Circulating Saturated Fatty Acids and Incident Type 2 Diabetes: A Systematic Review and Meta-Analysis

The effect of saturated fatty acids (SFAs) on incident type 2 diabetes (T2D) is controversial and few have systematically appraised the evidence. We conducted a comprehensive search of prospective studies examining these relationships that were published in PubMed, Web of Science, or EMBASE from 21 February 1989 to 21 February 2019. A total of 19 studies were included for systematic review and 10 for meta-analysis. We estimated the summarized relative risk (RR) and 95% confidence interval (95% CI) using a random (if I² > 50%) or a fixed effects model (if I² ≤ 50%). Although the included studies reported inconclusive results, the majority supported a protective effect of odd-chain and an adverse impact of even-chain SFAs. Meta-analysis showed that the per standard deviation (SD) increase in odd-chain SFAs was associated with a reduced risk of incident T2D (C15:0: 0.86, 0.76–0.98; C17:0: 0.76, 0.59–0.97), while a per SD increase in one even-chain SFA was associated with an increased risk of incident T2D (C14:0: 1.13, 1.09–1.18). No associations were found between other SFAs and incident T2D. In conclusion, our findings suggest an overall protective effect of odd-chain SFAs and the inconclusive impact of even- and very-long-chain SFAs on incident T2D.

Erythrocyte Saturated Fatty Acids and Incident Type 2 Diabetes in Chinese Men and Women: A Prospective Cohort Study

The association between circulating saturated fatty acids (SFAs) and incident type 2 diabetes (T2D) is reported in Western populations with inconsistent results, while evidence from Asian populations is scarce. We aimed to examine the associations between erythrocyte SFAs and incident T2D in a Chinese population. Between 2008 and 2013, a total of 2683 participants, aged 40⁻75 years, free of diabetes were included in the present analyses. Incident T2D cases were ascertained during follow-up visits. Gas chromatography was used to measure erythrocyte fatty acids at baseline. The Cox proportional hazards model was used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs). During 13,508 person years of follow-up, 216 T2D cases were identified. Compared with the first quartile, multivariable-adjusted HRs (95% CIs) of the fourth quartile were 1.20 (0.82⁻1.76; p = 0.242) for myristic acid (14-carbon tail, zero double bonds; 14:0), 0.69 (0.48⁻0.99; p = 0.080) for palmitic acid (16:0), 1.49 (1.02⁻2.19; p = 0.047) for stearic acid (18:0), 1.46 (1.00⁻2.12; p = 0.035) for arachidic acid (20:0), 1.48 (0.99⁻2.22; p = 0.061) for behenic acid (22:0), and 1.08 (0.74⁻1.56; p = 0.913) for lignoceric acid (24:0). Our findings indicate that individual erythrocyte SFAs are associated with T2D in different directions, with 18:0 and 20:0 SFAs positively associated with the risk, whereas no convincing inverse association for 16:0 SFAs.

The Effect of Chinese Herbal Medicine Formula mKG on Allergic Asthma by Regulating Lung and Plasma Metabolic Alternations

Asthma is a chronic inflammatory disorder of the airway and is characterized by airway remodeling, hyperresponsiveness, and shortness of breath. Modified Kushen Gancao Formula (mKG), derived from traditional Chinese herbal medicines (TCM), has been demonstrated to have good therapeutic effects on experimental allergic asthma. However, its anti-asthma mechanism remains currently unknown. In the present work, metabolomics studies of biochemical changes in the lung tissue and plasma of ovalbumin (OVA)-induced allergic asthma mice with mKG treatment were performed using ultra high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS). Partial least squares–discriminate analysis (PLS−DA) indicated that the metabolic perturbation induced by OVA was reduced after mKG treatment. A total of twenty-four metabolites involved in seven metabolic pathways were identified as potential biomarkers in the development of allergic asthma. Among them, myristic acid (L3 or P2), sphinganine (L6 or P4), and lysoPC(15:0) (L12 or P16) were detected both in lung tissue and plasma. Additionally, l-acetylcarnitine (L1), thromboxane B2 (L2), 10-HDoHE (L10), and 5-HETE (L11) were first reported to be potential biomarkers associated with allergic asthma. The treatment of mKG mediated all of those potential biomarkers except lysoPC(15:0) (P16). The anti-asthma mechanism of mKG can be achieved through the comprehensive regulation of multiple perturbed biomarkers and metabolic pathways.

Metabolites in Blood for Prediction of Bacteremic Sepsis in the Emergency Room

A metabolomics approach for prediction of bacteremic sepsis in patients in the emergency room (ER) was investigated. In a prospective study, whole blood samples from 65 patients with bacteremic sepsis and 49 ER controls were compared. The blood samples were analyzed using gas chromatography coupled to time-of-flight mass spectrometry. Multivariate and logistic regression modeling using metabolites identified by chromatography or using conventional laboratory parameters and clinical scores of infection were employed. A predictive model of bacteremic sepsis with 107 metabolites was developed and validated. The number of metabolites was reduced stepwise until identifying a set of 6 predictive metabolites. A 6-metabolite predictive logistic regression model showed a sensitivity of 0.91(95% CI 0.69–0.99) and a specificity 0.84 (95% CI 0.58–0.94) with an AUC of 0.93 (95% CI 0.89–1.01). Myristic acid was the single most predictive metabolite, with a sensitivity of 1.00 (95% CI 0.85–1.00) and specificity of 0.95 (95% CI 0.74–0.99), and performed better than various combinations of conventional laboratory and clinical parameters. We found that a metabolomics approach for analysis of acute blood samples was useful for identification of patients with bacteremic sepsis. Metabolomics should be further evaluated as a new tool for infection diagnostics.

Plasma free fatty acid levels influence Zn(2+) -dependent histidine-rich glycoprotein-heparin interactions via an allosteric switch on serum albumin

BACKGROUND

Histidine-rich glycoprotein (HRG) regulates coagulation through its ability to bind and neutralize heparins. HRG associates with Zn(2+) to stimulate HRG-heparin complex formation. Under normal conditions, the majority of plasma Zn(2+) associates with human serum albumin (HSA). However, free fatty acids (FFAs) allosterically disrupt Zn(2+) binding to HSA. Thus, high levels of circulating FFAs, as are associated with diabetes, obesity, and cancer, may increase the proportion of plasma Zn(2+) associated with HRG, contributing to an increased risk of thrombotic disease.

OBJECTIVES

To characterize Zn(2+) binding by HRG, examine the influence that FFAs have on Zn(2+) binding by HSA, and establish whether FFA-mediated displacement of Zn(2+) from HSA may influence HRG-heparin complex formation.

METHODS

Zn(2+) binding to HRG and to HSA in the presence of different FFA (myristate) concentrations were examined by isothermal titration calorimetry (ITC) and the formation of HRG-heparin complexes in the presence of different Zn(2+) concentrations by both ITC and ELISA.

RESULTS AND CONCLUSIONS

We found that HRG possesses 10 Zn(2+) sites (K' = 1.63 × 10(5) ) and that cumulative binding of FFA to HSA perturbed its ability to bind Zn(2+) . Also Zn(2+) binding was shown to increase the affinity with which HRG interacts with unfractionated heparins, but had no effect on its interaction with low molecular weight heparin (~ 6850 Da). [Correction added on 1 December 2014, after first online publication: In the preceding sentence, "6850 kDa" was corrected to "6850 Da".] Speciation modeling of plasma Zn(2+) based on the data obtained suggests that FFA-mediated displacement of Zn(2+) from serum albumin would be likely to contribute to the development of thrombotic complications in individuals with high plasma FFA levels.

NMR metabolomics profiling of blood plasma mimics shows that medium- and long-chain fatty acids differently release metabolites from human serum albumin

Metabolite profiling by NMR of body fluids is increasingly used to successfully differentiate patients from healthy individuals. Metabolites and their concentrations are direct reporters of body biochemistry. However, in blood plasma the NMR-detected free-metabolite concentrations are also strongly affected by interactions with the abundant plasma proteins, which have as of yet not been considered much in metabolic profiling. We previously reported that many of the common NMR-detected metabolites in blood plasma bind to human serum albumin (HSA) and many are released by fatty acids present in fatted HSA. HSA is the most abundant plasma protein and main transporter of endogenous and exogenous metabolites. Here, we show by NMR how the two most common fatty acids (FAs) in blood plasma - the long-chain FA, stearate (C18:0) and medium-chain FA, myristate (C14:0) - affect metabolite-HSA interaction. Of the set of 18 common NMR-detected metabolites, many are released by stearate and/or myristate, lactate appearing the most strongly affected. Myristate, but not stearate, reduces HSA-binding of phenylalanine and pyruvate. Citrate signals were NMR invisible in the presence of HSA. Only at high myristate-HSA mole ratios 11:1, is citrate sufficiently released to be detected. Finally, we find that limited dilution of blood-plasma mimics releases HSA-bound metabolites, a finding confirmed in real blood plasma samples. Based on these findings, we provide recommendations for NMR experiments for quantitative metabolite profiling.

[Investigation of fatty acid profile for diagnostic purposes in mouse melanoma]

The aim of this study was to investigate whether fatty acid profile is a suitable marker for diagnostic purposes in mouse melanoma. Twelve C57Bl/6 male mice were implanted with B16 mouse melanoma cells (106 cells/animal) orthotopically (subcutaneously). After the implantation 4-4 animals were bled by cardiac puncture following narcosis, at days 7, 14, and 21. In order to investigate fatty acid profiles a method based on extraction and HPLC-MS was developed. Signal intensities of 14 fatty acids were determined by mass spectrometry in tumor-free animals as well as tumor bearing animals at the three time points. Mathematical analysis showed non-significant profile changes when control (tumor-free) animals were compared to tumor-implanted ones as well as during tumor progression on week 1, 2 and 3. In case of three fatty acids (myristic acid, palmitoleic acid and eicosadienoic acid) a trend was observed during tumor progression but its statistical significance cannot be evaluated without further investigations. The fatty acid profile cannot be used for early diagnoses in mouse melanoma.

Dietary myristic acid at physiologically relevant levels increases the tissue content of C20:5 n-3 and C20:3 n-6 in the rat

This study was designed to investigate the effect of myristic acid on the biosynthesis and metabolism of highly unsaturated fatty acids, when it is supplied in a narrow physiological range in the diet of the rat (0.2-1.2% of total dietary energy). Three experimental diets were designed, containing 22% of total dietary energy as lipids and increasing doses of myristic acid (0.71, 3.00 and 5.57% of total fatty acids). Saturated fat did not exceed 31% of total fat and the C18:3 n-3 amount in each diet was strictly equal (1.6% of total fatty acids). After 7 weeks, the diets had no effect on plasma cholesterol level but greatly modified the liver, plasma and adipose tissue saturated, monounsaturated and polyunsaturated fatty acid profiles. Firstly, daily intakes of myristic acid resulted in a dose-dependent tissue accumulation of myristic acid itself. Palmitic acid was significantly increased in the tissues of the rats fed the higher dose of myristic acid. A dose-response accumulation of tissue C16:1 n-7 as a function of dietary C14:0 was also shown. Secondly, a main finding was that, among n-3 and n-6 polyunsaturated fatty acids, a dose-response accumulation of liver and plasma C20:5 n-3 and C20:3 n-6 (two precursors of eicosanoids) as a function of dietary C14:0 was shown. This result suggests that dietary myristic acid may participate in the regulation of highly unsaturated fatty acid biosynthesis and metabolism.

Association Between School Performance, Breast Milk Intake and Fatty Acid Profile of Serum Lipids in Ten-Year-Old Cleft Children

The fatty acid profiles of serum lipids were examined in 53 ten-year-old cleft children. The children presented with different cleft types (cleft lip, cleft lip and palate, isolated cleft palate and submucuous cleft palate) and were recruited from the Finnish Cleft Center. We also studied associations between serum lipid fatty acids and early breast milk intake, cognitive development in terms of preschool language learning and school achievement. The fatty acid profiles of serum lipids did not differ between boys and girls. The proportion of myristic acid in serum cholesteryl esters (CE) was higher and proportion of nervonic acid in phospholipids (PL) lower in children with isolated palatal clefts than in those with submucuous clefts. Out of the present children, 30% and 60% received breast milk less than 1 or 3 months, respectively. The proportions of docosahexaenoic acid in CE and in PL were significantly higher in the children whose breast milk intake was longer than 3 months. The number of children requiring special education was higher among those who received breast milk less than 1 month than among those with longer breast milk intake. In conclusion, the fatty acid profiles of serum lipids seem to be comparable among children with different cleft types. Short breast milk intake was associated with poorer school performance.

Influence of myristic acid supplementation on energy, fatty acid and calcium metabolism of sheep as affected by dietary calcium and forage : concentrate ratio

In a 6 x 6 Latin square arrangement, sheep of 41 kg body weight were fed myristic acid [C14:0; 50 g/kg dry matter (DM)] supplemented to two basal diets of forage : concentrate ratios of 1 : 1.5 and 1 : 0.5 and adjusted to dietary calcium (Ca) contents of either 4.2 or 9.0 g/kg DM (the latter only together with C14:0 supplementation). Various variables of energy, fatty acid and Ca metabolism were determined in combined digestibility and respiratory chamber measurements. With C14:0 addition the energy loss via the faeces increased (p < 0.05, post hoc test) without affecting energy digestibility of the complete diet. The apparent digestibility of supplemented C14:0 was higher (p < 0.01) with approximately 0.8 in the forage-based diet than in the concentrate-based diet (approximately 0.6). The elevated levels of plasma C14:0 were mainly accompanied by reduced C18:0 and C18:1 levels. The estimated apparent content of metabolizable energy (ME) of added C14:0 was either 24.5 MJ/kg (concentrate-based diet) or 32.1 MJ/kg (forage-based diet). Extra Ca equalized these differences between basal diets and ME contents amounted to 33.0 MJ/kg on average. As expected from corresponding slight shifts in energy metabolizability, the total efficiency of ME utilization increased (p < 0.1) with C14:0. The lower level of dietary Ca was still within the range recommended, but adding C14:0 to the concentrate-based diet reduced Ca retention in the body of the sheep from 0.9 to -0.1 g/day because of an impaired (p < 0.05, post hoc test) net Ca absorption, whereas no effect was found with the forage-based diet. With C14:0 addition, plasma total phosphorus (P) and serum calcitrol levels increased (p < 0.05, post hoc test) while Ca concentrations did not clearly reflect the reduced net Ca absorption. Increasing the dietary Ca content prevented adverse effects on Ca retention in the concentrate-based diet and improved Ca retention in the forage-based diet. In conclusion, the C14:0 supplementation reduced Ca availability in concentrate-based diets while an additional supply of Ca improved Ca and energy retention. Consequently, Ca supply should exceed recommended levels in diet types where dietary lipids are likely to reduce Ca availability and a compromise in basal diet type has to found to be able to profit best from the energetic value and the methane-suppressing properties of C14:0.

What does the measurement of whole-body fatty acid rate of appearance in plasma by using a fatty acid tracer really mean?

We evaluated the validity of using a single fatty acid tracer to assess total plasma long-chain free fatty acid (FFA) kinetics and the relationship between the rate of appearance (R(a)) of fatty acids in plasma and the fatty acid composition of adipose tissue triglyceride (TG). A mixture of [(13)C]-labeled myristate, palmitate, stearate, oleate, and linoleate was infused in healthy men during basal conditions and during conditions that stimulate (epinephrine infusion) and inhibit (insulin infusion) lipolysis of adipose tissue TGs. Calculated total FFA, R(a) based on palmitate, oleate, or linoleate tracers, was within 15% of the measured sum of the individual fatty acid R(a) under all conditions, whereas stearate and myristate tracers consistently underestimated and overestimated total FFA R(a), respectively. The fatty acid R(a) profile closely matched the fatty acid profile of subcutaneous adipose tissue TGs during epinephrine infusion, but not during basal conditions and insulin infusion. Our data support the common practice of using labeled palmitate or oleate as fatty acid tracers for assessing total plasma FFA kinetics and suggest that a source of lipids other than adipose tissue TG release fatty acids into the systemic circulation.

Longitudinal study of fatty acids in plasma and erythrocyte phospholipids during pregnancy

AIM

To assess the modifications of the main fatty acids (FA) in plasma and red blood cells during pregnancy.

METHODS

A longitudinal study of 36 normal pregnant women was carried out with 3 cut-off points: first trimester, second trimester and third trimester. 14 FA in plasma and erythrocyte phospholipids were measured using capillary gas chromatography. Measurements were expressed in percentages and in absolute values.

RESULTS

In plasma there was a significant increase in the proportion of saturated FA and a decrease in the proportion of long chain polyunsaturated fatty acids (PUFA) both in the omega 6 (omega 6) and omega 3 (omega 3) series. On the other hand, in erythrocyte phospholipids there was a decrease in the proportion of eicosapentaenoic acid and an increase in that of docosahexaenoic acid. In the omega 6 series, dihomo-gamma-linolenic acid increased, whereas the omega 6 docosapentaenoic acid decreased.

CONCLUSION

There was a significant decrease in the proportion of omega 3 PUFA in plasma from the first to the third trimester. Thus, it is suggested that the omega 3 PUFA intake during pregnancy should be increased in the last trimester.

Inborn errors of metabolism with a protein-restricted diet: effect on polyunsaturated fatty acids

Previous studies have shown that phenylketonuric patients display a deficiency in long-chain polyunsaturated fatty acids. A study has now been performed on 13 cases (5 with methylmalonic acidaemia and 8 with urea cycle disorders) whose dietary treatment also implies a limitation in protein-rich food. Plasma and red-cell phospholipid fatty acid profiles were studied. The most relevant results were a lower percentage of docosahexaenoic acid in plasma and red-cell phospholipids (0.91% +/- 0.53% vs 2.88% +/- 1.17% and 2.07% +/- 0.92% vs 3.62% +/- 1.01% (p < 0.001)) and a lower percentage of arachidonic acid in plasma (5.22% +/- 2.02% vs 8.3% +/- 2.11% (p < 0.001)). A long-chain polyunsaturated acid deficiency has also been confirmed in this group of metabolic patients and a dietary supplement is recommended since this population is subject to a special risk factor with regard to adequate psychomotor development. By extrapolating these data to the general population, the possibility can be inferred that long-chain polyunsaturated fatty acids are semi-essential in infant nutrition far beyond the breast-feeding period.