A 4-wk high-fructose diet alters lipid metabolism without affecting insulin sensitivity or ectopic lipids in healthy humans

BACKGROUND: High fructose consumption is suspected to be causally linked to the epidemics of obesity and metabolic disorders. In rodents, fructose leads to insulin resistance and ectopic lipid deposition. In humans, the effects of fructose on insulin sensitivity remain debated, whereas its effect on ectopic lipids has never been investigated. OBJECTIVE: We assessed the effect of moderate fructose supplementation on insulin sensitivity (IS) and ectopic lipids in healthy male volunteers (n = 7). DESIGN: IS, intrahepatocellular lipids (IHCL), and intramyocellular lipids (IMCL) were measured before and after 1 and 4 wk of a high-fructose diet containing 1.5 g fructose . kg body wt(-1) . d(-1). Adipose tissue IS was evaluated from nonesterified fatty acid suppression, hepatic IS from suppression of hepatic glucose output (6,6-2H2-glucose), and muscle IS from the whole-body glucose disposal rate during a 2-step hyperinsulinemic euglycemic clamp. IHCL and IMCL were measured by 1H magnetic resonance spectroscopy. RESULTS: Fructose caused significant (P < 0.05) increases in fasting plasma concentrations of triacylglycerol (36%), VLDL-triacylglycerol (72%), lactate (49%), glucose (5.5%), and leptin (48%) without any significant changes in body weight, IHCL, IMCL, or IS. IHCL were negatively correlated with triacylglycerol after 4 wk of the high-fructose diet (r = -0.78, P < 0.05). CONCLUSION: Moderate fructose supplementation over 4 wk increases plasma triacylglycerol and glucose concentrations without causing ectopic lipid deposition or insulin resistance in healthy humans.

Diethylhexylphthalate extracted by typical newborn lipid emulsions from polyvinylchloride infusion systems causes significant changes in histology of rabbit

Background: Looking for a candidate substance inducing hepatobiliary dysfunction under parenteral nutrition (PN) in newborns, we recently discovered that newborn infusions extract large amounts of the plasticizer diethylhexylphthalate (DEHP) from commonly used polyvinylchloride (PVC) infusion lines. This plasticizer is well known to be genotoxic and teratogenic in animals and to cause changes in various organs and enzyme systems even in humans. The aim of this study was to examine the effect of DEHP, extracted in the same way and in the same amount as in newborns, on livers of young rabbits. Methods: Prepubertal rabbits received lipid emulsion through central IV lines continuously for 3 weeks either via PVC or polyethylene (PE) infusion systems. Livers were examined after 1 and 3 weeks by light and electron microscopy. Results: By light microscopy, hydropic degeneration, single-cell necrosis, fibrosis, and bile duct proliferation were observed more in the PVC group. Electron microscopy revealed multiple nuclear changes, clusters and atypical forms of peroxisomes, proliferation of smooth endoplasmic reticulum, increased deposition of lipofuscin, and a mild perisinusoidal fibrosis only in the PVC group. These changes, which are generally regarded as reaction upon a toxic stimulus, could be exclusively attributed to DEHP. Conclusions: This investigation proved that DEHP produces toxin-like changes in livers of young rabbits in the same dose, duration, and method of administration as in newborn infants. For this reason, it is likely that DEHP is the substance that causes hepatobiliary dysfunction in newborns under PN. Possible modes of action of DEHP are proposed.

Differential effect of pioglitazone (PGZ) and rosiglitazone (RGZ) on postprandial glucose and lipid metabolism in patients with type 2 diabetes mellitus: a prospective, randomized crossover study

Postprandial metabolism is impaired in patients with type 2 diabetes (T2Dm). Two thiazolidinediones pioglitazone (PGZ) and rosiglitazone (RGZ) have similar effects on glycaemic control but differ in their effects on fasting lipids. This study investigated the effects of RGZ and PGZ on postprandial metabolism in a prospective, randomized crossover trial.

Reconstitution of mitochondrial ATP synthase into lipid bilayers for structural analysis

Mitochondrial F(1)F(o)-ATP synthase is a molecular motor that couples the energy generated by oxidative metabolism to the synthesis of ATP. Direct visualization of the rotary action of the bacterial ATP synthase has been well characterized. However, direct observation of rotation of the mitochondrial enzyme has not been reported yet. Here, we describe two methods to reconstitute mitochondrial F(1)F(o)-ATP synthase into lipid bilayers suitable for structure analysis by electron and atomic force microscopy (AFM). Proteoliposomes densely packed with bovine heart mitochondria F(1)F(o)-ATP synthase were obtained upon detergent removal from ternary mixtures (lipid, detergent and protein). Two-dimensional crystals of recombinant hexahistidine-tagged yeast F(1)F(o)-ATP synthase were grown using the supported monolayer technique. Because the hexahistidine-tag is located at the F(1) catalytic subcomplex, ATP synthases were oriented unidirectionally in such two-dimensional crystals, exposing F(1) to the lipid monolayer and the F(o) membrane region to the bulk solution. This configuration opens a new avenue for the determination of the c-ring stoichiometry of unknown hexahistidine-tagged ATP synthases and the organization of the membrane intrinsic subunits within F(o) by electron microscopy and AFM.

Oxidative stress and damage in liver, but not in brain, of Fischer 344 rats subjected to dietary iron supplementation with lipid-soluble [(3,5,5-trimethylhexanoyl)ferrocene]

Accumulation of iron probably predisposes the aging brain to progressive neuronal loss. We examined various markers of oxidative stress and damage in the brain and liver of 3- and 24-month-old rats following supplementation with the lipophilic iron derivative [(3,5,5-trimethylhexanoyl)ferrocene] (TMHF), which is capable of crossing the blood-brain barrier. At both ages, iron concentration increased markedly in the liver but failed to increase in the brain. In the liver of TMHF-treated young rats, levels of alpha- and gamma-tocopherols and glutathione (GSH) were also higher. In contrast, the brain displayed unaltered levels of the tocopherols and GSH. Malondialdehyde (MDA) level was also higher in the cerebrospinal fluid (CSF) and the liver but not in the brain. In old rats, the absence of an increase in iron concentration in the brain was reflected by unaltered concentrations of GSH, tocopherols, and MDA as compared to that in untreated rats. In the aging liver, concentrations of GSH and MDA increased with TMHF treatment. Morphological studies revealed unaltered levels of iron, ferritin, heme oxygenase-1 (HO-1), nitrotyrosine (NT), or MDA in the brains of both young and old rats treated with TMHF. In contrast, TMHF treatment increased the level of HO-1 in Kupffer cells, NT in hepatic endothelial cells, and MDA and ferritin in hepatocytes. Although these results demonstrated an increase in the biochemical markers of oxidative stress and damage in response to increasing concentrations of iron in the liver, they also demonstrated that the brain is well protected against dietary iron overload by using iron in a lipid-soluble formulation.

Lipopolysaccharides from atherosclerosis-associated bacteria antagonize TLR4, induce formation of TLR2/1/CD36 complexes in lipid rafts and trigger TLR2-induced inflammatory responses in human vascular endothelial cells

Infection with bacteria such as Chlamydia pneumonia, Helicobacter pylori or Porphyromonas gingivalis may be triggering the secretion of inflammatory cytokines that leads to atherogenesis. The mechanisms by which the innate immune recognition of these pathogens could lead to atherosclerosis remain unclear. In this study, using human vascular endothelial cells or HEK-293 cells engineered to express pattern-recognition receptors (PRRs), we set out to determine Toll-like receptors (TLRs) and functionally associated PRRs involved in the innate recognition of and response to lipopolysaccharide (LPS) from H. pylori or P. gingivalis. Using siRNA interference or recombinant expression of cooperating PRRs, we show that H. pylori and P. gingivalis LPS-induced cell activation is mediated through TLR2. Human vascular endothelial cell activation was found to be lipid raft-dependent and to require the formation of heterotypic receptor complexes comprising of TLR2, TLR1, CD36 and CD11b/CD18. In addition, we report that LPS from these bacterial strains are able to antagonize TLR4. This antagonistic activity of H. pylori or P. gingivalis LPS, as well as their TLR2 activation capability may be associated with their ability to contribute to atherosclerosis.

Effect of intensive lipid lowering with atorvastatin on renal function in patients with coronary heart disease: the Treating to New Targets (TNT) study

BACKGROUND AND OBJECTIVES: Data suggest that atorvastatin may be nephroprotective. This subanalysis of the Treating to New Targets study investigated how intensive lipid lowering with 80 mg of atorvastatin affects renal function when compared with 10 mg in patients with coronary heart disease. DESIGN, SETTING, PARTICIPANTS, ; MEASUREMENTS: A total of 10,001 patients with coronary heart disease and LDL cholesterol levels of <130 mg/dl were randomly assigned to double-blind therapy with 10 or 80 mg/d atorvastatin. Estimated GFR using the Modification of Diet in Renal Disease equation was compared at baseline and at the end of follow-up in 9656 participants with complete renal data. RESULTS: Mean estimated GFR at baseline was 65.6 +/- 11.4 ml/min per 1.73 m2 in the 10-mg group and 65.0 +/- 11.2 ml/min per 1.73 m2 in the 80-mg group. At the end of follow-up (median time to final creatinine measurement 59.5 months), mean change in estimated GFR showed an increase of 3.5 +/- 0.14 ml/min per 1.73 m2 with 10 mg and 5.2 +/- 0.14 ml/min per 1.73 m2 with 80 mg (P < 0.0001 for treatment difference). In the 80-mg arm, estimated GFR improved to > or = 60 ml/min per 1.73 m2 in significantly more patients and declined to < 60 ml/min per 1.73 m2 in significantly fewer patients than in the 10-mg arm. CONCLUSIONS: The expected 5-yr decline in renal function was not observed. Estimated GFR improved in both treatment groups but was significantly greater with 80 mg than with 10 mg, suggesting this benefit may be dosage related.

Lipid profiles for antiretroviral-naive patients starting PI- and NNRTI-based therapy in the Swiss HIV cohort study

BACKGROUND: Blood lipid abnormalities in patients on highly active antiretroviral therapy (HAART) have been associated with exposure to protease inhibitors (PIs), particularly ritonavir. First therapy with a non-nucleoside reverse transcriptase inhibitor (NNRTI) leads to relatively favourable lipid profiles. We report on medium-term lipid profiles (up to 5 years) for antiretroviral-naive patients starting NNRTI- and PI-based HAART in the Swiss HIV Cohort Study. METHODS: Since April 2000, blood samples taken at visits scheduled every 6 months have been analysed for cholesterol and triglyceride concentrations. For 1065 antiretroviral-naive patients starting HAART after April 2000, we estimated changes in concentration over time using multivariate linear regression with adjustment for baseline covariates, use of lipid-lowering drugs and whether the sample was taken in a fasting state. RESULTS: Non-high density lipoprotein (HDL) cholesterol levels increase with increasing exposure to either PI- or NNRTI-based therapy, HDL cholesterol levels increase and triglyceride levels decrease with increasing exposure to NNRTI-based therapy, whereas triglyceride levels increase with increasing exposure to PI-based therapy. Between NNRTI-based therapies, there is a slight difference in triglyceride levels, which tend to increase with increasing exposure to efavirenz and to decrease with increasing exposure to nevirapine. Of the three common PI-based therapies, nelfinavir appears to have a relatively favourable lipid profile, with little change with increasing exposure. Of the other two PI therapies, lopinavir with ritonavir has a more favourable profile than indinavir with ritonavir, with smaller increases in both non-HDL cholesterol and triglycerides and an increase in HDL cholesterol. Increasing exposure to abacavir is associated with a decrease in the level of triglycerides. CONCLUSION: In general, NNRTI-based therapy is associated with a more favourable lipid profile than PI-based therapy, but different PI-based therapies are associated with very different lipid profiles. Nelfinavir appears to have a relatively favourable lipid profile. Of the two boosted PI therapies, lopinavir appears to have a more favourable lipid profile than indinavir.

Modeling the influence of APOC3, APOE, and TNF polymorphisms on the risk of antiretroviral therapy-associated lipid disorders

BACKGROUND: Single-nucleotide polymorphisms in genes involved in lipoprotein and adipocyte metabolism may explain why dyslipidemia and lipoatrophy occur in some but not all antiretroviral therapy (ART)-treated individuals. METHODS: We evaluated the contribution of APOC3 -482C-->T, -455T-->C, and 3238C-->G; epsilon 2 and epsilon 4 alleles of APOE; and TNF -238G-->A to dyslipidemia and lipoatrophy by longitudinally modeling >2600 lipid determinations and 2328 lipoatrophy assessments in 329 ART-treated patients during a median follow-up period of 3.4 years. RESULTS: In human immunodeficiency virus (HIV)-infected individuals, the effects of variant alleles of APOE on plasma cholesterol and triglyceride levels and of APOC3 on plasma triglyceride levels were comparable to those reported in the general population. However, when treated with ritonavir, individuals with unfavorable genotypes of APOC3 and [corrected] APOE were at risk of extreme hypertriglyceridemia. They had median plasma triglyceride levels of 7.33 mmol/L, compared with 3.08 mmol/L in the absence of ART. The net effect of the APOE*APOC3*ritonavir interaction was an increase in plasma triglyceride levels of 2.23 mmol/L. No association between TNF -238G-->A and lipoatrophy was observed. CONCLUSIONS: Variant alleles of APOE and APOC3 contribute to an unfavorable lipid profile in patients with HIV. Interactions between genotypes and ART can lead to severe hyperlipidemia. Genetic analysis may identify patients at high risk for severe ritonavir-associated hypertriglyceridemia.

Lipid-poor adenomas on unenhanced CT: does histogram analysis increase sensitivity compared with a mean attenuation threshold?

OBJECTIVE: The purpose of our study was to evaluate the efficacy of CT histogram analysis for further characterization of lipid-poor adenomas on unenhanced CT. MATERIALS AND METHODS: One hundred thirty-two adrenal nodules were identified in 104 patients with lung cancer who underwent PET/CT. Sixty-five nodules were classified as lipid-rich adenomas if they had an unenhanced CT attenuation of less than or equal to 10 H. Thirty-one masses were classified as lipid-poor adenomas if they had an unenhanced CT attenuation greater than 10 H and stability for more than 1 year. Thirty-six masses were classified as lung cancer metastases if they showed rapid growth in 1 year (n = 27) or were biopsy-proven (n = 9). Histogram analysis was performed for all lesions to provide the mean attenuation value and percentage of negative pixels. RESULTS: All lipid-rich adenomas had more than 10% negative pixels; 51.6% of lipid-poor adenomas had more than 10% negative pixels and would have been classified as indeterminate nodules on the basis of mean attenuation alone. None of the metastases had more than 10% negative pixels. Using an unenhanced CT mean attenuation threshold of less than 10 H yielded a sensitivity of 68% and specificity of 100% for the diagnosis of an adenoma. Using an unenhanced CT threshold of more than 10% negative pixels yielded a sensitivity of 84% and specificity of 100% for the diagnosis of an adenoma. CONCLUSION: CT histogram analysis is superior to mean CT attenuation analysis for the evaluation of adrenal nodules and may help decrease referrals for additional imaging or biopsy.

Effect of GH on human skeletal muscle lipid metabolism in GH deficiency

Adult-onset growth hormone (GH) deficiency (GHD) is associated with insulin resistance and decreased exercise capacity. Intramyocellular lipids (IMCL) depend on training status, diet, and insulin sensitivity. Using magnetic resonance spectroscopy, we studied IMCL content following physical activity (IMCL-depleted) and high-fat diet (IMCL-repleted) in 15 patients with GHD before and after 4 mo of GH replacement therapy (GHRT) and in 11 healthy control subjects. Measurements of insulin resistance and exercise capacity were performed and skeletal muscle biopsies were carried out to assess expression of mRNA of key enzymes involved in skeletal muscle lipid metabolism by real-time PCR and ultrastructure by electron microscopy. Compared with control subjects, patients with GHD showed significantly higher difference between IMCL-depleted and IMCL-repleted. GHRT resulted in an increase in skeletal muscle mRNA expression of IGF-I, hormone-sensitive lipase, and a tendency for an increase in fatty acid binding protein-3. Electron microscopy examination did not reveal significant differences after GHRT. In conclusion, variation of IMCL may be increased in patients with GHD compared with healthy control subjects. Qualitative changes within the skeletal muscle (i.e., an increase in free fatty acids availability from systemic and/or local sources) may contribute to the increase in insulin resistance and possibly to the improvement of exercise capacity after GHRT. The upregulation of IGF-I mRNA suggests a paracrine/autocrine role of IGF-I on skeletal muscle.

Differential expression and localization of lipid transporters in the bovine mammary gland during the pregnancy-lactation cycle

The transport of lipids across mammary gland epithelial cells (MEC) determines milk lipid content and composition. We investigated the expression of lipid transporters and their regulators in comparison to blood metabolites during lactation and dry period (DP) in dairy cows. Repeated mammary gland biopsies and blood samples were taken from 10 animals at 7 stages of the pregnancy-lactation cycle. Expression levels of the specific mRNAs were determined by quantitative reverse transcription-PCR, whereas ABCA1 was localized by immunohistochemistry. Blood serum metabolites were determined by common enzymatic chemistries. Elevated mRNA profiles of ABCA1 and ABCA7 were found during DP as compared with lactation and were inversely associated with blood cholesterol levels. Elevated levels of ABCG2, NPC1, SREBP1, SREBP2, LXR alpha, and PPAR gamma were found postpartum, whereas ABCG1 did not differ between the functional stages of the mammary gland. The ABCA1 protein was localized in MEC and showed differential activity between DP and lactation suggesting a role of ABCA1 in the removal of excess cellular cholesterol from MEC during the DP. The expression profiles of ABCA7 and NPC1 may reflect a role of these transporters in the clearance of apoptotic cells and the intracellular redistribution of cholesterol, respectively. Regulation of lipid transporters in the mammary gland is partially associated with transcription factors that control lipid homeostasis.

High protein intake reduces intrahepatocellular lipid deposition in humans

BACKGROUND: High sugar and fat intakes are known to increase intrahepatocellular lipids (IHCLs) and to cause insulin resistance. High protein intake may facilitate weight loss and improve glucose homeostasis in insulin-resistant patients, but its effects on IHCLs remain unknown. OBJECTIVE: The aim was to assess the effect of high protein intake on high-fat diet-induced IHCL accumulation and insulin sensitivity in healthy young men. DESIGN: Ten volunteers were studied in a crossover design after 4 d of either a hypercaloric high-fat (HF) diet; a hypercaloric high-fat, high-protein (HFHP) diet; or a control, isocaloric (control) diet. IHCLs were measured by (1)H-magnetic resonance spectroscopy, fasting metabolism was measured by indirect calorimetry, insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp, and plasma concentrations were measured by enzyme-linked immunosorbent assay and gas chromatography-mass spectrometry; expression of key lipogenic genes was assessed in subcutaneous adipose tissue biopsy specimens. RESULTS: The HF diet increased IHCLs by 90 +/- 26% and plasma tissue-type plasminogen activator inhibitor-1 (tPAI-1) by 54 +/- 11% (P < 0.02 for both) and inhibited plasma free fatty acids by 26 +/- 11% and beta-hydroxybutyrate by 61 +/- 27% (P < 0.05 for both). The HFHP diet blunted the increase in IHCLs and normalized plasma beta-hydroxybutyrate and tPAI-1 concentrations. Insulin sensitivity was not altered, whereas the expression of sterol regulatory element-binding protein-1c and key lipogenic genes increased with the HF and HFHP diets (P < 0.02). Bile acid concentrations remained unchanged after the HF diet but increased by 50 +/- 24% after the HFHP diet (P = 0.14). CONCLUSIONS: Protein intake significantly blunts the effects of an HF diet on IHCLs and tPAI-1 through effects presumably exerted at the level of the liver. Protein-induced increases in bile acid concentrations may be involved. This trial was registered at www.clinicaltrials.gov as NCT00523562.