Preheat oven to moderate (350°). Spray twelve 2-1/2-inch muffin-pan cups with nonstick vegetable spray. Stir together buttermilk, water, egg and honey in 2-cup glass measure. Combine four, wheat and oat brans, baking soda, baking powder and cinnamon in large bowl. Add buttermilk mixture to dry ingredients along with apple, carrot and walnuts. Stir with wooden spoon to combine. Spoon batter into prepared muffin-pan cups. Bake in preheated moderate oven (350°) for 15 minutes or until muffins begin to pull away from sides of pan. Remove muffins from cups and cool on wire rack. Serve warm. * Note: Wheat bran and oat bran are available in some supermarkets and in health food stores. Nutrient Value Per Muffin: 75 calories, 2 g protein, 2 g fat, 13 g carbohydrate, 66 mg sodium, 23 mg cholesterol. bake 25