bluuebunny/crossref_metadata_2025 huggingface dataset:
Endurance training and GH administration in elderly women: effects on abdominal adipose tissue lipolysis
Authors: Lange Kai Henrik Wiborg , Lorentsen Jeanne , Isaksson Fredrik , Juul Anders , Rasmussen Michael Højby , Christensen Niels Juel , Bülow Jens , Kjær Michael
Published: December 2017

In the present study, the effect of endurance training alone and endurance training combined with recombinant human growth hormone (rhGH) administration on subcutaneous abdominal adipose tissue lipolysis was investigated. Sixteen healthy women [age 75 ± 2 yr (mean ± SE)] underwent a 12-wk endurance training program on a cycle ergometer. rhGH was administered in a randomized, double-blinded, placebo-controlled design in addition to the training program. Subcutaneous abdominal adipose tissue lipolysis was estimated by means of microdialysis combined with measurements of subcutaneous abdominal adipose tissue blood flow (ATBF; 133Xe washout). Whole body fat oxidation was estimated simultaneously by indirect calorimetry. Before and after completion of the training program, measurements were performed both at rest and during 60 min of continuous cycling at a workload corresponding to 60% of pretraining peak oxygen uptake. Endurance training alone did not affect subcutaneous abdominal adipose tissue lipolysis either at rest or during exercise, as reflected by identical levels of interstitial adipose tissue glycerol, subcutaneous abdominal ATBF, and plasma nonesterified fatty acids before and after completion of the training program. Similarly, no effect on subcutaneous abdominal adipose tissue lipolysis was observed when combining endurance training with rhGH administration. However, in both the placebo and the GH groups, fat oxidation was significantly increased during exercise performed at the same absolute workload after completion of the training program. We conclude that the changed lipid metabolism during exercise observed after endurance training alone or after endurance training combined with rhGH administration is not due to alterations in subcutaneous abdominal adipose tissue metabolism in elderly women.
Effect of angiotensin II on calcium reabsorption by the luminal membranes of the nephron
Authors: Charbonneau A. , Leclerc M. , Brunette M. G.
Published: December 2017

In the rat and the rabbit, a number of studies have reported the effects of angiotensin II (ANG II) on Na+reabsorption by the proximal (PT) and distal (DT) convoluted tubules of the kidney. The aim of the present study was to examine the effect of ANG II on Ca2+uptake by the luminal membranes of the PT and DT of the rabbit. Incubation of PT and DT with 10−12M ANG II enhanced the initial Ca2+uptake in the two segments. Dose-response experiments revealed, for Ca2+as well as for Na+transport, a biphasic action with a maximal effect at 10−12M. Ca2+transport by the DT luminal membrane presents a dual kinetic. ANG II action influenced the high-affinity Ca2+channel, increasing maximal velocity from 0.72 ± 0.03 to 0.90 ± 0.05 pmol · μg−1· 10 s−1( P < 0.05, n = 3) and leaving the Michaelis-Menten constant unchanged. The effect of ANG II was abolished by losartan, suggesting that the hormone is acting through AT1receptors. In the PT, calphostin C inhibited the effect of the hormone. It is therefore probable that protein kinase C is involved as a messenger. In the DT, however, neither Rp cAMP, calphostin C, nor econazole (a phospholipase A inhibitor) influenced the hormone action. Therefore, the mechanisms involved in the hormone action remain undetermined. Finally, we questioned whether ANG II acts in the same DT segment as does parathyroid hormone on Ca2+transport. The two hormones increased Ca2+transport, but their actions were not additive, suggesting that they both influence the same channels in the same segment of the distal nephron, i.e., the segment responsible for the high-affinity calcium channel.
Differential regulation of IGFBP-2 and IGFBP-5 gene expression by vitamin A status in Japanese quail
Authors: Fu Zhengwei , Noguchi Tadashi , Kato Hisanori
Published: December 2017

To investigate the involvement of the insulin-like growth factor (IGF) system in vitamin A (VA)-supported growth, we examined the effects of VA status on IGF binding protein (IGFBP)-2 and -5 gene expression in Japanese quail. VA deficiency caused a reduction in IGFBP-2 mRNA only in lung, without effect in other tissues. However, the expression of IGFBP-5 mRNA was more sensitive to the change of VA status. IGFBP-5 mRNA levels were significantly reduced by VA depletion in a tissue-specific manner, which preceded the decrease in body weight. A single injection of retinoic acid or retinol to VA-deficient quail did not affect the levels of IGFBP-2 mRNA, but it rapidly induced the expression of IGFBP-5 mRNAs in some tissues. These results are the first to show that gene expression of some IGFBPs in vivo are under the control of VA status and suggest a possible involvement of the IGF system in mediating the physiological actions of VA in the growth of Japanese quail.
Fetal hyperinsulinemia increases farnesylation of p21 Ras in fetal tissues
Authors: Stephens Elizabeth , Thureen Patti J. , Goalstone Marc L. , Anderson Marianne S. , Leitner J. Wayne , Hay William W. , Draznin Boris
Published: December 2017

Even though the role of fetal hyperinsulinemia in the pathogenesis of fetal macrosomia in patients with overt diabetes and gestational diabetes mellitus seems plausible, the molecular mechanisms of action of hyperinsulinemia remain largely enigmatic. Recent indications that hyperinsulinemia “primes” various tissues to the mitogenic influence of growth factors by increasing the pool of prenylated Ras proteins prompted us to investigate the effect of fetal hyperinsulinemia on the activitiy of farnesyltransferase (FTase) and the amounts of farnesylated p21 Ras in fetal tissues in the ovine experimental model. Induction of fetal hyperinsulinemia by direct infusion of insulin into the fetus and by either fetal or maternal infusions of glucose resulted in significant increases in the activity of FTase and the amounts of farnesylated p21 Ras in fetal liver, skeletal muscle, fat, and white blood cells. An additional infusion of somatostatin into hyperglycemic fetuses blocked fetal hyperinsulinemia and completely prevented these increases, specifying insulin as the causative factor. We conclude that the ability of fetal hyperinsulinemia to increase the size of the pool of farnesylated p21 Ras may prime fetal tissues to the action of other growth factors and thereby constitute one mechanism by which fetal hyperinsulinemia could induce macrosomia in diabetic pregnancies.
Effects of ischemia on sarcoplasmic reticulum Ca2+uptake and Ca2+release in rat skeletal muscle
Authors: Tupling R. , Green H. , Senisterra G. , Lepock J. , McKee N.
Published: December 2017

In this study, we investigated the hypothesis that prolonged ischemia would impair both sarcoplasmic reticulum (SR) Ca2+uptake and Ca2+release in skeletal muscle. To induce total ischemia (I), a tourniquet was placed around the upper hindlimb in 30 female Sprague-Dawley rats [wt = 256 ± 6.7 (SE) g] and inflated to 350 mmHg for 4 h. The contralateral limb served as control (C). Immediately after the 4 h of ischemia, mixed gastrocnemius and tibialis anterior muscle was sampled from both limbs, and both crude muscle homogenates and SR vesicles were prepared. In another 10 control animals (CC), muscles were sampled and prepared exactly the same way, but immediately after anesthetization. Ca2+uptake and Ca2+release were measured in vitro with Indo-I on both homogenates and SR vesicles. As hypothesized, submaximal Ca2+uptake was lower ( P < 0.05) in I compared with CC and C, by 25 and 45% in homogenates and SR vesicles, respectively. Silver nitrate (AgNO3)-induced Ca2+release, which occurred in two phases ( phase 1 and phase 2), was also altered in I compared with CC and C, in both muscle homogenates and SR vesicles. With ischemia, phase 1 peak Ca2+release was 26% lower ( P < 0.05) in SR vesicles only. For phase 2, peak Ca2+release was 54 and 24% lower ( P < 0.05) in SR vesicles and homogenates, respectively. These results demonstrate that prolonged skeletal muscle ischemia leads to a reduced SR Ca2+uptake in both homogenates and SR vesicles. The effects of ischemia on SR Ca2+release, however, depend on both the phase examined and the type of tissue preparation.
Recovery of13CO2from infused [1-13C]leucine and [1,2-13C2]leucine in healthy humans
Authors: Toth Michael J. , MacCoss Michael J. , Poehlman Eric T. , Matthews Dwight E.
Published: December 2017

Carbon (C) in the 1-position of leucine is released as CO2with the decarboxylation of α-ketoisocaproate (KIC). Carbon in the 2-position of leucine undergoes several additional metabolic steps before entering the tricarboxylic acid (TCA) cycle in the 1-position of acetyl-CoA, where it can be released as CO2or be incorporated into other compounds. This study examined the metabolic fate of C in the 2-position of leucine. We infused 11 healthy subjects with [1-13C]leucine and [1,2-13C2]leucine for 3.5–4 h to measure leucine kinetics and the oxidation of the tracers from enrichments of13C in blood and expired CO2. The fraction of leucine infused that was oxidized (fox) was used to define the degree of recovery of the13C label(s) for each tracer. As expected, leucine appearance (means ± SE) did not differ between tracers (13C1: 92.1 ± 3.1 vs.13C2: 89.2 ± 3.2 μmol · kg−1· h−1) when calculated using plasma leucine enrichments as an index of intracellular enrichment. A small (3%) but significant ( P = 0.048) difference between tracers was found when KIC was used to calculate leucine appearance (13C1: 118.0 ± 4.1 vs.13C2: 114.4 ± 4.5 μmol · kg−1· h−1). The value of foxwas 14 ± 1% for [1,2-13C2]leucine and was lower than the foxfor [1-13C]leucine (19 ± 1%). From the foxdata, we calculated that the recovery of the 2-13C label in breath CO2was 58 ± 6% relative to the 1-13C label. These findings show that, although a majority of the 2-13C label of leucine is recovered in breath CO2, a significant percentage (∼42%) is retained in the body, presumably by transfer to other compounds, via TCA exchange reactions.
Metabolic handling of intraduodenal vs. intravenous glucose in humans
Authors: Féry F. , Devière J. , Balasse E. O.
Published: December 2017

To determine whether the route of glucose administration affects whole body glucose metabolism, 14 healthy volunteers were randomly infused with intraduodenal (id) or intravenous (iv) glucose at 6 mg · kg−1 · min−1 for 180 min. Infused glucose was labeled with [2-3H]glucose in a first series of paired experiments designed to characterize kinetic parameters to be used in a second series of experiments in which [3-3H]- and [U-14C]glucose labeling was used to characterize the metabolic fate of infused glucose. Experiments with [2-3H]glucose showed that, after a lag period of only 20 min, id absorption averaged 105 ± 3% of infusion. During the final hour of id and iv infusion of [3-3H]glucose, tissue uptake averaged 98 ± 3 and 107 ± 4% of infusion, respectively, and was equally divided between glycolysis (3H2O production) and storage (uptake-glycolysis). Glucose oxidation (14CO2), total carbohydrate oxidation (indirect calorimetry), and net carbohydrate balance were also similar, but the thermic effect of glucose was significantly greater after id infusion. Because insulin and estimated portal vein glucose levels were similar during the final 80 min of both infusions, our results suggest that hepatic glucose storage (and therefore muscle storage estimated as whole body minus liver storage) is not affected by the route of glucose administration.
Inhibition of salivary secretion by lipopolysaccharide: possible role of prostaglandins
Authors: Lomniczi A. , Mohn C. , Faletti A. , Franchi A. , McCann S. M. , Rettori V. , Elverdin J. C.
Published: December 2017

Inducible (calcium-independent) nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) are important in the regulation of the function of different organs during infection. A single dose of lipopolysaccharide (LPS; 5 mg/kg ip) within 6 h increased NOS activity (20%) and prostaglandin E (PGE) content (100%) in submandibular glands (SMG) and blocked stimulated salivary secretion in adult male rats. The administration of an iNOS synthesis inhibitor, aminoguanidine (AG), with LPS decreased NOS activity and PGE content. Furthermore, the administration of meloxicam (MLX), an inhibitor of COX-2, blocked the increase in PGE and the production of NO. The incubation of slices of SMG in the presence of 3-morpholinosydnonimine, a donor of NO, increased the release of PGE highly significantly. The incubation of SMG in the presence of a PGE1 analog (alprostadil) increased the production of NO. These results indicate that LPS activates NOS, leading to NO release, which activates COX, generating PGEs that act back to further activate NOS, causing further generation of PGEs by activation of COX. Because the alprostadil administration inhibited stimulated salivation, LPS-induced inhibition of salivation appears to be caused by increased PGE production. Diminished salivary secretion produces poor oral health; thus the use of COX-2 inhibitors to counteract the effects of inhibited salivation should be considered.
Sulfate transport in porcine thyroid cells. Effects of thyrotropin and iodide
Authors: Cauvi David , Nlend Marie-Christine , Venot Nicole , Chabaud Odile
Published: December 2017

In porcine thyroid cells, thyroglobulin sulfation is controlled by thyrotropin (TSH) and iodide, which contribute to regulating the intracellular sulfate concentration, as we previously established. Here, we studied the transport of sulfate and its regulation by these two effectors. Kinetic studies were performed after [35S]sulfate was added to either the basal or apical medium of cell monolayers cultured without any effectors, or with TSH with or without iodide. The basolateral uptake rates were about tenfold higher than the apical uptake rates. TSH increased the basolateral and apical uptake values (by 24 and 9%, respectively, compared with unstimulated cells), and iodide inhibited these effects of TSH. On the basis of results of the pulse-chase experiments, the basolateral and apical effluxes appeared to be well balanced in unstimulated cells and in cells stimulated by both TSH and iodide: ∼40–50% of the intracellular radioactivity was released into each medium, whereas in the absence of iodide, 70% of the intracellular radioactivity was released on the basolateral side. The rates of transepithelial sulfate transport were increased by TSH compared with unstimulated cells, and these effects decreased in response to iodide. These results suggest that TSH and iodide may each control the sulfate transport process on two sides of the polarized cells, and that the absence of iodide in the TSH-stimulated cells probably results in an unbalanced state of sulfate transport.
Leucine and insulin activate p70 S6 kinase through different pathways in human skeletal muscle
Authors: Greiwe Jeffrey S. , Kwon Guim , McDaniel Michael L. , Semenkovich Clay F.
Published: December 2017

Amino acids and insulin have anabolic effects in skeletal muscle, but the mechanisms are poorly understood. To test the hypothesis that leucine and insulin stimulate translation initiation in human skeletal muscle by phosphorylating 70-kDa ribosomal protein S6 kinase (p70S6k), we infused healthy adults with leucine alone ( n = 6), insulin alone ( n= 6), or both leucine and insulin ( n = 6) for 2 h. p70S6k and protein kinase B (PKB) serine473phosphorylation were measured in vastus lateralis muscles. Plasma leucine increased from ∼116 to 343 μmol/l during the leucine-alone and leucine + insulin infusions. Plasma insulin increased to ∼400 pmol/l during the insulin-alone and leucine + insulin infusions and was unchanged during the leucine-alone infusion. Phosphorylation of p70S6k increased 4-fold in response to leucine alone, 8-fold in response to insulin alone, and 18-fold after the leucine + insulin infusion. Insulin-alone and leucine + insulin infusions increased PKB phosphorylation, but leucine alone had no effect. These results show that physiological concentrations of leucine and insulin activate a key mediator of protein synthesis in human skeletal muscle. They suggest that leucine stimulates protein synthesis through a nutrient signaling mechanism independent of insulin, raising the possibility that administration of branched-chain amino acids may improve protein synthesis in insulin-resistant states.
Metabolism of rabbit plasma-derived factor VII in relation to prothrombin in rabbits
Authors: Hatton Mark W. C. , Blajchman Morris A. , Sridhara Sampath , Southward Suzanne M. R. , Ross Bonnie , Kulzcycky Myron , Clarke Bryan J.
Published: December 2017

In the human circulation, factor VII is present in relatively low plasma concentration (0.01 μM) and has been reported to have a short half-life ( t½; 6 h). In contrast, prothrombin is present in a relatively high plasma concentration (2 μM) and has a relatively long catabolic half-life ( t½= ∼2–3 days). This report examines the metabolic characteristics of purified rabbit plasma factor VII and prothrombin, radiolabeled with125I and131I, respectively, in healthy young rabbits. From the plasma clearance curves of protein-bound radioactivities, fractional catabolic rates and compartmental distributions were calculated using a three-compartment model. Turnover of factor VII within the intravascular space (2.95 days) exceeded that of prothrombin (1.9 days). However, the whole body fractional catabolic rate of factor VII (0.34 days−1; catabolic t½= 2.04 days) was significantly slower than that of prothrombin (0.53 days−1; t½= 1.31 days). Furthermore, the fractional distributions of factor VII in the intravascular (0.14) and extravascular compartments (0.76) differed from those of prothrombin (0.29 and 0.53). Absolute quantities of factor VII and prothrombin catabolized by a 3-kg rabbit amounted to 0.18 and 24.0 mg/day, respectively (molar ratio of prothrombin to factor VII = 100). The molar ratio of catabolism was compared with the release rates of factor VII and prothrombin from rabbit livers perfused ex vivo. After correction for uptake of factor VII and prothrombin by the liver, the molar ratio of released prothrombin to factor VII in the perfusate was ∼293:1 over a 0.25- to 3-h interval. These results indicate that, compared with prothrombin, factor VII in the healthy rabbit circulates as a relatively long-lived protein. This behavior does not reflect that reported for factor VII in the human circulation.
Attenuation of age-related declines in glucagon-mediated signal transduction in rat liver by exercise training
Authors: Podolin Deborah A. , Wills Brandon K. , Wood Ian O. , Lopez Mark , Mazzeo Robert S. , Roth David A.
Published: December 2017

This study investigated alterations in glucagon receptor-mediated signal transduction in rat livers from 7- to 25-mo-old animals and examined the effects of exercise training on ameliorating these changes. Sixty-six young (4 mo), middle-aged (12 mo), and old (22 mo) male Fischer 344 rats were divided into sedentary and trained (treadmill running) groups. Isolated hepatic membranes were combined with [125I-Tyr10]monoiodoglucagon and nine concentrations of glucagon to determine maximal binding capacity (Bmax) and dissociation constant ( Kd). No alterations were found in Bmaxamong groups; however, middle-aged trained animals had significantly higher glucagon affinity (lower Kd; 21.1 ± 1.8 nM) than did their untrained counterparts (50.2 ± 7.1 nM). Second messenger studies were performed by measuring adenylyl cyclase (AC) specific activity under basal conditions and with four pharmacological stimulations to assess changes in receptor-dependent, G protein-dependent, and AC catalyst-dependent cAMP production. Age-related declines were observed in the old animals under all five conditions. Training resulted in increased cAMP production in the old animals when AC was directly stimulated by forskolin. Stimulatory G protein (Gs) content was reduced with age in the sedentary group; however, training offset this decline. We conclude that age-related declines in glucagon signaling capacity and responsiveness may be attributed, in part, to declines in intrinsic AC activity and changes in G protein [inhibitory G protein (Gi)/Gs] ratios. These age-related changes occur in the absence of alterations in glucagon receptor content and appear to involve both G protein- and AC-related changes. Endurance training was able to significantly offset these declines through restoration of the Gi/Gsratio and AC activity.
High-altitude acclimation increases the triacylglycerol/fatty acid cycle at rest and during exercise
Authors: McClelland Grant B. , Hochachka Peter W. , Reidy Shannon P. , Weber Jean-Michel
Published: December 2017

High-altitude acclimation alters lipid metabolism during exercise, but it is unknown whether this involves changes in rates of lipolysis or reesterification, which form the triacylglycerol/fatty acid (TAG/FA) cycle. We combined indirect calorimetry with [2-3H]glycerol and [1-14C]palmitate infusions to simultaneously measure total lipid oxidation, lipolysis, and rate of appearance (Ra) of nonesterified fatty acids (NEFA) in high-altitude-acclimated (HA) rats exercising at 60% maximal O2uptake (V˙o2 max). During exercise, relative total lipid oxidation (%V˙o2) equaled sea-level control (SL) values; however, acclimation greatly stimulated lipolysis (+75%) but had no effect on RaNEFA. As a result, TAG/FA cycling increased (+119%), due solely to an increase in recycling (+144%) within adipocytes. There was no change in either group in these variables with the transition from rest to exercise. We conclude that, in HA, 1) acclimation is a potent stimulator of lipolysis; 2) rats do not modify TAG/FA cycling with the transition to exercise; and 3) in normoxia, HA and SL derive the same fraction of their total energy from lipids and carbohydrates.
Amino acids and insulin are both required to regulate assembly of the eIF4E · eIF4G complex in rat skeletal muscle
Authors: Balage Michele , Sinaud Sandrine , Prod'Homme Magali , Dardevet Dominique , Vary Thomas C. , Kimball Scot R. , Jefferson Leonard S. , Grizard Jean
Published: December 2017

The respective roles of insulin and amino acids in regulation of skeletal muscle protein synthesis and degradation after feeding were examined in rats fasted for 17 h and refed over 1 h with either a 25 or a 0% amino acid/protein meal. In each nutritional condition, postprandial insulin secretion was either maintained (control groups: C25and C0) or blocked with diazoxide injections (diazoxide groups: DZ25and DZ0). Muscle protein metabolism was examined in vitro in epitrochlearis muscles. Only feeding the 25% amino acid/protein meal in the presence of increased plasma insulin concentration (C25group) stimulated protein synthesis and inhibited proteolysis in skeletal muscle compared with the postabsorptive state. The stimulation of protein synthesis was associated with increased phosphorylation of eukaryotic initiation factor (eIF)4E binding protein-1 (4E-BP1), reduced binding of eIF4E to 4E-BP1, and increased assembly of the active eIF4E · eIF4G complex. The p70 S6 kinase (p70S6k) was also hyperphosphorylated in response to the 25% amino acid/protein meal. Acute postprandial insulin deficiency induced by diazoxide injections totally abolished these effects. Feeding the 0% amino acid/protein meal with or without postprandial insulin deficiency did not stimulate muscle protein synthesis, reduce proteolysis, or regulate initiation factors and p70S6kcompared with fasted rats. Taken together, our results suggest that both insulin and amino acids are required to stimulate protein synthesis, inhibit protein degradation, and regulate the interactions between eIF4E and 4E-BP1 or eIF4G in response to feeding.
Body surface area prediction in normal-weight and obese patients
Authors: Livingston Edward H. , Lee Scott
Published: December 2017

None of the equations frequently used to predict body surface area (BSA) has been validated for obese patients. We applied the principles of body size scaling to derive an improved equation predicting BSA solely from a patient's weight. Forty-five patients weighing from 51.3 to 248.6 kg had their height and weight measured on a calibrated scale and their BSA calculated by a geometric method. Data were combined with a large series of published BSA estimates. BSA prediction with the commonly used Du Bois equation underestimated BSA in obese patients by as much as 20%. The equation we derived to relate BSA to body weight was a power function: BSA (m2) = 0.1173 × Wt (kg)0.6466. Below 10 kg, this equation deviated significantly from the BSA vs. body weight curve, necessitating a different set of coefficients: BSA (m2) = 0.1037 × Wt (kg)0.6724. Covariance of height and weight for patients weighing <80 kg reduced the Du Bois BSA-predicting equation to a power function, explaining why it provides good BSA predictions for normal-size patients but fails with obesity.
Impaired muscular contractile performance and adenine nucleotide handling in creatine kinase-deficient mice
Authors: Gorselink M. , Drost M. R. , Coumans W. A. , van Kranenburg G. P. J. , Hesselink R. P. , van der Vusse G. J.
Published: December 2017

Creatine kinase (CK) forms a small family of isoenzymes playing an important role in maintaining the concentration of ATP and ADP in muscle cells. To delineate the impact of a lack of CK activity, we studied contractile performance during a single maximal tetanic contraction and during 12 repeated tetanic contractions of intact dorsal flexors of CK knockout (CK−/−) mice. To investigate the effect on ATP regeneration, muscular high-energy phosphate content was determined at rest, immediately after the contraction series, and after a 60-s recovery period. Maximal torque of the dorsal flexors was significantly lower in CK−/− mice than in wild-type animals, i.e., 23.7 ± 5.1 and 33.3 ± 6.8 mN · m · g−1 wet wt, respectively. Lower muscle ATP (20.1 ± 1.4 in CK−/− vs. 28.0 ± 2.1 μmol/g dry wt in controls) and higher IMP (1.2 ± 0.5 in CK−/− vs. 0.3 ± 0.1 μmol/g dry wt in controls) levels at the onset of contraction may contribute to the declined contractility in CK−/− mice. In contrast to wild-type muscles, ATP levels could not be maintained during the series of 12 tetanic contractions of dorsal flexors of CK−/− mice and dropped to 15.5 ± 2.4 μmol/g dry wt. The significant increase in tissue IMP (2.4 ± 1.1 μmol/g dry wt) content after the contraction series indicates that ATP regeneration through adenylate kinase was not capable of fully compensating for the lack of CK. ATP regeneration via the adenylate kinase pathway is a likely cause of reduced basal adenine nucleotide levels in CK−/− mice.
Age-related decline in RMR in physically active men: relation to exercise volume and energy intake
Authors: Van Pelt Rachael E. , Dinneno Frank A. , Seals Douglas R. , Jones Pamela Parker
Published: December 2017

We tested the hypothesis that resting metabolic rate (RMR) declines with age in physically active men (endurance exercise ≥3 times/wk) and that this decline is related to weekly exercise volume (h/wk) and/or daily energy intake. Accordingly, we studied 137 healthy adult men who had been weight stable for ≥6 mo: 32 young [26 ± 1 (SE) yr] and 34 older (62 ± 1 yr) sedentary males (internal controls); and 39 young (27 ± 1 yr) and 32 older (63 ± 2 yr) physically active males (regular endurance exercise). RMR was measured by indirect calorimetry (ventilated hood system) after an overnight fast and ∼24 h after exercise. Because RMR is related to fat-free mass (FFM; r = 0.76, P < 0.001, current study), FFM was covaried to adjust RMR (RMRadj). RMRadjwas lower with age in both the sedentary (72.0 ± 2.0 vs. 64.0 ± 1.3 kcal/h, P < 0.01) and the physically active (76.6 ± 1.1 vs. 67.9 ± 1.2 kcal/h, P < 0.01) males. In the physically active men, RMRadjwas related to both exercise volume (no. of h/wk, regardless of intensity; r = 0.56, P < 0.001) and estimated energy intake ( r = 0.58, P < 0.001). Consistent with these relations, RMRadjwas not significantly different in subgroups of young and older physically active men matched either for exercise volume (h/wk; n = 11 each) or estimated energy intake (kcal/day; n = 6 each). These results indicate that 1) RMR, per unit FFM, declines with age in highly physically active men; and 2) this decline is related to age-associated reductions in exercise volume and energy intake and does not occur in men who maintain exercise volume and/or energy intake at a level similar to that of young physically active men.
Effect of ovarian hormones on mitochondrial enzyme activity in the fat oxidation pathway of skeletal muscle
Authors: Campbell S. E. , Febbraio M. A.
Published: December 2017

To examine the roles of 17β-estradiol (E2) and progesterone (Prog) in lipid metabolism, skeletal muscle enzyme activities were studied in female Sprague-Dawley rats. Groups included sham-operated rats (C) and ovariectomized rats treated with placebo (O), E2(E), Prog (P), both hormones at physiological doses (P + E), or both hormones with a high dose of E2(P + HiE). Hormone (or vehicle only) delivery was via time-release pellets inserted at the time of surgery, 15 days before metabolic testing. Results demonstrated that carnitine palmitoyltransferase maximal activity was 19, 21, and 19% lower ( P < 0.01) in O, P, and P + E rats, respectively, compared with C rats. Conversely, activity in E and P + HiE rats was 14 and 19% higher ( P < 0.01) than in C. β-Hydroxyacyl-CoA dehydrogenase (β-HAD) maximal activity was 20% lower ( P < 0.01) in O than in C rats; similarly, P and P + E rats were 18 and 19% lower, respectively ( P < 0.01); however, treatment with E2returned β-HAD activity to C levels. These results suggest that E2plays a role in lipid metabolism by increasing the maximal activity of key enzymes in the fat oxidative pathway of skeletal muscle.
Lipid deposition in rats centrally infused with leptin in the presence or absence of corticosterone
Authors: Arvaniti Konstantinia , Richard Denis , Picard Frédéric , Deshaies Yves
Published: December 2017

The aim of the present study was to assess whether the glucocorticoid corticosterone (Cort) modulates the effects of leptin on food intake and lipid deposition. Rats were subjected to a 6-day intracerebroventricular infusion of leptin and were either sham-adrenalectomized (Sham-ADX) or ADX and supplemented with 0 (C0), 40 (C40), or 80 mg (C80) of Cort. Investigation of potential peripheral sites of interaction of leptin and Cort included liver and plasma triglyceride (TG) content and lipoprotein lipase (LPL) activity in adipose and muscle tissues. The study confirmed the respective anorectic and orexigenic effects of leptin and Cort and revealed that the leptin-induced reduction in food intake was dampened by the high dose of Cort replacement. Such an interaction did not, however, extend to body and adipose tissue weights, which were lowered by leptin infusion independently of the Cort status. Leptin and ADX significantly reduced liver TG content and triglyceridemia, whereas Cort replacement significantly increased these variables. Central infusion of leptin also lowered plasma insulin levels, accompanied by a reduction in LPL activity of storage tissues (inguinal and epididymal white adipose tissue, 2- and 3-fold, respectively). In contrast, leptin infusion increased LPL activity in oxidative tissues (soleus and vastus lateralis muscles, 3- and 4-fold, respectively). Cort replacement prevented the ADX-induced fall in epididymal LPL activity but failed to do so in leptin-infused rats. The study demonstrates that, whereas the anorectic effect of leptin is dampened by high but physiological plasma levels of corticosterone, leptin can produce its effects on body weight, lipid transport and accumulation, and adipose and muscle LPL activity in the absence or presence of an intact hypothalamic-pituitary-adrenal axis.
An integrated2H and13C NMR study of gluconeogenesis and TCA cycle flux in humans
Authors: Jones John G. , Solomon Michael A. , Cole Suzanne M. , Sherry A. Dean , Malloy Craig R.
Published: December 2017

Hepatic glucose synthesis from glycogen, glycerol, and the tricarboxylic acid (TCA) cycle was measured in five overnight-fasted subjects by1H,2H, and13C NMR analysis of blood glucose, urinary acetaminophen glucuronide, and urinary phenylacetylglutamine after administration of [1,6-13C2]glucose,2H2O, and [U-13C3]propionate. This combination of tracers allows three separate elements of hepatic glucose production (GP) to be probed simultaneously in a single study: 1) endogenous GP, 2) the contribution of glycogen, phospho enolpyruvate (PEP), and glycerol to GP, and 3) flux through PEP carboxykinase, pyruvate recycling, and the TCA cycle. Isotope-dilution measurements of [1,6-13C2] glucose by1H and13C NMR indicated that GP in 16-h-fasted humans was 10.7 ± 0.9 μmol · kg−1· min−1.2H NMR spectra of monoacetone glucose (derived from plasma glucose) provided the relative2H enrichment at glucose H-2, H-5, and H-6 S, which, in turn, reflects the contribution of glycogen, PEP, and glycerol to total GP (5.5 ± 0.7, 4.8 ± 1.0, and 0.4 ± 0.3 μmol · kg−1· min−1, respectively). Interestingly,13C NMR isotopomer analysis of phenylacetylglutamine and acetaminophen glucuronide reported different values for PEP carboxykinase flux (68.8 ± 9.8 vs. 37.5 ± 7.9 μmol · kg−1· min−1), PEP recycling flux (59.1 ± 9.8 vs. 27.8 ± 6.8 μmol · kg−1· min−1), and TCA cycle flux (10.9 ± 1.4 vs. 5.4 ± 1.4 μmol · kg−1· min−1). These differences may reflect zonation of propionate metabolism in the liver.
Effects of 4-h ischemia and 1-h reperfusion on rat muscle sarcoplasmic reticulum function
Authors: Tupling R. , Green H. , Senisterra G. , Lepock J. , McKee N.
Published: December 2017

To investigate the hypothesis that ischemia and reperfusion would impair sarcoplasmic reticulum (SR) Ca2+regulation in skeletal muscle, Sprague-Dawley rats ( n = 20) weighing 290 ± 3.5 g were randomly assigned to either a control control (CC) group, in which only the effects of anesthetization were studied, or to a group in which the muscles in one hindlimb were made ischemic for 4 h and allowed to recover for 1 h (I). The nonischemic, contralateral muscles served as control (C). Measurements of Ca2+-ATPase properties in homogenates and SR vesicles, in mixed gastrocnemius and tibialis anterior muscles, indicated no differences between groups on maximal activity, the Hill coefficient, and Ca50, defined as the Ca2+concentration needed to elicit 50% of maximal activity. In homogenates, Ca2+uptake was lower ( P < 0.05) by 20–25%, measured at 0.5 and 1.0 μM of free Ca2+([Ca2+]f) in C compared with CC. In SR vesicles, Ca2+uptake was lower ( P < 0.05) by 30–38% in I compared with CC at [Ca2+]fbetween 0.5 and 1.5 μM. Silver nitrate induced Ca2+release, assessed during both the initial, early rapid ( phase 1), and slower, prolonged late ( phase 2) phases, in homogenates and SR vesicles, indicated a higher ( P < 0.05) release only in phase 1in SR vesicles in I compared with CC. These results indicate that the alterations in SR Ca2+regulation, previously observed after prolonged ischemia by our group, are reversed within 1 h of reperfusion. However, the lower Ca2+uptake observed in long-term, nonischemic homogenates suggests that altered regulation may occur in the absence of ischemia.
N-glycosylation of CRF receptor type 1 is important for its ligand-specific interaction
Authors: Assil Iman Q. , Abou-Samra Abdul B.
Published: December 2017

The corticotropin-releasing factor (CRF) receptor type 1 (CRFR1) contains five potential N-glycosylation sites: N38, N45, N78, N90, and N98. Cells expressing CRFR1 were treated with tunicamycin to block receptor glycosylation. The nonglycosylated receptor did not bind the radioligand and had a decreased cAMP stimulation potency in response to CRF. To determine which of the polysaccharide chain(s) is/are involved in ligand interaction, the polysaccharide chains were deleted using site-directed mutagenesis of the glycosylation consensus, N-X-S/T. Two sets of mutations were performed for each glycosylation site: N to Q and S/T to A, respectively. The single mutants Q38, Q45, Q78, Q90, Q98, A40, A47, A80, A92, and A100 and the double mutants A40/A47 and A80/A100 were well expressed, bound CRF, sauvagine (SVG), and urotensin-I (UTS-I) with a normal affinity, and increased cAMP accumulation with a high efficiency. In contrast, the combined mutations A80/A92/A100, A40/A80/A92/A100, and A40/A47/A80/A92/A100 had low levels of expression, did not bind the radioligand, and had a decreased cAMP stimulation. These data indicate the requirement for three or more polysaccharide chains for normal CRFR1 function.
Glucose uptake and glucose transporter proteins in skeletal muscle from undernourished rats
Authors: Agote María , Goya Luis , Ramos Sonia , Alvarez Carmen , Gavete M. Lucía , Pascual-Leone Ana M. , Escrivá Fernando
Published: December 2017

Undernutrition in rats impairs secretion of insulin but maintains glucose normotolerance, because muscle tissue presents an increased insulin-induced glucose uptake. We studied glucose transporters in gastrocnemius muscles from food-restricted and control anesthetized rats under basal and euglycemic hyperinsulinemic conditions. Muscle membranes were prepared by subcellular fractionation in sucrose gradients. Insulin-induced glucose uptake, estimated by a 2-deoxyglucose technique, was increased 4- and 12-fold in control and food-restricted rats, respectively. Muscle insulin receptor was increased, but phosphotyrosine-associated phosphatidylinositol 3-kinase activity stimulated by insulin was lower in undernourished rats, whereas insulin receptor substrate-1 content remained unaltered. The main glucose transporter in the muscle, GLUT-4, was severely reduced albeit more efficiently translocated in response to insulin in food-deprived rats. GLUT-1, GLUT-3, and GLUT-5, minor isoforms in skeletal muscle, were found increased in food-deprived rats. The rise in these minor glucose carriers, as well as the improvement in GLUT-4 recruitment, is probably insufficient to account for the insulin-induced increase in the uptake of glucose in undernourished rats, thereby suggesting possible changes in other steps required for glucose metabolism.
Effects of acetate infusion and hyperoxia on muscle substrate phosphorylation after onset of moderate exercise
Authors: Evans Melissa K. , Savasi Ingrid , Heigenhauser George J. F. , Spriet Lawrence L.
Published: December 2017

This study investigated whether increased muscle acetylcarnitine provision (acetate infusion) or hyperoxia (100% O2) would increase the rate of oxidative phosphorylation and reduce the reliance on muscle substrate phosphorylation after the onset of moderate exercise. Eight subjects completed three randomized trials, each separated by 1 wk: 1) saline infusion for 1 h before exercise, while breathing room air for 20 min before exercise and during 120 s of cycling at 65% maximal exercise (V˙o2 max) (CON), 2) saline infusion with 4 mmol/kg body wt sodium acetate, while breathing room air before and during exercise (ACE), and 3) saline infusion and breathing 100% O2before and during exercise (HYP). Muscle biopsies were sampled at rest and after 30 and 120 s of exercise. ACE increased muscle acetyl-CoA and acetylcarnitine contents at rest vs. CON and HYP [22.9 ± 2.8 vs. 8.9 ± 2.4 and 10.5 ± 1.8 μmol/kg dry muscle (dm); 11.0 ± 1.2 vs. 3.5 ± 1.3 and 4.0 ± 1.2 mmol/kg dm]. Acetate had no effect on resting pyruvate dehydrogenase activity in the active form (PDHa) among CON, ACE, and HYP. During exercise, acetyl-CoA and acetylcarnitine were unchanged in ACE but increased over time in the CON and HYP trials, and PDHaincreased similarly in all trials. Muscle phosphocreatine use, lactate accumulation, and substrate phosphorylation energy provision after 30 or 120 s of exercise were similar in all trials. In summary, increased acetylcarnitine availability did not accelerate the rate of oxidative phosphorylation at the onset of exercise, suggesting that this is not a site of extra substrate. Hyperoxia had no effect on substrate phosphorylation, suggesting that O2availability does not limit oxidative phsophorylation at the onset of moderate exercise.
IGFBP-3 binding to endothelial cells inhibits plasmin and thrombin proteolysis
Authors: Booth B. A. , Boes M. , Dake B. L. , Knudtson K. L. , Bar R. S.
Published: December 2017

Insulin-like growth factor-binding protein (IGFBP)-3 contains a highly basic COOH-terminal heparin-binding region, the P3 region, which is thought to be important in the binding of IGFBP-3 to endothelial cells. IGFBP-3 and IGFBP-4, and their chimeras IGFBP-34 and IGFBP-43, were treated with plasmin and with thrombin, proteases known to cleave IGFBP-3. IGFBP-3 was highly susceptible to plasmin, whereas IGFBP-4 was less so. Substitution of the P3 region for the P4 region in IGFBP-4 (IGFBP-43) increased the ability of the protease to digest IGFBP-43; substitution of the P4 region for the P3 region in IGFBP-3 (IGFBP-34) decreased the digestion of IGFBP-34. When 125I-labeled IGFBP-3 or125I-IGFBP-43 was first bound to vascular endothelial cells, subsequent proteolysis by either plasmin or thrombin was substantially inhibited. Proteolysis of125I-IGFBP-34 was not inhibited in the presence of endothelial cells. The P3 peptide was cleaved by plasmin but not by thrombin. We conclude that the P3 region is central to proteolysis of IGFBP-3 by plasmin and thrombin, processes which were inhibited by association of IGFBP-3 with endothelial cells.
Control of glycolysis in contracting skeletal muscle. I. Turning it on
Authors: Crowther Gregory J. , Carey Michael F. , Kemper William F. , Conley Kevin E.
Published: December 2017

Why does the onset of glycolytic flux in muscle lag the start of exercise? We tested the hypothesis that both elevated metabolite levels and muscle activity are required for flux to begin. Glycolytic flux was determined from changes in muscle pH, phosphocreatine concentration, and Piconcentration ([Pi]) as measured by31P magnetic resonance spectroscopy. Eight subjects performed rapid ankle dorsiflexions to ∼45% of maximal voluntary contraction force under ischemia at a rate of 1 contraction/s. Subjects completed two bouts of exercise separated by 1 min of ischemic rest. Glycolytic flux was activated by 27 s in the first bout, ceased during the ischemic rest period, and was activated more quickly in the second bout. Because the onset in both bouts occurred at approximately the same [Pi], ADP concentration, and AMP concentration, the activation of glycolysis appears to be related to the elevation of these metabolite concentrations. However, because no glycolytic flux occurred at rest, even when metabolite levels were high, both muscle activity and elevated metabolites are needed to turn on this pathway. We conclude that the delayed onset of glycolytic flux during exercise reflects the time needed to raise metabolites to flux-activating levels.
Cardiac rhythmicity among NTS neurons and its relationship to sympathetic outflow in rabbits
Authors: Hayward L. F. , Felder R. B.
Published: December 2017

The caudal nucleus tractus solitarius (NTS) is the primary termination site for baroreceptor afferents, but distinct pulse phasic activity is rarely recorded from NTS neurons. In the present study cross-correlation analysis was used to identify pulse phasic activity in NTS neurons in the anesthetized rabbit. Cross-correlation analysis demonstrated that 19 of 38 pressure-sensitive neurons had activity that correlated with the cardiac cycle, including 5 of 11 neurons activated by aortic depressor nerve stimulation, and 12 of 28 pressure-sensitive NTS neurons had activity that correlated with renal sympathetic nerve activity. Autocorrelation analysis identified 17 of 38 pressure-sensitive neurons that had rhythmic activity not related to the cardiac cycle (mean frequency 14.1 +/- 2 Hz). The results indicate that many NTS neurons do have pulse phasic activity consistent with baroreceptor input, but this activity is difficult to detect because it is distributed throughout the cardiac cycle.
Recognition of consensus CHO structure in ligands for selectins by novel antibody against sialyl Lewis X
Authors: Tamatani T. , Suematsu M. , Tezuka K. , Hanzawa N. , Tsuji T. , Ishimura Y. , Kannagi R. , Toyoshima S. , Homma M.
Published: December 2017

The selectins (L, E, and P) play an important role in the earliest events of the inflammatory response, leading to the “rolling” phenomenon. All selectins react with sialyl Lewis X (SLex) in vitro, possibly suggesting that their ligands have a consensus structure. 2H5 is a monoclonal antibody against SLex that blocks L-selectin-mediated adhesion. 2H5 inhibited adhesion of HL-60 cells to P- and E-selectin-producing COS cells in vitro and immunoprecipitated a P-selectin glycoprotein ligand-1-like glycoprotein from HL-60 cell lysate, suggesting that it recognizes a functional consensus structure on the ligands for all selectins. 2H5 reacted not only with human but also with rat and mouse neutrophils. 2H5 is the first antibody against SLex that recognizes neutrophils of nonhuman mammals. The carbohydrate structure recognized by 2H5 was present not only on high endothelial venules of rat lymphoid organs but also on the endothelial cells of nonlymphoid organs. Furthermore, administration of the antibody markedly inhibited L- and P-selectin-mediated neutrophil rolling and adhesion in rat mesenteric venules in vivo. These results provide evidence for the presence of a consensus carbohydrate structure on the ligands for all selectins. The consensus structure thus has the potential to serve as a therapeutic target.
Various cells release a stable small molecule that inhibits endothelium-dependent relaxation
Authors: Liu J. J. , Xie B. , Thurlow P. J. , Wiley J. S. , Chen J. R.
Published: December 2017

Previous studies have shown that neutrophils release a stable factor that inhibits endothelium-dependent relaxation. In the present studies, the effects of supernatants derived from various cells on endothelium-dependent relaxation were studied. Cells were obtained from seven sources: human hematopoietic cells including mononuclear leukocytes (MONO), polymorphonuclear leukocytes (PMNs), and chronic lymphocytic leukemia (CLL) cells; cells of the cardiovascular system including human endothelial cell line ECV304, human smooth muscle cells, and rat myocardial cells; and the tumor cell line HPB. These isolated or cultured cells were incubated for 1 h in Krebs solution to release the factor. The results showed that the supernatants from 10(5) cells/ml of all cells except the tumor cell line HPB produced a potent inhibitory effect on endothelium-dependent relaxation of rat aortic rings in response to acetylcholine and Ca2+ ionophores A23187 and ionomycin but not on endothelium-independent relaxation to nitroprusside and glyceryl trinitrate. When the concentration increased to 10(6) cell/ml, the supernatants from the tumor cell line HPB also slightly but significantly inhibited endothelium-dependent relaxation. The potency order was PMNs = MONO = CLL cells > cardiac cells > smooth muscle cells > the endothelial cell line ECV304 > the tumor cell line HPB. It seems that the hematopoietic cells and the cardiac cells are more active in release of the factor. The effect of this factor was rapid in onset and hard to wash out. A cyclooxygenase inhibitor or a thromboxane A2-prostaglandin H2 receptor antagonist partially but significantly reduced the effect of the factor.(ABSTRACT TRUNCATED AT 250 WORDS)