Tag Archives: Liver

Microbiology

Genetically-engineered probiotic could be a new way to reduce alcohol-induced health problems

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Reviewed by Emily Henderson, B.Sc.Apr 11 2023

Excessive alcohol consumption leads to painful hangovers and accompanying headaches, fatigue, and nausea. Drinking alcohol has also been linked to a raft of health problems in the human body, including heart disease, cirrhosis, and immune deficiency. One way to avoid those consequences would be to drink less, but researchers in China have introduced another way to mitigate hangovers and other adverse outcomes -; a genetically-engineered probiotic.

In a paper published this week in Microbiology Spectrum, the researchers described their approach and reported that in experiments on mice, the treatment reduced alcohol absorption, prolonged alcohol tolerance, and shortened the animals’ recovery time after exposure to alcohol. The probiotic hasn’t yet been tested on humans, but the authors predicted that if it confers the same benefits, it could present a new way to reduce alcohol-induced health problems, and liver problems in general.

Meng Dong, Ph.D, at the Chinese Academy of Science’s Institute of Zoology, who worked on the study, noted that clinical applications may extend beyond alcohol-related conditions. “We believe that genetically engineered probiotics will provide new ideas for the treatment of liver diseases,” she said.

The human body primarily uses forms of an enzyme called alcohol dehydrogenase, or ADH, to metabolize alcohol. But some variants are more effective than others: Some studies have found that a form called ADH1B, found primarily in East Asian and Polynesian populations, is 100 times more active than other variants. Previous studies on mice have shown that viral vectors genetically engineered to express ADH1B can accelerate the breakdown of alcohol, but that approach hasn’t been shown to be safe in humans.

Motivated by those findings, Dong and her colleagues looked for a safer delivery method, focusing on the probiotic Lactococcus lactis, a bacterium often used in fermentation. They used molecular cloning to introduce the gene for human ADH1B into a bacterial plasmid, which was then introduced into a strain of L. lactis. Lab tests confirmed that the probiotic secreted the enzyme. The researchers encapsulated the probiotic to ensure it would survive against stomach acid, then tested it on 3 groups of 5 mice, each exposed to different levels of alcohol.

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Untreated mice showed signs of drunkenness 20 minutes after exposure to alcohol. When the mice were placed on their backs, for example, they were unable to get back on their feet. But in the group that received a probiotic that expressed human ADH1B, half the mice were still able to turn themselves over an hour after alcohol exposure. A quarter never lost their ability to turn themselves over.

Further tests showed that 2 hours after exposure, blood alcohol levels in the control group continued to rise, while those in the probiotic-treated mice had begun to fall. In addition, the researchers found that treated mice showed lower levels of lipids and triglycerides in their livers, suggesting that the probiotic could alleviate alcohol-related damage to that organ.

The next step, Dong said, is to investigate whether the potential therapeutic effect of the modified probiotic extends to humans.

We are excited about the improvement of recombinant probiotics in acute alcohol-induced liver and intestinal damage.”

Meng Dong, Ph.D, Chinese Academy of Science’s Institute of Zoology

Source:

American Society for Microbiology

Journal reference:

Jiang, X., et al. (2023) Oral Probiotic Expressing Human Ethanol Dehydrogenase Attenuates Damage Caused by Acute Alcohol Consumption in Mice. Microbiology Spectrum. doi.org/10.1128/spectrum.04294-22.

Microbiology

Common Childhood Viruses Linked to Severe Hepatitis Outbreak

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A recent study led by researchers at UC San Francisco is making progress in uncovering the reasons behind a puzzling outbreak of acute severe hepatitis in healthy children that emerged in the spring of 2022, following the easing of COVID-19 lockdowns in 35 countries, including the United States.

The occurrence of pediatric hepatitis is uncommon and doctors were alarmed when they began to observe unexplained severe outbreaks. To date, approximately 1,000 cases have been reported, with 50 of these children requiring liver transplants and a minimum of 22 resulting in death.

In the study, published on March 30 in Nature, researchers linked the disease to co-infections from multiple common viruses, in particular a strain of adeno-associated virus type 2 (AAV2). AAVs are not known to cause hepatitis on their own. They need “helper” viruses, such as adenoviruses that cause colds and flu, to replicate in the liver.

Once they returned to school, children were more susceptible to infections with these common pathogens. The study suggests that for a small subset of these children, getting more than one infection at the same time may have made them more vulnerable to severe hepatitis.

“We were surprised by the fact that the infections we detected in these children were caused not by an unusual, emerging virus, but by common childhood viral pathogens,” said Charles Chiu, MD, Ph.D., professor of laboratory medicine and medicine in the Division of Infectious Diseases, director of the UCSF Clinical Microbiology Laboratory, and senior author of the paper.

“That’s what led us to speculate that the timing of the outbreak was probably related to the really unusual situations we were going through with COVID-19-related school and daycare closures and social restrictions,” Chiu said. “It may have been an unintended consequence of what we have experienced during the last two-to-three years of the pandemic.”

By August 2022, clusters of cases were reported in 35 countries, including the U. S., where 358 cases were under investigation. The Centers for Disease Control and Prevention (CDC) launched an investigation into the causes.

To conduct the study, which was backed by the CDC, researchers used polymerase chain reaction (PCR) along with various metagenomic sequencing and molecular-testing methods to examine plasma, whole blood, nasal swab and stool samples from 16 pediatric cases in six states — Alabama, California, Florida, Illinois, North Carolina, and South Dakota — from Oct. 1, 2021, to May 22, 2022. The specimens were compared with 113 control samples.

In genotyping the 14 available blood samples, adeno-associated virus 2 (AAV2) was detected in 93% of the cases and human adenoviruses (HAdVs) were found in all the cases; a specific type of adenovirus linked to gastroenteritis (HAdV-41) was found in 11 cases. Additional co-infections with Epstein-Barr, herpes, and enterovirus were found in 85.7% of cases.

Chiu noted the results mirrored the findings of two concurrent studies conducted in the United Kingdom, which identified the same AAV2 strain. All three studies identified co-infections from multiple viruses, and 75% of the children in the U.S. study had three or four viral infections.

Since AAVs are not considered pathogenic on their own, a direct causal link with severe acute hepatitis has yet to be established. The study notes, however, that children may be especially vulnerable to more severe hepatitis triggered by co-infections. While infections from adeno-associated viruses can occur at any age, the peak is typically between 1 and 5 years old, and the median age of the affected children in the study was 3 years old.

The clusters of acute severe hepatitis in children have recently waned, but Chiu said the best way to protect children from this unlikely outcome is by washing hands frequently and staying home when sick.

Reference: “Adeno-associated virus type 2 in US children with acute severe hepatitis” by Venice Servellita, Alicia Sotomayor Gonzalez, Daryl M. Lamson, Abiodun Foresythe, Hee Jae Huh, Adam L. Bazinet, Nicholas H. Bergman, Robert L. Bull, Karla Y. Garcia, Jennifer S. Goodrich, Sean P. Lovett, Kisha Parker, Diana Radune, April Hatada, Chao-Yang Pan, Kyle Rizzo, J. Bradford Bertumen, Christina Morales, Paul E. Oluniyi, Jenny Nguyen, Jessica Tan, Doug Stryke, Rayah Jaber, Matthew T. Leslie, Zin Lyons, Hayden D. Hedman, Umesh Parashar, Maureen Sullivan, Kelly Wroblewski, M. Steven Oberste, Jacqueline E. Tate, Julia M. Baker, David Sugerman, Caelin Potts, Xiaoyan Lu, Preeti Chhabra, Pediatric Hepatitis of Unknown Etiology Working Group, L. Amanda Ingram, Henry Shiau, William Britt, Luz Helena Gutierrez Sanchez, Caroline Ciric, Christina A. Rostad, Jan Vinjé, Hannah L. Kirking, Debra A. Wadford, R. Taylor Raborn, Kirsten St. George and Charles Y. Chiu, 30 March 2023, Nature.
DOI: 10.1038/s41586-023-05949-1

The study was funded by the Biomedical Advanced Research and Development Authority, the National Institute of Child Health and Human Development, and the U.S. Centers for Disease Control and Prevention.

University of California – San Francisco

Microbiology

Severe hepatitis outbreak caused by common childhood viral pathogens

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Reviewed by Emily Henderson, B.Sc.Mar 30 2023

A new UC San Francisco-led study brings scientists closer to understanding the causes of a mysterious rash of cases of acute severe hepatitis that began appearing in otherwise healthy children after COVID-19 lockdowns eased in the United States and 34 other countries in the spring of 2022.

Pediatric hepatitis is rare, and doctors were alarmed when they started seeing outbreaks of severe unexplained hepatitis. There have been about 1,000 cases to date; 50 of these children needed liver transplants and at least 22 have died.

In the study, publishing on March 30 in Nature, researchers linked the disease to co-infections from multiple common viruses, in particular a strain of adeno-associated virus type 2 (AAV2). AAVs are not known to cause hepatitis on their own. They need “helper” viruses, such as adenoviruses that cause colds and flus, to replicate in the liver.

Once they returned to school, children were more susceptible to infections with these common pathogens. The study suggests that for a small subset of these children, getting more than one infection at the same time may have made them more vulnerable to severe hepatitis.

We were surprised by the fact that the infections we detected in these children were caused not by an unusual, emerging virus, but by common childhood viral pathogens.”

Charles Chiu, MD, PhD, professor of laboratory medicine and medicine in the Division of Infectious Diseases, director of the UCSF Clinical Microbiology Laboratory, and senior author of the paper

“That’s what led us to speculate that the timing of the outbreak was probably related to the really unusual situations we were going through with COVID-19 related school and daycare closures and social restrictions,” Chiu said. “It may have been an unintended consequence of what we have experienced during the last two-to-three years of the pandemic.”

By August 2022, clusters of cases were reported in 35 countries, including the U. S., where 358 cases were under investigation. The Centers for Disease Control and Prevention (CDC) launched an investigation into the causes.

Testing for viruses

To conduct the study, which was backed by the CDC, researchers used polymerase chain reaction (PCR) along with various metagenomic sequencing and molecular-testing methods to examine plasma, whole blood, nasal swab and stool samples from 16 pediatric cases in six states -; Alabama, California, Florida, Illinois, North Carolina and South Dakota -; from Oct. 1, 2021, to May 22, 2022. The specimens were compared with 113 control samples.

In genotyping the 14 available blood samples, adeno-associated virus 2 (AAV2) was detected in 93% of the cases and human adenoviruses (HAdVs) were found in all the cases; a specific type of adenovirus linked to gastroenteritis (HAdV-41) was found in 11 cases. Additional co-infections with Epstein-Barr, herpes and enterovirus were found in 85.7% of cases.

Chiu noted the results mirrored the findings of two concurrent studies conducted in the United Kingdom, which identified the same AAV2 strain. All three studies identified co-infections from multiple viruses, and 75% of the children in the U.S. study had three or four viral infections.

Since AAVs are not considered pathogenic on their own, a direct causal link with the severe acute hepatitis has yet to be established. The study notes, however, that children may be especially vulnerable to more severe hepatitis triggered by co-infections. While infections from adeno-associated viruses can occur at any age, the peak is typically between 1 and 5 years old, and the median age of the affected children in the study was 3 years old.

The clusters of acute severe hepatitis in children have recently waned, but Chiu said the best way to protect children from this unlikely outcome is by washing hands frequently and staying home when sick.

Source:

University of California – San Francisco

Journal reference:

Servellita, V., et al. (2023). Adeno-associated virus type 2 in US children with acute severe hepatitis. Nature. doi.org/10.1038/s41586-023-05949-1.

Microbiology

NIH scientists discover an autoinflammatory disease caused by mutations in the LYN gene

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Reviewed by Emily Henderson, B.Sc.Mar 28 2023

Scientists have identified an autoinflammatory disease caused by mutations in the LYN gene, an important regulator of immune responses in health and disease. Named Lyn kinase-associated vasculopathy and liver fibrosis (LAVLI), the identification sheds light on how genes linked to certain illnesses can potentially be targets for treatment by repurposing existing drugs. The research, published in Nature Communications, was led by Adriana A. de Jesus, M.D. Ph.D., and Raphaela Goldbach-Mansky, M.D., M.H.S. of the Translational Autoinflammatory Diseases Section of the Laboratory of Clinical Immunology and Microbiology at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.

LAVLI was first discovered in a pediatric patient through genetic testing, which detected a mutation in LYN, the gene that encodes the Lyn kinase protein. Two additional, unrelated pediatric patients were later discovered to have two more mutations in the same gene. All three patients developed diseases linked to the LYN genetic mutation shortly after birth. Two patients developed liver fibrosis—excessive amounts of scar tissue caused by inflammation and repeated liver damage—in the first year of life. All three patients had perinatal onset of neutrophilic cutaneous small vessel vasculitis. This is an immune disorder characterized by inflammation from high numbers of neutrophils—white blood cells of the immune system—that can damage small blood vessels.

The study revealed Lyn kinase was always active and unable to shut down in the three patients with the LYN mutation, which increased neutrophil migration, altered inflammatory signals and activated scar and fibrosis-inducing liver cells. The results of this study suggest that Lyn kinase may be a potential therapeutic target for drugs that treat forms of non-syndromic small vessel vasculitis and other types of inflammation-induced liver fibrosis.

Source:

National Institutes of Health

Journal reference:

de Jesus, A. A., et al. (2023). Constitutively active Lyn kinase causes a cutaneous small vessel vasculitis and liver fibrosis syndrome. Nature Communications. doi.org/10.1038/s41467-023-36941-y.

Microbiology

Research identifies western diet-induced microbial and metabolic contributors to liver disease

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Reviewed by Emily Henderson, B.Sc.Mar 15 2023

New research from the University of Missouri School of Medicine has established a link between western diets high in fat and sugar and the development of non-alcoholic fatty liver disease, the leading cause of chronic liver disease.

The research, based in the Roy Blunt NextGen Precision Health Building at MU, has identified the western diet-induced microbial and metabolic contributors to liver disease, advancing our understanding of the gut-liver axis, and in turn the development of dietary and microbial interventions for this global health threat.

We’re just beginning to understand how food and gut microbiota interact to produce metabolites that contribute to the development of liver disease. However, the specific bacteria and metabolites, as well as the underlying mechanisms were not well understood until now. This research is unlocking the how and why.”

Guangfu Li, PhD, DVM, co-principal investigator, associate professor in the department of surgery and Department of Molecular Microbiology and Immunology

The gut and liver have a close anatomical and functional connection via the portal vein. Unhealthy diets change the gut microbiota, resulting in the production of pathogenic factors that impact the liver. By feeding mice foods high in fat and sugar, the research team discovered that the mice developed a gut bacteria called Blautia producta and a lipid that caused liver inflammation and fibrosis. That, in turn, caused the mice to develop non-alcoholic steatohepatitis or fatty liver disease, with similar features to the human disease.

“Fatty liver disease is a global health epidemic,” said Kevin Staveley-O’Carroll, MD, PhD, professor in the department of surgery, one of the lead researchers. “Not only is it becoming the leading cause of liver cancer and cirrhosis, but many patients I see with other cancers have fatty liver disease and don’t even know it. Often, this makes it impossible for them to undergo potentially curative surgery for their other cancers.”

As part of this study, the researchers tested treating the mice with an antibiotic cocktail administered via drinking water. They found that the antibiotic treatment reduced liver inflammation and lipid accumulation, resulting in a reduction in fatty liver disease. These results suggest that antibiotic-induced changes in the gut microbiota can suppress inflammatory responses and liver fibrosis.

Li, Staveley-O’Carroll and fellow co-principal investigator R. Scott Rector, PhD, Director of NextGen Precision Health Building and Interim Senior Associate Dean for Research -; are part of NextGen Precision Health, an initiative to expand collaboration in personalized health care and the translation of interdisciplinary research for the benefit of society. The team recently received a $1.2 million grant from the National Institutes of Health to fund this ongoing research into the link between gut bacteria and liver disease.

Source:

University of Missouri-Columbia

Journal reference:

Yang, M., et al. (2023). Western diet contributes to the pathogenesis of non-alcoholic steatohepatitis in male mice via remodeling gut microbiota and increasing production of 2-oleoylglycerol. Nature Communications. doi.org/10.1038/s41467-023-35861-1.

Microbiology

The right combination of bile salt hydrolases may offer a new approach to treat C. diff

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Reviewed by Emily Henderson, B.Sc.Mar 13 2023

Not all probiotics are created equal. In a new study, researchers found that certain enzymes within a class known as bile salt hydrolases (BSHs) can restrict Clostridioides difficile (C. diff.) colonization by both altering existing bile acids and by creating a new class of bile acids within the gut’s microbial environment. The work could lead to “designer” probiotics that protect against disease by introducing specific BSHs to the gut after antibiotic treatment.

Selecting the right suite of BSH-producing bacteria is critical, because the study found that interactions between BSHs and bile acids differ depending upon the type of bacteria the BSHs come from.

Certain bacteria within the gut microbiota contain BSH enzymes, which chemically modify bile acids. Bile acids are made in the liver and play an important role in modulating cholesterol levels, regulating fat absorption, shaping the immune system, and affecting which bacteria can colonize the gut.

Although researchers had long suspected a connection between BSHs from beneficial bacteria, the bile acid pool, gut microbial composition and host health, until now relatively little was known about how BSHs function and their potential impacts on host health.

The old dogma – that BSHs are needed for gut colonization because they render toxic bile acids non-toxic – oversimplified what’s actually happening.”

Casey Theriot, associate professor of infectious disease at North Carolina State University and co-corresponding author of the study

“The reality is that BSHs’ interactions are context-dependent, meaning they’re affected by the type of bacteria they come from,” Theriot says. “And they don’t just interact with bile acids produced by the host. BSHs in the microbiota can create and interact with a new class of bile acids called microbial conjugated bile acids (MCBAs) – bile acids that we didn’t even know existed until recently.”

In the new study, Theriot led a collaborative research team that included microbiologists, chemists, biochemists, and clinicians from NC State, the University of North Carolina at Chapel Hill, and the University of California, San Diego on a deep dive into BSHs.

Specifically, they looked at hundreds of BSHs from different Lactobacillaceae bacteria (which houses most probiotic strains) and then included BSHs from the gut microbiota (nearly 1,000 unique BSHs in total).

Matthew Redinbo, Kenan Distinguished Professor of Chemistry in UNC-Chapel Hill’s College of Arts and Sciences, and his departmental colleagues (led by then graduate student Morgan Walker) were instrumental in determining the structure of BSHs and how they “choose” to interact with bile acids, by either adding or taking away certain amino acids.

“We found the tiny molecular fingerprint that defined whether a BSH would ‘turn left’ or ‘turn right’ in terms of what they processed,” Redinbo says. “Knowing that allowed Casey’s team to steer the bile acid pool in whatever direction they wanted.”

The researchers used a cocktail of Lactobacillus BSHs to figure out if they could change the bile acid pool enough to alter C. diff colonization in both human stool samples collected from patients susceptible to C. diff infection (CDI) and in a mouse model of CDI. In both human stool samples and mice, the researchers saw that pre-treatment with BSH cocktails impacted C. diff colonization. Interestingly, the researchers noted elevated levels of MCBAs in the gut microbiota of the BSH-treated mice.

To determine whether the MCBAs were also involved in inhibiting C. diff germination and growth, they tested the MCBAs against C. diff in vitro. In most cases, the presence of MCBAs inhibited multiple steps of the C. diff life cycle.

“This is more evidence that BSHs are driving changes in the bile acid pool – including making MCBAs – that could serve to inhibit C. diff,” Theriot says. “We’ve uncovered a new function for BSH enzymes.”

“This work highlights the importance of BSHs as key intestinal enzymes and promising new therapeutics,” says Matt Foley, research scholar at NC State and co-first author of the study. “Using BSHs in combination with other strategies may offer a new approach to treat C. diff.“

The researchers see the work as the first step toward potential probiotics that could be customized to protect against a variety of bacterial infections and intestinal diseases. But first, more work must be done to determine how and why the BSHs decide which MCBAs to produce and/or target.

“This is an important illustration of how deciphering the biochemical and genetic basis for probiotic functionality both leads to a better understanding of how we can combat gut disease with novel modalities, and also practically design and formulate next-generation commercial probiotics,” says Rodolphe Barrangou, the Todd R. Klaenhammer Distinguished Professor in Probiotics Research at NC State and co-corresponding author of the study.

The work appears in Nature Microbiology and was supported by the National Institutes of Health, the National Science Foundation, IFF Corporation and the U.S. Environmental Protection Agency. The MCBA detection work was done by Erin Baker, formerly of NC State and currently at UNC-Chapel Hill, Allison Stewart of NC State, and Emily Gentry and Pieter Dorrestein from UCSD.

Source:

North Carolina State University

Journal reference:

Foley, M. H., et al. (2023). Bile salt hydrolases shape the bile acid landscape and restrict Clostridioides difficile growth in the murine gut. Nature Microbiology. doi.org/10.1038/s41564-023-01337-7.

Microbiology

In recent years, we have learned a lot about the crucial role gut microbes play in our health …

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In recent years, we have learned a lot about the crucial role gut microbes play in our health and well being. The extent of their influence can be surprising at times. Research has shown that gut microbes can impact the repair of tissue damage by fueling the production of a type of immune cell called Tregs, or regulatory T cells. These cells reside in various tissues and help regulate inflammation and immunity in different organs. But new work has shown that Tregs can also move around the body and respond when they are called to help fix injuries and tissue damage, such as in the muscles and liver. The findings, which used a mouse model and still have to be confirmed in humans, have been reported in the journal Immunity.

Image credit: Pixabay

There are Tregs that reside in the colon, and these cells are known to play an important role in the maintenance of gut health. The immune system in the gut has to protect us from infection while also ignoring the harmless or beneficial microbes in the gut microbiome. Gut microbes have also been known to affect Treg production. But colonic Tregs were thought to stay in the gut. In this study, the investigators found colonic Tregs among muscle cells.

First study author Bola Hanna, a research fellow in immunology at Harvard Medical School (HMS) noticed cells that looked like gut-derived Tregs among muscle tissue. The researchers wanted to known more about these mysterious cells. First, they confirmed the identity of the Tregs by analyzing gene expression and molecular characteristics. This indicated that these cells were just like colonic Tregs. Next, the investigators tagged those cells and watched as they moved around the bodies of a mouse model. The researchers assessed the antigens on these cells as well, confirming that they were equivalent to Tregs from the gut.

When a mouse model was created to lack these Tregs, and was then subjected to muscle injury, the mice had high levels of inflammation and difficulty healing. When healing did happen, it was accompanied by scarring.

In another experiment, mice were given antibiotics to reduce the levels of gut microbes. Once again, when muscle injury occurred, it took longer to heal. But if the gut microbiome was restored, normal healing commenced.

The colonic Tregs are promoting healing in muscles by reducing the levels of an inflammatory molecule called IL-17.

The investigators also found evidence of gut Tregs in different organs including the kidneys, liver, and spleen. In a mouse model of fatty liver disease, there were unusually high levels of colonic Tregs compared to healthy mice, suggesting that Tregs are influencing inflammation in a variety of tissues.

In the mouse model of fatty liver disease, symptoms got worse when the mice lacked Tregs, which also seems to confirm that colonic Tregs are playing an important role in countering the effects of inflammation due to fatty liver disease.

“Our observations indicate that gut microbes drive the production of a class of regulatory T cells that are constantly exiting the gut and act as sentries that sense damage at distant sites in the body and then act as emissaries to repair that damage,” explained senior study author Diane Mathis, a professor of immunology in the Blavatnik Institute at HMS. This work may also help scientists create therapies for fatty liver disease.

Sources: Harvard Medical School, Immunity


Carmen Leitch

Microbiology

First clinical trial of GABA/GAD focused exclusively on children with recent onset Type 1 diabetes

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Reviewed by Emily Henderson, B.Sc.Feb 22 2023

For the first time, humans with newly diagnosed Type 1 diabetes, or T1D, have received two treatments called GABA and GAD that have shown promise in animal studies and in isolated human pancreas islets. This investigator-initiated clinical trial, published in Nature Communications, focused exclusively on children with recent onset T1D.

Diabetes is a disease affecting two pancreatic hormones -; insulin and glucagon. In healthy people, insulin helps cells take up glucose from the blood when glucose levels are high. In contrast, glucagon helps the liver release glucose into the bloodstream when glucose levels are low. Thus, levels of blood glucose remain steady.

In T1D, autoantibodies destroy the pancreatic beta cells, insulin release is diminished, and glucagon release is excessive relative to the insulin deficiency. This can cause a vicious cycle of escalating blood glucose levels. Strategies to ameliorate or cure T1D, therefore, target the preservation of insulin-secreting beta cells and/or attenuation of the relative excess of alpha cell glucagon. Most importantly, concerning the inhibition of alpha cell glucagon in this trial by GABA/GAD, recent studies in animals made diabetic have shown that inhibition of glucagon leads to expansion of insulin-secreting beta cells and improvements in hyperglycemia.

Researchers in the study, led by University of Alabama at Birmingham physicians, were able to enroll children within the first five weeks of diagnosis, before the near total eradication of beta cells. Forty percent of the study participants were younger than 10 years old. The study -; which was constrained to lower-dose GABA therapy by the United States Food and Drug Administration because it was the first human trial with GABA -; did not achieve its primary outcome, the preservation of insulin production by beta cells. However, it did meet the clinically relevant secondary outcome of reduced serum glucagon. Significantly, the trial confirmed the safety and tolerability of oral GABA. Additionally, in collaboration with the immunology team of Hubert Tse, Ph.D., at the UAB Comprehensive Diabetes Center, a separate manuscript under review will describe a salutary effect of GABA alone and in combination with GAD on cytokine responses in peripheral blood mononuclear cells from trial participants.

GABA is gamma aminobutyric acid, a major inhibitory neurotransmitter. In the endocrine pancreas, GABA participates in paracrine regulation -; meaning a hormone that acts on nearby cells -; on the beta cells that produce insulin and the alpha cells that produce glucagon. In various mouse model studies, GABA was able to delay diabetes onset, and restore normal blood glucose levels after diabetes had already commenced. GABA treatment also led to significant decreases in the inflammatory cytokine expression that participates in the pathogenesis of T1D.

GAD is glutamic acid decarboxylase, the enzyme that acts on glutamate to form GABA. Animal and pancreatic islet cell studies show that immunization with GAD alone may help preserve beta cells. Both GABA and GAD are highly concentrated in the pancreatic islet, which is the autoimmune target of T1D.

The study, which was conducted between March 2015 and June 2019, screened 350 patients and enrolled 97, whose ages averaged 11 years. Forty-one took oral GABA twice a day; 25 took the oral GABA in combination with two injections of GAD, one at the baseline visit and one at the one-month visit. The remaining 31 children received a placebo treatment. Analysis after one year of treatment included 39 in the GABA group, 22 in the GABA/GAD group and 30 in the placebo group.

Given that GABA reduces immune inflammation at higher doses in several diabetic rodent models, it is plausible that increased GABA doses, or longer-acting preparations, could offer sufficiently prolonged, above-threshold GABA concentrations to preserve islet cells, particularly during stage 1 diabetes.”

Gail Mick, M.D., UAB Professor in the Department of Pediatrics’ Division of Pediatric Endocrinology and Diabetes

Mick and Kenneth McCormick, M.D., who recently retired from UAB Pediatrics, co-led the trial.

Alexandra Martin and Mick, UAB Department of Pediatrics, are co-first authors of the study, “A randomized trial of oral gamma aminobutyric acid (GABA) or the combination of GABA with glutamic acid decarboxylase (GAD) on pancreatic islet endocrine function in children with newly diagnosed type 1 diabetes.”

Other authors are Heather M. Choat, Alison A. Lunsford and Kenneth L. McCormick, UAB Department of Pediatrics; Hubert M. Tse, UAB Department of Microbiology; and Gerald G. McGwin Jr., Department of Epidemiology, UAB School of Public Health.

Source:

University of Alabama at Birmingham

Journal reference:

Martin, A., et al. (2022) A randomized trial of oral gamma aminobutyric acid (GABA) or the combination of GABA with glutamic acid decarboxylase (GAD) on pancreatic islet endocrine function in children with newly diagnosed type 1 diabetes. Nature Communications. doi.org/10.1038/s41467-022-35544-3.

Microbiology

Differences in gut microbiome diversity attributed to dietary patterns in children with obesity

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Dr. Chinta SidharthanBy Dr. Chinta SidharthanFeb 16 2023Reviewed by Benedette Cuffari, M.Sc.

In a recent study published in Microbiology Spectrum, researchers found that differences in the dietary patterns of children with normal weight and those who were overweight or obese contributed to variations in the gut microbiome diversity, virulence factors of gut bacteria, and metabolic function.

Study: Virulence factors of the gut microbiome are associated with BMI and metabolic blood parameters in children with obesity. Image Credit: Africa Studio / Shutterstock.com

Study: Virulence factors of the gut microbiome are associated with BMI and metabolic blood parameters in children with obesity. Image Credit: Africa Studio / Shutterstock.com

Background

A growing body of evidence indicates that gut microbiota has a significant role in various aspects of host metabolism, including digestion, harvesting of energy, and induction of low-grade inflammation. In addition, the genetic factors of the host, as well as other characteristics such as age, diet, immunity, and gender, influence the gut microbiome composition.

Research shows that bacterial diversity in the gut and the individual’s functional capacity vary between those with normal weight and obese individuals. Gut microbiome profile variations have also been linked to metabolic disorders, lipid accumulation, and inflammation.

Lipogenesis in the liver and the regulation of appetite through hormones are also associated with gut microbiome genes.

Aside from its role in adipogenesis, superoxide reduction, and the metabolism of vitamins, gut microbiota also regulates innate immunity and the systemic, low-grade inflammatory state that can contribute to fat deposition and obesity. Therefore, Dysbiosis, which is the imbalance of gut microbiota, combined with diet, likely has a significant role in the development of obesity.

About the study

In the present study, researchers conducted a cross-sectional analysis of data from 45 children between the ages of six and 12 to determine the association between gut microbiota and obesity.

Questionnaires were used to obtain information on dietary frequencies, gender, age, and body mass index (BMI). Based on the World Health Organization (WHO) z-scores, in which BMI is adjusted for gender and age, the children were classified into two categories of overweight and obese (OWOB) and normal weight (NW).

Data from food frequency questionnaires were used to classify the dietary habits of children into two nutritional patterns. To this end, Pattern 1 was characterized by complex carbohydrates and proteins, whereas Pattern 2 comprised simple carbohydrates and saturated fats.

Shotgun metagenomics was used to assess the taxonomic diversity of the gut microbiota and metabolic capacity from genomic deoxyribonucleic acid (DNA) extracted from fecal samples. Clade-specific markers were used for the taxonomic and functional assessment of the gut bacteria. Additionally, reverse Simpson and Shannon diversity indices were calculated.

The virulence factor database was used to screen for virulence factor genes, whereas multivariate linear modeling was used to determine the association between the taxa, virulence factors, and function of gut microbes and covariates of diet, serology, and anthropometric measurements.

Study findings

Significant differences between the alpha and beta diversity of the gut microbiota were observed between the children in the NW and OWOB groups, thus suggesting that specific phyla of bacteria contribute to higher levels of energy harvest.

Furthermore, species such as Ruminococcus species, Victivallis vadensis, Mitsuokella multacida, Alistipes species, Clostridium species, and Acinetobacter johnsonii were linked to healthier metabolic parameters.

In contrast, an increase in the abundance of bacteria such as Veillonellaceae, Lactococcus, Fusicatenibacter saccharivorans, Fusicatenibacter prausnitzii, Eubacterium, Roseburia, Dialister, Coprococcus catus, Bifidobacterium, and Bilophila was identified in children with pro-inflammatory conditions and obesity.

Bacteria such as Citrobacter europaeus, Citrobacter youngae, Klebsiella variicola, Enterococcus mundtii, Gemella morbillorum, and Citrobacter portucalensis were associated with higher lipid and sugar intake, as well as higher blood biochemistry values and anthropometric measurements.

Diets high in fats and simple carbohydrates have been associated with the abundance of Citrobacter and Klebsiella species in the gut. Moreover, previous studies have indicated that these bacterial species are potential markers of inflammation, obesity, and an increase in fasting glucose.

The metabolism of menaquinones and gamma-glutamyl was negatively associated with BMI. Furthermore, the microbiomes of children in the NW group preserved a more consistent alpha diversity of virulence factors, while OWOB microbiomes exhibited a dominance of virulence factors.

Differences in the metabolic capacities pertaining to biosynthesis pathways of vitamins, carriers, amino acids, nucleotides, nucleosides, amines, and polyamines, as well as the degradation of nucleotides, nucleosides, and carbohydrate-sugars, were also found between the NW and OWOB groups.

Conclusions

Dietary profiles and the diversity of gut microbiota were found to be interconnected and associated with changes in metabolic parameters, the dominance of virulence factors, and obesity. Changes in gut microbiome diversity and relative abundance have been linked to obesity, inflammatory responses, and metabolic disorders.

Taken together, the study findings suggested that the prevalence of virulence factors, as well as the metabolic and genetic roles of gut microbiota in increasing inflammation, can help identify individuals at an increased risk of childhood obesity.

Journal reference:
  • Murga-Garrido, S. M., Ulloa-Pérez, E. J., Díaz-Benítez, C. E., et al. (2023). Virulence factors of the gut microbiome are associated with BMI and metabolic blood parameters in children with obesity. Microbiology Spectrum. doi:10.1128/spectrum.03382-22
Microbiology

Penn scientists discover a cellular pathway that keeps Ebola virus from exiting human cells

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Reviewed by Emily Henderson, B.Sc.Feb 3 2023

In their evolutionary battle for survival, viruses have developed strategies to spark and perpetuate infection. Once inside a host cell, the Ebola virus, for example, hijacks molecular pathways to replicate itself and eventually make its way back out of the cell into the bloodstream, where it can spread further.

But our own cells, in the case of Ebola and many other viruses, aren’t without defenses. In a study published in the Proceedings of the National Academy of Sciences, a team led by University of Pennsylvania School of Veterinary Medicine scientists discovered a way human cells hamper the Ebola virus’ ability to exit.

An interaction between viral and host proteins prompts host cells to ramp up activity of a pathway responsible for digesting and recycling proteins, the team found. This activity, known as autophagy “self-eating,” allows fewer viral particles to reach the surface of a host cell, thus reducing the number that can exit into the bloodstream and further propagate infection.

This interaction seems to be part of an innate defense mechanism. Human cells appear to specifically target a key Ebola virus protein and direct it into the autophagy pathway, which is how cells process and recycle waste.”

Ronald N. Harty, professor at Penn Vet and senior author on the study

The investigation emerged from a longtime area of focus for Harty’s lab: the interaction between the viral protein VP40, found in both Ebola and Marburg viruses, and various human proteins. In the group’s previous work, they’ve found that one area of VP40, known as a PPXY motif, binds corresponding motifs known as WW domains on specific host proteins.

In many instances, this PPXY-WW interaction causes more viral particles to exit the cell in a process called “budding.” But in screening various host proteins thought to play a role in the process, Harty and postdoc Jingjing Liang, the study’s lead author, uncovered some that did the opposite upon binding VP40, causing budding to decrease. One of these was a protein called Bag3, on which they reported in a PLOS Pathogens paper in 2017.

Though Ebola is a potentially deadly virus, Harty and colleagues can safely study its workings in a Biosafety Level 2 laboratory, substituting virus-like particles (VLPs) that express VP40 for the virus itself. These VP40 VLPs are not infectious but can bud out from host cells like the real thing.

In the new work, the Penn Vet researchers and colleagues from the Texas Biomedical Research Institute dug deeper to learn about the mechanism by which Bag3 reduced budding. Bag3 is known as a “co-chaperone” protein, involved in forming a complex with other proteins and chaperoning them on their trip to be digested, ultimately in organelles called autolysosomes, part of the process of autophagy. Using VP40 VLPs, Harty’s group confirmed that VP40 bound to Bag3 and formed the protein complex. When the researchers added a compound that is known to block formation of this complex, they saw VP40 being released; VLP budding activity subsequently increased.

To follow the activity of VP40 in real time, the team used powerful confocal microscopy, labeling each actor of interest with a different fluorescent tag. They observed that Bag3 was involved in sequestering VP40 in vesicles in the cell that would go on to undergo autophagy. Stuck in these vesicles and destined for the cellular “recycling center,” VP40 was unable to move to the cell membrane and bud.

“I think one of the most interesting things that we showed is the selectivity of the cargo,” Liang says. “We show that autophagy doesn’t just happen passively. Bag3 acts through the PPXY-WW interaction to specifically target VP40 to undergo autophagy.”

When the researchers added the drug rapamycin, which enhances autophagy, VP40 sequestration went up and VLP budding went down. Rapamycin works by inhibiting the activity of a pathway governed by a protein complex called mTORC1, a cellular sensor that turns on protein synthesis when a cell needs raw material to grow. The researchers found this pathway appeared to be important in regulating Ebola infection; in experiments with live virus conducted in a Biosafety Level 4 laboratory, they observed that the virus could activate mTORC1 signaling, causing the cellular “factory” to produce materials the virus would need to expand and spread. In contrast, inhibiting mTORC1 with rapamycin directed the virus toward the autophagy pathway, where it would be digested by the cell’s autolysosomes.

“The virus wants the cell growing so it activates mTORC1,” says Harty. “Autophagy does the opposite, keeping the cellular materials in balance.”

Autophagy is important for normal cellular processes, ensuring that the cell doesn’t become cluttered with unnecessary or misfolded proteins and other materials floating around. But this work also suggests autophagy can be harnessed by the body to defend against harmful infection.

“Our conception is that this is part of the arms race between our bodies and the virus,” Liang says. “The virus wants to shape its environment to benefit itself and its own survival, so it evolved to manipulate mTORC1. But the cell can also use this pathway to defend against viral infection.”

With these insights into the human body’s innate defenses against Ebola, the researchers hope to see if autophagy may be a factor in other hemorrhagic viral infections, such as those that cause Marburg and Lassa fever. And while the current experiments were primarily conducted using human liver cell lines, the team would also like to test whether autophagy and the mTORC1 pathway are involved in viral defense in other cell types, such as the immune system’s macrophages, the primary cells involved in propagating infection.

Ultimately, Harty, Liang, and colleagues hope to find as many viral vulnerabilities as possible, helping inform drugs that could be one component of a therapeutic cocktail, each targeting different stages of infection, from viral entry to exit.

“This all ties together in our overall goal of understanding viral-host interactions and, by understanding them, working to intervene to slow or stop infection,” Harty says.

Source:

University of Pennsylvania

Journal reference:

Liang, J., et al. (2023) Chaperone-assisted selective autophagy targets filovirus VP40 as a client and restricts egress of virus particles. PNAS. doi.org/10.1073/pnas.2210690120.