Mechanistic Study of the Systolic Blood Pressure Lowering Effect of Dapagliflozin in Type 2 Diabetes

Dapagliflozin has been shown to lower clinic systolic and diastolic blood pressure in patients with type 2 diabetes mellitus. In particular, the reduction in SBP is impressive. The effect on circadian patterns of blood pressure measured by ambulatory blood pressure monitoring has not been established. The exact mechanism(s) by which dapagliflozin lowers clinic SBP is not clear although there has been speculation that it is due to a decrease in intravascular volume secondary to the osmotic diuresis produced by the drug. However, SBP is dependent on both pulse volume and vascular stiffness (impedance to ejection).

Dapagliflozin may have a favorable effect on vascular stiffness by a reduction in blood glucose resulting in decreased proximal arterial collagen cross-linking due to non-enzymatic glycosylation of proteins.

Dapagliflozin may also have a favorable effect on vascular stiffness by increasing urinary sodium excretion. Dapagliflozin is a sodium/glucose co-transporter inhibitor and the effects on sodium excretion are not clear. Increased sodium intake is associated with an increase in vascular stiffness.

An increase in vascular stiffness has been correlated with increased cardiovascular morbidity and mortality. Thus, it is important to know if dapagliflozin has an effect on vascular stiffness.

The current "gold standard" for vascular stiffness is aortic pulse wave velocity (aPWV). Other measures of vascular stiffness include: systolic blood pressure, pulse pressure and augmentation index. Also, measurement of calculated central blood pressure provides information that may not be apparent from measurement of brachial blood pressure.

Measures of intravascular volume status include: body weight, jugular venous pressure, orthostatic changes in blood pressure and heart rate.

It is important to recognize that some oral anti-diabetic drugs, e.g. sulfonylurea's are associated with an increase in systemic arterial blood pressure.

Hypothesis

That treatment of type 2 diabetes mellitus with dapagliflozin will result in a decrease in arterial stiffness

Primary Objectives

The primary objective of the study is to determine the effect of dapagliflozin (Appendix A), 10 mg daily, on parameters of arterial stiffness: aPWV, augmentation index (AI), 24-hour blood pressure patterns, SBP, and pulse pressure.

Key Questions

• What effect will dapagliflozin have on measures of arterial stiffness?
• What effect will dapagliflozin have on central blood pressure?
• Will dapagliflozin lower BP over the 24-hour period and will the pattern of BP change?
• Will dapagliflozin increase sodium excretion for 16 weeks?
• What will be the effect of dapagliflozin on intravascular volume status at 16 weeks?

Secondary Objectives

• Urinary sodium excretion
• Intravascular volume status: jugular venous pressure, body weight, orthostatic change in BP and pulse rate

Treatment

All patients will receive a background treatment with metformin. After randomization (2:1) patients will receive dapagliflozin, 10 mg daily or glimpiride (Appendix B), 4 mg daily. The treatment period will last ;16 weeks.

For high risk subjects, dapagliflozin therapy will begin with 5 mg with up-titration at 2 weeks. High risk subjects are those prone to volume depletion and are identified by signs of hypovolemia, e.g. low venous pressure, and a low arteriasl blood pressure.

Subjects will also be closely monitored for the development of hypoglycemia. This risk will be minimized by not enrolling subjects taking insulin. Subjects will be made aware of the signs of hypotlycemia, e.g. sweating and palpitation, and will be instructed to treat with ingestion of sugar, particularly fructose in orange juice.