Vitamin D pathway-related gene polymorphisms and their association with metabolic diseases: a literature review

Purpose: Given that the relationship between vitamin D status and metabolic diseases such as obesity and type 2 diabetes (T2D) remains unclear, this review will focus on the genetic associations, which are less prone to confounding, between vitamin D-related single nucleotide polymorphisms (SNPs) and metabolic diseases. Methods: A literature search of relevant articles was performed on PubMed up to December 2019. Those articles that had examined the association of vitamin D-related SNPs with obesity and/or T2D were included. Two reviewers independently evaluated the eligibility for the inclusion criteria and extracted the data. In total, 73 articles were included in this review. Results: There is a lack of research focussing on the association of vitamin D synthesis-related genes with obesity and T2D; however, the limited available research, although inconsistent, is suggestive of a protective effect on T2D risk. While there are several studies that investigated the vitamin D metabolism-related SNPs, the research focussing on vitamin D activation, catabolism and transport genes is limited. Studies on CYP27B1, CYP24A1 and GC genes demonstrated a lack of association with obesity and T2D in Europeans; however, significant associations with T2D were found in South Asians. VDR gene SNPs have been extensively researched; in particular, the focus has been mainly on BsmI (rs1544410), TaqI (rs731236), ApaI (rs7975232) and FokI (rs2228570) SNPs. Even though the association between VDR SNPs and metabolic diseases remain inconsistent, some positive associations showing potential effects on obesity and T2D in specific ethnic groups were identified. Conclusion: Overall, this literature review suggests that ethnic-specific genetic associations are involved. Further research utilizing large studies is necessary to better understand these ethnic-specific genetic associations between vitamin D deficiency and metabolic diseases

Age-related change in the retinoid X receptor beta gene expression in peripheral blood mononuclear cells of healthy volunteers : Effect of 13-cis retinoic acid supplementation

International audienceThe regulation of cell growth and differentiation and also expression of a number of genes by retinoids are mediated by nuclear retinoid receptors (RARs and/or RXRs). In this study we investigated age-related alteration in both RAR and RXR receptor subtypes gene expression and tissue transglutaminase (tTG) activity before and after supplementation with 13-cis retinoic acid (13cRA) in human peripheral blood mononuclear cells (PBMCs). Healthy men (40) were divided in two groups according to their age (young group: 26.1 +/- 4.1 years and old group: 65.4 +/- 3.8 years). Each volunteer received 13cRA (Curacne (R), 0.5 mg/(kg day)) during a period of 4 weeks. We have shown that RXR beta expression was decreased significantly (p = 0.0108) in PBMCs of elderly men when compared to that of young volunteers. Distribution of retinoic acid receptor subtype expression in PBMCs was found in the order: RXRP > RAR gamma > RXR alpha > RAR alpha. The tTG activity in PBMCs reflected a trend to be enhanced after 13-cis retinoic acid supplementation. In conclusion, we demonstrate a significant decrease in the expression of RXRP subtype of rexinoid receptors in PBMCs of healthy elderly men. Our data suggest that in healthy elderly men reduction of RXRP expression in PBMCs might be a common feature of physiological senescence

Joint Effects of Molecular Structure and Processing History on Specific Nucleation of Isotactic Polypropylene

Vztah mezi specifickou ?-nukleací, teplotní historií a molekulovou hmotností izotaktického polypropylenu (PP) byl pozorován širokoúhlou spektroskopií, diferenciální snímací kalorimetrií a skenovací elektronovou mikroskopií. Použitím vzorků se širokým rozmezím molekulových hmotností (Mw), od 240 000 do 1 300 000, bylo možné studovat vliv PP molekulové struktury na sensitivitu nukleace. N,N`-Dicyclohexylnaphthalene-2,6-dicarboxamide (NU 100) bylo použito jako ?-specifické nukleační činidlo a bylo přidáno v koncentraci 0; 0,01 a 0,03 hm. % do čistého PP. Následně byly vzorky lisovány při různých teplotách a časech. Vzorky obsahující 0,01 hm. % NU 100 vykazovaly dramatický pokles nukleační aktivity do ?-fáze se vzrůstající Mw, časem zpracování a teplotou. Tento efekt byl připsán částečné rozpustnosti činidla v PP tavenině a konkurenci mezi heterogenní ?-nukleací a sebe ?-nukleací.The interrelation between specific ?-nucleation, thermal history, and molecular weight of isotactic polypropylene (PP) has been investigated by wide-angle X-ray scattering, differential scanning calorimetry, and scanning electron microscopy. Samples with a broad range of molecular weight (Mw), from 240 000 to 1 300 000, allowed to examine the effect of PP molecular structure on the nucleation sensitivity. N,N`-Dicyclohexylnaphthalene-2,6-dicarboxamide (NU 100) was introduced in the concentrations of 0, 0.01, and 0.03 wt % as a ?-specific nucleating agent into neat PP. Specimens were then processed via compression molding at various processing temperatures and times. Samples containing 0.01 wt % of NU 100 showed a dramatic decrease of nucleation activity into ?-phase with increasing Mw, processing time, and temperature. This effect was ascribed to a partial solubility of nucleator in PP melt and a competition between heterogeneous ?-nucleation and self ?-nucleation