Association Between Preoperative Sleep Disturbance and Postoperative Delirium in Elderly: A Retrospective Cohort Study

Purpose

Postoperative sleep disturbance, characterized by diminished postoperative sleep quality, is a risk factor for postoperative delirium (POD); however, the association between pre-existing sleep disturbance and POD remains unclear. This study aimed to evaluate the association between preoperative sleep disturbance and POD in elderly patients after non-cardiac surgery.

Patients and methods

This retrospective cohort study was conducted at a single center and enrolled 489 elderly patients who underwent surgery between May 1, 2020, and March 31, 2021. Patients were divided into the sleep disorder (SD) and non-sleep disorder (NSD) groups according to the occurrence of one or more symptoms of insomnia within one month or sleep- Numerical Rating Scale (NRS)≥6 before surgery. The primary outcome was the incidence of POD. Propensity score matching analysis was performed between the two groups. Multiple logistic regression analysis was performed to identify the risk factors for POD.

Results

In both the unmatched cohort (16.0% vs 6.7%, P=0.003) and the matched cohort (17.0% vs 6.2%, P=0.023), the incidence of POD was higher in the SD group than in the NSD group. In addition, the postoperative sleep quality and the VAS score at postoperative 24 h were significantly lower in the SD group than in the NSD group. Multivariate logistic regression analysis indicated that age (Odds Ratio, 1.13 [95% CI: 1.04-1.23], P=0.003) and preoperative sleep disturbance (Odds Ratio, 3.03 [95% CI: 1.09-9.52], P=0.034) were independent risk factors for the development of POD.

Conclusion

The incidence of POD was higher in patients with pre-existing sleep disturbance than those without it. Whether improving sleep quality for preoperative sleep disturbance may help prevent POD remains to be determined.

Enzymatic Characterization and Coenzyme Specificity Conversion of a Novel Dimeric Malate Dehydrogenase from Bacillus subtilis

Malate is an important material to various industrials and clinical applications. Bacillus subtilis is a widely used biocatalyst tool for chemical production. However, the specific enzymatic properties of malate dehydrogenase from Bacillus subtilis (BsMDH) remain largely unknown. In the present study, BsMDH was cloned, recombinantly expressed and purified to test its enzymatic properties. The molecular weight of single unit of BsMDH was 34,869.7 Da. Matrix-Assisted Laser-Desorption Ionization-Time-of-Flight Mass Spectrometry and gel filtration analysis indicated that the recombinant BsMDH could form dimers. The k_cat/K_m values of oxaloacetate and NADH were higher than those of malate and NAD⁺, respectively, indicating a better catalysis in the direction of malate synthesis than the reverse. Furthermore, six BsMDH mutants were constructed with the substitution of amino acids at the coenzyme binding site. Among them, BsMDH-T7 showed a greatly higher affinity and catalysis efficiency to NADPH than NADH with the degree of alteration of 2039, suggesting the shift of the coenzyme dependence from NADH to NADPH. In addition, BsMDH-T7 showed a relatively lower K_m value, but a higher k_cat and k_cat/K_m than NADPH-dependent MDHs from Thermus flavus and Corynebacterium glutamicum. Overall, these results indicated that BsMDH and BsMDH-T7 mutant might be promising enzymes for malate production.

Heteroexpression and biochemical characterization of thermostable citrate synthase from the cyanobacteria Anabaena sp. PCC7120

The present study recombinantly expressed a citrate synthase from cyanobacteria Anabaena sp. PCC7120 (AnCS) in Escherichia coli and characterized its enzymatic activity. The molecular mass of native AnCS was 88,533.1 Da containing two 44,162.7 Da subunits. Recombinant AnCS revealed the highest activity at pH 9.0 and 25 °C. AnCS displayed high thermal stability with a half-life time (t_1/2) of approximately 6.5 h at 60 °C, which was more thermostable than most CS from general organisms, but less than those from hyperthermophilic bacteria. The K_m values of oxaloacetate and acetyl-CoA were 138.50 and 18.15 μM respectively, suggesting a higher affinity to acetyl-CoA than oxaloacetate. Our inhibition assays showed that AnCS activity was not severely affected by most metal ions, but was strongly inhibited by Cu²⁺ and Zn²⁺. Treatments with ATP, ADP, AMP, NADH, and DTT depressed the AnCS activity. Overall, our results provide information on the enzymatic properties of AnCS, which contributes to the basic knowledge on CS selection for industrial utilizations.

Expression and characterization of a thermostable citrate synthase from Microcystis aeruginosa PCC7806

Citrate synthase (CS) is an important enzyme in energy conversion and material circulation, participating in many important biochemical processes. In the present study, CS from Microcystis aeruginosa PCC7806 (MaCS) was cloned and expressed in Escherichia coli Rosetta (DE3). The recombinant MaCS was purified and its enzymological properties were characterized. The results showed that MaCS formed dimers in native status. The optimum temperature and pH of MaCS was 30°C and 8.2, respectively. MaCS displayed relative high thermal stability. Treatment at 50°C for 20 min only decreased 11.30% activity of MaCS and the half-life of MaCS was approximately 35 min at 55°C. The kcat and Km of acetyl-CoA and oxaloacetic acid were 17.133 s-1 (kcat) and 11.62 μM (Km), 24.502 s-1 and 103.00 μM, respectively. MaCS activity was not drastically inhibited by monovalent ions and NADH but depressed by divalent ions and some small molecular compounds, especially Mg2+, Zn2+, Co2+ and DTT. Overall, these data contributed to further understanding of energy metabolism in cyanobacteria and also provided basic information for industrial application of CS.

[Analysis on the risk factors of diabetic foot ulcer in diabetic patients of Uyghur nationality and Han nationality in the Xinjiang Uygur Autonomous Region]

Objective: To explore the risk factors of diabetic foot ulcer (DFU) in diabetic patients of Uyghur nationality and Han nationality in the Xinjiang Uygur Autonomous Region. Methods: Clinical data of 640 diabetic patients admitted to our ward from January 2015 to November 2016, conforming to the study criteria, were retrospectively analyzed. Patients were divided into DFU group (n=403) and non-DFU group (n=237) according to whether DFU occurred or not. The data of gender, age, nationality, body mass index (BMI), smoking, drinking, binge eating, triglyceride (TG), total cholesterol (TC), and high-density lipoprotein (HDL) of patients between two groups were compared with chi-square test and t test. Indexes with statistically significant differences between two groups were selected, and they were processed with non-conditional multivariate logistic regression analysis to screen the independent risk factors of DFU. The possible risk factors of DFU of patients of Uyghur nationality and Han nationality were further processed with non-conditional multivariate logistic regression analysis respectively to screen the independent risk factors of DFU of patients of Uyghur nationality and Han nationality. Results: (1) There were no statistically significant differences in gender, age, TC, and HDL of patients between two groups (with χ(2)=0.149, t values respectively 1.163, 1.033, and 1.026, P values above 0.05). There were statistically significant differences in nationality, BMI, smoking, drinking, binge eating, and TG of patients between two groups (with χ(2) values from 4.778 to 13.694, t values respectively 4.703 and 4.237, P<0.05 or P<0.01). (2) Nationality, BMI, smoking, drinking, binge eating, and TG were the independent risk factors of DFU(with odds ratios respectively 1.488, 1.527, 1.736, 1.738, 1.382, and 1.648, 95% confidence intervals respectively 1.315-3.175, 1.488-4.393, 1.834-4.675, 1.474-2.695, 1.342-4.678, and 1.105-6.747, P values below 0.05). (3) Smoking, drinking, binge eating, and TG were the independent risk factors of DFU in diabetic patients of Uyghur nationality (with odds ratios respectively 1.673, 1.387, 1.328, and 1.486, 95% confidence intervals respectively 1.384-1.765, 1.414-1.659, 1.423-1.687, and 1.150-1.670, P values below 0.05). BMI, smoking, and drinking were the independent risk factors of DFU in diabetic patients of Han nationality (with odds ratios respectively 2.442, 1.604, and 1.251, 95% confidence intervals respectively 2.223-2.699, 1.268-2.028, and 1.164-1.344, P<0.05 or P<0.01). Conclusions: Smoking, drinking, binge eating, and TG were the independent risk factors of DFU in diabetic patients of Uyghur nationality. BMI, smoking, and drinking were the independent risk factors of DFU in diabetic patients of Han nationality.