Obese Insulin Resistant Humans with Compensatory Hyperinsulinemia Dissociate Lipolysis from Glycemia as Possible Adaptive Response to Fatness
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ABSTRACT: High blood levels of free fatty acids link obesity with type-2 diabetes, but this connection remains poorly understood. We have investigated lipolysis and glucose homeostasis in recently diagnosed obese type-2 diabetics; in obese insulin resistant non-diabetic subjects (obese-IR) matched for age, sex, body composition and fasting insulin levels; and in healthy lean individuals. Our results show that obese-IR dissociate lipolysis from glycemic control, revealing that the action of compensatory hyperinsulinemia on blood glucose is not mediated by reduced lipolysis. In the obese adipose tissue free fatty acids and glycerol levels were elevated in spite of high local levels of insulin or lactate; correlated with adipocyte size and metabolic inflammation, with reduced adipose tissue mRNA levels of genes implicated in beta-adrenergic signaling, de-novo lipogenesis, and increased expression of genes implicated in adipose tissue hyperplasia. These results shed light on the nature of the interaction between lipolysis and glucose homeostasis and indicate an possible adaptive response to fatness.
Project description:OBJECTIVE: Acromegaly is a rare endocrine disorder with excess growth hormone (GH) production. This disorder has important metabolic effects in insulin resistance and lipolysis. The objective of this study was to explore transcriptional changes induced by GH in adipose tissue. METHODS: The patients underwent clinical and metabolic profiling including assessment of HOMA-IR. Explants of adipose tissue were assayed ex-vivo for lipolysis and ceramide levels. Adipose tissue was analyzed by RNA sequencing (RNA-seq). RESULTS: There was evidence of reduced insulin sensitivity based on the increase in fasting glucose, insulin and HOMA-IR score. We observed several previously reported transcriptional changes (IGF1, IGFBP3) as well as several novel transcriptional changes, some of which may be important for GH signal regulation (PTPN3 and PTPN4) and the effect of GH on growth and proliferation. Several transcripts could potentially be important in GH-induced metabolic changes. Specifically, induction of LPL, ABHD5, and ACVR1C could contribute to enhanced lipolysis and may explain the suggestive enhancement of adipose tissue lipolysis in acromegaly patients as reflected by glycerol release from the explants of the two groups of patients (p=0.09). Higher expression of SCD and TCF7L2 could contribute to insulin resistance. Expression of HSD11B1 was reduced and GR was increased, predicting modified glucocorticoid activity in acromegaly. CONCLUSIONS: We identified the acromegaly gene expression signature in human adipose tissue. The significance of altered expression of specific transcripts will enhance our understanding of the metabolic and proliferative changes associated with acromegaly. DESIGN: Patients with acromegaly (n=9) or non-functioning pituitary adenoma (n=11) were prospectively observed from March 2011 to June 2012. Sequencing was performed on RNA from 7 acromegaly patients and 11 controls.
Project description:OBJECTIVE: Acromegaly is a rare endocrine disorder with excess growth hormone (GH) production. This disorder has important metabolic effects in insulin resistance and lipolysis. The objective of this study was to explore transcriptional changes induced by GH in adipose tissue. METHODS: The patients underwent clinical and metabolic profiling including assessment of HOMA-IR. Explants of adipose tissue were assayed ex-vivo for lipolysis and ceramide levels. Adipose tissue was analyzed by RNA sequencing (RNA-seq). RESULTS: There was evidence of reduced insulin sensitivity based on the increase in fasting glucose, insulin and HOMA-IR score. We observed several previously reported transcriptional changes (IGF1, IGFBP3) as well as several novel transcriptional changes, some of which may be important for GH signal regulation (PTPN3 and PTPN4) and the effect of GH on growth and proliferation. Several transcripts could potentially be important in GH-induced metabolic changes. Specifically, induction of LPL, ABHD5, and ACVR1C could contribute to enhanced lipolysis and may explain the suggestive enhancement of adipose tissue lipolysis in acromegaly patients as reflected by glycerol release from the explants of the two groups of patients (p=0.09). Higher expression of SCD and TCF7L2 could contribute to insulin resistance. Expression of HSD11B1 was reduced and GR was increased, predicting modified glucocorticoid activity in acromegaly. CONCLUSIONS: We identified the acromegaly gene expression signature in human adipose tissue. The significance of altered expression of specific transcripts will enhance our understanding of the metabolic and proliferative changes associated with acromegaly.
Project description:5 arrays from obese insulin-resistant and lean insulin-sensitive females adipose tissue at fasting and after 3h hyperinsulinemia 5 arrays from obese insulin-resistant and lean insulin-sensitive females adipose tissue at fasting and after 3h hyperinsulinemia FIR x 5, FIS x 5, HIR x 5, HIS x 5 F=fasting, H=hyperinsulinemia, IR=Insulin-resistant, IS=Insulin-sensitive (FIR, FIS, HIR, HIS)
Project description:Subcutaneous adipose tissue and visceral adipose tissue samples were obtained from severely obese individuals that underwent bariatric surgery. The goal of this study was to compare genome-wide gene expression levels in the two tissue types from healthy and unhealthy severely obese individuals. Whole-transcriptome subcutaneous adipose tissue gene expression levels were determined in 73 individuals with a BMI >35 kg/m2. Whole-transcriptome visceral adipose tissue gene expression levels were determined in 69 individuals with a BMI >35 kg/m2. Modules of co-expressed genes likely to be functionally related were identfied and correlated with BMI, plasma levels of glucose, insulin, HbA1c, triglycerides, non-esterified fatty acids, ALAT, ASAT, C-reactive protein, and LDL- and HDL cholesterol.
Project description:Obesity is associated with impaired β-adrenergic receptor (Adrb1-3) signaling and lipolysis, leading to aberrant white adipose tissue (WAT) growth. WAT research has been centered on transcriptional and posttranslational regulations, but posttranscriptional regulation and mRNA modifications are poorly understood. Here, we unveil a METTL14/N6-methyladenosine (m6A) paradigm guiding β-adrenergic signaling and lipolysis. METTL14 complex installs m6A on RNA, regulating mRNA fate and translation. We found that feeding and insulin increased adipose Mettl14 and m6A levels. Adipose Mettl14 and m6A were upregulated in high fat diet (HFD)-induced obesity. Ablation of adipose Mettl14 decreased Adrb2, Adrb3, Atgl (encoding lipase), and Cig-58 (Atgl activator) transcript m6A contents while increasing their translation and protein levels, thereby enhancing adipose β-adrenergic signaling and lipolysis. Consequently, adipocyte-specific Mettl14 knockout mice were resistant to HFD-induced obesity, insulin resistance, glucose intolerance, and NAFLD. These results unravel a METTL14/m6A-based epitranscriptomic mechanism governing β-adrenergic signaling, lipolysis, and adipose growth in health and disease.
Project description:Obese Insulin Resistant Humans with Compensatory Hyperinsulinemia Dissociate Lipolysis from Glycemia as Possible Adaptive Response to Fatness
Project description:Impaired ability of insulin to stimulate cellular glucose uptake and regulate metabolism, that is insulin resistance (IR), links adiposity to metabolic disorders such as type 2 diabetes (T2D), dyslipidemia and cardiovascular disease (Langenberg, 2012). Both genetic and epigenetic factors are implicated in development of systemic IR (Vaag, 2001). IR is characterized by elevated levels of fasting insulin in the general circulation. The aim of this study is to explore whether white adipose tissue (WAT) epigenetic dysregulation is associated with systemic IR by global CpG methylation and gene expression profiling in subcutaneous and visceral adipose tissue. A secondary aim is to determine whether the DNA methylation signature in peripheral blood mononuclear cells reflect WAT methylation, and can be used as marker for systemic IR. DNA methylation was analyzed in DNA extracted from SAT (subcutaneous adipose tissue) and VAT (visceral adipose tissue) pieces, as well as PBMCs (peripheral blood mononuclear cells), using the Infinium Human Methylation 450 BeadChip assay. This data is from PBMCs.
Project description:Impaired ability of insulin to stimulate cellular glucose uptake and regulate metabolism, that is insulin resistance (IR), links adiposity to metabolic disorders such as type 2 diabetes (T2D), dyslipidemia and cardiovascular disease (Langenberg, 2012). Both genetic and epigenetic factors are implicated in development of systemic IR (Vaag, 2001). IR is characterized by elevated levels of fasting insulin in the general circulation. The aim of this study is to explore whether white adipose tissue (WAT) epigenetic dysregulation is associated with systemic IR by global CpG methylation and gene expression profiling in subcutaneous and visceral adipose tissue. A secondary aim is to determine whether the DNA methylation signature in peripheral blood mononuclear cells reflect WAT methylation, and can be used as marker for systemic IR. DNA methylation was analyzed in DNA extracted from SAT (subcutaneous adipose tissue) and VAT (visceral adipose tissue) pieces, as well as PBMCs (peripheral blood mononuclear cells), using the Infinium Human Methylation 450 BeadChip assay. This data is from SAT.
Project description:Impaired ability of insulin to stimulate cellular glucose uptake and regulate metabolism, that is insulin resistance (IR), links adiposity to metabolic disorders such as type 2 diabetes (T2D), dyslipidemia and cardiovascular disease (Langenberg, 2012). Both genetic and epigenetic factors are implicated in development of systemic IR (Vaag, 2001). IR is characterized by elevated levels of fasting insulin in the general circulation. The aim of this study is to explore whether white adipose tissue (WAT) epigenetic dysregulation is associated with systemic IR by global CpG methylation and gene expression profiling in subcutaneous and visceral adipose tissue. A secondary aim is to determine whether the DNA methylation signature in peripheral blood mononuclear cells reflect WAT methylation, and can be used as marker for systemic IR. DNA methylation was analyzed in DNA extracted from SAT (subcutaneous adipose tissue) and VAT (visceral adipose tissue) pieces, as well as PBMCs (peripheral blood mononuclear cells), using the Infinium Human Methylation 450 BeadChip assay. This data is from VAT (omental).
Project description:Impaired ability of insulin to stimulate cellular glucose uptake and regulate metabolism, that is insulin resistance (IR), links adiposity to metabolic disorders such as type 2 diabetes (T2D), dyslipidemia and cardiovascular disease (Langenberg, 2012). Both genetic and epigenetic factors are implicated in development of systemic IR (Vaag, 2001). IR is characterized by elevated levels of fasting insulin in the general circulation. The aim of this study is to explore whether white adipose tissue (WAT) epigenetic dysregulation is associated with systemic IR by global CpG methylation and gene expression profiling in subcutaneous and visceral adipose tissue. A secondary aim is to determine whether the DNA methylation signature in peripheral blood mononuclear cells reflect WAT methylation, and can be used as marker for systemic IR.