DR RAJEEV CHAWLA
Sr. Consultant Physician Diabetologist
Maharaja Agrasen Hospital
North Delhi Diabetes Centre
New Delhi
Prevention of Diabetic Complications
Rising prevalence of Diabetes Mellitus especially Type-2 DM in Urban
population is a serious concern. The countries with the largest number of
people with diabetes are and will also be in the year 2025, India, China and
the U.S.1 With the increasing prevalence of diabetes especially in
the middle age group populations who are commonly affected in India,2
the chances of developing micro & macro vascular complications are very
high & it is going to bring enormous burden on the family, society &
the health care providers involved in the management of diabetes due to high
morbidity & mortality. (Table 1)
In
a study of 3010 diabetics by Ramachandran. A,3 the prevalence of
microvascular complications was, Retinopathy 23.7%, Nephropathy 5.5%,
Neuropathy – 27.5% & prevalence of CHD 11.4 % & PVD was 4%. In our own
study from North Delhi Diabetes Centre.4 comprising 720 type-2
Diabetics, Retinopathy was seen in 21.2 %, microalbuminuria in 41%, Peripheral
Neuropathy in 15.3 %, CAD in 7% & PVD was in 7.4% of Patients.
·
Mortality increased by 2-3 folds.
·
Heart Disease & stroke
increased by 2-3 folds.
·
Blindness 10 times more common
than in the general population.
·
Gangrene and amputation about 20
times more common than in general population.
·
Second leading cause of Fatal
kidney disease.
·
Other chronic disabilities (e.g.
Neuropathy, Infections and sexual dysfunctions)
·
Hospitalization increased 2-3
folds.
(WHO expert committee on Diabetes Mellitus 1980.5
)
Hyperglycemia is a well known risk factor for
vascular complications both microvalcular and macrovascular in diabetes.
However unlike the clear & linear relationship of hyperglycemia with
microvascular disease, relationship with macrovascular disease & mortality
is clouded by many confounding risk factors like obesity, hypertension,
dyslipidemia and hyperinsulinemia.6 The risk for CAD with
hyperglycemia has been seen with blood sugar levels far below the cut off value
for the diagnosis of diabetes.7 Unlike microangiopathy where the
clock starts ticking with the onset of diabetes, in case of macroangiopathy,
the clock may start ticking a decade or two earlier.
Primary Prevention is an attempt to prevent onset
of complications associated with disease.
Secondary prevention aims at arresting or retarding
the progression of preexisting complications, hence, preventing the occurrence
of end point of particular
complications e.g. end stage renal failure due to diabetic nephropathy or blindness
due to diabetic retinopathy.
The Diabetes control and complication trial
(DCCT)8 was a landmark study conducted in United States from 1983 to
1993 in Type-1, diabetic patients. In the primary prevention group (726
patients with no retinopathy at baseline) internsive therapy reduced the risk
for development of retinopathy by 76% as compared to conventional therapy. In
patients with some eye changes (secondary prevention cohort) intensive
treatment slowed the progression of the disease by 54% & reduced the
development of proliferative or severe non proliferative retinopathy by 47%.
Intensive therapy also reduced the occurrence of microalbuminuria by 54%.
The United Kingdom
prospective Diabetes Study (UKPDS),9 the largest perspective
landmark trial has also demonstrated the increased risk of microvascular
complications with deteriorating glycemic control. There was 25% risk reduction
for microvascular end points, 21% risk reduction for cataract extration &
33% risk reduction for microalbuminuria.
It was the degree of
glycemic control which was important irrespective of type of therapy whether
SUs, insulin or metformin which was used.
Aggressive treatment of even mild to moderate hypertension to a mean of
144/82 mmHg goes a long way in reducing microvascular complications as
evidenced in UKPDS.10 It is more relevant in primary prevention of
nephropathy. In Type-2 Diabetes Mellitus,
hypertension may be part of coexisting essential hypertension but Type-1
Diabetes Mellitus it is always caused by diabetic nephropathy.
ACE inhibitors are drug of choice for all Type-I Diabetics with
microalbuminuria, even if normotensive but still there is not enough evidence
to suggest its usage in Type-2 Diabetics who are normotensive.
In diabetic rodents, deficiency of gamma – Linolenic acid has been
demonstrated. This leads to an imbalance between the lipo-oxygenase and
cyclo-oxygenase system and consequent deficient production of vasodilatory
prostaglandins. However, use of GLA supplements in diabetic neuropathy in
humans has only been partially successful.11
A series of new Aldose reductase inhibitors are now under long term
clinical trials. In animal studies, alpha tocopherol has proved beneficial, but
there is no convincing human data. Alpha Lipoic acid is another antioxidant
used in diabetic neuropathy with fair results as confirmed in ALADIN Study.12
Role of hyperglycemia per se in propagation of macrovascular
complications is less clear, Infact, risk for CAD with hyperglycemia has been
seen with blood sugar levels far below the cut off values even for the
diagnosis of diabetes.
The Whitehall Study13
clearly demonstrated a two-fold increase in CHD mortality after 10 yrs. in men
whose post load capillary glucose was as low as 98 mg%.
The Hoorn Study14.
is a prospective follow up study of 2363 oldermen from Netherlands & has
demonstrated that 2 hour plasma glucose and HBAic levels even in non-diabetic
range are associated with risk of cardiovascular mortality.
UKPDS although revealed
16% reduction in CAD risk by control of hyperglycemia but it failed to be
statistically significant. An impressive CAD risk reduction in a diabetic comes
from reduction in blood pressure, life style modification & most
importantly by lipids lowering drugs like statins as demonstrated in 4S study
where upto 30% CAD risk reduction was achieved. 15
Secondary Prevention of
Complications.
Unfortunately many Type-2 diabetics present with various micro &
macrovascular complications right at the time of diagnosis. About 10% of
patients might have evidence of retinopathy at the time of diagnosis, obviously
because of undetected Type-2 diabetes for several years. This deprives these
patients from primary prevention of microvascular complications.
Hence, any strategy is likely to be more effective in primary than in
secondary prevention. Secondary prevention can only yield good results if
emphasis is on picking up complications early by regular screening for
complications in all diabetics periodically as suggested by ADA also e.g.
Fundoscopy for DR Microalbuminuria for D.Nephropathy, Monofilament &
Biothesiometry for Peripheral Neuorpathy, ABI measurement for PVD & Lipids
estimation for CAD.
Future research has led to the discovery of many interlinking
mechanisms, which lead to manifestations of diabetic complications.
The discovery of RAGE
receptors (Receptors for Advanced Glycation End Products) & the macrophage
receptors explains how glucotoxicity occurs. Moreover, better understanding of
oxidative and carbonyl stress in diabetes, voasoactive and haemodynamic factors
along with genetic predisposition have opened doors for therapeutic
interventions in prevention of complications in diabetes.16-17
RAGE blockers, AGE lytics & development of Nerve growth factors
(NGF) are the possible therapeutic agents of the future.
Protein kinase C (PKC) beta fraction is an enzyme, which is elevated in
diabetics and has already been linked to both diabetic retinopathy and
nephropathy.
An inhibitor of PKC beta has been developed and is being used in
prevention & treatment of diabetic retinopathy & prevention of
Cardiomyopathy in rats.
Histamine is thought to inhibit occludin, a key pretein that regulates “
tight junctions”, permeability. As occludin is greatly reduced in retinas of
diabetic, hence, leakage from these junctions results in macular odema, the
type of retinopathy more commonly seen in Type – 2 diabetics. An antihistamine”
“Hismanal” is being tried to increase the levels of occludin in diabetic
retinas so offers hope to salvage eye sight in diabetics.18
Similarly a new neurotropin, Nerve growth factor–1 (NGF-1) has shown
exceptional promise in Laboratory in protecting both neurons and the schwann
cells even in presence of hyperglycemia. Although results with some aldose
reductase inhibitors were expected theoratically but Sorbinil has been quite
disappointing. Hence, a series of new aldose reductase inhibitors are now under
long term clinical trials.
Microalbuminuria is now considered an indicator of generalized
endothelial dysfunction, hence, correlates well with many macrovascular
complications like CAD, PVD and Stroke.19
Control of hypertension gains precedence over metabolic control, once
microalbuminuria has set in. Dual blockade of Renin Angiotensin system by ACE
inhibitors and ARBs have shown good results.20
Epidemiological data from US Renal Data System (USRDS) has revealed a
strong relationship between oestrogen deficiency and increased risk of diabetic
nephropathy as oestrogens increase matrix metalloproteinases in the measangial
cells thus promoting removal of measangial tissues. Hence, the role of
oestrogens in females with diabetic
nephropathy is being explored.21
References:
1.
King H, Aubert ER, Herman WH
Global burden of Diabetes 1995– 2025.-Prevalence, numerical estimates
and projections.
Diabetes care, 1998; 21 : 1414-1431
2.
Ramachandran A,Sneh Lata C,Vijay
V.
Rising Prevalence of NIDDM in Urban Population in India.Diabetologia
1997; 40: 232-7
3.
Ramachandran A, Diabetes
Research Centre, Chennai – Personal Communication.
4.
Chawla R, Rathore P.- North Delhi
Diabets centre.
To study the prevalence of Diabetic Peripheral Neuropathy by
Biothesiometric Evaluation & its co
association with other complications Novonordisk Diabetes update 2004
proceedings.
5.
WHO expert committee on Diabetes
Mellitus 1980; - Technical Report Series 646.
6.
Barrett-Connor E. – Does
hyperlipidaemia really cause coronary heart disease?
Diabetes care, 1997; 20: 152-6
7.
Balkau B, Bertrais S – Is there a
glycemic thereshold for mortality risk?
Diabetes Care, 1999; 22:696-9
8.
The Diabetes control and
complications trial Research group; the
effect of intensive treatment of diabetes on the development and progression of
long term complications in insulin dependent diabetes mellitus.
N Engl J Med 1993; 329 : 986 - 997
9.
UK prospective Diabetes Study
Group.
Intensive blood glucose control with sulphonyl ureas or insulin compared
with conventional treatment and risk of complications in pts with Type-2
diabetes (UKPDS, 33) Lancet 1998; 352:837-853.
10.
UK prospective Diabetes control
study group. Tight blood pressure control and risk of macrovascular &
microvascular complications in Type-2 diabetes.
BMJ 1998; 317: 703-713
11.
Ward J. D. _ improving prognosis
in Type-2 diabetes.
Diabetes Care1999; 22 (Suppl.2) : B 84-B 88
12.
Ziegler D, Hanefeld M, - The
ALADIN III Study group : treatment of symptomatic diabetic polyneuropathy with alpha
lipoic acid Diabetes Care 1999;
22:1296-1301
13.
Fuller J.H., Shipley M.J. Rose G.
et al
Coronary heart disease risk and impaired glucose tolerance : the
Whitehall study.
Lancet, 1980 ; 8183 : 1373 – 6
14.
Vegrde F., Dekker J. M., Ruke N.
G. et al
Hyperglycemia is associated with all cause and cardiovascular mortality
in the Hoorn population : the Hoorn Study, Diabetologia, 1999 : 42 : 926-31
15.
Pyorala K. Pedersen T. R; Olisson
A.G et al
Cholesterol lowering with simvastatin improves prognosis of diabetic
patients with coronary heart disease. A subgroup analysis of the Scandinavian
simvastatin survival study (4 S) - Diabetes Care, 1997; 20 : 614-20
16.
Baynes JW, Thorpe SR. Role of
oxidative stress in diabetic complications. A new prospective on an old
paradigm. Diabetes 1999; 48 : 1-9
17.
Oturai PS, Christensen M, Robin B
et al. Effects of advanced glycation end products inhibition and protein cross
linked breaking in diabetic rats. Diabetes 1999 ; 48 (Suppl-1) Abs, 151, A 35.
18.
Antonetti DA, Alistair JB, Khin S
et al.
-
Penn State Retine Research gropu
: vascular permeability in experimental diabetes is associated with reduced
endothelial occludin content. Diabetes 1998 ; 47: 1953 – 1959
19.
Castellino P, Shohat J, DeFronzo
RA.
Hyperfiltration and diabetic nephropathy ; is it the beginning ? or is
it the end : Semin Nephrol 1990 ; 10:228-241
20.
Rossing K, Christensen PK, Jensen
BR, Parving HH. ; Dual blockade of the renin Angiotensin system in diabetic
nephropathy. –
Diabetes Care 2002, 25; 95-100
21.
Striker G, Poter M, Elliot SJ et
al
Pathophysiology of diabetic nephropathy : role of oestrogens. In : Di
Mario U, Leonetti F, Signo A (Eds), Diabetes in New Millennium. John Wiley
& Sons Ltd. West Sussex UK 2000 ; 297 – 310
Date : 22nd
June 2004
To,
Dr.
Nitya Nand
Prof. Of
Medicine, PGIMS, Rohtak
President
Elect., IACM
Chairman
Scientific Committee
Respected Sir,
I am sorry to have got late in sending my article. Please find enclosed herewith the copy & CD of my topic “ Prevention of Diabetic Complications” to be presented in IACMCON – 2004 at Agra.
I again request you to please accommodate my session on 24th morning so as to enable me to proceed to chennai in the evening.
Thanking you,
With warm regards,
Yours Sincerely