William C. Heird

Protection against fatty liver but normal adipogenesis in mice lacking adipose differentiation-related protein.

ABSTRACT Adipose differentiation-related protein (ADFP; also known as ADRP or adipophilin), is a lipid droplet (LD) protein found in most cells and tissues. ADFP expression is strongly induced in cells with increased lipid load. We have inactivated the Adfp gene in mice to better understand its role in lipid accumulation. The Adfp-deficient mice have unaltered adipose differentiation or lipolysis in vitro or in vivo. Importantly, they display a 60% reduction in hepatic triglyceride (TG) and are resistant to diet-induced fatty liver. To determine the mechanism for the reduced hepatic TG content, we measured hepatic lipogenesis, very-low-density lipoprotein (VLDL) secretion, and lipid uptake and utilization, all of which parameters were shown to be similar between mutant and wild-type mice. The finding of similar VLDL output in the presence of a reduction in total TG in the Adfp-deficient liver is explained by the retention of TG in the microsomes where VLDL is assembled. Given that lipid droplets are thought to form from the outer leaflet of the microsomal membrane, the reduction of TG in the cytosol with concomitant accumulation of TG in the microsome of Adfp−/− cells suggests that ADFP may facilitate the formation of new LDs. In the absence of ADFP, impairment of LD formation is associated with the accumulation of microsomal TG but a reduction in TG in other subcellular compartments.

Fatty Acid Regulation of Gene Expression

Abstract: The development of obesity and associated insulin resistance involves a multitude of gene products, including proteins involved in lipid synthesis and oxidation, thermogenesis, and cell differentiation. The genes encoding these proteins are in essence the blueprints that we have inherited from our parents. However, what determines the way in which blueprints are interpreted is largely dictated by a collection of environmental factors. The nutrients we consume are among the most influential of these environmental factors. During the early stages of evolutionary development, nutrients functioned as primitive hormonal signals that allowed the early organisms to turn on pathways of synthesis or storage during periods of nutrient deprivation or excess. As single‐cell organisms evolved into complex life forms, nutrients continued to be environmental factors that interacted with hormonal signals to govern the expression of genes encoding proteins involved in energy metabolism, cell differentiation, and cell growth. Nutrients govern the tissue content and activity of different proteins by functioning as regulators of gene transcription, nuclear RNA processing, mRNA degradation, and mRNA translation, as well as functioning as posttranslational modifiers of proteins. One dietary constituent that has a strong influence on cell differentiation, growth, and metabolism is fat. The fatty acid component of dietary lipid not only influences hormonal signaling events by modifying membrane lipid composition, but fatty acids have a very strong direct influence on the molecular events that govern gene expression. In this review, we discuss the influence that (n‐9), (n‐6), and (n‐3) fatty acids exert on gene expression in the liver and skeletal muscle and the impact this has on intra‐ and interorgan partitioning of metabolic fuels.

Effect of dietary linoleic/alpha-linolenic acid ratio on growth and visual function of term infants

OBJECTIVES To determine the effect of alpha-linolenic acid (ALA) intake (or the dietary linoleic acid [LA]/ALA ratio) on the growth and visual function of term infants. STUDY DESIGN Normal term infants were assigned randomly and in masked fashion at birth to receive formulas with approximately 16% of total fatty acids as LA and 0.4%, 1.0%, 1.7%, or 3.2% of fatty acids as ALA (LA/ALA ratios of 44, 18.2, 9.7, and 4.8) for the first 4 months of life. The fatty acid pattern of plasma phospholipids was determined shortly after birth and at approximately 21, 60, and 120 days of age. Anthropometric data were obtained at the same times and also at approximately 240 days of age. Transient visual evoked responses (VERs) were measured at approximately 120 and 240 days of age. For comparisons, anthropometric and VER data also were obtained in infants who were exclusively breast-fed for the first 4 months of life. RESULTS Infants who received the formula with 3.2% ALA (LA/ALA ratio, 4.8) had higher plasma concentrations of phospholipid docosahexaenoic acid (DHA) but lower concentrations of arachidonic acid at 21, 60, and 120 days of age. Mean weight of this group at 120 days of age was 760 gm less (p < 0.05) than the mean weight of the group that received the formula with 0.4% ALA (LA/ALA ratio, 44). Despite differences in plasma phospholipid DHA contents among groups, neither VER latency nor amplitude differed significantly among formula groups or between any formula group and age-matched, breast-fed infants. CONCLUSIONS The highest versus the lowest ALA intake (or the lowest vs the highest LA/ALA ratio) resulted in higher plasma phospholipid DHA content from 21 to 120 days of age but was not associated with improved visual function as assessed by transient VER. Moreover, mean body weight of infants who received the highest versus lowest ALA intake was less at 120 days (p < 0.05). These data suggest that the lower LA/ALA ratios currently recommended for infant formulas should not be adopted until the effect of such ratios on growth are evaluated more completely.

Metabolic Acidosis Resulting from Intravenous Alimentation Mixtures Containing Synthetic Amino Acids

Abstract Hyperchloremic metabolic acidosis was observed in 11 infants receiving total parenteral nutrition containing mixtures of synthetic L-amino acids. The observed acidosis was not due to excessive gastrointestinal or renal losses of base as judged by the stool undetermined anion content and the urinary net acid excretion, nor was it due to infusion of preformed hydrogen ion as judged by the titratable acidity of the synthetic amino acid mixtures. Instead, the synthetic amino acid mixtures contain an excess of cationic amino acids in relation to anionic amino acids or other organic anions. Metabolism of these cationic amino acids results in a net excess of hydrogen ion, explaining the observed acidosis.

Effect of docosahexaenoic acid supplementation of lactating women on the fatty acid composition of breast milk lipids and maternal and infant plasma phospholipids

To determine whether docosahexaenoic acid (DHA) supplementation of breast-feeding mothers increases the DHA contents of breast milk and infant plasma phospholipids (PPs), breast-feeding women were randomly assigned to 3 DHA-supplementation groups (170-260 mg/d) or a control group. Group 1 (n = 6) consumed an algae-produced high-DHA triacylglycerol; group 2 (n = 6) consumed high-DHA eggs; group 3 (n = 6) consumed a high-DHA, low-eicosapentaenoic acid marine oil; and group 4 (n = 6) received no supplementation. From before to after supplementation (2 and 8 wk postpartum), mean (+/-SD) maternal PP DHA increased in groups 1, 2, and 3 by 1.20 +/- 0.53, 0.63 +/- 0.82, and 0.76 +/- 0.35 mol% of fatty acids, respectively (23-41%), but decreased in group 4 by 0.44 +/- 0.34 mol% (15%). Breast-milk DHA of groups 1, 2, and 3 increased by 0.21 +/- 0.16, 0.07 +/- 0.11, and 0. 12 +/- 0.07 mol%, respectively (32-91%) but decreased in group 4 by 0.03 +/- 0.04 mol% (17%). Mean infant PP DHA in groups 1, 2, and 3 increased by 1.63 +/- 0.79, 0.40 +/- 1.0, and 0.98 +/- 0.61 mol%, respectively (11-42%), but only by 0.18 +/- 0.74 mol% (5%) in group 4. Correlations between the DHA contents of maternal plasma and breast milk and of milk and infant PPs were significant. Breast-milk and maternal and infant PP 22:5n-6 concentrations were lowest in group 2. DHA supplementation increases the plasma and breast-milk DHA concentrations of lactating women, resulting in higher PP DHA concentrations in infants.

Cholesterol-lowering effect of soy protein in normocholesterolemic and hypercholesterolemic men.

Cardiovascular heart disease is a major health problem in the United States. Elevated blood cholesterol has been shown to significantly increase the risk of cardiovascular heart disease. The National Cholesterol Educational Program (NCEP) Step I diet, which restricts fat and cholesterol intakes, is usually recommended as the initial treatment to lower blood cholesterol. Soy protein has been shown to be hypocholesterolemic, particularly in hypercholesterolemic subjects. However, the hypocholesterolemic effect of soy protein in subjects with a blood total cholesterol concentration <5.17 mmol/L is not clear. To determine whether soy protein could enhance the hypocholesterolemic effect of the NCEP Step I diet, 13 normocholesterolemic and 13 hypercholesterolemic men aged 20-50 y were enrolled in a randomized, 2-part, crossover study. Subjects were fed either an NCEP Step I soy-protein diet or an NCEP Step I animal protein diet for 5 wk. After a washout period of 10-15 wk, the subjects were fed the alternate diet for 5 wk. The hypocholesterolemic effect of soy protein was found to be independent of age, body weight, pretreatment plasma lipid concentrations, and sequence of dietary treatment. Regardless of plasma lipid status, the soy-protein diet was associated with a statistically significant decrease in the plasma concentrations of LDL cholesterol (P = 0.029) as well as the in the ratio of plasma LDL cholesterol to HDL cholesterol (P = 0.005). Our results indicate that soy protein enhances the hypocholesterolemic effect of the NCEP Step I diet in both normocholesterolemic and hypercholesterolemic men.

Protection against Experimental Necrotizing Enterocolitis by Maternal Milk. I. Role of Milk Leukocytes

Summary: A ral model of necrotizing enterocolitis of the neonate in which maternal milk had been protective was studied to determine what components of the milk afforded protection and by what mechanism. Frozen and thawed rat milk was not protective, but formula supplemented with rat milk cells was. It was concluded that the cells provided protection. The cells, which are principally mononuclear phagocytes, can phagocytize and kill the Klebsiella pneumoniae strain used in the animal model. Animals with necrotizing enterolitis had peritonitis and bacteremia caused by this bacillus.Speculation: Milk mononuclear phagocytes may protect the neonatal rat from enterocolitis by their antibacterial and wound-healing activities or by their ability to enhance the neonatal immune response. The etiologic role of bacteria in this disease, not proven in these experiments, must be determined by experiments in germfree rats.

Polyunsaturated fatty acids and gene expression.

Purpose of reviewThis review focuses on the effect(s) of n-3 polyunsaturated fatty acids on gene transcription as determined by data generated using cDNA microarrays. Introduced within the past decade, this methodology allows detection of the expression of thousands of genes simultaneously and, hence, is a potentially powerful tool for studying the regulation of physiological mechanisms that are triggered or inhibited by nutrients. Recent findingsRecent data generated with cDNA microarrays not only confirm the effects of n-3 polyunsaturated fatty acids on regulation of lipolytic and lipogenic gene expression as determined by more traditional methods but also emphasize the tissue specificity of this regulation. cDNA microarray experiments also have expanded our understanding of the role of n-3 polyunsaturated fatty acids in regulation of expression of genes involved in many other pathways. These include: oxidative stress response and antioxidant capacity; cell proliferation; cell growth and apoptosis; cell signaling and cell transduction. SummaryThe cDNA microarray studies published to date show clearly that n-3 polyunsaturated fatty acids, usually provided as fish oil, modulate expression of a number of genes with such broad functions as DNA binding, transcriptional regulation, transport, cell adhesion, cell proliferation, and membrane localization. These effects, in turn, may significantly modify cell function, development and/or maturation.

Intermediates in endogenous synthesis of C22:6 omega 3 and C20:4 omega 6 by term and preterm infants.

Objective: To describe the ScvO2 levels at the lower (86-90%) and higher (91 - 96%) end of the currently recommended range of pulseoximetry (SpO2) in newborn infants with respiratory insufficiency. Design: a prospective observational study. Patients: 10 newborn infants (birthweight: 720 - 3400 grams) suffering from RDS and treated with mechanical ventilation and oxygen administration. Methods: SpO2 and ScvO2 were measured continuously by pulseoximetry, and by a fiberoptic catheter inserted into the right atrium via the umbilical vein, respectively. Measurements and Results: SpO2, ScvO2 were registered and venous admixture (Ven Adm) (100- SpO2)/(100 - ScvO2) was calculated every 15 minutes. For each patient the mean values of SpO2, ScvO2 and Ven Adm were calculated for both levels of oxygenation (table). In all patients ScvO2 was significantly reduced and Ven Adm was significantly increased at the lower range of oxygenation (p < 0.05; unpaired Students T test).

Intermediates in Endogenous Synthesis of C22:6ω3 and C20:4ω6 by Term and Preterm Infants

An alternative pathway of ω3 and ω6 fatty acid metabolism has been described in isolated rat hepatocytes and human fibroblasts. This alternative pathway, which is independent of Δ4 desaturation, involves elongation of C22:5ω3 and C22:4ω6 to C24 fatty acids,Δ6 desaturation of the C24 fatty acids and subsequent β oxidation of the desaturated products to C22:6ω3 and C22:5ω6. To determine whether this alternative pathway is operative in the human infant and also to obtain additional information concerning endogenous conversion of C18:3ω3 and C18:2ω6 to longer chain more unsaturated fatty acids, presence of [M + 18] isotopomers of ω3 and ω6 fatty acids in the plasma phospholipid fraction of term and preterm infants after administration of [U-13C]18:3ω3 and [U-13C]18:2ω6 was determined by negative chemical ionization gas chromatography/mass spectrometry. [M + 18] isotopomers of the following ω3 fatty acids were detected: C18:3, C18:4, C20:3, C20:4, C20:5, C22:4, C22:5, C22:6, C24:4 (two infants only), C24:5, and C24:6. [M + 18] isotopomers of ω6 fatty acids detected included only C18:2, C18:3, C20:2, C20:3, and C20:4, but sensitivity was insufficient to detect [M + 18] isotopomers of C22 and C24 ω6 fatty acids. Presence of[M + 18] isotopomers of C24:5ω3 and C24:6ω3 indicates that these fatty acids were synthesized endogenously from C18:3ω3. This plus thein vitro data strongly suggests that infants use the recently described alternative pathway in endogenous synthesis of C22:6ω3. However, involvement also of Δ4 desaturation cannot be excluded. Detection of [M + 18] isotopomers of C20:3ω3, C20:2ω6, and C22:4ω3 suggests that C18:3ω3, C18:2ω6, and C20:4ω3 are elongated as well as desaturated. The specific fate of these elongation products and their importance in endogenous synthesis of ω3 and ω6 long chain polyunsaturated fatty acids remain to be determined.