bluuebunny/crossref_metadata_2025 huggingface dataset:
Intracellular mechanisms underlying prostaglandin F2α-stimulated phasic myometrial contractions
Authors: Phillippe Mark , Saunders Trevania , Basa Andrew
Published: December 2017

These studies sought to test the hypothesis that prostaglandin F2α(PGF2α)-stimulated phasic myometrial contractions are characterized by the activation of the phosphatidylinositol-signaling pathway resulting in the generation of cytosolic calcium oscillations. For the experiments described in this report rat myometrial tissue was used, after the tissue was loaded with fura 2, to perform cytosolic calcium imaging studies and to perform computer-digitalized in vitro isometric contraction studies. Consistent with the above hypothesis, the cytosolic calcium-imaging studies demonstrated PGF2α-stimulated cytosolic calcium oscillations occurring simultaneously with phasic contractions. The in vitro isometric contraction studies confirmed that previously reported inhibitors of the phosphatidylinositol-signaling pathway and cytosolic calcium oscillation mechanisms resulted in significant inhibition of PGF2α-stimulated phasic myometrial contractions. In summary, these studies have provided substantial support for the hypothesis that PGF2α-stimulated phasic myometrial contractions are generated by intracellular signaling mechanisms involving activation of the phosphatidylinositol-signaling pathway and the production of cytosolic calcium oscillation-like phenomena.
Role of epinephrine and norepinephrine in the metabolic response to stress hormone infusion in the conscious dog
Authors: McGuinness Owen P. , Shau Vickie , Benson Eric M. , Lewis Mike , Snowden Robert T. , Greene James E. , Neal Doss W. , Cherrington Alan D.
Published: December 2017

The role of epinephrine and norepinephrine in contributing to the alterations in hepatic glucose metabolism during a 70-h stress hormone infusion (SHI) was investigated in four groups of chronically catheterized (20-h-fasted) conscious dogs. SHI increased glucagon (∼5-fold), epinephrine (∼10-fold), norepinephrine (∼10-fold), and cortisol (∼6-fold) levels. Dogs received either all the hormones (SHI; n = 5), all the hormones except epinephrine (SHI−Epi; n = 6), or all the hormones except norepinephrine (SHI−NE; n = 6). In addition, six dogs received saline only (Sal). Glucose production (Ra) and gluconeogenesis were assessed after a 70-h hormone or saline infusion with the use of tracer ([3-3H]glucose and [U-14C]alanine) and arteriovenous difference techniques. SHI increased glucose levels (108 ± 2 vs. 189 ± 10 mg/dl) and Ra(2.6 ± 0.2 vs. 4.1 ± 0.3 mg ⋅ kg−1⋅ min−1) compared with Sal. The absence of an increase in epinephrine markedly attenuated these changes (glucose and Rawere 140 ± 6 mg/dl and 2.7 ± 0.4 mg ⋅ kg−1⋅ min−1, respectively). Only 25% of the blunted rise in Racould be accounted for by an attenuation of the rise in net hepatic gluconeogenic precursor uptake (0.9 ± 0.1, 1.5 ± 0.1, and 1.1 ± 0.2 mg ⋅ kg−1⋅ min−1for Sal, SHI, and SHI−Epi, respectively). The absence of an increase in norepinephrine did not blunt the rise in arterial glucose levels, Ra, or net hepatic gluconeogenic precursor uptake (they rose to 195 ± 21 mg/dl, 3.7 ± 0.5 mg ⋅ kg−1⋅ min−1, and 1.7 ± 0.2 mg ⋅ kg−1⋅ min−1, respectively). In summary, during chronic SHI, the rise in epinephrine exerts potent stimulatory effects on glucose production principally by enhancing hepatic glycogenolysis, although the rise in circulating norepinephrine has minimal effects.
Maximal aerobic capacity in African-American and Caucasian prepubertal children
Authors: Trowbridge Christina A. , Gower Barbara A. , Nagy Tim R. , Hunter Gary R. , Treuth Margarita S. , Goran Michael I.
Published: December 2017

The purpose of this study was to examine differences in resting, submaximal, and maximal (V˙o 2 max) oxygen consumption (V˙o 2) in African-American ( n = 44) and Caucasian ( n = 31) prepubertal children aged 5–10 yr. RestingV˙o 2 was measured via indirect calorimetry in the fasted state. SubmaximalV˙o 2 andV˙o 2 max were determined during an all out, progressive treadmill exercise test appropriate for children. Dual-energy X-ray absorptiometry was used to determine total fat mass (FM), soft lean tissue mass (LTM), and leg soft LTM. Doubly labeled water was used to determine total energy expenditure (TEE) and activity energy expenditure (AEE). A significant effect of ethnicity ( P < 0.01) was found for V˙o 2 max but not resting or submaximalV˙o 2, with African-American children having absoluteV˙o 2 max ∼15% lower than Caucasian children (1.21 ± 0.032 vs. 1.43 ± 0.031 l/min, respectively). The lowerV˙o 2 max persisted in African-American children after adjustment for soft LTM (1.23 ± 0.025 vs. 1.39 ± 0.031 l/min; P< 0.01), leg soft LTM (1.20 ± 0.031 vs. 1.43 ± 0.042 l/min; P < 0.01), and soft LTM and FM (1.23 ± 0.025 vs. 1.39 ± 0.031 l/min; P < 0.01). The lowerV˙o 2 max persisted also after adjustment for TEE (1.20 ± 0.02 vs. 1.38 ± 0.0028 l/min P < 0.001) and AEE (1.20 ± 0.024 vs. 1.38 ± 0.028 l/min; P < 0.001). In conclusion, our data indicate that African-American and Caucasian children have similar rates of V˙o 2 at rest and during submaximal exercise, butV˙o 2 max is ∼15% lower in African-American children, independent of soft LTM, FM, leg LTM, TEE, and AEE.
Determination of local brain glucose level with [14C]methylglucose: effects of glucose supply and demand
Authors: Dienel Gerald A. , Cruz Nancy F. , Adachi Keiji , Sokoloff Louis , Holden James E.
Published: December 2017

Methylglucose can be used to assay brain glucose levels because the equilibrium brain-to-plasma distribution ratio for methylglucose ([Formula: see text]/[Formula: see text]) is quantitatively related to brain (Ce) and plasma (Cp) glucose contents. The relationship between Ce and[Formula: see text]/[Formula: see text]predicted by Michaelis-Menten kinetics has been experimentally confirmed when glucose utilization rate (CMRGlc) is maintained at normal, resting levels and Cp is varied in conscious rats. Theoretically, however, Ce and[Formula: see text]/[Formula: see text]should change when CMRGlc is altered and Cp is held constant; their relationship in such conditions was, therefore, examined experimentally. Drugs were applied topically to brains of conscious rats with fixed levels of Cp to produce focal alterations in CMRGlc, and Ce and[Formula: see text]/[Formula: see text]were measured. Plots of Ce as a function of[Formula: see text]/[Formula: see text]for each Cp produced straight lines; their slopes decreased as Cp increased. The results confirm that a single theoretical framework describes the relationship between Ce and[Formula: see text]/[Formula: see text]as either glucose supply or demand is altered over a wide range; they also validate the use of methylglucose to estimate local Ce under abnormal conditions.
Stimulation of Ca2+influx in αT3–1 gonadotrophs via the cAMP/PKA signaling system
Authors: Hezareh Marjan , Schlegel Werner , Rawlings Stephen R.
Published: December 2017

To investigate the regulation of free cytosolic calcium concentration ([Ca2+]i) by the adenosine 3′,5′-cyclic monophosphate (cAMP) signaling system in clonal gonadotrophs, microfluorimetric recordings were made in single indo 1-loaded αT3–1 cells. Forskolin, 8-bromoadenosine 3′,5′-cyclic monophosphate, or a low concentration (100 pM) of the hypothalamic factor pituitary adenylate cyclase-activating polypeptide (PACAP) stimulated Ca2+step responses or repetitive Ca2+transients, which were blocked by the removal of extracellular Ca2+by the dihydropyridine (DHP) (+)PN 200–110 or by preincubation with the protein kinase A (PKA) antagonist H-89 (10 μM). Thus activation of the cAMP/PKA system in αT3–1 gonadotrophs stimulates Ca2+influx through DHP-sensitive (L-type) Ca2+channels. In contrast, high PACAP concentrations (100 nM) stimulated biphasic Ca2+spike-plateau responses. The Ca2+spike was independent of extracellular Ca2+, and similar responses were observed by microperfusion of individual cells withd- myo-inositol 1,4,5-trisphosphate, suggesting the involvement of the phospholipase C (PLC) signaling pathway. The Ca2+plateau depended on Ca2+influx, was blocked by (+)PN 200–110, but was only partially blocked by H-89 pretreatment. In conclusion, PACAP stimulates [Ca2+]iincreases in αT3–1 gonadotrophs through both the PLC and adenylate cyclase signaling pathways. Furthermore, this is the first clear demonstration that the cAMP/PKA system can mediate changes in [Ca2+]iin gonadotroph-like cells.
Alterations in cardiac contractility and gene expression during low-T3syndrome: prevention with T3
Authors: Katzeff Harvey L. , Powell Saul R. , Ojamaa Kaie
Published: December 2017

The low-T3syndrome is a metabolic response resulting in a decreased serum triiodothyronine (T3) concentration that has uncertain effects on thyroid hormone-responsive gene expression and function. We measured cardiac myocyte gene expression and cardiac contractility in young adult female rats using chronic calorie deprivation as a model of the low-T3syndrome. Sarcoplasmic reticulum calcium adenosinetriphosphatase (SERCA2) and myosin heavy chain (MHC) isoform mRNA content were measured after 28 days on a 50% calorie-restricted diet (low T3) with or without T3treatment (6 μg ⋅ kg body wt−1⋅ day−1). The low-T3animals had decreased maximal rates of contraction (−13%; P < 0.05) and relaxation (−18%; P < 0.05) compared with the control and the T3-treated groups. There was a 21% ( P < 0.05) increase in left ventricular (LV) relaxation time in the low-T3animals vs. both control and T3-treated groups. The LV content of the SERCA2 mRNA was decreased significantly (37%) in the low-T3rats and was increased ( P < 0.05) with T3treatment vs. controls. The α-MHC mRNA isoform decreased in the low-T3animals but was unchanged in the T3-treated animals. T3supplementation normalized both cardiac function and phenotype of calorie-restricted animals, suggesting a role for the low-T3syndrome in the pathophysiological response to calorie restriction.
Glucagon-like peptide 1 inhibition of gastric emptying outweighs its insulinotropic effects in healthy humans
Authors: Nauck Michael A. , Niedereichholz Ulrich , Ettler Rainer , Holst Jens Juul , Ørskov Cathrine , Ritzel Robert , Schmiegel Wolff H.
Published: December 2017

Glucagon-like peptide 1 (GLP-1) has been shown to inhibit gastric emptying of liquid meals in type 2 diabetic patients. It was the aim of the present study to compare the action of physiological and pharmacological doses of intravenous GLP-1-(7—36) amide and GLP-1-(7—37) on gastric emptying in normal volunteers. Nine healthy subjects participated (26 ± 3 yr; body mass index 22.9 ± 1.6 kg/m2; hemoglobin A1C 5.0 ± 0.2%) in five experiments on separate occasions after an overnight fast. A nasogastric tube was positioned for the determination of gastric volume by use of a dye-dilution technique (phenol red). GLP-1-(7—36) amide (0.4, 0.8, or 1.2 pmol ⋅ kg−1 ⋅ min−1), GLP-1-(7—37) (1.2 pmol ⋅ kg−1 ⋅ min−1), or placebo was infused intravenously from −30 to 240 min. A liquid meal (50 g sucrose, 8% amino acids, 440 ml, 327 kcal) was administered at 0 min. Glucose, insulin, and C-peptide were measured over 240 min. Gastric emptying was dose dependently slowed by GLP-1-(7—36) amide ( P < 0.0001). Effects of GLP-1-(7—37) at 1.2 pmol ⋅ kg−1 ⋅ min−1were virtually identical. GLP-1 dose dependently stimulated fasting insulin secretion (−30 to 0 min) and slightly reduced glucose concentrations. After the meal (0–240 min), integrated incremental glucose ( P < 0.0001) and insulin responses ( P = 0.01) were reduced (dose dependently) rather than enhanced. In conclusion, 1) GLP-1-(7—36) amide or -(7—37) inhibits gastric emptying also in normal subjects, 2) physiological doses (0.4 pmol ⋅ kg−1 ⋅ min−1) still have a significant effect, 3) despite the known insulinotropic actions of GLP-1-(7—36) amide and -(7—37), the net effect of administering GLP-1 with a meal is no change or a reduction in meal-related insulin responses. These findings suggest a primarily inhibitory function for GLP-1 (ileal brake mechanisms).
Plasmin degradation of insulin-like growth factor-binding protein-5 (IGFBP-5): regulation by IGFBP-5-(201—218)
Authors: Campbell Phil G. , Andress Dennis L.
Published: December 2017

Using the major bone insulin-like growth factor-binding protein (IGFBP) IGFBP-5, we took a mechanistic approach in evaluating the role of the heparin-binding domain of IGFBP-5 in regulating plasmin (Pm) proteolysis of IGFBP-5. Using synthetic IGFBP-5 peptide fragments, we determined that the heparin-binding domain, IGFBP-5-(208—218), inhibits Pm proteolysis of intact IGFBP-5. The mechanism of action of IGFBP-5-(201—218) was by inhibiting Pm binding to substrate IGFBP-5. IGFBP-5-(201—218) action was independent of site of proteolysis, fluid, or solid phase interaction. In addition, IGFBP-5-(201—218) was found to inhibit plasminogen (Pg) activation to Pm. IGFBP-5-(201—218) did not directly inhibit the activity of Pm, urokinase Pg activator (PA), or tissue-type PA but acted as a competitive inhibitor of Pg activation by PA, which is in contrast to the stimulating effect of heparin on Pg activation. These data indicate that the heparin-binding domain contains the serine protease (Pg-to-Pm) binding site region of IGFBP-5, and that this region, which is presumed to represent a Pm-induced proteolytic product of IGFBP-5, is capable of regulating Pm action.
A new biological contribution of cyclo(His-Pro) to the peripheral inhibition of pancreatic secretion
Authors: Fragner Pascal , Presset Olivier , Bernad Nicole , Martinez Jean , Roze Claude , Aratan-Spire Sonia
Published: December 2017

The tripeptide pyro-Glu-His-Pro-NH2[thyrotropin-releasing hormone (TRH)] was isolated from the hypothalamus as a thyrotropin-releasing factor. It has a broad spectrum of central nervous system-mediated actions, including the stimulation of exocrine pancreatic secretion. TRH is also synthesized in the endocrine pancreas and found in the systemic circulation. Enzymatic degradation of TRH in vivo produces other bioactive peptides such as cyclo(His-Pro). Because of the short half-life of TRH and the stability of cyclo(His-Pro) in vivo, we postulated that at least part of the peripheral TRH effects on the exocrine pancreatic secretion may be attributed to cyclo(His-Pro), which has been shown to have other biological activities. This study determines in parallel the peripheral effects of TRH and cyclo(His-Pro) as well as the putative contribution of other TRH-related peptides on exocrine pancreatic secretion in rats. TRH and its metabolite cyclo(His-Pro) dose dependently inhibited 2-deoxy-d-glucose (2-DG)-stimulated pancreatic secretion. TRH and all the related peptides tested had no effect on the basal and cholecystokinin-stimulated amylase release from pancreatic acinar cells in vitro. These data indicate that cyclo(His-Pro) mimics the peripheral inhibitory effect of TRH on 2-DG-stimulated exocrine pancreatic secretion. This effect is not detected on isolated pancreatic acini. Our findings provide a new biological contribution for cyclo(His-Pro) with potential experimental and clinical applications.
Short-term training increases human muscle MCT1 and femoral venous lactate in relation to muscle lactate
Authors: Bonen A. , McCullagh K. J. A. , Putman C. T. , Hultman E. , Jones N. L. , Heigenhauser G. J. F.
Published: December 2017

We examined the effects of increasing a known lactate transporter protein, monocarboxylate transporter 1 (MCT1), on lactate extrusion from human skeletal muscle during exercise. Before and after short-term bicycle ergometry training [2 h/day, 7 days at 65% maximal oxygen consumption (V˙o 2 max)], subjects ( n = 7) completed a continuous bicycle ergometer ride at 30%V˙o 2 max (15 min), 60%V˙o 2 max (15 min), and 75% V˙o 2 max (15 min). Muscle biopsy samples (vastus lateralis) and arterial and femoral venous blood samples were obtained before exercise and at the end of each workload. After 7 days of training the MCT1 content in muscle was increased (+18%; P < 0.05). The concentrations of both muscle lactate and femoral venous lactate were reduced during exercise ( P < 0.05) that was performed after training. High correlations were observed between muscle lactate and venous lactate before training ( r = 0.92, P < 0.05) and after training ( r = 0.85, P < 0.05), but the slopes of the regression lines between these variables differed markedly. Before training, the slope was 0.12 ± 0.01 mM lactate ⋅ mmol lactate−1 ⋅ kg muscle dry wt−1, and this was increased by 33% after training to 0.18 ± 0.02 mM lactate ⋅ mmol lactate−1 ⋅ kg muscle dry wt−1. This indicated that after training the femoral venous lactate concentrations were increased for a given amount of muscle lactate. These results suggest that lactate extrusion from exercising muscles is increased after training, and this may be associated with the increase in skeletal muscle MCT1.
Sleep-endocrine effects of mifepristone and megestrol acetate in healthy men
Authors: Wiedemann Klaus , Lauer Christoph J. , Hirschmann Margarete , Knaudt Kristina , Holsboer Florian
Published: December 2017

Administration of steroid hormones was demonstrated to modulate the sleep electroencephalogram (EEG) and sleep-associated hormonal secretion in specific ways. The present study was conducted to compare the effects of mifepristone (Mif), a mixed glucocorticoid (GR) and progesterone receptor (PR) antagonist, and megestrol acetate (Meg), a PR agonist. Nine healthy men were pretreated with either placebo or 200 mg Mif or 320 mg Meg, or a combination of both. Changes in plasma adrenocorticotropic hormone (ACTH), cortisol, and growth hormone concentrations were registered every 30 min; sleep EEG recordings were obtained continuously. Administration of Mif increased the morning plasma ACTH and cortisol surges, whereas Meg had the opposite effect. Growth hormone secretion was lowered by Mif pretreatment and enhanced by Meg. Simultaneous administration of both compounds led to largely compensated effects. The sleep EEG changes induced by Mif were a slight increase in the time awake and a delayed onset of slow-wave sleep. Meg led to a reduction of rapid-eye-movement sleep. Simultaneous administration of Mif and Meg showed a synergism in increasing time awake and shallow sleep: it therefore may be concluded that the sleep EEG effects are mediated by an interaction of GR and PR in unknown mechanisms.
Metabolic inhibition impairs ATP-sensitive K+ channel block by sulfonylurea in pancreatic β-cells
Authors: Mukai Eri , Ishida Hitoshi , Kato Seika , Tsuura Yoshiyuki , Fujimoto Shimpei , Ishida-Takahashi Ayako , Horie Minoru , Tsuda Kinsuke , Seino Yutaka
Published: December 2017

The effect of metabolic inhibition on the blocking of β-cell ATP-sensitive K+ channels (KATP channels) by glibenclamide was investigated using a patch-clamp technique. Inhibition of KATP channels by glibenclamide was attenuated in the cell-attached mode under metabolic inhibition induced by 2,4-dinitrophenol. Under a low concentration (0.1 μM) of ATP applied in the inside-out mode, KATP channel activity was not fully abolished, even when a high dose of glibenclamide was applied, in contrast to the dose-dependent and complete KATP channel inhibition under 10 μM ATP. On the other hand, cibenzoline, a class Ia antiarrhythmic agent, inhibits KATP channel activity in a dose-dependent manner and completely blocks it, even under metabolic inhibition. In sulfonylurea receptor (SUR1)- and inward rectifier K+ channel (Kir6.2)-expressed proteins, cibenzoline binds directly to Kir6.2, unlike glibenclamide. Thus, KATPchannel inhibition by glibenclamide is impaired under the condition of decreased intracellular ATP in pancreatic β-cells, probably because of a defect in signal transmission between SUR1 and Kir6.2 downstream of the site of sulfonylurea binding to SUR1.
Total, resting, and activity-related energy expenditures are similar in Caucasian and African-American children
Authors: Sun Min , Gower Barbara A. , Nagy Tim R. , Trowbridge Chris A. , Dezenberg Carl , Goran Michael I.
Published: December 2017

There is some evidence to suggest that ethnic differences in energy expenditure in adults may modulate different propensities for obesity. However, there is lack of data for the components of energy expenditure in young children of different ethnic backgrounds. In this study, we examined total energy expenditure (TEE), resting energy expenditure (REE), and physical activity-related energy expenditure (AEE) in healthy prepubertal Caucasian (18 girls, 21 boys) and African-American (29 girls, 30 boys) children. TEE was measured over 14 days under free-living conditions with the doubly labeled water technique, REE was from indirect calorimetry after an overnight fast, and AEE was estimated from the difference between TEE and REE after reducing TEE by 10% to account for the thermic effect of feeding. Fat mass (FM) and fat-free mass (FFM) were measured by dual-energy X-ray absorptiometry. There were no significant effects of ethnicity or gender on TEE after adjustment for FFM or for both FFM and FM. For REE, there was no effect of ethnicity, but a significant effect of gender, with a higher REE in boys after adjustment for FFM and FM ( P < 0.001). For AEE, there were no significant effects of ethnicity or gender after adjustment for FFM or for FFM and FM. In conclusion, ethnicity was not a significant determinant for any of the components of energy expenditure. TEE, REE, and AEE were similar in Caucasian and African-American prepubertal children after adjustment for FFM or for FFM and FM.
The effect of exercise training on leptin levels in obese males
Authors: Pasman W. J. , Westerterp-Plantenga M. S. , Saris W. H. M.
Published: December 2017

The effect of endurance training on plasma leptin levels was investigated in 15 obese male subjects (age 37.3 ± 5.2 yr, body weight 96.5 ± 13.6 kg, and body mass index 29.8 ± 3.0 kg/m2) in a weight loss and exercise program. After 4 mo of treatment consisting of a very low energy diet (VLED) and endurance exercise training (3–4 times weekly, 1 h sessions, moderate intensity), two groups were formed. One group continued the exercise sessions (trained subjects, n = 7) and the other group stopped with the exercise program (control, n= 8). Measurements of anthropometry, aerobic power, and fasted blood samples were executed at fixed time points (0, 2, 4, 10, and 16 mo). With partial regression analysis, keeping the changes in insulin and body fat percentage constant, it was shown that the number of hours of exercise training was significantly correlated with changes in leptin levels, during the 16-mo period ( r = 0.56, P < 0.05). Changes in insulin levels were significantly related to the changes in leptin levels ( r = 0.47, P < 0.05), which were less for changes in body fat percentage ( r = 0.42, P = 0.07). During the VLED, the change in insulin concentration affected leptin levels significantly ( r = 0.79) but changes in body fat percentage were not noted. It is concluded that endurance exercise training decreased plasma leptin levels independently of changes in plasma insulin levels and body fat percentage.
5-Hydroxytryptamine-1 receptor activation inhibits endocrine pancreatic secretion in humans
Authors: Coulie Bernard , Tack Jan , Bouillon Roger , Peeters Theo , Janssens Jozef
Published: December 2017

The selective 5-hydroxytryptamine-1 receptor agonist sumatriptan inhibits exocrine pancreatic function in humans. No data are available on the effect of sumatriptan on fasting and postprandial endocrine pancreatic function in humans. To elucidate the influence of 5-hydroxytryptamine-1 receptor activation by sumatriptan on endocrine pancreatic function and blood glucose homeostasis, we determined plasma levels of somatostatin, glucagon, pancreatic polypeptide, insulin, and C-peptide before and after subcutaneous administration of sumatriptan (6 mg) in seven healthy volunteers, and we measured blood glucose and insulin plasma levels during an oral glucose tolerance test after placebo and after subcutaneous administration of sumatriptan (6 mg) in seven healthy volunteers. Sumatriptan significantly decreased the mean plasma levels of somatostatin, glucagon, pancreatic polypeptide, insulin and C-peptide ( P < 0.001) and also significantly decreased mean and peak plasma levels of insulin after an oral glucose challenge ( P < 0.02 and P = 0.04, respectively) without affecting glucose homeostasis. From our study, we speculate that activation of the 5-hydroxytryptamine-1 receptor inhibits endocrine pancreatic secretion.
Noradrenergic control of central oxytocin release during lactation in rats
Authors: Bealer Steven L. , Crowley William R.
Published: December 2017

Noradrenergic systems regulate the systemic release of oxytocin (OT) in lactating rats. However, a role for norepinephrine (NE) in release of OT within the magnocellular nuclei during suckling has not been established. These studies were designed to determine 1) if suckling induces NE release in the supraoptic (SON) and paraventricular (PVN) nuclei of conscious rats and 2) the role of NE in the central, intranuclear release of OT within these nuclei. Female Holtzman rats were implanted with microdialysis probes adjacent to the PVN or SON on lactation days 8- 12. The following day, the pups were isolated from the dams for 4 h. Microdialysis probes were perfused with artificial cerebrospinal fluid (ACSF) or with ACSF containing an α- or a β-adrenergic receptor antagonist. Dialysate was collected before, during, and after suckling and analyzed for NE or OT. In an additional experiment, an α- or β-adrenergic agonist was administered via the microdialysis probes into the PVN in nonsuckled, lactating rats. Extracellular NE increased in the PVN during suckling but was not detectable in the SON. OT concentrations in dialysates from the PVN and SON significantly increased during suckling. Blockade of either α- (in both PVN and SON) or β- (PVN) adrenergic receptors prevented the suckling-induced increase in central OT release. OT release was increased in nonsuckled, lactating rats by central application of either an α- or β-adrenergic agonist. These data demonstrate that intranuclear NE release is increased in the PVN by suckling and that subsequent stimulation of both α- and β-noradrenergic receptors mediates intranuclear OT release.
β3-Adrenergic agonist induces a functionally active uncoupling protein in fat and slow-twitch muscle fibers
Authors: Yoshida Toshihide , Umekawa Tsunekazu , Kumamoto Kenzo , Sakane Naoki , Kogure Akinori , Kondo Motoharu , Wakabayashi Yasuo , Kawada Teruo , Nagase Itsuro , Saito Masayuki
Published: December 2017

The mitochondrial uncoupling protein (UCP) has usually been found only in brown adipose tissue. We recently observed that a chronic administration of the β3-adrenergic agonist CL-316,243 (CL) induced the ectopic expression of UCP in white fat and skeletal muscle in genetic obese yellow KK mice. The aim of the present study was to examine whether UCP could be induced in nongenetic obese animals produced by neonatal injections of monosodiuml-glutamate (MSG). The daily subcutaneous injection of CL (0.1 mg/kg) to MSG-induced obese mice for 2 wk caused significant reductions of body weight (15%) and white fat pad weight (58%). Northern and Western blot analyses showed that CL induced significant expressions of UCP in the white fat and muscle, as well as in brown fat. Immunohistochemical observations revealed that the UCP stains in white fat were localized on multilocular cells and that those in muscle were localized on slow-twitch fibers rich in mitochondria. Immunoelectron microscopy confirmed the mitochondrial localization of UCP in the myocytes. The guanosine 5′-diphosphate (GDP) binding to mitochondria in brown fat doubled after the CL treatment. Moreover, significant GDP binding was detected in the white fat and muscle of the CL-treated mice, at about one-fourth and one-thirteenth the activity of brown fat, respectively, suggesting that ectopically expressed UCP is functionally active. We concluded that the β3-adrenergic agonist CL can induce functionally active UCP in white fat and slow-twitch muscle fibers of obese mice.
Distinct localization of GLUT-1, -3, and -5 in human monocyte-derived macrophages: effects of cell activation
Authors: Malide Daniela , Davies-Hill Theresa M. , Levine Mark , Simpson Ian A.
Published: December 2017

We determined subcellular localization of GLUT-1, GLUT-3, and GLUT-5 as human monocytes differentiate into macrophages in culture, and effects of the activating agents N-formyl-methionyl-leucyl-phenylalanine (fMLP) and phorbol myristate acetate (PMA). Western blot analysis demonstrated progressively increased GLUT-1, rapidly decreased GLUT-3, and a delayed increase of GLUT-5 expression during differentiation. Confocal microscopy revealed that each isoform displayed a unique subcellular distribution and cell-activation response. GLUT-1 was localized primarily to the cell surface but was also detected in the perinuclear region in a pattern characteristic of recycling endosomes. GLUT-3 exhibited predominantly a distinct vesicle-like staining but was present only in monocytes. GLUT-5 was found primarily at the cell surface but was detectable intracellularly. Activation with fMLP induced similar GLUT-1 and GLUT-5 redistributions from intracellular compartments toward the cell surface. PMA elicited a similar translocation of GLUT-1, but GLUT-5 was redistributed from the plasma membrane to a distinct intracellular compartment that appeared connected to the cell surface. These results suggest specific subcellular targeting of each transporter isoform and differential regulation of their trafficking pathways in cultured macrophages.
The large variability in melatonin blood levels in ewes is under strong genetic influence
Authors: Zarazaga Luis A. , Malpaux Benoît , Bodin Loys , Chemineau Philippe
Published: December 2017

The present study was conducted to assess the degree of genetic determination of the variability in the mean nocturnal plasma concentration of melatonin in sheep. Three hundred twelve ewes born from 18 males and with known genealogy were sampled at the summer and the winter solstices. The nocturnal plasma melatonin concentration was defined as the mean of four plasma samples taken at hourly intervals in the middle of the night (2200–0200). Identity of the father ( P < 0.001) and the solstice ( P < 0.05) were significant. Melatonin concentrations varied considerably among individuals [338.4 ± 197.5 (SD) pg/ml; range 26.6–981.3 pg/ml] and between rams regarding the melatonin concentrations of their daughters (range from 202.9 to 456.3 pg/ml). Inheritance was analyzed by a statistical model that allows discrimination of genetic effects from nongenetic effects and that estimates repeatability and heritability coefficients. Both the repeatability coefficient between solstices (0.60) and heritability coefficient [0.45 ± 0.07 (SE)] were high. These results demonstrate that the variability in plasma melatonin concentration in ewes is under strong genetic control.
The cAMP-response element mediates induction of secretogranin II by CHX and FSK in GH4C1cells
Authors: Jones Letetia C. , Scammell Jonathan G.
Published: December 2017

The effect of cAMP on secretogranin II (SgII) gene transcription in GH4C1(GH) cells is not observed unless protein synthesis is inhibited. We have defined elements in the SgII promoter that mediate regulation by cycloheximide (CHX) and forskolin (FSK) and characterized the nuclear proteins that interact with them. GH cells were transfected with p2774Luc, p351Luc, p242Luc, and p223Luc containing 2,612, 189, 80, and 61 bp of the SgII promoter upstream of the luciferase gene, respectively. Treatment with CHX and FSK increased promoter activity 8- to 12-fold in cells transfected with p2774Luc, p351Luc, and p242Luc but had no effect in cells transfected with p223Luc. The same 19-bp element (−80 to −62) mediates regulation by CHX alone, as CHX caused a 3.8-fold increase in activity in GH cells transfected with p242Luc but not p223Luc. Gel mobility shifts using sequences −84 to −53 resulted in three complexes, which contained cAMP response element-binding protein heterodimerized with cAMP response element modulator or activating transcription factor-1. No differences were observed in complex formation when cells were treated with either CHX, FSK, or CHX and FSK. Thus CHX affects the response to FSK in GH cells by inhibiting the synthesis of a protein, which does not itself interact with DNA or affect the binding of CRE-binding proteins with the SgII promoter, but likely interferes with the interaction of CRE-binding proteins with the general transcriptional machinery.
Insulin stimulation of glucose uptake in skeletal muscles and adipose tissues in vivo is NO dependent
Authors: Roy Denis , Perreault Mylène , Marette André
Published: December 2017

The purpose of this study was to investigate whether in vivo nitric oxide synthase (NOS) inhibition influences insulin-mediated glucose disposal in rat peripheral tissues. The NOS inhibitor NG-nitro-l-arginine methyl ester (l-NAME) or saline was infused constantly during a hyperinsulinemic-euglycemic clamp in normal rats. Glucose utilization rates of insulin-sensitive tissues (individual muscles, heart, and adipose tissues) were simultaneously determined using tracer infusion of 2-deoxy-d-[3H]glucose (2-[3H]DG). NOS blockade with l-NAME resulted in significant ( P < 0.05) reduction in both whole body glucose disposal (−16%, P < 0.01) and plasma 2-[3H]DG disappearance rate (−30%, P < 0.05) during hyperinsulinemic-euglycemic clamp.l-NAME significantly decreased insulin-stimulated glucose uptake in heart (−62%, P = 0.01), soleus (−42%, P = 0.05), red (−53%, P < 0.001) and white (−62%, P < 0.001) gastrocnemius, tibialis (−57%, P < 0.01), and quadriceps (−33%, P < 0.05) muscles. The NOS inhibitor also decreased insulin action in brown interscapular (−47%, P < 0.01), retroperitoneal (−52%, P = 0.07), and gonadal (−66%, P = 0.06) adipose tissues. In contrast to in vivo NOS blockade,l-NAME failed to affect basal or insulin-stimulated 2-[3H]DG transport in isolated soleus or extensor digitorum longus muscles in vitro. These results support the hypothesis that the action of insulin to augment glucose uptake by skeletal muscles and other peripheral insulin-sensitive tissues in vivo is NO dependent.
Insulin secretion rates estimated by two mathematical methods in pancreas-kidney transplant recipients
Authors: Christiansen Erik , Kjems Lise L. , Vølund Aage , Tibell Annika , Binder Christian , Madsbad Sten
Published: December 2017

After pancreas-kidney transplantation, it is difficult to obtain an accurate estimate of the insulin secretion of the pancreas graft, since several pitfalls are involved using peripheral C-peptide and/or insulin measurements in this determination. In this study, the individual kinetic parameters of C-peptide and then the rates of insulin secretion were estimated by two mathematical methods, the deconvolution method and the “combined model” during slow (oral glucose) and fast (intravenous glucagon) changes in insulin secretion in six successful pancreas-kidney transplant recipients with systemic delivery of insulin (Px), six nondiabetic kidney-transplant recipients with portal insulin secretion (Kx), six nondiabetic controls (NS), and six C-peptide-negative insulin-dependent diabetes mellitus patients (IDDM). Decreased C-peptide clearance and basal and poststimulatory hyperinsulinemia were found in both Px and Kx compared with NS ( P < 0.05). Similar glucose responses were observed after intravenous glucagon in all groups, whereas the responses after oral glucose were 30% higher in Px and Kx than in NS ( P < 0.05). During oral glucose and after intravenous glucagon, both mathematical methods resulted in significantly lower maximal and incremental insulin secretion rates (ISR) in Px than in Kx ( P < 0.05). In contrast, calculations of incremental ISR in NS and Px induced by the two β-cell stimuli were about the same but significantly higher in Kx than in NS ( P < 0.05). These results differed markedly from those obtained using peripheral measurements of insulin and C-peptide alone. In conclusion, when C-peptide clearance and insulin metabolism change, such as in pancreas-kidney transplant recipients, accurate evaluation of insulin secretion from the graft can be obtained only by using individual kinetics of the peptides before calculating the ISR. This study also clearly demonstrates that insulin secretion after pancreas transplantation is still defective.
Effect of pregnancy on the metabolic clearance rate and the volume of distribution of oxytocin in the baboon
Authors: Kowalski Wlodzimierz B. , Diveky Lubomir , Mehendale Ramkrishna , Parsons Michael , Wilson Laird
Published: December 2017

Pharmacokinetic parameters of oxytocin (OT) metabolism were determined during the last third of pregnancy and again 4–8 wk after delivery in the baboon. Animals were placed on a tether system with venous and arterial access and a continuous monitoring of uterine contractions during gestation. Two methods of determining OT pharmacokinetics were utilized (bolus injection vs. continuous infusion). The metabolic clearance rate of OT as determined during the bolus trials ( n = 7) was 22.2 ± 1.5 ml ⋅ min−1 ⋅ kg−1in pregnancy and 16.3 ± 1.4 ml ⋅ min−1 ⋅ kg−1postpartum ( P < 0.05), respectively, and 23.7 ± 2.8 vs. 16.9 ± 3.7 ml ⋅ min−1 ⋅ kg−1( P < 0.05), respectively, as determined during the 1-h infusion trials ( n = 4). The initial dilution volume and the volume of distribution at steady state of OT after administration did not differ between pregnant and postpartum animals ( P > 0.05). The mean residence time (MRT) of OT was shorter during pregnancy, 7.7 ± 0.8 vs. 10.8 ± 1.2 min postpartum ( P < 0.05). In summary, OT metabolism during pregnancy in the baboon is characterized by 1) increased clearance rate (1.4-fold), 2) accelerated turnover due to the shorter MRT, and 3) unaltered distribution.
Glutamate transport asymmetry in renal glutamine metabolism
Authors: Carter Patsy , Welbourne Tomas C.
Published: December 2017

d-Glutamate (Glu) was previously shown to block l-Glu uptake and accelerate glutaminase flux in cultured kidney cells [Welbourne, T. C., and D. Chevalier. Am. J. Physiol. 272 ( Endocrinol. Metab. 35): E367–E370, 1997]. To test whether d-Glu would be taken up by the intact functioning kidney and effect the same response in vivo, male Sprague-Dawley rats were infused withd-Glu (2.6 μmol/min), and renal uptake of d- andl-Glu was determined from chemical and radiolabeled arteriovenous Glu concentration differences times renal plasma flow. The amount removed was then compared with that amount filtered to obtain the antiluminal contribution. In the controls, l-Glu uptake measured as net removal was 33% of the arteriall-Glu load and not different from that filtered, 27%; however, the unidirectional uptake was actually 58% of the arterial load, indicating that antiluminal uptake contributes at least half to the overall Glu consumption. Surprisingly, the kidneys showed a more avid removal ofd-Glu, removing 73% of the arterial load, indicating uptake predominantly across the antiluminal cell surface. Furthermore, uptake ofd-Glu was associated with a 55% reduction in l-Glu uptake, with the residual amount taken up equivalent to that filtered;d-Glu did not increase the excretion of the l-isomer. However, elevating plasma l-Glu concentration reduced uptake of thed-isomer, suggesting a shared antiluminal transporter. Thus there is an apparent asymmetrical distribution of the d-Glu transporter. Under these conditions, kidney cortexl-Glu content decreased 44%, whereas net glutamine (Gln) uptake increased sevenfold (170 ± 89 to 1,311 ± 219 nmol/min, P < 0.01) and unidirectional uptake nearly threefold (393 ± 121 to 1,168 ± 161 nmol/min, P < 0.05); this large Gln consumption was paralleled by an increase in ammonium production so that the ratio of production to consumption approaches 2, consistent with accelerated Gln deamidation and subsequent Glu deamination. These results point to a functional asymmetry (antiluminal vs. luminal) for Glu transporter activity, which potentially plays an important role in modulating Gln metabolism and renal function.
Limitations in estimating gluconeogenesis and Cori cycling from mass isotopomer distributions using [U-13C6]glucose
Authors: Landau Bernard R. , Wahren John , Ekberg Karin , Previs Stephen F. , Yang Dawei , Brunengraber Henri
Published: December 2017

Tayek and Katz proposed calculating gluconeogenesis’s contributions to glucose production and Cori cycling from mass isotopomer distributions in blood glucose and lactate during [U-13C6]glucose infusion [Tayek, J. A., and J. Katz. Am. J. Physiol. 272 ( Endocrinol. Metab. 35): E476–E484, 1997]. However, isotopic exchange was not adequately differentiated from dilution, nor was condensation of labeled with unlabeled triose phosphates properly equated. We introduce and apply corrected equations to data from subjects fasted for 12 and 60 h. Impossibly low contributions of gluconeogenesis to glucose production at 60 h are obtained (23–41%). Distributions in overnight-fasted normal subjects calculate to only ∼18%. Cori cycling estimates are ∼10–15% after overnight fasting and 20% after 60 h of fasting. There are several possible reasons for the underestimates. The contribution of gluconeogenesis is underestimated because glucose production from glycerol and amino acids not metabolized via pyruvate is ascribed to glycogenolysis. Labeled oxaloacetate and α-ketoglutarate can exchange during equilibrium with circulating unlabeled aspartate, glutamate, and glutamine. Also, the assumption that isotopomer distributions in arterial lactate and hepatic pyruvate are the same may not be fulfilled.
Behavioral and endocrine traits of obesity-prone and obesity-resistant rats on macronutrient diets
Authors: Wang Jian , Alexander Jesline T. , Zheng Ping , Yu Hi Joon , Dourmashkin Jordan , Leibowitz Sarah F.
Published: December 2017

Patterns of eating behavior, body weight gain, and hormone changes were examined in normal-weight albino Sprague-Dawley rats on macronutrient diets. These diets consisted of either three separate jars with pure macronutrients, fat, carbohydrate and protein, from which to choose, or a single diet with different concentrations of fat and carbohydrate. Similar patterns on the choice-diet and single-diet paradigms were observed. During the first 7–10 days on these diets but not subsequently, the rats consuming a fat-rich diet exhibit significant hyperphagia, an increase in both total and fat intake that produces higher body weight gain. Compared with a 10% fat diet, a 30% fat diet is associated with a decline in insulin and corticosterone (CORT) levels, whereas a 60% fat diet produces an increase in circulating glucose. Levels of glucose are positively correlated with fat intake, and together these measures are consistently related to body fat. These relationships are most strongly expressed in rats that consume a fat-rich diet with >30% fat. Whereas insulin levels are also positively related to body fat, CORT is inversely related in these normal-weight subjects. In animals consuming a high-fat diet, a clear separation can be seen between “obesity-prone” (OP) rats with 100% greater body fat than “obesity-resistant” (OR) rats. The OP rats, which consume 15% more total calories, have significantly higher insulin and glucose levels. In animals that consume a diet with >30% fat, it is the OP but not the OR rats that exhibit a positive relation between fat intake, glucose levels, and body fat and reveal an additional association between carbohydrate intake, insulin, and body fat. Thus these rats on macronutrient diets exhibit distinct traits that relate behavior to hormone disturbances and adiposity and distinguish subjects that are prone vs. resistant to obesity.
Regional acetate kinetics and oxidation in human volunteers
Authors: Mittendorfer B. , Sidossis L. S. , Walser E. , Chinkes D. L. , Wolfe R. R.
Published: December 2017

We have used a 3-h primed continuous infusion of [1,2-13C]acetate in five fasted (24 h) volunteers to quantify splanchnic and leg acetate metabolism ( protocol 1). Fractional extraction of acetate by both tissues was high (∼70%), and simultaneous uptake and release of acetate were observed. Labeled carbon recovery in CO2was 37.9 ± 2.3% at the whole body level, 37.7 ± 1.5% across the splanchnic bed, and 37.3 ± 2.9% across the leg. Furthermore, we calculated whole body labeled carbon recovery during 15 h of [1,2-13C]acetate infusion in three volunteers ( protocol 2). Whole body acetate carbon recovery in CO2was significantly higher (66.7 ± 4.5%) after 15 h of tracer infusion than after 3 h. We conclude that acetate is rapidly taken up by the leg and splanchnic tissues and that the percent recovery of CO2from the oxidation of acetate is heavily dependent on the length of acetate tracer infusion. In the postabsorptive state, labeled carbon recovery from acetate across the leg and the splanchnic region is similar to the whole body CO2recovery.
Effect of hyperinsulinemia on plasma leptin concentrations and food intake in rats
Authors: Koopmans Sietse J. , Frolich Marijke , Gribnau Eric H. , Westendorp Rudi G. J. , DeFronzo Ralph A.
Published: December 2017

We investigated the dose- and time-dependent effect of insulin infusion on peripheral and portal plasma leptin concentrations in normal rats. Three groups were studied: group I: euglycemic (6 mmol/l) insulin (6 mU ⋅ kg−1⋅ min−1) clamps for 0, 2, 4, 12, and 24 h; group II: euglycemic insulin (18 mU ⋅ kg−1⋅ min−1) clamp for 2 h; and group III: euglycemic insulin (3 mU ⋅ kg−1⋅ min−1) clamp for 7 days. In group III, food intake was quantified during days 1–7. After an overnight fast, peripheral and portal plasma leptin levels were identical (1.5 ± 0.2 and 1.6 ± 0.2 ng/ml). Insulin infusion (6 mU ⋅ kg−1⋅ min−1) for 2 h had no effect on plasma leptin levels (1.5 ± 0.2 ng/ml). After 4 h (2.0 ± 0.2 ng/ml), 12 h (2.2 ± 0.4 ng/ml), and 24 h (2.7 ± 0.6 ng/ml; all P< 0.05) of insulin infusion, a progressive time-related increase in plasma leptin concentration was observed; portal vein leptin levels rose in parallel and were similar to peripheral levels. When insulin (18 mU ⋅ kg−1⋅ min−1) was infused for 2 h, plasma leptin levels increased to 3.0 ± 0.3 ng/ml ( P < 0.01). Seven days of constant insulin infusion (3 mU ⋅ kg−1⋅ min−1) resulted in a progressive increase in fasting plasma leptin and a parallel decrease in food intake. A mean increase in plasma leptin concentration of 1 ng/ml during the 7-day insulin infusion period was associated with a mean decrease in food intake of 2.5 g/day (multivariate ANOVA, P < 0.05). We conclude that the insulin-induced rise in peripheral and portal vein leptin levels is similar and both dose and time dependent. The inverse relationship between plasma leptin concentration and food intake during prolonged hyperinsulinemia, but not during short-term hyperinsulinemia, supports the role of leptin in long-term food consumption.