• Can We Use a Yeast Lipase in Enzyme Replacement Therapy for Pancreatic Exocrine Insufficiency?

Can We Use a Yeast Lipase in Enzyme Replacement Therapy for Pancreatic Exocrine Insufficiency?

An orally administered yeast lipase increases digestion of fat in a minipig model of pancreatic exocrine insufficiency (PEI), similar to that of pancreatin used in pancreatic enzyme replacement therapy, researchers report in the December issue of Gastroenterology.

Patients with PEI have decreased pancreatic secretion of digestive enzymes such as lipase. This leads to malnutrition in patients with diseases such as cystic fibrosis or chronic pancreatitis. Features of PEI include steatorrhea, a low coefficient of fat absorption, and deficiencies in fat-soluble vitamins and essential fatty acids.

Oral pancreatic enzyme replacement therapy is the first line of treatment for maldigestion secondary to PEI, but its effects have been unsatisfactory. The therapy comprises a combination of porcine-derived lipases, proteases, and amylases—these products of animal origin pose a potential risk for virus transmission.

Although recombinant human pancreatic lipase can be produced in the laboratory, industrial production is not likely, because this pancreatic lipase is not very active at a low pH and is not stable at pH values <4.

Yarrowia lipolytica

Yarrowia lipolytica

Ahmed Aloulou et al investigated whether lipase 2 produced by the yeast Yarrowia lipolytica (YLLIP2) might be used in pancreatic enzyme replacement therapy.

They analyzed the ability of YLLIP2 to digest triglycerides in a test meal and then its efficacy in reducing the amount of fat in feces of minipigs with PEI.

Aloulou et al found that in an in vitro test meal, YLLIP2 was highly stable and poorly degraded by pepsin. YLLIP2 had the highest activity of all lipases tested (vs recombinant dog gastric lipase or recombinant human pancreatic lipase) on triglyceride at pH 4−7.

Without bile, the highest specific activities of all 3 lipases were observed at pH 6, and YLLIP2 was more active (94±34 U/mg) than recombinant dog gastric lipase (24±4 U/mg) and or recombinant human pancreatic lipase (34±19 U/mg).

The activity of all lipases dropped when pH decreased, but YLLIP2 still had higher specific activities than recombinant human pancreatic lipase or recombinant dog gastric lipase at pH 4.

Adding bile resulted in a 1.5-fold increase in the specific activity of YLLIP2 at pH 6 (94±34 U/mg), but its specific activity decreased significantly at pH 4 (16±2 U/mg).

Based on the test meal experiments, the lipase activity of YLLIP2 (10 mg) was estimated to be equivalent to that of the currently used pancreatin (1200 mg; 100,000 US Pharmacopeia units) at pH 6.

To create an animal model of PEI, the authors induced steatorrhea in minipigs via embolization of the exocrine pancreas gland and pancreatic duct ligation. The minipigs were then given YLLIP2 (1, 4, 8, 40, or 80 mg/d) or pancreatin (100,000 US Pharmacopeia lipase units/d) for 9 days.

In this model, the coefficient of fat absorption values increased from 60.1% before surgery to 90.5% after administration of 1200 mg pancreatin. These absorption values increased to a range of 84.6%–90.0% after administration of only 4−80 mg YLLIP2 to the minipigs with PEI.

The effect of YLLIP2 did not depend on dose. Doses ≥4 mg were equally effective in reducing steatorrhea (reductions of 12.5 to 14.23 g fecal fat in 24 hours) and coefficient of fat absorption (increases of 24.1% to +28.5%)—as efficient as 1200 mg/d pancreatin.

Aloulou et al conclude that YLLIP2 is more potent than mammalian digestive lipases—particularly the lipase present in current pancreatic enzyme replacement therapies.

They explain that of the digestive enzymes, lipases are important because fat digestion provides the major source of calories from foods. New lipases could be used as stand-alone drugs to restore fat absorption in patients with PEI. An ideal lipase should remain stable and act on dietary triglycerides at low pH, because pancreatic bicarbonate secretion is impaired in patients with PEI and gastric acidity is poorly neutralized in the intestine; remain active in the presence of bile salts; and resist proteolytic digestion.

Microbial lipases are attractive enzymes for PERT because they are already produced at an industrial scale for various applications, and are expected to yield more satisfactory results than the pancreatin currently given to patients.

Most microbial lipases tested so far have been inactivated by gastric acidity or bile salts or degraded by digestive tract proteases. However, YLLIP2 shows the highest hydrolytic activity on long-chain triglycerides at low pH, is more active than recombinant dog gastric lipase at pH 4, and its adsorption is not inhibited by bile salts.

YLLIP2 has an enzymatic mechanism similar to that of human pancreatic lipase. YLLIP2 can generate a 2-monoglyceride molecule (2-MAG) from a molecule of triglyceride with the release of 2 fatty acids, which is sufficient to produce intestinally absorbable lipolysis products and ensure full fat absorption.

High doses of YLLIP2 were previously shown to be safe in rats, supporting the clinical development of this yeast lipase for treatment of PEI.

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