Yeah, a fifteen-fret uke will have two octaves. The lowest note is middle C. Then the E string (open) is the E above middle C, the A (also open) is the A above middle C, then fifteen frets down you have the second C above middle C. That's two octaves.
Yes, peanuts and peanut butter can aggravate arthritis. I was a peanut butter eater all my life, I am now 58.
Keep in mind, however, that peanuts are high in calories -- and some varieties contain sodium and saturated fat -- so eating too many may negatively affect your health. Peanuts are packed with vitamin E and manganese, two antioxidants that your body uses to prevent cellular damage.