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A new study evaluated the benefits of green tea polyphenols on glucose regulation and skeletal muscle metabolism in mice with elevated blood glucose levels.
Green tea is a popular drink in many parts of the world. The well-recognized benefits of green tea include its antioxidant, anti-inflammatory, anti-mutagenic and weight loss properties. Numerous studies have evaluated the properties of green tea and the researchers continue to discover new health benefits of green tea.
What is in a cup of green tea?
Tea contains polyphenols that are strong antioxidants with many biochemical activities. Green tea polyphenols mainly consist of epigallocatechin gallate (EGCG), which is the most powerful catechins. Research shows that EGCG can reduce the oxidative damage of DNA caused by highly reactive molecules called free radicals that are produced during various metabolic processes.
Oxidative stress in patients with type 2 diabetes causes skeletal muscle dysfunction
Glucose homeostasis is the body’s mechanism of regulating blood glucose levels by balancing the levels of insulin and glucagon, the hormones produced by the pancreas. Insulin lowers blood glucose by increasing glucose uptake in muscles and adipose tissue and by promoting glucose breakdown in the liver. Glucagon, on the other hand, promotes the production of glucose in response to a fall in blood glucose levels.
Patients with type 2 diabetes have prolonged elevated blood glucose levels that result in increased oxidative stress. This increased oxidative stress decreases transport of glucose to skeletal muscle, eventually causing skeletal muscle dysfunction, loss of muscle mass and muscle strength.
Polyphenolic compounds reduce complications of type 2 diabetes
Several studies have demonstrated the beneficial effects of flavonoids that are bioactive polyphenolic compounds, found in some supplements, bioactive components, and botanicals. These polyphenolic compounds help in maintaining the oxidant-antioxidant balance that prevents complications associated with high blood glucose levels in type 2 diabetes.
Tocotrienols, a group of chemicals that are part of the vitamin E family, are bioactive compounds that fight the free radical damage and act as anti-diabetic agents. Naturally found in rice bran oil, coconut oil, cocoa butter, barley, and wheat germ, tocotrienols offer unique health benefits.
Researchers study the benefits of green tea polyphenols and annatto-extracted tocotrienols
A team of researchers in the University of Texas, San Antonio, United States, investigated the potential benefits of green tea polyphenols and annatto-extracted tocotrienols both individually and in combination, on the health of skeletal muscle and regulation of glucose in obese mice.
The study, published recently in the Journal of Nutritional Biochemistry, was conducted on 48 male mice divided into 4 groups- tocotrienol, no tocotrienol, green tea polyphenols, and no green tea polyphenols. The researchers fed a high-fat diet to mice for 14 weeks. After treatment, the researchers performed various biochemical assays to test the mice for glucose levels, insulin tolerance and carried out pancreatic and skeletal muscle tissue analysis.
Both green tea and tocotrienols treatments increased muscle mass
The results of the study showed that the benefits of green tea polyphenols and tocotrienols reduce skeletal muscle damage due to diabetes and the researchers observed an increase in muscle mass after treatment with green tea and tocotrienols. These findings corroborate the evidence from other studies that suggest that the benefits of green tea extend to maintaining bone and muscle health.
Green tea polyphenols improved glucose tolerance and insulin resistance
The researchers observed that green tea polyphenols helped increase levels of insulin in blood that may result in improved glucose tolerance and reduced insulin resistance. Green tea was found to be more effective than tocotrienols in improving glucose regulation.
While both tocotrienols and green tea polyphenols have strong antioxidant properties, the results of this study did not show an added benefit of both these compounds used in combination.
Could the benefits of green tea be used for therapeutic purpose?
Muscle atrophy or sarcopenia is a condition associated with insulin resistance and increased blood glucose levels seen in diabetic patients. The results of this study are promising and suggest that benefits of green tea may be used in preventing muscle atrophy in patients with diabetes. The green tea polyphenols can improve muscle mass and function by reducing the oxidative stress and increasing the activity of certain mitochondrial enzymes.
In conclusion, the findings of this study highlight the benefits of green tea polyphenols in improving glucose regulation and improving skeletal muscle metabolism. These results help the researchers have a better understanding of how these bioactive compounds can be used as a therapeutic treatment to prevent complications of diseases such as diabetes.
Written by Preeti Paul, MS Biochemistry
Reference: Eunhee Chung et al., Effects of annatto-extracted tocotrienols and green tea polyphenols on glucose homeostasis and skeletal muscle metabolism in obese male mice. Journal of Nutritional Biochemistry 67 (2019) 36-43. https://doi.org/10.1016/j.jnutbio.2019.01.021