Heat preconditioning reduces subsequent ischemia reperfusion injury in rat kidney: a possible role for HSP-72

Improving the ability of the kidney to tolerate ischemic injury has important implication in renal transplantation. On the other hand, thermo tolerance describes the process in which hyperthermia induces a transient resistance of the stressed cells to subsequent episodes of oxidative stress. The current study was performed to evaluate the beneficial effect of heat preconditioning induced HSP-72 formation on renal ischemia reperfusion [I/R] induced damage. Four groups of rats [n=20/group] were included: Control sham-operated group [group I], heat-preconditioned sham-operated group [group II], I/R injury group [group III] and heat pre-conditioned I/R injury group [group IV]. Heat-preconditioning was induced 24h prior to sham operation and or I/R injury by increasing the core body temperature to [41 +/- 0.5°C] for 20min. The rat kidneys were subjected to ischemia by 20min of bilateral renal artery occlusion followed by reperfusion for 24 and 48h. After 24 and 48h of reperfusion, serum urea, creatinine, 24h urine out put and albumin content as well as the renal HSP-72 gene expression and MDA level were measured. Also light microscopic examination of renal tissue specimens was performed. It was found that group IV had a significant increase in renal HSP-72 gene expression compared to group III [898.36 +/- 107.82 versus 572.88 +/- 47.08 micro g/g tissue], associated with a significant improvement of its renal functions including serum urea, creatinine and 24h urine volume out put. Also there was a reduction in renal tissue injury detected by a significant decrease in urine albumin content, a significant decrease in renal MDA level and improvement in specimen microscopic picture compared to group III. The increase in HSP-72 expression and its renoprotective effect were significantly greater 24h after I/R than after 48h. Thus it can be concluded that upregulation of HSP-72 after heat preconditioning has a renal beneficial effect and can be a target for protection of renal functions during I/R injury

Effects of sleep deprivation on cellular immunity and interleukin-6 level in rats: increased dietary fat modulate sleep deprivation-induced immune change

Impairment of host defenses is chief among sleep deprivation outcomes, as evidenced by strikingly poor control over endogenous microorganisms. Interleukin [IL]-6 is a multifunctional cytokine. It is an inflammatory cytokine, which causes sickness manifestations. This cytokine might play a significant role in mediating the sleepiness and fatigue in the day after sleep deprivation. Leukocytosis has been a consistent finding in sleep deprivation inspite of the impaired immunity. Blood leukocyte differentials were performed to determine the cell types responsible for this finding of increased circulating white blood cell counts. Fatty acid composition of rodent diets can affect immune function as measured in vitro and in vivo and can modulates the immune response to different types of stress. This study was designed to investigate the effect of 4 days of sleep deprivation on the serum level of IL-6 and the differential count of white blood cells. Also to examine the effect of diet enriched with fat on the changes induced by sleep deprivation. Forty adult male albino rats were included in this study and were divided into 4 groups: Group I: [Control group] included 10 rats received standard rat chow and water and have normal sleep pattern, at -12 hours dark-light cycles. Group II: [Fat fed group] included 10 rats received standard rat chow enriched with corn oil and water, and have normal sleep pattern, at -12 hours dark-light cycles. Group III: [Sleep deprivation group] included 10 rats received standard rat chow and water, and was exposed to sleep deprivation. Group IV: [Fat fed and sleep deprived group] included 10 rats received standard rat chow enriched with corn oil and water, and was exposed to sleep deprivation in the same pattern as group III. Sleep deprivation was carried out by audio-visual mechanism. The results indicated decreased body weight, leukocytosis with neutrophilia and shift to the left, monocytosis and lymphopenia in sleep-deprived rats. The serum revealed an evolving pro-inflammatory state, as evidenced by high incidence of interleukin-6. Feeding the rats diet enriched with fat ameliorated the inflammatory state as evidenced by significant lower levels of IL-6 and partially corrected the change induced by sleep deprivation on the total and the differential blood count of WBCs. We can conclude that sleep deprivation has a considerable impact on the immune response. Nearly all of the immune-related events that emerged as responses to sleep deprivation have been implicated as a pro-inflammatory states that represents a risk factor for many diseases. Feeding sleep deprived rats a diet enriched in fatty acids ameliorated the effect of sleep deprivation on IL-6 secretion and partially attenuated the stimulation of inflammatory responses induced by sleep deprivation as indicated by partial correction of the body weight and WBCs count and composition

Impairment of the insulinotropic effect of gastric inhibitory polypeptide [GIP] in obese and diabetic rats is related to the down-regulation of its pancreatic receptors

The association of obesity with type 2 diabetes has been recognized for years. Insulin resistance induced by obesity increases the chances of developing diabetes mellitus in which insulin release is markedly reduced. In type 2 diabetes, there is a possibility that an important part of the impaired insulin secretion is due to loss of the insulinotropic effect of the gastric inhibitory polypeptide [GIP] hormone. The aim of this study was to detect changes that occur in the pancreatic GIP receptor expression and in GIP secretion in obese and type 2 diabetic rats in response to oral glucose administration and its relation to glucose and insulin plasma levels during oral glucose tolerance test [OGTT]. Three groups of rats [n=10/ group] were included in this study: A control group receiving standard chow for 10 weeks, an obese group, in which obesity was induced by feeding rats standard chow with the addition of 32% of the caloric intake as fat for 10 weeks and a type 2 diabetic group, receiving the standard chow with the addition of fructose as 66% of the caloric intake for 10 weeks. Parameters measured in all groups included: Obesity index, systolic blood pressure, serum triglycerides as well as plasma glucose, insulin and GIP levels at 0, 5, 10, 20, 60, 90 and 120min. of an OGTT and pancreatic islets GIP receptors gene expression [GIP-Rs] using PCR method. At the end of 10 weeks, the obese and diabetic groups both had significantly increased fasting plasma glucose levels and insulin resistance indices [HOMA-IR], in addition to significantly higher blood pressure and serum triglycerides levels compared to the control group, indicating the presence of insulin resistance. In addition, the obese group had a significantly increased obesity index and fasting GIP level compared to the control and diabetic groups. During the first 20min. following oral glucose intake, both the obese and the diabetic rats had a significant increase in the glucose excursion compared to that of the control group, with a more significant increase in the diabetic group compared to the obese group. Both the obese and diabetic groups had a significant decrease of early-insulin secretion compared to control, with a more significant decrease in the diabetic group compared to the obese group. During the first 20min. of the OGTT, there was also a significant increase in the incremental change of GIP from 0 to 20min [GIP delta 0-20] in the obese group [60.1 +/- 6.66pmol/L] compared to that of the control [33.96 +/- 4.69pmol/L] and the diabetic [29.34 +/- 2.62pmol/L] groups, which were not significantly different from each other. However, there was a significant decrease of GIP-Rs expression in both the obese [88.07 +/- 10.36 micro g/ml] and the diabetic [87.51 +/- 4.72 micro g/ml] groups compared to the control group [120.35 +/- 8.06 micro g/ml], indicating that the loss of the GIP insulinotropic effect in obese and diabetic rats during the first 20min. of OGTT was due to a reduction in pancreatic GIP-Rs. During the next 20 to 120min. following oral glucose load, plasma GIP was decreasing in all groups, however, the obese group had a significantly increased plasma glucose level compared to the control group and a significant hyperinsulinemia compared to the other two groups. Such hyperinsulinemia in the presence of a decreasing GIP secretion and reduced GIP-Rs indicates the possibility of up-regulation of another compensatory mechanism to overcome the GIP-Rs defect. Moreover, the diabetic group had a significantly increased plasma glucose level compared to that of the other two groups and its plasma insulin level was significantly lower than that of the control group until the 90min. interval and thereafter it showed a non-significant difference with that of the control group. This study revealed that both obese and diabetic rats had an impaired insulinotropic effect of GIP in response to oral glucose administration during OGTT due to impaired gene expression of its pancreatic receptors and not due to impaired secretion. Also there was an associated compensatory hyperinsulinemia in obese rats during the second hour of the OGTT, which may lead to exhaustion of B-cells on the long run, increasing the incidence of diabetes mellitus. Therefore GIP-Rs could be a potential target to prevent transition of obesity to diabetes and to improve insulin secretion in type 2 diabetes mellitus

Vitamin C supplement modulates heat shock protein 72 gene expression in skeletal muscle of rats with type 2 diabetes

Oxidative stress has been ascribed a role in the pathogenesis of diabetes and its complications and stress proteins have been shown to protect organisms in vitro and in vivo against oxidative stress. In this study we examined the HSP72 gene expression in skeletal muscle of type 2 diabetic rats induced by oral fructose administration [66% of total caloric intake] compared to control and the possibility to increase its level by oral administration of vitamin C [100mg/kg/day for 8 weeks]. The amount of HSP72 m RNA in muscles of diabetic rats was lower than in control non-diabetic group [20.3 +/- 6.37 versus 40.52 +/- 7.49 micro g/g tissue] and its expression increased significantly by vitamin C administration [51.41 +/- 22.54 micro g/g tissue]. There was an insignificant increase in muscle insulin-stimulated glucose uptake after vitamin C administration in diabetic rats [2.59 +/- 0.66mg/g tissue versus 2 +/- 0.7mg/g tissue in diabetics not receiving vitamin C]. The plasma glucose level following vitamin C administration in the diabetic group, showed a significant negative correlation with the expression of HSP72. The concentration of malondialdehyde [MDA] as a measure of lipid peroxidation increased significantly in diabetics [2.019 +/- 0.53 micro mol/g tissue] compared to control group [0.926 +/- 0.19 micro mol/g tissue] and administration of vitamin C in diabetic rats decreased the concentration of MDA insignificantly [1.55 +/- 0.47 micro mol/g tissue] compared to the diabetic group not receiving vitamin C. In conclusion, the finding of decreased levels of HSP72 expression and decreased insulin-stimulated glucose uptake in skeletal muscle of type 2 diabetic rats raises the possibility that heat shock proteins may be involved in the pathogenesis of skeletal muscle insulin resistance in type 2 diabetics. Administration of vitamin C could be used in diabetics to increase heat shock protein HSP72 expression and to improve insulin resistance

Effect of immediate and long term amino acids mixture administration on the mechanical performance and apoptotic parameters in isolated rabbit heart during ischemia reperfusion injury

Optimization of the post-ischemic myocardial function remains an elusive goal. The aim of this study was to investigate the effect of supplementation of a specific mixture of amino acids on ischemia and reperfusion induced damage in isolated rabbit heart. Four groups were included in this study: groupl [control group] with isolated hearts perfused with Krebs-Henseleit solution for 2 h, group2 [ischemia-reperfusion group], group 3 [immediate amino-acids group] in which the hearts were perfused with the specific amino-acids mixture added to Krebs solution and group 4 [long term amino-acids group] this group received oral amino-acids mixture for 25 days before decapitation. The isolated hearts of group 2, 3 and 4 were subjected to 30 minutes pre-ischemic perfusion then 30 minutes of ischemia followed by 60 minutes of post-ischemic reperfusion using the Langhendorff technique and cardiac developed pressure, diastolic pressure, contractility index [dp/dt] and heart rate were measured during these phases as well as in group 1 at the end of 2h perfusion. Creatine kinase [CK] was measured in the collected cardiac perfusate at the end of the ischemic phase. Apoptosis was assessed in the heart by measurement of Pas protein level in heart tissue at the end of post-ischemic reperfusion using Elisa and by histological examination of the heart using the light and electron microscopes. Immediate perfusion of the heart with the amino acid mixture in group 3 significantly improved its pre-ischemic developed pressure with a median of 169mmHg compared to that of group 1 [88.5mmHg], group 2 [81mrnHg] and group 4 [99mmHg]. Long term amino acids supplementation in group 4 increased insignificantly its pre-ischemic developed pressure compared to that of group 1 and 2 while it increased significantly group 4 developed pressure with a median of21mmHg compared to that of group 2 [6mmHg] during ischemia.However the developed pressure in group 3 and 4 didn't show any significant change compared to group 1 and 2 during the whole period of post-ischemic reperfusion. Moreover the rise in the diastolic pressure during the post-ischemic reperfusion phase at 10, 30 and 60 minutes was significantly reduced in group 3 with a median of 21.5mmHg at 10 minutes, 19mmHg at 30 minutes and 15.5mmHg at 60 minutes; also it was significantly reduced in group 4 with a median of 13 mmHg at lOmin, 15.75mmHg at 30min and 10,75mmHg at 60min as compared to group 2 diastolic pressure median which was 37.5mmHg at lOmin, 36.25mmHg at 30min and 35.5mmHg at 60min. However there was no significant change in the diastolic pressure during pre-ischemic and ischemic phases in group 3 and 4 compared to group 2. Moreover group 3 and 4 showed no significant change in the pre-ischemic, ischemic and post-ischemic dp/dt contractility index and in the heart rate compared to group 1 and 2. The creatine kinase as a parameter of cardiac ischemia was insignificantly reduced in group 3 and 4 compared to group 2. While Fas protein level as an index of apoptosis showed a significant decrease in group 4 compared to group 2 and 3. Light and electronic microscopic examination revealed a significant improvement in the apoptotic features in group 3 and 4 compared to group 2 with normal nuclear size with condensed chromatin in H and E. Nuclei in group 4 were closer in appearance to those of the control group with normal mitochondria. In conclusion both immediate and long-term amino acids improved the cardiac performance, improved myocytees survival through decreasing Fas activation in cardiac cells during myocardial ischemia-reperfusion and reduced ischemia-reperfusion damage suggesting that mixed amino acids supplementation may be clinically useful as adjunct to conventional anti-ischemic agents.