Transcript Lecture 22
Control of Energy The Original Biofuels Importance of Glucose Regulation • Too little – Brain problems • Too much – Osmotic water loss (cellular and systemic) – Damages blood vessels Role of the Pancreas 1. Digestion – secretes digestive enzymes 2. Metabolism • Regulation • • • • Carbohydrates Lipids Proteins Produces primary messengers (hormones) • • Insulin Glucagon • • Insulin discovered by Frederick Banting and Charles Best in 1921. Leonard Thompson (age 14, 65lbs) first patient successfully treated. • 51 amino acids • 2 chains linked by disulfide bonds • 5800 Dalton molecular weight Effects of Insulin • Nearly all cells (80%) increase glucose uptake (seconds) – Active transport – Primarily affects liver and muscle – Brain tissue is excepted • Alters phosphorylation of many key intracellular metabolic enzymes (minutes) • Alters protein synthesis and gene transcription (hours) Insulin Affects Tissues Differently • Muscle – Uptake of glucose and immediate use (exercise) or storage as glycogen (Exercising muscles can take up glucose without insulin) • Liver – Uptake of glucose and storage as glycogen • • • • Inhibits glycogen phosphorylase Activates glycogen synthase Inhibits glucose synthesis Promotes excess glucose conversion to fatty acids • Adipose Tissue – Promotes glucose uptake and conversion to glycerol for fat production Insulin and Fat Metabolism • Liver cells store glycogen only up to 5-6% – Remaining glucose metabolized to fat – Triglycerides are synthesized and release into blood • Adipose cells store fat – Inhibits breakdown of triglycerides – Stimulates uptake and use of glucose to form glycerol – Stimulates fatty acid uptake and conversion to triglycerides • Lack of insulin – Free fatty acids build up in blood – Liver metabolizes to produce phospholipids and cholesterol – Can lead to excess acetoacetic acid production and buildup of acetone (acidosis, which can lead to blindness and coma) Insulin and Protein Metabolism • Promotes – Transport of amino acids – Protein synthesis – Gene transcription • Inhibits protein degradation • Prevents glucose synthesis in liver – Preserves amino acids • Lack of insulin causes elimination of protein stores Most Cells Insulin Control Protein synthesis Muscle Glucose uptake Glycogen synthesis Gastrointestinal hormones Adipose Amino acids Pancreas amino acids Insulin triglycerides Glucose uptake Glycerol production Triglyceride breakdown Triglyceride synthesis Beta cells Liver Blood glucose Glucose uptake Glycogen synthesis Fatty acid synthesis Glucose synthesis Brain No effect Feedback glucose Effects of Glucagon • Prevents hypoglycemia – Powerful system to degrade glycogen – Increases glucose synthesis from amino acids • Increases with exercise independent of blood glucose • Exerts effects through cAMP second messenger system 1) 2) β – adrenergic stimulation glucagon Glucagon Control Triglyceride breakdown Triglyceride storage Exercise Amino acids Adipose Fatty acids Pancreas Alpha cells Epinephrine (stress) Liver Glycogen breakdown Glucose synthesis Glucose release Brain No effect Feedback Blood glucose Importance of Glucose Regulation • Too little – Brain problems • Too much – Osmotic water loss (cellular and systemic) – Damages blood vessels Diabetes Mellitus • Type I – Insulin dependent – Juvenile onset – Causes • Increased blood glucose (300-1,200 mg/100ml) • Increased blood fatty acids and cholesterol • Protein depletion – Treated with insulin injections – Increases risk of heart disease and stroke – Can cause acidosis and coma Diabetes Mellitus • Type II – Non-insulin dependent – Results from insulin insensitivity – Elevated insulin levels – Associated with obesity – Can lead to insulin dependent form – Treated with weight loss, diet restriction, exercise and drugs Diabetes • 143 million suffer worldwide (W.H.O.) – Expected to double by 2025 – Costs $143B annually • Treatment with insulin is not optimal – Does not mimic normal control system – Associated with serious health risks • Direct transplantation has not proven feasible – Immunosuppression causes problems • Use of semi permeable encapsulation may be possible – – – – Must optimize for nutrient exchange but immune isolation Biocompatible and structurally sound Prevent allergic responses Must provide glucose control • Other options may be effective (e.g., gene therapy) Microencapsulation Approach