LINAGLIPTIN IS AN INHIBITOR OF DPP-4, AN ENZYME THAT DEGRADES THE INCRETIN HORMONES GLUCAGON-LIKE PEPTIDE-1 (GLP-1) AND GLUCOSE-DEPENDENT INSULINOTROPIC POLYPEPTIDE (GIP). THUS, LINAGLIPTIN INCREASES THE CONCENTRATIONS OF ACTIVE INCRETIN HORMONES, STIMULATING THE RELEASE OF INSULIN IN A GLUCOSE-DEPENDENT MANNER AND DECREASING THE LEVELS OF GLUCAGON IN THE CIRCULATION. BOTH INCRETIN HORMONES ARE INVOLVED IN THE PHYSIOLOGICAL REGULATION OF GLUCOSE HOMEOSTASIS. INCRETIN HORMONES ARE SECRETED AT A LOW BASAL LEVEL THROUGHOUT THE DAY AND LEVELS RISE IMMEDIATELY AFTER MEAL INTAKE. GLP-1 AND GIP INCREASE INSULIN BIOSYNTHESIS AND SECRETION FROM PANCREATIC BETA CELLS IN THE PRESENCE OF NORMAL AND ELEVATED BLOOD GLUCOSE LEVELS. FURTHERMORE, GLP-1 ALSO REDUCES GLUCAGON SECRETION FROM PANCREATIC ALPHA CELLS, RESULTING IN A REDUCTION IN HEPATIC GLUCOSE OUTPUT.