Glucose use in fasted rats under sevoflurane anesthesia and propofol anesthesia

Time course changes in insulin sensitivity during cardiac surgery: A retrospective study on intraoperative glycemic management using an artificial pancreas

INTRODUCTION

Glycemic control is essential for improving the prognosis of cardiac surgery, although precise recommendations have not yet been established. Under a constant blood glucose level, the insulin infusion rate correlates with insulin resistance during glycemic control using an artificial pancreas (AP). We conducted this retrospective study to elucidate changes in intraoperative insulin sensitivity as a first step to creating glycemic control guidelines.

METHODS

Fifty-five cardiac surgery patients at our hospital who underwent intraoperative glycemic control using an AP were enrolled. Twenty-three patients undergoing surgical procedures requiring cardiac arrest under hypothermic cardiopulmonary bypass (CPB) with minimum rectal temperatures lower than 32°C, 13 patients undergoing surgical procedures requiring cardiac arrest under hypothermic CPB with minimum rectal temperatures of 32°C, eight patients undergoing on-pump beating coronary artery bypass grafting and 11 patients undergoing off-pump coronary artery bypass were assigned to groups A, B, C and D, respectively. We analyzed the time course of changes in the data derived from glycemic control using the AP.

RESULTS

Significant time course changes were observed in groups A and B, but not in groups C and D. Insulin resistance was induced after the start of hypothermic CPB in groups A and B, and the induced change was not resolved by the rewarming procedure, remaining sustained until the end of surgery.

CONCLUSIONS

Hypothermia is the predominant factor of the induced insulin resistance during cardiac surgery. Thus, careful glycemic management during hypothermic CPB is important. Prospective clinical studies are required to confirm the findings of this study.

Advanced Imaging Techniques for the Characterization of Subcellular Organelle Structure in Pancreatic Islet β Cells

Type 2 diabetes (T2D) affects more than 32.3 million individuals in the United States, creating an economic burden of nearly $966 billion in 2021. T2D results from a combination of insulin resistance and inadequate insulin secretion from the pancreatic β cell. However, genetic and physiologic data indicate that defects in β cell function are the chief determinant of whether an individual with insulin resistance will progress to a diagnosis of T2D. The subcellular organelles of the insulin secretory pathway, including the endoplasmic reticulum, Golgi apparatus, and secretory granules, play a critical role in maintaining the heavy biosynthetic burden of insulin production, processing, and secretion. In addition, the mitochondria enable the process of insulin release by integrating the metabolism of nutrients into energy output. Advanced imaging techniques are needed to determine how changes in the structure and composition of these organelles contribute to the loss of insulin secretory capacity in the β cell during T2D. Several microscopy techniques, including electron microscopy, fluorescence microscopy, and soft X-ray tomography, have been utilized to investigate the structure-function relationship within the β cell. In this overview article, we will detail the methodology, strengths, and weaknesses of each approach. © 2024 American Physiological Society. Compr Physiol 14:5243-5267, 2024.

Influence of general anaesthesia on circulating biomarkers of glucose metabolism in pigs

Pigs are widely used in metabolic research with procedures often requiring general anaesthesia. The aim was to investigate the effect of four different anaesthetic protocols: 1) isoflurane inhalation, 2) propofol infusion, 3) a mixture of tiletamine, zolazepam, medetomidine, ketamine and butorphanol (TZMKB)) and 4) ketamine combined with midazolam and xylazine (KMX)) on selected biomarkers during basal and glucose stimulated conditions. Eight domestic pigs were included in a cross-over design. Plasma concentrations of glucose, insulin, C-peptide, glucagon, cortisol, triglycerides, total cholesterol, aspartate amino transferase and alanine amino transferase, creatinine, urea, fructosamine, albumin, free fatty acids (FFAs) and glycerol were measured at baseline, during 2 h of anaesthesia and during 1 h of recovery. Intravenous glucose tolerance test (IVGTT, 0.5 g glucose/kg) was performed after 1 h of anaesthesia. Glucose disappearance rate and areas under the insulin, C-peptide and glucagon curves from the IVGTT were calculated. All four anaesthetic protocols affected glucose metabolism parameters significantly compared with un-anaesthetised pigs, which was particularly evident during IVGTT and for TZMKB and KMX anaesthesia. Propofol additionally influenced the plasma concentrations of triglycerides, FFAs and glycerol significantly. The remaining circulating biomarkers were largely unaffected by anaesthesia. These data underline the importance of considering the anaesthetic protocol in porcine studies of circulating metabolic biomarkers.

Influence of Different Sevoflurane Concentrations on Postoperative Cognitive Function in Aged Rats

BACKGROUND

Postoperative cognitive dysfunction may be associated with neuroinflammation, and sevoflurane suppresses surgery-induced inflammation. We hypothesized that low concentrations of sevoflurane would result in more impaired postoperative cognitive function compared to high concentrations.

METHODS

Aged male Sprague-Dawley rats (n = 21, 17-22 months) were randomly assigned to 1 of 3 groups: control (C), sevoflurane 2% (S2), and sevoflurane 4% (S4). Rats in the S2 and S4 groups underwent open femoral fracture and intramedullary fixation of the left hind limb under 2 hours of sevoflurane anesthesia. Neurological outcomes were evaluated using the Morris water maze (MWM) test, and histopathological outcomes were assessed 28 days after surgery.

RESULTS

The S2 group showed prolonged swimming latency compared to S4 on day 7 (difference of means, 34.4; 95% confidence interval [CI], 2.57-66.3; P = .031) and compared to the C group on day 9 (difference of means, -33.4; 95% CI, -65.3 to -1.55; P = .037). The intact CA1 cells in the S2 group were significantly less than those in the C and S4 groups (H statistic, 10.87; P = .006 versus C; P = .033 versus S4).

CONCLUSIONS

We found that low concentrations of sevoflurane prolonged the swimming latency of the MWM compared to high concentrations and reduced intact CA1 hippocampal neurons in aged rats. These results suggest that low-concentration sevoflurane anesthesia may be more detrimental than high concentration for spatial cognitive function and postoperative impairment of hippocampal CA1 cells in aged rats.

Sevoflurane-induced hyperglycemia is attenuated by salsalate in obese insulin-resistant mice

PURPOSE

Perioperative hyperglycemia is common and is associated with significant morbidity. Although patient characteristics and surgery influence perioperative glucose metabolism, anesthetics have a significant impact. We hypothesized that mice that were obese and insulin-resistant would experience greater hyperglycemia in response to sevoflurane anesthesia compared with lean controls. We further hypothesized that sevoflurane-induced hyperglycemia would be attenuated by salsalate pre-treatment.

METHODS

Lean and obese male C57BL/6J mice were anesthetized with sevoflurane for 60 min with or without pre-treatment of 62.5 mg·kg^-1 salsalate. Blood glucose, plasma insulin, and glucose uptake into different tissues were measured.

RESULTS

Under sevoflurane anesthesia, obese mice had higher blood glucose compared to lean mice. Increases in blood glucose were attenuated with acute salsalate pre-treatment at 60 min under anesthesia in obese mice (mean ± standard error of the mean [SEM], delta blood glucose; vehicle 5.79 ± 1.09 vs salsalate 1.91 ± 1.32 mM; P = 0.04) but did not reach statistical significance in lean mice (delta blood glucose, vehicle 4.39 ± 0.55 vs salsalate 2.79 ± 0.71 mM; P = 0.10). This effect was independent of changes in insulin but associated with an approx. 1.7-fold increase in glucose uptake into brown adipose tissue (vehicle 45.28 ± 4.57 vs salsalate 76.89 ± 12.23 µmol·g^-1 tissue·hr^-1; P < 0.001).

CONCLUSION

These data show that salsalate can reduce sevoflurane-induced hyperglycemia in mice. This indicates that salsalate may represent a new class of therapeutics that, in addition to its anti-inflammatory and analgesic properties, may be useful to reduce perioperative hyperglycemia.

Propofol Improved Glucose Tolerance Associated with Increased FGF-21 and GLP-1 Production in Male Sprague-Dawley Rats

Anesthetics, particularly volatile anesthetics, have been shown to impair glucose metabolism and cause hyperglycemia, closely linking them with mortality and morbidity as related to surgery. Beyond being an anesthetic used for general anesthesia and sedation, intravenous hypnotic propofol displays an effect on glucose metabolism. To extend the scope of propofol studies, its effects on glucose metabolism were evaluated in male Sprague-Dawley rats of various ages. Unlike chloral hydrate and isoflurane, propofol had little effect on basal glucose levels in rats at 2 months of age, although it did reduce chloral hydrate- and isoflurane-induced hyperglycemia. Propofol reduced postload glucose levels after either intraperitoneal or oral administration of glucose in both 7- and 12-month-old rats, but not those at 2 months of age. These improved effects regarding propofol on glucose metabolism were accompanied by an increase in insulin, fibroblast growth factor-21 (FGF-21), and glucagon-like peptide-1 (GLP-1) secretion. Additionally, an increase in hepatic FGF-21 expression, GLP-1 signaling, and FGF-21 signaling, along with a decrease in endoplasmic reticulum (ER) stress, were noted in propofol-treated rats at 7 months of age. Current findings imply that propofol may turn into insulin-sensitizing molecules during situations of existing insulin resistance, which involve FGF-21, GLP-1, and ER stress.

Postoperative hunger after outpatient surgery in patients anesthetized with propofol vs sevoflurane: a randomized-controlled trial

PURPOSE

Previous preclinical and preliminary clinical data suggest an appetite-stimulating effect of propofol compared with halogenated drugs. This study compared the effects of propofol with those of sevoflurane on recovery of hunger during the postoperative period.

METHODS

Patients undergoing outpatient transvaginal oocyte retrieval were randomized to propofol-remifentanil (propofol group) or sevoflurane-remifentanil (sevoflurane group) anesthesia. The primary endpoint was the time before feeling hungry (≥ 50/100 mm on a visual analogue scale). Secondary endpoints included plasma levels of ghrelin, leptin, and insulin (ten minutes, one hour, and two hours after anesthesia), caloric intake at first feed, and discharge readiness time.

RESULTS

In the 58 patients allocated to either the propofol or sevoflurane group, there was no difference in the median [interquartile range] recovery time of hunger (97 [75-138] vs 97 [80-140] min, respectively; median difference, 1; 95% confidence interval [CI], - 15 to 14; P = 0.91); caloric intake (245 [200-343] vs 260 [171-314] kcal; P = 0.39); or discharge readiness time (125 [85-153] vs 125 [95-174] min, P = 0.29). The groups showed no difference in crude plasma levels of ghrelin, leptin, and insulin at any time-point. When peptide plasma levels were expressed as a % change from baseline, there was a higher insulin plasma level one hour after anesthesia in the sevoflurane group (median difference, 4.9%; 95% CI, - 16.2 to 43.4) compared with the propofol group (median difference, - 21.2%; 95% CI, - 35.7 to 9.1; adjusted P = 0.01).

CONCLUSION

Propofol did not accelerate the recovery of hunger compared with sevoflurane after outpatient minor surgery. Moreover, propofol did not have distinguishable effects on other clinical or biological parameters associated with food intake.

TRIAL REGISTRATION

www.ClinicalTrials.gov (NCT02272166); registered 22 October, 2014.

Propofol inhibits stromatoxin-1-sensitive voltage-dependent K+ channels in pancreatic β-cells and enhances insulin secretion

Background

Proper glycemic control is an important goal of critical care medicine, including perioperative patient care that can influence patients’ prognosis. Insulin secretion from pancreatic β-cells is generally assumed to play a critical role in glycemic control in response to an elevated blood glucose concentration. Many animal and human studies have demonstrated that perioperative drugs, including volatile anesthetics, have an impact on glucose-stimulated insulin secretion (GSIS). However, the effects of the intravenous anesthetic propofol on glucose metabolism and insulin sensitivity are largely unknown at present.

Methods

The effect of propofol on insulin secretion under low glucose or high glucose was examined in mouse MIN6 cells, rat INS-1 cells, and mouse pancreatic β-cells/islets. Cellular oxygen or energy metabolism was measured by Extracellular Flux Analyzer. Expression of glucose transporter 2 (GLUT2), potassium channels, and insulin mRNA was assessed by qRT-PCR. Protein expression of voltage-dependent potassium channels (Kv2) was also assessed by immunoblot. Propofol’s effects on potassium channels including stromatoxin-1-sensitive Kv channels and cellular oxygen and energy metabolisms were also examined.

Results

We showed that propofol, at clinically relevant doses, facilitates insulin secretion under low glucose conditions and GSIS in MIN6, INS-1 cells, and pancreatic β-cells/islets. Propofol did not affect intracellular ATP or ADP concentrations and cellular oxygen or energy metabolism. The mRNA expression of GLUT2 and channels including the voltage-dependent calcium channels Cav1.2, Kir6.2, and SUR1 subunit of K_ATP, and Kv2 were not affected by glucose or propofol. Finally, we demonstrated that propofol specifically blocks Kv currents in β-cells, resulting in insulin secretion in the presence of glucose.

Conclusions

Our data support the hypothesis that glucose induces membrane depolarization at the distal site, leading to K_ATP channel closure, and that the closure of Kv channels by propofol depolarization in β-cells enhances Ca²⁺ entry, leading to insulin secretion. Because its activity is dependent on GSIS, propofol and its derivatives are potential compounds that enhance and initiate β-cell electrical activity.

Sevoflurane Impairs Insulin Secretion and Tissue-Specific Glucose Uptake In Vivo

The use of anaesthetics severely influences substrate metabolism. This poses challenges for patients in clinical settings and for the use of animals in diabetes research. Sevoflurane can affect regulation of glucose homoeostasis at several steps, but the tissue-specific response remains to be determined. The aim of the study was to investigate the pharmacological effect of sevoflurane anaesthesia on glucose homoeostasis during hyperinsulinaemic clamp conditions, the gold standard method for assessment of whole-body insulin sensitivity. Conscious mice (n = 6) and mice under sevoflurane anaesthesia (n = 8) underwent a hyperinsulinaemic clamp where constant infusion of insulin and donor blood was administered during variable glucose infusion to maintain isoglycaemia. 2-[1-¹⁴ C]-deoxy-D-glucose was infused to determine tissue-specific uptake of glucose in adipose tissue, heart, brain and skeletal muscle. Sevoflurane anaesthesia severely impaired insulin-stimulated whole-body glucose uptake demonstrated by a 50% lower glucose infusion rate (GIR). This was associated with decreased glucose uptake in brain, soleus, triceps and gastrocnemius muscles in sevoflurane-anaesthetized mice compared to conscious mice. Plasma-free fatty acids (FFA), a potent inducer of insulin resistance, increased by 42% in mice during sevoflurane anaesthesia. In addition, insulin secretion from pancreatic β-cell was lower in fasted, anaesthetized mice. Sevoflurane anaesthesia impairs insulin secretion, induces insulin resistance in mice and reduces glucose uptake in non-insulin-sensitive tissue like the brain. The underlying mechanisms may involve sevoflurane-induced mobilization of FFA.

Proteostasis in epicardial versus subcutaneous adipose tissue in heart failure subjects with and without diabetes

BACKGROUND

Cardiovascular diseases (CVDs) are leading cause of death and primary cause of morbidity and mortality in diabetic population. Epicardial adipose tissue (EAT) covers the heart's surface and is a source of biomolecules regulating heart and blood vessel physiology. The protective activation of the unfolded protein response (UPR) and autophagy allows the cardiomyocyte reticular network to restore energy and/or nutrient homeostasis and to avoid cell death. However, an excessive or prolonged UPR activation can trigger cell death. UPR activation is an early event of diabetic cardiomyopathies and deregulated autophagy is associated with CVDs.

RESULTS

An upregulation of UPR markers (glucose-regulated protein 78 KDa, glucose-regulated protein 94 KDa, inositol-requiring enzyme 1α, protein kinase RNA-like ER kinase and CCAAT/-enhancer-binding protein homologous protein (CHOP) gene) in EAT compared to subcutaneous adipose tissue (SAT), was observed as well as the UPR-related apoptosis marker caspase-4/procaspase-4 ratio but not in CHOP protein levels. Additionally, levels of ubiquitin and ubiquitinated proteins were decreased in EAT. Moreover, upregulation of autophagy markers (5' adenosine monophosphate-activated protein kinase, mechanistic target of rapamycin, Beclin 1, microtubule-associated protein light chain 3-II, lysosome-associated membrane protein 2, and PTEN-induced putative kinase 1) was observed, as well as an increase in the apoptotic Bim but not the ratio between Bim and the anti-apoptotic Bcl-2 in EAT. Diabetic patients show alterations in UPR activation markers but not in autophagy or apoptosis markers.

CONCLUSION

UPR and autophagy are increased in EAT compared to SAT, opening doors to the identification of early biomarkers for cardiomyopathies and novel therapeutic targets.

Effect of Propofol Continuous-Rate Infusion on Intravenous Glucose Tolerance Test in Dogs

Hyperglycemia causes perioperative complications and many anesthetics impair glucose metabolism and cause hyperglycemia. We evaluated the effects of propofol on blood glucose metabolism and insulin secretion during an intravenous glucose tolerance test (IVGTT) in dogs. Blood glucose, insulin, triglyceride, cholesterol, and free fatty acid (FFA) levels were measured in dogs during IVGTT in a conscious state and under the effect of 2.0% isoflurane, low-concentration propofol (0.2 mg/kg/min), and high-concentration propofol (0.4 mg/kg/min) anesthesia. Plasma glucose levels significantly increased in all of the treatment groups when compared with those in the conscious group. The prolonged half-life period of plasma glucose suggested that isoflurane and propofol attenuated glucose metabolism in dogs. Plasma insulin levels were significantly lower in the isoflurane group when compared with those in the other groups, whereas blood FFA levels were increased in the propofol groups when compared with the other groups. These results suggest that propofol itself does not directly raise plasma glucose levels, but attenuates glucose metabolism by accumulating FFA.

Erythropoietin ameliorates hyperglycemia in type 1-like diabetic rats

Background

Erythropoietin (EPO) is widely used in diabetic patients receiving hemodialysis. The role of EPO in glucose homeostasis remains unclear. Therefore, we investigated the effect of EPO on hyperglycemia in rats with type 1-like diabetes.

Methods

Rats with streptozotocin-induced type 1-like diabetes (STZ rats) were used to estimate the blood glucose-lowering effects of EPO, and changes in the expression levels of glucose transporter 4 (GLUT4) and the hepatic enzyme phosphoenolpyruvate carboxykinase (PEPCK) were identified by Western blot analysis.

Results

EPO attenuated the hyperglycemia in the STZ rats in a dose-dependent manner without altering the hematopoietic parameters, including the hematocrit and number of red blood cells. The involvement of the EPO receptor (EPOR) was identified using EPOR-specific antibodies. In addition, injection of EPO enhanced the glucose utilization, which was assessed using an intravenous glucose tolerance test in rats. However, blood insulin was not changed by EPO in this assay, showing the insulinotropic action of EPO. Moreover, EPO treatment increased the insulin sensitivity. Western blots indicated that the phosphorylation of AMP-activated protein kinase was enhanced by EPO to support the signaling caused by EPOR activation. Furthermore, the decrease in the GLUT4 level in skeletal muscle was reversed by EPO, and the increase in the PEPCK expression in liver was reduced by EPO, as shown in STZ rats.

Conclusion

Taken together, the results show that EPO injection may reduce hyperglycemia in diabetic rats through activation of EPO receptors. Therefore, EPO is useful for managing diabetic disorders, particularly hyperglycemia-associated changes. In addition, EPO receptor will be a good target for the development of antihyperglycemic agent(s) in the future.

Effect of sevoflurane on human hepatocellular carcinoma HepG2 cells under conditions of high glucose and insulin

Diabetes mellitus is associated with morbidity and progression of some cancers, such as hepatocellular carcinoma. It has been reported that sevoflurane, a volatile anesthetic agent commonly used in cancer surgery, can lead to lower overall survival rates than those observed when propofol is used to treat cancer patients, and sevoflurane increases cancer cell proliferation in in vitro studies. It has been also reported that glucose levels in rats anesthetized with sevoflurane were higher than those in rats anesthetized with propofol. We investigated the effect of sevoflurane, under conditions of high glucose and insulin, on cell proliferation in the human hepatocellular carcinoma cell line, HepG2. First, we exposed HepG2 cells to sevoflurane at 1 or 2 % concentration for 6 h in various glucose concentrations and then evaluated cell proliferation using the MTT assay. Subsequently, to mimic diabetic conditions observed during surgery, HepG2 cells were exposed to sevoflurane at 1 or 2 % concentration in high glucose concentrations at various concentrations of insulin for 6 h. One-percent sevoflurane exposure enhanced cell proliferation under conditions of high glucose, treated with 0.05 mg/l insulin. Our study implies that sevoflurane may affect cell proliferation in human hepatocellular carcinoma cells in a physiological situation mimicking that of diabetes.

Propofol (Diprivan®) and Intralipid® exacerbate insulin resistance in type-2 diabetic hearts by impairing GLUT4 trafficking

BACKGROUND

The IV anesthetic, propofol, when administered as fat emulsion-based formulation (Diprivan) promotes insulin resistance, but the direct effects of propofol and its solvent, Intralipid, on cardiac insulin resistance are unknown.

METHODS

Hearts of healthy and type-2 diabetic rats (generated by fructose feeding) were aerobically perfused for 60 minutes with 10 μM propofol in the formulation of Diprivan or an equivalent concentration of its solvent Intralipid (25 μM) ± insulin (100 mU•L). Glucose uptake, glycolysis, and glycogen metabolism were measured using [H]glucose. Activation of Akt, GSK3β, AMPK, ERK1/2, p38MAPK, S6K1, JNK, protein kinase Cθ (PKCθ), and protein kinase CCβII (PKCβII) was determined using immunoblotting. GLUT4 trafficking and phosphorylations of insulin receptor substrate-1 (IRS-1) at Ser307(h312), Ser1100(h1101), and Tyr608(hTyr612) were measured. Mass spectrometry was used to determine acylcarnitines, phospholipids, and sphingolipids.

RESULTS

Diprivan and Intralipid reduced insulin-induced glucose uptake and redirected glucose to glycogen stores in diabetic hearts. Reduced glucose uptake was accompanied by lower GLUT4 trafficking to the sarcolemma. Diprivan and Intralipid inactivated GSK3β but activated AMPK and ERK1/2 in diabetic hearts. Only Diprivan increased phosphorylation of Akt(Ser473/Thr308) and translocated PKCθ and PKCβII to the sarcolemma in healthy hearts, whereas it activated S6K1 and p38MAPK and translocated PKCβII in diabetic hearts. Furthermore, only Diprivan phosphorylated IRS-1 at Ser1100(h1101) in healthy and diabetic hearts. JNK expression, phosphorylation of Ser307(h312) of IRS-1, and PKCθ expression and translocation were increased, whereas GLUT4 expression was reduced in insulin-treated diabetic hearts. Phosphatidylglycerol, phosphatidylethanolamine, and C18-sphingolipids accumulated in Diprivan-perfused and Intralipid-perfused diabetic hearts.

CONCLUSIONS

Propofol and Intralipid promote insulin resistance predominantly in type-2 diabetic hearts.

Comparison of mechanisms underlying changes in glucose utilization in fasted rats anesthetized with propofol or sevoflurane: Hyperinsulinemia is exaggerated by propofol with concomitant insulin resistance induced by an acute lipid load

The effects of anesthesia with sevoflurane and with propofol on glucose utilization in rats were investigated. Sevoflurane significantly impairs glucose utilization whereas propofol does not. Both insulin secretion and sensitivity affect glucose utilization. Propofol is hydrophobic, and anesthesia with this agent is always accompanied by an acute lipid load, which can exaggerate insulin resistance. The role of the acute lipid load in the effects of anesthesia with sevoflurane and propofol on glucose utilization in fasted rats was investigated. Rats were allocated to groups anesthetized with sevoflurane and infused with physiological saline (group S) or 10% w/v lipid (group SL), or those anesthetized with propofol (group P). Intravenous glucose tolerance tests and insulin tolerance tests were then performed to measure glucose utilization, and blood glucose, plasma insulin, and plasma TNF-α levels were measured. In the intravenous glucose tolerance test, groups SL and P showed significantly higher plasma insulin levels than group S, and group P showed significantly higher plasma insulin levels than group SL. In the insulin tolerance test, groups SL and P showed insulin resistance compared to group S, but no significant difference was observed between groups SL and P. In summary, propofol anesthesia enhances insulin secretion and concomitantly exaggerates insulin resistance, compared with sevoflurane anesthesia. Propofol appears to be the main cause of hyperinsulinemia, and the acute lipid load exaggerates insulin resistance.

Metabolic phenotyping guidelines: assessing glucose homeostasis in rodent models

The pathophysiology of diabetes as a disease is characterised by an inability to maintain normal glucose homeostasis. In type 1 diabetes, this is due to autoimmune destruction of the pancreatic β-cells and subsequent lack of insulin production, and in type 2 diabetes it is due to a combination of both insulin resistance and an inability of the β-cells to compensate adequately with increased insulin release. Animal models, in particular genetically modified mice, are increasingly being used to elucidate the mechanisms underlying both type 1 and type 2 diabetes, and as such the ability to study glucose homeostasis in vivo has become an essential tool. Several techniques exist for measuring different aspects of glucose tolerance and each of these methods has distinct advantages and disadvantages. Thus the appropriate methodology may vary from study to study depending on the desired end-points, the animal model, and other practical considerations. This review outlines the most commonly used techniques for assessing glucose tolerance in rodents and details the factors that should be taken into account in their use. Representative scenarios illustrating some of the practical considerations of designing in vivo experiments for the measurement of glucose homeostasis are also discussed.