How to build a Mr. Olympia

Use It or Lose It

• Many physiological systems lose capacity if they are not used.

• Examples:

  • Skeletal musculature (space travel, immobilisation).

  • Bone strength.

  • Brain function.

• Question: Why don’t these biological systems protect physiological capacity during periods of low usage?

• Question: Is the decay in capacity, such as that occurs through ageing, inevitable? Why?

How Best to ‘Use It’

• A systematic program of use is called training.

• Exercise training is built from some combination of intensity and volume.

• Sprint versus endurance events have different training needs.

• Coaches and athletes have contrasting views on how best to balance intensity and volume, even in pursuit of a common goal.

What Defines a Mr. Olympia?

• Extremely high muscle mass.

• Extremely low body fat (particularly the subcutaneous depot).

• Dehydrated.

• Aesthetic ideals:

  • Balance.

  • Symmetry.

  • Proportion.

Genetics (‘G’ or nature)

• Predisposition to high muscularity.

• Large number of muscle fibres.

• Mainly large diameter type IIB fibres.

• Large resident population of satellite cells.

• Long muscle bellies with short attachments.

• Wide and deep musculoskeletal structure in the upper body, but narrow hips.

• High endogenous growth hormone, IGF-1 and other anabolic / androgenic hormones such as testosterone.

• High ‘responsiveness’ to exogenous anabolics.

• Psychologically driven (type A personality?), individualistic.

Environment (‘E’ or nurture)

• Nutritional background during development (including prenatal).

• Efficient, stimulating training.

• High intensity training (HIT).

• High volume training.

• Adequate rest and recovery.

• Nutrition to support the training effect.

• Amino acids to support muscle growth (none ‘limiting’).

• Total caloric intake positive during mass building, negative during peaking.

• Balanced diet including vitamins (enzyme co-factors) and minerals.

• Stimulants such as caffeine.

• Absence or limited inhibitory compounds (alcohol?).

The End Game

• If genetic potential for muscularity is reached, nature and nurture have combined optimally.

• Muscle protein synthesis has been sustained at high levels.

• Muscle gene expression has been sustained at high levels e.g. the mRNA encoding the fast twitch myosin and actin isoforms and associated contractile machinery (MYL1, MYH3, TNNT3, TNNC2).

Fostering Muscle Gene Expression

• Adult myofibres are multinucleate, so you need enough nuclei to service the molecular needs of the cytoplasmic volume.

• Regulatory machinery (e.g. key TF) driving myosin and actin gene expression is activated.

• There is enough biological material (nucleic acids, amino acids and ATP) to support the gene expression program.

The Prenatal Muscle Development Program

• Two waves of ‘myogenesis’ in most prenatal mammals:

  • First wave (Primary), mainly slow fibres.

  • Second wave (Secondary), mainly fast fibres.

• A small set of DNA binding Transcription Factors (TF) called Muscle Regulatory Factors (MRF) determine the differentiation of precursor cells into myoblasts.

• Forced expression of MyoD1 can orchestrate this developmental program in vitro.

Muscle Regulatory Factors

• MYF5, MyoD1, Myogenin and MRF4 expression during differentiation.

Differentiation of Muscle Cells

• Process:

  • Mesoderm.

  • Myoblasts (MyoD, Myf5).

  • Myocytes.

  • Withdrawal of cell cycle.

  • Myotubes (Myogenin, MRF4).

  • Fusion.

  • Myofiber (MHC, MCK, α-Actin).

  • Maturation.

Myogenesis

• Dermomyotome (Pax3*Pax7).

• Muscle Commitment (MRFS).

• Pax3 derived Pax7-.

• Embryonic myoblast.

• Fetal myoblast.

• Satellite cell.

• Nfix, Notch.

• Terminal Differentiation.

• 1° Fibers.

• Regeneration.

• Fibers.

• I Fibers:

  • Type 1 (slow).

  • Type 2A.

  • Type 2C/X.

  • Type 2B (fast).

• Developmental time (mouse, d.p.c.):

  • 10.5: slow twitching fibers + primary myogenesis.

  • 13.5: fast twitching fibers.

  • 17.5: secondary myogenesis.

  • Birth: post-natal myogenesis.

Adult Muscle Growth

• Number of muscle fibres fixed at birth (ceiling set as adults).

• Growth of existing fibres supported by a resident population of muscle stem cells called ‘satellite’ cells.

• Upon stimulation, these fuse to the existing myofibres and contribute new nuclei.

• These additional nuclei create greater potential for mRNA production and therefore further anabolism.

Satellite Cell Recruitment and Muscle Growth

• Process:

  • Quiescence (Satellite, Pax7 (+), MyoD (-)).

  • Activation (Pax7 (+) Myf5 (+) MyoD).

  • Proliferation (Myoblasts, Pax 7 (-) MyoD (+) MyoG).

  • Differentiation.

  • Fusion (Myocytes).

  • Maturation (Myotubes, MyoG/MRF4) to Myofiber.

• Time frame: 3 - 6 days.

• Question: Why does capacity for muscle growth diminish with ageing?

PPARGC1A

• In a muscle cell, PPARGC1A is induced by cellular information indicating more energy (ATP) is required.

• Cellular energy status is measured by ADP/ATP ratios (AMPK) and NAD+/NADH ratios (SIRT1).

• This combined information is channelled via PGC1A to drive expression of key muscle TF inc. MEF2C and NRF1.

PPARGC1A cont.

• Mouse over-expressing PPARGC1A in the skeletal musculature (‘TG’ or transgenic) has more of the red, type I slow oxidative fibres than the ‘WT.’

• These fibres express more myoglobin, have a higher mitochondrial content, a higher capillarity and the sarcomere makes use of the slow contractile isoforms such as MYL2.

• This TG mouse is a marathon runner.

MSTN

• Myostatin (MSTN or GDF8) is a signalling molecule (not a DNA binding TF).

• It interacts with other proteins, including Follistatin that is encoded by FSTL3.

• MSTN propagates its (negative or repressive) signal through binding to the receptor Activin IIB, as part of the broader TGF-beta signalling pathway.

• Question: What part of this pathway is modified in double muscled Belgium Blue cattle?

Manipulating More of the TGF-beta Axis

• Making a hyper-muscular mouse through transgenic manipulation of the TGF-beta axis.

• CONTROL, DOMINANT NEGATIVE ACTRIIB, FOLLISTATIN

Dystrophin and Muscular Dystrophy

• The dystrophin gene (DMD) is the largest human gene (79 exons!).

• It is located in the short arm (p for ‘petit’) of the X chromosome (Xp21.2).

• It encodes a protein that connects the inside of the muscle cell to the cell membrane.

• Duchennes MD occurs because the mutated DMD gene fails to produce functional dystrophin.

• Question: Why do girls usually not express the disease?

Alcohol and Muscle Performance

• Ethanol Metabolism:

  • Ethanol \xrightarrow{1. ADH} Acetaldehyde \xrightarrow{2. ALDH2} Acetate.

  • Ethanol Metabolism Side Reactions.

  • NAD^+ is converted to NADH during the above reactions.

  • \text{Alcohol} + O2 \xrightarrow{CYP2E1} Acetaldehyde + H2O in microsomes

• Locations:

  • ADH: Cytosol.

  • ALDH2: Mitochondria.

  • CYP2E1: Microsomes.

• Effects:

  • Acetaldehyde adducts formation.

  • Increase ROS formation.

  • Increase NADH: NAD^+ ratio.

ADH Tissue Specific Expression

• ADH expression varies across different tissues, as indicated by a chart showing relative expression levels in various human tissues.

Alcohol Flush Reaction

• Skin flushing as a consequence of accumulating acetaldehyde.

• More common in those of East Asian descent, ‘Asian glow.’

• Around 30–50% of East Asians carry the rs671 (ALDH2*2) allele on chromosome 12, which results in a less functional acetaldehyde dehydrogenase enzyme.

• Additionally, in around 80% of East Asians, the rapid accumulation of acetaldehyde is worsened by another gene variant; in this case the allele ADH1B*2, which results in the alcohol dehydrogenase enzyme converting alcohol to toxic acetaldehyde more quickly.

ALDH2*2 Allele

• A common ALDH2 allele is caused by a single nucleotide polymorphism (SNP).

• The SNP is a G to A mutation (G>A) at triplet codon 504 in exon 12 of the ALDH2 gene located on chromosome 12q24.

• This mutation results in the substitution of the amino acid glutamate (Glu) with lysine (Lys) during subsequent translation (Glu504Lys).

Codon Usage Table

• Glutamate (Glu or E) is encoded by GAA and GAG.

• Lysine (Lys or K) is encoded by AAA and AAG.

• The gene variant common in East Asians is converting either GAA → AAA or GAG → AAG.

Biochemical Properties of the Amino Acids

• The two amino acids have different biochemical properties.

• The performance of the encoded protein (the alcohol dehydrogenase enzyme) is changed.

• Amino acids share the NH_3^+ and COO^- in common, but the R group varies.

• Glutamate (Glu, E) is 147.1 Da and possesses a negatively charged R group.

• Lysine (Lys, K) is 146.2 Da and possesses a positively charged R group.