Effects of 25-Hydroxyvitamin D Levels on Renal Function: A Bidirectional Mendelian Randomization Study

Area of Science:

• Nephrology
• Endocrinology
• Genetics

Background:

• Observational studies on vitamin D and renal function have produced conflicting results.
• Understanding the causal relationship between 25-hydroxyvitamin D (25[OH]D) and kidney function is crucial for clinical practice.

Purpose of the Study:

• To investigate the association between serum 25-hydroxyvitamin D (25[OH]D) levels and renal function.
• To determine if altered renal function causally impacts 25(OH)D levels using Mendelian randomization (MR).

Main Methods:

• A two-sample Mendelian randomization (MR) study was conducted using European genetic data.
• Single nucleotide polymorphisms (SNPs) associated with 25(OH)D were analyzed for their effects on eGFR, BUN, and CKD risk.
• Reverse MR was performed using renal function-related SNPs to assess causal effects on 25(OH)D levels.

Main Results:

• No robust evidence was found for a causal effect of 25(OH)D on eGFR, BUN, or CKD.
• A decrease in 25(OH)D was associated with increased eGFR, while increased BUN and CKD were linked to higher 25(OH)D levels.
• Reverse MR analyses confirmed these associations, indicating kidney function influences 25(OH)D levels.

Conclusions:

• Genetically predicted CKD, elevated BUN, and reduced eGFR are associated with increased 25(OH)D levels in Europeans.
• This study found no evidence that 25(OH)D causally affects renal function.
• The findings suggest a unidirectional relationship where kidney function may influence vitamin D status.