RESUMEN
Diabetes is a multifactorial disease, caused by a complex interplay between environmental and genetic risk factors. Genetic determinants of particularly Type 1 Diabetes (T1D) and Type 2 Diabetes (T2D) have been studied extensively, whereas well-powered studies of Latent Autoimmune Diabetes in Adults (LADA) are lacking. So far available studies support a clear genetic overlap between LADA and T1D, however, with smaller effect sizes of the T1D-risk variants in LADA as compared to T1D. A genetic overlap between LADA and T2D is less clear. However, recent studies, including large numbers of LADA patients, provide different lines of evidence to support a genetic overlap between T2D and LADA. The genetic predisposition to LADA is yet to be explored in a study design, like a genome- wide association study, which allows for analyses of the genetic predisposition independently of prior hypothesis about potential candidate genes. This type of study may facilitate the discovery of risk variants associated with LADA independently of T1D and T2D, and is central in order to determine if LADA should be considered as an independent diabetic subtype. Extended knowledge about the genetic predisposition to LADA may also facilitate stratification of the heterogeneous group of LADA patients, which may assist the choice of treatment. This mini-review summarizes current knowledge of the genetics of LADA, and discusses the perspectives for future studies.
Asunto(s)
Diabetes Autoinmune Latente del Adulto/genética , Adulto , Diabetes Mellitus Tipo 1/genética , Diabetes Mellitus Tipo 2/genética , Predisposición Genética a la Enfermedad , Estudio de Asociación del Genoma Completo , HumanosRESUMEN
In this mini-review, we give an overview of what is known about the genetic architecture of obesity and related metabolic traits with a primary focus on recent insights from studies of historically small and isolated populations. We start by briefly explaining what genetic architecture is and why studies of isolated populations in general are valuable if we want a complete picture of the genetic architecture of diseases and other traits among humans. Then we contrast what is known about the genetic architecture of obesity and related metabolic traits among large outbred populations, like Europeans, with results from recent studies of isolated populations. Finally, we briefly discuss the perspectives of studying isolated populations to gain insight into genetic architecture in humans.
Asunto(s)
Predisposición Genética a la Enfermedad , Obesidad/genética , Sitios de Carácter Cuantitativo/genética , Humanos , Obesidad/patología , FenotipoRESUMEN
Fatty acids (FAs) are involved in cellular processes important for normal body function, and perturbation of FA balance has been linked to metabolic disturbances, including type 2 diabetes. An individual's level of FAs is affected by diet, lifestyle, and genetic variation. We aimed to improve the understanding of the mechanisms and pathways involved in regulation of FA tissue levels, by identifying genetic loci associated with inter-individual differences in erythrocyte membrane FA levels. We assessed the levels of 22 FAs in the phospholipid fraction of erythrocyte membranes from 2,626 Greenlanders in relation to single nucleotide polymorphisms genotyped on the MetaboChip or imputed. We identified six independent association signals. Novel loci were identified on chromosomes 5 and 11 showing strongest association with oleic acid (rs76430747 in ACSL6, beta (SE): -0.386% (0.034), p = 1.8x10-28) and docosahexaenoic acid (rs6035106 in DTD1, 0.137% (0.025), p = 6.4x10-8), respectively. For a missense variant (rs80356779) in CPT1A, we identified a number of novel FA associations, the strongest with 11-eicosenoic acid (0.473% (0.035), p = 2.6x10-38), and for variants in FADS2 (rs174570), LPCAT3 (rs2110073), and CERS4 (rs11881630) we replicated known FA associations. Moreover, we observed metabolic implications of the ACSL6 (rs76430747) and CPT1A (rs80356779) variants, which both were associated with altered HbA1c (0.051% (0.013), p = 5.6x10-6 and -0.034% (0.016), p = 3.1x10-4, respectively). The latter variant was also associated with reduced insulin resistance (HOMA-IR, -0.193 (0.050), p = 3.8x10-6), as well as measures of smaller body size, including weight (-2.676 kg (0.523), p = 2.4x10-7), lean mass (-1.200 kg (0.271), p = 1.7x10-6), height (-0.966 cm (0.230), p = 2.0x10-5), and BMI (-0.638 kg/m2 (0.181), p = 2.8x10-4). In conclusion, we have identified novel genetic determinants of FA composition in phospholipids in erythrocyte membranes, and have shown examples of links between genetic variants associated with altered FA membrane levels and changes in metabolic traits.
Asunto(s)
Membrana Eritrocítica/genética , Ácidos Grasos/genética , Polimorfismo de Nucleótido Simple/genética , Tamaño Corporal/genética , Carnitina O-Palmitoiltransferasa/genética , Coenzima A Ligasas/genética , Diabetes Mellitus Tipo 2/genética , Ácidos Docosahexaenoicos/genética , Ácidos Grasos Monoinsaturados/metabolismo , Femenino , Sitios Genéticos/genética , Genotipo , Hemoglobina Glucada/genética , Groenlandia , Humanos , Insulina/genética , Resistencia a la Insulina/genética , Masculino , Ácido Oléico/genética , Fosfolípidos/genéticaRESUMEN
Type 2 diabetes (T2D) affects millions of people worldwide. Improving the understanding of the underlying mechanisms and ultimately improving the treatment strategies are, thus, of great interest. To achieve this, identification of genetic variation predisposing to T2D is important. A large number of variants have been identified in large outbred populations, mainly from Europe and Asia. However, to elucidate additional variation, isolated populations have a number of advantageous properties, including increased amounts of linkage disequilibrium, and increased probability for presence of high frequency disease-associated variants due to genetic drift. Collectively, this increases the statistical power to detect association signals in isolated populations compared to large outbred populations. In this review, we elaborate on why isolated populations are a powerful resource for the identification of complex disease variants and describe their contributions to the understanding of the genetics of T2D.
Asunto(s)
Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/epidemiología , Variación Genética , Estudio de Asociación del Genoma Completo , Humanos , Desequilibrio de Ligamiento , Factores de RiesgoRESUMEN
Since 2007, discovery of genetic variants associated with general obesity and fat distribution has advanced tremendously through genome-wide association studies (GWAS). Currently, the number of robustly associated loci is 190. Even though these loci explain <3 % of the variance, they have provided us a still emerging picture of genomic localization, frequency and effect size spectra, and hints of functional implications. The translation into biological knowledge has turned out to be an immense task. However, in silico enrichment analyses of genes involved in specific pathways or expressed in specific tissues have the power to suggest biological mechanisms underlying obesity. Inspired by this, we highlight genes in five loci potentially mechanistically linked to leptin-receptor trafficking and signaling in primary cilia. The clinical application of genetic knowledge as prediction, prevention, or treatment strategies is unfortunately still far from reality. Thus, despite major advances, further research is warranted to solve one of the greatest health problems in modern society.
