Nicotinamide riboside supplementation alters body composition and skeletal muscle acetylcarnitine concentrations in healthy obese humans

Background: Nicotinamide riboside (NR) is an NAD(+) precursor that boosts cellular NAD(+) concentrations. Preclinical studies have shown profound metabolic health effects after NR supplementation. Objectives: We aimed to investigate the effects of 6 wk NR supplementation on insulin sensitivity, mitochondrial function, and other metabolic health parameters in overweight and obese volunteers. Methods: A randomized, double-blinded, placebo-controlled, crossover intervention study was conducted in 13 healthy overweight or obese men and women. Participants received 6 wk NR (1000 mg/d) and placebo supplementation, followed by broad metabolic phenotyping, including hyperinsulinemic-euglycemic clamps, magnetic resonance spectroscopy, muscle biopsies, and assessment of ex vivo mitochondrial function and in vivo energy metabolism. Results: Markers of increased NAD(+) synthesis-nicotinic acid adenine dinucleotide and methyl nicotinamide-were elevated in skeletal muscle after NR compared with placebo. NR increased body fat-free mass (62.65% +/- 2.49% compared with 61.32% +/- 2.58% in NR and placebo, respectively; change: 1.34% +/- 0.50%, P = 0.02) and increased sleeping metabolic rate. Interestingly, acetylcarnitine concentrations in skeletal muscle were increased upon NR (4558 +/- 749 compared with 3025 +/- 316 pmol/mg dry weight in NR and placebo, respectively; change: 1533 +/- 683 pmol/mg dry weight, P = 0.04) and the capacity to form acetylcarnitine upon exercise was higher in NR than in placebo (2.99 +/- 0.30 compared with 2.40 +/- 0.33 mmol/kg wet weight; change: 0.53 +/- 0.21 mmol/kg wet weight, P = 0.01). However, no effects of NR were found on insulin sensitivity, mitochondrial function, hepatic and intramyocellular lipid accumulation, cardiac energy status, cardiac ejection fraction, ambulatory blood pressure, plasma markers of inflammation, or energy metabolism. Conclusions: NR supplementation of 1000 mg/d for 6 wk in healthy overweight or obese men and women increased skeletal muscle NAD(+) metabolites, affected skeletal muscle acetylcarnitine metabolism, and induced minor changes in body composition and sleeping metabolic rate. However, no other metabolic health effects were observed.

Calorie Restriction-like Effects of 30 Days of Resveratrol Supplementation on Energy Metabolism and Metabolic Profile in Obese Humans

Johan Auwerx, Richardus Houtkooper, Dongryeol Ryu

Resveratrol is a natural compound that affects energy metabolism and mitochondrial function and serves as a calorie restriction mimetic, at least in animal models of obesity. Here, we treated 11 healthy, obese men with placebo and 150 mg/day resveratrol (resVida) in a randomized double-blind crossover study for 30 days. Resveratrol significantly reduced sleeping and resting metabolic rate. In muscle, resveratrol activated AMPK, increased SIRT1 and PGC-1α protein levels, increased citrate synthase activity without change in mitochondrial content, and improved muscle mitochondrial respiration on a fatty acid-derived substrate. Furthermore, resveratrol elevated intramyocellular lipid levels and decreased intrahepatic lipid content, circulating glucose, triglycerides, alanine-aminotransferase, and inflammation markers. Systolic blood pressure dropped and HOMA index improved after resveratrol. In the postprandial state, adipose tissue lipolysis and plasma fatty acid and glycerol decreased. In conclusion, we demonstrate that 30 days of resveratrol supplementation induces metabolic changes in obese humans, mimicking the effects of calorie restriction.

2011

The role of nicotinamide riboside kinases in mammalian NAD⁺ metabolism

Joanna Ratajczak

NAD+ has emerged as a central metabolic node and an important co-substrate for the activity of various enzymes, including the protein deacetylase SIRT1. Different strategies to increase NAD+ bioavailability have been shown to boost SIRT1 activity, which results in protection against metabolic disease, neurodegenerative disorders and certain types of cancer. Nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) have recently been discovered as new NAD+ precursors. Recent studies have shown that dietary supplementation with NR or NMN prevented against high-fat diet-induced body weight gain. However, the physiological role of NR in mammalian metabolism remains largely unexplored. In this project, we focused on the first step of NR metabolism â the phosphorylation of NR by nicotinamide riboside kinases (NRK1 and NRK2). We have investigated the role of NRKs in the metabolism of NAD+ precursors and mammalian physiology in vivo. The results obtained indicate that NRKs are the rate-limiting and essential step for NR- and NMN-driven NAD+ synthesis in hepatocytes and that NMN has to be extracellularly converted to NR for its use as an NAD+ precursor. Accordingly, animals lacking NRK1 have defects in NR/NMN utilization. We demonstrated that effective NR utilization is key for the maintenance of metabolic homeostasis as NRK1 whole-body KO mice display numerous alterations in glucose and lipid management. Using NRK1 liver-specific KO mice, we demonstrate that NRK1 is required to maintain hepatic NAD+ levels and mitochondrial function upon high-fat feeding. Consequently, NRK1LKO mice are sensitized to diet-induced glucose intolerance and insulin resistance. Finally, we show that both isoforms of NRK are redundant in mediating NR/NMN effects in muscle. Hence, this work identifies NRKs as a novel valuable target in the fight against metabolic disease and indicates that the regulation of NRK will enable us to find novel ways of enhancing NAD+ availability. Moreover, it has unveiled a critical role of NRK1 for the metabolism of diverse forms of Vitamin B3 and highlights how circulating NR is key to preserve metabolic health upon dietary challenges.

EPFL2017

An unbiased silencing screen in muscle cells identifies miR-320a, miR-150, miR-196b, and miR-34c as regulators of skeletal muscle mitochondria! metabolism

Pénélope Andreux, Johan Auwerx, Xu Wang

Objective: Strategies improving skeletal muscle mitochondrial capacity are commonly paralleled by improvements in (metabolic) health. We and others previously identified microRNAs regulating mitochondrial oxidative capacity, but data in skeletal muscle are limited. Therefore, the present study aimed to identify novel microRNAs regulating skeletal muscle mitochondria! metabolism. Methods and results: We conducted an unbiased, hypothesis-free microRNA silencing screen in C2C12 myoblasts, using >700 specific microRNA inhibitors, and investigated a broad panel of mitochondria! markers. After subsequent validation in differentiated C2C12 myotubes, and exclusion of microRNAs without a human homologue or with an adverse effect on mitochondria] metabolism, 19 candidate microRNAs remained. Human clinical relevance of these microRNAs was investigated by measuring their expression in human skeletal muscle of subject groups displaying large variation in skeletal muscle mitochondrial capacity. Conclusion: The results show that that microRNA-320a, microRNA-196b-3p, microRNA-150-5p, and microRNA-34c-3p are tightly related to in vivo skeletal muscle mitochondrial function in humans and identify these microRNAs as targets for improving mitochondrial metabolism. (C) 2017 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY-NC-ND license.

Elsevier Science Bv2017

The role of nicotinamide riboside kinases in mammalian NAD⁺ metabolism

Joanna Ratajczak

EPFL2017