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,...

References

Akira, K, Negishi, E, Yamamoto, C, Baba, S (1997) Evaluation of liver function by co-administration methodology using 13C-labelled benzoic acid and hippuric acid coupled with nuclear magnetic resonance spectroscopy J Pharm Pharmacol 49, 1242-1247 Allick, G, Sprangers, F, Weverling, GJ, Ackermans, MT, Meijer, AJ, Romijn, JA, Endert, E, Bisschop, PH, Sauerwein, HP (2004) Free fatty acids increase hepatic glycogen content in obese males Metabolism 53, 886-893 Ambrose, AM, Power, FW, Sherwin, CP...

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...

Pathophysiology

In health, the human body protects itself from clinically important hypoglycaemia very efficiently through a series of physiological and neuroendocrine responses, collectively described as 'counterregulation' (Amiel & Gale 1993). The major components of the counterregulatory hormone responses are shown in Figure 5.1. Blood glucose concentrations are normally very strictly regulated at 3.5-7 mmol l despite massive fluctuations in the rates at which tissues utilise glucose (rest vs exercise)...

Signs

The use of composite scores to assess clinical signs was pioneered by Dyck and colleagues Dyck et al. 1997 Dyck 2003 , who first described the Neuropathy Disability Score NDS and later the Neuropathy Impairment Score NIS . A modified NDS has been used in several large studies Young et al. 1993 Cabezas-Cerrato 1998 Abbott et al. 2002 and can also be used in the community by a trained nonspecialist. It has been shown to be the best predictor of foot ulceration and the best neuropathic end point...

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...

Exercise intolerance

In diabetic patients without evidence of heart disease, but with asymptomatic vagal CAN, exercise capacity greatest tolerable workload and maximal oxygen uptake , heart rate, blood pressure, cardiac stroke volume and hepatosplanchnic vascular resistance are diminished. Figure 16.1 Test battery for the detection and characterisation of cardiovascular autonomic neuropathy CAN . Figure 16.1 Test battery for the detection and characterisation of cardiovascular autonomic neuropathy CAN . A further...

Homa B Formulation

As with the HOMA method for insulin resistance see Chapter 3 , the calculation of the HOMA -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...

Liver intrahepatic lipids

As with skeletal muscle, elevated circulating free fatty acids FFA are associated with hepatic features of insulin resistance increased fasting endogenous glucose production EGP Hundal et al. 2000 , insufficient suppression of EGP in the postprandial state Singhal et al. 2002 Krssak et al. 2004 and defects in hepatic glycogen synthesis Krssak et al. 2004 in type 2 diabetes. Studies in young healthy volunteers have shown that experimentally elevated FFA concentration increased gluconeogenesis...

Thermal thresholds

Although most mechanoreceptors and free nerve endings can be stimulated by thermal energy, true cutaneous thermoreceptors are orders of magnitude more sensitive to shifts in temperature. The sensation of pain can be driven by high-intensity stimulation of thermore-ceptors, especially those sensitive to warming this activation can be assessed by measuring heat-pain thresholds Yaritsky et al. 1995 . As is the case with vibration, altered thermal thresholds have been well documented in patients...

Introduction

Diabetic autonomic neuropathy DAN may affect any organ innervated by the autonomic nervous system. Although DAN has been appreciated as a clinical entity since the classic report by Rundles 1945 , in the past it has received less attention than peripheral sensorimotor neuropathy. This is due on one hand to the fact that the onset of clinical features is insidious and severe clinical symptoms usually occur relatively late in the course of diabetes, and on the other hand, because non-invasive,...

Hovorka R. Isec Calculating Insulin Secretion Program Http Www.soi.city.ac.uk Sg331.

Potassium Glucose Transporter

Methods for the Assessment of p-Cell Function In Vivo The P cell plays a key role in the maintenance of glucose homeostasis and P-cell dysfunction is a characteristic feature of many states of glucose intolerance. Thus, the assessment of P-cell function is of fundamental importance in the study of metabolic disorders, particularly type 2 diabetes, and in the evaluation of drugs to treat P-cell dysfunction. At the present time, P-cell function continues to be very actively studied, as strategies...

Applications of PET for the assessment of skeletal muscle metabolism

By combining PET and the glucose-insulin clamp technique, insulin resistance for glucose was shown to localise in skeletal muscle in type 1 and type 2 diabetes Nuutila et al. 1993 Utriainen et al. 1998 . Using compartmental modeling, insulin is shown to affect transport and phosphorylation but not extracellular kinetics, with the transport step becoming the main site of control Kelley et al. 1999 Bertoldo et al. 2001 . Skeletal muscle free fatty acid uptake measured using 18-F-FTHA under...

Fluorescein angiography of the fundus

Fundus Angiography Diabetic Retinopathy

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...

Tdm

Bad control short term long amp short term good control good control Figure 11.12 Hepatic Glycogen Accumulation in Healthy and Diabetic Patients Rates of postprandial hepatic glycogen accumulation as measured in healthy men CON Krssak et al. 2004 and patients with type 2- and type 1 diabetes mellitus T2DM Krs's'a'k et al. 2004 T1DM Bischof et al. 2001, 2002 . A 50-60 decrease in this measure was observed by natural abundance 13C MR spectroscopy in both pathologies. Partial improvement was...

Standardised indices of insulin sensitivity derived from the M value

For purposes of comparison, M values should be standardised Ferrannini amp Mari 1998 . The steady state rate of whole body glucose metabolism is frequently normalised for bodyweight Mbw , fat free mass Mffm , rate of resting energy expenditure Mree and steady state plasma insulin concentration during the clamp M I Bergman etal. 1985 Ferrannini amp Mari 1998 . Normalisation of the M value for the mean steady state concentration of plasma glucose yields the metabolic clearance rate of glucose MCR...

Application of muscle morphology in type diabetes

Imcl Diabetes

Insulin resistance and type 2 diabetes are associated with a number of morphological characteristics in skeletal muscle. In humans, muscle fibre composition is more mixed than in rodents Johnson et al. 1973 . This has implications for many biochemical and metabolic abnormalities observed in studies of crude muscle extracts, as the functional and metabolic properties of muscle are to a large extent determined by its fibre type composition. Using the myofibrillar ATPase histochemical staining...

Strain gauge plethysmography

Strain gauge plethysmography has been developed since the early 1990s for assessment of endothelial function. Since the advent of mercury-in-rubber strain gauges, venous occlusion plethysmography has been easy to perform, and measurement of forearm blood flow FBF is now widely used to probe the mechanisms of human vascular control. The underlying principle of venous occlusion plethysmography is straightforward if venous return from the arm is obstructed and arterial inflow continues unimpeded,...

Info

It is the reciprocal of the logarithm of HOMA calculated with k 1. Therefore, the information obtained with the two indices is virtually the same. Since the liver is the primary organ responsible for maintaining basal glucose homeostasis, the sensitivity measured with basal glucose and insulin values is reputed to be a figure of hepatic insulin resistance. The agreement between HOMA-R and clamp-measured insulin sensitivity is controversial, ranging from very good to non-existing Pacini amp Mari...

Albumin excretion

The hallmark of diabetic nephropathy is the progressive rise in urinary protein excretion, which is primarily of glomerular origin. Our understanding of the natural history of diabetic nephropathy was revolutionised by the development of immunoassays specific for albumin and capable of detecting small mg l amounts, so-called microalbuminuria Keen amp Chlou-verakis 1963 . In clinical practice, urine albumin and creatinine are measured in a non-timed preferably early morning urine sample, and the...

Electrophysiology

Whole nerve electrophysiological procedures e.g. NCV, F-waves, sensory and or motor amplitudes have emerged as important methods for tracing the onset and progression of diabetic neuropathy Bril 2003 . Typically, neurophysiological studies show a reduction in the amplitude of sensory action potentials, which is most extreme in the lower limbs. Multiple consensus panels have recommended the inclusion of electrophysiology in the evaluation of DPN, as well as the use of these procedures as...

Dalla V.m. Masiero A. Roiter A.m. Et Al Is Podocyte Injury Relevant In Diabetic Nephropathy Studies In Patients With

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...

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...

Using rates of amino acid flux to determine wholebody protein turnover

Incorporation 13c Leucine

As noted earlier in this section, investigators are faced with several choices regarding measurements of amino acid flux and protein turnover. One of the more widely applied methods for quantifying amino acid and protein turnover centres on the use of a primed-infusion of 1-13C leucine Figure 10.2 . The flux of an amino acid e.g. leucine is described using the equation where Q is the rate of amino acid turnover in plasma or the flux , S is the rate of incorporation of the amino acid into...

Computed Tomography CT

Total Body Fat

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 100 HU...

Optical coherence tomography OCT

This new technique for high-resolution cross-sectional imaging of various ocular structures was introduced in 1991. With an axial resolution of 10 mu, it provides the best resolution of retinal architecture of any imaging technique currently available. Information may be stored on computer disks and easily accessed in the future. This feature makes OCT particularly useful in the assessment, diagnosis and treatment of macular disease. The limitations of OCT include the inability to obtain...

Dhap

Glucose Enrichment

Figure 8.2 Metabolic model showing the principal exchange reactions that result in enrichment of glucose-6-phosphate and gluconeogenic precursors from 2H2O. 1 glucose-6-phosphate isomerase 2 phosphoglucomutase 3 transaldolase 4 triose phosphate isomerase. glucose, glycogen or gluconeogenesis . Under fasting conditions, when the liver is a net exporter of glucose, enrichment of plasma glucose position 2 represents all glucose derived from G6P. Under isotopic steady state conditions, enrichment...

Bernard Landau Md

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...

Fasted state net glucose synthesis from hepatic GP

Nmr Spectra Paracetamol

Under these conditions, hepatic G6P is assumed to be entirely derived from gluconeogenesis and glycogenolysis activities and to be the sole source of plasma glucose synthesis, as shown in Figure 8.3. Because of extensive G6P-F6P exchange, position 2 is assumed to be enriched to the same level as body water and therefore it represents all G6P sources. Meanwhile, position 5 enrichment reflects the total gluconeogenic contribution. On this basis, the ratio of position 5 to position 2 enrichment H5...

Tracers for the study of triglyceriderich lipoprotein kinetics Chylomicrons

Chylomicrons are large lipoprotein particles that are formed by the small intestine during fat absorption. The amount of lipid fuel that traverses the circulation in the form of chylomicrons obviously varies with dietary fat consumption. In individuals on high-fat diets, however, it can equal or exceed FFA flux Miles et al. 2004 . The triglyceride transported in chylomicrons is metabolised by LPL, which is widely distributed in tissues but is most abundant in adipose tissue and skeletal muscle...

Retinal imaging

Fields Etdrs Standard Photos

In the ETDRS, assessment of diabeticretinopathy was based on seven field 30 stereo fundus photographs ETDRS 1991b . Field 1 is centred on the optic disc, Field 2 is centred on the macula and Field 3 is just temporal to the macula. Fields 4-7 are tangential to horizontal lines passing through the upper and lower poles of the disc and to a vertical line passing through its centre Figure 19.7 . This procedure may be unpleasant for the patient, time consuming and expensive for the community. It is...

Ncv

NCV is only gradually diminished by DPN, with estimates of a loss of 0.5m s-1 year-1 Arezzo 1997 . In a 10-year natural history study of 133 patients with newly diagnosed type 2 diabetes, NCV deteriorated in all six nerve segments evaluated, but the largest deficit was 3.9 m s for the sural nerve peroneal motor NCV was decreased by 3.0 m s over the same period Partanen 1995 . A similar slow progression of change in NCV was detected in the diabetes control and complications trial DCCT DCCT...

Limitations of human myotubes

Primary Cell Culture Satellite Cell

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...

The Snellen chart

Snellen Chart Hcvd

This chart is named after a Dutch ophthalmologist 1834-1908 . It consists of a series of letters of diminishing size as in Figure 19.1a. Each letter has an overall size five times the thickness of the lines composing the letter. The results of the test are expressed as a fraction, in which the numerator is the testing distance 6 m and the denominator is the distance at which a normal observer would be able to read the letter. Other test types, which are designed to be applicable to any...

Magnetic Resonance Imaging MRI and spectroscopy

Mri Spectroscopy Show Muscle

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...

Percutaneous needle biopsy of skeletal muscle

Needle Muscle Biopsy

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...

Silent myocardial infarction and ischaemia

In view of the increased prevalence of coronary artery disease CAD in diabetic patients, it is difficult to differentiate between the impact of coronary ischemia and CAN on cardiac autonomic function. In other words, silent ischemia in diabetic patients may either result from CAN or from autonomic dysfunction due to CAD itself, or both. In the Framingham study, the rates of unrecognised myocardial infarctions were 39 in diabetic subjects and 22 in non-diabetic subjects, but the difference was...

Clinical Assessment Symptoms

Many patients have difficulty in describing the symptoms of neuropathy. Pain and paresthe-siae are personal experiences, but there is marked variation in the description of symptoms between individuals with similar pathological lesions. This has important implications for the assessment of symptoms Huskisson 1976 clearly stated that 'pain is apersonal psychological experience and an external observer can play no part in its direct measurement.' When recording symptoms in clinical practice,...

Bicentennial

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