Is anyone certain that NR is inhibiting mTOR? That is, if we are upregulating SIRT1 via NAD+/NADH are we then certainly inhibiting mTOR?
Thx.
Does this help? The following studies seem to indicate, that, yes, NR increases SIRT1 (study 1) and SIRT1 negatively regulates mTOR (study 2).
STUDY 1 FULL TEXT: http://download.cell...termediate=true The NAD+ Precursor Nicotinamide Riboside Enhances Oxidative Metabolism and Protects against High-Fat Diet-Induced Obesity- NR efficiently increases NAD+ levels in mammalian cells and tissues
- NR supplementation increases SIRT1 and SIRT3 activities
- NR largely prevents the detrimental metabolic effects of high-fat feeding
- NR enhances mitochondrial function and endurance performance
SummaryAs NAD
+ is a rate-limiting cosubstrate for the sirtuin enzymes, its modulation is emerging as a valuable tool to regulate sirtuin function and, consequently, oxidative metabolism. In line with this premise, decreased activity of PARP-1 or CD38�both NAD
+ consumers�increases NAD
+ bioavailability, resulting in SIRT1 activation and protection against metabolic disease. Here we evaluated whether similar effects could be achieved by increasing the supply of nicotinamide riboside (NR), a recently described natural NAD
+ precursor with the ability to increase NAD
+ levels, Sir2-dependent gene silencing, and replicative life span in yeast. We show that NR supplementation in mammalian cells and mouse tissues increases NAD
+ levels and activates SIRT1 and SIRT3, culminating in enhanced oxidative metabolism and protection against high-fat diet-induced metabolic abnormalities. Consequently, our results indicate that the natural vitamin NR could be used as a nutritional supplement to ameliorate metabolic and age-related disorders characterized by defective mitochondrial function.
STUDY 2 FULL TEXT: http://www.plosone.o...al.pone.0009199 SIRT1 Negatively Regulates the Mammalian Target of Rapamycin
AbstractThe IGF/mTOR pathway, which is modulated by nutrients, growth factors, energy status and cellular stress regulates aging in various organisms. SIRT1 is a NAD+ dependent deacetylase that is known to regulate caloric restriction mediated longevity in model organisms, and has also been linked to the insulin/IGF signaling pathway. Here we investigated the potential regulation of mTOR signaling by SIRT1 in response to nutrients and cellular stress. We demonstrate that SIRT1 deficiency results in elevated mTOR signaling, which is not abolished by stress conditions. The SIRT1 activator resveratrol reduces, whereas SIRT1 inhibitor nicotinamide enhances mTOR activity in a SIRT1 dependent manner. Furthermore, we demonstrate that SIRT1 interacts with TSC2, a component of the mTOR inhibitory-complex upstream to mTORC1, and regulates mTOR signaling in a TSC2 dependent manner. These results demonstrate that SIRT1 negatively regulates mTOR signaling potentially through the TSC1/2 complex.