Surgery-Induced Weight Loss Is Associated With the Downregulation of Genes Targeted by MicroRNAs in Adipose Tissue.

CONTEXT: Molecular mechanisms associated with physiological variations in adipose tissue (AT) are not fully recognized. The most recent reports highlight the critical relevance of microRNAs (miRNAs) found in AT. OBJECTIVE: To identify changes in messenger RNA (mRNA) and miRNA expressions and their interaction in human AT before and after surgery-induced weight loss. Research Design and Setting: Genome-wide mRNA and miRNA expressions were assessed by microarrays in abdominal subcutaneous AT of 16 morbidly obese women before and 2 years after laparoscopic Roux-en-Y gastric bypass. The association of changes in miRNAs with their respective mRNA targets was studied. The results were replicated in publicly available microarray datasets. Validation was made by real-time polymerase chain reaction in additional fat samples from 26 age-matched lean women and in isolated human adipocytes. RESULTS: A total of 5018 different mRNA probe sets and 15 miRNAs were differentially expressed after surgery-induced weight loss. The clustering of similar expression patterns for gene products with related functions revealed molecular footprints that elucidate significant changes in cell cycle, development, lipid metabolism, and the inflammatory response. The participation of inflammation was demonstrated by results assessed in isolated adipocytes. Interestingly, when transcriptomes were analyzed taking into account the presence of miRNA target sites, miRNA target mRNAs were upregulated in obese AT (P value = 2 × 10(-181)) and inflamed adipocytes (P value = 4 × 10(-61)), according to the number of target sites harbored by each transcript. CONCLUSIONS: Current findings suggest impaired miRNA target gene expression in obese AT in close association with inflammation, both improving after weight loss.

Breast cancer 1 (BrCa1) may be behind decreased lipogenesis in adipose tissue from obese subjects.

CONTEXT: Expression and activity of the main lipogenic enzymes is paradoxically decreased in obesity, but the mechanisms behind these findings are poorly known. Breast Cancer 1 (BrCa1) interacts with acetyl-CoA carboxylase (ACC) reducing the rate of fatty acid biosynthesis. In this study, we aimed to evaluate BrCa1 in human adipose tissue according to obesity and insulin resistance, and in vitro cultured adipocytes. RESEARCH DESIGN AND METHODS: BrCa1 gene expression, total and phosphorylated (P-) BrCa1, and ACC were analyzed in adipose tissue samples obtained from a total sample of 133 subjects. BrCa1 expression was also evaluated during in vitro differentiation of human adipocytes and 3T3-L1 cells. RESULTS: BrCa1 gene expression was significantly up-regulated in both omental (OM; 1.36-fold, p = 0.002) and subcutaneous (SC; 1.49-fold, p = 0.001) adipose tissue from obese subjects. In parallel with increased BrCa1 mRNA, P-ACC was also up-regulated in SC (p = 0.007) as well as in OM (p = 0.010) fat from obese subjects. Consistent with its role limiting fatty acid biosynthesis, both BrCa1 mRNA (3.5-fold, p<0.0001) and protein (1.2-fold, p = 0.001) were increased in pre-adipocytes, and decreased during in vitro adipogenesis, while P-ACC decreased during differentiation of human adipocytes (p = 0.005) allowing lipid biosynthesis. Interestingly, BrCa1 gene expression in mature adipocytes was restored by inflammatory stimuli (macrophage conditioned medium), whereas lipogenic genes significantly decreased. CONCLUSIONS: The specular findings of BrCa1 and lipogenic enzymes in adipose tissue and adipocytes reported here suggest that BrCa1 might help to control fatty acid biosynthesis in adipocytes and adipose tissue from obese subjects.

Modulation of human monocyte CD36 by type 2 diabetes mellitus and other atherosclerotic risk factors.

BACKGROUND: The pathophysiological role of CD36 in atherosclerosis seems to be largely dependent on its pro-inflammatory function and ability to take up oxidized low-density lipoprotein. Controversy exists concerning the potential beneficial/harmful effects of vascular CD36 inhibition in atherosclerosis. However, as atherosclerosis in murine models does not result in clinical end points such as plaque rupture and thrombotic ischaemia, typical of human disease, clinical studies are required to understand the functional role of CD36 in human atherosclerosis. MATERIALS AND METHODS: Our aim was to investigate whether CD36 expression in monocytes is modulated by the presence of an increasing number of atherosclerotic risk factors, and specifically by hyperglycaemia because of diabetes mellitus. The study included 33 patients with advanced atherosclerosis and eight healthy blood donors, as controls. The patients were classified according to the presence of atherosclerotic risk factors. Diabetes mellitus was classified as either well-controlled or poorly controlled. Monocytes were exposed in vitro to low (5·5mM) or high glucose (26mM) concentrations for increasing times. RESULTS: Our results demonstrated that protein levels of glycated CD36 were significantly higher in patients with 3-4 atherosclerotic risk factors than in those with 0-2 atherosclerotic risk factors or in subjects with no atherosclerotic symptoms (P=0·04, in both cases). However, when we analysed just the poorly controlled diabetic patients, their glycated CD36 levels were lower. These data were corroborated by in vitro studies demonstrating that increasing glucose concentrations reduced glycated protein levels (P<0·05). CONCLUSIONS: Our results demonstrate that CD36 expression is altered by hyperglycaemia in atherosclerotic patients.

The gene expression of the main lipogenic enzymes is downregulated in visceral adipose tissue of obese subjects.

Contradictory findings regarding the gene expression of the main lipogenic enzymes in human adipose tissue depots have been reported. In this cross-sectional study, we aimed to evaluate the mRNA expression of fatty acid synthase (FAS) and acetyl-CoA carboxilase (ACC) in omental and subcutaneous (SC) fat depots from subjects who varied widely in terms of body fat mass. FAS and ACC gene expression were evaluated by real time-PCR in 188 samples of visceral adipose tissue which were obtained during elective surgical procedures in 119 women and 69 men. Decreased sex-adjusted FAS (-59%) and ACC (-49%) mRNA were found in visceral adipose tissue from obese subjects, with and without diabetes mellitus type 2 (DM-2), compared with lean subjects (both P < 0.0001). FAS mRNA was also decreased (-40%) in fat depots from overweight subjects (P < 0.05). Indeed, FAS mRNA was significantly and positively associated with ACC gene expression (r = 0.316, P < 0.0001) and negatively with BMI (r = -0.274), waist circumference (r = -0.437), systolic blood pressure (r = -0.310), serum glucose (r = -0.277), and fasting triglycerides (r = -0.226), among others (all P < 0.0001). Similar associations were observed for ACC gene expression levels. In a representative subgroup of nonobese (n = 4) and obese women (n = 6), relative FAS gene expression levels significantly correlated (r = 0.657, P = 0.034; n = 10) with FAS protein values. FAS protein levels were also inversely correlated with blood glucose (r = -0.640, P = 0.046) and fasting triglycerides (r = -0.832, P = 0.010). In conclusion, the gene expression of the main lipogenic enzymes is downregulated in visceral adipose tissue from obese subjects.