Novel role for epalrestat: protecting against NLRP3 inflammasome-driven NASH by targeting aldose reductase.

BACKGROUND: Nonalcoholic steatohepatitis (NASH) is a progressive and inflammatory subtype of nonalcoholic fatty liver disease (NAFLD) characterized by hepatocellular injury, inflammation, and fibrosis in various stages. More than 20% of patients with NASH will progress to cirrhosis. Currently, there is a lack of clinically effective drugs for treating NASH, as improving liver histology in NASH is difficult to achieve and maintain through weight loss alone. Hence, the present study aimed to investigate potential therapeutic drugs for NASH. METHODS: BMDMs and THP1 cells were used to construct an inflammasome activation model, and then we evaluated the effect of epalrestat on the NLRP3 inflammasome activation. Western blot, real-time qPCR, flow cytometry, and ELISA were used to evaluate the mechanism of epalrestat on NLRP3 inflammasome activation. Next, MCD-induced NASH models were used to evaluate the therapeutic effects of epalrestat in vivo. In addition, to evaluate the safety of epalrestat in vivo, mice were gavaged with epalrestat daily for 14 days. RESULTS: Epalrestat, a clinically effective and safe drug, inhibits NLRP3 inflammasome activation by acting upstream of caspase-1 and inducing ASC oligomerization. Importantly, epalrestat exerts its inhibitory effect on NLRP3 inflammasome activation by inhibiting the activation of aldose reductase. Further investigation revealed that the administration of epalrestat inhibited NLRP3 inflammasome activation in vivo, alleviating liver inflammation and improving NASH pathology. CONCLUSIONS: Our study indicated that epalrestat, an aldose reductase inhibitor, effectively suppressed NLRP3 inflammasome activation in vivo and in vitro and might be a new therapeutic approach for NASH.

Rationale and design of the Aldose Reductase Inhibition for Stabilization of Exercise Capacity in Heart Failure Trial (ARISE-HF) in patients with high-risk diabetic cardiomyopathy.

BACKGROUND: Diabetic cardiomyopathy (DbCM) is a specific form of heart muscle disease that may result in substantial morbidity and mortality in individuals with type 2 diabetes mellitus (T2DM). Hyperactivation of the polyol pathway is one of the primary mechanisms in the pathogenesis of diabetic complications, including development of DbCM. There is an unmet need for therapies targeting the underlying metabolic abnormalities that drive this form of Stage B heart failure (HF). METHODS: Aldose reductase (AR) catalyzes the first and rate-limiting step in the polyol pathway, and AR inhibition has been shown to reduce diabetic complications, including DbCM in animal models and in patients with DbCM. Previous AR inhibitors (ARIs) were limited by poor specificity resulting in unacceptable tolerability and safety profile. AT-001 is a novel investigational highly specific ARI with higher binding affinity and greater selectivity than previously studied ARIs. ARISE-HF (NCT04083339) is an ongoing Phase 3 randomized, placebo-controlled, double blind, global clinical study to investigate the efficacy of AT-001 (1000 mg twice daily [BID] and 1500 mg BID) in 675 T2DM patients with DbCM at high risk of progression to overt HF. ARISE-HF assesses the ability of AT-001 to improve or prevent decline in exercise capacity as measured by functional capacity (changes in peak oxygen uptake [peak VO2]) over 15 (and possibly 27) months of treatment. Additional endpoints include percentage of patients progressing to overt HF, health status metrics, echocardiographic measurements, and changes in cardiacbiomarkers. RESULTS: The ARISE-HF Trial is fully enrolled. CONCLUSIONS: This report describes the rationale and study design of ARISE-HF.

Comparative Evaluation of Aldose Reductase Inhibition in Polycystic Ovarian Syndrome-Induced Rats.

Polycystic ovary syndrome (PCOS) represents a spectrum of disorders, associated with hyperandrogenism, oligoanovulation, and polycystic ovaries. Aldose reductase (AR), a rate-limiting enzyme of polyol pathway, is responsible for maintenance of intracellular osmotic balance, facilitation of oocyte development, and organization of the granulosa cells in the ovary. Cyclic changes in the aldose reductase level were found during the 4-5 days estrus cycle in rat, which is regulated by gonadotropin-releasing hormone (GnRH). Irregular GnRH secretion in PCOS patients may lead to altered aldose reductase expression and ovarian dysfunction. Treatment with a novel AR inhibitor, fidarestat, has been reported to improve erythrocyte sorbitol content in diabetic patients. Hence, the potential role AR in pathogenesis of PCOS was investigated by inhibiting AR with fidarestat in PCOS-induced rats. Pre-pubertal female Sprague-Dawley rats were divided into five groups. PCOS is induced either by administering letrozole or by feeding high-fat diet for 90 days. After induction of PCOS, fidarestat treatment was given for 28 days and various parameters were measured. In PCOS-induced rats, parameters like food intake, body weight, insulin, OGTT, triglycerides, cholesterol, prolonged diestrus phase, ovary weight, and immunohistological localization AR were found to be significantly altered. Fidarestat treatment significantly improved ovary weight, ovarian aldose reductase localization in PCOS-induced rats. Improvement in all these parameters suggest involvement of aldose reductase in the pathogenesis of PCOS.

Effect of the combined probiotics with aflatoxin B1-degrading enzyme on aflatoxin detoxification, broiler production performance and hepatic enzyme gene expression.

In order to degrade aflatoxin B1 (AFB1), AFB1-degrading microbes (probiotics) such as Lactobacillus casei, Bacillus subtilis and Pichia anomala, and the AFB1-degrading enzyme from Aspergillus oryzae were selected and combined to make feed additive. Seventy-five 43-day-old male Arbor Acres broilers were randomly divided into 5 groups, 15 broilers for each group. The broilers were given with 5 kinds of diets such as the basal diet, 400 µg/kg AFB1 supplement without feed additive, and 200, 400, 800 µg/kg AFB1 supplement with 0.15% feed additive. The feeding experimental period was 30 d, which was used to determine production performance of broilers. In addition, serum, liver and chest muscle were selected for measuring AFB1 residues, gene expressions, microscopic and antioxidant analyses. The results showed that adding 0.15% feed additive in broiler diets could significantly relieve the negative effect of AFB1 on chicken's production performance and nutrient metabolic rates (P<0.05). It could also improve AFB1 metabolism, hepatic cell structure, antioxidant activity, and many hepatic enzyme gene expressions involved in oxidoreductase, apoptosis, cell growth, immune system and metabolic process (P<0.05). It could be concluded that the feed additive was able to degrade AFB1 and improve animal production.

Aldose reductase inhibitors and diabetic kidney disease.

Diabetic kidney disease, or diabetic nephropathy, is the leading cause of kidney failure in developed countries and is projected to place an increasingly heavy burden on medical, social and economic systems worldwide. Existing therapies can slow, but do not stop, disease progression. Recent data from preclinical models and patients with diabetes emphasize the need for reducing excess metabolic flux through aldose reductase, an enzyme that plays a critical role in transducing the metabolic abnormalities that cause fibrosis in the diabetic kidney. The background and developmental history of aldose reductase inhibitors are reviewed briefly, as are metabolic, hemodynamic and genetic data linking aldose reductase to diabetic kidney disease. A new paradigm defining the pathogenic role of aldose reductase, the 'metabolic flux hypothesis', is presented, along with updated pharmacological goals for achieving success with this class of inhibitors in diabetic kidney disease.

Correction of early subnormal superior hemiretinal DeltaPO(2) predicts therapeutic efficacy in experimental diabetic retinopathy.

PURPOSE: To test the hypothesis that regional retinal oxygenation responses to a hyperoxic inhalation challenge are associated with reported retinopathy outcomes after different therapies in rat models of diabetic retinopathy. METHODS: Six groups of rats were maintained for 3 months: controls (n = 8), untreated diabetic (n = 8), aminoguanidine (AMG)-treated diabetic (2.5 g/kg of diet; n = 6), untreated galactosemic (n = 7), AMG-treated galactosemic (n = 10), and WAY-509-treated (25 mg/kg body weight per day) galactosemic (n = 7). After 3 months, the change in oxygen tension was measured noninvasively from the superior to the inferior ora serrata, using a novel functional magnetic resonance imaging (fMRI) technique and a carbogen (a gas mixture of 5% carbon dioxide and 95% oxygen that has been used clinically, instead of 100% oxygen, to minimize the vasoconstrictive effects of pure O(2) on retinal blood flow and oxygenation) inhalation challenge. Retinal morphometric measurements were also obtained. RESULTS: Retinal lesions (acellular capillaries and pericyte ghosts) were not significantly (P > 0.05) present at 3 months in any experimental groups compared with the control group. Superior but not inferior hemiretinal change in partial pressure of oxygen (DeltaPO(2)) became significantly subnormal (P < 0.05) at 3 months of diabetes or galactosemia. Aminoguanidine, which has been found to inhibit the development of retinopathy in diabetic but not galactosemic rats, inhibited the development of a subnormal DeltaPO(2) in diabetes but not in galactosemia. WAY-509, which has been reported to inhibit retinopathy in galactosemic rats, inhibited the DeltaPO(2) defect in galactosemic rats. CONCLUSIONS: An early subnormal superior hemiretinal DeltaPO(2) after treatment appears to be a good predictor of the risk of development of retinopathy, as well as for assessing therapeutic efficacy in experimental diabetic retinopathy.

Diabetic nephropathy: new appraoches, new therapies

In the United States and in the industrialised countries of Europe, in Japan, India and Africa, diabetes is the condition most frequently associated with endstage renal disease (ESRD). In those countries where ESRD registries are maintained, diabetic nephropathy has been shown to have a higher prevalence than hypertension and glomerulonephritis among new ESRD patients, and Mauer and Chavers (1985) have described diabetes as"...the most important cause of ESRD in the Western world." In the US and the Caribbean, diabetes is predominantly Type 2 (NIDDM) with fewer than 10 percent of patients with diabetes being insulinopenic or C-peptide negative. Twenty years ago it was a commonly expressed view that diabetic nephropathy was an infrequent complication of Type 2 diabetes. Since that time a number of prospective studies of Type 1 and Type 2 diabetes have shown the diabetic nephropathy at comparable rates in the two groups of patients. The Diabetes Control and Complications Trial (DCCT) unequivocally linked the renal, retinal, and neurological complications of diabetes to hyperglycemia and to the failure to achieve so called "tight" glycemic control. Intensive diabetes therapy delayed the onset and slowed the progression of retinography and, additionally, delayed the development of microalbuminuria (>28 ug/min) and the development of overt nephropathy (albuminuria >208 ug/min) in patients with baseline microalbuminuria (DCCT Research Group, 1993). Whatever may be the mechanism(s) through which hyperglycemia produces micro and macrovasculopathy, indolent and slowly progressive process effect these end-results. Not surprisigly, abnormal glycosylated haemoglobin (HbA) levels best predict the development of the microvascular and marcovascular complications of diabetes (Harris and Eastman, 1996).(Au)

Diabetic-like retinopathy: early and late intervention therapies in galactose-fed rats.

PURPOSE: To determine whether the diabetic-like thickening of retinal capillary basement membrane (RCBM) that develops in the galactose-fed rat model of diabetic ocular complications could be halted or ameliorated after 4 or 8 months of galactosemia by treatment with ARI-509, a potent new aldose reductase inhibitor (ARI), or by withdrawal of the galactose diet. METHODS: Weanling female Sprague-Dawley rats were randomized into eight groups and fed laboratory chow plus 50% starch, control group (CON); 50% D-galactose, galactose-fed group (GAL); 50% D-galactose with ARI-509 at 25 mg/kg or 10 mg/kg body wt per day, high-dose prevention group (HDP) and low-dose prevention group (LDP), respectively; 50% D-galactose for 4 or 8 months and then intervention by addition of ARI-509 (25 mg/kg body wt per day), 4-month intervention group (4IN) and 8-month intervention group (8IN), respectively; or 50% D-galactose for 4 or 8 months and then intervention by withdrawing galactose and replacing it with the 50% starch diet, 4-month galactose withdrawal group (4GW) and 8-month galactose withdrawal group (8GW), respectively. After 4, 8, 16, and 24 months of the experimental diets, the levels of carbohydrates in tissues and the extent of RCBM thickening in capillaries of the outer plexiform layer were determined in all groups. RESULTS: Retinal polyol was reduced by 95% in all ARI-treated groups and by 100% in the 4GW and 8GW groups after withdrawal of the galactose. The mean RCBM thickness increased rapidly in GAL rats, becoming almost two times greater (189 +/- 9.4 nm) than in CON rats (103 +/- 3.4 nm) by 24 months. Treatment with ARI-509 in high and low doses (HDP, LDP) initiated with the introduction of the galactose diet significantly prevented RCBM thickening at all time points (P < 0.05). In contrast, intervention by withdrawing galactose from the diet or by adding the high dose of ARI-509 had no significant effect (P < 0.05) on RCBM thickening until the 24-month time point (4IN, 166 +/- 10.3 nm; 8IN, 161 +/- 8.2 nm; 4GW, 136 +/- 5.1 nm; 8GW, 163 +/- 9.6 nm). CONCLUSIONS: Both early and late interventions decreased RCBM thickening compared with that in untreated GAL rats. The decreased thickening, however, was not evident until 16 to 20 months after the intervention. Because RCBM thickening is one of the earliest changes in diabetic and galactosemic retinopathy, the findings suggest that RCBM thickening and possibly subsequent retinal lesions are caused by early biochemical alterations induced by the galactose diet that are not readily reversed. The delayed response to therapy is consistent with that observed in the Diabetes Control and Complications Trial. The cumulative evidence indicates that intervention should begin as early after onset of diabetes as possible, and long follow-up periods should be used to evaluate efficacy.

Effects of two aldose reductase inhibitors upon sorbitol output, D-glucose metabolism and insulin release in islets from normal and hereditarily diabetic rats.

The effects of two aldose reductase inhibitors, ARI 509 (4.0 microM) and tolrestat (40.0 microM), upon sorbitol output, D-[5-3H]glucose and D-[U-14C]glucose metabolism and insulin release were investigated in pancreatic islets prepared from normal rats or hereditarily diabetic animals (Goto-Kakizaki rats) and incubated in the presence of 16.7 mM D-glucose. At this hexose concentration, the output of sorbitol, the utilization of D-[5-3H]glucose, the oxidation of D-[U-14C]glucose and its conversion to 14C-labelled acidic metabolites and amino acids and the secretion of insulin were all much higher than those found in islets exposed to only 2.8 mM D-glucose. In both normal and diabetic rats, the aldose reductase inhibitors suppressed glucose-stimulated sorbitol output, but failed to affect the metabolism of D-[5(-3H]glucose or D-[U-14C]glucose and the secretory response to the hexose. These findings document the efficiency and specificity of ARI 509 and tolrestat as inhibitors of aldose reductase in islet cells, whilst arguing against any major role of sorbitol formation in the stimulus-secretion coupling process for glucose-induced insulin release and any major perturbation of those factors regulating the generation and output of sorbitol in islets of Goto-Kakizaki rats.

Nodal Na(+)-channel displacement is associated with nerve-conduction slowing in the chronically diabetic BB/W rat: prevention by aldose reductase inhibition.

Chronic nerve conduction showing in experimental diabetic neuropathy has been associated with decreased nodal Na+ permeability and an ultrastructurally identifiable loss of axo-glial junctions, which comprise the paranodal voltage channel barrier separating nodal Na+ channels from paranodal K+ channels. In human and experimental diabetic neuropathy these structural changes of the paranodal apparatus correlate closely with the nerve conduction defect. The present immunocytochemical study of the alpha-subunit of the Na+ channel examined whether the breach of the voltage channel barrier may account for a shift in the distribution of Na+ channels explaining decreased nodal Na+ permeability. Biobreeding Wistar (BB/W) rats diabetic for 4-8 months showed a progressive redistribution of nodal Na+ channels across the paranodal barrier into the paranodal and internodal domains which was associated with chronic nerve conduction slowing. The present data suggest that structural damage to the paranodal barrier system in diabetic nerve facilitates the lateral displacement of Na+ channels from the nodal axolemma thereby diminishing their nodal density and the nodal Na+ permeability associated with the chronic nerve conduction defect in experimental diabetes. These abnormalities were prevented by the treatment with an aldose reductase inhibitor, belonging to a class of drugs that, in neuropathic patients, improves nerve-conduction velocity and repairs axo-glial dysjunction of the paranodal apparatus.

Diabetic-like retinopathy ameliorated with the aldose reductase inhibitor WAY-121,509.

PURPOSE: To evaluate the efficacy of WAY-121,509, a potent new aldose reductase inhibitor (ARI), in preventing the retinopathy that develops in the galactose-fed rat model of diabetic ocular complications. METHODS: Sprague-Dawley rats were randomized into treatment and duration groups and fed diets with either 50% starch of 50% galactose with or without WAY-121,509 (25 mg/kg body weight per day). Progression of cataracts was monitored by slit-lamp biomicroscopy. After duration of 4, 8, 16, and 24 months, levels of plasma glucose and glycated hemoglobin, as well as erythrocyte and retinal galactose and galactitol, were measured in rats in each group. Retinal vasculatures of the 24-month rats were isolated by elastase digestion and analyzed by computer-assisted morphometry. RESULTS: Mature, diabetic-like cataracts developed within 5 weeks in all the galactose-fed, untreated rats, but only nonprogressive anterior cortical opacities were present in lenses of 85% of the ARI-treated galactosemic animals after 3 months. Plasma glucose remained the same in all groups. Erythrocyte and retinal galactose and glycated (galactosylated) hemoglobin were elevated with galactosemia and were unaffected by ARI treatment. Erythrocyte and retinal galactitol levels were decreased by 91% and 95%, respectively, with inhibitor treatment. At 24 months, capillary length, width, density, the number of microaneurysms, and the percent of capillary length involved in intraretinal microvascular abnormalities, expressed as hypercellular channels with diameters > 20 microns, were significantly increased by galactosemia and were attenuated in the galactose-fed, ARI-treated group. CONCLUSIONS: A dose of WAY-121,509 sufficient to reduce retinal polyol levels by 95% ameliorated the development of galactose-induced cataracts and diabetic-like retinopathy but was insufficient to prevent early lens opacifications or all the diabetic-like retinal microangiopathies.

Drug trials in neuropathy.

Drug trials in peripheral neuropathy have used different outcome measures, the choice of which has depended on the nature of the neuropathy and the hypothesis being tested. The majority of the published trials have relied on measuring impairment (reflecting the desirable sensitivity of these outcome measures), and only few have used measures of disability or handicap. Drug trials in inflammatory neuropathy (GBS and CIDP), diabetic, paraproteinaemic, and toxic neuropathies have been discussed in this chapter, to illustrate the different therapeutic approaches used in the literature. Future drug trials in peripheral neuropathy should pay more attention to disability and handicap measures.

Peripheral diabetic neuropathy: current concepts in treatment.

OBJECTIVE: To review pathophysiology and current concepts in the treatment of diabetic peripheral neuropathy (PN). DATA SOURCES: References were identified through a MEDLINE search of the English-language literature from 1976 through 1994. Additional references were obtained from reference lists of articles identified through the search. STUDY SELECTION AND DATA EXTRACTION: All articles were considered for possible inclusion in the review. Clinical trials that involved an adequate number of patients and review articles were selected. Information from articles that was judged by the authors to be significant was selected for discussion. DATA SYNTHESIS: PN affects 5-50% of people with diabetes in the US and most commonly is characterized by tingling or burning sensations, particularly in the calves, ankles, and feet, with a loss of vibratory sense. Treatment of PN, for the most part, has been unsatisfactory. Therapy has been directed toward either improving nerve function or alleviating symptoms of PN, including pain and paresthesia. Glycemic control may slow the progression of PN. Hyperglycemia also is associated with decreased pain threshold in patients with diabetes mellitus. The aldose reductase inhibitors, particularly tolrestat, have been shown to improve objective and subjective neurologic function. Pain or paresthesia has been treated effectively with antidepressants, lidocaine, mexiletine, and capsaicin. The anticonvulsants phenytoin and carbamazepine may be effective, but are associated with a greater degree of adverse effects. Experimental treatments, such as gamma-linolenic acid, gangliosides, uridine, and the corticotropin4-9 analog ORG 2766, have been effective in improving neurologic function. CONCLUSIONS: Treatment of PN remains unsatisfactory. Therapy should be directed toward prevention with glycemic control and symptomatic treatment of existing PN.

Galactosemia produces ARI-preventable nodal changes similar to those of diabetic neuropathy.

The present study was designed to examine the development of structural changes, characteristic of diabetic neuropathy, in chronic galactosemia and their responsiveness to inhibition of the polyol-pathway. Sprague-Dawley rats weighing 70-90 g were given a 50% galactose diet continued for 4 or 8 months. Half of these animals were simultaneously given the aldose reductase inhibitor (ARI) WAY 121-509. ARI-treatment normalized galactitol and myoinositol levels in the sciatic nerve. At 4 months, sciatic nerve conduction velocity (NCV) in galactosemic rats was reduced by 30% which was prevented in ARI-treated rats. At 8 months galactosemia reduced NCV to 58% of control values, while ARI-treatment for 8 months improved NCV to 71% of control values. ARI-treatment prevented in galactosemic rats nodal structural changes characteristic of diabetic neuropathy, whereas axonal atrophy was not affected by ARI-treatment, which may in part account for the only partial prevention of the NCV slowing at 8 months. Nerve fiber regeneration was increased 4-fold in ARI-treated rats compared with untreated galactosemic rats. These data suggest that chronic galactosemia produces a neuropathy structurally similar to diabetic neuropathy. The lack of an ARI-treatment effect on axonal atrophy suggests that this defect is not polyol related in galactosemia.