Origin of cholesterol transported in intestinal lymph: studies in patients with filarial chyluria.

In subjects fed a cholesterol-free diet there are three possible sources of intestinal lymph cholesterol: a) mucosal synthesis; b) absorption of endogenous (biliary) cholesterol; and c) transudation of plasma lipoproteins into the lacteals of the intestinal wall. To test these possibilities, the extent of transudation was measured by means of [3H]beta-sitosterol administered intravenously as a marker. Absorption of biliary cholesterol was reduced by oral administration of beta-sitosterol (9 g/day), and mucosal synthesis of cholesterol was evaluated by comparisons of plasma/lymph [14C]cholesterol specific activity ratios after intravenous administration of a single dose of labeled cholesterol. Studies were carried out on six patients with filarial chyluria. In five patients fed a cholesterol-free diet the results indicated that lymph cholesterol was largely derived by transudation of plasma lipoproteins into the lacteals from the intestinal blood supply, without contribution from de novo mucosal synthesis or from absorption of endogenous cholesterol. The intestinal lymph of one patient fed cholesterol (2 g/day) contained cholesterol originating mostly from plasma transudation and from dietary absorption, with little contribution from absorbed endogenous cholesterol. In all experiments the larger part of the cholesterol transported away from the intestine in the lymph was carried in chylomicrons, even though it had its origin in plasma lipoproteins.