TUESDAY, Oct. 7 (HealthDay News) -- A new analysis of existing research finds little evidence that circumcision protects gay men from infection with the AIDS virus, but the issue is still far from settled.

For one thing, studies conducted prior to the age of powerful AIDS drugs showed that circumcision did have a preventive effect. For another, no one has launched the most definitive type of research into the effects of circumcision on AIDS rates among gay men.

"There remains an open question as to whether circumcision will actually be a public health tool in the fight against AIDS for men who have sex with men," said Dr. Sten Vermund, director of the Vanderbilt Institute for Global Health.

It's already clear that circumcision lowers rates of AIDS infection by 50 percent to 60 percent among heterosexual men. Circumcision appears to provide protection, because it rids a man of cells inside the foreskin that seem to be especially susceptible to AIDS infection, explained study author Gregorio A. Millett, a senior behavioral scientist with the Centers for Disease Control and Prevention.

But the effects of circumcision on gay men have remained a topic of intense debate. "People are interested in finding out what other things can we add to the HIV arsenal," Millett said. "As for now, we're not sure [circumcision] is something we can add to the arsenal."

In the new study, Millett and colleagues conducted a meta-analysis of 15 studies that looked at a total of more 53,000 men, 52 percent of whom were circumcised. The findings are in the Oct. 8 issue of the Journal of the American Medical Association.

The more recent studies that the researchers analyzed failed to find a statistically significant protective effect from circumcision.

However, circumcised men had a 53 percent lower risk of becoming infected with HIV prior to 1996, the era that preceded the use of powerful AIDS drugs, Millett said. The meaning of that number isn't clear; it's possible that many of the men who avoided HIV infection in the older studies engaged in less risky sex, he added.

Vermund said the question of whether circumcision protects gay men from HIV won't be answered until a clinical trial is conducted. Such a study may require some participants to undergo circumcision to understand how it affects their risk of HIV.

Vermund, co-author of a commentary accompanying the new study, added: "It would be nice if the global community would say, 'Look, we continue to have a horrific problem in men who have sex with men around the world. We need to know whether circumcision is a tool that could reduce the incidents, and we're not going to know that unless we do the clinical trials.'"

Such a study would be difficult to launch in the United States, he said, but it might be possible in South America, where gay men are less likely to be circumcised.

More information

Learn more about HIV and circumcision from the Centers for Disease Control and Prevention.

FRIDAY, Oct. 3 (HealthDay News) -- A Chinese herbal remedy known as "horny goat weed" may indeed live up to its name as a natural version of Viagra.

Italian researchers report that laboratory studies show that the compound has the potential to treat erectile dysfunction, and possibly with fewer side effects than its pharmaceutical cousin.

"No in-vivo studies in an animal model have been performed at this regard, so a lot of work must be done. We would like to test in vivo [with animals] the molecule to understand if it really works in humans," said study lead author Mario Dell'Agli, of the University of Milan's laboratory of pharmacognosy. "At this stage of the research, we cannot say if the molecule we have synthesized possesses less side effects with respect to Viagra. However, this derivative seems to be in vitro [in lab tests] more selective than Viagra, because it targets [an enzyme involved in blood flow to the penis] more precisely."

The study was expected to be published in the Oct. 24 issue of the Journal of Natural Products, a publication of the American Chemical Society.

Viagra (sildenafil) is one of several prescription medications available and widely prescribed for erectile dysfunction, a condition that affects an estimated 18 million men in the United States. Viagra and other drugs like it can cause side effects such as headache, stomach problems and visual disturbances.

Horny goat weed, hailing primarily from southern China, has a long history as an aphrodisiac.

As part of a new screening program to find natural alternatives to Viagra, the study authors analyzed a number of herbal extracts long used for male impotence, including Ferula hermonis or Lebanese Viagra; Cinnamomum cassia or Chinese cinnamon; as well as Epimedium brevicornum aka horny goat weed. All three extracts are reputed to improve sexual performance.

The main active component of each extract was tested against an enzyme known as phosphodiesterase-5A1 (PDE5A1), which regulates blood supply to the penis. Inhibition of this enzyme results in more blood flow to the penis, resulting in an erection.

Icariin, the active ingredient of horny goat weed, inhibited PDE5A1 to a greater degree than the other compounds tested.

"The novelty of this work is the new molecule we have synthesized by icariin," Dell'Agli said. "It is derived by chemical modifications of the structure of icariin, which is the active ingredient purified from E. brevicornum (horny goat weed). The mechanism by which the molecule we have found might work in humans is the inhibition of phosphodiesterase 5 (PDE 5) in the corpus cavernosum [erectile tissue in the penis], which is the mechanism by which Viagra works. This is an in vitro study. It can be considered a pre-clinical study."

More information

The National Institutes of Health has more on erectile dysfunction.

WEDNESDAY, Oct. 1 (HealthDay News) -- The most pervasive global strain of HIV began spreading in humans around 1900 in sub-Saharan Africa, a new study claims.

The research, which is published in the current issue of Nature, found that HIV began spreading between 1884 and 1924, around the same time urban centers in west central Africa were established. This estimated time of origin is decades earlier than the previous estimate of 1930.

For the study, researchers analyzed tissue samples and uncovered the second-oldest genetic sequence of HIV-1 group M. They used this and other HIV-1 genetic sequences to construct a family tree of the origin of the viral strain and to estimate the time of origin of HIV-1 group M.

The researchers worked with a 1960 sample of HIV gene fragments from a wax-embedded lymph-node tissue biopsy from a woman in Kinshasa in the Democratic Republic of the Congo. This 1960 virus is the second-oldest known HIV-1 group M genetic sequence, with the oldest being a 1959 blood sample from a man also from Kinshasa.

"Previous work on HIV sequencing had been done on frozen samples, and there are only so many of those samples available," lead researcher Michael Worobey, an assistant professor of ecology and evolutionary biology at the University of Arizona in Tucson, said in a university news release.

"From that point on, the next oldest sequences that anyone has recovered are from the late 1970s and 1980s, the era when we knew about AIDS. Now, for the first time, we have been able to compare two relatively ancient HIV strains. That helped us to calibrate how quickly the virus evolved and make some really robust inferences about when it crossed into humans, how quickly the epidemic grew from that time and what factors allowed the virus to enter and become a successful human pathogen," said Worobey.

Previous studies have shown that HIV spread from chimpanzees to humans in southeastern Cameroon.

Worobey said that the HIV epidemic that resulted from the turn-of-the-century spread correlates to the urbanization of colonial Africa, principally the present-day city of Kinshasa in the Democratic Republic of the Congo.

The growth of cities and associated high-risk behaviors may have been a principal cause of the rapid spread of the virus.

Worobey is optimistic about the eventual extinction of the HIV virus.

"I think the picture that has emerged here, where changes the human population experienced may have opened the door to the spread of HIV, is a good reminder that we can make changes now that could help reverse the epidemic. If HIV has one weak spot, it is that it is a relatively poorly transmitted virus. From better testing and prevention, to wider use of the antiretroviral drug therapy, there are a number of ways to reduce transmission and force this virus back into extinction," he said.

More information

The U.S. Centers for Disease Control and Prevention have more about HIV.

FRIDAY, Aug. 29 (HealthDay News) -- Babies born prematurely to women who smoked during their pregnancy may be at higher risk of sudden infant death syndrome (SIDS) than premature infants born to nonsmoking moms, new research suggests.

The Canadian study is the first to compare the breathing reflexes of "preemies" born to smokers versus nonsmokers. The researchers found that these tiny babies were more likely to have impaired recovery from pauses in breathing if their mother had smoked during her pregnancy.

"Our study shows that preterm infants make incomplete and/or delayed recovery from interruptions in breathing," study author and neonatologist Dr. Shabih Hasan, a professor of pediatrics at the University of Calgary, said in an American Thoracic Society news release. "This has clear implications for their risk of SIDS."

The study, published in the first issue for September of the American Journal of Respiratory and Critical Care Medicine, involved 22 infants born spontaneously between 28 and 32 weeks of gestation. Twelve of the babies had mothers who smoked five or more cigarettes daily, while the moms of the other 10 babies did not smoke during their pregnancy. The team assessed factors such as the infants' breathing rate, interruptions in breathing, breathing recovery time, oxygen saturation in the blood, and heart rate.

While the team found no differences between the two groups in terms of respiratory rates and the number of breathing pauses, infants born to smoking mothers showed increases in heart rate during a short period of lowered oxygen. Babies born to nonsmoking women did not show such a change, indicating that they were less stressed when oxygen levels dipped. Babies born to women who smoked during pregnancy also took longer to recover from depleted blood oxygen levels than infants born to nonsmoking mothers.

Besides the risk of SIDS, "inability or delayed recovery from repeated low oxygen episodes can also be detrimental to brain development," Hasan noted. "There is increasing evidence that infants exposed to prenatal cigarette smoke are at high risk for developmental and behavioral disorders."

Hasan said the findings may help doctors and parents better identify those premature babies at higher risk of SIDS, so that they can be more closely monitored at home.

More information

There's more on SIDS at the Nemours Foundation  .