Renal Functional Response-Association With Birth Weight and Kidney Volume

Area of Science:

• Nephrology
• Physiology
• Public Health

Background:

• Low birth weight (LBW) is linked to fewer nephrons and reduced kidney function in adulthood.
• Renal functional response (RFR), an acute increase in glomerular filtration rate (GFR) post-protein load, may indicate kidney health.
• LBW's long-term effects on RFR and kidney structure warrant investigation.

Purpose of the Study:

• To examine the association between LBW, kidney volume, and RFR in middle-aged adults.
• To determine if birth weight influences kidney function adaptation to a protein load.
• To explore the relationship between kidney size, GFR, and RFR.

Main Methods:

• Study included adults aged 41-52 years, categorized by LBW (≤2300 g) or normal birth weight (NBW; 3500-4000 g).
• Glomerular filtration rate (GFR) measured via iohexol clearance; stimulated GFR (sGFR) assessed after a 100g protein load to calculate RFR.
• Kidney volume estimated using MRI; GFR indexed to kidney volume.

Main Results:

• No significant association found between birth weight and RFR.
• Larger kidney volume was positively associated with higher RFR (1.9 ml/min per SD increase; P=0.009).
• Higher GFR per kidney volume was negatively associated with RFR (-3.3 ml/min per SD increase; P<0.001).

Conclusions:

• Kidney size and GFR relative to kidney size are associated with RFR.
• Birth weight was not a determinant of RFR in this cohort of healthy middle-aged adults.
• These findings suggest kidney structure, not birth weight history, may be more critical for acute renal functional response.