The effects of chromium chloride, chromium nicotinate, and chromium picolinate on insulin internalization in cultured rat skeletal muscle cells was examined. Insulin internalization was markedly increased in cells cultured in a medium that contained chromium picolinate and the increased internalization rate was accompanied by a marked increase in the uptake of both glucose and leucine. The effect was specific for chromium picolinate since neither zinc picolinate nor any of the other forms of chromium tested was effective. The increased insulin internalization rate may result from an increase in membrane fluidity since chromium picolinate and to a lesser extent, chromium nicotinate, increased the membrane fluidity of synthetic liposomal membranes. The first rodent longevity study with the insulin-sensitizing nutrient chromium picolinate has reported a dramatic increase in both median and maximal lifespan.
Recent studies highlight the physiological role of insulin as a modulator of brain function.
Since both the pineal gland and thymus are dependent on insulin activity, chromium may aid their function as well. Thus, the longevity effect of chromium picolinate may depend primarily on delay or reversal of various age-related changes in the body's hormonal and neural milieu. A more general strategy of hypothalamic 'rejuvenation' is proposed for extending healthful lifespan. With these precedents, we treated adult rats with deprenyl for 3 weeks in order to get further insight in the mechanism by which deprenyl exerts such actions. We then studied the cellular expression of TH mRNA by in situ hybridization.