The role of lingual lipase in neonatal fat digestion

Lingual serous glands (von Ebner) contain a potent lipase that hydrolyses triglycerides to a mixture of partial glycerides (di- and monoglycerides), glycerol and free fatty acids. Studies in man and in rat have shown that similar lipolytic activity is present in oesophageal and gastric aspirates and suggest that the intragastric digestion of dietary fat is initiated by lingual lipase. In the rat the lingual serous glands are initiated in 19- to 20-day fetuses; lipase activity is first detected in 20-day-old fetuses and increases 14-fold by birth. The data suggest that in the fetus lipase activity originates predominantly in the serous demilune cells of mucous glands whereas after birth the enzyme is synthesized and stored in the rapidly differentiating serous glands. In man lipolytic activity is present in gastric aspirates as early as 26 weeks of gestational age. Our studies suggest that the lipolytic activity has characteristics similar to those of adult human and rat lingual lipase; the enzyme is present in the oesophageal pouch of infants with oesophageal atresia indicating that in infants, as in adults, it probably originates in the lingual serous glands. Since the enzyme is active in the absence of bile salts and has a low pH optimum it is ideally suited to act in the stomach and probably compensates in the premature for low pancreatic lipase activity. The lipolytic activity could be important, not only in the digestion of dietary fat, but in helping to overcome the temporary bile salt deficiency and to solubilize dietary fat through the formation of amphiphilic reaction products.