Insulin resistance is associated with MCP1-mediated macrophage accumulation in skeletal muscle in mice and humans

Inflammation is now recognized as a major factor contributing to type 2 diabetes (T2D). However, while the mechanisms and consequences associated with white adipose tissue inflammation are well described, very little is known concerning the situation in skeletal muscle. The aim of this study was to investigate, in vitro and in vivo, how skeletal muscle inflammation develops and how in turn it modulates local and systemic insulin sensitivity in different mice models of T2D and in humans, focusing on the role of the chemokine MCP1. Here, we found that skeletal muscle inflammation and macrophage markers are increased and associated with insulin resistance in mice models and humans. In addition, we demonstrated that intra-muscular TNFα expression is exclusively restricted to the population of intramuscular leukocytes and that the chemokine MCP1 was associated with skeletal muscle inflammatory markers in these models. Furthermore, we demonstrated that exposure of C2C12 myotubes to palmitate elevated the production of the chemokine MCP1 and that the muscle-specific overexpression of MCP1 in transgenic mice induced the local recruitment of macrophages and altered local insulin sensitivity. Overall our study demonstrates that skeletal muscle inflammation is clearly increased in the context of T2D in each one of the models we investigated, which is likely consecutive to the lipotoxic environment generated by peripheral insulin resistance, further increasing MCP1 expression in muscle. Consequently, our results suggest that MCP1-mediated skeletal muscle macrophages recruitment plays a role in the etiology of T2D.

Depressing mitochondria-reticulum interactions protects cardiomyocytes from lethal hypoxia-reoxygenation injury

BACKGROUND

Under physiological conditions, Ca(2+) transfer from the endoplasmic reticulum (ER) to mitochondria might occur at least in part at contact points between the 2 organelles and involves the VDAC1/Grp75/IP3R1 complex. Accumulation of Ca(2+) into the mitochondrial matrix may activate the mitochondrial chaperone cyclophilin D (CypD) and trigger permeability transition pore opening, whose role in ischemia/reperfusion injury is well recognized. We questioned here whether the transfer of Ca(2+) from ER to mitochondria might play a role in cardiomyocyte death after hypoxia-reoxygenation.

METHODS AND RESULTS

We report that CypD interacts with the VDAC1/Grp75/IP3R1 complex in cardiomyocytes. Genetic or pharmacological inhibition of CypD in both H9c2 cardiomyoblasts and adult cardiomyocytes decreased the Ca(2+) transfer from ER to mitochondria through IP3R under normoxic conditions. During hypoxia-reoxygenation, the interaction between CypD and the IP3R1 Ca(2+) channeling complex increased concomitantly with mitochondrial Ca(2+) content. Inhibition of either CypD, IP3R1, or Grp75 decreased protein interaction within the complex, attenuated mitochondrial Ca(2+) overload, and protected cells from hypoxia-reoxygenation. Genetic or pharmacological inhibition of CypD provided a similar effect in adult mice cardiomyocytes. Disruption of ER-mitochondria interaction via the downregulation of Mfn2 similarly reduced the interaction between CypD and the IP3R1 complex and protected against hypoxia-reoxygenation injury.

CONCLUSIONS

Our data (1) point to a new role of CypD at the ER-mitochondria interface and (2) suggest that decreasing ER-mitochondria interaction at reperfusion can protect cardiomyocytes against lethal reperfusion injury through the reduction of mitochondrial Ca(2+) overload via the CypD/VDAC1/Grp75/IP3R1 complex.

Endoplasmic reticulum stress contributes to heart protection induced by cyclophilin D inhibition

Preventing cyclophilin D (cypD) translocation to the inner mitochondrial membrane can limit lethal reperfusion injury through the inhibition of the opening of the mitochondrial permeability transition pore. Inhibition or loss of function of cypD may also result into an endoplasmic reticulum (ER) stress that has been shown to alter cell survival. We therefore questioned whether ER stress might play a role in the protection induced by CypD deficiency or inhibition. CypD-KO and NIM811 (a CypD inhibitor)-treated mice were subjected to a prolonged ischemia-reperfusion (I/R). Area at risk and infarct size was measured using blue dye and triphenyltetrazolium chloride staining. ER stress markers were measured in the hearts during the reperfusion phase. As expected, cypD-KO mice exhibited a decreased infarct size when compared to wild-type mice (8 ± 1 vs. 20 ± 4% of left ventricular weight; p < 0.01). CypD-deficient mice displayed an increased expression of ER stress proteins such as eukaryotic initiation factor 2α (eIF2α) or glucose regulated protein 78 (Grp78 or Bip). The ER stress inhibitor TUDCA prevented the infarct size reduction afforded by the loss of cypD function (mean infarct size averaged 21 ± 4% of LV weight, p < 0.01 vs. cypD-KO). Similar results were obtained when NIM811, an analog of cyclosporine A, was used to pharmacologically (instead of genetically) inhibit cypD function. This study suggests that the ER stress induced by the inhibition of cypD function plays a key role in protecting the heart against lethal ischemia-reperfusion injury.

Reduction of endoplasmic reticulum stress using chemical chaperones or Grp78 overexpression does not protect muscle cells from palmitate-induced insulin resistance

Endoplasmic reticulum (ER) stress is proposed as a novel link between elevated fatty acids levels, obesity and insulin resistance in liver and adipose tissue. However, it is unknown whether ER stress also contributes to lipid-induced insulin resistance in skeletal muscle, the major tissue responsible of insulin-stimulated glucose disposal. Here, we investigated the possible role of ER stress in palmitate-induced alterations of insulin action, both in vivo, in gastrocnemius of high-palm diet fed mice, and in vitro, in palmitate-treated C(2)C(12) myotubes. We demonstrated that 8 weeks of high-palm diet increased the expression of ER stress markers in muscle of mice, whereas ex-vivo insulin-stimulated PKB phosphorylation was not altered in this tissue. In addition, exposure of C(2)C(12) myotubes to either tuncamycine or palmitate induced ER stress and altered insulin-stimulated PKB phosphorylation. However, alleviation of ER stress by either TUDCA or 4-PBA treatments, or by overexpressing Grp78, did not restore palmitate-induced reduction of insulin-stimulated PKB phosphorylation in C(2)C(12) myotubes. This work highlights that, even ER stress is associated with palmitate-induced alterations of insulin signaling, ER stress is likely not the major culprit of this effect in myotubes, suggesting that the previously proposed link between ER stress and insulin resistance is less important in skeletal muscle than in adipose tissue and liver.

Inhibition of xanthine oxidase reduces hyperglycemia-induced oxidative stress and improves mitochondrial alterations in skeletal muscle of diabetic mice

Reactive oxygen species (ROS) have been widely implicated in the pathogenesis of diabetes and more recently in mitochondrial alterations in skeletal muscle of diabetic mice. However, so far the exact sources of ROS in skeletal muscle have remained elusive. Aiming at better understanding the causes of mitochondrial alterations in diabetic muscle, we designed this study to characterize the sites of ROS production in skeletal muscle of streptozotocin (STZ)-induced diabetic mice. Hyperglycemic STZ mice showed increased markers of systemic and muscular oxidative stress, as evidenced by increased circulating H(2)O(2) and muscle carbonylated protein levels. Interestingly, insulin treatment reduced hyperglycemia and improved systemic and muscular oxidative stress in STZ mice. We demonstrated that increased oxidative stress in muscle of STZ mice is associated with an increase of xanthine oxidase (XO) expression and activity and is mediated by an induction of H(2)O(2) production by both mitochondria and XO. Finally, treatment of STZ mice, as well as high-fat and high-sucrose diet-fed mice, with oxypurinol reduced markers of systemic and muscular oxidative stress and prevented structural and functional mitochondrial alterations, confirming the in vivo relevance of XO in ROS production in diabetic mice. These data indicate that mitochondria and XO are the major sources of hyperglycemia-induced ROS production in skeletal muscle and that the inhibition of XO reduces oxidative stress and improves mitochondrial alterations in diabetic muscle.

Dynamic regulation of mitochondrial network and oxidative functions during 3T3-L1 fat cell differentiation

Mitochondria have been shown to be impaired in insulin resistance-related diseases but have not been extensively studied during the first steps of adipose cell development. This study was designed to determine the sequence of changes of the mitochondrial network and function during the first days of adipogenesis. 3T3-L1 preadipocytes were differentiated into adipocytes without using glitazone compounds. At days 0, 3, 6, 9, and 12, mitochondrial network imaging, mitochondrial oxygen consumption, membrane potential, and oxidative phosphorylation efficiency were assessed in permeabilized cells. Gene and protein expressions related to fatty acid metabolism and mitochondrial network were also determined. Compared to preadipocytes (day 0), new adipocytes (days 6 and 9) displayed profound changes of their mitochondrial network that underwent fragmentation and redistribution around lipid droplets. Drp1 and mitofusin 2 displayed a progressive increase in their gene expression and protein content during the first 9 days of differentiation. In parallel with the mitochondrial network redistribution, mitochondria switched to uncoupled respiration with a tendency towards decreased membrane potential, with no variation of mtTFA and NRF1 gene expression. The expression of PGC1α and NRF2 genes and genes involved in lipid oxidation (UCP2, CD36, and CPT1) was increased. Reactive oxygen species (ROS) production displayed a nadir at day 6 with a concomitant increase in antioxidant enzyme gene expression. This 3T3-L1-based in vitro model of adipogenesis showed that mitochondria adapted to the increased number of lipid droplets by network redistribution and uncoupling respiration. The timing and regulation of lipid oxidation-associated ROS production appeared to play an important role in these changes.

HEXIM1 targets a repeated GAUC motif in the riboregulator of transcription 7SK and promotes base pair rearrangements

7SK snRNA, an abundant RNA discovered in human nucleus, regulates transcription by RNA polymerase II (RNAPII). It sequesters and inhibits the transcription elongation factor P-TEFb which, by phosphorylation of RNAPII, switches transcription from initiation to processive elongation and relieves pauses of transcription. This regulation process depends on the association between 7SK and a HEXIM protein, neither isolated partner being able to inhibit P-TEFb alone. In this work, we used a combined NMR and biochemical approach to determine 7SK and HEXIM1 elements that define their binding properties. Our results demonstrate that a repeated GAUC motif located in the upper part of a hairpin on the 5'-end of 7SK is essential for specific HEXIM1 recognition. Binding of a peptide comprising the HEXIM Arginine Rich Motif (ARM) induces an opening of the GAUC motif and stabilization of an internal loop. A conserved proline-serine sequence in the middle of the ARM is shown to be essential for the binding specificity and the conformational change of the RNA. This work provides evidences for a recognition mechanism involving a first event of induced fit, suggesting that 7SK plasticity is involved in the transcription regulation.

Mitochondrial dysfunction results from oxidative stress in the skeletal muscle of diet-induced insulin-resistant mice

Mitochondrial dysfunction in skeletal muscle has been implicated in the development of type 2 diabetes. However, whether these changes are a cause or a consequence of insulin resistance is not clear. We investigated the structure and function of muscle mitochondria during the development of insulin resistance and progression to diabetes in mice fed a high-fat, high-sucrose diet. Although 1 month of high-fat, high-sucrose diet feeding was sufficient to induce glucose intolerance, mice showed no evidence of mitochondrial dysfunction at this stage. However, an extended diet intervention induced a diabetic state in which we observed altered mitochondrial biogenesis, structure, and function in muscle tissue. We assessed the role of oxidative stress in the development of these mitochondrial abnormalities and found that diet-induced diabetic mice had an increase in ROS production in skeletal muscle. In addition, ROS production was associated with mitochondrial alterations in the muscle of hyperglycemic streptozotocin-treated mice, and normalization of glycemia or antioxidant treatment decreased muscle ROS production and restored mitochondrial integrity. Glucose- or lipid-induced ROS production resulted in mitochondrial alterations in muscle cells in vitro, and these effects were blocked by antioxidant treatment. These data suggest that mitochondrial alterations do not precede the onset of insulin resistance and result from increased ROS production in muscle in diet-induced diabetic mice.

[External radiotherapy and photodynamic therapy for esophageal carcinoma: a dangerous association?]

A 60-year-old man presented an oesophageal transmural necrosis fistulised in the trachea following curative photodynamic therapy (PDT) for a superficial recurrence of an oesophageal carcinoma, initially treated by radiochemotherapy. Two stents, a tracheal and an oesophageal one, were placed. Eight months later the patient is in complete remission with only mild swallowing problems. This complication, although unusual, has already been described by other teams with the association of radiochemotherapy and PDT. The present case study suggests that illumination dose should be lowered in this indication.

Changes in adiponectin, its receptors and AMPK activity in tissues of diet-induced diabetic mice

AIM

A high-fat and high-sucrose diet (HFHSD) is usually used to induce type 2-like diabetes in animal models. We investigated the effect of HFHSD on serum and tissue levels of adiponectin, its receptors and AMP-activated protein kinase (AMPK) activity in adipose tissue, skeletal muscle and the liver.

METHODS

C57Bl/6 male mice were fed either a standard diet or an HFHSD for four and 16 weeks, during which time glucose and insulin tolerance tests were performed.

RESULTS

After four weeks, the HFHSD-fed mice were obese and glucose-intolerant and, after 16 weeks, they were obese and diabetic. In general, four weeks of HFHSD feeding did not modify either circulating or tissue adiponectin levels, nor adiponectin receptors or AMPK activity in the tissues studied. A significant increase of circulating adiponectin was observed after 16 weeks of HFHSD feeding, whereas adiponectin expression was decreased in adipose tissue. Muscle expression of adiponectin was increased at 16 weeks in terms of both mRNA and protein levels, and correlated to adipose-specific gene expression. However, AdipoR1 mRNA levels and AMPK activity were decreased in muscle at 16 weeks, suggesting decreased sensitivity to adiponectin in the muscle of diabetic mice. Finally, liver adiponectin expression was detectable only at protein levels and was increased in HFHSD mice at 16 weeks, suggesting "contamination" by circulating adiponectin. AdipoR2 mRNA levels were significantly decreased, whereas AMPK was increased, in the liver at 16 weeks.

CONCLUSION

Overall, our data suggest that HFHSD-induced diabetes is not associated with adiponectin deficiency, but with tissue-specific defects of adiponectin-receptor expression and AMPK activity.

Nanoparticles of hydrophobically modified dextrans as potential drug carrier systems

Nanoparticles combining a hydrophobically modified dextran core and a polysaccharide surface coverage were elaborated. Their suitability for applications like drug delivery was evaluated. The selected polysaccharide, dextran, was chemically modified by the covalent attachment of hydrocarbon groups (aliphatic or aromatic) via the formation of ether links. According to the extent of modification, either water-soluble or water-insoluble dextran derivatives were obtained. The latter exhibited solubility in organic solvents like tetrahydrofuran or dichloromethane saturated with water. Water-soluble dextran derivatives were used as polymeric surfactants for the control of nanoparticles surface characteristics. Nanoparticles were prepared either by o/w emulsion or solvent-diffusion methods. The size and surface properties of dextran nanoparticles were correlated to processing conditions. The stability of colloidal suspensions was examined as a function of ionic strength and related to the particle surface characteristics. The redispersability of freeze-dried suspensions without the addition of cryoprotectant was demonstrated. Finally, the degradability of modified dextrans was compared to that of starting dextran, after enzymatic hydrolysis in the presence of dextranase.

Genetic algorithm optimisation combined with partial least squares regression and mutual information variable selection procedures in near-infrared quantitative analysis of cotton–viscose textiles

In this work, different approaches for variable selection are studied in the context of near-infrared (NIR) multivariate calibration of textile. First, a model-based regression method is proposed. It consists in genetic algorithm optimisation combined with partial least squares regression (GA-PLS). The second approach is a relevance measure of spectral variables based on mutual information (MI), which can be performed independently of any given regression model. As MI makes no assumption on the relationship between X and Y, non-linear methods such as feed-forward artificial neural network (ANN) are thus encouraged for modelling in a prediction context (MI-ANN). GA-PLS and MI-ANN models are developed for NIR quantitative prediction of cotton content in cotton-viscose textile samples. The results are compared to full-spectrum (480 variables) PLS model (FS-PLS). The model requires 11 latent variables and yielded a 3.74% RMS prediction error in the range 0-100%. GA-PLS provides more robust model based on 120 variables and slightly enhanced prediction performance (3.44% RMS error). Considering MI variable selection procedure, great improvement can be obtained as 12 variables only are retained. On the basis of these variables, a 12 inputs ANN model is trained and the corresponding prediction error is 3.43% RMS error.

L’arthrodèse capitato-lunaire par hauban dans l’arthrose du poignet

PURPOSE OF THE STUDY

Treatment of degenerative osteoarthritis of the wrist is aimed at preserving wrist motion and force while reducing pain. Limitation of the degenerative processes to certain joints raises the possibility of intracarpal arthrodesis, e.g. capitolunate arthrodesis. We present results of this procedure with a tension band wire in patients with arthritic degenerative disease of the wrist.

MATERIAL AND METHODS

The series included 20 patients reviewed at mean 47 months. Mean age was 53.5 years. Pain was the main complaint. Wrist force and motion were decreased in all patients. All patients presented osteoarthritic disease of the wrist with preservation of the radiolunate space. The operation consisted in total scaphoidectomy and capitolunate arthrodesis maintained with a tension band wire. Force, pain (Mayo clinic score) and force (Jamar dynamometer) were recorded. The Cooney function score was determined and six patients completed the French Dash questionnaire. Radiolunate and capitolunate angles were noted as well as the index of carpal height measured preoperatively and at last follow-up.

RESULTS

Nineteen of the 20 arthrodeses fused. A revision graft was successful for the one nonunion. Pain was the only clinical factor which improved significantly (p<0.0001) in all patients. Lunatum extension (DISI) and capitatum flexion did not have any effect on functional outcome. Sixteen patients resumed their activities at the same level.

DISCUSSION

The results of this series are similar to those in the literature concerning four-way arthrodesis. Capitatolunate arthrodesis with partial arthrodesis of the carpus has been proposed for arthritic degeneration of the wrist with a preserved radiolunate space. We prefer this procedure to four-way arthrodesis because useful motion and wrist force are preserved with constant and effective significant pain relief.

Population pharmacokinetic of total cisplatinum: Application to adaptative dosing with feed back in testicular cancer patient

2043

Background: Cisplatinum (CDDP) is major drug used in germ cell testicular cancer. Pharmacokinetics (PK)/pharmacodynamics relationships have been described after measurement of free CDDP in plasma, and subsequently, CDDP administration is standardized using body surface area (BSA) for only dose tailoring. Methods: Based on a rapid assay of total CDDP in plasma we have developed an alternative 120-hours continuous infusion schedule, coupled to a Bayesian adaptive dosing strategy. We present a retrospective evaluation of this schedule in 19 patients (66 courses) treated for testicular germ cell tumors. A NONMEM analysis was then performed to identify the covariates associated with total CDDP clearance. We compared doses effectively given to our patients with the ones calculated with BSA. Results: Plasma samples were analyzed to allow real-time Bayesian estimation of individual PK parameters with subsequent daily dose adjustment in order to reach a target Cend of 1.95 mg/l of total platinum. No statistical difference was observed between experimental and target values, and Cend adjustment was achieved with an overall 6.6% precision, a performance to be compared with the 54% inter-patient variability observed in drug clearance. Course number (CNB) was the only covariate to be correlated with total CDDP clearance. A weaker correlation was found with BSA, and only when considering first courses. Moreover, doses of CDDP administered were significantly higher than the ones classically normalized with BSA, thus leading to an overall greater exposure in our patients. Only few severe toxicities were reported, and all of the patients presented in this study were still alive and disease-free after a follow up of up to 15 years. Conclusions: Our alternative schedule is a convenient and safe strategy to ensure administration of optimal dose-intensity of CDDP, with limited side-effects in patients with testicular cancer. We demonstrate a linear correlation between course number and decrease of CDDP clearance (25%). This, highlights the critical importance of total drug accumulation on CDDP PK when several infusions are to be administered in a row, and therefore the need for developing dynamic dose individualization strategies that includes CNB.

No significant financial relationships to disclose.

Quantitative analysis of cotton-polyester textile blends from near-infrared spectra

Quantitative analysis of textile blends and textile fabrics is currently of particular interest in the industrial context. In this frame, this work investigates whether the use of Fourier transform (FT) near-infrared (NIR) spectroscopy and chemometrics is powerful for rapid and accurate quantitative analysis of cotton-polyester content in blend products. As samples of the same composition have many sources of variability that affect NIR spectra, indirect prediction is particularly challenging and a large sample population is required to design robust calibration models. Thus, a total of more than three-hundred cotton-polyester samples were selected covering the range from the 0% to 100% cotton and the corresponding NIR reflectance spectra were measured on raw fabrics. The data set obtained was used to develop multivariate models for quantitative prediction from reference measurements. A successful approach was found to rely on partial least squares (PLS) regression combined with genetic algorithms (GAs) for wavelength selection. It involved evaluating a set of calibration models considering different spectral regions. The results obtained considering 27.5% of the original variables yielded a prediction error (RMSEP) of 2.3 in percent cotton content. It demonstrates that FT-NIR spectroscopy has the potential to be used in the textile industry for the prediction of the composition of cotton-polyester blends. As a further consequence, it was observed that the spectral preprocessing and the complexity of the model are simplified compared to the full-spectrum approach. Also, the relevancy of the spectral intervals retained after variable selection can be discussed.

Lack of Association of IL-10 Promoter Gene Variants with Type 1 Diabetes in a French Population

Although genetic predisposition to type 1 diabetes shows a strong association with human leukocyte antigen (HLA) class II alleles, additional genes may influence the immune process and the progression of beta cell loss. Preliminary reports suggested that IL-10 gene polymorphisms contribute to susceptibility to type 1 diabetes. We analyzed the frequencies of three main variants of the promoter region of the IL-10 gene at the positions -1082, -819, and -592 in a cohort of 358 type 1 diabetic patients representing the same regional population pattern and 519 controls from the same region using an enzyme-linked oligonucleotide sorbent assay. We did not find any statistical association in the entire cohort or after stratification for high-risk HLA-DQ alleles. However, the IL-10 -1082 polymorphism was significantly associated with GAD and IA-2 antibodies at clinical onset. Such polymorphism is known to be associated with the reduction of secreted IL-10 which may support the concept of accelerated Th-1 T-cell reactivity. In conclusion, IL-10 promoter gene variants may contribute, but to a minor extent, to disease susceptibility in juvenile type 1 diabetes and should not be included in the routine genetic screening of high-risk individuals.

The Escherichia coli AmtB protein as a model system for understanding ammonium transport by Amt and Rh proteins

The Escherichia coli ammonium transport protein (AmtB) has become the model system of choice for analysis of the process of ammonium uptake by the ubiquitous Amt family of inner membrane proteins. Over the past 6 years we have developed a range of genetic and biochemical tools in this system. These have allowed structure/function analysis to develop rapidly, offering insight initially into the membrane topology of the protein and most recently leading to the solution of high-resolution 3D structures. Genetic analysis has revealed a novel regulatory mechanism that is apparently conserved in prokaryotic Amt proteins and genetic approaches are also now being used to dissect structure/function relationships in Amt proteins. The now well-recognised homology between the Amt proteins, found in archaea, eubacteria, fungi and plants, and the Rhesus proteins, found characteristically in animals, also means that studies on E. coli AmtB can potentially shed light on structure/function relationships in the clinically important Rh proteins.

Aqueous Solutions of Native and Hydrophobically Modified Polysaccharides: Temperature Effect

Amphiphilic polysaccharides, obtained by the attachment of various hydrocarbon groups onto dextran, are studied in aqueous solutions. The viscosity of their aqueous solutions is examined as a function of concentration and temperature in the range 25-65 degrees C. Varying polymer concentration, viscosity follows a polynomial development of Huggins equation in which the coefficients can be calculated from the Huggins constant determined in the dilute domain (Matsuoka-Cowman equation). For all polymers, the solution viscosity follows an Arrhenius-like variation with temperature. The activation energy of the aqueous solutions is determined as a function of polymer concentration and structural characteristics (nature and amount of grafted hydrocarbon groups). The variation of activation energy with polymer concentration is shown to be consistent with predictions based on the Matsuoka-Cowman equation combined with the equation of Andrade. This conclusion is extended to other polysaccharides using data from the literature.