Lipoic acid helped cells make their own glutathione by easing cysteine uptake
This 1997 lab study found that lipoic acid substantially raised reduced glutathione in several kinds of cultured human and animal cells. Once converted to its active form, it helped cells take up cysteine for making glutathione. In fresh human white blood cells it mainly restored cells that were short of glutathione rather than pushing healthy cells higher.
What they did
The researchers added lipoic acid to several types of cultured cells: human Jurkat T cells, human red blood cells, rat C6 glial cells, NB41A3 neuroblastoma cells and human peripheral blood lymphocytes, a type of white blood cell. They measured reduced glutathione and traced how lipoic acid produced its effect. They used flow cytometry, a method that measures individual cells, to look at thiol levels in fresh human lymphocytes.
What they found
Lipoic acid substantially increased reduced glutathione in the cells. This depended on cells converting it to dihydrolipoic acid, its reduced form, which then passed into the surrounding fluid and converted cystine into cysteine.
Cells take up cysteine readily through a different transporter from the one they use for cystine, which is weakly expressed in lymphocytes. This let the first enzyme of glutathione production work at its best. In fresh lymphocytes, lipoic acid mainly brought a subgroup of cells with very low thiol levels back to normal rather than raising levels above the usual range.
What it can't tell us
These were cells in a dish, and none were cartilage cells. The abstract does not give the concentrations used or how long the cells were treated. It does not show what lipoic acid taken by mouth does to glutathione in a person, let alone in cartilage.
Why it matters
This study explains one way lipoic acid could support glutathione: by helping cells get the cysteine they need to make it. The finding that it mainly restored depleted cells, rather than boosting normal ones, is an important limit on what it can be expected to do.
The paper
- Han D, Handelman G, Marcocci L et al. Lipoic acid increases de novo synthesis of cellular glutathione by improving cystine utilization. Biofactors 1997.
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