Protected Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs)
WebApplicationStyleManager.EnableUpperCase = False
This property has effect when used before the application main page is shown. You can access it in the Session_Start method located in the Global.asax file, after the WebApplication.SwitchToNewStyle method is called.
The result is demonstrated in the image below.
Alternatively, you can use the following properties to disable upper case for grid column, layout group and navigation group captions, individually.