Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction

Obesity and diabetes are established comorbidities for COVID-19. Adipose tissue demonstrates high expression of ACE2 which SARS- CoV-2 exploits to enter host cells. This makes adipose tissue a reservoir for SARS-CoV-2 viruses and thus increases the integral viral load. Acute viral infection results in ACE2 downregulation. This relative deficiency can lead to disturbances in other systems controlled by ACE2, including the renin-angiotensin system. This will be further increased in the case of pre-conditions with already compromised functioning of these systems, such as in patients with obesity and diabetes. Here, we propose that interactions of virally-induced ACE2 deficiency with obesity and/or diabetes leads to a synergistic further impairment of endothelial and gut barrier function. The appearance of bacteria and/or their products in the lungs of obese and diabetic patients promotes interactions between viral and bacterial pathogens, resulting in a more severe lung injury in COVID-19.

Obesity and diabetes as comorbidities for COVID-19: Underlying mechanisms and the role of viral-bacterial interactions.

Background— Circulating levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) are elevated in diabetic patients. We assessed the role of glucose in the regulation of circulating levels of IL-6, TNF-α, and interleukin-18 (IL-18) in subjects with normal or impaired glucose tolerance (IGT), as well as the effect of the antioxidant glutathione. Methods and Results— Plasma glucose levels were acutely raised in 20 control and 15 IGT subjects and maintained at 15 mmol/L for 5 hours while endogenous insulin secretion was blocked with octreotide. In control subjects, plasma IL-6, TNF-α, and IL-18 levels rose (P<0.01) within 2 hours of the clamp and returned to basal values at 3 hours. In another study, the same subjects received 3 consecutive pulses of intravenous glucose (0.33 g/kg) separated by a 2-hour interval. Plasma cytokine levels obtained at 3, 4, and 5 hours were higher (P<0.05) than the corresponding values obtained during the clamp. The IGT subjects had fasting plasma IL-6 and TNF-α levels ...

Inflammatory Cytokine Concentrations Are Acutely Increased by Hyperglycemia in Humans

Artificial light at night (ALAN), termed light pollution, is an increasingly important anthropogenic environmental pressure on wildlife. Exposure to unnatural lighting environments may have profound effects on animal physiology, particularly during early life. Here, we experimentally investigated for the first time the impact of ALAN on body mass and oxidative status during development, using nestlings of a free-living songbird, the great tit (Parus major), an important model species. Body mass and blood oxidative status were determined at baseline (=13 days after hatching) and again after a two night exposure to ALAN. Because it is very difficult to generalise the oxidative status from one or two measures we relied on a multi-biomarker approach. We determined multiple metrics of both antioxidant defences and oxidative damage: molecular antioxidants GSH, GSSG; antioxidant enzymes GPX, SOD, CAT; total non-enzymatic antioxidant capacity and damage markers protein carbonyls and TBARS. Light exposed nestlings showed no increase in body mass, in contrast to unexposed individuals. None of the metrics of oxidative status were affected. Nonetheless, our study provides experimental field evidence that ALAN may negatively affect free-living nestlings’ development and hence may have adverse consequences lasting throughout adulthood.

Artificial light at night affects body mass but not oxidative status in free-living nestling songbirds: an experimental study.

Reproduction is a demanding activity for animals, since they must produce, and in some cases protect and provision, their young. It is often overlooked that demands of reproduction may also be exacerbated by exposure to contaminants. In this study, we make use of an exceptional long-term dataset to perform a cross-sectional study on the long-lived wandering albatross (Diomedea exulans) in order to test the effects of reproduction, persistent organic pollutants [POPs: pesticides and polychlorinated biphenyls (PCBs)], mercury, individual age (3–47 years), and sex on the levels of plasma oxidative damage and inflammation. The results of our study support the hypothesis that oxidative damage may be a physiological cost of reproduction and that individuals carrying higher levels of organic or non-organic contaminants have higher oxidative damage. Levels of the inflammatory protein haptoglobin were similar between breeding and nonbreeding birds, with the exception of breeding males which had the lowest levels of haptoglobin. Our data also show an effect of age and of organic contaminants on the plasma oxidative damage level, but not on plasma haptoglobin. In addition, plasma oxidative damage level increased with red blood cell mercury concentration in females but not in males. Hence, our study highlights that the harmful effects of contaminants may come through interaction with factors like life stage or gender, suggesting potential for high variation in susceptibility to contamination among individuals.

/pdf/oxidative-stress-in-relation-to-reproduction-contaminants-53qmw1grgo.pdf

Oxidative stress in relation to reproduction, contaminants, gender and age in a long-lived seabird

Previously we reported that elevated circulating concentrations of the acute-phase (AP) protein ?2-macroglobulin (?2M), either as typically occurring in pregnant female rats or after administration to male rats, provides radioprotection, displayed as 100% survival of experimental animals exposed to total-body irradiation with 6.7?Gy (LD50/30) x-rays, that is as effective as that afforded by the synthetic radioprotector amifostine. The finding that amifostine administration induces a 45-fold increase in ?2M in the circulation led us to hypothesise that ?2M assumes an essential role in both natural and amifostine-mediated radioprotection in the rat. In the present work we examined the activation of cytoprotective mechanisms in rat hepatocytes after the exogenous administration of ?2M and amifostine. Our results showed that the IL6/JAK/STAT3 hepatoprotective signal pathway, described in a variety of liver-injury models, upregulated the ?2M gene in amifostine-pretreated animals. In both ?2M-?and amifostine-pretreated rats we observed the activation of the Akt signalling pathways that mediate cellular survival. At the cellular level this was reflected as a significant reduction of irradiation-induced DNA damage that allowed for the rapid and complete restoration of liver mass and ultimately at the level of the whole organism the complete restoration of body weight. We conclude that the selective upregulation of ?2M plays a central role in amifostine-provided radioprotection.

https://iopscience.iop.org/article/10.1088/0952-4746/30/3/011/pdf

The rat acute-phase protein α2-macroglobulin plays a central role in amifostine-mediated radioprotection

The acute inflammatory response of the liver associated with chronic food restriction was examined in adult female and male Wistar rats. The changes in the levels of serum markers of liver injury, AST and ALT and the appearance of a serum marker of inflammation, the acute phase protein (APP) haptoglobin (Hp) were assessed following turpentine treatment of well-nourished (WN) controls and undernourished (UN) rats. Undernutrition was induced by food restriction during a six week period by offering chow equivalent to 50% of the normal food intake. In the female rats undernutrition significantly potentiated liver injury and increased their sensitivity to the toxic effects of turpentine, which was opposite to the results obtained for males. Differences in the basal levels of AST, ALT and Hp between females and males imply that the effects of chronic food restriction on protein synthesis in the liver are gender related.

/pdf/the-effect-of-chronic-food-restriction-on-liver-acute-phase-2h3futhhbu.pdf

The effect of chronic food restriction on liver acute phase protein response in female and male Wistar rats

Haptoglobin is a hemoglobin-binding acute-phase protein which possesses anti-inflammatory and antioxidative properties. In this study, we investigated changes in protein expression of rat haptoglobin under diabetes-related inflammatory and oxidative stress conditions induced by an i.p. injection of streptozotocin. The progress of diabetes during an 8-week follow-up period was associated with the increased presence of haptoglobin in the serum and in the liver. This increase was most prominent during the first 2 weeks after which it started to decline. Temporary changes in haptoglobin expression strongly correlated with the serum levels of TNF-α and IL-6. Lower haptoglobin expression at the fourth week and thereafter correlated with a decrease in TNF-α concentration and changes in the TNF-α/IL-6 ratio. Based on the decrease of GSH/GSSG ratio and antioxidant enzyme activities in the liver until the end of fourth week, it was concluded that the liver was exposed to oxidative stress and injury which in the presence of the abovementioned inflammatory mediators lead to different haptoglobin expression profiles at different stages of diabetes. An inverse correlation was observed between the haptoglobin and free iron serum levels in diabetic rats. The higher levels of haptoglobin during the first 2 weeks were accompanied by a lower level of free iron. In view of the established function of haptoglobin, we discuss its possible role in decreasing oxidative stress during the early stage of diabetes.

Haptoglobin and the inflammatory and oxidative status in experimental diabetic rats: antioxidant role of haptoglobin

The importance of alpha2-macroglobulin (alpha2M) in natural radioprotection was studied by examining its radioprotective effectiveness in rat models of exogenously and endogenously, preexposure-increased alpha2M. Radioprotective efficacy was ascertained by the postirradiation survival rate, the restoration of body weight, and the leukocyte count, which were monitored during a 4-week follow-up period. The results were compared with the effects of a pretreatment with the synthetic radioprotective agent amifostine (Ami), which provides 100% protection in rats whole-body-irradiated by x-rays given in a dose of 6.7 Gy (LD50/30). Raising the plasma concentration of alpha2M 15-fold in male rats by a single intraperitoneal injection of purified protein provided 100% survival of irradiated animals. Female rats on the 19th day of pregnancy with endogenously elevated levels of alpha2M displayed improved survival (80%) compared with untreated rats (50% survival). After alpha2M administration, the pregnant, irradiated rats exhibited 100% survival. In both males and pregnant females, alpha2M administration promoted body weight and leukocyte postirradiation recovery as in Ami-pretreated rats. These findings, together with our observation that Ami administration induced a 45-fold increase in alpha2M in the circulation, led us to conclude that alpha2M has an essential role in both natural and amifostine-mediated radioprotection in the rat.

THE ACUTE-PHASE PROTEIN α2-MACROGLOBULIN PLAYS AN IMPORTANT ROLE IN RADIOPROTECTION IN THE RAT

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The rat acute-phase protein α2-macroglobulin plays a central role in amifostine-mediated radioprotection

The effect of chronic food restriction on liver acute phase protein response in female and male Wistar rats

Haptoglobin and the inflammatory and oxidative status in experimental diabetic rats: antioxidant role of haptoglobin

THE ACUTE-PHASE PROTEIN α2-MACROGLOBULIN PLAYS AN IMPORTANT ROLE IN RADIOPROTECTION IN THE RAT