Besides its role in glycogen synthesis, which of the followi
The synthesis of glycogen from glucose is called as glycogenesis.
Do you want your muscles to feel pumped all the time? Do you want more energy during your workouts? Then fill up your glycogen stores! Glycogen is the storage form of glucose (blood sugar). Muscle glycogen resynthesis or as some say glycogen supercompensation is an important aspect in bodybuilding. Some bodybuilders are so bent on only protein intake that they forget that 2/3 of total glycogen stores are found in skeletal muscle (the other 1/3 being found in the liver). The glycogen found in muscle is generally used for the muscle only and not to maintain blood sugar levels. The glycogen stores in the liver are responsible for maintaining proper blood sugar levels. There are several ways to enhance or improve glycogen stores which will be discussed in a latter part of this article. In this short synopsis of glycogen metabolism as it relates to bodybuilding, I want to explore the details of this interesting topic.
Glycogen biosynthesis via UDP-glucose in the ..
Let's start with some basics of glycogen metabolism. If you don't have some knowledge of biochemistry or just simply don't care how it works, please skip to the part about how to increase glycogen stores and current research on this topic. Carbohydrates, specifically glucose, are an important energy source for many human tissues including skeletal muscle. It would not be practical or efficient for your body to store significant amounts of glucose in solution. Therefore, carbohydrate reserves are stored in the form of the branch chained polysaccharide called glycogen. The average bodybuilder sustains about 85 millimoles of glycogen per kilogram of skeletal muscle. A millimole is a simple measurement of the amount of certain compounds in your body. Supercompensation glycogen studies have shown that a trained athlete can achieve at least 175 millimoles. I will discuss how to achieve these glycogen levels in a latter part of this article. When a glycogen-containing muscle cell requires glucose, say during weight training, glucose monomers are removed one at a time from glycogen molecules. This reaction is catalyzed by glycogen phosphorylase. The glucose at this point is released in the form of Glucose-1-phosphate. The first step of glycolysis (the energy producing pathway in muscle cells) is glucose-6-phosphate. Muscle cells contain an enzyme called phosphoglucomutase which can convert glucose 1-phosphate to glucose 6-phosphate at which point it can take part in the steps of glycolysis. Due to the attached phosphate group in this process, none of the glucose resulting from glycogen hydrolysis are able to leave the cell in which they were produced. Liver cells on the other hand, are able to dephosphorylate glucose. Due to this dephosphorylation, the glycogen stores in the liver can release glucose into the blood stream to regulate blood sugar. Glycogen synthesis (the production of glycogen to be stored ) requires the phosphorylation of glucose or the addition of a phosphate group. This allows for activation of the molecule as well as containment within muscle cells. After phosphorylation, glucose reacts with UTP (uridine tri-phosphate) to form UDP glucose. This reaction is effectively irreversible. UDP- glucose monomers are then converted to glycogen by the enzyme glycogen synthase (with the liberation of the UDP). Glycogen synthase activation is considered to be an important regulatory step in glycogen synthesis . Glycogenin, a glycoprotein, serves as a guide for all glycogen synthesis. It has a function of priming glycogen synthesis as well as activating glycogen synthase. I will discuss this interesting compound further a little later. Muscle glycogen reserves are mobilized in situations of stress. Phosphorylase kinase is an enzyme which catalyses glycogen phosphorylase. The activity of glycogen phosphorylase is increased by epinephrine (adrenaline). Muscle contraction is initiated by a rise in Ca+2 ion concentration. Ca+2 ions also increase the activity of phosphorylase kinase. Proper calcium intake is essential for muscle contraction . I would recommend at least 1600mg of calcium daily for bodybuilders. A secondary beneficial effect of calcium is that it has been shown to lower blood pressure. Magnesium and potassium supplementation may also be necessary for proper electrolyte balance if taking a calcium supplement.