Insulin Stimulates Phenylalanine Uptake across the Hind Limb in Fed Lambs

Wester, T.J.; Lobley, G. E.; Birnie, L M; Lomax, M.A.

doi:10.1093/jn/130.3.608

Cited by 39 publications

(21 citation statements)

References 12 publications

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“…Rumen fermentation also produces a more constant supply of nutrients and consequently plasma insulin concentrations tend to be lower and exhibit less diurnal variation than reported in singlestomached species (250,386) . Ruminal infusion of VFA has been reported to reduce VFI (387) , although it is still unclear as to how much of this anorexia is a result of local osmolarity effects or circulating signalling effects following absorption (21) .…”

Section: Unique Aspects Of Digestion In Ruminant Animalsmentioning

confidence: 85%

Neuroendocrine and physiological regulation of intake with particular reference to domesticated ruminant animals

et al. 2008

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The central nervous system undertakes the homeostatic role of sensing nutrient intake and body reserves, integrating the information, and regulating energy intake and/or energy expenditure. Few tasks regulated by the brain hold greater survival value, particularly important in farmed ruminant species, where the demands of pregnancy, lactation and/or growth are not easily met by often bulky plant-based and sometimes nutrient-sparse diets. Information regarding metabolic state can be transmitted to the appetite control centres of the brain by a diverse array of signals, such as stimulation of the vagus nerve, or metabolic 'feedback' factors derived from the pituitary gland, adipose tissue, stomach/abomasum, intestine, pancreas and/or muscle. These signals act directly on the neurons located in the arcuate nucleus of the medio-basal hypothalamus, a key integration, and hunger (orexigenic) and satiety (anorexigenic) control centre of the brain. Interest in human obesity and associated disorders has fuelled considerable research effort in this area, resulting in increased understanding of chronic and acute factors influencing feed intake. In recent years, research has demonstrated that these results have relevance to animal production, with genetic selection for production found to affect orexigenic hormones, feeding found to reduce the concentration of acute controllers of orexigenic signals, and exogenous administration of orexigenic hormones (i.e. growth hormone or ghrelin) reportedly increasing DM intake in ruminant animals as well as single-stomached species. The current state of knowledge on factors influencing the hypothalamic orexigenic and anorexigenic control centres is reviewed, particularly as it relates to domesticated ruminant animals, and potential avenues for future research are identified.

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Section: Unique Aspects Of Digestion In Ruminant Animalsmentioning

confidence: 85%

Neuroendocrine and physiological regulation of intake with particular reference to domesticated ruminant animals

et al. 2008

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“…For example, the ovine liver removes small amounts of absorbed BCAA [30,31] but a large proportion of histidine and phenylalanine are removed to support the synthesis of export proteins [33]. For the peripheral tissues (especially muscle), the BCAA have a major role in the regulation of protein synthesis [34,35] and hepatic bypass may act as an important signal of increased nutrient (protein) supply.…”

Section: Discussionmentioning

confidence: 99%

Effect of intake on whole body plasma amino acid kinetics in sheep

Savary-Auzeloux¹,

Hoskin

Lobley³

2003

Reprod. Nutr. Dev.

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-While both the quantity and quality of food ingested are potent regulators of whole body protein metabolism in ruminants, little data are available on responses across a wide range of intakes. The current study examined the responses in whole body protein flux (PrF) to such intake changes and compared these with the responses across the hind-quarters (in a companion study). Six growing sheep (6-8 months, 30-35 kg) received each of four intakes of dried grass pellets (0.5, 1.0, 1.5 and 2.5 times maintenance energy; M) for a minimum of 7 days. At each intake, a mixture of U-13 C amino-acids (AA) was infused intravenously for 10 h. Arterial plasma and blood were obtained over the last 4 h of infusion and the concentrations and the enrichments of thirteen 13 C labelled AA were determined. The absolute values for plasma Irreversible Loss Rate (ILR) but also converted PrF varied between the AA. PrF values were lower for histidine, methionine, aspartate, glycine and proline (range 68 to 174 g·d -1 at 1.5 M) than for isoleucine, leucine, valine and glutamate (range 275 to 400 g·d -1 at 1.5 M). These discrepancies may be explained by (1) the differential AA removal by the splanchnic tissues, (2) the de novo synthesis of the non-essential AA, (3) the transfer of AA from the erythrocytes or plasma to the tissues. The first two assumptions require further investigation whereas recent work has shown a minor role for AA transfers between erythrocytes and tissues. For most AA, ILR and PrF responded linearly to intake but curvilinear responses were observed for phenylalanine, lysine, leucine, isoleucine and tyrosine. These differences were not due to hind-quarter metabolism and may involve the digestive tract and liver.intake / whole body / kinetics / ovine / amino acid Reprod. Nutr. Dev. 43 (2003) 117-129 117

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“…In weaned rats, the response of protein synthesis in skeletal muscle to feeding can be blocked by anti-insulin serum and, in the fasting state insulin infusion stimulates muscle protein synthesis (Garlick et al, 1983;Preedy and Garlick, 1986). Insulin also stimulates whole-body protein synthesis in the fetal sheep and hindlimb protein synthesis in the lamb (Liechty et al, 1992;Wester et al, 2000). In contrast to studies performed in growing animals, most studies in adult animals and humans show little, if any, response of muscle protein synthesis to increases in circulating insulin (Gelfand and Barrett, 1987;Baillie and Garlick, 1992).…”

Section: Postnatal Ontogeny Of the Feeding-induced Stimulation Of Musmentioning

confidence: 99%

Postnatal ontogeny of skeletal muscle protein synthesis in pigs1,2

Davis

Suryawan

Orellana

et al. 2008

Journal of Animal Science

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The neonatal period is characterized by rapid growth and elevated rates of synthesis and accretion of skeletal muscle proteins. The fractional rate of muscle protein synthesis is very high at birth and declines rapidly with age. The elevated capacity for muscle protein synthesis in the neonatal pig is driven by the high ribosome content and, together with an increased efficiency of the translation process, promotes accelerated protein synthesis rates. Feeding profoundly stimulates muscle protein synthesis in neonatal pigs and the response decreases with age. The feeding-induced stimulation of muscle protein synthesis is modulated by an enhanced sensitivity to the postprandial increase in insulin and amino acids. The developmental decline in the response to insulin and amino acids parallels a marked decrease in the feeding-induced activation of translation initiation factors that regulate the binding of mRNA to the 40S ribosomal complex. The abundance and activation of many known positive regulators of the nutrient-and insulin-signaling pathways that are involved in translation initiation are high, whereas those of many negative regulators are low in skeletal muscle of younger pigs. Thus, the activation and(or) abundance of the positive regulators, such as the insulin receptor, insulin receptor-substrate-1, phosphoinositide-3 kinase, phosphoinositide-dependent kinase-1, protein kinase B, mammalian target of rapamycin, raptor, ribosomal protein S6 kinase-1, eukaryotic initiation factor (eIF) 4E-binding protein 1, and eIF4E associated with eIF4G, are greater in 7-d-old pigs than in 26-d-old pigs. The activation of negative regulators, including protein tyrosine phosphatase-1B, phosphatase and tensin homologue deleted on chromosome 10, protein phosphatase 2A, and tuberous sclerosis complex 1/2, are lower in 7-d-old pigs than in 26-d-old pigs. Thus, the developmental decline in the stimulation of skeletal muscle protein synthesis by insulin and amino acids is due in part to the developmentally related decrease in the activation of the signaling pathways that lead to translation initiation.

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Insulin Stimulates Phenylalanine Uptake across the Hind Limb in Fed Lambs

Cited by 39 publications

References 12 publications

Neuroendocrine and physiological regulation of intake with particular reference to domesticated ruminant animals

Neuroendocrine and physiological regulation of intake with particular reference to domesticated ruminant animals

Effect of intake on whole body plasma amino acid kinetics in sheep

Postnatal ontogeny of skeletal muscle protein synthesis in pigs1,2

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