No abstract

Males exhibit greater histologic and behavioral impairment after stroke than do age-matched females. However, the contribution of androgens to stroke outcome remains unclear. We compared outcomes from middle cerebral artery occlusion (MCAO) in castrated mice with those in testosterone-or dihydrotestosterone (DHT)-replaced castrated mice. Castrates treated with 1.5 mg testosterone or 0.5 mg DHT before MCAO showed smaller infarct volumes (hemisphere: 27 or 26%) at 24 h after 90 mins MCAO than did untreated castrates (37%), whereas 5 mg testosterone or 1.5 mg DHT exacerbated infarcts (53 or 51%). These outcomes were blocked by the androgen receptor antagonist, flutamide, suggesting that androgen receptors mediate these responses to ischemia. We further evaluated long-term outcomes with a milder 60-min MCAO in castrates treated with the protective 1.5 mg testosterone dose. Consistent with data obtained at 24 h reperfusion, the infarct volume was decreased at 9 days reperfusion. Neurobehavioral analysis showed that motor functional recovery was improved during the first 3 days of reperfusion, but not improved at 7 days. We conclude that testosterone exhibits dose-dependent and time-sensitive effects after ischemia and that testosterone is likely to be an important factor in sex-linked differences in cerebrovascular disease.

Acetyl-CoA is a fundamental metabolite for all life on Earth, and is also a key starting point for the biosynthesis of a variety of industrial chemicals and natural products. Here we design and construct a Synthetic Acetyl-CoA (SACA) pathway by repurposing glycolaldehyde synthase and acetyl-phosphate synthase. First, we design and engineer glycolaldehyde synthase to improve catalytic activity more than 70-fold, to condense two molecules of formaldehyde into one glycolaldehyde. Second, we repurpose a phosphoketolase to convert glycolaldehyde into acetyl-phosphate. We demonstrated the feasibility of the SACA pathway in vitro, achieving a carbon yield ~50%, and confirmed the SACA pathway by 13C-labeled metabolites. Finally, the SACA pathway was verified by cell growth using glycolaldehyde, formaldehyde and methanol as supplemental carbon source. The SACA pathway is proved to be the shortest, ATP-independent, carbon-conserving and oxygen-insensitive pathway for acetyl-CoA biosynthesis, opening possibilities for producing acetyl-CoA-derived chemicals from one-carbon resources in the future.