Strawberry flavonoid could spare diabetics from complications, fight Alzheimer's
Fisetin in strawberries could lessen complications of diabetes and more, according to a new study. Researchers from the Salk Institute are studying a flavonoid in strawberries called fisetin that might help control common complications of diabetes. The compound might also help prevent Alzheimer's disease and disorders of the nervous system, found in mouse studies.
Strawberry flavonoid might prevent type 1 and type 2 diabetes complications
Investigators at Salk Institute's Cellular Neurobiology Laboratory (CNL) discovered fisetin that is abundant in strawberries and also present in other fruits and vegetables enhanced memory in mice and promoted survival of neurons - specialized cells that transmit and receive electrical and chemical signals.
The finding, published in the June 27, 2011, issue of PLoS ONE, ..."describes for the first time a drug that prevents both kidney and brain complications in a type 1 diabetes mouse model," said David Schubert, Ph.D., professor and head of the Cellular Neurobiology Laboratory and one of the manuscript's co-authors. "Moreover, it demonstrates the probable molecular basis of how the therapeutic is working."
To find the benefits of the strawberry flavonoid for type 1 diabetes, the researchers studied Akita mice that have elevated blood sugars typical of juvenile onset diabetes. The mice also develop the same complications seen in both type 1 and type 2 diabetes, including kidney disease, neuropathy (nerve destruction) and diabetic retinopathy that can lead to blindness.
Pam Maher, Ph.D., a senior staff scientist in the CNL and corresponding study co-author first identified the protective effect of fisetin ten years ago.
Maher explains, “In plants, flavonoids act as sunscreens and protect leaves and fruit from insects. As foods they are implicated in the protective effect of the 'Mediterranean Diet.'"
After studying the strawberry compound in the lab and in mice, the researcher team hypothesized fisetin could target multiple organs to protect from diabetes complications.
Mice given fisetin in the diet continued to experience diabetes, but the strawberry flavonoid lowered protein levels in the urine that indicate nephropathy, or kidney damage from diabetes. Fisetin improved anxiety in the mice and reduced kidney enlargement.
Most mice put in a large area become exploratory," says Maher. "But anxious mice tend not to move around. Akita mice showed enhanced anxiety behavior, but fisetin feeding restored their locomotion to more normal levels."
The scientists also found lower levels of advanced glycation end-products, referred to as AGEs that correlated with increased production of an enzyme that removes precursors of the toxic AGE’s. High levels of advanced glycation end-products are thought to contribute to diabetes complications, inflammation and even cancer.
The effect of the strawberry compound on AGE’s leads the scientists to hypothesize fisetin might show promise for cancer prevention and Alzheimer’s disease from increased activity of enzyme glyoxalase 1 – the AGE antagonist.
Shubert says, “We and others have shown that diabetes may be a risk factor for Alzheimer's disease, making identification of a safe prophylactic like fisetin highly significant.”
Maher suggests the benefits of flavonoids and polyphenols in fruits and vegetables have been overly expounded to the public who may be ignoring the health benefits of eating fruits and vegetables.
"Polyphenolics like fisetin and those in blueberry extracts are found in fruits and vegetables and are related to each other chemically," she says. "There is increasing evidence that they all work in multiple diseases. Hopefully some combination of these compounds will eventually get to the clinic."
Funding needed to go forward with studies
The researchers note the difficulty in studying natural compounds for fighting disease that could be developed into pharmaceutical compounds, versus synthetic drugs.
In order to get the benefits for fighting diabetes complications, the researchers say it would mean eating 36 strawberries a day. Shubert says, "We will never know if a compound like fisetin works in humans until someone is willing to support a clinical trial."
For now Shubert says the best advice really is to, "Eat a balanced diet and as much freshly prepared organic food as possible, get some exercise, keep socially and mentally active and avoid sodas with sugar and highly processed foods since they can contain high levels of AGEs.”
The studies, conducted by the Salk Institute, show strawberries, high in the flavonoid fisetin ,might help prevent complications of diabetes, protect from Alzheimer’ disease and other nervous system disorders and potentially lower risk of cancer, also shown in lab culture studies. The researchers envision a time when fisetin like drugs can be taken as a supplement that would be well-absorbed and metabolized.
Maher P, Dargusch R, Ehren JL, Okada S, Sharma K, et al. (2011)
"Fisetin Lowers Methylglyoxal Dependent Protein Glycation and Limits the Complications of Diabetes"
PLoS ONE 6(6): e21226. doi:10.1371/journal.pone.0021226