Causal Relationships Between Mineralocorticoid Receptor Activation and Tubulointerstitial Nephritis and Lipid Metabolism Dysregulation: A Mendelian Randomization Study.

OBJECTIVES

To clarify the causal relationship between the level of cytoplasmic unactivated mineralocorticoid receptor (MR) and the development of tubulointerstitial nephritis (TIN), and to evaluate the impact of MR on dyslipidemia, particularly secondary hyperlipemia, in patients with diabetic kidney disease.

METHODS

We conducted a two-sample Mendelian randomization study using genome-wide association study (GWAS) summary data. Genetic variants associated with MR levels were selected as exposures, with TIN and lipid profiles [including low-density lipoprotein cholesterol (LDL-C), triglyceride, and high-density lipoprotein cholesterol] as outcomes. A two-step Mendelian randomization approach was used to assess TIN as a mediator, employing inverse variance weighted regression as the primary analysis, supplemented by Mendelian randomization-Egger, weighted median, and sensitivity analyses.

RESULTS

Cytoplasmic unactivated MR level exhibited a significant causal association with a decreased risk of TIN (OR = 0.8598, 95% CI [0.7775-0.9508], P < 0.001). Although no significant causal relationship was identified between MR level and secondary hyperlipemia, a potential association of cytoplasmic unactivated MR level with lower LDL-C levels was observed (OR = 0.9901, 95% CI [0.9821-0.9983], P = 0.018). Additionally, TIN exhibited causal links with secondary hyperlipemia (OR = 1.0016, 95% CI [1.0002-1.0029], P = 0.020) and elevated LDL-C (OR = 1.0111, 95% CI [1.0024-1.0199], P = 0.012), particularly LDL-C in European males (OR = 1.0230, 95% CI [1.0103-1.0358], P < 0.001). Inverse Mendelian randomization analysis revealed causal relationships between TIN and genetically predicted triglyceride (OR = 0.7027, 95% CI [0.6189-0.7978], P < 0.001), high-density lipoprotein cholesterol (OR = 1.1247, 95% CI [1.0019-1.2626], P = 0.046), and LDL-C (OR = 0.8423, 95% CI [0.7220-0.9827], P = 0.029). Notably, TIN mediated 16.7% of the causal association between MR and LDL-C levels.

CONCLUSIONS

MR plays a critical role in the development of TIN and lipid metabolism, highlighting the potential of MR-antagonists in reducing renal damage and lipid metabolism-associated complications.