Paul Bastenie et la recherche en diabétologie à l'ULB.

The present chapter deals with the contribution of Professor Paul A. Bastenie, as Chief of the Department of Medicine of the Saint-Pierre Hospital and Director of the Laboratory of Experimental Medicine at Brussels Free University, in the field of diabetes with emphasis on the role of insulin in glucose homeostasis. The knowledge and experimental work under consideration is covering the period from 1955 to 1974. They entail not only three treatises contributed by Bastenie but also fundamental and clinical investigations, such as those presented in eight doctoral dissertations submitted for aggregation examination at Brussels Free University. These theses are dealing with the measurement of glucose assimilation (V. Conard), the measurement of insulin activity in men (J.R.M. Franckson), the mechanisms of action of hypoglycemic drugs (R. Bellens), the study of energy metabolism in children (H. Loeb), the study of insulin secretion in vitro (W. Malaisse), the distribution of insulin in body fluids as influenced by the permeability and structure of blood capillaries (E. Rasio), the regulation of the extra-hepatic metabolism of ketone bodies in anesthetized dogs (E.O. Balasse) and the use of radioiodinated insulin as tracers in biology (H.A. Ooms).

Le présent article concerne la contribution du Professeur Paul A. Bastenie, en tant que Chef du Département de Médecine à l'Hôpital Saint-Pierre et de Directeur du Laboratoire de Médecine expérimentale à l'Université libre de Bruxelles, dans le domaine de la diabétologie, en particulier le rôle de l'insuline dans l'homéostasie glucidique. Le travail expérimental pris en considération couvre la période de 1955 à 1974. Il comporte non seulement trois traités contribués par Bastenie, mais également des investigations fondamentales et cliniques telles que celles présentées à l'Université libre de Bruxelles dans huit thèses d'agrégation de l'enseignement supérieur. Celles-ci concernent la mesure de l'assimilation de glucose (V. Conard), la mesure de l'activité de l'insuline chez l'homme (J.R.M. Franckson), les mécanismes d'action des drogues hypoglycémiantes (R. Bellens), le métabolisme énergétique de l'enfant (H. Loeb), la sécrétion insulinique in vitro (W. Malaisse), le passage capillaire de l'insuline (E. Rasio), le métabolisme extra-hépatique des corps cétoniques in vivo (E.O. Balasse) et l'emploi des insulines radioiodées comme traceurs en biologie (H.A. Ooms).

Oleate Abrogates Palmitate-Induced Lipotoxicity and Proinflammatory Response in Human Bone Marrow-Derived Mesenchymal Stem Cells and Osteoblastic Cells.

Osteoporosis is a metabolic bone disease associated with unequilibrated bone remodeling resulting from decreased bone formation and/or increased bone resorption, leading to progressive bone loss. In osteoporotic patients, low bone mass is associated with an increase of bone marrow fat resulting from accumulation of adipocytes within the bone marrow. Marrow adipocytes are active secretory cells, releasing cytokines, adipokines and free fatty acids (FA) that influence the bone marrow microenvironment and alter the biology of neighboring cells. Therefore, we examined the effect of palmitate (Palm) and oleate (Ole), 2 highly prevalent FA in human organism and diet, on the function and survival of human mesenchymal stem cells (MSC) and MSC-derived osteoblastic cells. The saturated FA Palm exerted a cytotoxic action via initiation of endoplasmic reticulum stress and activation of the nuclear factor κB (NF-κB) and ERK pathways. In addition, Palm induced a proinflammatory response, as determined by the up-regulation of Toll-like receptor 4 expression as well as the increase of IL-6 and IL-8 expression and secretion. Moreover, we showed that MSC-derived osteoblastic cells were more sensitive to lipotoxicity than undifferentiated MSC. The monounsaturated FA Ole fully neutralized Palm-induced lipotoxicity by impairing activation of the pathways triggered by the saturated FA. Moreover, Ole promoted Palm detoxification by fostering its esterification into triglycerides and storage in lipid droplets. Altogether, our data showed that physiological concentrations of Palm and Ole differently modulated cell death and function in bone cells. We therefore propose that FA could influence skeletal health.

The Mediterranean diet adoption improves metabolic, oxidative, and inflammatory abnormalities in Algerian metabolic syndrome patients.

This study was aimed to explore the effects of Mediterranean diet (MD) adoption on insulin resistance, oxidative, and inflammatory status in metabolic syndrome (MS) patients. Eighty four patients with MS were randomly recruited in the medical centers of Oran, Algeria. Eighteen healthy participants were selected as a control group. Among these 84 patients, only 36 patients completed the nutritional advices for 3 months. Patients were instructed to follow a Mediterranean-style diet and received some other selected nutritional and physical activity instructions. Anthropometric measurements were performed and a questionnaire was used to assess dietary intake. Blood samples were drawn at baseline and after 3 months of nutritional intervention from all subjects. At baseline, the MS patients were obese and had altered anthropometric parameters, higher systolic and diastolic blood pressure, plasma lipids, glucose, insulin, HOMA-IR, HbA1c, urea, creatinine, uric acid, and lower albumin compared to healthy subjects. A decrease in plasma, erythrocyte, and platelet antioxidant enzymes, and a rise in lipid and protein oxidation, plasma CRP, and fibrinogen were noted in the MS patients. Moreover, they had an unbalanced dietary pattern when compared to Mediterranean recommendations. Patients following the Mediterranean-style diet had significantly reduced weight, BMI, waist circumference, waist/hip circumference ratio, decreased systolic and diastolic blood pressure, plasma glucose, insulin, HOMA-IR, HbA1c, cholesterol, triacylglycerols, CRP, urea, creatinine, creatinine clearance, lipid and protein oxidation, and higher plasma, erythrocyte, and platelet antioxidant enzymes. In conclusion, a lifestyle intervention based mainly on nutritional advices improves metabolic, oxidative, and inflammatory abnormalities of metabolic syndrome.

Does NAD(P)H oxidase-derived H2O2 participate in hypotonicity-induced insulin release by activating VRAC in ß-cells?

NAD(P)H oxidase (NOX)-derived H(2)O(2) was recently proposed to act, in several cells, as the signal mediating the activation of volume-regulated anion channels (VRAC) under a variety of physiological conditions. The present study aims at investigating whether a similar situation prevails in insulin-secreting BRIN-BD11 and rat ß-cells. Exogenous H(2)O(2) (100 to 200 µM) at basal glucose concentration (1.1 to 2.8 mM) stimulated insulin secretion. The inhibitor of VRAC, 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) inhibited the secretory response to exogenous H(2)O(2). In patch clamp experiments, exogenous H(2)O(2) was observed to stimulate NPPB-sensitive anion channel activity, which induced cell membrane depolarization. Exposure of the BRIN-BD11 cells to a hypotonic medium caused a detectable increase in intracellular level of reactive oxygen species (ROS) that was abolished by diphenyleneiodonium chloride (DPI), a universal NOX inhibitor. NOX inhibitors such as DPI and plumbagin nearly totally inhibited insulin release provoked by exposure of the BRIN-BD11 cells to a hypotonic medium. Preincubation with two other drugs also abolished hypotonicity-induced insulin release and reduced basal insulin output: 1) N-acetyl-L-cysteine (NAC), a glutathione precursor that serves as general antioxidant and 2) betulinic acid a compound that almost totally abolished NOX4 expression. As NPPB, each of these inhibitors (DPI, plumbagin, preincubation with NAC or betulinic acid) strongly reduced the volume regulatory decrease observed following a hypotonic shock, providing an independent proof that VRAC activation is mediated by H(2)O(2). Taken together, these data suggest that NOX-derived H(2)O(2) plays a key role in the insulin secretory response of BRIN-BD11 and native ß-cells to extracellular hypotonicity.

Glycerol metabolism alteration in adipocytes from n3-PUFA-depleted rats, an animal model for metabolic syndrome.

Aquaglyceroporin 7 (AQP7) is a glycerol transporter expressed in adipocytes. Its expression has been shown to be modulated in obesity. Metabolic syndrome is characterized by abdominal obesity, insulin resistance, dyslipidemia, and hypertension. An animal model displaying several features of metabolic syndrome was used to study the AQP7 expression at both mRNA and protein level and glycerol flux in adipocytes. Second generation n3-PUFA depleted female rats is a good animal model for metabolic syndrome as it displays characteristic features such as liver steatosis, visceral obesity, and insulin resistance. Our data show a reduced expression of AQP7 at the protein level in adipose tissue from n3-PUFA-depleted rats, without any changes at the mRNA levels. [U-(14)C]-Glycerol uptake was not modified in adipocytes from n3-PUFA-depleted animals.

Amylin effect in extrapancreatic tissues participating in glucose homeostasis, in normal, insulin-resistant and type 2 diabetic state.

Amylin is co-secreted with insulin, responds to the same stimuli, is anorectic, lowers body weight by reducing fat mass, and is proposed for diabetes treatment. We examined the effect of a 3-day constant infusion of close to physiological doses of amylin in Wistar rats, on glucotransporter expression, glycogen content (G), glycogen synthase a activity (GSa) and glucose transport (GT), in liver, muscle and fat from insulin resistant (IR) and type 2 diabetic (T2D) models, compared to normal (N) animals; plasma glucose and insulin were measured. Plasma insulin in IR was higher than in N or T2D, and amylin normalized the value. In both, IR and T2D, liver G was lower than normal, accompanied by GLUT-2, mRNA and protein, higher and lower, respectively, than in N; amylin normalized G in both groups, without changes in GLUT-2, except for an mRNA increase in T2D. In IR and T2D, muscle GSa was reduced, together with respective over- and under-GLUT-4 expression; amylin induced only a trend toward GSa normalization in both groups. In isolated adipocytes, GT and GLUT-4 in IR and T2D were lower and higher, respectively, than in N; after amylin, not only GT was normalized in both groups but also the response to insulin was much more pronounced, including that in N, without major changes in GLUT-4. This suggests that the beneficial effect of amylin in states running with altered glucose homeostasis could occur by partially acting on the hexose metabolism of the liver and mainly on that of the adipose tissue.

Functional role of aquaglyceroporin 7 expression in the pancreatic beta-cell line BRIN-BD11.

Both mouse and rat pancreatic islet beta-cells were recently found to express aquaglyceroporin 7 (AQP7). In the present study, the expression and role of AQP7 in the function of BRIN-BD11 cells were investigated. AQP7 mRNA and protein were detected by RT-PCR and Western blot analysis, respectively. In an isoosmolar medium, the net uptake of [2-(3)H]glycerol displayed an exponential time course reaching an equilibrium plateau value close to its extracellular concentration. Within 2 min of incubation in a hypotonic medium (caused by a 50 mM decrease in NaCl concentration), the [2-(3)H]glycerol uptake averaged 143.2 +/- 3.8% (n = 24; P < 0.001) of its control value in isotonic medium, declining thereafter consistently with previously demonstrated volume regulatory decrease. When isoosmolarity was restored by the addition of 100 mM urea to the hypotonic medium, [2-(3)H]glycerol uptake remained higher (112.1 +/- 2.8%, n = 24; P < 0.001) than its matched control under isotonic conditions, indicating rapid entry of urea and water. Insulin release by BRIN-BD11 cells was 3 times higher in hypotonic than in isotonic medium. When glycerol (100 mM) or urea (100 mM) were incorporated in the hypotonic medium, the insulin release remained significantly higher than that found in the control isotonic medium, averaging respectively 120.2 +/- 4.2 and 107.0 +/- 3.8% of the paired value recorded in the hypotonic medium. These findings document the rapid entry of glycerol and urea in BRIN-BD11 cells, likely mediated by AQP7.

Hepatic steatosis in n-3 fatty acid depleted mice: focus on metabolic alterations related to tissue fatty acid composition.

BACKGROUND: There are only few data relating the metabolic consequences of feeding diets very low in n-3 fatty acids. This experiment carried out in mice aims at studying the impact of dietary n-3 polyunsaturated fatty acids (PUFA) depletion on hepatic metabolism. RESULTS: n-3 PUFA depletion leads to a significant decrease in body weight despite a similar caloric intake or adipose tissue weight. n-3 PUFA depleted mice exhibit hypercholesterolemia (total, HDL, and LDL cholesterol) as well as an increase in hepatic cholesteryl ester and triglycerides content. Fatty acid pattern is profoundly modified in hepatic phospholipids and triglycerides. The decrease in tissue n-3/n-6 PUFA ratio correlates with steatosis. Hepatic mRNA content of key factors involved in lipid metabolism suggest a decreased lipogenesis (SREBP-1c, FAS, PPAR gamma), and an increased beta-oxidation (CPT1, PPAR alpha and PGC1 alpha) without modification of fatty acid esterification (DGAT2, GPAT1), secretion (MTTP) or intracellular transport (L-FABP). Histological analysis reveals alterations of liver morphology, which can not be explained by inflammatory or oxidative stress. However, several proteins involved in the unfolded protein response are decreased in depleted mice. CONCLUSION: n-3 PUFA depletion leads to important metabolic alterations in murine liver. Steatosis occurs through a mechanism independent of the shift between beta-oxidation and lipogenesis. Moreover, long term n-3 PUFA depletion decreases the expression of factors involved in the unfolded protein response, suggesting a lower protection against endoplasmic reticulum stress in hepatocytes upon n-3 PUFA deficiency.

[An ionic determination of the insulinotropic action of insulin: not everyone agrees]. / Les déterminants ioniques de l'action insulinotrope des nutriments: non consensus omnium.

A recent model concerning the ionic determinants involved in the insulinotropic action of nutrients, namely an anion channel hypothesis, is presented, and selected experimental findings in support of such a model, are reviewed.

Rapid reduction of liver steatosis in omega3-depleted rats injected with a novel lipid emulsion.

The bolus intravenous administration of a novel medium-chain triglyceride: fish oil emulsion (MCT:FO) to normal subjects was recently found to increase within 60 min the amount of long-chain polyunsaturated omega3 fatty acids ( omega3) in platelet and leukocyte phospholipids and, hence, was proposed as a tool to prevent such pathological events as cardiac arrhythmia in selected patients who have to undergo urgent anesthesia and/or surgery. This study investigates whether other cells located outside the vascular bed may also benefit from this procedure for replenishing phospholipids with omega3. For such a purpose, the MCT:FO emulsion (1.0 ml) was injected into normal or omega3-depleted rats examined, one hour later, for the content and fatty acid pattern of liver triglycerides and phospholipids. Control experiments included the administration of saline or a medium-chain triglyceride:olive oil emulsion. The results reveal that the bolus intravenous injection of MCT:FO to the omega3-depleted rats resulted in the enrichment of liver phospholipids in omega3 and a marked reduction in hepatic steatosis. In conclusion, it is proposed that such a procedure may indeed allow a rapid supply of omega3 not only to circulating and vascular endothelial cells but also to extravascular cells, with a resulting correction of the biochemical and biophysical defects linked to a deficiency in these fatty acids.

Vitamin E transfer from lipid emulsions to plasma lipoproteins: mediation by multiple mechanisms.

The present study determined alpha-tocopherol mass transfer from an alpha-tocopherol-rich emulsion to LDL and HDL, and assessed the potential of different mechanisms to modulate alpha-tocopherol transfers. Emulsion particles rich in alpha-tocopherol were incubated in vitro with physiological concentrations of LDL or HDL. The influence of plasma proteins was assessed by adding human lipoprotein poor plasma (LPP) fraction with intact vs heat inactivated PLTP, or with a specific cholesteryl ester transfer protein (CETP) inhibitor, or by adding purified PLTP or pig LPP which lacks CETP activity. After 4 h incubation in absence of LPP, alpha-tocopherol content was increased by ~80% in LDL and ~160% in HDL. Addition of LPP markedly enhanced alpha-tocopherol transfer leading to 350-400% enrichment in LDL or HDL at 4 h. Higher (~10 fold) enrichment was achieved after 20 h incubation with LPP. Facilitation of alpha-tocopherol transfer was (i) more than 50% higher with human vs pig LPP (despite similar PLTP phospholipid transfer activity), (ii) reduced by specific CETP activity inhibition, (iii) not fully suppressed by heat inactivation, and (iv) not restored by purified PLTP. In conclusion, alpha-tocopherol content in LDL and HDL can be markedly raised by rapid transfer from an alpha-tocopherol-rich emulsion. Our results indicate that alpha-tocopherol mass transfer between emulsion particles and lipoproteins is mediated by more than one single mechanism and that this transfer may be facilitated not only by PLTP but likely also by other plasma proteins such as CETP.

Induction and reversibility of insulin resistance in rats exposed to exogenous D-fructose.

Long-term exposure of normal rats to a fructose-enriched diet or drinking water is currently used as an animal model for experimental insulin resistance. The present study deals with a comparison between rats given access to either a fructose-enriched diet or fructose-enriched drinking water. In both situations, a decrease in food intake and body weight gain, and the induction of insulin resistance with intolerance to D-glucose despite increased secretory response to the aldohexose of insulin-producing cells were documented. Moreover, the rats exposed to exogenous D-fructose displayed a lesser sensitivity to overnight fasting than control animals, in terms of the alteration of glucose homeostasis and reduction of the ratio between plasma insulin and D-glucose concentration. It is also shown that the fructose-induced insulin resistance, as assessed in a hyperinsulinemic-euglycemic clamp, represents a phenomenon reversed within 15-30 days after removal of the keto-hexose from the drinking water.

Glucose intolerance associated to insulin resistance and increased insulin secretion in rats depleted in long-chain omega3 fatty acids.

An intragastric D-glucose tolerance test was performed, after overnight starvation, in female rats depleted in long-chain polyunsaturated omega3 fatty acids (omega3D rats) and control rats of same age and gender. The plasma D-glucose and insulin concentrations, insulinogenic index, and HOMA for insulin resistance were all higher, after overnight starvation, in omega3D rats than in control animals. Over the 120-minute period following the intragastric administration of D-glucose, the area under the curve for the same four variables was also higher in omega3D rats than in control animals. In addition to visceral obesity, liver steatosis, hypertension, and cardiac hypertrophy, the omega3D rats thus display further features of the metabolic syndrome, namely glucose intolerance and insulin resistance, despite hyperinsulinemia.

Effects of diet supplementation with olive oil and guar upon fructose-induced insulin resistance in normal rats.

Exposure of normal rats to fructose-containing drinking water represents a current model of insulin resistance. The major aim of the present study was to assess the possible effect of diet supplementation with either olive oil or guar upon the metabolic consequences of exposure to exogenous fructose. For this purpose, the changes in body weight, plasma D-glucose and insulin concentrations, and D-glucose infusion rate during a hyperinsulinemic-euglycemic clamp were measured after 65 days exposure to exogenous fructose and either olive oil- or guar-enriched diet. The results were compared to those previously collected in control animals exposed for the same period to either tap water or the fructose-containing drinking water and a standard diet. Diet supplementation with olive oil or guar failed to affect the increase in the insulinogenic index and the decrease in insulin sensitivity and fasted/fed ratio for plasma insulin concentration caused by exogenous fructose. In the rats exposed to exogenous fructose, the olive oil-fed rats differed from other animals by the absence of a decrease in food intake and body weight gain, whilst the guar-fed rats differed from other animals in a lower plasma D-glucose concentration in fed state and an absence, at day 65, of a higher plasma D-glucose concentration than that at day 0 measured in after overnight fasting state. These findings argue in favour of guar, rather than olive oil, to oppose the effect of exogenous fructose on glucose homeostasis.

Changes in plasma LDL and HDL composition in patients undergoing cardiac surgery.

Changes of lipoprotein composition have been mainly reported in conditions of sepsis. This study characterized compositional changes in LDL and HDL during the acute phase response following cardiac surgery with cardiopulmonary bypass. Twenty-one patients undergoing cardiac surgery were included in this study. Blood samples were drawn before operation and on day 2 post-surgery. In parallel to plasma lipids and antioxidant status, lipoproteins were analyzed for lipid, apolipoprotein (apo), hydroperoxide and alpha-tocopherol content. Beyond decreases in lipid concentrations and antioxidant defenses, cardiac surgery induced substantial modifications in plasma lipoproteins. ApoB decrease in LDL fraction (-46%; P < 0.0001) reflected a marked reduction in the circulating particle number. LDL cholesteryl ester content relative to apoB concentration remained unchanged post-surgery while triglyceride (+113%; P < 0.001), free cholesterol (+22%; P < 0.05) and phospholipid (+23%; P < 0.025) were raised relative to apoB indicating increased particle size. In HDL, an abrupt rise of apoSAA (P < 0.05) was observed together with a decrease of apoA1 (-22%; P < 0.005). Cholesteryl ester content in HDL fraction decreased in parallel to apoA1 concentration while triglycerides, free cholesterol and phospholipids increased relative to apoA1. In contrast to unchanged alpha-tocopherol content, hydroperoxide content was increased in LDL and HDL. By comparison to sepsis, cardiac surgery induces a comparable reduction in circulating LDL but a more limited decrease in HDL particles. Furthermore, in contrast, cardiac surgery induces an increase in polar and non-polar lipids, as well as of particle size in both LDL and HDL.

Cardioprotective effect of spontaneous activity.

In the perspective of giving a better understanding of the cardioprotective effects attributable to the tandem low caloric intake and training, Lou/C rats would be an interesting model since these animals exhibit spontaneously these two characteristics for months, without any dietary manipulations or stressor stimuli. No information was so far available on their cardiac function. Therefore, the aim of this pilot study was (i) to document cardiac function before and after ischemia in this strain, and (ii) to investigate whether spontaneous wheel-running activity can improve the ability of cardiac muscle to recover its function after an ischemic period. Cardiac mechanical and metabolic functions were measured in isolated Langendorff hearts from Wistar sedentary, Lou/C sedentary, and Lou/C wheel-running male rats submitted to a 20-min low-flow ischemia and 20-min reperfusion. In Lou/C sedentary rats, rate-pressure product, an index of cardiac work, was decreased before ischemia as compared to Wistar sedentary animals (- 24 %, p < 0.05). After ischemia, cardiac mechanical function recovery did not significantly differ between these two groups. Nevertheless, flux of non-oxidative glycolysis was lower before and after ischemia in Lou/C sedentary animals than in Wistar sedentary rats. In Lou/C rats, during normoxic perfusion, wheel-running activity significantly decreased heart rate (- 15 %), oxygen consumption (- 2.2 %) and cardiac efficiency (- 37 %), whereas coronary flow and flux of non-oxidative glycolysis were significantly increased (+ 15 % and + 263 %, respectively). After ischemia, recovery of cardiac mechanical function and cardiac efficiency were improved in Lou/C wheel-running rats versus Lou/C sedentary animals (p < 0.05). In conclusion, the impact of ischemia-reperfusion is similar between Lou/C- and Wistar sedentary rats. Spontaneous wheel-running activity decreases cardiac efficiency before ischemia and confers a protection against ischemia- and reperfusion-induced injury in isolated Lou/C rat hearts.

Accelerated clearance of plasma triglycerides and free fatty acids in omega3-depleted rats.

The present study aims mainly at exploring the effects of a severe depletion in polyunsaturated long-chain omega3 fatty acids upon the fate of circulating lipids. The plasma concentration and fatty acid pattern of triglycerides, diglycerides, free fatty acids, and phospholipids were measured in omega3-depleted and control rats injected intravenously one hour before sacrifice with either saline, a control medium-chain triglyceride:olive oil emulsion or a medium-chain triglyceride:fish oil emulsion recently found to rapidly increase the phospholipid content of C20:5omega3 and C22:6omega3 in different cell types. The estimated fractional removal rate of the injected triglycerides and the clearance of free fatty acids from circulation were both higher in omega3-depleted rats than in control animals. The injection of the lipid emulsions apparently inhibited intracellular lipolysis, this being least pronounced in omega3-depleted rats. The increased clearance of circulating triglycerides and unesterified fatty acids in omega3-depleted rats may favor the cellular accumulation of lipids. In turn, such an accumulation and the lesser regulatory inhibition of tissular lipolysis may match the increased clearance of circulating unesterified fatty acids and, hence, account for the lack of any significant difference in plasma unesterified fatty acid concentration between these and control animals.

Rapid effects of the intravenous injection of a medium-chain triglyceride: fish oil emulsion on the triglyceride fatty acid pattern of soleus muscle from omega3 fatty acid-depleted rats.

Second generation rats depleted in long-chain polyunsaturated omega3 fatty acids display several features of the metabolic syndrome, including visceral obesity, liver steatosis, insulin resistance, hypertension, and cardiac hypertrophy. In the framework of an extensive study on such metabolic, hormonal and functional perturbations, the phospholipid fatty acid pattern and ex vivo metabolism of D-glucose were recently investigated in the soleus muscle of these omega3-depleted rats. The present study deals with the triglyceride fatty acid content and pattern of the soleus muscle in control animals and omega3-depleted rats. Some of the latter rats were injected intravenously 60-120 minutes before sacrifice with either an omega3 fatty acid-rich medium-chain triglyceride/fish oil emulsion (omega3-FO rats) or a control medium-chain triglyceride/olive oil emulsion (omega3-OO rats). The total fatty acid content of triglycerides was comparable in control and omega3-depleted rats and, in both cases, inversely related to their C20:4omega6 relative content. At variance with the situation found in control rats, no long-chain polyunsaturated omega3 fatty acid (C18:3omega3, C20:5omega3, C22:5omega3, C22:6omega3) was detected in the omega3-depleted rats. Unexpectedly, the triglyceride content in most long-chain polyunsaturated omega6 fatty acids (C18:2omega6, C20:3omega6, C20:4omega6 and C22:4omega6) had also decreased in the latter rats. Moreover, the activity of Delta9-desaturase was apparently increased in the omega3-depleted rats, as judged from the C16:1omega7/C16:0 and C18:1omega9/C18:0 ratios. The omega3-FO rats differed from omega3-OO rats by a lower contribution of C18:2omega6 metabolites (C18:3omega6, C20:3omega6, C20:4omega6 and C22:4omega6). These findings indicate that the prior injection of the medium-chain triglyceride/fish oil emulsion, known to increase the muscle phospholipid content in long-chain polyunsaturated omega3 fatty acids, may nevertheless accentuate the depletion in long-chain polyunsaturated omega6 fatty acids otherwise found in the triglycerides of omega3-depleted rats. Such a dual effect is reminiscent of that observed, under the same experimental conditions, for selected variables in D-glucose metabolism in the soleus muscle.

Alteration of adipocyte metabolism in omega3 fatty acid-depleted rats.

Presently an insufficient supply of long-chain polyunsaturated omega3 fatty acid is prevalent in Western populations leading to potential metabolic consequences. Based on this fact, this study deals mainly with various aspects of lipid metabolism in second generation female omega3-depleted rats. The parametrial fat and body weights were higher in omega3-depleted than control animals. This coincided with liver steatosis but did not alter heart triglyceride/phospholipid ratio. The net uptake of [U-14C] palmitate by adipocytes was also higher in omega3-depleted rats than in control animals. The uptake of D-[U- 4C] glucose or [1,2 (-14)C] acetate by adipocytes was lower, however in omega3-depleted than control animals and was unaffected by insulin in the former as distinct from latter animals. Despite comparable basal lipolysis, the increase in glycerol output from adipocytes provoked by theophylline was higher in omega3-depleted than control rats. The fatty acid pattern of lipids in adipose tissue was characterized in the omega3-depleted rats by a much lower omega3 content, higher apparent Delta 9-saturase and elongase activities, lower efficiency for the conversion of C18:2omega6 to C20:4omega6 and higher efficiency for the conversion of C18:3omega3 to C20:5omega3. These features were compared to those prevailing in liver and plasma lipids. The present study thus extends knowledge on the alteration of lipid metabolism resulting from a deficiency in long-chain polyunsaturated omega3 fatty acids.

Acute in vivo administration of a fish oil-containing emulsion improves post-ischemic cardiac function in n-3-depleted rats.

A novel i.v. lipid preparation (MCT:FO) containing 80% medium chain-triacylglycerols and 20% fish oil was recently developed to rapidly replenish cell membrane phospholipids with omega 3 (n-3) polyunsaturated fatty acids (PUFA). In regard of this property, we investigated the effect of a single i.v. administration of MCT:FO on the recovery of cardiac function after ischemia in control and n-3-depleted rats. Results were compared with those obtained either with a control preparation, where FO was replaced by triolein (MCT:OO), or with saline. Saline (1 ml) or lipid preparation (also 1 ml) was injected as a bolus via the left saphenous vein. After 60 min the heart was removed and perfused for 20 min in normoxic conditions according to Langendorff. Thereafter, the heart was subjected to a 20 min zero-flow normothermic ischemia, followed by 40 min reperfusion. Cardiac mechanical and metabolic functions were monitored. In control rats, the previous administration of a lipid preparation (MCT:FO or MCT:OO) versus saline improved cardiac function during aerobic reperfusion post-ischemia. N-3-depleted rats showed decreased basal cardiac function and impaired recovery following ischemia. However, the bolus injection of MCT:FO opposed the deleterious effect of long-term n-3-deficiency and, in this respect, was superior to MCT:OO over the first 20 min of reperfusion. This novel approach to rapidly correct n-3 PUFA-deficiency might be clinically relevant and offer interesting perspectives in the management of acute ischemic accidents.