N-3 fatty acids improve body composition and insulin sensitivity during energy restriction in the rat

Lipid Profiles of Five Essential Phospholipid Preparations for the Treatment of Nonalcoholic Fatty Liver Disease: A Comparative Study

Nonalcoholic fatty liver disease (NAFLD) is associated with an imbalance in fatty acid composition and can progress from simple steatosis to steatohepatitis, liver cirrhosis, and hepatocellular carcinoma. Essential phospholipids (EPL), which contain high levels of 1,2-dilinoleoylphosphatidylcholine, can be used to treat NAFLD. Polyenylphosphatidylcholine (PPC) preparations are external, commercially available EPL products. The lipid composition of five commercially available PPC preparations, including Essentiale Forte, Fortifikat, Hepatoprotect Regenerator, Fortifikat Forte, and Esentin Forte were compared, the outcome of which may impact physician choice in the treatment of NAFLD. Following lipid extraction, a comparative analysis of key lipid content was performed using a QTRAP6500+ triple quadruple ion trap hybrid mass spectrometer (Sciex) in nanoelectrospray ionization mode. The glycerophospholipid composition of each PPC was determined, including levels of phosphatidylcholine (PtdCho), and phosphatidylethanolamine (PtdEtn) species, as well as PtdCho:PtdEtn ratio. Of the five preparations analyzed, Essentiale Forte contained the highest PtdCho levels (61.9 mol%) and lowest PtdEtn levels (4.9 mol%). PtdCho 36:4 levels, a polyunsaturated species of PtdCho, were highest in Esentin Forte (39.3 mol%) and Essentiale Forte (38.3 mol%) compared with other PPCs (28.7-35.8 mol%). Levels of lysophosphatidylcholine, phosphatidylinositol, phosphatidic acid, and phosphatidylglycerol were low in all five preparations. Lipid composition was consistent between the preparations. The high PtdCho:PtdEtn ratio composition of Essentiale Forte compared with the other PPC analyzed, as well as the presence of polyunsaturated fatty acids, suggest it could be the most clinically beneficial commercially available hepatoprotective product in the treatment of NAFLD.

The Implications for Cells of the Lipid Switches Driven by Protein-Membrane Interactions and the Development of Membrane Lipid Therapy

The cell membrane contains a variety of receptors that interact with signaling molecules. However, agonist-receptor interactions not always activate a signaling cascade. Amphitropic membrane proteins are required for signal propagation upon ligand-induced receptor activation. These proteins localize to the plasma membrane or internal compartments; however, they are only activated by ligand-receptor complexes when both come into physical contact in membranes. These interactions enable signal propagation. Thus, signals may not propagate into the cell if peripheral proteins do not co-localize with receptors even in the presence of messengers. As the translocation of an amphitropic protein greatly depends on the membrane's lipid composition, regulation of the lipid bilayer emerges as a novel therapeutic strategy. Some of the signals controlled by proteins non-permanently bound to membranes produce dramatic changes in the cell's physiology. Indeed, changes in membrane lipids induce translocation of dozens of peripheral signaling proteins from or to the plasma membrane, which controls how cells behave. We called these changes "lipid switches", as they alter the cell's status (e.g., proliferation, differentiation, death, etc.) in response to the modulation of membrane lipids. Indeed, this discovery enables therapeutic interventions that modify the bilayer's lipids, an approach known as membrane-lipid therapy (MLT) or melitherapy.

Effects of Chinese Dietary Pattern of Fat Content, n-6/n-3 Polyunsaturated Fatty Acid Ratio, and Cholesterol Content on Lipid Profile in Rats

This study aims to investigate the effect of Chinese diet pattern of fat content (30% or 36.06%), n-6/n-3 polyunsaturated fatty acid (PUFA) ratio (5 : 1 or 9 : 1), and cholesterol content (0.04 or 0.057 g/kg total diet) on lipid profile using a rat model. Results showed that rats' body weights (BWs) were controlled by the simultaneous intakes of cholesterol level of 0.04 g/kg total diet and n-6/n-3 ratio of 5 : 1. In addition, under high-fat diet, increased cholesterol feeding led to increased total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) levels and decreased triacylglycerols (TG) in rats' plasma. However, high density lipoprotein cholesterol (HDL-C) level and the ratios of HDL-C/LDL-C and HDL-C/TC in rats' plasma increased in response to simultaneous intakes of low n-6/n-3 ratio (5 : 1) and cholesterol (0.04 g/kg total diet) even under high-fat diet. Moreover, as the n-6/n-3 PUFA ratio in the diet decreased, the proportion of n-3 PUFAs increased in plasma, liver, and muscle and resulted in the decrease of n-6/n-3 PUFA ratio.

Dietary fatty acids sex-specifically modulate guinea pig postnatal development via cortisol concentrations

Early ontogenetic periods and postnatal maturation in organisms are sex-specifically sensitive to hypothalamic-pituitary-adrenal (HPA)-axis activities, related glucocorticoid secretions, and their effects on energy balance and homeostasis. Dietary polyunsaturated (PUFAs) and saturated (SFAs) fatty acids potentially play a major role in this context because PUFAs positively affect HPA-axis functions and a shift towards SFAs may impair body homeostasis. Here we show that dietary PUFAs positively affect postnatal body mass gain and diminish negative glucocorticoid-effects on structural growth rates in male guinea pigs. In contrast, SFAs increased glucocorticoid concentrations, which positively affected testes size and testosterone concentrations in males, but limited their body mass gain and first year survival rate. No distinct diet-related effects were detectable on female growth rates. These results highlight the importance of PUFAs in balancing body homeostasis during male's juvenile development, which clearly derived from a sex-specific energetic advantage of dietary PUFA intakes compared to SFAs.

Membrane lipid alterations in the metabolic syndrome and the role of dietary oils

The metabolic syndrome is a cluster of pathological conditions, including hypertension, hyperglycemia, hypertriglyceridemia, obesity and low HDL levels that is of great concern worldwide, as individuals with metabolic syndrome have an increased risk of type-2 diabetes and cardiovascular disease. Insulin resistance, the key feature of the metabolic syndrome, might be at the same time cause and consequence of impaired lipid composition in plasma membranes of insulin-sensitive tissues like liver, muscle and adipose tissue. Diet intervention has been proposed as a powerful tool to prevent the development of the metabolic syndrome, since healthy diets have been shown to have a protective role against the components of the metabolic syndrome. Particularly, dietary fatty acids are capable of modulating the deleterious effects of these conditions, among other mechanisms, by modifications of the lipid composition of the membranes in insulin-sensitive tissues. However, there is still scarce data based of high-level evidence on the effects of dietary oils on the effects of the metabolic syndrome and its components. This review summarizes the current knowledge on the effects of dietary oils on improving alterations of the components of the metabolic syndrome. It also examines their influence in the modulation of plasma membrane lipid composition and in the functionality of membrane proteins involved in insulin activity, like the insulin receptor, GLUT-4, CD36/FAT and ABCA-1, and their effect in the metabolism of glucose, fatty acids and cholesterol, and, in turn, the key features of the metabolic syndrome. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

n-3 Fatty acids preserve muscle mass and insulin sensitivity in a rat model of energy restriction

In obese subjects, the loss of fat mass during energy restriction is often accompanied by a loss of muscle mass. The hypothesis thatn-3 PUFA, which modulate protein homoeostasis via effects on insulin sensitivity, could contribute to maintain muscle mass during energy restriction was tested in rats fed a high-fat diet (4 weeks) rich in 18 : 1n-9 (oleic acid, OLE-R), 18 : 3n-3 (α-linolenic acid, ALA-R) orn-3 long-chain (LC-R) fatty acid and then energy restricted (8 weeks). A control group (OLE-ad libitum(AL)) was maintained with AL diet throughout the study. Rats were killed 10 min after an i.v. insulin injection. All energy-restricted rats lost weight and fat mass, but only the OLE-R group showed a significant muscle loss. TheGastrocnemiusmuscle was enriched with ALA in the ALA-R group and with LC-PUFA in the ALA-R and LC-R groups. The proteolytic ubiquitin–proteasome system was differentially affected by energy restriction, with MAFbx and muscle ring finger-1 mRNA levels being decreased in the LC-R group (−30 and −20 %, respectively). RAC-αserine/threonine-protein kinase and insulin receptor substrate 1 phosphorylation levels increased in the LC-R group (+70 %), together with insulin receptor mRNA (+50 %). The ALA-R group showed the same overall activation pattern as the LC-R group, although to a lesser extent. In conclusion, dietaryn-3 PUFA prevent the loss of muscle mass associated with energy restriction, probably by an improvement in the insulin-signalling pathway activation, in relation to enrichment of plasma membranes inn-3 LC-PUFA.

Effects of n-3 polyunsaturated fatty acids high fat diet intervention on the synthesis of hepatic high-density lipoprotein cholesterol in obesity-insulin resistance rats

Background

n-3 polyunsaturated fatty acids (PUFA) have previously been demonstrated in association with a reduced risk of chronic diseases, including insulin resistance, cancer and cardiovascular disease. In the present study, we analyzed the effects of n-3 PUFA-rich perilla oil (PO) and fish oil (FO) high fat diet intervention against the synthesis of hepatic high-density lipoprotein cholesterol (HDL-c) in obesity-insulin resistance model rats.

Methods

In the modeling period, the male SD rats were randomly divided into 2 groups. The rats in the high fat (HF) group were given a high fat pure diet containing 20.62 % lard. In the intervention period, the model rats were intervened with purified high-fat diets rich in PO or FO, containing same energy content with high fat pure diet in HF. After the intervention, the protein and mRNA expressions status of the key genes involved in synthesis of hepatic HDL-c were measured for further analytic comparison.

Results

The obesity-insulin resistance model rats were characterized by surprisingly high levels of serum triglyceride (TG) and increased body weight (P < 0.05, each). After the intervention, there were no apparent changes in the serum HDL-c and total cholesterol (TCH). In addition, the FO could up-regulate the hepatic adenosine triphosphate (ATP) binding cassette transporter A1 (ABCA1) mRNA (P < 0.01) and protein expressions, as well as increase the level of serum apolipoprotein A-1 (apoA-1) (P < 0.0001), and elevate the hepatic apoA-1mRNA expression (P < 0.01). Different from FO, the PO specifically elevated the hepatic ABCA1mRNA expression (P < 0.01).

Conclusions

The FO high fat diets promoted the synthesis of HDL-c in the obesity-insulin resistance rats.

Role of selected amino acids on plasma IGF-I concentration in infants

PURPOSE

Insulin-like growth factor-I (IGF-I) is related to growth and its secretion is modified by protein intake in early infancy. We examined the relationship of dietary protein and circulating amino acids on plasma IGF-I levels and early growth.

METHODS

Healthy formula-fed infants (n = 213) were randomly assigned to receive either a protein-reduced infant formula with alpha-lactalbumin-enriched whey and free tryptophan and phenylalanine (IF) or an isocaloric standard formula without free amino acids (CF) for the first 120 days of life. A group of breastfed (BF) infants was studied as a non-randomized reference cohort. Biochemical variables were measured shortly after birth (subpopulation) and at an age of 120 days. A path analysis was used to explore the relationship between IGF-I, insulin and amino acids. Results are derived from secondary analyses of a randomized controlled trial.

RESULTS

Plasma concentrations of IGF-I at 120 days were significantly higher in IF than in CF infants [58.5 (15.0) vs. 53.7 (9.95) ng/mL; p = 0.020]. BF infants showed lower IGF-I concentrations of 41.6 (10.7) ng/mL. All amino acids but Thr and Cit had a more marked effect on insulin than on IGF-I level. Considering weight, sex and feeding group, Trp explained an equal percentage of variance of IGF-I and insulin (total R ² 12.5 % of IGF-I and 12.3 % of insulin), while branched-chain AA explained an up to twofold higher variance of insulin than IGF-I. Compared to CF, IF explained 18.9 % of the IGF-I level (p = 0.03), while for insulin no direct effect was detectable.

CONCLUSION

Higher IGF-I concentrations and growth velocities in infants receiving protein-reduced IF indicate that the protein concentration of an infant formula alone does not control IGF-I levels and growth. Other components (e.g., selected amino acids) of infant formulae might control directly or indirectly via insulin influence IGF-I.