Aldo-Keto Reductases 1B in Endocrinology and Metabolism

Cancer to Cataracts: The Mechanistic Impact of Aldo-Keto Reductases in Chronic Diseases

Aldo-keto reductases (AKRs) are a superfamily of promiscuous enzymes that have been chiseled by evolution to act as catalysts for numerous regulatory pathways in humans. However, they have not lost their promiscuity in the process, essentially making them a double-edged sword. The superfamily is involved in multiple metabolic pathways and are linked to chronic diseases such as cataracts, diabetes, and various cancers. Unlike other detoxifying enzymes such as cytochrome P450s (CYP450s), short-chain dehydrogenases (SDRs), and medium-chain dehydrogenases (MDRs), that participate in essential pathways, AKRs are more widely distributed and have members with interchangeable functions. Moreover, their promiscuity is ubiquitous across all species and participates in the resistance of pathogenic microbes. Moreover, the introduction of synthetic substrates, such as synthetic molecules and processed foods, results in unwanted "toxification" due to enzyme promiscuity, leading to chronic diseases.

AKR1B1 drives hyperglycemia-induced metabolic reprogramming in MASLD-associated hepatocellular carcinoma

Background & Aims

The mechanism behind the progressive pathological alteration in metabolic dysfunction-associated steatotic liver disease/steatohepatitis (MASLD/MASH)-associated hepatocellular carcinoma (HCC) is poorly understood. In the present study, we investigated the role of the polyol pathway enzyme AKR1B1 in metabolic switching associated with MASLD/MASH and in the progression of HCC.

Methods

AKR1B1 expression was estimated in the tissue and plasma of patients with MASLD/MASH, HCC, and HCC with diabetes mellitus. The role of AKR1B1 in metabolic switching in vitro was assessed through media conditioning, lentiviral transfection, and pharmacological probes. A proteomic and metabolomic approach was applied for the in-depth investigation of metabolic pathways. Preclinically, mice were subjected to a high-fructose diet and diethylnitrosamine to investigate the role of AKR1B1 in the hyperglycemia-mediated metabolic switching characteristic of MASLD-HCC.

Results

A significant increase in the expression of AKR1B1 was observed in tissue and plasma samples from patients with MASLD/MASH, HCC, and HCC with diabetes mellitus compared to normal samples. Mechanistically, in vitro assays revealed that AKR1B1 modulates the Warburg effect, mitochondrial dynamics, the tricarboxylic acid cycle, and lipogenesis to promote hyperglycemia-mediated MASLD and cancer progression. A pathological increase in the expression of AKR1B1 was observed in experimental MASLD-HCC, and expression was positively correlated with high blood glucose levels. High-fructose diet + diethylnitrosamine-treated animals also exhibited statistically significant elevation of metabolic markers and carcinogenesis markers. AKR1B1 inhibition with epalrestat or NARI-29 inhibited cellular metabolism in in vitro and in vivo models.

Conclusions

Pathological AKR1B1 modulates hepatic metabolism to promote MASLD-associated hepatocarcinogenesis. Aldose reductase inhibition modulates the glycolytic pathway to prevent precancerous hepatocyte formation.

Impact and implications

This research work highlights AKR1B1 as a druggable target in metabolic dysfunction-associated steatotic liver disease (MASLD) and hepatocellular carcinoma (HCC), which could provide the basis for the development of new chemotherapeutic agents. Moreover, our results indicate the potential of plasma AKR1B1 levels as a prognostic marker and diagnostic test for MASLD and associated HCC. Additionally, a major observation in this study was that AKR1B1 is associated with the promotion of the Warburg effect in HCC.

The p53 tumor suppressor regulates AKR1B1 expression, a metastasis-promoting gene in breast cancer

Alteration of metabolism in cancer cells is a central aspect of the mechanisms that sustain aggressive traits. Aldo-keto reductase 1 B1 (AKR1B1) catalyzes the reduction of several aldehydes to alcohols consuming NADPH. Nevertheless, the ability of AKR1B1 to reduce different substrates renders difficult to comprehensively ascertain its biological role. Recent evidence has implicated AKR1B1 in cancer; however, the mechanisms underlying its pro-oncogenic function remain largely unknown. In this work, we report that AKR1B1 expression is controlled by the p53 tumor suppressor. We found that breast cancer patients bearing wild-type TP53 have reduced AKR1B1 expression. In cancer cell lines, p53 reduced AKR1B1 mRNA and protein levels and repressed promoter activity in luciferase assays. Furthermore, chromatin immunoprecipitation assays indicated that p53 is recruited to the AKR1B1 promoter. We also observed that AKR1B1 overexpression promoted metastasis in the 4T1 orthotopic model of triple-negative breast cancer. Proteomic analysis of 4T1 cells overexpressing AKR1B1 showed that AKR1B1 exerts a marked effect on proteins related to metabolism, with a particular impact on mitochondrial function. This work provides novel insights on the link between the p53 pathway and metabolism in cancer cells and contributes to characterizing the alterations associated to the pathologic role of AKR1B1.

Effects of Different-Syllable Aggressive Calls on Food Intake and Gene Expression in Vespertilio sinensis

Social animals enjoy colony benefits but are also exposed to social stress, which affects their physiology in many ways, including alterations to their energy intake, metabolism, and even gene expression. Aggressive calls are defined as calls emitted during aggressive conflicts between individuals of the same species over resources, such as territory, food, or mates. Aggressive calls produced by animals in different aggressive states indicate different levels of competitive intentions. However, whether aggressive calls produced in different aggressive states exert different physiological effects on animals has yet to be determined. Importantly, bats live in clusters and frequently produce aggressive calls of different syllables, thus providing an ideal model for investigating this question. Here, we conducted playback experiments to investigate the effects of two types of aggressive calls representing different competitive intentions on food intake, body mass, corticosterone (CORT) concentration, and gene expression in Vespertilio sinensis. We found that the playback of both aggressive calls resulted in a significant decrease in food intake and body mass, and bats in the tonal-syllable aggressive-calls (tonal calls) playback group exhibited a more significant decrease when compared to the noisy-syllable aggressive-calls (noisy calls) playback group. Surprisingly, the weight and food intake in the white-noise group decreased the most when compared to before playback. Transcriptome results showed that, when compared to the control and white-noise groups, differentially expressed genes (DEGs) involved in energy and metabolism were detected in the noisy-calls playback group, and DEGs involved in immunity and disease were detected in the tonal-calls playback group. These results suggested that the playback of the two types of aggressive calls differentially affected body mass, food intake, and gene expression in bats. Notably, bat responses to external-noise playback (synthetic white noise) were more pronounced than the playback of the two aggressive calls, suggesting that bats have somewhat adapted to internal aggressive calls. Comparative transcriptome analysis suggested that the playback of the two syllabic aggressive calls disrupted the immune system and increased the risk of disease in bats. This study provides new insight into how animals differ in response to different social stressors and anthropogenic noise.

AKR1B8 deficiency drives severe DSS-induced acute colitis through invasion of luminal bacteria and activation of innate immunity

Background

Dysfunction of intestinal epithelial cells (IECs) promotes inflammatory bowel disease (IBD) and associated colorectal cancer (CRC). AKR1B8 deficiency impairs the IEC barrier function, leading to susceptibility to chronic colitis induced by dextran sulfate sodium (DSS), yet it remains unclear how acute colitic response is in AKR1B8 deficient mice.

Methods

AKR1B8 knockout (KO) and littermate wild type mice were exposed to oral 1.5% DSS in drinking water for 6 days. Disease activity index and histopathological inflammation scores by H&E staining were calculated for colitic severity; permeability was assessed by fluorescein isothiocyanate dextran (FITC-Dextran) probes and bacterial invasion and transmission were detected by in situ hybridization in mucosa or by culture in blood agar plates. Immunofluorescent staining and flow cytometry were applied for immune cell quantification. Toll-like receptor 4 (TLR4) and target gene expression was analyzed by Western blotting and qRT-PCR.

Results

AKR1B8 KO mice developed severe acute colitis at a low dose (1.5%) of DSS in drinking water compared to wild type controls. In AKR1B8 KO mice, FITC-dextran was penetrated easily and luminal bacteria invaded to the surface of IEC layer on day 3, and excessive bacteria translocated into the colonic mucosa, mesenteric lymph nodes (MLNs) and liver on day 6, which was much mild in wild type mice. Hyper-infiltration of neutrophils and basophils occurred in AKR1B8 KO mice, and monocytes in spleen and macrophages in colonic mucosa increased markedly compared to wild type mice. TLR4 signaling in colonic epithelial cells of AKR1B8 KO mice was activated to promote great IL-1β and IL-6 expression compared to wild type mice.

Conclusions

AKR1B8 deficiency in IECs drives severe acute colitis induced by DSS at a low dose through activation of the innate immunity, being a novel pathogenic factor of colitis.

Natural Compounds as Source of Aldose Reductase (AR) Inhibitors for the Treatment of Diabetic Complications: A Mini Review

BACKGROUND

Aldol reductase (AR) is the polyol pathway's main enzyme that portrays a crucial part in developing 'complications of diabetes' involving cataract, retinopathy, nephropathy, and neuropathy. These diabetic abnormalities are triggered tremendously via aggregation of sorbitol formation (catalyzed by AR) in the polyol pathway. Consequently, it represents an admirable therapeutic target and vast research was done for the discovery of novel molecules as potential AR inhibitors for diabetic complications.

OBJECTIVE

This review article has been planned to discuss an outline of diabetic complications, AR and its role in diabetic complications, natural compounds reported as AR inhibitors, and benefits of natural/plant derived AR inhibitors for the management of diabetic abnormalities.

RESULTS

The goal of AR inhibition remedy is to stabilize the increased flux of blood glucose and sorbitol via the 'polyol pathway' in the affected tissues. A variety of synthetic inhibitors of AR have been established such as tolrestat and sorbinil, but both of these face limitations including low permeability and health problems. Pharmaceutical industries and other scientists were also undertaking work to develop newer, active, and 'safe' AR inhibitors from natural sources. Therefore, several naturally found molecules were documented to possess a potent inhibitory action on AR activity.

CONCLUSION

Natural inhibitors of AR appeared as harmless pharmacological agents for controlling diabetic complications. The detailed literature throughout this article shows the significance of herbal extracts and phytochemicals as prospective useful AR inhibitors in treating diabetic complications.

Physiological and Pathological Roles of Aldose Reductase

Aldose reductase (AR) is an aldo-keto reductase that catalyzes the first step in the polyol pathway which converts glucose to sorbitol. Under normal glucose homeostasis the pathway represents a minor route of glucose metabolism that operates in parallel with glycolysis. However, during hyperglycemia the flux of glucose via the polyol pathway increases significantly, leading to excessive formation of sorbitol. The polyol pathway-driven accumulation of osmotically active sorbitol has been implicated in the development of secondary diabetic complications such as retinopathy, nephropathy, and neuropathy. Based on the notion that inhibition of AR could prevent these complications a range of AR inhibitors have been developed and tested; however, their clinical efficacy has been found to be marginal at best. Moreover, recent work has shown that AR participates in the detoxification of aldehydes that are derived from lipid peroxidation and their glutathione conjugates. Although in some contexts this antioxidant function of AR helps protect against tissue injury and dysfunction, the metabolic transformation of the glutathione conjugates of lipid peroxidation-derived aldehydes could also lead to the generation of reactive metabolites that can stimulate mitogenic or inflammatory signaling events. Thus, inhibition of AR could have both salutary and injurious outcomes. Nevertheless, accumulating evidence suggests that inhibition of AR could modify the effects of cardiovascular disease, asthma, neuropathy, sepsis, and cancer; therefore, additional work is required to selectively target AR inhibitors to specific disease states. Despite past challenges, we opine that a more gainful consideration of therapeutic modulation of AR activity awaits clearer identification of the specific role(s) of the AR enzyme in health and disease.

Propofol suppresses cell proliferation in gastric cancer cells through NRF2-mediated polyol pathway

Propofol, a widely used short‐acting intravenous sedative agent, has gradually gained attention due to the tumour‐suppressing role and non‐anaesthetic effect. Dysfunction of metabolic reprogramming has been recognised as a well‐documented factor for tumour progression. The aim of this study is to explore the effect of propofol on the polyol pathway in gastric cancer cells. In this study, we found that propofol treatment led to a significant downregulation of cell proliferation in BGC823 and GES‐1 cells, which was attributed to the decreased AR‐mediated polyol pathway. Both aldo‐keto reductase family 1, member B1 (AKR1B1) and AKR1B10 were significantly reduced in BGC823 and GES‐1 cells in response to propofol stimulation, leading to decreased AR activity and sorbitol level. Addition of sorbitol could reverse the inhibitory effect of propofol on cell proliferation. Mechanically, propofol treatment drastically inhibited phosphorylation and nuclear translocation of nuclear factor (erythroid‐derived 2)‐like 2 (NRF2), subsequently decreased the binding of NRF2 to AR promoter. Overexpression of NRF2 resulted in the recovery of AR expression in gastric cancer cell with propofol treatment. Taken together, these finding showed that propofol suppressed cell proliferation in BGC823 and GES‐1 cell through NRF2‐mediated polyol pathway, which would aid the selection of sedation for patients with gastric cancer.

Pleiotropic Actions of Aldehyde Reductase (AKR1A)

We provide an overview of the physiological roles of aldehyde reductase (AKR1A) and also discuss the functions of aldose reductase (AKR1B) and other family members when necessary. Many types of aldehyde compounds are cytotoxic and some are even carcinogenic. Such toxic aldehydes are detoxified via the action of AKR in an NADPH-dependent manner and the resulting products may exert anti-diabetic and anti-tumorigenic activity. AKR1A is capable of reducing 3-deoxyglucosone and methylglyoxal, which are reactive intermediates that are involved in glycation, a non-enzymatic glycosylation reaction. Accordingly, AKR1A is thought to suppress the formation of advanced glycation end products (AGEs) and prevent diabetic complications. AKR1A and, in part, AKR1B are responsible for the conversion of d-glucuronate to l-gulonate which constitutes a process for ascorbate (vitamin C) synthesis in competent animals. AKR1A is also involved in the reduction of S-nitrosylated glutathione and coenzyme A and thereby suppresses the protein S-nitrosylation that occurs under conditions in which the production of nitric oxide is stimulated. As the physiological functions of AKR1A are currently not completely understood, the genetic modification of Akr1a could reveal the latent functions of AKR1A and differentiate it from other family members.

The Role of AKR1B10 in Physiology and Pathophysiology

AKR1B10 is a human nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reductase belonging to the aldo-keto reductase (AKR) 1B subfamily. It catalyzes the reduction of aldehydes, some ketones and quinones, and interacts with acetyl-CoA carboxylase and heat shock protein 90α. The enzyme is highly expressed in epithelial cells of the stomach and intestine, but down-regulated in gastrointestinal cancers and inflammatory bowel diseases. In contrast, AKR1B10 expression is low in other tissues, where the enzyme is upregulated in cancers, as well as in non-alcoholic fatty liver disease and several skin diseases. In addition, the enzyme's expression is elevated in cancer cells resistant to clinical anti-cancer drugs. Thus, growing evidence supports AKR1B10 as a potential target for diagnosing and treating these diseases. Herein, we reviewed the literature on the roles of AKR1B10 in a healthy gastrointestinal tract, the development and progression of cancers and acquired chemoresistance, in addition to its gene regulation, functions, and inhibitors.

ER stress-induced adipocytes secrete-aldo-keto reductase 1B7-containing exosomes that cause nonalcoholic steatohepatitis in mice

Nonalcoholic steatohepatitis (NASH) is an increasingly prevalent liver disease linked to obesity and associated complications. Endoplasmic reticulum (ER) stress provokes dysfunction in lipid metabolism, which often leads to a progression of obesity-induced hepatic steatosis to NASH. However, the underlying mechanisms in which ER stress in adipose tissue induces hepatic pathology remain elusive. Here, we used male C57BL/6J mice to develop an animal model of NASH induced by a high fat (HFD) diet and methionine- and choline-deficient (MCD) diets. Using a gene-silencing approach with a recombinant lentiviral vector and extensive LC-MS/MS-based proteomics and lipidomics, we demonstrate that the ER stress-induced adipocyte-secreted exosome (ATEx) orchestrates lipid dynamics in the liver. We also noted that ATEx causes hepatic steatosis, inflammation, and fibrosis that lead to NASH through initial accumulation of glycerol and triglycerides in hepatocytes. We also determined that aldo-keto-reductase 1B7 (Akr1b7), a key mediator in liver lipid metabolism, is involved in ATEx-mediated NASH induction. Of note, Akr1b7 deficiency in ER stress-induced ATEx strongly protected the murine liver against HFD and MCD-induced NASH. Our results indicated that ER stress-induced, adipocyte-secreted ATEx triggers NASH by delivering exosomal AKR1B7 to, and elevating glycerol level, in hepatocytes. These findings suggest potential therapeutic strategie that target ATEx to prevent or manage obesity-induced NASH.

Aldose Reductase and the Polyol Pathway in Schwann Cells: Old and New Problems

Aldose reductase (AR) is a member of the reduced nicotinamide adenosine dinucleotide phosphate (NADPH)-dependent aldo-keto reductase superfamily. It is also the rate-limiting enzyme of the polyol pathway, catalyzing the conversion of glucose to sorbitol, which is subsequently converted to fructose by sorbitol dehydrogenase. AR is highly expressed by Schwann cells in the peripheral nervous system (PNS). The excess glucose flux through AR of the polyol pathway under hyperglycemic conditions has been suggested to play a critical role in the development and progression of diabetic peripheral neuropathy (DPN). Despite the intensive basic and clinical studies over the past four decades, the significance of AR over-activation as the pathogenic mechanism of DPN remains to be elucidated. Moreover, the expected efficacy of some AR inhibitors in patients with DPN has been unsatisfactory, which prompted us to further investigate and review the understanding of the physiological and pathological roles of AR in the PNS. Particularly, the investigation of AR and the polyol pathway using immortalized Schwann cells established from normal and AR-deficient mice could shed light on the causal relationship between the metabolic abnormalities of Schwann cells and discordance of axon-Schwann cell interplay in DPN, and led to the development of better therapeutic strategies against DPN.

S-allylmercaptocysteine improves nonalcoholic steatohepatitis by enhancing AHR/NRF2-mediated drug metabolising enzymes and reducing NF-κB/IκBα and NLRP3/6-mediated inflammation

PURPOSE

To investigate the novel molecular mechanisms of the antioxidant and anti-inflammatory properties of S-allylmercaptocysteine (SAMC) based on a transcriptomic study in a nonalcoholic steatohepatitis (NASH) rat model METHODS: NASH was induced in Sprague-Dawley rats by feeding with a high fat diet (HFD) for 12 weeks. 200 mg/kg SAMC was fed by oral gavage for 4 weeks from 9 to 12 week.

RESULTS

SAMC co-administration attenuated HFD-induced liver injury, including the increased serum ALT, hepatic oxidative stress and inflammation. Transcriptomic analysis revealed that SAMC dramatically induced the XRE- and ARE-driven drug metabolising enzymes (DMEs) including Akr7a3, Akr1b8, and Nqo1. The nuclear translocation of the upstream regulator of xenobiotics metabolism, AHR, and regulator of antioxidant responses, NRF2, were significantly increased by SAMC treatment. Furthermore, SAMC counteracted the effects of HFD on NF-κB/IκB and NLRP3/6 pathways with decreasing protein levels of ASC, cleaved caspase-1, IL-18, and IL-1β. These results were further verified in another mice NASH model induced by an MCD diet with SAMC co-administration.

CONCLUSION

We propose that SAMC triggers AHR/NRF2-mediated antioxidant responses which may further suppress the NLRP3/6 inflammasome pathway and NF-κB activation, contributing to the improvement of NASH.

Tolrestat acts atypically as a competitive inhibitor of the thermostable aldo-keto reductase Tm1743 from Thermotoga maritima

Tolrestat and epalrestat have been characterized as noncompetitive inhibitors of aldo-ketone reductase 1B1 (AKR1B1), a leading drug target for the treatment of type 2 diabetes complications. However, clinical applications are limited for most AKR1B1 inhibitors due to adverse effects of cross-inhibition with other AKRs. Here, we report an atypical competitive binding and inhibitory effect of tolrestat on the thermostable AKR Tm1743 from Thermotoga maritima. Analysis of the Tm1743 crystal structure in complex with tolrestat alone and epalrestat-NADP⁺ shows that tolrestat, but not epalrestat, binding triggers dramatic conformational changes in the anionic site and cofactor binding pocket that prevents accommodation of NADP⁺ . Enzymatic and molecular dynamics simulation analyses further confirm tolrestat as a competitive inhibitor of Tm1743.

Isolation and Identification of Lactic Acid Bacteria Probiotic Culture Candidates for the Treatment of Salmonella enterica Serovar Enteritidis in Neonatal Turkey Poults

The effect of Lactobacillus spp.-based probiotic candidates on Salmonella enterica serovar Enteritidis (SE) colonization was evaluated in two separate experiments. In each experiment, sixty-one day-of-hatch female turkey poults were obtained from a local hatchery. In both experiments, poults were challenged via oral gavage with 10⁴ cfu/poult of SE and randomly allocated to one of two groups (n = 30 poults): (1) the positive control group and (2) the probiotic treated group. Heated brooder batteries were used for housing each group separately and poults were allowed ad libitum access to water and unmedicated turkey starter feed. 1 h following the SE challenge, poults were treated with 10⁶ cfu/poult of probiotic culture via oral gavage or phosphate-buffered saline （PBS）to control groups. A total of 24 h post-treatment, poults were euthanized and the ceca and cecal tonsils from twenty poults were collected aseptically for SE recovery. In both trials, a significant reduction in the incidence and log₁₀ cfu/g of SE were observed in poults treated with the probiotic when compared with control poults (p ≤ 0.05). The results of the present study suggest that the administration of this lactic acid-producing bacteria (LAB)-based probiotic 1 h after an SE challenge can be useful in reducing the cecal colonization of this pathogen in neonatal poults.

Cyclooxygenase-2 is acutely induced by CCAAT/enhancer-binding protein β to produce prostaglandin E 2 and F 2α following gonadotropin stimulation in Leydig cells

Cyclooxygenase 2 (COX-2) is an inducible rate-limiting enzyme for prostanoid production. Because COX-2 represents one of the inducible genes in mouse mesenchymal stem cells upon differentiation into Leydig cells, we investigated COX-2 expression and production of prostaglandin (PG) in Leydig cells. Although COX-2 was undetectable in mouse testis, it was transiently induced in Leydig cells by human chorionic gonadotropin (hCG) administration. Consistent with the finding that Leydig cells expressed aldo-keto reductase 1B7 (PGF synthase) and PGE synthase 2, induction of COX-2 by hCG caused a marked increase in testicular PGF _2α and PGE ₂ levels. Using mouse Leydig cell tumor-derived MA-10 cells as a model, it was indicated by reporter assays and electron mobility shift assays that transcription of the COX-2 gene was activated by CCAAT/enhancer-binding protein β (C/EBPβ) with cAMP-stimulation. C/EBPβ expression was induced by cAMP-stimulation, whereas expression of C/EBP homolog protein (CHOP) was robustly downregulated. Transfection of CHOP expression plasmid inhibited cAMP-induced COX-2 promoter activity. In addition, CHOP reduced constitutive COX-2 expression in other mouse Leydig cell tumor-derived TM3 cells. These results indicate that COX-2 is induced in Leydig cells by activation of C/EBPβ via reduction of CHOP expression upon gonadotropin-stimulation to produce PGF _2α and PGE ₂ .

Structural variation during dog domestication: insights from gray wolf and dhole genomes

Several processes like phenotypic evolution, disease susceptibility and environmental adaptations, which fashion the domestication of animals, are largely attributable to structural variations (SVs) in the genome. Here, we present high-quality draft genomes of the gray wolf (Canis lupus) and dhole (Cuon alpinus) with scaffold N50 of 6.04 Mb and 3.96 Mb, respectively. Sequence alignment comprising genomes of three canid species reveals SVs specific to the dog, particularly 16 315 insertions, 2565 deletions, 443 repeats, 16 inversions and 15 translocations. Functional annotation of the dog SVs associated with genes indicates their enrichments in energy metabolisms, neurological processes and immune systems. Interestingly, we identify and verify at population level an insertion fully covering a copy of the AKR1B1 (Aldo-Keto Reductase Family 1 Member B) transcript. Transcriptome analysis reveals a high level of expression of the new AKR1B1 copy in the small intestine and liver, implying an increase in de novo fatty acid synthesis and antioxidant ability in dog compared to gray wolf, likely in response to dietary shifts during the agricultural revolution. For the first time, we report a comprehensive analysis of the evolutionary dynamics of SVs during the domestication step of dogs. Our findings demonstrate that retroposition can birth new genes to facilitate domestication, and affirm the importance of large-scale genomic variants in domestication studies.

Assessment of zero-valent iron-based nanotherapeutics for ferroptosis induction and resensitization strategy in cancer cells

Addressing nanomedicine resistance is critical for its ultimate clinical success; despite this, advancing the therapeutic designs for cancer therapy are rarely discussed in the literature.

Altered hepatic genes related to retinol metabolism and plasma retinol in patients with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD), especially non-alcoholic steatohepatitis (NASH) is a chronic liver disease commonly associated with hepatic fibrosis. NASH patients have an increased risk for hepatocellular carcinoma (HCC). An altered retinol metabolism is one of the pathways involved in the process of hepatic fibrosis, and enzymes involved in retinol metabolism have been associated with HCC. We aimed to determine the association between plasma retinol levels and hepatic expression of genes related to retinol metabolism, as well as to assess the hepatic expression of transcription factors regulated by retinoic acid in patients with NAFLD. Cross-sectional study where hepatic gene expression (Illumina microarray) and plasma retinol levels (HPLC) were measured in 17 patients with simple steatosis (SS), 15 with NASH, and 22 living liver donors (LD) as controls. Plasma retinol levels were higher in SS (1.53 ± 0.44 μmol/L) and NASH (1.51 ± 0.56 μmol/L) compared to LD (1.21 ± 0.38 μmol/L; p<0.05). AKR1B10 was highly overexpressed in NASH compared to SS (+6.2-fold) and LD (+9.9-fold; p = 4.89E-11). Retinaldehyde dehydrogenase 1 family, member A2 (ALDH1A2) and retinaldehyde dehydrogenase 1 family, member A3 (ALDH1A3), key enzymes for retinoic acid synthesis, were underexpressed in SS (-1.48 and -2.3-fold, respectively) and NASH (-1.47 and -2.6-fold, respectively) versus LD. In NASH, hepatic ALDH1A2 and ALDH1A3 were underexpressed and inversely correlated with plasma retinol levels, which may reduce retinoic acid in the liver. This, in addition to changes in expression of other genes involved in retinol metabolism, suggests a role for altered retinol homeostasis in NASH.

STAR and AKR1B10 are down-regulated in high-grade endometrial cancer

Endometrial cancer is the most frequent gynecological malignancy in the developed world. The majority of cases are estrogen dependent, and are associated with diminished protective effects of progesterone. Endometrial cancer is also related to enhanced inflammation and decreased differentiation. In our previous studies, we examined the expression of genes involved in estrogen and progesterone actions in inflammation and tumor differentiation, in tissue samples from endometrial cancer and adjacent control endometrium. The aims of the current study were to examine correlations between gene expression and several demographic characteristics, and to evaluate changes in gene expression with regard to histopathological and clinical characteristics of 51 patients. We studied correlations and differences in expression of 38 genes involved in five pathophysiological processes: (i) estrogen-stimulated proliferation; (ii) estrogen-dependent carcinogenesis; (iii) diminished biosynthesis of progesterone: (iv) enhanced formation of progesterone metabolites; and (v) increased inflammation and decreased differentiation. Spearman correlation coefficient analysis shows that expression of PAQR7 correlates with age, expression of SRD5A1, AKR1B1 and AKR1B10 correlate with body mass, while expression of SRD5A1 and AKR1B10 correlate with body mass index. When patients with endometrial cancer were stratified based on menopausal status, histological grade, myometrial invasion, lymphovascular invasion, and FIGO stage, Mann-Whitney U tests revealed significantly decreased expression of STAR (4.4-fold; adjusted p=0.009) and AKR1B10 (9-fold; adjusted p=0.003) in high grade versus low grade tumors. Lower levels of STAR might lead to decreased de-novo steroid hormone synthesis and tumor differentiation, and lower levels of AKR1B10 to diminished elimination of toxic electrophilic carbonyl compounds in high-grade endometrial cancer. These data thus reveal the potential of STAR and AKR1B10 as prognostic biomarkers, which calls for further validation at the protein level.

The Human Adrenal Gland Proteome Defined by Transcriptomics and Antibody-Based Profiling

The adrenal gland is a composite endocrine organ with vital functions that include the synthesis and release of glucocorticoids and catecholamines. To define the molecular landscape that underlies the specific functions of the adrenal gland, we combined a genome-wide transcriptomics approach using messenger RNA sequencing of human tissues with immunohistochemistry-based protein profiling on tissue microarrays. Approximately two-thirds of all putative protein coding genes were expressed in the adrenal gland, and the analysis identified 253 genes with an elevated pattern of expression in the adrenal gland, with only 37 genes showing a markedly greater expression level (more than fivefold) in the adrenal gland compared with 31 other normal human tissue types analyzed. The analyses allowed for an assessment of the relative expression levels for well-known proteins involved in adrenal gland function but also identified previously poorly characterized proteins in the adrenal cortex, such as the FERM (4.1 protein, ezrin, radixin, moesin) domain containing 5 and the nephroblastoma overexpressed (NOV) protein homolog. We have provided a global analysis of the adrenal gland transcriptome and proteome, with a comprehensive list of genes with elevated expression in the adrenal gland and spatial information with examples of protein expression patterns for corresponding proteins. These genes and proteins constitute important starting points for an improved understanding of the normal function and pathophysiology of the adrenal glands.

Evaluation of a selected lactic acid bacteria-based probiotic on Salmonella enterica serovar Enteritidis colonization and intestinal permeability in broiler chickens

Two experiments were conducted to evaluate the effect of a lactic acid bacteria-based probiotic (FloraMax-B11^®) against Salmonella enterica serovar Enteritidis intestinal colonization and intestinal permeability in broiler chickens. Experiment 1 consisted of two independent trials. In each trial, day-old broiler chicks were assigned to one of two groups: control + S. Enteritidis or probiotic + S. Enteritidis. At 72 h post-S. Enteritidis challenge, haematology and caecal content were evaluated for S. Enteritidis colonization. In Experiment 2, day-old broiler chicks were assigned to one of four groups: negative control; probiotic; control + S. Enteritidis; or probiotic + S. Enteritidis. At 72 h post-S. Enteritidis challenge, chickens in all groups were given an oral gavage dose of fluorescein isothiocyanate dextran (FITC-d). In both trials of Experiment 1, a significant reduction (P < 0.05) in colony-forming units/gram of S. Enteritidis in caecal content and a reduction in the incidence of S. Enteritidis enriched caecal samples were observed in probiotic + S. Enteritidis chickens. In addition, significant heterophilia and lymphopaenia were observed in control + S. Enteritidis chickens. In Experiment 2, a decrease in numbers of S. Enteritidis in caeca were observed in probiotic + S. Enteritidis chickens when compared to control + S. Enteritidis. Also, an increase in serum FITC-d concentration was detected in control + S. Enteritidis. These results suggest that early infection with S. Enteritidis can increase intestinal permeability, but the adverse effects can be prevented by the administration of the probiotic tested.

60 YEARS OF POMC: Adrenal and extra-adrenal functions of ACTH

The pituitary adrenocorticotropic hormone (ACTH) plays a pivotal role in homeostasis and stress response and is thus the major component of the hypothalamo-pituitary-adrenal axis. After a brief summary of ACTH production from proopiomelanocortin (POMC) and on ACTH receptor properties, the first part of the review covers the role of ACTH in steroidogenesis and steroid secretion. We highlight the mechanisms explaining the differential acute vs chronic effects of ACTH on aldosterone and glucocorticoid secretion. The second part summarizes the effects of ACTH on adrenal growth, addressing its role as either a mitogenic or a differentiating factor. We then review the mechanisms involved in steroid secretion, from the classical Cyclic adenosine monophosphate second messenger system to various signaling cascades. We also consider how the interaction between the extracellular matrix and the cytoskeleton may trigger activation of signaling platforms potentially stimulating or repressing the steroidogenic potency of ACTH. Finally, we consider the extra-adrenal actions of ACTH, in particular its role in differentiation in a variety of cell types, in addition to its known lipolytic effects on adipocytes. In each section, we endeavor to correlate basic mechanisms of ACTH function with the pathological consequences of ACTH signaling deficiency and of overproduction of ACTH.

Global gene expression profiling using heterologous DNA microarrays to analyze alterations in the transcriptome of Mus spretus mice living in a heavily polluted environment

Microarray platforms are a good approach for assessing biological responses to pollution as they enable the simultaneous analyses of changes in the expression of thousands of genes. As an omic and non-targeted methodology, this technique is open to unforeseen responses under particular environmental conditions. In this study, we successfully apply a commercial oligonucleotide microarray containing Mus musculus whole-genome probes to compare and assess the biological effects of living in a heavily polluted settlement, the Domingo Rubio stream (DRS), at the Huelva Estuary (SW Spain), on inhabitant free-living Mus spretus mice. Our microarray results show that mice living in DRS suffer dramatic changes in gene and protein expression compared with reference specimens. DRS mice showed alteration in the oxidative status of hepatocytes, with activation of both the innate and the acquired immune responses and the induction of chronic inflammation, accompanied by metabolic alterations that imply the accumulation of lipids in the liver (hepatic steatosis). The identified deregulated genes may be useful as biomarkers of environmental pollution.

Aldo-Keto Reductases 1B in Adrenal Cortex Physiology

Aldose reductase (AKR1B) proteins are monomeric enzymes, belonging to the aldo-keto reductase (AKR) superfamily. They perform oxidoreduction of carbonyl groups from a wide variety of substrates, such as aliphatic and aromatic aldehydes or ketones. Due to the involvement of human aldose reductases in pathologies, such as diabetic complications and cancer, AKR1B subgroup enzymatic properties have been extensively characterized. However, the issue of AKR1B function in non-pathologic conditions remains poorly resolved. Adrenal activities generated large amount of harmful aldehydes from lipid peroxidation and steroidogenesis, including 4-hydroxynonenal (4-HNE) and isocaproaldehyde (4-methylpentanal), which can both be reduced by AKR1B proteins. More recently, some AKR1B isoforms have been shown to be endowed with prostaglandin F synthase (PGFS) activity, suggesting that, in addition to possible scavenger function, they could instigate paracrine signals. Interestingly, the adrenal gland is one of the major sites for human and murine AKR1B expression, suggesting that their detoxifying/signaling activity could be specifically required for the correct handling of adrenal function. Moreover, chronic effects of ACTH result in a coordinated regulation of genes encoding the steroidogenic enzymes and some AKR1B isoforms. This review presents the molecular mechanisms accounting for the adrenal-specific expression of some AKR1B genes. Using data from recent mouse genetic models, we will try to connect their enzymatic properties and regulation with adrenal functions.

Substrate Specificity, Inhibitor Selectivity and Structure-Function Relationships of Aldo-Keto Reductase 1B15: A Novel Human Retinaldehyde Reductase

Human aldo-keto reductase 1B15 (AKR1B15) is a newly discovered enzyme which shares 92% amino acid sequence identity with AKR1B10. While AKR1B10 is a well characterized enzyme with high retinaldehyde reductase activity, involved in the development of several cancer types, the enzymatic activity and physiological role of AKR1B15 are still poorly known. Here, the purified recombinant enzyme has been subjected to substrate specificity characterization, kinetic analysis and inhibitor screening, combined with structural modeling. AKR1B15 is active towards a variety of carbonyl substrates, including retinoids, with lower kcat and Km values than AKR1B10. In contrast to AKR1B10, which strongly prefers all-trans-retinaldehyde, AKR1B15 exhibits superior catalytic efficiency with 9-cis-retinaldehyde, the best substrate found for this enzyme. With ketone and dicarbonyl substrates, AKR1B15 also shows higher catalytic activity than AKR1B10. Several typical AKR inhibitors do not significantly affect AKR1B15 activity. Amino acid substitutions clustered in loops A and C result in a smaller, more hydrophobic and more rigid active site in AKR1B15 compared with the AKR1B10 pocket, consistent with distinct substrate specificity and narrower inhibitor selectivity for AKR1B15.

Metabolomics reveals that aldose reductase activity due to AKR1B10 is upregulated in hepatitis C virus infection

To understand the changes in the metabolome of hepatitis C virus (HCV)-infected persons, we conducted a metabolomic investigation in both plasma and urine of 30 HCV-positive individuals using plasmas from 30 HCV-negative blood donors and urines from 30 healthy volunteers. Samples were analysed by gas chromatography-mass spectrometry and data subjected to multivariate analysis. The plasma metabolomic phenotype of HCV-positive persons was found to have elevated glucose, mannose and oleamide, together with depressed plasma lactate. The urinary metabolomic phenotype of HCV-positive persons comprised reduced excretion of fructose and galactose combined with elevated urinary excretion of 6-deoxygalactose (fucose) and the polyols sorbitol, galactitol and xylitol. HCV-infected persons had elevated galactitol/galactose and sorbitol/glucose urinary ratios, which were highly correlated. These observations pointed to enhanced aldose reductase activity, and this was confirmed by real-time quantitative polymerase chain reaction with AKR1B10 gene expression elevated sixfold in the liver. In contrast, AKR1B1 gene expression was reduced 40% in HCV-positive livers. Interestingly, persons who were formerly HCV infected retained the metabolomic phenotype of HCV infection without reverting to the HCV-negative metabolomic phenotype. This suggests that the effects of HCV on hepatic metabolism may be long lived. Hepatic AKR1B10 has been reported to be elevated in hepatocellular carcinoma and in several premalignant liver diseases. It would appear that HCV infection alone increases AKR1B10 expression, which manifests itself as enhanced urinary excretion of polyols with reduced urinary excretion of their corresponding hexoses. What role the polyols play in hepatic pathophysiology of HCV infection and its sequelae is currently unknown.

Aldose reductases influence prostaglandin F2α levels and adipocyte differentiation in male mouse and human species

Aldose reductases (AKR1B) are widely expressed oxidoreductases whose physiological function remains elusive. Some isoforms are genuine prostaglandin F2α (PGF2α) synthases, suggesting they might influence adipose homeostasis because PGF2α inhibits adipogenesis. This was shown by Akr1b7 gene ablation in the mouse, which resulted in increased adiposity related to a lower PGF2α content in fat. Yet humans have no ortholog gene for Akr1b7, so the role of aldose reductases in human adipose homeostasis remains to be explored. We analyzed expression of genes encoding human and mouse aldose reductase isoforms in adipose tissues and differentiating adipocytes to assess conserved mechanisms regulating PGF2α synthesis and adipogenesis. The Akr1b3 gene encoded the most abundant isoform in mouse adipose tissue, whereas Akr1b7 encoded the only isoform enriched in the stromal vascular fraction. Most mouse aldose reductase gene expression peaked in early adipogenesis of 3T3-L1 cells and diminished with differentiation. In contrast with its mouse ortholog Akr1b3, AKR1B1 expression increased throughout differentiation of human multipotent adipose-derived stem cells, paralleling PGF2α release, whereas PGF2α receptor (FP) levels collapsed in early differentiation. Pharmacological inhibition of aldose reductase using Statil altered PGF2α production and enhanced human multipotent adipose-derived stem adipocyte differentiation. As expected, the adipogenic effects of Statil were counteracted by an FP agonist (cloprostenol). Thus, in both species aldose reductase-dependent PGF2α production could be important in early differentiation to restrict adipogenesis. PGF2α antiadipogenic signaling could then be toned down through the FP receptor or aldose reductases down-regulation in human and mouse cells, respectively. Our data suggest that aldose reductase inhibitors could have obesogenic potential.

Genetic variants in AKR1B10 associate with human eating behavior

BACKGROUND

The human Aldoketoreductase 1B10 gene (AKR1B10) encodes one of the enzymes belonging to the family of aldoketoreductases and may be involved in detoxification of nutrients during digestion. Further, AKR1B10 mRNA (messenger ribonucleic acid) expression was diminished in brain regions potentially involved in the regulation of eating behavior in rats which are more sensitive to cocaine and alcohol. We hypothesized that the human AKR1B10 gene may also play a role in the regulation of human eating behavior.

RESULTS

We investigated the effects of 5 genetic variants of AKR1B10 on human eating behavior among 548 subjects from a German self-contained population, the Sorbs, and in 350 subjects from another independent German cohort. Among the Sorbs, we observed nominal associations with disinhibition at the 5' untranslated region (5' UTR) variant rs10232478 and the intragenic variants rs1834150 and rs782881 (all P ≤ 0.05). Further, we detected a relationship of rs1834150 and rs782881 with waist, smoking consumption (rs782881) and coffee consumption (rs1834150) (all P ≤ 0.05). Albeit non-significant, replication analyses revealed similar effect directions for disinhibition at rs1834150 (combined P = 0.0096). Moreover, in the replication cohort we found rs1834150 related to increased restraint scores with a similar direction as in the Sorbs (combined P = 0.0072).

CONCLUSION

Our data suggest that genetic variants in the AKR1B10 locus may influence human eating behavior.

Steroidogenesis-adrenal cell signal transduction

The purpose of this article is to review fundamentals in adrenal gland histophysiology. Key findings regarding the important signaling pathways involved in the regulation of steroidogenesis and adrenal growth are summarized. We illustrate how adrenal gland morphology and function are deeply interconnected in which novel signaling pathways (Wnt, Sonic hedgehog, Notch, β-catenin) or ionic channels are required for their integrity. Emphasis is given to exploring the mechanisms and challenges underlying the regulation of proliferation, growth, and functionality. Also addressed is the fact that while it is now well-accepted that steroidogenesis results from an enzymatic shuttle between mitochondria and endoplasmic reticulum, key questions still remain on the various aspects related to cellular uptake and delivery of free cholesterol. The significant progress achieved over the past decade regarding the precise molecular mechanisms by which the two main regulators of adrenal cortex, adrenocorticotropin hormone (ACTH) and angiotensin II act on their receptors is reviewed, including structure-activity relationships and their potential applications. Particular attention has been given to crucial second messengers and how various kinases, phosphatases, and cytoskeleton-associated proteins interact to ensure homeostasis and/or meet physiological demands. References to animal studies are also made in an attempt to unravel associated clinical conditions. Many of the aspects addressed in this article still represent a challenge for future studies, their outcome aimed at providing evidence that the adrenal gland, through its steroid hormones, occupies a central position in many situations where homeostasis is disrupted, thus highlighting the relevance of exploring and understanding how this key organ is regulated. © 2014 American Physiological Society. Compr Physiol 4:889-964, 2014.

Oxidative and reductive metabolism of lipid-peroxidation derived carbonyls

Extensive research has shown that increased production of reactive oxygen species (ROS) results in tissue injury under a variety of pathological conditions and chronic degenerative diseases. While ROS are highly reactive and can incite significant injury, polyunsaturated lipids in membranes and lipoproteins are their main targets. ROS-triggered lipid-peroxidation reactions generate a range of reactive carbonyl species (RCS), and these RCS spread and amplify ROS-related injury. Several RCS generated in oxidizing lipids, such as 4-hydroxy trans-2-nonenal (HNE), 4-oxo-2-(E)-nonenal (ONE), acrolein, malondialdehyde (MDA) and phospholipid aldehydes have been shown to be produced under conditions of oxidative stress and contribute to tissue injury and dysfunction by depleting glutathione and other reductants leading to the modification of proteins, lipids, and DNA. To prevent tissue injury, these RCS are metabolized by several oxidoreductases, including members of the aldo-keto reductase (AKR) superfamily, aldehyde dehydrogenases (ALDHs), and alcohol dehydrogenases (ADHs). Metabolism via these enzymes results in RCS inactivation and detoxification, although under some conditions, it can also lead to the generation of signaling molecules that trigger adaptive responses. Metabolic transformation and detoxification of RCS by oxidoreductases prevent indiscriminate ROS toxicity, while at the same time, preserving ROS signaling. A better understanding of RCS metabolism by oxidoreductases could lead to the development of novel therapeutic interventions to decrease oxidative injury in several disease states and to enhance resistance to ROS-induced toxicity.

New gene targets of PGC-1α and ERRα co-regulation in C2C12 myotubes

As a transcriptional coactivator, PGC-1α contributes to the regulation of a broad range of metabolic processes in skeletal muscle health and disease; however, there is limited information about the genes it transcriptionally regulates. To identify new potential gene targets of PGC-1α regulation, mouse C2C12 myotubes were screened by microarray analysis following PGC-1α overexpression. Genes with an mRNA expression of 2.5-fold or more (P < 0.001) were identified. From these, further genes were singled out if they had no previous connection to PGC-1α regulation or characterization in skeletal muscle, or were unannotated with no known function. Following confirmation of their regulation by PGC-1α using qPCR analysis, eight genes were focused on for further investigation (Akr1b10, Rmnd1, 1110008P14Rik, 1700021F05Rik, Mtfp1, Mrm1, Oxnad1 and Cluh). Bioinformatics indicated a number of the genes were linked to a range of metabolic-related functions including fatty acid oxidation, oxido-reductase activity, and mitochondrial remodeling and transport. Treating C2C12 myotubes for 6 h with AICAR, a known activator of AMP kinase and inducer of Pgc-1α gene expression, increased the mRNA levels of both Pgc-1α (P < 0.001) and of Mtfp1, Mrm1, Oxnad1 and Cluh (P < 0.05). Screening of the promoter and intron 1 regions also revealed all genes to contain either a consensus or near consensus response elements for the estrogen-related receptor α (ERRα), a key transcription factor-binding partner of PGC-1α in skeletal muscle. Furthermore, knockdown of endogenous ERRα levels partially or completely blocked the induction of gene expression of all genes by PGC-1α, while each gene was significantly upregulated in the presence of a constitutively active form of ERRα (P < 0.05) except for Akr1b10. These findings provide preliminary evidence for the novel regulation of these genes by PGC-1α and its signaling pathway in skeletal muscle.

Generation of human endometrial knockout cell lines with the CRISPR/Cas9 system confirms the prostaglandin F2α synthase activity of aldo-ketoreductase 1B1

Prostaglandins (PGs) are important regulators of female reproductive function. The primary PGs produced in the endometrium are PGE2 and PGF2α. Relatively little is known about the biosynthetic pathways leading to the formation of PGF2α. We have described the role of aldo-ketoreductase (AKR)1B1 in increased PGF2α production by human endometrial cells following stimulation with interleukin-1β (IL-1β). However, alternate PGF synthases are expressed concurrently in endometrial cells. A definite proof of the role of AKR1B1 would require gene knockout; unfortunately, this gene has no direct equivalent in the mouse. Recently, an efficient genome-editing technology using RNA-guided DNase Cas9 and the clustered regularly interspaced short palindromic repeats (CRISPR) system has been developed. We have adapted this approach to knockout AKR1B1 gene expression in human endometrial cell lines. One clone (16-2) of stromal origin generated by the CRISPR/Cas9 system exhibited a complete loss of AKR1B1 protein and mRNA expression, whereas other clones presented with partial edition. The present report focuses on the characterization of clone 16-2 exhibiting deletion of 68 and 2 nucleotides, respectively, on each of the alleles. Cells from this clone lost their ability to produce PGF2α but maintained their original stromal cell (human endometrial stromal cells-2) phenotype including the capacity to decidualize in the presence of progesterone (medroxyprogesterone acetate) and 8-bromo-cAMP. Knockout cells also maintained their ability to increase PGE2 production in response to IL-1β. In summary, we demonstrate that the new genome editing CRISPR/Cas9 system can be used in human cells to generate stable knockout cell line models. Our results suggest that genome editing of human cell lines can be used to complement mouse KO models to validate the function of genes in differentiated tissues and cells. Our results also confirm that AKR1B1 is involved in the synthesis of PGF2α.

Heterologous microarray analysis of transcriptome alterations in Mus spretus mice living in an industrial settlement

This work demonstrates the successful application of a commercial oligonucleotide microarray containing Mus musculus whole-genome probes to assess the biological effects of an industrial settlement on inhabitant Mus spretus mice. The transcriptomes of animals in the industrial settlement contrasted with those of specimens collected from a nearby protected ecosystem. Proteins encoded by the differentially expressed genes were broadly categorized into six main functional classes. Immune-associated genes were mostly induced and related to innate and acquired immunity and inflammation. Genes sorted into the stress-response category were mainly related to oxidative-stress tolerance and biotransformation. Metabolism-associated genes were mostly repressed and related to lipid metabolic pathways; these included genes that encoded 11 of the 20 cholesterol biosynthetic pathway enzymes. Crosstalk between members of different functional categories was also revealed, including the repression of serine-protease genes and the induction of protease-inhibitor genes to control the inflammatory response. Absolute quantification of selected transcripts was performed via RT-PCR to verify the microarray results and assess interindividual variability. Microarray data were further validated by immunoblotting and by cholesterol and protein-thiol oxidation level determinations. Reported data provide a broad impression of the biological consequences of residing in an industrial area.

Structural basis for the inhibition of AKR1B10 by caffeic acid phenethyl ester (CAPE)

Caffeic acid phenethyl ester (CAPE), the major bioactive component of honeybee propolis, is a potent selective inhibitor of aldo-keto reductase family member 1B10 (AKR1B10), and a number of derivatives hold promise as potential anticancer agents. However, sequence homology between AKR1B10 and other members of the superfamily, including critical phase I metabolizing enzymes, has resulted in a concern over the selectivity of any potential therapeutic agent. To elucidate the binding mode of CAPE with AKR1B10 and to provide a tool for future in silico efforts towards identifying selective inhibitors, the crystal structure of AKR1B10 in complex with CAPE was determined. The observed interactions provide an explanation for the selectivity exhibited by CAPE for AKR1B10, and could be used to guide further derivative design.