Computed Tomography-Derived Myosteatosis and Metabolic Disorders

Abstract

The role of ectopic adipose tissue infiltration into skeletal muscle (i.e., myosteatosis) for metabolic disorders has received considerable and increasing attention in the last 10 years. The purpose of this review was to evaluate and summarize existing studies focusing on computed tomography (CT)-derived measures of myosteatosis and metabolic disorders. There is consistent evidence that CT-derived myosteatosis contributes to dysglycemia, insulin resistance, type 2 diabetes mellitus, and inflammation, and, to some extent, dyslipidemia, independent of general obesity, visceral fat, and other relevant risk factors, suggesting that it may serve as a tool for metabolic risk prediction. Identification of which muscles should be examined, and the standardized CT protocols to be employed, are necessary to enhance the applicability of findings from epidemiologic studies of myosteatosis. Additional and longer longitudinal studies are necessary to confirm a role of myosteatosis in the development of type 2 diabetes mellitus, and examine these associations in a variety of muscles across multiple race/ethnic populations. Given the emerging role of myosteatosis in metabolic health, well-designed intervention studies are needed to investigate relevant lifestyle and pharmaceutical approaches.

Keywords: Adipose tissue; Diabetes mellitus, type 2; Dyslipidemias; Inflammation; Insulin resistance; Muscle, skeletal.

Fig. 1.

Representation of areas of interest (adipose tissue and muscle measures) derived from abdominal computed tomography (CT) scans in the Multi-Ethnic Study of Atherosclerosis (MESA) cohort. The morphologically discrete tissues measured during CT image processing are: subcutaneous area which lies between the dermis and the fascia of the abdominal muscles; visceral cavity area with the internal organs; and abdominal skeletal muscles. The specific muscle groups denoted by psoas muscles (yellow arrows), paraspinal muscles (green arrows), oblique muscles (red arrows), and rectus abdominis muscles (blue arrows). Adipose tissue is identified as being between –190 and –30 Hounsfield units (HU). Lean tissue is identified as being between 0 and 100 HU. Inter-muscular adipose tissue is the sum of the pixels within a given muscle fascia. Intramuscular fat is computed as the mean of the pixel HU values between 0 and 99 for a given muscle group, with a higher mean density value for muscle indicating less intramuscular fat.

Fig. 2.

Potential mechanisms underlying metabolic consequences of computed tomography-derived myosteatosis.