Effects of Treatment with Chromium Picolinate on Peripheral Amino Acid Availability and Brain Monoamine Function in the Rat

Elemental chromium (Cr) is an essential micronutrient. It is required for optimal insulin activity and normal carbohydrate and lipid metabolism. Tri-valent chromium (Cr³⁺) is recommended for the treatment of diabetes and obesity. There is evidence that Cr³⁺ may have antidepressant properties, possibly by enhancement of monoamine function through its ability to increase amino acid transport to the brain. The aim of the present study was to investigate further the possible effects of Cr³⁺ treatment on peripheral amino acid availability and brain monoamine function in the rat. We undertook three studies in rats. The first was a time-course study in which animals were administered single doses of 50 mg/kg of Cr³⁺ picolinate and the second a dose-response study in which animals were given either 20 or 50 mg/kg Cr³⁺ picolinate versus vehicle alone via the intra-peritoneal route. In the third, animals were fed a diet containing Cr³⁺ picolinate (100 mg/kg) or a similar control diet for two weeks and were then sacrificed. Blood was sampled and brains were removed for later analysis. Results from the Cr³⁺ time-course study defined an optimal time for sampling of two hours after dosing. Results from the second study showed dose-related responses to Cr³⁺ treatment for a number of measured biochemical parameters including serum corticosterone.

In the sub-chronic treatment study Cr³⁺ significantly increased serum free tryptophan (TRP), non-esterified free fatty acids (NEFFAs), corticosterone, together with brain TRP, serotonin (5-hydroxytryptamine, 5-HT), noradrenaline (NA) and pineal melatonin. From other studies in our laboratory we have shown that Cr³⁺ treatment can modify brain 5-HT function, perhaps by altering the sensitivity of central 5-HT_2A receptors. The peripheral effect of Cr³⁺ picolinate treatments and their consequential central effect on increased serotonergic and noradrenergic function may suggest that Cr³⁺ could have some antidepressant-like actions. Future studies to confirm this are to be done.

Cr³⁺ picolinate - TRP - 5-HT - NA - Melatonin - NEFFAs - corticosterone

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