INS and metabolic syndrome: We report for the first time that L-arabinose gavage elicited immediate and robust release of hydrogen in mice in a dose-and-time-dependent manner, which can be abolished by antibiotics treatment regardless of diet type; long-term L-arabinose administration effectively reduced body weight gain especially fat weight, improved insulin sensitivity, alleviated liver steatosis, systemic dyslipidemia and inflammation in mice on HFD.