Influence of nutrition on feline calcium oxalate urolithiasis with emphasis on endogenous oxalate synthesis

Abstract

The prevalence of calcium oxalate (CaOx) uroliths detected in cats with lower urinary tract disease has shown a sharp increase over the last decades with a concomitant reciprocal decrease in the occurrence of struvite (magnesium ammonium phosphate) uroliths. CaOx stone-preventative diets are available nowadays, but seem to be marginally effective, as CaOx urolith recurrence occurs in patients fed these diets. In order to improve the preventative measures against CaOx urolithiasis, it is important to understand its aetiopathogenesis. The main research focus in CaOx formation in cats has been on the role of Ca, whereas little research effort has been directed towards the role and origin of urinary oxalates. As in man, the exogenous origin of urinary oxalates in cats is thought to be of minor importance, although the precise contribution of dietary oxalates remains unclear. The generally accepted dietary risk factors for CaOx urolithiasis in cats are discussed and a model for the biosynthetic pathways of oxalate in feline liver is provided. Alanine:glyoxylate aminotransferase 1 (AGT1) in endogenous oxalate metabolism is a liver-specific enzyme targeted in the mitochondria in cats, and allows for efficient conversion of glyoxylate to glycine when fed a carnivorous diet. The low peroxisomal activity of AGT1 in cat liver is compatible with the view that felids utilised a low-carbohydrate diet throughout evolution. Future research should focus on understanding de novo biosynthesis of oxalate in cats and their adaptation(s) in oxalate metabolism, and on dietary oxalate intake and absorption by cats.

Urinary Calcium and Oxalate Excretion in Healthy Adult Cats Are Not Affected by Increasing Dietary Levels of Bone Meal in a Canned Diet

“…As the citrate concentrations in diets for cats are low, it can be hypothesized that the observed increase of urinary citrate in the group receiving the high Ca diet resulted from an increased citrate synthesis and excretion by the kidneys. Taking into consideration that a low urinary pH inhibits and a higher urinary pH stimulates the urinary citrate excretion [42], the small increase of the urinary pH observed with the high Ca diet could be an explanation for the higher urinary citrate concentrations in this group.…”

“…Citrate is a crystallisation inhibitor for Ca phosphate and CaOx uroliths [41]–[42] and can be provided with the diets or renally synthesised. As the citrate concentrations in diets for cats are low, it can be hypothesized that the observed increase of urinary citrate in the group receiving the high Ca diet resulted from an increased citrate synthesis and excretion by the kidneys.…”

Primary hyperoxaluria type III—a model for studying perturbations in glyoxylate metabolism

“…It is accepted that glyoxylate is distributed within the mitochondria, cytosol and peroxisomes [5][6][7]. Cytosolic glyoxylate can serve as a substrate of 3 reactions catalyzed by 2 cytosolic enzymes: 1.…”

Tratamento Da Urolitíase Em Cães E Gatos: Abordagens Não Cirúrgicas

“…A determinação falha da composição de cálculos urinários leva a formulação de terapias também equivocadas . As alterações dietéticas para tratamento das urolitíases em cães e gatos são na maioria derivadas de estudos epidemiológicos ou estudos clínicos em humanos ou roedores e poucos estudos foram efetivamente realizados nas espécies canina e felina (DIJCKER et al, 2011).…”