Imaging Cytoplasmic Lipid Droplets in Enterocytes and Assessing Dietary Fat Absorption

The primary function of the small intestine is digesting and absorbing nutrients from consumed food. Because of this, the small intestine is often thought of as a nutrient thoroughfare-enterocytes taking up nutrients on the apical side and then secreting nutrients from the basolateral side. The small intestine is not commonly thought of as a lipid storage organ; however, when meals and diets containing high amounts of fat are consumed, some dietary fat is stored in cytoplasmic lipid droplets (CLDs). The balance between storage and secretion of dietary fat by enterocytes is important in determining the physiological fate of dietary fat, including regulating blood lipid concentrations and energy balance. The existence of CLDs within enterocytes has likely evolved for three important physiological functions: (i) to allow the small intestine to efficiently absorb large amounts of energy dense fat, (ii) to control the rate of dietary fat entering circulation, and (iii) to alleviate lipotoxicity to enterocytes induced by high concentrations of free fatty acids, especially when a high fat meal is consumed. The purpose of this chapter is to provide methods for imaging CLDs in enterocytes and assessing different aspects of dietary fat absorption.