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In developing obesity, adipose tissue begins to secrete inflammatory factors. It actuates low-grade inflammation in the body and increases the risk of type 2 diabetes and cardiovascular diseases. Additionally, overweight induces changes also in the hepatic metabolism and fat begins to accumulate in the liver. Fatty liver disease remains first asymptomatic, but it can, at worst, lead to the development of liver cirrhosis and cancer.
Lingonberry is the most commonly used wild berry in Finland. Its chemical composition is rather well known, but the health-promoting effects of lingonberry remain poorly studied. In her doctoral thesis, M.Sc. Riitta Ryyti investigated the effects of lingonberry supplementation on low-grade inflammation and metabolic changes in an experimental model of obesity.
Lingonberry supplementation prevented the development of low-grade inflammation and increase in glucose and cholesterol levels, as well as weight and visceral fat gain, in mice on high-fat diet. The levels of inflammatory factors and leptin hormone were lower in the lingonberry group. Lingonberry supplementation also prevented the rise of serum ALT enzyme levels. Increased serum ALT may indicate liver cell damage induced by fatty liver.
"Lingonberry skin extract made from pomace had similar effects on glucose metabolism, and weight and visceral fat gain as the whole berry. Apparently, there are still effective substances present in the lingonberry skin parts, so they should also be utilized", Ryyti states.
The effects of high-fat diet on the gene expression profile in the liver were investigated with NGS-based genome-wide expression analysis. Altered expression of several hundred genes were detected. For example, the expression of multiple genes related to inflammation was increased.
"It was interesting to find out that lingonberry supplementation prevented the high-fat diet-induced changes in the expression of about 250 genes. These genes were related particularly to inflammation and lipid metabolism, and to the development of insulin resistance and type 2 diabetes", Ryyti says.
The present study aimed also to find out, which of the lingonberry compounds might be behind the detected effects. It was found that kaempferol, resveratrol, and proanthocyanidins increased the activation of macrophages towards the anti-inflammatory M2 phenotype. In addition, kaempferol and resveratrol attenuated the pro-inflammatory M1-type macrophage activation.
"I encourage everyone to add lingonberries as a part of healthy diet. Further research is, however, needed to confirm the translation of the detected effects to human obesity as well as to understand the underlying mechanisms and appropriate dosing", Ryyti says.
Public defence on Friday 23 August
The doctoral dissertation of M.Sc. Riitta Ryyti in the field of pharmacology titled Low-grade inflammation in obesity: Beneficial effects of lingonberry supplementation will be publicly examined at the Faculty of Medicine and Health Technology at Tampere University on Friday 23.8.2024 at 12 o’clock at Kauppi campus, Arvo building, hall F114 (Arvo Ylpön katu 34, Tampere). The opponent is Dr. Riitta Korpela from the University of Helsinki. The custos is Professor Eeva Moilanen from the Faculty of Medicine and Health Technology, Tampere University.