BACKGROUND/OBJECTIVES: Branched chain amino acids (BCAA) are among nutrients strongly linked with insulin sensitivity (IS) measures. We investigated the effects of a chronic increase of BCAA intake on IS in two groups of healthy subjects differing in their basal consumption of BCAA, that is, vegans and omnivores. SUBJECTS/METHODS: Eight vegans and eight matched omnivores (five men and three women in each group) received 15 g (women) or 20 g (men) of BCAA daily for 3 months. Anthropometry, blood analyses, glucose clamp, arginine test, subcutaneous abdominal adipose tissue (AT) and skeletal muscle (SM) biopsies (mRNA levels of selected metabolic markers, respiratory chain (RC) activity) were performed at baseline, after the intervention and after a 6 month wash-out period. RESULTS: Compared with omnivores, vegans had higher IS at baseline (GIR, glucose infusion rate: 9.6±2.4 vs 7.1±2.4 mg/kg/min, 95% CI for difference: 0.55 to 5.82) that declined after the intervention and returned to baseline values after the wash-out period (changes in GIR with 95% CI, 3-0 months: -1.64 [-2.5; -0.75] and 9-3 months: 1.65 [0.75; 2.54] mg/kg/min). No such change was observed in omnivores. In omnivores the intervention led to an increased expression of lipogenic genes (DGAT2, FASN, PPARγ, SCD1) in AT. SM RC activity increased in both groups. CONCLUSIONS: Negative impact of increased BCAA intake on IS was only detected in vegans, that is, subjects with low basal amino acids/BCAA intake, which appear to be unable to induce sufficient compensatory changes within AT and SM on a BCAA challenge.

Centre for Research on Diabetes Metabolism and Nutrition of 3rd Faculty of Medicine Charles University Prague Ruská 87 Prague 10 100 00 Czech Republic

Centre for Research on Diabetes Metabolism and Nutrition of 3rd Faculty of Medicine Charles University Prague Ruská 87 Prague 10 100 00 Czech Republic Department of Sport Medicine 3rd Faculty of Medicine Charles University Prague Ruská 87 Prague 10 100 00 Czech Republic

Centre for Research on Diabetes Metabolism and Nutrition of 3rd Faculty of Medicine Charles University Prague Ruská 87 Prague 10 100 00 Czech Republic Division of Clinical Physiology 2nd Department of Internal Medicine University Hospital Královské Vinohrady Šrobárova 50 Prague 10 100 34 Czech Republic Prague

Centre for Research on Diabetes Metabolism and Nutrition of 3rd Faculty of Medicine Charles University Prague Ruská 87 Prague 10 100 00 Czech Republic Division of Clinical Physiology 2nd Department of Internal Medicine University Hospital Královské Vinohrady Šrobárova 50 Prague 10 100 34 Czech Republic Prague Department of Sport Medicine 3rd Faculty of Medicine Charles University Prague Ruská 87 Prague 10 100 00 Czech Republic

Department of Anaesthesia and Intensive Care Medicine University Hospital Královské Vinohrady and 3rd Faculty of Medicine Charles University Šrobárova 50 Prague 10 100 34 Czech Republic Prague

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