Effect of Montelukast on Kidney and Vascular Function in Type 1 Diabetes

Inclusion Criteria: * Age 18-80 years * Type 1 diabetes for at least 5 years * Urine albumin to creatinine ratio 30-5000 mg/g on first morning void * eGFR 30-89 ml/min/1.73m2 at time of screening * Blood pressure \<140/90 mm Hg prior to randomization * Use of angiotensin converting enzyme inhibitor or angiotensin receptor blocker with stable dose for 4 weeks * BMI \< 40 kg/m2 (FMDBA measurements can be inaccurate in severely obese patients). * Stable anti-hypertensive regimen for at least one month prior to randomization * Stable regimen of insulin delivery, i.e. automated insulin delivery (AID) system or multiple daily injections) 4 weeks prior to randomization * Sedentary or recreationally active (≤2 days of vigorous aerobic exercise as vigorous exercise may affect vascular function measurements) * Able to provide consent Exclusion Criteria: * Significant comorbid conditions that lead the investigator to conclude that life expectancy is less than 1 year * Uncontrolled hypertension * Factors judged to limit adherence to interventions * Anticipated initiation of dialysis or kidney transplantation within 6 months * Current participation in another research study * Pregnancy or planning to become pregnant or currently breastfeeding * Allergy to aspirin * Severe hepatic impairment (Child-Pugh Class C) * History of major psychiatric disorder * Use of inhaled or systemic corticosteroids or long-acting beta agonists (higher risk of neuropsychiatric reaction) * Penicillin allergy * Iodine allergy * Shellfish allergy * Current use of phenobarbital, rifampin or carbamazepine