NEW YORK (AdAge.com) -- Although looking somewhat gawky and uncomfortable, NBC's Katie Couric still showed a lot of heart as she clumped up and down the runway at the Mercedes Benz Fashion Week kick off. But then, heart was the whole point. Ms. Couric led a list of celebrities who all did red dress struts as part of the Diet Coke-sponsored "Heart Truth" campaign in Bryant Park. The federal government program is designed to make women more aware of the danger of heart disease.