Objective: Human TNKS, encoding tankyrase 1 (TNKS1), localizes to a susceptibility locus for obesity and type 2 diabetes mellitus (T2DM). Here, we addressed the therapeutic potential of G007-LK, a TNKS-specific inhibitor, for obesity and T2DM.
Methods: We administered G007-LK to diabetic db/db mice and measured the impact on body weight, abdominal adiposity, and serum metabolites. Muscle, liver, and white adipose tissues were analyzed by quantitative RT-PCR and western blotting to determine TNKS inhibition, lipolysis, beiging, adiponectin level, mitochondrial oxidative metabolism and mass, and gluconeogenesis. Protein interaction and PARylation analyses were carried out by immunoprecipitation, pull-down and in situ proximity ligation assays.
Results: TNKS inhibition reduced body weight gain, abdominal fat content, serum cholesterol levels, steatosis, and proteins associated with lipolysis in diabetic db/db mice. We discovered that TNKS associates with PGC-1α and that TNKS inhibition attenuates PARylation of PGC-1α, contributing to increased PGC-1α level in WAT and muscle in db/db mice. PGC-1α upregulation apparently modulated transcriptional reprogramming to increase mitochondrial mass and fatty acid oxidative metabolism in muscle, beiging of WAT, and raised circulating adiponectin level in db/db mice. This was in sharp contrast to the liver, where TNKS inhibition in db/db mice had no effect on PGC-1α expression, lipid metabolism, or gluconeogenesis.
Conclusion: Our study unravels a novel molecular mechanism whereby pharmacological inhibition of TNKS in obesity and diabetes enhances oxidative metabolism and ameliorates lipid disorder. This happens via tissue-specific PGC-1α-driven transcriptional reprogramming in muscle and WAT, without affecting liver. This highlights inhibition of TNKS as a potential pharmacotherapy for obesity and T2DM.