A novel frameshift mutation in the lipoprotein lipase gene is rescued by alternative messenger RNA splicing.

BACKGROUND: Type I hyperlipoproteinemia, manifesting as chylomicronemia and severe hypertriglyceridemia, is a rare autosomal recessive disorder usually caused by mutations in the lipoprotein lipase gene (LPL). OBJECTIVE: We sought to determine whether mutations in LPL could explain the clinical indications of a patient presenting with pancreatitis and hypertriglyceridemia. METHODS: Coding regions of LPL were amplified by polymerase chain reaction and analyzed by nucleotide sequencing. The LPL messenger RNA transcript was also analyzed to investigate whether alternative splicing was occurring. RESULTS: The patient was homozygous for the mutation c.767_768insTAAATATT in exon 5 of the LPL gene. This mutation is predicted to result in either a truncated nonfunctional LPL, or alternatively a new 5' donor splice site may be used, resulting in a full-length LPL with an in-frame deletion of 3 amino acids. Analysis of messenger RNA from the patient showed that the new splice site is used in vivo. CONCLUSION: Homozygosity for a mutation in the LPL gene was consistent with the clinical findings. Use of the new splice site created by the insertion mutation rescues an otherwise damaging frameshift mutation, resulting in expression of an almost full-length LPL that is predicted to be partially functional. The patient therefore has a less severe form of type I hyperlipoproteinemia than would be expected if she lacked any functional LPL.

Effects of lipoprotein apheresis on PCSK9 levels.

BACKGROUND: PCSK9 (Proprotein Convertase Subtilisin/Kexin Type 9) increases LDL cholesterol (LDL-C) levels by stimulating the degradation of Low Density Lipoprotein receptors (LDL-r). This protein is now of high interest because antibodies which inhibit its effect on LDL-r are being developed. A severe hypercholesterolemia and / or an elevation of lipoprotein(a) can be treated with lipoprotein apheresis (LA) in high-risk patients. METHODS: We measured serum PCSK9 levels in patients eligible for the extracorporeal treatment: in 40 patients (Cohort I) who were treated with different systems before and after apheresis sessions and in the intervals between sessions. 10 patients (Cohort II) who were eligible but did not start LA yet served as controls. RESULTS: Patients' baseline serum PCSK9 levels were elevated relative to healthy volunteers and LA sessions acutely reduced the mean PCSK9 concentrations by 51%. Comparison of the effectiveness of the different LA methods demonstrated the DSA and HELP were more effective than the DALI system. After 24 h PCSK9 levels had returned to baseline compared to 8 days for the LDL-C concentrations to return to its pre-apheresis levels. In Cohort II baseline PCSK9 levels were similar to those in Cohort I. CONCLUSION: The acute reductions of PCSK9 by apheresis may be beneficial with respect to increasing the effectiveness of lipid-lowering drugs and with respect to an anti-atherosclerotic effect. In the future, antagonists to PCSK9 will probably be combined with or possibly replace LA in patients with a very high cardiovascular risk.

A case of adolescent hyperlipoproteinemia with xanthoma and acute pancreatitis, associated with decreased activities of lipoprotein lipase and hepatic triglyceride lipase.

Lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) enhance the hydrolysis of triglycerides (TG) transported by chylomicron (CM) and very-low-density lipoprotein (VLDL). We report a case of severe hyperchylomicronemia with high levels of remnant lipoprotein and total cholesterol (T-Chol) in a 15-year-old boy. Precise examination of the lipid profile showed decreased activities of both LPL and HTGL, although the protein mass for LPL and HTGL were maintained. In addition, bezafibrate treatment effectively ameliorated hypertriglyceridemia in this case. This is the first case of hyperchylomicronemia with decreased activities and unaffected protein masses for both LPL and HTGL, without overt immuno-dysfunction.

Novel mutations of CETP gene in Italian subjects with hyperalphalipoproteinemia.

Cholesteryl ester transfer protein (CETP) is a plasma glycoprotein that catalyses the transfer of cholesteryl esters from HDL to the other plasma lipoproteins. Genetic deficiency of CETP is one of the known causes of elevation of plasma HDL-C (primary hyperalphalipoproteinemia, HALP). We sequenced CETP gene in a group of 24 Italian subjects with primary HALP (HDL-C>80 mg/dl) suspected to have CETP deficiency. Two unrelated subjects both coming from the same geographical district, were found to be heterozygous for a nucleotide substitution in exon 6 (c.544C>T) and another subject was found to be heterozygous for a C>T transition in exon 9 (c.802C>T). Both mutations introduce a premature stop codon and are predicted to cause the production of truncated proteins (Q165X and R268X, respectively) devoid of function. The fourth proband was found to carry a T>C substitution in intron 15 (c.1407+2T>C) predicted to abolish the function of the donor splice site. To define the effect of this mutation on CETP pre-mRNA splicing we analysed CETP mRNA in COS-1 cells expressing a CETP minigene harbouring the mutation. The analysis of minigene transcript in COS-1 cells showed that IVS15+2T>C mutation caused the formation of an abnormal mRNA in which exon 14 joins directly to exon 16, predicted to encode a truncated peptide of 435 amino acids. In mutation carriers plasma CETP activity was found to be reduced by 38-60%. These are the first mutations in the CETP gene found in Italian subjects with HALP.

Association of an intronic haplotype of the LIPC gene with hyperalphalipoproteinemia in two independent populations.

Hepatic lipase (HL) plays a major role in the regulation of plasma lipids. Several groups seeking to find association between the gene encoding HL (LIPC) and plasma concentrations of high-density lipoprotein cholesterol (HDLc) using various methods and populations have reported conflicting results. We have approached the problem of demonstrating a relationship between the LIPC locus and HDLc by means of haplotype association using four single nucleotide polymorphisms (SNPs) (rs12594375G/A, rs8023503C/T, rs4775047C/T, and rs11634134T/A) located in intron 1 of the LIPC gene in two independent Japanese populations consisting of 2,970 and 1,638 individuals, respectively. Significant association between hyperalphalipoproteinemia and a specific haplotype in this intron was detected in both populations. When HDLc levels among the three haplotypic categories were analyzed [haplotype rs8023503C/rs12594375G (haplotype-1; H1) homozygotes (H1H1), haplotype rs8023503T/rs12594375A (haplotype-2; H2) homozygotes (H2H2), and heterozygotes (H1H2)], HDLc levels were lowest among H1H1 [mean +/- standard error (SE) = 58.4 +/- 0.4 mg/dl], highest among H2H2 (62.5 +/- 0.8 mg/dl), and intermediate among H1H2 (59.2 +/- 0.4 mg/dl) (P = 0.00011), indicating that H2 haplotype elevates plasma HDLc levels. This association was validated in the second population (n = 1,638) (P = 0.00070). The results provide convincing evidence that the LIPC locus influences HDL metabolism.

[Mechanisms of hypo and hyper alphalipoproteinemia in Chilean adults]. / Mecanismos de hipo e hiper alfalipoproteinemia en individuos adultos chilenos.

BACKGROUND: High density lipoprotein (HDL) cholesterol is inversely associated to atherosclerotic cardiovascular risk. Disturbances in HDL cholesterol plasma levels are frequent in the Chilean population, however the pathophysiological mechanisms are unknown. AIM: To evaluate the mechanisms involved in the hypo and hyper alfalipoproteinemias in Chilean subjects. MATERIALS AND METHODS: Twenty three subjects with hyperalphalipoproteinemia and 12 with hypoalphalipoproteinemia, paired with control subjects (col-HDL between 35 and 55 mg/dl) were studied. We measured plasma lipids, subfractions and sizing of HDL particles and enzymatic activity of cholesteryl ester transfer protein (CETP), lecithtin: cholesterol acyltransferase (LCAT), lipoprotein lipase (LPL) and hepatic lipase (LH). RESULTS: Subjects with hyperalphalipoproteinemia showed significantly higher levels of total HDL-cholesterol (70 +/- 2 vs 44 +/- 1 mg/dl), HDL 2 (30 +/- 3 vs 5 +/- 1 mg/dl), Apo A I (175 +/- 3 vs 146 +/- 4 mg/dl), lower HL activity (23.7 +/- 0.8 vs 32.4 +/- 1.8 mmol/h/l) and HDL particles of greater size, compared to their controls. Subjects with hypoalphalipoproteinemia, showed significantly lower levels of total HDL-cholesterol (26 +/- 1 vs 48 +/- 2 mg/dl), HDL 3 (21 +/- 1 vs 40 +/- 2 mg/dl), Apo A I (107 +/- 5 vs 145 +/- 7 mg/dl), lower LCAT activity (18.6 +/- 1.9 vs 26.2 +/- 1.6 nmol/h/ml) and smaller HDL particles, compared to their controls. CONCLUSION: Changes in hepatic lipase and lecithin cholesterol acyltransferase activities may explain the hyper and hypo alphalipoproteinemia respectively, in Chilean subjects.

A newly identified lipoprotein lipase (LPL) gene mutation (F270L) in a Japanese patient with familial LPL deficiency.

We have systematically investigated the molecular defects resulting in a primary lipoprotein lipase (LPL) deficiency in a Japanese male infant (proband SH) with fasting hyperchylomicronemia. Neither LPL activity nor immunoreactive LPL mass was detected in pre- or postheparin plasma from proband SH. DNA sequence analysis of the LPL gene of proband SH revealed homozygosity for a novel missense mutation of F270L (Phe(270)-->Leu/TTT(1065)-->TTG) in exon 6. The function of the mutant F270L LPL was determined by both biochemical and immunocytochemical studies. In vitro expression experiments on the mutant F270L LPL cDNA in COS-1 cells demonstrated that the mutant LPL protein was synthesized as a catalytically inactive form and its total amount was almost equal to that of the normal LPL. Moreover, the synthesized mutant LPL was non-releasable by heparin because the intracellular transport of the mutant LPL to the cell surface - by which normal LPL becomes heparin-releasable - was impaired due to the abnormal structure of the mutant LPL protein. These findings explain the failure to detect LPL activities and masses in pre- and postheparin plasma of the proband. The mutant F270L allele generated an XcmI restriction enzyme site in exon 6 of the LPL gene. The carrier status of F270L in the proband's family members was examined by digestion with XcmI. The proband was ascertained to be homozygous for the F270L mutation and his parents and sister were all heterozygous. The LPL activities and masses of the parents and the sister (carriers) were half or less than half of the control values. Regarding the phenotype of the carriers, the mother with a sign of hyperinsulinemia manifested hypertriglyceridemia (type IV hyperlipoproteinemia), whereas the healthy father and the sister were normolipidemic. Hyperinsulinemia may be a strong determinant of hypertriglyceridemia in subjects with heterozygous LPL deficiency.

Mutations of the human hepatic lipase gene in patients with combined hypertriglyceridemia/hyperalphalipoproteinemia and in patients with familial combined hyperlipidemia.

Hepatic lipase is an enzyme which hydrolyzes triglycerides from plasma lipoproteins and thus takes part in the metabolism of intermediate density lipoproteins and high-density lipoproteins. The search described here concentrated on mutations of the HL gene in 129 patients with combined hypertriglyceridemia/hyperalphalipoproteinemia and in 184 members of 19 families with familial combined hyperlipidemia. Controls were 100 subjects with favorable lipid values (age 46-51 years). Mutation screening and analysis were performed by temperature-gradient gel electrophoresis, allele-specific restriction genotyping, and sequencing. Six different missense mutations and four different silent mutations were found in the HL gene. The alleles Phe-267 and Gln-343 were detected only once in the patient group with hypertriglyceridemia and hyperalphalipoproteinemia and were not detected in the control group. The allele Met-383 was rare in both patients and controls. We found 9.3% of the patients and only 3.0% of controls to be carrying the Val-73-Met missense mutation. The allele Phe-334 was found in 5.43% of patients and in 2.0% of controls. The difference between the frequencies of these alleles was significant between male patients and male controls (Met-73 P=0.044; Phe-334 P=0.047). Also, the summarized odds ratio of 3.28 (95% confidence interval 1.23-8.73) demonstrates that mutation carriers are significantly more prevalent in the patients. Fifteen carriers of the Met-73 allele were found in six families of the familial combined hyperlipidemia group. Furthermore, six carriers of the Phe-334 allele were found in three families of the same group. In comparison to the controls the summarized odds ratio of 2.45 (95% confidence interval 0.89-6.71) barely missed the level of significance. The linkage between genotype and phenotype was incomplete. These results show an association of the missense mutations Val-73-Met and Leu-334-Phe as susceptibility alleles for combined forms of hyperlipidemia.

[Changes in the proteinase-inhibitor system of rats with hyperlipoproteinemia during transcerebral exposures to a 100-Hz-frequency pulse current and to an ultrahigh-frequency field]. / Izmeneniia v sisteme proteinazy--ingibitory u krys s giperlipoproteidemiei pri transtserebral'nykh vozdeistviiakh impul'snym tokom s chastotoi 100 Gts i ul'travysokochastotnym polem.

Experiments on 36 male rats with experimental hyperlipoproteinemia demonstrated that transcerebral exposure to impulse current (100 Hz, 2mA) aggravates atherogenic alterations, provokes hyperactivation of kallikrein-kinin system and unbalance of elastase inhibitory activity in the serum and myocardium. The latter may contribute to better vascular permeability for low-density lipoproteins, to development of edema of vascular intima, lability of cellular and lysosomal membranes with hydrolysis of elastine and collagen fibers of myocardial vessels and other organs. Transcerebral exposure to electromagnetic UHF field (40.68 MHz) is not hypolipidemic but has no negative effect on experimental atherosclerosis, promotes normalization of kallikrein-kinin system in the serum, activation of this system in the myocardium and cerebral cortex, correction of destructive processes in the serum and cerebral cortex with a risk of their development in the myocardium.

Paraoxonase and arylesterase activities in the serum of two hyperlipoproteinaemic patients after repeated extracorporal lipid precipitation.

The effect of heparin-induced extracorporal lipid precipitation (HELP) on the activities of paraoxonase (EC 3.1.8.1) and arylesterase (EC 3.1.1.2) was studied in serum of a patient with hyperlipoproteinaemia (A) and of a patient with non-insulin dependent diabetes mellitus and hyperlipoproteinaemia (B). The enzyme activities were measured spectrophotometrically (Tris-HCl buffer, pH 7.4, 37 degrees C) with paraoxon and phenylacetate as substrates of paraoxonase and arylesterase, respectively. Both patients underwent HELP applications once a week over a period of 7 weeks. Over that period no overall change was observed either in enzyme activities or in the lipid and protein content of the sera. However, each HELP session caused an immediate decrease of EDTA-insensitive arylesterase activity (on average 56% in A and 42% in B), while EDTA-sensitive arylesterase remained almost unaltered. Paraoxonase remained unchanged in A, but decreased in B (approximately 60%). Of the atherogenic lipoprotein parameters, the most pronounced decrease was found in VLDL-cholesterol and in triglycerides (on average 45% in A and 32% in B), while the anti-atherogenic HDL-cholesterol decreased < 10%. Possible implications of the effect of HELP on the enzyme activities studied remain to be explained.

Decreased neutrophil antioxidative enzyme activities and increased lipid peroxidation in hyperlipoproteinemic human subjects.

Neutrophils have the capacity to produce free radicals. Free radicals are associated with hyperlipoproteinemia and atherosclerotic processes. For this reason, neutrophil superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutathione reductase (GR), catalase (Cat) activities and thiobarbituric acid reactive substances (TBARS), as an index of lipid peroxidation, have been studied in hyperlipoproteinemic (HLP) and age-matched normolipidemic groups. Lipid parameters including triglycerides, total cholesterol, plasma TBARS, HDL-cholesterol, LDL-cholesterol, apo A-I, apo B have also been determined. Forty subjects (females 18, males 22) with HLP (mean age 43.8+/-8.7 (S.D.)) and 40 normolipoproteinemic subjects (females 17, males 23; mean age 46.4+/-11) were included in the study. Neutrophils were isolated by Percoll gradient centrifugation from venous blood samples. Methods used were as follows: INT method for SOD, UV method at 340 nm based on oxidation of NADPH for GSH-Px and GR, UV method at 240 nm based on degradation of hydrogen peroxide for catalase, and a method based on reaction with thiobarbituric acid for TBARS. Neutrophil SOD, GSH-Px, and catalase activities were found to be significantly low in the hyperlipoproteinemic group compared with the normolipoproteinemic group. GR activity did not differ between both groups. The mean TBARS level in the neutrophil fraction was found to be significantly higher in hyperlipoproteinemics than in that of the normolipoproteinemics. It was concluded that decreased neutrophil antioxidant enzyme activities in hyperlipoproteinemics may lead to insufficient detoxification of free radicals produced in these cells and contribute to increased lipid peroxidation.

Molecular genetic study of Finns with hypoalphalipoproteinemia and hyperalphalipoproteinemia: a novel Gly230 Arg mutation (LCAT[Fin]) of lecithin:cholesterol acyltransferase (LCAT) accounts for 5% of cases with very low serum HDL cholesterol levels.

In an attempt to identify genetic factors underlying extreme alterations of serum HDL cholesterol (HDL-C) concentrations, we examined two probands with HDL-C levels <0.2 mmol/L and subsequently screened two large cohorts of smoking men, one with very low (0.2 to 0.7 mmol/L, n=156) and the other with elevated (1.9 to 3.6 mmol/L, n=160) HDL-C levels, for the newly detected mutations as well as some other mutations proposed to affect HDL-C levels. One of the probands had corneal opacities, microalbuminuria, hypertriglyceridemia, and reduced LDL apoprotein B concentration; the other had anemia and presented with stomatocytosis in his peripheral blood. The first proband was found to be homozygous for a novel LCAT Gly230Arg (LCAT[Fin]) mutation, and the second was homozygous for an Arg399Cys mutation we described previously. Transient expression of the mutant LCAT(Fin) cDNA in COS cells disclosed markedly diminished LCAT enzyme activity. In the low-HDL-C group of men (n=156), 8 carriers of LCAT(Fin) and 1 carrier of the LCAT Arg399Cys were identified. In addition, the frequency of the lipoprotein lipase (LPL) Asn291Ser mutation was significantly (P<.05) higher in the low-HDL-C group (4.8%) than in the high-HDL-C group (1.6%). In addition, we identified 1 carrier of the intron 14G-->A mutation of cholesterol ester transfer protein (CETP) in the high-HDL-C group and subsequently demonstrated cosegregation of the mutant allele with elevated HDL-C levels in the proband's family. In conclusion, we have identified a novel LCAT gene Gly230Arg mutation (LCAT[Fin]), which, together with the LPL Asn291Ser mutation, represents a relatively common genetic cause of diminishing HDL-C levels, at least among Finns. This article also reports occurrence of a CETP mutation in subjects having non-Japanese roots.

Pathogenesis of dyslipoproteinemia in renal insufficiency: the role of lipoprotein lipase and hepatic lipase.

The lipoprotein pattern, observed in patients with renal failure, suggests impaired catabolism of triglyceride-rich lipoproteins. This is supported by the findings of numerous studies addressing the pathogenesis of the dyslipoproteinemia of uremia. Aberrant lipoprotein composition, resulting in disturbed substrate characteristics for lipoprotein lipase and unfavourable receptor ligand function, probably constitutes the primary pathology. The structural details of the lipoproteins that are responsible for this dysfunction are not yet established. In this regard, abnormal apolipoprotein pattern and, possibly more important, biological modifications must be taken into consideration. Low activity of lipoprotein lipase does not seem to be a primary pathogenetic factor. However, there is little doubt that it plays a contributory part. The role of hepatic lipase is controversial.

Lecithin:cholesterol acyltransferase overexpression generates hyperalpha-lipoproteinemia and a nonatherogenic lipoprotein pattern in transgenic rabbits.

Cholesterol esterification within plasma lipoprotein particles is catalyzed by lecithin:cholesterol acyltransferase (LCAT). The impact of the overexpression of this enzyme on plasma concentrations of the different plasma lipoproteins in an animal model expressing cholesteryl ester transfer protein was evaluated by generating rabbits expressing human LCAT. A 6.2-kilobase human genomic DNA construct was injected into the pronuclei of rabbit embryos. Of the 1002 embryos that were injected, 3 founder rabbits were characterized that expressed the human LCAT gene. As in mice and humans, the principal sites of mRNA expression in these rabbits is in the liver and brain, indicating that the regulatory elements required for tissue-specific expression among these species are similar. The alpha-LCAT activity correlated with the number of copies of LCAT that integrated into the rabbit DNA. Compared with controls, the high expressor LCAT-transgenic rabbits total and high density lipoprotein (HDL) cholesterol concentrations were increased 1.5-2.5-fold with a 3.1-fold increase in the plasma cholesterol esterification rate. Analysis of the plasma lipoproteins by fast protein liquid chromatography indicates that these changes reflected an increased concentration of apolipoprotein E-enriched, HDL1-sized particles, whereas atherogenic apolipoprotein B particles disappeared from the plasma. The concentrations of plasma HDL cholesterol were highly correlated with both human LCAT mass (r = 0.93; p = 0.001) and the log LCAT activity (r = 0.94; p < 0.001) in the transgenic rabbits. These results indicate that overexpression of LCAT in the presence of cholesteryl ester transfer protein leads to both hyperalpha-lipoproteinemia and reduced concentrations of atherogenic lipoproteins.

Inhibition of protein tyrosine kinase alters the effect of serum basic protein I on triacylglycerols and cholesterol differently in normal and hyperapoB fibroblasts.

We studied whether the stimulatory effect of human serum basic protein I (BP I) on the formation of cell triacylglycerols and cholesterol may be mediated through protein tyrosine kinase in normal fibroblasts, and whether there was a deficiency in such a process in cells from subjects with hyperapobetalipoproteinemia (hyperapoB). Genistein, a highly specific inhibitor of tyrosine kinase phosphorylation, was used as a probe. When BP I (428.0 nmol/L) alone was added to F-12 medium without genistein, the mean mass of cell triacylglycerols doubled in six normal cell lines from healthy subjects, an effect that was decreased by 50% in six cell lines from subjects with hyperapoB (P = .007). The addition of genistein with BP I to normal cells decreased the stimulation of triacylglycerol formation by BP I by about 50% (P = .008), whereas genistein had little effect in the BP I-treated hyperapoB cells. The effect of genistein on the stimulation of triglyceride and cholesterol production by BP I was shown to be both time and concentration (92.5 nmol/mL medium nadir) dependent. In normal fibroblasts. BP I stimulated the rate of incorporation of both [14C]acetate (P = .0001) and [3H]mevalonolactone (P = .002) into unesterified cholesterol, an effect that was markedly deficient in the hyperapoB cells (P = .0001 for [14C]acetate and P = .0002 for [3H]mevalonolactone). In normal but not hyper-apoB cells, genistein inhibited the significant stimulation by BP I of the rates of both [14C]acetate (P = .0001) and [3H]mevalonolactone (P = .04) incorporation into unesterified cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy and safety of controlled-release niacin in dyslipoproteinemic veterans.

OBJECTIVE: To evaluate the safety and efficacy of controlled-release niacin in patients with hyperlipoproteinemia. DESIGN: A retrospective cohort study. SETTING: A Department of Veterans Affairs Medical Center. PATIENTS: A consecutive sample of 969 predominantly elderly male veterans treated for dyslipoproteinemia with controlled-release niacin between October 1988 and October 1991. MAIN OUTCOME MEASURES: Primary outcomes were lipid levels and lipoprotein cholesterol response, alternations in levels of hepatic enzymes and blood chemistry test results, and characterization of niacin-induced hepatotoxicity abstracted from the patient's medical, laboratory, and pharmacy records. RESULTS: 93% (896 of 969) of the cohort was evaluable. Patients (age, 61.7 years [9.4 years], mean [SD]) were treated for 1 to 36 months (13.0 months [9.7 months]) with an average maintenance dose of 1.67 g/d (0.8 g/d). Niacin was discontinued in 48.5% (435 of 896) of the patients primarily because of adverse effects. Poor glycemic control led to discontinuation in 40.6% (43 of 106) of the patients with diabetes mellitus. The lipoprotein response was dose-related and favorable (levels of total cholesterol, -19.1%; low-density lipoprotein cholesterol, -24.0%; high-density lipoprotein cholesterol, +5.7%; and triglycerides, -32.5%). Statistically but not clinically meaningful dose-related increases were seen in levels of liver enzymes and serum glucose (aspartate aminotransferase, +29%; alanine aminotransferase, +23%; alkaline phosphatase, +25%; and glucose, +7%; P = 0.0001). Twenty of 896 (2.2%) and 42 of 896 (4.7%) patients met biochemical criteria for probable and for possible or probable niacin-induced hepatotoxicity, respectively. Predisposing factors included high dose, alcohol use, preexisting liver disease, and concurrent oral sulfonylurea therapy. CONCLUSIONS: Controlled-release niacin is effective in treating dyslipoproteinemia in selected middle-aged and elderly veterans, but approximately one half of patients discontinued the drug because of adverse effects or other causes including noncompliance. Niacin should be avoided in patients with hepatic dysfunction or a history of liver disease, patients with diabetes mellitus, and patients who abuse alcohol. Because controlled-release niacin seems to be more potent than crystalline niacin, product substitution without dose adjustment should be avoided.

Hyperlipoproteinemia type I in a patient with active lipoprotein lipase in adipose tissue and indications of defective transport of the enzyme.

This paper presents a case of typical hyperlipoproteinemia type I in a young woman. Her serum triglycerides varied between 2 and 90 mmol/l and she had substantial amounts of apolipoprotein B-48 in fasting plasma. She had no detectable lipoprotein lipase (LPL) activity in post-heparin plasma (less than 0.2 percent of normal). Southern blot analysis suggested no major defect in her LPL gene and Northern blot analysis of adipose tissue RNA showed normal-sized LPL-mRNA. A 2-h [35S]methionine incorporation experiment with adipose tissue pieces in vitro showed that she produced normal-sized LPL and had LPL catalytic activity in the tissue. The amounts were, however, only 5-10% of control. No detectable LPL radioactivity or catalytic activity was released from patient tissue even in the presence of heparin in the incubations. Immunofluorescent staining of adipose tissue biopsies from the patient showed LPL immunoreactivity only in adipocytes and little or none within the capillaries. Treatment of immunoprecipitated labeled LPL with endoglycosidase H showed that the oligosaccharide chains on her enzyme were of the high-mannose type and not processed as in controls. Taken together the data suggest that the patient synthesizes a relatively normal LPL protein which is core-glycosylated and folded into active enzyme as in normal subjects, but is not effectively transported via the Golgi to the cell surface.