Biology subjects

Sreedevi, K.

Publications and source records attributed to Sreedevi, K..

3 recordsLinked to original sources

bioRxiv2026

Cardiac REDD1 alters glucose and fatty acid metabolic gene expression via an mTORC1-independent, PPAR alpha-dependent mechanism and drives hypertrophic growth

BackgroundRegulated in development and DNA damage 1 (REDD1) is a highly inducible molecule that plays a role in numerous physiological and pathophysiological processes. It is a well-established negative regulator of mammalian target of rapamycin complex 1 (mTORC1), which is critical for maintaining elevated fatty acid-to-glucose oxidation ratio in the heart. In addition, REDD1 deletion results in hyperglycemia, suggesting that REDD1 is critical for tissue glucose metabolism. The role of REDD1 in regulating cardiac glucose and/or fatty acid metabolism in response to physiologic or pathophysiologic cues, however, remains unexplored. MethodsHerein, we utilize AC16 cardiomyocytes with REDD1 deletion, as well as mice with global or cardiomyocyte-specific deletion of Redd1, and their respective controls. We also subject these mice cardiac pressure overload using transverse aortic constriction (TAC) for 2 weeks or sham operation as a control. To examine the molecular regulators of glucose oxidation, we utilized qPCR and western blotting to evaluate pyruvate dehydrogenase (PDH) kinase (PDK) and phospho-PDH (pPDH) levels, respectively. We also directly measured PDH activity and glucose-driven cellular respiration. To investigate the complete REDD1-dependent transcriptome and metabolome, we performed RNA-sequencing (RNA-Seq) and untargeted metabolomics, respectively. To determine if the observed gene expression changes were dependent upon transcription factor peroxisome proliferator-activated receptor alpha (PPAR), we utilized an established pharmacologic PPAR inhibitor, GW6471. Here, we measured PPAR activity directly, as well as the expression of its target genes. In order to determine if our observed effects were mTORC1-dependent, we utilized mTORC1-specific inhibitor, everolimus. Finally, we measured cardiac hypertrophy using gravimetric analyses (heart weight (HW)-to-body weight (BW) or HW-to-tibia length (TL) ratios) and histological analyses of cardiomyocyte cross sectional area (CSA). We also measured mRNA and protein levels of pathological hypertrophic markers Natriuretic Peptide B (Nppb) and Cardiac Ankyrin Repeat Protein (CARP), respectively. ResultsOur data demonstrate that physiological levels of glucose induce REDD1 expression in cardiomyocytes. Further, we show that in cardiomyocytes or the hearts of mice with REDD1 deletion, there is elevated PDK4 expression, as well as increased levels of pPDH (S300 and/or S293) and reduced PDH activity. Interestingly, everolimus treatment has no effect on these alterations. In vitro, we also observe elevated glycolysis and glycolytic capacity, and reduced maximal respiratory capacity (MRC) in the presence of glucose. Interestingly, our RNA-Seq data reveals the upregulation of genes involved in fatty acid catabolism. Further, we demonstrate that PPAR activity is enhanced, and everolimus treatment also has no effect on this parameter. Additionally, we show that treatment of cardiomyocytes with GW6471 normalizes the expression of its target genes (PDK4, ACSL1) and levels of pPDH (S300), that are elevated in cells with REDD1 deletion. Finally, we observe elevated REDD1 in the hearts of mice following TAC. Moreover, we show reduced HW/BW, HW/TL, cardiomyocyte CSA, and levels of cardiac Nppb and CARP in mice with cardiomyocyte Redd1 deletion subjected to TAC versus controls also subjected to TAC. Importantly, TAC-induced reductions in cardiac Pdk4 and pPDH (S293 and S300), are normalized to control levels in mice with Redd1 deletion subjected to TAC. ConclusionsTogether, our findings suggest that physiological glucose-induced and pathological pressure overload-induced REDD1 is required for enhancing glucose oxidation and suppressing fatty acid oxidation in cardiomyocytes. In this way, REDD1 supports cardiac hypertrophic growth. We also outline a mechanism whereby REDD1 inhibits PPAR activity, thereby inhibiting the expression of its target genes, including PDK4 and those involved in fatty acid oxidation. Finally, we demonstrate that these effects are independent of REDD1s ability to inhibit mTORC1.

cell biology↗

bioRxiv2025

PERM1 Gene Delivery via AAV Prevents Heart Failure in a Mouse Model of Pressure Overload

Heart failure with reduced ejection fraction (HFrEF) remains a leading cause of mortality worldwide. A hallmark of HFrEF is impaired cardiomyocyte contractility accompanied by disrupted mitochondrial bioenergetics; however, no current therapy targets both pathologies simultaneously. PERM1, a striated muscle-specific regulator of mitochondrial bioenergetics, is downregulated in HFrEF patients. We recently demonstrated that overexpression of PERM1 via adeno-associated virus 9 (AAV9-PERM1) enhances both cardiac contractility and mitochondrial biogenesis in C57BL/6 mice. In this study, we evaluated the therapeutic potential of AAV9-PERM1 in a pressure overload-induced mouse model of HFrEF. C57BL/6 mice were treated with either AAV9-PERM1 or control AAV9-GFP (1x1012 GC/mouse), followed by transverse aortic constriction (TAC) surgery. At 4 weeks post-TAC, control mice receiving AAV-GFP exhibited reduced left ventricular ejection fraction (LVEF), whereas AAV-PERM1 preserved LVEF at baseline levels. This cardioprotective effect was sustained through 8 weeks. Notably, AAV9-PERM1 completely abrogated TAC-induced cardiac hypertrophy and fibrosis. Mitochondrial analysis revealed that AAV9-PERM1 preserved mitochondrial DNA copy number and TFAM protein levels, both of which were reduced by TAC in control hearts. AAV9-PERM1 also improved mitochondrial respiration using pyruvate and octanoylcarnitine as substrates and prevented TAC-induced impairments in oxidative capacity. While PGC-1 expression remained unchanged in control TAC hearts, it was modestly yet significantly upregulated by AAV9-PERM1 in both sham and TAC groups. In addition, AAV9-PERM1 suppressed TAC-induced increases in O-GlcNAcylation, a stress-related posttranslational modification of proteins. Co-immunoprecipitation further revealed interactions of PERM1 with creatine kinase and troponin C, key proteins in ATP transduction and contractility, suggesting a functional coupling between mitochondrial energetics and contractility. In conclusion, AAV-PERM1 gene therapy effectively preserves cardiac function under pressure overload by maintaining mitochondrial biogenesis, respiration capacity and contractility. This study further suggests AAV-PERM1 as a promising therapeutic strategy for HFrEF.

physiology↗

bioRxiv2024

Does PERM1 Regulate Systolic Cardiac Function? A Game of Numbers.

We and others demonstrated that PERM1 is a positive regulator of mitochondrial bioenergetics in the heart. However, discrepant results have emerged with regard to whether PERM1 loss-of-function affect cardiac contractility. In order to exclude the possibility that the reported negative results can be due to insufficient power of statistical test, we conducted a more robust echocardiography (Echo) analysis by increasing the sample size. We used Perm1-KO and their respective wildtype (WT) littermates, which were destined to tissue harvest. This yielded 84 WT mice and 88 Perm1-KO mice. We analyzed Echo-derived parameters of left ventricular (LV) systolic function. At the end of the study, ejection fraction (EF) was 65.43 {+/-} 7.13 in WT vs. 53.98 {+/-} 8.80 in Perm1-KO yielding p < 0.00000000000000004. Other parameters which reached statistically significant difference between WT and Perm1-KO (at p < 0.05) included LV fractional shortening (FS), LV diastolic and systolic diameters, LV anterior and posterior systolic wall thickness, LV posterior wall systolic thickening, stroke volume, and cardiac output (CO). Retrospectively, a p value < 0.05 was consistently achieved in assessment of EF only after average N per group reached 13. Larger minimal N per group were required for other parameters. Of interest, in both groups there were no correlation between EF% and CO. At the same time, in both groups EF strongly inversely correlated with LV diastolic diameter. This led us to a speculation that low EF may be in part compensated by an increased LV circumference, for the purpose of maintaining invariant CO. Indeed, the intergroup difference in CO (6%) was much smaller than the intergroup difference in EF (18%). We conclude that PERM1 does regulate cardiac mechanics. Changes caused by constitutive Perm1-KO can be conceptualized as reduced contractility partially compensated by increased LV circumference. This study underscores the importance of sufficiently large sample size for detecting significant differences in Echo data.

physiology↗