Week 4A: Integration Metabolism, Role of Organs, Feast/Famine, Diabetes Mellitus & Alcohol Flashcards
HC23-26
Kinetics curve of multidomain enzymes with regulatory and catalytic domains
Sigmoidal curve
> sum curve R-state and T-state.
> do not obey Michaelis Menten kinetics
Multidomain, regulated enzymes are usually the ..
catalysers of the committed step in a pathway.
is HMG-reductase a monomer?
No, a highly regulated dimer: committed step in cholesterol biosynthesis
Which enzyme is targeted by statins?
HMG-CoA reductase
> also upregulates LDLR: higher dose used in homozygous FH than heterozygous FH (familial hypercholesterolemia)
Phosphorylation regulation in glycogen metabolism
Glycogen phosphorylase (GP): breakdown and glycogen synthase (GS): synthesis.
> a-forms, normally in active R-state
> allosteric metabolites can overrule phosphorylation status
> phosphorylation of GP and GS via PKA for example
> activates GP, inactivates GS
Phosphorylation regulation in fatty acid metabolism (acetyl-CoA carboxylase in synthesis)
Active carboxylase when dephosphorylated by PP2A.
Inactive carboxylase when phosphorylated by AMPK (AMP-activated protein kinase)
Difference AMPK and adenylate kinase
AMPK uses AMP and ATP to phosphorylate a protein
> result, AMP still bound, ATP to ADP for phosphorylation.
Adenylate kinase: ADP + ADP <=> ATP + AMP for extra energy
Why is the regulation of acetyl-CoA carboxylase logic?
When high AMP, low energy, no FA synthesis wanted.
AMPK phosphorylates and inactivates ACC
Metabolite regulation of liver and muscle glycogen phosphorylase
Liver: glucose can allosterically bind and inactivate the GP-a for change to T-state (even when phosphorylated in a form)
Muscle: binding AMP to get in R state as GP-b
Binding ATP or G-6-P causes change to T-state. (enough energy, no breakdown glycogen needed)
> not necessarily in a or b form, but it shows the overruling of phosphorylation state
Why isn’t liver GP inactivated by AMP?
The liver is the glucose homeostasis regulator and can convert G-6-P to glucose with G6Pase and needs to consider other tissues needs, not only its own
Metabolites may overrule phosphorylation regulation of enzymes: Acetyl-CoA carboxylase
Phosphorylated ACC is inactive. But if it binds citrate (shows that there is enough energy, TCA cycle stopped), than partly active ACC. (FA synthesis committed step)
Which enzymes is regulated as regulatory filaments?
Acetyl-CoA carboxylase forms regulatory filaments
> Palmitoyl-CoA (intermediate FA oxidation/breakdown) causes filaments to disassemble (product inhibition) to inactive dimers > induces conformational changes as a regulator
Name catabolic pathways and anabolic pathways (interconnected)
Catabolic:
- oxidation
- oxidative decarboxylation
- oxidative deamination
Anabolic
- Reductive biosynthesis
- Carboxylation
- Synthesis
Control of metabolic fluxes
-Based on energy states: fed, fasted, starvation
-Irreversible steps set the pace
Manipulation of metabolic fluxes
-Changing enzyme activities at irreversible steps with the high flux control (short term)
-Changing multiple activities at the same time: controlled gene expression (long term)
An irreversible step is a reaction with a large .. value
Keq
= [C][D]/[A][B]
in A + B <=> C + D
And large negative dG0
> change flux by changing enzyme activity or amount of enzyme
Reversible step has a … dG0 and flux can be changed by …
small, flux changed by changing concentrations of reactants
ATP yield of 1 glucose
Glycolysis: 2 ATP and 2 NADH (22.5=5)= 7 ATP
-Pyruvate oxidation: 2 NADH = 5 ATP
-TCA cycle: 2 acetyl CoA yields 2 times 3 NADH + 1 FADH2 + 1 GTP so 2 (7.5 ATP [3+2.5] + 1.5 [FADH2] + 1 [GTP] = 20 ATP
> total 30-32 ATP
1 glucose yields 30-32 ATP, dependent on
Shuttle which is used (redox) across mitochondria for NADH of glycolysis
- Glycerol-3-phosphate
- Malate-aspartate
Glycerol-3-phosphate shuttle
shuttle in muscle: DHAP in cytosol converted to glycerol-3-P by cytoplasmic glycerol-3-P dehydrogenase (GAPDH, using NADH) in intermembrane space and glycerol-3-P and this is converted by mitochondrial GAPDH to DHAP (yielding FADH2).
> 2 cytosolic NADH and yields 2 mitochondrial FADH2: 1.5 ATP per FADH2: 3 ATP. 30 ATP total
> turbo glycolysis
Malate-acetate shuttle
shuttle in liver, brain and heart muscle: 32 ATP yield. NADH reduces oxaloacetate in cytosol to malate and transport to matrix and in matrix conversion malate to oxaloacetate and through a-ketoglutarate and aspartate (converted from glutamate, coupled to oxaloacetate> a-ketoglutarate) back to cytosol. In cytosol conversion a-ketoglutarate to oxaloacetate (oxidize NADH) and aspartate to glutamate (tranport to matrix)
> 2 cytosolic NADH to 2 NADH in matrix: 2.5 ATP per, total 5, total 32 ATP
What happens to the FADH2 from glycerol-3-phosphate shuttle
Flavoprotein which donates electrons to coenzyme Q in ubiquinone (Q) form (reduced to ubiquinol QH2).
What happens to beta-oxidation created FADH2?
Electron-transfer protein (ETF) with the FADH2 prosthetic group.
> gives to Q
malate-aspartate shuttle is slower than glycerol-3-phosphate shuttle?
More enzymes involved.
Where does the decarboxylation of pyruvate to acetyl-CoA by PDH take place?
Mitochondrial matrix
Succinate dehydrogenase (TCA cycle enzyme) is part of the …. complex (complex II)
Succinate-Q reductase
Three sources of FADH2 which give electrons to coenzyme Q (ubiquinone (Q))?
-Succinate-Q reductase (complex II, with succinate dehydrogenase)
-Electron-transfer flavoprotein (ETF, beta-oxidation > from acyl-CoA dehydrogenase)
-Glycerol-3-phosphate shuttle.
What happens to glycerol (C3) in the liver in the fasted state?
Precursor for gluconeogenesis via
-Glycerol > glycerol-3-P
Glycerol-3-P > Triose-P (yields NADH > 2 per glucose)
Extra yield lactate as substrate gluconeogenesis
Lactate (C3) requires extra NADH oxidation > yields 2 extra NADH per glucose made
How is the NADPH required for FA synthesis made?
Pentose Phosphate Pathway
Committed step enzymes for glycogen and glucose metabolism
Glycogenolysis: Glycogen phosphorylase (GP)
Glycolysis: Phosphofructokinase (PFK-1)
Glycolysis > TCA cycle: Pyruvate dehydrogenase
PPP: Glucose-6-P dehydrogenase
Gluconeogenesis: Pyruvate carboxylase (PC)
Committed step enzymes FA metabolism, Cholesterol biosynthesis, ketogenesis and urea cycle
FA breakdown: Carnitine Palmitoyl transferase I (CPT-I)
FA synthesis: Acetyl-CoA Carboxylase (ACC)
Cholesterol biosynthesis: HMG-CoA reductase
Ketogenesis: HMG-CoA synthetase
Urea cycle: Carbamoyl-phosphate synthetase
Which intermediate is formed when condensing citrulline and aspartate to argininosuccinate in urea cycle?
Citrulline-AMP (adenylated)
Structure urea: central carbon, two amino groups and oxygen atom. Where are the origins?
Amino group 1: Deamination
Amino group 2: aspartate
Carbon: Hydrogen carbonate (HCO3-, from hydration of CO2)
Oxygen: from water H2O in last step: Arginine + H2O > Ornithine + Urea
How are the TCA cycle and respiratory chain coupled? What is respiratory control
NADH activated carrier
> more oxygen required when more ATP needed in exercise: respiratory control
> halt both when enough ATP
How is ATP synthesis coupled to respiratory chain?
Proton gradient
> Halt when enough ATP: proton pumps stop, NADH concentration high and NAD+ low, TCA cycle stops (accumulation of acetyl-CoA and citrate as regulators ….)
How is urea cycle linked to gluconeogenesis?
Nitrogen metabolism of fumarate and aspartate
Argininosuccinate to arginine releases fumarate which is converted to oxaloacetate via malate.
> oxaloacetate to gluconeogenesis
> oxaloacetate to aspartate by deaminating an alpha-amino acid
> use aspartate in urea cycle
Pasteur effect glycolytic ATP vs mitochondrial ATP
Inhibition glycolysis by respiration
> preference for mitochondrial oxidation of pyruvate.
> in mitochondrial malfunction: glycolysis and lactate formation highly stimulated
Lactate dehydrogenase reaction
Lactate donates Hydride ion and hydrogen ion (H+) from the C2 carbon (count from carboxyl end) to NAD+ to form NADH, H+ and pyruvate.
> First: Removal H+
> NAD+ can take up hydride ion (H-: H+ + 2 e-)
Which amino acid side chain can take up H+?
Histidine
> in lactate dehydrogenase, lactates H+ transferred to active site His-195 and hydride ion to NAD+
Warburg effect
Using glycolysis when oxygen is available
> in tumor cells
> PDH strongly inhibited
> upregulation glycolysis
> downregulation mitochondrial respiration (increased membrane potential)
Important role for this factor in Warburg effect
Hypoxia-inducible factor 1-alpha (HIF-1alpha)
Altered gene expression in tumor cells for Warburg effect
Hypoxia
> activation HIF-1 transcription factor
> metabolic adaption: block PDH, increase glycolytic enzymes, and blood vessel growth stimulated
> without O2 as electron acceptor: respiratory chain is unable to generate proton motive force
Paradox of the Warburg effect in cancer cells
Lactate production with or without oxygen
> little but use of mitochondria
> anaerobic glycolysis rules
Which enzyme inhibits PDH and therefore oxidative phosphorylation
Pyruvate dehydrogenase kinase (PDK) phosphorylates and inhibits PDH
Drug to target Warburg effect
Dichloroacetate (DCA) activates PDH flux
> normalize mitochondrial protein motive force and inhibits tumor growth
> slows down tumor growth
> PDK inhibited
Fates pyruvate in liver
-To oxaloacetate by pyruvate carboxylase (gluconeogenesis, fasting)
-To acetyl-CoA by PDH (fed state)
> metabolic regulator of the fate: acetyl-CoA (accumulated when TCA cycle halted and high energy), activates PC and inactivates PDH.
Reciprocal regulation glycolysis/gluconeogenesis
F-2,6-BP
> Activates PFK-1, inactivates F-1,6-BPase
ATP/ADP
> ATP inactivates PFK-1 and PK
> ADP inactivates PC and PEP carboxylase
> AMP inactivates F-1,6-BPase
Citrate
> inactivates PFK-1 and activates F-1,6-BPase
Others
> Low pH (H+) inactivates PFK-1 (lactate production/ anaerobic)
> Alanine inhibits PK (substrate gluconeogenesis, signals starvation)
Reciprocal regulation in FA metabolism
Committed enzyme synthesis > ACC; acetyl-CoA carboxylase
> activated by citrate (feedforward stimulation)
> inhibited by palmitoyl-CoA (before committed step beta-oxidation)
Carnitine-palmitoyl transferase-1 (committed in beta-oxidation)
>Inhibited by malonyl-CoA, product of committed step in FA synthesis from Acetyl-CoA, HCO3- and ATP (to ADP + Pi)
HC24: Why do fats contain the most energy?
More reduced carbons: more energy for oxidation
> less polar and water attraction
> less osmotic value
Glucose and VLDL or Chylomicrons to TAGs in adipocytes
Glucose from liver
> Uptake by GLUT4, Glucose to glycerol-3-P
Fatty acids uptake by FATP and CD36, released by LPL out of VLDL (from liver) or chylomicrons (from intestine)
> FAs to acyl-CoA
> Glycerol-3-P + acyl-CoA > TAGs
TAG products from lipolysis in adipocyte in blood
-Glycerol: to liver
-FA-albumin complexes > to peripheral tissue
How are hormones produced by adipocytes called?
Adipokines
When are leptins secreted by adipocytes?
When the lipid droplet is full > feeling of saturation / satiety > enough eaten
Leptin signaling
Bind receptors in the arcuate nucleus (ARC) in the hypothalamus
> insulin has this function as well
> inhibition NPY and AgRP and activation POMC producing neurons > POMC increases MSH expression > decrease food intake
Obesity is often associated with … resistance
Leptin resistance
Additional satiety signals to the brain
-Response to feeding: intestinal cells secrete hormones cholecystokinin (CCK) from I cells and glucagon-like peptide (GLP-1) from L cells
GLP-1 function
GLP-1 is an incretin > hormones that prepare pancreatic beta cells to amplify their response to incoming glucose by increasing insulin secretion and biosythesis, while inhibiting glucagon secretion from alpha cells via insulin
How is glucagon and GLP-1 made
The human glucagon gene encodes for preproglucagon polypeptide (180 AA).
> during translation, signal peptide cleaved off by signal peptidase while proglucagon enters secretory pathway via lumen of RER
> in pancreatic alpha cells, proteases cleave proglucagon into mature glucagon and other peptides
> in intestinal L cells, proteases cleave proglucagon into GLP-1 and other peptides
Effect Semaglutide (Ozempic)
GLP-1 receptor agonist
> popular anti-obesity medication for treatment T2DM and decreases blood glucose levels in patients
Leptin -/- mice symptoms
Obese, insulin-resistant, diabetic
Molecular mechanism Ozempic
Bind to GLP-1 receptors and function as incretin
Functions liver in fasted and starved state as central regulator
-Fasted: producer glucose and FAs for other organs
-Starved: producer ketone bodies
In liver: glycolysis mainly for production …. for …
Acetyl-CoA, for FA synthesis, ketone bodies and other buidling blocks
Liver as internal energy source: mainly ….
Catabolism of amino acids
> transamination and citric acid cycle.
Brain as top consumer
60% glucose needs, constant needs
> needs a lot of glucose and ketone bodies in starvation
Why is FA oxidation not possible in brain
Blood brain barrier
> only oxidation glucose and ketone bodies
Erythrocytes have no mitochondria and use anaerobic glycolysis using LDH for NAD+ regeneration. Name two other types of this regeneration with cellular location and tissue type
- Glycerol-3-phosphate shuttle (mitochondria, oxidation, muscle)
- Malate-aspartate shuttle (mitochondria, oxidation, liver, brain and heart muscle)
Differences metabolism skeletal muscle and heart muscle
Fuels
> Skeletal: glucose mainly
> Heart: mainly FAs and ketone bodies
Lactate
>Skeletal: Producer
> Heart: consumer
O2 dependent
> Skeletal: not dependent
> Heart: completely O2 dependent
Shuttle for transport redox equivalents
> Skeletal: Glycerol-3-P shuttle
> Heart: Malate/aspartate shuttle
Glucose-alanine cycle
Muscle: glucose > pyruvate
Branched-chain amino acids > carbon skeletons for cellular respiration (energy) and glutamate (transamination)
Glutamate+pyruvate > Alanine (/ glutamine)
> blood
Liver: Alanine to pyruvate and glutamate
Glutamate to NH4+ (deamination) to urea (urea cycle)
Pyruvate to glucose (gluconeogenesis)
The master regulator of intracellular metabolism”:
mTOR complex
Lifting weights to failure and feeding lead to increased muscle mass, how?
Mechanoreceptors sense activity of muscle
> second signal: certain amino acids from diet like Leucine for which transporter proteins are needed.
> Combination leads to removal of inhibitors of mTOR complex 1 (inactive mTORC1) to active mTORC1
> mTORC1 activates protein synthesis and muscle hypertrophy
How does active mTORC1 promote protein synthesis
Bind to lysosomes and stimulate release building blocks for myofibrils and other muscle proteins.
Nitrogen transport through blood as glutamine
In muscle and other peripheral tissues in mitochondria:
NH4+ + Glutamate + ATP > Glutamine + ADP + Pi (glutamine synthase)
-Transport
Reaction in liver
Glutamine + H2O > Glutamate + NH4+ (Glutaminase)
Glutamate > NH4+ (glutamate dehydrogenase)
NH4+ > urea in urea cycle (CPS, carbamoyl-phosphate synthetase)
The liver enzymes glutaminase, glutamate dehydrogenase and carbamoyl phosphate synthase are all located in …
mitochondria
> NH4+ is toxic (ammonium ion) and should be compartmentilized
Protein breakdown is upregulated in starvation, how?
Autophagy initiated
> and protein breakdown in GI tract
How long does it take of starvation for ketone bodies to be in high level (ketosis)?
A week
Extreme starving characteristics and risks
Survival on vitamin supplements, potassium, sodium, non caloric drinks
> danger: low level of blood glucose, survival but not active, hypoglycemia
> continuous urea production from protein breakdown
> Danger: muscle breakdown
-Not an issue for skeletal muscle: grow it back later
-Issue for heart muscle breakdown
Adipocytes can secrete adipokines and …
cytokines
HC25: Which pathways are active in the fed state?
Insulin rules (high blood glucose)
> Uptake glucose by muscle and adipocytes
> Storage as glycogen and fat/TAGs
Which pathways are active in the fasted state?
Insulin levels drop, glucagon released in circulation by pancreatic alpha cells
> maintain glucose levels: glycogenolysis, gluconeogenesis in liver. Ketone body synthesis in liver.
What do muscles make from glucose in the fed state? And adipocytes? And which other tissues need lots of glucose?
Muscle: make glycogen and FAs > TAGs.
Adipocyte: make FAs > TAGs
Erythrocytes and brain need glucose
Transport lipids in fed state
From diet: Chylomicrons (intestine>lymph>blood)
From liver (made from glucose and incoming amino acids in liver) : VLDL
> Uptake by uscle and adipocytes to store as TAGs and use for energy (muscle)
> brain only uses glucose (and ketone bodies, not in fed state)
Effects of insulin
-Activation glycogen synthase, inhibition glycogen phosphorylase (inactivates GS kinase by phosphorylation by PKB)
-Activation glycolysis enzymes in liver, synthesis glucokinase
-Breakdown of glucose is promoted in liver: cells have enough ATP, but liver has to overrule system because it needs to do something with the glucose (for example by F-2,6-BP) > FA synthesis (high energy) > transport and storage in adipose tissue
-Inhibition gluconeogenesis enzymes
- Activation acetyl-CoA carboxylase synthesis (palmitate synthesis, to store energy in TAGs)
- Inhibition glucagon production > reciprocal regulation (inhibit alpha cells)
Glucagon effects
-Activation glycogen phosphorylase, inhibition glycogen synthase (through PKA which activates GP kinase and inactivates GS)
-Increase gluconeogenesis enzymes like pyruvate carboxylase
-Increase protein degradation in cell: autophagy
-Increase urea synthesis enzymes in liver
-increase TAG lipases activity in adipocytes (through PKA and Hormone sensitive lipase)
-inhibition acetyl-CoA carboxylase and enzymes Pentose Phosphate Pathway
-increase HMG-CoA synthase (ketone body synthesis committed)
Exercise while in the fed state result on glycogen metabolism
Overrule signal of fed state (Glycogen phosphorylase-b dephosphorylated, no glucagon yet) > adrenalin will facilitate that calcium can bind to calmodulin in phosphorylase kinase for activation
Fast glycogen regulation in liver (spontaneous exercise)
Adrenaline binds to alpha-adrenergic receptor
> Activation trimeric G-protein (GDP for GTP swap)
> Active G-protein activates Phospholipase C (PLC)
> PLC cleaves PIP2 to DAG and IP3
> IP3 facilitates Ca2+ release out of ER by binding IP3-sensitive Ca2+ channels.
> Ca2+ facilitates binding DAG to Protein Kinase C (PKC)
> Active PKC
> Ca2+ also activates GP kinase. Activation
Fast regulation glycogen breakdown in muscle cell
Muscle cell reacts to adrenaline (like liver) and nerve impulses (liver does not)
> Adrenaline binds beta-adrenergic receptor
> Activation G-protein which activates adenylate cyclase which makes cAMP that activates PKA.
> PKA activates GP kinase and inactivates GS
> Nerve impulse opens Ca2+ channels on PM.
> Ca2+ binds calmodulin (delta subunits in GP) in GP kinase
> activation as well
General regulation GP kinase by Ca2+ and PKA
GP-kinase binds Ca2+ by calmodulin subunits (because of adrenline in liver, muscle contraction in muscle)
> Partly active
GP kinase is also phosphorylated by PKA (because glucagon in liver, adrenaline in muscle)
> fully active
> extra step regulation: finetuning of enzyme activity
> Conversion GP-b to GP-a by GP kinase which is mostly in R-state, unless inhibited by glucose in liver or ATP/G-6-P in muscle (phosphorylation of both monomers using 2 ATP)
Allosteric activation GP-b
AMP, GP-b will be a bit active (overrules phosphorylation state)
When insulin rules in glycogen metabolism
Phosphorylation and deactivation GS kinase
PP1 can desphosphorylate and activate GS and inactivate GP
> Inhibition glucagon secretion, so PKA, GP kinase will not be active.
What is important during starvation in metabolism
-Sufficient glucose in blood (all times for brain and heart)
> amino acids for long term
> Prevent protein degradation by making ketone bodies (ketosis (high concentration ketone bodies in blood, after a week) is healthy back up mechanism)
-Prevent protein degradation
> lower pace at long term because of ketogenesis
> gluconeogenesis also a little active even after a month
Difference fasted state and starved state
-In starved state, all glycogen is gone (after 1.5 day)
-In muscle, fat breakdown is active, own fat storage. it takes free fatty acids from adipocytes.
Lipid metabolism during starvation
Lipolysis of TAGs in adipocytes > FFAs to liver.
> Liver uses FAs for beta-oxidation and makes ketone bodies from acetyl-CoA.
> Ketone bodies to brain and muscle
> FFAs also to muscle
> Muscle uses ketone bodies and FAs for fuel.
> Glycerol used by liver for gluconeogenesis: provide energy to brain and red blood cells via glucose
What happens to the released amino acids from proteolysis in muscle cells>
No storage space, transport alanine / glutamine to liver and breakdown to glucose (carbon skeleton) and urea
> glucose used to provide glucose for brain and red blood cell
Precursors gluconeogenesis in liver
-Alanine and glutamine from protein
-Lactate from red blood cells
-Glycerol from adipocytes
The cell contains limited amounts of ATP/ADP/AMP, NAD+/NADH and NADP+/NADPH. How is this possible during exercise?
Recycling of intermediates
HC26: Sources of plasma glucose
-DIet
-Glycogenolysis
-Gluconeogenesis
Insulin levels during day
Fluctuate: dependent on glucose intake
> ALWAYS basal level of glucose secretion to suppress alpha cells a bit in glucagon production.
Insulin injection during night for diabetics: how much?
For the whole night
Symtoms Diabetes mellitus type 1: blood glucose and urine
Sweet urine
High blood glucose (10 mM +)
Untreated T1DM is called starvation in the midst of plenty, explain
Beta cells in pancreas destroyed, high glucagon even when high blood glucose (signalling starved state)
> Glycogen breakdown in liver to glucose and release to blood
> No GLUT4 transporters on muscle and adipose
> Protein breakdown in muscle and amino acid breakdown to glucose (carbon skeletons) and urea in liver
> Breakdown fat to FAs in adipocytes, release as FFAs (high concentration in blood)
> FFAs taken up by liver to make ketone bodies: ketoacidosis in blood
> FAs in liver used for making VLDL and TAG transfer (increased in blood)
Concentrations of insulin, glucagon, glucose, ketone bodies and TAGs/FFAs in T1DM vs starvation
Insulin
> T1DM: absent, starvation: low
Glucagon
> T1DM: extremely high, starvation: increased (basal level insulin)
Glucose
> T1DM: extremely high, starvation: normal low
Ketone bodies
> T1DM: extremely high, starvation: moderately increased
TAGs/FFAs
> T1DM: high, starvation: normal
Ketosis means
High concentrations of ketone bodies in blood
> healthy back-up mechanism
Ketoacidosis meaning and process
Excessive amounts of ketone bodies in blood which leads to acidification of the blood.
> Release ketone bodies from hepatocytes: ketone bodies have negative charge and need cotransport of H+ to retain charge and voltage across membrane
> acidosis: dangerous for the blood: blood pH needs to be in brief window. (for function of blood components like HbA)
How can T1DM patients get unconscious, and solution?
Insulin injection but no meal in a panic situation
> insulin signals glucose uptake, but there is no dietary glucose
> Hypoglycermia: 2 mM
> Solution: inject glucagon or epinephrine intramusclular or intravenous glucose administration
Why do T1DM patients have an acetone smell breath?
Acetone is a product from the ketone body acetoacetate. Acetoacetate can be converted to acetone in a non-enzymatic spontaneous reaction. Acetone is a gas and in released in the breath and urine. (spontaneous decarboxylation, C4> C3)
> Acetoacetate is instable
How can dehydration occur with T1DM untreated?
High glucose excretion via urine which takes along a lot of water in the kidneys through osmosis
> a lot of hydrogen bond acceptors (O/N) and donors (OH/NH)
Patient with dehydration, deep and frequent acetone breath, and very high blood glucose (28 mM»_space; 10 mM). And acidosis (pH = 7.2, not in frame of 7.32-7.44). What is it and what to do?
-Ketoacidosis > untreated T1DM
-Ketone bodies in urine
> Buffer of pH in blood is bicarbonate (HCO3-): binds with H+ and breath out as CO2.
> remove acidity of the blood through CO2: deep and frequent breathing
> unconsciousness possible
Solution: intravenous insulin administration
Bond in the glycation of proteins?
Schiff base bond
> hemoglobin for example
> HbA1c (glycated) is parameter for blood glucose over time
Unconsciousness causes in T1DM
-Insulin injection but no meal
-Ketoacidosis very high: untreated T1DM or triggered by infection
Glycation of hemoglobin
Open chain glucose reducing aldehyde end at carbon-1 reacts with epsilon-amino residue of HbA beta chain N-terminal
> reversible spontaneous non-enzymatic linkage through Schiff base linkage (-HC(nr.1)=N-Lys-HbA)
> irreversible spontaneous non-enzymatic Amadori rearrangement to HbA1c (H2C(nr.1)-N(H)-Lys-HbA)
Problem glycation of proteins
loss of protein function and impaired elasticity of tissues such as blood vessels, skin, and tendons
> HbA1c increases chance of atherosclerosis and free radicals in erythrocytes
T2DM characteristics
-Threat at obesity
-BMI: 26 is borderline healthy and overweight
-Insulin resistance (insensitive)
-No deficiency of insulin secretion
Effect insulin resistance
-High insulin secretion
-GLUT4 inactive: no uptake glucose by muscle and adipocytes for storage
-Glycogen synthesis in liver not possible
Is the insulin receptor expressed in T2DM?
Yes, but the signal transduction upon insulin binding doesn’t function well.
Effects metabolism in T2DM
-No glycogen synthesis in liver
-No uptake glucose by GLUT4
-Hyperglycemia
-Glucose and amino acid carbon skeletons in liver (from diet) used to make fat and transport as VLDL secrtion
> Inreased FAs and TAGs in blood
> normal chylomicrons through diet fats.
-Brain and erythrocytes take up glucose like normal
Unregulated T2DM is less bad than T1DM, why
There is still insulin to dampen the glucagon secretion
> no ketoacidosis
How does T2DM develop?
-Substrate competition because of high FA in plasma
-Glycolipids in plasma membrane: insulin receptors have reduced affinity for insulin
Sources FAs in blood
-Food (chylomicrons)
-Fat from adipocytes: FFAs
Fatty liver risk in obese persons
In healthy persons: adipocytes store TAGs.
Overweight > liver and muscle can store TAGs, fatty liver.
Shulman hypothesis in T2DM for signalling and insulin resistance
-More fatty acids which can form DAG glycerol-3-P (FAs upregulated)
-DAG activates PKC (isozymes for liver and muscle)
-PKC phosphorylates the insulin receptor on the wrong place (on the serine or threonine, not the tyrosine)
> in some, but not all, insulin receptors
> those receptors are not properly activated
> Insulin binds receptor, but signal not properly transduced
> less signal transduction: insulin resistance
Prevention and treatment strategies T2DM
-Treatment is reducing weight and FFAs and prevention is lifestyle chages.
> PPAR-gamma (TF) / thiazolidinedione promote conversion FAs to fat in adipocytes
> ATP use promotes beta-oxidation of FAs to generate energy through TCA cycle (oxidized to CO2 and H2O)
Alcohol metabolism
Ethanol is converted to acetaldehyde by alcohol dehydrogenase. (in cytosol) (oxidation, yields 1 NADH)
Acetaldehyde is converted to acetic acid by aldehyde dehydrogenase (in mitochondria) (oxidation, yields 1 NADH)
Asian mutations in alcohol metabolism
-Increased activity alcochol dehydrogenase
-Decreased activity aldehyde dehydrogenase
-Accumulation acetaldehyde
> red flush, headache, accelerated heart rate, shortness breath, blurred vision etc
When a alcohol molecule is oxidized, it becomes a
aldehyde
Danger of aldehydes
Aldehyde group is reactive
> can cross link and form Schiff bases (think of glycation (schiff base) and glycosylation (cross links)
Inhibition of intake alcohol by disulfiram
> blocks aldehyde dehydrogenase
faster accumulation acetaldehyde, stop drinking faster because drunk symptoms
If a patient is unconscious with hypoglycemia (2.5 mM) and increased alcohol promillage (0.6). There is no creatine kinase in the blood. Is there a heart attack?
No.
> If there is no oxygen, (heart) muscle cells can burst > creatine kinase (for conversion creatine in creatine phosphate as reserve for substrate level phosphorylation) in blood.
> no heart attack, because no creatine kinase in blood
Alcohol patient has high aspartate aminotransferase in blood. This means:
Liver damage
> Increased aspartate deamination (increased urea cycle) in liver
> Aspartate aminotransferase in blood? > liver cells are dying and release enzymes in blood
Lactic acidosis in alcohol patient
Treatment high aspartate aminotransferase and lactate and low pH blood in unconscious alcohol patient
Intravenous glucose
> what happened: no meal: low glycogen level reserve
> Glycogenolysis insufficient to maintain blood glucose levels
-Gluconeogenesis in liver, but is damaged: hepatocytes die because of toxic acetaldehyde
> cirrhosis: liver less active
> patient skinny: muscle breakdown to generate amino acids as substrate
Consequences alcohol metabolism for glucose metabolism
-Generation high amount of NADH+ H+
-Pyruvate converted into lactate to regenerate NAD+
-Less pyruvate available for gluconeogenesis!
Gluconeogenesis inhibited by excessive alcohol intake: through NADH+ H+. and other effects
- Equilibrium lactate-pyruvate towards lactate
- equilibrium gycerol-triose phosphates towards glycerol (make NAD+) > fatty liver induced
- Transport of oxaloacetate via malate-shuttle towards mitochondria to regenerate NAD+
> Conversion NADPH into NADP+: glutathione regeneration disturbed: oxidative stress up
> TCA cycle blocked: Acetyl-CoA converted into ketone bodies: acidosis
Liver cirrhosis process
Fatty liver > apoptosis > inflammation (hepatitis) > scar tissue (fibrosis)
Alcohol and exercise dampens problems?
Burining ATP > use electron transport chain > NADH oxidized to NAD+ in oxidative phosphorylation instead of anaerobic glycolysis.
Activator of ketogenesis
Acetyl-CoA (substrate)
> beta-oxidation FAs
Muscles and brain can use ketone bodies for energy but not liver, why
No enzyme CoA-transferase for acetoacetate to acetoacetyl-CoA using succinyl-CoA > energy breakdown
> more acetyl-CoA from beta-oxidation, activate ketogenic enzymes
> liver is ketogenic, not ketolytic
When ketone body synthesis
When concentrations acetyl-CoA rise dramatically
> untreated T1DM and starvation
The HCO3- used by acetyl-CoA carboxylase in FA synthesis to make malonyl-CoA, where do these carbons appear in the FA?
Nowhere
During condensation in elongation cycle of malonyl-ACP and acetyl-ACP, it is removed as CO2.
Ketolysis
Acetoacetate + succinyl-CoA > acetoacetate-CoA + succinate (CoA transferase, not in liver)
Acetoacetate-CoA + CoA > 2 Acetyl-CoA (thiolase)
