Figure 1.

Palmitate upregulates NNMT expression in hepatocytes. A: NNMT catalyzes SAM-dependent methylation/degradation of nicotinamide, which serves as a predominant endogenous precursor for NAD⁺ biosynthesis via the salvage pathway. B: AML12 cells were treated with the indicated concentrations of palmitate for 16 h. NNMT gene expression was quantified using real time-qPCR. Data are expressed as means ± SD, n = 4 separate experiments. Differences between the 2 groups were determined using Student’s t test (*P < 0.05; ***P < 0.001 vs. control). C: AML12 cells were treated with the 0.4 mM palmitate for 16 h. Protein abundance of NNMT was detected by Western blotting. The signal of NNMT protein band was measured by densitometry and then divided by the signal of its corresponding actin abundance in the same sample. Data are expressed as means ± SD, n = 3 separate experiments. Student’s t test was used for statistical evaluation (***P < 0.001 vs. control). D: AML12 cells were treated with the 0.4 mM palmitate for 16 h. Intracellular total NAD (tNAD) concentrations were measured. Data are expressed as means ± SD, n = 3 separate experiments. Student’s t test was used for statistical evaluation (*P < 0.05 vs. control). NNMT, nicotinamide N-methyltransferase.