The association between retinal microvascular changes, metabolic risk factors, and liver histology in pediatric patients with non-alcoholic fatty liver disease (NAFLD)

Artificial intelligence in liver imaging: methods and applications

Liver disease is regarded as one of the major health threats to humans. Radiographic assessments hold promise in terms of addressing the current demands for precisely diagnosing and treating liver diseases, and artificial intelligence (AI), which excels at automatically making quantitative assessments of complex medical image characteristics, has made great strides regarding the qualitative interpretation of medical imaging by clinicians. Here, we review the current state of medical-imaging-based AI methodologies and their applications concerning the management of liver diseases. We summarize the representative AI methodologies in liver imaging with focusing on deep learning, and illustrate their promising clinical applications across the spectrum of precise liver disease detection, diagnosis and treatment. We also address the current challenges and future perspectives of AI in liver imaging, with an emphasis on feature interpretability, multimodal data integration and multicenter study. Taken together, it is revealed that AI methodologies, together with the large volume of available medical image data, might impact the future of liver disease care.

Insights into the liver-eyes connections, from epidemiological, mechanical studies to clinical translation

Maintenance of internal homeostasis is a sophisticated process, during which almost all organs get involved. Liver plays a central role in metabolism and involves in endocrine, immunity, detoxification and storage, and therefore it communicates with distant organs through such mechanisms to regulate pathophysiological processes. Dysfunctional liver is often accompanied by pathological phenotypes of distant organs, including the eyes. Many reviews have focused on crosstalk between the liver and gut, the liver and brain, the liver and heart, the liver and kidney, but with no attention paid to the liver and eyes. In this review, we summarized intimate connections between the liver and the eyes from three aspects. Epidemiologically, we suggest liver-related, potential, protective and risk factors for typical eye disease as well as eye indicators connected with liver status. For molecular mechanism aspect, we elaborate their inter-organ crosstalk from metabolism (glucose, lipid, proteins, vitamin, and mineral), detoxification (ammonia and bilirubin), and immunity (complement and inflammation regulation) aspect. In clinical application part, we emphasize the latest advances in utilizing the liver-eye axis in disease diagnosis and therapy, involving artificial intelligence-deep learning-based novel diagnostic tools for detecting liver disease and adeno-associated viral vector-based gene therapy method for curing blinding eye disease. We aim to focus on and provide novel insights into liver and eyes communications and help resolve existed clinically significant issues.

Obesity-induced ocular changes in children and adolescents: A review

Childhood obesity has reached epidemic levels worldwide. Overweight and obesity is associated with an increase in several inflammatory markers, leading to chronic low-grade inflammation responsible for macro- and microvascular dysfunction. While the impact of obesity on overall health is well-described, less is known about its ocular manifestations. Still, there are few studies in children and adolescents in this regard and they are inconsistent. However, some evidence suggests a significant role of overnutrition in the development of changes in retinal microvasculature parameters (wider venules, narrower arterioles, lower arteriovenous ratio). Higher values of intraocular pressure were found to be positively correlated with high body mass index (BMI) as well as obesity. In addition, the retinal nerve fiber layer (RNFL) values seem to be lower in obese children, and there is a significant negative correlation between RNFL values and anthropometric and/or metabolic parameters. Changes also could be present in macular retinal thickness and choroidal thickness as well as in the retinal vessel density in children with obesity. However, these associations were not consistently documented. The purpose of this review is to present the most current issues on child obesity and the related potential ocular effects through an overview of international publications from the years 1992-2022.

Bile Duct Ligation Impairs Function and Expression of Mrp1 at Rat Blood-Retinal Barrier via Bilirubin-Induced P38 MAPK Pathway Activations

Liver injury is often associated with hepatic retinopathy, resulting from accumulation of retinal toxins due to blood-retinal barrier (BRB) dysfunction. Retinal pigment epithelium highly expresses MRP1/Mrp1. We aimed to investigate whether liver injury affects the function and expression of retinal Mrp1 using bile duct ligation (BDL) rats. Retinal distributions of fluorescein and 2,4-dinitrophenyl-S-glutathione were used for assessing Mrp1 function. BDL significantly increased distributions of the two substrates and bilirubin, downregulated Mrp1 protein, and upregulated phosphorylation of p38 and MK2 in the retina. BDL neither affected the retinal distribution of FITC-dextran nor expressions of ZO-1 and claudin-5, demonstrating intact BRB integrity. In ARPE-19 cells, BDL rat serum or bilirubin decreased MRP1 expression and enhanced p38 and MK2 phosphorylation. Both inhibiting and silencing p38 significantly reversed the bilirubin- and anisomycin-induced decreases in MRP1 protein. Apparent permeability coefficients of fluorescein in the A-to-B direction (Papp, A-to-B) across the ARPE-19 monolayer were greater than Papp, B-to-A. MK571 or bilirubin significantly decreased Papp, A-to-B of fluorescein. Bilirubin treatment significantly downregulated Mrp1 function and expression without affecting integrity of BRB and increased bilirubin levels and phosphorylation of p38 and MK2 in rat retina. In conclusion, BDL downregulates the expression and function of retina Mrp1 by activating the p38 MAPK pathway due to increased bilirubin levels.

Dysregulated Neurovascular Control Underlies Declining Microvascular Functionality in People With Non-alcoholic Fatty Liver Disease (NAFLD) at Risk of Liver Fibrosis

Background/Aims

Increasing evidence shows that non-alcoholic fatty liver disease (NAFLD) is associated with dysregulation of microvascular perfusion independently of established cardio-metabolic risk factors. We investigated whether hepatic manifestations of NAFLD such as liver fibrosis and liver fat are associated with microvascular hemodynamics through dysregulation of neurovascular control.

Methods

Microvascular dilator (post-occlusive reactive hyperemia) and sympathetically mediated constrictor (deep inspiratory breath-hold) responses were measured at the forearm and finger, respectively, using laser Doppler fluximetry. Non-linear complexity-based analysis was used to assess the information content and variability of the resting blood flux (BF) signals, attributable to oscillatory flow-motion activity, and over multiple sampling frequencies.

Results

Measurements were made in 189 adults (113 men) with NAFLD, with (n = 65) and without (n = 124) type 2 diabetes mellitus (T2DM), age = 50.9 ± 11.7 years (mean ± SD). Microvascular dilator and constrictor capacity were both negatively associated with age (r = −0.178, p = 0.014, and r = −0.201, p = 0.007, respectively) and enhanced liver fibrosis (ELF) score (r = −0.155, p = 0.038 and r = −0.418, p < 0.0001, respectively). There was no association with measures of liver fat, obesity or T2DM. Lempel-Ziv complexity (LZC) and sample entropy (SE) of the BF signal measured at the two skin sites were associated negatively with age (p < 0.01 and p < 0.001) and positively with ELF score (p < 0.05 and p < 0.0001). In individuals with an ELF score ≥7.8 the influence of both neurogenic and respiratory flow-motion activity on LZC was up-rated (p < 0.0001).

Conclusion

Altered microvascular network functionality occurs in adults with NAFLD suggesting a mechanistic role for dysregulated neurovascular control in individuals at risk of severe liver fibrosis.

The impact of IGF-I, puberty and obesity on early retinopathy in children: a cross-sectional study

Background

Childhood obesity has been correlated with coronary heart disease, but the correlation with microvascular disease remains unclear. The retinal microcirculation is affected early in the process of atherosclerosis and it offers the opportunity to indirectly study the effects of obesity on small brain vessels. Insulin-like growth factor 1 (IGF-I) is involved in angiogenesis and it has a crucial role in retinal vascularization.

Methods

A single-centre cross-sectional study was performed in 268 children and adolescents (116 males; mean age 13.03 ± 1.9 years,) with overweight/obesity, in order to identify risk factors for early retinopathy.

Results

Nine patients (3.3%) showed signs of retinopathy, defined as arteriovenous crossings and/or papilledema. Body mass index and fat mass, analysed by Dual X-ray Absorptiometry, were not different in patients with or without retinopathy. Patients with retinopathy were pubertal and showed higher waist circumference (107.78 ± 15.83 versus 99.46 ± 10.85 cm; p: 0.027), waist circumference/height ratio (0.66 ± 0.07 versus 0.62 ± 0.05; p: 0.04) and IGF-I SDS (0.03 ± 1.3 versus − 0.66 ± 0.9; p: 0.04). Multivariate analysis (after correction for sex, age, family history of type 2 diabetes mellitus, obesity, cardiovascular disease, hypertension and dyslipidaemia) showed that waist circumference/height ratio and IGF-I SDS were the only variables independently correlated with the presence of retinopathy.

Conclusions

Retinal vascular changes may become evident as an early complication of overweight and obesity, even during childhood and adolescence. Relatively high levels of IGF-I during this phase may act as an additional risk factor for microvascular damage. The screening for retinopathy should be proposed to all children and adolescents with overweight/obesity.

NAFLD/NASH in patients with type 2 diabetes and related treatment options

Type 2 diabetes may reduce life expectancy and patients' quality of life due to its micro- and macro-vascular complications and to the higher risk of several types of cancer. An emerging important factor is represented by the hepatic involvement; it is recognized that excessive hepatic fat accumulation represents a typical feature of diabetic patients and that it also plays an important pathogenic role. It is now evident that non-alcoholic fatty liver disease (NAFLD), generally perceived as a benign condition, may have on the contrary an important deleterious impact for diabetic patients increasing the risk to develop cardiovascular complications but also serious hepatic diseases, in particular non-alcoholic steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma. Lifestyle intervention, bariatric surgery and several drug therapies have now accumulated evidence of efficacy in treating NASH. On the other hand, their durability and safety in the long-term is yet to be proven and their use may be sometimes associated with side effects or higher risk of adverse events limiting the regular administration or contraindicating it. Professional health care providers, building awareness about the importance of these hepatic complications, should put more efforts in primary prevention using a behavioral therapy needing a multidisciplinary approach, in secondary prevention applying on a regular basis in the clinical setting available predictive algorithms to identify the patients at higher cardiovascular and hepatologic risk, and in tertiary prevention treating, when not contraindicated, the diabetic patients preferentially with drugs with proven benefit on NAFLD/NASH.

Hypertension, diabetes, atherosclerosis and NASH: Cause or consequence?

Non-alcoholic fatty liver disease (NAFLD) has become one of the most common forms of chronic liver disease worldwide and its prevalence is expected to continue rising. NAFLD has traditionally been considered a consequence of metabolic syndrome (MetS). However, the link between NAFLD and MetS components, especially type 2 diabetes mellitus (T2DM), hypertension (HTN), and cardiovascular disease (CVD) is more complex than previously thought. Indeed, the adverse effects of NAFLD extend far beyond the liver, with a large body of clinical evidence now suggesting that NAFLD may precede and/or promote the development of T2DM, HTN and atherosclerosis/CVD. The risk of developing these cardiometabolic diseases parallels the underlying severity of NAFLD. Accumulating evidence suggests that the presence and severity of NAFLD is associated with an increased risk of incident T2DM and HTN. Moreover, long-term prospective studies indicate that the presence and severity of NAFLD independently predicts fatal and nonfatal CVD events. In this review, we critically discuss the rapidly expanding body of clinical evidence that supports the existence of a bi-directional relationship between NAFLD and various components of MetS, particularly T2DM and HTN, as well as the current knowledge regarding a strong association between NAFLD and CVD morbidity and mortality. Finally, we discuss the most updated putative biological mechanisms through which NAFLD may contribute to the development of HTN, T2DM and CVD.

Obesity, metabolic syndrome and diabetic retinopathy: Beyond hyperglycemia

Diabetic retinopathy (DR) is the most feared ocular manifestation of diabetes. DR is characterized by progressive retinal damage that may eventually result in blindness. Clinically, this blindness is caused by progressive damage to the retinal microvasculature, which leads to ischemia, retinal swelling, and neovascularization. Retinopathy is associated with both type 1 and type 2 diabetes, with DR being the leading cause of new onset blindness in United States adults. Despite this strong association with diabetes, it must be noted that the development of retinopathy lesions is multifactorial and may occur in individuals without an established history of diabetes. Metabolic syndrome is a multifactorial condition of central obesity, hypertriglyceridemia, dyslipidemia, hypertension, fasting hyperglycemia, and insulin resistance. Although several studies examined the individual components observed in the metabolic syndrome in relation to the development of DR, there is conflicting data as to the association of the metabolic syndrome with the development of retinopathy lesions in non-diabetic subjects. This review will summarize the current literature on the evidence of the metabolic syndrome on retinopathy in subjects with and without an established history of diabetes. This review will also discuss some of the mechanisms through which metabolic syndrome can contribute to the development of retinopathy.

Nonalcoholic fatty liver disease in Asia: emerging perspectives

As in the West, nonalcoholic fatty liver disease (NAFLD) is the commonest chronic liver disease in Asia, with a prevalence higher than 40 % in some countries. The risk factors for NAFLD development are similar to those in Western countries, including increased body mass index, diabetes, insulin resistance, and metabolic syndrome. NAFLD in Asians is associated with different extrahepatic manifestations involving the cardiovascular, gastrointestinal, and renal systems. A considerable proportion of Asians with NAFLD are described as having "lean" NAFLD. Present in approximately 20 % of the Asian population, lean NAFLD is closely linked with insulin resistance, diabetes, and other metabolic complications, but its association with disease progression to nonalcoholic steatohepatitis and cirrhosis remains to be defined. There is emerging evidence of the interactions of NAFLD with hepatitis B virus and hepatitis C virus infection in Asia. Unlike in Western countries, NAFLD constitutes only a minority of cirrhosis and hepatocellular carcinoma cases in Asia. Possible explanations are the lower prevalence of obesity and the overwhelming problem of viral hepatitis in Asia. With aging of the obesity cohort in Asia, NAFLD-related liver complications are expected to increase.

The Relationship between Nonalcoholic Fatty Liver Disease and Retinopathy in NHANES III

Background

Nonalcoholic fatty liver disease (NAFLD), an emerging multisystem disease, has the similar pathogenesis with diabetes and is prevalent in diabetes. This study investigated whether NAFLD is associated with retinopathy in individuals with diabetes and without diabetes.

Methods

The association between NAFLD and retinopathy was investigated in 5963 participants aged 40 years and older who participated in the NHANES III, a nationally representative, population-based and cross-sectional study. NAFLD was detected via ultrasonography, and fundus photographs were obtained to grade retinopathy patterns. We performed multivariate logistic regression analysis to investigate the relationship between the presence of retinopathy and NAFLD and diabetes.

Results

After adjusting for multiple covariates, NAFLD population had no evidence of retinopathy increase in population without diabetes (odds ratio [OR]: 0.77; 95% confidence interval [CI]: 0.48 to 1.26). In addition, NAFLD in individuals with diabetes was not significantly associated with retinopathy (OR: 0.77; 95% CI: 0.47 to 1.26), independent of age, gender, ethnicity, waist circumference, serum high-density lipoprotein (HDL) cholesterol, serum triglycerides, systolic blood pressure, and glycated hemoglobin.

Conclusions

In the US general population, NAFLD is not a precipitating factor of retinopathy in population with or without diabetes.

Noninvasive assessment of the retina and the choroid using enhanced-depth imaging optical coherence tomography shows microvascular impairments in childhood obesity

PURPOSE

To evaluate the retinal vascular diameters and macular and subfoveal choroidal thicknesses of obese and nonobese children using enhanced-depth imaging spectral domain optical coherence tomography (EDI SD-OCT).

METHODS

The retinal vascular diameters of the 4 largest retinal arterioles and venules and macular and subfoveal choroidal thickness measurements of 40 obese children (body mass index [BMI] z score above +2.0 standard deviations) were obtained by EDI SD-OCT and compared with those of 40 age- and sex-matched nonobese children. Anthropometric measures, including weight and height, were also obtained. BMI z score was defined using standardized protocols.

RESULTS

The mean BMI z scores of obese children were 2.59 ± 0.62; of nonobese children, -0.20 ± 0.92. The mean diameter of retinal arterioles was significantly smaller (P = 0.002) in obese children compared to nonobese children, whereas the mean diameter of retinal venules was larger (P = 0.008). The macular and subfoveal choroidal thicknesses were significantly thinner (P = 0.031 and 0.014, resp.) in obese children compared to nonobese children.

CONCLUSIONS

The narrower retinal arterioles, wider retinal venules, and thinner macular and subfoveal choroidal thicknesses in obese children seem to be associated with microvascular impairments in childhood obesity.