Robert H.J. Bandsma

Hepatobiliary cholesterol transport is not impaired in Abca1-null mice lacking HDL

The ABC transporter ABCA1 regulates HDL levels and is considered to control the first step of reverse cholesterol transport from the periphery to the liver. To test this concept, we studied the effect of ABCA1 deficiency on hepatic metabolism and hepatobiliary flux of cholesterol in mice. Hepatic lipid contents and biliary secretion rates were determined in Abca1(-/-), Abca1(+/-), and Abca1(+/+) mice with a DBA background that were fed either standard chow or a high-fat, high-cholesterol diet. Hepatic cholesterol and phospholipid contents in Abca1(-/-) mice were indistinguishable from those in Abca1(+/-) and Abca1(+/+) mice on both diets. In spite of the absence of HDL, biliary secretion rates of cholesterol, bile salts, and phospholipid were unimpaired in Abca1(-/-) mice. Neither the hepatic expression levels of genes controlling key steps in cholesterol metabolism nor the contribution of de novo synthesis to biliary cholesterol and bile salts were affected by Abca genotype. Finally, fecal excretion of neutral and acidic sterols was similar in all groups. We conclude that plasma HDL levels and ABCA1 activity do not control net cholesterol transport from the periphery via the liver into the bile, indicating that the importance of HDL in reverse cholesterol transport requires re-evaluation.

IL-10R polymorphisms are associated with very-early-onset ulcerative colitis

Background:Interleukin-10 (IL-10) signaling genes are attractive inflammatory bowel disease (IBD) candidate genes as IL-10 restricts intestinal inflammation, IL-10 polymorphisms have been associated with IBD in genome-wide association studies, and mutations in IL-10 and IL-10 receptor (IL-10R) genes have been reported in immunodeficient children with severe infantile-onset IBD. Our objective was to determine if IL-10R polymorphisms were associated with early-onset IBD (EO-IBD) and very-early-onset IBD (VEO-IBD). Methods:Candidate-gene analysis of IL10RA and IL10RB was performed after initial sequencing of an infantile onset-IBD patient identified a novel homozygous mutation. The discovery cohort included 188 EO-IBD subjects and 188 healthy subjects. Polymorphisms associated with IBD in the discovery cohort were genotyped in an independent validation cohort of 422 EO-IBD subjects and 480 healthy subjects. Results:We identified a homozygous, splice-site point mutation in IL10RA in an infantile-onset IBD patient causing a premature stop codon (P206X) and IL-10 insensitivity. IL10RA and IL10RB sequencing in the discovery cohort identified five IL10RA polymorphisms associated with ulcerative colitis (UC) and two IL10RB polymorphisms associated with Crohns disease (CD). Of these polymorphisms, two IL10RA single nucleotide polymorphisms, rs2228054 and rs2228055, were associated with VEO-UC in the discovery cohort and replicated in an independent validation cohort (odds ratio [OR] 3.08, combined P = 2 x 10−4; and OR 2.93, P = 6 x 10−4, respectively). Conclusions:We identified IL10RA polymorphisms that confer risk for developing VEO-UC. Additionally, we identified the first splice site mutation in IL10RA resulting in infantile-onset IBD. This study expands the phenotype of IL10RA polymorphisms to include both severe arthritis and VEO-UC.

Exenatide, a Glucagon-like Peptide-1 Receptor Agonist, Acutely Inhibits Intestinal Lipoprotein Production in Healthy Humans

Objectives—Incretin-based therapies for the treatment of type 2 diabetes mellitus improve plasma lipid profiles and postprandial lipemia, but their exact mechanism of action remains unclear. Here, we examined the acute effect of the glucagon-like peptide-1 receptor agonist, exenatide, on intestinal and hepatic triglyceride-rich lipoprotein production and clearance in healthy humans. Methods and Results—Fifteen normolipidemic, normoglycemic men underwent 2 studies each (SC 10 &mgr;g exenatide versus placebo), 4 to 6 weeks apart, in random order, in which triglyceride-rich lipoprotein particle kinetics were examined with a primed, constant infusion of deuterated leucine and analyzed by multicompartmental modeling under pancreatic clamp conditions. A fed state was maintained during each study by infusing a high-fat, mixed macronutrient, liquid formula at a constant rate directly into the duodenum via a nasoduodenal tube. Exenatide significantly suppressed the plasma concentration and production rate of triglyceride-rich lipoprotein-apolipoprotein B-48, but not of triglyceride-rich lipoprotein-apolipoprotein B-100. Conclusions—These results suggest a possible direct effect of exenatide on intestinal lipoprotein particle production, independent of changes in weight gain and satiety as seen in long-term studies and independent of changes in gastric emptying. This finding expands our understanding of the effects of exenatide in metabolic regulation beyond its primary therapeutic role in regulation of glucose homeostasis. Clinical Trial Registration—URL: http://www.clinicaltrials.gov, NCT01056549.

Increased de novo Lipogenesis and Delayed Conversion of Large VLDL into Intermediate Density Lipoprotein Particles Contribute to Hyperlipidemia in Glycogen Storage Disease Type 1a

Glycogen storage disease type 1a (GSD-1a) is a metabolic disorder characterized by fasting-induced hypoglycemia, hepatic steatosis, and hyperlipidemia. The mechanisms underlying the lipid abnormalities are largely unknown. To investigate these mechanisms seven GSD-1a patients and four healthy control subjects received an infusion of [1-13C]acetate to quantify cholesterogenesis and lipogenesis. In a subset of patients, [1-13C]valine was given to assess lipoprotein metabolism and [2-13C]glycerol to determine whole body lipolysis. Cholesterogenesis was 274 ± 112 mg/d in controls and 641 ± 201 mg/d in GSD-1a patients (p < 0.01). Plasma triglyceride-palmitate derived from de novo lipogenesis was 7.1 ± 9.4 and 86.3 ± 42.5 μmol/h in controls and patients, respectively (p < 0.01). Production of VLDL did not show a consistent difference between the groups, but conversion of VLDL into intermediate density lipoproteins was relatively retarded in all patients (0.6 ± 0.5 pools/d) compared with controls (4.3 ± 1.8 pools/d). Fractional catabolic rate of intermediate density lipoproteins was lower in patients (0.8 ± 0.6 pools/d) compared with controls (3.1 ± 1.5 pools/d). Whole body lipolysis was similar, i.e., 4.5 ± 1.9 μmol/kg/min in patients and 3.8 ± 1.9 μmol/kg/min in controls. Hyperlipidemia in GSD-1a is associated with strongly increased lipid production and a slower relative conversion of VLDL to LDL.

Bile Acids and Dysbiosis in Non-Alcoholic Fatty Liver Disease.

Background & Aims Non-alcoholic fatty liver disease (NAFLD) is characterized by dysbiosis. The bidirectional effects between intestinal microbiota (IM) and bile acids (BA) suggest that dysbiosis may be accompanied by an altered bile acid (BA) homeostasis, which in turn can contribute to the metabolic dysregulation seen in NAFLD. This study sought to examine BA homeostasis in patients with NAFLD and to relate that with IM data. Methods This was a prospective, cross-sectional study of adults with biopsy-confirmed NAFLD (non-alcoholic fatty liver: NAFL or non-alcoholic steatohepatitis: NASH) and healthy controls (HC). Clinical and laboratory data, stool samples and 7-day food records were collected. Fecal BA profiles, serum markers of BA synthesis 7-alpha-hydroxy-4-cholesten-3-one (C4) and intestinal BA signalling, as well as IM composition were assessed. Results 53 subjects were included: 25 HC, 12 NAFL and 16 NASH. Levels of total fecal BA, cholic acid (CA), chenodeoxycholic acid (CDCA) and BA synthesis were higher in patients with NASH compared to HC (p<0.05 for all comparisons). The primary to secondary BA ratio was higher in NASH compared to HC (p = 0.004), but ratio of conjugated to unconjugated BAs was not different between the groups. Bacteroidetes and Clostridium leptum counts were decreased in in a subset of 16 patients with NASH compared to 25 HC, after adjusting for body mass index and weight-adjusted calorie intake (p = 0.028 and p = 0.030, respectively). C. leptum was positively correlated with fecal unconjugated lithocholic acid (LCA) (r = 0.526, p = 0.003) and inversely with unconjugated CA (r = -0.669, p<0.0001) and unconjugated CDCA (r = - 0.630, p<0.0001). FGF19 levels were not different between the groups (p = 0.114). Conclusions In adults with NAFLD, dysbiosis is associated with altered BA homeostasis, which renders them at increased risk of hepatic injury.

C-reactive protein impairs hepatic insulin sensitivity and insulin signaling in rats: role of mitogen-activated protein kinases.

Plasma C‐reactive protein (CRP) concentration is increased in the metabolic syndrome, which consists of a cluster of cardiovascular disease risk factors, including insulin resistance. It is not known, however, whether CRP is merely a marker of accompanying inflammation or whether it contributes causally to insulin resistance. The objective of this study is to investigate the role that CRP may play in the development of insulin resistance. We examined the effect of single‐dose intravenous administration of purified human (h)CRP on insulin sensitivity in Sprague‐Dawley rats using the euglycemic, hyperinsulinemic clamp technique. hCRP was associated with impaired insulin suppression of endogenous glucose production with no reduction in peripheral tissue glucose uptake, suggesting that hCRP mediated insulin resistance in the liver but not extrahepatic tissues. We further assessed components of the insulin signaling pathway and mitogen‐activated protein kinases (MAPKs) in the liver. Liver tissues derived from hCRP‐treated rats showed reduced insulin‐stimulated insulin receptor substrate (IRS) tyrosine phosphorylation, IRS/phosphatidylinositol 3‐kinase (PI3K) association, and Akt phosphorylation, consistent with hCRP‐induced impairment of hepatic insulin signaling. Furthermore, hCRP enhanced phosphorylation of extracellular signal‐regulated kinase (ERK)1/2 and p38 MAPK as well as IRS‐1 Ser612. Finally, we observed in primary cultured rat hepatocytes that U0126 (a selective inhibitor of MAPK/ERK kinase1/2) corrected hCRP‐induced impairment of insulin signaling. Conclusions: hCRP plays an active role in inducing hepatic insulin resistance in the rat, at least in part by activating ERK1/2, with downstream impairment in the insulin signaling pathway. (HEPATOLOGY 2011)

Congenital portosystemic shunt: characterization of a multisystem disease.

Objectives: Congenital portosystemic shunts (CPSSs) are rare but increasingly recognized as a cause of important multisystem morbidity. We present new cases and a systematic literature review and propose an algorithm for the identification and care of affected patients. Methods: We reviewed the charts of consecutive patients seen in our pediatric liver clinic between 2003 and 2010 and systematically reviewed the literature of cases with CPSS. Results: We identified 316 published cases and 12 patients in our own clinic. Of the published cases (177 male), 185 had an extrahepatic and 131 an intrahepatic portosystemic shunt. Diagnosis was made at any age, from prenatal to late adulthood. Cardiac anomalies were found in 22% of patients. The main complications were hyperammonemia/neurological abnormalities (35%), liver tumors (26%), and pulmonary hypertension or hepatopulmonary syndrome (18%). The spectrum of neurological involvement ranged from changes in brain imaging, subtle abnormalities on neuropsychological testing, through learning disabilities to overt encephalopathy. Spontaneous shunt closure occurred mainly in infants with intrahepatic shunts. Therapeutic interventions included shunt closure by surgery or interventional radiology techniques (35%) and liver transplantation (10%) leading to an improvement of symptoms in the majority. These findings mirror the observations in our own patients. Conclusions: In this largest review of the reported clinical experience, we identify that children with CPSS may present with otherwise unexplained developmental delay, encephalopathy, pulmonary hypertension, hypoxemia, or liver tumors. When CPSS is diagnosed, children should be screened for all of these complications. Spontaneous closure of intrahepatic shunts may occur in infancy. Closure of the shunt is indicated in symptomatic patients and is associated with a favorable outcome.

Hepatic de novo synthesis of glucose 6-phosphate is not affected in peroxisome proliferator-activated receptor alpha-deficient mice but is preferentially directed toward hepatic glycogen stores after a short term fast

Apart from impaired β-oxidation, Pparα-deficient (Pparα–/–) mice suffer from hypoglycemia during prolonged fasting, suggesting alterations in hepatic glucose metabolism. We compared hepatic glucose metabolism in vivo in wild type (WT) and Pparα–/– mice after a short term fast, applying novel isotopic methods. After a 9-h fast, mice were infused with [U-13C]glucose, [2-13C]glycerol, [1-2H]galactose, and paracetamol for 6 h, and blood and urine was collected in timed intervals. Plasma glucose concentrations remained constant and were not different between the groups. Hepatic glycogen content was 69 ± 11 and 90 ± 31 μmol/g liver after 15 h of fasting in WT and Pparα–/– mice, respectively. The gluconeogenic flux toward glucose 6-phosphate was not different between the groups (i.e. 157 ± 9 and 153 ± 9 μmol/kg/min in WT and Pparα–/– mice, respectively). The gluconeogenic flux toward plasma glucose, however, was decreased in PPARα–/– mice (i.e. 142 ± 9 versus 124 ± 13 μmol/kg/min) (p < 0.05), accounting for the observed decrease (–15%) in hepatic glucose production in Pparα–/– mice. Expression of the gene encoding glucose-6-phosphate hydrolase (G6ph) was lower in the PPARα–/– mice compared with WT mice. In conclusion, Pparα–/– mice were able to maintain a normal total gluconeogenic flux to glucose 6-phosphate during moderate fasting, despite their inability to up-regulate β-oxidation. However, this gluconeogenic flux was directed more toward glycogen, leading to a decreased hepatic glucose output. This was associated with a down-regulation of the expression of G6ph in PPARα-deficient mice.

Chronic disease outcomes after severe acute malnutrition in Malawian children (ChroSAM): a cohort study

Summary Background Tackling severe acute malnutrition (SAM) is a global health priority. Heightened risk of non-communicable diseases (NCD) in children exposed to SAM at around 2 years of age is plausible in view of previously described consequences of other early nutritional insults. By applying developmental origins of health and disease (DOHaD) theory to this group, we aimed to explore the long-term effects of SAM. Methods We followed up 352 Malawian children (median age 9·3 years) who were still alive following SAM inpatient treatment between July 12, 2006, and March 7, 2007, (median age 24 months) and compared them with 217 sibling controls and 184 age-and-sex matched community controls. Our outcomes of interest were anthropometry, body composition, lung function, physical capacity (hand grip, step test, and physical activity), and blood markers of NCD risk. For comparisons of all outcomes, we used multivariable linear regression, adjusted for age, sex, HIV status, and socioeconomic status. We also adjusted for puberty in the body composition regression model. Findings Compared with controls, children who had survived SAM had lower height-for-age Z scores (adjusted difference vs community controls 0·4, 95% CI 0·6 to 0·2, p=0·001; adjusted difference vs sibling controls 0·2, 0·0 to 0·4, p=0·04), although they showed evidence of catch-up growth. These children also had shorter leg length (adjusted difference vs community controls 2·0 cm, 1·0 to 3·0, p<0·0001; adjusted difference vs sibling controls 1·4 cm, 0·5 to 2·3, p=0·002), smaller mid-upper arm circumference (adjusted difference vs community controls 5·6 mm, 1·9 to 9·4, p=0·001; adjusted difference vs sibling controls 5·7 mm, 2·3 to 9·1, p=0·02), calf circumference (adjusted difference vs community controls 0·49 cm, 0·1 to 0·9, p=0·01; adjusted difference vs sibling controls 0·62 cm, 0·2 to 1·0, p=0·001), and hip circumference (adjusted difference vs community controls 1·56 cm, 0·5 to 2·7, p=0·01; adjusted difference vs sibling controls 1·83 cm, 0·8 to 2·8, p<0·0001), and less lean mass (adjusted difference vs community controls −24·5, −43 to −5·5, p=0·01; adjusted difference vs sibling controls −11·5, −29 to −6, p=0·19) than did either sibling or community controls. Survivors of SAM had functional deficits consisting of weaker hand grip (adjusted difference vs community controls −1·7 kg, 95% CI −2·4 to −0·9, p<0·0001; adjusted difference vs sibling controls 1·01 kg, 0·3 to 1·7, p=0·005,)) and fewer minutes completed of an exercise test (sibling odds ratio [OR] 1·59, 95% CI 1·0 to 2·5, p=0·04; community OR 1·59, 95% CI 1·0 to 2·5, p=0·05). We did not detect significant differences between cases and controls in terms of lung function, lipid profile, glucose tolerance, glycated haemoglobin A1c, salivary cortisol, sitting height, and head circumference. Interpretation Our results suggest that SAM has long-term adverse effects. Survivors show patterns of so-called thrifty growth, which is associated with future cardiovascular and metabolic disease. The evidence of catch-up growth and largely preserved cardiometabolic and pulmonary functions suggest the potential for near-full rehabilitation. Future follow-up should try to establish the effects of puberty and later dietary or social transitions on these parameters, as well as explore how best to optimise recovery and quality of life for survivors. Funding The Wellcome Trust.

PEX2 is the E3 ubiquitin ligase required for pexophagy during starvation.

Sargent et al. identify the E3 ubiquitin ligase PEX2 as the causative agent of mammalian pexophagy. During amino acid starvation, PEX2 expression increases to ubiquitinate peroxisomal membrane proteins and signal peroxisome degradation by autophagy.