High-Fat Diet Increased Oxidative Stress and Mitochondrial Dysfunction Induced by Renal Ischemia-Reperfusion Injury in Rat

The role of redox signaling in mitochondria and endoplasmic reticulum regulation in kidney diseases

Kidney diseases are among the fastest worldwide growing pathologies. This growth together with their high mortality rate emphasizes the importance of generating vital information about the mechanism involved in their pathophysiology to determine possible therapeutic targets. Recently, mitochondrial damage and their implication in the reactive oxygen spices (ROS) signaling and redox homeostasis have emerged as a hub point in the pathologic mechanism involved in renal pathologies. ROS in low levels are necessary to maintain cell processes as well as the mitochondria homeostasis and its association with other organelles, especially the with the endoplasmic reticulum (ER). However, the information about how redox signaling interacts and interferes with other cellular processes and the mechanism involved has not been fully integrated. Furthermore, in higher concentrations, these ROS promotes pathologic pathways linked to renal disease progression like, mitochondrial biogenesis reduction, ER stress, calcium overload, inflammation, cell death and fibrosis. Therefore, the aim of this review is to describe the molecular mechanisms involved in the redox signaling influence on mitochondrial and ER homeostasis, focusing on lipid metabolism and ß-oxidation, mitochondrial biogenesis, inflammations, ER stress and calcium homeostasis, as well as the effects of these alteration in the genesis and development of renal disease, with emphasis in acute kidney injury (AKI) and chronic kidney disease (CKD).

The role of lipid profile in the relationship between skipping breakfast and hyperuricemia: a moderated mediation model

BACKGROUND

The prevalence of hyperuricemia is rising among oilfield workers in China. This study aimed to explore the underlying mechanisms between skipping breakfast and serum uric acid.

METHODS

A total of 21,676 participants aged 20--60 from a large oilfield company in China were included. Association analysis, multivariate logistic, subgroup analysis, and moderated mediation analysis were performed to assess the association between skipping breakfast and hyperuricemia.

RESULTS

We found that 24.48% of oilfield employees had hyperuricemia. The odds ratio of hyperuricemia linked to skipping breakfast was 0.78 (95%CI: 0.69--0.88). The association between skipping breakfast and hyperuricemia was mediated by TC (22.32%) and LDL-C (21.57%). Age moderated this mediation, with significant effects for skipping breakfast (ß: 0.553, 95%CI: 0.042--1.063) and TC (ß: -0.339, 95%CI: -0.586- -0.093). Similar results were observed for LDL-C mediation (ß: 0.522, 95%CI: 0.009--1.035; ß: -0.585, 95%CI: -0.894- -0.276).

CONCLUSION

Skipping breakfast positively influenced hyperuricemia through TC and LDL-C. Age moderated the relationship between skipping breakfast and serum uric acid. Greater attention should be given to young employees in Chinese oilfield enterprises, with dietary interventions implemented to reduce abnormal lipids metabolism and hyperuricemia.

Western diet exacerbates a murine model of Balkan nephropathy

Aristolochic acid (AA) ingestion causes Balkan nephropathy, characterized by tubular injury and progression to chronic kidney disease (CKD). AA is taken up by proximal tubule cells via organic anion transport and induces p21-mediated DNA damage response, but little is known about dietary modulating factors. Western diet (WD) is rich in saturated fats and sugars and can promote metabolic disorders and CKD progression. Here, we determined the impact of WD on AA-induced kidney injury. Five-week-old male C57BL/6J mice were fed WD or normal chow (NC) for 8 wk, followed by administration of AA every 3 days for 3 wk. Measurements were performed after the last injection and following a 3-wk recovery. Independent of dosing AA by body weight (3 mg/kg/day) or same dose/mouse (0.1125 mg/day), the AA-induced increase in plasma creatinine and reduction of hematocrit were greater in WD versus NC. This was associated with increased kidney gene expression in WD vs. NC of markers of DNA damage (p21), injury (Kim1 and Ngal), and inflammation (Tnfa) and kidney fibrosis staining. WD alone increased fractional excretion of indoxyl sulfate by 7.5-fold, indicating enhanced kidney organic anion transport. Kidney proteomics identified further WD-induced changes that could increase kidney sensitivity to AA and contribute to the altered response to AA including weakening of energy metabolism, potentiation of immune and infection pathways, and disruption in RNA regulation. In conclusion, WD can increase the susceptibility of mice to Balkan nephropathy, possibly in part through facilitating kidney uptake of the organic anion AA.NEW & NOTEWORTHY This study shows that a Western diet (WD) aggravates a murine model of Balkan nephropathy induced by the application of the organic anion and nephrotoxin aristolochic acid (AA). Mechanistically, this may involve WD-induced kidney organic anion secretion, which can facilitate the AA uptake into proximal tubular cells and thereby contribute to the injury. Kidney proteomics identified further changes induced by feeding a WD that could have increased the sensitivity of the kidney to stress and injury.

Role of mitochondria in reno-cardiac diseases: A study of bioenergetics, biogenesis, and GSH signaling in disease transition

Acute kidney injury (AKI) and chronic kidney disease (CKD) are global health burdens with rising prevalence. Their bidirectional relationship with cardiovascular dysfunction, manifesting as cardio-renal syndromes (CRS) types 3 and 4, underscores the interconnectedness and interdependence of these vital organ systems. Both the kidney and the heart are critically reliant on mitochondrial function. This organelle is currently recognized as a hub in signaling pathways, with emphasis on the redox regulation mediated by glutathione (GSH). Mitochondrial dysfunction, including impaired bioenergetics, redox, and biogenesis pathways, are central to the progression of AKI to CKD and the development of CRS type 3 and 4. This review delves into the metabolic reprogramming and mitochondrial redox signaling and biogenesis alterations in AKI, CKD, and CRS. We examine the pathophysiological mechanisms involving GSH redox signaling and the AMP-activated protein kinase (AMPK)-sirtuin (SIRT)1/3-peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α) axis in these conditions. Additionally, we explore the therapeutic potential of GSH synthesis inducers in mitigating these mitochondrial dysfunctions, as well as their effects on inflammation and the progression of CKD and CRS types 3 and 4.

Integrated Ultrasound Characterization of the Diet-Induced Obesity (DIO) Model in Young Adult c57bl/6j Mice: Assessment of Cardiovascular, Renal and Hepatic Changes

Consuming an unbalanced diet and being overweight represent a global health problem in young people and adults of both sexes, and may lead to metabolic syndrome. The diet-induced obesity (DIO) model in the C57BL/6J mouse substrain that mimics the gradual weight gain in humans consuming a "Western-type" (WD) diet is of great interest. This study aims to characterize this animal model, using high-frequency ultrasound imaging (HFUS) as a complementary tool to longitudinally monitor changes in the liver, heart and kidney. Long-term WD feeding increased mice body weight (BW), liver/BW ratio and body condition score (BCS), transaminases, glucose and insulin, and caused dyslipidemia and insulin resistance. Echocardiography revealed subtle cardiac remodeling in WD-fed mice, highlighting a significant age-diet interaction for some left ventricular morphofunctional parameters. Qualitative and parametric HFUS analyses of the liver in WD-fed mice showed a progressive increase in echogenicity and echotexture heterogeneity, and equal or higher brightness of the renal cortex. Furthermore, renal circulation was impaired in WD-fed female mice. The ultrasound and histopathological findings were concordant. Overall, HFUS can improve the translational value of preclinical DIO models through an integrated approach with conventional methods, enabling a comprehensive identification of early stages of diseases in vivo and non-invasively, according to the 3Rs.

Structural and systems characterization of phosphorylation on metabolic enzymes identifies sex-specific metabolic reprogramming in obesity

Coordination of adaptive metabolism through cellular signaling networks and metabolic response is essential for balanced flow of energy and homeostasis. Post-translational modifications such as phosphorylation offer a rapid, efficient, and dynamic mechanism to regulate metabolic networks. Although numerous phosphorylation sites have been identified on metabolic enzymes, much remains unknown about their contribution to enzyme function and systemic metabolism. In this study, we stratify phosphorylation sites on metabolic enzymes based on their location with respect to functional and dimerization domains. Our analysis reveals that the majority of published phosphosites are on oxidoreductases, with particular enrichment of phosphotyrosine (pY) sites in proximity to binding domains for substrates, cofactors, active sites, or dimer interfaces. We identify phosphosites altered in obesity using a high fat diet (HFD) induced obesity model coupled to multiomics, and interrogate the functional impact of pY on hepatic metabolism. HFD induced dysregulation of redox homeostasis and reductive metabolism at the phosphoproteome and metabolome level in a sex-specific manner, which was reversed by supplementing with the antioxidant butylated hydroxyanisole (BHA). Partial least squares regression (PLSR) analysis identified pY sites that predict HFD or BHA induced changes of redox metabolites. We characterize predictive pY sites on glutathione S-transferase pi 1 (GSTP1), isocitrate dehydrogenase 1 (IDH1), and uridine monophosphate synthase (UMPS) using CRISPRi-rescue and stable isotope tracing. Our analysis revealed that sites on GSTP1 and UMPS inhibit enzyme activity while the pY site on IDH1 induces activity to promote reductive carboxylation. Overall, our approach provides insight into the convergence points where cellular signaling fine-tunes metabolism.

Does cardiac impairment develop in ischemic renal surgery in rats depending on the reperfusion time?

Background

Renal dysfunction is known to cause heart failure. However, renal dysfunction associated with kidney surgeries (mediated by reperfusion injury) that affects the cardiac physiological function, especially during the recovery and repair phase of renal surgery is unknown.

Method

Male Wistar rats (238 ± 18 g) were subjected to renal sham and ischemia-reperfusion (IR-bilateral clamping for 15 min/45 min and reperfusion for 24 h/48 h/7 days) surgeries. At the end of the experiment, the heart was isolated from the animal (to exclude neurohormonal influence) and perfused for 60 min with Krebs-Hanseleit buffer to study the physiological changes.

Result

Renal artery bilateral occlusion for 45 min that creates ischemia, followed by 24 h of reperfusion did not impart any significant cardiac physiological functional decline but 48 h of reperfusion exhibited a significant decline in cardiac hemodynamic indices (Rate pressure product in x104 mmHg*beats/min: Sham- 3.53 ± 0.19, I45_R48-2.82 ± 0.21) with mild tissue injury. However, 7 days of reperfusion inflict significant physiological decline (Rate pressure product in x104 mmHg*beats/min - 2.5 ± 0.14) and tissue injury (Injury score- 4 ± 1.5) in isolated rat hearts. Interestingly, when the renal artery bilateral occlusion time was reduced to 15 min the changes in the hearts were negligible after 7 days. Cellular level exploration reveals a positive relation between functional deterioration of mitochondria and elevated mitochondrial oxidative stress and inflammation with cardiac physiological decline and injury linked with renal ischemia-reperfusion surgery.

Conclusion

Cardiac functional decline associated with renal surgery is manifested during renal repair or recovery. This decline depends on cardiac mitochondrial health, which is negatively influenced by the renal IR mediators and kidney function.

Melatonin Reduces Aggravation of Renal Ischemia-Reperfusion Injury in Obese Rats by Maintaining Mitochondrial Homeostasis and Integrity through AMPK/PGC-1α/SIRT3/SOD2 Activation

This study examined the potential benefits of melatonin against renal ischemia and reperfusion (IR) injury in obesity and explored the underlying mechanisms. Obesity was induced in Wistar rats by feeding a high-fat diet for 16 weeks. Three obese groups that underwent renal IR induction (30-min renal ischemia followed by 24-h reperfusion) were randomly assigned to receive melatonin at ischemic onset, reperfusion onset, or pretreatment for 4 weeks before IR induction. Groups of vehicle-treated obese and normal-diet-fed rats that underwent sham or IR induction were also included in the study. The results showed that renal functional and structural impairments after IR incidence were aggravated in obese rats compared to normal-diet-fed rats. The obese-IR rats also exhibited oxidative stress, mitochondrial dysfunction, apoptosis, and mitochondrial dynamics and mitophagy imbalances, which were all considerably improved upon melatonin treatment, irrespective of the treatment time. This study suggests the prophylactic and therapeutic efficacy of melatonin in IR-induced acute kidney injury (AKI) in obese individuals, which may improve the prognosis of AKI in these populations. The benefits of melatonin are likely mediated by the modification of various signaling molecules within the mitochondria that maintain mitochondrial redox balance and lead to the protection of mitochondrial homeostasis and integrity.

Impaired renal ischemia reperfusion recovery after bilateral renal artery ligation in rats treated with adenine: role of renal mitochondria

Vascular calcification (VC) and ischemia reperfusion (IR) injury is characterised to have mitochondrial dysfunction. However, the impact of dysfunctional mitochondria associated with vascular calcified rat kidney challenged to IR is not explored and is addressed in the present study. Male Wistar rats were treated with adenine for 20 days to induce chronic kidney dysfunction and VC. After 63 days, renal IR protocol was performed with subsequent recovery for 24 h and 7 days. Various mitochondrial parameters and biochemical assays were performed to assess kidney function, IR injury and its recovery. Adenine-induced rats with VC, decreased creatinine clearance (CrCl), and severe tissue injury demonstrated an increase in renal tissue damage and decreased CrCl after 24 h of IR (CrCl in ml: IR-0.220.02, VC-IR-0.050.01). Incidentally, the 24 h IR pathology in kidney was similar in both VC-IR and normal rat IR. But, the magnitude of dysfunction was higher with VC-IR due to pre-existing basal tissue alterations. We found severed deterioration in mitochondrial quantity and quality supported by low bioenergetic function in both VC basal tissue and IR challenged sample. However, post 7 days of IR, unlike normal rat IR, VC rat IR did not improve CrCl and corresponding mitochondrial damage in terms of quantity and its function were observed. Based on the above findings, we conclude that IR in VC rat adversely affect the post-surgical recovery, mainly due to the ineffective renal mitochondrial functional restoration from the surgery.

Selenoprotein Gene mRNA Expression Evaluation During Renal Ischemia-Reperfusion Injury in Rats and Ebselen Intervention Effects

Effects of selenoproteins on many renal diseases have been reported. However, their role in renal ischemia-reperfusion (I/R) injury is unclear. The present study was performed to investigate the impact of ebselen and renal I/R injury on the expression of selenoproteins. Sprague-Dawley rats were pretreated with or without ebselen (10 mg/kg) through a daily single oral administration from 3 days before renal I/R surgery. RT-qPCR (real-time quantitative PCR) was performed to determine the mRNA expression of 25 selenoprotein genes in the renal tissues. The expression levels of two selenoproteins, including GPX3 (glutathione peroxidase 3) and DIO1 (iodothyronine deiodinase 1), were evaluated by Western blot or/and IHF (immunohistofluorescence) assays. Furthermore, renal function, renal damage, oxidative stress, and apoptosis were assessed. The results showed that in renal I/R injury, the mRNA levels of 15 selenoprotein genes (GPX1, GPX3, GPX4, DIO1, DIO2, TXNRD2, TXNRD3, SEPHS2, MSRB1, SELENOF, SELENOK, SELENOO, SELENOP, SELENOS, and SELENOT) were decreased, whereas those of eight selenoprotein genes (GPX2, GPX6, DIO3, TXNRD1, SELENOH, SELENOM, SELENOV, and SELENOW) were increased. I/R also induced a reduction in the expression levels of GPX3 and DIO1 proteins. In addition, our results indicated that ebselen reversed the changes in those selenoprotein genes, excluding SELENOH, SELENOM, SELENOP, and SELENOT, in renal I/R injury and alleviated I/R-induced renal dysfunction, tissue damage, oxidative stress, and apoptosis. To our knowledge, this is the first study to investigate the changes of 25 mammalian selenoprotein genes in renal I/R injury kidneys. The present study also provided more evidence for the roles of ebselen against renal I/R injury.

High-fat diet-induced mitochondrial dysfunction is associated with loss of protection from ischemic preconditioning in renal ischemia reperfusion

Consumption of high-fat diet (HFD) promotes mitochondrial dysfunction and the latter act as a critical factor in determining the severity of ischemia-reperfusion (IR) injury in different cell types. Ischemic preconditioning (IPC), a well-known protocol that render IR protection in kidney works via mitochondria. In the present study, we evaluated how HFD kidney with underlying mitochondrial changes respond to precondition protocol after IR induction. Wistar male rats were used in this study and were divided into two groups: SD (standard diet; n = 18) and HFD (high-fat diet; n = 18), which were further subdivided into sham, ischemia-reperfusion, and precondition groups at the end of the dietary regimen. Blood biochemistry, renal injury marker, creatinine clearance (CrCl), mitochondrial quality (fission, fusion, and phagy), mitochondrial function via ETC enzyme activities and respiration, and signalling pathway were analysed. Sixteen weeks of HFD administration to the rat deteriorated the renal mitochondrial health measured via 10% decline in mitochondrial respiration index ADP/O (in GM), reduced mitochondrial copy number (55%), biogenesis (56%), low bioenergetics potential (19% complex I + III and 15% complex II + III), increased oxidative stress, and reduced expression of mitochondrial fusion genes compared with SD rats. IR procedure in HFD rat kidney inflicted significant mitochondrial dysfunction and further deteriorated copy number along with impaired mitophagy and mitochondrial dynamics. IPC could effectively ameliorate the renal ischemia injury in normal rat but failed to provide similar kind of protection in HFD rat kidney. Even though the IR-associated mitochondrial dysfunction in both normal and HFD rats were similar, the magnitude of overall dysfunction and corresponding renal injury and compromised physiology was high in HFD rats. This observation was further confirmed via in vitro protein translation assay in isolated mitochondria from normal and HFD rat kidney that showed significantly reduction in the response ability of mitochondria in HFD. In conclusion, the deteriorated mitochondrial function and its quality along with low mitochondrial copy number and downregulation of mitochondrial dynamic gene exhibited by HFD rat kidney augments the sensitivity of renal tissue towards the IR injury which leads to the compromised protective ability by ischemic preconditioning.

Isolated Mitochondrial Preparations and In organello Assays: A Powerful and Relevant Ex vivo Tool for Assessment of Brain (Patho)physiology

Mitochondria regulate multiple aspects of neuronal development, physiology, plasticity, and pathology through their regulatory roles in bioenergetic, calcium, redox, and cell survival/death signalling. While several reviews have addressed these different aspects, a comprehensive discussion focussing on the relevance of isolated brain mitochondria and their utilities in neuroscience research has been lacking. This is relevant because the employment of isolated mitochondria rather than their in situ functional evaluation, offers definitive evidence of organelle-specificity, negating the interference from extra mitochondrial cellular factors/signals. This mini-review was designed primarily to explore the commonly employed in organello analytical assays for the assessment of mitochondrial physiology and its dysfunction, with a particular focus on neuroscience research. The authors briefly discuss the methodologies for biochemical isolation of mitochondria, their quality assessment, and cryopreservation. Further, the review attempts to accumulate the key biochemical protocols for in organello assessment of a multitude of mitochondrial functions critical for neurophysiology, including assays for bioenergetic activity, calcium and redox homeostasis, and mitochondrial protein translation. The purpose of this review is not to examine each and every method or study related to the functional assessment of isolated brain mitochondria, but rather to assemble the commonly used protocols of in organello mitochondrial research in a single publication. The hope is that this review will provide a suitable platform aiding neuroscientists to choose and apply the required protocols and tools to address their particular mechanistic, diagnostic, or therapeutic question dealing within the confines of the research area of mitochondrial patho-physiology in the neuronal perspective.

ROS-Induced DNA-Damage and Autophagy in Oral Squamous Cell Carcinoma by Usnea barbata Oil Extract-An In Vitro Study

Oxidative stress is associated with aging, cancers, and numerous metabolic and chronic disorders, and phenolic compounds are well known for their health-promoting role due to their free-radical scavenging activity. These phytochemicals could also exhibit pro-oxidant effects. Due to its bioactive phenolic secondary metabolites, Usnea barbata (L.) Weber ex. F.H. Wigg (U. barbata) displays anticancer and antioxidant activities and has been used as a phytomedicine for thousands of years. The present work aims to analyze the properties of U. barbata extract in canola oil (UBO). The UBO cytotoxicity on oral squamous cell carcinoma (OSCC) CLS-354 cell line and blood cell cultures was explored through complex flow cytometry analyses regarding apoptosis, reactive oxygen species (ROS) levels, the enzymatic activity of caspase 3/7, cell cycle, nuclear shrinkage (NS), autophagy (A), and synthesis of deoxyribonucleic acid (DNA). All these studies were concomitantly performed on canola oil (CNO) to evidence the interaction of lichen metabolites with the constituents of this green solvent used for extraction. The obtained data evidenced that UBO inhibited CLS-354 oral cancer cell proliferation through ROS generation (316.67 × 10⁴), determining higher levels of nuclear shrinkage (40.12%), cell cycle arrest in G0/G1 (92.51%; G0 is the differentiation phase, while during G1 phase occurs preparation for cell division), DNA fragmentation (2.97%), and autophagy (62.98%) than in blood cells. At a substantially higher ROS level in blood cells (5250.00 × 10⁴), the processes that lead to cell death-NS (30.05%), cell cycle arrest in G0/G1 (86.30%), DNA fragmentation (0.72%), and autophagy (39.37%)-are considerably lower than in CLS-354 oral cancer cells. Our work reveals the ROS-mediated anticancer potential of UBO through DNA damage and autophagy. Moreover, the present study suggests that UBO pharmacological potential could result from the synergism between lichen secondary metabolites and canola oil phytoconstituents.

Serum triglycerides level is independently associated with renal outcomes in patients with non-dialysis chronic kidney disease: Results from KNOW-CKD study

To investigate whether high serum triglycerides (TG) level is associated with adverse renal outcomes in patients with non-dialysis chronic kidney disease (CKD), a total of 2,158 subjects from a prospective cohort study (Korean Cohort Study for Outcome in Patients With Chronic Kidney Disease) were divided into the quartile by serum TG level. The primary outcomes were composite renal events, which is defined as a composite of decline of kidney function (the first occurrence of > 50% decline of estimated glomerular filtration rate or doubling of serum creatinine from the baseline) or onset of end-stage renal disease (initiation of dialysis or kidney transplantation). During the median follow-up of 6.940 years, the cumulative incidence of composite renal event was significantly differed by serum TG level in Kaplan-Meier curve analysis (P < 0.001, by Log-rank test). Cox regression analysis demonstrated that, compared to that of the 1st quartile, the risk of composite renal event was significantly higher in the 4th quartile (adjusted hazard ratio 1.433, 95% confidence interval 1.046 to 1.964). The association between high serum TG level and adverse renal outcome remained consistent in the cause-specific hazard model. Subgroup analyses revealed that the association is modified by age, estimated glomerular filtration rate, and spot urine albumin-to-creatinine ratio. In conclusion, high serum TG level is independently associated with adverse renal outcomes in patients with non-dialysis CKD. Interventional studies are warranted to determine whether lowering serum TG levels may alter the natural course of CKD.

The role of lipid profile in the relationship between particulate matters and hyperuricemia: A prospective population study

CONTEXT

Recent studies in specific population subgroups (e.g., pregnant women) have suggested PM exposure increases the risk of hyperuricemia. However, no studies have examined this in the general population. Furthermore, the underlying mechanism through which PM impacts hyperuricemia risk is poorly understood.

OBJECTIVE

To assess the association between long-term exposure to PM and risk of hyperuricemia and whether this association is mediated by lipid profile.

METHODS

We included 5939 participants in Southwest China from the China Multi-Ethnic Cohort (baseline 2018-2019, follow-up 2020-2021). Long-term PM pollutants (PM₁, PM_2.5, PM₁₀) exposure for each individual was represented by the three-year average PM levels before the baseline survey. Hyperuricemia at follow-up was defined as the serum uric acid above 7.0 mg/dL in men and 6.0 mg/dL in women. Serum lipids were measured at baseline including total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG). The association of PM with hyperuricemia was accessed through logistic regression. The potential mediation effects of serum lipids were evaluated through causal mediation analyses.

RESULTS

A total of 837 participants were newly diagnosed with hyperuricemia. The odds ratios of hyperuricemia associated with an interquartile range (IQR) increase in PM₁, PM_2.5, and PM₁₀ (IQR: 21.10, 25.78, 30.43 μg m^-3) were 1.72 (95% CI: 1.23, 2.39), 2.68 (95% CI: 1.59, 4.49), and 1.81 (95% CI: 1.20, 2.72), respectively. The association between PM_2.5, PM₁, and PM₁₀ on hyperuricemia was mediated by HDL-C (10%) and LDL-C (3%).

CONCLUSION

Higher particulate matter exposure was associated with higher hyperuricemia incidence. The decline in HDL-C and rise in LDL-C partially mediated this association. These findings were conducive to scientific research about the underlying mechanism of PM on hyperuricemia.

High-fat diet affects autophagy and mitochondrial compartment in rat Harderian gland

The Harderian gland (HG) of Rattus norvegicus is an orbital gland secreting lipids that accumulate in excess under condition of increased lipid metabolism. To study the response elicitated by lipid overload in rat HG, we housed the animals in thermoneutral conditions (28-30°C) in association to high fat diet (HFD). In HFD rats alterated blood lipid levels result in lipid accumulation in HG as demonstrated by the increased gland weight and histochemical/ultrastructural analyses. The HFD-caused oxidative stress forces the gland to trigger antioxidant defense mechanisms and autophagic process, such as lipophagy and mitophagy. Induction of mitochondrial DNA (mtDNA) damage and repair was stronger in HFD-rat HGs. An increase in marker expression levels of mitochondrial biogenesis, fission, and fusion occurred to counteract mtDNA copy number reduction and mitophagy. Therefore, the results demonstrate that rat HG activates autophagy as survival strategy under conditions of increased lipid metabolism and suggest a key role for mitophagy and membrane dynamics in the mitochondrial adaptive response to HFD.

Short-term control of diet affects cisplatin-induced acute kidney injury through modulation of mitochondrial dynamics and mitochondrial GSH

Obesity affects acute kidney injury (AKI) induced by various clinical settings, including transplantation and cisplatin-cancer therapy. However, the effect of short-term food intake change remains to be defined. Here, we investigated the effects of short-term high-fat diet intake and food restriction on cisplatin-induced AKI. Mice were fed either a high-fat diet (HFD) or a low-fat diet (LFD) for 11 days or were not fed for 40 hh (fasting), before cisplatin administration. Cisplatin-induced functional and structural damages to kidneys in both HFD- and LFD-fed mice, with greater damages in HFD-fed mice than LFD-fed mice. HFD decreased mitochondrial total glutathione (tGSH) level, along with increases in the plasma and kidney cholesterol levels. Cisplatin caused the increase of kidney cholesterol levels and oxidative stress, along with the decrease of mitochondrial tGSH levels. In addition, cisplatin-induced mitochondrial damage and apoptosis of tubular cells in both HFD- and LFD-fed mice. An increase of Fis1 (mitochondria fission 1 protein), whereas a decrease of Opa1 (mitochondria fusion 1 protein) occurred by cisplatin. These cisplatin effects were greater in HFD-fed mice than in LFD-fed mice. Administration of mitochondria-specific antioxidant treatment during HFD feeding inhibited these cisplatin-induced changes. Fasting for 40 h also significantly reduced the cisplatin-induced changes mentioned above. These data demonstrate that short-term HFD intake worsens cisplatin-induced oxidative stress by the reduction of mitochondrial tGSH, resulting in increased cisplatin-induced nephrotoxicity. These data newly indicate that the control of calorie intake, even for a short period, affects kidney susceptibility to injury. Although most studies described the effects of a long-term high-fat diet on the kidneys, in this study, we found that even if a high-fat diet was consumed for a short-term, physiological changes and mitochondria tGSH decrease in the kidneys, and consequently increased cisplatin-nephrotoxic susceptibility. These data suggest the association of calorie intake with kidney susceptibility to cisplatin.