AZD7545, a novel inhibitor of pyruvate dehydrogenase kinase 2 (PDHK2), activates pyruvate dehydrogenase in vivo and improves blood glucose control in obese (fa/fa) Zucker rats

PDH (pyruvate dehydrogenase) is a key enzyme controlling the rate of glucose oxidation, and the availability of gluconeogenic precursors. Activation of PDH in skeletal muscle and liver may increase glucose uptake and reduce glucose production. This study describes the properties of AZD7545, a novel, small-molecule inhibitor of PDHK (PDH kinase). In the presence of PDHK2, AZD7545 increased PDH activity with an EC50 value of 5.2 nM. In rat hepatocytes, the rate of pyruvate oxidation was stimulated 2-fold (EC50 105 nM). A single dose of AZD7545 to Wistar rats increased the proportion of liver PDH in its active, dephosphorylated form in a dose-related manner from 24.7 to 70.3% at 30 mg/kg; and in skeletal muscle from 21.1 to 53.3%. A single dose of 10 mg/kg also significantly elevated muscle PDH activity in obese Zucker (fa/fa) rats. Obese, insulin-resistant, Zucker rats show elevated postprandial glucose levels compared with their lean counterparts (8.7 versus 6.1 mM at 12 weeks old). AZD7545 (10 mg/kg) twice daily for 7 days markedly improved the 24-h glucose profile, by eliminating the postprandial elevation in blood glucose. These results suggest that PDHK inhibitors may be beneficial agents for improving glucose control in the treatment of type 2 diabetes.

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PDH kinase inhibitors: a novel therapy for Type II diabetes?

Biochemical Society Transactions ◽

10.1042/bst0330367 ◽

2005 ◽

Vol 33 (2) ◽

pp. 367-370 ◽

Cited By ~ 58

Author(s):

R.M. Mayers ◽

B. Leighton ◽

E. Kilgour

Keyword(s):

Pyruvate Dehydrogenase ◽

Type Ii Diabetes ◽

Kinase Inhibitors ◽

Pyruvate Dehydrogenase Kinase ◽

Zucker Rats ◽

Oxidative Decarboxylation ◽

Type Ii ◽

Novel Therapy ◽

Specific Expression

The pyruvate dehydrogenase multienzyme complex catalyses the oxidative decarboxylation of pyruvate, which is an important regulatory step in oxidative metabolism. Phosphorylation of the E1 (pyruvate decarboxylase) subunit on one of three specific serine residues results in loss of enzyme activity. Four dedicated PDHK (pyruvate dehydrogenase kinase) isoenzymes have been identified, each of which display a distinct tissue-specific expression profile, and have differential regulatory properties. Thus PDHK play a key role in controlling the balance between glucose and lipid oxidation according to substrate supply. Increasing glucose oxidation by inhibiting PDHK may be an effective mechanism to increase glucose utilization; additionally, increasing pyruvate oxidation may further contribute to lowering of glucose level by decreasing the supply of gluconeogenic substrates. A number of PDHK inhibitors are now available to enable this mechanism to be evaluated as a therapy for diabetes. The isoenzyme selectivity profile of AZD7545 and related compounds will be described and evidence for their non-ATP-competitive mode of action presented. These compounds increase PDH activity in vivo, and when dosed chronically, improve glycaemic control in Zucker rats. Furthermore, glucose lowering has been demonstrated in the hyperglycaemic Zucker diabetic fatty rat. This result supports the hypothesis that inhibition of PDHK may be an effective therapy for Type II diabetes.

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Pyruvate dehydrogenase kinase-4 deficiency lowers blood glucose and improves glucose tolerance in diet-induced obese mice

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00536.2007 ◽

2008 ◽

Vol 295 (1) ◽

pp. E46-E54 ◽

Cited By ~ 105

Author(s):

Nam Ho Jeoung ◽

Robert A. Harris

Keyword(s):

Skeletal Muscle ◽

Blood Glucose ◽

Glucose Tolerance ◽

Pyruvate Dehydrogenase ◽

High Fat Diet ◽

Pyruvate Dehydrogenase Kinase ◽

Wild Type ◽

High Fat ◽

Pyruvate Dehydrogenase Kinase 4 ◽

Liver And Kidney

The effect of pyruvate dehydrogenase kinase-4 (PDK4) deficiency on glucose homeostasis was studied in mice fed a high-fat diet. Expression of PDK4 was greatly increased in skeletal muscle and diaphragm but not liver and kidney of wild-type mice fed the high-fat diet. Wild-type and PDK4−/− mice consumed similar amounts of the diet and became equally obese. Insulin resistance developed in both groups. Nevertheless, fasting blood glucose levels were lower, glucose tolerance was slightly improved, and insulin sensitivity was slightly greater in the PDK4−/− mice compared with wild-type mice. When the mice were killed in the fed state, the actual activity of the pyruvate dehydrogenase complex (PDC) was higher in the skeletal muscle and diaphragm but not in the liver and kidney of PDK4−/− mice compared with wild-type mice. When the mice were killed after overnight fasting, the actual PDC activity was higher only in the kidney of PDK4−/− mice compared with wild-type mice. The concentrations of gluconeogenic substrates were lower in the blood of PDK4−/− mice compared with wild-type mice, consistent with reduced formation in peripheral tissues. Diaphragms isolated from PDK4−/− mice oxidized glucose faster and fatty acids slower than diaphragms from wild-type mice. Fatty acid oxidation inhibited glucose oxidation by diaphragms from wild-type but not PDK4−/− mice. NEFA, ketone bodies, and branched-chain amino acids were elevated more in PDK4−/− mice, consistent with slower rates of oxidation. These findings show that PDK4 deficiency lowers blood glucose and slightly improves glucose tolerance and insulin sensitivity in mice with diet-induced obesity.

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Up-regulation of pyruvate dehydrogenase kinase isoform 4 (PDK4) protein expression in oxidative skeletal muscle does not require the obligatory participation of peroxisome-proliferator-activated receptor α (PPARα)

Biochemical Journal ◽

10.1042/bj20020754 ◽

2002 ◽

Vol 366 (3) ◽

pp. 839-846 ◽

Cited By ~ 32

Author(s):

Mark J. HOLNESS ◽

Karen BULMER ◽

Geoffrey F. GIBBONS ◽

Mary C. SUGDEN

Keyword(s):

Skeletal Muscle ◽

Protein Expression ◽

Pyruvate Dehydrogenase ◽

Skeletal Muscles ◽

Pyruvate Dehydrogenase Kinase ◽

Glucose Disposal ◽

Peroxisome Proliferator ◽

Peroxisome Proliferator Activated Receptor ◽

Anterior Tibialis

In insulin deficiency, increased lipid delivery and oxidation suppress skeletal-muscle glucose oxidation by inhibiting pyruvate dehydrogenase complex (PDC) activity via enhanced protein expression of pyruvate dehydrogenase kinase (PDK) isoform 4, which phosphorylates (and inactivates) PDC. Signalling via peroxisome-proliferator-activated receptor α (PPARα) is an important component of the mechanism enhancing hepatic and renal PDK4 protein expression. Activation of PPARα in gastrocnemius, a predominantly fast glycolytic (FG) muscle, also increases PDK4 expression, an effect that, if extended to all muscles, would be predicted to drastically restrict whole-body glucose disposal. Paradoxically, chronic activation of PPARα by WY14,643 treatment improves glucose utilization by muscles of insulin-resistant high-fat-fed rats. In the resting state, oxidative skeletal muscles are quantitatively more important for glucose disposal than FG muscles. We evaluated the participation of PPARα in regulating PDK4 protein expression in slow oxidative (SO) skeletal muscle (soleus) and fast oxidative-glycolytic (FOG) skeletal muscle (anterior tibialis) containing a high proportion of oxidative fibres. In the fed state, acute (24h) activation of PPARα by WY14,643 in vivo failed to modify PDK4 protein expression in soleus, but modestly enhanced PDK4 protein expression in anterior tibialis. Starvation enhanced PDK4 protein expression in both muscles, with the greater response in anterior tibialis. WY14,643 treatment in vivo during starvation did not further enhance upregulation of PDK4 protein expression in either muscle type. Enhanced PDK4 protein expression after starvation was retained in SO and FOG skeletal muscles of PPARα-deficient mice. Our data indicate that PDK4 protein expression in oxidative skeletal muscle is regulated by a lipid-dependent mechanism that is not obligatorily dependent on signalling via PPARα.

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Artificial Pancreas: from in-silico to in-vivo∗∗This work was supported by the Fondo per gli Investimenti della Ricerca di Base project Artificial Pancreas: In Silico Development and In Vivo Validation of Algorithms for Blood Glucose Control funded by Italian Ministero dell'Istruzione, dell'Universitä e della Ricerca.

IFAC-PapersOnLine ◽

10.1016/j.ifacol.2015.09.148 ◽

2015 ◽

Vol 48 (8) ◽

pp. 1300-1308 ◽

Cited By ~ 5

Author(s):

M. Messori ◽

C. Cobelli ◽

L. Magni

Keyword(s):

Blood Glucose ◽

Glucose Control ◽

In Silico ◽

Artificial Pancreas ◽

Blood Glucose Control ◽

In Vivo Validation

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Increased skeletal muscle glucose uptake by rosemary extract through AMPK activation

Applied Physiology Nutrition and Metabolism ◽

10.1139/apnm-2014-0430 ◽

2015 ◽

Vol 40 (4) ◽

pp. 407-413 ◽

Cited By ~ 21

Author(s):

Madina Naimi ◽

Theodoros Tsakiridis ◽

Theocharis C. Stamatatos ◽

Dimitris I. Alexandropoulos ◽

Evangelia Tsiani

Keyword(s):

Skeletal Muscle ◽

Blood Glucose ◽

Glucose Uptake ◽

Glucose Transporter ◽

Rosemary Extract ◽

Dependent Manner ◽

Ampk Activation ◽

Compound C ◽

Increase Glucose Uptake

Stimulation of the energy sensor AMP-activated kinase (AMPK) has been viewed as a targeted approach to increase glucose uptake by skeletal muscle and control blood glucose homeostasis. Rosemary extract (RE) has been reported to activate AMPK in hepatocytes and reduce blood glucose levels in vivo but its effects on skeletal muscle are not known. In the present study, we examined the effects of RE and the mechanism of regulation of glucose uptake in muscle cells. RE stimulated glucose uptake in L6 myotubes in a dose- and time-dependent manner. Maximum stimulation was seen with 5 μg/mL of RE for 4 h (184% ± 5.07% of control, p < 0.001), a response comparable to maximum insulin (207% ± 5.26%, p < 0.001) and metformin (216% ± 8.77%, p < 0.001) stimulation. RE did not affect insulin receptor substrate 1 and Akt phosphorylation but significantly increased AMPK and acetyl-CoA carboxylase phosphorylation. Furthermore, the RE-stimulated glucose uptake was significantly reduced by the AMPK inhibitor compound C, but remained unchanged by the PI3K inhibitor, wortmannin. RE did not affect GLUT4 or GLUT1 glucose transporter translocation in contrast with a significant translocation of both transporters seen with insulin or metformin treatment. Our study is the first to show a direct effect of RE on muscle cell glucose uptake by a mechanism that involves AMPK activation.

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