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In-vivo production of branched-chain amino acids, branched-chain keto acids, and β-hydroxy β-methylbutyric acid.

PURPOSE OF REVIEW
The branched-chain amino acids (BCAA), branched-chain keto acids (BCKA), and β-hydroxy β-methylbutyric acid (HMB) have regained interest as food ingredients in health and disease. To support nutritional strategies, it is critical to gain insight into the whole body and transorgan kinetics of these components. We, therefore, reviewed the most recent literature in this field on in vivo analysis of BCAA, BCKA, and HMB kinetics in health and disease.


RECENT FINDINGS
With a new comprehensive metabolic flux analysis BCAA, BCKA, and HMB whole body production, interconversion and disposal rates can be measured simultaneously. Recent studies have provided us with a better understanding of whole-body and transorgan kinetics under postabsorptive, postprandial, hibernating, and lactating conditions. In human pathophysiological conditions like COPD, obesity, and diabetes, the added value of BCAA kinetic measurements over the commonly used concentration measurements only, is discussed.


SUMMARY
This article highlights the importance of implementing BCAA, BCKA, and HMB kinetic studies to further advance the field by gaining more mechanistic insights and providing direction to the development of new targeted (nutritional) strategies.