let's take a look at the magical effect of vitamin K!
Vitamin K is a kind of fat-soluble vitamin, and its basic structure is 2-methyl-1,4-naphthoquinone, which is the chemical structure of vitamin K3. Vitamin K1 and vitamin K2 are common in nature, and vitamin K3 is artificially synthesized. The main difference between them is the difference in their side chain groups. Vitamin K is also called coagulation vitamin because it was initially discovered that the physiological function of vitamin K is mainly to promote the synthesis of prothrombin in the liver and regulate the synthesis of coagulation factors VII, IX, and X, thereby promoting blood coagulation.
1 Research progress of vitamin K
Vitamin K compounds were discovered in the 1930s, and it was initially believed that vitamin K was only related to the blood coagulation function of the body. In recent years, with the in-depth study of vitamin K-dependent bone protein in bone tissue, it was found that vitamin K has an effect on the metabolism of collagen tissue, especially bone tissue. Three kinds of vitamin K-dependent bone proteins have been found to participate in bone metabolism. They are bone-C carboxylated glutamate protein (BGP, referred to as osteocalcin), matrix-C carboxylated glutamate protein (MGP) and protein S. Among them, there are many studies on bone-C carboxylated glutamic acid protein, which is produced by osteoblasts. After being activated, the A helix in its peptide chain is closely combined with calcium ions in hydroxyapatite, and they precipitate together in the bone. In tissue, it promotes bone mineralization. It is generally believed that vitamin K participates in bone metabolism by regulating the post-translational carboxylation modification process of vitamin K-dependent bone proteins such as bone-C carboxylated glutamic acid protein, so the lack of vitamin K will interfere with the normal metabolism of bone tissue, and it is harmful to rats. Studies have shown that vitamin K deficiency leads to increased bone catabolism. In addition, it has also been reported that the carboxylation level of bone-C carboxylated glutamic acid protein in rats lacking vitamin K is decreased, which affects bone anabolism.
2 Research status of vitamin K in fish
Research on vitamin K in fish has also been limited to research on its blood coagulation function. Ponston reported that the coagulation time of brook salmon was delayed and the hematocrit value decreased in the absence of vitamin K, but the growth rate was not significantly affected; Taveekijakarn's study on oncorhynchus rhodurus of the genus Salmon showed that the vitamin K deficiency group had a mortality rate of 50 %; Udagawa believes that bottom fish will be affected by vitamin K deficiency during the spawning season. Grahl-Madsen's research on cod (average weight 1.7g) concluded that there was no significant difference in mortality, hematological indicators and coagulation time among the test groups with MSB content of 0-21.5mg per kilogram of dry feed. The minimum vitamin K requirement for fish is 0.2 mg per kg dry feed. However, studies on some fish suggest that vitamin K deficiency will not cause obvious physiological phenomena, such as Kitamura et al.’s research on rainbow trout, that vitamin K deficiency does not cause obvious symptoms, only anemia tendency. In addition, high amounts of vitamin K can have negative effects, which have been reported in mammals and fish. According to Grahl-Madsen, the body weight of cod in the group of 6.mg and 9.8mg of MSB per kilogram of dry feed increased faster than that of the group of 21.5mg of MSB. The growth of Atlantic salmon was also inhibited when the feeding amount was 30mg MSB/kg dry feed.
Recent studies have found that the lack of vitamin K will also affect the normal growth of fish bone tissue. Udagawa studied the effect of vitamin K1 and K3 in the bottom fish feed on the vertebrae, and found that the number of individuals with bone abnormalities in the vitamin K-deficient group increased significantly, and it is believed that vitamin K is necessary for its bone growth. In addition, it was also found that feeding a high amount of vitamin K3 would cause an increase in bone abnormality rate, while feeding a high amount of vitamin K1 had no abnormal changes in bone; at the same time, the abnormality of the vertebra itself in the vitamin K deficiency group and the K3 added area was higher than that in the K1 added area. There is a significant increase in the area, indicating that as vitamin K, K1 is more suitable than K3.
3Sources of Vitamin K
Natural sources of vitamin K mainly include vitamin K1 and vitamin K2. Vitamin K1 is also called phylloquinone PK, and its main source is plants. Vitamin K2, also known as menaquinone MK, mainly comes from bacteria. In addition, there are some synthetic vitamin K and many derivatives. Vitamin K as a fish feed additive is mainly vitamin K3, often in the form of its water-soluble menadione sodium bisulfite derivative (MSB). Vitamin K3 is a synthetic vitamin K, which itself has no biological activity. The major part of the absorption is excreted, and only a small amount is converted into active MK-4 in the liver, which is the case in both rats and cod. Therefore, the addition of MSB is often excessive in practical situations.
The vitamin K requirement of mammals is mainly met in two ways, one is food absorption; the other is synthesized by microorganisms in the digestive tract, but both food ingredients and antibiotics will affect the synthesis of vitamin K in the gut. There is no clear conclusion about the significance of vitamin K production in fish digestive tract. It is generally believed that the vitamin K requirement of salmon and trout is 10mg per kilogram of dry feed. If the vitamin K content in the food is low or antibiotics are added to the food, the blood clotting time will be prolonged, anemia will occur, and the gills, eyes and blood vessels will be damaged. Bleeding. However, no symptoms of vitamin K deficiency were found in the food of channel fish containing antibiotics.
4 Content and detection method of vitamin K in fish
Since vitamin K was discovered as an anticoagulant substance, indicators to evaluate the coagulation function of the body are used to reflect the status of vitamin K, such as the determination of vitamin K-dependent coagulation factors or prothrombin time, partial thromboplastin time, and blood coagulation. Tests, etc., but these are functional indicators, and when they are abnormal, it indicates that the body's vitamin K deficiency has reached a serious level. Theoretically, the content of vitamin K in serum is an index reflecting the vitamin K in the body. At present, high-pressure liquid chromatography can be used to measure the content of vitamin K in serum, liver and kidney, and muscle tissue by using fluorescence detector and electrochemical detector. However, the actual situation is that vitamin K in serum The content is quite low and quantitative determination is difficult. This is why the study of vitamin K lags far behind water-soluble vitamins and other fat-soluble vitamins, such as vitamins D, A, and E.
The content and form of vitamin K in fish are affected by the content and form of vitamin K in the food. For example, when the vitamin K fed to bottom fish is 25 mg/kg MSB and 2500 mg/kg MSB, the No PK can be detected in fish, but only a certain amount of MK-4 can be detected. Even if a high dose of MSB is fed, the amount of MK-4 will not be very high, indicating that vitamin K is only partly in the form of MK-4 Infiltrated into the fish body, on the contrary, if PK was fed, what was detected in the fish body was mainly PK instead of MK-4.
A certain amount of PK can be detected in the liver of some wild fishes, such as Far Eastern sardines, mackerel and sweetfish, but the corresponding MK-4 has not been detected in cultured fish fed with MSB-containing feed. The reason why PK but not MK accumulates in the liver is unclear, but it is speculated that PK and not MK play a role in preventing vitamin K deficiency in natural fish.
Because vitamin K is not easy to detect, and intestinal bacteria can partially synthesize it, it is difficult to determine the feeding amount, so the research on vitamin K has not attracted people's attention. Bone abnormality is a serious phenomenon in fish fry stage at present, but with the discovery of vitamin K's role in fish bone growth, its significance will attract people's attention.
