Alex Chacon and Jesse Felts 9-30-13 1. 2. 3. 4. Introduce energy balance as a key component of homeostasis Overview the breakdown of energy output and define basal metabolic rate Discuss hormonal control of energy balance throughout the body Introduce the thyroid as a regulator of basal metabolic rate (BMR) The property of a system that regulates its internal environment and tends to maintain a stable, relatively constant set of conditions ◦ ◦ ◦ ◦ ◦ pH Temperature Solute concentration Energy balance Etc. Weight maintenance Satiety Stress control and psychological wellness Energetic requirement for many cellular functions ◦ ATP, ADP, cAMP, GTP Input Output U.S. Department of Health and Human Services The set of life-sustaining chemical transformations within the cells of living organisms ◦ Catabolism – breakdown of organic components (sugar, fat, protein) for the purpose of harvesting energy ◦ Anabolism – synthesis of cellular components such as lipids, proteins, and nucleic acids Breaks large molecules into small ◦ Polysaccharides, lipids, nucleic acids, proteins monosaccharides, FAs, nucleotides, amino acids Degradation of monomers to release energy ◦ Glycolysis, Citric Acid Cycle, Electron Transport Chain ATP + heat ◦ Gluconeogenesis – breakdown of fat and protein to form glucose ◦ Glycogenolysis – breakdown of glycogen glucose Constructs large molecules from smaller ones ◦ Often powered by ATP hydrolysis ◦ Simple complex Growth and maturation ◦ Ex. bone mineralization ◦ Ex. muscle hypertrophy TEF – thermic effect of food: energy used in digestion, absorption and distribution of nutrients Energy used by normal cellular process at rest ◦ Breathing, body temperature regulation, cardiac contractions. ◦ 60-70% of your total daily output ◦ Fat is the main energy source burned 70% of ATP 30% of ATP is from carbohydrates What organ system uses the most energy in the entire body? Age: younger people have higher BMRs Growth: children and pregnant woman have higher BMRs ◦ Cell replication and division Body composition: lean tissue masshigher BMR ◦ Muscles burn energy even at rest ◦ Maintaining posture and muscle tone Diet and exercise “Input” and “output” Exercise recommendations for adults (CDC): ◦ 150 min/wk of moderate-intensity aerobic activity ◦ Muscle-strengthening activities 2 days/week Diet: ◦ balance calories with physical activity while maintaining healthy nutrition 4 kcal / gram of carbohydrates 4 kcal / gram protein 9 kcal / gram fat There are hundreds of metabolic diseases Some are more directly related to Energy balance: ◦ Diabetes, hyperthyroidism, hypothyroidism, obesity What are the three categories of energy output? ◦ What is the biggest one under your control? Cause; in general: ◦ Input > output ◦ Diet, Exercise, Genetic susceptibility Classification Association of obesity with many other medical conditions1: ◦ Insulin resistance, glucose intolerance, diabetes mellitus, hypertension (high blood pressure), dyslipidemia (high cholesterol), sleep apnea, arthritis, hyperuricemia, gall bladder disease, and certain types of cancer. (Pi-Sunyer 2010) Leading preventable cause of death worldwide (Barness 2007) Biochemical function determined by necessity ◦ May liberate, store, or transform energy containing molecules ◦ Facilitate transport of molecules Secretion of hormones regulated by feedback mechanisms ◦ Positive feedback - rare ◦ Negative feedback – most common in endocrine systems Stress hormone Acts systemically Synthesized by zona fasciulata of adrenal cortex in response to ACTH secretion by the pituitary gland 1. 2. 3. Stress induces Corticotropin Releasing Hormone (CRH) released by hypothalamus Adrenocortropic hormone (ACTH) secreted by pituitary into vascular system ACTH binding to adrenal cells in zona fasciulata biosynthesis and release of cortisol into vascular system Diverts energy from low priority activities to survive immediate threats (brain activity, etc.) Increases gluconeogenesis and glycogenolysis in liver Activates anti-stress and anti-inflammatory pathways Facilitates the efficacy of epinephrine/NorEp Counteracts insulin and inhibits peripheral glucose uptake ◦ Shuts down reproductive system ◦ Decreases bone and muscle formation ◦ ◦ ◦ ◦ Heightened in the morning to prepare for a new day Increase levels ◦ Prolonged physical and/or mental stress ◦ Burnout ◦ Starvation ◦ Caffeine ◦ Sleep deprivation Decrease levels ◦ De-stress and de-tox activities Massage, music, yoga, dancing ◦ Laughing and happiness ◦ Black tea ◦ Fish oil ◦ High levels of cortisol negative feedback. “Fight or flight” response Acts systemically Hormone AND neurotransmitter synthesized in central nervous system and adrenal medulla from tyrosine and phenylalanine 1. 2. 3. Stress induces Sympathetic Nervous System (SNS) activation and ACTH release by the pituitary gland Preganglionic sympathetic fibers and ACTH stimulate adrenal cells to produce adrenal precursors from tyrosine and phenylalanine Adrenal enzymes convert precursors norepinephrine epinephrine and release from the adrenal glands into the vascular system Prepares the body to expend high amounts of energy in a short period of time ◦ ◦ ◦ ◦ Increases HR, BP, RR Stimulates glycogenolysis Triggers lipolysis Facilitates stronger muscle contraction Shunts blood and energetic molecules from non-vital tissues Cortisol increases epinephrine synthesis from precursors in the adrenal medulla No feedback mechanism Action is terminated upon reuptake into nerve terminal endings, dilution, and catabolism by various tissues Intro video: http://www.youtube.com/watch?v=VCpjv8Yc Uow Major player in managing metabolism Hormones: ◦ T3 (triiodothyronine) ◦ T4 (thyroxine) ◦ Calcitonin Reduces blood Ca2+ What key element is incorporated in T3 and T4? Increase metabolism of proteins and carbohydrates Increases basal metabolic rate Other important effects: ◦ Increase heart rate, ventilation rate, increases sympathetic activity, and aids in brain development Low levels of thyroid hormones release of thyrotropin-releasing hormone (TRH) by hypothalamus release of thyroid-stimulating hormone (TSH) by anterior pituitary gland T3 and T4 produced Negative feedback loop Hyperthyroidism ◦ Excess T3 and/or T4 ◦ Every function of the body tends to speed up Hypothyroidism ◦ Deficiency of T3 and/or T4 ◦ Low metabolism ◦ Most common cause? Goiter ◦ Swelling of thyroid gland Barness LA, Opitz JM, Gilbert-Barness E (December 2007). "Obesity: genetic, molecular, and environmental aspects". Am. J. Med. Genet. A 143A(24): 3016– 34. doi:10.1002/ajmg.a.32035. PMID 18000969. Forrest D, Visser TJ. 2013. Thyroid Hormone signaling. Biochim Biophys Acta. 1830(7):3859. doi: 10.1016/j.bbagen.2013.03.001 Pi-Sunyer FX. Comorbidities of overweight and obesity: current evidence and research issues. St. Luke's-Roosevelt Hospital Center, Columbia University College of Physicians and Surgeons, New York, NY 10025, USA. "Dietary Guidelines for Americans, 2010." Health.gov.