Heat and cold stress upregulate the enzyme nicotinamide phosphoribosyltransferase (NAMPT), which converts nicotinamide to NAD+.
"we know that the conversion then of nicotinamide mononucleotide into NAD+ is there's an enzyme, nicotinamide phosphoribosyltransferase, that seems to be amped up by either the heat, being stressed by heat environment, or being stressed, low-grade stress—we call that hormesis—in a positive way of being in the cold." (said at 0:36:21)
The speaker misidentifies the enzymatic reaction catalyzed by nicotinamide phosphoribosyltransferase (NAMPT). NAMPT converts nicotinamide (NAM) and 5-phosphoribosyl-1-pyrophosphate (PRPP) into nicotinamide mononucleotide (NMN), serving as the rate-limiting enzyme in the NAD+ salvage pathway. The subsequent conversion of NMN into NAD+ is catalyzed by nicotinamide mononucleotide adenylyltransferase (NMNAT), not NAMPT. While cold exposure has been shown to upregulate NAMPT expression in rodent and human adipose tissue to support adaptive thermogenesis, attributing the conversion of NMN into NAD+ to NAMPT is biochemically incorrect.
- context: Adipose tissue NAD + biosynthesis is required for regulating adaptive thermogenesis and wh… (Proceedings of the National Academy of Sciences of the United States of America 2019)
"These metabolic abnormalities were rescued by treatment with nicotinamide mononucleotide (NMN), which bypasses the block in NAD + synthesis induced by NAMPT deficiency... We also found NAMPT expression in supraclavicular adipose tissue (where human BAT is localized) obtained from human subjects increased during cold exposure, suggesting our finding in rodents could apply to people." (abstract, results)
pubmedfull study (doi)