Injection Of P-407 Research Articles

Developing a model to predict the early risk of hypertriglyceridemia based on inhibiting lipoprotein lipase (LPL): a translational study

Hypertriglyceridemia (HTG) is an independent risk factor for atherosclerotic cardiovascular disease (ASCVD). One of the multiple origins of HTG alteration is impaired lipoprotein lipase (LPL) activity, which is an emerging target for HTG treatment. We hypothesised that early, even mild, alterations in LPL activity might result in an identifiable metabolomic signature. The aim of the present study was to assess whether a metabolic signature of altered LPL activity in a preclinical model can be identified in humans. A preclinical LPL-dependent model of HTG was developed using a single intraperitoneal injection of poloxamer 407 (P407) in male Wistar rats. A rat metabolomics signature was identified, which led to a predictive model developed using machine learning techniques. The predictive model was applied to 140 humans classified according to clinical guidelines as (1) normal, less than 1.7 mmol/L; (2) risk of HTG, above 1.7 mmol/L. Injection of P407 in rats induced HTG by effectively inhibiting plasma LPL activity. Significantly responsive metabolites (i.e. specific triacylglycerols, diacylglycerols, phosphatidylcholines, cholesterol esters and lysophospholipids) were used to generate a predictive model. Healthy human volunteers with the impaired predictive LPL signature had statistically higher levels of TG, TC, LDL and APOB than those without the impaired LPL signature. The application of predictive metabolomic models based on mechanistic preclinical research may be considered as a strategy to stratify subjects with HTG of different origins. This approach may be of interest for precision medicine and nutritional approaches.

NADPH oxidase participates in pancreatic injury in rats with acute hypertriglyceridemic pancreatitis by regulating Akt/GSK3 β pathway

Objective To investigate the aggravation of pancreatic tissue injury in rats with acute hypertriglyceridemic pancreatitis and the possible role of NADPH oxidase (NOX). Methods Thirty SPF rats were randomly (random number)divided into five groups: N group, H group, NLAP group, HLAP group and HAPO group. AMY, TG, TC and FFA levels were detected. The pathological changes of pancreas were observed under light microscope and the ultrastructural changes of pancreatic acinar cells were observed by TEM. Serum levels of MDA, SOD, IL-1β, TNF-α and LDH were detected. The expression of NOX4, p-Akt and p-GSK3β in pancreas was detected by immunofluorescence, and the expression of NF-κB and TNF-α in pancreas was detected by immunohistochemistry. Results Intraperitoneal injection of P-407 could significantly increase the levels of serum TG, TC and FFA in rats. After acute pancreatitis induced by L-Arg, the levels of serum AMY in the NLAP and HLAP groups were significantly increased, while Apocynin could significantly decrease the level of serum AMY. Compared with the NLAP group, the pathological injury of pancreatic tissue in the HLAP group was more serious, the level of inflammatory mediators was significantly increased, and the cell necrosis was more serious. After inhibiting NOX, the activation of Akt/GSK3β pathway was regulated and the pancreatic injury was improved. Conclusion In HTGP, NOX aggravates pancreatic injury by regulating the activation of Akt/GSK3 β pathway. Inhibition of NOX expression can play a protective role in pancreas injury of HTGP.. Key words: Hypertriglyceridemia; Acute pancreatitis; Pancreatic injury; NADPH oxidase; Oxidative stress

Effect of Garcinia kola biflavonoid fractions on some biochemical parameters of P407-induced hyperlipidemic albino rats: a phytopreventive and phytotherapeutic studies

The phytopreventive and phytotherapeutic effects of Garcinia kola biflavonoid fractions on some biochemical parameters in Poloxamer 407 (P407)-induced hyperlipidemic rats were studied for a period of 21 days. Sixty mixed sex Wistar rats weighing 150–200 g were divided into two major groups: (1) phytopreventive group comprising the following subgroups: normal control, P407-induced hyperlipidemic control, and groups treated orally with atorvastatin as standard drug, root bark, stem bark, and seed biflavonoid fractions of G. kola, respectively, for 19 days and made hyperlipidemic with a single intraperitoneal injection on day 19; (2) phytotherapeutic group comprising similar subgroups that were induced by an intraperitoneal injection of P407 every 48 h and treated with atorvastatin, root bark, stem bark, and seed biflavonoid fractions for 21 days. In both groups, atorvastatin, P407, and the G. kola biflavonoid fractions were administered at 10, 500, and 200 mg/kg body weight, respectively. Blood samples were collected from the rats in all the groups at the end of the experiment for determination of serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total protein (TP), albumin (ALB), total bilirubin (TB), conjugated bilirubin (CB), and fasting blood glucose (FBG) using Randox kits. Serum concentration of AST was significantly (p 0.05) different from the normal rats. These results highlight the efficacy of G. kola (root bark, stem bark, and seed) biflavonoid fractions in the amelioration of some undesirable effects of hyperlipidemia.

Preventive and Therapeutic Effects of Garcinia kola Biflavonoid Fractions on some Haematological Parameters of P407 Induced Hyperlipidemic Albino Rats

The preventive and therapeutic effects of Garcinia kola biflavonoid fractions on some haematological parameters in Poloxamer 407 (P407) induced hyperlipidemic rats was studied for a period of 21 days. Sixty mixed sex Wistar rats weighing 150-200 g were divided into two major groups; Preventive group comprising the following sub-groups: normal control, P407 induced hyperlipidemic control and groups treated orally with atorvastatin as standard drug, root bark, stem bark and seed biflavonoid fractions of Garcinia kola respectively for 19 days and made hyperlipidemic with a single intraperitoneal injection on day 19. Therapeutic group comprising similar subgroups were induced by an intraperitoneal injection of P407 every 48 hours and treated with atorvastatin, root bark, stem bark and seed biflavonoid fractions for 21 days. In both groups, atorvastatin, P407 and the Garcinia kola biflavonoid fractions were administered at 10 mg/kg, 500 mg/kg and 200 mg/kg body weight respectively. Blood samples were collected from the rats in all the groups at the end of the experiment for determination of some haematological parameters levels; Packed Cell Volume (PCV), Platelet, neutrophils, lymphocytes, Haemoglobin (Hb), Mean Corpuscular Haemoglobin (MCH), Mean Corpuscular Haemoglobin Concentration (MCHC), Mean Corpuscular Volume (MCV), Red Blood Cell (RBC) Count and White Blood Cell (WBC) Count were determined using the Sysmex Haematological Autoanalyzer. In both groups, atorvastatin and all biflavonoid fractions significantly (p 0.05) change on the level of neutrophils compared to hyperlipidemic control. The seed biflavonoid fraction significantly (p 0.05) change in the levels of the other determined haematological parameters in both groups. These results suggest that Garcinia kola (root bark, stem bark and seed) biflavonoid fractions could be potential drugs for the prevention and treatment of platelet-activity thrombosis as well as erythropoietic, protective and stimulating effect.

Poloxamer 407-induced atherosclerosis in mice appears to be due to lipid derangements and not due to its direct effects on endothelial cells and macrophages.

Coronary heart disease secondary to atherosclerosis is still the leading cause of death in the US. Animal models used for elucidating the pathogenesis of this disease primarily involve rabbits and pigs. Previous studies from this laboratory have demonstrated intraperitoneal injections of poloxamer 407 (P-407) in both male and female mice will lead to hyperlipidemia and atherosclerosis, suggesting the use of this polymer to develop a mouse model of atherosclerosis. In order to understand the mechanism of P-407-induced hyperlipidemia and vascular lesion formation, we evaluated the direct effects of P-407 on endothelial cell and macrophage functions in vitro, and its in vivo effects on the oxidation of circulating lipids following long-term (4 month) administration. Our results demonstrated that incubation of P-407 with human umbilical vein endothelial cells in culture did not influence either cell proliferation or interleukin-6 and interleukin-8 production over a concentration range of 0-40 microM. In addition, nitric oxide production by macrophages was not affected by P-407 over a concentration range of 0-20 microM. Finally, we demonstrated that while P-407 could not induce the oxidation of LDL-C in vitro, long-term (4 month) administration of P-407 in mice resulted in elevated levels of oxidized lipids in the plasma. Thus, it is suggested that the formation of atherosclerotic lesions in this mouse model of atherosclerosis does not result from either direct stimulation of endothelial cells or macrophage activation by P-407. Instead, these data would support the premise that oxidation of lipids (perhaps low-density lipoprotein cholesterol) by an indirect mechanism following injection of P-407 may represent one of the mechanisms responsible for atheroma formation.

Effect of poloxamer 407 on the activity of microsomal 3-hydroxy-3-methylglutaryl CoA reductase in rats.

A single 300-mg i.p. injection of poloxamer 407 (P-407, also called Pluronic F-127) in rats produces a marked hypercholesterolemia for a minimum of 96 h. The purpose of this investigation was to determine mechanisms by which P-407 causes hypercholesterolemia. The enzyme targeted for investigation is the rate-limiting enzyme in cholesterolgenesis, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Injection of P-407 in fasted rats resulted in a significant (p < 0.05) elevation in plasma cholesterol (61.2 +/- 4.2 mg/dl) as soon as 1 h after injection compared with sham-injected controls (50.1 +/- 3.7 mg/dl). Plasma cholesterol (CHO) 24 h after injection of P-407 was 449 +/- 57 mg/dl, with the fastest rate of accumulation occurring from 1 to 12 h (approximately 16.6 mg/dl/h). Over the concentration range of 0-5 mM, P-407 did not appear significantly to affect the activity of HMG-CoA reductase in vitro. However, the enzymatic activity assayed in microsomal fractions isolated from the livers of P-407-injected rats reached a maximum of 262 +/- 42.6 pmol mevalonate/min/mg approximately 15 h after injection, with a subsequent decline to control activity (94.1 +/- 8.7 pmol/min/mg) at approximately 40 h after injection. At 48 h after injection of P-407, the activity of HMG-CoA reductase significantly (p < 0.05) decreased below control values with a mean activity of 9.4 +/- 1.2 pmol/min/mg. The CHO concentrations in hepatic tissue were significantly (p < 0.01) increased at 2 h (3.26 +/- 0.19 mg/g) and 4 h (3.75 +/- 0.38 mg/g) and significantly (p < .01) reduced at 15 h (1.56 +/- 0.19 mg/g) after injection of P-407 compared with tissue CHO concentrations determined in control animals (2.65 +/- 0.18 mg/g). However, the hepatic CHO content appeared to return to control values by 24 h (mean +/- SEM, 2.61 +/- 0.08 mg/g) after injection. These data suggest that the activity of HMG-CoA reductase is regulated by some indirect mechanism(s) after injection of P-407 in rats.

The effect of pravastatin on hepatic 3-hydroxy-3-methylglutaryl CoA reductase obtained from poloxamer 407-induced hyperlipidemic rats.

A single 300-mg intraperitoneal injection of poloxamer 407 (P-407) to rats produces a marked hypercholesterolemia for a minimum of 96 hours and increases the activity of hepatic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase compared with the enzyme activity found in microsomal homogenates of control animals. We attempted to determine whether inhibition of microsomal HMG-CoA reductase by pravastatin sodium would yield similar values for the maximum reaction in velocity (Vmax) and the HMG-CoA reductase-pravastatin dissociation constant (Ki) when the enzyme was in the activated state compared with the control state. Knowledge of the respective values for Vmax and Ki would allow us to determine whether P-407-induced hypercholesterolemia in the rat was refractory to pravastatin treatment. Over a pravastatin concentration range of 0.5-50 nM, enzyme activity in vitro decreased as the drug's concentration increased. A standard Dixon plot of mean values of reciprocal reaction velocity versus pravastatin concentration yielded Ki of 3.7 and 4.1 nM for the control and activated states, respectively. The Vmax for conversion of HMG-CoA to mevalonate in vitro in the presence of pravastatin was 3.5-fold greater when assayed in microsomal homogenates obtained from P-407-injected rats compared with control animals. Dixon plot analysis of the data resulted in Vmax of 58.1 and 202 pmol.min-1.mg-1 for the control and activated states, respectively. These data suggest that whereas the Vmax is affected, injection of P-407 to rats does not alter the binding affinity of pravastatin for receptor(s) contained in HMG-CoA reductase as reflected by similar Ki values. This experimental animal model may be an additional screen with which to rank order the relative potency of HMG-CoA reductase inhibitors by determining the drug's effectiveness when HMG-CoA reductase is in an activated state.

Mechanism of poloxamer 407-induced hypertriglyceridemia in the rat

One 300 mg i.p. injection of the nonionic surfactant poloxamer 407 (Pluronic® F-127) produces a significant increase above control of both circulating cholesterol and triglyceride (TG) concentrations. The present study was conducted to determine the effect of poloxamer 407 (P-407) on the capacity to hydrolyze circulating TG by lipoprotein lipase (LPL) in an attempt to determine the mechanism of action of P-407. The concentration of TG in the rat following a single 300 mg i.p. injection of P-407 was marked, increasing from 84 ± 10 to 3175 ± 322 mg/dL at 24 hr. The maximal rate of TG accumulation (5.74 mg/dL/min) in the plasma of P-407-injected rats occurred between 2 and 4 hr post-injection. In vitro incubation of LPL with P-407 significantly inhibited enzyme activity with an inhibitory concentration at which 50% of the enzymatic activity was lost of approximately 24 μM. Concentrations of P-407 exceeding 350 μM in vitro completely inhibited LPL activity. The effects of P-407 on the enzymatic activity of LPL in post-heparin plasma obtained following a single 300 mg dose of P-407 to rats demonstrated greater than 95% suppression of LPL activity 3 hr post-injection compared with controls. Inhibition of LPL activity was greater than 90% as long as 24 hr following a single i.p. injection of P-407. However, while the heparin-releasable fraction of capillary-bound LPL was inhibited in the plasma, LPL activity significantly increased in cardiac and skeletal muscle in poloxamer-injected animals compared with sham-injected controls. Although there was no significant change in LPL activity in adipose tissue, testes, and lung resulting from P-407 treatment, LPL activity increased by 37% in myocardium, 69% in soleus, and 66% in gastronemius muscle in P-407-injected rats when compared with controls. Our studies would suggest that the predominant mechanism by which P-407 induced an increase in circulating TG was by a reduction in the rate at which TG was hydrolyzed due to inhibition of heparin-releasable LPL by the surfactant.