Functional Impact of the FADS1 rs174546 Single Nucleotide Polymorphism on Serum Lipid Levels: Insights from Molecular Mechanisms and Therapeutic Perspectives in Korean Population

SCOPE

Single nucleotide polymorphisms (SNP) in the fatty acid desaturase 1 (FADS1) gene is suggested as risk factor of metabolic diseases in genome-wide association studies (GWAS). This study hypothesized that FADS1_rs174546T associates with serum triglycerides (TG) in Korean Genome and Epidemiology Study (KoGES). In addition, functional study of SNP genotypes in cultured cells is performed.

METHODS AND RESULTS

FADS1_rs174546T is associated with high level of serum TG (effect size of variant: 6.48 ± 1.84 mg dL-1) in Korean individuals (normotriglyceridemia, n = 5128; hypertriglyceridemia, n = 3714). Functional study in cells with FADS1_rs174546T, shows reduced transcriptional activity, when compared with rs174546C. MiR-6728-3p, which is predicted to bind with rs174546T, decreases transcriptional activity of rs174546T but not in rs174546C, and it is reversed by miR-6728-3p inhibitor. Formononetin is selected as binding molecule to 3'-UTR of FADS1 and increases luciferase activity in both rs174546 (C/T). Moreover, formononetin compensates for the reduced luciferase activity by rs174546T and miR-6728-3p. Formononetin also increases endogenous FADS1 expression and long-chain polyunsaturated fatty acid (LC-PUFA) ratio.

CONCLUSION

FADS1_rs174546T is a crucial risk factor for hypertriglyceridemia in the Koreans potentially through the interaction with miR-6728-3p. Formononetin can be a potent dietary intervention to prevent and improve hypertriglyceridemia in both rs174546 (C/T) populations.

Genetic association between FADS and ELOVL polymorphisms and the circulating levels of EPA/DHA in humans: a scoping review

BACKGROUND

Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are two omega-3 fatty acids that can be synthesized out of their precursor alpha-linolenic acid (ALA). FADS and ELOVL genes encode the desaturase and elongase enzymes required for EPA and DHA synthesis from ALA; however, single nucleotide polymorphisms (SNPs) in FADS and ELOVL genes could modify the levels of EPA and DHA synthesized from ALA although there is no consensus in this area. This review aims to investigate EPA and DHA circulating levels in human blood and their association with FADS or ELOVL.

METHODS

PubMed, Cochrane, and Scopus databases were used to identify research articles. They were subsequently reviewed by two independent investigators.

RESULTS

Initially, 353 papers were identified. After removing duplicates and articles not meeting inclusion criteria, 98 full text papers were screened. Finally, this review included 40 studies investigating FADS and/or ELOVL polymorphisms. A total of 47 different SNPs in FADS genes were reported. FADS1 rs174537, rs174547, rs174556 and rs174561 were the most studied SNPs, with minor allele carriers having lower levels of EPA and DHA. SNPs in the FADS genes were in high linkage disequilibrium. SNPs in FADS were correlated with levels of EPA and DHA. No conclusion could be drawn with the ELOVL polymorphisms since the number of studies was too low.

CONCLUSION

Specific SNPs in FADS gene, such as rs174537, have strong associations with circulating levels of EPA and DHA. Continued investigation regarding the impact of genetic variants related to EPA and DHA synthesis is warranted.

The physicochemical stability and in vivo gastrointestinal digestion of flaxseed milk: Implication of microwave on flaxseed

The current study was to investigate how microwave on flaxseed affected the physicochemical stability and gastrointestinal digestion of oil bodies (OBs) in flaxseed milk. Flaxseed was subjected to moisture adjustment (30-35 wt%, 24 h), and microwave exposure (0-5 min, 700  W). Microwave treatment slightly weakened the physical stability of flaxseed milk indicated by Turbiscan Stability Index, but there were no visual phase separation during 21 days of storage at 4 °C. Upon microwave treatment, OBs experienced the layer-by-layer encapsulation into loose interface embedding by storage protein-gum polysaccharide complex from bulk phase, resulting in lower viscoelasticity of flaxseed milk. The OBs underwent earlier interface collapse and lipolysis during gastrointestinal digestion, followed by synergistic micellar absorption, faster chylomicrons transport within enterocytes of rats fed flaxseed milk. The accumulation of α-linolenic acid and synergistic conversion into docosapentaenoic and docosahexanoic acids in jejunum tissue were achieved accompanied by the interface remodeling of OBs in flaxseed milk.

Existing knowledge on Zn status biomarkers (1963-2021) with a particular focus on FADS1 and FADS2 diagnostic performance and recommendations for further research

The role of Zn in human health was discovered 60 years ago, and despite remarkable research efforts, a sufficiently sensitive and specific biomarker of Zn status is still lacking. Plasma/serum Zn, currently the best available and most accepted population Zn status indicator, responds well to severe Zn deficiency, yet, mild to moderate Zn deficiency states usually remain unrecognized. Identifying early-stage Zn deficiency requires additional robust markers of Zn status. This paper discusses the sensitivity, specificity, and responsiveness of plasma Zn concentrations to Zn interventions. It describes the biochemical and dietary basis for the causal association between Zn and fatty acid desaturases activity, FADS1 and FADS2, based on data collected through studies performed in animals and/or humans. The influence of potential confounders and covariates on the observed relationships is considered. Additional potential Zn biomarkers are discussed and suggestions for further research in this area are provided.

Gradually Increasing Vitamin E Dose Allows Increasing Dietary Polyunsaturation Level While Maintaining the Oxidation Status of Lipids and Proteins in Chicken Breast Muscle

Feeding broilers diets high in n-3 long-chain polyunsaturated fatty acids (n-3 PUFA) increases their incorporation into the meat but it may compromise meat quality due to oxidation of lipids and protein. Increased dietary vitamin E (vE) level downregulates this process, but its excessive level might exceed the physiological requirements for the maintenance of redox balance. This study investigated the sensory characteristics and oxidative status of meat from chickens fed diets supplemented with fish oil (FO) with or without gradually increasing doses of vE. The meat samples were obtained from a total of 27 female broilers of Ross 308 strain (9 birds per each of 3 dietary treatments), which were housed according to the standard management practice for commercial chicken houses over a period of 36 days. Chickens were fed diets containing 80 g/kg of supplemental fat, but the diets differed in fat composition; control diet (80 g/kg diet beef tallow as supplemental fat and a basal vE dose); 40 IU of dl-α-tocopheryl acetate; diet containing mixture of FO and beef tallow as supplemental fat (50:30 w/w g/kg diet) and a basal vE dose (E1), or diet (E2) as diet E1 but with gradually increasing vE dose (120/240 IU/kg diet fed between days 8–21 and days 22–36, respectively). The highest sensory quality and the lowest oxidative status of meat was found in the control chickens. FO decreased the sensory quality of the meat and increased lipid oxidation as well it had an impact on the lipid profile in muscle tissue (PUFA, n-3 ALA, EPA, DHA). Administration of a graded vE dose increased the sensory quality of the meat and did not limit lipid oxidation but maintained protein oxidation balance.

Diet Regulation of Long-Chain PUFA Synthesis: Role of Macronutrients, Micronutrients, and Polyphenols on Δ-5/Δ-6 Desaturases and Elongases 2/5

Deficiencies in the n-3 (ω-3) long-chain PUFAs (LC-PUFAs) EPA and DHA are associated with increased risk for the development of numerous diseases. Although n-3 LC-PUFAs can be obtained by consuming marine products, they are also synthesized endogenously through a biochemical pathway regulated by the Δ-5/Δ-6 desaturase and elongase 2/5 enzymes. This narrative review collates evidence from the past 40 y demonstrating that mRNA expression and activity of desaturase and elongase enzymes are influenced by numerous dietary components, including macronutrients, micronutrients, and polyphenols. Specifically, we highlight that both the quantity and the composition of dietary fats, carbohydrates, and proteins can differentially regulate desaturase pathway activity. Furthermore, desaturase and elongase mRNA levels and enzyme activities are also influenced by micronutrients (folate, vitamin B-12, vitamin A), trace minerals (iron, zinc), and polyphenols (resveratrol, isoflavones). Understanding how these various dietary components influence LC-PUFA synthesis will help further advance our understanding of how dietary patterns, ranging from caloric excesses to micronutrient deficiencies, influence disease risks.

Metabolomics Profile and Targeted Lipidomics in Multiple Tissues Associated with Feed Efficiency in Beef Steers

A study of multiple tissues was conducted to identify potential metabolic differences in cattle differing in feed efficiency. Individual feed intake and body weight was measured on 144 steers during 105 days on a high-concentrate ration. Steers were selected according to differences in average daily gain (ADG) with those with the greatest ADG (n = 8; 1.96 ± 0.02 kg/day) and least ADG (n = 8; 1.57 ± 0.02 kg/day), whose dry matter intake was within 0.32 SD of the mean intake (10.10 ± 0.05 kg/day). Duodenum, liver, adipose, and longissimus-dorsi were collected at slaughter, and metabolomics profiles were performed by ultra performance liquid chromatography quadrupole-time of-flight mass spectrometry. Principal components analyses, t-tests, and fold changes in tissues profile were used to identify differential metabolites between ADG groups. These were primarily involved in α-linolenic metabolism, which was downregulated in the greatest ADG as compared to least-ADG group in duodenum, adipose, and longissimus-dorsi. However, taurine and glycerophospholipids metabolisms were both upregulated in the greatest ADG compared with least-ADG group in the liver. The phospholipids and cholesterol were quantified in the tissues. Lipid transport and oxidation were the main common metabolic mechanisms associated with cattle feed efficiency. Combining analyses of multiple tissues may offer a powerful approach for defining the molecular basis of differences in performance among cattle for key production attributes.