Overexpression Of Lipoprotein Lipase Research Articles

Development of an Improved Adenovirus Vector and Its Application to the Treatment of Lifestyle-Related Diseases.

The number of patients with lifestyle-related diseases such as type 2 diabetes mellitus (T2DM) and metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as non-alcoholic fatty liver disease (NAFLD), has continued to increase worldwide. Therefore, development of innovative therapeutic methods targeting lifestyle-related diseases is required. Gene therapy has attracted considerable attention as an advanced medical treatment. Safe and high-performance vectors are essential for the practical application of gene therapy. Replication-incompetent adenovirus (Ad) vectors are widely used in clinical gene therapy and basic research. Here, we developed a novel Ad vector, named Ad-E4-122aT, exhibiting higher and longer-term transgene expression and lower hepatotoxicity than conventional Ad vectors. We also elucidated the mechanisms underlying Ad vector-induced hepatotoxicity during the early phase using Ad-E4-122aT. Next, we examined the therapeutic effects of the genes of interest, namely zinc finger AN1-type domain 3 (ZFAND3), lipoprotein lipase (LPL), and lysophospholipid acyltransferase 10 (LPLAT10), on lifestyle-related diseases using Ad-E4-122aT. We showed that the overexpression of ZFAND3 in the liver improved glucose tolerance and insulin resistance. Liver-specific LPL overexpression suppressed hepatic lipid accumulation and improved glucose metabolism. LPLAT10 overexpression in the liver suppressed postprandial hyperglycemia by increasing glucose-stimulated insulin secretion. Furthermore, we also focused on foods to advance research on the pathophysiology and treatment of lifestyle-related diseases. Cranberry and calamondin, which are promising functional foods, attenuated the progression of MASLD/NAFLD. Our findings will aid the development of new therapeutic methods, including gene therapy, for lifestyle-related diseases such as T2DM and MASLD/NAFLD.

Liver-specific overexpression of lipoprotein lipase improves glucose metabolism in high-fat diet-fed mice.

The liver is the main organ that regulates lipid and glucose metabolism. Ectopic lipid accumulation in the liver impairs insulin sensitivity and glucose metabolism. Lipoprotein lipase (LPL), mainly expressed in the adipose tissue and muscle, is a key enzyme that regulates lipid metabolism via the hydrolysis of triglyceride in chylomicrons and very-low-density lipoproteins. Here, we aimed to investigate whether the suppression level of hepatic lipid accumulation via overexpression of LPL in mouse liver leads to improved metabolism. To overexpress LPL in the liver, we generated an LPL-expressing adenovirus (Ad) vector using an improved Ad vector that exhibited considerably lower hepatotoxicity (Ad-LPL). C57BL/6 mice were treated with Ad vectors and simultaneously fed a high-fat diet (HFD). Lipid droplet formation in the liver decreased in Ad-LPL-treated mice relative to that in control Ad vector-treated mice. Glucose tolerance and insulin resistance were remarkably improved in Ad-LPL-treated mice compared to those in control Ad vector-treated mice. The expression levels of fatty acid oxidation-related genes, such as peroxisome proliferator-activated receptor α, carnitine palmitoyltransferase 1, and acyl-CoA oxidase 1, were 1.7–2.0-fold higher in Ad-LPL-treated mouse livers than that in control Ad-vector-treated mouse livers. Furthermore, hepatic LPL overexpression partly maintained mitochondrial content in HFD-fed mice. These results indicate that LPL overexpression in the livers of HFD-fed mice attenuates the accumulation of lipid droplets in the liver and improves glucose metabolism. These findings may enable the development of new drugs to treat metabolic syndromes such as type 2 diabetes mellitus and non-alcoholic fatty liver disease.

Whole-body insulin resistance and energy expenditure indices, serum lipids, and skeletal muscle metabolome in a state of lipoprotein lipase overexpression.

Overexpression of lipoprotein lipase (LPL) protects against high-fat-diet (HFD)-induced obesity and insulin resistance in transgenic rabbits; however, the molecular mechanisms remain unclear. Skeletal muscle is a major organ responsible for insulin-stimulated glucose uptake and energy expenditure. The main purpose of the current study was to examine the effects of the overexpression of LPL on the skeletal muscle metabolomic profiles to test our hypothesis that the mitochondrial oxidative metabolism would be activated in the skeletal muscle of LPL transgenic rabbits and that the higher mitochondrial oxidative metabolism activity would confer better phenotypic metabolic outcomes. Under a HFD, insulin resistance index was measured using the intravenous glucose tolerance test, and total energy expenditure (TEE) was measured by doubly-labeled water in control and LPL transgenic rabbits (n = 12, each group). Serum lipids, such as triglycerides and free fatty acid, were also measured. The skeletal muscle metabolite profile was analyzed using capillary electrophoresis time-of flight mass spectrometry in the two groups (n = 9, each group). A metabolite set enrichment analysis (MSEA) with muscle metabolites and a false discovery rate q < 0.2 was performed to identify significantly different metabolic pathways between the 2 groups. The triglycerides and free fatty acid levels and insulin resistance index were lower, whereas the TEE was higher in the LPL transgenic rabbits than in the control rabbits. Among 165 metabolites detected, the levels of 37 muscle metabolites were significantly different between the 2 groups after false discovery rate correction (q < 0.2). The MSEA revealed that the TCA cycle and proteinogenic amino acid metabolism pathways were significantly different between the 2 groups (P < 0.05). In the MSEA, all four selected metabolites for the TCA cycle (2-oxoglutaric acid, citric acid, malic acid, fumaric acid), as well as eight selected metabolites for proteinogenic amino acid metabolism (asparagine, proline, methionine, phenylalanine, histidine, arginine, leucine, isoleucine) were consistently increased in the transgenic rabbits compared with control rabbits, suggesting that these two metabolic pathways were activated in the transgenic rabbits. Some of the selected metabolites, such as citric acid and methionine, were significantly associated with serum lipids and insulin resistance (P < 0.05). The current results suggest that the overexpression of LPL may lead to increased activities of TCA cycle and proteinogenic amino acid metabolism pathways in the skeletal muscle, and these enhancements may play an important role in the biological mechanisms underlying the anti-obesity/anti-diabetes features of LPL overexpression.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

2017 George Lyman Duff Memorial Lecture: Fat in the Blood, Fat in the Artery, Fat in the Heart: Triglyceride in Physiology and Disease.

Cholesterol is not the only lipid that causes heart disease. Triglyceride supplies the heart and skeletal muscles with highly efficient fuel and allows for the storage of excess calories in adipose tissue. Failure to transport, acquire, and use triglyceride leads to energy deficiency and even death. However, overabundance of triglyceride can damage and impair tissues. Circulating lipoprotein-associated triglycerides are lipolyzed by lipoprotein lipase (LpL) and hepatic triglyceride lipase. We inhibited these enzymes and showed that LpL inhibition reduces high-density lipoprotein cholesterol by >50%, and hepatic triglyceride lipase inhibition shifts low-density lipoprotein to larger, more buoyant particles. Genetic variations that reduce LpL activity correlate with increased cardiovascular risk. In contrast, macrophage LpL deficiency reduces macrophage function and atherosclerosis. Therefore, muscle and macrophage LpL have opposite effects on atherosclerosis. With models of atherosclerosis regression that we used to study diabetes mellitus, we are now examining whether triglyceride-rich lipoproteins or their hydrolysis by LpL affect the biology of established plaques. Following our focus on triglyceride metabolism led us to show that heart-specific LpL hydrolysis of triglyceride allows optimal supply of fatty acids to the heart. In contrast, cardiomyocyte LpL overexpression and excess lipid uptake cause lipotoxic heart failure. We are now studying whether interrupting pathways for lipid uptake might prevent or treat some forms of heart failure.

Regulation of the human lipoprotein lipase gene by the forkhead box transcription factor FOXA2/HNF-3β in hepatic cells

Lipoprotein lipase (LPL) plays a major role in the hydrolysis of triglycerides (TG) from circulating TG-rich lipoproteins. The role of LPL in the liver has been controversial but recent studies in mice with liver LPL overexpression or deficiency have revealed important new roles of the enzyme in glucose and lipid metabolism. The objective of this study was to identify regulatory elements and factors that control the transcription of the human LPL gene in hepatocytes. Deletion analysis of the human LPL promoter revealed that the proximal region which harbors a binding site for the forkhead box transcription factor FOXA2/HNF-3β at position −47/−40 is important for its hepatic cell activity. Silencing of FOXA2 in HepG2 cells reduced the LPL mRNA and protein levels. Direct binding of FOXA2 to the novel binding site was established in vitro and ex vivo. Mutagenesis of the FOXA2 site reduced the basal activity and abolished the FOXA2-mediated transactivation of the LPL promoter. Ιnsulin decreased LPL mRNA levels in HepG2 cells and this was associated with phosphorylation of AKT and nuclear export of FOXA2. In summary, the data of the present study combined with previous findings on the role of FOXA2 in HDL metabolism and gluconeogenesis, suggest that FOXA2 is a key regulator of lipid and glucose homeostasis in the adult liver. Understanding the mechanisms by which FOXA2 exerts its functions in hepatocytes may open the way to novel therapeutic strategies for patients with metabolic diseases such as dyslipidemia, diabetes and the metabolic syndrome.

Effects of Overexpression of Lipoprotein Lipase (LPL) on Aβ Burden and Memory Function in LPL and APP-double-Transgenic Mice

Effects of Overexpression of Lipoprotein Lipase (LPL) on Aβ Burden and Memory Function in LPL and APP-double-Transgenic Mice

Lipoprotein lipase in chronic lymphocytic leukaemia – Strong biomarker with lack of functional significance

In chronic lymphocytic leukaemia (CLL), lipoprotein lipase (LPL) mRNA overexpression is an established poor prognostic marker, its function, however, is poorly understood. Measuring extracellular LPL enzymatic activity and protein, we found no difference between levels in CLL patients and those of controls, both before and after heparin treatment in vivo and in vitro. Investigating LPL knock down effects, we determined five potential downstream targets, of which one gene, STXBP3, reportedly is involved in fatty acid metabolism.While possibly reflecting an epigenetic switch towards an incorrect transcriptional program, LPL overexpression by itself does not appear to significantly influence CLL cell survival.

Lipoprotein lipase is frequently overexpressed or translocated in cervical squamous cell carcinoma and promotes invasiveness through the non-catalytic C terminus

Background:We studied the biological significance of genes involved in a novel t(8;12)(p21.3;p13.31) reciprocal translocation identified in cervical squamous cell carcinoma (SCC) cells.Methods:The rearranged genes were identified by breakpoint mapping, long-range PCR and sequencing. We investigated gene expression in vivo using reverse-transcription PCR and tissue microarrays, and studied the phenotypic consequences of forced gene overexpression.Results:The rearrangement involved lipoprotein lipase (LPL) and peroxisome biogenesis factor-5 (PEX5). Whereas LPL–PEX5 was expressed at low levels and contained a premature stop codon, PEX5–LPL was highly expressed and encoded a full-length chimeric protein (including the majority of the LPL coding region). Consistent with these findings, PEX5 was constitutively expressed in normal cervical squamous cells, whereas LPL expression was negligible. The LPL gene was rearranged in 1 out of 151 cervical SCCs, whereas wild-type LPL overexpression was common, being detected in 10 out of 28 tissue samples and 4 out of 10 cell lines. Forced overexpression of wild-type LPL and PEX5–LPL fusion transcripts resulted in increased invasiveness in cervical SCC cells, attributable to the C-terminal non-catalytic domain of LPL, which was retained in the fusion transcripts.Conclusion:This is the first demonstration of an expressed fusion gene in cervical SCC. Overexpressed wild-type or translocated LPL is a candidate for targeted therapy.

Fatty acids increase glucose uptake and metabolism in C2C12myoblasts stably transfected with human lipoprotein lipase

Cellular effects of FFA might differ from those of lipoprotein triglyceride (TG)-derived fatty acids (TGFA). The aim of the current study was to examine the relationship between lipoprotein lipase (LPL) expression, TGFA, or FFA availability and glucose metabolism in the absence of insulin in C2C12 myoblasts. Control myoblasts or myoblasts stably transfected with human lipoprotein lipase (C2/LPL; 15-fold greater LPL activity) were incubated for 12 h in fetal bovine serum-free medium in the absence or presence of Intralipid-20. Intracellular retention of labeled medium glucose was assessed in a subset of experiments. In the presence of Intralipid, medium glucose disappearance was increased in C2/LPL cells but not in control cells. In both cell types, glucose label retention in cellular TG was increased in the presence of Intralipid; incubation with albumin-bound oleate produced similar results. In the presence of Intralipid, the LPL hydrolytic inhibitor tetrahydrolipstatin blocked excess glucose retention in cellular TG but did not significantly decrease glucose disappearance in C2/LPL cells. Changes in glucose transport or hexokinase II did not explain the altered glucose disappearance in C2/LPL cells. Our results suggest that LPL overexpression in these cells leads to chronic metabolic adaptations that alter glucose uptake and retention.

Lipoprotein lipase: from gene to obesity

Lipoprotein lipase (LPL) is a multifunctional enzyme produced by many tissues, including adipose tissue, cardiac and skeletal muscle, islets, and macrophages. LPL is the rate-limiting enzyme for the hydrolysis of the triglyceride (TG) core of circulating TG-rich lipoproteins, chylomicrons, and very low-density lipoproteins (VLDL). LPL-catalyzed reaction products, fatty acids, and monoacylglycerol are in part taken up by the tissues locally and processed differentially; e.g., they are stored as neutral lipids in adipose tissue, oxidized, or stored in skeletal and cardiac muscle or as cholesteryl ester and TG in macrophages. LPL is regulated at transcriptional, posttranscriptional, and posttranslational levels in a tissue-specific manner. Nutrient states and hormonal levels all have divergent effects on the regulation of LPL, and a variety of proteins that interact with LPL to regulate its tissue-specific activity have also been identified. To examine this divergent regulation further, transgenic and knockout murine models of tissue-specific LPL expression have been developed. Mice with overexpression of LPL in skeletal muscle accumulate TG in muscle, develop insulin resistance, are protected from excessive weight gain, and increase their metabolic rate in the cold. Mice with LPL deletion in skeletal muscle have reduced TG accumulation and increased insulin action on glucose transport in muscle. Ultimately, this leads to increased lipid partitioning to other tissues, insulin resistance, and obesity. Mice with LPL deletion in the heart develop hypertriglyceridemia and cardiac dysfunction. The fact that the heart depends increasingly on glucose implies that free fatty acids are not a sufficient fuel for optimal cardiac function. Overall, LPL is a fascinating enzyme that contributes in a pronounced way to normal lipoprotein metabolism, tissue-specific substrate delivery and utilization, and the many aspects of obesity and other metabolic disorders that relate to energy balance, insulin action, and body weight regulation.

2008 Robert Levy Memorial Lecture—Tissue-Specific Regulation of Lipoprotein Lipase and Energy Balance: The Story Gets Even More Interesting

Lipoprotein lipase (LPL) is a multifunctional enzyme produced by and studied in many tissues, including adipose tissue, cardiac and skeletal muscle, islets, and macrophages. After synthesis by parenchymal cells, the lipase is transported to the capillary endothelium, where it is rate-limiting for the hydrolysis of the triglyceride (TG) core of the circulating TG-rich lipoproteins, chylomicrons, and very low density lipoproteins (VLDL). The reaction products, fatty acids and monoacylglycerol, are in part taken up by the tissues locally, where they are processed in a tissue-specific manner, e.g., stored as neutral lipids (TG &gt; cholesteryl esters[CE]) in adipose tissue, oxidized or stored in muscle, or as CE/TG in foam cells in macrophages. LPL is regulated in a tissue-specific manner. In adipose tissue, LPL is increased by insulin and meals but decreased by fasting, whereas muscle LPL is decreased by insulin and increased by fasting. In obesity, adipose tissue LPL is increased; however, the insulin dose-response curve is shifted to the right. After weight reduction and stabilization of the reduced obese state, adipose tissue LPL is increased, as is the response of the enzyme to insulin and meals. In skeletal muscle, insulin does not stimulate LPL nor is the enzyme activity changed in obesity; however, after weight reduction, LPL in skeletal muscle is decreased by 70%. These tissue-specific changes in LPL set the stage for lipid partitioning to help explain the recidivism of obesity. To examine this divergent regulation further, transgenic and knockout murine models of tissue-specific LPL expression have been developed. Mice with overexpression of LPL in skeletal muscle develop TG accumulation in muscle, develop insulin resistance, are protected from excessive weight gain, and increase their metabolic rate in the cold. When placed onto the LPL knockout and leptin deficient background, overexpression of LPL using an MCK promoter reduces obesity. Alternatively, a deletion of LPL in skeletal muscle reduces TG accumulation and increases insulin-mediated glucose transport into muscle but leads to lipid partitioning to other tissues, insulin resistance, and obesity. In the heart, loss of LPL is associated with hypertriglyceridemia and a greater utilization of glucose, implying that free fatty acids are not a sufficient fuel for optimal cardiac function. LPL is also produced in the brain, and that’s where the “story gets even more interesting.” We have just created mice with a neuron-specific deletion of LPL (NEXLPL−/−) using cre recombinase driven by the helix-loop-helix nuclear transcription factor NEX promoter. By 6 months of age, NEXLPL−/− mice weigh 50% more than their litter mates. This phenotype provides convincing evidence that lipoprotein sensing occurs in the brain and is important to energy balance and body weight regulation. Overall, LPL is a fascinating enzyme that contributes in a pronounced way to normal lipoprotein metabolism, tissue-specific substrate delivery and utilization, and to the many aspects of metabolism that relate to cardiovascular disease, including energy metabolism, insulin action, body weight regulation, and atherosclerosis.

Effects of lipoprotein lipase and statins on cholesterol uptake into heart and skeletal muscle

Regulation of cholesterol metabolism in cultured cells and in the liver is dependent on actions of the LDL receptor. However, nonhepatic tissues have multiple pathways of cholesterol uptake. One possible pathway is mediated by LPL, an enzyme that primarily hydrolyzes plasma triglyceride into fatty acids. In this study, LDL uptake and tissue cholesterol levels in heart and skeletal muscle of wild-type and transgenic mice with alterations in LPL expression were assessed. Overexpression of a myocyte-anchored form of LPL in heart muscle led to increased uptake of LDL and greater heart cholesterol levels. Loss of LDL receptors did not alter LDL uptake into heart or skeletal muscle. To induce LDL receptors, mice were treated with simvastatin. Statin treatment increased LDL receptor expression and LDL uptake by liver and skeletal muscle but not heart muscle. Plasma creatinine phosphokinase as well as muscle mitochondria, cholesterol, and lipid droplet levels were increased in statin-treated mice overexpressing LPL in skeletal muscle. Thus, pathways affecting cholesterol balance in heart and skeletal muscle differ.

Fasting decreases free fatty acid turnover in mice overexpressing skeletal muscle lipoprotein lipase

Skeletal muscle lipoprotein lipase (LPL) overexpression in mice results in whole-body insulin resistance and increased intramuscular triglyceride stores, but decreased plasma triglyceride concentration and unchanged plasma free fatty acid (FFA) concentration. The effects of skeletal muscle LPL overexpression and fasting duration on FFA kinetics are unknown. Transgenic mice with muscle-specific LPL overexpression (MCKhLPL) and control mice (Con) were studied at rest during a 50-minute constant infusion of [9,10- 3H]palmitate to determine FFA kinetics after both 4 and 16 hours of fasting. FFA concentration was not different between groups after the 4-hour (Con, 0.80 ± 0.06 mmol/L; MCKhLPL, 0.83 ± 0.07 mmol/L) and 16-hour (Con, 0.83 ± 0.04 mmol/L; MCKhLPL, 0.80 ± 0.07 mmol/L) fast. FFA turnover ( R a) was not significantly different between MCKhLPL and Con groups after the 4-hour fast (Con R a = 2.52 ± 0.36 μmol/min; MCKhLPL R a = 2.37 ± 0.27 μmol/min). However, FFA turnover was significantly decreased after the 16-hour fast in MCKhLPL mice vs controls (Con R a = 2.89 ± 0.52 μmol/min; MCKhLPL R a = 1.64 ± 0.17 μmol/min; P < .05). The significantly lower FFA R a in MCKhLPL vs control mice was due to a decrease in MCKhLPL FFA turnover from the 4- to 16-hour fast, whereas FFA turnover was unchanged in controls. The changes in FFA appearance after the 16-hour fast in MCKhLPL mice are most likely explained by increased reliance by skeletal muscle on plasma triglyceride as a fuel. These data suggest increased skeletal muscle LPL expression decreases dependence on plasma FFA during prolonged fasting in mice.

Use of prognostic factors in risk stratification at diagnosis and time of treatment of patients with chronic lymphocytic leukemia

To review risk stratification strategies used in chronic lymphocytic leukemia at diagnosis to predict aggressiveness of disease and, at time of treatment, to predict duration of response. Several new prognostic factors can better assist clinicians in predicting the aggressiveness of chronic lymphocytic leukemia at diagnosis and the likelihood of maintaining a prolonged remission with treatment. This article reviews older prognostic factors such as beta2-microglobulin and thymidine kinase activity that have been partially validated by recently completed large studies. New prognostic factors such as interphase cytogenetics, immunoglobulin heavy-chain gene mutational analysis, and relevant secondary surrogate markers of immunoglobulin heavy-chain gene, including methylation of the zeta-associated protein gene, lipoprotein lipase overexpression, telomere length, and telomerase activity are reviewed. Some prognostic factors (interphase cytogenetics) but not others (immunoglobulin heavy-chain gene mutational status, zeta-associated protein expression) predict the duration of response to fludarabine-based combination strategies. Recent advances in risk stratification provide clinicians with tools to better predict outcome of chronic lymphocytic leukemia at the time of treatment and response to treatment at the time of developing symptomatic disease.

Catalytically Inactive Lipoprotein Lipase Overexpression Increases Insulin Sensitivity in Mice

Abnormalities in lipoprotein lipase (LPL) function contribute to the development of hypertriglyceridemia, one of the characteristic disorders observed in the metabolic syndrome. In addition to the hydrolyzing activity of triglycerides, LPL modulates various cellular functions via its binding ability to the cell surface. Here we show the effects of catalytically inactive LPL overexpression on high-fat diet (HFD)-induced decreased systemic insulin sensitivity in mice. The binding capacity of catalytically inactive G188E-LPL to C2C12 skeletal muscle cells was not significantly different from that of wild type LPL. Insulin-stimulated IRS-1 phosphorylation and glucose uptake were increased by addition of wild type or mutant LPL in C2C12 cells. After 10 weeks' of HFD feeding, mice had significantly higher blood glucose levels than chow-fed mice in insulin tolerance tests. The blood glucose levels after insulin injection was significantly decreased in mutated LPL-overexpressing mice (G188E mice), as well as in wild type LPL-overexpressing mice (WT mice). Overexpression of catalytically inactive LPL, as well as wild type LPL, improved impaired insulin sensitivity in mice. These results show that decreased expression of LPL possibly causes the insulin resistance, in addition to hypertriglyceridemia, in metabolic syndrome.

Transthyretin knockouts are a new mouse model for increased neuropeptide Y

Transthyretin (TTR) has access to the brain and nerve through the blood and cerebrospinal fluid. To investigate TTR function in nervous system homeostasis, differential gene expression in wild-type (WT) and TTR knockout (KO) mice was assessed. Peptidylglycine alpha-amidating monooxygenase (PAM), the rate-limiting enzyme in neuropeptide maturation, is overexpressed in the peripheral (PNS) and central nervous system (CNS) of TTR KOs that, consequently, display increased neuropeptide Y (NPY) levels. NPY acts on energy homeostasis by increasing white adipose tissue lipoprotein lipase (LPL) and decreasing thermogenesis; accordingly, we show increased LPL expression and activity in white adipose tissue, PNS, and CNS as well as decreased body temperature in TTR KOs. Associated to increased NPY levels, TTR KOs display increased carbohydrate consumption and preference. In neuronal cells, absence of TTR is related to increased PAM activity, NPY levels and LPL expression, reinforcing that TTR is involved in neuropeptide maturation and that increased NPY correlates with LPL overexpression in the nervous system. Furthermore, we provide molecular insights to the reduced depressive behavior of TTR KOs, as NPY is anti-depressant. Our findings demonstrate that TTR KOs are a model for increased NPY and that TTR plays a role in nervous system physiology.

High expression of lipoprotein lipase in poor risk B-cell chronic lymphocytic leukemia

We investigated the pattern of lipoprotein lipase (LPL) expression in B-cell chronic lymphocytic leukemia (B-CLL) and assessed its prognostic relevance. Expression of LPL mRNA as well as protein was highly restricted to leukemic B cells. The intensity of intracellular immunoreactivity of LPL was higher in samples of patients with unmutated immunoglobulin heavy-chain variable region genes (IGV(H)) compared to those with mutated IGV(H) genes. LPL mRNA levels in peripheral blood mononuclear cells (PBMNC) from 104 CLL patients differed by 1.5 orders of magnitude between cases with mutated (N=51) or unmutated (N=53) IGV(H) (median: 1.33 vs 45.22 compared to normal PBMNC). LPL expression correlated strongly with IGV(H) mutational status (R=0.614; P<0.0001). High LPL expression predicted unmutated IGV(H) status with an odds ratio of 25.90 (P<0.0001) and discriminated between mutated and unmutated cases in 87 of 104 patients (84%). LPL expression was higher in patients with poor risk cytogenetics. High LPL expression was associated with a shorter treatment-free survival (median 40 vs 96 months, P=0.001) and a trend for a shorter median overall survival (105 months vs not reached). Our data establish LPL as a prognostic marker and suggest functional consequences of LPL overexpression in patients with B-CLL.

High lipoprotein lipase activity increases insulin sensitivity in transgenic rabbits

Lipoprotein lipase (LPL) is the rate-limiting enzyme in the hydrolysis of triglyceride-rich lipoproteins and plays an important role in glucose metabolism. To examine the hypothesis that increased LPL activity may alter insulin sensitivity, we investigated glucose metabolism and insulin sensitivity in transgenic (Tg) rabbits expressing the human LPL gene under the control of a β-actin promoter. An intravenous glucose tolerance test showed that the plasma glucose clearance rate was not significantly different between Tg and non-Tg rabbits; however, the area under the curve for insulin and free fatty acids in Tg rabbits was significantly reduced compared with that of non-Tg rabbits ( P < .05). Using the intravenous insulin tolerance test, we found that the area of under the curve of glucose of Tg rabbits was also significantly reduced ( P < .01). Furthermore, euglycemic-hyperinsulinemic clamp test revealed that the mean glucose infusion rate in Tg rabbits was significantly higher than in non-Tg rabbits ( P < .05). These results demonstrate that systemic overexpression of LPL increases whole-body insulin sensitivity and genetic manipulation of LPL genes may be a potential target for the treatment of diabetic patients.

Prognostic Relevance of Lipoprotein Lipase (LPL) Expression in B-CLL.

We investigated the pattern of lipoprotein lipase (LPL) expression in B-cell chronic lymphocytic leukemia (B-CLL) and assessed its prognostic and potential functional relevance. LPL mRNA levels in peripheral blood mononuclear cells (PBMNC) from 55 CLL patients differed by 2 orders of magnitude between cases with mutated (N=28) or unmutated (N=27) IGVH (median: 1.62 vs. 100.43 compared to normal PBMNC). LPL expression correlated strongly with IGVH mutational status (R=0.78; P<0.0001). High LPL expression (≥ 10) predicted unmutated IGVH status with an odds ratio of 128.71 (P < 0.0001) and discriminated between mutated and unmutated cases in 51 of 55 patients (93%). In an extended cohort of 104 patients, a trend for LPL as a prognostic factor regarding overall survival was found: While the median overall survival (OS) in patients with LPL expression of more than 10 was 105 months, the median OS was not reached in the low LPL group. Importantly, high LPL expression (≥ 10) was significantly associated with a short treatment-free survival (median 40 vs. 96 months, P = 0.001). By indirect immunofluorescence, LPL was detected in the cytoplasm of leukemic B-CLL cells and showed intense, large granular and punctate distribution. Fine granular and diffuse staining was observed in monocytes but no immunoreactivity was detected in T- cells. In order to compare the LPL protein expression unmutated (LPL mRNA high) and mutated (LPL mRNA low) samples from 10 patients (5 mutated and 5 unmutated) were prepared and stained under identical conditions.The intensity of intracellular immunoreactivity to LPL antibody in B-CLL cells was higher in each unmutated compared to the mutated samples. In order to investigate the association of LPL with other genes we performed gene expression profiling on 12 patient samples selected for high or low LPL yielding 251 differentially expressed genes: 171 genes associated with LPL only (group 1), 58 genes with LPL and mutational status (group 2) and 22 genes with mutational status only (group 3). While group 2 and 3 contained a number of genes previously described by Rosenwald and Klein*, a considerable number of genes associated with lipid metabolism were clustered in group 1, indicating a functional role of LPL in B-CLL cells. Our data establish LPL as a prognostic marker and suggest functional consequences of LPL overexpression in patients with B-CLL.