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A High-Fat Diet Is Associated With Endotoxemia That Originates From the Gut

2012; Elsevier BV; Volume: 142; Issue: 5 Linguagem: Inglês

10.1053/j.gastro.2012.01.034

1528-0012

Swaroop Pendyala, Jeanne M. Walker, Peter R. Holt,

Adipokines, Inflammation, and Metabolic Diseases

Endotoxemia, characterized by an excess of circulating bacterial wall lipopolysaccharide, is associated with systemic inflammation and the metabolic syndrome. Placing 8 healthy subjects on a Western-style diet for 1 month induced a 71% increase in plasma levels of endotoxin activity (endotoxemia), whereas a prudent-style diet reduced levels by 31%. The Western-style diet might, therefore, contribute to endotoxemia by causing changes in gastrointestinal barrier function or the composition of the microbiota. Endotoxemia might also develop in individuals with gastrointestinal barrier impairment. Therapeutic reagents that reduce endotoxemia might reduce systemic inflammation in patients with gastrointestinal diseases or metabolic syndrome. Endotoxemia, characterized by an excess of circulating bacterial wall lipopolysaccharide, is associated with systemic inflammation and the metabolic syndrome. Placing 8 healthy subjects on a Western-style diet for 1 month induced a 71% increase in plasma levels of endotoxin activity (endotoxemia), whereas a prudent-style diet reduced levels by 31%. The Western-style diet might, therefore, contribute to endotoxemia by causing changes in gastrointestinal barrier function or the composition of the microbiota. Endotoxemia might also develop in individuals with gastrointestinal barrier impairment. Therapeutic reagents that reduce endotoxemia might reduce systemic inflammation in patients with gastrointestinal diseases or metabolic syndrome. Endotoxin or lipopolysaccharide (LPS) is a major glycolipid component of the cell wall of gram-negative bacteria and, if absorbed into the circulation, activates the release of host-derived inflammatory mediators to induce a systemic inflammatory response. Endotoxemia occurs in obesity, is accompanied by several metabolic disorders, and is associated with low-grade systemic inflammation.1Wellen K.E. et al.J Clin Invest. 2005; 115: 1111-1119Crossref PubMed Scopus (3142) Google Scholar The source of and the mechanism for endotoxemia in obesity is controversial. Endotoxemia is derived from the gut and must reflect enhanced intestinal permeability or major changes in gut bacterial species.Lifestyle changes, including a Western-style diet, cause obesity, and previous studies have shown that an enriched-fat diet induces endotoxemia compared with a control diet.2Ghanim H. et al.Diabetes Care. 2009; 32: 2281-2287Crossref PubMed Scopus (371) Google Scholar Infusion of LPS leads to weight gain and insulin resistance.3Mehta N.N. et al.Diabetes. 2010; 59: 172-181Crossref PubMed Scopus (243) Google Scholar Others have reported acute rises in endotoxin levels with high energy intake.4Amar J. et al.Am J Clin Nutr. 2008; 87: 1219-1223Crossref PubMed Scopus (437) Google Scholar No direct demonstration of changes in endotoxemia with a Western-style diet compared with a more prudent diet has been reported. The present study describes these effects in subjects studied in metabolically controlled conditions.A detailed description of volunteer subjects and methods is available in Supplementary Patients and Methods. Briefly, 8 healthy subjects were fed a Western-style and a “prudent-style” diet for 1 month as inpatients hospitalized in a metabolic ward in a crossover study separated by a 1-month washout period. Blood endotoxin levels (endotoxemia) were measured by a neutrophil priming method that detects LPS from gram-negative organisms and is the only method approved by the Food and Drug Administration for this purpose. Serum cytokines were determined before and after each dietary study period.Our study shows that 4 weeks of feeding a Western-style diet induced highly significant increases (by 71%) in plasma endotoxin activity levels, in contrast to a major decrease (by 38%) after the prudent-style diet (Figure 1) (P < .001). Baseline endotoxin activity levels were about identical, and energy density and physical activity measurements were very similar. Simultaneously, the feeding of a prudent-style diet resulted in a significant decrease in serum tumor necrosis factor α with a trend for reduced monocyte chemotactic protein 1 and interleukin-8 levels (Table 1), whereas these levels were unchanged after the Western-style diet (Table 1). These changes were small but in line with previous data showing increased circulating cytokines accompanying endotoxemia.5Michie H.R. et al.N Engl J Med. 1988; 318: 1481-1486Crossref PubMed Scopus (1418) Google ScholarTable 1Changes in Serum Cytokine Concentrations (N = 8)CytokinesBefore diet, mean ± SD (pg/mL)After diet, mean ± SD (pg/mL)Change (%)Prudent diet TNF-α10 ± 2.58.4 ± 1.5−17aP ≤ .05. MCP-1195 ± 27178 ± 32−9 (NS) IL-61.6 ± 0.51.4 ± 0.3−11 (NS) IL-819 ± 1214 ± 1.6−28 (NS)Western diet TNF-α9 ± 1.69 ± 1.7−1 (NS) MCP-1198 ± 37180 ± 50−9 (NS) IL-61.8 ± 0.71.8 ± 0.8−2 (NS) IL-817 ± 815 ± 3.8−13 (NS)NOTE. Data before the 2 diets did not differ. Statistical analysis by paired t tests.IL, interleukin; MCP-1, monocyte chemotactic protein 1; NS, not significant; TNF, tumor necrosis factor.a P ≤ .05. Open table in a new tab Chronic endotoxemia commonly occurs in obesity and is an important factor inducing systemic inflammation leading to the metabolic syndrome.6Cani P.D. et al.Diabetologia. 2007; 50: 2374-2383Crossref PubMed Scopus (1310) Google Scholar Moderate increases in bacterial LPS have been described after fat-enriched meals in mice6Cani P.D. et al.Diabetologia. 2007; 50: 2374-2383Crossref PubMed Scopus (1310) Google Scholar and in volunteer subjects7Erridge C. et al.Am J Clin Nutr. 2007; 86: 1286-1292Crossref PubMed Scopus (544) Google Scholar as well as with a high energy intake.4Amar J. et al.Am J Clin Nutr. 2008; 87: 1219-1223Crossref PubMed Scopus (437) Google Scholar In the mouse, a high-fat diet induces endotoxemia, inflammation in visceral adipose tissue, and glucose imbalance ameliorated by antibiotics.8Cani P.D. et al.Diabetes. 2008; 57: 1470-1481Crossref PubMed Scopus (3177) Google ScholarCell wall products of luminal commensal microbiota that cross the gastrointestinal barrier can induce endotoxemia. Thus, endotoxemia must result either from changes in microbiota or/and increased gastrointestinal permeability. Intestinal microbiota are implicated in causing obesity,9Backhed F. et al.Proc Natl Acad Sci U S A. 2004; 101: 15718-15723Crossref PubMed Scopus (4186) Google Scholar and the diet including fiber intake can induce changes in gut microbiota.10Turnbaugh P.J. et al.Cell Host Microbe. 2008; 3: 213-223Abstract Full Text Full Text PDF PubMed Scopus (2030) Google Scholar Furthermore, increased gut permeability has been described with high-fat feeding in study subjects,11Brun P. et al.Am J Physiol Gastrointest Liver Physiol. 2007; 292: G518-G525Crossref PubMed Scopus (652) Google Scholar which can be modulated by increased proglucagon-derived peptide in the mouse.12Cani P.D. et al.Gut. 2009; 58: 1091-1103Crossref PubMed Scopus (1769) Google ScholarThe present study directly shows diet-modified endotoxemia in humans. The study was performed in only 8 subjects, but it had a crossover design in the same individuals at a metabolic inpatient facility under strict nutritional and activity controls13Pendyala S. et al.Am J Clin Nutr. 2011; 93: 234-242Crossref PubMed Scopus (91) Google Scholar whose endotoxin activity levels before diet administration were almost identical.The present study raises several questions. Does diet-induced endotoxemia in humans reflect changes in permeability or in microbiota? Is diet-induced endotoxemia an epiphenomenon or pathogenic in the absence of gastrointestinal disease? In gastrointestinal diseases that have been shown to be accompanied by increased intestinal permeability such as celiac disease or inflammatory bowel disease,14Gardiner K.R. et al.Gut. 1995; 36: 897-901Crossref PubMed Scopus (181) Google Scholar does diet-induced endotoxemia increase the risk of systemic inflammation? May feeding prebiotics or probiotics reduce endotoxemia and its concomitant complications? Endotoxin or lipopolysaccharide (LPS) is a major glycolipid component of the cell wall of gram-negative bacteria and, if absorbed into the circulation, activates the release of host-derived inflammatory mediators to induce a systemic inflammatory response. Endotoxemia occurs in obesity, is accompanied by several metabolic disorders, and is associated with low-grade systemic inflammation.1Wellen K.E. et al.J Clin Invest. 2005; 115: 1111-1119Crossref PubMed Scopus (3142) Google Scholar The source of and the mechanism for endotoxemia in obesity is controversial. Endotoxemia is derived from the gut and must reflect enhanced intestinal permeability or major changes in gut bacterial species. Lifestyle changes, including a Western-style diet, cause obesity, and previous studies have shown that an enriched-fat diet induces endotoxemia compared with a control diet.2Ghanim H. et al.Diabetes Care. 2009; 32: 2281-2287Crossref PubMed Scopus (371) Google Scholar Infusion of LPS leads to weight gain and insulin resistance.3Mehta N.N. et al.Diabetes. 2010; 59: 172-181Crossref PubMed Scopus (243) Google Scholar Others have reported acute rises in endotoxin levels with high energy intake.4Amar J. et al.Am J Clin Nutr. 2008; 87: 1219-1223Crossref PubMed Scopus (437) Google Scholar No direct demonstration of changes in endotoxemia with a Western-style diet compared with a more prudent diet has been reported. The present study describes these effects in subjects studied in metabolically controlled conditions. A detailed description of volunteer subjects and methods is available in Supplementary Patients and Methods. Briefly, 8 healthy subjects were fed a Western-style and a “prudent-style” diet for 1 month as inpatients hospitalized in a metabolic ward in a crossover study separated by a 1-month washout period. Blood endotoxin levels (endotoxemia) were measured by a neutrophil priming method that detects LPS from gram-negative organisms and is the only method approved by the Food and Drug Administration for this purpose. Serum cytokines were determined before and after each dietary study period. Our study shows that 4 weeks of feeding a Western-style diet induced highly significant increases (by 71%) in plasma endotoxin activity levels, in contrast to a major decrease (by 38%) after the prudent-style diet (Figure 1) (P < .001). Baseline endotoxin activity levels were about identical, and energy density and physical activity measurements were very similar. Simultaneously, the feeding of a prudent-style diet resulted in a significant decrease in serum tumor necrosis factor α with a trend for reduced monocyte chemotactic protein 1 and interleukin-8 levels (Table 1), whereas these levels were unchanged after the Western-style diet (Table 1). These changes were small but in line with previous data showing increased circulating cytokines accompanying endotoxemia.5Michie H.R. et al.N Engl J Med. 1988; 318: 1481-1486Crossref PubMed Scopus (1418) Google Scholar NOTE. Data before the 2 diets did not differ. Statistical analysis by paired t tests. IL, interleukin; MCP-1, monocyte chemotactic protein 1; NS, not significant; TNF, tumor necrosis factor. Chronic endotoxemia commonly occurs in obesity and is an important factor inducing systemic inflammation leading to the metabolic syndrome.6Cani P.D. et al.Diabetologia. 2007; 50: 2374-2383Crossref PubMed Scopus (1310) Google Scholar Moderate increases in bacterial LPS have been described after fat-enriched meals in mice6Cani P.D. et al.Diabetologia. 2007; 50: 2374-2383Crossref PubMed Scopus (1310) Google Scholar and in volunteer subjects7Erridge C. et al.Am J Clin Nutr. 2007; 86: 1286-1292Crossref PubMed Scopus (544) Google Scholar as well as with a high energy intake.4Amar J. et al.Am J Clin Nutr. 2008; 87: 1219-1223Crossref PubMed Scopus (437) Google Scholar In the mouse, a high-fat diet induces endotoxemia, inflammation in visceral adipose tissue, and glucose imbalance ameliorated by antibiotics.8Cani P.D. et al.Diabetes. 2008; 57: 1470-1481Crossref PubMed Scopus (3177) Google Scholar Cell wall products of luminal commensal microbiota that cross the gastrointestinal barrier can induce endotoxemia. Thus, endotoxemia must result either from changes in microbiota or/and increased gastrointestinal permeability. Intestinal microbiota are implicated in causing obesity,9Backhed F. et al.Proc Natl Acad Sci U S A. 2004; 101: 15718-15723Crossref PubMed Scopus (4186) Google Scholar and the diet including fiber intake can induce changes in gut microbiota.10Turnbaugh P.J. et al.Cell Host Microbe. 2008; 3: 213-223Abstract Full Text Full Text PDF PubMed Scopus (2030) Google Scholar Furthermore, increased gut permeability has been described with high-fat feeding in study subjects,11Brun P. et al.Am J Physiol Gastrointest Liver Physiol. 2007; 292: G518-G525Crossref PubMed Scopus (652) Google Scholar which can be modulated by increased proglucagon-derived peptide in the mouse.12Cani P.D. et al.Gut. 2009; 58: 1091-1103Crossref PubMed Scopus (1769) Google Scholar The present study directly shows diet-modified endotoxemia in humans. The study was performed in only 8 subjects, but it had a crossover design in the same individuals at a metabolic inpatient facility under strict nutritional and activity controls13Pendyala S. et al.Am J Clin Nutr. 2011; 93: 234-242Crossref PubMed Scopus (91) Google Scholar whose endotoxin activity levels before diet administration were almost identical. The present study raises several questions. Does diet-induced endotoxemia in humans reflect changes in permeability or in microbiota? Is diet-induced endotoxemia an epiphenomenon or pathogenic in the absence of gastrointestinal disease? In gastrointestinal diseases that have been shown to be accompanied by increased intestinal permeability such as celiac disease or inflammatory bowel disease,14Gardiner K.R. et al.Gut. 1995; 36: 897-901Crossref PubMed Scopus (181) Google Scholar does diet-induced endotoxemia increase the risk of systemic inflammation? May feeding prebiotics or probiotics reduce endotoxemia and its concomitant complications? Supplementary Patients and MethodsStudy Population and MethodsEight healthy volunteer subjects, 3 men and 5 postmenopausal women, aged 55–66 years (mean, 60 ± 3.5 years) who were participating in a crossover study of a Western-style diet and an experimental “prudent”-style diet were recruited. Their weight was 77 ± 15 kg, their body mass index was 26 ± 3.2 kg/m2, and they had been weight stable (<2% change) for more than 6 months before study. Exclusion criteria included a history of cancer, previous intestinal surgery, history suggestive of malabsorption, major medical problems, consumption of medications with anti-inflammatory properties, or any history of excessive bleeding. The study was approved by the institutional review board of The Rockefeller University (New York, NY).The subjects were studied in the metabolic beds of The Rockefeller University Hospital using a crossover study design. The subjects were fed a Western-style diet and a prudent-style diet with similar caloric density in random order for approximately 4 weeks with a 4-week washout period in between (Supplementary Table 1). The order of the diets did not influence the results. Physical activity was determined with a pedometer and was almost identical during the 2 dietary regimens. Fasting standard hematologic and biochemical tests, lipid profile, and serum insulin and C-reactive protein measurements were performed (Supplementary Table 2). Serum cytokines were measured in duplicate with a human proinflammatory 9-plex Multi-Spot Kit (Mesoscale Diagnostics, Gaithersburg, MD) with an intra-assay correlation and interassay variance of ≤10%.1Pendyala S. et al.Am J Clin Nutr. 2011; 93: 234-242Crossref PubMed Scopus (101) Google Scholar Monocyte chemotactic protein 1 (MCP-1) was measured with a human enzyme-linked immunosorbent assay kit.An endotoxin activity assay that uses a specific monoclonal antibody toward both soluble and protein-bound gram-negative bacterial LPS was used (Spectral Diagnostic Inc, Toronto, Ontario, Canada). Fasting EDTA anticoagulated whole blood was collected and tested in triplicate within an hour of collection in a photon-counting luminometer. This method uses an endotoxin antibody immune complex to prime neutrophils in blood to enhance their respiratory burst as a response to zymogen.2Romaschin A.D. et al.J Immunol Methods. 1998; 212: 169-185Crossref PubMed Scopus (114) Google Scholar This method detects LPS from gram-negative organisms and is the only assay approved by the Food and Drug Administration for this purpose.StatisticsPaired t tests were used to compare endotoxin activity levels before and after the individual diets.The Mann–Whitney sum test was used to compare endotoxin activity level changes between the 2 diets. Cytokine and biochemical measures were analyzed by paired t tests.Supplementary Table 1Diet CompositionEnergy (kcal)Fat (% of total calories)Saturated fat (% of total calories)Carbohydrates (% of total calories)Protein (% of total calories)Fiber (g)Calcium (mg)Western-style diet22094020.8402012.5450Prudent-style diet2214205.86020311055NOTE. The Western-style diet and the prudent-style diet were fed for approximately 4 weeks. The prudent-style diet contained less than 11% greater amounts of the “anti-inflammatory nutrients” 3-omega fatty acids, vitamin C, and vitamin E than the Western-style diet. Open table in a new tab Supplementary Table 2Biochemical DataWestern-style dietPrudent-style dietP valueGlucose (mg/dL)94 ± 991 ± 8NSInsulin (μIU/mL)9.9 ± 79.9 ± 4.9NSTriglycerides (mg/dL)101 ± 53115 ± 56NSTotal cholesterol (mg/dL)206 ± 19179 ± 25.06Low-density lipoprotein cholesterol (mg/dL)120 ± 14106 ± 19NSHigh-density lipoprotein cholesterol (mg/dL)61 ± 950 ± 13<.01NOTE. Values are expressed as mean ± SD at the end of diet administration in the 8 subjects studied.NS, not significant. Open table in a new tab Study Population and MethodsEight healthy volunteer subjects, 3 men and 5 postmenopausal women, aged 55–66 years (mean, 60 ± 3.5 years) who were participating in a crossover study of a Western-style diet and an experimental “prudent”-style diet were recruited. Their weight was 77 ± 15 kg, their body mass index was 26 ± 3.2 kg/m2, and they had been weight stable (<2% change) for more than 6 months before study. Exclusion criteria included a history of cancer, previous intestinal surgery, history suggestive of malabsorption, major medical problems, consumption of medications with anti-inflammatory properties, or any history of excessive bleeding. The study was approved by the institutional review board of The Rockefeller University (New York, NY).The subjects were studied in the metabolic beds of The Rockefeller University Hospital using a crossover study design. The subjects were fed a Western-style diet and a prudent-style diet with similar caloric density in random order for approximately 4 weeks with a 4-week washout period in between (Supplementary Table 1). The order of the diets did not influence the results. Physical activity was determined with a pedometer and was almost identical during the 2 dietary regimens. Fasting standard hematologic and biochemical tests, lipid profile, and serum insulin and C-reactive protein measurements were performed (Supplementary Table 2). Serum cytokines were measured in duplicate with a human proinflammatory 9-plex Multi-Spot Kit (Mesoscale Diagnostics, Gaithersburg, MD) with an intra-assay correlation and interassay variance of ≤10%.1Pendyala S. et al.Am J Clin Nutr. 2011; 93: 234-242Crossref PubMed Scopus (101) Google Scholar Monocyte chemotactic protein 1 (MCP-1) was measured with a human enzyme-linked immunosorbent assay kit.An endotoxin activity assay that uses a specific monoclonal antibody toward both soluble and protein-bound gram-negative bacterial LPS was used (Spectral Diagnostic Inc, Toronto, Ontario, Canada). Fasting EDTA anticoagulated whole blood was collected and tested in triplicate within an hour of collection in a photon-counting luminometer. This method uses an endotoxin antibody immune complex to prime neutrophils in blood to enhance their respiratory burst as a response to zymogen.2Romaschin A.D. et al.J Immunol Methods. 1998; 212: 169-185Crossref PubMed Scopus (114) Google Scholar This method detects LPS from gram-negative organisms and is the only assay approved by the Food and Drug Administration for this purpose. Eight healthy volunteer subjects, 3 men and 5 postmenopausal women, aged 55–66 years (mean, 60 ± 3.5 years) who were participating in a crossover study of a Western-style diet and an experimental “prudent”-style diet were recruited. Their weight was 77 ± 15 kg, their body mass index was 26 ± 3.2 kg/m2, and they had been weight stable (<2% change) for more than 6 months before study. Exclusion criteria included a history of cancer, previous intestinal surgery, history suggestive of malabsorption, major medical problems, consumption of medications with anti-inflammatory properties, or any history of excessive bleeding. The study was approved by the institutional review board of The Rockefeller University (New York, NY). The subjects were studied in the metabolic beds of The Rockefeller University Hospital using a crossover study design. The subjects were fed a Western-style diet and a prudent-style diet with similar caloric density in random order for approximately 4 weeks with a 4-week washout period in between (Supplementary Table 1). The order of the diets did not influence the results. Physical activity was determined with a pedometer and was almost identical during the 2 dietary regimens. Fasting standard hematologic and biochemical tests, lipid profile, and serum insulin and C-reactive protein measurements were performed (Supplementary Table 2). Serum cytokines were measured in duplicate with a human proinflammatory 9-plex Multi-Spot Kit (Mesoscale Diagnostics, Gaithersburg, MD) with an intra-assay correlation and interassay variance of ≤10%.1Pendyala S. et al.Am J Clin Nutr. 2011; 93: 234-242Crossref PubMed Scopus (101) Google Scholar Monocyte chemotactic protein 1 (MCP-1) was measured with a human enzyme-linked immunosorbent assay kit. An endotoxin activity assay that uses a specific monoclonal antibody toward both soluble and protein-bound gram-negative bacterial LPS was used (Spectral Diagnostic Inc, Toronto, Ontario, Canada). Fasting EDTA anticoagulated whole blood was collected and tested in triplicate within an hour of collection in a photon-counting luminometer. This method uses an endotoxin antibody immune complex to prime neutrophils in blood to enhance their respiratory burst as a response to zymogen.2Romaschin A.D. et al.J Immunol Methods. 1998; 212: 169-185Crossref PubMed Scopus (114) Google Scholar This method detects LPS from gram-negative organisms and is the only assay approved by the Food and Drug Administration for this purpose. StatisticsPaired t tests were used to compare endotoxin activity levels before and after the individual diets.The Mann–Whitney sum test was used to compare endotoxin activity level changes between the 2 diets. Cytokine and biochemical measures were analyzed by paired t tests.Supplementary Table 1Diet CompositionEnergy (kcal)Fat (% of total calories)Saturated fat (% of total calories)Carbohydrates (% of total calories)Protein (% of total calories)Fiber (g)Calcium (mg)Western-style diet22094020.8402012.5450Prudent-style diet2214205.86020311055NOTE. The Western-style diet and the prudent-style diet were fed for approximately 4 weeks. The prudent-style diet contained less than 11% greater amounts of the “anti-inflammatory nutrients” 3-omega fatty acids, vitamin C, and vitamin E than the Western-style diet. Open table in a new tab Supplementary Table 2Biochemical DataWestern-style dietPrudent-style dietP valueGlucose (mg/dL)94 ± 991 ± 8NSInsulin (μIU/mL)9.9 ± 79.9 ± 4.9NSTriglycerides (mg/dL)101 ± 53115 ± 56NSTotal cholesterol (mg/dL)206 ± 19179 ± 25.06Low-density lipoprotein cholesterol (mg/dL)120 ± 14106 ± 19NSHigh-density lipoprotein cholesterol (mg/dL)61 ± 950 ± 13<.01NOTE. Values are expressed as mean ± SD at the end of diet administration in the 8 subjects studied.NS, not significant. Open table in a new tab Paired t tests were used to compare endotoxin activity levels before and after the individual diets. The Mann–Whitney sum test was used to compare endotoxin activity level changes between the 2 diets. Cytokine and biochemical measures were analyzed by paired t tests. NOTE. The Western-style diet and the prudent-style diet were fed for approximately 4 weeks. The prudent-style diet contained less than 11% greater amounts of the “anti-inflammatory nutrients” 3-omega fatty acids, vitamin C, and vitamin E than the Western-style diet. NOTE. Values are expressed as mean ± SD at the end of diet administration in the 8 subjects studied. NS, not significant. High Fructose Consumption Can Induce EndotoxemiaGastroenterologyVol. 143Issue 3PreviewWe read the article speculating that a high-fat diet is associated with endotoxemia originating from the gut which is recently published in Gastroenterology by Pendyala et al.1 They also proposed that the Western-style diet could contribute to endotoxemia by causing changes in gastrointestinal barrier function or the composition of enteric flora. We offer the following comments. Full-Text PDF