Nicotinamide N-methyltransferase knockdown protects against diet-induced obesity.
Level 5 - mechanism / opinion, no new human data
Preclinical animal model and in vitro mechanistic research.
PubMed 24717514 · doi:10.1038/nature13198
What was done
DNA microarray analyses were performed on white adipose tissue (WAT) from mice with adipose-specific Glut4 knockout or overexpression and their respective controls. The investigators assessed NNMT expression in WAT and liver across obese and diabetic mouse models, evaluated the physiological effects of Nnmt knockdown on diet-induced obesity and cellular energy expenditure, and examined downstream biochemical pathways including S-adenosylmethionine (SAM) and NAD(+) levels, histone H3 lysine 4 methylation, polyamine flux enzymes (ODC, SSAT, PAO), diacetylspermine secretion, and adipocyte oxygen consumption.
What was found
The abstract reports no numerical values. Qualitatively, NNMT was identified as the most strongly reciprocally regulated gene in adipose Glut4-KO versus Glut4-overexpressing mice and was found to be upregulated in WAT and liver of obese and diabetic mice. Knockdown of Nnmt in WAT and liver protected mice from diet-induced obesity by increasing cellular energy expenditure. NNMT inhibition increased adipose SAM and NAD(+) levels, upregulated ODC and SSAT expression and activity via histone H3K4 methylation, increased diacetylspermine secretion and excretion, and increased adipocyte oxygen consumption in an ODC-, SSAT-, and PAO-dependent manner.
Why it matters
This work identifies NNMT as a metabolic regulator coupling NAD+ availability, methyl-donor balance, and polyamine flux to cellular energy expenditure, highlighting NNMT as a potential therapeutic target for metabolic disease.
Limits
The study is entirely preclinical, relying on rodent models and in vitro adipocyte assays with unknown direct translation to humans. The abstract does not report sample sizes, effect sizes, knockdown efficiency, or quantitative statistics.
Cited by
- supports High levels of NAD clearance through NNMT consume methyl groups and reduce SAMe.