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Hypoxia-inducible factor prolyl hydroxylase 1 (PHD1) deficiency promotes hepatic steatosis and liver-specific insulin resistance in mice.

Thomas A, Belaidi E, Aron-Wisnewsky J, van der Zon GC, Levy P, Clement K, Pepin JL, Godin-Ribuot D, Guigas B - Sci Rep (2016)

Bottom Line: Prolyl hydroxylases (PHDs) play an important role in regulating HIF-α isoform stability.PHD1 deficiency led to increase in glycolytic gene expression, lipogenic proteins ACC and FAS, hepatic steatosis and liver-specific insulin resistance.In conclusion, PHD1 deficiency promotes hepatic steatosis and liver-specific insulin resistance but does not worsen the deleterious effects of HFD on metabolic homeostasis.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire HP2, Université Grenoble Alpes, Grenoble, F-38042 France.

ABSTRACT
Obesity is associated with local tissue hypoxia and elevated hypoxia-inducible factor 1 alpha (HIF-1α) in metabolic tissues. Prolyl hydroxylases (PHDs) play an important role in regulating HIF-α isoform stability. In the present study, we investigated the consequence of whole-body PHD1 gene (Egln2) inactivation on metabolic homeostasis in mice. At baseline, PHD1-/- mice exhibited higher white adipose tissue (WAT) mass, despite lower body weight, and impaired insulin sensitivity and glucose tolerance when compared to age-matched wild-type (WT) mice. When fed a synthetic low-fat diet, PHD1-/- mice also exhibit a higher body weight gain and WAT mass along with glucose intolerance and systemic insulin resistance compared to WT mice. PHD1 deficiency led to increase in glycolytic gene expression, lipogenic proteins ACC and FAS, hepatic steatosis and liver-specific insulin resistance. Furthermore, gene markers of inflammation were also increased in the liver, but not in WAT or skeletal muscle, of PHD1-/- mice. As expected, high-fat diet (HFD) promoted obesity, hepatic steatosis, tissue-specific inflammation and systemic insulin resistance in WT mice but these diet-induced metabolic alterations were not exacerbated in PHD1-/- mice. In conclusion, PHD1 deficiency promotes hepatic steatosis and liver-specific insulin resistance but does not worsen the deleterious effects of HFD on metabolic homeostasis.

No MeSH data available.


Related in: MedlinePlus

PHD1 deficiency promotes hepatic steatosis.Livers from WT (open bars) and PHD−/− (black bars) mice on either low-fat (LFD) or high-fat (HFD) diet were sampled (A) after 12 weeks. Hepatic cholesterol (B) and triglycerides (TG, C) contents were determined. The mRNA expression of key genes involved in the regulation of hepatic TG synthesis (Srebf1: SREBP-1c; Acaca: ACC1; Fasn: FAS; Scd1: SCD1), cholesterol synthesis (Srebf2: SREBP2 ; Hmgcs2: HMGCoA synthase; Hmgcr: HMGCoA reductase) and fatty acid oxidation (Ppara: PPARα; Pdk4: PDK4 ;Cpt1a: CPT-1α; Acox1: acyl-coA oxidase 1) was measured by RT-qPCR (D). Liver ACC and FAS protein expression were studied by Western blot. Representative blots are shown in (E). Total protein expression was quantified by densitometric analysis and expressed as fold change relative to WT-LFD mice (F,G). HSP90 was used for internal housekeeping protein expression. The mRNA expression of key genes involved in hepatic glycolysis (H; Slc2a1:GLUT1; Slc2a2, GLUT2; Gapdh, GAPDH; Eno1, Enolase; Pklr, PK) and inflammation (I; Emr1: F4/80; Vsig4: VSIG4; Tnfa: TNFα; Il6: IL6) was measured by RT-qPCR. All the RT-qPCR results are expressed relative to the housekeeping gene RPLP0 as fold change vs WT-LFD mice. Data are means ± SEM (n = 4 for LFD-WT; n = 7 for LFD-PHD1−/−; n = 5 for HFD-WT; n = 7 for HFD-PHD1−/−). *p < 0.05 vs LFD mice, #p < 0.05 vs WT mice.
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f4: PHD1 deficiency promotes hepatic steatosis.Livers from WT (open bars) and PHD−/− (black bars) mice on either low-fat (LFD) or high-fat (HFD) diet were sampled (A) after 12 weeks. Hepatic cholesterol (B) and triglycerides (TG, C) contents were determined. The mRNA expression of key genes involved in the regulation of hepatic TG synthesis (Srebf1: SREBP-1c; Acaca: ACC1; Fasn: FAS; Scd1: SCD1), cholesterol synthesis (Srebf2: SREBP2 ; Hmgcs2: HMGCoA synthase; Hmgcr: HMGCoA reductase) and fatty acid oxidation (Ppara: PPARα; Pdk4: PDK4 ;Cpt1a: CPT-1α; Acox1: acyl-coA oxidase 1) was measured by RT-qPCR (D). Liver ACC and FAS protein expression were studied by Western blot. Representative blots are shown in (E). Total protein expression was quantified by densitometric analysis and expressed as fold change relative to WT-LFD mice (F,G). HSP90 was used for internal housekeeping protein expression. The mRNA expression of key genes involved in hepatic glycolysis (H; Slc2a1:GLUT1; Slc2a2, GLUT2; Gapdh, GAPDH; Eno1, Enolase; Pklr, PK) and inflammation (I; Emr1: F4/80; Vsig4: VSIG4; Tnfa: TNFα; Il6: IL6) was measured by RT-qPCR. All the RT-qPCR results are expressed relative to the housekeeping gene RPLP0 as fold change vs WT-LFD mice. Data are means ± SEM (n = 4 for LFD-WT; n = 7 for LFD-PHD1−/−; n = 5 for HFD-WT; n = 7 for HFD-PHD1−/−). *p < 0.05 vs LFD mice, #p < 0.05 vs WT mice.

Mentions: Hepatic insulin resistance is often associated with nonalcoholic steatohepatitis (NASH), which is characterized by inflammation and ectopic accumulation of TG in the liver. Strikingly, PDH1−/− mice on LFD exhibited visible steatosis and significantly higher hepatic cholesterol and TG content (Fig. 4A–C). This was associated with increased gene and protein expression of the lipogenic enzymes ACC and FAS (Fig. 4D–G) compared to WT mice. Of note, similar increase in lipogenic gene expression were also found in PDH1−/− mice on regular chow diet when compared with WT mice (Fig. S5). Interestingly, the expression of key genes involved in glycolysis were also upregulated in the liver from PDH1−/− mice (Fig. 4H). In addition, a higher expression of some inflammatory gene markers was observed in liver from LFD-fed PHD1−/− mice (Fig. 4I). As expected, HFD increased liver cholesterol and TG levels in WT mice, along with a compensatory down-regulation of proteins involved in hepatic de novo lipogenesis (Fig. 4A–I). However, neither hepatic lipid composition nor expression of lipogenic proteins significantly differed between WT and PHD1−/− mice on HFD, indicating that HFD-induced hepatic steatosis was not aggravated by PHD1 deficiency.


Hypoxia-inducible factor prolyl hydroxylase 1 (PHD1) deficiency promotes hepatic steatosis and liver-specific insulin resistance in mice.

Thomas A, Belaidi E, Aron-Wisnewsky J, van der Zon GC, Levy P, Clement K, Pepin JL, Godin-Ribuot D, Guigas B - Sci Rep (2016)

PHD1 deficiency promotes hepatic steatosis.Livers from WT (open bars) and PHD−/− (black bars) mice on either low-fat (LFD) or high-fat (HFD) diet were sampled (A) after 12 weeks. Hepatic cholesterol (B) and triglycerides (TG, C) contents were determined. The mRNA expression of key genes involved in the regulation of hepatic TG synthesis (Srebf1: SREBP-1c; Acaca: ACC1; Fasn: FAS; Scd1: SCD1), cholesterol synthesis (Srebf2: SREBP2 ; Hmgcs2: HMGCoA synthase; Hmgcr: HMGCoA reductase) and fatty acid oxidation (Ppara: PPARα; Pdk4: PDK4 ;Cpt1a: CPT-1α; Acox1: acyl-coA oxidase 1) was measured by RT-qPCR (D). Liver ACC and FAS protein expression were studied by Western blot. Representative blots are shown in (E). Total protein expression was quantified by densitometric analysis and expressed as fold change relative to WT-LFD mice (F,G). HSP90 was used for internal housekeeping protein expression. The mRNA expression of key genes involved in hepatic glycolysis (H; Slc2a1:GLUT1; Slc2a2, GLUT2; Gapdh, GAPDH; Eno1, Enolase; Pklr, PK) and inflammation (I; Emr1: F4/80; Vsig4: VSIG4; Tnfa: TNFα; Il6: IL6) was measured by RT-qPCR. All the RT-qPCR results are expressed relative to the housekeeping gene RPLP0 as fold change vs WT-LFD mice. Data are means ± SEM (n = 4 for LFD-WT; n = 7 for LFD-PHD1−/−; n = 5 for HFD-WT; n = 7 for HFD-PHD1−/−). *p < 0.05 vs LFD mice, #p < 0.05 vs WT mice.
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f4: PHD1 deficiency promotes hepatic steatosis.Livers from WT (open bars) and PHD−/− (black bars) mice on either low-fat (LFD) or high-fat (HFD) diet were sampled (A) after 12 weeks. Hepatic cholesterol (B) and triglycerides (TG, C) contents were determined. The mRNA expression of key genes involved in the regulation of hepatic TG synthesis (Srebf1: SREBP-1c; Acaca: ACC1; Fasn: FAS; Scd1: SCD1), cholesterol synthesis (Srebf2: SREBP2 ; Hmgcs2: HMGCoA synthase; Hmgcr: HMGCoA reductase) and fatty acid oxidation (Ppara: PPARα; Pdk4: PDK4 ;Cpt1a: CPT-1α; Acox1: acyl-coA oxidase 1) was measured by RT-qPCR (D). Liver ACC and FAS protein expression were studied by Western blot. Representative blots are shown in (E). Total protein expression was quantified by densitometric analysis and expressed as fold change relative to WT-LFD mice (F,G). HSP90 was used for internal housekeeping protein expression. The mRNA expression of key genes involved in hepatic glycolysis (H; Slc2a1:GLUT1; Slc2a2, GLUT2; Gapdh, GAPDH; Eno1, Enolase; Pklr, PK) and inflammation (I; Emr1: F4/80; Vsig4: VSIG4; Tnfa: TNFα; Il6: IL6) was measured by RT-qPCR. All the RT-qPCR results are expressed relative to the housekeeping gene RPLP0 as fold change vs WT-LFD mice. Data are means ± SEM (n = 4 for LFD-WT; n = 7 for LFD-PHD1−/−; n = 5 for HFD-WT; n = 7 for HFD-PHD1−/−). *p < 0.05 vs LFD mice, #p < 0.05 vs WT mice.
Mentions: Hepatic insulin resistance is often associated with nonalcoholic steatohepatitis (NASH), which is characterized by inflammation and ectopic accumulation of TG in the liver. Strikingly, PDH1−/− mice on LFD exhibited visible steatosis and significantly higher hepatic cholesterol and TG content (Fig. 4A–C). This was associated with increased gene and protein expression of the lipogenic enzymes ACC and FAS (Fig. 4D–G) compared to WT mice. Of note, similar increase in lipogenic gene expression were also found in PDH1−/− mice on regular chow diet when compared with WT mice (Fig. S5). Interestingly, the expression of key genes involved in glycolysis were also upregulated in the liver from PDH1−/− mice (Fig. 4H). In addition, a higher expression of some inflammatory gene markers was observed in liver from LFD-fed PHD1−/− mice (Fig. 4I). As expected, HFD increased liver cholesterol and TG levels in WT mice, along with a compensatory down-regulation of proteins involved in hepatic de novo lipogenesis (Fig. 4A–I). However, neither hepatic lipid composition nor expression of lipogenic proteins significantly differed between WT and PHD1−/− mice on HFD, indicating that HFD-induced hepatic steatosis was not aggravated by PHD1 deficiency.

Bottom Line: Prolyl hydroxylases (PHDs) play an important role in regulating HIF-α isoform stability.PHD1 deficiency led to increase in glycolytic gene expression, lipogenic proteins ACC and FAS, hepatic steatosis and liver-specific insulin resistance.In conclusion, PHD1 deficiency promotes hepatic steatosis and liver-specific insulin resistance but does not worsen the deleterious effects of HFD on metabolic homeostasis.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire HP2, Université Grenoble Alpes, Grenoble, F-38042 France.

ABSTRACT
Obesity is associated with local tissue hypoxia and elevated hypoxia-inducible factor 1 alpha (HIF-1α) in metabolic tissues. Prolyl hydroxylases (PHDs) play an important role in regulating HIF-α isoform stability. In the present study, we investigated the consequence of whole-body PHD1 gene (Egln2) inactivation on metabolic homeostasis in mice. At baseline, PHD1-/- mice exhibited higher white adipose tissue (WAT) mass, despite lower body weight, and impaired insulin sensitivity and glucose tolerance when compared to age-matched wild-type (WT) mice. When fed a synthetic low-fat diet, PHD1-/- mice also exhibit a higher body weight gain and WAT mass along with glucose intolerance and systemic insulin resistance compared to WT mice. PHD1 deficiency led to increase in glycolytic gene expression, lipogenic proteins ACC and FAS, hepatic steatosis and liver-specific insulin resistance. Furthermore, gene markers of inflammation were also increased in the liver, but not in WAT or skeletal muscle, of PHD1-/- mice. As expected, high-fat diet (HFD) promoted obesity, hepatic steatosis, tissue-specific inflammation and systemic insulin resistance in WT mice but these diet-induced metabolic alterations were not exacerbated in PHD1-/- mice. In conclusion, PHD1 deficiency promotes hepatic steatosis and liver-specific insulin resistance but does not worsen the deleterious effects of HFD on metabolic homeostasis.

No MeSH data available.


Related in: MedlinePlus