Investigation of Behavior and Plasma Levels of Corticosterone in Restrictive- and Ad Libitum-Fed Diet-Induced Obese Mice.

Diet-induced obesity (DIO) mice models are commonly used to investigate obesity-related health problems. Until now, only sparse data exist on the influence of DIO on behavior and stress hormones in mice. The present study investigates high-fat DIO with two different feeding regimes on behavioral parameters in mice. Various behavioral tests (open field, elevated plus maze, social interaction, hotplate) were performed with female BALB/c and male C57BL/6 mice after a feeding period of twelve weeks (restrictive vs. ad libitum and normal-fat diet vs. high-fat diet) to investigate levels of anxiety and aggression. BALB/c mice were DIO-resistant and therefore the prerequisite for the behavior analyses was not attained. C57BL/6 mice fed a high-fat diet had a significantly higher body weight and fat mass compared to C57BL/6 mice fed a control diet. Interestingly, the DIO C57BL/6 mice showed no changes in their aggression- or anxiety-related behavior but showed a significant change in the anxiety index. This was probably due to a lower activity level, as other ethological parameters did not show an altered anxiety-related behavior. In the ad libitum-fed DIO group, the highest corticosterone level was detected. Changes due to the feeding regime (restrictive vs. ad libitum) were not observed. These results provide a possible hint to a bias in the investigation of DIO-related health problems in laboratory animal experiments, which may be influenced by the lower activity level.

The Impact of High-Fat Diet and Restrictive Feeding on Natural Killer Cells in Obese-Resistant BALB/c Mice.

Background: The association of obesity and an increased risk for severe infections and various cancer types is well-described. Natural killer (NK) cells are circulating lymphoid cells and promoters of the immune response toward viruses and malignant cells. As demonstrated in previous studies the phenotype and functionality of NK cells is impaired in obesity. So far, the majority of animal studies were exclusively performed using ad libitum feeding regimes and it remained unclear whether NK cell alterations are mediated by obesity-associated immunological changes or by direct effects of the dietary composition. Therefore, the aim of the present study was to characterize NK cells in the peripheral blood of obese-resistant BALB/c mice supplied a normal-fat diet (NFD) or high-fat diet (HFD), ad libitum or in a restrictive manner. Methods: Twenty-eight BALB/c-mice were fed a NFD or HFD either ad libitum or in a restrictive feeding regime with 90% of the mean daily diet supply of the corresponding ad libitum group (each group n = 7). Blood and visceral adipose tissue were collected for flow cytometric analysis, analysis of plasma cytokine concentrations by multiplex immunoassay and real-time RT-PCR analyses. For statistical analyses two-way ANOVA with the factors "feeding regime" and "diet" was performed followed by a post-hoc Tukey's multiple comparison test and to compare means of the four mouse groups. Results: Ad libitum-feeding of a HFD in BALB/c mice has no influence on body weight gain, visceral fat mass, plasma cytokine concentrations, immune cell populations as well as the number, frequency and phenotype of NK cells. In contrast, restrictive feeding of a HFD compared to NFD led to significantly higher body weights, visceral fat mass and plasma interferon-γ concentrations which was associated with changes in the frequencies of granulocytes and NK cell subsets as well as in the surface expression of NK cell maturation markers. Conclusion: Results demonstrate for the first time that HFD-induced alterations in NK cells are consequences of the obese associated immunological profile rather than a direct effect of the dietary composition. These data can help to clarify the increased risk for cancer and severe infections in obesity.

High-Fat Diet and Feeding Regime Impairs Number, Phenotype, and Cytotoxicity of Natural Killer Cells in C57BL/6 Mice.

Overweight and obesity are major public health challenges worldwide. Obesity is associated with a higher risk for the development of several cancer types, but specific mechanisms underlying the link of obesity and cancer are still unclear. Natural killer (NK) cells are circulating lymphoid cells promoting the elimination of virus-infected and tumor cells. Previous investigations demonstrated conflicting results concerning the influence of obesity on functional NK cell parameters in small animal models. The aim of the present study was to clarify potential obesity-associated alterations of murine NK cells in vivo, implementing different feeding regimes. Therefore, C57BL/6 mice were fed a normal-fat diet (NFD) or high-fat diet (HFD) under restrictive and ad libitum feeding regimes. Results showed diet and feeding-regime dependent differences in body weight, visceral fat mass and plasma cytokine concentrations. Flow cytometry analyses demonstrated significant changes in total cell counts as well as frequencies of immune cell populations in peripheral blood comparing mice fed NFD or HFD in an ad libitum or restrictive manner. Mice fed the HFD showed significantly decreased frequencies of total NK cells and the mature CD11b+CD27+ NK cell subset compared to mice fed the NFD. Feeding HFD resulted in significant changes in the expression of the maturation markers KLRG1 and CD127 in NK cells. Furthermore, real-time PCR analyses of NK-cell related functional parameters in adipose tissue revealed significant diet and feeding-regime dependent differences. Most notable, real-time cytotoxicity assays demonstrated an impaired cytolytic activity of splenic NK cells toward murine colon cancer cells in HFD-fed mice compared to NFD-fed mice. In conclusion, our data demonstrate that feeding a high-fat diet influences the frequency, phenotype and function of NK cells in C57BL/6 mice. Interestingly, restricted feeding of HFD compared to ad libitum feeding resulted in a partial prevention of the obesity-associated alterations on immune cells and especially on NK cells, nicely fitting with the current concept of an advantage for interval fasting for improved health.

Dermatology in the Darwin anniversary. Part 1: Evolution of the integument.

The present review highlights the development of the integument and its adnexa from the primitive metazoans to man. The different stages of development represent independent, partially convergent evolutions rather than a continuous evolutionary line. The epidermis of the invertebrates (sponges, cnidaria, worms, echinoderms and arthropods) always consists of one layer of pluripotent cells. The barrier function of the integument at this level is achieved with physico-chemical barriers, toxin production, fortification of the epidermis in the form of a cuticula, a syncytium or a neodermis. The lower vertebrates (cyclostoma, fishes and amphibians) have a stratified epidermis harboring many secretory cells. In terrestrial amphibians the outermost cell layer of the epidermis is cornified, and the secretory cells are relocated in the dermis. Terminal differentiation and cornification of the epidermis in the birds and mammals result in a more uniform shape of the epithelium. Stem cells are now restricted to some basal regions of the epithelium. In the mammals the glands are located in the deeper layers of the skin. In contrast to other vertebrate integuments the human skin does not possess specialized structures such as feathers, scales or coats. However, waiving specialization allows for unique universality of the human skin compared to other vertebrates.

Dermatology in the Darwin anniversary. Part 2: Evolution of the skin-associated immune system.

The present review highlights the evolution of the skin-associated immune system from the invertebrates to the vertebrates and man. In the invertebrates a non-specific humoral immune response dominates. It includes antimicrobial peptides, oxidases, lysozyme, agglutinins, coagulins and melanin. The cellular immune system initially consists of undifferentiated mesenchymal stem cells. Later migrating phagocytes and natural killer cells occur. From the fishes on, dendritic cells are present, linking innate and adaptive immune responses. In addition to this unspecific but highly effective immune system, the specific immune response, based on genetic recombination, is present in the vertebrates starting with the chondral fishes. The adaptive immune system possesses unlimited numbers of highly specific antibodies and T-cell receptors, increasingly tissue specific MHC restriction, and cellular memory. Elements of the skin-associated adaptive immune system are first detectable in the teleost fishes in the form of intraepithelial IgM positive lymphocytes and dendritic cells. Moving up to mammals and man, the skin-associated immune system became more and more complex and effective.