Effects of chronic chromium picolinate treatment in uninephrectomized rat

Chromium picolinate [Cr(pic)3] is a nutritional supplement that is advocated as an adjuvant therapy for impaired glucose tolerance/type 2 diabetes because it improves glucose homeostasis. Because renal dysfunction is a major complication of type 2 diabetes, the potential impact of Cr(pic)3 on kidney function requires due consideration. This investigation takes added importance because the kidney is not only the principal route of elimination for chromium but also an organ that preferentially accumulates it. To avoid the confounding influence of chronic hyperglycemia, and its associated complications, we used the unilaterally nephrectomized (UNX) rat that shows impaired kidney function with age. We tested the hypothesis that chronic treatment of the UNX rat with Cr(pic)3 exacerbates the age-related decline in renal function. Accordingly, UNX rats were fed a diet lacking (eg, control; n=5) or containing 5 mg/kg of Cr(pic)3 (n=7) for 60 days. The treatment did not affect glucose tolerance as reflected by lack of any effect on changes in blood glucose concentration during glucose tolerance testing. Although nonfasting blood glucose concentrations were similar between the 2 groups, plasma insulin concentration was lower in the Cr(pic)3-treated group (P<.05), suggesting improved insulin sensitivity. Body weight, blood pressure, heart rate, daily food and fluid consumption, daily urinary fluid and electrolyte excretions, urine osmolality, and daily protein excretion were similar between the 2 groups before and during Cr(pic)3 treatment. Although renal excretory responses to acute administration of a 5% isotonic saline volume load were similar between the 2 groups, the Cr(pic)3-treated group displayed a more robust ability to excrete a 10% isotonic saline volume load, an effect primarily related to reduced tubular reabsorption of the filtered fluid and sodium loads. In conclusion, chronic Cr(pic)3 did not adversely affect renal function. Rather, the treatment improved the ability of the animal to dispose of an acute isotonic saline volume load, suggesting preservation of renal function in the UNX rat.