12 Chapter 1 Additionally, the intestine of malnourished children has been described to be severely impacted not only in function but also in structure49. Regarding the effects of malnutrition in the liver, hepatic steatosis, hypoalbuminemia and hypoglycemia are some of the common problems observed in malnourished children50,51. Hepatic steatosis in malnourished children has been linked to the observed impaired lipid metabolism.52,53 Moreover, the number of peroxisomes was found to be substantially decreased in the liver of malnourished children54. Current approaches for the study of malnutrition mostly rely on the use of animal models, including primates55, rats56 and more frequently, mice57,58 on low protein diets (LPD). These models, have shed some light onto the pathophysiology of malnutrition in the liver and the intestine and are able to recapitulate the specific phenotypes of the disease (e.g., hepatic steatosis, barrier dysfunction, etc.). Some of these studies also revealed dysfunctional mitochondria in the liver and the intestine of both mice and rats 56,58 while peroxisomal loss in the liver was recapitulated in the rat model56, but not yet studied in mice. While these models are physiologically relevant, and allow for a whole-body characterization of the disease, they are also limited by blood and tissue sampling and require large numbers of animals for large screenings. These limitations emphasize the need for relevant in vitro malnutrition models to study organ-specific phenotypes as well as intercellular communication. The role of peroxisomes and mitochondria in severe malnutrition An interesting feature of peroxisomes is their plasticity and their ability to respond to different stimuli and adapt to the cellular needs59. This behavior goes in line with the response observed in malnourished children fed low protein diets. Peroxisomes have been reported to substantially decrease in number in the liver of malnourished children and rodents on low protein diets (Figure 1)54,56–58. Moreover, mitochondria were also found to be impaired, characterized by defects in complexes I and IV in vivo, and reduced hepatic ATP levels. Dysfunction in both organelles might explain the accumulation of fatty acids in the liver of malnourished children leading to hepatic steatosis52. In the case of the intestine of mice fed an LPD, mitochondrial abundance was reduced with a clear reduction in protein expression of complexes I and V from the electron transport chain (ETC) (Figure 1). Moreover, levels of reactive oxygen species were found to be increased. These results, together with decreased autophagy, were causally linked to increased permeability observed
RkJQdWJsaXNoZXIy MTk4NDMw