Interaction of amino acids and insulin in the regulation of protein metabolism in growing animals

Davis, Teresa A.; Suryawan, Agus; Bush, Jill A.; O'Connor, Pamela M. J.; Thivierge, M. Carole

doi:10.4141/a02-120

Cited by 7 publications

(5 citation statements)

References 71 publications

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“…Approximately 90% of the infused AA, then, was used elsewhere. In monogastric animals, the acute response to a protein meal or AA infusion after fasting is an elevation in both AA and insulin concentrations (Gibson et al, 1996), either of which alone stimulates protein synthesis in muscle via signal transduction pathways that share several elements in common (Davis et al, 2003;Bolster et al, 2004). In adults, insulin appears to increase net protein accretion in muscle primarily through an inhibition of protein degradation, whereas extracellular AA continue to stimulate protein synthesis (Gibson et al, 1996).…”

Section: Responses To the Complete Aa MIXmentioning

confidence: 99%

“…These concentrations decreased, not because of loss into milk, but because of more efficient catabolism or deposition into body proteins. Essential AA (particularly Leu) and insulin, which are stimulatory to muscle and liver protein synthesis (Davis et al, 2003;Bolster et al, 2004), were elevated during imbalance (Table 3). On the other hand, glucagon, which stimulates activity of AA-degrading enzymes in the liver (Pestañ a, 1969;Tovar et al, 2002), was also increased, and plasma glucose and urea concentrations were higher, indicating faster breakdown of AA.…”

Section: Aa Imbalancesmentioning

confidence: 99%

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Responses to Amino Acid Imbalances and Deficiencies in Lactating Dairy Cows

Weekes

Luimes²,

Cant

2006

Journal of Dairy Science

103

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Lactating cows were exposed to large amino acid imbalances and deficiencies by i.v. infusion to characterize responses in milk production and plasma concentrations of metabolites and hormones. Six cows in early lactation were fed a basal diet of 9% CP and infused continuously for 6 d with saline (negative control), 1.1 kg/d of a complete amino acid mix (positive control), or the equivalent mix lacking Met, Lys, His, or all 3 branched-chain amino acids. All cows received all treatments in 6 successive periods in a Latin square design. Infusion of the complete amino acid mix resulted in an increase in the plasma concentrations of several essential amino acids, insulin, and glucagon. Milk protein production was stimulated by 19%, which accounted for 10% of the infused amino acid. Plasma urea, acetate, and beta-hydroxybutyrate concentrations were increased. Compared with saline, the amino acid mixtures lacking Met, Lys, or His increased essential amino acids, glucose, insulin, and glucagon concentrations in plasma, and decreased growth hormone. Plasma concentration of the essential amino acid absent from the infusate fell 2-fold but milk protein yield remained within 12% of its basal value. Dry matter intakes were depressed 35% over the first 2 d of infusion of imbalanced mixtures but recovered thereafter. Milk fat yields were increased 258 and 320 g/d by mixtures devoid of Lys and His, respectively. Correction of a Met, Lys, or His deficiency did not affect hormone concentrations in plasma and milk protein yield increased 27% due entirely to increased concentration of the single amino acid in plasma. Although imbalance and deficiency generated similar amino acid profiles in plasma, it was concluded that endocrine responses to total amino acid supply during imbalance can override imperfections in the circulating amino acid profile to maintain milk protein yield at higher levels than expected from deficiency states. Both imbalance and deficiency were characterized by a low protein:fat ratio in milk. Infusion of a mix of amino acids lacking Val, Ile, and Leu, despite a decrease in plasma Leu to 58% of its basal value, increased milk protein and fat yields to the same extent as the complete amino acid mix.

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Section: Responses To the Complete Aa MIXmentioning

confidence: 99%

Section: Aa Imbalancesmentioning

confidence: 99%

Responses to Amino Acid Imbalances and Deficiencies in Lactating Dairy Cows

Weekes

Luimes²,

Cant

2006

Journal of Dairy Science

103

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“…For constitutive proteins, including those that comprise muscle, net accretion reflects the balance between synthesis and degradation and thus changes in either, or both, processes can increase (or decrease) gain. Although a number of factors, both nutritional (Seve and Ponter 1997;Lobley 1998) and hormonal (Davis et al 2003), are known to stimulate protein synthesis in muscle, degradation can also be manipulated. Indeed, the rapid lean growth of certain genotypes (e.g., callipyge) has been linked to suppression of protein breakdown (Lorenzen et al 2000).…”

Section: Export Versus Constitutive Protein Synthesismentioning

confidence: 99%

Protein turnover—what does it mean for animal production?

Lobley¹

2003

Can. J. Anim. Sci.

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Lobley, G. E. 2003. Protein turnover-what does it mean for animal production? Can. J. Anim. Sci. 83: 327-340. The dynamics of protein turnover confer great advantages for homeothermy, plasticity and metabolic function in mammals. The different roles played by the various organs have led to aspects of protein synthesis and degradation that aid the various functions performed. The so-called "non-productive" organs such as the gastro-intestinal tract and liver produce large quantities of export proteins that perform vital functions. Not all these proteins are recovered, however, and thus function can result in lowered net conversion of plant protein to animal products. The splanchnic tissues also oxidize essential amino acids (AA). For example, the gut catabolizes leucine, lysine and methionine, but not threonine and phenylalanine, as part of a complex interaction between AA supply and tissue metabolic activity. Losses by oxidation and endogenous secretions can markedly alter the pattern of absorbed AA. The fractional rates of extraction of total AA inflow to the liver are low and this allows short-term flexibility in controlling supply to peripheral tissues. Recent evidence suggests that the role of the liver in AA catabolism is more a response to non-use by other tissues rather than an immediate regulation of supply to the periphery. Neither arterial supply of AA nor the rate of transport into peripheral tissues limits protein gain, except when supply is very limited. Rather, control is probably exerted via hormone-nutrient interactions.Key words: Protein synthesis, amino acid, gastro-intestinal tract, liver, muscle, mammary gland Lobley, G. E. 2003. Le taux de renouvellement des protéines-quelle est sa signification en production animale ? Can. J. Anim. Sci. 83: 327-340. La dynamique reliée au renouvellement des protéines confère une grande flexibilité aux mammifères pour maintenir leur homéothermie et leurs fonctions métaboliques. Les divers rôles joués par les organes les ont conduit à des niveaux différents de la synthèse et de la dégradation protéique en fonction des rôles métaboliques à accomplir. Les organes communément appelés « non-productifs » tels le système gastro-intestinal et le foie produisent des quantités importantes de protéines exportées qui accomplissent des fonctions vitales. Cependant, la récupération des ces protéines n'est pas complète et ces fonctions peuvent ainsi résulter en une diminution de la conversion nette des protéines végétales en produits animaux. De plus, le tissu splanchnique oxyde aussi les acides aminés (AA) essentiels. Par exemple, le système digestif catabolise la leucine, la lysine et la méthionine, mais non pas la thréonine et la phénylalanine. Les pertes causées par l'oxydation et les sécrétions endogènes peuvent profondément altérer le profil des AA absorbés. Le taux d'extraction hépatique du flux afférent des AA totaux est faible et ceci permet une flexibilité à court-terme pour contrôler l'apport aux tissus périphériques. Des évidence récentes suggèrent que le rôle ...

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“…Insulin (Bequette et al, 2001;Lemay et al, 2007;Bionaz and Loor, 2011), prolactin, glucocorticoid (Doppler et al, 1989), and hormones in the somatotropic axis (Cant et al, 1999) have all been shown to affect milk protein synthesis. However, these effects may not be all direct as the supply of some EAA affect the secretion of insulin (Davis et al, 2003;Bolster et al, 2004, Xiao et al, 2014, glucagon (Tovar et al, 2002), IGF-I (Wheelhouse et al, 1999;Noguchi, 2000;Stubbs et al, 2002), and parathyroid hormone (Conigrave et al, 2004). Supply of individual EAA may also affect protein synthesis through the mechanistic target of rapamycin complex 1 (mTORC1), which is an important intracellular signaling pathway that integrates environmental and intracellular signals to regulate cell growth and proliferation (Kim et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Effects of graded removal of lysine from an intravenously infused amino acid mixture on lactation performance and mammary amino acid metabolism in lactating goats

Guo

Lin

et al. 2017

Journal of Dairy Science

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To investigate responses of milk protein synthesis and mammary AA metabolism to a graded decrease of postruminal Lys supply, 4 lactating goats fitted with jugular vein, mammary vein, and carotid artery catheters and transonic blood flow detectors on the external pudic artery were used in a 4 × 4 Latin square experiment. Goats were fasted for 24 h and then received a 9-h intravenous infusion of an AA mixture plus glucose. Milk yield was recorded and samples were taken in h 2 to 8 of the infusion period; a mammary biopsy was performed in the last hour. Treatments were graded decrease of lysine content in the infusate to 100 (complete), 60, 30, or 0% as in casein. Lysine-removed infusions linearly decreased milk yield, tended to decrease lactose yield, and tended to increase milk fat to protein ratio. Milk protein content and yield were linearly decreased by graded Lys deficiency. Mammary Lys uptake was concomitantly decreased, but linear regression analysis found no significant relationship between mammary Lys uptake and milk protein yield. Treatments had no effects on phosphorylation levels of the downstream proteins measured in the mammalian target or rapamycin pathway except for a tended quadratic effect on that of eukaryotic initiation factor 2, which was increased and then decreased by graded Lys deficiency. Removal of Lys from the infusate linearly increased circulating glucagon and glucose. Removal of Lys from the infusate linearly decreased arterial and venous concentrations of Lys. Treatments also had a significant quadratic effect on venous Lys, suggesting mechanisms to stabilize circulating Lys at a certain range. The 2 infusions partially removing Lys resulted in a similar 20% decrease, whereas the 0% Lys infusion resulted in an abrupt 70% decrease in mammary Lys uptake compared with that of the full-AA mixture infusion. Consistent with the abrupt decrease, mammary Lys uptake-to-output ratio decreased from 2.2 to 0.92, suggesting catabolism of Lys in the mammary gland could be completely prevented when the animal faced severe Lys deficiency. Mammary blood flow was linearly increased, consistent with the linearly increased circulating nitric oxide by graded Lys deficiency, indicating mechanisms to ensure the priority of the mammary gland in acquiring AA for milk protein synthesis. Infusions with Lys removed increased mammary clearance rate of Lys numerically by 2 to 3 fold. In conclusion, the decreased milk protein yield by graded Lys deficiency was mainly a result of the varied physiological status, as indicated by the elevated circulating glucagon and glucose, rather than a result of the decreased mammary Lys uptake or depressed signals in the mTOR pathway. Mechanisms of Lys deficiency to promote glucagon secretion and mammary blood flow and glucagon to depress milk protein synthesis need to be clarified by future studies.

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Interaction of amino acids and insulin in the regulation of protein metabolism in growing animals

Cited by 7 publications

References 71 publications

Responses to Amino Acid Imbalances and Deficiencies in Lactating Dairy Cows

Responses to Amino Acid Imbalances and Deficiencies in Lactating Dairy Cows

Protein turnover—what does it mean for animal production?

Effects of graded removal of lysine from an intravenously infused amino acid mixture on lactation performance and mammary amino acid metabolism in lactating goats

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