In this study the effects of the Inhibition of the Sodium-Glucose Linked Transporter 2 in the kidney with empagliflozin compared to hydrochlorothiazide on blood pressure and on central sympathic nervous activity will be examined.

The drug empagliflozin is a selective oral inhibitor of the sodium-glucose co-transporter 2 (SGLT-2) in the kidney.On the market empagliflozin is approved for the treatment of type 2 Diabetes. The mechanism of action can be described as follows: SGLT-2 is responsible for 90% of the reabsorption of Glucose in the kidney. If this Transport System is inhibited the secretion of glucose via the urine is increased. Therefore the blood glucose concentration will be lowered.

It has been noted that the SGLT-2 drugs are lowering the blood pressure as well, but the specific characteristics of the durg leading to this effect have not been examined in adequate clinical trial up to now.

To evaluate the central sympathic nervous activity a microneurography will be performed in this study; this examination will provide Information if empagliflozin dose decrease the sympathic nervous activity. If this is the case new effects of empagliflozin have to be discussed, Otherwise it can be assumed that the blood pressure decrease is a result of an increase of urine volume. In this case the sympathic activity should be increased.

This study will be performed in parallel groups who will receive a double-blind, randomised treatment, either empagliflozin or hydrochlorothiazide. The hypothesis that empagliflozin - in contrast to hydrochlorthiazide - does not increase the sympathic nervous activity in obese, hypertensive subjects with type 2 Diabetes treated with metformin will be tested.

Inclusion Criteria:

• women and men >= 50 and <= 80 years of age
• type 2 diabetes mellitus for >=2 years
• only metformin monotherapy is allowed; metformin dose must have been stable for >=12 weeks

Exclusion Criteria:

• previous empagliflozin treatment within the last 3 months
• heart failure NYHA II - IV
• subjects who have received any investigational medicinal product or have used any investigational medical device within 30 days prior to the screening visit, or who are actively participating in any investigational medicinal product or medical device trial, or who are scheduled for any such trial during the course of the trial.