Retrieve Custom Data Annotations for create Custom LabelFor

Question

I am creating a custom LabelFor. Inside it want to get the DataAnnotations properties linked to attribute mainly DataAnnotations created by me and I'm not getting. Example: Obrigatorio

I need to get the values of DataAnnotations for the labelFor leave the fields in bold when required. And depending on the validation, leave customized with styles.

My Class

public class GrupoRisco : IEntidadeBase
{
    [Key]
    public int GrupoRiscoID { get; set; }
    [Obrigatorio]
    [Display(Name="Descrição")]
    public string Descricao { get; set; }
}

My Custom Atribute

public class Obrigatorio : RequiredAttribute
{
    public Obrigatorio()
    {
        ErrorMessage = "* Obrigatório";
    }
}

The attribute above is simple, but will create complex attributes.