Dietary Adaptation to High Starch Involves Increased Abundance of α-glucosidase and its mRNA

Abstract

Dietary flexibility in digestive enzyme activity is widespread invertebrates, but mechanisms are poorly understood. Fragmentaryevidence indicates that laboratory rats modulate intestinal•-glucosidase (AG) activity mainly by relying on rapid increase inenzyme transcription followed by translation and translocation to theintestinešs apical, brush border membrane (BBM). We performedthe first unified study of this overall process, relying on activity,transcriptomic and proteomic data from the same animals. We usedas our model nestling house sparrows (Passer domesticus), whichincrease their intestinal AG activity as they switch naturally from lowstarch insect diet to higher starch seed diet. Twenty-four hours after aswitch to a high starch diet, intestinal AG activity and mRNA wereincreased. The protein sucrase-isomaltase (SI), which is responsiblefor all maltase and sucrase activity, was the only hydrolase increasedin the BBM, and its abundance and activity were positivelycorrelated. This is the first demonstration that birds may rely on rapidincrease in enzyme abundance when adjusting to high starch diet.