Genetic Loss of Nicotinamide Nucleotide Transhydrogenase Prevents from Cardiometabolic Heart Failure with Preserved Ejection Fraction

Rationale: Heart failure with preserved ejection fraction (HFpEF) represents a common clinical endpoint of cardiometabolic diseases which impair myocardial diastolic relaxation. Although myocardial redox perturbations are known to accompany HFpEF, the specific role of mitochondrial oxidative stress has not been demonstrated yet. Objective: Based on an observation that C57BL6/N – but not C57BL6/J – mice develop diastolic dysfunction when provided an ad libitum high-fat and 0.5% N(ω)-nitro-L-arginine methyl ester (HFD+L-NAME) diet, we conducted a multi-cohort murine study to determine whether the loss of Nicotinamide Nucleotide Transhydrogenase (NNT), a mitochondrial transhydrogenase that couples NADPH:NADP+ to NADH:NAD+ homeostasis, protects mice from developing cardiometabolic alterations. Methods and Results: Two cohorts of 12-week-old male and female mice possessing wild-type (Nnt+/+) or deleted (Nnt-/-) NNT were challenged by HFD+L-NAME for 9 weeks (n = 6-10). Male Nnt+/+ mice developed obesity (23.2% Δ, P = 0.003), arterial hypertension (24 ± 5 Δ mmHg, P = 0.023), impaired glucose tolerance (P = 0.006), and reduced maximal treadmill running distance (-172 ± 73.1 Δ m, P = 0.006) following 9 weeks HFD+L-NAME, whereas male Nnt-/- mice did not. Female mice were protected from cardiometabolic dysfunction regardless of Nnt genotype. Cardiac functional and morphologic characterization revealed similar NNT-dependent and sex-specific increases in E/e′ (42.8 vs. 21.5, P < 0.001) and E/A (2.3 vs 1.4, P = 0.007) ratios, diastolic stiffness (0.09 vs 0.04 mmHg/μL, P = 0.02), and myocardial fibrosis (P = 0.02). Unsupervised transcriptomic analysis identified distinct genetic and dietary signatures, wherein Nnt+/+ exhibited disproportionate perturbations in various mitochondrial oxidative pathways following HFD+L-NAME. Our search for putative transcriptional regulators identified NNT-dependent suppression of NAD+ dependent deacetylase Sirt3. Conclusions: Taken together, these observations support that the genetic disruption of Nnt protects against both cardiac and metabolic consequences of HFD+L-NAME, thus highlighting a novel etiology-specific avenue for HFpEF therapeutics. ### Competing Interest Statement The authors have declared no competing interest.