HIGH PLASMA-CHOLESTEROL, BUT LOW TRIGLYCERIDES AND PLAQUE-FREE ARTERIES, IN MEXICAN FREE-TAILED BATS

Female mammals typically become hyperphagic from mid- to late pregnanc y and during lactation. Mexican free-tailed bats, Tadarida brasiliensi s mexicana, double their nightly food intake from late pregnancy to pe ak lactation and consume an insect diet that is exceptionally high in fat. During late pregnancy and throughout lactation, fasting plasma le vels of cholesterol in this insectivorous bat are high (215 +/- 8 mg/d l) and are nearly 10-fold higher than in three species of Old World fr ugivorous bats. Fasting triglycerides were unexpectedly low in T. bras iliensis (25 +/- 2 mg/dl), despite evidence of high fat intake during nightly feeding bouts (postprandial cholesterol and triglycerides, 268 +/- 18 and 122 +/- 20 mg/dl, respectively). High-density lipoprotein (HDL) cholesterol levels were extraordinarily high (124 +/- 5 mg/dl) a nd unaffected by feeding. Low-density lipoprotein cholesterol levels w ere correspondingly low (86 +/- 7 mg/dl). This unusual plasma lipid pr ofile was not associated with coronary or aortic atherosclerosis, nor was there evidence of hyperglycemia or hyperinsulinemia. A high-fat di et and high levels of cholesterol in T. brasiliensis are not correlate d with cardiovascular disease or (possibly) insulin resistance. Among several possible factors that might account for these observations, ni ghtly bouts of powered flight (commuting and foraging for food) may co ntribute to elevated HDL cholesterol, which may protect this species f rom developing atherosclerosis.