Different effects of γ-linolenic acid (GLA) supplementation on plasma and red blood cell phospholipid fatty acid composition and calcium oxalate kidney stone risk factors in healthy subjects from two race groups with different risk profiles pose questions about the GLA-arachidonic acid-oxaluria metabolic pathway: pilot study
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Fatty acid (FA) composition of phospholipids in plasma and red blood cells (RBC) can influence calciuria, oxaluria and renal stone formation. In this regard, the ratio of arachidonic acid (AA) and its precursor linoleic acid (LA) appears to be important. Administration of γ-linolenic acid (GLA) has been shown to increase the concentration of dihomo-gamma linoleic acid (DGLA) relative to AA indicating that it may attenuate biosynthesis of the latter. Such effects have not been investigated in race groups having difference stone occurrence rates. Black (B) and white (W) healthy males ingested capsules containing linoleic acid (LA) and GLA, for 30 days. Plasma and RBC total phospholipid (TPL) FA profiles, serum and 24 h urine biomarkers of hypercalciuria and urinary stone risk factors were determined on days 0 and 30. Data were tested for statistical significance using GraphPadInstat version 3.02. Concentration and percentage content of DGLA in plasma TPL increased in W but not in B. Arachidonic acid (AA) did not change in either group. There was no change in calcium excretion in either group but oxalate and citrate excretion increased in W. We suggest that elongation of GLA to DGLA may occur more rapidly than desaturation of DGLA to AA in W and that depressed activity of the enzyme elongase may occur in B. Calciuric and citraturic effects may be dependent on the quantity of LA or on the mass ratio of LA/GLA in the FA supplement. Questions about the mooted DGLA–AA–oxaluria pathway arise. We speculate that there exists a potential for using GLA as a conservative treatment for hypocitraturia. The observation of different responses in B and W indicates that such differences may play a role in stone formation and prevention.
KeywordsPhospholipid fatty acid composition n-6 Fatty acid supplementation Kidney stone risk factors Different race groups
The financial support of the South African Medical Research Council, the South African National Research Foundation and the University of Cape Town is gratefully acknowledged. The authors would like to extend their appreciation to Johanna van Wyk of the NCDRU of the SAMRC for her invaluable laboratory assistance analyzing plasma and RBC total phospholipid fatty acids.
Compliance with ethical standards
Conflict of interest
The authors declare that there are no conflicts of interest.
The study was approved by the Human Research Ethics Committee of the University of Cape Town (HRE REF: 366/2011) and was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
All participants gave their informed consent before their inclusion in the study.
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