Omega-3 and omega-6 fatty acids in the insulin resistance syndrome. Lipid and lipoprotein metabolism and atherosclerosis

Growth, metabolic markers, and cognition in 8-year old children born prematurely, follow-up of a randomized controlled trial with essential fatty acids

The study is a follow-up of a randomized, double-blinded, placebo-controlled trial of supplementation with docosahexaenoic acid (DHA) and arachidonic acid (AA) to 129 very low birth weight (VLBW; birth weight <1500 g) infants fed human milk. The main hypothesis was that supplementation would affect growth, metabolic markers, and cognitive function. The secondary aim was to describe predictors of metabolic markers and cognitive status at follow-up. Ninety-eight children met for 8-year follow-up with anthropometric measures, blood biomarkers, and cognitive testing. The intervention group had significantly lower insulin-like growth factor-1 (IGF-1) at 8 years, whereas no differences in growth or intelligence quotient (IQ) were found. For the total cohort, weight gain during first year of life was neither associated with BMI, metabolic markers, nor IQ at follow-up. Blood DHA at 8 years was positively associated with IQ.

CONCLUSIONS

The study is the first long-term follow-up of a randomized controlled trial with essential fatty acids investigating growth, metabolic factors, and IQ. IGF-1 levels were significantly lower in the intervention group at 8 years. First-year growth was not associated with BMI, metabolic markers, or IQ at follow-up. Current DHA status was a significant predictor of higher IQ at follow-up.

WHAT IS KNOWN

• Preterm children have increased risk of lower intelligence quotient (IQ), reduced growth, and abnormal metabolic status. • Early intake of docosahexaenoic acid (DHA) and arachidonic acid (AA), as well as early growth pattern, may influence both IQ and metabolic status. What is New: • Early intervention with DHA and AA led to reduced insulin-like growth factor-1 in blood at 8 years of age. • Weight gain during first year of life was neither associated with impaired metabolic markers nor improved IQ at follow-up. • Current DHA status was a significant predictor of higher IQ at 8 years, also when maternal education and birth weight were included in the model.

Dietary supplementation of omega-3 fatty acids rescues fragile X phenotypes in Fmr1-Ko mice

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) are known to critically influence brain development and functions. Dietary supplementation with n-3 PUFAs has been suggested as a non-pharmacological therapy for a number of developmental disorders, e.g., autistic spectrum disorders (ASD), but human studies so far have led to conflicting results. Furthermore, it has been hypothesized that the therapeutic impact of n-3 PUFAs on these disorders might be explained by their anti-inflammatory properties and their promoting effects on synaptic function and plasticity, but no clear evidence has been produced in this direction. We evaluated the impact of n-3 PUFA dietary supplementation in a mouse model of fragile X syndrome (FXS), i.e., a major developmental disease and the most frequent monogenic cause of ASD. Fmr1-KO and wild-type mice were provided with a diet enriched or not with n-3 PUFAs from weaning until adulthood when they were tested for multiple FXS-like behaviors. The brain expression of several cytokines and of brain-derived neurotrophic factor (BDNF) was concomitantly assessed as inflammatory and synaptic markers. n-3 PUFA supplementation rescued most of the behavioral abnormalities displayed by Fmr1-KO mice, including alterations in emotionality, social interaction and non-spatial memory, although not their deficits in social recognition and spatial memory. n-3 PUFAs also rescued most of the neuroinflammatory imbalances of KOs, but had a limited impact on their BDNF deficits. These results demonstrate that n-3 PUFAs dietary supplementation, although not a panacea, has a considerable therapeutic value for FXS and potentially for ASD, suggesting a major mediating role of neuroinflammatory mechanisms.

Long-term high fructose and saturated fat diet affects plasma fatty acid profile in rats

As the consumption of fructose and saturated fatty acids (FAs) has greatly increased in western diets and is linked with an increased risk of metabolic syndrome, the aim of this study was to investigate the effects of a moderate (10 weeks) and a prolonged (30 weeks) high fructose and saturated fatty acid (HFS) diet on plasma FA composition in rats. The effects of a few weeks of HFS diet had already been described, but in this paper we tried to establish whether these effects persist or if they are modified after 10 or 30 weeks. We hypothesized that the plasma FA profile would be altered between 10 and 30 weeks of the HFS diet. Rats fed with either the HFS or a standard diet were tested after 10 weeks and again after 30 weeks. After 10 weeks of feeding, HFS-fed rats developed the metabolic syndrome, as manifested by an increase in fasting insulinemia, total cholesterol and triglyceride levels, as well as by impaired glucose tolerance. Furthermore, the plasma FA profile of the HFS group showed higher proportions of monounsaturated FAs like palmitoleic acid [16:1(n-7)] and oleic acid [18:1(n-9)], whereas the proportions of some polyunsaturated n-6 FAs, such as linoleic acid [18:2(n-6)] and arachidonic acid [20:4(n-6)], were lower than those in the control group. After 30 weeks of the HFS diet, we observed changes mainly in the levels of 16:1(n-7) (decreased) and 20:4(n-6) (increased). Together, our results suggest that an HFS diet could lead to an adaptive response of the plasma FA profile over time, in association with the development of the metabolic syndrome.

Can vagus nerve stimulation halt or ameliorate rheumatoid arthritis and lupus?

Acetylcholine, the principal vagus neurotransmitter, inhibits inflammation by suppressing the production of pro-inflammatory cytokines through a mechanism dependent on the α7 nicotinic acetylcholine receptor subunit (alpha7nAChR) that explains why vagus nerve stimulation is anti-inflammatory in nature. Strong expression of alpha7nAChR in the synovium of rheumatoid arthritis and psoriatic arthritis patients was detected. Peripheral macrophages and synovial fibroblasts respond in vitro to specific alpha7nAChR cholinergic stimulation with potent inhibition of proinflammatory cytokines. Fibroblasts balance inflammatory mechanisms and arthritis development through feedback cholinergic stimulation by nearby immune cells. Collagen induced arthritis in alpha7nAChR^(-/-) mice was significantly severe and showed increased synovial inflammation and joint destruction compared to the wild-type mice. Similar to vagal nerve stimulation and alpha7nAChR agonists, polyunsaturated fatty acids: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) also suppress inflammation. In view of their similar anti-inflammatory actions, it is proposed that vagal nerve stimulation, alpha7nAChR agonists and EPA and DHA may augment the formation of anti-inflammatory lipid molecules: lipoxins, resolvins, protectins and maresins. This implies that therapies directed at regulation of the cholinergic and alpha7nAChR mediated mechanisms and enhancing the formation of lipoxins, resolvins, protectins and maresins may halt and/or ameliorate rheumatoid arthritis, lupus and other rheumatological conditions.

Adipose tissue arachidonic acid and the metabolic syndrome in Costa Rican adults

BACKGROUND & AIMS

Arachidonic acid, a precursor to a series of inflammatory mediators, may contribute to the development of insulin resistance. We examined the association between adipose tissue arachidonic acid and the metabolic syndrome in Costa Rica, a country in which the metabolic syndrome is highly prevalent.

METHODS

The 484 study participants each provided a fasting blood sample and an adipose tissue biopsy that was analyzed for fatty acid composition. Criteria for the metabolic syndrome were those established in the Third Report of the National Cholesterol Education Program Expert Panel. The data were analyzed by multivariate logistic regression.

RESULTS

Subjects with greater adipose tissue arachidonic acid content had an increasing risk of the metabolic syndrome across quintiles: odds ratio (95% confidence interval), 1.00; 1.51 (0.78-2.91); 2.40 (1.26-4.55); 3.50 (1.84-6.66); and 6.01 (3.11-11.61); test for trend, P<0.0001, after adjustment for age, gender and area of residence. Further adjustment for metabolic risk factors, including adipose fatty acids and body mass index, did not significantly modify the result. Adipose tissue arachidonic acid was also independently associated with abdominal obesity, hypertriglyceridemia, elevated fasting glucose, and high blood pressure.

CONCLUSIONS

This study identifies arachidonic acid as an important independent marker of metabolic dysregulation. A better understanding of the role of this fatty acid in the pathogenesis of the metabolic syndrome is warranted.

The Role of Consumption of Alpha-Linolenic, Eicosapentaenoic and Docosahexaenoic Acids in Human Metabolic Syndrome and Type 2 Diabetes- A Mini-Review

The human metabolic syndrome and its frequent sequela, type 2 diabetes are epidemic around the world. Alpha-linolenic acid (ALA, 18:3 n-3), eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3) consumption ameliorates some of these epidemics' features thus leading one to question if consumption of EPA and DHA, and their metabolic precursor ALA reduce the conversion of metabolic syndrome to type 2 diabetes and reduce the major cause of death in the metabolic syndrome and type 2 diabetes-myocardial infarction. Contributing to myocardial infarction are metabolic syndrome's features of dyslipidemia (including elevated total cholesterol and LDL-c), oxidation, inflammation, hypertension, glucose intolerance, overweight and obesity. Inflammation, glucose and lipid levels are variously influenced by disturbances in various adipocytokines which are in turn positively impacted by n-3 polyunsaturated fatty acid consumption. Type 2 diabetes has all these features though elevated total cholesterol and LDL-c are rarer. It is concluded that EPA and DHA consumption significantly benefits metabolic syndrome and type 2 diabetes primarily in terms of dyslipidemia (particularly hypertriglyceridemia) and platelet aggregation with their impact on blood pressure, glucose control, inflammation and oxidation being less established. There is some evidence that EPA and/or DHA consumption, but no published evidence that ALA reduces conversion of metabolic syndrome to type 2 diabetes and reduces death rates due to metabolic syndrome and type 2 diabetes. ALA's only published significance appears to be platelet aggregation reduction in type 2 diabetes.

Effects of N-3 PUFAs supplementation on insulin resistance and inflammatory biomarkers in hemodialysis patients

AIMS/HYPOTHESIS

It was suggested that polyunsaturated n-3 fatty acids (n-3 PUFAs) could improve insulin sensitivity and have an anti-inflammatory effects in overall population. This study investigates a possible effect of n-3 PUFAs supplementation on the insulin sensitivity and some inflammatory markers; hence, patients with chronic renal failure (CRF) on maintenance hemodialysis (MHD) are presented with insulin resistance.

METHODS

This study explored the ratio between red blood cells (RBC) phospholipid long chain fatty acids (LC FAs) and components of metabolic syndrome (MeS) in 35 patients (mean age 54.50 +/- 11.99 years) with CRF on MHD. Furthermore, the effects of omega-3 FA eight-week's supplementation (EPA+DHA, 2.4 g/d) on the MeS features and inflammatory markers TNF-alpha, IL 6, and hsCRP were examined.

RESULTS

Supplementation increased EPA and DHA levels in RBCs (p = 0.009 for EPA and p = 0.002 for DHA). Total n-6 PUFAs: n-3 PUFAs ratio tended to be lower after supplementation (p = 0.31), but not significantly. Data revealed a significant decrease of saturated FAs (SFA) (p = 0.01) as well as total SFA: n-3 PUFAs ratio during the treatment (p = 0.04). The values of serum insulin and calculated IR index-IR HOMA were reduced after supplementation (p = 0.001 for both). There was a significant decrease in the levels of all inflammatory markers (p = 0.01 for TNF alpha, p = 0.001 for IL 6, p = 0.001 for hsCRP, and p = 0.01 for ferritin). In multivariate regression analysis, only the changes in n-6 PUFAs: n-3 PUFAs ratio independently contributed to 40% of the variance in IR HOMA. The impact of changes in PUFAs level in RBCs membrane phospholipid fatty acids on inflammation markers was also registered. The changes in n-6: n-3 PUFAs ratio independently contributed to 18% of the variance in TNF alpha.

CONCLUSION

It was concluded that the EPA and DHA moderate dose administration in the patients with CRF on MHD had a beneficial effect on insulin resistance decrease. The anti-inflammatory effects of the supplemented PUFAs were also presented.

Effects of n-3 fatty acids in subjects with type 2 diabetes: reduction of insulin sensitivity and time-dependent alteration from carbohydrate to fat oxidation

BACKGROUND

Effects of fish oil supplements on metabolic variables are insufficiently clarified in type 2 diabetes.

OBJECTIVE

We aimed to investigate short-term (1 wk) and longer-term (9 wk) effects of n-3 fatty acids.

DESIGN

Twenty-six subjects with type 2 diabetes without hypertriacylglycerolemia participated in a double-blind controlled study. Median intake in the intervention group was 17.6 mL fish oil/d (1.8 g 20:5n-3, 3.0 g 22:6n-3, and 5.9 g total n-3 fatty acids). The control group received 17.8 mL corn oil/d (8.5 g 18:2n-6).

RESULTS

Plasma phospholipid 20:5n-3 and 22:6n-3 increased, whereas 18:2n-6 decreased, in the fish oil group compared with the corn oil group after 1 wk. The two n-3 fatty acids also increased in adipose tissue biopsy samples taken after 9 wk in the fish oil group. Glucose concentrations (home-monitored) were approximately 1 mmol/L higher in the fish oil group than in the corn oil group at the end of the intervention (P = 0.035). Glucose utilization measured by using an isoglycemic clamp was lowered in the fish oil group compared with that in the corn oil group at the end of the intervention (P = 0.049), whereas glucagon-stimulated C-peptide tended to increase (P = 0.078). The fish oil group utilized less fat for oxidation after 1 wk, with a change to more fat and less carbohydrate oxidation after 9 wk (P = 0.040), than did the corn oil group.

CONCLUSION

A high intake of fish oil moderately increases blood glucose and decreases insulin sensitivity in persons with type 2 diabetes without hypertriacylglycerolemia and alters carbohydrate and fat utilization in a time-dependent manner.

Relationship between total mercury concentration and fish size in two pelagic fish species: implications for consumer health

Total mercury concentrations were determined in different size classes of two pelagic fish species of great commercial importance, horse mackerel (Trachurus trachurus) and Mediterranean horse mackerel (Trachurus mediterraneus), to evaluate the relationship between total mercury concentration and fish size and to determine whether any differences might affect the quantitative assessment of mercury exposure for consumers. Mercury concentrations in horse mackerel and in Mediterranean horse mackerel were between 0.16 and 2.41 microg g(-1) of weight wet (mean, 0.68 microg g(-1)) and between 0.09 and 1.62 microg g(-1) (mean, 0.51 microg g(-1)), respectively. The regression curves revealed a significant relationship between mercury concentration and fish size (length and weight) for both species. Concentrations exceeding the proposed limit for human consumption were observed in 33.3% of the samples of both species and were associated with larger specimens. The consumption of the larger specimens could lead to an increase in mercury exposure for consumers. Estimated weekly intakes, calculated on the basis of concentrations relative to each size class, revealed a high exposure associated with the consumption of fish larger than 30 cm (horse mackerel, 11.63 to 20.16 microg/kg of body weight; Mediterranean horse mackerel, 5.86 to 13.55 microg/kg of body weight). An understanding of the factors leading to an increase in mercury exposure can help consumers make informed decisions about eating fish.

Elevated n-3 fatty acids in a high-fat diet attenuate the increase in PDH kinase activity but not PDH activity in human skeletal muscle

We tested the hypothesis that a high-fat diet (75% fat; 5% carbohydrates; 20% protein), for which 15% of the fat content was substituted with n-3 fatty acids, would not exhibit the diet-induced increase in pyruvate dehydrogenase kinase (PDK) activity, which is normally observed in human skeletal muscle. The fat content was the same in both the regular high-fat diet (HF) and in the n-3-substituted diet (N3). PDK activity increased after both high-fat diets, but the increase was attenuated after the N3 diet (0.051 +/- 0.007 and 0.218 +/- 0.047 min(-1) for pre- and post-HF, respectively; vs. 0.073 +/- 0.016 and 0.133 +/- 0.032 min(-1) for pre- and post-N3, respectively). However, the active form of pyruvate dehydrogenase (PDHa) activity decreased to a similar extent in both conditions (0.93 +/- 0.17 and 0.43 +/- 0.09 mmol/kg wet wt pre- and post-HF; vs. 0.87 +/- 0.19 and 0.39 +/- 0.05 mmol/kg wet wt pre- and post-N3, respectively). This suggested that the difference in PDK activity did not affect PDHa activation in the basal state, and it was regulated by intramitochondrial effectors, primarily muscle pyruvate concentration. Muscle glycogen content was consistent throughout the study, before and after both diet conditions, whereas muscle glucose-6-phosphate, glycerol-3-phosphate, lactate, and pyruvate were decreased after the high-fat diets. Plasma triglycerides decreased after both high-fat diets but decreased to a greater extent after the N3, whereas plasma free fatty acids increased after both diets, but to a lesser extent after the N3. In summary, PDK activity is decreased after a high-fat diet that is rich in n-3 fatty acids, although PDHa activity was unaltered. In addition, our data demonstrated that the hypolipidemic effect of n-3 fatty acids occurs earlier (3 days) than previously reported and is evident even when the diet has 75% of its total energy derived from fat.

Assessment of the influence of fatty acids on indices of insulin sensitivity and myocellular lipid content by use of magnetic resonance spectroscopy in cats

OBJECTIVE

To determine whether dietary fatty acids affect indicators of insulin sensitivity, plasma insulin and lipid concentrations, and lipid accumulation in muscle cells in lean and obese cats.

ANIMALS

28 neutered adult cats.

PROCEDURE

IV glucose tolerance tests and magnetic resonance imaging were performed before (lean phase) and after 21 weeks of ad libitum intake of either a diet high in omega-3 polyunsaturated fatty acids (3-PUFAs; n = 14) or high in saturated fatty acids (SFAs; 14).

RESULTS

Compared with the lean phase, ad libitum food intake resulted in increased weight, body mass index, girth, and percentage fat in both groups. Baseline plasma glucose or insulin concentrations and glucose area under the curve (AUC) were unaffected by diet. Insulin AUC values for obese and lean cats fed 3-PUFAs did not differ, but values were higher in obese cats fed SFAs, compared with values for lean cats fed SFAs and obese cats fed 3-PUFAs. Nineteen cats that became glucose intolerant when obese had altered insulin secretion and decreased glucose clearance when lean. Plasma cholesterol, triglyceride, and non-esterified fatty acid concentrations were unaffected by diet. Ad libitum intake of either diet resulted in an increase in both intra- and extramyocellular lipid. Obese cats fed SFAs had higher glycosylated hemoglobin concentration than obese cats fed 3-PUFAs.

CONCLUSION AND CLINICAL RELEVANCE

In obese cats, a diet high in 3-PUFAs appeared to improve long-term glucose control and decrease plasma insulin concentration. Obesity resulted in intra- and extramyocellular lipid accumulations (regardless of diet) that likely modulate insulin sensitivity.

Dietary PUFA and the metabolic syndrome in Indian Asians living in the UK

Indian Asians living in the UK have a 50% higher CHD mortality rate compared with the indigenous Caucasian population, which cannot be attributed to traditional risk factors. Instead, features of the metabolic syndrome, including raised plasma triacylglycerol, reduced HDL-cholesterol (HDL-C) and an increased proportion of small dense LDL particles, together with insulin resistance and central obesity, are prevalent among this population. The present review examines evidence to support the hypothesis that an imbalance in dietary PUFA intake, specifically a higher intake of n-6 PUFA in combination with the lower intake of the long-chain (LC) n-3 PUFA, plays an important role in the prevalence of the metabolic syndrome observed in Indian Asians. Data are presented to illustrate the impact of manipulation of the background n-6 PUFA intake (moderate or high n-6 PUFA) and the subsequent response to supplementation with LC n-3 PUFA on blood lipids and insulin action in a group of Indian Asian volunteers. The results demonstrate that supplementation with LC n-3 PUFA had no impact on insulin action in those subjects consuming either the moderate- or high-n-6 PUFA diet. In the postprandial phase reductions in plasma triacylglycerol concentrations were greater in those consuming the high-n-6 PUFA background diet subsequent to fish oil supplementation. The present study concludes that, contrary to the central hypothesis, the prevalence of metabolic abnormalities in Indian Asians compared with Caucasians may not be attributable to differences in intakes of n-6 and n-3 PUFA.

Increased n-6 polyunsaturated fatty acids do not attenuate the effects of long-chain n-3 polyunsaturated fatty acids on insulin sensitivity or triacylglycerol reduction in Indian Asians

BACKGROUND

Indian Asians in Western countries have a higher rate of coronary artery disease than do the indigenous white populations, and this higher rate may be influenced by a dietary imbalance of n-6 and n-3 polyunsaturated fatty acids (PUFAs).

OBJECTIVE

The objective of the study was to test the hypothesis that a high background dietary intake of n-6 PUFA attenuates the effects of fish-oil supplementation on insulin sensitivity and associated blood lipids of the metabolic syndrome.

DESIGN

Twenty-nine Indian Asian men were recruited to participate in a 12-wk dietary intervention trial. Volunteers were randomly assigned to receive either a moderate or a high n-6 PUFA diet featuring modified oils and spreads over a 6-wk period. After this 6-wk period, both groups were supplemented with 4.0 g fish oil/d (2.5 g eicosapentaenoic acid + docosahexaenoic acid) for an additional 6 wk in combination with the dietary treatment. Volunteers participated in a postprandial study and an insulin sensitivity test after the 6-wk dietary intervention and again after the fish-oil supplementation period.

RESULTS

There was no significant time x treatment interaction for blood lipids or insulin action after dietary intervention with the moderate or high n-6 PUFA diets in combination with fish oil. After the 6-wk period of fish oil supplementation, fasting and postprandial plasma triacylglycerol concentrations decreased significantly.

CONCLUSION

The background dietary n-6 PUFA concentration did not modulate the effect of fish-oil supplementation on blood lipids or measures of insulin sensitivity in this ethnic group.

Health benefits and potential risks related to consumption of fish or fish oil

The nutritional benefits of fish consumption relate to the utilization of proteins of high biological value, as well as certain minerals and vitamins that fish provide. Fish or fish oil contains omega-3 polyunsaturated fatty acids (PUFAs) that appear to play several useful roles for human health. Conversely, some carcinogenic contaminants are also stored in the adipose tissue of fish. The objective of this paper is to evaluate the potential health benefits and risks related to the consumption of fish or fish oil. Health benefits related to the consumption of fish or omega-3 PUFAs were obtained by an extensive literature search. Potential health risks related to carcinogenic contaminants (e.g., dioxin, PCB, etc.) in fish were estimated using the U.S. EPA-approved cancer risk assessment guidelines. Potential health risk estimates were evaluated by comparing them with the acceptable excess risk level of 10(-6)-10(-4). Scientific data indicate that the consumption of fish or fish oil containing omega-3 PUFAs reduces the risk of coronary heart disease, decreases mild hypertension, and prevents certain cardiac arrhythmias and sudden death. Risk estimates in humans for carcinogenic environmental contaminants in fish ranged from an excess risk level of 3x10(-6)-9x10(-4). These risk estimates appeared to meet the acceptable excess risk level criteria. Therefore, consumption of fish in accordance with the State of Michigan Fish Advisory Guidelines is safe and should be encouraged. The top 11 fish species [e.g., sardines, mackerel, herring (Atlantic and Pacific), lake trout, salmon (Chinook, Atlantic, and Sockeye), anchovy (European), sablefish, and bluefish] provide an adequate amount of omega-3 PUFAs (2.7-7.5g/meal) and appear to meet the nutritional recommendation of the American Heart Association.

Dietary n-3 PUFAs affect the blood pressure rise and cardiac impairments in a hyperinsulinemia rat model in vivo

The cardiovascular consequences of eicosapentaenoic acid (EPA)- and docosahexaenoic acid (DHA)-specific intake were evaluated in vivo in a hyperinsulinemia (HI) model induced by dietary fructose intake. Wistar rats were fed a diet containing (or not for control) either EPA or DHA. The rise in blood pressure (BP), heart rate, and ECG were continuously monitored using an intra-abdominal telemetry system. The myocardial phospholipid fatty acid profile was significantly affected by DHA intake but less by EPA intake. The data indicated a reduced rise in BP in both DHA and EPA HI groups compared with controls. This result was confirmed by tail-cuff measurement after 5 wk [133.3 +/- 1.67 and 142.5 +/- 1.12 mmHg in n-3 polyunsaturated fatty acid (PUFA) and control groups, respectively], whereas n-3 PUFA did not affect BP in non-HI rats (116.3 +/- 3.33 mmHg). The heart rate was lower in the HI DHA group than in the other two dietary HI groups. Moreover, DHA induced a significantly shorter QT interval. It is concluded that the cardioactive component of fish oils is DHA through a mechanism that may involve the cardiac adrenergic system.

Higher blood pressure among Inuit migrants in Denmark than among the Inuit in Greenland

STUDY OBJECTIVE

Previous studies of blood pressure among the Inuit have given inconsistent results and studies comparing Inuit migrants with those living in traditional Inuit areas are absent. The purpose of the study was to compare the blood pressure of the Inuit in Greenland with that of Inuit migrants in Denmark.

DESIGN

Questionnaire, interview, and clinical examination in a cross sectional random population sample.

SETTING

A population based survey among Inuit in Greenland and Inuit migrants in Denmark.

PARTICIPANTS

2046 Inuit aged >/or =18, 61% of the sample.

MAIN RESULTS

Age and gender adjusted blood pressures were 117/72 mm Hg in Greenland and 127/81 mm Hg among the migrants (p<0.001). In both populations, blood pressure increased with age and body mass index, and was higher among men and non-smokers. In Greenland, blood pressure increased with the level of school education. The associations with Inuit heritage, alcohol, diet, and physical activity were not significant. The difference between the two populations persisted after adjusting for age, gender, body mass index, education, and smoking. Among those who had completed high school, there was no difference between the systolic blood pressure of the two populations while the difference for diastolic blood pressure was much less than for those with less education.

CONCLUSIONS

Blood pressure was lower among the Inuit in Greenland than among the Inuit migrants in Denmark but the difference was absent (systolic pressure) or reduced (diastolic pressure) among the better educated. The results suggest that the blood pressure of the Inuit, especially Inuit men, may be responsive to factors related to the modern Western way of life.

Effects of dietary fats on red blood cell membrane insulin receptor in normo- and hypercholesterolemic miniature swine

It has been demonstrated that the type of dietary fat affects insulin receptors in various tissues in normal humans and animals by altering membrane fluidity. This study compares the effects of n-3 fatty acids from fish oil and n-6 fatty acids from corn oil on red blood cell membrane insulin receptors in normal and hypercholesterolemic minipigs. A group of minipigs were made hypercholesterolemic by feeding cholesterol and lard for 2 months; the other group served as controls and was fed stock diet. Both groups were then fed experimental diets containing either corn oil or menhaden oil or a mixture of the two for 23 additional weeks. Blood was collected at 0, 2, 12 and 23 weeks after the start of the experimental diets and membranes were prepared from the red blood cells. Insulin binding to red blood cell membranes was measured by radioreceptor assay. Plasma insulin was measured by radioimmunoassay. Insulin binding to red blood cell membrane was compared with the fluidity of the membrane measured and reported earlier. There was no significant effect of cholesterol feeding on plasma insulin concentrations. After 23 weeks on experimental diet plasma insulin was significantly higher in minipigs fed menhaden oil compared to those fed corn oil. No such effect was observed in hypercholesterolemic minipigs. No significant effect of either hypercholesterolemia or fish oil was observed on red blood cell insulin binding. A significant negative relationship was observed between insulin binding and anisotropy at 4°C for all probes but at 37°C significant negative relationship was observed only with polar probes. The data suggest that n-3 fatty acids from fish oil significantly increases plasma insulin in minipigs compared to n-6 fatty acids from corn oil. However, the unsaturation has no significant effect on insulin receptors on erythrocytes. Similarly, prior hypercholesterolemic state also has no effect on plasma insulin levels or the insulin binding to red blood cell membranes.

Treatment of hypertriglyceridemia by two diets rich either in unsaturated fatty acids or in carbohydrates: effects on lipoprotein subclasses, lipolytic enzymes, lipid transfer proteins, insulin and leptin

BACKGROUND

There is lack of agreement on which dietary regimen is most suitable for treatment of hypertriglyceridemia, especially if high triglyceride concentrations are not due to obesity or alcohol abuse. We compared the effects on blood lipids of a diet high in total and unsaturated fat with a low-fat diet in patients with triglyceride concentrations of > 2.3 mmol/l.

METHODS

Nineteen non-obese male outpatients with triglycerides ranging from 2.30 to 9.94 mmol/l received two consecutive diets for 3 weeks each: first a modified high-fat diet (39% total fat, 8% SFA, 15% monounsaturated fatty acids, 1.6% marine n-3 polyunsaturated fatty acids), and then a low-fat diet (total fat 28%, carbohydrates 54%).

RESULTS

The high-fat diet significantly decreased triglycerides (-63%), total cholesterol (-22%), VLDL cholesterol (-54%), LDL cholesterol ( 16%), total apoC-III (-27%), apoC-III in apoB containing lipoproteins (apoC-III LpB; -31%) and in HDL (apoC-III nonLpB; -29%), apoE in serum (-33%) and apoB-containing lipoproteins (nonHDL-E; -42%), LpA-I (-16%), insulin (-36%), and leptin (-26%) and significantly increased the means of HDL cholesterol (+8%), LDL size (+6%), lipoprotein lipase (LPL, +11%), hepatic lipase (+13%), and lecithin: cholesterol acyltransferase (LCAT, +2%). The subsequent low-fat diet increased triglycerides (+63%), VLDL cholesterol (+19%), apoC-III (+23%), apoC-III LpB (+44%) apoC-III nonLpB (+17%), apoE (+29%) and nonHDL-E (+43%), and decreased HDL cholesterol (-12%), LPL (-3%), and LCAT (-3%). Changes in triglycerides correlated with changes in LPL activity and insulin levels.

CONCLUSIONS

In hypertriglyceridemic patients, a modified diet rich in mono- and n-3 polyunsaturated fatty acids is more effective than a carbohydrate-rich low-fat diet in correcting the atherogenic lipoprotein phenotype.