ENDOCRINE SYSTEM: FALL2003
Q: WHY DO VERTEBRATES HAVE AN ENDOCRINE SYSTEM?
MARTIN G. LOW, DEPT. PHYSIOLOGY
Q: WHY DO VERTEBRATES HAVE AN ENDOCRINE SYSTEM? THE CARDIOVASCULAR SYSTEM, WHICH IS MOSTLY DEVOTED TO TRANSPORTING OXYGEN AND NUTRIENTS, CAN ALSO PROVIDE A HIGHLY EFFICIENT, BUT RELATIVELY SLOW SYSTEM FOR DELIVERING “SOLUBLE” MESSENGER MOLECULES TO ESSENTIALLY EVERY CELL IN THE BODY. A: ALTHOUGH IT ALLOWS EXTREMELY RAPID COMMUNICATION THE “HARD
WIRING” OF THE NERVOUS SYSTEM IS TOO “EXPENSIVE”, INEFFICIENT (AND HOWEVER TO ENSURE FIDELITY AND SPECIFICITY OF THE SIGNALLING UNNECCESARY) FOR THE DELIVERY OF MOLECULAR SIGNALS TO EVERY PROCESS THESE “SOLUBLE MESSENGERS” MUST BE GUIDED TO THE CORRECT DESTINATION BY A “MOLECULAR ADDRESS” CELL IN THE BODY.
ENDOCRINE SUMMARY OF THE MAJOR COMPONENTS OF THE 1 STIMULUS CELL A ENDOCRINE SYSTEM TRANSPORT VIA BLOODSTREAM TO CELL B DISTANT PARTS OF THE BODY BRAIN VASOPRESSIN
ANTERIOR LOBE POSTERIOR LOBE OXYTOCIN HORMONE OF PITUITARY OF PITUITARY SECRETION RESPONSE GnRH GHRH TRH CRH DIET 2 CELL A NEUROCRINE NEURON CELL B TSH ACTH GLUCOSE CALCIUM TRANSPORT VIA BLOODSTREAM TO DISTANT TARGET TISSUES PRL LH/FSH GH
HORMONE HORMONE
ADRENAL BREAST GONADS LIVER THYROID PANCREAS CORTEX PARATHYROID
3 SIGNALLING PARACRINE 4 AUTOCRINE BETWEEN “NEIGHBORING” IGF-1 PTH MILK T3 +T4 STEROIDS CELL CELL IDENTICAL GLUCAGON CELL CELL TYPE A TYPE B CELL CELLS OF SAME STEROIDS INSULIN SIGNALLING BETWEEN TYPE X TYPE X TYPE X “NEIGHBORING” BUT TYPE DIFFERENT CELLS VIA ECF ADRENAL CORTEX TARGET TISSUES FEEDBACK LOOPS
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BRAIN STRUCTURE & FUNCTION OF MAJOR HORMONES RH = RELEASING HORMONE M.W. CHEMICAL STRUCTURE MAJOR FUNCTION HYPOTHALAMUS HORMONE TRIIODOTHYRONINE (T3) <1000 IODINATED TYROSINE DERIVATIVES GROWTH, METABOLISM & IH RH IH = INHIBITORY THYROXINE (T4) <1000 DEVELOPMENT ULTRA HORMONE STEROIDS <1000 CHOLESTEROL DERIVATIVES '' SHORT L0OP ARG-VASOPRESSIN (ADH) ANTI-DIURETIC HORMONE ~1000 (S-S) LINKED CYCLIC NONAPEPTIDES OXYTOCIN ~1000 SUCKLING RESPONSE LONG LOOP GLUCAGON ~3,500 29-RESIDUE PEPTIDE PLASMA GLUCOSE SHORT PITUITARY LOOP CALCITONIN ~ 4,000 32-RESIDUE PEPTIDE PLASMA Ca
ADRENOCORICOTROPHIC 39-RESIDUE PEPTIDE DERIVED STIMULATES RELEASE LONG LOOP 4,500 OF CORTICAL STEROIDS HORMONE (ACTH) FROM 31K POMC PRECURSOR TROPIC HORMONE 51-RESIDUE PEPTIDE WITH PLASMA GLUCOSE
CALCIUM / GLUCOSE INSULIN 6,000 (S-S)-LINKED A AND B CHAINS LIPOLYSIS
PERIPHERAL ENDOCRINE THREE DIFFERENT PARATHYROID HORMONE 9,500 84-RESIDUE PEPTIDE PLASMA CALCIUM SECRETION
INDIRECT HOMEOSTATIC SIGNALS? GLAND MECHANISMS PROLACTIN (PRL) 23,000 198 /191 RESIDUE GLYCOPROTEINS WITH LACTOGENESIS
*PEPTIDE GROWTH HORMONE (GH) 22,000 ~ 80% HOMOLOGY GROWTH / METABOLISM *STEROID THYROID-STIMULATING STIMULATES RELEASE HORMONE HORMONE (TSH) 28,000 *THYROID GLYCOPROTEINS WITH: OF T3 AND T4 LUTEINZING HORMONE (LH) 30,000 COMMON ALPHA SUBUNIT REGULATION OF FOLLICLE-STIMULATING FEEDBACK REGULATION SPERMATOGENESIS HORMONE (FSH) 30,000 AND VARIABLE BETA SUBUNIT AND OOGENESIS TARGET TISSUES OF PITUITARY HORMONE CHORIONIC MAINTENANCE OF 57,000 LEPTIN: 16kDa 139-RESIDUE PEPTIDE SECRETION GONADOTROPHIN (hCG) CORPUS LUTEUM
CELL SURFACE RECEPTORS TRANSDUCERS AND MESSENGERS?: GROUP II CELL SURFACE RECEPTORS AND THEIR TRANSDUCERS: GROUP I RECEPTOR HORMONE RECEPTOR / HORMONE MAJOR TRANSDUCERS / MAJOR TRANSDUCERS _1, _2, _3 - ADRENERGIC THROMBOXANE A2 G PROTEIN : PLC-_ G PROTEIN : CYCLASE G PROTEIN : PLC-_ _1- ADRENERGIC G PROTEIN : PLC-_ THYROTROPIN-RELEASING HORMONE (TRH) _2- ADRENERGIC G PROTEIN : PLC-_ AND CYCLASE THYROID-STIMULATING HORMONE (TSH) G PROTEIN : CYCLASE M1- MUSCARINIC G PROTEIN : PLC-_ FOLLICLE-STIMULATING HORMONE (FSH) G PROTEIN : CYCLASE
D2-DOPAMINERGIC G PROTEIN : PLC-_ AND CYCLASE LUTEINIZING HORMONE (LH) G PROTEIN : CYCLASE HISTAMINE G PROTEIN : PLC-_ EPIDERMAL GROWTH FACTOR (EGF) RECEPTOR TYROSINE KINASE: PLC-_ BRADYKININ G PROTEIN : PLC-_ PLATELET-DERIVED GROWTH FACTOR (PDGF) RECEPTOR TYROSINE KINASE; PLC-_ ANGIOTENSIN G PROTEIN : PLC-_ INSULIN RECEPTOR TYROSINE KINASE; IRS-1 VASOPRESSIN G PROTEIN : PLC-_ GLUCAGON RECEPTOR TYROSINE KINASE; IRS-1 G PROTEIN : AND CYCLASE INSULIN -LIKE GROWTH FACTOR 1 ( IGF-1) CALCITONIN G PROTEIN : AND CYCLASE GROWTH HORMONE (GH) NON-RECEPTOR TYROSINE KINASE; JAK/Stat PARATHYROID HORMONE G PROTEIN : AND CYCLASE PROLACTIN (PRL) NON-RECEPTOR TYROSINE KINASE; JAK/Stat PROSTAGLANDIN E2 G PROTEIN : AND CYCLASE RECEPTOR Ser/Thr KINASE:Smad LEUKOTRIENES G PROTEIN : PLC-_ ACTIVIN/INHIBIN (TGF-_ FAMILY)
HORMONE SECRETION BY THE HYPOTHALAMUS/ PITUITARY GLAND
NEUROHYPOPHYSIS ADENOHYPOPHYSIS (POSTERIOR PITUITARY) HYPOTHALAMUS CONTROL AFTER 2 DAY FAST (ANTERIOR PITUITARY) GH SECRETION IS FASTING INCREASES NEUROCRINE CELLS TIGHTLY COUPLED GH SECRETION TO SLEEP PERIOD AND UNCOUPLES IT RELEASING FROM SLEEP PERIOD AND 1 MAGNITUDE GREATER MEDIAN EMINENCE INHIBITING DURING PUBERTY AND NEURAL STALK HORMONES
SUPERIOR ADH OXYTOCIN LONG 2 GH CONCENTRATION PORTAL VEIN HYPOPHYSEAL ARTERY 8am 2pm 8pm 2am 8am 8am 2pm 8pm 2am 8am 4 3 SHORTVEIN PORTAL ENDOCRINE CELLS INFERIOR HYPOPHYSEAL RETROGRADE ANTERIOR PITUITARY HORMONES ARTERY FLOW ALLOWS FEEDBACK INHIBITION ACTH GH PRL LH TSH FSH/LH GH SECRETORY RATE EFFERENT VEINS 8am 2pm 8pm 2am 8am 8am 2pm 8pm 2am 8am
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STRUCTURAL ORGANIZATION OF MAMMALIAN PREPROGLUCAGON
PREPROOPIOMELANOCORTIN 1 31 64 69 107/8 126 158
26 265 GRPP GLUCAGON IP-1 GLP-1 IP-2 GLP-2
GLICENTIN MPGF
146 + b-LIPOTROPIN (91) GLP-2 (1-33) - bioactive OXYNTOMODULIN GLUCAGON
MPGF GLP-2 (3-33) - bioinactive 76 + + ACTH + g -LIPOTROPIN (58) b-ENDORPHIN (31)
GLICENTIN INTESTINE* GLUCAGON OXYNTOMODULIN-1 PANCREAS GLP-1 MPGF BRAIN GLP-2 “ENTEROGLUCAGONS” * IP-2
GnRH PULSE FREQUENCY REGULATES HORMONES HAVE VARIABLE IN VIVO “STABILITY” SECRETION OF LH AND FSH PORTAL VEIN GnRH
POTENTIAL REASONS 1 PULSE / HOUR 1 PULSE / 3 HOURS 1 PULSE / HOUR FOR VARIABLE STABILITY
/ml) LH HORMONE t_ LH STEROIDS ARE HYDROPHOBIC ng FSH 3h AND MAY PARTITION INTO MEMBRANES AND ADIPOSE TISSUE CORTISOL 70 min HORMONE CLEAVED BY SPECIFIC PEPTIDASES IN PLASMA ALDOSTERONE 70 min PLASMA LH
LH 60 min HORMONE FORMS COMPLEX WITH FSH BINDING PROTEIN WHICH PROTECTS FSH ACTH I5 min IT FROM DEGRADATION PERIPHERAL CONCENTRATION (
ADH 8 min SHORT PEPTIDES ARE PARTICULARLY 0 10 20 30 40 VULNERABLE TO DEGRADATION INSULIN 5-8 min BECAUSE THERE ARE DAYS FEW CONSTRAINTS ON THEIR OXYTOCIN 3-5 min CONFORMATION HOURS
OTHER STEROID HORMONES INTRACELLULAR RECEPTORS:“LIGAND-ACTIVATEDER TRANSCRIPTION FACTORS” GLUCOCORTICOIDS (GR) PROGESTERONE (PR) TESTOSTERONE (AR) ESTROGEN (ER) HORMONES WITH INTRACELLULAR RECEPTORS ARE HYDROPHOBIC ALLOWING DIFFUSION 1 ACROSS PLASMA MEMBRANE STEROID HORMONES DIFFUSE ACROSS PLASMA MEMBRANE “CONSERVED” HIGHLY VARIABLE HIGHLY CONSERVED (66 AMINO ACID) 240 AMINO ACID STEROID HORMONES BIND TO SPECIFIC, SOLUBLE TRANSCRIPTION-ACTIVATION DNA-BINDING DOMAIN CONTAINING HORMONE-BINDING INTRACELLULAR RECEPTORS DOMAIN TWO “ZINC FINGERS” DOMAIN (STEROIDS ONLY) hsp90 hsp90 N C 2
GLUCOCORTICOSTEROID HORMONES BIND TO A NUCLEUS SOLUBLE INTRACELLULAR GR RECEPTOR: hsp90 CELL SURFACE RECEPTORS REQUIRE TRANSMEMBRANE SIGNALLING COMPLEX +
release of inhibitory 3 STEROID-RESPONSIVE hsp90 proteins reveals +ve HRE - ve HRE TARGET GENES THIS PROBLEM IS SOLVED BY UTILISING THE nuclear localization signal on ENERGY OF HORMONE BINDING AT THE CELL GR receptor POLYPEPTIDE HORMONES ARE - SURFACE TO ALTER CONFORMATION OF HYDROPHILIC AND CANNOT DIFFUSE TRANSMEMBRANE PROTEINS AND THEIR ACROSS THE PLASMA MEMBRANE INTERACTIONS WITH INTRACELLULAR GRE: GLUCOCORTICOID STEROID RECEPTORS TRANSLOCATE PROTEINS RESPONSE ELEMENT INTO THE NUCLEUS AND INTERACT WITH GRE’S, OTHER HRE’s AND COACTIVATOR HRE: HORMONE RESPONSE MOLECULES ELEMENT
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REGULATION OF TRANSCRIPTION BY NON-STEROIDAL HORMONES
NUCLEUS - NO HORMONES TRANSDUCER RX R NO TRANSCRIPTION COMPLEX
HORMONE-RESPONSIVEHORMONE-RESPONSIVE N HRE TARGETTARGET GENES GENES C MESSENGER CASCADE
RETINOID X RECEPTOR SUBUNIT (RX) METABOLISM REPRESSES TRANSCRIPTIONAL EXOCYTOSIS ACTIVATION BY HORMONE RECEPTOR (R) PLUS HORMONES NUCLEUS TRANSCRIPTION TRANSCRIPTION + TRANSCRIPTION PERMEABILITY PERMEABILITY VITAMIN D HORMONE-RESPONSIVE HRE TARGET GENES RETINOIC ACID ONE SIGNAL - MANY EFFECTS MANY SIGNALS - ONE EFFECT THYROID HORMONE HORMONE BINDING EFFECTS ON CELL FUNCTION MAY ONLY RELIEVES REPRESSION SAME HORMONE MAY HAVE BY RETINOID X DISTINCT EFFECTS IN DIFFERENT OCCUR IF CORRECT COMBINATION OF RECEPTOR TISSUES OR CELL TYPES HORMONES ACT SIMULTANEOUSLY ON , SAME CELL
G-PROTEIN COUPLED STIMULUS INDUCED DIMERIZATION TRANSDUCER COMPLEXES EGF/ PDGF
G PROTEIN: ADENYLYL CYCLASE TSH BINDING SITE EGF/PDGF METABOLISM G PROTEIN: PLC$ PDGF PDGF RECEPTOR TYROSINE KINASE: PLC_ SH2 DOMAINS TRANSDUCER RECEPTOR TYROSINE KINASE: IRS-1 CELL COMPLEXES RECEPTOR TYROSINE KINASE: Grb2-SoS CELL MEMBRANE non-RECEPTOR TYROSINE KINASE (JAK) MEMBRANE
SECRETION MESSENGER “2ND MESSENGER” CASCADES CASCADES cAMP PROTEIN KINASE A SMALL LIGAND 1,2- DAG PROTEIN KINASE C BINDING SITE ACCOMODATES G-PROTEIN - 1P3 Ca2+ CALMODULIN CATECHOLAMINES Y-P EFFECTS ON Ras: MAP KINASE P P CELLULAR P P FUNCTION Autophosphorylation OTHER IMPORTANT FEATURES DESENSITIZATION BY by intrinsic tyrosine kinase b-ark or pkc 1. AMPLIFICATION BY ENZYMES OR ION PERMEABILITY CHANNELS TRANSCRIPTION 2.“CROSS-TALK” BETWEEN PATHWAYS 3. RAPID DEGRADATION/ DEACTIVATION OF 2ND MESSENGERS
THE INSULIN RECEPTOR IS A GROWTH HORMONE AND PROLACTIN GROWTH FACTOR STABLE S-S LINKED DIMER RECEPTORS ARE LIGAND-INDUCED DIMERS RECPTOR SIGNAL TRANSDUCTION FROM CELL SURFACE RECEPTORS TO THE NUCLEUS ---Y-P S-S TYROSINE PHOSPHORYLATION OF -S-S- -S-S- RECEPTOR RECRUITS Grb2-Sos TO Grb2 PLASMA MEMBRANE PROTEIN KINASE C Sos ACTIVATION OF Ras BY GUANINE GTP GDP NUCLEOTIDE EXCHANGE FACTOR Ras Raf/MAPKKK ACTIVATED ATP MAPKKK BY RAS OR PROTEIN KINASE C -Y-P IRS-1 TYROSINE KINASE (JAK2) ADP MAPKK ACTIVATION OF MAP- KINASE ATP REQUIRES BOTH THREONINE AND TYROSINE PHOSPHORYLATION Stat MAPK ADP IGF-1 USES A SIMILAR MECHANISM Stat 5A DEFICIENT MICE DO NOT LACTATE NUCLEUS PHOSPHORYLATION OF TRANSCRIPTION FACTORS IN NUCLEUS
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RECEPTOR HETEROTRIMERIC G PROTEINS ACTIVATION Ras AND OTHER SMALL G PROTEINS SIGNAL IN
CYCLASE ACTIVATION GTP GDP Sos
NUCLEOTIDE EXCHANGE _ _ $ $ " CYCLASE " GTP Ras GTP GDP (inactive) Ras GTP NUCLEOTIDE GDP GDP (active) EXCHANGE ATP cAMP
HIGH INTRINSIC GTPase LOW INTRINSIC Pi = RAPID DEACTIVATION GTPase
GAP SIGNAL OUT GTPase Activating Protein
MULTIPLE ROLES OF INTRACELLULAR CALCIUM IONS P P 4 4 INOSITOL LIGAND-GATED PI-LINKED HO 3 5 P 3 5 P 1,4,5-TRISPHOSPHATE CALCIUM CHANNEL RECEPTOR IP3 VOLTAGE-SENSITIVE HO 2 6 OH 2 6 CALCIUM CHANNEL 1 1 G PROTEIN HYDROLYSIS P PLC PLC P Ca2+ P PHOSPHATIDYLINOSITOLS Ca2+ ARE HYDROLYSED BY IP 3 PHOSPHOLIPASE C INTO TWO CALCIUM IS “STORED” HO SECOND MESSENGERS IN THE ENDOPLASMIC PIP2 RETICULUM Ca 2 + /CALMODULIN
MYOSIN LIGHT 1,2-DIACYLGLYCEROL CHAIN KINASE PHOSPHORYLASE MULTIFUNCTIONAL (MLCK) KINASE CAM KINASE 3 CAM KINASES PHOSPHATIDYLINOSITOL
MYOSIN LIGHT PHOSPHORYLASE EUKARYOTIC CHAIN ELONGATION FACTOR II P
PI PI-4P PI-4,5P2 1,2-DAG PI-3,4,5P3 PHOSPHATIDYLINOSITOL P P P CYCLE 4 4-KINASE 4 4 4 5-KINASE P P PI 3,4 -P2 3 5 3 5 3 5 3 5 P PROTEIN KINASE C ACTIVATION PH BIND TO 2 6 2 6 2 6 2 6 DOMAINS 1 1 1 PI-3KINASE 1 PHOSPHOLIPASE C PI 3,4,5-P3 (PLC) MEDIATED P P P P PI HYDROLYSIS IS STIMULATED BY INSULIN ACTION PI 3-KINASE MANY HORMONES
PI PI 4-P PLC PI 4,5-P2 PHOSPHORYLATION RESYNTHESIS DEGRADATION Li + I IP IP2 IP3
Li + BLOCKS CALCIUM RELEASE RESYNTHESIS FROM ER VIA LIGAND GATED CHANNEL
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PHOSPHOLIPASE C ISOFORMS PLCd SEQUENCE MOTIFS INVOLVED IN SIGNAL TRANSDUCTION
N PH EF X Y C2 DOMAIN C
CATALYTIC SITES REGULATED BY Gaq DOMAIN EF HAND PH DOMAIN NAME MOTIF RECOGNIZED
PLCg src homology 2 SH2 pY-X-X-X N PH EF X SH2 SH2 SH3 Y C “phosphotyrosine-binding” PTB - _ -N-P-X-pY-
DOMAIN EF HAND REGULATED BY PH TYROSINE PHOSPHORYLATION src homology 3 SH3 “proline-rich region”
CATALYTIC SITE CATALYTIC SITE PLCb Pleckstrin Homology PH PI-Px headgroups N PH EF X Y C
CATALYTIC SITES _ =Hydrophobic residue REGULATED EF HAND BY Gaq
ARRANGEMENT OF BINDING DOMAINS PROTEIN LECTURE 3 AND CATALYTIC SITES src kinase --Myr----SH3----SH3----SH2----Tyr kinase--- Btk --PH----Pro----SH3----SH2----Tyr kinase---- Shc --PTB----SH2- (‘Collagen-like’) Grb-2 --SH3----SH2----SH3 Shp-2 (Syp) --SH2----SH2----PTPase PLCa ? PLCb --PH----PLC----PLC-- PLCg --PH----PLC----SH2----SH2----SH3----PLC PLCd --PH----PLC----PLC PKB --PH---- Ser/Thr kinase p120Ras-GAP --SH2----SH3----SH2----PH----GAP
INSULIN RECEPTOR SIGNALING PATHWAY INSULIN UPTAKE GLUCOSE PDK PKB
IRS-1 GLUT4 TRANSLOCATION PY PY GSK3 SH2 PI 3-KINASE INHIBITORS PI 3-KINASE e.g. WORTMANNIN BLOCK GLUCOSE UPTAKE GENE FATTY ACID GLYCOGEN EXPRESSIO SYNTHESIS SYNTHESIS INHIBITION OF LIPOLYSIS N
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SYNTHESIS AND SECRETION OF PEPTIDE HORMONES REGULATION OF PLASMA GLUCOSE BY INSULIN AND GLUCAGON
9. INCREASED HORMONE SYNTHESIS Pglucose glucose 1.TRANSCRIPTION AFTER CHRONIC STIMULATION P 2. ALTERNATIVE SPLICING AGONIST
NUCLEUS GLUCOSE: PANCREAS INSULIN INSULIN - SYNTHESIS
RECEPTOR b cell SECRETION t_ approx 5 min
CALCIUM-DEPENDENT 8.
AGONIST-INDUCED, - MOBILIZATION
mRNA EXOCYTOSIS PARACRINE INHIBITION OF ISLETS OF Ca2+ LANGERHANS BY INSULIN GLUCOSE: - UPTAKE ENDOPLASMIC RETICULUM 7. SECRETORY VESICLES ACCUMULATE CLOSE TO GLUCAGON GLUCAGON PANCREAS - UTILIZATION 3. TRANSLATION PLASMA MEMBRANE t_ approx 10 min SECRETION a cell 4. TRANSLOCATION - STORAGE 5. TISSUE-DEPENDENT PROTEOLYTIC PROCESSING. 6. PACKAGING (200X CONDENSATION) INTO TARGET TISSUES SECRETORY VESICLES (liver, muscle, adipose, etc.)
ISLETS OF LANGERHANS PHYSIOLOGICAL ROLE OF INSULIN BLOOD FLOWS RADIALLY FROM CENTER OF ISLET TO THE PERIPHERY FACILITATING PARACRINE MAINTENANCE OF NORMAL PLASMA GLUCOSE LEVELS IN 1 MILLION ISLETS EACH INHIBITION OF GLUCAGON SECRETION BY INSULIN CONTAINING ~2500 CELLS SPITE OF LARGE CHANGES DUE TO FOOD INTAKE
CORE FORMED BY BETA CELLS SECRETING INSULIN RAPID UPTAKE OF DIETARY GLUCOSE (60-70 % OF TOTAL) STIMULATION OF GLUCOSE TRANSPORT
AFTER A MEAL MANTLE FORMED BY a CELLS STIMULATION OF GLUCOSE UTILIZATION
SECRETING GLUCAGON (20-25%) UTILIZATION OF DIETARY GLUCOSE
ARTERIAL BLOOD STIMULATION OF GLYCOGEN SYNTHESIS
STIMULATION OF GLUCOSE OXIDATION STIMULATION OF LIPID SYNTHESIS
b CELL b CELL PRESERVATION OF ENERGY STORES
DURING A FAST Canaliculus INHIBITION OF GLYCOGEN DEGRADATION SECRETORY GRANULES INHIBITION OF GLUCONEOGENESIS INHIBITION OF LIPOLYSIS INHIBITION OF PROTEOLYSIS VENOUSVENOUS BLOODBLOOD
+ THESE CHANNELS ARE ALSO REGULATION OF K RESPONSE OF PLASMA GLUCOSE, GLUCAGON, ACTH AND GROWTH SENSITIVE TO OTHER STIMULI INSULIN SECRETION DEPOLARIZATIONSUCH AS ACETYLCHOLINE AND LEVELS TO INSULIN INJECTION BY GLUCOSE SUR CATECHOLAMINES
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- Ca2+ )
K+ dL 2+ 80 ATP/ADP Ca Pglucose
GLUCOSE Ca2+ ACTH OXIDATION GLUCOKINASE 60 Km INSULIN ~10mM SECRETION GLYCOLYSIS 40 GLUCAGON GLUCOSE ATP
GLUT2 (mg/ GLUCOSE PLASMA 20 GROWTH GLUT2 HORMONE KM >15mM 0 60 90 120 UNLIKE HEXOKINASE, GLUCOKINASE 30 IS NOT INHIBITED BY GLUCOSE-6-P GLUCOSE INSULIN INJECTION MINUTES
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RESPONSE OF PLASMA INSULIN AND GLUCAGON TISSUE/PLASMA DISTRIBUTION OF GLUCOSE AFTER A MEAL TO ORAL GLUCOSE 180 POOR GLUCOSE FOOD LIVER 75g 30g/h G TOLERANCE GLYCOGEN
PLASMA/ECF 10g/h FASTIN 150 75-100g Plasma 11g GLUT- 2 glucose 6g/h 120 NORMAL GLUCOSE GLUT- 1 TOLERANCE 10g/h BRAIN 7g/h 7g/h AVERAGE RBC’s LIVER 10g/h 90 VALUE
GLYCOGEN FED
14g/h GLUT- 2 75-100 g plasma Plasma KIDNEY 60 insulin
glucagon 14g/h PLASMA GLUCOSE (mg/dL) GLUCOSE PLASMA 0g/h 30 BELOW 60 mg/dl METABOLISM GLUT- 4 GLUT- 4 IS LIMITED BY GLUCOSE AVAILABILITY MUSCLE 300-400g ADIPOSE 0 URINE 1h 2h 3h 4h 5h
CORTISOL HELPS TO MAINTAIN PLASMA MUSCLE INSULIN LIVER INSULIN GLUCOSE LEVELS DURING A FAST BY MUSCLE STIMULATING GLUCONEOGENESIS/LIPOLYSIS AND INHIBITING LIPID SYNTHESIS FATTY ACIDS GLYCOGE PROTEIN N GLYCOGE GLUT4 N + + AMINO ACIDS FATTY ACIDS PROVIDE AN ABUNDANT PROTEIN AFTER SOURCE OF ENERGY BUT IN VERTEBRATES, GLUCOSE GLUCOSE (UNLIKE PLANTS),THEY CANNOT BE MEAL CONVERTED BACK TO GLUCOSE
GLUT2 IN DIABETES THERE IS NO GLUT4 INSULIN TO INHIBIT THIS PGLUCOSE GLUCAGON AMINO ACIDS PROCESS GLUCOSE GLUCOSE FATTY ACIDS GLYCOGE N ATP GLYCOGEN AMINO ACIDS GLUT2 + MUSCLE DURIN PROTEIN + GLUCONEOGENESIS GLUCOSE GLUCOSE-6-P LIPO GLUT4 LYSIS G GLUT4 LIPOLYSIS FAST PROTEOLYSIS GLUCOSE GLUT2 GLUT4 GLUCONEOGENESIS LIVER FAT DROPLET LATE IN FAST~12-15h AMINO ACIDS GLYCOGEN FATTY ACIDS GLUCOSE AMINO ACIDS ADIPOSE
DURING A FAST THE LIVER MOBILISES GLUCOSE SMALL INTESTINE STORED FAT IN ADIPOSE TISSUE AND DIETARY DIGESTION, ABSORPTION AND GLUCOSE CONVERTS IT TO KETOACIDS FOR EXPORT TO DIETARY FAT RESYNTHESIS OF TRIGLYCERIDES (TG) OTHER TISSUES FFA TG LIVER FFA
KETONE BODY SYNTHESIS CAPILLARY ENDOTHELIUM AFTER A MEAL THE LIVER GLUCOSE CAN BE CONVERTED SYNTHESIZES FREE FATTY ACIDS TO FAT, BUT FAT CANNOT BE CONVERTED HYDROLYSIS OF TRIGLYCERIDES FFA ACETYL CoA (FFA) FROM GLUCOSE AND BACK TO GLUCOSE TG FFA EXPORTS IT TO THE TISSUES AS FFA TRIGLYCERIDES “KETONE FFA BODIES” CAPILLARY ENDOTHELIUM LIVER MUSCLE HEART etc. FFA HYDROLYSIS OF TRIGLYCERIDES FATTY ACID SYNTHESIS ß-OXIDATION OF FATTY ACIDS TO ACETYL CoA ACETYL CoA FFA FFA
FREE FATTY ACIDS (FFA) HAVE MUSCLE, HEART etc. ADIPOSE TISSUE LOW SOLUBILITY AND ARE ADIPOSE TISSUE HYDROLYSIS OF STORED TRANSPORTED IN THE BLOOD ß OXIDATION OF FATTY ACIDS RESYNTHESIS AND STORAGE OF BOUND TO ALBUMIN OR TRIGLYCERIDES (TG) BY LIPASE FFA ACETYL CoA LIPOPROTEINS TRIGLYCERIDES
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exercise Arginine REM Sleep REGULATION OF GROWTH HORMONAL REGULATION OF METABOLISM STRESS PGLUCOSE HORMONE SECRETION preREM Sleep + + - PROTEIN GLUCOSE LIVER PLASMA THERE ARE 6 DISTINCT LIPOLYSIS GLYCOGEN GLUCOSE IGF BINDING PROTEINS DEGRADATION SYNTHESIS + IGFBP(1-6) . ONE OF THEM IS HYPOTHALAMUS - THE EXTRACELLULAR PORTION OF THE GH RECEPTOR INSULIN - SOMATOSTATIN / GHIH - + GHRH TRANSPORT IN BLOOD CORTISOL - “SOMATOMEDIN” PITUITARY
FREE IGF’s BOUND IGF’s GLUCAGON
GROWTH HORMONE BASAL GH ~ 10-10M GROWTH TOO LOW TO MEASURE HORMONE “SOMATOMEDIN” ACCURATELY GROWTH HORMONE IS SPECIES-SPECIFIC
BONE AND CARTILAGE CATECHOLAMINES ( ) (b) MANY TISSUES LIVER AND FIBROBLASTS SKELETAL (a-1) b METABOLIC EFFECTS: IGF-1 AND IGF-2 SECRETION GROWTH EFFECTS INCREASED LIPOLYSIS AND PROTEIN SYNTHESIS LEPTIN ? DECREASED GLUCOSE USE “SOMATOMEDIN” = GHIH = IGF-1/1GF-2
REM Sleep STRESS PGLUCOSE + + REGULATION OF ADRENAL - HORMONE SECRETION LECTURE 4 HYPOTHALAMUS - CORTISOL “ADDISON’S DISEASE” DESTRUCTION OF THE CRH + ADRENAL GLAND BY DISEASE - OR BY SURGICAL REMOVAL OF THE GLAND. THIS DISEASE IS LETHAL IF NOT TREATED BY HORMONE REPLACEMENT PITUITARY TRANSPORT IN BLOOD THERAPY
ACTH BOUND STEROIDS (90%) FREE STEROIDS (10%)
CORTISOL IS NOT STORED + ALDOSTERONE
ADRENAL CORTEX CHOLESTEROL * STEROIDS “ZONA FASCICULATA”
ACTH STIMULATES STEROID SYNTHESIS WITHIN ANDROGEN MINUTES DUE TO CHOLESTEROL ALREADY PRESENT IN MITOCHONDRIAL INNER MEMBRANE PRECURSORS
GLOMERULOSA ALL STEROIDOGENIC TISSUES STEROID SYNTHESIS CAPSULE CHOLESTEROL (C27) minus side + 20-keto chain GONADS PREGNENOLONE (C21) - SIDE CHAIN FASCICULATA DEHYDROEPIANDROSTERONE SULFATE (C19 :“DHEA-S”) ALDOSTERONE + 3-keto + 17-OH desmolase sulfotransferase PREGNENOLONE (C21) PROGESTERONE 17-OH PREGNENOLONE DEHYDROEPIANDROSTERONE” ADRENAL ’’DHEA” CORTEX CORTISOL RETICULARISMEDULLARETICULARIS + 21-OH + 17-OH + 3-keto + 3-keto desmolase
+ 11-OH 17-OH PROGESTERONE ANDROSTENEDIONE (C19) MEDULLA ANDROGENS MEDULLA CORTICOSTERONE + 21-OH 17-OH PREGNENOLONE TESTOSTERONE aromatase + 18-ALDEHYDE + 11-OH NOREPINEPHRINEEPINEPHRINE SECRETION OF INDIVIDUAL +3-keto ESTRONE STEROID HORMONES IS aromatase ALDOSTERONE (C21) CORTISOL (C21) RESTRICTED TO SPECIFIC REGIONS OF THE ADRENAL ADRENAL CORTEX CORTEX DIHYDROTESTOSTERONE (C19) ESTRADIOL (C19)
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SYNTHESIS AND “SECRETION” OF STEROID HORMONES BY ADRENAL CORTEX CHOLESTEROL 20 21 1 CHOLESTEROL IS TAKEN UP INTO MITOCHONDRIA 12 18 17 5-PREGNENOLONE EITHER DIRECTLY FROM PLASMA LDL/HDL OR FROM ) UPTAKE OF CHOLESTEROL 16 INTRACELLULAR CHOLESTEROL ESTERS “STORED” 11 H ESTER FROM LDL AND HDL KIDNEY 13 C 3 IN PLASMA IN LIPID DROPLETS C D 1 19 C O StAR facilitates transfer of 14 15 2 9 12 18 17 cholesterol molecules between 10 8 20,22-Desmolase ALDOSTERONE 11 16 2 inner and outer membranes A B P-450scc 13 3 7 C D Cholesterol in 5 1 19 Intracellular 4 6 9 14 15 Lipid droplets 2 10 8 DEHYDROGENASE scc DIFFUSION OF STEROIDS A B CORTISOL StAR C H P450 OUT OF CELL 3 7 3 C H3 5 4 4 6 P450c11 17-OH PROGESTERONE C O C O 12 11-HYDROXYLASE 11-DEOXYCORTISOL 18 12 18 OH 11 16 REMOVAL OF ANDROGEN 11 16 13 13 D PRECURSORS C SIDE CHAIN 17-OH PROGESTERONE C D 1 19 1 19 9 14 15 14 15 2 8 2 9 1010 )5 - PREGNENOLONE (C21) ENDOPLASMIC RETICULUM 1010 8 A B GONADS B 17-HYDROXYLASE A 7 OXIDATION OF STEROID NUCLEUS 7 5 3 BY SPECIFIC P-450 HYDROXYLASES O 5 O 6 4 6 PROGESTERONE
ANDROSTENEDIONE ESTRONE “PRE-RECEPTOR REGULATION” OF STEROID HORMONE ACTION O O 12 18 17 12 18 OH 11 16 11ß-HYDROXYSTEROID DEHYDROGENASE - (11ß-HSD) 13 11 D 13 C C D 1 19 1 19 14 15 17 2 9 9 14 15 10 8 2 10 817 A B A B 7 Aromatase 7 O 5 5 HO 11ß- HSD TYPE 1 (LIVER) 11ß- HSD TYPE 2 (KIDNEY) 4 6 4 6
OH OH CORTISOL ACTIVE CH 0H CORTISONE INACTIVE OH 12 18 17 12 18 2 11 11 C O C O 13 13 D 12 12 18 C C D OH 18 O OH 1 19 OH 1 19 16 15 16 11 13 9 14 9 14 15 1111 13 D 2 8 2 D 40 C 10 10 8 1 19 B 1 19 A A B 14 15 9 14 15 2 9 7 7 2 9 1010 8 5 Aromatase 1010 8 O 5 A B 6 HO A B 4 6 33 3 7 3 7 TESTOSTERONE ESTRADIOL 5 O 5 DIHYDROTESTOSTERONE O 4 6 4 6
LOCAL DEHYDROGENATION OF THE C11 HYDROXYL GROUP ON BINDING AFFINITIES OF STEROIDS TO PLASMA PROTEINS CORTISOL PROTECTS MINERALOCORTICOID RECEPTORS (MR ) FROM INAPPROPRIATE ACTIVATION SEX HORMONE CORTISOL BINDING BINDING GLOBULIN ALBUMIN ALDOSTERONE:MR Kd~1nM HORMONE PROTEIN (CBP) (SHBG) CORTISOL or CORTISONE : MR Kd~1nM CORTISOL or CORTISONE : GR Kd~10nM CORTISOL 76 1.6 0.003
IN SPITE OF THE HIGH AFFINITY OF CORTISOL / CORTISONE FOR THE MR IN CORTISONE 7.8 2.7 VITRO, GLUCOCORTICOIDS DO NOT BIND TO MR IN TARGET TISSUES. THIS IS 0.005 DUE TO THE “PRE-RECEPTOR INACTIVATION” OF CORTISOL BY 11ß-HSD2 ESTRADIOL 0.06 680 0.06
CORTISOL CORTISOL PREGNENOLONE 0.18 14 0.06
LIVER 11ß-HSD1 11ß-HSD2 ADIPOSE PROGESTERONE 24 8.8 0.06 GONADS OXIDATION OF C11 HYDROXYL
CORTISOL CORTISONE 17_ -OH-PROGESTERONE 55 9.9 0.4
GR MR KIDNEY,COLON SALIVARY TESTOSTERONE RESPONSE nucleus NO RESPONSE 5.3 1600 0.04 nucleus GLAND, HEART
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SYNTHESIS OF THYROID HORMONES: STEP- 2 COUPLING OF IODOTYROSINES SYNTHESIS OF THYROID HORMONES: STEP 1 - IODINATION I I HO I II
TYROSINE HO Tyr CH2CHCOOH- THYROGLOBULIN 5 ’ 5 NH2 HO Tyr CH2CHCOOH HO CH2CHCOOH + Tyr HO Tyr O Tyr NH2 TYROSINE NH2 3’ 3 IODINATION I I I I T I Thyroglobulin Thyroglobulin 4
HO MONOIODOTYROSINE (MIT) Tyr CH2CHCOOH- THYROGLOBULIN 3,5,3’5’-tetraiodothyronine Coupling of iodotyrosine moities results in the loss NH2 of the peptide linkage to thyroglobulin allowing thyroid Approximately 10% of the tyrosine residues on the hormones to diffuse across the cell membrane 550 amino acid residue Thyroglobulin molecule may I 3,5,3’-Triiodothyronine TYROSINE become iodinated by the enzyme - thyroid IODINATION peroxidase acting on the colloid at the luminal I I surface of the thyroid follicle. These reactions only occur in the thyroid at specific residues in HO Tyr CH2CHCOOH “Hormonogenic” sites located at the extreme ends of + Tyr CH2CHCOOH the Thyroglobulin molecule. HO NH2 NH2 Tyr O Tyr DIIODOTYROSINE (DIT) HO Tyr CH2CHCOOH- THYROGLOBULIN
I I NH2 I I I Thyroglobulin Thyroglobulin T3
I I
CH2CHCOOH Tyr + Tyr NH2 NH2
I I Thyroglobulin
3,5,3’5’-tetraiodothyronine SECRETION OF THYROID HORMONE STEP 3 4 ENDOCYTOSIS OF I I IODINATION OF THYROGLOBULIN ‘COLLOID’ IN FOLLICLE BY DEIODINATION BY THYROID PEROXIDASE PSEUDOPOD
TG 3 TG TG Tyr O Tyr CH2CHCOOH I
NH2 I I I I “DEACTIVATION” PATHWAY T4 “ACTIVATION” PATHWAY 5 5-deiodination FUSION OF PHAGOSOME Tyr O Tyr 5’- deiodination TG WITH LYSOSOMES TG 6 DEGRADATION DEGRADATION OF SELENODEIODINASES AND THYROGLOBULIN I I rT3 RECYCLING T I I I T3 I OF MIT/DIT 7 4 BY DEIODINASES T4 FREE THYROXINE RELEASED FROM PROTEIN INTO CYTOPLASM I Tyr O Other monovalent 2 8 Tyr CH2CHCOOH Tyr O Tyr CH2CHCOOH anions compete IODIDE UPTAKE “DIFFUSION” OF THYROXINE with iodide for BY Na/I THROUGH CELL MEMBRANE NH2 SYMPORTER Tyr NH2 uptake; sometimes I with useful medical T4> > >T3 I and experimental applications e.g. TCO ;Cl0 ; S 4 4 CN; IODIDE IN 3,3’,5’-Triiodothyronine (reverse T3) 3,5,3’-Triiodothyronine (T3) Additional metabolism?? I 1 ECF~20nM
EFFECTS OF THYROID HORMONE ON TARGET TISSUES THYROID HORMONES
MOST EFFECTS OF THYROID HORMONE ARE “PERMISSIVE”:
RELATIVE PLASMA BOUND TO THYROID HORMONE PROMOTES SYNTHESIS OF PROTEINS WHICH ARE THEN HORMONE PRODUCTION POTENCY CONCENTRATION PLASMA t_ REGULATED ACUTELY BY OTHER HORMONES. PROTEINS (µg/day) (µg/dL) (%) (days) THYROID DISEASES METABOLISM CONGENITAL HYPOTHYROIDISM THYROID HORMONE INCREASES: T + 80- 90 8 6-7 DUE TO “METABOLIC” DEFECT IN 4 99.95 BASAL METABOLIC RATE THYROID HORMONE SYNTHESIS BODY TEMPERATURE RESULTING IN MENTAL RETARDATION CARDIAC OUTPUT/ TACHYCARDIA MOBILIZATION OF ENERGY STORES UNCOMMON IN DEVELOPED COUNTRIES DUE TO EARLY POST- NATAL TESTING
T3 + + + + 4-8 (24)* 0.3 99.7 1-3 “ENDEMIC” HYPOTHYROIDISM DUE TO IODIDE DEFICENCY OR GOITROGENS. GROWTH AND DEVELOPMENT READILY PREVENTED BY THYROID HORMONE REQUIRED IN IODIDE SUPPLEMENTATION PERINATAL PERIOD FOR: OF FOOD rT3 - 2-3 (27) * 0.04 99.8 0.1 NEURAL DEVELOPMENT BONE GROWTH (GH) HYPERTHYROIDISM AUTOIMMUNE “GRAVES DISEASE” PITUITARY TUMOR THYROID TUMOR * VALUES IN PARENTHESES INDICATE PERIPHERAL CONVERSION WEIGHT LOSS
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THYROID DISEASES CALCIUM IN DIET PLASMA Ca2+ DISEASE THYROID SERUM SERUM TYPE TSH CAUSE OF DISEASE CALCIUM SENSOR STATUS T3 +T4 CHOLESTEROL DEFECT IN IODIDE TRAP OR DECREASE IN PLASMA CONGENITAL HYPO LOW HIGH CALCIUM STIMULATES THYROID HORMONE PARATHYROID PARATHYROID SYNTHESIS HORMONE (PTH) SECRETION VITAMIN D3 DIET: (i) LOW IN IODIDE IODIDE PTH DEFICIENCY HYPO LOW HIGH OR (ii) GOITROGENS PTH 25-(OH)-D3 PRESENT PO4 AUTOIMMUNE: DESTRUCTION OF THYROID BONE KIDNEY 1,25-(OH)2-D 3 GUT HYPO LOW TISSUE DUE TO INFLAMMATION Ca2+ THYROIDITIS HIGH BONE RESORPTION CALCIUM REABSORPTION PO4 AUTOANTIBODIES TO THE TSH BONE DEPOSITION PHOSPHATE EXCRETION AUTOIMMUNE: HYPER HIGH LOW GRAVES DISEASE RECEPTOR PROVIDE CONTINUOUS Ca 2+ Ca2+ UNREGULATED STIMULUS URINE via CALBINDINS THYROID TUMOR HYPER HIGH LOW UNREGULATED SYNTHESIS CALCIUM ABSORPTION AND SECRETION OF T3 AND T4 INCREASE IN PLASMA CALCIUM 2+ 99% INIS BONE; BOUND OF TO WHICH PROTEINS. 50% UNREGULATED SYNTHESIS STIMULATES CALCITONIN PLASMA Ca PITUITARY TUMOR HYPER HIGH HIGH <1% IN ECF; 100 CALCITONIN IS SECRETED FROM THE THYROID PARAFOLLICULAR CELLS PTH SECRETION EXHIBITS A STEEP INVERSE SIGMOIDAL DEPENDENCE ON EXTRACELLULAR Ca 2+ BUT IS CALCITONIN AN IMPORTANT PHYSIOLOGICAL SUBSTANCE? The observation that calcitonin (CT) at supraphysiological doses is hypocalcemic, led to the mistaken conclusion that it was important for calcium homeostasis and this idea has persisted to this day. INCREASED Ca2+ SUPRESSES Despite these findings there is no readily apparent pathology due to CT excess or deficiency and there PTH SECRETION VIA A G PROTEIN is no evidence that circulating CT is of substantial benefit to any mammal. ……….. . COUPLED MECHANISM 50 Mammalian CT at physiological doses is not essential and very likely the CT gene has survived because of the gene’s alternate mRNA pathway to produce calcitonin-gene-related peptide found in neural tissues. PTH RESPONSE HIRSCH,PF and BARUCH H, ENDOCRINE 2003, 201-208 MAXIMAL % 0 1.0 1.25 1.5 IONIZED CALCIUM (mM) 12