Leentje Cosemans

No evidence for a role of rare CYP27B1 functional variations in multiple sclerosis

Association studies have implicated common variants in the 12q14.1 region containing CYP27B1 in multiple sclerosis (MS). Rare CYP27B1 mutations cause autosomal recessive vitamin D–dependent rickets type 1, and it has recently been reported that heterozygous CYP27B1 mutations are associated with increased MS susceptibility and lower active vitamin D levels. By sequencing CYP27B1 in 134 multiplex families and genotyping the most common variant R389H in 2,608 MS patients and 1,987 controls from Italy and Belgium (a total of 4,729 individuals), we were unable to replicate these observations. These results provide evidence against a major role for CYP27B1 mutations in MS. ANN NEUROL 2013;73:433–437

Effect of tissue inhibitor of matrix metalloproteinases-1 on in vitro and in vivo adipocyte differentiation

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) play a role in development of obesity by contributing to adipogenesis, angiogenesis and extracellular matrix degradation. We have evaluated a potential functional role of TIMP-1, which inhibits most MMPs, in early stages of in vitro and in vivo adipogenesis. Overexpression of human TIMP-1 (hTIMP-1) in 3T3-F442A preadipocytes resulted in a somewhat slower differentiation into mature adipocytes, without affecting the total extent of differentiation. Local overexpression by injection of 3T3-F442A preadipocytes expressing hTIMP-1 in the back of NUDE mice kept on high fat diet (HFD) for 4 weeks, had no effect on de novo formed fat pad mass. The fat pads formed from the hTIMP-1 expressing cells did show a significantly larger blood vessel size as compared to control cells (57 + or - 4.8 microm(2) vs 38 + or - 1.4 microm(2), p=0.0017). No effect was observed on blood vessel density or on adipocyte size or density. Thus, local hTIMP-1 overexpression did not significantly affect early stages of adipogenesis as evaluated from the extent of in vitro adipocyte differentiation or of in vivo de novo adipose tissue formation.

TNFRSF1A coding variants in multiple sclerosis

Patients with the autoinflammatory disease Tumour Necrosis Factor receptor-associated periodic syndrome (TRAPS) who suffer from demyelinating disease have been described, and one of the milder TRAPS mutations (R92Q in the TNFRSF1A gene) has been suggested as a risk factor for multiple sclerosis (MS). In a study population of 967 MS patients and 1022 controls, we replicate association [P=5×10⁻⁴, 3% in patients versus 1% in controls, OR=2.26 (95% CI 1.41-3.61)], which appears independent of an established common risk variant in the same gene. No other non-synonymous variants in the same allele frequency range influencing risk of MS were observed.

Effect of plasminogen activator inhibitor-1 on adipogenesis in vivo

To study the functional role of plasminogen activator inhibitor-1 (PAI-1) in obesity, the effect of its overexpression on de novo adipogenesis was evaluated in murine models in vivo. Therefore, 3T3-F442A preadipocytes expressing murine PAI-1 (mPAI-1) or control cells were injected in the back of male NUDE mice, which were fed a high-fat diet (HFD) for four weeks. De novo fat pads that formed from the PAI-1 expressing cells were larger (21 +/- 2.4 mg vs. 14 +/- 1.4 mg; p = 0.017) and showed a higher adipocyte density (373 +/- 28 mm(-2) vs. 301 +/- 12 mm(-2); p = 0.03) as compared to those formed from control cells. In a second model, male NUDE mice were injected in the tail vein with an adenoviral construct expressing mPAI-1 or with the empty vector, and three days later with 3T3-F442A cells. After four weeks of HFD, total body weight and de novo fat pad weight were comparable for both groups. Mild adipocyte hypotrophy was observed in the de novo fat pads of the PAI-1 overexpressing mice (1180 +/- 33 microm(2) vs. 1285 +/- 32 microm(2); p = 0.024), whereas the blood vessel size was significantly smaller than in controls (30 +/- 1.8 microm(2) vs. 63 +/- 3.6 microm(2); p < 0.0001). Thus, the effect of local or systemic PAI-1 (over)expression on adipocyte or blood vessel size and density of de novo formed fat pads appears to be different, and concentration-dependent. Whereas local expression resulted in larger fat pads, systemic overexpression had no effect on de novo adipogenesis, although angiogenesis appeared to be impaired.

Blood vessel density in de novo formed adipose tissue is decreased upon overexpression of TIMP-1.

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) play a role in the development of obesity by contributing to adipogenesis, angiogenesis, and extracellular matrix degradation. We have evaluated a potential functional role of TIMP‐1, which inhibits most MMPs, in in vivo adipogenesis. Therefore, human (h) TIMP‐1 was overexpressed by injection in the tail vein of NUDE mice of an adenoviral vector 3 days before injection of 3T3‐F442A preadipocytes in the back. After 4 weeks of high‐fat diet, the de novo formed fat was analyzed. Overexpression of hTIMP‐1 had no effect on de novo formed fat pad mass. However, the blood vessel density of the fat pads from mice overexpressing hTIMP‐1 was significantly lower than in controls (587 ± 11 mm−2 vs. 806 ± 20 mm−2, P < 0.0001) whereas the adipocytes were somewhat larger (1,477 ± 44 µm2 vs. 1,285 ± 32 µm2, P = 0.03). Thus, in vivo hTIMP‐1 overexpression did not significantly affect the extent of de novo adipose tissue formation, but was associated with significantly lower blood vessel density.

Rare MEFV variants are not associated with risk to develop multiple sclerosis and severity of disease

Background: Recent studies suggest an association between rare variants in Mediterranean fever (MEFV), the gene underlying the auto-inflammatory disorder Familial Mediterranean Fever (FMF), the risk to develop multiple sclerosis (MS) and severity of MS. Objective: The objective of this study is to investigate these findings in a Belgian MS population and to test for association with additional clinical parameters such as treatment response. Methods: MEFV was sequenced in a cohort of MS patients (N=94) suffering from auto-inflammatory symptoms, systemic side-effects upon interferon-beta (IFN-β) treatment, or patients in whom glatiramer acetate was started as first choice due to severe fatigue. Five rare non-synonymous variants were detected in this cohort and subsequently genotyped in 915 MS patients and 763 healthy controls. Results: We observed no association between these alleles and susceptibility to MS (p-value=0.99) or disease severity (p-value=0.78). However, we did observe a correlation between carrying an MEFV variant and the development of systemic side-effects upon IFN-β treatment (p-value=0.022). Conclusion: In contrast to recent smaller studies, we did not find an association between carrying a rare variant in the MEFV gene and the risk to develop MS or disease severity. However, carrying rare variants in MEFV was associated with the development of severe systemic side-effects upon IFN-β treatment.