What is the role of brown adipose tissue in metabolic health: lessons learned and future perspectives in the long COVID?

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 different 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, adipokinins, obesity, VPF/VEGF, and pathogenesis. From the initial search through the database were identified 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 effects to whitening and browning fat phenomenons which reflect 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.

Long COVID prevalence and physiology-centered risks: population-based study in Ukraine.

AIM: Multifaceted long COVID caused by SARS-COV-2 affects all populations in the World and takes priority over any other research topics for health care. The purpose of study is to identify physiology-centered risks, prevalence, symptoms and laboratory findings in patients with long COVID in Ukraine. METHODS: A prospective, cohort study was carried out on 332 patients with long COVID after 4 weeks and more after acute infection COVID-19 from Jul 1, 2021, to Jul 1, 2022. Physiology-centered risks related to age, gender, body mass index (BMI), marital status and educational capacity, smoking, lifestyle, physical activity, and laboratory findings (before disease), and symptom distribution were analyzed. RESULTS: The cohort for the study consisted of 166 females and 107 males (mean age = 42; including young 18 (5.4%) and middle- and old-aged adults 314 (96.4%)). Increased BMI was in 61%, and less physical activity-65%. There were 4 clusters of symptoms related to physical, neurocognitive, pulmonary, and pain conditions. 95% of participants had ≥ 3 symptoms. The most common symptoms were fatigue (90%), muscular pain (85%), anosmia (70%), hair loss (70%), sleep disorders (70%), dyspnea (30%), and brain fog (25%). Among laboratory finding increased CRP (92.6%) and fibrinogen (82.7%) dominated. There are no differences between hospitalized and non-hospitalized patients in distribution symptoms. CONCLUSIONS: The prevalence of long COVID is 23%, and its physiology-centered risk factors are related to age more 38 years, female sex, unhealthy lifestyle, increased BMI, and increased inflammatory markers during COVID-19. The most common symptoms are associated with neurocognitive and pain clusters.

What is really 'Long COVID'?

The previous acute respiratory diseases caused by viruses originating from China or the middle east (e.g., SARS, MERS) remained fast developing short diseases without major sequalae or any long-lasting complications. The new COVID-19, on the other hand, not only that it rapidly spread over the world, but some patients never fully recovered or even if they did, a few weeks later started to complain not only of shortness of breath, if any, but general weakness, muscle pains and 'brain fog', i.e., fuzzy memories. Thus, these signs and symptoms were eventually labelled 'long COVID', for which the most widely used definition is 'new signs and symptoms occurring 4-8 weeks after recovering from acute stage of COVID-19'. The other most frequent manifestations associated with long COVID include headache, loss of memory, smell and of hair, nausea, and vomiting. Thus, long COVID is not a simple disease, but complex disorder of several organ systems malfunctioning; hence, it is probably more appropriate to call this a syndrome. The pathogenesis of long COVID syndrome is poorly understood, but initial and persistent vascular endothelial injury that often triggers the formation of microthrombi that if dislodged as emboli, damage several organs, especially in the brain, heart and kidney, by creating microinfarcts. The other major contributory mechanistic factor is the persistent cytokine storm that may last longer in long COVID patients than in others, probably triggered by aggregates of SARS-Co-2 discovered recently in the adrenal cortex, kidney and brain. The prevalence of long COVID is relatively high, e.g., initially varied 3-30%, and recent data indicate that 2.5% of UK population suffers from this syndrome, while in the US 14.7% of acute COVID-19 patients continued to have symptoms longer than 2 months. Thus, the long COVID syndrome deserves to be further investigated, both from clinical and basic research perspectives.

What is the role of brown adipose tissue in metabolic health: lessons learned and future perspectives in the long COVID?

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 different 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 identified 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 effects to whitening and browning fat phenomena which reflect 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.

Hydrogen Sulfide Prevents Mesenteric Adipose Tissue Damage, Endothelial Dysfunction, and Redox Imbalance From High Fructose Diet-Induced Injury in Aged Rats.

A high fructose diet (HFD) and advanced age are key factors for the gradual loss of physiological integrity of adipose tissue. Endogenous hydrogen sulfide (H2S) has beneficial effects on cytoprotection and redox balance. But its interactive effects on age-related damage of mesenteric vessels and connective and adipose tissues (MA) during HFD which could be the base of the development of effective physiological-based therapeutic strategy are unknown. The aim of study was to investigate age- and HFD-induced mesenteric cellular changes and activities of enzymes in H2S synthesis and to test the effects of sodium hydrosulfide (NaHS) which is considered an H2S donor on them. Adult and aged male rats on a standard diet (SD) or 4-week HFD were exposed to acute water-immersion restraint stress (WIRS) for evaluation of mesenteric subcellular and cellular adaptive responses by electron microscopy. The effects of exogenous NaHS (5.6 mg/kg/day for 9 days) versus vehicle on mesentery changes were investigated. Serum glucose level, thiobarbituric acid reactive substances (TBARS), and activities of cystathionine γ-lyase (CSE) and cystathionine ß-synthase (CBS), thiosulfate-dithiol sulfurtransferase (TST), and sulfite oxidase (SO) were examined by spectrophotometry. In both adult and aged SD groups, treatment with NaHS protected mesenteric cells after WIRS. In both groups, the treatment with NaHS also protected MA mitochondria, microvascular endothelial and sub-endothelial structures, and fibroblasts versus the vehicle-treated group that had signs of damage. HFD increased MA injury and mitochondrial changes in both aged and adult rats. HFD-associated malfunction is characterized by low activities of CSE, CBS, TST, SO, and increased TBARS. Finally, we demonstrated that pretreatment with NaHS inhibited MA and mitochondria alterations in aged rats exposed to HFD and WIRS, lowered TBARS, and enhanced H2S enzyme activities in contrast to the vehicle-treated group. Mitochondrial integrity alterations, endothelial damage, and redox imbalance are key factors for rat mesenteric adipose tissue damage during advanced age. These alterations and MA hypertrophic changes retain the central for HFD-induced damage. Moreover, H2S signaling contributes to MA and mitochondria redox balance that is crucial for advanced age and HFD injury. The future study of H2S donors' effects on mesenteric cells is fundamental to define novel therapeutic strategies against metabolic changes.

H2S Donors Reverse Age-Related Gastric Malfunction Impaired Due to Fructose-Induced Injury via CBS, CSE, and TST Expression.

OBJECTIVE: Excess of fructose consumption is related to life-treating conditions that affected more than a third of the global population. Therefore, to identify a newer therapeutic strategy for the impact prevention of high fructose injury in age-related malfunctions of the gastric mucosa (GM) in the animal model is important. METHODS: Adult and aged male rats were divided into control groups (standard diet, SD) and high fructose diet (HFD) groups; acute water immersion restraint stress (WIRS) was induced for evaluation of GM adaptive response and effects of testing the therapeutic potential of H2S-releasing compounds (H2S donors). Histological examination of gastric damage was done on hematoxylin-eosin stained slides. Cystathionine beta-synthase (CBS), Cystathionine gamma-lyase (CSE), and Thiosulfate-dithiol sulfurtransferase (TST) activities and oxidative index were assessed during exogenous administration of H2S donors: sodium hydrosulfide (NaHS) and the novel hybrid H2S-releasing aspirin (ATB-340). The results showed that HFD increased gastric damage in adult and aged rats. HFD-associated malfunction characterized by low activities of H2S key enzymes, inducing increased oxidation. Pretreatment with NaHS, ATB-340 of aged rats in the models of HFD, and WIRS attenuated gastric damage in contrast to vehicle-treated group (p < 0.05). The effect of ATB-340 was characterized by reverse oxidative index and increased CBS, CSE, and TST activities. In conclusion, H2S donors prevent GM age-related malfunctions by enhancement of CBS, CSE, and TST expression against fructose excess injury though reduction of oxidative damage.

Exposure to non-steroid anti-inflammatory drugs (NSAIDs) and suppressing hydrogen sulfide synthesis leads to altered structure and impaired function of the oesophagus and oesophagogastric junction.

INTRODUCTION: The non-steroid anti-inflammatory drugs (NSAIDs) are among the drugs that can commonly cause injury in the esophagus, such as non-reflux oesophagitis, with important clinical consequences. This injury may be 'silent' and therefore often overlooked. Recently, we established that hydrogen sulfide (H2S) is a critical mediator of esophageal mucosal protection and repair. The aim of the study was to determine the effect of naproxen, the most commonly used NSAIDs, on the oesophagus and oesophagogastric junction and its relation with suppression or stimulation of endogenous H2S synthesis during naproxen-induced oesophageal injury. METHODS: Rats were treated with vehicle (control) or naproxen, with or without being subjected to water immersion restricted stress (Takagi et al. Chem Pharm Bul 12:465-472, 1964). Subgroups of rats were pre-treated with an inhibitor of H2S synthesis cystathionine γ-lyase (CSE) or cystathionine ß-synthase (CBS), or with the Sodium sulphide (NaHS), which spontaneously generates H2S in solution. Damage of the oesophageal mucosa and oesophagogastric junction was estimated and scored using a histological damage index. RESULTS: Treatment with naproxen increased the thickness of the corneal and epithelial layers of the oesophagus, as well as producing disorganization of the muscle plate and irregular submucosal oedema. Both injury factors, stress and suppression of H2S synthesis resulted in the development of severe esophagitis and damage to the oesophagogastric junction. The damage was exacerbated by inhibitors of H2S biosynthesis, and attenuated by treatment with NaHS. CONCLUSIONS: Inhibition of endogenous H2S synthesis provides a novel experimental model that can be useful in preclinical studies NSAID-related non-reflux oesophagitis. H2S contributes significantly to mucosal defence in the oesophagus.

Cytoprotective effects of hydrogen sulfide in novel rat models of non-erosive esophagitis.

Non-erosive esophagitis is a chronic inflammatory condition of the esophagus and is a form of gastroesophageal reflux disease. There are limited treatment options for non-erosive esophagitis, and it often progresses to Barrett's esophagus and esophageal carcinoma. Hydrogen sulfide has been demonstrated to be a critical mediator of gastric and intestinal mucosal protection and repair. However, roles for H2S in esophageal mucosal defence, inflammation and responses to injury have not been reported. We therefore examined the effects of endogenous and exogenous H2S in rat models of non-erosive esophagitis. Mild- and moderate-severity non-erosive esophagitis was induced in rats through supplementation of drinking water with fructose, plus or minus exposure to water-immersion stress. The effects of inhibitors of H2S synthesis or of an H2S donor on severity of esophagitis was then examined, along with changes in serum levels of a pro- and an anti-inflammatory cytokine (IL-17 and IL-10, respectively). Exposure to water-immersion stress after consumption of the fructose-supplemented water for 28 days resulted in submucosal esophageal edema and neutrophil infiltration and the development of lesions in the muscular lamina and basal cell hyperplasia. Inhibition of H2S synthesis resulted in significant exacerbation of inflammation and injury. Serum levels of IL-17 were significantly elevated, while serum IL-10 levels were reduced. Treatment with an H2S donor significantly reduced the severity of esophageal injury and inflammation and normalized the serum cytokine levels. The rat models used in this study provide novel tools for studying non-erosive esophagitis with a range of severity. H2S contributes significantly to mucosal defence in the esophagus, and H2S donors may have therapeutic value in treating esophageal inflammation and injury.

Adolf Beck: a forgotten pioneer in electroencephalography.

Adolf Beck, born in 1863 at Cracow (Poland), joined the Department of Physiology of the Jagiellonian University in 1880 to work directly under the supervision of the prominent physiology professor, Napoleon Cybulski. Following his suggestion, Beck started experimental studies on the electrical brain activity of animals, especially in response to sensory stimulation. Beck placed electrodes directly on the surface of brain to localize brain potentials that were evoked by sensory stimuli. He observed spontaneous fluctuations in the electrical brain activity and noted that these oscillations ceased after sensory stimulation. He published these findings concerning the electrical brain activity, such as spontaneous fluctuations, evoked potentials, and desynchronization of brain waves, in 1890 in the German language Centralblatt für Physiologie. Moreover, an intense polemic arose between physiologists of that era on the question of who should claim being the founder of electroencephalography. Ultimately, Richard Caton from Liverpool showed that he had performed similar experiments in monkeys years earlier. Nevertheless, Beck added new elements to the nature of electrical brain activity. In retrospect, next to Richard Caton, Adolf Beck can be regarded, together with Hans Berger who later introduced the method to humans, as one of the founders of electroencephalography. Soon after his success, Beck got a chair at the Department of Physiology of the University at Lemberg, now Lviv National Medical University.

Effect of CCl4 and blocking H2S biosynthesis on oesophageal mucosa rats: model of nonerosive oesophagitis.

Nonerosive esophagitis (NEO) - a chronic inflammatory condition with diagnostic and therapy unclear approaches. The aim of study was to develop the new models of NEO using the chemical ulcerogens: carbon tetrachloride (CCl(4)), hydrogen sulfide (H(2)S). We modified the method of NEO with cytoprotective prostaglandins (COX) and H(2)S biosynthesis carried out on rats, divided into groups: 1st - vehicle (1 ml 0.9% NaCl), CCl(4) (twice 0.3 ml/200g/body weight); the next day 2(nd) - vehicle; 3(rd) - nonselective blocker of COX (naproxen; 30 mg/kg); 4(th) - ATB-346 (H(2)S-releasing naproxen; 43.5 mg/kg, «Antibe Therapeutics¼, Canada) with per os administration. After H(2)S-biosythesis modification by intraperitoneal administration of cystathionine g-lyase (CSE) inhibitor, DL-propargylglycine (PAG, 25 mg/kg), cystathionine-b-synthetase (CBS) inhibitor, O-carboxymethyl-hydroxylamine hemihydrochloride (CHH, 50 mg/kg) or H(2)S donor NaHS (100 mlmol/kg), stress was inducted by Takagi, 1964. The lower third of EM and esophagogastric junction were estimated via histological score index, IL-17, IL-10 by ELISA. The obtained data indicated the strong cytotoxic influence of CCl(4) on EM, corneal and epithelial layers thickness increasing, muscle plate and submucosal edema disorganization vs control and ATB-346 treatment. Over-expression of IL-17 was achieved using PAG and BCA vs control. WIRS-associated EM injury with blocking CSE, CBS characterized by submucosal oedema, neutophilic infiltration, destructive lesions, HSI rising up to 6 vs control. Increased IL-17 to 65% and decreased IL-10 in 30% vs control. H(2)S plays key role in the integrity of oesophageal mucosa and modification of H(2)S synthesis and CCl(4)-related injury can be novel approach of animal model production NEO, similar to human NERD and will help in its pathogenesis identification and preventive drugs creation.

Adolf Beck: A pioneer in electroencephalography in between Richard Caton and Hans Berger.

Adolf Beck, born in 1863 in Kraków (Poland), joined the Department of Physiology of the Jagiellonian University in 1889, to work directly under the prominent professor in physiology Napoleon Cybulski. Following his suggestion, Beck started studies on the electrical brain activity of animals. He recorded negative electrical potentials in several brain areas evoked by peripheral sensory impulses. Using this technique, Beck localised various centres in the brain of several animal species. In doing this, he discovered continuous electrical oscillations in the electrical brain activity and noted that these oscillations ceased after sensory stimulation. This was the first description of desynchronization in electrical brain potentials. He published these findings in 1890 in the German Centralblatt für Physiologie. Immediately, an intense discussion arose under physiologists on the question who could claim being the founder of electroencephalography. Ultimately, Richard Caton from Liverpool showed that he had performed similar experiments in monkeys years earlier. Nevertheless, Beck added several new elements to the nature of electrical brain activity, such as evoked potentials and desynchronization. In looking back, Adolf Beck can be regarded, next to Richard Caton and together with Hans Berger (who later introduced the electrical brain recording method to humans), as one of the founders of electroencephalography.

Impact on electroencephalography of Adolf Beck, a prominent Polish scientist and founder of the Lviv School of Physiology.

Adolf Beck (1863-1942) can be regarded as the co-founder of electroencephalography. His studies on the cerebral cortex of animals have facilitated the introduction of the electroencephalogram (EEG) as a main tool for studying the brain. The localization of senses on the cortex with evoked potentials and the description of the desynchronization of the electrical brain activity upon stimulation, are hallmarks of the research of Beck. He performed his groundbreaking studies under supervision of the famous Napoleon Cybulski at the Jagiellonian University in Cracow (Poland) between 1888 and 1895. In that last year Beck was appointed professor at the University of Lemberg (Lviv), where he founded the Department of Physiology and recruited scientists to the Lviv School of Physiology. Beck was the leading authority of the University of Lemberg in the most turbulent period of the town's history. Together with Cybulski he wrote the influential textbook 'Human physiology' in 1915.