A poli(ADP-ribóz) polimeráz-2 szerepének vizsgálata a SIRT1 aktivációjában, az energiaháztartásban és a sejtek NAD+ koncentrációjának modulálásában = Investigation of the role of poly(ADP-ribose) polymerase-2 in SIRT1 activation, energy expenditure and the modulation of cellular NAD+ concentrations

A projekt során a poli(ADP-ribóz polimeráz (PARP) enzimek metabolikus szerepét vizsgálatuk. A PARP-1-/- egerekben a harántcsíkolt izomban és a barna zsírszövetben emelkedett biológiai oxidációt tapasztaltunk. A megemelkedett biológiai oxidáció oka a SIRT1 aktivitás megnövekedése volt. Eredményeinkből úgy tűnik, hogy elsődlegesen a fenti fenotípus megjelenéséért a PARP-1 és a SIRT1 NAD+ iránti versengése felelős: a PARP-1 enzim törlése esetén több NAD+ molekula marad a SIRT1 számára. Kimutattuk, hogy PARP inhibitorok is hasonló fenotípust alakítanak ki. PARP-2-/- egerekben a harántcsíkolt izomban és a májban emelkedett biológiai oxidációt írtunk le, amely szintén a megemelkedett mitokondriális aktivitással volt kapcsolatban, amit a megnövekvő SIRT1 expresszió váltott ki. A PARP-2-/- egerekben pancreas beta sejt diszfukciót találtunk, ami rontja az egerek metabolikus rátermettségét. Eredményeink egy új, farmakológiailag befolyásolható útvonalat írtak le, amelyen keresztül befolyásolható a szervezet energiaegyensúlya. | On course of the project we investigated the role of poly(ADP-ribose) polymerases in metabolic regulation. In the striated muscle and brown adipose tissue of the PARP-1-/- mice we have observed increased mitochondrial activity. The increased mitochondrial activity was linked to increased SIRT1 activity. Our results suggest that primarily the competition for the limiting NAD+ pool drive SIRT1 activation: upon the deletion of PARP-1 NAD+ levels increase providing more substrate for SIRT1. We provided evidence that PARP inhibitors are equally capable of inducing mitochondrial biogenesis. In the striated muscle and liver of PARP-2-/- mice we have observed increased mitochondrial activity that is equally linked to enhanced SIRT1 activation, however it was driven by increased SIRT1 expression. Besides the metabolically favorable enhanced energy expenditure we have observed pancreatic beta cell dysfunction that hinders metabolic fitness of these mice. Our data describe a novel pathway for the intervention on whole body energy balance, moreover this pathway can be influenced by pharmacological inhibitors

PARP10 (ARTD10) modulates mitochondrial function

KA, L

Glycogen phosphorylase inhibitor N-(3,5-dimethyl-benzoyl)-N'-(β-Dglucopyranosyl) urea improves glucose tolerance under normoglycemic and diabetic conditions and rearranges hepatic metabolism

Glycogen phosphorylase (GP) catalyzes the breakdown of glycogen and largely contributes to hepatic glucose production making GP inhibition an attractive target to modulate glucose levels in diabetes. Hereby we present the metabolic effects of a novel, potent, glucose-based GP inhibitor (KB228) tested in vitro and in vivo under normoglycemic and diabetic conditions. KB228 administration enhanced glucose sensitivity in chow-fed and obese, diabetic mice that was a result of higher hepatic glucose uptake. Besides improved glucose sensitivity, we have observed further unexpected metabolic rearrangements. KB228 administration increased oxygen consumption that was probably due to the overexpression of uncoupling protein-2 (UCP2) that was observed in animal and cellular models. Furthermore, KB228 treatment induced mammalian target of rapamycin complex 2 (mTORC2) in mice. Our data demonstrate that glucose based GP inhibitors are capable of reducing glucose levels in mice under normo and hyperglycemic conditions. Moreover, these GP inhibitors induce accommodation in addition to GP inhibition - such as enhanced mitochondrial oxidation and mTORC2 signaling – to cope with the glucose influx and increased glycogen deposition in the cells, however the molecular mechanism of accommodation is unexplored