Cholesterol and triglyceride levels during hibernation - UPDATE January 31, 2010
January 31, 2010 - 7:04 PM CST
Seeing Lily lie there so quietly, made us think about her high cholesterol and triglyceride levels during hibernation and what a metabolic marvel she is.
Healthy levels for cholesterol or triglycerides in people are both below 200 milligrams per deciliter (200 mg/dL). Black bear levels are almost this low in early summer when cholesterol averages 248 mg/dL and triglycerides come in at a healthy 169 mg/dL. However, by early hibernation, when they’re living off their fat, cholesterol reaches 351 and triglycerides reach 355.
Is that a problem? No. We made those measurements in healthy wild bears back in our early studies in the 1970’s and 1980’s when we still were using tranquilizers. The amazing thing is that we have never found plaque in the veins of even the oldest wild bears we’ve examined, and we’ve found no evidence of cholesterol gall stones.
How do bears get away with these high levels and no related problems, even in winter with no exercise? Further tests showed that bears have two secrets.
- Their good cholesterol, HDL is their big number. People exercise and take statin drugs to lower their bad cholesterol (LDL, meaning low density lipoprotein) and raise their HDL. Bears do it without trying.
- The other secret is in the gall bladder. They have a super drug named ursodeoxycholic acid (UDCA), which dissolves gall stones.
Ursodeoxycholic acid from bears has been used to dissolve cholesterol in people. It’s the main ingredient driving poaching for gall bladders to satisfy Asian markets. A form of UDCA is used as a treatment after strokes to minimize the brain damage caused by a process call apoptosis. Usually, after a stroke, chemical signals tell cells around the stroke area to die and disappear. That process is called apoptosis. Injections of TUDCA (tauroursodeoxycholic acid) convince the cells not to commit suicide and continue living.
Ursodeoxycholic acid is particularly concentrated in the bile fluids of hibernating bears and is thought to play an important role in cellular protection in hibernating black bears. Much is unknown about black bear hibernation. Medical researchers are studying it for clues for improving human medicine.
And you thought she was just snoozing and caring for her cub!
—Lynn Rogers and Sue Mansfield, Biologists, North American Bear Center