The document discusses endoplasmic reticulum (ER) stress in diabetic complications. It begins by providing background on diabetes and the role of the ER. The ER is responsible for protein folding, modification and transport. Under stress, misfolded proteins accumulate and activate the unfolded protein response (UPR) pathway involving IRE1, PERK and ATF6. Persistent ER stress can lead to apoptosis and organ dysfunction. Conditions like diabetes with high protein load and misfolding in the pancreas and other tissues cause ER stress. Targeting ER stress pathways may provide novel treatment strategies for diabetes and related complications.

1. National Institute of Pharmaceutical Education and Research, Hyderabad
1
ENDOPLASMIC RETICULUM STRESS IN
DIABETIC COMPLICATIONS

3. Diabetes is among the most occurring metabolic disorders.
Insulin injection other therapy have been established.
Need of more cellular targets
ER stress have link with other organ dysfunction
Targeting ER stress is among the upcoming novel targets for
diabetic therapy
Non communicable diseases deaths are projected to increase by
15% globally between 2010 and 2020.

4. Transportation of proteins and other
carbohydrates to another organelle
Manage enzymatic processes
Various post-translational
modifications, including glycosylation
and disulphide bond formation
Secretory proteins folding,
modification, and assembling into
multiprotein complexes
Vital role in the synthesis of proteins,
lipids, glycogen and steroids.
Meusser B, Hirsch C, Jarosch E, Sommer T. 2011. ERAD & autophagy: the long road to destruction. Nat. Cell Biol. 7:766–72

5.  ERAD(ER-associated degradation):
Sometimes protein-folding machines fraction of secretory
proteins normally fails to fold properly in the ER
Secretory proteins have crucial signalling roles ( cell surface
receptors or polypeptide hormones)
Incompletely folded forms are not tolerated
Unfolded proteins are removed to the cytosol for subsequent
ubiquitination and degradation by the 26S proteasome

6. Autophagy
Another mechanism for disposing unfolded secretory proteins.
Under normal condition normal proteins are secreted.
Depletion of SPP1 and increased intracellular S1P triggers ER
stress and the UPR by activation of ATF6, IRE1α, and PERK,
resulting in autophagy.
PERK signaling also activates Akt, which protect cells from
apoptosis
Meusser B, Hirsch C, Jarosch E, Sommer T. 2011. ERAD & autophagy: the long road to destruction. Nat. Cell Biol. 7:766–72

7. Conditions whereby cell encounter environmental challenges
during which protein-folding demand in the ER exceeds capacity.
Imbalanced state of secretory proteins
Secretory proteins start to accumulate in incompletely modified
and unfolded forms at high levels within the ER.
Mutant forms of secretory proteins causes overproduction of
secretory proteins itself generate ER stress

8.  Involves four distinct processes:
Increase in the protein folding capacity through transcriptional
induction of ER chaperones
Reduction of the biosynthetic load by translational attenuation
Degradation of the misfolded proteins by ERAD
Apoptosis, at last to eliminate infected cells and maintain
homeostasis.

9. Translational
attenuation
Translational
attenuation
Degradation
by ERAD
Degradation
by ERAD
Apoptosis
Unfolded Protein
Transcriptional
activation(Chaperones)
Transcriptional
activation(Chaperones)
Ron D, Walter P. 2007. Signal integration in the endoplasmic reticulum unfolded protein response. Nat. Rev. Mol. Cell Biol. 8:519–
29

10. UPR:(unfolded protein response)
The presence of unfolded proteins in the ER during stress triggers
a set of intracellular signalling pathways.
Alert to cell for UPR
Protein kinase RNA (PKR)-like ER kinase (PERK)
Activating transcription factor-6 (ATF6)
Inositol-requiring enzyme-1 (IRE1a)

11. IRE1IRE1
bZIPbZIP
PERKPERK
Cell fate outcomeCell fate outcome
KinaseKinase
ER LUMEN
KinaseKinase
ATF6
T. Kudo, S. Kanemoto, H. Hara et al., “A molecular chaperone inducer protects neurons from ER stress,” Cell Death
Differentiation, vol. 15, no. 2, pp. 364–375, 2008.
ER stress

12. Three signalling proteins become activated through direct or indirect
binding of unfolded proteins
Signals from IRE1a, PERK, and ATF6 initially trigger transcriptional
programs .
Activation of ER chaperones, oxidoreductases, and ERAD components.
By increasing the complement of ER protein-folding and quality control
enzymes, the UPR enhances the cell’s capacity.
Allow pre existing proteins to fold before new ones are made.
Successful UPR restores homeostasis managing cell ER stress.

13. Condition whereby ER stress persists at high levels, the UPR
promotes programmed cell death, usually through
apoptosis.
Vigorous apoptopic process results into organ failure
Caused by an insufficient mass of functioning cells.
Degeneration of insulin-producing pancreatic islet β cells
causes diabetes.

14. Endoplasmic Reticulum Stress and Type 2 Diabetes Sung Hoon Back and Randal J. Kaufman Reviews in Advance,12
March,2014, 16.2-16.19

15. 25% of cellular ROS originates from the ER through the process of
oxidative protein folding.
Acts through protein disulfide isomerases (PDIs)
The ERO1 oxido-reductase transfers electrons from cysteine
sulfhydryl groups on ER-translocated proteins to molecular
oxygen, generating H2O2 as an ROS by product.
The b-cell ER needs to produce three disulfides for each molecule
of pro-insulin it synthesizes(i.e., 3 million disulfides/min per cell).
A large load of ROS is necessarily produced that needs to be
continually disposed of

16. D. Ron and P. Walter, “Signal integration in the endoplasmic reticulum unfolded protein response,” Nature Reviews Molecular
Cell Biology, vol. 8, no. 7, pp. 519–529, 2007

17. Diabetes-hyperglycemia and hyperlipidemiaDiabetes-hyperglycemia and hyperlipidemia
Altered cardiac
metabolism &
lipotoxicity
Altered cardiac
metabolism &
lipotoxicity
inflammationinflammation
Plasma glucose
level
Plasma glucose
level
FFAFFA
AutophagyAutophagy Insulin resistance
ApoptosisApoptosis
ER STRESS
Cardiac myopathy
T. Minamino and M. Kitakaze, “ER stress in cardiovascular disease,” Journal of Molecular and Cellular Cardiology, vol. 48, no. 6, pp.
1105–1110, 2010

18. ER STRESSER STRESS
Apoptopic β cellApoptopic β cell
Inflammatory responses(IFN ,IL 1β)
Nitric oxide
ATF3
SERCA 2b
CHOP
D. Ron and P. Walter, “Signal integration in the endoplasmic reticulum unfolded protein response,” Nature Reviews
Molecular Cell Biology, vol. 8, no. 7, pp. 519–529, 2007

19. ERER
STRESSSTRESS
ApoptopicApoptopic
β cell
ApoptopicApoptopic
β cell
FFA hyperinsulinimia
Insulin resistance
IRE1
p-junk CHOP p-akt
p-GSK-3β
Serine
p IRS-1
Kahn SE, Hull RL, Utzschneider KM. 2006. Mechanisms linking obesity toinsulin resistance and type
2 diabetes. Nature 444:840–46

20. β cells contain highly developed ER
Each β cell produces approximately 1million molecules of
insulin every minute
Complex series of molecular biosynthetic processes
The insulin precursors prepro-insulin( translocated into the ER
lumen )

21. Signal sequence is removed
Oxido-reductases
Insulin precursor Pre pro-insulin ( translocated into the ER lumen )
Formation of three intramolecular disulfides
Pro-insulin folds( native state in the ER)
Trafficking to downstream Golgi and secretory granules
endoproteases.
Removal of C-peptide
Generation of mature insulin
Pro-insulin

24. Performed with unnatural ER stress agents causing
apoptosis.
Measuring ER stress in β cells of living humans is currently
not feasible
Because the pancreatic islet β cell mass and insulin secretory
function during life cannot be studied simultaneously.
Pancreatic autopsy series from type 2 diabetic patients
technique used
Show a reduction in β -cell mass with activation in UPR
apoptotic markers.

25. Human type 2 diabetic islets contain protein aggregates in the
form of amyloid Islet .
Amyloid is composed of a 37-residue amyloidogenic polypeptide
called islet amyloid polypeptide (IAPP).
IAPP spontaneously forms ER membrane-damaging sheets of
amyloid
IAPP could be another ER stress link promoting b-cell death
through activation of the pro-apoptotic transcription factor
CHOP

26. DRUG MECHANISM POTENTIAL INDICATION
Bip inducer X Induction of GRP 78 Heart failure, stroke
Cs-866 (VESINO
INDUSTRIAL CO., LTD.)
Reduction of ER stress
by pressure overload
Heart failure, cardiac
hypertrophy
Curcumin Induction of GRP 94 Diabetic
cardiomyopathy
Salubrinal (Cayman
Chemical)
Prevention of elf2a
dephosphorylation
Cardiac hypertrophy
Tauroursodeoxycholic
acid(TUCD) (Bio-Gen,
Turkey)
Chemical chaperone Heart failure,
atherosclerosis
TNFα antibody Prevention of CHOP
induction
Cardiac hypertrophy
Sunitinib IRE1 activation Heart failure, cardiac
hypertrophy
Pioglitazone Decrease ER stress Cardioprotectin
Cohen FE, Kelly JW. Therapeutic approaches to protein-misfoldingb diseases. Nature. 2013 3426:905–909

27. Role of hyperglycemia or hyperlipidemia in β-cell failure in T2D.
Molecular mechanism of glucose level-dependent differential activation of
PERK and IREα in pancreatic β-cells
Lipid intermediates activate or inhibit the UPR
Mechanism of activation of UPR in β-cells by high glucose .
Is there any direct evidence of ER stress?
Molecular mechanisms involved in the formation of the toxic hIAPP oligomers
and UPR induction by hIAPP oligomers
• Further investigation is needed to identify effective chemical chaperones
that can improve ER function to prevent hyperactivation of the UPR.

28. ER maintains protein folding by UPR in manageable manner if it exceeds
capacity causes misfolding of proteins.
Results into activation of apoptopic pathways and other dysfunction.
ROS generation, mitochondrial dysfunction results into β cell failure.
Islet amyloid polypeptide (IAPP is important mechanism in diabetes.
Targeting pre-apoptopic pathways is essential to achieve more specific
actions.

29. L. Hiebert, J. Han, A.K. Mandal, Glycosaminoglycans, hyperglycemia and
disease, Antioxid. Redox Signal. (2014 Feb 4)
T.Miki, S. Yuda, H. Kouzu, T.Miura, Diabetic cardiomyopathy:
pathophysiology and clinical features, Heart Fail. Rev. 18 (2013) 149–166.
Ron D, Walter P. Signal integration in the endoplasmic reticulum
unfolded protein response. Nat Rev Mol Cell Biol. 2007;8:519 –529.
Jweied EE, McKinney RD, Walker LA, et al. Depressed cardiac myofilament
function in human diabetes mellitus Am J Physiol Heart Circ Physiol 2005;
289: H2478–H2483