Sunday, September 23, 2007


Popular summary below followed by abstract. The very popular antioxidant fad is beginning to show signs of being an iatrogenic disaster

BODY-BUILDING and nutritional supplements containing an antioxidant called N-acetylcysteine (NAC) may not be as safe as once thought. In the Journal of Clinical Investigation this week, scientists have reported that taking NAC can cause blood vessels to sense that they are not getting enough oxygen. This can lead to dangerously high blood pressure in the arteries that carry blood to the lungs -- a condition known as pulmonary arterial hypertension -- and cause swelling of the right side of the heart. The research team gave NAC to mice in their drinking water for three weeks, and compared their blood pressure and heart function to that of mice that did not receive NAC. The next step, say the authors, is to work out whether the levels of NAC found in supplements may be harmful to humans.



S-Nitrosothiols signal hypoxia-mimetic vascular pathology

By Lisa A. Palmer et al.

NO transfer reactions between protein and peptide cysteines have been proposed to represent regulated signaling processes. We used the pharmaceutical antioxidant N-acetylcysteine (NAC) as a bait reactant to measure NO transfer reactions in blood and to study the vascular effects of these reactions in vivo. NAC was converted to S-nitroso-N-acetylcysteine (SNOAC), decreasing erythrocytic S-nitrosothiol content, both during whole-blood deoxygenation ex vivo and during a 3-week protocol in which mice received high-dose NAC in vivo. Strikingly, the NAC-treated mice developed pulmonary arterial hypertension (PAH) that mimicked the effects of chronic hypoxia. Moreover, systemic SNOAC administration recapitulated effects of both NAC and hypoxia. eNOS-deficient mice were protected from the effects of NAC but not SNOAC, suggesting that conversion of NAC to SNOAC was necessary for the development of PAH. These data reveal an unanticipated adverse effect of chronic NAC administration and introduce a new animal model of PAH. Moreover, evidence that conversion of NAC to SNOAC during blood deoxygenation is necessary for the development of PAH in this model challenges conventional views of oxygen sensing and of NO signaling.

Hormone link to cancers

This sounds reasonable but is not conclusive

HUMAN growth hormone could be responsible for several types of cancer, including breast cancer, a University of Queensland researcher has found. Mike Waters, from UQ's Institute for Molecular Bioscience, said the hormone was needed for normal human growth and it worked by using a messenger protein called IGF1 (insulin-like growth factor). "There's quite a bit of work that implicates IGF1 in promoting cancers so this is an important way that growth hormone could be promoting cancers," Professor Waters said.

Growth hormone is produced by the pituitary gland and stimulates even growth in the body after birth. It also plays a significant role in metabolism, minimising the amount of fat in the body and stimulating glucose production. Professor Waters said studies on people whose pituitary glands failed to produce growth hormone showed they remained cancer free. "In the absence of growth hormone the cancer rate is markedly lower and there's a worldwide survey that's just been done of 220-odd people that didn't find a single malignancy in people who had deficient growth hormone action," he said. "That also correlates with animal studies in rats and mice where without growth hormone you treat them with cancer-causing chemicals and they don't get tumours."

The research could have major implications for the global pharmaceutical industry where the sale of human growth hormone is worth more than $2 billion a year. Human growth hormone is often used by bodybuilders. Professor Waters said "knocking down" the hormone or blocking its action could inhibit cancer and stop tumour growth.

So far his research has only been able to partially disable the hormone. "We need to get the knock down more effective - if we can really knock it down we should be able to stop a hell of a lot of cancers," Professor Waters said. In a second-pronged attack on cancer, the professor has found that the target for growth hormone, its receptor, is within the cell nucleus. "So we've sent the receptor to the cell's nucleus using a special means and that's caused the cell to become cancerous," he said of the research that has been published by the National Academy of Sciences in the US.



Just some problems with the "Obesity" war:

1). It tries to impose behavior change on everybody -- when most of those targeted are not obese and hence have no reason to change their behaviour. It is a form of punishing the innocent and the guilty alike. (It is also typical of Leftist thinking: Scorning the individual and capable of dealing with large groups only).

2). The longevity research all leads to the conclusion that it is people of MIDDLING weight who live longest -- not slim people. So the "epidemic" of obesity is in fact largely an "epidemic" of living longer.

3). It is total calorie intake that makes you fat -- not where you get your calories. Policies that attack only the source of the calories (e.g. "junk food") without addressing total calorie intake are hence pissing into the wind. People involuntarily deprived of their preferred calorie intake from one source are highly likely to seek and find their calories elsewhere.

4). So-called junk food is perfectly nutritious. A big Mac meal comprises meat, bread, salad and potatoes -- which is a mainstream Western diet. If that is bad then we are all in big trouble.

5). Food warriors demonize salt and fat. But we need a daily salt intake to counter salt-loss through perspiration and the research shows that people on salt-restricted diets die SOONER. And Eskimos eat huge amounts of fat with no apparent ill-effects. And the average home-cooked roast dinner has LOTS of fat. Will we ban roast dinners?

6). The foods restricted are often no more calorific than those permitted -- such as milk and fruit-juice drinks.

7). Tendency to weight is mostly genetic and is therefore not readily susceptible to voluntary behaviour change.

8). And when are we going to ban cheese? Cheese is a concentrated calorie bomb and has lots of that wicked animal fat in it too. Wouldn't we all be better off without it? And what about butter and margarine? They are just about pure fat. Surely they should be treated as contraband in kids' lunchboxes! [/sarcasm].

Trans fats:

For one summary of the weak science behind the "trans-fat" hysteria, see here. Trans fats have only a temporary effect on blood chemistry and the evidence of lasting harm from them is dubious. By taking extreme groups in trans fats intake, some weak association with coronary heart disease has at times been shown in some sub-populations but extreme group studies are inherently at risk of confounding with other factors and are intrinsically of little interest to the average person.


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