REGULATION OF BODY WEIGHTTHE BIOCHEMISTRY OF APPETITE AND ENERGY EXPENDITURE

REGULATION OF BODY WEIGHT

OVERVIEW ORGAN SPECIALIZATION METABOLIC PATHWAYS HOMEOSTASIS

PROTEINS INVOLVED IN WEIGHT REGULATION DYSREGULATION

STARVATION OBESITY DIABETES: TYPES I AND II

DIETING ATKINS DIET

OVERVIEW 1 NORMAL METABOLISM IS A HIGHLY CONTROLLED AND REGULATED

BALANCE BETWEEN ANABOLISM AND CATABOLISM

CATABOLIC PROCESSES RELEASE CHEMICAL ENERGY STORED IN COMPLEX MOLECULES ENERGY SAVED AS ATP, NADH, NADPH, FADH2 OR USED AS NEEDED IN VARIOUS PROCESSES

ANABOLIC PROCESSES BUILD COMPLEX MOLECULES FROM SIMPLER MOLECULES REQUIRE ENERGY, USUALLY FROM ATP, NADH, NADPH

METABOLIC FUELS (STORAGE MOLECULES) PROTEINS POLYSACCHARIDES LIPIDS

NUCLEOTIDE METABOLISM :ONLY A VERY SMALL ROLE IN ENERGY BALANCE (AT THE LEVEL OF PYRIMIDINE CATABOLISM)

OVERVIEW 2

PATHWAYS INVOLVED IN ENERGY METABOLISM ARE INTERRELATED

REVIEW THE MAJOR PATHWAYS INVOLVED IN FUEL METABOLISM AND THEIR REGULATION

GLYCOLYTIC/GLUCONEOGENIC GLYCOGEN METABOLISM FATTY ACID METABOLISM CITRIC ACID CYCLE AMINO ACID METABOLISM PENTOSE PHOSPHATE PATHWAY OXIDATIVE PHOSPHORYLATION

OVERVIEW 3 : COMPARTMENTALIZATION

TWO COMPARTMENTS IN WHICH METABOLISM IS DIVIDED: CYTOSOL

GLYCOLYSIS GLUCONEOGENESIS GLYCOGEN BREAKDOWN AND SYNTHESIS PENTOSE PHOSPHATE PATHWAY FATTY ACID SYNTHESIS AMINO ACID DEGRADATION AND UREA CYCLE

MITOCHONDRIA CITRIC ACID CYCLE OXIDATIVE PHOSPHORYLATION FATTY ACID OXIDATION AMINO ACID DEGRADATION AND UREA CYCLE

MEMBRANE TRANSPORT BETWEEN CYTOSOL AND MITOCHONDRIA

OVERVIEW 4

MITOCHONDRIAL-CYTOSOLIC INTERFACE

MITOCHONDRIAL MEMBRANE TRANSPORTERS:

PYRUVATE TRANSPORTER CARNITINE/ACYLCARNITINE TRANSPORTER CITRATE TRANSPORTER ASPARTATE TRANSPORTER MALATE TRANSPORTER CITRULLINE TRANSPORTER ORNITHINE TRANSPORTER OTHERS

OVERVIEW 5 ORGANS ARE SPECIALIZED WITH REGARD TO

METABOLISM DIFFERENT METABOLIC NEEDS AND FUNCTIONS INTER-ORGAN COORDINATION

WE WILL LOOK AT HOW SPECIFIC METABOLIC FUNCTIONS ARE DISTRIBUTED AMONG THE FOLLOWING ORGANS:

BRAIN MUSCLE (SKELETAL AND HEART) LIVER KIDNEY ADIPOSE TISSUE

ORGAN SPECIALIZATION: MUSCLE MUSCLE FUELS:

GLUCOSE FROM GLYCOGEN

FATTY ACIDS

KETONE BODIES

GLYCOGEN GLYCOGEN GLUCOSE-6-PHOSPHATE

G-6-P ENTERS GLYCOLYTIC PATHWAY MUSCLE LACKS G-6-PHOSPHATASE

SO CANNOT GENERATE GLUCOSE FOR EXPORT

MUSCLE CAN SYNTHESIZE GLYCOGEN FROM GLUCOSE 1% - 2% OF MASS IN RESTED MUSCLE GLYCOGEN MOBILIZED FASTER THAN FAT GLUCOSE METABOLISM BOTH AEROBIC AND ANAEROBIC

FAT METABOLISM ONLY AEROBIC

MUSCLE CANNOT CARRY OUT GLUCONEOGENESIS MUSCLE CONTRACTION

DRIVEN BY ATP HYDROLYSIS AEROBIC OR ANAEROBIC

NEEDS ATP REGENERATION

ATP RESUPPLY INITIALLY FROM PHOSPHOCREATINE (1st 4s OF MAX. EXERTION)

PHOSPHOCREATINE + ADP CREATINE + ATP RESPIRATION (GLYCOLYSIS OF G-6-P) ANAEROBIC DEGRADATION TO LACTATE

WHEN GLYCOLYTIC FLUX > KREBS, OXPHOS FLUXES

MUSCLE LACTATE

pH MUSCLE FATIGUE TRANSFERRED TO LIVER VIA BLOOD

HEART MUSCLE AEROBIC PRIMARILY FATTY ACIDS AS FUEL CAN ALSO USE

GLUCOSE (FROM SMALL GLYCOGEN STORE) KETONE BODIES PYRUVATE, LACTATE

MUSCLE CARBOHYDRATE METABOLISM IN MUSCLE SOLELY

SERVES MUSCLE

CAN’T EXPORT GLUCOSE

CAN’T PARTICIPATE IN GLUCONEOGENESIS

IN STARVATION PROTEOLYTIC DEGRADATION OF MUSCLE TO

AMINO ACIDS

MUSCLE METABOLISM

GLUCOSE GLYCOGEN

LACTATE PYRUVATE H2O + CO2

TO LIVER

AMINO ACIDS PROTEINS

ALANINE

TO LIVER

FATTY ACIDS +KETONE BODIES

INTOBLOOD

FROM LIVER

INTERORGAN PATHWAYS IN-CLASS EXERCISE ***

DURING MAXIMUM EXERTION, MUSCLES GENERATE LACTATE, WHICH IS RELEASED INTO THE BLOODSTREAM.

(1) SHOW THE PATHWAY BY WHICH GLUCOSE IS SYNTHESIZED FROM LACTATE IN THE LIVER.

(2) WHY ARE SEPARATE COMPARTMENTS NEEDED FOR THIS.

(3) WHY DOESN’T MUSCLE RELEASE PYRUVATE DIRECTLY FOR UPTAKE BY THE LIVER TO REGENERATE GLUCOSE, INSTEAD OF CONVERTING IT TO LACTATE?

(4) WHAT IS THE NET COST, IN TERMS OF NUCLEOSIDE TRIPHOSPHATES, OF ONE SYNTHETIC CYCLE?

ADIPOSE TISSUE STORES AND RELEASES FATTY ACIDS STORAGE

SUBCUTANEOUS INTRA-ABDOMINAL SKELETAL MUSCLE

FATTY ACIDS TRANSPORT: AS LIPOPROTEINS LIPOPROTEINS: NONCOVALENT PROTEIN-LIPID COMPLEX

CHYLOMICRONS (INTESTINAL MUCOSA) DIETARY TG, CHOL TISSUES

VLDLS (SYNTHESIZED IN LIVER) : LIVER TISSUE; TG, CHOL HDLS (PLASMA) : TISSUELIVER CHOL. TRANSPORT

STORED AS TRIGLYCERIDES

TRIACYLGLYCEROLS FATTY ACID ACYLATION TO ACYL-CoA

ATP-DEPENDENT ACYL-CoA SYNTHETASES

FATTY ACYL-CoA + GLYCEROL-3-PHOSPHATE STORED TRIACYLGLYCEROLS

GLUCOSE DHAP (GLYCOLYSIS) DHAP + NADH + H+ G-3-P + NAD+

HYDROLYSIS OF TRIACYLGLYCEROLS FOR FUEL FATTY ACIDS + GLYCEROL

WHEN GLUCOSE IS PLENTIFUL, GLYCOLYSIS PREDOMINATES DHAP G-3-P FATTY ACIDS STORED AS TRIACYLGLYCEROLS

ADIPOSE TISSUE

TRIACYLGLYCEROLS WELL-FED

FATTY ACIDS

+

GLYCEROL

GLUCOSE

WELL-FED STATE

FROM LIVER

TO LIVERTRIACYLGLYCEROLS FROM LIVER

WELL-FED

BRAIN

20 % OF RESTING O2 CONSUMPTION FUEL FOR PLASMA MEMBRANE Na+- K+ ATPase

MAINTAINS NEURONAL MEMBRANE POTENTIAL

GLUCOSE IS PRIMARY FUEL BRAIN DOESN’T STORE MUCH GLYCOGEN

REQUIRES STEADY SUPPLY OF GLUCOSE

DURING FASTING, STARVATION KETONE BODIES

BRAIN

KETONE BODIES

GLUCOSE

H2O + CO2

TO BLOOD

FROMLIVER

LIVER A “CENTRAL CLEARINGHOUSE” FOR METABOLITES ALL NUTRIENTS ABSORBED BY INTESTINES DRAIN

DIRECTLY INTO THE LIVER VIA THE PORTAL VEIN EXCEPT FATTY ACIDS

REGULATES BLOOD GLUCOSE LEVEL RESPONDS TO:

INSULIN GLUCAGON EPINEPHRINE BLOOD GLUCOSE LEVEL

LIVER

WHAT HAPPENS AFTER CHO INGESTION? LIVER CELLS ARE PERMEABLE TO GLUCOSE

INSULIN HAS NO DIRECT EFFECT ON UPTAKE

WHEN [GLUCOSE] ~ 6 mM LIVER CONVERTS IT TO G-6-P GLUCOKINASE IS THE ENZYME

AN ISOZYME OF HEXOKINASE REVIEW ENZYME KINETICS OF BOTH

KM = 0.1 mM FOR HEXOKINASE; 5 mM FOR GLUCOKINASE

HYPERBOLIC VS SIGMOIDAL KINETICS

LIVER

EARLY SATURATION OF HEXOKINASE INHIBITION BY G-6-P

GLUCOKINASE ACTIVITY LINEAR AT HIGHER [GLUCOSE] NOT INHIBITED BY G-6-P

GLUCOKINASE IS MONOMERIC ALLOSTERISM DOESN’T EXPLAIN KINETICS

OTHER ABSORBED SUGARS G-6-P IN LIVER

CENTRAL ROLE OF GLUCOSE-6-PHOSPHATE IN CHO METABOLISM ITS FATE DEPENDS ON DEMAND FOR GLUCOSE

G6P GLUCOSE (G-6-PHOSPHATASE) WHEN BLOOD [GLUCOSE] < 5 mM TRANSPORT TO PERIPHERAL ORGANS

G6P GLYCOGEN WHEN GLUCOSE DEMAND IS LOW WHEN GLUCAGON AND/OR EPINEPHRINE LEVELS

INDICATES GLUCOSE DEMAND GLYCOGEN G-6-P GLUCOSE

G-6-P PYRUVATE (GLYCOLYSIS) ACETYL CoA OXIDIZED BY C.A. CYCLE AND OXPHOS OR USED FOR FATTY ACID SYNTHESIS ALSO PHOSPHOLIPIDS, CHOLESTEROL PYRUVATE DEHYDROGENASE

G-6-P HEXOSE-MONOPHOSPHATE SHUNT

INTERORGAN PATHWAYSIN-CLASS STUDY QUESTION ***

AMINO ACIDS CAN BE TRANSAMINATED TO ALANINE IN MUSCLE BY USING PYRUVATE AS THE -KETOACID SUBSTRATE. ALANINE IS RELEASED INTO THE BLOODSTREAM AND CIRCULATES TO THE LIVER.

(1) SHOW HOW ALANINE IS CONVERTED TO GLUCOSE IN THE LIVER.

(2) SHOW THE FATE(S) OF THE AMINO GROUPS TRANSFERRED BY THE AMINO ACIDS METABOLIZED THIS WAY IN MUSCLE

(3) SHOW THE FLUX OF ALANINE’S AMINO GROUP FROM ITS ENTRY INTO THE LIVER TO ITS EXIT AS UREA. START WITH 2 MOLECULES OF ALA.

IN-CLASS STUDY QUESTION EXPLAIN WHY ALCOHOL CONSUMPTION AFTER

STRENUOUS EXERCISE, OR ACCIDENTALLY BY A FASTING CHILD, CAUSES HYPOGLYCEMIA (A LOW BLOOD GLUCOSE LEVEL)

CLINICAL CASE STUDY A THREE MONTH OLD BABY IS REFERRED TO A DEVELOPMENTAL PEDIATRICIAN

BECAUSE SHE HAS POOR HEAD CONTROL, IS HYPOTONIC, AND IS NOT DEVELOPING IN A TYPICAL FASHION. ON EXAMINATION, SHE SHOWS GLOBAL DEVELOPMENTAL DELAY (AT THE LEVEL OF A ONE MONTH OLD) AND IS FEELS LIKE A “RAG DOLL” WHEN PICKED UP. SHE HAS DECREASED MUSCLE MASS AND IS NOT FEEDING WELL. SHE HAD A NORMAL EXAMINATION AT BIRTH, BUT WAS “SMALL FOR GESTATIONAL AGE”. HEAD CIRCUMFERENCE IS NOW IN THE “MICROCEPHALIC” RANGE.

THE PEDIATRICIAN CONSIDERED A METABOLIC CAUSE FOR THE BABY’S SYMPTOMS, AMONG OTHER CAUSES, AND DID AN EXTENSIVE “METABOLIC WORKUP”. ABNORMAL RESULTS INCLUDED: INCREASED SERUM [PYRUVATE], [LACTATE], [AMMONIA] INCREASED LEVELS OF SERUM ALANINE AND CITRULLINE LOW SERUM [ASPARTATE] LOW FASTING BLOOD GLUCOSE LEVEL BORDERLINE LOW BLOOD pH

*NOTE: THE PHLEBOTOMIST WAS INSTRUCTED TO TRANSPORT THE LACTATE AND PYRUVATE IMMEDIATELY TO THE LAB ON ICE.

CLINICAL CASE STUDY: CONTINUED THE REMAINDER OF THE BLOOD STUDIES WERE NORMAL. AFTER THE

LABS RETURN, A FIBROBLAST CULTURE IS OBTAINED AND A PYRUVATE CARBOXYLASE DEFICIENCY IS DIAGNOSED.

BEFORE THE RESULTS OF THE FIBROBLAST CULTURE ARE AVAILABLE, THE INFANT DEVELOPS A VIRAL SYNDROME WITH FEVER, DEVELOPS SEIZURES AND DIES.

QUESTIONS:

EXPLAIN THE BIOCHEMICAL BASIS FOR EACH OF THE ABNORMAL LAB FINDINGS

“PSYCHOMOTOR RETARDATION” IS THE RESULT OF A LACK OF THE NEUROTRANSMITTERS GLU, ASP AND GABA. WHY DOES PYRUVATE CARBOXYLASE DEFICIENCY RESULT IN DEFICIENCIES OF THESE?

IF THIS INFANT HAD NOT DIED, WHAT WOULD HAVE BEEN SOME POTENTIAL TREATMENTS?

HORMONAL INFLUENCES ON METABOLISM

EPINEPHRINE CYCLIC AMP AS SECONDARY MESSENGER

GLUCAGON CYCLIC AMP AS SECONDARY MESSENGER

INSULIN

ACTIONS OF EPINEPHRINE

AS AN INSULIN ANTAGONIST ACTIVATES MUSCLE GLYCOGEN PHOSPHORYLASE

GLUCOSE-6-P USED IN GLYCOLYSIS

TRIGGERS PHOSPHORYLATION (ACTIVATION) OF HORMONE-SENSITIVE LIPASE IN FAT CELLS MOBILIZES FAT BY HYDROLYZING TGs

GLYCOGEN BREAKDOWN IN LIVER ACTIVATES GLUCONEOGENESIS IN LIVER INHIBITS FATTY ACID SYNTHESIS

THE ACTIONS OF GLUCAGON ACTIONS RESTRICTED TO THE LIVER

BINDS TO A GLUCAGON RECEPTOR cAMP AS A SECONDARY MESSENGER PROTEIN KINASE A IS ACTIVATED

PHOSPHORYLATION

CONTROL AT LEVEL OF PROTEIN PHOSPHORYLN’ OF GLYCOGEN PHOSPHORYLASE ACTIVITY OF GLYCOGEN SYNTHASE ACTIVITY OF PYRUVATE KINASE GLYCOLYTIC ACTIVITY OF FRUCTOSE -2,6-BIPHOSPHATASE F-2,6-P PFK1 GLYCOLYTIC ACTIVITY

AN INSULIN ANTAGONIST

THE ACTIONS OF GLUCAGON RATES OF GLYCOGENOLYSIS

G-6-PHOSPHATASE IN LIVER G-6-PHOSPHATE GLUCOSE + Pi

RATES OF GLYCOGEN SYNTHESIS RATE OF GLYCOLYSIS IN LIVER

CONSERVE GLUCOSE FOR OTHER ORGANS RATES OF GLUCONEOGENESIS

GENERATES GLUCOSE FOR RELEASE TO BLOOD RATES OF FATTY ACID SYNTHESIS

FAT BECOMES ENERGY SOURCE TO PRESERVE BLOOD GLUCOSE LEVELS

EPINEPHRINE AND GLUCAGON ARE INSULIN ANTAGONISTS AFTER BINDING TO THEIR RECEPTORS, THEIR

INTRACELLULAR SIGNALS ARE MEDIATED BY THE TRANSIENT ACTIVATION OF STIMULATORY G- HETEROTRIMERIC PROTEINS

ADENYLATE CYCLASE IS ACTIVATED cAMP IS A “SECONDARY MESSENGER”

HETEROTRIMERIC G PROTEINS

MEDIATE SIGNAL TRANSDUCTION :

LIGAND+RECEPTOR HET G PROTEIN TARGET

AMPLIFICATION OF EXTRACELLULAR SIGNALL-R COMPLEX ACTIVATES MANY HET G PROTEINS

HET G PROTEINS BIND GTP AND GDPINACTIVE FORM: HET G PROTEIN + GDPACTIVE FORM : HET G PROTEIN + GTP

INACTIVE FORM + GTP ACTIVE FORM + GDP -THIS IS AN EXCHANGE REACTION -REQUIRES LIGAND BOUND TO RECEPTOR

HET G PROTEINS HYDROLYZE GTP TO GDP + Pi

CAUSES DEACTIVATION OF ACTIVATED G PROTEINA SLOW PROCESS (2 – 3 MIN-1)

ACTIVATED HET G PROTEIN ACTIVATES ADENYLATE CYCLASE

HETEROTRIMERIC G PROTEINS

ONE OF A LARGER FAMILY OF “G PROTEINS”G PROTEINS BIND GDP AND GTPG PROTEINS HAVE GTPase ACTIVITYAMONG THEIR FUNCTIONS ARE:

SIGNAL TRANSDUCTION VESICLE TRAFFICKINGTRANSLATIONTARGETING (SIGNAL RECOGNITION)

(NOTE THAT THE GTPase ACTS AS AN “ENERGASE” AND NOT A HYDROLASE IN THESE)

HETEROTRIMERIC G PROTEINS INCREASE CYCLIC AMPI.E., A SIGNAL TRANSDUCTION FUNCTION

RECEPTOR

ADENYLATECYCLASE

GDP

HORMONE

INACTIVE HETEROTRIMERIC G PROTEIN

GTP

L B

I IP LI AD Y

ER

EXTRACELLULAR

INTRACELLULAR

RECEPTOR

ADENYLATECYCLASE

GTP

GTP-GDP EXCHANGE REACTION ACTIVATED G PROTEIN

HORMONE-RECEPTOR COMPLEX

GDP

RECEPTOR

ADENYLATECYCLASE

ADENYLATE CYCLASE IS ACTIVATED AND CYCLIC AMP IS PRODUCED IF THE RECEPTOR IS A “STIMULATORY” ONE

HORMONE-RECEPTOR COMPLEX

GTP

4 ATP 4 cAMP + 4 PPi

RECEPTOR

ADENYLATECYCLASE

GDP

HORMONE

BOUND GTP IS HYDROLYZED AND AC IS DEACTIVATED

+ PPi

G PROTEIN-COUPLED RECEPTORS

INTEGRAL MEMBRANE PROTEINS 7 TRANSMEMBRANE HELICES

1 % OF HUMAN GENOME CODES FOR THESE RECEPTORS FOR

CATECHOLAMINES EICOSANOIDS MOST PEPTIDE AND PROTEIN HORMONES OLFACTION AND GUSTATION LIGHT SENSING (RHODOPSIN)

MOST IMPORTANT CLASS OF DRUG TARGETS (~ 50 % OF NEW DRUG EFFORTS)

CYCLIC AMP

A “SECONDARY MESSENGER” ATP 3’,5’- cAMP + PPi (ADENYLATE CYCLASE)

cAMP + H2O AMP (PHOSPHODIESTERASE)

REQUIRED FOR ACTIVITY OF PROTEIN KINASE A ALSO KNOWN AS cAMP-DEPENDENT PKA, OR cAPK

cAPK PHOSPHORYLATES SPECIFIC Ser AND/OR Thr PHOSPHORYLASE b KINASE GLYCOGEN SYNTHASE

cAMP PHYSIOLOGIC EFFECTS MEDIATED BY ACTIVATION OF SPECIFIC PROTEIN KINASES

CYCLIC AMP GLUCAGON AND EPINEPHRINE cAMP LEVELS THIS cAPK ACTIVITY cAPK ACTIVITY

PHOSPHORYLATION RATES DEPHOSPHORYLATION RATES

PHOSPHORYLATION OF ENZYMES OF GLYCOGEN METABOLISM GET GLYCOGEN BREAKDOWN WHY?

ACTIVATION OF GLYCOGEN PHOSPHORYLASE INACTIVATION OF GLYCOGEN SYNTHASE

OPPOSITE HAPPENS WHEN [cAMP] DECREASES

THE ADENYLATE CYCLASE SIGNALING SYSTEM

REFER TO THE MECHANISM OF RECEPTOR-MEDIATED ACTIVATION/INHIBITION OF AC ON PAGE 676 OF THE VOET&VOET TEXT

INSULIN ACTIONS: PERIPHERAL STIMULATES GLUCOSE UPTAKE IN

ADIPOSE TISSUE MUSCLE

STIMULATES GLUCOSE STORAGE AS GLYCOGEN IN LIVER MUSCLE

STIMULATES STORAGE AS FAT IN ADIPOCYTES PROMOTES DIFFERENTIATION OF WHITE FAT CELLS ACTIVATES LIPOPROTEIN LIPASE INHIBITS HORMONE-SENSITIVE LIPASE INHIBITS GLUCONEOGENESIS IN LIVER INHIBITS GROWTH HORMONE RELEASE INHIBITS CATECHOLAMINES

STARVATION NORMAL DISTRIBUTION OF NUTRIENTS

AFTER A MEAL PROTEINS AMINO ACIDS IN GUT

ABSORBED BY INTESTINAL MUCOSA PORTAL VEIN CIRCULATION TO LIVER

PROTEIN SYNTHESIS IF EXCESS, OXIDATION FOR ENERGY

IF NOT METABOLIZED IN LIVER PERIPHERAL CIRCULATION FOR METABOLISM

SERINE FROM RENAL GLY METABOLISM ALANINE FROM INTESTINAL GLN METABOLISM

NO DEDICATED STORAGE FOR AMINO ACIDS

STARVATIONIN-CLASS STUDY QUESTIONS

DURING STARVATION, GLUCOSE IS SYNTHESIZED FROM PROTEOLYTIC DEGRADATION OF PROTEINS (MOSTLY MUSCLE).

EXPLAIN HOW THE REACTIONS OF THE GLUCOSE-ALANINE CYCLE OPERATE DURING STARVATION.

WHAT KIND OF MOLECULE CAN BE CONSIDERED AS A KIND OF STORAGE DEPOT FOR AMINO ACIDS?

HOW DOES IT DIFFER FROM OTHER FUEL-STORAGE MOLECULES?

GLUCONEOGENESIS

PHOSPHOENOLPYRUVATE

PYRUVATE

OXALOACETATE

ADP

ATP

PYRUVATE KINASE

ATP + CO2ADP + PiPYRUVATE CARBOXYLASE

GTP

CO2 + GDP

PEP CARBOXYKINASE

CITRICACID

CYCLE

ACETYL-CoA

CITRICACID

CYCLEACTIVATES

ACTIVATES

ALANINE FROM LIVER

STARVATION NORMAL DISTRIBUTION OF NUTRIENTS AFTER A

MEAL CARBOHYDRATES DEGRADED IN GUT PORTAL VEIN CIRCULATION TO LIVER DIETARY GLUCOSE

~1/3 CONVERTED TO GLYCOGEN IN LIVER ~1/3 CONVERTED TO GLYCOGEN IN MUSCLE REMAINDER OXIDIZED FOR IMMEDIATE ENERGY

GLUCOSE IN BLOOD INSULIN INSULIN STIMULATES:

GLUCOSE UPTAKE GLYCOGEN SYNTHESIS: BODY STORES ~ 24 HR SUPPLY OF

CARBOHYDRATE

STARVATION

NORMAL DISTRIBUTION OF NUTRIENTS AFTER A MEAL FATTY ACIDS

PACKAGED AS CHYLOMICRONS CIRCULATED FIRST IN LYMPH AND

BLOODSTREAM NOT DIRECTLY DELIVERED TO LIVER

UPTAKE BY ADIPOSE TISSUE TRIACYLGLYCEROLS

FAT METABOLISM REGULATION F.A. OXIDATION REGULATED BY BLOOD [FATTY

ACID] CONTROLLED BY TG HYDROLYSIS IN FAT CELLS MITOCHONDRIAL OXIDN’ ACETYL-CoA

KETONE BODIES + OXALOACETATE CITRATE

CITRIC ACID CYCLE TRANSPORTED TO CYTOSOL

TRICARBOXYLATE TRANSPORT SYSTEM CITRATE + CoA ACETYL-CoA + OXALOACETATE + ADP + Pi

ATP-CITRATE LYASE IS THE ENZYME F.A. SYNTHESIS TGS

ACETYL-CoA CARBOXYLASE IS 1st COMMITTED STEP

THE METABOLIC CONSEQUENCES OF STARVATION

WHEN [GLUCOSE] , GLUCAGON RELEASED GLYCOGEN BREAKDOWN IN LIVER

RELEASES GLUCOSE

PROMOTES GLUCONEOGENESIS FROM AMINO ACIDS, LACTATE

AT SAME TIME, INSULIN MOBILIZATION OF FATTY ACIDS FROM FAT INHIBITS GLUCOSE UPTAKE BY MUSCLE

MUSCLE USES FATTY ACIDS FOR FUEL LACTATE PRODUCTION

STARVATION EVENTUALLY LIVER GLYCOGEN DEPLETED

RELIANCE ON GLUCONEOGENESIS CANNOT SYNTHESIZE GLUCOSE FROM F.A.s

WHY NOT? SOURCE OF GLUCONEOGENIC INTERMEDIATES

AMINO ACIDS FROM MUSCLE BREAKDOWN GLYCEROL FROM TRIACYLGLYCEROL BREAKDOWN

AFTER A FEW DAYS OF STARVATION: KETONE BODIES SYNTHESIZED IN LIVER

FROM FATTY ACID OXIDATION ALTERNATE FUEL FOR BRAIN

STARVATION

FATTY ACID BREAKDOWN AFTER PROLONGED STARVATION SPARES MUSCLE BREAKDOWN

SURVIVAL TIME ULTIMATELY DEPENDS ON FAT STORES

NORMAL ADIPOSE STORE CAN SUSTAIN LIFE FOR ONLY ~ 3 MONTHS

STARVATION

STUDY QUESTION

EXPLAIN THE BIOCHEMICAL CHANGES SEEN AS THE BODY ADAPTS TO STARVATION.

LIST THE ORDER IN WHICH THE LIVER USES THE FOLLOWING SUBSTANCES TO PROVIDE THE BODY WITH METABOLIC FUEL DURING STAR-VATION: GLYCOGEN, FATTY ACIDS, MUSCLE PROTEIN, NON-MUSCLE PROTEIN

PROTEINS INVOLVED IN BODY WEIGHT REGULATION

LEPTIN INSULIN GHRELIN PYY3-36

NEUROPEPTIDE Y (NPY) AgRP (AGOUTI-RELATED PEPTIDE) PRO-OPIOMELANOCORTIN (POMC) -MELANOCYTE STIMULATING HORMONE (-MSH) COCAINE AND AMPHETAMINE-REGULATED

TRANSCRIPT (CART)

APPETITE CONTROL AT HYPOTHALAMIC LEVEL

HYPOTHALAMUS

ARCUATE NUCLEUS

NPY/AgRP

POMC/CART

LEPTIN AND INSULIN

+-PYY3-36

GHRELIN

+

-

INSULIN OR LEPTIN RECEPTOR

GHRELINRECEPTOR

Y2R(AN NPY RECEPTOR SUBTYPE)

DIRECT EFFECTS OF PROTEINS ON NEURONS IN ARCUATE NUCLEUS

OTHERNEURONS

-

MSHRECEPTOR

LEPTIN A MONOMERIC PROTEIN OF 146 RESIDUES DISCOVERED IN 1994 EXPRESSED ONLY BY FAT CELLS

REFLECTS QUANTITY OF BODY FAT FAT LEPTIN APPETITE SIGNAL TRANSDUCTION:

LEPTIN BINDS TO OB-R PROTEIN IN HYPOTHALAMUS

ALSO CONTROLS ENERGY EXPENDITURE ( METAB. RATE)

IN OBESITY, LEPTIN BUT LACK OF EXPECTED IN APPETITE “LEPTIN RESISTANCE” SATURATION EFFECT AT BLOOD-BRAIN BARRIER

LEPTIN ***LEPTIN HAS PERIPHERAL EFFECTS AS WELL AS

CNS EFFECT PERIPHERAL OB RECEPTORS STIMULATES FATTY ACID OXIDATION IN NON-

ADIPOSE TISSUE INHIBITS LIPID ACCUMULATION IN NON-ADIPOSE

TISSUE ACTIVATION OF AMPK INACTIVATION OF ACETYL-CoA

CARBOXYLASE (BY PHOSPHORYLATION) [MALONYL-CoA] INHIBITION OF CARNITINE PALMITOYL TRANSFERASE

I TRANSPORT OF FATTY ACYL-CoA INTO MITOCHONDRIA

DOES NOT PREVENT OBESITY, THOUGH

LEPTIN “THRIFTY GENE” HYPOTHESIS

SHORT-TERM FAT STORAGE IN ADIPOSE TISSUE PROTECTION FROM INTERMITTENT FAMINES

PREVENTION OF ACCUMULATION IN NON-ADIPOSE TISSUES DURING SHORT-TERM OBESITY PROTECTS AGAINST: CAD, INSULIN RESISTANCE, DIABETES

LEPTIN INJECTIONS APPETITE OBESITY IN INDIVIDUALS WITH LEPTIN DEFICIENCY RARE CONDITION G DELETED IN CODON 133 FRAMESHIFT MUTN’ INACTIVE

LEPTIN IN OVERFED RODENTS RESISTANT TO LEPTIN, IN-JECTION OF

LEPTIN INTO CNSBIOLOGICAL ACTIVITY

LEPTIN SUMMARY

WEIGHT-CONTROL IN NON-OBESE

CONCENTRATION WITHOUT EFFECT IN OBESE LEPTIN RESISTANCE

RESPONSIBLE FOR LONG-TERM WEIGHT PROBLEMS

LEPTIN E100(Zhang F, Basinski MB, et al. 1997. “Crystal structure of the obese protein leptin-E-100”. Nature 387(8):206-209.)

X-RAY STRUCTURE OF LEPTIN E100

(WILD-TYPE HUMAN LEPTIN IS DIFFICULT TO CRYSTALLIZE BECAUSE IT AGGREGATES EXTENSIVELY. SUBSTITUTION OF Glu FOR Trp AT POSITION 100 RESULTS IN THE PROTEIN LEPTIN-E100 WHICH CRYSTALLIZES READILY AND HAS COMPARABLE BIOLOGIC ACTIVITY TO THE WILD-TYPE. ON A STRUCTURAL BASIS, LEPTIN BELONGS TO THE LONG-CHAIN HELICAL CYTOKINE FAMILY, OF WHICH HUMAN GROWTH HORMONE IS ANOTHER MEMBER.)

SEE PDB 1AX8 A MONOMER, 146 RESIDUES, ONE DOMAIN IDENTIFY THE FOUR-HELIX BUNDLE ONE DISULFIDE BOND: IDENTIFY THE CYS RESIDUES INVOLVED IDENTIFY E100 IDENTIFY Tyr 61 WITHIN A HYDROPHOBIC POCKET

A BURIED Tyr ON THIS HELIX IS CONSERVED IN LONG-CHAIN HELICAL CYTOKINES

WHAT ATOM H-BONDS TO THE –OH GROUP OF Tyr61

PROTEINS: GHRELIN A PEPTIDE SECRETED BY GASTRIC MUCOSA ON AN

EMPTY STOMACH (FASTING GHRELIN LEVELS) 28 RESIDUES REQUIRES OCTANOYLATION OF SER3 FOR

ACTIVITY ALSO RELEASES GROWTH HORMONE GHRELIN DURING FASTING

APPETITE FOOD INTAKE FAT UTILIZATION

INJECTIONS OF GHRELIN DO THE SAME THINGS IN OBESITY, GHRELIN LEVELS ARE

GHRELIN ACTIVATES NPY/AgRP NEURONS IN ARCUATE

NUCLEUS IN HYPOTHALAMUS THESE ARE APPETITE-STIMULATING NEURONS

SHORT-TERM APPETITE CONTROL OVERPRODUCTION OBESITY

PRADER-WILLI SYNDROME HIGHEST LEVELS OF GHRELIN EVER MEASURED IN HUMANS

GHRELIN LEVELS IN MOST OBESE PEOPLE ARE LOWER THAN IN NON-OBESE

GHRELIN GHRELIN LEVELS WHEN WEIGHT IS LOST WHILE

DIETING OPPOSES EFFECTS OF DIETING

IN GASTRIC BYPASS SURGERY, GHRELIN LEVEL AND STAY THAT WAY NOT SURE WHY

GASTRIC BYPASS SURGERY

PROTEINS: PYY3-36

A PEPTIDE SECRETED BY GI TRACT IN PROPORTION TO CALORIC INTAKE

FOOD INTAKE

ACTIONS IN ARCUATE NUCLEUS INHIBITS NPY/AgRP NEURONS STIMULATE POMC/CART CELLS

POMC RELEASE POMC PROCESSING IN HYPOTHALAMUS RELEASE OF -MSH

-MSH INHIBIT FOOD INTAKE; ENERGY USE CART INHIBIT FOOD INTAKE; ENERGY USE

INSULIN AS A HORMONAL SIGNAL IN THE BRAIN

STIMULATES POMC/CART CELLS SATIETY INCREASES ENERGY EXPENDITURE

INHIBITS NPY/AgRP CELLS DECREASES APPETITE (SATIETY) INHIBITS ENERGY EXPENDITURE

APPETITE CONTROL AT HYPOTHALAMIC LEVEL: SUMMARY (1) APPETITE CONTROL CENTER IN HYPOTHALAMUS ARCUATE NUCLEUS

TWO CELL TYPES: (SECRETE NEUROPEPTIDES) NPY/AgRP (NEUROPEPTIDE Y/AGOUTI-RELATED

PEPTIDE) POMC/CART (PRO-OPIOMELANOCORTIN/COCAINE AND

AMPHETAMINE-REGULATED TRANSCRIPT) NPY AND AgRP:

STIMULATE APPETITE INHIBIT ENERGY EXPENDITURE

POMC CONVERTED TO -MSH CART AND -MSH:

INHIBIT FOOD INTAKE STIMULATE ENERGY EXPENDITURE

APPETITE CONTROL AT HYPOTHALAMIC LEVEL: SUMMARY (2) NEUROPEPTIDE SECRETION REGULATED BY:

LEPTIN GHRELIN INSULIN PYY3-36

APPETITE CONTROL AT HYPOTHALAMIC LEVEL: SUMMARY (3) LEPTIN AND INSULIN:

(1) STIMULATE POMC/CART NEURONS CART AND -MSH LEVELS(2) INHIBIT NPY/AgRP NEURONS NPY AND AgRP

NET EFFECTS: SATIETY AND APPETITE

GHRELIN STIMULATES NPY/AgRP NPY AND AgRP SECRETION APPETITE

PYY3-36 IS A HOMOLOGUE OF NPY BINDS TO AN INHIBITORY RECEPTOR ON NPY/AgRP

SECRETION OF NPY AND AgRP APPETITE

OBESITY

OBESITY A MAJOR PUBLIC HEALTH PROBLEM

30% OF U.S. ADULTS ARE OBESE (NHANES 1999-2000) THIS HAS DOUBLED OVER THE PAST 20 YEARS!

ANOTHER 35 % ARE OVERWEIGHT (NHANES) 15 % OF CHILDREN AND ADOLESCENTS ARE OVERWEIGHT

WENT FROM 11 % - 15 % OVER PAST 20 YEARS 300,000 PEOPLE DIE EACH YEAR FROM OBESITY-RELATED

DISEASES WORLDWIDE > 1 BILLION OVERWEIGHT WORLDWIDE > 300 MILLION OBESE PROJECTING TO 2008: OBESITY RATE OF 38%

OBESITY OBESITY ACCOUNTS FOR 5.5 % - 7.8 % OF ALL

HEALTH CARE EXPENDITURES HEALTH RISKS OF OBESITY

TYPE II DIABETES ( 10X INCREASE IN PAST 20 YEARS) HEART ATTACK STROKE SOME CANCERS

BREAST, COLON DEPRESSION

OBESITY DEFINITIONS

OVERWEIGHT: BMI > 25 KG / M2

OBESITY: BMI > 30 KG / M2

CALCULATE YOUR OWN BMI AND WRITE THE VALUE ON A SHEET OF PAPER. WE’LL COLLECT THESE AND DETERMINE THE CLASS DISTRIBUTION OF BMIs

http://nhlbisupport.com/bmi/

OBESITY MAJOR FACTORS DRIVING THE OBESITY EPIDEMIC:

THE PHYSICAL ENVIRONMENT! OVERCONSUMPTION

EASY AVAILABILITY OF FOODS ENERGY-DENSE LARGE PORTIONS

DECREASING FREQUENCY OF FAMILY MEALS FAST FOOD RESTAURANTS

ADVERTISING TO CHILDREN REDUCED PHYSICAL ACTIVITY

IN JOBS REQUIRING PHYSICAL ACTIVITY GENERAL CONVENIENCES ENERGY EXPENDITURES SEDENTARY ACTIVITIES

TV, VIDEO GAMES, WWW

OBESITY FACTORS DRIVING INCREASE IN OBESITY:

THE SOCIAL ENVIRONMENT TECHNOLOGY PRODUCTIVITY

FASTER PACE OF LIFE INCREASED STRESS NOT ENOUGH TIME WALLMARTS : GETTING MORE FOR LESS

CHANGING FAMILY STRUCTURE INCREASE IN BOTH PARENTS WORKING INCREASE IN SINGLE-PARENT FAMILIES

SOCIAL ENVIRONMENT PHYS. ENVT. RECIPROCITY

OBESITY BIOLOGICAL FACTORS INVOLVED IN OBESITY

INDIVIDUAL DIFFERENCES IN HEIGHT, WEIGHT

GENETIC (GIVEN ADEQUATE ACCESS TO FOOD) WEIGHT (BMI), HEIGHT ARE DISTRIBUTED AROUND A

MEAN VALUE IN THE POPULATION HEREITABILITY OF OBESITY = THAT OF HEIGHT AND

WEIGHT

DEFINITION OF OBESITY: A FIXED “THRESEHOLD” VALUE SHIFTING THE POPULATION CURVE TO THE RIGHT

LARGE INCREASE IN AREA UNDER THE CURVE BEYOND THRESHOLD

OBESITY BIOLOGICAL FACTORS INVOLVED IN OBESITY

GENETIC DIFFERENCES IN DRIVE TO EAT 5% - 6% OF SEVERLY OBESE CHILDREN HAVE

SINGLE GENE MUTATIONS 10 % OF MORBIDLY OBESE CHILDREN

WITHOUT DOCUMENTED GENE DEFECTS COME FROM HIGHLY INBRED FAMILIES

“THRIFTY GENE HYPOTHESIS”

DRIVE TO EAT IS “HARDWIRED”; DRIVE TO NOT EAT IS WEAKER AND CAN BE OVERRIDDEN

OBESITY THE THERMODYNAMICS OF OBESITY

THE “FIRST LAW” : LAW OF CONSERVATION OF ENERGY ENERGY STORED = ENERGY INTAKE – ENERGY EXPENDED THERE IS NO WAY AROUND THIS! EXCESS ENERGY STORED PRIMARILY AS TRIGLYCERIDES IN

FAT CELLS “POSITIVE ENERGY BALANCE”

CENTRAL REGULATORY MECHANISMS A “LIPOSTAT” (IN HYPOTHALAMUS)

BODY MAINTAINS FAT RESERVES AT WHATEVER THEY ARE WITHIN ~ 1% OVER YEARS

PEOPLE TEND TO “DEFEND” HIGHEST ATTAINED WEIGHT

OBESITY A VARIATION ON THE “SECOND LAW”

YOU CANNOT GET MORE FOR LESS

IMPROVEMENTS IN QUALITY OF LIFE IN ONE AREA WILL OFTEN HAVE UNINTENDED AND UNEXPECTED NEGATIVE CONSEQUENCES IN OTHER AREAS.

WILL YOUR GENERATION AND THOSE SUCCEEDING IT HAVE A LESSER LIFE EXPECTANCY THAN MINE?

OBESITY SOME “BOTTOM LINE” COMMENTS

DESPITE THE GENETICS, THE OBESITY EPIDEMIC IS A CONSEQUENCE OF THE FIRST LAW OF THERMODYNAMICS

EVOLUTION HAS BEEN DIRECTED ALONG THE LINES OF ENERGY STORAGE LONG-TERM MAINTENANCE OF WEIGHT LOSS IS DIFFICULT

DIETING MAY BRING SHORT-TERM WEIGHT REDUCTIONS BUT NOT LONG-TERM ONES

PREVENTION IS THE BEST APPROACH INDIVIDUAL EFFORTS POPULATION EFFORTS

GENETIC OR ENVIRONMENTAL?

BIOCHEMISTRY OF OBESITY

PROTEIN AND GLYCOGEN LEVELS ARE REGULATED NARROWLY

FAT STORES ARE NOT, SO: EXCESS FAT INTAKE COMPARED TO FAT OXIDN’ WITH EXCESS FAT INTAKE, CHO-DERIVED

ACETYL-CoA IS NOT A SIGNIFICANT SOURCE OF F.A.s

ADIPOSE TISSUE MASS INCREASE IN # OF FAT CELLS INCREASE IN SIZE OF FAT CELLS

BIOCHEMISTRY OF OBESITY STEADY STATE EVENTUALLY REACHED

FAT STORAGE = FAT MOBILIZATION % BODY FAT DIETARY FAT INTAKE LEPTIN RESISTANCE DEVELOPS

HYPOTHALAMIC SET-POINT IS RAISED APPETITE NOT SUPPRESSED ENERGY METABOLISM (IN NON-ADIPOSE TISSUE)

HIGH CONCENTRATIONS OF F.F.A.s INSULIN RESISTANCE DECREASES FUSION OF GLUT4-CONTAINING VESICLES

WITH PLASMA MEMBRANE (MORE ABOUT THIS LATER) GLUCOSE ENTERS CELL

BIOCHEMISTRY OF OBESITY PANCREAS MUST INSULIN PRODUCTION

CAUSES APPETITE (“HYPERPHAGIA”)

INSULIN PRODUCTION AND STORAGE OF F.A.s IN ADIPOSE TISSUE

DIETING AMERICAN HEART ASSOCIATION RECOMMENDS:

PROTEIN: 10% – 15% CARBOHYDRATES: 55% – 60% FAT: 25% - 30%

IN-CLASS EXERCISE: PREDICT THE BIOCHEMICAL RESPONSE TO HAVING A DIET CONSISTING OF NO FAT, 70% CARBOHYDRATES AND 30% PROTEIN.

IN-CLASS EXERCISE: DO THE SAME FOR A DIET WITH 0% CARBOHYDRATES, 70% FAT AND 30% PROTEIN.

BIOCHEMISTRY OF THE ATKINS DIET IT’S A HIGH FAT, HIGH PROTEIN, LOW CARBOHYDRATE DIET

PROTEIN IS USED FOR: TISSUE BUILDING AND REPAIR CONVERSION TO GLUCOSE FOR ENERGY

LOW CARBOHYDRATE INTAKE: PROTEIN-DERIVED GLUCOSE CANNOT SUSTAIN ENERGY NEEDS FAT MUST BE BURNED LESS INSULIN PRODUCED BECAUSE LESS GLUCOSE ABSORBED

FATS HIGH SATIETY FACTOR INGESTED FAT IS NOT STORED (LOW INSULIN)

EXCESS FAT IS CATABOLIZED AND EXCRETED

ATKINS DIET: STUDY QUESTIONS *** EXPLAIN WHAT HAPPENS TO THE ACTIVITY OF THE

CITRIC ACID CYCLE WHEN SOMEONE IS ON THE ATKINS DIET.

WHAT EFFECT DOES THIS HAVE ON FAT METABOLISM?

BIOCHEMISTRY OF ATKINS DIET DISADVANTAGES:

HIGH SATURATED FAT DIET INCREASES RISK OF HEART DISEASE

A DIET LOW IN FRUITS FRUITS ARE PROTECTIVE IN CANCER

BLADDER, GI TRACT, PROSTATE

KETOGENESIS IS NEEDED TO PRODUCE ENERGY PERPETUAL STATE OF KETOSIS SIMILAR TO LONG-TERM STARVATION

SYMPTOMS OF KETOSIS: ABDOMINAL: PAIN, NAUSEA, VOMITING (DEHYDRATION), LIVER

FUNCTION ABNORMALITIES NEUROLOGIC: FATIGUE, HEADACHE METABOLIC: K+ LOSS, Ca++ LOSS, RTA HEMATOLOGIC: HEMOLYTIC ANEMIA CARDIAC: CARDIOMYOPATHY (POSSIBLY REVERSIBLE)

BIOCHEMISTRY OF THE ATKINS DIET ACID-BASE EFFECTS:

KETONE BODIES BLOOD pH A LOW pH GFR RENAL TUBULAR REABSORPTION OF Ca++

CALCIUM IN URINE Ca++ SALTS MOBILIZED FROM BONE

PO42- NEEDED TO BUFFER ACID LOAD TO KIDNEY

OSTEOPOROSIS

CALCIURIA STONE FORMATION

BIOCHEMISTRY OF ATKINS DIET ADVANTAGES

IT WORKS IN THE SHORT RUN TG AND HDL CHOLESTEROL LEVELS IMPROVED

RISK/BENEFIT ANALYSIS: PROBABLY NOT FAVORABLE

WEIGHT LOSS NOT SUSTAINED (UNLESS YOU STAY ON THE DIET)

IT’S UNHEALTHY CAN RESULT IN SIGNIFICANT MORBIDITY CAN RESULT IN PREMATURE DEATH

BIOCHEMISTRY OF THE ATKINS DIET DESPITE ALL OF THE FANCY BIOCHEMISTRY, THE

BOTTOM LINE IS THAT INCREASED FAT IN THE DIET CAUSES EARLY AND SUSTAINED SATIETY, WHICH ULTIMATELY RESULTS IN LESS DAILY INTAKE OF CALORIES. IT’S STILL A CONSEQUENCE OF THE “FIRST LAW OF THERMODYNAMICS” (ENERGY IN – ENERGY OUT).

THERE ARE NO SAFE FAD DIETS THAT BOTH WORK AND ARE HEALTHY AT THE SAME TIME.

YOU WILL ALWAYS GAIN THE WEIGHT BACK AFTER YOU STOP THE DIET.

A CLINICAL CASE STUDY A 20 YEAR OLD, 5’ 4”, 180# FEMALE COLLEGE STUDENT WHO

HAS BEEN OVERWEIGHT SINCE THE AGE OF 3 YEARS VISITS THE INFIRMARY BECAUSE SHE HASN’T BEEN FEELING WELL LATELY. SHE HAS BEEN HAVING HEADACHES AND CONSTIPATION FOR A FEW MONTHS AND SOMETIMES SHE DOESN’T THINK AS CLEARLY AS SHE USED TO. HER PERIODS HAVE BECOME IRREGULAR AND NOW SHE HAS ABDOMINAL PAIN, BACK PAIN AND RED URINE. HER FRIENDS HAVE TOLD HER THAT HER BREATH SMELLS “FUNNY”.

IN TAKING A HISTORY, YOU LEARN THAT SHE HAS BEEN EXPERIMENTING WITH THE ATKINS DIET FOR THE PAST 5 OR 6 MONTHS AND HAS LOST OVER 40 POUNDS.

CLINICAL CASE STUDY: CONTINUED HER PHYSICAL EXAM IS GENERALLY NORMAL

EXCEPT FOR SOME ABDOMINAL TENDERNESS AND A SWEET SMELL TO HER BREATH.

LABORATORY STUDIES SHOWED A LOW INSULIN LEVEL, A BLOOD GLUCOSE OF 60 mg/dL (LOW), AND AN ABNORMALLY LOW BLOOD pH. A URINALYSIS SHOWED RED BLOOD CELLS, A LOW pH, AND A MARKEDLY ELEVATED CALCIUM/CREATININE RATIO. HER CHOLESTEROL LEVEL IS 190 mg/dL.

AN ABDOMINAL X-RAY (“KUB”) SHOWED SOME KIDNEY STONES

CLINICAL CASE STUDY: CONTINUED QUESTIONS:

WHY DOES HER BREATH SMELL SWEET? WHY IS SHE HAVING TROUBLE THINKING? WHY ARE HER INSULIN LEVELS LOW? WHY IS HER BLOOD pH LOW? WHY IS HER URINARY CALCIUM EXCRETION INCREASED? WHY IS HER URINARY pH DECREASED? WHY HASN’T THE CHOLESTEROL LEVEL CHANGED MUCH,

DESPITE THE FACT THAT SHE’S EATING MORE FAT?

DRUGS AND DIET XENICAL

INTESTINAL LIPASE INHIBITORS MERIDIA (SIBUTRAMINE)

AMPHETAMINE-LIKE NE AND SEROTONIN RE-UPTAKE INHIBITION

PHENTERMINE (PART OF “REDUX”)

FUTURE ANTI-OBESITY DRUGS RIMBONABANT

INHIBITS CANNABINOID RECEPTORS CNTF (CILIARY NEUROTROPHIC

FACTOR) (“AXOKINE”) CNTF AND LEPTIN RECEPTORS VERY

MUCH ALIKE CNTF DOESN’T GENERATE RESISTANCE

MELANOCORTINS AND RECEPTORS -MSH

BIOCHEMISTRY OF DIABETES TYPE I

INSULIN ABSENT OR ALMOST ABSENT AUTOIMMUNE GENETIC PREDISPOSITION

CLASS II MHC PROTEINS MOSTLY IN CHILDREN

TYPE II INSULIN RESISTANCE

OBESE GENETIC PREDISPOSITION

USUALLY IN > 40 YEAR OLDS NOW SEEN MORE FREQUENTLY IN OBESE YOUTH

BIOCHEMISTRY OF DIABETES BLOOD GLUCOSE LEVELS RISE

“HYPERGLYCEMIA” OSMOTIC EFFECT DEHYDRATION POLYDYPSIA

GYCOSURIA OSMOTIC LOSS OF WATER

POLYURIA GLUCOSE ENTRY INTO CELLS IMPAIRED ALTERNATE FUEL NEEDED HYDROLYSIS OF TRIACYLGLYCEROLS

INCREASED FATTY ACID OXIDATION KETONE BODIES

KETOACIDOSIS GLUCONEOGENESIS

BIOCHEMISTRY OF DIABETES KETOACIDOSIS

A STRESS ON BUFFER CAPACITY OF BLOOD KIDNEYS

EXCRETION OF EXCESS H+ INTO URINE ACCOMPANIED BY EXCRETION OF

NH4+

Na+

K+ INORGANIC PHOSPHATE WATER

DEHYDRATION AND BLOOD VOLUME SHOCK

BIOCHEMISTRY OF DIABETES

[K+] IN BLOOD IS MAINTAINED BY LOSS OF K+ FROM CELLS “WHEN pH IS LOW, K+ MUST GO” TOTAL BODY K+ DEPELETION

INAPPROPRIATE REHYDRATION AND INSULIN ADMINISTRATION WITHOUT SUPPLEMENTING K+ CAN CARDIAC ARYTHMIAS AND DEATH

GLUCOSE TRANSPORT PROTEIN: GLUT4 LOCATED IN MEMBRANES OF

INTRACELLULAR VESICLES TRANSLOCATED TO AND FUSED TO CELL MEMBRANE

TRIGGERED BY INSULIN BINDING TO INSULIN RECEPTORS “EXOCYTOSIS”

RATE OF GLUCOSE ENTRY INTO CELL A PASSIVE TRANSPORT Vmax BECAUSE OF INCREASED # OF GLUT4s

MOSTLY IN MUSCLE AND FAT CELLS WHEN INSULIN LEVELS TRANSPORTERS RELOCATE

INTO CELL “ENDOCYTOSIS”

DEFECTS IN GLUT4 INSULIN RESISTANCE

GLUCOSE TRANSPORT PROTEINS

OTHER GLUCOSE TRANSPORTERS

GLUT1 : ERYTHROCYTES GLUT2 : PANCREATIC β-CELLS AND LIVER

CELLS GLUT3 : BRAIN, PLACENTA, FETAL

MUSCLE

INSULIN ACTIONS AS A NEURAL SIGNAL

INSULIN RECEPTORS IN HYPOTHALAMUS NEURONAL REGULATION OF

FOOD INTAKE (INCREASES APPETITE) BODY WEIGHT

ACTIONS MEDIATED BY INSULIN SIGNALING SYSTEM SIGNAL TRANSDUCTION REQUIRES BINDING OF INSULIN TO INSULIN

RECEPTORS

INSULIN PROINSULIN INSULIN + C-PEPTIDE

SITE SPECIFIC CLEAVAGE AT THE SEQUENCES: ARG-ARG LYS-ARG BOTH ARE COMMON SIGNALS FOR PROTEOLYTIC PROCESSING

2 INSULIN MONOMERS DIMERIZE ANTIPARALLEL -SHEET ASSOCIATION C-TERMINAL OF B-CHAIN

3 INSULIN DIMERS HEXAMER ASSOCIATION REQUIRES Zn2+

Zn2+ RELEASED WHEN INSULIN SECRETED HEXAMERS ARE STORED IN CELLS OF PANCREAS RECOMBINANT SYNTHESIS OF INSULIN ANALOGS

“LISPRO” INSULIN: USUAL INSULIN OF CHOICE IN DIABETICS PRO28 AND LYS29 ON B-CHAIN ARE SWITCHED

INSULIN MONOMERS DO NOT DIMERIZE FASTER ONSET OF BIOLOGICAL ACTIVITY (15 MINUTES AFTER SC ADMIN.)

C-PEPTIDE: NO BIOLOGIC FUNCTION

PROTEINS: INSULIN IN PERIPHERAL TISSUES INSULIN HAS 2 CHAINS LINKED BY 2 DISULFIDE BRIDGES

THE “A” CHAIN: 21 AMINO ACIDS THE “B” CHAIN: 30 AMINO ACIDS

GENE PRODUCT IS “PREPROINSULIN” GENE IS ON SHORT ARM OF CHROMOSOME #11 AFTER TRANSLOCATION TO THE E.R. 23 N-TERMINAL

AMINO ACIDS ARE REMOVED “PROINSULIN” PROINSULIN: CHAINS “A” AND “B” , 3 –S-S- BONDS, AND

“C” PEPTIDE SINGLE CHAIN OF 86 AMINO ACIDS

PROINSULIN PACKAGED IN SECRETORY GRANULES

THE INSULIN RECEPTOR

A RECEPTOR TYROSINE KINASE A TRANSMEMBRANE GLYCOPROTEIN HAS A CYTOPLASMIC PTK DOMAIN A PERMANENT DIMER (2 AND 2

SUBUNITS) 2 s ARE LINKED BY DISULFIDE BOND EACH LINKED TO A BY –S-S- BOND

THE INSULIN RECEPTOR WHEN INSULIN BINDS TO InsR,

CONFORMATIONAL CHANGE OCCURS PTK DOMAINS FACE EACH OTHER CROSS PHOSPHORLYATION

3 SPECIFIC TYR RESIDUES ARE PHOSPHORYLATED “AUTOPHOSPHORYLATION”

ACTIVATED TYRs CAN FURTHER PHOSPHORYLATE AT: OTHER TYRs OUTSIDE OF PTK DOMAIN CYTOPLASMIC PROTEIN

SIMILAR RTKs FOR OTHER PROTEIN GROWTH

FACTORS EGF, PDGF, FGF

THE INSULIN RECEPTOR THE Y-KINASE ACTIVITY OF THE RTK DEPENDS ON:

DEGREE OF PHOSPHORYLATION AT THE 3 Y-SIDE CHAINS FULL ACTIVITY WHEN Y1163 IS PHOSPHORYLATED SIDE CHAINS OF SER AND THR NOT LONG ENOUGH TO

REACH ACTIVE SITE MAIN TARGETS OF INSULIN-RTKs

“INSULIN RECEPTOR SUBSTRATES” 1 AND 2 WHEN PHSOPHORYLATED, INTERACTIONS WITH

PROTEINS THAT HAVE Src HOMOLOGY 2 DOMAINS THESE BIND phospho-Tyr WITH HIGH AFFINITY Phospho-Ser and phospho-Thr NOT BOUND WELL

SH2 DOMAINS

PDB EXERCISES EXPLORE THE XRAY STRUCTURE OF

THE PTK DOMAIN OF InsR: PDB ID 1IRK (UNPHOSPHORYLATED) PDB ID 1IR3 (PHOSPHORYLATED)

INSULIN

S-S S-S

P

P

P

S-S

S-S

IRS-1P

PTK DOMAIN HAS Y-KINASE ACTIVITY

AUTOPHOSPHORYLATION OF PTK DOMAINS OF InsR

ACTIVATION LOOP

Y

Y

Y

Y1158

MEMBRANE

TRANSMEMBRANE PART OF -SUBUNITS

Y1162

Y1163

INSULIN RECEPTOR SUBSTRATE-1

INSULIN SIGNALING SYSTEM (1) INSULIN BINDS TO THE INSULIN RECEPTOR

AUTOPHOSPHORYLATION AT TYR RESIDUES -SUBUNITS OF IR

PROTEINS BOUND AND TYR-PHOSPHORYLATED BY THESE phosTYRs Shc

phosShc STIMULATES MAPK Gab-1

phosGab-1 ACTIVATES MAPK ALSO APS/Cbl Complex

phosAPS/Cbl STIMULATES TC10 (A G-PROTEIN) ALSO REGULATES GLUCOSE TRANSPORT INDEPENDENT OF PI3K

INVOLVES LIPID RAFTS AND CAVEOLAE IRS Proteins

phosIRS ACTIVATES PHOSPHOINOSITIDE CASCADE PI3K INTERMEDIATE STIMULATES: GLYCOGEN SYNTHESIS, GLUCOSE TRANSPORT, CELL GROWTH AND DIFFERENTIATION

INSULIN SIGNALING SYSTEM (2) OTHER CASCADES ACTIVATED:

MAPK (PHOSPHORYLATION) PI3K (PHOSPHORYLATION)

MAPK CASCADE REGULATES GENE EXPRESSION

CELLULAR GROWTH DIFFERENTIATION Myc, Fos, Jun PROTEINS (TRANSCRIPTION FACTORS)

PI3K CASCADE CHANGES PHOSPHORYLATION STATES OF SOME ENZYMES

STIMULATES GLYCOGEN SYNTHESIS CONTROL OF VESICLE TRAFFICKING

GLUT4 GLUCOSE TRANSPORTER TRANSLOCATED TO CELL SURFACE RATE OF GLUCOSE TRANSPORT INTO CELL

INSULIN SIGNALING: SHORT SLIDE PROTEINS THAT BIND TO pY RESIDUES OF IR

Shc Gab-1 Aps/Cbl Complex IRS Proteins

PHOSPHORYLATION CASCADES ACTIVATED MAPK: PHOSPHORYLATES NUCLEAR TRANSCRIPTION FACTORS (Myc,Fos,Jun) GENE EXPRESSION PI3K:

STIMULATES GLYCOGEN SYNTHESIS GLUCOSE TRANSPORT INTO CELL BY STIMULATING

TRANSLOCATION OF GLUT4 TRANSPORTERS

WHAT IS THE LINK BETWEEN OBESITY AND TYPE II DIABETES? WHAT CAUSES INSULIN RESISTANCE? ONE PROPOSAL BY GERALD SHULMAN (2005)

FFAs DIFFUSE INTO MUSCLE CELLS PRODUCTION OF FATTY ACYL-CoA ACTIVATION OF PROTEIN KINASE C (PKC) TRIGGERING OF A SER/THR KINASE CASCADE PHOSPHORYLATION OF IRS-1

INCREASES SER/THR PHOSPHORYLATION DECREASES TYR PHOSPHORYLATION BY INSULIN SIGNAL

DECREASE IN TYR PHOS. ACTIVATION OF PI3K RATE OF FUSION OF GLUT4-VESICLES GLUCOSE ENTERING CELL

(FATTY ACIDS CAUSE INSULIN RESISTANCE BY DIRECTLY INHIBITING INSULIN-STIMULATED GLUCOSE TRANSPORT ACTIVITY)

From: Lowell BB, Shulman GI. 2005. “Mitochondrial Dysfunction and Type 2 diabetes”. Science. 307: 384-387.

STUDY QUESTION

• EXPLAIN HOW INCREASED FREE FATTY ACIDS CAUSES INSULIN RESISTANCE.