Improving Reproducibility to Enhance Scientific Rigor through Consideration of Mouse Diet

Abstract

Animal husbandry conditions, including rodent diet, constitute an example highlighting the importance of reporting experimental variables to enhance scientific rigor. In the present study, we examine the effects of three common rodent diets including two chows (Purina 5015 and Teklad 2019) and one purified ingredient diet (AIN-76A) on growth anthropometrics (body weight), behavior (nest building, actigraphy, passive avoidance) and blood biomarkers (ketones, glucose, amino acid profiles) in male and female C57BL/6J mice. We find increased body weight in response to the chows compared to purified ingredient diet albeit selectively in male mice. We did not find significantly altered behavior in female or male wild type C57BL/6J mice. However, amino acid profiles changed as an effect of sex and diet. These data contribute to a growing body of knowledge indicating that rodent diet impacts experimental outcomes and needs to be considered in study design and reporting.

Effects of Soy Protein Isolate on Fragile X Phenotypes in Mice

“…Rest-activity rhythms were assessed as previously described [ 15 , 48 , 56 ]. Briefly, individually housed mice were tested under standard lighting conditions in home-made Plexiglas chambers containing passive infrared sensors mounted on the underside of the lids.…”

“…Passive Avoidance: Learning and memory were assessed as previously described [ 11 , 48 , 56 ]. Specifically, mice were acclimated to the experimental room for at least 20 min prior to testing in a foot shock passive avoidance paradigm using an aversive stimulator/scrambler (Med Associates Inc., St. Albans, VT, USA).…”

“…Amino acids in blood plasma were quantified by ion-exchange chromatography on a Hitachi High-Technologies L-8900 Amino Acid Analyzer with a column (PF High SPE, 6.0 × 40 mm, Hitachi 855-4515, Tokyo, Japan) as previously described [ 57 ] with minor modifications [ 48 ]. Specifically, frozen plasma samples (50 μL each) were thawed and the samples mixed with 5 μL of 35% sulfosalicyclic acid (SSA) solution to achieve a 1:10 SSA to specimen ratio.…”

“…Prior rodent work in our laboratory indicates that soy/grain-based Purina 5015 chow increases susceptibility to audiogenic-induced seizures in mouse models of FXS ( Fmr1 KO ), Alzheimer’s disease (Tg2576) and Down syndrome (Ts65Dn) [ 25 ] and exacerbates weight gain in both wild type (WT) and Fmr1 KO mice [ 11 , 48 ] ( Table 1 ). Retrospective medical record and survey analyses indicate that parental-reported use of soy-based infant formula is associated with increased incidence of seizures, autistic behaviors, allergies and gastrointestinal (GI) problems [ 23 , 49 , 50 , 51 , 52 , 53 ].…”

Timing of standard chow exposure determines the variability of mouse phenotypic outcomes and gut microbiota profile

“…A hexokinase II knockdown study demonstrated significant effects of chow on mouse body weight, heart weight, and hexokinase phenotypes 9 . Another example comparing the effects of standard chow to a purified diet (AIN-76A) found that the chow diet drove differences in food intake and plasma essential amino acid levels in inbred C57BL/6 mice 10 . Lastly, differences in chow diets with variable fiber sources were found to induce differences in the distribution of gut bacterial communities in outbred CD-1 mice 11 .…”