KLF5 Is Induced by FOXO1 and Causes Oxidative Stress and Diabetic Cardiomyopathy

RATIONALE

Diabetic cardiomyopathy (DbCM) is a major complication in type-1 diabetes, accompanied by altered cardiac energetics, impaired mitochondrial function, and oxidative stress. Previous studies indicate that type-1 diabetes is associated with increased cardiac expression of KLF5 (Krüppel-like factor-5) and PPARα (peroxisome proliferator-activated receptor) that regulate cardiac lipid metabolism.

OBJECTIVE

In this study, we investigated the involvement of KLF5 in DbCM and its transcriptional regulation.

METHODS AND RESULTS

KLF5 mRNA levels were assessed in isolated cardiomyocytes from cardiovascular patients with diabetes and were higher compared with nondiabetic individuals. Analyses in human cells and diabetic mice with cardiomyocyte-specific FOXO1 (Forkhead box protein O1) deletion showed that FOXO1 bound directly on the KLF5 promoter and increased KLF5 expression. Diabetic mice with cardiomyocyte-specific FOXO1 deletion had lower cardiac KLF5 expression and were protected from DbCM. Genetic, pharmacological gain and loss of KLF5 function approaches and AAV (adeno-associated virus)-mediated Klf5 delivery in mice showed that KLF5 induces DbCM. Accordingly, the protective effect of cardiomyocyte FOXO1 ablation in DbCM was abolished when KLF5 expression was rescued. Similarly, constitutive cardiomyocyte-specific KLF5 overexpression caused cardiac dysfunction. KLF5 caused oxidative stress via direct binding on NADPH oxidase (NOX)4 promoter and induction of NOX4 (NADPH oxidase 4) expression. This was accompanied by accumulation of cardiac ceramides. Pharmacological or genetic KLF5 inhibition alleviated superoxide formation, prevented ceramide accumulation, and improved cardiac function in diabetic mice.

CONCLUSIONS

Diabetes-mediated activation of cardiomyocyte FOXO1 increases KLF5 expression, which stimulates NOX4 expression, ceramide accumulation, and causes DbCM.

Sex-Specific Human Cardiomyocyte Gene Regulation in Left Ventricular Pressure Overload

OBJECTIVE

To assess gene expression in cardiomyocytes isolated from patients with aortic stenosis, hypothesizing that maladaptive remodeling and inflammation-related genes are higher in male vs female patients.

PATIENTS AND METHODS

In this study, 34 patients with aortic stenosis undergoing aortic valve replacement from March 20, 2016, through May 24, 2017, at the German Heart Centre in Berlin, Germany, were included. Isolated cardiomyocytes from interventricular septum samples were used for gene expression analysis. Clinical and echocardiographic data were collected preoperatively.

RESULTS

Age, body mass index, systolic and diastolic blood pressure, comorbidities, and medication were similar between the 17 male and 17 female patients. The mean ± SD left ventricular end-diastolic diameter (52±9 vs 45±4 mm; P=.007) and posterior wall thickness (14.2±2.5 vs 12.1±1.6 mm; P=.03) were higher in male vs female patients, while ejection fraction was lower in male patients (49%±14% vs 59%±5%; P=.01). Focusing on structural genes involved in the development of cardiac hypertrophy and remodeling, we found that most were expressed higher in male vs female patients. Our modeling analysis revealed that 2 inflammation-related genes, CCN2 and NFKB1, were negatively related to ejection fraction, with this effect being male specific (P=.03 and P=.02, respectively).

CONCLUSION

These findings provide novel insight into cardiomyocyte-specific molecular changes related to sex differences in pressure overload and a significant male-specific association between cardiac function and inflammation-related genes. Considering these sex differences may contribute toward a more accurate design of research and the development of more appropriate therapeutic approaches for both male and female patients.

Abstract 490: Sex-Specific Inflammatory Gene Expression in the Hypertrophied and Failing Human Heart

Heart failure (HF) is a devastating syndrome with poor prognosis that is most often preceded by a left ventricular (LV) pressure overload (PO) disorder, such as aortic stenosis (AS). As pressure inside the LV increases, LV hypertrophy (LVH) develops. Persistent inflammation is known to be detrimental to the heart, which might promote HF. LVH manifests differently between men and women and there are pronounced sex differences in disease progression and outcome. However, the mechanisms that cause these differences are poorly understood. Hypothesizing significant sex differences, we aimed at studying the expression of inflammatory and remodeling genes in cardiomyocytes (CMs) isolated from the LV septum of AS patients ( n = 34; 50% men; 67.5 ± 9.6 years old) undergoing aortic valve replacement. Echocardiography was performed 1 week before surgery and 20.06 ± 9.7 days after surgery. Ethics committee approval and patient consent were obtained. There was no significant difference between men and women in age, body mass index, systolic and diastolic blood pressure, co-morbidities and medication. Posterior wall thickness ( P = 0.02), LV end diastolic diameter ( P = 0.007) and mass index ( P = 0.03) were higher in men than women. Preoperative ejection fraction (EF) was significantly lower in men than women ( P = 0.01). Postoperative EF levels improved in men reaching those of women. Compared to female CMs, male CMs had significantly higher levels of CTGF ( P = 0.03) and NFKB1 ( P = 0.01), as well as ACTC1 ( P = 0.03), GATA4 ( P = 0.03), GJA1 ( P = 0.03), MYH6 ( P = 0.02), MYL4 ( P = 0.03), NPPA ( P = 0.03) and NPPB ( P = 0.05). We found a negative association between gene expression and postoperative EF in men only for GATA4 ( r = -0.77, P = 0.01), GJA1 ( r = -0.69, P = 0.03), MYH6 ( r = -0.69, P = 0.04), MYH7 ( r = -0.82, P = 0.008), MYL4 ( r = -0.71, P = 0.03), NPPA ( r = -0.9, P = 0.001) and NPPB ( r = -0.79, P = 0.01). In end-stage HF, the levels of the chemokine receptor CXCR4 were higher ( P = 0.04) in LV samples of female ( n = 5) vs. male ( n = 4) patients. Collectively, in PO and HF, the expression of inflammatory and remodeling genes is regulated in a sex-specific manner, which may contribute to the mechanisms underlying sex differences in disease progression and outcome.

Abstract 548: Cardiomyocyte-KLF5 Expression is Increased by FOXO1 and Accounts for Cardiomyopathy in Type-1 Diabetes

Cardiomyopathy in type 1 diabetes (T1D) is accompanied by altered cardiac energetics, impaired mitochondrial function and oxidative stress. We showed previously increased cardiac expression of Krüppel-like factor 5 (KLF5) and Peroxisome Proliferator Activated Receptor (PPAR)α at late T1D stage in mice. We confirmed that KLF5 expression is higher in cardiomyocytes of diabetic patients than in non-diabetic individuals. Mechanistic analyses in human cardiomyocyte cells (AC16) and in mice with cardiomyocyte-specific FOXO1 deletion (αMHC- Foxo1 -/- ) revealed that FOXO1 activation accounts for the increased KLF5 expression via direct binding on Klf5 promoter. Both pharmacologic and cardiomyocyte-specific inhibition of KLF5 alleviated diabetic-related cardiac dysfunction. Accordingly, mice with doxycycline-mediated cardiomyocyte-specific KLF5 constitutive expression (αMHC-rtTA- Klf5 ) recapitulated cardiomyopathy even in the absence of T1D. We also showed that diabetic PPARα -/- mice had elevated cardiac KLF5 expression and cardiac dysfunction, suggesting that KLF5-driven diabetic cardiomyopathy is PPARα-independent. Furthermore, cardiomyocyte KLF5 upregulation was associated with oxidative stress, increased NADPH oxidase (NOX)4 expression, lower NADPH levels and impaired cellular Ca 2+ handling. Conversely, KLF5 inhibition prevented NOX4 upregulation and alleviated cardiac superoxide formation. Lipidomic analysis followed by Euclidean clustering showed strong correlation of lipidome profiles between αMHC-rtTA- Klf5 mice and diabetic C57BL/6 mice, while diabetic αMHC- Klf5 -/- mice and diabetic C57BL/6 mice that were treated with pharmacologic KLF5 inhibitor grouped with the non-diabetic C57BL/6 mice. Further analysis of individual lipid species showed increased ceramide accumulation in diabetic C57BL/6 and αMHC-rtTA- Klf5 mice that was reversed upon KLF5 inhibition. Treatment of αMHC-rtTA- Klf5 mice and diabetic C57BL/6 mice with the antioxidant LGM2605 improved partially cardiac dysfunction. In conclusion, cardiomyocyte KLF5 expression is activated by FOXO1 and drives diabetic cardiomyopathy in a non-PPARα-dependent manner, suggesting KLF5 inhibition as a therapeutic intervention in T1D cardiomyopathy.