Rodent models and metabolomics in non-alcoholic fatty liver disease: What can we learn?

Non-alcoholic fatty liver disease(NAFLD)prevalence has increased drastically in recent decades,affecting up to 25%of the world’s population.NAFLD is a spectrum of different diseases that starts with asymptomatic steatosis and continues with development of an inflammatory response called steatohepatitis,which can progress to fibrosis.Several molecular and metabolic changes are required for the hepatocyte to finally vary its function;hence a“multiple hit”hypothesis seems a more accurate proposal.Previous studies and current knowledge suggest that in most cases,NAFLD initiates and progresses through most of nine hallmarks of the disease,although the triggers and mechanisms for these can vary widely.The use of animal models remains crucial for understanding the disease and for developing tools based on biological knowledge.Among certain requirements to be met,a good model must imitate certain aspects of the human NAFLD disorder,be reliable and reproducible,have low mortality,and be compatible with a simple and feasible method.Metabolism studies in these models provides a direct reflection of the workings of the cell and may be a useful approach to better understand the initiation and progression of the disease.Metabolomics seems a valid tool for studying metabolic pathways and crosstalk between organs affected in animal models of NAFLD and for the discovery and validation of relevant biomarkers with biological understanding.In this review,we provide a brief introduction to NAFLD hallmarks,the five groups of animal models available for studying NAFLD and the potential role of metabolomics in the study of experimental NAFLD.

Effects of normobaric cyclic hypoxia exposure on mesenchymal stem-cell differentiation–pilot study on bone parameters in elderly

BACKGROUND Mesenchymal stem cells(MSC)of bone marrow are the progenitor of osteoblasts and adipocytes.MSC tend to differentiate into adipocytes,instead of osteoblasts,with aging.This favors the loss of bone mass and development of osteoporosis.Hypoxia induces hypoxia inducible factor 1αgene encoding transcription factor,which regulates the expression of genes related to energy metabolism and angiogenesis.That allows a better adaptation to low O2 conditions.Sustained hypoxia has negative effects on bone metabolism,favoring bone resorption.Yet,surprisingly,cyclic hypoxia(CH),short times of hypoxia followed by long times in normoxia,can modulate MSC differentiation and improve bone health in aging.AIM To evaluate the CH effect on MSC differentiation,and whether it improves bone mineral density in elderly.METHODS MSC cultures were induced to differentiate into osteoblasts or adipocytes,in CH(3%O2 for 1,2 or 4 h,4 d a week).Extracellular-matrix mineralization and lipid-droplet formation were studied in MSC induced to differentiate into osteoblast or adipocytes,respectively.In addition,gene expression of marker genes,for osteogenesis or adipogenesis,have been quantified by quantitative real time polymerase chain reaction.The in vivo studies with elderly(>75 years old;n=10)were carried out in a hypoxia chamber,simulating an altitude of 2500 m above sea level,or in normoxia,for 18 wk(36 CH sessions of 16 min each).Percentages of fat mass and bone mineral density from whole body,trunk and right proximal femur(femoral,femoral neck and trochanter)were assessed,using dual-energy X-ray absorptiometry.RESULTS CH(4 h of hypoxic exposure)inhibited extracellular matrix mineralization and lipid-droplet formation in MSC induced to differentiate into osteoblasts or adipocytes,respectively.However,both parameters were not significantly affected by the other shorter hypoxia times assessed.The longest periods of hypoxia downregulated the expression of genes related to extracellular matrix formation,in MSC induced to differentiate into osteoblasts.Interestingly,osteocalcin(associated to energy metabolism)was upregulated.Vascular endothelial growth factor an expression and low-density lipoprotein receptor related protein 5/6/dickkopf Wnt signaling pathway inhibitor 1(associated to Wnt/β-catenin pathway activation)increased in osteoblasts.Yet,they decreased in adipocytes after CH treatments,mainly with the longest hypoxia times.However,the same CH treatments increased the osteoprotegerin/receptor activator for nuclear factor kappa B ligand ratio in both cell types.An increase in total bone mineral density was observed in elderly people exposed to CH,but not in specific regions.The percentage of fat did not vary between groups.CONCLUSION CH may have positive effects on bone health in the elderly,due to its possible inhibitory effect on bone resorption,by increasing the osteoprotegerin/receptor activator for nuclear factor kappa B ligand ratio.

Influence of olive oil and its components on mesenchymal stem cell biology

Extra virgin olive oil is characterized by its high content of unsaturated fatty acid residues in triglycerides,mainly oleic acid,and the presence of bioactive and antioxidant compounds.Its consumption is associated with lower risk of suffering chronic diseases and unwanted processes linked to aging,due to the antioxidant capacity and capability of its components to modulate cellular signaling pathways.Consumption of olive oil can alter the physiology of mesenchymal stem cells(MSCs).This may explain part of the healthy effects of olive oil consumption,such as prevention of unwanted aging processes.To date,there are no specific studies on the action of olive oil on MSCs,but effects of many components of such food on cell viability and differentiation have been evaluated.The objective of this article is to review existing literature on how different compounds of extra virgin olive oil,including residues of fatty acids,vitamins,squalene,triterpenes,pigments and phenols,affect MSC maintenance and differentiation,in order to provide a better understanding of the healthy effects of this food.Interestingly,most studies have shown a positive effect of these compounds on MSCs.The collective findings support the hypothesis that at least part of the beneficial effects of extra virgin olive oil consumption on health may be mediated by its effects on MSCs.