Team:UST Beijing/HP/Gold
Background
We pay respectful attention to the traditional Chinese medicine such as notoginseng. We learned that notoginseng has much beneficial effect to our body and helps us to keep away from cardiovascular diseases. However, unfortunately, bioavailability of the active ingredients of notoginseng is very low, which holds back its efficacy.
All the time, the notoginseng is hard to be absorbed by the body because of its glycosylation. So we want to solve this problem by means of synthetic biology.
What we plan to do
We plan to build a new kind of E.coli producing β-glucosidase which digests glycosides from ginsenosides, just like what our intestines can do. For notoginseng root solid fermentation, since one of the main decomposition products is arabinose, we wish this special kind of E.coli we build can transform its metabolic pathways under the control of arabinose. Take these into consideration, we plan to build a double plasmid system.
What is notoginseng?
Panax notoginseng is a plant of the Araliaceae ginseng species. As a valuable medicine, it has a cultivation history of more than 400 years in China.
As a traditional Chinese herbal medicine, its biological characteristics have been very detailed. In recent years, there are about 700 peer-reviewed scientific reports related to P. notoginseng published annually. Main reports concentrated in the the separation and extraction of chemical composition and pharmacology pharmaco-dynamics. The complex chemical composition in P. notoginseng is closely related to the effects. Currently, more than 100 compounds have been found in P. notoginseng, among which the active ingredients are mainly saponins and dencichine. Our project focuses on saponins and its effect to our body.
P. Notoginseng pharmacological effects are mainly reflected in the blood system, cardiovascular system, cerebrovascular system, nervous system, metabolism, immune regulation system, and so on. We studied the process after saponins got into our body and were absorbed. Furthermore, we tried to form model of the regulation in balancing cholesterol levels.
How our body keep cholesterol in balance?
Cholesterol is a waxy, fatty steroid substance. Some of cholesterol comes from our diets. Since cholesterol is present in all mammals, we consume it whenever we eat meat. However, most of the cholesterol circulating in bloodstream is produced within our own body. The intestines, adrenal glands and reproductive organs produce some, but most is produced by liver.
Another factor that accounts for high blood levels is that circulating cholesterol is recycled or reabsorbed. When the liver excretes it along with bile, about 50% is reabsorbed through the small intestine and ends up back in the bloodstream.
Lipoproteins carrying a large amount of cholesterol have a lower density, which makes them less buoyant and more likely to stick to the insides of the arteries. Lipoproteins carrying a smaller amount of cholesterol are denser, more buoyant and less likely to clog arteries. They actually help to carry the less dense lipoproteins back to the liver.
For the sake of simplicity, health care professionals refer to these two kinds of lipoproteins as LDL (low density lipoproteins) and HDL (high density lipoproteins. In common terms, we often hear that LDL is bad and HDL is good.
The ABCA1 gene belongs to a group of genes called the ATP-binding cassette family, which provides instructions for making proteins that transport molecules across cell membranes. The ABCA1 protein is produced in many tissues, with high amounts found in the liver and in immune system cells called macrophages. This protein moves cholesterol and certain fats called phospholipids across the cell membrane to the outside of the cell. These substances are then picked up by a protein called apolipoprotein A-I (apoA-I), which is produced from the APOA1 gene. ApoA-I, cholesterol, and phospholipids combine to make HDL. Once in the liver, cholesterol and phospholipids are redistributed to other tissues or removed from the body. The process of removing excess cholesterol from cells is extremely important for balancing cholesterol levels and maintaining cardiovascular health.
Pharmacokinetics of ginsenoside in body
As reported, using HPLC –UV method to determine the percentages of two of main active saponins in P.notogindeng, ginsenoside Rb1, and ginsenoside Rg1. Results indicated that the recovery were 97.95% for ginsenoside Rb1, and 108.73% for ginsenoside R_g1, relative standard deviation were 1.56% for ginsenoside Rb1, and 2.34% for ginsenoside Rg1, and content percentages were 30.62% and 32.20% for ginsenoside Rb1 and ginsenoside Rg1 Octanol-water system was used to determine the apparent partition coefficients of ginsenoside Rb1 and Rg1 from P.notoginseng, and the effects of heat, light and pH on stability of ginsenoside Rb1, and Rg1 were studied. Results showed that the apparent partition coefficients were between 4 and 5 for both of ginsenoside Rb1 and Rg1. Both of them were sensitive to light, heat and acid condition, and were relatively stable in normal and alkalescence condition.
HPLC method was established to analysis ginsenoside Rb1 andRg1, in biological samples such as serum. Results showed that this method which was sensitive, effective and repeatable can meet the requirement to the biological samples. Then the pharmacokinetic features of ginsenoside Rb1 and Rg1 from P.notoginseng in rats were elucidated. The decline of ginsenoside Rb1, in serum could be described by a two-compartment model. The half-life of αphase was 29.40 min and that of β phase was18.57h. Ginsenoside R_b1, was absorbed from the digestive tract and the absolute bioavailability via P.O. was 4.35%. The pharmacokinetics of Rg1 in rats also could be described by a two-compartment model.
We reason that glycosides of ginsenosides are the main cause for the low absolute bioavailability of P.notoginseng, so that much of the benefits of notoginseng root can not come into effect. We try to find a method which may enhance absorption and increase bioavailbility using synthetic biology.
Reference
1.Xia Pengguo, Zhang Shuncang, Liang Zongsuo, Qi Zhihong. Research history and overview of chemical constituents of Panax notoginseng. Chinese Traditional and Herbal Drugs. 2014(45): 2564-2570. 2.Xu Qingfang. Degree thesis. 2003. 3.Balance Your Cholesterol Naturally: http://www.lowercholesterolinfo.com/ 4.Gene Home Reference: https://ghr.nlm.nih.gov/gene/ABCA1
