Natriuretic peptides promote glucose uptake in a cGMP-dependent manner in human adipocytes

Figure 1. Natriuretic peptide receptor expression in human adipose tissue in obesity and type 2 diabetes. Human adipose tissue gene expression of GC-A (A), NPRC (B), and the ratio of GC-A-to-NPRC (C) as a function of the obesity class. Human adipose GC-A (D) and NPRC (E) mRNA levels in subjects with normal glucose tolerance (NGT), prediabetes (Pre-D) and type 2 diabetes (T2D). (F) Relationship between human adipose GC-A gene expression and fasting blood glucose (n = 311 from cohort 1). **p < 0.01, ***p < 0.0001 vs. NGT (n = 33–144 per group from cohort 1).

Figure 2. Human adipose tissue gene expression from microarrays of GC-A (A), NPRC (B), and the ratio of GC-A-to-NPRC (C) in lean versus obese individuals from cohort 2 (n = 56). Correlation between adipose GC-A expression and HOMA-IR (D) and de novo lipogenesis measured in isolated adipocytes (E). ***p < 0.0001 vs. lean.

Figure 3. Natriuretic peptides promote glucose uptake in a cGMP-dependent manner in human adipocytes. (A) Dose-response effect of ANP on 2-deoxyglucose uptake in human isolated adipocytes (n = 13). (B) Dose-response effect of ANP on 2-deoxyglucose uptake in human isolated adipocytes from lean (n = 14) versus overweight/obese subjects (n = 9). #p = 0.06 vs. lean. (C) Dose-response effect of BNP on 2-deoxyglucose uptake in differentiated hMADS adipocytes (n = 8). (D) BNP (100 nM)-mediated glucose uptake in absence or presence of (Rp)-8-pCPT-cGMPS 100 µM (PKG inhibitor, PKGi) in differentiated hMADS adipocytes (n = 8). *p < 0.05, **p < 0.01, ***p < 0.0001 vs. 0 or control.

Figure 4. Natriuretic peptides activate Akt-signalling in a cGMP-dependent manner in hMADS adipocytes. Representative blots (A) and quantitative bar graphs of Akt Ser473 phosphorylation relative to total Akt (B), Akt Thr308 phosphorylation relative to total Akt (C), AS160 Thr642 phosphorylation relative to total AS160 (D), in response to 20 min and 60 min treatment with BNP 100 nM in absence or presence of (Rp)-8-pCPT-cGMPS 100 µM (PKG inhibitor, PKGi). *p < 0.05, **p < 0.01, ***p < 0.0001 vs. control (n = 6).

Figure 5. Natriuretic peptides activate mTOR-signalling in a cGMP-dependent manner in hMADS adipocytes. Representative blots (A) and quantitative bar graphs of mTOR Ser2448 phosphorylation relative to total mTOR (B), Raptor Ser792 phosphorylation relative to total Raptor (C), Rictor Thr1135 phosphorylation relative to total Rictor (D), in response to 20 min and 60 min treatment with BNP 100 nM in absence or presence of (Rp)-8-pCPT-cGMPS 100 µM (PKG inhibitor, PKGi). *p < 0.05, **p < 0.01, ***p < 0.0001 vs. control (n = 6).

Figure 6. Natriuretic peptides enhance glucose metabolism in human adipocytes. Effect of acute BNP 100 nM treatment on glucose oxidation (A), glucose incorporation into glycerol (B), and glucose incorporation into fatty acids (FA) (C) in hMADS adipocytes. (D) Effect of 100 nM BNP on glucose incorporation into FA in human isolated adipocytes. *p < 0.05 vs. control (n = 4–7). (E) Schematic model of NP-mediated glucose uptake in human adipocytes. Natriuretic peptides (NP) bind to a transmembrane receptor bearing a guanylyl cyclase activity called GC-A. Binding of NP to GC-A induces the production of cGMP and activation of cGK-I which activate Akt and mTORC2. Activation of mTORC2 phosphorylates Akt at Ser473 and enhances downstream signalling to the Rab-GTPase AS160 which promotes membrane GLUT4 translocation and glucose uptake. NP therefore promote glucose uptake and enhance glucose incorporation into glycerol and FA pools through de novo lipogenesis.