Lipoprotein Lipase Messenger RNA Research Articles

Antiobesity Effects of Lactobacillus paracasei Subsp. paracasei, L. casei 431 on High-Fat Diet-Induced Obese Rats.

Obesity is currently regarded as a global concern, and the key objectives of the global health strategy include its prevention and control. Probiotic supplementation can help achieve these objectives. This study aimed to assess whether a probiotic strain Lactobacillus paracasei ssp. paracasei, Lactobacillus casei 431 (henceforth, L. casei 431) possesses antiobesogenic properties. High-fat diet-induced obese Sprague-Dawley rats were treated with L. casei 431 for 10 weeks, and the outcomes were compared with those of rats treated with the antiobesity medication orlistat. Body weights, epididymal fat, and tissues from mice were assessed. Furthermore, serological and histological analyses were performed. Epididymal fat accumulation was significantly reduced in groups administered L. casei 431 and orlistat. Furthermore, L. casei 431 and orlistat treatments lowered serum alanine transaminase, aspartate aminotransferase, and triglyceride (TG) levels. Hematoxylin and eosin staining of the liver and epididymal adipose tissues showed that the L. casei 431-treated groups exhibited reduced lipid buildup and adipocyte size. Furthermore, sterol regulatory element-binding protein 1c, adipose TG lipase, and lipoprotein lipase messenger RNA (mRNA) levels were upregulated, leading to lipid oxidation and degradation, in L. casei 431-supplemented groups. Furthermore, carnitine palmitoyltransferase 1, a major factor in lipolysis, was consistently upregulated at the protein level after L. casei 431 administration. Collectively, these results demonstrate the potential of L. casei 431 in alleviating obesity in rats through optimizing lipid metabolism and some related biomarkers.

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Subcutaneous heparin for treatment of hypertriglyceridemia-induced pancreatitis

I read with great interest the article by Twilla and Mancell1 on the use of insulin and heparin in hypertriglyceridemia-induced acute pancreatitis. Hypertriglyceridemia is the third most common cause of acute pancreatitis in the United States and is associated with considerable morbidity.2 In addition to aggressive hydration and analgesia, the treatment of pancreatitis in such cases should focus on rapid reduction of the serum triglyceride level. Unfortunately, treatment guidelines based on controlled studies are lacking, and clinical experience is limited to case reports. Variable success has been reported with insulin, heparin, plasmapheresis, and antihyperlipidemic medications. Among these treatments, the use of insulin has been the least controversial. It works via modulation of lipoprotein lipase messenger RNA,3 and its action may be slow or inadequate.4 Unfractionated heparin may have a faster effect by releasing endothelial lipoprotein lipase. However, the efficacy and safety of heparin either alone or in combination with insulin in this situation have been a bone of contention.4,5 I describe here the successful treatment of two patients with hypertriglyceridemia-induced pancreatitis with subcutaneous unfractionated heparin.

Metformin promotes induction of lipoprotein lipase in skeletal muscle through activation of adenosine monophosphate–activated protein kinase

Metformin is known to increase lipoprotein lipase (LPL) mass level in serum. Lipoprotein lipase is produced by adipose tissue and skeletal muscles. This study aimed to examine the effect of metformin on LPL production in adipocytes and skeletal muscle cells and to investigate the mechanism by which metformin enhances LPL production. 3T3-L1 preadipocytes and L6 skeletal muscle cells were incubated with metformin or 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR). Lipoprotein lipase activity, LPL protein expression, and LPL messenger RNA (mRNA) expression were measured. Metformin increased LPL activity only in skeletal muscle cells. To clarify the mechanism of this phenomenon, AICAR, which is well known as an activator of adenosine monophosphate–activated protein kinase (AMPK), was used. Metformin and AICAR enhanced phosphorylated AMPK in skeletal muscle cells by Western blot analysis. Like metformin, AICAR increased LPL activity only in skeletal muscle cells. Both metformin and AICAR also enhanced LPL protein and LPL mRNA expressions in skeletal muscle cells but not in adipocytes. Phosphorylated AMPK protein expression was decreased when AMPK signaling was interfered by AMPK α small interfering RNA. Lipoprotein lipase activity and LPL expression, which were enhanced by 1 μmol/L metformin, were reduced by AMPK α small interfering RNA. These results suggest that metformin increases LPL activity, LPL protein expression, and LPL mRNA expression through activation of AMPK in skeletal muscle cells but not in adipocytes.

Lipoprotein Lipase Expression in Livers of Morbidly Obese Patients Could be Responsible for Liver Steatosis

Most patients with morbid obesity develop non-alcoholic fatty liver disease (NAFLD). The origins of lipid deposition in the liver and the effects of bariatric surgery in the obese with NAFLD are controversial. We analyzed lipids and lipoprotein lipase (LPL) in both plasma and liver biopsies performed before and 12-18 months after Roux-en-Y gastric bypass surgery in 26 patients. In the livers of morbidly obese patients, the levels of LPL messenger RNA (mRNA) were higher (4.5-fold) before surgery than afterwards than control livers. In these patients, LPL activity was also significantly higher (91 +/- 7 mU/g) than in controls (51 +/- 3 mU/g, p = 0.0026) and correlated with the severity of the liver damage. All hepatic lipids were significantly increased in obese patients; however, after bariatric surgery, these lipids, with the exception of NEFA, tended to recover to normal levels. The liver of obese patients presented higher LPL activity than controls, and unlike the controls, this enzyme could be synthesized in the liver because it also present LPL mRNA. The presence of the LPL activity could enable the liver to capture circulating triacylglycerides, thus favoring the typical steatosis observed in these patients.

Exercise Physiology versus Inactivity Physiology: An Essential Concept for Understanding Lipoprotein Lipase Regulation

Some health-related proteins such as lipoprotein lipase may be regulated by qualitatively different processes over the physical activity continuum, sometimes with very high sensitivity to inactivity. The most powerful process known to regulate lipoprotein lipase protein and activity in muscle capillaries may be initiated by inhibitory signals during physical inactivity, independent of changes in lipoprotein lipase messenger RNA.

1,25-Dihydroxyvitamin D induces lipoprotein lipase expression in 3T3-L1 cells in association with adipocyte differentiation.

1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] is known to modulate the development of bone and other mesenchymal cell types. Since osteoblasts and adipocytes are thought to arise in bone marrow from a common progenitor, this work examined the effects of 1,25-(OH)2D3 on adipocyte development, and in particular on the expression of lipoprotein lipase (LPL), which is an early marker for the differentiated adipocyte. 3T3-L1 preadipocytes were cultured in the presence of 1,25-(OH)2D3 (10(-9) to 10(-7) M) for up to 7 days. LPL activity was measured in the medium and cell extracts, and LPL messenger RNA levels were measured by Northern blotting. When compared to control cells, 10(-7) M 1,25-(OH)2D3 increased medium LPL activity by 2- to 3-fold and cellular LPL by 1.5-fold. Significant increases in medium and cellular LPL were observed at 10(-9) M and were maximal at 10(-7) M. Along with the increase in LPL activity, there was an increase in LPL messenger RNA by 2-fold at 5 days, and by 5-fold at 7 days. In addition to an increase in LPL, 1,25-(OH)2D3 increased expression of aP2, an adipocyte-specific marker associated with differentiation. After the addition of 1,25-(OH)2D3, there was a decrease in 3T3-L1 cell number, which is consistent with differentiation, and a decrease in vitamin D receptors. Finally, these cells developed a different morphology. 1,25-(OH)2D3-treated cells assumed a rounded appearance, although without detachment from the dish and without the degree of lipid accumulation usually associated with the addition of insulin, isbutylmethylxanthine, and dexamethasone. It is concluded that 1,25-(OH)2D3 induced LPL expression in 3T3-L1 cells through an induction of differentiation-dependent mechanism(s). These findings suggest an important role for 1,25-(OH)2D3 in normal adipocyte differentiation.

Oxysterols present in atherosclerotic tissue decrease the expression of lipoprotein lipase messenger RNA in human monocyte-derived macrophages.

The presence of oxysterols in macrophages isolated from atherosclerotic tissue and the effect of oxysterols on the regulation of lipoprotein lipase (LPL) mRNA were studied. Both rabbit and human macrophages, freshly isolated from atherosclerotic aorta, show about the same distribution of oxysterols, analyzed by isotope dilution mass spectrometry, except that all three preparations of human arterial-derived macrophages contained high levels of 27-hydroxycholesterol, which was not found in rabbit macrophages. To determine if oxysterols regulate LPL expression, human monocyte-derived macrophages were incubated with different oxysterols. Incubation with 7 beta-hydroxycholesterol and 25-hydroxycholesterol resulted in a 70-75% reduction of LPL mRNA, analyzed by quantitative RT-PCR. Cholesterol and other tested oxysterols showed no effect on macrophage LPL mRNA expression compared with control. LPL activity in the medium was also reduced after exposure of the macrophages to 7 beta-hydroxycholesterol and 25-hydroxycholesterol. In conclusion, we have demonstrated accumulation of oxysterols in macrophage-derived foam cells isolated from atherosclerotic aorta. There was suppression of LPL mRNA in human monocyte-derived macrophages after incubation with 7 beta-hydroxycholesterol and 25-hydroxycholesterol. It is tempting to suggest that an exposure to oxysterols may explain our earlier observation of a low level of LPL mRNA in arterial foam cells.

Epidermal growth factor promotes adipogenesis of 3T3-L1 cell in vitro.

We have reported the importance of epidermal growth factor (EGF) for the induction of obesity in mice. In this study, we studied the effects of EGF on the induction of lipogenic enzymes and on the accumulation of triglyceride in a differentiated mouse adipocyte cell in vitro. Mouse 3T3-L1 preadipocytic cells differentiated into mature adipocytes after the differentiation procedure by insulin, dexamethasone, and methyl-isobutyl-xanthine. 125I-EGF binding studies in the differentiated 3T3-L1 cells showed specific 125I-EGF bindings, and they expressed gene transcripts for EGF receptors by reverse transcription and polymerase chain reaction at all differentiative stages examined. Although EGF showed inhibitory effects on the triglyceride accumulation when administered to the preadipocytic 3T3-L1 cells, EGF enhanced the adipogenesis in the differentiated cells in dose- and time-dependent manners. Administration of EGF at 0.1-1 nM from 4 days after the differentiation procedure for 10 days, significantly enhanced the acyl-Co A synthetase and lipoprotein lipase messenger RNA levels, both of which are rate-limiting enzymes to synthesize triglyceride in adipocytes. Moreover, 0.1-1 nM EGF increased the amounts of triglyceride accumulated in the cells, in proportion to the acyl-Co A synthetase and lipoprotein lipase messenger RNA levels. EGF rather failed the adipogenesis at 10 nM. Time course studies revealed that 1 nM EGF significantly increased the intracellular triglyceride levels from 4 through 16 days administration. These results suggest that EGF shows biphasic effects on adipocytes: although EGF inhibits preadipocytes differentiation into mature adipocytes, it promotes adipogenesis in the differentiated adipocytes.

Leukemia inhibitory factor induces changes in lipid metabolism in cultured adipocytes.

Cytokines induce a number of changes in lipid metabolism that can produce hyperlipidemia. Leukemia inhibitory factor (LIF), a recently discovered cytokine, has been suggested to play a role in the cancer cachexia syndrome through its ability to decrease lipoprotein lipase (LPL) activity. This study explores the mechanism by which LIP decreases LPL activity in cultured adipocytes and determines its effects on fatty acid synthesis and lipolysis to see if it shares the same catabolic effects on fat cells as seen with other cytokines, such as tumor necrosis factor (TNF). LIF decreased LPL activity in cultured adipocytes by 44% compared with an 85% decrease produced by TNF. Although the percent decrease in LPL activity is not as great in LIF-incubated adipocytes as in TNF-incubated adipocytes, the half-maximal doses for both cytokines are similar. LPL messenger RNA levels paralleled LPL activity in the LIF-treated adipocytes, suggesting that the effect of LIF on LPL activity is predominantly mediated through transcriptional regulation. In contrast to TNF, LIF tended to increase the de novo synthesis of fatty acids. Acetyl coenzyme-A carboxylase messenger RNA levels paralleled the changes seen in fatty acid synthesis for both cytokines. LIF caused a small increase in lipolysis, whereas TNF increased lipolysis by greater than 2-fold. These results demonstrate that the catabolic effects of LIF are weaker than those of TNF and are predominantly directed toward decreasing LPL activity, which may contribute to the hyperlipidemia associated with infection, inflammation, and cancer.

The Effects of Weight Loss on the Activity and Expression of Adipose-Tissue Lipoprotein Lipase in Very Obese Humans

Lipoprotein lipase is an enzyme in adipose tissue that hydrolyzes circulating triglycerides and thereby generates the fatty acids used in the synthesis of triglyceride in fat cells. To determine whether the activity and expression of lipoprotein lipase are affected by weight loss, we studied lipoprotein lipase in the adipose tissue of nine very obese subjects before and after a program of weight reduction. The subjects' mean (+/- SEM) initial weight was 136 +/- 7.3 kg, and the body-mass index (weight in kilograms divided by the square of the height in meters) ranged from 33.3 to 52.8 (mean, 43.0 +/- 2.5). Biopsies of adipose tissue were performed before weight loss and after it, when weight had been stable for three months. The weight reduction was achieved by a very-low-calorie diet (mean weight loss, 42.5 +/- 6.8 kg). After weight loss, the level of heparin-releasable lipoprotein lipase activity increased in all patients, from 3.8 +/- 1.1 to 7.1 +/- 1.6 neq of free fatty acid released per minute per 10(6) cells (P less than 0.05). In addition, the amount of lipoprotein lipase immunoreactive protein increased from 6.3 +/- 1.7 to 24.4 +/- 6.9 ng per 10(6) cells (P less than 0.05), and there was also an increase in the level of lipoprotein lipase messenger RNA as measured by Northern blotting. There was a strongly positive correlation between the initial body-mass index and the magnitude of the increase in lipoprotein lipase activity (r = 0.80, P less than 0.01) and immunoreactive protein (r = 0.92, P less than 0.01). We conclude that weight loss in very obese subjects leads to the increased activity and expression of lipoprotein lipase, thereby potentially enhancing lipid storage and making further weight loss more difficult.

Cell-free translation of avian adipose tissue lipoprotein lipase messenger RNA

Poly(A) + mRNA isolated from chicken adipose tissue directed cell-free translation in a rabbit reticulocyte lysate system. Immunoadsorption with polyclonal antibodies against lipoprotein lipase detected a protein of 56 ± 2 kDa. Immunodetection of this protein was prevented by inclusion of purified lipoprotein lipase in the assay mixture. Identification of the 56 kDa protein as lipoprotein lipase was confirmed by immunoadsorption to the monoclonal antibody CAL 1–11. Inclusion of dog pancreatic microsomal membranes in the translation system resulted in isolation of an additional protein of 62 kDa. Treatment of the 62 kDa protein with endo- β- N-acetylglycosaminidase H or endo- β- N-acetylglucosaminidase F decreased the observed molecular mass to that of the primary translation product, indicating that the increase in molecular mass resulted from the addition of N-linked oligosaccharides. Starving and refeeding chickens prior to poly(A) + mRNA isolation resulted in a 3-fold increase in the amount of immunodetectable lipoprotein lipase synthesized.

Human lipoprotein lipase complementary DNA sequence.

Lipoprotein lipase is a key enzyme of lipid metabolism that acts to hydrolyze triglycerides, providing free fatty acids for cells and affecting the maturation of circulating lipoproteins. It has been proposed that the enzyme plays a role in the development of obesity and atherosclerosis. The human enzyme has been difficult to purify and its protein sequence was heretofore undetermined. A complementary DNA for human lipoprotein lipase that codes for a mature protein of 448 amino acids has now been cloned and sequenced. Analysis of the sequence indicates that human lipoprotein lipase, hepatic lipase, and pancreatic lipase are members of a gene family. Two distinct species of lipoprotein lipase messenger RNA that arise from alternative sites of 3'-terminal polyadenylation were detected in several different tissues.