Treatment with a \u03b2-2-adrenoceptor agonist stimulates glucose uptake in skeletal muscle and improves glucose homeostasis, insulin resistance and hepatic steatosis in mice with diet-induced obesity

Anastasia Kalinovich,Carina Halleskog,Joris Hoeks,Sten Van Beek,Tore Bengtsson,Claes-Göran Östenson,Alice Åslund,Mia Rinde,Anna Sandström,Jessica Olsen,Nodi Dehvari,Elisabete Forsberg,Gert Schaart,Evelyn Zacharewicz,Roger Berlin

doi:10.1007/s00125-020-05171-y

Abstract

Aims/hypothesisChronic stimulation of β2-adrenoceptors, opposite to acute treatment, was reported to reduce blood glucose levels, as well as to improve glucose and insulin tolerance in rodent models of diabetes by essentially unknown mechanisms. We recently described a novel pathway that mediates glucose uptake in skeletal muscle cells via stimulation of β2-adrenoceptors. In the current study we further explored the potential therapeutic relevance of β2-adrenoceptor stimulation to improve glucose homeostasis and the mechanisms responsible for the effect.MethodsC57Bl/6N mice with diet-induced obesity were treated both acutely and for up to 42 days with a wide range of clenbuterol dosages and treatment durations. Glucose homeostasis was assessed by glucose tolerance test. We also measured in vivo glucose uptake in skeletal muscle, insulin sensitivity by insulin tolerance test, plasma insulin levels, hepatic lipids and glycogen.ResultsConsistent with previous findings, acute clenbuterol administration increased blood glucose and insulin levels. However, already after 4 days of treatment, beneficial effects of clenbuterol were manifested in glucose homeostasis (32% improvement of glucose tolerance after 4 days of treatment, p < 0.01) and these effects persisted up to 42 days of treatment. These favourable metabolic effects could be achieved with doses as low as 0.025 mg kg−1 day−1 (40 times lower than previously studied). Mechanistically, these effects were not due to increased insulin levels, but clenbuterol enhanced glucose uptake in skeletal muscle in vivo both acutely in lean mice (by 64%, p < 0.001) as well as during chronic treatment in diet-induced obese mice (by 74%, p < 0.001). Notably, prolonged treatment with low-dose clenbuterol improved whole-body insulin sensitivity (glucose disposal rate after insulin injection increased up to 1.38 ± 0.31%/min in comparison with 0.15 ± 0.36%/min in control mice, p < 0.05) and drastically reduced hepatic steatosis (by 40%, p < 0.01) and glycogen (by 23%, p < 0.05).Conclusions/interpretationClenbuterol improved glucose tolerance after 4 days of treatment and these effects were maintained for up to 42 days. Effects were achieved with doses in a clinically relevant microgram range. Mechanistically, prolonged treatment with a low dose of clenbuterol improved glucose homeostasis in insulin resistant mice, most likely by stimulating glucose uptake in skeletal muscle and improving whole-body insulin sensitivity as well as by reducing hepatic lipids and glycogen. We conclude that selective β2-adrenergic agonists might be an attractive potential treatment for type 2 diabetes. This remains to be confirmed in humans.Graphical abstract

Highlights

Type 2 diabetes mellitus is characterised by impaired glucose homeostasis resulting from insulin resistance in peripheral tissues, such as liver and skeletal muscle, as well as from relative impairments in insulin release by pancreatic β-cells
Beneficial effects of clenbuterol on glucose tolerance occur after 4 days of treatment and persist for a prolonged period of time Previously, we have shown significant increases in glucose uptake in L6 myotubes upon acute incubation with the β2-adrenergic agonist clenbuterol [2]
To confirm and elaborate on these results, we demonstrated that acute clenbuterol-mediated glucose uptake in L6 cells occurs in a dose-dependent manner, with doses as low as 10−8 mol/l significantly enhancing glucose uptake by 42% (p < 0.01, Fig. 1a)

Summary

Introduction

Type 2 diabetes mellitus is characterised by impaired glucose homeostasis resulting from insulin resistance in peripheral tissues, such as liver and skeletal muscle, as well as from relative impairments in insulin release by pancreatic β-cells. We and others have shown that β2-AR stimulation, using a relatively high dosage of the β2-AR agonist clenbuterol, improved glucose tolerance in diet-induced obese (DIO) mice [2], Goto–Kakizaki rats [2] and Zucker fatty rats [4]—wellestablished rodent models for human type 2 diabetes. In line with these data, β2-AR-ablation resulted in hyperglycaemia in mice [5, 6]

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Results

Conclusion