Lipase Secretion Research Articles

In vitro polyphenol effects on activity, expression and secretion of pancreatic bile salt-dependent lipase

The relationship between cholesterol and atherosclerosis has gained wide credence and red wine polyphenols have been shown to have an anti-atherogenic activity. In the present in vitro studies, we have evaluated and compared the effects of resveratrol, an active compound of red wine, and of a whole red wine polyphenolic extract (RWE) on the pancreatic bile salt-dependent lipase (BSDL). BSDL is involved in the duodenal hydrolysis of lipid esters and in part of cholesteryl esters thus favoring the bioavailability of free cholesterol. Resveratrol and RWE decrease the human and rat enzyme activities. Resveratrol and RWE also impaired the secretion of BSDL by the rat pancreatic AR4-2J cells used as secreting model. This effect is reversed by the removal of resveratrol or RWE from the cell culture medium. Further, resveratrol (but not RWE) affects the transcription of the gene encoding BSDL and dramatically diminishes the quantity of the enzyme that is expressed and secreted by AR4-2J cells. Results suggest that the hypolipemic effects of red wine polyphenols could partly originate from the inhibition of BSDL activity and secretion in the duodenum. In vivo, these effects could decrease the hydrolysis of dietary lipid esters and likely the absorption of free cholesterol.

Enhancement of the Efficiency of Secretion of Heterologous Lipase in Escherichia coli by Directed Evolution of the ABC Transporter System

The ABC transporter (TliDEF) from Pseudomonas fluorescens SIK W1, which mediated the secretion of a thermostable lipase (TliA) into the extracellular space in Escherichia coli, was engineered using directed evolution (error-prone PCR) to improve its secretion efficiency. TliD mutants with increased secretion efficiency were identified by coexpressing the mutated tliD library with the wild-type tliA lipase in E. coli and by screening the library with a tributyrin-emulsified indicator plate assay and a microtiter plate-based assay. Four selected mutants from one round of error-prone PCR mutagenesis, T6, T8, T24, and T35, showed 3.2-, 2.6-, 2.9-, and 3.0-fold increases in the level of secretion of TliA lipase, respectively, but had almost the same level of expression of TliD in the membrane as the strain with the wild-type TliDEF transporter. These results indicated that the improved secretion of TliA lipase was mediated by the transporter mutations. Each mutant had a single amino acid change in the predicted cytoplasmic regions in the membrane domain of TliD, implying that the corresponding region of TliD was important for the improved and successful secretion of the target protein. We therefore concluded that the efficiency of secretion of a heterologous protein in E. coli can be enhanced by in vitro engineering of the ABC transporter.

The influence of the enzymatic composition of lamb rennet paste on some properties of experimentally produced PDO Fiore Sardo cheese

An experiment on PDO (Protected Designation of Origin) Fiore Sardo cheese making was carried out to assess the influence of rennet paste on cheese quality. Four different preparations of lamb rennet paste (A, B, C and D) were used. Rennet A came exclusively from suckling lambs slaughtered immediately after suckling, rennet B from suckling lambs not fed for 12 h, and rennets C and D from suckling lambs allowed to graze and slaughtered in the same way as A and B, respectively. In vitro lipolysis and multiple cheese-making trials were carried out for each rennet. The enzymatic composition of the prepared rennets was different. Lipolytic activity was assessed in vitro by measuring the quantity of free fatty acids released by hydrolysis of a sheep milk cream substrate. Rennet A had the greatest lipolytic activity, which had a strong preference for esters of short-chain fatty acids. The cheeses made using the different rennets did not differ significantly in their moisture, protein and fat content or in the nitrogen fractions which resulted from proteolysis. The cheese produced with rennet A had the highest lipolysis. Short-chain fatty acids, in particular butyric acid, were prevalent, as they were in the in vitro trials. The diet and the presence of milk in the abomasa was responsible for the enzymatic peculiarities of rennet A. Suckling stimulated the secretion of pre-gastric lipase from the pharingeal tissue. Thus, if one wishes to produce a rennet with the particular enzymatic composition necessary for a particular cheese, the diet and the slaughtering conditions of the lambs should be controlled.

Dose-response for inhibition by amylin of cholecystokinin-stimulated secretion of amylase and lipase in rats

Background and aims The neuroendocrine hormone amylin, cosecreted with insulin from pancreatic β-cells in response to nutrient ingestion, has several physiologic actions to limit the rate of nutrient uptake, including the slowing of gastric emptying. Methods To investigate whether amylin might modulate digestive enzyme secretion from the exocrine pancreas, anesthetized Sprague Dawley rats were cannulated via the pancreatic duct and the secretory response (flow, amylase and lipase) to cholecystokinin (1 μg s.c.) was measured in the absence and in the presence of 0.1, 0.3 and 1 μg s.c. doses of amylin. Results Amylin alone did not affect pancreatic secretion, but it dose-dependently inhibited cholecystokinin-stimulated amylase secretion by up to 58% and lipase secretion by up to 67%. The ED 50's for these responses were 0.21 μg ± 0.18 log and 0.11 μg ± 0.05 log, respectively, doses that result in excursions of plasma amylin concentration that are within the reported physiological range. Amylin did not evoke cell signalling in the Ar42j model of pancreatic acinar cells, and responses to amylin were not observed in either Ar42j cells or isolated pancreatic acini in a microphysiometer indicating that the effect of amylin was indirect. Conclusions Inhibition of stimulated pancreatic enzyme secretion is likely to be a physiological, extrapancreatic, action of amylin. Amylinergic mechanisms modulating both gastric emptying and pancreatic enzyme secretion may thus match, respectively, the appearance of substrate and enzymes in the gut lumen.

Fat absorption in cystic fibrosis mice is impeded by defective lipolysis and post-lipolytic events

Cystic fibrosis (CF) is frequently associated with progressive loss of exocrine pancreas function, leading to incomplete digestion and absorption of dietary fat. Supplementing patients with pancreatic lipase reduces fat excretion, but it does not completely correct fat malabsorption, indicating that additional pathological processes affect lipolysis and/or uptake of lipolytic products. To delineate the role of such (post) lipolytic processes in CF-related fat malabsorption, we assessed fat absorption, lipolysis, and fatty acid uptake in two murine CF models by measuring fecal fat excretion and uptake of oleate- and triolein-derived lipid. Pancreatic and biliary function was investigated by determining lipase secretion and biliary bile salt (BS) secretion, respectively. A marked increase in fecal fat excretion was observed in cftr null mice but not in homozygous DeltaF508 mice. Fecal BS loss was enhanced in both CF models, but biliary BS secretion rates were similar. Uptake of free fatty acid was delayed in both CF models, but only in null mice was a specific reduction in lipolytic activity apparent, characterized by strongly reduced triglyceride absorption. Impaired lipolysis was not due to reduced pancreatic lipase secretion. Suppression of gastric acid secretion partially restored lipolytic activity and lipid uptake, indicating that incomplete neutralization of gastric acid impedes fat absorption. We conclude that fat malabsorption in cftr null mice is caused by impairment of lipolysis, which may result from aberrant duodenal pH regulation.

Secretory expression of thermostable T1 lipase through bacteriocin release protein

The extracellular production of T1 lipase was performed by co-expression of pJL3 vector encoding bacteriocin release protein in prokaryotic system. Secretory expression was optimized by considering several parameters, including host strains, inducer (IPTG) concentration, media, induction at A 600 nm , temperature, and time of induction. Among the host strains tested, Origami B excreted out 18,100 U/ml of lipase activity into culture medium when induced with 50 μM IPTG for 12 h. The Origami B harboring recombinant plasmid pGEX/T1S and pJL3 vector was chosen for further study. IPTG at 0.05 mM, YT medium, induction at A 600 nm of 1.25, 30 °C, and 32 h of induction time were best condition for T1 lipase secretion with Origami B as a host.

Role of N-linked glycosylation in the secretion and activity of endothelial lipase

Human endothelial lipase (EL), a member of the triglyceride lipase gene family, has five potential N-linked glycosylation sites, two of which are conserved in both lipoprotein lipase and hepatic lipase. Reduction in molecular mass of EL after treatment with glycosidases and after treatment of EL-expressing cells with the glycosylation inhibitor tunicamycin demonstrated that EL is a glycosylated protein. Each putative glycosylation site was examined by site-directed mutagenesis of the asparagine (Asn). Mutation of Asn-60 markedly reduced secretion and slightly increased specific activity. Mutation of Asn-116 did not influence secretion but increased specific activity. In both cases, this resulted from decreased apparent K(m) and increased apparent V(max). Mutation of Asn-373 did not influence secretion but significantly reduced specific activity, as a result of a decrease in apparent V(max). Mutation of Asn-471 resulted in no reduction in secretion or specific activity. Mutation of Asn-449 resulted in no change in secretion, activity, or molecular mass, indicating that the site is not utilized. The ability of mutants secreted at normal levels to mediate bridging between LDL and cell surfaces was examined. The Asn-373 mutant demonstrated a 3-fold decrease in bridging compared with wild-type EL, whereas Asn-116 and Asn-471 were similar to wild-type EL.

Ambient pH-regulated enzime secretion in endophytic and pathogenic isolates of the fungal genus Colletotrichum

In fungi a genetic system ensures that enzymes are secreted mainly at ambient pH values corresponding to their optima of activity. Although a great deal of information has been obtained concerning this environmental response, there is a lack of studies involving phytopathogenic, endophytic and entomopathogenic fungi as well as different aspects of fungus-host interactions. This study compares in a plate-clearing assays, the effect of ambient pH in the secretion of amylase, cellulase, lipase, pectinase and protease by endophytic, phytopathogenic, and entomopathogenic isolates belonging to several species of Colletotrichum. All enzymes were secreted in a pH-dependent manner by all isolates. Endophytes and pathogens showed distinct patterns of protease secretion, with optima at alkaline and acid growth conditions, respectively. In liquid medium, a Pi-repressible acid phosphatase of an endophytic isolate responded to ambient pH, having a 14-fold increase in secreted specific activity at acid pH, as compared to alkaline pH. Furthermore, part of a Colletotrichum pacC homologue gene, coding for a transcriptional factor responsible for pH-regulated gene expression, was cloned. Ambient pH seems to be a general factor controlling enzyme secretion in fungus-host interactions through a conserved genetic circuit.

Modulating amylase and lipase secretion in the pancreatic graft by somatostatin administration: preliminary results of a prospective, randomized trial

Pancreas transplantation is a routine method for the treatment of diabetes mellitus. One of the main challenges of a transplant with extraperitoneal placement of the pancreatic graft is impaired wound healing due to massive amylase and lipase secretion by the pancreatic graft, evoking edemtous fluid. From February 2002 through January 2003, we performed pancreatic transplant procedures in 21 patients who were prospectively and randomly assigned to two groups: 8 organ donors and the recipients were administered somatostatin by continuous infusion. Thirteen grafts were harvested and transplanted without somatostatin infusion. The two groups did not show significantly differences in mean donor or recipient ages, weights, of serum amylase and lipase content values or drain output until day 6. There was a significantly lower lipase in the drain output of transplant recipients given somatostatin (12.5 and 54.2 μmol/L, respectively; P < .05). Neither the post-pancreatic transplant wound healing nor the number of rejection episodes were affected by somatostatin administration.

Enhanced lipoprotein lipase secretion and foam cell formation by macrophages of patients with growth hormone deficiency: possible contribution to increased risk of atherogenesis?

GH deficiency is associated with increased prevalence of atherosclerosis, and recent data indicate a proatherogenic role for macrophage lipoprotein lipase (LPL) in the arterial wall. In this pilot study, we determined LPL expression and foam cell formation in monocyte-derived macrophages of 12 control subjects and nine patients with GH deficiency without GH replacement therapy. LPL mRNA levels, mass, and activity were increased in macrophages of patients with GH deficiency. In these subjects, macrophage LPL activity correlated with body mass index and fat mass. Incubation of patient macrophages with IGF-I for 24 h or differentiation of monocytes isolated from GH-deficient patients into macrophages in the presence of this growth factor decreased the amount of LPL mass. Compared with control cells, macrophages derived from GH-deficient patients took up and stored increased amounts of proatherogenic lipoproteins and were more easily converted to foam cells. In the supernatants of these cells, increased levels of free fatty acids and TNFalpha were also documented. These results demonstrate that macrophages of patients with GH deficiency secrete increased amounts of proatherogenic cytokines and are more susceptible to foam cell formation. These alterations may contribute to the increased cardiovascular risk in patients with GH deficiency.

Legionella pneumophila type II protein secretion promotes virulence in the A/J mouse model of Legionnaires' disease pneumonia.

Legionella pneumophila, the gram-negative agent of Legionnaires' disease, possesses type IV pili and a type II protein secretion (Lsp) system, both of which are dependent upon the PilD prepilin peptidase. By analyzing multiple pilD mutants and various types of Lsp mutants as well as performing trans-complementation of these mutants, we have confirmed that PilD and type II secretion genes are required for L. pneumophila infection of both amoebae and human macrophages. Based upon a complete analysis of lspDE, lspF, and lspG mutants, we found that the type II system controls the secretion of protease, RNase, lipase, phospholipase A, phospholipase C, lysophospholipase A, and tartrate-sensitive and tartrate-resistant acid phosphatase activities and influences the appearance of colonies. Examination of the developing L. pneumophila genome database indicated that the organism has two other loci (lspC and lspLM) that are predicted to promote secretion and thus a set of genes that is comparable to the type II secretion genes in other gram-negative bacteria. In contrast to lsp mutants, L. pneumophila pilus mutants lacking either the PilQ secretin, the PspA pseudopilin, or pilin were not defective for colonial growth, secreted activities, or intracellular replication. L. pneumophila dot/icm mutants were also not impaired for type II-dependent exoenzymes. Upon intratracheal inoculation into A/J mice, lspDE, lspF, and pilD mutants, but not pilus mutants, exhibited a reduced ability to grow in the lung, as measured by competition assays. The lspF mutant was also defective in an in vivo kinetic assay. Examination of infected mouse sera revealed that type II secreted proteins are expressed in vivo. Thus, the L. pneumophila Lsp system is a virulence factor and the only type II secretion system linked to intracellular infection.

Leptin Increases Lipoprotein Lipase Secretion by Macrophages: Involvement of Oxidative Stress and Protein Kinase C

Recent data suggest that plasma leptin may represent a cardiovascular risk factor in diabetic patients. To gain further insight into the role of leptin in atherogenesis associated with diabetes, we investigated in the present study the role of this hormone in the regulation of macrophage lipoprotein lipase (LPL), a proatherogenic cytokine overexpressed in patients with type 2 diabetes. Treatment of human macrophages with leptin (1-10 nmol/l) increased LPL expression, at both the mRNA and protein levels. Pretreatment of these cells with anti-leptin receptor (Ob-R) antibody, protein kinase C (PKC) inhibitors, calphostin C, and GF109203X, or the antioxidant N-acetylcysteine (NAC) blocked the effects of leptin. Similar results were observed in leptin-treated J774 macrophages. In these cells, leptin increased the membrane expression of conventional PKC isoforms and downregulation of endogenous PKC expression abolished the effects of leptin on macrophage LPL expression. In leptin-treated J774 cells, enhanced LPL synthetic rate and increased binding of nuclear proteins to the activated protein-1 (AP-1) consensus sequence of the LPL gene promoter were also observed. This latter effect was abrogated by GF109203X. Overall, these data demonstrate that binding of leptin at the macrophage cell surface increases, through oxidative stress- and PKC-dependent pathways, LPL expression. This effect appears to be exerted at the transcriptional level and to involve AP-1 activation.

The improvement of lipase secretion and stability by addition of inert compounds into Acinetobacter calcoaceticus cultures.

Acinetobacter calcoaceticus BD413 produces variable amounts of an exocellular lipase that becomes rapidly inactivated upon secretion. To achieve high yield and protect the enzyme, we assayed the addition of several inert compounds to cell-free supernatants, cell fractions, and whole cultures. Glass beads, poly(ethylene glycol) 600, Triton X-100, saccharose, gum arabic, and beta-cyclodextrin were among the compounds tested. beta-Cyclodextrin and gum arabic (and saccharose to a lesser extent) were effective enzyme stabilizers in cell-free supernatants, while gum arabic, glass beads, and Triton X-100 improved lipase secretion from cells, and, therefore, total lipase yield (30-50%, according to the additive). In whole cultures, beta-cyclodextrin was the most effective additive, particularly in combination with glass beads or gum arabic. Indeed, cultures containing beta-cyclodextrin plus gum arabic were able to maintain 95% (+/- 1.5%) of the initial lipase activity for more than 16 h, while control cultures with no additives maintained only 10% (+/- 4%) of the enzyme activity after the same period. In conclusion, the addition of inert compounds in cultures may be considered a useful approach for achieving increased yield and lipase stabilization, amenable for downstream processing.

Effect of nordihydroguaiaretic acid on the secretion of lipoprotein lipase.

Nordihydroguaiaretic acid (NDGA), an inhibitor of lipoxygenase, inhibits the secretion of proteins and causes the redistribution of resident Golgi proteins into the endoplasmic reticulum (ER). In this study, the effect of NDGA on lipoprotein lipase (LPL) secretion was investigated in 3T3-L1 adipocytes, and compared with those of brefeldin A (BFA), a well-known fungal metabolite that exhibits similar ER-Golgi redistribution. Both BFA and NDGA blocked secretions of LPL. In the presence of BFA, the active and dimeric LPL was accumulated in adipocytes. After endoglycosidase H (endo H) digestion, the proportion of LPL subunits with partially endo H-sensitive oligosaccharide was significantly increased with BFA. However, in the presence of NDGA, the cellular LPL became inactive, and only the endo H-sensitive fraction of the LPL subunit was observed. An increase of the aggregated forms was observed in the fractions of the sucrose-density gradient ultracentrifugation. These properties of LPL in the NDGA-treated cells were similar to those of LPL that is retained in ER, and the effects of NDGA could not be reversed by BFA. These results indicate that the inhibitory mechanism of NDGA on the LPL secretion is functionally different from the ER-Golgi redistribution that is induced by BFA.

Acute regulation of hepatic lipase secretion by rat hepatocytes.

Hepatic lipase is involved in cholesterol uptake by the liver. Although it is known that catecholamines are responsible for the daily variation of enzyme activity, the mechanisms involved are poorly understood. Rat hepatocytes incubated with adrenaline or other Ca(2+)-mobilizing hormones were used as an experimental model. Adrenaline reduced in a similar proportion the secretion of both hepatic lipase and albumin. The effect of adrenaline disappeared completely in cells exposed to cycloheximide. Adrenaline decreased incorporation of [35S]Met into cellular and secreted proteins, but it affected neither degradation of [35S]Met-prelabeled proteins nor the abundance of total and specific (albumin, hepatic lipase, beta-actin) mRNA. Other Ca(2+)-mobilizing agents had the opposite effect on hepatic lipase secretion: it was decreased by vasopressin but was increased by epidermal growth factor. Vasopressin and epidermal growth factor had the opposite effect on [35S]Met incorporation into cellular and secreted proteins, but neither affected hepatic lipase mRNA. The acute effect of adrenaline, vasopressin, and epidermal growth factor on hepatic lipase secretion is the consequence of the effect of these hormones on protein synthesis and is therefore nonspecific.

Primary culture of porcine pancreatic acinar cells.

The methodology of acinar cell culture has become of primary importance in the research of pancreatic physiology and pharmacology. To develop a method for primary culture of porcine pancreatic acinar cells. Dispersed pancreatic acinar cells were made by RPMI-1640 medium containing collagenase III. After purification, the isolated acinar cells were cultured in RPMI-1640 medium with 2.5% fetal bovine serum. The morphologic characteristics of acinar cells were described. (3)H-thymidine incorporation of acinar cells and activity of amylase or lipase were determined during the culture. There were no remarkable morphologic changes in the pancreatic acinar cells during the 20-day culture. The acini showed the tendency of gathering but did not attach to the walls of the culture disks. Incorporation of (3)H-thymidine in acinar cells in the primary culture was well kept. The secretion of amylase or lipase from acini decreased with the time of culture. In the primary culture of acinar cells from porcine pancreas developed in this study, the acinar cells retained normal morphology and ability of growth but not secretion of amylase or lipase. The method would be beneficial for further experiments on acini of porcine pancreas.

Recognizing and diagnosing pancreatic insufficiency in infants.

1. Peter Francis Belamarich, MD 1. Einstein College of Medicine-Children’s Hospital at Montefiore Bronx, NY 1. Exocrine Pancreatic Dysfunction. Cystic Fibrosis. Gaskin K. In: Walker WA, Durie PR, Hamilton JR, Walker-Smith JA, Watkins JB, eds.Pediatric Gastrointestinal Disease, Hamilton, Ontario, Canada: BC Decker Inc;.2000;:1353–1369 2. Pancreatic Function Tests. Huynh H, Couper R. In: Walker WA, Durie PR, Hamilton JR, Walker-Smith JA, Watkins JB, eds.Pediatric Gastrointestinal Disease, Hamilton, Ontario, Canada: BC Decker Inc.2000;:1515–1528 3. Hereditary and Childhood Disorders of the Pancreas. Lopez MJ, Grand RJ. In: Feldman MH, Sleisenger MH, Scharschmidt BF, eds.Sleisenger and Fordtran’s Gastrointestinal and Liver Disease Philadelphia, Pa: WB Saunders.1998;:782–808 Pancreatic insufficiency (PI) is uncommon among infants, but it is important to recognize. Early diagnosis followed by oral enzyme replacement therapy can avert the significant morbidity that follows upon severe malnutrition in infancy. In addition, for the majority of infants who have PI and subsequently are found to have cystic fibrosis, early diagnosis allows genetic counseling to be offered and can help prevent progression of associated pulmonary disease. The pathophysiology of pancreatic insufficiency is complex. Malabsorption results from inadequate secretion of the approximately 20 enzymes and cofactors derived from the pancreatic acini as well as from insufficient bicarbonate secretion from the ductal epithelium. Without adequate bicarbonate to neutralize gastric acid, whatever limited pancreatic lipase is available cannot function optimally, and bile salt micellization of dietary fat droplets also is impaired. Thus, fat digestion takes a “double hit,” and fat malabsorption becomes a prominent clinical feature of PI. Protein maldigestion and malabsorption are also substantial, but they are more commonly subclinical. Quantitative studies of pancreatic enzyme secretion have shown that the pancreas has a tremendous functional reserve. Significant fat malabsorption does not occur until lipase secretion is below 2% of normal values. Thus, clinically apparent PI represents not mild or …

Peroxisome proliferator-activated receptor (PPAR) agonists decrease lipoprotein lipase secretion and glycated LDL uptake by human macrophages

Lipoprotein lipase (LPL) acts independently of its function as triglyceride hydrolase by stimulating macrophage binding and uptake of native, oxidized and glycated LDL. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors expressed in monocyte/macrophages, where they control cholesterol homeostasis. Here we study the role of PPARs in the regulation of LPL expression and activity in human monocytes and macrophages. Incubation of human monocytes or macrophages with PPARα or PPARγ ligands increases LPL mRNA and intracellular protein levels. By contrast, PPAR activators decrease secreted LPL mass and enzyme activity in differentiated macrophages. These actions of PPAR activators are associated with a reduced uptake of glycated LDL and could influence atherosclerosis development associated with diabetes.

Homologous expression of the lipase and ABC transporter gene cluster, tliDEFA, enhances lipase secretion in Pseudomonas spp.

The ABC transporter TliDEF was found to be an efficient secretory apparatus for extracellular lipase TliA in Pseudomonas fluorescens. For the enhanced secretion of the lipase, we tried to coexpress tliA and tliDEF in various Pseudomonas species. Whereas the coexpression of tliA and tliDEF was required for the lipase secretion in P. fragi, the expression of tliA was sufficient for the lipase secretion in P. fluorescens, P. syringae, and P. putida, indicating the existence of compatible ABC transporter in these species. However, P. fluorescens harboring tliDEFA secreted much more lipase than P. fluorescens harboring only tliA, but the tliDEF was functional only at temperatures below 30 degrees C. The recombinant P. fluorescens overexpressing tliDEFA showed the highest secretion level, 217 U/ml. OD (optical density) (28 microg/ml. OD) of lipase in Luria-Bertani medium under microaerated conditions. With the increase of aeration, the lipase production was decreased and the lipase seemed to be degraded as the cells entered the cell death phase. These results demonstrate that P. fluorescens can be used as a host system for the secretory production of the lipase using the ABC transporter, thus producing lipase in over 14% of the total protein.

Differential effect of combined lipase deficiency (cld/cld) on human hepatic lipase and lipoprotein lipase secretion

Combined lipase deficiency (cld) is a recessively inherited disorder in mice associated with a deficiency of LPL and hepatic lipase (HL) activity. LPL is synthesized in cld tissues but is retained in the endoplasmic reticulum (ER), whereas mouse HL (mHL) is secreted but inactive. In this study we investigated the effect of cld on the secretion of human HL (hHL) protein mass and activity. Differentiated liver cell lines were derived from cld mice and their normal heterozygous (het) littermates by transformation of hepatocytes with SV40 large T antigen. After transient transfection with lipase expression constructs, secretion of hLPL activity from cld cells was only 12% of that from het cells. In contrast, the rate of secretion of hHL activity and protein mass per unit of expressed hHL mRNA was identical for the two cell lines. An intermediate effect was observed for mHL, with a 46% reduction in secretion of activity from cld cells. The ER glucosidase inhibitor, castanospermine, decreased secretion of both hLPL and hHL from het cells by ~70%, but by only ~45% from cld cells. This is consistent with data suggesting that cld may result from a reduced concentration of the ER chaperone calnexin. In conclusion, our results demonstrate a differential effect of cld on hLPL, mHL, and hHL secretion, suggesting differential requirements for activation and exit of the enzymes from the ER.—Boedeker, J. C., M. H. Doolittle, and A. L. White. Differential effect of combined lipase deficiency (cld/cld) on human hepatic lipase and lipoprotein lipase secretion.