scholarly journals Regulation of Milk Protein Synthesis by Free and Peptide-Bound Amino Acids in Dairy Cows

Biology ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1044
Author(s):  
Miaomiao Zhou ◽  
Lianbin Xu ◽  
Feng-Qi Zhao ◽  
Hongyun Liu
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Dairy Cows ◽  
Milk Protein ◽  
Utilization Efficiency ◽  
Lactation Performance ◽  
Protein Requirements ◽  
Complex Biological Process ◽  
Underlying Mechanisms

Milk protein (MP) synthesis in the mammary gland of dairy cows is a complex biological process. As the substrates for protein synthesis, amino acids (AAs) are the most important nutrients for milk synthesis. Free AAs (FAAs) are the main precursors of MP synthesis, and their supplies are supplemented by peptide-bound AAs (PBAAs) in the blood. Utilization of AAs in the mammary gland of dairy cows has attracted the great interest of researchers because of the goal of increasing MP yield. Supplying sufficient and balanced AAs is critical to improve MP concentration and yield in dairy cows. Great progress has been made in understanding limiting AAs and their requirements for MP synthesis in dairy cows. This review focuses on the effects of FAA and PBAA supply on MP synthesis and their underlying mechanisms. Advances in our knowledge in the field can help us to develop more accurate models to predict dietary protein requirements for dairy cows MP synthesis, which will ultimately improve the nitrogen utilization efficiency and lactation performance of dairy cows.

scholarly journals Whole-body fluxes and partitioning of amino acids to the mammary gland of cows fed fresh pasture at two levels of intake during early lactation

2003 ◽  
Vol 90 (2) ◽  
pp. 271-281 ◽  
Author(s):  
D. Pacheco ◽  
M.H. Tavendale ◽  
G. W. Reynolds ◽  
T. N. Barry ◽  
J. Lee ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Dairy Cows ◽  
Milk Protein ◽  
Essential Amino Acids ◽  
Whole Body ◽  
Early Lactation ◽  
Isoleucine Leucine ◽  
Ad Libitum

The utilisation of essential amino acids (EAA) by the mammary gland of lactating dairy cows fed fresh forages was studied to provide basic information useful in designing strategies to increase the production of milk protein from pasture-fed dairy cows. The relationship between the flux of EAA in the whole body and their uptake by the mammary gland was determined in four cows in early lactation (length of time in milk 44 (SD 14·5) d) producing 21 (SD 4·0) kg milk/d. The cows were maintained in metabolism stalls and fed fresh perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) pasturead libitumor restricted to 75 %ad libitumintake. The whole-body fluxes of amino acids (AA) were measured using an arterio-venous infusion of universally13C-labelled AA. Whole-body fluxes of fourteen AA were estimated. Isotope dilution indicated that mammary utilisation accounted for one-third of the whole-body flux of EAA, with individual AA ranging between 17 and 35 %. Isoleucine, leucine, valine and lysine were the EAA with the greatest partitioning towards the mammary gland (up to 36 % of the whole-body flux), which could reflect a potentially limiting effect on milk protein synthesis. In the case of AA with low partitioning to the mammary gland (for example, histidine), it is suggested that non-mammary tissues may have priority over the mammary gland and therefore the supply of this AA may also limit milk protein synthesis.

Milk Protein Precursors in the Goat During Late Lactation

1993 ◽  
Vol 1993 ◽  
pp. 1-1
Author(s):  
B.J. Bequette ◽  
F.R.C. Backwell ◽  
A.G. Calder ◽  
J.A. Metcalf ◽  
D. Wray-Cahen ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Milk Protein ◽  
Protein S ◽  
Dairy Goats ◽  
Protein Precursor ◽  
Previous Hypothesis ◽  
Casein Protein ◽  
Isotope Kinetics

Previously, we have reported on work in dairy goats using stable isotope kinetics to examine the precursors for milk protein synthesis (1). Contrary to a previous hypothesis (2), these results suggested that blood free amino acids (AA) are not simply transported into the mammary gland and incorporated directly into milk protein. Although the latter may still occur, a substantial amount of the AA for milk protein synthesis appears to be channelled through constitutive mammary gland protein(s) first. Moreover, the data indicated that a proportion (12-20%) of the casein protein precursor may be derived from extra-mammary sources other than blood free AA, e.g. peptides and/or proteins. It may be possible therefore to alter milk protein synthesis by the provision of different forms of precursor amino acids. Since the previous study was in goats during early lactation (day 61 ± 11), the present study reports on the precursors for milk protein synthesis in goats during late lactation, and allows a comparison between stages of lactation.

scholarly journals Effects of jugular-infused lysine, methionine, and branched-chain amino acids on milk protein synthesis in high-producing dairy cows

2011 ◽  
Vol 94 (4) ◽  
pp. 1952-1960 ◽  
Author(s):  
J.A.D.R.N. Appuhamy ◽  
J.R. Knapp ◽  
O. Becvar ◽  
J. Escobar ◽  
M.D. Hanigan
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Dairy Cows ◽  
Milk Protein ◽  
Branched Chain Amino Acids ◽  
Branched Chain

scholarly journals Effects of a High-Grain Diet With a Buffering Agent on Milk Protein Synthesis in Lactating Goats

2021 ◽  
Vol 8 ◽  
Author(s):  
Meilin He ◽  
Xintian Nie ◽  
Huanhuan Wang ◽  
Shuping Yan ◽  
Yuanshu Zhang
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Amino Acid ◽  
Milk Production ◽  
Milk Protein ◽  
Time Of Flight ◽  
Lactating Goats ◽  
Rumen Acidosis ◽  
Buffering Agent

Chinese dairy industries have developed rapidly, providing consumers with high-quality sources of nutrition. However, many problems have also appeared during the development process, especially the low quality of milk. To improve milk quality, a large amount of concentrated feed is usually added to the diet within a certain period of time, which increases the milk production to a certain extent. However, long-term feeding with high-concentration feed can lead to subacute rumen acidosis. Therefore, the present study aimed to determine the effect of adding a buffer on subacute rumen acidosis, and the improvement of milk production and milk quality. We also aimed to study the mechanism of promoting mammary gland lactation. A total of 12 healthy mid-lactating goats were randomly divided into two groups, they were high-grain diet group (Control) and buffering agent group. To understand the effects of high-grain diets with buffers on amino acids in jugular blood and the effects of amino acids on milk protein synthesis, Milk-Testing™ Milkoscan 4000, commercial kits, and high-performance liquid chromatography (HPLC) measurements were integrated with the milk protein rate, the amino acid concentration in jugular venous blood samples, quantitative real-time PCR, comparative proteomics, and western blotting to study differentially expressed proteins and amino acids in mammary gland tissues of goats fed high-grain diets. Feeding lactating goats with buffering agent increased the percentage of milk protein in milk, significantly increased the amino acid content of jugular blood (p < 0.05), and increase the amino acid transporter levels in the mammary gland. Compared with the high-grain group, 2-dimensional electrophoresis technology, matrix-assisted laser desorption/ionization-time of flight/time of flight proteomics analyzer, and western blot analysis further verified that the expression levels of beta casein (CSN2) and lactoferrin (LF) proteins in the mammary glands of lactating goats were higher when fed a high-grain diets and buffers. The mechanism of increased milk protein synthesis was demonstrated to be related to the activation of mammalian target of rapamycin (mTOR) pathway signals.

Amino Acid Metabolism in Dairy Cows and their Regulation in Milk Synthesis

2019 ◽  
Vol 20 (1) ◽  
pp. 36-45 ◽  
Author(s):  
Feiran Wang ◽  
Haitao Shi ◽  
Shuxiang Wang ◽  
Yajing Wang ◽  
Zhijun Cao ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Mammary Gland ◽  
Dairy Cows ◽  
Milk Fat ◽  
Milk Protein ◽  
Regulatory Element ◽  
Mammalian Target Of Rapamycin ◽  
Input Output ◽  
Output Ratio ◽  
Group 2

Background: Reducing dietary Crude Protein (CP) and supplementing with certain Amino Acids (AAs) has been known as a potential solution to improve Nitrogen (N) efficiency in dairy production. Thus understanding how AAs are utilized in various sites along the gut is critical. Objective: AA flow from the intestine to Portal-drained Viscera (PDV) and liver then to the mammary gland was elaborated in this article. Recoveries in individual AA in PDV and liver seem to share similar AA pattern with input: output ratio in mammary gland, which subdivides essential AA (EAA) into two groups, Lysine (Lys) and Branchedchain AA (BCAA) in group 1, input: output ratio > 1; Methionine (Met), Histidine (His), Phenylalanine (Phe) etc. in group 2, input: output ratio close to 1. AAs in the mammary gland are either utilized for milk protein synthesis or retained as body tissue, or catabolized. The fractional removal of AAs and the number and activity of AA transporters together contribute to the ability of AAs going through mammary cells. Mammalian Target of Rapamycin (mTOR) pathway is closely related to milk protein synthesis and provides alternatives for AA regulation of milk protein synthesis, which connects AA with lactose synthesis via α-lactalbumin (gene: LALBA) and links with milk fat synthesis via Sterol Regulatory Element-binding Transcription Protein 1 (SREBP1) and Peroxisome Proliferatoractivated Receptor (PPAR). Conclusion: Overall, AA flow across various tissues reveals AA metabolism and utilization in dairy cows on one hand. While the function of AA in the biosynthesis of milk protein, fat and lactose at both transcriptional and posttranscriptional level from another angle provides the possibility for us to regulate them for higher efficiency.

Metabolism of leucine by the isolated perfused goat udder

1983 ◽  
Vol 50 (4) ◽  
pp. 413-424 ◽  
Author(s):  
Eddy Roets ◽  
Anne-Marie Massart-Leën ◽  
Georges Peeters ◽  
Roger Verbeke
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Milk Protein ◽  
Lipid Synthesis ◽  
Mammary Glands ◽  
Plasma Leucine ◽  
Free Plasma ◽  
Casein Synthesis

SUMMARYSeven lactating goat mammary glands from 6 goats were perfused for several hours in the presence of [U-14C]L-leucine (4 experiments) or [2-3H; l-14C]DL-leucine (3 experiments) and received adequate quantities of glucose, acetate and amino acids. Radioactivity in casein was mainly recovered in leucine and 90% of casein leucine was derived from free plasma leucine. About 64% of the leucine molecules were used for casein synthesis. Up to 12% of the molecules were channelled into lipid synthesis, while the remaining (up to 24%) were metabolized to CO2. From the 3H/14C ratio of casein and casein leucine, it was calculated that 70–80% of the leucine molecules were reversibly transaminated before their incorporation into milk protein. However, only 4–8% of the plasma leucine molecules were transaminated during passage through the udder. Different pools for oxidation and for protein synthesis may be present in the goat mammary gland.

scholarly journals Effects of Insulin and Postruminal Supply of Protein on Use of Amino Acids by the Mammary Gland for Milk Protein Synthesis

2000 ◽  
Vol 83 (1) ◽  
pp. 93-105 ◽  
Author(s):  
T.R. Mackle ◽  
D.A. Dwyer ◽  
K.L. Ingvartsen ◽  
P.Y. Chouinard ◽  
D.A. Ross ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Milk Protein

Evidence for the utilization of peptides for milk protein synthesis in the lactating dairy goat in vivo

1996 ◽  
Vol 271 (4) ◽  
pp. R955-R960 ◽  
Author(s):  
F. R. Backwell ◽  
B. J. Bequette ◽  
D. Wilson ◽  
J. A. Metcalf ◽  
M. F. Franklin ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Milk Protein ◽  
Indirect Evidence ◽  
Dairy Goat ◽  
Dairy Goats ◽  
Milk Casein ◽  
Amino Acid Precursors

Precursors for milk protein synthesis have been examined in lactating dairy goats using arteriovenous difference and isotope kinetic techniques. Certain amino acids, such as phenylalanine and histidine, are taken up by the mammary gland in quantities that are insufficient to account for their output in milk protein. Some amino acids have been shown to be present in significant quantities (10-30% of total non-protein-bound amino acids) as peptides (< 1,500 Da) in the arterial supply to the mammary gland, although methodological considerations make it difficult to accurately assess the extent of their uptake across the tissue bed. Indirect evidence for the utilization of peptides for milk protein synthesis in vivo has been obtained, however, by examination of the kinetics of milk casein labeling during long-term (24 h) systemic infusion of [1-13C]phenylalanine and [1-13C]leucine. Comparison of plateau enrichments for blood, plasma, and casein indicate that, although, for leucine, the plasma free pool seems to provide all the leucine for milk protein synthesis, sources other than the labeled plasma free amino acids contribute phenylalanine (10-20%) for casein biosynthesis. These findings raise questions relating to the type and source of amino acid precursors used by tissues for protein synthesis.

scholarly journals Increasing Mammary Protein Synthesis through Endocrine and Nutritional Signals

2001 ◽  
Author(s):  
Mark A. McGuire ◽  
Amichai Arieli ◽  
Israel Bruckental ◽  
Dale E. Bauman
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Milk Yield ◽  
Milk Protein ◽  
Primary Cultures ◽  
Principal Component ◽  
Branched Chain Amino Acids ◽  
Igf System ◽  
Branched Chain

Objectives To determine endocrine factors that regulate the partitioning of amino acids by the mammary gland. To evaluate dietary flow and supply of energy and amino acids and their effects on milk protein synthesis and endocrine status. To use primary cultures of cow mammary epithelial cells to examine the role of specific factors on the rates and pattern of milk protein synthesis. Milk protein is an increasingly valuable component of milk but little is known regarding the specific hormonal and nutritional factors controlling milk protein synthesis. The research conducted for this project has determined that milk protein synthesis has the potential to be enhanced much greater than previously believed. Increases of over 25% in milk protein percent and yield were detected in studies utilizing abomasal infusion of casein and a hyperinsulinemic-euglycemic clamp. Thus, it appears that insulin, either directly or indirectly, can elicit a substantial increase in milk protein synthesis if additional amino acids are supplied. For additional amino acids, casein provided the best response even though substantial decreases in branched chain amino acids occur when the insulin clamp is utilized. Branched chain amino acids alone are incapable of supporting the enhanced milk protein output. The mammary gland can vary both blood flow and extraction efficiency of amino acids to support protein synthesis. A mammary culture system was used to demonstrate specific endocrine effects on milk protein synthesis. Insulin-like growth factor-I when substituted for insulin was able to enhance casein and a-lactalbumin mRNA. This suggests that insulin is a indirect regulator of milk protein synthesis working through the IGF system to control mammary production of casein and a-lactalbumin. Principal component analysis determined that carbohydrate had the greatest effect on milk protein yield with protein supply only having minor effects. Work in cattle determined that the site of digestion of starch did not affect milk composition alone but the degradability of starch and protein in the rumen can interact to alter milk yield. Cows fed diets with a high degree of rumen undegradability failed to specifically enhance milk protein but produced greater milk yield with similar composition. The mammary gland has an amazing ability to produce protein of great value. Research conducted here has demonstrated the unprecedented potential of the metabolic machinery in the mammary gland. Insulin, probably signaling the mammary gland through the IGF system is a key regulator that must be combined with adequate nutrition in order for maximum response.

scholarly journals Translational Mechanisms that Govern Milk Protein Levels and Composition

2004 ◽  
Author(s):  
Itamar Barash ◽  
Robert E. Rhoads
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Total Protein ◽  
Milk Protein ◽  
Molecular Mechanisms ◽  
Mrna Translation ◽  
Cytoplasmic Polyadenylation ◽  
Translational Initiation ◽  
Lactogenic Hormones

Original objectives: The long term objective of the project is to achieve higher content of protein in the milk of ruminants by modulating the translational machinery in the mammary gland. The first specific aim of the BARD proposal was to characterize responsiveness of various experimental systems to combination of lactogenic hormones and amino acids with particular emphasis on discrimination between the control of total protein synthesis and milk protein synthesis. Based on the results, we planned to proceed by characterizing the stage of protein synthesis in which the stimulation by lactogenic hormones and amino acid occur and finally we proposed to identify which components of the translation machinery are modified. Background to the topic: Milk protein is the most valuable component in milk, both for direct human consumption and for manufacturing cheese and other protein-based products. Attempts to augment protein content by the traditional methods of genetic selection and improved nutritional regimes have failed. The proposal was based on recent results suggesting that the limiting factor for augmenting protein synthesis in the bovine mammary gland is the efficiency of converting amino acids to milk proteins. Major conclusions, solutions, achievements: Insulin and prolactin synergistically stimulate â-casein mRNA translation by cytoplasmatic polyadenylation. The interaction between insulin and prolactin was demonstrated two decades ago as crucial for milk-protein synthesis, but the molecular mechanisms involved were not elucidated. We found in differentiated CID 9 mouse mammary epithelial cells line that insulin and prolactin synergistically increases the rate of milk protein mRNA translation. We focused on â-casein, the major milk protein, and found that the increase in â-casein mRNA translation was reflected in a shift to larger polysomes, indicating an effect on translational initiation. Inhibitors of the PI3K, mTOR, and MAPK pathways blocked insulin-stimulated total protein and â-casein synthesis but not the synergistic stimulation. Conversely, cordycepin, a polyadenylation inhibitor, abolished synergistic stimulation of protein synthesis without affecting insulin-stimulated translation. The poly(A) tract of â-casein mRNA progressively increased over 30 min of treatment with insulin plus prolactin. The 3’-untranslated region of â-casein mRNA was found to contain a cytoplasmic polyadenylation element (CPE), and in reporter constructs, this was sufficient for the translational enhancement and mRNA-specific polyadenylation. Furthermore, insulin and prolactin stimulated phosphorylation of cytoplasmic polyadenylation element binding protein (CPEB) but did not increase cytoplasmic polyadenylation. 

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