Obesity, a key global health issue, is defined as a chronic physical illness by the World Health Organization, and we have sounded the alarm concerning the worldwide epidemic growth in obesity. Moreover, the prevalence of childhood obesity has been steadily increasing over the past several decades, and most obese children and teenagers are advised to change their unhealthy diet. Piglet is recognized to be an excellent model for childhood obesity, because of its genetic and physiological features that are very similar to humans. Therefore, it is urgent to seek a preventive dietary intervention for the children and is necessary to unravel the molecular mechanism underlying lipid metabolism using piglet populations.

A study in piglets has found that branched-chain amino acids (BCAA) supplementation in low-protein (LP) diets could alter the body fat condition, and this effect was likely modulated by the expression of lipid metabolic regulators in dorsal subcutaneous adipose (DSA), abdominal subcutaneous adipose (ASA), and perirenal adipose (PRA) tissues in a depot-specific manner. These findings, by researchers at the Institute of Subtropical Agriculture of the Chinese Academy of Sciences, have been published in Journal of Agricultural and Food Chemistry.

BCAA, including leucine, isoleucine, and valine, function as direct-acting nutrient signals involved in the regulation of protein synthesis in skeletal muscle. The white adipose tissue (WAT), normally divided into subcutaneous and visceral adipose depots according to the anatomical location, is capable of metabolizing substantial amounts of BCAA, and the adipose depots are characterized by metabolic differences that are due to genetic regulation of preadipocyte differentiation and the local microenvironment. However, whether BCAA play a unique role in lipid metabolism in different adipose depots are still unclear at present.

In the current study, researchers investigated the concentrations of circulating adipokines and the gene expression of lipid metabolic regulators in a piglet model. The researchers collected blood and adipose tissue samples, including DSA, ASA, and PRA.

They found that the LP diet led to increasing leptin concentration in serum, but it could be obviously alleviated by the addition of BCAA, which represents, to some extent, an altered whole-body lipid metabolism. In addition, in DSA, the mRNA and protein levels for lipogenic-related genes were highest in the LP treatment but lowest in the treatment of LP diet supplemented with twice BCAA (LP + 2B). Unexpectedly, in ASA and PRA, the expression levels for those genes were significantly elevated in the LP + 2B treatment, which indicated that the various adipose depots may respond diversely to the dietary BCAA supplementation in a depot-specific regulation manner.

"Our results also showed that the signaling pathway of extracellular signal-regulated protein kinases 1/2 and peroxisome proliferator-activated receptor γ appeared to play a role in the process of regulation. These observations provide new insights into the emerging role of BCAA in regulating adipose tissue," said LI Yinghui, a doctoral student primarily performing this research.

This study was supported by the grants from the National Basic Research Program of China (2013CB127305, 2012CB124704), the Nature Science Foundation of Hunan Province (S2014J504I), the Youth Innovation Promotion Association CAS (2016326), the Major Project of Hunan Province (2015NK1002), Key Project of Research and Development Plan of Hunan Province (2016NK2170), and the National Science and Technology Ministry (2014BAD08B11).