Serum cystatin C and stroke risk: a national cohort and Mendelian randomization study.

Purpose: The debate over the causal and longitudinal association between cystatin C and stroke in older adults persists. Our aim was to assess the link between cystatin C levels, both measured and genetically predicted, and stroke risk. Methods: This study employed a retrospective cohort design using samples of the China Health and Retirement Longitudinal Study (CHARLS), which is a nationally representative cohort recruiting individuals aged 45 years or above. A multivariate logistic model and the two-sample Mendelian randomization framework were used to investigate the longitudinal and genetically predicted effect of serum cystatin C on stroke. Results: The study population had a mean age of 59.6 (SD ±9.5), with 2,996 (46.1%) women. After adjusting for confounding factors, compared to those in the first quartile of cystatin C, those in the last quartile had the greatest risk of stroke incidence [odds ratio (OR), 1.380; 95% confidence interval (CI), 1.046-1.825]. The Mendelian randomization analysis showed that a genetically predicted cystatin C level was positively associated with total stroke (OR by inverse variance-weighted method, 1.114; 95% CI, 1.041-1.192). Conclusions: This national cohort study suggests that higher serum cystatin C is associated with an increased risk of total stroke, which is further supported by Mendelian randomization.

Efficient preparation of c-di-AMP at gram-scale using an immobilized Vibrio cholerae dinucleotide cyclase DncV.

Cyclic di-AMP is a bacterial nucleotide second messenger and evaluated as a potential vaccine adjuvant candidate. Here, we report a practical and economical enzymatic method for gram-scale preparation of c-di-AMP using an immobilized Vibrio cholerae dinucleotide cyclase DncV. The method mainly includes four steps: preparation of DncV-immobilized resin, enzymatic synthesis of c-di-AMP, purification using macroporous absorption resin SP207, and desiccation using rotary evaporation and lyophilization. Enzymatic synthesis is the most critical step, and almost all substrate ATP was converted to c-di-AMP under an optimum condition in which 300 mL of 300 mM NH4Ac/NH3 pH 9.5 buffer supplemented with 20 mM MnCl2, 10 mM ATP and 4 mL of DncV-immobilized resin containing ∼19 mg DncV were incubated at 30 °C overnight. After purification, up to 1 g of the diammonium salt of c-di-AMP with weight purity of ≥98% was obtained as white powder, which corresponds to an overall yield of ∼80% based on the ATP input into the reaction. The method is easily performed in laboratory to prepare c-di-AMP on a gram scale and could be used in industry on a large scale.

A sensitive LC-MS/MS method to quantify methylergonovine in human plasma and its application to a pharmacokinetic study.

Methylergonovine (ME) is a semisynthetic ergot alkaloid that is used for the treatment and prophylaxis of postpartum hemorrhage. In recent years, methylergonovine has been effective in the control of refractory headaches and is likely to be employed as chemosensitizers for cancer. However, this alkaloid sometimes causes elevated blood pressure. Therefore, a sensitive and accurate method for the quantification of this drug in biological matrices is necessary. In this study, ME was extracted from 500µL plasma samples by a liquid-liquid extraction under alkaline conditions and detected using positive multi-reaction-monitoring mode (+MRM) mass spectrometry. The method was validated according to US FDA guidelines and covered a working range from 0.025 to 10ng/mL with a lower limit of quantification (LLOQ) of 0.025ng/mL. In conclusion, a rapid, sensitive, selective and accurate quantification by an LC-MS/MS method was developed and successfully applied to a clinical pharmacokinetics study in female volunteers after a single intramuscular injection or oral administration of a 0.2mg dose of ME maleate. It is suitable for both preclinical and clinical studies on ME.