image: Researchers used human intestinal organoids in their study. This confocal immunofluorescence image shows a stem cell-derived human intestinal organoid treated with zinc.
Credit: The Hackam Lab, Johns Hopkins Medicine
Researchers from Johns Hopkins Children’s Center say they have identified a gene pathway involving the mineral zinc in mice that may someday point the way to using zinc-based supplements to directly help people with a rare disorder called short bowel syndrome (SBS).
The findings, published Oct. 7 in Nature Communications, help advance efforts toward more effective, potential treatment regimens for both children and adults with the debilitating condition.
SBS, which affects 10,000–20,000 adults and children in the United States, is marked by damage to and shortening of the small intestine. While in rare cases, children can be born with SBS, it is more often a complication of conditions such as necrotizing enterocolitis — a disease that affects the intestines of premature infants.
Children with SBS have a reduced ability to absorb nutrients from the diet, often require intravenous nutritional support, and experience significant complications including malnutrition, dehydration, unintentional weight loss and death. Treatment and management approaches — including special diets, surgical procedures and, occasionally, small bowel transplants, are only partially effective, and often result in side effects including infection and extended hospital stays.
“Short bowel syndrome is a huge problem, and has a great impact on patients who experience this condition and their families,” says David Hackam, surgeon-in-chief and co-director of Johns Hopkins Children’s Center and senior author of the study. Their study was designed, he said, to identify whether there may be new treatment options for patients with this disease. Surprisingly, they identified a previously unrecognized role for zinc, to protect and even grow what bowel remains in people with SBS.
In the first part of their study, researchers used a mouse model with SBS, which exhibited characteristics similar to humans with the disease. Researchers examined what a shortened bowel looks like over time, and discovered that the villi — tiny, hairlike, fingerlike projections in the small intestine that absorb the food and nutrients you eat — started to naturally grow and become longer.
“The villi were adapting — you could say that they were reaching out for more food,” says Hackam. However, according to Hackam, these villi could not fully “catch up” or heal.
Next, the researchers examined how the healing process would work in humans with SBS, and identified possible gene pathways that may help intestines adapt or “speed up” the healing process. To do that, they implanted human-induced stem cells into a mouse, so it would develop humanlike intestines.
The researchers then used single cell RNA sequencing to measure how specific genes are expressed. That enabled them to map multiple gene pathways in the model’s intestines, and examine which genes affected recovery, says Hackam.
After a month of recovery from the implantation of humanlike intestines, researchers studied all of the genes that were either turned on or turned off as the intestines adapted and tried to heal. They discovered that the zinc transport genes known as SLC39A4 and SLC39A5, which are found in the small intestine and are key to transporting zinc in the body, were upregulated, or turned on, and affected the ability of the bowel to recover. Using quantitative polymerase chain reaction (qPCR), a method that measures gene levels by looking at how much RNA is present, researchers found that the levels of these zinc transporter genes in the intestines of the experimental models were up to 4 or 5 times higher than in control subjects.
Next, to assess whether supplementing with zinc could help advance or “speed up” intestinal function and healing, the researchers fed the mice with SBS a liquid, high-zinc diet, (65 milligrams per kilogram per day of zinc acetate). Mice on a high-zinc diet not only gained more weight compared with those on standard or zinc-depleted diets, but they also experienced a partial reversal of the typical effects of SBS. By the end of the first week, mice on the standard liquid, zinc-depleted diet (13.5 milligrams per kilogram per day of zinc acetate) had lost more weight (13.38 ± 1.11%), while those receiving extra zinc had significantly less weight loss (7.1 ± 1.19%). Importantly, the high-zinc diet led to better survival rates, 85.7% compared to 66.67%, and improved the capacity of the intestines to absorb nutrients and fluids due to longer and healthier intestinal villi. “Overall, we found that boosting zinc intake helped the mice recover better and increased their chances of survival,” says Maame Sampah, a research fellow and surgical trainee working with Hackam at Johns Hopkins Children’s Center and a co-author of the study.
To confirm these findings in human tissue samples, researchers examined tissue from 26 people (14 with SBS) who underwent endoscopic or surgical procedures between 2008 and 2020 at Washington University in St Louis. The analysis revealed those with SBS had much higher levels of RNA from the gene SLC39A5, while levels of the other key zinc gene, SLC39A4, were the same in both groups. However, the proteins made by these genes — the zinc transporter proteins, ZIP4 and ZIP5 — ended up in different locations within the intestinal cells of patients with SBS compared with controls. Researchers say these findings suggest that the intestines of these patients were working overtime to grab as much zinc as possible, and highlight the therapeutic potential of using the supplement as a treatment for SBS management.
Researchers caution that further studies on animals and in clinical trials must be done to test whether zinc supplements are safe and effective for therapy in people. However, they believe the findings offer an opportunity to better understand short bowel syndrome.
“Our study findings provide a lot of hope for patients and families who are struggling with SBS, says Hackam. “There may be potential new treatment regimens on the horizon that are safe and effective.”
Along with Hackam and Sampah, authors from Johns Hopkins are Hannah Moore, Raheel Ahmad, Johannes Duess, Peng Lu, Carla Lopez, Steve Steinway, Daniel Scheese, Zachariah Raouf, Koichi Tsuboi, Jeffrey Ding, Connor Caputo, Madison McFarland, William Fulton, Sanxia Wang, Meghan Wang, Thomas Prindle, Samuel Alaish and Chhinder Sodhi. Authors from Washington University School of Medicine, St. Louis, are Vered Gazit and Deborah Rubin.
The study was funded by grants from the National Institutes of Health under award numbers R35GM141956 and T32DK007713.
No authors declared conflicts of interest under Johns Hopkins University School of Medicine policies.
Journal
Nature Communications