28 research outputs found
Group space scan of flavor symmetries for nearly tribimaximal lepton mixing
We present a systematic group space scan of discrete Abelian flavor
symmetries for lepton mass models that produce nearly tribimaximal lepton
mixing. In our models, small neutrino masses are generated by the type-I seesaw
mechanism. The lepton mass matrices emerge from higher-dimension operators via
the Froggatt-Nielsen mechanism and are predicted as powers of a single
expansion parameter \epsilon that is of the order of the Cabibbo angle
\theta_C\simeq 0.2. We focus on solutions that can give close to tribimaximal
lepton mixing with a very small reactor angle \theta_{13}\approx 0 and find
several thousand explicit such models that provide an excellent fit to current
neutrino data. The models are rather general in the sense that large leptonic
mixings can come from the charged leptons and/or neutrinos. Moreover, in the
neutrino sector, both left- and right-handed neutrinos can mix maximally. We
also find a new relation \theta_{13}\lesssim\epsilon^3 for the reactor angle
and a new sum rule \theta_{23}\approx\pi/4+\epsilon/\sqrt{2} for the
atmospheric angle, allowing the models to be tested in future neutrino
oscillation experiments.Comment: 18 pages, 2 tables, 2 figures, references added, final version to
appear in JHE
Lipolysis drives expression of the constitutively active receptor GPR3 to induce adipose thermogenesis
Thermogenic adipocytes possess a therapeutically appealing, energy-expending capacity, which is canonically cold-induced by ligand-dependent activation of beta-adrenergic G protein-coupled receptors (GPCRs). Here, we uncover an alternate paradigm of GPCR-mediated adipose thermogenesis through the constitutively active receptor, GPR3. We show that the N terminus of GPR3 confers intrinsic signaling activity, resulting in continuous Gscoupling and cAMP production without an exogenous ligand. Thus, transcriptional induction of Gpr3 represents the regulatory parallel to ligand-binding of conventional GPCRs. Consequently, increasing Gpr3 expression in thermogenic adipocytes is alone sufficient to drive energy expenditure and counteract metabolic disease in mice. Gpr3 transcription is cold-stimulated by a lipolytic signal, and dietary fat potentiates GPR3-dependent thermogenesis to amplify the response to caloric excess. Moreover, we find GPR3 to be an essential, adrenergic-independent regulator of human brown adipocytes. Taken together, our findings reveal a noncanonical mechanism of GPCR control and thermogenic activation through the lipolysis-induced expression of constitutively active GPR3.Diabetes mellitus: pathophysiological changes and therap