Nathalie Reix

Extensive study of human insulin immunoassays: promises and pitfalls for insulin analogue detection and quantification.

Abstract Background: Over the last few decades, new synthetic insulin analogues have been developed. Their measurement is of prime importance in the investigation of hypoglycaemia, but their quantification is hampered by variable cross-reactivity with many insulin assays. For clinical analysis, it has now become essential to know the potential cross-reactivity of analogues of interest. Methods: In this work, we performed an extensive study of insulin analogue cross-reactivity using numerous human insulin immunoassays. We investigated the cross-reactivity of five analogues (lispro, aspart, glulisine, glargine, detemir) and two glargine metabolites (M1 and M2) with 16 commercial human insulin immunoassays as a function of concentration. Results: The cross-reactivity values for insulin analogues or glargine metabolites ranged from 0% to 264%. Four assays were more specific to human insulin, resulting in negligible cross-reactivity with the analogues. However, none of the 16 assays was completely free of cross-reactivity with analogues or metabolites. The results show that analogue cross-reactivity, which varies to a large degree, is far from negligible, and should not be overlooked in clinical investigations. Conclusions: This study has established the cross-reactivity of five insulin analogues and two glargine metabolites using 16 immunoassays to facilitate the choice of the immunoassay(s) and to provide sensitive and specific analyses in clinical routine or investigation.

Metabolomic profile of the adrenal gland: from physiology to pathological conditions

In this study, we i) assessed the metabolic profile of the normal adrenal cortex and medulla of adult human subjects by means of (1)H-high-resolution magic-angle spinning nuclear magnetic resonance (HRMAS NMR) spectroscopy; ii) compared the biochemical profile of adenoma (Ad), adrenal cortical carcinoma (ACC), and pheochromocytoma (PCC) samples with that of healthy adrenal tissue samples; and iii) investigated the metabolic differences between ACCs and Ads as well as between ACCs and PCCs. Sixty-six tissue samples (13 adrenal cortical tissue, eight medullary tissue, 13 Ad, 12 ACC, and 20 PCC samples) were analyzed. Adrenaline and noradrenaline were undetectable in cortical samples representing the metabolic signature of the tissue derived from neural crest. Similarity between the metabolic profile of Ads and that of the normal adrenal cortex was shown. Inversely, ACC samples clearly made up a detached group exhibiting the typical stigmata of neoplastic tissue such as choline-containing compounds, biochemical markers of anaerobic processes, and increased glycolysis. Significantly higher levels of lactate, acetate, and total choline-containing compounds played a major role in the differentiation of ACCs from Ads. Moreover, the high fatty acid content of ACCs contributed to the cluster identification of ACCs. Of the 14 sporadic PCC samples, 12 exhibited predominant or exclusive noradrenaline secretion. The noradrenaline:adrenaline ratio was inverted in the normal medullary tissue samples. Multiple endocrine neoplasia type 2- and NF1-related PCC samples exhibited both adrenaline and noradrenaline secretion. In the von Hippel-Lindau disease-related PCC samples, only noradrenaline secretion was detected by HRMAS NMR spectroscopy. This study is one of the first applications of metabolomics to adrenal pathophysiology and it is the largest study to report HRMAS NMR data related to the adrenal cortex and adrenal cortical tumors.

Thyroid-stimulating hormone and free thyroxine on the ADVIA Centaur immunoassay system: A multicenter assessment of analytical performance.

OBJECTIVES We assessed the analytical performance of the TSH and FT4 assays on ADVIA Centaur in a multicenter national evaluation. DESIGN AND METHODS A precision study and a method comparison were performed. Reference values stated by the manufacturer were checked from 379 normal subjects. RESULTS For TSH and FT4, the intra-assay CVs were below 2.3 and 5.2%, respectively, and the inter-assay CVs below 4.4% and 7.2%, respectively. Therefore, the precision and reproducibility were acceptable. Bland-Altman bias plots revealed good correlation and agreement with Cobas assays. TSH and FT4 data yielded reference ranges of 0.64-3.24 mIU/L and 10.5-18.9 pmol/L, respectively. CONCLUSION These assays demonstrate reliable characteristics. The reference ranges obtained can be used for interpretation of thyroid function.

Should functional sensitivity of a new thyroid stimulating hormone immunoassay be monitored routinely? The ADVIA Centaur® TSH3-UL assay experience

OBJECTIVES We emphasize the importance of routine follow-up of subnormal TSH concentrations with QC materials. DESIGN AND METHODS The functional sensitivity (FS) of the ADVIA Centaur system TSH assay was assessed. We report the values yielded for QC materials in two clinical laboratories. RESULTS The FS was <0.02 mIU/L. The low-TSH QC (a serum pool) showed unacceptable between-lot imprecision (mean 0.0252 mIU/L, CV 22%). CONCLUSION We do encourage healthcare laboratories to constitute low-TSH serum pools to ensure that the results they report meet 3rd-generation criteria.

Les insulines intelligentes : une nouvelle forme de pancréas artificiel

Resume Developper un systeme de delivrance de l’insuline regule par la glycemie est l’un des defis d’optimisation de l’insulinotherapie. Les dispositifs externes de pancreas artificiels sont encore en cours de perfectionnement pour etre autonomes, mais, depuis les annees 1990, s’est developpe le concept « d’insulines intelligentes ». Dans ces systemes, l’insuline est contenue dans un microgel injectable, gluco-stimulable et capable de delivrer de l’insuline en fonction de la glycemie. Ce systeme, une fois mis au point, serait une revolution pour les patients, les liberant de l’adaptation des doses, des hypoglycemies, du port de materiel (pompes, capteurs) mais aussi des traitements immunosuppresseurs necessaires dans les greffes de pancreas ou d’ilots. Il reste neanmoins un long chemin a parcourir avant les premiers essais cliniques. Le but de cette revue est d’exposer les differents concepts developpes et leur interet en clinique, mais egalement leurs limites.

A Metabolomic Approach (1H HRMAS NMR Spectroscopy) Supported by Histology to Study Early Post-transplantation Responses in Islet-transplanted Livers

Intrahepatic transplantation of islets requires a lot of islets because more than 50% of the graft is lost during the 24 hours following transplantation. We analyzed, in a rat model, early post-transplantation inflammation using systemic inflammatory markers, or directly in islet-transplanted livers by immunohistochemistry. 1H HRMAS NMR was employed to investigate metabolic responses associated with the transplantation. Inflammatory markers (Interleukin-6, α2-macroglobulin) are not suitable to follow islet reactions as they are not islet specific. To study islet specific inflammatory events, immunohistochemistry was performed on sections of islet transplanted livers for thrombin (indicator of the instant blood-mediated inflammatory reaction (IBMIR)) and granulocytes and macrophages. We observed a specific correlation between IBMIR and granulocyte and macrophage infiltration after 12 h. In parallel, we identified a metabolic response associated with transplantation: after 12 h, glucose, alanine, aspartate, glutamate and glutathione were significantly increased. An increase of glucose is a marker of tissue degradation, and could be explained by immune cell infiltration. Alanine, aspartate and glutamate are inter-connected in a common metabolic pathway known to be activated during hypoxia. An increase of glutathione revealed the presence of antioxidant protection. In this study, IBMIR visualization combined with 1H HRMAS NMR facilitated the characterization of cellular and molecular pathways recruited following islet transplantation.

L’insuline par voie orale : promesses et réalités

Resume L’insuline est l’agent hypoglycemiant le plus efficace employe dans le traitement du diabete. L’ajout dans l’armamentarium antidiabetique d’une formulation d’insuline administrable par voie orale offrirait une perspective prometteuse dans la gestion du diabete. En effet, une telle formulation permettrait une administration portale de l’insuline, avec les repercussions benefiques connues d’un premier passage hepatique, et, de plus, une excellente acceptation par le patient. Plusieurs strategies ont ete developpees afin d’assurer une protection de l’insuline face a l’hydrolyse enzymatique en milieu gastro-intestinal, et pour promouvoir son absorption et son transport au travers de l’epithelium intestinal. Nous presentons une revue de ces differentes strategies, ainsi qu’une presentation des cinq essais cliniques majeurs en cours.