See below. Smoking increases production of stress hormones (your body wants to fight the toxins you're inhaling). Stress hormones cause increased glucose production ("fight or flight") which exacerbates diabetes. More importantly, smoking causes increased inflammation in your arteries. Diabetes does this too. So, now, you have double arterial inflammation - increasing heart attack & stroke risk.
Many ways. For example, the combination great increases your risk of heart disease. The combo can greatly affect your circulation and lead to losing goes and amputations. It's a bad combo. :/.