Greater adipose tissue infiltration in skeletal muscle among older men of African ancestry.
BACKGROUND
There is substantial variability across ethnic groups in the predisposition to obesity and associated metabolic abnormalities. Skeletal muscle fat has been identified as an important depot that increases with aging and may contribute to the development of diabetes.


OBJECTIVE
We tested whether men of African ancestry have greater calf intermuscular adipose tissue (IMAT), compared to Caucasian men, and whether IMAT is associated with type 2 diabetes (T2D).


METHODS
We measured fasting serum glucose, body mass index, total body fat by dual-energy x-ray absorptiometry, and calf skeletal muscle composition by quantitative computed tomography in 1105 Caucasian and 518 Afro-Caribbean men aged 65+.


RESULTS
Compared to Caucasian men, we found greater IMAT and lower sc adipose tissue in Afro-Caribbean men at all levels of total adiposity (P < 0.0001), including the subset of men matched on age and dual-energy x-ray absorptiometry total body fat percentage (P < 0.001). In addition, IMAT was 29 and 23% greater, whereas sc adipose tissue was 6 and 8% lower among Caucasian and Afro-Caribbean men with T2D, respectively, compared to men without T2D (P < 0.01). Observed differences in intermuscular and sc fat, both ethnic and between men with and without T2D, were independent of age, height, calf skeletal muscle and total adipose tissue, and lifestyle factors.


CONCLUSIONS
Our analyses suggest that despite lower total adiposity, skeletal muscle fat infiltration is greater among African than among Caucasian ancestry men and is associated with T2D in both ethnic groups. Additional studies are needed to determine the mechanisms contributing to ethnic differences in skeletal muscle adiposity and to define the metabolic and health implications of this fat depot.
Miljkovic
Iva
I
Department of Epidemiology, Center for Aging and Population Health, University of Pittsburgh, 130 North Bellefield Avenue, Room 542, Pittsburgh, PA 15213, USA. miljkovici@edc.pitt.edu
Cauley
Jane A
JA
Petit
Moira A
MA
Ensrud
Kristine E
KE
Strotmeyer
Elsa
E
Sheu
Yahtyng
Y
Gordon
Christopher L
CL
Goodpaster
Bret H
BH
Bunker
Clareann H
CH
Patrick
Alan L
AL
Wheeler
Victor W
VW
Kuller
Lewis H
LH
Faulkner
Kimberly A
KA
Zmuda
Joseph M
JM
D000273:Adipose Tissue / Q000033:anatomy & histology / Q000378:metabolism*; D050154:Adiposity; D000368:Aged; D000375:Aging / Q000378:metabolism*; D044383:Black People; D001823:Body Composition; D015992:Body Mass Index; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D016138:Walking; D044465:White People