A USF Health-led team finds that the compound fenchol has the same beneficial effect as gut-derived metabolites in reducing neurotoxic amyloid-beta in the brain

TAMPA, Fla. (Oct. 5, 2021) – Fenchol, a natural compound abundant in some plants including basil, can help protect the brain against Alzheimer’s disease pathology, a preclinical study led by University of South Florida Health (USF Health) researchers suggests.

The new study published Oct. 5 in the Frontiers in Aging Neuroscience, discovered a sensing mechanism associated with the gut microbiome that explains how fenchol reduces neurotoxicity in the Alzheimer’s brain.

Emerging evidence indicates that short-chain fatty acids (SCFAs)– metabolites produced by beneficial gut bacteria and the primary source of nutrition for cells in your colon — contribute to brain health. The abundance of SCFAs is often reduced in older patients with mild cognitive impairment and Alzheimer’s disease, the most common form of dementia. However, how this decline in SCFAs contributes to Alzheimer’s disease progression remains largely unknown.

Gut-derived SCFAs that travel through the blood to the brain can bind to and activate free fatty acid receptor 2 (FFAR2), a cell signaling molecule expressed on brain cells called neurons.

“Our study is the first to discover that stimulation of the FFAR2 sensing mechanism by these microbial metabolites (SCFAs) can be beneficial in protecting brain cells against toxic accumulation of the amyloid-beta (Aβ) protein associated with Alzheimer’s disease,” said principal investigator Hariom Yadav, PhD, professor of neurosurgery and brain repair at the USF Health Morsani College of Medicine, where he directs the USF Center for Microbiome Research.

Study principal investigator Hariom Yadav, PhD, directs the USF Microbiome Research Center housed at the USF Health Morsani College of Medicine. | Photo by Allison Long, USF Health Communications and Marketing

One of the two hallmark pathologies of Alzheimer’s disease is hardened deposits of Aβ that clump together between nerve cells to form amyloid protein plaques in the brain. The other is neurofibrillary tangles of tau protein inside brain cells. These pathologies contribute to the neuron loss and death that ultimately cause the onset of Alzheimer’s, a neurodegenerative disease characterized by loss of memory, thinking skills and other cognitive abilities.

Dr. Yadav and his collaborators delve into molecular mechanisms to explain how interactions between the gut microbiome and the brain might influence brain health and age-related cognitive decline. In this study, Dr. Yadav said, the research team set out to uncover the “previously unknown” function of FFAR2 in the brain.

The researchers first showed that inhibiting the FFAR2 receptor (thus blocking its ability to “sense” SCFAs in the environment outside the neuronal cell and transmit signaling inside the cell) contributes to the abnormal buildup of the Aβ protein causing neurotoxicity linked to Alzheimer’s disease.

Then, they performed large-scale virtual screening of more than 144,000 natural compounds to find potential candidates that could mimic the same beneficial effect of microbiota produced SCFAs in activating FFAR2 signaling. Identifying a natural compound alternative to SCFAs to optimally target the FFAR2 receptor on neurons is important, because cells in the gut and other organs consume most of these microbial metabolites before they reach the brain through blood circulation, Dr. Yadav noted.

Dr. Yadav’s team narrowed 15 leading compound candidates to the most potent one. Fenchol, a plant-derived compound that gives basil its aromatic scent, was best at binding to the FFAR’s active site to stimulate its signaling.

Alzheimer’s disease model of the worm C. elegans treated with the plant-derived compound fenchol (Above) and with a DMSO placebo (Below). Fenchol reduced accumulation of amyloid-β (green dots) in the organism’s head, compared to the placebo. | Images courtesy of Hariom Yadav, PhD, of the University of South Florida, first appeared as Fig. 4d in Frontiers in Aging Neuroscience, DIO: 10.3389/fnagi.2021.735933

Further experiments in human neuronal cell cultures, as well as Caenorhabditis (C.) elegans (worm) and mouse models of Alzheimer’s disease demonstrated that fenchol significantly reduced excess Aβ accumulation and death of neurons by stimulating FFAR2 signaling, the microbiome sensing mechanism. When the researchers more closely examined how fenchol modulates Aβ-induced neurotoxicity, they found that the compound decreased senescent neuronal cells, also known as “zombie” cells, commonly found in brains with Alzheimer’s disease.

Zombie cells stop replicating and die a slow death. Meanwhile, Dr. Yadav said, they build up in diseased and aging organs, create a damaging inflammatory environment, and send stress or death signals to neighboring healthy cells, which eventually also change into harmful zombie cells or die.

“Fenchol actually affects the two related mechanisms of senescence and proteolysis,” Dr. Yadav said of the intriguing preclinical study finding. “It reduces the formation of half-dead zombie neuronal cells and also increases the degradation of (nonfunctioning) Aβ, so that amyloid protein is cleared from the brain much faster.”

Before you start throwing lots of extra basil in your spaghetti sauce or anything else you eat to help stave off dementia, more research is needed — including in humans.

In exploring fenchol as a possible approach for treating or preventing Alzheimer’s pathology, the USF Health team will seek answers to several questions. A key one is whether fenchol consumed in basil itself would be more or less bioactive (effective) than isolating and administering the compound in a pill, Dr. Yadav said. “We also want to know whether a potent dose of either basil or fenchol delivered by nasal spray would be a quicker way to get the compound into the brain.”

The USF Health-led research was supported in part by grants from the National Institutes of Health, the U.S. Department of Defense, and the NIH-funded Wake Forest Clinical and Translational Science Institute.

About USF Health
USF Health’s mission is to envision and implement the future of health. It is the partnership of the USF Health Morsani College of Medicine, the College of Nursing, the College of Public Health, the Taneja College of Pharmacy, the School of Physical Therapy and Rehabilitation Sciences, the Biomedical Sciences Graduate and Postdoctoral Programs, and USF Health’s multispecialty physicians group. The University of South Florida is a high-impact global research university dedicated to student success. Over the past 10 years, no other public university in the country has risen faster in U.S. News and World Report’s national university rankings than USF. For more information, visit health.usf.edu

About Frontiers
Frontiers is one of the largest and highest-cited open access publishers in the world. Access to research results and data is open, free and customized online to help solve the critical challenges we face as humanity. All journals are led and peer-reviewed by editorial boards of more than 100,000 top researchers across more than 900 academic disciplines. https://twitter.com/FrontNeurosci

Initial transdisciplinary projects focus on neuroscience-related topics

The USF Initiative on Microbiomes has awarded its first seed grants to help advance new transdisciplinary microbiome research across departments and colleges.

The inaugural Microbiome Research Awards were presented to principal investigators Juan Sanchez-Ramos, MD, PhD, of the USF Health Morsani College of Medicine, and Monica Uddin, PhD, of the USF College of Public Health. Seed funding was provided by the Office of the USF Health Senior Vice President.

Juan Sanchez-Ramos, MD, PhD

Dr. Sanchez-Ramos, a professor of neurology, and molecular pharmacology and physiology, received $120,000 and the part-time assistance of a technician for his project “The role of the gut microbiome in clinical progression of Huntington’s disease (HD).” His co-principal investigator is Amber Southwell, PhD, assistant professor at the Burnett School of Biomedical Sciences, University of Central Florida.

The gut microbiome has been implicated in several metabolic and neurologic diseases and may contribute to metabolic dysfunction in HD, an inherited, fatal neurodegenerative disease. In this study, the researchers will delineate and compare gut microbial changes in overweight and underweight HD patients and in unaffected individuals. They will also assess the effect of human HD gut microbiome on disease in an HD mouse model (underweight and overweight). The project is expected to yield preliminary data for development of experimental therapies to regulate metabolism in HD.

Monica Uddin, PhD

Dr. Uddin, a public health professor with the USF Genomics Program and the Global Health and Infectious Disease Research Program, received $150,000 for her project “The role of human gut microbiota in treatment-resistant depression and response to transcranial magnetic stimulation (TMS).”  Her co-principal investigators are Glenn Currier, MD, MPH, professor and chair of psychiatry, Morsani College of Medicine, and Adetola Louis-Jacques, MD, assistant professor of obstetrics and gynecology in the Morsani College of Medicine and the USF College of Nursing.

Recent preclinical work has revealed that the gut microbiome is strongly associated with symptoms of depression and major depressive disorder. But little is known about how intestinal florae may differ in patients who respond to anti-depression treatment versus those who do not respond despite several attempts. USF Health researchers will characterize the composition and function of gut microbes in patients electing to undergo TMS when standard treatments don’t work. TMS, a procedure using magnetic fields to stimulate brain nerve cells to improve depression symptoms, has been highly effective in treating treatment-resistant depression but does not provide relief to all patients. This project aims to identify gut microbiome-related biomarkers distinguishing TMS responders from non-responders, both to help inform treatment choices and, ultimately, enhance mental health outcomes.

Christian Brechot, MD, PhD, is spearheading the USF Initiative on Microbiomes.

“The initiation of the Microbiome awards is a highlight of the USF Initiative on Microbiomes, meant to engage a transdisciplinary mindset across our academic community.  These awards provide substantial financial assistance to novel projects and we are very grateful to Dr Charles Lockwood, Dr. Paul Sanberg and Dr. Stephen Liggett for their support,” said Christian Brechot, MD, PhD, senior associate dean for research in global affairs at MCOM, associate vice president for international partnerships and innovation, and professor of internal medicine.

“We expect this seed funding will lead to preliminary results needed to pursue full National Institutes of Health or National Science Foundation grant applications. The second call will be advertised soon and further emphasize transdisciplinary research integrating the strengths of different colleges. I believe this strategy will significantly contribute to the success of our USF Initiative on Microbiomes.”

The winning projects were selected from among nine applications.  The next call for award applications will be late January 2020.

USF’s Microbiome Research initiative continues to gain momentum as USF Health and Moffitt Cancer Center faculty met recently to begin exploring how both institutions might best use their collective resources to advance in the emerging, complex field.

A panel of faculty and staff from USF Health and Moffitt Cancer Center discuss infrastructure, equipment and expertise needed to facilitate collaboration and expand microbiome research.

The July 1 Joint Workshop on Microbiomes and Cancer followed USF Health’s first Microbiome Joint Workshop with the University of Florida in May. USF Health and Moffitt scientists and clinicians presented several research topics, ranging from the implications of gut bacteria on colorectal cancer and role of the microbiome in cancer-treatment induced cardiac complications, to microbes as potential biomarkers of cancer treatment outcomes.

Stephen Liggett, MD, associate vice president for research at USF Health, and Thomas Sellers, PhD, director and executive vice president of Moffitt, welcomed workshop participants.

“We hope to take advantage of the brainpower, informatics, facilities and instrumentation between Moffitt and USF Health to move our microbiome research initiative forward in a collaborative and synergistic manner,” Dr. Liggett said.

Thomas Sellers, PhD, director and executive vice president of Moffitt, told participants that one in five cancers is caused by infection. “That just signals how important this (microbiome initiative) can be.”

“This microbiome initiative is an excellent example of how no one institution and no one individual can do the science independently. It takes a village,” said Dr. Sellers, who noted USF and Moffitt’s longstanding history of working together on medical education and cancer biology.

“There’s a lot of strength among the people in this room, some of whom may not have known they were going to be the world’s future microbiome experts. I’m optimistic about this first step in what could be a long and productive collaboration.”

The growth of basic, translational and clinical research centered on microbial populations in environments and hosts is still in its early stages. Just last month, 36 universities identified their institutions as “highly focused” on microbiome studies at the National Microbiome Centers Meeting in Irvine, Calif.

“Most were created over the past two years, and not all focus on the human microbiome,” said Christian Brechot, MD, PhD, associate vice president for international partnerships and innovation, senior associate dean for research in global affairs, and professor of infectious disease and international medicine at the USF Health Morsani College of Medicine. “One characteristic shared by successful centers was that they all started with internal seed grants.”

Source: National Microbiome Centers Meeting, Irvine, CA, June 2019

At the workshop with Moffitt, Dr. Brechot confirmed that nine projects related to USF’s first call for Microbiome Research Awards, are being evaluated (two of the nine focused on cancer). These seed grants will support collaborative research between faculty members from at least two different departments or colleges.

USF Health has a foundation of microbiome research projects headed by individual investigators in medicine, nursing and public health and of supporting infrastructure, including the USF Genomics Program and Omics Hub, the Health Informatics Institute, and core facilities in proteomics and lipidomics. But, Dr. Brechot noted, achieving preeminence in microbiome research requires partnering with other leading institutions, like the University of Florida and Moffitt, to identify potential collaborative pilot projects, build stronger crossdisciplinary teams, and share resources needed to be competitive in attracting external grant funding.

Hua Pan, PhD, assistant professor of cardiovascular sciences at USF Health, is working with Washington University and Moffitt to study whether alterations in the gut microbiome can help predict which patients would be most susceptible to cancer treatment-induced cardiac complications.

A roundtable discussion moderated by Dr. Brechot and Anna Giuliano, PhD, director of Moffitt’s Center for Immunization and Infection Research in Cancer, began addressing the infrastructure, equipment and expertise needed to facilitate collaboration and expand research.

Charles Lockwood, MD, senior vice president for USF Health and MCOM dean, delivered the workshop’s closing remarks.

“Microbiome research is perfect for where we’re headed, because it literally impacts every other area of research,” said Dr. Lockwood, who cited the links between an imbalance in microbial populations (dysbiosis) and Parkinson’s disease, coronary artery disease, and infection-associated preterm births, as just a few examples. “We’ve got to be part of that… and we’re committed to (strategically) resourcing it.”

Anna Giuliano, PhD, director of Moffitt’s Center for Immunization and Infection Research in Cancer, said the challenge is translating complex microbiome research into interventions that will alter the course of disease. “Each cancer is unique… and molecular pathways can vary even within the same cancer.”

-Photos by Freddie Coleman, USF Health Communications and Marketing

University of South Florida neonatologist Akhil Maheshwari, MD, and his team advance research to understand, detect and identify novel treatments for necrotizing enterocolitis, or NEC, a life-threatening inflammatory bowel disease that may afflict premature newborns.

“As we’ve become better at controlling lung disease in premature infants, NEC has emerged as the single largest killer of premature babies,” said Dr. Maheshwari, a physician-scientist who holds the Pamela and Leslie Muma Endowed Chair in Neonatology in the Department of Pediatrics,  USF Health Morsani College of Medicine. Dr. Maheshwari also serves as medical director of the Jennifer Leigh Muma Neonatal Intensive Care Unit (NICU) at Tampa General Hospital.

Akhil Maheshwari, MD, holds the Pamela and Leslie Muma Endowed Chair in Neonatology in the USF Health Department of Pediatrics.

   Listen to Dr. Maheshwari talk about the impact of NEC.

The serious gastrointestinal disorder happens when the small or large intestine becomes inflamed and the lining of the intestinal wall starts to die off.  In the United States, it affects up to 10 percent of extremely low birth weight infants (less than 3.5 lbs.), with a mortality rate of 50 percent. Among premature infants in developing countries, such as India or China, NEC is more common.

With advances in technology and best clinical care practices, more extremely preterm infants are surviving with fewer complications, but NEC remains one of the most challenging diseases confronting neonatologists and pediatric surgeons. The causes of the dreaded condition remain unclear, and there is no treatment.

Translational research enlightened by clinical experience

Caring for tiny, fragile patients in Tampa General Hospital’s NICU adds perspective to the research Dr. Maheshwari conducts in his laboratory at the Morsani College of Medicine. “The vantage point I have as a neonatologist lets me observe NEC in the clinical setting, and I strive in the laboratory to translate this information to understand its pathophysiology,” said the USF Health professor of pediatrics, molecular medicine, and public health.

Over the last decade, Dr. Maheshwari’s group, and others, have found that a third of all instances of NEC in extremely premature infants occurs within 48 hours of receiving a blood transfusion.  He was recently awarded a five-year, $1.5-million R01 grant from the National Heart, Blood and Lung Institute, National Institutes of Health, to understand how blood transfusions may cause bowel injury in premature infants and develop new ways to prevent or treat this condition.

The newborn patients treated at Tampa General Hospital’s Muma Neontal Intensive Care Unit by Dr. Maheshwari, the unit’s medical director, are the among the most fragile and sickest.

In the U.S., necrotizing enterocolitis, or NEC, affects up to 10 percent of extremely low birth weight infants (less than 3.5 lbs.), with a mortality rate of 50 percent.  Causes of the life-threatening inflammatory bowel disease, a focus of Dr. Maheshwari’s research, remain unclear.

   Dr. Maheshwari discusses his latest NIH grant.

Supported by the latest NIH grant, Dr. Maheshwari will use a newborn mouse model to test whether red blood cell transfusions induce intestinal injury, whether the underlying anemia present in almost all premature newborns aggravates this injury, or whether both play a role in causing NEC. The USF researchers will also evaluate whether several standard blood bank practices — longer red blood cell storage, red blood cell washing to remove potentially hazardous electrolytes, and irradiation of transfused blood to help reduce risk of infection — can alter the severity of intestinal injury.

While many critically ill premature infants are stabilized within their first two weeks in the neonatal intensive care unit, within the second to third week a small proportion experience rapid onset of NEC without warning. “I see infants in the unit who were doing well and then die suddenly,” Dr. Maheshwari said. “The impact of this disease can be devastating, both emotionally and in terms of health care costs.”

There is no definitive diagnostic test to identify the disease in its earliest stages; abdominal X-rays can only diagnose when NEC has progressed to severe intestinal damage, including sometimes bowel perforation or peritonitis, Dr. Maheshwari said. Consequently, clinicians err on the side of caution if they suspect NEC — monitoring the condition with X-rays and extensive bloodwork, halting regular feedings, administering IV fluids and antibiotics and counseling an anxious family about what to expect if a NEC diagnosis is confirmed.

“The number of infants in the NICU who undergo testing for NEC is about 10 times more than the number who actually have the disease,” he said.

Half of the babies with confirmed NEC require surgery to excise the damaged intestinal tissue, and 50 percent who go to the operating room die, Dr. Maheshwari said. “The other half who survive end up with anatomically short intestines, so they depend on IV nutrition and often develop nutritional and developmental deficiencies that can affect brain growth.  They are at risk for lifelong complications.”

Mohan Kumar Krishnan, PhD, a research associate in Dr. Maheshwari’s laboratory, uses quantitative real-time polymerase chain reaction (PCR) to monitor amplification of gene expression. The technique helps the researchers determine how the immune system is responding to bacteria in the gut.

Key findings of Dr. Maheshwari’s laboratory

Researchers now believe that three things must all be present in the premature infant’s gut for NEC to occur:  bacteria, inflammation, and a unique signature of white blood cells (monocytes and macrophages) not found in adults with inflammatory bowel diseases.

In addition to the study of red blood cell transfusion-associated NEC, Dr. Maheshwari’s team focuses on two other lines of investigation — determining whether modifying the premature infant’s feedings can alter the immature, hyper-inflammatory nature of macrophages and identifying how the bowel’s inflammatory response in a premature infant differs from that in an adult, so the macrophages might be modified to prevent or treat NEC. The researchers hypothesize that the aggravated inflammatory response seen in the bowels of preterm infants happens because these very small babies with immature immune systems have not yet formed the adaptive mechanisms needed to tolerate the bacteria in their guts.

Dr. Maheshwari (center) with his research team, from left to right: Mohan Kumar Krishnan, PhD, research associate; Tanjing Song, PhD; senior biological scientist; Chitra Palanivel, PhD, postdoctoral research scholar; Kopperuncholan Namachivayam, PhD, research associate; and Thais Queliz Pena, MD, neonatology fellow.

Among some of their most significant findings:

• First to show that premature infants may be at risk of NEC because of a lack of the protein known as transforming growth factor-β2 (TGF-β2), which suppresses inflammatory responses.

• Demonstrated that infants whose bowel injury escalates to NEC have low blood levels of TGFβ2 since birth. “TGFβ2 is the first biomarker that can be obtained on day 1 to help predict which infants are most likely to develop NEC. Its 60-percent accuracy rate is still a six-fold improvement over the way we predict NEC now – by degree of prematurity,” Dr. Maheshwari said.

• While mothers who deliver preterm infants produce breast milk containing a large amount of TGF-β2, Dr.Maheshwari found that the beneficial growth factor in the mothers’ milk is largely biologically inactive. The USF researchers are investigating ways to activate the mother’s milk-borne TGFβ2 – in essence stimulating the milk to undergo the maturation needed to suppress unnecessary inflammation and protect the baby against NEC.

• Discovered that an acute drop in monocyte count in premature infants could be used as a diagnostic test to differentiate NEC from more benign causes of feeding intolerance like prematurity itself. A study led by Dr. Maheshwari found that 70 percent of premature infants with NEC experienced more than a 20-percent drop in monocytes in their blood.

• Recently identified a unique subtype of monocyte, formed in the newborn’s liver, which infiltrates the intestine of premature infants and may promote bowel injury. The subtype could be a new target for treating NEC.

   Dr. Maheshwari gives an example of how a laboratory discovery may change clinical practice.

Dr. Maheshwari was recently awarded a five-year, $1.5-million R01 grant from the NIH’s National Heart, Blood and Lung Institute to study how blood transfusions may cause bowel injury in premature infants and develop new ways to prevent or treat this condition.

In addition to his NIH-supported NEC research, Dr. Maheshwari has a $143,000 American Heart Association grant to study ways to block systemic inflammation and multi-organ dysfunction in very ill babies put on a treatment known extracorpeal membrane oxygenation (ECMO), which uses a heart-lung bypass machine.

“Dr Maheshwari’s work is highly innovative and has relevance well beyond the field of neonatology,” said Patricia Emmanuel, professor and chair of pediatrics at the USF Health Morsani College of Medicine.  “He brings great curiosity and passion to his research and is a wonderful role model for fellows and residents.”

Endowment key to  research benefitting tiniest newborns

The endowment by Pam and Les Muma to advance USF-TGH research and care for the sickest newborns helps support the infrastructure of Dr. Maheshwari’s highly specialized laboratory, including a machine that can measure a drop of a blood so tiny it fits on the head of a pin.

“Endowments are so critical,” Dr. Maheshwari said. “The equipment needed for the type of research we do is very specific for premature newborns, and doesn’t exist in most universities.”

Dr. Maheshwiari came to USF in 2014 from the University of Illinois at Chicago (UIC), where he was an associate professor pediatrics and chief of the Division of Neonatology. Prior to his tenure at UIC, he was an assistant professor at the University of Alabama at Birmingham and received several young investigator awards, including the American Gastroenterological Association Research Scholar Award and the Procter and Gamble GI Scholar Award.

The Muma endowment supports highly specialized equipment in Dr. Maheshwari’s neonatal research laboratory, including a machine that can measure a drop of a blood so tiny it fits on the head of a pin.

Dr. Maheshwari is a member of the editorial board of Maternal Health, Neonatology and Perinatology and several other professional journals and served on several grant review panels. He holds six provisional patents for new anti-inflammatory agents.

He earned his medical degree from the Institute of Medical Sciences, Varanasi, India, completed a pediatrics residency at the University of Florida, and received fellowship training in neonatology at USF.

Dr. Maheshwari with research associate Kopperuncholan Namachivayam, who works at a hematology analyzer that counts and separates various blood cell types including immune cells the researchers are interested in studying.

Photos by Eric Younghans, USF Health Communications