bluuebunny/crossref_metadata_2025 huggingface dataset:
Endotoxin-induced migration of monocytes and PECAM-1 phosphorylation are abrogated by PAF receptor antagonists
Authors: Shen Yamin , Sultana Chand , Arditi Moshe , Kim Kwang Sik , Kalra Vijay K.
Published: December 2017

The trafficking of monocytes across the endothelial lining of the blood vessel increases in response to bacterial infection at sites of inflammation. However, the molecular events involved in the diapedesis of monocytes in response to endotoxin are not completely understood. Our studies revealed that signaling by lipopolysaccharide (LPS) in human umbilical vein endothelial cells (HUVEC) resulted in a threefold increase in the transendothelial migration of monocyte-like HL-60 cells and a sevenfold increase in the phosphorylation of platelet endothelial cell adhesion molecule-1 (PECAM-1). The transmigration induced by LPS was inhibited by an antibody to PECAM-1. Both the phosphorylation of PECAM-1 and transendothelial migration of monocytes were inhibited by a platelet-activating factor (PAF) receptor antagonist, indicating the autocrine effect of PAF in these events. Treatment of HUVEC with LPS caused a fourfold increase in PAF receptor mRNA expression that was completely blocked by the PAF receptor antagonist. We conclude that PAF, generated by HUVEC in response to LPS or gram-negative bacterial infection, acts in an autocrine manner, causing PECAM-1 phosphorylation and thus the transendothelial migration of monocytes.
Arginine-induced insulin release is decreased and glucagon increased in parallel with islet NO production
Authors: Henningsson Ragnar , Lundquist Ingmar
Published: December 2017

Nitric oxide (NO) produced by islet constitutive NO synthase (cNOS) is a putative modulator of islet hormone secretion. We show here for the first time that the release of insulin induced byl-arginine orl-homoarginine is inhibited and that of glucagon stimulated in parallel with the rate of islet NO production. It was found thatl-homoarginine was ≈25–30% less potent thanl-arginine as an insulin secretagogue but equally potent as a glucagon secretagogue. Biochemical determination of islet cNOS activity revealed that the NO production with l-homoarginine as substrate was only ≈40% of that ofl-arginine. Selective inhibition of islet cNOS potentiated insulin release during amino acid stimulation. Moreover, inhibition of cNOS suppressed glucagon release, more so with l-arginine than with l-homoarginine as secretagogue, reflecting the relative rates of their NO production. In K+-depolarized islets, inhibition of cNOS enhanced the insulin response tol-arginine by 50% and that tol-homoarginine by 23%, largely corresponding to their relative NO production. The intracellular NO donor hydroxylamine dose dependently inhibited insulin but increased glucagon secretion in K+-depolarized and amino acid-stimulated islets. We conclude that both amino acids have a dual action on insulin release, since their stimulatory effects are reduced in parallel with the rates of their NO production. Furthermore, the greater NO production induced byl-arginine relative tol-homoarginine corresponds to NO-mediated increases in glucagon release. These NO effects are mainly exerted independently of membrane depolarization events.
Gluconeogenesis and the Cori cycle in 12-, 20-, and 40-h-fasted humans
Authors: Katz Joseph , Tayek John A.
Published: December 2017

Six subjects were infused with [U-13C]glucose (0.03–0.05 mg ⋅ kg−1 ⋅ min−1) starting 8–9 h after a meal, and the production of glucose, the recycling of glucose (the Cori cycle), the dilution of glucose by unlabeled carbon into the hepatic lactate-pyruvate pool, and gluconeogenesis were determined in these fasted volunteers by use of mass isotopomer analysis and equations previously described [J. A. Tayek and J. Katz. Am. J. Physiol.272 ( Endocrinol. Metab. 35): E476–E484, 1997]. A primed continuous 11-h infusion was started at 6:00 AM, and the above parameters were calculated after 3 h (for the 12-h fast) and at the end of the infusion (for the 20-h fast). Another group of five subjects was fasted for 40 h, and the above parameters were calculated as before. At 12, 20, and 40 h of fasting, respectively, blood glucose was 93 ± 2, 83 ± 2, and 71 ± 2 (SE) mg/dl; glucose production was 2.3, 1.8, and 1.77 mg ⋅ kg−1 ⋅ min−1; the recycling of labeled carbon was 8, 15, and 15%, and that of glucose molecules (Cori cycle) was 18, 35, and 36%; the contribution of gluconeogenesis to glucose production was 41, 71, and 92% or 0.96, 1.29, and 1.64 mg ⋅ kg−1 ⋅ min−1; and the contribution of other sources to glucose production was 1.37, 0.53, and 0.15 mg ⋅ kg−1 ⋅ min−1. The recycling of glucose is important in prolonged fasting for the maintenance of plasma glucose concentration. We demonstrate here that gluconeogenesis can be easily measured and that it accounts for ∼90% of glucose production after a 40-h fast.
Influence of age, hyperglycemia, leptin, and NPY on islet blood flow in obese-hyperglycemic mice
Authors: Carlsson Per-Ola , Andersson Arne , Jansson Leif
Published: December 2017

This study aimed to elucidate possible age-related changes in islet blood perfusion in lean and obese C57BL/6 mice. Obese mice aged 1 mo were hyperglycemic and hyperinsulinemic and had an increased islet blood flow compared with age-matched lean mice. This augmented blood flow could be abolished by pretreatment with leptin. The islet blood perfusion was, in contrast to this, markedly decreased in obese 6- to 7-mo-old animals compared with age-matched lean mice. Reversal of hyperglycemia, but not hyperinsulinemia, in these obese mice with phlorizin normalized the islet blood flow. Spontaneous reversal of hyperglycemia, but not hyperinsulinemia, was seen in the 12-mo-old obese mice. Islet blood perfusion in obese mice at this age did not differ compared with lean mice. It is suggested that the initial increase in islet blood flow in obese mice is due to the leptin deficiency. The subsequent decrease in islet blood perfusion is probably caused by the chronic hyperglycemia. The described islet blood flow changes may be of importance for impairment of islet function in obese-hyperglycemic mice.
Regulation of hepatic glutamine metabolism during exercise in the dog
Authors: Halseth Amy E. , Rhéaume Nathalie , Messina Allison B. , Reed Erica K. , Krishna Mahesh G. , Flakoll Paul J. , Lacy D. Brooks , Wasserman David H.
Published: December 2017

The goal of this study was to determine how liver glutamine (Gln) metabolism adapts to acute exercise in the 18-h-fasted dogs ( n = 7) and in dogs that were glycogen depleted by a 42-h fast ( n = 8). For this purpose, sampling (carotid artery, portal vein, and hepatic vein) and infusion (vena cava) catheters and Doppler flow probes (portal vein, hepatic artery) were implanted under general anesthesia. At least 16 days later an experiment, consisting of a 120-min equilibration period, a 30-min basal sampling period, and a 150-min exercise period was performed. At the start of the equilibration period, a constant-rate infusion of [5-15N]Gln was initiated. Arterial Gln flux was determined by isotope dilution. Gut and liver Gln release into and uptake from the blood were calculated by combining stable isotopic and arteriovenous difference methods. The results of this study show that 1) in the 18-h-fasted dog, ∼10% and ∼35% of the basal Gln appearance in arterial blood is due to Gln release from the gut and liver, respectively, whereas ∼30% and ∼25% of the basal Gln disappearance is due to removal by these tissues; 2) extending the fast to 42 h does not affect basal arterial Gln flux or the contribution of the gut to arterial Gln fluxes but decreases hepatic Gln release, causing a greater retention of gluconeogenic carbon by the liver; 3) moderate-intensity exercise increases hepatic Gln removal from the blood regardless of fast duration but does not affect the hepatic release of Gln; and 4) Gln plays an important role in channeling nitrogen into the ureagenic pathway in the basal state, and this role is increased by ∼80% in response to exercise. These studies illustrate the quantitative importance of the splanchnic bed contribution to arterial Gln flux during exercise and the ability of the liver to acutely adapt to changes in metabolic requirements induced by the combined effects of fasting and exercise.
Effects of estrogen and estrous cycle on glucocorticoid and catecholamine responses to stress in sheep
Authors: Komesaroff Paul A. , Esler Murray , Clarke Iain J. , Fullerton Meryl J. , Funder John W.
Published: December 2017

There have been relatively few studies of the effects of estrogen on hormonal responses to stress. We therefore studied changes in ACTH, cortisol, norepinephrine (NE), and epinephrine (Epi) after stress induced by a barking dog (audiovisual stressor) and insulin-induced hypoglycemia (metabolic stressor) in ovariectomized sheep treated with estradiol or placebo and in intact sheep in the follicular and luteal phases of the estrous cycle. Both stressors produced acute increases in ACTH, cortisol, Epi, and NE. A high physiological dose of estradiol significantly reduced the ACTH and cortisol responses to both stressors but did not affect Epi and NE responses. Plasma ACTH and cortisol responses to both stressors and Epi and NE responses to insulin were lower in the follicular than in the luteal phase, but catecholamine responses to the audiovisual stressor did not change during the estrous cycle. We conclude that in sheep, estrogen attenuates glucocorticoid responses to stress and that hormonal changes during the estrous cycle affect glucocorticoid responses to both metabolic and audiovisual stressors and catecholamine responses to a metabolic stressor.
Dopaminergic control of angiotensin II-induced vasopressin secretion in vitro
Authors: Rossi Noreen F.
Published: December 2017

Because dopamine influences arginine vasopressin (AVP) release, the present studies were designed to ascertain the dopamine receptor subtype that potentiates angiotensin II-induced AVP secretion in cultured hypothalamo-neurohypophysial explants. Dopamine (a nonselective D1/D2 agonist), apomorphine (a D2 ≫ D1 agonist), and SKF-38393 (a selective D1 agonist) dose dependently increased AVP secretion. Maximal AVP release was observed with 5 μM dopamine, 307 ± 66% ⋅ explant−1 ⋅ h−1, 1 μM SKF-38393, 369 ± 41% ⋅ explant−1 ⋅ h−1, and 0.1 μM apomorphine, 374 ± 67% ⋅ explant−1 ⋅ h−1. Selective D1 antagonism with 1 μM SCH-23390 blocked AVP secretion to values no different from basal. Domperidone (D2 antagonist), phenoxybenzamine (nonselective adrenergic antagonist), and prazosin (α1-antagonist) failed to prevent release. D1 antagonism also prevented AVP secretion to 1 μM angiotensin II [angiotensin II, 422 ± 87% ⋅ explant−1 ⋅ h−1vs. angiotensin II plus SCH-23390, 169 ± 28% ⋅ explant−1 ⋅ h−1( P < 0.05)], but D2 and α1-adrenergic blockade did not. In contrast, AT1 receptor inhibition with 0.5 μM losartan blocked angiotensin II- but not dopamine-induced AVP release. AT2antagonism had no effect. Although subthreshold doses of the agonists did not increase AVP secretion (0.05 μM dopamine, 133 ± 44% ⋅ explant−1 ⋅ h−1; 0.01 μM SKF-38393, 116 ± 26% ⋅ explant−1 ⋅ h−1;and 0.001 μM angiotensin II, 104 ± 29% ⋅ explant−1 ⋅ h−1), the combination of dopamine and angiotensin II provoked a significant rise in AVP [420 ± 83% ⋅ explant−1 ⋅ h−1( P < 0.01)]. Similar results were observed with SKF-38393 and angiotensin II, and the AVP response was blocked to basal levels by either D1 or AT1 antagonism. These findings support a role for D1 receptor activation to increase AVP release and mediate angiotensin II-induced AVP release within the hypothalamo-neurohypophysial system. The data also suggest that the combined subthreshold stimulation of receptors that use distinct intracellular pathways can prompt substantial AVP release.
Adenovirus-mediated transfer of a modified human proinsulin gene reverses hyperglycemia in diabetic mice
Authors: Short Daniel K. , Okada Shuichi , Yamauchi Keishi , Pessin Jeffrey E.
Published: December 2017

The human proinsulin cDNA was introduced into a replication-defective adenovirus and was found to confer proinsulin expression to a hepatocyte (H4-II-E) cell line upon infection. A second virus was constructed in which the dibasic prohormone convertase recognition sequence was mutated to a tetrabasic furin cleavage site. Cells infected with this virus synthesized both proinsulin and mature insulin. Gel filtration chromatography, competition of insulin binding, and activation of the insulin receptor kinase activity demonstrated that this mature insulin was functionally identical to that of authentic processed insulin. Injection of these viral constructs into the external jugular vein of mice resulted in insulin gene expression in the liver. Expression from the mutated proinsulin virus dramatically improved the glycemic state of diabetic mice. However, the effects of the viral infection were transient, being maximal at ∼5–7 days and returning to steady-state levels by 14–21 days. These data demonstrate that somatic cell insulin gene delivery by the use of recombinant adenovirus can be used to transiently reverse the diabetic state in mice.
Calorie restriction increases cell surface GLUT-4 in insulin-stimulated skeletal muscle
Authors: Dean David J. , Brozinick Joseph T. , Cushman Samuel W. , Cartee Gregory D.
Published: December 2017

Reduced calorie intake [calorie restriction (CR); 60% of ad libitum (AL)] leads to enhanced glucose transport without altering total GLUT-4 glucose transporter abundance in skeletal muscle. Therefore, we tested the hypothesis that CR (20 days) alters the subcellular distribution of GLUT-4. Cell surface GLUT-4 content was higher in insulin-stimulated epitrochlearis muscles from CR vs. AL rats. The magnitude of this increase was similar to the CR-induced increase in glucose transport, and GLUT-4 activity (glucose transport rate divided by cell surface GLUT-4) was unaffected by diet. The CR effect was specific to the insulin-mediated pathway, as evidenced by the observations that basal glucose transport and cell surface GLUT-4 content, as well as hypoxia-stimulated glucose transport, were unchanged by diet. CR did not alter insulin’s stimulation of insulin receptor substrate (IRS)-1-associated phosphatidylinositol 3-kinase (PI3K) activity. Muscle abundance of IRS-2 and p85 subunit of PI3K were unaltered by diet, but IRS-1 content was lower in CR vs. AL. These data demonstrate that, despite IRS-1-PI3K activity similar to AL, CR specifically increases insulin’s activation of glucose transport by enhancing the steady-state proportion of GLUT-4 residing on the cell surface.
Evaluation of exercise and training on muscle lipid metabolism
Authors: Bergman B. C. , Butterfield G. E. , Wolfel E. E. , Casazza G. A. , Lopaschuk G. D. , Brooks G. A.
Published: December 2017

To evaluate the hypothesis that endurance training increases intramuscular triglyceride (IMTG) oxidation, we studied leg net free fatty acid (FFA) and glycerol exchange during 1 h of cycle ergometry at two intensities before training [45 and 65% of peak rate of oxygen consumption (V˙o 2 peak)] and after training [65% pretrainingV˙o 2 peak, same absolute workload (ABT), and 65% posttrainingV˙o 2 peak, same relative intensity (RLT)]. Nine male subjects (178.1 ± 2.5 cm, 81.8 ± 3.3 kg, 27.4 ± 2.0 yr) were tested before and after 9 wk of cycle ergometer training, five times per week at 75%V˙o 2 peak. The power output that elicited 66.1 ± 1.1% ofV˙o 2 peak before training elicited 54.0 ± 1.7% after training due to a 14.6 ± 3.1% increase inV˙o 2 peak. Training significantly ( P < 0.05) decreased pulmonary respiratory exchange ratio (RER) values at ABT (0.96 ± 0.01 at 65% pre- vs. 0.93 ± 0.01 posttraining) but not RLT (0.95 ± 0.01). After training, leg respiratory quotient (RQ) was not significantly different at either ABT (0.98 ± 0.02 pre- vs. 0.98 ± 0.03 posttraining) or RLT (1.01 ± 0.02). Net FFA uptake was increased at RLT but not ABT after training. FFA fractional extraction was not significantly different after training or at any exercise intensity. Net glycerol release, and therefore IMTG lipolysis calculated from three times net glycerol release, did not change from rest to exercise or at ABT but decreased at the same RLT after training. Muscle biopsies revealed minor muscle triglyceride changes during exercise. Simultaneous measurements of leg RQ, net FFA uptake, and glycerol release by working legs indicated no change in leg FFA oxidation, FFA uptake, or IMTG lipolysis during leg cycling exercise that elicits 65% pre- and 54% posttrainingV˙o 2 peak. Training increases working muscle FFA uptake at 65%V˙o 2 peak, but high RER and RQ values at all work intensities indicate that FFA and IMTG are of secondary importance as fuels in moderate and greater-intensity exercise.
Resistance training reduces the acute exercise-induced increase in muscle protein turnover
Authors: Phillips S. M. , Tipton K. D. , Ferrando A. A. , Wolfe R. R.
Published: December 2017

We examined the effect of resistance training on the response of mixed muscle protein fractional synthesis (FSR) and breakdown rates (FBR) by use of primed constant infusions of [2H5]phenylalanine and [15N]phenylalanine, respectively, to an isolated bout of pleiometric resistance exercise. Trained subjects, who were performing regular resistance exercise (trained, T; n = 6), were compared with sedentary, untrained controls (untrained, UT; n = 6). The exercise test consisted of 10 sets (8 repetitions per set) of single-leg knee flexion (i.e., pleiometric muscle contraction during lowering) at 120% of the subjects’ predetermined single-leg 1 repetition maximum. Subjects exercised one leg while their contralateral leg acted as a nonexercised (resting) control. Exercise resulted in an increase, above resting, in mixed muscle FSR in both groups (UT: rest, 0.036 ± 0.002; exercise, 0.0802 ± 0.01; T: rest, 0.045 ± 0.004; exercise, 0.067 ± 0.01; all values in %/h; P< 0.01). In addition, exercise resulted in an increase in mixed muscle FBR of 37 ± 5% (rest, 0.076 ± 0.005; exercise, 0.105 ± 0.01; all values in %/h; P < 0.01) in the UT group but did not significantly affect FBR in the T group. The resulting muscle net balance (FSR − FBR) was negative throughout the protocol ( P < 0.05) but was increased in the exercised leg in both groups ( P < 0.05). We conclude that pleiometric muscle contractions induce an increase in mixed muscle protein synthetic rate within 4 h of completion of an exercise bout but that resistance training attenuates this increase. A single bout of pleiometric muscle contractions also increased the FBR of mixed muscle protein in UT but not in T subjects.
Rapid and accurate13CO2isotopic measurement in whole blood: comparison with expired gas
Authors: Dangin Martial , Desport Jean Claude , Gachon Pierre , Beaufrère Bernard
Published: December 2017

Determination of13CO2enrichment on the CO2 released from blood by acid has been used in situations in which breath sampling is difficult. This method can be improved by measuring this enrichment on the CO2 spontaneously released from blood. Therefore, simultaneous comparisons of13CO2content between breath and arterialized blood added with or without acid were performed in 51 samples from human studies, using the statistical method of Bland and Altman (J. M. Bland and D. G. Altman. Lancet 1: 307–310, 1986). Strong relationships exist between the methods ( r > 0.99) expressed in atom percent excess (APE). Compared with breath, the acid method overestimates the13CO2enrichment (0.318 ± 0.632 APE × 1,000, P < 0.001). The acid-free method shows similar enrichments to breath (0.003 ± 0.522 APE × 1,000, P = 0.97) with good precision and degree of agreement (95% confidence interval 0.15 APE × 1,000). The analysis can be performed up to 5 days after sampling with a good reproducibility. In conclusion, measuring13CO2enrichments on the CO2spontaneously released from blood is feasible, gives identical results to the breath method, and lessens operator manipulations. It allows study of situations in which the breath sampling method is not feasible.
Thermoregulatory and soporific effects of very low dose melatonin injection
Authors: van den Heuvel Cameron J. , Kennaway David J. , Dawson Drew
Published: December 2017

The effect of a rapid increase in circulating melatonin on body temperatures and sleepiness was investigated in eight young adults at 1000. Melatonin administered intravenously at 10- and 30-μg doses, but not 3 μg, resulted in elevated plasma and saliva levels consistent with endogenous levels measured in adults at night. Melatonin at 10 and 30 μg significantly attenuated the daytime increase in rectal core temperature ( P < 0.05 for both). The mean maximum rectal core temperature differences between saline and melatonin treatment were 0.11 ± 0.03°C, 0.16 ± 0.04°C, and 0.18 ± 0.04°C after the 3-, 10-, and 30-μg melatonin doses, respectively. All three doses significantly increased hand temperature compared with saline ( P < 0.05) within 30 min. The mean maximum hand temperature differences were 0.72 ± 0.12°C (3 μg), 0.95 ± 0.15°C (10 μg), and 0.65 ± 0.11°C (30 μg). Foot temperature and subjective sleepiness measures did not change at any melatonin dose. The results suggest that daytime intravenous injection of melatonin to achieve normal nocturnal levels in young adults may produce significant thermoregulatory changes without soporific effects.
Effect of hyperglycemia-hyperinsulinemia on whole body and regional fatty acid metabolism
Authors: Sidossis Labros S. , Mittendorfer Bettina , Chinkes David , Walser Eric , Wolfe Robert R.
Published: December 2017

The effects of combined hyperglycemia-hyperinsulinemia on whole body, splanchnic, and leg fatty acid metabolism were determined in five volunteers. Catheters were placed in a femoral artery and vein and a hepatic vein. U-13C-labeled fatty acids were infused, once in the basal state and, on a different occasion, during infusion of dextrose (clamp; arterial glucose 8.8 ± 0.5 mmol/l). Lipids and heparin were infused together with the dextrose to maintain plasma fatty acid concentrations at basal levels. Fatty acid availability in plasma and fatty acid uptake across the splanchnic region and the leg were similar during the basal and clamp experiments. Dextrose infusion decreased fatty acid oxidation by 51.8% (whole body), 47.4% (splanchnic), and 64.3% (leg). Similarly, the percent fatty acid uptake oxidized decreased at the whole body level (53 to 29%), across the splanchnic region (30 to 13%), and in the leg (48 to 22%) during the clamp. We conclude that, in healthy men, combined hyperglycemia-hyperinsulinemia inhibits fatty acid oxidation to a similar extent at the whole body level, across the leg, and across the splanchnic region, even when fatty acid availability is constant.
Pyruvate dehydrogenase activation in inactive muscle during and after maximal exercise in men
Authors: Putman C. T. , Matsos M. P. , Hultman E. , Jones N. L. , Heigenhauser G. J. F.
Published: December 2017

Pyruvate dehydrogenase activity (PDHa) and acetyl-group accumulation were examined in the inactive deltoid muscle in response to maximal leg exercise in men. Seven subjects completed three consecutive 30-s bouts of maximal isokinetic cycling, with 4-min rest intervals between bouts. Biopsies of the deltoid were obtained before exercise, after bouts 1 and 3, and after 15 min of rest recovery. Inactive muscle lactate (LA) and pyruvate (PYR) contents increased more than twofold ( P < 0.05) after exercise ( bout 3) and remained elevated after 15 min of recovery ( P < 0.05). Increased PYR accumulation secondary to LA uptake by the inactive deltoid was associated with greater PDHa, which progressively increased from 0.71 ± 0.23 mmol ⋅ min−1⋅ kg wet wt−1at rest to a maximum of 1.83 ± 0.30 mmol ⋅ min−1⋅ kg wet wt−1after bout 3( P < 0.05) and remained elevated after 15 min of recovery (1.63 ± 0.24 mmol ⋅ min−1⋅ kg wet wt−1; P < 0.05). Acetyl-CoA and acetylcarnitine accumulations were unaltered. Increased PDHaallowed and did not limit the oxidation of LA and PYR in inactive human skeletal muscle after maximal exercise.
A surrogate measure of whole body leucine transport across the cell membrane
Authors: Hovorka Roman , Carroll Paul V. , Gowrie Ian J. , Jackson Nicola C. , Russell-Jones David L. , Umpleby A. Margot
Published: December 2017

Based on a mass-balance model, a surrogate measure of the whole body leucine transport into and out of cells under steady-state conditions was calculated as u/ΔTTR, where u is the infusion rate of (stable label) leucine tracer and ΔTTR is the difference between the tracer-to-tracee ratio of extracellular and intracellular leucine. The approach was evaluated in ten healthy subjects [8 males and 2 females; age, 31 ± 9 (SD) yr; body mass index, 24.0 ± 1.6 kg/m2] who received a primed (7.58 μmol/kg) constant intravenous infusion (7.58 μmol ⋅ kg−1 ⋅ h−1) ofl-[1-13C]leucine over 180 min (7 subjects) or 240 min (3 subjects). Five subjects were studied on two occasions ≥1 wk apart to assess reproducibility. Blood samples taken during the last 30 min of the leucine infusion were used to determine plasma leucine concentration (129 ± 35 μmol/l), TTR of leucine (9.0 ± 1.5%), and TTR of α-ketoisocaproic acid (6.7 ± 0.8%). The latter TTR was taken as the measure of the free intracellular leucine TTR. The whole body inward and outward transport was 6.66 ± 3.82 μmol ⋅ kg−1 ⋅ min−1; the rate of leucine appearance due to proteolysis was 1.93 ± 0.24 μmol ⋅ kg−1 ⋅ min−1. A positive linear relationship between the inward transport and plasma leucine was observed ( P < 0.01), indicating the presence of the mass effect of leucine on its own transport. The transport was highly variable between subjects (between-subject coefficient of variation 57%) but reproducible (within-subject coefficient of variation 17%). We conclude that reproducible estimates of whole body transport of leucine across the cell membrane can be obtained under steady-state conditions with existing experimental and analytical procedures.
Mechanism of adipose tissue iNOS induction in endotoxemia
Authors: Kapur Sonia , Marcotte Bruno , Marette André
Published: December 2017

The aim of the present study was to investigate the mechanism of adipose tissue inducible nitric oxide synthase (iNOS) induction in endotoxemia. Systemic administration of the bacterial endotoxin lipopolysaccharide (LPS) to rats for ≤8 h markedly increased iNOS mRNA and protein levels in white and brown adipose tissues. This effect was comparable to or greater than the induction of iNOS in liver, kidney, or skeletal muscle. iNOS activity was also found to be greatly enhanced in both white and brown adipose tissues of LPS-treated rats (an ∼12- to 20-fold increase). Treatment of cultured 3T3-L1 adipocytes with LPS, tumor necrosis factor-α (TNF-α), or interferon-γ (IFN-γ) alone failed to induce iNOS activity. However, when used in combination, TNF-α, IFN-γ, and LPS markedly and synergistically increased iNOS activity in these cells. In conclusion, these results suggest that adipose tissue is a major site of iNOS expression in endotoxemia. Our data further indicate that iNOS induction can be reproduced in vitro in cultured adipocytes and that a concerted action of cytokines and endotoxin is needed for maximal activation of the enzyme.
Plasma leptin levels and triglyceride secretion rates in VMH-lesioned obese rats: a role of adiposity
Authors: Suga Asako , Hirano Tsutomu , Inoue Shuji , Tsuji Masatomi , Osaka Toshimasa , Namba Yoshio , Miura Masakazu , Adachi Mitsuru
Published: December 2017

To explore the role of adiposity on hypertriglyceridemia associated with obesity, we examined the relation between triglyceride secretion rate (TGSR) and plasma leptin, insulin, or insulin resistance in ventromedial hypothalamus (VMH)-lesioned rats in the dynamic and static phases (2 and 14 wk after lesions, respectively). VMH-lesioned rats gained body weight (BW) at fivefold higher rates in the dynamic phase compared with sham-operated control (sham) rats, and BW gain reached a plateau in the static phase. Parametrial fat pad mass was increased 2.5-fold in VMH-lesioned rats compared with sham rats in both phases. Leptin levels were sixfold higher in VMH-lesioned rats of the dynamic phase and even higher in the static phase. Insulin levels were twofold higher in VMH-lesioned rats than in sham rats in both phases. In the dynamic phase, VMH-lesioned rats had 2-fold higher plasma triglyceride (TG) levels and 2.6-fold higher TGSRs, whereas steady-state plasma glucose (SSPG) values, an indicator of insulin resistance, were lower. SSPG values became significantly higher in VMH-lesioned rats in the static phase, but TGSR was not further accelerated. TGSR was significantly associated with leptin, independent of insulin. Leptin was highly correlated with BW, fat mass, and nonesterified fatty acids (NEFA). These results suggest that adiposity itself plays a critical role in TGSR probably through increased NEFA flux from enlarged adipose tissues. Insulin resistance is not associated with the overproduction of TG in this animal model for obesity.
The obese gene is expressed in lean littermates of the genetically obese mouse (C57BL/6Job/ob)
Authors: Haller Edwin W. , Wittmers Lorentz E. , Haller Irina V. , Regal Ronald R.
Published: December 2017

Some individuals of the mixed group of “lean” littermates (+/ ob and +/+) of (C57BL/6J ob/ob) often suggest phenotypic characteristics of ob/ob animals. Therefore, it was of interest to determine whether expression of the ob gene had physiological significance in +/ ob animals. Body weight (BW), fasting blood glucose (FBG), and body core temperature (Tr) were monitored between 62 and 364 days of age in +/+ and +/ obmice. Among females but not males, +/ ob mice were heavier ( P = 0.003) and FBG levels were greater ( P = 0.04) than in +/+ animals. Comparison of Trindicated differences suggesting falling Tr in +/ ob but rising Tr in +/+ mice with age in males but not females. Multivariate analysis of variance yielded genotype effects for both males ( P = 0.002) and females ( P = 0.02). BW, FBG, and Tr alone were sufficient at the 75% level for genotypic characterization and separation of +/? animals as +/ ob or +/+; clearly, expression of the ob gene in heterozygotes of the +/ ob animal may make the mixed +/? group inappropriate as lean controls.
Effect of long-term caloric restriction and exercise on muscle bioenergetics and force development in rats
Authors: Horská Alena , Brant Larry J. , Ingram Donald K. , Hansford Richard G. , Roth George S. , Spencer Richard G. S.
Published: December 2017

We evaluated the hypothesis that long-term caloric restriction and exercise would have beneficial effects on muscle bioenergetics and performance in the rat. By themselves, each of these interventions is known to increase longevity, and bioenergetic improvements are thought to be important in this phenomenon. Accordingly, we investigated rats that underwent long-term caloric restriction and were sedentary, ad libitum-fed rats permitted to exercise by daily spontaneous wheel running (AE), and the combination of the dietary and exercise interventions (RE). Ad libitum-fed, sedentary rats comprised the control group.31P NMR spectra of the gastrocnemius muscle (GM) were collected in vivo at rest and during two periods of electrical stimulation. Neither caloric restriction nor exercise affected the ratio of phosphocreatine to ATP or pH at rest. During the first stimulation and after recovery, the RE group had a significantly smaller decline in pH than did the other groups ( P < 0.05). During the second period of stimulation, the decrease in pH was much smaller in all groups than during the first stimulation, with no differences observed among the groups. The combination of caloric restriction and exercise resulted in a significant attenuation in the decline in developed force during the second period of stimulation ( P < 0.05). A biochemical correlate of this was a significantly higher concentration of citrate synthase in the GM samples from the RE rats (32.7 ± 5.4 μmol ⋅ min−1⋅ g−1) compared with the AE rats (17.6 ± 5.7 μmol ⋅ min−1⋅ g−1; P < 0.05). Our experiments thus demonstrated a synergistic effect of long-term caloric restriction and free exercise on muscle bioenergetics during electrical stimulation.
Platelet-activating factor may act as an endogenous pulse generator for sheep of luteolytic PGF2αrelease
Authors: Chami O. , Megevand A. , Ott T. , Bazer F. , O’Neill C.
Published: December 2017

Pulsatile release of uterine prostaglandin F2α(PGF2α) induces luteolysis in ruminants. However, the mechanism(s) that initiates and maintains luteolysis has not been defined. The present study tested the hypothesis that the endogenous PGF2αpulse generator is uterine-derived platelet-activating factor (PAF). Ovariectomized ewes were given exogenous progesterone (P), estradiol (E), or both (P+E, mimicking the normal luteal phase). Only ewes treated with steroids released PAF into the uterine lumen and had increased PAF:acetylhydrolase activity in the uterine lumen. Steroid treatment also influenced the capacity of the uterus to release PGF2αin response to exogenous PAF. PAF infusion did not affect plasma PGF2αmetabolite (PGFM) levels in control (no steroid treatment) ewes but increased plasma PGFM levels in P+E ewes ( P < 0.001) and ewes treated with P or E alone ( P < 0.05). Infusion of PAF followed by or coincident with oxytocin (OT) acted in a synergistic manner to increase plasma PGFM levels. Repeated infusion of PAF into the uterus at 1-h intervals induced tachyphylaxis of the PGFM response to PAF; however, sensitivity of the uterus to PAF returned spontaneously by the 6th h. Interferon-τ (IFN-τ) inhibits pulsatile release of PGF2αduring pregnancy to prevent luteolysis. Exogenous recombinant ovine IFN-τ (50 μg) inhibited the uterine response to PAF alone or the combined effects of PAF and OT. These results indicate that uterine PAF fulfills many of the criteria for an endogenous PGF2αpulse-generator: steroid induction of PAF production and uterine responsiveness to PAF-induced release of PGF; synergistic stimulation of PAF-induced PGF release by OT; inhibition of PAF effects by IFN-τ; and PAF’s ability to induce pulses of PGF with a periodicity during a period of chronic exposure of the uterus to PAF.
Effect of a selective rise in hepatic artery insulin on hepatic glucose production in the conscious dog
Authors: Sindelar Dana K. , Igawa Kayano , Chu Chang A. , Balcom Jim H. , Neal Doss W. , Cherrington Alan D.
Published: December 2017

In the present study we compared the hepatic effects of a selective increase in hepatic sinusoidal insulin brought about by insulin infusion into the hepatic artery with those resulting from insulin infusion into the portal vein. A pancreatic clamp was used to control the endocrine pancreas in conscious overnight-fasted dogs. In the control period, insulin was infused via peripheral vein and the portal vein. After the 40-min basal period, there was a 180-min test period during which the peripheral insulin infusion was stopped and an additional 1.2 pmol ⋅ kg−1⋅ min−1of insulin was infused into the hepatic artery (HART, n = 5) or the portal vein (PORT, n = 5, data published previously). In the HART group, the calculated hepatic sinusoidal insulin level increased from 99 ± 20 (basal) to 165 ± 21 pmol/l (last 30 min). The calculated hepatic artery insulin concentration rose from 50 ± 8 (basal) to 289 ± 19 pmol/l (last 30 min). However, the overall arterial (50 ± 8 pmol/l) and portal vein insulin levels (118 ± 24 pmol/l) did not change over the course of the experiment. In the PORT group, the calculated hepatic sinusoidal insulin level increased from 94 ± 30 (basal) to 156 ± 33 pmol/l (last 30 min). The portal insulin rose from 108 ± 42 (basal) to 192 ± 42 pmol/l (last 30 min), whereas the overall arterial insulin (54 ± 6 pmol/l) was unaltered during the study. In both groups hepatic sinusoidal glucagon levels remained unchanged, and euglycemia was maintained by peripheral glucose infusion. In the HART group, net hepatic glucose output (NHGO) was suppressed from 9.6 ± 2.1 μmol ⋅ kg−1⋅ min−1(basal) to 4.6 ± 1.0 μmol ⋅ kg−1⋅ min−1(15 min) and eventually fell to 3.5 ± 0.8 μmol ⋅ kg−1⋅ min−1(last 30 min, P < 0.05). In the PORT group, NHGO dropped quickly ( P < 0.05) from 10.0 ± 0.9 (basal) to 7.8 ± 1.6 (15 min) and eventually reached 3.1 ± 1.1 μmol ⋅ kg−1⋅ min−1(last 30 min). Thus NHGO decreases in response to a selective increase in hepatic sinusoidal insulin, regardless of whether it comes about because of hyperinsulinemia in the hepatic artery or portal vein.
Substrate metabolism when subjects are fed carbohydrate during exercise
Authors: Horowitz Jeffrey F. , Mora-Rodriguez Ricardo , Byerley Lauri O. , Coyle Edward F.
Published: December 2017

This study determined the effect of carbohydrate ingestion during exercise on the lipolytic rate, glucose disappearance from plasma (Rd Glc), and fat oxidation. Six moderately trained men cycled for 2 h on four separate occasions. During two trials, they were fed a high-glycemic carbohydrate meal during exercise at 30 min (0.8 g/kg), 60 min (0.4 g/kg), and 90 min (0.4 g/kg); once during low-intensity exercise [25% peak oxygen consumption (V˙o2 peak)] and once during moderate-intensity exercise (68%V˙o2 peak). During two additional trials, the subjects remained fasted (12–14 h) throughout exercise at each intensity. After 55 min of low-intensity exercise in fed subjects, hyperglycemia (30% increase) and a threefold elevation in plasma insulin concentration ( P < 0.05) were associated with a 22% suppression of lipolysis compared with when subjects were fasted (5.2 ± 0.5 vs. 6.7 ± 1.2 μmol ⋅ kg−1⋅ min−1, P < 0.05), but fat oxidation was not different from fasted levels at this time. Fat oxidation when subjects were fed carbohydrate was not reduced below fasting levels until 80–90 min of exercise, and lipolysis was in excess of fat oxidation at this time. The reduction in fat oxidation corresponded in time with the increase in Rd Glc. During moderate-intensity exercise, the very small elevation in plasma insulin concentration (∼3 μU/ml; P < 0.05) during the second hour of exercise when subjects were fed vs. when they were fasted slightly attenuated lipolysis ( P < 0.05) but did not increase Rd Glcor suppress fat oxidation. These findings indicate that despite a suppression of lipolysis after carbohydrate ingestion during exercise, the lipolytic rate remained in excess and thus did not limit fat oxidation. Under these conditions, a reduction in fat oxidation was associated in time with an increase in glucose uptake.
Platelet-stimulated thrombin and PDGF are normalized by insulin and Ca2+channel blockers
Authors: Kahn Nighat N.
Published: December 2017

Coronary artery disease is accelerated in chronic spinal cord injury (SCI). Because prostacyclin (PGI2) may retard atherogenesis through its inhibitory effects on platelet function, the role of PGI2on SCI platelets was determined. The SCI platelets were neither hypersensitive to aggregating agonists nor resistant to the inhibitory effect of PGI2, but PGI2failed to inhibit platelet-stimulated thrombin generation and the release of platelet-derived growth factor (PDGF) in SCI. Because thrombin and PDGF are atherogenic mitogens, the generation of these mitogens was investigated. Both the release of PDGF and thrombin generation in SCI platelets were higher when compared with control ( n = 12). Treatment of non-SCI platelets with 100 nM PGE1(a stable probe of PGI2) inhibited the release of the mitogens by 90% ( P< 0.001), with no effect on SCI platelets. Scatchard analysis of prostaglandin E1(PGE1) binding showed a 70% decrease of PGI2receptors on the SCI platelet surface. Treatment of SCI platelets with insulin or Ca2+channel blockers restored the PGI2-receptor number and “normalized” the inhibition of PDGF release and thrombin generation by PGI2.
Mechanism of endothelin-1-(1—31)-induced calcium signaling in human coronary artery smooth muscle cells
Authors: Inui Daisuke , Yoshizumi Masanori , Okishima Naoko , Houchi Hitoshi , Tsuchiya Koichiro , Kido Hiroshi , Tamaki Toshiaki
Published: December 2017

We have found that human chymase produces a 31-amino acid endothelin [ET-1-(1—31)] from the 38-amino acid precursor (Big ET-1). We examined the mechanism of synthetic ET-1-(1—31)-induced intracellular Ca2+signaling in cultured human coronary artery smooth muscle cells. ET-1-(1—31) increased the intracellular free Ca2+concentration ([Ca2+]i) in a concentration-dependent manner (10−14-10−10M). This ET-1-(1—31)-induced [Ca2+]iincrease was not affected by phosphoramidon, Bowman-Birk inhibitor, and thiorphan. The ET-1-(1—31)-induced [Ca2+]iincrease was not influenced by removal of extracellular Ca2+but was inhibited by thapsigargin. ET-1-(1—31) at 10−12M did not cause Ca2+influx, whereas 10−7M ET-1-(1—31) evoked marked Ca2+influx, which was inhibited by nifedipine. ET-1-(1—31) also increased inositol trisphosphate formation. These results suggest that the ET-1-(1—31)-induced [Ca2+]iincrease at relatively low concentrations is attributable to the release of Ca2+from inositol trisphosphate-sensitive intracellular stores, whereas Ca2+influx into the cells evoked by high concentration of ET-1-(1—31) probably occurs through voltage-dependent Ca2+channels. We concluded that the physiological activity of ET-1-(1—31) may be attributable to Ca2+mobilization from intracellular stores rather than influx of Ca2+from extracellular space.
Mitochondrial proton leak in brown adipose tissue mitochondria ofUcp1-deficient mice is GDP insensitive
Authors: Monemdjou Shadi , Kozak Leslie P. , Harper Mary-Ellen
Published: December 2017

Mice deficient in mitochondrial uncoupling protein (UCP) 1 are cold sensitive, despite abundant expression of the homologues, Ucp2 and Ucp3 (S. Enerbäck, A. Jacobsson, E. M. Simpson, C. Guerra, H. Yamashita, M.-E. Harper, and L. P. Kozak. Nature 387: 90–94, 1997). We have analyzed characteristics of mitochondrial proton leak from brown adipose tissue (BAT) of Ucp1-deficient mice and normal controls and conducted the first top-down metabolic control analysis of oxidative phosphorylation in BAT mitochondria. Because purine nucleotides inhibit UCP1 and because UCP2 and the long form of UCP3 have putative purine nucleotide-binding regions, we predicted that proton leak in BAT mitochondria from Ucp1-deficient mice would be sensitive to GDP. On the contrary, although control over mitochondrial oxygen consumption and proton leak reactions at state 4 are strongly affected by 1 mM GDP in mitochondria from normal mice, there is no effect in UCP1-deficient mitochondria. In the presence of GDP, the overall kinetics of proton leak were not significantly different between Ucp1-deficient mice and controls. In its absence, state 4 respiration in normal BAT mitochondria was double that in its presence. Leak-dependent oxygen consumption was higher over a range of membrane potentials in its absence than in its presence. Thus proton leak, potentially including that through UCP2 and UCP3, is GDP insensitive. However, our measurements were made in the presence of albumin and may not allow for the detection of any fatty acid-induced UCP-mediated leak; this possibility requires investigation.
Peripheral injection of growth hormone stimulates protein intake in aged male and female Lou rats
Authors: Veyrat-Durebex Christelle , Gaudreau Pierrette , Coxam Veronique , Gaumet Nathalie , Alliot Josette
Published: December 2017

It is well established that growth hormone (GH) induces growth rate and food efficiency and stimulates protein accretion in young mammals. Senescence is characterized by metabolic and hormonal disorders, particularly a decrease in protein turnover, which could be correlated to a decrease in GH and insulin-like growth factor I (IGF-I) secretion. We have shown that body weight, protein intake, and IGF-I plasma levels are greatly decreased with aging in Lou/C rats, particularly in males. In order to specify the GH effect on protein intake during aging, males and females (6, 19, and 24 mo) placed on a self-selection regimen were injected daily with a physiological dose of human GH (0.023 mg/rat sc). No GH effect on caloric intake was observed. Nevertheless, GH treatment stimulated body weight in older rats. It also increased protein intake in females and older males (19–24 mo). This stimulating effect was positively correlated with the degree of weight loss in senescent rats, suggesting that the decrease in protein intake observed with aging could be a marker of senescence.
Estrogen receptors (ERα/ERβ) in normal and pathological growth of the human myometrium: pregnancy and leiomyoma
Authors: Benassayag C. , Leroy M. J. , Rigourd V. , Robert B. , Honoré J. C. , Mignot T. M. , Vacher-Lavenu M. C. , Chapron C. , Ferré F.
Published: December 2017

The distributions of the mRNAs for estrogen receptors (ERα and ERβ) and their binding properties in myometria of pregnant and nonpregnant women and in leiomyoma were studied. RT-PCR analysis indicated that the term pregnancy myometria had little ERα mRNA, whereas the amounts of ERβ mRNAs in pregnant or nonpregnant myometria appeared to be similar. Both ERα and ERβ mRNA were greater in certain leiomyoma than in normal nonpregnant myometria. The binding kinetics revealed that two specific binding sites (with high or low affinity) for 17β-estradiol were present in the nonpregnant myometrium. Only the low-affinity binding sites were detectable in late-pregnancy myometria and in leiomyoma, and their capacities were increased two- to threefold ( P < 0.001) in leiomyoma. The pregnancy- and leiomyoma-related changes in myometrial ER status, especially the low concentration of ERα mRNA and the lack of high-affinity ER in pregnant women, plus the increased ERα and ERβ mRNAs and the increased low-affinity ER in some leiomyoma, suggest that the redistribution of ER subtypes is associated with the pathological and/or normal growth of the myometrium.
Regulation of the genes for arginase isoforms and related enzymes in mouse macrophages by lipopolysaccharide
Authors: Salimuddin  , Nagasaki Akitoshi , Gotoh Tomomi , Isobe Hirotaka , Mori Masataka
Published: December 2017

Arginase exists in two isoforms, the hepatic (arginase I) and extrahepatic types (arginase II). Arginase I is markedly induced in rat peritoneal macrophages and rat tissues in vivo by bacterial lipopolysaccharide (LPS). In contrast, both arginase I and arginase II are induced in LPS-activated mouse peritoneal macrophages. In the present study, expression of arginase isoforms and related enzymes was studied in mouse tissues in vivo and in peritoneal macrophages with RNA blot and immunoblot analyses and enzyme assay. When mice were injected intraperitoneally with LPS, inducible nitric oxide synthase (iNOS) and arginase II were induced early in the lung and spleen. mRNAs for argininosuccinate synthase (AS) and ornithine decarboxylase (ODC) were also induced early. In comparison, arginase I was induced later in the lung. Early induction of iNOS, arginase II, AS, ODC, and cationic amino acid transporter 2 and late induction of arginase I were observed in LPS-activated peritoneal macrophages. These results indicate that the genes for the two arginase isoforms are regulated differentially. Possible roles of the arginase isoforms in the regulation of nitric oxide production and in polyamine synthesis are discussed.