Intestinal aspects of lipid absorption: in review

1989 ◽  
Vol 67 (3) ◽  
pp. 179-191 ◽  
Author(s):  
A. B. R. Thomson ◽  
M. Keelan ◽  
M. L. Garg ◽  
M. T. Clandinin
Keyword(s):  
Dietary Fat ◽  
De Novo ◽  
Membrane Lipid ◽  
Dietary Fats ◽  
Lipid Absorption ◽  
Limiting Factor ◽  
Adaptive Responses ◽  
Phospholipid Biosynthesis ◽  
New Knowledge ◽  
Rate Limiting

The rapidly evolving field of lipid absorption is reviewed with the thrust of new knowledge focused on the interpendency of the luminal and cellular phases of absorption. To date little attention has been paid to factors that regulate the phospholipid biosynthesis in the enterocyte. The availability of 20:4ω6 may be the rate-limiting factor for phospholipid synthesis. The source of 20:4ω6 is unknown, whether it be synthesized de novo the enterocyte or entirely originating from degradation of bile phospholipid. It has been established that dietary fat can modulate the enterocyte membrane lipid composition and transport properties. Specified fats such as as fish oils rich in 20:5ω3 and 22:6ω3 have been implicated as protective against hypercholesterolemia. However, the effects of these dietary fats on the transport of nutrients across the enterocyte are not yet known, nor are the mechanisms responsible for the adaptive responses of the brush border identified.

scholarly journals Is apolipoprotein A-IV rate limiting in the intestinal transport and absorption of triglyceride?

2013 ◽  
Vol 304 (12) ◽  
pp. G1128-G1135 ◽  
Author(s):  
Alison B. Kohan ◽  
Fei Wang ◽  
Xiaoming Li ◽  
Abbey E. Vandersall ◽  
Sarah Huesman ◽  
...  
Keyword(s):  
Intestinal Mucosa ◽  
Dietary Fat ◽  
Intestinal Transport ◽  
Dietary Lipid ◽  
Lipid Absorption ◽  
Lymphatic Transport ◽  
Apolipoprotein A ◽  
Rate Limiting

Apolipoprotein A-IV (apoA-IV) is synthesized by the intestine and secreted when dietary fat is absorbed and transported into lymph associated with chylomicrons. We have recently demonstrated that loss of apoA-IV increases chylomicron size and delays its clearance from the blood. There is still uncertainty, however, about the precise role of apoA-IV on the transport of dietary fat from the intestine into the lymph. ApoA-IV knockout (KO) mice do not have a gross defect in dietary lipid absorption, as measured by oral fat tolerance and fecal fat measurements. Here, using the in vivo lymph fistula mouse model, we show that the cumulative secretion of triglyceride (TG) into lymph in apoA-IV KO mice is very similar to that of wild-type (WT) mice. However, the apoA-IV KO mice do have subtle changes in TG accumulation in the intestinal mucosa during a 6-h continuous, but not bolus, infusion of lipid. There are no changes in the ratio of esterified to free fatty acids in the intestinal mucosa of the apoA-IV KO, however. When we extended these findings, by giving a higher dose of lipid (6 μmol/h) and for a longer infusion period (8 h), we found no effect of apoA-IV KO on intestinal TG absorption. This higher lipid infusion most certainly stresses the intestine, as we see a drastically lower absorption of TG (in both WT and KO mice); however, the loss of A-IV does not exacerbate this effect. This supports our hypothesis that apoA-IV is not required for TG absorption in the intestine. Our data suggest that the mechanisms by which the apoA-IV KO intestine responds to intestinal lipid may not be different from their WT counterparts. We conclude that apoA-IV is not required for normal lymphatic transport of TG.

scholarly journals The Effects of Human BDH2 on the Cell Cycle, Differentiation, and Apoptosis and Associations with Leukemia Transformation in Myelodysplastic Syndrome

2020 ◽  
Vol 21 (9) ◽  
pp. 3033
Author(s):  
Wen-Chi Yang ◽  
Sheng-Fung Lin ◽  
Shu-Chen Wang ◽  
Wan-Chi Tsai ◽  
Chun-Chieh Wu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Myelodysplastic Syndrome ◽  
De Novo ◽  
Ferritin Level ◽  
Limiting Factor ◽  
Poor Prognostic Factor ◽  
Cycle Arrest ◽  
Differentiation And Proliferation ◽  
Rate Limiting

Iron overload is related to leukemia transformation in myelodysplastic syndrome (MDS) patients. Siderophores help to transport iron. Type 2-hydroxybutyrate dehydrogenase (BDH2) is a rate-limiting factor in the biogenesis of siderophores. Using qRT-PCR, we analyze BDH2mRNA expression in the bone marrow (BM) of 187 MDS patients, 119 de novo acute myeloid leukemia (AML) patients, and 43 lymphoma patients with normal BM. Elevated BDH2mRNA expression in BM is observed in MDS patients (n = 187 vs. 43, normal BM; P = 0.009), and this is related to ferritin levels. Patients with higher BDH2 expression show a greater risk of leukemia progression (15.25% vs. 3.77%, lower expression; P = 0.017) and shorter leukemia-free-survival (medium LFS, 9 years vs. 7 years; P = 0.024), as do patients with a ferritin level ≥350 ng/mL. Additionally, we investigate the mechanisms related to the prognostic ability of BDH2 by using BDH2-KD THP1. The cell cycle analysis, surface markers, and special stain studies indicate that BDH2-KD induces differentiation and decreases the growth rate of THP1 cells, which is associated with the retardation of the cell cycle. Moreover, many genes, including genes related to mitochondrial catabolism, oncogenes, tumor suppressor genes, and genes related to cell differentiation and proliferation influence BDH2-KD THP1 cells. Herein, we demonstrate that BDH2 is involved in cell cycle arrest and the inhibition of differentiation in malignant cells. Furthermore, the high BDH2 expression in MDS patients could be suggestive of a poor prognostic factor. This study provides a foundation for further research on the roles of BDH2 and iron metabolism in the pathogenesis of MDS.

scholarly journals Arginine de novo and nitric oxide production in disease states

2012 ◽  
Vol 303 (10) ◽  
pp. E1177-E1189 ◽  
Author(s):  
Yvette C. Luiking ◽  
Gabriella A. M. Ten Have ◽  
Robert R. Wolfe ◽  
Nicolaas E. P. Deutz
Keyword(s):  
De Novo ◽  
Limiting Factor ◽  
Arginine Metabolism ◽  
Metabolic Fate ◽  
Body Protein ◽  
No Donors ◽  
Disease States ◽  
Acute And Chronic Stress ◽  
Nos Inhibitors ◽  
Rate Limiting

Arginine is derived from dietary protein intake, body protein breakdown, or endogenous de novo arginine production. The latter may be linked to the availability of citrulline, which is the immediate precursor of arginine and limiting factor for de novo arginine production. Arginine metabolism is highly compartmentalized due to the expression of the enzymes involved in arginine metabolism in various organs. A small fraction of arginine enters the NO synthase (NOS) pathway. Tetrahydrobiopterin (BH4) is an essential and rate-limiting cofactor for the production of NO. Depletion of BH4 in oxidative-stressed endothelial cells can result in so-called NOS3 “uncoupling,” resulting in production of superoxide instead of NO. Moreover, distribution of arginine between intracellular transporters and arginine-converting enzymes, as well as between the arginine-converting and arginine-synthesizing enzymes, determines the metabolic fate of arginine. Alternatively, NO can be derived from conversion of nitrite. Reduced arginine availability stemming from reduced de novo production and elevated arginase activity have been reported in various conditions of acute and chronic stress, which are often characterized by increased NOS2 and reduced NOS3 activity. Cardiovascular and pulmonary disorders such as atherosclerosis, diabetes, hypercholesterolemia, ischemic heart disease, and hypertension are characterized by NOS3 uncoupling. Therapeutic applications to influence (de novo) arginine and NO metabolism aim at increasing substrate availability or at influencing the metabolic fate of specific pathways related to NO bioavailability and prevention of NOS3 uncoupling. These include supplementation of arginine or citrulline, provision of NO donors including inhaled NO and nitrite (sources), NOS3 modulating agents, or the targeting of endogenous NOS inhibitors like asymmetric dimethylarginine.

scholarly journals Phosphorylation of LCB1 subunit of serine palmitoyltransferase stimulates its activity and modulates sphingolipid biosynthesis in Arabidopsis

2020 ◽  
Author(s):  
Yuan Li ◽  
Hanwei Cao ◽  
Tingting Dong ◽  
Xiaoke Wang ◽  
Liang Ma ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
De Novo ◽  
Membrane Lipid ◽  
Signal Molecules ◽  
Serine Palmitoyltransferase ◽  
Cellular Processes ◽  
Molecular Pattern ◽  
Long Chain Base ◽  
Rate Limiting ◽  
Sphingolipid Biosynthesis

Abstract Sphingolipids are the structural elements for membrane lipid bilayers and the signal molecules for many cellular processes. Serine palmitoyltransferase (SPT) is the first committed and rate-limiting enzyme in the de novo sphingolipids biosynthetic pathway. The core SPT was previously suggested as a heterodimer consisting of LCB1 and LCB2 subunits. The SPT activity was shown to be inhibited by orosomucoid proteins (ORMs) and stimulated by small subunits of SPT (ssSPT). However, whether LCB1 is modified and how the modification regulates SPT activity have been unclear. Here, we show that activation of MPK3 and MPK6 by upstream MKK9 and Flg22 (a pathogen-associated molecular pattern) treatment increases SPT activity and induces the accumulation of sphingosine long-chain base (LCB) t18:0 in Arabidopsis thaliana; the activated MPK3 and MPK6 phosphorylate AtLCB1. Phosphorylation of AtLCB1 strengthens its binding with AtLCB2b, promotes its binding with ssSPTs, and stimulates the higher-order-oligomer and active SPT complexes formation. Our findings suggest a novel regulatory mechanism of SPT activity.

scholarly journals Lipid Acyl Chain Remodeling in Yeast

2015 ◽  
Vol 8s1 ◽  
pp. LPI.S31780 ◽  
Author(s):  
Mike F. Renne ◽  
Xue Bao ◽  
Cedric H. De Smet ◽  
Anton I. P. M. De Kroon
Keyword(s):  
Intracellular Transport ◽  
De Novo ◽  
Acyl Chain ◽  
Model Organism ◽  
Lipid Synthesis ◽  
Membrane Lipid ◽  
Lipid Homeostasis ◽  
Synthetic Process ◽  
Acyl Chains ◽  
Phospholipid Acyl Chain

Membrane lipid homeostasis is maintained by de novo synthesis, intracellular transport, remodeling, and degradation of lipid molecules. Glycerophospholipids, the most abundant structural component of eukaryotic membranes, are subject to acyl chain remodeling, which is defined as the post-synthetic process in which one or both acyl chains are exchanged. Here, we review studies addressing acyl chain remodeling of membrane glycerophospholipids in Saccharomyces cerevisiae, a model organism that has been successfully used to investigate lipid synthesis and its regulation. Experimental evidence for the occurrence of phospholipid acyl chain exchange in cardiolipin, phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine is summarized, including methods and tools that have been used for detecting remodeling. Progress in the identification of the enzymes involved is reported, and putative functions of acyl chain remodeling in yeast are discussed.

Freezing in Silicon at Large Undercooling

1989 ◽  
Vol 157 ◽  
Author(s):  
P.A. Stolk ◽  
A. Polman ◽  
W.C. Sinke
Keyword(s):  
Interface Temperature ◽  
Limiting Factor ◽  
Time Resolved ◽  
Large Undercooling ◽  
Explosive Crystallization ◽  
Crystallization Speed ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Rate Limiting

ABSTRACTPulsed laser irradiation is used to induce epitaxial explosive crystallization of amorphous silicon layers buried in a (100) oriented crystalline matrix. This process is mediated by a self-propagating liquid layer. Time-resolved determination of the crystallization speed combined with numerical calculation of the interface temperature shows that freezing in silicon saturates at 16 m/s for large undercooling (> 130 K). A comparison between data and different models for melting and freezing indicates that the crystallization behavior at large undercooling can be described correctly if the rate-limiting factor is assumed to be diffusion in liquid Si at the solid/liquid interface.

Dietary fat ratios and liver plasma membrane lipid composition

Lipids ◽  
1988 ◽  
Vol 23 (9) ◽  
pp. 829-833 ◽  
Author(s):  
Michael W. Hamm ◽  
Anna Sekowski ◽  
Roni Ephrat
Keyword(s):  
Plasma Membrane ◽  
Lipid Composition ◽  
Dietary Fat ◽  
Membrane Lipid ◽  
Membrane Lipid Composition ◽  
Liver Plasma Membrane ◽  
Plasma Membrane Lipid

Impaired nitric oxide production in coronary endothelial cells of the spontaneously diabetic BB rat is due to tetrahydrobiopterin deficiency

2000 ◽  
Vol 349 (1) ◽  
pp. 353-356 ◽  
Author(s):  
Cynthia J. MEININGER ◽  
Rebecca S. MARINOS ◽  
Kazuyuki HATAKEYAMA ◽  
Raul MARTINEZ-ZAGUILAN ◽  
Jose D. ROJAS ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
De Novo ◽  
Diabetic Rats ◽  
Bb Rat ◽  
No Production ◽  
Gtp Cyclohydrolase I ◽  
Gtp Cyclohydrolase ◽  
Bb Rats ◽  
Metabolic Basis ◽  
Rate Limiting

Endothelial cells (EC) from diabetic BioBreeding (BB) rats have an impaired ability to produce NO. This deficiency is not due to a defect in the constitutive isoform of NO synthase in EC (ecNOS) or alterations in intracellular calcium, calmodulin, NADPH or arginine levels. Instead, ecNOS cannot produce sufficient NO because of a deficiency in tetrahydrobiopterin (BH4), a cofactor necessary for enzyme activity. EC from diabetic rats exhibited only 12% of the BH4 levels found in EC from normal animals or diabetes-prone animals which did not develop disease. As a result, NO synthesis by EC of diabetic rats was only 18% of that for normal animals. Increasing BH4 levels with sepiapterin increased NO production, suggesting that BH4 deficiency is a metabolic basis for impaired endothelial NO synthesis in diabetic BB rats. This deficiency is due to decreased activity of GTP-cyclohydrolase I, the first and rate-limiting enzyme in the de novo biosynthesis of BH4. GTP-cyclohydrolase activity was low because of a decreased expression of the protein in the diabetic cells.

Regulation of ornithine decarboxylase by hypoxia in pulmonary artery smooth muscle cells

1996 ◽  
Vol 271 (1) ◽  
pp. L31-L37 ◽  
Author(s):  
K. S. Harrod ◽  
J. W. Olson ◽  
M. N. Gillespie
Keyword(s):  
Smooth Muscle ◽  
Pulmonary Artery ◽  
Smooth Muscle Cells ◽  
Mrna Stability ◽  
De Novo ◽  
Hypoxic Exposure ◽  
Polyamine Synthesis ◽  
Mrna Content ◽  
Pulmonary Artery Smooth Muscle ◽  
Rate Limiting

The polyamines are a family of low-molecular-weight organic cations that play essential intracellular regulatory roles in cell growth and differentiation. Elevations in cellular polyamine contents necessary for most physiological and pathological events in the lung appear to be driven by increase de novo synthesis. In contrast, increases in lung cell polyamines required for hypoxic pulmonary vascular disease can be attributed to augmented transmembrane polyamine transport which may, in turn, be the result of hypoxia-related decreases in the activity of the initial and generally rate-limiting enzyme in de novo polyamine synthesis, ornithine decarboxylase (ODC). To begin to define the unusual mechanism whereby hypoxia governs polyamine regulatory pathways, the present study examined the impact of varying severity and durations of hypoxic exposure on ODC activity and mRNA content in cultured bovine main pulmonary artery smooth muscle cells (PASMC). The effect of hypoxia on the activity of another rate-limiting enzyme in polyamine synthesis, S-adenosylmethionine decarboxylase (AdoMet-DC), also was examined. Hypoxia caused time-dependent decreases in ODC and AdoMet-DC activities that were related to the severity of hypoxic exposure. Similarly, ODC mRNA content also was depressed by hypoxic exposure. The relationship between the decline in ODC activity and mRNA content was roughly linear. To determine whether hypoxia impairs ODC mRNA stability, two different inhibitors of transcription and Northern analyses were used to follow the decay in ODC mRNA abundance in hypoxic and normoxic PASMC. Densitometric scanning of Northern analysis indicated that ODC mRNA stability did not differ between hypoxic and normoxic PASMC. These results suggest that the reduction in ODC activity provoked by hypoxia in cultured bovine PASMC can be ascribed in part to a diminished transcriptional rate rather than to alterations in mRNA stability.

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