Diabetes mellitus causes oxidative stress through increased production of reactive oxygen species. This damages cells and tissues over time. The document discusses several pathways by which ROS are generated in diabetes and damage occurs, including advanced glycation end products, the polyol pathway, and activation of protein kinase C. It also describes the Nrf2/Keap1 pathway which regulates the body's antioxidant response. Various natural and synthetic antioxidants that can help reduce oxidative stress in diabetes are reviewed, such as alpha-lipoic acid, vitamins C and E, flavonoids, and plant extracts. Targeting specific pathways like the polyol pathway or AGE formation with inhibitors or antioxidants may help prevent complications of diabetes.

1. Protective activity of
Antioxidants and Recent
advances in treatment of
Diabetes mellitus
Praveen Kumar.S
M.Pharm 2nd semester
Department of pharmacology
PSG College of pharmacy

2. Contents
• Introduction on diabetes mellitus
• What is oxidative stress
• Why ros are bad?
• Source of oxidative stress in Diabetes mellitus.
• Nrf 2/Keap 1/ARB pathway.
• Nrf 2/Keap 1/ARB therapauetic target.
• Antioxidants for oxidative stress in diabetes mellitus.
• Antidiabetic plant show antioxidant activity
• References

3. Diabetes mellitus
• Diabetes mellitus is a group of metabolic diseases characterized by
hyperglycemia resulting from defects of insulin action, insulin secretion or
both .
• Hyperglycemia in the course of diabetes usually leads to the development
of microvascular complications, and diabetic patients are more prone to
accelerated atherosclerotic macrovascular disease.
• Hyperglycemia increases oxidative stress, which contributes to the
impairment of the main processes that fail during diabetes, insulin action
and insulin secretion.

4. Oxidative stress
• Oxidative stress is defined as general in excess formation or
insufficient removal of highly reactive oxygen species(ROS)and
reactive nitrogen species(RNS)
• ROS include free radical such as superoxide .o2-,hydroxyl
OH,peroxyl RO2,hydroperoxyl HRO2- as well as non radical species
such as hydrogen peroxide H2O2 and hydrochlorus acid HOCL.
• RNS include free radicals like nitric oxide NO,and nitrogen dioxide
NO2- as well asnonradical such as peroxynitrite (ONOO-),nitrous
oxide (HNO2).
• .O2-,.NO and ONOO- are the most widely studied species and play
important role in diabetic cardiovascular complications.

5. Generation of reactive oxygen species in
Diabetes mellitus

6. Why reactive oxygen species are bad?
• ROS -stimulate oxidation of low-density lipoprotein (LDL), and ox-LDL, which is not recognized by the LDL receptor, can
be taken up by scavenger receptors in macrophages leading to foam cell formation and atherosclerotic plaques .
• , •O2 -- Activate in diabetic several pathway accelerated formation of Advanced glycation end products (AGE), polyol
pathway, hexosamine pathway and PKC,
• •O2- and H2O2 stimulate stress-related signaling mechanisms such as NF-κB, p38-MAPK and STAT-JAK- in VSMC
migration and proliferation.
• •O2 immediately reacts with •NO generating cytotoxic
1. ONOO alters function of biomolecules by protein nitration - lipid peroxidation .
• As recently reviewed by Turko et al, increased levels of nitrotyrosine - apoptosis of myocytes, endothelial cells and
fibroblasts in diabetes .
2. ONOO causes single-strand DNA breakage which in turn activates nuclear enzyme poly(ADP-ribose) polymerase
(PARP)
3. It decreases •NO bioavailability causing,
• Impaired relaxation and inhibition of the antiproliferative effects of •NO .
• ONOO- oxidizes tetrahydrobiopterin (BH4), an important cofactor for NOS, - causes uncoupling of NOS, - produces •O2

8. Sources of oxidative stress in diabetes
• Direct evidence of oxidative stress in diabetes,
1. Measurement of oxidative stress marker as plasma and
urinary F2-isoprostane
2. Plasma and tissue level of nitrotyrosine and O2-
• Multiple sources for oxidative Stress in diabetes as Enzymatic
and Non-enzymatic, mitochondrial electron transport chain
pathway.
1. Non enzymatic source Originate from oxidative biochemistry
of glucose. AGE pathway,Polyol pathway.
2. Enzymatic source-NadpH oxidase,xanthine Oxidases.

9. Mitochondria l electron transport
chain

11. The Nrf2/Keap1/ARE Pathway

12. The Nrf2/Keap1/ARE Pathway as a
Therapeutic Target

13. Antioxidant
• Antioxidants are substances able to slow or inhibit the oxidation
of other molecules.
• Preceding experimental studies and clinical trials have
suggested
• the efficacy of antioxidants in preventing diabetes complication.
• The therapeutic strategy uses the antioxidants as a substrate,
combined drug, synthetic antioxidants, and drug with
antioxidants activity.
• In general, the medicinal plants with antioxidants activity are
considered for the treatment of diabetes mellitus

14. Antioxidants for diabetes mellitus
• The enzymatic antioxidant systems, such as copper, zinc, manganese
superoxide dismutase, gluthatione peroxidase, gluthathione reductase,
and catalase may remove the ROS directly or sequentially, preventing their
excessive accumulation and consequent adverse effects.
• Non-enzymatic antioxidant systems consist of scavenging molecules that
are endogenously produced such as glutathione, ubichinol, and uric acid
or derivatives of the diet such as vitamins C and E, carotenoids, lipoic acid,
selenium,
• Exercise training results in an up-regulation of antioxidant defense
mechanisms in various tissues,

15. Overview of an antioxidant role

16. Alpha-lipolic acid
• Alpha-lipoic acid (ALA) It is the only antioxidant capable of
dissolving in both water and fats .
• ALA can be biosynthesized in plants and animals where it is
metabolized to dihydrolipoic acid (DHLA) upon uptake into cells.
• Both ALA and DHLA are potent free radical scavengers that are also
involved in the regeneration of vitamins C and E and oxidized
glutathione within the cell . ALA is also a cofactor for a number of
• In experimental models, ALA was reported to decrease lipid
peroxidation, reduce oxidative stress,and improve nerve blood flow
and distal, sensory, and motor nerve conduction in diabetic animals .
• ALA is known to reduce oxidative stress by inhibiting hexosamine
and AGEs pathways

17. Vitamin-E
• It is naturally occurring lipophilic antioxidant exists as tocopherol and
tocotrienol. It defends the cell against oxidative damage.
• The studies in an animal model have shown supplementation of Vitamin E
decreases the hepatic lipid peroxide level in streptozotocin-induced rats..
• During diabetic condition, the antioxidant enzymes SOD, CAT, and GPX
decreased. However, the oral administration of Vitamin E (440 mg/kg of
body weight, once a week for 30 days) significantly Increased SOD and
GSH-Px activity and decreased the hydroperoxide level due to an
improvement of glycemia
• During diabetic condition, the excess glucose attached to hemoglobin to
produce glycosylated hemoglobin. It is an important marker for diabetes
which is prevented Vitamin E treated rat in diabetic condition.
.

18. Vitamin-C
• It is powerful antioxidants scavenging free radicals in aqueous compartment. It is essential to
convert Vitamin E free radicals to Vitamin E, as a cofactor required for hydroxylation reaction in
human.
• The most important function of Vitamin C is key chain-breaking antioxidants in the aqueous
phase. It provides stability to the cell membrane.
• The research conducted by Yazd Diabetes Research Center, Iran, has been reported that totally
84 diabetic patients received 500 mg or 1000 mg of ascorbic acid daily for 6 weeks. The daily
consumption of 1000 mg of Vitamin C may be beneficial in reducing blood glucose level and
lipids.,
• Eriksson and Kohvakka studied the effect of Vitamin C supplementation (2 g/day for 90 days) in
56 diabetic patients; the result has shown the high-dose supplementation reduced the level of
fasting blood glucose, HbA1c and improve glycemic control [20]. Frequent intake of Vitamin C
dietary source was found to decrease the risk of Type 2 diabetes in a population-based studies.

19. Flavonoids
• Flavonoids are the largest and the most important group of polyphenolic
compounds in plants and are found in fruits, vegetables, grains, bark, roots,
stems,flowers, tea, and wine .
• Flavonoids such as proanthocyanidin ,luteolin , hesperidin , fisetin ,
epigallocatechingallate , rutin , and quercetin have been shown to possess
antioxidant activities which protect against diabetic nephropathy.
• Other antioxidants are taurine, acetyl L-carnitine, and N-acetylcysteine
which have been demonstrated to reduce the progression of DN.

20. Strategies Targeted against Individual Oxidative Stress
Pathways.
• The pathways of hyperglycaemia-induced oxidative stress
discussed earlier are potential therapeutic targets in DN.
• Some of the interventions have resulted in specific therapies,
for example, aldose reductase inhibitors, PKC inhibitors, and
anti-AGE agents.

21. Aldose Reductase Inhibitors. In the preceding sections
• we have discussed the importance of aldose reductase enzymein the
accumulation of sorbitol and fructose.
• Therefore, aldose reductase inhibitors (ARIs) are agents that reduce the
flux of glucose into the polyol pathway thereby preventing the harmful
effects of excess sorbitol and fructose in neurons.
• Results from in vivo and in vitro animal studies highlighted the positive
effect of inhibiting aldose reductase on DN
• These studies have been the foundation for embarking on several clinical
trials with ARIs with antioxidant activities such as Fidarestat (SNK-860) ,
Epalrestat , and Ranirestat (AS-3201).

22. PKC Inhibitors.
• PKC is involved in the activation of key regulatory proteins responsible for
nerve function and synthesis of neurotransmitters. Inhibiting PKC was
reported to suppress neuropathic pain .
• Ruboxistaurin, a specific inhibitor of PKC-1b that possesses antioxidant
effects,improves nerve conduction velocity (NCV) and endoneurial blood
flow in diabetic rats .
• In clinical trials, Ruboxistaurin reduces the progression of DN [164] but
fails to achieve its primary end-points, vibration detection threshold (VDT)
and symptoms reduction.

23. Anti-AGE Agents.
• Anti-AGE agents prevent the formation and accumulation of AGEs.
• They also counteract the AGE-RAGE interactions that might
aggravate the oxidative stress damage in DN. Examples are
Benfotiamine, Aminoguanidine, and Aspirin which are known for their
antioxidant properties through the inhibition of AGE formation .
• Benfotiamine has been reported to increase transketolase enzyme
activity which directs AGE substrates to the pentose phosphate
pathway resulting in the reduction of hyperglycaemic damage.
• It also inhibits the increase in UDP-N-acetylglucosamine (UDP-
GlcNAc) that induces the hexosamine pathway activity ultimately
reducing tissue AGEs.

24. Selenium
• It is important trace element, naturally present in many foods. It exists in organic and
inorganic forms.
• Selenomethionine and selenocysteine belong to organic form; selenate and selenite are
inorganic forms.
• Mostly the inorganic selenite presents in the soil.
• Selenium plays a major role in thyroid hormone metabolism and immune functions.
• The inorganic selenium compound sodium selenate and sodium selenite involved in
insulin signaling cascade by activation of kinases.
• In animal experimental studies shown selenate stimulate glucose uptake and involved
phosphorylation of insulin receptor and and the oral administration or intraperitoneal
injection of daily doses of selenate for 3-8 weeks in streptozotocin induced diabetic rat,
the result shown that the raised glucose level to be reduced

25. Shows antidiabetic plants show antioxidant
activity Extract Dose Efficacy
Ethanolic
extract of the
bulb
500 mg/kg body
weight of rat
Significantly
decreased the blood
sugar level
Aqueous extract
of leaves
500 mg/kg body
weight of mice
Hypoglycemic and
hepatoprotective
effect.
Plant name
Alium sativum
Aloe Vera

26. Seed powder 500 and 1000 mg/kg
body weight of rat
Hypoglycemic
Activity.
Thottal vadi
choornam
(Leaves and
roots)
100 and 200 mg/kg
body weight of rat
Hypoglycemic
activity
Alcoholic
extract of bitter
melon
0.5-1.5 g/kg body
weight of rabbits.
Hypoglycemic
activity
Syzygium cumini Walp. (Eugenia jambolana)
Mimosa pudica

27. Ethanolic
extract. (Aerial
part)
0.1, 0.2, and 0.4
g/body
weight of rat.
Hypoglycemic and
hypotriglyceridemic
Effect.
Andrographis paniculata

28. References
• A REVIEW ON ROLE OF ANTIOXIDANTS IN DIABETES
DEEPA RAJENDIRAN1,2, SUBBULAKSHMI PACKIRISAMY3, KRISHNAMOORTHY
GUNASEKARAN4
• Oxidative Stress in Diabetes Mellitus and the Role Of Vitamins with Antioxidant Actions
Maria-Luisa Lazo-de-la-Vega-Monroy andCristina Fernández-Mejía
• Oxidative stress and the use of antioxidants in diabetes: Linking basic science to clinical
practice
Jeanette Schultz Johansen†1, Alex K Harris†2, David J Rychly2 and Adviye Ergul*2,3
• The Nrf2/Keap1/ARE Pathway and Oxidative Stress as a Therapeutic Target in Type II
Diabetes Mellitus
Joshua A. David, William J. Rifkin, Piul S. Rabbani, and Daniel J. Ceradin

29. Thank you