Late Dietary Intervention Limits Benefits of Soy Protein or Flax Oil in Experimental Polycystic Kidney Disease

Abstract

Background/Aims: Dietary soy protein and flax oil retard kidney disease progression when initiated in the early stages of disease in several experimental models, including the Han:SPRD-cy rat. However, individuals with kidney disease often do not become aware of their condition until injury to the kidney is extensive. The objective of this study was to determine whether initiating these interventions in established disease would alter further progression of renal injury. Methods: Two-month-old adult male Han:SPRD-cy rats were given either a flax oil diet (7% flax oil), a soy protein diet (20% soy protein) or a control diet (7% corn oil, 20% casein) for 4 months. Renal disease progression was assessed by examining morphological, immunohistochemical and biochemical parameters. Results: Compared to controls, there was 21–24% less staining of proliferating cells, 21–24% less oxidative damage and 13–15% less renal inflammation in kidneys from rats given dietary soy protein and flax oil. Renal cystic growth and fibrosis and serum creatinine levels were not altered by these dietary treatments. Conclusions: Late intervention with dietary soy protein and flax oil reduces some disease-associated pathologies in established renal disease in Han:SPRD-cy rats. The potential benefits of the antioxidant and anti-inflammatory effects on ultimate renal disease outcome in the long term remains to be determined.

Effects of Dietary Conjugated Linoleic Acid in Advanced Experimental Polycystic Kidney Disease

“…We also have examined the effects of dietary soy protein and flax oil on advanced PKD [6]. Similar to the study herein, there was improvement in renal inflammation, cell proliferation, and oxidative damage in adult Han:SPRD- cy rats after 16 weeks on diet, but no improvement in renal function with either of these dietary interventions.…”

“…This model has been used to investigate the effects of a number of dietary interventions on the progression of PKD including soy protein in both early [3,4,5] and late stages of disease [6], flax [6,7,8,9], creatine supplementation [10], protein restriction [11], dietary fat level and type [12, 13] and citrate supplementation [14]. …”

Efficacy of flax oil in preventing postoperative peritoneal adhesions

“…Fibrin bands and the hyaluronic acid-rich matrix that fills the cavity between these bands provide a suitable environment for collagen synthesis. Real adhesions occur following the synthesis of collagen [1,2,[8][9][10].…”

“…Various models have been developed for generating experimental PPA, including abrasion, local excision of the peritoneum, ischemic injury, placement of a foreign body in the peritoneal cavity (e.g., talcum powder), thermal injury, and bacterial contamination [20][21][22][23][24][25][26]. We have utilized an abrasion model, due to its ability to mimic mechanical trauma, which can occur after laparotomy.…”

“…Oxidative stability of flax oil is measured at 110 C at the rate of 20 L=h airflow rate [5]. Because of rich omega 3 (n À 3) fatty acids flax oil has antiproliferative, anti-inflammatory, anti-edema, and antioxidant effects [6][7][8].…”