The multiple roles of sucrase-isomaltase in the intestinal physiology

Abstract

Osmotic diarrhea and abdominal pain in humans are oftentimes associated with carbohydrate malabsorption in the small intestine due to loss of function of microvillar disaccharidases. Disaccharidases are crucial for the digestion and the subsequent absorption of carbohydrates. This review focuses on sucrase-isomaltase as the most abundant intestinal disaccharidase and the primary or induced pathological conditions that affect its physiological function. Congenital defects are primary factors which directly influence the transport and function of sucrase-isomaltase in a healthy epithelium. Based on the mutation type and the pattern of inheritance, a mutation in the sucrase-isomaltase gene may exert a variety of symptoms ranging from mild to severe. However, structure and function of wild type sucrase-isomaltase can be also affected by secondary factors which influence its structure and function either specifically via certain inhibitors and therapeutic agents or generally as a part of intestinal pathogenesis, for example in the inflammatory responses. Diagnosis of sucrase-isomaltase deficiency and discriminating it from other gastrointestinal intolerances can be latent in the patients because of common symptoms observed in all of these cases.Here, we summarize the disorders that implicate the digestive function of sucrase-isomaltase as well as the diagnostic and therapeutic strategies utilized to restore normal intestinal function.

Keywords: Carbohydrate maldigestion; Congenital sucrase-isomaltase deficiency; Gastrointestinal intolerance; Gut microbiota; Inflammation; Sucrase-isomaltase.

Fig. 1

Multifactorial causes of primary or secondary sucrase-isomaltase deficiencies. The SI function in cleaving carbohydrates depends on the correct transport of the enzymatically competent protein to the BBM. This process occurs via association of SI with lipid rafts in the trans-Golgi network vesicles that are transported to the BBM along the actin cytoskeleton. The digestive capacity of SI can be affected by primary genetic mutations that target the SI gene. On the other hand, environmental factors can also influence expression and function of SI. The induced or secondary effects on the SI function can be elicited by altered epithelial cell integrity or the cytoskeletal organization of the enterocytes as well as changes in the healthy protective microflora. In some cases, the structure and function of SI can be directly influenced by certain therapeutics or dietary components. Together, alterations in the intestinal physiology triggered for example by inflammation can exert adverse effects on the trafficking and function of SI. The maldigested carbohydrates will in turn moderate the gut microbiota differently from healthy conditions and may render subsequent negative influences on the intestinal physiology