Effects of Pelleting, Irradiation, and Autoclaving of Rodent Feed on MPV and MNV Infectivity

Effects of starch-rich or fat-rich diets on metabolism, adiposity, and glycemia in immune-biased, C57BL/6 and BALB/c mice

Diet is an essential factor to maintain health by regulating host metabolism and immunity. Host immunity acts as a critical regulator of metabolic changes. By using differentially immune-biased mice C57BL/6 and BALB/c, we demonstrated the metabolic consequence of consuming diets rich in non-resistant starch (starch-rich), unsaturated fat (sunflower oil-rich), and saturated fat (coconut oil-rich) for shorter (four weeks) or longer (eight weeks) duration. Time kinetics of various diets on two differentially immune-biased mice revealed that starch-rich and unsaturated fat-rich diets reduced insulin resistance (IR) and visceral adiposity in BALB/c mice. In contrast, a saturated fat-rich diet enhanced both parameters. In C57BL/6 mice, a fat-rich diet enhanced IR with time while visceral adiposity remained unchanged. Eight weeks' consumption of a saturated fat-rich diet led to the highest visceral adiposity in C57BL/6 mice, while the same diet resulted in the maximum IR in BALB/c mice. The current report presented a detailed metabolomic analysis of treatments with various diets using a) uni- and b) multi-variate analyses. We also calculated the differential index for each treatment for each mouse strain using a vector analysis of the multivariate linear discriminant data. The outcome of the vector analysis of metabolite profiles identified metabolites that affected lipid and glucose metabolism to establish the inter-strain physiological differences.

Assessing Elimination of Mouse Kidney Parvovirus from Cages by Mechanical Washing

Mouse kidney parvovirus (MKPV), a newly identified parvovirus of the genus Chaphamaparvovirus, causes inclusion body nephropathy in severely immunocompromised mice and is prevalent in research mouse colonies. As nonenveloped viruses, mammalian parvoviruses are stable and generally resist thermal inactivation; however, as a novel and highly divergent parvovirus, the thermal stability of MKPV is undefined. This study aimed to evaluate the ability of cage sanitization in a mechanical washer to eliminate MKPV. Cages contaminated by MKPV-infected mice were assigned to 1 of 3 treatment groups: 1) control (bedding change only); 2) sanitization in a tunnel washer (88°C final rinse for 20 s); or 3) sanitization in a tunnel washer followed by autoclave sterilization (121 °C for 20 min). The presence of MKPV on the cage's interior surface was assessed by PCR of cage swab extracts collected before and after cage treatment. After treatment and swabbing, each cage housed 4 MKPV-negative CD1 mice. Each group of naive CD1 mice was assigned to one of the treatment groups and was housed in a cage from this group for two, 1 wk periods. At 12, 17, and 20 wk after the first exposure, renal tissue was collected from 1 test mouse per cage and assessed for MKPV by PCR. MKPV was detected by PCR on the surface of 63% of the pretreatment cages. All cages sanitized in a tunnel washer with or without sterilization were PCR negative after treatment. Seven of 10 mice housed in untreated cages contained a mouse positive for MKPV by 20 wk after exposure. None of the mice housed in cages sanitized in a tunnel washer with or without sterilization tested positive for MKPV at any time point. This study indicates that MKPV contaminated caging can result in MKPV infection of mice, and the use of a tunnel washer at the temperature and duration evaluated was sufficient to remove MKPV nucleic acid and prevent MKPV transmission.

High-Coverage Metabolome Analysis Reveals Significant Diet Effects of Autoclaved and Irradiated Feed on Mouse Fecal and Urine Metabolomics

SCOPE

Using metabolomics to study the relations of nutrition and health requires stringent control of the experimental conditions used in an animal model. This work investigates the diet effects of autoclaved and irradiated feed on mouse urine and fecal metabolomics.

METHODS AND RESULTS

C57BL/6 mice are fed normal-irradiation sterilized diet (n = 9), autoclave sterilized diet (n = 9), and high-irradiation sterilized diet (n = 9) for 4 weeks. Differential chemical isotope labeling liquid chromatography mass spectrometry is used to quantify the metabolome variations of urine and feces collected at five time points. Significant differences are observed in urine or fecal metabolomes of mice fed autoclaved diet versus mice fed high-irradiation diet or fed normal-irradiation diet, while the differences are small between the mice fed normal-irradiation and high-irradiation diet. Correlation studies of metabolite changes of diet- and aging-related biomarkers indicate a large overlap of significantly affected metabolites by the two factors.

CONCLUSIONS

Diet can be a confounding factor that needs to be carefully considered when a metabolomics study is designed and metabolomic results of a mouse model of nutritional or other biological study are interpreted. Using the same sterilized diet for a given metabolomics project is essential to control the diet effect.

The Influence of Feed and Drinking Water on Terrestrial Animal Research and Study Replicability

For more than 50 years, the research community has made strides to better determine the nutrient requirements for many common laboratory animal species. This work has resulted in high-quality animal feeds that can optimize growth, maintenance, and reproduction in most species. We have a much better understanding of the role that individual nutrients play in physiological responses. Today, diet is often considered as an independent variable in experimental design, and specialized diet formulations for experimental purposes are widely used. In contrast, drinking water provided to laboratory animals has rarely been a consideration in experimental design except in studies of specific water-borne microbial or chemical contaminants. As we advance in the precision of scientific measurements, we are constantly discovering previously unrecognized sources of experimental variability. This is the nature of science. However, science is suffering from a lack of experimental reproducibility or replicability that undermines public trust. The issue of reproducibility/replicability is especially sensitive when laboratory animals are involved since we have the ethical responsibility to assure that laboratory animals are used wisely. One way to reduce problems with reproducibility/replicability is to have a strong understanding of potential sources of inherent variability in the system under study and to provide "…a clear, specific, and complete description of how the reported results were reached [1]." A primary intent of this review is to provide the reader with a high-level overview of some basic elements of laboratory animal nutrition, methods used in the manufacturing of feeds, sources of drinking water, and general methods of water purification. The goal is to provide background on contemporary issues regarding how diet and drinking water might serve as a source of extrinsic variability that can impact animal health, study design, and experimental outcomes and provide suggestions on how to mitigate these effects.