Nicotinamide N-methyltransferase is a novel regulator of energy expenditure

项目摘要 本提案的总体目标是研究烟酰胺N- 甲基转移酶（NNMT）调节能量消耗和肥胖。NNMT催化S- 腺苷甲硫氨酸（SAM）依赖性甲基化的烟酰胺（维生素B3），前体 烟酰胺腺嘌呤二核苷酸（NAD+）。NNMT是一种独特的酶，因为它调节SAM和 NAD+，细胞能量代谢的两种基本代谢物。SAM提供底物丙胺 并为组蛋白甲基化提供甲基。两种多胺 代谢和组蛋白甲基化参与调节能量消耗。NAD+是 Sirt 1是一种去乙酰化酶，调节与能量代谢相关的多个重要靶点。 申请方发现NNMT在肥胖症患者的脂肪组织和肝脏中升高。生物敲击 使用反义寡核苷酸（阿索）降低脂肪组织和肝脏中的NNMT， 预防饮食引起的肥胖和改善胰岛素敏感性。NNMT敲低 增加SAM和NAD+水平，增强多胺通量和增强单甲基化、二甲基化和三甲基化 赖氨酸4对脂肪组织中H3（H3 K4）组蛋白甲基化的影响。总体假设是：NNMT是一个 能量消耗和肥胖的新调节剂，它通过引起代谢产物 分流导致细胞SAM和NAD+水平的变化，这反过来又调节能量消耗。 在目标1中，我们将使用药理学和遗传学方法进一步阐明NNMT在以下方面的作用： 调节能量消耗。对于药理学方法，我们将使用N-甲基烟酰胺（MNA）， NNMT反馈抑制剂，以抑制NNMT活性。对于遗传方法，我们计划生成 脂肪特异性NNMT敲除小鼠。我们将调查这些人的能量消耗和肥胖， 小鼠在目标2中，我们将确定SAM的改变介导以下效应的机制： 能量消耗的NNMT。我们将重点关注SAM调节的多胺代谢和组蛋白 甲基化在目标3中，我们将研究NAD+和NAD+依赖性Sirt 1是否参与了 NNMT调节的能量消耗。 该方案在新发现、新机理、综合性等方面具有很强的创新性 接近。它还具有重要的翻译意义。NNMT ASO和MNA都可能是 直接用于临床试验。事实上，MNA已被用于人类研究其血管舒张作用。

PROJECT SUMMARY The overall goal of the current proposal is to investigate the novel roles of nicotinamide N- methyltransferase (NNMT) in regulating energy expenditure and adiposity. NNMT catalyzes the S- adenosylmethionine (SAM)-dependent methylation of nicotinamide (vitamin B3), a precursor of nicotinamide adenine dinucleotide (NAD+). NNMT is a unique enzyme in that it regulates both SAM and NAD+, two fundamental metabolites for cellular energy metabolism. SAM provides substrate propylamine for polyamine metabolism and donates a methyl group for histone methylation. Both polyamine metabolism and histone methylation are involved in regulating energy expenditure. NAD+ is a cofactor of Sirt1, a deacetylase that regulates multiple important targets related to energy metabolism. The applicant found that NNMT was elevated in adipose tissue and liver in obesity. Biologically knocking down NNMT in adipose tissue and liver using antisense oligonucleotides (ASO) increased energy expenditure, prevented diet-induced obesity and improved insulin sensitivity. NNMT knockdown increased SAM and NAD+ levels, enhanced polyamine flux and augmented mono-, di- and tri-methylation of lysine 4 on H3 (H3K4) histone methylation in adipose tissue. The overall hypothesis is: NNMT is a novel regulator of energy expenditure and adiposity, and it exerts its effects by causing metabolite shunting leading to changes in cellular SAM and NAD+ levels, which in turn regulate energy expenditure. In Aim 1, we will use pharmacological and genetic approaches to further elucidate the roles of NNMT in regulating energy expenditure. For pharmacological approach, we will use N-methylnicotinamide (MNA), an NNMT feedback inhibitor, to inhibit NNMT activity. For genetic approach, we plan to generate adipose-specific NNMT knockout mice. We will investigate energy expenditure and adiposity in these mice. In Aim 2, we will determine the mechanisms by which alterations in SAM mediate the effects of NNMT on energy expenditure. We will focus on SAM-regulated polyamine metabolism and histone methylation. In Aim 3, we will investigate whether NAD+ and NAD+-dependent Sirt1 are involved in NNMT-regulated energy expenditure. The proposal is highly innovative in the aspects of new discovery, novel mechanisms and comprehensive approaches. It also has significant translational implications. Both NNMT ASOs and MNA can potentially be used directly in clinical trials. In fact, MNA has been used in humans for studying its vasorelaxation effects.