| 1. |
- Pekkinen, M., et al.
(författare)
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Osteoporosis and skeletal dysplasia caused by pathogenic variants in SGMS2
- 2019
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Ingår i: Jci Insight. - : American Society for Clinical Investigation. - 2379-3708. ; 4:7
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Tidskriftsartikel (refereegranskat)abstract
- Mechanisms leading to osteoporosis are incompletely understood. Genetic disorders with skeletal fragility provide insight into metabolic pathways contributing to bone strength. We evaluated 6 families with rare skeletal phenotypes and osteoporosis by next-generation sequencing. In all the families, we identified a heterozygous variant in SGMS2, a gene prominently expressed in cortical bone and encoding the plasma membrane-resident sphingomyelin synthase SMS2. Four unrelated families shared the same nonsense variant, c.148C>T (p.Arg50*), whereas the other families had a missense variant, c.185T>G (p.IIe62Ser) or c.191T>G (p.Met64Arg). Subjects with p.Arg50* presented with childhood-onset osteoporosis with or without cranial sclerosis. Patients with p.IIe62Ser or p.Met64Arg had a more severe presentation, with neonatal fractures, severe short stature, and spondylometaphyseal dysplasial Several subjects had experienced peripheral facial nerve palsy or other neurological manifestations. Bone biopsies showed markedly altered bone material characteristics, including defective bone mineralization. Osteoclast formation and function in vitro was normal. While the p.Arg50* mutation yielded a catalytically inactive enzyme, p.IIe62Ser and p.Met64Arg each enhanced the rate of de novo sphingomyelin production by blocking export of a functional enzyme from the endoplasmic reticulum. SGMS2 pathogenic variants underlie a spectrum of skeletal conditions, ranging from isolated osteoporosis to complex skeletal dysplasia, suggesting a critical role for plasma membrane-bound sphingomyelin metabolism in skeletal homeostasis.
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| 2. |
- Sevastianova, K., et al.
(författare)
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Effect of short-term carbohydrate overfeeding and long-term weight loss on liver fat in overweight humans
- 2012
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Ingår i: American Journal of Clinical Nutrition. - : Elsevier BV. - 0002-9165. ; 96:4, s. 727-734
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Tidskriftsartikel (refereegranskat)abstract
- Background: Cross-sectional studies have identified a high intake of simple sugars as an important dietary factor predicting nonalcoholic fatty liver disease (NAFLD). Objective: We examined whether overfeeding overweight subjects with simple sugars increases liver fat and de novo lipogenesis (DNL) and whether this is reversible by weight loss. Design: Sixteen subjects [BMI (kg/m(2)): 30.6 +/- 1.2] were placed on a hypercaloric diet (>1000 kcal simple carbohydrates/d) for 3 wk and, thereafter, on a hypocaloric diet for 6 mo. The subjects were genotyped for rs739409 in the PNPLA3 gene. Before and after overfeeding and after hypocaloric diet, metabolic variables and liver fat (measured by proton magnetic resonance spectroscopy) were measured. The ratio of palmitate (16:0) to linoleate (18:2n-6) in serum and VLDL triglycerides was used as an index of DNL. Results: Carbohydrate overfeeding increased weight (+/- SEM) by 2% (1.8 +/- 0.3 kg; P < 0.0001) and liver fat by 27% from 9.2 +/- 1.9% to 11.7 +/- 1.9% (P = 0.005). DNL increased in proportion to the increase in liver fat and serum triglycerides in subjects with PNPLA3-148II but not PNPLA3-148MM. During the hypocaloric diet, the subjects lost 4% of their weight (3.2 +/- 0.6 kg; P < 0.0001) and 25% of their liver fat content (from 11.7 +/- 1.9% to 8.8 +/- 1.8%; P < 0.05). Conclusions: Carbohydrate overfeeding for 3 wk induced a >10-fold greater relative change in liver fat (27%) than in body weight (2%). The increase in liver fat was proportional to that in DNL. Weight loss restores liver fat to normal. These data indicate that the human fatty liver avidly accumulates fat during carbohydrate overfeeding and support a role for DNL in the pathogenesis of NAFLD. This trial was registered at www.hus.fi as 235780. Am J Clin Nutr 2012;96:727-34.
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| 3. |
- Do, Hai Thi, et al.
(författare)
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Fibroblast Growth Factor-21 (FGF21) Regulates Low-density Lipoprotein Receptor (LDLR) Levels in Cells via the E3-ubiquitin Ligase Mylip/Idol and the Canopy2 (Cnpy2)/Mylip-interacting Saposin-like Protein (Msap)
- 2012
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Ingår i: Journal of Biological Chemistry. - : AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC. - 0021-9258 .- 1083-351X. ; 287:16, s. 12602-12611
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Tidskriftsartikel (refereegranskat)abstract
- The LDLR is a critical factor in the regulation of blood cholesterol levels that are altered in different human diseases. The level of LDLR in the cell is regulated by both transcriptional and post-transcriptional events. The E3 ubiquitin ligase, myosin regulatory light chain-interacting protein (Mylip)/inducible degrader of the LDL-R (Idol) was shown to induce degradation of LDLR via protein ubiquitination. We have here studied novel factors and mechanisms that may regulate Mylip/Idol in human hepatocyte cells and in mouse macrophages. We observed that FGF21 that is present in serum in different conditions reduced Mylip/Idol at the RNA and protein level, and increased LDLR levels and stability in the cells. FGF21 also enhanced expression of Canopy2 (Cnpy2)/MIR-interacting Saposin-like protein (Msap) that is known to interact with Mylip/Idol. Overexpression of Cnpy2/Msap increased LDLRs, and knockdown experiments showed that Cnpy2/Msap is crucial for the FGF21 effect on LDLRs. Experiments using DiI-labeled LDL particles showed that FGF21 increased lipoprotein uptake and the effect of FGF21 was additive to that of statins. Our results are consistent with an important role of FGF21 and Cnpy2/Msap in the regulation of LDLRs in cultured cells, which warrants further studies using human samples.
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| 4. |
- Kouri, V. P., et al.
(författare)
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Neutrophils produce interleukin-17B in rheumatoid synovial tissue
- 2014
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Ingår i: Rheumatology. - : Oxford University Press (OUP). - 1462-0324 .- 1462-0332. ; 53:1, s. 39-47
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Tidskriftsartikel (refereegranskat)abstract
- Objective: T helper 17 (Th17) and mast cells produce IL-17A in RA and critically contribute to the pathogenesis of RA. However, the complete IL-17 cytokine profile in RA is unknown. The aim of the study was to systematically study the expression of IL-17 family cytokines in RA. Methods: The expression of all IL-17 cytokines in RA synovium and pannus as well as in the synovium of OA was determined using quantitative RT-PCR (qRT-PCR). IL-17A and IL-17B were immunostained. Peripheral blood neutrophils were analysed for IL-17B. The effect of IL-17B alone or in combination with TNF-α was tested in vitro on fibroblasts and endothelial cells. Results: In all tissues IL-17B was the most expressed IL-17 family cytokine, found in lining but most strongly expressed in human neutrophil elastase containing polymorphonuclear cells. This pattern was distinct from that of IL-17A, which was found in mast cell tryptase immunoreactive cells. Circulating neutrophils contained IL-17B, verifying the in vivo results. Fibroblasts up-regulated the expression of IL-17RB, a putative receptor of IL-17B, after TNF-α stimulation. IL-17B significantly enhanced TNF-α-induced production of G-CSF and IL-6 in fibroblasts. Conclusion: IL-17B, which is present in synovium, may contribute to the pathogenesis of RA. IL-17B can enhance the effects of TNF-α on the production of cytokines and chemokines that control immune cell trafficking and neutrophil homeostasis in the inflamed tissues. © The Author 2013. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved.
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| 5. |
- Lallukka, S., et al.
(författare)
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Adipose tissue is inflamed in NAFLD due to obesity but not in NAFLD due to genetic variation in PNPLA3
- 2013
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Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 1432-0428 .- 0012-186X. ; 56:4, s. 886-892
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Tidskriftsartikel (refereegranskat)abstract
- The rs738409 C > G single-nucleotide polymorphism in PNPLA3 leads to a missense mutation (I148M) which increases liver fat but does not cause insulin resistance. We hypothesised that patients with non-alcoholic fatty liver disease (NAFLD) due to the PNPLA3 variant ('PNPLA3 NAFLD'aEuro parts per thousand= PNPLA3-148MM) do not have adipose tissue (AT) inflammation in contrast with those with NAFLD due to obesity ('obese NAFLD'). Biopsy specimens of AT were taken, and PNPLA3 genotype and liver fat (H-1-magnetic resonance spectroscopy) were determined in 82 volunteers, who were divided into groups based on either median BMI (obese 36.2 +/- 0.7 kg/m(2); non-obese 26.0 +/- 0.4 kg/m(2)) or PNPLA3 genotype. All groups were similar with respect to age and sex. The PNPLA3 subgroups were equally obese (PNPLA3-148MM, 31.1 +/- 1.3 kg/m(2); PNPLA3-148II, 31.2 +/- 0.8 kg/m(2)), while the obese and non-obese subgroups had similar PNPLA3 genotype distribution. Gene expression of proinflammatory (MCP-1, CD68) and anti-inflammatory (Twist1, ADIPOQ) markers was measured using quantitative real-time RT-PCR. Liver fat was similarly increased in obese NAFLD (9.5 +/- 1.3% vs 5.1 +/- 0.9%, obese vs non-obese, p = 0.007) and PNPLA3 NAFLD (11.4 +/- 1.7% vs 5.3 +/- 0.8%, PNPLA3-148MM vs PNPLA3-148II, p < 0.001). Fasting serum insulin was higher in the obese than the non-obese group (76 +/- 6 vs 47 +/- 6 pmol/l, p < 0.001), but similar in PNPLA3-148MM and PNPLA3-148II (60 +/- 8 vs 62 +/- 5 pmol/l, NS). In obese vs non-obese, MCP-1 and CD68 mRNAs were upregulated, whereas those of Twist1 and ADIPOQ were significantly downregulated. AT gene expression of MCP-1, CD68, Twist1 and ADIPOQ was similar in PNPLA3-148MM and PNPLA3-148II groups. PNPLA3 NAFLD is characterised by an increase in liver fat but no insulin resistance or AT inflammation, while obese NAFLD has all three of these features.
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