What is Malic acid?
Malic acid is a naturally occurring organic acid that
plays a role in the complex process of deriving ATP, the energy currency that
runs the body, from food. It is synthesized in the body through the citric acid
cycle.
Malic acid importance to the production of energy in the body during both
aerobic and anaerobic conditions is well established.
Malic acid, an alpha-hydroxy organic acid, is sometimes referred to as a
fruit acid. This is because
Malic acid is found in apples and other fruits.
Malic acid is also found in plants and animals, including humans. In fact,
Malic acid, in
the form of its anion malate, is a key intermediate in the major biochemical
energy-producing cycle in cells known as the citric acid or Krebs cycle located
in the cells' mitochondria.
Malic acid, also known as apple acid, hydroxybutanedioic acid and
hydroxysuccinic acid, is a chiral molecule. The naturally occurring stereoisomer
is the L-form. The L-form is also the biologically active one. There is some
preliminary evidence that Malic acid, in combination with magnesium, may be
helpful for some with fibromyalgia.
Malic acid sold as a supplement is mainly
derived from apples and, therefore, is the L-form. L- Malic acid has the
following chemical structure.
Mechanism of Malic acid
Malic acid is absorbed from the gastrointestinal tract from whence
Malic acid
is transported via the portal circulation to the liver. There are a few enzymes
that metabolize
Malic acid. Malic enzyme catalyzes the oxidative decarboxylation
of L-malate to pyruvate with concomitant reduction of the cofactor NAD+
(oxidized form of nicotinamide adenine dinucleotide) or NADP+ (oxidized form of
nicotinamide adenine dinucleotide phosphate). These reactions require the
divalent cations magnesium or manganese. Three isoforms of malic enzyme have
been identified in mammals: a cytosolic NADP+-dependent malic enzyme, a
mitochondrial NADP+-dependent malic enzyme and a mitochondrial NAD(P)+-dependent
malic enzyme. The latter can use either NAD+ or NADP+ as the cofactor but
prefers NAD+. Pyruvate formed from malate can itself be metabolized in a number
of ways, including metabolism via a number of metabolic steps to glucose. Malate
can also be metabolized to oxaloacetate via the citric acid cycle. The
mitochondrial malic enzyme, particularly in brain cells, may play a key role in
the pyruvate recycling pathway, which utilizes dicarboxylic acids and
substrates, such as glutamine, to provide pyruvate to maintain the citric acid
cycle activity when glucose and lactate are low.
Clearly, the metabolism of
Malic acid is complex and what any of the above
has to do, if anything, with
Malic acids' putative activity in those with
fibromyalgia is entirely unclear.
Malic acid is both derived from food sources and synthesized in the body
through the citric acid cycle.
Malic acid
importance to the production of energy in the
body during both aerobic and anaerobic conditions is well established. Under
aerobic conditions, the oxidation of malate to oxaloacetate provides reducing
equivalents to the mitochondria through the malate-aspartate redox shuttle.
During anaerobic conditions, where a buildup of excess of reducing equivalents
inhibits glycolysis,
Malic acid's simultaneous reduction to succinate and
oxidation to oxaloacetate is capable of removing the accumulating reducing
equivalents. This allows
Malic acid to reverse hypoxia's inhibition of
glycolysis and energy production. This may allow
Malic acid to improve energy
production in Primary fibromyalgia (FM), reversing the negative effect of the
relative hypoxia that has been found in these patients.
Important benefits of Malic acid
supplementation can include:
Fibromyalgia.
Chronic Fatigue Syndrome.
Hypoxia-related conditions (respiratory and circulatory
insufficiency)
Many in the medical industry believe that
Malic acid may be beneficial when used
in connection with fibromyalgia. However, results have been mixed in studies of
Malic acid's possible effects in those with fibromyalgia. In one study,
fibromyalgia patients were randomized to receive a combination of 200 milligrams
of
Malic acid and 50 milligrams of magnesium per tablet (three tablets twice a
day) or placebo for four weeks. This was followed by a six-month, open-label
trial with dose escalating up to six tablets twice a day. Outcome variables were
measures of pain and tenderness, as well as functional and psychological
measures.
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