Long-term effects of dietary high protein on renal health in the pig model

Abstract

The impact of habitually consuming a high protein (HP) diet at the upper limit of the acceptable macronutrient distribution range (AMDR) on kidney health is unknown. The current study was designed to test the hypothesis that long-term consumption of a diet providing 35% of energy as protein will have negative consequences on renal health, as assessed in a pig model. Methods: Adult female, non-pregnant, commercial pigs (Genesus) were randomized to receive either NP (15% energy from protein) or HP (35% energy from protein) isocaloric diets for either 4 or 8 months. Diets contained whole protein sources with an animal: plant ratio of 2:1 in the NP diet to mimic the average Canadian diet. The increased protein in the HP diet was achieved by increasing egg and dairy protein sources. Body composition was measured by dual-energy X-ray absorptiometry. Glomerular volume and kidney fibrosis were evaluated on kidney sections by quantitative image analysis. The inflammatory marker monocyte chemoattractant protein-1 (MCP-1) and the growth factor transforming growth factor beta-1(TGFβ1) were assessed in renal tissue using commercial ELISA kits. Results: Pigs given the HP diet had lower body weights and percentage of body fat. Pigs consuming the HP diet had significantly higher glomerular filtration rates (GFR) and larger kidneys. Renal MCP-1 levels and renal fibrosis also were significantly higher in pigs given the HP diet, while proteinuria and renal TGFβ1 expression did not differ. Conclusion: These findings suggest that, despite the potential benefit of the HP diet on body composition, long-term intakes of protein at the upper limit of the AMDR may compromise renal health in healthy female pigs.