Wolfgang Wendler

Identification of binding proteins for cholesterol absorption inhibitors as components of the intestinal cholesterol transporter

To identify protein components of the intestinal cholesterol transporter, rabbit small intestinal brush border membrane vesicles were submitted to photoaffinity labeling using photoreactive derivatives of 2‐azetidinone cholesterol absorption inhibitors. An integral membrane protein of M r 145.3±7.5 kDa was specifically labeled in brush border membrane vesicles from rabbit jejunum and ileum. Its labeling was concentration‐dependently inhibited by the presence of cholesterol absorption inhibitors whereas bile acids, D‐glucose, fatty acids or cephalexin had no effect. The inhibitory potency of 2‐azetidinones to inhibit photolabeling of the 145 kDa protein correlated with their in vivo activity to inhibit intestinal cholesterol absorption. These results suggest that an integral membrane protein of M r 145 kDa is (a component of) the cholesterol absorption system in the brush border membrane of small intestinal enterocytes.

Sulfonylthiadiazoles with an Unusual Binding Mode as Partial Dual Peroxisome Proliferator‐Activated Receptor (PPAR) γ/δ Agonists with High Potency and in vivo Efficacy

Compounds that simultaneously activate the peroxisome proliferator‐activated receptor (PPAR) subtypes PPARγ and PPARδ have the potential to effectively target dyslipidemia and type II diabetes in a single pharmaceutically active molecule. The frequently observed side effects of selective PPARγ agonists, such as edema and weight gain, are expected to be overcome by using partial instead of full agonists for this nuclear receptor family. Herein we report the discovery, synthesis, and optimization of a novel series of sulfonylthiadiazoles that are active as partial agonists. The initial compound 6 was discovered by high‐throughput screening as a moderate partial PPARδ agonist; its optimization was based on the X‐ray crystal structure in complex with PPARδ. In contrast to other PPARδ agonists, this ligand does not interact directly with residues from the activation helix AF‐2, which might be linked to its partial agonistic effect. Interestingly, the thiadiazole moiety fills a novel subpocket, which becomes accessible after moderate conformational rearrangement. The optimization was focused on introducing conformational constraints and replacing intramolecular hydrogen bonding interactions. Highly potent molecules with activity as dual partial PPARγ/δ agonists in the low nanomolar range were then identified. One of the most active members, compound 20 a, displayed EC50 values of 1.6 and 336 nM for PPARδ and γ, respectively. The X‐ray crystal structure of its complex with PPARδ confirms our design hypothesis. Compound 20 a clearly displayed in vivo activity in two chronic mice studies. Lipids were modified in a beneficial way in normolipidemic mice, and the development of overt diabetes could be prevented in pre‐diabetic db/db mice. However, body weight gain was similar to that observed with the PPARγ agonist rosiglitazone. Hence, active compounds from this series can be considered as valuable tools to elucidate the complex roles of dual PPARγ/δ agonists for potential treatment of metabolic syndrome.