Impact of Isoorientin on Metabolic Activity and Lipid Accumulation in Differentiated Adipocytes

Abstract

The current study explored the effect of isoorientin on the metabolic activity and lipid accumulation in fully differentiated 3T3-L1 adipocytes. To achieve this, the 3T3-L1 pre-adipocytes were differentiated for eight days and treated with various concentrations of isoorientin (0.1–100 μM) for four hours. Subsequently, the metabolic activity, lipid accumulation, and mitochondrial respiration were assessed. Furthermore, to unravel the molecular mechanisms that might elucidate the bioactivity of isoorientin, protein expression of the genes involved in insulin signaling and energy expenditure, such as AKT and AMPK, were investigated. The results showed that isoorientin, at different doses, could block lipid storage and enhance glycerol release, with a concomitant improvement of the metabolic activity and mitochondrial function. Although the observed beneficial effects of isoorientin on these cultured 3T3-L1 adipocytes were not consistent at all concentrations, it was clear that doses between 1 and 10 μM were most effective compared to the untreated control. Moreover, the activity of isoorientin was comparable to tested positive controls of CL-316,2431, isoproterenol, insulin, and metformin. Mechanistically, protein expression of AKT and AMPK, was enhanced with isoorientin exposure, suggesting their partial role in modulating lipid metabolism and mitochondrial biogenesis. Indeed, our results showed that isoorientin has the ability to enhance mitochondrial respiration, as we observed an increase in the ATP and oxygen consumption rate. Therefore, we concluded that isoorientin has a potential to impact mitochondrial activity, lipid metabolism and energy expenditure using an in vitro experimental model of obesity.

Rooibos Flavonoids, Aspalathin, Isoorientin, and Orientin Ameliorate Antimycin A-Induced Mitochondrial Dysfunction by Improving Mitochondrial Bioenergetics in Cultured Skeletal Muscle Cells

“…An overwhelming number of studies have indeed provided evidence that rooibos and their flavonoids have a great potential that can decrease cellular oxidative damage in various models of metabolic disease, resulting in improved intracellular antioxidant capacity [20,[39][40][41]. In addition, evidence from recent research by our group indicates that aspalathin and isoorientin have the potential to reverse conditions of insulin resistance by improving energy metabolism and mitochondrial respiration [42,43]. We have observed a similar effect in this study.…”

The effects of a green Rooibos (Aspalathus linearis) extract on metabolic parameters and adipose tissue biology in rats fed different obesogenic diets

“…However, the long-term effects of possible GRT-mediated suppression of ASC adipogenic capacity warrants further attention. The suppression of adipogenesis/lipogenesis by GRT in ASCs is consistent with findings for Rooibos constituents in cultured 3T3-L1 adipocytes, [18][19][20][21] and our study provides the first evidence that Rooibos could affect ASC biology in vivo. However, intracellular lipid accumulation was the only marker of ASC function included in this study, and therefore the mechanisms and pathways impacted by obesogenic diets and GRT in ASCs remain to be identified.…”

“…13 In addition, in vitro studies in a variety of cell-types including muscle, liver and fat cells have shown that aspalathin and GREs can enhance the activation of metabolic signalling pathways such as AMP-activated protein kinase (AMPK), Akt and insulin signalling, resulting in improved cellular glucose uptake. [13][14][15][16][17] Anti-adipogenic and anti-lipogenic actions of fermented Rooibos extracts (FREs) 18 and individual phenolic constituents of Rooibos such as rutin, 19 vitexin, 20 orientin 20 and iso-orientin 21 have also been demonstrated in vitro in 3T3-L1 immortalised pre-adipocytes, but similar studies have not been performed ex vivo in cultured ASCs.…”

Orientin Improves Substrate Utilization and the Expression of Major Genes Involved in Insulin Signaling and Energy Regulation in Cultured Insulin-Resistant Liver Cells

“…In addition, effective upregulation of Ampk and Cpt1 could suggest that orientin plays a major role in controlling mitochondrial beta-oxidation and energy metabolism. This is consistent with in vitro biological effects observed with using another dietary flavone (isoorientin) in cultured adipocytes, also exposed to high levels of palmitate [12,21]. These are all vital molecular mechanisms that are linked with the therapeutic actions of well-known drugs such as metformin, which are accredited for targeting the reversal of hepatic insulin resistance to improve metabolic function [22].…”