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  • Fractal pattern identified at molecular scale in nature for first time

    Fractal pattern identified at molecular scale in nature for first time

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    Illustration of the citrate synthase enzyme assembling into triangular fractal structures

    Courtesy of Franziska L. Sendker

    A bacterium has evolved an enzyme that assembles in a fractal structure, a mathematical pattern that repeats itself at smaller scales.

    Fractal patterns are found throughout nature on large, macroscopic scales, like in romanesco broccoli or fern plants, but until now they have never been identified at the molecular scale.

    Georg Hochberg at the Max Planck Institute for Terrestrial Microbiology in Marburg, Germany, and his colleagues discovered the molecular fractal in an enzyme used by the cyanobacterium Synechococcus elongatus. The enzyme, citrate synthase, is used by a wide variety of organisms as part of the Krebs cycle, a series of chemical reactions that generate energy. But in S. elongatus, the enzyme can take the unusual form of a triangle containing ever-smaller triangular gaps – known as a Sierpiński triangle.

    Electron microscope image of a triangular fractal structure made up of enzyme monomers

    Courtesy of Franziska L. Sendker

    The citrate synthase consists of a single building block, or monomer, that can assemble into different shapes, some of which help break down molecules in the Krebs cycle. Using an electron microscope, Hochberg and his team found that in S. elongatus, the monomers can assemble into a triangular form containing six monomers, which can itself combine with two others to form an 18-monomer shape. This can then combine with two more to form a 54-monomer shape, which is again triangular and resembles a Sierpiński triangle.

    By comparing the fractal enzyme to genetic sequences from other bacteria, the team also traced its evolutionary history. “It popped into existence very suddenly and was then almost immediately lost again by a few different versions of bacteria, and only stuck around in this one cyanobacterium, which makes our discovery of it almost more bizarre, because our chances of finding it were basically near zero,” says Hochberg.

    Although the researchers suspect the fractal shape may have given the bacterium some evolutionary advantage, they couldn’t find any obvious effect caused by removing the enzyme in lab experiments. “The cyanobacteria does not seem to care at all if it’s there or not,” says team member Franziska Sendker, also at the Max Planck Institute for Terrestrial Microbiology.

    “Perhaps there might actually be more of these complex, fractal-like shapes around in nature, just because people haven’t really looked for them,” says Ard Louis at the University of Oxford. “Fractals are simple, algorithmically. They should be relatively easy to evolve. Even if they are not adaptive, they may very well exist in a wider range of protein complexes.”

    It would be interesting to see if the two-dimensional triangular structure might be combined into three-dimensional shapes like a tetrahedron, says Nico Bruns at the Technical University of Darmstadt in Germany. “It would make a nano-size container with defined edges with an interior and exterior, and then you’re in the realm of protein cages and capsules that you can use to encapsulate and release products and other molecules of interest.”

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  • High blood levels of TMAO predicts chronic kidney disease risk in future

    High blood levels of TMAO predicts chronic kidney disease risk in future

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    New findings from Cleveland Clinic and Tufts University researchers show high blood levels of TMAO (trimethylamine N-oxide) predicts future risk of developing chronic kidney disease over time.

    The findings build on more than a decade of research spearheaded by Stanley Hazen, M.D., Ph.D., and a team related to the gut microbiome’s role in cardiovascular health and disease, including the adverse effects of TMAO, a byproduct formed by the gut bacteria from nutrients abundant in red meat, eggs and other animal source foods.

    The study, published in the Journal of the American Society of Nephrology, was a collaboration between a Cleveland Clinic research team led by Dr. Hazen and investigators from the Food is Medicine Institute at the Friedman School of Nutrition Science and Policy at Tufts University, including first author Meng Wang, Ph.D., and co-senior author Dariush Mozaffarian, M.D., Dr.PH.

    The large-scale study measured blood levels of TMAO over time in two large National Institutes of Health populations and followed the kidney function of more than 10,000 U.S. adults with normal kidney function at baseline over an average follow-up period of 10 years. The investigators found that participants with elevated TMAO blood levels were at increased risk for future development of chronic kidney disease.

    Higher TMAO levels were also associated with a faster rate of declining kidney function in people with normal or impaired kidney function at baseline. These associations were independent of sociodemographic characteristics, lifestyle habits, diet and other known risk factors for kidney disease. The findings also are consistent with earlier reported preclinical model studies showing TMAO directly fosters both kidney functional decline and tissue fibrosis.

    The findings indicate a remarkably strong clinical link between elevated TMAO and increased risk for developing chronic kidney disease. The results are from individuals of diverse ethnic and sociodemographic backgrounds who had normal kidney function at the start. The diversity of the participants helps ensure the results are generalizable.”


    Dr. Stanley Hazen, chair of the Department of Cardiovascular and Metabolic Sciences and at Cleveland Clinic’s Lerner Research Institute and co-section head of Preventive Cardiology in the Heart, Vascular & Thoracic Institute

    Chronic kidney disease is a major and growing public health challenge in both the U.S. and globally, affecting about 10-15% of the population worldwide. It also is a strong risk factor for cardiovascular disease. The study showed that TMAO levels were as strong or even stronger an indicator of chronic kidney disease risk than the well-known risk factors such as diabetes, hypertension, advancing age and race.

    The study results reinforce the growing body of evidence indicating that lowering TMAO with prescribed drugs could be an effective treatment in patients at risk for, or with early signs of, kidney disease.

    “Our study is a crucial complement to studies in preclinical models supporting TMAO as a novel biological risk factor for chronic kidney disease,” said Dr. Wang, research assistant professor at the Friedman School. “TMAO levels are highly modifiable by both lifestyle-like diet and pharmacologic interventions. Besides using novel drugs to lower TMAO in patients, using dietary interventions to lower TMAO in the general population could be a cost-efficient and low-risk preventive strategy for chronic kidney disease development.”

    Plans for future studies include examining genetic data to help assess the potential cause-and-effect relationship between TMAO and chronic kidney disease, as well as studying more definitively whether lifestyle changes may prevent chronic kidney disease development and progression.

    Dr. Hazen also directs Cleveland Clinic’s Center for Microbiome and Human Health and holds the Jan Bleeksma Chair in Vascular Cell Biology and Atherosclerosis.

    This research was supported by grants from the National Institutes of Health, as well as the American Heart Association Postdoctoral Fellowship.

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    Journal reference:

    Wang, M., et al. (2024). The Gut Microbial Metabolite Trimethylamine N-oxide, Incident CKD, and Kidney Function Decline. Journal of the American Society of Nephrology. doi.org/10.1681/ASN.0000000000000344.

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  • Distal colonocytes targeted by C. rodentium recruit T-cell help for barrier defence

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  • Gut-friendly psychobiotics could brighten moods and fight depression

    Gut-friendly psychobiotics could brighten moods and fight depression

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    In a recent review published in the journal Nutrients, researchers investigated the psychobiotic treatment of depression by restoring microbial balance and regulating the microbiome-gut-brain (MGB) axis.

    Depression is a global health concern that causes pain, lost productivity, higher healthcare expenditures, and a high risk of suicide. Dysbiosis, a disruption in gut microbiome homeostasis, can affect the gut-brain axis (GBA), resulting in microbial alterations. Psychobiotics, which have favorable effects on the gut barrier, immunological responses, cortisol expression, and the hypothalamic-pituitary-adrenal (HPA) axis, might be used as a supportive treatment for depression, particularly in treatment-recalcitrant depression (TRD) cases.

    The Power of Psychobiotics in Depression: A Modern Approach through the Microbiota–Gut–Brain Axis: A literature Review. Image Credit: T. L. Furrer / ShutterstockThe Power of Psychobiotics in Depression: A Modern Approach through the Microbiota–Gut–Brain Axis: A literature Review. Image Credit: T. L. Furrer / Shutterstock

    About the review

    In the present review, researchers presented clinical evidence and elucidated the underlying mechanisms of psychobiotic therapies for depression via their effects on gut-brain communication.

    Association between the gut-brain axis and depressive disorders

    Depression is a complex biological disorder influenced by a variety of molecular mechanisms, such as neurotransmitter reduction, a decrease in brain-derived neurotrophic factor (BDNF), an abnormally stressed HPA axis, an increase in pro-inflammatory gut microbial responses, and vagus nerve interaction between gut microbiota and brain. The GBA and intestinal microbes are inextricably linked, with MGB influencing neurobehavioral outcomes via endocrine, neuronal, and immunological mechanisms. Dysbiosis, or a disruption in the GBA axis, can alter the intestinal microbiome, influencing neuronal function, immunology, and gut inflammation.

    Chronic stress impairs intestinal homeostasis and changes gut microbial composition, increasing Faecalibaculum and Clostridium in individuals while decreasing Lactobacillus and Bifidobacterium. Recent animal models have demonstrated a relationship between the gut-brain axis and stress sensitivity and resilience. The intestinal microbiome influences inflammatory responses and brain states and is associated with psychiatric conditions such as major depressive disorder, bipolar disorder, psychosis, schizophrenia, anorexia nervosa, anxiety disorders, obsessive-compulsive disorder, post-traumatic stress disorder, and attention-deficit hyperactivity disorder (ADHD).

    Graphical Abstract

    Graphical Abstract

    Gut microbial metabolites involved in antidepressant actions

    The gut microbiome is a vital metabolite source, facilitating communications between the gut and the central nervous system. These metabolites consist of tryptophan, gamma-aminobutyric acid (GABA), serotonin, histamine, 5-hydroxytryptamine (5-HT), short-chain fatty acids (SCFAs), acetylcholine, and dopamine (DA). Microbial metabolites impact various mechanisms important for mental health, such as immunological and neuroendocrine system development, nutrition metabolism modulation, and xenobiotic transformation. They also help to maintain gut barrier function, strengthen the intestinal mucosa, and keep dangerous infections and poisons out of circulation. SCFAs are necessary for emotional states and cognition, impacting the host’s brain via G-protein-coupled receptors. They supply energy to colonocytes, protect the intestinal barrier, regulate inflammatory responses, and regulate hunger hormones. Increased SCFAs can reduce neuroinflammation and boost BDNF synthesis, boosting brain neuroplasticity.

    Impact of probiotic gut microbes on depression

    Psychobiotics are probiotic bacteria that boost mental health by improving the intestinal barrier and modifying the immune response in the gut-associated lymphoid tissue (GALT), which plays a role in inflammation development. The gut microbiota is crucial in the pathophysiology of depression since it regulates inflammatory processes. Bifidobacterium breve boosts BDNF levels, lowers interleukin-6 (IL-60) and TNF-alpha (TNF-α) levels, and enhances cognitive function.

    Lactic acid bacteria (LAB) reduce neuroinflammation, lower kynurenine levels, and promote tight junction (TJ) expression. Lactobacillus plantarum 299v boosts dopamine levels and helps with selective serotonin reuptake inhibitor (SSRI) therapy, resulting in better cognitive performance and lower kynurenine levels. Akkermansia muciniphila suppresses inflammatory cytokines in microglial cells, which lowers depressive-like behavior. Clostridium butyricum protects against neurological dysfunction, whereas Faecalibacterium prausnitzii lowers corticosterone and C-reactive protein (CRP) levels while boosting IL-10 levels and lowering cognitive impairment in Alzheimer’s disease rats.

    Clinical evidence highlighting the psychobiotic features of bacterial strains

    Postbiotics such as Bacillus coagulans MTCC 5856 and Bifidobacterium longum 1714 can help with irritable bowel syndrome (IBS) symptoms and depression. Probiotics such as Bifidobacterium longum 1714 and NCC3001 help to decrease stress and enhance memory. When coupled with antidepressants, these probiotics can effectively cure TRD. Probiotics such as Lactobacillus casei Shirota and Lactobacillus gasseri CP2305, at 2.5 × 109 CFU/g, enhance general health and lower mood disorders. Multi-strain probiotic medication also boosts general health, alleviates anxiety symptoms, and reduces inflammation. Lactobacillus gasseri fermented black soybean beverage helps healthy individuals sleep better and feel less stressed. Probiotic milk drinks and fermented soybean seed paste improve cognitive performance in individuals with moderate cognitive impairment and Alzheimer’s disease.

    The review highlights probiotics’ involvement in lowering depressive symptoms and their importance in mental health. The gut microbiota is crucial for digestion, food absorption, and psychiatric concerns such as stress reduction and anxiety. With a shift in the emphasis in modern life from infectious disorders to more common mental illnesses such as depression, good dietary habits and optimal intestinal function are critical for mental well-being, with probiotics playing an important role.

    Journal reference:

    • Dziedzic, A.; Maciak, K.; Bliźniewska-Kowalska, K.; Gałecka, M.; Kobierecka, W.; Saluk, J. The Power of Psychobiotics in Depression: A Modern Approach through the Microbiota–Gut–Brain Axis: A literature Review. Nutrients 2024, 16, 1054. DOI: 10.3390/nu16071054, https://www.mdpi.com/2072-6643/16/7/1054

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  • How microbes influence healing and infection risks

    How microbes influence healing and infection risks

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    In a recent Nature Reviews Microbiology study, researchers review how the wound microbiota interferes with skin repair processes and facilitates infection onset by modulating host immune responses.

    Study: The wound microbiota: microbial mechanisms of impaired wound healing and infection. Image Credit: A3pfamily / Shutterstock.com

    Background

    The skin protects the human body from the potentially harmful effects of invading pathogens and chemicals. Any injury or damage to the skin can lead to wound development; therefore, dressing and infection control are standard practices of wound care.

    The wound-healing process involves coagulation, hemostasis, inflammation, cell proliferation and migration, and tissue remodeling. Any alteration to these processes can lead to delayed wound healing and the development of a chronic wound.

    Non-healing and chronic wounds are associated with certain risk factors, including advanced age and the presence of specific comorbidities, such as diabetes, obesity, systemic diseases, immunosuppressive diseases, and autoimmune diseases.

    Microorganisms colonizing in wounds, collectively referred to as the wound microbiota, can significantly impact the healing process. While some microorganisms facilitate faster skin repair, some can acquire virulence factors and antibiotic resistance, thereby increasing the risk of infection.

    Both exogenous and endogenous microorganisms can contaminate an open wound. The wound can facilitate microbial growth by exposing subcutaneous tissues and nutrients, which can subsequently lead to the colonization of microorganisms in the wound. This type of colonization can cause local infection and biofilm formation, which has the potential to spread to other tissues and organs.

    Wound microbiota composition

    The most common microbial populations found in both acute and chronic wounds include Staphylococcus spp., Pseudomonas spp., Corynebacterium spp., Enterococcus spp., Streptococcus spp. and Cutibacterium spp, all of which are microorganisms that are also commonly found in healthy skin microbiota.

    Staphylococcus aureus

    A skin wound can significantly alter its surrounding environment through the secretion of molecules from damaged tissues to support the growth, invasion, adhesion, and migration of pathogens such as Staphylococcus aureus. High abundance of fibronectin- and collagen-binding proteins facilitates Staphylococcus aureus to easily invade broken skin and induce intracellular infection.

    Staphylococcus aureus also produces pore-forming toxins that disrupt the host cell membrane to prevent immune clearance. Furthermore, serine proteases produced by this bacterium act as enterotoxins that induce chronic inflammation and create severe, non-healing diabetic wounds.

    Staphylococcus aureus has multiple master regulators, including the accessory gene regulator quorum-sensing system and sarA, which help activate its virulence factors. Glucose transporters acquired by Staphylococcus aureus further induce the production of virulence factors under hyperglycemic conditions.

    Pseudomonas aeruginosa

    Pseudomonas aeruginosa is a pathogen that can be found in burn wounds, chronic surgical wounds, and diabetic wounds. High-level antibiotic resistance and robust ability to form biofilm allow Pseudomonas aeruginosa to create chronic and non-healing wounds. Pseudomonas aeruginosa also comprises a type III secretion system that controls the production of effector toxins, further facilitating the production of virulence factors.

    Streptococcus

    Streptococcus spp., including β-Hemolytic group A streptococci (GAS), group B streptococci (GBS), and group C streptococci, can be found in invasive and non-invasive wounds.

    GAS bacteria contain multiple adhesins that promote their access to diverse tissue surfaces. Virulence factors present in GAS bacteria work in synergy to bind to and activate host plasminogens and create a proteolytic environment that alters wound-site architecture.    

    Anaerobic bacteria

    Anaerobic bacteria commonly found in wound infections include Finegoldia magna, B. fragilis, and Clostridium perfringens. These bacteria can be introduced to the wound during injury, such as bite or abdominal penetrating wounds. In diabetic or other chronic wounds, these bacteria thrive in conditions of low tissue oxygenation and can exist in mixed facultative and obligate anaerobes communities.

    Fungi

    Candida albicans is a fungal species most commonly found in chronic, surgical, and burn wounds. These fungi can enter host cells by binding to E-cadherin and triggering endocytosis. The pathogenicity of C. albicans is dependent on its ability to switch between yeast and a highly invasive hyphal phenotype.

    Viruses

    Viruses can also impact wound healing and skin repair processes. Whereas specific bacteriophages can worsen wound infections by increasing the virulence of bacteria they have infected, other bacteriophages can improve wound healing by changing bacterial virulence.

    Risk factors for wound infection

    The outcomes of wound microbial infections primarily depend on microbial virulence, polymicrobial interactions, and complex crosstalk between microbes and the wound microenvironment.

    Multidrug-resistant pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) or multidrug-resistant Pseudomonas aeruginosa, can complicate the treatment of wound infections. Likewise, a compromised immune system or certain genetic factors can further delay the wound-healing process and increase the risk of infection.

    Microbial virulence is also an important determinant of wound outcomes and treatment modalities. Wound bioburden, characterized by microbial load, microbial diversity, and the presence of pathogenic microbes, is a key contributor to delayed wound healing and infection onset.

    Journal reference:

    • Uberoi, A., McCready-Vangi, A., & Grice, E. A. (2024). The wound microbiota: microbial mechanisms of impaired wound healing and infection. Nature Reviews Microbiology. doi:10.1038/s41579-024-01035-z.

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  • Blast exposure can cause intestinal permeability, study shows

    Blast exposure can cause intestinal permeability, study shows

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    A study by New York and Rocky Mountain U.S. Department of Veterans Affairs researchers showed blast exposure can cause intestinal permeability, a condition that can lead to gut bacteria entering the bloodstream and causing problems in other parts of the body. The study was the first to show a connection between blasts and intestinal permeability in a real-world operational setting.

    Researchers found biomarkers of intestinal permeability and signs of bacteria in the blood in 23 of 30 military breachers who were exposed to controlled, low-level explosive blasts during training. The biomarkers were observed between one and 16 hours after blast exposure, suggesting a direct connection.

    Intestinal permeability is a condition in which materials in the gastrointestinal tract can pass through the cells lining the intestinal walls. While the human body naturally has some intestinal permeability to allow nutrients to pass through the gut, when the barrier is too loose harmful substances such as bacteria can pass through into the rest of the body.

    Participants also reported headache, dizziness, concentration problems, and slow thinking after blast exposure. These symptoms are often seen in people with mild traumatic brain injury (TBI). Analysis suggested bacterial leakage could add to mild traumatic brain injury to increase mental symptoms. Previous research has shown a connection between gut bacteria and cognitive performance.

    About 20% of post-9/11 active duty Service members and Veterans have reported at least one mild TBI, with more than a third of these being caused by blast-related injuries. TBI research has shown pressure waves caused by explosions can cause internal injuries to the vasculature of the brain. While the entire body is susceptible to this type of damage from blasts, less is known about how the digestive tract may be affected. To the best of the author’s knowledge, this is the first study to show a direct connection between blasts and intestinal permeability with associated cognitive symptoms.

    The authors suggest treatment of blast-related TBI should also take into consideration intestinal integrity, the gut microbiota, and bacterial effects such as systemic inflammation.

    The study appeared in the March 21, 2024, issue of the International Journal of Molecular Sciences.

    Source:

    Veterans Affairs Research Communications

    Journal reference:

    Liu, Q., et al. (2024). Association of Blast Exposure in Military Breaching with Intestinal Permeability Blood Biomarkers Associated with Leaky Gut. International Journal of Molecular Sciences. doi.org/10.3390/ijms25063549.

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  • Researchers develop handheld device for rapid bacterial detection

    Researchers develop handheld device for rapid bacterial detection

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    Hear the words E. coli or salmonella and food poisoning comes to mind. Rapid detection of such bacteria is crucial in preventing outbreaks of foodborne illness. While the usual practice is to take food samples to a laboratory to see the type and quantity of bacteria that forms in a petri dish over a span of days, an Osaka Metropolitan University research team has created a handheld device for quick on-site detection.

    Led by Professor Hiroshi Shiigi of the Graduate School of Engineering, the team experimented with a biosensor that can simultaneously detect multiple disease-causing bacterial species within an hour.

    The palm-sized device for detection can be linked to a smartphone app to easily check bacterial contamination levels.”

    Professor Hiroshi Shiigi, Graduate School of Engineering, Osaka Metropolitan University

    His team synthesized organic metallic nanohybrids of gold and copper that do not interfere with each other, so that electrochemical signals can be distinguished on the same screen-printed electrode chip of the biosensor. These organic−inorganic hybrids are made up of conductive polymers and metal nanoparticles. The antibody for the specific target bacteria was then introduced into these nanohybrids to serve as electrochemical labels.

    Results confirmed that the synthesized nanohybrids functioned as efficient electrochemical labels, enabling the simultaneous detection and quantification of multiple bacteria in less than an hour.

    “This technique enables rapid determination of the presence or absence of harmful bacteria prior to shipment of food and pharmaceutical products, thereby helping to quickly ensure safety at the manufacturing site,” Professor Shiigi said.

    The team aims to develop new organic metallic nanohybrids to simultaneously detect even more bacterial species.

    The findings were published in Analytical Chemistry.

    Source:

    Osaka Metropolitan University

    Journal reference:

    Itagaki, S., et al. (2024). Simultaneous Electrochemical Detection of Multiple Bacterial Species Using Metal–Organic Nanohybrids. Analytical Chemistry. doi.org/10.1021/acs.analchem.3c04587.

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  • Exploring prebiotics and probiotics as dual fighters against depression and obesity

    Exploring prebiotics and probiotics as dual fighters against depression and obesity

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    Depression is among the most prevalent and potentially serious mental health disorders, accounting for up to 800,000 suicides a year. The risk factors for depression have, therefore, undergone much exploration.

    A recent study published online in Nutrients deals with the interactions between depression and nutrition, coupled with exercise.

    Study: The Role of Gut Microbiota, Nutrition, and Physical Activity in Depression and Obesity—Interdependent Mechanisms/Co-Occurrence. Image Credit: Bits And Splits/Shutterstock.comStudy: The Role of Gut Microbiota, Nutrition, and Physical Activity in Depression and Obesity—Interdependent Mechanisms/Co-Occurrence. Image Credit: Bits And Splits/Shutterstock.com

    About depression

    Depressive disorders include several categories, including persistent depressive disorder (dysthymia), premenstrual dysphoric disorder, as well as depression induced by addictive drugs or medications or by medical conditions.

    All are characterized by sadness and irritability, with bodily and mental changes. The effect is a lowered quality of life and impaired functioning.

    Moreover, depression is known to increase the risk for a number of metabolic diseases, such as diabetes, obesity, and ischemic heart disease.

    Conversely, dietary patterns are linked to mental health as well as malnutrition. For instance, excessive fat intake leads to chronic inflammation and obesity.

    Obesity

    Obesity is defined as the accumulation of body fat in excess, as measured by the body mass index (BMI) and the body fat percentage. It is associated with a higher risk of cardiovascular disease (CVD), insulin resistance, cancer, and nerve damage.

    Risk factors for obesity are well-known and include gender, age, smoking, apart from the consumption of excessive fat and of processed foods, which are typical of Western diets.

    Obesity and depression often affect the same individual, along with anxiety disorders. They have a common mechanism of action, as seen by their bidirectional association.

    People who are depressed often indulge in comfort eating, which may increase body weight, especially if the person is also inactive. The risk of obesity in people undergoing emotional stress is almost 40% higher.

    Similarly, obese people are almost 20% more likely to become anxious or depressed because of negative self-image as well as adverse social perceptions that they are too lazy or undisciplined to regulate their diet and their weight. The treatment of depression with antidepressants is effective but may cause weight increase.

    Unfortunately, both obesity and depression are among the most prevalent disorders globally and have a high death rate, leading to powerful scientific interest in their interrelationships.

    Gut microbiota

    The gut microbiota is essential to proper energy storage and metabolism, but shows marked variability in obese vs lean individuals. This includes lower diversity and fewer commensal bacteria but more pathogenic microbes in the obese. The resulting aberration in metabolism may contribute to obesity.

    The need for a rational diet along with therapies like psychotherapy and medication to treat patients with depression is stressed by some scientists.

    In addition, probiotics and prebiotics may be required, along with nutritional supplements, to correct dysbiosis and vitamin deficiencies.

    Probiotics and gut microbiota

    The researchers sought to understand how gut microbes may be useful in treating both obesity and depression and the role of probiotics and prebiotics in such therapy.

    The review suggests that about 57% of the composition of the gut microbiota responds to dietary patterns.

    Probiotics strengthen the gut barrier and modulate the immune system. Their use is associated with improving depressive symptoms, perhaps by supplying vitamin D and short-chain fatty acids (SCFAs), which combat inflammation.

    Some strains of probiotic bacteria directly affect neural pathways. They inhibit the depression-inducing hypothalamic–pituitary–adrenal axis (HPA axis), and promote the secretion of the anti-stress neurotransmitter GABA, also known as gamma-aminobutyric acid.

    Others produce gut neurotransmitters that also affect the brain, affecting the mood for the better.

    Some clinical trials in humans suggest a positive effect of probiotics on depressive disorders as well as on obesity and related metabolic conditions like insulin resistance, type 2 diabetes, and nonalcoholic fatty liver disease (NAFLD).

    Further research is essential to validate these results, especially as probiotics work well on gut health and overall disease control only as part of a holistic management strategy, including proper diet, exercise, stress regulation, and adequate sleep.

    Bacterial strains linked to improved neural pathways, sometimes called psychobiotics, include multiple Lactobacillus strains like Lactobacillus casei Shirota, Lactobacillus fermentum NS8 and NS9, and Lactobacillus rhamnosus JB-1, as well as Bifidobacterium strains like Bifidobacterium longum Rosell-175, Bifidobacterium longum 1714, and Bifidobacterium longum NCC3001.

    Diet and mental health

    The brain receives a good share of absorbed nutrients and utilizes them to keep itself healthy. For instance, regeneration, neuroplasticity, and an adequate antioxidant reserve depend on the proper supply of nutrients to the brain.

    Supplementation with fatty acids like eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), magnesium, folate, and vitamins E and D have been suggested to be beneficial in countering or mitigating severe depression and reducing neuroinflammation.

    Specific diets like the Mediterranean diet (MD), the DASH (Dietary Approaches to Stop Hypertension), or vegetarian diets have frequently been assessed for their relationship with physical and mental health.

    The authors of the current study found reduced depression and obesity risk with both the DASH and the MD, but contradictory data with vegetarian and vegan diets. However, high-quality vegetarian diets were protective against depression, underlining the pivotal role of diet quality in the type of diet chosen.

    Physical activity and obesity/mood disorders

    There is ample evidence that weight management is aided by increasing the overall energy expenditure and improving the mood, with reduced anxiety and depression. Aerobic exercise has been recommended for its ability to build fitness and help reduce weight.

    Physical exercise is linked with lengthening telomeres, a metabolic health biomarker. It is also associated with better brain health, sleep quality, and reduced depressive symptoms.

    Physical exercise is also linked to better gut microbiota composition, stronger commensals, and more anti-inflammatory bacteria.

    Early-life exercise may promote the development of bacteria that can help the host adapt to changing conditions and promote healthy brain development.

    The broader impact of obesity and depression

    Depression is associated with increased mortality and morbidity, absenteeism, severe decreases in the quality of life, and reduced productivity.

    Obesity, which is currently estimated to have a prevalence of 30% in the USA, also has profound impacts on personal and social health. It reduces female fertility, promotes loss of cognitive ability, reduces the lifespan, and may increase employment difficulty.

    Conclusions

    Obesity and depression have common origins and act to exacerbate each other. This interrelationship significantly impacts the quality of life. One possible explanation for their connections may be via gut dysbiosis.

    This has stimulated much study on the potential use of probiotics and prebiotics in depression and anxiety, as well as in obesity.

    “Encouraging findings from existing research underscore the need for robust clinical trials to evaluate the therapeutic potential of microbiota modulation.”

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  • How gut microbiome influences obesity onset differently in men and women

    How gut microbiome influences obesity onset differently in men and women

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    New research being presented at this year’s European Congress on Obesity (ECO) in Venice, Italy (12-15 May) identifies changes in the composition of gut bacteria that may play a key role in the onset and development of obesity, with differences in men and women, which might affect the metabolism of different nutrients and therefore the presence of bioactive molecules in the gut that influence the development of metabolic disease.

    The gut microbiota consists of a complex community of microorganisms (bacteria, viruses, fungi and protozoa) which inhabit the gastrointestinal tract. Disruption in this community (dysbiosis) significantly affects metabolic health and influences the risk of certain diseases, including obesity. However, it is still unclear which species represent a greater or lesser likelihood of developing obesity, as well as the impact of these species on our metabolic health.

    To find out more, researchers analyzed metagenomic and metabolomic data from a Spanish population to understand the mechanisms by which these microorganisms are involved in the development of obesity.

    They examined the fecal metabolome-;the diverse collection of metabolites (small molecules) found in the gut and shed in feces that are produced by gut bacteria as a byproduct of metabolizing food and make their way into the bloodstream impacting health.

    Overall, 361 adult volunteers (251 women/110 men, average (median age 44 years old) were included from the Spanish Obekit study-;a randomized trial examining the relationship between genetic variants and the response to a hypocaloric diet.

    All participants (65 normal-weight, 110 overweight, and 186 with obesity) were classified according to an obesity (OB) index-;LOW (BMI≤ 30 kg/m²; fat mass percentage ≤ 25% [women] or ≤ 32% [men]; waist circumference ≤88 cm [women] or ≤ 102 cm [men]) or HIGH (BMI > 30 kg/m²; fat mass >25% [women] or >32% [men]; waist circumference >88 cm [women] or >102 cm [men]) level of obesity.

    Researchers made sure that participants in the LOW and HIGH groups were matched for sex and age.

    Genetic microbiota profiling was done to identify the different types, composition, diversity, and relative abundance of bacteria present in stool samples of the participants.

    The analysis revealed that individuals with a HIGH OB index were characterised by significantly lower levels of Christensenella minuta-;a bacterium which has consistently been linked to leanness and health.

    In men, greater abundance of Parabacteroides helcogenes and Campylobacter canadensis species-;were strongly associated with higher BMI, fat mass, and waist circumference.

    Whereas in women, greater abundance of three species-;Prevotella micans, Prevotella brevis and Prevotella sacharolitica-;were highly predictive of higher BMI, fat mass and waist circumference, but not in men.

    In further untargeted metabolomics analyses, that looked at a broader range of metabolic compounds in the blood, researchers found variation in the abundance of certain metabolites-;especially higher levels of bioactive lipids-;phospholipids (implicated in the development of metabolic disease and critical modulators of insulin sensitivity) and sphingolipids (that play a role in the development of diabetes and the emergence of vascular complications)-;in participants with a HIGH OB index.

    Our findings reveal how an imbalance in distinct bacterial groups are likely to play an important role in the onset and development of obesity, with considerable differences between the sexes, which might affect the metabolism of different bioactive molecules present in the metabolome that influence the development of metabolic disease.”


    Dr Paula Aranaz, lead author from the Centre for Nutrition Research at the University of Navarra in Spain

    She adds, “Gut microbiome composition, specifically higher levels of the Christensenella minuta bacterium, appeared to protect against obesity. Whereas the species that influence the risk of developing obesity appear to be different between the sexes and interventions to help prevent an obesity-favourable microbiome may need to be different in men and women. Further research is needed to better understand when the switch to an obesity favorable gut microbiota may take place, and therefore the right timing for possible interventions.”

    She concludes, “We hope that this study demonstrates that using metagenomics in combination with metabolomics enables researchers to study the mechanisms involved in the development of metabolic diseases such as obesity with a high degree of confidence. This novel, broader approach could help to develop nutritional precision strategies for weight loss that modify the presence of specific bacteria strains, or the levels of bioactive molecules.”

    Despite the important findings, the authors note some limitations, including the small sample size (especially for men) and that the study was conducted in one area in Spain, and because climate, geography, diet, and culture are known to influence the gut microbiome, the findings might be not generalizable to other populations.

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  • Climate change boosts infectious disease spread, hits the vulnerable hardest

    Climate change boosts infectious disease spread, hits the vulnerable hardest

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    An article published in The Journal of Infectious Diseases describes how climate change may influence the transmission efficacy of several vector-, water-, and food-borne infections and to what extent these changes can impact socioeconomically deprived and vulnerable populations.

    Article: Climate Change and Contagion: The Circuitous Impacts From Infectious Diseases. Image Credit: Scott Book / ShutterstockArticle: Climate Change and Contagion: The Circuitous Impacts From Infectious Diseases. Image Credit: Scott Book / Shutterstock

    Background

    Earth’s temperature is increasing gradually due to excessive greenhouse gas emissions. The global 10-year average temperature jumped to 1.15 °C above preindustrial levels in 2022. While climate change can directly impact heat waves, floods, and droughts, it can indirectly influence the transmission potency of many infectious pathogens.

    The contagious nature and epidemic potential of these pathogens can be a potential public health concern, especially for marginalized and vulnerable populations who contribute the least to greenhouse gas emissions but are disproportionately affected by the detrimental effects of climate change.

    Vector-borne infections

    Dengue is a vector-borne infection transmitted to humans via an infected Aedes mosquito bite. Due to increasing rates of urbanization, human mobility, and climate change, more than 50% of the global population is currently at risk of contracting dengue.

    Global warming is predicted to facilitate the abundance and global distribution of dengue vectors (Aedes mosquito). Higher altitudes and temperate regions are predicted to experience higher transmissibility, which can negatively affect naïve populations of these regions because of the absence of pre-existing immunity and equipped healthcare systems.

    West Nile virus (WNV) is also transmitted to humans through infected mosquito bites. Higher ambient temperature can improve WNV fitness by increasing its replication inside mosquitoes, accelerating its growth rate, and reducing intervals between blood meals.

    Spring temperate is a robust predictor of WNV transmission in Europe. Depending on geographic regions and climatic conditions, the risk of WNV infection is predicted to increase by fivefold in Europe during 2040 – 2060. Western Europe is predicted to experience the most significant outbreaks of WNV infections.

    Food-borne infections

    The frequency of food-borne infections caused by Salmonella increases in summer months as temperate conditions facilitate the replication of this bacteria. Higher temperatures and heavy rainfall also influence the temporal and geographic distribution of Campylobacter in Northern Europe.

    The number of Campylobacter cases is predicted to increase by 200-fold by 2100. An extension of the transmission season (summer months), together with other types of climate change, might be responsible for this rise.

    Water-borne infections

    About 1.4 million deaths occur worldwide annually due to illnesses caused by contaminated water, poor sanitation, and lack of basic hygiene in households, schools, and healthcare centers.  

    Climate change has become a leading cause of water-borne infections. Increased global temperature induces water evaporation from oceans and a subsequent increase in atmospheric moisture content. These changes cause heavy rainfall and floods, which in turn contribute to increased outbreaks of water-borne infections.

    It has been estimated that the number of excess deaths due to temperature-attributable enteric infections could range between 10,000 and 75,000 per year by 2050–2065, considering optimistic and pessimistic conditions, respectively.

    A significant expansion of marine bacteria (Vibrio parahaemolyticus and Vibrio vulnificus) habitats in brackish water has been observed in recent years due to ocean warming. These bacterial populations can cause severe gastrointestinal infections and wound infections, which can further progress to more severe outcomes, including necrotizing fasciitis, septicemia, and death.  

    Considering medium to high emission conditions, Vibrio vulnificus population is expected to expand to every US state along the seaboard by 2080. This can lead to a simultaneous increase in infection risks in the coming decades.

    Adaptation to climate change

    Challenges associated with controlling climate change-attributable infection rates can be overcome to some extent by continuous monitoring of epidemic precursors of infections through early warning systems.

    The risk from climate change is determined by climate hazard, vulnerability, and exposure. Novel big data sources can be explored to capture the complex and nonlinear interactions between these factors.

    Smart traps that utilize mosquito sensors with machine learning algorithms and bio-acoustic recordings of live insects can be used to identify indigenous or invasive vector species.

    Detection of community transmission before clinical diagnosis can be achieved through monitoring wastewater pathogens.    

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