Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst growth and declining kidney function. Inflammatory pathways, including those mediated by monocyte chemoattractant protein-1 (MCP-1), are increasingly recognized as contributors to disease progression. Metabolic alterations in cystic epithelial cells may influence inflammatory signaling, suggesting a potential role for dietary interventions targeting metabolic pathways.

This study is a prospective, randomized, open-label crossover trial designed to evaluate the effect of a carbohydrate restricted, plant dominant dietary intervention on urinary MCP-1 levels in adults with ADPKD. Participants will be randomized to one of two sequences: dietary intervention followed by usual diet, or usual diet followed by dietary intervention, with a washout period between study phases. Each study period will last 12 weeks.

The primary objective is to assess within subject differences in urinary MCP-1/creatinine ratio between the dietary intervention and usual diet conditions. Secondary outcomes include measures of metabolic parameters, insulin resistance, dietary adherence, and safety.

This study aims to explore whether a structured dietary approach may influence intrarenal inflammatory activity in ADPKD and provide preliminary data to inform future interventional studies.

Inclusion Criteria:

1. Age ≥18
2. Diagnosis of ADPKD based on established clinical or genetic criteria (PKD 1/PKD2)
3. Estimated glomerular filtration rate (eGFR) between 45 and 90 mL/min/1.73 m²
4. Mayo Imaging Classification class 1C-1E based on MRI-derived height-adjusted total kidney volume.
5. Stable kidney function, defined as no acute kidney injury and no decline in eGFR >20% within the preceding 3 months
6. Stable antihypertensive and chronic medications for at least 4 weeks prior to enrollment
7. Ability and willingness to adhere to the prescribed dietary intervention
8. Ability to provide written informed consent

Exclusion Criteria:

1. eGFR <45 mL/min/1.73 m² or requirement for dialysis
2. History of kidney transplantation
3. Significant albuminuria, defined as urine albumin to creatinine ratio (UACR) >300 mg/g
4. Poorly controlled or unstable diabetes mellitus (e.g., HbA1c >8% or clinically significant glycemic variability or frequent hypoglycemia)
5. Use of Tolvaptan at the time of screening or within the study period
6. Current adherence to a ketogenic or carbohydrate restricted diet
7. Unintentional weight loss >5% within the preceding 3 months
8. Active infection, inflammatory disease, or malignancy that may influence inflammatory markers
9. Current use of systemic corticosteroids or immunosuppressive therapy
10. Active or symptomatic nephrolithiasis
11. Serum bicarbonate <20 mmol/L
12. Pregnancy or breastfeeding
13. Known eating disorder or condition limiting adherence to dietary interventions
14. Participation in another interventional study within the previous 3 months
15. Any condition that, in the opinion of the investigators, would interfere with study participation or interpretation of results