The vitamin D receptor (VDR) gene rs11568820 variant is associated with type 2 diabetes and impaired insulin secretion in Italian adult subjects, and associates with increased cardio-metabolic risk in children

BACKGROUND AND AIMS

1α,25-dihydroxyvitamin-D3, the biologically active vitamin D, plays a central role in several metabolic pathways through the binding to the vitamin D receptor (VDR). VDR has been shown to be involved in cardiovascular diseases, cancer, autoimmunity and type 2 diabetes mellitus (T2DM). Several polymorphisms in the VDR gene have been described. Among these, the rs11568820 G-to-A nucleotide substitution was found to be functional, modulating the transcription of the VDR gene. Objective of this study was to perform an association study between rs11568820 polymorphism and T2DM in a cohort of Italian adults with T2DM and in non-diabetic controls. To add further insight into the role of VDR gene we explored whether this association begins early in life in overweight/obese children, or becomes manifest only in adulthood.

METHODS AND RESULTS

As many as 1788 adults and 878 children were genotyped for the rs11568820 polymorphism. All participants underwent oral glucose tolerance tests (OGTT), with measurement of glucose and insulin levels. Indices of insulin-resistance and secretion were also calculated. The AA genotype was significantly more frequent in adults with T2DM compared to controls (7.5% vs. 4.6%, P = 0.037), and conferred a higher risk of T2DM (ORHom = 1.69C.I. = [1.13-2.53], P = 0.011). In the adult cohort, rs11568820 was also associated with reduced indices of β-cell insulin secretion. In children, the AA genotype was associated with 2 h high-normal glucose, a marker of cardio-metabolic risk.

CONCLUSIONS

Our study demonstrates for the first time that VDR gene AA carriers have higher risk of T2DM and impaired insulin secretion. In children, the association between AA homozygous and high-normal 2h glucose suggests that mild alterations associated with this genotype may appear early in life.

Effects of angiopoietin-like protein 3 deficiency on postprandial lipid and lipoprotein metabolism

The consequences of angiopoietin-like protein 3 (ANGPTL3) deficiency on postprandial lipid and lipoprotein metabolism has not been investigated in humans. We studied 7 homozygous (undetectable circulating ANGPTL3 levels) and 31 heterozygous (50% of circulating ANGPTL3 levels) subjects with familial combined hypolipidemia (FHBL2) due to inactivating ANGPTL3 mutations in comparison with 35 controls. All subjects were evaluated at fasting and during 6 h after a high fat meal. Postprandial lipid and lipoprotein changes were quantified by calculating the areas under the curve (AUCs) using the 6 h concentration data. Plasma changes of β-hydroxybutyric acid (β-HBA) were measured as marker of hepatic oxidation of fatty acids. Compared with controls, homozygotes showed lower incremental AUCs (iAUCs) of total TG (-69%, P < 0.001), TG-rich lipoproteins (-90%, P < 0.001), apoB-48 (-78%, P = 0.032), and larger absolute increase of FFA (128%, P < 00.1). Also, heterozygotes displayed attenuated postprandial lipemia, but the difference was significant only for the iAUC of apoB-48 (-28%; P < 0.05). During the postprandial period, homozygotes, but not heterozygotes, showed a lower increase of β-HBA. Our findings demonstrate that complete ANGPTL3 deficiency associates with highly reduced postprandial lipemia probably due to faster catabolism of intestinally derived lipoproteins, larger expansion of the postprandial FFA pool, and decreased influx of dietary-derived fatty acids into the liver. These results add information on mechanisms underlying hypolipidemia in FHBL2.

Neutral lipid-storage disease with myopathy and extended phenotype with novel PNPLA2 mutation

INTRODUCTION

Neutral lipid-storage disease with myopathy is caused by mutations in PNPLA2, which produce skeletal and cardiac myopathy. We report a man with multiorgan neutral lipid storage and unusual multisystem clinical involvement, including cognitive impairment.

METHODS

Quantitative brain MRI with voxel-based morphometry and extended neuropsychological assessment were performed. In parallel, the coding sequences and intron/exon boundaries of the PNPLA2 gene were screened by direct sequencing.

RESULTS

Neuropsychological assessment revealed global cognitive impairment, and brain MRI showed reduced gray matter volume in the temporal lobes. Molecular characterization revealed a novel homozygous mutation in exon 5 of PNPLA2 (c.714C>A), resulting in a premature stop codon (p.Cys238*).

CONCLUSIONS

Some PNPLA2 mutations, such as the one described here, may present with an extended phenotype, including brain involvement. In these cases, complete neuropsychological testing, combined with quantitative brain MRI, may help to characterize and quantify cognitive impairment.

Hydroxypyridinones with enhanced iron chelating properties. Synthesis, characterization and in vivo tests of 5-hydroxy-2-(hydroxymethyl)pyridine-4(1H)-one

an tautomeric changes positively influence coordinating ability?

Alterations of intestinal lipoprotein metabolism in diabetes mellitus and metabolic syndrome

Diabetes and metabolic syndrome are associated with abnormal postprandial lipoprotein metabolism, with a significant delay in the clearance of many lipid parameters, including triglycerides and chylomicrons. Abnormal concentrations of plasma lipids can result from changes in the production, conversion, or catabolism of lipoprotein particles. Whereas the liver is involved in controlling serum lipid levels through synthesis of liver derived triglyceride-rich lipoproteins and low-density lipoprotein metabolism, the intestine also has a major role in lipoprotein production. Postprandial lipemia results from increases in apoB-48 availability, lipogenesis, and the synthesis and absorption of cholesterol in the enterocytes. Increased intestinal lipoprotein production prolongs postprandial lipemia in patients with diabetes and MetS, and may contribute directly to atherogenesis in these patients.

Familial Hypercholesterolemia in Cardiac Rehabilitation: a new field of interest

Familial hypercholesterolemia (FH) is a frequently undiagnosed genetic disease characterized by substantial elevations of low-density lipoprotein cholesterol (LDL-C). The prevalence of heterozygous FH (HeFH) in the general population is 1:500 inhabitants, while the prevalence of homozygous FH (HoFH) is 1:1.000.000. If FH is not identified and aggressively treated at an early age, affected individuals have a 20-fold increased lifetime risk of coronary heart disease compared with the general population. This narrative review provide a concise overview of recommendations for diagnosis and treatment of adults and children with FH, and discuss the utility of considering FH as a comorbidity at the entry of Cardiac Rehabilitation programmes.

Atherogenic dyslipidemia in children: evaluation of clinical, biochemical and genetic aspects

The precursors of atherogenic dyslipidemia (AD) are not well defined. Therefore, we investigated 62 non-obese, non-diabetic AD and 221 normolipemic children. Anthropometric parameters, blood pressure and biochemical measures were obtained in index children, their parents and all available siblings. The heritability (h²) of anthropometric and biochemical traits was estimated by SOLAR. Rare and common variants in APOA1 and LPL genes were screened by re-sequencing. Compared to normolipemic, AD children showed increased body mass index, waist circumference, plasma glucose, insulin, ApoB, HOMA-IR, hs-CRP and lower adiponectin (p<0.001 for all). Metabolic syndrome was present in 40% of AD while absent in controls. All traits (except adiponectin and hs-CRP) showed a strong familial aggregation, with plasma glucose having the highest heritability (89%). Overall, 4 LPL loss-of-function mutations were detected (p.Asp9Asn, p.Ser45Asn, p.Asn291Ser, p.Leu365Val) and their cumulative prevalence was higher in AD than in control children (0.073 vs. 0.026; P=0.038). The LPL p.S447* gain-of-function mutation, resulted to be less frequent in AD than in control children (0.064 vs. 0.126; P=0.082). No variant in the APOA1 gene was found. Our data indicate that AD is a rather common dyslipidemia in childhood; it associates with metabolic abnormalities typical of insulin resistant state and shows a strong familial aggregation. LPL variants may contribute to the development of AD phenotype.

The history of Autosomal Recessive Hypercholesterolemia (ARH). From clinical observations to gene identification

The most frequent form of monogenic hypercholesterolemia, also known as Familial Hypercholesterolemia (FH), is characterized by plasma accumulation of cholesterol transported in Low Density Lipoproteins (LDLs). FH has a co-dominant transmission with a gene-dosage effect. FH heterozygotes have levels of plasma LDL-cholesterol (LDL-C) twice normal and present xanthomas and coronary heart disease (CHD) in adulthood. In rare FH homozygotes plasma LDL-C level is four times normal, while xanthomas and CHD are present from infancy. Most FH patients are carriers of mutations of the LDL receptor (LDLR); a minority of them carry either mutations in the Apolipoprotein B (ApoB), the protein constituent of LDLs which is the ligand for LDLR, or gain of function mutations of PCSK9, the protein responsible for the intracellular degradation of the LDLR. From 1970 to the mid 90s some publications described children with the clinical features of homozygous FH, who were born from normocholesterolemic parents, strongly suggesting a recessive transmission of FH. In these patients the involvement of LDLR and APOB genes was excluded. Interestingly, several patients were identified in the island of Sardinia (Italy), whose population has a peculiar genetic background due to geographical isolation. In this review, starting from the early descriptions of patients with putative recessive hypercholesterolemia, we highlight the milestones that led to the identification of a novel gene involved in LDL metabolism and the characterization of its encoded protein. The latter turned out to be an adaptor protein required for the LDLR-mediated endocytosis of LDLs in hepatocytes. The loss of function of this protein is the cause of Autosomal Recessive Hypercholesterolemia (ARH).

Non-alcoholic fatty liver disease, metabolic syndrome and patatin-like phospholipase domain-containing protein3 gene variants

BACKGROUND & AIMS

Non-alcoholic fatty liver disease was traditionally interpreted as a condition which may progress to liver-related complications. However, the increased mortality is primarily a result of cardiovascular diseases. It has been suggested that fatty liver can be considered as the hepatic consequence of the metabolic syndrome. The aim was to describe the different clinical presentations of non-alcoholic fatty liver disease on the basis of the patatin-like phospholipase domain-containing protein3 (PNPLA3) rs738409 gene variant.

METHODS

Fatty liver was defined by ultrasonographic Hamaguchi's criteria in 211 consecutive subjects with non-alcoholic fatty liver disease. The rs738409 polymorphism was determined by TaqMan assays. Metabolic syndrome was defined according to ATPIII modified criteria.

RESULTS

Prevalence of PNPLA3-148II, PNPLA3-148IM, and PNPLA3-148MM genotypes was 45.0%, 40.7%, and 14.3% respectively. Prevalence of metabolic syndrome progressively increased with the severity of liver steatosis (from 52.5% to 65.2%, and 82.3% respectively, p<0.01). The PNPLA3-148MM group had significantly lower mean serum triglycerides (p<0.001), Framingham cardiovascular risk score (p<0.01) and lower prevalence of metabolic syndrome (p<0.05) and its components. Age and HOMA-IR were positive independent predictors of metabolic syndrome, while a negative independent association was found between metabolic syndrome and the homozygotes PNPLA3 I148M variant.

CONCLUSIONS

We suggest a lower prevalence of MetS and reduced cardiovascular risk in NAFLD patients with PNPLA3MM genotype.

Subclinical atherosclerosis in systemic lupus erythematosus and antiphospholipid syndrome: focus on β2GPI-specific T cell response

OBJECTIVE

Systemic Lupus Erythematosus (SLE) and antiphospholipid syndrome (APS) are associated with a high prevalence of atherosclerosis. β2 glycoprotein I (β2GPI) represents a link between autoimmunity and endothelial dysfunction. Recently, β2GPI reactive T cells have been identified; however, their role in atherosclerosis is still under investigation. We evaluated early atherosclerosis in patients with SLE and APS and investigated T cell reactivity to β2GPI and its relationship with atherosclerotic process.

APPROACH AND RESULTS

Fifty SLE, 18 patients with primary APS (PAPS), and 25 healthy controls were enrolled. Demographic and clinical data, including traditional cardiovascular risk factors, were recorded. Monocyte β2GPI and Tissue Factor (TF) expression and peripheral blood mononuclear cell response to β2GPI stimulation were evaluated. Doppler ultrasound was performed to investigate flow-mediated dilatation (FMD) and carotid intima-media thickness (IMT). We detected an increase in mean IMT and a decrease in FMD in patients with SLE versus controls (P<0.05 and P=0.0001, respectively) and a decrease in FMD in patients with PAPS versus controls (P<0.05). Monocyte β2GPI and TF expression was higher in patients with SLE and PAPS than in controls (P=0.006 and P=0.001, respectively); no correlation of monocyte β2GPI and TF with IMT or FMD was detected. β2GPI induced peripheral blood mononuclear cell proliferation in 32% of patients with SLE, 25% of patients with PAPS yet in none of the controls. Proliferative response to β2GPI correlated with a history of arterial thrombosis, thrombocytopenia, and IMT >0.9 mm.

CONCLUSIONS

A significant percentage of patients with SLE and PAPS show a β2GPI-specific T cell reactivity, which is associated with subclinical atherosclerosis.

Stereospecific generation of homochiral helices in coordination polymers built from enantiopure binaphthyl-based ligands

The novel enantiopure spacer 2,2′-dimethoxy-1,1′-binaphthyl-3,3′-bis(4-pyridyl-amido) has been designed to prepare helical coordination polymers here investigated by means of experimental and theoretical data.

Arterial function and structure after a 1-year lifestyle intervention in children with nonalcoholic fatty liver disease

BACKGROUND AND AIMS

Lifestyle modification has been the mainstay of controlling childhood obesity and has proved to be effective in reducing cardiovascular risk factors. However, it is currently unknown whether the subclinical atherosclerotic changes associated with nonalcoholic fatty liver disease (NAFLD) in such population are reversible.

METHODS AND RESULTS

We analyzed changes of brachial flow-mediated dilation (FMD), carotid intima-media thickness (cIMT), clinical, laboratory, and imaging data in 120 obese children with NAFLD, at the end of a 1-year intervention program with diet and physical exercise. The lifestyle intervention led to a significant mean decrease of body mass index (BMI)-standard deviation score (SDS), waist circumference (WC) and fat mass, along with diastolic blood pressure, triglycerides, liver enzymes, insulin, insulin resistance (homeostasis model assessment of insulin resistance, HOMA-IR), and high-sensitivity C-reactive protein. At the end of the study, FMD improved (P < 0.0001), while cIMT did not change significantly (P = 0.20). A significant decrease in hepatic fat content as measured by magnetic resonance imaging was also observed. Changes in FMD were inversely associated with changes in BMI-SDS, WC, total cholesterol, non-HDL cholesterol, liver enzymes, HOMA-IR, physical activity, and hepatic fat content. After including in the model all the significant variables as well as age, gender, pubertal status, and baseline FMD values, changes in FMD were significantly and independently associated with changes in WC and total cholesterol.

CONCLUSION

Also in obese children with NAFLD arterial function may be restored by improving metabolic risk factors and reducing visceral adiposity following a 1-year lifestyle intervention.

Clinical characteristics and plasma lipids in subjects with familial combined hypolipidemia: a pooled analysis

Angiopoietin-like 3 (ANGPTL3) regulates lipoprotein metabolism by modulating extracellular lipases. Loss-of function mutations in ANGPTL3 gene cause familial combined hypolipidemia (FHBL2). The mode of inheritance and hepatic and vascular consequences of FHBL2 have not been fully elucidated. To get further insights on these aspects, we reevaluated the clinical and the biochemical characteristics of all reported cases of FHBL2. One hundred fifteen FHBL2 individuals carrying 13 different mutations in the ANGPTL3 gene (14 homozygotes, 8 compound heterozygotes, and 93 heterozygotes) and 402 controls were considered. Carriers of two mutant alleles had undetectable plasma levels of ANGPTL3 protein, whereas heterozygotes showed a reduction ranging from 34% to 88%, according to genotype. Compared with controls, homozygotes as well as heterozygotes showed a significant reduction of all plasma lipoproteins, while no difference in lipoprotein(a) [Lp(a)] levels was detected between groups. The prevalence of fatty liver was not different in FHBL2 subjects compared with controls. Notably, diabetes mellitus and cardiovascular disease were absent among homozygotes. FHBL2 trait is inherited in a codominant manner, and the lipid-lowering effect of two ANGPTL3 mutant alleles was more than four times larger than that of one mutant allele. No changes in Lp(a) were detected in FHBL2. Furthermore, our analysis confirmed that FHBL2 is not associated with adverse clinical sequelae. The possibility that FHBL2 confers lower risk of diabetes and cardiovascular disease warrants more detailed investigation.

Metabolic consequences of adipose triglyceride lipase deficiency in humans: an in vivo study in patients with neutral lipid storage disease with myopathy

CONTEXT

The role of adipose triglyceride lipase (ATGL) in intermediate substrates metabolism has not been fully elucidated in humans.

OBJECTIVE

Our objective was to evaluate the consequences of ATGL deficiency on body fat distribution, insulin sensitivity, fatty acids metabolism, and energy substrate utilization.

DESIGN AND SETTING

Body composition and organ fat content were measured by bioimpedance and (1)H nuclear magnetic resonance spectroscopy; heart glucose metabolism by [(18)F]deoxyglucose positron emission tomography and insulin sensitivity and β-cell function by oral glucose tolerance and 2-step euglycemic-hyperinsulinemic clamp. Lipolysis ([(2)H5]glycerol turnover) and indirect calorimetry were evaluated at fasting, after oral glucose load, during the clamp, and also during an iv epinephrine infusion. These metabolic investigations were carried out during hospitalization.

PATIENTS

Three patients affected by neutral lipid storage disease with myopathy (NLSDM) due to homozygosity for loss-of-function mutations in the ATGL gene and 6 sex-, age-, and body mass index-matched controls were studied.

RESULTS

As expected, NLSDM patients showed diffuse, although heterogeneous, fat infiltration in skeletal muscles associated with increased visceral fat. Although heart and liver were variably affected, fat content in the pancreas was increased in all patients. Compared with healthy controls, NLSDM patients showed impaired insulin response to glucose possibly related to the severe pancreatic steatosis, preserved whole-body insulin sensitivity, and a shift toward glucose metabolism in the heart. Fasting nonesterified fatty acid concentrations as well as basal lipolytic rates and the antilipolytic effect of insulin were normal in NLSDM patients, whereas the lipolytic effect of norepinephrine was impaired. Finally, no significant abnormality in the respiratory quotient was noted in NLSDM patients.

CONCLUSIONS

In humans, ATGL has a remarkable effect on cellular lipid droplet handling, and its lack causes both perivisceral, skeletal muscle, and pancreas fat accumulation; in contrast, the impact on whole-body insulin sensitivity and fatty acid metabolism is minor.

The angiopoietin-like protein 3: a hepatokine with expanding role in metabolism

PURPOSE OF REVIEW

Cumulating evidence are revealing roles of angiopoietin-like proteins (ANGPTLs) in lipid, glucose, and energy metabolism. In this review, we discuss the recent developments in understanding the specific role in metabolic processes of the liver-derived ANGPTL3.

RECENT FINDINGS

Several groups have reported clinical and metabolic characterization of individuals with loss-of-function variants in ANGPTL3 showing familial combined hypolipidemia, a syndrome characterized by marked reduction of all plasma lipoproteins. Their findings indicate that in humans, ANGPTL3 has a broader action on apoB and apoA-I-containing lipoproteins, as well as on free fatty acid and adipose tissue metabolism.

SUMMARY

The identification of loss-of-function ANGPTL3 mutation is shedding light on a possible role of ANGPTL3 at the crossroads of lipoproteins, fatty acids, and glucose metabolism, thus making ANGPTL3 an attractive protein to target the cardio-metabolic risk.

Heritability, genetic correlation and linkage to the 9p21.3 region of mixed platelet-leukocyte conjugates in families with and without early myocardial infarction

BACKGROUND AND AIMS

Variations in mixed platelet-leukocyte conjugate formation in human whole blood could be genetically determined. We quantified platelet and leukocyte activation and interaction in families with or without early myocardial infarction and evaluated their heritability, genetic correlation and linkage to the 9p21.3 region.

METHODS AND RESULTS

The study population included 739 subjects (≥ 15 years old) from 54 large pedigrees, 23 with and 31 without familial myocardial infarction. Mixed platelet-leukocyte conjugates and markers of platelet or leukocyte activation (P-selectin, CD11b and L-selectin surface expression) were measured both before and after in vitro blood stimulation with collagen-ADP. All traits had significant genetic components (17.5-65.3% of the phenotypic variability), while shared household effects (0-39.6%) and environmental covariates (0-10.2%) tended to be smaller. Stimulated platelet-polymorphonuclear leukocyte (PMN) and platelet-monocyte conjugates showed the highest linkage to the 9p21.3 region (LOD = 0.94 and 1.33, respectively; empirical p value = 0.017 and 0.009). PMN markers resulted strongly genetically correlated between them in bivariate analysis among pairs of quantitative traits.

CONCLUSION

This study supports a genetic regulation of human mixed platelet-leukocyte conjugates.

Angptl3 Deficiency Is Associated With Increased Insulin Sensitivity, Lipoprotein Lipase Activity, and Decreased Serum Free Fatty Acids

Objective—

Angiopoietin-like 3 (Angptl3) is a regulator of lipoprotein metabolism at least by inhibiting lipoprotein lipase activity. Loss-of-function mutations in ANGPTL3 cause familial combined hypolipidemia through an unknown mechanism.

Approach and Results—

We compared lipolytic activities, lipoprotein composition, and other lipid-related enzyme/lipid transfer proteins in carriers of the S17X loss-of-function mutation in ANGPTL3 and in age- and sex-matched noncarrier controls. Gel filtration analysis revealed a severely disturbed lipoprotein profile and a reduction in size and triglyceride content of very low density lipoprotein in homozygotes as compared with heterozygotes and noncarriers. S17X homozygotes had significantly higher lipoprotein lipase activity and mass in postheparin plasma, whereas heterozygotes showed no difference in these parameters when compared with noncarriers. No changes in hepatic lipase, endothelial lipase, paraoxonase 1, phospholipid transfer protein, and cholesterol ester transfer protein activities were associated with the S17X mutation. Plasma free fatty acid, insulin, glucose, and homeostatic model assessment of insulin resistance were significantly lower in homozygous subjects compared with heterozygotes and noncarriers subjects.

Conclusions—

These results indicate that, although partial Angptl3 deficiency did not affect the activities of lipolytic enzymes, the complete absence of Angptl3 results in an increased lipoprotein lipase activity and mass and low circulating free fatty acid levels. This latter effect is probably because of decreased mobilization of free fatty acid from fat stores in human adipose tissue and may result in reduced hepatic very low density lipoprotein synthesis and secretion via attenuated hepatic free fatty acid supply. Altogether, Angptl3 may affect insulin sensitivity and play a role in modulating both lipid and glucose metabolism.

[Two uncommon extrapulmonary forms of Mycoplasma pneumoniae infection]

Mycoplasma pneumonia is the second most frequent bacterium in pneumonia and the leading intracellular type. M. pneumoniae pulmonary infection is characterized by a slower onset profile and a lower biological inflammatory picture than pneumococcal infection. Both upper and lower respiratory tracts are often affected and sometimes a Kawasaki-like syndrome can be associated, with conjunctivitis or cheilitis. Extrapulmonary forms of the disease can occur, whether or not it is associated with pulmonary infection. We report two cases: in the first case, a renal form of M. pneumoniae disease developed in a 6-year-old girl, with membranous proliferative glomerulonephritis expressed as a picture of impure nephritic syndrome with decreased serum complement concentration, following an upper respiratory infection. Diagnosis was obtained by means of a kidney biopsy. The second case occurred in an 8-year-old girl who expressed, after a respiratory tract infection, neurological symptoms such as ocular flutter, perception disorder, and ataxia. This onset is typical of post-infectious rhombencephalitis. Biological investigations and imaging were normal. In both cases, M. pneumoniae infection was diagnosed on the basis of immunoglobulin M-positive serology. Direct exploration of the bacterium was negative, due to its fragility and delayed diagnostic hypothesis. Several forms of M. pneumoniae infection are either the direct effect of the bacterium or are secondary to a cross-immunological reaction. As its frequency is increasing, M. pneumoniae infection should be raised as a cause of atypical, less well-known extrapulmonary forms of the disease.