Cold Pressor Test Influences the Cardio-Ankle Vascular Index in Healthy Overweight Young Adults

Objective

The cold pressor test (CPT) has been shown a potential sympathoexcitatory stimulus which increases aortic pulse wave velocity and the aortic augmentation index, suggesting that noninvasively, arterial stiffness parameters are altered by the CPT. The cardio-ankle vascular index (CAVI) is widely used for reflecting arterial stiffness, and the ankle-brachial index (ABI) for evaluating peripheral artery disease in obesity. We aimed to assess CAVI and ABI in overweight young adults in the context of sympathetic activation by using the CPT.

Methods

160 participants were divided into 2 groups: 86 normal-weight (body mass index [BMI] 18.50-22.99 kg/m²) and 74 overweight (BMI ≥23 kg/m²). The CPT was performed by immersing a participant's left hand into cold water (3-5°C) for 3 min, and CAVI and ABI assessment.

Results

At baseline, the CAVI in the overweight group was significantly less than that in the normal-weight group (5.79 ± 0.85 vs. 6.10 ± 0.85; p < 0.05). The mean arterial pressure (MAP) for overweight was significantly greater than that for normal-weight subjects (93.89 ± 7.31 vs. 91.10 ± 6.72; p < 0.05). During the CPT, the CAVI increased in both normal-weight and overweight subjects, the CAVI value was greater during the CPT in overweight subjects by 14.36% (6.62 ± 0.95 vs. 5.79 ± 0.85, p < 0.05) and in normal-weight subjects by 8.03% (6.59 ± 1.20 vs. 6.10 ± 0.85, p < 0.05) than those baseline values. The CPT evoked an increase in systolic blood pressure (SBP), diastolic BP (DBP), heart rate (HR,) and pulse pressure (PP) in both groups. After a 4-min CPT period, the CAVI returned values similar to the baseline values in both groups, and the SBP, DBP, MAP, and PP in overweight participants were significantly higher than those in normal-weight participants. However, there was no significant difference in the ABI at baseline, during CPT, and post-CPT in either group.

Conclusions

Our results indicated that the CAVI was influenced by sympathetic activation response to the CPT in both normal-weight and overweight young adults. Specifically, during the CPT, the percentage change of the CAVI in overweight response was greater in normal-weight participants than baseline values in each group. The ABI was not found significantly associated with CPT. These findings suggesting that sympathoexcitatory stimulus by CPT influence CAVI results.

Activity of Plasmodium vivax promoter elements in Plasmodium knowlesi, and a centromere-containing plasmid that expresses NanoLuc throughout the parasite life cycle

Background

Plasmodium knowlesi is now the major cause of human malaria in Malaysia, complicating malaria control efforts that must attend to the elimination of multiple Plasmodium species. Recent advances in the cultivation of P. knowlesi erythrocytic-stage parasites in vitro, transformation with exogenous DNA, and infection of mosquitoes with gametocytes from culture have opened up studies of this pathogen without the need for resource-intensive and costly non-human primate (NHP) models. For further understanding and development of methods for parasite transformation in malaria research, this study examined the activity of various trans-species transcriptional control sequences and the influence of Plasmodium vivax centromeric (pvcen) repeats in plasmid-transfected P. knowlesi parasites.

Methods

In vitro cultivated P. knowlesi parasites were transfected with plasmid constructs that incorporated Plasmodium vivax or Plasmodium falciparum 5′ UTRs driving the expression of bioluminescence markers (firefly luciferase or Nanoluc). Promoter activities were assessed by bioluminescence, and parasites transformed with human resistant allele dihydrofolate reductase-expressing plasmids were selected using antifolates. The stability of transformants carrying pvcen-stabilized episomes was assessed by bioluminescence over a complete parasite life cycle through a rhesus macaque monkey, mosquitoes, and a second rhesus monkey.

Results

Luciferase expression assessments show that certain P. vivax promoter regions, not functional in the more evolutionarily-distant P. falciparum, can drive transgene expression in P. knowlesi. Further, pvcen repeats may improve the stability of episomal plasmids in P. knowlesi and support detection of NanoLuc-expressing elements over the full parasite life cycle from rhesus macaque monkeys to Anopheles dirus mosquitoes and back again to monkeys. In assays of drug responses to chloroquine, G418 and WR9910, anti-malarial half-inhibitory concentration (IC₅₀) values of blood stages measured by NanoLuc activity proved comparable to IC₅₀ values measured by the standard SYBR Green method.

Conclusion

All three P. vivax promoters tested in this study functioned in P. knowlesi, whereas two of the three were inactive in P. falciparum. NanoLuc-expressing, centromere-stabilized plasmids may support high-throughput screenings of P. knowlesi for new anti-malarial agents, including compounds that can block the development of mosquito- and/or liver-stage parasites.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03773-4.

Validation of Plasmodium vivax centromere and promoter activities using Plasmodium yoelii

Plasmodium vivax is the leading cause of malaria outside Africa and represents a significant health and economic burden on affected countries. A major obstacle for P. vivax eradication is the dormant hypnozoite liver stage that causes relapse infections and the limited antimalarial drugs that clear this stage. Advances in studying the hypnozoite and other unique biological aspects of this parasite are hampered by the lack of a continuous in vitro laboratory culture system and poor availability of molecular tools for genetic manipulation. In this study, we aim to develop molecular tools that can be used for genetic manipulation of P. vivax. A putative P. vivax centromere sequence (PvCEN) was cloned and episomal centromere based plasmids expressing a GFP marker were constructed. Centromere activity was evaluated using a rodent malaria parasite Plasmodium yoelii. A plasmid carrying PvCEN was stably maintained in asexual-stage parasites in the absence of drug pressure, and approximately 45% of the parasites retained the plasmid four weeks later. The same retention rate was observed in parasites possessing a native P. yoelii centromere (PyCEN)-based control plasmid. The segregation efficiency of the plasmid per nuclear division was > 99% in PvCEN parasites, compared to ~90% in a control parasite harboring a plasmid without a centromere. In addition, we observed a clear GFP signal in both oocysts and salivary gland sporozoites isolated from mosquitoes. In blood-stage parasites after liver stage development, GFP positivity in PvCEN parasites was comparable to control PyCEN parasites. Thus, PvCEN plasmids were maintained throughout the parasite life cycle. We also validated several P. vivax promoter activities and showed that hsp70 promoter (~1 kb) was active throughout the parasite life cycle. This is the first data for the functional characterization of a P. vivax centromere that can be used in future P. vivax biological research.

BDNF Val66Met polymorphism and serum concentrations of BDNF with smoking in Thai males

Many studies have suggested that brain-derived neurotrophic factor (BDNF) is involved in the reward system of addiction, and that nicotine may induce alterations in BDNF gene expression and its protein level within the mesocorticolimbic system. We investigated the BDNF levels and biochemical-hematological parameters of smoker and non-smoker groups, and examined the association of the Val66Met BDNF gene polymorphism with BDNF serum levels and cigarette smoking. The study sample comprised 311 Thai volunteers (200 smokers; 111 non-smokers). The levels of serum BDNF and biochemical-hematological parameters were determined. The Val66Met BDNF polymorphism was genotyped by the polymerase chain reaction-restriction fragment length polymorphism technique. The smoker group had significantly higher serum BDNF levels than the non-smoker group (8.3 vs 6.5 ng/mL, P < 0.05). BDNF concentrations correlated positively with hemoglobin, hematocrit, red blood cell count, white blood cell count, platelet count, number of cigarettes smoked, and thiocyanate level (P < 0.05). No association was found between the BDNF Val66Met genotype and the serum BDNF level. The BDNF Val66Met polymorphism was not significantly associated with the smoking status of the Thai males in this study. Cigarette smoking may be one factor that determines the serum BDNF level, but the BDNF Val66Met polymorphism probably does not influence susceptibility to smoking among Thai males.

Association between retinol-binding protein and renal function among Asian subjects with type 2 diabetes mellitus: a cross-sectional study

Retinol-binding protein 4 (RBP4) has been suggested as new adipokine, possibly linking obesity to type 2 diabetes mellitus (T2DM). Since the kidneys are the main site of RBP4 degradation and since renal failure is a frequent co-morbid condition with diabetes mellitus, we evaluated the association among RBP4, renal function and T2DM in an Asian population. RBP4 serum levels were analyzed in 110 subjects (50 with T2DM) using an enzyme-linked immunosorbent assay (ELISA). Based on a cut-off estimated glomerular filtration rate (eGFR) of 60 ml/min per 1.73 m2 (calculated according the abbreviated MDRD formula which uses serum creatinine level, age and gender) and on the T2DM status, subjects were assigned to four subgroups: Group A- controls with an eGFR > 60 ml/min per 1.73 m2, Group B - controls with an eGFR < 60 ml/min per 1.73 m2, Group C- T2DM subjects with an eGFR > 60 ml/min per 1.73 m2, and Group D - T2DM subjects with an eGFR < 60 ml/ min per 1.73 m2. In both the T2DM and control groups, RBP4 levels were higher in subjects with an eGFR < 60 ml/min per 1.73 m2 than in subjects with an eGFR > 60 ml/min per 1.73 m2. However, the difference was only significant between the control groups (p < 0.05). After adjusting for age, gender, BMI, eGFR and the presence of T2DM, eGFR, not T2DM, was associated with plasma RBP4 levels (p < 0.05). These results suggest among Asians the eGFR, but not the presence of T2DM, is a major determinant of RBP4 serum levels. The eGFR should be taken into account when evaluating the role of RBP4 in the pathogenesis of insulin resistance and T2DM.

Methylenetetrahydrofolate reductase (MTHFR) polymorphism (C677T) in relation to homocysteine concentration in overweight and obese Thais

We analyzed the association between MTHFR (C677T) gene polymorphism with serum concentrations of homocysteine, folate, and vitamin B12 in 37 male and 112 female overweight/ obese Thai volunteers (BMI > or = 25.00 kg/m2), and compared them with 23 male and 90 female control subjects (BMI = 18.5-24.99 kg/m2). Statistically significant higher levels of serum homocysteine were found in the overweight/obese subjects than the control subjects (p < 0.05). Serum folic acid levels in the overweight/obese subjects were significantly lower than the control subjects (p < 0.05). When the data were grouped according to homocysteine concentration and MTHFR gene polymorphism, there were significantly higher homocysteine concentrations in the overweight/obese subjects than the control subjects in wild type gene polymorphism (CC) in the hyperhomocysteine group (homocysteine >10.0 mmol/l) (p < 0.05), but in genotype polymorphism (CC, CT, TT) there were lower folic acid and vitamin B12 concentrations in the overweight/obese subjects than in the control subjects. In the hyperhomocysteine groups, there was no significant difference in the frequencies of MTHFR (C677T) gene polymorphism between the overweight/obese subjects and the control subjects. Folic acid and gene polymorphism were found to be significantly related to the overweight/ obese and control groups in logistic regression analysis (p < 0.05). The results support the supposition that folic acid is more important than vitamin B12.