Tag Archives: Glycine

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

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.

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.

Simple blood tests for telomeric protein could provide a valuable screen for certain cancers

Once thought incapable of encoding proteins due to their simple monotonous repetitions of DNA, tiny telomeres at the tips of our chromosomes seem to hold a potent biological function that’s potentially relevant to our understanding of cancer and aging.

Reporting in the Proceedings of the National Academy of Science, UNC School of Medicine researchers Taghreed Al-Turki, PhD, and Jack Griffith, PhD, made the stunning discovery that telomeres contain genetic information to produce two small proteins, one of which they found is elevated in some human cancer cells, as well as cells from patients suffering from telomere-related defects.

Based on our research, we think simple blood tests for these proteins could provide a valuable screen for certain cancers and other human diseases. These tests also could provide a measure of ‘telomere health,’ because we know telomeres shorten with age.”

Jack Griffith, PhD, the Kenan Distinguished Professor of Microbiology and Immunology and Member of the UNC Lineberger Comprehensive Cancer Center

Telomeres contain a unique DNA sequence consisting of endless repeats of TTAGGG bases that somehow inhibit chromosomes from sticking to each other. Two decades ago, the Griffith laboratory showed that the end of a telomere’s DNA loops back on itself to form a tiny circle, thus hiding the end and blocking chromosome-to-chromosome fusions. When cells divide, telomeres shorten, eventually becoming so short that the cell can no longer divide properly, leading to cell death.

Scientist first identified telomeres about 80 years ago, and because of their monotonous sequence, the established dogma in the field held that telomeres could not encode for any proteins, let alone ones with potent biological function.

In 2011 a group in Florida working on an inherited form of ALS reported that the culprit was an RNA molecule containing a six-base repeat which by a novel mechanism could generate a series of toxic proteins consisting of two amino acids repeating one after the other. Al-Turki and Griffith note in their paper a striking similarity of this RNA to the RNA generated from human telomeres, and they hypothesized that the same novel mechanism might be in play.

They conducted experiments – as described in the PNAS paper – to show how telomeric DNA can instruct the cell to produce signaling proteins they termed VR (valine-arginine) and GL (glycine-leucine). Signaling proteins are essentially chemicals that trigger a chain reaction of other proteins inside cells that then lead to a biological function important for health or disease.

Al-Turki and Griffith then chemically synthesized VR and GL to examine their properties using powerful electron and confocal microscopes along with state-of-the-art biological methods, revealing that the VR protein is present in elevated amounts in some human cancer cells, as well as cells from patients suffering from diseases resulting from defective telomeres.

“We think it’s possible that as we age, the amount of VR and GL in our blood will steadily rise, potentially providing a new biomarker for biological age as contrasted to chronological age,” said Al-Turki, a postdoctoral researcher in the Griffith lab. “We think inflammation may also trigger the production of these proteins.”

Griffith noted, “When you go against current thinking, you are usually wrong because you are bucking many people who’ve worked so diligently in their fields. But occasionally scientists have failed to put observations from two very distant fields together and that’s what we did. Discovering that telomeres encode two novel signaling proteins will change our understanding of cancer, aging, and how cells communicate with other cells.

“Many questions remain to be answered, but our biggest priority now is developing a simple blood test for these proteins. This could inform us of our biological age and also provide warnings of issues, such as cancer or inflammation.”

Journal reference:

Al-Turki, T., et al. (2023) Mammalian Telomeric RNA (TERRA) can be translated to produce valine-arginine and glycine-leucine dipeptide repeat proteins. PNAS. doi.org/10.1073/pnas.2221529120.