Browsing by Author "Gilbert, Keenen Gregory George"

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    The drug interaction between N-acetylcysteine, ascorbic acid-2 phosphate and metformin
    (Stellenbosch : Stellenbosch University, 2023-11) Gilbert, Keenen Gregory George; Van de Vyver, Mari; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Dept. of Medicine. Division of Clinical Pharmacology.
    ENGLISH ABSTRACT: Background: Type 2 diabetes (T2DM) is a glucose metabolism disorder. Its prevalence is increasing rapidly in sub-Saharan Africa with it negatively impacting global health systems and the economy. The South African Department of Health management objectives for thetreatment of T2DM is to relieve symptoms, prevent acute metabolic and long-term complications, improve quality of life and productivity of patients and reduce the economic burden on individuals, family, and community. However, despite achieving glucose control, >80% of T2DM patients still develop co-morbidities because of persistent oxidative stress and inflammation. Adjuvant treatments using antioxidants are effective at counteracting oxidative stress, it is however unclear if these treatments will interfere with the insulin-sensitizing function of metformin, which is available as the first-line oral medication for the treatment of T2DM. This study therefore investigated if there is any drug interaction between metformin and the antioxidants, N-acetylcysteine (NAC) and ascorbic acid-2-phosphate (AAP). Methods: In vitro experiments were performed using C2C12 skeletal muscle myoblasts under different treatment periods and pretreatments to determine if the antioxidants NAC and AAP alters glucose uptake and thus the requirement for Metformin. Cellular growth and viability under low and high glucose culture conditions were assessed over a period of 48 hours. Additionally, a dose response experiment over a period of 6 days exposing cells to 5 different concentrations of NAC and AAP was performed to determine the optimal and non-toxic concentration of the specific antioxidants. Glucose uptake was assessed using fluorescent microscopy and the 2NBDG assay under various conditions (insulin, metformin) following pretreatment (24h) with either NAC and/or AAP. The beneficial effect(s) of combination therapy was also determined by assessing the Total Antioxidant Capacity (colorimetric assay) and reactive oxygen species (ROS) (fluorometric assay) within the culture supernatants with and without NAC and/or AAP pretreatment (24h). Results: Over the 48-hour period, cells cultured in high glucose conditions had a significantly (p<0,0001) higher cell number per 10mm2 plate surface area when compared to cells cultured in low glucose conditions. The optimal concentrations of NAC and AAP was determined to be 3.75mM and 0.6mM, respectively. The combination of AAP, NAC and metformin treatment significantly decreased ROS levels (2-fold, p<0.05) and increased the total antioxidant capacity (p<0.01) (11.57±5.66 U/mL) when compared to metformin treatment on its own (0.81±2.48 U/mL). The pretreatment (24h) of cells with a combination of AAP/NAC prior to glucose tarvation (2h) and exposure to either insulin (30min) and/or metformin (2h) significantly increased glucose uptake compared to cells without pre-treatment. Conclusion: There is a comparable effect between metformin, NAC and AAP when used in combination with each other, which reduces oxidative stress in vitro. Additionally, the combination of metformin, NAC and AAP improves glucose uptake in C2C12 mouse myoblasts in vitro that resulted in altered glucose profiles. Thus, patients taking adjuvant antioxidants may require glucose monitoring and changes in metformin requirements. This study warrants further investigation to determine the precise mechanism of action underlying the synergistic effect observed between NAC, AAP and metformin affecting glucose uptake. Screening the efficacy of other anti-diabetic agents and antioxidants that target both glucose homeostasis and oxidative stress within a diabetic microenvironment as well as its associated comorbidities is furthermore recommended.