C. Kirschbaum et al., EFFECTS OF FASTING AND GLUCOSE-LOAD ON FREE CORTISOL RESPONSES TO STRESS AND NICOTINE, The Journal of clinical endocrinology and metabolism, 82(4), 1997, pp. 1101-1105
The availability of energy appears to exert important regulatory funct
ions in pituitary-adrenal stress responses. In two studies, the effect
s of short-term fasting and subsequent glucose administration on the f
ree cortisol response to psychological stress and nicotine consumption
were investigated. Study 1: After fasting for 8-11 h, healthy young m
en ingested either 100 g glucose (n = 13) or water (n = 12). One hour
later they were exposed to a psychosocial stress task (Trier Social St
ress Test). A third group also ingested 100 g glucose, but they were n
ot exposed to any additional treatment (n = 10). Capillary blood gluco
se levels were in the lower euglycemic range before and significantly
elevated after the glucose load (64.9 +/- 9.8 vs. 162.5 +/- 43.5 mg/dL
; F = 149.04, P < 0.001). Although glucose load per se did not affect
free cortisol levels, psychosocial stress induced a large cortisol res
ponse in glucose-treated subjects. In contrast, fasted subjects who re
ceived tap water did not respond to the Trier Social Stress Test with
significant changes in cortisol levels (F = 6.27, P < 0.001). Both gro
ups responded with a similar increase in heart rates (F = 33.53, P < 0
.001) with no statistically significant difference between glucose and
water-treated subjects. Study 2: Twelve habitual smokers received 100
g glucose or tap water after fasting for at least 8 h on two separate
sessions (cross-over, random sequence). Forty-five min after glucose/
water ingestion, they smoked two cigarettes with a nicotine content of
1.0 mg/cigarette. Subjects were euglycemic before smoking, with a sig
nificant rise of glucose levels after consumption of 100 g glucose (64
.4 +/- 8.3 vs. 143.5 +/- 40.0 mg/dL; F = 40.25, P < 0.001). As in Exp
1, subjects showed a substantially larger free cortisol response to ni
cotine under glucose load compared with water load (F = 4.91, P < 0.00
1). From these data we conclude that the free cortisol response to sti
mulation is under significant control of centers responsible for monit
oring energy availability. Low glucose levels appear to inhibit adreno
cortical responsiveness in healthy subjects. In agreement with results
from animal studies, the present results suggest that ready access to
energy is a prerequisite for hypothalamus-pituitary-adrenal stress re
sponses.