There is a contradictory preprint (that hasn’t passed peer review) on ACE2 mRNA expression in smokers’ lungs being higher than non-smokers; but there is data saying the opposite happens in animal models of mice exposed to smoke:
https://pubmed.ncbi.nlm.nih.gov/20178811-losartan-attenuates...
There is also an inaccurate preprint on ethnic groups and ACE2 expression with a low n count which also didn’t pass peer review.
ACE2 loss is probably bad, having more ACE2 probably doesn’t drive disease severity:
https://twitter.com/__philipn__/status/1229568317167243264?s...
Relative ace2 reduction correlates w disease severity; viral load growth the same between groups - check out study! Chinese paper discusses this as well:
https://pubmed.ncbi.nlm.nih.gov/32061198-inhibitors-of-ras-m...