Investigating the ameliorative potential of Aspalathus linearis and Cyclopia intermedia against lipid accumulation, lipolysis, oxidative stress and inflammation

Mamushi, Mokadi Peggy (2020-03)

Thesis (MSc)--Stellenbosch University, 2020.

Thesis

Background Despite the availability of several treatment regimens, obesity continues to be one of the greatest health challenges of the 21st century. In recent years, plant polyphenols have attracted increasing attention as nutraceuticals that are able to prevent or treat obesity and its co-morbidities. However, the first-line screening of these compounds is hampered by the shortage of in vitro experimental models that mimic the complex pathophysiology of obesity (excess lipid accumulation, basal lipolysis, inflammation and oxidative stress) in vivo. The aim of this study was two-fold. Firstly, establish a 3T3-L1 adipocyte in vitro model that more closely mimics obesity in vivo, and secondly to investigate the ameliorative properties of Aspalathus linearis, Cyclopia intermedia and their major polyphenols against these conditions. Methods For the experimental model, 3T3-L1 pre-adipocytes were differentiated in 5.5 mM, 25 mM or 33 mM glucose concentrations for 7 or 14 days. Lipid accumulation, basal lipolysis, oxidative stress, inflammation, mitochondrial activity and gene expression were assessed using Oil Red O staining, glycerol release, 2',7'-dichlorfluorescein-diacetate fluorescence to quantify reactive oxygen species, monocyte chemoattractant protein-1 secretion, the 3- [4, 5-Dimethylthiazol-2-yl]-2, 5 diphenyltetrazolium bromide assay and quantitative real time polymerase chain reaction, respectively. The ameliorative effects of Aspalathus linearis (Afriplex GRTTM) and Cyclopia intermedia (CPEF) against these conditions were investigated by acute and chronic treatment of the optimised experimental model with various concentrations of these plant extracts and their major polyphenol Aspalathin and Mangiferin respectively. Results Collectively lipid accumulation, basal lipolysis, oxidative stress, inflammation and expression of associated genes were higher after differentiation in 33 mM for 14 days compared to lower glucose concentrations and 7 days, thus these conditions were selected as the experimental model. Neither acute nor chronic treatment with 0.1 to 100 µg/ml of Aspalathus linearis and Cyclopia intermedia, and 0.1 to 100 µM of Aspalathin and Mangiferin significantly decreased lipid content. However, all treatments decreased basal lipolysis and increased mitochondrial activity. Conclusion Differentiation of 3T3-L1 pre-adipocytes in 33 mM glucose for 14 days increased basal lipolysis, oxidative stress and inflammation compared to lower glucose concentrations and differentiation for 7 days. Aspalathus linearis, Cyclopia intermedia, Aspalathin and Mangiferin ameliorated the increased basal lipolysis under these conditions. This study showed that differentiation in 33 mM glucose for 14 days may offer potential as an experimental model that more closely mimics obesity in vivo and may thus improve first-line screening for anti-obesity therapeutics. Aspalathus linearis, Cyclopia intermedia and their major polyphenol Aspalathin and Mangiferin, respectively may have potential as antilipolytic agents that are able to ameliorate obesity-associated basal lipolysis.

Agtergrond Ten spyte van die beskikbaarheid van verskeie behandelingsregimes, bly vetsug steeds een van die grootste gesondheidsuitdagings van die 21ste eeu. In die onlangse verlede het polifenole, afkomstig vanaf plante, toenemende aandag getrek as funksionele voedingsmiddels wat vetsug en die ko-morbiditeit daarvan kan voorkom of behandel. Die eerste-lyn-sifting van hierdie verbindings word egter belemmer deur die tekort aan in vitro eksperimentele modelle wat die komplekse patofisiologie van vetsug (oortollige lipiedakkumulasie, lipolise, inflammasie en oksidatiewe stres) in vivo kan naboots. Die doel van hierdie studie was tweeledig. Die eerste doelwit was om 'n 3T3-L1-adiposiet in vitro-model op te stel wat vetsug in vivo naboots, en tweedens om die verligtingseienskappe van Aspalathus linearis, Cyclopia intermedia en hul belangrikste polifenole teen hierdie toestande te ondersoek. Metodes Vir die eksperimentele model is 3T3-L1 pre-adiposiete vir 7 of 14 dae in 5.5 mM, 25 mM of 33 mM glukosekonsentrasies gedifferensieer. Lipiedakkumulasie, lipolise, oksidatiewe stres, inflammasie, mitochondriale aktiwiteit en geenuitdrukking is onderskeidelik bepaal met behulp van “Oil Red O”-kleuring, gliserolvrystelling, 2', 7'-dichlorfluoresceïne-diasetaat fluoressensie om reaktiewe suurstofspesies te bepaal, monosiet chemo-aantrekkingskrag proteïen-1 sekresie, die 3- [4, 5-dimetieltiazol-2-yl]-2, 5 difenieltetrazoliumbromied-toets en kwantitatiewe reële tyd polimerase kettingreaksie. Die verbeteringseffekte van Aspalathus linearis (Afriplex GRTTM) en Cyclopia intermedia (CPEF) op hierdie toestande is ondersoek deur die akute en chroniese behandeling van die geoptimaliseerde eksperimentele model met verskillende konsentrasies van hierdie plantekstrakte en hul belangrikste polifenole, Aspalathin en Mangiferin, onderskeidlik. Resultate Lipiedakkumulasie, lipolise, oksidatiewe stres, inflammasie en uitdrukking van gepaardgaande gene was gesamentlik hoër na differensiasie in 33 mM glukose vir 14 dae in vergelyking met laer glukosekonsentrasies en 7 dae; dus is hierdie toestande as die eksperimentele model gekies. Nie akute of chroniese behandeling met 0,1 tot 100 µg/ml Aspalathus linearis en Cyclopia intermedia, en 0,1 tot 100 µM Aspalathin en Mangiferin het die lipiedinhoud beduidend verlaag nie. Al die behandelings het egter lipolise verminder en mitochondriale aktiwiteit verhoog. Gevolgtrekking Differensiasie van 3T3-L1 pre-adiposiete in 33 mM glukose vir 14 dae het lipolise, oksidatiewe stres en inflammasie verhoog, vergeleke met laer glukosekonsentrasies en differensiasie vir 7 dae. Aspalathus linearis, Cyclopia intermedia, Aspalathin en Mangiferin het die verhoogde lipolise onder hierdie toestande verlig. Hierdie studie bewys dat die differensiasie in 33 mM glukose vir 14 dae potensiaal bied as 'n eksperimentele model wat vetsug in vivo naboots en sodoende eerstelyn-sifting vir terapie teen vetsug kan verbeter. Aspalathus linearis en Cyclopia intermedia en hul belangrikste polifenole, Aspalathin en Mangiferin, toon dus potensiaal as antilipolitiese middels wat vetsug-geassosieerde lipolise kan verlig.

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