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Worldwide, the number of people suffering from obesity continues to increase(1). Obesity is characterised by increases in both the abdominal subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT). SAT is considered to have more protective properties in relation to cardiometabolic risk factors(2), whereas VAT is detrimental to cardiometabolic health(3,4).
Obesity is also associated with elevated levels of plasma branched-chain amino acids (BCAA)(5). The BCAA valine, leucine and isoleucine are associated with insulin resistance(6-11). Acute increases in plasma amino acids worsen insulin sensitivity(12), and higher levels of dietary protein intake is associated with impaired glucose metabolism(13). Furthermore, levels of baseline circulating BCAA predicted the development of incident diabetes in a large longitudinal cohort study(11)suggesting that the relationship between BCAA and insulin resistance may be causal. However, the relationship between BCAA and detailed parameters of body composition, specifically VAT, has yet to be reported.
[...]-Aminoisobutyric acid (B-AIBA), a small molecule metabolite, was recently identified using a metabolomics approach as a possible novel myokine that increases browning of white adipocytes in response to physical activity and was found to be inversely associated with cardiometabolic risk including fasting glucose, insulin and homeostasis model assessment (HOMA) in addition to TAG and cholesterol(14). As B-AIBA can be formed by the catabolism of thymine and valine(14,15)this may represent a possible pathway through which BCAA exert their metabolic effects. The catabolism of BCAA, valine in particular, could decrease circulating BCAA while increasing B-AIBA, both of which are associated with improved insulin resistance.
In the present study we investigated the association of BCAA and B-AIBA with each other and with detailed body composition parameters, including SAT and VAT, for the first time. We hypothesised that BCAA would be positively associated with VAT while B-AIBA would be negatively associated with VAT. This hypothesis was evaluated in a cross-sectional study of lean and obese men and women for whom detailed metabolic evaluations were performed.
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