Receptor antibodies as novel therapeutics for diabetes

Antibodies to receptors can block or mimic hormone action. Taking advantage of receptor isoforms, co-receptors and other receptor modulating proteins, antibodies and other designer ligands can enhance tissue specificity and provide new approaches to the therapy of diabetes and other diseases

Differential effects of angiopoietin-like 4 in brain and muscle on regulation of lipoprotein lipase activity

Objective: Lipoprotein lipase (LPL) is a key regulator of circulating triglyceride rich lipoprotein hydrolysis. In brain LPL regulates appetite and energy expenditure. Angiopoietin-like 4 (Angptl4) is a secreted protein that inhibits LPL activity and, thereby, triglyceride metabolism, but the impact of Angptl4 on central lipid metabolism is unknown. Methods: We induced type 1 diabetes by streptozotocin (STZ) in whole-body Angptl4 knockout mice (Angptl4-/-) and their wildtype littermates to study the role of Angptl4 in central lipid metabolism. Results: In type 1 (streptozotocin, STZ) and type 2 (ob/ob) diabetic mice, there is a ~2-fold increase of Angptl4 in the hypothalamus and skeletal muscle. Intracerebroventricular insulin injection into STZ mice at levels which have no effect on plasma glucose restores Angptl4 expression in hypothalamus. Isolation of cells from the brain reveals that Angptl4 is produced in glia, whereas LPL is present in both glia and neurons. Consistent with the in vivo experiment, in vitro insulin treatment of glial cells causes a 50% reduction of Angptl4 and significantly increases LPL activity with no change in LPL expression. In Angptl4-/- mice, LPL activity in skeletal muscle is increased 3-fold, and this is further increased by STZ-induced diabetes. By contrast, Angptl4-/- mice show no significant difference in LPL activity in hypothalamus or brain independent of diabetic and nutritional status. Conclusion: Thus, Angptl4 in brain is produced in glia and regulated by insulin. However, in contrast to the periphery, central Angptl4 does not regulate LPL activity, but appears to participate in the metabolic crosstalk between glia and neurons

Receptor-isoform-selective insulin analogues give tissue-preferential effects

International audienceThe relative expression patterns of the two insulin receptor isoforms, +/- exon11 (IR-B/A respectively), are tissue dependent. Therefore we have developed insulin analogues with different binding affinities for the two isoforms, to test whether tissue-preferential biological effects can be attained. In rats and mice, IR-B is the most prominent isoform in liver (<95%) and fat (<90%), whereas in muscles IR-A is the dominant isoform (<95%). As a consequence, insulin analogue INS-A, which has a higher relative affinity for human IR-A, had a higher relative potency (compared to human insulin, HI) for glycogen synthesis in rat muscle strips (26%) than for glycogen accumulation in rat hepatocytes (5%) and for lipogenesis in rat adipocytes (4%). In contrast, the INS-B analogue, which has an increased affinity for human IR-B, had higher relative potencies (compared to HI) for inducing glycogen accumulation (75%) and lipogenesis (130%) than for affecting muscle (45%). For the same blood glucose lowering effect upon acute i.v. dosing to mice, INS-B gave a significantly higher degree of IR phosphorylation in liver than HI. These in vitro and in vivo results indicate that insulin analogues with IR isoform-preferential binding affinity are able to elicit tissue-selective biological responses, depending on the IR-A/B expression