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Ricci, Taylor Annelia

University of British Columbia

Background: Endothelial cells are modulate vascular tone and interface with systemic circulation. Riboflavin is a B-vitamin that is involved in redox and energy metabolism as flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). FAD/FMN are also required for the synthesis of vasodilatory nitric oxide (NO) by endothelial nitric oxide synthase (eNOS). However, the role of riboflavin in endothelial NO production and vascular homeostasis is not understood. The objective of my thesis was to determine the role of riboflavin on vascular function. Methods: Male and female C57BL/6J Nos3-/- mice (homozygous eNOS knockout) and Nos3+/+ littermates were fed a control diet (6mg/kg riboflavin) or low riboflavin (1mg/kg riboflavin) diet from weaning for 8 weeks (n=5-7 mice/sex/diet/genotype). Thoracic aorta was collected to assess ex vivo vascular endothelial-dependent and independent function, intima media thickness, and endothelial gene expression. Serum was collected for analysis of one-carbon metabolites. Results: Male and female mice fed the low riboflavin diet had lower (p<0.05) serum riboflavin concentrations; Nos3-/- mice had higher (p<0.001) serum riboflavin than Nos3+/+ mice. Riboflavin-deficient male mice had impaired endothelial-dependent vasodilation(Nos3-/-p<0.05; Nos3+/+ p=0.17) in response to acetylcholine (with ibuprofen, a prostaglandin inhibitor) compared to genotype-matched control male mice. Riboflavin-deficient male mice had increased sensitivity to endothelial-independent vasodilator, sodium nitroprusside (Nos3-/-p=0.05; Nos3+/+ p=0.19). In contrast, endothelial-dependent vasorelaxationwas mildly improved (p=0.08) in riboflavin-deficient Nos3+/+ female mice; but not in Nos3-/- females. Riboflavin deficiency did not affect endothelial-independent function in female Nos3+/+ or Nos3-/- mice. Bulk RNA sequencing revealed 21 upregulated genes in male Nos3+/+mice fed a low riboflavin diet; including Atf3 which has been implicated in the pathology of atherosclerosis. Gene ontology pathway enrichment showed that upregulated genes were implicated in pathways involved in metabolic regulation, oxidative stress, and nitrogen handling. Conclusion: Low riboflavin status has a sex-specific effect on endothelial-dependent and -independentrelaxation. The effect of riboflavin deficiency on endothelial-independent relaxation, even in the absence of eNOS, suggests a role for riboflavin on other compensatory vasodilatory factors and/or smooth muscle NO sensitivity. Low riboflavin status may induce a proatherogenic gene expression profile through the upregulation of inflammatory and oxidative stress genes, prior to functional changes.

Text

2025-02-18

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/90380

Women+ and Children’s Health Sciences

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/