Vitamins, I learned them, but immediately forgot them. They were first dropped in the middle of metabolism, which, as a whole, went in one ear until the test and then promptly proceeded out the other ear. They were sprinkled into the curriculum through the rest of the year and popped up in different blocks in the first year, like neuro, renal, etc. So in my time off over the summer there might be some value in committing some of these vitamin guys to memory. Vitamins as a whole seemed to be irrelevant, stand alone pieces of information that when it came to learning them, it seemed like something that a superficial knowledge of them would be sufficient for tests and potentially the rest of my career.(I know this might sound bad but that type of thinking was something I went back and forth on frequently over my first year.) So practically speaking if someone were to ask me “what are vitamins for?” I would probably answer vaguely the B vitamins, are involved in making energy/metabolism(as cofactors), and there other vitamins that act as signaling messengers. My goal would be to avoid nuance, but if I got asked further I would have to admit I don’t know the complexities. So these posts will hopefully help us come to a better understanding of vitamins. So let’s start with the first of the B vitamins, then progress though A,B,C,D,E and K vitamins.

B1 – or thiamine, is essential for the function of a few enzymes used in a couple metabolism pathways. For class we needed to know that thiamine was a cofactor for the 

• alpha-Ketoglutarate dehydrogenase
• pyruvate dehydrogenase which links glycolysis to the TCA cycle

First Aid also lists transketolase, and branched chain ketoacid dehydrogenase listed as enzymes for which B1 is a cofactor. 

There are a few diseases that present with thiamine deficiency as a result of alcoholism and fad diets. 

• Wernicke encephalopathy – acute and reversible, like threatening, neurologic
  • reversible – Treat with thiamine injections
  • Symptoms include – nystagmus, ataxia, ophthalmoplegia and confusion

• Korsakoff syndrome where alcoholism causes an increase thiamine excretion and decrease in thiamine uptake in the small intestine
  • Irreversible
  • Symptoms include – alcohol induced amnesia disorder, confabulation is the sign/buzzword I saw on a test.

The mnemonic COAT RACK might be helpful to remember the symptoms of Wernicke and Korsakoff respectively.

• Wernicke encephalopathy symptoms:
  • Confusion 
  • Ophthalmoplegia
  • Ataxia
  • Thiamine deficiency

• Korsakoff symptoms:
  • Retrograde amnesia
  • Anterograde amnesia
  • Confabulation!
  • Korsakoff disease

The reason a thiamine deficiency is related to a decrease in brain function is due to the fact the brain is heavily dependent upon glucose for energy. The fundamental idea is if there is not enough glucose the brain doesn’t work as well. While the patient will have generalized confusion, the mammillary bodies are affected and are responsible for the patient’s amnesia. The mamillary bodies play a key role in the Papez circuit in the brain which is a loop for memory and learning the information in the mammillary bodies goes to the anterior thalamus, through the cingulate gyrus through the entorhinal cortex, through the amygdala and back through the fornix in to the mammillary glands again and the circuit continues. 

As an aside: when I was learning neuroanatomy nothing clicked for me until I started learning things in the context of how it relates to the thalamus. I was able to work the different thalamic nuclei backward and forwards which helped me a ton. 

Dry and wet beriberi

• Dry beriberi is a polyneuropathy with symmetric muscle wasting in the extremities

• Wet beriberi is high output cardiac failure – with dilated cardiomyopathy
  • This might be a bit contradictory on the surface, how can it be high-output cardiac failure? I believe it’s important to focus on the decrease in peripheral resistance that occurs with wet beriberi, as the key factor. If you see a significant decrease in peripheral resistance, a weakened heart can still have high-output in spite of the fact that it’s failing. 

I used osmosis, First Aid, and Step-up to medicine as references to help make this post