Study of <em>In Vivo</em> Glucose Metabolism in High-fat Diet-fed Mice Using Oral Glucose Tolerance Test (OGTT) and Insulin Tolerance Test (ITT)

Abstract

Obesity represents the most important single risk factor in the pathogenesis of type 2 diabetes, a disease which is characterized by a resistance to insulin-stimulated glucose uptake and a gross decompensation of systemic glucose metabolism. Despite considerable progress in the understanding of glucose metabolism, the molecular mechanisms of its regulation in health and disease remain under-investigated, while novel approaches to prevent and treat diabetes are urgently needed. Diet derived glucose stimulates the pancreatic secretion of insulin, which serves as the principal regulator of cellular anabolic processes during the fed-state and thus balances blood glucose levels to maintain systemic energy status. Chronic overfeeding triggers meta-inflammation, which leads to alterations in peripheral insulin receptor-associated signaling and thus reduces the sensitivity to insulin-mediated glucose disposal. These events ultimately result in elevated fasting glucose and insulin levels as well as a reduction in glucose tolerance, which in turn serve as important indicators of insulin resistance. Here, we present a protocol for the generation and metabolic characterization of high-fat diet (HFD)-fed mice as a frequently used model of diet-induced insulin resistance. We illustrate in detail the oral glucose tolerance test (OGTT), which monitors the peripheral disposal of an orally administered glucose load and insulin secretion over time. Additionally, we present a protocol for the insulin tolerance test (ITT) to monitor whole-body insulin action. Together, these methods and their downstream applications represent powerful tools to characterize the general metabolic phenotype of mice as well as to specifically assess alterations in glucose metabolism. They may be especially useful in the broad research field of insulin resistance, diabetes and obesity to provide a better understanding of pathogenesis as well as to test the effects of therapeutic interventions.

Prenatal alcohol exposure programmes offspring disease: insulin resistance in adult males in a rat model of acute exposure

“…Glucose concentration curves for the ITT were inverted before calculating AUGC as previously described (Gardebjer et al . ; Nagy & Einwallner, ). Acute 1st phase insulin secretion was calculated as the AUIC from basal to 5 min post‐glucose bolus and 2nd phase insulin secretion as the AUIC from 5 to 90 min post‐bolus.…”

<p>Guidelines and Considerations for Metabolic Tolerance Tests in Mice</p>

“…Proceed with the following mouse until the basal levels of each mouse are collected. 8. Start with glucose i.p.…”

“…After 15 min, measure blood glucose levels with the glucometer of each mouse in the same order as they were injected. 8 Resume to measure blood glucose and get the values for 30, 60, 90 and 120 mins after glucose injection ( Figure 2F).…”

“…However, the outcome of the tests and reproducibility of results can have great variability if the procedure is not correctly performed. By using the most relevant literature [5][6][7][8] and our experience, [9][10][11] in this review, we standardize and describe easy-to-follow detailed protocols for main MTT, and highlight the advantages, limitations and important caveats of each of these methods. groups, husbandry and fasting conditions.…”

Prenatal alcohol exposure programs offspring disease: Insulin resistance in adult males in a rat model of acute exposure

“…Area under the glucose (AUGC) and insulin (AUIC) curves were calculated using the trapezius method with baseline defined as the basal level prior to injection (Allison et al ., 1995). Glucose concentration curves for the ITT were inverted before calculating AUGC as previously described (Gardebjer et al ., 2015; Nagy & Einwallner, 2018). Acute 1 st phase insulin secretion was calculated as the AUIC from basal to 5 min post-glucose bolus and 2 nd phase insulin secretion as the AUIC from 5 to 90 min post-bolus.…”