Molecular evolution and expression profile of the chemerine encoding gene RARRES2 in baboon and chimpanzee

BACKGROUND: Chemerin, encoded by the retinoic acid receptor responder 2 (RARRES2) gene is an adipocytesecreted protein with autocrine/paracrine functions in adipose tissue, metabolism and inflammation with a recently described function in vascular tone regulation, liver, steatosis, etc. This molecule is believed to represent a critical endocrine signal linking obesity to diabetes. There are no data available regarding evolution of RARRES2 in non-human primates and great apes. Expression profile and orthology in RARRES2 genes are unknown aspects in the biology of this multigene family in primates. Thus; we attempt to describe expression profile and phylogenetic relationship as complementary knowledge in the function of this gene in primates. To do that, we performed A RT-PCR from different tissues obtained during necropsies. Also we tested the hypotheses of positive evolution, purifying selection, and neutrality. And finally a phylogenetic analysis was made between primates RARRES2 protein. RESULTS: RARRES2 transcripts were present in liver, lung, adipose tissue, ovary, pancreas, heart, hypothalamus and pituitary tissues. Expression in kidney and leukocytes were not detectable in either species. It was determined that the studied genes are orthologous. CONCLUSIONS: RARRES2 evolution fits the hypothesis of purifying selection. Expression profiles of the RARRES2 gene are similar in baboons and chimpanzees and are also phylogenetically related.

Genética de la obesidad / Genetics of obesity

La obesidad es la acumulación excesiva de tejido adiposo, consecuencia del desequilibrio energético. Los cambios en la disponibilidad y características de los alimentos y en la actividad física en las últimas décadas han dado lugar a que la ingestión de energía exceda al gasto. Esta tendencia se observa en todos los grupos de edad y en numerosos países. La respuesta a estos cambios ambientales que afectan a la dieta y actividad física es variada, y ciertos individuos y poblaciones parecen tener mayor predisposición al desarrollo de la obesidad y de sus comorbilidades. En la obesidad, en etapas tempranas de la vida, es importante diferenciar la obesidad ocasionada por anormalidades genéticas de aquellas formas comunes. Numerosas alteraciones genéticas se caracterizan por la obesidad. En algunos casos mutaciones en un solo gen, pueden tener un efecto importante sobre el índice de masa corporal (IMC). Este manuscrito presenta los aspectos genéticos de formas poco frecuentes y comunes de obesidad, con especial interés en la población infantil. También presenta diferentes abordajes metodológicos empleados en investigaciones sobre la genética de la obesidad y la variación en el IMC, incluyendo estudios de asociación de genes candidatos, barrido del genoma, asociación del genoma y estudios de perfil transcripcional. Actualmente, la obesidad se considera una enfermedad compleja con bagaje poligénico. Algunos alelos han sido asociados a la obesidad común y el IMC; sin embargo, los efectos observados son modestos y se requieren replicaciones en diferentes poblaciones para confirmar el efecto de estas variantes y establecer los mecanismos que explican su contribución a la obesidad.

Obesity is the excessive deposition of adipose tissue resulting of energy imbalance. The changes in food availability and characteristics, as well as the decrease in physical activity during the last decades have favored the energy imbalance causing that energy intake exceeds energy expenditure. This trend has been observed in all age groups across different countries. The response to environmental changes affecting diet and physical activity is widely diverse and certain subjects and populations seem to be more prone to develop obesity and its related comorbidities. In early onset obesity it is important to differentiate between obesity due to rare genetic abnormalities from the common forms. Numerous genetic abnormalities are characterized by obesity. In some cases, single gene mutations can have a very important effect on body mass index (BMI). The present manuscript addresses the rare and common forms of obesity with special regard to observations in children. It also discusses different methodological approaches currently used for the study of genetic factors influencing common obesity or variation in BMI, including the candidate gene approach, genome scan, genome-wide association studies and gene expression studies. Nowadays obesity is considered a complex disease with a polygenic background. Some gene variants have been associated with common obesity and variation in BMI. However, the effects observed seem to be minor and replications in different populations are required to confirm the effect of the identified alleles and to establish the mechanisms that explain their contribution to obesity.