Myo-Inositol & D-Chiro-Inositol
Cyclohexanehexol
Myo-inositol, also known as inositol (cyclohexanehexol), is a cyclic carbohydrate with six hydroxyl groups. It has long been considered a B vitamin (vitamin B8). However, it is not considered an essential nutrient because it is formed from glucose. Each kidney produces about 2 g of myo-inositol per day, and the average dietary intake is 0.5–1.0 g/day. The liver and brain also synthesize myo-inositol, although in much smaller quantities compared to the kidneys. However, it is important to note that in the brain, myo-inositol levels reach concentrations 10 to 15 times higher than those in the blood. It is important to note that dietary caffeine intake increases the need for myo-inositol. Aging, antibiotic use, sugar intake, sodium deficiency, insulin resistance, and type 1 and type 2 diabetes increase the need for myo-inositol. Foods rich in inositol-forming substances, such as liver, grains, seeds, and beans, are not consumed in sufficient quantities. Therefore, from a nutritional point of view, our intake of inositol is much lower compared to what people should consume.
Myo-inositol and polycystic ovary syndrome: Polycystic ovary syndrome (PCOS) affects 5%–21% of women during their reproductive years. Insulin resistance is a common finding in patients with PCOS, regardless of body mass index (BMI). Indeed, approximately 70%–80% of women with PCOS and central obesity and 15%–30% of lean women with PCOS have insulin resistance and compensatory hyperinsulinemia.
Both myo-inositol and D-chiro-inositol are involved in intracellular insulin signaling and are also important for the oxidative utilization of glucose and its storage as glycogen.
The epimerase enzyme that converts myo-inositol to D-chiro-inositol is insulin-dependent, and this conversion is reduced in insulin-resistant tissues. In people with type 2 diabetes, there is a decrease in urinary D-chiro-inositol and an increase in urinary excretion of myo-inositol. Thus, a deficiency of myo-inositol or impaired function/expression of the enzyme that converts myo-inositol to D-chiro-inositol can lead to insulin resistance (which can further lead to a deficiency of D-chiro-inositol because the epimerase that converts myo-inositol to D-chiro-inositol is insulin-sensitive).
In a 12-week randomized controlled trial of 50 overweight women with polycystic ovary syndrome (PCOS), taking myo-inositol in the morning resulted in significant reductions in plasma LH (luteinizing hormone), prolactin, testosterone, insulin, and the LH:FSH (luteinizing hormone: follicle-stimulating hormone) ratio, and improved insulin sensitivity. The birth rate was also significantly improved with myo-inositol, and menstrual cycles were regulated in subjects with irregular cycles. In addition, Kamenov et al. found that myo-inositol improved ovulation, leading to higher pregnancy and delivery rates. A decrease in BMI and improvement in insulin resistance were also noted. This study also found that about 61.7% of patients with PCOS ovulated after taking myo-inositol. Several meta-analyses of randomized controlled trials have shown that myo-inositol monotherapy, and when combined with D-chiro-inositol, is effective in patients with PCOS.
Insulin-resistant states lead to increased urinary loss of myo-inositol, primarily due to glucose-mediated inhibition of myo-inositol reabsorption in the kidney. Decreased myo-inositol decreases D-chiro-inositol, with deficiency of both contributing to insulin resistance in skeletal muscle, liver, and fat cells. Myo-inositol is involved in fertility, oogenesis, embryogenesis, regenerative processes (transcriptional control, mRNA export, and DNA repair), and fat metabolism. Myo-inositol inhibits glucose absorption in the duodenum and reduces the rise in blood glucose.
Abnormalities in the ratio of myo-inositol to D-chiro-inositol in plasma and urine may be an early marker of insulin resistance and type 2 diabetes. Furthermore, myo-inositol deficiency worsens insulin resistance. Inositol compounds also reduce hyperglycemia in a dose-dependent manner and promote muscle glycogen storage.
The conversion of myo-inositol to D-chiro-inositol is severely impaired by insulin resistance in insulin-sensitive tissues (muscle, adipose tissue, and liver). Therefore, a low D-chiro-inositol: myo-inositol ratio may be a measure of insulin resistance. Indeed, low levels of D-chiro-inositol are typical in the urine and muscle tissue of patients with type 2 diabetes. Myo-inositol deficiency will reduce D-chiro-inositol levels and worsen insulin resistance. At sites of diabetic microvascular complications (kidney, nerve, eye), a simultaneous decrease in intracellular myo-inositol and accumulation of intracellular sorbitol are often observed, which is why myo-inositol supplementation is justified in patients diagnosed with diabetes.
Myo-inositol at a dose of 2 g twice daily reduces the incidence of gestational diabetes. These studies also noted reduced insulin requirements, late-term deliveries, and fewer episodes of neonatal hypoglycemia.
It is important that the preparation has a precisely defined ratio of myo-inositol to D-chiro-inositol, as they exert a synergistic effect, which is very important for the treatment of polycystic ovary syndrome, and the best preparations are those containing myo-inositol:D-chiro-inositol in a ratio of 40:1, which is satisfied by the preparation Ovarinova.
Myo-inositol should be considered in patients with insulin resistance, metabolic syndrome, type 1 diabetes, type 2 diabetes, PCOS, and in those with gestational diabetes or those at risk for it. Elevated glucose levels reduce myo-inositol levels in tissues and increase its breakdown and elimination by the kidneys. Myo-inositol has been used safely for decades in many studies in people with insulin resistance and polycystic ovary syndrome.