Effect of dietary fats on erythrocyte membrane lipid composition and membrane-bound enzyme activities

Inhibitory Action of Omega-3 and Omega-6 Fatty Acids Alpha-Linolenic, Arachidonic and Linoleic acid on Human Erythrocyte Acetylcholinesterase

Acetylcholinesterase (AChE, E.C. 3.1.1.7) termed as the true cholinesterase functions to end cholinergic transmission at synapses. Due to its diverse expression in non-neural tissues such as erythrocytes and bones along with its various molecular forms, researchers seek a non-classical role for this protein. Here, the inhibitory action of unsaturated 18 carbon fatty acids linoleic acid and alpha-linolenic acid and 20 carbon fatty acid arachidonic acid on AChE were investigated. Enzyme activity was measured in kinetic assay method according to Ellman assay utilizing acetylthiocholine. Analysis of the activity data revealed that among the fatty acids examined the IC₅₀ values differed according to the length of the fatty acid and the number of the double bonds. Arachidonic acid, a 20-carbon fatty acid with 4 unsaturated bonds (20:4 n-6, cis 5,8,11,14) displayed an IC₅₀ value of 2.78 µM and K_i value of 396.35 µM. Linoleic acid, an essential 18-carbon fatty acid (18:2 n-6, cis 9,12) had an IC₅₀ value of 7.95 µM and K_i value of 8027.55 µM. The IC₅₀ value of alpha-linolenic acid, 18-carbon fatty acid (18:3 n-3, cis-9,12,15) was found as 179.11 µM. Analysis of the data fit the inhibition mechanism for linoleic, alpha-linolenic and arachidonic acid as mixed-type; non-competitive. Molecular docking complied with these results yielding the best score for arachidonic acid. The alkenyl chain of the fatty acids predictably reached to the catalytic site while the carboxylate strongly interacted with the peripheric anionic site.

Vitamin A deficiency suppresses high fructose-induced triglyceride synthesis and elevates resolvin D1 levels

BACKGROUND/AIMS

Vitamin A and its metabolites are known to regulate lipid metabolism. However so far, no study has assessed, whether vitamin A deficiency per se aggravates or attenuates the development of non-alcoholic fatty liver disease (NAFLD). Therefore, here, we tested the impact of vitamin A deficiency on the development of NAFLD.

METHODS

Male weanling Wistar rats were fed one of the following diets; control, vitamin A-deficient (VAD), high fructose (HFr) and VAD with HFr (VADHFr) of AIN93G composition, for 16weeks, except half of the VAD diet-fed rats were shifted to HFr diet (VAD(s)HFr), at the end of 8(th) week.

RESULTS

Animals fed on VAD diet with HFr displayed hypotriglyceridemia (33.5mg/dL) with attenuated hepatic triglyceride accumulation (8.2mg/g), compared with HFr diet (89.5mg/dL and 20.6mg/g respectively). These changes could be partly explained by the decreased activity of glycerol 3-phosphate dehydrogenase (GPDH) and the down-regulation of stearoyl CoA desaturase 1 (SCD1), both at gene and protein levels, the key determinants of triglyceride biosynthesis. On the other hand, n-3 long chain polyunsaturated fatty acid, docosahexaenoic acid and its active metabolite; resolvin D1 (RvD1) levels were elevated in the liver and plasma of VAD diet-fed groups, which was negatively associated with triglyceride levels. All these factors confer vitamin A deficiency-mediated protection against the development of hepatic steatosis, which was also evident from the group shifted from VAD to HFr diet.

CONCLUSIONS

Vitamin A deficiency attenuates high fructose-induced hepatic steatosis, by regulating triglyceride synthesis, possibly through GPDH, SCD1 and RvD1.

Neurochemical and behavioural impact of C18 fatty acids in male mice postweaning

Dietary components, particularly essential fatty acids, affect the expression and maintenance of normal physiological phenotypes. However, the influence of C18 fatty acids that are abundantly present in the normal diet is unclear. We focused on the behavioural and neurochemical effects of C18 fatty acids during postweaning development in male mice. An AIN-93G diet supplemented with 8% stearic acid (C18:0), 3% oleic acid (C18:1), 3% linoleic acid (C18:2) or 3% α-linolenic acid (C18:3) was provided from four weeks of age for eight weeks. At 12 weeks of age, novel exploratory behaviour and social interaction tests were carried out. One week after the last behavioural test, the brain of each mouse was removed. The frequency of social interactive behaviour was decreased by approximately 70% in the C18:0 group compared to the basal diet group, but there was no difference in cumulative time. The frequency of social interaction showed a positive correlation to cumulative time in mice fed with the experimental diets except for C18:0. Dietary C18 fatty acids following weaning had no impact on brain fatty acid composition except for the C18:3 diet. Furthermore, the neurochemical properties to be especially noted were that choline acetyltransferase activity was absolutely higher in C18:0 diet-fed mice than in the other groups, especially in the frontal cortex where it was 1.7-fold higher than in the basal diet-fed group. The present results reveal a significant possibility of neurochemical and behavioural effects of dietary fatty acids, and saturated fatty acids are of special importance during the postweaning period.

Large litters rearing changes brain expression of GLUT3 and acetylcholinesterase activity in adult rats

Effects of malnutrition in the brain are more pronounced during the period of growth spurt, corresponding to the suckling in rodents. Neuronal glucose transporter GLUT3 expression and acetylcholinesterase activity were studied in the brain of adult young rats (84 days old) suckled in litters formed by 6 (control group) or 12 pups (malnourished group). In the adult rats, brain weight, blood glucose levels and GLUT3 expression were decreased in malnourished group (5%, 18%, 58%, respectively, P<0.001, Student's t test) compared to the control. Increased activity of acetylcholinesterase was found in cerebral cortex homogenates and a significant interaction (P=0.019, ANOVA two-way, Tukey's test) was found between nutritional state and homogenate fraction. In summary, malnutrition during suckling period decreased GLUT3 expression and increased acetylcholinesterase activity in the rat brain that could contribute to possible cognitive deficits and changes of brain metabolic activity.

Calcium and Magnesium ATPase Activities in Women with Varying BMIs

OBJECTIVE

Intracellular calcium (Ca) is increased in obese humans, and magnesium (Mg)-ATPase activity is increased in monosodium glutamate-induced obese rats. The aims of this study were to test the hypotheses that Ca-ATPase activity is negatively correlated with BMI, and that Mg-ATPase activity is positively correlated with BMI and Ca-ATPase activity in obese women.

RESEARCH METHODS AND PROCEDURES

Thirty healthy adult women, with BMIs of 20 to 40, donated a single sample of whole blood and were interviewed as to medical history and family history of obesity. Erythrocyte membranes were isolated and assayed for Ca-ATPase and Mg-ATPase. Weight and height were self-reported. Regression analysis was used to determine relationship between BMI and enzyme activity. Family history of obesity served as a covariant.

RESULTS

Ca-ATPase was negatively correlated with increasing BMI (r = - 0.38, p = 0.02). The relationship between BMI and Ca-ATPase remained valid after controlling for family history of obesity (r = -0.36, p = 0.03). There was a positive correlation between Mg-ATPase activity and Ca-ATPase (r = 0.42, p = 0.024), and this relationship remained valid after controlling for BMI and family history of obesity (r = 0.41, p = 0.03).

DISCUSSION

Ca-ATPase activity decreases as BMI increases. Decreased ATPase activity may contribute to increased intracellular calcium, previously reported in obese persons. Further studies are needed to determine whether a drop in Ca-ATPase activity can serve as a marker for the development of obesity.

Dietary polyunsaturated fatty acids improve cholinergic transmission in the aged brain

The cholinergic theory of aging states that dysfunction of cholinergic neurons arising from the basal forebrain and terminating in the cortex and hippocampus may be involved in the cognitive decline that occurs during aging and Alzheimer's disease. Despite years of research, pharmacological interventions to treat or forestall the development of Alzheimer's disease have primarily focused on enhancing cholinergic transmission, either through increasing acetylcholine (ACh) synthesis or inhibition of the acetylcholinesterase enzyme responsible for ACh hydrolysis. However, recent studies have indicated that dietary supplementation can impact the cholinergic system, particularly during aging. The purpose of the present review is to examine the relevant research suggesting that cholinergic functioning may be maintained during aging via consuming a diet containing polyunsaturated fatty acids (PUFAs). The data reviewed herein indicate that, at least in animal studies, inclusion of PUFAs in the diet can improve cholinergic transmission in the brain, possibly leading to improvements in cognitive functioning.

Role of diet in cholesterol gallstone formation

BACKGROUND

There is a high prevalence of gallstone disease in Western countries as a consequence of genetic, biochemical, and environmental factors. Animal and clinical studies have explored the importance of dietary elements. Overwhelming but conflicting information has been reported about the relationship between specific dietary components and gallstone disease. Although the detailed biochemical pathways have been described in experimental models, human studies are mainly epidemiological.

METHODS

We performed a Medline search with the terms "diet", "gallstones", "cholesterol", "risk factors", including results from 1965 to 2006 and the author's personal library to review the relationship between dietary factors and cholesterol gallstone disease.

RESULTS

We identified over 150 references and present their results with respect to the author's criteria.

CONCLUSIONS

The best delineated relationship between cholesterol gallstones and diet was found in the studies that analyzed total calorie intake, refined sugars and fiber. The possible mechanisms are discussed in base of experimental studies.

Effect of the type of dietary fat on biliary lipid composition and bile lithogenicity in humans with cholesterol gallstone disease

OBJECTIVE

The effect of the type of dietary fat on bile lipids and lithogenicity is unclear. This study compared the effects of two dietary oils that differed in fatty acid profile on biliary lipid composition in humans.

METHODS

Female patients who had cholesterol gallstones and were scheduled for elective cholecystectomy were studied. For 30 d before surgery, subjects were kept on diets that contained olive oil (olive oil group, n = 9) or sunflower oil (sunflower oil group, n = 9) as the main source of fat. Gallbladder bile and stones were sampled at surgery. After cholecystectomy, duodenal samples were collected by nasoduodenal intubation during fasting and after administration of mixed liquid meals that included the corresponding dietary oil. Duodenal and gallbladder bile samples were analyzed for cholesterol, phospholipids, and total bile acids by established methods. Individual bile acid conjugates in gallbladder bile were measured by high-performance liquid chromatography. Gallstones were analyzed by semiquantitative polarizing light microscopy.

RESULTS

Despite marked differences in the absolute concentration of biliary lipids and total lipid content, manipulation of dietary fat ingestion did not influence the cholesterol saturation or the profile of individual bile acids in gallbladder bile obtained from patients who had gallstones. All but one subject had mixed cholesterol stones. A cholesterol saturation index of hepatic bile in fasted cholecystectomized patients was similar in both dietary groups and indicative of supersaturation. In response to the test meal, the cholesterol saturation index decreased significantly in patients given the olive oil diet, reaching values lower than one at 120 min postprandially. In contrast, hepatic bile secreted by patients who consumed sunflower oil appeared supersaturated (cholesterol saturation index >1.5) throughout the experiment.

CONCLUSIONS

Our results suggest that the type of dietary fat habitually consumed can influence bile composition in humans. In gallbladder, this influence was noted in the presence of more concentrated bile in the olive oil group. However, this was not translated into a modification of cholesterol saturation, which is likely due to the fact that cholesterol gallstones were present by the time the dietary intervention started. The finding that a typical postprandial variation in hepatic bile lithogenicity occurred only in olive oil patients was revealing. While keeping in mind the methodologic limitations of this part of the study, some gastrointestinal and metabolic mechanisms for this effect are discussed.

The effects of phytase and phytic acid on the loss of endogenous amino acids and minerals from broiler chickens

1. The effects of myo-inositol hexaphosphate (IP6) and phytase (EC 3.1.3.26) on the excretion of endogenous compounds were investigated using growing broiler chickens. 2. A total of 32 female Ross broilers were used in a precision feeding assay involving a 2 x 2 factorial arrangement of treatments. The materials administered were glucose, glucose + 1000 units of phytase activity (FTU), glucose + 1 g of IP6 and glucose + 1 g of IP6 + 1000 FTU. Excreta were collected quantitatively over a 48-h period following intubation of the test materials. The excretion of nitrogen, amino acids, minerals, sialic acid and phytate phosphorus was determined. 3. The ingestion of 1 g of IP6 by broilers increased the excretion of endogenous nitrogen, amino acids, iron, sodium, sulphur and sialic acid compared with birds fed on glucose. Supplementation of IP6 with exogenous phytase reduced the excretion of endogenous amino acids, calcium, sodium, phytate phosphorus and sialic acid compared with birds fed IP6. 4. It can be concluded that IP6 increases the excretion of endogenous minerals and amino acids in broiler chickens. Part of the beneficial effects of the addition of exogenous phytases to the diets of poultry appears to be mediated through a reduction in endogenous losses of these nutrients.

Prostate cancer risk and consumption of fish oils: a dietary biomarker-based case-control study

Experimental studies suggest that the risk of prostate cancer is reduced with the intake of long-chain n-3 polyunsaturated fatty acids derived from marine foods, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, few human studies have been conducted due to difficulties in assessing the dietary intake of these fatty acids. The authors examined the relationship between prostate cancer risk and EPA and DHA in erythrocyte biomarkers in a population-based case-control study in Auckland, New Zealand during 1996-1997 involving 317 prostate cancer cases and 480 age-matched community controls. Reduced prostate cancer risk was associated with high erythrocyte phosphatidylcholine levels of EPA (multivariate relative risk = 0.59; 95% confidence interval 0.37-0.95, upper vs lowest quartile) and DHA (multivariate relative risk = 0.62; 95% confidence interval 0.39-0.98, upper vs lowest quartile). These analyses support evidence from in vitro experiments for a reduced risk of prostate cancer associated with dietary fish oils, possibly acting via inhibition of arachidonic acid-derived eicosanoid biosynthesis.

Palmolein and groundnut oil have comparable effects on blood lipids and platelet aggregation in healthy Indian subjects

Substitution of palmolein (POL) for groundnut oil (GNO) doubles saturated fatty acids and decreases by half the linoleic acid (18:2n-6) content of Indian diets. The effects of this substitution on selected parameters of cardiovascular risk and membrane functions were studied in middle-aged subjects. Both metabolic (short-term) and "in-home" (long-term) studies were conducted, and the subjects were crossed over from GNO to POL or vice versa. During both studies and in both sexes, blood pressure, plasma levels of total cholesterol and triglycerides and their distributions in various lipoprotein fractions were not altered. The lower 18:2n-6 and higher 16:0 intakes were reflected in fatty acid compositions of cholesteryl esters and triglycerides. However, the plasma and platelet phospholipid fatty acid patterns did not shift toward saturation. The observation that the levels of long-chain polyunsaturated fatty acids in phospholipids were similar at the end of GNO and POL regimens indicates that 18:2n-6 furnished during POL regimen may be sufficient to maintain the levels of arachidonic acid in cell membranes. Platelet aggregation, erythrocyte membrane fluidity, and activity of Na+, K+ ATPase, a membrane-bound enzyme, were essentially similar at the end of the two oil regimens. These results indicate that POL is comparable to GNO and may not induce hypercholesterolemia in Indian subjects consuming cereal-based diets containing 30% total fat calories and low cholesterol.

Influence of cell culture conditions on diet-induced changes in lymphocyte fatty acid composition

The effect of a range of dietary lipids on the fatty acid composition and membrane fluidity of lymphocytes was investigated. The effects of subsequent culture of these lymphocytes in medium containing autologous serum, foetal calf serum or a serum-free supplement were assessed; this was considered important, since many studies investigating the effects of dietary lipid manipulation on immune function have used protocols involving a variety of cell culture conditions when performing tests of immune function. Weanling Lewis rats were fed for 10 weeks on a low-fat (LF; 20 g/kg) diet or on high fat diets containing 200 g/kg of either hydrogenated coconut oil (HCO), olive oil (OO), safflower oil (SO), evening primrose oil (EPO) or menhaden oil (MO). The fatty acid composition of the phospholipid fractions of lymphocytes from the spleen was altered by dietary lipid manipulation, whereas the fatty acid composition of thymic lymphocytes was not modified significantly. In general, the changes in the fatty acid composition of spleen lymphocytes reflected the fatty acid composition of the diets themselves. Despite the considerable changes in the fatty acid composition of lymphocytes from spleen, dietary lipid manipulation had no effect on the plasma membrane fluidity of these cells. Culturing lymphocytes in autologous serum allowed some, but not all, of the diet-induced changes in fatty acid composition to be maintained. The effects of dietary lipid manipulation were totally reversed when lymphocytes were cultured in FCS. Culturing lymphocytes in serum-free medium not only reversed any effects of dietary manipulation, but also markedly increased the appearance of palmitoleic and oleic acids, at the expense of palmitic and stearic acids, suggesting activation of the delta 9 desaturase when these cells were cultured in the absence of exogenous lipid. This study suggests that cell culture conditions have significant influence on the changes in lymphocyte fatty acid composition brought about by dietary lipid manipulation and may therefore influence the outcome of functional tests.

Fat diet, osmotic fragility of erythrocytes and inotropic response of rat heart papillary muscle to noradrenaline stimulation: early appearance of the diet effect by lovastatin

Intake of lovastatin, an inhibitor of endogenous cholesterol synthesis, leads to a compensatory increase in the uptake of cholesterol from plasma (low density lipoprotein endocytosis). The drug might exert effects also by facilitating uptake of fatty acids carried in low density lipoprotein. It has been reported that dietary fat may alter physical properties of erythrocytes as well as adrenergic effects in heart muscle. We have therefore studied osmotic fragility of erythrocytes and inotropic and lusitropic responses of isolated heart papillary muscles taken from rats fed for 3 weeks either a purified high fat diet (olive oil/coconut oil 16 g/6 g/100 g diet), prepared plus and minus lovastatin, or similar diets in which 4 g/100 g diet of the olive oil was replaced by cod liver oil. Three weeks feeding of a high fat diet containing cod liver oil did not affect osmotic fragility of erythrocytes or indices of inotropy or lusitropy in papillary muscles in response to noradrenaline stimulation neither in the absence nor in the presence of lovastatin. In contrast, purified high fat diet lacking cod liver oil increased osmotic fragility in a fraction of the erythrocytes. When lovastatin was added to this diet the osmotic fragility was increased for the whole population of erythrocytes. In this situation the "relaxation-onset index"--an index of early relaxation in the papillary muscles--was shifted to higher concentrations of noradrenaline. Thus, intake of lovastatin may lead to an early appearance of effects of dietary fat on osmotic fragility of erythrocytes and on heart muscle responses to catecholamines. These effects of lovastatin are, however, apparently dependent upon the kind of dietary fat as they are prevented by the presence of cod liver oil.