Semisynthetic Bile Acid FXR and TGR5 Agonists: Physicochemical Properties, Pharmacokinetics, and Metabolism in the Rat

Abstract

We report on the relationship between the structure-pharmacokinetics, metabolism, and therapeutic activity of semisynthetic bile acid analogs, including 6a-ethyl-3a,7a-dihydroxy-5b-cholan-24-oic acid (a selective farnesoid X receptor [FXR] receptor agonist), 6a-ethyl-23(S)-methyl-3a,7a,12a-trihydroxy-5b-cholan-24-oic acid (a specific Takeda G protein-coupled receptor 5 [TGR5] receptor agonist), and 6a-ethyl-3a,7a-dihydroxy-24-nor-5b-cholan-23-sulfate (a dual FXR/TGR5 agonist). We measured the main physicochemical properties of these molecules, including ionization constants, water solubility, lipophilicity, detergency, and protein binding. Biliary secretion and metabolism and plasma and hepatic concentrations were evaluated by high-pressure liquid chromatography-electrospray-mass spectrometry/mass spectrometry in bile fistula rat and compared with natural analogs chenodeoxycholic, cholic acid, and taurochenodexycholic acid and intestinal bacteria metabolism was evaluated in terms of 7a-dehydroxylase substrate-specificity in anaerobic human stool culture. The semisynthetic derivatives detergency, measured in terms of their critical micellar concentration, was quite similar to the natural analogs. They were slightly more lipophilic than the corresponding natural analogs, evaluated by their 1-octanol water partition coefficient (log P), because of the ethyl group in 6 position, which makes these molecules very stable toward bacterial 7-dehydroxylation. The hepatic metabolism and biliary secretion were different: 6a-ethyl-3a,7a-dihydroxy-5b-cholan-24-oic acid, as chenodeoxycholic acid, was efficiently conjugated with taurine in the liver and, only in this form, promptly and efficiently secreted in bile. 6a-Ethyl-23(S)-methyl-3a,7a,12a-trihydroxy-5b-cholan-24-oic acid was poorly conjugated with taurine because of the steric hindrance of the methyl at C23(S) position metabolized to the C23(R) isomer and partly conjugated with taurine. Conversely, 6a-ethyl-3a,7a-dihydroxy-24-nor-5b-cholan-23-sulfate was secreted in bile unmodified and as 3-glucuronide. Therefore, minor structural modifications profoundly influence the metabolism and biodistribution in the target organs where these analogs exert therapeutic effects by interacting with FXR and/or TGR5 receptors.

G Protein-Coupled Bile Acid Receptor TGR5 Activation Inhibits Kidney Disease in Obesity and Diabetes

“…29 INT-777, due to its relatively low intestinal absorption, can effectively activate TGR5 in enteroendocrine cells, triggering GLP-1 secretion, and because of its systemic biodistribution can activate TGR5 in different districts, including the kidney. 30 INT-777 treatment in mice with DIO leads to enhanced mitochondrial function in muscle, brown adipose tissue, and enteroendocrine cells, resulting in increased energy expenditure and incretin secretion, and inducing a range of beneficial metabolic effects that include resistance to weight gain and hepatic steatosis, preservation of liver and pancreatic function, and maintenance of glucose homeostasis and insulin sensitivity. 21 In addition, INT-777 exerts, via TGR5 activation, immune modulatory and anti-inflammatory effects leading to inhibition of macrophage NFkB signaling and to prevention of atherosclerotic lesion formation.…”

Chlamydia pneumoniae acute liver infection affects hepatic cholesterol and triglyceride metabolism in mice

“…Bile acids and their metabolites were identified and quantified by high-pressure liquid chromatography-electrospray-mass spectrometry/mass spectrometry (HPLC-ES-MS/MS) by optimized methods suitable for use in pure standard solution in plasma and bile samples after appropriate clean-up pre-analytical procedures [31]. One ml of phosphate buffer (5 mM, pH 7.2) was added to liver aliquots weighing approximately 0.3 g. The mixture was homogenized using a potter washed with methanol (3 Â 0.5 ml).…”

A dual agonist of farnesoid X receptor (FXR) and the G protein–coupled receptor TGR5, INT-767, reverses age-related kidney disease in mice

“…INT-767 is a semi-synthetic analogue of the endogenous FXR agonist chenodeoxycholic acid (CDCA), with one fewer carbon on the side chain and a sulfate ester, lacking the COOH group of CDCA. INT-767 has similar lipophilicity and detergency to CDCA but with a much lower pKa (<1), similar to taurine-conjugated CDCA (25). INT-767 is 300 times more potent than CDCA in FXR activation and about 5 times more potent than lithocholic acid (LCA), the endogenous TGR agonist, in TGR activation (26).…”

“…INT-767 is 300 times more potent than CDCA in FXR activation and about 5 times more potent than lithocholic acid (LCA), the endogenous TGR agonist, in TGR activation (26). INT-767 shows efficient intestinal absorption and its biliary excretion is facilitated by 3-glucuronididation (25 (26). INT-767 has also marked anti-inflammatory (27), anti-atherosclerotic (28), and anticholestatic effects (29).…”