The phrasing of the title and paper steer the interpretation towards reducing cysteine as a method for increasing weight loss, however I think that the much more interesting takeaway is this:
> Notably, restoration of up to 75% cystine levels in the diet of Cth−/− CysF mice that were undergoing weight loss was sufficient to completely rescue the body weight
This might indicate that cysteine depletion could be one mechanism present in some wasting diseases, and that strategic supplementation of cysteine may be beneficial in reducing excessive weight loss in such diseases. I would be quite interested to see future research in this area.
jdnier · 20h ago
An overview of other studies investigating cysteine and glycine sources and effects (from 2023; video or transcript):
Cysteine is also an irreplaceable building block of vital proteins required to sustain life. It’s unclear if there is any potential benefit of applying these findings to the problem of human weight loss or fitness.
gus_massa · 20h ago
I agree, for example Pepsin[1] that is the protein inside the stomach that split proteins has Cysteine [2]
> Pepsin forms three between the sulfur atoms of cysteine residues in the peptide chain which hold important roles in the folding of the protein and stabilizing the two domains
Cysteine is not an essential amino acid. Humans can synthesize it from methionine.
nkmnz · 12h ago
These mice were GMO’d to be incapable of synthesising cysteine.
bell-cot · 18h ago
Wikipedia's disclaimers on that: "Cysteine can usually be synthesized by the human body under normal physiological conditions if a sufficient quantity of methionine is available."
User23 · 16h ago
I would make a stronger statement and say that this belongs squarely on the effect and not the cause side.
I could be wrong, but I doubt it. Amino acid depletion sounds way more likely to be due to some kind of disruption in homeostasis rather than dietary intake.
poirot2 · 18h ago
Funny because cysteinuria doesn’t do this (pee out cysteine)
biomcgary · 16h ago
Cysteine plays a key role in redox metabolism and removing reactive oxygen species (ROS). During brown fat burning, high flux of electrons increases the NADH/NAD⁺ and FADH₂/FAD ratios — shifting redox state toward a more reduced environment, which is exactly what you would need if deprived of cysteine.
zajio1am · 21h ago
(In mice)
mbil · 20h ago
This 2012 study in humans says
> Since this was also a noninterventional study, two possibilities for interpretation of the findings were either that a high cysteine somehow promotes obesity or that obesity influences cysteine turnover, thereby raising plasma tCys.
"Systemic cysteine depletion in mice causes lethal weight loss"
I didn't read much after that
dr_kiszonka · 19h ago
Maybe you should have.
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jostmey · 20h ago
This should only act as a clue into driving weight loss. Depleting of cysteine is severe. It would be depriving a team from writing html and discovery the code runs faster… very drastic imposition
RS-232 · 18h ago
Cysteine protease inhibitors could be used to reduce free cysteine available to cells. Some natural sources of those are papaya, kiwi, pineapple, fig, apples, and rice.
meew0 · 17h ago
Cysteine proteases are named after their reaction mechanism, which involves a key cysteine residue within the enzyme. It doesn't have anything to do with the amino acids in the cleaved proteins.
drob518 · 13h ago
So, does taking NAC make me fat? If I stop taking NAC, will it help me lose weight?
derbOac · 8h ago
Another linked article suggests that NAC administration if anything causes weight loss, and has a lot of opposite effects as cysteine. I don't think they're interchangeable.
drob518 · 36m ago
Interesting. I missed that.
nkmnz · 12h ago
According to the article, you’ll lose so much weight that you need euthanasia if you stop taking NAC - but only if you’re also a mice that also happens to be genetically modified to not produce any Cysteine biologically. Oh, and you shouldn’t eat anything containing cysteine naturally.
drob518 · 10h ago
Gotcha. So basically I’m going to be fat no matter what, you’re saying.
burnt-resistor · 3h ago
If only there were NAC that doesn't stink opening the bottle.
> Notably, restoration of up to 75% cystine levels in the diet of Cth−/− CysF mice that were undergoing weight loss was sufficient to completely rescue the body weight
This might indicate that cysteine depletion could be one mechanism present in some wasting diseases, and that strategic supplementation of cysteine may be beneficial in reducing excessive weight loss in such diseases. I would be quite interested to see future research in this area.
https://nutritionfacts.org/hnta-video/how-to-get-less-cystei...
> Pepsin forms three between the sulfur atoms of cysteine residues in the peptide chain which hold important roles in the folding of the protein and stabilizing the two domains
[1] https://en.wikipedia.org/wiki/Pepsin
[2] https://biology.kenyon.edu/BMB/jsmol2021/Cat_Marko/index.htm...
I could be wrong, but I doubt it. Amino acid depletion sounds way more likely to be due to some kind of disruption in homeostasis rather than dietary intake.
> Since this was also a noninterventional study, two possibilities for interpretation of the findings were either that a high cysteine somehow promotes obesity or that obesity influences cysteine turnover, thereby raising plasma tCys.
https://onlinelibrary.wiley.com/doi/full/10.1038/oby.2011.93
I didn't read much after that
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