Fish oil minimises feed intake and improves insulin sensitivity in Zucker fa/fa rats

Long-chain n-3 PUFA (LC n-3 PUFA) prevent, in rodents, insulin resistance (IR) induced by a high-fat and/or fructose diet but not IR induced by glucocorticoids. In humans, contrasting effects have also been reported. We investigated their effects on insulin sensitivity, feed intake (FI) and body weight gain in genetically insulin resistant male obese (fa/fa) Zucker (ZO) rats during the development of obesity. ZO rats were fed a diet supplemented with 7 % fish oil (FO) + 1 % corn oil (CO) (wt/wt) (ZOFO), while the control group was fed a diet containing 8 % fat from CO (wt/wt) (ZOCO). Male lean Zucker (ZL) rats fed either FO (ZLFO) or CO (ZLCO) diet were used as controls. FO was a marine-derived TAG oil containing EPA 90 mg/g + DHA 430 mg/g. During an oral glucose tolerance test, glucose tolerance remained unaltered by FO while insulin response was reduced in ZOFO only. Liver insulin sensitivity (euglycaemic-hyperinsulinaemic clamp + 2 deoxyglucose) was improved in ZOFO rats, linked to changes in phosphoenolpyruvate carboxykinase expression, activity and glucose-6-phosphatase activity. FI in response to intra-carotid insulin/glucose infusion was decreased similarly in ZOFO and ZOCO. Hypothalamic ceramides levels were lower in ZOFO than in ZOCO. Our study demonstrates that LC n-3 PUFA can minimise weight gain, possibly by alleviating hypothalamic lipotoxicity, and liver IR in genetically obese Zucker rats.

Long-chain n-3 PUFA given before and throughout gestation and lactation in rats prevent high-fat diet-induced insulin resistance in male offspring in a tissue-specific manner

This study investigated whether long-chain n-3 PUFA (LC n-3 PUFA) given to pregnant rats fed a high-fat (HF) diet may prevent fetal programming in male offspring at adulthood. Six weeks before mating, and throughout gestation and lactation, female nulliparous Sprague-Dawley rats were given a chow (C) diet, HF (60·6 % fat from maize, rapeseed oils and lard) or HF in which one-third of fat was replaced by fish oil (HF n-3). At weaning, the three offspring groups were randomly separated in two groups fed C diet, or HF without LC n-3 PUFA, for 7 weeks until adulthood. Glucose tolerance and insulin sensitivity were assessed by an oral glucose tolerance test both at weaning and at adulthood. Insulin signalling was determined in liver, muscle and adipose tissue by quantification of the phosphorylation of Akt on Ser 473 at adulthood. At weaning, as at adulthood, offspring from HF-fed dams were obese and displayed glucose intolerance (GI) and insulin resistance (IR), but not those from HFn-3 fed dams. Following the post-weaning C diet, phosphorylation of Akt was strongly reduced in all tissues of offspring from HF dams, but to a lesser extent in liver and muscle of offspring from HFn-3 dams. However, it was abolished in all tissues of all offspring groups fed the HF post-weaning diet. Thus, LC n-3 PUFA introduced in a HF in dams partially prevented the transmission of GI and IR in adult offspring even though they were fed without LC n-3 PUFA from weaning.

Clinical pathways in the management of the obese: Pre- and postoperative aspects

INTRODUCTION

Bariatric surgery (BS) leads to substantial weight loss accompanied by reversal of several obesity-related co-morbidities and reduced mortality. However, surgery is associated with risks and its nearly irreversible characteristic requires a clearly established pre- and postoperative clinical pathway. In France, this pathway relies on recommendations made by the High Authority of Health (Haute Autorité de santé (HAS)) in 2009; an update is awaited in 2023.

PREOPERATIVE ASPECTS

BS should be proposed only after failure of well-conducted medical treatment and is intended for patients whose body mass index (BMI) is ≥40kg/m² or for those with BMI ≥35kg/m² who also have co-morbidities amenable to improvement, and in whom there are no contra-indications, particularly, those related to general anesthesia or psychological factors. The success and safety of surgical management requires preparation of the patient with regard to dietetic and nutritional counseling, and physical activity. The possibility of complications must be recognized and communicated, including, in view of the large variability of outcomes between individuals, the risk of failure and regain of weight.

POSTOPERATIVE ASPECTS

Prior to the operation, patients should be informed of and accept the program of postoperative clinical and laboratory follow-up, as well as the need for lifelong supplementation in micronutrients and the financial implications including what patients may have to pay out of their own pocket.

CONCLUSION

Surgical management of obesity cannot replace the multidisciplinary medical management of severe obesity. The results obtained by BS are sustainable only if the patient adheres to the proposed modalities. New drugs such a GLP-1 analogues have opened encouraging perspectives as possible alternatives to BS in certain indications.

French recommendations on the prevention and treatment of osteoporosis secondary to bariatric surgery

INTRODUCTION

This article presents the initial recommendations of the Groupe de Recherche et d'Information sur les Ostéoporoses (Osteoporosis Research and Information Group [GRIO]) and the Société Française de Rhumatologie (French Rheumatology Society [SFR]) on the prevention and treatment of osteoporosis secondary to bariatric surgery.

METHODS

The recommendations were produced by a working group comprising 4 expert rheumatologists, 3 medically qualified nutritionists, 2 obesity surgeons, 1 physical activity specialist, and 1 patient-association representative.

RESULTS

The following generally recommended measures apply to all patients with an indication for bariatric surgery or who have already undergone bariatric surgery: normalize calcium and protein intake, attain a 25(OH) vitamin D concentration of between 30 and 60ng/mL; prevent the risk of falls, and introduce a suitable regimen of physical activity. An initial assessment of fracture risk should be routinely performed - ideally before the first bariatric surgery procedure - (i) in the case of RYGB and biliopancreatic diversion, regardless of age, (ii) in patients at high risk of fracture, regardless of age, and (iii) in all menopausal women and all men ≥ 50 years old, regardless of the type of bariatric surgical procedure. The fracture risk assessment is based on a determination of osteoporosis risk factors and bone mineral density measurements. Anti-osteoporosis treatment - zoledronic acid as the first line of treatment - is indicated for menopausal women and men ≥ 50 years old with (i) a history of severe fracture, regardless of T-score, (ii) a history of non-severe fracture and a T-score ≤ -1, and (iii) no history of fracture and a T-score ≤ -2.

CONCLUSIONS

There is an increased risk of fracture after bariatric surgery. Clinicians should focus their attention on patients at high fracture risk such as postmenopausal women and men older than 50 years. More research is necessary to direct and support guidelines.

[Definition, epidemiology and prognosis of undernutrition in adults]

DEFINITION, EPIDEMIOLOGY AND PROGNOSIS OF UNDERNUTRITION IN ADULTS Undernutrition is a pernicious and very frequent disease, particularly in hospitals (30 to 40% of adults) where it tends to worsen during the stay. The Covid-19 epidemic has further increased its prevalence. Its pernicious nature is that it is often considered as a symptom accompanying a pre-existing acute or chronic illness and not a disease in its own right. Even in 2022, in addition to the lack of prevention in at-risk populations, it very often remains undetected and/or insufficiently treated. However, it is accompanied by excess mortality and an increased risk of multiple complications: poorer healing, more frequent infections (particularly nosocomial), reduced immunity, increased prevalence of pressure sores, fistula in surgery, poorer quality of life, loss of autonomy, increased duration of artificial ventilation, and more difficult recovery from a pathology, particularly in the elderly. To this must be added an additional cost of care for one given disease or a group of given diseases. Its early diagnosis and management have proven to be effective: reduction of mortality, comorbidities and societal costs.

Activation of chicken gamma-delta T lymphocytes by a purified ulvan extract

Chicken γδ T lymphocytes are present in a variety of tissues such as blood, spleen and intestine. They constitute a major cytotoxic population. In chicken, Salmonella immunization as well as vaccination against Newcastle disease virus are accompanied by an increase of γδ T lymphocytes in peripheral blood, which may be activated, and thus represent a protective immune response. It has been published that activation of avian γδ T cells can occur in a MHC non-restricted manner. Ulvans are complex sulfated polysaccharides composed of disaccharide repetitions found in the cell walls of green algae belonging to the genus Ulva. We recently demonstrated that a purified ulvan extract activates chicken heterophils and monocytes in vivo through TLR2 and TLR4 receptors when given in drinking water. We demonstrate here, that the same extract given once in drinking water at 25 and 50 mg/l, results in increased membrane expression of Major Histocompatibility Complex class 2 as soon as day 2, as detected using flow cytometry. We conclude chicken γδ T lymphocytes to be activated, or at least primed, in vivo, with the extract. Further experiments are required to fully understand whether their activation or priming is the result of direct and/or indirect mechanisms.

Up in the air: drone images reveal underestimation of entanglement rates in large rorqual whales

Entanglement in fishing gear is a significant threat to many cetaceans. For the 2 largest species, the blue whale Balaenoptera musculus and the fin whale B. physalus, reports of entangled individuals are rare, leading to the assumption that entanglements are not common. Studies of interaction with fisheries in other species often rely on the presence of scars from previous entanglements. Here, scar detection rates were first examined in humpback Megaptera novaeangliae, fin and blue whales using standard vessel-based photo-identification photographs collected between 2009 and 2016 in the Gulf of St. Lawrence, Canada. We then examined aerial images of fin whales collected with a drone in 2018 and 2019 and compared both methods. Entanglement rates were 6.5% for fin and 13.1% for blue whales using photo-identification images of individuals. Prominent scarring was observed around the tail and caudal peduncle, visible only when animals lifted those body sections above water when diving. For the small subset of pictures which captured the entire caudal peduncle, entanglement rates ranged between 60% for blue and 80% for fin whales. This result was similar to the 85% entanglement rate estimated in humpback whales. The assessment of aerial-based photography yielded an entanglement rate of 44.1 to 54.7% in fin whales. Scars were always around the peduncle, often the tail, rarely the dorsal fin and never around the pectoral fins, while the mouth cannot be examined from above. Thus, in species that do not regularly expose their tail or peduncle, aerial imagery is the preferred method to quantify entanglement rates by assessment of scars.

Contrasted central effects of n-3 versus n-6 diets on brain functions in diet-induced obesity in minipigs

INTRODUCTION

N3 polyunsaturated fatty acids (n-3 PUFAs) exert anti-inflammatory effects for the hypothalamus, but their extra-hypothalamic outcome lack documentation. We evaluated the central consequences of the substitution of saturated fatty acids with n-3 or n-6 PUFA in obesogenic diets.

METHODS

Twenty-one miniature pigs were fed ad libitum obesogenic diets enriched in fat provided either as lard, fish oil (source for n-3 PUFAs), or sunflower oil (source for n-6 PUFAs) for ten weeks. The blood-brain barrier (BBB) permeability was quantified by CT perfusion. Central autonomic network was evaluated using heart rate variability, and PET 18FDG was performed to assess brain metabolism.

RESULTS

BBB permeability was higher in lard group, but heart rate variability changed only in fish oil group. Brain connectivity analysis and voxel-based comparisons show regional differences between groups except for the cingulate cortex in fish oil vs. sunflower oil groups.

DISCUSSION

: The minute changes in brain metabolism in obese pigs feed with fish oil compared with saturated fatty acids were sufficient to induce detrimental changes in heart rate variability. On the contrary, the BBB's decreased permeability in n-3 and n-6 PUFAs groups was protective against an obesity-driven damaged BBB.

Fostering infant food texture acceptance: A pilot intervention promoting food texture introduction between 8 and 15 months

Healthy infant feeding practices form the basis of healthy eating behaviour later in life. The effect of providing parents with recommendations on textured food introduction between 8 and 15 months on children's experience with and acceptance of textured foods was studied. Sixty parent/child dyads were randomly assigned to a control group (CG) receiving current French recommendations and an intervention group (IG) receiving a brochure with supplementary advice, tips and monthly counselling on food texture introduction. After the intervention, parents completed self-report measures about the introduction of 188 food items, including purees, soft/small pieces, hard/large pieces and double textures. Children's acceptance of eight textured foods was assessed in a laboratory setting. Parents in the IG introduced more soft/small food pieces (P = 0.004) but not more complex textures (P = 0.15). There was no group difference in children acceptance for any of the textured foods offered in the laboratory. Independent of their study group, children's exposure to texture was associated with birth order, self-feeding with fingers, low gagging frequency and seldom use of commercial baby foods. Higher acceptance was associated with higher exposure to food pieces but not to pureed foods (either smooth or rough) and with children's eating behavioural traits (high food enjoyment, high food responsiveness and low food fussiness). This pilot intervention demonstrated that providing information can be effective in promoting the introduction of small and soft food pieces, but the most effective way to influence the introduction of more challenging textures (hard pieces and double texture) is uncertain. Further research should focus on the identification of barriers to complex texture introduction and on how building on this knowledge for a population-based public health intervention.

Are marine n-3 fatty acids protective towards insulin resistance? From cell to human

Marine n-3 fatty acids improve most of the biochemical alterations associated with insulin resistance (IR). Experimental models of dietary-induced IR in rodents have shown their ability (often at a very high dose) to prevent IR, but with sometimes a tissue specific effect. However, in a high sucrose diet-induced IR rat model, they are unable to reverse IR once installed; in other rodent models (dexamethasone, Zucker rats), they are inefficacious perhaps because of the severity of IR. The very low incidence of type-2 diabetes (T2D) in Inuits in the 1960s, which largely increased over the following decades in parallel to the replacement of their traditional marine food for a western diet strongly suggests a protective effect of marine n-3 towards the risk of T2D; this was confirmed by reversal of its incidence in intervention studies reintroducing their traditional food. In healthy subjects and insulin-resistant non-diabetic patients, most trials and meta-analyses conclude to an insulin-sensitising effect and to a very probable preventive or alleviating effect towards IR. Concerning the risk of T2D, concordant data allow us to conclude the protective effect of marine n-3 in Asians while suspicion exists of an aggravation of risk in Westerners, but with the possibility that it could be explained by a high heterogeneity of studies performed in this population. Some longitudinal cohorts in US/European people showed no association or a decreased risk. Further studies using more homogeneous doses, sources of n-3 and assessment of insulin sensitivity methods are required to better delineate their effects in Westerners.

Effects of Oral Glucose on Intermediary Metabolism in Continuous Ambulatory Peritoneal Dialysis Patients versus Healthy Subjects

Objective

To explore the mechanisms and metabolic consequences of the insulin resistance of patients treated by continuous ambulatory peritoneal dialysis (CAPD).

Design

CAPD patients and healthy subjects ingested a similar mean oral glucose load per kilogram of fat-free mass (FFM) [1.20 ± 0.03 g/(kg FFM) vs 1.20 ± 0.06 g/(kg FFM); CAPD vs healthy subjects]. Substrate oxidation was monitored over 6 hours using indirect calorimetry.

Setting

Peritoneal dialysis unit of a tertiary-care institutional center.

Outcome Measures

Glycemia, insulinemia, substrate oxidation.

Patients

Six CAPD patients (68 ± 5 yr) and 6 healthy subjects (24 ± 1 yr). The CAPD patients had similar body mass index (21.4 ± 1.3 vs 22.9 ± 1.1 kg/m2), a higher percent fat (25.8% ± 3.7% vs 16% ± 2.2%; p < 0.05), and a lower FFM (42.2 ± 2.2 kg vs 56.5 ± 2.6 kg; p < 0.01) than healthy subjects.

Results

The CAPD patients displayed a higher glycemic and insulinemic responses to glucose than did healthy subjects (p < 0.05), but similar glucose oxidation and storage. Lipid oxidation and plasma nonesterified fatty acids were not increased in CAPD patients versus healthy subjects, in spite of a higher adiposity. Fat oxidation was related to fat mass in CAPD patients (r2 = 0.77, p < 0.05) but not in healthy subjects (r2 = 0.05).

Conclusion

CAPD patients display an insulin -resistance not explained by an increased lipid oxidation. The maintenance of intracellular glucose utilization at the expense of higher glycemic and insulinemic responses suggests a defective glucose transport.

MON-453 Endocrine, Bone, and Metabolic Disorders in Adults after Allogeneic Stem-Cell Transplant

Introduction Allogeneic hematopoietic stem cell transplantations (allo-HSCT) is often indicated in malignant hematologic diseases. Conditioning regimens, used to reduce the tumor burden and to prevent transplant rejection, are based on chemotherapy alone or combined with total body irradiation (TBI). Endocrine complications are frequent transplant-related side effects. They have been well described in children studies but less in adulthood. Objective To assess retrospectively endocrine, bone and metabolic disorders in adult patients, 12 months after allo-HSCT. Patients & Methods Inclusion criteria were : patients treated with allo-HSCT from 2006 to 2016 for a malignant hematologic disease; adult and in complete remission at exploration. Exclusion criteria were : anteriority of brain radiotherapy and prior HSCT. Twelve months after HSCT, each patient underwent fasting measurement of IGF1, TSH, fT4, FSH, LH, sex steroids, glycemia, insulin level, and lipid profile. Unless contraindication, adrenal and growth hormone functions were assessed with insulin hypoglycemia test. A dual X-ray absorptiometry was also performed. Results During the inclusion period, 249 patients received allo-HSCT at our institution. Among them, 148 stayed in complete remission 12 months after HSCT and 63 have been explored in our department. The study sample consisted of the 45 patients meeting the inclusion/exclusion criteria. 40 patients had insulin hypoglycemia test. Hypopituitarism was observed in 20 patients (44%) (14 GH deficiency, 8 central adrenal deficiency, 2 central hypothyroidism and 1 central hypogonadism). No predictive factor was found. One patient had central adrenal deficiency after 12 Gy TBI regimen without any corticotherapy. Hypothyroidism was observed in 6 patients (13,6 %), evenly distributed in subclinical, overt and central hypothyroidism. The risk of developing hypothyroidism was higher in patients aged less than 30 y/o at transplantation (OR = 8,5). All premenopausal women (n = 16) had premature ovarian failure. Half of the 18 men were suspected to have spermatogenesis disorder (elevated FSH). Five men had elevated LH with normal testosterone, and one had central hypogonadism possibly attributed to his obesity. Bone mineral density (BMD) was decreased in 33 patients (77 %). Twelve (28 %) had osteoporosis. Conditioning regimen with busulfan was protective of BMD decrease (OR = 0,66 [0,5-0,85], P = 0,02). Obesity was more frequent (20 %) than our national prevalence (14 %). There were no increase in insulino-resistance and diabetes prevalences. Twenty patients (45 %) had dyslipidemia, 14 of them hypertriglyceridemia. Conclusion Our study shows a high frequency of endocrine, bone and metabolic disorders 12 months after allo-HSCT during adulthood. Hypopituitarism is more frequent that previously described, using the gold standard of the GH and adrenal function exploration.

Identifying the ideal profile of French yogurts for different clusters of consumers

Identifying the sensory properties that affect consumer preferences for food products is an important feature of product development. Different methods, such as external preference mapping or partial least squares regression, are used to establish relationships between sensory data and consumer preferences and to identify sensory attributes that drive consumer preferences, by highlighting optimum products. Plain French yogurts were evaluated by a sensory profiling method performed by 12 trained judges. In parallel, 180 consumers were asked to score their overall liking and complete a cognitive restraint questionnaire. After hierarchical cluster analysis on the liking scores, preference mapping using a quadratic regression model was performed. Five clusters of consumers were identified as a function of different preference patterns. Contrary to our expectations, fat levels were not discriminating. For each cluster, the results of preference mapping enabled the identification of optimum products. A comparison of the 5 sensory profiles revealed numerous differences between key sensory attributes. For example, one consumer cluster had a strong preference for products perceived as very thick, grainy, but with a less flowing texture, less sticky, whey presence and color, in contrast to other clusters. In addition, each segment of consumers was characterized according to the results of the cognitive restraint questionnaire.

Interaction of low dose of fish oil and glucocorticoids on insulin sensitivity and lipolysis in healthy humans: A randomized controlled study

SCOPE

This study examined the interaction of fish oil (FO) with dexamethasone on glucose and lipid metabolisms in healthy subjects.

METHODS AND RESULTS

The study included two consecutive parts. Part A (randomized) in 16 subjects studied the effects of dexamethasone (2 days, 2 mg/day) versus placebo (lactose), part B (two parallel subgroups of eight) studied the interaction of FO (3 wk, 840 mg/day of EPA + DHA) with dexamethasone. Insulin sensitivity of lipolysis (d5-glycerol infusion + microdialysis), endogenous glucose production, and muscle glucose uptake were assessed by a three-step hot insulin clamp and substrate oxidation by indirect calorimetry. Dexamethasone induced liver and peripheral insulin resistance, an increase in fat oxidation, and a decrease in suppression of plasma nonesterified fatty acids (NEFAs). FO amplified the effects of dexamethasone by increasing liver and muscle insulin resistance, by reducing suppression of plasma NEFAs and fat oxidation and by increasing adipose tissue (AT) lipolysis.

CONCLUSION

FO, given at a moderate dose in healthy subjects prior to a very short-term (2 days) low dose of a synthetic glucocorticoid, worsened its deleterious effects on insulin sensitivity. The enhancing effect of FO on fat oxidation and AT lipolysis might be a protective effect toward an increase in fat mass.

Polyunsaturated fatty acids inhibit PI3K activity in a yeast-based model system

The phosphatidylinositol 3-kinase (PI3K) pathway controls the regulation of cell growth, proliferation, migration and apoptosis. In many tumors, the PI3K gene is mutated or overexpressed, and/or the PI3K pathway is hyperactive. PI3K is therefore a potential pharmacological target for the development of anti-tumor drugs. Some polyunsaturated fatty acids (PUFA), when given in the diet, may lead to a decrease in PI3K activity. We used a yeast-based model to reconstitute the PI3K/PTEN/Akt pathway to study the effects of long-chain polyunsaturated n-3 fatty acids on PI3K, and found that various PUFA were able to alleviate toxicity induced by overexpression of PI3K. The various PUFA had no significant effect on the steady-state level of PI3K catalytic subunit proteins (p110alpha) in yeast. However, depletion of phosphatidylinositol 4,5-bisphosphate due to overexpression of the p110alpha subunit was significantly reduced by treating the yeast cells with the various PUFA. The inhibition of mammalian PI3K, expressed in an exogenous cellular context in yeast, is likely to be a direct effect of these PUFA on PI3K rather than on other mammalian endogenous or environmental factors. These results are particularly promising given the abundance of active PUFA in marine foodstuffs and especially fish oils.

Long-chain n-3 polyunsaturated fatty acids dissociate phosphorylation of Akt from phosphatidylinositol 3'-kinase activity in rats

We examined whether a low amount of dietary long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) modulated phosphatidylinositol 3'-kinase (PI 3-kinase) activity and downstream Akt phosphorylation differently in normal or insulin-resistant rats. Rats were fed for 28 days with either a control diet containing 14.6% of metabolizable energy (ME) as peanut-rape oil (PR) or an n-3 diet where 4.9% of ME as PR was replaced by fish oil. Over the last 5 days, rats received 9 per thousand NaCl or dexamethasone (1 mg/kg). Insulin stimulation of both PI 3-kinase activity and Akt serine(473) phosphorylation and modulation of GLUT4 content were studied in liver, muscle, and adipose tissue (AT). Glucose tolerance and insulin sensitivity were determined by an oral glucose challenge. In muscle and AT, LC n-3 PUFA abolished insulin-stimulated PI 3-kinase activity. These effects were not paralleled by defects in Akt serine(473) phosphorylation, which was even increased in AT. Dexamethasone abolished insulin-stimulated PI 3-kinase activity in all tissues, whereas Akt serine(473) phosphorylation was markedly reduced in muscle but unaltered in liver and AT. Such tissue-specific dissociating effects of LC n-3 PUFA on PI 3-kinase/Akt activation took place without alteration of glucose metabolism. Maintenance of a normal glucose metabolism by the n-3 diet despite abolition of PI 3-kinase activation was likely explained by a compensatory downstream Akt serine(473) phosphorylation. The inability of LC n-3 PUFA to prevent insulin resistance by dexamethasone could result from the lack of such a dissociation.

Free fatty acids and insulin resistance

PURPOSE OF REVIEW

Dysregulation of free fatty acid metabolism is a key event responsible for insulin resistance and type 2 diabetes. According to the glucose-fatty acid cycle of Randle, preferential oxidation of free fatty acids over glucose plays a major role in insulin sensitivity and the metabolic disturbances of diabetes mellitus. However, other mechanisms are now described to explain the molecular basis of insulin resistance.

RECENT FINDINGS

Recent studies have suggested that local accumulation of fat metabolites such as ceramides, diacylglycerol or acyl-CoA, inside skeletal muscle and liver, may activate a serine kinase cascade leading to defects in insulin signalling and glucose transport. Inflammation and oxidative stress are also potent mechanisms which could lead to a state of insulin resistance. Finally, modulation of transcription by free fatty acids through their binding to peroxisome proliferator-activated receptors could also contribute to impaired glucose metabolism.

SUMMARY

The increase in free fatty acid flux resulting from increased lipolysis secondary to adipose-tissue insulin resistance induces or aggravates insulin resistance in liver and muscle through direct or indirect (from triglyceride deposits) generation of metabolites, altering the insulin signalling pathway. Alleviating the excess of free fatty acids is a target for the treatment of insulin resistance.

Interaction of fish oil and a glucocorticoid on metabolic responses to an oral glucose load in healthy human subjects

Compared with saturated fat, n-3 long-chain PUFA-rich fish oil improves insulin sensitivity in rats. We studied whether n-3 long-chain PUFA could prevent insulin resistance induced by dexamethasone (a glucocorticoid) in healthy human volunteers. A group of eight subjects was studied twice after a 2 d dexamethasone treatment, before and after a 3-week supplementation with fish oil (providing daily doses of 1.1 g 20 : 5n-3 and 0.7 g 22 : 6n-3). The subjects were studied during the basal state and over the 6 h following an oral glucose load (1 g/kg). Plasma glucose fluxes were traced with [6,6-2H2]glucose and [13C]glucose (naturally 13C-enriched corn glucose). Substrate oxidation was obtained from indirect calorimetry. Following fish oil supplementation, plasma glucose fluxes and substrate oxidation were maintained despite a 17 % reduction (P<0.05) in the area under the curve of plasma insulin response, suggesting an insulin-sensitizing effect.

Adipose tissue compensates for defect of phosphatidylinositol 3'-kinase induced in liver and muscle by dietary fish oil in fed rats

The present work aimed to study in rats whether substitution of a low level of fish oil (FO; 2.2% of calories) into a low-fat diet (6.6% of calories from fat as peanut-rape oil or control diet) 1) has a tissue-specific effect on insulin signaling pathway and 2) prevents dexamethasone-induced alteration of insulin signaling in liver, muscle, and adipose tissue. Sixteen rats were used for study of insulin signaling, and sixteen rats received an oral glucose load (3 g/kg). Eight rats/group consumed control diet or diet containing FO over 5 wk. Four rats from each group received a daily intraperitoneal injection of saline or dexamethasone (1 mg.kg(-1).day(-1)) for the last 5 days of feeding. In liver, FO decreased phosphatidylinositol 3'-kinase (PI 3'-kinase) activity by 54% compared with control diet. A similar result was obtained in muscle. In both liver and muscle, FO clearly amplified the effect of dexamethasone. FO did not alter early steps of insulin signaling, and in muscle GLUT4 protein content remained unaltered. In adipose tissue, FO increased PI 3'-kinase activity by 74%, whereas dexamethasone decreased it by 65%; inhibition of PI 3'-kinase activity by dexamethasone was similar in rats fed FO or control diet, and GLUT4 protein content was increased by 61% by FO. Glycemic and insulinemic responses to oral glucose were not modified by FO. In conclusion, FO increased PI 3'-kinase activity in adipose tissue while inhibiting it in liver and muscle. The maintenance of whole body glucose homeostasis suggests an important role of adipose tissue for control of glucose homeostasis.

Negative impact of hypocaloric feeding and energy balance on clinical outcome in ICU patients

BACKGROUND AND AIMS

Critically ill patients with complicated evolution are frequently hypermetabolic, catabolic, and at risk of underfeeding. The study aimed at assessing the relationship between energy balance and outcome in critically ill patients.

METHODS

Prospective observational study conducted in consecutive patients staying > or = 5 days in the surgical ICU of a University hospital. Demographic data, time to feeding, route, energy delivery, and outcome were recorded. Energy balance was calculated as energy delivery minus target. Data in means+/-SD, linear regressions between energy balance and outcome variables.

RESULTS

Forty eight patients aged 57+/-16 years were investigated; complete data are available in 669 days. Mechanical ventilation lasted 11+/-8 days, ICU stay 15+/-9 was days, and 30-days mortality was 38%. Time to feeding was 3.1+/-2.2 days. Enteral nutrition was the most frequent route with 433 days. Mean daily energy delivery was 1090+/-930 kcal. Combining enteral and parenteral nutrition achieved highest energy delivery. Cumulated energy balance was between -12,600+/-10,520 kcal, and correlated with complications (P < 0.001), already after 1 week.

CONCLUSION

Negative energy balances were correlated with increasing number of complications, particularly infections. Energy debt appears as a promising tool for nutritional follow-up, which should be further tested. Delaying initiation of nutritional support exposes the patients to energy deficits that cannot be compensated later on.

N-3 long chain polyunsaturated fatty acids: a nutritional tool to prevent insulin resistance associated to type 2 diabetes and obesity?

n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA), mainly eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3), are present in mammal tissues both from endogenous synthesis from desaturation and elongation of 18:3 n-3 and/or from dietary origin (marine products and fish oils). In rodents in vivo, n-3 LC-PUFA have a protective effect against high fat diet induced insulin resistance. Such an effect is explained at the molecular level by the prevention of many alterations of insulin signaling induced by a high fat diet. Indeed, the protective effect of n-3 LC-PUFA results from the following: (a) the prevention of the decrease of phosphatidyl inositol 3' kinase (PI3 kinase) activity and of the depletion of the glucose transporter protein GLUT4 in the muscle; (b) the prevention of the decreased expression of GLUT4 in adipose tissue. In addition, n-3 LC-PUFA inhibit both the activity and expression of liver glucose-6-phosphatase which could explain the protective effect with respect to the excessive hepatic glucose output induced by a high fat diet. n-3 LC-PUFA also decrease muscle intramyofibrillar triglycerides and liver steatosis. This last effect results on the one hand, from a decreased expression of lipogenesis enzymes and of delta 9 desaturase (via a depleting effect on sterol response element binding protein 1c (SREBP-1c). On the other hand, n-3 LC-PUFA stimulate fatty acid oxidation in the liver (via the activation of peroxisome proliferator activated receptor alpha (PPAR-alpha)). In patients with type 2 diabetes, fish oil dietary supplementation fails to reverse insulin resistance for unclear reasons, but systematically decreases plasma triglycerides. Conversely, in healthy humans, fish oil has many physiological effects. Indeed, fish oil reduces insulin response to oral glucose without altering the glycaemic response, abolishes extraggression at times of mental stress, decreases the activation of sympathetic activity during mental stress and also decreases plasma triglycerides. These effects are encouraging in the perspective of prevention of insulin resistance but further clinical and basic studies must be designed to confirm and complete our knowledge in this field.

Fish-oil supplementation reduces stimulation of plasma glucose fluxes during exercise in untrained males

The present study examined the effects of a 3-week fish-oil supplementation (6 g/d) on the rate of plasma glucose disappearance (Rd glucose), hepatic glucose production (HGP), carbohydrate oxidation and lipid oxidation during exercise. Six untrained males (23+/-1 years; 67.6+/-2.7 kg) performed two 90 min cycling exercise sessions at 60 % of maximal O2 output separated by 20 d. During the 20 d before the first test, they ingested 6 g olive oil/d, then 6 g fish oil/d during the 20 d before the second test. Plasma glucose fluxes and lipolysis were traced using 6,6-[(2)H2]glucose and 1,1,2,3,3-[(2)H5]glycerol respectively. Substrates oxidation was obtained from indirect calorimetry. At rest HGP and the Rd glucose were similar after olive oil and fish oil (1.83 (SE 0.05) v. 1.67 (SE 0.11) mg/kg per min). During exercise, fish oil reduced the stimulation of both the Rd glucose (5.06 (SE 0.23) v. 6.37 (SE 0.12) mg/kg per min; P<0.05) and HGP (4.88 (SE 0.24) v. 5.91 (SE 0.21) mg/kg per min; P<0.05). Fish oil also reduced glucose metabolic clearance rate (6.93 (SE 0.29) v. 8.30 (SE 0.57) ml/min). Carbohydrate oxidation tended to be less stimulated by exercise after fish oil than after olive oil (12.09 (SE 0.60) v. 13.86 (se 1.11) mg/kg per min; NS). Lipid oxidation tended to be more stimulated by exercise after fish oil (7.34 (SE 0.45) v. 6.85 (SE 0.17) mg/kg per min; NS). Glycaemia, lactataemia, insulinaemia and glucagonaemia were similarly affected by exercise after fish oil and olive oil. Lipolysis at rest was similar after fish oil and olive oil (2.92 (SE 0.42) v. 2.94 (SE 0.28) micromol/kg per min) and similarly stimulated by exercise (6.42 (SE 0.75) v. 6.77 (SE 0.72) micromol/kg per min). It is concluded that fish oil reduced the Rd glucose by 26 % by reducing glucose metabolic clearance rate, possibly by facilitating fat oxidation, and reduced HGP by 21%, possibly by a feedback mechanism.

Fish oil prevents the adrenal activation elicited by mental stress in healthy men

OBJECTIVES

A diet rich in n-3 fatty acids (fish oils) is associated with reduced risks of cardiovascular and metabolic diseases, but the mechanisms remain incompletely understood. Sympathoadrenal activation is postulated to be involved in the pathogenesis of these diseases, and may be inhibited by n-3 fatty acids. We therefore evaluated the effects of a diet supplemented with n-3 fatty acids on the stimulation of the sympathetic nervous system and of stress hormones elicited by a mental stress.

METHODS

Seven human volunteers were studied on two occasions, before and after 3 weeks of supplementation with 7.2 g/day fish oil. On each occasion, the concentrations of plasma cortisol, and catecholamines, energy expenditure (indirect calorimetry), and adipose tissue lipolysis (plasma non esterified fatty acid concentrations) were monitored in basal conditions followed by a 30 min mental stress (mental arithmetics and Stroop's test) and a 30 min recovery period.

RESULTS

In control conditions, mental stress significantly increased heart rate, mean blood pressure, and energy expenditure. It increased plasma epinephrine from 60.9 +/- 6.2 to 89.3 +/- 16.1 pg/ml (p<0.05), plasma cortisol from 291 +/- 32 to 372 +/- 37 micromol/l (p<0.05) and plasma non esterified fatty acids from 409 +/- 113 to 544 +/- 89 micromol/l (p<0.05). After 3 weeks of a diet supplemented with n-3 fatty acids, the stimulation by mental stress of plasma epinephrine, cortisol, energy expenditure, and plasma non esterified fatty acids concentrations, were all significantly blunted.

CONCLUSION

Supplementation with n-3 fatty acids inhibits the adrenal activation elicited by a mental stress, presumably through effects exerted at the level of the central nervous system.

N-3 polyunsaturated fatty acids prevent the defect of insulin receptor signaling in muscle

A high-fat diet containing polyunsaturated fatty acids (PUFA: n-3 or n-6) given for 4 wk to 5-wk-old male Wistar rats induced a clear hyperglycemia (10.4 +/- 0.001 mmol/l for n-6 rats and 10.1 +/- 0.001 for n-3 rats) and hyperinsulinemia (6.6 +/- 0.8 ng/ml for n-6 rats and 6.4 +/- 1.3 for n-3 rats), signs of insulin resistance. In liver, both diets (n-3 and n-6) significantly reduced insulin receptor (IR) number, IR and IR substrate (IRS)-1 tyrosine phosphorylation, and phosphatidylinositol (PI) 3'-kinase activity. In contrast, in leg muscle, IR density, as determined by Western blotting, was not affected, whereas IR and IRS-1 tyrosine phosphorylation in response to insulin treatment was restored in animals fed with n-3 PUFA to normal; in n-6 PUFA, the phosphorylation was depressed, as evidenced by Western blot analysis using specific antibodies. In addition, PI 3'-kinase activity and GLUT-4 content in muscle were maintained at normal levels in rats fed with n-3 PUFA compared with rats fed a normal diet. In rats fed with n-6 PUFA, both PI 3'-kinase activity and GLUT-4 content were reduced. Furthermore, in adipose tissue and using RT-PCR, we show that both n-3 and n-6 PUFA led to slight or strong reductions in p85 expression, respectively, whereas GLUT-4 and leptin expression was depressed in n-6 rats. The expression was not affected in n-3 rats compared with control rats. In conclusion, a high-fat diet enriched in n-3 fatty acids maintained IR, IRS-1 tyrosine phosphorylation, and PI 3'-kinase activity and total GLUT-44 content in muscle but not in liver. A high-fat diet (n-3) partially altered the expression of p85 but not that of GLUT-4 and leptin mRNAs in adipose tissue.

Acute metabolic effects of dialysis fluids during CAPD

Because the osmotic agents currently used for peritoneal dialysis, ie, glucose or amino acids, are also substrates, a metabolic transfer occurs during their peritoneal absorption. After the delivery of a 3.86% glucose dialysis solution, about 100% of the glucose absorbed through the peritoneal is oxidized. So, this glucose contributes fully to the energy load of the patients. Peritoneal glucose delivery also entertains hyperglycaemia and hyperinsulinaemia as compared to oral glucose. When compared to healthy subjects, oral glucose in continuous ambulatory peritoneal dialysis (CAPD) patients induces a higher glycaemic and insulinaemic response. This traduces insulin resistance in CAPD patients even after months of that renal replacement therapy. When amino acids are used in place of glucose in dialysis solution, they stimulate whole body protein turnover and are used mainly for protein synthesis. When a meal is coingested, protein breakdown is inhibited which reinforces the positive effect of the solution on protein balance.