GPCRs and Insulin Receptor Signaling in Conversation: Novel Avenues for Drug Discovery

2019 ◽  
Vol 19 (16) ◽  
pp. 1436-1444 ◽  
Author(s):  
Manveen K. Gupta ◽  
Neelakantan T. Vasudevan
Keyword(s):  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Adipose Tissue ◽  
Drug Discovery ◽  
Treatment Modalities ◽  
Dpp Iv ◽  
Sulfonyl Urea ◽  
Insulin Receptor Signaling ◽  
Major Treatment

Type 2 diabetes is a major health issue worldwide with complex metabolic and endocrine abnormalities. Hyperglycemia, defects in insulin secretion and insulin resistance are classic features of type 2 diabetes. Insulin signaling regulates metabolic homeostasis by regulating glucose and lipid turnover in the liver, skeletal muscle and adipose tissue. Major treatment modalities for diabetes include the drugs from the class of sulfonyl urea, Insulin, GLP-1 agonists, SGLT2 inhibitors, DPP-IV inhibitors and Thiazolidinediones. Emerging antidiabetic therapeutics also include classes of drugs targeting GPCRs in the liver, adipose tissue and skeletal muscle. Interestingly, recent research highlights several shared intermediates between insulin and GPCR signaling cascades opening potential novel avenues for diabetic drug discovery.

scholarly journals Analysis of gene expression profiles in insulin-sensitive tissues from pre-diabetic and diabetic Zucker diabetic fatty rats

2005 ◽  
Vol 34 (2) ◽  
pp. 299-315 ◽  
Author(s):  
Young Ho Suh ◽  
Younyoung Kim ◽  
Jeong Hyun Bang ◽  
Kyoung Suk Choi ◽  
June Woo Lee ◽  
...  
Keyword(s):  
Gene Expression ◽  
Insulin Resistance ◽  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Adipose Tissue ◽  
Expression Profiles ◽  
Gene Expression Profiles ◽  
Zucker Diabetic Fatty Rats ◽  
Zdf Rats

Insulin resistance occurs early in the disease process, preceding the development of type 2 diabetes. Therefore, the identification of molecules that contribute to insulin resistance and leading up to type 2 diabetes is important to elucidate the molecular pathogenesis of the disease. To this end, we characterized gene expression profiles from insulin-sensitive tissues, including adipose tissue, skeletal muscle, and liver tissue of Zucker diabetic fatty (ZDF) rats, a well characterized type 2 diabetes animal model. Gene expression profiles from ZDF rats at 6 weeks (pre-diabetes), 12 weeks (diabetes), and 20 weeks (late-stage diabetes) were compared with age- and sex-matched Zucker lean control (ZLC) rats using 5000 cDNA chips. Differentially regulated genes demonstrating > 1.3-fold change at age were identified and categorized through hierarchical clustering analysis. Our results showed that while expression of lipolytic genes was elevated in adipose tissue of diabetic ZDF rats at 12 weeks of age, expression of lipogenic genes was decreased in liver but increased in skeletal muscle of 12 week old diabetic ZDF rats. These results suggest that impairment of hepatic lipogenesis accompanied with the reduced lipogenesis of adipose tissue may contribute to development of diabetes in ZDF rats by increasing lipogenesis in skeletal muscle. Moreover, expression of antioxidant defense genes was decreased in the liver of 12-week old diabetic ZDF rats as well as in the adipose tissue of ZDF rats both at 6 and 12 weeks of age. Cytochrome P450 (CYP) genes were also significantly reduced in 12 week old diabetic liver of ZDF rats. Genes involved in glucose utilization were downregulated in skeletal muscle of diabetic ZDF rats, and the hepatic gluconeogenic gene was upregulated in diabetic ZDF rats. Genes commonly expressed in all three tissue types were also observed. These profilings might provide better fundamental understanding of insulin resistance and development of type 2 diabetes.

scholarly journals MECHANISMS IN ENDOCRINOLOGY: Skeletal muscle lipotoxicity in insulin resistance and type 2 diabetes: a causal mechanism or an innocent bystander?

2017 ◽  
Vol 176 (2) ◽  
pp. R67-R78 ◽  
Author(s):  
Charlotte Brøns ◽  
Louise Groth Grunnet
Keyword(s):  
Insulin Resistance ◽  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Adipose Tissue ◽  
Cellular Localization ◽  
Future Research ◽  
Causal Mechanism ◽  
Increased Risk ◽  
Adipose Tissue Expandability

Dysfunctional adipose tissue is associated with an increased risk of developing type 2 diabetes (T2D). One characteristic of a dysfunctional adipose tissue is the reduced expandability of the subcutaneous adipose tissue leading to ectopic storage of fat in organs and/or tissues involved in the pathogenesis of T2D that can cause lipotoxicity. Accumulation of lipids in the skeletal muscle is associated with insulin resistance, but the majority of previous studies do not prove any causality. Most studies agree that it is not the intramuscular lipids per se that causes insulin resistance, but rather lipid intermediates such as diacylglycerols, fatty acyl-CoAs and ceramides and that it is the localization, composition and turnover of these intermediates that play an important role in the development of insulin resistance and T2D. Adipose tissue is a more active tissue than previously thought, and future research should thus aim at examining the exact role of lipid composition, cellular localization and the dynamics of lipid turnover on the development of insulin resistance. In addition, ectopic storage of fat has differential impact on various organs in different phenotypes at risk of developing T2D; thus, understanding how adipogenesis is regulated, the interference with metabolic outcomes and what determines the capacity of adipose tissue expandability in distinct population groups is necessary. This study is a review of the current literature on the adipose tissue expandability hypothesis and how the following ectopic lipid accumulation as a consequence of a limited adipose tissue expandability may be associated with insulin resistance in muscle and liver.

scholarly journals 4126 Intermuscular adipose tissue secretes pro-inflammatory, extracellular matrix, and lipid signals related to insulin resistance and type 2 diabetes

2020 ◽  
Vol 4 (s1) ◽  
pp. 9-9
Author(s):  
Darcy Kahn ◽  
Simona Zarini ◽  
Emily Macias ◽  
Amanda Garfield ◽  
Kathleen Harrison ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Extracellular Matrix ◽  
Adipose Tissue ◽  
Functional Role ◽  
Vastus Lateralis ◽  
Laparoscopic Bariatric Surgery ◽  
Intermuscular Adipose Tissue

OBJECTIVES/GOALS: Intermuscular adipose tissue (IMAT) has been associated with insulin resistance and type 2 diabetes, yet mechanistic studies addressing the functional role of IMAT are lacking. The aim of this work was to identify novel mechanisms by which IMAT may directly impact skeletal muscle metabolism. METHODS/STUDY POPULATION: We quantified the secretome of IMAT, subcutaneous adipose tissue (SAT), and visceral adipose tissue (VAT) to determine if there are differences between depots in the secretion of cytokines, eicosanoids, FFAs and proteins that influence metabolic function. SAT and VAT biopsies from patients undergoing laparoscopic bariatric surgery and IMAT extracted from vastus lateralis biopsies of individuals with Obesity were cultured for 48 hours in DMEM, and the conditioned media was analyzed using nanoflow HPLC-MS, multiplex ELISAs and LC/MS/MS for proteins, cytokines and eicosanoids/FFA, respectively. RESULTS/ANTICIPATED RESULTS: IMAT secretion of various extracellular matrix proteins (fibrinogen-β, collagenV1a3, fibronectin) was significantly different than VAT and SAT. Pro-inflammatory cytokine secretion of IFNg, TNFa, IL-8 and IL-13 from IMAT was higher than VAT and significantly higher than SAT (p < 0.05). IMAT secretes significantly more pro-inflammatory eicosanoids TXB2 and PGE2 than VAT (p = 0.02, 0.05) and SAT (p = 0.01, 0.04). IMAT and VAT have significantly greater basal lipolysis assessed by FFA release rates compared to SAT (p = 0.01, 0.04). DISCUSSION/SIGNIFICANCE OF IMPACT: These data begin to characterize the disparate secretory properties of SAT, VAT and IMAT and suggest a metabolically adverse secretome of IMAT, that due to its proximity to skeletal muscle may play an important functional role in the pathogenesis of insulin resistance and type 2 diabetes.

scholarly journals Association between Interleukin-15 and Obesity: Interleukin-15 as a Potential Regulator of Fat Mass

2008 ◽  
Vol 93 (11) ◽  
pp. 4486-4493 ◽  
Author(s):  
Anders Rinnov Nielsen ◽  
Pernille Hojman ◽  
Christian Erikstrup ◽  
Christian Philip Fischer ◽  
Peter Plomgaard ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Adipose Tissue ◽  
Fat Mass ◽  
Negative Association ◽  
Tissue Mass ◽  
Adipose Tissue Mass ◽  
Interleukin 15 ◽  
Total Fat

Objective: IL-15 decreases lipid deposition in preadipocytes and decreases the mass of white adipose tissue in rats, indicating that IL-15 may take part in regulating this tissue. IL-15 is expressed in human skeletal muscle and skeletal muscle may be a source of plasma IL-15 and in this way regulate adipose tissue mass. Design: The relation between skeletal muscle IL-15 mRNA expression, plasma IL-15, and adipose tissue mass was studied in 199 humans divided into four groups on the basis of obesity and type 2 diabetes. Furthermore, using a DNA electrotransfer model, we assessed the effect of IL-15 overexpression in skeletal muscle of mice. Results: In humans, multiple regression analysis showed a negative association between plasma IL-15 and total fat mass (P &lt; 0.05), trunk fat mass (P &lt; 0.01), and percent fat mass (P &lt; 0.05), independent of type 2 diabetes. Negative associations were also found between muscle IL-15 mRNA and obesity parameters. IL-15 overexpression in skeletal muscle of mice reduced trunk fat mass but not sc fat mass. Conclusions: Our results indicate that IL-15 may be a regulator of trunk fat mass.

scholarly journals Dipeptidyl-Peptidase-IV Inhibition Augments Postprandial Lipid Mobilization and Oxidation in Type 2 Diabetic Patients

Endocrinology ◽  
2009 ◽  
Vol 150 (2) ◽  
pp. 1069-1069
Author(s):  
Michael Boschmann ◽  
Stefan Engeli ◽  
Kerstin Dobberstein ◽  
Petra Budziarek ◽  
Anke Strauss ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Adipose Tissue ◽  
Standardized Test ◽  
Dipeptidyl Peptidase ◽  
Dipeptidyl Peptidase Iv ◽  
Diabetic Patients ◽  
Lipid Mobilization ◽  
Postprandial Lipid

Abstract Context: Dipeptidyl-peptidase-IV (DPP-4) inhibition increases endogenous GLP-1 activity resulting in improved glycemic control in patients with type 2 diabetes mellitus. The metabolic response may be explained in part by extra-pancreatic mechanisms. Objective: We tested the hypothesis that DPP-4 inhibition with vildagliptin elicits changes in adipose tissue and skeletal muscle metabolism. Design: Randomized, double blind, crossover study. Setting: Academic clinical research center. Patients: Twenty patients with type 2 diabetes, body mass index between 28 and 40 kg/m2. Intervention: Seven days treatment with the selective DPP-4 inhibitor vildagliptin or placebo. Standardized test meal on day seven. Main Outcome Measures: Venous DPP-4 activity, catecholamines, free fatty acids, glycerol, glucose, (pro)insulin; dialysate glucose, lactate, pyruvate, glycerol. Results: Fasting and postprandial venous insulin, glucose, glycerol, triglycerides and free fatty acid concentrations were not different with vildagliptin and with placebo. Vildagliptin augmented the postprandial increase in plasma norepinephrine. Furthermore, vildagliptine increased dialysate glycerol and lactate concentrations in adipose tissue while suppressing dialysate lactate and pyruvate concentration in skeletal muscle. The respiratory quotient increased with meal ingestion but was consistently lower with vildagliptin. Conclusions: Our study is the first to suggest that DPP-4 inhibition augments postprandial lipid mobilization and oxidation. The response may be explained by sympathetic activation rather than a direct effect on metabolic status.

scholarly journals Increased AQP7 abundance in skeletal muscle from obese men with type 2 diabetes

2018 ◽  
Vol 315 (3) ◽  
pp. E367-E373 ◽  
Author(s):  
Janne Lebeck ◽  
Esben Søndergaard ◽  
Søren Nielsen
Keyword(s):  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Adipose Tissue ◽  
Protein Abundance ◽  
Tissue Samples ◽  
Triglyceride Accumulation ◽  
Meal Intake ◽  
Fasting And Refeeding ◽  
Subcutaneous Adipose

Aquaglyceroporin 7 (AQP7) facilitates the transport of glycerol across cell membranes. In mice, fasting and refeeding regulate adipose tissue AQP7 abundance, and a role in controlling triglyceride accumulation in adipose tissue has been proposed. AQP7 is also expressed in skeletal muscle, where its function remains to be determined. Here, the abundance of AQP7 in abdominal subcutaneous adipose tissue (SAT) and skeletal muscle was evaluated in the overnight fasted and postprandial state in eight lean and eight obese men with type 2 diabetes (T2D). A biopsy from SAT and muscle was collected after an overnight fast and 2 h after ingestion of a low-fat test meal. Palmitate turnover was evaluated using a [9,10-3H] palmitate dilution technique. Tissue samples were analyzed by immunoblotting. Meal intake did not affect AQP7 expression in SAT or skeletal muscle. No association between the SAT AQP7 abundance and palmitate turnover was found. SAT AQP7 abundance was similar in lean and obese T2D men, whereas muscle AQP7 abundance was more than fourfold higher in obese T2D men. In conclusion, meal intake did not affect AQP7 protein abundance in SAT or skeletal muscle. In addition, SAT AQP7 expression does not appear to be involved in the regulation of adipose tissue lipolysis. However, in contrast to SAT AQP7, skeletal muscle AQP7 protein abundance is markedly increased in obese T2D men, potentially contributing to the excess lipid accumulation in skeletal muscle in type 2 diabetes.

scholarly journals Associations between insulin resistance and TNF-α in plasma, skeletal muscle and adipose tissue in humans with and without type 2 diabetes

Diabetologia ◽  
2007 ◽  
Vol 50 (12) ◽  
pp. 2562-2571 ◽  
Author(s):  
P. Plomgaard ◽  
A. R. Nielsen ◽  
C. P. Fischer ◽  
O. H. Mortensen ◽  
C. Broholm ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Adipose Tissue ◽  
Tnf Α

scholarly journals Fatty acid metabolism in obesity and type 2 diabetes mellitus

2003 ◽  
Vol 62 (3) ◽  
pp. 753-760 ◽  
Author(s):  
E. E. Blaak
Keyword(s):  
Diabetes Mellitus ◽  
Insulin Resistance ◽  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Type 2 Diabetes Mellitus ◽  
Adipose Tissue ◽  
Fatty Acid ◽  
Acid Oxidation ◽  
Acid Uptake

Disturbances in pathways of lipolysis and fatty acid handling are of importance in the aetiology of obesity and type 2 diabetes mellitus. There is evidence that a lowered catecholamine-mediated lipolytic response may play a role in the development and maintenance of increased adipose tissue stores. Increased adipose tissue stores, a disturbed insulin-mediated regulation of lipolysis and subnormal skeletal muscle non-esterified fatty acid (NEFA) uptake under conditions of high lipolytic rate may increase circulating NEFA concentrations, which may promote insulin resistance and cardiovascular complications. In addition, a disturbance of NEFA uptake by adipose tissue postprandially is also a critical determinant of plasma NEFA concentration. Furthermore, evidence is increasing that insulin-resistant muscle is characterised by a lowered ability to oxidise fatty acids. A dysbalance between fatty acid uptake and fatty acid oxidation may in turn be a factor promoting accumulation of lipid intermediates and triacylglycerols within skeletal muscle, which is strongly associated with skeletal muscle insulin resistance. The present review describes the reported disturbances in pathways of lipolysis and skeletal muscle fatty acid handling, and discusses underlying mechanisms and metabolic consequences of these disturbances.

scholarly journals Impairment of insulin-stimulated GLUT4 translocation in skeletal muscle and adipose tissue in the Tsumura Suzuki obese diabetic mouse: a new genetic animal model of type 2 diabetes

2001 ◽  
pp. 785-790 ◽  
Author(s):  
T Miura ◽  
W Suzuki ◽  
E Ishihara ◽  
I Arai ◽  
H Ishida ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Animal Model ◽  
Adipose Tissue ◽  
Plasma Membrane ◽  
Blood Glucose ◽  
Low Density ◽  
Glut4 Translocation ◽  
Genetic Animal Model

BACKGROUND: In skeletal muscle and adipocytes, insulin-stimulated glucose transport has been known to occur through the translocation of glucose transporter (GLUT) 4 from the intracellular pool to the plasma membrane. The Tsumura Suzuki obese diabetic (TSOD) mouse, a new genetic animal model of type 2 diabetes, develops moderate degrees of obesity and diabetes that are especially apparent in animals more than 11 weeks old. A defect in insulin stimulation of GLUT4 translocation also contributes to the characteristics of type 2 diabetes. OBJECTIVE: To characterize this mouse further, we examined the alteration in insulin-stimulated GLUT4 translocation in the skeletal muscle and adipose tissue. METHODS: For glucose and insulin tolerance tests, the mice were given glucose or insulin and blood samples were collected. After isolation of low-density microsomal membrane and plasma membrane from skeletal muscle and adipose tissue, insulin-stimulated translocation of GLUT4 in these TSOD mice was examined by Western blot. RESULTS AND CONCLUSIONS: TSOD mice showed a significant increase in blood glucose after the glucose load, and exhibited a significantly attenuated decrease in blood glucose concentrations after administration of insulin, compared with that in control Tsumura Suzuki non-obese (TSNO) mice. The insulin-stimulated translocation of GLUT4 from low-density microsomal membranes to plasma membrane was significantly reduced in both skeletal muscle and adipose tissue of TSOD mice. These results indicate that the reduced insulin sensitivity in diabetic TSOD mice is presumably due, at least in part, to the impaired GLUT4 translocation by insulin in both skeletal muscle and adipocytes.

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