BIOL 320 1st Edition Lecture 19 Outline of Last Lecture I Nutrition Metabolism a Major Nutrients II Digestion of Nutrients III Lipid Metabolism a Lipid Catabolism Outline of Current Lecture IV Lipid Metabolism V Plasma Cholesterol Levels VI Cholesterol VII Non Dietary Factors Affecting Cholesterol VIII Interconversion Pathways of Nutrients IX Absorptive State X Insulin Control Absorptive State XI Postabsorptive State XII Tissues Organs Fuel Use XIII Postabsorptive Hormonal Neural Control XIV Liver Metabolism XV Energy Balance Body Fat XVI Regulation of Food Intake Current Lecture Lipid Metabolism Synthesis of Structural Materials o Phospholipids important component of myelin cell membranes o The liver Synthesizes lipoproteins for transport of cholesterol fats Makes tissue factor clotting protein Synthesizes cholesterol for acetyl CoA Uses cholesterol bile salts o Certain endocrine organs use cholesterol to synthesize steroid hormone Plasma Cholesterol Levels Liver produces cholesterol o At a basal level regardless of dietary intake o In response to satur fatty acids Saturated fatty acids o Stimulate liver synthesis of cholesterol o Inhibit cholesterol excretion from body Unsaturated fatty acids o Enhance excretion of cholesterol Trans fats o Increase LDLs reduce HDLs Unsaturated Omega 3 fatty acids in cold water fish o Lower proportions of saturated fats cholesterol o Have anti arrhythmic effects on heart o Help prevent spontaneous clotting o Lower blood pressure Cholesterol Importance structural base for bile salts steroid hormones vitamin D Transport via lipoproteins o HDL high density lipoproteins transport cholesterol to liver for excretion o LDL low density lipoproteins transport cholesterol to peripheral tissues excess creates plaques regulates cholesterol synthesis o VLDL very low density lipoproteins transport triglycerides mostly to adipose tissue Heart attack risk artery damage o Lowered risk higher ratio of HDL than LDL o Higher risk higher ratio of LDL than HDL Non Dietary Factors Affecting Cholesterol LDL levels increased HDL levels decreased by stress smoking coffee drinking HDL levels increased by aerobic exercise estrogen Body shape correlates with cholesterol levels o Apples correlate with high cholesterol levels high LDL o Pears correlate with low cholesterol levels low LDL Interconversion Pathways of Nutrients Absorptive State Principle Pathways Insulin Control Absorptive State Secretion stimulated by o Elevated blood glucose o Elevated blood amino acids o Gastrin cholecystokinin CCK secretin Postabsorptive State Tissues Organ Fuel Use Brain o Fuel Stores none o Preferred Fuel prefers glucose Resting skeletal muscle o Fuel Stores glycogen o Preferred Fuel fatty acids Active skeletal muscle o Fuel Stores none o Preferred Fuel glucose Heart muscle o Fuel Stores none o Preferred Fuel fatty acids Adipose o Fuel Stores triglycerides o Preferred Fuel fatty acids Liver o Fuel Stores glycogen triglycerides o Preferred Fuel fatty acids amino acids glucose Postabsoptive Hormonal Neural Controls Liver Metabolism Packages fatty acids for storage and transport Synthesizes plasma proteins Forms nonessential amino acids Converts ammonia from deamination to urea Stores glucose as glycogen regulates blood glucose homeostasis Stores vitamins conserves iron degrades hormones and detoxifies Energy Balance Body Fat Regulation of Food Intake Two distinct sets of hypothalamic neurons o LHA neurons promote hunger when stimulated by neuropeptides e g NPY o VMN neurons cause satiety through release of CRH when stimulated by appetite suppressing peptides e g POMC CART peptides