Nervous System Health and NTs

Question 1

Key factors affecting nervous system health

Answer 1

• Lifestyle ― environment and our response to it.
• Nerve cell structure and function ― cell membrane integrity via EFAs, phospholipids, myelin, antioxidants, removal of toxins, minerals.
• Hormonal and immune ― oestrogen, testosterone, thyroxine, cortisol, adrenaline, cytokines (inflammation), neurotrophic factors.
• Energy ― relies on a steady flow of glucose and rich in mitochondria.
• Gastrointestinal health ― the ‘second brain’

Question 2

Gut brain axis (GBA)

Answer 2

Gut brain axis (GBA) = bidirectional communication between the central and enteric nervous system.

• Vagus nerve connects GIT and brain, and contains 80% afferent (sensory) and 20% efferent fibres
• Gut microbiota play a key role in supporting health of this axis. Dysbiosis can result in extra intestinal disorders, including nervous and mental health disorders.

Question 3

GBA and microbes

Answer 3

• Modulating NT production ― e.g., serotonin which functions as a key NT in the GBA at both its terminals.
• Bacterial metabolites ― e.g., SCFAs support the intestinal barrier, mucosal serotonin release and influence memory and learning processes.
• Modulation of afferent sensory nerves e.g., L. reuteri has been shown to enhance neuron excitability, modulating gut motility and pain perception.
• BDNF production ― gut microbiota can modulate BDNF function in the CNS via changes in NT function or by changes in brain SCFAs.

Question 4

Gut barrier function is a key influence on the GBA.

Answer 4

• Diet induced changes in the gut microbiome can lead to a compromised mucus layer, allowing access of luminal microbes to extensions of dendritic cells, resulting in activation of these cells by both pathogens and commensals.
• This local immune activation can lead to ↑ permeability of the tight junctions that further compromises the intestinal barrier.
• This can result in ‘metabolic endotoxemia’, where immune activation in different organs occurs, including the brain.
• Elevated levels of LPS have been associated with neuroinflammation and conditions such as depression.

Question 5

Key factors influencing general nervous function

Answer 5

• Inflammation, oxidative stress, toxic load
• Decreased expression of neurotrophic factors such as BDNF and nerve growth factor (NGF).
• Mitochondrial changes: Relate to inflammation and oxidative stress, reduced neurotrophic factors, ageing, nutritional deficits.

Question 6

Neurotransmitters (NTs)

Answer 6

Neurotransmitters (NTs) = chemical messengers released from a pre-synaptic terminal, causing an excitatory or inhibitory effect on the post synaptic cell.
* NT imbalances are the result of an underlying cause , and are often associated with multifactorial issues, such as inadequate nutrition, high stress, toxicity, SNPs, poor digestive health, drug use, etc.

Question 7

NT Synthesis

Answer 7

NT synthesis is from specific substrates (e.g., amino acids) using nutritional co factors (e.g., vitamin B6).

Question 8

Methylation

Answer 8

Methyl folate for biopterin (BH4) co-factor for serotonin and dopamine).
SAMe (methyl folate and B12) for melatonin and adrenaline.

Question 9

Neurotransmitter balance

Answer 9

NTs need to be inactivated and removed via enzyme breakdown, diffusion or reabsorption. Reuptake transporters are important mechanisms (targeted by e.g., SSRIs).

Question 10

Key enzymes

Answer 10

• Monoamine oxidase (MAO) breaks down monoamines: serotonin, adrenaline, noradrenaline and dopamine.
• Catechol O methyl transferase (COMT) breaks down adrenaline, noradrenaline and dopamine using a methyl group from SAMe.