Longevity Briefs: A Compound In Tomatoes And Carrots Extends Average Lifespan In Worms

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

The problem:

Carotenoids are vibrant pigments found in many fruits and vegetables, widely recognised as being beneficial for health due to their antioxidant properties (they are able to neutralise harmful reactive oxygen species produced a a byproduct of cellular metabolism), and because they include precursors to essential vitamins. However, one particular carotenoid called phytoene has largely been overlooked. Unlike its colourful relatives, phytoene has no colour and was mostly thought to be a precursor in the production of other carotenoids, with little to no biological effects by itself. In this study, researchers investigate the effects of phytoene in worms, and present evidence that it actually has some quite substantial effects.

The discovery:

Researchers procured pure phytoene and phytoene-rich extracts from two microalgae species, Chlorella sorokiniana and Dunaliella bardawil, which were specifically cultivated to accumulate high levels of phytoene. Phytoene was then administered to C.elegans worms. These are nematode worms commonly used to study the effects of compounds on lifespan, since they only live two weeks or so (which allows changes in average lifespan to be measured in a short experiment).

After checking that the presence phytoene didn’t have any toxic effects or interfere with the growth of C.elegans, groups of 150 worms were exposed to juglone, a toxin that causes the generation of harmful reactive oxygen species. They were then exposed to varying concentrations of phytoene or a control solution. Researchers found that the two highest concentrations of phytoene were associated with significantly improved survival (39% increased survival for the lower concentration and 53% for the higher concentration) compared to controls, suggesting that phytoene protected the worms against reactive oxygen species.

Researchers then moved to a ‘humanised’ C.elegans model that had been genetically engineered to produce the human form of amyloid-β 42, a protein implicated in Alzheimer’s disease. This causes progressive paralysis in the worms over time. Groups of 90 worms were given phytoene, phytoene-containing extracts or a control. Researchers found that on day 2 of the experiment, 62% of worms in the control groups were paralysed vs 43% in the group that received pure phytoene, suggesting a protective effect against amyloid-β 42 toxicity.

Finally, researchers looked at whether phytoene had any effect on worm lifespan. They found that pure phytoene was associated with 15.5% increase in median lifespan (the age by which 50% of worms were dead) compared to the control groups (120 worms per condition). While not explicitly highlighted or statistically analysed, it appears from the data (see the graph below) that phytoene may have extended maximum lifespan. That is to say that by the time virtually all of the worms in the control groups had died (days 23 -25), 5-10% of the worms in the experimental groups were able to survive for a few more days.

The implications:

This research suggests that phytoene intake is not inconsequential for health, and is able to extend lifespan in worms, probably through its antioxidant properties. It also appeared to protect against amyloid-β 42 toxicity, suggesting a potential effect against Alzheimer’s disease. This, combined with the fact that phytoene can be extracted in large quantities from certain species of microalagae, could make phytoene a promising dietary supplement for investigation in humans. However, before we get too excited, it’s important to remember that studies in worms can’t be extrapolated to humans. Dietary antioxidants, while thought to be beneficial, have typically not been found to produce consistent lifespan extension in mammals, and there’s no definitive evidence that they increase human lifespan. While that may be the case, foods that are rich in phytoene such as tomatoes, carrots and peppers are healthy in other ways, so consuming more of them as part of your diet certainly isn’t a bad idea.