Targeting AMP Kinase in Myeloid Cells to Reduce Atherosclerosis

The SGLT2 inhibitor canagliflozin suppresses lipid synthesis and interleukin-1 beta in ApoE deficient mice

Sodium-glucose cotransporter 2 inhibitors such as canagliflozin lower blood glucose and reduce cardiovascular events in people with type 2 diabetes through mechanisms that are not fully understood. Canagliflozin has been shown to increase the activity of the AMP-activated protein kinase (AMPK), a metabolic energy sensor important for increasing fatty acid oxidation and energy expenditure and suppressing lipogenesis and inflammation, but whether AMPK activation is important for mediating some of the beneficial metabolic effects of canagliflozin has not been determined. We, therefore, evaluated the effects of canagliflozin in female ApoE-/- and ApoE-/-AMPK β1-/- mice fed a western diet. Canagliflozin increased fatty acid oxidation and energy expenditure and lowered adiposity, blood glucose and the respiratory exchange ratio independently of AMPK β1. Canagliflozin also suppressed liver lipid synthesis and the expression of ATP-citrate lyase, acetyl-CoA carboxylase and sterol response element-binding protein 1c independently of AMPK β1. Canagliflozin lowered circulating IL-1β and studies in bone marrow-derived macrophages indicated that in contrast with the metabolic adaptations, this effect required AMPK β1. Canagliflozin had no effect on the size of atherosclerotic plaques in either ApoE-/- and ApoE-/-AMPK β1-/- mice. Future studies investigating whether reductions in liver lipid synthesis and macrophage IL-1β are important for the cardioprotective effects of canagliflozin warrant further investigation.

Testosterone Increases the Expression and Phosphorylation of AMP Kinase α in Men With Hypogonadism and Type 2 Diabetes

CONTEXT

Adenosine 5'-monophosphate-activated protein kinase-α (AMPKα) is a mediator of exercise-induced glucose uptake in skeletal muscle.

OBJECTIVE

We evaluated whether AMPKα expression and phosphorylation are reduced in skeletal muscle and adipose tissue of patients with hypogonadotropic hypogonadism (HH), and whether testosterone replacement therapy results in restoration of the expression and phosphorylation of AMPKα.

DESIGN

This is a secondary analysis of a previously completed trial that showed an insulin-sensitizing effect of testosterone therapy in men with type 2 diabetes and HH.

SETTING

Clinical research center at university.

PATIENTS

Thirty-two men with HH and 32 eugonadal men were compared at baseline.

INTERVENTIONS

Men with HH were treated with intramuscular injections of testosterone or placebo every 2 weeks for 22 weeks. Quadriceps muscle biopsies and subcutaneous abdominal fat biopsies were obtained before and after 4-hour euglycemic hyperinsulinemic clamp, prior to and after testosterone or placebo therapy.

OUTCOME MEASURES AND RESULTS

mRNA expression of AMPKα in hypogonadal men was lower by 37% in adipose tissue and 29% in skeletal muscle, respectively, compared with levels in eugonadal men, while phosphorylated AMPKα was lower by 22% and 28%, respectively. Following testosterone replacement, the expression of AMPKα did not alter in the fasting state but increased markedly by 41% and 46% in adipose tissue and muscle, respectively, after the clamp. In contrast, phosphorylated AMPKα increased by 69% in muscle after testosterone therapy but did not change following the clamp.

CONCLUSIONS

Testosterone modulates the expression of AMPKα and phosphorylated AMPKα. These effects may contribute to the improved insulin sensitivity following testosterone therapy.