Association of urinary calcium excretion with serum calcium and vitamin D levels

Contexte de recherche Mon projet de thèse en médecine concerne l'exploration des facteurs associés à l'excrétion urinaire de calcium durant 24h dans une étude populationnelle suisse. Les données qui ont été utilisées sont issues d'une étude populationnelle connue sous le nom de « Swiss survey on Salt intake », qui a été effectuée entre janvier 2010 et mars 2012 et avait pour but principal d'investiguer la consommation de sel de la population suisse. L'étude a regroupé plusieurs centres d'investigations dans toute la Suisse (11 centres dans 9 cantons), dans trois langues nationales (français, allemand et italien) et concerne des participants âgés de plus de 15 ans. Cette étude avait l'avantage de collecter des données anthropométriques, sanguines, urinaires, de lister les traitements et de poser des questions sur le style de vie (alcool, activité physique, etc.). A notre connaissance, peu d'articles populationnels explorent les facteurs associés à l'excrétion urinaire de calcium durant 24h et notamment l'association de celle-ci avec le calcium corrigé sanguin et la 250H-vitamine D2*3 sanguin chez les hommes et les femmes. Méthodes Après exclusions des données manquantes, 1293 participants sur 1550 ont été retenus pour l'analyse statistique. Celle-ci a été effectuée grâce au logiciel Stata 12. Nous avons utilisé la régression linéaire multiple dont la variable dépendante était l'excrétion urinaire de calcium durant 24h en stratifiant les analyses par sexe (en raison des interactions statistiques significatives entre calcémie et sexe, et entre vitamine D et sexe). Les variables indépendantes comprenaient des variables en lien avec l'excrétion urinaire de calcium (vingt-quatre covariables au total) dont la 250H-vitamine D2+3 (avec la variabilité saisonnière) et la calcémie (calcium sérique corrigé par les protéines). Résultats D'importantes différences entre hommes et femmes ont été observées : une association positive entre l'excrétion urinaire de calcium durant 24h et la calcémie corrigée a été trouvée chez les femmes mais pas chez les hommes. En parallèle, nous relevons une association positive entre l'excrétion urinaire de calcium durant 24h et la 250H-vitamine D2+3 chez les hommes mais pas chez les femmes (liée essentiellement à la présence 250H-vitamine D3 en quantité bien plus importante que la 250H-vitamine D2). Nous soulevons deux hypothèses possibles pour expliquer ces importances différences hommes-femmes. La première hypothèse est l'influence des hormones sexuelles. La seconde hypothèse est la contribution des facteurs diététiques. De nouvelles analyses et de nouvelles études populationnelles sont nécessaires pour confirmer ou infirmer ces hypothèses. Perspectives Une prochaine étape sera d'explorer l'influence de l'excrétion urinaire de sodium, de potassium et d'urée sur les associations observées afin d'étudier une possible influence de l'alimentation sur ces résultats. Une autre étape consistera à doser les hormones sexuelles dans les échantillons de cette étude ou dans ceux d'une autre étude. La prévalence de l'hypercalciurie dans cette étude (9 % chez les hommes et 8.1% chez les femmes) est plus basse que dans d'anciennes études non-populationnelles. Il paraît important de mentionner qu'il existe peu de données sur les normes de calciurie dans la population générale et qu'il n'existe pas de consensus international claire concernant la définition de l'hypercalciurie. Cette prévalence élevée est notamment pertinente dans la cadre des néphrolithiasés, qui sont connues pour être plus fréquentes chez les hommes que chez les femmes. Enjeux Les différences hommes-femmes observées pourraient avoir des implications pour améliorer notre compréhension des mécanismes impliqués dans les lithiases urinaires et dans le risque cardiovasculaire associé ainsi que dans notre compréhension des mécanismes associés à l'ostéoporose.

Longitudinal monitoring of endogenous steroids in human serum by UHPLC-MS/MS as a tool to detect testosterone abuse in sports.

The detection of testosterone abuse in sports is routinely achieved through the 'steroidal module' of the Athlete Biological Passport by GC-MS(/MS) quantification of selected endogenous anabolic androgenic steroids (EAAS) from athletes' urines. To overcome some limitations of the "urinary steroid profile" such as the presence of confounding factors (ethnicity, enzyme polymorphism, bacterial contamination, and ethanol), ultrahigh performance liquid chromatography (UHPLC) measurements of blood concentrations of testosterone, its major metabolites, and precursors could represent an interesting and complementary strategy. In this work, two UHPLC-MS/MS methods were developed for the quantification of testosterone and related compounds in human serum, including major progestogens, corticoids, and estrogens. The validated methods were then used for the analyses of serum samples collected from 19 healthy male volunteers after oral and transdermal testosterone administration. Results from unsupervised multiway analysis allowed variations of target analytes to be assessed simultaneously over a 96-h time period. Except for alteration of concentration values due to the circadian rhythm, which concerns mainly corticosteroids, DHEA, and progesterone, significant variations linked to the oral and transdermal testosterone administration were observed for testosterone, DHT, and androstenedione. As a second step of analysis, the longitudinal monitoring of these biomarkers using intra-individual thresholds showed, in comparison to urine, significant improvements in the detection of testosterone administration, especially for volunteers with del/del genotype for phase II UGT2B17 enzyme, not sensitive to the main urinary marker, T/E ratio. A substantial extension of the detection window after transdermal testosterone administration was also observed in serum matrix. The longitudinal follow-up proposed in this study represents a first example of 'blood steroid profile' in doping control analysis, which can be proposed in the future as a complement to the 'urinary module' for improving steroid abuse detection capabilities.

Store-operated Ca2+ Entry Mediated by Orai1 and TRPC1 Participates to Insulin Secretion in Rat β-Cells.

Store-operated Ca(2+) channels (SOCs) are voltage-independent Ca(2+) channels activated upon depletion of the endoplasmic reticulum Ca(2+) stores. Early studies suggest the contribution of such channels to Ca(2+) homeostasis in insulin-secreting pancreatic β-cells. However, their composition and contribution to glucose-stimulated insulin secretion (GSIS) remains unclear. In this study, endoplasmic reticulum Ca(2+) depletion triggered by acetylcholine (ACh) or thapsigargin stimulated the formation of a ternary complex composed of Orai1, TRPC1, and STIM1, the key proteins involved in the formation of SOCs. Ca(2+) imaging further revealed that Orai1 and TRPC1 are required to form functional SOCs and that these channels are activated by STIM1 in response to thapsigargin or ACh. Pharmacological SOCs inhibition or dominant negative blockade of Orai1 or TRPC1 using the specific pore mutants Orai1-E106D and TRPC1-F562A impaired GSIS in rat β-cells and fully blocked the potentiating effect of ACh on secretion. In contrast, pharmacological or dominant negative blockade of TRPC3 had no effect on extracellular Ca(2+) entry and GSIS. Finally, we observed that prolonged exposure to supraphysiological glucose concentration impaired SOCs function without altering the expression levels of STIM1, Orai1, and TRPC1. We conclude that Orai1 and TRPC1, which form SOCs regulated by STIM1, play a key role in the effect of ACh on GSIS, a process that may be impaired in type 2 diabetes.

Polymorphisms cyclooxygenase-2 -765G>C and interleukin-6 -174G>C are associated with serum inflammation markers in a high cardiovascular risk population and do not modify the response to a Mediterranean diet supplemented with virgin olive oil or nuts

Inflammation is involved in cardiovascular diseases. Some studies have found that the Mediterranean diet (MD) can reduce serum concentrations of inflammation markers. However, none of these studies have analyzed the influence of genetic variability in such a response. Our objective was to study the effect of the -765G.C polymorphism in the cyclooxygenase-2 (COX-2) gene and the -174G.C polymorphism in the interleukin-6 (IL-6) gene on serum concentrations of IL-6, C-reactive protein, intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule-1 as well as their influence on the response toa nutritional interventionwithMD.An intervention study ina high cardiovascular riskMediterranean population (314 men and 407 women) was undertaken. Participants were randomly assigned to consume a low-fat control diet or a MD supplementedwith virgin olive oil ornuts.Measureswereobtained at baseline and after a 3-mointervention period.At baseline, the COX-2 -765G.C polymorphismwas associated with lower serum IL-6 (5.85 6 4.82 in GG vs. 4.74 6 4.14 ng/L in C-allele carriers; P ¼ 0.002) and ICAM-1 (265.8 6 114.8 in GG vs. 243.0 6 107.1 mg/L in C-carriers; P ¼ 0.018) concentrations. These differences remained significant aftermultivariate adjustment. The IL-6 -174G.C polymorphism was associatedwith higher (CC vs. G-carriers) serumICAM-1concentrations in bothmenandwomenandwithhigherserumIL-6 concentrations inmen.Following the dietary intervention, no significant gene x diet interactions were found. In conclusion, although COX-2 -765G.C and IL-6 -174G.C polymorphismswere associatedwith inflammation, consuming aMD(either supplemented with virgin olive oil or nuts) reduced the concentration of inflammation markers regardless of these polymorphisms.

Insulin-Like growth-factor 1 myocardial expression decreases in chronic alcohol consumption

Background Chronic alcohol ingestion may cause severe biochemical and pathophysiological derangements to skeletal muscle. Unfortunately, these alcohol-induced events may also prime skeletal muscle for worsened, delayed, or possibly incomplete repair following acute injury. As alcoholics may be at increased risk for skeletal muscle injury, our goals were to identify the effects of chronic alcohol ingestion on components of skeletal muscle regeneration. To accomplish this, age- and gender-matched C57Bl/6 mice were provided normal drinking water or water that contained 20% alcohol (v/v) for 18-20 wk. Subgroups of mice were injected with a 1.2% barium chloride (BaCl2) solution into the tibialis anterior (TA) muscle to initiate degeneration and regeneration processes. Body weights and voluntary wheel running distances were recorded during the course of recovery. Muscles were harvested at 2, 7 or 14 days post-injection and assessed for markers of inflammation and oxidant stress, fiber cross-sectional areas, levels of growth and fibrotic factors, and fibrosis. Results Body weights of injured, alcohol-fed mice were reduced during the first week of recovery. These mice also ran significantly shorter distances over the two weeks following injury compared to uninjured, alcoholics. Injured TA muscles from alcohol-fed mice had increased TNFα and IL6 gene levels compared to controls 2 days after injury. Total protein oxidant stress and alterations to glutathione homeostasis were also evident at 7 and 14 days after injury. Ciliary neurotrophic factor (CNTF) induction was delayed in injured muscles from alcohol-fed mice which may explain, in part, why fiber cross-sectional area failed to normalize 14 days following injury. Gene levels of TGFβ1 were induced early following injury before normalizing in muscle from alcohol-fed mice compared to controls. However, TGFβ1 protein content was consistently elevated in injured muscle regardless of diet. Fibrosis was increased in injured, muscle from alcohol-fed mice at 7 and 14 days of recovery compared to injured controls. Conclusions Chronic alcohol ingestion appears to delay the normal regenerative response following significant skeletal muscle injury. This is evidenced by reduced cross-sectional areas of regenerated fibers, increased fibrosis, and altered temporal expression of well-described growth and fibrotic factors.

Long-term treatment with insulin induces apoptosis in brown adipocytes: role of oxidative stress

Trying to define the precise role played by insulin regulating the survival of brown adipocytes, we have used rat fetal brown adipocytes maintained in primary culture. The effect of insulin on apoptosis and the mechanisms involved were assessed. Different from the known effects of insulin as a survival factor, we have found that long-term treatment (72 h) with insulin induces apoptosis in rat fetal brown adipocytes. This process is dependent on the phosphatidylinositol 3-kinase/mammalian target of rapamycin/p70 S6 kinase pathway. Short-term treatment with the conditioned medium from brown adipocytes treated with insulin for 72 h mimicked the apoptotic effect of insulin. During the process, caspase 8 activation, Bid cleavage, cytochrome c release, and activation of caspases 9 and 3 are sequentially produced. Treatment with the caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp (Z-VAD), prevents activation of this apoptotic cascade. The antioxidants, ascorbic acid and superoxide dismutase, also impair this process of apoptosis. Moreover, generation of reactive oxygen species (ROS), probably through reduced nicotinamide adenine dinucleotide phosphate oxidases, and a late decrease in reduced glutathione content are produced. According to this, antioxidants prevent caspase 8 activation and Bid cleavage, suggesting that ROS production is an important event mediating this process of apoptosis. However, the participation of uncoupling protein-1, -2, and -3 regulating ROS is unclear because their levels remain unchanged upon insulin treatment for 72 h. Our data suggest that the prolonged hyperinsulinemia might cause insulin resistance through the loss of brown adipose tissue.

Insulin secretion in health and disease: nutrients dictate the pace.

NlmCategory="UNASSIGNED">Insulin is a key hormone controlling metabolic homeostasis. Loss or dysfunction of pancreatic β-cells lead to the release of insufficient insulin to cover the organism needs, promoting diabetes development. Since dietary nutrients influence the activity of β-cells, their inadequate intake, absorption and/or utilisation can be detrimental. This review will highlight the physiological and pathological effects of nutrients on insulin secretion and discuss the underlying mechanisms. Glucose uptake and metabolism in β-cells trigger insulin secretion. This effect of glucose is potentiated by amino acids and fatty acids, as well as by entero-endocrine hormones and neuropeptides released by the digestive tract in response to nutrients. Glucose controls also basal and compensatory β-cell proliferation and, along with fatty acids, regulates insulin biosynthesis. If in the short-term nutrients promote β-cell activities, chronic exposure to nutrients can be detrimental to β-cells and causes reduced insulin transcription, increased basal secretion and impaired insulin release in response to stimulatory glucose concentrations, with a consequent increase in diabetes risk. Likewise, suboptimal early-life nutrition (e.g. parental high-fat or low-protein diet) causes altered β-cell mass and function in adulthood. The mechanisms mediating nutrient-induced β-cell dysfunction include transcriptional, post-transcriptional and translational modifications of genes involved in insulin biosynthesis and secretion, carbohydrate and lipid metabolism, cell differentiation, proliferation and survival. Altered expression of these genes is partly caused by changes in non-coding RNA transcripts induced by unbalanced nutrient uptake. A better understanding of the mechanisms leading to β-cell dysfunction will be critical to improve treatment and find a cure for diabetes.

Response of hexokinase enzymes and the insulin system to dietary carbohydrates in the common carp, Cyprinus carpio.

The response of the common carp to diets with varying amounts of digestible starch, provided either as pea meal (LP, HP, 30 and 46% peas, respectively) or as cereal (LW, HW, 30 and 46% wheat, respectively), was studied and compared with the response to a carbohydrate-free protein-rich diet (CF). Here we focused on the utilisation of dietary carbohydrates by examining the relationship between dietary starch intake, hepatic hexokinase activities, circulating insulin and muscle insulin receptor system. Plasma glucose concentration and hepatic high Km hexokinase (glucokinase, GK) activity were not affected by the content of digestible starch, but 6 h after feeding enzyme activity was higher in the fish fed carbohydrate diets. Similarly, low Km hexokinase (HK) activity was also higher in the fish 24 h after feeding. Fat gain and protein retention were significantly improved by increased digestible starch intake, especially in the HP group, which in turn, presented the highest plasma insulin levels. Glycogen stores were moderately increased by the ingestion of digestible starch. The number of insulin receptors was greater in the CF group than in fish on carbohydrates, except the HP group. Our results confirmed that the common carp uses dietary carbohydrates efficiently, especially when there are provided by peas. This efficiency might be related to the enhanced response of postprandial insulin observed in the HP group.

Metabolic syndrome and nonalcoholic fatty liver disease: Is insulin resistance the link?

Metabolic syndrome (MetS) is a disease composed of different risk factors such as obesity, type 2 diabetes or dyslipidemia. The prevalence of this syndrome is increasing worldwide in parallel with the rise in obesity. Nonalcoholic fatty liver disease (NAFLD) is now the most frequent chronic liver disease in western countries, affecting more than 30% of the general population. NAFLD encompasses a spectrum of liver manifestations ranging from simple steatosis to nonalcoholic steatohepatitis (NASH), fibrosis and cirrhosis, which may ultimately progress to hepatocellular carcinoma. There is accumulating evidence supporting an association between NAFLD and MetS. Indeed, NAFLD is recognized as the liver manifestation of MetS. Insulin resistance is increasingly recognized as a key factor linking MetS and NAFLD. Insulin resistance is associated with excessive fat accumulation in ectopic tissues, such as the liver, and increased circulating free fatty acids, which can further promote inflammation and endoplasmic reticulum stress. This in turn aggravates and maintains the insulin resistant state, constituting a vicious cycle. Importantly, evidence shows that most of the patients developing NAFLD present at least one of the MetS traits. This review will define MetS and NAFLD, provide an overview of the common pathophysiological mechanisms linking MetS and NAFLD, and give a perspective regarding treatment of these ever growing metabolic diseases.

Association between resistin levels and cardiovascular disease events in older adults: The health, aging and body composition study.

OBJECTIVE: Prospective data on the association between resistin levels and cardiovascular disease (CVD) events are sparse with conflicting results. METHODS: We studied 3044 aged 70-79 years from the Health, Aging, and Body Composition Study. CVD events were defined as coronary heart disease (CHD) or stroke events. «Hard » CHD events were defined as CHD death or myocardial infarction. We estimated hazard ratio (HR) and 95% confidence intervals (CI) according to the quartiles of serum resistin concentrations and adjusted for clinical variables, and then further adjusted for metabolic disease (body mass index, fasting plasma glucose, abdominal visceral and subcutaneous adipose tissue, leptin, adiponectin, insulin) and inflammation (C-reactive protein, interleukin-6, tumor necrosis factors-α). RESULTS: During a median follow-up of 10.1 years, 559 patients had « hard » CHD events, 884 CHD events and 1106 CVD Events. Unadjusted incidence rate for CVD events was 36.6 (95% CI 32.1-41.1) per 1000 persons-year in the lowest quartile and 54.0 per 1000 persons-year in the highest quartile (95% CI 48.2-59.8, P for trend < 0.001). In the multivariate models adjusted for clinical variables, HRs for the highest vs. lowest quartile of resistin was 1.52 (95% CI 1.20-1.93, P < 0.001) for « Hard » CHD events, 1.41 (95% CI 1.16-1.70, P = 0.001) for CHD events and 1.35 (95% CI 1.14-1.59, P = 0.002) for CVD events. Further adjustment for metabolic disease slightly reduced the associations while adjustment for inflammation markedly reduced the associations. CONCLUSIONS: In older adults, higher resistin levels are associated with CVD events independently of clinical risk factors and metabolic disease markers, but markedly attenuated by inflammation.

Islet Brain 1 Protects Insulin Producing Cells against Lipotoxicity.

Chronic intake of saturated free fatty acids is associated with diabetes and may contribute to the impairment of functional beta cell mass. Mitogen activated protein kinase 8 interacting protein 1 also called islet brain 1 (IB1) is a candidate gene for diabetes that is required for beta cell survival and glucose-induced insulin secretion (GSIS). In this study we investigated whether IB1 expression is required for preserving beta cell survival and function in response to palmitate. Chronic exposure of MIN6 and isolated rat islets cells to palmitate led to reduction of the IB1 mRNA and protein content. Diminution of IB1 mRNA and protein level relied on the inducible cAMP early repressor activity and proteasome-mediated degradation, respectively. Suppression of IB1 level mimicked the harmful effects of palmitate on the beta cell survival and GSIS. Conversely, ectopic expression of IB1 counteracted the deleterious effects of palmitate on the beta cell survival and insulin secretion. These findings highlight the importance in preserving the IB1 content for protecting beta cell against lipotoxicity in diabetes.

CDK4 is an essential insulin effector in adipocytes.

Insulin resistance is a fundamental pathogenic factor that characterizes various metabolic disorders, including obesity and type 2 diabetes. Adipose tissue contributes to the development of obesity-related insulin resistance through increased release of fatty acids, altered adipokine secretion, and/or macrophage infiltration and cytokine release. Here, we aimed to analyze the participation of the cyclin-dependent kinase 4 (CDK4) in adipose tissue biology. We determined that white adipose tissue (WAT) from CDK4-deficient mice exhibits impaired lipogenesis and increased lipolysis. Conversely, lipolysis was decreased and lipogenesis was increased in mice expressing a mutant hyperactive form of CDK4 (CDK4R24C). A global kinome analysis of CDK4-deficient mice following insulin stimulation revealed that insulin signaling is impaired in these animals. We determined that insulin activates the CCND3-CDK4 complex, which in turn phosphorylates insulin receptor substrate 2 (IRS2) at serine 388, thereby creating a positive feedback loop that maintains adipocyte insulin signaling. Furthermore, we found that CCND3 expression and IRS2 serine 388 phosphorylation are increased in human obese subjects. Together, our results demonstrate that CDK4 is a major regulator of insulin signaling in WAT.

Galactofuranose in Mycoplasma mycoides is important for membrane integrity and conceals adhesins but does not contribute to serum resistance.

Mycoplasma mycoides subsp. capri (Mmc) and subsp. mycoides (Mmm) are important ruminant pathogens worldwide causing diseases such as pleuropneumonia, mastitis and septicaemia. They express galactofuranose residues on their surface, but their role in pathogenesis has not yet been determined. The M. mycoides genomes contain up to several copies of the glf gene, which encodes an enzyme catalysing the last step in the synthesis of galactofuranose. We generated a deletion of the glf gene in a strain of Mmc using genome transplantation and tandem repeat endonuclease coupled cleavage (TREC) with yeast as an intermediary host for the genome editing. As expected, the resulting YCp1.1-Δglf strain did not produce the galactofuranose-containing glycans as shown by immunoblots and immuno-electronmicroscopy employing a galactofuranose specific monoclonal antibody. The mutant lacking galactofuranose exhibited a decreased growth rate and a significantly enhanced adhesion to small ruminant cells. The mutant was also 'leaking' as revealed by a β-galactosidase-based assay employing a membrane impermeable substrate. These findings indicate that galactofuranose-containing polysaccharides conceal adhesins and are important for membrane integrity. Unexpectedly, the mutant strain showed increased serum resistance.