Racial differences in insulin resistance and mid-thigh fat deposition in postmenopausal women.
OBJECTIVE
To determine whether racial differences in insulin resistance between African American (AA) and white women exist in postmenopausal women and whether they are related to physical fitness and/or obesity.


METHODS
We studied 35 obese AA (n = 9) and white (n = 26) women of comparable maximal oxygen consumption, obesity, and age. Total body fat was measured by DXA. Abdominal and mid-thigh low-density lean tissue (a marker of intramuscular fat) were determined with computed tomography. Glucose utilization (M) was measured during the last 30 minutes of a 3-hour hyperinsulinemic-euglycemic clamp. Insulin sensitivity was estimated from the relationship of M to the concentration of insulin during the last 30 minutes of the clamp.


RESULTS
The percentage of fat and total body fat mass were similar between AA and white women, whereas fat-free mass was higher in African American women. Visceral adipose tissue was not different between groups, but subcutaneous abdominal fat was 17% higher in the AA than in the white women. AA women had an 18% greater mid-thigh muscle area (p < 0.01) and a 34% greater mid-thigh low-density lean tissue area than the white women. Fasting glucose concentrations were not different, but fasting insulin concentrations were 29% higher in AA women. Glucose utilization was 60% lower in the AA women because of a lower non-oxidative glucose disposal. Insulin sensitivity was 46% lower in the AA women.


CONCLUSIONS
AA postmenopausal women have more mid-thigh intramuscular fat, lower glucose utilization, and are less insulin sensitive than white women despite comparable fitness and relative body fat levels.
Ryan
Alice S
AS
Department of Medicine, Division of Gerontology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA. aryan@grecc.umaryland.edu
Nicklas
Barbara J
BJ
Berman
Dora M
DM
D000005:Abdomen; D000273:Adipose Tissue; D000368:Aged; D044383:Black People; D001786:Blood Glucose / Q000032:analysis; D001823:Body Composition; D001824:Body Constitution; D015992:Body Mass Index; D005215:Fasting; D005260:Female; D015309:Glucose Clamp Technique; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology; D010101:Oxygen Consumption; D017698:Postmenopause; D013848:Thigh; D044465:White People; D001741:Black or African American
D001786:Blood Glucose; D007328:Insulin