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AMPK-mTOR pathway is involved in glucose-modulated amino acid sensing and utilization in the mammary glands of lactating goats.

ABSTRACT: Background:The local supply of energy-yielding nutrients such as glucose seems to affect the synthesis of milk components in the mammary gland (MG). Thus, our study was conducted to investigate the effects of locally available MG glucose supply (LMGS) on amino acid (AA) sensing and utilization in the MG of lactating dairy goats. Six dosages of glucose (0, 20, 40, 60, 80, and 100?g/d) were infused into the MG through the external pudendal artery to investigate the dose-dependent changes in mammary AA uptake and utilization (Exp.1) and the changes in mRNA and protein expression of the AMPK-mTOR pathway (Expt.2). Results:In Exp.1, total milk AA concentration was highest when goats were infused with 60?g/d glucose, but lower when goats were infused with 0 and 100?g/d glucose. Increasing LMGS quadratically changed the percentages of ?S2-casein and ?-lactalbumin in milk protein, which increased with infusions from 0 to 60?g/d glucose and then decreased with infusions between 60 and 100?g/d glucose. The LMGS changed the AA availability and intramammary gland AA utilization, as reflected by the mammary AA flux indexes. In Exp.2, the mRNA expression of LALBA in the MG increased quadratically with increasing LMGS, with the highest expression at dose of 60?g/d glucose. A high glucose dosage (100?g/d) activated the general control nonderepressible 2 kinase, an intracellular sensor of AA status, resulting in a reduced total milk AA concentration. Conclusions:Our new findings suggest that the lactating MG in dairy goats may be affected by LMGS through regulation of the AA sensory pathway, AA utilization and protein synthesis, all being driven by the AMPK-mTOR pathway.

SUBMITTER: Cai J

PROVIDER: S-EPMC7060552 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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AMPK-mTOR pathway is involved in glucose-modulated amino acid sensing and utilization in the mammary glands of lactating goats.

Cai Jie J Wang Diming D Zhao Feng-Qi FQ Liang Shulin S Liu Jianxin J

Journal of animal science and biotechnology 20200214

<h4>Background</h4>The local supply of energy-yielding nutrients such as glucose seems to affect the synthesis of milk components in the mammary gland (MG). Thus, our study was conducted to investigate the effects of locally available MG glucose supply (LMGS) on amino acid (AA) sensing and utilization in the MG of lactating dairy goats. Six dosages of glucose (0, 20, 40, 60, 80, and 100 g/d) were infused into the MG through the external pudendal artery to investigate the dose-dependent changes i ...[more]

PMID: 32166025

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Project description:To investigate the role of glucose in regulating milk fatty acid synthesis, 6 lactating Guanzhong dairy goats were infused with 0, 60, or 100 g/d glucose via the external pubic artery in a 3 × 3 repeated Latin square experiment. A concomitant in vitro experiment was conducted to investigate possible mechanisms whereby glucose regulates milk fatty acid synthesis. RNA sequencing was used for cellular transcriptome analysis. Drugs, MK-2206, rapamycin, and dorsomorphin were used to block cellular mammalian AMP-activated protein kinase (AMPK), AKT serine/threonine kinase 1, and mechanistic target of rapamycin kinase signaling pathways, respectively. Carbohydrate response element binding protein (ChREBP) was knockdown and overexpressed to investigate its role in regulating milk fatty acid synthesis in mammary epithelial cells. Glucose infusion linearly elevated the concentration of C8:0 (P = 0.039) and C10:0 (P = 0.041) in milk fat while it linearly decreased (P = 0.049) that of C16:0. This result was in agreement with the upregulation of genes related to de novo synthesis of fatty acids and lipid droplet formation, including adipose differentiation-related protein, butyrophilin subfamily 1 member A1, fatty acid synthase (FASN) and ChREBP. Their expression increased (P < 0.05) linearly in the lactating goat mammary gland. In vitro, glucose linearly stimulated the expression of genes related to de novo synthesis of fatty acids and cellular triacylglycerol in cultured mammary epithelial cells. RNA sequencing and inhibition studies revealed that glucose induced transcriptomic changes increasing lipogenic pathways, with AMPK responding to glucose by controlling ChREBP and FASN. Knockdown and overexpression of ChREBP highlighted its essential role in lipogenesis. The knockdown and overexpression of ChREBP protein also revealed an essential role in regulating the de novo synthesis of fatty acids. Collectively, our data highlight that glucose supplementation promotes de novo fatty acid synthesis via the AMPK-ChREBP axis, hence increasing milk fat yield in the goat mammary gland. Results from the current study provide possible strategies to manipulate the fatty acid composition as well as improve ruminant milk quality.

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AMPK-mTOR pathway is involved in glucose-modulated amino acid sensing and utilization in the mammary glands of lactating goats.

Publications

AMPK-mTOR pathway is involved in glucose-modulated amino acid sensing and utilization in the mammary glands of lactating goats.

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