Nicotinamide adenine dinucleotide (NAD) is a cofactor in redox reactions and an essential mediator of energy metabolism. The redox balance between NAD⁺ and NADH affects various diseases, cell differentiation, and aging, and in recent years there has been a growing need for measurement techniques with improved accuracy. However, NAD(H) measurements, representing both NAD⁺ and NADH, have been limited by the compound’s properties. We achieved highly sensitive simultaneous measurement of NAD⁺ and NADH under non-ion pairing, mobile phase conditions of water, or methanol containing 5 mM ammonium acetate. These were achieved using a simple pre-treatment and 7-min analysis time. Use of the stable isotope ¹³C₅-NAD⁺ as an internal standard enabled validation close to BMV criteria and demonstrated the robustness of NAD(H) determination. Measurements using this method showed that brain NAD(H) levels correlate strongly with plasma NAD(H) levels in the same mouse, indicating that NAD(H) concentrations in brain tissue are reflected in plasma. As NAD(H) is involved in various neurodegenerative diseases and cerebral ischemia, as well as brain diseases such as mitochondrial myopathies, monitoring changes in NADH levels in plasma after drug administration will be useful for development of future diagnostics and therapeutics.

Tacrolimus (TAC)-induced chronic nephrotoxicity (TAC nephrotoxicity) has a detrimental effect on long-term kidney graft survival. However, the pathogenesis of TAC nephrotoxicity remains largely unknown. We explored it by focusing on metabolic changes in renal tissues. In this study, mice were separated into TAC and control groups (n = 5/group). TAC was administered to the TAC group (1 mg/kg/d for 28 days) subcutaneously. The control group was similarly treated with normal saline. Renal tissue metabolomes were evaluated. Renal fibrosis was observed only in the TAC group. Metabolomic analysis showed that carnitine and related metabolites were substantially lower in the TAC group than in the control group, presumably due to impaired biosynthesis and reabsorption. Low carnitine levels impair antioxidation in renal tissues and β-oxidation in mitochondria, which may lead to renal tissue damage. This metabolomic analysis revealed that carnitine deficiency in renal tissue appears to explain TAC nephrotoxicity.

Despite advances in systemic chemotherapy, patients with gastric cancer (GC) and peritoneal metastases (PMs) continue to have poor prognoses. Intraperitoneal (IP) administration of Paclitaxel (PTX) combined with systemic chemotherapy shows promise in treating PMs from GC. However, methods of drug administration need to be optimized to maximize efficacy. In this study, we utilized a mouse model with PMs derived from a human GC cell line, administering PTX either IP or intravenously (IV), and Carboplatin (CBDCA) IV 0, 1, and 4 days after PTX administration. The PMs were resected 30 min later, and concentrations of PTX and CBDCA in resected tumors were measured using liquid chromatography–tandem mass spectrometry (LC-MS/MS). Results indicated that PTX concentrations were higher with IP administration than with IV administration, with significant differences observed on days 0 and 1. CBDCA concentrations 4 days post-IP PTX administration were higher than with simultaneous IV PTX administration. These findings suggest that IP PTX administration enhances CBDCA concentration in peritoneal tumors. Therefore, sequential IV administration of anti-cancer drugs appears more effective than simultaneous administration with IP PTX, a strategy that may improve prognoses for patients with PMs.

Aflibercept and brolucizumab, two anti-VEGF agents used as intravitreal injections in ophthalmology, differ significantly in molecular weight (aflibercept—115 kDa and brolucizumab—26 kDa). Using aqueous humor samples collected after drug administration, we measured and performed a comparative analysis of pharmacokinetics and half-lives of these drugs in the human eye. Since the quantification of monoclonal antibodies (mAbs) using antigen–antibody reactions, such as ELISA, is influenced by endogenous ligands or anti-drug antibodies, we employed nano-surface and molecular-orientation limited proteolysis (nSMOL), combined with liquid chromatography–tandem mass spectrometry (LC-MS/MS), for accurate measurements. Aqueous humor samples were collected from 59 eyes of 59 patients treated with aflibercept and 52 eyes of 52 patients treated with brolucizumab. Samples were obtained with a median post-injection period of 30 (range, 2–49) days for aflibercept and 28 (range, 4–60) days for brolucizumab. A population pharmacokinetic (PPK) analysis revealed that the half-life of aflibercept in human aqueous humor was significantly shorter than that of brolucizumab, 2.88 days versus 9.00 days, respectively (p = 1.16 × 10⁻⁷). Using the same mass spectrometry conditions, we calculated the half-lives of the two drugs. These results may be useful for optimizing the efficacy of these drugs in clinical practice.

Immunosuppressants are essential for preventing allograft rejection; however, they require therapeutic drug monitoring to maintain efficacy and to prevent severe complications such as opportunistic infections. Calcineurin inhibitors (CIs) are primarily distributed in red blood cells, whereas mycophenolic acid (MPA) and its metabolites are found in plasma. These differences necessitate separate analyses for each drug, increasing laboratory workload, analytical complexity, and patient burden. We developed a liquid chromatography–tandem mass spectrometry method for simultaneous quantification of CIs such as tacrolimus (Tac), everolimus (Eve), sirolimus (Sir), cyclosporine A (CycA) and MPA in 2.8-µL whole-blood samples, with a hematocrit-based correction to estimate plasma-equivalent MPA concentrations. Performance of this method was assessed by comparison with conventional immunoassay results using linear regression and Bland–Altman analyses, demonstrating excellent agreement, with strong linearity (R² > 0.995) at 0.900), indicating high accuracy and reproducibility. This new approach may be particularly beneficial for hospitalized patients with limited venous access, pediatric populations, and in remote care settings where frequent blood sampling is challenging because of simultaneous quantification and fewer sample volume requirements.

Nicotinamide adenine dinucleotide (NAD) is a critical cofactor in mitochondrial energy production. The NADH/NAD⁺ ratio, reflecting the balance between NADH (reduced) and NAD^{+ (}oxidized⁾, is a key marker for the severity of mitochondrial diseases. We recently developed a streamlined LC-MS/MS method for the precise measurement of NADH and NAD⁺. Utilizing this technique, we quantified NADH and NAD⁺ levels in fibroblasts derived from pediatric patients and in a Leigh syndrome mouse model in which mitochondrial respiratory chain complex I subunit Ndufs4 is knocked out (KO). In patient-derived fibroblasts, NAD⁺ levels did not differ significantly from those of healthy controls (p = 0.79); however, NADH levels were significantly elevated (p = 0.04), indicating increased NADH reductive stress. This increase, observed despite comparable total NAD(H) levels between the groups, was attributed to elevated NADH levels. Similarly, in the mouse model, NADH levels were significantly increased in the KO group (p = 0.002), further suggesting that NADH elevation drives reductive stress. This precise method for NADH measurement is expected to outperform conventional assays, such as those for lactate, providing a simpler and more reliable means of assessing disease progression.