Glomerular and tubular function in glycogen storage disease

Area of Science:

• Nephrology
• Pediatric Endocrinology
• Metabolic Disorders

Background:

• Glycogen Storage Diseases (GSD) are a group of inherited metabolic disorders affecting glucose metabolism.
• Hepatic GSDs, including GSD-I, GSD-III, and GSD-IX, can have significant systemic complications.
• Renal involvement in GSDs, particularly GSD-I, requires further investigation to understand underlying mechanisms.

Purpose of the Study:

• To assess urinary protein and calcium excretion in patients with hepatic GSDs.
• To evaluate renal function, including inulin (Cinulin) and para-aminohippuric acid (CPAH) clearances, in these patients.
• To investigate the relationship between GSD type, age, and renal parameters.

Main Methods:

• Studied 77 patients with GSD: 30 GSD-I, 25 GSD-III, and 22 GSD-IX.
• Measured urinary albumin, retinol-binding protein (RBP), N-acetyl-beta-D-glucosaminidase (NAG), and calcium excretion.
• Performed inulin and CPAH clearance tests in 33 patients.

Main Results:

• GSD-I patients showed significantly higher excretion of albumin, RBP, NAG, and calcium compared to GSD-III and GSD-IX.
• GSD-I patients exhibited higher Cinulin clearance, indicating hyperfiltration, but normal CPAH clearance.
• In GSD-I, Cinulin and NAG excretion correlated inversely with age, while albumin excretion correlated positively with age.

Conclusions:

• GSD-I is associated with hyperfiltration and renal tubular proteinuria preceding significant albuminuria.
• Proximal renal tubular dysfunction, potentially due to glucose-6-phosphatase deficiency, may be the primary issue in GSD-I.
• Glomerular hyperfiltration appears to be a secondary phenomenon in GSD-I patients.