The increase of lifestyle-related diseases in Asia has recently become remarkably serious. This has been associated with a change in dietary habits that may alter the complex gut microbiota and its metabolic function in Asian people. Notably, the penetration of modern Western diets into Asia, which has been accompanied by an increase in fat content and decrease in plant-derived dietary fiber, is restructuring the Asian gut microbiome. In this review, we introduce the current status of obesity and diabetes in Asia and discuss the links of changes in dietary style with gut microbiota alterations which may predispose Asian people to metabolic diseases.

On March 11, 2020, the World Health Organization declared a pandemic of coronavirus infectious disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and imposed the biggest public health challenge for our civilization, with unforeseen impacts in the subsequent years. Similar to other respiratory infections, COVID-19 is associated with significant changes in the composition of the upper respiratory tract microbiome. Studies have pointed to a significant reduction of diversity and richness of the respiratory microbiota in COVID-19 patients. Furthermore, it has been suggested that Prevotella, Staphylococcus, and Streptococcus are associated with severe COVID-19 cases, while Dolosigranulum and Corynebacterium are significantly more abundant in asymptomatic subjects or with mild disease. These results have stimulated the search for new microorganisms from the respiratory microbiota with probiotic properties that could alleviate symptoms and even help in the fight against COVID-19. To date, the potential positive effects of probiotics in the context of SARS-CoV-2 infection and COVID-19 pandemics have been extrapolated from studies carried out with other viral pathogens, such as influenza virus and respiratory syncytial virus. However, scientific evidence has started to emerge demonstrating the capacity of immunomodulatory bacteria to beneficially influence the resistance against SARS-CoV-2 infection. Here we review the scientific knowledge regarding the role of the respiratory microbiota in viral infections in general and in the infection caused by SARS-CoV-2 in particular. In addition, the scientific work that supports the use of immunomodulatory probiotic microorganisms as beneficial tools to reduce the severity of respiratory viral infections is also reviewed. In particular, our recent studies that evaluated the role of immunomodulatory Dolosigranulum pigrum strains in the context of SARS-CoV-2 infection are highlighted.

Chronic inflammation caused by gut dysbiosis is associated with the pathophysiology of metabolic disease. Synbiotics are useful for ameliorating gut dysbiosis; however, it remains unclear what types of bacteria act as key markers for synbiotic-driven improvement of chronic inflammation. Here, we performed a post hoc analysis of a 24-week randomized controlled study using synbiotics to investigate the association between gut microbiota and inflammatory markers. We characterized the responders who showed lower interleukin-6 (IL-6) levels in response to synbiotic supplementation among 86 obese patients with type 2 diabetes mellitus. In our baseline analysis, the relative abundances of Bifidobacterium adolescentis and Alistipes onderdonkii correlated positively with IL-6, lipopolysaccharide binding protein (LBP), and high-sensitivity C-reactive protein (Hs-CRP) levels. The relative abundance of Eubacterium rectale correlated positively with LBP and Hs-CRP levels, and that of Bacteroides thetaiotaomicron correlated positively with LBP levels. Based on our responder analysis, patients with higher body mass indices (over 30 kg/m² on average), low abundances of Bacteroides caccae and Parabacteroides merdae at baseline and 24 weeks, and minimal changes in the relative abundance of E. rectale and Shannon index from baseline showed decreased IL-6 levels compared with baseline. However, glycemic control in responders was unchanged. In conclusion, we identified four bacterial species (B. adolescentis, A. onderdonkii, E. rectale, and B. thetaiotaomicron) related to chronic inflammation and predictive markers (B. caccae, P. merdae, and severity of obesity) in responders to synbiotic supplementation among obese patients with type 2 diabetes.

Recent research has confirmed that moderate-intensity exercise affects the gut microbiome composition and improves cardiac function in an animal model after myocardial infarction (MI). However, few studies have investigated the effects of exercise on glucose and lipid metabolism in patients with coronary heart disease (CHD) receiving a statin treatment and successful percutaneous coronary intervention (PCI). Meanwhile, since statin therapy may lead to the risk of an increase in blood glucose level in CHD patients, we hypothesized that moderate-intensity exercise may be helpful for regulating glucose-lipid metabolism and stabilizing the blood glucose level in CHD patients. Therefore, to confirm our conjecture, we conducted a clinical retrospective study and animal experiment, respectively. The clinical study involved a total of 501 statin-treated patients with CHD after PCI. According to the study protocol, patients were divided into the following three groups: a non-exercise group, exercise at the recommended standard group, and exercise not at the recommended standard group. We found that qualified moderate-intensity exercise decreased blood glucose and lipid levels at follow-up at a mean of 2.2 years, and the incidence of new-onset diabetes showed a downward trend compared with the non-exercise and exercise not at the recommended standard groups. Furthermore, we used a high-fat rat model to explore an additional mechanism of the beneficial effects of exercise-based management on glucose-lipid metabolism apart from the known mechanism. We used 16S rRNA high-throughput sequencing technology to analyze the changes induced by exercise in the composition of intestinal flora in experimental rats. We found that rats that exercised with or without statin administration had lower plasma glucose and lipid levels and that these parameters were higher in the control and statin-treated rats that did not exercise. These results were consistent with the human study. The results from high-throughput sequencing of the intestinal flora of rats showed, to the best of our knowledge, that exercise leads to an increased relative abundance of Akkermansia muciniphila, which contributes to improved glucose and lipid metabolism. Based on our current results, we suggest that moderate-intensity exercise can improve glucose and lipid metabolism and prevent statin treatment-related side effects, such as hyperglycemia, in patients after PCI. Exercise could facilitate the applicability of statins for lower lipid levels. Exercise training also provides additional benefits, such as alteration of the gut microbiota, which contributes to improved glucose and lipid metabolism.

Intestinal parasitic infections can change gut microbiota and short-chain fatty acids (SCFAs). We aimed to study the interaction among Strongyloides stercoralis, human gut microbiota, and serum SCFAs in a community. Fifty-two subjects in Donchang sub-district, Khon Kaen Province, northeastern Thailand, were included based on specific inclusion and exclusion criteria. Characteristics of the participants were matched between those positive for S. stercoralis infection alone (no other intestinal parasites; Ss+, n=26) and uninfected controls (infection status confirmed by polymerase chain reaction (PCR); Ss−, n=26). Serum short-chain fatty acids were evaluated by gas chromatography-mass spectrometry. DNA was extracted from individual faecal samples and then pooled into two groups (Ss+ and Ss−) for amplification and sequencing of the V3–V4 region of the 16S gene with next-generation technology. We explored the impact of infection with S. stercoralis on the faecal microbiota: individuals infected with this parasite exhibited increased alpha diversity of bacteria. At the genus level, gut microbiota in Ss+ patients showed high abundances of Escherichia-Shigella and Bacteroides but low abundances of the genera Bifidobacterium, Lactobacillus, and Blautia. PCR of individual samples to identify certain species of interest gave results consistent with those from next-generation sequencing of pooled samples and showed that significantly more Ss+ samples contained Bacteroides fragilis. Intriguingly, a major SCFA, acetic acid, was significantly decreased in S. stercoralis infection. In conclusion, S. stercoralis infection caused an imbalance of gut microbiota and decreased acetic acid in serum. This information adds to the knowledge concerning the effect of intestinal nematode-related chronic diseases.

Lactococcus lactis subsp. cremoris C60 is a probiotic strain that induces diverse functional modifications in immune cells. In this report, as a novel effect of C60 on myeloid lineage cells, we show that C60 enhances the immunological function of macrophages that consequently promotes CD4+ T cell activity in an antigen-dependent manner. Heat-killed (HK) C60 induced the production of pro-inflammatory cytokines in thioglycolate-elicited peritoneal macrophages (TPMs) much stronger than Toll-like receptor (TLR) ligand stimulation. The HK-C60 treatment also augmented the expression of antigen-presenting and co-stimulatory molecules, such as major histocompatibility complex (MHC) class II, CD80, and CD86, as well as antigen uptake in TPMs. These HK-C60-mediated functional upregulations in TPMs resulted in the promotion of CD4+ T cell activation in an antigen-dependent manner. Interestingly, the TPMs that originated from the mice fed the HK-C60 diet showed pre-activated characteristics, which was confirmed by the upregulation of cytokine production and antigen presentation-related molecule expression under lipopolysaccharide (LPS) stimulation. Furthermore, the antigen-dependent CD4+ T cell activation was also enhanced by the TPMs. This implied that antigen presentation activity was enhanced in the TPMs that originated from the HK-C60 diet mice. Thus, C60 effectively upregulates the immunological function of macrophages that directly connects to CD4+ T cell-based adaptive immunity.

The biological activities of acetic acid bacteria (AAB) as Gram-negative bacteria have attracted our interests, especially in their inhibitory effects on allergic responses. To clarify the underlying mechanism that improves allergic symptoms by ingestion of the AAB Gluconacetobacter hansenii, we examined whether different extracts of heat-killed G. hansenii GK-1 could reduce the interleukin (IL)-4 production of immune cells from food-allergic model of OVA23-3, transgenic mice with ovalbumin (OVA)-specific T-cell-receptor genes. A hot-water extract fraction (FII) of G. hansenii GK-1 significantly decreased the in vitro IL-4 production of spleen cells of OVA23-3 mice compared with those stimulated with OVA alone. The IL-4 inhibitory effect was also observed for FIV (purified lipopolysaccharide (LPS) fraction), but the activity was lower than for FII or LPS from Escherichia coli. Unlike LPS from Escherichia coli, FIV significantly inhibited the LPS-induced IL-6 production of the spleen cells. The addition of FII or FIV to a Foxp3⁺T cell-inducing culture showed that FII significantly promoted the rate of Foxp3⁺CD4⁺T cells of OVA-stimulated mesenteric lymph node cells from recombination-activating-gene (RAG)-2-deficient food-allergic inflammatory OVA23-3 (R23-3) mice with suppression of IL-4 production, while FIV induced Foxp3⁺T cells from RAG-2-deficient DO11.10 non-inflammatory mice. Structure analysis showed a lack of O-antigen in FIV, which seemed to lead to the weak biological activities of FIV observed. The present study suggests that extracts of G. hansenii GK-1 to inhibit IL-4 production of immune cells and/or promote regulatory T cell differentiation synergistically play important roles in improving allergic symptoms safely as well as normal condition.

Eight bacterial strains were used in this study to examine the survival of intestinal bacteria in immune cell cultures under aerobic and anaerobic culture conditions. With the addition of penicillin G and streptomycin, viable Clostridium clostridioforme and Fusobacterium varium cells did not decrease after 6 or 24 hr, even under aerobic conditions. Without antibiotics, eight bacterial strains did not decrease until 4 or 6 hr later, under both aerobic and anaerobic conditions. Escherichia coli numbers increased by more than 10 times under both conditions. In order to examine the effects of live gut bacteria on various immune cells, the viability of bacteria should be checked in cell culture media and under different conditions.