Cisplatin and Oxaliplatin Toxicity: Importance of Cochlear Kinetics as a Determinant for Ototoxicity

Background Cisplatin is a commonly used platinum anti-cancer drug. Regrettably cisplatin has dose-limiting ototoxic side effects, e.g. the drug can induce an irreversible hearing loss. The ototoxic mechanisms of cisplatin have not been elucidated in the human ear and no clinically useful oto-protectors are yet available. Cisplatin is a necessary part of many treatment regimes. Its beneficial therapeutic effects might be reduced if cisplatin was excluded from the treatment in order to protect the hearing function. In this work the ototoxic effects of cisplatin are studied with the aim to better understand the mechanisms behind the irreversible hearing loss induced by this drug. Oxaliplatin is a second generation platinum-derivative anti-cancer drug, free from ototoxic side effects in clinical practice. The effects of oxaliplatin on the inner ear have been studied in this work and the results are compared with cisplatin treatment. The two drugs differ regarding both anti-cancer effects and side effects, which could be attributed to differences in pharmacokinetic factors, cellular uptake and apoptotic mechanisms. The thioredoxin redox system with the enzyme thioredoxin reductase (TrxR) was studied in cochleae due to a suggested DNA-independent apoptotic mechanism of the hair cells. The cochlear pharmacokinetics of cisplatin was assessed and the transport protein organic cation transporter 2 (OCT2) was studied in relation to the ototoxic effect of cisplatin. Material and methods Cultured human colon carcinoma cells and cell cultures of rat organ of Corti were used for apoptosis studies in vitro following exposure to cisplatin and oxaliplatin. Cisplatin and oxaliplatin were administered i.v. to guinea pigs, followed by in vivo sampling of blood, cerebrospinal fluid (CSF) and scala tympani (ST) perilymph. Liquid chromatography with post-column derivatization was used to determine the concentration of parent drug in the samples. Electrophysiological hearing thresholds and the loss of hair cells were assessed to evaluate their ototoxic effects. Phenformin, a potential blocker of OCT2 was administered and the ototoxic side effect of cisplatin was evaluated. For immunohistochemical studies, cochlea from rat, guinea pig and pig were used, where TrxR and OCT2 were evaluated in the cochlea. TrxR-assays were used to measure the TrxR activity in cochlear tissue, both in vivo and in vitro. Results The results from the in vitro studies showed that addition of either cisplatin or oxaliplatin to the culture medium in organ of Corti cell cultures caused a similar amount of outer hair cell loss and inhibition of TrxR activity. Cisplatin exposure to cultured human colon carcinoma cells also reduced the activity of TrxR. The results from the in vivo studies showed that a considerable concentration of cisplatin was present in ST perilymph as compared with weak concentrations of oxaliplatin after high dose oxaliplatin i.v. Ten minutes after cisplatin administration, its concentration in ST perilymph was 4-fold higher in the basal turn of the cochlea as compared to the apex. Cisplatin could be analysed in ST perilymph for up to 120 min. Phenformin i.v. did not reduce the ototoxic side-effect of cisplatin. Positive immunoreactivity to TrxR was evident in both hair cells and spiral ganglion cells. Futhermore, OCT2 was expressed in the supporting cells of organ of Corti and in the spiral ganglion cells. Conclusion The transport of cisplatin to the vulnerable cells of hearing seems to be of major importance for the ototoxic effects. An early high concentration of cisplatin in the base of the cochlea and delayed elimination of cisplatin from ST perilymph may be related to the cisplatin-induced loss of outer hair cells in the basal turn of the cochlea. Cisplatin and oxaliplatin both cause similar ototoxic effects when the organ of Corti is directly exposed in vitro. The thioredoxin redox system with the TrxR enzyme may well play a critical role in cisplatininduced ototoxicity. The presence of OCT2 in the supporting cells indicates that this transport protein is primarily not involved in the uptake of cisplatin from the systemic circulation but rather from the deeper compartments of the cochlea. The knowledge elicited in this work will hopefully suggest objectives for further studies in order to develop oto-protective treatments to preserve the hearing of cisplatin treated patients

Fasting and postprandial remnant-like particle cholesterol concentrations in obese participants are associated with plasma triglycerides, insulin resistance, and body fat distribution

Elevated plasma concentrations of remnant-like particle cholesterol (RLP-C) are atherogenic. However, factors that determine RLP-C are not fully understood. This study evaluates which factors affect RLP-C in the fasting and postprandial state, using multiple regression analyses in a large cohort of lean and obese participants. All participants (n = 740) underwent a test meal challenge containing 95 energy % (en%) fat (energy content 50% of predicted daily resting metabolic rate). Fasting and postprandial concentrations of circulating metabolites were measured over a 3-h period. Obese participants (n = 613) also participated in a 10-wk weight loss program (-2510 kJ/d), being randomized to either a low-fat or a high-fat diet (20-25 vs. 40-45en% fat). Postprandial RLP-C was associated with fasting RLP-C, waist:hip ratio (WHR), HOMA(IR) (homeostasis model assessment index for insulin resistance) (P < 0.001), and age, independently of BMI and gender [adjusted R(2) (adj. R(2)) = 0.70). These factors were also related to fasting RLP-C (P < 0.010), along with gender and physical activity (adj. R(2) = 0.23). The dietary intervention resulted in significantly lower fasting RLP-C concentrations, independently mediated by weight loss, improvements in HOMA(IR), and the fat content of the prescribed diet. However, after inclusion of plasma triglyceride (TG), HDL-cholesterol, and FFA concentrations in the models, HOMA(IR) and WHR no longer significantly predicted fasting RLP-C, although WHR remained a predictor of postprandial RLP-C (P = 0.002). Plasma TG was strongly associated with both fasting and postprandial RLP-C (P < 0.001). In conclusion, plasma RLP-C concentrations are mainly associated with plasma TG concentrations. Interestingly, the high-fat diet was more effective at decreasing fasting RLP-C concentrations in obese participants than the low-fat diet

Role of Receptor-Interacting Protein 140 in human fat cells

<p>Abstract</p> <p>Background</p> <p>Mice lacking <it>Receptor-interacting protein 140 (RIP140) </it>have reduced body fat which at least partly is mediated through increased lipid and glucose metabolism in adipose tissue. In humans, <it>RIP140 </it>is lower expressed in visceral white adipose tissue (WAT) of obese versus lean subjects. We investigated the role of <it>RIP140 </it>in human subcutaneous WAT, which is the major fat depot of the body.</p> <p>Methods</p> <p>Messenger RNA levels of <it>RIP140 </it>were measured in samples of subcutaneous WAT from women with a wide variation in BMI and in different human WAT preparations. <it>RIP140 </it>mRNA was knocked down with siRNA in <it>in vitro </it>differentiated adipocytes and the impact on glucose transport and mRNA levels of target genes determined.</p> <p>Results</p> <p><it>RIP140 </it>mRNA levels in subcutaneous WAT were decreased among obese compared to lean women and increased by weight-loss, but did not associate with mitochondrial DNA copy number. <it>RIP140 </it>expression increased during adipocyte differentiation <it>in vitro </it>and was higher in isolated adipocytes compared to corresponding pieces of WAT. Knock down of <it>RIP140 </it>increased basal glucose transport and mRNA levels of <it>glucose transporter 4 </it>and <it>uncoupling protein-1</it>.</p> <p>Conclusions</p> <p>Human <it>RIP140 </it>inhibits glucose uptake and the expression of genes promoting energy expenditure in the same fashion as the murine orthologue. Increased levels of human <it>RIP140 </it>in subcutaneous WAT of lean subjects may contribute to economize on energy stores. By contrast, the function and expression pattern does not support that <it>RIP140 </it>regulate human obesity.</p

Genetic polymorphisms and weight loss in obesity: A randomised trial of hypo-energetic high-versus low-fat diets

OBJECTIVES: To study if genes with common single nucleotide polymorphisms (SNPs) associated with obesity-related phenotypes influence weight loss (WL) in obese individuals treated by a hypo-energetic low-fat or high-fat diet. DESIGN: Randomised, parallel, two-arm, open-label multi-centre trial. SETTING: Eight clinical centres in seven European countries. PARTICIPANTS: 771 obese adult individuals. INTERVENTIONS: 10-wk dietary intervention to hypo-energetic (-600 kcal/d) diets with a targeted fat energy of 20%-25% or 40%-45%, completed in 648 participants. OUTCOME MEASURES: WL during the 10 wk in relation to genotypes of 42 SNPs in 26 candidate genes, probably associated with hypothalamic regulation of appetite, efficiency of energy expenditure, regulation of adipocyte differentiation and function, lipid and glucose metabolism, or production of adipocytokines, determined in 642 participants. RESULTS: Compared with the noncarriers of each of the SNPs, and after adjusting for gender, age, baseline weight and centre, heterozygotes showed WL differences that ranged from -0.6 to 0.8 kg, and homozygotes, from -0.7 to 3.1 kg. Genotype-dependent additional WL on low-fat diet ranged from 1.9 to -1.6 kg in heterozygotes, and from 3.8 kg to -2.1 kg in homozygotes relative to the noncarriers. Considering the multiple testing conducted, none of the associations was statistically significant. CONCLUSIONS: Polymorphisms in a panel of obesity-related candidate genes play a minor role, if any, in modulating weight changes induced by a moderate hypo-energetic low-fat or high-fat diet

TFAP2B influences the effect of dietary fat on weight loss under energy restriction

BACKGROUND: Numerous gene loci are related to single measures of body weight and shape. We investigated if 55 SNPs previously associated with BMI or waist measures, modify the effects of fat intake on weight loss and waist reduction under energy restriction. METHODS AND FINDINGS: Randomized controlled trial of 771 obese adults. (Registration: ISRCTN25867281.) One SNP was selected for replication in another weight loss intervention study of 934 obese adults. The original trial was a 10-week 600 kcal/d energy-deficient diet with energy percentage from fat (fat%) in range of 20-25 or 40-45. The replication study used an 8-weeks diet of 880 kcal/d and 20 fat%; change in fat% intake was used for estimation of interaction effects. The main outcomes were intervention weight loss and waist reduction. In the trial, mean change in fat% intake was -12/+4 in the low/high-fat groups. In the replication study, it was -23/-12 among those reducing fat% more/less than the median. TFAP2B-rs987237 genotype AA was associated with 1.0 kg (95% CI, 0.4; 1.6) greater weight loss on the low-fat, and GG genotype with 2.6 kg (1.1; 4.1) greater weight loss on the high-fat (interaction p-value; p = 0.00007). The replication study showed a similar (non-significant) interaction pattern. Waist reduction results generally were similar. Study-strengths include (i) the discovery study randomised trial design combined with the replication opportunity (ii) the strict dietary intake control in both studies (iii) the large sample sizes of both studies. Limitations are (i) the low minor allele frequency of the TFAP2B polymorphism, making it hard to investigate non-additive genetic effects (ii) the different interventions preventing identical replication-discovery study designs (iii) some missing data for non-completers and dietary intake. No adverse effects/outcomes or side-effects were observed. CONCLUSIONS: Under energy restriction, TFAP2B may modify the effect of dietary fat intake on weight loss and waist reduction

The ADAMTS (A Disintegrin and Metalloproteinase with Thrombospondin motifs) family

The ADAMTS (A Disintegrin and Metalloproteinase with Thrombospondin motifs) enzymes are secreted, multi-domain matrix-associated zinc metalloendopeptidases that have diverse roles in tissue morphogenesis and patho-physiological remodeling, in inflammation and in vascular biology. The human family includes 19 members that can be sub-grouped on the basis of their known substrates, namely the aggrecanases or proteoglycanases (ADAMTS1, 4, 5, 8, 9, 15 and 20), the procollagen N-propeptidases (ADAMTS2, 3 and 14), the cartilage oligomeric matrix protein-cleaving enzymes (ADAMTS7 and 12), the von-Willebrand Factor proteinase (ADAMTS13) and a group of orphan enzymes (ADAMTS6, 10, 16, 17, 18 and 19). Control of the structure and function of the extracellular matrix (ECM) is a central theme of the biology of the ADAMTS, as exemplified by the actions of the procollagen-N-propeptidases in collagen fibril assembly and of the aggrecanases in the cleavage or modification of ECM proteoglycans. Defects in certain family members give rise to inherited genetic disorders, while the aberrant expression or function of others is associated with arthritis, cancer and cardiovascular disease. In particular, ADAMTS4 and 5 have emerged as therapeutic targets in arthritis. Multiple ADAMTSs from different sub-groupings exert either positive or negative effects on tumorigenesis and metastasis, with both metalloproteinase-dependent and -independent actions known to occur. The basic ADAMTS structure comprises a metalloproteinase catalytic domain and a carboxy-terminal ancillary domain, the latter determining substrate specificity and the localization of the protease and its interaction partners; ancillary domains probably also have independent biological functions. Focusing primarily on the aggrecanases and proteoglycanases, this review provides a perspective on the evolution of the ADAMTS family, their links with developmental and disease mechanisms, and key questions for the future

Adipose tissue pathways involved in weight loss of cancer cachexia

White adipose tissue (WAT) constitutes our most expandable tissue and largest endocrine organ secreting hundreds of polypeptides collectively termed adipokines. Changes in WAT mass induce alterations in adipocyte secretion and function, which are linked to disturbed whole-body metabolism. Although the mechanisms controlling this are not clear they are dependent on changes in gene expression, a complex process which is regulated at several levels. Results in recent years have highlighted the role of small non-coding RNA molecules termed microRNAs (miRNAs), which regulate gene expression via post-transcriptional mechanisms. The aim of this thesis was to characterize global gene expression levels and describe novel miRNAs and adipokines controlling the function of human WAT in conditions with pathological increases or decreases in WAT mass. Obesity and cancer cachexia were selected as two models since they are both clinically relevant and characterized by involuntary changes in WAT mass. In Study I, expressional analyses were performed in subcutaneous WAT from cancer patients with or without cachexia and obese versus non-obese subjects. In total, 425 transcripts were found to be regulated in cancer cachexia. Pathway analyses based on this set of genes revealed that processes involving extracellular matrix, actin cytoskeleton and focal adhesion were significantly downregulated, whereas fatty acid metabolism was upregulated comparing cachectic with weight-stable cancer subjects. Furthermore, by overlapping these results with microarray data from an obesity study, many transcripts were found to be reciprocally regulated comparing the two conditions. This suggests that WAT gene expression in cancer cachexia and obesity are regulated by similar, albeit opposing, mechanisms. In Study II, the focus was on the family of fibroblast growth factors (FGFs), members of which have recently been implicated in the development of obesity and insulin resistance. A retrospective analysis of global gene expression data identified several FGFs (FGF1/2/7/9/13/18) to be expressed in WAT. However, only one, FGF1, was actively secreted from WAT and predominantly so from the adipocyte fraction. Moreover, FGF1 release was increased in obese compared to non-obese subjects, but was not normalized by weight loss. Although the clinical significance of these findings is not yet clear, it can be hypothesized that FGF1 may play a role in WAT growth, possibly by promoting fat cell proliferation and/or differentiation. In Study III, we identified adipose miRNAs regulated in obesity. Out of eleven miRNAs regulated by changes in body fat mass, ten controlled the production of the pro-inflammatory chemoattractant chemokine (C-C motif) ligand 2 (CCL2) when overexpressed in fat cells and for two, miR-126 and -193b, signaling circuits were defined. In Study IV, a novel adipokine, semaphorin 3C (SEMA3C), was identified by combining transcriptome and secretome data. Detailed studies focusing on SEMA3C revealed that this factor was secreted from adipocytes and induced the expression of extracellular matrix and matricellular genes in preadipocytes. Furthermore, SEMA3C mRNA levels correlated with interstitial fibrosis and insulin resistance in WAT derived from subjects with a wide range in BMI. In summary, the results presented in this thesis have delineated transcriptional alterations in WAT in two clinically relevant conditions, obesity and cancer cachexia. This has allowed the identification of novel adipokines and microRNAs with potential pathophysiological importance. These findings form the basis for further studies aiming at understanding the central role of WAT in disorders associated with metabolic complications

Mitochondrial Redox Metabolism in Trypanosomatids Is Independent of Tryparedoxin Activity

Tryparedoxins (TXNs) are oxidoreductases unique to trypanosomatids (including Leishmania and Trypanosoma parasites) that transfer reducing equivalents from trypanothione, the major thiol in these organisms, to sulfur-dependent peroxidases and other dithiol proteins. The existence of a TXN within the mitochondrion of trypanosomatids, capable of driving crucial redox pathways, is considered a requisite for normal parasite metabolism. Here this concept is shown not to apply to Leishmania. First, removal of the Leishmania infantum mitochondrial TXN (LiTXN2) by gene-targeting, had no significant effect on parasite survival, even in the context of an animal infection. Second, evidence is presented that no other TXN is capable of replacing LiTXN2. In fact, although a candidate substitute for LiTXN2 (LiTXN3) was found in the genome of L. infantum, this was shown in biochemical assays to be poorly reduced by trypanothione and to be unable to reduce sulfur-containing peroxidases. Definitive conclusion that LiTXN3 cannot directly reduce proteins located within inner mitochondrial compartments was provided by analysis of its subcellular localization and membrane topology, which revealed that LiTXN3 is a tail-anchored (TA) mitochondrial outer membrane protein presenting, as characteristic of TA proteins, its N-terminal end (containing the redox-active domain) exposed to the cytosol. This manuscript further proposes the separation of trypanosomatid TXN sequences into two classes and this is supported by phylogenetic analysis: i) class I, encoding active TXNs, and ii) class II, coding for TA proteins unlikely to function as TXNs. Trypanosoma possess only two TXNs, one belonging to class I (which is cytosolic) and the other to class II. Thus, as demonstrated for Leishmania, the mitochondrial redox metabolism in Trypanosoma may also be independent of TXN activity. The major implication of these findings is that mitochondrial functions previously thought to depend on the provision of electrons by a TXN enzyme must proceed differently

Serum Progranulin Concentrations May Be Associated With Macrophage Infiltration Into Omental Adipose Tissue

OBJECTIVE—Progranulin is an important molecule in inflammatory response. Chronic inflammation is frequently associated with central obesity and associated disturbances; however, the role of circulating progranulin in human obesity, type 2 diabetes, and dyslipidemia is unknown

Identification of Thioredoxin Glutathione Reductase Inhibitors That Kill Cestode and Trematode Parasites

Parasitic flatworms are responsible for serious infectious diseases that affect humans as well as livestock animals in vast regions of the world. Yet, the drug armamentarium available for treatment of these infections is limited: praziquantel is the single drug currently available for 200 million people infected with Schistosoma spp. and there is justified concern about emergence of drug resistance. Thioredoxin glutathione reductase (TGR) is an essential core enzyme for redox homeostasis in flatworm parasites. In this work, we searched for flatworm TGR inhibitors testing compounds belonging to various families known to inhibit thioredoxin reductase or TGR and also additional electrophilic compounds. Several furoxans and one thiadiazole potently inhibited TGRs from both classes of parasitic flatworms: cestoda (tapeworms) and trematoda (flukes), while several benzofuroxans and a quinoxaline moderately inhibited TGRs. Remarkably, five active compounds from diverse families possessed a phenylsulfonyl group, strongly suggesting that this moiety is a new pharmacophore. The most active inhibitors were further characterized and displayed slow and nearly irreversible binding to TGR. These compounds efficiently killed Echinococcus granulosus larval worms and Fasciola hepatica newly excysted juveniles in vitro at a 20 µM concentration. Our results support the concept that the redox metabolism of flatworm parasites is precarious and particularly susceptible to destabilization, show that furoxans can be used to target both flukes and tapeworms, and identified phenylsulfonyl as a new drug-hit moiety for both classes of flatworm parasites