lactoferrin and Hyperlipidemias

Lactoferrin is an innate immune system protein with anti-inflammatory and antioxidant activities. We aimed to evaluate circulating lactoferrin levels in association with lipid concentrations, and parameters of oxidative stress and inflammation in subjects with morbid obesity after an acute fat intake. The effects of a 60 g fat overload on circulating lactoferrin and antioxidant activities were evaluated in 45 severely obese patients (15 men and 30 women, BMI 53.4 +/- 7.2 kg/m(2)). The change in circulating lactoferrin after fat overload was significantly and inversely associated with the free fatty acid (FFA) change. In those subjects with the highest increase in lactoferrin (in the highest quartile), high-density lipoprotein (HDL)-cholesterol decreased after fat overload to a lesser extent (P = 0.03). In parallel to lipid changes, circulating lactoferrin concentrations were inversely linked to the variations in catalase (CAT) and glutathione reductase (GSH-Rd). Baseline circulating lactoferrin concentration was also inversely associated with the absolute change in antioxidant activity after fat overload, and with the change in C-reactive protein (CRP). Furthermore, those subjects with higher than the median value of homeostasis model assessment of insulin secretion (HOMA(IS)) had significantly increased lactoferrin concentration after fat load (885 +/- 262 vs. 700 +/- 286 ng/ml, P = 0.03). Finally, we further explored the action of lactoferrin in vitro. Lactoferrin (10 micromol/l) led to significantly lower triglyceride (TG) concentrations and lactate dehydrogenase activity (as expression of cell viability) in the media from adipose explants obtained from severely obese subjects. In conclusion, circulating lactoferrin concentrations, both at baseline and fat-stimulated, were inversely associated with postprandial lipemia, and parameters of oxidative stress and fat-induced inflammation in severely obese subjects.

Topics: Adipose Tissue; Adult; Antioxidants; C-Reactive Protein; Catalase; Cell Survival; Cholesterol, HDL; Dietary Fats; Fatty Acids, Nonesterified; Female; Glutathione Reductase; Humans; Hyperlipidemias; Insulin; Insulin Secretion; L-Lactate Dehydrogenase; Lactoferrin; Lipids; Male; Middle Aged; Obesity, Morbid; Oxidative Stress; Postprandial Period; Triglycerides

The hepatic removal of triglyceride-rich chylomicrons during the postprandial phase represents an important step towards determining the bioavailability of dietary lipids amongst the peripheral tissues. Indeed, elevated postprandial lipemia is often associated with obesity and increased risk of coronary heart disease. The milk protein, lactoferrin, has been shown to inhibit hepatic chylomicron remnant removal by the liver, resulting in increased postprandial lipemia. Despite numerous studies on potential targets for lactoferrin, the molecular mechanisms underlying the effect of lactoferrin remain unclear. We recently demonstrated that the lipolysis stimulated lipoprotein receptor (LSR) contributes to the removal of triglyceride-rich lipoproteins during the postprandial phase. Here, we report that while lactoferrin does not have any significant effect on LSR protein levels in mouse Hepa1-6 cells, this protein colocalizes with LSR in cells but only in the presence of oleate, which is needed to obtain LSR in its active form as lipoprotein receptor. Ligand blotting using purified LSR revealed that lactoferrin binds directly to the receptor in the presence of oleate and prevents the binding of triglyceride-rich lipoproteins. Both C- and N-lobes of lactoferrin as well as a mixture of peptides derived from its hydrolysis retained the ability to bind LSR in its active form. We propose then that the elevated postprandial lipemia observed upon lactoferrin treatment in vivo is mediated in part by its direct interaction with free fatty acid activated LSR, thus preventing clearance of chylomicrons and their remnants through the LSR pathway.

Topics: Animals; Blotting, Western; Cattle; Cell Line, Tumor; Chylomicrons; Fatty Acids; Hyperlipidemias; Lactoferrin; Lipoproteins, VLDL; Male; Mass Spectrometry; Mice; Mice, Inbred C57BL; Postprandial Period; Receptors, LDL; Triglycerides

A high odds ratio has been reported for hyperlipidemia and periodontal diseases in humans, and the severity of periodontitis seems to correlate with the hyperlipidemic status of the patients. Early studies indicated that the lipoprotein-containing fraction of the serum enhances the leukotoxic activity of the periodontopathogen Actinobacillus actinomycetemcomitans against human polymorphonuclear leukocytes (PMNL). The protease inhibitors of normal serum account for this enhancement, while delipidated serum has no effect on the leukotoxin-dependent PMNL cytolysis. No information exists for the effect of serum lipoproteins or hyperlipidemic serum. The aim of this study was to evaluate the role of serum lipoproteins in the interaction of the leukotoxin of A. actinomycetemcomitans with human PMNL. Purified leukotoxin was mixed with human PMNL prepared from venous blood of healthy subjects and various varying amounts of hyperlipidemic or delipidated serum, or purified serum lipoproteins. The cytolytic activity of leukotoxin was determined by activity of the cytosol enzyme lactate dehydrogenase released from injured PMNL. The degranulating activity of the toxin was measured through the release of the granule components elastase and lactoferrin. Normal human serum without leukotoxin-neutralizing antibodies caused a 4-fold enhancement of the leukotoxic activity when present at concentrations of 5-10% in the reaction mixture. Serum lipoproteins had no effect when added at concentrations that occur normally in serum. At high concentrations, purified low density and very low-density lipoproteins increased the leukotoxicity of the mixture. Nevertheless, hyperlipidemic serum prepared from a normal serum by the addition of autologous lipoproteins had no influence on the leukotoxin-caused cytolysis compared to the normal serum. Pre-incubation of PMNL for 1 h in hyperlipidemic or delipidated serum had no effect on the leukotoxin-induced degranulation of PMNL. The results indicate that the cytotoxic interactions of A. actinomycetemcomitans leukotoxin against human PMNL are not influenced by the presence of serum lipoproteins.

Topics: Aggregatibacter actinomycetemcomitans; Comorbidity; Coronary Disease; Cytoplasmic Granules; Disease Susceptibility; Dose-Response Relationship, Drug; Exotoxins; Humans; Hyperlipidemias; L-Lactate Dehydrogenase; Lactoferrin; Leukocyte Elastase; Lipoproteins; Neutrophils; Periodontal Diseases

Chylomicron remnants bound to rabbit alveolar macrophages with high-affinity (Kd = 3.3 +/- 0.71 microgram of protein/mL). The binding of chylomicron remnants was competitively inhibited in the presence of unlabeled remnants and to a lesser extent by unlabeled low-density lipoproteins. Pretreatment of cells with either trypsin or pronase inhibited degradation in a dose and time dependent manner, suggesting involvement of a cell surface protein. Chylomicron remnants were degraded by alveolar macrophages from Watanabe heritable hyperlipidemic (WHHL) rabbits, which are devoid of LDL receptor activity. Moreover, colchicine and monensin which are endocytotic and lysozomal inhibitors, respectively, did not have any effect on the degradation of chylomicron remnants by macrophages from normal rabbits. The absence of divalent cations was found to enhance chylomicron remnant degradation by macrophages. Activated alpha 2-macroglobulin and lactoferrin had no effect on chylomicron remnant degradation, indicating that the low-density lipoprotein receptor-related protein was not involved. In addition, the scavenger receptor inhibitors polyinosinic acid and fucoidan increased degradation of chylomicron remnant-ruling out uptake as a consequence of lipoprotein modification. Rather, the phagocytotic inhibitor cytochalasan D was found to significantly decrease chylomicron remnant degradation. Collectively, our data show that chylomicron remnants are metabolized by phagocytotic pathways initiated after binding to a cell surface protein which is distinct from the LDL receptor, LRP, or scavenger receptors.

Topics: alpha-Macroglobulins; Animals; Binding, Competitive; Cells, Cultured; Chylomicrons; Colchicine; Edetic Acid; Endopeptidases; Humans; Hyperlipidemias; Kinetics; Lactoferrin; Lipoproteins, LDL; Macrophages, Alveolar; Monensin; Phagocytosis; Rabbits; Reference Values