David Iggman

Effects of n−6 PUFAs compared with SFAs on liver fat, lipoproteins, and inflammation in abdominal obesity: a randomized controlled trial

BACKGROUND Replacing SFAs with vegetable PUFAs has cardiometabolic benefits, but the effects on liver fat are unknown. Increased dietary n-6 PUFAs have, however, also been proposed to promote inflammation-a yet unproven theory. OBJECTIVE We investigated the effects of PUFAs on liver fat, systemic inflammation, and metabolic disorders. DESIGN We randomly assigned 67 abdominally obese subjects (15% had type 2 diabetes) to a 10-wk isocaloric diet high in vegetable n-6 PUFA (PUFA diet) or SFA mainly from butter (SFA diet), without altering the macronutrient intake. Liver fat was assessed by MRI and magnetic resonance proton (1H) spectroscopy (MRS). Proprotein convertase subtilisin/kexin type-9 (PCSK9, a hepatic LDL-receptor regulator), inflammation, and adipose tissue expression of inflammatory and lipogenic genes were determined. RESULTS A total of 61 subjects completed the study. Body weight modestly increased but was not different between groups. Liver fat was lower during the PUFA diet than during the SFA diet [between-group difference in relative change from baseline; 16% (MRI; P < 0.001), 34% (MRS; P = 0.02)]. PCSK9 (P = 0.001), TNF receptor-2 (P < 0.01), and IL-1 receptor antagonist (P = 0.02) concentrations were lower during the PUFA diet, whereas insulin (P = 0.06) tended to be higher during the SFA diet. In compliant subjects (defined as change in serum linoleic acid), insulin, total/HDL-cholesterol ratio, LDL cholesterol, and triglycerides were lower during the PUFA diet than during the SFA diet (P < 0.05). Adipose tissue gene expression was unchanged. CONCLUSIONS Compared with SFA intake, n-6 PUFAs reduce liver fat and modestly improve metabolic status, without weight loss. A high n-6 PUFA intake does not cause any signs of inflammation or oxidative stress. Downregulation of PCSK9 could be a novel mechanism behind the cholesterol-lowering effects of PUFAs. This trial was registered at clinicaltrials.gov as NCT01038102.

Effects of an isocaloric healthy Nordic diet on insulin sensitivity, lipid profile and inflammation markers in metabolic syndrome – a randomized study (SYSDIET)

Different healthy food patterns may modify cardiometabolic risk. We investigated the effects of an isocaloric healthy Nordic diet on insulin sensitivity, lipid profile, blood pressure and inflammatory markers in people with metabolic syndrome.

Overfeeding Polyunsaturated and Saturated Fat Causes Distinct Effects on Liver and Visceral Fat Accumulation in Humans

Excess ectopic fat storage is linked to type 2 diabetes. The importance of dietary fat composition for ectopic fat storage in humans is unknown. We investigated liver fat accumulation and body composition during overfeeding saturated fatty acids (SFAs) or polyunsaturated fatty acids (PUFAs). LIPOGAIN was a double-blind, parallel-group, randomized trial. Thirty-nine young and normal-weight individuals were overfed muffins high in SFAs (palm oil) or n-6 PUFAs (sunflower oil) for 7 weeks. Liver fat, visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (SAT), total adipose tissue, pancreatic fat, and lean tissue were assessed by magnetic resonance imaging. Transcriptomics were performed in SAT. Both groups gained similar weight. SFAs, however, markedly increased liver fat compared with PUFAs and caused a twofold larger increase in VAT than PUFAs. Conversely, PUFAs caused a nearly threefold larger increase in lean tissue than SFAs. Increase in liver fat directly correlated with changes in plasma SFAs and inversely with PUFAs. Genes involved in regulating energy dissipation, insulin resistance, body composition, and fat-cell differentiation in SAT were differentially regulated between diets, and associated with increased PUFAs in SAT. In conclusion, overeating SFAs promotes hepatic and visceral fat storage, whereas excess energy from PUFAs may instead promote lean tissue in healthy humans.

Replacing dairy fat with rapeseed oil causes rapid improvement of hyperlipidaemia: a randomized controlled study.

Abstract.  Iggman D, Gustafsson I‐B, Berglund L, Vessby B, Marckmann P, Risérus U (Clinical Nutrition and Metabolism, Uppsala University, Uppsala; Center for Clinical Research Dalarna, Falun; Örebro University, Grythyttan, Sweden; Odense University Hospital and Institute of Clinical Research, University of Southern Denmark, Odense, Denmark). Replacing dairy fat with rapeseed oil causes rapid improvement of hyperlipidaemia: a randomized controlled study. J Intern Med 2011; 270: 356–364.

Plasma alkylresorcinols C17:0/C21:0 ratio, a biomarker of relative whole-grain rye intake, is associated to insulin sensitivity: a randomized study

Background/Objectives:Few studies have used biomarkers of whole-grain intake to study its relation to glucose metabolism. We aimed to investigate the association between plasma alkylresorcinols (AR), a biomarker of whole-grain rye and wheat intake, and glucose metabolism in individuals with metabolic syndrome (MetS).Subjects/Methods:Participants were 30–65 years of age, with body mass index 27–40 kg/m2 and had MetS without diabetes. Individuals were recruited through six centers in the Nordic countries and randomized to a healthy Nordic diet (ND, n=96), rich in whole-grain rye and wheat, or a control diet (n=70), for 18–24 weeks. In addition, associations between total plasma AR concentration and C17:0/C21:0 homolog ratio as an indication of the relative whole-grain rye intake, and glucose metabolism measures from oral glucose tolerance tests were investigated in pooled (ND+control) regression analyses at 18/24 weeks.Results:ND did not improve glucose metabolism compared with control diet, but the AR C17:0/C21:0 ratio was inversely associated with fasting insulin concentrations (P=0.002) and positively associated with the insulin sensitivity indices Matsuda ISI (P=0.026) and disposition index (P=0.022) in pooled analyses at 18/24 weeks, even after adjustment for confounders. The AR C17:0/C21:0 ratio was not significantly associated with insulin secretion indices. Total plasma AR concentration was not related to fasting plasma glucose or fasting insulin at 18/24 weeks.Conclusions:The AR C17:0/C21:0 ratio, an indicator of relative whole-grain rye intake, is associated with increased insulin sensitivity in a population with MetS.

Serum Cathepsin S Is Associated With Decreased Insulin Sensitivity and the Development of Type 2 Diabetes in a Community-Based Cohort of Elderly Men

OBJECTIVE To investigate associations between serum cathepsin S, impaired insulin sensitivity, defective insulin secretion, and diabetes risk in a community-based sample of elderly men without diabetes. RESEARCH DESIGN AND METHODS Serum cathepsin S, insulin sensitivity (euglycemic-hyperinsulinemic clamp), and insulin secretion (early insulin response during an oral glucose tolerance test) were measured in 905 participants of the Uppsala Longitudinal Study of Adult Men (mean age, 71 years). Thirty participants developed diabetes during 6 years of follow-up. RESULTS After adjustment for age, anthropometric variables, and inflammatory markers, higher cathepsin S was associated with decreased insulin sensitivity (regression coefficient per SD increase −0.09 [95% CI −0.14 to −0.04], P = 0.001), but no association with early insulin response was found. Moreover, higher cathepsin S was associated with a higher risk for developing diabetes (odds ratio per SD increase 1.48 [1.08–2.01], P = 0.01). CONCLUSIONS Cathepsin S activity appears to be involved in the early dysregulation of glucose and insulin metabolism.

Role of different dietary saturated fatty acids for cardiometabolic risk

Abstract There is clinical and observational evidence to suggest that saturated fatty acids (SFA) increase cardiovascular disease risk compared with polyunsaturated fatty acids from vegetable oils. Replacing SFA intake has thus been a public health target, but the role of individual SFA in metabolic disease is still incompletely understood. Observational data indicate that all SFA may not necessarily be detrimental. The cholesterol-raising effect of SFA differs among individual SFA and possibly also with regard to cardiovascular and metabolic risk factors. The impact of dietary SFA on cardiovascular disease remains somewhat controversial, possibly due to such individual differences. In this article, we will also separately discuss the effects of dairy SFA, including biomarkers, as a means to elucidate these relationships between fatty acids, foodstuffs and cardiometabolic disease.

Impact of polyunsaturated and saturated fat overfeeding on the DNA-methylation pattern in human adipose tissue: a randomized controlled trial

Background: Dietary fat composition can affect ectopic lipid accumulation and, thereby, insulin resistance. Diets that are high in saturated fatty acids (SFAs) or polyunsaturated fatty acids (PUFAs) have different metabolic responses.Objective: We investigated whether the epigenome of human adipose tissue is affected differently by dietary fat composition and general overfeeding in a randomized trial.Design: We studied the effects of 7 wk of excessive SFA (n = 17) or PUFA (n = 14) intake (+750 kcal/d) on the DNA methylation of ∼450,000 sites in human subcutaneous adipose tissue. Both diets resulted in similar body weight increases. We also combined the data from the 2 groups to examine the overall effect of overfeeding on the DNA methylation in adipose tissue.Results: The DNA methylation of 4875 Cytosine-phosphate-guanine (CpG) sites was affected differently between the 2 diets. Furthermore, both the SFA and PUFA diets increased the mean degree of DNA methylation in adipose tissue, particularly in promoter regions. However, although the mean methylation was changed in 1797 genes [e.g., alpha-ketoglutarate dependent dioxygenase (FTO), interleukin 6 (IL6), insulin receptor (INSR), neuronal growth regulator 1 (NEGR1), and proopiomelanocortin (POMC)] by PUFAs, only 125 genes [e.g., adiponectin, C1Q and collagen domain containing (ADIPOQ)] were changed by SFA overfeeding. In addition, the SFA diet significantly altered the expression of 28 transcripts [e.g., acyl-CoA oxidase 1 (ACOX1) and FAT atypical cadherin 1 (FAT1)], whereas the PUFA diet did not significantly affect gene expression. When the data from the 2 diet groups were combined, the mean methylation of 1444 genes, including fatty acid binding protein 1 (FABP1), fatty acid binding protein 2 (FABP2), melanocortin 2 receptor (MC2R), MC3R, PPARG coactivator 1 α (PPARGC1A), and tumor necrosis factor (TNF), was changed in adipose tissue by overfeeding. Moreover, the baseline DNA methylation of 12 CpG sites that was annotated to 9 genes [e.g., mitogen-activated protein kinase 7 (MAPK7), melanin concentrating hormone receptor 1 (MCHR1), and splicing factor SWAP homolog (SFRS8)] was associated with the degree of weight increase in response to extra energy intake.Conclusions: SFA overfeeding and PUFA overfeeding induce distinct epigenetic changes in human adipose tissue. In addition, we present data that suggest that baseline DNA methylation can predict weight increase in response to overfeeding in humans. This trial was registered at clinicaltrials.gov as NCT01427140.

Role of Dietary Fats in Modulating Cardiometabolic Risk During Moderate Weight Gain: A Randomized Double-Blind Overfeeding Trial (LIPOGAIN Study)

Background Whether the type of dietary fat could alter cardiometabolic responses to a hypercaloric diet is unknown. In addition, subclinical cardiometabolic consequences of moderate weight gain require further study. Methods and Results In a 7‐week, double‐blind, parallel‐group, randomized controlled trial, 39 healthy, lean individuals (mean age of 27±4) consumed muffins (51% of energy [%E] from fat and 44%E refined carbohydrates) providing 750 kcal/day added to their habitual diets. All muffins had identical contents, except for type of fat; sunflower oil rich in polyunsaturated fatty acids (PUFA diet) or palm oil rich in saturated fatty acids (SFA diet). Despite comparable weight gain in the 2 groups, total: high‐density lipoprotein (HDL) cholesterol, low‐density lipoprotein:HDL cholesterol, and apolipoprotein B:AI ratios decreased during the PUFA versus the SFA diet (−0.37±0.59 versus +0.07±0.29, −0.31±0.49 versus +0.05±0.28, and −0.07±0.11 versus +0.01±0.07, P=0.003, P=0.007, and P=0.01 for between‐group differences), whereas no significant differences were observed for other cardiometabolic risk markers. In the whole group (ie, independently of fat type), body weight increased (+2.2%, P<0.001) together with increased plasma proinsulin (+21%, P=0.007), insulin (+17%, P=0.003), proprotein convertase subtilisin/kexin type 9, (+9%, P=0.008) fibroblast growth factor‐21 (+31%, P=0.04), endothelial markers vascular cell adhesion molecule–1, intercellular adhesion molecule–1, and E‐selectin (+9, +5, and +10%, respectively, P<0.01 for all), whereas nonesterified fatty acids decreased (−28%, P=0.001). Conclusions Excess energy from PUFA versus SFA reduces atherogenic lipoproteins. Modest weight gain in young individuals induces hyperproinsulinemia and increases biomarkers of endothelial dysfunction, effects that may be partly outweighed by the lipid‐lowering effects of PUFA. Clinical Trial Registration URL: http://ClinicalTrials.gov. Unique identifier: NCT01427140.

Association of adipose tissue fatty acids with cardiovascular and all-cause mortality in elderly men

Importance The major polyunsaturated fatty acids in adipose tissue objectively reflect long-term dietary intake, and may provide more reliable information than would self-reported intake. Whether adipose tissue fatty acids predict cardiovascular and all-cause mortality needs investigation. Objective To investigate associations between adipose tissue fatty acids and cardiovascular and overall mortality in a cohort of elderly men. Design, Setting, and Participants We hypothesized that polyunsaturated fatty acids reflecting dietary intake, are inversely associated with cardiovascular and all-cause mortality. In the Swedish cohort study Uppsala Longitudinal Cohort of Adult Men, buttock fatty acid composition was analyzed by gas-liquid chromatography in 1992 to 1993 and 2008. The study participants were followed during 11 311 person-years, between 1991 and 2011 (median follow-up, 14.8 years). In this community-based study that took place from 1970 to 1973, all men born in 1920 to 1924 in Uppsala, Sweden, were invited and 2322 (82%) were included (at age 50 years). At the reinvestigation at age 71 years, 1221 (73%) of the 1681 invited men participated. Adipose tissue biopsy specimens were taken in a subsample of 853 men. There was no loss to follow-up. Exposures Adipose tissue proportions of 4 polyunsaturated fatty acids that were considered to mainly reflect dietary intake (linoleic acid, 18:2n-6; α-linolenic acid, 18:3n-3; eicosapentaenoic acid, 20:5n-3; and docosahexaenoic acid, 22:6n-3) comprised primary analyses, and all other available fatty acids were secondary analyses. Main Outcomes and Measures Hazard ratios (HRs) for cardiovascular and all-cause mortality using Cox proportional hazards regression analyses, performed in 2015. Results Among the 853 Swedish men, there were 605 deaths, of which 251 were cardiovascular deaths. After adjusting for risk factors, none of the 4 primary fatty acids were associated with cardiovascular mortality (HR, 0.92-1.05 for each standard deviation increase; P ≥ .27). Linoleic acid was inversely associated with all-cause mortality (HR, 0.90; 95% CI, 0.82-0.98; P = .02) and directly associated with intake (P < .001). In secondary analyses, palmitoleic acid, 16:1n-7 (HR, 1.11; 95% CI, 1.02-1.21; P = .02) was associated with higher all-cause mortality, whereas heptadecanoic acid, 17:0, tended to be associated with lower all-cause mortality (HR, 0.89; 95% CI, 0.79-1.00; P = .05). Arachidonic:linoleic acid ratio was associated with both cardiovascular (HR, 1.15; 95% CI, 1.05-1.31; P = .04) and all-cause (HR, 1.13; 95% CI, 1.04-1.23; P = .005) mortality. Conclusions and Relevance Adipose tissue linoleic acid was inversely associated with all-cause mortality in elderly men, although not significantly with cardiovascular mortality.