Table 1.
Profile changes in dogs (n = 9) maintained on a hypercaloric high-fat diet for 22 weeks.
Fig 1.
Metabolic changes in dogs maintained on a hypercaloric high-fat diet for 22 weeks.
(A) Magnetic resonance scanning shows a substantial increase of fat content in the abdominal region after prolonged fat feeding. (B) Relationship between fasting plasma anandamide and insulin or C-peptide (C) Relationship between fasting plasma 2-AG and insulin or C-peptide. Association was determined using Spearman correlation. Lines represent non-linear (second-order polynomial) fit of the plots.
Fig 2.
Supraphysiologic concentrations of anandamide enhance in vitro insulin secretion.
(A) Anandamide stimulates basal insulin secretion in control-diet (n = 7) and high-fat diet (HFD) animals (n = 6) at 3 mmol/L glucose (3G). (B) Anandamide also potentiates glucose-stimulated insulin secretion in both groups at 15 mmol/L glucose (15G). Islets were incubated with anandamide or CB1R antagonist rimonabant (R) at 10 μmol/L for 1 h. Experiments on every animal were done in quadruplicate. Data are mean±S.E.M. (C) At the doses tested to stimulate insulin secretion, anandamide did not impair islet viability. Green and red colors represent viable and non-viable cells, respectively. Staining of islet batches from a same animal is representative of 3 independent experiments. Note the complete loss of islet viability (red stain) at 1000 μmol/L, consistent with a massive release of insulin as measured by ELISA (data not shown). Total magnification: 100X. (D) Relative mRNA expression of CB1R, CB2R, and TRPV1 to 18S in intact islets from control (n = 4) and HFD animals (n = 6–7).
Fig 3.
Physiological concentrations of anandamide enhance in vitro insulin secretion.
(A) In islets from control-diet dogs (n = 7), anandamide significantly increased basal insulin secretion at 3 mmol/L glucose (3G) and GSIS at 15 mmol/L glucose (15G). Islets were incubated for 1 h with either anandamide (10 nmol/L) or cannabinoid receptor antagonists (100 nmol/L), as indicated. CB1R, CB2R, and TRPV1 antagonists rimonabant (R), AM630, and iodoresiniferatoxin (IRTX), respectively, were added prior to stimulation with high glucose and anandamide. Plots indicate the mean of 3–9 replicates for each dog. (B) When tested alone, none of the antagonist drugs had effect on islet viability compared with vehicle (n = 3). Total magnification: 100X. (C) Islets were continuously perifused with glucose 3 mmol/L and challenged with 15 mmol/L glucose (15G) from t = 0, as shown with the horizontal bar, in presence (n = 3) or absence (n = 3) of anandamide (10 nmol/L). Anandamide perifusion started concomitant with 15G, as indicated by the arrow. Plots of perifusion experiments represent means; bars represent S.E.M. P value represent the difference in overall profile between treatment and control during the second phase (t = 9–36 min). Analysis was performed using mixed-model linear regression to account for repeated measures.
Fig 4.
Anandamide significantly enhances insulin and glucagon secretion.
Insulin, glucagon, and somatostatin concentrations were measured in batches of 100 islets from control-diet animals (n = 7) during static incubation with anandamide 10 μmol/L for 1 h. 3G, 3 mmol/L; 15G, 15 mmol/L glucose. Data are mean±S.E.M.