Non-peptidyl small molecule, adenosine, 5′-Se-methyl-5′-seleno-, 2′,3′-diacetate, activates insulin receptor and attenuates hyperglycemia in type 2 diabetic Leprdb/db mice

Abstract

The pathophysiology of type 2 diabetes mellitus (T2D) is characterized by reduced or absent insulin receptor (INSR) responsiveness to its ligand, elevated hepatic glucose output and impaired glucose uptake in peripheral tissues, particularly skeletal muscle. Treatments to reduce hyperglycemia and reestablish normal insulin signaling are much sought after. Any agent which could be orally administered to restore INSR function, in an insulin-independent manner, would have major implications for the management of this global disease. We have discovered a non-peptidyl small molecule, adenosine, 5′-Se-methyl-5′seleno-, 2′,3′-diacetate [referred to as non-peptidyl compound #43 (NPC43)], which restores INSR signaling in the complete absence of insulin. Initial screening of numerous compounds in human HepG2 liver cells revealed that NPC43 significantly inhibited glucose production. The compound was potently anti-hyperglycemic and anti-hyperinsulinemic in vivo, in insulin-resistant T2D Lepr db/db mice, following either acute or chronic treatment by oral gavage and intraperitoneal injection, respectively. The compound acted at the level of INSR and activated it in both liver and skeletal muscle of Lepr db/db mice. In cell culture, the compound activated INSR in both liver and skeletal muscle cells; furthermore, it cooperated with insulin to depress glucose-6-phosphatase catalytic subunit (G6pc) expression and stimulate glucose uptake, respectively. Our results indicated that the compound directly interacted with INSRα, triggering appropriate phosphorylation and activation of the receptor and its downstream targets. Unlike insulin, NPC43 did not activate insulin-like growth factor 1 receptor in either liver or skeletal muscle. We believe this compound represents a potential oral and/or injectable insulin replacement therapy for diabetes and diseases associated with insulin resistance.

Oral administration of NPC43 counters hyperglycemia and activates insulin receptor in streptozotocin-induced type 1 diabetic mice

“…However, it should also be pointed out that we previously have demonstrated that NPC43 inhibits hepatic gluconeogenesis in T2D mice, through Insr/Akt activation and G6pc suppression. 8 In the present study, we again observed NPC43driven Insr/Akt activation in the liver (figures 4-5) and so would surmise that suppressed gluconeogenesis may contribute to reducing blood glucose in T1D also.…”

“…9 In brief, STZ (Cat #S0130, Sigma-Aldrich, St Louis, Missouri) was dissolved in 0.05 M sodium citrate buffer and intraperitoneally injected into male C57BL/6J mice (4-5 weeks old) at a dose of 55 mg/ kg body weight (mpk) daily for 5 days. After STZ injection, these mice were housed in the pathogenfree vivarium for 14-48 days and blood glucose levels were measured using a glucometer as described in Lan et al 8 Serum insulin levels in these mice at 48 days post-intraperitoneal STZ treatment were also determined using Thermo Fisher Scientific's Mouse Insulin ELISA-Kit (Cat #EMINS), according to the manufacturer's protocol.…”

“…Blood glucose levels in each mouse before oral gavage (0 time point) and post-treatment (at 1-5 hour time points) were determined using a glucometer as described previously. 8 The change in blood glucose level in individual mice was obtained by subtracting the glucose level right before oral gavage from the blood glucose level at each time-period after oral gavage.…”

“…At 1, 2 and 3 hours post-NPC43 injection, blood glucose levels in these mice, which had free access to water but not chow, were measured as described previously. 8 Western blot analysis Forty-eight days post-STZ induction, liver tissue was collected for protein analysis from saline-treated and NPC43-treated mice, 3 hours after oral administration. Separately, STZ-induced T1D mice at 48 days post-STZ treatment were also fasted for 2 hours and orally administered with saline or NPC43 (5.4 mpk) for 5 min prior to harvesting skeletal muscle (gastrocnemius).…”

“…NPC43 also cooperates with insulin to stimulate skeletal muscle glucose uptake and attenuates hepatic G6pc-driven gluconeogenesis. 8 Therefore, it is important to establish if NPC43 can similarly activate INSR and ameliorate hyperglycemia in T1D. In this report, streptozotocin (STZ)-induced T1D mice were administered NPC43 orally and intraperitoneally.…”