[Note: This is an extract from a Part 3 text about the effect of a low-calorie diet on the ageing process.]
Adapted from ‘The Serious Search for an Anti-Aging Pill’. Copyright © 2006 Scientific American, a division of Nature America, Inc. All rights reserved.
No treatment on the market today has been proved to slow human aging. But one intervention, consumption of a low-calorie yet nutritionally balanced diet, works incredibly well in a broad range of animals, increasing longevity and prolonging good health. Those findings suggest that caloric restriction could delay aging and increase longevity in humans, too. But what if someone could create a pill that mimicked the physiological effects of eating less without actually forcing people to eat less, a ‘caloric-restriction mimetic’? ·
The best-studied candidate for a caloric-restriction mimetic, 2DG (2-deoxy-D-glucose), works by interfering with the way cells process glucose. It has proved toxic at some doses in animals and so cannot be used in humans. But it has demonstrated that chemicals can replicate the effects of caloric restriction; the trick is finding the right one.
Cells use the glucose from food to generate ATP (adenosine triphosphate), the molecule that powers many activities in the body. By limiting food intake, caloric restriction minimizes the amount of glucose entering cells and decreases ATP generation. When 2DG is administered to animals that eat normally, glucose reaches cells in abundance but the drug prevents most of it from being processed and thus reduces ATP synthesis. Researchers have proposed several explanations for why interruption of glucose processing and ATP production might retard aging. One possibility relates to the ATP-making machinery’s emission of free radicals, which are thought to contribute to aging and to such age-related diseases as cancer by damaging cells. Reduced operation of the machinery should limit their production and thereby constrain the damage. Another hypothesis suggests that decreased processing of glucose could indicate to cells that food is scarce (even if it isn’t) and induce them to shift into an anti-aging mode that emphasizes preservation of the organism over such ‘luxuries’ as growth and reproduction.
Questions 1 – 3
Complete the flow-chart below.
Choose NO MORE THAN TWO WORDS from the passage for each answer.
Write your answers in boxes 1-3 on your answer sheet.
How a caloric-restriction mimetic works
CR mimetic
↓
less 1 ………… is processed
↓
production of ATP is decreased
Theory 1:
Theory 2:
cells less damaged by disease because
fewer 2 ………… are emitted
cells focus on 3 ………… because
food is in short supply
Answers
1 glucose
2 free radicals
3 preservation