Low-grade inflammation (LGI) has been suggested to be involved in the development of chronic diseases. Healthy dietary patterns, such as the Mediterranean diet (MD), may decrease the markers of LGI. ...Healthy Nordic diet (HND) has many similarities with MD, but its effects on LGI are less well known. Both of these dietary patterns emphasize the abundant use of fruits and vegetables (and berries in HND), whole grain products, fish, and vegetable oil (canola oil in HND and olive oil in MD), but restrict the use of saturated fat and red and processed meat. The aim of this narrative review is to summarize the results of studies, which have investigated the associations or effects of HND on the markers of LGI. Altogether, only two publications of observational studies and eight publications of intervention trials were found through the literature search. Both observational studies reported an inverse association between the adherence to HND and concentration of high sensitivity C-reactive protein (hsCRP). A significant decrease in the concentration of hsCRP was reported in two out of four intervention studies measuring hsCRP. Single intervention studies reported the beneficial effects on interleukin 1Ra and Cathepsin S. Current evidence suggests the beneficial effects on LGI with HND, but more carefully controlled studies are needed to confirm the anti-inflammatory effects of the HND.
Wide-scale profiling technologies including metabolomics broaden the possibility of novel discoveries related to the pathogenesis of type 2 diabetes (T2D). By applying non-targeted metabolomics ...approach, we investigated here whether serum metabolite profile predicts T2D in a well-characterized study population with impaired glucose tolerance by examining two groups of individuals who took part in the Finnish Diabetes Prevention Study (DPS); those who either early developed T2D (n = 96) or did not convert to T2D within the 15-year follow-up (n = 104). Several novel metabolites were associated with lower likelihood of developing T2D, including indole and lipid related metabolites. Higher indolepropionic acid was associated with reduced likelihood of T2D in the DPS. Interestingly, in those who remained free of T2D, indolepropionic acid and various lipid species were associated with better insulin secretion and sensitivity, respectively. Furthermore, these metabolites were negatively correlated with low-grade inflammation. We replicated the association between indolepropionic acid and T2D risk in one Finnish and one Swedish population. We suggest that indolepropionic acid, a gut microbiota-produced metabolite, is a potential biomarker for the development of T2D that may mediate its protective effect by preservation of β-cell function. Novel lipid metabolites associated with T2D may exert their effects partly through enhancing insulin sensitivity.
Aims/hypothesis
Our aim was to investigate the fasting proportions of fatty acids and estimated desaturase and elongase activities in three different lipid fractions in plasma, phospholipids (PLs), ...cholesteryl esters (CEs) and triacylglycerols (TGs), as predictors for the worsening of glycaemia (area under the glucose curve in an OGTT glucose AUC) and incident type 2 diabetes in a 5.9 year follow-up of the Metabolic Syndrome in Men population-based cohort.
Methods
Fatty acid proportions were measured in plasma PL, CE and TG fractions in 1,364 Finnish men aged 45–68 years at baseline. The prospective follow-up study included only men who were non-diabetic at baseline and had data available at follow-up (
n
= 1,302). A total of 71 participants developed new type 2 diabetes during follow-up.
Results
After adjusting for confounding factors, total saturated fatty acids, palmitoleic acid (16:1
n
-7), dihomo-γ-linolenic acid (20:3
n
-6) and estimated stearoyl-CoA desaturase 1 and Δ
6
-desaturase (D6D) enzyme activities significantly predicted the worsening of glycaemia whereas total polyunsaturated fatty acid, linoleic acid (18:2
n
-6) and elongase activity predicted a decrease in the glucose AUC. Estimated D6D activity and dihomo-γ-linolenic acid (20:3
n
-6) were associated with an increased risk of incident type 2 diabetes. Results were consistent across the three different lipid fractions. However, fatty acid proportions in the PL and CE fractions were stronger predictors for glycaemia and incident type 2 diabetes compared with fatty acid proportions in the TG fraction.
Conclusions/interpretation
Selected fatty acid proportions of plasma lipid fractions and their ratios, which reflect desaturase and elongase enzyme activities, may be good biomarkers for the worsening of glycaemia and incident type 2 diabetes.
The fatty acid compositions of plasma lipids and cell membranes of certain tissues are modified by dietary fatty acid composition. Furthermore, many other factors (age, sex, ethnicity, health status, ...genes, and gene × diet interactions) affect the fatty acid composition of cell membranes or plasma lipid compartments. Therefore, it is of great importance to understand the complexity of mechanisms that may modify fatty acid compositions of plasma or tissues. We carried out an extensive literature survey of gene × diet interaction in the regulation of fatty acid compositions. Most of the related studies have been observational studies, but there are also a few intervention trials that tend to confirm that true interactions exist. Most of the studies deal with the desaturase enzyme cluster (
,
) in chromosome 11 and elongase enzymes. We expect that new genetic variants are being found that are linked with the genetic regulation of plasma or tissue fatty acid composition. This information is of great help to understanding the contribution of dietary fatty acids and their endogenic metabolism to the development of some chronic diseases.
Nontargeted metabolite profiling allows for concomitant examination of a wide range of metabolite species, elucidating the metabolic alterations caused by dietary interventions.
The aim of the ...current study was to investigate the effects of dietary modifications on the basis of increasing consumption of whole grains, fatty fish, and bilberries on plasma metabolite profiles to identify applicable biomarkers for dietary intake and endogenous metabolism.
Metabolite profiling analysis was performed on fasting plasma samples collected in a 12-wk parallel-group intervention with 106 participants with features of metabolic syndrome who were randomly assigned to 3 dietary interventions: 1) whole-grain products, fatty fish, and bilberries healthy diet (HD); 2) a whole-grain-enriched diet with the same grain products as in the HD intervention but with no change in fish or berry consumption; and 3) refined-wheat breads and restrictions on fish and berries (control diet). In addition, correlation analyses were conducted with the food intake data to define the food items correlating with the biomarker candidates.
Nontargeted metabolite profiling showed marked differences in fasting plasma after the intervention diets compared with the control diet. In both intervention groups, a significant increase was observed in 2 signals identified as glucuronidated alk(en)-ylresorcinols corrected P value (Pcorr) < 0.05, which correlated strongly with the intake of whole-grain products (r = 0.63, P < 0.001). In addition, the HD intervention increased the signals for furan fatty acids 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (CMPF), hippuric acid, and various lipid species incorporating polyunsaturated fatty acids (Pcorr < 0.05). In particular, plasma CMPF correlated strongly with the intake of fish (r = 0.47, P < 0.001) but not with intakes of any other foods.
Novel biomarkers of the intake of health-beneficial food items included in the Nordic diet were identified by the metabolite profiling of fasting plasma and confirmed by the correlation analyses with dietary records. The one with the most potential was CMPF, which was shown to be a highly specific biomarker for fatty fish intake. This trial was registered at clinicaltrials.gov as NCT00573781.
Type 2 diabetes (T2D) can be prevented or postponed by lifestyle modifications as shown by previous intervention studies. In most of these studies, participants have received resource-demanding ...individual counseling. In the 3-year T2D-GENE trial with lifestyle intervention, we investigated whether a less resource-demanding form of group and internet-based counseling is feasible and effective in preventing T2D in people with an increased risk for T2D. Altogether, 628 middle-aged to elderly men either with a high number or low number of T2D risk alleles were recruited. Five to seven group sessions were organized during the intervention, in addition to information and activities delivered via the web portal, and weekly monitoring of body weight and physical activity. Four-day food records with personal feedback were documented five times during the study. Of the 549 participants completing the study, over 90% participated in the group sessions and kept the food records. The four self-feedback tasks delivered during the second and the third years of the study were completed by 80-89% of the participants. In conclusion, a group and web portal-based lifestyle intervention is applicable for middle-aged to elderly men as a lifestyle modification aiming to prevent T2D.
The health benefits of substituting dietary polyunsaturated fatty acids (PUFAs) for saturated fatty acids are well known. However, limited information exists on how the response to dietary intake of ...linoleic acid (LA; 18:2n–6) is modified by polymorphisms in the fatty acid desaturase (FADS) gene cluster.
The aim of the current study was to test the hypothesis that the FADS1 rs174550 genotype modifies the effect of dietary LA intake on the fatty acid composition of plasma lipids, fasting glucose, and high-sensitivity C-reactive protein (hsCRP).
Associations were investigated between genotype, plasma PUFAs, fasting glucose, and hsCRP concentrations in the cross-sectional, population-based Metabolic Syndrome in Men cohort (n = 1337). In addition, 62 healthy men from the cohort who were homozygotes for the TT or CC genotype of the FADS1 rs174550 were recruited to a 4-wk intervention (FADSDIET) with an LA-enriched diet. The fatty acid composition of plasma PUFAs and concentrations of plasma fasting glucose, serum hsCRP, and plasma lipid mediators (eicosanoids and related analogs) were measured at the beginning and end of the 4-wk intervention period.
In the FADSDIET trial, the plasma LA proportion increased in both genotype groups in response to an LA-enriched diet. Responses in concentrations of serum hsCRP and plasma fasting glucose and the proportion of arachidonic acid (20:4n–6) in plasma phospholipids and cholesteryl esters differed between genotype groups (interaction of diet × genotype, P < 0.05). In TT homozygous subjects, plasma eicosanoid concentrations correlated with the arachidonic acid proportion in plasma and with hsCRP (r = 0.4–0.7, P < 0.05), whereas in the CC genotype there were no correlations.
Our findings show that the FADS1 genotype modifies metabolic responses to dietary LA. The emerging concept that personalized dietary counseling should be modified by the FADS1 genotype needs to be tested in larger randomized trials. The study was registered at clinicaltrials.gov as NCT02543216.
3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) is a metabolite produced endogenously from dietary sources of furan fatty acids. The richest source of furan fatty acids in human diet is ...fish. CMPF was recently shown to be elevated in fasting plasma in individuals with gestational diabetes and type 2 diabetes, and mechanistically high level of CMPF was linked to β cell dysfunction. Here we aimed to study the association between plasma CMPF level and glucose metabolism in persons with impaired glucose metabolism.
Plasma CMPF concentration was measured from plasma samples of the study participants in an earlier controlled dietary intervention. All of them had impaired glucose metabolism and two other characteristics of the metabolic syndrome. Altogether 106 men and women were randomized into three groups for 12 weeks with different fish consumption (either three fatty fish meals per week, habitual fish consumption or maximum of one fish meal per week). Associations between concentration of CMPF and various glucose metabolism parameters at an oral glucose tolerance test at baseline and at the end of the study were studied.
Fasting plasma CMPF concentration was significantly increased after a 12-week consumption of fatty fish three times per week, but the concentration remained much lower compared to concentrations reported in diabetic patients. Increases of plasma CMPF concentrations mostly due to increased fish consumption were not associated with impaired glucose metabolism in this study. Instead, elevated plasma CMPF concentration was associated with decreased 2-hour insulin concentration in OGTT.
Moderately elevated concentration of CMPF in plasma resulting from increased intake of fish is not harmful to glucose metabolism. Further studies are needed to fully explore the role of CMPF in the pathogenesis of impaired glucose metabolism.
ClinicalTrials.gov NCT00573781.
Lipoprotein(a) Lp(a) is a causal, genetically determined cardiovascular risk factor. Limited evidence suggests that dietary unsaturated fat may increase serum Lp(a) concentration by 10–15 %. Linoleic ...acid may increase Lp(a) concentration through its endogenous conversion to arachidonic acid, a process regulated by the fatty acid desaturase (FADS) gene cluster. We aimed to compare the Lp(a) and other lipoprotein trait-modulating effects of dietary alpha-linolenic (ALA) and linoleic acids (LA). Additionally, we examined whether FADS1 rs174550 genotype modifies Lp(a) responses.
A genotype-based randomized trial was performed in 118 men homozygous for FADS1 rs174550 SNP (TT or CC). After a 4-week run-in period, the participants were randomized to 8-week intervention diets enriched with either Camelina sativa oil (ALA diet) or sunflower oil (LA diet) 30–50 mL/day based on their BMI. Serum lipid profile was measured at baseline and at the end of the intervention.
ALA diet lowered serum Lp(a) concentration by 7.3 % (p = 0.003) and LA diet by 9.5 % (p < 0.001) (p = 0.089 for between-diet difference). Both diets led to greater absolute decreases in individuals with higher baseline Lp(a) concentration (p < 0.001). Concentrations of LDL cholesterol (LDL-C), non-HDL-C, remnant-C, and apolipoprotein B were lowered more by the ALA diet (p < 0.01). Lipid or lipoprotein responses were not modified by the FADS1 rs174550 genotype.
A considerable increase in either dietary ALA or LA from vegetable oils has a similar Lp(a)-lowering effect, whereas ALA may lower other major atherogenic lipids and lipoproteins to a greater extent than LA. Genetic differences in endogenous PUFA conversion may not influence serum Lp(a) concentration.
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•Diets enriched with either n-3 alpha-linolenic or n-6 linoleic acid decrease serum Lp(a) concentration by 7–10 %.•Alpha-linolenic acid may have more beneficial effect on other atherogenic lipoprotein traits, compared to linoleic acid.•The FADS1 rs174550 genotype does not modulate diet-induced changes in Lp(a) concentration or other lipoprotein traits.
Epidemiologic evidence suggests that diets rich in whole grains are associated with a reduced risk of developing chronic diseases and all-cause mortality. However, the molecular mechanisms behind ...these beneficial metabolic effects are poorly understood.
Our aim was to investigate novel trimethylated (betainized) compounds from mice and humans, and their association with whole grain–rich diets and insulin resistance and insulin secretion.
Fasting plasma samples were obtained in a mouse (C57BL/6J male) feeding trial and a controlled dietary intervention. The mouse trial involved feeding the mice a rye and wheat bran–enriched feed which was compared with a high-fat diet. In the human trial, participants recruited from Kuopio, Finland (n = 69) and Naples, Italy (n = 54) with characteristics of the metabolic syndrome were randomly assigned to either a whole grain–enriched diet or a control diet for 12 wk. Plasma concentrations of betainized compounds were analyzed with the use of liquid chromatography-tandem mass spectrometry. Insulin resistance and insulin secretion were assessed in an oral-glucose-tolerance test and a meal-glucose-tolerance test.
The betaines that were increased in mouse plasma after bran-enriched feeding were identified de novo via chemical synthesis and liquid chromatography-tandem mass spectrometry, and confirmed to be associated with an increased intake of whole-grain products in humans. In particular, the concentrations of pipecolic acid betaine were increased at the end of the whole-grain intervention in both the Kuopio cohort (P < 0.001) and the Naples cohort (P < 0.05), and these concentrations inversely correlated with the postprandial glucose concentration. Furthermore, the concentration of valine betaine was substantially increased during the intervention in Naples (P < 0.001) with an inverse correlation with the postprandial insulin concentration. In addition, the concentrations of other betaines, e.g., glycine betaine and proline betaine, correlated with glucose and insulin concentrations at the end of the intervention.
Novel betainized compounds in humans are associated with diets rich in whole grains, and they improve insulin resistance and insulin secretion. These results suggest that these novel compounds may contribute to the beneficial effects of whole grain–rich diets.
The studies were registered at clinicaltrials.gov as NCT00945854 (Naples) and NCT00573781 (Kuopio).
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