Not so fast: Paradoxically increased variability in the glucose tolerance test due to food withdrawal in continuous glucose-monitored mice

• DOI: 10.1016/j.molmet.2023.101795
• Publication Date: 2023-08-26T15:19:16Z
• Authors: William B. Rubio; Marissa D. Cortop...; Deepti Ramachandran; Samuel J. Walker; Elizabeth M. Balough; Jiefu Wang; Alexander S. Banks
• Keywords: Corticosterone; Glucose tolerance test; Carbohydrate Metabolism; Bolus (digestion)

This study was performed to determine the effect of fasting on reproducibility glucose tolerance test. Due individual variation in animal feeding behaviors, animals prior metabolic and behavioral experiments is widely held reduce inter-subject parameters preclinical rodent models. Reducing variability especially important for studies where initial metabolite levels can influence magnitude experimental interventions, but also imposes stress that may distort variables interest. One such intervention test (GTT) which measures maximum response recovery following a bolus exogenous glucose. We sought investigate how affects mice GTT. Using simultaneous continuous monitoring (CGM) indirect calorimetry, we quantified blood glucose, physical activity, body temperature, rates, food consumption minute-to-minute basis adult male 4 weeks. tested effects 4-hr or 18-hr fast GTT examine withdrawal light dark photoperiods. Studies were with additional without implanted CGM probes. Contrary our expectations, during photoperiod promotes paradoxical increase inter-animal rate, glycemia, tolerance. hyperglycemic hyper-metabolic phenotype increased corticosterone consistent deprivation, even well-fed mice. find undergoing an entered torpor, hibernation-like state. In addition low temperature torpor associated 56 mg/dl lower than those seen ad libitum access food. Moreover, time spent Our results suggest before testing, perhaps other experiments, have opposite intended increase, rather decrease, variability.