A sufficient b-cell mass is crucial for preventing diabetes, and perinatal b-cell proliferation is important in determining the adult b-cell mass. However, it is not yet known how perinatal b-cell proliferation is regulated. Here, we report that serotonin regulates b-cell proliferation through serotonin receptor 2B (HTR2B) in an autocrine/paracrine manner during the perinatal period. In b-cell-specific Tph1 knockout (Tph1 bKO) mice, perinatal b-cell proliferation was reduced along with the loss of serotonin production in b-cells. Adult Tph1 bKO mice exhibited glucose intolerance with decreased b-cell mass. Disruption of Htr2b in b-cells also resulted in decreased perinatal b-cell proliferation and glucose intolerance in adulthood. Growth hormone (GH) was found to induce serotonin production in b-cells through activation of STAT5 during the perinatal period. Thus, our results indicate that GH-GH receptor-STAT5-serotonin-HTR2B signaling plays a critical role in determining the b-cell mass by regulating perinatal b-cell proliferation, and defects in this pathway affect metabolic phenotypes in adults.

The health of their populations and efficient health care systems are of critical importance to the economic and social well-being of nations. Accurate and comparable peptide/protein measurements are required in support of diagnosis, prognosis, monitoring and treatment of widespread diseases (e.g. diabetes). The required consistency of measurement results can be achieved by making them traceable to stated references and through the development of Reference Measurement Systems. The review mainly concentrates on the progress made in the Protein Analysis Working Group of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM-PAWG) in establishing Primary Calibration Reference Services in the emerging area of health markers such as peptides/proteins. Primary Calibration Reference Services are technical capabilities for composition assignment, commonly as the mass fraction content, of pure substances or solutions thereof. It is a core technical competency for National Measurement Institutes (NMIs). A limited number of key comparisons, foreseen by the CCQM-PAWG strategy, are discussed that enable NMIs providing measurement services in peptide/protein analysis to test and demonstrate their capabilities. In addition, the review examines the development and improvement of analytical methods and metrological models that are required to meet the needs of NMIs and associated clinical stakeholders.

An element-based reductive approach provides an effective means of realizing International System of Units (SI) traceability for high-purity biological standards. Here, we develop an absolute protein quantification method using double isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS) combined with microwave-assisted acid digestion for the first time. We validated the method and applied it to certify the candidate protein certified reference material (CRM) of human growth hormone (hGH). The concentration of hGH was determined by analysing the total amount of sulfur in hGH. Next, the size-exclusion chromatography method was used with ICP-MS to characterize and quantify sulfur-containing impurities. By subtracting the contribution of sulfur-containing impurities from the total sulfur content in the hGH CRM, we obtained a SI-traceable certification value. The quantification result obtained with the present method based on sulfur analysis was in excellent agreement with the result determined via a well-established protein quantification method based on amino acid analysis using conventional acid hydrolysis combined with an ID liquid chromatography-tandem mass spectrometry. The element-based protein quantification method developed here can be generally used for SI-traceable absolute quantification of proteins, especially pure-protein standards.

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We describe a capillary electrophoresis-mass spectrometry (CE-MS) method for newborn screening of a representative amino acid metabolic disease, namely, phenylketonuria (PKU). Underivatized phenylalanine and tyrosine in a dried blood spot (DBS) were simultaneously determined by CE-MS equipped with an ionophore membrane-packed sheathless electrospray ionization interface, which was developed by our group. The method was optimized for rapid determination of the underivatized amino acids, phenylalanine and tyrosine extracted from a DBS. Under the optimized conditions, the limit of detection of phenylalanine and tyrosine (signal-to-noise ratio, 3) was 0.03 and 0.07 mg/L in DBS, respectively, with a CE run time of less than 3 min. For repeated runs of a sample, coefficients of variation (CVs) for migration time were less than 3.7%, whereas CVs for the area ratio under the curve were 2.1 and 2.9% for 20 consecutive runs of 49.5 mg/kg Phe and 36.2 mg/kg Tyr, respectively. However, the relative standard deviations of intra- and interday assays for DBS samples were <6.2 and <5.8%, respectively, which were substantially due to sample extraction from DBS. The analytical method was applied to real clinical samples of Korean neonates, and results were compared with those of conventional methods for PKU diagnosis, which required reference analytical methods such as isotope dilution CE-MS or high-performance liquid chromatography-mass spectrometry for quality assurance of the conventional kit-based assays. The distinct advantages of high sensitivity and extremely low sample volume, as well as a simple, easy, and economic sample pretreatment, were demonstrated for the proposed method.

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