This research was conducted with grant funding from the Anthony M. Marchionne Foundation (70256-23284) and TCU IS. The authors thank Danielle DelPriore, Amanda Morin, and Christopher Rodeheffer for their helpful contributions towards shaping these methods.&#160;The authors would also like to thank Hannah Bradshaw and Randi Proffitt Leyva for their assistance with filming this protocol.

<ol>
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The authors have nothing to disclose.

This manuscript outlines a simple, inexpensive procedure for manipulating blood glucose, as well as a procedure for measuring resulting changes in the cognitive accessibility of target words and concepts. The above outlined methods can be applied to a wide range of research areas including social psychology, cognitive psychology, and nutrition sciences. Given that this method may be used by people in multiple research areas (some that do not typically use survey data), this section will present some tips on critical step...

Researchers in cognitive psychology and neuroscience have long studied the impact of blood glucose fluctuations on the brain, cognition, and behavior1. For example, researchers have found that fluctuations in blood glucose predict differences in memory (verbal, digit span, working, and episodic)1-5, attention6,7, puzzle solving8, and performance on tasks of varying levels of cognitive demand2,9,10. This research finds that increasing blood glucose enhances attention and memory, and that these effects are strongest when working on cognitively demanding tasks, and in those of older age1,3.
In recent decades, research on the impact of blood glucose fluctuations on human psychology has also become a topic of interest in the field of social psychology11-13. Fluctuations in blood glucose have been linked to changes in mood14, motivation15, self-control11-13, attitudes16,17, prejudice18, and to changes in decision-making in consumer19, eating20,21, and financial domains22. Because these results transcend a wide variety of dependent variables, the message about the role of blood glucose in decision-making is clear: blood glucose is the critical form of energy to the brain, and depletions in blood glucose lead to important changes in cognition and self regulation11,13,15.
Given the important role that blood glucose plays in various psychological and behavioral outcomes, the current manuscript offers a simple method for manipulating blood glucose that researchers can use for testing a range of cognitions and behaviors. Additionally, the current manuscript provides a method for assessing the cognitive accessibility of target words or concepts that may change in response to fluctuations in blood glucose using a lexical decision task. The efficiency of the present methods make them ideal for experimental research, as they effectively manipulate blood glucose and measure cognitive changes using relatively inexpensive, commercially-available products. The affordability of the present blood glucose manipulation makes it easier to run the large numbers of participants needed to obtain the adequate power needed to detect statistically significant differences in behavior caused by any manipulated changes in blood glucose23. Additionally, the lexical decision task is useful in that it can reveal implicit changes in cognition not easily accessed through more explicit measures such as self-report surveys24.
The described blood glucose manipulation task involves an 8 hour fasting period followed by the directed consumption of a caloric or a calorie-free drink22. After fasting for eight hours, participants are randomly assigned to consume either a sugar sweetened beverage or water. This method also allows for the testing of any unique effects produced by non-caloric sweeteners (e.g. aspartame, sucralose), which taste sweet like traditional caloric sweeteners, but do not contain the sugars needed to raise blood glucose levels20,22,25. If interested in the effects of non-calorically sweetened beverages, this task includes an optional, 3rd between-subjects condition in which participants consume a &#34;zero-calorie&#34; drink. The current method has been applied successfully in multiple social psychological paradigms12,18,22, and offers a shorter way to test for the effects of changes in blood glucose upon self-regulation than previously used measures like glucose tolerance tests26.
The authors also provide a procedure for assessing the cognitive accessibility of target words, or concepts, using a lexical decision task27,28. In this task, letter strings and words are presented via computer in rapid-fire format, and typically fall into a few distinct conceptual categories (in the described research, the categories were: high fat food words, low fat food words, non-words). Participants are asked to quickly identify (typically via keystroke) whether a string of letters (e.g. fhens; pizza) is a word or a non-word. The reaction speed in which participants correctly identify letter strings in each conceptual category measures the relative ease with which the participant is able to mentally process words in that concept category. Quicker reactions mean that a concept is more mentally accessible, and thus, &#34;on someone&#39;s mind&#34;24,29,30. As a consequence, lexical decision tasks make useful dependent variables, and can also be used as effective manipulation checks to measure if a recently primed concept (see reference30 for more information on priming) is indeed subsequently more cognitively accessible than it would be in the absence of a prime. Although the lexical decision task is a task that has been used in social psychology for decades29, the current manuscript presents some minor variations to the procedure, a link to an editable program template27, and an empirically validated list of words from the authors&#39; previous work that measures the cognitive accessibility of healthy versus non healthy foods20. It is the authors&#39; hope that the further adaptation of these two procedures will help lead to innovations in the fields of social psychological research, in eating behavior and energy regulation research, and will facilitate further comparative research that combines the perspectives and methodology of&#160;multiple disciplines.

<table><tbody><tr><td>Survey Building Software</td><td>Qualtrics</td><td>Qualtrics Research Suite</td><td>Alternative survey building softwares/applications include Survey Monkey, Google Forms, Media Lab, and Inquisit software.</td></tr><tr><td>Behavioral Task Software (for lexical decision task)</td><td>Inquisit</td><td>Inquisit 4 Lab (4.0.8.0)</td><td>Alternative behavioral task softwares/applications include Media Lab/Direct RT or programming the task into an internet browser using a programming language of your choice (such as java).</td></tr><tr><td>Batch File&amp;nbsp;</td><td>Microsoft&amp;nbsp;</td><td>Microsoft Notepad; Windows</td><td></td></tr><tr><td>Lexical Decision Task Template</td><td>Millisecond</td><td>Millisecond survey library, cited template author is linked on page</td><td>Can build a lexical decision task by hand in other behavioral task softwares.</td></tr><tr><td>Participant Scheduling and Compensation Software</td><td>SONA systems</td><td>SONA systems scheduling software</td><td>Appointments can be arranged manually, too.</td></tr><tr><td>Statistical Analysis Software</td><td>IBM</td><td>IBM SPSS Statistics Standard, 22</td><td>Alternate softwares include SAS and R.</td></tr><tr><td>Blood glucose manipulating beverege paradigm</td><td>Coca Cola&amp;nbsp;</td><td>Sprite, Sprite Zero, Sparkling water</td><td>Can use any store brand sugary beverage, non calorically sweetened beverage, and sparkling water beverage, as long as beverages are not easily discernable from each other by sight.&amp;nbsp;</td></tr><tr><td>Lancet</td><td>Assure</td><td>Assure Lanets 23 gauge</td><td>Many brands of testing lancets available both online and at local pharmacies.</td></tr><tr><td>Blood glucose testing meter</td><td>Bayer&#039;s</td><td>Breeze 2</td><td>Many brands of testing meters available both online and at local pharmacies.</td></tr><tr><td>Blood glucose testing strips</td><td>Bayer&#039;s</td><td>Breeze 2</td><td>Many brands of testing strips available both online and at local pharmacies, but they must be compatible with your chosen meter.</td></tr><tr><td>&amp;nbsp;Nitrile exam gloves (400 count)</td><td>Kirkland</td><td>Kirkland Signature Nitrile Exam Gloves</td><td>Any medical grade exam glove that provides sufficient protection from blood exposure can be used.</td></tr><tr><td>Disinfecting wipes</td><td>Lysol</td><td>Lysol Disinfecting Wipes Lemon Scent</td><td>Any wipe that can kill off any bloodborne or contact born contaminants.</td></tr></tbody></table>

a method for manipulating blood glucose and measuring resulting changes in cognitive accessibility of target stimuli

Much research in social psychology has investigated the impact of bodily energy need on cognition and decision-making. As such, blood glucose, the body's primary energy source, has been of special interest to researchers for years. Fluctuations in blood glucose have been linked to a variety of changes in cognitive and behavioral processes, such as self-control, political attitudes, and eating behavior. To help meet growing interest in the links between bodily energy need and these processes, this manuscript offers a simple methodology to experimentally manipulate blood glucose using a fasting procedure followed by administration of a sugar-sweetened, unsweetened, or artificially-sweetened beverage. This is followed by presentation of a method for measuring resulting changes in implicit cognition using a lexical decision-task. In this task, participants are asked to identify whether strings of letters are words or non-words and response latencies are recorded. Sample results from a recent publication are presented as an example of the applications for the experimental manipulation of blood glucose and the lexical decision task measures.

Participants
The above methods were implemented in a study run by Hill and colleagues20 at a midsize, private university in the southern United States. The undergraduate population at the university provided the subject sample and participants received partial course credit as compensation for study participation. Using the exact methods outlined in the current manuscript protocol, the authors ran participants through...

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A Method for Manipulating Blood Glucose and Measuring Resulting Changes in Cognitive Accessibility of Target Stimuli

The authors introduce a method for manipulating blood glucose and measuring resulting changes in cognitive accessibility of target words using a lexical decision task.

Much research in social psychology has investigated the impact of bodily energy need on cognition and decision-making.  As such, blood glucose, the body's ...

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Research

JoVE Journal

Behavior

9.0K Views.  Texas Christian University. The authors introduce a method for manipulating blood glucose and measuring resulting changes in cognitive accessibility of target words using a lexical decision task.

Video: A Method for Manipulating Blood Glucose and Measuring Resulting Changes in Cognitive Accessibility of Target Stimuli

Hyperinsulinemic-Euglycemic Clamp in the Conscious Rat

Type 2 diabetes (T2D) is rapidly rising in prevalence. Characterized by either inadequate insulin production or the inability to utilize insulin produced, T2D results in elevated blood glucose levels. The "gold-standard" in assessing insulin sensitivity is a hyperinsulinemic-euglycemic clamp or insulin clamp. In this procedure, insulin is infused at a constant rate resulting in a drop in blood glucose. To maintain blood glucose at a constant level, exogenous glucose (D50) is infused into the venous circulation. The amount of glucose infused to maintain homeostasis is indicative of insulin sensitivity. Here, we show the basic clamp procedure in the chronically catheterized, unrestrained, conscious rat. This model allows blood to be collected with minimal stress to the animal. Following the induction of anesthesia, a midline incision is made and the left common carotid artery and right jugular vein are catheterized. Inserted catheters are flushed with heparinized saline, then exteriorized and secured. Animals are allowed to recover for 4-5 days prior to experiments, with weight gain monitored daily. Only those animals who regain weight to pre-surgery levels are used for experiments. On the day of the experiment, rats are fasted and connected to pumps containing insulin and D50. Baseline glucose is assessed from the arterial line and used a benchmark throughout the experiment (euglycemia). Following this, insulin is infused at a constant rate into the venous circulation. To match the drop in blood glucose, D50 is infused. If the rate of D50 infusion is greater than the rate of uptake, a rise in glucose will occur. Similarly, if the rate is insufficient to match whole body glucose uptake, a drop will occur. Titration of glucose continues until stable glucose readings are achieved. Glucose levels and glucose infusion rates during this stable period are recorded and reported. Results provide an index of whole body insulin sensitivity. The technique can be refined to meet specific experimental requirements. It is further enhanced by the use of radioactive tracers that can determine tissue specific insulin-stimulated glucose uptake as well as whole body glucose turnover.

The hyperinsulinemic-euglycemic clamp is the "gold standard" for the assessment of insulin action. Insulin is infused at a constant rate stimulating glucose uptake. The amount of exogenous glucose infused to counter this drop is indicative of insulin sensitivity. Here the procedure is performed on a conscious, unrestrained rat.

Type 2 diabetes (T2D) is rapidly rising in prevalence. Characterized by either inadequate insulin production or the inability to utilize insulin produced, ...

Medicine

Hyperinsulinemic-euglycemic Clamps in Conscious, Unrestrained Mice

Type 2 diabetes is characterized by a defect in insulin action. The hyperinsulinemic-euglycemic clamp, or insulin clamp, is widely considered the "gold standard" method for assessing insulin action in vivo. During an insulin clamp, hyperinsulinemia is achieved by a constant insulin infusion. Euglycemia is maintained via a concomitant glucose infusion at a variable rate. This variable glucose infusion rate (GIR) is determined by measuring blood glucose at brief intervals throughout the experiment and adjusting the GIR accordingly. The GIR is indicative of whole-body insulin action, as mice with enhanced insulin action require a greater GIR. The insulin clamp can incorporate administration of isotopic 2[14C]deoxyglucose to assess tissue-specific glucose uptake and [3-3H]glucose to assess the ability of insulin to suppress the rate of endogenous glucose appearance (endoRa), a marker of hepatic glucose production, and to stimulate the rate of whole-body glucose disappearance (Rd).
The miniaturization of the insulin clamp for use in genetic mouse models of metabolic disease has led to significant advances in diabetes research. Methods for performing insulin clamps vary between laboratories. It is important to note that the manner in which an insulin clamp is performed can significantly affect the results obtained. We have published a comprehensive assessment of different approaches to performing insulin clamps in conscious mice1 as well as an evaluation of the metabolic response of four commonly used inbred mouse strains using various clamp techniques2. Here we present a protocol for performing insulin clamps on conscious, unrestrained mice developed by the Vanderbilt Mouse Metabolic Phenotyping Center (MMPC; URL: www.mc.vanderbilt.edu/mmpc). This includes a description of the method for implanting catheters used during the insulin clamp. The protocol employed by the Vanderbilt MMPC utilizes a unique two-catheter system3. One catheter is inserted into the jugular vein for infusions. A second catheter is inserted into the carotid artery, which allows for blood sampling without the need to restrain or handle the mouse. This technique provides a significant advantage to the most common method for obtaining blood samples during insulin clamps which is to sample from the severed tip of the tail. Unlike this latter method, sampling from an arterial catheter is not stressful to the mouse1. We also describe methods for using isotopic tracer infusions to assess tissue-specific insulin action. We also provide guidelines for the appropriate presentation of results obtained from insulin clamps.

The hyperinsulinemic-euglycemic clamp, or insulin clamp, is the gold standard for assessing insulin action in vivo. A method for performing insulin clamps in mice is described. This includes a method for arterial catheterization that permits experiments to be performed in conscious, unrestrained mice with minimal stress.

Type 2 diabetes is characterized by a defect in insulin action. The hyperinsulinemic-euglycemic clamp, or insulin clamp, is widely considered the "gold ...

Quantitative and Temporal Control of Oxygen Microenvironment at the Single Islet Level

Simultaneous oxygenation and monitoring of glucose stimulus-secretion coupling factors in a single technique is critical for modeling pathophysiological states of islet hypoxia, especially in transplant environments. Standard hypoxic chamber techniques cannot modulate both stimulations at the same time nor provide real-time monitoring of glucose stimulus-secretion coupling factors. To address these difficulties, we applied a multilayered microfluidic technique to integrate both aqueous and gas phase modulations via a diffusion membrane. This creates a stimulation sandwich around the microscaled islets within the transparent polydimethylsiloxane (PDMS) device, enabling monitoring of the aforementioned coupling factors via fluorescence microscopy. Additionally, the gas input is controlled by a pair of microdispensers, providing quantitative, sub-minute modulations of oxygen between 0-21%. This intermittent hypoxia is applied to investigate a new phenomenon of islet preconditioning. Moreover, armed with multimodal microscopy, we were able to look at detailed calcium and KATP channel dynamics during these hypoxic events. We envision microfluidic hypoxia, especially this simultaneous dual phase technique, as a valuable tool in studying islets as well as many ex vivo tissues.

Microfluidic oxygen control confers more than just convenience and speed over hypoxic chambers for biological experiments. Especially when implemented via diffusion through a membrane, microfluidic oxygen can provide simultaneous liquid and gas phase modulations at the microscale-level. This technique enables dynamic multi-parametric experiments critical for studying islet pathophysiology.

Simultaneous oxygenation and monitoring of glucose stimulus-secretion coupling factors in a single technique is critical for modeling pathophysiological ...

Bioengineering

Hippocampal Insulin Microinjection and In vivo Microdialysis During Spatial Memory Testing

Glucose metabolism is a useful marker for local neural activity, forming the basis of methods such as 2-deoxyglucose and functional magnetic resonance imaging. However, use of such methods in animal models requires anesthesia and hence both alters the brain state and prevents behavioral measures. An alternative method is the use of in vivo microdialysis to take continuous measurement of brain extracellular fluid concentrations of glucose, lactate, and related metabolites in awake, unrestrained animals. This technique is especially useful when combined with tasks designed to rely on specific brain regions and/or acute pharmacological manipulation; for example, hippocampal measurements during a spatial working memory task (spontaneous alternation) show a dip in extracellular glucose and rise in lactate that are suggestive of enhanced glycolysis1-3,4-5, and intrahippocampal insulin administration both improves memory and increases hippocampal glycolysis6. Substances such as insulin can be delivered to the hippocampus via the same microdialysis probe used to measure metabolites. The use of spontaneous alternation as a measure of hippocampal function is designed to avoid any confound from stressful motivators (e.g. footshock), restraint, or rewards (e.g. food), all of which can alter both task performance and metabolism; this task also provides a measure of motor activity that permits control for nonspecific effects of treatment. Combined, these methods permit direct measurement of the neurochemical and metabolic variables regulating behavior.

Hippocampal Insulin Microinjection and In vivo Microdialysis During Spatial Memory Testing

Modulation of hippocampally-dependent spatial working memory by direct intrahippocampal microinjection, accompanied and followed by in vivo microdialysis for metabolites in conscious, behaving animals.

Glucose metabolism is a useful marker for local neural activity, forming the basis of methods such as 2-deoxyglucose and functional magnetic resonance ...

Neuroscience

Membrane Potential Dye Imaging of Ventromedial Hypothalamus Neurons From Adult Mice to Study Glucose Sensing

Studies of neuronal activity are often performed using neurons from rodents less than 2 months of age due to the technical difficulties associated with increasing connective tissue and decreased neuronal viability that occur with age. Here, we describe a methodology for the dissociation of healthy hypothalamic neurons from adult-aged mice. The ability to study neurons from adult-aged mice allows the use of disease models that manifest at a later age and might be more developmentally accurate for certain studies. Fluorescence imaging of dissociated neurons can be used to study the activity of a population of neurons, as opposed to using electrophysiology to study a single neuron. This is particularly useful when studying a heterogeneous neuronal population in which the desired neuronal type is rare such as for hypothalamic glucose sensing neurons. We utilized membrane potential dye imaging of adult ventromedial hypothalamic neurons to study their responses to changes in extracellular glucose. Glucose sensing neurons are believed to play a role in central regulation of energy balance. The ability to study glucose sensing in adult rodents is particularly useful since the predominance of diseases related to dysfunctional energy balance (e.g.&#160;obesity) increase with age.

The activity of single neurons from adult-aged mice can be studied by dissociating neurons from specific brain regions and using fluorescent membrane potential dye imaging. By testing responses to changes in glucose, this technique can be used to study the glucose sensitivity of adult ventromedial hypothalamic neurons.

Studies of neuronal activity are often performed using neurons from rodents less than 2 months of age due to the technical difficulties associated with ...

Studying the Hypothalamic Insulin Signal to Peripheral Glucose Intolerance with a Continuous Drug Infusion System into the Mouse Brain

Insulin regulates systematic metabolism in the hypothalamus and the peripheral insulin response. An inflammatory reaction in peripheral adipose tissues contributes to type 2 diabetes mellitus (T2DM) development and appetite regulation in the hypothalamus. Chemokine CCL5 and C-C chemokine receptor type 5 (CCR5) levels have been suggested to mediate arteriosclerosis and glucose intolerance in type 2 diabetes mellitus (T2DM). In addition, CCL5 plays a neuroendocrine role in the hypothalamus by regulating food intake and body temperature, thus, prompting us to investigate its function in hypothalamic insulin signaling and the regulation of peripheral glucose metabolism.
The micro-osmotic pump brain infusion system is a quick and precise way to manipulate CCL5 function and study its effect in the brain. It also provides a convenient alternative approach to generating a transgenic knockout animal. In this system, CCL5 signaling was blocked by intracerebroventricular (ICV) infusion of its antagonist, MetCCL5, using a micro-osmotic pump. The peripheral glucose metabolism and insulin responsiveness was detected by the Oral Glucose Tolerance Test (OGTT) and Insulin Tolerance Test (ITT). Insulin signaling activity was then analyzed by protein blot from tissue samples derived from the animals.
After 7-14 days of MetCCL5 infusion, the glucose metabolism and insulin responsiveness was impaired in mice, as seen in the results of the OGTT and ITT. The IRS-1 serine302 phosphorylation was increased and the Akt activity was reduced in mice hypothalamic neurons following CCL5 inhibition. Altogether, our data suggest that blocking CCL5 in the mouse brain increases the phosphorylation of IRS-1 S302 and interrupts hypothalamic insulin signaling, leading to a decrease in insulin function in peripheral tissues as well as the impairment of glucose metabolism.

This protocol studies the role of chemokine (C-C motif) ligand 5 (CCL5) in the hypothalamus by delivering an antagonist, MetCCL5, into the mouse brain using a micro-osmotic pump brain infusion system. This transient inhibition of CCL5 activity interrupted hypothalamic insulin signaling, leading to glucose intolerance and peripheral systemic insulin sensitivity.

Insulin regulates systematic metabolism in the hypothalamus and the peripheral insulin response. An inflammatory reaction in peripheral adipose tissues ...

Acclimation Prior to an Intraperitoneal Insulin Tolerance Test to Mitigate Stress-Induced Hyperglycemia in Conscious Mice

The insulin tolerance test is commonly used in metabolic studies to assess whole body insulin sensitivity in rodents. It is a relatively simple test that involves measurement of blood glucose levels over time following a single intraperitoneal injection of insulin. Given that it is performed in the conscious state and blood is often collected via a tail snip, it has the potential to elicit a stress response from animals due to anxiety associated with handling and blood collection. As such, a stress-induced rise in blood glucose can occur, making it difficult to detect and interpret the primary endpoint measure, namely an insulin-mediated reduction in blood glucose. This has been seen in many mouse strains, and is quite common in diabetic db/db mice, where glucose levels can increase, rather than decrease, after insulin administration. Here, we describe a method of acclimating mice to handling, injections and blood sampling prior to performing the insulin tolerance test. We find that this lowers stress-induced hyperglycemia and results in data that more accurately reflects whole body insulin sensitivity.

Stress-induced elevations in glucose levels can confound interpretation of data derived from a conscious intraperitoneal insulin tolerance test in mice. In this article, we describe a method to acclimate the mice to handling, injections and blood sampling prior to performing the insulin tolerance test in order to limit stress-induced hyperglycemia.

The insulin tolerance test is commonly used in metabolic studies to assess whole body insulin sensitivity in rodents. It is a relatively simple test that ...

Surgical Installation of Hyperglycemic and Hypoglycemic Clamps in Mice

Hyperglycemic Clamp and Hypoglycemic Clamp in Conscious Mice

Diabetes mellitus (DM) is caused by insufficient insulin release from the pancreatic &#946;-cells (Type1 DM) and insulin sensitivity in muscles, liver, and adipose tissues (Type2 DM). Insulin injection treats DM patients but leads to hypoglycemia as a side effect. Cortisol and catecholamines are released to activate glucose production from the liver to recover hypoglycemia, called counter-regulatory responses (CRR). In DM research using rodent models, glucose tolerance tests and 2-deoxy-glucose injection are used to measure insulin release and CRR, respectively. However, blood glucose concentrations change persistently during experiments, causing difficulties in assessing net insulin release and CRR. This article describes a method in which blood glucose is kept at 250 mg/dL or 50 mg/dL in conscious mice to compare the release of insulin and CRR hormones, respectively.
Polyethylene tubing is implanted in the mice's carotid artery and jugular vein, and the mice are allowed to recover from the surgery. The jugular vein tubing is connected to a Hamilton syringe with a syringe pump to enable insulin or glucose infusion at a constant and variable rate. The carotid artery tubing is for blood collection. For the hyperglycemic clamp, 30% glucose is infused into the vein, and blood glucose levels are measured from the arterial blood every 5 min or 10 min. The infusion rate of 30% glucose is increased until the blood glucose level becomes 250 mg/dL. Blood is collected to measure insulin concentrations. For hypoglycemic clamp, 10 mU/kg/min insulin is infused together with 30% glucose, whose infusion rate is variable to maintain 50 mg/dL of blood glucose level. Blood is collected to measure counter-regulatory hormones when both glucose infusion and blood glucose reach a steady state. Both hyperglycemic and hypoglycemic clamps have the same surgical procedure and experimental setups. Thus, this method is useful for researchers of systemic glucose metabolism.

Author Spotlight: Investigating the Blood Glucose Homeostasis in Murine Brain Using a Cost-Effective Hyperglycemic And Hypoglycemic Clamp Technique

A hyperglycemic clamp is used for measuring insulin release with a maintained higher blood glucose concentration. A hypoglycemic clamp is for measuring glucose production induced by counter-regulatory responses. Both methods use the same surgical procedure. Here, we present a clamp technique to assess systemic glucose metabolism.

Diabetes mellitus (DM) is caused by insufficient insulin release from the pancreatic &#946;-cells (Type1 DM) and insulin sensitivity in muscles, liver, ...

Simple Continuous Glucose Monitoring in Freely Moving Mice

Mice are a common model organism used to study metabolic diseases such as diabetes mellitus. Glucose levels are typically measured by tail-bleeding, which requires handling the mice, causes stress, and does not provide data on freely behaving mice during the dark cycle. State-of-the-art continuous glucose measurement in mice requires inserting a probe into the aortic arch of the mouse, as well as a specialized telemetry system. This challenging and expensive method has not been adopted by most labs. Here, we present a simple protocol involving the utilization of commercially available continuous glucose monitors used by millions of patients to measure glucose continuously in mice as a part of basic research. The glucose-sensing probe is inserted into the subcutaneous space in the back of the mouse through a small incision to the skin and is held in place tightly using a couple of sutures. The device is sutured to the mouse skin to ensure it remains in place. The device can measure glucose levels for up to 2 weeks and sends the data to a nearby receiver without any need to handle the mice. Scripts for the basic data analysis of glucose levels recorded are provided. This method, from surgery to computational analysis, is cost-effective and potentially very useful in metabolic research.

Here, we describe a simple method to implant a commercial continuous glucose monitor designed for patients onto mice and provide the scripts to analyze the results.

Mice are a common model organism used to study metabolic diseases such as diabetes mellitus. Glucose levels are typically measured by tail-bleeding, which ...

Biology

Osmotic Minipump Implantation for Increasing Glucose Concentration in Mouse Cerebrospinal Fluid

Diabetes increases the risk of cognitive decline and impairs brain function. Whether or not this relationship between high glucose and cognitive deficits is causal remains elusive. Moreover, whether these deficits are mediated by an increase in glucose levels in cerebrospinal fluid (CSF) and/or blood is also unclear. There are very few studies investigating the direct effects of high CSF glucose levels on central nervous system (CNS) function, especially on learning and memory, since current diabetes models are not sufficiently developed to address such research questions. This article describes a method to chronically increase CSF glucose levels for 4 weeks by continuously infusing glucose into the lateral ventricle using osmotic minipumps in mice. The protocol was validated by measuring glucose levels in CSF. This protocol increased CSF glucose levels to ~328 mg/dL after infusion of a 50% glucose solution at a 0.25 &#181;L/h flow rate, compared to a CSF glucose concentration of ~56 mg/dL in mice that received artificial cerebrospinal fluid (aCSF). Furthermore, this protocol did not affect blood glucose levels. Therefore, this method can be used to determine the direct effects of high CSF glucose on brain function or a specific neural pathway independently of changes in blood glucose levels. Overall, the approach described here will facilitate the development of animal models for testing the role of high CSF glucose in mediating features of Alzheimer&#39;s disease and/or other neurodegenerative disorders associated with diabetes.

This article describes a detailed protocol to increase glucose concentration in the cerebrospinal fluid (CSF) of mice. This approach can be useful for studying the effects of high CSF glucose on neurodegeneration, cognition, and peripheral glucose metabolism in mice.

Diabetes increases the risk of cognitive decline and impairs brain function. Whether or not this relationship between high glucose and cognitive deficits ...

A Method for Manipulating Blood Glucose and Measuring Resulting Changes in Cognitive Accessibility of Target Stimuli

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