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THE CENTRAL IMPORTANCE OF AMPK, AMPK AS A FUEL SENSOR,AMPK AS AN IMPORTANT TARGET FOR EXERCISE AND DIABETIC CONTROL DRUGS.

GROUP2 ,TEAM 4 JUNE 14,2016

2 OUTLINE

Definition of AMPK Central importance of AMPK Effect of AMPK on exercise AMPK as target for anti-diabetic drugs.

3AMPK

(5’ adenosine monophosphate-activated protein)

Also known activated protein kinase. Is a an enzyme that plays a role in cellular energy

homeostasis. It`s master metabolic regulator It is a trimeric protein formed from 3 subunits It has catalytic α & regulatory two β and three γ sub

units

4 Isoforms of AMPK

Each sub unit has its own iso-forms, with different tissue specificity

The a subunit has α1 & a2 isoforms The B subunit has β1&β2 isoforms The y sub unit has γ1, γ 2 , γ 3 isoforms The a2 β2 γ1 predominates in skeletal muscle whereas in liver

a1 β2 γ1 is abundant

5 AMPK structure

6 Contd…

The γ sub unit has 4 cystathionine beta synthase(CBS) domains which gives AMPK ability to detect the shift of AMP/ATP ratio

These 4 domains form two binding site for AMP During the binding of AMP, y-sub unit undergoes conformational

change exposing catalytic a sub unit AMPK is activated when phosphorylation take place at Threonine-172

by AMPKK

7 AMPK Found almost everywhere.

In organisms ranging from yeast to humans In a number of tissues like- liver, brain and

skeletal muscle.

8 CENTRAL IMPORTANCE OF AMPK

Acts a metabolic master switch regulator- maintaining energy homeostasis.

Acts a major cellular energy sensor, which can be attributed to it`s sensitivity to AMP/ATP ratio

Its activity increase when there ATP demand by cells

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AMPK AS A FUEL SENSOR Metabolic input to this sensor determine whether its

protein kinase activity take place.

When cellular energy levels are high, as signalled by high ATPS concentration ,AMPK becomes inactive.

When cellular energy levels are depleted, as signalled by high AMP concentration, AMPK becomes active.

10 Activation

AMPK is phosphorylated by at least 3 different AMPK kinases 1. by calmodulin-dependent kinase kinase (CaMkkB)2. Serine-threonine kinases,LKB13. Transforming growth factor-B

11 CONTD… Its activation by switch cells from active ATP consumption

pathways to active ATP production pathways. It inhibits of energy-consuming anabolic biosynthetic

pathways like Fatty acid and protein synthesis…… And activates of ATP-producing catabolic pathways like fat

acid and glucose oxidation. These rapid events are called short-term regulatory

processes but it also exerts long term effects at gene expression and protein synthesis

12 Glucose sensor in the hypothalamus

Hypothalamic AMPK activity is increased during fasting when AMP level is high and decreased during refeeding when the level of AMP lowers

AMPK activation leads to increased food intake

13 AMPK target key enzymes in energy production and consumption

Activation of AMPK leads to phosphorylation of many enzyme in energy metabolism.

AMPK effect on transcription factor also leads to diminished expression of genes encoding biosynthetic enzymes and elevated expression of catabolic genes.

Enzymes involved in energy production are phosphorylated and become activated so that they stimulate glycolysis.

e.g.PFK1

Enzymes involved in energy consumption are phosphorylated and become inactivated so that they inhibit glycogenesis.

e.g. Glycogen synthase, acetyl coA carboxylase etc..

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AMPK activity regulation is through direct activation by AMP (allosterically) Activation by other kinases (like upstream kinases) inhibition by protein phosphatases.

REGULATION OF AMPK

15 Central role of AMPK in regulation of metabolism

16 AMPK as target for exercise

AMPK is activated by any stress that increases in AMP/ATP.

This includes hypoxia, heart shock, exercises, and glucose deprivation.

The activation initiates signalling cascades that stimulate changes in glucose, fatty acid metabolism and gene expression.

17 Cont`d

Several groups have recently hypothesized that exercise increases glucose uptake via an insulin-independent mechanism mediated by the activation of AMP-activated protein kinase (AMPK)

18 Why is AMPK a target for antidiabetic drugs

1. improve glycemic control in T2D subjects because activation of AMPK when cellular energy is low provides an alternative pathway for the uptake of glucose.

2. AMPK activation can improve insulin sensitivity and metabolic health. Elevated glucose production by the liver is a major cause of fasting hyperglycemia in T2D and AMPK can control glucose production.

3. A common characteristic of T2D is high circulating lipid levels. In T2D patients insulin release is defective so AMPK can regulate lipolysis.

19 AMPK as target for exercise and diabetic drugs Type 2 diabetes is caused by Insulin resistance Defects of insulin secretion by β-cells. AMP-activated protein kinase (AMPK) is one of the probable target of major anti-

diabetic drugs, Metformin- Activated AMPK in hepatocytes. TZDs Salicylate Phenobarbital 2-DeoxyglucoseHormones insulin sensitizing adipokines (e.g., adiponectin). Leptin in skeletal muscle.

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METFORMIN(dimethyl biguanide) Is a derivative of biguanide found to be effective in lowering blood glucose in

animals. Its sister drug phenoformin(phenetylbiguanide). Its major effect is known to be reduction of high hepatic glucose production in type 2

diabetics Metformin inhibit complex I of the respiration chain, suggesting that it might activate

AMPK.

21 Thiazolidinedione(TZD)

Are representatives of another major class of anti-diabetic drug piogliglitazone rosiglitazone troglitazone Have direct target activation of AMPK They activate AMPK both by a hormonal (adiponectin dependent mechanism) and

by a cell autonomous (adiponectin independent mechanism)

22 2-Deoxyglucose(2-DG)

Taken up by a cell and converted to 2-deoxyglucose-6-phosphate by hexokinase which is not metabolized beyond that point.

It is inhibitor of glycolysis hence, it also activate AMPK in part by depleting ATP due to is rapid and uncontrolled phosphorylation by hexokinase.

It does not inhibit oxygen uptake.

23 Salicylate

Traditionally extracted from a willow bark. It is also produced by many plants as a hormone used in a defense

response triggered by infection by fungi and other pathogens. Acetyl Salicylate( ASA, trade name aspirin) is a derivative that is easier

to take orally than salicylate. ASA rapidly broken down to salicylate once it enters the circulation. Salicylate is not directly synthesized by humans.

24 Phenobarbital

It is a particularly effective inducer of cytochrome P450 enzymes that catalyze oxidation of hydrophobic drugs.

Induction of P450 enzyme by phenobarbital is mediated by AMPK. Activates AMPK , like biguanides and thiazolidinedione, because it is an

inhibitor of respiratory chain.

25 Hormones that ellict anti-diabetic effect.Leptin secreted by adipocytes Acts on the brain to regulate food intake and body weight. Leptin increases the AMP/ATP in skeletal muscle thus, activating AMPK.Adiponectin Secreted by adipose tissue. Circulates at high concentration in the plasma. Activates AMPK through signalling.

26 activated AMPK can induce food intake through its action in the hypothalamus but will likely be undesirable for pharmaceutical targeting of AMPK for the treatment of T2D and obesity.

27 References

AMPK signaling in metabolic regulation, ebook by yun Chau Long and Juleen R. Zierath

AMPK as a New Target for Antidiabetic Drugs, ebook by Arie Gruzman, Gali Babai, and Shlomo Sasson

en.wikipedia.org/wiki/AMP-activated_protein_kinase AMPK signaling:the fuel sensor and regulator pathway,

docs.abcam.com/pdf/cardiovascular/ampk_signaling.pdf AMPK: key sensor of fuel and energy status,

physiologyonline.physiology.org/content/21/1/48 

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