Confusion over red wine and diabetes

“Super-food” compounds in wine “can work as well as a daily dose of medication for people with type 2 diabetes,” the Daily Express has claimed. The newspaper says that “drinking a small glass of red wine every day can help treat diabetes”.

This story is based on laboratory research that looked at how well polyphenol compounds found in red wine can bind to a protein called PPARγ. The protein, which is targeted by the anti-diabetes drug rosiglitazone, plays an important role in glucose and fat metabolism in the body. However, while the research found that these polyphenol compounds were also able to bind to PPARγ in the laboratory, this does not mean they will have the same effects on the body as rosiglitazone. It is important to note that rosiglitazone can no longer be marketed in the EU for the treatment of diabetes as it was found to be associated with an increased risk of certain cardiovascular problems.

Further studies in cells and animals would be needed to determine whether the compounds identified in this study could potentially have anti-diabetic effects in humans. Until this is proven, it is inaccurate and premature to suggest that people can treat their diabetes with red wine.

Where did the story come from?

The study was carried out by researchers from the Christian Doppler Laboratory for Receptor Biotechnology and the University of Natural Resources and Life Sciences in Austria. No sources of funding were reported by the study. The study was published in the peer-reviewed scientific journal, Food and Function.

The Daily Express and Daily Mail both report on this study. Both suggest that red wine could help “treat” diabetes and the Express _ states that certain compounds found in wine “can work as well as a daily dose of medication for people with type 2 diabetes”. These conclusions are not supported by this research, which only looked at the ability of red wine and some of the compounds it contains to bind to a particular protein in the laboratory. The _Daily Mail does point out that “the study didn't look at the effects of wine on people”, and includes a quote from an expert who notes the lack of clinical relevance of these findings. It also adds that “the alcohol in wine is high in calories and can lead to weight gain, which can outweigh the benefits of these chemicals”.

Both papers report benefits of a “small glass of wine” but include pictures of women drinking what appear to be large glasses. Depending on its alcoholic strength, a large glass of wine (275ml) will typically meet or exceed a woman’s recommended maximum alcohol intake of two to three units a day.

What kind of research was this?

This was a laboratory study looking at the chemical properties of red wine. In particular, it looked at how different chemicals found in red wine bind to a protein called “peroxisome proliferator-activated receptor γ” (PPARγ), which has an important role in glucose and fat metabolism in the body.

The researchers wanted to look at this because moderate consumption of red wine has been linked to a lower risk of cardiovascular disease as well as type 2 diabetes, obesity and high blood pressure. Certain compounds found in wine called polyphenolic compounds, such as resveratrol, have been found to bind strongly to PPARγ. The researchers wanted to identify which polyphenolic compounds in wine bind most strongly to PPARγ, and calculate the equivalent concentration of the antidiabetic drug rosiglitazone needed to match the effect.

This type of study can show how molecules bind to each other in the laboratory, but cannot prove what effect a molecule will have once in the body. This type of study cannot tell us what effect red wine or the compounds it contains would have on the risk of diabetes or on people with diabetes.

What did the research involve?

The researchers assessed twelve Austrian wine varieties for their binding to PPARγ: two whites and ten reds. They also looked at the PPARγ-binding abilities of the polyphenolic compounds found in one of the wines that was particularly rich in these compounds.

The researchers used special techniques to assess the chemical composition of the wines and to separate their components. They tested a total of 121 compounds. They also used other chemical techniques to determine the antioxidant ability of the wines. Finally, they looked at the ability of the wines or isolated compounds from the wines to bind to PPARγ, using an assay where the test substances “compete” with a fluorescently labelled compound to bind to PPARγ. Substances binding to PPARγ more strongly will stop more of the fluorescently labelled compound from binding to PPARγ, which can be measured in the laboratory.

The researchers compared the ability of the wine compounds to bind to PPARγ with that of rosiglitazone, using available data on how well the drug binds to PPARγ. Rosiglitazone is a drug that was used up until recently to treat type 2 diabetes and acts by binding to PPARγ.

What were the basic results?

The researchers found that two polyphenolic compounds found in wine, ellagic acid and epicatechin gallate, were the compounds that bound to PPARγ the strongest. These compounds had a similar affinity for PPARγ to the anti-diabetes drug rosiglitazone.

The researchers found that all of the red wines tested had the ability to bind PPARγ, with 100ml of the various tested red wines having an equivalent binding effect as about 1.8mg to 18mg of rosiglitazone. This is between a quarter and four times the daily dose of rosiglitazone.

How did the researchers interpret the results?

The researchers suggest that the ability of red wine to reduce the risk of metabolic diseases such as diabetes may be explained in part by the fact that it contains compounds that can bind to PPARγ.

Conclusion

This laboratory study has looked at the ability of red wine and its polyphenol compounds to bind to PPARγ, an important protein in glucose and fat metabolism within the body. Some of the compounds were found to be capable of binding to PPARγ with a strength similar to that of the anti-diabetes drug rosiglitazone.

However, just because these compounds can bind to PPARγ in the laboratory does not mean that they or red wine can be used as a treatment for diabetes. Although these compounds may share certain chemical properties with rosiglitazone, they may differ in other ways, meaning that they are likely to have differing effects on the body. It is also important to note that rosiglitazone can no longer be marketed in the EU, as it was found to be associated with an increased risk of certain cardiovascular problems, a risk that was judged to outweigh its potential benefits.

Further studies in cells and animals would be needed to determine whether the PPARγ-binding compounds identified in this study could potentially have anti-diabetic effects.