Methionine supply during the periparturient period enhances insulin signaling, amino acid transporters, and mechanistic target of rapamycin pathway proteins in adipose tissue of Holstein cows

The objective was to perform a proof-of-principle study to evaluate the effects of methionine (Met) and arginine (Arg) supply on protein abundance of amino acid, insulin signaling, and glutathione metabolism-related proteins in subcutaneous adipose tissue (SAT) explants under ceramide (Ce) challenge. SAT from four lactating Holstein cows was incubated with one of the following media: ideal profile of amino acid as the control (IPAA; Lys:Met 2.9:1, Lys:Arg 2:1), increased Met (incMet; Lys:Met 2.5:1), increased Arg (incArg; Lys:Arg 1:1), or incMet plus incArg (Lys:Met 2.5:1 Lys:Arg 1:1) with or without 100 μM exogenous cell-permeable Ce (N-Acetyl-d-sphingosine). Ceramide stimulation downregulated the overall abundance of phosphorylated (p) protein kinase B (AKT), p-mechanistic target of rapamycin (mTOR), and p-eukaryotic elongation factor 2 (eEF2). Without Ce stimulation, increased Met, Arg, or Met + Arg resulted in lower p-mTOR. Compared with control SAT stimulated with Ce, increased Met, Arg, or Met + Arg resulted in greater activation of mTOR (p-mTOR/total mTOR) and AKT (p-AKT/total AKT), with a more pronounced response due to Arg. The greatest protein abundance of glutathione S-transferase Mu 1 (GSTM1) was detected in response to increased Met supply during Ce stimulation. Ceramide stimulation decreased the overall protein abundance of the Na-coupled neutral amino acid transporter SLC38A1 and branched-chain alpha-ketoacid dehydrogenase kinase (BCKDK). However, compared with controls, increased Met or Arg supply attenuated the downregulation of BCKDK induced by Ce. Circulating ceramides might affect amino acid, insulin signaling, and glutathione metabolism in dairy cow adipose tissue. Further in vivo studies are needed to confirm the role of rumen-protected amino acids in regulating bovine adipose function.

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The Cationic Amino Acid Transporters CAT1 and CAT3 Mediate NMDA Receptor Activation-Dependent Changes in Elaboration of Neuronal Processes via the Mammalian Target of Rapamycin mTOR Pathway

Journal of Neuroscience ◽

10.1523/jneurosci.4489-06.2007 ◽

2007 ◽

Vol 27 (3) ◽

pp. 449-458 ◽

Cited By ~ 31

Author(s):

Y. Huang ◽

B. N. Kang ◽

J. Tian ◽

Y. Liu ◽

H. R. Luo ◽

...

Keyword(s):

Amino Acid ◽

Nmda Receptor ◽

Mammalian Target Of Rapamycin ◽

Receptor Activation ◽

Mtor Pathway ◽

Target Of Rapamycin ◽

Amino Acid Transporters ◽

Cationic Amino Acid ◽

Neuronal Processes ◽

Nmda Receptor Activation

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Up-Regulation of the Excitatory Amino Acid Transporters EAAT1 and EAAT2 by Mammalian Target of Rapamycin

Cellular Physiology and Biochemistry ◽

10.1159/000452516 ◽

2016 ◽

Vol 39 (6) ◽

pp. 2492-2500 ◽

Cited By ~ 3

Author(s):

Abeer Abousaab ◽

Nestor Luis Uzcategui ◽

Bhaeldin Elsir ◽

Florian Lang

Keyword(s):

Amino Acid ◽

Excitatory Amino Acid ◽

Mammalian Target Of Rapamycin ◽

Synaptic Cleft ◽

Target Of Rapamycin ◽

Amino Acid Transporters ◽

Protein Abundance ◽

Excitatory Amino Acid Transporters ◽

Neuronal Excitation ◽

Electrode Voltage

Background: The excitatory amino-acid transporters EAAT1 and EAAT2 clear glutamate from the synaptic cleft and thus terminate neuronal excitation. The carriers are subject to regulation by various kinases. The EAAT3 isoform is regulated by mammalian target of rapamycin (mTOR). The present study thus explored whether mTOR influences transport by EAAT1 and/or EAAT2. Methods: cRNA encoding wild type EAAT1 (SLC1A3) or EAAT2 (SLC1A2) was injected into Xenopus oocytes without or with additional injection of cRNA encoding mTOR. Dual electrode voltage clamp was performed in order to determine electrogenic glutamate transport (IEAAT). EAAT2 protein abundance was determined utilizing chemiluminescence. Results: Appreciable IEAAT was observed in EAAT1 or EAAT2 expressing but not in water injected oocytes. IEAAT was significantly increased by coexpression of mTOR. Coexpression of mTOR increased significantly the maximal IEAAT in EAAT1 or EAAT2 expressing oocytes, without significantly modifying affinity of the carriers. Moreover, coexpression of mTOR increased significantly EAAT2 protein abundance in the cell membrane. Conclusions: The kinase mTOR up-regulates the excitatory amino acid transporters EAAT1 and EAAT2.

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