Adipose tissue mitochondrial dysfunction in human obesity is linked to a specific DNA methylation signature in adipose-derived stem cells.

BACKGROUND: A functional population of adipocyte precursors, termed adipose-derived stromal/stem cells (ASCs), is crucial for proper adipose tissue (AT) expansion, lipid handling, and prevention of lipotoxicity in response to chronic positive energy balance. We previously showed that obese human subjects contain a dysfunctional pool of ASCs. Elucidation of the mechanisms underlying abnormal ASC function might lead to therapeutic interventions for prevention of lipotoxicity by improving the adipogenic capacity of ASCs. METHODS: Using epigenome-wide association studies, we explored the impact of obesity on the methylation signature of human ASCs and their differentiated counterparts. Mitochondrial phenotyping of lean and obese ASCs was performed. TBX15 loss- and gain-of-function experiments were carried out and western blotting and electron microscopy studies of mitochondria were performed in white AT biopsies from lean and obese individuals. RESULTS: We found that DNA methylation in adipocyte precursors is significantly modified by the obese environment, and adipogenesis, inflammation, and immunosuppression were the most affected pathways. Also, we identified TBX15 as one of the most differentially hypomethylated genes in obese ASCs, and genetic experiments revealed that TBX15 is a regulator of mitochondrial mass in obese adipocytes. Accordingly, morphological analysis of AT from obese subjects showed an alteration of the mitochondrial network, with changes in mitochondrial shape and number. CONCLUSIONS: We identified a DNA methylation signature in adipocyte precursors associated with obesity, which has a significant impact on the metabolic phenotype of mature adipocytes.

Endobarrier® in Grade I Obese Patients with Long-Standing Type 2 Diabetes: Role of Gastrointestinal Hormones in Glucose Metabolism.

BACKGROUND: The purpose of this study was to evaluate the efficacy and safety of Endobarrier® in grade 1 obese T2DM patients with poor metabolic control and the role of gastro-intestinal hormone changes on the metabolic outcomes. METHODS: Twenty-one patients aged 54.1 ± 9.5 years, diabetes duration 14.8 ± 8.5 years, BMI 33.4 ± 1.9 kg/m2, and HbA1c 9.1 ± 1.3 %, under insulin therapy, were implanted with Endobarrier®. Fasting concentrations of PYY, ghrelin and glucagon, and AUC for GLP-1 after a standard meal test were determined prior to and at months 1 and 12 after implantation. RESULTS: Patients lost 14.9 ± 5.7 % of their total body weight. HbA1c decreased 1.3 % in the first month, but at the end of the study, the reduction was 0.6 %. HbA1c ≤ 7 % was achieved in 26.3 % of patients. No differences in GLP-1 AUC values were found before and after implant. Fasting plasma ghrelin and PYY concentrations increased from month 1 to 12. Conversely, fasting plasma glucagon concentrations decreased at month 1 and increased thereafter. Weight (ß 0.152) and HbA1c decrease at month 1 (ß 0.176) were the only variables predictive of HbA1c values at 12 months (adjusted R 2 for the model 0.693, p = 0.001). Minor adverse events occurred in 14 % of patients and major events in 9.5 %. CONCLUSIONS: Endobarrier® in T2DM patients with grade I obesity and poor metabolic control is associated with significant weight decrease and moderate reduction in HbA1c at month 12. Our data do not support a role for GLP-1 in the metabolic improvement in this subset of patients.

Obesity Determines the Immunophenotypic Profile and Functional Characteristics of Human Mesenchymal Stem Cells From Adipose Tissue.

UNLABELLED: Adipose tissue is a major source of mesenchymal stem cells (MSCs), which possess a variety of properties that make them ideal candidates for regenerative and immunomodulatory therapies. Here, we compared the immunophenotypic profile of human adipose-derived stem cells (hASCs) from lean and obese individuals, and explored its relationship with the apparent altered plasticity of hASCs. We also hypothesized that persistent hypoxia treatment of cultured hASCs may be necessary but not sufficient to drive significant changes in mature adipocytes. hASCs were obtained from subcutaneous adipose tissue of healthy, adult, female donors undergoing abdominal plastic surgery: lean (n=8; body mass index [BMI]: 23±1 kg/m2) and obese (n=8; BMI: 35±5 kg/m2). Cell surface marker expression, proliferation and migration capacity, and adipogenic differentiation potential of cultured hASCs at two different oxygen conditions were studied. Compared with lean-derived hASCs, obese-derived hASCs demonstrated increased proliferation and migration capacity but decreased lipid droplet accumulation, correlating with a higher expression of human leukocyte antigen (HLA)-II and cluster of differentiation (CD) 106 and lower expression of CD29. Of interest, adipogenic differentiation modified CD106, CD49b, HLA-ABC surface protein expression, which was dependent on the donor's BMI. Additionally, low oxygen tension increased proliferation and migration of lean but not obese hASCs, which correlated with an altered CD36 and CD49b immunophenotypic profile. In summary, the differences observed in proliferation, migration, and differentiation capacity in obese hASCs occurred in parallel with changes in cell surface markers, both under basal conditions and during differentiation. Therefore, obesity is an important determinant of stem cell function independent of oxygen tension. SIGNIFICANCE: The obesity-related hypoxic environment may have latent effects on human adipose tissue-derived mesenchymal stem cells (hASCs) with potential consequences in mature cells. This study explores the immunophenotypic profile of hASCs obtained from lean and obese individuals and its potential relationship with the altered plasticity of hASCs observed in obesity. In this context, an altered pattern of cell surface marker expression in obese-derived hASCs in both undifferentiated and differentiated stages is demonstrated. Differences in proliferation, migration, and differentiation capacity of hASCs from obese adipose tissue correlated with alterations in cell surface expression. Remarkably, altered plasticity observed in obese-derived hASCs was maintained in the absence of hypoxia, suggesting that these cells might be obesity conditioned.