bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the GABAA agonist gaboxadol on nocturnal sleep and hormone secretion in healthy elderly subjects
Authors: Lancel Marike , Wetter Thomas C. , Steiger Axel , Mathias Stefan
Published: December 2017

Aging is associated with a dramatic decrease in sleep intensity and continuity. The selective GABAA receptor agonist gaboxadol has been shown to increase non-REM sleep and the duration of the non-REM episodes in rats and sleep efficiency in young subjects and to enhance low-frequency activity in the electroencephalogram (EEG) within non-REM sleep in both rats and humans. In this double-blind, placebo-controlled study, we investigated the influence of an oral dose of 15 mg of gaboxadol on nocturnal sleep and hormone secretion (ACTH, cortisol, prolactin, growth hormone) in 10 healthy elderly subjects (6 women). Compared with placebo, gaboxadol did not affect endocrine activity but significantly reduced perceived sleep latency, elevated self-estimated total sleep time, and increased sleep efficiency by decreasing intermittent wakefulness and powerfully augmented low-frequency activity in the EEG within non-REM sleep. These findings indicate that gaboxadol is able to increase sleep consolidation and non-REM sleep intensity, without disrupting REM sleep, in elderly individuals and that these effects are not mediated by a modulation of hormone secretion.
Regional physiological adaptation of the central nervous system deiodinases to iodine deficiency
Authors: Peeters Robin , Fekete Csaba , Goncalves Carla , Legradi Gabor , Tu Helen M. , Harney John W. , Bianco Antonio C. , Lechan Ronald M. , Larsen P. Reed
Published: December 2017

The goal of the present investigation was to analyze the types 2 (D2) and 3 (D3) iodothyronine deiodinases in various structures within the central nervous system (CNS) in response to iodine deficiency. After 5–6 wk of low-iodine diet (LID) or LID + 2 μg potassium iodide/ml (LID+KI; control), rats' brains were processed for in situ hybridization histochemistry for D2 and D3 mRNA or dissected, frozen in liquid nitrogen, and processed for D2 and D3 activities. LID did not affect weight gain or serum triiodothyronine, but plasma thyroxine (T4) was undetectable. In the LID+KI animals, D3 activities were highest in the cerebral cortex (CO) and hippocampus (HI), followed by the olfactory bulb and was lowest in cerebellum (CE). Iodine deficiency decreased D3 mRNA expression in all CNS regions, and these changes were accompanied by three- to eightfold decreases in D3 activity. In control animals, D2 activity in the medial basal hypothalamus (MBH) was similar to that in pituitary gland. Of the CNS D2-expressing regions analyzed, the two most responsive to iodine deficiency were the CO and HI, in which an ∼20-fold increase in D2 activity occurred. Other regions, i.e., CE, lateral hypothalamus, MBH, and pituitary gland, showed smaller increases. The distribution of and changes in D2 mRNA were similar to those of D2 activity. Our results indicate that decreases in the expression of D3 and increases in D2 are an integral peripheral component of the physiological response of the CNS to iodine deficiency.
Involvement of thioredoxin in the regulation of growth hormone secretion in rat pituitary cell cultures
Authors: Hata Ikue , Shigematsu Yosuke , Ohshima Yusei , Tsukahara Hirokazu , Fujisawa Kazuo , Hiraoka Masahiro , Nakamura Hajime , Masutani Hiroshi , Yodoi Junji , Kotsuji Fumikazu , Sudo Masakatsu , Mayumi Mitsufumi
Published: December 2017

We report here an examination of the effect of thioredoxin (TRX) on the secretion of growth hormone (GH) from rat anterior pituitary cells in vitro. Treatment of rat pituitary cells with growth hormone-releasing factor (GRF), but not GH, led to a significant increase in intracellular TRX protein levels. GRF, recombinant human TRX (rhTRX), and a combination thereof were all shown to induce immediate GH secretion from pituitary cells, as evidenced by perifusion experiments. RhTRX, but not other reducing agents such as β-mercaptoethanol and N-acetyl-l-cysteine, augmented GRF-stimulated and -unstimulated GH secretion from rat pituitary cells in a dose-dependent manner. RhTRX did not significantly affect the GH mRNA expression of pituitary cells stimulated in the presence or absence of GRF. In addition, rhTRX-augmented GH secretion was not significantly affected by the presence of cycloheximide. Collectively, these findings suggest that TRX is induced by stimulation with GRF and plays a regulatory role in GH secretion from rat anterior pituitary cells by enhancing the secretion of stored GH, rather than by the synthesis of GH.
BCAA intake affects protein metabolism in muscle after but not during exercise in humans
Authors: Blomstrand Eva , Saltin Bengt
Published: December 2017

Branched-chain amino acids (BCAA) or a placebo was given to seven subjects during 1 h of ergometer cycle exercise and a 2-h recovery period. Intake of BCAA did not influence the rate of exchange of the aromatic amino acids, tyrosine and phenylalanine, in the legs during exercise or the increase in their concentration in muscle. The increase was ∼30% in both conditions. On the other hand, in the recovery period after exercise, a faster decrease in the muscle concentration of aromatic amino acids was found in the BCAA experiment (46% compared with 25% in the placebo condition). There was also a tendency to a smaller release (an average of 32%) of these amino acids from the legs during the 2-h recovery. The results suggest that BCAA have a protein-sparing effect during the recovery after exercise, either that protein synthesis has been stimulated and/or protein degradation has decreased, but the data during exercise are too variable to make any conclusions about the effects during exercise. The effect in the recovery period does not seem to be mediated by insulin.
Parathyroid hormone receptor internalization is independent of protein kinase A and phospholipase C activation
Authors: Tawfeek Hesham A. W. , Che Jian , Qian Fang , Abou-Samra Abdul B.
Published: December 2017

Parathyroid hormone (PTH) and PTH-related peptide (PTHrP) binding to their common receptor stimulates second messenger accumulation, receptor phosphorylation, and internalization. LLC-PK1cells expressing a green fluorescent protein-tagged PTH/PTHrP receptor show time- and dose-dependent receptor internalization. The internalized receptors colocalize with clathrin-coated pits. Internalization is stimulated by PTH analogs that bind to and activate the PTH/PTHrP receptor. Cell lines expressing a mutant protein kinase A regulatory subunit that is resistant to cAMP and/or a mutant receptor (DSEL mutant) that does not activate phospholipase C internalize their receptors normally. In addition, internalization of the wild-type receptor and the DSEL mutant is stimulated by the PTH analog [Gly1,Arg19]hPTH-(1–28), which does not stimulate phospholipase C. Forskolin, IBMX, and the active phorbol ester, phorbol-12-myristate-13-acetate, did not promote receptor internalization or increase PTH-induced internalization. These data indicate that ligand-induced internalization of the PTH/PTHrP receptor requires both ligand binding and receptor activation but does not involve stimulation of adenylate cyclase/protein kinase A or phospholipase C/protein kinase C.
Elevated IGF-II mRNA and phosphorylation of 4E-BP1 and p70S6kin muscle showing clenbuterol-induced anabolism
Authors: Sneddon A. A. , Delday M. I. , Steven J. , Maltin C. A.
Published: December 2017

Muscle wasting affects large numbers of people, but few therapeutic approaches exist to treat and/or reverse this condition. The β2-adrenoceptor agonist clenbuterol produces a muscle-specific protein anabolism in both normal and catabolic muscle and has been used to limit muscle wasting in humans. Because clenbuterol appears to interact with or mimic innervation, its effect on the expression of the neurotrophic agents insulin-like growth factor (IGF)-II and H19 and their putative pathways was examined in normal rat plantaris muscle. The results showed that the well-documented early effects of clenbuterol on protein metabolism were preceded by elevated levels of IGF-II and H19 transcripts together with increased phosphorylation of eukaryotic initiation factor (eIF)4E binding protein-1 (4E-BP1) and p70S6k. By 3 days, transcript levels for IGF-II and H19 and 4E-BP1 and p70S6kphosphorylation had returned to control values. These novel findings indicate that clenbuterol-induced muscle anabolism is potentially mediated, at least in part, by an IGF-II-induced activation of 4E-BP1 and p70S6k.
Effects of fatty acids and growth hormone on liver fatty acid binding protein and PPARα in rat liver
Authors: Carlsson Linda , Lindén Daniel , Jalouli Masoumeh , Oscarsson Jan
Published: December 2017

The aim of this study was to investigate the interaction between long-chain fatty acids (LCFA) and growth hormone (GH) in the regulation of liver fatty acid binding protein (LFABP) and peroxisome proliferator-activated receptor-α (PPARα). Cultured rat hepatocytes were given oleic acid (OA; 500 μM) and GH (100 ng/ml) for 3 days. LFABP mRNA increased 3.6-fold by GH and 5.7-fold by OA, and combined incubation with GH and OA increased LFABP mRNA 17.6-fold. PPARα mRNA was decreased 50% by GH, but OA had no effect. Hypophysectomized (Hx) female rats were treated withl-thyroxine, cortisol, GH, and dietary fat for 7 days. PPARα mRNA levels were three- to fourfold higher in Hx than in normal female rats. GH decreased PPARα mRNA 50% in Hx rats. Dietary triglycerides (10% corn oil) increased LFABP mRNA and cytosolic LFABP about twofold but had no effect on PPARα mRNA in Hx rats. GH and dietary triglycerides had an additive effect on LFABP expression. Dietary triglycerides increased mitochondrial hydroxymethylglutaryl-CoA synthase mRNA only in the presence of GH. The diet increased serum triglycerides in Hx rats, and GH treatment prevented this increase. Addition of cholesterol to the diet did not influence LFABP levels but mitigated increased hepatic triglyceride content. In summary, these studies show that GH regulates LFABP expression independently of PPARα. Moreover, GH has different effects on PPARα-responsive genes and does not counteract the effect of LCFA on the expression of these gene products.
New equations for estimating body cell mass from bioimpedance parallel models in healthy older Germans
Authors: Dittmar Manuela , Reber Helmut
Published: December 2017

The objectives of this study were to assess for elderly Germans the validity of existing equations for predicting body cell mass (BCM) and to develop from single- and multifrequency bioimpedance (SFBIA, MFBIA) models new prediction equations. In a data-splitting approach, validation and cross-validation were performed in 160 healthy elderly (60- to 90-yr) subjects. BCM was determined using a tetrapolar bioimpedance analyzer (800 μA; 4 fixed frequencies: 1, 5, 50, and 100 kHz; electrodes placed to hand, wrist, ankle, and foot) and whole body40K counting as a reference method. New prediction equations were derived by multiple stepwise regression analysis. The Bland-Altman procedure was used for methods comparison. Relative to whole body counting, the manufacturer's equation overestimated BCM by 9% in men ( P < 0.0001, paired t-test) and 4% in women ( P = 0.002). Compared with the manufacturer's equation, the newly derived equations ( r = 0.92, RMSE = 6–9%) improved accuracy (pure error = 13 vs. 7–8%) and reduced bias and limits of agreement. SFBIA and MFBIA equations did not differ in precision or accuracy. We conclude that the newly derived equations improved BCM estimates in the elderly compared with existing equations. There was no advantage of MFBIA over SFBIA equations.
Cardiac responses to insulin-induced hypoglycemia in nondiabetic and intensively treated type 1 diabetic patients
Authors: Russell Raymond R. , Chyun Deborah , Song Steven , Sherwin Robert S. , Tamborlane William V. , Lee Forrester A. , Pfeifer Michael A. , Rife Frances , Wackers Frans J. T. , Young Lawrence H.
Published: December 2017

Insulin-induced hypoglycemia occurs commonly in intensively treated patients with type 1 diabetes, but the cardiovascular consequences of hypoglycemia in these patients are not known. We studied left ventricular systolic [left ventricular ejection fraction (LVEF)] and diastolic [peak filling rate (PFR)] function by equilibrium radionuclide angiography during insulin infusion (12 pmol · kg−1 · min−1) under either hypoglycemic (∼2.8 mmol/l) or euglycemic (∼5 mmol/l) conditions in intensively treated patients with type 1 diabetes and healthy nondiabetic subjects ( n = 9 for each). During hypoglycemic hyperinsulinemia, there were significant increases in LVEF (ΔLVEF = 11 ± 2%) and PFR [ΔPFR = 0.88 ± 0.18 end diastolic volume (EDV)/s] in diabetic subjects as well as in the nondiabetic group (ΔLVEF = 13 ± 2%; ΔPFR = 0.79 ± 0.17 EDV/s). The increases in LVEF and PFR were comparable overall but occurred earlier in the nondiabetic group. A blunted increase in plasma catecholamine, cortisol, and glucagon concentrations occurred in response to hypoglycemia in the diabetic subjects. During euglycemic hyperinsulinemia, LVEF also increased in both the diabetic (ΔLVEF = 7 ± 1%) and nondiabetic (ΔLVEF = 4 ± 2%) groups, but PFR increased only in the diabetic group. In the comparison of the responses to hypoglycemic and euglycemic hyperinsulinemia, only the nondiabetic group had greater augmentation of LVEF, PFR, and cardiac output in the hypoglycemic study ( P < 0.05 for each). Thus intensively treated type 1 diabetic patients demonstrate delayed augmentation of ventricular function during moderate insulin-induced hypoglycemia. Although diabetic subjects have a more pronounced cardiac response to hyperinsulinemia per se than nondiabetic subjects, their response to hypoglycemia is blunted.
Different role of insulin in GLUT-1 and -4 regulation in heart and skeletal muscle during perinatal hypothyroidism
Authors: Ramos S. , Goya L. , Alvarez C. , Martín M. A. , Agote M. , Escrivá F. , Pascual-Leone A. M.
Published: December 2017

Two groups of hypothyroid rats were used; one group was given 2-mercapto-1-methylimidazole (MMI) treatment in the drinking water of the mothers and was killed at 2 and 4 days of life, and the other group was given similar MMI treatment and then was thyroidectomized at 5 days of life and killed at 8 or 20 days. Serum insulin, growth hormone (GH), and insulin-like growth factor I (IGF-I) were decreased in MMI-treated rats but increased in MMI-treated plus thyroidectomized rats. No significant reduction of thyroid hormones was observed in 2-day-old MMI rats. Protein and mRNA expression of GLUT-1 increased, and those of GLUT-4 decreased, in the heart in all populations independent of changes in insulin, GH, and IGF-I levels. However, GLUT-4 protein and mRNA expression in quadriceps and gastrocnemius skeletal muscles decreased at 4 days and increased at 8 and 20 days of life in parallel with insulin, GH, and IGF-I levels. GLUT-1 in the skeletal muscles seemed regulated posttranscriptionally and presented a decrease of mRNA expression in all stages studied. A differential sensitivity to insulin regulation of GLUT-1 and GLUT-4 glucose transporters seems to be one of the causes for the tissue-specific regulation of these glucose transporters in heart and skeletal muscles during the perinatal period.
Evaluation of dietary assessment instruments against doubly labeled water, a biomarker of habitual energy intake
Authors: Trabulsi Jillian , Schoeller Dale A.
Published: December 2017

Epidemiological studies of diet and disease rely on the accurate determination of dietary intake and subsequent estimates of nutrient exposure. Although methodically developed and tested, the instruments most often used to collect self-reported intake data are subject to error. It had been assumed that this error was only random in nature; however, an increasing body of literature suggests that systematic error in the reporting of true dietary intake exists as well. Here, we review studies in which dietary intake by self report was determined while energy expenditure was simultaneously measured using the doubly labeled water (DLW) method. In seeking to establish the relative accuracy of each instrument to capture true habitual energy intake, we conclude that none of the self-reported intake instruments demonstrates greater accuracy against DLW. Instead, it is evident that the physical and psychological characteristics of study participants play a significant role in the underreporting bias observed in these studies. Further research is needed to identify underreporters and to determine how to account for this bias in studies of diet and health.
Glucose and forskolin regulate IAPP gene expression through different signal transduction pathways
Authors: Ding Wei-Qun , Holicky Eileen , Miller Laurence J.
Published: December 2017

Molecular mechanisms for the regulation of islet amyloid polypeptide (IAPP) gene expression remain unclear. In the present study, we investigated the effects of glucose and forskolin on IAPP gene regulation in the INS-1 islet β-cell line. Both glucose and forskolin increased the level of expression of this gene, as measured by Northern blot analysis, and increased IAPP gene transcription in a time- and concentration-dependent manner, as demonstrated in a reporter gene assay. Although inhibition of protein kinase A activity with H-89 eliminated the effect of forskolin on this gene, the glucose effect was unaffected. This supported the predominant use of a protein kinase A-independent signaling pathway for glucose regulation of the IAPP gene. Electrophoretic mobility shift assay further indicated that glucose and forskolin regulated expression of this gene by targeting different elements of the promoter. Mutation of the cAMP regulatory element flanking the IAPP coding region resulted in the loss of most of the forskolin-stimulated IAPP gene promoter activity, whereas glucose-enhanced IAPP gene transcription was unaffected. These results demonstrate parallel and distinct regulatory pathways involved in glucose- and forskolin-induced IAPP gene expression in this model β-cell system.
Human aging is associated with altered TNF-α production during hyperglycemia and hyperinsulinemia
Authors: Kirwan John P. , Krishnan Raj K. , Weaver James A. , Del Aguila Luis F. , Evans William J.
Published: December 2017

Changes in tumor necrosis factor-α (TNF-α) may provide a mechanism to explain impaired glucose metabolism with advancing age. Hyperglycemic clamps (180 min, 10 mM) were performed on seven older [67 ± 2 yr; body mass index (BMI) 24.7 ± 1.0 kg/m2] and seven younger (22 ± 1 yr; BMI 21.8 ± 1.3 kg/m2) healthy sedentary males with normal glucose tolerance. TNF-α production at basal and at the end of 180 min of hyperglycemia and hyperinsulinemia was measured ex vivo from lipopolysaccharide-stimulated (1 ng/ml) peripheral blood mononuclear cells. Plasma glucose, insulin, and C-peptide levels were similar in both groups at basal and during the last 30 min of the hyperglycemic clamp. Glucose infusion rates were lower ( P < 0.004) in the older group compared with the young, indicating decreased insulin action among the older subjects. Basal TNF-α secretion was similar in older and younger subjects. TNF-α was suppressed ( P < 0.02) in the younger group (230 ± 46 vs. 126 ± 49 pg/ml; basal vs. clamp) but not in the older group (153 ± 37 vs. 182 ± 42 pg/ml), with significant group differences in response ( P < 0.05). A significant correlation was observed between the level of suppression in TNF-α production and insulin action (Kendall's rank, τ = 0.40, P < 0.05). Furthermore, the TNF-α response during the clamp was related to fat mass ( r = 0.88, P < 0.001) and abdominal fat ( r = 0.81, P < 0.003). In conclusion, these findings suggest a possible mechanism by which TNF-α may modulate glucose metabolism in younger people. Aging and modest increases in adiposity prevent the “normal” suppression of TNF-α production after a sustained postprandial-like hyperglycemic-hyperinsulinemic stimulus, which may contribute in part to the decline in insulin sensitivity in older men.
Deficiencies of folate and vitamin B6exert distinct effects on homocysteine, serine, and methionine kinetics
Authors: Cuskelly Geraldine J. , Stacpoole Peter W. , Williamson Jerry , Baumgartner Thomas G. , Gregory Jesse F.
Published: December 2017

Folate and vitamin B6act in generating methyl groups for homocysteine remethylation, but the kinetic effects of folate or vitamin B6deficiency are not known. We used an intravenous primed, constant infusion of stable isotope-labeled serine, methionine, and leucine to investigate one-carbon metabolism in healthy control ( n = 5), folate-deficient ( n = 4), and vitamin B6-deficient ( n = 5) human subjects. The plasma homocysteine concentration in folate-deficient subjects [15.9 ± 2.1 (SD) μmol/l] was approximately two times that of control (7.4 ± 1.7 μmol/l) and vitamin B6-deficient (7.7 ± 2.1 μmol/l) subjects. The rate of methionine synthesis by homocysteine remethylation was depressed ( P = 0.027) in folate deficiency but not in vitamin B6deficiency. For all subjects, the homocysteine remethylation rate was not significantly associated with plasma homocysteine concentration ( r = −0.44, P = 0.12). The fractional synthesis rate of homocysteine from methionine was positively correlated with plasma homocysteine concentration ( r = 0.60, P= 0.031), and a model incorporating both homocysteine remethylation and synthesis rates closely predicted plasma homocysteine levels ( r = 0.85, P = 0.0015). Rates of homocysteine remethylation and serine synthesis were inversely correlated ( r = −0.89, P < 0.001). These studies demonstrate distinctly different metabolic consequences of vitamin B6and folate deficiencies.
Chronic exposure to β-hydroxybutyrate impairs insulin action in primary cultures of adult cardiomyocytes
Authors: Tardif Annie , Julien Nathalie , Pelletier Amélie , Thibault Gaétan , Srivastava Ashok K. , Chiasson Jean-Louis , Coderre Lise
Published: December 2017

Type 1 and type 2 diabetic patients often show elevated plasma ketone body concentrations. Because ketone bodies compete with other energetic substrates and reduce their utilization, they could participate in the development of insulin resistance in the heart. We have examined the effect of elevated levels of ketone bodies on insulin action in primary cultures of adult cardiomyocytes. Cardiomyocytes were cultured with the ketone body β-hydroxybutyrate (β-OHB) for 4 or 16 h, and insulin-stimulated glucose uptake was evaluated. Although short-term exposure to ketone bodies was not associated with any change in insulin action, our data demonstrated that preincubation with β-OHB for 16 h markedly reduced insulin-stimulated glucose uptake in cardiomyocytes. This effect is concentration dependent and persists for at least 6 h after the removal of β-OHB from the media. Ketone bodies also decreased the stimulatory effect of phorbol 12-myristate 13-acetate and pervanadate on glucose uptake. This diminution could not be explained by a change in either GLUT-1 or GLUT-4 protein content in cardiomyocytes. Chronic exposure to β-OHB was associated with impaired protein kinase B activation in response to insulin and pervanadate. These results indicate that prolonged exposure to ketone bodies altered insulin action in cardiomyocytes and suggest that this substrate could play a role in the development of insulin resistance in the heart.
Inhibition by adenylyl cyclase-cAMP system of ET-1-induced HSP27 in osteoblasts
Authors: Hatakeyama Daijiro , Kozawa Osamu , Niwa Masayuki , Matsuno Hiroyuki , Kato Kanefusa , Tatematsu Norichika , Shibata Toshiyuki , Uematsu Toshihiko
Published: December 2017

We have previously reported that endothelin-1 (ET-1) stimulates heat shock protein (HSP) 27 induction in osteoblast-like MC3T3-E1 cells and that p38 mitogen-activated protein (MAP) kinase acts at a point downstream from protein kinase C (PKC) in HSP27 induction. In the present study, we investigated the effect of the adenylyl cyclase-cAMP system on ET-1-stimulated induction of HSP27 in MC3T3-E1 cells. Dibutyryl-cAMP (DBcAMP) dose dependently inhibited the HSP27 accumulation stimulated by ET-1. Forskolin and cholera toxin significantly suppressed the ET-1-stimulated accumulation of HSP27. However, dideoxyforskolin, a forskolin derivative that does not activate cAMP, failed to suppress the ET-1-induced HSP27 accumulation. Forskolin reduced the p38 MAP kinase phosphorylation induced by ET-1 or 12- O-tetradecanoylphorbol-13-acetate (TPA). PGE1, an extracellular agonist that activates cAMP production, reduced the ET-1-induced HSP27 accumulation. In addition, the phosphorylation of p38 MAP kinase induced by ET-1 or TPA was suppressed by PGE1. Forskolin, DBcAMP, and PGE1suppressed the ET-1-stimulated increase in the mRNA level for HSP27. These results indicate that the adenylyl cyclase-cAMP system has an inhibitory role in ET-1-stimulated HSP27 induction in osteoblasts and that the effect is exerted at the point between PKC and p38 MAP kinase in osteoblasts.
Activation of Elk-1, an Ets transcription factor, by glucose and EGF treatment of insulinoma cells
Authors: Bernal-Mizrachi Ernesto , Wen Wu , Srinivasan Shanthi , Klenk Alison , Cohen David , Permutt M. Alan
Published: December 2017

Elk-1, a member of the ternary complex factor family of Ets domain proteins that bind serum response elements, is activated by phosphorylation in a cell-specific manner in response to growth factors and other agents. The purpose of the current study was to determine whether Elk-1 activation contributes to glucose-/depolarization-induced Ca2+-dependent induction of immediate early response genes in pancreatic islet β-cells. The results of experiments in insulinoma (MIN6) cells demonstrated that Elk-1-binding sites (Ets elements) in the Egr-1 gene promoter contribute to transcriptional activation of the gene. Treatment with either epidermal growth factor (EGF), a known inducer of β-cell hyperplasia, glucose, or KCl-induced depolarization resulted in Ser383phosphorylation and transcriptional activation of Elk-1 (4 ± 0.3-, P = 0.003, 2.3 ± 0.19-, P = 0.002, and 2.2 ± 0.1- fold, P= 0.001 respectively). The depolarization response was inhibited by the Ca2+channel blocker verapamil and by the MEK inhibitor PD98059 (53 ± 6 and 55 ± 0.5%, respectively). EGF-induced activation of Elk-1 was also inhibited by PD98059 (60 ± 5%). A dominant negative Ras produced partial inhibition (42%) of the depolarization-induced Elk-1 transcriptional activation. Transfection with a constitutively active Ca2+/calmodulin kinase IV plasmid also resulted in Elk-1 transcriptional activation. Experiments with p38, phosphatidylinositol 3-kinase, and protein kinase A inhibitors indicated that these pathways are not involved. We conclude that Elk-1 activation contributes to glucose-/depolarization-induced Ca2+-dependent induction of immediate early growth response genes in pancreatic islet β-cells. Furthermore, the results demonstrated a convergence of nutrient- and growth factor-mediated signaling pathways on Elk-1 activation through induction of Ras/mitogen-activated protein kinase ERK-1 and -2. The role of these pathways in the glucose-induced proliferation of islet β-cells can now be assessed.
Increases in muscle MCT are associated with reductions in muscle lactate after a single exercise session in humans
Authors: Green H. , Halestrap A. , Mockett C. , O'Toole D. , Grant S. , Ouyang J.
Published: December 2017

To investigate the effects of a single session of prolonged cycle exercise [60% peak O2 uptake (V˙o 2 peak) for 5–6 h] on metabolic adaptations in working vastus lateralis muscle, nine untrained males (peak O2 uptake = 47.2 ± 1.1 ml · kg−1 · min−1, means ± SE) were examined before (Pre) and at 2 (Post-2), 4 (Post-4), and 6 (Post-6) days after the training session. On the basis of 15 min of cycle exercise at 59% V˙o 2 peak, it was found that training reduced ( P < 0.05) exercise muscle lactate (mM) at Post-2 (6.65 ± 0.69), Post-4 (7.74 ± 0.63), and Post-6 (7.78 ± 1.2) compared with Pre (10.9 ± 1.3). No effect of training was observed on exercise ATP, phosphocreatine, and glycogen levels. After the single session of training, plasma volumes were elevated ( P < 0.05) at Post-2 (6.7 ± 1.7%), Post-4 (5.86 ± 1.9), and Post-6 (5.13 ± 2.5). The single exercise session also resulted in elevations ( P< 0.05) in the monocarboxylate transporters MCT1 and MCT4 throughout the 6 days after exercise. Although epinephrine and norepinephrine both increased with exercise, only norepinephrine was reduced ( P < 0.05) with training and only at Post-4. These results indicate that regulation of cellular lactate levels occurs rapidly and independently of other metabolic adaptations. It is proposed that increases in MCT and plasma volume are at least partly involved in the lower muscle lactate content observed after the training session by increasing lactate membrane transport and removal, respectively.
Role of IGF-I and IGFBPs in the changes of mass and phenotype induced in rat soleus muscle by clenbuterol
Authors: Awede Bonaventure L. , Thissen Jean-Paul , Lebacq Jean
Published: December 2017

Clenbuterol induces hypertrophy and a slow-to-fast phenotype change in skeletal muscle, but the signaling mechanisms remain unclear. We hypothesized that clenbuterol could act via local expression of insulin-like growth factor I (IGF-I). Administration of clenbuterol to 3-mo-old female Wistar rats resulted in a 10 and 13% increase of soleus muscle mass after 3 and 9 days, respectively, reaching 16% after 4 wk. When associated with triiodothyronine, clenbuterol induced a dramatic slow-to-fast phenotype change. In parallel, clenbuterol administration induced in soleus muscle a fivefold increase in IGF-I mRNA levels associated with an eightfold increase in IGF-binding protein (IGFBP)-4 and a fivefold increase of IGFBP-5 mRNA levels on day 3. This increased IGF-I gene expression was associated with an increase in muscle IGF-I content, already detected on day 1 and persisting until day 5 without increase in serum IGF-I concentrations. These data show that muscle hypertrophy induced by clenbuterol is associated with a local increase in muscle IGF-I content. They suggest that clenbuterol-induced muscle hypertrophy could be mediated by local production of IGF-I.
Identification of a novel glucose transporter-like protein—GLUT-12
Authors: Rogers Suzanne , Macheda Maria L. , Docherty Susan E. , Carty Maynard D. , Henderson Michael A. , Soeller Walter C. , Gibbs E. Michael , James David E. , Best James D.
Published: December 2017

Facilitative glucose transporters exhibit variable hexose affinity and tissue-specific expression. These characteristics contribute to specialized metabolic properties of cells. Here we describe the characterization of a novel glucose transporter-like molecule, GLUT-12. GLUT-12 was identified in MCF-7 breast cancer cells by homology to the insulin-regulatable glucose transporter GLUT-4. The GLUT-12 cDNA encodes 617 amino acids, which possess features essential for sugar transport. Di-leucine motifs are present in NH2and COOH termini at positions similar to the GLUT-4 FQQI and LL targeting motifs. GLUT-12 exhibits 29% amino acid identity with GLUT-4 and 40% to the recently described GLUT-10. Like GLUT-10, a large extracellular domain is predicted between transmembrane domains 9 and 10. Genomic organization of GLUT-12 is highly conserved with GLUT-10 but distinct from GLUTs 1–5. Immunofluorescence showed that, in the absence of insulin, GLUT-12 is localized to the perinuclear region in MCF-7 cells. Immunoblotting demonstrated GLUT-12 expression in skeletal muscle, adipose tissue, and small intestine. Thus GLUT-12 is potentially part of a second insulin-responsive glucose transport system.
Age-associated increase in rat ventricular ANP gene expression correlates with cardiac hypertrophy
Authors: Younes A. , Boluyt M. O. , O'Neill L. , Meredith A. L. , Crow M. T. , Lakatta E. G.
Published: December 2017

Atrial natriuretic peptide (ANP), a cardiac-specific hormone, is stored in the atria and released in response to atrial stretch. During cardiac hypertrophy, ANP gene expression is markedly upregulated in the left ventricle (LV). Because the hearts of normotensive senescent rats exhibit left atrial (LA) and left ventricular (LV) hypertrophy and dilatation, we examined ANP mRNA levels by Northern blot analysis and ANP peptide concentrations by radioimmunoassay in atria, LVs, and plasma of rats at 2, 6, 18, and 22-24 mo of age. Compared with LVs of 6-mo-old rats, the LV-to-body weight ratio was elevated 30% by 18 mo of age, whereas levels of ANP mRNA were elevated twofold (not significant) and sevenfold (P < 0.05) in the LV of 18- and 22- to 24-mo-old rats, respectively. The concentration of immunoreactive ANP (ir-ANP) exhibited a four- to fivefold increase in LVs of 18- and 22- to 24-mo-old rats compared with values for 6-mo-old rats (43 +/- 4 pmol/g wet wt; means +/- SE). Among 18-and 22- to 24-mo-old rats a significant correlation was observed between ANP peptide concentration and LV hypertrophy (r 2 = 0.64). Levels of ANP mRNA and ir-ANP in the atria exhibited only modest changes with aging.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of inhibiting neutral endopeptidase and kininase II on coronary and systemic hemodynamics in rats
Authors: Maxwell A. J. , Husseini W. K. , Piedimonte G. , Hoffman J. I.
Published: December 2017

To determine whether neutral endopeptidase (NEP) and kininase II (angiotensin-converting enzyme, ACE) influence coronary hemodynamics, we compared the effects of inhibiting NEP, ACE, or both before and after isoproterenol (50 mg/kg ip). We measured flow and resistance using radioactive microspheres in 90 anesthetized rats which received the NEP inhibitor phosphoramidon (2.5 mg/kg), the ACE inhibitor captopril (2.5 mg/kg), both combined, or vehicle alone. Before isoproterenol, inhibiting NEP, ACE, or both increased left ventricular blood flow by 48 +/- 10 (SE), 33 +/- 9, and 10 +/- 6%, respectively, and decreased left ventricular vascular resistance by 26 +/- 6, 31 +/- 10, and 10 +/- 6%, respectively. After isoproterenol, NEP inhibition augmented the decrease in left ventricular vascular resistance (25 +/- 6% decrease within 90 s of isoproterenol vs. 8 +/- 5% in controls). ACE inhibition did not augment the decrease in resistance but inhibiting both enzymes did so to a lesser extent than inhibiting NEP. These effects cannot be explained by vascular responses secondary to changes of myocardial oxygen consumption. We conclude that NEP and ACE are regulators of myocardial blood flow.
Antagonism of vasopressin V1 receptors in NTS attenuates baroreflex control of renal nerve activity
Authors: Hegarty A. A. , Felder R. B.
Published: December 2017

Previous work has shown that arginine vasopressin (AVP) present in the nucleus tractus solitarius (NTS) contributes to the control of peripheral cardiovascular parameters such as arterial pressure, heart rate, and sympathetic activity. In this study, we attempted to elucidate the influence of AVP in the NTS on baroreflex control of mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) in urethan-anesthetized rats. To test the baroreflex, the aortic depressor nerve (ADN) was stimulated over a range of frequencies (1-15 Hz) to produce frequency-response curves for MAP and RSNA. The vasopressin V1-receptor antagonist [d(CH2)5Tyr(Me)]AVP (aAVP) was microinjected bilaterally or unilaterally into the caudal NTS to eliminate the influence of endogenous AVP on decreases in MAP and RSNA elicited by ADN stimulation. Bilateral microinjection of 10 or 100 ng aAVP significantly attenuated the decreases in RSNA elicited by ADN stimulation. Decreases in MAP were only attenuated following bilateral microinjection of 100 ng aAVP. Unilateral microinjection of the same doses of aAVP did not influence baroreflex control of MAP or RSNA. These results indicate that endogenous AVP within the NTS contributes to cardiovascular regulation. They also suggest that AVP within the NTS may specifically influence baroreflex control of RSNA.
Endotoxin-induced left ventricular depression is blocked by nitrogen mustard or dimethylthiourea in rabbits
Authors: Nishikawa Y. , Lew W. Y.
Published: December 2017

We examined endotoxin-induced myocardial depression in 31 anesthetized rabbits using left ventricular end-systolic and end-diastolic pressure-volume relationships (sonomicrometers). In the control group, endotoxin (100 micrograms/kg iv) induced systolic depression (> 10% increase in end-systolic volume at matched end-systolic pressure) in 9 of 16 and diastolic dilation (> 10% increase in end-diastolic volume at matched end-diastolic pressure) in 8 of 16 rabbits within 7 h, unrelated to hypotension, acidosis, or hypoxia. Seven rabbits were pretreated with nitrogen mustard (1-2 mg/kg iv 4 and 2 days before) to decrease circulating neutrophils and monocytes by 98%. Endotoxin did not induce systolic depression in any rabbit (P = 0.01 compared with control), and diastolic dilation developed in one rabbit (P = 0.12). In eight rabbits pretreated with dimethylthiourea (DMTU; 500 mg/kg iv 30 min before), an intracellular free radical scavenger, systolic depression developed in one (P = 0.05) and diastolic dilation in five (P = 0.44). We conclude that cells inhibited by nitrogen mustard (e.g., neutrophils, monocytes, or macrophages) mediate endotoxin-induced left ventricular systolic depression. DMTU inhibited endotoxin-induced systolic but not diastolic dysfunction.
Mechanisms of endotoxin-induced dilatation of cerebral arterioles
Authors: Brian J. E. , Heistad D. D. , Faraci F. M.
Published: December 2017

Lipopolysaccharide (LPS; endotoxin) produces dilatation of cerebral arterioles in vivo which may be due, in part, to expression of inducible nitric oxide (NO) synthase. We tested the hypothesis that aminoguanidine, an inhibitor of inducible NO synthase, would reduce endotoxin-induced dilatation of cerebral arterioles. Because mechanisms other than expression of inducible NO synthase may contribute to endotoxin-induced dilatation of cerebral arterioles, we also tested the hypothesis that calcitonin gene-related peptide (CGRP) contributes to vascular responses to endotoxin. Cerebral arteriolar diameter was measured using a closed cranial window in anesthetized rabbits under control conditions [77 +/- 3 (SE) microns] and during topical application of endotoxin (100 micrograms/ml). After 4 h, diameter of cerebral arterioles increased by 41 +/- 5%. Coapplication of aminoguanidine (0.3 mM) with endotoxin reduced vasodilatation at all time points (30 min to 4 h). Relative to control values, endotoxin treatment increased guanosine 3',5'-cyclic monophosphate (cGMP) concentration in cerebrospinal fluid (CSF) by approximately 20 fold at 4 h. Aminoguanidine attenuated the endotoxin-induced increased in CSF cGMP concentration. Aminoguanidine (0.3 mM) did not alter acetylcholine-mediated dilatation of cerebral arterioles. Coapplication of CGRP-(8-37) (0.5 microM), a specific blocker of CGRP receptors, with endotoxin significantly reduced vasodilatation in response to endotoxin at 2, 3, and 4 h. Thus 1) aminoguanidine inhibits endotoxin- but not acetylcholine-mediated dilatation of cerebral arterioles, and 2) activation of CGRP receptors mediates a portion of endotoxin-induced dilation of cerebral arterioles.
Effect of aging and hypertension on contractility of resistance arteries: modulation by endothelial factors
Authors: Lang M. G. , Noll G. , Luscher T. F.
Published: December 2017

The effects of aging and hypertension on contraction were examined in rat mesenteric resistance arteries of 12- and 74-wk-old Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). The vessels were suspended in myographs (37 degrees C, 95% O2-5% CO2) filled with modified Krebs-Ringer bicarbonate solution. Isometric tension was measured. Contractions to KCl (100 mM) were similar in adult WKY and SHR; they increased in senescent WKY (P < 0.05) but decreased in senescent SHR (P < 0.05). Responses to norepinephrine (% of KCl) were comparable in all four groups. However, blockade of nitric oxide (NO) production with NG-nitro-L-arginine methyl ester (L-NAME) enhanced the sensitivity to norepinephrine in senescent animals, particularly in SHR. Inhibition of cyclooxygenase with indomethacin prevented increased sensitivity to norepinephrine after NO blockade. Responses to angiotensin (ANG) II were not affected by aging and hypertension, but the thromboxane receptor antagonist SQ-30741 reduced ANG II-induced contractions only in SHR of both ages (P < 0.05). Aging increased responses to ANG I in SHR but decreased it in WKY (P < 0.05). In quiescent rings with endothelium, acetylcholine caused contractions in the presence of L-NAME in adult and senescent SHR but not in WKY (P < 0.05). SQ-30741 prevented these contractions (P < 0.05). Contractions to the thromboxane analogue U-46619 were reduced only in senescent SHR (P < 0.05). Thus aging increases and hypertension decreases contractility of smooth muscle in rat mesenteric resistance arteries.(ABSTRACT TRUNCATED AT 250 WORDS)
Role of myosin phosphorylation and [Ca2+]i in myogenic reactivity and arteriolar tone
Authors: Zou H. , Ratz P. H. , Hill M. A.
Published: December 2017

The aim of this study was to define the relationship between intraluminal pressure, intracellular calcium concentration ([Ca2+]i), and myosin light-chain (MLC) phosphorylation in isolated arterioles exhibiting myogenic tone. Cremaster muscles were removed from anesthetized rats, and arterioles (approximately 100-microns diam) were dissected from surrounding tissues and cannulated on glass pipettes. Vessels were warmed to 34 degrees C and initially pressurized to 70 mmHg in the absence of intraluminal flow. For [Ca2+]i measurements, vessels were loaded with 5 microM fura 2, and fluorescence emitted by excitation at 340 and 380 nm was measured. Data were considered in terms of changes in the fluorescence ratio (340/380 nm) and collected at steady-state intraluminal pressures between 30 and 170 mmHg. For measurement of MLC phosphorylation, vessels were frozen in acetone-dry ice followed by sonication in homogenizing buffer. Homogenates were separated by two-dimensional gel electrophoresis, and proteins were visualized by silver staining. MLC phosphorylation was quantitated photodensitometrically, and results are expressed as percent total 20-kDa MLC. Increasing intraluminal pressure resultedin significant constriction with increased [Ca2+]i and MLC phosphorylation. For example, the fluorescence ratio was 0.80 +/- 0.04 at 30 mmHg compared with 1.02 +/- 0.05 at 120 mmHg (n = 7 vessels); corresponding MLC-phosphorylation values were 27.7 +/- 1.6 and 39.6 +/- 3.0% (n = 6). MLC phosphorylation in arterioles superfused with 0 mM Ca(2+)-2 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) was 8.5 +/- 0.7%.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of thiol-modifying agents on KATP channels in guinea pig ventricular cells
Authors: Coetzee W. A. , Nakamura T. Y. , Faivre J. F.
Published: December 2017

ATP-sensitive K+ (KATP) channels are thought only to open during conditions of metabolic impairment (e.g., myocardial ischemia). However, the regulation of KATP channel opening during ischemia remains poorly understood. We tested whether thiol (SH) group oxidation, which is known to occur during ischemia, may be involved in KATP channel regulation. Inside-out membrane patches were voltage clamped at a constant potential (O mV) in asymmetrical K+ solutions. The effects of compounds that specifically modify SH groups [p-chloromercuri-phenylsulfonic acid (pCMPS), 5-5'-dithio-bis(2-nitrobenzoic acid) [DTNB], and thimerosal] were tested. The membrane-impermeable compound, pCMPS (> or = 5 microM), caused a quick and irreversible inhibition of KATP channel activity. The reducing agent, dl-dithiothreitol (DTT) (3 mM) was able to reverse this inhibition. DTNB (500 microM) caused a rapid, but spontaneously reversible, block of KATP channel activity. After DTNB, no change was observed in single channel conductance. Oxidized glutathione (GSSG, 3 mM) did not block KATP channel activity. Thimerosal (100-500 microM) induced a DTT-reversible block of partially rundown KATP channels, or channels that underwent complete rundown; these channels were reactivated with trypsin (1 mg/ml). Thimerosal did not block KATP channels that had a high degree of activity. However, the ATP sensitivity was decreased; the concentration of ATP needed to half-maximally inhibit the channel (Ki) was increased from 47 +/- 12 to 221 +/- 35 microM (n = 6, P < 0.05). This was not due to a spontaneous change with time.(ABSTRACT TRUNCATED AT 250 WORDS)
Role of nitric oxide in adenosine receptor-mediated relaxation of porcine coronary artery
Authors: Abebe W. , Hussain T. , Olanrewaju H. , Mustafa S. J.
Published: December 2017

In the present study, using porcine coronary artery rings in vitro, we examined the role of the nitric oxide (NO) pathway in endothelium-dependent vasorelaxant effects of the 5'-uronamide adenosine agonists, 5'-(N-ethylcarboxamido)adenosine (NECA) and 2-[p-(2-carboxyethyl)]phenylethyl-amino-5'-N-ethylcarboxamidoadenosine (CGS-21680) as opposed to the endothelium-independent actions of the C2- and N6-substituted analogues, 2-chloroadenosine (CAD) and N6-cyclopentyladenosine (CPA). The NO synthase inhibitor, NG-monomethyl-L-arginine (L-NMMA, 30 microM), and the NO-destroying agent, 6-anilino-5,8-quinolinedione (LY-83583, 10 microM), attenuated the relaxations of endothelium-intact but not -denuded rings to NECA and CGS-21680. The effect of L-NMMA on NECA-induced relaxation was reversed by L-arginine (100 microM), a substrate for NO synthesis. In the endothelium-intact tissues, both NECA and CGS-21680 elicited enhanced production of nitrite, a stable metabolite of NO. This was also attenuated by L-NMMA or endothelium removal. Furthermore, NECA (10 microM) induced augmentation of guanosine 3',5'-cyclic monophosphate (cGMP) production in the intact arteries, which was also inhibited by L-NMMA, LY-83583, or endothelium removal. In contrast, vasorelaxant responses generated by CAD and CPA were not altered by either L-NMMA or LY-83583. Both agents (10 microM) were also unable to alter nitrite and/or guanosine 3',5'-cyclic monophosphate (cGMP) levels of the coronary artery.(ABSTRACT TRUNCATED AT 250 WORDS)
Endothelium-dependent and -independent vasodilation of isolated rat aorta induced by caffeine
Authors: Hatano Y. , Mizumoto K. , Yoshiyama T. , Yamamoto M. , Iranami H.
Published: December 2017

Caffeine (10(-4)-10(-3) M) induced concentration-dependent relaxations of phenylephrine-precontracted rat aortic rings with endothelium. Endothelial denudation significantly, but only partially, attenuated caffeine-induced relaxation. Pretreatment with NG-nitro-L-arginine, oxyhemoglobin, and methylene blue attenuated the relaxations to an extent similar to endothelial denudation. Guanosine 3',5'-cyclic monophosphate (cGMP) and adenosine 3',5'-cyclic monophosphate (cAMP) contents of aortic strips with endothelium increased significantly after exposure to caffeine (10(-3) M). Endothelial denudation attenuated caffeine-induced cGMP increase. Pretreatment with ryanodine (2 x 10(-5) M), which has been shown to combine with receptors on endoplasmic reticulum (ER) of endothelium, attenuated caffeine-induced relaxation and cGMP content increase of rings with endothelium. Pretreatment with caffeine potentiated sodium nitroprusside-induced relaxations and cGMP increase of rings without endothelium. These results demonstrated that caffeine-induced relaxation comprises two components. In the endothelium-dependent mechanism, caffeine promotes nitric oxide synthesis in endothelium by release of Ca2+ from ER through a ryanodine-sensitive Ca2+ channel, and the suppression of cGMP degradation also contributes to the relaxation. In the endothelium-independent mechanism, caffeine acts as a 3',5'-cyclic-nucleotide phosphodiesterase inhibitor.