Liver triacylglycerols and free fatty acids in streptozotocin-induced diabetic rats have atypical n-6 and n-3 pattern

Effects of Simvastatin on the Metabolism of Fatty Acids in Combined Secondary Prevention of Coronary Heart Disease: Dosage and Gender Differences between the Effects

BACKGROUND

Statins are currently used for secondary prevention of Coronary Heart Disease (CHD), as the lipid-lowering therapy with them is proven safe and effective.

OBJECTIVE

The purpose of this research is to investigate the dose-dependent effect of statins used for secondary prevention of coronary heart disease, as well as mechanisms of quantitative and qualitative changes in lipoproteins, fatty acids and cholesterol in the blood and tissues of people of both sexes.

METHODS

In a clinical trial (n=125, of which 89 patients belong to group 1 and 36 to group 2) and an experiment on laboratory animals (n = 100), simvastatin reduced the total level of fatty acids in blood plasma, when given in the amount that was within the therapeutic dose range.

RESULTS

This effect was achieved through a drug-induced improvement in the capacity of hepatic cells to absorb Low-density (LDL) and Very-low-density (VLDL) lipoproteins.

CONCLUSION

Considering the formation of saturated fatty acids, statin performed better in males. With Omega-3 polyunsaturated fatty acids involved, changes in lipoproteins, cholesterol and fatty acids (liver and myocardium) were similar to those caused by small doses of a statin drug. Effects of the combination of bisoprolol and acetylsalicylic acid were completely different from those caused by the use of statin.

High dietary n6/n3 ratio decreases eicosapentaenoic to arachidonic acid ratios and upregulates NFκB/p50 expression in short-term low-dose streptozotocin and high-fructose rat model of diabetes

We studied the influence of dietary n6/n3 ratio and docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids supplementation on fatty acid profile, lipid peroxidation and NFκ/p50 expression in diabetes type 2. Treatments consisted of three dietary n6/n3 ratios: 6 (Control), 50 (high n6) and 1 (DHA and EPA supplemented). Half of the rats in each of the dietary treatments were made diabetic using the fructose/low-streptozotocin model. The Control and high n6 diets decreased EPA/ARA (arachidonic acid) ratios in the plasma and in the hepatic tissue suggesting proinflammatory fatty acid profile. The high n6 diet additionally increased the 4-HNE and NFκ/p50 expression in the hepatic tissue. These changes were the consequence of a decrease in the plasma content of DHA and EPA and an increase in the content of arachidonic acid in the liver neutral lipids. The supplementation with the DHA and EPA attenuated the change in EPA/ARA ratios, which imply the importance of the n6/n3 ratio in diabetes type 2.

Hepatic Lipogenesis and Brain Fatty Acid Profile in Response to Different Dietary n6/n3 Ratios and DHA/EPA Supplementation in Streptozotocin Treated Rats

SCOPE

We investigated the interaction between streptozotocin (STZ)-induced diabetes and dietary n6/n3 ratio, and its influence on lipogenesis.

METHODS AND RESULTS

The animals were treated with STZ and fed with different dietary n6/n3 ratios: 1, 7, and 60, or supplemented with DHA/EPA. Gene expression was assessed by RT-PCR and protein expression by western blotting and immunohistochemistry. Fatty acid profile was determined by GC-MS. Pancreas and liver histology were assessed by hematoxylin and eosin (H&E) staining. STZ-induced characteristic changes in all STZ treated groups, including: increased blood glucose, decreased body mass, increased lipid peroxidation and CD36 expression, decreased 16:1n7 and 18:1n7, increases in 20:3n6, decreases in phospholipid (PL) content of 20:4n6, as well as decreases in the expression of SREBP1c, Δ-9-desaturase (Δ9D), and Δ-5-desaturase (Δ5D). Additionally, other changes occurred that were dependent on the n6/n3 ratio. Among the diabetic groups, the lower n6/n3 ratio caused higher lipid peroxidation and CD36 expression, a greater decrease in 20:4n6 and decreased Δ6-desaturase (Δ6D) expression, while the higher n6/n3 ratio caused increased partitioning of 20:4n6 into hepatic neutral lipids (NL), a decrease in 20:5n3 content, and increased β-oxidation.

CONCLUSION

Presented data suggest that the n6/n3 ratio could significantly influence lipogenesis, lipid peroxidation, and β-oxidation in STZ-induced diabetes, which could have clinical significance.

An ultrasonic assisted extraction procedure to free fatty acids from the liver samples of mice

A procedure was evaluated for the extraction of 16 free fatty acids (FFAs) from liver. Ultrasonic energy was used for the extraction and the variables affecting the extraction efficiency were investigated. The best conditions for extraction were: 2 mL isopropanol-n-hexane (3:2, v/v), 20 min and 80 w. Recoveries ranging from 87.00 to 120.00% were obtained under the optimum conditions, and the linearity as correlation coefficient was higher than 0.9914. Analytical results for the 16 FFAs in the same liver sample, analyzed by ultrasound-assisted and conventional extraction, showed acceptable agreement, thus suggesting the possibility of using ultrasound-assisted extraction instead of the conventional procedure. Moreover, the ultrasound-assisted extraction was successfully applied to the determination of FFAs in the liver of mice with hyperlipidemia and normal mice.

Maternal diabetes in pregnancy: early and long-term outcomes on the offspring and the concept of "metabolic memory"

The adverse outcomes on the offspring from maternal diabetes in pregnancy are substantially documented. In this paper, we report main knowledge on impacts of maternal diabetes on early and long-term health of the offspring, with specific comments on maternal obesity. The main adverse outcome on progenies from pregnancy complicated with maternal diabetes appears to be macrosomia, as it is commonly known that intrauterine exposure to hyperglycemia increases the risk and programs the offspring to develop diabetes and/or obesity at adulthood. This “fetal programming”, due to intrauterine diabetic milieu, is termed as “metabolic memory”. In gestational diabetes as well as in macrosomia, the complications include metabolic abnormalities, degraded antioxidant status, disrupted immune system and potential metabolic syndrome in adult offspring. Furthermore, there is evidence that maternal obesity may also increase the risk of obesity and diabetes in offspring. However, women with GDM possibly exhibit greater macrosomia than obese women. Obesity and diabetes in pregnancy have independent and additive effects on obstetric complications, and both require proper management. Management of gestational diabetes mellitus and maternal obesity is essential for maternal and offspring's good health. Increasing physical activity, preventing gestational weight gain, and having some qualitative nutritional habits may be beneficial during both the pregnancy and offspring's future life.

Cod liver oil supplementation improves cardiovascular and metabolic abnormalities in streptozotocin diabetic rats

Abnormalities in the metabolism of essential fatty acids and the results of increased oxidative stress have been implicated in cardiovascular disorders observed in diabetes mellitus. This study, therefore, aimed to investigate the effects of cod liver oil (CLO, Lysi Ltd, Iceland), which comprises mainly an antioxidant vitamin A, n:3 polyunsaturated fatty acids (n:3 PUFAs), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), on cardiovascular abnormalities in streptozotocin (STZ)-diabetic rats. Two days after single STZ (55 mg kg−1, i.p.) or vehicle injection, diabetes was verified by increased blood glucose, and non-diabetic and diabetic rats were left untreated or treated with CLO (0.5 mL kg−1 daily, by intragastric probing) for 12 weeks. Plasma glucose, triacylglycerol and cholesterol concentrations were significantly elevated in 12-week untreated-diabetic rats; CLO provided better weight gain, entirely prevented the plasma lipid abnormalities, but partially controlled the glycaemia in diabetic rats. In isolated aorta rings, diabetes resulted in increased phenylephrine-induced vasoconstriction and isoprenaline-induced vasorelaxation, impaired endothelium-dependent vasodilatation and unchanged responsiveness to sodium nitroprusside. CLO treatment completely prevented endothelial deficiency, partly corrected the phenylephrine-induced vasoconstriction and did not affect the responses to isoprenaline and sodium nitroprusside in diabetic aorta. Diabetes also produced a marked decrease in the rate of spontaneously beating right atria and a significant increase in basal contractile force of left ventricular papillary muscle. The responsiveness of right atria to the positive chronotropic effect of isoprenaline was significantly decreased in diabetic rats, and was increased in CLO-treated diabetic rats. The positive chronotropic effect of noradrenaline was markedly increased in diabetic atria, but prevented by CLO treatment. Diabetes also resulted in an increased positive inotropic response of papillary muscle to both noradrenaline and isoprenaline, which were prevented by CLO treatment. CLO treatment also resulted in lower tissue sensitivity (pD2) to these agonists in diabetic papillary muscle. Ventricular hydroxy-proline content was found to be unchanged among the experimental groups. The ultrastructure of diabetic myocardium displayed various degenerations (i.e. intracellular oedema, myofibrillar fragmentation, condensed pleomorphic mitochondria, thick capillary irregular basement membrane, swollen endothelial cells), which were partially prevented by CLO treatment. We conclude that the supplementation with CLO is effective in preventing cardiovascular disorders observed in experimental diabetes.

Maternal arachidonic acid supplementation improves neurodevelopment of offspring from healthy and diabetic rats

Maternal diabetes may compromise infant arachidonic acid status and development. This study tested if maternal arachidonic acid supplementation improves neurodevelopment in rat offspring. Dams were randomized into 6 groups using a 3x2 design: Saline-Placebo, streptozotocin-induced diabetes with glucose controlled at <13mmol/L, or poorly controlled at 13-20mmol/L using insulin; and fed either control or an arachidonic acid (0.5% of fat) diet throughout reproduction. Offspring were tested on post-natal days 3 and 5 for righting response, days 7 and 9 for negative geotaxis, day 14 for wire hanging endurance, days 18 and 24 for rota rod endurance, and day 28 for Morris water maze performance. Only the poorly controlled group had impaired day 7 geotaxis and day 18 rota rod performance (p<0.02), but this improved with maternal arachidonic acid supplementation (p<0.0006). Arachidonic acid improved the wire hanging endurance (p=0.0003) and water maze latency (p=0.0021), suggesting enhanced neurodevelopment in all offspring.

Hyperglycemia-induced alterations in synaptosomal membrane fluidity and activity of membrane bound enzymes: beneficial effect of N-acetylcysteine supplementation

Diabetic encephalopathy is characterized by impaired cognitive functions that appear to underlie neuronal damage triggered by glucose driven oxidative stress. Hyperglycemia-induced oxidative stress in diabetic brain may initiate structural and functional changes in synaptosomal membranes. The objective of the present study was to examine the neuroprotective role of N-acetylcysteine (NAC) in hyperglycemia-induced alterations in lipid composition and activity of membrane bound enzymes (Na(+),K(+)-ATPase and Ca(2+)-ATPase) in the rodent model of type 1 diabetes. Male Wistar rats weighing between 180 and 200 g were rendered diabetic by a single injection of streptozotocin (50 mg/kg body weight, i.p.). The diabetic animals were administered NAC (1.4-1.5 g/kg body weight) for eight weeks and lipid composition along with membrane fluidity were determined. A significant increase in lipid peroxidation was observed in cerebral cortex of diabetic rats. NAC administration on the other hand lowered the hyperglycemia-induced lipid peroxidation to near control levels. The increased lipid peroxidation following chronic hyperglycemia was accompanied by a significant increase in the total lipids which can be attributed to increase in the levels of cholesterol, triglycerides and glycolipids. On the contrary phospholipid and ganglioside levels were decreased. Hyperglycemia-induced increase in cholesterol to phospholipid ratio reflected decrease in membrane fluidity. Fluorescence polarization (p) with DPH also confirmed decrease in synaptosomal membrane fluidity that influenced the activity of membrane bound enzymes. An inverse correlation was found between fluorescence polarization with the activities of Na(+),K(+)-ATPase (r(2)=0.416, P<0.05) and Ca(2+) ATPase (r(2)=0.604, P<0.05). NAC was found to significantly improve lipid composition, restore membrane fluidity and activity of membrane bound enzymes. Our results clearly suggest perturbations in lipid composition and membrane fluidity as a major factor in the development of diabetic encephalopathy. Furthermore, NAC administration ameliorated the effect of hyperglycemia on oxidative stress and alterations in lipid composition thereby restoring membrane fluidity and activity of membrane bound enzymes.

Glycerolipid metabolism and signaling in health and disease

Maintenance of body temperature is achieved partly by modulating lipolysis by a network of complex regulatory mechanisms. Lipolysis is an integral part of the glycerolipid/free fatty acid (GL/FFA) cycle, which is the focus of this review, and we discuss the significance of this pathway in the regulation of many physiological processes besides thermogenesis. GL/FFA cycle is referred to as a "futile" cycle because it involves continuous formation and hydrolysis of GL with the release of heat, at the expense of ATP. However, we present evidence underscoring the "vital" cellular signaling roles of the GL/FFA cycle for many biological processes. Probably because of its importance in many cellular functions, GL/FFA cycling is under stringent control and is organized as several composite short substrate/product cycles where forward and backward reactions are catalyzed by separate enzymes. We believe that the renaissance of the GL/FFA cycle is timely, considering the emerging view that many of the neutral lipids are in fact key signaling molecules whose production is closely linked to GL/FFA cycling processes. The evidence supporting the view that alterations in GL/FFA cycling are involved in the pathogenesis of "fatal" conditions such as obesity, type 2 diabetes, and cancer is discussed. We also review the different enzymatic and transport steps that encompass the GL/FFA cycle leading to the generation of several metabolic signals possibly implicated in the regulation of biological processes ranging from energy homeostasis, insulin secretion and appetite control to aging and longevity. Finally, we present a perspective of the possible therapeutic implications of targeting this cycling.

Altered lipid catabolism in the vitamin A deficient liver

The transcriptome pattern of metabolic genes in vitamin A deficient (VAD) liver has been compared to the vitamin A-sufficient (VAS) state using the Mouse 32k oligonucleotide (70mer) array. In VAD liver there was a decrease in expression of genes encoding enzymes of mitochondrial fatty acid (FA) oxidation; these genes included fatty acyl CoA ligase, carnitine o-palmitoyl transferase 1, medium chain acyl-CoA dehydrogenase, 3-ketoacyl CoA thiolase, and citrate synthase. Particularly affected was peroxisome metabolism, as genes encoding enzymes of peroxisomal FA oxidation and transport proteins were differentially expressed. These genes included those encoding acyl-CoA oxidase 1, the peroxisomal bifunctional enzyme, peroxisomal thiolase, and carnitine o-octanoyl transferase, the enzyme involved in shuttling FAs from the peroxisome to the mitochondrion. Most genes that were differentially expressed with chronic vitamin A depletion were responsive to treatment with all-trans retinoic acid (RA). Consistent with the decreased expression of genes involved in FA oxidation, we found an increase in hepatic macrocytic lipid accumulation and triglyceride levels. The relevant nuclear receptor gene that was differentially expressed in the VAD liver was that encoding the peroxisome proliferator-activated receptor (PPAR) alpha, the mRNA levels for which were decreased in VAD liver and increased with all-trans RA treatment. Down regulation of the PPAR alpha gene is the likely cause of the altered expression pattern of the above metabolic genes in VAD liver.

Low contribution of n-3 polyunsaturated fatty acids to plasma and erythrocyte membrane lipids in diabetic young adults

Hypoinsulinemia characteristic to type 1 diabetes may theoretically inhibit the conversion of essential fatty acids to their longer-chain metabolites. Fatty acids were determined in plasma and erythrocyte membrane lipids in young diabetic adults (n=34) and in age-matched healthy controls (n=36). Values of linoleic acid (56.01 [5.02] versus 51.05 [7.32], % by wt, median [range from the first to the third quartile], P<0.00l) and arachidonic acid (AA) (11.17 [2.98] versus 9.69 [1.95] P<0.001) were significantly higher in diabetic subjects than in controls. However, alpha-linolenic acid values did not differ, and docosahexaenoic acid (0.43 [0.12] versus 0.57 [0.29], P<0.01) values were significantly lower in diabetic than in control subjects. Significant inverse correlations were found between AA and hemoglobin A(1c) values in the phospholipid (r=-0.40, P<0.05) and sterol ester (r=-0.40, P<0.05) fractions. The data obtained in the present study suggest that the availability of n-3 long-chain polyunsaturated fatty acid may be reduced in young diabetic adults.

Streptozotocin-induced type 1 diabetes mellitus alters the morphology, secretory function and acyl lipid contents in the isolated rat parotid salivary gland

Diabetes mellitus (DM) is associated with numerous conditions including hypo-secretion of digestive enzymes. This study investigated the morphology, secretory function (alpha-amylase release) and acyl lipid contents in the isolated parotid gland of STZ-induced diabetic and age-matched control rats in order to provide insights into diabetes-induced salivary insufficiency. The techniques employed included light microscopy, colourimetric and gas chromatography (GC) analysis, respectively. Diabetes mellitus was induced in adult male Wistar rats by a single intraperitoneal (IP) injection of streptozotocin (STZ) (60 mg per kg body weight). Control animals were injected with a similar volume of citrate buffer. The animals were tested for DM 4 days after STZ injection and 2 months later when they were humanely killed for the experiment. The morphological results showed diabetic parotid glands to be extensively infiltrated with lipid droplets of various magnitudes, whereas glands from control animals display normal structure with the absence of lipid droplets. The analysis of parotid secretory function revealed a significant (p < 0.05) dose-dependent decrease in alpha-amylase release in response to noradrenaline (NA) in STZ-treated glands when compared to age-match control parotid glands. Furthermore, the levels of acyl lipids (16:0, 16:1, 18:0 and 18:1) in diabetic parotid glands was significantly (p < 0.01) reduced compared to control glands, along with a reduced ratio of 16:1/16:0. The results indicate DM can elicit changes in the morphology, secretory function and acyl fatty acid quantity in the isolated rat parotid gland.

The effect of dietary n-3 long-chain polyunsaturated fatty acids on femur mineral density and biomarkers of bone metabolism in healthy, diabetic and dietary-restricted growing rats

INTRODUCTION

Dietary fish oil promotes bone formation in healthy states, but its effect during insulin deficiency or nutrient restriction is unclear.

METHODS

Eighty weanling male rats were randomized to receive an injection of streptozotocin to induce insulin deficiency (diabetes) or saline (control) and a diet containing soy oil or corn + fish oil for 35 days. Half of the saline-injected rats were randomized to 20% dietary restriction. Measurements were growth, biomarkers of bone metabolism and femur bone mass.

RESULTS

Density of femur was elevated in the corn + fish group and reduced in the diabetes group. Plasma osteocalcin and bone prostaglandin E2 (PGE2) were reduced by the corn + fish diet. N-telopeptide, IGF-1, bone PGE2 and urinary Ca were highest and calcitriol lowest in the diabetes group.

CONCLUSIONS

These data suggest that the benefit of a diet high in n-3 long-chain polyunsaturated fatty acid is most advantageous to long bone density in healthy states.

Plasma AA and DHA levels are not compromised in newly diagnosed gestational diabetic women

OBJECTIVE

The polyunsaturated fatty acids, arachidonic (AA) and docosahexaenoic (DHA), are vital structural and functional components of the neural, vascular and visual systems. There is increased demand for these fatty acids during pregnancy. Diabetes impairs the synthesis of both AA and DHA. We have investigated the possibility that pregnancy-induced diabetes compromises the levels of plasma AA and DHA in newly diagnosed expectant mothers.

DESIGN

Cross-sectional study.

SETTING

London, UK.

SUBJECTS AND METHODS

Venous blood was obtained from 44 women with gestational diabetes mellitus (GDM) and from the same number of nondiabetics, during the third trimester. Fatty acid composition of plasma choline phosphoglycerides (CPG), triglycerides (TG) and cholesterol esters (CE) was analysed.

RESULTS

The GDM women had higher levels of AA (20:4n-6; P<0.0001) and AA/linoleic acid ratio (20:4n-6/18:2n-6; P<0.01) in the CPG, and linoleic acid (LA; P<0.0001), total n-6 (P<0.01), DHA (P<0.05) and n-3 metabolites (P<0.05) in TG compared to their nondiabetic counterparts. Similarly, AA (P<0.0001), osbond acid (22:5n-6; P<0.05), total n-6 metabolites (P<0.0001), AA/LA (P<0.0001) and n-6 metabolites/LA (P<0.01) were higher in the CE of the GDM women. There was no difference in the levels of DHA in CPG and CE between the two groups (P>0.05).

CONCLUSIONS

The results of this study do not provide evidence that the activity of delta-6 or delta-5 desaturases, which are vital for the synthesis of AA and DHA, is compromised by pregnancy-induced diabetes. However, since the samples were taken at diagnosis, it is conceivable that the duration of the diabetes was too short to have a discernable adverse effect on the levels of AA and DHA in plasma lipids.