Acute suppression of VLDL1 secretion rate by insulin is associated with hepatic fat content and insulin resistance

Surveillance of the liver in type 2 diabetes: important but unfeasible?

Fatty liver plays a pivotal role in the pathogenesis of the metabolic syndrome and type 2 diabetes. According to an updated classification, any individual with liver steatosis and one or more features of the metabolic syndrome, without excess alcohol consumption or other known causes of steatosis, has metabolic dysfunction-associated steatotic liver disease (MASLD). Up to 60-70% of all individuals with type 2 diabetes have MASLD. However, the prevalence of advanced liver fibrosis in type 2 diabetes remains uncertain, with reported estimates of 10-20% relying on imaging tests and likely overestimating the true prevalence. All stages of MASLD impact prognosis but fibrosis is the best predictor of all-cause and liver-related mortality risk. People with type 2 diabetes face a two- to threefold increase in the risk of liver-related death and hepatocellular carcinoma, with 1.3% progressing to severe liver disease over 7.7 years. Because reliable methods for detecting steatosis are lacking, MASLD mostly remains an incidental finding on imaging. Regardless, several medical societies advocate for universal screening of individuals with type 2 diabetes for advanced fibrosis. Proposed screening pathways involve annual calculation of the Fibrosis-4 (FIB-4) index, followed by a secondary test such as transient elastography (TE) for intermediate-to-high-risk individuals. However, owing to unsatisfactory biomarker specificity, these pathways are expected to channel approximately 40% of all individuals with type 2 diabetes to TE and 20% to tertiary care, with a false discovery rate of up to 80%, raising concerns about feasibility. There is thus an urgent need to develop more effective strategies for surveying the liver in type 2 diabetes. Nonetheless, weight loss through lifestyle changes, pharmacotherapy or bariatric surgery remains the cornerstone of management, proving highly effective not only for metabolic comorbidities but also for MASLD. Emerging evidence suggests that fibrosis biomarkers may serve as tools for risk-based targeting of weight-loss interventions and potentially for monitoring response to therapy.

Hepatic insulin resistance and muscle insulin resistance are characterized by distinct postprandial plasma metabolite profiles: a cross-sectional study

BACKGROUND

Tissue-specific insulin resistance (IR) predominantly in muscle (muscle IR) or liver (liver IR) has previously been linked to distinct fasting metabolite profiles, but postprandial metabolite profiles have not been investigated in tissue-specific IR yet. Given the importance of postprandial metabolic impairments in the pathophysiology of cardiometabolic diseases, we compared postprandial plasma metabolite profiles in response to a high-fat mixed meal between individuals with predominant muscle IR or liver IR.

METHODS

This cross-sectional study included data from 214 women and men with BMI 25-40 kg/m2, aged 40-75 years, and with predominant muscle IR or liver IR. Tissue-specific IR was assessed using the muscle insulin sensitivity index (MISI) and hepatic insulin resistance index (HIRI), which were calculated from the glucose and insulin responses during a 7-point oral glucose tolerance test. Plasma samples were collected before (T = 0) and after (T = 30, 60, 120, 240 min) consumption of a high-fat mixed meal and 247 metabolite measures, including lipoproteins, cholesterol, triacylglycerol (TAG), ketone bodies, and amino acids, were quantified using nuclear magnetic resonance spectroscopy. Differences in postprandial plasma metabolite iAUCs between muscle and liver IR were tested using ANCOVA with adjustment for age, sex, center, BMI, and waist-to-hip ratio. P-values were adjusted for a false discovery rate (FDR) of 0.05 using the Benjamini-Hochberg method.

RESULTS

Sixty-eight postprandial metabolite iAUCs were significantly different between liver and muscle IR. Liver IR was characterized by greater plasma iAUCs of large VLDL (p = 0.004), very large VLDL (p = 0.002), and medium-sized LDL particles (p = 0.026), and by greater iAUCs of TAG in small VLDL (p = 0.025), large VLDL (p = 0.003), very large VLDL (p = 0.002), all LDL subclasses (all p < 0.05), and small HDL particles (p = 0.011), compared to muscle IR. In liver IR, the postprandial plasma fatty acid (FA) profile consisted of a higher percentage of saturated FA (p = 0.013), and a lower percentage of polyunsaturated FA (p = 0.008), compared to muscle IR.

CONCLUSION

People with muscle IR or liver IR have distinct postprandial plasma metabolite profiles, with more unfavorable postprandial metabolite responses in those with liver IR compared to muscle IR.

Combined untargeted and targeted lipidomics approaches reveal potential biomarkers in type 2 diabetes mellitus cynomolgus monkeys

BACKGROUND

The significantly increasing incidence of type 2 diabetes mellitus (T2DM) over the last few decades triggers the demands of T2DM animal models to explore the pathogenesis, prevention, and therapy of the disease. The altered lipid metabolism may play an important role in the pathogenesis and progression of T2DM. However, the characterization of molecular lipid species in fasting serum related to T2DM cynomolgus monkeys is still underrecognized.

METHODS

Untargeted and targeted LC-mass spectrometry (MS)/MS-based lipidomics approaches were applied to characterize and compare the fasting serum lipidomic profiles of T2DM cynomolgus monkeys and the healthy controls.

RESULTS

Multivariate analysis revealed that 196 and 64 lipid molecules differentially expressed in serum samples using untargeted and targeted lipidomics as the comparison between the disease group and healthy group, respectively. Furthermore, the comparative analysis of differential serum lipid metabolites obtained by untargeted and targeted lipidomics approaches, four common serum lipid species (phosphatidylcholine [18:0_22:4], lysophosphatidylcholine [14:0], phosphatidylethanolamine [PE] [16:1_18:2], and PE [18:0_22:4]) were identified as potential biomarkers and all of which were found to be downregulated. By analyzing the metabolic pathway, glycerophospholipid metabolism was associated with the pathogenesis of T2DM cynomolgus monkeys.

CONCLUSION

The study found that four downregulated serum lipid species could serve as novel potential biomarkers of T2DM cynomolgus monkeys. Glycerophospholipid metabolism was filtered out as the potential therapeutic target pathway of T2DM progression. Our results showed that the identified biomarkers may offer a novel tool for tracking disease progression and response to therapeutic interventions.

Phenotypic and metabolomic characteristics of mouse models of metabolic associated steatohepatitis

BACKGROUND

Metabolic associated steatohepatitis (MASH) is metabolic disease that may progress to cirrhosis and hepatocellular carcinoma. Mouse models of diet-induced MASH, which is characterized by the high levels of fats, sugars, and cholesterol in diets, are commonly used in research. However, mouse models accurately reflecting the progression of MASH in humans remain to be established. Studies have explored the potential use of serological metabolites as biomarkers of MASH severity in relation to human MASH.

METHODS

We performed a comparative analysis of three mouse models of diet-induced MASH in terms of phenotypic and metabolomic characteristics; MASH was induced using different diets: a high-fat diet; a Western diet; and a high-fat, high-cholesterol diet. Liver cirrhosis was diagnosed using standard clinical approaches (e.g., METAVIR score, hyaluronan level, and collagen deposition level). Mouse serum samples were subjected to nuclear magnetic resonance spectroscopy-based metabolomic profiling followed by bioinformatic analyses. Metabolomic analysis of a retrospective cohort of patients with hepatocellular carcinoma was performed; the corresponding cirrhosis scores were also evaluated.

RESULTS

Using clinically relevant quantitative diagnostic methods, the severity of MASH was evaluated. Regarding metabolomics, the number of lipoprotein metabolites increased with both diet and MASH progression. Notably, the levels of very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) significantly increased with fibrosis progression. During the development of diet-induced MASH in mice, the strongest upregulation of expression was noted for VLDL receptor. Metabolomic analysis of a retrospective cohort of patients with cirrhosis indicated lipoproteins (e.g., VLDL and LDL) as predominant biomarkers of cirrhosis.

CONCLUSIONS

Our findings provide insight into the pathophysiology and metabolomics of experimental MASH and its relevance to human MASH. The observed upregulation of lipoprotein expression reveals a feedforward mechanism for MASH development that may be targeted for the development of noninvasive diagnosis.

Bariatric surgery improves postprandial VLDL kinetics and restores insulin-mediated regulation of hepatic VLDL production

Dyslipidemia in obesity results from excessive production and impaired clearance of triglyceride-rich (TG-rich) lipoproteins, which are particularly pronounced in the postprandial state. Here, we investigated the impact of Roux-en-Y gastric bypass (RYGB) surgery on postprandial VLDL1 and VLDL2 apoB and TG kinetics and their relationship with insulin-responsiveness indices. Morbidly obese patients without diabetes who were scheduled for RYGB surgery (n = 24) underwent a lipoprotein kinetics study during a mixed-meal test and a hyperinsulinemic-euglycemic clamp study before the surgery and 1 year later. A physiologically based computational model was developed to investigate the impact of RYGB surgery and plasma insulin on postprandial VLDL kinetics. After the surgery, VLDL1 apoB and TG production rates were significantly decreased, whereas VLDL2 apoB and TG production rates remained unchanged. The TG catabolic rate was increased in both VLDL1 and VLDL2 fractions, but only the VLDL2 apoB catabolic rate tended to increase. Furthermore, postsurgery VLDL1 apoB and TG production rates, but not those of VLDL2, were positively correlated with insulin resistance. Insulin-mediated stimulation of peripheral lipoprotein lipolysis was also improved after the surgery. In summary, RYGB resulted in reduced hepatic VLDL1 production that correlated with reduced insulin resistance, elevated VLDL2 clearance, and improved insulin sensitivity in lipoprotein lipolysis pathways.

Hepatic fatty acid and glucose handling in metabolic disease: Potential impact on cardiovascular disease risk

The prevalence of metabolic diseases, including type 2 diabetes mellitus (T2DM) and metabolic dysfunction-associated steatotic liver disease (MASLD) is increasing. Although invariably associated with obesity, the importance of fat deposition in non-adipose tissue organs has yet to be fully explored. Pathological ectopic fat deposition within the liver (known as (MASLD)) has been suggested to underlie the development of T2DM and is now emerging as an independent risk factor for cardiovascular disease (CVD). The process of hepatic de novo lipogenesis (DNL), that is the synthesis of fatty acids from non-lipid precursors (e.g. glucose), has received much attention as it sits at the intersect of hepatic glucose and fatty acid handling. An upregulation of the DNL pathway has been suggested to be central in the development of metabolic diseases (including MASLD, insulin resistance, and T2DM). Here we review the evidence to determine if hepatic DNL may play a role in the development of MASLD and T2DM and therefore underlie an increased risk of CVD.

Quartet of APOCs and the Different Roles They Play in Diabetes

APOA1 and APOB are the structural proteins of high-density lipoprotein and APOB-containing lipoproteins, such as low-density lipoprotein and very low-density lipoprotein, respectively. The 4 smaller APOCs (APOC1, APOC2, APOC3, and APOC4) are exchangeable apolipoproteins; they are readily transferred among high-density lipoproteins and APOB-containing lipoproteins. The APOCs regulate plasma triglyceride and cholesterol levels by modulating substrate availability and activities of enzymes interacting with lipoproteins and by interfering with APOB-containing lipoprotein uptake through hepatic receptors. Of the 4 APOCs, APOC3 has been best studied in relation to diabetes. Elevated serum APOC3 levels predict incident cardiovascular disease and progression of kidney disease in people with type 1 diabetes. Insulin suppresses APOC3 levels, and accordingly, elevated APOC3 levels associate with insulin deficiency and insulin resistance. Mechanistic studies in a mouse model of type 1 diabetes have demonstrated that APOC3 acts in the causal pathway of diabetes-accelerated atherosclerosis. The mechanism is likely due to the ability of APOC3 to slow the clearance of triglyceride-rich lipoproteins and their remnants, thereby causing an increased accumulation of atherogenic lipoprotein remnants in lesions of atherosclerosis. Less is known about the roles of APOC1, APOC2, and APOC4 in diabetes.

[The lipidosis of the liver of dairy cows: Part 1 - Role of insulin and the Growth Hormone-IGF-1 axis]

Lipidosis of the liver of dairy cows is a metabolic disease known since many years and is caused by an uptake of nonesterified fatty acids (NEFA) into the liver cells, limited metabolism of NEFA (oxidation and production of β-hydroxybutyrate), and resynthesis in relation to a low efflux as triglyceride (TG). The pathogenesis of lipidosis includes a) an augmented release of NEFA by mobilisation of adipose tissue, b) uptake of NEFA into the liver cells, c) metabolism of NEFA and d) re-synthesis of triglyceride and e) an efflux of TG as very low density lipoprotein (VLDL). The steps a-e are postpartum modified by hormones as an increase of growth hormone, a pronounced insulin resistance in combination with a decreased insulin and of IGF-1 concentrations. These hormonal changes are related to an uncoupling of the growth hormone-IGF-1-axis with enhanced lipolysis and consequences mentioned above. These alterations are associated with inflammation, oxidative and endoplasmatic stress. The metabolic and hormonal alterations are the result of the selection of dairy cows primarily for milk production without adequate food intake with the consequence of lipidosis, ketosis and further health risks (production diseases).

Remnant Cholesterol Is an Independent Predictor of Type 2 Diabetes: A Nationwide Population-Based Cohort Study

OBJECTIVE

Although the atherogenic effect of remnant cholesterol (remnant-C) has been widely recognized, the relationship between remnant-C and glucose metabolism remains unclear. This retrospective, longitudinal study investigated the relationship between remnant-C and incident type 2 diabetes (T2D) in a nationwide cohort of Korean adults.

RESEARCH DESIGN AND METHODS

A total of 8,485,539 Korean adults without diabetes participated in the national health screening in 2009 and were followed up until 2019. The relationship between remnant-C quartiles and incident T2D was examined by Cox regression models. The risk of incident T2D over the continuum of remnant-C was examined with cubic spline analysis.

RESULTS

During the median follow-up period of 9.28 years, 584,649 individuals (6.8%) developed T2D. In multivariable-adjusted analyses, participants in the upper quartile of remnant-C had a higher risk of T2D, with hazard ratios of 1.25 (95% CI 1.24-1.27) in the second quartile, 1.51 (95% CI 1.50-1.53) in the third quartile, and 1.95 (95% CI 1.93-1.97) in the fourth quartile, compared with the lowest quartile. The increase in the risk of T2D owing to high remnant-C concentration was more profound in individuals with fewer traditional T2D risks, such as women, and absence of metabolic abnormalities, including impaired fasting glucose, hypertension, and atherogenic dyslipidemia. Moreover, the magnitude of the increased risk for incident T2D in individuals with higher remnant-C quartiles was higher in younger participants than older participants.

CONCLUSIONS

These findings indicate that remnant-C profiles provide additional information in predicting future progression of T2D, independent of the conventional lipid parameters.

Quantifying the contribution of triglycerides to metabolic resilience through the mixed meal model

Despite the pivotal role played by elevated circulating triglyceride levels in the pathophysiology of cardio-metabolic diseases many of the indices used to quantify metabolic health focus on deviations in glucose and insulin alone. We present the Mixed Meal Model, a computational model describing the systemic interplay between triglycerides, free fatty acids, glucose, and insulin. We show that the Mixed Meal Model can capture deviations in the post-meal excursions of plasma glucose, insulin, and triglyceride that are indicative of features of metabolic resilience; quantifying insulin resistance and liver fat; validated by comparison to gold-standard measures. We also demonstrate that the Mixed Meal Model is generalizable, applying it to meals with diverse macro-nutrient compositions. In this way, by coupling triglycerides to the glucose-insulin system the Mixed Meal Model provides a more holistic assessment of metabolic resilience from meal response data, quantifying pre-clinical metabolic deteriorations that drive disease development in overweight and obesity.

In Vitro and In Vivo Validation of GATA-3 Suppression for Induction of Adipogenesis and Improving Insulin Sensitivity

Impaired adipogenesis is associated with the development of insulin resistance and an increased risk of type 2 diabetes (T2D). GATA Binding Protein 3 (GATA3) is implicated in impaired adipogenesis and the onset of insulin resistance. Therefore, we hypothesize that inhibition of GATA3 could promote adipogenesis, restore healthy fat distribution, and enhance insulin signaling. Primary human preadipocytes were treated with GATA3 inhibitor (DNAzyme hgd40). Cell proliferation, adipogenic capacity, gene expression, and insulin signaling were measured following well-established protocols. BALB/c mice were treated with DNAzyme hgd40 over a period of 2 weeks. Liposomes loaded with DNAzyme hgd40, pioglitazone (positive), or vehicle (negative) controls were administered subcutaneously every 2 days at the right thigh. At the end of the study, adipose tissues were collected and weighed from the site of injection, the opposite side, and the omental depot. Antioxidant enzyme (superoxide dismutase and catalase) activities were assessed in animals’ sera, and gene expression was measured using well-established protocols. In vitro GATA3 inhibition induced the adipogenesis of primary human preadipocytes and enhanced insulin signaling through the reduced expression of p70S6K. In vivo GATA3 inhibition promoted adipogenesis at the site of injection and reduced MCP-1 expression. GATA3 inhibition also reduced omental tissue size and PPARγ expression. These findings suggest that modulating GATA3 expression offers a potential therapeutic benefit by correcting impaired adipogenesis, promoting healthy fat distribution, improving insulin sensitivity, and potentially lowering the risk of T2D.

Postprandial Plasma Lipidomics Reveal Specific Alteration of Hepatic-derived Diacylglycerols in Nonalcoholic Fatty Liver Disease

BACKGROUND & AIMS

Hepatic energy metabolism is a dynamic process modulated by multiple stimuli. In nonalcoholic fatty liver disease (NAFLD), human studies typically focus on the static fasting state. We hypothesized that unique postprandial alterations in hepatic lipid metabolism are present in NAFLD.

METHODS

In a prospective clinical study, 37 patients with NAFLD and 10 healthy control subjects ingested a standardized liquid meal with pre- and postprandial blood sampling. Postprandial plasma lipid kinetics were characterized at the molecular lipid species level by untargeted lipidomics, cluster analysis, and lipid particle isolation, then confirmed in a mouse model.

RESULTS

There was a specific increase of multiple plasma diacylglycerol (DAG) species at 4 hours postprandially in patients with NAFLD but not in controls. This was replicated in a nonalcoholic steatohepatitis mouse model, where postprandial DAGs increased in plasma and concomitantly decreased in the liver. The increase in plasma DAGs appears early in the disease course, is dissociated from NAFLD severity and obesity, and correlates with postprandial insulin levels. Immunocapture isolation of very low density lipoprotein in human samples and stable isotope tracer studies in mice revealed that elevated postprandial plasma DAGs reflect hepatic secretion of endogenous, rather than meal-derived lipids.

CONCLUSIONS

We identified a selective insulin-related increase in hepatic secretion of endogenously derived DAGs after a mixed meal as a unique feature of NAFLD. DAGs are known to be lipotoxic and associated with atherosclerosis. Although it is still unknown whether the increased exposure to hepatic DAGs contributes to extrahepatic manifestations and cardiovascular risk in NAFLD, our study highlights the importance of extending NAFLD research beyond the fasting state.

Metabolism of triglyceride-rich lipoproteins in health and dyslipidaemia

Accumulating evidence points to the causal role of triglyceride-rich lipoproteins and their cholesterol-enriched remnants in atherogenesis. Genetic studies in particular have not only revealed a relationship between plasma triglyceride levels and the risk of atherosclerotic cardiovascular disease, but have also identified key proteins responsible for the regulation of triglyceride transport. Kinetic studies in humans using stable isotope tracers have been especially useful in delineating the function of these proteins and revealing the hitherto unappreciated complexity of triglyceride-rich lipoprotein metabolism. Given that triglyceride is an essential energy source for mammals, triglyceride transport is regulated by numerous mechanisms that balance availability with the energy demands of the body. Ongoing investigations are focused on determining the consequences of dysregulation as a result of either dietary imprudence or genetic variation that increases the risk of atherosclerosis and pancreatitis. The identification of molecular control mechanisms involved in triglyceride metabolism has laid the groundwork for a 'precision-medicine' approach to therapy. Novel pharmacological agents under development have specific molecular targets within a regulatory framework, and their deployment heralds a new era in lipid-lowering-mediated prevention of disease. In this Review, we outline what is known about the dysregulation of triglyceride transport in human hypertriglyceridaemia.

Association of Two Indices of Insulin Resistance Marker with Abnormal Liver Function Tests: A Cross-Sectional Population Study in Taiwanese Adults

Background and objectives: Insulin resistance (IR) is frequently associated with chronic low-grade inflammation and has an important role as a mediator in the development of liver disease. Thus, this study aimed to explore the relationship between two indexes of IR and abnormal liver function parameters. Materials and Methods: This cross-sectional study obtained data of 41,510 men and 92,357 women aged ≥30 years from a private health screening institute in Taiwan. Two IR indexes namely triglyceride-glucose (TyG) index and triglycerides to high-density lipoprotein cholesterol (TG/HDL-C) ratio were used to examine their relationship to predict abnormal liver function parameters (aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), and alkaline phosphatase (ALP)). Results: Positive trend was shown for the association of TyG index in the highest quintile (Q5) and risk of high AST (OR = 1.45, 95% CI: 1.33–1.57), high ALT (OR = 1.85, 95% CI: 1.73–1.97), high GGT (OR = 2.04, 95% CI: 1.93–2.15), and high ALP (OR = 1.13, 95% CI: 1.07–1.19) compared with the median quintile (Q3) in the fully adjusted model. Similarly, participants in the Q5 of the TG/HDL-C ratio were associated with 1.38 (95% CI: 1.27–1.49), 1.71 (95% CI: 1.61–1.82), 1.75 (95% CI: 1.66–1.84), and 1.21 (1.16–1.27) odds for having high AST, ALT, GGT, and ALP respectively. The AUC (95% CI) value of the TyG index for predicting high AST, high ALT, and high GGT was 0.699 (0.692–0.705), 0.738 (0.734–0.742), and 0.752 (0.749–0.755), respectively. Meanwhile, the AUC (95% CI) of the TG/HDL-C ratio for predicting high AST, high ALT, and high GGT was 0.680 (0.673–0.686), 0.738 (0.734–0.742), 0.734 (0.731–0.738), respectively. Conclusions: Our study supported that the TyG index and TG/HDL-C ratio may be useful as non-invasive methods to predict the existence of impaired liver function in the early stage.

Non-alcoholic Fatty Liver Disease and Carbohydrate Restricted Diets: A Case Report and Literature Review

Non-alcoholic fatty liver disease is the accumulation of excessive fat in the liver. Various treatment options are available to manage the condition, among which carbohydrate restriction has been shown to reduce liver fat accumulation, liver inflammation, serum liver enzyme levels, and hepatic de-novo lipogenesis in people with non-alcoholic fatty liver disease. Here, we present a case report of a 25-year-old South Asian patient presenting with right upper quadrant pain, fatigue, and headaches. After confirmation of non-Alcoholic fatty liver disease (NAFLD) diagnosis by biopsy, the patient initiated a low-carbohydrate diet. Four months after which significant improvement was noticed in clinical and laboratory parameters. Peer-reviewed publications were then sourced from online databases to explore the efficacy of low-carbohydrate diets for NAFLD. Our results were compared with the existing data. However, limited literature existed for such an intervention in the South Asian population therefore, the case report is novel. Combined with findings from the literature, our results from the case report supported our hypothesis that carbohydrate restriction might promote a reduction in hepatic fat accumulation and inflammation in patients with NAFLD and diabetes in various ethnicities including South Asians.

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.

Fibrosis of the diabetic heart: Clinical significance, molecular mechanisms, and therapeutic opportunities

In patients with diabetes, myocardial fibrosis may contribute to the pathogenesis of heart failure and arrhythmogenesis, increasing ventricular stiffness and delaying conduction. Diabetic myocardial fibrosis involves effects of hyperglycemia, lipotoxicity and insulin resistance on cardiac fibroblasts, directly resulting in increased matrix secretion, and activation of paracrine signaling in cardiomyocytes, immune and vascular cells, that release fibroblast-activating mediators. Neurohumoral pathways, cytokines, growth factors, oxidative stress, advanced glycation end-products (AGEs), and matricellular proteins have been implicated in diabetic fibrosis; however, the molecular links between the metabolic perturbations and activation of a fibrogenic program remain poorly understood. Although existing therapies using glucose- and lipid-lowering agents and neurohumoral inhibition may act in part by attenuating myocardial collagen deposition, specific therapies targeting the fibrotic response are lacking. This review manuscript discusses the clinical significance, molecular mechanisms and cell biology of diabetic cardiac fibrosis and proposes therapeutic targets that may attenuate the fibrotic response, preventing heart failure progression.

Metabolic-associated fatty liver disease and lipoprotein metabolism

BACKGROUND

Non-alcoholic fatty liver disease, or as recently proposed 'metabolic-associated fatty liver disease' (MAFLD), is characterized by pathological accumulation of triglycerides and other lipids in hepatocytes. This common disease can progress from simple steatosis to steatohepatitis, and eventually end-stage liver diseases. MAFLD is closely related to disturbances in systemic energy metabolism, including insulin resistance and atherogenic dyslipidemia.

SCOPE OF REVIEW

The liver is the central organ in lipid metabolism by secreting very low density lipoproteins (VLDL) and, on the other hand, by internalizing fatty acids and lipoproteins. This review article discusses recent research addressing hepatic lipid synthesis, VLDL production, and lipoprotein internalization as well as the lipid exchange between adipose tissue and the liver in the context of MAFLD.

MAJOR CONCLUSIONS

Liver steatosis in MAFLD is triggered by excessive hepatic triglyceride synthesis utilizing fatty acids derived from white adipose tissue (WAT), de novo lipogenesis (DNL) and endocytosed remnants of triglyceride-rich lipoproteins. In consequence of high hepatic lipid content, VLDL secretion is enhanced, which is the primary cause of complex dyslipidemia typical for subjects with MAFLD. Interventions reducing VLDL secretory capacity attenuate dyslipidemia while they exacerbate MAFLD, indicating that the balance of lipid storage versus secretion in hepatocytes is a critical parameter determining disease outcome. Proof of concept studies have shown that promoting lipid storage and energy combustion in adipose tissues reduces hepatic lipid load and thus ameliorates MAFLD. Moreover, hepatocellular triglyceride synthesis from DNL and WAT-derived fatty acids can be targeted to treat MAFLD. However, more research is needed to understand how individual transporters, enzymes, and their isoforms affect steatosis and dyslipidemia in vivo, and whether these two aspects of MAFLD can be selectively treated. Processing of cholesterol-enriched lipoproteins appears less important for steatosis. It may, however, modulate inflammation and consequently MAFLD progression.

Joint effect of changes in physical activity and weight on incident non-alcoholic fatty liver disease

BACKGROUND

Increases in physical activity (PA) and weight have opposite effects on the risk of non-alcoholic fatty liver disease (NAFLD), but their joint effect remains unknown. We examined the dose-effect of PA increase for NAFLD prevention and the amount of PA increase required to offset the deleterious effect of weight gain.

METHODS

We analysed 47 058 participants who were extracted from the Taiwan MJ cohort, aged 20-50 years, without NAFLD at baseline, and followed at 1-5 years between 1997 and 2016. The outcome was incident NAFLD, diagnosed by ultrasonography. PA was measured by metabolic equivalents (METs) and duration (hour/week). We used flexible parametric survival models to estimate the HRs of annual change in PA and body mass index (BMI), controlling for their interaction and baseline covariates.

RESULTS

During 138 646 person-years of follow-up, 12 836 participants (40.6% men and 20.1% women) developed incident NAFLD. The HR (95% CI) of annual PA increase of 1 MET-hour/week was 0.88 (0.85-0.92) after controlling for weight change. Moreover, 28 min/week of moderate-intensity PA could neutralise NAFLD risk elevated by annual BMI increase of 0.1 kg/m² at the end of year 3. We also observed an extra 35% risk reduction when PA increase (1 MET-hour/week) and weight loss (0.1 kg/m²) occurred simultaneously.

CONCLUSIONS

Annual PA increase of 1 MET-hour/week was associated with a 12% lower NAFLD risk. PA increase can counteract the harmful effect of weight gain and there is a synergistic effect from PA increase and weight loss.

Potential Alteration of Statin-Related Pharmacological Features in Diabetes Mellitus

Objective

Type 2 diabetes mellitus is a chronic metabolic disease caused by insulin resistance or insulin deficiency resulting in elevated blood glucose levels. Poorly controlled diabetes is associated with the development of cardiovascular disease and dyslipidemia. 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statin) are an important class of therapeutic agents used to control hyperlipidemia and prevent cardiovascular disease in diabetic and nondiabetic patients. Since the effect of diabetes on the pharmacokinetics and pharmacodynamics of drugs and toxins has been shown, the aim was to review previous studies on the efficacy of statins such as atorvastatin, simvastatin, pravastatin, pitavastatin, fluvastatin, and rosuvastatin in clinical and preclinical studies in both diabetic and nondiabetic groups.

Method

For this purpose, Web of Science, PubMed, Scopus, and Google Scholar databases were reviewed, and related English articles published until October 2020 were included in this review article.

Results

The findings revealed that diabetes affected statin effectiveness through changes in pharmacokinetic parameters such as clearance and biotransformation biomarkers at mRNA and protein levels. Plasma and serum concentrations of statins were accompanied by alteration in cellular activities including oxidative stress, Akt inhibition, and endothelial nitric oxide synthase (eNOS) and phosphorylation that were reflected in changes in the adverse drug reaction profile of the differing statins.

Conclusion

Given that dyslipidemia frequently accompanies diabetes and statin therapy is common, more clinical studies are needed regarding the effects of diabetes on the effectiveness of these drugs.

Increased particle size of triacylglycerol-enriched remnant lipoproteins, but not their plasma concentration or lipid content, augments risk prediction of incident type 2 diabetes

AIMS/HYPOTHESIS

Type 2 diabetes prevention requires the accurate identification of those at high risk. Beyond the association of fasting serum triacylglycerols with diabetes, triacylglycerol-enriched remnant lipoproteins (TRLs) more accurately reflect pathophysiological changes that underlie progression to diabetes, such as hepatic insulin resistance, pancreatic steatosis and systemic inflammation. We hypothesised that TRL-related factors could improve risk prediction for incident diabetes.

METHODS

We included individuals from the Brazilian Longitudinal Study of Adult Health cohort. We trained a logistic regression model for the risk of incident diabetes in 80% of the cohort using tenfold cross-validation, and tested the model in the remaining 20% of the cohort (test set). Variables included medical history and traits of the metabolic syndrome, followed by TRL-related measurements (plasma concentration, TRL particle diameter, cholesterol and triacylglycerol content). TRL features were measured using NMR spectroscopy. Discrimination was assessed using the area under the receiver operating characteristic curve (AUROC) and the area under the precision-recall curve (AUPRC).

RESULTS

Among 4463 at-risk individuals, there were 366 new cases of diabetes after a mean (±SD) of 3.7 (±0.63) years of follow-up. We derived an 18-variable model with a global AUROC of 0.846 (95% CI: 0.829, 0.869). Overall TRL-related markers were not associated with diabetes. However, TRL particle diameter increased the AUROC, particularly in individuals with HbA_1c <39 mmol/mol (5.7%) (hold-out test set [n = 659]; training-validation set [n = 2638]), but not in individuals with baseline HbA_1c 39-46 mmol/mol (5.7-6.4%) (hold-out test set [n = 233]; training-validation set [n = 933]). In the subgroup with baseline HbA_1c <39 mmol/mol (5.7%), AUROC in the test set increased from 0.717 (95% CI 0.603, 0.818) to 0.794 (95% CI 0.731, 0.862), and AUPRC in the test set rose from 0.582 to 0.701 when using the baseline model and the baseline model plus TRL particle diameter, respectively. TRL particle diameter was highly correlated with obesity, insulin resistance and inflammation in those with impaired fasting glucose at baseline, but less so in those with HbA_1c <39 mmol/mol (5.7%).

CONCLUSIONS/INTERPRETATION

TRL particle diameter improves the prediction of diabetes, but only in individuals with HbA_1c <39 mmol/mol (5.7%) at baseline. These data support TRL particle diameter as a risk factor that is changed early in the course of the pathophysiological processes that lead to the development of type 2 diabetes, even before glucose abnormalities are established. Graphical abstract.

Does Lipocalin-2 Affect Metabolic Syndrome in Hepatic Infections?

Background and objective

Lipocalin-2 (LCN-2) is an adipokine that plays a protective role in various inflammatory disorders and regulates innate immune response to acute and chronic infections. However, scant information is available regarding the relationship between serum LCN-2 levels and type 2 diabetes mellitus (T2DM) occurring concurrently with chronic hepatic infections. The present study sought to investigate the association of LCN-2 with T2DM patients with hepatic infections.

Methods

The association of LCN-2 with T2DM, hepatic steatosis, and inflammation was tested in 37 non-T2DM noninfectious individuals (group A, control group) and 55 age-matched patients with T2DM and chronic infection (group B). Anthropometric data were measured and the body-fat percentage was calculated using bioelectrical impedance analysis (BIA). Hemoglobin (Hb), fasting plasma glucose (FPG), hemoglobin A1c (HbA1c), liver function enzymes (LFEs), lipid profile, and total leukocyte count (TLC) were measured. Serum LCN-2 levels were measured using a commercially available sandwich enzyme-linked immunosorbent assay method.

Results

Levels of LCN-2 were significantly elevated in group B (1896.90 ± 73.13 ng/ml) versus control group A (263.58 ± 15.66 ng/mL; p<0.001). LCN-2 correlated moderately with alanine aminotransferase (ALT) (r=0.369), alkaline phosphatase ALP (r=0.419), and HbA1c (r=0.341) (p<0.01). All correlations were lost when adjusted for the presence of hepatitis, indicating that liver infection exacerbates insulin resistance.

Conclusion

Based on our findings, circulating LCN-2 is elevated in T2DM subjects with hepatitis B co-infection and may contribute towards deranged inflammatory response.

Low-Density Lipoprotein (LDL)-Triglyceride and Its Ratio to LDL-Cholesterol as Diagnostic Biomarkers for Nonalcoholic Steatohepatitis

Background

Nonalcoholic fatty liver disease (NAFLD) is the most common type of liver disease, but it is difficult to distinguish its pathogenic phenotype, nonalcoholic steatohepatitis (NASH), from nonalcoholic fatty liver (NAFL) without a liver biopsy. We analyzed serum lipids, including low-density lipoprotein triglyceride (LDL-TG), to elucidate their usefulness for diagnosing NASH.

Patients and Methods

Serum samples obtained from 35 NASH and 9 NAFL biopsy-confirmed patients and 6 healthy volunteers (HLT) were studied for 13 lipid-related markers and compared between HLT, NAFL, and NASH groups. The relationship between histological findings and the lipid markers was also analyzed.

Results

There were significant differences in triglyceride, LDL-TG, the ratio of LDL-TG to the LDL-cholesterol (LDL-TG/LDL-C), small dense LDL-C, and apolipoprotein E between the three groups. Among the 5 lipid components, serum LDL-TG level and the ratio of LDL-TG to the LDL-cholesterol (LDL-TG/LDL-C) were significantly elevated in NASH. The median concentrations of LDL-TG in HLT, NAFL, and NASH were 9, 15, and 20 mg/dL (P &lt; 0.001), and those of LDL-TG/LDL-C were 0.097, 0.102, and 0.173 (P &lt; 0.001), respectively. Although the degree of steatosis was not correlated with the LDL-TG/LDL-C, the ratio was significantly higher in patients with lobular inflammation (P = 0.071), ballooning (P = 0.031), and fibrosis (P &lt; 0.001). The area under the receiver operating characteristic curve of the ratio for distinguishing NASH from NAFL was 0.857. The rest of studied markers showed no significant utility.

Conclusion

Serum LDL-TG levels and the LDL-TG/LDL-C ratio might serve as simple and noninvasive diagnostic biomarkers for NASH.

Spironolactone reversed hepato-ovarian triglyceride accumulation caused by letrozole-induced polycystic ovarian syndrome: tissue uric acid-a familiar foe

Polycystic ovarian syndrome (PCOS) is a complex endocrine disease among women of reproductive age and is one of the main causes of infertility. Non-alcoholic fatty liver disease (NAFLD), the most prominent chronic liver disease in adults, is characterized by excess hepatic triglyceride (TG) accumulation. PCOS women have increased risk of NAFLD and uric acid has been documented to have a positive correlation with subclinical tissue damage and might be the link in the cystic. Spironolactone (SPL) is a mineralocorticoid receptor (MR) blocker that has been in wide clinical use for some decades. In this research, we investigated the effects of SPL on ovarian and hepatic tissue damage in experimental PCOS rats induced by letrozole (LET). A total of eighteen adult female Wistar rats were used for this study and the animals divided into 3 groups are treated with vehicle, LET (1 mg/kg), and LET+SPL (SPL; 0.25 mg/kg), p.o. once daily respectively for 21 uninterrupted days. Results showed that LET treatment induced features of PCOS characterized by increased plasma testosterone (T) and luteinizing hormone (LH) together with increased body weight. Abnormal ovarian and hepatic histomorphological changes were also observed with elevated uric acid (UA) and TG accumulation in both tissues respectively. Treatment with SPL however attenuated the elevated testosterone in the LET-induced PCOS model accompanied with a reversal in the observed ovarian and hepatic UA, TG accumulation, and altered histomorphological changes. Taken together, spironolactone reversed the PCOS-induced ovarian and hepatic tissue damage by suppressing tissue UA and TG accumulation.

Pancreatic Fat is not significantly correlated with β-cell Dysfunction in Patients with new-onset Type 2 Diabetes Mellitus using quantitative Computed Tomography

Objective: Type 2 diabetes mellitus (T2DM) is a chronic condition resulting from insulin resistance and insufficient β-cell secretion, leading to improper glycaemic regulation. Previous studies have found that excessive fat deposits in organs such as the liver and muscle can cause insulin resistance through lipotoxicity that affects β-cell function. The relationships between fat deposits in pancreatic tissue, the function of β-cells, the method of visceral fat evaluation and T2DM have been sought by researchers. This study aims to elucidate the role of pancreatic fat deposits in the development of T2DM using quantitative computed tomography (QCT), especially their effects on islet β-cell function. Methods: We examined 106 subjects at the onset of T2DM who had undergone abdominal QCT. Estimated pancreatic fat and liver fat were quantified using QCT and calculated. We analysed the correlations with Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) scores and other oral glucose tolerance test-derived parameters that reflect islet function. Furthermore, correlations of estimated pancreatic fat and liver fat with the area under the curve for insulin (AUC_INS) and HOMA-IR were assessed with partial correlation analysis and demonstrated by scatter plots. Results: Associations were found between estimated liver fat and HOMA-IR, AUC_INS, the modified β-cell function index (MBCI) and Homeostatic Model Assessment β (HOMA-β). However, no significant differences existed between estimated pancreas fat and those parameters. Similarly, after adjustment for sex, age and body mass index, only estimated liver fat was correlated with HOMA-IR and AUC_INS. Conclusions: This study suggests no significant correlation between pancreatic fat deposition and β-cell dysfunction in the early stages of T2DM using QCT as a screening tool. The deposits of fat in the pancreas and the resulting lipotoxicity may play an important role in the late stage of islet cell function dysfunction as the course of T2DM progresses.

The Systemic Redox Status Is Maintained in Non-Smoking Type 2 Diabetic Subjects Without Cardiovascular Disease: Association with Elevated Triglycerides and Large VLDL

Decreased circulating levels of free thiols (R-SH, sulfhydryl groups) reflect enhanced oxidative stress, which plays an important role in the pathogenesis of cardiometabolic diseases. Since hyperglycemia causes oxidative stress, we questioned whether plasma free thiols are altered in patients with type 2 diabetes mellitus (T2DM) without cardiovascular disease or renal function impairment. We also determined their relationship with elevated triglycerides and very low density lipoproteins (VLDL), a central feature of diabetic dyslipidemia. Fasting plasma free thiols (colorimetric method), lipoproteins, VLDL (nuclear magnetic resonance spectrometry), free fatty acids (FFA), phospholipid transfer protein (PLTP) activity and adiponectin were measured in 79 adult non-smoking T2DM subjects (HbA1c 51 ± 8 mmol/mol, no use of insulin or lipid lowering drugs), and in 89 non-smoking subjects without T2DM. Plasma free thiols were univariately correlated with glucose (r = 0.196, p < 0.05), but were not decreased in T2DM subjects versus non-diabetic subjects (p = 0.31). Free thiols were higher in subjects with (663 ± 84 µmol/L) versus subjects without elevated triglycerides (619 ± 91 µmol/L; p = 0.002). Age- and sex-adjusted multivariable linear regression analysis demonstrated that plasma triglycerides were positively and independently associated with free thiols (β = 0.215, p = 0.004), FFA (β = 0.168, p = 0.029) and PLTP activity (β = 0.228, p = 0.002), inversely with adiponectin (β = −0.308, p < 0.001) but not with glucose (β = 0.052, p = 0.51). Notably, the positive association of free thiols with (elevated) triglycerides appeared to be particularly evident in men. Additionally, large VLDL were independently associated with free thiols (β = 0.188, p = 0.029). In conclusion, circulating free thiols are not decreased in this cohort of non-smoking and generally well-controlled T2DM subjects. Paradoxically, higher triglycerides and more large VLDL particles are likely associated with higher plasma levels of thiols, reflecting lower systemic oxidative stress.

Hepatic Fatty Acid Balance and Hepatic Fat Content in Humans With Severe Obesity

OBJECTIVE

Nonalcoholic fatty liver disease can lead to hepatic inflammation/damage. Understanding the physiological mechanisms that contribute to excess hepatic lipid accumulation may help identify effective treatments.

DESIGN

We recruited 25 nondiabetic patients with severe obesity scheduled for bariatric surgery. To evaluate liver export of triglyceride fatty acids, we measured very-low-density lipoprotein (VLDL)-triglyceride secretion rates the day prior to surgery using an infusion of autologous [1-14C]triolein-labeled VLDL particles. Ketone body response to fasting and intrahepatic long-chain acylcarnitine concentrations were used as indices of hepatic fatty acid oxidation. We measured intraoperative hepatic uptake rates of plasma free fatty acids using a continuous infusion of [U-13C]palmitate, combined with a bolus dose of [9,10-3H]palmitate and carefully timed liver biopsies. Total intrahepatic lipids were measured in liver biopsy samples to determine fatty liver status. The hepatic concentrations and enrichment from [U-13C]palmitate in diacylglycerols, sphingolipids, and acyl-carnitines were measured using liquid chromatography/tandem mass spectrometry.

RESULTS

Among study participants with fatty liver disease, intrahepatic lipid was negatively correlated with VLDL-triglyceride secretion rates (r = -0.92, P = 0.01) but unrelated to hepatic free fatty acid uptake or indices of hepatic fatty acid oxidation. VLDL-triglyceride secretion rates were positively correlated with hepatic concentrations of saturated diacylglycerol (r = 0.46, P = 0.02) and sphingosine-1-phosphate (r = 0.44, P = 0.03).

CONCLUSION

We conclude that in nondiabetic humans with severe obesity, excess intrahepatic lipid is associated with limited export of triglyceride in VLDL particles rather than increased uptake of systemic free fatty acids.

The regulation of hepatic fatty acid synthesis and partitioning: the effect of nutritional state

Nonalcoholic fatty liver disease (NAFLD) is an increasing global public health burden. NAFLD is strongly associated with type 2 diabetes mellitus, obesity and cardiovascular disease and begins with intrahepatic triacylglycerol accumulation. Under healthy conditions, the liver regulates lipid metabolism to meet systemic energy needs in the fed and fasted states. The processes of fatty acid uptake, fatty acid synthesis and the intracellular partitioning of fatty acids into storage, oxidation and secretion pathways are tightly regulated. When one or more of these processes becomes dysregulated, excess lipid accumulation can occur. Although genetic and environmental factors have been implicated in the development of NAFLD, it remains unclear why an imbalance in these pathways begins. The regulation of fatty acid partitioning occurs at several points, including during triacylglycerol synthesis, lipid droplet formation and lipolysis. These processes are influenced by enzyme function, intake of dietary fats and sugars and whole-body metabolism, and are further affected by the presence of obesity or insulin resistance. Insight into how the liver controls fatty acid metabolism in health and how these processes might be affected in disease would offer the potential for new therapeutic treatments for NAFLD to be developed.

Cytokines and inflammation in adipogenesis: an updated review

The biological relevance of cytokines is known for more than 20 years. Evidence suggests that adipogenesis is one of the biological events involved in the regulation of cytokines, and pro-inflammatory cytokines (e.g., TNFα and IL-1β) inhibit adipogenesis through various pathways. This inhibitory effect can constrain the hyperplastic expandability of adipose tissues. Meanwhile, chronic low-grade inflammation is commonly observed in obese populations. In some individuals, the impaired ability of adipose tissues to recruit new adipocytes to adipose depots during overnutrition results in adipocyte hypertrophy, ectopic lipid accumulation, and insulin resistance. Intervention studies showed that pro-inflammatory cytokine antagonists improve metabolism in patients with metabolic syndrome. This review focuses on the cytokines currently known to regulate adipogenesis under physiological and pathophysiological circumstances. Recent studies on how inhibited adipogenesis leads to metabolic disorders were summarized. Although the interplay of cytokines and lipid metabolism is yet incompletely understood, cytokines represent a class of potential therapeutic targets in the treatment of metabolic disorders.

Syncing Exercise With Meals and Circadian Clocks

Circadian rhythms, meals, and exercise modulate energy metabolism. This review explores the novel hypothesis that there is an optimal time of day to exercise to improve 24 h glycemia and lipemia in individuals with type 2 diabetes.

Hepatic fatty acid synthesis and partitioning: the effect of metabolic and nutritional state

When we consume dietary fat, a series of complex metabolic processes ensures that fatty acids are absorbed, transported around the body and used/stored appropriately. The liver is a central metabolic organ within the human body and has a major role in regulating fat and carbohydrate metabolism. Studying hepatic metabolism in human subjects is challenging; the use of stable isotope tracers and measurement of particles or molecules secreted by the liver such as VLDL-TAG and 3-hydroxybutyrate offers the best insight into postprandial hepatic fatty acid metabolism in human subjects. Diet derived fatty acids are taken up by the liver and mix with fatty acids coming from the lipolysis of adipose tissue, and those already present in the liver (cytosolic TAG) and fatty acids synthesised de novo within the liver from non-lipid precursors (known as de novo lipogenesis). Fatty acids are removed from the liver by secretion as VLDL-TAG and oxidation. Perturbations in these processes have the potential to impact on metabolic health. Whether fatty acids are partitioned towards oxidation or esterification pathways appears to be dependent on a number of metabolic factors; not least ambient insulin concentrations. Moreover, along with the phenotype and lifestyle factors (e.g. habitual diet) of an individual, it is becoming apparent that the composition of the diet (macronutrient and fatty acid composition) may play pivotal roles in determining if intra-hepatic fat accumulates, although what remains to be elucidated is the influence these nutrients have on intra-hepatic fatty acid synthesis and partitioning.

Ideal cardiovascular health associated with fatty liver: Results from a multi-ethnic survey

BACKGROUND AND AIMS

Little is known about the role of liver enzymes as predictors of non-liver-related morbidity and mortality. The ideal cardiovascular health (CVH) score proposed by the American Heart Association (AHA) can be used to predict mortality and morbidity. We investigated the association of the CVH score with liver enzymes and the risk of non-alcoholic fatty liver disease (NAFLD) among US adults.

METHODS

By using the National Health and Nutrition Examination Survey database (cross-sectional), the CVH score was calculated as meeting ideal levels of the following components: 4 behaviors (smoking, body mass index, physical activity and diet adherence) and 3 factors (total cholesterol, blood pressure and fasting glucose).

RESULTS

Individuals with a higher CVH score ("better CVH") had a more favorable profile of liver biomarkers. Adjusted (for age, gender, race, poverty to income ratio, education, marital status and alcohol intake) linear regression indicated significant and negative associations between liver biomarkers and CVH score: (β = -0.069, p < 0.001) for alanine aminotransferase, (β = -0.095, p < 0.001), aspartate aminotransferase, (β = -0.067, p < 0.001), alkaline phosphatase and (β = -0.125, p < 0.001) and fatty liver index. In the logistic regression, with the same confounders, individuals with a higher CVH score had 12% less likelihood of NAFLD compared with those with a lower score. Furthermore, each CVH metric separately was inversely linked to the risk of NAFLD.

CONCLUSIONS

For the first time among US adults, our findings shed light on the role CVH on liver biomarkers.

Sodium acetate improves disrupted glucoregulation and hepatic triglyceride content in insulin-resistant female rats: involvement of adenosine deaminase and dipeptidyl peptidase-4 activities

Combined oral contraceptive (COC) treatment has been shown to be associated with glucose deregulation and increased triglyceride levels, but the mechanisms are elusive. Soluble dipeptidyl peptidase-4 (sDPP-4) and adenosine deaminase (ADA) are involved in the initiation and/or progression of cardiometabolic disorders. We therefore, hypothesized that increased DPP-4 and ADA activities are involved in glucose deregulation and hepatic triglyceride accumulation induced by COC treatment. This study also investigated whether short-chain fatty acid, acetate, would protect against COC-induced dysmetabolic effects. Female Wistar rats received (p.o.) vehicle and COC (1.0 μg ethinylestradiol plus 5.0 μg levonorgestrel) with or without sodium acetate (ACE; 200 mg) for 8 weeks. Treatment with COC led to increased plasma triglyceride-glucose index, 1-h postload glucose response, insulin, free fatty acid, insulin resistance, and impaired glucose tolerance. COC treatment also resulted in increased plasma and hepatic triglycerides (TG), TG/HDL-cholesterol ratio, malondialdehyde, uric acid, lactate dehydrogenase, DPP-4, ADA, and xanthine oxidase (XO) activities. On the other hand, COC led to reduction in nitric oxide level. However, ACE significantly ameliorated the alterations induced by COC treatment, but XO activity remains elevated during COC treatment. This result also demonstrates that increased DPP-4 and ADA activities are at least in part involved in glucose deregulation and hepatic TG accumulation induced by COC treatment. Therefore, sodium acetate would impact positively on cardiometabolic disorders, at least in part, by inhibition of DPP-4 and ADA activities.

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.

New insights into ANGPLT3 in controlling lipoprotein metabolism and risk of cardiovascular diseases

Dyslipidemia, characterized by elevation of plasma low density lipoprotein cholesterol (LDL-C), triglyceride (TG) and reduction of plasma high density lipoprotein cholesterol (HDL-C), has been verified as a causal risk factor for cardiovascular diseases (CVD), leading to a high mortality rate in general population. It is important to understand the molecular metabolism underlying dyslipidemia in order to reduce the risk and to develop effective therapeutic approaches against CVD. ANGPTL3 (human) or Angptl3 (mouse), one member of the angiopoietin-like protein (ANGPTL) family, has been identified as an important regulator of lipid metabolism by inhibiting LPL and EL activity. Results have demonstrated that inactivation of Angptl3 in mice could obviously reduce the level of TG, LDL-C and the atherosclerotic lesion size, leading to a lower risk for dyslipidemia and CVD. Additionally, in humans, carriers with homozygous LOF mutations in ANGPTL3 have lower plasma LDL-C, TG levels and lower risk of atherosclerosis compared to the non-carriers. Here, we collect the latest data and results, giving a new insight into the important role of ANGPTL3 in controlling lipoprotein metabolism. Finally, we introduce two update reports on the antisense oligonucleotide and monoclonal antibody-based inactivation of ANGPTL3 in human clinical trials, to identify that ANGPTL3 could be a novel and effective target for the treatment of dyslipidemia and CVD.

Sex- and Age-Specific Optimal Anthropometric Indices as Screening Tools for Metabolic Syndrome in Chinese Adults

OBJECTIVES

To compare the predictive ability of six anthropometric indices for identification of metabolic syndrome (MetS) and to determine their optimal cut-off points among Chinese adults.

METHODS

A total of 59,029 participants were enrolled. Body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR), a body shape index (ABSI), body roundness index (BRI), and conicity index (CI) were measured. Receiver-operating characteristic curves analyses were performed to determine the discriminatory power of these indices for the identification of cardiometabolic risks and diagnosis of MetS. The differences in the area under the curve (AUC) values among the indices were evaluated. The Youden index was used to determine the optimal cut-off points.

RESULTS

WHtR and BRI exhibited the highest AUC values for identifying MetS and most cardiometabolic risk factors in both sexes, whereas ABSI showed the lowest AUC value. The general optimal cut-off points in women were 23.03 kg/m² for BMI, 77.25 cm for WC, 0.490 for WHtR, and 3.179 for BRI; those in men were 24.64 kg/m² for BMI, 87.25 cm for WC, 0.510 for WHtR, and 3.547 for BRI. The AUC values and cut-off points of the indices were also analyzed in each age and BMI category.

CONCLUSIONS

In Chinese adults, WHtR and BRI showed a superior predictive power for MetS in both sexes, which can be used as simple and effective screening tools for cardiometabolic risks and MetS in clinical practice.

Triglyceride-Rich Lipoproteins and Remnants: Targets for Therapy?

It is now evident that elevated circulating levels of triglycerides in the non-fasting state, a marker for triglyceride (TG)-rich remnant particles, are associated with increased risk of premature cardiovascular disease (CVD). Recent findings from basic and clinical studies have begun to elucidate the mechanisms that contribute to the atherogenicity of these apoB-containing particles. Here, we review current knowledge of the formation, intravascular remodelling and catabolism of TG-rich lipoproteins and highlight (i) the pivotal players involved in this process, including lipoprotein lipase, glycosylphosphatidylinositol HDL binding protein 1 (GPIHBP1), apolipoprotein (apo) C-II, apoC-III, angiopoietin-like protein (ANGPTL) 3, 4 and 8, apoA-V and cholesteryl ester transfer protein; (ii) key determinants of triglyceride (TG) levels and notably rates of production of very-low-density lipoprotein 1 (VLDL1) particles; and (iii) the mechanisms which underlie the atherogenicity of remnant particles. Finally, we emphasise the polygenic nature of moderate hypertriglyceridemia and briefly discuss modalities for its clinical management. Several new therapeutic strategies to attenuate hypertriglyceridemia have appeared recently, among which those targeted to apoC-III appear to hold considerable promise.

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.

Kinetics of plasma triglycerides in abdominal obesity

PURPOSE OF REVIEW

Abdominal obesity is associated with a number of important metabolic abnormalities including liver steatosis, insulin resistance and an atherogenic lipoprotein profile (termed dyslipidemia). The purpose of this review is to highlight recent progress in understanding the pathogenesis of this dyslipidemia.

RECENT FINDINGS

Recent results from kinetic studies using stable isotopes indicate that the hypertriglyceridemia associated with abdominal obesity stems from dual mechanisms: (1) enhanced secretion of triglyceride-rich lipoproteins and (2) impaired clearance of these lipoproteins. The over-secretion of large triglyceride-rich VLDLs from the liver is linked to hepatic steatosis and increased visceral adiposity. The impaired clearance of triglyceride-rich lipoproteins is linked to increased levels of apolipoprotein C-III, a key regulator of triglyceride metabolism.

SUMMARY

Elucidation of the pathogenesis of the atherogenic dyslipidemia in abdominal obesity combined with the development of novel treatments based on apolipoprotein C-III may in the future lead to better prevention, diagnosis and treatment of the atherogenic dyslipidemia in abdominal obesity.

The triglyceride and glucose index (TyG) is an effective biomarker to identify nonalcoholic fatty liver disease

Background

The triglyceride and glucose index (TyG) has been proposed as a marker of insulin resistance. We aimed to investigate the ability of TyG, through comparing with the predictive value of alanine aminotransferase (ALT), to identify individuals at risk for nonalcoholic fatty liver disease (NAFLD).

Methods

A cross-sectional study was conducted in a Chinese health examination cohort of 10 761 people aged above 20 years. NAFLD was diagnosed by ultrasonography.

Results

Compared with the participants in the lowest quartile of TyG, the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for NAFLD were 1.8 (1.5–2.1), 3.0 (2.5–3.5), and 6.3 (5.3–7.5) for those in the second, the third, and the fourth quartile of TyG, whereas the corresponding ORs (95% CI) for NAFLD were 1.5 (1.3–1.7), 1.9 (1.6–2.2), and 3.1 (2.6–3.7) for the upper three quartiles of ALT. These results suggested that TyG was superior to ALT in association with NAFLD risk. According to the ROC analysis, the optimal cut-off point of TyG for NAFLD was 8.5 and the area under the ROC curve (AUC) was 0.782 (95% CI 0.773–0.790), with 72.2 and 70.5% sensitivity and specificity, respectively. The AUC of TyG was larger than that of ALT (0.715 (95% CI 0.705–0.725), P for difference <0.0001), whereas the largest AUC was obtained when adding TyG to ALT (0.804 (95% CI 0.795–0.812), P for difference <0.0001).

Conclusions

TyG is effective to identify individuals at risk for NAFLD. A TyG threshold of 8.5 was highly sensitive for detecting NAFLD subjects and may be suitable as a diagnostic criterion for NAFLD in Chinese adults.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-017-0409-6) contains supplementary material, which is available to authorized users.

Three single nucleotide polymorphisms associated with type 2 diabetes mellitus in a Chinese population

An Indian study recently observed three new loci: rs9552911 in the SGCG, rs1593304 near PLXNA4 and rs4858889 in SCAP associated with type 2 diabetes mellitus (T2DM) in a south Asian population. The present study aimed to validate these findings in a Chinese population. We genotyped the above three single-nucleotide polymorphisms (SNPs), rs9552911, rs1593304, and rs4858889, in a group of 1,972 Chinese individuals, comprising of 966 type 2 diabetic patients and 976 controls. Anthropometric variables and biochemical traits were measured in all the participants. The association analyses of genotype-disease and genotype-traits were estimated. The genotype frequency of rs9552911 differed statistically between the cases and controls (P=0.017). The difference was also evident between the cases and controls in non-obese participants (P=0.033). In addition, the SNP rs9552911 was associated with weight (P=0.033), total cholesterol (P=0.006) and low-density lipoprotein-cholesterol (P=0.007). The SNP rs1593304 was associated with β-cell function estimated by the homeostatic model assessment of β-cell function (P=0.041). However, there was no significant association between rs4858889 and T2DM. In conclusion, the results show that the SNP rs9552911 was associated with T2DM, possibly by affecting body mass index and lipid metabolism. The SNP rs1593304 may impair β-cell function.

Suppression of Type-II Diabetes with Dyslipidemia and Nephropathy by Peels of Musa cavendish Fruit

Musa cavendish, peels has local and traditional use to promote wound healing, hyperglycemia, ulceration etc. The present work investigated the lipid lowering; nephroprotective and glucose lowering properties of ethanolic extract of peels of Musa cavendish (EMC) in alloxan-induced diabetic rats. The EMC 250, 500 and 1000 mg/kg/day and the vehicle were administered orally to alloxan-induced diabetic rats (n = 6) for 3 weeks. Changes in plasma glucose, lipid profile along with kidney function before and after treatment with EMC were recorded. The ethanolic extract of peels of Musa cavendish reduced blood glucose, serum triglyceride, cholesterol, LDL cholesterol and creatinine levels and improvement in body weight, liver glycogen, serum HDL cholesterol, serum albumin and total protein level when compared with untreated rats. Musa cavendish has lipid lowering, nephroprotective and antidiabetic property by regulating glucose uptake in the liver and muscles by restoring the intracellular energy balance.

BMI history and risk of incident fatty liver: a population-based large-scale cohort study

BACKGROUND AND AIMS

Most physicians might consider that fatty liver would develop along with increasing body weight; however, an association between BMI history and incident fatty liver has not been clarified as yet.

METHODS

We carried out a population-based cohort study that included 4427 healthy Japanese individuals who received yearly health-checkup programs over a decade. Fatty liver was diagnosed using ultrasonography.

RESULTS

During the observational period, 38.7% (case/N=1002/2588) of men and 17.3% (319/1847) of women were diagnosed with fatty liver. Among these, only 18.9% (189 of 1002 participants) of men and 18.5% (59 of 319) of women developed fatty liver when they reached the lifetime maximum BMI. Adjusted odds ratio of the difference between lifetime maximum BMI and BMI at age 20 years (ΔBMImax-20 years) for incident fatty liver was 1.33 [95% confidence interval (CI) 1.28-1.39, P<0.001] in men or 1.40 (95% CI 1.33-1.49, P<0.001) in women. According to receiver operator characteristic (ROC) analysis, the optimal cut-off points of ΔBMImax-20 years for incident fatty liver were 4.82 kg/m [area under ROC curve 0.70 (95% CI 0.68-0.72), P<0.001] in men and 4.11 kg/m [area under ROC curve 0.76 (95% CI 0.73-0.79), P<0.001] in women.

CONCLUSION

The ΔBMImax-20 years was associated with an increased risk of incident fatty liver. In addition, more patients developed fatty liver not at the maximum point of BMI history, but after that. Therefore, it is useful to check ΔBMImax-20 years and to continue observing the individuals for detection of fatty liver.

The Effects of Insulin Resistance on Individual Tissues: An Application of a Mathematical Model of Metabolism in Humans

Whilst the human body expends energy constantly, the human diet consists of a mix of carbohydrates and fats delivered in a discontinuous manner. To deal with this sporadic supply of energy, there are transport, storage and utilisation mechanisms, for both carbohydrates and fats, around all tissues of the body. Insulin-resistant states such as type 2 diabetes and obesity are characterised by reduced efficiency of these mechanisms. Exactly how these insulin-resistant states develop, for example whether there is an order in which tissues become insulin resistant, is an active area of research with the hope of gaining a better overall understanding of insulin resistance. In this paper, we use a previously derived system of 12 first-order coupled differential equations that describe the transport between, and storage in, different tissues of the human body. We briefly revisit the derivation of the model before parametrising the model to account for insulin resistance. We then solve the model numerically, separately simulating each individual tissue as insulin resistant, and discuss and compare these results, drawing three main conclusions. The implications of these results are in accordance with biological intuition. First, insulin resistance in a tissue creates a knock-on effect on the other tissues in the body, whereby they attempt to compensate for the reduced efficiency of the insulin-resistant tissue. Second, insulin resistance causes a fatty liver, and the insulin resistance of tissues other than the liver can cause fat to accumulate in the liver. Finally, although insulin resistance in individual tissues can cause slightly reduced skeletal muscle metabolic flexibility, it is when the whole body is insulin resistant that the biggest effect on skeletal muscle flexibility is seen.

The role of ANGPTL3 in controlling lipoprotein metabolism

Angiopoietin-like protein 3 (ANGPTL3) is a secretory protein regulating plasma lipid levels via affecting lipoprotein lipase- and endothelial lipase-mediated hydrolysis of triglycerides and phospholipids. ANGPTL3-deficiency due to loss-of-function mutations in the ANGPTL3 gene causes familial combined hypobetalipoproteinemia (FHBL2, OMIM # 605019), a phenotype characterized by low concentration of all major lipoprotein classes in circulation. ANGPTL3 is therefore a potential therapeutic target to treat combined hyperlipidemia, a major risk factor for atherosclerotic coronary heart disease. This review focuses on the mechanisms behind ANGPTL3-deficiency induced FHBL2.

Basal and insulin-regulated VLDL1 and VLDL2 kinetics in men with type 2 diabetes

AIMS/HYPOTHESIS

Hypertriacylglycerolaemia is a hallmark of diabetic dyslipidaemia with increased concentrations of triacylglycerol (TG)-rich VLDL1 particles. However, whether VLDL1 secretion or removal is abnormal in type 2 diabetes remains unclear. The aim of this study was to compare basal and insulin-mediated VLDL1- and VLDL2-TG kinetics in men with type 2 diabetes and healthy men using a novel direct VLDL1- and VLDL2-TG labelling method.

METHODS

Twelve men with type 2 diabetes and 12 healthy men matched for age and BMI were recruited. VLDL1- and VLDL2-TG turnover were measured during a 4 h basal period and a 3.5 h hyperinsulinaemic clamp period using a primed-constant infusion of ex vivo labelled VLDL1-TG and VLDL2-TG.

RESULTS

Basal VLDL1-TG and VLDL2-TG secretion rates were similar in men with diabetes and healthy men. During hyperinsulinaemia, VLDL1-TG secretion rates were suppressed significantly in both groups, whereas no suppression of VLDL2-TG secretion rate was observed. VLDL1-TG to VLDL2-TG transfer rate was not significantly different from zero in both groups, while VLDL1-TG fatty acid oxidation rate was substantial, with a contribution to total energy expenditure of approximately 15% during postabsorptive conditions. VLDL1 and VLDL2 particle size (TG/apolipoprotein B [apoB] ratio) and apoB-100 concentration were unaltered by hyperinsulinaemia in men with type 2 diabetes, but significantly reduced in healthy men.

CONCLUSIONS/INTERPRETATION

Insulin inhibits VLDL1-TG secretion rate similarly in age- and BMI-matched men with type 2 diabetes and healthy men, while VLDL2-TG secretion is unaltered by hyperinsulinaemia. However, VLDL1- and VLDL2-apoB levels are not lowered by hyperinsulinaemia in men with type 2 diabetes, which is indicative of a diminished hepatic response to insulin.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01564550.

Alcoholic vs non-alcoholic fatty liver in rats: distinct differences in endocytosis and vesicle trafficking despite similar pathology

Background

Non-alcoholic and alcoholic fatty liver disease (NAFLD and AFLD, respectively) are major health problems, as patients with either condition can progress to hepatitis, fibrosis, and cirrhosis. Although histologically similar, key differences likely exist in these two models. For example, altered content of several vesicle trafficking proteins have been identified in AFLD, but their content in NAFLD is unknown. In this study, we compared select parameters in NAFLD and AFLD in a rat model.

Methods

We fed either Lieber- DeCarli liquid control or alcohol-containing (35 % as calories) diet (AFLD model) or lean or high-fat (12 or 60 % derived from fat, respectively) pellets (NAFLD model) for 8–10 weeks, n = 8 in each model. Serum, hepatocytes and liver tissue were analyzed. Liver injury markers were measured in serum, triglyceride content and endocytosis (binding and internalization of ¹²⁵I- asialoorosomucoid) was measured in isolated hepatocytes, and content of selected trafficking proteins (Rab3D, Rab7 and Rab18) were determined in whole liver tissue.

Results

Although liver injury markers and triglyceride content were similar in both models, binding and internalization of ¹²⁵I- asialoorosomucoid was significantly impaired in the hepatocytes from AFLD, but not NAFLD, animals. In addition, protein content of the asialoglycoprotein receptor (ASGPR) and three trafficking proteins, Rab3D, Rab7and Rab18, were significantly decreased after alcohol, but not high-fat feeding. Levels of protein carbonylation, amount of glutathione stores, and lipid peroxidation were similar irrespective of the insult to the livers that resulted in fatty liver.

Conclusion

Impairments in protein trafficking in AFLD are likely a direct result of alcohol administration, and not a function of fatty liver.

Hypertriglyceridemia in an outpatient department--Significance as an atherosclerotic risk factor

BACKGROUND

Although a relationship between elevated triglycerides (TG) and cardiovascular diseases is generally accepted, its extent is still discussed. This retrospective study analyzed the incidence of cardiovascular events (CVE) and pancreatitis as well as the therapeutic regimen in patients being treated for hypertriglyceridemia (HTG) at an outpatient department.

METHODS

The cohort included 183 patients with mild and 49 patients with severe HTG; subgroups were formed and compared according to gender, presence of metabolic vascular syndrome (MVS) and lipid values.

RESULTS

Patients in this study seem to have had CVE at younger age than reported event rates in the general population. TG levels, rates of CVE and pancreatitis were reduced in all groups during therapy, which could be linked to use of omega-3 fatty acids and fibrates. Patients with persisting severe HTG as a result of incompliance showed massive risk for pancreatitis.

CONCLUSION

Although no significant association between TG levels and CVE could be established, the combination of HTG and other cardiovascular risk factors such as MVS seems to be especially dangerous. The lipid-lowering drug therapy appeared to be effective with respect to CVE and pancreatitis incidence.