Association of Dietary Protein Intake With Nocturnal Blood Pressure Dipping in Potential Living Kidney Donors

OBJECTIVES: Although high dietary protein intake (DPI) is associated with glomerular hyperfiltration potentially worsening kidney function, it is associated with lower blood pressure. Abnormal nocturnal blood pressure dipping patterns are associated with albuminuria and declined kidney function; however, the association of DPI with nocturnal dipping is yet unquantified. METHODS: A single-center cohort study included living kidney donors (LKD) undergoing living kidney donation in 2021 and having pre-donation 24-hour ambulatory blood pressure. Cross-sectional association between pre-donation DPI and NSD was examined by multiple linear regression. RESULTS: Among 14 LKD, mean ± SD was 44 ± 12 and 50% were female. Mean ± SD day- and night-time systolic blood pressure were 122 ± 10 (95%CI 117,128) and 109 ± 11 (95%CI 102,115), respectively (mean(diff) 14; 95%CI 9, 18; P < 0.001). Day- and night-time diastolic blood pressure were 78 ± 6 (95%CI 74, 82) and 66 ± 9 (95%CI 61, 71), respectively (meandiff 12 ± 6; 95%CI 8, 16; P < 0.001). Mean nocturnal systolic dipping (NSD) was 11 ± 6 (95%CI 7, 15) and nocturnal diastolic dipping (NDD) was 16 ± 9 (95%CI 11, 20) (mean(diff) −4 ± 6; 95% CI −8, −1; P < 0.001). Mean body weight was 73 ± 1 kg and DPI was 1.5 ± 1.9 g/kg/day. Mean serum creatinine and cystatin C were 0.81 ± 0.15 mg/dL and 0.74 ± 0.14 mg/L, respectively. Every 1 g/kg/day increase in DPI was associated with 2.58 mmHg significantly increase in NSD (β -2.58; 95%CI −3.88, −1.28; P < 0.001) and 2.09 mmHg decrease in NDD but no statistical significance (β -2.09; 95%CI −4.67, 0.50; p 0.104). After adjusting for age, gender, ethnicity, pre-donation body mass index, dietary sodium intake, dietary potassium intake, and the interaction term between age (≤45 vs >45 years old) and gender, the association of DPI with NSD and DDP was greater and statistically significant (β(NSD) −3.22; 95%CI −5.54, −0.90; P 0.016 and β(NDD) −4.90; 95%CI −9.68, −0.13; P 0.046). CONCLUSIONS: Higher DPI is associated with greater NSD and NDD independent of dietary sodium and potassium intake in generally healthy individuals with normal kidney function as potential LKD. Glomerular hyperfiltration associated with higher DPI may involve blood pressure regulation, and potential mechanisms of nocturnal dipping related to DPI require additional longitudinal studies. FUNDING SOURCES: None.