Differential Effect of Non-Purified and Semi-Purified Standard Diets on Kynurenine and Peripheral Metabolites in Male C57BL/6J Mice

Abstract

The kynurenine (Kyn) pathway plays crucial roles in several inflammation-induced disorders such as depression. In this study, we measured Kyn and other related molecules in the blood plasma, brain, and urine of male C57BL/6J mice (B6) fed non-purified (MF) and semi-purified (AIN-93G and AIN-93M) standard rodent diets. Mice fed MF had increased plasma Kyn levels compared with those on AIN93-based diets, as well as decreased hippocampal Kyn levels compared with those fed AIN-93G. Previous studies showed that branched chain amino acids (BCAAs) suppress peripheral blood Kyn transportation to the brain, but plasma BCAA levels were not significantly different between the diet groups in our study. Urine metabolome analysis revealed that feed ingredients affected the excretion of many metabolites, and MF-fed mice had elevated excretion of kynurenic and quinolinic acids, pivotal metabolites in the Kyn pathway. Collectively, the level of critical metabolites in the Kyn pathway in the central and peripheral tissues was strongly affected by feed ingredients. Therefore, feed selection is a critical factor to ensure the reproducibility of experimental data in studies involving rodent models.

Comparison of the Nutritional Status of Swiss Albino Mice Fed on Either a Purified or Cereal-Based Diet for 15 weeks

“…The rise of nutrition-related diseases such as diabetes mellitus, obesity, hypertension, and their comorbidities has created the need for animal research on treatment interventions and disease mechanisms. Mice are widely used as animal models in biomedical research, and manipulation of diet is the most effective way of regulating their health status, growth rate, reproduction, and survival rates [ 12 , 15 ]. We found that animals fed on either CBD or AIN-93M had similar weight.…”

“…On the other hand, purified animal diets are composed of refined ingredients which serve as a source of a single nutrient, for example, isolated proteins such as casein, corn starch, sucrose, maltodextrin, soybean oil, purified vitamins, and minerals [ 11 , 12 ]. Purified diets are well defined and have open formulas that have minimal variability from batch to batch [ 2 , 9 ].…”

“…They have been shown to improve reproducibility of animal studies [ 13 ]. Since they allow modification of individual nutrients, they can be used to create pathological status such as deficiencies or excesses as well as study nutrient-toxin relationships [ 2 , 12 ]. Nevertheless, they have the disadvantages of being low in soluble fibre, reduced palatability, and increased costs of production [ 9 , 13 , 14 ].…”