Plasma Fatty Acid Biomarkers of Dairy Consumption Are Associated with Sex-Dependent Effects on Metabolic Syndrome Components in Mexican Adolescents.

INTRODUCTION: During adolescence, dairy product intake has shown conflicting associations with metabolic syndrome (MetS) components, which are risk factors for cardiovascular disease (CVD). This study aims to investigate the association between plasma fatty acids (FAs) C15:0, C17:0, and t-C16:1n-7, as biomarkers of dairy intake, with MetS and its components in Mexican adolescents. METHODS: A sample of 311 participants from the Early Life Exposure in Mexico City to Environmental Toxicants (ELEMENT) cohort was included in this cross-sectional analysis. FA concentrations were measured in plasma as a percentage of total FA. We used quantile regression models stratified by sex to evaluate the association between FA quantiles and MetS components, adjusting for age, socioeconomic status (SES), sedentary behavior, BMI z-score, pubertal status, and energy intake. RESULTS: We found significant associations between dairy biomarkers and the median of MetS variables. In females, t-C16:1n-7 was associated with a decrease of 2.97 cm in WC (Q4 vs. Q1; 95% CI: -5.79, -0.16). In males, C15:0 was associated with an increase of 5.84 mm/Hg in SBP (Q4 vs. Q1; CI: 1.82, 9.85). For HDL-C, we observed opposite associations by sex. C15:0 in males was associated with decreased HDL-C (Q3 vs. Q1: ß = -4.23; 95% CI: -7.98, -0.48), while in females, C15:0 and t-C16:1n-7 were associated with increased HDL-C (Q3 vs. Q1: ß = 4.75; 95% CI: 0.68, 8.82 and Q4 vs. Q1: ß = 6.54; 95% CI: 2.01, 11.07), respectively. Additionally, in both sexes, different levels of C15:0, C17:0, and t-C16:1n-7 were associated with increased triglycerides (TG). CONCLUSION: Our results suggest that adolescent dairy intake may be associated in different directions with MetS components and that associations are sex-dependent.

Trans-palmitoleic acid does not modify the inflammasome expression in a rodent model of diet-induced obesity.

BACKGROUND: Metabolic disorders such as obesity and type 2 diabetes (T2D) coincide with an increased expression of pro-inflammatory factors. The NLRP3 inflammasome is a complex that activates the pro-inflammatory cytokine IL-1ß. (NOD-like receptor protein 3). Some nutrients, such as fatty acids, influence inflammatory processes. For example, in clinical studies, higher trans-palmitoyl acid (TP) concentrations coincide with lower adiposity and lower risk of developing T2D. This study aims to evaluate the effect of TP on NLRP3 expression in a rodent model of diet-induced obesity (DIO). METHODS: C57BL/6J mice were fed ad libitum with a control or a high-fat diet (HFD), added with or without TP (3 g/kg diet), for 11 weeks. IL-1ß was quantified in serum, and NLRP3-related gene expression was explored in epididymal adipose tissue. RESULTS: Despite increased weight gain in both high-fat groups, the high-fat TP group gained less weight than the high-fat group. In addition, NLRP3 and caspase-1 expression was higher in the HFD groups, but no differences were observed between the HFD and the HFD TP groups. Serum IL-1ß levels were not different among groups. CONCLUSIONS: Diet supplementation with TP prevents weight gain and has a neutral influence over NLRP3 expression and IL-1ß concentration in a DIO mice model.

INTRODUCCIÓN: Las alteraciones metabólicas como la obesidad y diabetes tipo 2 (DT2) coinciden con la expresión aumentada de factores proinflamatorios. Un complejo que induce la activación de la citocina proinflamatoria IL-1ß es el inflamasoma NLRP3 (NOD-like receptor protein 3). Algunos nutrimentos, como los ácidos grasos, influencian los procesos inflamatorios. Por ejemplo, en estudios clínicos, mayores concentraciones del ácido trans-palmitoléico (TP) coinciden con una menor adiposidad y un menor riesgo de desarrollar DT2. El objetivo de este estudio fue evaluar el efecto del TP sobre la expresión del inflamasoma NLRP3 en un modelo de obesidad inducida por dieta (OID) en roedores. MÉTODOS: Se alimentaron ratones C57BL/6J ad libitum con una dieta control o alta en lípidos (AL), adicionada o no con TP (3 g/kg dieta), durante 11 semanas. Se cuantificó la concentración de IL-1ß en elsuero de los animales, y en el tejido adiposo epididimal se midió la expresión de los componentes del inflamasoma. RESULTADOS: A pesar del aumento de peso en ambos grupos de dieta con alto contenido en lípidos, el grupo alto en lípidos TP ganó menos peso que el grupo AL. Por otro lado, la expresión de genes del inflamasoma resultó mayor en los grupos AL, pero no se encontraron diferencias entre los grupos AL y AL TP. Además, no se observaron diferencias en la concentración de IL-1ß en suero entre grupos. CONCLUSIONES: La dieta suplementada con TP previno el aumento del peso corporal, pero no modificó la expresión de los componentes del inflamasoma ni la concentración de IL-1ß en suero.

Trans-palmitoleic acid does not modify the inflammasome expression in a rodent model of diet-induced obesity / El ácido trans-palmitoléico no modifica la expresión del inflamasoma en un modelo murino de obesidad inducida por dieta

Abstract Background: Metabolic disorders such as obesity and type 2 diabetes (T2D) coincide with an increased expression of pro-inflammatory factors. The NLRP3 inflammasome is a complex that activates the pro-inflammatory cytokine IL-1β. (NOD-like receptor protein 3). Some nutrients, such as fatty acids, influence inflammatory processes. For example, in clinical studies, higher trans-palmitoyl acid (TP) concentrations coincide with lower adiposity and lower risk of developing T2D. This study aims to evaluate the effect of TP on NLRP3 expression in a rodent model of diet-induced obesity (DIO). Methods: C57BL/6J mice were fed ad libitum with a control or a high-fat diet (HFD), added with or without TP (3 g/kg diet), for 11 weeks. IL-1β was quantified in serum, and NLRP3-related gene expression was explored in epididymal adipose tissue. Results: Despite increased weight gain in both high-fat groups, the high-fat TP group gained less weight than the high-fat group. In addition, NLRP3 and caspase-1 expression was higher in the HFD groups, but no differences were observed between the HFD and the HFD TP groups. Serum IL-1β levels were not different among groups. Conclusions: Diet supplementation with TP prevents weight gain and has a neutral influence over NLRP3 expression and IL-1β concentration in a DIO mice model.

Resumen Introducción: Las alteraciones metabólicas como la obesidad y diabetes tipo 2 (DT2) coinciden con la expresión aumentada de factores proinflamatorios. Un complejo que induce la activación de la citocina proinflamatoria IL-1β es el inflamasoma NLRP3 (NOD-like receptor protein 3). Algunos nutrimentos, como los ácidos grasos, influencian los procesos inflamatorios. Por ejemplo, en estudios clínicos, mayores concentraciones del ácido trans-palmitoléico (TP) coinciden con una menor adiposidad y un menor riesgo de desarrollar DT2. El objetivo de este estudio fue evaluar el efecto del TP sobre la expresión del inflamasoma NLRP3 en un modelo de obesidad inducida por dieta (OID) en roedores. Métodos: Se alimentaron ratones C57BL/6J ad libitum con una dieta control o alta en lípidos (AL), adicionada o no con TP (3 g/kg dieta), durante 11 semanas. Se cuantificó la concentración de IL-1β en elsuero de los animales, y en el tejido adiposo epididimal se midió la expresión de los componentes del inflamasoma. Resultados: A pesar del aumento de peso en ambos grupos de dieta con alto contenido en lípidos, el grupo alto en lípidos TP ganó menos peso que el grupo AL. Por otro lado, la expresión de genes del inflamasoma resultó mayor en los grupos AL, pero no se encontraron diferencias entre los grupos AL y AL TP. Además, no se observaron diferencias en la concentración de IL-1β en suero entre grupos. Conclusiones: La dieta suplementada con TP previno el aumento del peso corporal, pero no modificó la expresión de los componentes del inflamasoma ni la concentración de IL-1β en suero.

Can individual fatty acids be used as functional biomarkers of dairy fat consumption in relation to cardiometabolic health? A narrative review.

In epidemiological studies, dairy food consumption has been associated with minimal effect or decreased risk of some cardiometabolic diseases (CMD). However, current methods of dietary assessment do not provide objective and accurate measures of food intakes. Thus, the identification of valid and reliable biomarkers of dairy product intake is an important challenge to best determine the relationship between dairy consumption and health status. This review investigated potential biomarkers of dairy fat consumption, such as odd-chain, trans- and branched-chain fatty acids (FA), which may improve the assessment of full-fat dairy product consumption. Overall, the current use of serum/plasma FA as biomarkers of dairy fat consumption is mostly based on observational evidence, with a lack of well-controlled, dose-response intervention studies to accurately assess the strength of the relationship. Circulating odd-chain SFA and trans-palmitoleic acid are increasingly studied in relation to CMD risk and seem to be consistently associated with a reduced risk of type 2 diabetes in prospective cohort studies. However, associations with CVD are less clear. Overall, adding less studied FA such as vaccenic and phytanic acids to the current available evidence may provide a more complete assessment of dairy fat intake and minimise potential confounding from endogenous synthesis. Finally, the current evidence base on the direct effect of dairy fatty acids on established biomarkers of CMD risk (e.g. fasting lipid profiles and markers of glycaemic control) mostly derives from cross-sectional, animal and in vitro studies and should be strengthened by well-controlled human intervention studies.

Trans-palmitoleic acid reduces adiposity via increased lipolysis in a rodent model of diet-induced obesity.

Obesity is defined as increased adiposity, which leads to metabolic disease. The growth of adipose tissue depends on its capacity to expand through hyperplasia or hypertrophy, in order to buffer energy surplus. Also, during the establishment of obesity, adipose tissue expansion reflects adipose lipid metabolism (lipogenesis and/or lipolysis). It is well known that dietary factors can modify lipid metabolism promoting or preventing the development of metabolic abnormalities that concur with obesity. Trans-palmitoleic acid (TP), a biomarker of dairy consumption, has been associated with reduced adiposity in clinical studies. Thus, we aimed to evaluate the effect of TP over adiposity and lipid metabolism-related genes in a rodent model of diet-induced obesity (DIO). To fulfil this aim, we fed C57BL/6 mice with a Control or a High-Fat diet, added with or without TP (3 g/kg diet), during 11 weeks. Body weight and food intake were monitored, fat pads were weighted, histology of visceral adipose tissue was analysed and lipid metabolism-related gene expression was explored by qPCR. Results show that TP consumption prevented weight gain induced by high-fat diet, reduced visceral adipose tissue weight and adipocyte size, while increasing the expression of lipolytic molecules. In conclusion, we show for the first time that TP influences adipose tissue metabolism, specifically lipolysis, resulting in decreased adiposity and reduced adipocyte size in a DIO mice model.

Cis- and Trans-Palmitoleic Acid Isomers Regulate Cholesterol Metabolism in Different Ways.

Hypercholesterolemia is a preventable risk factor for atherosclerosis and cardiovascular disease. However, the mechanisms whereby cis-palmitoleic acid (cPOA) and trans-palmitoleic acid (tPOA) promote cholesterol homeostasis and ameliorate hypercholesterolemia remain elusive. To investigate the effects of cPOA and tPOA on cholesterol metabolism and its mechanisms, we induced hypercholesterolemia in mice using a high-fat diet and then intragastrically administered cPOA or tPOA once daily for 4 weeks. tPOA administration reduced serum cholesterol, low-density lipoprotein, high-density lipoprotein, and hepatic free cholesterol and total bile acids (TBAs). Conversely, cPOA had no effect on these parameters except for TBAs. Histological examination of the liver, however, revealed that cPOA ameliorated hepatic steatosis more effectively than tPOA. tPOA significantly reduced the expression of 3-hydroxy-3-methyl glutaryl coenzyme reductase (HMGCR), LXRα, and intestinal Niemann-Pick C1-Like 1 (NPC1L1) and increased cholesterol 7-alpha hydroxylase (CYP7A1) in the liver, whereas cPOA reduced the expression of HMGCR and CYP7A1 in the liver and had no effect on intestinal NPC1L1. In summary, our results suggest that cPOA and tPOA reduce cholesterol synthesis by decreasing HMGCR levels. Furthermore, tPOA, but not cPOA, inhibited intestinal cholesterol absorption by downregulating NPC1L1. Both high-dose tPOA and cPOA may promote the conversion of cholesterol into bile acids by upregulating CYP7A1. tPOA and cPOA prevent hypercholesterolemia via distinct mechanisms.

Supplementation with Seabuckthorn Oil Augmented in 16:1n-7t Increases Serum Trans-Palmitoleic Acid in Metabolically Healthy Adults: A Randomized Crossover Dose-Escalation Study.

BACKGROUND: In animal models cis-palmitoleic acid (9-hexadecenoic acid; 16:1n-7c), a lipokine, improves insulin sensitivity, inflammation, and lipoprotein profiles; in humans trans-palmitoleic acid (16:1n-7t) has been associated with lower incidence of type 2 diabetes. The response to dose-escalation of supplements containing cis- and trans-palmitoleic acid has not been evaluated. OBJECTIVES: We examined dose-escalation effects of oral supplementation with seabuckthorn oil and seabuckthorn oil augmented in 16:1n-7t on serum phospholipid fatty acids (PLFAs). METHODS: Thirteen participants (7 women and 6 men; age 48 ± 16 y, BMI 30.4 ± 3.7 kg/m2) participated in a randomized, double-blind, crossover, dose-escalation trial of unmodified seabuckthorn oils relatively high in 16:1n-7c (380, 760, and 1520 mg 16:1n-7c/d) and seabuckthorn oils augmented in 16:1n-7t (120, 240, and 480 mg 16:1n-7t/d). Each of the 3 escalation doses was provided for 3 wk, with a 4-wk washout period between the 2 supplements. At the end of each dose period, fasting blood samples were used to determine the primary outcomes (serum concentrations of the PLFAs 16:1n-7t and 16:1n-7c) and the secondary outcomes (glucose homeostasis, serum lipids, and clinical measures). Trends across doses were evaluated using linear regression. RESULTS: Compared with baseline, supplementation with seabuckthorn oil augmented in 16:1n-7t increased phospholipid 16:1n-7t by 26.6% at the highest dose (P = 0.0343). Supplementation with unmodified seabuckthorn oil resulted in a positive trend across the dose-escalations (P-trend = 0.0199). No significant effects of either supplement were identified on blood glucose, insulin, lipids, or other clinical measures, although this dosing study was not powered to detect such effects. No carryover or adverse effects were observed. CONCLUSIONS: Supplementation with seabuckthorn oil augmented in 16:1n-7t and unmodified seabuckthorn oil moderately increased concentrations of their corresponding PLFAs in metabolically healthy adults, supporting the use of supplementation with these fatty acids to test potential clinical effects in humans.This trial was registered at clinicaltrials.gov as NCT02311790.

Current intakes of trans-palmitoleic (trans-C16:1 n-7) and trans-vaccenic (trans-C18:1 n-7) acids in France are exclusively ensured by ruminant milk and ruminant meat: A market basket investigation.

High circulating levels of trans-palmitoleic acid (TPA) are associated with a lower risk of type 2 diabetes in humans. Thus, the origin of circulating TPA matters. Direct intakes of TPA are ensured by dairy products, and perhaps by partially hydrogenated oils (PHOs). Indirect intakes of TPA rely on dietary trans-vaccenic acid (TVA), which occurs in ruminant-derived foods and PHOs. As it is usually assumed that PHOs are not used any longer, we analyzed here a wide range of foods currently available at retail in France. We report that TPA and TVA (1) do occur in ruminant milk and meat, dairy products and in foreign PHOs, (2) do occur in dairy fat-containing foods and (3) do not occur in dairy fat-free foods. Together, our findings demonstrate that ruminant fats are the only contributors to circulating levels of TPA in humans.

Trans-palmitoleic acid (trans-9-C16:1, or trans-C16:1 n-7): Nutritional impacts, metabolism, origin, compositional data, analytical methods and chemical synthesis. A review.

Since the early 2010s, dietary trans-palmitoleic acid (trans-9-hexadecenoic acid, trans-9-C16:1 in the Δ-nomenclature, trans-C16:1 n-7 in the Ω-nomenclature, TPA) has been epidemiologically associated with a lower risk of type 2 diabetes in humans. Thanks to these findings, TPA has become a nutrient of interest. However, there is a lot of unresolved crucial questions about this dietary fatty acid. Is TPA a natural trans fatty acid? What kind of foods ensures intakes in TPA? What about its metabolism? How does dietary TPA act to prevent type 2 diabetes? What are the biological mechanisms involved in this physiological effect? Clearly, it is high time to answer all these questions with the very first review specifically dedicated to this intriguing fatty acid. Aiming at getting an overview, we shall try to give an answer to all these questions, relying on appropriate and accurate scientific results. Briefly, this review underlines that TPA is indeed a natural trans fatty acid which is metabolically linked to other well-known natural trans fatty acids. Knowledge on physiological impacts of dietary TPA is limited so far to epidemiological data, awaiting for supplementation studies. In this multidisciplinary review, we also emphasize on methodological topics related to TPA, particularly when it comes to the quantification of TPA in foods and human plasma. As a conclusion, we highlight promising health benefits of dietary TPA; however, there is a strong lack in well-designed studies in both the nutritional and the analytical area.

Comparing the simultaneous determination of cis- and trans-palmitoleic acid in fish oil using HPLC and GC.

BACKGROUND: Cis- and trans-palmitoleic acids (Cis-POA and trans-POA) are isomers of palmitoleic acid, a monounsaturated fatty acid which affects glucose and lipid metabolism, and reduces insulin resistance. Trans-POA is used as a biomarker for indicating the risk of type II diabetes and coronary heart disease, but no methods of analysis or distinguishing between cis-POA and trans-POA have yet been reported. METHOD: An accurate and precise HPLC method was developed to determine cis- and trans-POA simultaneously, and compared with results from a GC method. Cis- and trans-POA were analyzed by HPLC on a reverse-phase BDS-C18 column, equilibrated and eluted with acetonitrile (A) and water (B). In the established and validated GC method used for comparison, potassium hydroxide ester exchange was chosen to derivatize the cis- and trans-POA, before being determined. RESULTS: The calibration curves for cis- and trans-POA were linear over the range 0.05 to 500 µg/mL. The HPLC method exhibited good sensitivity, precision and accuracy. The limits of detection (LOD) for cis- and trans-POA were 0.2 and 0.05 µg/mL, respectively. The method successfully determined cis- and trans-POA in fish oil. For the GC method, the contents of cis-POA quantified were similar to those from the HPLC method, but the contents of trans-POA revealed significant variation between the two methods. CONCLUSIONS: After a comprehensive consideration of the characteristics of the saponification and methyl esterification methods which have been tested and verified, the HPLC method was found to be suitable for determining cis- and trans-POA contents in fish oil. It was also suggested that in natural fish oil, cis-POA may be in the glyceride state, and trans-POA almost completely in the free acid form. In comparison with the GC method, the HPLC method provided a simpler process and faster analyses for identifying and determining cis- and trans-POA. The study has also provided technical support for studying the pharmacological differences and relationship between structure and activity of cis- and trans-POA. This could help physicians to analyze patients' samples more quickly in 10 min and therefore provide a more rapid diagnosis of problems relating to the risk of type II diabetes and coronary heart disease.

Retroconversion of dietary trans-vaccenic (trans-C18:1 n-7) acid to trans-palmitoleic acid (trans-C16:1 n-7): proof of concept and quantification in both cultured rat hepatocytes and pregnant rats.

Trans-palmitoleic acid (trans-C16:1 n-7 or trans-Δ9-C16:1, TPA) is believed to improve several metabolic parameters according to epidemiological data. TPA may mainly come from direct intakes: however, data are inconsistent due to its very low amount in foods. Instead, TPA might arise from dietary trans-vaccenic acid (trans-C18:1 n-7, TVA), which is more abundant in foods. TVA chain-shortening would be involved, but formal proof of concept is still lacking to our knowledge. Therefore, the present study aimed at providing in vitro and in vivo evidence of TVA retroconversion to TPA. First, fresh rat hepatocytes cultured with growing doses of TVA were able to synthesize growing amounts of TPA, according to a 10% conversion rate. In addition, TPA was found in secreted triacylglycerols (TAG). Inhibiting peroxisomal ß-oxidation significantly reduced TPA synthesis, whereas no effect was observed when mitochondrial ß-oxidation was blocked. Second, pregnant female rats fed a TVA-supplemented diet free of TPA did metabolize dietary TVA, leading to detectable amounts of TPA in the liver. Apart from the brain, TPA was also found in all analyzed tissues, including the mammary gland. Hepatic peroxisomal ß-oxidation of dietary TVA, combined with exportation of TPA under VLDL-TAG, may explain amounts of TPA in other tissues. In conclusion, dietary TVA undergoes peroxisomal ß-oxidation and yields TPA. Thus, not only TPA circulating levels in humans can be explained by dietary TPA itself, but dietary TVA is also of importance.

Biomarkers of dairy fat intake and risk of cardiovascular disease: A systematic review and meta analysis of prospective studies.

BACKGROUND: Circulating biomarkers of dairy fat provide objective measures of dairy fat intake and facilitate conclusions relevant to populations with different diets and susceptibility to cardiovascular diseases (CVD). OBJECTIVE: To assess the relationship between circulating pentadecanoic acid (15:0), heptadecanoic acid (17:0) and trans-palmitoleic acid (trans-16:1n-7) and the risk of CVD. METHODS: Pubmed, Medline and Embase were searched for prospective cohort studies of the relationship between biomarkers of dairy fat and CVD risk, which included coronary heart disease (CHD), stroke, heart failure and CVD mortality, supplemented by bibliographies of retrieved articles and previous reviews. For each study, relative risks (RR) and 95% confidence intervals (CI) were extracted and pooled with the random effect model. RESULTS: Thirteen studies involving 7,680 CVD cases were included. The pooled RRs of the risk of CVD for the top third vs. bottom third 15:0, 17:0 and trans-16:1n-7 level were 0.94 (95%CI: 0.77-1.15), 0.82 (95% CI: 0.68-0.99) and 0.82 (95% CI: 0.67-1.02), respectively. Subgroup analysis indicated that there were no associations between the concentration of 15:0 with CHD and stroke, but a negative relationship with heart failure (RR = 0.72, 95% CI: 0.55-0.95). Null association was observed between circulating 17:0 and trans-16:1n-7 level and subtypes of CVD except for only one study which reported a negative relationship between 17:0 and heart failure. CONCLUSION: Higher dairy fat exposure is not associated with an increased risk of CVD.

Trans-fatty acids and mortality in patients referred for coronary angiography: the Ludwigshafen Risk and Cardiovascular Health Study.

AIMS: Trans-fatty acids (TFAs) are generated by the food industry and also occur naturally in trace amounts in dairy products. For the latter, beneficial health effects have been claimed, while there are numerous reports about TFA of industrial origin being hazardous to human health. Therefore, we aimed to investigate the association of TFA with mortality in the Ludwigshafen Risk and Cardiovascular Health (LURIC) study. METHODS AND RESULTS: The fatty acid composition of erythrocyte membranes was analysed using the HS-Omega-3 Index(®) methodology in 3259 participants of the LURIC study at baseline. During a median of 10.0 years of follow-up, a total of 975 (29.9%) study participants died, 614 (18.8%) from cardiovascular causes including 254 (7.8%) sudden cardiac deaths (SCDs). Association of TFA with clinical outcome was investigated with Cox proportional hazards regression. Total TFAs were inversely associated with mortality due to cardiovascular causes or SCD. This was mainly driven by the naturally occurring TFA C16:1n-7t (trans-palmitoleic acid). The reduced risk of SCD associated with C16:1n-7t persisted after multivariate adjustment with a hazard ratio of 0.63 (0.46-0.86) for the third tertile compared with the first tertile. There was no association of any TFA subgroup with an increased risk of adverse outcomes. CONCLUSIONS: In contrast to previous findings, the low concentrations of total TFAs found in LURIC were inversely associated with adverse cardiac outcomes. While the naturally occurring TFA C16:1n-7t was associated with reduced risk, no increased risk was found for industrially produced TFAs.