A new study shows that injecting natural hormones directly into the intestine can reduce cognitive impairment associated with stroke in the long term. The results of this study confirm that a healthy gut means a healthy brain, and pave the way for treatments to reduce the chronic sequelae of stroke.
Many studies support this, and it is now almost a given. The gut and brain are linked, and the health of one directly affects the health of the other.
Worldwide, one in four people over the age of 25 will suffer a stroke in their lifetime. Sudden symptoms that indicate a stroke are well known and are treated with intensive physical and occupational therapy. However, the long-term effects of stroke (for example, cognitive impairment and depression caused by damage to brain cells and neurons) can be difficult to treat. But a new study by researchers at Texas A&M University taps into the gut-brain connection and uses naturally occurring hormones to protect the brain from the long-term damage of stroke.
“Stroke is one of the main causes of dementia and AD (Alzheimer’s disease),” said Dr. Farida Sorabji, chair of the university’s Department of Neuroscience and Experimental Therapeutics and corresponding author of the study. . “Stroke has acute, immediate effects, but it also has long-term effects that impact the quality of life of patients as well as carers, so understanding how to improve long-term outcomes is of great importance. There is a lot of interest.”
Rather than external signs and symptoms, the researchers were interested in the less obvious internal effects: what happens in the gut after a stroke.
“Some people cannot lift their arms, their face droops to one side, and they have slurred speech,” Sorabji explained. “This is classic and happens very quickly. What we found is that within minutes of a stroke, normal intestinal anatomy is completely destroyed. That’s what it means.
Strokes usually cause leaks in the intestinal wall, which acts as a barrier between the intestines and the rest of the body. Digestive bacteria can leave the intestines through leaky walls and harm other body systems, including the brain. Even if the bacteria do not reach the brain, they can trigger an inflammatory response throughout the body that worsens the effects of stroke, further damaging the brain and increasing the risk of long-term cognitive impairment.
“If you just repair the brain, you’ll see short-term benefits, but you won’t see long-term improvements because your gut is still leaky,” Sorabji says. “It (causes inflammation) and it’s always affecting brain function in the long term.”
The study showed that the hormone insulin-like growth factor-1 (IGF-1) reduces, but does not reduce, levels of small inflammatory proteins called cytokines in the brain area where the stroke occurred. was conducted based on previous research. The impact of IGF-1 on cytokines circulating outside the brain remains unanswered. They gave rats with left-sided strokes either IGF-1 or a placebo for 48 hours 4 hours after the stroke. They then tested cognitive abilities and sensorimotor function in addition to assessing gut health.
Researchers found that the effectiveness of IGF-1 treatment was dependent on its route of administration. When delivered intravenously and traveling through the bloodstream, it provides “powerful neuroprotection” by reducing infarct size (the area deprived of blood and oxygen due to a stroke) and improving sensorimotor performance in the short term. has been brought. , but does not affect cognitive impairment in the long term. However, delivering it directly to the intestine had the opposite effect. While acute outcomes were not improved, chronic cognitive impairment was “definitely improved.”
When IGF-1 was delivered to the intestine, it was not detected in the brain, so the researchers believe that IGF-1 acts on the body’s peripheral immune organs, affecting the immune cells that produce IGF-1 and causing brain damage. We hypothesized that this would prevent the degeneration of
“This study strongly suggests that the gut is a direct or intermediate target for long-term benefits on stroke outcomes,” the researchers said. “This study adds to the growing literature that improving gut health can aid in recovery from acute neurological injury and, conversely, that gut health can influence neurological function. .”
In addition to studying IGF-1, researchers are also investigating transplanting healthy intestinal stem cells into the intestine damaged by stroke. Sohrabji was the lead author of a 2023 study that investigated this as a new treatment.
“We were pretty confident that[stem cells]would repair the intestine,” Sohrabji said. “What we didn’t know, and what was a pleasant surprise to us, was that in the process we also improved stroke outcomes. As a result (of the treatment), the amount of dead tissue in the brain from stroke decreased decreased, and cognitive function was maintained.”
Researchers plan to continue their work to develop treatments that reduce the long-term cognitive effects experienced by patients after stroke.
The study was published in the journal Brain, Behavior, and Immunity.
Source: Texas A&M University
