Low serum 25-hydroxyvitamin D concentrations associate with non-alcoholic fatty liver disease in adolescents independent of adiposity

Nutritional Approaches in Children with Overweight or Obesity and Hepatic Steatosis

Childhood obesity is a global public health problem. Worldwide, 41 million children under 5 years and 340 million children and adolescents between 5 and 19 years are overweight. In addition, the recent COVID-19 epidemic has further amplified this social phenomenon. Obesity is a condition associated with various comorbidities, such as nonalcoholic fatty liver disease (NAFLD). The pathophysiology of NAFLD in obesity is intricate and involves the interaction and dysregulation of several mechanisms, such as insulin resistance, cytokine signaling, and alteration of the gut microbiota. NAFLD is defined as the presence of hepatic steatosis in more than 5% of hepatocytes, evaluated by histological analysis. It can evolve from hepatic steatosis to steatohepatitis, fibrosis, cirrhosis, hepatocellular carcinoma, and end-stage liver failure. Body weight reduction through lifestyle modification remains the first-line intervention for the management of pediatric NAFLD. Indeed, studies suggest that diets low in fat and sugar and conversely rich in dietary fibers promote the improvement of metabolic parameters. This review aims to evaluate the existing relationship between obesity and NAFLD in the pediatric population and to assess the dietary patterns and nutritional supplementations that can be recommended to prevent and manage obesity and its comorbidities.

Non-alcoholic fatty liver disease is associated with decreased bone mineral density in upper Egyptian patients

Nonalcoholic fatty liver disease (NAFLD) has been linked with a number of extra hepatic diseases and could be a potential risk factor of decreasing bone mineral density. To determine whether Upper Egyptian patients with NAFLD are at risk of developing osteoporosis. Cross sectional study was done on a total 100 individuals; 50 patients diagnosed with NAFLD (based on ultrasound imaging) crossed-matched with 50 individuals without NAFLD based on age, sex and body mass index. Bone mineral density, serum calcium and phosphorus levels, serum parathyroid hormone, serum vitamin D and fasting insulin level were assessed. Osteoporosis was prevalent in NAFLD patients versus to controls (19/50 vs. 0/50; P < 0.001). There was significant decrease in bone mineral density in NAFLD patients than controls (- 2.29 ± 0.4 vs. - 1.53 ± 0.1; P < 0.001). There was a statistical significance decrease in serum vitamin D and calcium levels in NAFLD patients than controls. Furthermore, vitamin D levels in the NAFLD group was a predictor for osteoporosis (OR 0.614; 95% CI 0.348-0.825). Patients with NAFLD tend to have a significant decrease in bone density, vitamin D, and serum calcium levels than controls.

Beneficial Effect of Vitamin D on Non-Alcoholic Fatty Liver Disease (NAFLD) Progression in the Zebrafish Model

A major cause of chronic liver disease, cirrhosis, and hepatocellular carcinoma, non-alcoholic fatty liver disease (NAFLD) results from excessive liver fat accumulation. Vitamin D (VitD) plays multiple important roles in diverse physiologic processes. Here, we describe the role of VitD in the complex pathogenesis of NAFLD and explore the possible therapeutic role of VitD supplementation in NAFLD therapy. To compare the effect of VitD to other interventions such as low-calorie diet, we induced NAFLD in young adult zebrafish (Danio rerio, AB strain) and monitored the effects of VitD supplementation on the disease course. The zebrafish administered with high-dose VitD (1.25 μg) had significantly reduced liver fat compared to those that received low-dose VitD (0.049 μg) or caloric restriction. Gene expression analysis revealed that VitD downregulated several pathways that may play a role in NAFLD etiology, which affected fatty acid metabolism, vitamins and their cofactors, ethanol oxidation, and glycolysis. The pathway analysis revealed that the cholesterol biosynthesis pathway and the isoprenoid biosynthetic process pathway were significantly upregulated whereas the small molecule catabolic process pathway significantly downregulated following the exposure of NAFLD zebrafish model to high VitD dose. Therefore, our findings suggest the association of novel biochemical pathways with NAFLD and highlight the potential of VitD supplementation to reverse the severity of NAFLD, especially in younger people.

Serum 25-hydroxyvitamin D levels and the risk of non-alcoholic fatty liver: A two-sample Mendelian randomization study

BACKGROUND

Accumulated studies have shown that low expression of 25-hydroxyvitamin D [25(OH)D] was significantly associated with the risk of non-alcoholic fatty liver disease (NAFLD). However, the exact causality is still unknown. The aim of this study was to investigate whether levels of 25(OH)D are associated with risk of NAFLD, using a two-sample Mendelian randomization (MR).

METHODS

Data from a recent large vitamin D genome-wide association study (GWAS) on 417,580 Europeans were utilized, and the largest published histology-based NAFLD GWAS study (1,483 cases and 17,781 healthy controls) for genetic variants predicted to cause NAFLD were searched. All genetic datasets for the MR analyses were obtained using publicly available summary statistics based on individuals of European ancestry from the MR-Base and NHGRI-EBI GWAS Catalog database. Inverse-variance weighted (IVW) MR approach was used to estimate causal effects in the main analysis, complemented by 4 additional methods to control for pleiotropy. Sensitivity analyses were conducted to verify whether heterogeneity and pleiotropy can bias the MR results.

RESULTS

The MR analysis did not provide strong evidence for the causal association of circulating 25(OH)D with NAFLD by IVW method (OR = 0.746, 95%CI 0.517-1.078; P = 0.119). The results were consistent using four other MR methods. Sensitivity analysis using all different analytical approaches yielded similar results. There was no evidence for pleiotropy (MR-Egger intercept: -0.0003758, P = 0.970). The replication process also showed consistent results using IVW method (P = 0.710).

CONCLUSION

This study indicates that serum 25(OH)D levels did not possess an obvious effect on the risk of NAFLD. The associations in previous studies may be due to residual confounding or reverse causation.

Analysis of clinical findings and serum micronutrients in pediatric patients with nonalcoholic fatty liver disease

Aim: Serum micronutrient levels play an important role in liver metabolism. This study examines risk factors and diagnostic methods for patients on follow-up due to nonalcoholic fatty liver disease (NAFLD). NAFLD and the control groups were compared for clinical findings, serum ferritin, B12, and vitamin D levels, and their relationship with NAFLD was examined. Material and Method: Included in the study were 60 NAFLD patients and 66 other children that formed the control group. The two groups were compared in serum lipid profile, aminotransferase, insulin, glucose, and HOMA-IR. Ultrasonography (USG) and Shear wave elastography (SWE) were performed on all patients. Both groups were then analyzed in terms of serum ferritin, B12, and vitamin D levels. Results: NAFLD and control groups were compared in terms of USG and SWE results. 35% (n=21)of the patients in the NAFLD group had grade 1, 55% (n=33) had grade 2 and 10% (n=6) had grade 3 adiposity. HOMA-IR and insulin levels were higher in the NAFLD group (p=0.02; p=0.001). While the serum ferritin level of the patients in the NAFLD group was higher than the control group (p=0.001); the B12 level was lower (p=0.006). In terms of vitamin D, there was no difference (p=0.368). Conclusion: It is essential to identify risk factors in children on follow-up due to NAFLD. USG and liver function tests remain the first option in the diagnosis and screening of NAFLD in children. Serum ferritin, B12, and vitamin D levels of children on follow-up due to NAFLD should be analyzed in consideration of liver fattening.

Meta-analysis: global prevalence, trend and forecasting of non-alcoholic fatty liver disease in children and adolescents, 2000-2021

BACKGROUND

NAFLD is increasing in children.

AIMS

To determine the recent trend and forecast the future global prevalence of paediatric NAFLD METHODS: We searched PubMed, Embase, Web of Science and Cochrane library databases from inception to 1 May 2021 for studies of children and adolescents (≤21 years) with NAFLD. Obesity was defined with weight at ≥95th percentile and overweight as 85th to <95th percentile as per the Center for Disease Control BMI-for-age percentile cut-offs.

RESULTS

From 3350 titles and abstracts, we included 74 studies (276,091 participants) from 20 countries/regions. We included 14 studies in the general NAFLD prevalence analysis, yielding an overall prevalence of 7.40% (95% CI: 4.17-12.81) regardless of the diagnostic method, and 8.77% (95% CI: 3.86-18.72) by ultrasound. Among continents with more than one study, the prevalence of NAFLD was 8.53% (95% CI: 5.71-12.55) for North America, 7.01% (95% CI: 3.51-13.53) for Asia, and 1.65% (95% CI: 0.97-2.80) for Europe. NAFLD prevalence regardless of the diagnostic method was 52.49% (95% CI: 46.23-58.68, 9159 participants) and 39.17% (95% CI: 30.65-48.42, 5371 participants) among obese and overweight/obese participants, respectively. For the general population, trend analysis from 2000 to 2017 indicates an increasing global prevalence of paediatric NAFLD from 4.62% to 9.02% at a yearly increase of 0.26%, whereas forecast analysis predicts a prevalence of 30.7% by 2040.

CONCLUSION

The prevalence of paediatric NAFLD varies by region and is 52.49% overall among the obese population and 7.40% in the general population. It is predicted to reach 30.7% by 2040.

Factors early in life associated with hepatic steatosis

BACKGROUND

The rise in prevalence of non-alcoholic fatty liver disease (NAFLD) mirrors the obesity epidemic. NAFLD is insidious but may gradually progress from simple steatosis to steatohepatitis, fibrosis and cirrhosis and/or hepatocellular carcinoma. Intervention strategies to ameliorate developmental programming of NAFLD may be more efficacious during critical windows of developmental plasticity.

AIM

To review the early developmental factors associated with NAFLD.

METHODS

Databases MEDLINE via PubMed, and EMBASE and Reference Citation Analysis were searched and relevant publications up to April 30, 2021 were assessed. Original research studies that included risk factors associated with early development of NAFLD in human subjects were included. These factors include: Maternal factors, intrauterine and prenatal factors, post-natal factors, genetic and ethnic predisposition, childhood and adolescence environmental factors. Studies were excluded if they were review articles or animal studies, case reports or conference abstracts, or if NAFLD was not clearly defined and assessed radiologically.

RESULTS

Of 1530 citations identified by electronic search, 420 duplicates were removed. Of the 1110 citations screened from title and abstract, 80 articles were included in the final analysis. Genetic polymorphisms such as patatin-like phospholipase domain-containing protein 3 (PNPLA3) and membrane-bound O-acyltransferase domain-containing protein 7 (MBOAT7) were associated with increased risk of NAFLD. Familial factors such as maternal obesogenic environment and parental history of hepatic steatosis was associated with offspring NAFLD. Longer duration of exclusive breastfeeding in infancy was associated with a lower risk of developing NAFLD later in life while metabolic dysfunction and/or obesity in adolescence was associated with increased risk of NAFLD. Studies relating to socioeconomic factors and its association with NAFLD reported confounding results.

CONCLUSION

Maternal metabolic dysfunction during pregnancy, being exclusively breastfed for a longer time postnatally, diet and physical activity in childhood and adolescence are potential areas of intervention to decrease risk of NAFLD.

Relationship of Vitamin D Deficiency and Fatty Liver in Children as Defined by Multiple Imaging and Histologic Endpoints

Objectives

The relationship between vitamin D deficiency (VDD) and pediatric nonalcoholic fatty liver disease (NAFLD) remains uncertain due to conflicting results and few studies with histologic endpoints. We therefore used multiple imaging and histologic NAFLD endpoints to more comprehensively assess the association between VDD and NAFLD in a large pediatric population.

Methods

Data were obtained from an ongoing pediatric NAFLD study in Bronx, NY. Briefly, overweight and obese children aged 2-18 years with alanine aminotransferase (ALT) levels ≥ 35 U/L were serially enrolled. Liver biopsy was obtained in accordance with clinical guidelines. All participants had liver imaging, namely, controlled attenuation parameter (CAP; Echosens, France) to assess steatosis and, to assess fibrosis, vibration controlled transient elastography (VCTE; FibroScan™, Echosens, France) and acoustic radiation force impulse (ARFI; Philips, Netherlands) imaging. Levels of 25-hydroxyvitamin D were measured serologically.

Results

N=276 (88%) of 315 participants had 25-OH vitamin D results, of whom 241 (87%) were Hispanic, 199 (72%) were male, and 92 (33%) underwent liver biopsy. VDD was univariately associated with high waist circumference (p=0.004), high-density lipoprotein level (p=0.01), season (p=0.009), and CAP score (p=0.01). In multivariate analysis, only waist circumference (p=0.0002) and biopsy inflammation grade (p=0.03) were associated with VDD, though the latter had not approximated statistical significance in univariate analysis (p=0.56). There was no association between VDD and hepatic steatosis, ballooning, NAFLD Activity Score, ARFI or VCTE elasticity scores.

Conclusions

VDD was not associated with NAFLD defined by imaging and histologic endpoints, except for a possible relation with histologic inflammation grade.

The Association between Vitamin D and Nonalcoholic Fatty Liver Disease Assessed by Controlled Attenuation Parameter

BACKGROUND

An association between nonalcoholic fatty liver disease (NAFLD) and low vitamin D levels has been suggested. We investigated the relationship between vitamin D and NAFLD assessed by controlled attenuation parameter (CAP).

METHODS

We conducted a retrospective cohort study of apparently healthy subjects who underwent Fibroscan during health screening tests. NAFLD was diagnosed using CAP values.

RESULTS

Among the 1202 subjects (mean age 57.2 years, 60.6% male), 630 (52.4%) subjects had NAFLD with CAP ≥ 248 dB/m. Multivariable analysis was conducted after adjusting for metabolic risk factors including diabetes, hypertension, hypercholesterolemia, body mass index, high-density lipoprotein cholesterol, triglyceride and smoking. Higher vitamin D levels showed a lower risk of NAFLD compared to the lowest quartile of vitamin D in a dose-dependent manner (OR 0.68, 95% CI 0.47-1.00 in Q2 vs. Q1; OR 0.65, 95% CI 0.44-0.94 in Q3 vs. Q1; and OR 0.64, 95% CI 0.44-0.94 in Q4 vs. Q1). The highest quartile of vitamin D showed a decreased risk of a severe grade of steatosis (CAP ≥ 302 dB/m) compared to the lowest quartile (OR 0.52, 95% CI 0.31-0.87 in Q4 vs. Q1).

CONCLUSIONS

Higher levels of serum vitamin D were associated with a decreased risk of CAP-defined NAFLD, compared to low levels of serum vitamin D. The association between NAFLD and vitamin D suggests that vitamin D may exert a protective role against NAFLD.

A randomized controlled clinical trial comparing calcitriol versus cholecalciferol supplementation to reduce insulin resistance in patients with non-alcoholic fatty liver disease

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the world with no definite treatment. Insulin resistance (IR) and low serum vitamin D are closely linked to NAFLD. Since there is no comparative study on the effect of calcitriol with cholecalciferol on NAFLD based on homeostasis model of insulin resistance (HOMA-IR) as an IR indicator, so we designed this research.

METHODS

A double blind randomized clinical trial was conducted on patients with NAFLD with concomitant vitamin D deficiency/insufficiency at two referral tertiary teaching medical centers, from July 2017 to January 2019. Patients were randomly divided into two groups: calcitriol (1 mcg/day) and cholecalciferol (50,000 IU/week) for 8 weeks. Before and after the intervention, anthropometric and laboratory data were measured and HOMA-IR was calculated for each patient.

RESULTS

54 patients completed the trial. In total, calcitriol supplementation improved serum insulin levels as well as IR based on the HOMA-IR index, significantly compared to the cholecalciferol group. HOMA-IR decreased 1.8 times more in patients receiving calcitriol than in those receiving cholecalciferol, which was clinically meaningful. The observed changes were more pronounced in patients with higher baseline body mass index. Moreover, calcitriol was more associated with a significant decrease in liver enzymes and cholesterol levels comparing to cholecalciferol.

CONCLUSION

Based on the findings of this study, the use of calcitriol supplementation significantly reduced HOMA-IR as an IR indicator in NAFLD patients, compared to cholecalciferol. To confirm this findings, further studies with larger sample sizes are recommended.

The association between vitamin D status and non-alcoholic fatty liver disease in adults: a hospital-based study

Background

The association between vitamin D levels and non-alcoholic fatty liver disease (NAFLD) has been increasingly determined in recent researches. The aim of this study was to determine the association between vitamin D levels, measured as serum 25-hydroxy vitamin D (25(OH)D) and NAFLD. Serum 25(OH)D was prospectively determined in 80 patients. Of them, 40 subjects had NAFLD, whereas 40 subjects served as healthy control. Vitamin D deficiency was defined as serum 25(OH)D level < 20 ng/ml. Receiver operating characteristic (ROC) and regression analysis methods were used in our analysis.

Results

About 70% of patients with NAFLD had vitamin D deficiency, but only 35% in the control group had. The mean serum 25 (OH)D was significantly lower in patients with NAFLD than the healthy control group (16.13 ± 10.23 versus 27.35 ± 10.58 ng/mL; P < 0.001). ROC curve analysis revealed that serum 25(OH)D level of less than 11.2 ng/ml increases the risk of NAFLD with 45% sensitivity and 97.5% specificity (Serum 25(OH)D level ≤ 18.1 ng/ml in males and ≤ 9.4 ng/ml in females increase the risk of NAFLD). Multivariate regression analysis showed that vitamin D deficiency, high age, and high BMI were associated with a significant high risk of NAFLD.

Conclusion

NAFLD patients have low serum vitamin D concentrations, suggesting that vitamin D may have a role in the development of NAFLD. Future studies are recommended to determine the important therapeutic implications of vitamin D for the prophylaxis or the treatment of NAFLD.

Association between Serum Vitamin D Metabolites and Metabolic Function in Healthy Asian Adults

The association between low vitamin D status and the development of type 2 diabetes mellitus is well established; however, intervention trials that increased serum vitamin D (through ultraviolet B exposure or dietary supplementation) provide mixed outcomes. Recent evidence suggests that metabolites directly related to vitamin D receptor activation-1α,25-dihydroxyvitamin D₃ and 24R,25-dihydroxyvitamin D₃-may be better markers of vitamin D repletion status. We tested the hypothesis that a vitamin D metabolite (VDM) index, calculated as the sum of normalized fasting serum concentrations of 1α,25-dihydroxyvitamin D₃ and 24R,25-dihydroxyvitamin D₃, is associated with metabolic function. We measured subcutaneous and visceral adipose tissue volume, intrahepatic triglyceride content, maximum oxygen uptake, insulin sensitivity (4 h hyperinsulinemic-euglycemic clamp), and insulin secretion (3 h meal tolerance test with mathematical modeling) and calculated the VDM index in 65 healthy Asian adults. Subjects with a low VDM index had lower peripheral insulin sensitivity and beta-cell function compared to subjects with a high VDM index (both p < 0.05), matched for age, sex, BMI, and serum 25-hydroxyvitamin D₃. Serum 25-hydroxyvitamin D₃ was not associated with peripheral insulin sensitivity or beta-cell function. Our results suggest that, rather than enhancing vitamin D substrate availability, upregulation of vitamin D action is more likely to lead to improvements in glucose homeostasis.

Lifestyle modification in NAFLD/NASH: Facts and figures

The development of non-alcoholic fatty liver disease is closely linked to lifestyle factors, namely excessive caloric intake coupled with reduced physical activity and exercise. This review aims to examine the evidence behind lifestyle change as a tool to improve hepatic steatosis and liver histology in patients with non-alcoholic fatty liver disease/non-alcoholic steatohepatitis. Furthermore, potential barriers to adopting lifestyle changes and strategies to overcome these barriers in the clinical setting are discussed.

Vitamin D deficiency: prevalence and association with liver disease severity in pediatric nonalcoholic fatty liver disease

BACKGROUND/OBJECTIVES

To determine associations between serum 25-hydroxyvitamin D (25(OH)-D) concentrations and histologic nonalcoholic fatty liver disease (NAFLD) severity.

SUBJECTS/METHODS

Clinical, laboratory, and histology data were collected retrospectively in a pediatric cohort with biopsy-confirmed NAFLD. Serum 25(OH)-D concentrations were used to define vitamin D deficiency (≤20 ng/ml), insufficiency (21-30 ng/ml), and sufficiency (≥31 ng/ml).

RESULTS

In all, 234 patients (78% non-Hispanic, median age 14 years) were included. The majority (n = 193) were either vitamin D insufficient (50%) or deficient (32%). Eighty-four patients (36%) reported taking vitamin D supplements at the time of biopsy; serum 25(OH)-D concentrations were not higher in those supplemented. There were no differences in the demographic, clinical, and laboratory characteristics of the three vitamin D status groups. Severity of steatosis, ballooning, lobular/portal inflammation, and NAFLD activity score were also not different between the groups. The proportion of patients with significant fibrosis (stage ≥ 2) was higher in those with insufficiency (29%) compared to those who were sufficient (17%) or deficient (15%, p = 0.04). After controlling for important covariates selected from age, body mass index, ethnicity, vitamin D supplementation, and season, the insufficient group had increased odds of a higher fibrosis score compared to the sufficient group (adjusted OR, 2.04; 95%CI, 1.02-4.08).

CONCLUSIONS

Vitamin D deficiency and insufficiency are common in children with NAFLD, but not consistently related with histologic disease severity. Prospective longitudinal studies are needed to determine optimal dosing strategies to achieve sufficiency and to determine whether adequate supplementation has an impact on histology.

The Level of Vitamin D in Children and Adolescents with Nonalcoholic Fatty Liver Disease: A Meta-Analysis

Background

The relationship between vitamin D level and NAFLD has not been investigated in children and adolescents. We performed a meta-analysis of published observational studies to assess this association between vitamin D levels (measured as serum 25-hydroxy vitamin D [25(OH)D]) and NAFLD in this age group.

Methods

Relevant studies conducted before May 20, 2018, were identified from the following electronic databases: PubMed, the Cochrane Library, Embase, and the Chinese CNKI databases. The quality of the included studies was evaluated using the Newcastle Ottawa Scale, and associations between vitamin D levels and NAFLD were estimated using standardised mean differences (SMD) and 95% confidence interval (CI). Subgroup and sensitivity analysis were used to identify sources of heterogeneity, and publication bias was evaluated using funnel plots.

Results

Eight articles were included in this meta-analysis. A significant difference was observed between low 25(OH)D levels and NAFLD in children and adolescents (SMD = -0.59, 95%CI = -0.98, -0.20, P <  0.01). Subgroup analysis revealed no differences in the study type, geographic location, BMI, and age subgroups.

Conclusions

Low vitamin D levels were associated with NAFLD in children and adolescents.

Obesity and hypovitaminosis D: causality or casualty?

Epidemiological studies reported that vitamin D deficiency represents an increasingly widespread phenomenon in various populations. Vitamin D deficiency is considered a clinical syndrome determined by low circulating levels of 25-hydroxyvitamin D (25(OH)D), which is the biologically-inactive intermediate and represents the predominant circulating form. Different mechanisms have been hypothesized to explain the association between hypovitaminosis D and obesity, including lower dietary intake of vitamin D, lesser skin exposure to sunlight, due to less outdoor physical activity, decreased intestinal absorption, impaired hydroxylation in adipose tissue and 25(OH)D accumulation in fat. However, several studies speculated that vitamin D deficiency itself could cause obesity or prevent weight loss. The fat-solubility of vitamin D leads to the hypothesis that a sequestration process occurs in body fat depots, resulting in a lower bioavailability in the obese state. After investigating the clinical aspects of vitamin D deficiency and the proposed mechanisms for low 25(OH)D in obesity, in this manuscript we discuss the possible role of vitamin D replacement treatment, with different formulations, to restore normal levels in individuals affected by obesity, and evaluate potential positive effects on obesity itself and its metabolic consequences. Food-based prevention strategies for enhancement of vitamin D status and, therefore, lowering skeletal and extra-skeletal diseases risk have been widely proposed in the past decades; however pharmacological supplementation, namely cholecalciferol and calcifediol, is required in the treatment of vitamin D insufficiency and its comorbidities. In individuals affected by obesity, high doses of vitamin D are required to normalize serum vitamin D levels, but the different liposolubility of different supplements should be taken into account. Although the results are inconsistent, some studies reported that vitamin D supplementation may have some beneficial effects in people with obesity.

Association between Vitamin D Levels and Nonalcoholic Fatty Liver Disease: Potential Confounding Variables

Nonalcoholic fatty liver disease (NAFLD), historically considered to be the hepatic component of the metabolic syndrome, is a spectrum of fat-associated liver conditions, in the absence of secondary causes, that may progress to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. Disease progression is closely associated with body weight or fatness, dyslipidemia, insulin resistance, oxidative stress, and inflammation. Recently, vitamin D deficiency has been linked to the pathogenesis and severity of NAFLD because of vitamin D "pleiotropic" functions, with roles in immune modulation, cell differentiation and proliferation, and regulation of inflammation. Indeed, several studies have reported an association between vitamin D and NAFLD/NASH. However, other studies have failed to find an association. Therefore, we sought to critically review the current evidence on the association between vitamin D deficiency and NAFLD/NASH, and to analyze and discuss some key variables that may interfere with this evaluation, such as host-, environment-, and heritability-related factors regulating vitamin D synthesis and metabolism; definitions of deficient or optimal vitamin D status with respect to skeletal and nonskeletal outcomes including NAFLD/NASH; methods of measuring 25(OH)D; and methods of diagnosing NAFLD as well as quantifying adiposity, the cardinal link between vitamin D deficiency and NAFLD.

The Liver in Children With Metabolic Syndrome

Non-alcoholic fatty liver disease (NAFLD) is recognized as an emerging health risk in obese children and adolescents. NAFLD represents a wide spectrum of liver conditions, ranging from asymptomatic steatosis to steatohepatitis. The growing prevalence of fatty liver disease in children is associated with an increased risk of metabolic and cardiovascular complications. NAFLD is considered the hepatic manifestation of Metabolic Syndrome (MetS) and several lines of evidence have reported that children with NAFLD present one or more features of MetS. The pathogenetic mechanisms explaining the interrelationships between fatty liver disease and MetS are not clearly understood. Altough central obesity and insulin resistance seem to represent the core of the pathophysiology in both diseases, genetic susceptibility and enviromental triggers are emerging as crucial components promoting the development of NAFLD and MetS in children. In the present review we have identified and summarizied studies discussing current pathogenetic data of the association between NAFLD and MetS in children.

Role of Nutrition in the Pathogenesis and Prevention of Non-alcoholic Fatty Liver Disease: Recent Updates

Non-alcoholic fatty liver disease (NAFLD) is an acquired metabolic disease characterized by triglycerides (TGs) deposition in liver induced by other factors rather than alcohol consumption. NAFLD significantly contributes to liver diseases in children and adults. NAFLD pathogenesis is associated with age, gender, race and ethnicity. Insulin resistance, hyperinsulinemia, elevated plasma free fatty acids (FFAs), fatty liver, hepatocyte injury, liver inflammation, oxidative stress, mitochondrial dysfunction, imbalanced pro-inflammatory cytokines, and fibrosis are the characteristics of NAFLD. Factors including genetic and epigenetic pathways, sedentary lifestyle, sleep, and diet composition affect NAFLD pathogenesis. In this review, we discuss the aetiology, risk factors and pathogenesis of NAFLD. Special focus is given to macro and micro nutrition as causing factors and their role in the prevention of NAFLD pathogenesis.

Genetic polymorphisms of the hepatic pathways of fatty liver disease after living donor liver transplantation

BACKGROUND & AIMS

Fatty liver disease is an important complication associated with liver transplantation, and the cytochrome P-450 system of the donor liver may be involved in its pathogenesis. To explore the effects of the CYP27A1, CYP27B1, CYP2R1, and vitamin D receptor pathways on vitamin D maintenance after living donor liver transplantation, we investigated the interplay between serum 25(OH)D and common variants in 60 paired donors and recipients who underwent living donor liver transplantation.

METHODS

We prospectively collected 60 donor/recipient pairs from our liver transplantation programmes and extracted serum DNA to evaluate single nucleotide polymorphisms in CYP27A1 rs4674344, CYP27B1 rs10877012, CYP2R1 rs10741657, and VDR rs2228530 alleles using real-time polymerase chain reaction. We measured serum 25(OH)D concentrations of donors (D-D0) and recipients before (R-D0) and after (R-D30) living donor liver transplantation for comparison with repeated-measures analysis of variance in generalized estimating equations analysis.

RESULTS

Fatty liver disease was noted in 28.3% of the cases after living donor liver transplantation, and the graft rejection rate was 25%. There were significant differences in low serum 25(OH)D concentrations between D-D0 and R-D0 and between R-D0 and R-30 groups. Significant associations were observed for serum CYP27A1 rs4674344 in recipients and donors as well as for graft liver tissue with VDR rs2228530. There was no significant relationship with serum CYP27B1 rs10877012 in recipients and donors or with graft liver tissue with CYP2R1 rs10741657.

CONCLUSIONS

Donor/recipient CYP27A1 rs4674344 and graft VDR rs2228570 may be related to low serum 25(OH)D and may play a major role in the development of fatty liver disease in recipients after living donor liver transplantation.

Vitamin D status and associated genetic polymorphisms in a cohort of UK children with non-alcoholic fatty liver disease

BACKGROUND

Vitamin D deficiency has been associated with non-alcoholic fatty liver disease (NAFLD). However, the role of polymorphisms determining vitamin D status remains unknown.

OBJECTIVES

The objectives of this study were to determine in UK children with biopsy-proven NAFLD (i) their vitamin D status throughout a 12-month period and (ii) interactions between key vitamin D-related genetic variants (nicotinamide adenine dinucleotide synthase-1/dehydrocholesterol reductase-7, vitamin D receptor, group-specific component, CYP2R1) and disease severity.

METHODS

In 103 paediatric patients with NAFLD, serum 25-hydroxyvitamin D (25OHD) levels and genotypes were determined contemporaneously to liver biopsy and examined in relation to NAFLD activity score and fibrosis stage.

RESULTS

Only 19.2% of children had adequate vitamin D status; most had mean 25OHD levels considered deficient (<25 nmol·L^-1 , 25.5%) or insufficient (<50 nmol·L^-1 , 55.3%). Patients had significantly lower 25OHD levels in winter months (95% CI: 22.7-31.2 nmol·L^-1 ) when compared with spring (30.5-42.1 nmol·L^-1 ; P = 0.0089), summer (36.3-47.2 nmol·L^-1 ; P < 0.0001) and autumn (34.2-47.5 nmol·L^-1 ; P = 0.0003). Polymorphisms in the nicotinamide adenine dinucleotide synthase-1/dehydrocholesterol reductase-7 (rs3829251, rs12785878) and vitamin D receptor (rs2228570) genes were independently associated with increased steatosis; while a group-specific component variant (rs4588) was associated with increased inflammation in liver biopsies.

CONCLUSIONS

Children with NAFLD in the UK have particularly low winter vitamin D status, with vitamin D insufficiency prevalent throughout the year. Polymorphisms in the vitamin D metabolic pathway are associated with histological severity of paediatric NAFLD.

Vitamin D in pediatric age: consensus of the Italian Pediatric Society and the Italian Society of Preventive and Social Pediatrics, jointly with the Italian Federation of Pediatricians

Vitamin D plays a pivotal role in the regulation of calcium-phosphorus metabolism, particularly during pediatric age when nutritional rickets and impaired bone mass acquisition may occur.Besides its historical skeletal functions, in the last years it has been demonstrated that vitamin D directly or indirectly regulates up to 1250 genes, playing so-called extraskeletal actions. Indeed, recent data suggest a possible role of vitamin D in the pathogenesis of several pathological conditions, including infectious, allergic and autoimmune diseases. Thus, vitamin D deficiency may affect not only musculoskeletal health but also a potentially wide range of acute and chronic conditions. At present, the prevalence of vitamin D deficiency is high in Italian children and adolescents, and national recommendations on vitamin D supplementation during pediatric age are lacking. An expert panel of the Italian Society of Preventive and Social Pediatrics reviewed available literature focusing on randomized controlled trials of vitamin D supplementation to provide a practical approach to vitamin D supplementation for infants, children and adolescents.

VITAMIN D DEFICIENCY, A NONINVASIVE MARKER OF STEATOHEPATITIS IN PATIENTS WITH OBESITY AND BIOPSY PROVEN NONALCOHOLIC FATTY LIVER DISEASE

CONTEXT

Nonalcoholic fatty liver disease (NAFLD) includes simple steatosis, steatohepatitis (NASH) which can evolve with progressive fibrosis, cirrhosis and hepatocellular carcinoma. As liver biopsy cannot be used as a screening method, noninvasive markers are needed.

OBJECTIVE

The aim of this study was to test if there is a significant association between vitamin D deficit and the severity of NAFLD.

DESIGN

The patients were divided into two groups (vitamin D insufficiency/deficiency) and statistical analyses were performed on the correlation of clinical and biochemical characteristics with histopathological hepatic changes.

SUBJECTS AND METHODS

We prospectively studied 64 obese patients referred for bariatric surgery between 2014 and 2016 to our Surgical Unit. Anthropometric, clinical measurements, general and specific biological balance were noted. NAFLD diagnosis and activity score (NAS) were evaluated on liver biopsies.

RESULTS

Increased serum fibrinogen was correlated with NASH (p=0.005) and higher NAS grade. T2DM was positively correlated with liver fibrosis (p=0.002). 84.37% of the patients had vitamin D deficit and 15.62% were vitamin D insufficient. Lobular inflammation correlated with vitamin D deficit (p=0.040). Fibrosis (p=0.050) and steatohepatitis (p=0.032) were independent predictors of low vitamin D concentration.

CONCLUSIONS

Vitamin D status in conjunction with other parameters - such as T2DM - or serum biomarkers - namely fibrinogen level and PCR level - may point out the aggressive forms of NAFLD and the need for liver biopsy for appropriate management.

Effects of activated carbon N-acetylcysteine sustained-release microcapsule on dipeptidyl peptidase IV expression in young rats with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) in children has become the most common liver disease influencing adolescent health and one of the most influencing chronic liver diseases among children in Chinese wealthy families, particularly in coastal regions. However, the medicine available for the treatment of NAFLD is deficient. In order to solve this problem, our team studied the activated carbon N-acetylcysteine (NAC) sustained-release microcapsule, which improves the oxidation resistance, bioavailability and drug stability of acetylcysteine and reduces toxic and side effects. In addition, it accords with the characteristics of medication in infants and children. The present study mainly discusses whether the activated carbon NAC sustained-release microcapsule has effects on dipeptidyl peptidase IV (DPPIV) activity and protein in young rats with NAFLD, and whether it has the effect of an DPPIV inhibitor, hoping to provide new thoughts and methods with respect of basic studies on young rats with NAFLD/non-alcoholic steatohepatitis.

The pharmacological management of NAFLD in children and adolescents

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) represents a spectrum, including 'simple' steatosis, non-alcoholic steatohepatitis (NASH), and fibrosis. Increasing prevalence of NAFLD has followed the international rise in obesity and lifestyle modification is the mainstay therapy for children. To date, pharmacological trials have had varying efficacy but a large number of new agents are in early phase trials for adults. Areas covered: This review explores the effect of current and potential future paediatric NAFLD treatments in terms of histological and biochemical endpoints. The potential for the extension of adult treatments to children is discussed, as well as what limits the use of certain agents in children. Expert commentary: No drugs have yet to be licenced for NAFLD. Trial heterogeneity makes comparison of drugs between studies challenging. FXR agonists are yet to be trialled in children but may represent a safe and potentially efficacious therapy. Future treatments would likely encompass a multimodal approach that may include bariatric surgery.

NASPGHAN Clinical Practice Guideline for the Diagnosis and Treatment of Nonalcoholic Fatty Liver Disease in Children: Recommendations from the Expert Committee on NAFLD (ECON) and the North American Society of Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN)

Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent chronic liver disease that occurs in the setting of insulin resistance and increased adiposity. It has rapidly evolved into the most common liver disease seen in the pediatric population and is a management challenge for general pediatric practitioners, subspecialists, and for health systems. In this guideline, the expert committee on NAFLD reviewed and summarized the available literature, formulating recommendations to guide screening and clinical care of children with NAFLD.

Docosahexanoic Acid Plus Vitamin D Treatment Improves Features of NAFLD in Children with Serum Vitamin D Deficiency: Results from a Single Centre Trial

BACKGROUND

There are no licensed treatments for non alcoholic fatty liver disease (NAFLD) in adults or children. In NAFLD, several studies have shown a benefit of omega-3 fatty acid treatment on lipid profile, insulin-sensitivity and hepatic steatosis and it has also been suggested that Vitamin D treatment has potential antifibrotic properties in liver disease.

TRIAL DESIGN

To date, however, there are no studies that have tested the combination of Docosahexanoic acid (DHA) and vitamin D treatment which may benefit the whole spectrum of disease in NAFLD. Our aim therefore, was to test the effect of daily DHA (500 mg) plus vitamin D (800 IU) treatment, in obese children with biopsy-proven NAFLD and vitamin D deficiency, in a randomized, double-blind placebo-controlled trial.

METHODS

The 41/43 patients completed the study (18-treatment, 23-placebo). At 12 months: i) the main outcome was liver histology improvement, defined by NAS; ii) the secondary outcome was amelioration of metabolic parameters.

RESULTS

DHA plus vitamin D treatment reduced the NAFLD Activity Score (NAS), in the treatment group (5.4 v1.92; p<0.001 for baseline versus end of study). There was no change in fibrosis score, but a reduction of the activation of hepatic stellate cells (HSC) and fibrillar collagen content was noted (3.51±1.66 v. 1.59±1.37; p = 0.003) in treatment group. Moreover, the triglycerides (174.5 vs. 102.15 mg/dl), ALT (40.25 vs. 24.5 UI/l) and HOMA-IR (4.59 vs. 3.42) were all decreased with treatment.

CONCLUSION

DHA plus vitamin D treatment improved insulin-resistance, lipid profile, ALT and NAS. There was also decreased HSC activation and collagen content with treatment.

Low 25-hydroxyvitamin D level is not an independent risk factor for hepatosteatosis in obese children

BACKGROUND

Obesity is an important risk factor for non-alcoholic fatty liver disease. Few studies have evaluated the association between vitamin D and non-alcoholic fatty liver disease in obese children. Therefore, we conducted a study to examine the relationship of vitamin D levels and hepatosteatosis in obese children.

METHODS

One hundred and eleven children with obesity participated in this study. Hepatosteatosis was diagnosed and graded using ultrasonography in all patients. Study participants were divided based on the presence of hepatosteatosis into two subgroups (hepatosteatosis and non-hepatosteatosis). Serum levels of 25-hydroxyvitamin D, calcium, phosphate, alkaline phosphatase, parathormone, and lipids were measured and compared.

RESULTS

Hepatosteatosis existed in 52% of obese children without chronic diseases. There was no statistically significant difference in the vitamin D level between the hepatosteatosis and non-hepatosteatosis groups. Alanine aminotransferase levels and the triglycerides-to-high density lipoprotein ratio were significantly higher, and the high density lipoprotein levels were significantly lower in the hepatosteatosis group compared to the non-hepatosteatosis group.

CONCLUSIONS

Vitamin D deficiency is not directly related with hepatosteatosis. A high ALT level and a high triglycerides-to-HDL ratio and low HDL levels are more significant in hepatic steatosis in obese children.

High fat diet enriched with saturated, but not monounsaturated fatty acids adversely affects femur, and both diets increase calcium absorption in older female mice

Diet induced obesity has been shown to reduce bone mineral density (BMD) and Ca absorption. However, previous experiments have not examined the effect of high fat diet (HFD) in the absence of obesity or addressed the type of dietary fatty acids. The primary objective of this study was to determine the effects of different types of high fat feeding, without obesity, on fractional calcium absorption (FCA) and bone health. It was hypothesized that dietary fat would increase FCA and reduce BMD. Mature 8-month-old female C57BL/6J mice were fed one of three diets: a HFD (45% fat) enriched either with monounsaturated fatty acids (MUFAs) or with saturated fatty acids (SFAs), and a normal fat diet (NFD; 10% fat). Food consumption was controlled to achieve a similar body weight gain in all groups. After 8wk, total body bone mineral content and BMD as well as femur total and cortical volumetric BMD were lower in SFA compared with NFD groups (P<.05). In contrast, femoral trabecular bone was not affected by the SFAs, whereas MUFAs increased trabecular volume fraction and thickness. The rise over time in FCA was greater in mice fed HFD than NFD and final FCA was higher with HFD (P<.05). Intestinal calbindin-D9k gene and hepatic cytochrome P450 2r1 protein levels were higher with the MUFA than the NFD diet (P<.05). In conclusion, HFDs elevated FCA overtime; however, an adverse effect of HFD on bone was only observed in the SFA group, while MUFAs show neutral or beneficial effects.

A Guide to Non-Alcoholic Fatty Liver Disease in Childhood and Adolescence

Non-Alcoholic Fatty Liver Disease (NAFLD) is now the most prevalent form of chronic liver disease, affecting 10%–20% of the general paediatric population. Within the next 10 years it is expected to become the leading cause of liver pathology, liver failure and indication for liver transplantation in childhood and adolescence in the Western world. While our understanding of the pathophysiological mechanisms underlying this disease remains limited, it is thought to be the hepatic manifestation of more widespread metabolic dysfunction and is strongly associated with a number of metabolic risk factors, including insulin resistance, dyslipidaemia, cardiovascular disease and, most significantly, obesity. Despite this, ”paediatric” NAFLD remains under-studied, under-recognised and, potentially, undermanaged. This article will explore and evaluate our current understanding of NAFLD in childhood and adolescence and how it differs from adult NAFLD, in terms of its epidemiology, pathophysiology, natural history, diagnosis and clinical management. Given the current absence of definitive radiological and histopathological diagnostic tests, maintenance of a high clinical suspicion by all members of the multidisciplinary team in primary and specialist care settings remains the most potent of diagnostic tools, enabling early diagnosis and appropriate therapeutic intervention.

Combined Association of Vitamin D and Sex Hormone Binding Globulin With Nonalcoholic Fatty Liver Disease in Men and Postmenopausal Women: A Cross-Sectional Study

This study aimed to explore the combined associations of 25(OH)-vitamin D and sex hormone binding globulin (SHBG) with nonalcoholic fatty liver disease (NAFLD) in men and postmenopausal women. Our data, which were based on the population, were collected from 16 sites in East China in 2014. There were 2700 men with a mean age of 53 years and 1461 women over 55 who were considered postmenopausal enrolled in the study. Levels of 25(OH)D and SHBG were measured using chemiluminescence assay. NAFLD was measured using liver ultrasound. Multivariable-adjusted logistic regression models examined associations of 25(OH)D and SHBG tertiles with odds of mild and moderate-severe NAFLD. Both the low 25(OH)D and low SHBG groups were significantly associated with higher odds of mild NAFLD (men: OR 1.37, 95% CI 1.05, 1.78 in low 25(OH)D group; OR 1.73, 95% CI 1.23, 2.45 in low SHBG group; women: OR 1.51, 95% CI 1.08, 2.12 in low 25(OH)D group; OR 2.16, 95% CI 1.48, 3.14 in low SHBG group) and moderate-severe NAFLD (men: OR 1.61, 95% CI 1.24, 2.10 in low 25(OH)D group; OR 3.42, 95% CI 2.41, 4.87 in low SHBG group; women: OR 1.66, 95% CI 1.14, 2.42 in low 25(OH)D group; OR 6.84, 95% CI 4.31, 10.84 in low SHBG group). However, the combined association of low 25(OH)D and low SHBG was much larger, especially in moderate-severe NAFLD (men: OR 6.57, 95% CI 3.87, 11.18; women: OR 8.16, 95% CI 3.98, 16.73). The associations were independent of age, total testosterone, abdominal obesity, diabetes, and lipid profile. The negative associations of 25(OH)D and SHBG levels with NAFLD are strongest when viewed in combination in men and postmenopausal women. Further studies should determine the cause-effect relationship and investigate the underlying mechanisms of this finding.

Vitamin D Status and Bone Mineral Density in Obese Children with Nonalcoholic Fatty Liver Disease

Whether nonalcoholic fatty liver disease (NAFLD) is related to vitamin D and bone health in obese children is unknown. The aim of this study was to evaluate vitamin D status and bone mineral density (BMD) in obese children according to their condition within the NAFLD spectrum. Anthropometric data, laboratory tests, and abdominal ultrasonography were obtained from 94 obese children. The subjects were divided into three groups according to NAFLD spectrum: normal liver, simple steatosis, and nonalcoholic steatohepatitis (NASH). Although there were no differences in vitamin D levels between the three groups, these groups showed significant differences in highly sensitive C-reactive protein (P=0.044), homeostasis model assessment of insulin resistance (HOMA-IR) (P=0.02), hepatic fibrosis scores (P<0.05), and trunk fat percentage (P=0.025). Although there were significant differences in BMDs, the age-matched BMD z-scores were not significantly different between the three groups. Serum vitamin D levels were negatively correlated with age (r=-0.368, P=0.023), serum uric acid levels (r=-0.371, P=0.022), fibrosis 4 (FIB4) (r=-0.406, P=0.011), and HOMA-IR (r=-0.530, P=0.001) in obese children with NASH. Multiple regression analysis for vitamin D in the NASH group revealed age and HOMA-IR as significant factors. In conclusion, inflammatory markers, hepatic fibrosis scores, trunk fat, and insulin resistance may reflect the spectrum of NAFLD in obese children, whereas vitamin D levels and BMD may not. In patients with NASH, however, low serum vitamin D is associated with hepatic fibrosis and insulin resistance, but not with bone health status.

Assessment of Diet and Physical Activity in Paediatric Non-Alcoholic Fatty Liver Disease Patients: A United Kingdom Case Control Study

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in children, with prevalence rising alongside childhood obesity rates. This study aimed to characterise the habitual diet and activity behaviours of children with NAFLD compared to obese children without liver disease in the United Kingdom (UK). Twenty-four biopsy-proven paediatric NAFLD cases and eight obese controls without biochemical or radiological evidence of NAFLD completed a 24-h dietary recall, a Physical Activity Questionnaire (PAQ), a Dutch Eating Behavior Questionnaire (DEBQ) and a 7-day food and activity diary (FAD), in conjunction with wearing a pedometer. Groups were well matched for age and gender. Obese children had higher BMI z-scores (p = 0.006) and BMI centiles (p = 0.002) than participants with NAFLD. After adjusting for multiple hypotheses testing and controlling for differences in BMI, no differences in macro- or micronutrient intake were observed as assessed using either 24-h recall or 7-day FAD (p > 0.001). Under-reporting was prevalent (NAFLD 75%, Obese Control 87%: p = 0.15). Restrained eating behaviours were significantly higher in the NAFLD group (p = 0.005), who also recorded more steps per day than the obese controls (p = 0.01). In conclusion, this is the first study to assess dietary and activity patterns in a UK paediatric NAFLD population. Only a minority of cases and controls were meeting current dietary and physical activity recommendations. Our findings do not support development of specific dietary/ physical activity guidelines for children with NAFLD; promoting adherence with current general paediatric recommendations for health should remain the focus of clinical management.

Dietary supplements and pediatric non-alcoholic fatty liver disease: Present and the future

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in children. High prevalence of pediatric obesity and sedentary lifestyle has augmented the incidence of NAFLD in children. Obesity is associated with an increased risk of NAFLD through various mechanisms such as intensification of insulin resistance and increased levels of inflammatory markers. There is no approved medical intervention for treatment of pediatric NAFLD; the only proven strategy in management of pediatric NAFLD is lifestyle modification. Recently, the effects of nutritional supplements have been examined in the management of pediatric NAFLD. The purpose of this review is to summarize the studies evaluating the effects of nutritional supplements on pediatric NAFLD and explain the future direction in this field.

Adiposity and Cardiometabolic Risk in Children With and Without Antipsychotic Drug Treatment

CONTEXT

Pediatric obesity is common, particularly in children treated with antipsychotic medications. Antipsychotic exposure can increase cardiometabolic risk by increasing adiposity, and possibly via other adiposity-independent pathways.

OBJECTIVE

The objectives were to characterize relationships of adiposity with intrahepatic triglyceride (IHTG) content and carotid intima media thickness (CIMT) in children with and without antipsychotic drug treatment, and to explore whether vitamin D alters any effects in these relationships.

DESIGN

This was a cross-sectional case-control study.

SETTING

The setting was an academic medical center.

PATIENTS OR OTHER PARTICIPANTS

Participants were 44 children (ages, 6-19 y): 25 cases treated with antipsychotic and other psychotropic drug therapies and 19 untreated controls, frequency-matched on age, gender, and body mass index.

MAIN OUTCOME MEASURES

Main outcome measures were dual-energy x-ray absorptiometry percentage body fat (DEXA %fat), IHTG measured by magnetic resonance spectroscopy, and CIMT measured by ultrasonography. Fasting blood glucose, insulin, lipids, C-reactive protein, and liver enzymes were also evaluated.

RESULTS

There were no significant differences between cases and controls on measures of IHTG, CIMT, or DEXA %fat. In combined crude and adjusted analyses, DEXA %fat predicted IHTG (R(2) = 0.30) but not CIMT. Low levels of vitamin D were associated with larger effects of DEXA %fat on IHTG.

CONCLUSION

In treated and untreated children alike, adiposity is a significant predictor of liver fat content. This relationship was altered by low vitamin D level. These results suggest a modifiable pathway to hepatic steatosis. Further research is needed to test the hypothesis that children with high adiposity and low vitamin D have particularly increased risks for the development of fatty liver.

Vitamin d deficiency attenuates high-fat diet-induced hyperinsulinemia and hepatic lipid accumulation in male mice

It is increasingly recognized that vitamin D deficiency is associated with increased risks of metabolic disorders among overweight children. A recent study showed that vitamin D deficiency exacerbated inflammation in nonalcoholic fatty liver disease through activating toll-like receptor 4 in a high-fat diet (HFD) rat model. The present study aimed to further investigate the effects of vitamin D deficiency on HFD-induced insulin resistance and hepatic lipid accumulation. Male ICR mice (35 d old) were randomly assigned into 4 groups as follows. In control diet and vitamin D deficiency diet (VDD) groups, mice were fed with purified diets. In HFD and VDD+HFD groups, mice were fed with HFD. In VDD and VDD+HFD groups, vitamin D in feed was depleted. Feeding mice with vitamin D deficiency diet did not induce obesity, insulin resistance, and hepatic lipid accumulation. By contrary, vitamin D deficiency markedly alleviated HFD-induced overweight, hyperinsulinemia, and hepatic lipid accumulation. Moreover, vitamin D deficiency significantly attenuated HFD-induced up-regulation of hepatic peroxisome proliferator-activated receptor γ, which promoted hepatic lipid uptake and lipid droplet formation, and its target gene cluster of differentiation 36. In addition, vitamin D deficiency up-regulated carnitine palmitoyltrans 2, the key enzyme for fatty acid β-oxidation, and uncoupling protein 3, which separated oxidative phosphorylation from ATP production, in adipose tissue. These data suggest that vitamin D deficiency is not a direct risk factor for obesity, insulin resistance, and hepatic lipid accumulation. Vitamin D deficiency alleviates HFD-induced overweight, hyperinsulinemia, and hepatic lipid accumulation through promoting fatty acid β-oxidation and elevating energy expenditure in adipose tissue.

Can skin exposure to sunlight prevent liver inflammation?

Liver inflammation contributes towards the pathology of non-alcoholic fatty liver disease (NAFLD). Here we discuss how skin exposure to sunlight may suppress liver inflammation and the severity of NAFLD. Following exposure to sunlight-derived ultraviolet radiation (UVR), the skin releases anti-inflammatory mediators such as vitamin D and nitric oxide. Animal modeling studies suggest that exposure to UVR can prevent the development of NAFLD. Association studies also support a negative link between circulating 25-hydroxyvitamin D and NAFLD incidence or severity. Clinical trials are in their infancy and are yet to demonstrate a clear beneficial effect of vitamin D supplementation. There are a number of potentially interdependent mechanisms whereby vitamin D could dampen liver inflammation, by inhibiting hepatocyte apoptosis and liver fibrosis, modulating the gut microbiome and through altered production and transport of bile acids. While there has been a focus on vitamin D, other mediators induced by sun exposure, such as nitric oxide may also play important roles in curtailing liver inflammation.

Vitamin D deficiency in chronic liver disease

Vitamin D is an important secosteroid hormone with known effect on calcium homeostasis, but recently there is increasing recognition that vitamin D also is involved in cell proliferation and differentiation, has immunomodulatory and anti-inflammatory properties. Vitamin D deficiency has been frequently reported in many causes of chronic liver disease and has been associated with the development and evolution of non-alcoholic fatty liver disease (NAFLD) and chronic hepatitis C (CHC) virus infection. The role of vitamin D in the pathogenesis of NAFLD and CHC is not completely known, but it seems that the involvement of vitamin D in the activation and regulation of both innate and adaptive immune systems and its antiproliferative effect may explain its importance in these liver diseases. Published studies provide evidence for routine screening for hypovitaminosis D in patients with liver disease. Further prospectives studies demonstrating the impact of vitamin D replacement in NAFLD and CHC are required.

Vitamin D insufficiency and insulin resistance in obese adolescents

Obese adolescents represent a particularly vulnerable group for vitamin D deficiency which appears to have negative consequences on insulin resistance and glucose homeostasis. Poor vitamin D status is also associated with future risk of type 2 diabetes and metabolic syndrome in the obese. The biological mechanisms by which vitamin D influences glycemic control in obesity are not well understood, but are thought to involve enhancement of peripheral/hepatic uptake of glucose, attenuation of inflammation and/or regulation of insulin synthesis/secretion by pancreatic β cells. Related to the latter, recent data suggest that the active form of vitamin, 1,25-dihydroxyvitamin D, does not impact insulin release in healthy pancreatic islets; instead they require an environmental stressor such as inflammation or vitamin D deficiency to see an effect. To date, a number of observational studies exploring the relationship between the vitamin D status of obese adolescents and markers of glucose homeostasis have been published. Most, although not all, show significant associations between circulating 25-hydroxyvitamn D concentrations and insulin sensitivity/resistance indices. In interpreting the collective findings of these reports, significant considerations surface including the effects of pubertal status, vitamin D status, influence of parathyroid hormone status and the presence of nonalcoholic fatty liver disease. The few published clinical trials using vitamin D supplementation to improve insulin resistance and impaired glucose tolerance in obese adolescents have yielded beneficial effects. However, there is a need for more randomized controlled trials. Future investigations should involve larger sample sizes of obese adolescents with documented vitamin D deficiency, and careful selection of the dose, dosing regimen and achievement of target 25-hydroxyvitamn D serum concentrations. These trials should also include clamp-derived measures of in vivo sensitivity and β-cell function to more fully characterize the effects of vitamin D replenishment on insulin resistance.