The effect of dietary omega-3 polyunsaturated fatty acids on plasma lipids and lipoproteins of C57BL/6 mice is age and sex specific

The Lipid Intensive Drug Therapy for Sepsis Phase II Pilot Clinical Trial

OBJECTIVES

Low cholesterol levels in early sepsis patients are associated with mortality. We sought to test if IV lipid emulsion administration to sepsis patients with low cholesterol levels would prevent a decline or increase total cholesterol levels at 48 hours.

DESIGN

Phase II, adaptive, randomized pilot clinical trial powered for 48 patients.

SETTING

Emergency department or ICU of an academic medical center.

PATIENTS

Sepsis patients (first 24 hr) with Sequential Organ Failure Assessment greater than or equal to 4 or shock.

INTERVENTIONS

Patients meeting study criteria, including screening total cholesterol levels less than or equal to 100 mg/dL or high-density lipoprotein cholesterol (HDL-C) + low-density lipoprotein cholesterol (LDL-C) less than or equal to 70 mg/dL, were randomized to receive one of three doses of lipid emulsion administered twice in 48 hours or no drug (controls). The primary endpoint was a change in serum total cholesterol (48 hr - enrollment) between groups.

MEASUREMENTS AND MAIN RESULTS

Forty-nine patients were enrolled and randomized. Two patients randomized to lipid emulsion were withdrawn before drug administration. Data for 24 control patients and 23 lipid emulsion patients were analyzed. The mean change in total cholesterol from enrollment to 48 hours was not different between groups and was 5 mg/dL ( sd 20) for lipid emulsion patients, and 2 mg/dL ( sd 18) for control patients ( p = 0.62). The mean changes in HDL-C and LDL-C were similar between groups. Mean change in triglycerides was elevated in lipid emulsion patients (61 mg/dL, sd 87) compared with controls (20 mg/dL, sd 70, p = 0.086). The 48-hour change in SOFA score was -2 (interquartile range [IQR] -4, -1) for control patients and -2 (IQR -3, 0) for lipid emulsion patients ( p = 0.46).

CONCLUSIONS

Administration of IV lipid emulsion to early sepsis patients with low cholesterol levels did not influence change in cholesterol levels from enrollment to 48 hours.

Sex-Dependent Effects of Eicosapentaenoic Acid on Hepatic Steatosis in UCP1 Knockout Mice

Visceral obesity may be a driving factor in nonalcoholic fatty liver disease (NAFLD) development. Previous studies have shown that the omega-3 polyunsaturated fatty acid, eicosapentaenoic acid (EPA), ameliorates obesity in high-fat (HF) fed male, C57Bl/6 mice at thermoneutral conditions, independent of uncoupling protein 1 (UCP1). Our goals herein were to investigate sex-dependent mechanisms of EPA in the livers of wild type (WT) and UCP1 knockout (KO) male and female mice fed a HF diet (45% kcal fat; WT-HF, KO-HF) with or without supplementation of 36 g/kg EPA (WT-EPA, KO-EPA). KO significantly increased body weight in males, with no significant reductions with EPA in the WT or KO groups. In females, there were no significant differences in body weight among KO groups and no effects of EPA. In males, liver TGs were significantly higher in the KO-HF group and reduced with EPA, which was not observed in females. Accordingly, gene and protein markers of mitochondrial oxidation, peroxisomal biogenesis and oxidation, as well as metabolic futile cycles were sex-dependently impacted by KO and EPA supplementation. These findings suggest a genotypic difference in response to dietary EPA supplementation on the livers of male and female mice with diet-induced obesity and housed at thermoneutrality.

Maternal omega-3 fatty acids maintained positive maternal lipids and cytokines profile, and improved pregnancy outcomes of C57BL/6 mice

Omega (n)-3 polyunsaturated fatty acids (PUFA) are known to regulate lipid metabolism and inflammation; however, the regulation of maternal lipid metabolism and cytokines profile by n-3 PUFA during different gestation stages, and its impact on fetal sustainability is not known. We investigated the effects of maternal diet varying in n-3 PUFA prior to, and during gestation, on maternal metabolic profile, placental inflammatory cytokines, and fetal outcomes. Female C57BL/6 mice were fed either a high, low or very low (9, 3 or 1% w/w n-3 PUFA) diet, containing n-6:n-3 PUFA of 5:1, 20:1 and 40:1, respectively for two weeks before mating, and throughout pregnancy. Animals were sacrificed prior to mating (NP), and during pregnancy at gestation days 6.5, 12.5 and 18.5. Maternal metabolic profile, placental cytokines and fetal outcomes were determined. Our results show for the first time that a maternal diet high in n-3 PUFA prevented dyslipidemia in NP mice, and maintained the expected lipid profile during pregnancy. However, females fed the very low n-3 PUFA diet became hyperlipidemic prior to pregnancy, and carried this profile into pregnancy. Maternal diet high in n-3 PUFA maintained maternal plasma progesterone and placental pro-inflammatory cytokines profile, and sustained fetal numbers throughout pregnancy, while females fed the low and very-low n-3 PUFA diet had fewer fetuses. Our findings demonstrate the importance of maternal diet before, and during pregnancy, to maintain maternal metabolic profile and fetus sustainability. These findings are important when designing dietary strategies to optimize maternal metabolism during pregnancy for successful pregnancy outcome.

Lipid intensive drug therapy for sepsis pilot: A Bayesian phase I clinical trial

OBJECTIVES

Cholesterol may be protective in sepsis. Patients with early sepsis may have critically low cholesterol levels that are associated with poor outcomes. The study objective was to test the safety of a fish oil-containing lipid injectable emulsion for stabilizing early cholesterol levels in sepsis.

METHODS

Phase I Bayesian optimal interval design trial of adult patients with septic shock (Sequential Organ Failure Assessment score ≥4 or vasopressor dependence). Using sequential dose escalation, participants received 2 doses of 1.0 to 1.6 g/kg of lipid emulsion (Smoflipid 20% lipid emulsion) within 48 hours of enrollment. Cholesterol levels, function, and organ failure were assessed serially during the first 7 days of hospital admission.

MEASUREMENTS AND MAIN RESULTS

A total of 10 patients with septic shock were enrolled. One patient withdrew for social reasons. Another patient had an unrelated medical complication and received 1 drug dose. Of 9 patients, mean age was 58 years (SD 16), median Sequential Organ Failure Assessment was 8, and 28-day mortality was 30%. No serious adverse events related to lipid infusion occurred. The six occurrences of non-serious adverse events possibly related to lipid infusion included hyperglycemia (1), elevated triglycerides (3), anemia (1), and vascular access redness/pain (1) for all doses. The mean change in total cholesterol levels from enrollment was -7 (SD 16.6) at 48 hours and 14 (SD 25.2) at 7 days.

CONCLUSIONS

Fish oil-containing lipid emulsion administration during early septic shock was safe. Further studies are needed to assess effects on cholesterol levels, function, and organ failure.

CLINICAL TRIAL REGISTRATION

NCT03405870.

Conversion of dietary polyunsaturated fats between humans and rodents: A review of allometric scaling models

The purpose of this research was to explore various allometric scaling models for dietary nutrients to improve translational validity between preclinical experimental rodent models and humans, focusing on polyunsaturated fats. Currently, there is no authoritative document that provides standardized guidelines for which dietary designs can be based on to improve translational fidelity between species. This paper reviews the challenges of using a rodent model, the major allometric scaling models, the use of these mathematical models to extrapolate human equivalent doses, and then tests one of these models using data generated in mice, with comparisons of data generated in human clinical trials. Mice were fed diets containing micro- and macronutrient compositions that approximated the US diet based on energy distribution and were then supplemented with increasing levels of various n-3 and n-6 polyunsaturated fatty acids at human equivalent doses. Changes in plasma and erythrocyte fatty acid phospholipid compositions were determined and compared to corresponding data generated in humans. Our findings suggest that basing lipid composition on percent of energy may result in comparable outcomes between mice and humans and that extrapolation of non-energy producing nutrients between species might be done using differences in energy needs (based on food intake).

Effect of Conjugated Linoleic Acid on Memory and Reflex Maturation in Rats Treated During Early Life

In the critical period of neurodevelopment (gestation and lactation), maternal consumption of essential fatty acids (FAs) can alter the offspring cognitive function permanently causing damage. Lipids can regulate neurotrophin and compose brain tissue. However, the effects of maternal consumption of a mixture of conjugated linoleic acid (CLA) on an offspring nervous system are not completely clear. We aimed to investigate the impacts of different CLA concentrations mixed into the maternal diet during early life on neonatal reflex maturation and cognitive functions of the offspring. Three groups were formed: control (CG): receiving a standard diet; CLA1: receiving a diet containing 1% of CLA, and CLA3: receiving a diet containing 3% of CLA, offered during gestation and lactation. After birth, the reflex responses of the offspring were observed from the 1st to the 21st day. After weaning, the animals' anxiety and memory were assessed using open field (OF) and novel object recognition tests. Fatty acids in the breast milk and the offspring's brain were also quantified. The data were analyzed using one-way ANOVA and the Kruskal-Wallis test. CLA1 presented accelerated palmar grasp disappearance versus CLA3 and negative-geotaxis versus CG; and the CLA3 presented increases for most reflexes (cliff-avoidance, vibrissa-placing, negative-geotaxis, and auditory-startle response), and decrease in reflexes palmar grasp and free-fall righting versus CG (p < 0.05). CLA3 group explored less of the OF in the second exposure. CLA1 and CLA3 presented an increased exploration ratio for new objects, which indicates memory improvement. The milk tested from CLA3 demonstrated an increase in polyunsaturated fatty acids (PUFAs), and a decrease in monounsaturated fatty acids. The amount of CLA in milk was greater in CLA1 and CLA3 and in the brain offspring both presented moderated amounts of CLA. Maternal treatment with the CLA mixture induced anticipated reflex maturation and improved memory in the offspring. Even though CLA was detected in the brains in only trace amounts, offspring's brain PUFA and SFA levels were increased. Further studies aimed to delineate the effect of maternal CLA supplementation on offspring's brain lipid metabolism and long-term neurologic outcome are needed to confirm these findings.

The Role of Omega-3 Fatty Acids in Reverse Cholesterol Transport: A Review

The beneficial effects of omega-3 polyunsaturated fatty acids (n-3 PUFAs) on cardiovascular disease have been studied extensively. However, it remains unclear to what extent n-3 PUFAs may impact Reverse Cholesterol Transport (RCT). RCT describes a mechanism by which excess cholesterol from peripheral tissues is transported to the liver for hepatobiliary excretion, thereby inhibiting foam cell formation and the development of atherosclerosis. The aim of this review is to summarize the literature and to provide an updated overview of the effects of n-3 PUFAs on key players in RCT, including apoliprotein AI (apoA-I), ATP-binding cassette transporter A1 (ABCA1), ABCG1, apoE, scavenger receptor class B type I (SR-BI), cholesteryl ester transfer protein (CETP), low-density lipoprotein receptor (LDLr), cholesterol 7 alpha-hydroxylase (CYP7A1) and ABCG5/G8. Based on current knowledge, we conclude that n-3 PUFAs may beneficially affect RCT, mainly by influencing high-density lipoprotein (HDL) remodeling and by promoting hepatobiliary sterol excretion.

A high fat-high sucrose diet enriched in blue mussels protects against systemic inflammation, metabolic dysregulation and weight gain in C57BL/6 mice

High fat-high sucrose (HF-HS) diet, known as the western diet, has been shown to induce the onset of obesity via increasing metabolic inflammation, insulin resistance and adipose tissue dysfunction. Hyperleptinemia, hyperglycemia and dyslipidemia are also the primary observations of obesogenic diet induced obesity. We have previously reported anti-adipogenic and insulin sensitizing effects of blue mussels (BM) using 3T3-L1 cells. BM is a rich source of omega-3 polyunsaturated fatty acids, phytosterols and other micronutrients that has been shown to elicit benefits under obese conditions using in-vitro cell culture models. However, no studies to date have established the anti-obesity effects, safety and efficacy of BM in an in-vivo animal model. In the present study, we fed a HF-HS diet supplemented with different concentrations of BM freeze-dried powder (1.25, 2.5 and 5% w/w) to C57BL/6 mice for 12weeks. A HF-HS diet caused rapid weight gain, hyperglycemia, dyslipidemia, hyperleptinemia, and increased plasma levels of inflammatory cytokines; interleukin (IL)-6 and tumor necrosis factor (TNF)-α. Incorporating 2.5% BM in the HF-HS diet prevented weight gain, dyslipidemia, hyperglycemia and reduced the levels of inflammatory cytokines and leptin mRNA expression. Furthermore, plasma from 2.5% BM increased cholesterol efflux capacity of J774 macrophage cells, compared to plasma from HF-HS diet. There was no effect of 1.25% BM on any tested parameters, while 5% BM was not palatable after four weeks. In conclusion, our findings have established the efficacy and safety of BM using C57BL/6 mice, demonstrating that BM has the potential to target obesity and related complications.

A low-fat diet enriched in fish oil increased lipogenesis and fetal outcome of C57BL/6 mice

There is clear evidence that nutritional strategy employed during pregnancy has profound influence on the offspring health outcomes. However, the effect of the quality and the quantity of maternal fat intake on maternal metabolic profile during different stages of pregnancy and its impact on pregnancy sustainability is not known. Female C57BL/6 mice (7 weeks old) were fed diets varying in the quantity of fat (5% vs 11%) for two weeks prior to mating and throughout pregnancy. The 5% fat diet was enriched with longer chain omega (n)-3 polyunsaturated fatty acids (PUFA) from fish oil. Maternal plasma and tissues were collected before mating and during pregnancy at days 6.5, 12.5 and 18.5. Plasma lipids, glucose, insulin, progesterone and estradiol levels were measured. Cholesterol efflux capacity of maternal plasma as well as the mRNA expression of placental steroidogenic acute regulatory protein and hepatic lipogenic genes (acetyl-CoA carboxylase-1, fatty acid synthase, diacylglycerol acyltransferase-2 and stearoyl-CoA desaturase-1) was determined. Feto-placental weight and fetuses sustained throughout gestation were recorded. A low-fat maternal diet enriched with n-3 PUFA increased maternal plasma triacylglycerol and the mRNA expression of rate-limiting lipogenic enzymes, along with increasing cholesterol efflux capacity (P < 0.05), likely to meet fetal lipid demand during pregnancy. Furthermore, diet enriched with longer chain n-3 PUFA increased the maternal plasma concentration of progesterone and estradiol during pregnancy (P < 0.05), which coincides with an increase in the number of fetuses sustained till day 18.5. These novel findings may be important when designing dietary strategies to optimize reproductive capability and pregnancy outcomes.

An obesogenic diet enriched with blue mussels protects against weight gain and lowers cholesterol levels in C57BL/6 mice

Obesity is linked to several health complications, such as cardiovascular disease, insulin resistance, and hypertension. Dyslipidemia in obesity is one of the prime causes for health complications. We have previously shown that blue mussels (BM) are a rich source of omega (n)-3 polyunsaturated fatty acids (PUFA) and increase the mRNA expression of peroxisome-proliferator activated receptor and adiponectin, thereby inducing anti-obesity and insulin sensitizing effects in vitro. However, the in vivo effects of BM on obesity and metabolic regulation are not known. We hypothesized that dietary intake of BM will prevent weight gain and improve lipid profile of C57BL/6 mice fed a high-fat diet (HFD). Mice were fed a HFD supplemented with 5% w/w BM (BM-HFD) for 4 weeks, and then switched to a HFD for 4 weeks. Mice fed a BM-HFD showed significantly lower body weight gain and abdominal fat, compared to the HFD. Furthermore, a BM-HFD significantly reduced plasma and hepatic total and low-density lipoprotein (LDL)-cholesterol, compared to HFD. The decrease in cholesterol levels coincided with inhibition of hepatic sterol regulatory element-binding protein-2 and HMG-CoA reductase mRNA expression, and an increase in LDL-receptor gene expression in the BM-HFD group, compared to the HFD group. In conclusion, our findings have established that BM reduces body weight gain in mice. BM may have potential to lower cholesterol levels by inhibiting cholesterol synthesis, thereby protecting against obesity and perhaps heart disease.

Fatty acyl composition of lysophosphatidylcholine is important in atherosclerosis

Atherosclerosis is a major cause of death for mankind. Although the pathophysiology of atherosclerosis is a complex and multifactorial process, growing body of evidence has identified phospholipids-mediated signaling as an important factor in the induction and progression of atherosclerosis. Lysophosphatidylcholine (LPC) is a major phospholipid in oxidized low-density lipoprotein, and is generally considered to be atherogenic. However, some studies have shown anti-atherogenic properties of LPC. The controversial findings surrounding the pro- or anti-atherogenic properties of LPC appear to be due to the chain length and the degree of saturation of the fatty acyl moiety of LPC. Studies have suggested that the presence of omega (n)-polyunsaturated fatty acids (PUFA) at the sn-1 position of LPC modulates the inflammatory response thereby making LPC anti-atherogenic. We have recently shown that feeding a diet high in n-3 PUFA resulted in the enrichment of LPC in both plasma and liver of C57BL/6 mice with n-3 PUFA. Others have also shown that supplementation with fish oil leads to preferential incorporation of n-3 PUFA into LPC. We also found that plasma obtained from mice fed a diet high in n-3 PUFA showed higher cholesterol efflux capacity compared to animals fed a low n-3 PUFA diet, despite no changes in high-density lipoprotein concentrations. We are therefore hypothesizing that n-3 PUFA enriched LPC has anti-atherogenic properties by promoting cholesterol efflux from macrophages and by reducing inflammation. Our anticipated long term objective is to establish that the fatty acyl moiety of LPC can be used as a potential biomarker for the risk of developing atherosclerosis. Validating this hypothesis would have a substantial impact on the public health with respect to early diagnosis of cardiovascular risks, and designing dietary based therapeutic strategies for the prevention and management of atherosclerosis and other heart related diseases.