Effect of nutrients on plasma corticosteroid concentration in cold-stressed rats

Little is known about the mechanisms as to how nutrients affect plasma corticosteroids in cold-stressed and starved animals. Therefore, cold-stressed rats (maintained at 7 degrees C) were fasted (control) or fed a balanced diet (casein 20 wt%, fat 5 wt%, starch 70 wt% and vitamin-mineral premix 5 wt%) or the following dietary nutrients for 72 h: casein, lard, starch, glycerol, stearic acid, leucine or glutamic acid. The animals were then killed and plasma corticosteroid concentrations (PCC) were determined. PCC were significantly reduced (p < 0.05) in cold-stressed animals fed a balanced diet (16.95 micrograms/100 ml plasma) compared to the fasted cold-stressed controls (FCSC) (24.16 micrograms/100 ml plasma). Additionally, corticosteroid concentrations (micrograms/100 ml plasma) of animals fed the following specific nutrients were also significantly lower than the FCSC values: starch (15.53), lard (12.01), stearic acid (12.74), glycerol (13.32) and leucine (16.03). Casein and glutamic acid did not significantly alter plasma corticosteroid levels relative to the FCSC concentration. It is concluded that certain specific building blocks of nutrient classes, i.e. stearic acid or glycerol, can alter PCC to the same extent as the parent compound (lard), however the individual components of casein, a complex nutrient, i.e. leucine, a ketogenic amino acid, versus glutamic acid, a glycogenic amino acid, may elicit a different PCC effect.