BIOL 320 1st EditionLecture 19Outline of Last Lecture I. Nutrition & Metabolisma. Major NutrientsII. Digestion of NutrientsIII. Lipid Metabolisma. Lipid CatabolismOutline of Current Lecture IV. Lipid MetabolismV. Plasma Cholesterol LevelsVI. CholesterolVII. Non-Dietary Factors Affecting CholesterolVIII. Interconversion Pathways of NutrientsIX. Absorptive StateX. Insulin Control Absorptive StateXI. Postabsorptive StateXII. Tissues/Organs Fuel UseXIII. Postabsorptive: Hormonal & Neural ControlXIV. Liver MetabolismXV. Energy Balance & Body FatXVI. Regulation of Food IntakeCurrent LectureLipid Metabolism- Synthesis of Structural Materialso -Phospholipids = important component of myelin & cell membraneso -The liver: --Synthesizes: lipoproteins for transport of cholesterol & fats --Makes: tissue factor (clotting protein) --Synthesizes: cholesterol (for acetyl CoA) --Uses cholesterol --> bile saltso -Certain endocrine organs use cholesterol to synthesize steroid hormonePlasma Cholesterol Levels- Liver produces cholesterol:o At a basal level regardless of dietary intakeo In response to satur. fatty acids- Saturated fatty acidso Stimulate liver synthesis of cholesterolo Inhibit cholesterol excretion from body- Unsaturated fatty acidso Enhance excretion of cholesterol- Trans fatso Increase LDLs & reduce HDLs- Unsaturated Omega-3 fatty acids (in cold-water fish)o Lower proportions of saturated fats & cholesterolo Have anti-arrhythmic effects on hearto Help prevent spontaneous clottingo Lower blood pressureCholesterol:- -Importance: structural base for bile salts, steroid hormones, & vitamin D- -Transport: via lipoproteinso --HDL: high density lipoproteins; transport cholesterol to liver for excretiono --LDL: low density lipoproteins; transport cholesterol to peripheral tissues…excess creates plaques; regulates cholesterol synthesiso --VLDL: very low density lipoproteins; transport triglycerides mostly to adipose tissue- -Heart attack risk: artery damage o --Lowered risk: higher ratio of HDL than LDLo --Higher risk: higher ratio of LDL than HDLNon-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 LDLo --"Pears" correlate with low cholesterol levels & low LDLInterconversion Pathways of NutrientsAbsorptive State: Principle PathwaysInsulin Control Absorptive State- -Secretion stimulated by:o --Elevated blood [glucose]o --Elevated blood [amino acids]o --Gastrin, cholecystokinin (CCK), & secretinPostabsorptive StateTissues/Organ Fuel Use:- Brain:o -Fuel Stores: noneo -Preferred Fuel: prefers glucose- Resting skeletal muscle:o -Fuel Stores: glycogeno -Preferred Fuel: fatty acids- Active skeletal muscle:o -Fuel Stores: noneo -Preferred Fuel: glucose- Heart muscle:o -Fuel Stores: noneo -Preferred Fuel: fatty acids- Adipose:o -Fuel Stores: triglycerideso -Preferred Fuel: fatty acids- Liver:o -Fuel Stores: glycogen, triglycerideso -Preferred Fuel: fatty acids, amino acids, glucosePostabsoptive: Hormonal & Neural ControlsLiver 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 detoxifiesEnergy Balance & Body FatRegulation of Food Intake- Two distinct sets of hypothalamic neuronso 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