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.

Amino acid transportation, sensing and signal transduction in the mammary gland: key molecular signalling pathways in the regulation of milk synthesis

2020 ◽  
Vol 33 (2) ◽  
pp. 287-297
Author(s):  
Zhihui Wu ◽  
Jinghui Heng ◽  
Min Tian ◽  
Hanqing Song ◽  
Fang Chen ◽  
...  
Keyword(s):  
Amino Acids ◽  
Mammary Gland ◽  
Milk Protein ◽  
Building Blocks ◽  
Branched Chain Amino Acids ◽  
Signalling Pathways ◽  
Recent Advances ◽  
Branched Chain ◽  
Molecular Signalling Pathways

AbstractThe mammary gland, a unique exocrine organ, is responsible for milk synthesis in mammals. Neonatal growth and health are predominantly determined by quality and quantity of milk production. Amino acids are crucial maternal nutrients that are the building blocks for milk protein and are potential energy sources for neonates. Recent advances made regarding the mammary gland further demonstrate that some functional amino acids also regulate milk protein and fat synthesis through distinct intracellular and extracellular pathways. In the present study, we discuss recent advances in the role of amino acids (especially branched-chain amino acids, methionine, arginine and lysine) in the regulation of milk synthesis. The present review also addresses the crucial questions of how amino acids are transported, sensed and transduced in the mammary gland.

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

Influence of branched-chain amino acids and branched-chain keto acids on protein synthesis in isolated hepatocytes

Hepatology ◽  
1987 ◽  
Vol 7 (2) ◽  
pp. 324-329 ◽  
Author(s):  
Wolfgang Base ◽  
Carl Barsigian ◽  
Alisa Schaeffer ◽  
Ellen Shaw ◽  
Jose Martinez ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Isolated Hepatocytes ◽  
Branched Chain Amino Acids ◽  
Keto Acids ◽  
Branched Chain ◽  
Branched Chain Keto Acids

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 Amino acid infusion increases the sensitivity of muscle protein synthesis in vivo to insulin. Effect of branched-chain amino acids

1988 ◽  
Vol 254 (2) ◽  
pp. 579-584 ◽  
Author(s):  
P J Garlick ◽  
I Grant
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Branched Chain Amino Acids ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Branched Chain

Rates of muscle protein synthesis were measured in vivo in tissues of post-absorptive young rats that were given intravenous infusions of various combinations of insulin and amino acids. In the absence of amino acid infusion, there was a steady rise in muscle protein synthesis with plasma insulin concentration up to 158 mu units/ml, but when a complete amino acids mixtures was included maximal rates were obtained at 20 mu units/ml. The effect of the complete mixture could be reproduced by a mixture of essential amino acids or of branched-chain amino acids, but not by a non-essential mixture, alanine, methionine or glutamine. It is concluded that amino acids, particularly the branched-chain ones, increase the sensitivity of muscle protein synthesis to insulin.

Protein synthesis in human tumour and muscle is enhanced more by TPN than by solutions enriched with branched-chain amino acids

1990 ◽  
Vol 9 ◽  
pp. 21-22 ◽  
Author(s):  
M.A. McNurlan ◽  
S.D. Heys ◽  
K.G.M. Park ◽  
J. Broom ◽  
D. Brown ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Branched Chain Amino Acids ◽  
Human Tumour ◽  
Branched Chain

scholarly journals Effect of endurance training and branched-chain amino acids on the signaling for muscle protein synthesis in CKD model rats fed a low-protein diet

2017 ◽  
Vol 313 (3) ◽  
pp. F805-F814 ◽  
Author(s):  
Takuya Yoshida ◽  
Sachika Kakizawa ◽  
Yuri Totsuka ◽  
Miho Sugimoto ◽  
Shinji Miura ◽  
...  
Keyword(s):  
Amino Acids ◽  
Renal Function ◽  
Protein Synthesis ◽  
Sham Group ◽  
Treadmill Exercise ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Branched Chain Amino Acids ◽  
Low Protein ◽  
Branched Chain

A low-protein diet (LPD) protects against the progression of renal injury in patients with chronic kidney disease (CKD). However, LPD may accelerate muscle wasting in these patients. Both exercise and branched-chain amino acids (BCAA) are known to increase muscle protein synthesis by activating the mammalian target of rapamycin (mTOR) pathway. The aim of this study was to investigate whether endurance exercise and BCAA play a role for increasing muscle protein synthesis in LPD-fed CKD (5/6 nephrectomized) rats. Both CKD and sham rats were pair-fed on LPD or LPD fortified with a BCAA diet (BD), and approximately one-half of the animals in each group was subjected to treadmill exercise (15 m/min, 1 h/day, 5 days/wk). After 7 wk, renal function was measured, and soleus muscles were collected to evaluate muscle protein synthesis. Renal function did not differ between LPD- and BD-fed CKD rats, and the treadmill exercise did not accelerate renal damage in either group. The treadmill exercise slightly increased the phosphorylation of p70s6 kinase, a marker of mTOR activity, in the soleus muscle of LPD-fed CKD rats compared with the sham group. Furthermore, BCAA supplementation of the LPD-fed, exercise-trained CKD rats restored the phosphorylation of p70s6 kinase to the same level observed in the sham group; however, the corresponding induced increase in muscle protein synthesis and muscle mass was marginal. These results indicate that the combination of treadmill exercise and BCAA stimulates cell signaling to promote muscle protein synthesis; however, the implications of this effect for muscle growth remain to be clarified.

Tumour and Host Tissue Responses to Branched-Chain Amino Acid Supplementation of Patients with Cancer

1994 ◽  
Vol 86 (3) ◽  
pp. 339-345 ◽  
Author(s):  
M. A. McNurlan ◽  
S. D. Heys ◽  
K. G. M. Park ◽  
J. Broom ◽  
D. S. Brown ◽  
...  
Keyword(s):  
Amino Acids ◽  
Body Weight ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Cancer Patients ◽  
Muscle Tissue ◽  
Branched Chain Amino Acids ◽  
Saline Control ◽  
Intravenous Nutrition ◽  
Branched Chain

1 Rates of protein synthesis have been measured from the incorporation of 57 mg of l-[1-13C]leucine/kg for 90 min into muscle tissue and colorectal tumours removed at surgery from cancer patients. 2. For the 20 h preceding surgery and during the measurement of protein synthesis, the patients received intravenous saline, conventional intravenous nutrition (0.2 g of N and 103 non-protein kJ/kg body weight) or intravenous nutrition enriched with the branched-chain amino acids leucine, isoleucine and valine (0.2 g of N with 30% from branched-chain amino acids and 103 non-protein kJ/kg body weight). 3. Conventional intravenous nutrition resulted in a significant stimulation of the rate of protein synthesis in both muscle tissue (2.64 ± 0.75%/day versus 1.78 ± 0.51%/day in saline control, means ± SD) and tumour tissue (43.9 ± 10.3%/day versus 22.6 ± 5.6%/day in saline control). 4. Pre-operative nutrition enriched with branched-chain amino acids was less effective than conventional intravenous nutrition in stimulating protein synthesis in both muscle and tumour. The rates of protein synthesis were 2.12 ± 0.41%/day in muscle and 33.7 ± 5.3%/day in the tumours. 5. The expression of proliferating cell nuclear antigen in sections of the tumours showed changes with intravenous feeding of the two different amino acid mixtures that were similar to the changes in protein synthesis, and these two variables were significantly correlated. This is evidence that feeding with conventional mixtures and mixtures enriched with branched-chain amino acids stimulates tumour growth. 6. In this study the mixture enriched with branched-chain amino acids provided no clear advantage for cancer patients, since a smaller response to branched-chain amino acids was observed in both tumours and host muscle tissue.

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