IBG-2 Seminar Prof. Dr. Yves Desjardins, Agr. – Université Laval, Québec, Canada

Institut de Nutrition et des Aliments Fonctionnels
Centre de recherche en horticulture

Diabetes prevention: a role for berry fruits ?

On secondary metabolites of plants and their impact on health

The occurrence of obesity is taking alarming proportions worldwide. This pandemic affects billions of people and represents a major health challenge for our modern societies. The burden of obesity reduces life expectancy, and is associated with an explosive incidence of type-2 diabetes (T2D). This insidious disease is silent until certain organs are irreparably damaged. It is thus essential to develop innovative and effective solutions to prevent T2D knowing that it is possible to avoid and prevent the appearance and outcome of this disease by adopting a healthy lifestyle and making the proper food choices. One of the key factors in the aetiology of T2D is the chronic inflammation caused by overweight, which in turn induces resistance to insulin. To overcome this state, the pancreas must produce more insulin; in the long run, the cells producing insulin become exhausted and must be replaced by injection to control glycaemia. Pharmacological options to treat this disease like metformin, PPARγ agonists (Thiazolidinediones : TZD) and sulfonylurea, are not always effective and display many side effects.
Research shows that polyphenols from berries and particularly from blueberries can prevent the outcome of T2D and reduce the biomarkers linked to the metabolic syndrome. Apart from their antioxidant capacity, berry polyphenols trigger signalling pathways leading to an improve glucose uptake in muscle and adipose tissues. These molecules can also inhibit the accumulation of advanced glycation end-products and the activity of sugar hydrolytic enzymes, while activating enzymes involved in the energy metabolism like AMPK and the activity of agonists like PPARγ. Polyphenols can also reduce cellular inflammation and particularly the expression of COX-2 and iNOS in adipose tissues.
Recently, a new class of plant molecule displaying a strong bioactivity against diabetes has been uncovered. Indeed, abscisic acid (ABA), a sesquiterpenoid involved in stress responses and dormancy in plants, has also been shown to be active against T2D. ABA activates PPARγ receptors as does TZD and increase the sensitivity to insulin in animal models. ABA also appears to increase the secretion of insulin like sulphonylurea. Finally, studies suggest that ABA can activate AMPK through the action of PPARγ. We have recently shown that ABA is found in high titer in cranberries, blueberries and strawberries. Our recent results show that this molecule has a complex multi-level action on energy metabolism, which could explain the positive effect of berries on diabetes. This presentation will provide an overview of the mechanisms by which polyphenols and terpenoids can reduce the incidence of metabolic disorders leading to diabetes.