Molecular analysis of three known and one novel LPL variants in patients with type I hyperlipoproteinemia.

BACKGROUND AND AIMS: Type I hyperlipoproteinemia, also known as familial chylomicronemia syndrome (FCS), is a rare autosomal recessive disorder caused by variants in LPL, APOC2, APOA5, LMF1 or GPIHBP1 genes. The aim of this study was to identify novel variants in the LPL gene causing lipoprotein lipase deficiency and to understand the molecular mechanisms. METHODS AND RESULTS: A total of 3 individuals with severe hypertriglyceridemia and recurrent pancreatitis were selected from the Lipid Clinic at Sahlgrenska University Hospital and LPL was sequenced. In vitro experiments were performed in human embryonic kidney 293T/17 (HEK293T/17) cells transiently transfected with wild type or mutant LPL plasmids. Cell lysates and media were used to analyze LPL synthesis and secretion. Media were used to measure LPL activity. Patient 1 was compound heterozygous for three known variants: c.337T > C (W113R), c.644G > A (G215E) and c.1211T > G (M404R); patient 2 was heterozygous for the known variant c.658A > C (S220R) while patient 3 was homozygous for a novel variant in the exon 5 c.679G > T (V227F). All the LPL variants identified were loss-of-function variants and resulted in a substantial reduction in the secretion of LPL protein. CONCLUSION: We characterized at the molecular level three known and one novel LPL variants causing type I hyperlipoproteinemia showing that all these variants are pathogenic.

Genetic diagnosis of familial hypercholesterolaemia by targeted next-generation sequencing.

OBJECTIVES: The aim of this study was to combine clinical criteria and next-generation sequencing (pyrosequencing) to establish a diagnosis of familial hypercholesterolaemia (FH). DESIGN, SETTING AND SUBJECTS: A total of 77 subjects with a Dutch Lipid Clinic Network score of ≥ 3 (possible, probable or definite FH clinical diagnosis) were recruited from the Lipid Clinic at Sahlgrenska Hospital, Gothenburg, Sweden. Next-generation sequencing was performed in all subjects using SEQPRO LIPO RS, a kit that detects mutations in the low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), proprotein convertase subtilisin/kexin type 9 (PCSK9) and LDLR adapter protein 1 (LDLRAP1) genes; copy-number variations in the LDLR gene were also examined. RESULTS: A total of 26 mutations were detected in 50 subjects (65% success rate). Amongst these, 23 mutations were in the LDLR gene, two in the APOB gene and one in the PCSK9 gene. Four mutations with unknown pathogenicity were detected in LDLR. Of these, three mutations (Gly505Asp, Ile585Thr and Gln660Arg) have been previously reported in subjects with FH, but their pathogenicity has not been proved. The fourth, a mutation in LDLR affecting a splicing site (exon 6-intron 6) has not previously been reported; it was found to segregate with high cholesterol levels in the family of the proband. CONCLUSIONS: Using a combination of clinical criteria and targeted next-generation sequencing, we have achieved FH diagnosis with a high success rate. Furthermore, we identified a new splicing-site mutation in the LDLR gene.

Bone disorders in patients with chronic liver disease awaiting liver transplantation.

BACKGROUND: An important complication of chronic liver disease is osteodystrophy, which includes osteoporosis and the much rarer osteomalacia. Both conditions are associated with significant morbidity through fractures resulting in pain, deformity, and immobility. Liver transplantation may further deteriorate bone metabolism. The aim of the present study was to investigate the frequency and severity of hepatic osteodystrophy among patients with liver cirrhosis who were referred for liver transplantation. We also evaluated modifications in bone metabolism after liver transplantation. MATERIALS AND METHODS: We recruited 35 consecutive patients with chronic liver disease who were undergoing assessment for transplantation over a 1-year period. Bone mass in the total skeleton and proximal hip was evaluated using a dual-energy X-ray absorptiometry device (Lunar Prodigy Advance, GE Healthcare, USA). According to World Health Organization recommendations, osteoporosis was defined as a T score < -2.5 and osteopenia as T score between -1 and -2.5. RESULTS: We enrolled in the study 35 patients, including 8 females and 27 males of overall mean age of 57 +/- 7, who showed a viral etiology (57%) or alcohol etiology (28%), Child-Pugh 8.7 +/- 2.3. The overall prevalence of osteodystrophy was 40% (26% osteopenia and 14% osteoporosis). No difference was evident according to gender, severity of liver disease (Child-Pugh, Model for End-stage Liver Disease), or origin of liver disease. A subgroup of 10 transplanted patients reached 3-month follow-up, showing total body T score with a significant decrease after 3 months while femoral T scores tended to decrease insignificantly. CONCLUSIONS: This study revealed a high prevalence of low bone mineral density among cirrhotic patients before liver transplantation. We suggest that both bone mineral density and biochemical examinations should be considered to be routine tests to identify the status of bone mass and bone metabolism among recipients prior to liver transplantation.