d-chiro-Inositol is absorbed but not synthesised in rodents

Abstract

d-chiro-Inositol (DCI) and pinitol (1D-3-O-methyl-chiro-inositol) are distinctive inositols reported to possess insulin-mimetic properties. DCI-containing compounds were abundant in common laboratory animal feed. By GC-MS of 6 M-HCl hydrolysates, Purina Laboratory Rodent Diet 5001 (diet 5001) contained 0.23% total DCI by weight with most found in the Lucerne and soy meal components. In contrast, only traces of l-chiro-inositol were observed. The DCI moiety was present in a water-soluble non-ionic form of which most was shown to be pinitol. To measure the absorption of dietary inositols, rats were fed diet 5001 in a balance study or given purified pinitol or [2H6]DCI. More than 98% of the total DCI fed to rats as diet 5001, purified pinitol or [2H6]DCI was absorbed from the gastrointestinal tract. Rats chronically on diet 5001 consumed 921 μmol total DCI/kg body weight pet d but excreted less than 5.3% in the stool and urine, suggesting that the bulk was metabolized. The levels of pinitol or DCI in plasma, stool, or urine remained relatively stable in mice fed Purina PicoLab® Rodent Diet 20 5053 over a 5-week period, whereas these values declined to very low levels in mice fed a pinitol/DCI-deficient chemically-defined diet. To test whether DCI was synthesized or converted from myo-inositol, mice were treated with heavy water or [2H6]myo-inositol. DCI was neither synthesized endogenously from 2H-labelled water nor converted from [2H6]myo-inositol. DCI and pinitol in rodents appear to be derived solely from the diet.

Decreased myo-inositol to chiro-inositol (M/C) ratios and increased M/C epimerase activity in PCOS theca cells demonstrate increased insulin sensitivity compared to controls

“…In this connection it is important to point out that the presence of the myo-inositol to chiro-inositol epimerase has been questioned in a recent paper by Lin, Gopalan and Ostlund entitled, "D-chiro-inositol is Absorbed but not Synthesized" [45]. The authors fed rats a chiro-inositol free diet for 10 or 12 weeks and then tested for chiro-inositol synthesis with heavy water or labeled myo-inositol.…”

d-chiro-Inositol Attenuates Epinephrine-stimulated Hepatic Glucose Output in the Isolated Perfused Liver Independently of Insulin

“…Circulating levels of DCI following DCI administration in rat models of diabetes have not been reported so direct comparison with the concentration of DCI (200 μM) used in our perfusion experiments is not possible. In nondiabetic rats endogenous circulating plasma levels of DCI are maintained within the low micromolar range and derived almost exclusively from standard chow diets, which are comparatively rich in DCI content [ 13 ] . It is less clear what circulating DCI levels are in diabetic rats as renal excretion of DCI is selectively increased compared to the nondiabetic state [ 14 ] .…”

Is prenatal myo‐inositol deficiency a mechanism of CNS injury in galactosemia?

“…PtdIns-4,5-P 2 and Ins-1,4,5-P 3 Calcium and protein kinase C signaling (Nishizuka 1988 (Larner et al 2003;Lin et al 2009) Ins-1,2,3,4,5,6-P 6 Endogenous iron "chelation" (Hawkins et al 1993;Irvine 2005) Fig. 3 The two known roles of myo-inositol (Ins) in mammalian physiology and the key biochemical pathways are depicted.…”