Dietary Reference Intakes based on chronic disease endpoints: outcomes from a case study workshop for omega 3's EPA and DHA

Given the focus on developing Dietary Reference Intakes (DRIs) based on chronic disease risk reduction and recent research for omega-3 long chain PUFA since the last DRI review, the Canadian Nutrition Society convened a panel of stakeholders for a 1-day workshop in late 2019. Attendees discussed the new NASEM guidelines for establishing DRI values based on chronic disease risk endpoints and the strength of current evidence for EPA and DHA as it relates to the new guidelines. Novelty: Summarizes evidence and expert opinions regarding the potential for reviewing DRI values for EPA and DHA and cardiovascular disease risk and early development.

Metabolically healthy obesity: is there a link with polyunsaturated fatty acid intake and status?

The aim of this study was to compare dietary intake and status of polyunsaturated fatty acids (PUFA) in plasma and erythrocyte phospholipids metabolically healthy and unhealthy, and obese and nonobese persons. Metabolic health status in 171 participants was defined according to criteria for metabolic syndrome. Obese and nonobese metabolically unhealthy persons (MUHO and MUHNO) had higher energy intake of n-6 PUFA (7.82 ± 1.03 and 7.49 ± 0.86) and lower intake of n-3 PUFA (0.60 ± 0.12 and 0.62 ± 0.11) compared to obese and nonobese metabolically healthy persons (MHO and MHNO) (5.92 ± 0.63 and 5.72 ± 0.67; 1.20 ± 0.07 and 1.22 ± 0.09, respectively) and a higher n-6/n-3 PUFA ratio. The plasma level of n-6 PUFA was lower in the MUHO and MUHNO groups (38.49 ± 3.71 and 38.53 ± 2.19) compared to MHNO (40.90 ± 2.43), while n-3 PUFA status was lower in obese than in nonobese persons (3.58 ± 0.79 and 3.50 ± 1.02 vs. 4.21 ± 0.80 and 4.06 ± 1.15). The MHO group had a higher eicosapentaenoic/arachidonic acid ratio and estimated desaturase (SCD16, D6D) and elongase activity in plasma phospholipids compared to MHNO. The low intake of n-3 PUFA is directly associated with metabolic risk factors. These results indicated that obesity is closely associated with low levels of n-3 PUFA in plasma phospholipids, suggesting that dietary modifications including n-3 PUFA supplementation appear to be suitable therapeutic strategy in obese persons.

DHA supplementation during prenatal ethanol exposure alters the expression of fetal rat liver genes involved in oxidative stress regulation

Prenatal ethanol (EtOH) exposure is known to induce adverse effects on fetal brain development. Docosahexaenoic acid (DHA) has been shown to alleviate these effects by up-regulating antioxidant mechanisms in the brain. The liver is the first organ to receive enriched blood after placental transport. Therefore, it could be negatively affected by EtOH, but no studies have assessed the effects of DHA on fetal liver. This study examined the effects of maternal DHA intake on DHA status and gene expression of key enzymes of the glutathione antioxidant system in the fetal liver after prenatal EtOH exposure. Pregnant Sprague-Dawley dams were intubated with EtOH for the first 10 days of pregnancy, while being fed a control or DHA-supplemented diet. Fetal livers were collected at gestational day 20, and free fatty acids and phospholipid profile, as well as glutathione reductase (GR) and glutathione peroxidase-1 (GPx1) gene expressions, were assessed. Prenatal EtOH exposure increased fetal liver weight, whereas maternal DHA supplementation decreased fetal liver weight. DHA supplementation increased fetal liver free fatty acid and phospholipid DHA independently of EtOH. GR and GPx1 messenger RNA (mRNA) expressions were significantly increased and decreased, respectively, in the EtOH-exposed group compared with all other groups. Providing DHA normalized GR and GPx1 mRNA expression to control levels. This study shows that maternal DHA supplementation alters the expression of fetal liver genes involved in the glutathione antioxidative system during prenatal EtOH exposure. The fetal liver may play an important role in mitigating the signs and symptoms of fetal alcohol spectrum disorders in affected offspring.

Modification of gene expression in rat cardiomyocytes by linoleic and docosahexaenoic acids 1

Regulation of cardiac fatty acid metabolism is central to the development of cardiac hypertrophy and heart failure. We investigated the effects of select fatty acids on the expression of genes involved in immediate early as well as inflammatory and hypertrophic responses in adult rat cardiomyocytes. Cardiac remodeling begins with upregulation of immediate early genes for c-fos and c-jun, followed by upregulation of inflammatory genes for nuclear factor kappa B (NF-κB) and nuclear factor of activated T-cells (NFAT). At later stages, genes involved in hypertrophic responses, such as atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), are upregulated. Adult rat cardiomyocytes were treated with palmitic acid, a saturated fatty acid; oleic acid, a monounsaturated fatty acid; linoleic acid, a polyunsaturated fatty acid belonging to the n-6 class; and docosahexaenoic acid, a polyunsaturated fatty acid belonging to the n-3 class. Linoleic acid produced a greater increase in the mRNA expression of c-fos, c-jun, NF-κB, NFAT3, ANP, and BNP relative to palmitic acid and oleic acid. In contrast, docosahexaenoic acid caused a decrease in the expression of genes involved in cardiac hypertrophy. Our findings suggest that linoleic acid may be a potent inducer of genes involved in cardiac hypertrophy, whereas docosahexaenoic acid may be protective against the cardiomyocyte hypertrophic response.

Omega-3 polyunsaturated fatty acid docosahexaenoic acid and its role in exhaustive-exercise-induced changes in female rat ovulatory cycle

Exhaustive exercises can cause delayed menarche or menstrual cycle irregularities in females. Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) are incorporated into a wide range of benefits in many physiological systems. Our work aimed to assess the role of ω-3 PUFA docosahexaenoic acid (DHA) on the deleterious effects of exhaustive exercise on the female reproductive system in rats. Virgin female rats were randomly divided into 4 groups (12 rats in each): control group, omega-3 group treated with DHA, exhaustive exercise group, and exhaustive exercised rats treated with DHA. Omega-3 was given orally to the rats once daily for 4 estrous cycles. Exhaustive exercises revealed lower levels in progesterone and gonadotropins together with histopathological decrease in number of growing follicles and corpora lutea. Moreover, the exercised rats showed low levels of ovarian antioxidants with high level of caspase-3 and plasma cortisol level that lead to disruption of hypothalamic-pituitary-gonadal axis. ω-3 PUFA DHA has beneficial effects on the number of newly growing follicles in both sedentary and exercised rats with decreasing the level of caspase-3 and increasing the antioxidant activity in ovaries. Exhaustive exercises can cause ovulatory problems in female rats that can be improved by ω-3 supplementation.

Efficacy of docosahexaenoic acid-choline-vitamin E in paediatric NASH: a randomized controlled clinical trial

Nonalcoholic steatohepatitis (NASH), a progressive form of nonalcoholic fatty liver disease, is one of the most common hepatic diseases in children. We conducted a randomized controlled clinical trial on children with biopsy-proven NASH based on a combinatorial nutritional approach compared with placebo. Participants were assigned to lifestyle modification plus placebo or lifestyle modification plus a mix containing docosahexaenoic acid, choline, and vitamin E (DHA-CHO-VE). Forty children and adolescents participated in the entire trial. The primary outcome was the improvement of liver hyperechogenicity. Secondary outcomes included alterations of alanine aminotransferase (ALT) and other metabolic parameters. Furthermore, changes of serum bile acids (BA) and plasma fibroblast growth factor 19 (FGF19) levels were evaluated as inverse biomarkers of disease severity. At the end of the study, we observed a significant decrease in severe steatosis in the treatment group (50% to 5%, p = 0.001). Furthermore, although the anthropometric and biochemical measurements in the placebo and DHA-CHO-VE groups were comparable at baseline, at the end of the study ALT and fasting glucose levels improved only in the treatment group. Finally, we found that BA levels were not influenced whereas FGF19 levels were significantly increased by DHA-CHO-VE. The results suggest that a combination of DHA, VE, and CHO could improve steatosis and reduce ALT and glucose levels in children with NASH. However, further studies are needed to assess the impact of a DHA and VE combination on repair of liver damage in paediatric NASH.

Dietary fish oil delays hypoxic skeletal muscle fatigue and enhances caffeine-stimulated contractile recovery in the rat in vivo hindlimb

Oxygen efficiency influences skeletal muscle contractile function during physiological hypoxia. Dietary fish oil, providing docosahexaenoic acid (DHA), reduces the oxygen cost of muscle contraction. This study used an autologous perfused rat hindlimb model to examine the effects of a fish oil diet on skeletal muscle fatigue during an acute hypoxic challenge. Male Wistar rats were fed a diet rich in saturated fat (SF), long-chain (LC) n-6 polyunsaturated fatty acids (n-6 PUFA), or LC n-3 PUFA DHA from fish oil (FO) (8 weeks). During anaesthetised and ventilated conditions (normoxia 21% O₂ (SaO₂-98%) and hypoxia 14% O₂ (SaO₂-89%)) the hindlimb was perfused at a constant flow and the gastrocnemius-plantaris-soleus muscle bundle was stimulated via sciatic nerve (2 Hz, 6-12V, 0.05 ms) to established fatigue. Caffeine (2.5, 5, 10 mM) was supplied to the contracting muscle bundle via the arterial cannula to assess force recovery. Hypoxia, independent of diet, attenuated maximal twitch tension (normoxia: 82 ± 8; hypoxia: 41 ± 2 g·g^-1 tissue w.w.). However, rats fed FO sustained higher peak twitch tension compared with the SF and n-6 PUFA groups (P < 0.05), and the time to decline to 50% of maximum twitch tension was extended (SF: 546 ± 58; n-6 PUFA: 522 ± 58; FO: 792 ± 96 s; P < 0.05). In addition, caffeine-stimulated skeletal muscle contractile recovery was enhanced in the FO-fed animals (SF: 41 ± 3; n-6 PUFA: 40 ± 4; FO: 52 ± 7% recovery; P < 0.05). These results support a physiological role of DHA in skeletal muscle membranes when exposed to low-oxygen stress that is consistent with the attenuation of muscle fatigue under physiologically normoxic conditions.

Eicosapentaenoic acid and docosahexaenoic acid increase the degradation of amyloid-β by affecting insulin-degrading enzyme

Omega-3 polyunsaturated fatty acids (PUFAs) have been proposed to be highly beneficial in Alzheimer's disease (AD). AD pathology is closely linked to an overproduction and accumulation of amyloid-β (Aβ) peptides as extracellular senile plaques in the brain. Total Aβ levels are not only dependent on its production by proteolytic processing of the amyloid precursor protein (APP), but also on Aβ-clearance mechanisms, including Aβ-degrading enzymes. Here we show that the omega-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increase Aβ-degradation by affecting insulin-degrading enzyme (IDE), the major Aβ-degrading enzyme secreted into the extracellular space of neuronal and microglial cells. The identification of the molecular mechanisms revealed that EPA directly increases IDE enzyme activity and elevates gene expression of IDE. DHA also directly stimulates IDE enzyme activity and affects IDE sorting by increasing exosome release of IDE, resulting in enhanced Aβ-degradation in the extracellular milieu. Apart from the known positive effect of DHA in reducing Aβ production, EPA and DHA might ameliorate AD pathology by increasing Aβ turnover.