Preperitoneal fat as a non-invasive marker of increased risk of severe non-alcoholic fatty liver disease in patients with type 2 diabetes

CT and MR imaging of the properitoneal fat pad: a pictorial essay

The properitoneal fat pad is a distinctive anatomical structure located in the midline of anterior abdominal wall between the transversalis fascia and parietal peritoneum. It has variable size and configuration depending on the gender and nutritional status of individuals, but CT and MR images of the upper abdomen can readily depict its shape and adipose composition. The purpose of this essay is to illustrate the CT and MRI features of normal properitoneal fat pad, and the spectrum of pathological processes that affect it among patients. This information can be relevant to the practicing radiologists and clinicians for the correct diagnosis and management of such conditions because most lesions of this fat pad produce nonspecific symptoms.

An unwelcome inheritance: childhood obesity after diabetes in pregnancy

Diabetes in pregnancy affects 20 million women per year and is associated with increased risk of obesity in offspring, leading to insulin resistance and cardiometabolic disease. Despite the substantial public health ramifications, relatively little is known about the pathophysiological mechanisms underlying obesity in these high-risk children, which creates a barrier to successful intervention. While maternal glucose itself is undeniably a major stimulus upon intrauterine growth, the degree of offspring hyperinsulinism and disturbed lipid metabolism in mothers and offspring are also likely to be implicated in the disease process. The aim of this review is to summarise current understanding of the pathophysiology of childhood obesity after intrauterine exposure to maternal hyperglycaemia and to highlight possible opportunities for intervention. I present here a new unified hypothesis for the pathophysiology of childhood obesity in infants born to mothers with diabetes, which involves self-perpetuating twin cycles of pancreatic beta cell hyperfunction and altered lipid metabolism, both acutely and chronically upregulated by intrauterine exposure to maternal hyperglycaemia.

Correlation of hepatic transient elastography measurements and abdominal adiposity in children: A cross-sectional study

BACKGROUND

Transient elastography is a non-invasive assessment of steatosis (measured as the controlled attenuation parameter, [CAP]) and fibrosis (measured as liver stiffness measurement, [LSM]) in patients with pediatric non-alcoholic fatty liver disease (NAFLD). Abdominal adiposity is considered the most important factor for metabolic dysregulation including NAFLD. However, there is lack of a correlation between transient elastography measurements and abdominal adiposity. Accordingly, this study aimed to assess the correlation between transient elastography measurements and abdominal adiposity in children.

METHODS

This cross-sectional study included 137 children who visited the Taipei Veterans General Hospital. Hepatic steatosis (CAP) and fibrosis (LSM), were assessed by transient elastography. Abdominal adiposity including subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and preperitoneal adipose tissue (PPT) was assessed using abdominal sonography. The correlation between transient elastography measurements and abdominal adiposity was assessed using multiple linear regression.

RESULTS

In total, 137 children were included in this study. SAT and VAT were significantly associated with CAP, whereas SAT was significantly associated with LSM. An increment of 1 mm in SAT increased CAP and LSM by 5.56 dB/m and 0.06 kPa, respectively.

CONCLUSION

Certain abdominal adiposities, especially SAT, are significantly associated with CAP and LSM, as determined by transient elastography. Simple abdominal adiposity measured using sonography may be useful for the early detection of pediatric NAFLD.

The Visceral Adiposity Index Is a Better Predictor of Excess Visceral Fat in Military Pilots: A Cross-sectional Observational Study

INTRODUCTION

Visceral adipose tissue (VAT) is related to cardiometabolic risk. Estimating it using the visceral adiposity index (VAI) could identify this risk in the Brazilian Air Force (BAF) aviator population. The aim here is to verify the predictive capacity of the VAI for identifying visceral fat areas compared to traditional obesity indicators in BAF pilots.

MATERIALS AND METHODS

Forty male BAF pilots were recruited. The study was conducted in two stages: the first applied a structured questionnaire to characterize the sample and identify sedentary behavior and the second obtained nutritional, anthropometric, and body composition data, carrying out biochemical and magnetic resonance imaging tests and investigating physical activity level in this stage. The comparison of the predictive capacity of the VAI with that of other adiposity indicators (body mass index [BMI], waist circumference, waist-height ratio, waist-hip ratio, and neck circumference) for detecting increased VAT and the determination of the optimal cutoff points for the different adiposity indicators were carried out using receiving operating characteristic (ROC) curves. An association was verified between the adiposity indicators and excess visceral fat using Poisson regression analysis with robust variance.

RESULTS

The VAI presented a better predictive capacity for VAT (area under the ROC curve = 0.941), while the BMI did not present diagnostic accuracy (95% CI < 0.5). The strength of the association with high visceral fat was also greater for the VAI than for the other indicators evaluated.

CONCLUSIONS

The VAI was shown to be a better predictor of excess VAT in relation to the other indicators studied. As it is a more easy-access and lower-cost technique than resonance, it enables greater applicability in tracing and monitoring the visceral obesity of a large contingent of military personnel.

Nutritional ultrasound®: Conceptualisation, technical considerations and standardisation

Nutritional ultrasound® is a new concept that uses ultrasound to assess body composition. It is composed of the evaluation of fat-free mass and fat mass. It is an emerging, economical, portable, non-invasive technique that evaluates the musculoskeletal area with linear, broadband, multifrequency probes, with a depth field of 20-100mm. It quantifies muscle modifications in malnutrition and provides information on functional changes (echogenicity). Although there are no validated specific cut-off points, the anterior rectum area of the quadriceps can be used as a criterion for malnutrition. The distribution of adipose tissue provides information on the energy reserve and the inflammatory pattern. It is important to integrate nutritional ultrasound® measures in clinical practice adapted to different settings and pathologies. It is necessary to establish training plans in nutritional ultrasound® for use by Endocrinology and Nutrition Specialists, with the aim of improving the diagnosis and treatment of their patients.

Body composition measured by bioelectrical impedance analysis is a viable alternative to magnetic resonance imaging in children with nonalcoholic fatty liver disease

OBJECTIVE

To determine the relationship between bioelectrical impedance analysis (BIA) and magnetic resonance imaging (MRI) obtained measures of body composition in children with nonalcoholic fatty liver disease (NAFLD).

METHODS

Youth with obesity and NAFLD who had BIA and abdominal MRI testing were included. BIA measured skeletal muscle mass (SMM), appendicular lean mass (ALM), trunk muscle mass (TMM), and percent body fat. MRI measured total psoas muscle surface area (tPMSA) and fat compartments. Univariate analysis described the relationship between BIA- and MRI-derived measurements. Multivariable regression analyses built a model with body composition measured via MRI.

RESULTS

115 patients (82 (71%) male, 38 (33%) Hispanic, median age14 years) were included. There was a strong correlation between tPMSA and SMM, ALM, and TMM (correlation coefficients [CCs]: 0.701, 0.689, 0.708, respectively; all P < .001). Higher SMM, ALM, and TMM were associated with higher tPMSA. This association remained after controlling for age, sex, ethnicity, type 2 diabetes mellitus status, and body mass index z-score. Total fat mass by BIA and MRI-determined total, subcutaneous, and intraperitoneal fat area correlated significantly (CCs: 0.813, 0.808, 0.515, respectively; all P < .001). In univariate regression, higher total fat mass by BIA was associated with increased total fat area and increased fat in each of the four regions measured by MRI. After controlling for confounders, the association between total fat mass by BIA and total fat area by MRI persisted.

CONCLUSIONS

BIA measures of muscle and fat mass correlate strongly with MRI measures of tPMSA and fat areas in children with obesity and NAFLD.

Magnetic Resonance Imaging Assessment of Abdominal Ectopic Fat Deposition in Correlation With Cardiometabolic Risk Factors

PURPOSE

Ectopic fat accumulation and abdominal fat distribution may have different cardiometabolic risk profiles. This study aimed to assess the associations between various magnetic resonance imaging (MRI)-acquired fat depots and cardiometabolic risk factors.

METHODS

A total of 320 subjects with median age of 59 years, 148 men and 172 women, were enrolled in the study. Visceral adipose tissue (VAT) area and fat fraction (FF), subcutaneous adipose tissue (SAT) area and FF at the L1-L2 levels, preperitoneal adipose tissue (pPAT) area and FF, hepatic FF, pancreatic FF, and intramuscular FF were assessed by MRI FF maps. The associations of various MRI-acquired fat depots with blood pressure, glucose, and lipid were examined using sex-stratified linear regression. Logistic regression stratified by sex was used to analyze the association of various MRI-acquired fat depots with the risk of hypertension, T2DM, and dyslipidemia.

RESULTS

The intraclass correlation coefficient (ICC) values were >0.9, which suggested good interobserver and intraobserver agreement. VAT area, V/S, hepatic fat, pancreatic fat, and pPAT rather than SAT area were significantly associated with multiple cardiometabolic risk factors (all p < 0.05). However, the patterns of these correlations varied by sex and specific risk factors. Also, VAT and SAT FF were only significantly associated with multiple cardiometabolic risk factors in women (all p < 0.05).

CONCLUSIONS

VAT, hepatic fat, pancreatic fat, and pPAT were associated with cardiovascular metabolic risk factors independent of BMI. The patterns of these correlations were related to gender. These findings further the understanding of the association between ectopic fat deposition and cardiometabolic risk factors and help to better understand the obesity heterogeneity.

The relationship between visceral adiposity and cardiometabolic risk in Chinese women with polycystic ovary syndrome

OBJECTIVE

To compare the extent to which visceral adiposity, as measured by mesenteric fat thickness, contribute to cardiometabolic risk, especially insulin resistance, in women with PCOS and healthy control.

METHODS

This is a cross-sectional study with a total of 190 women with PCOS fulfilling the Rotterdam diagnostic criteria. Women without PCOS were recruited from a previous study, which comprised 416 healthy women controls with normal glucose tolerance. All subjects underwent OGTT, biochemical assessment, and sonographic assessment with measurements of mesenteric, preperitoneal and subcutaneous fat thickness.

RESULTS

Mesenteric fat thickness was strongly correlated to cardiometabolic traits including blood pressure, fasting and 2-h glucose, triglycerides, HOMA-IR; and was negatively correlated to HDL-C in both cohorts (all p < 0.01). In PCOS, positive correlation was observed between mesenteric fat thickness and free androgen index (p < 0.01). Compared with controls, the regression line between mesenteric fat and HOMA-IR is much steeper in PCOS (p < 0.01).

CONCLUSION

Women with PCOS remain more insulin resistant compared to controls at any given degree of visceral adiposity.

Magnetic resonance imaging for the assessment of pathological hepatic findings in nonalcoholic fatty liver disease

The prevalence of nonalcoholic fatty liver disease (NAFLD) is expected to increase because of the current epidemics of obesity and diabetes, and NAFLD has become a major cause of chronic liver disease worldwide. Liver fibrosis is associated with poor long-term outcomes in patients with NAFLD. Additionally, increased mortality and liver-related complications are primarily seen in patients with nonalcoholic steatohepatitis (NASH); however, nonalcoholic fatty liver (NAFL) is believed to be benign and non-progressive. Therefore, distinguishing between NASH and NAFL is clinically important. Liver biopsy is the gold standard method for the staging of liver fibrosis and distinguishing between NASH and NAFL. Unfortunately, liver biopsy is an invasive and expensive procedure. Therefore, noninvasive methods, to replace biopsy, are urgently needed for the staging of liver fibrosis and diagnosing NASH. In this review, we discuss the recent studies on magnetic resonance imaging (MRI), including magnetic resonance elastography, proton density fat fraction measurement, and multiparametric MRI (mpMRI) that can be used in the assessment of NASH components such as liver fibrosis, steatosis, and liver injury including inflammation and ballooning.

Vitamin D status and non-alcoholic fatty liver disease in patients with type 1 diabetes

PURPOSE

In patients with type 1 diabetes (T1D), the prevalence of non-alcoholic fatty liver disease (NAFLD) ranges from 10 to 53% and contrasting evidence suggests that vitamin D deficiency may favor liver fat accumulation. Here, we investigated the association between vitamin D status and NAFLD in adults with T1D.

METHODS

220 consecutive adult T1D patients on multiple daily injections or continuous subcutaneous insulin infusion and not taking calcium or vitamin D supplements were included. Patient characteristics, 25(OH)D serum levels, and metabolic parameters were analyzed. Vitamin D status was defined as sufficiency ( ≥ 75 nmol/L; 30 ng/ml), insufficiency (50-75 nmol/L; 20-30 ng/ml), or deficiency ( < 50 nmol/L; 20 ng/ml). NAFLD was diagnosed at ultrasound examination and graded 0-3.

RESULTS

NAFLD was present in 57 patients (29.5%): 51 grade 1, 5 grade 2, and 1 grade 3. Median 25(OH)D levels were 53 nmol/L (IQR 38-70) in patients with NAFLD and 50 nmol/L (34-69) in patients without (p = 0.46). At multivariable analysis, NAFLD was not associated with 25(OH)D levels (p = 0.42) or vitamin D deficiency (p = 0.55), while BMI (OR 1.16, 95% CI 1.07-1.27) and serum triglycerides (OR 1.02, 95% CI 1.01-1.03) were independently associated with NAFLD.

CONCLUSIONS

Vitamin D status appears to have no link with low-grade NAFLD in patients with type 1 diabetes.

Relationship between abdominal fat stores and liver fat, pancreatic fat, and metabolic comorbidities in a pediatric population with non-alcoholic fatty liver disease

PURPOSE

To define the relationship between compartmental abdominal fat stores, liver and pancreatic fat fractions, and type 2 diabetes mellitus (T2DM) in children with non-alcoholic fatty liver disease (NAFLD).

METHODS

This was a retrospective study of patients with NAFLD who underwent abdominal MRI between August 2015 and July 2017. Using an axial multi-echo Dixon-based sequence, liver fat fraction (LFF) and pancreatic fat fraction (PFF) were measured. The fat image was used to quantify abdominal fat depots (thickness, cross-sectional area) at the L2 vertebral level. Multivariable models with stepwise selection were created for prediction of LFF, PFF, and T2DM status based upon variables of clinical interest.

RESULTS

86 patients (70% male, 25% Hispanic, 58% Caucasian, 11% African American) with a mean age of 14.2 ± 3.2 years were included. 19 (22%) patients were pre-diabetic or diabetic. Only ethnicity was a predictor of LFF (P = 0.0023) with Hispanic ethnicity associated with the highest LFF. Depending on the model, either total abdominal fat area (P = 0.0003) or patient weight (P = 0.008) were the only predictors of PFF. No patient variable predicted T2DM status.

CONCLUSIONS

In our population, there was an association between ethnicity and LFF, with the highest LFF in Hispanics. The presence or severity of hepatic steatosis could not be predicted based on patient size or the distribution of abdominal fat in our cohort. Neither LFF nor PFF were predictive of T2DM.

Accuracy of imaging methods for steatohepatitis diagnosis in non-alcoholic fatty liver disease patients: A systematic review

BACKGROUND & AIMS

Non-invasive tests to diagnose non-alcoholic steatohepatitis (NASH) are urgently needed. This systematic review aims to evaluate imaging accuracy in diagnosing NASH among non-alcoholic fatty liver disease (NAFLD) patients, using liver biopsy as reference.

METHODS

Eligible studies were systematic reviews and cross-sectional/cohort studies of NAFLD patients comparing imaging with histology, considering accuracy and/or associations. MEDLINE, Scopus, EMBASE and Cochrane Library databases were searched up to April 2018. Studies were screened on title/abstract, then assessed for eligibility on full-text. Data were extracted using a predesigned form. Risk of bias was assessed using Quality Assessment of Diagnostic Accuracy Studies-2 tool.

RESULTS

Of the 641 studies screened, 61 were included in scoping review, 30 of which (with accuracy results) in data synthesis. Imaging techniques included: elastography (transient elastography-TE, acoustic radiation force impulse-ARFI, magnetic resonance elastography-MRE), ultrasound (US), magnetic resonance (MR), computed tomography and scintigraphy. Histological NASH definition was heterogeneous. In 28/30 studies, no prespecified threshold was used (high risk of bias). AUROCs were up to 0.82 for TE, 0.90 for ARFI, 0.93 for MRE and 0.82 for US scores. MR techniques with higher accuracy were spectroscopy (AUROC = 1 for alanine), susceptibility-weighted imaging (AUROC = 0.91), multiparametric MR (AUROC = 0.80), optical analysis (AUROC = 0.83), gadoxetic acid-enhanced MR (AUROCs = 0.85) and superparamagnetic iron oxide-enhanced MR (AUROC = 0.87). Results derived mostly from single studies without independent prospective validation.

CONCLUSIONS

There is currently insufficient evidence to support the use of imaging to diagnose NASH. More studies are needed on US and MR elastography and non-elastographic techniques, to date the most promising methods.

Abdominal subcutaneous fat thickness and homeostasis model assessment of insulin resistance as simple predictors of nonalcoholic steatohepatitis

Background: Obesity, insulin resistance, and diabetes are major risk factors for nonalcoholic fatty liver disease (NAFLD). This study aims to evaluate the association between different grades of NAFLD and abdominal subcutaneous fat thickness with the homeostasis model assessment of insulin resistance (HOMA-IR). Methods: In this pilot study, 59 obese nondiabetic participants with NAFLD were enrolled. Total cholesterol, Hb_A1c, and HOMA-IR were measured. Abdominal subcutaneous fat thickness in the midline just below the xiphoid process in front of the left lobe of the liver (LSFT) and in the umbilical region (USFT), and the degree of hepatic steatosis, were evaluated by ultrasound scans, and their correlation with the degree of steatosis and the NAFLD Activity Score in liver biopsy was assessed. Results: Of the 59 studied participants, 15 had mild, 17 had moderate, and 27 had severe hepatic steatosis by abdominal ultrasound. The mean ± SD HOMA-IR level in NAFLD patients was 5.41±2.70. The severity of hepatic steatosis positively correlated with body mass index (P<0.001), HOMA-IR (P<0.001), serum triglycerides (P=0.001), LSFT (P<0.001), and USFT (P<0.001). Receiver operating characteristics analysis showed that LSFT at a cut-off of 3.45 cm is the most accurate predictor of severe hepatic steatosis, with 74.1% sensitivity and 84.4% specificity. The best cut-off of USFT for identifying severe hepatic steatosis is 4.55 cm, with 63% sensitivity and 81.3% specificity. Conclusion: Abdominal subcutaneous fat thicknesses in front of the left lobe of the liver and in the umbilical region, together with HOMA-IR, are reliable indicators of the severity of NAFLD in obese nondiabetic individuals.

PEGylation Regulates Self-Assembled Small-Molecule Dye-Based Probes from Single Molecule to Nanoparticle Size for Multifunctional NIR-II Bioimaging

To date, small-molecule dye-based probes have been at the forefront of research in biomedical imaging, especially in the second near-infrared (NIR-II) window (1.0-1.7 µm). However, how to precisely regulate the synthesized size of NIR-II organic dye-based probes remains challenging. Moreover, systematic studies on whether the size of NIR-II probes affects optical/pharmacokinetic properties are still rare. Here, an ingenious PEGylation strategy is developed to regulate the self-assembly size of organic dye-based (CH1055 scaffold) NIR-II probes (SCH1-SCH4) from nanoparticles to the single molecule, and the relationship between their size and chemical/physical properties is thoroughly investigated. Based on their own merits, nanoprobe SCH1 (≈170 nm), with outstanding fluorescent brightness (quantum yield ≈0.14%), performs accurate tracing of the lymphatic system as well as identification of vessel networks in mice brains with excellent signal-to-background ratio images. Meanwhile, rapidly excreted SCH4, showing fast and high passive liver tumor uptake and promising tumor/normal tissue ratios (>7), is capable of facilitating precise image-guided tumor surgery, and also demonstrates the first example of the assessment of liver fibrosis in the NIR-II window.