Hepatic fat is a stronger correlate of key clinical and molecular abnormalities than visceral and abdominal subcutaneous fat in youth

Non-alcoholic fatty liver disease in obese subjects as related to increasing insulin resistance and deteriorating glucose control: Three years of follow-up from a longitudinal survey

Purpose

This observational trial was performed to evaluate liver parameters in overweight or obese subjects in the context of insulin resistance and glucose control over time.

Subjects/Methods

Insulin resistance, glucose control and several parameters for liver integrity were monitored in 177 overweight (BMI > 28 kg/m2) subjects over a mean of 30 months. Volunteers were categorized according to insulin resistance (HOMAIR score) and glucose control in subjects with normal glucose control (NGT), impaired glucose control (IGT), or diabetes mellitus type 2 (T2DM). Liver fat and fibrosis were evaluated by sonographic elastography (FibroScan®) and clinical scores, such as the AST/ALT ratio, fatty liver index (FLI), and NAFLD fibrosis score (NFS).

Results

Liver fat fraction as estimated by the controlled attenuation parameter (CAP), and the FLI were significantly higher in subjects with T2DM compared to IGT and NGT. While fasting insulin levels and the HOMAIR score continuously increased over time, no change in CAP or FLI occurred during follow up. CAP was correlated with FLI (r = 0.50; p < 0.0001) and the HOMAIR score (r = 0.32; p < 0.0001). An inverse correlation was observed between serum adiponectin levels and FLI (r = -0.37; p < 0.0001), the HOMAIR score (r = -0.19; p < 0.001, and CAP (r = -0.15; p < 0.01).

Conclusions

In subjects with a BMI ≥ 28 kg/m2, liver fat fraction is significantly elevated in those with T2DM compared to IGT or NGT. Liver fat fraction is associated with deteriorating insulin sensitivity and loss of glucose control. Despite a continuous increase in insulin resistance, no change in liver fat content or stiffness occurred over 30 months.

The challenging role of micro-RNAs in non-alcoholic fatty liver disease in children with obesity: is it time for a new era?

INTRODUCTION

As the pediatric obesity epidemic, nonalcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease in childhood. Pediatric NAFLD pathophysiology is tangled and still unclear, but insulin resistance (IR), genetics, epigenetics, oxidative stress, and inflammation act as key players. Due to the increased cardiometabolic risk of these patients, several biomarkers have been proposed for early NAFLD identification, but their clinical utility is poor. Recently, hepatic dysregulation of microRNAs (miRNAs) has been linked to metabolic dysfunction, which in turn implied in NAFLD development. Evidence on the intriguing role of miRNAs in NAFLD pathogenesis has emerging especially in at-risk children such as those with obesity. However, pediatric evidence supporting their potential use as early noninvasive NAFLD tools is still limited but promising.

AREAS COVERED

We provided an overview on the emerging role of miRNAs in pediatric NAFLD by addressing some issues regarding their pathophysiological link with the metabolic milieu and their role as reliable NAFLD markers in children with obesity.

EXPERT OPINION

Strong evidence supports a potential role of miRNAs as early biomarkers of NAFLD in children with obesity. They might represent a valid diagnostic and targeted therapeutic tool due to its close pathogenic link with the metabolic milieu.

Problems and Challenges Associated with Renaming Non-alcoholic Fatty Liver Disease to Metabolic Associated Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) has become the world’s largest chronic liver disease in the 21st century, affecting 20%–30% of the world’s population. As the epidemiology, etiology, and pathogenesis of NAFLD have been studied in-depth, it has been gradually recognized that most patients with NAFLD have one or more combined metabolic abnormalities known as metabolic syndrome. In 2020, the international expert group changed the name of NAFLD to metabolic-associated fatty liver disease (MAFLD) and proposed new diagnostic criteria for MAFLD and MAFLD-related liver cirrhosis, as well as the conceptual framework of other cause-related fatty liver diseases to avoid diagnosis based on the exclusion of other causes and better reflect its pathogenesis. However, there are still many ambiguities in the term, and changing the name does not address the unmet key needs in the field. The change from NAFLD to MAFLD was not just a change of definition. The problems and challenges are summarized as follows: epidemiology, children, rationality of “metabolism,” diagnostic criteria, double/multiple causes, drug discovery, clinical trials, and awareness raising. Metabolic-associated fatty liver disease has complex disease characteristics, and there are still some problems that need to be solved.

MRI-based quantification of adipose tissue distribution in healthy adult cats during body weight gain

The incidence of obesity in pet population increased over the last decades. Cats have been suggested as model for human obesity because of similar co-morbidities as diabetes and dyslipidaemia. Aim of this study were to quantify the distribution of visceral and subcutaneous adipose tissue (VAT, SAT respectively) in healthy adult cats during feeding-induced body weight (BW) gain by MRI, and to correlate it to the increased hepatic fat fraction (HFF). Cats received a commercial dry food ad libitum for 40 weeks and were longitudinally scanned three times. VAT and SAT were determined from Dixon MRI data by a dedicated software solution (ATLAS, established in human and rodents). HFF was quantified from a commercially available sequence. At both individual and group level, normalized adipose tissue volumes significantly increased longitudinally, with median VAT/SAT ratio always < 1. With increased BW, more than proportional increased total adipose tissue was observed together with more than proportional increased HFF. HFF is disproportionately high in overweight cats compared to SAT and VAT accumulation in the 40 weeks observation period. Quantitative unbiased MRI examination of different body fat components is useful in longitudinal monitoring of obesity in cats.

Longitudinal comparison of insulin resistance and dyslipidemia in children with and without perinatal HIV infection in South Africa

INTRODUCTION

HIV infection is associated with insulin resistance and dyslipidaemia driven by HIV-associated immune dysregulation and antiretroviral therapy (ART). Children living with perinatally acquired HIV (CHIV) face many decades of exposure to these factors. We evaluated the longitudinal trajectory of insulin resistance and dyslipidaemia in CHIV and HIV-exposed uninfected children (CHEU), compared with children HIV-unexposed (CHU).

METHODS

Four hundred and eighty-five children (141 CHIV, 169 CHEU, 175 CHU) aged 5-16 years, previously part of CHER and P1060 trials, were followed annually at Tygerberg Children's Hospital, South Africa. The primary outcome was Homeostatic Model Assessment of Insulin Resistance (HOMA-IR). Secondary outcomes included low-density lipoprotein (LDL) cholesterol, triglyceride-to-HDL ratio, android fat mass and SBP. Outcomes were evaluated using linear mixed effects models, adjusting for potential confounders.

RESULTS

CHIV had 73% greater HOMA-IR than CHU in ages 6-8 years (95% CI 15.9-158.2%, P < 0.001), and 24.7% greater HOMA-IR than CHU in ages 9-10 years (0.3-55.1%, P = 0.04). By 10-11 years, the difference was not significant (P = 0.161). Longitudinally, triglyceride-to-HDL was 47.94% (34.50-62.73%, P < 0.001) higher in CHIV vs. CHU; LDL was 0.25 mmol/l (0.10-0.39, P = 0.001) higher in CHIV vs. CHU; android fat mass was 11.57% (-21.11 to -0.87%, P = 0.035) lower in CHIV than CHU. No significant difference in SBP was found. CHEU and CHU had similar outcomes.

CONCLUSION

Early-treated CHIV have elevated insulin resistance, which resolves with time. Triglyceride-to-HDL ratio and LDL cholesterol were elevated into puberty. CHIV should be monitored for insulin resistance, dyslipidaemia and subclinical cardiovascular disease.

Vitamin D and ω-3 Polyunsaturated Fatty Acids towards a Personalized Nutrition of Youth Diabetes: A Narrative Lecture

After the discovery of insulin, nutrition has become central in the management of diabetes in order to limit glycemic rise after meals, optimize metabolic control, and prevent complications. Over the past one hundred years, international scientific societies have consecutively refined nutritional needs and optimized food intake for the treatment of diabetes. In particular, over the past century, nutrition applied with pumps for the administration of insulin and continuous glucose monitoring have allowed substantial advancement in the treatment of type 1 diabetes mellitus. The role of some substances, such as vitamin D and n-3 polyunsaturated fatty acids, have been proposed without univocal conclusions, individually or in combination, or in the diet, to improve the nutrition of type 1 and type 2 diabetes. This second condition, which is highly associated with overweight, should be prevented from childhood onwards. Personalized nutrition could bypass the problem, reaching a scientific conclusion on the individual subject. This article focuses on childhood and adolescent diabetes, aims to provide a narrative summary of nutrition over the past century, and promotes the concept of personalized nutrition to pediatricians and pediatric diabetologists as a possible tool for the treatment of type 1 diabetes and the prevention of type 2 diabetes.

Body composition trajectories from birth to 5 years and hepatic fat in early childhood

BACKGROUND

Adiposity is an established risk factor for pediatric nonalcoholic fatty liver disease (NAFLD), but little is known about the influence of body composition patterns earlier in life on NAFLD risk.

OBJECTIVES

We aimed to examine associations of body composition at birth and body composition trajectories from birth to early childhood with hepatic fat in early childhood.

METHODS

Data were from the longitudinal Healthy Start Study in Colorado. Fat-free mass index (FFMI), fat mass index (FMI), percentage body fat (BF%), and BMI were assessed at birth and/or ∼5 y in >1200 children by air displacement plethysmography and anthropometrics. In a subset (n = 285), hepatic fat was also assessed at ∼5 y by MRI. We used a 2-stage modeling approach: first, we fit body composition trajectories from birth to early childhood using mixed models with participant-specific intercepts and linear slopes (i.e., individual deviations from the population average at birth and rate of change per year, respectively); second, associations of participant-specific trajectory deviations with hepatic fat were assessed by multivariable-adjusted linear regression.

RESULTS

Participant-specific intercepts at birth for FFMI, FMI, BF%, and BMI were inversely associated with log-hepatic fat in early childhood in models adjusted for offspring demographics and maternal/prenatal variables [back-transformed β (95% CI) per 1 SD: 0.93 (0.88, 0.99), 0.94 (0.88, 0.99), 0.94 (0.89, 0.99), and 0.90 (0.85, 0.96), respectively]. Whereas, faster velocities for BF% and BMI from birth to ∼5 y were positively associated with log-hepatic fat [back-transformed β (95% CI) per 1 SD: 1.08 (1.01, 1.15) and 1.08 (1.02, 1.15), respectively]. These latter associations of BF% and BMI velocities with childhood hepatic fat were attenuated to the null when adjusted for participant-specific intercepts at birth.

CONCLUSIONS

Our findings suggest that a smaller birth weight, combined with faster adiposity accretion in the first 5 y, predicts higher hepatic fat in early childhood. Strategies aiming to promote healthy body composition early in life may be critical for pediatric NAFLD prevention.This study was registered voluntarily at clinicaltrials.gov as NCT02273297.

Visceral fat and arterial stiffness in youth with healthy weight, obesity, and type 2 diabetes

BACKGROUND AND OBJECTIVES

Visceral fat is associated with increased cardiovascular risk in adults, but studies in youth are limited. We assessed associations between visceral fat and arterial stiffness in youth with healthy weight, obesity and type 2 diabetes and determined whether relationships were independent of clinical estimates of body fatness.

METHODS

This cross-sectional sample included youth ages 10-23 years (67% female, 56% non-black) with healthy weight (body mass index [BMI] = 5th-85th percentile, n = 236), obesity (BMI ≥ 95th percentile, n = 224) and type 2 diabetes (BMI ≥ 95th percentile, n = 145). Visceral fat was assessed via dual-energy X-ray absorptiometry. Carotid-femoral pulse wave velocity (PWV) was assessed via applanation tonometry. Obesity and type 2 diabetes groups were combined for final analyses. Analyses accounted for age, sex, ancestry and mean arterial pressure.

RESULTS

Visceral fat and PWV were greater in youth with obesity versus healthy weight (p < 0.001). In youth with obesity, but not healthy weight, visceral fat was positively associated with PWV (p < 0.001) and was predictive of PWV beyond BMI and waist circumference.

CONCLUSIONS

Visceral fat likely contributes to subclinical cardiovascular complications in youth. Since cardiovascular health tracks from adolescence to adulthood, longitudinal studies in youth with obesity are required to define the role of visceral fat in lifelong cardiovascular disease risk.

Whole-Body MRI-Derived Adipose Tissue Characterization and Relationship to Pulmonary Function Impairment

Background: Specification of adipose tissues by whole-body magnetic resonance imaging (MRI) was performed and related to pulmonary function parameters in a population-based cohort. Methods: 203 study participants underwent whole-body MRI and pulmonary function tests as part of the KORA (Cooperative Health Research in the Augsburg Region) MRI study. Both visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were derived from the T1-Dixon sequence, and hepatic adipose tissue from the proton density fat fraction (PDFFhepatic). Associations between adipose tissue parameters and spirometric indices such as forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) and Tiffeneau-index (FEV1/FVC) were examined using multivariate linear regression analysis excluding cofounding effects of other clinical parameters. Results: VAT (β = −0.13, p = 0.03) and SAT (β = −0.26, p < 0.001), but not PDFFhepatic were inversely associated with FEV1, while VAT (β = −0.27, p < 0.001), SAT (β = −0.41, p < 0.001), and PDFFhepatic (β = −0.17, p = 0.002) were inversely associated with FVC. PDFFhepatic was directly associated with the Tiffeneau index (β = 2.46, p < 0.001). Conclusions: In the adjusted linear regression model, VAT was inversely associated with all measured spirometric parameters, while PDFFhepatic revealed the strongest association with the Tiffeneau index. Non-invasive adipose tissue quantification measurements might serve as novel biomarkers for respiratory impairment.

Dietary sugar restriction reduces hepatic de novo lipogenesis in boys with fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) in children resulting from the obesity epidemic is widespread and increasing. Although the complexities of pediatric NAFLD are recognized, screening and therapies in children remain limited. Moreover, pediatric NAFLD diagnosis fails to consider insulin resistance and metabolic dysfunction as important determinants. In this issue of the JCI, Cohen et al. explored the contribution of dietary factors to the pathogenesis of NAFLD in adolescent boys with biopsy-proven NAFLD and control participants. Notably, dietary sugar restriction over 8 weeks decreased de novo lipogenesis (DNL) and hepatic fat. The change in DNL correlated with changes in insulin and weight, but not with changes in hepatic fat, supporting the relevance of metabolic dysfunction to NAFLD. These results confirm the pathological link between excessive dietary sugar intake and NAFLD in children and support recent recommendations to change the nomenclature of NAFLD to metabolic associated fatty liver disease (MAFLD).

Hepatic Fat in Early Childhood Is Independently Associated With Estimated Insulin Resistance: The Healthy Start Study

BACKGROUND

Fatty liver disease is a common metabolic abnormality in adolescents with obesity but remains understudied in early childhood.

OBJECTIVES

To describe hepatic fat deposition in prepubertal children and examine cross-sectional associations with metabolic markers and body composition.

METHODS

Data were from 286 children ages 4 to 8 years old in the Healthy Start Study, a longitudinal prebirth cohort in Colorado (USA). Assessments included magnetic resonance imaging to quantify hepatic and abdominal fats, fasting blood draws to measure metabolic markers, and air displacement plethysmography to measure body composition (fat mass and fat-free mass).

RESULTS

The median (interquartile range) for hepatic fat was 1.65% (1.24%, 2.11%). Log-transformed hepatic fat was higher in Hispanic [mean (95% CI): 0.63 (0.52, 0.74)] vs non-Hispanic white children [0.46 (0.38, 0.53), P = 0.01] and children with overweight/obesity [0.64 (0.49, 0.79)] vs normal-weight [0.47 (0.40, 0.53), P = 0.02]. Higher log-hepatic fat was associated with higher insulin [β (95% CI): 1.47 (0.61, 2.33) uIU/mL, P = 0.001] and estimated insulin resistance (homeostatic model assessment) [0.40 (0.20, 0.60), P < 0.001] in the full sample and glucose [5.53 (2.84, 8.21) mg/dL, P < 0.001] and triglycerides [10.92 (2.92,18.91) mg/dL, P = 0.008] in boys, in linear regression models adjusted for sociodemographics, maternal/perinatal confounders, and percentage body fat. Log-hepatic fat was also associated with abdominal subcutaneous adipose tissue [SAT; 7.37 (1.12,13.60) mm2, P = 0.02] in unadjusted models, but this was attenuated and insignificant after adjusting for confounders.

CONCLUSIONS

While hepatic fat was low in children 4 to 8 years old, it was independently associated with estimated insulin resistance and exhibited sex-specific associations with glucose and triglycerides, suggesting hepatic fat may be an early indicator of metabolic dysfunction in youth.

Magnetic Resonance Spectroscopy of Hepatic Fat from Fundamental to Clinical Applications

The number of individuals suffering from fatty liver is increasing worldwide, leading to interest in the noninvasive study of liver fat. Magnetic resonance spectroscopy (MRS) is a powerful tool that allows direct quantification of metabolites in tissue or areas of interest. MRS has been applied in both research and clinical studies to assess liver fat noninvasively in vivo. MRS has also demonstrated excellent performance in liver fat assessment with high sensitivity and specificity compared to biopsy and other imaging modalities. Because of these qualities, MRS has been generally accepted as the reference standard for the noninvasive measurement of liver steatosis. MRS is an evolving technique with high potential as a diagnostic tool in the clinical setting. This review aims to provide a brief overview of the MRS principle for liver fat assessment and its application, and to summarize the current state of MRS study in comparison to other techniques.

The Role of Hepatic Fat Accumulation in Glucose and Insulin Homeostasis-Dysregulation by the Liver

Accumulation of hepatic triacylglycerol (TG) is associated with obesity and metabolic syndrome, which are important pathogenic factors in the development of type 2 diabetes. In this narrative review, we summarize the effects of hepatic TG accumulation on hepatic glucose and insulin metabolism and the underlying molecular regulation in order to highlight the importance of hepatic TG accumulation for whole-body glucose metabolism. We find that liver fat accumulation is closely linked to impaired insulin-mediated suppression of hepatic glucose production and reduced hepatic insulin clearance. The resulting systemic hyperinsulinemia has a major impact on whole-body glucose metabolism and may be an important pathogenic step in the development of type 2 diabetes.