Benefits of black tea and green tea: An Antihypertensive study

Compounds in both green and black tea relax blood vessels by activating ion channel proteins in the blood vessel wall, according to a new study from the University of California, Irvine. The research sheds light on tea's antihypertensive effects and could pave the way for the development of novel blood pressure drugs.

Geoffrey Abbott, PhD, a professor in the Department of Physiology and Biophysics at the University of California, Irvine, made the finding, which was published in Cellular Physiology and Biochemistry. "KCNQ5 potassium channel activation underlies vasodilation by tea," a paper titled "KCNQ5 potassium channel activation underlies vasodilation by tea," was first authored by Kaitlyn Redford, a graduate student in the Abbott Lab.

According to the findings, two catechin-type flavonoid chemicals found in tea (epicatechin gallate and epigallocatechin-3-gallate) activate a specific type of ion channel protein known as KCNQ5, which permits potassium ions to diffuse out of cells and lower neuronal excitability. Because KCNQ5 is found in the smooth muscle that lines blood arteries, it was hypothesized that its activation by tea catechins would relax blood vessels, which was validated by researchers at the University of Copenhagen.

"We discovered that particular catechins bind to the foot of the voltage sensor, which is the portion of KCNQ5 that allows the channel to open in response to cellular excitation, using computer modelling and mutagenesis studies." According to Abbott, "this binding allows the channel to open considerably more quickly and early in the cellular excitation process."

Because hypertension affects up to one-third of the world's adult population and is the leading modifiable risk factor for worldwide cardiovascular disease and premature mortality, new techniques to treating hypertension have immense potential to enhance global public health. Previous research has shown that drinking green or black tea can lower blood pressure by a modest but constant amount, and catechins have been linked to this effect. The discovery of KCNQ5 as a novel target for tea catechins' hypertensive actions should help with medicinal chemistry optimization for better potency and efficacy.

KCNQ5 is expressed in numerous areas of the brain, where it modulates electrical activity and signalling between neurons, in addition to its involvement in modulating vascular tone. There are pathogenic KCNQ5 gene variations that disrupt channel function and cause epileptic encephalopathy, a severe debilitating developmental condition characterized by frequent seizures. Because catechins may traverse the blood-brain barrier, their capacity to activate KCNQ5 could point to a future technique for repairing malfunctioning KCNQ5 channels and alleviating brain excitability disorders caused by them.

Tea has been manufactured and eaten for almost 4,000 years, and around 2 billion cups of tea are consumed each day around the world, second only to water in terms of volume consumed. The three most popular caffeinated teas (green, oolong, and black) are all made from the leaves of the evergreen Camellia sinensis plant, with the distinctions originating from differing levels of fermentation during the tea-making process.

In nations such as the United Kingdom and the United States, black tea is typically blended with milk before being drank. When black tea was directly administered to cells containing the KCNQ5 channel, the researchers discovered that adding milk blocked the tea's beneficial KCNQ5-activating effects. Abbott, on the other hand, claims that "We don't feel that this indicates that in order to reap the benefits of tea, one must drink it without milk. We are certain that the environment in the human stomach would separate the catechins from the proteins and other compounds in milk that would otherwise prevent catechins from exerting their positive effects."

Other investigations have confirmed this concept, with tea providing antihypertensive effects regardless of milk consumption. Using mass spectrometry, the researchers discovered that heating green tea to 35 degrees Celsius changes its chemical composition, making it more effective in activating KCNQ5.

"This temperature is obtained once tea is drunk, regardless of whether it is consumed iced or heated," Abbott noted, "since human body temperature is roughly 37 degrees Celsius." "As a result, simply drinking tea activates its antihypertensive characteristics."

The National Institutes of Health, the National Institute of General Medical Sciences, the National Institute of Neurological Disorders and Stroke, the Lundbeck Foundation, and the Danmarks Frie Forskningsfond all contributed to this research.

Reference:

Kaitlyn E. Redford, Salomé Rognant, Thomas A. Jepps, Geoffrey W. Abbott. KCNQ5 Potassium Channel Activation Underlies Vasodilation by Tea. Cellular Physiology and Biochemistry, 2021 DOI: 10.33594/000000337