Sugar leads to early death, but not due to obesity

Study with the participation of the PMI Cluster of Excellence points out that the reduced life expectancy due to sugar consumption could have other causes than previously assumed

We all know that consuming too much sugar is unhealthy. It increases our risk of developing metabolic disorders, such as obesity and diabetes, and can shorten our life expectancy by several years. It is widely believed that this reduction in lifespan is caused by metabolic defects. However, this assumption could be wrong, as shown by a new study published yesterday in the journal Cell Metabolism by researchers from the Imperial College London in collaboration with researchers from Kiel University and the University Medical Center Schleswig-Holstein (UKSH), Campus Kiel. The results suggest that instead the accumulation of a natural waste product, uric acid, may be related to sugar-related shortened life expectancy.

Sugar consumption increases uric acid levels

The London team has investigated the influence of sugary food on the life span of fruit flies. “Just like humans, flies fed a high-sugar diet show many hallmarks of metabolic disease – for instance, they become fat and insulin resistant,” says Dr. Helena Cochemé of the Imperial College London, principal investigator of the study. “Obesity and diabetes are known to increase mortality in humans, and so people always assumed that this was how excess sugar is damaging for survival in flies”. However, like salt, sugar also causes dehydration. Therefore, the researchers gave the fruit flies additional water. Surprisingly they found that flies fed a high-sugar diet did not show a reduced lifespan, simply by providing them with an extra source of water to drink. Unexpectedly, these flies still exhibited the typical metabolic defects associated with high dietary sugar.

Based on this water effect, the team decided to focus on the fly renal system. They showed that excess dietary sugar caused the flies to accumulate a molecule called uric acid. Uric acid is an end-product from the breakdown of purines, which are important building blocks in our DNA. But uric acid is also prone to crystallise, giving rise to kidney stones in the fly. Researchers could prevent these stones, either by diluting their formation with drinking water or by blocking the production of uric acid with a drug. In turn, this protected against the shortened survival associated with a sugar-rich diet. “Although the sugar-fed fruit flies live longer if we give them more water, they are still uhealthy. But our study suggests that disruption of the purine pathway is the limiting factor for survival in high-sugar-fed flies. This means that early death by sugar is not necessarily a direct consequence of obesity itself”, said Cochemé.

Increased uric acid levels through sugar in humans

A similar mechanism could also work in humans, as researchers of the Cluster of Excellence “Precision Medicine in Chronic Inflammation” (PMI) have shown. A team led by Professor Christoph Kaleta, Professor Andre Franke, Professor Matthias Laudes and Professor Wolfgang Lieb - all from Kiel University - has investigated the influence of sugar-rich nutrition in healthy humans. “Strikingly, just like flies, we found that dietary sugar intake in humans was associated with worse kidney function and higher purine levels in the blood”, says Prof. Christoph Kaleta from the Institute for Experimental Medicine at Kiel University.

Accumulation of uric acid is a known direct cause of kidney stones in humans, as well as gout, a form of inflammatory arthritis. Uric acid levels also tend to increase with age, and can predict the onset of metabolic diseases such as diabetes. “It will be interesting to investigate how the accumulation of uric acid due to increased sugar consumption is related to metabolic diseases such as diabetes and whether it might even have a direct effect on life expectancy in humans," said Kaleta. "In the future, we might also be able to find new therapeutic targets and strategies that promote healthy ageing," predicts Kaleta.

Contact:

Prof. Christoph Kaleta
Institute for Experimental Medicine, Kiel University
0049 431 500-30340
c.kaleta@iem.uni-kiel.de

a pile of sugar
© Pixabay

Too much sugar can shorten life expectancy by several years. However, at least in fruit flies, the cause for this is not, as previously assumed, obesity and diabetes resulting from sugar consumption.

Fruitfly Drosophila
© C. Urban, Uni Kiel.

Fruit flies that had been fed a sugary diet died earlier than conspecifics with other food. The effect could be prevented by an additional water source.

Professor Christoph Kaleta from Kiel University
© T. Böschen, Uni Kiel.

Professor Christoph Kaleta, member of the Cluster of Excellence "Precision Medicine in Chronic Inflammation" (PMI) and head of the Medical Systems Biology group at the Institute for Experimental Medicine, CAU.

Original publication:

Esther van Dam, …, Wolfgang Lieb, Matthias Laudes, Andre Franke, Christoph Kaleta, and Helena M.
Cochemé, “Sugar-Induced Obesity and Insulin Resistance Are Uncoupled from Shortened Survival
in Drosophila”, Cell Metabolism (2020). https://doi.org/10.1016/j.cmet.2020.02.016

 

About the Cluster of Excellence PMI

The Cluster of Excellence "Precision Medicine in Chronic Inflammation" (PMI) is being funded from 2019 to 2025 through the German Excellence Strategy (ExStra). It succeeds the "Inflammation at Interfaces” Cluster, which was already funded in two periods of the Excellence Initiative (2007-2018). Around 300 members from eight institutions at four locations are involved: Kiel (Kiel University, University Medical Center Schleswig-Holstein (UKSH), Muthesius University of Fine Arts and Design, Kiel Institute for the World Economy (IfW), Leibniz Institute for Science and Mathematics Education (IPN)), Lübeck (University of Lübeck, University Medical Center Schleswig-Holstein (UKSH)), Plön (Max Planck Institute for Evolutionary Biology) and Borstel (Research Center Borstel - Leibniz Lung Center).

The goal is to translate interdisciplinary research findings on chronic inflammatory diseases of barrier organs to healthcare more intensively, as well as to fulfil previously unsatisfied needs of the patients. Three points are important in the context of successful treatment, and are therefore at the heart of PMI research: the early detection of chronic inflammatory diseases, the prediction of disease progression and complications, and the prediction of individual responses to treatment.

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