Aims/hypothesis: Tankyrase (TNKS) is a ubiquitously expressed molecular scaffold that is implicated in diverse processes. The catalytic activity of TNKS modifies substrate proteins through poly-ADP-ribosylation (PARsylation) and is responsive to cellular energetic state. Global deficiency of the TNKS protein in mice accelerates glucose utilisation and raises plasma adiponectin levels. The aim of this study was to investigate whether the PARsylation activity of TNKS in adipocytes plays a role in systemic glucose homeostasis.
Methods: To inhibit TNKS-mediated PARsylation, we fed mice with a diet containing the TNKS-specific inhibitor G007-LK. To genetically inactivate TNKS catalysis in adipocytes while preserving its function as a molecular scaffold, we used an adipocyte-selective Cre transgene to delete TNKS exons that encoded the catalytic domain at the C-terminus. Tissue-specific insulin sensitivity in mice was investigated using hyperinsulinaemic-euglycaemic clamps. To model adipose-liver crosstalk ex vivo, we applied adipocyte-conditioned media to hepatocytes and assessed the effect on gluconeogenesis.
Results: The TNKS inhibitor G007-LK improved glucose tolerance and insulin sensitivity and promptly increased plasma adiponectin levels. In female mice, but not in male mice, adipocyte-selective genetic inactivation of TNKS catalysis improved hepatic insulin sensitivity and post-transcriptionally increased plasma adiponectin levels. Both pharmacological and genetic TNKS inhibition in female mouse-derived adipocytes induced a change in secreted factors to decrease gluconeogenesis in primary hepatocytes.
Conclusions/interpretation: Systemic glucose homeostasis is regulated by the PARsylation activity of TNKS in adipocytes. This regulation is mediated in part by adipocyte-secreted factors that modulate hepatic glucose production. Pharmacological TNKS inhibition could potentially be used to improve glucose tolerance.
Keywords: Adipokines; Adiponectin; Glucose homeostasis; Hepatic glucose production; Insulin sensitivity; Mouse genetic model; Poly-ADP-ribosylation (PARsylation); Tankyrase (TNKS); Tissue-specific knockout.