THURSDAY, July 22 (HealthDay News) -- A new animal study offers the first direct bit of evidence that ozone, a major component of smog, may trigger the death of heart cells.

In small early tests with rats, U.S. researchers found that exposure to ground-level ozone over several weeks boosted the activity of tumor necrosis factor-alpha (TNF-A), an indication of inflammation. Increased TNF-A levels have been linked to a drop in levels of a heart-protective protein called Caveolin-1 (Cav1). This protein is believed to protect the heart by binding to a chemical called p38MAPK alpha, which is a known cell death signaling chemical.

Levels of the heart-protective Cav1 protein decreased in the hearts of rats exposed to ozone compared to the hearts of rats who breathed filtered air.

"We believe the decreased levels of Cav1 make more unbound p38MAPK alpha available for telling the heart cells to die. That link between Cav1 and (ozone) has never been shown in the heart," Rajat Sethi, an assistant professor in the pharmaceutical sciences department at Texas A&M Health Science Center's college of pharmacy, said in an American Heart Association news release.

The study was to be presented Wednesday at an American Heart Association meeting in California.

"Several studies have already shown that air pollution increases the risk of coronary arteriosclerosis and heart attack. Post-menopausal women have been shown to have an increased risk of stroke as well from fine particulate matter in air pollution," Dr. Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York City, said in a news release.

"Now there is evidence (in rats) that ozone, a key component among others in smog, can trigger a direct effect on cardiac tissue through a cascade of inflammatory mediators. The endpoint in this domino effect can result in death of heart cells -- a heart attack, in essence," he said.

The researchers cautioned, however, that more evidence was needed before human studies can begin.

More information

The U.S. National Institute of Environmental Health Sciences has more about air pollution and cardiovascular health.

THURSDAY, July 22 (HealthDay News) -- People with extremely low levels of "bad" cholesterol as a result of taking statins don't seem to benefit from increased levels of "good" cholesterol, a new study suggests.

The conventional wisdom has been that to reduce the risk of heart attack and stroke you should lower your LDL, or "bad," cholesterol and increase your HDL, or "good," cholesterol. But researchers made a surprising discovery: for those with rock-bottom levels of LDL cholesterol induced by high-dose statin therapy, high HDL levels don't seem to matter.

Statins include widely used medications such as Crestor, Lipitor and Zocor.

For people not taking a statin (in the case of this study, Crestor), high concentrations of good cholesterol still offered heart protection, the researchers found.

"HDL cholesterol is a well-established 'protective risk factor' for heart disease, which has lead to speculation that drugs capable of increasing HDL cholesterol might be beneficial," said lead researcher Dr. Paul Ridker, the Eugene Braunwald Professor of Medicine at Harvard Medical School and director of the Center for Cardiovascular Disease Prevention at Brigham and Women's Hospital in Boston.

However, most of that data comes from studies of patients in the West with high levels of LDL cholesterol, he said. "In this work, we wanted to know if HDL cholesterol levels remain an important predictor of risk when we dropped LDL cholesterol down to very low ranges rarely seen in the West," he said.

The report on the randomized, double-blind trial is published in the July 22 online edition of The Lancet.

For the study, Ridker's team used data from the JUPITER trial, in which people with average to low levels of bad cholesterol were given 20 milligrams of rosuvastatin (Crestor) daily.

In many patients, the drug reduced LDL cholesterol levels to the low levels seen among Aboriginal populations, but not usually seen among people in developed countries, the researchers noted.

During a follow-up of up to five years, people taking Crestor had a 54 percent reduction in heart attack and 48 percent decrease in stroke.

In addition, people taking Crestor had a 46 percent reduction in revascularization (surgery to restore an adequate blood supply to part of the body through a blood vessel graft, like a coronary bypass) and a 43 percent decrease in venous thromboembolism (a blood clot in the leg). There was also a 20 percent decrease in total mortality.

However, when the researchers looked at the effect of "good" cholesterol on reducing the risk of heart attack and stroke, they found no significant relationship between levels of good cholesterol and cardiovascular risk among people taking Crestor.

Among people in the trial given a placebo, levels of good cholesterol remained predictive of cardiovascular risk. Among people with the highest levels of HDL cholesterol, the risk of heart attack or stroke was about half that of those with the lowest HDL levels, Ridker's group found.

"One of the implications of this work is to rethink just how important HDL cholesterol remains once we get LDL levels very low with potent statin therapy," Ridker said. "Clinically, these data suggest that once on a high-dose statin, it is unclear if HDL cholesterol remains an important determinant of residual risk."

"These data do not diminish our need to find out once and for all whether potent HDL-raising agents might improve cardiovascular outcomes," Ridker said. The researchers said that further clincial trials were needed to make that determination.

The JUPITER trial was funded by the pharmaceutical giant AstraZeneca, the maker of Crestor.

Dr. Gregg C. Fonarow, director of the Ahmanson-UCLA Cardiomyopathy Center at the University of California, Los Angeles, said that "while statin therapy lowers the risk of cardiovascular events by 25 to 50 percent, it has been speculated that low HDL cholesterol levels may account for a large component of the residual vascular risk that remains despite statin therapy."

In the cases of primary prevention patients treated with statins, this latest finding challenges that hypothesis, Fonarow said.

"The most evidence-based and effective approach to reduce the risk of heart attack and stroke is lowering LDL cholesterol with maximally tolerated doses of statin therapy, along with lifestyle modification, even in the setting of low HDL," he said.

More information

For more information on cholesterol, visit the American Heart Association  .

WEDNESDAY, July 21 (HealthDay News) -- No new patients will be permitted to enroll in a safety study of the controversial diabetes drug Avandia until further notice, the U.S. Food and Drug Administration announced Wednesday.

But under the partial clinical trial hold, those patients already enrolled in the TIDE (Thiazolidinedione Intervention With Vitamin D Evaluation) trial will be allowed to continue to participate, the agency said in a news release.

An FDA advisory panel last week ruled that Avandia (rosiglitazone) does boost users' heart risks, but it also decided that the drug should stay on the market because there's no definitive evidence of an increased risk.

The FDA said Wednesday that it is evaluating available data on Avandia's safety and the discussions from last week's advisory panel meeting. When the review is complete, the agency will inform the public about the findings and what they mean for the drug's status and the TIDE trial.

GlaxoSmithKline, which makes Avandia, was told by the FDA to update researchers, institutional review boards and ethics committees involved in the TIDE trial about new safety information presented at the FDA advisory panel meeting. That information can be used to update informed consent information for people already enrolled in the TIDE trial, the FDA said.

GSK agreed to conduct the TIDE trial in 2007 after concerns about the safety of Avandia first became public. The goal of the trial is to determine whether Avandia poses greater heart risks than a competing drug called Actos.

In a news release, the drug company confirmed that it will suspend enrollment of new patients in the TIDE trial and send a summary of recent safety data and a summary of the FDA advisory panel meeting to all TIDE researchers and institutional review boards.

"This pause in enrollment will give clinical trial investigators and patients time to learn about the data presented to the FDA Advisory Committee and the Committee's recommendations," Dr. Ellen Strahlman, GSK's chief medical officer, said in the news release.

"Patients with questions about the use of Avandia should talk with their physicians," she added.

More information

The U.S. National Library of Medicine has more about rosiglitazone.

THURSDAY, June 24 (HealthDay News) -- Ninety percent of Americans are eating more salt than they should, a new government report reveals.

In fact, salt is so pervasive in the food supply it's difficult for most people to consume less. Too much salt can increase your blood pressure, which is major risk factor for heart disease and stroke.

"Nine in 10 American adults consume more salt than is recommended," said report co-author Dr. Elena V. Kuklina, an epidemiologist in the Division of Heart Disease and Stroke Prevention at the U.S. Centers for Diseases Control and Prevention.

Kuklina noted that most of the salt Americans consume comes from processed foods, not from the salt shaker on the table. You can control the salt in the shaker, but not the sodium added to processed foods, she said.

"The foods we eat most, grains and meats, contain the most sodium," Kuklina said. These foods may not even taste salty, she added.

Grains include highly processed foods high in sodium such as grain-based frozen meals and soups and breads. The amount of salt from meats was higher than expected, since the category included luncheon meats and sausages, according to the CDC report.

Because salt is so ubiquitous, it is almost impossible for individuals to control, Kuklina said. It will really take a large public health effort to get food manufacturers and restaurants to reduce the amount of salt used in foods they make, she said.

This is a public health problem that will take years to solve, Kuklina said. "It's not going to happen tomorrow," she stressed.

"The American food supply is, in a word, salty," agreed Dr. David Katz, director of the Prevention Research Center at Yale University School of Medicine. "Roughly 80 percent of the sodium we consume comes not from our own salt shakers, but from additions made by the food industry. The result of that is an average excess of daily sodium intake measured in hundreds and hundreds of milligrams, and an annual excess of deaths from heart disease and stroke exceeding 100,000."

"As indicated in a recent IOM [Institute of Medicine] report, the best solution to this problem is to dial down the sodium levels in processed foods," Katz added. "Taste buds acclimate very readily. If sodium levels slowly come down, we will simply learn to prefer less salty food. That process, in the other direction, has contributed to our current problem. We can reverse-engineer the prevailing preference for excessive salt."

The report is published in the June 25 issue of the CDC's Morbidity and Mortality Weekly Report.

For about 70 percent of adults, salt intake should be limited to 1,500 milligrams (mg) a day, but only 5.5 percent of these adults meet that level, according to the report.

For others, the recommended amount of daily salt intake is less than 2,300 mg a day, according to the report.

Reducing your salt intake is not only important for people with high blood pressure, Kuklina said. It's good for everybody, "even if you don't have hypertension," she said.

There are some things people can do to reduce their salt intake, Kuklina said. You can eat fewer processed foods and focus on fresh and frozen foods. You also can read the product labels to see how much salt is in the food and opt for low-sodium foods, she said.

Also, Kuklina advises rinsing canned vegetables and beans in water to remove salt.

The data for the report was collected from 3,922 individuals who took part in the 2005-2006 National Health and Nutrition Examination Survey.

Samantha Heller, a dietitian, nutritionist and exercise physiologist, commented that "nearly 80 percent of our sodium intake comes from processed, restaurant, frozen and prepared foods."

Research suggests that reducing sodium intake to 2,300 mg/day for healthy folks and to 1,500 mg/day for people with high blood pressure, who are middle-aged, older or black will reap substantial health benefits, Heller said.

"Food companies have indicated that they will lower the sodium in some of their products, but it will take time before that happens, and only some products will have lowered sodium. The truth is that dropping our intake to 1,500 to 2,300 milligrams a day is difficult to do and unrealistic for most people," she said.

Consumers will be best served by cooking more foods at home. It saves money and helps reduce the intake of dietary sodium, saturated fats, trans fats, refined carbohydrates and excess calories, Heller said.

"Any reduction in dietary sodium is a move in the right direction," she added. "We can help ourselves by increasing our awareness of where sodium is hidden in foods, reading food labels -- look for milligrams of sodium per serving -- ignore the percent on the label -- checking the sodium in the foods served at restaurants we frequent when it is available and taking charge of our health and what we eat by making more of our meals at home."

More information

For more information on limiting salt, visit the U.S. National Heart, Lung, and Blood Institute.