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Current Diabetes Reviews
ISSN: 1573-3998
eISSN: 1875-6417
SCIENCE
BENTHAM
Send Ord ers for Reprints to reprints@benthamscience.ae
Current Diabetes Reviews, 2017, 13, 3-10
3
REVIEW ARTICLE
Chronic Complications of Diabetes Mellitus: A Mini Review
1875-6417/17 $58.00+.00 © 2017 Bentham Science Publishers
Mohamed Lotfy1, Jennifer Adeghate2, Huba Kalasz3, Jaipaul Singh4 and Ernest Adeghate5,*
1Department of Biology, College of Science, United Arab Emirates University, United Arab Emirates; School of Foren-
sic and Investigative Sciences, University of Central Lancashire, Preston PR1 2HE, England, UK; National Research
Centre ( NRC), Hormones Department, Cairo, Egypt; 2Department of Anatomy, Semmelweis University, Budapest, Hun-
gary; 3Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary; 4School of
Forensic and Investigative Sciences and School of Pharmacy and Biomedical Sciences, University of Central Lanca-
shire, Preston PR1 2HE, England, UK; 5Department of Anatomy, College of Medicine & Health Sciences, United Arab
Emirates University, Al Ain, United Arab Emirates
A R T I C L E H I S T O R Y
Received: May 22, 2015
Revised: October 05, 2015
Accepted: October 15, 2015
DOI:
10.2174/1573399812666151016101
622
Abstrac t: Introduction: Diabetes mellitus (DM) is a major metabolic disorder currently affecting
over 350 million people worldwide. Also, another one billion people in th e world are pre-diabetic,
who may eventually end up with full- blown diabetes. It costs around 1,200 billion USD to diagnose,
treat and care for both type 1 DM (T1DM) and type 2 DM (T2DM) patients globally. The disorder is
rapidly increasing out of proportion in both developed and developing countries, especially T2DM,
which is associated with modern lifestyle habits such as reduced physical activity, diet, obesity and
genetic factors. If left untreated, DM can lead to a number of diseases and long-term complications
leading subsequently to death.
Areas Covered: In this mini review, we aim to highlight a number of complications, cascades or
pathways (polyol, hexosamine, protein kinase C, advanced glycation-end product) of events and cel-
lular, sub-cellular and molecular mechanisms associated with DM-induced hyperglycaemia (HG).
Conclusion: Chronic complications of DM are caused largely by HG-induced cellular and molecular
impairment of neural and vascular structure and function. HG-induced oxidative stress is a major
contributor in the development of long-term complications of DM. DM-induced neuropathy and an-
giopathy, in turn, may lead to the dysfunction of cells, tissues and organ systems.
Keywords: Diabetes mellitus, long-term complications, oxidative stress, advanced glycation-end products, hyperglycaemia,
angiopathy, neuropathy.
1. PATHOMECHANISMS OF DIABETES COMPLI-
CATIONS
Diabetic complications associated with hyperglycaemia
(HG) impair the metabolism of carbohydrates, fats, proteins
and electrolytes, all of which can disrupt the vascular system
[1]. Many endothelial capillary cells are damaged under
these conditions, including those in the retina, renal glomeru-
lus, and both central and peripheral nerves, due to excessive
harmful accumulation of glucose in these cells [2]. The criti-
cal mechanisms involved in the development of diabetic
complications are mainly induced by chronic HG, impaired
lipid catabolism, exaggerated production of reactive oxygen
species (ROS) and a reduced antioxidant protective system,
that all lead to insulin-resistance and increased damage of
beta-cells in the p ancreas [3]. Table 1 shows a few of the
long-term complications of diabetes associated with HG in
different tissues and organ systems.
*Address correspondence to this author at the Department of Anatomy,
College of Med icine and Health Sciences, United Arab Emirates University,
P.O. Box 17666, Al Ain, United Arab Emirates; Tel: +971-3-7137496;
Fax: +917-3 -7672033; E-mail: eadeghate@uaeu.ac.ae
A. The Polyol Pathway
Essential enzymes in the polyol pathway include aldose
reductase and sorbitol dehydrogenase. Elevated blood
glucose levels or HG increase aldose reductase activity that
converts glucose to sorbitol. Intracellular sorbitol accumula-
tion increases cellular osmotic injury, and exaggerates oxida-
tive stress. Sorbitol dehydrogenase eventually converts sor-
bitol to fructose [4]. Amplified action of both enzymes in the
polyol pathway will deplete more of the NADPH needed for
reformation of the reduced glutathione antioxidant co-factor,
which in turn worsens the oxidative stress [2]. Furthermore,
the Protein Kinase-C (PKC) pathway is stimulated under the
influence of aldose reductase, via diacylglycerol production
[5]. Figure 1 depicts the pathways associated with diabetic
complications due to HG in different cell types in the body.
B. Increased Hexosamine Pathway Activity
When blood glucose level increases, the normal glycoly-
sis pathway shif ts to the hexosamine pathway. This, in turn,
worsens diabetic complications and increases the burdens of
oxidative stress via the production of excess uridine diphos-
phate-N-acetyl glucosamine (UDP-GlcNAc) [2]. The over-
4 Current Diabetes Reviews, 2017, Vol. 13, No. 1 Lotfy et al.
production of UDP-GlcNAc enhances O-glycosylation of the
transcription factor Sp1. A defective Sp1 will stimulate the
productive of genes that play a role in the development of
long-term complications of DM. In fact, elevated levels of
UDP-GlcNAc are seen in tissues of diabetic subjects with
severe long-term complications [6]. Increased SP1 glycosy-
lation has also been shown to increase the tissue level of
transforming growth factor-1 (TGF-1) and plasminogen
activator inhibitor-1 (PAI-1), which in turn induces expres-
sion of some harmful genes responsible for the development
of angiopathy [6]. Elevated expression of either PAI-1 or
TGF-1 leads to stimulation of vascular atherosclerosis, fi-
brosis and reduction of mesangial cell differentiation, respec-
tively [7]. In addition to the hexosamine pathway, a dual
effect by the PKC pathway occurs, resulting in an increase in
the expression of PAI-1, which aggravates diabetic compli-
cations. Moreover, normal glucose metabolism is impaired
in DM due to excess formation of N-Acetylglucosamine
(GlcNAc) via the hexosamine pathway, promoting increased
production of hydrogen peroxide, a free radical that can sup-
press gene expression of glucose transporter 2, glucokinase
and insulin [8].
C. Protein kinase-C Activation
During prolonged increases in blood glucose levels, the
PKC pathway is an added element in diabetic complications.
Hyperglycaemia induces the production of diacylglycerol,
which promotes activation of the PKC pathway [9]. Stimula-
tion of the PKC pathway worsens d iabetic injuries via the
overproduction of angiogenic proteins, such as vascular en-
dothelial growth factor (VEGF), atherogenetic proteins, such
as methylglyoxal (MGO), as well as other proteins, such as
transforming growth factor-1, fibronectin, nuclear factor-
Kappa B, PAI-1 and other factors. PKC also promotes ab-
normal vascular permeability, hypoxia, induction of pro-
inflammatory genes, and an in crease in insulin- resistance
with reduction of anti-atherosclerotic elements [10-15].
D. Increased Formation of Advanced Glycation-end
Products
Chronically elevated intracellular glucose levels in DM
can lead to an increase in the formation of reactiv e
dicarbonyl species including methylglyoxal (MGO), which
binds to protein molecules and produce advanced glycation-
end products (AGEs) [9]. Accumulation of AGEs in cells
disrupts their normal metabolic activities and alters gene
expression of DNA. In addition, increased dispersal of AGEs
to the extracellular matrix can impair cellular signaling, and
may stimulate receptor-binding of AGEs [16, 17]. Exagger-
ated recep tor-ligation of AGEs induces a greater expression
of nuclear factor-Kappa B, which stimulates many cellular
cascades involved in the production of inflammatory factors
and markers including tumor necrosis factor (TNF) and dif-
ferent in terleuk ins that ultimately lead to cell death [18, 19].
Furthermore, increased receptor-binding by AGEs worsens
oxidative stress through overproduction of ROS [20].
E. Diabetes and Oxidative Stress
Prolonged HG stimulates excessive production of ROS,
resulting in oxidativ e stress, which in DM, is mainly accom-
panied by a reduced protective antioxidant system [21].
Therefore, the increased production of ROS overcomes the
antioxidant defence abilities of the body [22]. Oxidative
stress is prominent under elevated levels of blood glycolip-
Table 1. A summa ry of diabetes complicat ions (see text).
1. Central and peripheral nervous systems
•Brain stroke
•Autonomic neuropathy
•Peripheral neuropathy (Motor & sensory dysfunc-
tions)
2. Eye
•Retinopathy
•Cataracts
•Blindness
3. Cardiovascular system
•Cardiomyopathy
•Myocardial infarction
•Atherosclerosis
•Hypertension
•Endothelial cell dysfunction
4. Oral cavity
•Oral disease (Caries, gingivitis, periodontal ab-
normalities, infections)
5. Renal system
•Nephropathy
•Proteinuria
•Glucosuria
•Kidney failure
6. Gastrointestinal system
•Delayed gastric emptying
•Diarrhea
•Constipation
•Dyspepsia
•Exocrine gland insufficiency
7. Genital system
•Impotence
•Sexual dysfunction
•Urogenital dysfunction
8. Skin and soft tissues
•Wound healing impairment
•Skin infection
9. Bone
•Osteopenia, fractures
10. Foot
•Foot ulceration
•Foot amputation
Complications of Diabetes Current Diabetes Reviews, 2017, Vol. 13, No. 1 5
ids, glycoproteins and hypertension, all of which are associ-
ated with DM [9]. The development of diabetic complica-
tions can be delayed and reduced with proper use of hypo-
glycaemic treatments and regular physical activity (exercise)
that keep blood glucose levels within the normal range [23].
The protective antioxidant system includes enzymes such
as glutathione peroxidase, catalase and superoxide dismu-
tase, that oppose the harmful effects of oxidative stress. This
defence system also comprises of some non-enzymatic
molecules including beta-carotene, glutathione, reduced glu-
tathione, flavonoids, bilirubin and vitamins E and C. Sup-
pression of the antioxidant system increases the vulnerability
of cellular DNA, proteins and lipids under oxidative stress
[24]. Excessive production of free radicals in DM has been
shown to impair mitochondrial activity by penetrating mito-
chondrial membrane and destroying mitochondrial DNA
[25], leading to loss of cytochrome C and entrance of Bax
proteins into the mitochondria. All of these will eventually
lead to cell death [26]. Impairment of beta-cells is mainly
associated with HG in type 2 DM, leading to decreased pro -
duction and secretion of adequate amounts of insulin re-
quired to maintain normoglycaemia. In addition, HG also
suppresses pancreatic beta cell repair that would be needed
to compensate for the increased demand for insulin [27].
Insulin gene expression is also suppressed under the toxic
effect of HG in DM [28].
F. Diabetes and Immune System
Infections are increasingly prevalent in diabetic patients
due to immune system deficiency [29]. Diabetic patients
with normal blood glucose levels are able to recover cellular
function, because infectious organisms are less active in
states of normoglycaemia, but several fold more active in
HG [30]. Susceptibility to infection among diabetic patients
with urinary and respiratory tract infections and skin diseases
is much higher compared to healthy individuals [31].
Type 1 DM is an autoimmune disease characterized by
an inflammatory response against pancreatic beta-cells. Ge-
netic susceptibility is strongly suspected in the etiopatho-
genesis of Type 1 DM. Anti-insulin autoantibody produc-
tion, as demonstrated in type 1 DM, is the main cause [32].
Beta-cell destruction is the end-point of a chronic inflamma-
tory process in the pancreatic islets of Langerhans. With
time, T-cells invade pancreatic islets and destroy beta-cells
[33]. In type 2 DM, there is a strong association between
chronic inflammation and delayed wound healing, prolonged
infection, obesity, atherosclerosis, insulin-resistance, and
increased immunocytokine production [34]. Type 1 DM is
also associated with a significant reduction in the number of
lymphocytes and neutrophils in the blood of diabetic patients
compared to healthy age-matched controls. Moreover, both
cell types release significantly less intracellular free calcium
upon stimulation with secretagogues and agonists [35].
2. CLASSICAL COMPLICATIONS OF DIABETES
MELLITUS
A. Macrovascular Diabetes Complications
Hyperglycaemia (HG) is the main manifestation of DM,
which in turn can impair the structure and function of many
tissues in the body, especially the vascular system. As the
Fig. (1). Flow chart showing hyperglycaemia-induced cellular pathways that may lead to the development of diabetes complications.
Glucose
Polyol
Pathway
Glucose
Sbil
Polyol
Pathway
Glucose
S
or
bi
to
l
Fructose
Glucose6
Ph h t
Ph
osp
h
a
t
eHexosamine Pathway
Fructose6 Glucosamine
6
Ph h t
Uridine
Di h h t
Phosphate
6
Ph
osp
h
a
t
e
Di
p
h
osp
h
a
t
e
ProteinKinaseCPathway
Glyceraldehyde Dih
y
drox
y
acetone Gl
y
cerol
D
ill l
Protein
3Phosphate
yy
Phosphate
y
Phosphate
D
i
acy
l
g
l
ycero
l
KinaseC
Advanced
Glycation
End
Products Pathway
Advanced
Glycation
End
Products
Pathway
Methylglyoxal AdvancedGlycation EndProducts
Pyruvate
Pyruvate
6 Current Diabetes Reviews, 2017, Vol. 13, No. 1 Lotfy et al.
HG becomes chronic with time, it can severely damage the
vascular system via MGO and other mediators. Vascular
complications in DM is classified into two categories,
namely macrovascular, which includes coronary and periph-
eral arterial disease, and microvascular, which is associated
with other DM-induced long-term complications such as
neuropathy, retinopathy, nephropathy and in part, diabetic
foot and cardiovascular diseases [36].
The endothelial cell impairments involved in macrovas-
cular complications have many inducing elements, including
elevated blood glucose levels, MGO, lipids, and inflamma-
tory factors [37]. DM is also associated with excessive pro-
duction of ROS, which in turn can induce vasoconstriction
with accelerated lipid peroxidation and inflammatory reac-
tions leading to atherosclerosis [38]. Atherosclerosis is a
process of increased lipid deposition, especially low-density
lipoprotein (LDL), in the sub-endothelial layer of large blood
vessels. Atherosclerosis occurs more often in patients with
DM as compared to patients without DM [39]. In addition to
this, atherosclerosis increases the endothelial penetrability of
blood vessels, which is prominent in DM [40]. The antioxi-
dant and anti-inflammatory protective actions of high-
density lipoprotein (HDL) are suppressed with increased
inflammation due to excessive liberation of ROS, which in-
duces oxidation of phospholipids and sterols [41]. Other
macrovascu lar complications, such as calcification and
plaque formation, can add to the development of severe vas-
cular comp lications [42].
i. Diabetic Coronary Artery Disease
Coronary artery disease (CAD), stroke and peripheral ar-
terial disease (PAD) are common in DM, leading to a high
mortality rate among diabetic patients [9]. DM-induced car-
diomyopathy is mainly associated with dyslipidaemia and
increased blood pressure. Development of prominent cardiac
fibrosis associated with cardiomyopathy is further enhanced
by overproduction of oxidative free radicals that disrupt
myocardial cells, leading to dysregulation of cellular calcium
homeostasis, contractile dysfunction, remodelling of the
myocardium and subsequently, death of cardiomyocytes.
Oxidative stress inhibits the antioxidant protective system in
diabetic patients [43].
B. Microvascular Diabetic Complications
On the other hand, diabetic microvascular complications
are mainly associated with impairment of vascular perme-
ability that affects different tissues and organs of the body
including the kidneys, retina and nerves [44]. Chronic, un-
treated and prolonged HG can further cause vascular perme-
ability, disruption of glycocalyx structure, increase in water
and protein retention, resulting in generalized edema [40]. At
the same time, PKC is elevated in DM-induced HG leading
to an increased vascular permeability via an elevation of
extracellular fluids and apoptosis of angiogenic cells [15].
Vascular endothelial growth factor (VEGF) is an impor-
tant element in tissue neogenesis and vascular healing. How-
ever, VEGF has also an initiatory destructive role in mi-
crovascular diabetic complications [45]. VEGF can directly
influence glomerular permeability as well [46, 47]. Although
suppression of VEGF slows the development of proliferative
diabetic retinopathy [48], VEGF-inhibition can also lead to
an increase in DM-induced hypertension and glomerular
proteinuria, with diminished vascular wound healing [49,
50].
i. Diabetic Nephropathy
Diabetic nephropathy is associated with morphological
impairment of the glomerular endothelial cell barrier [51]
and the glomerular basement membrane. This, in turn, leads
to an elevation of protein filtration in urine, reflecting dis-
turbed protein degradation in the diabetic patient [52]. Oxi-
dative stress progression in DM can induce gene expression
of angiotensinogen, leading to renal function impairment
[53, 54]. Diabetic nephropathy is a disease that patients can
genetically be susceptible to, but can also be induced by cer-
tain environmental insults [55]. Approximately one-third of
all uncontrolled diabetic patients will suffer from diabetic
nephropathy ending with renal dialysis. This can either be
due to the previously mentioned genetic susceptibility and/or
the reaction of cytokines with reactive oxygen species or
advanced glycation end products. The early indicator of dia-
betic nephropathy is increased urinary albumin excretion
[56].
ii. Diabetic Retinopathy
In numerous cases, DM is indirectly diagnosed via an eye
test for impaired vision. If left untreated, DM can lead to
blindness. Risk of blindness in diabetic subjects is associated
with prolonged incidence of retinopathy, which in most pa-
tients is usually revealed to have been going on for decades,
with the risk of losing vision increasing in time [57]. HG can
induce diabetic retinopathy through stimulation of PKC. The
activation of PKC can result in elevation of many metabolic
pathways, stimulation of cell growth and apoptosis, and in-
crease in cellular permeability. Changes in these processes
are associated with the progression of different diabetes-
induced vascular complications, including cardiomyopathy,
atherosclerosis, neuropathy, nephropathy and retinopathy
[58]. In addition, HG and states of oxidative stress associated
with diabetic retinopathy also stimulate certain apoptotic
growth factors that may contribute to diabetic cataract for-
mation [4, 59]. Furthermore, the elevated glucose level in
retinal cells of diabetic individuals may lead to increased risk
of retinopathy and accompanying blindness [60, 61]. Moreo-
ver, elevated levels of ROS due to provoked oxidative stress
can lead to an increase in lipid peroxidation, and a concomi-
tant impairment of the antioxidant protective system, all of
which prompt DNA injury in the retina of diabetic patients
[2, 57, 62].
C. Diabetic Neuropathy
The progression of diabetic neuropathic complications is
highly accelerated after prolonged years of HG [10]. Chronic
HG may lead to either sensory or motor neuropathic prob-
lems or autonomic nervous system dysfunction, including
arrhythmias, gastroparesis, incontinence and sexual dysfunc-
tion [63]. However, patients with long-term diabetes may
have one or more types of neuropathies.
i. Peripheral Neuropathy
Diabetic peripheral neuropathy is one of the major com-
plications affecting patients with DM. This can lead to either
Complications of Diabetes Current Diabetes Reviews, 2017, Vol. 13, No. 1 7
sensory or sensorimotor neuropathies that increase the risk of
foot ulceration and amputation in some cases of uncontrolled
diabetic patients [64]. Chronically elevated blood glucose
levels and the r esulting activated polyol pathway, w ith re-
duced blood supply to endoneurial tissues, are all associated
with reduced protective nitric oxide formation and Na+/K+-
ATPase dysfunction [7]. Concurrently, neural cell regenera-
tion is severely reduced due to an inhibition of insulin-like-
growth factor [65]. An increased activation of the polyol
pathway diminishes NADPH, which is otherwise required
for activation of glutathione reductase, aldose reductase and
endothelial nitric oxide synthase. This all leads to worsening
of oxidative stress and acceleration of neurodegradation.
Moreover , elevation of intraneural sorbito l can induce nerve
cell necrosis and subsequently, cellular degradation [10, 66].
Glycation of proteins within nerves in patients with DM
[67], destabilizes the cytoskeleton, and contributes to slow-
ing of axonal transport and nerve impulses while accelerat-
ing nerve degeneration [68].
ii. Autonomic Neuropathy
a. Diabetes and Gastrointestinal Dysfunction
Autonomic neuropathy may cause abnormal function of
the digestive system. Diabetic patients with autonomic neu-
ropathy may complain of symptoms such as early satiety,
bloating, nausea, vomiting, abdominal pain and heartburn.
Slowed stomach emptying, or gastroparesis, is usually de-
tected in diabetic patients with prolonged HG. Diabetic en-
teropathy also leads to acid reflux disease, delayed bowel
movement, constipation, diarrhoea, and increased rate of
bacterial, viral and fungal gastrointestinal tract infections.
Furthermore, diabetes-induced HG is associated with sali-
vary and exocrine pancreatic insufficiencies due to a reduc-
tion in the synthesis and secretion of amylase, an important
digestive enzyme responsible for the breakdown of carbohy-
drates [69, 70].
b. Diabetes and Erectile Dysfunction
Erectile dysfunction is a common complication of DM,
and is mainly related to disturbed communication between
vascular and neuronal systems due to either weakened blood
circulation in penile tissue or impairment of neuronal stimu-
lation [71]. In addition to the vascular and neuronal distur-
bance related to erectile dysfunction in diabetic patients,
there are other elements involved, including hormonal
changes, chronic diseases, malnutrition, penile tissue infec-
tion and psychological influences [72]. Impotence related to
DM is much more frequent in diabetic than in non-diabetic
men [73]. Increased free radicals, such as malondialdehyde,
are believed to disrupt the neuronal and vascular activities
controlling penile erection [74]. Impaired ejaculation and
diminished satisfaction are other symptoms that diabetic
patients may encounter [75].
D. Diabetic Foot and Wound Healing
Diabetic foot occurs as an interplay of abnormal structure
and function of blood vessels and nerves leading to reduced
angiogenesis [76], loss of sensation, unhealed secondary
wound infections, ulceration and subsequently foot amputa-
tion [77]. Diabetic foot ulceration is mainly due to neuropa-
thy and ischemia occurring together. Diabetic foot is associ-
ated with increased incidence of foot trauma due to
decreased proprioception. The underlying ischemia results in
impaired wound-healing in the injured area(s), and superim-
posed infections lead to ulceration [78]. The symptoms of
diabetic neuropathic foot include but not limited to numb-
ness and tingling sensation, pain that may be sharp in nature
and sensitivity to touch. Neuropathic diabetic foot also has
reduced pain sensation [79]. Diabetic foot is associated with
morbidity because of leg amputation [80]. Persistently un-
successful wound-healing in diabetic foot syndrome can also
occur even with sufficient medical therapy [81]. Prolonged,
non-healing foot ulcers are a ground for foot amputation
[82]. All stages of the complex wound-healing cascade are
impaired in DM and compounded by many factors including
inflammation, proliferation, angiogenesis, apoptosis, reduced
chemotaxis and matrix formation, diminished b acterial resis-
tance, and deterioration of the antioxidant protective system.
All of these lead to failure of wound-healing [83]. Also, pe-
ripheral vascular disease is prevalent in the legs of patients
with uncontrolled d iabetes due to atherosclerosis that may
ultimately lead to foot amputation [3].
3. NON-CLASSICAL CHRONIC COMPLICATIONS
OF DIABETES MELLITUS
A. Periodontal Disease
DM can be diagnosed through dental examination due to
diabetic complications affecting the oral cavity. Impairment
of the immune system in diabetic p atients enhances the de-
velopment of periodontal disease due to increased bacterial
accumulation between teeth and gingiva, accelerating gum
infection and promoting bone demolition. Chronic periodon-
titis can lead to gum retraction, swelling, bleeding, fetor ex
ore and tooth loss. Diabetic patients also experience salivary
insufficiency, which is associated with a reduction in sali-
vary amylase and fluid secretion [84].
B. Diabetic Bone Diseases
Impairment of insulin-secretion, which is asso ciated with
type 1 diabetes, can lead to diminished bone mineral density
with an elevated bone fracture rate [85, 86]. An exaggerated
production of glycation-end products in DM is associated
with the progression of diabetic complications including
microangiopathy and atherosclerosis, which can also lead to
diabetic bone disease [87].
C. Diabetes and Skin Disorders
Manifestations of diabetes can also involve the skin.
Chronic dermal infections are due to increased blood glucose
supply to the skin. The HG in turn increases the occurrence
of bacterial and fungal infections, leading to pruritus and
other symptoms of skin disease. In addition to HG, increased
accumulation of subcutaneous adipose tissue related to obe-
sity stimulates colonization and growth of Candida albicans.
Also, skin dehydration may lead to changes in the normal
dermal flora, and give way to colonization by pathogenic
bacteria. Furthermore, DM is associated with delayed
wound-healing [88] as discussed in earlier section.
8 Current Diabetes Reviews, 2017, Vol. 13, No. 1 Lotfy et al.
4. OTHER CONDITIONS THAT MAY BE ASSOCI-
ATED WITH DIABETES MELLITUS
A. Hypertension
It is now known that DM is a major risk factor in the de-
velopment of hypertension. Moreover, diabetes-induced hy-
pertension is one of the influencing causes of cardiovascular
disease, including heart failure and other long-term compli-
cations, such as retinopathy, nephropathy and cerebrovascu-
lar accidents [36]. There is extensive evidence showing that
controlling hypertension in DM can significantly diminish
these diabetic complications [89]. End-stage renal disease is
mainly associated with increased hypertension in DM, HG
and glycated haemoglobin, all of which can lead to microal-
buminuria due to reduced glomerular filtration [90].
B. Obesity
Obesity is a leading risk factor for many chronic diseases
including insulin-resistance, type 2 DM, gastroesophageal
reflux, hypertension, dyslipidemia, cardiovascular diseases
and certain types of cancers [91]. Obesity can develop due to
modern lifestyle habits such as excessive food intake, re-
duced physical activity, environmental factors, psychological
effects and genetic susceptibility, which all have an effect on
general health and mortality [92]. Increased body weight can
also be related to hormonal and neuronal disturbances [93].
In addition to the harmful effect of HG on the progres-
sion of cardiovascular diseases, increased levels of choles-
terol, LDL, total cholesterol, triglycerides and low level of
HDL cholesterol may contribute to th e development of heart
disease in diabetic patients [94]. Obesity in children also
increases the risk of insulin-resistance, disturbed lipid me-
tabolism and hypertension [95]. Moreover, obesity hastens
the ageing process, reduces the quality of life and increases
morbidity and mortality even at an early age in life [96].
5. CONTROLLING DIABETIC COMPLICATIONS
There is now sufficient evidence that diabetes can cause
many of the complications that have been outlined in this
mini review. It is particularly noteworthy that diabetes is
associated with ageing, and millions of people in the world
are diabetic. People should endeavor to keep their blood glu-
cose values at or close to the normal levels. This can be done
via both pharmacological and/or non-pharmacological inter-
ventions involving daily exercise of 30 min per day or 3
hours per week. People with mild and severe chronic DM
have to comply with daily intake of hypoglycemic drugs,
including insulin, and they must also exercise every day.
Adherence to both non-pharmacological and pharmacologi-
cal treatments, as well as knowledge about DM can defi-
nitely improve the quality of life of diabetic patients.
CONCLUSION
In conclusion, this mini review provides an overview of
the different long-term complications associated with DM-
induced HG. The review highlighted different ways on how
DM can induce physiological and biochemical dysfunctions
in the body. In the absence of early diagnosis and treatment,
DM-induced long-term complications may lead to severe
morbidity or death.
LIST OF ABBREVIATIONS
DM = Diabetes Mellitus
T1DM = Type 1 DM
T2DM = Type 2 DM
PKC = Protein Kinase-C
GlcNAc = N-Acetylglucosamine
UDP-GlcNAc = Uridine Diphosphate-N-acetyl
Glucosamine
PAI-1 = Plasminogen Activator
Inhibitor-1
TGF-1 = Transforming Growth Factor-1
VEGF = Vascular Endothelial Growth
Factor
AGEs = Advanced Glycation End
Products
ROS = Reactive Oxygen Species
LDL = Low-density Lipoprotein
HDL = High-density Lipoprotein
VEGF = Vascular Endothelial Growth
Factor
HG = Hyperglycaemia
MGO = Methylglyoxal
PAD = Peripheral Arterial Disease
CAD = Coronary Artery Disease
CONFLICT OF INTEREST
The authors confirm that this article content has no con-
flict of interest.
ACKNOWLEDGEMENTS
Declared none.
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