Original Research

NAD Metabolism Regulates Proliferation of Macrophages in Atherosclerosis

Sinha, Satyesh^{^,}
Swichkow, Chantle R.^{^,}
Farahi, Lia^{^,}
Péterfy, Miklós
Pan, Calvin
Zhou, Zhiqiang
Seldin, Marcus
Mack, Julia J.
Davis, Richard C.
Shih, Diana
Lusis, Aldons J.

Department of Medicine/Division of Cardiology, University of California Los Angeles. (S.S., C.R.S., L.F., M.P., C.P., Z.Z., J.J.M., R.C.D., D.S., A.J.L.)
Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles. (S.S., C.R.S., L.F., M.P., C.P., Z.Z., J.J.M., R.C.D., D.S., A.J.L.)
Department of Human Genetics, University of California Los Angeles. (S.S., C.R.S., L.F., M.P., C.P., Z.Z., J.J.M., R.C.D., D.S., A.J.L.)
Molecular Biology Institute, University of California Los Angeles. (J.J.M.)
Department of Biomedical Sciences, Western University of Health Sciences, Pomona, CA (M.P.).
Department of Biological Chemistry and Center for Epigenetics and Metabolism, University of California, Irvine (M.S.).

*

S. Sinha, C.R. Swichkow, and L. Farahi are cofirst authors.

For Sources of Funding and Disclosures, see page XXX.

Supplemental Material is available at https://www.ahajournals.org/doi/suppl/10.1161/ATVBAHA.125.323185.

Correspondence to: Aldons J. Lusis, PhD, Department of Medicine/Division of Cardiology, University of California, Los Angeles. Los Angeles, CA 90095-1679. Email [email protected]

Arteriosclerosis, Thrombosis, & Vascular Biology Publish Ahead of Print, September 11, 2025. | DOI: 10.1161/ATVBAHA.125.323185

BACKGROUND:

In genetic studies with the Hybrid Mouse Diversity Panel, we previously identified a chromosome 9 locus for atherosclerosis. We now identify NNMT (nicotinamide N-methyltransferase), an enzyme that degrades nicotinamide, as the causal gene in the locus and show that the underlying mechanism involves salvage of nicotinamide to nicotinamide adenine dinucleotide (NAD).

METHODS:

Gain/loss of function studies in macrophages were performed to examine the role of NAD levels in macrophage proliferation and apoptosis in atherosclerosis.

RESULTS:

Global inhibition of NNMT using an antisense oligonucleotide reduced atherosclerosis lesion area 5- to 10-fold in both male and female mice on a hyperlipidemic background. Selective inhibition of NNMT in liver and adipose, the major tissues expressing high levels of the enzyme, using siRNA, had little or no effect on atherosclerosis. Therefore, we hypothesized that levels of NAD in macrophages might contribute. This was confirmed by showing that transplantation with bone marrow from Nnmt knockout mice resulted in reduced lesional macrophage proliferation, increased macrophage apoptosis, and reduced atherosclerosis. Consistent with this conclusion, reduced expression of macrophage CD38, an enzyme that degrades NAD, reduced both macrophage proliferation and atherosclerosis. Moreover, cultured macrophages from heterozygous Nnmt knockout mice exhibited reduced proliferation, increased apoptosis, and an increased NAD/NADH ratio.

CONCLUSIONS:

These findings reveal a role for nicotinamide salvage and NAD turnover in macrophage proliferation and survival in the context of atherosclerosis.