How do I style the title item in Navigation menu

Question

I have

    <item android:title="Request"> 
        <menu> 
            <item android:title="Start" /> 
        </menu>     
    </item> 

How do I make "Request" as bold.

To style the sub item - 'Start', I've used android:textStyle but it doesn't work for the super/ header/category/ title item (Request).

styles.xml

<style name="Appearance">
    <item name="android:fontFamily">sans-serif-light</item>
    <item name="android:textColor">@drawable/drawer_item</item>
    <item name="android:textStyle">bold</item>
</style>

Output:

how do I style the title item ??? which style item works for it?