Inhibiting amylolytic enzymes by both acarbose and cellobiose as a prelude to treating type II diabetes mellitus

Abstract

Inhibition of starch-degrading enzymes, α-amylase and α-glucosidase, provides a measure to ameliorate type II diabetes mellitus (T2D) by limiting the amount of glucose produced from dietary starch that would subsequently be absorbed into the bloodstream. This study investigated the inhibitory potential of cellobiose in amylolytic enzymes alone and also assessed its synergistic effects when combined with the gold AGI standard, acarbose. Firstly, the pharmacokinetic properties prediction and gastrointestinal digestibility simulation of cellobiose were investigated. Following, in silico molecular docking, in vitro enzyme inhibition, and UV spectroscopy were then used to investigate the inhibitory potential of cellobiose. Lastly, single and combined acarbose and cellobiose were investigated for their inhibition of the amylolytic enzyme cocktail. Cellobiose showed drug-likeness properties and did not possess any toxicity. In addition, it was found to remain stable under gastrointestinal simulated conditions. Acarbose (-7.3 kcal/mol and -8.2 kcal/mol) had the highest binding affinity than cellobiose (-6.0 kcal/mol and -7.5 kcal/mol) for both α-amylase and α-glucosidase, respectively. Upon binding of the compounds to the targets in vitro, acarbose (Ki = 0.012 mM) is a reversible uncompetitive inhibitor, while cellobiose (Ki = 2.2 mM) is a reversible non-competitive inhibitor of α-amylase. On the other hand, both acarbose (Ki = 0.08 mM) and cellobiose (Ki = 14 mM) are reversible competitive inhibitors of α-glucosidase. A combination of acarbose and cellobiose in different ratios resulted in more synergistic results than antagonistic or additive effects, with a 0.005: 1.25 mM (acarbose: cellobiose) being the best combination. The results of the study showed that although cellobiose is not a better inhibitor of amylolytic enzymes, its combination with acarbose leads to synergism which may reduce side effects presented by the gold AGI standard and, as a result, both have the potential to be used for T2D treatment.