Understand and prevent type 2 diabetes
Yu-Chiang Lai will defend his PhD thesis ”Role of glycogen content on glucose uptake and glycogen synthase in skeletal muscles: The effect of contraction and insulin” for the degree of Philosophiae doctor (PhD) at Norwegian School of Sport Sciences on Thursday, the 8th of April 2010.
| 26.03.2010 
Carbohydrate is an important energy substrate when athletes train and participate in competitions. However, the regulation of carbohydrate metabolism is important for all people and type 2 diabetes is a common disease where the problem is a poor regulation of blood glucose.
In humans, carbohydrates are mainly stored as muscle glycogen. Glycogen is used during exercise and fatigue occurs when the stores are depleted. Glycogen is synthesized from blood glucose, and a carbohydrate rich diet is important to refill the glycogen stores.
Although the topic has been studied for many years there are still much we do not understand about the regulation of glycogen metabolism.
Regulation of glycogen synthesis after exercise
The primary aim of this thesis was to investigate the regulation of glycogen synthesis. Lai has performed four studies to investigate different aspects about regulation of glycogen synthesis after exercise.
More specifically, Lai’s studies have focused on regulation and phosphorylation of the enzyme (glycogen synthase) that synthesizes glycogen. However, regulation of glucose uptake and activation of important signaling molecules like AMPK, PKB and AS160 was also studied.
The studies have been performed on rodent muscles and the results contribute to better understanding of the basic mechanism for the regulation of carbohydrate metabolism, which again could be useful for a better understanding and preventing type 2 diabetes.
The glycogen stores in muscles are limited and the feed-back inhibition of glycogen synthesis was initially investigated.
Findings
These data showed that high glycogen content increased phosphorylation of glycogen synthase which decreased glycogen synthase affinity for its substrate UDP-glucose. This novel finding seems an important mechanism for regulation of glycogen content in muscles.
A major novel finding was that muscle contraction strongly increased glycogen synthase affinity for UDP-glucose, which contributes to the rapid glycogen synthesis after exercise.
However, glycogen synthase affinity for glucose 6-phosphate is also regulated, which makes it difficult to study the enzyme and the results in the present thesis highlight that glycogen synthase activity needs to be carefully evaluated to understand how glycogen synthesis is regulated after exercise.
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Yu-Chiang Lai (born 070579) is from Taiwan, where he has a master degree in Sports Science from Taipei Physical Education College, Taiwan. Lai started his PhD studies autumn 2005 at the Department of Physical Performance, Norwegian School of Sport Sciences. The research for Lai’s PhD-thesis has been performed at the Department of Physiology, National Institute of Occupational Health with Professor Jørgen Jensen as supervisor. Professor Jostein Hallén has been co-supervisor.
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Evaluation committee:
Head Professor Hans A. Dahl, Norwegian School of Sport Sciences and University of Oslo, Oslo, Norway
1.opponent Professor Sten Lund, Aarhus University Hospital, Aarhus Sygehus, Denmark
2.opponent Professor Eva Blomstrand, Swedish School of Sport and Health Sciences and Karolinska Institute, Stockholm, Sweden
Programme:
10.15 am -11.00 am Trial lecture: Potential defects in insulin signalling and glucose metabolism in skeletal muscles from type II diabetic patients.
13.00 pm -16.00 pm PhD presentation and defense