High corn oil dietary intake improves health and longevity of aging mice

All You Can Feed: Some Comments on Production of Mouse Diets Used in Biomedical Research with Special Emphasis on Non-Alcoholic Fatty Liver Disease Research

The laboratory mouse is the most common used mammalian research model in biomedical research. Usually these animals are maintained in germ-free, gnotobiotic, or specific-pathogen-free facilities. In these facilities, skilled staff takes care of the animals and scientists usually don’t pay much attention about the formulation and quality of diets the animals receive during normal breeding and keeping. However, mice have specific nutritional requirements that must be met to guarantee their potential to grow, reproduce and to respond to pathogens or diverse environmental stress situations evoked by handling and experimental interventions. Nowadays, mouse diets for research purposes are commercially manufactured in an industrial process, in which the safety of food products is addressed through the analysis and control of all biological and chemical materials used for the different diet formulations. Similar to human food, mouse diets must be prepared under good sanitary conditions and truthfully labeled to provide information of all ingredients. This is mandatory to guarantee reproducibility of animal studies. In this review, we summarize some information on mice research diets and general aspects of mouse nutrition including nutrient requirements of mice, leading manufacturers of diets, origin of nutrient compounds, and processing of feedstuffs for mice including dietary coloring, autoclaving and irradiation. Furthermore, we provide some critical views on the potential pitfalls that might result from faulty comparisons of grain-based diets with purified diets in the research data production resulting from confounding nutritional factors.

The Influence of Different Fat Sources on Steatohepatitis and Fibrosis Development in the Western Diet Mouse Model of Non-alcoholic Steatohepatitis (NASH)

Non-alcoholic steatohepatitis (NASH) is the leading cause of chronic liver injury and the third most common reason for liver transplantations in Western countries. It is unclear so far how different fat sources in Western diets (WD) influence the development of NASH. Our study investigates the impact of non-trans fat (NTF) and corn oil (Corn) as fat source in a WD mouse model of steatohepatitis on disease development and progression. C57BL/6J wildtype (WT) mice were fed “standard” WD (WD-Std), WD-NTF or WD-Corn for 24 weeks. WT animals treated with WD-NTF exhibit distinct features of the metabolic syndrome compared to WD-Std and WD-Corn. This becomes evident by a worsened insulin resistance and elevated serum ALT, cholesterol and triglyceride (TG) levels compared to WD-Corn. Animals fed WD-Corn on the contrary tend to a weakened disease progression in the described parameters. After 24 weeks feeding with WD-NTF and WD-Std, WD-Corn lead to a comparable steatohepatitis initiation by histomorphological changes and immune cell infiltration compared to WD-Std. Immune cell infiltration results in a significant increase in mRNA expression of the pro-inflammatory cytokines IL-6 and TNF-α, which is more pronounced in WD-NTF compared to WD-Std and WD-Corn. Interestingly the fat source has no impact on the composition of accumulating fat within liver tissue as determined by matrix-assisted laser desorption/ionization mass spectrometry imaging of multiple lipid classes. The described effects of different fat sources on the development of steatohepatitis finally resulted in variations in fibrosis development. Animals treated with WD-NTF displayed massive collagen accumulation, whereas WD-Corn even seems to protect from extracellular matrix deposition. Noteworthy, WD-Corn provokes massive histomorphological modifications in epididymal white adipose tissue (eWAT) and severe accumulation of extracellular matrix which are not apparent in WD-Std and WD-NTF treatment. Different fat sources in WD-Std contribute to strong steatohepatitis development in WT mice after 24 weeks treatment. Surprisingly, corn oil provokes histomorphological changes in eWAT tissue. Accordingly, both WD-NTF and WD-Corn appear suitable as alternative dietary treatment to replace “standard” WD-Std as a diet mouse model of steatohepatitis whereas WD-Corn leads to strong changes in eWAT morphology.

High-Cholesterol Diet Disrupts the Levels of Hormones Derived from Anterior Pituitary Basophilic Cells

Emerging evidence shows that elevated cholesterol levels are detrimental to health. However, it is unclear whether there is an association between cholesterol and the pituitary. We investigated the effects of a high-cholesterol diet on pituitary hormones using in vivo animal studies and an epidemiological study. In the animal experiments, rats were fed a high-cholesterol or control diet for 28 weeks. In rats fed the high-cholesterol diet, serum levels of thyroid-stimulating hormone (TSH; also known as thyrotrophin), luteinising hormone (LH) and follicle-stimulating hormone (FSH) produced by the basophilic cells of the anterior pituitary were elevated in a time-dependent manner. Among these hormones, TSH was the first to undergo a significant change, whereas adrenocorticotrophic hormone (ACTH), another hormone produced by basophilic cells, was not changed significantly. As the duration of cholesterol feeding increased, cholesterol deposition increased gradually in the pituitary. Histologically, basophilic cells, and especially thyrotrophs and gonadotrophs, showed an obvious increase in cell area, as well as a potential increase in their proportion of total pituitary cells. Expression of the β-subunit of TSH, FSH and LH, which controls hormone specificity and activity, exhibited a corresponding increase. In the epidemiological study, we found a similar elevation of serum TSH, LH and FSH and a decrease in ACTH in patients with hypercholesterolaemia. Significant positive correlations existed between serum total cholesterol and TSH, FSH or LH, even after adjusting for confounding factors. Taken together, the results of the present study suggest that the high-cholesterol diet affected the levels of hormones derived from anterior pituitary basophilic cells. This phenomenon might contribute to the pituitary functional disturbances described in hypercholesterolaemia.

The expression characteristics of mt-ND2 gene in chicken

Subunit 2 of NADH dehydrogenase (ND2) is encoded by the mt-ND2 gene and plays a critical role in controlling the production of the mitochondrial reactive oxygen species. Our study focused on exploring the mt-ND2 tissue expression patterns and the effects of energy restriction and dietary fat (linseed oil, corn oil, sesame oil or lard) level (2.5% and 5%) on its expression in chicken. The results showed that mt-ND2 gene was expressed in the 15 tissues of hybrid chickens with the highest level in heart and lowest level in pancreas tissue; 30% energy restriction did not significantly affect mt-ND2 mRNA level in chicken liver tissue. Both the mt-ND2 mRNA levels in chicken pectoralis (p < 0.05) and hepatic tissues (p < 0.05) at 42 d-old were affected by the type of dietary fats in 5% level, while not in abdominal fat tissues. The expression of mt-ND2 in hepatic tissues was down-regulated with chicken age (p < 0.01). The interactive effect of dietary fat types with chicken age (p < 0.05) was significant on mt-ND2 mRNA level. The study demonstrated that mt-ND2 gene was extensively expressed in tissues, and the expression was affected by dietary fat types and chicken age.

Questioning the preclinical paradigm: natural, extreme biology as an alternative discovery platform

The pace at which science continues to advance is astonishing. From cosmology, microprocessors, structural engineering, and DNA sequencing our lives are continually affected by science-based technology. However, progress in treating human ailments, especially age-related conditions such as cancer and Alzheimer's disease, moves at a relative snail's pace. Given that the amount of investment is not disproportionately low, one has to question why our hopes for the development of efficacious drugs for such grievous illnesses have been frustratingly unrealized. Here we discuss one aspect of drug development –rodent models – and propose an alternative approach to discovery research rooted in evolutionary experimentation. Our goal is to accelerate the conversation around how we can move towards more translative preclinical work.