As Sumpup described, one effect of the SGLT2 inhibitors is to lower blood glucose by preventing glucose resorption in the kidney, resulting in increased urinary glucose excretion. However, many believe the mechansim of cardioprotection by SGLT2 inhibitors to be much more complex than simply blood glucose control. Sumpup's suggestion that glucose control in type 2 diabetics is all about diet ignores these other cardioprotective mechanisms. 

Also, blood glucose control is much more than diet. There are many other factors beyond just dietary carbohydrate that contribute to insulin resistance and blood glucose control including, but not limited to, dietary, genetic, epigenetic, development, lifestyle, inflammation and aging. Insulin resistance in various tissues can effect liver glucose production, glucose uptake and disposal by muscle and other peripheral tissues, rate of conversion of carbohydrate into fat, adipocyte fatty acid release, and many other facets of metabolism. There are many causes of insulin resistance, and this has been and still is a subject of intensive research. Yes, diets high in rapidly absorbed simple carbohydrate are like metabolic poison, but blood glucose control and insulin resistance is much more complex than just dietary carbohydrate.

Here is a good review on the potential SGLT2 cardioprotective mechanisms by Bart Staels entitled "Cardiovascular Protection by Sodium Glucose Cotransporter 2 Inhibitors: Potential Mechanisms"

https://www.ncbi.nlm.nih.gov/pubmed/28526184

From the abstract: "An antiatherosclerotic effect is considered unlikely given the speed of the observed decrease in cardiovascular mortality. Hemodynamic effects, such as reductions in blood pressure and intravascular volume, and involving osmotic diuresis, may provide a more plausible explanation. Metabolic effects, such as cardiac fuel energetics, and hormonal effects, such as increased glucagon release, may also contribute to the results observed during EMPA-REG OUTCOME. This review discusses the main hypotheses suggested to date."

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