Read the papers that inspired Professor Del Prato

Rossetti L, Shulman GI, Zawalich W, De Fronzo RA. Effect of Chronic Hyperglycemia on In Vivo Insulin Secretion in Partially Panceatectomized Rats. J Clin Invest. 1989 (Oct):80; 1037-1044.
http://pubmed.ncbi.nlm.nih.gov/3308956/

Zinman B, Wanner C, Lachin JM, Fitchett D, Bluhmki E, Hantel S, Mattheus M, Devins T, Johansen OE, Woerle HJ, Broedl UC, Inzucchi SE. EMPA-REG OUTCOME Investigators. Empagliflozin, Cardiovascular Outcomes, and Mortality in Type 2 Diabetes. NEJM. 2015 (Nov): 2117-2128.
http://pubmed.ncbi.nlm.nih.gov/26378978/