Monday, February 06, 2012

Vitamin D could help combat the effects of aging in eyes

If you are a mouse. Since mice have short lives and we have long ones, studying aging in mice and hoping it will generalize to humans is considerable optimism

Researchers funded by the Biotechnology and Biological Sciences Research Council (BBSRC) have found that vitamin D reduces the effects of ageing in mouse eyes and improves the vision of older mice significantly. The researchers hope that this might mean that vitamin D supplements could provide a simple and effective way to combat age-related eye diseases, such as macular degeneration (AMD), in people.

The research was carried out by a team from the Institute of Ophthalmology at University College London and is published in the current issue of the journal Neurobiology of Ageing.

Professor Glen Jeffery, who led the work, explains "In the back of the eyes of mammals, like mice and humans, is a layer of tissue called the retina. Cells in the retina detect light as it comes into the eyes and then send messages to the brain, which is how we see. This is a demanding job, and the retina actually requires proportionally more energy than any other tissue in the body, so it has to have a good supply of blood. However, with ageing the high energy demand produces debris and there is progressive inflammation even in normal animals. In humans this can result in a decline of up to 30% in the numbers of light receptive cells in the eye by the time we are 70 and so lead to poorer vision."

The researchers found that when old mice were given vitamin D for just six weeks, inflammation was reduced, the debris partially removed, and tests showed that their vision was improved.

The researchers identified two changes taking place in the eyes of the mice that they think accounted for this improvement. Firstly, the number of potentially damaging cells, called macrophages, were reduced considerably in the eyes of the mice given vitamin D. Macrophages are an important component of our immune systems where they work to fight off infections. However in combating threats to the aged body they can sometimes bring about damage and inflammation. Giving mice vitamin D not only led to reduced numbers of macrophages in the eye, but also triggered the remaining macrophages to change to a different configuration. Rather than damaging the eye the researchers think that in their new configuration macrophages actively worked to reduce inflammation and clear up debris.

The second change the researchers saw in the eyes of mice given vitamin D was a reduction in deposits of a toxic molecule called amyloid beta that accumulates with age. Inflammation and the accumulation of amyloid beta are known to contribute, in humans, to an increased risk of age-related macular degeneration (AMD), the largest cause of blindness in people over 50 in the developed world. The researchers think that, based on their findings in mice, giving vitamin D supplements to people who are at risk of AMD might be a simple way of helping to prevent the disease.

Professor Jeffery said "When we gave older mice the vitamin D we found that deposits of amyloid beta were reduced in their eyes and the mice showed an associated improvement of vision. People might have heard of amyloid beta as being linked to Alzheimer's disease and new evidence suggests that vitamin D could have a role in reducing its build up in the brain. So, when we saw this effect in the eyes as well, we immediately wondered where else these deposits might be being reduced."

Professor Jeffery and his team then went on to study some of the blood vessels of their mice. They found that the mice that had been given the vitamin D supplement also had significantly less amyloid beta built up in their blood vessels, including in the aorta.

Professor Jeffery continues "Finding that amyloid deposits were reduced in the blood vessels of mice that had been given vitamin D supplements suggests that vitamin D could be useful in helping to prevent a range of age-related health problems, from deteriorating vision to heart disease."

Professor Jeffery thinks that this link between vitamin D and a range of age-related diseases might be linked to our evolutionary history. For much of human history our ancestors lived in Africa, probably without clothes, and so were exposed to strong sunlight all year round. This would have triggered vitamin D production in the skin. Humans have only moved to less sunny parts of the world and adopted clothing relatively recently and so might not be well adapted to reduced exposure to the sun. Secondly, life expectancy in the developed world has increased greatly over the past few centuries, so reduced exposure to vitamin D is now coupled with exceptionally long lifespan.

Professor Jeffery said "Researchers need to run full clinical trials in humans before we can say confidently that older people should start taking vitamin D supplements, but there is growing evidence that many of us in the Western world are deficient in vitamin D and this could be having significant health implications."

Professor Douglas Kell, BBSRC Chief Executive said "Many people are living to an unprecedented old age in the developed world. All too often though, a long life does not mean a healthy one and the lives of many older people are blighted by ill health as parts of their bodies start to malfunction.

"If we are to have any hope of ensuring that more people can enjoy a healthy, productive retirement then we must learn more about the changes that take place as animals age. This research shows how close study of one part of the body can lead scientists to discover new knowledge that is more widely applicable. By studying the fundamental biology of one organ scientists can begin to draw links between a number of diseases in the hope of developing preventive strategies."


Drinking three cups of tea a day 'can lower your blood pressure'

"Our objective was to assess the effects of regular black tea consumption (3 cups/d) for 6 months on 24-hour ambulatory BP"

But the effect they found was really tiny, possibly due to chance alone in such a small sample. Journal article here

It's good news for the two-thirds of Britons who have a cup of tea every day - enjoying a brew may significantly reduce your blood pressure. Scientists at The University of Western Australia and Unilever discovered that drinking three cups of tea a day lowers systolic and diastolic blood pressure.

However, researchers based their findings on drinking black tea and the effect of drinking tea with milk is not known.

Tea is the world's second-most popular drink, after water. It is full of polyphenols, antioxidants that have been shown to stop cancer cells from growing. Another study from Harvard University found the drink could boost immune function.

Now researchers have found more proof that it keeps the heart healthy. Lead author Research Professor Jonathan Hodgson said: 'There is already mounting evidence that tea is good for your heart health, but this is an important discovery because it demonstrates a link between tea and a major risk factor for heart disease.'

Blood pressure measurement consists of two numbers. The first is the systolic and measures blood pressure when the heart beats, or contracts to push blood through the body. The second number is the diastolic and measures the amount of pressure in between beats, when the heart is at rest.

In the small study, 95 Australian participants aged between 35 and 75 were recruited to drink either three cups of black tea or a placebo with the same flavour and caffeine content, but not derived from tea.

After six months, the researchers found that compared with the placebo group, participants who drank black tea had a lower systolic and diastolic blood pressure of between 2 and 3 mmHg (millimetres of mercury).

The authors believe a 2 to 3mmHg drop in blood pressure across the board would lead to a 10 per cent drop in the number of people with hypertension and heart disease.

Dr Hodgson wrote: 'A large proportion of the general population has blood pressure within the range included in this trial, making results of the trial applicable to individuals at increased risk of hypertension.'

He added that more research is required to better understand how tea may reduce blood pressure, although earlier studies reported a link between tea drinking and the improved health of people's blood vessels.

The study is published this week in the Archives of Internal Medicine.

Tracy Parker, Heart Health Dietitian at the British Heart Foundation (BHF), told Mail Online: 'It is important to understand that a cuppa won't cancel out a poor diet or lifestyle. There is evidence that antioxidant properties in tea could provide heart health benefits, but more research is required to better understand how tea may reduce blood pressure.

'In the meantime, cutting down on salt and alcohol, eating more fruit and vegetables, and keeping physically active are all well established ways of lowering your blood pressure.'


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