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Zinöcker MK, Svendsen K, Dankel SN. The homeoviscous adaptation to dietary lipids (HADL) model explains controversies over saturated fat, cholesterol, and cardiovascular disease risk. Am J Clin Nutr 2021; 113:277-289. [PMID: 33471045 DOI: 10.1093/ajcn/nqaa322] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 10/09/2020] [Indexed: 12/16/2022] Open
Abstract
SFAs play the leading role in 1 of the greatest controversies in nutrition science. Relative to PUFAs, SFAs generally increase circulating concentrations of LDL cholesterol, a risk factor for atherosclerotic cardiovascular disease (ASCVD). However, the purpose of regulatory mechanisms that control the diet-induced lipoprotein cholesterol dynamics is rarely discussed in the context of human adaptive biology. We argue that better mechanistic explanations can help resolve lingering controversies, with the potential to redefine aspects of research, clinical practice, dietary advice, public health management, and food policy. In this paper we propose a novel model, the homeoviscous adaptation to dietary lipids (HADL) model, which explains changes in lipoprotein cholesterol as adaptive homeostatic adjustments that serve to maintain cell membrane fluidity and hence optimal cell function. Due to the highly variable intake of fatty acids in humans and other omnivore species, we propose that circulating lipoproteins serve as a buffer to enable the rapid redistribution of cholesterol molecules between specific cells and tissues that is necessary with changes in dietary fatty acid supply. Hence, circulating levels of LDL cholesterol may change for nonpathological reasons. Accordingly, an SFA-induced raise in LDL cholesterol in healthy individuals could represent a normal rather than a pathologic response. These regulatory mechanisms may become disrupted secondarily to pathogenic processes in association with insulin resistance and the presence of other ASCVD risk factors, as supported by evidence showing diverging lipoprotein responses in healthy individuals as opposed to those with metabolic disorders such as insulin resistance and obesity. Corresponding with the model, we suggest alternative contributing factors to the association between elevated LDL cholesterol concentrations and ASCVD, involving dietary factors beyond SFAs, such as an increased endotoxin load from diet-gut microbiome interactions and subsequent chronic low-grade inflammation that interferes with fine-tuned signaling pathways.
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Affiliation(s)
| | - Karianne Svendsen
- Department of Nutrition, University of Oslo, Oslo, Norway.,The Lipid Clinic, Department of Endocrinology, Morbid Obesity and Preventive Medicine, Oslo University Hospital, Oslo, Norway
| | - Simon Nitter Dankel
- Mohn Nutrition Research Laboratory, Department of Clinical Science, University of Bergen, Bergen, Norway
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Alphonse PAS, Jones PJH. Revisiting Human Cholesterol Synthesis and Absorption: The Reciprocity Paradigm and its Key Regulators. Lipids 2015; 51:519-36. [PMID: 26620375 DOI: 10.1007/s11745-015-4096-7] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 11/09/2015] [Indexed: 12/22/2022]
Abstract
Hypercholesterolemia is a major risk factor for cardiovascular disease. Cholesterol homeostasis in the body is governed by the interplay between absorption, synthesis, and excretion or conversion of cholesterol into bile acids. A reciprocal relationship between cholesterol synthesis and absorption is known to regulate circulating cholesterol in response to dietary or therapeutic interventions. However, the degree to which these factors affect synthesis and absorption and the extent to which one vector shifts in response to the other are not thoroughly understood. Also, huge inter-individual variability exists in the manner in which the two systems act in response to any cholesterol-lowering treatment. Various factors are known to account for this variability and in light of recent experimental advances new players such as gene-gene interactions, gene-environmental effects, and gut microbiome hold immense potential in offering an explanation to the complex traits of inter-individual variability in human cholesterol metabolism. In this context, the objective of the present review is to provide an overview on cholesterol metabolism and discuss the role of potential factors such as genetics, epigenetics, epistasis, and gut microbiome, as well as other regulators in modulating cholesterol metabolism, especially emphasizing the reciprocal relationship between cholesterol synthesis and absorption. Furthermore, an evaluation of the implications of this push-pull mechanism on cholesterol-lowering strategies is presented.
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Affiliation(s)
- Peter A S Alphonse
- Human Nutritional Sciences, University of Manitoba, Winnipeg, MB, Canada. .,Richardson Centre for Functional Foods and Nutraceuticals (RCFFN), University of Manitoba, 196, Innovation Drive, SmartPark, Winnipeg, MB, R3T 2N2, Canada.
| | - Peter J H Jones
- Human Nutritional Sciences, University of Manitoba, Winnipeg, MB, Canada.,Richardson Centre for Functional Foods and Nutraceuticals (RCFFN), University of Manitoba, 196, Innovation Drive, SmartPark, Winnipeg, MB, R3T 2N2, Canada.,Food Science, University of Manitoba, Winnipeg, MB, Canada
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3
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Fryer LGD, Jones B, Duncan EJ, Hutchison CE, Ozkan T, Williams PA, Alder O, Nieuwdorp M, Townley AK, Mensenkamp AR, Stephens DJ, Dallinga-Thie GM, Shoulders CC. The endoplasmic reticulum coat protein II transport machinery coordinates cellular lipid secretion and cholesterol biosynthesis. J Biol Chem 2013; 289:4244-61. [PMID: 24338480 PMCID: PMC3924288 DOI: 10.1074/jbc.m113.479980] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Triglycerides and cholesterol are essential for life in most organisms. Triglycerides serve as the principal energy storage depot and, where vascular systems exist, as a means of energy transport. Cholesterol is essential for the functional integrity of all cellular membrane systems. The endoplasmic reticulum is the site of secretory lipoprotein production and de novo cholesterol synthesis, yet little is known about how these activities are coordinated with each other or with the activity of the COPII machinery, which transports endoplasmic reticulum cargo to the Golgi. The Sar1B component of this machinery is mutated in chylomicron retention disorder, indicating that this Sar1 isoform secures delivery of dietary lipids into the circulation. However, it is not known why some patients with chylomicron retention disorder develop hepatic steatosis, despite impaired intestinal fat malabsorption, and why very severe hypocholesterolemia develops in this condition. Here, we show that Sar1B also promotes hepatic apolipoprotein (apo) B lipoprotein secretion and that this promoting activity is coordinated with the processes regulating apoB expression and the transfer of triglycerides/cholesterol moieties onto this large lipid transport protein. We also show that although Sar1A antagonizes the lipoprotein secretion-promoting activity of Sar1B, both isoforms modulate the expression of genes encoding cholesterol biosynthetic enzymes and the synthesis of cholesterol de novo. These results not only establish that Sar1B promotes the secretion of hepatic lipids but also adds regulation of cholesterol synthesis to Sar1B's repertoire of transport functions.
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Affiliation(s)
- Lee G D Fryer
- From the Endocrinology Centre, William Harvey Research Institute, Queen Mary University of London and Barts and The London School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, United Kingdom
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4
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van der Wulp MYM, Verkade HJ, Groen AK. Regulation of cholesterol homeostasis. Mol Cell Endocrinol 2013; 368:1-16. [PMID: 22721653 DOI: 10.1016/j.mce.2012.06.007] [Citation(s) in RCA: 129] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Revised: 05/17/2012] [Accepted: 06/11/2012] [Indexed: 12/28/2022]
Abstract
Hypercholesterolemia is an important risk factor for cardiovascular disease. It is caused by a disturbed balance between cholesterol secretion into the blood versus uptake. The pathways involved are regulated via a complex interplay of enzymes, transport proteins, transcription factors and non-coding RNA's. The last two decades insight into underlying mechanisms has increased vastly but there are still a lot of unknowns, particularly regarding intracellular cholesterol transport. After decades of concentration on the liver, in recent years the intestine has come into focus as an important control point in cholesterol homeostasis. This review will discuss current knowledge of cholesterol physiology, with emphasis on cholesterol absorption, cholesterol synthesis and fecal excretion, and new (possible) therapeutic options for hypercholesterolemia.
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Ramprasath VR, Jones PJH, Buckley DD, Woollett LA, Heubi JE. Decreased plasma cholesterol concentrations after PUFA-rich diets are not due to reduced cholesterol absorption/synthesis. Lipids 2012; 47:1063-71. [PMID: 22965757 DOI: 10.1007/s11745-012-3708-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 07/30/2012] [Indexed: 12/18/2022]
Abstract
Plasma cholesterol concentrations increase with consumption of high saturated fatty acid (SFA) and decrease with high polyunsaturated fatty acid (PUFA) diets, leading to shifts in lipid levels consistent with reduction in heart disease risk. Direct measurements of cholesterol absorption, one of the key regulators of plasma cholesterol levels, have not been performed in humans after consumption of high PUFA diets. Thus, cholesterol absorption and fractional synthesis rates (FSRs) were measured in 16 healthy adults (8 males and 9 females) using a randomized cross-over study with a diet containing high (PUFA/SFA) P/S ratio (2:1) and a low P/S ratio (0.5:1). Cholesterol absorption and fractional cholesterol synthetic rates were measured using stable isotopes after 20 days of dietary intervention. Diet did not affect cholesterol absorption or synthesis. There was a significant decrease in plasma cholesterol concentrations (P < 0.02), specifically LDL-cholesterol (P < 0.02), without a change in HDL-cholesterol or triacylglycerol concentrations. Intraluminal cholesterol solubilization and plasma sterol (cholesterol biosynthetic intermediates and plant sterols) levels were not affected by diet. Thus, consumption of diets with a high P/S ratio reduces plasma total and LDL-cholesterol concentrations independent of shifts in cholesterol absorption or synthesis.
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Affiliation(s)
- Vanu R Ramprasath
- Richardson Centre for Functional Foods and Nutraceuticals, University of Manitoba, Winnipeg, R3T 2N2, Canada
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6
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Forsythe CE, French MA, Goh YK, Clandinin MT. Cholesterolaemic influence of palmitic acid in thesn-1, 3v.thesn-2 position with high or low dietary linoleic acid in healthy young men. Br J Nutr 2007; 98:337-44. [PMID: 17391563 DOI: 10.1017/s0007114507704993] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Healthy young men were fed four diets for 2 weeks each providing natural fats containing palmitic acid (16 : 0) predominantly in thesn-1, 3 position of dietary TAG or containing 16 : 0 predominantly in thesn-2 position with low or high levels of linoleic acid (18 : 2n-6). Two treatments supplied 16 : 0 in thesn-1, 3 positions from palmstearin with low (3 % energy) or high (>7 % energy) 18 : 2n-6 and two treatments supplied 16 : 0 in thesn-2 position from lard with high or low levels of 18 : 2n-6. Diets contained 30–35 % energy as fat, 7–11 % energy as 16 : 0 and moderate levels of cholesterol. Fasting serum cholesterol and lipoprotein concentrations were measured. Cholesterol fractional synthesis rate (FSR) was determined by2H incorporation. Diets providing 16 : 0 in thesn-2 position resulted in lower fasting serum total cholesterol (TC) and a lower TC:HDL ratio than diets providing 16 : 0 in thesn-1, 3 positions. Diets with high levels of 18 : 2n-6 significantly decreased the TC:HDL ratio, reaffirming the well-known cholesterol-reducing effect of 18 : 2n-6. A lower non-esterified cholesterol FSR was observed with low dietary levels of 18 : 2n-6. No differences between dietary treatments were found for serum HDL-cholesterol, LDL-cholesterol or TAG. It is concluded that dietary fats containing 16 : 0 in thesn-2 position may result in slightly lower fasting TC than diets providing 16 : 0 in thesn-1, 3 positions, while the level ofn-6 polyunsaturated fat influences endogenous cholesterol synthesis.
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Affiliation(s)
- C E Forsythe
- Alberta Institute for Human Nutrition, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Canada
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Vogt JA, Ishii-Schrade KB, Pencharz PB, Jones PJH, Wolever TMS. L-rhamnose and lactulose decrease serum triacylglycerols and their rates of synthesis, but do not affect serum cholesterol concentrations in men. J Nutr 2006; 136:2160-6. [PMID: 16857835 DOI: 10.1093/jn/136.8.2160] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Colonic short-chain fatty acids (SCFA) may affect hepatic lipid metabolism. Lactulose increases colonic acetate production, whereas L-rhamnose increases propionate. To test the effects of oral L-rhamnose and lactulose for 28 d on fasting concentrations and hepatic synthesis of lipids in humans, 18 men were administered 25 g/d of L-rhamnose, lactulose, or d-glucose for 4 wk in a partially randomized crossover design, with blood collected from fasting subjects on the first and last day of each period. Cholesterol and triacylglycerol (TG) synthesis rates were determined using deuterated water uptake rate over the last 24 h of each period. Postprandial blood lipids, and glucose and insulin were assessed in 11 subjects on d 28. Fasting serum cholesterol was unchanged; however, when expressed as a percentage change, TG were decreased, relative to baseline (P < 0.04), by L-rhamnose (-10%) and lactulose (-10%), compared with D-glucose, which increased serum TG (+11%). Net TG-fatty acid (TGFA) synthesis on d 28 was lower with L-rhamnose (2.42 +/- 0.38 g/d) and lactulose (2.62 +/- 0.35 g/d) than with D-glucose (2.96 +/- 0.31 g/d, P < 0.01). We conclude that these results do not support a primary role for propionate in the cholesterol-lowering effect of soluble fiber. However, both lactulose and L-rhamnose lowered serum TG (expressed as a percentage change) and TGFA synthesis, compared with d-glucose, which increased them. Although these data are consistent with inhibition of TGFA synthesis by SCFA, other aspects of the metabolism of these sugars cannot be ruled out as putative agents of their TG-lowering effects.
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Affiliation(s)
- Janet A Vogt
- Clinical Nutrition and Risk Factor Modification Centre, St. Michael's Hospital, Toronto, ON, Canada
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8
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Klass DM, Bührmann K, Sauter G, Del Puppo M, Scheibner J, Fuchs M, Stange EF. Biliary lipids, cholesterol and bile synthesis: different adaptive mechanisms to dietary cholesterol in lean and obese subjects. Aliment Pharmacol Ther 2006; 23:895-905. [PMID: 16573792 DOI: 10.1111/j.1365-2036.2006.02836.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
BACKGROUND Increased biliary cholesterol secretion together with elevated cholesterol synthesis may predispose obese subjects to cholesterol gallstone formation. AIM To investigate whether processing of dietary cholesterol is altered in obesity, we enrolled eight lean and seven obese subjects in a double-blind crossover study. METHODS Cholesterol consumption was 300 mg/day on low and 1300 mg/day on high cholesterol diet. After 3 weeks on either diet, hepatic bile was collected to determine biliary lipid secretion, and bile salt composition by high-performance liquid chromatography and cholesterol saturation index was calculated. Cholesterol synthesis was measured employing mass isotopomer distribution analysis. Bile acid synthesis via neutral and acidic pathway was assessed by serum levels of 7alpha-hydroxy-4-cholesten-3-one and 27-hydroxycholesterol. RESULTS Cholesterol synthesis was increased in obese compared with lean and feedback inhibited only in obese. On low cholesterol diet, cholesterol secretion was doubled in obese but bile acid composition and synthesis was similar between the two groups. After high cholesterol diet, cholesterol saturation index and bile secretion were unchanged. In contrast to obese, lean increased bile acid synthesis only via the acidic pathway. CONCLUSIONS Dietary cholesterol appears to preferentially induce bile acid synthesis via the acidic pathway in lean, whereas cholesterol synthesis was inhibited in obese. Thus, stable cholesterol saturation index may be achieved by different mechanisms.
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Affiliation(s)
- D M Klass
- Division of Gastroenterology, University Hospital of Schleswig-Holstein, Campus Lübeck, Germany
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9
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Demmers TA, Jones PJH, Wang Y, Krug S, Creutzinger V, Heubi JE. Effects of early cholesterol intake on cholesterol biosynthesis and plasma lipids among infants until 18 months of age. Pediatrics 2005; 115:1594-601. [PMID: 15930221 DOI: 10.1542/peds.2004-0997] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND The endogenous cholesterol fractional synthesis rate (FSR) is related inversely to infant dietary cholesterol at 4 months of age; however, it remains to be established whether this effect is permanent, possibly contributing to later hypercholesterolemia. OBJECTIVE To determine whether levels of dietary cholesterol in infancy induced changes in FSR and plasma lipid levels that persisted at 18 months. METHODS A prospective clinical trial was conducted with 47 infants, from their first week of life until 18 months of age, who received human milk (HM) until weaned (n = 15) or were randomized to receive modified cow's milk formula (MCF) with added cholesterol (n = 15) or cow's milk formula (CF) (n = 17) for 12 months. Cholesterol contents of HM, MCF, and CF were 120, 80, and 40 mg/L, respectively. FSR and plasma lipid levels were measured at 4 and 18 months. RESULTS At 4 months, total cholesterol and low-density lipoprotein cholesterol levels were higher for infants fed HM and MCF, compared with CF. High-density lipoprotein cholesterol levels were higher in the MCF group than in the HM and CF groups. FSR in the HM group (0.034 +/- 0.005 pools per day) was lower than that in the CF group (0.052 +/- 0.005 pools per day). There was no difference between the HM and MCF (0.047 +/- 0.005 pools per day) groups or between the MCF and CF groups. At 18 months, there were no differences in FSRs or plasma lipid profiles between the groups. CONCLUSION Although cholesterol intake before weaning affects FSRs and plasma lipid profiles at 4 months, these differences do not persist after weaning to an unrestricted diet at 18 months. This provides additional evidence that there is no imprinting of FSR in infancy with differing dietary levels of cholesterol.
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Affiliation(s)
- Théa A Demmers
- School of Dietetics and Human Nutrition, McGill University, 21111 Lakeshore Rd, Montreal, QC, H9X 3V9, Canada
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Schwartz CC, VandenBroek JM, Cooper PS. Modeling Cholesterol in Humans: Update and Dealing with the Problem of Exchange in Vivo Using the Blood Cell-Lipoprotein Paradigm. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 537:207-19. [PMID: 14995038 DOI: 10.1007/978-1-4419-9019-8_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Affiliation(s)
- Charles C Schwartz
- Department of Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298, USA.
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11
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St-Onge MP, Farnworth ER, Savard T, Chabot D, Mafu A, Jones PJH. Kefir consumption does not alter plasma lipid levels or cholesterol fractional synthesis rates relative to milk in hyperlipidemic men: a randomized controlled trial [ISRCTN10820810]. BMC COMPLEMENTARY AND ALTERNATIVE MEDICINE 2002; 2:1. [PMID: 11825344 PMCID: PMC65674 DOI: 10.1186/1472-6882-2-1] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/09/2001] [Accepted: 01/22/2002] [Indexed: 11/29/2022]
Abstract
BACKGROUND Fermented milk products have been shown to affect serum cholesterol concentrations in humans. Kefir, a fermented milk product, has been traditionally consumed for its potential health benefits but has to date not been studied for its hypocholesterolemic properties. METHODS Thirteen healthy mildly hypercholesterolemic male subjects consumed a dairy supplement in randomized crossover trial for 2 periods of 4 wk each. Subjects were blinded to the dairy supplement consumed. Blood samples were collected at baseline and after 4 wk of supplementation for measurement of plasma total, low-density lipoprotein, and high-density lipoprotein cholesterol and triglyceride concentrations, as well as fatty acid profile and cholesterol synthesis rate. Fecal samples were collected at baseline and after 2 and 4 wk of supplementation for determination of fecal short chain fatty acid level and bacterial content. RESULTS Kefir had no effect on total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol or triglyceride concentrations nor on cholesterol fractional synthesis rates after 4 wk of supplementation. No significant change on plasma fatty acid levels was observed with diet. However, both kefir and milk increased (p < 0.05) fecal isobutyric, isovaleric and propionic acids as well as the total amount of fecal short chain fatty acids. Kefir supplementation resulted in increased fecal bacterial content in the majority of the subjects. CONCLUSIONS Since kefir consumption did not result in lowered plasma lipid concentrations, the results of this study do not support consumption of kefir as a cholesterol-lowering agent.
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Affiliation(s)
- Marie-Pierre St-Onge
- School of Dietetics and Human Nutrition, McGill University, Ste-Anne-de-Bellevue, Canada
| | - Edward R Farnworth
- Food Research and Development Center, Agriculture Canada, St-Hyacinthe, Canada
| | - Tony Savard
- Food Research and Development Center, Agriculture Canada, St-Hyacinthe, Canada
| | - Denise Chabot
- Food Research and Development Center, Agriculture Canada, St-Hyacinthe, Canada
| | - Akier Mafu
- Food Research and Development Center, Agriculture Canada, St-Hyacinthe, Canada
| | - Peter JH Jones
- School of Dietetics and Human Nutrition, McGill University, Ste-Anne-de-Bellevue, Canada
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Raeini-Sarjaz M, Vanstone CA, Papamandjaris AA, Wykes LJ, Jones PJ. Comparison of the effect of dietary fat restriction with that of energy restriction on human lipid metabolism. Am J Clin Nutr 2001; 73:262-7. [PMID: 11157322 DOI: 10.1093/ajcn/73.2.262] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Dietary fat and energy have been implicated as factors controlling circulating total and LDL-cholesterol concentrations. Whether these factors work independently or synergistically in regulating human cholesterol metabolism remains to be fully elucidated. OBJECTIVE The objective was to determine whether the effects of fat restriction on circulating lipid concentrations and synthesis differ from those of energy restriction in hypercholesterolemic subjects fed controlled diets. DESIGN Eleven men (LDL > 3.6 mmol/L) participated in a randomized crossover study. Subjects consumed 4 prepared diets, each for 4 wk and separated by 6 wk, that contained either typical amounts of fat and energy (TF), low amounts of fat but adequate energy (LF), low amounts of fat and energy through carbohydrate restriction (LFE), or typical amounts of fat and low energy through carbohydrate restriction (LE). RESULTS Body weights declined (P < 0.001) after the LE and LFE diets. Total cholesterol concentrations were not significantly different between the diets. LDL cholesterol was lower (P < 0.05) after the LF and LFE diets (8.2% and 8.0%, respectively) than after the TF diet. The LE diet increased HDL cholesterol (46.8%) and decreased triacylglycerols (22.7%), whereas the LF diet increased triacylglycerols (23.6%), relative to the TF diet. LDL:HDL decreased after the LE and LFE diets (P < 0.05). Cholesterol fractional synthesis rates after the LF, LE, and LFE diets were lower (35.2%, 27.7%, and 25.5%, respectively; P < 0.05) relative to the TF diet. CONCLUSION Reductions in both dietary fat and energy may modify LDL cholesterol by lowering cholesterol biosynthesis; however, the increase in HDL cholesterol and the suppression of triacylglycerol concentrations and LDL:HDL suggests that favorable plasma lipid profiles were also achieved through energy restriction alone.
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Affiliation(s)
- M Raeini-Sarjaz
- School of Dietetics and Human Nutrition, McGill University, Ste Anne de Bellevue, Canada
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13
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Gremaud G, Piguet C, Baumgartner M, Pouteau E, Decarli B, Berger A, Fay LB. Simultaneous assessment of cholesterol absorption and synthesis in humans using on-line gas chromatography/ combustion and gas chromatography/pyrolysis/isotope-ratio mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2001; 15:1207-1213. [PMID: 11445904 DOI: 10.1002/rcm.365] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A number of dietary components and drugs are known to inhibit the absorption of dietary and biliary cholesterol, but at the same time can compensate by increasing cholesterol synthesis. It is, therefore, necessary to have a convenient and accurate method to assess both parameters simultaneously. Hence, we validated such a method in humans using on-line gas chromatography(GC)/combustion and GC/pyrolysis/isotope-ratio mass spectrometry (IRMS). Cholesterol absorption was measured using the ratio of [(13)C]cholesterol (injected intravenously) to [(18)O]cholesterol (administered orally). Simultaneously, cholesterol synthesis was measured using the deuterium incorporation method. Our methodology was applied to 12 mildly hypercholesterolemic men that were given a diet providing 2685 +/- 178 Kcal/day (mean +/- SD) and 255 +/- 8 mg cholesterol per day. Cholesterol fractional synthesis rates ranged from 5.0 to 10.5% pool/day and averaged 7.36% +/- 1.78% pool/day (668 +/- 133 mg/day). Cholesterol absorption ranged from 36.5-79.9% with an average value of 50.8 +/- 15.4%. These values are in agreement with already known data obtained with mildly hypercholesterolemic Caucasian males placed on a diet similar to the one used for this study. However, our combined IRMS method has the advantage over existing methods that it enables simultaneous measurement of cholesterol absorption and synthesis in humans, and is therefore an important research tool for studying the impact of dietary treatments on cholesterol parameters.
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Affiliation(s)
- G Gremaud
- Nestlé Research Center, Nestec Ltd, Vers-chez-les-Blanc, P.O. Box 44, 1000 Lausanne 26, Switzerland
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Cunnane S, Trotti D, Ryan M. Specific linoleate deficiency in the rat does not prevent substantial carbon recycling from [14C]linoleate into sterols. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)31974-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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15
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Matthan NR, Raeini-Sarjaz M, Lichtenstein AH, Ausman LM, Jones PJ. Deuterium uptake and plasma cholesterol precursor levels correspond as methods for measurement of endogenous cholesterol synthesis in hypercholesterolemic women. Lipids 2000; 35:1037-44. [PMID: 11026626 DOI: 10.1007/s11745-000-0616-9] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To assess the validity of two techniques used to measure human cholesterol synthesis, the rate of uptake of deuterium (D) into plasma free cholesterol (FC), and plasma cholesterol precursor (squalene, lanosterol, desmosterol and lathosterol) levels were compared in 14 women [65-71 yr with low density lipoprotein-cholesterol (LDL-C) > or = 3.36 mmol x L(-1)]. Subjects consumed each of six diets for 5-wk periods according to a randomized crossover design. The experimental diets included a baseline diet (39% energy as fat, 164 mg chol x 4.2 MJ(-1)) and five reduced-fat diets (30% of energy as fat), where two-thirds of the fat was either soybean oil; squeeze, tub or stick margarines; or butter. Fractional and absolute synthesis rates (FSR and ASR) of FC were determined using the deuterium incorporation (DI) method, while cholesterol precursor levels were measured using gas-liquid chromatography. Data were pooled across diets for each variable and correlation coefficients were calculated to determine if associations were present. There was good agreement among levels of the various cholesterol precursors. In addition, FSR in pools/d (p x d(-1)) and ASR in grams/d (g x d(-1)) were strongly associated with lathosterol (r= 0.72 and 0.71, P= 0.0001), desmosterol (r= 0.75 and 0.75, P = 0.0001), lanosterol (r = 0.67 and 0.67), and squalene (r = 0.69 and 0.68) when levels of the precursors were expressed as micromol x mmol(-1) C. Significant but lower correlations were observed between the D uptake and plasma cholesterol precursor levels when the latter were expressed in absolute amounts (micromol x L(-1)). The wide range of fatty acid profiles of the experimental diets did not influence the degree of association between methods. In conclusion, the DI method and levels of some cholesterol precursors correspond as methods for shortterm measurement of cholesterol synthesis.
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Affiliation(s)
- N R Matthan
- School of Dietetics and Human Nutrition, McGill University, Macdonald Campus, Ste-Anne-de-Bellevue, Quebec, Canada
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16
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Hydrogenated fat consumption affects cholesterol synthesis in moderately hypercholesterolemic women. J Lipid Res 2000. [DOI: 10.1016/s0022-2275(20)32392-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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17
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Haggarty P, Shetty P, Thangam S, Kumar S, Kurpad A, Ashton J, Milne E, Earl C. Free and esterified fatty acid and cholesterol synthesis in adult males and its effect on the doubly-labelled water method. Br J Nutr 2000; 83:227-34. [PMID: 10884710 DOI: 10.1017/s0007114500000295] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The purpose of the present study was to estimate whole-body fatty acid and cholesterol synthesis in weight-stable adults and to determine the likely effect on the doubly-labelled water (DLW) method for measuring energy expenditure. Synthesis was measured by 2H incorporation over 14 d in six adult males in approximate energy balance following noradrenaline infusion to maximize mobilization of free fatty acid from adipose tissue. The inter-individual variation in synthesis rates was large and in one subject the proportion of free fatty acid synthesized was ten times that of the mean of the rest of the group; the fasting concentration of esterified fatty acid in this subject was five times that of the rest of the group indicating likely violation of the assumptions underlying the calculation of whole-body synthesis. After 14 d of labelling in the other five subjects, 0.9 (SEM 0.3)% of the circulating free fatty acid, 9.3 (SEM 3.0)% of the esterified fatty acid, 14.6 (SEM 2.4)% of the free cholesterol and 28.3 (SEM 3.7)% of esterified cholesterol had been synthesized de novo. A high rate of synthesis correlated with a low pre-dose 2H abundance both within and between lipid classes suggesting that natural 2H abundance variations in some lipid classes may be used to determine their metabolic origin. Whole-body synthetic rates were 8 g/d for fatty acid and 0.3-0.5 g/d for cholesterol. These values correspond to very small errors on DLW-derived estimates of CO2 production; -2.5 litres/d for fatty acid and -0.1 to -0.2 litres/d for cholesterol. These results, obtained in subjects typically consuming a diet with a lower fat and cholesterol content that the typical Western diet, suggest that the DLW method is unlikely to be affected by fatty acid and cholesterol synthesis in subjects in energy balance consuming a typical Western diet.
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Affiliation(s)
- P Haggarty
- Rowett Research Institute, Bucksburn, Aberdeen, UK.
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18
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Mazier MJ, Jones PJ. Dietary fat saturation, but not the feeding state, modulates rates of cholesterol esterification in normolipidemic men. Metabolism 1999; 48:1210-5. [PMID: 10535380 DOI: 10.1016/s0026-0495(99)90257-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
To determine whether the rates of cholesterol esterification in normal individuals are affected by diets differing in fats, nine men were randomly assigned to three groups receiving a diet rich in monounsaturated (MONO), polyunsaturated (POLY), or saturated (SAT) fat for 2 weeks using a crossover design. Subjects drank a dose of deuterium oxide, and the fractional esterification rate (FER) was calculated during fed and unfed periods. Total esterified cholesterol was calculated as the product of the FER and pool size, the latter obtained from a decay curve following injection of [4-14C]-cholesterol. The POLY diet produced the lowest serum cholesterol concentration and the SAT diet the highest (P < .001). For cholesterol ester (CE) deuterium enrichment, an interaction was noted between diet and time (P < .01). The FER was greater (P < .003) in subjects fed the POLY diet versus either of the other diets, although the amount of esterified cholesterol produced, expressed as either milligrams per day (P < .103) or milligrams per kilogram of body weight per day (P < .100), did not differ among groups. No effect of the feeding state was found for either the FER (P < .187) or total esterified cholesterol expressed as milligrams per day (P < .146) or milligrams per kilogram of body weight per day (P < .128). The results suggest that the diet fat type, but not the feeding state, may be responsible for serum esterified cholesterol concentrations.
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Affiliation(s)
- M J Mazier
- School of Dietetics and Human Nutrition, McGill University, Ste. Anne de Bellevue, Quebec, Canada
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19
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Gil-Villarino A, García-Fuentes E, Zafra MF, García-Peregrín E. Coconut oil induces short-term changes in lipid composition and enzyme activity of chick hepatic mitochondria. J Nutr Biochem 1999; 10:325-30. [PMID: 15539306 DOI: 10.1016/s0955-2863(99)00004-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/1998] [Accepted: 01/25/1999] [Indexed: 10/17/2022]
Abstract
We studied the short-term effects of a 20% coconut oil supplementation to the chick diet on lipid composition of liver and hepatic mitochondria, and changes that occurred in mitochondrial-associated enzymes as a result of this diet. No significant differences were observed in the lipid contents of liver when young chicks were fed the experimental diet, whereas hepatic mitochondria rapidly changed in response to this diet. Total cholesterol significantly increased in mitochondria at 24 hours of coconut oil diet feeding and decreased when dietary treatment was prolonged for 5 to 14 days. Changes in total mitochondrial phospholipids showed an inverse profile. A significant decrease in phosphatidylethanolamine and an increase in sphingomyelin were found at 24 hours. The cholesterol/phospholipid molar ratio significantly and rapidly (24 hours) increased in mitochondria from treated animals. Cytochrome oxidase activity drastically increased after 24 hours of experimental diet feeding and lowered to the control values when dietary manipulation was prolonged for 5 to 14 days. ATPase activity showed an inverse profile. Changes in cytochrome oxidase activity were parallel to changes in the cholesterol/phospholipid molar ratio, whereas changes in ATPase activity showed an inverse correlation with changes in this molar ratio. To our knowledge, this is one of the first reports on the very rapid response (24 hours) of mitochondrial lipid composition and function to saturated fat feeding.
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Affiliation(s)
- A Gil-Villarino
- Department of Biochemistry and Molecular Biology, Faculty of Sciences, University of Granada, Granada, Spain
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20
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Castillo M, Hortal JH, Gil-Villarino A, Luque P, Iglesias J, García-Peregrín E. Differential effects of dietary fat on chick plasma and liver composition and HMG-CoA reductase activity. J Nutr Biochem 1999; 10:198-204. [PMID: 15539290 DOI: 10.1016/s0955-2863(98)00086-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/1997] [Accepted: 09/21/1998] [Indexed: 11/16/2022]
Abstract
The comparative effects of diet supplementation with 10% saturated fat rich in 12:0 and 14:0 fatty acids (coconut oil), without and with 1% added cholesterol, and with 10% unsaturated fat rich in n-3 polyunsaturated fatty acids (menhaden oil) on cholesterol metabolism in neonatal chicks were examined to clarify the different mechanisms of their hyper- and hypolipidemic action. Supplementation of coconut oil produced a significant hypercholesterolemia after 7 days of treatment, with a similar increase in the amount of both free and esterified cholesterol. Supplementation of coconut oil plus cholesterol produced a higher increase of plasma cholesterol levels (approximately two to three times higher than those found with standard diet). However, supplementation of menhaden oil induced a significant decrease in total cholesterol after only 2 weeks of treatment. Levels of plasma triglycerides did not change by coconut oil addition to the diet, but a significant increase was observed after coconut oil plus cholesterol feeding. Menhaden oil produced a transient decrease in plasma triglycerides. Hepatic 3-hydroxy-3-methylglutaryl-CoA reductase activity did not change with coconut oil treatment. However, both coconut oil plus cholesterol and menhaden oil supplemented diets drastically decreased reductase activity after 1 week of dietary manipulation. These results show that different nutrients with the same inhibitory effect on reductase activity produced opposite effects on plasma cholesterol content, suggesting the existence of important differences in the regulatory mechanisms implied in cholesterol biosynthesis and its accumulation in plasma.
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Affiliation(s)
- M Castillo
- Department of Biochemistry and Molecular Biology, University of Granada, Granada, Spain
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21
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Bayley TM, Alasmi M, Thorkelson T, Krug-Wispe S, Jones PJ, Bulani JL, Tsang RC. Influence of formula versus breast milk on cholesterol synthesis rates in four-month-old infants. Pediatr Res 1998; 44:60-7. [PMID: 9667372 DOI: 10.1203/00006450-199807000-00010] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We investigated whether supplementation of regular formula (RF) with cholesterol (Ch) (RF+Ch) influenced circulating Ch levels and de novo synthesis compared with their breast-fed (BF) counterparts in 4-mo-old infants. The incorporation rate of deuterium in body water into erythrocyte membrane-free Ch over 48 h was used as an index of cholesterogenesis. Plasma total-Ch and LDL-Ch concentrations were highest (p < 0.02) in BF infants, compared with infants in the RF-fed groups. Infants in the RF+Ch groups showed an intermediate response; their plasma total-Ch and LDL-Ch concentrations were not significantly different from the BF or the RF-fed groups. Plasma total/HDL-Ch and LDL/HDL-Ch ratios were higher (p < 0.05) in BF, and higher in RF+Ch-fed infants, compared with those fed RF, whereas not different between BF and RF+Ch-fed infants. At 4 mo of age, Ch FSR was 4-fold lower (p < 0.0001) in BF versus other groups, but not significantly different between RF- and RF+Ch-fed infants. Thus, despite addition of Ch to the concentration found in breast milk, FSR remained elevated compared with that of the group fed breast milk, with an intermediate response in circulating Ch levels. It is speculated that factors other than Ch intake account for the differential Ch metabolism between formula-fed and BF infants.
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Affiliation(s)
- T M Bayley
- School of Dietetics and Human Nutrition, Macdonald Campus of McGill University, Ste-Anne-de Bellevue, Quebec, Canada
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22
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Castillo M, Hortal JH, Aguilera JA, Linares A, García-Peregrín E. Synergism between the effects of dietary cholesterol and coconut oil on plasma, liver and lipoprotein composition of neonatal chick. Int J Biochem Cell Biol 1998; 30:707-18. [PMID: 9695027 DOI: 10.1016/s1357-2725(98)00029-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The nature of the synergism between dietary factors and the development of atherosclerosis has not been fully defined. Our studies showed that simultaneous supplementation of 10% saturated fat rich in 12:0 and 14:0 fatty acids (coconut oil) plus 1% cholesterol to the diet produced a sharp increase of plasma cholesterol, indicating a synergic influence of both dietary constituents. This increase was especially patent in the VLDL fraction, modifying the distribution of other lipid components between the core and the surface of these particles. These changes are consistent with the atherogenic function of VLDL and its responsiveness to dietary manipulation.
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Affiliation(s)
- M Castillo
- Department of Biochemistry and Molecular Biology, Faculty of Sciences, University of Granada, Spain
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23
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Jones P, Ausman L, Croll D, Feng J, Schaefer E, Lichtenstein A. Validation of deuterium incorporation against sterol balance for measurement of human cholesterol biosynthesis. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)33881-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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24
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Howell TJ, MacDougall DE, Jones PJ. Phytosterols partially explain differences in cholesterol metabolism caused by corn or olive oil feeding. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)32575-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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25
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Cuchel M, Schaefer EJ, Millar JS, Jones PJ, Dolnikowski GG, Vergani C, Lichtenstein AH. Lovastatin decreases de novo cholesterol synthesis and LDL Apo B-100 production rates in combined-hyperlipidemic males. Arterioscler Thromb Vasc Biol 1997; 17:1910-7. [PMID: 9351353 DOI: 10.1161/01.atv.17.10.1910] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The effect of lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, on the kinetics of de novo cholesterol synthesis and apolipoprotein (apo) B in very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), and low-density lipoprotein (LDL) was investigated in five male patients with combined hyperlipidemia. Subjects were counseled to follow a Step 2 diet and were treated with lovastatin and placebo in randomly assigned order for 6-week periods. At the end of each experimental period, subjects were given deuterium oxide orally and de novo cholesterol synthesis was assessed from deuterium incorporation into cholesterol and expressed as fractional synthesis rate (C-FSR) and production rate (C-PR). Simultaneously, the kinetics of VLDL, IDL, and LDL apo B-100 were studied in the fed state using a primed-constant infusion of deuterated leucine to measure fractional catabolic rates (FCR) and production rates (PR). Drug treatment resulted in significant decreases in total cholesterol (-29%), VLDL cholesterol (-40%), LDL cholesterol (-27%), and apo B (-16%) levels and increases in HDL cholesterol (+13%) and apolipoprotein (apo) A-I (+11%) levels. Associated with these plasma lipoprotein responses was a significant reduction in both de novo C-FSR (-40%; P = .04) and C-PR (-42%; P = .03). Treatment with lovastain in these patients had no significant effect on the FCR of apoB-100 in VLDL, IDL, or LDL, but resulted in a significant decrease in the PR of apoB-100 in IDL and LDL. Comparing the kinetic data of these patients with those of 10 normolipidemic control subjects indicates that lovastatin treatment normalized apoB-100 IDL and LDL PR. The results of these studies suggest that the declines in plasma lipid levels observed after treatment of combined hyperlipidemic patients with lovastatin are attributable to reductions in the C-FSR and C-PR of de novo cholesterol synthesis and the PR of apoB-100 containing lipoproteins. The decline in de novo cholesterol synthesis, rather than an increase in direct uptake of VLDL and IDL, may have contributed to the decline in the PR observed.
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Affiliation(s)
- M Cuchel
- Lipid Research Laboratory, New England Medical Center, Boston, MA, USA
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26
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Mazier MJ, Jones PJ. Diet fat saturation and feeding state modulate rates of cholesterol synthesis in normolipidemic men. J Nutr 1997; 127:332-40. [PMID: 9039836 DOI: 10.1093/jn/127.2.332] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
To determine whether diets differing in fats affect cholesterol synthesis in normal individuals, nine men were randomly assigned to three groups that received three diets in a crossover design for 2 wk. Diets were either monounsaturated (MONO), polyunsaturated (POLY), or saturated (SAT). Subjects then drank a dose of deuterium oxide, and unesterified cholesterol fractional synthesis rates (FSR) were calculated during consecutive fed and unfed periods. Absolute synthesis was calculated as the product of FSR and pool size, the latter obtained from a decay curve following a [4-(14)C]cholesterol injection. Serum cholesterol concentrations varied with each diet consumed (P = 0.001); the SAT diet produced the highest and the POLY diet the lowest. Triglyceride concentrations were highest when subjects consumed the SAT diet and lowest with the POLY diet (P = 0.03); values obtained with the MONO diet did not differ significantly from those seen otherwise. HDL cholesterol concentrations were lowest when the SAT diet was consumed, highest when subjects were fed the MONO diet (P = 0.05), and midway but not significantly different with the POLY diet. Cholesterol FSR were greater when subjects consumed (P = 0.001) rather than not, and FSR during 12-h periods were greater (P = 0.045) when subjects ate the POLY diet rather than the SAT diet. Absolute synthesis was also greater (P = 0.04) when subjects were fed, but did not differ with fat type (P = 0.789). Results suggest that cholesterol synthesis is greater when men are fed than when they are not fed, and reduced synthesis is not responsible for the effect of different fats on cholesterol concentrations.
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Affiliation(s)
- M J Mazier
- Division of Human Nutrition, School of Family and Nutritional Sciences, University of British Columbia, Vancouver, Canada
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27
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Jones PJ, Pappu AS, Hatcher L, Li ZC, Illingworth DR, Connor WE. Dietary cholesterol feeding suppresses human cholesterol synthesis measured by deuterium incorporation and urinary mevalonic acid levels. Arterioscler Thromb Vasc Biol 1996; 16:1222-8. [PMID: 8857917 DOI: 10.1161/01.atv.16.10.1222] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The objective of this study was to measure the response of cholesterol biosynthesis in subjects to three different amounts of dietary cholesterol: 50 (low), 350 (medium), and 650 (high) mg cholesterol per 2800 kcal. Individuals with low (n = 7), normal (n = 12), and elevated (n = 11) plasma cholesterol concentrations consumed in random order solid-food test diets (15%, 55%, and 30% of energy as protein, carbohydrate, and fat, respectively) at each dietary cholesterol level. The three diets were consumed for 4 weeks each, and each dietary phase was separated by a 4-week washout period. During the final week of each diet, 0.7 g D2O was given per kilogram of body water and deuterium incorporation into the erythrocyte cholesterol pool was measured for 24 hours. Urinary mevalonate levels were also determined in samples obtained during two consecutive 24-hour periods. Both techniques provided measurements of whole-body cholesterol biosynthesis. In all subjects the cholesterol synthesis rate as measured by deuterium incorporation was significantly lower (P < .05) after the transition from low- to medium- and low- to high-cholesterol diets. Urinary mevalonate excretion decreased after the change from the medium- to high- (P < .05) and low- to high- (P < .01) cholesterol diets. Although correspondence between the two methods was poor, they both indicated some suppression of cholesterol synthesis by dietary cholesterol. The response of cholesterogenesis to different amounts of dietary cholesterol was related to the rate of synthesis under depressed conditions of the low-cholesterol diet. These findings indicate modest downregulation of synthesis in response to dietary cholesterol in humans, independent of plasma cholesterol levels.
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Affiliation(s)
- P J Jones
- School of Dietetics and Human Nutrition, McGill University, Montreal, Canada
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28
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Hughes TA, Heimberg M, Wang X, Wilcox H, Hughes SM, Tolley EA, Desiderio DM, Dalton JT. Comparative lipoprotein metabolism of myristate, palmitate, and stearate in normolipidemic men. Metabolism 1996; 45:1108-18. [PMID: 8781298 DOI: 10.1016/s0026-0495(96)90010-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
This project was designed to test the hypothesis that long-chain saturated fatty acids (myristate, palmitate, and stearate) are metabolized differently in human subjects, and that these differences may therefore account for the changes in plasma lipoprotein composition when these fatty acids are altered in the diet. Ethyl esters of each of the stable-isotope-labeled fatty acids (2H3- or 2H4-myristate, 13C16-palmitate, and 13C18-stearate) were fed to five nonhyperlipidemic men. The concentration of each labeled fatty acid was monitored for up to 72 hours as the fatty acids were assimilated into the lipid components (phospholipid [PL], triglyceride [TG], and cholesteryl ester [CE]) of the plasma lipoproteins (TG-rich lipoproteins [TRL], intermediate-density [IDL], low-density [LDL], and high-density lipoprotein [HDL]). Over 95% of the myristate was incorporated into TG, whereas 33% and 9% of the stearate and 18% and 7% of the palmitate were incorporated into PL and CE, respectively. The mean residence times (MRTs) for myristate in TG (8.6 to 9.9 hours) and PL (6.7 to 10.9 hours) in the individual lipoprotein subfractions were significantly shorter than for either palmitate (TG, 12.7 to 15.3 hours; PL, 19.6 to 21.3 hours) or stearate (TG, 10.7 to 15.5 hours; PL, 17.8 to 19.9 hours). The MRTs for stearate were shorter than for palmitate in PL. These data indicate that TG fatty acid in general, and myristate TG in particular, is the most rapidly cleared of the saturated fatty acids. There was a rapid transfer of labeled TG and PL between the lipoproteins. We were unable to detect any significant amount of stearate desaturation or elongation. In conclusion, these data demonstrate that myristate, palmitate, and stearate are metabolized in unique ways, and that it may therefore be inappropriate to continue to regard all "saturated fatty acids" as metabolically similar in clinical studies. Rather, it is important that we elucidate more clearly the specific metabolic pathway of each fatty acid to understand the mechanisms by which it alters plasma lipoprotein concentrations and composition and influences atherogenesis.
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Affiliation(s)
- T A Hughes
- Department of Medicine, University of Tennessee, Memphis, USA
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29
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Cuchel M, Schwab US, Jones PJ, Vogel S, Lammi-Keefe C, Li Z, Ordovas J, McNamara JR, Schaefer EJ, Lichtenstein AH. Impact of hydrogenated fat consumption on endogenous cholesterol synthesis and susceptibility of low-density lipoprotein to oxidation in moderately hypercholesterolemic individuals. Metabolism 1996; 45:241-7. [PMID: 8596497 DOI: 10.1016/s0026-0495(96)90061-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The effects of replacing corn oil with corn oil margarine in stick form on endogenous cholesterol synthesis and susceptibility of low-density lipoprotein (LDL) to oxidation were assessed in 14 middle-aged and elderly men and women aged 63 +/- 12 years (mean +/- SD) with moderate hypercholesterolemia (mean LDL-cholesterol [LDL-C], 4.24 +/- 0.59 mmol/L at the time of recruitment). Subjects consumed each of two diets for 32-day periods, one enriched in corn oil, which contained 30% of energy as fat (7% saturated fatty acid [SFA], 9% monounsaturated fatty acid [MUFA] [0.4% 18:1n9 trans], and 11% polyunsaturated fatty acid [PUFA]) and 85 mg cholesterol/4.2 MJ, and one enriched in stick corn oil margarine, which contained 30% fat (8% SFA, 12% MUFA [4.2% 18:1n9trans], and 8% PUFA) and 77 mg cholesterol/4.2 MJ. Both diets were isocaloric and supplied by a metabolic research kitchen. Mean total cholesterol levels were lowest (P = .039) when subjects consumed the corn oil-enriched diet (5.01 +/- 0.51 mmol/L) as compared with the margarine-enriched diet (5.30 +/- 0.58 mmol/L). LDL-C levels were 3.24 +/- 0.51 and 3.50 +/- 0.54 mmol/L when subjects consumed corn oil-and margarine-enriched diets, respectively (P = .058). There were no significant differences in high-density lipoprotein cholesterol (HDL-C) or triglyceride concentrations between the two experimental periods. Consumption of the margarine-enriched diet versus the corn oil-enriched diet tended to result in lower cholesterol fractional synthetic rates ([C-FSRs] 0.0466 +/- 0.0175 and 0.0668 +/- 0.0298, respectively, P = .080) and cholesterol absolute synthetic rates ([C-ASRs] 1.1761 +/- 0.5375 and 1.6954 +/- 0.8685, respectively, P = .092); however, differences did not reach statistical significance. Consumption of the margarine-enriched diet versus the corn oil-enriched diet resulted in a significantly higher concentration of alpha-tocopherol in both plasma and LDL(P = .004 and P = .011, respectively). LDL particle size tended to be smaller after subjects consumed the margarine-enriched diet versus the corn oil-enriched diet (P = .103). Susceptibility of LDL to oxidation was similar after consumption of the corn oil- and margarine-enriched diets. These data suggest that an increased rate of endogenous cholesterol synthesis did not contribute to the higher plasma cholesterol concentrations during the period when subjects consumed the margarine-enriched diet. Therefore, the increase in cholesterol concentration resulting from margarine consumption was likely attributable, at least in part, to a decreased catabolic rate of cholesterol. Additionally, susceptibility of LDL to in vitro oxidation was not altered by consumption of hydrogenated fat.
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Affiliation(s)
- M Cuchel
- Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA
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