Genomics Flashcards
Epigenetics
As an organism grows and develops, carefully orchestrated chemical reactions activate and deactivate parts of the genome at strategic times and in specific locations. Epigenetics is the study of these chemical reactions and the factors that influence them.”
Video on epigenetics
https://www.youtube.com/watch?v=81rFpRsF80c&feature=youtu.be
Intro to Nutrigenomics
Health/Diet (Nutrition in between)
Diet/Genomics (Microarrays, proteomics, metabolomics, epigenomics between)
Genomics/Health (longevity, markers, behvaioral genomics in between)
within all three: (health, diet, genomics) Nutrigenomics
Nutrigenomics vs. Nutrigenetics
Nutritional genomics covers nutrigenomics, which explores the effects of nutrients on the genome, proteome and metabolome,
nutrigenetics, the major goal of which is to elucidate the effect of genetic variation on the interaction between diet and disease.”
If ApoE, may want to suggest dietary changes, however you cannot say it is because of higher risk of Alzheimers. Need to provide supportive literature for docs when sending referral. Need to have a kick-ass disclosure to protect yourself on every level.
Statutory Definition of Nutrigenomics
Nutritional genomics means the consideration of biochemical or genetic information to evaluate how genetics effect gene function and how genetic variation alters nutrient response, including the study of how dietary and other lifestyle choices influence the function of humans at the molecular, cellular, organismal and populational levels.”
Genetics 101/DNA Replication
https://www.facebook.com/AAMB.UK/videos/vb.305735409443436/304240952939950/?type=3
Methylation Basics
what is methylation?
The most common methylated base in humans is 5-methylcytosine.
1.A methyl group is 1 carbon and 3 hydrogens
2.Methylation is the process of adding or subtracting this group from different compounds.
What is the function of methylation?
1. Gene regulation
2. Biotransformation
3. Neurotransmitter synthesis
4. Hormone catabolism (estrogen)
5. DNA and histone synthesis
6. Energy production
7. Build and maintain cell membranes (phosphatidylcholine/serine)
To Add or not to add a methyl donor
-Adding a methyl group or hypermethylation silences gene expression
-Removing a methyl group or hypomethylation activates gene expression.
To silence gene – hyper methylation
To silence, adding in methyl donors.
If heathy, do not want to add methyl donors. Adding donors tells body to stop making DNA, stop transcription. Many supplements are full of methylated micronutrients.
Body should do a good job of methyl donors on it’s own.
Adding them in “shouts” at metabolic pathways. Do not want to add methyl donors in 99% of the time. Methylation only one way to turn on/off genes… many more: Acetylation, etc. Not always methyl donor turning things on/off.
What Negatively Impacts Methylation
- Insufficient cofactors or substrates
- Medications that block absorption (antacids, methotrexate, metformin, etc.)
- High dose niacin depletes methyl groups
- Environmental toxins, heavy metals, and chemical exposure
- Too much substrate causes feedback inhibition
- Genetic mutations
- Mental state
Blocked absorption creates insufficient cofactors and substrates. Too much Vitamin C causes diarrhea – lower doses to actually absorb. Transporters can only handle about 500 mg at a time. Absorption is 98% or so. One dose of 1000mg of Vit C, transporters only handle 50% and the rest is flushed out of the system. Vitamin C is not fat soluble. Vitamin D is, so want a liposomal delivery system. Not for Vitamin C.
What is a SNP?
https://www.youtube.com/watch?v=moQdU7nH-jg
Basics of homocystein metabolism
1.Methionine is methylated homocysteine
2. This is a breakdown product of SAM SAH via AHCY (adenosylhomocysteinase)
3. The only difference is the addition of a methyl group on homocysteine.
4. Methionine = homocysteine + Methyl group
homocysteine metabolism
Dietary Folate/Folic Acid
DHFR/NADPH (DHF > THF)
MTHFD/NADP > 10- Formyl THF
5, 10 Methylene THF>MTHFD1> 10-Formyl THF
5,10 Methylene THF > MTHFR (FAD, NADP),
MTHFR > 5-MTHF> MTR/MTRR (vitamin B12) > Methionine
Betaine > DMG
Methionine uses conversion of Betaine to DMG to make Homocysteine (CBS , B6)> Cystathionine >
Taurine, glutathione, sulfate
BHMT (Zn) is in the conversion with Homocysteine to Methionine
Methylation pathway also recycles B12. Recycles methyl donor to pass off to MTHFR to create methyl donor (methylate folate). Homocysteine can go back to methionine, but not as common as the Glutathione pathway.
Homocysteine catabolism
Three Possible Routes:
MTR/MTRR (50%) – Vitamin B12 and Folate
BHMT – TMG and Zinc
CBS (50%) – Vitamin B6 – Only eliminating route
May use choline/phosphatidylcholine in place of TMG for those with BHMT SNPs that are sensitive to methyl donors as choline is the precursor to betaine.
Betaine may be increased by consumption of beets and Swiss chard.
Not much zinc needed to get methlylation going. Folate interacts, but is not required (first route). CBS Cystationine beta synthase? When client says sensitive to active B vitamins… actually mean methylated.
MTR/MTRR
- Methionine synthase
- Methionine synthase reductase
- Function: Recycles homocysteine back into methionine in order to produce SAM (S-adenosylmethionine)
- SAM: the universal methyl donor
- MTR Cofactor: Zinc, blocked by lead, aluminum and mercury.
- MTRR Cofactors: SAM, FAD, NAD, blocked by lead
Methionine Synthase
(MTR/MTRR)
- Methionine Synthase
- Methionine Synthase Reductase
- Accounts for half of homocysteine catabolism.
- Recycles homocysteine back to methionine.
- IS the connection between one carbon metabolism and methylation.
Methionine>Homocysteine>MTR/MTRR (vitamin B12)> Methionine
BHMT
- Betaine-homocysteine S-methyltransferase
- Cofactor and enzymes: zinc, DMG->TMG via choline, blocked by glucocorticoids.
- Function: Supplies a methyl group to convert
homocysteine back to methionine and betaine to dimethylglycine (DMG) - Betaine + homocysteine → dimethylglycine +
methionine - Mutations may increase homocysteine levels
(theoretically)
How many patients do you have that are Zinc deficient.
Betaine Homocysteine Methyltransferase (BHMT)
- Betaine-Homocysteine S-Methyltransferase
- The short cut through the methylation cycle.
- Supplies a methyl group to convert homocysteine back to methionine and betaine to dimethylglycine (DMG).
CBS overview
- Cystathionine Beta Synthase
- Cofactor: Vitamin B6 (pyridoxal-5-phosphate)
- Function: Converts homocysteine to cystathionine
>Blocked by lead - Product: Hydrogen sulfide (H2S) and cystathionine
- CBS C699T, C1080T, and C1985T variants are fast forward enzymes
- CBS A360A and CBS C9150T variants are slow enzymes.
- Slow or fast CBS mutations may result in autism, down syndrome, connective tissue disease, cancer and homocystinuria.
- (much more on this later)
Cystathionine Beta Synthase
- Cystathionine Beta Synthase
- Accounts for half of homocysteine catabolism
- The only true disposal route
- Converts homocysteine to cystathionine
Case Study : Homocysteine and stress case study
John is a busy executive working 70 hours per week. His symptoms include insomnia, stress and has occasional diarrhea and anxiety.
>You ran an initial four-point adrenal stress index (ASI) which indicated that cortisol is elevated throughout the day.
>A serum homocysteine was also run and was lab high at 16 mmol/L (range is 4-16 mmol/L).
>An organic acids test was also run which includes methylmalonic acid (MMA), formiminoglutamate (FIGLU) and xanthurenate which assess vitamin B12, folate and vitamin B6 status respectively. When elevated these markers indicate a cellular insufficiency. While xanthurenate levels were normal, both MMA and FIGLU were elevated.
>How would you proceed? Are there any SNPs that you would expect to find? Do you think that there is a relationship between stress and homocysteine?
MTR/MTRR
Perhaps MTHFR
Probably block from Homocysteine to cystathionine – B6 deficiency, Probably blocked at Mtr/Mtrr – maybel MTHFR snp. Inflammatory markers not the whole picture.
Stress and methylation
> Talk to me about what you see here.
What is the chemical difference between Epinephrine and Norepinephrine?
What enzymatic process is being catalyzed by PNMT?
What do you think it means for those under chronic stress?
What do you think about their methylation status?
How about their Hcy Levels?
Difference between norepinephrine and Epinephrine is methyl donor – CH3. Stress uses up methyl donors = elevated levels of homocysteine whether system is broken or not.
Simplified Focus on MTHFR- The celebrity SNP
1.URea cycle
2. BH4 Cycle (Tryptophan to Serotonin, Tyrosine> Dopamine)
3. MTHFR
4. Folate Cycle with 5-MethylTHF+ > Methyl B12
5. Mehtylation Cycle (Mehionine) , SAMe, SAH,
6. Homocysteine> B6 input
7. Cysteine>
8. Glutathione
MTHFR
- Methylene Tetrahydrofolate Reductase
- Key Variants: C677T and A1298C
a. C677T heterozygous=40% loss of function
b. C677T homozygous=75% loss of function
c. A1298C heterozygous=20% loss of function
d. A1298C homozygous=40% loss of function
e. Compound heterozygous=40%loss of function - Cofactor(s): Riboflavin, NADH, and ATP
- Approximately 45% of the population has 1 copy of MTHFR C677T (Esp. Mexican, Italian, and Chinese).
MTHFR pathway
Draw and study
Consequences of MTHFR
- C677T variant will increase homocysteine, A1298C will not.
- Increases risk for neural tube defects, miscarriage, dementia, mood disorders, peripheral artery disease, colon cancer, and acute leukemia.
- Common in those with ADHD, autism, depression, Alzheimer’s disease, Parkinson’s disease, coronary artery disease and those with detoxification challenges.
MTHFR Case Study
A 25 year old woman who is 5’4” tall and weighs 178 lbs has been trying to get pregnant for the last year. She has conceived three times only to miscarry early in the first trimester. She has come to you for help in figuring out the problem.
You start by looking at a recent CBC that her gynecologist ran and notice that her MCV is functionally high at 98 (80.0-98.0).
As the next step you decide to run homocysteine, MMA and FIGLU.
Homocysteine: 18
MMA: elevated
FIGLU: elevated
Which SNPs would you expect to find and why?
What role do you think obesity plays in fertility?
MTHFR, MTR/MTRR
PCOS/estrogen dominance.
Macrocytic anemia
3 -6 minutes in
DHF dietary folate
Dihydrofolate Reductase (DHFR)
rs7387, rs19972026, rs1643649, rs1643659, rs1677693, rs1650697
Cofactor NADPH
Codes the enzyme dihydrofolate reductase used in conversion of dihydrofolate into tetrahydrofolate
Dihydrofolate is reduced to tetrahydrofolate and NADPH is oxidized to NADP+
Is the precursor to both one carbon metabolism AND neurotransmitter synthesis.
Causes difficulty in conversion of synthetic folic acid into the active form of folate
Fortification with folic acid is a problem as it requires two DHFR steps for conversion as compared to only one required with natural folate
DHFR is the target for anticancer and antibiotic therapies such as methotrexate and trimethoprim (folate is required by rapidly dividing cancer cells to make thymine therefore inhibition of DHFR can limit growth and proliferation of cancer cells)
“Leucovorin does not require reduction by DHFR to participate in reactions in which folates are used as a source of 1-carbon moieties. Moreover, leucovorin is rapidly converted to other reduced folates, thereby restoring the pool of reduced folates.” (Chuang V.T.G. and Suno, M., 2012 p. 1350)
Consider dosing folinic acid (calcium folinate) rather than L-methylfolate
DHFR and Folic Acid Case Study
A middle-aged, depressed man eating a SAD diet comes to you after visiting a naturopathic physician. The ND prescribed Deplin (prescription L-methylfolate) after running the following labs:
Homocysteine: 10
Serum folate: elevated
FIGLU: Elevated
MMA: Normal
Xanthurenate: Normal
What SNPs would you expect to find and why? Do you think that Deplin is the correct intervention?
Answer:Absence of B12 def., folic acid and methyl folate is not working because of DHFR
Probably has MTHFR
Probably getting too much folic acid through SAD inducing the condition without the SNP?
catecholamine production
Neurotransmitters and hormones from phenylalanine and Tyrosine
The essential amino acid phenylalinine breaks down to tyrosine.
Tyrosine is used in the production of Thyroid hormones, melatonin in skin, and the neurotransmitters, dopamine, norepinephrine, and epinephrine are excreted jointly as vanilmandelate.
High levels of these breaksdown products in the urine identify a high turnover, low levels may indicate inadequate production.
Tetrahydrobiopterin (BH4)
Cofactor required for hydroxylation of aromatic amino acids (i.e. phenylalanine to tyrosine, tyrosine to DOPA and tryptophan to serotonin)
Cofactor in nitric oxide production from arginine
Guanosine triphosphate (GTP) is converted to dihydroneopterin triphosphate catalyzed by guanosine triphosphate cyclohydrolase (GTPCH)
6-Pyruvoyl tetrahydropterin synthase (PTPS) (cofactor magnesium) converts dihydroneopterin triphosphate into 6-pyruvoyl-tetrahydropterin
A final conversion to BH4 is made via the enzyme sepiapterin reductase (SR) using NADPH and NADP as cofactors
BH4 is subsequently used to produce the monoamines dopamine, norepinephrine, epinephrine and serotonin as well as nitric oxide.
BH4 Status
“Restricted BH4 cofactor availability has also been suggested as an etiologic factor in neurological diseases, including DOPA-responsive dystonia, Alzheimer disease, Parkinson disease, autism and depression; as well as in other conditions such as insulin sensitivity and vascular disease. BH4 is obligatory for the activity of all nitric oxide (NO) synthase isoforms and glycerl-ether mono-oxygenase. By its regulation of neuronal NO synthase, BH4 is a neuroprotective factor. Low BH4 levels are also associated with impaired eNOS activity, leading to endothelial dysfunction.”
May be measured via BH4 blood levels, 5-HIAA, 5-MTHF, HVA, Phe/Tyr ratio and Phe blood levels.
Lower BH4 status is often found in depressed individuals.
Depressed individuals often low in BH4
Depression, not get out of bed, not eat, not going places – serotonin
Dopamine wants to go out and do things, don’t enjoy them. – binge eating, sex addicts, etc may be dopamine deficient.
Anxious often excess of neurotransmitter, epinephrine, norepinephrine. Anything pushing dopamine also pushes epinephrine, norepinephrine. Work on anxiety first then address dopamine.
Without proper methyl donors, BH4 status is low
BH4 and Neurotransmitter Synthesis
Notice the connection between DHFR and BH4…what do you think occurs when you have a functional block in DHFR? What causes a functional block in DHFR again? Folic acid
Can look at neurotransmitters through OATs example, elevated HVA and low VMA then dopamine not moving to norepinephrine then cofactor deficiency or snp.
Walsh theory re: depression – copper, vitamin C affects conversion of dopamine to epinepherine
Elevated dopamine – halucinations, mood changes, bipoloar, schizophrenia – induced by supplements may not be able to correct and must be careful.
BH4 and Folate
BH2 is important for the regeneration of BH4 (susceptible to oxidation).
Dihydrofolate reductase (DHFR) is thought to be involved in BH4 regeneration.
“Nitric oxide (NO) derived from endothelial NO synthase (eNOS) has been implicated in the adaptive response to hypoxia. An imbalance between 5,6,7,8-tetrahydrobiopterin (BH4) and 7,8-dihydrobiopterin (BH2) can result in eNOS uncoupling and the generation of superoxide instead of NO. Dihydrofolate reductase (DHFR) can recycle BH2 toBH4, leading to eNOS recoupling.”
Folate (5-MTHF) is responsible for regenerating oxidized BH4.
“In the absence of an adequate amount of BH4, 5-MTHF “stands in” for BH4 at the enzyme level. The chemical structures of BH4 and 5-MTHF are similar enough that eNOS will accept 5-MTHF as a substitute cofactor.” (Miller 2008 p.220)
May account for why folate may have an antidepressant effect.
BH4, Phenylanine, and Tyrosine
BH4 Rx ( sapropterin) and discuss supplementation for Bh4 ( niacin, Vit C, folate, b6, mg)
Dopamine depression may also have hypothyroid
Iron overload may lead to hyperthyroid
BH4 is required for the conversion of phenylalanine to tyrosine as a cofactor along with iron for phenylalanine 4-hydroxylase (PAH).
It is also required for the subsequent conversion of tyrosine to DOPA as the cofactor along with iron for tyrosine hydroxylase (TH).
Therefore without proper production of BH4 you will have low dopamine levels which ultimately will also cause decreased production of norepinephrine and epinephrine.
Methylation and Neurotransmitters **DHFR
PAH requires BH4 and iron to catalyze Phenylalanine to Tyrosine
BH4 is also required for the conversion of tyrosine to DOPA
Remember that BH4 is formed via methylation.
VMA is the metabolic breakdown product of norepinephrine and epinephrine
HVA is the metabolic breakdown product of dopamine
Decreased levels of these neurotransmitters can cause depression, sleep disturbances, anxiety and fatigue.
This is the link between methylation and neurotransmitters.
Which SNP/Gene is it that again directly links methylation and neurotransmitters?
DHFR…not MTHFR
Neurotransmitter case study
A 35 year old woman who has been complaining of fatigue, binge eating and depression. Her internist ran some lab work with the following results:
MCV: 80 (80.0-98.0)
Serum iron: 39 mcg/dL (40-155 mcg/dL)
Ferritin: 20 mcg/L (12-150 mcg/L)
TSH: 5.0 (0.35-5.5)
Free T4: 1.0 ng/dL (0.8-2.8 ng/dL)
Functional range is 1.0-2.0 ng/dL
Free T3: 2.7 nmol/L (1.23-3.53 nmol/L)
Functional range is 3.0-3.5 nmol/L)
After looking at these labs you decide to run a NutrEval to assess her neurotransmitter and amino acid levels. Her results are as follows:
Phenylalanine: elevated
Tyrosine: low
HVA: low
VMA: low
What SNPs would you expect to find and why? Do you see any clinical diagnoses? What recommendations would you make (remember cofactors)?
BH4 deficiency, possible PAH
Not converting phe to tyr
Fe is cofactor
Microcytic presentation of red blood cell – Iron or B6 deficiency
Serine Hydroxymethyltransferase (SHMT)
rs9909104, rs1979299
Cofactor—vitamin B6 as the active P5P
Encodes the enzyme serine hydroxymethyltransfase which is involved in cellular one-carbon pathways
We are going to go around the Wheels, so follow along! SHMT is not on the “big” picture, but it is important. It is known as the “gut dysbiosis” SNP.
Requires Vitamin B6 for one carbon metabolism
Catalyzes the reversible, simultaneous conversions of L-serine to glycine and tetrahydrofolate to 5,10-methylenetetrahydrofolate (requires SAM)
Also catalyzes conversion of 5,10-methenyltetrahydrofolate to 10-formyltetrahydrofolate
“The SHMT1 1420C>T SNP (rs1979277; exon 12) has been associated with protection from rectal cancer and with CVD risk in a gene-gene interaction with MTHFR rs1801133 (C677T). SHMT1 rs1979277 reduces the sumoylation of SHMT1, impairing its translocation to the nucleus, suggesting that it reduces nuclear folate metabolism and thymidylate synthesis. The SHMT1 TA haplotype, which includes rs1979277, was associated with higher RBC folate and the CG haplotype was lower RBC folate.”(Zick, Groh and MacFarlane, 2015 pp. 1301-2)
On its own SHMT is the “gut dysbiosis gene” resulting in an increased risk of CVD and CR cancer risk- however in association with MTHFR C671, the risk is remediated. Thus not all SNPs are bad.
CBS overview
- Cystathionine Beta Synthase
- Cofactor: Vitamin B6 (pyridoxal-5-phosphate)
- Function: Converts homocysteine to cystathionine
>Blocked by lead - Product: Hydrogen sulfide (H2S) and cystathionine
- CBS C699T, C1080T, and C1985T variants are fast forward enzymes
- CBS A360A and CBS C9150T variants are slow enzymes.
- Slow or fast CBS mutations may result in autism, down syndrome, connective tissue disease, cancer and homocystinuria.
CBS pathway overview
- Cystathionine Beta Synthase
- Accounts for half of homocysteine catabolism
- The only true disposal route
- Converts homocysteine
CBS Upregulation
- Decreased levels of vitamin B6 and magnesium
- Decreased levels of homocysteine, GSH
- Compromised ability to recycle homocysteine back the universal methyl donor SAM)
- Increased levels of ammonia drain methyl donors and increases levels of nitric oxide to counteract increased ammonia.
- Hydrogen Sulfide increases cortisol and glutamate (excitotoxicity)
Hypomethylating changing balance between SA and SO. When not methylating… creating ammonia and increases cortisol levels.
Glutamate, inflammatory
Excess ammonia – relieve strain on kidney, lessen protein – presentation is brain fog
CBS Upregulation and SUOX
1.Increased flux of sulfur through CBS forces sulfur too quickly downstream
2.This will put undo stress on the enzyme 3. SUOX (Sulfite Oxidase) and depletes molybdenum, SUOX’s cofactor
SUOX has a low capacity
4. A reduced sulfur diet for a few days (never long term) and molybdenum supplementation can help with sulfur intolerance
CBS Upregulation Clinical/Lab Findings
- Elevated urinary sulfates: typically greater than 800. If consistently greater than 1000 then high CBS activity is likely; Sulfur flatulence, sulfur food intolerance, Sulfa drug reactions and halitosis. (Brain Fog!)
- Elevated ammonia and/or sulfate levels along with elevated Orotate, Citrate and Isocitrate on an Organic Acids Test (OAT) indicate elevated ammonia. (Ammonia depletes BH4, leading to insufficient dopamine and serotonin production)
- Typically has an elevated xanthurenate on an OAT test
- Also will have high Taurine - Taurine is synthesized via Cysteine – found on amino acids tests.
- To combat sulfur intolerance: Try a reduced sulfur diet (cruciferous vegetables, eggs) and reduced protein diet for a few days along with molybdenum, the cofactor for SUOX.
CBS Downregulation
- Hypertension/Cardiovascular disorders
- Potentially elevates homocysteine levels and moderately elevates xanthurenate—check MTHFR C677T status.
- Consider N-acetyl cysteine (NAC) to help increase GSH levels, magnesium and P5P.
- Decreased risk of breast cancer with CBS A360A
- Elevates nitrous oxide
- Breathing difficulty/asthma
- Often found in those with autism spectrum disorders