Protein turnover during puberty in normal children

1996 ◽  
Vol 270 (1) ◽  
pp. E79-E84 ◽  
Author(s):  
S. A. Arslanian ◽  
S. C. Kalhan
Keyword(s):  
Insulin Action ◽  
Fat Free Mass ◽  
Whole Body ◽  
Constant Infusion ◽  
Healthy Children ◽  
Normal Children ◽  
Factor I ◽  
Leucine Kinetics ◽  
Igf I ◽  
Percent Suppression

To investigate whether insulin resistance of puberty involves protein metabolism, we compared whole body leucine kinetics in 20 prepubertal Tanner I (TI), and 21 pubertal Tanner II-IV (TII-IV) healthy children. Leucine flux (LRa), oxidation (LOX), and nonoxidative disposal (NOXLD) were measured during primed constant infusion of [1-13C]leucine at baseline and during a stepwise hyperinsulinemic (10 and 40 mU.m-2.min-1)euglycemic clamp in combination with indirect calorimetry. At baseline LRa and LOX were lower in TII-IV vs. TI [LRa: 3.59 +/- 0.17 vs. 4.05 +/- 0.18 mumol.min-1.kg-1 fat-free mass (FFM), P = 0.036; LOX: 0.45 +/- 0.03 vs. 0.59 +/- 0.04 mumol.min-1. FFM-1, P = 0.005], but NOXLD was similar. Insulin-like growth factor I (IGF-I) levels correlated inversely with LRa, NOXLD, and LOX. Energy expenditure correlated positively with LRa, LOX, and NOXLD. During the clamp absolute and percent suppression in LRa were significantly lower in TII-IV than TI. In conclusion, 1) proteolysis and protein oxidation are lower during puberty compared with prepuberty, whereas protein synthesis is unchanged; 2) insulin action in inhibiting proteolysis is decreased during puberty; and 3) increased pubertal IGF-I levels may play a role in decreased protein degradation.

Glucose tolerance and insulin action in healthy centenarians

1996 ◽  
Vol 270 (5) ◽  
pp. E890-E894 ◽  
Author(s):  
G. Paolisso ◽  
A. Gambardella ◽  
S. Ammendola ◽  
A. D'Amore ◽  
V. Balbi ◽  
...  
Keyword(s):  
Glucose Tolerance ◽  
Plasma Glucose ◽  
Insulin Action ◽  
Glucose Tolerance Test ◽  
Tolerance Test ◽  
Fat Free Mass ◽  
Whole Body ◽  
Glucose Disposal ◽  
Oral Glucose ◽  
Aged Subjects

Advancing age has been found to be associated with a decline in insulin action. Nevertheless, no study has been conducted in healthy centenarians. Our study investigates glucose tolerance and insulin action in centenarians. Fifty-two subjects were enrolled. The subjects were divided in three groups as follows: 1) adults (< 50 yr; n = 20);2) aged subjects (> 75 yr; n = 22); and 3) centenarians (> 100 yr; n = 14). Body composition was studied by bioimpedance analysis. In all subjects, an oral glucose tolerance test and euglycemic glucose clamp were performed. Centenarians have a lower fat-free mass (FFM) than aged subjects and adults, whereas fasting plasma glucose, triglycerides, free fatty acids, urea, and creatinine were not different in the groups studies. Centenarians had a 2-h plasma glucose concentration (6.0 +/- 0.2 mmol/l) that was lower than that in aged subjects (6.6 +/- 0.5 mmol/l, P < 0.05) but not different from adults [6.4 +/- 0.4 mmol/l, P = not significant (NS)]. During the clamp, plasma glucose and insulin concentrations were similar in the three groups. In these conditions, centenarians had a whole body glucose disposal (34.1 +/- 0.6 mumol.kg FFM-1.min 1) that was greater than that in aged subjects (23.3 +/- 0.5 mumol.kg FFM-1.min-1 P < 0.01) but not different from adults (34.6 +/- 0.5 mumol/kg x min, P = NS). In conclusion, our study demonstrates that centenarians compared with aged subjects had a preserved glucose tolerance and insulin action.

Passive immunization against circulating insulin-like growth factor-I (IGF-I) increases protein catabolism in lambs: evidence for a physiological role for circulating IGF-I

1992 ◽  
Vol 135 (2) ◽  
pp. 279-284 ◽  
Author(s):  
J. B. Koea ◽  
B. W. Gallaher ◽  
B. H. Breier ◽  
R. G. Douglas ◽  
S. Hodgkinson ◽  
...  
Keyword(s):  
Growth Factor ◽  
Protein Turnover ◽  
Passive Immunization ◽  
Physiological Role ◽  
Whole Body ◽  
Insulin Like Growth Factor ◽  
Protein Catabolism ◽  
Factor I ◽  
Igf I ◽  
Growth Factor I

ABSTRACT Primed constant infusions of [14C]urea were used to determine the acute effect of passive immunization against circulating free and protein-bound insulin-like growth factor-I (IGF-I) on the rate of net protein catabolism (NPC) in castrated male lambs fasted for 48 h. Following an intravenous bolus of 50 ml IGF-I antiserum, the rate of NPC increased to a peak 30 min after injection of 1·69 ± 0·16 g/kg per day from a baseline value of 1·45±0·22 g/kg per day (P<0·05, n = 4). In three animals given 50 ml equivalents of the purified immunoglobulin fraction, NPC increased from 1·31 ±0·20 to 1·59±0·16 g/kg per day (P<0·05). A similar trend was observed in animals given 25 ml antiserum (n = 4). The rate of NPC did not increase following a bolus of non-immune serum in control animals and the rate of NPC in the treated lambs returned to control levels within 60 min of antibody injection. Plasma insulin and glucose concentrations in both the treated and control groups were unchanged throughout the study. These data suggest that circulating IGF-I has a physiological role in regulating whole body protein turnover during starvation and possibly other catabolic states. The effect of immunoneutralization of circulating IGF-I is transient and this suggests that while IGF-I has an endocrine role in the regulation of protein turnover, other regulatory mechanisms are involved. Journal of Endocrinology (1992) 135, 279–284

scholarly journals Insulin-Like Growth Factor I Circumvents Defective Insulin Action in Human Myotonic Dystrophy Skeletal Muscle Cells1

Endocrinology ◽  
1999 ◽  
Vol 140 (9) ◽  
pp. 4244-4250 ◽  
Author(s):  
Denis Furling ◽  
André Marette ◽  
Jack Puymirat
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Growth Factor ◽  
Insulin Receptor ◽  
Glucose Uptake ◽  
Insulin Action ◽  
Factor I ◽  
Impaired Insulin ◽  
Igf I ◽  
Impaired Insulin Action

Abstract Primary human skeletal muscle cell cultures derived from muscles of a myotonic dystrophy (DM) fetus provided a model in which both resistance to insulin action described in DM patient muscles and the potential ability of insulin-like growth factor I (IGF-I) to circumvent this defect could be investigated. Basal glucose uptake was the same in cultured DM cells as in normal myotubes. In DM cells, a dose of 10 nm insulin produced no stimulatory effect on glucose uptake, and at higher concentrations, stimulation of glucose uptake remained significantly lower than that in normal myotubes. In addition, basal and insulin-mediated protein synthesis were both significantly reduced compared with those in normal cells. In DM myotubes, insulin receptor messenger RNA expression and insulin receptor binding were significantly diminished, whereas the expression of GLUT1 and GLUT4 glucose transporters was not affected. These results indicate that impaired insulin action is retained in DM cultured myotubes. The action of recombinant human IGF-I (rhIGF-I) was evaluated in this cellular model. We showed that rhIGF-I is able to stimulate glucose uptake to a similar extent as in control cells and restore normal protein synthesis level in DM myotubes. Thus, rhIGF-I is able to bypass impaired insulin action in DM myotubes. This provides a solid foundation for the eventual use of rhIGF-I as an effective treatment of muscle weakness and wasting in DM.

scholarly journals Whole body leucine flux in HIV-infected patients treated with or without protease inhibitors

2006 ◽  
Vol 290 (4) ◽  
pp. E685-E693 ◽  
Author(s):  
Magali Prod’homme ◽  
Cécile Rochon ◽  
Michèle Balage ◽  
Henri Laurichesse ◽  
Igor Tauveron ◽  
...  
Keyword(s):  
Amino Acid ◽  
Protein Metabolism ◽  
Glucose Infusion ◽  
Fat Free Mass ◽  
Whole Body ◽  
Constant Infusion ◽  
Body Protein ◽  
X Ray ◽  
Immunodeficiency Virus

The present study was carried out to assess the effects of protease inhibitor (PI) therapy on basal whole body protein metabolism and its response to acute amino acid-glucose infusion in 14 human immunodeficiency virus (HIV)-infected patients. Patients treated with PIs (PI+, 7 patients) or without PIs (PI−, 7 patients) were studied after an overnight fast during a 180-min basal period followed by a 140-min period of amino acid-glucose infusion. Protein metabolism was investigated by a primed constant infusion of l-[1-13C]leucine. Dual-energy X-ray absorptiometry for determination of fat-free mass (FFM) and body fat mass measured body composition. In the postabsorptive state, whole body leucine balance was 2.5 times ( P < 0.05) less negative in the PI+ than in the PI− group. In HIV-infected patients treated with PIs, the oxidative leucine disposal during an acute amino acid-glucose infusion was lower (0.58 ± 0.09 vs. 0.81 ± 0.07 μmol·kg FFM−1·min−1 using plasma [13C]leucine enrichment, P = 0.06; or 0.70 ± 0.10 vs. 0.99 ± 0.08 μmol·kg FFM−1·min−1 using plasma [13C]ketoisocaproic acid enrichment, P = 0.04 in PI+ and PI− groups, respectively) than in patients treated without PIs. Consequently, whole body nonoxidative leucine disposal (an index of protein synthesis) and leucine balance (0.50 ± 0.10 vs. 0.18 ± 0.06 μmol·kg FFM·−1·min−1 in PI+ and PI− groups respectively, P < 0.05) were significantly improved during amino acid-glucose infusion in patients treated with PIs. However, whereas the response of whole body protein anabolism to an amino acid-glucose infusion was increased in HIV-infected patients treated with PIs, any improvement in lean body mass was detected.

IGF-I alters skeletal muscle substrate metabolism and blunts recovery from insulin-induced hypoglycemia

1996 ◽  
Vol 270 (4) ◽  
pp. E545-E551 ◽  
Author(s):  
M. A. Hussain ◽  
O. Schmitz ◽  
J. S. Christiansen ◽  
N. J. Christensen ◽  
K. G. Alberti ◽  
...  
Keyword(s):  
Ketone Bodies ◽  
Whole Body ◽  
Elevated Plasma ◽  
Glucose Levels ◽  
Factor I ◽  
Vascular Bed ◽  
Igf I ◽  
The Face ◽  
Delayed Recovery ◽  
Hormone Responses

Eight healthy subjects were treated with saline or insulin-like growth factor I (IGF-I, 10 micrograms.kg-1.h-1 sc) for 3 days in a crossover randomized fashion. Substrate balances across the forearm skeletal vascular bed were determined in the postabsorptive state and during a hyperinsulinemic euglycemic clamp. In the basal state, net forearm uptake of free fatty acids and ketone bodies was increased during IGF-I administration in the face of elevated plasma levels of these substrates, whereas basal glucose levels and forearm glucose balance were unchanged. However, whole body and net forearm glucose uptakes were more markedly stimulated by insulin (+20 and +8%, respectively) in the IGF-I period. Additionally, counterregulatory hormone responses were examined during insulin-induced stepwise hypoglycemia. Responses of growth hormone and glucagon were blunted, those of cortisol and epinephrine were more marked, and that of norepineprine was unchanged during IGF-I administration. These changes were accompanied with delayed recovery from hypoglycemia.

Phenylarsine oxide and denervation effects on hormone-stimulated glucose transport

1988 ◽  
Vol 255 (2) ◽  
pp. E159-E165 ◽  
Author(s):  
M. O. Sowell ◽  
K. A. Robinson ◽  
M. G. Buse
Keyword(s):  
Skeletal Muscle ◽  
Glucose Transport ◽  
Insulin Action ◽  
Denervated Muscle ◽  
Phenylarsine Oxide ◽  
Early Step ◽  
Factor I ◽  
Igf I ◽  
Receptor Number ◽  
Stimulation Of

Insulin and insulin-like growth factor I (IGF-I) stimulate glucose transport in skeletal muscle through separate receptors. The proximal postreceptor events in coupling insulin and IGF-I receptors to glucose transport have been suggested to differ. Denervation of skeletal muscle produces a postreceptor insulin resistance presumably at an early step in the signaling cascade. We examined the effects of denervation and phenylarsine oxide (PAO), an agent believed to block insulin action on transport at a postreceptor step, on insulin and IGF-I stimulated 2-deoxy-D-glucose transport in isolated solei. Denervation (24 h) produced severe IGF-I resistance without affecting IGF-I receptor number or affinity. PAO inhibited insulin and IGF-I stimulation of transport in control muscles by approximately 90 and approximately 70%, respectively. In denervated muscle PAO inhibited transport stimulation by both hormones less than in controls. Conclusions are that 1) skeletal muscle insulin and IGF-I receptors signal transport mainly through a PAO-sensitive mechanism, but IGF-I's action involves a larger PAO-resistant component; 2) the denervation-induced postreceptor resistance of glucose transport to both hormones involves primarily the PAO-sensitive pathway.

Comparison of leucine kinetics in endurance-trained and sedentary humans

1999 ◽  
Vol 86 (1) ◽  
pp. 320-325 ◽  
Author(s):  
Linda S. Lamont ◽  
Arthur J. McCullough ◽  
Satish C. Kalhan
Keyword(s):  
Body Weight ◽  
Oxygen Consumption ◽  
Maximal Oxygen Consumption ◽  
Kinetic Studies ◽  
Fat Free Mass ◽  
Whole Body ◽  
Tissue Mass ◽  
Cross Sectional ◽  
Leucine Oxidation ◽  
Leucine Kinetics

Whole body leucine kinetics was compared in endurance-trained athletes and sedentary controls matched for age, gender, and body weight. Kinetic studies were performed during 3 h of rest, 1 h of exercise (50% maximal oxygen consumption), and 2 h of recovery. When leucine kinetics were expressed both per unit of body weight and per unit of fat-free mass, both groups demonstrated an increase in leucine oxidation during exercise ( P < 0.01). Trained athletes had a greater leucine rate of appearance during exercise and recovery compared with their sedentary counterparts ( P < 0.05) and an increased leucine oxidation at all times on the basis of body weight ( P < 0.05). However, all of these between-group differences were eliminated when leucine kinetics were corrected for fat-free tissue mass. Therefore, correction of leucine kinetics for fat-free mass may be important when cross-sectional investigations on humans are performed. Furthermore, leucine oxidation, when expressed relative to whole-body oxygen consumption during exercise, was similar between groups. It is concluded that there was no difference between endurance-trained and sedentary humans in whole body leucine kinetics during rest, exercise, or recovery when expressed per unit of fat-free tissue mass.

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