Limits...
Molecular regulation of urea cycle function by the liver glucocorticoid receptor.

Okun JG, Conway S, Schmidt KV, Schumacher J, Wang X, de Guia R, Zota A, Klement J, Seibert O, Peters A, Maida A, Herzig S, Rose AJ - Mol Metab (2015)

Bottom Line: Serum urea levels were consistently affected by GC/GR gain- (∼+32%) and loss (∼-30%) -of-function.Combined liver-specific GR loss-of-function with DEX treatment revealed a tissue-autonomous role for the GR to coordinate an upregulation of liver urea production rate in vivo and ex vivo, and prevent hyperammonaemia and associated neuromuscular dysfunction in vivo.Liver mRNA expression profiling and GR-cistrome mining identified Arginase I (ARG1) a urea cycle gene targeted by the liver GR.

View Article: PubMed Central - PubMed

Affiliation: Division of Neuropediatrics and Metabolic Medicine, University Children's Hospital, Heidelberg, Germany.

ABSTRACT

Objective: One of the major side effects of glucocorticoid (GC) treatment is lean tissue wasting, indicating a prominent role in systemic amino acid metabolism. In order to uncover a novel aspect of GCs and their intracellular-receptor, the glucocorticoid receptor (GR), on metabolic control, we conducted amino acid and acylcarnitine profiling in human and mouse models of GC/GR gain- and loss-of-function.

Methods: Blood serum and tissue metabolite levels were determined in Human Addison's disease (AD) patients as well as in mouse models of systemic and liver-specific GR loss-of-function (AAV-miR-GR) with or without dexamethasone (DEX) treatments. Body composition and neuromuscular and metabolic function tests were conducted in vivo and ex vivo, the latter using precision cut liver slices.

Results: A serum metabolite signature of impaired urea cycle function (i.e. higher [ARG]:[ORN + CIT]) was observed in human (CTRL: 0.45 ± 0.03, AD: 1.29 ± 0.04; p < 0.001) and mouse (AAV-miR-NC: 0.97 ± 0.13, AAV-miR-GR: 2.20 ± 0.19; p < 0.001) GC/GR loss-of-function, with similar patterns also observed in liver. Serum urea levels were consistently affected by GC/GR gain- (∼+32%) and loss (∼-30%) -of-function. Combined liver-specific GR loss-of-function with DEX treatment revealed a tissue-autonomous role for the GR to coordinate an upregulation of liver urea production rate in vivo and ex vivo, and prevent hyperammonaemia and associated neuromuscular dysfunction in vivo. Liver mRNA expression profiling and GR-cistrome mining identified Arginase I (ARG1) a urea cycle gene targeted by the liver GR.

Conclusions: The liver GR controls systemic and liver urea cycle function by transcriptional regulation of ARG1 expression.

No MeSH data available.


Related in: MedlinePlus

Mouse models of GR loss- and gain of function reveal a role from the liver glucocorticoid receptor in controlling urea cycle function. A: Serum urea levels from mice chronically treated with Dexamethasone (Dex) or corresponding Vehicle (Veh); n = 4/group. B: Serum urea levels from whole-body GRdim/dim or wildtype (WT) littermate mice chronically treated with Dex or corresponding Veh; n = 4–5/group. C: Serum urea (C), amino acid (D) as well as liver amino acid (E) levels in mice pre-treated with adeno-associated virus to express a negative control miR (AAV-miR-NC) or GR-specific miRNA (AAV-miR-GR); n = 9/group. Data are mean ± SEM. Effect of genotype/knockdown: *p < 0.05, **p < 0.01, ***p < 0.001. Effect of Dex: #p < 0.05, ##p < 0.01, ###p < 0.001.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4588454&req=5

fig2: Mouse models of GR loss- and gain of function reveal a role from the liver glucocorticoid receptor in controlling urea cycle function. A: Serum urea levels from mice chronically treated with Dexamethasone (Dex) or corresponding Vehicle (Veh); n = 4/group. B: Serum urea levels from whole-body GRdim/dim or wildtype (WT) littermate mice chronically treated with Dex or corresponding Veh; n = 4–5/group. C: Serum urea (C), amino acid (D) as well as liver amino acid (E) levels in mice pre-treated with adeno-associated virus to express a negative control miR (AAV-miR-NC) or GR-specific miRNA (AAV-miR-GR); n = 9/group. Data are mean ± SEM. Effect of genotype/knockdown: *p < 0.05, **p < 0.01, ***p < 0.001. Effect of Dex: #p < 0.05, ##p < 0.01, ###p < 0.001.

Mentions: Amino acid profiling reveals altered urea cycle function by the HPA-liver GR axis in human and mouse. To examine whether dysfunctional HPA axis and thus whole body glucocorticoid action affects novel aspects of metabolic function, we conducted amino acid/acylcarnitine profiling in Addison's patients versus aged-matched controls. In the fasted state, analysis of the serum from Addison's patients revealed higher amounts of tyrosine (TYR) and arginine (ARG), lower amounts of ornithine (ORN) and citrulline (CIT), and no change in any other amino acid (Figure 1A and Figure. S1A) or acylcarnitine species (Figure S1B). In particular, there was a heightened ratio of serum [ARG]:[ORN + CIT] in Addison's patients (1.29 ± 0.04) versus controls (0.45 ± 0.03; p < 0.001). Given that ARG, ORN and CIT are key metabolites within the urea cycle [33], we then examined serum urea, and we observed lower serum urea in Addison's patients. Importantly, this pattern was observed whether we examined serum taken from the postabsorptive or postprandial state (data not shown). In contrast to Addison's patients, whose condition is characterized by low circulating glucocorticoid levels [18], chronic treatment with the glucocorticoid-like drug dexamethasone (DEX) resulted in higher serum urea levels in mice (Figure 2A). As dexamethasone is a selective glucocorticoid receptor (GR) agonist [5], we tested whether there was an interaction between DEX treatment and GR function by examining the response to DEX in whole-body GR loss-of-function transgenic mice, which express a mutant GR incapable of dimerization function [19], and thus transcriptional effectiveness of the GR [19], particularly through canonical palindromic GR DNA binding motifs [35]. In particular, while DEX resulted in higher serum urea, this effect was absent in GRdim mice (Figure 2B), meaning that the effect of DEX to increase urea cycle rate is most likely conferred by systemic GR action. Given that the complete urea cycle in vivo mainly occurs in the liver parenchyma [33], we then tested whether urea cycle function is also affected in a mouse model of liver hepatocyte GR loss-of-function (AAV-miR-GR) [13]. Indeed, serum urea (Figure 2C) and the serum levels of the urea cycle metabolites ARG (↑), ORN (↓) and CIT (↓) were affected (Figure 2D) with a heightened ratio of serum [ARG]:[ORN + CIT] in AAV-miR-GR (2.20 ± 0.19) versus AAV-miR-NC (0.97 ± 0.13; p < 0.001). Importantly, a similar pattern was observed in the liver (Figure 2E). Furthermore, hepatocyte-specific GR loss-of-function resulted in higher amounts of TYR in serum and liver with several other amino acid (Figure S2A–B) and acylcarnitine species (Figure S2C–D), such as MET, GLN/GLU, and GLY, also being affected. Altogether, these data indicate that the liver GR modulates urea cycle function in vivo.


Molecular regulation of urea cycle function by the liver glucocorticoid receptor.

Okun JG, Conway S, Schmidt KV, Schumacher J, Wang X, de Guia R, Zota A, Klement J, Seibert O, Peters A, Maida A, Herzig S, Rose AJ - Mol Metab (2015)

Mouse models of GR loss- and gain of function reveal a role from the liver glucocorticoid receptor in controlling urea cycle function. A: Serum urea levels from mice chronically treated with Dexamethasone (Dex) or corresponding Vehicle (Veh); n = 4/group. B: Serum urea levels from whole-body GRdim/dim or wildtype (WT) littermate mice chronically treated with Dex or corresponding Veh; n = 4–5/group. C: Serum urea (C), amino acid (D) as well as liver amino acid (E) levels in mice pre-treated with adeno-associated virus to express a negative control miR (AAV-miR-NC) or GR-specific miRNA (AAV-miR-GR); n = 9/group. Data are mean ± SEM. Effect of genotype/knockdown: *p < 0.05, **p < 0.01, ***p < 0.001. Effect of Dex: #p < 0.05, ##p < 0.01, ###p < 0.001.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588454&req=5

fig2: Mouse models of GR loss- and gain of function reveal a role from the liver glucocorticoid receptor in controlling urea cycle function. A: Serum urea levels from mice chronically treated with Dexamethasone (Dex) or corresponding Vehicle (Veh); n = 4/group. B: Serum urea levels from whole-body GRdim/dim or wildtype (WT) littermate mice chronically treated with Dex or corresponding Veh; n = 4–5/group. C: Serum urea (C), amino acid (D) as well as liver amino acid (E) levels in mice pre-treated with adeno-associated virus to express a negative control miR (AAV-miR-NC) or GR-specific miRNA (AAV-miR-GR); n = 9/group. Data are mean ± SEM. Effect of genotype/knockdown: *p < 0.05, **p < 0.01, ***p < 0.001. Effect of Dex: #p < 0.05, ##p < 0.01, ###p < 0.001.
Mentions: Amino acid profiling reveals altered urea cycle function by the HPA-liver GR axis in human and mouse. To examine whether dysfunctional HPA axis and thus whole body glucocorticoid action affects novel aspects of metabolic function, we conducted amino acid/acylcarnitine profiling in Addison's patients versus aged-matched controls. In the fasted state, analysis of the serum from Addison's patients revealed higher amounts of tyrosine (TYR) and arginine (ARG), lower amounts of ornithine (ORN) and citrulline (CIT), and no change in any other amino acid (Figure 1A and Figure. S1A) or acylcarnitine species (Figure S1B). In particular, there was a heightened ratio of serum [ARG]:[ORN + CIT] in Addison's patients (1.29 ± 0.04) versus controls (0.45 ± 0.03; p < 0.001). Given that ARG, ORN and CIT are key metabolites within the urea cycle [33], we then examined serum urea, and we observed lower serum urea in Addison's patients. Importantly, this pattern was observed whether we examined serum taken from the postabsorptive or postprandial state (data not shown). In contrast to Addison's patients, whose condition is characterized by low circulating glucocorticoid levels [18], chronic treatment with the glucocorticoid-like drug dexamethasone (DEX) resulted in higher serum urea levels in mice (Figure 2A). As dexamethasone is a selective glucocorticoid receptor (GR) agonist [5], we tested whether there was an interaction between DEX treatment and GR function by examining the response to DEX in whole-body GR loss-of-function transgenic mice, which express a mutant GR incapable of dimerization function [19], and thus transcriptional effectiveness of the GR [19], particularly through canonical palindromic GR DNA binding motifs [35]. In particular, while DEX resulted in higher serum urea, this effect was absent in GRdim mice (Figure 2B), meaning that the effect of DEX to increase urea cycle rate is most likely conferred by systemic GR action. Given that the complete urea cycle in vivo mainly occurs in the liver parenchyma [33], we then tested whether urea cycle function is also affected in a mouse model of liver hepatocyte GR loss-of-function (AAV-miR-GR) [13]. Indeed, serum urea (Figure 2C) and the serum levels of the urea cycle metabolites ARG (↑), ORN (↓) and CIT (↓) were affected (Figure 2D) with a heightened ratio of serum [ARG]:[ORN + CIT] in AAV-miR-GR (2.20 ± 0.19) versus AAV-miR-NC (0.97 ± 0.13; p < 0.001). Importantly, a similar pattern was observed in the liver (Figure 2E). Furthermore, hepatocyte-specific GR loss-of-function resulted in higher amounts of TYR in serum and liver with several other amino acid (Figure S2A–B) and acylcarnitine species (Figure S2C–D), such as MET, GLN/GLU, and GLY, also being affected. Altogether, these data indicate that the liver GR modulates urea cycle function in vivo.

Bottom Line: Serum urea levels were consistently affected by GC/GR gain- (∼+32%) and loss (∼-30%) -of-function.Combined liver-specific GR loss-of-function with DEX treatment revealed a tissue-autonomous role for the GR to coordinate an upregulation of liver urea production rate in vivo and ex vivo, and prevent hyperammonaemia and associated neuromuscular dysfunction in vivo.Liver mRNA expression profiling and GR-cistrome mining identified Arginase I (ARG1) a urea cycle gene targeted by the liver GR.

View Article: PubMed Central - PubMed

Affiliation: Division of Neuropediatrics and Metabolic Medicine, University Children's Hospital, Heidelberg, Germany.

ABSTRACT

Objective: One of the major side effects of glucocorticoid (GC) treatment is lean tissue wasting, indicating a prominent role in systemic amino acid metabolism. In order to uncover a novel aspect of GCs and their intracellular-receptor, the glucocorticoid receptor (GR), on metabolic control, we conducted amino acid and acylcarnitine profiling in human and mouse models of GC/GR gain- and loss-of-function.

Methods: Blood serum and tissue metabolite levels were determined in Human Addison's disease (AD) patients as well as in mouse models of systemic and liver-specific GR loss-of-function (AAV-miR-GR) with or without dexamethasone (DEX) treatments. Body composition and neuromuscular and metabolic function tests were conducted in vivo and ex vivo, the latter using precision cut liver slices.

Results: A serum metabolite signature of impaired urea cycle function (i.e. higher [ARG]:[ORN + CIT]) was observed in human (CTRL: 0.45 ± 0.03, AD: 1.29 ± 0.04; p < 0.001) and mouse (AAV-miR-NC: 0.97 ± 0.13, AAV-miR-GR: 2.20 ± 0.19; p < 0.001) GC/GR loss-of-function, with similar patterns also observed in liver. Serum urea levels were consistently affected by GC/GR gain- (∼+32%) and loss (∼-30%) -of-function. Combined liver-specific GR loss-of-function with DEX treatment revealed a tissue-autonomous role for the GR to coordinate an upregulation of liver urea production rate in vivo and ex vivo, and prevent hyperammonaemia and associated neuromuscular dysfunction in vivo. Liver mRNA expression profiling and GR-cistrome mining identified Arginase I (ARG1) a urea cycle gene targeted by the liver GR.

Conclusions: The liver GR controls systemic and liver urea cycle function by transcriptional regulation of ARG1 expression.

No MeSH data available.


Related in: MedlinePlus