Metabolic remodeling in cardiac hypertrophy and heart failure with reduced ejection fraction occurs independent of transcription factor EB in mice

Background

A metabolic shift from fatty acid (FAO) to glucose oxidation (GO) occurs during cardiac hypertrophy (LVH) and heart failure with reduced ejection fraction (HFrEF), which is mediated by PGC-1α and PPARα. While the transcription factor EB (TFEB) regulates the expression of both PPARGC1A/PGC-1α and PPARA/PPARα, its contribution to metabolic remodeling is uncertain.

Methods

Luciferase assays were performed to verify that TFEB regulates PPARGC1A expression. Cardiomyocyte-specific Tfeb knockout (cKO) and wildtype (WT) male mice were subjected to 27G transverse aortic constriction or sham surgery for 21 and 56 days, respectively, to induce LVH and HFrEF. Echocardiographic, morphological, and histological analyses were performed. Changes in markers of cardiac stress and remodeling, metabolic shift and oxidative phosphorylation were investigated by Western blot analyses, mass spectrometry, qRT-PCR, and citrate synthase and complex II activity measurements.

Results

Luciferase assays revealed that TFEB increases PPARGC1A/PGC-1α expression, which was inhibited by class IIa histone deacetylases and derepressed by protein kinase D. At baseline, cKO mice exhibited a reduced cardiac function, elevated stress markers and a decrease in FAO and GO gene expression compared to WT mice. LVH resulted in increased cardiac remodeling and a decreased expression of FAO and GO genes, but a comparable decline in cardiac function in cKO compared to WT mice. In HFrEF, cKO mice showed an improved cardiac function, lower heart weights, smaller myocytes and a reduction in cardiac remodeling compared to WT mice. Proteomic analysis revealed a comparable decrease in FAO- and increase in GO-related proteins in both genotypes. A significant reduction in mitochondrial quality control genes and a decreased citrate synthase and complex II activities was observed in hearts of WT but not cKO HFrEF mice.

Conclusions

TFEB affects the baseline expression of metabolic and mitochondrial quality control genes in the heart, but has only minor effects on the metabolic shift in LVH and HFrEF in mice. Deletion of TFEB plays a protective role in HFrEF but does not affect the course of LVH. Further studies are needed to elucidate if TFEB affects the metabolic flux in stressed cardiomyocytes.

Activation of Tripartite Motif Containing 63 Expression by Transcription Factor EB and Transcription Factor Binding to Immunoglobulin Heavy Chain Enhancer 3 Is Regulated by Protein Kinase D and Class IIa Histone Deacetylases

Rationale

The ubiquitin–proteasome system (UPS) is responsible for skeletal muscle atrophy. We showed earlier that the transcription factor EB (TFEB) plays a role by increasing E3 ubiquitin ligase muscle really interesting new gene-finger 1(MuRF1)/tripartite motif-containing 63 (TRIM63) expression. MuRF 1 ubiquitinates structural proteins and mediates their UPS-dependent degradation. We now investigated how TFEB-mediated TRIM63 expression is regulated.

Objective

Because protein kinase D1 (PKD1), histone deacetylase 5 (HDAC5), and TFEB belong to respective families with close structural, regulatory, and functional properties, we hypothesized that these families comprise a network regulating TRIM63 expression.

Methods and Results

We found that TFEB and transcription factor for immunoglobulin heavy-chain enhancer 3 (TFE3) activate TRIM63 expression. The class IIa HDACs HDAC4, HDAC5, and HDAC7 inhibited this activity. Furthermore, we could map the HDAC5 and TFE3 physical interaction. PKD1, PKD2, and PKD3 reversed the inhibitory effect of all tested class IIa HDACs toward TFEB and TFE3. PKD1 mediated nuclear export of all HDACs and lifted TFEB and TFE3 repression. We also mapped the PKD2 and HDAC5 interaction. We found that the inhibitory effect of PKD1 and PKD2 toward HDAC4, HDAC5, and HDAC7 was mediated by their phosphorylation and 14-3-3 mediated nuclear export.

Conclusion

TFEB and TFE3 activate TRIM63 expression. Both transcription factors are controlled by HDAC4, HDAC5, HDAC7, and all PKD-family members. We propose that the multilevel PKD/HDAC/TFEB/TFE3 network tightly controls TRIM63 expression.

Angiotensin II Induces Skeletal Muscle Atrophy by Activating TFEB-Mediated MuRF1 Expression

RATIONALE

Skeletal muscle wasting with accompanying cachexia is a life threatening complication in congestive heart failure. The molecular mechanisms are imperfectly understood, although an activated renin-angiotensin aldosterone system has been implicated. Angiotensin (Ang) II induces skeletal muscle atrophy in part by increased muscle-enriched E3 ubiquitin ligase muscle RING-finger-1 (MuRF1) expression, which may involve protein kinase D1 (PKD1).

OBJECTIVE

To elucidate the molecular mechanism of Ang II-induced skeletal muscle wasting.

METHODS AND RESULTS

A cDNA expression screen identified the lysosomal hydrolase-coordinating transcription factor EB (TFEB) as novel regulator of the human MuRF1 promoter. TFEB played a key role in regulating Ang II-induced skeletal muscle atrophy by transcriptional control of MuRF1 via conserved E-box elements. Inhibiting TFEB with small interfering RNA prevented Ang II-induced MuRF1 expression and atrophy. The histone deacetylase-5 (HDAC5), which was directly bound to and colocalized with TFEB, inhibited TFEB-induced MuRF1 expression. The inhibition of TFEB by HDAC5 was reversed by PKD1, which was associated with HDAC5 and mediated its nuclear export. Mice lacking PKD1 in skeletal myocytes were resistant to Ang II-induced muscle wasting.

CONCLUSION

We propose that elevated Ang II serum concentrations, as occur in patients with congestive heart failure, could activate the PKD1/HDAC5/TFEB/MuRF1 pathway to induce skeletal muscle wasting.