Overfeeding polyunsaturated and saturated fat causes distinct effects on liver and visceral fat accumulation in humans

ω-6 Polyunsaturated Fatty Acids and Cardiometabolic Health: Current Evidence, Controversies, and Research Gaps

The 2015 Dietary Guidelines for Americans recommend limiting the intake of saturated fatty acids (SFAs) to <10% of energy/d and replacing dietary SFAs with unsaturated fatty acids. A Presidential Advisory from the American Heart Association recently released its evaluation of the relation between dietary fats and cardiovascular disease (CVD), and also recommended a shift from SFAs to unsaturated fatty acids, especially polyunsaturated fatty acids (PUFAs), in conjunction with a healthy dietary pattern. However, the suggestion to increase the intake of PUFAs in general, and omega-6 (n-6) PUFAs in particular, continues to be controversial. This review was undertaken to provide an overview of the evidence and controversies regarding the effects of ω-6 PUFAs on cardiometabolic health, with emphasis on risks and risk factors for CVD (coronary heart disease and stroke) and type 2 diabetes mellitus (T2D). Results from observational studies show that higher intake of ω-6 PUFAs, when compared with SFAs or carbohydrate, is associated with lower risks for CVD events (10-30%), CVD and total mortality (10-40%), and T2D (20-50%). Findings from intervention studies on cardiometabolic risk factors suggest that ω-6 PUFAs reduce concentrations of LDL cholesterol and non-HDL cholesterol in a dose-dependent manner compared with dietary carbohydrate, and have a neutral effect on blood pressure. Despite the concern that ω-6 fatty acids increase inflammation, current evidence from studies in humans does not support this view. In conclusion, these findings support current recommendations to emphasize consumption of ω-6 PUFAs as a replacement of SFAs; additional randomized controlled trials with cardiometabolic disease outcomes will help to more clearly define the benefits and risks of this policy.

Changes in Types of Dietary Fats Influence Long-term Weight Change in US Women and Men

Background

The relation between dietary fat intake and body weight remains controversial. Few studies have examined long-term changes in types of dietary fat and weight change in longitudinal studies.

Objective

The objective of this study was to examine associations between intake of different types of fat and long-term weight change in US women and men.

Methods

The association between changes in consumption of varying types of fat and weight change was examined every 4 y through the use of multivariate models adjusted for age, baseline body mass index, and change in percentage energy from protein, intake of cereal fiber, fruits, and vegetables, alcohol use, and other lifestyle covariates in 3 prospective US cohorts, including 121,335 men and women free of diabetes, cardiovascular disease, cancer, or obesity over a 20- to 24-y follow-up. Dietary intakes and body weight were assessed via validated questionnaires. Cohort-specific results were pooled with the use of a random-effect meta-analysis.

Results

Compared with equivalent changes in carbohydrate intake, a 5% increase in energy from saturated fatty acid (SFA) and a 1% increase in energy from trans-fat were associated with 0.61 kg (95% CI: 0.54, 0.68 kg) and 0.69 kg (95% CI: 0.56, 0.84 kg) greater weight gain per 4-y period, respectively. A 5% increase in energy from polyunsaturated fatty acid (PUFA) was associated with less weight gain (-0.55 kg; 95% CI: -0.81, -0.29 kg). Increased intake of monounsaturated fatty acid (MUFA) from animal sources by 1% was associated with weight gain of 0.29 kg (95% CI: 0.25, 0.33 kg), whereas MUFA from plant sources was not associated with weight gain.

Conclusions

Different dietary fats have divergent associations with long-term weight change in US men and women. Replacing saturated and trans-fats with unsaturated fats, especially PUFAs, contributes to the prevention of age-related weight gain. These trials were registered at clinicaltrials.gov as NCT00005152 and NCT00005182.

3D Chemical Shift-Encoded MRI for Volume and Composition Quantification of Abdominal Adipose Tissue During an Overfeeding Protocol in Healthy Volunteers

BACKGROUND

Overweight and obesity are major worldwide health concerns characterized by an abnormal accumulation of fat in adipose tissue (AT) and liver.

PURPOSE

To evaluate the volume and the fatty acid (FA) composition of the subcutaneous adipose tissue (SAT) and the visceral adipose tissue (VAT) and the fat content in the liver from 3D chemical-shift-encoded (CSE)-MRI acquisition, before and after a 31-day overfeeding protocol.

STUDY TYPE

Prospective and longitudinal study.

SUBJECTS

Twenty-one nonobese healthy male volunteers.

FIELD STRENGTH/SEQUENCE

A 3D spoiled-gradient multiple echo sequence and STEAM sequence were performed at 3T.

ASSESSMENT

AT volume was automatically segmented on CSE-MRI between L2 to L4 lumbar vertebrae and compared to the dual-energy X-ray absorptiometry (DEXA) measurement. CSE-MRI and MR spectroscopy (MRS) data were analyzed to assess the proton density fat fraction (PDFF) in the liver and the FA composition in SAT and VAT. Gas chromatography-mass spectrometry (GC-MS) analyses were performed on 13 SAT samples as a FA composition countermeasure.

STATISTICAL TESTS

Paired t-test, Pearson's correlation coefficient, and Bland-Altman plots were used to compare measurements.

RESULTS

SAT and VAT volumes significantly increased (P < 0.001). CSE-MRI and DEXA measurements were strongly correlated (r = 0.98, P < 0.001). PDFF significantly increased in the liver (+1.35, P = 0.002 for CSE-MRI, + 1.74, P = 0.002 for MRS). FA composition of SAT and VAT appeared to be consistent between localized-MRS and CSE-MRI (on whole segmented volume) measurements. A significant difference between SAT and VAT FA composition was found (P < 0.001 for CSE-MRI, P = 0.001 for MRS). MRS and CSE-MRI measurements of the FA composition were correlated with the GC-MS results (for ndb: r_MRS/GC-MS  = 0.83 P < 0.001, r_{CSE-MRI/GC-MS}  = 0.84, P = 0.001; for nmidb: r_MRS/GC-MS  = 0.74, P = 0.006, r_{CSE-MRI/GC-MS}  = 0.66, P = 0.020) DATA CONCLUSION: The follow-up of liver PDFF, volume, and FA composition of AT during an overfeeding diet was demonstrated through different methods. The CSE-MRI sequence associated with a dedicated postprocessing was found reliable for such quantification.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1587-1599.

Determinants of ectopic liver fat in metabolic disease

Common obesity-associated hepatic steatosis (nonalcoholic fatty liver disease (NAFLD)) and insulin resistance are mainly caused by dysfunctional adipose tissue. This adipose tissue dysfunction leads to increased delivery of NEFA and glycerol to the liver that (i) drives hepatic gluconeogenesis and (ii) facilitates the accumulation of lipids and insulin signaling inhibiting lipid intermediates. Dysfunctional adipose tissue can be caused by impaired lipid storage (overflow hypothesis, characterized by large visceral adipocytes) or increased lipolysis (due to impaired postprandial suppression of lipolysis in inflamed, insulin-resistant adipocytes). In line with the adipose tissue expandability hypothesis the amount and distribution of adipose tissue correlate with its dysfunction and thus with liver fat. This relationship is however modified by endocrine effects on lipid storage and lipolysis as well as dietary effects on hepatic lipogenesis and lipid oxidation. The association between body composition characteristics like visceral obesity or fat cell size and ectopic liver fat is modified by these influences. Phenotyping obesity according to metabolic risk should integrate body composition characteristics, endocrine parameters and information on diet.

Low-dose developmental bisphenol A exposure alters fatty acid metabolism in Fischer 344 rat offspring

BACKGROUND

Bisphenol A (BPA) is an endocrine disruptor and also a suggested obesogen and metabolism-disrupting chemical. Accumulating data indicates that the fatty acid (FA) profile and their ratios in plasma and other metabolic tissues are associated with metabolic disorders. Stearoyl-CoA desaturase 1 (SCD-1) is a key regulator of lipid metabolism and its activity can be estimated by dividing the FA product by its precursor measured in blood or other tissues.

OBJECTIVE

The primary aim of this study was to investigate the effect of low-dose developmental BPA exposure on tissue-specific FA composition including estimated SCD-1 activity, studied in 5- and 52-week (wk)-old Fischer 344 (F344) rat offspring.

METHODS

Pregnant F344 rats were exposed to BPA via their drinking water corresponding to 0: [CTRL], 0.5: [BPA0.5], or 50 µg/kg BW/day: [BPA50], from gestational day 3.5 until postnatal day 22.

RESULTS

BPA0.5 increased SCD-16 (estimated as the 16:1n-7/16:0 ratio) and SCD-18 (estimated as the 18:1n-9/18:0 ratio) indices in inguinal white adipose tissue triglycerides (iWAT-TG) and in plasma cholesterol esters (PL-CE), respectively, in 5-wk-old male offspring. In addition, BPA0.5 altered the FA composition in male offspring, e.g. by decreasing levels of the essential polyunsaturated FA linoleic acid (18:2n-6) in iWAT-and liver-TG. No differences were observed regarding the studied FAs in 52-wk-old offspring, although a slightly increased BW was observed in 52-wk-old female offspring.

CONCLUSIONS

Low-dose developmental BPA exposure increased SCD-16 in iWAT-TG and SCD-18 in PL-CE of male offspring, which may reflect higher SCD-1 activity in these tissues. Altered desaturation activity and signs of altered FA composition are novel findings that may indicate insulin resistance in the rat offspring. These aforementioned results, together with the observed increased BW, adds to previously published data demonstrating that BPA can act as a metabolism disrupting chemical.

Fatty Acid Profiles of Various Vegetable Oils and the Association between the Use of Palm Oil vs. Peanut Oil and Risk Factors for Non-Communicable Diseases in Yangon Region, Myanmar

The majority of vegetable oils used in food preparation in Myanmar are imported and sold non-branded. Little is known about their fatty acid (FA) content. We aimed to investigate the FA composition of commonly used vegetable oils in the Yangon region, and the association between the use of palm oil vs. peanut oil and risk factors for non-communicable disease (NCD). A multistage cluster survey was conducted in 2016, and 128 oil samples from 114 households were collected. Data on NCD risk factors were obtained from a household-based survey in the same region, between 2013 and 2014. The oils most commonly sampled were non-branded peanut oil (43%) and non-branded palm oil (19%). Non-branded palm oil had a significantly higher content of saturated fatty acids (36.1 g/100 g) and a lower content of polyunsaturated fatty acids (9.3 g/100 g) than branded palm oil. No significant differences were observed regarding peanut oil. Among men, palm oil users had significantly lower mean fasting plasma glucose levels and mean BMI than peanut oil users. Among women, palm oil users had significantly higher mean diastolic blood pressure, and higher mean levels of total cholesterol and triglycerides, than peanut oil users. Regulation of the marketing of non-branded oils should be encouraged.

Studying non-alcoholic fatty liver disease: the ins and outs of in vivo, ex vivo and in vitro human models

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing. Determining the pathogenesis and pathophysiology of human NAFLD will allow for evidence-based prevention strategies, and more targeted mechanistic investigations. Various in vivo, ex situ and in vitro models may be utilised to study NAFLD; but all come with their own specific caveats. Here, we review the human-based models and discuss their advantages and limitations in regards to studying the development and progression of NAFLD. Overall, in vivo whole-body human studies are advantageous in that they allow for investigation within the physiological setting, however, limited accessibility to the liver makes direct investigations challenging. Non-invasive imaging techniques are able to somewhat overcome this challenge, whilst the use of stable-isotope tracers enables mechanistic insight to be obtained. Recent technological advances (i.e. normothermic machine perfusion) have opened new opportunities to investigate whole-organ metabolism, thus ex situ livers can be investigated directly. Therefore, investigations that cannot be performed in vivo in humans have the potential to be undertaken. In vitro models offer the ability to perform investigations at a cellular level, aiding in elucidating the molecular mechanisms of NAFLD. However, a number of current models do not closely resemble the human condition and work is ongoing to optimise culturing parameters in order to recapitulate this. In summary, no single model currently provides insight into the development, pathophysiology and progression across the NAFLD spectrum, each experimental model has limitations, which need to be taken into consideration to ensure appropriate conclusions and extrapolation of findings are made.

Effects of free omega-3 carboxylic acids and fenofibrate on liver fat content in patients with hypertriglyceridemia and non-alcoholic fatty liver disease: A double-blind, randomized, placebo-controlled study

BACKGROUND

Treatment with omega-3 fatty acids and fenofibrates reduces serum triglyceride levels, but few studies have compared the effect of these agents on liver fat.

OBJECTIVE

The aim of the EFFECT I trial (NCT02354976) was to determine the effects of free omega-3 carboxylic acids (OM-3CA) and fenofibrate on liver fat in overweight or obese individuals with non-alcoholic fatty liver disease and hypertriglyceridemia.

METHODS

Seventy-eight patients were randomized to receive oral doses of 4 g OM-3CA (n = 25), 200 mg fenofibrate (n = 27), or placebo (n = 26) for 12 weeks in a double-blind, parallel-group study. Liver proton density fat fraction (PDFF) and volume, pancreas volume, and adipose tissue volumes were assessed by magnetic resonance imaging.

RESULTS

Changes in liver PDFF at 12 weeks were not significantly different across treatment groups (relative changes from baseline: placebo, +4%; OM-3CA, -2%; and fenofibrate, +17%). The common PNPLA3 genetic polymorphism (I148M) did not significantly influence the effects of OM-3CA or fenofibrate on liver PDFF. Fenofibrate treatment significantly increased liver and pancreas volumes vs placebo treatment, and the changes in liver and pancreas volumes were positively correlated (rho 0.45, P = .02). Total liver fat volume increased significantly in patients using fenofibrate vs OM-3CA (+23% vs -3%, P = .04). Compared with OM-3CA, fenofibrate increased total liver fat and liver volume. Serum triglycerides decreased with OM-3CA (-26%, P = .02) and fenofibrate (-38%, P < .001) vs placebo. In contrast to OM-3CA, fenofibrate reduced plasma docosahexaenoic acid levels and increased plasma acetylcarnitine and butyrylcarnitine levels, estimated delta-9 desaturase activity and the concentration of urine F2-isoprostanes.

CONCLUSIONS

OM-3CA and fenofibrate reduced serum triglycerides but did not reduce liver fat. Fenofibrate increased total liver volume and total liver fat volume vs OM-3CA, indicating a complex effect of fenofibrate on human hepatic lipid metabolism.

Saturated Fat Is More Metabolically Harmful for the Human Liver Than Unsaturated Fat or Simple Sugars

OBJECTIVE

Nonalcoholic fatty liver disease (i.e., increased intrahepatic triglyceride [IHTG] content), predisposes to type 2 diabetes and cardiovascular disease. Adipose tissue lipolysis and hepatic de novo lipogenesis (DNL) are the main pathways contributing to IHTG. We hypothesized that dietary macronutrient composition influences the pathways, mediators, and magnitude of weight gain-induced changes in IHTG.

RESEARCH DESIGN AND METHODS

We overfed 38 overweight subjects (age 48 ± 2 years, BMI 31 ± 1 kg/m², liver fat 4.7 ± 0.9%) 1,000 extra kcal/day of saturated (SAT) or unsaturated (UNSAT) fat or simple sugars (CARB) for 3 weeks. We measured IHTG (¹H-MRS), pathways contributing to IHTG (lipolysis ([²H₅]glycerol) and DNL (²H₂O) basally and during euglycemic hyperinsulinemia), insulin resistance, endotoxemia, plasma ceramides, and adipose tissue gene expression at 0 and 3 weeks.

RESULTS

Overfeeding SAT increased IHTG more (+55%) than UNSAT (+15%, P < 0.05). CARB increased IHTG (+33%) by stimulating DNL (+98%). SAT significantly increased while UNSAT decreased lipolysis. SAT induced insulin resistance and endotoxemia and significantly increased multiple plasma ceramides. The diets had distinct effects on adipose tissue gene expression.

CONCLUSIONS

Macronutrient composition of excess energy influences pathways of IHTG: CARB increases DNL, while SAT increases and UNSAT decreases lipolysis. SAT induced the greatest increase in IHTG, insulin resistance, and harmful ceramides. Decreased intakes of SAT could be beneficial in reducing IHTG and the associated risk of diabetes.

Weight loss and metabolic health effects from energy-restricted Mediterranean and Central-European diets in postmenopausal women: A randomized controlled trial

We conducted a randomized controlled trial to examine the effect of two energy-restricted diets on body weight (BW), visceral fat (VF) loss, and the risk factors for metabolic syndrome. A total of 144 centrally obese postmenopausal women were assigned to the moderate in fat Mediterranean diet (MED) or to the Central European diet (CED), which is moderate in carbohydrates and high in dietary fiber (DF), for 16 weeks. BW, waist circumference and VF were significantly reduced by 8.8%, 7.0%, and 24.6%, respectively, over the trial (P < 0.001), with no difference between groups. A similar trend was seen for total cholesterol, triglycerides, glucose, and blood pressure. Within each diet group, the more adherent participants lost significantly more BW than did their less adherent counterparts. VF was significantly reduced only in women who were more adherent to the CED, and the reduction in VF correlated with an increase in the proportion of DF. Short-term dietary treatment with the CED or the MED was associated with similar improvements in some anthropometric, lipid, and nonlipid parameters; however, adequate adherence to the prescribed diet is important in weight loss success and in achieving improvements in metabolic health.

Long-Term Dietary Intake of Chia Seed Is Associated with Increased Bone Mineral Content and Improved Hepatic and Intestinal Morphology in Sprague-Dawley Rats

Chia seeds (Salvia hispanica) provide an unusually high content of α-linolenic acid with several potential health benefits, but few studies have examined the long-term intake of n-3 fatty acid-rich plant foods such as chia. In this work, we investigated some of the effects of a diet containing 10% chia seeds versus a conventional isocaloric diet for 10 and 13 months on body measurements, musculoskeletal system, the liver, and the intestines of 20 male Sprague-Dawley rats assigned into two groups. The n-6/n-3 ratios for the control and chia diets were 7.46 and 1.07, respectively. For the first 10 months of the diet, the body parameters and weights were similar, but at 13 months, the bone mineral content (BMC) of the chia-fed rats was significantly higher than that of the controls whether in total or proximal areas of the left tibia. Also, significant positive correlations were found between the age of the chia group and the bone mineral density, BMC, weight of the musculoskeletal system, final body weight, and skin weight. Liver and intestinal examinations showed improved morphology associated with lower lipid deposit in hepatocytes and increased intestinal muscle layers and crypt size in the chia group. This study provides new data suggesting the potential benefits associated with the long-term intake of chia seeds.

Meal rich in rapeseed oil increases 24-h fat oxidation more than meal rich in palm oil

The fatty acid composition of the diet has been linked to the prevalence of diabetes and cardiovascular diseases. Compared with monounsaturated fatty acids, saturated fatty acids decrease fat oxidation and diet-induced thermogenesis. A potential limitation of previous studies was the short duration (≦5h) of calorimetry used. The present study compared the effects of a meal rich in saturated and unsaturated fatty acids on 24-h of fat oxidation. Ten males participated in two sessions of indirect calorimetry in a whole-room metabolic chamber. At each session, subjects consumed three meals rich in palm oil (44.3% as saturated, 42.3% as monounsaturated and 13.4% as polyunsaturated fatty acid) or rapeseed oil (11.7% as saturated, 59.3% as monounsaturated and 29.0% as polyunsaturated fatty acid). Fat oxidation over 24-h was significantly higher in the meal rich in rapeseed oil (779 ± 202 kcal/day) than that rich in palm oil (703 ± 158 kcal/day, P < 0.05), although energy expenditure was similar between both meal conditions. Meal rich in unsaturated fatty acids increased the oxidation of exogenous and/or endogenous fat. The results of a long calorimetry period indicate that rapeseed oil offered an advantage toward increased 24-h fat oxidation in healthy young males.

Lipid accumulation product and visceral adiposity index are associated with dietary patterns in adult Americans

In the present study, we aimed to examine the association between lipid accumulation product (LAP) and visceral adiposity index (VAI) with dietary pattern (DP) in the US adults. Participants of the National Health and Nutrition Examination Survey (NHANES) with data available on dietary intake from 2005 to 2010 were included. DPs were derived by principal component analysis. We applied analysis of covariance and multivariable-adjusted linear regressions accounting for the masked variance and utilizing the proposed weighting methodology. The analytical sample comprised 18,318 participants (mean age = 45.8 years), of whom 48.3% (n = 8607) were men with no age difference by gender (P = .126). The first DP was representative of a diet rich in carbohydrate and sugar, total fat and saturated fatty acid (SFA), high-caloric dieatry pattern; the second DP was highly loaded with vitamins, minerals and fiber (nutrient-dense dietary patten), and the third DP was mainly representative of high dietary polyunsaturated fatty acids (PUFAs) and monounsaturated fatty acids (MUFAs) (healthy fat DP). The adjusted (age, sex, race, physical activity, smoking, C-reactive protein) mean of LAP, VAI and glucose homeostasis indices increased across increasing quarters of the first DP score (all P < .001), while across increasing score of the second DP, the adjusted mean of LAP, VAI, glucose homeostasis indices decreased (all P < .001). Findings were similar in adjusted linear regressions models. Our findings support that affordable measurements, such as VAI and LAP, could be good alternative surrogate markers of visceral fat. They are also significantly related to DPs in same line as with glucose/insulin homeostasis and anthropometric indices.

Linoleic acid, glycemic control and Type 2 diabetes

Dietary fat quality, especially the intake of specific types of fatty acids, impacts the risk of many chronic diseases, including cardiovascular diseases, certain cancers and type 2 diabetes (T2DM). A recent pooled analysis involving 20 studies from around the world revealed that higher linoleic acid (18:2n-6 LA) biomarker is associated with dose-dependent decreases in the incidence of T2DM. This latest study corroborates earlier cross-sectional studies and intervention trials showing that biomarkers of LA intake are associated with reduced risk of T2DM and better glycemic control and/or insulin sensitivity. This review highlights key clinical trials that have evaluated the role of LA in glycemia and the related condition, insulin sensitivity.

Pediatric Age Palm Oil Consumption

Palm oil is widely used in the food industry for its chemical/physical properties, low cost and wide availability. Its widespread use has provoked an intense debate about whether it is a potential danger to human health. In a careful review of the scientific literature, we focused on nutritional characteristics and health effects of the use of palm oil with regards to children, seeking to determine whether there is evidence that justifies fears about the health effects of palm oil. Our review showed that palm oil represents a significant source of saturated fatty acids, to which scientific evidence attributes negative health effects when used in excess, especially with regards to cardiovascular diseases. However, to date, there is no evidence about the harmful effects of palm oil on the health of children. Nevertheless, palm oil has possible ill health effects linked to its composition of fatty acids: its consumption is not correlated to risk factors for cardiovascular diseases in young people with a normal weight and cholesterol level; the elderly and patients with dyslipidaemia or previous cardiovascular events or hypertension are at a greater risk. Therefore, the matter is not palm oil itself but the fatty-acid-rich food group to which it belongs. The most important thing is to consume no more than 10% of saturated fatty acids, regardless of their origin and regardless of one’s age. Correct information based on a careful analysis of the scientific evidence, rather than a focus on a singular presumed culprit substance, should encourage better lifestyles.

Is non-alcoholic fatty liver disease a reflection of what we eat or simply how much we eat?

Non-alcoholic fatty liver disease (NAFLD) is an increasingly common and potentially serious condition, which has emerged with the obesity epidemic. This disease can progress to cirrhosis and hepatocellular cancer. Associated comorbidities, such as cardiovascular disease and type 2 diabetes, are common. Obesity is the key risk factor and diet appears to be a critical factor in the pathogenesis of NAFLD. We reviewed studies undertaken on human subjects investigating which dietary components initiate excess hepatic triglyceride deposition. Most experimental diets used high-calorie excesses, or extreme proportions of fat or carbohydrate, not typical of current dietary patterns. Hypercaloric diets, where the additional calories were predominantly either fat or carbohydrates, increased intrahepatocellular lipids. The type of fat appeared important, with diets high in saturated fatty acids favoring hepatic fat accumulation which was substantially lower with polyunsaturated fatty acids. The effect of dietary fructose on markers of NAFLD did not appear to be worse than that of glucose. The initiation of excess hepatic triglycerides is likely to be a complex interaction of energy and nutrients with more than one dietary factor involved. It was not possible to disentangle the hepatic effects of excess energy from that of different macronutrient distributions in current literature. Further investigation is needed to determine the type of diet that is likely to lead to the development of NAFLD. A better understanding of the contribution of diet to pathogenesis of NAFLD would better inform prevention strategies.

Dietary supplementation with hybrid palm oil alters liver function in the common Marmoset

Hybrid palm oil, which contains higher levels of oleic acid and lower saturated fatty acids in comparison with African palm oil, has been proposed to be somehow equivalent to extra virgin olive oil. However, the biological effects of its consumption are poorly described. Here we have explored the effects of its overconsumption on lipid metabolism in a non-human primate model, the common marmoset. Dietary supplementation of marmoset with hyperlipidic diet containing hybrid palm oil for 3 months did not modify plasma lipids levels, but increased glucose levels as compared to the supplementation with African palm oil. Liver volume was unexpectedly found to be more increased in marmosets consuming hybrid palm oil than in those consuming African palm oil. Hepatic total lipid content and circulating transaminases were dramatically increased in animals consuming hybrid palm oil, as well as an increased degree of fibrosis. Analysis of liver miRNAs showed a selective modulation of certain miRNAs by hybrid palm oil, some of which were predicted to target genes involved in cell adhesion molecules and peroxisomal pathways. Our data suggest that consumption of hybrid palm oil should be monitored carefully, as its overconsumption compared to that of African palm oil could involve important alterations to hepatic metabolism.

Investigation of Adipose Tissue Fatty Acid Composition in Men with Uronephrolithiasis and Metabolic Syndrome

Background

Fatty acids (FA) and their metabolites are closely related to some mechanisms involved in the development of uronephrolithiasis. The aim of this study was to evaluate the relationship between FA composition and type of kidney stones.

Material/Methods

Abdominal adipose tissue fatty acid methyl esters of 71 men with nephrolithiasis were identified by GC/MS, and the type of kidney stones was identified using FTIR infrared spectroscopy. Patients were divided into groups according to diagnosis of metabolic syndrome (MS) and type of kidney stone. The composition of FA was compared within different groups of patients with different types of kidney stones and between the patients and healthy individuals (control group) (n=100).

Results

Individuals with nephrolithiasis had a significantly higher level of monounsaturated fatty acids (MUFA) and a lower level of polyunsaturated fatty acids (PUFA) versus healthy individuals. Patients with MS had a higher level of 18: 1ω9 and a lower level of 16: 1ω7 than patients without MS. Individuals with nephrolithiasis, but without MS, had a higher level of saturated fatty acids (SFA) compared to controls. The level of PUFA was higher in the control group (p<0.0001) compared to individuals with uronephrolithiasis, with or without MS. PUFA, ω – 6 PUFA, and 18: 2ω6 were higher in patients with calcium-based kidney stones without MS versus patients with uric acid kidney stones with MS.

Conclusions

The levels of MUFA were significantly higher and the levels of PUFA were significantly lower in patients with uronephrolithiasis compared to controls.

Dietary linoleic acid intake and blood inflammatory markers: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

The aim of the present study was to investigate the effect of increasing dietary linoleic acid (LA) intake on the blood concentrations of inflammatory markers including cytokines, acute phase reactants and adhesion molecules in adults.

METHODS

We comprehensively searched PubMed, Embase and Cochrane Library for eligible studies. Overall, 30 randomized controlled studies involving 1377 subjects were included for meta-analysis.

RESULTS

No significant effect of higher LA intake was observed for cytokines: tumor necrosis factor (SMD: -0.01; 95% CI: -0.19 to 0.17), interleukin-6 (SMD: 0.11, 95% CI: -0.07 to 0.29), adiponectin (SMD: 0.17, 95% CI: -0.17 to 0.50) and monocyte chemoattractant protein 1 (SMD: 0.14, 95% CI: -0.33 to 0.60). Pooled effect size from 16 studies showed that the C-reactive protein (CRP) concentration was not significantly affected by increasing LA intake (SMD = 0.09, 95% CI: -0.05 to 0.24). However, subgroup and meta-regression analysis suggested that in subjects with a more profound increase of dietary LA intake, LA might increase the blood CRP level. Other acute phase reactants including fibrinogen and plasminogen activator inhibitor-1 and adhesion molecules were not significantly changed when LA was increased in diet. No significant heterogeneity or publication bias was observed, although only a limited number of eligible studies were included for some markers.

CONCLUSION

Our meta-analysis suggested that increasing dietary LA intake does not have a significant effect on the blood concentrations of inflammatory markers. However, the extent of change in dietary LA intake might affect the effect of LA supplementation on CRP.

Improvements in the conception rate, milk composition and embryo quality of rabbit does after dietary enrichment with n-3 polyunsaturated fatty acids

This work attempts to confirm the effect of an enriched diet with n-3 polyunsaturated fatty acids (PUFA) trying to mitigate the reproductive performances issues such as low conception rate of primiparous rabbits. A total of 127 does were fed ad libitum throughout their two first cycles with two diets with different fat sources: mixed fat in the control and salmon oil in the enriched one, with 3.19 g/100 g (n=63 does) and 28.77 g/100 g (n=64 does) of n-3 of the total fatty acid, respectively. Feed intake was similar between groups (P>0.05). Plasma progesterone concentration was higher in the enriched females than in control ones at 7 (30.9±2.18 v. 23.9±2.30 ng/ml, respectively; P=0.029) and 14 (38.7±2.18 v. 28.2±2.30 ng/ml, respectively; P=0.001) days of first gestation. Considering both cycles, reproductive parameters of mothers (fertility, duration of gestation and prolificacy) and litter parameters (weight at parturition and weaning, mortality and average daily gain (ADG) of kits during lactation) were similar in both groups. However, individual measurements of neonates of enriched group improved 5.87%, 7.10% and 18.01% (P0.05), but embryo apoptosis rate was higher in control group than in enriched one (31.1±4.56% v. 17.1±3.87%, respectively; P<0.05). In conclusion, dietary PUFA enrichment from the rearing and throughout two productive cycles improved plasma progesterone during pregnancy, fertility, milk fatty acid profile and neonates development of primiparous supporting the beneficial effect of n-3 PUFA supplementation in rabbit does.

Vegetarian diet, food substitution, and nonalcoholic fatty liver

Objectives:

Vegetarian diets have been shown to improve insulin resistance and reduce body weight, but the effects on nonalcoholic fatty liver require further confirmation. We aim to investigate the association between vegetarian diets, major food groups, and nonalcoholic fatty liver, and to compare the degree of liver fibrosis between vegetarians and nonvegetarians in those with fatty liver.

Materials and Methods:

We analyzed cross-sectional data from the Tzu Chi Health Study which included 2127 nonvegetarians and 1273 vegetarians who did not smoke or habitually drink alcohol and had no hepatitis B or hepatitis C. Fatty liver and liver fibrosis were determined using ultrasonography and the nonalcoholic fatty liver disease fibrosis score, respectively. Diet was assessed through a validated food frequency questionnaire.

Results:

Vegetarian diets were associated with lower odds of fatty liver (odds ratio = 0.79, 95% confidence interval: 0.68–0.91) after adjusting for age, gender, education, history of smoking and alcohol drinking. Adjustment for body mass index (BMI) attenuated the protective association. Vegetarians had less severe fibrosis than nonvegetarians. Replacing a serving of soy with a serving of meat or fish was associated with 12%–13% increased risk, and replacing a serving of whole grains with a serving of refined grains, fruits, and fruit juice was associated with 3%–12% increased the risk of fatty liver.

Conclusion:

Vegetarian diets, replacing meat and fish with soy, and replacing refined carbohydrates with whole grains, may be inversely associated with nonalcoholic fatty liver related to BMI.

Links between Dietary Protein Sources, the Gut Microbiota, and Obesity

The association between the gut microbiota and obesity is well documented in both humans and in animal models. It is also demonstrated that dietary factors can change the gut microbiota composition and obesity development. However, knowledge of how diet, metabolism and gut microbiota mutually interact and modulate energy metabolism and obesity development is still limited. Epidemiological studies indicate an association between intake of certain dietary protein sources and obesity. Animal studies confirm that different protein sources vary in their ability to either prevent or induce obesity. Different sources of protein such as beans, vegetables, dairy, seafood, and meat differ in amino acid composition. Further, the type and level of other factors, such as fatty acids and persistent organic pollutants (POPs) vary between dietary protein sources. All these factors can modulate the composition of the gut microbiota and may thereby influence their obesogenic properties. This review summarizes evidence of how different protein sources affect energy efficiency, obesity development, and the gut microbiota, linking protein-dependent changes in the gut microbiota with obesity.

Effect of Distinct Lifestyle Interventions on Mobilization of Fat Storage Pools: CENTRAL Magnetic Resonance Imaging Randomized Controlled Trial

BACKGROUND

We aimed to assess whether distinct lifestyle strategies can differentially affect specific body adipose depots.

METHODS

We performed an 18-month randomized controlled trial among 278 sedentary adults with abdominal obesity (75%) or dyslipidemia in an isolated workplace with a monitored provided lunch. Participants were randomized to isocaloric low-fat or Mediterranean/low-carbohydrate (MED/LC) diet+28 g walnuts/day with/without added moderate physical activity (PA; 80% aerobic; supervised/free gym membership). Overall primary outcome was body fat redistribution, and the main specific end point was visceral adipose tissue (VAT). We further followed the dynamics of different fat depots (deep and superficial subcutaneous, liver, pericardial, muscle, pancreas, and renal sinus) by magnetic resonance imaging.

RESULTS

Of 278 participants (age, 48 years, 89% men, body mass index, 30.8 kg/m²), 86% completed the trial with good adherence. The low-fat group preferentially decreased reported fat intake (-21.0% versus -11.5% for the MED/LC; P<0.001), and the MED/LC group decreased reported carbohydrates intake (-39.5% versus -21.3% for the low-fat group; P<0.001). The PA⁺ groups significantly increased the metabolic equivalents per week versus the PA^- groups (19.0 versus 2.1; P=0.009). Whereas final moderate weight loss was indifferent, exercise attenuated the waist circumference rebound with the greatest effect in the MED/LC^PA+ group (P<0.05). VAT (-22%), intrahepatic (-29%), and intrapericardial (-11%) fats declines were higher than pancreatic and femur intermuscular fats (1% to 2%) loss. Independent of weight loss, PA⁺ with either diet had a significantly greater effect on decreasing VAT (mean of difference, -6.67cm²; 95% confidence interval, -14.8 to -0.45) compared with PA^-. The MED/LC diet was superior to the low-fat diet in decreasing intrahepatic, intrapericardial, and pancreatic fats (P<0.05 for all). In contrast, renal sinus and femoral intermuscular fats were not differentially altered by lifestyle interventions but by weight loss per se. In multivariate models further adjusted for weight loss, losing VAT or intrahepatic fat was independently associated with improved lipid profile, losing deep subcutaneous adipose tissue with improved insulin sensitivity, and losing superficial subcutaneous adipose tissue remained neutral except for an association with decreased leptin.

CONCLUSIONS

Moderate weight loss alone inadequately reflects the significant lifestyle effects on atherogenic and diabetogenic fat depots. The MED/LC diet mobilizes specific ectopic fat depots, and exercise has an independent contribution to VAT loss. Fat depots exhibit diverse responsiveness and are differentially related to cardiometabolic markers. Distinct lifestyle protocols may uniquely induce fat mobilization from specific anatomic sites.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01530724.

Fatty Acid Proportions in Plasma Cholesterol Esters and Phospholipids Are Positively Correlated in Various Swedish Populations

Background: Fatty acid (FA) proportions in cholesterol esters (CEs) and plasma phospholipids are widely used as dietary biomarkers. Information on how proportions in these fractions correlate could have implications for interpretation and use of FA biomarkers in observational and interventional studies.Objective: We investigated correlations between FA proportions in CEs and phospholipids in free-living individuals and assessed how diet-induced alterations of FA proportions correlate between fractions.Methods: Spearman's rank correlation coefficients (r_s) between FA proportions (percentage of total FAs) in circulating CEs and phospholipids were calculated separately in 8 individual study populations including Swedish females and males (N = 2052; age range: 11-84 y), and pooled by inverse-variance weighted meta-analysis. In addition, study populations were stratified by age, sex, body mass index (BMI; in kg/m²), and diabetes status, and strata-specific r_s were pooled by meta-analysis. In 2 randomized trials (N = 79) in which dietary saturated FAs were isocalorically replaced with unsaturated FAs, treatment-wise calculations of r_s were conducted between FA changes in CEs and phospholipids.Results: Overall, FA proportions in CEs and phospholipids correlated well and especially strongly for polyunsaturated FAs (PUFAs), with pooled r_s (95% CIs) ranging from 0.74 (0.72, 0.76) for α-linolenic acid to 0.92 (0.91, 0.93) for eicosapentaenoic acid. Weak correlations (pooled r_s < 0.4) were observed only for palmitic acid and stearic acid, with pooled r_s (95% CIs): 0.29 (0.24, 0.33) and 0.30 (0.25, 0.34), respectively. Overall, correlations were not affected by age, sex, BMI, or diabetes status. Strong correlations (r_s ≥ 0.6) between diet-induced FA changes in CEs and phospholipids were observed for most PUFAs.Conclusions: Proportions of most FAs in CEs and phospholipids ranked individuals similarly, suggesting that FA proportions in these fractions can be used interchangeably in populations of diverse age, sex, body composition, and diabetes status. Caution is advised, however, when comparing results from studies assessing palmitic acid or stearic acid in different lipid fractions.

Progressing Insights into the Role of Dietary Fats in the Prevention of Cardiovascular Disease

Dietary fats have important effects on the risk of cardiovascular disease (CVD). Abundant evidence shows that partial replacement of saturated fatty acids (SAFA) with unsaturated fatty acids improves the blood lipid and lipoprotein profile and reduces the risk of coronary heart disease (CHD). Low-fat diets high in refined carbohydrates and sugar are not effective. Very long-chain polyunsaturated n-3 or omega-3 fatty acids (n-3 VLCPUFA) present in fish have multiple beneficial metabolic effects, and regular intake of fatty fish is associated with lower risks of fatal CHD and stroke. Food-based guidelines on dietary fats recommend limiting the consumption of animal fats high in SAFA, using vegetable oils high in monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA), and eating fatty fish. These recommendations are part of a healthy eating pattern that also includes ample intake of plant-based foods rich in fiber and limited sugar and salt.

Dietary omega-3 and omega-6 polyunsaturated fatty acids modulate hepatic pathology

Recent evidence has suggested that dietary polyunsaturated fatty acids (PUFAs) modulate inflammation; however, few studies have focused on the pathobiology of PUFA using isocaloric and isolipidic diets and it is unclear if the associated pathologies are due to dietary PUFA composition, lipid metabolism or obesity, as most studies compare diets fed ad libitum. Our studies used isocaloric and isolipidic liquid diets (35% of calories from fat), with differing compositions of omega (ω)-6 or long chain (Lc) ω-3 PUFA that were pair-fed and assessed hepatic pathology, inflammation and lipid metabolism. Consistent with an isocaloric, pair-fed model we observed no significant difference in diet consumption between the groups. In contrast, the body and liver weight, total lipid level and abdominal fat deposits were significantly higher in mice fed an ω-6 diet. An analysis of the fatty acid profile in plasma and liver showed that mice on the ω-6 diet had significantly more arachidonic acid (AA) in the plasma and liver, whereas, in these mice ω-3 fatty acids such as eicosapentaenoic acid (EPA) were not detected and docosahexaenoic acid (DHA) was significantly lower. Histopathologic analyses documented that mice on the ω-6 diet had a significant increase in macrovesicular steatosis, extramedullary myelopoiesis (EMM), apoptotic hepatocytes and decreased glycogen storage in lobular hepatocytes, and hepatocyte proliferation relative to mice fed the Lc ω-3 diet. Together, these results support PUFA dietary regulation of hepatic pathology and inflammation with implications for enteral feeding regulation of steatosis and other hepatic lesions.

Treatment of NAFLD with diet, physical activity and exercise

Lifestyle intervention can be effective when treating non-alcoholic fatty liver diseases (NAFLD) patients. Weight loss decreases cardiovascular and diabetes risk and can also regress liver disease. Weight reductions of ⩾10% can induce a near universal non-alcoholic steatohepatitis resolution and fibrosis improvement by at least one stage. However, modest weight loss (>5%) can also produce important benefits on the components of the NAFLD activity score (NAS). Additionally, we need to explore the role of total calories and type of weight loss diet, micro- and macronutrients, evidence-based benefits of physical activity and exercise and finally support these modifications through established behavioural change models and techniques for long-term maintenance of lifestyle modifications. Following a Mediterranean diet can reduce liver fat even without weight loss and is the most recommended dietary pattern for NAFLD. The Mediterranean diet is characterised by reduced carbohydrate intake, especially sugars and refined carbohydrates (40% of the calories vs. 50-60% in a typical low fat diet), and increased monounsaturated and omega-3 fatty acid intake (40% of the calories as fat vs. up-to 30% in a typical low fat diet). Both TV sitting (a reliable marker of overall sedentary behaviour) and physical activity are associated with cardio-metabolic health, NAFLD and overall mortality. A 'triple hit behavioural phenotype' of: i) sedentary behaviour, ii) low physical activity, and iii) poor diet have been defined. Clinical evidence strongly supports the role of lifestyle modification as a primary therapy for the management of NAFLD and NASH. This should be accompanied by the implementation of strategies to avoid relapse and weight regain.

Isocaloric Dietary Changes and Non-Alcoholic Fatty Liver Disease in High Cardiometabolic Risk Individuals

Non-alcoholic fatty liver disease (NAFLD) incorporates an extensive spectrum of histologic liver abnormalities, varying from simple triglyceride accumulation in hepatocytes non-alcoholic fatty liver (NAFL) to non-alcoholic steatohepatitis (NASH), and it is the most frequent chronic liver disease in the industrialized world. Beyond liver related complications such as cirrhosis and hepatocellular carcinoma, NAFLD is also an emerging risk factor for type 2 diabetes and cardiovascular disease. Currently, lifestyle intervention including strategies to reduce body weight and to increase regular physical activity represents the mainstay of NAFLD management. Total caloric intake plays a very important role in both the development and the treatment of NAFLD; however, apart from the caloric restriction alone, modifying the quality of the diet and modulating either the macro- or micronutrient composition can also markedly affect the clinical evolution of NAFLD, offering a more realistic and feasible treatment alternative. The aim of the present review is to summarize currently available evidence from randomized controlled trials on the effects of different nutrients including carbohydrates, lipids, protein and other dietary components, in isocaloric conditions, on NAFLD in people at high cardiometabolic risk. We also describe the plausible mechanisms by which different dietary components could modulate liver fat content.

Influence of dietary macronutrients on liver fat accumulation and metabolism

The liver is a principal metabolic organ within the human body and has a major role in regulating carbohydrate, fat, and protein metabolism. With increasing rates of obesity, the prevalence of non-alcoholic fatty liver disease (NAFLD) is growing. It remains unclear why NAFLD, which is now defined as the hepatic manifestation of the metabolic syndrome, develops but lifestyle factors such as diet (ie, total calorie and specific nutrient intakes), appear to play a key role. Here we review the available observational and intervention studies that have investigated the influence of dietary macronutrients on liver fat content. Findings from observational studies are conflicting with some reporting that relative to healthy controls, patients with NAFLD consume diets higher in total fat/saturated fatty acids, whilst others find they consume diets higher in carbohydrates/sugars. From the limited number of intervention studies that have been undertaken, a consistent finding is a hypercaloric diet, regardless of whether the excess calories have been provided either as fat, sugar, or both, increases liver fat content. In contrast, a hypocaloric diet decreases liver fat content. Findings from both hyper- and hypo-caloric feeding studies provide some suggestion that macronutrient composition may also play a role in regulating liver fat content and this is supported by data from isocaloric feeding studies; fatty acid composition and/or carbohydrate content/type appear to influence whether there is accrual of liver fat or not. The mechanisms by which specific macronutrients, when consumed as part of an isocaloric diet, cause a change in liver fat remain to be fully elucidated.

Lifestyle precision medicine: the next generation in type 2 diabetes prevention?

The driving force behind the current global type 2 diabetes epidemic is insulin resistance in overweight and obese individuals. Dietary factors, physical inactivity, and sedentary behaviors are the major modifiable risk factors for obesity. Nevertheless, many overweight/obese people do not develop diabetes and lifestyle interventions focused on weight loss and diabetes prevention are often ineffective. Traditionally, chronically elevated blood glucose concentrations have been the hallmark of diabetes; however, many individuals will either remain 'prediabetic' or regress to normoglycemia. Thus, there is a growing need for innovative strategies to tackle diabetes at scale. The emergence of biomarker technologies has allowed more targeted therapeutic strategies for diabetes prevention (precision medicine), though largely confined to pharmacotherapy. Unlike most drugs, lifestyle interventions often have systemic health-enhancing effects. Thus, the pursuance of lifestyle precision medicine in diabetes seems rational. Herein, we review the literature on lifestyle interventions and diabetes prevention, describing the biological systems that can be characterized at scale in human populations, linking them to lifestyle in diabetes, and consider some of the challenges impeding the clinical translation of lifestyle precision medicine.

Effects of plant- and animal-based high-fat diets on lipid storage and distribution in environmental bacteria-colonized gnotobiotic mice

Different edible oils such as lard and soybean oil have been reported to interact with the gut microbiota, affecting host lipid metabolism. However, whether bacteria derived from the environment influence host lipid metabolism remains unclear. This study aimed to clarify the roles of environmental bacteria in host lipid storage and distribution with various edible oils. Gnotobiotic C57BL/6JNarl mice were inoculated with Lysinibacillus xylanilyticus and Paenibacillus azoreducens and then fed either a normal diet (LabDiet 5010, control group) or a diet containing 60% lard (L-group) or soybean oil (S-group) for 18 months. Interestingly, the S-group accumulated massive amounts of white adipose tissue compared to the L- and control groups, while the L-group displayed more hepatic steatosis and fatty droplets than the other groups. The expression of fatty acid synthase (FAS), hydroxymethylglutaryl-coenzyme A reductase (HMGCR), sterol regulatory element-binding protein 2 (SREBP2), and peroxisome proliferator-activated receptor gamma (PPARγ) in the livers of the L-group were markedly elevated compared to the S-group. FAS and PPARγ protein levels were also markedly elevated. However, there were no differences in the expression of the pro-inflammatory cytokines interleukin-6 and tumor necrosis factor-α between the groups. Our results suggest that environmental bacteria may affect host hepatic inflammation and lipid distribution in the presence of high-fat diets, with different effects depending on the fat type consumed.

Circulating linoleic acid and alpha-linolenic acid and glucose metabolism: the Hoorn Study

PURPOSE

Data on the relation between linoleic acid (LA) and alpha-linolenic acid (ALA) and type 2 diabetes mellitus (T2DM) risk are scarce and inconsistent. The aim of this study was to investigate the association of serum LA and ALA with fasting and 2 h post-load plasma glucose and glycated hemoglobin (HbA1c).

METHOD

This study included 667 participants from third examination (2000) of the population-based Hoorn study in which individuals with glucose intolerance were overrepresented. Fatty acid profiles in serum total lipids were measured at baseline, in 2000. Diabetes risk markers were measured at baseline and follow-up in 2008. Linear regression models were used in cross-sectional and prospective analyses.

RESULTS

In cross-sectional analyses (n = 667), serum LA was inversely associated with plasma glucose, both in fasting conditions (B = -0.024 [-0.045, -0.002]) and 2 h after glucose tolerance test (B = -0.099 [-0.158, -0.039]), but not with HbA1c (B = 0.000 [-0.014, 0.013]), after adjustment for relevant factors. In prospective analyses (n = 257), serum LA was not associated with fasting (B = 0.003 [-0.019, 0.025]) or post-load glucose (B = -0.026 [-0.100, 0.049]). Furthermore, no significant associations were found between serum ALA and glucose metabolism in cross-sectional or prospective analyses.

CONCLUSIONS

In this study, serum LA was inversely associated with fasting and post-load glucose in cross-sectional, but not in prospective analyses. Further studies are needed to elucidate the exact role of serum LA and ALA levels and dietary polyunsaturated fatty acids in glucose metabolism.

Adverse effects of fructose on cardiometabolic risk factors and hepatic lipid metabolism in subjects with abdominal obesity

BACKGROUND

Overconsumption of dietary sugars, fructose in particular, is linked to cardiovascular risk factors such as type 2 diabetes, obesity, dyslipidemia and nonalcoholic fatty liver disease. However, clinical studies have to date not clarified whether these adverse cardiometabolic effects are induced directly by dietary sugars, or whether they are secondary to weight gain.

OBJECTIVES

To assess the effects of fructose (75 g day^-1 ), served with their habitual diet over 12 weeks, on liver fat content and other cardiometabolic risk factors in a large cohort (n = 71) of abdominally obese men.

METHODS

We analysed changes in body composition, dietary intake, an extensive panel of cardiometabolic risk markers, hepatic de novo lipogenesis (DNL), liver fat content and postprandial lipid responses after a standardized oral fat tolerance test (OFTT).

RESULTS

Fructose consumption had modest adverse effects on cardiometabolic risk factors. However, fructose consumption significantly increased liver fat content and hepatic DNL and decreased β-hydroxybutyrate (a measure of β-oxidation). The individual changes in liver fat were highly variable in subjects matched for the same level of weight change. The increase in liver fat content was significantly more pronounced than the weight gain. The increase in DNL correlated positively with triglyceride area under the curve responses after an OFTT.

CONCLUSION

Our data demonstrated adverse effects of moderate fructose consumption for 12 weeks on multiple cardiometabolic risk factors in particular on liver fat content despite only relative low increases in weight and waist circumference. Our study also indicates that there are remarkable individual differences in susceptibility to visceral adiposity/liver fat after real-world daily consumption of fructose-sweetened beverages over 12 weeks.

Pancreatic size and fat content in diabetes: A systematic review and meta-analysis of imaging studies

Objectives

Imaging studies are expected to produce reliable information regarding the size and fat content of the pancreas. However, the available studies have produced inconclusive results. The aim of this study was to perform a systematic review and meta-analysis of imaging studies assessing pancreas size and fat content in patients with type 1 diabetes (T1DM) and type 2 diabetes (T2DM).

Methods

Medline and Embase databases were performed. Studies evaluating pancreatic size (diameter, area or volume) and/or fat content by ultrasound, computed tomography, or magnetic resonance imaging in patients with T1DM and/or T2DM as compared to healthy controls were selected. Seventeen studies including 3,403 subjects (284 T1DM patients, 1,139 T2DM patients, and 1,980 control subjects) were selected for meta-analyses. Pancreas diameter, area, volume, density, and fat percentage were evaluated.

Results

Pancreatic volume was reduced in T1DM and T2DM vs. controls (T1DM vs. controls: -38.72 cm3, 95%CI: -52.25 to -25.19, I2 = 70.2%, p for heterogeneity = 0.018; and T2DM vs. controls: -12.18 cm3, 95%CI: -19.1 to -5.25, I2 = 79.3%, p for heterogeneity = 0.001). Fat content was higher in T2DM vs. controls (+2.73%, 95%CI 0.55 to 4.91, I² = 82.0%, p for heterogeneity<0.001).

Conclusions

Individuals with T1DM and T2DM have reduced pancreas size in comparison with control subjects. Patients with T2DM have increased pancreatic fat content.

Palmitate and oleate exert differential effects on insulin signalling and glucose uptake in human skeletal muscle cells

Saturated fatty acids are implicated in the development of insulin resistance, whereas unsaturated fatty acids may have a protective effect on metabolism. We tested in primary human myotubes if insulin resistance induced by saturated fatty acid palmitate can be ameliorated by concomitant exposure to unsaturated fatty acid oleate. Primary human myotubes were pretreated with palmitate, oleate or their combination for 12 h. Glucose uptake was determined by intracellular accumulation of [3H]-2-deoxy-d-glucose, insulin signalling and activation of endoplasmic reticulum (ER) stress by Western blotting, and mitochondrial reactive oxygen species (ROS) production by fluorescent dye MitoSOX. Exposure of primary human myotubes to palmitate impaired insulin-stimulated Akt-Ser473, AS160 and GSK-3β phosphorylation, induced ER stress signalling target PERK and stress kinase JNK 54 kDa isoform. These effects were virtually abolished by concomitant exposure of palmitate-treated myotubes to oleate. However, an exposure to palmitate, oleate or their combination reduced insulin-stimulated glucose uptake. This was associated with increased mitochondrial ROS production in palmitate-treated myotubes co-incubated with oleate, and was alleviated by antioxidants MitoTempo and Tempol. Thus, metabolic and intracellular signalling events diverge in myotubes treated with palmitate and oleate. Exposure of human myotubes to excess fatty acids increases ROS production and induces insulin resistance.

International society of sports nutrition position stand: diets and body composition

Position Statement: The International Society of Sports Nutrition (ISSN) bases the following position stand on a critical analysis of the literature regarding the effects of diet types (macronutrient composition; eating styles) and their influence on body composition. The ISSN has concluded the following. 1) There is a multitude of diet types and eating styles, whereby numerous subtypes fall under each major dietary archetype. 2) All body composition assessment methods have strengths and limitations. 3) Diets primarily focused on fat loss are driven by a sustained caloric deficit. The higher the baseline body fat level, the more aggressively the caloric deficit may be imposed. Slower rates of weight loss can better preserve lean mass (LM) in leaner subjects. 4) Diets focused primarily on accruing LM are driven by a sustained caloric surplus to facilitate anabolic processes and support increasing resistance-training demands. The composition and magnitude of the surplus, as well as training status of the subjects can influence the nature of the gains. 5) A wide range of dietary approaches (low-fat to low-carbohydrate/ketogenic, and all points between) can be similarly effective for improving body composition. 6) Increasing dietary protein to levels significantly beyond current recommendations for athletic populations may result in improved body composition. Higher protein intakes (2.3–3.1 g/kg FFM) may be required to maximize muscle retention in lean, resistance-trained subjects under hypocaloric conditions. Emerging research on very high protein intakes (>3 g/kg) has demonstrated that the known thermic, satiating, and LM-preserving effects of dietary protein might be amplified in resistance-training subjects. 7) The collective body of intermittent caloric restriction research demonstrates no significant advantage over daily caloric restriction for improving body composition. 8) The long-term success of a diet depends upon compliance and suppression or circumvention of mitigating factors such as adaptive thermogenesis. 9) There is a paucity of research on women and older populations, as well as a wide range of untapped permutations of feeding frequency and macronutrient distribution at various energetic balances combined with training. Behavioral and lifestyle modification strategies are still poorly researched areas of weight management.

Current and future strategies for the nutritional management of cardiometabolic complications of androgen deprivation therapy for prostate cancer

Androgen deprivation therapy (ADT) is used widely as part of a combined modality for the treatment of prostate cancer. However, ADT has also been associated with the development of cardiometabolic complications that can increase mortality from cardiovascular events. There is emerging evidence to suggest that ADT-related cardiometabolic risk can be mitigated by diet and lifestyle modification. While the clinical focus for a nutritional approach for achieving this effect is unclear, it may depend upon the timely assessment and targeting of dietary changes to the specific risk phenotype of the patient. The present review aims to address the metabolic origins of ADT-related cardiometabolic risk, existing evidence for the effects of dietary intervention in modifying this risk, and the priorities for future dietary strategies.

Gene-Diet Interactions in Type 2 Diabetes: The Chicken and Egg Debate

Consistent evidence from both experimental and human studies indicates that Type 2 diabetes mellitus (T2DM) is a complex disease resulting from the interaction of genetic, epigenetic, environmental, and lifestyle factors. Nutrients and dietary patterns are important environmental factors to consider in the prevention, development and treatment of this disease. Nutritional genomics focuses on the interaction between bioactive food components and the genome and includes studies of nutrigenetics, nutrigenomics and epigenetic modifications caused by nutrients. There is evidence supporting the existence of nutrient-gene and T2DM interactions coming from animal studies and family-based intervention studies. Moreover, many case-control, cohort, cross-sectional cohort studies and clinical trials have identified relationships between individual genetic load, diet and T2DM. Some of these studies were on a large scale. In addition, studies with animal models and human observational studies, in different countries over periods of time, support a causative relationship between adverse nutritional conditions during in utero development, persistent epigenetic changes and T2DM. This review provides comprehensive information on the current state of nutrient-gene interactions and their role in T2DM pathogenesis, the relationship between individual genetic load and diet, and the importance of epigenetic factors in influencing gene expression and defining the individual risk of T2DM.

Impact of fat mass and distribution on lipid turnover in human adipose tissue

Differences in white adipose tissue (WAT) lipid turnover between the visceral (vWAT) and subcutaneous (sWAT) depots may cause metabolic complications in obesity. Here we compare triglyceride age and, thereby, triglyceride turnover in vWAT and sWAT biopsies from 346 individuals and find that subcutaneous triglyceride age and storage capacity are increased in overweight or obese individuals. Visceral triglyceride age is only increased in excessively obese individuals and associated with a lower lipid removal capacity. Thus, although triglyceride storage capacity in sWAT is higher than in vWAT, the former plateaus at substantially lower levels of excess WAT mass than vWAT. In individuals with central or visceral obesity, lipid turnover is selectively increased in vWAT. Obese individuals classified as ‘metabolically unhealthy' (according to ATPIII criteria) who have small subcutaneous adipocytes exhibit reduced triglyceride turnover. We conclude that excess WAT results in depot-specific differences in lipid turnover and increased turnover in vWAT and/or decreased turnover in sWAT may result in metabolic complications of overweight or obesity.

Lipid turnover in tissues can be calculated from ratios of different carbon isotopes. Here the authors use this approach to study lipid turnover in two distinct adipose tissue depots and find that, in obese individuals, visceral fat is more lipolytic than subcutaneous fat.

Liver fat: a relevant target for dietary intervention? Summary of a Unilever workshop

Currently it is estimated that about 1 billion people globally have non-alcoholic fatty liver disease (NAFLD), a condition in which liver fat exceeds 5 % of liver weight in the absence of significant alcohol intake. Due to the central role of the liver in metabolism, the prevalence of NAFLD is increasing in parallel with the prevalence of obesity, insulin resistance and other risk factors of metabolic diseases. However, the contribution of liver fat to the risk of type 2 diabetes mellitus and CVD, relative to other ectopic fat depots and to other risk markers, is unclear. Various studies have suggested that the accumulation of liver fat can be reduced or prevented via dietary changes. However, the amount of liver fat reduction that would be physiologically relevant, and the timeframes and dose-effect relationships for achieving this through different diet-based approaches, are unclear. Also, it is still uncertain whether the changes in liver fat per se or the associated metabolic changes are relevant. Furthermore, the methods available to measure liver fat, or even individual fatty acids, differ in sensitivity and reliability. The present report summarises key messages of presentations from different experts and related discussions from a workshop intended to capture current views and research gaps relating to the points above.

Specific Macronutrients Exert Unique Influences on the Adipose-Liver Axis to Promote Hepatic Steatosis in Mice

BACKGROUND & AIMS

The factors that distinguish metabolically healthy obesity from metabolically unhealthy obesity are not well understood. Diet has been implicated as a determinant of the unhealthy obesity phenotype, but which aspects of the diet induce dysmetabolism are unknown. The goal of this study was to investigate whether specific macronutrients or macronutrient combinations provoke dysmetabolism in the context of isocaloric, high-energy diets.

METHODS

Mice were fed 4 high-energy diets identical in calorie and nutrient content but different in nutrient composition for 3 weeks to 6 months. The test diets contained 42% carbohydrate (sucrose or starch) and 42% fat (oleate or palmitate). Weight and glucose tolerance were monitored; blood and tissues were collected for histology, gene expression, and immunophenotyping.

RESULTS

Mice gained weight on all 4 test diets but differed significantly in other metabolic outcomes. Animals fed the starch-oleate diet developed more severe hepatic steatosis than those on other formulas. Stable isotope incorporation showed that the excess hepatic steatosis in starch-oleate-fed mice derived from exaggerated adipose tissue lipolysis. In these mice, adipose tissue lipolysis coincided with adipocyte necrosis and inflammation. Notably, the liver and adipose tissue abnormalities provoked by starch-oleate feeding were reproduced when mice were fed a mixed-nutrient Western diet with 42% carbohydrate and 42% fat.

CONCLUSIONS

The macronutrient composition of the diet exerts a significant influence on metabolic outcome, independent of calories and nutrient proportions. Starch-oleate appears to cause hepatic steatosis by inducing progressive adipose tissue injury. Starch-oleate phenocopies the effect of a Western diet; consequently, it may provide clues to the mechanism whereby specific nutrients cause metabolically unhealthy obesity.

Fatty acid composition in serum cholesterol esters and phospholipids is linked to visceral and subcutaneous adipose tissue content in elderly individuals: a cross-sectional study

BACKGROUND

Visceral adipose tissue (VAT) and truncal fat predict cardiometabolic disease. Intervention trials suggest that saturated fatty acids (SFA), e.g. palmitic acid, promote abdominal and liver fat storage whereas polyunsaturated fatty acids (PUFA), e.g. linoleic acid, prevent fat accumulation. Such findings require investigation in population-based studies of older individuals. We aimed to investigate the relationships of serum biomarkers of PUFA intake as well as serum levels of palmitic acid, with abdominal and total adipose tissue content.

METHODS

In a population-based sample of 287 elderly subjects in the PIVUS cohort, we assessed fatty acid composition in serum cholesterol esters (CE) and phospholipids (PL) by gas chromatography and the amount of VAT and abdominal subcutaneous (SAT) adipose tissue by magnetic resonance imaging (MRI), liver fat by MR spectroscopy (MRS), and total body fat, trunk fat and leg fat by dual-energy X-ray absorptiometry (DXA). Insulin resistance was estimated by HOMA-IR.

RESULTS

VAT and trunk fat showed the strongest correlation with insulin resistance (r = 0.49, P < 0.001). Linoleic acid in both CE and PL was inversely related to all body fat depots (r = -0.24 to -0.33, P < 0.001) including liver fat measured in a sub-group (r = -0.26, P < 0.05, n = 73), whereas n-3 PUFA showed weak inverse (18:3n-3) or positive (20:5n-3) associations. Palmitic acid in CE, but not in PL, was directly correlated with VAT (r = 0.19, P < 0.001) and trunk fat (r = 0.18, P = 0.003). Overall, the significant associations remained after adjusting for energy intake, height, alcohol, sex, smoking, education and physical activity. The inverse correlation between linoleic acid and VAT remained significant after further adjustment for total body fat.

CONCLUSIONS

Serum linoleic acid is inversely related to body fat storage including VAT and trunk fat whereas palmitic acid was less consistently but directly associated, in line with recent feeding studies. Considering the close link between VAT and insulin resistance, a potential preventive role of plant-based PUFA in VAT accumulation warrants further study.

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.

"We are what our bacteria eat": The role of bacteria in personalizing nutrition therapy in gastrointestinal conditions

The theme for the 2016 World Digestive Health Day is "Your Diet and Gut Health". The World Gastroenterology Organization thereby wishes to raise awareness of the relationship between what we eat and gastrointestinal symptoms. World Digestive Health Day (WDHD) is celebrated each year on May 29. This brief review article on behalf of the New Zealand Society of Gastroenterology will highlight recent developments in this highly active area of research with a special emphasis on gastrointestinal disorders.

Serum Fatty Acids, Desaturase Activities and Abdominal Obesity - A Population-Based Study of 60-Year Old Men and Women

Abdominal obesity is a key contributor of metabolic disease. Recent trials suggest that dietary fat quality affects abdominal fat content, where palmitic acid and linoleic acid influence abdominal obesity differently, while effects of n-3 polyunsaturated fatty acids are less studied. Also, fatty acid desaturation may be altered in abdominal obesity. We aimed to investigate cross-sectional associations of serum fatty acids and desaturases with abdominal obesity prevalence in a population-based cohort study. Serum cholesteryl ester fatty acids composition was measured by gas chromatography in 60-year old men (n = 1883) and women (n = 2015). Cross-sectional associations of fatty acids with abdominal obesity prevalence and anthropometric measures (e.g., sagittal abdominal diameter) were evaluated in multivariable-adjusted logistic and linear regression models, respectively. Similar models were employed to investigate relations between desaturase activities (estimated by fatty acid ratios) and abdominal obesity. In logistic regression analyses, palmitic acid, stearoyl-CoA-desaturase and Δ6-desaturase indices were associated with abdominal obesity; multivariable-adjusted odds ratios (95% confidence intervals) for highest versus lowest quartiles were 1.45 (1.19–1.76), 4.06 (3.27–5.05), and 3.07 (2.51–3.75), respectively. Linoleic acid, α-linolenic acid, docohexaenoic acid, and Δ5-desaturase were inversely associated with abdominal obesity; multivariable-adjusted odds ratios (95% confidence intervals): 0.39 (0.32–0.48), 0.74 (0.61–0.89), 0.76 (0.62–0.93), and 0.40 (0.33–0.49), respectively. Eicosapentaenoic acid was not associated with abdominal obesity. Similar results were obtained from linear regression models evaluating associations with different anthropometric measures. Sex-specific and linear associations were mainly observed for n3-polyunsaturated fatty acids, while associations of the other exposures were generally non-linear and similar across sexes. In accordance with findings from short-term trials, abdominal obesity was more common among individuals with relatively high proportions of palmitic acid, whilst the contrary was true for linoleic acid. Further trials should examine the potential role of linoleic acid and its main dietary source, vegetable oils, in abdominal obesity prevention.

What have human experimental overfeeding studies taught us about adipose tissue expansion and susceptibility to obesity and metabolic complications?

Overfeeding experiments, in which we impose short-term positive energy balance, help unravel the cellular, physiological and behavioural adaptations to nutrient excess. These studies mimic longer-term mismatched energy expenditure and intake. There is considerable inter-individual heterogeneity in the magnitude of weight gain when exposed to similar relative caloric excess reflecting variable activation of compensatory adaptive mechanisms. Significantly, given similar relative weight gain, individuals may be protected from/predisposed to metabolic complications (insulin resistance, dyslipidaemia, hypertension), non-alcoholic fatty liver disease and cardiovascular disease. Similar mechanistic considerations underpinning the heterogeneity of overfeeding responses are pertinent in understanding emerging metabolic phenotypes, for example, metabolically unhealthy normal weight and metabolically healthy obesity. Intrinsic and extrinsic factors modulate individuals' overfeeding response: intrinsic factors include gender/hormonal status, genetic/ethnic background, baseline metabolic health and cardiorespiratory fitness; extrinsic factors include macronutrient (fat vs carbohydrate) content, fat/carbohydrate composition and overfeeding pattern. Subcutaneous adipose tissue (SAT) analysis, coupled with metabolic assessment, with overfeeding have revealed how SAT remodels to accommodate excess nutrients. SAT remodelling occurs either by hyperplasia (increased adipocyte number) or by hypertrophy (increased adipocyte size). Biological responses of SAT also govern the extent of ectopic (visceral/liver) triglyceride deposition. Body composition analysis by DEXA/MRI (dual energy X-ray absorptiometry/magnetic resonance imaging) have determined the relative expansion of SAT (including abdominal/gluteofemoral SAT) vs ectopic fat with overfeeding. Such studies have contributed to the adipose expandability hypothesis whereby SAT has a finite capacity to expand (governed by intrinsic biological characteristics), and once capacity is exceeded ectopic triglyceride deposition occurs. The potential for SAT expandability confers protection from/predisposes to the adverse metabolic responses to overfeeding. The concept of a personal fat threshold suggests a large inter-individual variation in SAT capacity with ectopic depot expansion/metabolic decompensation once one's own threshold is exceeded. This review summarises insight gained from overfeeding studies regarding susceptibility to obesity and related complications with nutrient excess.

Food-Predicting Stimuli Differentially Influence Eye Movements and Goal-Directed Behavior in Normal-Weight, Overweight, and Obese Individuals

Obese individuals have been shown to exhibit abnormal sensitivity to rewards and reward-predicting cues as for example food-associated cues frequently used in advertisements. It has also been shown that food-associated cues can increase goal-directed behavior but it is currently unknown, whether this effect differs between normal-weight, overweight, and obese individuals. Here, we investigate this question by using a Pavlovian-to-instrumental transfer (PIT) task in normal-weight (N = 20), overweight (N = 17), and obese (N = 17) individuals. Furthermore, we applied eye tracking during Pavlovian conditioning to measure the participants' conditioned response as a proxy of the incentive salience of the predicted reward. Our results show that the goal-directed behavior of overweight individuals was more strongly influenced by food-predicting cues (i.e., stronger PIT effect) than that of normal-weight and obese individuals (p < 0.001). The weight groups were matched for age, gender, education, and parental education. Eye movements during Pavlovian conditioning also differed between weight categories (p < 0.05) and were used to categorize individuals based on their fixation style into "high eye index" versus "low eye index" as well. Our main finding was that the fixation style exhibited a complex interaction with the weight category. Furthermore, we found that normal-weight individuals of the group "high eye index" had higher body mass index within the healthy range than individuals of the group "low eye index" (p < 0.001), but this relationship was not found within in the overweight or obese groups (p > 0.646). Our findings are largely consistent with the incentive sensitization theory predicting that overweight individuals are more susceptible to food-related cues than normal-weight controls. However, this hypersensitivity might be reduced in obese individuals, possibly due to habitual/compulsive overeating or differences in reward valuation.