Abstract 466: Stigmasterol Accumulation in ABCG8 Knockout Mice Does Not Account for Xenosterol Toxicity
Xenosterol accumulation mice deficient in sterolin function leads to significant toxicity, with infertility, decreased body fat accumulation, macrothrombocytopenia, cardiac fibrosis and premature death1, 2. The predominant xenosterols are phytosterols derived from the diet and are a mixture of sitosterol (typically 70%), campesterol (~20%) and stigmasterol (~5-10%). Although sitosterol has been shown to have some biological effect in tissue culture, only stigmasterol has been shown to have a potent biological effect, by activating the transcriptional factor, Lxr3. To delineate whether all of the toxic biological effects were mediated by stigmasterol accumulation, we designed a diet that was supplemented with highly enriched stigmasterol (>80% purity) and fed this to Abcg8 knockout mice. Stigmasterol accumulation in the plasma and tissues was comparable to the levels observed in mice fed a mixed phytosterol-enriched diet that had been shown to result in toxicity.
Over a 12-week period, both male and female Abcg8 knockout mice gained normal amounts of weight, body fat, showed no disturbances in tail-cuff measured blood pressure, and plasma analyses showed no abnormalities of platelet counts or volumes, blood glucose, plasma cholesterol, despite accumulation of stigmasterol in the plasma and tissues. Fertility testing showed no abnormalities. Gene expression analyses of livers did not show any consistent patterns, although Lxr target genes were not up-regulated.
These data do not support the concept that stigmasterol accumulation, at levels of 5-10mg/dL in plasma, account for the xenosterol-mediated toxicity observed.
1. McDaniel, A.L., H.M. Alger, J.K. Sawyer, K.L. Kelley, N.D. Kock, J.M. Brown, R.E. Temel, and L.L. Rudel, Phytosterol feeding causes toxicity in ABCG5/G8 knockout mice. Am J Pathol, 2013. 182(4): p. 1131-8.
2. Solca, C., G.S. Tint, and S.B. Patel, Dietary xenosterols lead to infertility and loss of abdominal adipose tissue in sterolin-deficient mice. J Lipid Res, 2013. 54(2): p. 397-409.
3. Yang, C., L. Yu, W. Li, F. Xu, J.C. Cohen, and H.H. Hobbs, Disruption of cholesterol homeostasis by plant sterols. J. Clin. Invest., 2004. 114(6): p. 813-22.
Author Disclosures: S.B. Patel: None.
- © 2014 by American Heart Association, Inc.