Methodological considerations when studying the skeletal response to glucose intolerance using the diet-induced obesity model

Abstract

The prevalence of obesity and type 2 diabetes mellitus (T2DM) continues to rise, and as a result, research aimed at understanding the molecular basis for the co-morbidities has become an area of much scientific interest. Among the more recently recognized chronic complications of T2DM is the increased risk of fracture, especially hip fracture, that has been reported independent of bone mineral density (BMD). A widely used animal model to study how the development and progression of impaired glucose tolerance affect the skeleton has been the diet-induce obesity (DIO) model. As the name implies, this model employs the use of a version of high-fat diets to induce obesity and the subsequent metabolic perturbations that occur with T2DM. Although the model offers a number of advantages, the literature reveals some inconsistent results. Upon further review, discrepancies in the choice of the experimental high-fat diets and the control diets have become a point of major concern. The variability between diets and study design has made it difficult to compare data and results across studies. Therefore, this review aims to provide guidelines that should be employed when designing studies using DIO models of T2DM.

The common use of improper control diets in diet-induced metabolic disease research confounds data interpretation: the fiber factor

“…No diet is without flaws and a good example of a needed ‘improvement’ in purified diets is the inclusion of a source(s) of soluble fiber for gut health. Having said this, among nutritionally trained scientists, purified diets are considered a ‘cleaner’, more controlled diet choice compared to GB diets [ 4 , 7 , 21 ]. Knowing the inherent differences between GB diets and purified diets allows the researcher to design their diet study well and judge papers in which animals fed purified diets were compared directly to those fed GB diets.…”

Effects of different diets used in diet-induced obesity models on insulin resistance and vascular dysfunction in C57BL/6 mice

“…Furthermore SCDs show different nutrient contents from batch to batch 12 . Commonly chow diets are grain-based and supplemented with fats, vitamins and minerals 13 . Every ingredient is rich on nutrients but also biologically active non-nutrients like heavy metals and phytoestrogens.…”

Drosophila melanogaster in nutrition research—the importance of standardizing experimental diets

“…For instance, in some studies, lard (usually 15%) is used to induce an obese phenotype whereas in other studies coconut oil (about 20–30%) is administered [5]. In this regard, it is noteworthy that these two major fat sources do not only differ substantially in their composition, relevant variations are also observed between different lard and coconut oil batches [6]. Lard consists of approximately 40% saturated, 45% monounsaturated, and 15% polyunsaturated fatty acids whereby the three dominant fatty acids are palmitic acid, oleic acid, and stearic and linoleic acid.…”

“…In contrast, coconut oil contains mostly saturated fatty acids (about 90%) and only minor amounts of monounsaturated and polyunsaturated fatty acids (about 6% and 2%, respectively). It is characterized by high amounts of lauric, myristic, capric, and caprylic acid which differ significantly from lard [6].…”