bluuebunny/crossref_metadata_2025 huggingface dataset:
Involvement of organum vasculosum of lamina terminalis and preoptic area in interleukin 1 beta-induced ACTH release
Authors: Katsuura G. , Arimura A. , Koves K. , Gottschall P. E.
Published: December 2017

Intravenous administration of recombinant human interleukin 1 beta (IL-1 beta, 1 micrograms/100 g body wt) resulted in a marked elevation of plasma adrenocorticotropic hormone (ACTH) levels, with peak levels at 10 min, in conscious unrestrained rats. One week after the placement of a lesion by radiofrequency or microinjection of kainic acid in the organum vasculosum of lamina terminalis (OVLT) but not in subfornical organ, ACTH response to intravenous IL-1 beta was enhanced, whereas both radiofrequency-induced lesion and kainic acid in the preoptic area (POA) suppressed the response. Indomethacin or a prostaglandin E (PGE) antagonist microinjected into the OVLT or POA suppressed or abolished the response. On the other hand, PGE, but not PGD2, microinjected into the POA increased plasma ACTH levels. These results suggest an important role for the OVLT, which lacks blood-brain barrier, as a possible site of entry of blood-borne IL-1 beta into the brain and for the POA, which may contain the neurons required for the response. Involvement of PGE in the OVLT and POA in the ACTH response to intravenous IL-1 beta is also suggested.
Importance of blood glucose concentration in regulating lipolysis during fasting in humans
Authors: Klein S. , Holland O. B. , Wolfe R. R.
Published: December 2017

The importance of the decline in blood glucose concentration on lipolysis and the lipolytic effect of epinephrine was evaluated during short-term fasting. Lipolytic rates were determined by infusing [2H5]glycerol and [1-13C]palmitic acid. Five volunteers were studied after 12 h of fasting before and during epinephrine infusion and after 84 h of fasting, before and during glucose infusion when plasma glucose was restored to postabsorptive values, and during glucose plus epinephrine infusion. In another protocol, five volunteers were given glucose intravenously throughout fasting to maintain plasma glucose at postabsorptive levels and isotopic studies were performed after 12 and 84 h of fasting before and during epinephrine infusion. Glucose infusion after 84 h of fasting restored glucose and insulin concentrations and lipolytic rates toward 12-h fasting values. When euglycemia was maintained throughout fasting, plasma insulin still declined (P less than 0.05) and lipolytic rates still increased (P less than 0.05). Despite similar glucose concentrations, the lipolytic response to epinephrine infusion was greater after 84 h than after 12 h of fasting in both protocols (P less than 0.05). These studies demonstrate that the decline in plasma glucose contributes to, but is not required for, the increase in lipolysis during fasting. The increase in epinephrine-stimulated lipolysis that occurs during fasting is not dependent on a decrease in plasma glucose concentration.
Exercise increases susceptibility of muscle glucose transport to activation by various stimuli
Authors: Cartee G. D. , Holloszy J. O.
Published: December 2017

The insulin sensitivity of glucose transport in skeletal muscle is enhanced after exercise. In this study, stimulation of transport of the nonmetabolizable glucose analogue 3-O-methylglucose by the insulin-mimetic agents vanadate and H2O2 was markedly enhanced in rat epitrochlearis muscles 18 h after a bout of swimming. This increase in susceptibility of the glucose transport process in muscle to stimulation by insulin-mimetic agents that act beyond the insulin-binding step provides evidence that the increased insulin sensitivity results from an effect of exercise on a later step in the activation of glucose transport. Hypoxia and insulin appear to stimulate glucose transport by different pathways in muscle as evidenced by an additivity of their maximal effects. The effect of a submaximal hypoxic stimulus on muscle sugar transport was greatly amplified 3 h after exercise. This increase in susceptibility of glucose transport to stimulation by hypoxia after exercise suggests that the increased sensitivity is not limited to the insulin sensitive pathway. In contrast to exercise (i.e., swimming), in vitro muscle contractions did not result in an increase in sensitivity of muscle glucose transport to insulin, raising the possibility that a humoral factor is necessary for this effect.
Stimulation of porcine thyroid cell alkalinization and growth by EGF, phorbol ester, and diacylglycerol
Authors: Takasu N. , Komiya I. , Nagasawa Y. , Asawa T. , Shinoda T. , Yamada T. , Shimizu Y.
Published: December 2017

We studied the effects of epidermal growth factor (EGF), 12-O-tetradecanoylphorbol-13-acetate (TPA), and 1-oleoyl-2-acetyl-glycerol (OAG) on cytoplasmic pH (pHi) and cell growth in cultured porcine thyroid cells. pHi was measured using 2',7'-bis(2-carboxyethyl-5,6-carboxyfluorescein (BCECF), an internalized fluorescent pH indicator. EGF, TPA, and OAG alkalinized the thyroid cells and stimulated their growth. These EGF-, TPA-, and OAG-stimulated cell alkalinization and growth depended on extracellular Na concentrations and were inhibited by amiloride, an inhibitor of Na(+)-H+ exchanger, indicating that EGF-, TPA-, and OAG-stimulated cell alkalinization and growth may occur through activation of Na(+)-H+ exchange. Alkalinization seems to be involved in thyroid cell growth. TPA (a tumor-promoting phorbol ester) and OAG (synthetic diacylglycerol), both potent activators of protein kinase C, imitate the action of EGF in rapidly elevating pHi and stimulating cell growth in thyroid cells. Trifluoperazine, an inhibitor of protein kinase C, inhibited EGF-, TPA-, and OAG-stimulated cell alkalinization and growth. The data suggest that activation of protein kinase C may be involved in the mechanism of EGF-stimulated cell alkalinization and growth of the thyroid cells.
Differential regulation of corticotropin-releasing hormone mRNA in rat brain
Authors: Frim D. M. , Robinson B. G. , Pasieka K. B. , Majzoub J. A.
Published: December 2017

Corticotropin-releasing hormone (CRH), a major hypothalamic component of the hypothalamic-pituitary-adrenal axis, has been localized to both the paraventricular nucleus (PVN) and cerebral cortex. Adrenalectomy causes an increase in PVN CRH content, whereas its effect on cortical CRH content is not clear. In the present study, adrenalectomy resulted in a threefold rise in the CRH mRNA content of anatomic micropunches of the PVN of individual rats (P less than 0.001), which was abolished by dexamethasone replacement. In parietal cortex, adrenalectomy did not affect CRH mRNA content, whereas hypophysectomy resulted in a twofold rise in CRH mRNA content (P less than 0.02), which was not significantly reduced by dexamethasone replacement. These results demonstrate that the CRH gene is negatively regulated by glucocorticoid in the PVN but not in cerebral cortex and that the increase in cortical CRH mRNA content after hypophysectomy may be evidence for negative regulation of cortical CRH gene expression by a second pituitary-dependent factor other than glucocorticoid.
[1-13C; methyl-2H3]methionine kinetics in humans: methionine conservation and cystine sparing
Authors: Storch K. J. , Wagner D. A. , Burke J. F. , Young V. R.
Published: December 2017

Methionine (Met) conservation in healthy young adult men (4/diet group) was explored by supplying one of the following three L-amino acid based diets: 1) adequate Met but no cystine; 2) neither Met nor cystine; or 3) no Met but cystine supplementation. After 5 days, subjects received a continuous intravenous infusion of L-[1-13C; methyl-2H3]Met for 5 h while the diet was given as small isocaloric isonitrogenous meals. Estimates were made of rates of Met incorporation into protein synthesis (S) and release from body proteins (B), transmethylation (TM), remethylation of homocysteine (RM), and transsulfuration (TS). For the adequate Met diet, the rates were S = 24 +/- 2, B = 18 +/- 1, TM = 12.4 +/- 1.7, RM = 4.7 +/- 1.1, and TS = 7.6 +/- 0.6 (SE) mumol.kg-1.h-1. The sulfur amino acid-devoid diet significantly (P less than 0.05) reduced S, TM, RM, and TS. Supplementation of this diet with cystine reduced Met oxidation (P = 0.05). Therefore, two loci are quantitatively important regulatory points in Met conservation in vivo: 1) the distribution of Met between the pathways of protein anabolism and TM (Met locus) and 2) the distribution of homocysteine between RM and TS (homocysteine locus).
Cerebral blood flow and substrate utilization in insulin-treated diabetic subjects
Authors: Grill V. , Gutniak M. , Bjorkman O. , Lindqvist M. , Stone-Elander S. , Seitz R. J. , Blomqvist G. , Reichard P. , Widen L.
Published: December 2017

We compared regional cerebral blood flow (rCBF) and arteriojugular vein differences of glucose, ketones, glycerol, lactate, pyruvate, and O2 in eight subjects with well-controlled insulin-dependent diabetes mellitus (IDDM) and in six healthy volunteers. Duration of diabetes was 19.4 +/- 2.1 yr. Measurements were performed before and after 120 min of insulin infusion and concomitant Biostator-controlled normoglycemia. Net uptake of ketones was seen in IDDM subjects before but not after insulin. Net uptake of glucose did not differ significantly between groups. During normoglycemia the molar ratio of O2 to glucose uptake was lower in IDDM than in nondiabetic subjects (4.68 vs. 5.50; P less than 0.05; Wilcoxon test). Small but significant release of lactate and pyruvate was seen in IDDM but not in nondiabetic subjects. The rCBF was measured by 11CH3F and position emission tomography. Global mean CBF was higher in IDDM subjects (64.9 +/- 5.9 vs. 49.3 +/- 2.7 ml.100 g-1.min-1, means +/- SE in nondiabetic subjects, P less than 0.05). rCBF was enhanced in many cortical and subcortical areas, whereas it was decreased in the head of the caudate nucleus. Neuropsychological testing did not reveal obvious cognitive dysfunction. The results imply that a larger fraction of glucose is nonoxidatively metabolized in the IDDM subjects and furthermore indicate an abnormal rCBF pattern in these subjects.
Validation of two-pool model for in vivo ketone body kinetics
Authors: Bailey J. W. , Haymond M. W. , Miles J. M.
Published: December 2017

Previous studies have indicated that simultaneous infusions of two ketone body tracers ([13C]acetoacetate and [14C]beta-hydroxybutyrate) provide accurate estimates of exogenous ketone body inflow when an open two-pool model is employed. In the present studies, net hepatic ketone body production was determined from surgically placed arterial, portal venous, and hepatic venous catheters in conscious diabetic (n = 6) and 4-day fasted (n = 7) dogs. [13C]acetoacetate and [14C]beta-hydroxybutyrate were infused simultaneously, and ketone body production was calculated from either acetoacetate (AcAc) single-isotope data, beta-hydroxybutyrate (beta-OHB) single-isotope data, the sum of individual fluxes, or the two-pool model. In fasted animals, both the AcAc single-isotope calculation and the sum of individual fluxes overestimated net hepatic production by approximately 50% (P less than 0.05), whereas the beta-OHB single-isotope calculation and the two-pool model gave accurate estimates. In the diabetic animals, the beta-OHB single-isotope calculation underestimated net hepatic production by approximately 30% (P less than 0.05). The sum of individual fluxes overestimated net hepatic production by approximately 46% (P less than 0.05), whereas both the AcAc single-isotope calculation and the two-pool model gave accurate estimates. In conclusion, single-isotope methods give erroneous estimates of net hepatic production of ketone bodies. In contrast, a two-pool model provided an accurate estimate of net hepatic production and thus appears to be suitable for determination of ketone body kinetics in humans.
Endothelin receptors in human placenta: relationship to vascular resistance and thromboxane release
Authors: Wilkes B. M. , Mento P. F. , Hollander A. M. , Maita M. E. , Sung S. , Girardi E. P.
Published: December 2017

This investigation was performed to study the potential role of endothelin in the modulation of fetoplacental vascular resistance in the human placenta. Full-term placentas from uncomplicated pregnancies were studied within 30 min of delivery. The umbilical artery and vein to a single placental cotyledon were cannulated and the artery perfused with RPMI media (0.82 ml/min). Endothelin 1 caused a sustained dose-dependent increase in perfusion pressure. Infused endothelin 1 (50 nM) stimulated thromboxane release 2.3-fold compared with basal values. Thromboxane release persisted for 15 min after discontinuation of endothelin. Properties of human placental endothelin 1 receptors were defined in binding studies performed on a crude membrane fraction of placental cotyledons. Binding was saturable, reached steady state by 3 h at 25 degrees C, and was linear with protein concentration. Scatchard analysis of binding data indicated a single class of high-affinity binding sites with a Kd of 36.1 +/- 9.7 pM and a density of 185.4 +/- 9.6 fmol/mg protein (n = 5). The potency order for competitive inhibition of the binding of 125I-labeled endothelin 1 was endothelin 1 greater than endothelin 2 = endothelin 3 = sarafotoxin S6b greater than big endothelin (human) = big endothelin (porcine). Phenylephrine, bradykinin, norepinephrine, atrial natriuretic factor, diltiazem, U46619, and angiotensin II did not displace 125I-endothelin 1 from its receptors. These experiments demonstrate that endothelin 1 is a potent pressor substance in the human fetoplacental cotyledon. Pressor effects of endothelin may be mediated by a combination of direct effects and stimulation of vasoconstrictor prostanoids.
Hepatic apo B-100 lipoproteins and plasma LDL heterogeneity in African green monkeys
Authors: Murthy V. N. , Marzetta C. A. , Rudel L. L. , Zech L. A. , Foster D. M.
Published: December 2017

The contribution of hepatic apolipoprotein (apo) B-100 lipoproteins to plasma low-density lipoprotein (LDL) metabolic heterogeneity was examined in African green monkeys. Hepatic 3H-labeled very low-density lipoproteins (VLDL) (d less than 1.006, where d is density in g/ml) or hepatic 131I-labeled LDL (1.030 less than d less than 1.063) were isolated from perfused livers and injected simultaneously with autologous plasma 125I-LDL into African green monkeys. Serial blood samples were taken, and the distribution of radioactivity among various subfractions of apo B-100 lipoproteins was determined using density-gradient ultracentrifugation. Compartmental models were developed to describe simultaneously the kinetics of hepatic lipoproteins and plasma LDL. In five of seven studies, the metabolic behavior of LDL derived from radiolabeled hepatic lipoprotein precursors differed from the metabolic behavior of radiolabeled autologous plasma LDL. These differences could be described by different models supporting two hypotheses with different physiological interpretations: 1) lipoproteins of donor and recipient animals are kinetically distinct, and/or 2) plasma LDL derived from various potential sources are kinetically distinct. Compartmental modeling was used to test these hypotheses, which were not accessible to testing by conventional experimental methodologies. The kinetic analyses of these studies suggest that plasma LDL may be derived from a variety of precursors, including hepatic VLDL and hepatic LDL, with each source giving rise to metabolically distinct plasma LDL.
Role of insulin and branched-chain amino acids in regulating protein metabolism during fasting
Authors: Frexes-Steed M. , Warner M. L. , Bulus N. , Flakoll P. , Abumrad N. N.
Published: December 2017

This study examines the independent effects of insulin and amino acids on protein metabolism after a 12-h and 4-day fast in healthy volunteers. Leucine (Leu) kinetics were examined during sequential insulin infusions of 0 (group I) or 0.0125 (groups II and III), 1.2, and 10 mU.kg-1.min-1. Plasma Leu was maintained at 12-h fasted levels in groups I and II and at 84-h fasted levels in group III. Four-day fast (vs. 1 day, P less than 0.01) was associated with a 79% drop in plasma insulin and elevations in plasma Leu (122%), Leu rates of appearance (Ra) (21%), and Leu oxidation (56%), and no change in nonoxidative rates of disappearance (Rd). Insulin resulted in a dose-dependent suppression of endogenous Leu Ra with group III = I greater than II. Leu oxidation rose 1.7-fold in group III at the highest insulin dose but remained stable in the two other groups. In conclusion, 4-day fasting is associated with enhanced proteolysis and Leu oxidation with no change in nonoxidative Rd (protein synthesis). Elevated branched-chain (and other) amino acids were required to restore tissue sensitivity and specificity to the effects of insulin on protein metabolism after 4 days of fasting.
Effect of exercise on insulin action, glucose tolerance, and insulin secretion in aging
Authors: Kahn S. E. , Larson V. G. , Beard J. C. , Cain K. C. , Fellingham G. W. , Schwartz R. S. , Veith R. C. , Stratton J. R. , Cerqueira M. D. , Abrass I. B.
Published: December 2017

To assess the effect of exercise training on the insulin resistance and impaired pancreatic B-cell function of aging, we studied 13 healthy older men (ages 61-82 yr) before and after 6 mo intensive endurance exercise. An index of insulin sensitivity (SI) was measured using Bergman's minimal model. Intravenous glucose tolerance was quantified using the glucose disappearance constant (KGlc) while oral glucose tolerance was assessed after a 100-g glucose load. B-cell function was evaluated by measuring the acute insulin response (AIR) to glucose injection at fasting glucose (AIRGlc) and the AIR to arginine at multiple clamped glucose levels. Exercise produced an endurance training effect as demonstrated by an 18% increase in maximum O2 consumption (VO2max) [38.2 +/- 1.4 to 45.0 +/- 1.1 (SE) ml.kg fat-free mass-1.min-1, P less than 0.001]. An unchanged fasting glucose (5.3 +/- 0.2 to 5.4 +/- 0.2 mM) despite a reduced fasting insulin (61 +/- 6 to 48 +/- 6 pM, P less than 0.01) suggested exercise training improved insulin sensitivity. This was confirmed by a 36% increase in SI from 3.47 +/- 0.41 to 4.71 +/- 0.42 x 10(-5) min-1/pM (P = 0.01). Intravenous glucose tolerance did not change as measured by KGlc, which was 1.46 +/- 0.09 before and 1.48 +/- 0.16%/min after exercise training. Likewise, the incremental glucose response to oral glucose (633 +/- 49-618 +/- 45 mM.min) was unchanged. B-cell function was decreased as reflected by AIRGlc (351 +/- 73-245 +/- 53 pM, P less than 0.01) and the AIRArg at maximal glycemic potentiation (AIRmax, 1,718 +/- 260-1,228 +/- 191 pM, P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)
Beta-adrenergic blockade decreases norepinephrine release in humans
Authors: Rosen S. G. , Supiano M. A. , Perry T. J. , Linares O. A. , Hogikyan R. V. , Smith M. J. , Halter J. B.
Published: December 2017

Beta-Adrenergic blockade with propranolol (PRP) has been reported to cause an increase in plasma norepinephrine (NE) levels in humans, which suggests that a reflex increase in sympathetic nervous system (SNS) vasoconstrictor tone compensates for the hypotensive effect of beta-adrenergic blockade. However, plasma NE levels are an indirect measure of SNS activity. We have developed a two-compartment model of NE kinetics to estimate NE release into an extravascular compartment as a more comprehensive measure of systemic SNS activity. To determine whether beta-adrenergic blockade alters extravascular NE release, we studied nine healthy subjects during sequential infusions of saline and PRP. During PRP infusion, there was an increase in plasma NE levels [1.03 +/- 0.13 to 1.27 +/- 0.21 (SE) nM; P = 0.05], but the extravascular NE release rate decreased significantly (15.5 +/- 1.6 to 9.2 +/- 1.2 nmol.min-1.m-2, P = 0.0002). The plasma NE concentration increased despite the fall in extravascular NE release rate primarily because the clearance of NE from plasma declined (1.55 +/- 0.08 to 1.18 +/- 0.07 l.min-1.m-2, P = 0.0001); the NE spillover rate into plasma did not change (1.73 +/- 0.18 to 1.75 +/- 0.23 nmol.min-1.m-2, P = 0.89). We conclude that PRP decreases extravascular NE release in humans. Suppression of SNS activity may be an additional mechanism of action of nonselective beta-adrenergic antagonists in humans.
Activation of PKC inhibits NaF-induced inositol phospholipid turnover in rat insulinoma cells
Authors: Yamatani T. , Yamaguchi A. , Nakamura A. , Morishita T. , Kadowaki S. , Fujita T. , Chiba T.
Published: December 2017

An investigation was done to elucidate the regulatory role of protein kinase C (PKC) in insulin release and also the effects of PKC activation on NaF-induced inositol phospholipid (PI) turnover in and insulin release from rat insulinoma cells (RINr). NaF stimulated insulin secretion in association with an increase in [3H]inositol phosphate formation in RINr cells. Furthermore, NaF induced a rapid decrease in 32P-labeling of phosphatidylinositol-4,5-diphosphate (PIP2) with a concomitant increase of [32P]phosphatidic acid in prelabeled cells. In contrast, NaF had no effect on cyclic AMP production. Although phorbol 12,13-dibutyrate (PDBu) also stimulated insulin release, on concomitant administration of NaF and PDBu, insulin secretion was clearly less than that expected on the basis of an additive action. Moreover, PDBu significantly inhibited NaF-enhanced PI turnover. However, this inhibition was abolished after downregulating PKC by pretreating RINr cells with PDBu. Thus NaF-induced insulin release from RINr cells appears to involve enhancement of PI turnover. Moreover, because NaF is known to activate guanine nucleotide binding proteins (G proteins) directly, PKC activation appears to induce a mechanism that inhibits stimulus-secretion coupling at a level between G protein and phospholipase C-induced PIP2 hydrolysis.
Glutamine transport and metabolism in denervated rat skeletal muscle
Authors: Hundal H. S. , Babij P. , Watt P. W. , Ward M. R. , Rennie M. J.
Published: December 2017

Rat skeletal muscle glutamine fell by 40% from 4.18 to 2.5 mumols/g wet weight (P less than 0.01) after 4 days of denervation. Over the same period net glutamine efflux from denervated hindlimbs [i.e., arteriovenous (a-v) concentration differences x blood flow] increased 3.5-fold (from -6.72 +/- 1.73 to -26 +/- 4.81 nmol.min-1.g-1, P less than 0.001). Gastrocnemius glutamine synthetase activity fell 48% after denervation (from 475 +/- 81 to 248 +/- 39 nmol.min-1.g-1, P less than 0.001), but glutaminase activity was not significantly altered (17 nmol.min-1.g-1). The maximal activity (Vmax) of the unidirectional Na(+)-dependent glutamine transporter (system Nm) was depressed by 45% from 1,020 +/- 104 to 571 +/- 9 nmol.min-1.g-1 (P less than 0.01), but the concentration at which transport was half maximal (Km) was not significantly altered (control 8.1 +/- 0.6 mM; denervated 6.52 +/- 0.12). Hindlimb denervation resulted in an increase of intramuscular Na+ by 17% and a fall of K+ by 12%, and the resting membrane potential in isolated muscles decreased from -75 +/- 10 to -59.5 +/- 5.5 mV. Membrane potential of perfused denervated muscle, isolated after acute addition of the Na+ channel blocker tetrodotoxin (TTX, 3 microM), repolarized to -66.4 +/- 3.2 mV. In perfused denervated preparations TTX caused an acute recovery of Vmax of unidirectional glutamine transport to 848 +/- 75 nmol.min-1.g-1; Km was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)
Bradykinin attenuates glucagon-induced leucine oxidation in humans
Authors: Hartl W. H. , Miyoshi H. , Jahoor F. , Klein S. , Elahi D. , Wolfe R. R.
Published: December 2017

Trauma and injury are associated with accelerated protein loss. Counterregulatory hormones are possible mediators of this response. In the present study, the effect of glucagon and glucagon plus bradykinin on leucine and urea kinetics was examined in nine normal volunteers during somatostatin infusion and basal insulin replacement. Bradykinin was given because of its prostaglandin-stimulating qualities and the potential anabolic action of prostaglandins. Physiological hyperglucagonemia elicited a small but significant reduction of total leucine flux and rate of urea synthesis. Simultaneously, leucine oxidation increased by 70%. The simultaneous infusion of bradykinin did not alter glucagon-related changes in urea or leucine kinetics. Bradykinin, however, significantly attenuated the stimulation of leucine oxidation by glucagon. These results suggest that glucagon and tissue factors are involved in controlling leucine metabolism in humans.
Rapid nongenomic inhibition of renal 25-hydroxyvitamin D3 1-hydroxylase by 1,25-dihydroxyvitamin D3
Authors: Dick I. M. , Retallack R. , Prince R. L.
Published: December 2017

The physiological role of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] in inhibition of its own formation remains obscure. This study utilizes a kidney slice system to study the effect of physiological concentrations of 1,25(OH)2D3 on 25-hydroxyvitamin D3 1-hydroxylase (1-hydroxylase) formation in vitamin D-replete rats fed a normal-phosphate (NP) or low-phosphate (LP) diet. In vitro, 1-hydroxylase activity was assessed by measuring 1,25(OH)2D3 accumulation at 30 or 60 min after addition of 25-hydroxyvitamin D3 substrate. Degradation of 1,25(OH)2D3 was also assessed over 60 min. Rats fed the LP diet had a threefold increase in 1-hydroxylase activity but the same rate of degradation of 1,25(OH)2D3 as those fed the NP diet. The addition of 50 pM 1,25(OH)2D3 caused a proportional inhibition of 1-hydroxylase in NP and LP rats when added before or 10 min after addition of substrate but not at later time points; 150 pM 1,25(OH)2D3 completely inhibited 1-hydroxylase in the NP but not the LP rats. This inhibitory effect was not reversed by actinomycin D or cycloheximide. These results indicate that physiological concentrations of 1,25(OH)2D3 directly and rapidly modulate 1-hydroxylase activity via a nongenomic mechanism in both LP and NP diet rats.
Characteristics of glutamine transport in sarcolemmal vesicles from rat skeletal muscle
Authors: Ahmed A. , Taylor P. M. , Rennie M. J.
Published: December 2017

Amino acid transport was measured in rat sarcolemmal vesicles (approximately 0.5 microliters/mg protein). Initial (45 s) uptake of glutamine tracer was stereospecific and saturable [Km 90 +/- 14 microM; maximum velocity (Vmax) 60 +/- 3 pmol.mg protein-1.min-1], it was Na+ dependent (but tolerated Li+ instead), and was stimulated by inside negative membrane potential. Transport of glutamine (5 microM) was inhibited by asparagine, histidine, alanine, serine, and phenylalanine at 1 mM (25-74%), but leucine and N-methylaminoisobutyric acid (MeAIB) did not significantly inhibit glutamine uptake. Glutamine efflux was accelerated by an outwardly directed Na+ concentration gradient. L-[14C]asparagine uptake was Na+ dependent and strongly inhibited by glutamine. L-[3H]serine uptake was Na+ dependent but did not tolerate Li(+)-for-Na+ substitution. L-[3H]phenylalanine uptake was Na+ independent. Differences between the ion dependence of glutamine, serine, and phenylalanine uptake and the lack of glutamine transport inhibition by MeAIB indicated that glutamine is not transported by systems ASC, L, or A. The properties of the glutamine transporter in sarcolemmal vesicles resemble those of the system Nm previously characterized in perfused skeletal muscle.
Effect of hypoinsulinemia and hyperglycemia on fetal glucose utilization
Authors: DiGiacomo J. E. , Hay W. W.
Published: December 2017

The present studies were performed to determine the effect of normal levels of insulin on fetal glucose metabolism and to measure the acute changes in insulin secretion and concentration that occur in response to a hyperglycemia stimulus. In fetal sheep, infusion of somatostatin alone decreased fetal insulin concentration 4 microU/ml (33%) from the basal value without a significant change in fetal glucose concentration, umbilical glucose uptake (UGU), or fetal glucose utilization rate (GUR). Glucose plus somatostatin infusion produced a significantly lower insulin concentration (54% lower, P less than 0.005) and GUR (22% lower, P less than 0.05) at glucose concentration approximately 40 mg/dl compared with glucose infusion alone. No significant difference was seen at glucose concentration of approximately 30 mg/dl. These results indicate that fetal glucose metabolism is responsive not only to changes in glucose but also insulin concentrations; however, a relatively large change in insulin (greater than 5 microU/ml) is necessary to produce a measurable response. These quantitative aspects of fetal insulin effect must be considered when assessing the role of insulin in the regulation of fetal glucose metabolism.
Total energy expenditure in burned children using the doubly labeled water technique
Authors: Goran M. I. , Peters E. J. , Herndon D. N. , Wolfe R. R.
Published: December 2017

Total energy expenditure (TEE) was measured in 15 burned children with the doubly labeled water technique. Application of the technique in burned children required evaluation of potential errors resulting from nutritional intake altering background enrichments during studies and from the high rate of water turnover relative to CO2 production. Five studies were discarded because of these potential problems. TEE was 1.33 +/- 0.27 times predicted basal energy expenditure (BEE), and in studies where resting energy expenditure (REE) was simultaneously measured, TEE was 1.18 +/- 0.17 times REE, which in turn was 1.16 +/- 0.10 times predicted BEE. TEE was significantly correlated with measured REE (r2 = 0.92) but not with predicted BEE. These studies substantiate the advantage of measuring REE to predict TEE in severely burned patients as opposed to relying on standardized equations. Therefore we recommend that optimal nutritional support will be achieved in convalescent burned children by multiplying REE by an activity factor of 1.2.
Glucose transporter protein content and glucose transport capacity in rat skeletal muscles
Authors: Henriksen E. J. , Bourey R. E. , Rodnick K. J. , Koranyi L. , Permutt M. A. , Holloszy J. O.
Published: December 2017

The relationships among fiber type, glucose transporter (GLUT-4) protein content, and glucose transport activity stimulated maximally with insulin and/or contractile activity were studied by use of the rat epitrochlearis (15% type I-20% type II2a-65% type IIb), soleus (84-16-0%), extensor digitorum longus (EDL, 3-57-40%), and flexor digitorum brevis (FDB, 7-92-1%) muscles. Insulin-stimulated 2-deoxy-D-glucose (2-DG) uptake was greatest in the soleus, followed (in order) by the FDB, EDL, and epitrochlearis. On the other hand, contractile activity induced the greatest increase in 2-DG uptake in the FDB, followed by the EDL, soleus, and epitrochlearis. The effects of insulin and contractile activity on 2-DG uptake were additive in all the muscle preparations, with the relative rates being FDB greater than soleus greater than EDL greater than epitrochlearis. Quantitation of the GLUT-4 protein content with the antiserum R820 showed the following pattern: FDB greater than soleus greater than EDL greater than epitrochlearis. Linear regression analysis showed that whereas a relatively low and nonsignificant correlation existed between GLUT-4 protein content and 2-DG uptake stimulated by insulin alone, significant correlations existed between GLUT-4 protein content and 2-DG uptake stimulated either by contractions alone (r = 0.950) or by insulin and contractions in combination (r = 0.992). These results suggest that the differences in maximally stimulated glucose transport activity among the three fiber types may be related to differences in their content of GLUT-4 protein.
Fluxes and membrane transport of amino acids in rat liver under different protein diets
Authors: Fafournoux P. , Remesy C. , Demigne C.
Published: December 2017

The aim of the present work was to evaluate in vivo the role of the transport step in hepatic amino acid metabolism. To vary hepatic utilization of amino acids, rats were adapted to diets containing various concentrations of casein (5, 15, and 60%). In rats fed 5 or 15% casein diets, Gln and Glu were released by the liver, and there was a significant uptake of Ala. Hepatic fluxes of amino acids increased considerably after adaptation to high-casein diet (up to 1.55 mumol.min-1.g liver-1 for Ala), because of the rise in afferent concentrations as well as enhanced uptake percentage (peaking at 60–75% for most glucogenic amino acids). Adaptation to a high-protein diet led to induction of not only system A but also of most of the other transport systems (Gly, anionic, T, y+, and to a lesser extent system N); only systems ASC and L were unchanged. The study of amino acid repartition between liver and plasma with different diets indicates that transport could modulate utilization of Ala, Ser, Thr, Gly, Gln, and Asp. For Arg and Asn, present in very low concentrations in liver under any condition, the transport step should be the major locus of control of their metabolism. For amino acids chiefly transported by nonconcentrative systems, such as aromatic amino acids, cellular metabolism could also be limited by the transport process. In conclusion, during adaptation to a high-protein diet, there is apparently a coordinated adaptation of amino acid transport and of their intracellular metabolism. For some amino acids, induction of catabolic enzymes seems greater than that of transport, so that the transport step may play an important role in control of metabolic fluxes. For example, concentration of amino acids such as Thr may be markedly depressed in rats adapted to a high-protein diet.
Dexamethasone increases glucose cycling, but not glucose production, in healthy subjects
Authors: Wajngot A. , Khan A. , Giacca A. , Vranic M. , Efendic S.
Published: December 2017

We established that measurement of glucose fluxes through glucose-6-phosphatase (G-6-Pase; hepatic total glucose output, HTGO), glucose cycling (GC), and glucose production (HGP), reveals early diabetogenic changes in liver metabolism. To elucidate the mechanism of the diabetogenic effect of glucocorticoids, we treated eight healthy subjects with oral dexamethasone (DEX; 15 mg over 48 h) and measured HTGO with [2-3H]glucose and HGP with [6-3H]glucose postabsorptively and during a 2-h glucose infusion (11.1 mumol.kg-1.min-1). [2-3H]- minus [6-3H]glucose equals GC. DEX significantly increased plasma glucose, insulin, C peptide, and HTGO, while HGP was unchanged. In controls and DEX, glucose infusion suppressed HTGO (82 vs. 78%) and HGP (87 vs. 91%). DEX increased GC postabsorptively (three-fold) P less than 0.005 and during glucose infusion (P less than 0.05) but decreased metabolic clearance and glucose uptake (Rd), which eventually normalized, however. Because DEX increased HTGO (G-6-Pase) and not HGP (glycogenolysis + gluconeogenesis), we assume that DEX increases HTGO and GC in humans by activating G-6-Pase directly, rather than by expanding the glucose 6-phosphate pool. Hyperglycemia caused by peripheral effects of DEX can also contribute to an increase in GC by activating glucokinase. Therefore, measurement of glucose fluxes through G-6-Pase and GC revealed significant early effects of DEX on hepatic glucose metabolism, which are not yet reflected in HGP.
Nitrogen sparing by 2-ketoisocaproate in parenterally fed rats
Authors: Yagi M. , Matthews D. E. , Walser M.
Published: December 2017

In rats receiving total parenteral nutrition with or without sodium 2-ketoisocaproate (KIC; 2.48 g.kg-1.day-1), L-[1-13C]leucine and [1–14C]KIC were constantly infused for 6 h. CO2 production, 14CO2 production, 13CO2 enrichment, urinary urea nitrogen (N) plus ammonia N and total urinary N were measured. Whole body protein synthesis (S) was calculated in non-KIC-infused rats and also in unfed rats infused with [1–14C]leucine from fractional oxidation of labeled leucine (1-F), where F is fractional utilization for protein synthesis, and urea N plus ammonia N excretion (C) as S = C x F/(1-F). Addition of KIC caused a significant reduction in N excretion and a significant improvement in N balance. Fractional oxidation of labeled KIC increased, whereas fractional utilization of labeled KIC for protein synthesis decreased, but the extent of incorporation of infused KIC into newly synthesized protein (as leucine) amounted to at least 40% of the total rate of leucine incorporation into newly synthesized whole body protein. We conclude that addition of KIC spares N in parenterally fed rats and becomes a major source of leucine for protein synthesis.
Reversal of enhanced muscle glucose transport after exercise: roles of insulin and glucose
Authors: Gulve E. A. , Cartee G. D. , Zierath J. R. , Corpus V. M. , Holloszy J. O.
Published: December 2017

Exercise stimulates insulin-independent glucose transport in skeletal muscle and also increases the sensitivity of the glucose transport process in muscle to insulin. A previous study [D. A. Young, H. Wallberg-Henriksson, M. D. Sleeper, and J. O. Holloszy. Am. J. Physiol. 253 (Endocrinol. Metab. 16): E331–E335, 1987] showed that the exercise-induced increase in glucose transport activity disappears rapidly when rat epitrochlearis muscles are incubated for 3 h in vitro in the absence of insulin and that 7.5 microU/ml insulin in the incubation medium apparently slowed the loss of enhanced sugar transport. We examined whether addition of insulin several hours after exercise increases glucose transport to the same extent as continuous insulin exposure. Addition of 7.5 microU/ml insulin 2.5 h after exercise (when glucose transport has returned to basal levels) increased sugar transport to the same level as that which resulted from continuous insulin exposure. This finding provides evidence for an increase in insulin sensitivity rather than a slowing of reversal of the exercise-induced increase in insulin-independent glucose transport activity. Glucose transport was enhanced only at submaximal, not at maximal, insulin concentrations. Exposure to a high concentration of glucose and a low insulin concentration reduced the exercise-induced increase in insulin-sensitive glucose transport. Incubation with a high concentration of 2-deoxy-D-glucose (2-DG) did not alter the increase in insulin sensitivity, even though a large amount of 2-DG entered the muscle and was phosphorylated.(ABSTRACT TRUNCATED AT 250 WORDS)
Brain glucose utilization and transport and cortical function in chronic vs. acute hypoglycemia
Authors: Pelligrino D. A. , Segil L. J. , Albrecht R. F.
Published: December 2017

We compared regional brain capillary permeability-surface area products for glucose transfer (PSin), cerebral glucose utilization (rCMRGlc) rates, and brain tissue glucose levels (GlCbr) in N2O-sedated, paralyzed, and artificially ventilated rats during normoglycemia (NG), insulin-induced acute hypoglycemia (AH), or chronic hypoglycemia (CH) [hypoglycemic plasma glucose (Glcp) = 2.2–2.3 mumol/ml]. In addition, a comparative assessment of brain function in AH vs. CH was performed employing somatosensory-evoked response (SSER) technology. A double-label (3H and 14C) 2-deoxy-D-glucose method was used for the simultaneous assessment of PSin and rCMRGlc. Compared with normoglycemic controls, AH resulted in significant 40-50% reductions in rCMRGlc in 10 of 11 regions analyzed (cerebellum unchanged). In CH vs. AH, significantly higher values for rCMRGlc, Glcbr/Glcp ratios, and PSin were seen in 8, 8, and 5 regions, respectively. No differences in rCMRGlc were observed when comparing CH vs. NG groups. Furthermore, CH rats were able to sustain normal SSER at levels of hypoglycemia (1.5 mumol/ml) that, when imposed acutely, resulted in attenuated SSER. Thus CH is associated with an enhanced blood-brain glucose transport capacity in many (but not all) brain regions. This in turn increases rCMRGlc and improves the general cerebral function compared with that seen during AH.
Protein metabolism after injury with turpentine: a rat model for clinical trauma
Authors: Wusteman M. , Wight D. G. , Elia M.
Published: December 2017

Subcutaneous injections of turpentine induced discrete aseptic abscesses in rats without detectable injury to other tissues. Hypoalbuminemia and high circulating concentrations of alpha 2-macroglobulin were present after 48 h. Liver size, protein content, and protein fractional synthetic rate (FSR) were all increased, whereas loss of muscle protein occurred together with similar (45-50%) reductions in both intramuscular glutamine concentrations ([Gln]i, mmol/l intracellular water) and FSR. The rats became anorexic, but pair feeding (50% ad libitum for 48 h) produced a 22% increase in muscle [Gln]i and only an 18% reduction in muscle FSR. Dietary restriction therefore did not demonstrate the positive relationship between muscle [Gln]i and FSR, which has been observed in animal trauma studies. It is concluded that subcutaneous injections of turpentine produce many of the features of the acute-phase response to injury, and therefore this technique is recommended as a convenient laboratory model for studying various aspects of the protein metabolic response to injury.
Phenylalanine flux, oxidation, and conversion to tyrosine in humans studied with L-[1-13C]phenylalanine
Authors: Zello G. A. , Pencharz P. B. , Ball R. O.
Published: December 2017

Phenylalanine metabolism was determined in 41 studies of adult males (n = 10) consuming an energy-sufficient diet and receiving graded levels of dietary phenylalanine and excess tyrosine (40 mg.kg-1.day-1). After a dietary adaptation period to either 4.2 or 14.0 mg.kg-1.day-1 of phenylalanine; flux, plasma concentration, oxidation, and conversion to tyrosine were measured at test phenylalanine intakes of 5, 7, 10, 14, 21, 28, or 60 mg.kg-1.day-1. Oxidation was low and constant (1.3 mumol.kg-1.h-1) at intakes at or below 10 mg.kg-1.day-1 and increased linearly above this level. Conversion to tyrosine was minimal (2.1%) at these intakes. Breakpoint analysis showed the phenylalanine requirement with excess tyrosine to be 9.1 mg.kg-1.day-1. Plasma phenylalanine concentrations confirmed this estimate of requirement. Prior adaptation did not significantly affect overall flux, plasma concentration, or oxidation nor did it affect the requirement estimate. With the assumption that tyrosine can supply two-thirds of the aromatic amino acid requirement, these data suggest that the aromatic amino acid requirement should be 30 mg.kg-1.day-1 and the World Health Organization recommendation of 14 mg.kg-1.day-1 is an underestimate.
Hemodynamic effects of leukotriene C4 in ovine fetus
Authors: Meyer B. A. , Walsh S. W. , Parisi V. M.
Published: December 2017

Leukotrienes are synthesized during pregnancy and produce cardiovascular effects in adults. We hypothesized that leukotriene C4 would cause vasoconstriction in the fetus and placenta. Eight near-term, unanesthetized ovine fetuses were studied before and after infusion of 10 micrograms leukotriene C4 (LTC4) into the fetal vena cava. Cardiovascular monitoring of maternal and fetal arterial pressures and heart rates was performed. Fetal blood flows were measured by the radioactive-microsphere technique. Sustained elevations in systolic and diastolic blood pressure and decreased fetal heart rate began by 1 min and returned to baseline by 30 min. Arterial pH fell from 7.33 +/- 0.01 to 7.29 +/- 0.01 at 15 min (P less than 0.05) and to 7.29 +/- 0.01 at 30 min (P less than 0.05), with a significant increase in base deficit from 0.7 +/- 0.7 to 3.5 +/- 0.7 at 15 min (P less than 0.05) and to 2.9 +/- 1.0 at 30 min (P less than 0.05). Fetal PO2 and PCO2 were unchanged. Significant decreases in blood flow and resistance were seen in the umbilical placental circulation as well as in fetal skeletal muscle and intestine. Blood flow and resistance were unchanged in the renal and adrenal vascular beds. Fetal administration of LTC4 caused no changes in maternal cardiovascular parameters. These findings represent the first in vivo studies of the effects of a lipoxygenase metabolite on fetal-placental blood flow.
Effect of surgical injury and intraoperative hypothermia on whole body protein metabolism
Authors: Taggart D. P. , McMillan D. C. , Preston T. , Shenkin A. , Wheatley D. J. , Burns H. J.
Published: December 2017

Whole body protein turnover and urinary nitrogen and 3-methyl-L-histidine (3-MH) excretion were measured before and after cardiac surgery using cardiopulmonary bypass in 20 male patients randomized to an intraoperative blood temperature of 28 or 20 degrees C. Rates of whole body protein synthesis (WBPS) and breakdown (WBPB) were determined from the 15N isotopic enrichment of urinary urea, ammonium, and from a calculated end-product average (EPA) after a primed 24-h infusion of [15N]glycine. In the postoperative period, there was a 40% increase in median nitrogen excretion in the 28 degrees C group (P less than 0.03) and a 22% increase in the 20 degrees C group (P = 0.10). There was a 79% increase in the median postoperative 3-MH excretion in the 28 degrees C group (P = 0.01) and a 66% increase in the median postoperative 3-MH excretion in the 20 degrees C group (P less than 0.01). Postoperatively, there was a 23% fall in the median value of WBPS in the 28 degrees C group (P less than 0.01) and an 11% fall in the 20 degrees C group [not significant (NS)] measured by 15N enrichment of urinary urea. In contrast, when WBPS was measured from isotopic enrichment of urinary ammonium, there was an increase in the median value of the postoperative rates of WBPS in both groups, by 20% in the 28 degrees C group (P = NS) and 29% in the 20 degrees C group (P = 0.03). There was no significant change in the rate of WBPS and WBPB, judged by the postoperative EPA in either group.(ABSTRACT TRUNCATED AT 250 WORDS)
Glutamine and glucose metabolism in rat splenocytes and mesenteric lymph node lymphocytes
Authors: Wu G. Y. , Field C. J. , Marliss E. B.
Published: December 2017

The metabolism of glutamine (2 mM) and glucose (5 mM) was studied in splenocytes and mesenteric lymph node lymphocytes of Wistar-Furth rats to assess their relative importance as energy substrates. The major products from glutamine were ammonia, glutamate, aspartate, and CO2, whereas those from glucose were lactate, pyruvate, and CO2 in cells from both lymphoid organs. The individual rates of glutamine and glucose metabolism were decreased in the presence of both substrates, compared with the rates when present separately. The rates of glucose and some (but not all) aspects of glutamine metabolism were higher (P less than 0.01) in splenocytes than in mesenteric lymphocytes. In cells from both lymphoid organs, glutamine and glucose could potentially contribute almost equal amounts of ATP in the presence of both substrates. Glutamine and glucose individually were able to provide sufficient amounts of ATP to maintain its concentrations in the cells throughout a 2-h incubation period at the same levels as with both substrates present. We also found that splenocyte concentration (3.3-100 x 10(6) cells/ml) in the incubations is an important determinant of rates of metabolite formation from glutamine when expressed per 10(6) cells. We conclude that glucose is not the only quantitatively significant energy substrate or even the major one for lymphocytes, because glutamine at near-physiological concentration can be readily utilized by these cells.