Antisense oligonucleotide knockdown (ASO-KD) of nicotinamide N-methyltransferase (NNMT) in high-fat diet (HFD)–fed mice has been reported to reduce weight gain and plasma insulin levels and to improve glucose tolerance. Using NNMT-ASO-KD or NNMT knockout mice (NNMT−/−), we tested the hypothesis that Nnmt deletion protects against diet-induced obesity and its metabolic consequences in males and females on obesity-inducing diets. We also examined samples from a human weight reduction (WR) study for adipose NNMT (aNNMT) expression and plasma 1-methylnicotinamide (MNAM) levels. In Western diet (WD)–fed female mice, NNMT-ASO-KD reduced body weight, fat mass, and insulin level and improved glucose tolerance. Although NNMT−/− mice fed a standard diet had no obvious phenotype, NNMT−/− males fed an HFD showed strongly improved insulin sensitivity (IS). Furthermore, NNMT−/− females fed a WD showed reduced weight gain, less fat, and lower insulin levels. However, no improved glucose tolerance was observed in NNMT−/− mice. Although NNMT expression in human fat biopsy samples increased during WR, corresponding plasma MNAM levels significantly declined, suggesting that other mechanisms besides aNNMT expression modulate circulating MNAM levels during WR. In summary, upon NNMT deletion or knockdown in males and females fed different obesity-inducing diets, we observed sex- and diet-specific differences in body composition, weight, and glucose tolerance and estimates of IS.

The transcription factor NF-E2-related factor 2 (Nrf2) induces cytoprotective genes, but has also been linked to the regulation of hepatic energy metabolism. In order to assess the pharmacological potential of hepatic Nrf2 activation in metabolic disease, Nrf2 was activated over 7 weeks in mice on Western diet using two different siRNAs against kelch-like ECH-associated protein 1 (Keap1), the inhibitory protein of Nrf2. Whole genome expression analysis followed by pathway analysis demonstrated successful knock-down of Keap1 expression and induction of Nrf2-dependent genes involved in anti-oxidative stress defense and biotransformation, proving the activation of Nrf2 by the siRNAs against Keap1. Neither the expression of fatty acid- nor carbohydrate-handling proteins was regulated by Keap1 knock-down. Metabolic profiling of the animals did also not show effects on plasma and hepatic lipids, energy expenditure or glucose tolerance. The data indicate that hepatic Keap1/Nrf2 is not a major regulator of glucose or lipid metabolism in mice.

Nicotinamide N-methyltransferase (NNMT) is expressed in most tissues including muscle, adipose tissue, liver and digestive organs. Recent research suggests the involvement of NNMT in the pathogenesis of obesity, insulin resistance and related metabolic disease. Antisense oligonucleotide (ASO) knockdown in high-fat diet (HFD)-fed mice led to reduced weight gain, relative fat mass, plasma insulin levels and improved glucose tolerance. We tested the hypothesis, that genetic NNMT deletion protects mice on HFD and Western diet (WD) against obesity and explored the metabolic effects of NNMT. Using NNMT ASO treatment and a NNMT knockout mouse (NNMT-/-), we investigate the effects of NNMT deletion on energy metabolism, glucose homeostasis and the development of obesity. We also examined data from a human study concerning NNMT expression and 1-methylnicotinamide (MNA) levels regarding weight reduction. In WD-fed mice, NNMT ASO treatment improved acute glucose tolerance, reduced weight gain and fat mass increase and, consequently, lowered plasma insulin levels. NNMT-/- mice exhibited virtually no MNA but threefold higher nicotinamide levels. Whereas NNMT-/- male and female mice on normal chow revealed no metabolic phenotype, NNMT-/- males on HFD showed improved glucose infusion rates, nearly complete insulin-mediated suppression of endogenous glucose production and an enhanced glucose uptake during a hyperinsulinemic-euglycemic clamp. Furthermore, NNMT-/- females on WD showed reduced weight gain, less fat mass and lower plasma insulin levels compared to controls. While NNMT gene expression in human fat biopsies increased over weight loss, corresponding plasma MNA levels significantly declined after weight reduction, suggesting that other mechanisms rather than adipose NNMT expression modulate circulating MNA levels during weight reduction. In conclusion, we observed an improvement of basal metabolic parameters and insulin sensitivity in NNMT-deficient mouse models. Disclosure S. Brachs: Research Support; Self; Sanofi-Aventis Deutschland GmbH. J. Polack: None. M. Brachs: Research Support; Spouse/Partner; Sanofi. K. Jahn-Hofmann: None. R. Elvert: Employee; Self; Sanofi. A. Pfenninger: None. F. Bärenz: None. D. Margerie: Employee; Self; Sanofi-Aventis Deutschland GmbH. K. Mai: None. A. Kannt: Employee; Self; Sanofi. Stock/Shareholder; Self; Sanofi. J. Spranger: Research Support; Self; Sanofi R&D.

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