George 2015 Abstract MiPschool Cape Town 2015

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Regulation of LCAD and SIRT3 activities by NAD+ in skeletal muscle of fructose-fed rats.


George S, Ojuka E (2015)

Event: MiPschool Cape Town 2015

Excess fructose consumption has been shown to mediate mitochondrial β-oxidation dysfunction in skeletal muscle, resulting in decreased fattyacid mediated respiration and elevated levels of long chain acylcarnitine intermediates [1]. It has been observed that fructose decreases the expression of LCAD (long chain acyl-CoA dehydrogenase) [2], the rate limiting enzyme in β-oxidation, and of SIRT3 (the NAD+-dependent deacetylase that regulates the activity of LCAD) [1]. Regular exercise has been shown to restore mitochondrial function, including β-oxidation, and improve insulin sensitivity in type-2 diabetics. Studies in mice and rats have found that exercise increases NAD+ levels (3), SIRT3 levels (4) and fatty acid oxidation (5). These observations suggest that a) the fructose-induced dysfunction in β-oxidation might be due to its effect on the NADH/NAD+ ratio in cells and b) a program of exercise might ameliorate the effects of fructose on β-oxidation. Therefore, the proposed study aims to test the following hypotheses: a) Fructose-induced decline in LCAD and SIRT3 activities results from decreased NAD+ levels. b) Regular exercise will ameliorate fructose-induced β-oxidation dysfunction in skeletal muscle by augmenting LCAD and SIRT3 activities as well as NAD+ content. c) Improvements in β-oxidation, SIRT3 activity and LCAD function by exercise result from increased NAD+ levels in cells. A rat model will be used to test these hypotheses. Rats will be randomly placed in one of the following treatment groups for 8 weeks: a) no treatment (control), b) 10% fructose water, c) 10% fructose + nicotidamide ribosome (an NAD+-boosting agent), d) 10% fructose + exercise, e) 10% fructose + exercise + FK866 (an inhibitor of the NAD+ salvage pathway) f) exercise, g) 10% glucose. All rats will receive chow and water ad libitum. The following parameters will be measured: a) abdominal fat weight, b) plasma free fatty acids, insulin, and glucose levels, c) acylcarnitine levels in blood and skeletal muscle by ESI-MS/ MS, and d) mitochondrial β-oxidation in permeabilized skeletal muscle fibres using high-resolution respirometry with long chain acylcarnitines + malate as substrates. In addition, the activities and/or levels of LCAD, SIRT3, Citrate Synthase and NADH/NAD+ will be measured.

O2k-Network Lab: ZA Cape Town Smith J, O2k-Network Manager South Africa, ZA Cape Town Ojuka EO

Labels: MiParea: Exercise physiology;nutrition;life style 

Organism: Rat  Tissue;cell: Skeletal muscle  Preparation: Permeabilized tissue 

Pathway:HRR: Oxygraph-2k 


UCT/MRC Research Unit Exercise Sc & Sports Medicine, Dept Human Biol Univ Cape Town, Sport Science, South Africa. - [email protected]