Abstract EN:

Mitochondrial dysfunction is implicated in the early stages of diabetes but is not targeted by the available therapies. Mitochondrial functions can be activated by the bile acids-activated GPCR TGR5, in muscle and in adipose tissue. This double effect of TGR5, on mitochondria and GLP-1 secretion, positions this receptor as an interesting target to prevent the early onset of metabolic diseases. To further explore TGR5 potential, our principal challenge was to identify more potent and more selective TGR5 agonists devoid of the pleiotropic effects of bile acids, the only TGR5 agonists known so far. To this end, we used a TGR5 activity assay to screen a plant library. Among the plant extracts tested, Olea Europaea leaves was shown to exhibit an activity supported by the triterpenoid oleanolic acid. In vivo, oleanolic acid showed anti-hyperglycemic activity, improved glucose tolerance and decreased weight gain. Furthermore, oleanolic acid enhanced mitochondria in muscle both in vitro and in vivo. A SAR study based on the triterpenoid scaffold led us to synthetize RG239, a more potent TGR5 agonist in vitro which is inactive in vivo, probably because of poor bioavailability. RG239 is an interesting pharmacological tool to understand TGR5 biology. Indeed, RG239 was shown to induce mitochondria activity and number in muscle and intestinal cell lines in a TGR5 dependant manner. In addition, RG239 stimulated GLP-1 secretion in intestinal enteroendocrine cells in a TGR5 dependant-manner. Altogether, these results confirm TGR5 as therapeutical target and triterpenoids as potential therapeutical agents in the prevention/mitochondria and treatment/GLP-1 of metabolic diseases.