Nutrition Metabolism and Energy Balance II Flashcards
Regulation of Blood Glucose:
Insulin (hypoglycemic): Released when blood glucose is high, stimulates by pancreas:
- Glycogen formation in the liver.
- Glucose uptake by cells, lowering blood glucose.
Glucagon (hyperglycemic): Released when blood glucose is low, stimulates:
- Glycogen breakdown in the liver, raising blood glucose.
Normal Blood Glucose: ~90 mg/100 ml.
Insulin promotes glucose uptake by cells by binding to insulin receptors on the cell membrane, triggering a signaling cascade that facilitates the translocation of glucose transporters to the cell surface.
Diabetes Mellitus (DM):
Type 1 DM: Autoimmune destruction of pancreatic β-cells → absolute insulin deficiency.
Type 2 DM: Insulin resistance → pancreas produces insulin, but cells don’t respond properly.
Insulin Mechanism:
Without insulin: Glucose can’t enter cells.
With insulin: GLUT4 transporters move glucose into cells.
Consequences of Insulin Deficit:
High blood glucose: Liver breaks down glycogen; muscles break down proteins.
Fat breakdown (lipolysis) → ketone bodies → ketoacidosis (low pH).
Symptoms: Polyuria, polydipsia, polyphagia, ketonuria, dehydration
Type 1 DM:
Fatty acid metabolism → ketones (ketoacidosis).
Severe cases: Hyperpnea, heart problems, coma.
Type 2 DM Risk Factors:
Obesity: Decreases insulin sensitivity.
Increased FFAs/TGs → insulin resistance and β-cell damage.
Hyperinsulinism:
Excess insulin → hypoglycemia (low blood glucose).
Symptoms: Anxiety, confusion, unconsciousness.
Treatment: Sugar ingestion.
Carbohydrate Metabolism:
Glucose homeostasis: Converts galactose/fructose to glucose.
Glycogenesis: Stores glucose as glycogen; releases glucose via glycogenolysis when blood glucose is low.
Gluconeogenesis: Converts amino acids and glycerol to glucose when glycogen is exhausted.
All by liver
Fat Metabolism:
Beta oxidation: Breakdown of fatty acids to acetyl-CoA.
Ketone production: Converts acetyl-CoA to ketone bodies for energy.
Cholesterol synthesis: Liver Converts acetyl-CoA to cholesterol and bile salts.
Lipoproteins: Synthesizes lipoproteins for transporting fats and cholesterol.
Protein Metabolism:
Urea synthesis: Removes ammonium from the body.
Plasma proteins: Synthesizes clotting proteins, albumin, etc.
Amino acid metabolism: Deaminates amino acids for glucose/ATP production.
Vitamin/Mineral Storage:
Stores vitamins A, D, B12, and iron.
Biotransformation:
Detoxification: Metabolizes alcohol, drugs, and toxins for excretion.
Bilirubin: Processes bilirubin from RBC breakdown and excretes in bile.
Cholesterol Metabolism:
Cholesterol synthesis: 85% made by the liver, used for bile salts, steroid hormones, and cell membranes.
Cholesterol transport: Through lipoproteins (HDL, LDL, VLDL, chylomicrons).
Types of Lipoproteins:
HDLs: Transport excess cholesterol to the liver.
LDLs: Transport cholesterol to tissues.
VLDLs: Transport triglycerides to tissues.
Chylomicrons: Transport dietary fats.
Regulation of Blood Cholesterol:
LDL: High levels = atherosclerosis risk.
HDL: High levels are protective.
Dietary impact:
Saturated fats increase LDL production.
Unsaturated fats help excrete cholesterol in bile.
Trans fats increase LDL and decrease HDL.
Omega-3 fatty acids lower blood pressure and improve cholesterol.
Factors Influencing Cholesterol:
Body shape: “Apple” shape (abdominal fat) → higher LDL, “Pear” shape (hip/thigh fat) → lower LDL.
Exercise & hormones: Regular exercise and estrogens increase HDL, lower LDL.
Neural Signals: Vagal nerve and GI tract communication play a role in appetite regulation.
Thyroid Gland Overview:
Location: Butterfly-shaped gland in the anterior neck, on the trachea below the larynx.
Structure:
Isthmus: Connects the two lobes.
Follicles: Produce thyroglobulin.
Colloid: Fluid with thyroglobulin and iodine (precursor to thyroid hormones).
Parafollicular cells: Produce calcitonin.
Thyroid Hormones:
T4 (Thyroxine): Major form, contains 4 iodine atoms.
T3 (Triiodothyronine): Active form, contains 3 iodine atoms.
Both are lipid-soluble amine hormones.
Functions of Thyroid Hormone:
Increases basal metabolic rate (BMR) and heat production (calorigenic effect).
Regulates tissue growth and development (important for skeletal, nervous, and reproductive systems).
Maintains blood pressure (increases adrenergic receptors).
Effects of Imbalance:
Hyposecretion: Low BMR, weight gain, cold intolerance, mental dullness, low heart rate.
Hypersecretion: High BMR, weight loss, heat intolerance, irritability, high heart rate.
Thyroid Hormone Synthesis:
Thyroglobulin is made and stored in follicles.
Iodine is absorbed and oxidized.
Iodine attaches to tyrosine (MIT, DIT).
T3 (MIT + DIT) and T4 (DIT + DIT) are formed.
Hormones released into blood, T4 converts to T3 in tissues.
Thyroid Hormone (TH):
T4 & T3 are transported by TBGs; T3 is more active than T4.
Negative Feedback: Low TH stimulates TSH; high TH inhibits it.
Graves’ Disease (hyperthyroidism): Autoimmune, causing weight loss, rapid heartbeat, exophthalmos. Treated with surgery or radioactive iodine.
Myxedema (hypothyroidism): Causes dry skin, sluggishness, and a goiter (if iodine-deficient).
Energy Balance:
Energy intake must equal energy output for stable body weight.
Obesity (BMI > 30) increases risks like diabetes, heart disease, and osteoarthritis.
Food Intake Regulation:
Short-term: Gut signals, blood nutrients, and hormones (e.g., ghrelin increases hunger, leptin decreases hunger).
Long-term: Leptin adjusts hunger based on fat stores. Leptin resistance occurs in obesity.
Metabolic Rate:
BMR: Energy needed at rest, influenced by thyroid hormones.
Hyperthyroidism: Increased BMR, weight loss, muscle atrophy.
Hypothyroidism: Slowed metabolism, weight gain, cognitive issues.
TMR: Total energy use including activity and food digestion.
Body Temperature Regulation:
Heat is generated during metabolism to maintain body temperature (~37°C).
Core temperature is regulated; skin temperature fluctuates.
Mechanisms of Heat Exchange:
Radiation: Heat loss through infrared rays (50% of body heat loss).
Conduction: Heat transfer between objects in direct contact (e.g., skin and hot water).
Convection: Heat transfer to surrounding air (15–20% of heat loss).
Evaporation: Heat loss through evaporation of water (sensible and insensible heat loss).
Heat Balance:
Heat production: Basal metabolism, muscular activity (shivering), thyroid hormones, and epinephrine.
Heat loss: Radiation, conduction, convection, and evaporation.
Hypothalamus and Thermoregulation:
Thermoregulatory Centers:
Heat-loss center: Activated when temperature rises.
Heat-promoting center: Activated when temperature drops.
Heat-Promoting Mechanisms:
Vasoconstriction and shivering to conserve heat.
Non-shivering thermogenesis (mainly in infants).
Heat-Loss Mechanisms:
Vasodilation and sweating to release heat.
Voluntary: Wearing lighter clothing or reducing activity.
Hyperthermia:
Heat Stroke: Body temperature above ~41°C, leading to hypothermic failure and potentially fatal positive feedback.
Hypothermia:
Caused by prolonged cold exposure; symptoms include slowed vital signs, drowsiness, and ultimately coma or death below 21°C.
Weight would likely increase due to loss of satiety signals and constant hunger.
Fever:
Cause: Infection, cancer, allergies, or CNS injuries.
Mechanism: Pyrogens from macrophages raise the hypothalamic set point, triggering heat production and increasing body temperature.
Hypothermia
Low body temp, vital signs slow, leads to coma/death.
Fever
High temp from infection, boosts immunity.
Metabolic Disorders
PKU: Can’t process phenylalanine.
Galactosemia: High galactose, brain issues.
Glycogen Storage: Enzyme missing, organ enlargement.
Metabolic Syndrome
5 risk factors: waist, BP, glucose, triglycerides, HDL. Increases heart disease and diabetes risk.
Age-Related Changes
Slower metabolism, muscle loss, weight gain.
Clinical Terms
Appetite: Desire for food.
Familial Hypercholesterolemia: High cholesterol, early heart disease.
Pica: Eating nonfood items.
Protein Malnutrition: Marasmus (calorie), Kwashiorkor (protein).
Skin-Fold Test: Measures body fat.
