BCAA stands for branched chain amino acids. It is referred to 3 essential amino acids-leucine, isoleucine & valine which are considered to be building blocks of protein. These proteins facilitate building new proteins, providing energy for muscles & controlling glucose metabolism. Due to these roles, BCAA is considered to be an important pre workout diet since it is used to stimulate protein synthesis, aid in muscle growth & reduce muscle soreness post workout. However, it is important to note here that BCAA supplements are not the only source for these essential amino acids. Food items such as eggs, lentils, dairy products, nuts, red meat & beans offer these 3 essential amino acids. Please note that BCAA made up of above mentioned essential amino acids must be consumed from diet since our body does not produce themselves.
Certain metabolites of BCAA can be toxic in high concentrations. As such our body has developed a complex system of enzymes for breaking down & preventing buildup of excess BCAA in the bloodstream. As compared to other amino acids which are broken by the liver, BCAA(s) are broken down in skeletal muscles. The rate at which we catabolise BCAA determines the level of BCAA that is circulated in the bloodstream.
Gut plays an important role in BCAA absorption. Before BCAA coming from our diet is broken down, it is first absorbed in our bloodstream. This happens in our gut. BCAA in our food items such as egg, meat & dairy are in the form of proteins; large chains of amino acids that are linked together. In order for BCAA to be absorbed into the bloodstream, dietary proteins must be first broken down by our digestive system into individual amino acids called peptides.
Ideally, this is how protein in broken down into amino acids
Protein→ Peptides→Amino Acid
On the other hand, BCAA coming from supplements are free form BCAA. This free form BCAA is not required to be digested & it can rapidly be absorbed in the bloodstream.
Once BCAA is absorbed in the bloodstream, it is taken up by cells in different tissues including skeletal muscles & adipose tissues. BCAA then enters -mitochondria, the energy powerhouse from where it is broken down into steps by different enzymes.
The branched-chain acyl CoAs, resulting from the first two steps of breakdown by enzymes, are further broken down by other enzymes to produce the molecules acetyl-CoA and succinyl-CoA. These two molecules formed can be used to generate energy &/or, they can be used to build glucose
The second step of BCAA breakdown through BCKDH enzyme, determines how quickly & effectively BCAA is broken down. Lower BCKDH activity results in a high circulating level of BCAA & reduced BCAA breakdown.
This reduced or impaired breakdown of BCAA is linked to various health conditions including obesity, type 2 diabetes & fatty liver. It is this high circulatory level of BCAA that can cause insulin resistance which is the basic reason for occurrence of type 2 diabetes.
Under insulin resistance, tissues become less responsive to insulin, thereby preventing glucose to enter the cells. This in turn increases the blood sugar level. This causes inflammation & oxidative stress which damages blood vessels & other organs. Since insulin resistance leads to high fat deposition & low fat breakdown, it results in weight gain & obesity(accumulation of fat around organs). There are several possible mechanisms which can lead to reduced or impaired BCAA breakdown leading to insulin resistance. As such impaired breakdown of BCAA can result in accumulation of various metabolites one of which is formed from breakdown of valine. This leads to fat accumulation in muscle tissue. Besides, accumulation of other BCAA metabolites can also impact normal functioning of mitochondria reducing its ability to generate energy.
Our genetic makeup can impact our ability to break down BCAA coming from food we eat. Certain variants of the PPM1k gene can lower the activity of BCKDH enzyme. Besides certain lifestyle factors such as BMI, body composition & insulin response also impact breakdown of BCAA.Individuals who are overweight & obese are said to suffer from reduced breakdown of BCAA. Regular workout can help you improve the activity of the BCKDH enzyme that breaks down BCAA.
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