of outpatient weight maintenance. Fatty acids in serum lipid fractions and adipose tissue were quantitated by gas chromatography. Using multiple regression adjusted for age and initial value, IPRs were determined for the changes induced by VLCD and by the year of weight maintenance. There were few IPRs in nonessential fatty acids. By contrast, there were numerous IPRs for essential fatty acids (EFA), especially in the n‐3 family across the VLCD. Following the maintenance year, however, frequent IPRs for nonessential fatty acids were seen, particularly in serum PC, and strong IPRs were seen for 18:3 n‐3 and 20:5 n‐3 across multiple fractions. These results infer the existence of strong genetic factors determining both the nonessential and EFA compositions of tissue lipids in humans independent of diet. Of particular note were the consistent IPRs for n‐3 fatty acids despite dietary stress, indicating that the conservation and distribution of this EFA family are subject to considerable genetic variance in humans.
Increased Fat Intake, Impaired Fat Oxidation, and Failure of Fat Cell Proliferation Result in Ectopic Fat Storage, Insulin Resistance, and Type 2 Diabetes Mellitus
Authors: RAVUSSIN ERIC , SMITH STEVEN R.
Published: July 2010

Abstract: It is widely accepted that increasing adiposity is associated with insulin resistance and increased risk of type 2 diabetes. The predominant paradigm used to explain this link is the portal/visceral hypothesis. This hypothesis proposes that increased adiposity, particularly in the visceral depots, leads to increased free fatty acid flux and inhibition of insulin action via Randle's effect in insulin‐sensitive tissues. Recent data do not entirely support this hypothesis. As such, two new paradigms have emerged that may explain the established links between adiposity and disease. (A) Three lines of evidence support the ectopic fat storage syndrome. First, failure to develop adequate adipose tissue mass in either mice or humans, also known as lipodystrophy, results in severe insulin resistance and diabetes. This is thought to be the result of ectopic storage of lipid into liver, skeletal muscle, and the pancreatic insulin‐secreting beta cell. Second, most obese patients also shunt lipid into the skeletal muscle, the liver, and probably the beta cell. The importance of this finding is exemplified by several studies demonstrating that the degree of lipid infiltration into skeletal muscle and liver correlates highly with insulin resistance. Third, increased fat cell size is highly associated with insulin resistance and the development of diabetes. Increased fat cell size may represent the failure of the adipose tissue mass to expand and thus to accommodate an increased energy influx. Taken together, these three observations support the acquired lipodystrophy hypothesis as a link between adiposity and insulin resistance. (B) The endocrine paradigm developed in parallel with the ectopic fat storage syndrome hypothesis. Adipose tissue secretes a variety of endocrine hormones, such as leptin, interleukin‐6, angiotensin II, adiponectin (also called ACRP30 and adipoQ), and resistin. From this viewpoint, adipose tissue plays a critical role as an endocrine gland, secreting numerous factors with potent effects on the metabolism of distant tissues. These two new paradigms provide a framework to advance our understanding of the pathophysiology of the insulin‐resistance syndrome.
New Approaches to Gene Discovery with Animal Models of Obesity and Diabetes
Authors: COLLIER GREG , WALDER KEN , DE SILVA ANDREA , TENNE‐BROWN JANETTE , SANIGORSKI ANDREW , SEGAL DAVID , KANTHAM LAKSHMI , AUGERT GUY
Published: July 2010

Abstract: DNA‐based approaches to the discovery of genes contributing to the development of type 2 diabetes have not been very successful despite substantial investments of time and money. The multiple gene‐gene and gene‐environment interactions that influence the development of type 2 diabetes mean that DNA approaches are not the ideal tool for defining the etiology of this complex disease. Gene expression‐based technologies may prove to be a more rewarding strategy to identify diabetes candidate genes. There are a number of RNA‐based technologies available to identify genes that are differentially expressed in various tissues in type 2 diabetes. These include differential display polymerase chain reaction (ddPCR), suppression subtractive hybridization (SSH), and cDNA microarrays. The power of new technologies to detect differential gene expression is ideally suited to studies utilizing appropriate animal models of human disease. We have shown that the gene expression approach, in combination with an excellent animal model such as the Israeli sand rat (Psammomys obesus), can provide novel genes and pathways that may be important in the disease process and provide novel therapeutic approaches. This paper will describe a new gene discovery, beacon, a novel gene linked with energy intake. As the functional characterization of novel genes discovered in our laboratory using this approach continues, it is anticipated that we will soon be able to compile a definitive list of genes that are important in the development of obesity and type 2 diabetes.
Relationship between Insulin Resistance and Muscle Triglyceride Content in Nonobese and Obese Experimental Models of Insulin Resistance Syndrome
Authors: DIVIŠOVÁ JANA , KAZDOVÁ LUDMILA , HUBOVÁ MIRIAM , MESCHIŠVILI ELEN
Published: July 2010

Abstract: In nonobese hereditary hypertriglyceridemic (HTg) rats and obese HTg Koletsky SHROB/Kol rats, muscle triglyceride accumulation and its relationship to glucose homeostasis and tissue sensitivity to insulin action were examined. Soleus muscle and diaphragm triglyceride contents were markedly increased in HTg rats as compared with controls and were further increased in obese animals. On the other hand, glucose intolerance and impairment of insulin‐stimulated in vitro glycogen synthesis were of a similar degree in nonobese as well as obese animals. Results indicate that insulin resistance did not increase proportionally to muscle triglyceride content.
Insulin Resistance in the Hereditary Hypertriglyceridemic Rat Is Associated with an Impairment of Δ‐6 Desaturase Expression in Liver
Authors: GAŠPERÍKOVÁ D. , DEMCÁKOVÁ E. , UKROPEC J. , KLIMEŠ I. , ŠEBÖKOVÁ E.
Published: July 2010

Abstract: Our previous studies have shown that insulin resistance (IR) in the hereditary hypertriglyceridemic (hHTg) rat is accompanied by a specific fatty acid (FA) profile in insulin target tissues, possibly due to a defect in the desaturation pathway. Increased dietary intake of n‐3 polyunsaturated fatty acids (PUFAs) was shown to shape FA composition and to improve insulin sensitivity in this animal strain. Thus, the aim of this study is twofold: (1) to evaluate a defect in the FA desaturation by direct measurement of enzyme activity and gene expression for Δ‐6 desaturase (Δ‐6 D) in liver of hHTg rats and (2) to investigate the effect of dietary n‐3 PUFAs on hepatic Δ‐6 D in relation to tissue FA composition. Male Wistar or hHTg rats were fed ad libitum for 21 days either the basal or fish oil (FO)‐supplemented diets. Triglyceride (Tg) levels in serum and tissue lipid extracts were measured with the aid of a commercially available enzymatic set. Hepatic activity of the Δ‐6 D was determined radiometrically in a microsomal fraction using 1‐14C‐linoleic acid as a substrate. The Δ‐6 D mRNA levels were measured using the Northern blot technique. Tissue FA composition was determined by gas chromatography in the total phospholipid fraction after TLC separation. Increased levels of Tg in hHTg rat circulation were accompanied by raised accumulation of Tg in skeletal muscles. FO feeding lowered the concentration of Tg in serum and prevented their accumulation in skeletal muscles of hHTg rats. A pronounced decrease in the hepatic Δ‐6 D activity in hHTg rats (by about 80%) was not further diminished by FO feeding. On the other hand, the activity of Δ‐6 D in liver of control rats was reduced by about 40% after FO supplementation. These changes were paralleled by a decrease in the Δ‐6 D index as calculated from the liver phospholipid FA profile. In particular, an increase in the amount of 18:2 n‐6 and a decrease in arachidonic acid and PUFA n‐6 metabolites were found. The results indicate that a decrease of insulin action in hHTg rats is accompanied by an impairment of the hepatic Δ‐6 D activity already at the gene level, which is not further affected by n‐3 PUFA supplementation.
Heart Remodeling in the Hereditary Hypertriglyceridemic Rat
Authors: SIMKO F. , LUPTAK I. , MATUSKOVA J. , BABAL P. , PECHANOVA O. , BERNATOVA I. , HULIN I.
Published: July 2010

Abstract:Aim—The hereditary hypertriglyceridemic (hHTg) rat is characterized by insulin resistance, hypertension, and hypertriglyceridemia. Thus, we investigated whether (a) remodeling of the heart left ventricle (LV) is present under the given hypertensive situation and (b) whether this potential alteration could be influenced by an inhibition of the angiotensin converting enzyme (ACE) and/or by a blockade of nitric oxide production.Methods—Five groups of rats were investigated: control Wistar (C) rats, hHTg rats, hHTg rats given captopril (100 mg/kg/day) (hHTg + CAP) orNG‐nitro‐l‐arginine methyl ester (L‐NAME, 40 mg/kg/day) (hHTg + L‐NAME), and hHTg rats given the combination of both drugs (hHTg + CAP + L‐NAME) for 28 days. Systolic blood pressure (SBP) was measured by tail‐cuff plethysmography each week. After cervical dislocation, the relative weights of the left and right ventricles (LV/BW, RV/BW) were obtained, the LV nucleic acid concentrations were analyzed, and the fibrosis amount was quantified with aid of a semiquantitative histological technique.Results—In the hHTg group, the increased SBP (141.7 ± 4.4 vs. 117.2 ± 3.1 mmHg in controls) was linked to hypertrophy of the LV (1.63 ± 0.05 vs. 1.30 ± 0.03 g/kg in controls) with only a minimum of fibrosis. DNA concentration in the LV was decreased (0.45 ± 0.03 vs. 0.69 ± 0.04 mg/g w.w. in controls) in the hHTg group. Captopril normalized SBP and decreased the LV/BW (1.44 ± 0.04 g/kg). Chronic administration of L‐NAME to the hHTg rats additionally enhanced (189.3 ± 5.9 mmHg) the already raised SBP, stimulated fibrosis development, and increased DNA concentration (0.54 ± 0.02 mg/g w.w.) in the LV compared to hHTg group, yet without additional weight increase of the LV. The combined treatment of the hHTg rats with CAP and L‐NAME resulted in normal SBP and the development of LV hypertrophy, and fibrosis was substantially reduced.Conclusions—(a) The heart of hHTg rats carries signs of LV hypertrophy with minimal fibrosis. (b) Nevertheless, LV fibrosis was increased in the hHTg + L‐NAME group. (c) Captopril normalized SBP and decreased the extent of LV hypertrophy in both the nontreated hHTg and the hHTg + L‐NAME groups and (d) substantially reduced the development of LV fibrosis in the hHTg + L‐NAME group. LVH in hHTg rats may be induced by sympathoadrenal system activation, circulating volume enlargement, and impairment of nitric oxide (NO) production rather than by activation of the renin‐angiotensin‐aldosterone system.
Effect of BRX‐220 against Peripheral Neuropathy and Insulin Resistance in Diabetic Rat Models
Authors: KÜRTHY MARIA , MOGYORÓSI TAMÁS , NAGY KÁROLY , KUKORELLI TIBOR , JEDNÁKOVITS ANDREA , TÁLOSI LÁSZLÓ , BÍRÓ KATALIN
Published: July 2010

Abstract: Bimoclomol (BML), a symptomatic antidiabetic agent, has been developed by Biorex R & D Co. to treat diabetic neuropathy and retinopathy. BRX‐220, an orally active member of the BRX family, has been developed to treat diabetic complications and insulin resistance (IR) as a follow‐up compound. The effect of BRX‐220 on peripheral neuropathy was examined in rats with diabetes (type 1) induced by administration of a β‐cell toxin, streptozotocin (STZ, 45 mg/kg iv). Nerve functions were evaluated by electrophysiological measurements of muscle motor and sensory nerve conduction velocities (MNCV and SNCV, respectively). MNCV and SNCV decreased in diabetic rats by 25% (p < 0.001). A 1‐month preventive treatment with BRX‐220 (2.5, 5, 10, and 20 mg/kg po) dose‐dependently improved diabetes‐related deficits in MNCV (51.3%, 71.3%, 86.1%, and 91.3%) and SNCV (48.9%, 68.5%, 86.1%, and 93.2%). Insulin sensitivity was measured using the insulin tolerance test (ITT), both in STZ diabetic and in Zucker diabetic fatty (ZDF) rats (model of type 2 diabetes). Severe IR was detected in STZ diabetic and ZDF rats. This resistance was significantly (p < 0.05) reduced by BRX‐220 treatment.
Differences in Oral Temperature and Body Shape in Two Populations with Different Propensities for Obesity
Authors: VOZAROVA B. , WEYER C. , BOGARDUS C. , RAVUSSIN E. , TATARANNI P. A.
Published: July 2010

Abstract: Objective—Body temperature is a function of heat production and heat dissipation. Substantial interindividual variability has been reported in healthy humans. We hypothesized that Pima Indians, a population with a high prevalence of abdominal obesity, may have a lower surface area relative to volume, that is, lower radiating area, and therefore a higher body temperature compared to Caucasians. Methods—Body composition, including volume (hydrodensitometry), and oral temperature were assessed in 69 nondiabetic Caucasian [age, 30 ± 7 years; body fat, 21 ± 8% (mean ± SD)] and 115 Pima Indian males [age, 27 ± 6 years; body fat, 28 ± 6%]. Surface area was estimated from height, weight, and waist circumference (Bouchard's equation). In 47 Pima Indians, measures of insulin sensitivity (M, hyperinsulinemic euglycemic clamp) were available. Results—Compared to Caucasians, Pima Indians had a higher oral temperature [36.4 ± 0.3°C vs. 36.3 ± 0.3°C (mean ± SD), p < 0.04] and lower surface area relative to volume (2.19 ± 0.05 vs. 2.23 ± 0.26 m2, p < 0.0001). Surface area relative to volume was negatively correlated with oral temperature (r=−0.14, p < 0.05), but in a multiple linear regression model it did not entirely explain the ethnic difference in oral temperature. Oral temperature was inversely correlated with M (r=−0.28, p < 0.05). Conclusions−Pima Indians have higher oral temperature and lower surface area relative to volume than Caucasians. The ethnic difference in temperature does not seem to be entirely explained by differences in body composition and body shape. Interestingly, higher oral temperature was associated with insulin resistance, a risk factor for type 2 diabetes.
Intima‐Media Thickness and Atherosclerotic Plaques in Familial Defective Apolipoprotein B‐100 and Familial Hypercholesterolemia
Authors: KAISER M. , TEMELKOVA‐KURKTSCHIEV T. , HANEFELD M.
Published: July 2010

Abstract: Familial defective apolipoprotein B‐100 (FDB) is a genetic disorder characterized by a decreased binding of low‐density lipoprotein (LDL) particles to the LDL receptor due to defective apo B‐100. Impaired LDL clearance could also be due to defects of the LDL receptor (familial hypercholesterolemia, FH). FDB was suggested to be clinically indistinguishable from classical FH. The measurement of the intima‐media thickness (IMT) is an accepted method for the direct evaluation of early atherosclerosis. Thus, the aim of this study was to examine the IMT in patients with FDB in comparison to FH. Our data indicate that IMT in FDB does not differ from IMT in FH.
The Na/Ca‐K Exchanger Gene Family
Authors: SZERENCSEI ROBERT T. , WINKFEIN ROBERT J. , COOPER CONAN B. , PRINSEN CLEMENS , KINJO TASHI G. , KANG KYEONGJIN , SCHNETKAMP PAUL P.M.
Published: July 2010

Abstract: Ca2+ extrusion driven by both the inward Na+ gradient as well as the outward K+ gradient is essential for visual transduction in retinal rod and cone photoreceptors because it removes Ca2+ that enters photoreceptors via the cGMP‐gated and light‐sensitive channels. We have cloned rod and cone Na/Ca‐K exchanger (NCKX) cDNAs from several species, and we have cloned NCKX cDNAs from lower organisms that lack vertebrate‐type vision. Although in situ NCKX physiology has only been documented for vertebrate photoreceptors, it is now clear that NCKX gene products have a much broader distribution pattern. Here, we review some of the structural and functional features that have emerged from our studies on different members of the NCKX gene family.