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Public defence

Public defence in chemistry: Jiyun Liu

Title: Polyphenols in Swedish berries and pulses - characterization and in vivo effects of fractions from lingonberries and brown beans in an Apoe- /- mouse model
Subject: Chemistry
Faculty: Faculty of Health and Life Sciences 
Date: Friday December 17 2021 at 09.00 am
Place: Room Lapis, building Vita, Kalmar
External reviewer: Associate Professor Anne-Maria Pajari, Helsinki University
Examining committee: Docent Galia Zamaratskaia, SLU
Docent Björn Karlsson, Linnaeus University
Professor Yvonne Granfeldt, Lunds University
Chairperson: Professor Sven Tågerud, Department of Chemistry and Biomedical Sciences, Linnaeus University
Main supervisor: Professor Cornelia Witthöft, Department of Chemistry and Biomedical Sciences, Linnaeus University
Examiner: Professor Ian Nicholls, Department of Chemistry and Biomedical Sciences, Linnaeus University
Spikning: Friday November 26 2021 at 2.00 pm, Showroom, building Vita, Kalmar


Title: Polyphenols in Swedish berries and pulses – characterization and in vivo effects of fractions from lingonberries and brown beans in an Apoe-/- mouse model

Abstract: Consumption of berries and pulses can protect against atherosclerosis and other metabolic diseases, by modulating plasma lipid profile, gut microbiota, and microbiota-dependent metabolites. These nutritional benefits are often attributed to high content of polyphenols (flavonoids and phenolic acids) and dietary fiber. In this thesis, methods for quantification of flavonoids in berry and pulse matrices were developed. The methods were used for characterization of polyphenols in Swedish berries and pulses. The nutritional benefits of lingonberries, brown beans, and their polyphenol and fiber fractions, were then investigated in an Apoe-/- mouse model.

The method developed for flavonoid analysis, based on reversed phase HPLC-UV/MS, and extraction procedures were optimized for the berry and pulse matrices, and used to characterize the flavonoids in four Swedish berry species and polyphenols in eight Swedish pulse species (raw and cooked). The fiber and flavonoid fractions from lingonberries and the fiber fraction from brown beans were isolated and evaluated for their in vivo effects on atherosclerosis, compared with whole lingonberries and brown beans. Lingonberries, brown beans, and the isolated fractions were added to a high-fat diet and fed to Apoe-/- mice for 10.5 weeks, to determine their effects on atherosclerotic plaque amount, plasma lipids, gut microbiota, cecal short-chain fatty acids (SCFAs), and plasma methylamines and creatinine.

The results showed that the optimized analytical methods were capable of quantifying flavonoids in berries and pulses with high precision and recovery. Swedish berries and pulses were found to be good sources of polyphenols. Hydrothermal processing decreased the polyphenol content in pulses by 50-85%, mainly due to leaching into the processing water. In the study on mice, the whole lingonberry diet resulted in 50% lower atherosclerotic plaque amount, but not positively affect the lipid profile. The lingonberry fiber fraction diet doubled the butyric acid concentration in cecum contents and decreased growth of Akkermansia in gut microbiota. Compared with the high-fat control diet, whole bean and its fiber fraction stimulated growth of Bifidobacterium and formation of cecal SCFAs. The diets with whole bean, its fiber fraction, and the two fractions from lingonberry, but not the diet containing whole lingonberry, resulted in higher plasma trimethylamine N-oxide (TMAO) concentrations in the Apoe-/- mice.

On comparing the diets, it was concluded that the whole lingonberry, but not the lingonberry flavonoid and fiber fractions, resulted in less atherosclerotic plaques. Whole brown bean and the bean fiber fraction showed a tendency for less atherosclerotic plaques. The effects on plasma lipids, gut microbiota, and microbiota-dependent metabolites in the Apoe-/- mouse model were mainly caused by flavonoids in the case of lingonberries and by fiber in the case of brown beans.

Key words: lingonberry, brown bean, flavonoids, phenolic acids, dietary fiber, HPLC-UV/MS, atherosclerotic plaque, plasma lipid, gut microbiota, short-chain fatty acids, trimethylamine N-oxide, Apoe-/- mice.