The role of bile acids in reducing the metabolic complications of obesity after bariatric surgery: a systematic review.

BACKGROUND: Bariatric surgery is currently the most efficacious treatment for obesity and its associated metabolic co-morbidities, such as diabetes. The metabolic improvements occur through both weight-dependent and weight-independent mechanisms. Bile acids (BAs) have emerged as key signalling molecules that have a central role in modulating many of the physiological effects seen after bariatric surgery. This systematic review assesses the evidence from both human and animal studies for the role of BAs in reducing the metabolic complications of obesity following bariatric surgery. METHODS: We conducted a systematic search of Medline and Embase databases to identify all articles investigating the role of BAs in mediating the metabolic changes observed following bariatric surgery in both animal and human studies. Boolean logic was used with relevant search terms, including the following MeSH terms: 'bile acids and salts', 'bariatric surgery', 'metabolic surgery', 'gastrointestinal tract/surgery' and 'obesity/surgery'. RESULTS: Following database searches (n=1197), inclusion from bibliography searches (n=2) and de-duplication (n=197), 1002 search results were returned. Of these, 132 articles were selected for full-text review, of which 38 articles were deemed relevant and included in the review. The findings support the effects of BAs on satiety, lipid and cholesterol metabolism, incretins and glucose homoeostasis, energy metabolism, gut microbiota and endoplasmic reticulum stress following bariatric surgery. Many of these metabolic effects are modulated through the BA receptors FXR and TGR5. We also explore a possible link between BAs and carcinogenesis following bariatric surgery. CONCLUSIONS: Overall there is good evidence to support the role of BAs in the metabolic effects of bariatric surgery through the above mechanisms. BAs could serve as a novel therapeutic pharmacological target for the treatment of obesity and its associated co-morbidities.

Indoleamine 2,3-dioxygenase, an emerging target for anti-cancer therapy.

The inability of the host immune system to control tumor growth appears to result from dominant mechanisms of immune suppression that prevent the immune system from effectively responding in a way that consistently results in tumor rejection. Among the many possible mediators of tumoral immune escape, the immunoregulatory enzyme, indoleamine 2,3-dioxygenase (IDO), has recently gained considerable attention. IDO is a heme-containing, monomeric oxidoreductase that catalyzes the first and rate-limiting step in the degradation of the essential amino acid tryptophan to N formyl-kynurenine. Tryptophan depletion as well as the accumulation of its metabolites results in a strongly inhibitory effect on the development of immune responses by blocking T cell activation, inducing T cell apoptosis and promoting the differentiation of naïve T cells into cells with a regulatory phenotype (T(regs)). Recent data obtained from preclinical tumor models demonstrate that IDO inhibition can significantly enhance the antitumor activity of various chemotherapeutic and immunotherapeutic agents. These results, coupled with data showing that increased IDO expression is an independent prognostic variable for reduced overall survival in cancer patients, suggest that IDO inhibition may represent an effective strategy to treat malignancies, either alone or in combination with chemotherapeutics or other immune based therapies. This review will focus on the role of IDO as a mediator of peripheral immune tolerance, evidence that IDO becomes dysregulated in human cancers, and the latest progress on the development of IDO inhibitors as a novel anti-cancer therapy.

Low intensity resistance exercise for breast cancer patients with arm lymphedema with or without compression sleeve.

Clinical trials of the effect of physical exercise on breast cancer related arm lymphedema (ALE) are very rare. The aim of this study was to examine if controlled low intensity arm exercises with weights, with or without a compression sleeve, influence breast cancer related ALE. Thirty-one breast cancer treated patients with small or moderate ALE were included in the study. A specifically designed arm exercise program was performed with or without compression sleeve on different days and in a randomized order. Measurements were performed before, directly after and 24 hours after the exercise intervention, with water displacement method and multiple frequency bioelectrical impedance analysis (n=10) for volume of the arms and Borg's scale for perceived exertion during training. There was an increase of total arm volume of the lymphedema arm immediately after the exercise intervention for both with and without sleeve conditions (p < 0.01). At 24 hours, no volume increase was found compared to pre-exercise and both groups showed tendency towards reduced lymphedema relative volume (p < 0.05). The patient's rating of perceived exertion was low regardless of whether a sleeve was worn, but was significantly higher when exercising with the sleeve. We conclude that low intensity exercises can be performed by patients with arm lymphedema without risk of worsening the edema. Exercises without the sleeve may be of benefit provided compression sleeve is worn regularly.

Discovery of macrocyclic hydroxamic acids containing biphenylmethyl derivatives at P1', a series of selective TNF-alpha converting enzyme inhibitors with potent cellular activity in the inhibition of TNF-alpha release.

SAR exploration at P1' using an anti-succinate-based macrocyclic hydroxamic acid as a template led to the identification of several bulky biphenylmethyl P1' derivatives which confer potent porcine TACE and anti-TNF-alpha cellular activities with high selectivity versus most of the MMPs screened. Our studies demonstrate for the first time that TACE has a larger S1' pocket in comparison to MMPs and that potent and selective TACE inhibitors can be achieved by incorporation of sterically bulky P1' residues.

Photochemically enhanced binding of small molecules to the tumor necrosis factor receptor-1 inhibits the binding of TNF-alpha.

The binding of tumor necrosis factor alpha (TNF-alpha) to the type-1 TNF receptor (TNFRc1) plays an important role in inflammation. Despite the clinical success of biologics (antibodies, soluble receptors) for treating TNF-based autoimmune conditions, no potent small molecule antagonists have been developed. Our screening of chemical libraries revealed that N-alkyl 5-arylidene-2-thioxo-1,3-thiazolidin-4-ones were antagonists of this protein-protein interaction. After chemical optimization, we discovered IW927, which potently disrupted the binding of TNF-alpha to TNFRc1 (IC(50) = 50 nM) and also blocked TNF-stimulated phosphorylation of Ikappa-B in Ramos cells (IC(50) = 600 nM). This compound did not bind detectably to the related cytokine receptors TNFRc2 or CD40, and did not display any cytotoxicity at concentrations as high as 100 microM. Detailed evaluation of this and related molecules revealed that compounds in this class are "photochemically enhanced" inhibitors, in that they bind reversibly to the TNFRc1 with weak affinity (ca. 40-100 microM) and then covalently modify the receptor via a photochemical reaction. We obtained a crystal structure of IV703 (a close analog of IW927) bound to the TNFRc1. This structure clearly revealed that one of the aromatic rings of the inhibitor was covalently linked to the receptor through the main-chain nitrogen of Ala-62, a residue that has already been implicated in the binding of TNF-alpha to the TNFRc1. When combined with the fact that our inhibitors are reversible binders in light-excluded conditions, the results of the crystallography provide the basis for the rational design of nonphotoreactive inhibitors of the TNF-alpha-TNFRc1 interaction.

Cyclic imides as potent and selective alpha-1A adrenergic receptor antagonists.

We disclose a new compound class of potent and selective alpha-1A adrenergic receptor antagonists exemplified by the geminally, disubstituted cyclic imide 7. The optimization of lead compounds resulting in the cyclic imide motif is highlighted. The results of in vitro and in vivo studies of selected compounds are presented.

Design, synthesis, and structure-activity relationships of macrocyclic hydroxamic acids that inhibit tumor necrosis factor alpha release in vitro and in vivo.

To search for TNF-alpha (tumor necrosis factor alpha) converting enzyme (TACE) inhibitors, we designed a new class of macrocyclic hydroxamic acids by linking the P1 and P2' residues of acyclic anti-succinate-based hydroxamic acids. A variety of residues including amide, carbamate, alkyl, sulfonamido, Boc-amino, and amino were found to be suitable P1-P2' linkers. With an N-methylamide at P3', the 13-16-membered macrocycles prepared exhibited low micromolar activities in the inhibition of TNF-alpha release from LPS-stimulated human whole blood. Further elaboration in the P3'-P4' area using the cyclophane and cyclic carbamate templates led to the identification of a number of potent analogues with IC(50) values of

Biology of TACE inhibition.

Studies conducted over the past decade have demonstrated a central role for tumour necrosis factor alpha (TNFalpha) in inflammatory diseases. As a result of this work, a number of biological agents that neutralise the activity of this cytokine have entered the clinic. The recent clinical data obtained with etanercept and infliximab highlight the relevance of this strategy. TNFalpha converting enzyme (TACE) is the metalloproteinase that processes the 26 kDa membrane bound precursor of TNFalpha (proTNFalpha) to the 17 kDa soluble component. Although a number of proteases have been shown to process proTNFalpha, none do so with the efficiency of TACE. A series of orally bioavailable, selective, and potent TACE inhibitors are currently in clinical development. These inhibitors effectively block TACE mediated processing of proTNFalpha and can reduce TNF production by lipopolysaccharide stimulated whole blood by >95%. Through a series of studies it is shown here that >80% of the unprocessed proTNFalpha is degraded intracellularly. The remainder appears to be transiently expressed on the cell surface. Although, in vitro, TACE inhibition has also been implicated in shedding of p55 and p75 surface TNFalpha receptors, the in vivo data cast doubt on the consequences of this finding. In a mouse model of collagen-induced arthritis, the inhibitors are efficacious both prophylactically and therapeutically. The efficacy seen is equivalent to strategies that neutralise TNFalpha. In many studies greater efficacy is observed with the TACE inhibitors, presumably owing to greater penetration to the site of TNFalpha production.

Phenylacetamides as selective alpha-1A adrenergic receptor antagonists.

A novel class of potent and selective alpha-1a receptor antagonists has been identified. The structures of these antagonists were derived from truncating the 4-aryl dihydropyridine subunit present in known alpha-1a antagonists. The design principles which led to the discovery of substituted phenylacetamides, the synthesis and SAR of key analogues, and the results of select in vitro and in vivo studies are described.

Cutting edge: a dominant negative form of TNF-alpha converting enzyme inhibits proTNF and TNFRII secretion.

TNF-alpha converting enzyme (TACE) is the protease responsible for processing proTNF from the 26-kDa membrane-anchored precursor to the secreted 17-kDa TNF-alpha. We show here that a deletion mutant of TACE (dTACE), lacking the pro and catalytic domains of the protease, acts as a dominant negative for proTNF processing in transfected HEK293 cells. We used the same system to test the effect of dTACE on TNFRII processing. Overexpression of dTACE with TNFRII resulted in >80% inhibition of TNFRII shedding. Although significant inhibition of TNF-alpha and TNFRII shedding was achieved with dTACE, we could not detect a cell surface accumulation of the noncleaved substrates above that observed in the absence of dTACE. Our results suggest that TNFRII is a substrate for TACE, and that dTACE is capable of interfering with the function of endogenous TACE, either by binding and sequestering TACE substrates via the disintegrin domain, transmembrane domain, or cytoplasmic tail, or by some other mechanism that has yet to be determined.

Cloning and characterization of ADAMTS11, an aggrecanase from the ADAMTS family.

Aggrecan is responsible for the mechanical properties of cartilage. One of the earliest changes observed in arthritis is the depletion of cartilage aggrecan due to increased proteolytic cleavage within the interglobular domain. Two major sites of cleavage have been identified in this region at Asn(341)-Phe(342) and Glu(373)-Ala(374). While several matrix metalloproteinases have been shown to cleave at Asn(341)-Phe(342), an as yet unidentified protein termed "aggrecanase" is responsible for cleavage at Glu(373)-Ala(374) and is hypothesized to play a pivotal role in cartilage damage. We have identified and cloned a novel disintegrin metalloproteinase with thrombospondin motifs that possesses aggrecanase activity, ADAMTS11 (aggrecanase-2), which has extensive homology to ADAMTS4 (aggrecanase-1) and the inflammation-associated gene ADAMTS1. ADAMTS11 possesses a number of conserved domains that have been shown to play a role in integrin binding, cell-cell interactions, and extracellular matrix binding. We have expressed recombinant human ADAMTS11 in insect cells and shown that it cleaves aggrecan at the Glu(373)-Ala(374) site, with the cleavage pattern and inhibitor profile being indistinguishable from that observed with native aggrecanase. A comparison of the structure and expression patterns of ADAMTS11, ADAMTS4, and ADAMTS1 is also described. Our findings will facilitate the study of the mechanisms of cartilage degradation and provide targets to search for effective inhibitors of cartilage depletion in arthritic disease.

Aggrecanase. A target for the design of inhibitors of cartilage degradation.

In arthritic diseases there is a gradual erosion of cartilage that leads to a loss of joint function. Aggrecan, which provides cartilage with its properties of compressibility and elasticity, is the first matrix component to undergo measurable loss in arthritis. This loss of aggrecan appears to be due to an increased rate of degradation, that can be attributed to proteolytic cleavage of the core protein within the interglobular domain (IGD). Two major sites of cleavage have been identified within the IGD. One, between the amino acids Asn341-Phe342, where the matrix metalloproteinases (MMPs) have been shown to clip; and the other, between Glu373-Ala374, which is attributed to a novel protease, "aggrecanase." We have generated aggrecanase in conditioned media from IL-1-stimulated bovine nasal cartilage and have used an enzymatic assay to evaluate this proteinase activity. In these studies we follow the generation of aggrecanase and MMPs in response to IL-1 in this system and examine the contribution of these enzymes in aggrecan degredation. Our data suggest that aggrecanase is a key enzyme in cartilage aggrecan degradation that represents a novel target for cartilage protection therapy in arthritis.

Purification and cloning of aggrecanase-1: a member of the ADAMTS family of proteins.

We purified, cloned, and expressed aggrecanase, a protease that is thought to be responsible for the degradation of cartilage aggrecan in arthritic diseases. Aggrecanase-1 [a disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS-4)] is a member of the ADAMTS protein family that cleaves aggrecan at the glutamic acid-373-alanine-374 bond. The identification of this protease provides a specific target for the development of therapeutics to prevent cartilage degradation in arthritis.

The fate of pro-TNF-alpha following inhibition of metalloprotease-dependent processing to soluble TNF-alpha in human monocytes.

Human monocytes rapidly produce TNF-alpha following activation by bacterial LPS. The message for TNF-alpha encodes a 26-kDa protein that is proteolytically processed to the secreted 17-kDa form. Sequencing of the N terminus of the protein secreted by monocytes shows processing of the 26-kDa pro-TNF-alpha to a mature form at the projected metalloprotease cleavage site to generate 17-kDa TNF-alpha with the N terminus VRSSSR-. The addition of hydroxamic acid-based metalloprotease inhibitors to the cell culture is capable of blocking >95% of the production of soluble TNF-alpha and leads to a transient, but reproducible, increase in cell surface TNF-alpha as measured by FACS analysis. The cell surface TNF-alpha was demonstrated to increase the cell's ability to kill L929 tumor targets and induce PG production from human gingival fibroblasts. The buildup of cell surface TNF-alpha is unable to account for the TNF-alpha that is not secreted when inhibitor is present. Pulse-chase analysis of the cells demonstrates rapid degradation of the pro-TNF-alpha that remains unprocessed in the monocytes. Through inhibition of processing and secretion by brefeldin A, processing was shown to occur at a postendoplasmic reticulum site and is closely associated with movement to the cell surface.

Association of interleukin-1-induced, NF kappa B DNA-binding activity with collagenase gene expression in human gingival fibroblasts.

During earlier examination of interleukin-1 (IL-1)-induced matrix metalloproteinase gene expression in human gingival fibroblasts a highly induced immediate early gene, I kappa B-alpha, a NF kappa B DNA-binding inhibitor, was identified. The aim now was to investigate whether recombinant (r)IL-1 beta induces the stimulation of NF kappa B and its inhibitor proteins in human gingival fibroblasts and to understand if inhibition of its activity affects collagenase gene expression. Primary gingival fibroblasts (human) were treated with rIL-1 beta to determine the effect on NF kappa B-like DNA-binding activity. IL-1 induced the production of steady-state mRNA levels of I kappa B-alpha in the cultured fibroblasts. Nuclear run-on transcription studies demonstrated that rIL-1 induction of I kappa B-alpha may be transcriptionally regulated. Using electrophoretic mobility gel-shift assays it was shown that rIL-1 activates NF kappa B-like, DNA-binding activity in these fibroblasts. NF kappa B-like DNA-binding activity was rapidly induced and turned over in gingival fibroblasts with peak activity at 30 min after rIL-1 treatment. Further, treatment with chymotrypsin protease inhibitor and antioxidant inhibitor prevented IL-1-induced, NF kappa B-like, DNA-binding activity and collagenase mRNA production. When coupled with the existence of NF kappa B consensus DNA-binding sites on the collagenase gene promoter, these findings suggest that the stimulation of NF kappa B in gingival fibroblasts by rIL-1 could play an important part in the regulation of their collagenase gene expression. The ability of IL-1 to stimulate this expression may define a pivotal role for this cytokine in the pathogenesis of periodontitis.

The total chemical synthesis of monocyte chemotactic protein-1 (MCP-1).

The affinity-based N (alpha)-amino protecting group tetrabenzo[a,c,g,i]fluorenyl-17 methoxycarbonyl (Tbfmoc) has been utilized as a hydrophobic probe to allow the simple, quick and highly effective isolation of a 76 residue cysteine-containing protein (MCP-1). The base-labile Tbfmoc group can be removed under very mild conditions, which preserve the thiol-containing protein in the reduced state. Oxidative folding was then used to furnish the biologically active beta-chemokine MCP-1.

Modification of tumor necrosis factor-alpha (TNF-alpha) production by the Na(+)-dependent HCO3- cotransport in lipopolysaccharide-activated human monocytes.

Tumor necrosis factor-alpha (TNF-alpha) is produced and secreted from monocytes in response to activation with lipopolysaccharide (LPS). The role of Na+ and HCO3- in the production of TNF-alpha by monocytes was investigated; it was observed that replacement of Na+ in the culture medium with sucrose or choline chloride inhibited TNF-alpha production completely. The addition of Na+ to Na(+)-free culture medium restored TNF-alpha production with an EC50 value of 35 mmol/l. The amiloride analog 5-(N-ethyl-N-isopropyl)amiloride (EIPA), an inhibitor of the Na+/H+ antiporter, inhibited TNF-alpha production with an EC50 of 3.3 microM. Without HCO3- in the culture medium TNF-alpha production was inhibited by 92%. Total protein synthesis was inhibited by 85% in the absence of Na+ but did not change in the absence of bicarbonate in the culture medium. Intracellular pH (pHi) which increased from 6.90 in control monocyte to 7.40 in response to activation with LPS was abrogated to pHi of 6.95 in the absence of Na+ but did not change in the absence of HCO3- in the culture medium. In the presence of 100 microM phloretin or DIDS the pHi of activated monocyte was reduced to control value, TNF-alpha production was inhibited completely and total protein synthesis was inhibited by 61%. These data suggest that (1) TNF-alpha production, as other proteins, is dependent on the pHi of monocytes,and (2) TNF-alpha production, in contrast to total protein, is modulated by Na(+)-dependent HCO3-.