Findings from Studies Are Congruent with Obesity Having a Viral Origin, but What about Obesity-Related NAFLD?

Infection has recently started receiving greater attention as an unusual causative/inducing factor of obesity. Indeed, the biological plausibility of infectobesity includes direct roles of some viruses to reprogram host metabolism toward a more lipogenic and adipogenic status. Furthermore, the probability that humans may exchange microbiota components (virome/virobiota) points out that the altered response of IFN and other cytokines, which surfaces as a central mechanism for adipogenesis and obesity-associated immune suppression, is due to the fact that gut microbiota uphold intrinsic IFN signaling. Last but not least, the adaptation of both host immune and metabolic system under persistent viral infections play a central role in these phenomena. We hereby discuss the possible link between adenovirus and obesity-related nonalcoholic fatty liver disease (NAFLD). The mechanisms of adenovirus-36 (Ad-36) involvement in hepatic steatosis/NAFLD consist in reducing leptin gene expression and insulin sensitivity, augmenting glucose uptake, activating the lipogenic and pro-inflammatory pathways in adipose tissue, and increasing the level of macrophage chemoattractant protein-1, all of these ultimately leading to chronic inflammation and altered lipid metabolism. Moreover, by reducing leptin expression and secretion Ad-36 may have in turn an obesogenic effect through increased food intake or decreased energy expenditure via altered fat metabolism. Finally, Ad-36 is involved in upregulation of cAMP, phosphatidylinositol 3-kinase, and p38 signaling pathways, downregulation of Wnt10b expression, increased expression of CCAAT/enhancer binding protein-beta, and peroxisome proliferator-activated receptor gamma 2 with consequential lipid accumulation.

Exposomes and metabolic health through a physical activity lens: a narrative review

In this narrative review, we provide an overview of the role of physical activity as part of differing exposomes (our combined non-genetic exposures from conception onwards) and environmental influences on metabolic health. We discuss ‘beneficial’ exposomes (green/natural outdoor spaces, sun exposure, healthy diets and features of built environments) that could synergise with physical activity to prevent metabolic dysfunction, particularly that related to lifestyle diseases of obesity, type-2 diabetes and metabolic syndrome. Physical activity may also reduce the capacity of some adverse exposomes, specifically those with significant levels of air pollution, to contribute towards metabolic dysfunction. Other exposomes, such as those experienced during pandemics (including COVID-19), potentially limit opportunities for physical activity, and there may be unexpected combined effects of physical activity with other infections (e.g. adenovirus-36) on metabolic health. Finally, we discuss how environments could be better optimised to create exposomes that promote the health benefits of physical activity and likely future directions of this research field.