The Impact of Linoleic Acid on Infant Health in the Absence or Presence of DHA in Infant Formulas

Both linoleic acid (LA) and α-linolenic acid (ALA) are essential dietary fatty acids, and a balanced dietary supply of these is of the utmost importance for health. In many countries across the globe, the LA level and LA/ALA ratio in breast milk (BM) are high. For infant formula (IF), the maximum LA level set by authorities (e.g., Codex or China) is 1400 mg LA/100 kcal ≈ 28% of total fatty acid (FA) ≈ 12.6% of energy. The aims of this study are: (1) to provide an overview of polyunsaturated fatty acid (PUFA) levels in BM across the world, and (2) to determine the health impact of different LA levels and LA/ALA ratios in IF by reviewing the published literature in the context of the current regulatory framework. The lipid composition of BM from mothers living in 31 different countries was determined based on a literature review. This review also includes data from infant studies (intervention/cohort) on nutritional needs regarding LA and ALA, safety, and biological effects. The impact of various LA/ALA ratios in IF on DHA status was assessed within the context of the current worldwide regulatory framework including China and the EU. Country averages of LA and ALA in BM range from 8.5-26.9% FA and 0.3-2.65% FA, respectively. The average BM LA level across the world, including mainland China, is below the maximum 28% FA, and no toxicological or long-term safety data are available on LA levels > 28% FA. Although recommended IF LA/ALA ratios range from 5:1 to 15:1, ratios closer to 5:1 seem to promote a higher endogenous synthesis of DHA. However, even those infants fed IF with more optimal LA/ALA ratios do not reach the DHA levels observed in breastfed infants, and the levels of DHA present are not sufficient to have positive effects on vision. Current evidence suggests that there is no benefit to going beyond the maximum LA level of 28% FA in IF. To achieve the DHA levels found in BM, the addition of DHA to IF is necessary, which is in line with regulations in China and the EU. Virtually all intervention studies investigating LA levels and safety were conducted in Western countries in the absence of added DHA. Therefore, well-designed intervention trials in infants across the globe are required to obtain clarity about optimal and safe levels of LA and LA/ALA ratios in IF.

Dietary Intake and Biomarkers of α-Linolenic Acid and Mortality: A Meta-Analysis of Prospective Cohort Studies

Background: The association between α-linolenic acid (ALA) and mortality is inconsistent and has not been summarized systematically.

Objective: The purpose was to conduct a meta-analysis that synthesized the results of prospective cohort studies to investigate associations between ALA intake and mortality.

Methods: We conducted a comprehensive search on PubMed, Embase, and Web of Science databases on May 1, 2021, for relevant prospective cohort studies which reported associations of ALA (assessed by dietary surveys and/or ALA concentrations in body tissues) with mortality from all-cause, cardiovascular disease (CVD), and other diseases. Multivariable-adjusted relative risks (RRs) were pooled by a random or fixed-effects model.

Results: A total of 34 prospective cohort studies, of which 17 reported dietary ALA intake, 14 for ALA biomarkers, and the remaining 3 reported both of intake and biomarkers. The studies included 6,58,634 participants, and deaths were classified into all-cause mortality (56,898), CVD mortality (19,123), and other diseases mortality (19,061). Pooled RRs of ALA intake were 0.93 (95% CI: 0.86, 1.01, I² = 71.2%) for all-cause mortality, 0.90 (95% CI: 0.83, 0.98, I² = 22.1%) for CVD mortality, and 0.94 (95% CI: 0.83, 1.06, I² = 73.3%) for other diseases mortality. The two-stage random-effects dose-response analysis showed a linear relationship between dietary ALA intake and CVD-mortality and each 0.5% energy increment of ALA intake was associated with a 5% lower risk of CVD-mortality (RR: 0.95; 95% CI: 0.90, 1.00). Pooled RRs per SD increment of ALA biomarkers were 0.99 (95% CI: 0.96, 1.01, I² = 27%) for all-cause mortality, 1.00 (95% CI: 0.98, 1.03, I² = 0%) for CVD mortality and 0.98 (95% CI: 0.95, 1.01, I² = 0%) for other diseases mortality.

Conclusions: This meta-analysis summarizing the available prospective cohort studies indicated that ALA intake was associated with reduced risk of mortality, especially CVD mortality. Our findings suggest that ALA consumption may be beneficial for death prevention. Systematic Review Registration:https://www.crd.york.ac.uk/PROSPERO; identifier: CRD42021264532.

Effects of Dietary Perilla Cake Supplementation in Growing Pig on Productive Performance, Meat Quality, and Fatty Acid Profiles

The objective of this study was to determine the effect of perilla cake (PC) supplementation in a growing pig diet on overall growing performance, meat quality, and fatty acid profile. A total of 24 barrow grower crossbred pigs (Large White × Landrace) × Duroc with an initial average body weight of 26.33 kg were fed with a basal diet supplemented with PC at 0%, 5%, and 10% in (PC0, PC5, and PC10, respectively) for 12 weeks. At the end of the experimental period, pigs were slaughtered to determine carcass traits and meat quality. Back fat, abdominal fat, and longissimus dorsi (LD) muscle were collected to investigate fatty acid composition. The results show that the average daily gain (ADG) in the PC10 significantly increased. However, PC supplementation did not influence carcass traits and meat quality except the color as described by lightness (L*). Dietary PC supplementation significantly increased the α-linolenic acid (ALA, C18:3 cis-9, 12, 15), whereas n6/n3 ratio decreased significantly in all tissues investigated. Thus, it can be concluded that the supplementation of PC in growing pig diet is a potential way to increase the fatty acid composition to that required for healthier meat.

Effects of increasing intake of soybean oil on synthesis of testosterone in Leydig cells

Background

Soybean oil is a very common edible oil in daily life. With the changes in the dietary composition, the intake of soybean oil increased. However, the effects of dietary intake of soybean oil on testosterone production are still unclear.

Methods

In order to study the effects of increasing intake of soybean oil on the synthesis of testosterone in Leydig cells, we fed male C57BL/6 mice on the diet which added 20% soybean salad oil (SOY group). We detected the hormone levels by enzyme-linked immunosorbent assay (ELISA) kits and serum fatty acid composition by gas chromatography, and analyzed the expression of steroidogenic enzymes by Real-Time PCR or immunoblotting analysis.

Results

After the 16-week feeding period, serum linoleic acid (LA) and α-linolenic acid (ALA) significantly increased and serum palmitic acid (PA) significantly decreased in SOY group mice. Compared to the normal diet (ND group), increasing intake of soybean oil raised the luteinizing hormone (LH) levels and up-regulated luteinizing hormone/chorionic gonadotropin receptor (LHCGR), steroidogenic acute regulatory protein (StAR) and cytochrome P450 family 11 subfamily A member I (CYP11A1). Testosterone levels in SOY group were higher than that in the ND group, and significantly difference showed.

Conclusions

Increasing intake of soybean oil could raise the serum LA and ALA levels and decrease serum PA levels. This could activate the LH/LHCGR pathway and improve the function of steroid synthesis in Leydig cells, and finally lead to the elevated testosterone levels.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-021-00580-1.

Regulation mechanism of silkworm pupa oil PUFAs on cholesterol metabolism in hepatic cell L-02

BACKGROUND

Silkworm pupa oil polyunsaturated fatty acid (SPO PUFA) has been confirmed to have a cholesterol-lowering function.

METHODS AND RESULTS

The effect of SPO PUFA and its main component, α-linolenic acid (ALA), on the metabolism of cholesterol and its regulation was investigated. The model of lipid denatured cells were constructed to carry out lipid accumulation, cholesterol metabolism and transformation. Real-time PCR and western blots were also used to analyze the expression levels of related genes and proteins to investigate the cholesterol efflux regulation mechanism. The data indicated that SPO PUFA and ALA dose-dependently decreased intracellular total cholesterol (TC) and enhanced total bile acid (TBA). They could also promote cholesterol removal by enhancing bile acid secretion and by upregulating genes LXRα, PPARγ, ABCA1, ABCG1, and CYP7A1, which were regulated by LXRα/PPARγ-ABCA1/ABCG1-CYP7A1 nuclear receptor signal pathways.

CONCLUSIONS

This study is of great significance in maintaining the balance of cholesterol and lipid metabolism, and in reducing the risk of steatohepatitis. © 2019 Society of Chemical Industry.

Association between Breastmilk LC PUFA, Carotenoids and Psychomotor Development of Exclusively Breastfed Infants

The first months of infant life are crucial for proper neurodevelopment, which may be influenced by several factors, including nutrition and nutrients (e.g., long-chain polyunsaturated fatty acids (LC PUFA) and carotenoids) of which the concentration in breastmilk is diet-dependent. This study analysed the relationship between the average concentrations of selected LC PUFA and carotenoids in breastmilk samples from the first and third months of lactation and the psychomotor development of exclusively breastfed infants at the sixth month of life. Infant psychomotor development was assessed using the Children Development Scale (DSR). The average age of infants during the assessment was 6.6 ± 0.2 months and 30.9 ± 3.8 years for mothers (n = 39 mother⁻infant pairs). The average concentration of docosahexaenoic acid (DHA) was 0.50% of fatty acids. The average concentration of carotenoids was 33.3 nmol/L for β-carotene, 121 nmol/L for lycopene and 33.3 nmol/L for lutein + zeaxanthin. The total results of the Performance scale and Motor subscale were 39 centiles and 4.1 points, respectively. Adjusted multivariate regression models revealed associations between breastmilk DHA and motor development (β = 0.275; p ≤ 0.05), α-linolenic acid (ALA; β = 0.432; p ≤ 0.05), n-3 LC PUFA (β = 0.423; p ≤ 0.05) and β-carotene (β = 0.359; p ≤ 0.05). In addition, an association between the Perception subscale and DHA was observed (β = 0.316; p ≤ 0.05; model 2). There were no significant associations between the overall Performance scale scores. Due to the positive association between concentrations of n-3 LC PUFA (ALA and DHA) and β-carotene in breastmilk and infant motor development, it is important to provide these nutrients with breastmilk. According to the diet-dependent concentration of these compounds in breastmilk, breastfeeding mothers should have a diet abundant in dietary sources of these nutrients, e.g., fish, nuts, seeds, vegetable oils, vegetables and fruits.

Production of omega 3-rich oils from underutilized chia seeds. Comparison between supercritical fluid and pressurized liquid extraction methods

Chia seeds constitute a promising source of α-linolenic acid (ALA). In the present work, an underutilized and cheaper set of chia seeds, which were discarded after the harvest according to quality criteria - named in this work as low oil content seeds (LOCS) - have been evaluated as a potential source for obtaining PUFA-enriched oils against the commonly studied high-quality chia seeds denoted as high oil content seeds (HOCS) in this study. Two efficient and environmental friendly techniques, supercritical fluid extraction (SFE) and pressurized liquid extraction (PLE), were evaluated to optimize the extraction process of chia oil. At 60 °C, by using pressurized food-grade ethanol, recoveries close to 100% were achieved from both sets of seeds in a short extraction time (10 min). By using SFE, the greatest oil extraction yield (>95%) was attained at the highest pressure and temperature conditions (45 MPa and 60 °C) after 240 min. At the early stage of SFE extraction, both LOCS and HOCS exhibited a similar kinetic behavior, reaching oil extraction rates of 0.59 g oil/min and 0.64 g oil/min, respectively. No differences were found between the fatty acid profile of the oils extracted from LOCS and HOCS both by PLE and SFE. ALA and linoleic acid (LA) concentrations ranged between 65-68% and 17-23% respectively, and a predominance of high molecular weight triglycerides (≥ CN50), was found in all extracted oils. In conclusion, LOCS might constitute a new suitable raw material for the production of ALA-enriched oils. Concerning the extraction methods assayed, the oil was almost entirely recovered by both PLE and SFE at the used conditions.

Antialgal effects of α-linolenic acid on harmful bloom-forming Prorocentrum donghaiense and the antialgal mechanisms

Harmful algal blooms (HABs) induced by Prorocentrum donghaiense occur frequently and cause a serious threat to the marine ecosystem. In this study, antialgal effects of α-linolenic acid (ALA) that is generally extracted from diverse macroalga on P. donghaiense were investigated. Specifically, the growth, cellular morphology and ultrastructure, reactive oxygen species (ROS) content, mitochondrial membrane potential (MMP), cytochrome C (Cyt-C), and caspase-9,3 activity of untreated and treated P. donghaiense were investigated. The results showed that ALA significantly inhibited the growth of P. donghaiense. Under ALA exposure, the cellular morphology and ultrastructure were damaged. ALA also induced ROS overproduction in the algal cells, decreased MMP, induced Cyt-C release, and activated caspase-9,3, which strongly relates to algal apoptosis. In summary, this study revealed the responses of morphology and physiology of P. donghaiense when exposed under ALA, and shows the potential of biotechnology on controlling P. donghaiense.

ALA/LA ameliorates glucose toxicity on HK-2 cells by attenuating oxidative stress and apoptosis through the ROS/p38/TGF-β1 pathway

Background

Growing evidence indicates that oxidative stress (OS) plays a pivotal role in Diabetic nephropathy (DN). In a previous study we demonstrated that ALA/LA protected HK-2 cells against high glucose-induced cytotoxicity. So we aimed to establish the glucose injury model of HK-2 cells and investigate the beneficial effects of ALA/LA on high glucose-induced excessive production of TGF-β1 and the possible mechanisms mediating the effects.

Methods

The expression of OS markers in high glucose-induced HK-2 cells treated with ALA/LA., including the antioxidant enzymes and reactive oxygen species (ROS) production, as well as the apoptosis rate were assayed by ELISA and flow cytometry. The p38/transforming growth factor β₁ (TGF-β₁) signal pathway were measured by real-time RT-PCR and western blot.

Results

The modeling condition of glucose toxicity on HK-2 cells was at the glucose concentration of 40.9 mM. ALA/LA can significantly increase the activities of antioxidant enzymes and decrease ROS production stimulated by high glucose. The study also found that ALA/LA caused a decrease in the apoptosis rate and TGF-β₁ level of HK-2 cells under high glucose stress through the ROS/p38 pathway.

Conclusions

ALA/LA exerts protective effects in vitro through inhibition of ROS generation, down regulation of the activation of the p38MAPK pathway and the expression of TGF-β₁ in HK-2 cells.

RNA Sequencing and Coexpression Analysis Reveal Key Genes Involved in α-Linolenic Acid Biosynthesis in Perilla frutescens Seed

Perilla frutescen is used as traditional food and medicine in East Asia. Its seeds contain high levels of α-linolenic acid (ALA), which is important for health, but is scarce in our daily meals. Previous reports on RNA-seq of perilla seed had identified fatty acid (FA) and triacylglycerol (TAG) synthesis genes, but the underlying mechanism of ALA biosynthesis and its regulation still need to be further explored. So we conducted Illumina RNA-sequencing in seven temporal developmental stages of perilla seeds. Sequencing generated a total of 127 million clean reads, containing 15.88 Gb of valid data. The de novo assembly of sequence reads yielded 64,156 unigenes with an average length of 777 bp. A total of 39,760 unigenes were annotated and 11,693 unigenes were found to be differentially expressed in all samples. According to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, 486 unigenes were annotated in the “lipid metabolism” pathway. Of these, 150 unigenes were found to be involved in fatty acid (FA) biosynthesis and triacylglycerol (TAG) assembly in perilla seeds. A coexpression analysis showed that a total of 104 genes were highly coexpressed (r > 0.95). The coexpression network could be divided into two main subnetworks showing over expression in the medium or earlier and late phases, respectively. In order to identify the putative regulatory genes, a transcription factor (TF) analysis was performed. This led to the identification of 45 gene families, mainly including the AP2-EREBP, bHLH, MYB, and NAC families, etc. After coexpression analysis of TFs with highly expression of FAD2 and FAD3 genes, 162 TFs were found to be significantly associated with two FAD genes (r > 0.95). Those TFs were predicted to be the key regulatory factors in ALA biosynthesis in perilla seed. The qRT-PCR analysis also verified the relevance of expression pattern between two FAD genes and partial candidate TFs. Although it has been reported that some TFs are involved in seed development, more direct evidence is still needed to verify their function. However, these findings can provide clues to reveal the possible molecular mechanisms of ALA biosynthesis and its regulation in perilla seed.

Could post-weaning dietary chia seed mitigate the development of dyslipidemia, liver steatosis and altered glucose homeostasis in offspring exposed to a sucrose-rich diet from utero to adulthood?

The present work analyzes the effects of dietary chia seeds during postnatal life in offspring exposed to a sucrose-rich diet (SRD) from utero to adulthood. At weaning, chia seed (rich in α-linolenic acid) replaced corn oil (rich in linoleic acid) in the SRD. At 150 days of offspring life, anthropometrical parameters, blood pressure, plasma metabolites, hepatic lipid metabolism and glucose homeostasis were analyzed. Results showed that chia was able to prevent the development of hypertension, liver steatosis, hypertriglyceridemia and hypercholesterolemia. Normal triacylglycerol secretion and triacylglycerol clearance were accompanied by an improvement of de novo hepatic lipogenic and carnitine-palmitoyl transferase-1 enzymatic activities, associated with an accretion of n-3 polyunsaturated fatty acids in the total composition of liver homogenate. Glucose homeostasis and plasma free fatty acid levels were improved while visceral adiposity was slightly decreased. These results confirm that the incorporation of chia seed in the diet in postnatal life may provide a viable therapeutic option for preventing/mitigating adverse outcomes induced by an SRD from utero to adulthood.

Mechanisms Involved in the Improvement of Lipotoxicity and Impaired Lipid Metabolism by Dietary α-Linolenic Acid Rich Salvia hispanica L (Salba) Seed in the Heart of Dyslipemic Insulin-Resistant Rats

This study explores the mechanisms underlying the altered lipid metabolism in the heart of dyslipemic insulin-resistant (IR) rats fed a sucrose-rich diet (SRD) and investigates if chia seeds (rich in α-linolenic acid 18:3, n-3 ALA) improve/reverse cardiac lipotoxicity. Wistar rats received an SRD-diet for three months. Half of the animals continued with the SRD up to month 6. The other half was fed an SRD in which the fat source, corn oil (CO), was replaced by chia seeds from month 3 to 6 (SRD+chia). A reference group consumed a control diet (CD) all the time. Triglyceride, long-chain acyl CoA (LC ACoA) and diacylglycerol (DAG) contents, pyruvate dehydrogenase complex (PDHc) and muscle-type carnitine palmitoyltransferase 1 (M-CPT1) activities and protein mass levels of M-CPT1, membrane fatty acid transporter (FAT/CD36), peroxisome proliferator activated receptor α (PPARα) and uncoupling protein 2 (UCP2) were analyzed. Results show that: (a) the hearts of SRD-fed rats display lipotoxicity suggesting impaired myocardial lipid utilization; (b) Compared with the SRD group, dietary chia normalizes blood pressure; reverses/improves heart lipotoxicity, glucose oxidation, the increased protein mass level of FAT/CD36, and the impaired insulin stimulated FAT/CD36 translocation to the plasma membrane. The enhanced M-CPT1 activity is markedly reduced without similar changes in protein mass. PPARα slightly decreases, while the UCP2 protein level remains unchanged in all groups. Normalization of dyslipidemia and IR by chia reduces plasma fatty acids (FAs) availability, suggesting that a different milieu prevents the robust translocation of FAT/CD36. This could reduce the influx of FAs, decreasing the elevated M-CPT1 activity and lipid storage and improving glucose oxidation in cardiac muscles of SRD-fed rats.