Initiation of the Gut Microbiome Targeted Compound 3,3‐Dimethyl‐1‐butanol at Mid‐life Prevents Age‐related Vascular Dysfunction
Authors: Casso Abigail G. , VanDongen Nicholas S. , Ziemba Brian P. , Greenberg Nathan T. , Nguyen Kathy H. , Clayton Zachary S. , Seals Douglas R. , Brunt Vienna E. 
Published: April 2020

Aging induces vascular dysfunction (arterial stiffening and endothelial dysfunction) mediated by superoxide‐driven oxidative stress and reduced nitric oxide (NO) bioavailability, which increases risk of cardiovascular (CV) diseases. A potential intervention target is the gut microbiome‐derived metabolite trimethylamine N‐oxide (TMAO), which increases in circulation with advancing age, is associated with higher CV risk, and can be inhibited by the food‐derived compound 3,3‐dimethyl‐1‐butanol (DMB).PurposeTo determine if DMB initiated at mid‐life (i.e., prior to the onset of dysfunction) prevents the development of age‐related vascular dysfunction.MethodsMiddle‐aged (18 mo) male C57BL/6 mice received drinking water with (n=24) or without (control: n=27) 1% DMB until sacrifice at 21, 24, or 27 mo of age (n=7–13/age/treatment). Arterial stiffness was assessed serially in vivo by aortic pulse wave velocity (aPWV). Endothelial function (ex vivo carotid artery endothelium‐dependent dilation [EDD] to acetylcholine), plasma TMAO (LC‐MS) and aortic superoxide (electron paramagnetic resonance spectroscopy) were assessed post‐sacrifice. To determine the prevention of age‐related vascular dysfunction with DMB, functional measures were made in a reference group of young (5 mo) male C57BL/6 mice (YC, n=12).ResultsPlasma TMAO increased with age vs YC (3.1±0.5 μM), but tended to be lower in DMB (5.6±0.5 μM) vs control (6.9±0.8 μM) mice at 24 and 27 mo (p=0.15). In control mice, aPWV was similar to YC (356±14 cm/s) at 18/21 mo (359±12/368±11 cm/s, both p>0.54), but increased with age (24 mo: 386±12 cm/s, p=0.06 vs 18 mo; 27 mo: 432±10 cm/s, p<0.001 vs 18 mo); this increase was attenuated by ~50% in DMB mice (aPWV at 24 mo: 359±9 cm/s; 27 mo: 388±9 cm/s, both p=0.01 vs control). Age‐related declines in peak EDD were apparent in control mice at 24 mo (79±3 vs YC 93±2%, p<0.001) and 27 mo (76±3%, p<0.0001 vs YC) and were fully prevented by DMB (24 mo: 91±3%; 27 mo: 93±1%; both p<0.05 vs control). The effects of DMB at 24 and 27 mo (data combined across these ages) were mediated by reduced aortic superoxide production (control 4.7±0.5 vs DMB 3.1±0.4 AU, p=0.01), which reduced tonic superoxide‐associated suppression of EDD (normalization of EDD with superoxide dismutase mimetic TEMPOL) and restored NO‐mediated dilation (the difference in peak EDD in the absence vs presence of the NO synthase inhibitor L‐NAME: control 45±6 vs DMB 69±4%, p<0.01). There were no differences in smooth muscle sensitivity to NO (peak dilation to sodium nitroprusside; 96±1 vs 98±1%, p=0.12), indicating improvements in EDD were endothelium‐specific.ConclusionSupplementation with DMB from mid‐life through old age in mice prevented the development of arterial stiffening and endothelial dysfunction. DMB may be a promising therapeutic strategy for preventing age‐related vascular dysfunction and thereby reducing CV risk with aging in humans.Support or Funding InformationR01 HL1348870‐02S1, R21 AG060884, F32 HL140875