Micro-CT Analysis of Fat in the Killifish<i>Nothobranchius furzeri</i>

Aging is associated with an increase in body fat mass and a concomitant decrease in lean mass and bone density in mammals. Body adiposity can also be redistributed with age, resulting in abdominal fat accumulation and subcutaneous fat reduction. In addition, specific variation in fat distribution is considered to be a risk factor for a number of age-related metabolic disorders. Micro computed tomography (micro-CT) is a nondestructive high-resolution imaging method that uses planar X-ray images captured at various angles around a sample of interest to yield a three-dimensional array of radiodensity values, which can then be used to computationally extract the adipose volume in situ using its innate contrast properties. This method was successfully used to study adipose tissue dynamics in rodents and more recently in zebrafish. The naturally short-lived African turquoise killifish is an emerging model organism to study the biology of aging. Like mammals, killifish also have different fat deposits (visceral and subcutaneous), making them a suitable model to study age-related changes in fat mass and distribution. However, procedures allowing precise quantification of fat content and distribution are missing in this species. Here, we provide an optimized protocol to measure and quantify fat distribution in turquoise killifish by micro-CT scan analysis and show the applicability of the method in young and old animals of both sexes.