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eIF6 coordinates insulin sensitivity and lipid metabolism by coupling translation to transcription.

Brina D, Miluzio A, Ricciardi S, Clarke K, Davidsen PK, Viero G, Tebaldi T, Offenhäuser N, Rozman J, Rathkolb B, Neschen S, Klingenspor M, Wolf E, Gailus-Durner V, Fuchs H, Hrabe de Angelis M, Quattrone A, Falciani F, Biffo S - Nat Commun (2015)

Bottom Line: Cells with reduced eukaryotic initiation factor 6 (eIF6) do not increase translation in response to insulin.The outcome of the translational activation by eIF6 is a reshaping of gene expression with increased levels of lipogenic and glycolytic enzymes.Finally, eIF6 levels modulate histone acetylation and amounts of rate-limiting fatty acid synthase (Fasn) mRNA.

View Article: PubMed Central - PubMed

Affiliation: INGM, 'Romeo ed Enrica Invernizzi', 20122 Milano, Italy.

ABSTRACT
Insulin regulates glycaemia, lipogenesis and increases mRNA translation. Cells with reduced eukaryotic initiation factor 6 (eIF6) do not increase translation in response to insulin. The role of insulin-regulated translation is unknown. Here we show that reduction of insulin-regulated translation in mice heterozygous for eIF6 results in normal glycaemia, but less blood cholesterol and triglycerides. eIF6 controls fatty acid synthesis and glycolysis in a cell autonomous fashion. eIF6 acts by exerting translational control of adipogenic transcription factors like C/EBPβ, C/EBPδ and ATF4 that have G/C rich or uORF sequences in their 5' UTR. The outcome of the translational activation by eIF6 is a reshaping of gene expression with increased levels of lipogenic and glycolytic enzymes. Finally, eIF6 levels modulate histone acetylation and amounts of rate-limiting fatty acid synthase (Fasn) mRNA. Since obesity, type 2 diabetes, and cancer require a Fasn-driven lipogenic state, we propose that eIF6 could be a therapeutic target for these diseases.

No MeSH data available.


Related in: MedlinePlus

eIF6 activity cell autonomously controls fatty acid synthesis, glycolysis and ATP levels.(a) Outline of the analysis. Primary hepatocytes from mice were isolated and assayed as specified. Experiments performed on biological replicates. All data are expressed as percentage of controls (wt), analysing primary cells from littermate couples of mice. (b) De novo lipogenesis, measured by labelling with D-[6-14C]-glucose and subsequent fatty acid analysis, is reduced in cells from eIF6 het mice. Cells were kept in 100 nM insulin and 20 mM glucose. N=6 (c) Lactate secretion, an index of glycolysis flux, is reduced in hepatocytes from eIF6 het mice. Basal values are around 30 pm μg−1 proteins per hour. N=6. (d) Fatty acid oxidation is not significantly affected (basal values of control around 1,000 c.p.m. μg−1 proteins). N=4 (e–g) ATP content depends from eIF6 levels: (e) ATP decreased in eIF6 het mice compared with wt ones. (f) Acute depletion of eIF6 leads to a reduction of ATP levels in eIF6+/+ cells, whereas (g) restoration of eIF6 levels leads to an increase in ATP in eIF6+/− cells. (h) Lactate secretion as in (f) after eIF6 shRNA in AML12 cells. (i) ATP as in (d), after eIF6 shRNA in AML12 cells. In all panels, data are represented as mean±s.d. Statistical P values were calculated by two-tailed t-test (*P value ≤0.05, ***P≤0.001). (e–i), N=3.
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f2: eIF6 activity cell autonomously controls fatty acid synthesis, glycolysis and ATP levels.(a) Outline of the analysis. Primary hepatocytes from mice were isolated and assayed as specified. Experiments performed on biological replicates. All data are expressed as percentage of controls (wt), analysing primary cells from littermate couples of mice. (b) De novo lipogenesis, measured by labelling with D-[6-14C]-glucose and subsequent fatty acid analysis, is reduced in cells from eIF6 het mice. Cells were kept in 100 nM insulin and 20 mM glucose. N=6 (c) Lactate secretion, an index of glycolysis flux, is reduced in hepatocytes from eIF6 het mice. Basal values are around 30 pm μg−1 proteins per hour. N=6. (d) Fatty acid oxidation is not significantly affected (basal values of control around 1,000 c.p.m. μg−1 proteins). N=4 (e–g) ATP content depends from eIF6 levels: (e) ATP decreased in eIF6 het mice compared with wt ones. (f) Acute depletion of eIF6 leads to a reduction of ATP levels in eIF6+/+ cells, whereas (g) restoration of eIF6 levels leads to an increase in ATP in eIF6+/− cells. (h) Lactate secretion as in (f) after eIF6 shRNA in AML12 cells. (i) ATP as in (d), after eIF6 shRNA in AML12 cells. In all panels, data are represented as mean±s.d. Statistical P values were calculated by two-tailed t-test (*P value ≤0.05, ***P≤0.001). (e–i), N=3.

Mentions: Changes in blood cholesterol and in ATP liver levels raise the question whether the metabolic changes driven by eIF6 are cell autonomous or due to indirect systemic events such as, for instance, reduced food intake/absorption or increased basal metabolic rate. We analysed metabolic parameters from primary hepatocytes isolated from mice (Fig. 2a). eIF6 het hepatocytes have 50% eIF6 protein compared with wt (Supplementary Fig. 2a), and, consistent with the in vivo phenotype, they fail to increase protein synthesis after insulin stimulation (Supplementary Fig. 2b). Glucose uptake of eIF6 het cells was identical to wt, consistent with the normal GTT observed in vivo (Supplementary Fig. 2c). Glucose uptake was also normal in eIF6-depleted 3T3-L1 cells (Supplementary Fig. 2d). Notably, primary eIF6 het hepatocytes, compared with wt ones, showed a significant reduction of de novo lipogenesis (Fig. 2b). Insulin stimulates glycolysis. We found that primary het hepatocytes had a significant reduction of glycolysis, as measured by lactate secretion (Fig. 2c). Fatty acid oxidation under feeding (Fig. 2d) was not significantly changed between wt and het. Hepatocytes from eIF6 het mice also had a reduction in ATP concentration (Fig. 2e). These results mirror the liver condition, in vivo, as described in Fig. 1. To investigate if eIF6 acutely controlled ATP levels, we either silenced eIF6 by lentiviral-mediated shRNA in wt hepatocytes or re-expressed eIF6 by lentiviral-mediated infection in het hepatocytes. Briefly, we found that, in wt hepatocytes, eIF6 acute depletion reduced intracellular ATP (Fig. 2f), whereas eIF6 overexpression, in het ones, increased it (Fig. 2g). We asked whether eIF6 might steer the metabolic activity of established cell lines. AML12 cells are derived from non-tumourigenic murine liver hepatocytes. In AML12 cells, we found that depletion of eIF6 by shRNA reduced glycolysis, measured as lactate secretion (Fig. 2h), and ATP content (Fig. 2i).


eIF6 coordinates insulin sensitivity and lipid metabolism by coupling translation to transcription.

Brina D, Miluzio A, Ricciardi S, Clarke K, Davidsen PK, Viero G, Tebaldi T, Offenhäuser N, Rozman J, Rathkolb B, Neschen S, Klingenspor M, Wolf E, Gailus-Durner V, Fuchs H, Hrabe de Angelis M, Quattrone A, Falciani F, Biffo S - Nat Commun (2015)

eIF6 activity cell autonomously controls fatty acid synthesis, glycolysis and ATP levels.(a) Outline of the analysis. Primary hepatocytes from mice were isolated and assayed as specified. Experiments performed on biological replicates. All data are expressed as percentage of controls (wt), analysing primary cells from littermate couples of mice. (b) De novo lipogenesis, measured by labelling with D-[6-14C]-glucose and subsequent fatty acid analysis, is reduced in cells from eIF6 het mice. Cells were kept in 100 nM insulin and 20 mM glucose. N=6 (c) Lactate secretion, an index of glycolysis flux, is reduced in hepatocytes from eIF6 het mice. Basal values are around 30 pm μg−1 proteins per hour. N=6. (d) Fatty acid oxidation is not significantly affected (basal values of control around 1,000 c.p.m. μg−1 proteins). N=4 (e–g) ATP content depends from eIF6 levels: (e) ATP decreased in eIF6 het mice compared with wt ones. (f) Acute depletion of eIF6 leads to a reduction of ATP levels in eIF6+/+ cells, whereas (g) restoration of eIF6 levels leads to an increase in ATP in eIF6+/− cells. (h) Lactate secretion as in (f) after eIF6 shRNA in AML12 cells. (i) ATP as in (d), after eIF6 shRNA in AML12 cells. In all panels, data are represented as mean±s.d. Statistical P values were calculated by two-tailed t-test (*P value ≤0.05, ***P≤0.001). (e–i), N=3.
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f2: eIF6 activity cell autonomously controls fatty acid synthesis, glycolysis and ATP levels.(a) Outline of the analysis. Primary hepatocytes from mice were isolated and assayed as specified. Experiments performed on biological replicates. All data are expressed as percentage of controls (wt), analysing primary cells from littermate couples of mice. (b) De novo lipogenesis, measured by labelling with D-[6-14C]-glucose and subsequent fatty acid analysis, is reduced in cells from eIF6 het mice. Cells were kept in 100 nM insulin and 20 mM glucose. N=6 (c) Lactate secretion, an index of glycolysis flux, is reduced in hepatocytes from eIF6 het mice. Basal values are around 30 pm μg−1 proteins per hour. N=6. (d) Fatty acid oxidation is not significantly affected (basal values of control around 1,000 c.p.m. μg−1 proteins). N=4 (e–g) ATP content depends from eIF6 levels: (e) ATP decreased in eIF6 het mice compared with wt ones. (f) Acute depletion of eIF6 leads to a reduction of ATP levels in eIF6+/+ cells, whereas (g) restoration of eIF6 levels leads to an increase in ATP in eIF6+/− cells. (h) Lactate secretion as in (f) after eIF6 shRNA in AML12 cells. (i) ATP as in (d), after eIF6 shRNA in AML12 cells. In all panels, data are represented as mean±s.d. Statistical P values were calculated by two-tailed t-test (*P value ≤0.05, ***P≤0.001). (e–i), N=3.
Mentions: Changes in blood cholesterol and in ATP liver levels raise the question whether the metabolic changes driven by eIF6 are cell autonomous or due to indirect systemic events such as, for instance, reduced food intake/absorption or increased basal metabolic rate. We analysed metabolic parameters from primary hepatocytes isolated from mice (Fig. 2a). eIF6 het hepatocytes have 50% eIF6 protein compared with wt (Supplementary Fig. 2a), and, consistent with the in vivo phenotype, they fail to increase protein synthesis after insulin stimulation (Supplementary Fig. 2b). Glucose uptake of eIF6 het cells was identical to wt, consistent with the normal GTT observed in vivo (Supplementary Fig. 2c). Glucose uptake was also normal in eIF6-depleted 3T3-L1 cells (Supplementary Fig. 2d). Notably, primary eIF6 het hepatocytes, compared with wt ones, showed a significant reduction of de novo lipogenesis (Fig. 2b). Insulin stimulates glycolysis. We found that primary het hepatocytes had a significant reduction of glycolysis, as measured by lactate secretion (Fig. 2c). Fatty acid oxidation under feeding (Fig. 2d) was not significantly changed between wt and het. Hepatocytes from eIF6 het mice also had a reduction in ATP concentration (Fig. 2e). These results mirror the liver condition, in vivo, as described in Fig. 1. To investigate if eIF6 acutely controlled ATP levels, we either silenced eIF6 by lentiviral-mediated shRNA in wt hepatocytes or re-expressed eIF6 by lentiviral-mediated infection in het hepatocytes. Briefly, we found that, in wt hepatocytes, eIF6 acute depletion reduced intracellular ATP (Fig. 2f), whereas eIF6 overexpression, in het ones, increased it (Fig. 2g). We asked whether eIF6 might steer the metabolic activity of established cell lines. AML12 cells are derived from non-tumourigenic murine liver hepatocytes. In AML12 cells, we found that depletion of eIF6 by shRNA reduced glycolysis, measured as lactate secretion (Fig. 2h), and ATP content (Fig. 2i).

Bottom Line: Cells with reduced eukaryotic initiation factor 6 (eIF6) do not increase translation in response to insulin.The outcome of the translational activation by eIF6 is a reshaping of gene expression with increased levels of lipogenic and glycolytic enzymes.Finally, eIF6 levels modulate histone acetylation and amounts of rate-limiting fatty acid synthase (Fasn) mRNA.

View Article: PubMed Central - PubMed

Affiliation: INGM, 'Romeo ed Enrica Invernizzi', 20122 Milano, Italy.

ABSTRACT
Insulin regulates glycaemia, lipogenesis and increases mRNA translation. Cells with reduced eukaryotic initiation factor 6 (eIF6) do not increase translation in response to insulin. The role of insulin-regulated translation is unknown. Here we show that reduction of insulin-regulated translation in mice heterozygous for eIF6 results in normal glycaemia, but less blood cholesterol and triglycerides. eIF6 controls fatty acid synthesis and glycolysis in a cell autonomous fashion. eIF6 acts by exerting translational control of adipogenic transcription factors like C/EBPβ, C/EBPδ and ATF4 that have G/C rich or uORF sequences in their 5' UTR. The outcome of the translational activation by eIF6 is a reshaping of gene expression with increased levels of lipogenic and glycolytic enzymes. Finally, eIF6 levels modulate histone acetylation and amounts of rate-limiting fatty acid synthase (Fasn) mRNA. Since obesity, type 2 diabetes, and cancer require a Fasn-driven lipogenic state, we propose that eIF6 could be a therapeutic target for these diseases.

No MeSH data available.


Related in: MedlinePlus