Insulin stimulated whole body glucose metabolism

During euglycaemic hyperinsulinaemia, skeletal muscle is primarily responsible for the insulin dependent increase of whole body glucose metabolism (Figure 4.4 and 4.6A) DeFronzo etal. 1985). The contribution of the liver to whole body glucose metabolism is small under these conditions. However, splanchnic glucose uptake and thus the contribution of the liver to whole body glucose metabolism increases under hyperglycaemic hyperin-sulinaemic conditions (Basu et al. 2004 Krssak et al. 2004)....

Application of muscle biopsy in diabetes

Insulin resistance in skeletal muscle is a major hallmark of type 2 diabetes (Beck-Nielsen & Groop 1994 Beck-Nielsen 1998 Beck-Nielsen et al. 2003). During the past two decades, skeletal muscle biopsies have been increasingly applied in the search for biochemical and molecular abnormalities responsible for insulin resistance. It is evident that type 2 diabetes is caused by a complex interplay between genetic and environmental factors. The latter include intrauterine malnutrition and...

Preparation of the insulin infusion

The insulin infusate is prepared with human insulin, which is added to isotonic saline. The insulin infusion pump must be calibrated and must provide sufficient fine gears to allow the administration of the calculated insulin dose. In order to prevent the absorption of the hormone in plastic surfaces, 2 ml of the individual's blood per 48 ml of the infusate is added to the infusate (Sherwin etal. 1974 DeFronzo etal. 1979). The effectiveness of this method can be proven by measuring the insulin...

Regulation of endogenous glucose output during euglycaemic hyperinsulinaemia

Hyperinsulinaemia dose dependently inhibits endogenous glucose output (Kolterman etal. 1981 DeFronzo 1988), which is mainly of hepatic origin (Ekberg etal. 1999). An important regulator of hepatic glucose release is the relationship of hepatic sinusoidal concentrations of insulin and glucagon (Cherrington 1999). Although irrelevant during a hyperinsulinaemic clamp test performed at euglycaemia, hyperglycaemia per se also exerts a powerful inhibitory effect on endogenous glucose output (Bell...

Computed Tomography CT

Signal intensity in the CT images corresponds to the linear attenuation coefficient, which depends on physical properties (including density) of tissue within the volume of interest. Signal intensity is expressed in so-called computed tomography numbers or Hounsfield units (HU), which range from -1,000 to +3,095 (4,096 values). Based on their density and the resulting differences in X-ray attenuation, muscle and fat tissue display different ranges of intensity (-190 to -30 HU for fat and 0 to...

Body fat distribution and insulin resistance Skeletal muscle intramyocellular lipids

Overabundance of plasma triglycerides and free fatty acids entering the circulation by lipol-ysis from adipose tissue or by ingestion from food is frequently associated with pathophys-iology of insulin resistance and diabetes mellitus (Defronzo 2004). Results of radioactive tracer and stable isotope dilution studies have suggested that both hepatic and peripheral muscle tissues are involved in the development of insulin resistance (Defronzo 1988). Focusing on glucose uptake in skeletal muscle,...

The insulin infusate

Where insulin is to be infused over prolonged periods, it is important to be sure that the concentration of the infusate remains stable. The dose is often estimated in milliunits of insulin per kilogram body weight, although using the body surface area is preferable, especially where subjects of different sizes are to be compared. Body surface area relates more precisely to volume of distribution. The specific requirements for individual studies are discussed below. Insulin sticks to plastic...

Fluorescein angiography of the fundus

Fluorescein Angiography

No other single technique has had more impact on retinal investigation than fundus photography with the dye fluorescein. It has contributed to the diagnosis and treatment of chorioretinal diseases, elucidated poorly understood retinal diseases and served as an indispensable research modality. Sodium fluorescein is a yellow-red dye with a molecular weight of 376.67. It is used in 10 or 25 sterile aqueous solution. When injected, usually into the antecubital vein, 80 of it is bound to plasma...

Radioactive vs stable isotopes

The study of amino acid kinetics is typically concerned with measuring the flow of carbon and or nitrogen. The choice of whether to use radioactive or stable isotopes typically depends on an investigator's experience, the research question(s) being asked and the facilities that are available. We consider here three factors that have likely contributed to the increased use of stable isotopes over radioactive isotopes. First, concerns for safety and improvements in nuclear magnetic resonance...

Investigating the pathogenesis of problematic hypoglycaemia

In order to investigate counterregulatory mechanisms, it is important to produce hypogly-caemia in a controlled laboratory setting where physiological and cognitive responses can be measured accurately and reproducibly. Two variables can be measured the ability to counterregulate, in which the subject's ability to arrest a falling glucose is determined and the elements of the counterregulatory responses themselves, in which the hypoglycaemic challenge is strictly controlled by the investigator,...

Tracers for the study of adipose tissue lipolysis Free fatty acids

Free fatty acids (FFAs) are the major lipid fuel in the circulation, with a relatively high flux rate that can be estimated at approximately 100g day in healthy adults (Miles et al. 2004). The use of tracers for the study of FFA kinetics is nearly 50 years old (Frederickson & Gordon 1958), but there has been a renewed interest in FFA metabolism in recent years because of evidence that elevated FFA levels are likely mediators of insulin resistance (Boden et al. 1991), endothelial dysfunction...

References

Anderson S, Blouch K, Bialek J, Deckert M, Parving HH, Myers BD 2000 Glomerular permselectivity in early stages of overt diabetic nephropathy Kidney Int 58, 2129-2137 Annet L, Hermoye L, Peeters F, Jamar F, Dehoux JP, Van beers BE 2004 Glomerular filtration rate, an assessment with dynamic contrast-enhanced MRI and a cortical-compartment model in the rabbit kidney J Magn Reson Imaging 20, 843-849 Arun CS, Stoddart J, Mackin P, MacLeod JM, New JP, Marshall SM 2003 Significance of...

Limitations of human myotubes

Mature Human Myotubes

Cell culture techniques are dependent on aseptic conditions. The laboratory has to be equipped with the necessary cell culturing facilities and has to have good laboratory practice GLP . Although the technique seems simple, success with cultures of human myotubes depends on technicians with appropriate aseptic skills and the ability to diagnose problems as they arise. It is important to realise that we are dealing with a primary culture system, with restrictions such as limited lifespan of...

Percutaneous needle biopsy of skeletal muscle

Bergstrom Needle

Extensive investigation of the metabolism of normal and abnormal tissue requires a simple method for tissue sampling. The percutaneous muscle biopsy technique developed and introduced by Bergstrom in the 1960s provides a simple and repeatable sampling method Bergstrom 1962, 1975 , which has made skeletal muscle one of the few tissues suitable for direct studies of structure and metabolic functions in human subjects. The percutaneous muscle biopsy procedure has been used widely to study many...

Homa

As with the HOMA method for insulin resistance see Chapter 3 , the calculation of the HOMA P-cell function index HOMA-B requires only fasting glucose and insulin measurements. A model-based version of the method HOMA2, http www.dtu.ox.ac.uk homa web search keywords homa calculator,site dtu.ox.ac.uk is recommended, although a formula is also available HOMA-B constant X fasting insulin fasting glucose - 3.5 Matthews et al. 1985 . The advantages of the HOMA2 computer index have not been...

Coupling nitrogen balance and isotope tracers

Measurements of total nitrogen intake and output can be used to calculate protein nutritional status Leverton amp Gram 1949 Hegsted 1978 . This approach is based on principles of chemical mass-balance, and although practical matters concerning collecting total nitrogen waste make this method difficult to implement, measurements of nitrogen balance generally permit a reliable determination of protein homeostasis. Use of the method requires special consideration since urinary nitrogen may occur...

Advantages and limitations of needle biopsy

The needle biopsy circumvents many of the disadvantages of the open muscle biopsy, which include higher costs, the need for general anaesthetic, increased scarring and the inconvenience of repeated biopsies Goldberger et al. 1978 Edwards et al. 1980, 1983 . The fact that many of our patients and control subjects have participated in several studies involving muscle biopsies emphasises that this technique is easy to learn, repeatable and relatively atraumatic. It is a safe procedure that is...

Magnetic Resonance Imaging MRI and spectroscopy

Body Fat Distribution Mri

Positioning of measured samples in strong homogeneous magnetic fields forces protons within the sample to align according to the direction of the magnetic field and thus create a macroscopic magnetisation of the sample. Interaction of spins with externally applied radiofrequency RF waves at the resonant frequency changes the magnitude and direction Figure 13.3 Assessment of Abdominal Fat Storage by Computed Tomography CT Representative cross-sectional abdominal CT scans of a lean A and an obese...

Nomenclature of glycaemic targets of clamp tests

In healthy subjects an insulin clamp performed at fasting plasma glucose concentration is termed an euglycaemic insulin clamp test. In general, when the target of plasma glucose concentration is above the fasting level, this is termed a hyperglycaemic insulin clamp test. The latter should not be mixed up with the hyperglycaemic glucose clamp test, which is performed without concomitant infusion of insulin and which can be used to assess endogenous insulin secretion in response to glucose...

Hypoglycaemia Recording Form

Todays date dd mm yy Time of hypo Did you have any warning symptoms Q YES Q NO If yes, please indicate which, if any, of the following occurred tick more than one box if necessary Confusion Sweating Drowsiness Weakness Dizziness Warmness Difficulty speaking Pounding heart Inability to concentrate Shivering Unsteady on feet Yellow vision Double vision Blurred vision Hunger Thirst Nausea Anxiety Tiredness Tingling lips Trembling Headache Abdominal pain Other specify How did the intensity of these...

Info

Amiel BSc, MD, FRCP, RD Lawrence Professor of Diabetic Medicine, Gene and Cell Based Therapy, Diabetes Research Group, Diabetes, Endocrinology and Metabolism, King's College London School of Medicine, London, UK Henning Beck-Nielsen MD, DMSc, Head of the Department of Endocrinology, Odense University Hospital, Professor of Endocrinology, University of Southern Denmark, and Head of the Danish PhD School of Molecular Metabolism, Odense, Denmark Ayad Al-Bermani MD, Specialist...

Blood sampling site arterial venous or arterialised venous blood sampling

Matched hyperinsulinaemia rates of whole body glucose metabolism can only be directly compared among individuals if the concentration of glucose perfusing their glucose utilising tissues is the same Bergman etal. 1985 . The concentration of plasma glucose physiologically declines during the perfusion of glucose utilising tissues. In addition, pancreatic insulin secretion is regulated by the arterial blood glucose concentration. Early studies applying the glucose clamp technique measured the...

Vldl

Very low density lipoproteins VLDL are of interest for two reasons. First, they are the obligate precursor of low density lipoproteins LDL Dietschy et al. 1993 . Second, together with chylomicrons, VLDLs represent the major vehicle for transport of triglycerides in the circulation. VLDL triglyceride secretion by the liver is controlled to some extent by the supply of FFA to that tissue Lewis et al. 1995 , with additional acute regulation by insulin Sparks amp Sparks 1994 . Hepatic VLDL...