ObjectiveType 2 diabetes and obesity are emerging pandemics in the 21st century creating worldwide urgency for the development of novel and safe therapies. We investigated trace amine-associated receptor 1 (TAAR1) as a novel target contributing to the control of glucose homeostasis and body weight.MethodsWe investigated the peripheral human tissue distribution of TAAR1 by immunohistochemistry and tested the effect of a small molecule TAAR1 agonist on insulin secretion in vitro using INS1E cells and human islets and on glucose tolerance in C57Bl6, and db/db mice. Body weight effects were investigated in obese DIO mice.ResultsTAAR1 activation by a selective small molecule agonist increased glucose-dependent insulin secretion in INS1E cells and human islets and elevated plasma PYY and GLP-1 levels in mice. In diabetic db/db mice, the TAAR1 agonist normalized glucose excursion during an oral glucose tolerance test. Sub-chronic treatment of diet-induced obese (DIO) mice with the TAAR1 agonist resulted in reduced food intake and body weight. Furthermore insulin sensitivity was improved and plasma triglyceride levels and liver triglyceride content were lower than in controls.ConclusionsWe have identified TAAR1 as a novel integrator of metabolic control, which acts on gastrointestinal and pancreatic islet hormone secretion. Thus TAAR1 qualifies as a novel and promising target for the treatment of type 2 diabetes and obesity.

No abstract

Therapeutic antibodies administered intravitreally are the current standard of care to treat retinal diseases. The ocular half-life (t 1/2) is a key determinant of the duration of target suppression. To support the development of novel, longer-acting drugs, a reliable determination of t 1/2 is needed together with an improved understanding of the factors that influence it. A model-based meta-analysis was conducted in humans and nonclinical species (rat, rabbit, monkey, and pig) to determine consensus values for the ocular t 1/2 of IgG antibodies and Fab fragments. Results from multiple literature and in-house pharmacokinetic studies are presented within a mechanistic framework that assumes diffusion-controlled drug elimination from the vitreous. Our analysis shows, both theoretically and experimentally, that the ocular t 1/2 increases in direct proportion to the product of the hydrodynamic radius of the macromolecule (3.0 nm for Fab and 5.0 nm for IgG) and the square of the radius of the vitreous globe, which varies approximately 24-fold from the rat to the human. Interspecies differences in the proportionality factors are observed and discussed in mechanistic terms. In addition, mathematical formulae are presented that allow prediction of the ocular t 1/2 for molecules of interest. The utility of these formulae is successfully demonstrated in case studies of aflibercept, brolucizumab, and PEGylated Fabs, where the predicted ocular t 1/2 values are found to be in reasonable agreement with the experimental data available for these molecules.

Troglitazone, a thiazolidinedione (TZD) type insulin sensitizer for the treatment of diabetes, was withdrawn from the U.S. market after several fatal cases of hepatotoxicity. Although the mechanism(s) of these idiosyncratic adverse reactions are not completely understood, circumstantial evidence suggests at least a partial contribution of reactive metabolite formation. Despite isolated case reports of hepatotoxicity, the other TZD derivatives pioglitazone and rosiglitazone are comparatively safe. Herein, we report on the bioactivation potential of these drugs and their TZD ring isotope-labeled 2-(15)N-3,4,5-(13)C(3) analogues in rat and human liver microsomes supplemented with glutathione (GSH). Screening for GSH adducts as surrogate markers for reactive intermediate formation was performed by liquid chromatography tandem mass spectrometry. Chemical characterization of the GSH conjugates was conducted by acquisition of their respective product ion spectra and the comparison between unlabeled and stable isotope-labeled TZD derivatives. The data suggest that all drugs undergo bioactivation processes via a common metabolic activation on the TZD ring, yielding disulfide type GSH conjugates as evidenced by the loss of labeled positions in the TZD moiety. Additional bioactivation processes leading to GSH adducts not involving TZD ring scission were evident for troglitazone. In human liver microsomes at low substrate concentrations, only troglitazone yielded a predominant GSH adduct not involving TZD ring scission. This property may contribute, together with other factors such as the relatively high dose administered as well as its potential to induce hepatic cholestasis and oxidative stress, to the hepatotoxicity of this drug.

The skin sensitizers, 5-chloro-2-methylisothiazol-3-one (MCI) and 2-methylisothiazol-3-one (MI), have been synthesized isotopically labeled with (13)C at all carbon positions. The reactivity of 3-[(13)C]-, 4-[(13)C]-, and 5-[(13)C]MCI and MI toward a series of model nucleophiles for protein amino acid residues, i.e., butylamine, imidazole, sodium propanethiolate, and sodium phenoxide, was followed by (13)C and (1)H[(13)C] NMR spectroscopy. While MCI was found to react quantitatively with sodium propanethiolate and butylamine and significantly with imidazole and sodium phenoxide, MI reacted only with sodium propanethiolate. Reaction of MCI with nonthiol nucleophiles proceeded through an initial addition-elimination at position 5, leading to stable substitution adducts in the case of imidazole and sodium phenoxide. In the case of butylamine, the initial adduct was subjected to extra reactions at the sulfur atom through a cleavage of the S-N bond, leading to open adducts of the thioamide or amide type. Experiments carried out with N-acetyl-Cys, in excess or in deficiency, indicated that thiol nucleophiles reacted first at the sulfur atom through a cleavage of the S-N bond followed by extra nucleophilic reactions leading to open adducts of the mercaptothioester or mercaptoester type. Reaction of MCI with thiol nucleophiles gave products consistent with the formation of a reactive thioacyl chloride intermediate able to react with other nucleophiles present in the reaction medium. As a consequence, N-acetyl-Cys was found to be able to activate MCI toward N(alpha)-acetyl-Lys under physiological conditions to form adducts of the thioamide or amide type. Thus MCI, a strong sensitizer, and MI, a weak sensitizer, were found to react with different nucleophiles through different mechanisms. Although both MCI and MI can react with thiol nucleophiles, only MCI is capable of significantly reacting with amino nucleophiles of the Lys or His type. Moreover, MCI could be activated by a prior reaction with thiols.