In recent decades, the role of hydrogen sulfide (H2S), a gas mediator and signaling agent, has been studied in the regulation of intercellular signaling and intracellular signal transduction pathways with various physiological and pathophysiological effects in cells and tissues. These cellular pathways are responsible for changes in metabolism, epigenetic, and cellular behavior. There are enzymatic and non-enzymatic pathways of endogenous hydrogen sulfide biosynthesis. Numerous studies have shown the diverse effects of H2S on the physiological processes of neurotransmission in the brain, vascular smooth muscle relaxation in synergy with nitric oxide (NO), apoptosis, autophagy, angiogenesis, aging, inflammation, redox system, manifestations of oxidative stress, protein, as well as bioenergetic effects and systemic bioregulatory effects, including ANS. Recently, it was shown that H2S signaling is often dysregulated in different dysfunctions. The effect of H2S on insulin secretion and protection of the heart, kidneys, and brain from ischemic damage, and hypoxia is known. The availability of H2S as a bioregulator has led to changes in cytoprotection, scavenger’s function, and antiinflammatory activities in the digestive system, as well as it could be a molecular target for the creating new safe hybrid compounds, esp., H2S-realized nonsteroidal anti-inflammatory drugs. Our recent research has shown a cytoprotective effect on the mucous membrane of the esophagus and stomach. Thiosulfate sulfurtransferase (TST, EC 2.8.1.1)-derived H2S plays an important role in maintaining redox balance but its effects on mesenteric integrity in aspects of age-related changes and during stress response or high-carbohydrate diet are still limited.

Metabolic physiology plays a key role in maintaining our health and resilience. Metabolic disorders can lead to serious illnesses, including obesity. The pathogenesis of the new long COVID syndrome in individuals with long-term recovery after SARS-Co-2 infection is still incomplete. Thus there is growing attention in the study of adipose tissue activities, especially brown adipose tissue (BAT) and associated resilience which plays a crucial role in diferent types of obesity as potential targets for pharmacologic and nutritional interventions in the context of obesity and long COVID. The number of studies examining mechanisms underlying BAT has grown rapidly in the last 10 years despite of role of BAT in individuals with COVID-19 and long COVID is modest. Therefore, this review aims to sum up data examining BAT activities, its resilience in health, obesity, and the possible link to long COVID. The search was conducted on studies published in English mostly between 2004 and 2022 in adult humans and animal models. Database searches were conducted using PubMed, Scopus, and Google Scholar for key terms including adipose tissue, BAT, adipokines, obesity, VPF/VEGF, and pathogenesis. From the initial search through the database were identifed relevant articles that met inclusion and exclusion criteria and our data regarding adipose tissues were presented in this review. It will discuss adiposity tissue activities. Current literature suggests that there are BAT integral efects to whitening and browning fat phenomena which refect the homeostatic metabolic adaptive ability for environmental demand or survival/adaptive mechanisms. We also review neural and vascular impacts in BAT that play a role in resilience and obesity. Finally, we discuss the role of BAT in the context of long COVID in basic research and clinical research.