(Glucose) Metabolism

glucagon on fats

•Activates adipose cell lipase, making increased amounts of FA available for energy

Metabolism of Glucose, Fat & Protein

•Glucose, fatty acids, proteins are the fuels used for energy in the body. •The liver and hormones from the pancreas control this fuel supply

Insulin on Glucose

•Increases glucose transport into skeletal muscle & adipose tissue •Increases glycogen synthesis •Decreases gluconeogenesis

Glycogenolysis

-The physiologic process of breaking down glycogen to increase blood glucose concentration to optimal levels; occurs when blood glucose levels are low.

Hormones:

chemical messengers that are secreted and affect cells of the body for growth, reproduction, fluid and electrolyte balance.

Glycogen:

The storage form of glucose

insulin on fat

•Promotes fatty acid & triglyceride synthesis by liver •Increases the transport of fatty acids into adipose cells •Increases conversion of FA to Triglycerides •Maintains fat storage by inhibiting break-down of stored Triglycerides by lipase

Glucagon on glucose

•Promotes glycogen breakdown •Increases gluconeogenesis

Glucose regulation:

•The process of maintaining optimal blood glucose levels •Normal levels in patients WITHOUT diabetes: 70-99 mg/dL)(fasting) and 100-140 mg/dL (2-hour post-prandial)

Glycogenesis (Glycogen + genesis [formation of])

-The conversion of glucose to glycogen for storage in the liver.

Fat metabolism

Triglycerides = 3 fatty acids linked by a glycerol molecule. Triglycerides are stored in adipose tissue. •With low insulin levels, lipase causes break down of triglycerides •Fatty acids are transported to tissues who use it for energy (most cells Excluding brain, nervous tissue and RBCs) •Excess FA are converted to ketones (ketoacids) and released into the blood. Ketones CAN be used by the brain, heart and muscle.

Insulin on Proteins

- Increases active transport of amino acids into cells - increases protein synthesis by increasing transcription of mRNA and accelerating protein synthesis by rRNA - decreases protein breakdown by enhancing uses of glucose and fatty acids as fuel

Counter-regulatory hormone: Epinephrine

- Raises blood glucose - in times of stress, causes glycogenolysis in the liver and skeletal muscle cells - has a lipolytic effect on adipose cells - ONLY responsible for symptoms of hypoglycemia

Glucose Metabolism and Storage

- The brain and nervous system rely almost exclusively on glucose as a fuel source - After a meal, food is broken down in the upper intestine and absorbed, partly as glucose.

Counter-regulatory hormone: Glucocorticoid hormone (Cortisol)

- raises blood glucose - during fasting or periods of starvation, stimulates gluconeogenesis; decreases tissue use of glucose - modulates immune response which results in overall anti-inflammatory response

Counter-regulatory hormone: Growth Hormone

- raises blood glucose - during periods of fasting, mobilizes fatty acids from adipose tissue; antagonizes insulin effects

Glucagon:

A hormone secreted by alpha cells, produced in response to a cellular deficiency of glucose

Gluconeogenesis

Formation of glucose from non-carbohydrate sources (fats and proteins)

Glucose metabolism

Glucose is metabolized to be used by the body as energy & fuel •Insulin is secreted to promote glucose uptake into body cells •Most(about 2/3) of blood glucose is stored in the liver as glycogen. •Skeletal muscle contains glycogen stores; this glycogen can be used solely as a fuel source for the muscle. •With excess glycogen, glucose is converted into fatty acids by the liver & stored as triglycerides in adipose tissue.

glucagon on proteins

Increases amino acid uptake by liver cells & their conversion to glucose by gluconeogenesis

Protein metabolism

Proteins are used to form genes, enzymes, contractile structures in muscle, bone matrix and hemoglobin. Most of the stored amino acids are contained in body proteins. •WITH LOW INSULIN AVAILABILITY: Since fatty acids CANNOT be converted to glucose, the body must break down proteins and use the amino acids in gluconeogenesis during periods when metabolic needs for glucose exceed glucose intake. •Excess amino acids can be converted to fatty acids, ketones, or glucose and then stored or used as metabolic fuel

Metabolism:

The processes of chemical reactions that occur in the body's cells, necessary to produce energy, repair cells, and maintain life. Nutrients (carbohydrates, fats and proteins) must be broken down (metabolized) into chemicals

insulin

•Produced by beta cells of the pancreas - Promotes glucose uptake by cells; provides for storage of glucose as glycogen - Inhibits fat and glycogen breakdown - Inhibits gluconeogenesis; increases protein synthesis •Insulin enters the portal circulation; travels directly to the liver, then to the general circulation - About 50% is used or degraded (broken down) - Has a half-life of ~ 6 minute

glucagon

•Produced by the alpha cells of the islets of Langerhans in the pancreas •Maintains blood glucose between meals and periods of fasting •Typically acts when blood glucose < 70 mg/dL •Travels through the portal vein to the liver; initiates glycogenolysis •Increases the transport of amino acids into the liver and stimulates their conversion to glucose (gluconeogenesis)