def manage_style(layers_idx):
    for layer in layers_idx:
        manager = layer.styleManager()
        manager.renameStyle('', 'default')
        styles = layer.listStylesInDatabase()
        number_styles = styles[0]
        related_styles_idx = styles[1][0:number_styles]
        related_styles_names = styles[2][0:number_styles]
        related_styles = zip(related_styles_idx, related_styles_names)
        for style in related_styles:
            xml_style = layer.getStyleFromDatabase(style[0], '')
            manager.addStyle(style[1], QgsMapLayerStyle(xml_style))

        manager.setCurrentStyle(related_styles[0][1])
        manager.removeStyle('default')

registry = QgsMapLayerRegistry.instance()
registry.layersAdded.connect(manage_style)