How isoflavone levels in common rodent diets can interfere with the value of animal models and with experimental results

Abstract

SummaryPhytoestrogens are a diverse group of plant-derived compounds structurally or functionally mimicking mammalian oestrogens. A variety of effects, in vitro, in animal models and in humans, have been attributed to these compounds. It is generally not appreciated that many commercial rodent diets are formulated with soy as a source of protein and thus large daily doses of phytoestrogens in the form of isoflavones are delivered to the animals. The content of isoflavones in laboratory diets depends on a number of factors and, therefore, varies considerably, both between different formulations, and also from batch to batch of the same formulation. Dietary isoflavones can influence a number of different endpoints, rendering the dietary levels of such compounds an important experimental factor to consider. The levels of isoflavones in common laboratory diets are reviewed in relation to the dietary levels influencing different endpoints.

Dietary Elimination of Soybean Components Enhances Allergic Immune Response to Peanuts in BALB/c Mice

“…This dietary manipulation can be a useful tool to study food allergy in mouse strains that are amenable for genetic manipulations. Batch-to-batch variations in isoflavone content in rodent diets [2,3,7] may contribute to fluctuations in the experimental data, especially those involving the immune system. Therefore, it is important to check and control the isoflavone content in rodent diet formulations when designing animal experiments to obtain reliable and reproducible experimental data.…”

“…In addition, soybeans are an abundant source of immune-modulatory and phytoestrogenic compounds called isoflavones. Several reports show the impact of dietary isoflavones on various aspects of animal research [1,2,3,4,5]. Circulating isoflavone levels are an important factor in research involving animal models.…”

“…While phytoestrogenic effects of isoflavones on animal physiology are well recognized, the specific influence of dietary isoflavones on the immune response is still not clear [6]. Significant batch-to-batch variations of isoflavone content in rodent chow are well documented [2,3,7]. These variations could influence the outcome of the research and also potentially affect reproducibility of experimental results.…”

Usefulness of immature golden hamster (Mesocricetus auratus) as a model for uterotrophic assay

“…With regards to diet, many laboratory animal feeds exhibit oestrogenic activity (6,15,31). It was found that soy isoflavones present in feed at high amounts interfere with the value of animal models and with experimental results (10). An example of this was a decreased sensitivity of immature rats (5) and hamsters (20) in the uterotrophic bioassay.…”

Influence of dietary soy isoflavones on immature hamster uterotrophic and Hershberger assays

“…These assays are also applicable for testing dietary compounds either as single ingredients, mixtures, or as a part of diet. However, the assays are often confounded by the presence of bioactive compounds in the diet (13).…”