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Extracellular degradation of lipoprotein lipase in rat adipose tissue
Gengshu Wu, Gunilla Olivecrona, Thomas Olivecrona
BMC Cell Biology , 2005, DOI: 10.1186/1471-2121-6-4
Abstract: When explants of rat epididymal adipose tissue were incubated, LPL mass and activity decreased rapidly. Mass and activity within adipocytes remained constant for at least six hours, demonstrating that it was the extracellular portion of the enzyme that decreased. Adipocytes isolated from the explants after three or six hours of incubation retained their ability to secrete LPL to the medium. Addition of a cocktail of protease inhibitors to the incubation medium slowed down the decrease of LPL mass. Chloroquine was without effect, indicating that the degradation was not lysosomal. 125I-labeled LPL added to the medium was degraded to acid soluble products, indicating that the degradation occurred extracellularly. Fragmentation of the labelled lipase occurred in conditioned medium and this process was virtually abolished by two MMP inhibitors.The decrease of LPL mass and activity that occurs when explants of rat adipose tissue are incubated is due to proteolysis of extracellular LPL. The adipocytes continue to produce and secrete the enzyme. The effect of inhibitors indicates, but does not prove, that the degradation is mediated by MMPs. It appears that this process is accelerated in the tissue fragments compared to intact tissue.Lipoprotein lipase (LPL) hydrolyzes triglycerides in very low-density lipoproteins and chylomicrons [1]. Tissue-specific regulation of LPL activity is a major mechanism to distribute lipids among tissues according to the physiological needs [2]. Current information indicates that in adipose tissue, the regulation is post-translational and occurs by a shift of the lipase protein towards an inactive form under the influence of another gene with short-lived message and product [3]. This information derives from in vivo experiments. To study the underlying mechanism an in vitro model is urgently needed. Experiments with isolated adipocytes do not seem to bring out the mechanism and the in vivo experiments indicate that it is the extracellular LPL t
Linking nutritional regulation of Angptl4, Gpihbp1, and Lmf1 to lipoprotein lipase activity in rodent adipose tissue
Olessia Kroupa, Evelina Vorrsj?, Rinke Stienstra, Frits Mattijssen, Stefan K Nilsson, Valentina Sukonina, Sander Kersten, Gunilla Olivecrona, Thomas Olivecrona
BMC Physiology , 2012, DOI: 10.1186/1472-6793-12-13
Abstract: The system underwent moderate circadian oscillations, for LPL in phase with food intake, for ANGPTL4 and GPIHBP1 in the opposite direction. Studies with cycloheximide showed that whereas LPL protein turns over rapidly, ANGPTL4 protein turns over more slowly. Studies with the transcription blocker Actinomycin D showed that transcripts for ANGPTL4 and GPIHBP1, but not LMF1 or LPL, turn over rapidly. When food was withdrawn the expression of ANGPTL4 and GPIHBP1 increased rapidly, and LPL activity decreased. On re-feeding and after injection of insulin the expression of ANGPTL4 and GPIHBP1 decreased rapidly, and LPL activity increased. In ANGPTL4?/? mice adipose tissue LPL activity did not show these responses. In old, obese rats that showed signs of insulin resistance, the responses of ANGPTL4 and GPIHBP1 mRNA and of LPL activity were severely blunted (at 26?weeks of age) or almost abolished (at 52?weeks of age).This study demonstrates directly that ANGPTL4 is necessary for rapid modulation of LPL activity in adipose tissue. ANGPTL4 message levels responded very rapidly to changes in the nutritional state. LPL activity always changed in the opposite direction. This did not happen in Angptl4?/? mice. GPIHBP1 message levels also changed rapidly and in the same direction as ANGPTL4, i.e. increased on fasting when LPL activity decreased. This was unexpected because GPIHBP1 is known to stabilize LPL. The plasticity of the LPL system is severely blunted or completely lost in insulin resistant rats.Lipoprotein lipase (LPL) is produced by parenchymal cells in some tissues (e.g. adipocytes, myocytes), secreted, and transported to the luminal side of capillaries. Here the enzyme hydrolyzes triglycerides in chylomicrons and VLDL and thereby makes fatty acids available for tissue metabolism. LPL activity is rapidly modulated by the nutritional state and plays a major role in distribution of fatty acids between tissues [1,2] .The rapid daily modulations of LPL activity are mainly p
Lipoprotein lipase deficiency.  [cached]
Shankar K,Bava H,Shetty J,Joshi M
Journal of Postgraduate Medicine , 1997,
Abstract: A rare case of a 3 month old child with lipoprotein lipase deficiency who presented with bronchopneumonia is reported. After noticing lipaemic serum and lipaemia retinalis, a diagnosis of hyperlipoproteinaemia was considered. Lipoprotein lipase deficiency was confirmed with post heparin lipoprotein lipase enzyme activity estimation.
Lipoprotein lipase links vitamin D, insulin resistance, and type 2 diabetes: a cross-sectional epidemiological study
Yifan Huang, Xiaoxia Li, Maoqing Wang, Hua Ning, Lima A, Ying Li, Changhao Sun
Cardiovascular Diabetology , 2013, DOI: 10.1186/1475-2840-12-17
Abstract: The study cohort consisted of 2708 subjects (1326 males, 1382 females; mean age 48.5 ± 12.6?years) in main communities of Harbin, China. Serum 25(OH)D, LPL, free fatty acids (FFAs), fasting glucose (FG), fasting insulin, lipid profile, apoA and apoB concentrations were measured.Serum 25(OH)D concentration was positively associated with LPL (β = 0.168, P < 0.001). LPL was inversely associated with IR and T2D. Subjects in the lowest quartile of LPL had the highest risk of IR [odds ratio (OR) = 1.85, 95% CI = 1.22-2.68] and T2D (OR = 1.65, 95% CI = 1.14-2.38). Serum 25(OH)D was also inversely associated with IR and T2D. Vitamin D deficiency [25(OH)D < 20?ng/ml] was associated with an increasing risk of IR (OR = 1.91, 95% CI = 1.23-2.76) and T2D (OR = 2.06, 95% CI = 1.37-3.24). The associations of 25(OH)D with IR and T2D were attenuated by further adjustment for LPL.LPL is associated with serum 25(OH)D, IR and T2D in the Chinese population. These results suggest a potential mediating role of LPL in the associations of 25(OH)D with IR and T2D.Lipoprotein lipase (LPL) is a member of the so-called lipase superfamily which includes hepatic lipase, pancreatic lipase and LPL itself [1]. Although it is mainly synthesized by the parenchymal cells in adipose, skeletal and cardiac muscle, LPL has its physiological site of action at the capillary endothelial cell surface where the enzyme catalyzes the lipolysis of triglyceride (TG) to provide free fatty acids (FFAs) and 2-monoacylglycerol for tissue utilization [2,3]. Therefore, LPL plays a central role in lipid metabolism and is widely distributed in various tissues. In addition to its effect on the lipid metabolism, LPL is also directly or indirectly implicated in some pathophysiological conditions such as insulin resistance (IR) and type 2 diabetes (T2D). Reduction of LPL is observed in patients with T2D and individuals with IR [4-6]. Low LPL activity accompanied by high TG was observed in diabetic dyslipidemia [7].In addition
Refeeding-Induced Brown Adipose Tissue Glycogen Hyper-Accumulation in Mice Is Mediated by Insulin and Catecholamines  [PDF]
Christopher M. Carmean, Alexandria M. Bobe, Justin C. Yu, Paul A. Volden, Matthew J. Brady
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0067807
Abstract: Brown adipose tissue (BAT) generates heat during adaptive thermogenesis through a combination of oxidative metabolism and uncoupling protein 1-mediated electron transport chain uncoupling, using both free-fatty acids and glucose as substrate. Previous rat-based work in 1942 showed that prolonged partial fasting followed by refeeding led to a dramatic, transient increase in glycogen stores in multiple fat depots. In the present study, the protocol was replicated in male CD1 mice, resulting in a 2000-fold increase in interscapular BAT (IBAT) glycogen levels within 4–12 hours (hr) of refeeding, with IBAT glycogen stores reaching levels comparable to fed liver glycogen. Lesser effects occurred in white adipose tissues (WAT). Over the next 36 hr, glycogen levels dissipated and histological analysis revealed an over-accumulation of lipid droplets, suggesting a potential metabolic connection between glycogenolysis and lipid synthesis. 24 hr of total starvation followed by refeeding induced a robust and consistent glycogen over-accumulation similar in magnitude and time course to the prolonged partial fast. Experimentation demonstrated that hyperglycemia was not sufficient to drive glycogen accumulation in IBAT, but that elevated circulating insulin was sufficient. Additionally, pharmacological inhibition of catecholamine production reduced refeeding-induced IBAT glycogen storage, providing evidence of a contribution from the central nervous system. These findings highlight IBAT as a tissue that integrates both canonically-anabolic and catabolic stimulation for the promotion of glycogen storage during recovery from caloric deficit. The preservation of this robust response through many generations of animals not subjected to food deprivation suggests that the over-accumulation phenomenon plays a critical role in IBAT physiology.
Effects of heparin on the uptake of lipoprotein lipase in rat liver
Lucyna Neuger, Senén Vilaró, Carmen Lopez-Iglesias, Jitendra Gupta, Thomas Olivecrona, Gunilla Olivecrona
BMC Physiology , 2004, DOI: 10.1186/1472-6793-4-13
Abstract: Rat livers were found to contain substantial amounts of LPL, most of which was catalytically inactive. After injection of heparin, LPL mass in liver increased for at least an hour. LPL activity also increased, but not in proportion to mass, indicating that the lipase soon lost its activity after being bound/taken up in the liver. To further study the uptake, bovine LPL was labeled with 125I and injected. Already two min after injection about 33 % of the injected lipase was in the liver where it initially located along sinusoids. With time the immunostaining shifted to the hepatocytes, became granular and then faded, indicating internalization and degradation. When heparin was injected before the lipase, the initial immunostaining along sinusoids was weaker, whereas staining over Kupffer cells was enhanced. When the lipase was converted to inactive before injection, the fraction taken up in the liver increased and the lipase located mainly to the Kupffer cells.This study shows that there are heparin-insensitive binding sites for LPL on both hepatocytes and Kupffer cells. The latter may be the same sites as those that mediate uptake of inactive LPL. The results support the hypothesis that turnover of endothelial LPL occurs in part by transport to and degradation in the liver, and that this transport is accelerated after injection of heparin.Lipoprotein lipase (LPL) hydrolyses triglycerides in chylomicrons and VLDL and thereby makes fatty acids available for cellular uptake and use in metabolic processes [1,2]. Relatively high levels of LPL mRNA are found in adipose tissue, heart, red skeletal muscle and lactating mammary gland [3,4]. Parenchymal cells, such as adipocytes and myocytes, synthesize and secrete the enzyme, which is then transferred to the endothelium and anchored to the oligosaccharide chains of heparan sulfate proteoglycans (HSPG) [1,2]. There is continuous recycling of the enzyme between the luminal and abluminal side of the endothelial cells, and perha
Increased Mesohippocampal Dopaminergic Activity and Improved Depression-Like Behaviors in Maternally Separated Rats Following Repeated Fasting/Refeeding Cycles  [PDF]
Jeong Won Jahng,Sang Bae Yoo,Jin Young Kim,Bom-Taeck Kim,Jong-Ho Lee
Journal of Obesity , 2012, DOI: 10.1155/2012/497101
Abstract: We have previously reported that rats that experienced 3 h of daily maternal separation during the first 2 weeks of birth (MS) showed binge-like eating behaviors with increased activity of the hypothalamic-pituitary-adrenal axis when they were subjected to fasting/refeeding cycles repeatedly. In this study, we have examined the psychoemotional behaviors of MS rats on the fasting/refeeding cycles, together with their brain dopamine levels. Fasting/refeeding cycles normalized the ambulatory activity of MS rats, which was decreased by MS experience. Depression-like behaviors, but not anxiety, by MS experience were improved after fasting/refeeding cycles. Fasting/refeeding cycles did not significantly affect the behavioral scores of nonhandled (NH) control rats. Fasting/refeeding cycles increased dopamine levels not only in the hippocampus but also in the midbrain dopaminergic neurons in MS rats, but not in NH controls. Results demonstrate that fasting/refeeding cycles increase the mesohippocampal dopaminergic activity and improve depression-like behaviors in rats that experienced MS. Together with our previous paper, it is suggested that increased dopamine neurotransmission in the hippocampus may be implicated in the underlying mechanisms by which the fasting/refeeding cycles induce binge-like eating and improve depression-like behaviors in MS rats.
Effects of fasting and refeeding on expression of MAFbx and MuRF1 in chick skeletal muscle
QingHe Li,JinXiu Li,He Lan,Nan Wang,XiaoXiang Hu,Li Chen,Ning Li
Science China Life Sciences , 2011, DOI: 10.1007/s11427-011-4226-2
Abstract: The present study investigated the effects of fasting and refeeding on the expression of proteasome-related genes and their downstream targets in the skeletal muscles of chicks. Seven-day-old chicks were fasted for 24 or 48 h and then refed for 4 h. The expression levels of MAFbx and MuRF1, which function as E3 ligases in the ubiquitin-proteasome system, were investigated at the mRNA and protein levels. MAFbx and MuRF1 expression were increased by fasting and these increases were downregulated by refeeding. The expression of the target proteins of these E3 ligases, MyoD and M-CK, was also analyzed. The levels of these proteins were downregulated by fasting, and these decreases were rescued by refeeding. The results of this study indicate that fasting stimulates MAFbx and MuRF1 expression in chicks, possibly leading to increased degradation of their corresponding target proteins.
Lipoprotein lipase and obesity  [PDF]
Masataka Kusunoki, Kazuhiko Tsutsumi, Daisuke Sato, Takao Nakamura
Health (Health) , 2012, DOI: 10.4236/health.2012.412A203
Abstract:

Obesity is one of the fast-growing major diseases in developed and developing countries. As has been persuasively argued, long-term imbalance between intake and expenditure of fat is a central factor in the etiology of obesity. Obesity aggravates insulin resistance and promotes cardiovascular diseases and atherosclerosis. We hypothesized that elevating lipoprOtein lipase (LPL) activity in skeletal muscle would cause an improvement of obesity. To test this hypothesis, we studied the effects of the LPL activator NO-1886 inobese animals. NO-1886 elevated LPL activity in skeletal muscle, and improved obesity as well as insulin resistance in obese rats. Furthermore, NO-1886 mitigated body weight gain induced by pioglitazone without suppressive effect on the adiponectin-increasing action of pioglitazone. LPL activators hold a lot of promise of curing several diseases shown above in clinical scene.

Lipoprotein particle distribution and skeletal muscle lipoprotein lipase activity after acute exercise
Michael Harrison, Niall M Moyna, Theodore W Zderic, Donal J O’Gorman, Noel McCaffrey, Brian P Carson, Marc T Hamilton
Lipids in Health and Disease , 2012, DOI: 10.1186/1476-511x-11-64
Abstract: Using a randomized cross-over design, very low density lipoprotein (VLDL) responses were evaluated in eight men on the morning after i) an inactive control trial (CON), ii) exercising vigorously on the prior evening for 100?min followed by fasting overnight to maintain an energy and carbohydrate deficit (EX-DEF), and iii) after the same exercise session followed by carbohydrate intake to restore muscle glycogen and carbohydrate balance (EX-BAL).The intermediate, low and high density lipoprotein particle concentrations did not differ between trials. Fasting triglyceride (TG) determined biochemically, and mean VLDL size were lower in EX-DEF but not in EX-BAL compared to CON, primarily due to a reduction in VLDL-TG in the 70–120?nm (large) particle range. In contrast, VLDL-TG was lower in both EX-DEF and EX-BAL compared to CON in the 43–55?nm (medium) particle range. VLDL-TG in smaller particles (29–43?nm) was unaffected by exercise. Because the majority of VLDL particles were in this smallest size range and resistant to change, total VLDL particle concentration was not different between any of these conditions. Skeletal muscle lipoprotein lipase (LPL) activity was also not different across these 3 trials. However, in CON only, the inter-individual differences in LPL activity were inversely correlated with fasting TG, VLDL-TG, total, large and small VLDL particle concentration and VLDL size, indicating a regulatory role for LPL in the non-exercised state.These findings reveal a high level of differential regulation between different sized triglyceride-rich lipoproteins following exercise and feeding, in the absence of changes in LPL activity.Single sessions of exercise transiently reduce serum triglycerides (TG). This exercise effect is not always apparent immediately post-exercise, it can occur after a delay of hours and is generally maximal on the day following intense and prolonged exercise [1,2]. Reductions in serum triglycerides of 18 – 22% are typically observed
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