Effects of short-term high dose intake of evening primrose oil on plasma and cellular fatty acid compositions, alpha-tocopherol levels, and erythropoiesis in normal and type 1 (insulin-dependent) diabetic men

Vitamin D and Evening Primrose Oil Administration Improve Glycemia and Lipid Profiles in Women with Gestational Diabetes

Limited data are available assessing the effects of vitamin D and evening primrose oil (EPO) administration on markers of insulin resistance and lipid concentrations in gestational diabetes mellitus (GDM). This study was designed to evaluate the effects of vitamin D and EPO administration on insulin resistance and lipid concentrations among women with GDM. In this prospective randomized, double-blind, placebo-controlled clinical trial, 60 participants with GDM were divided into 2 groups of either 1000 IU vitamin D3 and 1000 mg EPO or placebo for 6 weeks. At the beginning and end of the study, fasting blood samples were obtained from the participants to measure related variables. After 6 weeks of intervention, changes in fasting plasma glucose (-3.6 ± 7.5 vs. +1.5 ± 11.4 mg/dL, P = 0.04), serum insulin concentrations (-2.0 ± 5.3 vs. +4.6 ± 10.7 µIU/mL, P = 0.004), homeostasis model of assessment (HOMA) insulin resistance (-0.5 ± 1.1 vs. +1.1 ± 2.5, P = 0.003), HOMA-B cell function (-7.7 ± 23.3 vs. +17.4 ± 42.9, P = 0.007) and the quantitative insulin sensitivity check index (+0.01 ± 0.02 vs. -0.01 ± 0.02, P = 0.007) in the vitamin D plus EPO group were significantly different from the placebo group. In addition, compared with the placebo, vitamin D and EPO supplementation resulted in significant reductions in serum TAG (-20.0 ± 54.3 vs. +34.3 ± 38.2 mg/dL, P < 0.001), VLDL (-4.0 ± 10.9 vs. +6.9 ± 7.6 mg/dL, P < 0.001), TC (-22.1 ± 32.6 vs. +5.3 ± 20.1 mg/dL, P < 0.001), LDL concentrations (-18.0 ± 25.5 vs. +1.8 ± 15.7 mg/dL, P = 0.001) and TC/HDL (-0.3 ± 0.4 vs. +0.3 ± 0.5 mg/dL, P < 0.001). We did not observe any significant effect of vitamin D and EPO supplementation on serum HDL concentrations.

CLINICAL TRIAL REGISTRATION NUMBER

http://www.irct.ir : IRCT201509115623N52.

The effects on plasma, red cell and platelet fatty acids of taking 12 g/day of ethyl-eicosapentaenoate for 16 months: dihomogammalinolenic, arachidonic and docosahexaenoic acids and relevance to Inuit metabolism

A patient with mantle cell lymphoma took 12g/day of ethyl-eicosapentaenoate for 16 months. Compared to reference values, eicosapentaenoic and docosapentaenoic acids were elevated in plasma, red cells and platelets but docosahexaenoic acid levels were in the normal range. Arachidonic acid levels were moderately reduced but dihomogammalinolenic acid levels remained in the normal range. In spite of a long chain n-3 fatty acid intake higher than in most Inuit populations, arachidonic acid levels remained considerably higher in this patient than in the Inuit. The implications for understanding of fatty acid metabolism in humans are discussed.

Linoleic acid metabolism in the spontaneously diabetic rat: delta6-desaturase activity vs. product/precursor ratios

The activity of delta6-desaturase of linoleic acid, a rate-limiting step in the formation of arachidonic acid, is decreased in animal models of severe, uncontrolled diabetes. The aim of the study was to measure the activity of liver microsomal delta6-desaturase of spontaneously diabetic BioBreeding/Edinburgh rats receiving subcutaneous insulin daily and of genetically related nondiabetic animals. The activity of delta6-desaturase was then compared with indices of activity (plasma lipid fatty acid product/precursor ratios) frequently used in human studies. Diabetic rats treated with insulin had 75 +/- 8% of the activity of microsomal delta6-desaturase of nondiabetic controls (P < 0.05). Insulin withdrawal tended to reduce the activity further (61% of control), although the activity did not differ from insulin-treated diabetic rats. The ratio of plasma phospholipid or cholesteryl ester gamma-linolenic over linoleic acid was not decreased in insulin-treated diabetic rats. By contrast, the ratio of gamma-linolenic over linoleic acid of microsomes was almost three-fold higher in insulin-treated diabetic rats (P < 0.05). The gamma-linolenic over linoleic acid ratio as an index of activity gave inconsistent results in insulin-deprived rats. The ratio of gamma-linolenic over linoleic acid of cholesteryl esters did not differ between control and diabetic rats, nor did it correlate with microsomal delta6-desaturase activity. Furthermore, the index of delta6-desaturase activity, derived from the fatty acid composition of microsomal phospholipids, did not correlate with microsomal delta6-desaturase activity. Diabetes, even when controlled by regular insulin injections, reduces the metabolism of linoleic acid, but the effect is less than previously published. The fatty acid compositions of plasma and liver microsomal lipids are not reliable indices of delta6-desaturase activity in diabetes.

Gamma-linolenic acid does not augment long-chain polyunsaturated fatty acid omega-3 status

Augmentation of long chain polyunsaturated omega3 fatty acid (LCPUFA omega3) status can be reached by consumption of fish oil or by improvement of the conversion of alpha-linolenic acid (ALA) to LCPUFA omega3. Since gamma-linolenic acid (GLA) might activate the rate-limiting delta-6 desaturation, we investigated whether GLA augments LCPUFA omega3 status. Eight adults received 1.4 g GLA for 4 weeks and subsequently 2.2 g ALA+1.4 g GLA daily during another 4 weeks. Another seven adults received a daily oral dose of 2.2 g ALA for 4 weeks, and subsequently 2.2 g ALA+1.4 g GLA during another 4 weeks. ALA, or ALA+GLA, did not significantly augment EPA and DHA contents. We conclude that the LCPUFA omega3 status can not be improved by supplementation of low dose GLA, neither by co-supplementation of ALA. Poor conversion of ALA to LCPUFA omega3 may be caused by preferential beta-oxidation of ALA, negative feedback of arachidonic acid from the omnivorous diet, or by the low dietary ALA/LA ratio.

Influence of fasting on circulating levels of alpha-tocopherol and beta-carotene. Effect of short-term supplementation

We investigated the influence of fasting on the levels of alpha-tocopherol in plasma, erythrocytes and platelets, and on plasma beta-carotene. Six apparently healthy adults were subjected to 17-h feed-fasting experiments at various days before, during and after supplementation with alpha-tocopherol (455 mg/day, 41 days) and beta-carotene (25 mg/day, 24 days). Adipose tissue alpha-tocopherol and beta-carotene were measured at regular intervals. Supplementation increased alpha-tocopherol and beta-carotene in all compartments, except for beta-carotene in adipose tissue. Discontinuation caused a rapid return to baseline, except for adipose tissue alpha-tocopherol and plasma beta-carotene. Fasting caused linear increases of free fatty acids, consistent (but small) increases of plasma alpha-tocopherol and inconsistent increases of plasma beta-carotene. There were no fasting-related changes in other compartments. We conclude that fasting is unable to increase alpha-tocopherol and beta-carotene in circulating lipoproteins and cells to a considerable extent, both at baseline levels and after short-term supplementation. Maintenance of high levels may necessitate regular high oral intakes.

Essential fatty acid deficiency in renal failure: can supplements really help?

Abnormal fatty acid metabolism may contribute to clinical problems such as itching, abnormal perspiration, susceptibility to infection, delayed wound healing, anemia, and increased hemolysis, as seen in patients with chronic renal failure. A double-blind study of patients on hemodialysis who received either fish oil, olive oil, or safflower oil documented that patients may have increased levels of the proinflammatory prostaglandin PGE2 and that fish oil intervention may decrease these levels, change the fatty acid profile, improve hematocrit levels, and improve patient perception of symptoms of pruritus.

Effects of malnutrition on the erythrocyte fatty acid composition and plasma vitamin E levels of Pakistani children

Erythrocyte fatty acids and plasma vitamin E concentrations were determined in 47 grade 2 and 21 grade 3 malnourished Pakistani children (ages 4-56 months). Data were compared with those of 26 age- and sex-matched apparently healthy controls. Evaluation with three statistical approaches revealed that both grade 2 and grade 3 malnourished children had decreased erythrocyte omega6 fatty acids and to a lesser extent decreased omega3 fatty acids. These decreases were compensated for by increased omega9 fatty acids. The patients tended to have lower plasma vitamin E concentrations. We conclude that malnourished Pakistani children have low essential fatty acid status, notably those of the omega6 series. The combination of low erythrocyte 22:6omega3 and a low 22:5omega6/22:4omega6 ratio in grade 2 patients suggests low delta4-desaturation activity, which may be due to impaired peroxisomal beta-oxidation.

Oxidation of low-density lipoprotein in NIDDM: its relationship to fatty acid composition

The increased risk of atherosclerotic disease in diabetic subjects may be due to enhanced foam cell formation following an increased susceptibility of low density lipoprotein to oxidative modification. This study has compared fatty acid content and lipoprotein oxidisability in 10 non-insulin-dependent diabetic subjects with that in 10 control subjects. Both groups were normocholesterolaemic and the diabetic subjects had higher triglyceride levels (2.2 +/- 0.4 vs 1.2 +/- 0.2 mmol/l, p < 0.05). The fatty acid composition was compared in low density lipoprotein following Folch extraction, separation by thin layer chromatography (for the lipid classes) and analysis by gas liquid chromatography. Low density lipoprotein oxidisability was assessed by conjugated diene and thiobarbituric acid reacting substance formation in the presence of copper ions. The esterified/free cholesterol ratio was higher in the low density lipoprotein from patients compared to control subjects (2.9 +/- 0.1 vs 1.9 +/- 0.3, p < 0.05). Linoleic acid in the cholesteryl ester fraction of the lipoprotein was higher in the patients than in the control subjects (48.2 +/- 2.2% vs 42.4 +/- 3.4%, p < 0.05) as was the total quantity of linoleic acid in the cholesteryl ester fraction (317.8 +/- 68.0 vs 213.2 +/- 28.0 micrograms/mg protein, p < 0.05) and in the low-density lipoprotein as a whole (443.2 +/- 70.0 vs 340.2 +/- 28.2 micrograms/mg protein, p < 0.05). Lipoprotein oxidisability was also increased in the diabetic group with increased formation of thiobarbituric acid reacting substances (35.6 +/- 7.2 vs 22.3 +/- 3.5 nmol/mg protein, p < 0.05, increased total diene formation (502 +/- 60 vs 400 +/- 30 nmol/mg protein, p < 0.05) and increased rate of diene formation (7.2 +/- 0.6 vs 5.1 +/- 0.9 nmol diene.mg protein-1.min-1, p < 0.05). This study indicates that low-density lipoprotein from diabetic subjects is more susceptible to oxidation. This could, in vivo, accelerate foam-cell formation thereby increasing atherosclerotic risk in diabetic subjects.

Serum fatty acid profiles in type I and type II diabetes: metabolic alterations of fatty acids of the main serum lipids

Fatty acid profiles of various lipid fractions were determined in carefully selected insulin-dependent and non-insulin-dependent diabetics to assess relationships between serum fatty acid composition and type of diabetes. Clear-cut hypertriglyceridemia with slight hypercholesterolemia was found in both diabetic types. The decrease of lignoceric acid in sphingomyelin is the only alteration found in both types of diabetes. In the insulin-dependent diabetics, there were increases in levels of oleic acid and of alpha-linolenic acid in esterified cholesterol, and in levels of alpha-linolenic acid in the triglyceride fraction. In the non-insulin-dependent diabetics, there were increases in levels of oleic acid and total monounsaturated fatty acids in the triglyceride fraction and there was an increase in levels of saturated fatty acids and a decrease in levels of polyunsaturated acids in phosphatidylcholine; in sphingomyelin, dihomogamma-linoleic acid levels were enhanced. Arachidonic acid levels were normal in our patient population.

The effect of borage oil consumption on the composition of individual phospholipids in human platelets

The effect of supplementation with borage oil containing gamma-linolenic acid (GLA, 18:3n-6) on the levels and fatty acid compositions of individual human platelet phospholipids was evaluated. For this purpose, male volunteers were given an average daily intake of 5.23 g of GLA (as borage oil) for 42 days, after which the supplement was withdrawn for an additional 42-day period. No significant differences were found in the relative amounts of the choline phospholipids (PC), ethanolamine phospholipids (PE), phosphatidylserine (PS), phosphatidylinositol (PI), and sphingomyelin (SPH) at days 0, 22, 43, 64, and 85. However, marked differences were observed in the fatty acid compositions of all the phospholipids including a marked, and reversible, rise in the level of dihomo-gamma-linolenic acid (DGLA, 20:3n-6), without a significant elevation in arachidonic acid (AA, 20:4n-6) and decreases in n-3 polyunsaturated fatty acids. In the case of PC, a net rise in DGLA of 1.8 mol% was observed by day 22 (from 2.1 to 3.9 mol%). The DGLA/AA ratios at day 43 exhibited considerable variability across phospholipids with PC greater than PS greater than PE = PI; the PC, PE, PS, and PI accounted for 67.6, 16.7, 12.9, and 2.6%, respectively, of the total DGLA in platelet phospholipids. Interestingly, despite the lack of DGLA in SPH, this phospholipid exhibited a marked enrichment in nervonic acid (NA, 24:1n-9) from 16.2 to 24.7 mol% upon borage oil consumption. The observed alterations may represent biochemical strategies for adaptation to dietary fatty acid modifications and the regulation of platelet membrane functioning.

Fatty acid composition of serum lipids and erythrocyte membranes in type 2 (non-insulin-dependent) diabetic men

The fatty acid (FA) composition of serum lipids and erythrocytes was studied in 21 men with non-insulin-dependent diabetes mellitus (NIDDM) and in 14 normal subjects matched for age, sex, body weight, and dietary intake. Lower levels of linoleic acid and higher levels of highly unsaturated FA (daughter) of n-3 and n-6 family FA, reflected in a higher unsaturation index, were found in serum phospholipids (S-PL), in phospholipids of erythrocyte membranes (ery-PL), and in serum cholesterolesters (S-CHE). The unsaturation index of serum phospholipids significantly correlated with glycosylated hemoglobin A1c (P less than .05) and blood glucose levels after glucose load (P less than .001). The results suggest that elongation and desaturation of essential FA (linoleic acid in particular) are increased. The above changes may be associated with accelerated atherosclerosis in type 2 diabetics.

Fatty acid composition of serum cholesterol esters in different degrees of glucose intolerance: a population-based study

The fatty acid composition of serum cholesterol esters was investigated in 325 subjects with normal glucose tolerance, 97 subjects with impaired glucose tolerance (IGT), and 98 subjects with non-insulin-dependent diabetes mellitus (NIDDM) identified by population-based screening. The proportions of palmitic acid (16:0) and palmitoleic acid (16:1) in serum cholesterol esters increased from the normal glucose tolerance group to the IGT and diabetic groups. On the other hand, the proportion of linoleic acid (18:2) was lower in diabetic subjects than in the subjects with IGT or normal glucose tolerance. The proportions of gamma-linolenic (18:3), dihomo-gamma-linoleic (20:3), and arachidonic (20:4) acids were highest in diabetic subjects and lowest in subjects with normal glucose tolerance. Our findings suggest that subjects with NIDDM or IGT have had higher dietary intake of saturated fatty acids. Both serum insulin and blood glucose concentrations probably have an effect on the elongation and desaturation of fatty acids, but the metabolism of linoleic acid to prostaglandin precursors seems to be different in different types of diabetes, NIDDM patients showing no abnormalities. The possibility that the fatty acid composition of plasma and membrane lipids has a role in insulin resistance and blood glucose regulation deserves further investigation.

Pathogenesis of diabetic neuropathy: the role of the n-6 essential fatty acids and their eicosanoid derivatives

A substantial disturbance of the metabolism of the n-6 essential fatty acids exists in both human and experimental diabetes mellitus. Disturbances of the essential fatty acids and of the 1- and 2-series prostaglandins derived from them create a variety of microvascular, haemorheological, and other abnormalities leading to reduced blood flow and neural hypoxia which will in turn produce a cycle of hypoxia. Disturbance of the n-6 pathway may also result in functional and structural abnormalities of the axon, the myelin, and membrane-bound proteins such as enzymes and receptors. Metabolic disturbances identified previously may have a synergistic effect in enhancing these pathogenetic changes.

Alpha- and gamma-tocopherol in plasma, red blood cells, and platelets during plasma exchange

The effect of a rapid reduction of plasma lipoproteins on the alpha- and gamma-tocopherol levels in plasma, erythrocytes, and platelets was studied. Sixteen successive plasma exchange procedures performed weekly in an adult with heterozygous familial hypercholesterolemia were evaluated. Plasma exchange was done by intermittent flow centrifugation, exchanging one plasma volume against a 4% human albumin solution. Plasma exchange reduced in plasma alpha-tocopherol from 41.5 +/- 8.9 to 23.6 +/- 4.8 mumol/L and gamma-tocopherol from 4.9 +/- 4.1 to 2.4 +/- 2.1 mumol/L, without changing their ratios to total lipids. It diminished alpha-tocopherol in platelets from 12.97 +/- 4.37 to 10.03 +/- 1.78 mumol/10(13) cells and gamma-tocopherol from 1.43 +/- 0.55 to 1.06 +/- 0.41 mumol/10(13) cells, but did not affect erythrocyte tocopherols. The total amount removed per procedure was 47.57 +/- 13.65 mumol for alpha-tocopherol and 4.70 +/- 3.59 mumol for gamma-tocopherol. Plasma exchange increased the number of erythrocytes from 3.67 +/- 0.10.10(12) to 4.05 +/- 0.13.10(12) cells/L, without affecting their volume. Platelet count did not change, but mean platelet volume decreased from 7.7 +/- 0.5 to 6.9 +/- 0.5 fl and platelet distribution width from 15.1 +/- 0.4 to 14.9 +/- 0.5. Thus, plasma exchange reduces plasma alpha- and gamma-tocopherol to the same extent as total lipids, and decreases these tocopherols in circulating platelets, along with a reduction in platelet size and, compared to the change in erythrocyte count, a fall of platelet number.(ABSTRACT TRUNCATED AT 250 WORDS)