Background:
Excess adiposity is associated with higher levels of certain inflammatory markers that have been linked to cardiometabolic disease. Lean skeletal muscle is the largest regulator of glucose metabolism but few population-based studies have examined the associations between muscle and inflammation. Therefore, we studied the relationships between abdominal muscle mass [area] and density with selected measures of adiposity-associated inflammation.
Methods:
Nearly 2,000 subjects enrolled in the Multi-Ethnic Study of Atherosclerosis underwent computed tomography (CT) of the abdomen and had venous fasting blood drawn concomitantly. The CT scans were interrogated for visceral and subcutaneous fat, as well as lean muscle areas and densities in the rectus abdominus, obliques, paraspinus and psoas muscle groups. We then categorized the muscle in locomotion (psoas) and stabilization groups (rectus, obliques and paraspinus). The blood samples were assayed for interleukin-6, resistin, C-reactive protein, and tumor necrosis factor - alpha. Multivariable linear regression was used to determine the independent associations between muscle area and density with each of the aforementioned adipokines.
Results:
The mean age was 64.7 years and 49% were female. Forty percent were non-Hispanic White, 26% were Hispanic/ Latino American, 21% were African American, 13% were Chinese American. The mean BMI was 28.0 kg/m
2
and 30% were obese (BMI > 30 kg/m
2
). With adjustment for age, gender, race, dyslipidemia, diabetes, hypertension, eGFR, coronary artery calcium, physical activity, sedentary behavior, selected adipokines and both subcutaneous and visceral fat, a 1-SD increment in the mean densities for total abdominal muscle, total stabilization muscle and total locomotive muscle were each significantly associated with lower levels of interleukin-6 (-15%, -15% and -9%, p < 0.01 for all) and resistin (-0.11, -0.11 and -0.07 ng/mL, p < 0.02 for all), but not CRP or TNF-alpha. These associations remained significant after additional adjustment for muscle area in the corresponding muscle group. Conversely, the areas of the muscle variables were not independently associated with any of the adipokines, especially after adjustment for muscle density. There were no significant interactions between ethnicity and both muscle area and density for any of the adipokines.
Conclusions:
Higher densities of several muscle groups in the abdomen are significantly associated with lower interleukin-6 and resistin levels, independent of the muscle area in these groups. Techniques that either enhance or maintain muscle density levels may reduce the risk of cardiometabolic diseases linked to adverse levels of inflammation.
Psoas Muscle Density Evaluated by Chest CT and Long-Term Mortality in COPD Patients