A Long-Acting FGF21 Molecule, PF-05231023, Decreases Body Weight and Improves Lipid Profile in Non-human Primates and Type 2 Diabetic Subjects.

FGF21 plays a central role in energy, lipid, and glucose homeostasis. To characterize the pharmacologic effects of FGF21, we administered a long-acting FGF21 analog, PF-05231023, to obese cynomolgus monkeys. PF-05231023 caused a marked decrease in food intake that led to reduced body weight. To assess the effects of PF-05231023 in humans, we conducted a placebo-controlled, multiple ascending-dose study in overweight/obese subjects with type 2 diabetes. PF-05231023 treatment resulted in a significant decrease in body weight, improved plasma lipoprotein profile, and increased adiponectin levels. Importantly, there were no significant effects of PF-05231023 on glycemic control. PF-05231023 treatment led to dose-dependent changes in multiple markers of bone formation and resorption and elevated insulin-like growth factor 1. The favorable effects of PF-05231023 on body weight support further evaluation of this molecule for the treatment of obesity. Longer studies are needed to assess potential direct effects of FGF21 on bone in humans.

The phytoestrogen coumestrol is a naturally occurring antagonist of the human pregnane X receptor.

Antagonizing the action of the human nuclear xenobiotic receptor pregnane X receptor (PXR) may have important clinical implications in preventing drug-drug interactions and improving therapeutic efficacy. We provide evidence that a naturally occurring phytoestrogen, coumestrol, is an antagonist of the nuclear receptor PXR (NR1I2). In transient transfection assays, coumestrol was able to suppress the agonist effects of SR12813 on human PXR activity. PXR activity was assessed and correlated with effects on the metabolism of the anesthetic tribromoethanol and on gene expression in primary human hepatocytes. We found that coumestrol was able to suppress the effects of PXR agonists on the expression of the known PXR target genes, CYP3A4 and CYP2B6, in primary human hepatocytes as well as inhibit metabolism of tribromoethanol in humanized PXR mice. Coumestrol at concentrations above 1.0 microm competed in scintillation proximity assays with a labeled PXR agonist for binding to the ligand-binding cavity. However, mammalian two-hybrid assays and transient transcription data using ligand-binding-cavity mutant forms of PXR show that coumestrol also antagonizes coregulator recruitment. This effect is likely by binding to a surface outside the ligand-binding pocket. Taken together, these data imply that there are antagonist binding site(s) for coumestrol on the surface of PXR. These studies provide the basis for development of novel small molecule inhibitors of PXR with the ultimate goal of clinical applications toward preventing drug-drug interactions.

Cloning, tissue expression, and regulation of beagle dog CYP4A genes.

In addition to its function as a fatty acid hydroxylase, the peroxisome proliferator-activated receptor alpha (PPARalpha) target gene, CYP4A, has been shown to be important in the conversion of arachidonic acid to the potent vasoconstrictor 20-hydroxyeicosatetraenoic acid, suggesting a role for this enzyme in mediating vascular tone. In the present study, the cDNA sequence of beagle dog CYP4A37, CYP4A38, and CYP4A39 from the liver was determined. Open reading frame analysis predicted that CYP4A37, CYP4A38, and CYP4A39 each comprised 510 amino acids with approximately 90% sequence identity to one another, and approximately 71 and 78% sequence identity to rat CYP4A1 and human CYP4A11, respectively. PCR analysis revealed that the three dog CYP4A isoforms are expressed in kidney > liver >> lung >> intestine > skeletal muscle > heart. Treatment of primary dog hepatocytes with the PPARalpha agonists GW7647X and clofibric acid resulted in an increase in CYP4A37, CYP4A38, and CYP4A39 mRNA expression (up to fourfold), whereas HMG-CoA synthase mRNA expression was increased to a greater extent (up to 10-fold). These results suggest that dog CYP4A37, CYP4A38, and CYP4A39 are expressed in a tissue-dependent manner and that beagle dog CYP4A is not highly inducible by PPARalpha agonists, similar to the human CYP4A11 gene.

Guggulsterone activates multiple nuclear receptors and induces CYP3A gene expression through the pregnane X receptor.

Gugulipid is an extract of the guggul tree, Commiphora mukul, that is used to treat hyperlipidemia in humans. The lipid-lowering activity is found in the stereoisomers and plant sterols Z-guggulsterone and E-guggulsterone. The molecular basis for the lipid-lowering action of guggulsterone has been suggested to be antagonism of the farnesoid X receptor, a member of the nuclear receptor superfamily of ligand-activated transcription factors. To determine whether guggulsterone has the ability to function as an agonist of other nuclear receptor family members, we screened a panel of these proteins for their ability to transactivate reporter genes. Here, we show that guggulsterones activate the estrogen receptor alpha isoform, progesterone receptor, and pregnane X receptor. Concentration-response analysis using reporter gene assays indicate that guggulsterones activate these three receptors with EC(50) values in the low micromolar range. Furthermore, we show that guggulsterone-mediated activation of the pregnane X receptor induces the expression of CYP3A genes in both rodent and human hepatocytes. Protein interaction assays indicate that guggulsterones interact directly with pregnane X receptor, thereby modulating interaction with protein cofactors. We introduce a novel method to screen herbal remedies for their ability to activate pregnane X receptor. Pregnane X receptor activation is known to cause herb-drug interactions, and our data suggest that gugulipid therapy should be used cautiously in patients taking prescription medications that are metabolized by CYP3A family members. Moreover, our data suggest the need for additional studies of guggulsterones agonist activity against estrogen receptor alpha isoform and the progesterone receptor.