Metabolism of melatonin by cytochrome P450s in rat liver mitochondria and microsomes

Abstract: In the present study we provide direct evidence for the involvement of rat microsomal cytochrome P450s in melatonin O‐demethylation and hydroxylation at two different positions: 2 and 6, as well as generation of N¹‐acetyl‐N²‐formyl‐5‐methoxy‐kynuramine (AFMK) and two unknown products. Moreover, we found that mitochondrial cytochrome P450s also converts melatonin into AFMK, N‐acetylserotonin, 2‐hydroxymelatonin, 6‐hydroxymelatonin and the same two unknown products. Eadie–Hofstee plots for 6‐hydroxylation and O‐demethylation reactions were curvilinear for all tested fractions, suggestive of involvement of at least two components, one with a high affinity and low capacity, and another with a low affinity and high capacity. Mitochondrial cytochrome P450s exhibited higher affinity (suggesting lower K_m value) and higher V_max for melatonin 6‐hydroxylation and O‐demethylation for both high‐affinity and low‐affinity components as compared with microsomal enzymes. The intrinsic clearance for melatonin hydroxylation by high‐ and low‐affinity components displayed the highest values in all tested fractions, indicating that both mitochondrial and microsomal cytochrome P450s metabolize melatonin principally by 6‐hydroxylation, with O‐demethylation representing a minor metabolic pathway.     

Involvement of the cGMP pathway in mediating the insulin-inhibitory effect of melatonin in pancreatic beta-cells

Recent investigations have demonstrated an influence of melatonin on insulin secretion in pancreatic beta-cells. The effects are receptor-mediated via two parallel signaling pathways. The aim of this study was to examine the relevance of a second melatonin receptor (MT2) as well as the involvement of a third signaling cascade in mediating melatonin effects, i.e. the cyclic guanosine monophosphate (cGMP) pathway. Our results demonstrate that the insulin-inhibiting effect of melatonin could be partly reversed by preincubation with the unspecific melatonin receptor antagonist luzindole as well as by the MT2-receptor-specific antagonist 4P-PDOT (4-phenyl-2-propionamidotetraline). As melatonin is known to modulate cGMP concentration via the MT2 receptor, these data indicate transmission of the melatonin effects via the cGMP transduction cascade. Molecular investigations established the presence of different types of guanylate cyclases, cGMP-specific phosphodiesterases and cyclic nucleotide-gated channels in rat insulinoma beta-cells (INS1). Moreover, variations in mRNA expression were found when comparing day and night values as well as different states of glucose metabolism. Incubation experiments provided evidence that 3-isobutyl-1-methylxanthine (IBMX)-stimulated cGMP concentrations were significantly decreased in INS1 cells exposed to melatonin for 1 hr in a dose- and time-dependent manner. This effect could also be reversed by application of luzindole and 4P-PDOT. Stimulation with 8-Br-cGMP resulted in significantly increased insulin production. In conclusion, it could be demonstrated that the melatonin receptor subtype MT2 as well as the cGMP signaling pathway are involved in mediating the insulin-inhibiting effect of melatonin.     

Development of reduced-intensity hematopoietic stem cell transplantation in the National Cancer Center Hospital,Japan

Reduced-intensity hematopoietic stem cell transplantation (RIST) is a new approach of stem cell transplantation, which has shown promising features as reported in multiple phase I and II studies. Elderly patients, who are not eligible for conventional myeloablative hematopoietic stem cell transplantation (HSCT), are now treatable with RIST. It has also reduced regimen-related toxicity and provided better prognosis in short-term follow-up than that of conventional HSCT. Favorable results have been reported particularly in hematological malignancies, such as chronic myelocytic leukemia and malignant lymphoma. Among solid tumors, metastatic renal cell carcinoma was found to respond well to RIST. Clinical studies are currently being conducted to evaluate the efficacy of RIST in other types of solid tumors. However, the mechanism of graft-versus-host disease and graft-versus-tumor remains unclear. More knowledge on the mechanism is crucial to enhance antitumor effect and to further improve the prognosis.     

Role of intra-arterial steroid administration in the management of steroid-refractory acute gastrointestinal graft-versus-host disease

We report here a case of severe steroid-refractory gastrointestinal graft-versus-host disease treated with intra-arterial administration of corticosteroids. A 53-year-old female with non-Hodgkin's lymphoma received peripheral blood hematopoietic stem cell transplant from her HLA-matched sibling. She developed grade II skin and grade IV gastrointestinal graft-versus-host disease with no hepatic involvement. Therapy with oral prednisone easily controlled her skin rash but she had profuse diarrhea that did not respond to high dose intravenous corticosteroids and denileukin diftitox. Infusion of methyl-prednisolone into superior and inferior mesenteric arteries produced dramatic improvement of diarrhea, with complete resolution of gastrointestinal graft-versus-host disease.     

Coordinated regulation of melatonin synthesis and degradation genes in rice leaves in response to cadmium treatment

We investigated the expression patterns of genes involved in melatonin synthesis and degradation in rice leaves upon cadmium (Cd) treatment and the subcellular localization sites of melatonin 2‐hydroxylase (M2H) proteins. The Cd‐induced synthesis of melatonin coincided with the increased expression of melatonin biosynthetic genes including tryptophan decarboxylase (TDC), tryptamine 5‐hydroxylase (T5H), and N‐acetylserotonin methyltransferase (ASMT). However, the expression of serotonin N‐acetyltransferase (SNAT), the penultimate gene in melatonin biosynthesis, was downregulated, suggesting that melatonin synthesis was counter‐regulated by SNAT. Notably, the induction of melatonin biosynthetic gene expression was coupled with the induction of four M2H genes involved in melatonin degradation, which suggests that genes for melatonin synthesis and degradation are coordinately regulated. The induced M2H gene expression was correlated with enhanced M2H enzyme activity. Three of the M2H proteins were localized to the cytoplasm and one M2H protein was localized to chloroplasts, indicating that melatonin degradation occurs both in the cytoplasm and in chloroplasts. The biological activity of 2‐hydroxymelatonin in the induction of the plant defense gene expression was 50% less than that of melatonin, which indicates that 2‐hydroxymelatonin may be a metabolite of melatonin. Overall, our data demonstrate that melatonin synthesis occurs in parallel with melatonin degradation in both chloroplasts and cytoplasm, and the resulting melatonin metabolite 2‐hydroxymelatonin also acts as a signaling molecule for defense gene induction.     

Lowering of oxidative stress in hemodialysis patients by dialysate cleaning: in relation to arteriosclerosis

The objective of this study was to investigate changes in oxidative stress associated with the cleaning of the dialysate. Thirty-six dialysis patients were studied. Changes in soluble CD-14 (sCD-14), malondialdehyde-low-density lipoprotein (MDA-LDL), and oxidized-LDL (Ox-LDL) were monitored for 1 year before and 1 year after dialysate cleaning. The mean endotoxin (ET) level in the dialysate had previously been confirmed to decrease from 39.0 EU/L to an undetectable level after the cleaning. The mean levels of sCD-14, MDA-LDL, and Ox-LDL decreased significantly after the cleaning (sCD-14, P < 0.0001; MDA-LDL, P < 0.001; Ox-LDL, P < 0.001). One year after the cleaning, six cases still showed high levels of MDA-LDL and Ox-LDL. Cardiovascular events occurred in four of those six cases within 2.8 years after the cleaning. These four patients suffered from strong oxidative stress during dialysis, even after the cleaning. We therefore concluded that high levels of MDA-LDL and Ox-LDL are improved in dialysis patients by cleaning of the dialysate. These results indicate that even a dialysate containing 50 EU/L or less ET may stimulate monocytes and cause oxidative stress. They also suggest that even low levels of ET may aggravate arteriosclerosis in dialysis patients. Thus, in order to prevent cardiovascular events in dialysis patients, it is necessary to purify the dialysate.     

Strategies for improving the outcomes of small-for-size grafts in adult-to-adult living-donor liver transplantation

Living-donor liver transplantation (LDLT) has been refined and accepted as a valuable treatment for patients with end-stage liver disease in order to overcome the shortage of organs and mortality on the waiting list. However, graft size problems, especially small-for-size (SFS) grafts, remain the greatest limiting factor for the expansion of LDLT, especially in adult-to-adult transplantation. Various attempts have been made to overcome the problems regarding SFS grafts, such as increasing the graft liver volume and/or controlling excessive portal inflow to a small graft, with considerable positive outcomes. Recent innovations in basic studies have also contributed to the treatment of SFS syndrome. Herein, we review the literature and assess our current knowledge of the pathogenesis and treatment strategies for the use of SFS grafts in adult-to-adult LDLT.     

Controversies on the prognostic value of interim FDG‐PET in advanced‐stage Hodgkin lymphoma

Hodgkin lymphoma, even in advanced‐stage, is a highly curable malignancy, but treatment is associated with short‐term toxicity and long‐term side effects. Early predictive markers are required to identify those patients who do not require the full‐length standard therapy (and thus qualify for therapy de‐escalation) and those patients who will not be cured by standard therapy (and thus qualify for therapy escalation). Multiple trials have assessed the value of ¹⁸F‐fluoro‐2‐deoxy‐d ‐glucose positron emission tomography (FDG‐PET) after a few cycles of chemotherapy (also known as ‘interim FDG‐PET’) in predicting outcome in advanced‐stage Hodgkin lymphoma. Furthermore, multiple interim FDG‐PET‐adapted trials, in which patients with positive interim FDG‐PET scans are assigned to escalated therapies, and patients with negative interim FDG‐PET scans are assigned to de‐escalated therapies, have recently been published or are currently ongoing, with generally heterogeneous results. The present article reports the currently available evidence (and controversies) on the prognostic value of interim FDG‐PET in advanced‐stage Hodgkin lymphoma in patients with positive and negative interim FDG‐PET findings following continuation of standard chemotherapy or escalated/de‐escalated therapy.     

Comparison of the efficacy and tolerability of simvastatin and atorvastatin in the treatment of hypercholesterolemia

BACKGROUND: Simvastatin and atorvastatin are effective statins for treating hypercholesterolemia. HYPOTHESIS: The study was undertaken to compare the efficacy and tolerability of simvastatin 20 and 40 mg/day and atorvastatin 10 and 20 mg/day. METHODS: In this multinational, open-label, crossover study, 258 patients with primary hypercholesterolemia were randomized after 4 weeks of diet plus placebo to once-daily administration of a starting dose sequence of simvastatin (20 mg) or atorvastatin (10 mg), or a higher dose sequence of simvastatin (40 mg) or atorvastatin (20 mg) for 6 weeks. Patients were then switched after a 1-week washout to the corresponding starting or higher dose of the alternate drug for a second 6-week period. The primary endpoint was the mean percent change from baseline to Week 6 in low-density lipoprotein (LDL) cholesterol; percent changes from baseline in total cholesterol, high-density lipoprotein cholesterol, triglycerides, and apolipoprotein B were also compared. Safety was assessed through adverse experiences and laboratory measurements. RESULTS: Both statins produced statistically significant improvements in all measured plasma lipids and lipoproteins. The main treatment comparison showed no statistically significant difference in changes in LDL cholesterol and triglycerides, whereby the overall effects were comparable when doses of 20 mg and 40 mg of simvastatin were compared with atorvastatin 10 mg and 20 mg. The mean percent reductions for LDL cholesterol from baseline to Week 6 ranged from 35-42% for the entire study cohort. An LDL cholesterol level < or = 130 mg/dl (3.4 mmol/l) was achieved in approximately 70% of patients treated with both drugs in this study. Simvastatin and atorvastatin were well tolerated at the doses studied. CONCLUSION: In patients with hypercholesterolemia, the most commonly used doses of simvastatin and atorvastatin produced similar changes in LDL cholesterol and achieved an LDL cholesterol level < or = 130 mg/dl (3.4 mmol/l) in a similar number of patients. Both statins were well tolerated.     

Metformin reduces the rate of small intestinal glucose absorption in type 2 diabetes

In rodents, metformin slows intestinal glucose absorption, potentially increasing exposure of the distal gut to glucose to enhance postprandial glucagon‐like peptide‐1 (GLP‐1) secretion. We evaluated the effects of metformin on serum 3‐O‐methylglucose (3‐OMG; a marker of glucose absorption) and plasma total GLP‐1 concentrations during a standardized intraduodenal infusion of glucose and 3‐OMG in patients with type 2 diabetes. A total of 12 patients, treated with metformin 850 mg twice daily or placebo for 7 days each in a double‐blind, randomized, crossover design (14 days’ washout between treatments), were evaluated on days 5 or 8 of each treatment (6 subjects each). On each study day, 30 minutes after ingesting 850 mg metformin or placebo, patients received an infusion of glucose (60 g + 5 g 3‐OMG, dissolved in water to 240 mL) via an intraduodenal catheter over the course of 120 minutes. Compared with placebo, metformin was associated with lower serum 3‐OMG ( P < .001) and higher plasma total GLP‐1 ( P = .003) concentrations. The increment in plasma GLP‐1 after metformin vs placebo was related to the reduction in serum 3‐OMG concentrations ( P = .019). Accordingly, metformin inhibits small intestinal glucose absorption, which may contribute to augmented GLP‐1 secretion in type 2 diabetes.     

Analysis of K-ras, BRAF, and PIK3CA mutations in laterally-spreading tumors of the colorectum

Background and Aims: Laterally‐spreading tumors (LST) are a newly‐recognized category of colorectal neoplasia, and are defined as lesions larger than 10 mm in diameter and extending circumferentially rather than vertically. However, genetic features of this new category of tumors are not fully elucidated. The aim of this study was to evaluate genetic alterations in LST. Methods: We examined K‐ras, BRAF, and phosphoinositide‐3‐kinase catalytic‐α polypeptide (PIK3CA) mutations in 101 LST, including 68 LST‐granular type (LST‐G) and 33 LST‐non‐granular type by direct sequencing. As controls, we examined these gene mutations in 66 protruded colon adenomas (10 mm or larger) and 44 advanced colon cancers. Results: K‐ras, BRAF, and PIK3CA mutations were observed in 59 (58%), zero (0%), and three (3%) LST, respectively. LST‐G morphology in the right‐sided colon was significantly correlated with the existence of K‐ras mutations, whereas a size of 20 mm or larger was the only predictor of mutations in the left‐sided colorectum. The frequency of K‐ras mutations in LST was particularly marked in the left‐sided colorectum compared to protruded adenomas or advanced cancers (LST vs protruded adenomas, P < 0.001; LST vs advanced cancers, P = 0.002), whereas in the right‐sided colon, K‐ras mutations were equally frequent. PIK3CA mutations were not familiar in either LST (3%) or advanced cancers (9%). Conclusions: K‐ras mutations were involved in colorectal LST in different manners according to tumor location.     

Serum concentration of complement components of the lectin pathway in maintenance hemodialysis patients, and relatively higher levels of L-Ficolin and MASP-2 in Mannose-binding lectin deficiency

Mannose-binding lectin (MBL), L-ficolin and MBL associated serine protease-2 (MASP-2) are molecules involved in initiation of the lectin pathway (LP) in the complement system. Although MBL deficiency is observed in almost 10% of healthy people, studies of associations between MBL deficiency and end-stage renal disease (ESRD) remain rare. The objective of the present study is to clarify the significance of the LP in maintenance hemodialysis (HD) patients, especially in terms of MBL levels. Two hundred and forty-four HD patients who had been followed up for 74±84months and 199 healthy controls were included in this study. Measurements of serum concentrations of MBL, L-ficolin, and MASP-2 were performed. Low serum MBL levels (<0.1μg/mL) in the patients were confirmed by examination of a point mutation in the Mbl-2 gene. Seventeen HD patients (7%) and 20 healthy controls (10%) had MBL deficiency. During the follow-up period, 99 patients died. There was no significant difference in the frequency of deaths by infectious diseases between MBL deficient and non-deficient patients. In both patients and healthy controls with MBL deficiency, the serum concentration of L-ficolin tended to be high, and that of MASP-2 was significantly high (P<0.05). MBL deficiency is not a risk factor for HD induction or life-threatening infections. It is postulated that the elevation of concentration of the two components of the LP, L-ficolin and MASP-2, may compensate for the insufficient activity of the LP in MBL deficiency.     

Application of deep sequence technology in hepatology

Deep sequencing technologies are currently cutting edge, and are opening fascinating opportunities in biomedicine, producing over 100‐times more data compared to the conventional capillary sequencers based on the Sanger method. Next‐generation sequencing (NGS) is now generally defined as the sequencing technology that, by employing parallel sequencing processes, producing thousands or millions of sequence reads simultaneously. Since the GS20 was released as the first NGS sequencer on the market by 454 Life Sciences, the competition in the development of the new sequencers has become intense. In this review, we describe the current deep sequencing systems and discuss the application of advanced technologies in the field of hepatology.     

Case of Ileal Ulcer in Blind Pouch Syndrome

Blind pouch syndrome is a postoperative complication that can follow end‐to‐side or side‐to‐side anastomosis of the small or large intestine. We examined a patient with melena resulting from blind pouch syndrome that developed 46 years after small intestinal anastomosis. Preoperative diagnosis of anastomotic ulcer was established using a long colonoscope. This assessment of the location and nature of the lesion greatly facilitated surgical correction.     

Pronounced variation in bile acid synthesis in humans is related to gender, hypertriglyceridaemia and circulating levels of fibroblast growth factor 19

Abstract. Gälman C, Angelin B, Rudling M. (Karolinska Institutet at Karolinska University Hospital, Stockholm). Pronounced variation in bile acid synthesis in humans is related to gender, hypertriglyceridaemia and circulating levels of fibroblast growth factor 19 (Rapid Communication). J Intern Med 2011; doi:10.1111/j.1365‐2796.2011.02466.x Background. Bile acid (BA) synthesis is essential in cholesterol and lipid homoeostasis. Methods. Serum samples from 435 normal and 23 cholecystectomized subjects were obtained after overnight fasting and assayed for markers of BA and cholesterol synthesis, as well as cholesterol absorption. We determined whether BA synthesis was related to fibroblast growth factor 19 (FGF19; a circulating metabolic regulator that is thought to inhibit BA synthesis), gender, age and serum lipids. Results. Bile acid synthesis varied more than 9‐fold in normal individuals and was 29% higher in men than in women. Whilst low‐density lipoprotein cholesterol increased with age, BA and cholesterol synthesis were stable. BA production was positively correlated with serum triglycerides (TGs), and 35% of individuals with a high level (>95th percentile) of BA synthesis had hypertriglyceridaemia (HTG) (>95th percentile). Serum FGF19 levels varied by 7‐fold in normal individuals and were related inversely to BA synthesis but were not related to gender, plasma lipids or history of cholecystectomy. Conclusions. Bile acid synthesis has a wide inter‐individual variation, is lower in women than in men and is correlated positively with serum TGs. High BA production is frequently linked to HTG. Age‐related hypercholesterolaemia is not associated with changes in BA or cholesterol production, nor to an increase in cholesterol absorption. In humans, the circulating level of FGF19 may regulate hepatic BA production under fasting conditions.