Associations between higher plasma ferritin and hepcidin levels with liver stiffness in patients with type 2 diabetes: An exploratory study

BACKGROUND

Currently, there is no information about the association between circulating levels of ferritin and hepcidin and liver fibrosis in patients with type 2 diabetes mellitus (T2DM) and non-alcoholic fatty liver disease (NAFLD).

METHODS

We enrolled 153 patients with T2DM with no known liver diseases, who consecutively attended our diabetes outpatient service and who underwent liver ultrasonography and liver stiffness measurement (LSM) by vibration-controlled transient elastography (Fibroscan® for the non-invasive assessment of liver fibrosis). Plasma ferritin and hepcidin concentrations were measured with an electrochemiluminescence immunoassay and mass spectrometry-based assay, respectively.

RESULTS

After stratification of patients by LSM tertiles [1st tertile median LSM: 3.6 (interquartile range: 3.3-4.0) kPa, 2nd tertile: 5.3 (4.9-5.9) kPa and 3rd tertile: 7.9 (6.7-9.4) kPa], we found that plasma ferritin and hepcidin concentrations increased across LSM tertiles [median ferritin: 68.7 (interquartile range: 25.1-147) vs. 85.8 (48.3-139) vs. 111 (59.3-203) μg/L, p = 0.021; median hepcidin: 2.5 (1.1-5.2) vs. 4.4 (2.5-7.3) vs. 4.1 (1.9-6.8) nmol/L, p = 0.032]. After adjustment for age, sex, diabetes duration, waist circumference, haemoglobin A1c, HOMA-insulin resistance score, triglycerides, haemoglobin, presence of hepatic steatosis on ultrasonography and patatin-like phospholipase domain-containing-3 (PNPLA3) rs738409 genetic variant, higher plasma ferritin levels were associated with greater LSM values (adjusted-odds ratio 2.10, 95% confidence interval 1.23-3.57, p = 0.005). Higher plasma hepcidin levels were also associated with greater LSM values (adjusted-odds ratio 1.90, 95% confidence interval 1.15-3.13, p = 0.013).

CONCLUSIONS

Higher levels of plasma ferritin and hepcidin were associated with greater NAFLD-related liver fibrosis (assessed by LSM) in patients with T2DM, even after adjustment for established cardiometabolic risk factors, diabetes-related variables and other potential confounders.

IGF1 and PPARG polymorphisms are associated with reduced estimated glomerular filtration rate in a cohort of children and adolescents with type 1 diabetes

INTRODUCTION

Several genetic loci have been associated with diabetic nephropathy; however, the underlying genetic mechanisms are still poorly understood, with no robust candidate genes identified yet.

AIM

We aimed to determine whether two polymorphisms, previously associated with renal decline, influence kidney impairment evaluating their association with markers of renal function in a pediatric population with type 1 diabetes (T1D).

MATERIAL AND METHODS

Renal function was evaluated by glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR) in a cohort of pediatric subjects with T1D (n = 278). Risk factors for diabetes complications (diabetes duration, blood pressure, HbA1c) were assessed. The IGF1 rs35767 and PPARG rs1801282 SNPs were genotyped by TaqMan RT-PCR system. An additive genetic interaction was calculated. Association analysis between markers of renal function and both SNPs or their additive interaction were performed.

RESULTS

Both SNPs showed a significant association with eGFR: the A allele of rs35767 or the C allele of rs1801282 were associated to reduced eGFR compared to G alleles. Multivariate regression analysis adjusted for age, sex, z-BMI, T1D duration, blood pressure and Hba1c values showed that the additive genetic interaction was independently associated with lower eGFR (β = -3.59 [-6.52 to -0.66], p = 0.017). No associations were detected between SNPs, their additive interaction and ACR.

CONCLUSIONS

These results provide new insight into the genetic predisposition to renal dysfunction, showing that two polymorphisms in IGF1 and PPARG genes can lead to a reduction in renal filtration rate leading these patients to be exposed to a higher risk of early renal complications.

Crosstalk between genetic variability of adiponectin and leptin, glucose-insulin system and subclinical atherosclerosis in patients with newly diagnosed type 2 diabetes. The Verona Newly Diagnosed Type 2 Diabetes Study 14

AIM

To evaluate the relationship of genetic variability of adiponectin (ADIPOQ), leptin (LEP) and leptin receptor (LEPR) genes with glucose-insulin system and markers of subclinical atherosclerosis (ATS) in patients with newly diagnosed type 2 diabetes.

MATERIALS AND METHODS

In 794 subjects we performed: 1) euglycemic hyperinsulinemic clamp to assess insulin sensitivity; 2) mathematical modelling of a 5h-OGTT to estimate β-cell function; 3) resting ECG; 4) carotid artery and lower limb artery eco-doppler sonography to identify ATS; 5) genotyping of tag-SNPs within ADIPOQ, LEP and LEPR gene.

RESULTS

Regression analyses showed: 1) adiponectin levels were negatively associated with BMI, waist-to-hip ratio and triglycerides and positively with HDL and insulin sensitivity (p-all<0.03); 2) leptin levels were positively associated with BMI, HDL-cholesterol and plasma triglycerides and negatively with insulin sensitivity (p-all<0.001). Two SNPs (rs1501299 and rs2241767) within ADIPOQ gene were associated with circulating levels of adiponectin. The ADIPOQ-GAACA haplotype was associated with plasma adiponectin (p=0.034; β=-0.24), ECG abnormalities (p=0.012; OR=2.76), carotid ATS (p=0.025; OR=2.00) and peripheral limb artery ATS (p=0.032; OR=1.90). The LEP-CTA haplotype showed an association with ischemic ECG abnormalities (p=0.017; OR=2.24). Finally, LEPR-GAACGG was associated with circulating leptin (p=0.005; β=-0.31) and worst β-cell function (p=0.023; β=-15.10). Omnibus haplotype analysis showed that ADIPOQ haplotypes were associated with levels of adiponectin and common carotid artery ATS, LEP with peripheral limb artery ATS, whereas LEPR haplotypes influenced circulating levels of leptin.

CONCLUSIONS

Results of this study reinforce knowledge on adipokines' role in regulating glucose metabolism; in particular highlighted the potential atherogenic role of leptin and the anti atherogenic role of adiponectin.

Lower heart rate variability, an index of worse autonomic function, is associated with worse beta cell response to a glycemic load in vivo-The Maastricht Study

OBJECTIVE

We investigated, using population-based data, whether worse autonomic function, estimated from lower 24-hour heart rate variability (HRV), was associated with beta cell function, assessed from beta cell response during an oral glucose tolerance test (OGTT).

RESEARCH DESIGN AND METHODS

We used cross-sectional data from The Maastricht Study, a population-based cohort study (N = 2,007; age, mean ± SD:60 ± 8 years; 52% men; and 24% with type 2 diabetes). We used linear regression analyses with adjustment for potential confounders (demographic, cardiovascular, and lifestyle factors) to study the associations of time- and frequency-domain HRV (composite scores) with overall beta cell response (estimated from a composite score calculated from: C-peptidogenic index, overall insulin secretion, beta cell glucose sensitivity, beta cell potentiation factor, and beta cell rate sensitivity). In addition, we tested for interaction by sex and glucose metabolism status.

RESULTS

After full adjustment, lower time- and frequency-domain HRV was significantly associated with lower overall beta cell response composite score (standardized beta, -0.055 [-0.098; -0.011] and - 0.051 [-0.095; -0.007], respectively). These associations were not modified by sex and there was no consistent pattern of interaction by glucose metabolism status.

CONCLUSION

The present etiological study found that worse autonomic function, estimated from lower HRV, was associated with worse beta cell function, estimated from a composite score in a population-based sample which covered the entire spectrum of glucose metabolism. Hence, autonomic dysfunction may contribute to beta cell dysfunction and, ultimately, to the alteration of glucose metabolism status from normal glucose metabolism to prediabetes and type 2 diabetes.

Association between PNPLA3 rs738409 variant and 5-year estimated glomerular filtration rate decline in post-menopausal women with type 2 diabetes: A panel-data analysis

BACKGROUND AND AIMS

Little is known about the relationship between patatin-like phospholipase domain-containing protein-3 (PNPLA3) rs738409 variant and decline in estimated glomerular filtration rate (eGFR) over time in individuals with type 2 diabetes (T2DM).

METHODS AND RESULTS

We enrolled an outpatient sample of 46 post-menopausal women with T2DM and preserved kidney function at baseline (in 2017), who were followed through 2022. eGFR and albuminuria were measured annually. Genotyping of PNPLA3 rs738409 was performed by TaqMan-based RT-PCR system. Overall, 25 (54.3%) patients had PNPLA3 rs738409 CC (homozygous wild-type) genotype and 21 had CG or GG genotypes. During the 5-year follow-up, the presence of rs738409 CG/GG genotypes was associated with faster eGFR decline (coefficient: -6.55; 95% CI -11.0 to -2.08; p = 0.004 by random-effects panel data analysis). This association remained significant even after adjustment for 5-year changes in age, hemoglobin A1c, hypertension status, albuminuria and use of sodium-glucose co-transporter-2 inhibitors or glucagon-like peptide-1 receptor agonists.

CONCLUSIONS

This pilot study suggests that in post-menopausal T2DM women with preserved kidney function at baseline, the risk allele (G) of PNPLA3 rs738409 is associated with a faster eGFR decline during a 5-year follow-up, independent of annual changes in common renal risk factors and use of certain glucose-lowering medications.

Oral Microbiota in Children and Adolescents with Type 1 Diabetes Mellitus: Novel Insights into the Pathogenesis of Dental and Periodontal Disease

The oral microbiota can be influenced by multiple factors, but only a few studies have focused on the role of glycemic control in determining early alterations of oral microbiota and their association with pathogenesis of both periodontitis and caries. The aim of this study is to evaluate the interplay between bacteria composition, oral hygiene, and glycemic control in a cohort of children with T1D. A total of 89 T1D children were enrolled (62% males, mean age: 12.6 ± 2.2 years). Physical and clinical characteristics, glucometabolic parameters, insulin treatment, and oral hygiene habits data were collected. Microbiological analysis was performed from saliva samples. A high prevalence of cariogenic and periodontopathogens bacteria in our cohort was detected. In particular, in all subjects Actinomyces spp., Aggregatibacter actinomycetemcomitans, Prevotella intermedia, and Lactobacillus spp. were isolated. S. mutans was found in about half of the analyzed sample (49.4%), in particular in patients with imbalance values of glycemic control. Moreover, a higher presence of both S. mutans and Veillonella spp. was detected in subjects with poorer glycemic control, in terms of HbA1c, %TIR and %TAR, even adjusting for age, sex, and hygiene habits as covariates. Virtuous oral hygiene habits, such as frequency of toothbrush changes and professional oral hygiene, negatively correlated with the simultaneous presence of Tannerella forsythia, Treponema denticola, and Porphyromonas gingivalis, red complex bacteria. Our study shows it is crucial to pay attention to glycemic control and regular oral hygiene to prevent the establishment of an oral microbiota predisposing to dental and periodontal pathology in subjects with T1D since childhood.

FADS cluster variants are associated with insulin sensitivity in children and adolescents with overweight and obesity

Changes in the desaturation activity of LC-PUFAs may influence insulin sensitivity by modulating the relative abundance of omega-3. The aim of this cross-sectional study was to assess the association between genetic variants of fatty acid desaturase cluster genes (FADS1, FADS2, FADS3) and insulin sensitivity in a cohort of children and adolescents with obesity. Anthropometric evaluation, lipid profile, glucose metabolism parameters and the genotype of rs1535 on FADS2 gene were assessed. In 162 obese children and adolescents (12.6 ± 2.3 years; BMI 30.9 ± 7.3), we found a significant association between an index of insulin sensitivity, i.e., Matsuda index, and rs1535 (B = -0,192; p = 0.008), BMI (B = -0,003; p < 0.001), and triglycerides (B = -0,034; p < 0.001), independent of age and sex [R² = 0.35; p = <0.001]. In conclusion, FADS cluster variants were associated with insulin sensitivity in a population of children and adolescents with obesity, contributing to identify individuals who may benefit from personalised prevention and treatment nutritional strategies since childhood.

Early marker of ocular neurodegeneration in children and adolescents with type 1 diabetes: the contributing role of polymorphisms in mir146a and mir128a genes

BACKGROUND

Early ocular neurodegenerative signs of diabetic neuropathy (DN) can be found in children and adolescents with type 1 diabetes (T1D). No data are available on the potential role of polymorphisms in miRNAs genes in predisposing T1D subjects to these signs.

AIMS

To determine whether MIR146A rs2910164 and MIR128A rs11888095 polymorphisms are associated with early retinal and corneal neurodegenerative changes in pediatric patients with T1D.

METHODS

A total of 140 T1D children/adolescents underwent spectral domain-optical coherence tomography (SD-OCT) and in vivo confocal microscopy (IVCM) with measurement of retinal and corneal nerve fiber parameters. Risk factors for diabetes complications (diabetes duration, blood pressure, HbA1c) were recorded. Genotyping of rs2910164 and rs1188095 SNPs and genotype-phenotype association analysis were performed.

RESULTS

The C allele of rs2910164 in MIR146A was associated with higher values of IVCM parameters and minimum rim width (MRW) of the peripapillary region of optic nerve head measured in the retina, whereas the T allele of rs1188095 in MIR128A was associated with a significant impairment of them. Multiple regression analysis showed that MIR146A and MIR128A polymorphisms were significantly associated with corneal nerve fiber length (beta = 0.225 and - 0.204, respectively) and other IVCM parameters, independently from age, diabetes duration, HbA1c and systolic blood pressure percentile. Similar results were found for MRW (beta = 0.213 and - 0.286, respectively).

CONCLUSIONS

These results provide new insight into the genetic predisposition to DN showing that two polymorphisms in MIR146A and MIR128A genes could significantly contribute to the development of early ocular preclinical signs of DN.

Cardiovascular risk factors in children and adolescents with type 1 diabetes mellitus: the role of insulin resistance and associated genetic variants

INTRODUCTION

Type 1 diabetes (T1D) is associated with increased risk of cardiovascular disease. Insulin resistance is an important cardiovascular risk factor (CVRF), also in subjects with T1D, but the influence of the genetic predisposition of insulin resistance on cardiovascular risk is still unknown in T1D. We aimed to determine whether a genetic score composed of six variants, previously associated to insulin resistance and type 2 diabetes (T2D) risk, associates with insulin sensitivity and known CVRFs in children and adolescents with T1D.

MATERIALS AND METHODS

330 children and adolescents (174 males; mean age 15.7±3.5 years) with T1D were genotyped for the following genetic variants: rs1801278 (IRS1), rs1044498 (ENPP1), rs2295490 (TRIB3), rs1801282 (PPARG), rs780094 (GCKR), and rs35767 (IGF1). An additive genetic risk score (GRS) and cardiovascular risk score (CVRS) were calculated. Anthropometric, glycemic control, insulin sensitivity, blood pressure, and biochemical parameters were assessed. Multivariate regression between evaluated phenotypes and GRS were performed.

RESULTS

We found a significant association between the GRS and estimated insulin sensitivity [β=-0.027 (-0.040 to -0.013), R2=0.86, p=<0.001], diastolic blood pressure [β=0.68 (0.08-1.27), R2=0.20, p=0.026], triglycerides [β=4.26 (1.74-6.77), R2=0.13, p=0.001], waist to height ratio [β=0.003 (0.001-0.006), R2=0.75, p=0.010], non-HDL-cholesterol [β=3.63 (1.39-5.87), R2=0.12, p=0.002], and CVRS [β=0.063 (0.008-0.118), R2=0.19, p=0.025], independent of age, sex, BMI, pubertal stage, diabetes duration, HbA1c, type of treatment and total insulin requirement. The addition of the GRS to established clinical risk factors significantly improved the discriminatory capability of the regression model for predicting subjects with more CVRFs (C-statistic 0.89 [95%CI 0.84-0.95] vs. 0.83 [0.73-0.93]; p = 0.037).

CONCLUSIONS

Insulin resistance and T2D risk-associated genetic variants influence insulin sensitivity and known cardiovascular risk factors in children and adolescents with T1D.

Serum zonulin as an index of glucose dysregulation in children and adolescents with overweight and obesity

Increased intestinal permeability has an important role in metabolic dysregulation. In this cross-sectional study, we examined whether serum intestinal permeability marker zonulin and related pro-inflammatory molecules were associated with the oral disposition index, a predictor for the development of type 2 diabetes, in a cohort of children and adolescents with overweight and obesity. Ninety-two children and adolescents were recruited [Male: 43; 12.7 (2.35) years; BMI SDS: 2.7 (0.96)]. Anthropometric and clinical parameters, lipid profile, glucose metabolism and plasma levels of zonulin, lipopolysaccharide-binding protein and Interleukin-6 were measured. We found an association between oral disposition index and zonulin (β = -0.243; p = 0.019) and age (β = -0.307; p = 0.004), independent of sex and BMI SDS [R²  = 0.16; p = 0.005]. Our results show an association between serum zonulin concentration and oral disposition index supporting the hypothesis of increased intestinal permeability as a possible risk factor for glucose metabolism dysregulation in children and adolescents with obesity.

Association between lower plasma adiponectin levels and higher liver stiffness in type 2 diabetic individuals with nonalcoholic fatty liver disease: an observational cross-sectional study

PURPOSE

Little is known about the association between plasma adiponectin levels and nonalcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus (T2DM). We examined whether there is an association between lower plasma adiponectin levels and the presence/severity of NAFLD in people with T2DM.

METHODS

We cross-sectionally recruited 79 men with non-insulin-treated T2DM and no known liver diseases, who had consecutively attended our diabetes outpatient service over a 6-month period and who underwent both ultrasonography and Fibroscan-measured liver stiffness (LSM). Nine single nucleotide polymorphisms (PNPLA3 rs738409 and other genetic variants) associated with NAFLD were investigated.

RESULTS

Among the 79 participants included (mean age 67 ± 10 years, BMI 27.7 ± 4 kg/m²), 28 did not have NAFLD, 32 had steatosis alone, and 19 had NAFLD with coexisting significant fibrosis (LSM ≥ 7.0 kPa by Fibroscan®). Compared to those without NAFLD, patients with hepatic steatosis alone and those with hepatic steatosis and coexisting significant fibrosis had lower high-molecular-weight adiponectin levels (5.5 [IQR 2.3-7.6] vs. 2.4 [1.8-3.7] vs. 1.6 [1.0-2.9] µg/mL; p < 0.001). After adjustment for age, body mass index, insulin resistance, and the PNPLA3 rs738409 variant, lower plasma adiponectin levels were found to be associated with increased odds of both steatosis alone (adjusted-odds ratio [OR] 2.44, 95% CI 1.04-5.56, p = 0.042) and NAFLD with coexisting significant fibrosis (adjusted-OR 3.84, 95% CI 1.23-10.0, p = 0.020). Similar findings were observed after adjustment for the other eight genotyped NAFLD-related polymorphisms.

CONCLUSION

Lower plasma adiponectin levels are closely associated with the presence and severity of NAFLD in men with T2DM, pointing to a role of adiponectin in NAFLD development and progression.

Genetic Variation in Antioxidant Response Modulates the Level of Oxidative Stress in Youth with Type 1 Diabetes and Poor Glycemic Control

Background: The minor allele of the single nucleotide polymorphism (SNP) rs2364723 of NFE2L2, a gene encoding a master antioxidant transcription factor, has been associated with poor cardiovascular outcomes and with complications of type 2 diabetes. We assessed the association between rs2364723 of NFE2L2 and oxidative stress in children/adolescents with type 1 diabetes (T1D). Methods: In 384 children/adolescents with T1D (age 15.7 ± 3.2 years, 207 males), we assessed the oxidative stress by measuring the concentration of derivatives of reactive oxygen metabolites (d-ROMs) and we genotyped the rs2364723 SNP by real time polymerase chain reaction. Results: The concentration of d-ROMs was 372.8 ± 64.6 Carratelli units. The minor genotype (CC) of rs2364723 at NFE2L2 was associated with higher concentration of derivatives of d-ROMs in the subgroup with HbA1c ≥ 8% (B = 47.85, p for genotype ∗ HbA1c interaction = 0.019). Conclusions: The carriers of the minor genotype of rs2364723 may have increased oxidative stress compared to their counterparts with other genotypes, especially in case of poor glycemic control. This observation needs to be replicated and confirmed in larger independent cohorts of youth with T1D.

MAFLD and CKD: An Updated Narrative Review

Accumulating evidence now indicates that non-alcoholic fatty liver disease (NAFLD), which is the most common chronic liver disease observed in clinical practice worldwide, is independently associated with an increased risk of incident chronic kidney disease (CKD). Given that NAFLD is linked to insulin resistance, obesity and type 2 diabetes mellitus, an international panel of experts have recently proposed a name change from NAFLD to metabolic associated fatty liver disease (MAFLD). Since the diagnostic criteria for NAFLD and MAFLD are different, observational studies assessing the potential concordance (or even superiority) of MAFLD, compared with NAFLD, in detecting patients at increased risk of hepatic and extra-hepatic complications (including CKD) are required. Hence, in the last two years, some observational studies have investigated the potential relationship between MAFLD and CKD. The result is that, at present, evidence regarding the concordance or even superiority of MAFLD, compared with NAFLD, in detecting patients at higher risk of CKD is still preliminary, although some data indicate that MAFLD identifies patients with CKD as accurately as NAFLD. In this narrative review, we will discuss: (a) the epidemiological evidence assessing the association between NAFLD and risk of incident CKD, (b) the epidemiological data investigating the association between MAFLD and risk of CKD and (c) the biological mechanisms underlying the association between NAFLD/MAFLD and CKD.

Association between KLF6 rs3750861 polymorphism and plasma ceramide concentrations in post-menopausal women with type 2 diabetes

BACKGROUND AND AIM

Based on the emerging role of Kruppel-like factor 6 (KLF6) in lipid metabolism, we examined whether there is a relationship between the KLF6 rs3750861 genetic variant and plasma ceramide levels in people with type 2 diabetes mellitus (T2DM).

METHODS AND RESULT

We measured six previously identified plasma ceramides, which have been associated with increased cardiovascular risk [Cer(d18:1/16:0), Cer(d18:1/18:0), Cer(d18:1/20:0), Cer(d18:1/22:0), Cer(d18:1/24:0) and Cer(d18:1/24:1)] amongst 101 Caucasian post-menopausal women with T2DM, who consecutively attended our diabetes outpatient service during a 3-month period. Plasma ceramides were measured by targeted liquid chromatography-tandem mass spectrometry assay. Genotyping of the KLF6 rs3750861 polymorphism was performed by TaqMan-Based RT-PCR system. Overall, 87 (86.1%) patients had KLF6 rs3750861 C/C genotype and 14 (13.9%) had C/T or T/T genotypes. After adjustment for age, diabetes-related variables, use of lipid-lowering drugs and other potential confounders, patients with C/T or T/T genotypes had higher plasma Cer(d18:1/18:0) (0.159 ± 0.05 vs. 0.120 ± 0.04 μmol/L, p = 0.012), Cer(d18:1/20:0) (0.129 ± 0.04 vs. 0.098 ± 0.03 μmol/L, p = 0.008), and Cer(d18:1/24:1) (1.236 ± 0.38 vs. 0.978 ± 0.36 μmol/L, p = 0.032) compared with those with C/C genotype.

CONCLUSIONS

The C/T or T/T genotypes of rs3750861 in the KLF6 gene were closely associated with higher levels of specific plasma ceramides in post-menopausal women with T2DM.

Haplotypes of the genes (GCK and G6PC2) underlying the glucose/glucose-6-phosphate cycle are associated with pancreatic beta cell glucose sensitivity in patients with newly diagnosed type 2 diabetes from the VNDS study (VNDS 11)

BACKGROUND

Elevated fasting plasma glucose has been associated with increased risk for development of type 2 diabetes (T2D). The balance between glucokinase (GCK) and glucose-6-phosphate catalytic subunit 2 (G6PC2) activity are involved in glucose homeostasis through glycolytic flux, and subsequent insulin secretion.

AIM

In this study, we evaluated the association between the genetic variability of G6PC2 and GCK genes and T2D-related quantitative traits.

METHODS

In 794 drug-naïve, GADA-negative, newly diagnosed T2D patients (VNDS; NTC01526720) we performed: genotyping of 6 independent tag-SNPs within GCK gene and 5 tag-SNPs within G6PC2 gene; euglycaemic insulin clamp to assess insulin sensitivity; OGTT to estimate beta-cell function (derivative and proportional control; DC, PC) by mathematical modeling. Genetic association analysis has been conducted using Plink software.

RESULTS

Two SNPs within GCK gene (rs882019 and rs1303722) were associated to DC in opposite way (both p < 0.004). Two G6PC2 variants (rs13387347 and rs560887) were associated to both parameters of insulin secretion (DC and PC) and to fasting C-peptide levels (all p < 0.038). Moreover, subjects carrying the A allele of rs560887 showed higher values of 2h-plasma glucose (2hPG) (p = 0.033). Haplotype analysis revealed that GCK (AACAAA) haplotype was associated to decreased fasting C-peptide levels, whereas, the most frequent haplotype of G6PC2 (GGAAG) was associated with higher fasting C-peptide levels (p = 0.001), higher PC (β = 6.87, p = 0.022) and the lower 2hPG (p = 0.012).

CONCLUSION

Our findings confirmed the role of GCK and G6PC2 in regulating the pulsatility in insulin secretion thereby influencing insulin-signaling and leading to a gradual modulation in glucose levels in Italian patients with newly diagnosed T2D.

Oxidative stress in youth with type 1 diabetes: Not only a matter of gender, age, and glycemic control

AIMS

We assessed whether oxidative stress (OS) is increased in children/adolescents with type 1 diabetes (T1D) compared to healthy peers. Moreover, we searched for OS predictors in the T1D population.

METHODS

We compared the concentration of serum derivatives of reactive oxygen metabolites (d-ROMs) in 412 children/adolescents with T1D (3.6-23.5 years old) to that of 138 healthy children/adolescents (1.2-19.2 years old) by ANOVA adjusted for age, gender, and BMI z-score (z-BMI). Applying a general linear model, in a subgroup of 331 patients using continuous glucose monitoring, we searched for predictors of d-ROMs among 3-day, 2-week, and 4-week metrics of glucose control and variability, such as mean blood glucose, percent time in range (70-180 mg/dl,TIR_70-180), coefficient of variation, and others, as well as among conventional cardiovascular risk factors like current and average HbA1c, z-BMI, blood pressure percentiles, and lipid concentrations recorded retrospectively over the entire follow-up period.

RESULTS

D-ROMs levels were significantly higher in children/adolescents with T1D compared to controls [371.9 (64.2) versus 324.9 (46.3), p < 10^-16]. Sex (B = 49.1, ƞ² = 0.14, p = 1.3 * 10^-9), age < 12 years in boys (B = 79.4, ƞ² = 0.074, p = 10^-7),3-day TIR_70-180 (B = -0.87, ƞ² = 0.048, p = 6.5 * 10^-5), and z-BMI (B = 7.4, ƞ² = 0.016, p = 0.022) predicted d-ROMs with an overall R² of 0.278.

CONCLUSIONS

OS is increased in youth with T1D and only partially predicted by gender, age, glucose control, and anthropometry. Other potential determinants of OS in this population should be targeted in future studies.

The risk of metabolic derangements is higher in children and adolescents with overweight or obesity born small for gestational age

BACKGROUND AND AIMS

Birth weight (BW) has been associated with the risk of obesity and metabolic derangements in children and adults. The aims of this study were: i. to evaluate the distribution of BW in a sample of overweight and obese children and adolescents compared with the general reference population; ii. to explore the relationship between the BW and insulin resistance and other cardiometabolic derangements in a population of children and adolescents with overweight and obesity.

METHODS AND RESULTS

710 overweight and obese children and adolescents were recruited and categorized into small (SGA), appropriate (AGA), and large (LGA) for gestational age, according to the BW percentile. Arterial blood pressure, lipid profile, glucose metabolism and hepatic steatosis were evaluated to assess cardiometabolic obesity-related derangements. The distribution of BW categories in our population was significantly different compared with the general population (SGA 6.9% vs. 8.6%, AGA 74.6% vs. 81.4%, LGA 18.5% vs. 10%; p < 0.0001). We found a higher frequency of prediabetes conditions (21.7% vs 8.9%, OR 2.97, 95% CI 1.38-6.38, p = 0.005) and borderline/high low-density lipoprotein cholesterol (31.8% vs 18.6%, OR 2.13, 95% CI 1.09-4.18, p = 0.033) in overweight and obese children born SGA compared to those born non-SGA, independently of age, sex, and BMI.

CONCLUSIONS

BW is a risk factor of cardiometabolic derangements in a population of children and adolescents with overweight and obesity. Therefore, adequate obesity prevention strategies should be planned for children born SGA to minimize their risk to become obese and to reduce their short- and long-term cardiometabolic risks.

Association between MBOAT7 rs641738 polymorphism and non-alcoholic fatty liver in overweight or obese children

BACKGROUND AND AIM

The association between non-alcoholic fatty liver (NAFL) and the variant rs641738 within the membrane bound O-acyltransferase domain-containing 7 (MBOAT7) gene is currently uncertain, especially in the paediatric population. We examined whether there is an association between this genetic variant and NAFL in a large multicentre, hospital-based cohort of Italian overweight/obese children.

METHODS AND RESULTS

We studied 1760 overweight or obese children [mean age (SD): 11.1(2.9) years, z-body mass index (zBMI) 3.2(0.9)], who underwent ultrasonography for the diagnosis of NAFL. A subgroup of these children (n = 182) also underwent liver biopsy. Genotyping of the MBOAT7 rs641738 polymorphism was performed by TaqMan-Based RT-PCR system in each subject. Overall, 1131 (64.3%) children had ultrasound-detected NAFL; 528 (30%) had rs641738 CC genotype, 849 (48.2%) had rs641738 CT genotype, and 383 (21.8%) had rs641738 TT genotype, respectively. In the whole cohort, the interaction of MBOAT7 genotypes with zBMI was not associated with NAFL after adjustment for age, sex, serum triglycerides, serum alanine aminotransferase levels and patatin-like phospholipase domain-containing protein-3 (PNPLA3) genotype (adjusted-odds ratio 1.02 [95% CI 0.98-1.06]). Similarly, no association was found between MBOAT7 genotypes and NAFL after stratification by obesity status. MBOAT7 genotypes were not associated with the presence of non-alcoholic steatohepatitis or the stage of liver fibrosis in a subgroup of 182 children with biopsy-proven NAFLD.

CONCLUSIONS

The results of this study did not show any significant contribution of MBOAT7 rs641738 polymorphism to the risk of having either NAFL on ultrasonography or NASH on histology in a large hospital-based cohort of Italian overweight/obese children.

Glucose Tolerance Stages in Cystic Fibrosis Are Identified by a Unique Pattern of Defects of Beta-Cell Function

OBJECTIVE

We aimed to assess the order of severity of the defects of 3 direct determinants of glucose regulation-beta-cell function, insulin clearance, and insulin sensitivity-in patients with cystic fibrosis (CF), categorized according their glucose tolerance status, including early elevation of mid-level oral glucose tolerance test (OGTT) glucose values (>140 and <200 mg/dL), referred to as AGT140.

METHODS

A total of 232 CF patients aged 10 to 25 years underwent OGTT. Beta-cell function and insulin clearance were estimated by OGTT mathematical modeling and OGTT-derived biomarkers of insulin secretion and sensitivity were calculated. The association between glucometabolic variables and 5 glucose tolerance stages (normal glucose tolerance [NGT], AGT140, indeterminate glucose tolerance [INDET], impaired glucose tolerance [IGT], cystic fibrosis-related diabetes CFRD]) was assessed with a general linear model.

RESULTS

Beta-cell function and insulin sensitivity progressively worsened across glucose tolerance stages (P < 0.001), with AGT140 patients significantly differing from NGT (all P < 0.01). AGT140 and INDET showed a degree of beta-cell dysfunction similar to IGT and CFRD, respectively (all P < 0.01). Insulin clearance was not significantly associated with glucose tolerance stages (P = 0.162). Each stage of glucose tolerance was uniquely identified by a specific combination of defects of the direct determinants of glucose regulation.

CONCLUSIONS

In CF patients, each of the 5 glucose tolerance stages shows a unique pattern of defects of the direct determinants of glucose regulation, with AGT140 patients significantly differing from NGT and being similar to IGT. These findings suggest that AGT140 should be recognized as a distinct glucose tolerance stage and that reconsideration of the grade of glucometabolic deterioration across glucose tolerance stages in CF is warranted.

Coronavirus disease 2019 (COVID-19) in children and/or adolescents: a meta-analysis

BACKGROUND

To assess the overall prevalence of clinical signs, symptoms, and radiological findings in children and/or adolescents with COVID-19.

METHODS

We systematically researched in PubMed, Scopus and Web of Science databases observational studies describing COVID-19 in children and/or adolescents until April 11, 2020. Data regarding clinical and radiological features were extracted from eligible studies and meta-analysis was performed using random-effects modeling.

RESULTS

We examined 19 eligible studies for a total of 2855 children and/or adolescents with COVID-19. Approximately 47% of subjects had fever (95% confidence interval [CI] 22-72%; I² = 98.6%), 37% cough (95%CI 15-63%; I² = 98.6%), 4% diarrhea (95%CI 0-12%; I² = 92.2%), 2% nasal congestion (95%CI 0-7%; I² = 87.7%), 1% dyspnea (95%CI 0-7%; I² = 91.5%) and 0% abdominal pain (95%CI 0-1%; I² = 76.3%). Subjects presented mild symptoms in 79% (95%CI 65-91%; I² = 93.5%) of cases, whereas only 4% (95%CI 1-9%; I² = 76.4%) were critical. Among those with pneumonia on computed tomography, 26.4% (95%CI 13-41%; I² = 80.8%) presented a unilateral involvement, 16% (95%CI 5-29%, I² = 81.2%) had bilateral involvement and 9% (95%CI 0-24%; I² = 88.7%) had interstitial pneumonia.

CONCLUSIONS

Children and/or adolescents tend to have a mild COVID-19 course with a good prognosis.

IMPACT

Compared to adults, children and/or adolescents tend to have a mild COVID-19 course with a good prognosis. This study provides new and consistence information on the clinical and radiological characteristics of COVID-19 in pediatrics. This study may help to fight COVID-19 in pediatric population.

Nonalcoholic Fatty Liver Disease and Estimated Insulin Resistance in Obese Youth: A Mendelian Randomization Analysis

CONTEXT

Nonalcoholic fatty liver disease (NAFLD) is associated with insulin resistance (IR) and predicts type 2 diabetes. Currently, it is uncertain whether NAFLD may directly cause IR or vice versa.

OBJECTIVE

To test the hypothesis that NAFLD is causally related to IR.

DESIGN AND METHODS

We performed a Mendelian randomization (MR) in 904 obese children/adolescents using an NAFLD-related genetic risk score (GRS) as an instrumental variable. We assessed NAFLD by ultrasonography and IR by homeostasis model assessment (HOMA-IR). We also interrogated the MAGIC Consortium dataset of 46 186 adults to assess the association between PNPLA3 rs738409 (ie, the most robust NAFLD-related polymorphism) and HOMA-IR, and we performed a 2-sample MR with 2 large datasets to test reverse causation (HOMA-IR increasing the risk of NAFLD).

RESULTS

Nonalcoholic fatty liver disease prevalence increased by 20% for every increase in the GRS (β-coefficient = 0.20, P < 0.001), and NAFLD was associated with ln-HOMA-IR (β-coefficient = 0.28, P < 0.001). Thus, the expected increase in ln-HOMA-IR for every increase in the GRS (expected β-coefficient) was 0.056 (0.28*0.20) in the case of complete NAFLD-HOMA-IR causal association, and 0.042 in the case of 75% causality. In our cohort, the GRS did not predict ln-HOMA-IR (β-coefficient = 0.007, P = 0.75). In the MAGIC cohort, the PNPLA3 rs738409 did not associate with ln-HOMA-IR. The 2-sample MR failed to show a causal association between ln-HOMA-IR and NAFLD.

CONCLUSIONS

Our study shows that genetically-influenced NAFLD does not increase HOMA-IR, and genetically-influenced HOMA-IR does not increase the risk of NAFLD. Shared pathogenic pathways or NAFLD subtypes not "captured" by our MR design might underpin the association between NAFLD and HOMA-IR.

PNPLA3 I148M gene variant and chronic kidney disease in type 2 diabetic patients with NAFLD: Clinical and experimental findings

BACKGROUND AND AIMS

Emerging evidence suggests an association between patatin-like phospholipase domain-containing protein-3 (PNPLA3) rs738409 (I148M protein variant) and risk of chronic kidney disease (CKD), but the mechanisms underpinning this association are poorly understood.

METHODS

We studied 157 patients with type 2 diabetes (T2DM) who underwent ultrasonography and vibration-controlled transient elastography for diagnosing nonalcoholic fatty liver disease (NAFLD). CKD was defined as estimated glomerular filtration rate (e-GFR) <60 mL/min/1.73 m² and/or abnormal albuminuria. We surveyed PNPLA3 mRNA expression in human tissues, using the liver as a positive control, and also measured PNPLA3 mRNA and protein expression levels in human cell lines represented in the kidney and the liver.

RESULTS

In all, 112 patients had NAFLD and 43 had CKD. Patients homozygous for the I148M variant (n = 11) had lower e-GFR levels (60.6 ± 11.7 vs 77.8 ± 15.9 vs 83.5 ± 16.5 mL/min/1.73 m² , P = .0001) and higher prevalence of CKD (63.6% vs 24.2% vs 25.0%, P = .028), compared to those with I/M (n = 66) and I/I (n = 80) PNPLA3 genotype. The association of I148M homozygosity with lower e-GFR levels (P < .0001) and higher risk of CKD (adjusted-odds ratio 6.65; 95% CI 1.65-26.8, P = .008) was independent of liver disease severity (as detected by liver stiffness ≥7kPa) and other risk factors. PNPLA3 mRNA expression was greatest in liver and renal cortex, and podocytes showed high PNPLA3 mRNA and protein levels, comparable to that of hepatocytes and hepatic stellate cells respectively.

CONCLUSIONS

The PNPLA3 I148M variant was associated with CKD, independently of common renal risk factors and severity of NAFLD PNPLA3 expression levels were particularly high in renal podocytes.

Risk of Kidney Dysfunction IN Nafld

Background:

The timely identification of traditional and non-traditional precursors and risk factors for chronic kidney disease (CKD) (a common systemic disease defined as a decreased kidney function documented by reduced glomerular filtration rate, or markers of kidney damage, or both) is relevant in clinical practice, as CKD increases the risk of end-stage renal disease and other serious comorbidities. A possible relationship between non-alcoholic fatty liver disease (NAFLD) (which is to date the most common chronic disease worldwide) and CKD has recently gained significant attention of researchers.

Methods :

A systematic literature search using appropriate keywords was made in order to identify relevant articles that have investigated the association between NAFLD and CKD.

Results:

Several observational studies and meta-analyses have reported the existence of an independent association between NAFLD and risk of CKD in patients with and without diabetes. However, whilst the association between NAFLD and risk of prevalent CKD is strong across various patient populations, whether NAFLD is independently associated with the development and progression of CKD is still debatable. Moreover, emerging evidence now suggests a potential association between patatin-like phospholipase domain-containing protein-3 (PNPLA3) rs738409 genotype (the most important genetic variant associated to NAFLD) and decreasing kidney function, independent of NAFLD.

Conclusions :

Convincing evidence now indicates that CKD is increased among patients with NAFLD. For this reason, patients with NAFLD should be regularly monitored for renal function and, on the other hand , NAFLD should be considered in all patients with CKD, especially if they are obese or have type 2 diabetes.

PNPLA3 gene and kidney disease

Chronic kidney disease (CKD) is a disease regularly seen in clinical practice. At present, CKD is described as a change of kidney structure and/or function and it is classified in relation to cause, values of glomerular filtration rate and albuminuria category. Seeing that CKD is closely linked to the development of end-stage renal disease and other comorbidities, the determination of additional independent predictors for CKD is clinically necessary. At present, there is evidence associating non-alcoholic fatty liver disease (NAFLD) with CKD, thereby suggesting that NAFLD patients may require intensive surveillance to reduce their risk of CKD. In 2008, genome-wide association studies documented an association between the variant rs738409 (C > G p.I148M) in the patatin-like phospholipase domain containing 3 (PNPLA3) gene (mainly implicated in the lipid regulation) and the entire spectrum of NAFLD (i.e., liver steatosis, non-alcoholic steatohepatitis, fibrosis, and hepatocellular carcinoma). In the last years, accumulating epidemiological evidence suggests the existence of a relationship between PNPLA3 rs738409 and risk of CKD, indicating that rs738409 may also contribute to the kidney injury. This is of particular scientific interest, as such association may explain, at least in part, the epidemiological association between liver and kidney disease. In this narrative review, we will discuss the accumulating evidence regarding the association between PNPLA3 rs738409 and risk of CKD, the putative biological mechanisms underpinning such relationship, and the possible future perspective.

Screening for non-alcoholic fatty liver disease using liver stiffness measurement and its association with chronic kidney disease and cardiovascular complications in patients with type 2 diabetes

AIM

Despite the high prevalence and serious clinical implications of non-alcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus (T2DM), NAFLD is usually overlooked during routine diabetes care. This study explored the proportion of NAFLD cases and increased liver fibrosis (LF), and the association between LF and either chronic kidney disease (CKD) or cardiovascular complications in T2DM patients.

METHODS

The study included 137 patients with non-insulin-treated T2DM and no known liver disease consecutively attending our diabetes outpatients' service who underwent liver ultrasonography and liver stiffness measurement (LSM) using vibration-controlled transient elastography (FibroScan®).

RESULTS

The proportion of patients with hepatic steatosis on ultrasonography was 73.7%, and the proportion with significant LF was 17.5% with an LSM cut-off ≥7kPa or 10.2% with an LSM cut-off ≥8.7kPa. The presence of CKD (estimated GFR <60mL/min/1.73m² and/or abnormal albuminuria) increased significantly across LSM tertiles (from around 15% in tertile 1 to 45% in tertile 3). Cardiovascular complications (previous ischaemic heart disease, ischaemic stroke, permanent atrial fibrillation) also tended to increase across LSM tertiles (from around 15% to 30%). After adjusting for established risk factors and potential confounders, LSM tertile 3 remained significantly associated with an approximately threefold higher risk of prevalent CKD (adjusted OR: 3.28, 95% CI: 1.22-8.90; P=0.019), but not for cardiovascular complications.

CONCLUSION

These results suggest that NAFLD and significant LF (as assessed by FibroScan®) are very commonly seen in T2DM outpatients with no known liver disease attending a secondary-care diabetes service, and that increased LF is associated with a greater proportion of chronic vascular complications, especially CKD.

Contribution of a genetic risk score to clinical prediction of hepatic steatosis in obese children and adolescents

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is the commonest liver disease in children and adolescents in Western countries. Complex traits arise from the interplay between environmental and genetic factors in the pathogenesis of NAFLD.

AIMS

We examined the association between NAFLD and eleven single nucleotide polymorphisms (SNPs) at genetic loci potentially associated with liver damage (GCKR, MBOAT7, GPR120), oxidative stress (SOD2), lipid metabolism (PNPLA3, TM6SF2, LPIN1, ELOVL2, FADS2, MTTP) and fibrogenesis (KLF6) in a paediatric population. A genetic risk score (GRS) was performed taking into account both these SNPs and clinical risk factors.

METHODS

We recruited a cohort of 514 obese children and adolescents (mean age [±SD]: 11.2 ± 2.8 years, z-BMI 3.3 ± 0.8). NAFLD was identified by ultrasonography. Genotyping was performed by TaqMan-based RT-PCR system.

RESULTS

The overall prevalence of NAFLD was 67.5% (347 patients). Among the eleven genotyped SNPs, the genetic variants in TM6SF2 rs58542926 (OR = 4.13, p = 0.002), GCKR rs1260326 (OR = 1.53, p = 0.003), PNPLA3 rs738409 (OR = 1.58, p = 0.004) and ELOVL2 rs2236212 (OR = 1.34, p = 0.047) were significantly associated with a higher risk of NAFLD. Addition of a 11-polymorphism GRS to established clinical risk factors significantly (albeit modestly) improved the discriminatory capability of the regression model for predicting the risk of NAFLD (with SNPs C-statistic 0.81 [95%CI 0.75-0.88] vs. 0.77 [0.70-0.84] without SNPs; p = 0.047).

CONCLUSIONS

NAFLD was strongly associated with three genetic variants, TM6SF2 rs58542926, PNPLA3 rs738409 and GCKR rs1260326, and more slightly with ELOVL2 rs2236212, in obese children and adolescents. Addition of a 11-polymorphism GRS to clinical risk factors improved the predictability of NAFLD.

Vitamin D affects insulin sensitivity and β-cell function in obese non-diabetic youths

OBJECTIVE

Vitamin D may potentially play a central role in glucose homeostasis and β-cell function (BCF), although studies are not consistent. Aim of our study was to test the hypotheses of a direct relationship between vitamin D, insulin sensitivity (IS) and BCF in overweight and obese non-diabetic children.

DESIGN AND METHODS

Cross-sectional study carried out at the Childhood Obesity Outpatient Clinic, University Hospital of Verona. One hundred twenty-two Caucasian overweight and obese children (age: 12.8 ± 0.2 years) were enrolled. Exclusion criteria: genetic or endocrine causes of obesity, chronic diseases or therapies. Patients underwent oral glucose tolerance test. HOMA-IR, Matsuda index and insulinogenic index were calculated. BCF was reconstructed by mathematical modeling and described by Derivative and Proportional Control. Total 25-hydroxyvitamin D and vitamin D-binding protein (VDBP) were measured. Two SNPs (rs4588 and rs7041) in the VDBP gene were studied, and bioavailable vitamin D (BVD) was calculated.

RESULTS

Hypovitaminosis D was documented in 90% of patients. Forty-seven subjects were homozygous for both SNPs. Total vitamin D was positively correlated with Matsuda index (P = 0.002), VDBP (P = 0.045), and negatively with BMI SDS (P = 0.043), HOMA-IR (P = 0.008), HOMA-B (P = 0.001), IGI (P = 0.007), derivative control (P = 0.036) and proportional control (P = 0.018). Total vitamin D, adjusted for age, gender, BMI SDS, puberty and seasonality of vitamin D measurement, was a predictor of Matsuda index, HOMA-IR, HOMA-B, IGI, proportional control (all P < 0.05). BVD was positively correlated with total vitamin D (P < 0.001) and negatively with BMI SDS (P = 0.041).

CONCLUSIONS

Hypovitaminosis D negatively influences BCF and IS, suggesting that vitamin D levels might be implicated in glucose metabolism impairment in overweight and obese individuals.

A renal genetic risk score (GRS) is associated with kidney dysfunction in people with type 2 diabetes

This study aims to investigate whether renal and cardiovascular phenotypes in Italian patients with type 2 diabetes (T2D) could be influenced by a number of disease risk SNPs recently found in genome-wide association studies (GWAS). In 1591 Italian subjects with T2D: (1) 47 SNPs associated to kidney function and/or chronic kidney disease (CKD) and 49 SNPs associated to cardiovascular disease (CVD) risk were genotyped; (2) urinary albumin/creatinine (A/C) ratio, glomerular filtration rate (eGFR) and lipid profile were assessed; (3) a standard electrocardiogram was performed; (4) two genotype risk scores (GRS) were computed (a renal GRS calculated selecting 39 SNPs associated with intermediate traits of kidney damage and a cardiovascular GRS determined selecting 42 SNPs associated to CVD risk phenotypes). After correction for multiple comparisons, the renal GRS was not associated to A/C ratio (p = 0.33), but it was significantly related to decreased eGFR (p = 0.005). No association between the cardiovascular GRS and electrocardiogram was detected. Thus, in Italian patients with T2D a renal GRS might predict the decline in glomerular function, suggesting that the clock of diabetes associated CKD starts ticking long before hyperglycemia. Our data support the feasibility of gene-based prediction of complications in people with T2D.

Analysis of RBFOX1 gene expression in lymphoblastoid cell lines of Italian discordant autism spectrum disorders sib-pairs

Several lines of evidence suggest that RBFOX1 is a key regulator of transcriptional and splicing programs in neural cells during development, and that it is expressed in a neuronal module enriched for known autism susceptibility genes. We have investigated its expression by semiquantitative RT-PCR in accessible nonbrain resources in eighteen autism spectrum disorder sib-pairs belonging to the Italian Autism Network cohort. RBFOX1 gene expression was detected in lymphoblastoid cell lines but not in lymphocytes. No significant differences between autism spectrum disorders and non-affected brothers were found. We were not able to replicate in lymphoblastoid cell lines the previously reported RBFOX1 gene downregulation in autism, even if a trend was observed. This might be due to less pronounced transcription level differences in RBFOX1 gene expression in lymphoblastoid cell lines than in brain samples.

Enantiomer discrimination illustrated by high-resolution crystal structures of the human nuclear receptor hRARgamma

The human retinoic acid receptor (hRAR) is a member of the nuclear receptor superfamily that regulates the transcription of target genes in a ligand-dependent manner. The three hRAR isotypes are targets for retinoids that are used in the treatment of various diseases, including breast cancer and skin diseases. Drug efficiency and safety depend on the pharmacological activity of enantiomers, which can differ because of the chiral environment generated by the target. We report the crystal structures of the hRARgamma ligand-binding domain bound to two enantiomers, the active BMS270394 and the inactive BMS270395, solved at 1.6 A and 1.7 A resolution, respectively. The crystal structures reveal that in both enantiomers, the hydroxyl moiety attached to the chiral center forms a hydrogen bond to the Met-272 sulfur atom, thus imposing a conformation of BMS270395 that differs significantly from that observed for BMS270394 and other known retinoids. BMS270395 adopts an energetically unfavorable conformation, accounting for its inactivity; in contrast, the conformation of BMS270394 is close to an energy minimum. Our high-resolution data allow rationalization of enantiomer discrimination by the receptor and provide a model system for the pharmacological properties of enantiomeric pairs.

Two distinct actions of retinoid-receptor ligands

Signalling by all-trans retinoic acid is mediated through RXR-RAR retinoid receptor heterodimers, in which RXR has been considered to act as a transcriptionally silent partner. However, we show here that in cultured NB4 (ref. 6) human acute promyelocytic leukaemia cells treated with either an RAR-alpha-selective agonist alone, or certain RAR-alpha antagonists in combination with an RXR agonist, receptor-DNA binding is induced in vivo, resulting in expression of the target genes of retinoic acid as well as acute promyelocytic leukaemia protein (PML) relocation to nuclear bodies and differentiation before apoptosis. These results indicate that RAR-alpha ligands can induce two separate events: one enables RXR-RAR-alpha heterodimers to bind to DNA in vivo and allows RXR agonists to act; the other induces transcriptional activity of RAR-alpha. The availability of receptor-specific synthetic retinoids that can induce distinct receptor functions has potential in extending the therapeutic repertoire of retinoids.