Effects of a single exercise bout on insulin sensitivity in black and white individuals.
BACKGROUND
Previous research suggests non-Hispanic blacks (blacks) are more insulin resistant than non-Hispanic whites (whites). Physical activity can play an important role in reducing insulin resistance. However, it is unknown whether racial differences exist in response to exercise. Therefore, the purpose of this study was to compare metabolic responses to a single bout of exercise in blacks and age-, sex-, and body mass index-matched whites.


METHODS
Whole-body insulin sensitivity, glucose storage, glucose oxidation, and respiratory exchange ratio (RER) were assessed during a hyperinsulinemic-euglycemic clamp in normoglycemic blacks (n = 11) and whites (n = 10). Outcome measures were evaluated in a sedentary control condition and 12 h after treadmill walking at 75% of maximal heart rate for 75 min.


RESULTS
In the control condition, there were no differences in insulin sensitivity between blacks and whites (P = 0.54). During the clamp, glucose oxidation and insulin-stimulated RER values were significantly higher in blacks compared with whites (P = 0.04 and P < 0.01, respectively). Despite similar RER values during exercise, RER values at 60, 90, and 120 min after exercise in blacks were also significantly higher compared with whites (P < 0.05). After exercise, there were no significant improvements in insulin sensitivity (P = 0.57) or glucose storage (P = 0.42) in blacks or whites; however, glucose oxidation was significantly lower in both racial groups (P < 0.05).


CONCLUSIONS
These data suggest that insulin sensitivity is similar in blacks and age-, sex-, and body mass index-matched whites, but the glucose disposal pathways (storage vs. oxidation) are somewhat different. Compared with whites, blacks appear to have a greater capacity to increase glucose oxidation immediately after exercise and during insulin stimulation.
Hasson
Rebecca E
RE
University of Massachusetts Amherst, Department of Kinesiology, Amherst, Massachusetts 01003, USA.
Granados
Kirsten
K
Chipkin
Stuart
S
Freedson
Patty S
PS
Braun
Barry
B
D000293:Adolescent; D000328:Adult; D044383:Black People; D001786:Blood Glucose / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism; D007333:Insulin Resistance / Q000208:ethnology* / Q000502:physiology*; D008297:Male; D013997:Time Factors; D044465:White People; D055815:Young Adult
D001786:Blood Glucose; D007328:Insulin