Glucose transport and glucose metabolism in diabetes and cancer Xiaozhuo Chen, October 8, 2015.

Glucose transport and glucose metabolism in diabetes and cancer

Xiaozhuo Chen, October 8, 2015

2008

Age-adjusted Percentage of U.S. Adults Who Were Obese or Who Had Diagnosed Diabetes

Obesity (BMI ≥30 kg/m2)

Diabetes

1994

1994

2000

2000

<14.0% 14.0-17.9% 18.0-21.9% 22.0-25.9% >26.0%

<4.5% 4.5-5.9% 6.0-7.4% 7.5-8.9% >9.0%

CDC’s Division of Diabetes Translation. National Diabetes Surveillance System available at http://www.cdc.gov/diabetes/statistics

2008

Center for Disease Control and Prevention (CDC) Predicts that about 1/3 of children born in 2000 in the US will develop type 2 diabetes.  

Predicted break-down statistics: Hispanics - females 53%, Hispanic males 45%, Blacks - females 49%, males 40%, Whites – females 31%, males 27%

Numbers of people with diabetes (in millions) for 2000 and 2010 (top and middle values, respectively), and the percentage increase.

Zimmet et al. Nature 414:782-787 (2001)

The prevalence of type 2 diabetes mellitus among Chinese in Hong Kong, Singapore, Taiwan and Mauritius, compared with that in the People's Republic of China6

Zimmet et al. Nature 414:782-787 (2001)

Moller D. Nature414:821-827 (2001)

Organs involved in glucose metabolism and in diabetes

Positive and negative regulations (signals) in glucose metabolism between tissues

Adipose (fat) tissue is now considered as an endocrine organ

Type 2 diabetes

Lingapa & Farley, Physiological Medicine, 2000

Type 2 diabetes

Comparison of normal glucose metabolism with glucose metabolism in diabetes

Why Insulin and Insulin Signaling Pathway are Needed?

Reality: Unpredictable cycle of feeding and then starvation that ensues between meals

Solution: Store nutrients in the forms that can be used as energy sources during periods of fasting – glucose, amino acids and fatty acids as nutrients, and glycogen, protein, and lipids as storage macromolecules

Insulin: Master hormone that regulates the energy homoestasis

Most potent anabolic hormone known

-Pancreatic Islet Cells are the Source of Insulin

-cells with insulin

-cells with glucagon

Pancreatic islet

How Relatively Stable Blood Glucose Concentration is Maintained ?

HepatocytesLiver

After a meal Before a meal

The idealized diagram shows the fluctuation of blood sugar (red) and the sugar-lowering hormone insulin (blue) in humans during the course of a day containing three meals. In addition, the effect of a sugar-rich versus a starch-rich meal is highlighted.

Fast actions

Slow actions

Insulin Actions

Human Proinsulin

Insulin undergoes extensive posttranslational modification along the production pathway. Production and secretion are largely independent; prepared insulin is stored awaiting secretion. Both C-peptide and mature insulin are biologically active. Cell components and proteins in this image are not to scale.

Computer-generated image of six insulin molecules assembled in a hexamer, highlighting the threefold symmetry, the zinc ions holding it together, and the histidine residues involved in zinc binding. Insulin is stored in the body as a hexamer, while the active form is the monomer.

Insulin release from pancreas oscillates with a period of 3–6 minutes

Structure of Insulin Receptor

Pierre De Meyts and Jonathan Whittaker

Insulin binding domain

Transmembranedomain

Intracellular tyrosine kinase domain

Insulin

P IRS

PI3K

Akt P

IR

Glut4

Insulin-mediated glucose transport signaling pathway

Glucose Uptake AssayInsulin

P IRS

PI3K

Akt P

IR

glucose

Insulin-mediated glucose transport signaling pathway

GLUT4 translocation

Insulin

P IRS

PI3K

Akt P

IR

Glut4

Insulin-mediated glucose transport signaling pathway

Glucose Uptake AssayInsulin

P IRS

PI3K

Akt P

IR

glucose

Insulin-mediated glucose transport signaling pathway

Insulin-mediated signaling pathwayInsulin

P IRS

PI3K

Akt P

IR

glucose

Glucose uptake assay

2 deoxy-D-[3H]-glucose

Glut4

Glucose transporters

Structural model of the major insulin-responsive glucose transporter GLUT4

Signal transduction in insulin action

Alternative (supplementary) glucose transport pathway

Current known insulin receptor mediated signaling pathways

Three steps that provide functional divergence for insulin signaling

PI-3 Kinase

1. Type 1A PI-3K in adipocytes

2. Heterodimer – p85 regulatory subunit and a p110 catalytic subunit

3. IRS1 and/or IRS2 bind PI-3K via SH-2 domain on p85, which then activates p110

4. 6 isoforms of p85 regulatory subunits – tissue specific expression

5. Function of PI-3K is to convert phosphotidylinositol 4,5-bisphosphate (PIP2) to PI 3,4,5-triphosphate (PIP3)

6. Activates three Ser/Thr kinases – Akt/PKB, atypical PKC isoforms and phosphoinositide-dependent kinases (PDK-1 and PDK-2)

Three steps that provide functional divergence for insulin signaling

Akt / PKB (Protein kinase B)

1. 3 isoforms, Akt-2 is most highly expressed in adipocytes

2. Phosphorylation and activation of Akt involve 3’ phosphoinositides and the action of PDK

3. Contains PH domain

4. The downstream targets of Akt/PTB have not been identified.

5. Required for insulin-mediated glucose transport

6. Involved in multiple other insulin responses

7. Represents an important mechanism for “cross-talk” between PI-3K pathway and other pathways regulating gene transcription and mitogenic effects.

Negative regulations of insulin signaling

What is Insulin Resistance?

1. Impaired insulin-mediated glucose uptake in peripheral cells

2. Impaired suppression of gluconeogenesis by the

liver

3. Impaired suppression of lipolysis in adipocytes

Summary

Insulin receptor (IR) is a pre-formed tetrameric transmembrane protein with two and two subunits linked by disulfide bonds.

Extracellular -subunits of IR form the insulin binding site and intracellular subunits possess tyrosine kinase activity

Insulin binding to the a subunits of IR triggers a conformational change in the subunits and activates the tyrosine kinase activity of the subunits. Each -subunit trans-phosphorylates Tyr residues on the other -subunit (autophosphorylation).

Activated IR phosphorylates insulin receptor substrate proteins (IRSs)

Summary II

Phosphorylated tyrosine on IRS serves as docking site for PI-3K, and moves PI-3K from cytosol to the inner side of plasma membrane

PI-3K converts PIP2 into PIP3 by phosphorylation

PIP3 moves Akt (PKB) next to membrane bound protein kinases and protein kinases phosphorylates and activates Akt

Akt indirectly activates GLUT4, inducing the translocation of GLUT4 from cytoplasm to the plasma membrane and triggering transport of glucose into the adipocyte (also muscle) cells

Summary III (Common themes in signal transduction)

Tyrosine kinase receptors for most growth factors

Docking (often SH2 domain to phosphorylated Tyr) for protein-protein interaction near receptor

Multiple protein factors (often kinases) for signal amplification and potential crosstalk with other regulatory pathways

May have alternative pathway(s) for further fine tuning for the signal

Signal inhibitors and attenuators such as phosphatases and/or serine/threonine kinases coexist with activators

Temporal and spatial regulation of signal

II. Glucose transport and glucose metabolism in cancer

Positron Emission Tomography (PET) Scan

Esophageal cancer

Tracer: Glucose analogue – 18F-fluorodeoxyglucose

Hallmarks of cancer 2000

Oncogenic signaling

Loss of tumor suppression

Invasion and metastasis

Telomere and telomerase

New blood vessel formation

Resistance of apoptosis

Cell 2000; 100:57-70.

Hallmarks of cancer - 2010

Immuno-evasion

Inflammation

Cancer metabolism

Cancer genomics

Cell 2011;144:646-74

http://en.wikipedia.org/wiki/Positron_emission_tomographyhttp://en.wikipedia.org/wiki/File:PET-MIPS-anim.gifhttp://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=4237470

(18)F-FDG ((18)F-fluoro-2-deoxyglucose) uptake on positron emission tomography (PET)

More than 90% of all cancers show increased glucose uptake and glucose metabolism

Liver metastases of a colorectal tumor

Used for diagnosis, prognosis

Glucose metabolism and the Warburg effect

Warburg effect – Upregulated aerobic glycolysis and lactate production even in the presence of O2 in cancer cells.

Gatenby, et al. Nat. Rev. Cancer 2004; 4, 891-899.

Otto H. Warburg

German Biochemist

(1883-1970)http://www.nobelprize.org/nobel_prizes/medicine/laureates/1931/#

O2

O2

Nature Reviews Cancer 4, 891-899, 2004

Glucose metabolism and the Warburg effect

Warburg effect – Upregulated aerobic glycolysis and lactate production even in the presence of O2 in cancer cells.

Tumor cell

Normal cell

Molecular mechanisms driving the Warburg effect.

Cairns, et al., Nat. Rev. Cancer 11, 85-89 (2011).

ATP synthesis under normoxia and hypoxia conditions

What are the purposes of the Warburg effect?

1.For ATP synthesis? (Is there a shortage of ATP in cancer?)

2.For biosynthesis of other important biomass?

3.For ROS?

Cancer Metabolism: pathways and regulators

Science 324, 1029 (2009)

Therapeutic Targeting of Hallmarks of Cancer

Hanahan and Weinberg. Cell 144, 646-674 (2011).

Study guide

1.Insulin signaling pathway – key protein factors in the pathway

2. How and where is Insulin produced and how its secretion regulated?

3.How insulin induces Glut4 translocation and glucose transport?

4.Type 2 diabetes and insulin resistance

5.Glucose transporters relevant to cancer (Glut1 – 3)

6.What is the Warburg effect?

7.How the Warburg effect regulated?

8.How to inhibit the Warburg effect to block cancer growth?

The Glucose Transporter Gene Family

Glucose

Glut1 inhibitor

?Out

In

Inhibitors targeting glucose metabolism

Modified from Oncogene (2006) 25, 4633–4646

mitochondrion

Cell membrane

D