Fatty acid composition of adipose tissue in humans. Implications for the dietary fat-serum cholesterol-CHD issue

Intestinal Microbiota-Derived Short Chain Fatty Acids in Host Health and Disease

Intestinal microbiota has its role as an important component of human physiology. It produces metabolites that module key functions to establish a symbiotic crosstalk with their host. Among them, short chain fatty acids (SCFAs), produced by intestinal bacteria during the fermentation of partially and non-digestible polysaccharides, play key roles in regulating colon physiology and changing intestinal environment. Recent research has found that SCFAs not only influence the signal transduction pathway in the gut, but they also reach tissues and organs outside of the gut, through their circulation in the blood. Growing evidence highlights the importance of SCFAs level in influencing health maintenance and disease development. SCFAs are probably involved in the management of host health in a complicated (positive or negative) way. Here, we review the current understanding of SCFAs effects on host physiology and discuss the potential prevention and therapeutics of SCFAs in a variety of disorders. It provides a systematic theoretical basis for the study of mechanisms and precise intake level of SCFAs to promote human health.

Optimal delipidation solvent to secure extracellular matrix from human perirenal adipose tissue

The objective of this study was to select the optimal delipidation solvent for preparation of human perirenal adipose tissue-derived extracellular matrix (ECM). Human perirenal adipose tissue can be obtained in large amounts during surgery, and it can be an alternative source of human ECM. Delipidation is an essential procedure for the ECM preparation, because lipid strongly inhibits regeneration of target tissue. Isopropanol has been widely used as a delipidation solvent for adipose tissue. However, because adipose tissue is mostly composed of nonpolar lipid, a nonpolar solvent might be more effective for delipidation. We evaluated the delipidation efficiency of acetone, chloroform, methanol, ether, ethanol, isopropanol, water, chloroform/methanol, ethanol/heptane, ether/methanol, hexane/ethanol, and butanol/methanol solvents for ECM extraction from human perirenal adipose tissue. Among them, acetone-treated adipose tissue showed the greatest delipidation efficiency (93.05%), significantly lower residual DNA content, and the greatest residual collagen concentration (42.49 ± 0.05 μg/g). In addition, acetone-treated tissue also had well-preserved ultrastructure with high porosity and significantly low in vitro cytotoxicity. These results suggested that acetone may be an optimal delipidation solvent for extraction of ECM from human perirenal adipose tissue.

Statement on additional scientific evidence in relation to the essential composition of total diet replacement for weight control

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to revise the Opinion on the essential composition of total diet replacements for weight control (TDRs) regarding the minimum content of linoleic acid (LA) and alpha-linolenic acid (ALA) and the maximum content of magnesium (Mg). Through a comprehensive literature search, human studies were retrieved reporting on LA and ALA concentrations in adipose tissue (AT), on weight loss and gallstone formation following TDR consumption and on diarrhoea after supplemental Mg intake. The distribution of the amount of LA and ALA release from AT during weight loss when consuming TDRs was estimated using statistical simulations. Using the fifth percentile, the coverage of the adequate intake (AI) for both FA was estimated. For the risk of developing diarrhoea when consuming TDRs with an Mg content of 350 mg/day, four cross-over studies using 360-368 mg Mg/day were reviewed. The Panel concludes that (1) there is no need to add LA to TDRs, as the amount released from AT during weight loss when consuming TDRs is sufficient to cover the AI for LA; (2) a minimum of 0.8 g/day ALA is needed in TDRs in order to meet the AI for ALA; (3) the minimum fat content of TDRs of 20 g/day as derived in the Panel's previous opinion is proposed to be maintained until the availability of further evidence, given the considerable uncertainty as to the amount of fat required for reducing the risk of gallstone formation; and (4) the likelihood that Mg-induced diarrhoea occurs at a severity that may be considered of concern for overweight and obese individuals consuming TDRs is low when the total maximum Mg content in TDRs is 350 mg/day.

Optimization of extracellular matrix extraction from human perirenal adipose tissue

Human adipose tissue includes useful substrates for regenerative medicine such as the extracellular matrix (ECM), but most perirenal fat tissue is wasted after kidney surgery. Since a lot of adipose tissue can be procured after a kidney, we extracted ECM from human perirenal adipose tissue and optimized the extraction process. To verify the efficacy for ECM extraction, we compared the products in several steps. Perirenal adipose tissue was either finely homogenized or underwent crude manual dissection. The amount of extracted ECM was quantified with ELISA for verification of the initial tissue downsizing effect. To validate the drying effect for fast and complete delipidation, tissues were prepared in a dry or wet phase, and residual lipids were visualized with Oil-Red-O staining. The extracted lipid was assayed at each time point to quantify the appropriate delipidation time. To select the optimal decellularization method, tissues were treated with physical, chemical, or enzymatic method, and the residual cell debris were identified with histological staining. The biochemical properties of the ECM extracted by the above methods were analyzed. The ECM extracted by fine homogenization showed a significantly enhanced amount of collagen, laminin and fibronectin compared to the crude dissection method. The dried tissue showed fast and complete lipid elimination compared to the wet tissue. Complete delipidation was achieved at 45 min after acetone treatment. Additionally, 1% triton X-100 chemical treatment showed complete decellularization with well-preserved collagen fibers. Biochemical analysis revealed preserved ECM proteins, a high cell proliferation rate and normal cell morphology without cell debris or lipids. The established process of homogenization, drying, delipidation with acetone, and decellularization with Triton X-100 treatment can be an optimal method for ECM extraction from human perirenal adipose tissue. Using this technique, human perirenal adipose tissue may be a valuable source for tissue engineering and regenerative medicine.

The impact of dietary fatty acids on human adipose tissue

Nutrition is a major variable factor in human environments. The composition of nutrients has changed markedly in recent decades which may contribute to the increased prevalence of metabolic diseases, such as obesity and type 2 diabetes. Fat is an important component of the diet which comes in various forms with fatty acids (FA) of different carbon chain lengths and saturation degrees. In addition to being an energy supply, FA function as potent signalling molecules and influence transcriptional activity. Among other tissues, dietary FA target white adipose tissue function, which is central in maintaining metabolic health. This review focuses on the possible role of dietary FA composition and its effect on human white adipose tissue expandability and transcriptional response. Altogether, the existing literature suggests that unsaturated fat has more benign effects on adipose tissue distribution when compared to long-chain saturated fat. However, the mechanisms of action remain poorly characterised.

Biomarker of long-chain n-3 fatty acid intake and breast cancer: Accumulative evidence from an updated meta-analysis of epidemiological studies

Objective: We aimed to summarize the up-to-date epidemiology evidence on biomarkers of long-chain (LC) n-3 fatty acid (FA) intake in relation to breast cancer (BC).Methods: Epidemiology studies determining FA levels in biospecimen (circulating blood or adipose tissue (AT)) were identified from PubMed, EMBASE, and Cochrane Library databases until March 2018. Multivariate-adjusted risk ratios (RRs) with 95% confidence intervals (CIs) were pooled using a random-effect model. Difference in biospecimen proportions of LC n-3 FA between BC cases and non-cases were analyzed as a standardized mean difference (SMD).Results: Thirteen cohort and eleven case-control studies were eligible for the present meta-analysis. The estimated SMD was -0.14 (95% CI: -0.27, -0.11) for LC n-3 FA and -0.27 (95% CI: -0.42, -0.11) for LC n-3/n-6 FA ratio. When comparing the top tertiles with the bottom baseline levels, circulating LC n-3 FA was significantly associated with a lower risk of BC (RR: 0.84, 95% CI: 0.74, 0.96), but not AT (RR: 1.02, 95% CI: 0.70, 1.48). Significant inverse dose-response associations were observed for each 1% increment of circulating 20:5n-3 and 22:6n-3.Conclusion: This meta-analysis highlights that circulating LC n-3 FA as a biomarker of intake may be an independent predictive factor for BC, especially 20:5n-3 and 22:6n-3.

Linoleic Acid in Adipose Tissue and Development of Ischemic Stroke: A Danish Case-Cohort Study

Background

We investigated the association between the content of linoleic acid in adipose tissue, a biomarker of long‐term intake of linoleic acid, and the risk of ischemic stroke and its subtypes.

Methods and Results

The Danish cohort study Diet, Cancer and Health included 57 053 patients aged 50 to 65 years at enrollment. All participants had an adipose tissue biopsy performed at enrollment, while information on ischemic stroke during follow‐up was obtained from the Danish National Patient Register. Stroke diagnoses were all validated and classified according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification. Cases and a randomly drawn subcohort of 3500 patients had their fatty acid composition in adipose tissue determined by gas chromatography. Hazard ratios with 95% confidence intervals were calculated using weighted Cox proportional hazard regression. During 13.5 years of follow‐up, 1879 ischemic stroke cases were identified, for which 1755 adipose biopsies were available, while adipose biopsies were available for 3203 participants in the subcohort. When comparing the highest and the lowest quartiles of adipose tissue content of linoleic acid there was a negative association with the rate of total ischemic stroke (hazard ratio, 0.78; 95% confidence interval, 0.65–0.93) and large artery atherosclerosis (hazard ratio, 0.61; 95% confidence interval, 0.43–0.88), while there was an indication of a negative association with small‐vessel occlusion (hazard ratio, 0.87; 95% confidence interval, 0.69–1.11). There was no clear association with the rate of cardioembolism.

Conclusions

The content of linoleic acid in adipose tissue was inversely associated with the risk of total ischemic stroke and stroke caused by large artery atherosclerosis.

Deep subcutaneous adipose tissue lipid unsaturation associates with intramyocellular lipid content

BACKGROUND

Obese twins have lower saturated and higher long-chain polyunsaturated fatty acids (FA) in subcutaneous adipose tissue (SAT) compared to their lean monozygotic (MZ) co-twin. Whether this holds for metabolically distinct deep (DSAT) and superficial (SSAT) depots is unknown. Here we use non-invasive magnetic resonance spectroscopy (MRS) to measure the FA unsaturation in body mass index (BMI) discordant MZ twins in DSAT and SSAT and their relationship to ectopic fat content and body fat distribution. The main finding is further confirmed in an independent cohort using standardized measurement times.

METHODS

MRS and magnetic resonance imaging were used to measure DSAT and SSAT unsaturation and their relationship to intramyocellular lipids (IMCL), hepatocellular lipids (HCL) and the amount of subcutaneous (SAT) and visceral adipose tissue (VAT) in 16 pairs of healthy monozygotic twins (MZ) discordant for BMI. A second independent cohort of 12 healthy volunteers was used to measure DSAT unsaturation and IMCL with standardized measurement time. One volunteer also underwent repeated random measurements of DSAT unsaturation and IMCL.

RESULTS

In accordance with biopsy studies SSAT unsaturation was higher in the heavier twins (15.2±1.0% vs. 14.4±1.5%, P=0.024) and associated with SAT volume (R=0.672, P=0.001). DSAT unsaturation did not differ between twins (11.4±0.8 vs. 11.0±1.0, P=0.267) and associated inversely with IMCL content (R=-0.462, P=0.001). The inverse association between DSAT unsaturation and IMCL was also present in the participants of the second cohort (R=-0.641, P=0.025) and for the repeated sampling at random of one person (R=-0.765, P=0.027).

CONCLUSIONS

DSAT and SSAT FA unsaturation shows distinct associations with obesity and IMCL in MZ twins, reflecting compartment-specific metabolic activities. The FA unsaturation in the DSAT depot associates inversely with IMCL content, which raises the possibility of cross talk between the DSAT depot and the rapid turnover IMCL depot.

Short- and medium-chain fatty acids in energy metabolism: the cellular perspective

Short- and medium-chain fatty acids (SCFAs and MCFAs), independently of their cellular signaling functions, are important substrates of the energy metabolism and anabolic processes in mammals. SCFAs are mostly generated by colonic bacteria and are predominantly metabolized by enterocytes and liver, whereas MCFAs arise mostly from dietary triglycerides, among them milk and dairy products. A common feature of SCFAs and MCFAs is their carnitine-independent uptake and intramitochondrial activation to acyl-CoA thioesters. Contrary to long-chain fatty acids, the cellular metabolism of SCFAs and MCFAs depends to a lesser extent on fatty acid-binding proteins. SCFAs and MCFAs modulate tissue metabolism of carbohydrates and lipids, as manifested by a mostly inhibitory effect on glycolysis and stimulation of lipogenesis or gluconeogenesis. SCFAs and MCFAs exert no or only weak protonophoric and lytic activities in mitochondria and do not significantly impair the electron transport in the respiratory chain. SCFAs and MCFAs modulate mitochondrial energy production by two mechanisms: they provide reducing equivalents to the respiratory chain and partly decrease efficacy of oxidative ATP synthesis.

Pathways of polyunsaturated fatty acid utilization: implications for brain function in neuropsychiatric health and disease

Essential polyunsaturated fatty acids (PUFAs) have profound effects on brain development and function. Abnormalities of PUFA status have been implicated in neuropsychiatric diseases such as major depression, bipolar disorder, schizophrenia, Alzheimer's disease, and attention deficit hyperactivity disorder. Pathophysiologic mechanisms could involve not only suboptimal PUFA intake, but also metabolic and genetic abnormalities, defective hepatic metabolism, and problems with diffusion and transport. This article provides an overview of physiologic factors regulating PUFA utilization, highlighting their relevance to neuropsychiatric disease.

Use of in vivo magnetic resonance spectroscopy for studying metabolic diseases

Owing to the worldwide obesity epidemic and the sedentary lifestyle in industrialized countries, the number of people with metabolic diseases is explosively increasing. Magnetic resonance spectroscopy (MRS), which is fundamentally similar to magnetic resonance imaging, can detect metabolic changes in vivo noninvasively. With its noninvasive nature, (1)H, (13)C and (31)P MRS are being actively utilized in clinical and biomedical metabolic studies to detect lipids and important metabolites without ionizing radiation. (1)H MRS can quantify lipid content in liver and muscle and can detect other metabolites, such as 2-hydroxyglutarate, in vivo. Of interest, many studies have indicated that hepatic and intramyocellular lipid content is inversely correlated with insulin sensitivity in humans. Thus, lipid content can be utilized as an in vivo biomarker for detecting early insulin resistance. Employing (13)C MRS, hepatic glycogen synthesis and breakdown can be directly detected, whereas (31)P MRS provides in vivo adenosine triphosphate (ATP) synthesis rates by saturation transfer methods in addition to ATP content. These in vivo data can be very difficult to assess by other methods and offer a critical piece of metabolic information. To aid the reader in understanding these new methods, fundamentals of MRS are described in this review in addition to promising future applications of MRS and its limitations.

A novel fatty acid profile index--the lipophilic index--and risk of myocardial infarction

The lipophilic index (LI), a mean measure of fatty acid melting points, has been proposed to capture overall fatty acid profile and may play an important role in the etiology of coronary heart disease. We aimed to determine the association between LI in diet and in adipose tissue and metabolic risk factors for myocardial infarction (MI) and risk of MI. We used a population-based, matched case-control study of nonfatal first acute MI conducted in Costa Rica between 1994 and 2004, with 1,627 case-control pairs. The LI is defined as the mean of the melting points of specific fatty acids in diet or adipose tissue. LIs in diet and adipose tissue were significantly associated with higher plasma triglyceride concentrations, low-density lipoprotein cholesterol concentrations, and low-density:high-density lipoprotein cholesterol ratio. Comparing extreme quintiles for the LI in diet or adipose tissue, the odds ratios for MI were 1.57 (95% confidence interval: 1.22, 2.02; P for trend < 0.001) for dietary LI and 1.30 (95% confidence interval: 1.00, 1.69; P for trend = 0.02) for adipose tissue LI in the multivariable models. We hypothesize that a higher LI in diet and in adipose tissue represents decreased fatty acid fluidity and could play an important role in the etiology of coronary heart disease.

Serum and adipose tissue fatty acid composition as biomarkers of habitual dietary fat intake in elderly men with chronic kidney disease

BACKGROUND

Fatty acid (FA) composition in serum cholesterol esters (CE) and adipose tissue (AT) reflect the long-term FA intake in the general population. Because both dietary intake and FA biomarkers associate with renal function, our aim was to identify which CE and AT FAs are useful biomarkers of habitual FA intake in individuals with chronic kidney disease (CKD).

METHODS

Cross-sectional analysis was performed in 506 men (aged 70 years) with a glomerular filtration rate (GFR) of <60 mL/min per 1.73 m(2) from the Uppsala Longitudinal Study of Adult Men cohort. Dietary habits were evaluated with a 7-day dietary record. FA compositions in CE and AT were analyzed by gas-liquid chromatography in two random subsamples of 248 and 318 individuals, respectively.

RESULTS

Both CE and AT linoleic acid and docosahexaenoic acid (DHA) were strongly associated with their corresponding intake, after adjustments for non-dietary factors. The proportions of eicosapentaenoic acid (EPA) and palmitic acid in CE and AT moderately correlated with dietary intake, whereas correlations of other FAs were weaker or absent. Proportions of EPA and DHA in CE and AT were positively associated with the total energy-adjusted fish intake. Results were confirmed in adequate reporters as identified by the Goldberg cutoff method. These relationships held constant, regardless of a GFR above or below 45 mL/min per 1.73 m(2) or the prevalence of microalbuminuria.

CONCLUSIONS

Proportions of EPA, DHA, palmitic and linoleic acid in serum CE and AT are good indicators of their dietary intake in men with CKD. They can be considered valid biomarkers for epidemiological studies and assessment of compliance.

Ischemic stroke and n-3 fatty acids

The content of fatty acids in subcutaneous adipose tissue was measured to determine whether differences of fatty acids correlate with presence or absence of cerebral infarction in individual patients. Adipose tissue microbiopsies was sampled from 10 patients with computed tomography (CT) verified cerebral infarction and 10 matched control subjects, and assayed for content of fatty acids by gas-liquid chromatographic analysis. There were no differences in levels of n-3 fatty acids of marine origin. Patients with cerebral infarction had statistically significant lower levels of the essential fatty acids linoleic acid (mean+/-SE, 8.9+/-0.4 v 10.7+/-0.5%) (P<.05) and linolenic acid (0.80+/-0.05 v 1.00+/-0.06%) (P<.05) and high levels of palmitoleic acid (8.5+/-0.6% v 5.7+/-0.4%) (P<.005) indicative of increased lipid synthesis de novo, which might explain the depressed levels of fatty acids primarily supplied by the diet. Although significant differences in levels of essential fatty acids were found, no judgment could be made regarding a causal relationship between essential fatty acids and cerebral infarction. The present study does not support the hypothesis of an association between dietary fatty acids (e.g., fish consumption) and ischemic stroke.

Long-TE 1H MRS suggests that liver fat is more saturated than subcutaneous and visceral fat

Cross-talk between adipose tissue and liver is disturbed in the metabolic syndrome. Moreover, the relative fatty acid composition of adipose and liver fat is poorly characterized. Long-TE (1)H MRS can determine the unsaturation and polyunsaturation of adipose tissue. The aim of this study was to use long-TE (1)H MRS to determine the composition of liver fat and its relation to adipose tissue composition. Sixteen subjects with increased liver fat (>5%) were recruited for the study. Using TE = 200  ms, we were able to resolve the olefinic (=CH, 5.3  ppm) and water (H(2)O, 4.7  ppm) resonances in liver spectra and to obtain a repeatable estimate of liver fat unsaturation (coefficient of variation, 2.3%). With TE = 135  ms, the diallylic (=C-CH(2)-C=, 2.8  ppm) resonance was detectable in subjects with a liver fat content above 15%. Long-TE (1)H MRS was also used to determine the unsaturation in subcutaneous (n = 16) and visceral (n = 11) adipose tissue in the same subjects. Liver fat was more saturated (double bonds per fatty acid chain, 0.812 ± 0.022) than subcutaneous (double bonds per fatty acid chain, 0.862 ± 0.022, p < 0.0004) or visceral (double bonds per fatty acid chain, 0.865 ± 0.033, p < 0.0004) fat. Liver fat unsaturation correlated with subcutaneous unsaturation (R = 0.837, p < 0.0001) and visceral unsaturation (R = 0.879, p < 0.0004). The present study introduces a new noninvasive method for the assessment of the composition of liver fat. The results suggest that liver fat is more saturated than subcutaneous or visceral adipose tissue, which may be attributed to differences in de novo lipogenesis.

Maternal dietary fat intake during gestation and lactation alters tissue fatty acid composition in the adult offspring of C57Bl/6 mice

We investigated the effects of maternal dietary fat intake during gestation and lactation on the tissue fatty acid composition of the adult offspring. Female C57Bl/6 mice were fed high fat diets enriched with lard or safflower oil or chow during mating, gestation and lactation. The offspring obtained from each group of mothers were continued on diets rich in lard, safflower oil or chow post-weaning until 11 weeks of age. Livers and hearts were collected for fatty acid analysis. A maternal diet rich in safflower oil was associated with enrichment of hepatic tissue with n-3 polyunsaturated fatty acids in the offspring fed chow post-weaning compared to the offspring fed chow throughout. However, a continuous exposure to a safflower oil- as well as lard-rich diet during the pre- and post-weaning time periods was associated with reduced content of docosahexaenoic acid in both liver and heart tissues compared to the offspring fed chow throughout. In conclusion, this study demonstrated lasting effects of maternal dietary fat intake, as well as an interaction between pre- and post-weaning diets, on the tissue fatty composition in adult offspring.

Characterizing human adipose tissue lipids by long echo time 1H-MRS in vivo at 1.5 Tesla: validation by gas chromatography

The aim of this study was to investigate the use of (1)H-MRS with various echo times to characterize subcutaneous human adipose tissue (SAT) triglyceride composition and to validate the findings with fatty acid (FA) analysis of SAT biopsies by gas chromatography (GC). (1)H-MRS spectra were acquired with a 1.5 Tesla clinical imager from the SAT of 17 healthy volunteers, with 10 undergoing SAT biopsy. Spectra were localized with PRESS and a series of echo times; 30, 50, 80, 135, 200, 300 and 540 ms were acquired with TR = 3000 ms. Prior knowledge from phantom measurements was used to construct AMARES fitting models for the lipid spectra. SAT FA composition were compared with serum lipid levels and subject characteristics in 17 subjects.Long TE (135, 200 ms) spectra corresponded better with the GC data than short TE (30, 50 ms) spectra. TE = 135 ms was found optimal for determining diallylic content (R = 0.952, p < 0.001) and TE = 200 ms was optimal for determining olefinic content (R = 0.800, p < 0.01). The improved performance of long TE spectra is a result of an improved baseline and better peak separation, due to J-modulation and suppression of water. The peak position of the diallylic resonance correlated with the average double bond content of polyunsatured fatty acids with R = 0.899 (p < 0.005). The apparent T(2) of the methylene resonance displayed relatively small inter-individual variation, 88.1 +/- 1.1 ms (mean +/- SD). The outer methyl triplet line of omega-3 PUFA at 1.08 ppm could be readily detected and quantitated from spectra obtained at TE = 540. The omega-3 resonance correlated with the omega-3 content determined by GC with R = 0.737 (p < 0.05, n = 8). Age correlated significantly with SAT diallylic content (R = 0.569, p = 0.017, n = 17), but serum lipid levels showed no apparent relation to SAT FA composition. We conclude that long TE (1)H-MRS provides a robust non-invasive method for characterizing adipose tissue triglycerides in vivo.

A minimal model for hepatic fatty acid balance during fasting: application to PPAR alpha-deficient mice

The purpose of this study is to identify the hierarchy of importance amongst pathways involved in fatty acid (FA) metabolism and their regulators in the control of hepatic FA composition. A modeling approach was applied to experimental data obtained during fasting in PPARalpha knockout (KO) mice and wild-type mice. A step-by-step procedure was used in which a very simple model was completed by additional pathways until the model fitted correctly the measured quantities of FA in the liver. The resulting model included FA uptake by the liver, FA oxidation, elongation and desaturation of FA, which were found active in both genotypes during fasting. From the model analysis we concluded that PPARalpha had a strong effect on FA oxidation. There were no indications that this effect changes during the fasting period, and it was thus considered to be constant. In PPARalpha KO mice, FA uptake was identified as the main pathway responsible for FA variation in the liver. The models showed that FA were oxidized at a constant and small rate, whereas desaturation of FA also occurred during fasting. The latter observation was rather unexpected, but was confirmed experimentally by the measurement of delta-6-desaturase mRNA using real-time quantitative PCR (QPCR). These results confirm that mathematical models can be a useful tool in identifying new biological hypotheses and nutritional routes in metabolism.

N-6 from different sources protect from metabolic alterations to obese patients: a factor analysis

First, to analyze the interactions among fatty acids (FAs) from diet, plasma and subcutaneous and visceral adipose tissue (AT), and second, the relationship among FAs from these different sources and obesity-related alterations in extreme obesity. We studied 20 extreme obese subjects. A food-frequency questionnaire was used to determine the FA intakes. Serum and AT (subcutaneous and visceral) FA concentrations were determined by gas chromatography. Cardiometabolic risk parameters were assessed. Principal factor analysis was performed to define specific FA factors in the metabolic alterations. We found important associations among diet, plasma, and AT FA and cardiometabolic parameters. In this regard, it is interesting to highlight the negative associations between plasma cholesterol and dietary n-3 FA. In the subcutaneous depot, as occurred in plasma, n-6 and polyunsaturated FAs (PUFA) were negatively associated with triacylglycerols (TGs). Factor analysis revealed TGs as the unique cardiovascular risk parameter appearing in the first factor (F1), together with n-6 (load factor = 0.94) and PUFA (0.91). Besides, n-3 from diet and plasma appeared in the third factor inversely related to cholesterol, low-density lipoprotein cholesterol (LDL-c), and insulin. In an opposite way, dietary and AT trans FAs and saturated FA (SFA) were associated to an increase of the metabolic risk. We have shown, for the first time, the importance of n-6 and PUFAs composition as protective factors against metabolic alterations in extreme obese subjects. These findings support current dietary recommendations to increase PUFA intakes and restrict saturated and trans FA intakes even in extreme obesity.

Inflammation and skin cholesterol in LDLr-/-, apoA-I-/- mice: link between cholesterol homeostasis and self-tolerance?

Diet-fed low density lipoprotein receptor-deficient/apolipoprotein A-I-deficient (LDLr-/-, apoA-I-/-) mice accumulate a 10-fold greater mass of cholesterol in their skin despite a 1.5- to 2-fold lower plasma cholesterol concentration compared with diet-fed LDLr-/- mice. The accumulation of cholesterol predominantly in the skin has been shown to occur in a growing number of other hypercholesterolemic double knockout mouse models sharing deficits in genes regulating cellular cholesterol homeostasis. Exploring the relationship between cholesterol balance and inflammation, we have examined the time course of cholesterol accumulation in a number of extrahepatic tissues and correlated with the onset of inflammation in diet-fed LDLr-/-, apoA-I-/- mice. After 4 weeks of diet, LDLr-/-, apoA-I-/- mice showed a significant increase in skin cholesterol mass compared with LDLr-/- mice. In addition, after 4 weeks on the diet, cholesterol accumulation in the skin was also found to be associated with macrophage infiltration and accompanied by increases in tumor necrosis factor-alpha, cyclooxygenase-2, and langerin mRNA, which were not seen in the liver. Overall, these data suggest that as early as 4 weeks after starting the diet, the accumulation of skin cholesterol and the onset of inflammation occur concurrently. In summary, the use of hypercholesterolemic LDLr-/-, apoA-I-/- mice may provide a useful tool to investigate the role that apoA-I plays in maintaining cholesterol homeostasis and its relationship to inflammation.

Upregulated liver conversion of alpha-linolenic acid to docosahexaenoic acid in rats on a 15 week n-3 PUFA-deficient diet

We quantified incorporation rates of plasma-derived alpha-linolenic acid (alpha-LNA, 18:3n-3) into "stable" liver lipids and the conversion rate of alpha-LNA to docosahexaenoic acid (DHA, 22:6n-3) in male rats fed, after weaning, an n-3 PUFA-adequate diet (4.6% alpha-LNA, no DHA) or an n-3 PUFA-deficient diet (0.2% alpha-LNA, no DHA) for 15 weeks. Unanesthetized rats were infused intravenously with [1-14C]alpha-LNA, and arterial plasma was sampled until the liver was microwaved at 5 min. Unlabeled alpha-LNA and DHA concentrations in arterial plasma and liver were reduced >90% by deprivation, whereas unlabeled arachidonic acid (20:4n-6) and docosapentaenoic acid (22:5n-6) concentrations were increased. Deprivation did not change alpha-LNA incorporation coefficients into stable liver lipids but increased synthesis-incorporation coefficients of DHA from alpha-LNA by 6.6-, 8.4-, and 2.3-fold in triacylglycerol, phospholipid, and cholesteryl ester, respectively. Assuming that synthesized-incorporated DHA eventually would be secreted within lipoproteins, calculated liver DHA secretion rates equaled 2.19 and 0.82 micromol/day in the n-3 PUFA-adequate and -deprived rats, respectively. These rates exceed the published rates of brain DHA consumption by 6- and 10-fold, respectively, and should be sufficient to maintain normal and reduced brain DHA concentrations, respectively, in the two dietary conditions.

Fasting whole blood as a biomarker of essential fatty acid intake in epidemiologic studies: comparison with adipose tissue and plasma

Biomarkers could provide a more accurate measure of long-term intake than questionnaires. Adipose tissue is considered the best indicator of long-term essential fatty acid intake, but other tissues may prove equally valid. The authors evaluated the ability of fasting whole blood, relative to fasting plasma and adipose tissue, to reflect fatty acid intake. Costa Rican men (n = 99) and women (n = 101) completed a 135-item food frequency questionnaire and provided adipose tissue and blood samples from 1999 to 2001. Fatty acids were identified by using capillary gas chromatography. Correlation coefficients adjusted for age, sex, and body mass index were calculated. Diet-tissue correlation coefficients for alpha-linolenic acid and linoleic acid, respectively, were 0.38 and 0.43 in whole blood, 0.51 and 0.52 in adipose tissue, and 0.39 and 0.41 in plasma. High correlations were observed between whole-blood alpha-linolenic and linoleic acid and adipose tissue (r = 0.59 and r = 0.67) and plasma (r = 0.96 and r = 0.88), respectively. Results show that fasting whole blood is a suitable biomarker of long-term essential fatty acid intake, and its performance is comparable to that of fasting plasma. Thus, fasting whole blood could be the sample of choice in epidemiologic studies because of its ability to predict intake, its accessibility, and minimum sample processing.

Changes in adipose tissue gene expression with energy-restricted diets in obese women

BACKGROUND

The effect of energy restriction and macronutrient composition on gene expression in adipose tissue is not well defined.

OBJECTIVE

The aim of the study was to investigate the effect of different low-energy diets on gene expression in human adipose tissue.

DESIGN

Forty obese women were randomly assigned to a moderate-fat, moderate-carbohydrate diet or a low-fat, high-carbohydrate hypoenergetic (-600 kcal/d) diet for 10 wk. Subcutaneous adipose tissue samples were obtained before and after the diet period. High-quality RNA samples were obtained from 23 women at both time points, and these samples were hybridized to microarrays containing the 8500 most extensively described human genes. The results were confirmed by separate messenger RNA measurements.

RESULTS

Both diets resulted in weight losses of approximately 7.5% of baseline body weight. A total of 52 genes were significantly up-regulated and 44 were down-regulated as a result of the intervention, and no diet-specific effect was observed. No major effect on lipid-specific transcription factors or genes regulating signal transduction, lipolysis, or synthesis of acylglycerols was observed. Most changes were modest (<25% of baseline), but all genes regulating the formation of polyunsaturated fatty acids from acetyl-CoA and malonyl-CoA were markedly down-regulated (35-60% decrease).

CONCLUSIONS

Macronutrients have a secondary role in changes in adipocyte gene expression after energy-restricted diets. The most striking alteration after energy restriction is a coordinated reduction in the expression of genes regulating the production of polyunsaturated fatty acids.

Effects of exercise on the fatty-acid composition of blood and tissue lipids

This article reviews the effects of acute and chronic exercise on the fatty-acid composition of animal and human tissues (plasma, skeletal muscle, heart, adipose tissue, liver, artery and erythrocytes), as reported in 68 studies spanning four decades. The most consistently observed effect has been an increase in the relative amount of unsaturated, especially monounsaturated, non-esterified fatty acids in plasma of both animals and humans after acute exercise. Chronic exercise seems to increase the proportion of polyunsaturated fatty acids and omega6 fatty acids, while decreasing the proportion of monounsaturated fatty acids in animal and human adipose tissue. Additionally, chronic exercise seems to decrease the relative amount of unsaturated fatty acids in liver lipids of animals and humans. There is no consensus regarding the effect of exercise on the fatty-acid composition of lipids in any other tissue. In general, the effects of exercise are independent of nutrition and, regarding skeletal muscle, muscle fibre type. The available literature shows that, in addition to modifying the concentrations of animal and human tissue lipids, exercise also changes their fatty-acid profile. Unfortunately, the available studies are so much divided among exercise models, species and biological samples that a cohesive picture of the plasticity of the fatty-acid pattern of most tissues toward exercise has not emerged. Future studies should focus on determining the fatty-acid profile of separate lipid classes (rather than total lipids) in separate subcellular fractions (rather than whole tissues), examining tissues and organs on which no data are available and exploring the mechanisms of the exercise-induced changes in fatty-acid composition.

Arachidonic acid in adipose tissue is associated with nonfatal acute myocardial infarction in the central valley of Costa Rica

Arachidonic acid (AA), a precursor of prothrombotic eicosanoids, is potentially atherogenic, but epidemiologic data are scarce. We evaluated the hypothesis that increased AA in adipose tissue is associated with increased risk of nonfatal acute myocardial infarction (MI), and if so, whether this association is related to dietary or adipose tissue linoleic acid. We studied the association between AA and MI in 466 cases of a first nonfatal acute MI, matched on age, gender, and residence to 466 population controls. Fatty acids (FA) were assessed by GC in adipose tissue samples collected from all subjects. Odds ratios (OR) and 95% CI were calculated from multivariate conditional logistic regression models. Subjects in the highest quintile of adipose tissue AA (0.64% of total FA) had a higher risk of nonfatal acute MI than those in the lowest quintile (0.29% of total FA), after adjusting for potential confounders including (n-3) and trans FAs (OR = 1.94, 95% CI: 1.07, 3.53, P for trend = 0.026). Adipose tissue AA was not correlated with dietary AA (r = 0.07), linoleic acid (r = 0.04), or other dietary (n-6) FAs, or with adipose tissue linoleic acid (r = -0.07). These data suggest that the association between MI and adipose tissue AA is not related to dietary intake of (n-6) FAs including linoleic acid. Better understanding of the metabolic factors that increase AA in adipose tissue is urgently needed.

In vivo characterization of fatty acids in human adipose tissue using natural abundance 1H decoupled 13C MRS at 1.5 T: clinical applications to dietary therapy

Natural abundance proton-decoupled (13)C magnetic resonance spectroscopy was used to establish the in vivo lipid composition of normal adipose tissue and the corresponding effects of altered lipid diets. Experiments were performed on a standard 1.5 T clinical MR scanner using a double-tuned (1)H-(13)C coil. Peaks from double-bonded and methylene carbons were analyzed. Normal lipid composition was established in 20 control subjects. For comparison, five subjects on altered lipid diets were studied. Four subjects were on a fish oil supplement diet or predominantly seafood diet (polyunsaturated fatty acids), and one subject was on a Lorenzo's oil diet (monounsaturated fatty acids). Well-resolved (13)C spectra were obtained from the calf adipose tissue with a total acquisition time of 10 min. Model oil solutions were used to identify specific (13)C resonances. Subjects on lipid diets showed significantly elevated levels of monounsaturated and polyunsaturated fatty acids for Lorenzo's and fish oil diets, respectively. We conclude that (13)C MR spectroscopy can readily detect changes in lipid composition due to medium- and long-term therapeutic lipid diets. Since the examination is rapid, robust and noninvasive, opportunities arise for large clinical trials of preventive or therapeutic diets to be performed with (13)C MRS on a clinical MR scanner.

n-3 Polyunsaturated fatty acids, fatal ischemic heart disease, and nonfatal myocardial infarction in older adults: the Cardiovascular Health Study

BACKGROUND

Little is known about the relation of the dietary intake of n-3 polyunsaturated fatty acids, ie, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) from fatty fish and alpha-linolenic acid from vegetable oils, with ischemic heart disease among older adults.

OBJECTIVE

We investigated the associations of plasma phospholipid concentrations of DHA, EPA, and alpha-linolenic acid as biomarkers of intake with the risk of incident fatal ischemic heart disease and incident nonfatal myocardial infarction in older adults.

DESIGN

We conducted a case-control study nested in the Cardiovascular Health Study, a cohort study of adults aged > or = 65 y. Cases experienced incident fatal myocardial infarction and other ischemic heart disease death (n = 54) and incident nonfatal myocardial infarction (n = 125). Matched controls were randomly selected (n = 179). We measured plasma phospholipid concentrations of n-3 polyunsaturated fatty acids in blood samples drawn approximately 2 y before the event.

RESULTS

A higher concentration of combined DHA and EPA was associated with a lower risk of fatal ischemic heart disease, and a higher concentration of alpha-linolenic acid with a tendency to lower risk, after adjustment for risk factors [odds ratio: 0.32 (95% CI: 0.13, 0.78; P = 0.01) and 0.52 (0.24, 1.15; P = 0.1), respectively]. In contrast, n-3 polyunsaturated fatty acids were not associated with nonfatal myocardial infarction.

CONCLUSIONS

Higher combined dietary intake of DHA and EPA, and possibly alpha-linolenic acid, may lower the risk of fatal ischemic heart disease in older adults. The association of n-3 polyunsaturated fatty acids with fatal ischemic heart disease, but not with nonfatal myocardial infarction, is consistent with possible antiarrhythmic effects of these fatty acids.

Adipose tissue biomarkers of fatty acid intake

BACKGROUND

Biomarkers can provide a more accurate measure of long-term intake than can dietary questionnaires.

OBJECTIVE

The objective was to identify which adipose tissue fatty acids are suitable biomarkers of intake as assessed with a validated food-frequency questionnaire.

DESIGN

Costa Rican men with a mean (+/- SD) age of 56 +/- 11 y (n = 367) and women aged 60 +/- 10 y (n = 136) completed a 135-item food-frequency questionnaire and provided an adipose tissue sample. Fifty fatty acids were identified by capillary gas chromatography. Correlation coefficients were calculated after adjustment for age, sex, body mass index, and smoking status.

RESULTS

The best adipose tissue marker for total intake of saturated fatty acids was 15:0 + 17:0 (r = 0.18). Both 15:0 and 17:0 were also the best correlates of dairy product intake (r = 0.31 for each). The diet-adipose tissue correlations for n-3 fatty acids were r = 0.34 for 18:3, r = 0.15 for 20:5, and r = 0.18 for 22:6. Fish intake correlated significantly with these adipose tissue n-3 fatty acids. Dietary and adipose tissue n-6 fatty acids were highly correlated: 18:2 (r = 0.58) and 18:3 (r = 0.24). The best indicators of total trans fatty acid intake were ct18:2n-6 and tc18:2n-6 (r = 0.58 for each); total 18:1 trans fatty acid (r = 0.45) and 16:1 trans fatty acid (r = 0.16) were the next best indicators.

CONCLUSIONS

Adipose tissue is a suitable biomarker of dietary fatty acid intake, particularly for n-3 and n-6 cis polyunsaturated fatty acids and trans fatty acids. Ideally, adipose tissue and dietary questionnaires should complement, rather than substitute for, each other in epidemiologic studies.

Adipose fat quality vs. quantity: relationships with children's serum lipid levels

BACKGROUND

There is a controversy as to the relative importance of obesity vs quality of dietary fat in the prediction of serum lipoproteins in children. A reason for this is an apparent lack of studies implementing biomarkers of long-term dietary fat intake among children. The objective of the present study was to assess the relative contribution of degree of obesity, fat centrality, and quality of adipose tissue fat in the prediction of serum lipids in 12-year-old children.

METHODS

Pupils came from 40 schools randomly selected among 541 primary schools in three different provinces of the island of Crete. One thousand forty-six pupils were examined at age 6. At age 9, a representative sample from the original cohort (n = 579) was randomly selected for reevaluation. At the age of 12, a representative sample of 831 pupils was reexamined. At ages 6, 9, and 12, serum lipid measures were obtained from 941, 458, and 791 children, respectively. At age 12, data were obtained on pupils' anthropometry, serum lipids, dietary intake, physical fitness, and physical activity. Adipose tissue fatty acid data were obtained from a subsample of 194 children at age 12.

RESULTS

Regression analyses indicated that children's serum triglycerides related positively to body mass index and waist-hip ratio (WHR). Serum HDL-C related negatively to WHR and positively to endurance run test, an index of physical fitness. Dietary fatty acids, assessed by a single administration of 3-day weighed-food records, did not relate to serum lipids. However, serum HDL-C related negatively to sum of adipose polyunsaturated fatty acids, a measure of long-term polyunsaturated fat intake.

CONCLUSIONS

It appears that obesity and fat centrality are stronger predictors of children's serum lipids than the quality of long-term dietary fat intake or adipose tissue fatty acid composition. It is possible that this finding may relate to the particular subcutaneous depot studied. It is suggested that future studies study abdominal rather than buttock adipose tissue fatty acid composition in relation to children's serum lipid levels.

Single measurement of serum phospholipid fatty acid as a biomarker of specific fatty acid intake in middle-aged Japanese men

OBJECTIVE

To assess the utility of serum phospholipid fatty acid (FA) levels as a biochemical indicator of habitual dietary fatty acid intake in Japanese, whose diet is characterized by low fat intake and high intake of n-3 polyunsaturated fatty acids (PUFA) of marine origin.

SUBJECTS AND METHODS

Eighty-seven male volunteers from four public health center districts that were part of the Japan Public Health Center based Prospective Study (JPHC Study) cohort I, were included in this study. Habitual intake of fatty acid was obtained by 7 day weighed dietary records four times (in one area only twice) in 1994--1995. Blood was collected twice, in February and August of the same year, and the composition of FA in serum phospholipid was analyzed by gas chromatography. The correlation coefficient between serum phospholipid FA levels and fatty acid intake was calculated.

RESULTS

High correlations were observed for eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA), which are marine origin n-3 PUFA (r=0.75, 0.49, 0.50, respectively). No significant correlation was observed for saturated fatty acid (SFA), although the monounsaturated fatty acid (MUFA), palmitoleic acid and oleic acid intake were moderately correlated (r=0.22, 0.35, respectively). The correlations for EPA, DPA and DHA were similar in both samples collected in February and August.

CONCLUSIONS

These data suggest that in populations with a high and stable over time intake of n-3 PUFA of marine origin, a single measurement of serum phospholipids reflects the ranking of habitual intake of marine origin n-3 PUFA.

High serum coenzyme Q10, positively correlated with age, selenium and cholesterol, in Inuit of Greenland. A pilot study

Greenlanders (Eskimos) have low prevalence of ischaemic heart disease, partly explained by a lower extent of atherosclerosis and a low n-6/n-3 ratio of polyunsaturated fatty acids. As atherosclerosis is also a result of oxidative stress, the total antioxidative readiness could have a substantial impact. From a health survey we chose the subpopulation from the most remote area, where the traditional Greenlandic diet with high intake of sea mammals and fish predominates. The mean (SD) of S-CoQ10 in males was 1.495 (0.529) nmol/ml and 1.421 (0.629) nmol/ml in females, significantly higher (p < 0.001) compared to a Danish population. In a linear multiple regression model the S-CoQ10 level is significantly positively associated with age and S-selenium in males, and S-total cholesterol in females. The high level of CoQ10 in Greenlanders probably reflects diet, since no bioaccumulation takes place, and it could probably be a substantial part of the antioxidative defense.