Liposome-encapsulated peptide PDBSN ameliorates high-fat-diet-induced obesity and improves metabolism homeostasis.

In recent years, the obese and overweight population has increased rapidly, which has become a worldwide public health problem. However, effective medication is lacking. Our previous study identified a novel peptide, PDBSN (GLSVADLAESIMKNL), that could significantly restrict adipocyte differentiation in vitro, but its in vivo function has not been determined. Thus, in this study, we encapsulated the peptide into liposomes attached with two ligands (visceral-adipose-tissue-targeting peptide and cell-penetrating peptide) to improve stability and specificity. We then tested the peptide's function in HFD (high-fat diet)-induced obese mice and found that PDBSN could reduce weight gain and improve insulin resistance as well as lipid homeostasis. These results suggest that PDBSN may be a potential candidate for anti-obesity drug discovery.

Oxidant injury to the alveolar epithelium: biochemical and pharmacologic studies.

This multifaceted study involved a combined biochemical and cellular analysis of oxidant metabolism by a lung cell at risk from injury by endogenous and environmental oxidants, the pulmonary alveolar type II epithelial cell. Within the framework of this study, a method was developed for effectively delivering antioxidant enzymes and alpha-tocopherol to the intracellular compartment of alveolar epithelial cells. Alveolar type II cells are key sources of pulmonary surfactant phospholipids and apoproteins and serve as progenitors of type I alveolar epithelium, thus playing an important role in the re-epithelialization of the lung alveolus after exposure to pulmonary oxidants. The type I and II pulmonary epithelium also play an essential collaborative role in maintaining the integrity of the air-blood barrier of the lung. Because of these critical properties of the alveolar epithelium and their recognized sensitivity to oxidant stress derived from diverse sources, such as activated inflammatory cells, hyperoxia, the environmental oxidants and nitrogen dioxide, and surgical procedures, such as cardiopulmonary bypass and lung transplantation, we endeavored to understand more about the oxidant metabolism and antioxidant pharmacology of these cells. In our experiments, we made the observation that loss of differentiated oxidant generation and antioxidant properties of type II cells occurs very rapidly in vitro. For example, we observed a 50% to 75% reduction in the specific activities of type II cell superoxide dismutase, catalase, and glutathione peroxidase, all critical scavengers of cell superoxide and hydrogen peroxide and key enzymes in the attenuation of hydroxyl radical formation. Although the differentiated characteristics of the type II cell antioxidant defenses changed in vitro, they may have become more reflective of type I alveolar epithelial cells. The type I cell is the most vulnerable for oxidant damage in the alveolus because of its large surface area and the possibility of a reduced antioxidant capacity compared to type II alveolar epithelium. In spite of this limitation, we were able to culture type II cells and study their adaptive and toxic responses to exogenously administered oxidant stress. We also observed that a significant source of self-generated oxidants in type II cells was the enzyme xanthine oxidase. Normal rates of oxidant production by this enzyme had an inhibitory effect on incorporation of biosynthetic precursors into surfactant phospholipids; these effects were eliminated by the xanthine oxidase inhibitor, allopurinol.(ABSTRACT TRUNCATED AT 400 WORDS)

Protection of lactate dehydrogenase against protease digestion by encapsulation in liposomes.

Lactate dehydrogenase (LDH) was entrapped in phosphatidylcholine liposomes to evaluate the protective effect of liposomes against protease digestion. Three different preparations of LDH either encapsulated in liposomes, unencapsulated in liposomes or in the absence of liposomes were incubated with the protease trypsin. The loss of LDH activity was measured at intervals over a 12-hour period. The degradation rate of LDH was found to be the same when LDH was unencapsulated in the presence or absence of liposomes. However, when LDH was entrapped in liposomes the degradation rate was 4 to 24 folds slower. This finding indicates that encapsulation of a protein in a liposome protects the protein from the degrading effects of a protease enzyme.

Stabilizing protein formulations during air-jet nebulization.

Whilst some proteins can be effectively administered to the lungs using a nebulizer, others, such as lactate dehydrogenase (LDH) are degraded during air-jet nebulization. In order to deliver LDH by nebulization a protective delivery system or carrier may therefore be appropriate. The aim of this study was to produce and characterize a formulation of LDH, which retains enzyme activity during nebulization. Chitosan, a biocompatible, biodegradable and bioadhesive polysaccharide polymer, was included in the formulations studied as a potential protective agent. Complexes of LDH with chitosan of different molecular weights and concentrations were assessed for size, zeta potential, aerosol droplet size and delivery from a jet nebulizer. The highest molecular weight chitosan had the greatest complex size and a net positive charge of +29.7mV. Jet nebulization resulted in aerosol droplets with median size in the range 2.36-3.52µm. Nebulization of LDH solution resulted in enzyme denaturation and reduced activity. The stability of LDH was greatly improved in formulations with chitosan; with greater than 50% total LDH available in a nebulizer delivered to the lower stage of a two-stage impinger, with up to 62% retained enzyme activity. The nonionic surfactant Tween 80 also improved the stability of LDH to nebulization and had an additive protective effect when included, with chitosan, in formulations. These findings suggest chitosan may be a useful excipient in the preparation of stable protein formulations for jet nebulization.

Testis specific lactate dehydrogenase as target for immunoliposomes.

PROBLEM: Is it possible to deliver therapeutic agents to testis through specific targeting? METHOD OF STUDY: Immunoliposomes are designed by incorporating antibodies to lactate dehydrogenase-C4 (LDH-C(4)), which is the product of a testis specific gene. Their targeting and delivering ability is investigated in vitro and in vivo. RESULTS: It is observed that LDHC(4)-immunoliposomes are able to discriminate and recognize antigens on spermatozoa and testes both in vitro and in vivo. CONCLUSION: Specific targeting through LDH-C(4) appears to be a feasible strategy for delivering therapeutic as well as anti-spermatogenic agents to testis.

Extracellular administration of lactate dehydrogenase and its effects on human plaque pH and acid anion concentrations.

The effect of lactate dehydrogenase (LDH) on human plaque pH and acid anion concentrations in vivo was investigated. Rinsing with sucrose solutions supplemented with LDH (1 or 2 U/ml) gave rise to reduced pH fall, decreased cH area and an increase in the mean minimum pH when compared with rinsing with sucrose only (p less than 0.05). Mean acid anion estimations showed that plaque fluid concentrations of lactate, acetate and proprionate significantly decrease (p less than 0.05) following rinsing with sucrose containing LDH at both levels and decreases in succinate when 1 U/ml LDH was present, whereas formate concentrations were only significantly lower when 2 U/ml LDH was added to sucrose rinses. It is thought that the ability of LDH to produce an alteration in the acid end-products of plaque metabolism may provide some protection against dental caries.