Intramyocellular Lipid and Insulin Resistance: Differential Relationships in European and African Americans

Abstract

Insulin resistance has been associated with the accumulation of fat within skeletal muscle fibers as intramyocellular lipid (IMCL). Here, we have examined in a cross-sectional study the interrelationships among IMCL, insulin sensitivity, and adiposity in European Americans (EAs) and African Americans (AAs). In 43 EA and 43 AA subjects, we measured soleus IMCL content with proton-magnetic resonance spectroscopy, insulin sensitivity with hyperinsulinemic–euglycemic clamp, and body composition with dual-energy X-ray absorptiometry. The AA and EA subgroups had similar IMCL content, insulin sensitivity, and percent fat, but only in EA was IMCL correlated with insulin sensitivity (r = −0.47, P < 0.01), BMI (r = 0.56, P < 0.01), percent fat (r = 0.35, P < 0.05), trunk fat (r = 0.47, P < 0.01), leg fat (r = 0.40, P < 0.05), and waist and hip circumferences (r = 0.54 and 0.55, respectively, P < 0.01). In a multiple regression model including IMCL, race, and a race by IMCL interaction, the interaction was found to be a significant predictor (t = 1.69, DF = 1, P = 0.0422). IMCL is related to insulin sensitivity and adiposity in EA but not in AA, suggesting that IMCL may not function as a pathophysiological factor in individuals of African descent. These results highlight ethnic differences in the determinants of insulin sensitivity and in the pathogenesis of the metabolic syndrome trait cluster.

Body adiposity index as a risk factor for the metabolic syndrome in postmenopausal Caucasian, African American, and Filipina women

“…BAI was previously shown to diverge from %BF measurements at the extremities of the range in Caucasian adults [29]. Previous studies showed increased insulin resistance in African American compared to Caucasian women [31]. However, hip circumference in African American women can be wider than in Caucasian and Filipina women without manifestation of any characteristics of the MetS, thus hip circumference may be a less accurate indicator of body adiposity in older African American women because of differences in fat distribution [32].…”

Development of a Weighted Cardiometabolic Disease Staging (CMDS) System for the Prediction of Future Diabetes

“…Results: Fasting glucose, 2-hour glucose, waist circumference, and blood pressure components contributed similarly for the prediction of future diabetes (CMDS scores,23,21,26,and 20, respectively). The area under the receiver operating characteristic curve was 0.7158 for the CMDS scoring system, whereas it was 0.7053 for the Framingham diabetes score.…”

Skeletal Muscle Lipid Peroxidation and Insulin Resistance in Humans

“…Vastus lateralis biopsies were performed after an overnight fast as described (7). Adipose tissue was removed and samples were divided, frozen in liquid nitrogen, and stored at Ϫ80 C. All tissue samples were carefully treated without reducing agents and with only two freeze-thaw cycles since collection (one after tissue collection and the other after preparing homogenate).…”

“…Reactive aldehydes such as 4-hydroxynonenal (HNE) are biomarkers of lipid peroxidation and have been associated with intramyocellular lipid (IMCL) accumulation in sedentary individuals (4). It is widely postulated that lipid peroxides modify mitochondrial proteins and critical components of the insulin signaling pathway (5,6), leading to impaired stimulation of glucose uptake, mitochondrial damage, and additional oxidative stress, thereby propagating a deleterious cycle (7). However, few data have been reported to substantiate this theory.…”