Bezuidenhout 2015 Abstract MiPschool Cape Town 2015

A study of the effects of fructose feeding & exercise on SIRT 3 regulation in skeletal muscle.

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Bezuidenhout N, Ojuka E (2015)

Event: MiPschool Cape Town 2015

In the past three decades the consumption of fructose, in the form of high fructose corn syrup (HFCS), has increased considerably with a concurrent rise in obesity and insulin resistance (IR) [1], however the exact mechanisms remain unclear. Evidence suggests elevated reactive oxygen species (ROS) production and down regulation of Sirt3 to be a likely cause [2]. Sirt3 a key regulator of the enzymes involved in energy homeostasis, has been shown to be associated with the development of these diseases [3]. Sirt3 expression is known to be regulated by the binding of the estrogen related receptor alpha (ERR) on the Sirt3 estrogen related receptor binding element (ERRE) and up-regulated by exercise, which has been shown to protect against IR [4]. We therefore hypothesize that Sirt3 down regulation in high fructose feeding is due to increased ROS production, and is associated with hypoacetylation of the histones at the ERRE of the Sirt3 gene. Furthermore we propose that exercise will increase the expression of Sirt3 through hyperacetylation of the histones at the same promoter region and enhance antioxidant capacity to restore Sirt3 expression and mitochondrial function. . Adult male Wistar rats (200-300g; 90 days old), will be divided into four groups, control (10% glucose), HFCS (8%), exercise (10% glucose) and exercise (8% HFCS). All groups will have ad libitum access to standard rat chow and drinking water and the sugars administered in the drinking water for a period of 8 weeks. Hereafter the exercise groups will undergo high-intensity intermittent swimming exercises. Western blot analysis and RT-PCR will be used to determine the levels of expression of Sirt3 and various antioxidant enzymes. Mitochondrial respiration, with pyruvate/malate, glutamate/ malate, malate/octanoyl carnitine as substrates, will be assessed to determine mitochondrial dysfunction with regard to glucose and fatty acid metabolism, using the Oroboros Oxygraph-2k. Additionally mitochondrial ROS levels will be determined with the use of immunohistochemistry and fluorometry. Binding of the estrogen related receptor to ERRE will be measured using chromatin immunoprecipitation and nuclease accessibility assay techniques.

• O2k-Network Lab: ZA Cape Town Smith J, ZA Cape Town Ojuka EO

Labels: MiParea: Respiration, Exercise physiology;nutrition;life style, Patients 

Stress:Oxidative stress;RONS  Organism: Rat 

Regulation: Substrate 

Pathway: N  HRR: Oxygraph-2k, O2k-Fluorometer 

Affiliations

Univ Cape Town, Med Research Council, Dept Human Biol, Unit Exercise Sc Sports Med, Cape Town; South Africa. - [email protected]

References

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2. Rahman I, Marwick J, Kirkham P (2004) Redox modulation of chromatin remodelling: impact on histone acetylation and deacetylation, NF-kappaB and pro-inflammatory gene expression. Biochemical Pharmacology 68:1255-67.
3. Jing E, Emanuelli B, Hirschey MD, Boucher J, Lee KY, Lombard D, Verdin EM, Kahn CR (2011) Sirtuin-3 regulates skeletal muscle metabolism and insulin signalling via altered mitochondrial oxidation and reactive oxygen species production. Proceedings Nat Acad Sc 108:14608-13.
4. Bidwell AJ, Fairchild TJ, Redmond J, Wang L, Keslacy S, Kanaley JA (2014) Physical activity offsets the negative effects of a high-fructose diet. Med Sc Sport Exercise 46:2091-8.