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OBJECTIVE: To explore the associations among mannose, indexes of insulin resistance (IR) and secretion, and long-term cardiovascular outcomes. RESEARCH DESIGN AND METHODS: Fasting mannose was assayed in 1,403 participants, one-half of which had a first myocardial infarction (MI) with either normal glucose tolerance (n = 1,045) or newly detected dysglycemia (i.e., impaired glucose tolerance or type 2 diabetes; n = 358). Regression models were used to explore mannose associations with surrogate indexes of IR/insulin secretion. Multivariate Cox models were used to investigate the independent association between high (higher quartile) versus low (lower three quartiles) mannose and major adverse cardiac events (MACE) (n = 163) during the 10-year follow-up. RESULTS: Mannose was independently associated with IR indexes (all P ≤ 0.001). High versus low mannose was independently associated with MACE (hazard ratio 1.54, 95% CI 1.07–2.20) in the overall population. CONCLUSIONS: Mannose might represent a new biomarker able to track early, potentially detrimental glucometabolic alterations independently of glycemic state. [ABSTRACT FROM AUTHOR]

The current guidelines for sweat chloride analysis identify the procedures for sweat collection, but not for chloride assay, which is usually performed by methods originally not aiming at the low concentrations of chloride found in sweat. To overcome this limitation, we set up, characterized, and adopted an original inductively coupled plasma mass spectrometry (ICP-MS) method for sweat chloride determination, which was designed for its easy use in a clinical laboratory. The method was linear in the range 8.5E−3 to 272.0E−3 mM, precision exhibited a relative standard deviation < 6%, and accuracy was in the range 99.7–103.8%. Limit of blank, limit of detection, and limit of quantitation were 2.1 mM, 3.2 mM, and 7.0 mM, respectively, which correspond to real concentrations injected into the mass spectrometer of 3.9E−3 mM for LOD and 8.5E−3 mM for LOQ. At first, the method was tested on 50 healthy volunteers who exhibited a mean chloride concentration of 15.7 mM (25–75th percentile 10.1–19.3 mM, range 2.8–37.4 mM); then, it was used to investigate two patients with suspected cystic fibrosis, who exhibited sweat chloride values of 65.6 mM and 81.2 mM, respectively. Moreover, the method was cross-validated by assaying 50 samples with chloride concentration values in the range 10–131 mM, by both ICP-MS and coulometric titration, which is the technology officially used in Tuscany for cystic fibrosis newborn screening. The reference analytical performances and the relatively low cost of ICP-MS, accompanied by the advantageous cost of a single sweat chloride assay, make this technology the best candidate to provide a top reference method for the quantification of chloride in sweat. The method that we propose was optimized and validated for sweat samples ≥ 75 mg, which is the minimum amount requested by the international protocols. However, the method sensitivity and, in addition, the possibility to reduce the sample dilution factor, make possible the quantification of chloride even in samples weighting < 75 mg that are discarded according to the current guidelines. [ABSTRACT FROM AUTHOR]

N-acetylaspartate is a human endogenous compound synthesized by neurons, which is involved in neuronal metabolism. It is used as a marker in brain magnetic resonance spectroscopy to investigate several neurological and metabolic disorders, that can be related to a variation of its concentration with respect to reference values. N-acetylaspartate is present also in biological fluids, such as plasma, urine, and cerebrospinal fluid, where it can be quantified. Here we describe the development and validation, in compliance with the EMA guidelines, of a novel assay method for the quantification of N-acetylaspartate in plasma based on tandem mass spectrometry coupled to liquid chromatography. Its peculiarity lies in the fact that sample preparation includes an esterification step, which significantly improves the chromatographic performances and, consequently, also the method sensitivity, reproducibility and accuracy. Instrumental LLOQ is 0.06 ng/mL, i.e. at least 300 times lower than the medium N-acetylaspartate concentration in samples, accuracy is in the range 98–103%, while precision lies between 1 and 3%. The method robustness was tested in about 1000 injections of plasma samples, 96 of which were used also to assess the reference ranges in control subjects (16.46–63.40 ng/mL). Controls were then compared to plasma samples from type 2 diabetic patients. Contrary to brain magnetic resonance spectroscopy, which demonstrated a decrease in the N-acetylaspartate levels in right frontal and parieto-temporal region of type 2 diabetic patients, plasma analysis showed no statistical difference with respect to controls. However, the method here described can be profitably used in studies concerning different disorders with CNS involvement, as confirmed by reports available in the literature. [ABSTRACT FROM AUTHOR]

The present paper describes the development and the validation process – in compliance with the EMA guidelines – of a method based on tandem mass spectrometry coupled to liquid chromatography for the accurate quantification of mannose in human plasma samples. The quick sample preparation procedure, simplified by the absence of any derivatization step, makes the assay suitable for routine use in a clinical chemistry laboratory. The method validation yielded satisfactory selectivity, with a good separation of mannose from its epimers (glucose and galactose), linearity over the whole concentration range of interest (0.31–40 μg/mL), reproducibility with RSD <10%, and accuracy in the range 96–104%. Instrumental LLOD (0.31 μg/mL) and LLOQ (1.25 μg/mL) were good enough to detect endogenous plasma mannose levels and in agreement with recent data from the literature. Sensitivity was affected by a 5-fold dilution factor, which, if necessary, can be reduced. The method robustness was proven in >600 injections, most of them being of plasma samples, used also to assess the reference ranges in healthy subjects (9.93 ± 3.37 μg/mL) and type 2 diabetic patients (23.47 ± 6.19 μg/mL). • We developed and validated an HPLC-MS-MS assay method to detect d -mannose. • It was validated in compliance with EMA guidelines. • Reproducibility (RSD) <10% and accuracy was in the range 96–104%. • Instrumental LLOD and LLOQ were 0.31 and 1.25 μg/mL, respectively. • Reference concentrations: 9.93 ± 3.37 μg/mL (controls)and 23.47 ± 6.19 μg/mL (diabetics). [ABSTRACT FROM AUTHOR]

In the clinical laboratories, dehydroepiandrostenedione (DHEA) is usually quantified by immunoassay-based methods, which are often affected by cross-reactivity with endogenous interferences, such as 4-androsten-3β-ol-17-one. The interfering compounds lead to a poor accuracy of the measurements, mainly at a low concentration level. The present paper describes a validated method based on tandem mass spectrometry coupled to liquid chromatography, for the accurate quantification of DHEA in serum. The peculiarity of this method is the use of calibrators and quality controls prepared by adding measured amounts of DHEA-D, a stable isotope-labeled analogue of DHEA, to real serum from healthy subjects. DHEA-D is used in place of DHEA, which is usually present in unstripped serum at physiological levels, as it has the same basic structure, provides an equivalent instrumental response, and can be easily distinguish by DHEA by mass spectrometry due to its different m/ z value. The method proved to be sensitive, with a LLOD of 0.09 ng/mL and a LLOQ of 0.23 ng/mL, and selective, with overall performances that allow its use on a routine basis. [ABSTRACT FROM AUTHOR]

Background: Plasma mannose, an emerging novel biomarker of insulin resistance, is associated with both diabetes mellitus and coronary atherosclerosis, but the relationship between mannose concentrations and myocardial infarction (MI) across different glycaemic states remains to be elucidated. The aim of this study was to investigate the independent association between mannose and a first MI in a group of subjects characterized according to their glycaemic state. Methods: Fasting plasma mannose concentrations were analysed in 777 patients 6–10 weeks after a first myocardial infarction and in 770 matched controls by means of high-performance liquid chromatography coupled to tandem mass spectrometry. Participants without known diabetes mellitus were categorized by an oral glucose tolerance test (OGTT) as having normal glucose tolerance (NGT, n = 1045), impaired glucose tolerance (IGT, n = 246) or newly detected type 2 diabetes (T2DM, n = 112). The association between mannose and MI was investigated across these glycaemic states by logistic regression. Results: Mannose levels increased across the glycaemic states (p < 0.0001) and were significantly associated with a first MI in the whole study population (odds ratio, OR: 2.2; 95% CI 1.4 to − 3.5). Considering the different subgroups separately, the association persisted only in subjects with NGT (adjusted OR: 2.0; 95% CI 1.2–3.6), but not in subgroups with glucose perturbations (adjusted OR: 1.8, 95% CI 0.8–3.7). Conclusions: Mannose concentrations increased across worsening levels of glucose perturbations but were independently associated with a first MI only in NGT individuals. Thus, mannose might be a novel, independent risk marker for MI, possibly targeted for the early management of previously unidentified patients at high cardiovascular risk. [ABSTRACT FROM AUTHOR]

OBJECTIVE To explore the complementary effects of a combination of dipeptidyl peptidase 4 and sodium-glucose cotransporter 2 inhibitors added to metformin on hormonal and metabolic responses to meal ingestion. RESEARCH DESIGN AND METHODS Forty-five patients (age 58 ± 8 years; HbA1c 58 ± 6 mmol/mol; BMI 30.7 ± 3.2 kg/m²) with type 2 diabetes uncontrolled with metformin were evaluated at baseline and 3 and 28 days after 5 mg saxagliptin (SAXA), 10 mg dapagliflozin (DAPA), or 5 mg saxagliptin plus 10 mg dapagliflozin (SAXA+DAPA) using a mixed-meal tolerance test (MMTT) spiked with dual-tracer glucose to assess glucose metabolism, insulin secretion, and sensitivity. RESULTS At day 3, fasting and mean MMTT glucose levels were lower with SAXA+DAPA (-31.1 ± 1.6 and -91.5 ± 12.4 mg/dL) than with SAXA (-7.1 ± 2.1 and -53 ± 10.5 mg/dL) or DAPA (-17.0 ± 1.1 and -42.6 ± 10.0 mg/dL, respectively; P < 0.001). Insulin secretion rate (SAXA+DAPA +75%; SAXA +11%; DAPA +3%) and insulin sensitivity (+2.2 ± 1.7, +0.4 ± 0.7, and +0.4 ± 0.4 mg · kg-1 · min-1, respectively) improved with SAXA+DAPA (P < 0.007). Mean glucagon-like peptide 1 (GLP-1) was higher with SAXA+DAPA than with SAXA or DAPA. Fasting glucagon increased with DAPA and SAXA+DAPA but not with SAXA. Fasting endogenous glucose production (EGP) increased with SAXA+DAPA and DAPA. During MMTT, EGP suppression was greater (48%) with SAXA+DAPA (vs. SAXA 44%; P = 0.02 or DAPA 34%; P = 0.2). Metabolic clearance rate of glucose (MCRglu) increased more with SAXA+DAPA. At week 4, insulin secretion rate, β-cell glucose sensitivity, and insulin sensitivity had further increased in the SAXA+DAPA group (P = 0.02), with no additional changes in GLP-1, glucagon, fasting or MMTT EGP, or MCRglu. CONCLUSIONS SAXA+DAPA provided superior glycemic control compared with DAPA or SAXA, with improved β-cell function, insulin sensitivity, GLP-1 availability, and glucose clearance. [ABSTRACT FROM AUTHOR]

N-acetylaspartate (NAA) is the second most abundant metabolite in the human brain; although it is assumed to be a proxy for a neuronal marker, its function is not fully elucidated. NAA is also detectable in plasma, but its relation to cerebral NAA levels, cognitive performance, or features of cerebral disease has not been investigated. To study whether circulating NAA tracks cerebral NAA levels, and whether circulating NAA correlates with cognitive function and features of cerebral small vessel disease (SVD). Two datasets were analyzed. In dataset 1, structural MRI was acquired in 533 subjects to assess four features of cerebral SVD. Cognitive function was evaluated with standardized test scores (N = 824). In dataset 2, brain 1H-MRS from the occipital region was acquired (N = 49). In all subjects, fasting circulating NAA was measured with mass spectrometry. Dataset 1: in univariate and adjusted for confounders models, we found no correlation between circulating NAA and the examined features of cerebral SVD. In univariate analysis, circulating NAA levels were associated inversely with the speed in information processing and the executive function score, however these associations were lost after accounting for confounders. In line with the negative findings of dataset 1, in dataset 2 there was no correlation between circulating and central NAA or total NAA levels. This study indicates that circulating NAA levels do not reflect central (occipital) NAA levels, cognitive function, or cerebral small vessel disease in man. [ABSTRACT FROM AUTHOR]

High mannose has previously associated with insulin resistance and cardiovascular disease (CVD). Our objective is to establish whether mannose is associated with anatomical evidence of coronary artery disease (CAD). Plasma mannose concentrations were measured by liquid chromatography/tandem mass spectrometry in a discovery cohort (n = 513) and a validation cohort (n = 221) of carefully phenotyped individuals. In both cohorts CAD was quantitated using state-of-the-art imaging techniques (coronary computed coronary tomography angiography (CCTA), invasive coronary angiography and optical coherence tomography). Information on subsequent CVD events/death was collected. Associations of mannose with angiographic variables and biomarkers were tested using univariate and multivariate regression models. Survival analysis was performed using the Kaplan-Meier estimator. Mannose was related to indices of CAD and features of plaque vulnerability. In the discovery cohort, mannose was a marker of quantity and quality of CCTA-proven CAD and subjects with a mannose level in the top quartile had a significantly higher risk of CVD events/death (p = 3.6e-5). In the validation cohort, mannose was significantly associated with fibrous cap thickness < 65 μm (odds ratio = 1.32 per each 10 μmol/L mannose change [95% confidence interval, 1.05–1.65]) and was an independent predictor of death (hazard ratio for mannose≥ vs < 84.6 μmol/L: 4.0(95%CI, 1.4–11.3), p = 0.006). The current data add novel evidence that high mannose is a signature of CAD with a vulnerable plaque phenotype, consistently across measures of severity of vessel involvement and independent of the traditional correlates of CVD, and that it is an independent predictor of incident adverse outcomes. • High mannose concentration is emerging as a novel marker of cardiovascular disease • In the discovery cohort, mannose was a marker of coronary artery disease (CAD). • In the validation cohort, mannose was associated with fibrous cap thickness. • In both cohorts high mannose was an independent predictor of adverse outcomes. • High mannose might be a signature of CAD with a vulnerable plaque phenotype. [ABSTRACT FROM AUTHOR]

Background: The glucosuria induced by sodium-glucose cotransporter-2 inhibitors (SGLT2i) stimulates endogenous (hepatic) glucose production (EGP) blunting the decline in HbA1c. We hypothesized that, in response to glucosuria, a renal signal is generated and stimulated EGP. Aim: To examine the effect of acute administration of dapagliflozin (DAPA) in nondiabetic, renal transplant subjects on SGLT2i-induced stimulation of EGP. Methods: 20 subjects [10 with intact native kidneys (IK) and 10 with bilateral nephrectomy (NK)] underwent measurement of EGP ([6,6-2H2]-glucose) before and for 6 hours after administration of DAPA or placebo (PLC) on 2 separate days. Results: DAPA induced greater glucosuria in subjects with IK versus NK (8.6±1.1 vs. 5.5±0.5 grams/6-hrs; p=0.02). During 6-hour, plasma glucose decreased slightly and similarly in both groups, with no difference compared to PLC. Following PLC, there was a progressive time-related decline in EGP that was similar in both groups. Following DAPA, EGP declined in both groups but the decrement in EGP was 56% greater in the NK. During DAPA, urinary glucose excretion was correlated with EGP (r = 0.34, p<0.05). Plasma insulin, C-peptide, glucagon, pre-hepatic insulin/glucagon ratio, lactate, alanine and pyruvate concentrations were similar in PLC and DAPA. β-hydroxybutyrate increased with DAPA in the IK, while a small increase was observed only at 360 min in the NK. Plasma epinephrine did not change after DAPA and PLC in both groups. Following DAPA, plasma norepinephrine increased slightly in the IK and decreased in the NK. Conclusions: In NK subjects the hepatic compensatory response to acute SGLT2i-induced glucosuria was attenuated compared to diabetic subjects with IK, suggesting a SGLT2i-mediated stimulation of hepatic glucose production via efferent renal nerves in an attempt to compensate for the urinary glucose loss, i.e., a renal-hepatic axis. Disclosure: G. Daniele: None. C. Solis-Herrera: Consultant; Self; Lexicon Pharmaceuticals, Inc. A. Dardano: None. A. Mari: Consultant; Self; Lilly Diabetes. Research Support; Self; Boehringer Ingelheim International GmbH. A. Tura: None. L. Giusti: None. J.J. Kurumthodathu: None. A.A.G. Brocchi: None. B. Campi: None. A. Saba: None. A. Bianchi: None. C. Tregnaghi: None. M. Egidi: None. M. Abdul-Ghani: None. R.A. DeFronzo: None. S. DelPrato: None. [ABSTRACT FROM AUTHOR]