Lipid peroxidation of kidney of the turtle Mauremys reevesii caused by cadmium

Metabolic regulation reduces the oxidative damage of arid lizards in response to moderate heat events

Climate warming poses a significant threat to species worldwide, particularly those inhabiting arid and semi-arid regions where extreme temperatures are increasingly prevalent. However, empirical studies investigating how moderate heat events affect the physiological processes of arid and semi-arid animals are largely scarce. To address this knowledge gap, we used an arid and semi-arid lizard species (Phrynocephalus przewalskii) as a study system. We manipulated thermal environments to simulate moderate heat events (43.5 ± 0.3°C during the heating period) for lizards and examined physiological and biochemical traits related to survival, metabolism, locomotion, oxidative stress, and telomere length. We found that the body condition and survival of the lizards were not significantly affected by moderate heat events, despite an increase in body temperature and a decrease in locomotion at high test temperatures were detected. Mechanistically, we found that the lizards exhibited down-regulated metabolic rates and enhanced activities of antioxidative enzymes, resulting in reduced oxidative damage and stable telomere length under moderate heat events. Based on these findings, which indicated a beneficial regulation of fitness by physiological and biochemical processes, we inferred that moderate heat events did not have a detrimental effect on the toad-headed agama, P. przewalskii. Overall, our research contributes to understanding the impacts of moderate heat events on arid and semi-arid species and highlights the adaptive responses and resilience exhibited by the toad-headed agama in the face of climate warming.

Effect of cadmium on histopathological injuries and ultra-structural changes of kidney of the turtle Mauremys reevesii

This research investigated the effect of cadmium on the tissue and cell of kidney of the turtle Mauremys reevesii. Twenty turtles were injected with cadmium at 0, 7.5, 15, 30 mg/kg separately and five turtles were taken in each group at two weeks after exposure. Kidneys were immediately excised and macroscopic pathological changes were observed, then the kidneys were fixed in 4% paraformaldehyde for histopathological examination and fixed in 2.5% (v/v) glutaraldehyde for examination of ultra-structure. The tissues of kidney presented varying degrees of histopathological lesions in cadmium treated turtles by a dose-dependent manner under the light microscope. Under transmission electron microscope, renal tubules cells presented varying degrees of dose-dependent lesions. The results indicated that cadmium can cause cell damages to the kidney, in particular to the mitochondria. Mitochondria can be used as one biomarker in the monitoring of cadmium pollution and its quantitative risk assessments.

Climate warming has divergent physiological impacts on sympatric lizards

Climate warming is expected to affect the vulnerability of sympatric species differentially due to their divergent traits, but the underlying physiological mechanisms of those impacts are poorly understood. We conducted field warming experiments (present climate vs. warm climate) using open-top chambers to determine the effects of climate warming on active body temperature, oxidative damage, immune competence, growth and survival in two sympatric desert-dwelling lizards, Eremias multiocellata and Eremias argus from May 2019 to September 2020. Our climate warming treatment did not affect survival of the two species, but it did increase active body temperatures and growth rate in E. multiocellata compared to E. argus. Climate warming also induced greater oxidative damage (higher malondialdehyde content and catalase activity) in E. multiocellata, but not in E. argus. Further, climate warming increased immune competence in E. multiocellata, but decreased immune competence in E. argus, with regards to white blood cell counts, bacteria killing ability and relative expression of immunoglobulin M. Our results suggest that climate warming enhances body temperature, and thereby oxidative stress, immune competence and growth in E. multiocellata, but decreases immune competence of E. argus, perhaps as a cost of thermoregulation to maintain body temperatures under climate warming. The divergent physiological effects of climate warming on sympatric species may have profound ecological consequences if it eventually leads to changes in reproductive activities, population dynamics and community structure. Our study highlights the importance of considering interspecific differences in physiological traits when we evaluate the impact of climate warming on organisms, even for those closely-related species coexisting within the same geographical area.

Dietary intake of household cadmium-contaminated rice caused genome-wide DNA methylation changes on gene/hubs related to metabolic disorders and cancers

Cadmium (Cd) contamination in food has raised broad concerns in food safety and human health. The toxicity of Cd to animals/humans have been widely reported, yet little is known about the health risk of dietary Cd intake at the epigenetic level. Here, we investigated the effect of a household Cd-contaminated rice (Cd-rice) on genome-wide DNA methylation (DNAm) changes in the model mouse. Feeding Cd-rice increased kidney Cd and urinary Cd concentrations compared with the Control rice (low-Cd rice), whereas supplementation of ethylenediamine tetraacetic acid iron sodium salt (NaFeEDTA) in the diet significantly increased urinary Cd and consequently decreased kidney Cd concentrations. Genome-wide DNAm sequencing revealed that dietary Cd-rice exposure caused the differentially methylated sites (DMSs), which were mainly located in the promoter (32.5%), downstream (32.5%), and intron (26.1%) regions of genes. Notably, Cd-rice exposure induced hypermethylation at the promoter sites of genes Caspase-8 and interleukin-1β (Il-1β), and consequently, their expressions were down-regulated. The two genes are critical in apoptosis and inflammation, respectively. In contrast, Cd-rice induced hypomethylation of the gene midline 1 (Mid1), which is vital to neurodevelopment. Furthermore, 'pathways in cancer' was significantly enriched as the leading canonical pathway. Supplementation of NaFeEDTA partly alleviated the toxic symptoms and DNAm alternations induced by Cd-rice exposure. These results highlight the broad effects of elevated dietary Cd intake on the level of DNAm, providing epigenetic evidence on the specific endpoints of health risks induced by Cd-rice exposure.

Effects of Cadmium on Kidney Function of the Freshwater Turtles Mauremys reevesii

This research studied the effects of cadmium on kidney function of the freshwater turtles Mauremys reevesii. Turtles were injected intraperitoneally with 0, 7.5, 15, and 30 mg kg^-1 cadmium separately for once. The samples were gathered to check the kidney index, the contents of TP in kidney tissue, and the levels of CRE and BUN in the plasma of the turtles. Results showed that the concentration of TP was overall decreased with the extension of cadmium exposure time and the increasing of the exposure dose of cadmium. The CRE content in the plasma of each treatment group increased with the prolongation of exposure time in a dose-dependent, and the BUN levels of all poisoned groups showed a trend of increasing. The kidney index of treated turtles increased. In summary, cadmium could induce the increase of turtle kidney index, the content of CRE and BUN in plasma, and the decrease of TP content in the kidney.

Association of blood cadmium and metabolic syndrome: a cross-sectional analysis of National Health and Nutrition Examination Survey 2017-2020

Previous findings have reported the role of different types of heavy metals in cardiometabolic diseases. In the present research, we aim to evaluate the association between blood cadmium levels and Metabolic Syndrome (MetS) based on the large-sample NHANES data. Public availably data from NHANES 2017-2020 cycle was obtained. Participants were divided into MetS and non-MetS groups according to waist circumference (WC), triglyceride (TG), high-density lipoprotein (HDL), blood pressure (BP) and fasting plasma glucose (FPG) levels based on the National Cholesterol Education Program (NCEP) criteria. Student's t test, Mann-Whitney U test, and Chi-square test were performed for univariate analysis. Multivariate logistic analysis was performed to explore the relationship between blood cadmium and MetS and research findings were presented in forest plot. We also investigated the association of blood cadmium and MetS in subgroups stratified by age, gender and race. Population with MetS had significantly higher levels of blood [0.30 (0.18-0.54) vs. 0.24 (0.15-0.46) ug/L, p < 0.001] and urinary cadmium levels [0.29 (0.17-0.52) vs. 0.20 (0.09-0.42) ug/L, p < 0.001] compared with those without MetS. Higher blood cadmium concentrations were also observed in participants with elevated WC (0.28 vs. 023 ug/L, p < 0.001], TG (0.28 vs. 0.26 ug/L, p = 0.029), BP (0.33 vs. 0.23 ug/L, p < 0.001) and FPG (0.29 vs. 0.24 ug/L, p < 0.001) compared with those with normal metabolic parameters. Multivariate logistic regression showed that one-unit increasement of blood cadmium was associated with 1.25 times higher prevalence ratios for MetS after adjusting potential confounders (95% CI: 1.06-1.48, p = 0.0083). The associations between serum cadmium concentrations and MetS components were then evaluated, and the results showed higher blood cadmium levels were associated with higher risk for elevated TG, low HDL and elevated BP when treated as continuous variable. When treated as categorical variable, only BP was found positively associated with blood cadmium. Stratified multiple logistic regression analysis indicated that the positive association between blood cadmium and MetS remained significant in subjects less than 60 years old and female subgroup. In conclusion, the cross-sectional survey suggested the positive association between blood cadmium levels and risk for MetS, prospective research need to be conducted for further evaluation of the causal relationship between blood cadmium and MetS.

Heat wave induces oxidative damage in the Chinese pond turtle (Mauremys reevesii) from low latitudes

Introduction

Global warming has led to frequent heat waves, causing global organisms to face severe survival challenges. However, the way in which heat waves threaten the fitness and survival of animals remains largely unclear. Oxidative damage and immunity are widely considered the link between heat waves and threats to animals.

Methods

To evaluate the oxidative damage caused by heat waves and to reveal the physiological resistance to heat waves by the antioxidant defense of animals from different latitudes, we exposed both high-latitude (Zhejiang) and low-latitude (Hainan) populations of Chinese pond turtle (Mauremys reevesii) to simulate heat waves and a moderate thermal environment for 1 week, respectively. Next, we compared the oxidative damage by malondialdehyde (MDA) and antioxidant capacity by superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and total antioxidant capacity (T-AOC) in the liver tissues and evaluated the innate immunity by serum complement protein levels (C3, C4) and lysozyme activity in plasma of turtles.

Results and discussion

We found that heat waves significantly increased the content of MDA and the activity of CAT, whereas it decreased the activity of SOD, T-AOC, and GSH/GSSG in turtles from low latitudes. Furthermore, heat waves increased CAT activity but decreased GSH/GSSG in turtles from high latitudes. Although the turtles from high latitudes had higher levels of innate immunity, the heat waves did not affect the innate immunity of C3, C4, or lysozyme in either population. These results indicate that the low-latitude population suffered higher oxidative damage with lower antioxidant capacities. Therefore, we predict that Chinese pond turtles from low latitudes may be more vulnerable to heat waves caused by climate warming. This study reveals the physiological and biochemical resistance to heat waves in Chinese pond turtles from different latitudes and highlights the importance of integrative determination of fitness-related responses in evaluating the vulnerability of ectotherms from different latitudes to climate warming.