Glucose supplementation does not interfere with fasting-induced protection against renal ischemia/reperfusion injury in mice

Preoperative Short-Term Restriction of Sulfur-Containing Amino Acid Intake for Prevention of Acute Kidney Injury After Cardiac Surgery: A Randomized, Controlled, Double-Blind, Translational Trial

Background Acute kidney injury (AKI) is a major risk factor for chronic kidney disease and increased mortality. Until now, no compelling preventive or therapeutic strategies have been identified. Dietary interventions have been proven highly effective in organ protection from ischemia reperfusion injury in mice and restricting dietary intake of sulfur-containing amino acids (SAA) seems to be instrumental in this regard. The UNICORN trial aimed to evaluate the protective impact of restricting SAA intake before cardiac surgery on incidence of AKI. Methods and Results In this single-center, randomized, controlled, double-blind trial, 115 patients were assigned to a SAA-reduced formula diet (LowS group) or a regular formula diet (control group) in a 1:1 ratio for 7 days before scheduled cardiac surgery. The primary end point was incidence of AKI within 72 hours after surgery, secondary end points included increase of serum creatinine at 24, 48, and 72 hours as well as safety parameters. Quantitative variables were analyzed with nonparametric methods, while categorical variables were evaluated by means of Chi-square or Fisher test. SAA intake in the group with SAA reduced formula diet was successfully reduced by 77% (group with SAA reduced formula diet, 7.37[6.40-7.80] mg/kg per day versus control group, 32.33 [28.92-33.60] mg/kg per day, P<0.001) leading to significantly lower serum levels of methionine. No beneficial effects of SAA restriction on the rate of AKI after surgery could be observed (group with SAA reduced formula diet, 23% versus control group, 16%; P=0.38). Likewise, no differences were recorded with respect to secondary end points (AKI during hospitalization, creatinine at 24, 48, 72 hours after surgery) as well as in subgroup analysis focusing on age, sex, body mass index and diabetes. Conclusions SAA restriction was feasible in the clinical setting but was not associated with protective properties in AKI upon cardiac surgery. Registration URL: https://www.clinicaltrials.gov; Unique Identifier: NCT03715868.

Pre-Operative Fasting Provides Long Term Protection Against Chronic Renal Damage Induced by Ischaemia Reperfusion Injury in Wild Type and Aneurysm Prone Fibulin-4 Mice

OBJECTIVE

Renal ischaemia reperfusion injury (IRI) is inevitable during open repair of pararenal aortic aneurysms. Pre-operative fasting potently increases resistance against IRI. The effect of fasting on IRI was examined in a hypomorphic Fibulin-4 mouse model (Fibulin-4^+/R), which is predisposed to develop aortic aneurysms.

METHODS

Wild type (WT) and Fibulin-4^+/R mice were either fed ad libitum (AL) or fasted for two days before renal IRI induction by temporary clamping of the renal artery and vein of both kidneys. Six hours, 48 h, and seven days post-operatively, serum urea levels, renal histology, and mRNA expression levels of inflammatory and injury genes were determined to assess kidney function and damage. Additionally, matrix metalloproteinase activity in the kidney was assessed six months after IRI.

RESULTS

Two days of fasting improved survival the first week after renal IRI in WT mice compared with AL fed mice. Short term AL fed Fibulin-4^+/R mice showed improved survival and kidney function compared with AL fed WT mice, which could not be further enhanced by fasting. Both fasted WT and Fibulin-4^+/R mice showed improved survival, kidney function and morphology compared with AL fed mice six months after renal IRI. Fibulin-4^+/R kidneys of fasted mice showed reduced apoptosis together with increased matrix metalloprotease activity levels compared with AL fed Fibulin-4^+/R mice, indicative of increased matrix remodelling.

CONCLUSION

Fibulin-4^+/R mice are naturally protected against the short-term, but not long-term, consequences of renal IRI. Pre-operative fasting protects against renal IRI and prevents (long-term) deterioration of kidney function and morphology in both WT and Fibulin-4^+/R mice. These data suggest that pre-operative fasting may decrease renal damage in patients undergoing open abdominal aneurysm repair.

Protein and calorie restriction may improve outcomes in living kidney donors and kidney transplant recipients

Previously, we and others showed that dietary restriction protects against renal ischemia-reperfusion injury in animals. However, clinical translation of preoperative diets is scarce, and in the setting of kidney transplantation these data are lacking. In this pilot study, we investigated the effects of five days of a preoperative protein and caloric dietary restriction (PCR) diet in living kidney donors on the perioperative effects in donors, recipients and transplanted kidneys. Thirty-five kidney donors were randomized into either the PCR, 30% calorie and 80% protein reduction, or control group without restrictions. Adherence to the diet and kidney function in donors and their kidney recipients were analyzed. Perioperative kidney biopsies were taken in a selected group of transplanted kidneys for gene expression analysis. All donors adhered to the diet. From postoperative day 2 up until month 1, kidney function of donors was significantly better in the PCR-group. PCR-donor kidney recipients showed significantly improved kidney function and lower incidence of slow graft function and acute rejection. PCR inhibited cellular immune response pathways and activated stress-resistance signaling. These observations are the first to show that preoperative dietary restriction induces postoperative recovery benefits in humans and may be beneficial in clinical settings involving ischemia-reperfusion injury.

Preconditioning strategies to prevent acute kidney injury

Acute kidney injury is a common clinical disorder resulting in significantly increased morbidity and mortality. However, despite extensive research, strategies for prevention or treatment are still lacking in routine clinical practice. Already decades ago, several preconditioning strategies (e. g. ischemic/hypoxic preconditioning and calorie restriction) have been published and their extraordinary effectiveness - especially in rodents - has raised the hope for powerful clinical tools to prevent acute kidney injury. However, the underlying mechanisms are still not completely understood and translation to the clinics has not been successful yet. In this review, the most attractive strategies and the current mechanistic concepts are introduced and discussed. Furthermore, we present clinical trials evaluating the feasibility of preconditioning in the clinical setting.

A signature of renal stress resistance induced by short-term dietary restriction, fasting, and protein restriction

During kidney transplantation, ischemia-reperfusion injury (IRI) induces oxidative stress. Short-term preoperative 30% dietary restriction (DR) and 3-day fasting protect against renal IRI. We investigated the contribution of macronutrients to this protection on both phenotypical and transcriptional levels. Male C57BL/6 mice were fed control food ad libitum, underwent two weeks of 30%DR, 3-day fasting, or received a protein-, carbohydrate- or fat-free diet for various periods of time. After completion of each diet, renal gene expression was investigated using microarrays. After induction of renal IRI by clamping the renal pedicles, animals were monitored seven days postoperatively for signs of IRI. In addition to 3-day fasting and two weeks 30%DR, three days of a protein-free diet protected against renal IRI as well, whereas the other diets did not. Gene expression patterns significantly overlapped between all diets except the fat-free diet. Detailed meta-analysis showed involvement of nuclear receptor signaling via transcription factors, including FOXO3, HNF4A and HMGA1. In conclusion, three days of a protein-free diet is sufficient to induce protection against renal IRI similar to 3-day fasting and two weeks of 30%DR. The elucidated network of common protective pathways and transcription factors further improves our mechanistic insight into the increased stress resistance induced by short-term DR.

Surgical injury induces local and distant adipose tissue browning

The adipose organ, which comprises brown, white and beige adipocytes, possesses remarkable plasticity in response to feeding and cold exposure. The development of beige adipocytes in white adipose tissue (WAT), a process called browning, represents a promising route to treat metabolic disorders. While surgical procedures constantly traumatize adipose tissue, its impact on adipocyte phenotype remains to be established. Herein, we studied the effect of trauma on adipocyte phenotype one day after sham, incision control, or surgical injury to the left inguinal adipose compartment. Caloric restriction was used to control for surgery-associated body temperature changes and weight loss. We characterized the trauma-induced cellular and molecular changes in subcutaneous, visceral, interscapular, and perivascular adipose tissue using histology, immunohistochemistry, gene expression, and flow cytometry analysis. After one day, surgical trauma stimulated adipose tissue browning at the site of injury and, importantly, in the contralateral inguinal depot. Browning was not present after incision only, and was largely independent of surgery-associated body temperature and weight loss. Adipose trauma rapidly recruited monocytes to the injured site and promoted alternatively activated macrophages. Conversely, PDGF receptor-positive beige progenitors were reduced. In this study, we identify adipose trauma as an unexpected driver of selected local and remote adipose tissue browning, holding important implications for the biologic response to surgical injury.

Preoperative dietary restriction reduces intimal hyperplasia and protects from ischemia-reperfusion injury

OBJECTIVE

Whereas chronic overnutrition is a risk factor for surgical complications, long-term dietary restriction (reduced food intake without malnutrition) protects in preclinical models of surgical stress. Building on the emerging concept that acute preoperative dietary perturbations can affect the body's response to surgical stress, we hypothesized that short-term high-fat diet (HFD) feeding before surgery is detrimental, whereas short-term nutrient/energy restriction before surgery can reverse negative outcomes. We tested this hypothesis in two distinct murine models of vascular surgical injury, ischemia-reperfusion (IR) and intimal hyperplasia (IH).

METHODS

Short-term overnutrition was achieved by feeding mice a HFD consisting of 60% calories from fat for 2 weeks. Short-term dietary restriction consisted of either 1 week of restricted access to a protein-free diet (protein/energy restriction) or 3 days of water-only fasting immediately before surgery; after surgery, all mice were given ad libitum access to a complete diet. To assess the impact of preoperative nutrition on surgical outcome, mice were challenged in one of two fundamentally distinct surgical injury models: IR injury to either kidney or liver, or a carotid focal stenosis model of IH.

RESULTS

Three days of fasting or 1 week of preoperative protein/energy restriction attenuated IH development measured 28 days after focal carotid stenosis. One week of preoperative protein/energy restriction also reduced plasma urea, creatinine, and damage to the corticomedullary junction after renal IR and decreased aspartate transaminase, alanine transaminase, and hemorrhagic necrosis after hepatic IR. However, exposure to a HFD for 2 weeks before surgery had no significant impact on kidney or hepatic function after IR or IH after focal carotid stenosis.

CONCLUSIONS

Short-term dietary restriction immediately before surgery significantly attenuated the vascular wall hyperplastic response and improved IR outcome. The findings suggest plasticity in the body's response to these vascular surgical injuries that can be manipulated by novel yet practical preoperative dietary interventions.

Improving the outcome of kidney transplantation by ameliorating renal ischemia reperfusion injury: lost in translation?

Kidney transplantation is the treatment of choice in patients with end stage renal disease. During kidney transplantation ischemia reperfusion injury (IRI) occurs, which is a risk factor for acute kidney injury, delayed graft function and acute and chronic rejection. Kidneys from living donors show a superior short- and long-term graft survival compared with deceased donors. However, the shortage of donor kidneys has resulted in expansion of the donor pool by using not only living- and brain death donors but also kidneys from donation after circulatory death and from extended criteria donors. These grafts are associated with an increased sensitivity to IRI and decreased graft outcome due to prolonged ischemia and donor comorbidity. Therefore, preventing or ameliorating IRI may improve graft survival. Animal experiments focus on understanding the mechanism behind IRI and try to find methods to minimize IRI either before, during or after ischemia. This review evaluates the different experimental strategies that have been investigated to prevent or ameliorate renal IRI. In addition, we review the current state of translation to the clinical setting. Experimental research has contributed to the development of strategies to prevent or ameliorate IRI, but promising results in animal studies have not yet been successfully translated to clinical use.

Protein and Calorie Restriction Contribute Additively to Protection from Renal Ischemia Reperfusion Injury Partly via Leptin Reduction in Male Mice

BACKGROUND

Short-term dietary restriction (DR) without malnutrition preconditions against surgical stress in rodents; however, the nutritional basis and underlying nutrient/energy-sensing pathways remain poorly understood.

OBJECTIVES

We investigated the relative contribution of protein restriction (PR) vs. calorie restriction (CR) to protection from renal ischemia reperfusion injury (IRI) and changes in organ-autonomous nutrient/energy-sensing pathways and hormones underlying beneficial effects.

METHODS

Mice were preconditioned on experimental diets lacking total calories (0-50% CR) or protein/essential amino acids (EAAs) vs. complete diets consumed ad libitum (AL) for 1 wk before IRI. Renal outcome was assessed by serum markers and histology and integrated over a 2-dimensional protein/energy landscape by geometric framework analysis. Changes in renal nutrient/energy-sensing signal transduction and systemic hormones leptin and adiponectin were also measured. The genetic requirement for amino acid sensing via general control non-derepressible 2 (GCN2) was tested with knockout vs. control mice. The involvement of the hormone leptin was tested by injection of recombinant protein vs. vehicle during the preconditioning period.

RESULTS

CR-mediated protection was dose dependent up to 50% with maximal 2-fold effect sizes. PR benefits were abrogated by EAA re-addition and additive with CR, with maximal benefits at any given amount of CR occurring with a protein-free diet. GCN2 was not required for functional benefits of PR. Activation and repression of nutrient/energy-sensing kinases, AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin complex 1 (mTORC1), respectively, on PR reflected a state of negative energy balance, paralleled by 13% weight loss and an 87% decrease in leptin, independent of calorie intake. Recombinant leptin administration partially abrogated benefits of dietary preconditioning against renal IRI.

CONCLUSIONS

In male mice, PR and CR both contributed to the benefits of short-term DR against renal IRI independent of GCN2 but partially dependent on reduced circulating leptin and coincident with AMPK activation and mTORC1 repression.

Rotterdam: main port for organ transplantation research in the Netherlands

This overview describes the full spectrum of current pre-clinical and clinical kidney-, liver-, heart- and lung transplantation research performed in Erasmus MC - University Medical Centre in Rotterdam, The Netherlands. An update is provided on the development of a large living donor kidney transplantation program and on optimization of kidney allocation, including the implementation of a domino kidney-donation program. Our current research efforts to optimize immunosuppressive regimens and find novel targets for immunosuppressive therapy, our recent studies on prevention of ischemia-reperfusion-induced graft injury, our newest findings on stimulation of tissue regeneration, our novel approaches to prevent rejection and viral infection, and our latest insights in the regulation of allograft rejection, are summarized.

Benefits of short-term dietary restriction in mammals

Dietary or calorie restriction (DR, CR), defined as reduced food intake without malnutrition, imparts many benefits in model organisms. Extended longevity is the most popularized benefit but the least clinically relevant due to the requirement for long-term food restriction. DR also promotes stress resistance and metabolic fitness. Emerging data in experimental models and in humans indicate that these benefits occur rapidly upon initiation of DR, suggesting potential clinical relevance. Here we review data on the ability of short-term DR to induce beneficial effects on clinically relevant endpoints including surgical stress, inflammation, chemotherapy and insulin resistance. The encouraging results obtained in these preclinical and clinical studies, and the general lack of mechanistic understanding, both strongly suggest the need for further research in this emerging area.

Does artificial nutrition improve outcome of critical illness?

Nutritional support is generally considered an essential component in the management of critically ill patients. The existing guidelines advocate early enteral nutrition, with the optimal timing for the addition of parenteral nutrition to insufficient enteral feeding being the subject of transatlantic controversy. The unphysiologic intervention of artificial nutrition in critically ill patients, however, may evoke complications and side effects. Besides the classically described complications, suppression of autophagy, potentially important for cellular repair and organ recovery, was elucidated only recently. The question whether artificial nutrition in critical illness improves or worsens outcome as compared with starvation has so far not been adequately addressed. This paper provides a critical analysis of the existing literature on ICU nutrition, highlighting important methodological shortcomings of many trials and meta-analyses and underlining the urgent need for high-quality research in this field. Recent adequately designed randomized controlled trials suggest that trophic enteral feeding during the first week of critical illness is as good as full enteral feeding and that early addition of parenteral nutrition to insufficient enteral nutrition does not provide any benefit and worsens morbidity.

Preoperative diet impacts the adipose tissue response to surgical trauma

BACKGROUND

Short-term changes in preoperative nutrition can have profound effects on surgery-related outcomes such as ischemia/reperfusion injury in preclinical models. Dietary interventions that lend protection against stress in animal models (eg, fasting, dietary restriction [DR]) impact adipose tissue quality/quantity. Adipose tissue holds high surgical relevance because of its anatomic location and large tissue volume, and it is ubiquitously traumatized during surgery. Yet the response of adipose tissue to trauma under clinically relevant circumstances including dietary status remains poorly defined. We hypothesized that preoperative diet alters the adipose tissue response to surgical trauma.

METHODS

A novel mouse model of adipose tissue surgical trauma was employed. Dietary conditions (diet-induced obesity [DIO], preoperative DR) were modulated before application of surgical adipose tissue trauma in the context of clinically common scenarios (different ages, simulated bacterial wound contamination). Local/distant adipose tissue phenotypic responses were measured as represented by gene expression of inflammatory, tissue remodeling/growth, and metabolic markers.

RESULTS

Surgical trauma had a profound effect on adipose tissue phenotype at the site of trauma. Milder but significant distal effects on non-traumatized adipose tissue were also observed. DIO exacerbated the inflammatory aspects of this response, and preoperative DR tended to reverse these changes. Age and lipopolysaccharide (LPS)-simulated bacterial contamination also impacted the adipose tissue response to trauma, with young adult animals and LPS treatment exacerbating the proinflammatory response.

CONCLUSION

Surgical trauma dramatically impacts both local and distal adipose tissue biology. Short-term preoperative DR may offer a strategy to attenuate this response.

Reducing elective vascular surgery perioperative risk with brief preoperative dietary restriction

Brief preoperative dietary interventions emphasizing reduced calorie and protein intake will decrease perioperative morbidity and mortality associated with vascular operative procedures by modulating maladaptive response to operative stress.