Multiple stressors and the response of vascular endothelial cells: the effect of aging and diabetes.
BACKGROUND
The present study examined the effects of local heat, global heat, and the interaction between these two endothelial stressors on the blood flow of the skin of the foot in people who are older and who have diabetes.


METHODS
Subjects who were older (mean age 64.2 +/- 5.9 years) and were younger (mean age 25.7 +/- 2.9 years) and subjects who had diabetes (mean age 62 +/- 5.9 years, mean duration 13.2 +/- 9.1 years) participated. Subjects were exposed to three global temperatures (16 degrees C, 24 degrees C, and 32 degrees C), and the blood flow response was recorded on the foot with a laser Doppler flow meter for 30 s following applications of local heat (30 degrees C, 33.5 degrees C, and 37 degrees C) using a Peltier junction to clamp the skin for 2 min.


RESULTS
All three groups significantly increased blood flow from the 16-24 degrees C environments for the 37 degrees C application of local heat (P(Younger) = 0.02, P(Older) = 0.02, P(Diabetes) = 0.01). Those with diabetes and those who were older only increased blood flow 5% and 6% from the 24-32 degrees C environment, which was not statistically significant (P(Older) = 0.12, P(Diabetes) = 0.14).


CONCLUSIONS
There appears to be considerable blood flow reserve in younger subjects to tolerate heat stress. In contrast, older subjects and those with diabetes reach a critical level after which additional heat does not cause in increase in blood flow.
McLellan
Katie
K
Department of Physical Therapy, School of Allied Health Professions, Loma Linda University, Loma Linda, California 92350, USA.
Petrofsky
Jerrold S
JS
Zimmerman
Grenith
G
Prowse
Michelle
M
Bains
Gurinder
G
Lee
Scott
S
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001783:Blood Flow Velocity; D003920:Diabetes Mellitus / Q000503:physiopathology*; D004730:Endothelium, Vascular / Q000254:growth & development* / Q000503:physiopathology*; D006358:Hot Temperature; D006801:Humans; D008875:Middle Aged; D012016:Reference Values; D012867:Skin / Q000098:blood supply*; D012881:Skin Temperature / Q000502:physiology*; D013696:Temperature; D055815:Young Adult