Circadian rhythm of white blood cell aggregation and free radical status in healthy volunteers

Circadian rhythms of risk factors and management in atherosclerotic and hypertensive vascular disease: Modern chronobiological perspectives of an ancient disease

Atherosclerosis, a chronic inflammatory disease of the arteries that appears to have been as prevalent in ancient as in modern civilizations, is predisposing to life-threatening and life-ending cardiac and vascular complications, such as myocardial and cerebral infarctions. The pathogenesis of atherosclerosis involves intima plaque buildup caused by vascular endothelial dysfunction, cholesterol deposition, smooth muscle proliferation, inflammatory cell infiltration and connective tissue accumulation. Hypertension is an independent and controllable risk factor for atherosclerotic cardiovascular disease (CVD). Conversely, atherosclerosis hardens the arterial wall and raises arterial blood pressure. Many CVD patients experience both atherosclerosis and hypertension and are prescribed medications to concurrently mitigate the two disease conditions. A substantial number of publications document that many pathophysiological changes caused by atherosclerosis and hypertension occur in a manner dependent upon circadian clocks or clock gene products. This article reviews progress in the research of circadian regulation of vascular cell function, inflammation, hemostasis and atherothrombosis. In particular, it delineates the relationship of circadian organization with signal transduction and activation of the renin-angiotensin-aldosterone system as well as disturbance of the sleep/wake circadian rhythm, as exemplified by shift work, metabolic syndromes and obstructive sleep apnea (OSA), as promoters and mechanisms of atherogenesis and risk for non-fatal and fatal CVD outcomes. This article additionally updates advances in the clinical management of key biological processes of atherosclerosis to optimally achieve suppression of atherogenesis through chronotherapeutic control of atherogenic/hypertensive pathological sequelae.

Circadian rhythm and time-of-day-effects of (anti)oxidant biomarkers for epidemiological studies

Various biomarkers of oxidative stress and redox status have been used in a number of clinical and epidemiological studies related to diseases and conditions that involve disturbances of the redox balance. However, a comprehensive study of diurnal variations of a set of biomarkers has not been conducted so far. Therefore, the aim of this study is to investigate circadian rhythm and time-of-day-effects of a set of frequently used biomarkers of oxidative stress, redox and antioxidant status in serum/plasma. These biomarkers include Reactive Oxygen Metabolites (ROM), Biological Antioxidant Potency (BAP), Total Thiols in Proteins (TTP), high-sensitive C-Reactive Protein (CRP) and Uric Acid (UA). During a 24-hr study, blood sampling was conducted 6 times at 4-hr intervals. The presence of circadian rhythm was analyzed with CircWave analysis, whereas the effect of time was analyzed with Repeated Measures ANOVA (RM-ANOVA). Thereby, the main focus was on the time points in working hours (8, 12 and 16 hr), which are used frequently in practice. Of all investigated biomarkers, only TTP in males demonstrated statistically significant circadian rhythm (p = 0.040). A statistically significant effect between all six time points with RM-ANOVA was observed for ROM, TTP and UA in both genders, and for BAP in females only. No statistically significant differences were observed between the time points 8 hr and 12 hr for any of the biomarkers that were assessed in our study. In conclusion, diurnal variations in some of the studied biomarkers that we demonstrate here should be taken into account when designing and conducting clinical and epidemiological studies. It is advised to standardize the time of sampling with a preference in the morning hours.

A dose-response study of aerobic training for oxygen uptake, oxidative stress and cardiac autonomic function in type 2 diabetes mellitus: study protocol for a randomized controlled trial

Background

Cardiac autonomic neuropathy is a commonly overlooked complication of type 2 diabetes mellitus (T2DM) characterized by an imbalance between sympathetic and parasympathetic supply to the heart, which contributes to cardiovascular morbidity and mortality. T2DM has also been shown to negatively influence oxygen kinetics and increase oxidative stress, which may be linked to the development of various chronic complications. Aerobic training has been reported to improve oxygen uptake, antioxidant defense, and cardiac autonomic function in T2DM; however, the effects of varying doses of exercise on these variables are not known. Therefore, the aim of the present study is to explore the effects of manipulating training variables (volume and intensity) on the regulation of oxygen uptake response, oxidative stress, and cardiac autonomic function in patients with T2DM.

Methods

We will recruit 60 patients with T2DM, who will be randomly allocated into one of the three aerobic training groups: low-intensity, low-volume training; low-intensity, high volume-training; high-intensity, high-volume training; or to the control group receiving no supervised exercise. All participants will be assessed for the rate of oxygen uptake, levels of antioxidant enzymes and cardiac autonomic function at baseline and after 12 weeks of training. Secondary outcome measures will include cardiometabolic risk factors and body composition.

Discussion

Despite a large body of evidence on the efficacy of aerobic training in the prevention and treatment of T2DM, there is no unequivocal exercise prescription for the same. Oxygen kinetics and oxidative stress are highly sensitive to the magnitude of physical activity. It would therefore, be interesting to study their interaction with chronic exposure to various doses of exercises and explore the optimal volume and intensity to bring about improvements in these parameters.

Trial registration

Clinical Trials Registry – India, CTRI2017/08/009459. Registered on 23 August 2017. Retrospectively registered.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2671-y) contains supplementary material, which is available to authorized users.

An active lifestyle induces positive antioxidant enzyme modulation in peripheral blood mononuclear cells of overweight/obese postmenopausal women

AIMS

The aim of this study was to investigate the effects of an active lifestyle on mitochondrial functioning, viability, bioenergetics, and redox status markers in peripheral blood mononuclear cells (PBMC) of overweight/ obese postmenopausal women.

MATERIALS AND METHODS

We performed a cross-sectional study with postmenopausal women aged 45–64 years and body mass index N 25 kg/m2, divided into physically active (n = 23) and sedentary (n = 12) groups. Mitochondria functioning and viability, bioenergetics and redox status parameters were assessed in PBMC with spectrophotometric and fluorometric assays.

KEY FINDINGS

No differences were found in the enzyme activity of complexes I and II of the electron transport chain (ETC), mitochondrial superoxide dismutase (MnSOD) activity, methyl-tetrazolium reduction levels and reduced glutathione and oxidized glutathione levels between the groups. However, the physically active group presented higher levels of reactive oxygen species (ROS) (P= 0.04) and increased catalase (CAT) (P= 0.029), total (P= 0.011) and cytosolic SOD (CuZnSOD) (P= 0.009) activities.

SIGNIFICANCE

An active lifestyle that includes aerobic exercise for at least 30 min, three times per week may improve antioxidant enzyme activities in PBMC in overweight/obese postmenopausal women, without changes in the activity of the ETC enzymes. However, this low intensity physical activity is not able to induce relevant mitochondrial adaptations.

Relationship between the levels of oxidative stress in mesenteric and peripheral serum and clinicopathological variables in colorectal cancer

OBJECTIVE

To explore the differences existing between the levels of oxidative stress in peripheral and mesenteric serum in patients with colorectal cancer.

MATERIAL AND METHODS

One hundred fifty patients with colorectal cancer who underwent surgery between May 2005 and March 2010 were prospectively analyzed. The differences between oxidative stress parameters in their peripheral and mesenteric blood were measured. The associations between peripheral and mesenteric levels and the staging and clinicopathological variables were investigated.

RESULTS

Oxidative stress parameters were higher in patients with advanced tumor staging (p<0.01), lymph node invasion (p<0.01), and venous invasion (p<0.01). Differences between oxidative stress parameters in peripheral and mesenteric blood samples were also observed.

CONCLUSIONS

The mesenteric levels of the oxidative stress markers were higher than the peripheral levels in these colorectal cancer patients. Higher levels of these oxidative stress markers are associated with an advanced state of cancer.

The effect of different training programs on antioxidant status, oxidative stress, and metabolic control in type 2 diabetes

We compared the effects of 12 weeks of 3 different exercise types on type 2 diabetic (T2DM) male and female human subjects, randomly divided into 4 groups: aerobic training (AT; n = 11), strength training (ST; n = 10), combined training (CBT; n = 10), and no training (NT; n = 12). Metabolic control, anthropometric parameters, lipid and hematological profiles, kidney and liver function markers, hormones, antioxidant enzymes, and oxidative stress markers were assessed prior to and after the training programs. At baseline, fasting blood glucose and hemoglobin A(1c) in the ST group were higher than in the NT group; after the training, we no longer observed differences in these groups, suggesting an improvement on these parameters. In the AT group, catalase and superoxide dismutase activity, nitrite concentration, levels of sulfhydryl groups, and peak rate of oxygen consumption were elevated after the training (p < 0.05). No changes were observed in antioxidant enzymes or oxidative stress markers in the ST group. The levels of sulfhydryl groups diminished in the NT group (p < 0.01) and increased in the CBT group (p < 0.05). These data demonstrate that the AT program for the T2DM subjects provided important upregulation in antioxidant enzymes and increased nitric oxide bioavailability, which may help minimize oxidative stress and the development of the chronic complications of diabetes. We propose that the beneficial effects observed in the metabolic parameters of the ST group occurred in response to the poor baseline metabolic health n this group, and not necessarily in response to the training itself.

Exploration of oxidative stress and inflammatory markers in relation to urinary phthalate metabolites: NHANES 1999-2006

Phthalate exposure has been associated with a wide range of adverse health outcomes in limited epidemiologic studies, and inflammation and oxidative stress have been hypothesized as potential mechanisms involved. In the present study we investigated associations between urinary concentrations of phthalate metabolites and potential blood markers of oxidative stress (bilirubin) and inflammation (alkaline phosphatase [ALP], absolute neutrophil count [ANC], ferritin [adjusted for iron status], and fibrinogen), using data from 10,026 participants in the National Health and Nutrition Examination Survey (NHANES) recruited between 1999 and 2006. After adjustment for covariates we found that bilirubin was inversely associated with several phthalate metabolites (all p-values <0.0001), including the metabolites of di-2-ethylhexyl phthalate (DEHP) and dibutyl phthalate (DBP), in addition to monobenzyl phthalate (MBzP) and mono-(3-carboxypropyl) phthalate (MCPP). Since bilirubin is a potent antioxidant these relationships suggest that phthalates may be associated with increased oxidative stress. Many of the same metabolites were also significantly and positively related with ANC, ALP, and ferritin, suggesting phthalates may be associated with increased inflammation. These markers may be useful in other studies of low-dose exposure to environmental contaminants.

Protein oxidation markers in women with and without gestational diabetes mellitus: a possible relation with paraoxonase activity

AIMS

To clarify the levels of protein oxidation markers such as protein carbonyl (PCO), protein hydroperoxides (P-OOH), advanced oxidation protein products (AOPP) and nitrotyrosine (NT), as well as antioxidative enzymes such as paraoxonase (PON-1) in women with and without gestational diabetes mellitus (GDM).

METHODS

The study was conducted on 23 women with GDM and 22 women without GDM. The levels of the P-OOH, AOPP, and PON-1 were determined by colorimetric methods; whereas NT and PCO levels were measured by ELISA.

RESULTS

The concentrations of protein oxidation markers were significantly increased and PON1 activity was significantly decreased in GDM group compared to those of normal pregnant women. The control group showed a significant negative correlation between PON-1 and PCO (r=-0.451, p=0.027); whereas in GDM group, there was a significant positive correlation between P-OOH and HbA1c (r=0.89, p=0.001). There was no significant correlation between AOPP, PON-1, P-OOH, PCO, and HbA1c in either group.

CONCLUSIONS

There is evidence of a possible association between protein oxidation and decreased PON1 activity in GDM. The increase in protein oxidation parameters in the GDM group leading to decreased PON1 activity might, we think, create a predisposition for clinical complications in GDM group.

Alterations of platelet biochemical and functional properties in newly diagnosed type 1 diabetes: a role in cardiovascular risk?

BACKGROUND

The involvement of platelets in the pathogenesis of diabetic vascular complications is supported by several studies. Type 1 diabetic (T1D) platelets show increased adhesiveness and aggregation related to a modification of nitric oxide synthase activity. Moreover, different cell types from diabetic patients showed a decreased membrane Na(+) /K(+) -ATPase activity, which might be involved in diabetic complications. The aim of this study was to investigate whether T1D at onset is able to induce alterations of platelet physicochemical and functional properties and whether these changes are affected by hyperglycaemia.

METHODS

The study was performed on 50 young subjects: 30 patients (1-14 years) affected by T1D and 20 age- and gender-matched healthy subjects. We analyzed platelet membrane fluidity by fluorescent anisotropy of 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene and 1,6-diphenyl-1,3,5-hexatriene, Na(+) /K(+) -ATPase, nitric oxide, and peroxynitrite production.

RESULTS

In T1D subjects, we observed an increased fluidity in the plasma membrane outer part and greater rigidity in the internal part compared with that in controls. Na(+) /K(+) -ATPase activity and nitric oxide levels were significantly reduced, while peroxynitrite production was increased compared with that in controls. Moreover, correlations found between the above parameters were correlated with fasting glycaemia and haemoglobin A(1c).

CONCLUSIONS

T1D patients exhibit structural and functional modifications of platelet membrane properties and alterations of nitric oxide metabolism due to diabetes per se and not to chronic hyperglycaemia, insulin therapy, or ageing. These results support the hypothesis that oxidative attack could be an important early event in the pathogenesis of diabetic complications.

Spatio-temporal variation in territory quality and oxidative status: a natural experiment in the Seychelles warbler (Acrocephalus sechellensis)

1. Fluctuations in the quality of the habitat in which an animal lives can have major consequences for its behaviour and physiological state. In poor-quality habitat with low food availability, metabolically intensive foraging activity is likely to result in increased generation of reactive oxygen species, while scarcity of food can lead to a weakening of exogenously derived antioxidant defences. The consequent oxidant/antioxidant imbalance may lead to elevated oxidative stress. 2. Although the link between food availability and oxidative stress has been studied in the laboratory, very little is known about this relationship in the wild. Here, we investigate the association between territory quality (measured through food availability) and oxidative stress in the Seychelles warbler (Acrocephalus sechellensis). 3. Seychelles warblers are insectivorous birds that inhabit a fixed feeding territory year round. Individuals experience profound and rapid local fluctuations in territory quality within these territories, owing to changing patterns of vegetation defoliation resulting from seasonal changes in prevailing wind direction and wind-borne salt spray. 4. As expected, oxidant generation (measured as reactive oxygen metabolites; ROMs) was higher when territory quality was low, but there was no correlation between territory quality and antioxidant capacity (OXY). The negative correlation between territory quality and ROMs was significant between individuals and approached significance within individuals, indicating that the pattern resulted from individual responses to environmental variation. 5. ROMs and OXY levels within individuals were positively correlated, but the relationship between territory quality and ROMs persisted after including OXY as a covariate, implying that oxidative stress occurs in low territory quality conditions. 6. Our results indicate that the oxidative stress balance of an individual is sensitive to relatively short-term changes in territory quality, which may have consequences for the birds' fitness.

Identifying mechanisms of chronotolerance and chronoefficacy for the anticancer drugs 5-fluorouracil and oxaliplatin by computational modeling

We use an automaton model for the cell cycle to assess the toxicity of various circadian patterns of anticancer drug delivery so as to enhance the efficiency of cancer chronotherapy. Based on the sequential transitions between the successive phases G1, S (DNA replication), G2, and M (mitosis) of the cell cycle, the model allows us to simulate the distribution of cell cycle phases as well as entrainment by the circadian clock. We use the model to evaluate circadian patterns of administration of two anticancer drugs, 5-fluorouracil (5-FU) and oxaliplatin (l-OHP). We first consider the case of 5-FU, which exerts its cytotoxic effects on cells in S phase. We compare various circadian patterns of drug administration differing by the time of maximum drug delivery. The model explains why minimum cytotoxicity is obtained when the time of peak delivery is close to 4a.m., which temporal pattern of drug administration is used clinically for 5-FU. We also determine how cytotoxicity is affected by the variability in duration of cell cycle phases and by cell cycle length in the presence or absence of entrainment by the circadian clock. The results indicate that the same temporal pattern of drug administration can have minimum cytotoxicity toward one cell population, e.g. of normal cells, and at the same time can display high cytotoxicity toward a second cell population, e.g. of tumour cells. Thus the model allows us to uncover factors that may contribute to improve simultaneously chronotolerance and chronoefficacy of anticancer drugs. We next consider the case of oxaliplatin, which, in contrast to 5-FU, kills cells in different phases of the cell cycle. We incorporate into the model the pharmacokinetics of plasma thiols and intracellular glutathione, which interfere with the action of the drug by forming with it inactive complexes. The model shows how circadian changes in l-OHP cytotoxicity may arise from circadian variations in the levels of plasma thiols and glutathione. Corroborating experimental and clinical results, the simulations of the model account for the observation that the temporal profiles minimizing l-OHP cytotoxicity are in antiphase with those minimizing cytotoxicity for 5-FU.

Variation in basal heat shock protein 70 is correlated to core temperature in human subjects

Heat shock proteins are highly conserved proteins and play an important chaperone role in aiding the folding of nascent proteins within cells. The heat shock protein response to various stressors, both in vitro and in vivo, is well characterised. However, basal levels of heat shock protein 70 (Hsp70) have not previously been investigated. Monocyte-expressed Hsp70 was determined every 4 h, over a 24 h time period, in 17 healthy male subjects (177 +/- 6.4 cm, 75.7 +/- 10.9 kg, 19.8 +/- 4.3 years) within a temperature and activity controlled environment. Core temperature was measured at 5-min intervals during the 24 h period. Hsp70 showed significant diurnal variation (F = 7.4; p < 0.001), demonstrating peaks at 0900 and 2100 hours, and a nadir at 05.00. Core temperature followed a similar temporal trend (range = 35.96-38.10 degrees C) and was significantly correlated with Hsp70 expression (r(s) = 0.44; p < 0.001). These findings suggest a high responsiveness of Hsp70 expression in monocytes to slight variations in core temperature.

Diurnal variations in salivary protein carbonyl levels in normal and cognitively impaired human subjects

Oxidative stress has been documented in tissues and biofluids of subjects with sporadic Alzheimer disease (AD) and mild cognitive impairment (MCI). The aim of this study was to determine whether (a) salivary protein carbonyls are elevated in AD and MCI subjects, (b) salivary protein carbonyl contents in these groups exhibit diurnal variation, and (c) apolipoprotein E epsilon 4 (apoE epsilon 4) carrier status impacts salivary carbonyl concentrations or rhythmicity in the AD and MCI cohorts. Unstimulated saliva was collected at fixed intervals between 8 AM: and 10 PM: from 15 AD subject , 21 MCI subjects, and 30 cognitively-intact controls. Salivary protein carbonyl concentrations were measured by ELISA. ApoE genotyping was performed on the AD and MCI individuals. For all groups, mean protein carbonyl contents were significantly elevated at 2 PM: relative to other time points surveyed. Mean salivary protein carbonyl concentrations did not differ among the diagnostic groups. ApoE epsilon 4 carriers exhibited less temporal variation in salivary protein carbonyls relative to noncarriers. Thus, protein carbonyl content exhibits diurnal variation in adult human saliva. ApoE epsilon 4 carrier status may impact oropharyngeal disease expression by attenuating the inherent diurnal variability in salivary redox homeostasis. Salivary protein carbonyls do not differentiate AD and MCI from normal individuals. In conclusion, oxidative stress has been documented in tissues and biofluids of subjects with sporadic AD and MCI. This article demonstrates that levels of protein carbonyls, a marker of oxidative stress, exhibit robust diurnal variation in the saliva of normal elderly, MCI, and AD subjects. Apolipoprotein E epsilon 4 allele carrier status may attenuate this temporal variability in salivary redox homeostasis and thereby impact the natural history of oropharyngeal diseases.

Chronobiology of hemostasis and inferences for the chronotherapy of coagulation disorders and thrombosis prevention

The hemostatic system in its multiple components displays an intricate organization in time which is characterized by circadian (approximately 24-hour), circaseptan (approximately 7-day), menstrual (approximately monthly), and circannual (approximately yearly) bioperiodicities. The interaction of the rhythms of the variables participating in hemostasis determine transient risk states of thromboembolic events, including myocardial infarction and stroke, and of hemorrhage and hemorrhagic events, each with a unique timing. The circadian staging of the rhythms in vascular, cellular, and coagulation factors that favors blood coagulation and thrombosis coincides with the daily minimum in fibrinolytic activity; as a result there is elevated risk in the morning of acute myocardial infarction and stroke. Similar hemostatic rhythms may determine the epidemiology of thromboembolic and hemorrhagic events during the week, month and year. This article focuses on the large-amplitude circadian rhythms operative in the hemostatic system. Their implication for preventive and curative pharmacotherapy of hemostatic disorders is presented, with discussion of related problems.

The effect of time of day and exercise on platelet functions and platelet-neutrophil aggregates in healthy male subjects

Platelet activation state changes by exercise. The effect of exercise time on platelet activation state and formation of platelet-neutrophil aggregates are not known yet. In this study the effect of exercise and time of day were examined on platelet activity with platelet-neutrophil aggregates. Ten moderately active males aged 27+/- 1.63 (mean+/-S.D.) years completed sub-maximal (70% VO(2max)) exercise trials for 30 min. Blood pressure (BP) was recorded. Venous blood samples were obtained at rest, immediately post-exercise and after 30 min of recovery. Whole blood was analysed for haematocrit (Hct), haemoglobin (Hb), platelet count (PC), mean platelet count (MPV) and platelet aggregation (PA). Platelet-neutrophil aggregates and beta-thromboglobulin (beta-TG) levels were assayed. Platelet count showed significant increase after morning exercise ((236+/- 32)x10(9) l(-1) versus (202+/- 34)x10(9) l(-1) baseline, p < 0.05). Exercise resulted in significantly lower MPV after the evening exercise (9.16+/- 0.5 fl versus 9.65+/- 0.36 fl, p < 0.05). Platelet aggregation by adenosine diphosphate (ADP) decreased after morning exercise and the recovery aggregation levels were significantly different at two different times of the day (68+/- 20% a.m. versus 80+/- 12% p.m., p < 0.05). It was also showed that platelet-neutrophil aggregates increased significantly from baseline after both exercises. Exercise-induced platelet-neutrophil aggregates were higher in the evening (10.7+/- 1.3% p.m. versus 6.4+/- 1.8% a.m., p < 0.0001). It is therefore concluded that besides platelet-platelet aggregation, exercise can cause platelet- neutrophil aggregates. In addition, time of day has an effect on platelet activation related events. Circadian variations of physiological parameters may have an effect on thrombus formation by platelet activation.

Protein oxidation parameters in type 2 diabetic patients with good and poor glycaemic control

AIM

In order to examine the influence of oxidative stress on protein oxidation, type 2 diabetic patients without clinical evidence of complications, either in good or poor glycaemic control, were studied.

METHODS

Plasma protein carbonyl (PCO), total thiol (T-SH), and advanced oxidation protein products (AOPP) levels as markers of protein oxidation, and lipid hydroperoxide (LHP) levels as markers of lipid peroxidation were determined. Glycated haemoglobin (HbA1c) levels were used as an index of glycaemic control. The subjects were divided into two groups according to their HbA1c level at inclusion as follows: good HbA1c<=7%, and poor HbA1c > 7%.

RESULTS

Plasma PCO and AOPP levels of diabetic patients with poor glycaemic control were increased significantly compared with those of the diabetic patients with good glycaemic control. The decreased plasma T-SH level in the diabetic patients with poor glycaemic control was not statistically significant. On the other hand, plasma LHP levels were increased significantly in the diabetic patients with poor GC compared with those of the diabetic patients with good glycaemic control.

CONCLUSION

This study supports the hypothesis that poor glycaemic control is an important factor in generation of increased protein oxidation in type 2 diabetic patients clinically free of complications. Increase in plasma PCO, AOPP, and LHP levels in the diabetic patients with poor glycaemic control may contribute to the development of diabetic complications.

Lipid peroxidation and resistance to oxidation in patients with type 2 diabetes mellitus

We investigated lipid peroxidation, resistance of plasma and red blood cells to oxidation, and antioxidant defense system in erythrocytes and sera in patients with type 2 diabetes mellitus. One group included newly diagnosed 20 patients and the other included 20 patients treated with oral antidiabetic agents (OAD). Twenty healthy subjects served as controls. Serum and red blood cell malondialdehyde (MDA), glutathione (GSH), resistance to oxidation, and plasma thiol (total -SH) levels were measured. In addition, glycated hemoglobin, serum fructosamine, uric acid, total protein, total cholesterol, triglyceride and glucose levels were determined. Although newly diagnosed patients had higher serum and erythrocyte MDA levels than those of controls, the highest levels of MDA were determined in patients treated with OAD. MDA levels after exposing to oxidation increased in OAD group more than in newly diagnosed patients. Total -SH and erythrocyte GSH levels of the both diabetic groups were lower than controls. These results show that serum and erythrocyte lipid peroxidation was increased in diabetic patients. The sera of the patients showed a decreased resistance against oxidation. We therefore suggest that the effect of increased free radicals may be prevented by antioxidant systems in early stages of type 2 diabetes but in advanced stages this relationship is impaired owing to decreased antioxidant activity. Decreased red blood cell GSH and serum total -SH levels may be due to a compensation mechanism of the antioxidants.

Circadian rhythms, oxidative stress, and antioxidative defense mechanisms

Endogenous circadian and exogenously driven daily rhythms of antioxidative enzyme activities and of low molecular weight antioxidants (LMWAs) are described in various phylogenetically distant organisms. Substantial amplitudes are detected in several cases, suggesting the significance of rhythmicity in avoiding excessive oxidative stress. Mammalian and/or avian glutathione peroxidase and, as a consequence, glutathione reductase activities follow the rhythm of melatonin. Another hint for an involvement of melatonin in the control of redox processes is seen in its high-affinity binding to cytosolic quinone reductase 2, previously believed to be a melatonin receptor. Although antioxidative protection by pharmacological doses of melatonin is repeatedly reported, explanations of these findings are still insufficient and their physiological and chronobiological relevance is not yet settled. Recent data indicate a role of melatonin in the avoidance of mitochondrial radical formation, a function which may prevail over direct scavenging. Rhythmic changes in oxidative damage of protein and lipid molecules are also reported. Enhanced oxidative protein modification accompanied by a marked increase in the circadian amplitude of this parameter is detected in the Drosophila mutant rosy, which is deficient in the LMWA urate. Preliminary evidence for the significance of circadian rhythmicity in diminishing oxidative stress comes from clock mutants. In Drosophila, moderately enhanced protein damage is described for the arrhythmic and melatonin null mutant per0, but even more elevated, periodic damage is found in the short-period mutant per(s), synchronized to LD 12:12. Remarkably large increases in oxidative protein damage, along with impairment of tissue integrity and--obviously insufficient--compensatory elevations in protective enzymes are observed in a particularly vulnerable organ, the Harderian gland, of another short-period mutant tau, in the Syrian hamster. Mice deficient in the per2 gene homolog are reported to be cancer-prone, a finding which might also relate to oxidative stress. In the dinoflagellate Lingulodinium polyedrum [Gonyaulax polyedra], various treatments that cause oxidative stress result in strong suppressions of melatonin and its metabolite 5-methoxytryptamine (5-MT) and to secondary effects on overt rhythmicity. The glow maximum, depending on the presence of elevated 5-MT at the end of subjective night, decreases in a dose-dependent manner already under moderate, non-lethal oxidative stress, but is restored by replenishing melatonin. Therefore, a general effect of oxidative stress may consist in declines of easily oxidizable signaling molecules such as melatonin, and this can have consequences on the circadian intraorganismal organization and expression of overt rhythms. Recent findings on a redox-sensitive input into the core oscillator via modulation of NPAS2/BMAL1 or CLK/BMAL1 heterodimer binding to DNA indicate a direct influence of cellular redox balance, including oxidative stress, on the circadian clock.

Periodic dip of lipidperoxidation in humans: a redox signal to synchronize peripheral circadian clocks?

The output generated by the endogenous circadian clock to control circadian functions and temporal organization in metazoans is unknown. Redox state perturbations generated by reactive oxygen species (ROS) and antioxidants are known to influence the expression of a number of genes and signal transduction pathways. Evidence has been recently provided that the reduced redox cofactors NAD and NADP both regulate clock gene activity in the suprachiasmatic nucleus (SCN) and are induced by it. Significant periodic variations of lipidperoxidation in human blood with a dip at 04.00 h have been previously reported. Such variations could be expected to alter the cellular redox state, thus possibly functioning as periodic redox signals from the master clock. To verify the existence of the mentioned variations the serum levels of malondialdehyde (MDA), a marker of lipidperoxidation, were monitored by High-Performance Liquid Chromatography in 39 healthy subjects at 3-h intervals over a 24-h period. Throughout the test period, only biological noise could be detected in all test persons. However, the normalized MDA levels at 03.00 h were significantly lower (p < 0.05 to < 0.00005) in 38 (97%) of the cases and showed a significantly lower standard deviation (p < 0.004) than at any of the other 3-h intervals, indicating a periodic dip of lipidperoxidation (PDL) in diurnal active subjects. We hypothesize that the PDL, on the basis of its time of appearance, its frequency and its potential influence on cellular redox state, represents a periodic systemic redox output of the SCN, in terms of a relatively short and sudden interruption of the daily oxidative noise. According to recent research, it could be the result of redox alterations induced by the SCN activity and at the same time the pathway by which the master clock resets and synchronizes peripheral oscillators to the light/dark cycle. Additionally, the antioxidative function of the pineal gland activity postulated elsewhere could play a part in generating the described phenomenon. The PDL could be useful as a circadian phase marker in research dealing with treatment of jet lag and other sleep disorders.

Smokers lack morning increase in platelet sensitivity to nitric oxide

This study investigated whether a circadian variation is present in the sensitivity of platelets to nitric oxide (NO) and, if so, if long-term smoking modifies it. Blood samples were taken at 0:00, 6:00, 9:00, 12:00, and 18:00 from 14 nonsmokers and 10 smokers. Dose-response curves for platelet aggregation by collagen were constructed in both the presence and absence of 1.0 micro M of NOR-3, a NO donor. The antiaggregation properties of NOR-3 were quantified by the half maximal concentration (EC50) ratio in the presence of NOR-3 to that in its absence. Platelet aggregation showed a monophasic circadian rhythm, with the lowest levels at 6:00 and the highest at 18:00 in both groups. However, there was a significant (p < 0.01) upward shifting of platelet aggregation in the smokers. A circadian variation in sensitivity to NOR-3 also was demonstrated in the nonsmokers. The sensitivity was lowest at 6:00 (1.68 +/- 0.19), increased significantly at 9:00 (2.58 +/- 0.26; p < 0.01), and remained high at 12:00 (2.47 +/- 0.21; p < 0.05). In smokers, however, a circadian variation in platelet sensitivity to NOR-3 was not found. Furthermore, the sensitivity was significantly lower at 9:00 and 12:00 in smokers (1.94 +/- 0.26 and 1.76 +/- 0.13, respectively; p < 0.05 for both) than in nonsmokers. Thus, long-term smoking impairs the normal morning increase in platelet sensitivity to NO, making platelets in smokers more thrombogenic during the hazardous hours.

Circadian rhythmicity of whole-blood glutathione in healthy subjects

OBJECTIVES

Physiologic rhythms of antioxidants have been the subject of considerable interest in recent years. Physiologically, it is known that 24-h variability in whole-blood glutathione (GSH) could depend on various factors, such as meal composition, protein dietary content, meal-related hormonal modifications, and stress. Experiments were conducted to determine if the circadian variations previously observed in hepatic concentrations of reduced glutathione in animals also occurred in healthy volunteers.

METHODS

The circadian periodicity of whole-blood glutathione was explored. All parameters were measured enzymatically at 4-h intervals over a 24-h period.

RESULTS

Circadian rhythms were not found. The rhythms peak for glutathione content occurred at 9 h with a small peak at 21 h. The nadir occurred at 17 h and 1 h.

CONCLUSION

These data show that despite this wide distribution of glutathione throughout the day we could not find any significant intertime variability.

Oxidative protein damage in early stage Type 1 diabetic patients

To examine the influence of oxidative stress on oxidative protein damage, we studied 51 young Type 1 diabetic patients clinically free of complications and 48 healthy normolipidaemic age-matched controls. We determined: (1) plasma carbonyl (PCO), plasma total thiol (T-SH), and nitrotyrosine (NT) levels as markers of oxidative protein damage; (2) plasma lipid hydroperoxide (LHP), and nitric oxide (NO) levels as markers of oxidative stress; (3) plasma total antioxidant capacity (TAO), ceruloplasmin (Cp), transferrin (TRF), unsaturated iron binding capacity (UIBC), erythrocyte glutathione (GSH), and erythrocyte superoxide dismutase (SOD) as markers of free radical scavengers. There were no significant differences in the levels of these markers between prepubertal diabetic patients and the controls. The levels of both of PCO and LHP were increased in adolescent and young adult Type 1 diabetic patients with respect to their controls. In the adolescent group, patient versus control values for PCO were 1.04+/-0.067 versus 0.67+/-0.0274 nmol/mg and for LHP they were 2. 10+/-1.09 versus 1.00+/-0.4 nmol/mg. In the young adult group, patient versus control values for PCO were 0.99+/-0.054 versus 0. 66+/-0.02 nmol/mg and for LHP they were 1.96+/-0.78 versus 1.15+/-0. 4 nmol/mg. TAO levels were significantly decreased in adolescent diabetic patients compared to their controls (0.92+/-0.27 vs. 1. 86+/-0.37) and in young adult diabetic patients compared to their controls (0.80+/-0.27 vs. 2.11+/-0.54 nmol/mg). T-SH was not different between diabetic patients and the controls. Serum NT, NO, and erythrocyte SOD levels were not different either between three groups of diabetic patients or between the patients and their controls. We attribute this lack of difference to limited disease duration. Changes in markers of oxidative stress other than NT, NO, and SOD observed in adolescent and young adult early stage Type 1 diabetic patients contribute to the imbalance in the redox status of the plasma. We attribute this imbalance to metal-catalyzed protein oxidation in both groups of Type 1 diabetic patients clinically free from complications.

Neutrophils may contribute to the morbidity and mortality of claudicants

Peripheral arterial occlusive disease is a common cause of morbidity in middle-aged men; 5 per cent of those aged over 50 years suffer from intermittent claudication. While claudication itself is not fatal, claudicants have a mortality rate approximately three times that of non-claudicating men of the same age, mainly from cardiovascular disease. This review examines the evidence for involvement of the neutrophil in this increased mortality and describes the possible pathogenesis. It also discusses how treatment of claudication may modify neutrophil behaviour, reducing subsequent mortality and morbidity rates.