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The rate of gut inflammatory diseases is growing in modern society. Previously, we showed that caloric restriction (CR) shapes gut microbiota composition and diminishes the expression of inflammatory factors along the gastrointestinal (GI) tract. The current project aimed to assess whether prominent dietary restrictive approaches, including intermittent fasting (IF), fasting-mimicking diet (FMD), and ketogenic diet (KD) have a similar effect as CR. We sought to verify which of the restrictive dietary approaches is the most potent and if the molecular pathways responsible for the impact of the diets overlap. We characterized the impact of the diets in the context of several dietary restriction-related parameters, including immune status in the GI tract; microbiota and its metabolites; bile acids (BAs); gut morphology; as well as autophagy-, mitochondria-, and energy restriction-related parameters. The effects of the various diets are very similar, particularly between CR, IF, and FMD. The occurrence of a 50 kDa truncated form of occludin, the composition of the microbiota, and BAs distinguished KD from the other diets. Based on the results, we were able to provide a comprehensive picture of the impact of restrictive diets on the gut, indicating that restrictive protocols aimed at improving gut health may be interchangeable.

Environmental cues influence microglial interaction with their neuronal landscape, often causing changes in microglial functional identity. This process demands rapid energy production, which is supported by an optimized mitochondrial network. Whether mitochondrial adaptations define a microglial functional state is unknown due to limitations in mitochondrial visualization and manipulation within their microenvironment. Here, we investigate the mitochondrial network of individual microglia in physiological and dysfunctional conditions during a naive or injury-induced mouse retinal environment. After optic nerve crush (ONC) injury, we identify mitochondrial and microglial phenotypic remodeling that is distinct from the naive environment. Remarkably, knockout of uncoupling protein 2 (UCP2) causes transient, stress-induced mitochondrial hyperfusion only in males after ONC, even though both sexes suffer from increased intrinsic stress levels. When we compare key metabolic genes between sexes in physiological conditions, only males exhibit a metabolic transition towards glycolysis in the injury-induced environment, which attenuates in UCP2 knockout resulting in acutely accelerated retinal ganglion cell death. Our data shows that the cell-extrinsic ONC environment and cell-intrinsic UCP2KO manipulation triggers several microglial states distinguishable by mitochondrial networks that are heavily influenced by sex and injury-induced stress.

Intestinal ischemia reperfusion injury (IRI) is a frequent complication of equine colic. Several mechanisms may be involved in adaptation of the intestinal epithelium to IRI and might infer therapeutic potential, including hypoxia-inducible factor (HIF) 1α, AMP-activated protein kinase (AMPK), nuclear factor-erythroid 2-related factor 2 (NRF2), and induction of autophagy. However, the mechanisms supporting adaptation and thus cellular survival are not completely understood yet. We investigated the activation of specific adaptation mechanisms in both no and low flow ischemia and reperfusion simulated in equine jejunum epithelium in vivo. We found an activation of HIF1α in no and low flow ischemia as indicated by increased levels of HIF1α target genes and phosphorylation of AMPKα tended to increase during ischemia. Furthermore, the protein expression of the autophagy marker LC3B in combination with decreased expression of nuclear-encoded mitochondrial genes indicates an increased rate of mitophagy in equine intestinal IRI, possibly preventing damage by mitochondria-derived reactive oxygen species (ROS). Interestingly, ROS levels were increased only shortly after the onset of low flow ischemia, which may be explained by an increased antioxidative defense, although NFR2 was not activated in this setup. In conclusion, we could demonstrate that a variety of adaptation mechanisms manipulating different aspects of cellular homeostasis are activated in IRI irrespective of the ischemia model, and that mitophagy might be an important factor for epithelial survival following small intestinal ischemia in horses that should be investigated further.