1. Quasi vitamins: myo-Inositol
Domina Petric, MD

2. Chemical nature
Myo-inositol is a water-soluble, hydroxylated, cyclic six-carbon compound (cis-1,2,3,5-trans-4,6-cyclohexanehexol).
It is the only one of the nine possible stereoisomeric forms of cyclohexitol with biological activity.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

3. Biosynthesis from glucose
Mammals can synthesize myo-inositol de novo ultimately from glucose.
Biosynthetic capacity has been found in kidney and other tissues in humans.
The biosynthesis involves the cyclization of glucose 6-phosphate to inositol 1-phosphate by inositol-1-phosphate synthase, followed by a dephosphorylation by inositol-1-phosphatase.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

4. inositol containing phospholipids
Dietary sources
myo-Inositol occurs in foods in three forms:
free myo-inositol
phytic acid
inositol containing phospholipids
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

5. The predominant form occurring in plant materials is phytic acid.
Dietary sources
The richest sources of myo-inositol are the seeds of plants (beans, grains and nuts).
The predominant form occurring in plant materials is phytic acid.
Most mammals have little or no intestinal phytase activity and phytic acid is poorly utilized as a source of either myo-inositol or phosphorus.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

6. Free myo-inositol predominates in brain and kidney.
Dietary sources
In animal products, myo-inositol occurs in free form as well as in inositol-containing phospholipids (primarily phosphatidylinositol).
Free myo-inositol predominates in brain and kidney.
Phospholipid inositol predominates in skeletal muscle, heart, liver and pancreas.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

7. Colostrum, 200-500 mg/liter Mature milk, 100-200 mg/liter
Human milk
Human milk is relatively rich in myo-inositol:
Colostrum, mg/liter
Mature milk, mg/liter
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

8. Vegetables Vegetable Myo-Inositol mg/g Asparagus 0,29-0,68 Green beans
0,55-1,93
White beans
2,83-4,40
Red beans
2,49
Broccoli
0,11-0,30
Cabbage
0,18-0,70
Carrot
0,52
Pea
1,16-2,35
Okra
0,28-1,17
Potato
0,97
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

9. Diary products, eggs and nuts
Diary product/eggs/nuts
Myo-inositol mg/g
Milk
0,04
Ice cream
0,09
Cheese
0,01-0,09
Whole egg
Egg yolk
0,34
Almond
2,78
Peanut
1,33-3,04
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

10. Fruits and cereals Fruits/cereals Myo-inositol mg/g Apple 0,10-0,24
Cantaloupe
3,55
Grape
0,07-0,16
Grapefruit
1,17-1,99
Orange
3,07
Peach
0,19-0,58
Pear
0,46-0,73
Strawberry
0,13
Watermelon
0,48
Rice
0,15-0,30
Wheat
1,42-11,5
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

11. Meats and fish Meats/fish Myo-Inositol mg/g Beef 0,09-0,37 Chicken
0,30-0,39
Lamb
0,37
Pork
0,14-0,42
Turkey
0,08-0,23
Beef liver
0,64
Chicken liver
1,31
Pork liver
0,17
Tuna
0,11-0,15
Trout
0,11
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

12. Absorption
The enteric absorption of free myo-inositol occurs by active transport.
The uptake of myo-inositol from the small intestine is virtually complete.
The enteric absorption of phytic acid depends on the ability to digest that form and on the amounts of divalent cations in the diet/meal.
Most mammals do not absorbe phytic acid.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

13. Transport
myo-Inositol is transported in the blood predominantly in the free form.
The normal circulating concentration of myo-inositol in humans is about 30 µM.
A small but significant amount of phosphatidylinositol (PI) is found in association with the circulating lipoproteins.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

14. Transport
Free myo-inositol is taken up by an active transport process in some tissues (kidney, brain) and by carrier-mediated diffusion in others (liver).
The active process requires Na+ and energy, and is inhibited by high levels of glucose.
Untreated diabetics show impaired tissue uptake and impaired urinary excretion of myo-inositol.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

15. Metabolism
Free myo-inositol is converted to PI within cells either by de novo synthesis by reacting with the liponucleotide cytidine diphosphate (CDP)-diacylglycerol, or by an exchange with endogenous PI.
Phosphatidylinositol can, in turn, be sequentially phosphorylated to the monophosphate (phosphatidylinositol 4-phosphate, PIP) and diphosphate (phosphatidylinositol 4,5-diphosphate, PIP2) forms by membrane kinases.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

16. Metabolism
In tissues, myo-inositol is found as the free form, as PI, PIP and PIP2.
The myo-inositol-containing phospholipids tend to be enriched in stearic acid (predominantly at the 1-position) and arachidonic acid (predominantly at the 2- position) in comparison with the fatty acid compositions of other phospholipids.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

17. Metabolism
The turnover of the myo-inositol phospholipids is accomplished intracellularly.
Phosphatidylinositol phosphates can be catabolized by cellular phosphomonoesterases (phosphatases), ultimately to yield PI.
In the presence of cytidine monophosphate, PI synthetase functions (in the reverse direction) to break down that form to yield CDP-diacylglycerol and myo-inositol.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

18. Metabolism
The kidney appears to perform most of the further catabolism of myo-inositol, first clearing it from the plasma and converting it to glucose and, then, oxidizing it to CO2 via the pentose phosphate shunt.
The metabolism of myo-inositol appears to be relatively rapid.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

19. Metabolic functions
The metabolically active form of myo-inositol is phosphatidylinositol, which is thought to have several physiologically important roles: ● Effecter of the structure and function of membranes ● Source of arachidonic acid for eicosanoid production ● Mediator of cellular responses to external stimuli
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

20. Health effects
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

21. Preterm infants
Three randomized, clinical trials have found inositol supplementation to improve survival and reduce retinopathy of prematurity, bronchial dysplasia and intraventricular hemorrhage.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

22. Psoriasis
A small, randomized clinical trial with psoriasis patients found supplementation with inositol to reduce the severity of symptoms.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

23. Psychiatric disorders
Because mood stabilizers such as lithium, valproate and carbamazepine function by the stabilization of inositol signaling, it has been suggested that inositol may have value in the treatment of depression and other psychiatric disorders.
11/17/2018
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc

24. Literature
Combs GF. The Vitamins. Fundamental Aspects in Nutrition and Health. Elsevier Inc
11/17/2018