Project description:Lifestyle intervention can improve insulin sensitivity in obese youth yet few studies have examined the biological mechanisms underlying improvements. Therefore, the purpose of this study was to explore biological pathways associated with intervention-induced improvements in insulin sensitivity. Fifteen (7M/8F) overweight/obese (BMI percentile=96.3M-BM-11.1) Latino adolescents (15.0M-BM-10.9 years) completed a 12-week lifestyle intervention that included weekly nutrition education and 180 minutes of moderate-vigorous exercise per week. Insulin sensitivity, estimated by an oral glucose tolerance test and the Matsuda Index, increased 29.2% post intervention (2.4M-BM-10.3 to 3.1M-BM-10.3, p=0.01). Global microarray analysis profiling from whole blood was performed to examine changes in gene expression and to explore biological pathways that were significantly changed in response to the intervention. A total of 1,459 probes corresponding to mRNA transcripts (717 up, 742 down) were differentially expressed with a fold changeM-bM-^IM-%1.2 and P<0.05. Among the genes identified were hexokinase 3 (HK3), ATPase, H+ transporting V0 subunit e2 (ATPV0E), and sterol regulatory element binding transcription factor 1 (SREBF1), and endothelial cell adhesion molecule (ESAM). There were 8 pathways identified that met the criteria for significance, including insulin signaling, type 1 diabetes, and glycerophospholipid metabolism. Participants that increased insulin sensitivity exhibited five times the number of significant genes altered compared to non-responders (1,144 vs. 230). These findings offer insight into the molecular mechanisms underlying health improvements among high-risk Latino youth. Lifestyle interventions may contribute to improved insulin sensitivity through pathways related to insulin signaling and immune response. Further, genetic factors may mediate response to lifestyle intervention. Fifteen (7M/8F) overweight/obese Latino Youth Whole blood RNA samples evaluated pre and post intervention.
Project description:Lifestyle intervention can improve insulin sensitivity in obese youth yet few studies have examined the biological mechanisms underlying improvements. Therefore, the purpose of this study was to explore biological pathways associated with intervention-induced improvements in insulin sensitivity. Fifteen (7M/8F) overweight/obese (BMI percentile=96.3±1.1) Latino adolescents (15.0±0.9 years) completed a 12-week lifestyle intervention that included weekly nutrition education and 180 minutes of moderate-vigorous exercise per week. Insulin sensitivity, estimated by an oral glucose tolerance test and the Matsuda Index, increased 29.2% post intervention (2.4±0.3 to 3.1±0.3, p=0.01). Global microarray analysis profiling from whole blood was performed to examine changes in gene expression and to explore biological pathways that were significantly changed in response to the intervention. A total of 1,459 probes corresponding to mRNA transcripts (717 up, 742 down) were differentially expressed with a fold change≥1.2 and P<0.05. Among the genes identified were hexokinase 3 (HK3), ATPase, H+ transporting V0 subunit e2 (ATPV0E), and sterol regulatory element binding transcription factor 1 (SREBF1), and endothelial cell adhesion molecule (ESAM). There were 8 pathways identified that met the criteria for significance, including insulin signaling, type 1 diabetes, and glycerophospholipid metabolism. Participants that increased insulin sensitivity exhibited five times the number of significant genes altered compared to non-responders (1,144 vs. 230). These findings offer insight into the molecular mechanisms underlying health improvements among high-risk Latino youth. Lifestyle interventions may contribute to improved insulin sensitivity through pathways related to insulin signaling and immune response. Further, genetic factors may mediate response to lifestyle intervention.
Project description:We evaluated the potential importance of adipose tissue (AT) oxygenation on AT biology and insulin sensitivity in people. AT oxygen partial pressure (pO2), branched chain amino acid (BCAA) catabolism and marker of inflammation were determined in three groups stratified by adiposity and insulin sensitivity: 1) metabolically-healthy lean (MHL); 2) metabolically-healthy obese (MHO); and 3) metabolically-unhealthy obese (MUO). AT pO2 progressively declined from the MHL to the MHO to the MUO group, and was positively associated with hepatic and whole-body insulin sensitivity. AT pO2 was positively associated with AT expression of genes involved in BCAA catabolism and negatively associated with plasma BCAA concentrations. Although AT pO2 was negatively associated with AT markers of inflammation, it was not associated with plasma adipokine concentrations. These results support the notion that reduced AT pO2 in people with obesity contributes to insulin resistance by decreasing AT BCAA catabolism and thereby increasing plasma BCAA concentrations.
Project description:OBJECTIVE Diet intervention in obese adults is the first strategy to induce weight loss and to improve insulin sensitivity. We hypothesized that improvements in insulin sensitivity after weight loss from a short-term dietary intervention tracks with alterations in expression of metabolic genes and abundance of specific lipid species. RESEARCH DESIGN AND METHODS Eight obese, insulin resistant, non-diabetic adults were recruited to participate in a three-week low calorie diet intervention study (1000 kcal/day). Fasting blood samples and vastus lateralis skeletal muscle biopsies were obtained before and after the dietary intervention. Clinical chemistry and measures of insulin sensitivity were determined. Unbiased microarray gene expression and targeted lipidomic analysis of skeletal muscle was performed. RESULTS Body weight was reduced, insulin sensitivity (HOMA-IR) was enhanced, and serum insulin concentration and blood lipid (triglyceride, cholesterol, LDL and HDL) levels were improved after dietary intervention. Gene set enrichment analysis of skeletal muscle revealed that oxidative phosphorylation and inflammatory processes were among the most enriched KEGG-pathways identified after dietary intervention. mRNA expression of PDK4 and MLYCD increased, while SCD decreased in skeletal muscle after dietary intervention. Dietary intervention altered the intramuscular lipid profile of skeletal muscle, with changes in content of phosphatidylcholine and triglyceride species among the pronounced. CONCLUSIONS Short-term diet intervention and weight loss in obese adults alters metabolic gene expression and reduces specific phosphatidylcholine and triglyceride species in skeletal muscle, concomitant with improvements in clinical outcomes and enhanced insulin sensitivity.
Project description:Obesity is a critical health concern, and identifying new biomarkers has become essential for better understanding the progression to disease such as type 2 diabetes. DNA methylation has become a useful epigenetic biomarker in part due to its susceptibility to disease influence. Detecting methylation changes in blood is important as it is an easily accessible, compared to the insulin responsive tissue skeletal muscle. The aim of our study was to identify methylation changes in whole blood that were strongly associated with obesity associated insulin resistance. Whole blood was obtained from lean (n=10; BMI= 23.6±0.7 kg/m2) and obese (n=10; BMI= 34.4±1.3 kg/m2) participants in combination with euglycemic hyperinsulinemic clamps to assess insulin sensitivity. We performed the next generation technique, reduced representation bisulfite sequencing (RRBS) on isolated genomic DNA. There were 49 significantly altered differentially methylated cytosines (DMCs; q<0.05). Of these, solute carrier family 19 member 1 (SLC19A1) was also identified using a differentially methylated region approach. The sites for this gene were significantly correlated (P<0.05) with body mass index, body fat percent, and the clamp Rd. Moreover, the decrease in SLC19A1 methylation was similar to the change previously found in skeletal muscle. Pyrosequencing confirmed the changes in methylation at Chr.21:46,957,915 in both tissues. These results demonstrate that the methylation status of SLC19A1 provides a new potential epigenetic biomarker for obesity related insulin resistance.
Project description:This study aimed to investigate the mechanism of SYT on lipid metabolism and insulin sensitivity in high-fat diet (HFD)-induced obese mice by means of combining lipidomics and proteomics. The obese mice models were developed via HFD feeding for 20 consecutive weeks. Mice in the treatment group were given metformin and SYT respectively, and the effects of SYT on body weight, blood glucose, insulin sensitivity, fat accumulation in the organs, and pathological changes in the liver were monitored. Lipid metabolism was examined by lipidomics. Further determination of signaling pathways was detected by proteomics. The biological contributions of the compounds detected in SYT's chemical fingerprint were predicted by network pharmacology. Overall, our study provides supportive evidence for the mechanism of SYT's therapeutic effect on dysregulated lipid metabolism in diabesity.
Project description:We screened intronic microRNAs dysregulated in liver of obese mouse models to identify previously uncharacterized coding host genes that may contribute to the pathogenesis of obesity-associated insulin resistance and type 2 diabetes mellitus. Our approach identified the expression of Ectodysplasin A (Eda), the causal gene of X-linked hypohidrotic ectodermal dysplasia (XLHED; MIM 305100) was strongly increased in liver of obese mouse models both in rodents and humans.Eda expression in murine liver is controlled via PPARγ activation, increases in circulation and promotes JNK activation and inhibitory serine phosphorylation of IRS1 in skeletal muscle. Consistently, bi-directional modulation of hepatic Eda expression in mouse models affects systemic glucose metabolism with alterations of muscle insulin signaling, revealing a novel role of EDA as an obesity-associated hepatokine, which impairs insulin sensitivity in skeletal muscle.
Project description:Tirzepatide (LY3298176), a dual GIP and GLP-1 receptor agonist, has been shown to deliver enhanced glycemic control and superior weight loss compared to a selective GLP-1 receptor (GLP-1R) agonist in patients with type 2 diabetes mellitus. However, the mechanism by which tirzepatide improves efficacy and how GIP receptor (GIPR) agonism contributes to the therapy is not fully understood. Here, hyperinsulinemic-euglycemic clamp studies were used to show that tirzepatide is a highly effective insulin sensitizer, improving insulin sensitivity in obese mice to a greater extent than GLP-1R agonism. To determine if GIPR agonism contributes to the insulin sensitization, we compared the effect of tirzepatide in obese wild-type and Glp-1r null mice. In the absence of GLP-1R induced weight loss, tirzepatide improved systemic insulin sensitivity by enhancing glucose disposal in WAT. To corroborate these results, chronic treatment with a long-acting GIPR agonist (LAGIPRA) was also found to enhance insulin sensitivity by increasing insulin stimulated glucose uptake in WAT. Interestingly, the effect of tirzepatide and LAGIPRA on insulin sensitivity was associated with reduced branched chain amino and keto acids in the circulation. Whole-body insulin sensitization was associated with pronounced upregulation of genes associated with the catabolism of glucose, lipid and BCAAs in brown adipose tissue. Together, our studies show that tirzepatide improved insulin sensitivity in a weight-dependent and -independent manner. These results highlight how GIPR agonism contributes to the therapeutic profile of dual GIP and GLP-1 receptor agonism, offering mechanistic insights into the clinical efficacy of tirzepatide.
Project description:Purpose: To determine how STAT1 activity in white adipocytes affects insulin sensitivity. Methods: Adipocyte specific (ADIPOQ-Cre) STAT1 fl/fl mice (STAT1 fKO) and littermate controls (STAT1 fl/fl) were placed on 60% HFD for 18 weeks, followed by metabolic phenoptying and tissue harvest for RNA-seq Results: STAT1 expression in WAT inversely correlated with fasting plasma glucose in both obese mice and humans. Metabolomic and gene expression profiling established STAT1 deletion in adipocytes (STAT1 fKO) enhanced mitochondrial function and accelerated TCA cycle flux coupled with subcutaneous WAT hyperplasia. STAT1 fKO reduced WAT inflammation, but insulin resistance persisted in obese mice. Rather, elimination of type I cytokine interferon gamma (IFNg) activity enhanced insulin sensitivity in diet-induced obesity. Conclusions: Our findings reveal a permissive mechanism that bridges WAT inflammation to whole-body insulin sensitivity.
Project description:Over 40 % of microRNAs are located in introns of coding genes, and many intronic microRNAs are co-regulated with their host genes. In such cases of co-regulation, the products of host genes and their intronic microRNAs can cooperate to coordinately regulate biologically important pathways. Therefore, we screened intronic microRNAs dysregulated in liver of obese mouse models to identify previously uncharacterized coding host genes that may contribute to the pathogenesis of obesity-associated insulin resistance and type 2 diabetes mellitus. Our approach identified that expression of both Ectodysplasin A (Eda), the causal gene of X-linked hypohidrotic ectodermal dysplasia (XLHED; MIM 305100) and its intronic microRNA, miR-676, was strongly increased in liver of obese mouse models. Moreover, hepatic EDA expression is increased in obese human subjects, reduced upon weight loss, and its hepatic expression correlates with systemic insulin resistance. Eda expression in murine liver is controlled via PPARg activation, increases in circulation and promotes JNK activation and inhibitory serine phosphorylation of IRS1 in skeletal muscle. Consistently, bi-directional modulation of hepatic Eda expression in mouse models affects systemic glucose metabolism with alterations of muscle insulin signaling, revealing a novel role of EDA as an obesity-associated hepatokine, which impairs insulin sensitivity in skeletal muscle.