Response of protein synthesis in human skeletal muscle to insulin: an investigation with L-[2H5]phenylalanine

McNurlan, Margaret A.; Essén, P.; Thorell, Anders; Calder, Andrew A.; Anderson, Susan E.; Ljungqvist, Olle; Sandgren, Anna; Grant, I. S.; Tjäder, Inga; Ballmer, Peter E.

doi:10.1152/ajpendo.1994.267.1.e102

Cited by 55 publications

(67 citation statements)

References 21 publications

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“…The results from the current study could potentially resolve some of the controversies in the literature on in vivo effects of insulin on muscle protein synthesis (3,11,14,(25)(26)(27)(28)(29). All of these previous studies are based on total (mixed) muscle protein synthesis, representing an average of several individual muscle proteins.…”

Section: Discussionmentioning

confidence: 77%

Tissue-Specific Regulation of Mitochondrial and Cytoplasmic Protein Synthesis Rates by Insulin

et al. 2001

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In vivo studies have reported conflicting effects of insulin on mixed tissue protein synthesis rates. To test the hypothesis that insulin has differential effects on synthesis rates of various protein fractions in different organs, we infused miniature swine (n ‫؍‬ 8 per group) with saline, insulin alone (at 0.7 mU/kg ؊1 ⅐ min ؊1 ), or insulin plus an amino acid mixture for 8 h. Fractional synthesis rate (FSR) of mitochondrial and cytoplasmic proteins in liver, heart, and skeletal muscle, as well as myosin heavy chain (MHC) in muscle, were measured using L-[1-13 C]leucine as a tracer. The FSR of mitochondrial and cytoplasmic proteins were highest in liver, followed by heart and then muscle. Mitochondrial FSR in muscle was higher during insulin and insulin plus amino acid infusions than during saline. Insulin had no significant effect on FSR of MHC in muscle. In contrast, FSR of both mitochondrial and cytoplasmic proteins were not stimulated by insulin in liver. Insulin also did not increase FSR of mitochondrial in heart, whereas insulin and amino acid stimulated FSR of cytoplasmic protein. In conclusion, insulin stimulates the synthesis of muscle mitochondrial proteins, with no significant stimulatory effect on synthesis of sarcoplasmic and MHC. These results demonstrate that insulin has different effects on synthesis rates of specific protein fractions in the liver, heart, and skeletal muscle. Diabetes

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Section: Discussionmentioning

confidence: 77%

Tissue-Specific Regulation of Mitochondrial and Cytoplasmic Protein Synthesis Rates by Insulin

et al. 2001

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“…Of all the hormones that may in¯uence protein metabolism in the short term, by far the most important is insulin. There is general agreement that infusion of insulin in both normal subjects and untreated diabetics reduces protein breakdown in the whole body and in muscle (Fukegawa et al 1985;Tessari et al, 1988;McNurlan et al 1994). There are four studies in which amino acids have been infused, ®rst without and then with insulin (Bennet et al 1990a,b;Pacy et al 1991;Tessari et al 1988).…”

Section: Fasting and Feedingmentioning

confidence: 99%

The mysteries of nitrogen balance

Waterlow¹

1999

Nutr. Res. Rev.

112

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The ®rst part of this review is concerned with the balance between N input and output as urinary urea. I start with some observations on classical biochemical studies of the operation of the urea cycle. According to Krebs, the cycle is instantaneous and automatic, as a result of the irreversibility of the ®rst enzyme, carbamoyl-phosphate synthetase 1 (EC 6.3.5.5; CPS-I), and it should be able to handle many times the normal input to the cycle. It is now generally agreed that acetyl glutamate is a necessary co-factor for CPS-1, but not a regulator. There is abundant evidence that changes in dietary protein supply induce coordinated changes in the amounts of all ®ve urea-cycle enzymes. How this coordination is achieved, and why it should be necessary in view of the properties of the cycle mentioned above, is unknown. At the physiological level it is not clear how a change in protein intake is translated into a change of urea cycle activity. It is very unlikely that the signal is an alteration in the plasma concentration either of total amino-N or of any single amino acid. The immediate substrates of the urea cycle are NH 3 and aspartate, but there have been no measurements of their concentration in the liver in relation to urea production. Measurements of urea kinetics have shown that in many cases urea production exceeds N intake, and it is only through transfer of some of the urea produced to the colon, where it is hydrolysed to NH 3 , that it is possible to achieve N balance. It is beginning to look as if this process is regulated, possibly through the operation of recently discovered urea transporters in the kidney and colon. The second part of the review deals with the synthesis and breakdown of protein. The evidence on whole-body protein turnover under a variety of conditions strongly suggests that the components of turnover, including amino acid oxidation, are in¯uenced and perhaps regulated by amino acid supply or amino acid concentration, with insulin playing an important but secondary role. Molecular biology has provided a great deal of information about the complex processes of protein synthesis and breakdown, but so far has nothing to say about how they are coordinated so that in the steady state they are equal. A simple hypothesis is proposed to ®ll this gap, based on the self-evident fact that for two processes to be coordinated they must have some factor in common. This common factor is the amino acid pool, which provides the substrates for synthesis and represents the products of breakdown. The review concludes that although the achievement and maintenance of N balance is a fact of life that we tend to take for granted, there are many features of it that are not understood, principally the control of urea production and excretion to match the intake, and the coordination of protein synthesis and breakdown to maintain a relatively constant lean body mass.

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“…Albumin and fibrinogen fractional synthetic rates were measured using a validated phenylalanine flooding dose technique previously described in detail [12,[24][25][26][27][28]. Briefly, patients were asked to attend the department after an overnight fast and an intravenous cannula was placed into each antecubital fossa vein.…”

Section: Study Protocolmentioning

confidence: 99%

“…The methods for the assessment of hepatic protein synthesis using deuterated phenylalanine have been described elsewhere [26], but briefly the rate of fibrinogen synthesis was reflected by the incorporation of labelled phenylalanine into the plasma pool of fibrinogen. For free phenylalanine analysis, 1 ml plasma samples were diluted with 1 ml of deionised water.…”

Section: Sample Preparationmentioning

confidence: 99%

Reprioritisation of Liver Export Protein Synthesis in Patients with Decompensated Alcoholic Liver Disease

Rafferty

McMillan²,

Preston³

et al. 2016

J Hepatol Gastroint Dis

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Response of protein synthesis in human skeletal muscle to insulin: an investigation with L-[2H5]phenylalanine

Cited by 55 publications

References 21 publications

Tissue-Specific Regulation of Mitochondrial and Cytoplasmic Protein Synthesis Rates by Insulin

Tissue-Specific Regulation of Mitochondrial and Cytoplasmic Protein Synthesis Rates by Insulin

The mysteries of nitrogen balance

Reprioritisation of Liver Export Protein Synthesis in Patients with Decompensated Alcoholic Liver Disease

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