Browsing by Author "Driescher, Natasha Darne"

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    Establishing a rodent model of long-term consumption of sugar-sweetened beverages
    (Stellenbosch : Stellenbosch University, 2014-12) Driescher, Natasha Darne; Essop, M. Faadiel; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.
    ENGLISH ABSTRACT: Introduction- Cardiovascular complications contribute dramatically to morbidity and mortality incidence amongst individuals who have developed type 2 diabetes (T2D), with myocardial insulin resistance (IR) playing an important role. Poor lifestyle choices and dietary habits such as increased sugar-sweetened beverage (SSB) consumption have emerged as key contributors to the global ‘epidemic’ of obesity, diabetes and heart disease. However, the underlying mechanisms whereby SSBs drive the onset of cardio-metabolic complications remain unclear. For the current study, we hypothesized that long-term SSB consumption will trigger downstream glucose metabolic pathways with physiologically damaging outcomes. Specifically we proposed that increased glucose availability (due to SSB consumption) activates non-oxidative glucose pathways (NOGPs), i.e. polyol pathway, hexosamine biosynthetic pathway (HBP), advanced glycation end-products (AGE), and PKC activation that may in turn contribute to cardio-metabolic complications. Methodology- Male Wistar rats (~200 g) were gavaged daily with 3-5.1 mL of well-known, local SSBs and ASBs for a total period of six months. Dietary behavior and phenotypic changes were monitored on a weekly basis, while systemic (fasted) triglyceride, cholesterol and glucose levels at various time points during the study period. Furthermore, we performed oral glucose tolerance tests (OGTTs) biweekly, and also determined overall weight gain and organ tissue mass. Myocardial NOGPs were evaluated using commercially available kits and by Western blotting techniques. Results- Our data reveal that after six months the different soda groups displayed minimal macroscopic changes, therefore possibly representing a relatively early stage in terms of SSB-mediated cardio-metabolic complications. However, we also found several changes at the biochemical level but with distinct signatures for the Jive® group compared to the Coca Cola® and Coke Light® groups. Here Jive® consumption for six months resulted in early signs of cardiac and skeletal muscle hypertrophy, together with increased liver mass and perturbed adipocyte ultrastructure. We also established that the majority of the myocardial NOGPs were activated that may have contributed to some of the changes already found and that may lead to the onset of future complications. The Coca Cola® and Coke Light® groups exhibited alterations in liver mass and altered adipocyte ultrastructure together with lower glucose clearance after six months suggesting onset of IR. These data also clearly show that the HBP may be a universal pathway that was activated in all of the soda groups, with potential long-term detrimental physiological effects. Conclusion- This study managed to successfully establish a novel in vivo rat model of chronic SSB and artificially sweetened beverage (ASB) consumption. We demonstrated that SSB consumption resulted in minimal macroscopic alterations but that it did trigger variable postprandial excursions together with the induction of several myocardial NOGPs. Thus the current study shows that long-term SSB intake activates potentially detrimental metabolic pathways that may place organisms at risk of developing cardio-metabolic complications despite an apparently “healthy” phenotype.