Treatment of EFA deficiency with dietary triglycerides or phospholipids in a murine model of extrahepatic cholestasis

Time-series metabolomics insights into the progressive characteristics of 3,5-diethoxycarbonyl-1,4-dihydrocollidine-induced cholestatic liver fibrosis in mice

Cholestasis is characterized by obstruction of bile flow and can lead to serious liver injury. With sustained damage, cholestasis can progress to cholestatic liver fibrosis (CLF), and cirrhosis. Non-invasive, predictive, and reliable metabolites based on the early and progressive stages of CLF are urgently needed. Based on the 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-induced CLF mouse model, serum metabolic profiling via a time-series strategy with ultra-performance liquid chromatography-LTQ-Orbitrap-based metabolomics, combined with histological progression, was used to find CLF-specific metabolites, and explore their dynamic changes in progressive stages of CLF. Compared to those in the control group, DDC-induced groups showed a substantial elevation in cholestatic liver injury and fibrosis indices. Next, 21 differential serum metabolites were selected and identified between the normal (control) and DDC groups, and 12 of them were greatly altered over time. Among these, taurocholic acid, tauromuricholic acid, LysoPE (20:2), sulfoglycolithocholic acid, and taurohyodeoxycholic acid were associated with the progression of the hepatocyte injury index, alanine aminotransferase. More importantly, docosahexaenoic acid, arachidonic acid, proline, leucine, and linoleic acid were associated with the progression of liver fibrosis index, liver hydroxyproline. Moreover, the differential metabolites that were related to hepatocyte injury and liver fibrosis were further validated in DDC-induced mice at weeks 4 and 8. Overall, this work provides data on differential metabolites for the progressive pathology of CLF.

Advances in exogenous docosahexaenoic acid-containing phospholipids: Sources, positional isomerism, biological activities, and advantages

In recent years, docosahexaenoic acid-containing phospholipids (DHA-PLs) have attracted much attention because of theirs unique health benefits. Compared with other forms of docosahexaenoic acid (DHA), DHA-PLs possess superior biological effects (e.g., anticancer, lipid metabolism regulation, visual development, and brain and nervous system biochemical reactions), more intricate metabolism mechanisms, and a stronger attraction to consumer. The production of DHA-PLs is hampered by several challenges associated with the limited content of DHA-PLs in natural sources, incomplete utilization of by-products, few microorganisms for DHA-PLs production, high cost, and complex process of artificial preparation of DHA-PLs. In this article, the sources, biological activities, and commercial applications of DHA-PLs were summarized, with intensive discussions on advantages of DHA-PLs over DHA, isomerism of DHA in phospholipids (PLs), and brain health. The excellent biological characteristics of DHA-PLs are primarily concerned with DHA and PLs. The metabolic fate of different DHA-PLs varies from the position of DHA in PLs to polar groups in DHA-PLs. Overall, well understanding of DHA-PLs about their sources and characteristics is critical to accelerate the production of DHA-PLs, economically enhance the value of DHA-PLs, and improve the applicability of DHA-PLs and the acceptance of consumers.

Vegetable lecithins: A review of their compositional diversity, impact on lipid metabolism and potential in cardiometabolic disease prevention

Vegetable lecithins, widely used in the food industry as emulsifiers, are a mixture of naturally occurring lipids containing more than 50% of phospholipids (PL). PL exert numerous important physiological effects. Their amphiphilic nature notably enables them to stabilise endogenous lipid droplets, conferring them an important role in lipoprotein transport, functionality and metabolism. In addition, beneficial effects of dietary lecithin on metabolic disorders have been reported since the 1990s. This review attempts to summarize the effects of various vegetable lecithins on lipid and lipoprotein metabolism, as well as their potential application in the treatment of dyslipidemia associated with metabolic disorders. Despite controversial data concerning the impact of vegetable lecithins on lipid digestion and intestinal absorption, the beneficial effect of lecithin supplementation on plasma and hepatic lipoprotein and cholesterol levels is unequivocal. This is especially true in hyperlipidemic patients. Furthermore, the immense compositional diversity of vegetable lecithins endows them with a vast range of biochemical and biological properties, which remain to be explored in detail. Data on the effects of vegetable lecithins alternative to soybean, both as supplements and as ingredients in different foods, is undoubtedly lacking. Given the exponential demand for vegetable products alternative to those of animal origin, it is of primordial importance that future research is undertaken in order to elucidate the mechanisms by which individual fatty acids and PL from various vegetable lecithins modulate lipid metabolism. The extent to which they may influence parameters associated with metabolic disorders, such as intestinal integrity, low-grade inflammation and gut microbiota must also be assessed.

Absorption rate of krill oil and fish oil in blood and brain of rats

BACKGROUND

Krill (Euphausia superba) is a small marine crustacean with a lipid content. The mechanism of Krill oil function is not clear yet and research reports on the absorption rate of the phospholipids of krill oil in the blood and brain are very poor.

METHODS

We studied the effect of oral short-term and long-term administration of Krill oils (KOs) on bioavailability in the blood and brain of rats. For short-term testing of fish and KO bioavailability, rats were divided into four groups: normal, fish oil (FO), Krill oil 1 (KO), and Krill oil 2 (CKO). The blood and brain were collected at 2, 4, 8, 12, 24, and 48 h after oral administration (1000 mg/rat). Five hundred milligrams of FO, KO, and CKO were orally administered daily for 2 weeks for long-term administration, and then the brain and blood were collected.

RESULTS

Two types of KOs showed high content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the PL. The EPA content of CKO and KO were 41.13 and 32.49%, respectively. After short-term KO administration, KO showed a higher EPA content than CKO in the blood after 2 h. KO showed higher content of DHA than CKO even after 2 h. FO increased until 8 h, but then decreased rapidly until 12 h. Although the total unsaturated fatty acid (UFA) content of KOs was lower than the total UFS content in FO, the remaining UFS content in the brain was higher than that in FO over time. Following oral administration of FO, KO, and CKO for 1 and 2 weeks, triglycerides (TG) and PL contents in the blood for KOs were slightly higher than for FO. EPA and DHA levels in the brain were slightly higher in KOs following long-term administration, but the difference was not significant.

CONCLUSIONS

Base on these findings, KOs have functional potential for the brain and vascular diseases, and can be utilized as a multi-functional material composed mainly of functional ingredients.

Clinical Relationship between Cholestatic Disease and Pituitary-Dependent Hyperadrenocorticism in Dogs: A Retrospective Case Series

Background

A high prevalence of cholestatic disease, including gallbladder mucocele (GBM), has been reported in dogs with naturally occurring pituitary‐dependent hyperadrenocorticism (PDH).

Hypothesis/Objectives

Differences exist in the clinical features of dogs with PDH and concurrent cholestatic disease, and also is the management of these dogs with trilostane.

Animals

Sixty‐five client‐owned dogs with naturally occurring PDH.

Methods

This was a retrospective, observational case series. Each dog was treated with trilostane for at least 3 months before the study, and had a good clinical response, as determined by owners. Statistical comparisons of clinical signs, results of routine blood tests, basal and post‐ACTH cortisol concentration, and optimal trilostane dosage were made after dogs were separated into the following 3 groups by ultrasonographic imaging: normal on ultrasound (NOU) group, cholestasis group, and GBM group.

Results

The GBM group had more severe clinical signs and significantly different total serum cholesterol concentration and post‐ACTH stimulation cortisol concentration at the time of diagnosis. Dogs that weighed <6 kg had a significantly higher prevalence of cholestatic disease than did the other dogs (P = .003). The optimal trilostane dosages for the GBM and cholestasis groups were 2.5 and 1.5 times the dosage of the NOU group, respectively (P < .001).

Conclusions and Clinical Importance

Gallbladder disease associated with cholestatic disease is correlated with PDH in dogs, in both its clinical features and drug management. These findings may be associated with hypercholesterolemia, unidentified genetic factors, and the hydrophobic nature of trilostane.

Promising therapies for treatment of nonalcoholic steatohepatitis

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) has become the most common etiology for abnormal aminotransferase levels and chronic liver disease. Its growing prevalence is largely linked to the presence of metabolic syndrome, particularly diabetes and insulin resistance. It is estimated that 60-80% of the type 2 diabetic population has NAFLD. NAFLD encompasses a range of conditions ranging from simple steatosis to non-alcoholic steatohepatitis (NASH). A subset of patients with hepatic steatosis progress to NASH, while 15-20% of patients with NASH develop cirrhosis. This progression is thought to be multifactorial, and there are currently no FDA-approved medications for the treatment of NASH.

AREAS COVERED

We review drugs currently in Phase II and III clinical trials for treatment of NAFLD and NASH, including their mechanisms of action, relationship to the pathophysiology of NASH, and rationale for their development.

EXPERT OPINION

The treatment of NASH is complex and necessitates targeting a number of different pathways. Combination therapy, preferably tailored toward the disease stage and severity, will be needed to achieve maximum therapeutic effect. With multiple agents currently being developed, there may soon be an ability to effectively slow or even reverse the disease process in many NAFLD/NASH patients.

Supplementation of krill oil with high phospholipid content increases sum of EPA and DHA in erythrocytes compared with low phospholipid krill oil

Background

Bioavailability of krill oil has been suggested to be higher than fish oil as much of the EPA and DHA in krill oil are bound to phospholipids (PL). Hence, PL content in krill oil might play an important role in incorporation of n-3 PUFA into the RBC, conferring properties that render it effective in reducing cardiovascular disease (CVD) risk. The objective of the present trial was to test the effect of different amounts of PL in krill oil on the bioavailability of EPA and DHA, assessed as the rate of increase of n-3 PUFA in plasma and RBC, in healthy volunteers.

Methods and design

In a semi randomized crossover single blind design study, 20 healthy participants consumed various oils consisting of 1.5 g/day of low PL krill oil (LPL), 3 g/day of high PL krill oil (HPL) or 3 g/day of a placebo, corn oil, for 4 weeks each separated by 8 week washout periods. Both LPL and HPL delivered 600 mg of total n-3 PUFA/day along with 600 and 1200 mg/day of PL, respectively.

Results

Changes in plasma EPA, DPA, DHA, total n-3 PUFA, n-6:n-3 ratio and EPA + DHA concentrations between LPL and HPL krill oil supplementations were observed to be similar. Intake of both forms of krill oils increased the RBC level of EPA (p < 0.001) along with reduced n-6 PUFA (LPL: p < 0.001: HPL: p = 0.007) compared to control. HPL consumption increased (p < 0.001) RBC concentrations of EPA, DPA, total and n-3 PUFA compared with LPL. Furthermore, although LPL did not alter RBC n-6:n-3 ratio or the sum of EPA and DHA compared to control, HPL intake decreased (p < 0.001) n-6:n-3 ratio relative to control with elevated (p < 0.001) sum of EPA and DHA compared to control as well as to LPL krill oil consumption. HPL krill oil intake elevated (p < 0.005) plasma total and LDL cholesterol concentrations compared to control, while LPL krill oil did not alter total and LDL cholesterol, relative to control.

Conclusions

The results indicate that krill oil with higher PL levels could lead to enhanced bioavailability of n-3 PUFA compared to krill oil with lower PL levels.

Trial registration

Clinicaltrials.gov# NCT01323036.

Development of omega-3 phospholipid-based solid dispersion of fenofibrate for the enhancement of oral bioavailability

This research aimed to develop the omega-3 phospholipids based solid dispersion to improve the oral bioavailability of fenofibrate. The omega-3 phospholipids based solid dispersion formulation (OPSD) was prepared by an antisolvent precipitation with immediate freeze-drying and the optimal composition of the formulation was determined as the ratios of sucrose to krill oil of 5:1 (w/w), krill oil to fenofibrate of 1.5:1 (w/w), and antisolvent to solvent of 6:4 (v/v). The developed OPSD formulation was characterized by using scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), and differential scanning calorimetry (DSC), which indicated the crystalline state of fenofibrate in the OPSD. The drug release profiles were also examined at different pHs. The OPSD achieved almost complete dissolution within 15 min, while the untreated powder and physical mixture exhibited minimal dissolution (less than 10% even after 2h). Furthermore, this formulation effectively increased the oral drug exposure in rats, as the Cmax and AUC of fenofibric acid (an active metabolite) were enhanced by approximately 6-7 folds. These results suggest that the OPSD formulation should be promising for improving the oral bioavailability of fenofibrate.

Enhanced increase of omega-3 index in healthy individuals with response to 4-week n-3 fatty acid supplementation from krill oil versus fish oil

BACKGROUND

Due to structural differences, bioavailability of krill oil, a phospholipid based oil, could be higher than fish oil, a triglyceride-based oil, conferring properties that render it more effective than fish oil in increasing omega-3 index and thereby, reducing cardiovascular disease (CVD) risk.

OBJECTIVE

The objective was to assess the effects of krill oil compared with fish oil or a placebo control on plasma and red blood cell (RBC) fatty acid profile in healthy volunteers.

PARTICIPANTS AND METHODS

Twenty four healthy volunteers were recruited for a double blinded, randomized, placebo-controlled, crossover trial. The study consisted of three treatment phases including krill or fish oil each providing 600 mg of n-3 polyunsaturated fatty acids (PUFA) or placebo control, corn oil in capsule form. Each treatment lasted 4 wk and was separated by 8 wk washout phases.

RESULTS

Krill oil consumption increased plasma (p = 0.0043) and RBC (p = 0.0011) n-3 PUFA concentrations, including EPA and DHA, and reduced n-6:n-3 PUFA ratios (plasma: p = 0.0043, RBC: p = 0.0143) compared with fish oil consumption. Sum of EPA and DHA concentrations in RBC, the omega-3 index, was increased following krill oil supplementation compared with fish oil (p = 0.0143) and control (p < 0.0001). Serum triglycerides and HDL cholesterol concentrations did not change with any of the treatments. However, total and LDL cholesterol concentrations were increased following krill (TC: p = 0.0067, LDL: p = 0.0143) and fish oil supplementation (TC: p = 0.0028, LDL: p = 0.0143) compared with control.

CONCLUSIONS

Consumption of krill oil was well tolerated with no adverse events. Results indicate that krill oil could be more effective than fish oil in increasing n-3 PUFA, reducing n-6:n-3 PUFA ratio, and improving the omega-3 index.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01323036.

Multiscale structures of lipids in foods as parameters affecting fatty acid bioavailability and lipid metabolism

On a nutritional standpoint, lipids are now being studied beyond their energy content and fatty acid (FA) profiles. Dietary FA are building blocks of a huge diversity of more complex molecules such as triacylglycerols (TAG) and phospholipids (PL), themselves organised in supramolecular structures presenting different thermal behaviours. They are generally embedded in complex food matrixes. Recent reports have revealed that molecular and supramolecular structures of lipids and their liquid or solid state at the body temperature influence both the digestibility and metabolism of dietary FA. The aim of the present review is to highlight recent knowledge on the impact on FA digestion, absorption and metabolism of: (i) the intramolecular structure of TAG; (ii) the nature of the lipid molecules carrying FA; (iii) the supramolecular organization and physical state of lipids in native and formulated food products and (iv) the food matrix. Further work should be accomplished now to obtain a more reliable body of evidence and integrate these data in future dietary recommendations. Additionally, innovative lipid formulations in which the health beneficial effects of either native or recomposed structures of lipids will be taken into account can be foreseen.

Omega-3 fatty acids for the treatment of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) has been recognized as a major health burden. It is the most important cause of chronic liver disease and a major independent cardiovascular risk factor. Lacking a definite treatment for NAFLD, a specific diet and an increase in physical activity represent the most commonly used therapeutic approaches. In this review, major literature data about the use of omega-3 polyunsaturated fatty acids (n-3 PUFAs) as a potential treatment of NAFLD have been described. n-3 PUFAs, besides having a beneficial impact on most of the cardio-metabolic risk factors (hypertension, hyperlipidemia, endothelial dysfunction and atherosclerosis) by regulating gene transcription factors [i.e., peroxisome proliferator-activated receptor (PPAR) α, PPARγ, sterol regulatory element-binding protein-1, carbohydrate responsive element-binding protein], impacts both lipid metabolism and on insulin sensitivity. In addition to an enhancement of hepatic beta oxidation and a decrease of the endogenous lipid production, n-3 PUFAs are able to determine a significant reduction of the expression of pro-inflammatory molecules (tumor necrosis factor-α and interleukin-6) and of oxygen reactive species. Further strengthening the results of the in vitro studies, both animal models and human intervention trials, showed a beneficial effect of n-3 PUFAs on the severity of NAFLD as expressed by laboratory parameters and imaging measurements. Despite available results provided encouraging data about the efficacy of n-3 PUFAs as a treatment of NAFLD in humans, well-designed randomized controlled trials of adequate size and duration, with histological endpoints, are needed to assess the long-term safety and efficacy of PUFA, as well as other therapies, for the treatment of NAFLD and non-alcoholic steatohepatitis patients. It is worthwhile to consider that n-3 PUFAs cannot be synthesized by the human body and must be derived from exogenous sources (fish oil, flaxseeds, olive oil) which are typical foods of the Mediterranean diet, known for its beneficial effects in preventing obesity, diabetes and, in turn, cardiovascular events. According to these data, it is important to consider that most of the beneficial effects of n-3 PUFAs can also be obtained by an equilibrate nutrition program.

Structural elucidation of molecular species of pacific oyster ether amino phospholipids by normal-phase liquid chromatography/negative-ion electrospray ionization and quadrupole/multiple-stage linear ion-trap mass spectrometry

Although marine oysters contain abundant amounts of ether-linked aminophospholipids, the structural identification of the various molecular species has not been reported. We developed a normal-phase silica liquid chromatography/negative-ion electrospray ionization/quadrupole multiple-stage linear ion-trap mass spectrometric (NPLC-NI-ESI/Q-TRAP-MS(3)) method for the structural elucidation of ether molecular species of serine and ethanolamine phospholipids from marine oysters. The major advantages of the approach are (i) to avoid incorrect selection of isobaric precursor ions derived from different phospholipid classes in a lipid mixture, and to generate informative and clear MS(n) product ion mass spectra of the species for the identification of the sn-1 plasmanyl or plasmenyl linkages, and (ii) to increase precursor ion intensities by "concentrating" lipid molecules of each phospholipid class for further structural determination of minor molecular species. Employing a combination of NPLC-NI-ESI/MS(3) and NPLC-NI-ESI/MS(2), we elucidated, for the first time, the chemical structures of docosahexaenoyl and eicosapentaenoyl plasmenyl phosphatidylserine (PS) species and differentiated up to six isobaric species of diacyl/alkylacyl/alkenylacyl phosphatidylethanolamine (PE) in the US pacific oysters. The presence of a high content of both omega-3 plasmenyl PS/plasmenyl PE species and multiple isobaric molecular species isomers is the noteworthy characteristic of the marine oyster. The simple and robust NPLC-NI-ESI/MS(n)-based methodology should be particularly valuable in the detailed characterization of marine lipid dietary supplements with respect to omega-3 aminophospholipids.

Reduced brain content of arachidonic acid and docosahexaenoic acid is related to the severity of liver fibrosis

BACKGROUND

Cognitive deficiency noted post-liver transplantation might be a result of consequential metabolic derangement before liver transplantation. Long-chain polyunsaturated fatty acids, especially arachidonic acid (AA) and docosahexaenoic acid (DHA), affect the development of the central nervous system and its absorption is influenced by obstructive jaundice.

AIM

To investigate the possible relationship between the brain content of AA and DHA with the severity of obstructive jaundice using a bile duct ligation rat model.

METHODS

Sprague-Dawley rats were divided into three groups: Sham (n = 5): rats received sham operation on P17 (17 days after delivery) and were sacrificed on P31; BDL2w (n = 5): rats received bile duct ligation and were sacrificed on P31; BDL4w (n = 7): rats received bile duct ligation and were sacrificed on P45. Liver function test, histopathology, and fatty acid composition of the brain tissues were analyzed.

RESULT

The Sham group had significantly lowered total/direct bilirubin level (0.6 + 0.1/0.3 + 0.1 mg/dl) as compared to the BDL2w group (3.8 + 1.5/1.6 + 1.0 mg/dl) and the BDL4w group (4.3 + 0.6/3.3 + 0.5 mg/dl) (P = 0.04 and 0.008, respectively). Liver fibrosis and inflammatory changes of hepatocytes increased from the Sham group, the BDL2w group, to the BDL4w group. The Sham group had significantly higher AA and DHA content. The brain content of AA and DHA correlated negatively to the duration of bile duct ligation, the total/direct bilirubin level, and the degree of liver fibrosis.

CONCLUSION

Our results demonstrated that reduced AA and DHA content in the brain of rats which received bile duct ligation is closely related to both the severity of liver fibrosis and the impairment of liver function.

Determination of digestibility, tissue deposition, and metabolism of the omega-3 fatty acid content of krill protein concentrate in growing rats

Krill protein concentrate (KPC) consists of high-quality protein (77.7% dry basis) and lipids (8.1% dry basis) that are rich (27% of total fatty acids) in omega-3 polyunsaturated fatty acids (omega-3 PUFAs). The objective of the study was to determine digestibility, tissue deposition, metabolism, and tissue oxidative stability of the omega-3 PUFAs provided by KPC. Young female Sprague-Dawley rats (n = 10/group) were fed ad libitum isocaloric diets for 4 weeks with either 10% freeze-dried KPC or 10% casein. The casein diet contained 5.3% added corn oil (CO), whereas the KPC contained 5.3% total lipids from 0.9% krill oil (KO) provided by KPC and 4.4% added corn oil (KO + CO). Fatty acid compositions of various tissues were analyzed by gas chromatography. Lipid peroxidation was determined by thiobarbituric acid reactive substances (TBARS). Total antioxidant capacity and urinary eicosanoid metabolites were determined by enzyme immunoassay. The omega-3 PUFAs provided in KO from KPC increased (P = 0.003) docosahexaenoic acid (DHA) concentration in the brain. DHA and eicosapentaenoic acid (EPA) content in fat pads and liver were increased (P < 0.01), whereas the omega-6 PUFA, arachidonic acid (AA), was decreased (P < 0.01) in rats fed the KPC diet containing the KO + CO mixture compared to rats fed the casein diet containing pure CO. Feeding the KPC diet decreased pro-inflammatory 2-series prostaglandin and thromboxane metabolites. There was no significant difference in TBARS or total antioxidant capacity in the tissues of rats fed the different diets. On the basis of the study results, the low amount of omega-3 PUFAs provided by the KO content of KPC provides beneficial effects of increasing tissue EPA and DHA deposition and reduced AA-derived 2-series eicosanoid metabolites without increasing lipid peroxidation. Therefore, consumption of KPC has the potential to provide a healthy and sustainable source of omega-3 PUFAs.

Effects of n-3 long chain polyunsaturated fatty acid supplementation on visual and cognitive development throughout childhood: a review of human studies

The present paper evaluates the most recent randomized controlled trials assessing the efficacy of n-3 LCPUFA supplementation (with or without n-6 LCPUFA) during pregnancy, lactation, infancy and childhood on visual and cognitive development. Available evidence suggests a beneficial effect of maternal n-3 LCPUFA supplementation during pregnancy and lactation on cognitive development of infants and children, but not for visual development. Evidence for an effect of LCPUFA supplementation of preterm and term infants on cognitive development of infants remains inconclusive. However, supplementing term infants with daily doses of 100 mg docosahexaenoic acid plus 200 mg arachidonic acid improves visual development as measured by electrophysiological tests. Evidence for benefits of n-3 LCPUFA on cognitive development in healthy children older than 2 years of age is too limited to allow a clear conclusion. Taken together, the evidence for potential benefits of LCPUFA supplementation is promising but yet inconclusive.

Mice raised on milk transgenically enriched with n-3 PUFA have increased brain docosahexaenoic acid

The brain contains high levels of the long-chain n-3 FA DHA (22:6n-3), mainly in the gray matter and synaptosomes. Adequate intake of DHA is crucial for optimal nervous system function, particularly in infants. Supplementation of infant formulas with DHA at levels similar to human breast milk is recommended for biochemical and functional benefits to neonates. We generated transgenic mice that produce elevated levels of n-3 PUFA in their milk by expressing the Caenorhabditis elegans n-3 FA desaturase under the control of a lactation-induced goat beta-casein promoter. To examine the postnatal effects of consuming the n-3-enriched milk, we compared the growth and brain and plasma FA composition of mouse pups raised on milk from transgenic dams with those observed for pups raised on milk from nontransgenic dams. A significant decrease in arachidonic acid (ARA, 20:4n-6) and concomitant increases in n-3 PUFA were observed in the phospholipid fraction of transgenic mouse milk. The n-6:n-3 FA ratios were 4.7 and 34.5 for the transgenic and control milk phospholipid fractions, respectively. DHA and DPA (22:5n-6) comprised 15.1% and 2.8% of brain FA from weanling mice nursed on transgenic dams, as compared with 6.9% and 9.2% for weanling mice nursed on control dams, respectively. This transgenic mouse model offers a unique approach to disassociate the effects and fetal programming resulting from a high n-6:n-3 FA ratio gestational environment from the postnatal nutritional effects of providing milk with differing n-6:n-3 FA ratios.

Lymphatic chylomicron size is inversely related to biliary phospholipid secretion in mice

Biliary phospholipids (PL) stimulate dietary fat absorption by facilitating intraluminal lipid solubilization and by providing surface components for chylomicron (CM) assembly. Impaired hepatic PL availability induces secretion of large very-low-density lipoproteins, but it is unclear whether CM size depends on biliary PL availability. Biliary PL secretion is absent in multidrug resistance protein 2-deficient (Mdr2(-/-)) mice, whereas it is strongly increased in essential fatty acid (EFA)-deficient mice. We investigated lymphatic CM size and composition in mice with absent (Mdr2(-/-)) or enhanced (EFA deficient) biliary PL secretion and in their respective controls under basal conditions and during enteral lipid administration. EFA deficiency was induced by feeding mice a high-fat, EFA-deficient diet for 8 wk. Lymph was collected by mesenteric lymph duct cannulation with or without intraduodenal lipid administration. Lymph was collected in 30-min fractions for up to 4 h, and lymphatic lipoprotein size was determined by dynamic light-scattering techniques. Lymph lipoprotein subfractions were isolated by ultracentrifugation, and lipid composition was measured. Lymphatic CMs were significantly larger in Mdr2(-/-) mice than in Mdr2(+/+) controls either without (+50%) or with (+25%) enteral lipid administration, and molar core-surface ratios were increased [triglyceride (TG)-to-PL ratio: 4.4 +/- 1.4 in Mdr2(-/-) mice vs. 2.7 +/- 0.8 in Mdr2(+/+) mice, P < 0.001]. In contrast, EFA-deficient mice secreted lipoproteins into lymph that were significantly smaller than in EFA-sufficient controls (173 +/- 32 vs. 236 +/- 47 nm), with correspondingly decreased core-surface ratios (TG-to-PL ratio: 3.0 +/- 1.0 in EFA-deficient mice vs. 6.0 +/- 1.9 in EFA-sufficient mice, P < 0.001). CM size increased during fat absorption in both EFA-deficient and EFA-sufficient mice, but the difference between the groups persisted. In conclusion, the present results strongly suggest that the availability of biliary PL is a major determinant of the size of intestinally produced lipoproteins both under basal conditions and during lipid absorption. Altered CM size may have physiological consequences for postprandial CM processing.

Essential fatty acid deficiency in mice is associated with hepatic steatosis and secretion of large VLDL particles

Essential fatty acid (EFA) deficiency in mice decreases plasma triglyceride (TG) concentrations and increases hepatic TG content. We evaluated in vivo and in vitro whether decreased hepatic secretion of TG-rich very low-density lipoprotein (VLDL) contributes to this consequence of EFA deficiency. EFA deficiency was induced in mice by feeding an EFA-deficient (EFAD) diet for 8 wk. Hepatic VLDL secretion was quantified in fasted EFAD and EFA-sufficient (EFAS) mice using the Triton WR-1339 method. In cultured hepatocytes from EFAD and EFAS mice, VLDL secretion into medium was measured by quantifying [(3)H]-labeled glycerol incorporation into TG and phospholipids. Hepatic expression of genes involved in VLDL synthesis and clearance was measured, as were plasma activities of lipolytic enzymes. TG secretion rates were quantitatively similar in EFAD and EFAS mice in vivo and in primary hepatocytes from EFAD and EFAS mice in vitro. However, EFA deficiency increased the size of secreted VLDL particles, as determined by calculation of particle diameter, particle sizing by light scattering, and evaluation of the TG-to-apoB ratio. EFA deficiency did not inhibit hepatic lipase and lipoprotein lipase activities in plasma, but increased hepatic mRNA levels of apoAV and apoCII, both involved in control of lipolytic degradation of TG-rich lipoproteins. EFA deficiency does not affect hepatic TG secretion rate in mice, but increases the size of secreted VLDL particles. Present data suggest that hypotriglyceridemia during EFA deficiency is related to enhanced clearance of altered VLDL particles.

Alterations in growth hormone receptor abundance regulate growth hormone signaling in murine obstructive cholestasis

Children with cholestatic liver diseases, in particular biliary atresia, may develop an acquired growth hormone (GH) resistance. This is characterized by normal GH secretion, reduced liver GH receptor (GHR) abundance, and reduced circulating insulin-like growth factor I (IGF-I). Consequences include linear growth failure, reduced muscle mass, and increased perioperative morbidity and mortality. However, the molecular basis for altered GH signaling in liver and skeletal muscle in cholestatic liver disease is not known. We hypothesized that reduced IGF-I expression in obstructive cholestasis would be associated with downregulation of the GHR and impaired phosphorylation of signal transducers and activators of transcription (STAT5). Body composition was determined in C57BL/6J male mice after bile duct ligation (BDL) relative to pair-fed (PF) and ad libitum-fed controls. GHR, STAT5, Sp3, and IGF-I expression and/or DNA binding were assessed using immunoblots, electrophoretic mobility shift assays, and/or real time RT-PCR. Fat-free mass was reduced in PF mice relative to ad libitum-fed controls. BDL led to a further reduction in fat mass and fat-free mass relative to PF controls. TNF-alpha was increased in liver and skeletal muscle of BDL mice. This was associated with reduced GH-dependent STAT5 activation and IGF-I RNA expression. GHR expression was reduced in BDL mice; in liver, this was associated with reduced Sp3 binding to a GHR gene promoter cis element. Wasting in murine obstructive cholestasis is due to combined effects of reduced caloric intake and biliary obstruction. GH resistance due to downregulation of GHR expression may be attributed primarily to the obstructive cholestasis; therapies that specifically increase GHR expression may restore GH signaling in this setting.