Copper and feel good hormones

This post is about peptide hormones that make us feel good. It is not about dopamine and serotonin… The copper enzyme Peptidylglycine α-Amidating Monooxygenase (PAM) is responsible for the clipping of peptides to form common hormones we know as vasopressin, oxytocin, α-MSH, and β-endorphin. [1]

How PAM works

PAM is actually two enzymes in one. PHM uses copper to tag with oxygen. PAL snips at the tagged carbon.

The top panel covers what a peptide bond is. The bottom panel describes how the dual function enzyme PAM tags and clips the peptide resulting in the N-terminal (butt) of glycine. This is just something to think about. Copper is required for the production of some very important peptide hormones. We still do not know why the C-terminal amidation is so important. Many think it neutralizes the charge and increases binding to the hormone receptor.

PAM^+/- mice are just messed up

A 2011 study found that mice with only one functional copy of the PAM gene, PAM^+/-, had increased anxiety and decreased cold tolerance. [2] Copper deficiency in wildtype mice mimicked these symptoms. Discussion was given to PAM sometimes ending up in the nucleus. Gene transcripts for copper handling proteins were found to be altered in two key locations: the heart and the pituitary gland. Note that Thyrotropin-releasing hormone (TRH) is released from hypothalamic neurons that act on neurons of the pituitary gland.. that product ACTH, that acts on the adrenal gland to release cortisol… All of these feeds back on TRH.

Why these mice felt anxious and whether the bad feelings were due to TRH-Gly getting stuck in the hypothalamus was not really a topic of discussion. Just that the hypothalamus connects to the pituitary gland brings us to the next topic.

PAM and amidated pituitary hormones

Some quick comments before getting into hard core science.

• Oxytocin is the cuddling a cute puppy or a baby peptide. It is involved in all aspects of making more of one’s own species…. or a suitable surrogate of another species.
• Vassopressin, also arginine vasopressin (AVP), is released by diurnal variations in sunline as well as changes in the osmolality (salt content) of the blood. AVP is similar to oxytocin, but does some very different things too such as increasing water channels in the kidney to aid in water absorption. The Wikipedia page on Vassopressin does a good job of comparing and contrasting AVP and oxytocin.
• α-Melanocyte stimulating hormone, or α-MSH, is what tells our melanocytes to start producing melanin in response to sunshine. Is α-MSH the “Sunshine on my shoulders makes me happy” hormone? Maybe yes, maybe no. α-MSH is cleaved from same precursor as
• Endorphins bind to the same receptors as opioid pain killers. Endorpins are the eating chocolate, listening to music, meditation, sex, laughter, and sunshine hormones.

Oxytocin

A pictorial overview of oxytocin throughout the lifespan of the animal.

A study from 1992 demonstrated that guinea pig dams made copper deficient (0.8 microgram Cu/g diet) required 0.5 to 6.2 U oxytocin to injections to induce delivery of pups. [4] Many of the pups died of internal hemorrhaging, possibly due to lack of lysyl oxidase crosslinking of collagen. [4] In Cu adequate dams, pup survival was at 79%, Only 28% of pups survived in copper deficient dams.

In another study pregnant rats were placed on the copper-deficient or copper-adequate treatment 7 days after mating. The “purified” diet contained 0.35 mg Cu/kg and 42 mg Fe/kg by chemical analysis. Offspring and dams on the copper-deficient treatment drank deionized water, whereas copper adequate treatment groups drank water that contained 20 mg Cu/L by adding CuSO₄ to the drinking water. [5] Decreased PAM activity showed up in the mid brains and atria of the heart. [5] We will not get into whether Cu(II) in drinking water is optimally bioavailable. Decreased superoxide dismutase SOD and cytochrome C oxidase CCO activity was noted.

Vasopressin aka AVP

The Yoshimura review made no mention of PAM being involved in AVP synthesis. They did state that AVP is made in the hypothalamus in response to stress. [5] The reader is invited to consult [6] for a comprehensive review of the tissue distribution of the three receptors of AVP and their physiological functioning. The Song and Albers (2018) review made the point that many rodent studies have demonstrated that oxytocin and AVP can bind to each others receptors, all of which are G-protein coupled receptors. [7] IF we can trust Wikipedia, AVPR1A couples with Gα_q/11, AVPR1B couples with Gα_q/11 , and AVPR2 with Gα_s, while the oxytocin receptor couples with Gα_q.

In summary, AVP and oxytocin are very similar in sequence and structure. They can bind to the same receptors. The oxytocin and AVPR1 rceptors have similar down stream signalling via PLC.

Pro opiomelanocortin

This gene contains many peptide hormones in one transcript. Then a protease comes and cleaves the new protein into many peptide hormones.

A short term copper deficient human study…

A 1998 human study investigated the effect of a low copper diet on plasma opioid peptides. In this study in 11 healthy young volunteers were fed foods low in copper but adequate in all other nutrients. [7]

1. 0.66 mg/day for 24 days (marginal Cu)
2. 0.38 mg/day for 42 days (low Cu) ↓ ceruloplasmin & plasma Cu, ACTH
3. 2.49 mg/day for 24 days (adequate Cu). ↑ ceruloplasmin & plasma Cu

TPlasma β-endorphin, Leu-enkephalin, Met-enkephalin, and Adrenocorticotropic hormone (ACTH), as measured by immunoassay, did not significantly change between the start and finish of each study period. [8] intake.

PAM^+/- mice and a mass spectrometry technique

Yes ground up pituitary glands were involved in these experiments. Not only were the masses of these peptides measured with mass spectrometry, but also the masses of the fragments of busted up peptides. This allowed the investigators to detect new modifications of the peptide hormones. Recall that JP is the joining peptide between

ManyC-terminal amidated peptides were detected. Just a few showed statistically significant change. It has been hard to pin down a function for the joining peptide. More interest seems to be in AVP in terms of cardiovascular health than emotional health.

Where PAM is expressed

In spite of PAM being involved in production of “fee good”hormones, it’s most abundantly expressed in the heart and a few other organs we are interested in This particular immunocytochemistry image of the heart from Protein Atlas looks like PAM is in some sort of vesicle. In spite of its abundance in the heart, its function is kind of hard to pin down. mRNA data indicates that PAM is comparatively abundance in the hypothalamus of the brain. The heart expression is kind of hard to ignore. There is an interest in measuring secreted PAM as an indicator of heart disease. A 96 well plate assay for detecting PAM activity in the serum has been developed by a company called Pam-t.com. [10]

References

1. Bousquet-Moore, D., Mains, R. E., & Eipper, B. A. (2010). Peptidylgycine α-amidating monooxygenase and copper: a gene-nutrient interaction critical to nervous system function. Journal of neuroscience research, 88(12), 2535–2545. PMC free article
2. Bousquet-Moore, D., Prohaska, J. R., Nillni, E. A., Czyzyk, T., Wetsel, W. C., Mains, R. E., & Eipper, B. A. (2010). Interactions of peptide amidation and copper: novel biomarkers and mechanisms of neural dysfunction. Neurobiology of disease, 37(1), 130–140. PMC free article
3. Lee, H. J., Macbeth, A. H., Pagani, J. H., & Young, W. S., 3rd (2009). Oxytocin: the great facilitator of life. Progress in neurobiology, 88(2), 127–151. PMC free article
4. Richmond VL. (1992) Oxytocin-induced parturition in copper-deficient guinea pigs. Lab Anim Sci. 1992 Apr;42(2):190-2. PMID: 1318454.
5. Prohaska, J. R., Gybina, A. A., Broderius, M., & Brokate, B. (2005). Peptidylglycine-alpha-amidating monooxygenase activity and protein are lower in copper-deficient rats and suckling copper-deficient mice. Archives of biochemistry and biophysics, 434(1), 212–220. PMC free article
6. Yoshimura, M., Conway-Campbell, B., & Ueta, Y. (2021). Arginine vasopressin: Direct and indirect action on metabolism. Peptides, 142, 170555. PMC free article
7. Song, Z., & Albers, H. E. (2018). Cross-talk among oxytocin and arginine-vasopressin receptors: Relevance for basic and clinical studies of the brain and periphery. Frontiers in neuroendocrinology, 51, 14–24. PMC free article
8. Bhathena SJ, Werman MJ, Turnlund JR. Opioid Peptides, Adrenocorticotrophic Hormone and Dietary Copper Intake in Humans. Nutr Neurosci. 1998;1(1):59-67.
9. Yin, P., Bousquet-Moore, D., Annangudi, S. P., Southey, B. R., Mains, R. E., Eipper, B. A., & Sweedler, J. V. (2011). Probing the production of amidated peptides following genetic and dietary copper manipulations. PloS one, 6(12), e28679. PMC free article
10. Kaufmann, P., Bergmann, A., & Melander, O. (2021). Novel insights into peptide amidation and amidating activity in the human circulation. Scientific reports, 11(1), 15791. PMC free article