Rapid quantification of insulin degludec by immunopurification combined with liquid chromatography high-resolution mass spectrometry

First Dimension Trap-and-Elute Combined with Second Dimension Reversed-Phase Liquid Chromatography Separation Using a Two-Dimensional-Liquid Chromatography-Tandem Mass Spectrometry System for Sensitive Quantification of Human Insulin and Six Insulin Analogs in Plasma: Improved Chromatographic Resolution and Stability Testing

Multidimensional chromatography coupled to tandem mass spectrometry (MS/MS), including simple sample preparation with protein precipitation, anion conversion with ammonium hydroxide, and solid-phase extraction using mixed-mode anion exchange in a 96-well plate format, has been validated for rapid simultaneous analysis of human insulin and its six analogs (lispro, glulisine, glargine, degludec, detemir, and aspart) in human plasma. This method is critical for clinical diagnostics, forensic investigations, and anti-doping efforts due to the widespread use of these substances. In the present study, improved chromatographic resolution was achieved using a first-dimension trap-and-elute configuration with an XBridge C18 (2.1 × 20 mm, 3.5 µm) trap column combined with second dimension separation on a Cortecs Ultra-High-Performance Liquid Chromatography (UHPLC) C18+ (2.1 × 100 mm, 1.6 µm) analytical column implemented within a two-dimensional-LC-MS/MS system. The total chromatographic run time was 11 min. This setup increases both the resolution and sensitivity of the method. A mobile phase consisting of 0.8% formic acid (FA) in water and 0.7% FA in acetonitrile was used for gradient elution. Bovine insulin was used as the internal standard. MS detection was performed in positive electrospray ionization mode, and the ion suppression due to matrix effects was evaluated. Validation criteria included linearity, precision, accuracy, recovery, lower limit of quantitation, matrix effect, and stability tests with and without protease inhibitor cocktail under different conditions (short-term stability, long-term stability, and freeze-thaw stability). The concentration range for all insulins was 50-15 000 pg/mL, with limits of quantification below the therapeutic reference range for all analytes. Intra-run precision ranged from 1.1% to 5.7%, inter-run precision from 0.7% to 5.9%, and overall recovery from 96.9% to 114.3%. The validated method has been implemented successfully by the Department of Forensic Medicine at our hospital for the investigation of unexplained deaths.

Optimized LC-MS/MS method for quantifying insulin degludec and liraglutide in rat plasma and Tissues: Application in pharmacokinetics and biodistribution

We present an ultra-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous detection of insulin degludec (I-Deg) and liraglutide (LIRA) in rat plasma and tissues, characterized by its sensitivity and selectivity. Chromatographic separation was achieved using an Acquity UPLC BEH C18 column, leveraging a mobile phase of acetonitrile and water (both with 0.1 % formic acid) under gradient elution over a run time of 7.5 min. The mass spectrometer operated in positive electrospray ionization multiple reaction monitoring (MRM) mode, tracking transitions of m/z 1221.6 → 641.6 for I-Deg, m/z 938.7 → 1064.1 for LIRA, and m/z 1184.7 → 454.4 for the internal standard. Validation ranged from 5 to 100 ng/mL, exhibiting robust linearity (r2 > 0.99) and limits of detection (LOD) of 1.63-2.02 ng/mL for I-Deg and 0.96-1.62 ng/mL for LIRA. Limits of quantification (LOQ) were 2.38-4.76 ng/mL for I-Deg and 3.22-4.40 ng/mL for LIRA. Notably, no significant matrix effects were detected. Stability was confirmed under various conditions, and precision metrics (intraday RSD 1.68-8.05 % for I-Deg and 1.11-7.69 % for LIRA; interday RSD 1.39-8.61 % for I-Deg and 1.06-8.83 % for LIRA) alongside accuracy (90.5-114.9 % for I-Deg and 92.7-113.7 % for LIRA) were within acceptable ranges. The method was successfully applied to pharmacokinetic and biodistribution studies following simultaneous subcutaneous administration of LIRA and I-Deg in rats.

Effects of Aerobic Exercise on Systemic Insulin Degludec Concentrations in People with Type 1 Diabetes

BACKGROUND

There is conflicting evidence on the effect of exercise on systemic insulin concentrations in adults with type 1 diabetes.

METHODS

This prospective single-arm study examined the effect of exercise on systemic insulin degludec (IDeg) concentrations. The study involved 15 male adults with type 1 diabetes (age 30.7 ± 8.0 years, HbA1c 6.9 ± 0.7%) on stable IDeg regimen. Blood samples were collected every 15 minutes at rest, during 60 minutes of cycling (66% VO₂max) and until 90 minutes after exercise termination. IDeg concentrations were quantified using high-resolution mass-spectrometry and analyzed applying generalized estimation equations.

RESULTS

Compared to baseline, systemic IDeg increased during exercise over time (P < .001), with the highest concentrations observed toward the end of the 60-minute exercise (17.9% and 17.6% above baseline after 45 minutes and 60 minutes, respectively). IDeg levels remained elevated until the end of the experiment (14% above baseline at 90 minutes after exercise termination, P < .001).

CONCLUSIONS

A single bout of aerobic exercise increases systemic IDeg exposure in adults on a stable basal IDeg regimen. This finding may have important implications for future hypoglycemia mitigation strategies around physical exercise in IDeg-treated patients.

High-throughput seminal fluid identification by automated immunoaffinity mass spectrometry

The identification of semen during a criminal investigation may be a critical component in the prosecution of a sexual assault. Commonly employed enzymatic and affinity-based methods for detection lack specificity, are time-consuming, and only provide a presumptive indication that semen is present where microscopic visualization is unable to meet the throughput demands. Contrary to traditional approaches, protein mass spectrometry provides true confirmatory results, but multiday sample preparation and nanoflow sample separation requirements have limited the practical applicability of these approaches. Aiming at streamlining sexual assault screening by mass spectrometry, the work here coupled a 60-minute rapid tryptic digestion, semenogelin-II peptide affinity purification on an Agilent AssayMap Bravo automation platform, and a 3-minute targeted LC-MS/MS method on an Agilent 6495 triple quadrupole mass spectrometer operating in multiple reaction monitoring mode for detecting semenogelin-II peptides in sexual assault samples. The developed assay was assessed using casework-type samples and was successful in detecting trace levels (0.0001 μl) of semen recovered from both cotton and vaginal swabs, as well as semen recovered from vaginal swabs during menses or adulterated with personal lubricants. This work represents a promising technique for high-throughput seminal fluid identification in sexual assault-type samples by mass spectrometry.