Relationship between adipose tissue lipolytic activity and skeletal muscle insulin resistance in nondiabetic women

CONTEXT

Increased adipose tissue lipolytic activity is considered an important factor in the pathogenesis of skeletal muscle insulin resistance associated with obesity.

OBJECTIVE

The objective of the study was to evaluate the relationship between the rate of release of free fatty acids (FFA) into plasma and skeletal muscle insulin sensitivity in human subjects.

METHODS

We determined the palmitate rate of appearance (Ra) per kilogram fat-free mass (an index of FFA availability to lean tissues) during basal conditions and during insulin infusion (to simulate postprandial insulin concentrations) and skeletal muscle insulin sensitivity, defined as the percent increase in the glucose rate of disappearance, in 110 nondiabetic women (body mass index 20.6-46.4 kg/m(2)) by using the hyperinsulinemic-euglycemic clamp procedure in conjunction with stable isotope tracer methods.

RESULTS

Basal (r(s) = -0.379, P < 0.001) and insulin-suppressed (r(s) = -0.631, P < 0.001) palmitate Ra correlated negatively with skeletal muscle insulin sensitivity. However, the strength of the correlation was greater for palmitate Ra during insulin infusion than palmitate Ra during basal conditions (P = 0.0007) when lipolytic rates and FFA availability were reduced to less than 20% of basal values. The relative suppression of palmitate Ra correlated directly with the relative stimulation of glucose rate of disappearance during insulin infusion (r(s) = 0.530, P < 0.001).

CONCLUSION

These data suggest that the correlation between FFA kinetics and muscle glucose metabolism is due to multiorgan insulin resistance rather than a direct effect of FFA itself on skeletal muscle insulin action and challenge the view that increased adipose tissue lipolytic rate is an important cause of insulin resistance.

Multiorgan insulin sensitivity in lean and obese subjects

OBJECTIVE

To provide a comprehensive assessment of multiorgan insulin sensitivity in lean and obese subjects with normal glucose tolerance.

RESEARCH DESIGN AND METHODS

The hyperinsulinemic-euglycemic clamp procedure with stable isotopically labeled tracer infusions was performed in 40 obese (BMI 36.2 ± 0.6 kg/m(2), mean ± SEM) and 26 lean (22.5 ± 0.3 kg/m(2)) subjects with normal glucose tolerance. Insulin was infused at different rates to achieve low, medium, and high physiological plasma concentrations.

RESULTS

In obese subjects, palmitate and glucose R(a) in plasma decreased with increasing plasma insulin concentrations. The decrease in endogenous glucose R(a) was greater during low-, medium-, and high-dose insulin infusions (69 ± 2, 74 ± 2, and 90 ± 2%) than the suppression of palmitate R(a) (52 ± 4, 68 ± 1, and 79 ± 1%). Insulin-mediated increase in glucose disposal ranged from 24 ± 5% at low to 253 ± 19% at high physiological insulin concentrations. The suppression of palmitate R(a) and glucose R(a) were greater in lean than obese subjects during low-dose insulin infusion but were the same in both groups during high-dose insulin infusion, whereas stimulation of glucose R(d) was greater in lean than obese subjects across the entire physiological range of plasma insulin.

CONCLUSIONS

Endogenous glucose production and adipose tissue lipolytic rate are both very sensitive to small increases in circulating insulin, whereas stimulation of muscle glucose uptake is minimal until high physiological plasma insulin concentrations are reached. Hyperinsulinemia within the normal physiological range can compensate for both liver and adipose tissue insulin resistance, but not skeletal muscle insulin resistance, in obese people who have normal glucose tolerance.

Molecular mechanism underlying the cerebral effect of Gly-Pro-Glu tripeptide bound to L-dopa in a Parkinson's animal model

Oxidative stress is a critical contributing factor to neurodegenerative disorders. Therefore, the inhibition of ROS formation, responsible for chronic detrimental neuroinflammation, is an important strategy for preventing the neurodegenerative disease and for neuroprotective therapy. Gly-Pro-Glu (GPE) is the N-terminal tripeptide of insulin-like growth factor-I, which is naturally cleaved in the plasma and brain tissues. GPE has neuroprotective effects since it crosses the blood-CSF and the functional CSF-brain barriers and binds to glial cells. It has been shown that GPE improves motor behaviour in rats after 6-OHDA lesion, although it does not rescue dopaminergic neurons. Thus, we hypothesized that the GPE therapeutic efficacy in a Parkinson model might be improved by combining GPE to L: -dopa. Here, we used an animal model that represents a progressive chronic Parkinson's disease (PD) model, characterized by high levels of oxidative stress and inflammation. We showed that the co-drug, in which L: -dopa is covalently linked to the GPE tripeptide, by down-regulating the expression of inflammatory genes, decreases the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced inflammatory response and, by up-regulating tyrosine hydroxylase, reduces MPTP-induced neurotoxicity. Furthermore, by determining the nuclear translocation/activation of Nrf2 and NF-κB, we showed that systemic administration of the co-drug activates Nrf2-induced antioxidant response while suppressing NF-κB inflammatory pathway. Data suggest that the binding of L: -dopa to GPE tripeptide might represent a promising strategy to supply L: -dopa to parkinsonian patients.

Validation of a novel index to assess insulin resistance of adipose tissue lipolytic activity in obese subjects

Insulin resistance in adipose tissue increases the release of free fatty acids into the circulation, which likely contributes to impaired insulin action in liver and skeletal muscle associated with obesity. However, reliable assessment of adipose tissue insulin resistance requires performing a hyperinsulinemic-euglycemic clamp procedure in conjunction with a fatty acid tracer infusion to determine insulin-mediated suppression of lipolytic rate. We developed a simpler method for evaluating adipose tissue insulin resistance in vivo, determined as the product of palmitate rate of appearance into the bloodstream and plasma insulin concentration during basal conditions. We validated our Adipose Tissue Insulin Resistance Index (ATIRI) by comparison with an assessment of adipose tissue insulin resistance determined by using the hyperinsulinemic-euglycemic clamp procedure in conjunction with a palmitate tracer infusion in 47 obese nondiabetic subjects (body mass index: 40.1 ± 9.3 kg/m(2)). We found the ATIRI correlated closely with adipose tissue insulin resistance assessed during the clamp procedure (r =-0.854, P < 0.001). These results demonstrate that the ATIRI provides a reliable index of adipose tissue insulin resistance in obese subjects.

[Walking efficiency of blind people on trapezoidal and sinusoidal section tactile leading indicators]

Gait of visually impaired subjects (VIS) is worse than that of sighted ones. VIS can use tactile ground surface indicators to optimize their walking efficiency. Aim of the study was to compare VIS walking efficiency on either trapezoidal and sinusoidal shape leading indicators. VIS walking on the sinusoidal leading indicators showed a worsening of the time-distance parameters (a longer stance phase, a shorter swing phase and shorter step and stride lengths), reduced lower limb joint excursions and increased center of mass oscillations. In conclusion sinusoidal tactile indicators induce a stiffening of joints and a loss of balance with an increased risk of fall.

Walking strategies of visually impaired people on trapezoidal- and sinusoidal-section tactile groundsurface indicators

The visual system in walking serves to perceive feedback or feed-forward signals. Therefore, visually impaired persons (VIP) have biased motor control mechanisms. The use of leading indicators (LIs) and long canes helps to improve their walking efficiency. The aims of this study were to compare the walking efficiency of VIP on trapezoidal- and sinusoidal-section LIs using an optoelectronic motion analysis system. VIP displayed a significantly longer stance phase, a shorter swing phase and shorter step and stride lengths when they walked on the sinusoidal LI than when they walked on the trapezoidal LI. Compared with the trapezoidal LI, VIP walking on the sinusoidal LI displayed significantly lower joint ranges of motion. The centre of mass lateral displacement was wider for VIP walking on the sinusoidal LI than on the trapezoidal LI. Some significant differences were also found in sighted persons walking on both LIs. In conclusion, the trapezoidal shape enabled visually impaired subjects to walk more efficiently, whereas the sinusoidal shape caused dynamic balance problems. STATEMENT OF RELEVANCE: These findings suggest that VIP can walk more efficiently, with a lower risk of falls, on trapezoidal-section than on sinusoidal-section LIs. These results should be considered when choosing the most appropriate ground tactile surface indicators for widespread use.

Abstract P2-10-05: Referral to Genetic Services (GS) and Mutation Yield in 1132 Individuals at Risk for Hereditary Breast Ovarian Cancer Syndromes (HBOC)

Background: Family history directs referral of unaffected individuals to GS and is the main strategy to identify hereditary breast ovarian cancer syndrome. In unaffected individuals with known familial mutations, potentially life saving information can be provided to a large number of these individuals at a very modest cost.

Objectives: 1) To determine the rate of deleterious mutations in high risk individuals, based on pedigree, and 2) to identify the origin of their referral. Methods:

Over a 5-year period (2004 -2009) we analyzed the source of referral for genetic testing and the mutations detected in 1132 consecutively tested individuals. Of 1132 patients tested for BRCA1 or BRCA2 mutations, 420 were unaffected by cancer and 712 had breast or ovarian cancer at the time consultation. We excluded those from families who were previously tested at our institution to limit the bias for mutation positivity.

Results:

Seven hundred and sixty five patients were tested via comprehensive BRCA analysis (63 patients also had BART analysis) and of those only 7% (55) had deleterious mutations. Only 3% (24) had mutations in BRCA1 gene, and 29 patients had deleterious mutations in BRCA2. Of the 63 patients who underwent BART only 3% (2) had large deletions in BRCA1 gene. Two hundred and seventy three patients were tested for the three known Ashkenazi mutations and 20% (57) had deleterious mutations 10% (28) in BRCA1 gene and 10% (29) in BRCA 2. Ninety four patients were tested for known family mutations with single site analysis and there were (57%) 54 had deleterious mutations 27% (26) in BRCA 1 gene and 29% (28) in BRCA 2. Referring source was: self 283 (25%), GYN 430 (38%), surgeon 283 (25%), PCP 136 (12%) cases. Conclusions:

Single site testing of a known mutation costs ∼ 400$ and in 94 patients (8%) gave rapid information about cancer risk. Of these 27% (26) unaffected individuals were identified as carrying deleterious mutations and 73% (68) individuals found out their cancer risk was average. The yield of testing by comprehensive BRCA analysis was 7%, M3 panel detected 20% deleterious mutation and single site analysis for known familial mutations had the lower cost and higher yield of 57%. Primary care physicians identified only 12% of patients with high risk for hereditary cancer syndromes.

Discussion:

Although family history is the cornerstone of high-risk patient referral to GS, primary care physicians referred only 12% of all patients at risk for HBOC. Attention to family history and increased public awareness of hereditary risk are effective means of identifying at risk populations for referral for GS. The yield of mutation detection is highest and cost effective in families with known mutations. Our yield of 57% detection in families with known mutations is likely an indication that not all family members at risk seek genetic counseling or are referred at the same center.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-10-05.

Optimizing Burn Treatment in Developing Low-and Middle-Income Countries with Limited Health Care Resources (Part 2)

The present review of the literature aims at analysing the challenges facing burn management in low- and middleincome countries (LMICs) and exploring probable modalities to optimize burn management in these countries. In Part 1, the epidemiology of burn injuries and the formidable challenges for proper management due to limited resources and inaccessibility to sophisticated skills and technologies in LMICs were presented. Part II will discuss the actual state of burn injuries management in LMICs.

Optimizing burn treatment in developing low- and middle-income countries with limited health care resources (part 1)

In developing countries burn injuries are much more common than in the USA and Europe or other affluent developed countries, due to poverty, overcrowding, and illiteracy, and are associated with higher mortality rates. The high incidence makes burns an endemic health hazard in these countries. Over 90% of burn-related fatalities occur in developing or low- and middle-income countries (LMICs), with south-east Asia alone accounting for over half of fire-related deaths. Management of burns and their sequelae even in the well-equipped, modern burn units of advanced affluent societies remains demanding despite advances in surgical techniques and development of tissue-engineered biomaterials available to these burn centres. Undoubtedly, in a developing country with limited resources and inaccessibility to sophisticated skills and technologies, management of burns constitutes a major challenge. The present review of the literature analyses the challenges facing burn management in LMICs and explores probable modalities to optimize burn management in these countries. The review will be published in three parts. Part I will present the epidemiology of burn injuries and challenges for management in LMICs. Part II will be about management of burn injuries in LMICs and Part III will discuss strategies for proper prevention and burn care in LMICs.

Methods for assessing intrahepatic fat content and steatosis

PURPOSE OF REVIEW

Intrahepatic fat content is increasingly being recognized as an integral part of metabolic dysfunction. This article reviews available methods for the assessment of hepatic steatosis.

RECENT FINDINGS

Apart from liver biopsy, there are several noninvasive radiologic modalities for evaluating nonalcoholic fatty liver disease. Ultrasonography, computed tomography, and traditional MRI remain largely qualitative methods for detecting mild to severe degrees of steatosis rather than quantitative methods for measuring liver fat content, even though novel attempts to collect objective quantitative information have recently been developed. Still, their sensitivity at mild degrees of steatosis is poor. Undoubtedly, most methodological advances have occurred in the field of MRI and magnetic resonance spectroscopy, which currently enable the accurate quantification of intrahepatic fat even at normal or near normal levels. Xenon computed tomography was also recently shown to offer another objective tool for the quantitative assessment of steatosis, although more validation studies are required.

SUMMARY

Several modalities can be used for measuring intrahepatic fat and assessing steatosis; the choice will ultimately depend on the intended use and available resources.

[Understanding the different functions of vitamin D]

Exposure of the skin to sunlight is now considered the most important source of vitamin D in Western countries. It is presumed to contribute approximately two thirds of the total requirement, leaving the remaining one third to the few foods naturally rich in this vitamin. In the skin, vitamin D is synthesized as a cholesterol chain which undergoes structural modifications following exposure to UVB rays. Once produced in the skin or absorbed in the gut as cholecalciferol, vitamin D enters the blood to be transported by a specific vitamin D binding protein, which is synthesized in the liver and has a powerful buffering capacity. The transport system carries the metabolites to the sites of further activation (25-hydroxylation in the liver and 1alpha-hydroxylation in the kidney), ultimately resulting in the production of calcitriol. This last compound, now regarded as a hormone, circulates freely in minimal amounts and, compared with the other metabolites, shows the highest affinity for the vitamin D receptor (VDR). The mechanism of VDR activation is rather complex, resulting in either stimulation or inhibition of protein synthesis. Importantly, besides its presence in parathyroid, bone, kidney and intestine, this receptor has been demonstrated in several tissues, where its stimulation results in a reduced proliferation rate and increased differentiation. Accordingly, vitamin D is now regarded as a complex hormonal system, involved not only in the regulation of divalent ions and bone, but also in the proliferation and differentiation of numerous cell types with potential involvement in several diseases like cancer, immune diseases, diabetes, hypertension and heart failure.

The driving brain: the CNS in the pathogenesis and treatment of anorexia-cachexia syndrome

Over the past few years, medical care has dramatically improved knowledge of the pathogenic mechanisms of diseases, leading to more effective therapies as well as improved technologies, yielded to enhance survival for diseases that, just a few decades ago, would have been considered lethal. Unfortunately, not all diseases can be completely defeated. In many circumstances, therapies may delay the progression of the disease, leading to improved survival but bringing new issues to light. Of particular interest are nutritional and metabolic alterations due to both prolonged clinical course of disease and long-term therapies. Anorexia-cachexia syndrome often complicates the course of chronic illnesses. Anorexia (i.e., loss of appetite) and cachexia (i.e., loss of weight due to lean body mass and fat-mass wasting) are both associated with a number of diseases. The aim of this article is to highlight the clinical impact of the anorexia-cachexia syndrome and to review current and future etiologic therapeutic approaches.

Concentrations of cytokines IL-6 and IL-10 in plasma of burn patients: their relationship to sepsis and outcome

Burn injury induces a suppression of the Th1 response, which is associated with an increased susceptibility to conditions of infection, morbidity, and mortality. It is well established that cytokines modulate the pathogenesis of burn injury. In this study, plasma levels of interleukin-6 (IL-6) and interleukin-10 (IL-10) were determined in burn patients and correlated with the severity of sepsis. Sixty adult burn patients (total body surface area burned, 8-80%) were included in the study, of whom 34 developed sepsis and 14 died. The nonseptic group consisted of 26 patients. Thirty-one healthy blood donors served as controls. Patients were not treated with antibiotics until sepsis occurred. Plasma samples were collected immediately post-burn and after several days, and cytokine concentrations were determined by ELISA. Within three days, all the patients presented high levels of circulating IL-6, which were significantly higher in septic patients than in nonseptic patients (349 ± 278 vs 63 ± 56 pg/ml, p < 0.001).IL-10 levels were higher in septic patients than in nonseptic patients at all times in our study. The value of 60 pg/ml shows a sensitivity of 92% and a specificity of 93% in the differentiation of survivor from nonsurvivor septic patients. In this study the high value of circulating IL-10 on day 3 suggests that cytokine may discriminate between nonsurvivor septic and survivor septic patients.

Efficient gene transfer in skeletal muscle with AAV-derived bicistronic vector using the FGF-1 IRES

IRESs (internal ribosome entry sites) are RNA elements behaving as translational enhancers in conditions of global translation blockade. IRESs are also useful in biotechnological applications as they allow expression of several genes from a single mRNA. Up to now, most IRES-containing vectors use the IRES from encephalomyocarditis virus (EMCV), highly active in transiently transfected cells but long and not flexible in its positioning relative to the gene of interest. In contrast, several IRESs identified in cellular mRNAs are short and flexible and may therefore be advantageous in gene transfer vectors such as those derived from the adeno-associated virus (AAV), where the size of the transgene expression cassette is limited. Here, we have tested bicistronic AAV-derived vectors expressing two luciferase genes separated by the EMCV- or fibroblast growth factor 1 (FGF-1) IRES. We demonstrate that the AAV vector with the FGF-1 IRES, when administrated into the mouse muscle, leads to efficient expression of both transgenes with a stable stoechiometry, for at least 120 days. Interestingly, the bicistronic mRNA containing the FGF-1 IRES leads to transgene expression 10 times superior to that observed with EMCV, in vivo. AAV vectors featuring the FGF-1 IRES may thus be advantageous for gene therapy approaches in skeletal muscle involving coexpression of genes of interest.

Idefix insulator activity can be modulated by nearby regulatory elements

Insulators play important roles in controlling gene activity and maintaining regulatory independence between neighbouring genes. In this article, we show that the enhancer-blocking activity of the insulator present within the LTR retrotransposon Idefix can be abolished if two copies of the region containing the insulator—specifically, the long terminal repeat (LTR)—are fused to the retrotransposon's 5′ untranslated region (5′ UTR). The presence of this combination of two [LTR-5′ UTR] modules is a prerequisite for the loss of enhancer-blocking activity. We further show that the 5′ UTR causes flanking genomic sequences to be displaced to the nuclear periphery, which is not observed when two insulators are present by themselves. This study thus provides a functional link between insulators and independent genomic modules, which may cooperate to allow the specific regulation of defined genomic loci via nuclear repositioning. It further illustrates the complexity of genomic regulation within a chromatic environment with multiple functional elements.

[Comparison among ecography, scintigraphy and surgery in the localization of parathyroid glands in uremic patients undergoing parathyroidectomy]

BACKGROUND

Sensitivity and specificity of the most widely employed techniques of parathyroid glands localization, namely echography and scintigraphy, are mostly obtained with short-term follow-up data and do not underline the existence of a methodological problem. As a matter of fact, both methods identify only pathological glands, with no "normal" results; therefore "true negatives" cannot be obtained. Aim of our study was to compare, by means of a statistically appropriate approach, the results of echography, scintigraphy and surgery with the data obtained after a mid term follow-up period, enabling us to discover all parathyroid glands.

METHODS

Twenty six consecutive dialysis patients (14M/12F; age 50+/-12 years) underwent echography and scintigraphy immediately before a total parathyroidectomy with autotransplantation and were followed-up for 6 months to recognize all the existing glands (PTH levels and scintigraphy).

RESULTS

Total identified glands were: 73 by scintigraphy, 86 by echography, 99 by surgery and 103 by follow-up data. The concordance indexes (K0) between the number of glands effectively present in the individual patient (follow-up data) and those identified with each method were rather low with scintigraphy (0.071) and echography (0.218), and acceptable (0.578) with surgery. The number of patients correctly classified was: 9/26 (34,6%) with scintigraphy, 13/26 (50%) with echography and 22/26 (85%) with surgery. Finally, the number of wrongly identified glands (from zero to three) in each patient was similar with scintigraphy (65,4%) and echography (50%) and significantly better with surgery (15,6%; p<0.01).

CONCLUSIONS

The most reliable technique to identify parathyroid glands in uremic subjects is surgery, nonetheless a meticulous clinical follow-up is necessary to recognize all of them.

Factors related to oral hygiene in persons with scleroderma

OBJECTIVES

The purpose of this study was to assess potential risk factors for the development of poor oral hygiene and increased dental caries in individuals with scleroderma.

METHODS

Twenty-two subjects with scleroderma participated in this study. All subjects were examined with the Patient Hygiene Performance (PHP) Index, which assesses the extent of plaque and debris over a tooth surface. In addition, oral aperature, xerostomia and dominant upper extremity strength, motion, skin thickness, and dexterity were measured.

RESULTS

None of the subjects had good or excellent hygiene. Fifteen subjects had fair oral hygiene and seven subjects had poor oral hygiene as measured by the PHP Index. Significant differences were seen between these two groups for oral aperture, percentage of teeth with caries, skin thickness, dexterity and finger flexion. Dexterity and joint motion correlated significantly with the number of decayed surfaces and number of caries. Oral aperture correlated with the PHP Index and the number of dental caries.

CONCLUSIONS

Subjects with poor oral hygiene required more time to complete manual dexterity task and had decreased hand strength and joint motion. Moreover, these same subjects had more contractures, scars, ulcers, and higher skin scores (more disease activity) than subjects in the fair hygiene group. In addition to frequent dental exam and routine cleaning, dental personnel may want to consider exercises to increase oral aperature and investigate toothbrush and dental floss selection used by persons with scleroderma.

Functional expression of mammalian bitter taste receptors in Caenorhabditis elegans

Bitter taste has evolved as a central warning signal against the ingestion of potentially toxic substances appearing in the environment. The molecular events in the perception of bitter taste start with the binding of specific water-soluble molecules to G protein-coupled receptors (GPCR) called T2Rs and expressed at the surface of taste receptor cells. The functional characterisation of T2R receptors is far from been completed due to the difficulty to functionally express them in heterologous systems. Taking advantage of the parallelisms between the Caenorhabditis elegans (C. elegans) and mammalian GPCR signalling pathways, we developed a C. elegans-based expression system to express functional human and rodent GPCRs of the T2R family. We generated transgenic worms expressing T2Rs in ASI chemosensory neurons and performed behavioural assays using a variety of bitter tastants. As a proof of the concept, we generated transgenic worms expressing human T2R4 or its mouse ortholog T2R8 receptors, which respond to two bitter tastants previously characterised as their functional ligands, 6-n-propyl-2-thiouracil and denatoniun. As expected, expression of human T2R4 or its mouse ortholog T2R8 in ASI neurons counteracted the water-soluble avoidance to 6-n-propyl-2-thiouracil and denatoniun observed in control wild-type worms. The expression in ASI neurons of human T2R16, the ligand of which, phenyl-beta-d-glucopyranoside, belong to a chemically different group of bitter tastants, also counteracted the water-soluble avoidance to this compound observed in wild-type worms. These results indicate that C. elegans is a suitable heterologous expression system to express functional T2Rs providing a tool to efficiently search for specific taste receptor ligands and to extend our understanding of the molecular basis of gustation.