Gamma-linolenic acid dietary supplementation can reverse the aging influence on rat liver microsome delta 6-desaturase activity

We have recently demonstrated that in rats the process of delta 6-desaturation of linoleic and alpha-linolenic acids slows with aging. One method of counteracting the effect of slowed desaturation of linoleic acid would be to provide the 6-desaturated metabolite, gamma-linolenic acid (18:3(n-6) GLA) directly. We have here investigated the 6-desaturation of both linoleic and alpha-linolenic acids in liver microsomes of young and old rats given GLA in the form of evening primrose oil (EPO) (B diet) in comparison to animals given soy bean oil alone (A diet), monitoring also the fatty acid composition of liver microsomes and relating this to the microviscosity of the membranes. In young rats the different experimental diets did not produce any difference in delta 6-desaturase (D6D) activity on either substrate suggesting that, when D6D activity is at or near its peak, the variations in diet tested are unable to influence it. In the old animals the rate of 6-desaturation of linoleic and particularly of alpha-linolenic acid was significantly greater in the B diet fed animals than in the A diet fed. The effects of the diets on the fatty acid composition of liver microsomes were consistent with the findings with regard to 6-desaturation. Administration of GLA partially corrected the abnormalities of n-6 essential fatty acid (EFA) metabolism by raising the concentration of 20:4(n-6) and other 6-desaturated EFAs. Furthermore, the GLA rich diet also increased the levels of dihomo-gamma-linolenic acid and of 6-desaturated n-3 EFAs in the liver microsomes. The microviscosity of microsomal membranes as indicated by DPH polarization was correlated with the unsaturation index of the same membranes. There was a very strong correlation between the two. In both young and old rats the B diet reduced the microviscosity and increased the unsaturation index. However, the effect was much greater in the old animals.

Essential fatty acid diet supplementation. Effects on peripheral nerve and skeletal muscle function and capillarization in streptozocin-induced diabetic rats

Effects of essential fatty acids on nerve conduction, hypoxic resistance, skeletal muscle contractile properties, and capillary density were examined in streptozocin-induced diabetic rats. Nondiabetic and diabetic controls and three diabetic groups treated with 10% supplements of corn oil, evening primrose oil (Efamol), or a mixture of 80% evening primrose oil and 20% fish oil (Efamol Marine) for 2 mo were used. Efamol and Efamol Marine increased plasma gamma-linolenic acid levels, but arachidonic acid was elevated only with Efamol. Diabetes resulted in 15-29% reductions in sciatic motor and sensory saphenous nerve conduction velocity. Efamol prevented conduction deficits more effectively than Efamol Marine, and corn oil had no effect. In vitro measurement of sciatic nerve hypoxic resistance revealed a 49% increase in the time taken for action potential amplitude to decline by 50% with diabetes. Corn oil had no significant effect. With Efamol, hypoxic resistance was within the nondiabetic range. Efamol Marine produced intermediate results. Functional improvements may relate to enhanced vasa nervorum perfusion, because endoneurial capillary density increased by 22% with Efamol, angiogenesis perhaps resulting from eicosanoid production from arachidonic acid. Soleus muscle contractions were prolonged by diabetes. This was partially corrected by treatment, Efamol being most effective. Extensor digitorum longus muscle had reduced tetanic tension with diabetes, and this was prevented by all treatments. Soleus showed a modest increase in capillarization with Efamol, which may have contributed to reduced susceptibility to fatigue. The data suggest involvement of abnormal fatty acid metabolism in the etiology of diabetic neuropathy and myopathy.

The effects of evening primrose oil, safflower oil and paraffin on plasma fatty acid levels in humans: choice of an appropriate placebo for clinical studies on primrose oil

In a number of diseases, plasma levels of linoleic acid are normal or elevated while those of gamma-linolenic acid (18:3n-6, GLA) and further metabolites are below normal. Evening primrose oil (EPO), similar to safflower oil (SFO) except that it contains 8-9% of 18:3n-6, has been proposed as a therapeutic agent in these diseases, such as atopic eczema. There is argument as to whether an appropriate placebo for clinical studies on EPO should be an inert material such as paraffin, or a linoleic acid--containing oil such as SFO. We have therefore compared in normal humans the effects on plasma fatty acids of administering EPO, SFO and paraffin for 10 days. Paraffin had no effect on any fatty acid in any fraction. EPO raised the level of 20:3n-6 (dihomo-gamma-linolenic acid, DGLA) the immediate metabolite of GLA but had no significant effect on arachidonic acid. In surprising contrast, SFO raised the levels of linoleic and of arachidonic acids, without raising those of DGLA. This suggests that linoleic acid may be rapidly converted to arachidonic acid by a tightly linked enzyme sequence: GLA, in contrast, may be rapidly converted to DGLA but then only slowly on to arachidonic acid. These results are consistent with recent in vitro observations by others on rat hepatocytes and human fibroblasts.

Possible involvement of delta-6-desaturase in control of melanoma growth by gamma-linolenic acid

This study examined the effects of linoleic acid (LA) and gamma-linolenic acid (GLA) on BL6 melanoma growth in cell culture and of safflower oil (SFO) which contains LA and evening primrose oil (EPO) which contains GLA, on melanoma growth when grown in mice. The delta-6-desaturase activity of the melanoma cells in the two systems was also examined and an attempt made to relate the activity of the enzyme to the effects of GLA on cell and tumour growth. LA and GLA were found to be equipotent in inhibiting growth of the in vitro cultured BL6 cells which were found to contain an appreciable level of delta-6-desaturase activity. EPO was however found to be a more potent promoter of in vivo melanoma growth in mice than SFO. Melanomas grown in mice were found to lack delta-6-desaturase activity suggesting that the EPO diet, by providing GLA, was able to compensate for the loss of enzyme activity in the melanomas. The possibility that melanomas in mice have a requirement for GLA for growth while in in vitro cultured cells excess GLA inhibits the growth of the cells through an increase in lipid peroxidation is discussed.

Effects of age and dietary essential fatty acids on desaturase activities and on fatty acid composition of liver microsomal phospholipids of adult rats

The combined effects of age and dietary n-6 and n-3 fatty acids were studied in 3-, 6- and 9-month-old rats. At each age, two groups were fed diets containing 5% (w/w) of vegetable oils rich in either 18:3n-6 (borage group) or 18:3n-6 plus 18:4n-3 (black currant group), for a period increasing with age. A control group was fed the essential fatty acids 18:2n-6 and 18:3n-3 only. For each group, delta 6, delta 5 and delta 9 desaturase activities were measured in liver microsomes, and fatty acid composition was determined in microsomal phospholipids. Desaturase activity varied as a function of age and dietary lipids. delta 6 Desaturation of 18:3n-3 was more sensitive to these factors while delta 6 desaturation of 18:2n-6 and delta 9 desaturation were more dependent on season than the other two. Desaturase activity was influenced more by the black currant than by the borage diet, especially at 6 and 9 months of age. A large proportion of arachidonic acid was maintained in the microsomes independent of the diet. Changes in the fatty acid composition did not strictly reflect the differences in desaturase activities. The effects of the two factors (age and diet) on the activities of the desaturases are complex, suggesting that the enzymes are susceptible to other factors as well.

Effect of evening primrose oil as food supplement on reproduction in the mink

The effects of addition of evening primrose oil (EPO) to a mink diet in the breeding season on the reproductive performance and kit and female performance during the lactation period were investigated in an experiment with 4 groups of male and female mink. Matings were carried out so that control males were mated to both control and supplemented females. Similarly, supplemented males mated both control and supplemented females. Reproductive results were evaluated both on a group basis and as an effect of male or female treatment, respectively. After males supplemented with EPO, there was a tendency for reduced rate of stillborn kits and kit losses during the first 21 days of life. These effects could not be explained physiologically. Female treatment did not affect reproductive performance, but there was a tendency for lower weight losses during lactation for EPO-supplemented females. Kit performance during the lactation period was independent of experimental treatment.

The role of n-3 essential fatty acids in brain and behavioral development: a cross-fostering study in the mouse

A cross-fostering design was used to examine the effects on brain and behavioral development in mice of pre- and/or postnatal dietary supplementation with n-3 fatty acids. Pregnant mice were fed either of two liquid diets, control (con) or experimental (exp). Each diet provided 3% of the calories in the form of n-6 fatty acids; the experimental diet was supplemented with an additional 1.5% from long chain n-3 fatty acids derived from fish oil. There were four treatment groups, with all pups fostered at birth. These groups were (prenatal diet/postnatal diet): Group 1. exp/exp; Group 2, exp/con; Group 3, con/exp; Group 4, con/con; a fifth control group (unfostered) was fed lab chow (LC) throughout the study. Animals from the exp/exp and con/con groups were weaned onto lab chow for later behavioral assessment. Prenatal n-3 supplementation resulted in a small acceleration of behavioral development. The adult animals did not differ on visual discrimination learning nor did they differ in visual acuity. During development the fatty acid composition of the brain membrane phospholipids reflected closely that of the pre- and postnatal dietary conditions. Levels of 22:5n-3 and 22:6n-3 increased in the n-3 supplemented groups, accompanied by a decrease in levels of 22:4n-6 and 22:5n-6; the net effect of these changes was to increase the total levels of C22 fatty acids. While these results support considerable plasticity of the fatty acid composition of the developing brain with respect to the immediate dietary availability of n-3 compounds, they do not support long term effects on learning capacity of n-3 supplementation during the developmental period.

The effects of chronic ethanol administration on rat liver and erythrocyte lipid composition: modulatory role of 'evening primrose oil'

The effects of chronic administration of ethanol on the lipid composition of erythrocytes and liver of rats were investigated. Ethanol was chronically administered alone or in combination with Evening Primrose Oil (containing 10% v/v gamma-linolenic acid) in a nutritionally balanced milk diet. Chronic administration of ethanol alone significantly decreased the content of arachidonic acid in erythrocyte membranes, whereas the concomitant administration of Evening Primrose Oil reversed this effect. The triacylglycerol content was significantly increased in the microsomal fraction of the liver after chronic ethanol administration. Ethanol also significantly increased the ratio of cholesterol:cholesteryl esters in the microsomal fraction. The arachidonic acid content of the whole liver fraction was significantly reduced after chronic administration of ethanol, whereas concomitant administration of Evening Primrose Oil did not reverse this effect. The administration of Evening Primrose Oil during chronic ethanol intake may have beneficial effects, as it reverses some of the effects of ethanol on erythrocyte and hepatocyte membrane lipids which may be detrimental to health.

Effect of evening primrose oil as food supplement on reproduction in the blue fox

Addition of evening primrose oil (EPO) to a blue fox diet in the reproduction period was evaluated in an experiment with 2 groups, each of 12 male and 25 female blue foxes, regarding the effects on reproductive performance. The experiment was carried out as a field trial and the experimental period lasted from March 10 until the end of the mating season (males) or early July (females). During this period the control group was fed the standard diet of the farm and the experimental group was fed the same diet supplemented with 4.5 g EPO and 2.5 mg zinc sulphate per animal and day. An addition of 10 mg vitamin E per 500 mg EPO was made. The results were evaluated regarding male and female treatment effects. There was an increased rate of abortions in the EPO-group, but simultaneously a non-significant decrease in the frequency of barren females, resulting in a similar level of females without litters in both groups. A tendency for increased litter size in the EPO group was found, mainly as an effect of male treatment, which might indicate an effect on semen quality.

Is there a role for dietary essential fatty acids in gastroduodenal mucosal protection?

A great deal is known about methods to diminish intragastric acid concentration, but far less is known about the ability of the gastroduodenal mucosa to resist injury or accelerate its healing. One group of compounds that plays a key role in the endogenous ability of the mucosa to protect itself against injury and perhaps to accelerate healing is the prostaglandins (PGs). The gastroduodenal mucosa synthesizes PGs from fatty acids precursors--predominantly linoleic and arachidonic. PGE1 or PGE2 have been shown to possess cytoprotective activity in the stomach and duodenum. In laboratory animals, linoleic acid feeding increased PG synthesis and diminished injury. When presented in a detergent solubilized form, arachidonic acid can also provide acute protection against injury by alcohol, bile acids, and aspirin. Arachidonic acid can also promote angiogenic response and thereby, perhaps, accelerate the healing process. Epidemiological evidence points toward a parallel between the decrease in peptic ulcer disease virulence and incidence and the total ingestion of linoleic acid by the population in the U.S. and the United Kingdom. Therefore, dietary essential fatty acids may play a key role in mucosal defense and restitution, and perhaps in the diminished incidence and virulence of peptic ulcer disease in the Western world.

Lipid and cell metabolic changes associated with essential fatty acid enrichment of articular chondrocytes

Observations of impaired chondrocyte metabolism in essential fatty acid (EFA) deficiency as well as EFA protection against development of osteoarthrosis in inbred mice suggest the existence of a relationship between EFA, chondrocyte metabolism, and cartilage degeneration. To explore this relationship further, the fatty acid content of lipids in normal fetal bovine chondrocytes was manipulated by in vitro exposure to media supplemented with 100 microM arachidonic acid (20:4) or oleic acid (18:1). Chondrocytes rapidly and differentially incorporated both fatty acids into their lipid pools. The predominant acceptor was triacylglycerols. A 980% enrichment of arachidonic acid was associated with increased concentrations of fatty acids, increased 35SO4 and [3H]proline incorporation into matrix macromolecules (170% and 54-103%, respectively), and a 24-fold elevation in chondrocyte prostaglandin synthesis. No metabolic effects elicited observed in cells enriched by 377% with 18:1 oleic acid. The metabolic effects elicited by 20:4 arachidonic acid were abolished by pretreatment of cells with indomethacin, suggesting that the cellular responses to essential fatty acid loading may be associated with induced increases in prostaglandin synthesis. The data indicate that excessive in vitro accumulation of arachidonic acid is associated with an increase in synthetic activity that is causally related to increased prostaglandin synthesis and elevated levels of cellular fatty acids.

Effects of linoleic and gamma-linolenic acids (efamol evening primrose oil) on fatty acid-binding proteins of rat liver

We have studied the effects of Efamol evening primrose oil (EPO) on fatty acid-binding proteins (L-FABP) of rat liver. EPO contains 72% cis-linoleic acid and 9% cis-gamma linolenic acid. EPO has been clinically used for treatment of a number of diseases in humans and animals. EPO is also known to lower cholesterol level in humans and animals. Feeding of an EPO supplemented diet to rats (n = 9) for 2 months decreases the oleate binding capacity of purified L-FABP of rat liver whereas the palmitate binding activity was increased by 38%. However, EPO feeding did not alter the L-FABP concentrations significantly as measured by using the fluorescence fatty acid probe, dansylamino undecanoic acid. Endogenous fatty acid analysis of L-FABPs revealed significant qualitative and quantitative changes in fatty acid pattern after EPO feeding. EPO feeding decreased the endogenous palmitate level by 53% and oleate level by 64% in L-FABPs and also EPO feeding decreased the total endogenous fatty acid content from 62 nanomole per mg of protein to 42 nanomole per mg of L-FABP (n = 3).

Intravenous amino acids stimulate human gallbladder emptying and hormone release

Gallbladder stasis during prolonged total parenteral nutrition (TPN) has been documented. We have examined the effect of intravenous amino acid infusion on human gallbladder contraction and release of cholecystokinin (CCK). Five healthy adult volunteers were given amino acid infusions at different rates (65, 125, 240, and 600 mg.kg-1.h-1). The volume of the gallbladder was calculated by means of ultrasonographic measurements. Plasma samples were analyzed for CCK immunoreactivity. Gallbladder and hormone responses after intravenous amino acids were compared with responses after a fat meal, after a protein meal, and after ingestion of an oral amino acid mixture. We found that intravenous amino acids stimulated human gallbladder contraction in a dose-related manner. The mechanism of stimulation may be through the release of CCK although significant correlation was not demonstrated. The magnitude of response is similar to that seen after meal stimulation. To compare the delivery of amino acids during a standard meal and during each dose of intravenous amino acids, peripheral plasma levels of dietary amino acids were measured after a standard commercially prepared enteral supplement meal and after each dose of intravenous amino acids. Our lower doses of amino acid infused resulted in levels of circulating amino acid comparable to those after a meal. The induction of gallbladder contraction and release of CCK in human recipients of parenteral nutrition may be of value in some circumstances.

The effect of gamma-linolenic acid, an in vitro cytostatic substance contained in evening primrose oil, on primary liver cancer. A double-blind placebo controlled trial

The cytostatic effects of essential fatty acid metabolic intermediates and of some prostaglandins and leukotrienes in vitro have been extensively documented. The essential fatty acids (EFAs) exhibit no side-effects when taken as a dietary supplement, even in large doses. Primary Liver Cancer (PLC) is a fatal disease in our area as it is always multifocal in nature. In vitro studies have shown a cytostatic effect of gamma-linolenic acid (GLA) on primary liver cancer cells. In a double-blind placebo controlled trial, using Evening Primrose Oil (as a source of GLA) as a dietary supplement in PLC patients, no statistically significant effect was observed on survival time or liver size. There was however a statistical significant beneficial effect on Gamma Glutamyl transferase values as a measure of liver function. No side-effects were observed. The large size of tumour and the low doses of GLA used in this trial probably explain the lack of significant effect on survival times.

Blood pressure and serum lipids from SHR after diets supplemented with evening primrose, sunflowerseed or fish oil

Spontaneously hypertensive rats (SHR) at 4 weeks of age were fed a diet supplemented with sunflowerseed oil (SO), evening primrose oil (EPO), fish oil (FO) or EPO + FO for 22 weeks. A diet with commercially available pellets served as control. Systolic blood pressure was significantly lower during and after FO, EPO and EPO + FO, whereas the lower level after SO was not significant when compared with the controls. Serum triglycerides and total cholesterol were lowest after EPO followed FO. The combination of both EPO and FO resulted in unexpected high values of triglycerides and cholesterol. HDL-cholesterol was likewise highest after EPO + FO. The results indicate a quantitatively different depression of blood pressure and serum lipids from SHR by individual polyunsaturated fatty acids (PUFA).

Effects of safflower oil and evening primrose oil in men with a low dihomo-gamma-linolenic level

Low levels of essential polyunsaturated fatty acids of the n-6 series are associated with coronary heart disease. Linoleic acid, but not gamma-linolenic acid requires the activity of delta 6-desaturase for its conversion to dihomo-gamma-linolenic and arachidonic acid. Evening primrose oil (EPO) and safflower oil (SO) are rich in linoleic acid, but EPO contains also 9% gamma-linolenic acid. The effect of EPO (10, 20 and 30 ml/day) and SO (20 ml/day) for 4 months on the deposition of linoleic acid metabolites in adipose tissue of 4 groups of 6-9 men with low adipose dihomo-gamma-linolenic acid was examined. EPO but not SO increased adipose dihomo-gamma-linolenic acid level from 0.080 +/- 0.005% to 0.101 +/- 0.005% (P less than 0.01; 20 ml/day for 4 months). Adipose dihomo-gamma-linolenic/linoleic acid ratio increased with EPO from 0.99 +/- 0.16 X 10(2) to 1.13 +/- 0.14 X 10(2) and fell on SO from 1.04 +/- 0.10 X 10(2) to 0.90 +/- 0.07 X 10(2) (P less than 0.01). Similar qualitative changes in the relative amount of dihomo-gamma-linolenic acid in serum triglyceride and cholesteryl ester fractions were observed. At the dose of 20 ml/day, SO and EPO did not differ in their effect on serum cholesterol (7.13 +/- 0.43 vs. 7.33 +/- 0.42 mmol/l (NS)), LDL-cholesterol (5.10 +/- 0.32 vs. 4.88 +/- 0.46 mmol/l (NS)) nor did the 2 oils differ in their effect on HDL-cholesterol. These results suggest that linoleic acid is not readily converted to dihomo-gamma-linolenic acid due to a low activity of delta 6-desaturase in these highly selected men. EPO was not an effective hypocholesterolaemic agent in this study.

Enhancement of endocrine pancreatic secretions by essential fatty acids

Recent studies have suggested the beneficial effects of essential fatty acids in postoperative patients receiving total parenteral nutrition. While there is abundant information on the role of glucose and amino acids on insulin release, the effect of essential fatty acids on endocrine pancreatic secretions is not clear. Since linoleic and linolenic acids are constituents of TPN solutions as well as dietary fat, our aim was to examine their effect on the endocrine pancreatic function, using isolated islets. In each experiment, six islets microdissected from three mice were preperifused at the rate of 1 ml/min with Krebs-Ringer bicarbonate (KRB) buffer pH 7.4 containing 2% bovine albumin and 5.5 mM glucose (basal) with continuous supply of 95%/5%, O2/CO2 for 1 hr, after which basal samples were collected on ice every minute. The perifusion was continued for 20 min after the addition of a mixture of 10 mM linoleic acid and 5 mM linolenic acid to the KRB. During each perifusion phase, effluent samples were also collected for insulin and glucagon assay. The mean integrated area under the curve/20 min showed an increase in both insulin and glucagon secretions with the addition of fatty acids. Hence insulin increased from a basal 3154.8 +/- 953.7 to 8393.0 +/- 2073.1 pg (P less than 0.025, n = 6) and glucagon increased from 193.7 +/- 46.9 to 1566.1 +/- 411.2 pg (P less than 0.0025, n = 5). The fatty-acid-induced insulin but not glucagon secretion was blocked by the addition of 2 mM palmoxirate an inhibitor of fatty acid oxidation.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary change and coronary heart disease

Dietary changes a hundred years ago in Europe, America and Australia were needed to feed their growing industrial populations. By 1909 margarines were first made by the hydrogenation of marine oils and, later, vegetable oils as a substitute for butter, thereby introducing saturated fats. The demise of the highly nutritious herring and its oil's hydrogenation into margarines seems to have coincided with a big increase in coronary heart disease (CHD). The Japanese escaped such changes to their rice diet by the influence of the inevitable annual monsoon while southern Europe's CHD immunity may hinge on its permanent olive oil and vitamin C antioxidant staples. Britain's 'angina pectoris' probably arose following the enclosures which changed arable (strip) into animal farming in the middle ages but cases rose only slowly from Heberden's 100 in 1802 to McKenzie's 200 by 1923. It seems likely, therefore, that much of the sudden increase to 2000 reported by Maurice Cassidy in 1945, despite the impact of this century's increased longevity on CHD, will be due to dietary change together with smoking's increasing impact.

The effect of endogenous essential and nonessential fatty acids on the uptake and subsequent agonist-induced release of arachidonate

We have demonstrated that the uptake and agonist-induced release of a pulse of arachidonate are influenced by the size and composition of preexisting endogenous fatty acid pools. EFD-1 cells, an essential fatty acid-deficient mouse fibrosarcoma cell line, were incubated with radiolabeled (14C or 3H] arachidonate, linoleate, eicosapentaenoate (EPA), palmitate, or oleate in concentrations of 0-33 microM for 24 h. After 24 h, the cells were pulsed with 0.67 microM radiolabeled (3H or 14C, opposite first label) arachidonate for 15 min and then stimulated with 10 microM bradykinin for 4 min. Because EFD-1 cells contain no endogenous essential fatty acids, we were able to create essential fatty acid-repleted cells for which the specific activity of the newly constructed endogenous essential fatty acid pool was known. Loading the endogenous pool with the essential fatty acids arachidonate, eicosapentaenoate, or linoleate (15-20 nmol of fatty acid incorporated/10(6) cells) decreased the uptake of a pulse of arachidonate from 200 to 100 pmol/10(6) cells but had no effect on palmitate uptake. The percent of arachidonate incorporated during the pulse which was released upon agonist stimulation increased 2-fold (4-8%) as the endogenous pool of essential fatty acids was increased from 0 to 15-20 nmol/10(6) cells. This 8% release was at least 3-fold greater than the percent release from the various endogenous essential fatty acid pools. In contrast, loading the endogenous pool with the nonessential fatty acids oleate or palmitate to more than 2-3 times their preexisting cellular level had no effect on the uptake of an arachidonate pulse. Like the essential fatty acids, increasing endogenous oleate increased (by 2-fold) the percent release of arachidonate incorporated during the pulse, whereas endogenous palmitate had no effect on subsequent agonist-induced release from this arachidonate pool. These studies show that preexisting pools of essential and nonessential fatty acids exert different effects on the uptake and subsequent releasability of a pulse of arachidonate.

Trophic effect of Efamol on the rat small-intestinal mucosa

1. The hypothesis that triacylglycerols are trophic to the small-intestinal mucosa of the rat was tested by comparing the action of the essential fatty acid-rich oil Efamol with that of glucose. 2. Two groups of nine female Wistar rats were pair-fed Vivonex HN with 50% calorie substitution by glucose or Efamol for 21 days. 3. Body weight gain was greater with glucose than with Efamol, but, despite this, whole gut weight, mucosal weight and mucosal protein were increased by Efamol in all small-intestinal segments. Total mucosal DNA was also increased with a significant change in the middle small-intestinal segment. These changes were associated with an increased crypt cell production rate. 4. Fasting plasma levels of peptidyltyrosyltyrosine ('peptide YY'), but not of enteroglucagon, were significantly elevated in the Efamol-fed group. 5. The data show a trophic effect of Efamol on the rat small-intestinal mucosa. Possible mechanisms are discussed.

Essential fatty acid treatment--effects on nerve conduction, polyol pathway and axonal transport in streptozotocin diabetic rats

This study was designed to examine the effect of dietary supplementation with essential fatty acids (evening primrose oil--5% weight:weight added to the diet) on acute neurophysiological and neurochemical defects in streptozotocin-diabetic rats. Diabetic rats, which were not given evening primrose oil, showed highly significant elevations of nerve sorbitol and fructose combined with a depletion of nerve myo-inositol. In those animals there was also a 40% reduction (p less than 0.02) in the accumulation of axonally transported substance P-like immunoreactivity proximal to a 12 h sciatic nerve ligature together with reduced motor nerve conduction velocity (13% [p less than 0.001] and 20% [p less than 0.001] in two separate experiments). Treatment of other diabetic rats with evening primrose oil prevented completely the development of the motor nerve conduction velocity deficit without affecting sorbitol, fructose or myo-inositol levels or the deficit in axonal transport of substance P. In a second experiment, treatment of diabetic rats with evening primrose oil was associated with significant attenuation of the conduction velocity deficit, but not complete prevention.