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

Relationship between dietary macronutrient composition and non-alcoholic fatty liver disease in lean and non-lean populations: a cross-sectional study

OBJECTIVE

The current study aimed to customize dietary changes for lean patients with non-alcoholic fatty liver disease (NAFLD).

DESIGN

The current study was done with a population-based cross-sectional design. The FFQ was used to analyse dietary macronutrient intake and ultrasonography results for NAFLD diagnosis. The study subjects were divided into the lean and non-lean groups based on their BMI (< 25 and ≥ 25). Multivariable logistic regression was used to evaluate the relationship between dietary macronutrients and NAFLD. Substitution analyses were also performed.

SETTING

Amol and its suburban areas in Iran.

PARTICIPANTS

Adults in the age range of 18 to < 65 with full relevant data.

RESULTS

Among the total study subjects (2308), 46·7 % had fatty liver. The substitution of polysaccharides for animal protein and SFA in the lean group resulted in a significant NAFLD reduction, whereas the substitution of SFA for all types of macronutrients, except for n-6 and mono-disaccharides, led to a significant increase in NAFLD (P < 0·05). In non-lean participants, the substitution of MUFA for mono-disaccharides resulted in a significant reduction of NAFLD (P < 0·05). In this group, the substitution of SFA and mono-disaccharides for MUFA, and n-6 for all macronutrients, except vegetable protein and SFA, were significantly related to an increase in NAFLD (P < 0·05).

CONCLUSIONS

Lower lean NAFLD is correlated with increasing polysaccharides in exchange for SFA and animal protein intake, whereas lower non-lean NAFLD is correlated with increasing MUFA in exchange for mono-disaccharides and reducing n-6 and SFA.

Impact of Replacement of Individual Dietary SFAs on Circulating Lipids and Other Biomarkers of Cardiometabolic Health: A Systematic Review and Meta-Analysis of Randomized Controlled Trials in Humans

Little is known of the impact of individual SFAs and their isoenergetic substitution with other SFAs or unsaturated fatty acids (UFAs) on the prevention of cardiometabolic disease (CMD). This systematic literature review assessed the impact of such dietary substitutions on a range of fasting CMD risk markers, including lipid profile, markers of glycemic control and inflammation, and metabolic hormone concentrations. Eligible randomized controlled trials (RCTs) investigated the effect of isoenergetic replacements of individual dietary SFAs for ≥14 d on ≥1 CMD risk markers in humans. Searches of the PubMed, Embase, Scopus, and Cochrane CENTRAL databases on 14 February, 2021 identified 44 RCTs conducted in participants with a mean ± SD age of 39.9 ± 15.2 y. Studies' risk of bias was assessed using the Cochrane Risk of Bias tool 2.0 for RCTs. Random-effect meta-analyses assessed the effect of ≥3 similar dietary substitutions on the same CMD risk marker. Other dietary interventions were described in qualitative syntheses. We observed reductions in LDL-cholesterol concentrations after the replacement of palmitic acid (16:0) with UFAs (-0.36 mmol/L; 95% CI: -0.50, -0.21 mmol/L; I2 = 96.0%, n = 18 RCTs) or oleic acid (18:1n-9) (-0.16 mmol/L; 95% CI: -0.28, -0.03 mmol/L; I2 = 89.6%, n = 9 RCTs), with a similar impact on total cholesterol and apoB concentrations. No effects on other CMD risk markers, including HDL-cholesterol, triacylglycerol, glucose, insulin, or C-reactive protein concentrations, were evident. Similarly, we found no evidence of a benefit from replacing dietary stearic acid (18:0) with UFAs on CMD risk markers (n = 4 RCTs). In conclusion, the impact of replacing dietary palmitic acid with UFAs on lipid biomarkers is aligned with current public health recommendations. However, owing to the high heterogeneity and limited studies, relations between all individual SFAs and biomarkers of cardiometabolic health need further confirmation from RCTs. This systematic review was registered at www.crd.york.ac.uk/prospero/ as CRD42020084241.

Circulating oestradiol determines liver lipid deposition in rats fed standard diets partially unbalanced with higher lipid or protein proportions

The ingestion of excess lipids often produces the accumulation of liver fat. The modulation of diet energy partition affects this process and other metabolic responses, and oestrogens and androgens are implied in this process. Ten-week-old male and female rats were fed with either standard rat chow (SD), SD enriched with coconut oil (high-fat diet, HF), SD enriched with protein (high-protein diet, HP) or a ‘cafeteria’ diet (CAF) for 1 month. HF and CAF diets provided the same lipid-derived percentage of energy (40 %), HP diet protein energy derived was twice (40 %) that of the SD. Animals were killed under anaesthesia and samples of blood and liver were obtained. Hepatic lipid content showed sex-related differences: TAG accumulation tended to increase in HF and CAF fed males. Cholesterol content was higher only in the CAF males. Plasma oestradiol in HF and HP males was higher than in CAF. Circulating cholesterol was inversely correlated with plasma oestradiol. These changes agreed with the differences in the expression of some enzymes related to lipid and energy metabolism, such as fatty acid synthetase or phosphoglycolate phosphatase. Oestrogen protective effects extend to males with ‘normal’ diets, that is, not unbalanced by either lipid or protein, but this protection was not enough against the CAF diet. Oestradiol seems to actively modulate the liver core of 2C-3C partition of energy substrates, regulating cholesterol deposition and lactate production.

The interactions between dietary fats intake and Caveolin 1 rs 3807992 polymorphism with fat distribution in overweight and obese women: a cross-sectional study

BACKGROUND

It has been reported that dietary fats and genetic factors in individuals are associated with the pattern of fat distribution. This study aimed to evaluate the interaction between dietary fats intake and Caveolin1 (CAV-1) rs 3807s992 polymorphism with fat distribution in overweight and obese women.

METHODS

A total of 221 participants were included in the current cross-sectional study. Body composition, biochemical parameters were evaluated by body composition analyzer and Pars Azmoon kits and genotypes determination was performed by PCR-RFLP, dietary fats were measured using a validated semi-quantitative food frequency questionnaire (FAQ).

RESULTS

The frequency of GG, AA and AG genotypes were 53.1, 24.6, and 22.3%, respectively, and the mean intake of total dietary fat intake was 97.47 ± 36.87 g. There was positive significant interaction between total fat intake and AA genotype on visceral fat level (p = 0.001), trunk fat (p = 0.01) and waist circumference (p = 0.05), positive significant interaction between total fat intake and AG genotype on the waist to hip ratio (WHR) (p = 0.02) and visceral fat level (p = 0.05), positive borderline significant interaction between saturated fatty acid and AA genotype on the trunk fat (p = 0.06), and between trans-fatty acids and AG genotype on WHR (p = 0.04), visceral fat level (p = 0.01), and between monounsaturated fatty acid and AG genotype on WHR (p = 0.04), and a borderline interaction between polyunsaturated fatty acid and AA genotypes on visceral fat level (p = 0.06), negative significant interaction between AG genotypes and linolenic acid on WHR (p = 0.04), borderline significant interaction between ALA and AG genotype on WHR (p = 0.06).

CONCLUSIONS

Our findings showed that CAV-1 rs 3807992 polymorphism and dietary fats were associated with fat distributions in individuals.

Prevention of NAFLD-associated HCC: Role of lifestyle and chemoprevention

In many countries worldwide, the burden of hepatocellular carcinoma (HCC) associated with non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) is increasing. Preventive strategies are needed to counteract this trend. In this review, we provide an overview of the evidence on preventive strategies in NAFLD-associated HCC. We consider the impact of lifestyle factors such as weight loss, physical activity, smoking, dietary patterns and food items, including coffee and alcohol, on both HCC and NAFLD/NASH. Furthermore, evidence on chemopreventive treatments, including aspirin, antidiabetic treatments and statins is summarised. The role of adjuvant therapies for tertiary prevention of HCC is briefly reviewed.

Dietary carbohydrates and fats in nonalcoholic fatty liver disease

The global prevalence of nonalcoholic fatty liver disease (NAFLD) has dramatically increased in parallel with the epidemic of obesity. Controversy has emerged around dietary guidelines recommending low-fat-high-carbohydrate diets and the roles of dietary macronutrients in the pathogenesis of metabolic disease. In this Review, the topical questions of whether and how dietary fats and carbohydrates, including free sugars, differentially influence the accumulation of liver fat (specifically, intrahepatic triglyceride (IHTG) content) are addressed. Focusing on evidence from humans, we examine data from stable isotope studies elucidating how macronutrients regulate IHTG synthesis and disposal, alter pools of bioactive lipids and influence insulin sensitivity. In addition, we review cross-sectional studies on dietary habits of patients with NAFLD and randomized controlled trials on the effects of altering dietary macronutrients on IHTG. Perhaps surprisingly, evidence to date shows no differential effects between free sugars, with both glucose and fructose increasing IHTG in the context of excess energy. Moreover, saturated fat raises IHTG more than polyunsaturated or monounsaturated fats, with adverse effects on insulin sensitivity, which are probably mediated in part by increased ceramide synthesis. Taken together, the data support the use of diets that have a reduced content of free sugars, refined carbohydrates and saturated fat in the treatment of NAFLD.

Partial Replacement of Dietary Fat with Polyunsaturated Fatty Acids Attenuates the Lipopolysaccharide-Induced Hepatic Inflammation in Sprague-Dawley Rats Fed a High-Fat Diet

In this study, we investigated whether the partial replacement of dietary fat with polyunsaturated fatty acids (PUFAs) ameliorated the lipopolysaccharide (LPS)-induced hepatic inflammation in rats fed a high-fat diet. Male Sprague-Dawley rats were divided into three groups and provided each of the following diets: (1) high-fat diet (HFD), (2) HFD with perilla oil (PO), and (3) HFD with corn oil (CO). After 12 weeks of dietary intervention, the rats were intraperitoneally injected with LPS (5 mg/kg) from Escherichia coli O55:B5 or phosphate-buffered saline (PBS). Following LPS stimulation, serum insulin levels were increased, while PO and CO lowered the serum levels of glucose and insulin. In the liver, LPS increased the triglyceride levels, while PO and CO alleviated the LPS-induced hepatic triglyceride accumulation. In the LPS injected rats, the mRNA expression of genes related to inflammation and endoplasmic reticulum (ER) stress was attenuated by PO and CO in the liver. Furthermore, hepatic levels of proteins involved in the nuclear factor kappa-light-chain-enhancer of activated B cells/mitogen-activated protein kinase pathways, antioxidant response, and ER stress were lowered by PO- and CO-replacement. Therefore, the partial replacement of dietary fat with PUFAs alleviates LPS-induced hepatic inflammation during HFD consumption, which may decrease metabolic abnormalities.

Diet and Liver Adiposity in Older Adults: The Multiethnic Cohort Adiposity Phenotype Study

BACKGROUND

Diet plays a key role in the pathogenesis of nonalcoholic fatty liver disease. Limited data exist regarding specific nutrients and food groups and liver fat continuously, particularly among different ethnicities.

OBJECTIVES

We aimed to determine the relationship between usual dietary intake and accurately measured liver fat content in a multiethnic population.

METHODS

Participants from the Multiethnic Cohort were recruited into the cross-sectional Adiposity Phenotype Study including women and men aged 60-77 y and 5 race/ethnic groups (African American, Japanese American, Latino, Native Hawaiian, and white). They filled out a detailed FFQ and underwent abdominal MRI for liver fat quantification and whole-body DXA for total adiposity. Intake of a priori-selected dietary factors (total and macronutrient energy, specific micronutrients, and food groups) was analyzed in relation to liver fat by estimating the mean percentage liver fat for quartiles of each dietary factor in a general linear model that adjusted for age, sex, race/ethnicity, percentage body fat, and daily energy intake (kcal/d).

RESULTS

In total, 1682 participants (mean age: 69.2 y; 51% female) were included. Mean ± SD liver fat percentage was 5.7 ± 4.6. A significant positive association with liver fat was found across quartiles of percentage energy from fat, saturated fat, cholesterol, total red meat, red meat excluding processed red meat, and coffee (Bonferroni-adjusted P-trend < 0.05). A significant inverse association was observed for dietary fiber, vitamin C, and vitamin E (Bonferroni-adjusted P-trend < 0.05).

CONCLUSIONS

This study of ethnically diverse older adults shows that certain dietary factors, in particular red meat and saturated fat from red meat, were strongly associated with liver fat, whereas dietary fiber was inversely associated with liver fat, replicating some of the previous studies conducted mostly in whites.

Overfeeding Saturated Fat Increases LDL (Low-Density Lipoprotein) Aggregation Susceptibility While Overfeeding Unsaturated Fat Decreases Proteoglycan-Binding of Lipoproteins

Supplemental Digital Content is available in the text.

Objective:

We recently showed that measurement of the susceptibility of LDL (low-density lipoprotein) to aggregation is an independent predictor of cardiovascular events. We now wished to compare effects of overfeeding different dietary macronutrients on LDL aggregation, proteoglycan-binding of plasma lipoproteins, and on the concentration of oxidized LDL in plasma, 3 in vitro parameters consistent with increased atherogenicity.

Approach and Results:

The participants (36 subjects; age, 48±10 years; body mass index, 30.9±6.2 kg/m²) were randomized to consume an extra 1000 kcal/day of either unsaturated fat, saturated fat, or simple sugars (CARB) for 3 weeks. We measured plasma proatherogenic properties (susceptibility of LDL to aggregation, proteoglycan-binding, oxidized LDL) and concentrations and composition of plasma lipoproteins using nuclear magnetic resonance spectroscopy, and in LDL using liquid chromatography mass spectrometry, before and after the overfeeding diets. LDL aggregation increased in the saturated fat but not the other groups. This change was associated with increased sphingolipid and saturated triacylglycerols in LDL and in plasma and reduction of clusterin on LDL particles. Proteoglycan binding of plasma lipoproteins decreased in the unsaturated fat group relative to the baseline diet. Lipoprotein properties remained unchanged in the CARB group.

Conclusions:

The type of fat during 3 weeks of overfeeding is an important determinant of the characteristics and functional properties of plasma lipoproteins in humans.

Registration:

URL: http://www.clinicaltrials.gov; Unique identifier NCT02133144.

Nonalcoholic fatty liver disease (NAFLD) from pathogenesis to treatment concepts in humans

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) comprises hepatic alterations with increased lipid accumulation (steatosis) without or with inflammation (nonalcoholic steatohepatitis, NASH) and/or fibrosis in the absence of other causes of liver disease. NAFLD is developing as a burgeoning health challenge, mainly due to the worldwide obesity and diabetes epidemics.

SCOPE OF REVIEW

This review summarizes the knowledge on the pathogenesis underlying NAFLD by focusing on studies in humans and on hypercaloric nutrition, including effects of saturated fat and fructose, as well as adipose tissue dysfunction, leading to hepatic lipotoxicity, abnormal mitochondrial function, and oxidative stress, and highlights intestinal dysbiosis. These mechanisms are discussed in the context of current treatments targeting metabolic pathways and the results of related clinical trials.

MAJOR CONCLUSIONS

Recent studies have provided evidence that certain conditions, for example, the severe insulin-resistant diabetes (SIRD) subgroup (cluster) and the presence of an increasing number of gene variants, seem to predispose for excessive risk of NAFLD and its accelerated progression. Recent clinical trials have been frequently unsuccessful in halting or preventing NAFLD progression, perhaps partly due to including unselected cohorts in later stages of NAFLD. On the basis of this literature review, this study proposed screening in individuals with the highest genetic or acquired risk of disease progression, for example, the SIRD subgroup, and developing treatment concepts targeting the earliest pathophysiolgical alterations, namely, adipocyte dysfunction and insulin resistance.

Effect of Healing Meditation on stress and eating behavior in overweight and obese women: A randomized clinical trial

BACKGROUND

A randomized, parallel-controlled, blinded clinical trial was conducted to evaluate the effect of Healing Meditation on stress and eating behavior of women undergoing standard weight-loss treatment.

MATERIALS AND METHODS

An outpatient clinic in Brazil, 55 women with overweight and obesity were included and randomized: 27 for the Meditation Group, and 28 for the Control Group. Randomization was stratified by body mass index category and based on blocks of four. For eight weeks, in addition to the standard weight loss treatment, the Intervention Group underwent a Healing Meditation program, and the Control Group participated in a round table to observe compliance. Reduction in stress and changes in eating behavior were assessed at baseline, and in the 8th, and 16th week using the Perceived Stress Scale, the Dutch Eating Behavior Questionnaire, and Binge Eating Scale.

RESULTS

The sample mean age was 49 ± 11 years, 72.7% were obese, with a predominance of mixed (49.1%) and black (41.8%) ethnicity. After eight weeks, the Meditation Group showed a mean reduction in total stress of -17.4 (IC 95% -19.5 to -15.3 p < 0.001). In eating behavior, a mean reduction of -7.9 (p < 0.001) in external eating, of -11.4 (p < 0.0001) in emotional eating, and a rise of 9.6 (p < 0.0001) in restrained eating were found. Score levels remained stable between the 8th and 16th week. Binge eating had a mean variation of -22.2%(p = 0.011).

CONCLUSION

The addition of Healing Meditation to the standard weight-loss treatment may significantly reduce stress and produce positive changes in the eating behavior of overweight and obese women.

TRIAL REGISTRATION

RBR-7564FD.

Associations between fatty acid composition in serum cholesteryl esters and liver fat, basal fat oxidation, and resting energy expenditure: a population-based study

BACKGROUND

We have repeatedly shown in short-term feeding trials that a high intake of dietary n-6 PUFAs, i.e. linoleic acid, prevents liver fat accumulation compared with saturated fat. However, population-based data is lacking and the mechanisms behind such effects are unclear.

OBJECTIVE

To investigate associations between serum cholesteryl ester (CE) fatty acids and liver fat, basal fat oxidation [respiratory quotient (RQ)], and resting energy expenditure (REE). We hypothesized that PUFA in particular is inversely associated with liver fat and that such a relation is partly explained by a PUFA-induced increase in basal fat oxidation or REE.

METHODS

Cross-sectional analyses using linear regression models in a population-based cohort with data on serum CE fatty acid composition and liver fat (n = 308).

RESULTS

Linoleic acid (18:2n-6) (β = -0.03, 95% CI: -0.06, -0.001) and Δ5 desaturase index were inversely associated, whereas, γ-linolenic acid (18:3n-6) (β = 0.59, 95% CI: 0.28, 0.90), dihomo-γ-linolenic acid (20:3n-6) (β = 1.20, 95% CI: 0.65, 1.75), arachidonic acid (20:4n-6) (β = 0.08, 95% CI: 0.002, 0.16), palmitoleic acid (16:1n-7) (β = 0.37, 95% CI: 0.04, 0.70), Δ6 desaturase, and stearoyl CoA desaturase-1 (SCD-1) index were directly associated with liver fat after adjustment for confounders. Several serum CE fatty acids were correlated with both liver fat and REE, but only the association between DHA (22:6n-3) and liver fat was clearly attenuated after adjustment for REE (from β = -0.63 95% CI: -1.24, -0.02 to β = -0.34, 95% CI: -0.95, 0.27). Palmitoleic acid and SCD-1 were weakly inversely correlated with RQ but could not explain a lower liver fat content.

CONCLUSIONS

Several serum CE fatty acids are associated with liver fat, among them linoleic acid. Although we identified novel associations between individual fatty acids and RQ and REE, our findings imply that PUFAs might prevent liver fat accumulation through mechanisms other than enhanced whole-body energy metabolism.

Carob Pulp: A Nutritional and Functional By-Product Worldwide Spread in the Formulation of Different Food Products and Beverages. A Review

Carob (Ceratonia siliqua L.) pod is a characteristic fruit from the Mediterranean regions. It is composed by seeds, the valuable part due to the extraction of locust bean gum, and the pulp, considered a by-product of the fruit processing industry. Carob pulp is a mixture of macro- and micronutrients, such as carbohydrates, vitamins and minerals, and secondary metabolites with functional properties. In the last few years, numerous studies on the chemical and biological characteristics of the pulp have been performed to encourage its commercial use. Its potential applications as a nutraceutical ingredient in many recipes for food and beverage elaborations have been extensively evaluated. Another aspect highlighted in this work is the use of alternative processes or conditions to mitigate furanic production, recognized for its toxicity. Furthermore, carob pulp’s similar sensorial, chemical and biological properties to cocoa, the absence of the stimulating alkaloids theobromine and caffeine, as well as its low-fat content, make it a healthier potential substitute for cocoa. This paper reviews the nutritional and functional values of carob pulp-based products in order to provide information on the proclaimed health-promoting properties of this interesting by-product.

Efficacy of Dietary Manipulations for Depleting Intrahepatic Triglyceride Content: Implications for the Management of Non-alcoholic Fatty Liver Disease

PURPOSE OF REVIEW

Understanding the effects of dietary manipulations on intrahepatic triglyceride (IHTG) balance will have important implications for the prevention and treatment of non-alcoholic fatty liver disease (NAFLD).

RECENT FINDINGS

Reducing calorie intake to induce weight loss is the most potent intervention to decrease IHTG. Carbohydrate restriction during the initial stages of weight loss may be particularly beneficial, but at later stages, the amount of weight loss predominates over diet composition. By contrast, during weight stability, restricting calories from fat seems to be optimal for depleting liver fat. The degree of dietary fat saturation and the glycemic index of the carbohydrate have inconsistent effects on IHTG. Recently, the matrix of some foods (e.g., dairy) has been inversely associated with NAFLD. Dietary macronutrients differ in their effects on liver fat depending on the energy balance and the matrix of the food in which they are consumed. Therefore, investigations into dietary approaches for managing NAFLD should shift their perspective from that of isolated nutrients to that of whole foods and diets and include useful mechanistic insights.

Chronic n-3 fatty acid intake enhances insulin response to oral glucose and elevates GLP-1 in high-fat diet-fed obese mice

n-3 polyunsaturated fatty acids (PUFA) can exert beneficial effects on glucose homeostasis, especially in obese rodents. Gut incretin hormones regulate glucose and lipid homeostasis, but their involvement in the above effects is not entirely clear. This study aims to assess the effects of chronic n-3 PUFA administration on the insulin and incretin responses in C57BL/6N obese male mice subjected to oral glucose tolerance test (oGTT) after 8 weeks of feeding a corn-oil-based high-fat diet (cHF). The weight gain and adiposity were partially reduced in mice fed cHF in which some of the corn oil was replaced with n-3 PUFA concentrate containing ∼60% DHA and EPA in a 3 : 1 ratio. In addition, these mice had improved glucose tolerance, which was consistent with an increased insulin response to oral glucose and plasma glucagon-like peptide-1 (GLP-1) levels. While the stimulatory effects of n-3 PUFA on GLP-1 levels could not be attributed to changes in intestinal or plasma dipeptidyl peptidase-4 activity, their beneficial effects on glucose tolerance were abolished when mice were pretreated with the GLP-1 receptor antagonist exendin 9-39. Moreover, chronic n-3 PUFA intake prevented the detrimental effects of cHF feeding on glucose-stimulated insulin secretion in the pancreatic islets. Collectively, our data suggest that n-3 PUFA may modulate postprandial glucose metabolism in obese mice through a GLP-1-based mechanism. The significance of these findings in terms of the effective DHA and EPA ratio of the n-3 PUFA concentrate as well as the effect of n-3 PUFA in humans requires further research.

Effects of Three-Month Administration of High-Saturated Fat Diet and High-Polyunsaturated Fat Diets with Different Linoleic Acid (LA, C18:2n-6) to α-Linolenic Acid (ALA, C18:3n-3) Ratio on the Mouse Liver Proteome

The aim of the study was to evaluate the effect of different types of high-fat diets (HFDs) on the proteomic profile of mouse liver. The analysis included four dietary groups of mice fed a standard diet (STD group), a high-fat diet rich in SFAs (SFA group), and high-fat diets dominated by PUFAs with linoleic acid (LA, C18:2n-6) to α-linolenic acid (ALA, C18:3n-3) ratios of 14:1 (14:1 group) and 5:1 (5:1 group). After three months of diets, liver proteins were resolved by two-dimensional gel electrophoresis (2DE) using 17 cm non-linear 3-10 pH gradient strips. Protein spots with different expression were identified by MALDI-TOF/TOF. The expression of 13 liver proteins was changed in the SFA group compared to the STD group (↓: ALB, APOA1, IVD, MAT1A, OAT and PHB; ↑: ALDH1L1, UniProtKB-Q91V76, GALK1, GPD1, HMGCS2, KHK and TKFC). Eleven proteins with altered expression were recorded in the 14:1 group compared to the SFA group (↓: ARG1, FTL1, GPD1, HGD, HMGCS2 and MAT1A; ↑: APOA1, CA3, GLO1, HDHD3 and IVD). The expression of 11 proteins was altered in the 5:1 group compared to the SFA group (↓: ATP5F1B, FTL1, GALK1, HGD, HSPA9, HSPD1, PC and TKFC; ↑: ACAT2, CA3 and GSTP1). High-PUFA diets significantly affected the expression of proteins involved in, e.g., carbohydrate metabolism, and had varying effects on plasma total cholesterol and glucose levels. The outcomes of this study revealed crucial liver proteins affected by different high-fat diets.

Dietary Interventions in Liver Diseases: Focus on MAFLD and Cirrhosis

Purpose of Review

Dietary interventions (DI) aimed at improving overweight and metabolic abnormalities in metabolic dysfunction-associated fatty liver disease (MAFLD) and at reducing malnutrition and sarcopenia in cirrhosis should become part of routine care in hepatology. This review focuses on recent advances in this field.

Recent Findings

In patients with MAFLD, a gradual reduction, respectively, of 7–10% of body weight if overweight or of 3–5% if lean, obtained by moderately reducing caloric intake, is effective to improve liver disease. Intermittent energy restriction might be an alternative to continuous energy restriction with higher adherence. Qualitative dietary adjustments should include increased intake of unprocessed foods including fruits and vegetables, whole grains, fiber, and unsaturated fatty acids (FAs), for example, through a Mediterranean diet. Refined carbohydrates (CHOs), saturated FA (SFAs), red meat, and processed meat should be limited. DI studies in HIV-infected subjects with MAFLD are very limited, and this is a field for future research. In patients with cirrhosis, DI should aim at correcting malnutrition and improving skeletal muscle mass. Daily diet contents should aim at achieving 30–35 kcal/kg of body weight, including 1.2–1.5 g/kg proteins, and oral or enteral supplementation might be used in patients unable to achieve these targets. In some studies, branched-chain amino acids (BCAAs) proved to be effective in improving muscle mass and were associated with a lower risk of hepatic encephalopathy. Obesity requires adjustment of the above-mentioned targets, and its management is challenging. Studies looking at the efficacy of DI recommended by the existing guidelines on clinical endpoints are a field for future research.

Summary

Dietary interventions are able to improve MAFLD and show potential to reduce complications in liver disease. Despite its key importance, there are many barriers limiting the implementation of DI in patients with chronic liver disease. Patients’ empowerment is crucial and should be the focus of specific educational programs. In addition, liver clinics would benefit from multidisciplinary teams involving experts in nutrition, physical exercise, primary care physicians, and psychologists when needed.

Direct and indirect control of hepatic glucose production by insulin

There is general agreement that the acute suppression of hepatic glucose production by insulin is mediated by both a direct and an indirect effect on the liver. There is, however, no consensus regarding the relative magnitude of these effects under physiological conditions. Extensive research over the past three decades in humans and animal models has provided discordant results between these two modes of insulin action. Here, we review the field to make the case that physiologically direct hepatic insulin action dominates acute suppression of glucose production, but that there is also a delayed, second order regulation of this process via extrahepatic effects. We further provide our views regarding the timing, dominance, and physiological relevance of these effects and discuss novel concepts regarding insulin regulation of adipose tissue fatty acid metabolism and central nervous system (CNS) signaling to the liver, as regulators of insulin's extrahepatic effects on glucose production.

100th anniversary of the discovery of insulin perspective: insulin and adipose tissue fatty acid metabolism

Insulin inhibits systemic nonesterified fatty acid (NEFA) flux to a greater degree than glucose or any other metabolite. This remarkable effect is mainly due to insulin-mediated inhibition of intracellular triglyceride (TG) lipolysis in adipose tissues and is essential to prevent diabetic ketoacidosis, but also to limit the potential lipotoxic effects of NEFA in lean tissues that contribute to the development of diabetes complications. Insulin also regulates adipose tissue fatty acid esterification, glycerol and TG synthesis, lipogenesis, and possibly oxidation, contributing to the trapping of dietary fatty acids in the postprandial state. Excess NEFA flux at a given insulin level has been used to define in vivo adipose tissue insulin resistance. Adipose tissue insulin resistance defined in this fashion has been associated with several dysmetabolic features and complications of diabetes, but the mechanistic significance of this concept is not fully understood. This review focusses on the in vivo regulation of adipose tissue fatty acid metabolism by insulin and the mechanistic significance of the current definition of adipose tissue insulin resistance. One hundred years after the discovery of insulin and despite decades of investigations, much is still to be understood about the multifaceted in vivo actions of this hormone on adipose tissue fatty acid metabolism.

Plasma ω-3 and ω-6 PUFA Concentrations and Risk of Atrial Fibrillation: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Current literature examining the prospective relation of circulating omega-3 (n-3) and omega-6 (n-6) PUFAs and atrial fibrillation (AF) is limited to predominantly white populations.

OBJECTIVES

We investigated the association of circulating n-3 and n-6 PUFAs with incident AF in participants from the Multi-Ethnic Study of Atherosclerosis.

METHODS

A total of 6229 participants (mean age = 62 y; 53% female; 39% white, 27% black, 22% Hispanic, and 12% Chinese) who were free of baseline AF and with plasma phospholipid PUFAs measured at baseline using GC were prospectively followed for the development of AF. Incident AF was ascertained using International Classification of Diseases-9 codes from hospital discharge records and Medicare claims data with follow-up through 2014. Multivariable Cox proportional hazards regression analysis was performed to determine the risk of incident AF.

RESULTS

During a median follow-up of 12.9 y, 813 (13%) participants developed AF. Each higher SD increment in arachidonic acid (AA; 20:4n-6) concentrations was associated with an 11% decreased risk of incident AF (HR: 0.89; 95% CI: 0.82, 0.96). Similarly, higher overall n-6 PUFA concentrations were also associated with a reduced AF risk (HR per SD increment: 0.93; 95% CI: 0.87, 1.00). Although no significant overall associations were observed for any individual n-3 PUFAs, higher circulating concentrations of DHA (22:6n-3) and EPA (20:5n-3) were associated with a decreased AF risk in blacks and Hispanics (DHA only) but not whites or Chinese Americans.

CONCLUSIONS

In a multiethnic cohort of individuals free of baseline cardiovascular disease, higher plasma concentrations of n-6 PUFAs, particularly AA, were associated with a reduced risk of incident AF. Important differences in AF risk were also noted across race/ethnicity for the n-3 PUFAs DHA and EPA.

Polyunsaturated fatty acids as modulators of fat mass and lean mass in human body composition regulation and cardiometabolic health

It is now recognized that the amount and type of dietary fat consumed play an important role in metabolic health. In humans, high intake of polyunsaturated fatty acids (PUFAs) has been associated with reductions in cardiovascular disease risk, improvements in glucose homeostasis, and changes in body composition that involve reductions in central adiposity and, more recently, increases in lean body mass. There is also emerging evidence, which suggests that high intakes of the plant-based essential fatty acids (ePUFAs)-n-6 linoleic acid (LA) and n-3 α-linolenic acid (ALA)-have a greater impact on body composition (fat mass and lean mass) and on glucose homeostasis than the marine-derived long-chain n-3 PUFA-eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In addition, high intake of both ePUFAs (LA and ALA) may also have anti-inflammatory effects in humans. The purpose of this review is to highlight the emerging evidence, from both epidemiological prospective studies and clinical intervention trials, of a role for PUFA, in particular ePUFA, in the long-term regulation of body weight and body composition, and their impact on cardiometabolic health. It also discusses current notions about the mechanisms by which PUFAs modulate fat mass and lean mass through altered control of energy intake, thermogenesis, or lean-fat partitioning.

Comparison of Osmotic Resistance, Shape and Transmembrane Potential of Erythrocytes Collected from Healthy and Fed with High Fat-Carbohydrates Diet (HF-CD) Pigs-Protective Effect of Cistus incanus L. Extracts

Long-term high fat-carbohydrates diet (HF-CD) contributes to the formation of irreversible changes in the organism that lead to the emergence of civilization diseases. In this study, the impact of three-month high-fat diet on the physical properties of erythrocytes (RBCs) was studied. Furthermore, the biological activity of Cistus incanus L. extracts, plant known with high pro-health potential, in relation to normal and HF-CD RBCs, was determined. Obtained results have shown that, applied HF-CD modified shape, membrane potential and osmotic resistance of erythrocytes causing changes in membrane lipid composition and the distribution of lipids. The impact of HF-CD on physical properties of RBCs along with atherosclerotic lesions of the artery was visible, despite the lack of statistically significant changes in blood morphology and plasma lipid profile. This suggests that erythrocytes may be good markers of obesity-related diseases. The studies of biological activity of Cistus incanus L. extracts have demonstrated that they may ameliorate the effect of HF-CD on erythrocytes through the membrane-modifying and antioxidant activity.

Treatment of NAFLD with intermittent calorie restriction or low-carb high-fat diet - a randomised controlled trial

Background & Aims

The first-line treatment for non-alcoholic fatty liver disease (NAFLD) is weight reduction. Several diets have been proposed, with various effects specifically on liver steatosis. This trial compared the effects of intermittent calorie restriction (the 5:2 diet) and a low-carb high-fat diet (LCHF) on reduction of hepatic steatosis.

Methods

We conducted an open-label randomised controlled trial that included 74 patients with NAFLD randomised in a 1:1:1 ratio to 12 weeks' treatment with either a LCHF or 5:2 diet, or general lifestyle advice from a hepatologist (standard of care; SoC). The primary outcome was reduction of hepatic steatosis as measured by magnetic resonance spectroscopy. Secondary outcomes included transient elastography, insulin resistance, blood lipids, and anthropometrics.

Results

The LCHF and 5:2 diets were both superior to SoC treatment in reducing steatosis (absolute reduction: LCHF: -7.2% [95% CI = -9.3 to -5.1], 5:2: -6.1% [95% CI = -8.1 to -4.2], SoC: -3.6% [95% CI = -5.8 to -1.5]) and body weight (LCHF: -7.3 kg [95% CI = -9.6 to -5.0]; 5:2: -7.4 kg [95% CI = -8.7 to -6.0]; SoC: -2.5 kg [95% CI =-3.5 to -1.5]. There was no difference between 5:2 and LCHF (p = 0.41 for steatosis and 0.78 for weight). Liver stiffness improved in the 5:2 and SoC but not in the LCHF group. The 5:2 diet was associated with reduced LDL levels and was tolerated to a higher degree than LCHF.

Conclusions

The LCHF and 5:2 diets were more effective in reducing steatosis and body weight in patients with NAFLD than SoC, suggesting dietary advice can be tailored to meet individual preferences.

Lay summary

For a person with obesity who suffers from fatty liver, weight loss through diet can be an effective treatment to improve the condition of the liver. Many popular diets that are recommended for weight reduction, such as high-fat diets and diets based on intermittent fasting, have not had their effects on the liver directly evaluated. This study shows that both a low-carb high-fat and the 5:2 diet are effective in treating fatty liver caused by obesity.

Clinical Trials Registration

This study is registered at Clinicaltrials.gov (NCT03118310).

The Impact of Macronutrient Intake on Non-alcoholic Fatty Liver Disease (NAFLD): Too Much Fat, Too Much Carbohydrate, or Just Too Many Calories?

Non-alcoholic fatty liver disease (NAFLD) is a growing epidemic, in parallel with the obesity crisis, rapidly becoming one of the commonest causes of chronic liver disease worldwide. Diet and physical activity are important determinants of liver fat accumulation related to insulin resistance, dysfunctional adipose tissue, and secondary impaired lipid storage and/or increased lipolysis. While it is evident that a hypercaloric diet (an overconsumption of calories) promotes liver fat accumulation, it is also clear that the macronutrient composition can modulate this risk. A number of other baseline factors modify the overfeeding response, which may be genetic or environmental. Although it is difficult to disentangle the effects of excess calories vs. specifically the individual effects of excessive carbohydrates and/or fats, isocaloric, and hypercaloric dietary intervention studies have been implemented to provide insight into the effects of different macronutrients, sub-types and their relative balance, on the regulation of liver fat. What has emerged is that different types of fat and carbohydrates differentially influence liver fat accumulation, even when diets are isocaloric. Furthermore, distinct molecular and metabolic pathways mediate the effects of carbohydrates and fat intake on hepatic steatosis. Fat accumulation appears to act through impairments in lipid storage and/or increased lipolysis, whereas carbohydrate consumption has been shown to promote liver fat accumulation through de novo lipogenesis. Effects differ dependent upon carbohydrate and fat type. Saturated fat and fructose induce the greatest increase in intrahepatic triglycerides (IHTG), insulin resistance, and harmful ceramides compared with unsaturated fats, which have been found to be protective. Decreased intake of saturated fats and avoidance of added sugars are therefore the two most important dietary interventions that can lead to a reduction in IHTG and potentially the associated risk of developing type 2 diabetes. A healthy and balanced diet and regular physical activity must remain the cornerstones of effective lifestyle intervention to prevent the development and progression of NAFLD. Considering the sub-type of each macronutrient, in addition to the quantity, are critical determinants of liver health.

A Priori and a Posteriori Dietary Patterns among Pregnant Women in Johannesburg, South Africa: The NuPED Study

Dietary pattern analyses allow assessment of the diet as a whole. Limited studies include both a priori and a posteriori dietary pattern analyses. This study aimed to explore the diet of pregnant women in urban South Africa through both a priori and a posteriori dietary pattern analyses and associated maternal and household factors. Dietary data were collected during early pregnancy using a quantified food frequency questionnaire from 250 pregnant women enrolled in the Nutrition During Pregnancy and Early Development (NuPED) cohort. A priori dietary patterns were determined using the Diet Quality Index-International (DQI-I), and a posteriori nutrient patterns using exploratory factor analysis. Based on the DQI-I, the study population followed a borderline low-quality diet. Three a posteriori nutrient patterns were identified: Pattern 1 “plant protein, iron, thiamine, and folic acid”; pattern 2 “animal protein, copper, vitamin A, and vitamin B₁₂”; pattern 3 “fatty acids and sodium”. Pattern 1 was associated with higher dietary quality (p < 0.001), lower maternal educational level (p = 0.03) and socioeconomic status (p < 0.001). Pattern 3 was significantly associated with lower dietary quality. The low dietary quality among pregnant women residing in urban South Africa should be addressed to ensure optimal maternal and offspring health outcomes.

Eucaloric diets enriched in palm olein, cocoa butter, and soybean oil did not differentially affect liver fat concentration in healthy participants: a 16-week randomized controlled trial

BACKGROUND

Effects of dietary fat quality on liver fat remain to be elucidated. Inconsistent evidence may be influenced by fatty acid saturation, chain-length, and regio-specificity within triacylglycerol (TAG) molecules.

OBJECTIVES

We aimed to compare eucaloric diets enriched in palm olein (POo), cocoa butter (COB), and soybean oil (SBO) on liver fat concentration in healthy participants. Secondary outcomes included visceral (VAT) and abdominal subcutaneous (aSCAT) adipose tissue, plus other obesity and cardiometabolic health outcomes.

METHODS

Eighty-three healthy participants (20-45 y, BMI 18.5-27.5 kg/m2) commenced and 64 completed a 16-wk randomized parallel intervention, preceded by a 2-wk run-in. Participants consumed identical eucaloric background diets differing in test fats [contributing 20% total energy intake (%E)], providing 33%E total fat with the following ratios for PUFAs/SFAs/MUFAs: POo, 4.2/13.5/15%E; SBO, 14.4/8.8/9.4%E; COB, 2.3/19.5/11%E. Liver fat and abdominal adiposity were measured at weeks 0 and 16 using 1H-magnetic resonance spectroscopy/imaging; all other outcomes were measured at 0, 4, 8, 12, and 16 wk.

RESULTS

Fat quality did not affect liver fat concentration, VAT, aSCAT, obesity indexes, blood pressure, liver enzymes, leptin, or fasting glucose. Body fat mass decreased with SBO and COB compared with POo. SBO decreased serum total cholesterol (TC), LDL cholesterol, and TC:HDL cholesterol relative to POo [estimated marginal mean (95% CI) differences: -0.57 (-0.94, -0.20) mmol/L; -0.37 (-0.68, -0.07) mmol/L; and -0.42 (-0.73, -0.11) mmol/L, respectively]. No diet differences were observed on HDL cholesterol, TAG, apoA1, apoB, apoB:apoA1, or fecal free fatty acids (FFAs), except for lower FFA pentadecanoic acid (15:0) with COB than with SBO and POo.

CONCLUSIONS

In healthy adults, when consumed as part of eucaloric typical Australian diets, 3 different dietary fat sources did not differentially affect liver fat concentration and amounts of adipose tissue. Effects on serum lipids were inconsistent across lipid profiles. The findings must be confirmed in metabolically impaired individuals before recommendations can be made.

Krill Oil Supplementation Reduces Exacerbated Hepatic Steatosis Induced by Thermoneutral Housing in Mice with Diet-Induced Obesity

Preclinical evidence suggests that n-3 fatty acids EPA and DHA (Omega-3) supplemented as phospholipids (PLs) may be more effective than triacylglycerols (TAGs) in reducing hepatic steatosis. To further test the ability of Omega-3 PLs to alleviate liver steatosis, we used a model of exacerbated non-alcoholic fatty liver disease based on high-fat feeding at thermoneutral temperature. Male C57BL/6N mice were fed for 24 weeks a lard-based diet given either alone (LHF) or supplemented with Omega-3 (30 mg/g diet) as PLs (krill oil; ω3PL) or TAGs (Epax 3000TG concentrate; ω3TG), which had a similar total content of EPA and DHA and their ratio. Substantial levels of TAG accumulation (~250 mg/g) but relatively low inflammation/fibrosis levels were achieved in the livers of control LHF mice. Liver steatosis was reduced by >40% in the ω3PL but not ω3TG group, and plasma ALT levels were markedly reduced (by 68%) in ω3PL mice as well. Krill oil administration also improved hepatic insulin sensitivity, and its effects were associated with high plasma adiponectin levels (150% of LHF mice) along with superior bioavailability of EPA, increased content of alkaloids stachydrine and trigonelline, suppression of lipogenic gene expression, and decreased diacylglycerol levels in the liver. This study reveals that in addition to Omega-3 PLs, other constituents of krill oil, such as alkaloids, may contribute to its strong antisteatotic effects in the liver.

Management of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease is a very common medical condition, driven by a combination of genetic and lifestyle factors, ultimately producing a severe chronic liver disease and increased cardiovascular risk. Most people are asymptomatic for a long time, and their daily life is unaffected, leading to difficulty in identifying and managing people who slowly progress to non-alcoholic steatohepatitis (NASH), NASH-cirrhosis, and eventually hepatocellular carcinoma. Despite advances in the understanding of pathogenic mechanisms and the identification of liver fibrosis as the strongest factor in predicting disease progression, no specific treatments have been approved by regulatory agencies. Outside controlled trials, treatment is generally limited to lifestyle intervention aimed at weight loss. Pioglitazone remains the drug of choice to reduce progression of fibrosis in people with diabetes, although it is often used off-label in the absence of diabetes. Vitamin E is mainly used in children and may be considered in adults without diabetes. Several drugs are under investigation according to the agreed targets of reduced NASH activity without worsening of fibrosis or improving fibrosis without worsening of NASH. Anti-inflammatory, anti-fibrotic agents and metabolism modulators have been tested in either phase III or phase IIb randomized controlled trials; a few failed, and others have produced marginally positive results, but only a few are being tested in extension studies. The development of non-invasive, easily repeatable surrogate biomarkers and/or imaging tools is crucial to facilitate clinical studies and limit liver biopsy.

Mitochondrial Dysfunction is a Key Pathway that Links Saturated Fat Intake to the Development and Progression of NAFLD

Non-Alcoholic fatty liver disease (NAFLD) is the most common form of liver disease and is characterized by fat accumulation in the liver. Hypercaloric diets generally increase hepatic fat accumulation, whereas hypocaloric diets decrease liver fat content. In addition, there is evidence to suggest that moderate amounts of unsaturated fatty acids seems to be protective for the development of a fatty liver, while consumption of saturated fatty acids (SFA) appears to predispose toward hepatic steatosis. Recent studies highlight a key role for mitochondrial dysfunction in the development and progression of NAFLD. It is proposed that changes in mitochondrial structure and function are key mechanisms by which SFA lead to the development and progression of NAFLD. In this review, it is described how SFA intake is associated with liver steatosis and decreases the efficiency of the respiratory transport chain. This results in the production of reactive oxygen species and damage to nearby structures, eventually leading to inflammation, apoptosis, and scarring of the liver. Furthermore, studies demonstrating that SFA intake affects the composition of mitochondrial membranes are presented, and this process accelerates the progression of NAFLD. It is likely that events are intertwined and reinforce each other, leading to a constant deterioration in health.

Fatty Acid Metabolism and Associations with Insulin Sensitivity Differs Between Black and White South African Women

PURPOSE

Genetic differences in desaturase genes and consequently fatty acid metabolism have been reported. The aims were to examine ethnic differences in serum fatty acid composition and desaturase indices, and assess the ethnic-specific associations with insulin sensitivity (IS) and liver fat in black and white South African (SA) women.

METHODS

In this cross-sectional study including 92 premenopausal black (n = 46) and white (n = 46) SA women, serum fatty acid composition was measured in cholesteryl ester (CE) and nonesterified fatty acid (NEFA) fractions. Desaturase activities were estimated as product-to-precursor ratios: stearoyl-CoA desaturase-1 (SCD1-16, 16:1n-7/16:0); δ-5 desaturase (D5D, 20:4n-6/20:3n-6), and δ-6 desaturase (D6D, 18:3n-6/18:2n-6). Whole-body IS was estimated from an oral glucose tolerance test using the Matsuda index. In a subsample (n = 30), liver fat and hepatic IS were measured by 1H-magnetic resonance spectroscopy and hyperinsulinemic euglycemic clamp, respectively.

RESULTS

Despite lower whole-body IS (P = .006), black women had higher CE D5D and lower D6D and SCD1-16 indices than white women (P < .01). CE D6D index was associated with lower IS in white women only (r = -0.31, P = .045), whereas D5D index was associated with higher IS in black women only (r = 0.31, P = .041). In the subsample, D6D and SCD1-16 indices were positively and D5D was negatively associated with liver fat (P < .05). Conversely, CE SCD1-16 was negatively associated with hepatic IS (P < .05), but not independently of liver fat.

CONCLUSIONS

Ethnic differences in fatty acid-derived desaturation indices were observed, with insulin-resistant black SA women paradoxically showing a fatty acid pattern typical for higher insulin sensitivity in European populations.

Oxidative Stress in NAFLD: Role of Nutrients and Food Contaminants

Non-alcoholic fatty liver disease (NAFLD) is often the hepatic expression of metabolic syndrome and its comorbidities that comprise, among others, obesity and insulin-resistance. NAFLD involves a large spectrum of clinical conditions. These range from steatosis, a benign liver disorder characterized by the accumulation of fat in hepatocytes, to non-alcoholic steatohepatitis (NASH), which is characterized by inflammation, hepatocyte damage, and liver fibrosis. NASH can further progress to cirrhosis and hepatocellular carcinoma. The etiology of NAFLD involves both genetic and environmental factors, including an unhealthy lifestyle. Of note, unhealthy eating is clearly associated with NAFLD development and progression to NASH. Both macronutrients (sugars, lipids, proteins) and micronutrients (vitamins, phytoingredients, antioxidants) affect NAFLD pathogenesis. Furthermore, some evidence indicates disruption of metabolic homeostasis by food contaminants, some of which are risk factor candidates in NAFLD. At the molecular level, several models have been proposed for the pathogenesis of NAFLD. Most importantly, oxidative stress and mitochondrial damage have been reported to be causative in NAFLD initiation and progression. The aim of this review is to provide an overview of the contribution of nutrients and food contaminants, especially pesticides, to oxidative stress and how they may influence NAFLD pathogenesis.

Effect of Overeating Dietary Protein at Different Levels on Circulating Lipids and Liver Lipid: The PROOF Study

Background: During overeating, a low protein diet slowed the rate of weight gain and increased the energy cost of the added weight, suggesting that low protein diets reduced energy efficiency. The Protein Overfeeding (PROOF) study explored the metabolic changes to low and high protein diets, and this sub-study examined the changes in body composition and blood lipids when eating high and low protein diets during overeating. Methods: Twenty-three healthy volunteers (M = 14; F = 9) participated in an 8-week, parallel arm study where they were overfed by ~40% with diets containing 5% (LPD = low protein diet), 15% (NPD = normal protein diet), or 25% (HPD = high protein diet) protein. Dual energy X-ray absorptiometry (DXA) and computer tomography (CT) were used to quantify whole body and abdominal fat and intrahepatic lipid, respectively. Metabolites were measured by standard methods. Results: Protein intake and fat intake were inversely related since carbohydrate intake was fixed. Although overeating the LPD diet was associated with a significant increase in high density lipoprotein (HDL)-cholesterol (p < 0.001) and free fatty acids (p = 0.034), and a significant decrease in fat free mass (p < 0.0001) and liver density (p = 0.038), statistical models showed that dietary protein was the main contributor to changes in fat free mass (p = 0.0040), whereas dietary fat was the major predictor of changes in HDL-cholesterol (p = 0.014), free fatty acids (p = 0.0016), and liver fat (p = 0.0007). Conclusions: During 8 weeks of overeating, the level of dietary protein intake was positively related to the change in fat free mass, but not to the change in HDL-cholesterol, free fatty acids, and liver fat which were, in contrast, related to the intake of dietary fat.

Abdominal Fat and Metabolic Health Markers but Not PNPLA3 Genotype Predicts Liver Fat Accumulation in Response to Excess Intake of Energy and Saturated Fat in Healthy Individuals

Background: Saturated fat (SFA) has consistently been shown to increase liver fat, but the response appears variable at the individual level. Phenotypic and genotypic characteristics have been demonstrated to modify the hypercholesterolemic effect of SFA but it is unclear which characteristics that predict liver fat accumulation in response to a hypercaloric diet high in SFA.

Objective: To identify predictors of liver fat accumulation in response to an increased intake of SFA.

Design: We pooled our two previously conducted double-blind randomized trials (LIPOGAIN and LIPOGAIN-2, clinicaltrials.gov NCT01427140 and NCT02211612) and used data from the n = 49 metabolically healthy men (n = 32) and women (n = 17) randomized to a hypercaloric diet through addition of SFA-rich muffins for 7–8 weeks. Associations between clinical and metabolic variables at baseline and changes in liver fat during the intervention were analyzed using Spearman rank correlation. Linear regression was used to generate a prediction model.

Results: Liver fat increased by 33% (IQR 5.4–82.7%; P < 0.0001) in response to excess energy intake and this was not associated (r = 0.17, P = 0.23) with the increase in body weight (1.9 kg; IQR 1.1–2.9 kg). Liver fat accumulation was similar (P = 0.28) in carriers (33%, IQR 14–79%) and non-carriers (33%, IQR −11 to +87%) of the PNPLA3-I148M variant. Baseline visceral and liver fat content, as well as levels of the liver enzyme γ-glutamyl transferase (GT), were the strongest positive predictors of liver fat accumulation—in contrast, adiponectin and the fatty acid 17:0 in adipose tissue were the only negative predictors in univariate analyses. A regression model based on eight clinical and metabolic variables could explain 81% of the variation in liver fat accumulation.

Conclusion: Our results suggest there exists a highly inter-individual variation in the accumulation of liver fat in metabolically healthy men and women, in response to an increased energy intake from SFA and carbohydrates that occurs over circa 2 months. This marked variability in liver fat accumulation could largely be predicted by a set of clinical (e.g., GT and BMI) and metabolic (e.g., fatty acids, HOMA-IR, and adiponectin) variables assessed at baseline.

Do Lower-Carbohydrate Diets Increase Total Energy Expenditure? An Updated and Reanalyzed Meta-Analysis of 29 Controlled-Feeding Studies

BACKGROUND

The effect of macronutrient composition on total energy expenditure (TEE) remains controversial, with divergent findings among studies. One source of heterogeneity may be study duration, as physiological adaptation to lower carbohydrate intake may require 2 to 3 wk.

OBJECTIVE

We tested the hypothesis that the effects of carbohydrate [expressed as % of energy intake (EI)] on TEE vary with time.

METHODS

The sample included trials from a previous meta-analysis and new trials identified in a PubMed search through 9 March 2020 comparing lower- and higher-carbohydrate diets, controlled for EI or body weight. Three reviewers independently extracted data and reconciled discrepancies. Effects on TEE were pooled using inverse-variance-weighted meta-analysis, with between-study heterogeneity assessed using the I2 statistic. Meta-regression was used to quantify the influence of study duration, dichotomized at 2.5 wk.

RESULTS

The 29 trials ranged in duration from 1 to 140 d (median: 4 d) and included 617 participants. Difference in carbohydrate between intervention arms ranged from 8% to 77% EI (median: 30%). Compared with reported findings in the prior analysis (I2 = 32.2%), we found greater heterogeneity (I2 = 90.9% in the reanalysis, 81.6% in the updated analysis). Study duration modified the diet effect on TEE (P < 0.001). Among 23 shorter trials, TEE was reduced on lower-carbohydrate diets (-50.0 kcal/d; 95% CI: -77.4, -22.6 kcal/d) with substantial heterogeneity (I2 = 69.8). Among 6 longer trials, TEE was increased on low-carbohydrate diets (135.4 kcal/d; 95% CI: 72.0, 198.7 kcal/d) with low heterogeneity (I2 = 26.4). Expressed per 10% decrease in carbohydrate as %EI, the TEE effects in shorter and longer trials were -14.5 kcal/d and 50.4 kcal/d, respectively. Findings were materially unchanged in sensitivity analyses.

CONCLUSIONS

Lower-carbohydrate diets transiently reduce TEE, with a larger increase after ∼2.5 wk. These findings highlight the importance of longer trials to understand chronic macronutrient effects and suggest a mechanism whereby lower-carbohydrate diets may facilitate weight loss.

Nutrients, Genetic Factors, and Their Interaction in Non-Alcoholic Fatty Liver Disease and Cardiovascular Disease

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in Western countries and expose patients to increased risk of hepatic and cardiovascular (CV) morbidity and mortality. Both environmental factors and genetic predisposition contribute to the risk. An inappropriate diet, rich in refined carbohydrates, especially fructose, and saturated fats, and poor in fibers, polyunsaturated fats, and vitamins is one of the main key factors, as well as the polymorphism of patatin-like phospholipase domain containing 3 (PNPLA3 gene) for NAFLD and the apolipoproteins and the peroxisome proliferator-activated receptor (PPAR) family for the cardiovascular damage. Beyond genetic influence, also epigenetics modifications are responsible for various clinical manifestations of both hepatic and CV disease. Interestingly, data are accumulating on the interplay between diet and genetic and epigenetic modifications, modulating pathogenetic pathways in NAFLD and CV disease. We report the main evidence from literature on the influence of both macro and micronutrients in NAFLD and CV damage and the role of genetics either alone or combined with diet in increasing the risk of developing both diseases. Understanding the interaction between metabolic alterations, genetics and diet are essential to treat the diseases and tailoring nutritional therapy to control NAFLD and CV risk.

Magnitude of Central Obesity and its Associated Factors Among Adults in Urban Areas of Northwest Ethiopia

PURPOSE

Obesity is becoming one of the most common public health problems worldwide. In particular, central obesity which indicates abnormal fat accumulation in the abdominal regions is highly associated with the risk of getting cardiometabolic diseases and their progression to end stage diseases or death. However, in developing countries, including Ethiopia less attention has been given to analyze the magnitude and associated factors of it. Therefore, we aimed to determine the prevalence of central obesity and its associated factors among adults in urban areas of Northwest Ethiopia.

METHODS

A cross-sectional study was conducted among 773 adults who lived in urban areas of Northwest Ethiopia from April 1 to May 30, 2019. Central obesity was assessed using both waist to hip ratio and waist circumference of the participants. Data were analyzed using STATA 14.0. The factors associated with central obesity were identified by binary logistic regression analyses using 95% confidence interval and the degree of association of the factors was measured using adjusted odds ratio (AOR). P-value <0.05 was used to declare statistical significance.

RESULTS

The prevalence of central obesity with waist circumference and waist to hip ratio definition criteria was 37.6% and 35.7%, respectively. According to body mass index, about 26.26% and 10.29% of the study participants were overweight and obese, respectively. A one-year increase in age (AOR=1.05; 95%CI: 1.03-1.07), being female (AOR=9.62; 95%CI: 4.84-19.12) and eating of liquid oils (AOR=2.58; 95%CI: 1.71-3.90) were found to have statistically significant variables with central obesity.

CONCLUSION

The prevalence of central obesity was relatively high in comparison with similar studies. Thus, governmental and nongovernmental organizations that work in the health system as well as health professionals should focus on the preventive measure of central obesity to control its associated disorders at an early stage.

Body composition, not dietary fatty acid composition, explains metabolic responses following a high-fat meal in premenopausal normal-weight women: a single-blind, randomised, crossover study

The aim of this study was to examine the effect of three different fatty acid (FA)-rich meals enriched in either SFA, MUFA or PUFA on postprandial metabolic responses in premenopausal, normal-weight women. For this randomised, single-blind, crossover study, three high-fat (HF) meals rich in either SFA, MUFA or PUFA (65 % energy from fat; 35 % of participants’ total daily energy needs) were tested. For each visit, anthropometrics and RMR were measured following a 12–15 h fast. Then, participants consumed one of the HF meals, and respiratory gases were collected using indirect calorimetry for 3 h postprandially. Energy expenditure (EE) following a SFA-rich meal was significantly higher than a MUFA-rich meal (P = 0·04; η2 = 0·19), but SFA was not significantly different from PUFA. There was a trend towards significance in EE between PUFA and MUFA (P = 0·06). After adjusting for fat-free mass (FFM), there were no longer condition or time effects for EE, although FFM remained a significant predictor (P = 0·005; η2 = 0·45). There were no significant differences between conditions for dietary-induced thermogenesis or substrate oxidation. The relationship between fat mass (FM) and both total fat oxidation (r 0·62; P = 0·025) and total change in RER following a MUFA-rich meal was observed (r −0·55; P = 0·05). In conclusion, weight loss through increases in EE may be best achieved by increasing FFM rather than selection of FA type. Further, a relationship exists between FM and fat oxidation following a MUFA-rich meal, most likely due to an unidentified mechanism.

Lifestyle interventions affecting hepatic fatty acid metabolism

PURPOSE OF REVIEW

Prevalence of metabolic-associated fatty liver disease (MAFLD) is increasing, and as pharmacological treatment does not exist, lifestyle interventions (i.e. diet and exercise) represent the cornerstone management and treatment strategy. Although the available data clearly demonstrate that changes in lifestyle influence intrahepatic triglyceride (IHTG) content, the mechanisms through which this is achieved are seldom investigated. Here, we review recent evidence demonstrating the influence of lifestyle interventions on hepatic fatty acid metabolism and IHTG content.

RECENT FINDINGS

Diet and exercise influence IHTG content through various, and often interrelated factors. These include alterations in whole-body and tissue-specific insulin sensitivity, which may influence the flux of fatty acid and lipogenic substrates to the liver, and changes in intrahepatic fatty acid synthesis and partitioning. Notably, there are only a few studies that have investigated intrahepatic fatty acid metabolism in vivo in humans before and after an intervention.

SUMMARY

Lifestyle interventions represent an effective means of influencing hepatic fatty acid metabolism. IHTG content is decreased without weight-loss either through exercise or by changing the macronutrient composition of the diet, although what the optimal macronutrient composition is to achieve this has yet to be defined.

Effects of dietary macronutrients on liver fat content in adults: a systematic review and meta-analysis of randomized controlled trials

Dietary macronutrient composition may affect hepatic liver content and its associated diseases, but the results from human intervention trials have been equivocal or underpowered. We aimed to assess the effects of dietary macronutrient composition on liver fat content by conducting a systematic review and meta-analysis of randomized controlled trials in adults. Four databases (PubMed, Embase, Web of Science, and COCHRANE Library) were systematically searched for trials with isocaloric diets evaluating the effect of dietary macronutrient composition (energy percentages of fat, carbohydrates, and protein, and their specific types) on liver fat content as assessed by magnetic resonance techniques, computed tomography or liver biopsy. Data on change in liver fat content were pooled by random or fixed-effects meta-analyses and expressed as standardized mean difference (SMD). We included 26 randomized controlled trials providing data for 32 comparisons on dietary macronutrient composition. Replacing dietary fat with carbohydrates did not result in changes in liver fat (12 comparisons, SMD 0.01 (95% CI -0.36; 0.37)). Unsaturated fat as compared with saturated fat reduced liver fat content (4 comparisons, SMD -0.80 (95% CI -1.09; -0.51)). Replacing carbohydrates with protein reduced liver fat content (5 comparisons, SMD -0.33 (95% CI -0.54; -0.12)). Our meta-analyses showed that replacing carbohydrates with total fat on liver fat content was not effective, while replacing carbohydrates with proteins and saturated fat with unsaturated fat was. More well-performed and well-described studies on the effect of types of carbohydrates and proteins on liver fat content are needed, especially studies comparing proteins with fats.

Dietary Options for Rodents in the Study of Obesity

Obesity and its associated metabolic diseases are currently a priority research area. The increase in global prevalence at different ages is having an enormous economic and health impact. Genetic and environmental factors play a crucial role in the development of obesity, and diet is one of the main factors that contributes directly to the obesogenic phenotype. Scientific evidence has shown that increased fat intake is associated with the increase in body weight that triggers obesity. Rodent animal models have been extremely useful in the study of obesity since weight gain can easily be induced with a high-fat diet. Here, we review the dietary patterns and physiological mechanisms involved in the dynamics of energy balance. We report the main dietary options for the study of obesity and the variables to consider in the use of a high-fat diet, and assess the progression of obesity and diet-induced thermogenesis.

Lauric Acid versus Palmitic Acid: Effects on Adipose Tissue Inflammation, Insulin Resistance, and Non-Alcoholic Fatty Liver Disease in Obesity

Simple Summary

The aim of this study was to compare the effect of palmitic acid (PA), a long-chain fatty acid, and lauric acid (LA), a medium-chain fatty acid, on obesity-related metabolic disorders. We used a mouse model of diet-induced obesity and fed them a modified high fat diet supplemented with 3% PA or LA for 12 wk. An LA diet led to an increase in visceral fat mass with a reduction in inflammation compared to the PA diet. We also noted that PA significantly increased systemic insulin resistance whereas LA showed only a trend towards an increase compared to lean control mice. The expression of a protein involved in muscle glucose uptake was higher in LA-treated mice compared to the PA-treated group, indicating improved muscle glucose uptake in LA-fed mice. Analysis of liver samples showed that hepatic steatosis was higher in both PA and LA-fed mice compared to lean controls. Markers of liver inflammation were not altered significantly in mice receiving PA or LA. Our data suggest that compared to PA, LA exerts less adverse effects on metabolic disorders and this could be due to the differential effects of these fatty acids in fat and muscle.

Abstract

Coconut oil, rich in medium-chain saturated fatty acids (MCSFA), in particular, lauric acid (LA), is known to exert beneficial metabolic effects. Although LA is the most abundant saturated fatty acid in coconut oil, the specific role of LA in altering obesity-related metabolic disorders remains unknown. Here, we examined the effects of supplementing a high fat (HF) diet with purified LA on obesity-associated metabolic derangements in comparison with palmitic acid (PA), a long-chain saturated fatty acid. Male C57BL/6 mice were fed a control chow diet (CD) or an HF diet supplemented with 3% LA (HF + LA) or PA (HF + PA) for 12 wk. Markers of adipose tissue (AT) inflammation, systemic insulin resistance (IR), and hepatic steatosis, were assessed. The body weight and total fat mass were significantly higher in both HF + LA and HF + PA diet-fed groups compared to CD controls. However, the visceral adipose tissue (VAT) mass was significantly higher (p < 0.001) in HF + LA-fed mice compared to both CD as well as HF + PA-fed mice. Interestingly, markers of AT inflammation were promoted to a lesser extent in HF + LA-fed mice compared to HF + PA-fed mice. Thus, immunohistochemical analysis of VAT showed an increase in MCP-1 and IL-6 staining in HF + PA-fed mice but not in HF + LA-fed mice compared to CD controls. Further, the mRNA levels of macrophage and inflammatory markers were significantly higher in HF + PA-fed mice (p < 0.001) whereas these markers were increased to a lesser extent in HF + LA-fed group. Of note, the insulin tolerance test revealed that IR was significantly increased only in HF + PA-fed mice but not in HF + LA-fed group compared to CD controls. While liver triglycerides were increased significantly in both HF + PA and HF + LA-fed mice, liver weight and plasma markers of liver injury such as alanine aminotransferase and aspartate aminotransferase were increased significantly only in HF + PA-fed mice but not in HF + LA-fed mice. Taken together, our data suggest that although both LA and PA increased AT inflammation, systemic IR, and liver injury, the extent of metabolic derangements caused by LA was less compared to PA in the setting of high fat feeding.

Role of diet and lifestyle modification in the management of nonalcoholic fatty liver disease and type 2 diabetes

Nonalcoholic fatty liver disease (NAFLD) is considered as the hepatic evidence of insulin resistance which is the hallmark of type 2 diabetes. NAFLD is considered as the risk factor for developing type 2 diabetes and has a high frequency of occurrence in those with existing type 2 diabetes. Compared with patients with only NAFLD or type 2 diabetes, these patients show a poor metabolic profile and increase mortality. Hence, effective treatment strategies are necessary. Here, we review the role of diet and lifestyle modification in the management of NAFLD and type 2 diabetes. Based on the available studies, it has been shown that the addition of any kind of physical activity or exercise is beneficial for patients with both NAFLD and type 2 diabetes. Proper dietary management leads to weight loss are also effective in improving metabolic parameters in patients with both NAFLD and type 2 diabetes. In conclusion, it is clear that increasing physical activity or exercise is effective in improving metabolic parameters in patients who are suffering with both NAFLD and type 2 diabetes.

Long-term effects of a food pattern on cardiovascular risk factors and age-related changes of muscular and cognitive function

INTRODUCTION

The mean age of the German population increased over the last years, which resulted in a higher prevalence of cardiovascular diseases, type 2 diabetes, cognitive impairment, sarcopenia and bone fractures. Current evidence indicates a preservation of human wellbeing in the elderly by a healthy diet, although the recommended macronutrient composition and quality remains unclear and needs further long-term investigation. In this context we investigate the effect of a specific dietary pattern on age-related disorders in a randomized controlled multi-center trial (RCT).

METHODS

We assess the effect of a specific dietary pattern (NutriAct) with a high proportion of unsaturated fat, plant proteins and fibres (fat 35%-40% of total energy (%E) of which 15%E-20%E monounsaturated fatty acids (MUFA) and 10%E-15%E polyunsaturated fatty acids (PUFA), 15%E-25%E proteins, ≥30 g fibres per day and 35%E-45%E carbohydrates) on age-related impairment of health within a 36-months RCT conducted in the region of Berlin and Potsdam. 502 eligible men (n = 183) and women (n = 319), aged 50 to 80 years, with an increased risk to develop age-related diseases were randomly assigned to either an intervention group focusing on NutriAct dietary pattern or a control group focusing on usual care and dietary recommendations in accordance to the German Nutrition Society (DGE). In the intervention group, 21 nutrition counsellings as well as supplementation of rapeseed oil, oil cake and specific designed foods are used to achieve the intended NutriAct dietary pattern.The primary outcome is a composite endpoint of age-related disorders, including cardiovascular morbidity, decline of cognitive function as well as clinical features of sarcopenia. Secondary outcomes include diet-induced effects on quality of life, depression, frailty, cardiovascular function, bone density, fat distribution pattern, glucose, lipid and energy metabolism, as well as the identification of biomarkers linked with age-related disorders.

DISCUSSION

The findings of this trial will provide clinically relevant information regarding dietary effects on age-related impairment of health and will contribute to the definition of the optimal macronutrient composition in the context of healthy aging in the German population.

The biology of human overfeeding: A systematic review

This systematic review has examined more than 300 original papers dealing with the biology of overfeeding. Studies have varied from 1 day to 6 months. Overfeeding produced weight gain in adolescents, adult men and women and in older men. In longer term studies, there was a clear and highly significant relationship between energy ingested and weight gain and fat storage with limited individual differences. There is some evidence for a contribution of a genetic component to this response variability. The response to overfeeding was affected by the baseline state of the groups being compared: those with insulin resistance versus insulin sensitivity; those prone to obesity versus those resistant to obesity; and those with metabolically abnormal obesity versus those with metabolically normal obesity. Dietary components, such as total fat, polyunsaturated fat and carbohydrate influenced the patterns of adipose tissue distribution as did the history of low or normal birth weight. Overfeeding affected the endocrine system with increased circulating concentrations of insulin and triiodothyronine frequently present. Growth hormone, in contrast, was rapidly suppressed. Changes in plasma lipids were influenced by diet, exercise and the magnitude of weight gain. Adipose tissue and skeletal muscle morphology and metabolism are substantially altered by chronic overfeeding.