Background Tetrahydrobiopterin is a cofactor of endothelial NO synthase ( eNOS ), which is critical to embryonic heart development. We aimed to study the effects of sapropterin (Kuvan), an orally active synthetic form of tetrahydrobiopterin on eNOS uncoupling and congenital heart defects ( CHD s) induced by pregestational diabetes mellitus in mice. Methods and Results Adult female mice were induced to pregestational diabetes mellitus by streptozotocin and bred with normal male mice to produce offspring. Pregnant mice were treated with sapropterin or vehicle during gestation. CHD s were identified by histological analysis. Cell proliferation, eNOS dimerization, and reactive oxygen species production were assessed in the fetal heart. Pregestational diabetes mellitus results in a spectrum of CHD s in their offspring. Oral treatment with sapropterin in the diabetic dams significantly decreased the incidence of CHD s from 59% to 27%, and major abnormalities, such as atrioventricular septal defect and double‐outlet right ventricle, were absent in the sapropterin‐treated group. Lineage tracing reveals that pregestational diabetes mellitus results in decreased commitment of second heart field progenitors to the outflow tract, endocardial cushions, and ventricular myocardium of the fetal heart. Notably, decreased cell proliferation and cardiac transcription factor expression induced by maternal diabetes mellitus were normalized with sapropterin treatment. Furthermore, sapropterin administration in the diabetic dams increased eNOS dimerization and lowered reactive oxygen species levels in the fetal heart. Conclusions Sapropterin treatment in the diabetic mothers improves eNOS coupling, increases cell proliferation, and prevents the development of CHD s in the offspring. Thus, sapropterin may have therapeutic potential in preventing CHD s in pregestational diabetes mellitus.

word count: 248Main text word count: 4,612Figures: 9; Tables: 1 Supplementary Table: 1; Supplementary Figure: 1References: 50All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/304006 doi: bioRxiv preprint first posted online Apr. 18, 2018; 2 ABSTRACT Aims: Tetrahydrobiopterin (BH4) is a co-factor of endothelial nitric oxide synthase (eNOS), which is critical to embryonic heart development. We aimed to study the effects of sapropterin (Kuvan®), an orally active synthetic form of BH4 on eNOS uncoupling and congenital heart defects (CHDs) induced by pregestational diabetes in mice.Methods: Adult female mice were induced to pregestational diabetes by streptozotocin and bred with normal males to produce offspring. Pregnant mice were treated with sapropterin or vehicle during gestation. CHDs were identified by histological analysis. Cell proliferation, eNOS dimerization and reactive oxygen species (ROS) production were assessed in the fetal heart. Results:Pregestational diabetes results in a spectrum of CHDs in their offspring. Oral treatment with sapropterin in the diabetic dams significantly decreased the incidence of CHDs from 59% to 27% and major abnormalities, such as atrioventricular septal defect and double outlet right ventricle were absent in the sapropterin treated group. Lineage tracing reveals that pregestational diabetes results in decreased commitment of second heart field progenitors to the outflow tract, endocardial cushions, and ventricular myocardium of the fetal heart. Notably, decreased cell proliferation and cardiac transcription factor expression induced by maternal diabetes were normalized with sapropterin treatment. Furthermore, sapropterin administration in the diabetic dams increased eNOS dimerization and lowered ROS levels in the fetal heart.Conclusions: Sapropterin treatment in the diabetic mothers improves eNOS coupling, increases cell proliferation and prevents the development of CHDs in the offspring. Thus, sapropterin may have therapeutic potential in preventing CHDs in pregestational diabetes.

Maternal cigarette smoking is a risk factor for congenital heart defects (CHDs). Nicotine replacement therapies are often offered to pregnant women following failed attempts of smoking cessation. However, the impact of nicotine on embryonic heart development is not well understood. In the present study, the effects of maternal nicotine exposure (MNE) during pregnancy on foetal heart morphogenesis were studied. Adult female mice were treated with nicotine using subcutaneous osmotic pumps at 0.75 or 1.5 mg/kg/day and subsequently bred with male mice. Our results show that MNE dose‐dependently increased CHDs in foetal mice. CHDs included atrial and ventricular septal defects, double outlet right ventricle, unguarded tricuspid orifice, hypoplastic left ventricle, thickened aortic and pulmonary valves, and ventricular hypertrophy. MNE also significantly reduced coronary artery size and vessel abundance in foetal hearts. Moreover, MNE resulted in higher levels of oxidative stress and altered the expression of key cardiogenic regulators in the developing heart. Nicotine exposure reduced epicardial‐to‐mesenchymal transition in foetal hearts. In conclusion, MNE induces CHDs and coronary artery malformation in mice. These findings provide insight into the adverse outcomes of foetuses by MNE during pregnancy.

Chronic Kidney Disease (CKD) affects 10-16% of the US population and its incidence is rising due to increasing prevalence of associated risk factors. Renal replacement therapy is required to treat late stage CKD and hemodialysis is the preferred modality for many patients. Vascular access is required for hemodialysis and arteriovenous fistulas (AVF) are currently the gold standard. This review intended to collate current knowledge on AVF outcomes regarding both the patient and fistula. Scopus and Medline were utilized to identify relevant literature. Inclusion and exclusion criteria were applied to narrow search results. Among CKD patients, 33.5-77.4% require a central venous catheter (CVC) before dialysis through a fistula. Many patients (33-51%) use a CVC regardless of AVF creation due to fistula immaturity or failure. There are large variations in AVF creation policies internationally; 16% of American hemodialysis patients use a fistula compared to 72% of German patients. Primary patency and primary AVFs' failure ranges from 60-70% and 20-26%, respectively. AVFs reduce morbidity and mortality in CKD. At present, too many patients are receiving hemodialysis through a CVC. Inadequate referral times for AVF creation can lead to fistula immaturity or failure in the intervention. Many countries are lagging behind recommended AVF creation rates published by the Kidney Disease Outcomes Quality Initiative. There is a paucity of literature concerning when a patient should be referred for AVF creation. It is paramount to have better predictive outcome measures and more clarity as to when patients will benefit from an AVF.