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[Depression of serum esterase and lipoprotein lipase activities in acute and longitudinal actions of ethanol].

Esterase (LCAT) and lipoprotein lipase (LPL) activities of blood serum, and a range of blood serum lipoproteins (LP) in acute and chronic ethanol intoxication were examined in healthy persons and patients with alcohol abuse. Ethanol inhibited LCAT and LPL activities, and increased apoA-containing LP in blood serum. These changes are considered as a basis for depression of a direct and reverse transportation of cholesterol in blood circulation under the action of ethanol.

Adult↗

A single Ser259Arg mutation in the gene for lipoprotein lipase causes chylomicronemia in Moroccans of Berber ancestry.

Lipoprotein lipase (LPL) is the rate-limiting enzyme for the hydrolysis of triglyceride-rich lipoproteins. Numerous LPL gene mutations have been described as a cause of familial chylomicronemia in various populations. In general, allelic heterogeneity is observed in LPL deficiency in different populations. However, a founder effect has been reported in certain populations, such as French Canadians. Although familial chylomicronemia is observed in Morocco, the molecular basis for the disease remains unknown. Here, we report two unrelated Moroccan families of Berber ancestry, ascertained independently in Holland and France. In both probands, familial chylomicronemia manifested in infancy and was complicated with acute pancreatitis at age 2 years. Both probands were homozygous for a Ser259Arg mutation, which results in the absence of LPL catalytic activity both in vivo and in vitro. In heterozygous relatives, a partial decrease in plasma LPL activity was observed, sometimes associated with combined hyperlipidemia. This mutation previously unreported in other populations segregated on an identical haplotype, rarely observed in Caucasians, in both families. Therefore, LPL deficiency is a cause of familial chylomicronemia in Morocco and may result from a founder effect in patients of Berber ancestry.

Adolescent↗

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 I(2) -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.

Animals↗

Abnormal lipoprotein-lipase-mediated plasma triglyceride removal in untreated diabetes mellitus associated with hypertriglyceridemia.

Hypertriglyceridemia is common in untreated diabetes mellitus. An abnormality in the interaction of lipoprotein lipase with endogenous circulating plasma lipoprotein triglyceride has been demonstrated in untreated diabetes. These diabetics have a decreased maximal removal capacity for plasma triglyceride (27.0 mg TG/kh/hr) and increased Km (390 mg/dl) for endogenous plasma triglyceride-lipoprotein lipase interaction compared to that found in nondiabetic hypertriglyceridemic subjects (Vmax, 32.0; km, 157). Diabetics treated for at least two months have a maximal removal capacity and Km similar to that of nondiabetic subjects (Vmax, 32.7; Km, 192). No evidence for an increase in triglyceride production due to diabetes per se was found. When diabetic subjects with triglyceride levels over 400 mg/dl were selected for study, most were found to have an independent familial form of hypertriglyceridemia.

Adolescent↗

Tissue-specific expression of human lipoprotein lipase. Effect of the 3'-untranslated region on translation.

Lipoprotein lipase (LPL) is a central enzyme in lipoprotein metabolism and is expressed predominantly in adipose tissue and muscle. In these tissues, the regulation of LPL is complex and often opposite in response to the same physiologic stimulus. In addition, much regulation of LPL occurs post-transcriptionally. The human LPL cDNA is characterized by a long 3'-untranslated region, which has two polyadenylation signals. In this report, human adipose tissue expressed two LPL mRNA species (3.2 and 3.6 kb) due to an apparent random choice of sites for mRNA polyadenylation, whereas human skeletal and heart muscle expressed predominantly the longer 3.6-kb mRNA form. To determine whether there was any functional significance to this tissue-specific mRNA expression, poly(A)-enriched RNA from adipose tissue and muscle were translated in vitro, and the poly(A)-enriched RNA from muscle was more efficiently translated into LPL protein. The increased translatability of the 3.6-kb form was also demonstrated by cloning the full-length 3.2- and 3.6-kb LPL cDNA forms, followed by in vitro translation of in vitro prepared transcripts. To confirm that this increased efficiency of translation occurred in vivo, Chinese hamster ovary cells were transfected with the 3.2- and 3.6-kb LPL cDNAs. Cells transfected with the 3.6-kb construct demonstrated increased LPL activity and synthesis, despite no increase in levels of LPL mRNA. Thus, human muscle expresses the 3.6-kb form of LPL due to a non-random choice of polyadenylation signals, and this form is more efficiently translated than the 3.2-kb form.

Adipose Tissue↗

Effects of sex steroids on hepatic and lipoprotein lipase activity and mRNA in the rat.

In humans, sex steroids have been implicated in the regulation of hepatic and lipoprotein lipase activity. Therefore, the effects of orchidectomy and subsequent androgen or estrogen administration on hepatic lipase (HL) and adipose tissue and heart lipoprotein lipase (LPL) were examined. Relative to intact controls, orchidectomy of male rats resulted in no significant change in HL activity and mRNA, or in heart and adipose tissue LPL activity and mRNA levels. Subsequently, a subcutaneous silastic tubing, delivering either testosterone, dihydrotestosterone, nandrolone, or 17 beta-estradiol, was implanted for 5 weeks. All substitution treatments had a tendency to reduce HL activity and to induce HL mRNA levels. This effect was, however, only significant for testosterone which resulted in a decrease in HL activity (238 +/- 15 vs. 328 +/- 31 mU/g tissue; p vs. control < 0.05) and an increase in HL mRNA (166 +/- 11 vs. 100 RAU; p vs. control < 0.01). No significant effects of androgens on LPL expression either in heart or adipose tissue were observed. Adipose tissue LPL activity (20 +/- vs. 35 +/- 4 mU/g; p vs. control < 0.05) and mRNA (28 +/- 4 vs. 100 RAU; p vs. control < 0.001) levels, but not heart LPL, however, were diminished substantially after 17 alpha-estradiol treatment. In conclusion, rat HL is influenced by testosterone, while adipose tissue, but not heart LPL, is reduced after estrogen administration.

Adipose Tissue↗

Lipoprotein lipase gene polymorphism and lipid profile in patients with hypertriglyceridemia.

AIM: To assess lipid profile and the genotype distribution of lipoprotein lipase gene polymorphism at Pvu II polymorphic site within the intron between exons 6 and 7 in patients with hypertriglyceridemia. METHODS: Pvu II polymorphism was determined in 116 hypertriglyceridemic patients and 50 normolipidemic controls from Zagreb, Croatia. DNA was extracted from peripheral blood mononuclear cells. Polymerase chain reaction was used for amplification of 6th intron, which was then restricted with Pvu II-restriction endonuclease. Serum lipid and lipoprotein fractions were determined by standard enzymatic methods. Cholesterol concentrations in HDL subfractions, HDL2 and HDL3, were determined after precipitation with polyethyleneglycol. Apolipoproteins (apo) A-I and B were determined by immunonephelometry. RESULTS: Triglycerides showed a positive correlation with total cholesterol (r=0.222, 95% CI=0.041-0.389, p=0.017) and inverse correlation with HDL-cholesterol (r= -0.278, 95% CI= -0.449 to -0.088, p=0.005), especially with HDL3-cholesterol (r= -0.333, 95% CI= -0.497 to -0.147, p=0.001). The respective frequencies for genotypes /, +/, and +/+ were 22, 58, and 36 in the patient group, and 17, 17, and 16 in the control group. Serum triglycerides in the patient group, expressed as median in mmol/L, were 3.30 (range, 2.60-10.90), 3.60 (range, 2.50-21.50), and 3.99 (range, 2.50-15.56), respectively. Serum concentration of triglycerides differed significantly between the +/+ and / genotype (p=0.043). CONCLUSION: There is an association between genetic variation at the locus for lipoprotein lipase and high serum triglyceride levels. This might prove useful in the detection of individuals susceptible to the development of hypertriglyceridemia, as well as a marker in the analysis of this genetic defect in patient families.

Aged↗