Pickled Pigs and Hyperthermia By: Long Xin Chen, Yi Min Liang, Alena Tran, Michelle Yee October 10th, 2017 PHM 142 - Metabolic Biochemistry & Immunology PHM142 Fall 2017 Instructor: Dr. Jeffrey Henderson

Presentation Outline Introduction Genetics of Malignant Hyperthermia Pickled Pigs & How it Relates to Humans Pathophysiology Diagnostics, Preventions and Treatments Presentation Summary Presentation Outline

Hyperthermia What is it? Risen in body temperature (above 38.5 °C) due to failed thermoregulation Most severe form is heat stroke Can be deadly, function of proteins in cell membranes can be adversely affected Causes: Dehydration from not drinking enough water Confined in poorly ventilated environment Drugs can influence ex) Alcohol http://www.thechiropracticoffice.ca/uncategorized/heat-stroke- and-athletesmississaugachiropractor/ What is it? Rise in body temperature due to failed thermoregulation (body produces or absorbs more head than it dissipates) Causes Commonly caused by heat strokes, adverse drug reactions (CNS; rare) Special case: Malignant hyperthermia - rare complication on some types of general anesthesia Symptoms Introduction

Malignant Hyperthermia Rare, inherited disorder, life-threatening Mutation that results buildup of calcium in muscle, leads to massive metabolic reaction Most people are unaware that they have this mutation Result of severe reaction to triggering agents Triggering agents: Halogenated anesthetic gases Muscle relaxant succinylcholine Other drugs May experience: Rapid heart rate Muscle Spasms Acidosis Organ dysfunction and failure Special case: Malignant hyperthermia - rare complication on some types of general anesthesia Symptoms Introduction

Pickled Pigs How it relates to humans MH in pigs is termed “porcine stress syndrome” Triggered by stress, anaesthesia or intense exercise Autosomal recessive disorder due to a defective ryanodine receptor Death from porcine stress syndrome = pickled pigs Pale, soft, exudative meat due to drop in muscle pH and degradation of muscle proteins How it relates to humans Pig models are used for research Similar mutations in pigs that led researchers to discover the mutation in humans What is it? Rise in body temperature due to failed thermoregulation (body produces or absorbs more head than it dissipates) Causes Commonly caused by heat strokes, adverse drug reactions (CNS; rare) Special case: Malignant hyperthermia - rare complication on some types of general anesthesia Symptoms Introduction

Genetics of Malignant Hyperthermia Autosomal dominant inheritance pattern Different genetic mutations are categorized into at least 6 forms of malignant hyperthermia susceptibility (MHS) Mutated genes are associated with calcium channels of skeletal muscles Calcium-release channels Dihydropyridine receptors Brandom (2006) Sci World J Rosenberg et al. (2015) Orphanet J Rare Dis NIH U.S. National Library of Medicine (2016) Large genetic component associated with MH. MH follows an autosomal dominant inheritance pattern, hence one copy of the gene associated with MH is already sufficient to display the disease symptoms and severe reaction to certain drugs during surgery. Associated genes that are mutated are involved in skeletal muscle function. There are at least 6 forms of malignant hyperthermia susceptibility (MHS), which are categorized by gene mutations. Mutations observed in RYR1, CACNA1S and CACNA2D1 have been linked to MHS1, 5 and 3 respectively. The remainder forms are still under investigation. Genetics

RYR1 Located on 19q13.2 Encodes for homotetrameric ryanodine receptor (RYR1) channel MHS1, MHS2, and MHS3 At least 217 mutations identified to increase risk of malignant hyperthermia Mostly single amino acid point mutations in important gene regions Mutations alter the structure of the RYR1 channels, leading to overaccumulation of Ca2+ in skeletal muscles Brandom (2006) Sci World J Rosenberg et al. (2015) Orphanet J Rare Dis NIH U.S. National Library of Medicine (2016) Located on the long arm of chromosome 19 at the 13.2 position. The gene expresses ryanodine receptor 1 proteins, which are involved with the formation of channels transporting Ca ions into cells. Image from https://ghr.nlm.nih.gov/gene/RYR1#conditions Genetics

CACNA1S Located on 1q32.1 Encodes for calcium voltage-gated channel subunit alpha1 S Forms dihydropyridine receptor, which activate RYR1 channels MHS5 2 mutations linked to malignant hyperthermia: Arg1086Cys Arg1086His Mutations cause improper activation of RYR1 channels Image from https://ghr.nlm.nih.gov/gene/CACNA1S#conditions Brandom (2006) Sci World J Rosenberg et al. (2015) Orphanet J Rare Dis NIH U.S. National Library of Medicine (2016) Located on long arm of chromosome 1, position 32.1. Genetics

Genetics Summary Genetic Mutation Mutated RYR1: Structural Alteration of RYR1 channel Mutated CACNA1S: Improper activation of RYR1 channels (response to certain drugs) Overaccumulation of Ca2+ in skeletal muscles Malignant Hyperthermia Symptoms Brandom (2006) Sci World J Rosenberg et al. (2015) Orphanet J Rare Dis NIH U.S. National Library of Medicine (2016) Mutation Open more easily and close slowly in response to drug Symptoms such as: Abnormalities in skeletal muscle contractability leading to muscle rigidity, heat generation, and excess acid production leading to acidosis. Genetics

Normal Muscle Physiology Ach released, binds to receptors Action potential reaches T-tubules Conformation change at DHP is transmitted to RYR1 Calcium released from SR, muscle contracts Reuptake of calcium into SR via calcium-ATPase pump DHP = dihydropyrimidine receptor RYR1 = ryanodine receptor subtype 1 Normal Muscle Physiology

Pathophysiology Trigger agents induce prolonged opening of RYR1 Uncontrolled release of calcium → continuous muscle activation Excessive stimulation of aerobic and anaerobic metabolism→ metabolic acidosis Increased oxygen consumption→ hypoxemia Increase in ATP usage → heat production Depletion of ATP→ muscle rigidity, rhabdomyolysis Pathophysiology

Treatment Prepare and administer dantrolene. This is a direct-acting skeletal muscle relaxant through inhibiting the release of calcium ions from the sarcoplasmic reticulum Begin cooling measures Treat cardiac arrhythmias as needed Correct hyperkalemia with hyperventilation, glucose and insulin. MacLennan, 1992 Rosenberg et al., 2003 Treatment

Diagnostic/Prevention Muscle Contracture Test: Caffeine Halothane Contracture Test: Skeletal muscle biopsy from patient’s thigh Access muscle contractile properties upon exposure to ryanodine receptor agonists: caffeine, halothane Abnormally high levels of contractile force indicate malignant hyperthermia sensitivity Sensitivity > Specificity https://www.mhaus.org/testing/introduction-to-mh-testing/testing-for-malignant-hyperthermia-mh-susceptibility-how-do-i-counsel-my-patients/ Malignant Hyperthermia Association of US Diagnostic/Prevention

Diagnostic/Prevention Muscle Contracture Test: Caffeine Halothane Contracture Test Genetic Testing (RYR1 gene sequencing) Thorough anesthetic history should be considered before undergoing anesthesia. Individuals undergoing general anesthetics for more than 30 minutes should have their temperature monitored. http://img.medscapestatic.com/pi/meds/ckb/83/11383tn.jpg https://fm.cnbc.com/applications/cnbc.com/resources/img/editorial/2015/10/20/103093726-GettyImages-530021923.530x298.jpg?v=1480353520 Rosenberg et al., 2003 Diagnostic/Prevention

Summary Summary Introduction Hyperthermia is the result of body temperature rise due to poor thermoregulation Malignant Hyperthermia is an inherited mutation that alters function of Ca2+ release channels in SR Malignant Hyperthermia in pigs is called “porcine stress syndrome” and is autosomal recessive Genetics in Humans Malignant Hyperthermia in humans is autosomal dominant, and genetic mutation lead to different forms of malignant hyperthermia susceptibility Genetic mutations are often associated with calcium channels of skeletal muscles such as Ca2+-release channels in the sarcoplasmic reticulum and dihydropyridine receptors (adjacent voltage-gated channels) Examples of genetic mutations include RYR1 and CACNA1S Pathophysiology Prolonged opening of RYR1→ uncontrolled release of calcium→ sustained muscle activity Diagnostics, Preventions & Treatments Dantrolene is used to immediately treat MH, it is a direct-acting skeletal muscle relaxant through inhibiting the release of calcium ions from the sarcoplasmic reticulum Diagnostic tools include: muscle contracture test using caffeine and halothane & genetic testing (RYR1 gene sequencing) Summary

References References Farley R. Inherited diseases of Ion Transport.Cell Physiology Source Book. 2012 doi:10.1016/B978-0-12-387738-3.00030-5 Schneiderbanger D, Johannsen S, Roewer N, Schuster F. Management of malignant hyperthermia: diagnosis and treatment. Therapeutics and Clinical Risk Management. 2014;10:355-362. doi:10.2147/TCRM.S47632. Silverthorn D. Human Physiology: An Integrated Approach 7th edition. San Francisco: Pearson Education Anon. The Chiropractic Office. Available from: http://www.thechiropracticoffice.ca/uncategorized/heat-stroke-and-athletesmississaugachiropractor/ [Accessed from 9th October 2017]. Ording H. Pathophysiology of malignant hyperthermia. Ann Fr Anesth Reanim 8, 411-416 (1989). Kolh, M.E., Horne, M.L., Martz, R. Dantrolene in human malignant hyperthermia. Aneshesiology 56, 254-262 (1982). MacLennan, D.H. The genetic basis of malignant hyperthermia.TiPS 13, 330-334 (1992). Anon. Testing for malignant hyperthermia susceptibility: how do I counsel my patients? Available from: https://www.mhaus.org/testing/introduction-to-mh-testing/testing-for-malignant-hyperthermia-mh-susceptibility-how-do-i-counsel-my-patients/ [Access from 9th October 2017] Rosenberg, H., Sambuughin, N., Riazi, S., Dirksen, R. Malignant hyperthermia susceptibility. Gene Reviews (2003). Rosenberg, H., Pollock, N., Schiemann, A., Bulger, T., Stowell, K. Malignant hyperthermia: a review. Orphanet J Rare Dis 10: 93. DOI 10.1186/s13023-015-0310-1 (2015) Brandom, B.W., Genetics of malignant hyperthermia. Sci World J 6, 1722-1730. DOI 10.1100/tsw.2006.289 (2006) NIH U.S. National Library of Medicine. Malignant hyperthermia. Available from: https://ghr.nlm.nih.gov/condition/malignant-hyperthermia#statistics [Accessed from 9th October 2017] NIH U.S. National Library of Medicine. CACNA1S gene. Available from: https://ghr.nlm.nih.gov/gene/CACNA1S [Accessed from 9th October 2017] NIH U.S. National Library of Medicine. RYR1 gene. Available from: https://ghr.nlm.nih.gov/gene/RYR1 [Accessed from 9th October 2017] References

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