96 replies to this topic

[Kevn]

Hmmm... a slight change of vision? I haven't noticed any change of vision, and would be concerned if I did. (I take two a day, and have been for a few months.) Gen6k, why do you say "slight change of vision," and/or what particular changes in your vision have you noticed?

[motorcitykid]

Is it a reach to think that magnesium threonate might cause glycation?



Mol Cell Biochem. 1996 Jun 21;159(2):123-7.
Studies on L-threose as substrate for aldose reductase: a possible role in preventing protein glycation.
Devamanoharan PS, Varma SD.
Abstract
L-threose is a product of ascorbate oxidation and degradation. By virtue of its free aldehyde group it can form Schiff-bases with tissue proteins, altering their normal function. In this study, we have examined the possibility of its detoxification to L-threitol by aldose reductase in the lens. The rat lens enzyme present in fresh homogenate as well as after 100 fold purification was found to utilize L-threose with a km of 7.1 x 10(-4) M. The specificity of the reaction was affirmed by its inhibition with sorbinil and quercetin, the well known aldose reductase inhibitors. Further studies on the role of this enzyme in preventing toxicity due to degradation products of ascorbate are in progress.
PMID: 8858562
→ source (external link)

Exp Eye Res. 1994 Jun;58(6):665-74.
Ascorbic acid glycation: the reactions of L-threose in lens tissue.
Ortwerth BJ, Speaker JA, Prabhakaram M, Lopez MG, Li EY, Feather MS.
Abstract
L-Threose is a significant degradation product of ascorbic acid at pH 7.0 in the presence of oxygen. When compared to several other ascorbate-derived degradation products, it had the greatest ability to glycate and crosslink lens proteins in vitro. To determine whether L-threose was formed in the lens, the sugars in a TCA-soluble extract from human lenses were reduced to polyols with NaBH4, acetylated and analysed by gas-liquid chromatography. The threitol levels measured were 3.4 +/- 0.8 micrograms per lens (n = 4). GC-MS measurements made after reduction with NaBD4 indicated that threitol, but little or no threose, was originally present in the human lens. Rat lenses were incubated with [1-13C]D-threose for 24 hr, and considerable D-threitol formation was seen by NMR spectroscopy. Analysis of the lenses after medium removal showed that only [1-13C]threitol was present within the lenses indicating a rapid reduction of threose within the lens, presumably by aldose reductase. Assays with human recombinant aldose reductase and with human lens cortical and nuclear extracts all exhibited sorbinil-inhibitable aldose reductase activity with L-threose as substrate. This was confirmed by incubating a preparation of [1-14C]L-tetrose (a mixture of 40% L-threose and 45% L-erythrose) with both the pure aldose reductase and crude lens extracts followed by the subsequent identification of the [1-14C]L-threitol formed by thin layer chromatography. L-Threose degrades very slowly in 0.1 M phosphate buffer at pH 7.0, but the addition of a four-fold excess of N alpha-acetyl-L-lysine accelerated the rate of disappearance of threose 30-fold, indicating a rapid glycation reaction. When [1-14C]L-tetrose was incubated with a complete bovine lens homogenate, a linear incorporation into protein was observed over a 24 hr period. Increasing levels of lens extract exhibited increasing incorporation into protein. These data confirm a rapid reactivity of L-threose with lens protein and argue that glycation would occur in vivo in spite of the presence of aldose reductase.

[Pirate]

Is anyone still taking magnesium l-threonate long term? How does it compare to "lesser" forms? Is the alleged mental clarity worth up scaling from a "lesser" form?

I've been taking it for about 3 weeks. It helps with falling sleep and staying asleep for sure, and with constipation for sure too. But, I'm guessing I can get these benefits from magnesium elsewhere.

[norepinephrine]

Yeah, those are the pretty standard benefits that all magnesium supplements generally have.

After viewing ScienceGuy's thread on the matter, I think I'm gonna stick with regular old magnesium malate and glycinate. Maybe taurate too.

[anagram]

zinc histidine complex is taken up by cells in a very controlled manner, as if this was the form of zinc that our bodies are supposed to absorb.

http://www.ncbi.nlm....pubmed/19782114

Perhaps magnesium theronate is naturally the form of magnesium cells uptake.

[eon]

magnesium l-threonate has been available since I first heard of it last year. It is expensive. Just wondering if the magnesium threonine is the same as "threonate". magnesium threonine is said to be an amino acid. Not sure what magnesium l-threonate is exactly but they seem to share the same "carrier" which is threonic acid. Correct me if I'm wrong. I've seen the threonine in bulk powder form but the threonate only in pill form.

[brosci]

Is it a reach to think that magnesium threonate might cause glycation?



Mol Cell Biochem. 1996 Jun 21;159(2):123-7.
Studies on L-threose as substrate for aldose reductase: a possible role in preventing protein glycation.
Devamanoharan PS, Varma SD.
Abstract
L-threose is a product of ascorbate oxidation and degradation. By virtue of its free aldehyde group it can form Schiff-bases with tissue proteins, altering their normal function. In this study, we have examined the possibility of its detoxification to L-threitol by aldose reductase in the lens. The rat lens enzyme present in fresh homogenate as well as after 100 fold purification was found to utilize L-threose with a km of 7.1 x 10(-4) M. The specificity of the reaction was affirmed by its inhibition with sorbinil and quercetin, the well known aldose reductase inhibitors. Further studies on the role of this enzyme in preventing toxicity due to degradation products of ascorbate are in progress.
PMID: 8858562
→ source (external link)

Exp Eye Res. 1994 Jun;58(6):665-74.
Ascorbic acid glycation: the reactions of L-threose in lens tissue.
Ortwerth BJ, Speaker JA, Prabhakaram M, Lopez MG, Li EY, Feather MS.
Abstract
L-Threose is a significant degradation product of ascorbic acid at pH 7.0 in the presence of oxygen. When compared to several other ascorbate-derived degradation products, it had the greatest ability to glycate and crosslink lens proteins in vitro. To determine whether L-threose was formed in the lens, the sugars in a TCA-soluble extract from human lenses were reduced to polyols with NaBH4, acetylated and analysed by gas-liquid chromatography. The threitol levels measured were 3.4 +/- 0.8 micrograms per lens (n = 4). GC-MS measurements made after reduction with NaBD4 indicated that threitol, but little or no threose, was originally present in the human lens. Rat lenses were incubated with [1-13C]D-threose for 24 hr, and considerable D-threitol formation was seen by NMR spectroscopy. Analysis of the lenses after medium removal showed that only [1-13C]threitol was present within the lenses indicating a rapid reduction of threose within the lens, presumably by aldose reductase. Assays with human recombinant aldose reductase and with human lens cortical and nuclear extracts all exhibited sorbinil-inhibitable aldose reductase activity with L-threose as substrate. This was confirmed by incubating a preparation of [1-14C]L-tetrose (a mixture of 40% L-threose and 45% L-erythrose) with both the pure aldose reductase and crude lens extracts followed by the subsequent identification of the [1-14C]L-threitol formed by thin layer chromatography. L-Threose degrades very slowly in 0.1 M phosphate buffer at pH 7.0, but the addition of a four-fold excess of N alpha-acetyl-L-lysine accelerated the rate of disappearance of threose 30-fold, indicating a rapid glycation reaction. When [1-14C]L-tetrose was incubated with a complete bovine lens homogenate, a linear incorporation into protein was observed over a 24 hr period. Increasing levels of lens extract exhibited increasing incorporation into protein. These data confirm a rapid reactivity of L-threose with lens protein and argue that glycation would occur in vivo in spite of the presence of aldose reductase.

Bump.

 

I remember reading about this glycation concern a while back.  Is this a realistic issue with Mg threonate at typical dosages?