I'm the one who gave my cat NR. As was mentioned, it seemed to do wonders, until it didn't. You know cats, they are near death one day, and back on their feet the next, sort of. We thought we were going to lose ours last winter, but miracles of miracles, she is still with us, even given her frailty. Her main problem has been her autoimmune condition (raw skin caused by scratching, for which she received transdermal prednisolone 10% cream in her ear twice daily, and shots of something more powerful every 2-3 months or so. That keeps that at bay pretty well. However, her arthritis has developed in the last year (bad front limp) and cat chondroitin and glucosamine don't seem to help. So when it's appears really bad, she get buccal Buprenorphine for pain.
The NR seemed to help a lot initially with everything for about 6-9 months. I had difficulties trying to decide the best dose, as there are no references for this, the vet didn't have a clue, and so it was trial and error. Cat's need B3, the amounts is very small, and of course, NR is not what is specified. Humans take a lot more NR that is needed of a B3 as well. So I started with approx 50mg NR (excluding filler) in food and eventually reduced to approx 15mg. Day and evening dosing worked best, not morning for some reason... because of throwing up in the morning if dosed then She does this regularly anyway for almost any reason... to much food, wrong food, medicine in her food, you probably know how that goes with cats!
Currently, no NR, glucosamine or chondroitin, rather a tiny amt of UltraCur curcumin (protein attached curcumin) in her food, doesn't seem to bother her and may help with inflammation and general health. Cats are a mystery in so many ways, just like us! Good luck and let us know if you come up with any effective treatments with NMN, NR, or anything else.