Intermuscular Adipose Tissue Content and Intramyocellular Lipid Fatty Acid Saturation Are Associated with Glucose Homeostasis in Middle-Aged and Older Adults

BACKGROUND: Insulin resistance is associated with the higher content of intermuscular adipose tissue (IMAT) and the saturation of intramyocellular lipid (IMCL), but a paucity of data exist in humans. This study examined associations among IMAT content, IMCL saturation, and fasting glucose concentration in middle-aged and older adults with overweight or obesity. METHODS: Seventy-five subjects (26 males, 49 females) were recruited and thigh muscle and IMAT were assessed using magnetic resonance imaging. Vastus lateralis tissue was acquired from a subset of nine subjects and IMCL content and saturation were assessed using nonlinear dual complex microscopy. RESULTS: The characteristics of the 75 subjects were as follows: age 59±11 years, body mass index 30±5 kg/m², fasting glucose concentration 5.2±0.5 mmol/L, fasting insulin concentration 12.2±7.3 µU/mL, fasting homeostatic model assessment of insulin resistance (HOMA-IR) 2.9±2.0 (mean±SD). IMAT to muscle tissue (MT) volume ratio was positively associated with the saturated fatty acid to unsaturated fatty acid ratio in IMCL. IMAT:MT was positively associated with fasting glucose concentration and HOMA-IR. IMCL saturation was positively associated with fasting glucose concentration while muscle cell area, IMCL area, and % IMCL in muscle cell were not associated with fasting glucose concentration. CONCLUSION: These results indicate that higher intermuscular fat content and IMCL saturation may impact fasting glucose concentration in middle-aged and older adults with overweight or obesity. The centralization of adipose tissue in the appendicular region of the body may promote insulin resistance.

Decreased Intermuscular Adipose Tissue due to Caloric Restriction in Obese Korean Women

BACKGROUND: This study investigated the effects of caloric restriction on thigh intermuscular adipose tissue (IMAT) and the associations of IMAT and metabolic risk factors. METHODS: Thirty-three obese Korean women (BMI 27.2+/-2.5 kg/m2; 32.3+/-8.7 years) were tested before and after 12 weeks of 354.7 kcal/day dietary caloric restriction: waist circumference (WC); %fat according to bioimpedence; subcutaneous adipose tissue (SAT); visceral adipose tissue (VAT); IMAT using single-slice CT scans at the levels of L4/L5 and mid-thigh (midpoint between the anterior iliac crest and patella); fasting levels of leptin, glucose, insulin, triglycerides, total-C, LDL-C, HDL-C, and HOMA-IR. Paired t-test and Spearman correlation analysis were performed. RESULTS: WC, %fat, leptin, glucose, total-C, abdominal SAT and VAT, and mid-thigh IMAT decreased (P<0.05), and %change in mid-thigh IMAT correlated with %change in HOMA-IR (P<0.05). CONCLUSION: Caloric restriction decreased the mid-thigh IMAT in obese Korean women, which may be correlated with reduction of metabolic risk.