Physiology of alpha glucosidases in carbohydrate metabolism
Alpha-glucosidases represent enzymes found on the brush border of the small intestine, vital for the digestion and absorption of carbohydrates. These enzymes execute the hydrolysis of alpha-glycosidic bonds of disaccharides and oligosaccharides, ultimately yielding absorbable monosaccharides such as glucose.
In the small intestine, two main types of alpha-glucosidases, namely sucrase-isomaltase and maltase-glucoamylase, are prominent. Sucrase-isomaltase is responsible for the hydrolysis of alpha-1,4-glycosidic bonds present in sucrose, producing glucose. On the contrary, maltase-glucoamylase catalyzes the hydrolysis of alpha-1,4-glycosidic bonds in maltose and oligosaccharides, primarily generating glucose.
Mechanism of action of acarbose
Alpha-glucosidase inhibitors (AGIs) function as pseudocarbohydrates in the intestine, challenging carbohydrates ingested for the alpha-glucosidase enzymes located on the brush border of the gut epithelium. These enzymes play a crucial role in the breakdown of complex carbohydrates, such as oligosaccharides and polysaccharides, into easily absorbable monosaccharides.
Acarbose, a pseudo-tetrasaccharide, has an affinity for the alpha-glucosidase enzyme. Through competitive inhibition with carbohydrates ingested for the alpha-glucosidase enzyme, acarbose, along with other AGIs, delay carbohydrate digestion and glucose absorption. This results in improved postprandial glycemic control in patients with diabetes.
Practice Guide
For optimal treatment of postprandial hyperglycemia, acarbose is recommended at the commencement of a meal, specifically with the first bite. This allows acarbose to effectively inhibit alpha-glucosidase enzymes in the intestinal tract at the beginning of carbohydrate digestion. The initial dose for acarbose is typically set at 25 mg, administered three times daily. Depending on the individual patient’s response and tolerance, this can be incrementally adjusted to a maximum dose of 100 mg, administered three times daily.
Despite its effectiveness, acarbose may induce certain gastrointestinal side effects, such as bloating, flatulence, and diarrhea, which could potentially hinder its acceptability among patients. However, these adverse effects can often be ameliorated by administering a lower initial dose and proceeding with a gradual titration to achieve the desired glycemic control. It should also be noted that hypoglycemia is generally not a prominent concern when acarbose is administered as monotherapy. However, the risk of hypoglycemia may increase when acarbose is used in conjunction with insulin or other hypoglycemic agents, so caution is warranted in these scenarios.
References
- Sim L, Willemsma C, Mohan S, Naim HY, Pinto BM, Rose DR (2010) Structural Basis for Substrate Selectivity in Human Maltase-Glucoamylase and Sucrase-Isomaltase N-terminal Domains. J Biol Chem 285:17763–17770
- Gericke B, Schecker N, Amiri M, Naim HY (2017) Structure-function analysis of human sucrase-isomaltase identifies key residues required for catalytic activity. J Biol Chem 292:11070–11078
- Kuttel MM, Naidoo KJ (2005) Free energy surfaces for the alpha(1 –> 4)-glycosidic linkage: implications for polysaccharide solution structure and dynamics. J Phys Chem B 109:7468–7474
- DiNicolantonio JJ, Bhutani J, O’Keefe JH (2015) Acarbose: safe and effective for lowering postprandial hyperglycaemia and improving cardiovascular outcomes. Open Heart 2:e000327
- Altay M (2022) Acarbose is again on the stage. World J Diabetes 13:1–4
- Coniff R, Krol A (1997) Acarbose: a review of US clinical experience. Clin Ther 19:16–26; discussion 2-3
- Rosak C, Nitzsche G, König P, Hofmann U (1995) The effect of the timing and the administration of acarbose on postprandial hyperglycaemia. Diabet Med J Br Diabet Assoc 12:979–984
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