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K Cianflone

Publications and source records attributed to K Cianflone.

At least 55 records · Page 3Linked to original sources
PubMed1997

The acylation stimulating protein pathway: clinical implications.

OBJECTIVES: The present review will focus particularly on acylation stimulating protein (ASP) and its role in adipose tissue. Two issues will be addressed (1) in vitro biochemical characterization of ASP in cell culture studies, and (2) in vivo clinical relevance for normal physiology and in pathological conditions. CONCLUSIONS: Fat is In! There can be no question that in recent years fat tissue has become recognized as more than just a passive storage site. It is a metabolically active tissue that, under normal conditions, allows the efficient clearance of triglyceride and glucose for storage as energy. Under abnormal conditions, adipose tissue dysfunction is associated with obesity, diabetes and coronary heart disease. Adipose tissue function may be controlled by many factors.

Adipocytes↗
PubMed1997

ASP stimulates glucose transport in cultured human adipocytes.

OBJECTIVE: The purpose of the present study was to examine the effect of Acylation Stimulating Protein (ASP) on glucose transport in cultured subcutaneous adipocytes. DESIGN AND SUBJECTS: Subcutaneous adipose tissue was obtained from non-obese, healthy females (18-32 y old) undergoing mammoplasty reduction. Preadipocytes were isolated and differentiated into adipocytes. MEASUREMENTS: Following the exposure of preadipocytes and adipocytes to ASP or insulin, glucose transport was assessed as [3H] 2-deoxy glucose uptake. The measurements were normalised per total cell protein. RESULTS: ASP increases specific membrane glucose transport in both preadipocytes and adipocytes in a time and concentration dependent manner. Stimulation in both cell types is rapid (within minutes), reaching a maximal effect between 1 and 4 h. However, after 24 h exposure to ASP, there is a downregulation in the response. The ASP response is greater following differentiation of preadipocytes to adipocytes and is compared to that of insulin. Dose response studies demonstrated a five-fold greater sensitivity of adipocytes (half-maximal concentration of ASP on adipocytes = 0.5 microM, preadipocytes = 2.3 microM). CONCLUSION: These results demonstrate that ASP not only stimulates triglyceride synthesis, but also glucose transport in differentiated human adipocytes and is consistent with a physiologically important role for ASP in postprandial energy storage.

Adipocytes↗
PubMed1997

The acylation-stimulating protein pathway and regulation of postprandial metabolism.

Much has recently been learned about the processes involved in postprandial triacylglycerol clearance. As discussed previously, important differences in the metabolism of chylomicrons and VLDL have become apparent. The ASP pathway has also been recognized and appears to play a critical role in chylomicron metabolism. The ASP pathway is activated in order to trap the fatty acids released from chylomicrons by the action of LPL and there is now unequivocal in vivo evidence in human subjects that ASP is generated by adipocytes in the postprandial period. These findings match the in vitro data showing that chylomicrons, but not the other plasma lipoproteins or fatty acids, activate the generation of ASP by cultured human adipocytes. An inverse relationship appears to exist between the proportion of fatty acids taken up by adipocytes and that released into the general circulation. Too great a release into the general circulation because of diminished trapping of fatty acids released from chylomicrons appears to be critical in the pathogenesis of the dyslipoproteinaemias associated with hyperapo B or FCHL and omental obesity. Evidence has been presented that dysfunction of the ASP pathway may be one of the causes of this disorder. Put differently, the ASP pathway is essential for the normal clearance and disposition of dietary fatty acids. Binding of chylomicrons to capillary endothelium followed by lipolysis by LPL results in the sudden liberation of fatty acids, and in the marked generation of ASP by adipocytes. The ASP that is generated is essential if LPL is to continue to form fatty acids at a normal rate. It is essential also if the fatty acids which are formed are to enter the adipocyte rather than exit into the general circulation. The transport vehicle, the chylomicron, therefore stimulates the formation of the peptide, ASP, which is responsible for its successful metabolism. Thus, the ASP pathway provides the metabolic coordination between the chylomicron and the adipocyte, which we describe as microenvironmental metabolic regulation and which we believe is essential for the normal clearance of dietary triacylglycerol from plasma.

Adipocytes↗
PubMed1997

Acylation stimulating protein and the adipocyte.

ASP constitutes a metabolic bridge integrating events in the circulation with the adipocyte microenvironment and regulation of a key adipose function-storage of fat. Dysregulation of the ASP pathway may have important metabolic consequences and may be associated with both obesity on one hand and cardiovascular disease on the other hand. Clearly, many in vitro and in vivo studies remain to be done to establish clearly such links and future work on ASP promises to be both exciting and rewarding.

Adipocytes↗
PubMed1997

Acute in vitro production of acylation stimulating protein in differentiated human adipocytes.

We have previously shown that in normolipidemic healthy adults, plasma acylation stimulating protein (ASP) increases postprandially and is produced in vitro by cultured differentiated human adipocytes. The present studies were undertaken to examine the influence of specific plasma components on endogenous ASP production in cultured human adipocytes. The results demonstrate that neither glucose nor fatty acids (over a wide range of concentrations) had any substantial effect on ASP production. Insulin increased ASP production up to 2-fold (208% +/- 18%, P < 0.01). However, the most profound increase in ASP was generated by the addition of chylomicrons to the cell culture medium. Chylomicrons (CHYLO) obtained from postprandial plasma increased ASP production in a time- and concentration-dependent manner, producing up to a 150-fold increase in ASP at the highest concentration of CHYLO tested (500 microg triacylglycerol/mL medium (P < 0.001)). By contrast, very low (VLDL), high (HDL), and low density lipoproteins (LDI) had only marginal effects. The effects on ASP parallelled the changes in adipocyte C3 secretion (the precursor protein of ASP). As with ASP, glucose, oleate, insulin, and hepatic lipoproteins (VLDL, LDL, and HDL) had little or no effect on C3 secretion. In contrast, CHYLO had an even greater effect on C3 secretion than on ASP generation. Finally, the effects of CHYLO on generation of ASP and C3 were not dependent on lipolysis of CHYLO by lipoprotein lipase (LPL). These results are consistent with the changes in plasma ASP seen postprandially, and suggests a role of ASP as a positive feedback regulator of triacylglycerol synthesis in adipose tissue.

Adipocytes↗
PubMed1997

Plasma acylation-stimulating protein in coronary artery disease.

To date, plasma levels of acylation-stimulating protein (ASP) have been determined only in normal and obese individuals. Accordingly. ASP was measured in fasting samples obtained from 59 age-matched controls and 208 patients with documented coronary artery disease (CAD). Overall, plasma ASP was significantly higher in the CAD subjects compared to the control subjects (55.3 +/- 1.8 nmol/L CAD versus 32.0 +/- 2.6 nmol/L control, P < .0005). In the control group, the distribution of plasma ASP values was unimodal whereas in the coronary group it was significantly skewed to the right. The coronary group was subdivided into those with pronounced elevation of apoB (a marked type II phenotype, n = 13), those with hypertriglyceridemia with a normal apoB (n = 17), and the remaining CAD subjects (n = 178). In the first two groups, ASP did not differ significantly from control subjects (43 +/- 2.8 nmol/L and 49 +/- 4.4 nmol/L respectively). By contrast, in the remaining CAD subjects, both the mean ASP level (56.8 +/- 2.0 nmol/L, P < .001 by ANOVA) and the proportion of patients with a markedly elevated ASP (25.3% were > 95th percentile, P < .005 versus control by X2) were significantly increased. When this third group was divided into tertiles by plasma apoB and triglyceride there was a direct relationship between plasma ASP and these two parameters. Linear regression analysis demonstrated an association between plasma ASP and plasma triglyceride (P < .05), VLDL cholesterol (P < .025), and VLDL apoB (P < .05). Finally, when all of the CAD subjects were divided by apoE phenotype, there appeared to be a relationship between plasma ASP and apoE phenotype such that ASP was higher in E2 subjects, intermediate in E3 subjects, and lower in E4 subjects. The present data document plasma ASP levels in a number of dyslipoproteinemic states and suggest a relation between the adipsin-ASP pathway and other metabolic determinants of lipoprotein metabolism.

Acylation↗
PubMed1997

Functional bioactive recombinant acylation stimulating protein is distinct from C3a anaphylatoxin.

Acylation stimulating protein (ASP) acts upon adipose tissue to stimulate triglyceride synthesis and glucose transport. The aim of the present study was to produce recombinant ASP and to measure its bioactivity. The cDNA region of the parent complement C3 sequence coding for ASP (C3adesArg) was cloned and expressed in E. coli. Bioactivity of the purified recombinant material was tested by determining its effect on triglyceride synthesis, glucose transport, and competition binding assays. In standard assays, concentrations of 5.5 microM recombinant ASP (rASP) stimulated triglyceride synthesis comparably to plasma ASP (pASP): 228% versus 237%, respectively, in 3T3 preadipocytes and 568% versus 440% in human differentiated adipocytes. rASP also increased glucose transport in L6 myocytes (163% at 10 microm rASP) and in human differentiated adipocytes (334% rASP vs. 329% pASP at 5 microM). rASP competitively displaced radiolabeled plasma ASP from high affinity association with the cell surface in both human differentiated adipocytes and 3T3 preadipocyte fibroblasts. Furthermore, immunoprecipitation of rASP and pASP with a specific monoclonal antibody abolished stimulation of cellular triglyceride synthesis. Lastly, we contrasted the structure:function activities of the arginated (C3a) and desarginated (ASP) proteins. The lipogenic activity and the anaphylatoxic activity result from distinct structural domains of the polypeptides. Thus rASP retains full biologic ASP activity and may provide a tool to study structure-function relationships in this physiologic system.

Adipocytes↗
PubMed1996

The effect of individual amino acids on ApoB100 and Lp(a) secretion by HepG2 cells.

The rate at which HepG2 cells secrete apoB100 lipoproteins is inversely related to the concentration of amino acids in the medium (Zhang, Z., Sniderman, A. D., Kalant, D., Vu, H., Monge, J. C., Tao, Y., and Cianflone, K. (1993) J. Biol. Chem. 268, 26920-26926). The purpose of the present study was to determine the effect of individual amino acids on apoB100 and lipoprotein secretion. Asparagine was associated with modestly increased secretion. The branched chain amino acids (leucine, isoleucine, and valine) and lysine had minor inhibitory effects. The other amino acids, by contrast, decreased apoB secretion, although the magnitude of the effect varied considerably, the most potent being tyrosine, cysteine, phenylalanine, tryptophan, methionine, and glutamine. Although the effect on Lp(a) generally paralleled that on apoB100, it was usually much less pronounced. No amino acid caused a marked decrease in albumin, apoAI, or total protein secreted from the HepG2 cells. The amino acid effect on apoB was paralleled by similar decreases in secreted cholesterol ester (CE) primarily in the low density lipoprotein density range (d < 1.006-1.063 g/ml), although there was no significant change in intracellular CE. Neither intracellular nor secreted triglycerides (TG) or free cholesterol changed, resulting in a slightly larger TG-enriched particle being secreted. The effect was confirmed in cultured primary hamster hepatocytes, where a mixture of amino acids also caused a decrease in apoB secretion (up to 40%). ApoAI appeared to increase as with the HepG2 cells. Secreted CE paralleled apoB . There was no change in intracellular or secreted TG or free cholesterol, resulting in a substantially larger TG-rich particle being secreted. mRNA for apoB100 increased with asparagine, decreased moderately with branched chain amino acids, and decreased further with glutamine, as shown by dot blot and Northern blotting. Pulse-chase studies indicated that there was no change in apoB secretion efficiency under any condition. These results extend our previous observations by demonstrating specificity of the amino acid effect on apoB100 secretion. Although an effect on transcription is the likely mechanism, the exact basis for this remains to be determined.

Amino Acids↗
PubMed1996

Inhibition of lipoprotein lipase induced cholesterol ester accumulation in human hepatoma HepG2 cells.

It has been suggested previously that lipoprotein lipase may act as a ligand to enhance binding and uptake of lipoprotein particles. In the present study we have examined the capacity of bovine milk lipoprotein lipase to induce intracellular accumulation of triglyceride and cholesterol ester by VLDL (Sr 60-400) isolated from Type IV hypertriglyceridemic subject (HTg-VLDL) in HepG2 cells, independent of its lipolytic activity. We have also attempted to elucidate the cellular receptor mechanisms responsible for these effects. HTg-VLDL-mediated increases in intracellular triglyceride and cholesterol ester were dependent on the presence of an active lipase. Bovine milk lipoprotein lipase (LPL) increases triglyceride mass by 301% +/- 28% (P < 0.0005) and cholesterol ester mass by 176% +/- 12% (P < 0.0005). These HTg-VLDL-mediated increases in intracellular triglyceride and cholesterol ester did not occur when heat-inactivated lipase was used. Rhizopus lipase could replace LPL and cause equivalent increases in intracellular triglyceride and cholesterol ester (472% +/- 61%(P < 0.005) and 202% +/- 25% (P < 0.025) respectively vs. control). HTg-VLDL treated with LPL and reisolated also caused equivalent increases (274% +/- 18%(P < 0.01) and 177% +/- 12% (P < 0.005) for triglyceride and cholesterol ester). LDL also caused increases in intracellular cholesterol ester (189% +/- 20%(P < 0.005)), although three times more LDL cholesterol had to be added to achieve the same effect. These LDL-induced increases were effectively blocked by monoclonal antibodies directed against the B,E receptor binding domains of apo B (-97% +/- 13% (P < 0.0005) with anti-apo B 5E11 and -68% +/- 13% (P < 0.05) for anti-apo B B1B3) or by anti-B,E receptor antibodies (-77% +/- 7% (P < 0.01) antibody C7). These same antibodies had little effect on the HTg-VLDL+LPL-induced increases in cholesterol ester (+21%, +15% and -22% for 5E11, B1B3 and C7, respectively). Monoclonal anti-apo E antibodies also had no effect on LDL-mediated increases in intracellular cholesterol ester, but had a small and significant effect on VLDL-mediated increases in cholesterol ester. However, heparin, which interferes with cell surface proteoglycan interaction, was very effective at blocking HTg-VLDL-mediated increases in cholesterol ester in the presence of LPL (-86% +/- 8% P < 0.0005). Heparin was also effective in the presence of Rhizopus lipase (-79%) or lipolyzed re-isolated HTg-VLDL (-95%). These results suggest that lipoprotein lipase may enhance the uptake process beyond its role in lipolytic remodelling but does not appear to be an absolute requirement. In contrast, heparin had no effect on LDL-mediated cholesterol ester accumulation. Lactoferrin, which inhibits interaction with the low density lipoprotein receptor-related protein (LRP), was also very effective at inhibiting HTg-VLDL increases in intracellular cholesterol ester (-95% +/- 6%, P < 0.01). However, there was no effect of either heparin or lactoferrin on HTg-VLDL-mediated triglyceride accumulation. Thus cell surface heparin sulphate may facilitate intracellular lipid acquisition by providing a stabilizing bridge with the lipoproteins and enhance uptake through receptor-mediated processes such as LRP.

Animals↗
PubMed1996

Cardiovascular disease in peritoneal dialysis.

Cardiovascular morbidity and mortality remain high in ESRD patients. Lipid abnormalities in CAPD may be more important than in hemodialysis. Vessel calcification may have a role in atherosclerotic heart disease, but this is only an inference from several clinical observations, and it remains to be defined more clearly as a risk factor. Left ventricular hypertrophy is frequent in this patient population, and is associated with specific clinical patterns and an increased risk of death. Erythropoietin treatment of anemia and tight blood pressure controls have proved to help in reversing severe left ventricular hypertrophy. Finally, we describe a syndrome of the hypertrophic, high cardiac output hemodialysis heart, which is characterized by a high cardiac output in hemodialysis patients. It is associated with left ventricular hypertrophy and eventually right ventricular hypertrophy with tricuspid insufficiency. This may require fistula revision and even a switch peritoneal dialysis.

Cardiovascular Diseases↗
PubMed1996

[Adipsin system--acylation-stimulation protein (ASP) and hyperapo-B].

Acylation Stimulating Protein (ASP) is a small basic protein which was isolated from the human plasma and which has been shown to be the most potent stimulant yet discovered of triglyceride synthesis. The initial observation were made in vitro, but there is now in vivo evidence that the adipsina-ASP system has an important regulatory role in triglyceride clearance from plasma. Studies in normals have shown that the higher the fasting and the peak ASP plasma levels are after an oral fat load, the faster the triglyceride clearance from plasma. Moreover, decreased function of the adipsina-ASP system appears to lead to increased delivery of free fatty acids and triglyceride-rich chylomicron remnants to the liver with a consequent increase in the rate of secretion of B100 lipoprotein particles. That is to say, defective function of this system is one of the causes of hyperapoB which in turn is one of the commonest dyslipoproteinemias associated with premature coronary artery disease.

Apolipoproteins B↗
PubMed1995

Differentiation-induced production of ASP in human adipocytes.

Acylation Stimulating Protein (ASP) is a human plasma protein that stimulates both triacylglycerol synthesis and glucose transport. ASP is identical to C3adesArg and is generated by the interaction of factor B, complement C3 and adipsin. We have demonstrated that mature fat cells express messages for factors B, complement C3 and adipsin; that human pre-adipocytes, when cultured under differentiating conditions to produce adipocytes, generate ASP in the culture medium; and that human adipocytes also become more responsive to ASP as they differentiate. The aim of this study, therefore, was to examine the temporal production of ASP during adipocyte differentiation in relation to other adipose specific factors involved in lipogenesis. The results demonstrate that (i) there was little ASP production by differentiating adipocytes over the first 7 days, with a marked increase in ASP thereafter (up to sixfold); (ii) this increase was paralleled by large increases in the message level of factor B and complement C3 and moderate increases in adipsin message; (iii) increases in lipoprotein lipase (LPL) message and glycerol-3-phosphate dehydrogenase (GPDH) activity (both key enzymes for substrate supply for triacylglycerol synthesis) occurred earlier than the increase in ASP; and (iv) in spite of the increase in LPL and GPDH, triacylglycerol synthetic capacity only markedly increases following the increase in ASP production in adipocytes. Although the present study cannot be interpreted as showing causality with respect to triacylglycerol synthesis, it does point to an important role for ASP in human adipose tissue physiology.

Adipocytes↗
PubMed1995

Metabolic disruptions in the adipocyte-hepatocyte fatty acid axis as causes of HyperapoB.

HyperapoB is the atherogenic dyslipoproteinemia characterized by increased numbers of LDL particles in plasma due to increased secretion of B100 lipoprotein particles by the liver. The lipid phenotype in affected patients is variable but an increased plasma apoB points to the increased LDL particle number. The adipocyte-hepatocyte fatty acid axis refers to the traffic in fatty acids from adipocytes to hepatocytes and back again. Our central thesis is that a reduced rate of adipocyte triglyceride synthesis leads to increased traffic to and fro along this axis. This article outlines the ways in which impaired adipose tissue function leads to increased flux of fatty acids to the liver which leads, in turn, to increased secretion of hepatic B100 particles. The Adipsin-ASP pathway is a newly described biological pathway which appears to play a critical role in regulating adipose tissue triglyceride synthesis. Impaired function of this pathway appears to be the commonest reason for the increased fatty acid traffic in the adipocyte-hepatocyte axis leading to HyperapoB.

Adipocytes↗
PubMed1995

The acylation stimulating protein-adipsin system.

Considerable evidence indicates that obesity, and in particular abdominal obesity, is a risk factor for both heart disease and non-insulin dependent diabetes mellitus. In spite of this, little is known of the regulation of triacylglycerol synthesis in adipose tissue other than by insulin. Acylation stimulating protein (ASP), a human plasma protein, stimulates triacylglycerol synthesis in adipose tissue and is also produced by human adipocytes. ASP may play a physiological role in the regulation of efficiency of adipose tissue fat storage and affect clearance of triglycerides from plasma.

3T3 Cells↗
PubMed1995

Signal transduction pathway of acylation stimulating protein: involvement of protein kinase C.

Acylation Stimulating Protein (ASP) was recently purified to homogeneity from human plasma and shown to be identical to C3adesArg. ASP stimulates triglycerides synthesis in human skin fibroblasts and primary human adipocytes. In vitro differentiation of human preadipocytes to mature fat cells results in increased expression and accumulation of ASP in the medium. These differentiated human adipocytes are also much more responsive to ASP than preadipocytes. The object of this study was to investigate the signal transduction pathway by which ASP causes triglyceride synthesis (TGS) to increase in human cultured fibroblasts and adipocytes. No evidence was found for a protein kinase A-mediated response. ASP action was consistent with a protein kinase C (PKC)-mediated pathway in that: 1) the effect of ASP on TGS was mimicked by 1-10 nM phorbol 12-myristate 13-acetate (PMA), a potent activator of PKC; (202% ASP vs. 178% PMA stimulation); 2) the effect of PMA and ASP were non-additive with respect to TGS; 3) staurosporine (50 nM) and GF109203X (bisindolymaleimide) at 1 microM, both competitive inhibitors of the ATP-binding site on PKC, inhibited both ASP and PMA stimulation of TGS (-59% and -65% for ASP and -84% and -99% for PMA, respectively); 4) Calphostin C (0.8 microM) which interacts with the regulatory domain of PKC also inhibited the ASP- and PMA-mediated stimulation of PKC (-76% +/- 11% inhibition for ASP and -99% +/- 20% inhibition for PMA), although in all cases the inhibition of PMA-stimulated triglyceride synthesis was greater; 5) ASP caused a time-dependent increase in intracellular diacylglycerol accumulation; and finally 6) stimulation by ASP caused an increase in PKC activity and a time-dependent translocation of PKC (maximal effect at 30 min) from the soluble intracellular compartment to a membrane-bound fraction (basal activity 22% in the membrane-bound fraction, ASP 54%, P < 0.05 and PMA 69% P < 0.0025). Taken together, the data are consistent with the conclusion that ASP acts to stimulate triglyceride synthesis via activation of the protein kinase C pathway.

Blood Proteins↗