This is a dose-ranging study to evaluate the safety, pharmacokinetics, and tolerability of multiple doses of an oral, sustained release formulation of sodium nitrite (TV1001sr) in subjects with DNP. The primary objective is to assess the safety and tolerability of multiple doses of twice daily 40 mg and 80 mg TV1001sr compared with placebo over a 12 week treatment period and the pharmacokinetics of the sustained release formulation of sodium nitrite. Secondary objectives are to evaluate the pharmacokinetics and markers of functional improvement including pain questionnaires, quantitative sensory testing and changes in markers of diabetes.