257-OR: Short-Term Hyperglucagonemia Induces Adipose Tissue Insulin Resistance and Inflammation In Vivo

Abstract

Although the effect of glucagon on glucose metabolism has been well characterized, its effect on adipose tissue and lipid metabolism in humans in vivo has been poorly studied with controversial results. We examined the effect of short-term hyperglucagonemia on adipocyte metabolism in 8 healthy normal glucose tolerant subjects (5M/3F, age=35±5, BMI = 24±1) who received a 12-hour (6PM to 6AM) glucagon infusion (6ng/kg/min) with 14C-glycerol infusion; subcutaneous abdominal adipose tissue biopsy was obtained at 6AM. 8 weeks later subjects returned for a repeat study with 12-hour infusion of normal saline. Plasma glucagon increased from 57±3 to 219±21 pg/ml within one hour and remained elevated throughout the study. Glycerol turnover rate (5.1±0.6 vs. 3.8±0.6 µmol/kg•min, p<0.05) increased by 34%, and the adipose tissue insulin resistance index (fasting plasma FFA x Insulin) more than doubled (5.8±0.8 vs. 2.8±0.7 mM•mU/L, p<0.05) after 12-hour glucagon infusion compared to saline. mRNA expression of genes involved in lipolysis in adipose tissue were upregulated after glucagon infusion (ATGL, 1.14±0.07 vs. 0.77±0.03; HSL, 1.17±0.03 vs. 0.9±0.13; MGL, 1.2±0.04 vs. 0.82±0.2, all p<0.05). Plasma concentration of proinflammatory markers (IL-1β, 0.65±0.05 vs. 0.49±0.05 pg/mL; TNF-α, 2.03±0.23 vs. 1.75±0.17 pg/mL, both p<0.05) and lipidomes involved in inflammatory pathways (lysophosphatidylcholine, 126±11 vs. 51±7 nmol/ml, p<0.005; phosphatidylcholine, 385±24 vs. 306±25 nmol/ml, p<0.01; ceramide, 1.7±0.2 vs. 1.2±0.2 nmol/ml, p<0.01) also increased after 12-hour glucagon infusion. H&E and CD68 immunofluorescence staining in adipose tissue displayed the crown-like structures (CLS) and increased infiltration of macrophages following glucagon infusion. Conclusion: Short-term (12-hour) physiologic hyperglucagonemia stimulates adipose tissue lipolysis, induces adipocyte insulin resistance, and promotes adipose tissue and systemic inflammation. Disclosure X. Chen: None. M. Fourcaudot: None. L. Norton: None. R. A. Defronzo: Other Relationship; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Intarcia Therapeutics, Inc., Janssen Pharmaceuticals, Inc., Novo Nordisk, Research Support; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Janssen Pharmaceuticals, Inc., Merck & Co., Inc., Speaker’s Bureau; Self; AstraZeneca, Novo Nordisk. D. Tripathy: None. Funding Foundation for Advancing Veterans’ Health Research