Continuous pH-stat titration method for the assay of lipoprotein lipase activity in vitro

Evaluating anti-obesity potential, active components, and antioxidant mechanisms of Moringa peregrina seeds extract on high-fat diet-induced obesity

There are no medical drugs that provide an acceptable weight loss with minimal adverse effects. This study evaluated the Moringa peregrina (MP) seed extract's anti-obesity effect. Twenty-four (6/each group) male Sprague Dawley rats were divided into group Ι (control), group ΙΙ (high-fat diet [HFD]), group ΙΙΙ (HFD+ MP [250 mg/kg b.wt]), and group ΙV (HFD+ MP [500 mg/kg b.wt]). MP administration significantly ameliorated body weight gains and HFD induced elevation in cholesterol, triglycerides, LDL, and reduced HDL. Moreover, MP seed oil showed high free radical-scavenging activity, delayed β-carotene bleaching and inhibited lipoprotein and pancreatic lipase enzymes. High-performance liquid chromatography (HPLC) revealed three major active components: crypto-chlorogenic acid, isoquercetin, and astragalin. Both quantitative Real-time PCR (RT-PCR) and western blotting revealed that MP seeds oil significantly decreased the expression of lipogenesis-associated genes such as peroxisome proliferator-activated receptors gamma (PPARγ) and fatty acid synthase (FAS) and significantly elevated the expression of lipolysis-associated genes (acetyl-CoA carboxylase1, ACCl). The oil also enhanced phosphorylation of AMP-activated protein kinase alpha (AMPK-α) and suppressed CCAAT/enhancer-binding protein β (C/EBPβ). In conclusion, administration of M. peregrina seeds oil has anti-obesity potential in HFD-induced obesity in rats. PRACTICAL APPLICATIONS: M. peregrina seeds oil had a potential anti-obesity activity that may be attributed to different mechanisms. These included decreasing body weight, and body mass index and improving lipid levels by decreasing total cholesterol, triglycerides and LDL-C, and increasing HDL-C. Also, M. peregrina seeds oil regulated adipogenesis-associated genes, such as downregulating the expression of (PPARγ, C/EBPα, and FAS) and improving and upregulating the expression and phosphorylation of AMPKα and ACCl. Despite that M. peregrina extract has reported clear anti-obesity potential through animal and laboratory studies, the available evidence-based on human clinical trials are very limited. Therefore, further studies are needed that could focus on clinical trials investigating anti-obesity potential different mechanisms of M. peregrina extract in humans.

Label-Free Fluorescence Quantification of Hydrolytic Enzyme Activity on Native Substrates Reveals How Lipase Function Depends on Membrane Curvature

Lipases are important hydrolytic enzymes used in a spectrum of technological applications, such as the pharmaceutical and detergent industries. Because of their versatile nature and ability to accept a broad range of substrates, they have been extensively used for biotechnological and industrial applications. Current assays to measure lipase activity primarily rely on low-sensitivity measurements of pH variations or visible changes of material properties, like hydration, and often require high amounts of proteins. Fluorescent readouts, on the other hand, offer high contrast and even single-molecule sensitivity, albeit they are reliant on fluorogenic substrates that structurally resemble the native ones. Here we present a method that combines the highly sensitive readout of fluorescent techniques while reporting enzymatic lipase function on native substrates. The method relies on embedding the environmentally sensitive fluorescent dye pHrodo and native substrates into the bilayer of liposomes. The charged products of the enzymatic hydrolysis alter the local membrane environment and thus the fluorescence intensity of pHrodo. The fluorescence can be accurately quantified and directly assigned to product formation and thus enzymatic activity. We illustrated the capacity of the assay to report the function of diverse lipases and phospholipases both in a microplate setup and at the single-particle level on individual nanoscale liposomes using total internal reflection fluorescence (TIRF). The parallelized sensitive readout of microscopy combined with the inherent polydispersity in sizes of liposomes allowed us to screen the effect of membrane curvature on lipase function and identify how mutations in the lid region control the membrane curvature-dependent activity. We anticipate this methodology to be applicable for sensitive activity readouts for a spectrum of enzymes where the product of the enzymatic reaction is charged.

C-terminal region of Candida rugosa lipases affects enzyme activity and interfacial activation

Candida rugosa contains several lipase (CRLs) genes, and CRLs show diverse enzyme activity despite being highly homologous across their entire protein family. Previous studies found that LIP4 has a high esterase activity and a low lipolytic activity and lacks interfacial activation. To investigate whether the C-terminal region of the CRLs mediates enzymatic activity, chimeras were generated in which the C-terminus of LIP4 from either residue 374, 396, 417, or 444 to residue 534 was swapped with the corresponding peptide from the isoform LIP1. A chimeric lipase containing the C-terminus from 396 to 534 of LIP1 on a LIP4 scaffold showed activity similar to that of commercial CRL on triolein, and lipolytic activity increased 2-6-fold over that of LIP4. Moreover, interfacial activation was also observed in the chimeric lipase. To improve its enzymatic properties, a novel glycosylation site was added at residue 314. The new glycosylated lipase showed improved thermostability and enhancement in enzymatic activity, indicating its potential for use in further application.

Inhibitory effect of morinda citrifolia L. On lipoprotein lipase activity

Efficacy of Morinda citrifolia L. leaf (MLE) and fruit extracts (MFE) in inhibiting lipoprotein lipase (LPL) was determined in vitro. The result of the study showed that the highest inhibition on the LPL activity was exhibited by MLE (66%+/- 2.1%), which is significantly higher than that demonstrated by MFE (54.5%+/- 2.5%), green tea extract (GTE) (54.5%+/- 2.6%), and catechin (43.6%+/- 6.1%). Percent of LPL inhibition increase with concentration of the extracts. Quantitative analysis of the extracts revealed the presence of high levels of (+)-catechin at 63.5 +/- 17 and 53.7 +/- 5.7 mg/g in MLE and MFE, respectively, although not as high as that found in GTE (530.6 +/- 42 mg/g). Appreciable amount of epicatechin was found in all extracts tested, while rutin was only found in MLE and MFE. The study suggested that both leaf and fruit of M. citrifolia may be used as antiobesity agents in body weight management.

Determination of the kinetic properties of platycodin D for the inhibition of pancreatic lipase using a 1,2-diglyceride-based colorimetric assay

A 1, 2-diglyceride-based multi-step colorimetric assay to measure the pancreatic lipase activity was applied for the determination of the kinetic profiles of the lipase inhibition with a slight modification and the validity verification. With this assay method, our study revealed that platycodin D, one of major constituents of Platycodi Radix, inhibits the pancreatic lipase activity in a competitive type, with the value of Kl being 0.18 +/- 0.02 mM. In addition, PD has affected the values of Km,app and Kcat/Km in a dose- dependent manner. The results shed a meaningful light on how PD mediates lipid metabolism in the intestinal tracts. On the other hand, since the revised assay is sensitive, rapid, and does not affect the accuracy to the kinetic properties, it is applicable not only to evaluation of the kinetic properties of the pancreatic lipase, but also to high-throughput screening of pancreatic lipase activity.

Determination of the kinetic properties of platycodin D for the inhibition of pancreatic lipase using a 1, 2-diglyceride-based colorimetric assay

A 1,2-diglyceride-based multi-step colorimetric assay to measure the pancreatic lipase activity was applied for the determination of the kinetic profiles of the lipase inhibition with a slight modification and the validity verification. With this assay method, our study revealed that platycodin D, one of major constituents of Platycodi Radix, inhibits the pancreatic lipase activity in a competitive type, with the value of KI being 0.18+/-0.02 mM. In addition, PD has affected the values of K(m,app) and Kcat/Km in a dose-dependent manner. The results shed a meaningful light on how PD mediates lipid metabolism in the intestinal tracts. On the other hand, since the revised assay is sensitive, rapid, and does not affect the accuracy to the kinetic properties, it is applicable not only to evaluation of the kinetic properties of the pancreatic lipase, but also to high-throughput screening of pancreatic lipase activity.

A URA3-promoter deletion in a pYES vector increases the expression level of a fungal lipase in Saccharomyces cerevisiae

A simple deletion of the URA3 promoter from a Saccharomyces cerevisiae expression plasmid was performed. The promoter-deleted plasmid is shown to have an increased expression level of a fungal lipase gene. The deletion probably causes a poor expression of the URA3 selection marker, probably resulting in a higher copy number per cell of the plasmid. This higher copy number can increase the transcript level per cell and there by the expression level. In the case of the fungal lipase gene, the expression level with defined inoculum is increased at least three times. The principle is most likely similar to the LEU2d plasmids described previously. A part of the 2-micron origin of the pYES type plasmid was also deleted by the URA3 promoter deletion without affecting transformation frequency. The URA3 promoter can easily be deleted from most pYES type plasmids by the described method.

Hydrolysis of plasma triacylglycerol-rich lipoproteins from immature and laying hens (Gallus domesticus) by lipoprotein lipase in vitro

Very-low-density (VLD) lipoproteins and portomicrons were isolated from the plasma of immature and laying hens and their size, lipid composition and susceptibility to hydrolysis by lipoprotein lipase were compared. In agreement with other studies, VLD lipoproteins from laying hens were found to be smaller and have a different lipid composition than VLD lipoproteins from immature hens. Portomicrons from immature and laying hens had mean diameters of about 150 nm and similar lipid compositions. Hydrolysis of VLD lipoproteins from immature hens, and portomicrons from immature and laying hens, proceeded rapidly until at least 40% of the substrate had been used. In contrast only 1--15% of laying-hen VLD-lipoprotein triacylglycerol was readily hydrolysis occurred slowly. The limited susceptibility of laying-hen VLD lipoproteins appeared to be due to their low content of lipoprotein lipase activator apoprotein, which occurred despite an abundance of activator in the high-density lipoproteins of laying-hen plasma. The results provide further evidence that the liver of the laying hen synthesizes specialized lipoproteins. Their limited susceptibility to hydrolysis by lipoprotein lipase is probably a major factor in ensuring transport of lipid to yolk rather than to other tissues. The form of transport of dietary lipid, however, is similar in immature and laying hens.

In vitro reciprocal exchange of apoproteins and nonpolar lipids between human high density lipoproteins and an artificial triglyceride-phospholipid emulsion (Intralipid)

To determine the nature of lipid and apoprotein exchange between human high density lipoproteins (HDL) and Intralipid particles of Sf greater than 400 (ILIP) we have studied their in vitro interaction during incubation in aqueous buffer and in lipoprotein-deficient serum (LPDS). We found that ILIP acquires apo A-I, apo A-IV and apo E from LPDS, and that this uptake is inhibited by the presence of HDL, which readily donate C-apoproteins to the ILIP surface. In the absence of LPDS exchange of only polar lipids occurred between ILIP and HDL, with HDL gaining phospholipid from, and donating free cholesterol to this fat emulsion. In the presence of LPDS the exchange of nonpolar lipids occurred between the two particles: in the case of HDL, cholesteryl ester content decreased, accompanied by an increase in triglyceride, causing a decrease in the hydrated density of the lipoprotein and an increase in its molecular weight; in the case of ILIP, reciprocal changes in lipid content were seen as a loss of triglyceride and the appearance of cholesteryl esters. When compared to literature data, our findings indicate that Intralipid Sf greater than 400 particles exhibit an in vitro behavior which is remarkably similar to that of nascent chylomicrons with respect to the exchange of A- and C-apoproteins and surface polar lipids with HDL. We postulate that since ILIP and HDL can participate in a LPDS-dependent exchange of non-polar core lipids, that this process may occur when this fat emulsion is administered in vivo.

Properties and metabolic fate of two very low density lipoprotein subfractions from rhesus monkey serum

Physical, chemical and physiological approaches were used to examine the properties of two very low density lipoproteins, VLDL-I (slow-beta), and VLDL-II (pre-beta), which were isolated by agarose column chromatography from the serum of rhesus monkeys fed either Purina Chow or one of four hyperlipidemic diets containing 0.5-20% cholesterol suspended in either coconut oil, peanut oil, mixed coconut oil and butter fat or lard. In the coconut oil-fed hyperlipidemic animals, the majority of the apolar lipids of VLDL-I was represented by cholesteryl esters. The small percentage of triacylglycerol (15%) had a fatty acid composition which resembled that of the fatty acid in each of the diets. In turn, VLDL-II had a triacylglycerol-rich core and differed from VLDL-I in apolipoprotein distribution (VLDL-I: low molecular weight apolipoprotein B, 36%; apolipoprotein E, 64%; and VLDL-II: high molecular weight apolipoprotein B, 38%; apolipoprotein E, 3%; and apolipoprotein C, 65%). Both VLDLs were hydrolyzed in vitro by milk lipoprotein lipase by first-order kinetics although VLDL-I exhibited a slightly slower reaction rate. When an oral dose of [3H]retinol was given to one of the animals, both VLDLs became labeled but the specific activity of VLDL-I was six times higher than that of VLDL-II and the other lipoproteins. We conclude that VLDL-I represents a cholesteryl ester-rich lipoprotein probably of intestinal origin, whereas VLDL-II may be a particle of hepatic derivation modified by its interaction with the other plasma lipoproteins.

Immunoenzymehistochemical demonstration of the binding of low density lipoproteins to cultured human fibroblasts

Using as indirect cytochemical immunoperoxidase technique, we were able to demonstrate the binding of low density lipoprotein to cultured human fibroblasts. With this technique, fibroblasts from a patient suffering from homozygous hyperlipoproteinaemia type IIa did not show this binding. The method described here allows study of the localization of unmodified low density lipoproteins binding to cultured fibroblasts.

Purification and properties of two lipases from pig adipose tissue

Two lipases were purified from pig adipose tissue after delipidation by a mild and effective procedure using mixtures of chloroform and butanol. This was followed by hydrophobic adsorption chromatography on aminohexyl-Sepharose 4B coupled with octanoic acid, gel filtration on Sephadex G-100, and isoelectric focusing. Two electrophoretically and chromatographically pure enzymes were obtained, which had the same molecular weight (60 000 +/- 3000) and specific activity, and almost identical amino acid compositions; the isoelectric points, i.e. 5.2 and 5.5, differed.

Apoproteins of human serum high density lipoproteins. Isolation and characterization of the peptides of Sephadex fraction V from normal subjects and patients with abeta-lipoproteinemia

1. Sephadex fraction V, obtained from human serum high density lipoprotein apoprotein (HDL apoprotein) of normal subjects and of patients with abetalipoproteinemia, was resolved by DEAE-cellulose ion exchange column chromatography into several fractions which were defined in terms of amino acid composition, NH2- and COOH-terminsls, sialic acid content, immunologic and electrophoretic properties, and in vitro activation of purified lipoprotein lipase from rat adipose tissue. 2. Fraction V of HDL apoprotein of both normal and abetalipoproteinemic subjects was found to contain polypeptides corresponding to apolipoproteins C-I, C-II, C-III-1, and C-III-2, which had been described previously in very low-density lipoproteins (VLDL). The content of apo C-III-1 in abetalipoproteinemia-HDL was very low, whereas the percentage, by weight, of apo C-I was about twice as high as that in the normal subjects studied. Furthermore, both normal and abetalipoproteinemia-HDL apoprotein contained a previously unreported peptide which had a molecular weight of about 7 000 and electrophoretic, chemical, and immunological properties distinct from those of the known C apolipoproteins. Of all of the peptides comprising fraction V, only apo C-II activated a purified preparation of rat adipose tissue lipoprotein lipase. This was the case for both normal and abetalipoproteinemic subjects.