Clinical and ultrasound features of difficult-to-treat rheumatoid arthritis: A multicenter RA ultrasound cohort study.

OBJECTIVE: The optimal strategy for difficult-to-treat (D2T) rheumatoid arthritis (RA) has not been identified, and the ultrasound characteristics of D2T RA have not been reported. We investigated the clinical characteristics and factors contributing to the outcome in D2T RA in a multicentre RA ultrasound observational cohort. METHOD: We reviewed 307 Japanese patients diagnosed with RA who underwent treatment with biological and targeted synthetic disease-modifying anti-rheumatic drugs (b/tsDMARDs). We compared the differences in patient characteristics between the D2T RA and non-D2T RA groups. We examined the factors contributing to a good response [defined as b/tsDMARD continuation and Clinical Disease Activity Index (CDAI) ≤ 10 at 12 months] in the D2T RA patient group. RESULTS: Forty-three patients (14%) were categorized as D2T RA and the remaining 264 (86%) as non-D2T RA at baseline. The grey-scale (GS) score, disease duration, and CDAI at the initiation of treatment were significantly higher in the D2T RA group than in the non-D2T RA group. In contrast, the power Doppler (PD) score was not significantly different between the two groups. Of the 43 D2T RA patients, 20 achieved a good response. The introduction of CTLA4-Ig (n = 5) was significantly associated with a good response in analysis based on inverse probability weighting with propensity score. GS and PD scores at baseline were not significantly associated with therapeutic response at 12 months in D2T RA patients. CONCLUSIONS: Patients with D2T RA had high clinical and ultrasound activity and poor responses to treatment with b/tsDMARDs. CTLA4-Ig was associated with a good response at 12 months in D2T RA patients.

Ultrasound efficacy of targeted-synthetic disease-modifying anti-rheumatic drug treatment in rheumatoid arthritis: a multicenter prospective cohort study in Japan.

OBJECTIVE: This study investigated the effectiveness of treatment with Janus kinase (JAK) inhibitors in rheumatoid arthritis (RA) assessed by ultrasonography (US) activity, and the influence of patient characteristics and previous treatments. METHOD: This prospective study assessed 60 treatment initiations among 53 Japanese patients diagnosed with RA who underwent treatment with JAK inhibitors during June 2013 to February 2020. Of the 53 patients, seven patients were enrolled in duplicate because they were treated with two different JAK inhibitors at different periods. For each case, the improvement rate on the power Doppler (PD) score was assessed at 6 month follow-up. Median improvement rate of PD score was used to classify cases as either US responders or non-responders, and patient characteristics were compared between the two groups. RESULTS: All indicators of clinical disease activity and US activity showed a significant improvement at 3 months compared with baseline. Although the JAK inhibitor-cycler group and the interleukin-6 (IL-6) inhibitor inadequate response (IR) group tended to show a later improvement for US activity, all indicators of clinical disease activity and US activity showed a significant improvement at 6 months compared with baseline for both groups. Multivariate analysis showed that concomitant methotrexate use and an IR to the previous biologic or targeted-synthetic disease-modifying anti-rheumatic drug (b/tsDMARD) treatment were independently and significantly associated with US responders. CONCLUSION: Use of a JAK inhibitor in combination with methotrexate and an absence of IR to any previous b/tsDMARDs demonstrated superior effectiveness for patients with RA.

Significance of anti-Ro/SSA antibodies in the response and retention of abatacept in patients with rheumatoid arthritis: a multicentre cohort study.

Objective: To determine whether the positivity of baseline anti-Ro/Sjögren's syndrome antigen A (SSA) antibodies influences the response to abatacept, we compared therapeutic responses between anti-Ro/SSA antibody-negative and -positive patients with rheumatoid arthritis (RA) using a multicentre RA ultrasonography prospective cohort. Method: We reviewed Japanese patients with RA who started abatacept as the first biological disease-modifying anti-rheumatic drug between June 2013 and April 2018. We assessed 28-joint Disease Activity Score-erythrocyte sedimentation rate (DAS28-ESR) change between baseline and 6 or 12 months after treatment in RA patients treated with abatacept, and European League Against Rheumatism (EULAR) response at 6 and 12 months. The Global OMERACT-EULAR Synovitis Score (GLOESS) was calculated at baseline and at 6 and 12 months. Results: Overall, 51 patients were enrolled and divided into anti-Ro/SSA antibody-negative and -positive groups of 35 and 16, respectively. Median age at baseline was significantly higher in the anti-Ro/SSA antibody-negative group (p = 0.04). The retention rate and percentage of EULAR good responders at 12 months were significantly higher in the anti-Ro/SSA antibody-negative group (both p = 0.02). Anti-Ro/SSA antibody-negative patients exhibited larger decreases in both DAS28-ESR and DAS28-C-reactive protein at 12 months than anti-Ro/SSA antibody-positive patients (p = 0.02 and 0.04, respectively). GLOESS decreased significantly at 6 months in anti-Ro/SSA antibody-negative patients (p = 0.03). Multivariate analyses showed that anti-Ro/SSA antibody positivity was an independent factor associated with change in the DAS28-ESR at 6 months (p < 0.05). Conclusion: Anti-Ro/SSA antibody positivity predicts a poor response to abatacept and low retention rate.

Discrepancy between clinical and ultrasound remissions in rheumatoid arthritis: a multicentre ultrasound cohort study in Japan.

Objectives: Using multicentre ultrasound (US) cohort data among patients with rheumatoid arthritis (RA), we aimed to identify baseline factors that permit differentiation between two patient cohorts achieving US remission and clinical remission, and to determine the factors contributing to the discrepancy.Method: We reviewed 248 Japanese patients diagnosed with RA who underwent treatment with biological disease-modifying anti-rheumatic drugs at 13 centres. We performed US assessments of the synovia of 22 joints. We assessed the percentages of patients with clinical remission and US remission, defined as total power Doppler scores of 0 at 12 months.Results: The 87 patients who achieved US remission were divided into a group that achieved both clinical and US remission (n = 53) and a group that achieved US remission only (n = 34). Baseline factors that were significantly and independently associated with clinical remission at 12 months among patients who also achieved US remission included short disease duration, the presence of concomitant methotrexate use, and low patient global assessment score (p < 0.05, p < 0.05, and p < 0.005, respectively).Conclusions: RA patients with baseline high patient global assessment scores and long disease duration at baseline were unlikely to achieve clinical remission even after achieving US remission. Objective joint assessments using US provide additional information of potential importance for the management of RA.

Anti-citrullinated protein antibody titre as a predictor of abatacept treatment persistence in patients with rheumatoid arthritis: a prospective cohort study in Japan.

Objective: Successful rheumatoid arthritis (RA) outcome depends on treatment efficacy in the early stages of the disease and its sustainability. It is thus critical to identify factors predicting treatment persistence with biological agents, such as abatacept. We compared clinical profiles, including early changes in autoantibody titres at 3 months, between patients with RA demonstrating sustained persistence and those discontinuing abatacept treatment.Method: We prospectively enrolled 71 and 78 active RA patients treated with abatacept and tumour necrosis factor inhibitors (TNF-Is), respectively, who had previous disease-modifying anti-rheumatic drug) failure. Clinical characteristics were compared between non-continuation and continuation groups stratified according to abatacept or TNF-I persistence for at least 12 months from treatment initiation.Results: Significantly larger decreases in rheumatoid factor titre and anti-citrullinated protein autoantibody (ACPA) titre were observed in the continuation group of abatacept therapy at 3 months, and early reduction in ACPA titre remained a significant and independent predictor of sustained persistence with abatacept in multivariate analysis. In addition, we obtained the area under the receiver operator characteristics curve of 0.904 from a model including baseline ACPA titre and reduction of ACPA titre at 3 months. Sustained reduction of RA disease activity score at 12 months was significantly and independently associated with reduced ACPA titre at 3 months.Conclusions: Persistence with abatacept and sustained therapeutic response are associated with an early reduction in ACPA titre. Prediction of abatacept continuation and efficacy will facilitate the optimal design of therapy in the early stages of RA.

Factors predictive of long-term mortality in lupus nephritis: a multicenter retrospective study of a Japanese cohort.

BACKGROUND: Lupus nephritis (LN) is a major determinant of mortality in systemic lupus erythematosus (SLE). Here we evaluated the association between complete renal response (CR) and mortality in LN. METHODS: We retrospectively analyzed the cases of 172 of 201 patients with LN for whom data on the therapeutic response at 6 and 12 months after induction therapy were available. The patients underwent a renal biopsy at Nagasaki University Hospital and community hospitals in Nagasaki between the years 1990 and 2016. We determined the CR rates at 6 and 12 months after induction therapy initiation and evaluated the predictive factors for CR and their relationship with mortality. We performed univariate and multivariable competing risks regression analyses to determine the factors predictive of CR. The patients' survival data were analyzed by the Kaplan-Meier method with a log-rank test. RESULTS: The median follow-up duration after renal biopsy was 120 months (interquartile range: 60.3-191.8 months). The 5-, 10-, 15- and 20-year survival rates of our cohort were 99.3, 94.6, 92.0 and 85.4%, respectively. During follow-up, nine patients (5.2%) died from cardiovascular events, infection, malignancy and other causes. The multivariate analysis revealed that the following factors were predictive of CR. At 6 months: male gender (odds ratio (OR) 0.23, 95% confidence interval (CI) 0.08-0.65, p = 0.0028), proteinuria (g/gCr) (OR 0.83, 95% CI 0.71-0.97, p = 0.0098) and index of activity (0-24) (OR 0.84, 95% CI 0.71-0.99, p = 0.0382). At 12 months: male gender (OR 0.25, 95% CI 0.09-0.67, p = 0.0043) and index of activity (0-24) (OR 0.82, 95% CI 0.69-0.98, p = 0.0236). The Kaplan-Meier analysis showed that compared to not achieving CR at 12 months, achieving CR at 12 months was significantly correlated with the survival rate (OR 0.18, 95% CI 0.04-0.92, p = 0.0339). CONCLUSIONS: Our results suggest that the survival rate of patients with LN is associated with the achievement of CR at 12 months after induction therapy, and that male gender and a higher index of activity (0-24) are the common predictive factors for failure to achieve CR at 6 and 12 months.

Human immunology studies using organ donors: Impact of clinical variations on immune parameters in tissues and circulation.

Organ donors are sources of physiologically healthy organs and tissues for life-saving transplantation, and have been recently used for human immunology studies which are typically confined to the sampling of peripheral blood. Donors comprise a diverse population with different causes of death and clinical outcomes during hospitalization, and the effects of such variations on immune parameters in blood and tissues are not known. We present here a coordinate analysis of innate and adaptive immune components in blood, lymphoid (bone marrow, spleen, lymph nodes), and mucosal (lungs, intestines) sites from a population of brain-dead organ donors (2 months-93 years; n = 291) across eight clinical parameters. Overall, the blood of donors exhibited similar monocyte and lymphocyte content and low serum levels of pro-inflammatory cytokines as healthy controls; however, donor blood had increased neutrophils and serum levels of IL-8, IL-6, and MCP-1 which varied with cause of death. In tissues, the frequency and composition of monocytes, neutrophils, B lymphocytes and T cell subsets in lymphoid or mucosal sites did not vary with clinical state, and was similar in donors independent of the extent of clinical complications. Our results reveal that organ donors maintain tissue homeostasis, and are a valuable resource for fundamental studies in human immunology.

Interference Effect between ϕ and Λ(1520) Production Channels in the γp→K

The ϕ-Λ(1520) interference effect in the γp→K^{+}K^{-}p reaction has been measured for the first time in the energy range from 1.673 to 2.173 GeV. The relative phases between ϕ and Λ(1520) production amplitudes were obtained in the kinematic region where the two resonances overlap. The measurement results support strong constructive interference when K^{+}K^{-} pairs are observed at forward angles but destructive interference for proton emission at forward angles. Furthermore, the observed interference effect does not account for the sqrt[s]=2.1 GeV bump structure in forward differential cross sections for ϕ photoproduction. This fact suggests possible exotic structures such as a hidden-strangeness pentaquark state, a new Pomeron exchange, or rescattering processes via other hyperon states.

Phosphorylated neurofilament subunit NF-H as a biomarker for evaluating the severity of spinal cord injury patients, a pilot study.

STUDY DESIGN: A pilot cross-sectional study of patients with acute cervical spinal cord injury (SCI). OBJECTIVES: The precise evaluation of the severity of SCI is important for developing novel therapies. Although several biomarkers in cerebrospinal fluid have been tested, few analyses of blood samples have been reported. A novel biomarker for axonal injury, phosphorylated form of the high-molecular-weight neurofilament subunit NF-H (pNF-H), has been reported to be elevated in blood from rodent SCI model. The aim of this study is to investigate whether pNF-H values in blood can serve as a biomarker to evaluate the severity of patients with SCI. SETTING: Tokyo Metropolitan Bokutoh Hospital and National Rehabilitation Center, Japan. METHODS: This study enrolled 14 patients with acute cervical SCI. Sequential plasma samples were obtained from 6 h to 21 days after injury. Patients were classified according to American Spinal Injury Association impairment scale (AIS) at the end of the follow-up (average, 229.1 days). Plasma pNF-H values were compared between different AIS grades. RESULTS: In patients with complete SCI, pNF-H became detectable at 12 h after injury and remained elevated at 21 days after injury. There was a statistically significant difference between AIS A (complete paralysis) patients and AIS C (incomplete paralysis) patients. CONCLUSIONS: Plasma pNF-H was elevated in accordance with the severity of SCI and reflected a greater magnitude of axonal damage. Therefore, pNF-H is a potential biomarker to independently distinguish AIS A patients (complete SCI) from AIS C-E patients (incomplete SCI). However, further studies are required to evaluate its utility in predicting prognosis of patients in the incomplete category.

Norzotepine, a major metabolite of zotepine, exerts atypical antipsychotic-like and antidepressant-like actions through its potent inhibition of norepinephrine reuptake.

The antipsychotic drug zotepine [ZTP; 2-[(8-chlorodibenzo[b,f]thiepin-10-yl)oxy]-N,N-dimethylethan-1-amine] is known to have not only atypical antipsychotic effects but also antidepressive effects in schizophrenia patients. Norzotepine [norZTP; N-desmethylzotepine, 2-[(8-chlorodibenzo[b,f]thiepin-10-yl)oxy]-N-methylethan-1-amine] has been postulated to be a major metabolite of ZTP in humans. Here, we characterized norZTP through several in vitro studies and in animal models of psychosis, depression, and extrapyramidal symptoms (EPS) and compared the pharmacological profiles with those of ZTP. Although both compounds showed similar overall neurotransmitter receptor binding profiles, norZTP showed 7- to 16-fold more potent norepinephrine reuptake inhibition than ZTP. In a pharmacokinetic study, both ZTP and norZTP showed good brain permeability when administered individually in mice, although norZTP was not detected in either plasma or brain after intraperitoneal injection of ZTP. In the methamphetamine-induced hyperlocomotion test in mice, norZTP and ZTP showed similar antipsychotic-like effects at doses above 1 mg/kg i.p. In contrast, unlike ZTP, norZTP did not induce catalepsy up to 10 mg/kg i.p. norZTP significantly antagonized the hypothermia induced by reserpine [(3beta,16beta,17alpha,18beta,20alpha)-11,17-dimethoxy-18-[(3,4,5-trimethoxybenzoyl)oxy]yohimban-16-carboxylic acid methyl ester], suggesting in vivo inhibition of the norepinephrine transporter. In the forced-swim test, norZTP exerted an antidepressant-like effect at the effective doses for its antipsychotic action, whereas ZTP neither antagonized reserpine-induced hypothermia nor showed antidepressant-like effect. These results collectively demonstrate that norZTP exerts more potent inhibitory action than ZTP on norepinephrine transporters both in vitro and in vivo, presumably accounting for its antidepressant-like effect and low EPS propensity. Given that norZTP is the major metabolite observed in humans, norZTP may contribute to the unique clinical profiles of its mother compound, ZTP.

Near-threshold Lambda(1520) production by the gamma(p)-->K{+}Lambda(1520) reaction at forward K+ angles.

Differential cross sections and photon-beam asymmetries for the gamma(p)-->K{+}Lambda(1520) reaction have been measured with linearly polarized photon beams at energies from the threshold to 2.4 GeV at 0.6or=5/2 or by a new reaction process, for example, an interference effect with the phi photoproduction having a similar bump structure in the cross sections.

Pathophysiological role of leptin in obesity-related hypertension.

To explore the pathophysiological role of leptin in obesity-related hypertension, we examined cardiovascular phenotypes of transgenic skinny mice whose elevated plasma leptin concentrations are comparable to those seen in obese subjects. We also studied genetically obese KKA(y) mice with hyperleptinemia, in which hypothalamic melanocortin system is antagonized by ectopic expression of the agouti protein. Systolic blood pressure (BP) and urinary catecholamine excretion are elevated in transgenic skinny mice relative to nontransgenic littermates. The BP elevation in transgenic skinny mice is abolished by alpha(1)-adrenergic, beta-adrenergic, or ganglionic blockers at doses that do not affect BP in nontransgenic littermates. Central administration of an alpha-melanocyte-stimulating hormone antagonist causes a marked increase in cumulative food intake but no significant changes in BP. The obese KKA(y) mice develop BP elevation with increased urinary catecholamine excretion relative to control KK mice. After a 2-week caloric restriction, BP elevation is reversed in nontransgenic littermates with the A(y) allele, in parallel with a reduction in plasma leptin concentrations, but is sustained in transgenic mice overexpressing leptin with the A(y) allele, which remain hyperleptinemic. This study demonstrates BP elevation in transgenic skinny mice and obese KKA(y) mice that are both hyperleptinemic, thereby suggesting the pathophysiological role of leptin in some forms of obesity-related hypertension.

Glucocorticoid receptor activation is involved in producing abnormal phenotypes of single-prolonged stress rats: a putative post-traumatic stress disorder model.

Post-traumatic stress disorder (PTSD) is a stress-related mental disorder caused by traumatic experience, and presents with characteristic symptoms, such as intrusive memories, a state of hyperarousal, and avoidance, that endure for years. Single-prolonged stress (SPS) is one of the animal models proposed for PTSD. Rats exposed to SPS showed enhanced inhibition of the hypothalamo-pituitary-adrenal (HPA) axis, which has been reliably reproduced in patients with PTSD, and increased expression of glucocorticoid receptor (GR) in the hippocampus. In this study, we characterized further neuroendocrinologic, behavioral and electrophysiological alterations in SPS rats. Plasma corticosterone recovered from an initial increase within a week, and gross histological changes and neuronal cell death were not observed in the hippocampus of the SPS rats. Behavioral analyses revealed that the SPS rats presented enhanced acoustic startle and impaired spatial memory that paralleled the deficits in hippocampal long-term potentiation (LTP) and depression. Contextual fear memory was enhanced in the rats 1 week after SPS exposure, whereas LTP in the amygdala was blunted. Interestingly, blockade of GR activation by administering 17-beta-hydroxy-11-beta-/4-/[methyl]-[1-methylethyl]aminophenyl/-17-alpha-[prop-1-ynyl]estra-4-9-diene-3-one (RU40555), a GR antagonist, prior to SPS exposure prevented potentiation of fear conditioning and impairment of LTP in the CA1 region. Altogether, SPS caused a number of behavioral changes similar to those described in PTSD, which marks SPS as a putative PTSD model. The preventive effects of a GR antagonist suggested that GR activation might play a critical role in producing the altered behavior and neuronal function of SPS rats.

Purinergic P2X receptor activation induces emetic responses in ferrets and Suncus murinus (house musk shrews).

BACKGROUND AND PURPOSE: Despite the rapid progress made in understanding the significant role played by signalling via extracellular ATP in physiology and pathology, there has been no clear information generated on its involvement in the emetic response. EXPERIMENTAL APPROACH: In the present study, the emetogenic potential of extracellular ATP signalling in mammalian species was examined using ferrets and Suncus murinus (house musk shrews). A slowly degradable ATP analogue, alpha,beta-methyleneATP (alpha,beta-meATP), was used to activate the P2X receptors, and either the non-selective P2 receptor antagonist, pyridoxal phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), or the specific P2X(3) homomer and P2X(2/3) heteromer antagonist, A-317491, were tested against the agonist-induced response. KEY RESULTS: Intraperitoneal injection of alpha,beta-meATP produced significant emetic responses in ferrets (1 - 30 mg kg(-1)) and in Suncus murinus (5 - 50 mg kg(-1)). The responses occurred frequently within the first 10 min after administration, much less frequently from 11 to 60 min and no responses occurred later than 60 min. The emetic responses were completely inhibited by intraperitoneal pre-treatment with PPADS (100 mg kg(-1)) or A-317491 (100 mg kg(-1)). Abdominal surgical vagotomy did not reduce the emetic response in Suncus murinus significantly. CONCLUSIONS AND IMPLICATIONS: These results for the first time indicate that the activation of P2X receptors evokes emetic responses in mammalian species. The P2X(3) homomer and.or P2X(2/3) heteromer in the area postrema could be responsible for the emetic response. This finding contributes to the elucidation of the roles played by extracellular ATP signalling in various emetic symptoms.

Tacrolimus (FK506) attenuates biphasic cytochrome c release and Bad phosphorylation following transient cerebral ischemia in mice.

Tacrolimus (FK506) has a neuroprotective action on cerebral infarction produced by cerebral ischemia, however, detailed mechanisms underlying this action have not been fully elucidated. We examined temporal profiles of survival-and death-related signals, Bad phosphorylation, release of cytochrome c (cyt.c), activation of caspase 3 and DNA fragmentation in the brain during and after middle cerebral artery occlusion (MCAo) in mice, and then examined the effect of tacrolimus on these signals. C57BL/6J mice were subjected to transient MCAo by intraluminal suture insertion for 60 min. Tacrolimus (1 mg/kg, i.p.) was administered immediately after MCAo. There were biphasic increases in the release of cyt.c in the ischemic core and penumbra; with the first increase toward the end of the occlusion period and the second increase 3-12 h after reperfusion. Tacrolimus significantly inhibited the increase of cytosolic cyt.c during ischemia and reperfusion. Phosphorylated Bad, Ser-136 (P-Bad(136)) and Ser-155 (P-Bad(155)) were detected 30 min after MCAo and after reperfusion in the ischemic cortex, respectively. Tacrolimus increased P-Bad(136) during ischemia and prolonged P-Bad(155) expression after reperfusion. Tacrolimus also decreased caspase-3 and terminal deoxynucleotidyl transferase-mediated DNA nick-end labeling-positive cells, and reduced the size of infarct 24 h after reperfusion. Our study provided the first evidence that the neuroprotective action of tacrolimus involved inhibition of biphasic cyt.c release from mitochondria, possibly via up-regulation of Bad phosphorylation at different sites after focal cerebral ischemia and reperfusion.

Interaction of lipoprotein lipase with phospholipid vesicles. Role of apolipoprotein C-II and heparin.

Lipoprotein lipase is bound to heparin-like molecules at the surface of capillary endothelial cells. For maximal activity, the enzyme requires apolipoprotein C-II, a protein constituent of triacylglycerol-rich lipoproteins. In this report, the interactions of apolipoprotein C-II, heparin and sonicated vesicles of dipalmitoylphosphatidylcholine with purified bovine milk lipoprotein lipase were studied by gel filtration on Bio-Gel A5m. In the presence of vesicles of dipalmitoylphosphatidylcholine (1 mg), lipoprotein lipase (25 micrograms) associated with phospholipids even in the absence of apolipoprotein C-II. With limited phospholipid (40 micrograms), the amount of enzyme which associated with lipid decreased in the presence of apolipoprotein C-II (20 micrograms). Human plasma apolipoprotein C-III, another protein constituent of triacylglycerol-rich lipoproteins, also caused a decrease in the amount of enzyme associated with phospholipid. These results suggest that apolipoprotein C-II does not increase the activity of the enzyme by facilitating its interaction with a lipid interface. In the absence of lipid, lipoprotein lipase and apolipoprotein C-II (molar ratio, 1 : 1) eluted from Bio-Gel A5m as two separate components. The interaction of heparin with lipoprotein lipase was studied using a specific [3H]heparin, which was isolated by affinity chromatography on immobilized lipoprotein lipase; the [3H]heparin eluted with 0.6 M NaCl. Specific [3H]heparin coeluted with lipoprotein lipase when the enzyme was associated with phospholipid; the [3H]heparin was released from the enzyme by 0.75 M NaCl.

Preparation and properties of immobilized lipoprotein lipase.

Purified bovine milk lipoprotein lipase has been covalently attached to CH-Sepharose with water-soluble carbodiimide. The immobilized enzyme retained enzymic activity and was stimulated 7-fold by the addition of human apolipoprotein C-II. Both [3H]heparin and 125I-labeled apolipoprotein C-II bound to the immobilized enzyme; unlabeled heparin and apolipoprotein C-II competed for binding of their respective labeled compounds. Apolipoprotein C-II did not compete for binding of [3H]heparin and vice versa. Human apolipoprotein C-III did not bind to the immobilized enzyme nor did it compete for apolipoprotein C-II binding. We conclude from these studies that both apolipoprotein C-II and heparin interact with immobilized lipoprotein lipase and that they have different binding sites.

Post-heparin plasma hepatic triacylglycerol lipase-catalyzed hydrolysis of tributyrin. Effect of lipid interface.

The mechanism of action of hepatic triacylglycerol lipase (EC 3.1.1.3) was examined by comparing the hydrolysis of a water-soluble substrate, tributyrin, with that of triolein by hepatic triacylglycerol lipase purified from human post-heparin plasma. The hydrolyzing activities toward tributyrin and triolein were coeluted from heparin-Sepharose at an NaCl concentration of 0.7 M. The maximal velocity of hepatic triacylglycerol lipase (Vmax) for tributyrin was 17.9 mumol/mg protein per h and the Michaelis constant (Km) value was 0.12 mM, whereas the Vmax for triolein was 76 mumol/mg per h and the Km value was 2.5 mM. The hydrolyses of tributyrin and triolein by hepatic triacylglycerol lipase were inhibited to similar extends by procainamide, NaF, Zn2+, Cu2+, Mn2+, SDS and sodium deoxycholate. Triolein hydrolysis was inhibited by the addition of tributyrin. Triolein hydrolysis was also inhibited by the addition of dipalmitoylphosphaidylcholine vesicles. In contrast, the additions of triolein emulsified with Triton X-100 and dipalmitoylphosphatidylcholine vesicles enhanced the rate of tributyrin hydrolysis by hepatic triacylglycerol lipase. In the presence of dipalmitoylphosphatidylcholine, the Vmax and Km values of hepatic triacylglycerol lipase for tributyrin were 41 mumol/mg protein per h and 0.12 mM, respectively, indicating that the enhancement of hepatic triacylglycerol lipase activity for tributyrin by dipalmitoylphosphatidycholine vesicles was mainly due to increase in the Vmax. The enhancement of hepatic triacylglycerol lipase activity for tributyrin by phospholipid was not correlated with the amount of tributyrin associated with the phospholipid vesicles. On Bio-Gel A5m column chromatography, glycerol tri[1-14C]butyrate was not coeluted with triolein emulsion, and hepatic triacylglycerol lipase activity was associated with triolein emulsion even in the presence of 2 mM tributyrin. These results suggest that hepatic triacylglycerol lipase has a catalytic site for esterase activity and a separate site for lipid interface recognition, and that on binding to a lipid interface the conformation of the enzyme changes, resulting in enhancement of the esterase activity.

Effect of dextran sulfate on the interaction between very low density lipoprotein and lipoprotein lipase.

The effect of dextran sulfate on the interaction between very low density lipoprotein (VLDL) and purified bovine milk lipoprotein was studied. Dextran sulfate increased VLDL-triacylglycerol hydrolysis by lipoprotein lipase about 2-fold, but did not alter the Km value for triacylglycerol in VLDL. Strong association of dextran sulfate with the VLDL-lipoprotein lipase complex was demonstrated by gel filtration on BioGel A-5m, although dextran sulfate did not bind to VLDL and only very slightly to lipoprotein lipase. These findings suggest that dextran sulfate increases triacylglycerol hydrolysis in VLDL by binding to the VLDL-lipoprotein lipase complex.

Involvement of agouti-related protein, an endogenous antagonist of hypothalamic melanocortin receptor, in leptin action.

To understand the role of agouti-related protein (AGRP), an endogenous antagonist of hypothalamic melanocortin receptor, in leptin action, we produced a full-length recombinant AGRP and examined its effect on the satiety effect of leptin. We also studied leptin's regulation of hypothalamic AGRP mRNA expression. A single intracerebroventricular (i.c.v.) injection of AGRP significantly increased cumulative food intake and body weight in a dose-dependent manner in rats. The leptin-induced inhibition of food intake and body weight was reversed by co-injection of AGRP in a dose-dependent manner. Hypothalamic AGRP mRNA expression was upregulated in leptin-deficient ob/ob mice and leptin receptor-deficient db/db mice and downregulated in lethal yellow agouti mice (KKAy mice) with hyperleptinemia. A single i.c.v. injection of leptin reversed the increased AGRP mRNA levels in ob/ob mice but not in db/db mice. In control mice and KKAy mice, AGRP mRNA expression was upregulated during fasting, when plasma leptin concentrations were decreased. No significant increase in AGRP mRNA expression was noted during fasting in control mice and KKAy mice treated with leptin. This study provides the first direct evidence that AGRP is a negative regulator of leptin action, and leptin downregulates hypothalamic AGRP production. Because leptin is shown to increase hypothalamic alpha-melanocyte stimulating hormone (alpha-MSH) production, our data suggest that its action via the hypothalamic melanocortin system is determined by the balance between the levels of its agonist and antagonist, alpha-MSH and AGRP.