Abstract
Nicotinamide N-methyltransferase (NNMT) is a cytosolic enzyme that catalyzes the transfer of a methyl group from the co-factor S-adenosyl-L-methionine (SAM) onto the substrate, nicotinamide (NA) to form 1-methyl-nicotinamide (MNA). Higher NNMT expression and MNA concentrations have been associated with obesity and type-2 diabetes. Here we report a small molecule analog of NA, JBSNF-000088, that inhibits NNMT activity, reduces MNA levels and drives insulin sensitization, glucose modulation and body weight reduction in animal models of metabolic disease. In mice with high fat diet (HFD)-induced obesity, JBSNF-000088 treatment caused a reduction in body weight, improved insulin sensitivity and normalized glucose tolerance to the level of lean control mice. These effects were not seen in NNMT knockout mice on HFD, confirming specificity of JBSNF-000088. The compound also improved glucose handling in ob/ob and db/db mice albeit to a lesser extent and in the absence of weight loss. Co-crystal structure analysis revealed the presence of the N-methylated product of JBSNF-000088 bound to the NNMT protein. The N-methylated product was also detected in the plasma of mice treated with JBSNF-000088. Hence, JBSNF-000088 may act as a slow-turnover substrate analog, driving the observed metabolic benefits.
Highlights
Nicotinamide N-methyltransferase (NNMT) is a cytosolic enzyme that catalyzes the N-methylation of nicotinamide by transferring a methyl group from S-adenosyl-L-methionine (SAM) to nicotinamide (NA) resulting in the formation of 1-methyl-nicotinamide (MNA) and S-adenosyl-L-homocysteine (SAH)[1,2]
The activity of JBSNF-000088 against human NNMT (hNNMT) was confirmed by an alternative LCMS/MS detection method with an IC50 of 2.4 μM (Fig. 1D)
We report a small molecule, JBSNF-000088 which is a substrate analog of nicotinamide, that inhibits NNMT activity across species, reduces plasma MNA levels by ~50% and drives insulin sensitization, glucose metabolism and body weight reduction in diet-induced obesity (DIO) mice
Summary
Nicotinamide N-methyltransferase (NNMT) is a cytosolic enzyme that catalyzes the N-methylation of nicotinamide by transferring a methyl group from S-adenosyl-L-methionine (SAM) to nicotinamide (NA) resulting in the formation of 1-methyl-nicotinamide (MNA) and S-adenosyl-L-homocysteine (SAH)[1,2]. Several reports have indicated a role of NNMT in obesity, insulin resistance and type 2 diabetes (T2D)[4,6,7]. Interventions to improve insulin sensitivity such as exercise and bariatric surgery were shown to decrease NNMT expression in adipose tissue and result in reduction of plasma MNA levels[4]. Till date there are no reports on the feasibility of using small molecule modulators of NNMT in preclinical animal models of metabolic disease to validate NNMT as a pharmacological drug target. The objective of the current study was to identify selective small molecule modulators of NNMT with drug like properties and to test them in preclinical animal models of obesity, insulin resistance and diabetes to provide the first proof of concept for a small molecule targeting NNMT for treating metabolic disorders. We demonstrate the pharmacological benefits of a small molecule modulator of NNMT for the first time and explain its mechanism of action
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