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Overactivity of a brain enzyme, called p70 S6 Kinase 1, or S6K, may play a role in preventing weight gain and obesity, said researchers at Albert Einstein College of Medicine of Yeshiva University.

For the study, scientists focussed on the hypothalamus in the brain, which controls body temperature, hunger, and thirst. Specialized nerve cells in the hypothalamus sense whether the body contains adequate amounts of nutrients and stored body fat. The cells then send out signals telling other parts of the brain to adjust food intake, metabolic rates, and physical activity accordingly — keeping the body’s caloric intake in balance with calories burned.

Thus, in order to delve in detail into the nutrient-sensing pathways and how they go awry in metabolic disorders, the researchers focused on an enzyme called p70 S6 Kinase 1, or S6K, which plays a role in regulating the growth and proliferation of all cells, including nerve cells.

“It turns out that this enzyme, and the pathway it regulates, is nutrient sensitive — that is, S6K activity increases in the presence of carbohydrates and protein. This led us to believe that S6K might not only be involved in maintaining the structure and function of individual cells, but also in regulating the energy balance of the whole body,” said the study’s principal investigator, Gary J Schwartz, Ph.D., professor of medicine and neuroscience at Einstein.

To test their hypothesis, the researchers injected rats with special viruses that selectively raise or lower S6K activity. They injected the viruses directly into the lower-middle, or mediobasal, portion of the hypothalamus, an area rich in nutrient-sensing nerve cells.

“When we raised the activity of the enzyme, we saw reductions in food intake, in body weight, and in production of peptides [small chains of amino acids] that normally stimulate feeding. When we lowered S6K activity, we saw essentially the opposite response,” said Dr Schwartz.

Schwartz said that it was important how increased S6K activity reduced the rats” food intake by reducing the average size of meals rather than changing the number of meals over the course of a day.

Thus, the animals apparently were sated faster and therefore ate less at every meal.

In another experiment, the researchers tested whether increased S6K activity would protect against the natural tendency of mammals on a high-fat diet to overeat.

When animals on a high-fat diet were given the S6K-enhancing virus, they overate less and gained weight more slowly than control animals, the researchers report. In addition, the virus-enhanced animals had lower body-fat levels and better glucose tolerance than the control group.

On the whole, the study shows that S6K acts as a kind of food-sensing thermostat in mammals, increasing or decreasing feeding behaviour and metabolism to maintain a normal energy balance.

“These findings show that it may be possible to control obesity and other human metabolic disorders by developing drugs that regulate S6K activity,” said Schwartz.

The findings were reported in Cell Metabolism.

The Vatican raised its opposition to embryonic stem cell research, the morning-after pill, in vitro fertilization and human cloning to a new level Friday in a major new document on bioethics.

But in the document, the Vatican also said it approved of some forms of gene therapy and encouraged stem cell research using adult cells. And it said parents could in good conscience inoculate their children with vaccines produced with cells derived from aborted fetuses.

The Vatican’s Congregation for the Doctrine of the Faith issued “The Dignity of a Person” to answer bioethical questions that have emerged in the two decades since its last such document was published.

With it, the Vatican has essentially confirmed in a single, authoritative instruction the opinions of the Pontifical Academy for Life, a Vatican advisory body that has debated these issues for years.

The Vatican’s overall position is formed by its belief that human life begins at conception, and must be afforded all the consequent respect and dignity from that moment on. The Vatican also holds that human life should be created through intercourse between husband and wife, not in a petri dish.

As a result, the Vatican said it opposed the morning-after pill, even if it doesn’t cause an abortion, because an abortion was “intended.” In the use of drugs such as RU-486, which causes the elimination of the embryo once it is implanted, the “sin of abortion” is committed; their use is thus “gravely immoral.”

The Vatican also said it opposed in vitro fertilization because it involves separating conception from the “conjugal act” and often results in the destruction of embryos. The Vatican supports, however, techniques that help couples overcome obstacles to getting pregnant.

In the document, the Vatican elaborated on a host of issues surrounding assisted fertility, saying it:

_Opposed the selective reduction of embryos often used in in vitro procedures since it essentially is abortion.

_Opposed pre-implantation diagnosis of embryos since it may be followed by the destruction of those embryos deemed defective or otherwise undesirable.

_Opposed freezing embryos, since it is “incompatible with the respect owed to human embryos” and also means they were created in vitro.

It said that, while freezing eggs is not in itself immoral, it becomes unacceptable when it occurs for the sake of artificial procreation.

The Vatican lauded as “praiseworthy” the suggestion by some to let infertile couples “adopt” the thousands of frozen embryos that have been produced in vitro over the years. But it said such adoptions present a host of medical, psychological and legal problems.

The instruction also weighed in on research involving stem cells, cloning and gene therapy.

The Vatican stressed that it fully supported research involving adult stem cells. But it said obtaining stem cells from a living embryo, even for the sake of effective therapies, was “gravely illicit.”

It said gene therapy on regular cells in the body other than reproductive ones was in principle morally licit since it sought to “restore the normal genetic configuration of the patient or to counter damage caused by genetic anomalies.”

But it said that cell therapy which seeks to correct genetic defects with the aim of transmitting the therapy onto offspring was more problematic.

“Because the risks connected to any genetic manipulation are considerable and as yet not fully controllable, in the present state of research, it is not morally permissible to act in a way that may cause harm to the resulting progeny,” the document said.

In the document, the Vatican also:

_Repeated its opposition to human cloning for both medical therapies and reproduction. Such techniques could result in an individual being subjected to a form of “biological slavery from which it would be difficult to free himself.”

_Said parents could in good conscience use a vaccine for their children that was developed using cell lines from an “illicit origin.” Religious groups in the United States have pressed the Vatican to issue a statement concerning the morality of using vaccines developed using cell lines derived from aborted fetuses.

“Grave reasons may be morally proportionate to justify the use of such ‘biological material,’” the instruction said, adding that the parents would have to make known their disagreement with the way the vaccines were developed and press for alternatives.

But the document was very strong in stressing that researchers using such material were in a different position and had a greater degree of responsibility. It said they had a moral duty to remove themselves from the “evil aspects” of the original, illicit act — even if they and their institutions had nothing to do with it.