In a prospective single centre placebo-controlled trial over ten weeks, 24 CKD II-III patients (eGFR 30-89 ml/min per 1.73 m2) with DM II will be randomized to enalapril 20mg per day after a two week run-in phase. Thereafter, patients will either receive eplerenone 25mg (n=12) or a placebo (n=12) for eight weeks. Eplerenone will be increased to 50mg under close monitoring of serum potassium levels. Employing a novel mass-spectrometry ( MS)-based method, quantification of up to 10 different Ang metabolites (Ang I, Ang II, Ang 1-7, Ang 1-9, Ang 2-10, Ang 1-5, Ang 2-7, Ang 3-7, Ang 3-8 and Ang 2-8) will be performed simultaneously out of blood sera (after run-in phase and after 10 weeks).

Inclusion Criteria:

• CKD II to III and diabetes mellitus type 2
• CKD will be defined according to estimated glomerular filtration rate (eGFR) with the MDRD formula
• eGFR between 30 and 89 ml/min
• albumin excretion rates > 300 mg/24 hours (UACR > 300 mg/gram) or > 200 mg/g if already receiving any RAS blockade Patients should be hypertonic stage I or II according to the European guidelines (Chobanian et al. JAMA 2003)

Exclusion Criteria:

• Age < 18 years
• UACR > 3500mg/g
• severe hypertension
• pregnancy
• unwilling or inability to sign the informed consent
• coronary heart disease
• systolic blood pressure < 130 mmHg
• additional RAS interfering drugs (ACEis, ARBs, direct renin inhibitors)
• 25-hydroxy vitamin D levels below 16.6±8.3 pg/ml
• 1,25-dihydroxy vitamin D 33.1±15.5 pg/ml

Intolerance to eplerenon or an excipient of it:

tablettcore: Lactose-Monohydrat Mikrokristalline Cellulose (E 460) Croscarmellose-sodium (E 468) Hypromellose (E 464) Sodiumdodecylsulfat Talkum (E 553b) Magnesiumstearat (E 470b)

filmcoat

Opadry, yellow:

Hypromellose (E 464) Titandioxid (E 171) Macrogol 400 Polysorbat 80 (E 433) Yellow ironoxide (E 172) Red ironoxide (E 172)

• Patients with Serumpotassium > 5,0 mmol/l at start of the treatment
• Patients with severe renal insufficiency (eGFR <30ml/min./1.73 m2)
• Patients with severe liver insufficiency (Child-Pugh class C)
• Patients taking potassium saving diuretics, potassium supplements or strong CYP3A4-inhibitors (z. B. Itraconazol, Ketoconazol, Ritonavir, Nelfinavir, Clarithromycin, Telithromycin und Nefazodon)