Browsing by Author "Obonye, Nnini"

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    The effect of an aspalathin-rich rooibos extract on inflammatory crosstalk between adipocytes and muscle cells
    (Stellenbosch : Stellenbosch University, 2021, 2021-12) Obonye, Nnini; Muller, Christo; Mazibuko-Mbeje, Sithandiwe; Strijdom, Hans; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Medical Physiology.
    ENGLISH ABSTRACT: The skeletal muscle not only plays a role in maintaining posture and generating force (contraction), but also is a dynamic metabolically active tissue that plays a central role in the regulation of glucose metabolism. Western diets and a sedentary lifestyle reduce the contribution of skeletal muscle to the regulation of blood glucose. In addition, inflammation resulting from chronic elevated levels of pro-inflammatory cytokines is implicated in the development of insulin resistance, metabolic disease and loss of skeletal muscle mass. The gut plays a central role in the maintenance of metabolic health and disease. Metabolic disease is associated with gut dysbiosis and “leaky” gut syndrome releasing lipopolysaccharide (LPS) into the circulation driving a chronic proinflammatory cytokine response. To date there have been numerous studies demonstrating that Aspalathus linearis (rooibos) plant polyphenols protect against the development of metabolic diseases. The aim of this study was three-fold. Firstly, study the effects of LPS on skeletal muscle growth and metabolism in vitro using murine C2C12 myoblasts. Secondly, to study the effect(s) of 3T3-L1 adipocyte derived adipokines on LPS-induced pro-inflammatory cytokine secretion by myoblasts, and thirdly, to investigate the effect of an aspalathin-rich green rooibos extract (Afriplex GRT™) on the LPSinduced immune responses. To establish the skeletal muscle model of inflammation, C2C12 myoblasts were exposed to LPS (0.1 μg/mL and 1 μg/mL) for 24 hours and treated with Afriplex GRTTM (GRT) (1 μg/mL and 10 μg/mL) for 24 hours. Cell viability, inflammation (IL-6 secretion), glucose uptake, and expression of relevant genes and proteins were assessed. Furthermore, C2C12 myoblasts were differentiated in the presence of LPS to assess the effects of inflammation on myogenesis. A coculture system using C2C12 myoblasts and 3T3-L1 pre-adipocytes and mature adipocytes were used to study the secretion of IL-6 and adiponectin. LPS was a potent inducer of pro-inflammatory IL-6 cytokine response, specifically in myoblasts as opposed to myotubules, suggesting that IL-6 is differentially regulated in myotubules. Myoblasts exposed to LPS during differentiation results in decreased myotube width and number suggesting that metabolic endotoxemia affects muscle mass and potentially affecting skeletal muscle energy metabolism. The myogenic regulatory factors, myogenin, MyoD and myostatin were downregulated by LPS during myoblast differentiation. In co-culture, LPS significantly increased IL-6 secretion in both myoblasts and 3T3-L1 pre-adipocytes, whereas IL-6 secretion was modulated by the differentiated 3T3-L1 adipocytes in co-culture. A dramatic increase in adiponectin levels secreted by the differentiated 3T3-L1 adipocytes compared to the preadipocytes could have accounted for the lower IL-6 secretion in the co-culture. GRT was unable to ameliorate the effects of LPS-induced inflammation.
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    N-Acetyl cysteine ameliorates hyperglycemia-induced cardiomyocyte toxicity by improving mitochondrial energetics and enhancing endogenous Coenzyme Q9/10 levels
    (Elsevier, 2019) Dludla, Phiwayinkosi V.; Orlando, Patrick; Silvestri, Sonia; Mazibuko-Mbeje, Sithandiwe E.; Johnson, Rabia; Marcheggiani, Fabio; Cirilli, Ilenia; Muller, Christo J. F.; Louwa, Johan; Obonye, Nnini; Nyawo, Thembeka; Nkambule, Bongani B.; Tiano, Luca
    ENGLISH ABSTRACT: The diabetic heart has been linked with reduced endogenous levels of coenzyme Q9/10 (CoQ), an important antioxidant and component of the electron transport chain. Although CoQ has displayed cardioprotective potential in experimental models of diabetes, the impact of N-acetyl cysteine (NAC) on mitochondrial energetics and endogenous levels of CoQ remains to be clarified. To explore these effects, high glucose-exposed H9c2 cardiomyocytes were used as an experimental model of hyperglycemia-induced cardiac injury. The results showed that high glucose exposure caused an increased production of reactive oxygen species (ROS), which was associated with impaired mitochondrial energetics as confirmed by a reduction of maximal respiration rate and depleted ATP levels. These detrimental effects were consistent with significantly reduced endogenous CoQ levels and accelerated cell toxicity. Although metformin demonstrated similar effects on mitochondrial energetics and cell viability, NAC demonstrated a more pronounced effect in ameliorating cytosolic and mitochondrial ROS production. Interestingly, the ameliorative effects of NAC against hyperglycemia-induced injury were linked with its capability to enhance endogenous CoQ levels. Although such data are to be confirmed in other models, especially in vivo studies, the overall findings provide additional evidence on the therapeutic mechanisms by which NAC protects against diabetes-induced cardiac injury.