Good Cholesterol May Not be Good for Diabetics
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LEXINGTON, Ky. (Jan. 14, 2008) – Researchers and the general public have long
thought that levels of so called "good cholesterol" – high-density lipoprotein
(HDL) – were heart healthy.
However, a groundbreaking new study from University of Kentucky researchers argues that "good cholesterol" actually increases the risk of heart disease in diabetics.
In a study published in the most recent edition of the American Journal of Physiology, Eric Smart and a team of UK researchers conclude high levels of HDL actually can increase the risk of both heart disease and diabetes.
"Carved in stone over the years from the research done by a Nobel Prize winner in the 1980s is that HDL is supposed to be good for the heart and LDL (low-density lipoprotein) is bad," Smart, a biochemist and vice chair of research in the UK College of Medicine. said. "Cardiologists try to lower LDL and raise HDL for cardiac protection. We addressed diabetes and cardiovascular disease in our research and found that having high levels of HDL could be counter-productive. We didn't expect this outcome when we made the discovery. But, it's profound because it says that HDL doesn't always have to be good for you."
The researchers made their discovery while investigating HDL and diabetes over the past year. In short, the researchers found that in people with diabetes, HDL molecules bind with a natural compound called myristic acid, which somehow causes the HDL to inhibit the body's natural production of nitric oxide, a substance known to protect against cardiovascular disease. Myristic acid is a long-chain fatty acid suspected of increasing cardiovascular risk, Smart said.
The effect was observed in both men and women with diabetes, according to Smart. In effect, HDL in diabetics may reverse its usual role, becoming a potential threat rather than a protectant, the study indicates.
It is still unclear why HDL and myristic acid latch onto each other in people with diabetes, or exactly how that inhibits nitric oxide production.
The UK group is the first to observe and report this phenomenon in research.
"What we found was that all of the HDL we looked at, whether it came from people or mice with diabetes, inhibited nitric oxide," Smart said. "It was a major surprise to find that it worked the same way in mice and humans."
Medical information and advice about cholesterol and diets have been reported, as well as the development of cholesterol drugs, based on the fact that high levels of good cholesterol, HDL, are best and that bad cholesterol, LDL, is bad. Smart stressed, however, that individuals should not try to lower their HDL levels based on one piece of research. And he said the best advice for people with diabetes continues to be a healthy diet coupled with moderate exercise.
The next step, according to Smart, is to determine why and how myristic acid attaches to HDL molecules in diabetics, and where the compound comes from. Smart says myristic acid is found in many foods, but said he suspects the body also manufactures it.
The hope, he said, is one day to develop a drug to keep HDL and myristic acid from combining in people with diabetes.
"I think this has a lot of implications for looking at diabetes and other types of illnesses to see whether HDL gets modified," Smart said. "Unfortunately, the way HDL and LDL are presented as good and bad in the media may give people the impression that we understand everything, and that if you just lower your LDL you'll be safe. But we need to know a lot more."
Information about the Kentucky Pediatric Research Institute is available online.
However, a groundbreaking new study from University of Kentucky researchers argues that "good cholesterol" actually increases the risk of heart disease in diabetics.
In a study published in the most recent edition of the American Journal of Physiology, Eric Smart and a team of UK researchers conclude high levels of HDL actually can increase the risk of both heart disease and diabetes.
"Carved in stone over the years from the research done by a Nobel Prize winner in the 1980s is that HDL is supposed to be good for the heart and LDL (low-density lipoprotein) is bad," Smart, a biochemist and vice chair of research in the UK College of Medicine. said. "Cardiologists try to lower LDL and raise HDL for cardiac protection. We addressed diabetes and cardiovascular disease in our research and found that having high levels of HDL could be counter-productive. We didn't expect this outcome when we made the discovery. But, it's profound because it says that HDL doesn't always have to be good for you."
The researchers made their discovery while investigating HDL and diabetes over the past year. In short, the researchers found that in people with diabetes, HDL molecules bind with a natural compound called myristic acid, which somehow causes the HDL to inhibit the body's natural production of nitric oxide, a substance known to protect against cardiovascular disease. Myristic acid is a long-chain fatty acid suspected of increasing cardiovascular risk, Smart said.
The effect was observed in both men and women with diabetes, according to Smart. In effect, HDL in diabetics may reverse its usual role, becoming a potential threat rather than a protectant, the study indicates.
It is still unclear why HDL and myristic acid latch onto each other in people with diabetes, or exactly how that inhibits nitric oxide production.
The UK group is the first to observe and report this phenomenon in research.
"What we found was that all of the HDL we looked at, whether it came from people or mice with diabetes, inhibited nitric oxide," Smart said. "It was a major surprise to find that it worked the same way in mice and humans."
Medical information and advice about cholesterol and diets have been reported, as well as the development of cholesterol drugs, based on the fact that high levels of good cholesterol, HDL, are best and that bad cholesterol, LDL, is bad. Smart stressed, however, that individuals should not try to lower their HDL levels based on one piece of research. And he said the best advice for people with diabetes continues to be a healthy diet coupled with moderate exercise.
The next step, according to Smart, is to determine why and how myristic acid attaches to HDL molecules in diabetics, and where the compound comes from. Smart says myristic acid is found in many foods, but said he suspects the body also manufactures it.
The hope, he said, is one day to develop a drug to keep HDL and myristic acid from combining in people with diabetes.
"I think this has a lot of implications for looking at diabetes and other types of illnesses to see whether HDL gets modified," Smart said. "Unfortunately, the way HDL and LDL are presented as good and bad in the media may give people the impression that we understand everything, and that if you just lower your LDL you'll be safe. But we need to know a lot more."
Information about the Kentucky Pediatric Research Institute is available online.