Preoperative fasting induces protection against renal ischemia/reperfusion injury by a corticosterone-independent mechanism

Continuous Monochromatic Blue Light Exacerbates High-Fat Diet-Induced Kidney Injury via Corticosterone-Mediated Oxidative Stress

Excessive illumination is one of the most severe environmental factors that impacts the organism. There is growing evidence that obesity significantly contributes to the onset of chronic kidney disease. However, the effect of continuous light on the kidney and which color can produce an apparent phenomenon remains elusive. In this study, C57BL/6 mice given either a normal diet (LD-WN) or a high-fat diet (LD-WF) were subjected to a light cycle of 12 h of illumination followed by 12 h of darkness for 12 weeks. Meanwhile, 48 high-fat diet mice were given a 24 h monochromatic light exposure of varying colors (white, LL-WF; blue, LL-BF; green, LL-GF) for 12 weeks. As expected, the LD-WF mice showed significant obesity, kidney injury, and renal dysfunction compared with the LD-WN group. LL-BF mice had worse kidney injury than LD-WF mice, including higher Kim-1 and Lcn2. The kidney of the LL-BF group showed marked glomerular and tubular injury, with decreased levels of Nephrin, Podocin, Cd2ap, and α-Actinin-4 compared to LD-WF. LL-BF also reduced the antioxidant capacity, including GSH-Px, CAT, and T-AOC, increased the production of MDA, and inhibited the activation of the NRF2/HO-1 signaling pathway. Furthermore, LL-BF upregulated the mRNA levels of the pro-inflammatory factors Tnf-α, Il-6, and Mcp-1, decreasing the inhibitory inflammatory Il-4 expression. We observed increased plasma corticosterone (CORT), renal glucocorticoid receptors (GR) expression, Hsp90, Hsp70, and P23 mRNA levels. These findings suggested that LL-BF increased CORT secretion and affected glucocorticoid receptors (GR) in comparison to the LD-WF group. Moreover, in vitro research demonstrated that CORT treatment increased oxidative stress and inflammation, which was counteracted by adding a GR inhibitor. Thus, the sustained blue light worsened kidney damage, possibly by inducing elevated CORT and increasing oxidative stress and inflammation via GR.

The combined effect of zinc oxide nanoparticles and milrinone on acute renal ischemia/reperfusion injury in rats: Potential underlying mechanisms

AIM

To investigate the efficacy of zinc oxide nanoparticles (ZnO-NPs) and/or milrinone (MIL) on renal ischemia/reperfusion injury (I/RI) in rats and their possible underlying mechanisms.

MATERIALS AND METHODS

Forty-eight adult male Sprague-Dawley albino rats were randomly assigned into six equal-sized groups (n = 8): normal control, sham-operated, I/R group (45 min/24 h), ZnO-NPs group (10 mg/Kg i.p.), MIL group (0.5 mg/Kg i.p.), and ZnO-NPs + MIL group in the same previous doses.

KEY FINDINGS

In comparison to the I/R-operated group, administration of either ZnO-NPs or MIL significantly decreased serum creatinine and urea concentrations, and renal vascular permeability (p < 0.05). The oxidative stress was significantly declined, as evidenced by increased GPx, CAT, and SOD activities and decreased MDA and NO concentrations. Renal expressions of TNF-α, NF-κB, KIM-1, NGAL, and caspase-3 decreased significantly, while Nrf2 increased significantly. Histopathology investigation revealed improvement with minimal renal lesions and fibrosis after ZnO-NPs or MIL treatments. The combined treatments synergistically improved the studied parameters more than either treatment alone. These findings were validated by molecular modeling, which revealed that MIL inhibited TNF-α, NF-kB, caspase-3, KIM-1 and NGAL.

SIGNIFICANCE

Both ZnO-NPs and MIL exerted cytoprotective effects against acute renal I/RI, and a combination of both was found to be even more effective. This renoprotective effect is suggested to be mediated through activation of Nrf2 and the prevention of the NF-κB activation-induced oxidative stress and inflammation, which may strengthen the potential role of ZnO-NPs or MIL in renal I/RI protection during surgical procedures.

Short-Term Preoperative Calorie and Protein Restriction Is Feasible in Healthy Kidney Donors and Morbidly Obese Patients Scheduled for Surgery

Introduction. Surgery-induced oxidative stress increases the risk of perioperative complications and delay in postoperative recovery. In mice, short-term preoperative dietary and protein restriction protect against oxidative stress. We investigated the feasibility of a calorie- and protein-restricted diet in two patient populations. Methods. In this pilot study, 30 live kidney donors and 38 morbidly obese patients awaiting surgery were randomized into three groups: a restricted diet group, who received a synthetic liquid diet with 30% fewer calories and 80% less protein for five consecutive days; a group who received a synthetic diet containing the daily energy requirements (DER); and a control group. Feasibility was assessed using self-reported discomfort, body weight changes, and metabolic parameters in blood samples. Results. Twenty patients (71%) complied with the restricted and 13 (65%) with the DER-diet. In total, 68% of the patients reported minor discomfort that resolved after normal eating resumed. The mean weight loss on the restricted diet was significantly greater (2.4 kg) than in the control group (0 kg, p = 0.002), but not in the DER-diet (1.5 kg). The restricted diet significantly reduced levels of serum urea and plasma prealbumin (PAB) and retinol binding protein (RBP). Conclusions. A short-term preoperative calorie- and protein-restricted diet is feasible in kidney donors and morbidly obese patients. Compliance is high and can be objectively measured via changes in urea, PAB, and RBP levels. These results demonstrate that this diet can be used to study the effects of dietary restriction on surgery-induced oxidative stress in a clinical setting.

Fasting protects against the side effects of irinotecan treatment but does not affect anti-tumour activity in mice

BACKGROUND

The main limitation to the use of irinotecan in the treatment of colorectal cancer is the severity of side effects, including neutropaenia and diarrhoea. Here, we explored the effects of 3 days of fasting on irinotecan-induced toxicities, on plasma, liver and tumour pharmacokinetics and on anti-tumour activity in mice.

EXPERIMENTAL APPROACH

Male BALB/c mice received C26 colon carcinoma cells subcutaneously. They were randomized 1:1 into equally sized ad libitum fed and fasted groups after which they were treated with irinotecan. Weight and adverse side effects were recorded daily. At the end of the experiment, tumours were resected and weighed, and concentrations of irinotecan and its active metabolite SN-38 were determined in plasma and tumour.

KEY RESULTS

Fasting prevented the diarrhoea and visible signs of discomfort induced by irinotecan. Ad libitum fed animals developed leucopenia compared with untreated controls, whereas fasted mice did not. Irinotecan suppressed tumour growth equally in both treated groups, compared with untreated controls. Levels of the active irinotecan metabolite SN-38 9 (calculated as AUC values) were significantly lower in fasted mice in both plasma and liver, but not in tumour tissue.

CONCLUSIONS AND IMPLICATIONS

Fasting protected against irinotecan-induced side effects without interfering with its anti-tumour efficacy. Fasting induced a lower systemic exposure to SN-38, which may explain the absence of adverse side effects, while tumour levels of SN-38 remained unchanged. These data offer important new approaches to improve treatment with irinotecan in patients.

Serotonin 2C receptor contributes to gender differences in stress-induced hypophagia in aged mice

The combination of depression and anorexia may influence morbidity and progressive physical disability in the elderly. Gender differences exist in hypothalamic-pituitary-adrenal axis activation following stress exposure. The objective of this study was to investigate gender differences in feeding behavior under novelty stress in aged mice. Food intake measurement, immunohistochemical assessment, and mRNA expression analysis were conducted to investigate the role of serotonin 2C receptor (5-HT(2C)R) and its relationship with ghrelin in stress-induced suppression of feeding behavior in aged mice. After exposure to novelty stress, a 21-fold increase in plasma corticosterone and remarkable suppression of food intake were observed in aged male mice. Furthermore, a 5-HT(2C)R agonist suppressed food intake in aged male mice. Novelty stress induced a 7-fold increase in 5-HT(2C)R and c-Fos co-expressing cells in the paraventricular nucleus of the hypothalamus in aged male mice but caused no change in aged female mice. Plasma acylated ghrelin levels decreased in stressed aged male mice and administration of the 5-HT(2C)R antagonist inhibited this decrease. The 5-HT(2C)R antagonist also reversed the suppression of food intake in estrogen receptor α agonist-treated aged male mice. Therefore, conspicuously suppressed feeding behavior in novelty stress-exposed aged male mice may be mediated by 5-HT(2C)R hypersensitivity, leading to hypoghrelinemia. The hypersensitivity may partly be due to estrogen receptor activation in aged male mice.

Preoperative fasting protects against renal ischemia-reperfusion injury in aged and overweight mice

Ischemia-reperfusion injury (IRI) is inevitable during kidney transplantation leading to oxidative stress and inflammation. We previously reported that preoperative fasting in young-lean male mice protects against IRI. Since patients are generally of older age with morbidities possibly leading to a different response to fasting, we investigated the effects of preoperative fasting on renal IRI in aged-overweight male and female mice. Male and female F1-FVB/C57BL6-hybrid mice, average age 73 weeks weighing 47.2 grams, were randomized to preoperative ad libitum feeding or 3 days fasting, followed by renal IRI. Body weight, kidney function and survival of the animals were monitored until day 28 postoperatively. Kidney histopathology was scored for all animals and gene expression profiles after fasting were analyzed in kidneys of young and aged male mice. Preoperative fasting significantly improved survival after renal IRI in both sexes compared with normal fed mice. Fasted groups had a better kidney function shown by lower serum urea levels after renal IRI. Histopathology showed less acute tubular necrosis and more regeneration in kidneys from fasted mice. A mRNA analysis indicated the involvement of metabolic processes including fatty acid oxidation and retinol metabolism, and the NRF2-mediated stress response. Similar to young-lean, healthy male mice, preoperative fasting protects against renal IRI in aged-overweight mice of both genders. These findings suggest a general protective response of fasting against renal IRI regardless of age, gender, body weight and genetic background. Therefore, fasting could be a non-invasive intervention inducing increased oxidative stress resistance in older and overweight patients as well.

Dietary restriction and fasting arrest B and T cell development and increase mature B and T cell numbers in bone marrow

Dietary restriction (DR) delays ageing and extends life span. Both long- and short-term DR, as well as short-term fasting provide robust protection against many “neuronal and surgery related damaging phenomena” such as Parkinson’s disease and ischemia-reperfusion injury. The exact mechanism behind this phenomenon has not yet been elucidated. Its anti-inflammatory actions prompted us to thoroughly investigate the consequences of DR and fasting on B and T cell compartments in primary and secondary lymphoid organs of male C57Bl/6 mice. In BM we found that DR and fasting cause a decrease in the total B cell population and arrest early B cell development, while increasing the number of recirculating mature B cells. In the fasting group, a significant reduction in peripheral B cell counts was observed in both spleen and mesenteric lymph nodes (mLN). Thymopoiesis was arrested significantly at double negative DN2 stage due to fasting, whereas DR resulted in a partial arrest of thymocyte development at the DN4 stage. Mature CD3⁺ T cell populations were increased in BM and decreased in both spleen and mLN. Thus, DR arrests B cell development in the BM but increases the number of recirculating mature B cells. DR also arrests maturation of T cells in thymus, resulting in depletion of mature T cells from spleen and mLN while recruiting them to the BM. The functional relevance in relation to protection against organ damage needs to be determined.

Altered mitochondrial functioning induced by preoperative fasting may underlie protection against renal ischemia/reperfusion injury

We reported previously that the robust protection against renal ischemia/reperfusion (I/R) injury in mice by fasting was largely initiated before the induction of renal I/R. In addition, we found that preoperative fasting downregulated the gene expression levels of complexes I, IV, and V of the mitochondrial oxidative phosphorylation (OXPHOS) system, while it did not change those of complexes II and III. Hence, we now investigated the effect of 3 days of fasting on the functioning of renal mitochondria in order to better understand our previous findings. Fasting did not affect mitochondrial density. Surprisingly, fasting significantly increased the protein expression of complex II of the mitochondrial OXPHOS system by 19%. Complex II-driven state 3 respiratory activity was significantly reduced by fasting (46%), which could be partially attributed to the significant decrease in the enzyme activity of complex II (16%). Fasting significantly inhibited Ca(2+) -dependent mitochondrial permeability transition pore opening that is directly linked to protection against renal I/R injury. The inhibition of the mitochondrial permeability transition pore did not involve the expression of the voltage-dependent anion channel by fasting. In conclusion, 3 days of fasting clearly induces the inhibition of complex II-driven mitochondrial respiration state 3 in part by decreasing the amount of functional complex II, and inhibits mitochondrial permeability transition pore opening. This might be a relevant sequence of events that could contribute to the protection of the kidney against I/R injury.