What is diabetes mellitus, Epidemiology of diabetes, Diabetes diagnosis, Features of diabetes, WHO classification of Diabetes Mellitus, Complications of diabetes, Metabolic alterations of diabetes, Oral glucose tolerance test, WHO criteria of OGTT interpretation, Classification of diabetes mellitus, Gestational diabetes, Pre-diabetes, Insulin, Biosynthesis of insulin, Insulin actions, Hypoglycemia, Impaired fasting glucose, Insulin structure

1. Diagnosis of Diabetes Mellitus
Dr. Subir KumarMandal
MBBS,M.Phil(Biochemistry)

2. Diabetes Mellitus
• Diabetes mellitus is derived from the Greek word “diabetes”
meaning Siphon - to pass through and the Latin word
“mellitus” meaning Honeyed or Sweet.
• This is because in diabetes excess sugar is found in blood as
well as the urine. It was known in the 17th century as the
“pissing evil”.
• Diabetes mellitus is a group of metabolic diseases
characterized by elevated blood glucose levels
(hyperglycemia) resulting from defects in insulin secretion,
insulin action or both.

3. Diabetes Mellitus
• The term diabetes mellitus describes a metabolic disorder of
multiple etiology characterized by chronic hyperglycemia with
disturbances of carbohydrate, fat and protein metabolism
resulting from defects in insulin secretion, insulin action, or
both (WHO).
• Diabetes mellitus is the 3rd leading cause of death (after heart
disease and cancer) in many developed countries. It affects
about 6-8% of general population. In Bangladesh 8.4 million
or 10% of the total population are affected in diabetes mellitus
(WHO).

4. Diabetes Mellitus
• Recent estimates indicate there were 171 million people in the
world with diabetes in the year 2000 and this is projected to
increase to 366 million by 2030.
• Diabetes mellitus is associated with reduced life expectancy,
significant morbidity and diminished quality of life.
• The American Diabetes Association (ADA) estimated the
national costs of diabetes in the USA for 2002 to be $US 132
billion, increasing to $US 192 billion in 2020.

5. Diabetes Mellitus
• Diabetes mellitus may present with characteristic symptoms
such as thirst, polyuria, blurring of vision, and weight loss. In
its most severe forms, ketoacidosis or a non– ketotic
hyperosmolar state may develop and lead to stupor, coma and,
in absence of effective treatment, death.
• Chronic hyperglycemia is associated with microvascular and
macrovascular complications that can lead to visual
impairment, blindness, kidney disease, nerve damage,
amputations, heart disease, and stroke.

6. WHO Criteria of Diabetes Mellitus
 Diabetes
• Fasting plasma glucose ≥7.0 mmol/l (126 mg/dl)
• 2–h plasma glucose* or
≥11.1 mmol/l (200
mg/dl)
 Impaired Glucose Tolerance (IGT)
• Fasting plasma glucose <7.0 mmol/l (126 mg/dl)
• 2–h plasma glucose* and
≥7.8 and <11.1 mmol/l
(140 mg/dl and 200
mg/dl)

7. WHO Criteria of Diabetes Mellitus
 Impaired Fasting Glucose (IFG)
• Fasting plasma glucose 6.1 to 6.9 mmol/l
(110 mg/dl to 125 mg/dl)
• 2–h plasma glucose* and (if measured)
<7.8 mmol/l (140 mg/dl)
 The following Table summarizes the 2006 WHO
recommendations for the diagnostic criteria for diabetes
and intermediate hyperglycemia.

8. Etiological Classification of DM
1. Type-I DM (beta-cell destruction, usually leading to
absolute insulin deficiency)
2. Type-II DM (may range from predominantly insulin
resistance with relative insulin deficiency to a
predominantly secretary defect with or without insulin
resistance)
3. Gestational diabetes**

9. Etiological Classification of DM
4. Other specifictypes
a. Genetic defects of beta-cell function.
b. Genetic defects in insulin action.
c. Diseases of the exocrine pancreas.
d. Endocrinopathies.
e. Drug- or chemical-induced.
f. Infections.
g. Uncommon forms of immune-mediated
diabetes.
h. Other genetic syndromes sometimes
associated with
diabetes.

10. Type-I Diabetes Mellitus
• Caused by the immune destruction of the beta cells of the pancreas.
• Antibodies to islet cells and insulin are present at diagnosis.
• Insulin secretion gradually diminishes.
• May present at any age, but most common in childhood and
adolescence.
• Insulin by injection is necessary for survival.
• Contributing factors:
– Genetic predisposition
– Environmental triggers (infection or other stress)

12. Type-II Diabetes Mellitus
• Caused by insulin resistance in the liver and skeletal muscle,
increased glucose production in the liver, over production of
free fatty acids by fat cells and relative insulin deficiency.
• Insulin secretion decreases with gradual beta cell failure.
• Reductions in blood glucose levels often can be achieved with
changes in food intake and physical activity patterns. Oral
medication and/or insulin injections are eventually required.

13. Type-II Diabetes Mellitus
• Contributing factors:
– Obesity
– Age (onset of puberty is associated with increased insulin
resistance)
– Lack of physical activity
– Genetic predisposition
– Racial/ethnic background (African American, Native American,
Hispanic
and Asian/Pacific Islander)
– Conditions associated with insulin resistance, (e.g. polycystic
ovary

15. Gestational Diabetes
• Gestational diabetes is a type of diabetes that develops or is
first recognized during pregnancy. It is caused by hormone
progesterone & HPL (human placental lactogen) produced
during pregnancy that have insulin antagonistic activity.
• Female are at risk for gestational diabetes if she had a previous
pregnancy with gestational diabetes, Had a baby born
weighing over 9 pounds, Is overweight or obese, Is more than
25 years old, Have a family history of diabetes & She is being
treated for HIV.

16. Gestational Diabetes
• Most women are screened for gestational diabetes at 24-28
weeks gestation during prenatal care.
• Gestational diabetes increases risk of developing type-II
diabetes, large baby (a condition known as macrosomia). This
may cause discomfort during the last few months of
pregnancy.
• Large babies are more likely to suffer from birth trauma. Soon
after delivery, baby may have low blood sugar. This can be
treated with early feedings and should not result in any long-
term consequences after birth.

17. Gestational Diabetes

18. Other specific types
 Genetic defects of beta-cell function
• Chromosome 20, HNF4a (MODY1)
• Chromosome 7, glucokinase (MODY2)
• Chromosome 12, HNF1a (MODY3)
• Chromosome 13, IPF-1 (MODY4)
• Mitochondrial DNA 3243 mutation
• Others
 Genetic defects in insulin action
• Type A insulin resistance
• Leprechaunism
• Rabson-Mendenhall syndrome
• Lipoatrophic diabetes
• Others
 Diseases of the exocrine pancreas
• Fibrocalculous pancreatopathy
• Pancreatitis
• Trauma / pancreatectomy
• Neoplasia
• Cystic fibrosis
• Haemochromatosis
• Others
 Endocrinopathies
• Cushing's syndrome
• Acromegaly
• Phaeochromocytoma
• Glucagonoma
• Hyperthyroidism
• Somatostatinoma
• Others

19. Other specific types
 Infections
• Congenital rubella
• Cytomegalovirus
• Others
 Drug- or Chemical-induced Diabetes
• Nicotinic acid
• Glucocorticoids
• Thyroid hormone
• Alpha-adrenergic agonists
• Beta-adrenergic agonists
• Thiazides
• Dilantin
• Pentamidine
• Vacor
• Interferon-alpha therapy
• Others

20. Other specific types
 Uncommon forms of immune-mediated
diabetes
• Insulin autoimmune syndrome (antibodies to insulin)
• Anti-insulin receptor antibodies
• "Stiff Man" syndrome
• Others
 Other Genetic Syndromes sometimes
associated with diabetes
• Down's syndrome
• Friedreich's ataxia
• Huntington's chorea
• Klinefelter's syndrome
• Lawrence-Moon-Biedel syndrome
• Myotonic dystrophy
• Porphyria
• Prader-Willi syndrome
• Turner's syndrome
• Wolfram's syndrome
• Others

21. Oral Glucose Tolerance Test
• The oral glucose tolerance test (OGTT) is principally used for
diagnosis when blood glucose levels are equivocal, during
pregnancy, or in epidemiological studies.
• The OGTT should be administered in the morning after at least
three days of unrestricted diet (greater than 150 g of
carbohydrate daily) and usual physical activity.
• Recent evidence suggests that a reasonable (30–50g)
carbohydrate containing meal should be consumed on the
evening before the test.

22. Oral Glucose Tolerance Test
• The test should be preceded by an overnight fast of 8–14
hours, during which water may be drunk. Smoking is not
permitted during the test.
• The presence of factors that influence interpretation of the
results of the test must be recorded (e.g. medications,
inactivity, infection, etc.).
• After collection of the fasting blood sample, the subject should
drink 75 g of anhydrous glucose or 82.5 g of glucose
monohydrate in 250–300 ml of water over the course of 5

23. Oral Glucose Tolerance Test
• For children, the test load should be 1.5 to 1.75 g of glucose
per kg body weight up to a total of 75 g of glucose in a similar
volume of water by ratio.
• Timing of the test is from the beginning of the drink. Blood
samples must be collected 2 hours after the test load.
• Unless the glucose concentration can be determined
immediately, the blood sample should be collected in a tube
containing Sodium fluoride (6 mg per ml whole blood).

24. Oral Glucose Tolerance Test
• After collection of blood sample in test tube immediately
centrifuged to separate the plasma; the plasma should be
frozen until the glucose concentration can be estimated.
Indication of OGTT
Fasting blood glucose = 6.1-6.9 mmol/L
Random blood glucose = 7.8-11.0 mmol/L

25. Oral Glucose Tolerance Test
• In case of pregnant women, 100 gm oral glucose is
recommended.
• For individuals with suspected mal-absorption, intravenous
GTT is carried out.

26. Oral Glucose Tolerance Test
 Dawn Effect:
Hypoglycemia at midnight increase secretion of Cortisol, Growth
hormone and Catecholamine. Cortisol secretion peak in between 4 am
& 5 am. and 6 am & 9 am. So fasting blood test done at 8.00 A.M. to
avoid morning hyperglycemia.
 Insulin Surge:
When rapid rise (abnormally) of blood glucose after eating, this
normally leads to insulin secretion (insulin spike) which in turn
initiates rapid glucose uptake by tissues either accumulating it as
glycogen or utilizing it for energy production.

27. OGTT Interpretation
Diagnostic criteria for Oral Glucose Tolerance Test (WHO 1999)
Condition Plasma glucose concentrationas mmol/L(mg/dl)
Normal Impaired glucose tolerance Diabetes
Fasting <6.1 mmol/L <7.0 mmol/L >7.0 mmol/L
(<110 mg/dl) (<126 mg/dl) (>126 mg/dl)
2 hours after <7.8 mmol/L <11.1 mmol/L >11.1 mmol/L
glucose (<140 mg/dl) (<200 mg/dl) (>200 mg/dl)

28. Biochemical Indices of Diabetes
1. Estimation of Glycated Hemoglobin (HbA1C)
2. Plasma Fructosamine
3. Microalbuminuria (albumin excretion is 30-300 mg/day)
4. Serum lipids

29. HbA1C
• The HbA1C blood test- also called glycosylated hemoglobin,
glycohemoglobin or A1c, estimates the average blood sugar
over the previous 2-3 months.
• The HbA1c test is a way to assess blood glucose control over
time. It represents an “average” blood glucose level over the
previous 100 days. However, it does not replace the need for
home blood glucose monitoring on a daily basis.

30. HbA1C
• Normally, some of the glucose (sugar) in the bloodstream
attaches itself to proteins in our body. Hemoglobin, which is
part of our red blood cells, is one of those proteins. This
process is called glycosylation (β- globin chain of HbA) and is
permanent.
• Once the sugar is attached to the hemoglobin, it stays there for
the life of the red blood cell, which is about 100 days (3
months). The higher the level of blood sugar, the more sugar
attaches to hemoglobin and the higher the percent of
hemoglobin which is glycosylated (HbA1c). This is why the
results are given as a percentage.

31. HbA1C
• Normal ranges vary slightly depending on the laboratory being
used. In general, the normal range of HbA1c is 4 % to 6 % in
people without diabetes.
• The WHO Consultation concluded that HbA1c can be used as
a diagnostic test for diabetes. An HbA1c of 6.5% is
recommended as the cut point for diagnosing diabetes.

32. Plasma Fructosamine Concentration
• It is formed by non enzymatic glycosylation of plasma protein
(predominantly albumin). Its normal value is 1.5-2.4 mmol/L.
• It reflects the state of Glycemic control for preceding 2 weeks.

33. Pre-Diabetes
• Pre-diabetes (impaired fasting glucose or impaired glucose
tolerance) is a condition in which blood glucose levels are
higher than normal but not high enough to be diagnosed as
type 2 diabetes.Impaired Fasting Glucose Impaired Glucose Tolerance
IFG is diagnosed when the fasting blood glucose
level is higher than the normal range, but does not
rise abnormally after having a 75 gram glucose
drink**.
IGT is diagnosed when the blood glucose level at 2
hours during an Oral Glucose Tolerance Test **is
higher than the normal range but not high enough
to diagnosetype2 diabetes.

34. Impaired Fasting Glucose
• Also known as pre-diabetes, this is a condition in which
fasting* blood glucose levels are higher than normal but not
high enough to be diagnosed as type-II diabetes.
• It occurs when too much glucose is released into the
bloodstream from the liver overnight. The liver is mainly
responsible for keeping a proper supply of glucose in the blood
when we have not eaten for several hours. In impaired fasting
glucose, the liver does not respond normally to the hormone
insulin and this is called ‘hepatic insulin resistance’. This

35. Impaired Glucose Tolerance
• This condition is also known as pre-diabetes. Blood glucose
levels are higher than normal but still not high enough to be
diagnosed as type 2 diabetes.
• It occurs when the insulin produced does not work properly or
there isn’t enough insulin released to meet the demand, or a
combination of both. The result can be too much glucose in the
blood throughout the day and after meals or on waking, or a
combination of all three.

36. Metabolic Changes in Diabetes
1. Hyperglycemia
2. Glucose toxicity (osmotic effects)
3. Ketoacidosis
4. Hypertriglyceridemia

37. Metabolic Changes in Diabetes

38. Management of Diabetes
1. Dietary management: A diabetic patient is advised to
consume low calories, high protein and high fiber rich diet.
2. Hypoglycemic drugs: The oral hypoglycemic drugs are
broadly of two categories- Sulfonylureas and Biguanides.
The later are less commonly used these days due to side
effects. Sulfonylureas such as acetohexamide, tolbutamide &
glibenclamide are frequently used. They promote the
secretion of endogenous insulin and thus help in reducing
blood glucose level.

39. Management of Diabetes
3. Insulin: Several types of insulin preparations are
commercially available- Short acting insulin (action lasts for
about 6 hours), Long acting insulin ( action lasts for several
hours), Intermediate acting insulin (NPH-Neutral Protamine
Hagedorn) etc.
4. Exercise.

40. Management of Diabetes

41. Insulin
Insulin is a polypeptide hormone produced by the β– cells of
islets of Langerhans of pancreas. It has profound influence on
the metabolism of carbohydrate, fat and protein.
Structure: Human insulin (M.W. 5734) contains 51 amino
acids, arranged in two polypeptide chains. The chain A has 21
amino acids while B has 30 amino acids, which are linked
together by two disulfide bridges. The insulin molecule also
contains an intramolecular disulfide bridge between amino acid
residues of the A-chain.

43. Biosynthesis of Insulin
Biosynthesis: Insulin is synthesized in the beta cells of
pancreas in the form of preproinsulin which is the ultimate
precursor and the gene for this protein synthesis is located on
chromosome 11. Within a minute after synthesis it is
discharged into cisternal space of rough endoplasmic reticulum
where it is cleaved into proinsulin by proteolytic enzymes.
Proinsulin with a C (connecting chain) peptide linking A and B
chains is then transported by microvesicles to the Golgi
apparatus for packaging and storage.

44. Biosynthesis of Insulin

45. Biosynthesis of Insulin
• By the process of proteolysis, C-peptide (31 amino acids, MW
3000) is splited off and insulin is produced, which is composed
of Chain-A & Chain-B connected by disulfide bonds.
• In the β–cells, insulin combines with zinc to form complexes.
In this form, insulin is stored in the granules of the cytosol
which is released in response to various stimuli by exocytosis.

46. Biosynthesis of Insulin
• Measurement of serum C-peptide often helpful for assessing
pancreatic β-cell function, for diagnosis of various
hypoglycemic conditions, Islet cell tumor etc. C-peptide is
essential for proper insulin folding. Also, because of its longer
half-life in plasma, the C-peptide is a good indicator of insulin
production & secretion.
• Normal fasting insulin concentration is 0.2-0.8 ng/ml.
• Normal fasting C-peptide concentration is 1-2 ng/ml.

47. Types of Insulin

48. Rapid Actions of Insulin
1. Increases peripheral uptake of glucose.
2. Increases amino acid uptake into cells.
3. Stimulates potassium influx into cell leading to hypokalemia.

49. Metabolic Effects of Insulin

50. Hypoglycemia
• When the blood glucose concentration falls to less than 3.3
mmol/L, the symptoms of Hypoglycemia appear.
• The manifestations include headache, anxiety, confusion,
sweating, slurred speech, seizures and coma, and, if not
corrected, death. All these symptoms are directly and indirectly
related to the deprivation of glucose supply to the central
nervous system (particularly the brain) due to a fall in blood
glucose level.

51. Hypoglycemia

52. Types of Hypoglycemia
1. Post-prandial hypoglycemia: This is also called reactive
hypoglycemia and is observed in subjects with an elevated
insulin secretion following a meal. This causes transient
hypoglycemia and is associated with mild symptoms. The
patient is advised to eat frequently rather than the 3 usual
meals.
2. Fasting hypoglycemia : Low blood glucose concentration in
fasting is not very common. However, fasting hypoglycemia
is observed in patients with pancreatic β-cell tumor
(insulinoma) and hepatocellular damage.

53. Types of Hypoglycemia
3. Hypoglycemia due to alcohol intake : In some individuals
who are starved or engaged in prolonged exercise, alcohol
consumption may cause hypoglycemia. This is due to the
accumulation of NADH (during the course of alcohol
metabolism by alcohol dehydrogenase) which diverts the
pyruvate and oxaloacetate (substrates of gluconeogenesis) to
form, respectively, lactate and malate. The net effect is that
gluconeogenesis is reduced due to alcohol consumption.

54. Types of Hypoglycemia
4. Hypoglycemia due to insulin overdose: The most common
complication of insulin therapy in diabetic patients is
hypoglycemia. This is particularly observed in patients who
are on intensive treatment regime.
5. Hypoglycemia in premature infants: Premature and
underweight infants have smaller stores of liver glycogen, low
muscle & adipose tissue mass, malfunctioned gluconeogenic
enzymes and are susceptible to hypoglycemia.

55. Hypoglycemia
Lab. Investigations:
1. Blood glucose concentration- Low.
2. Serum insulin concentration- High in insulinoma.
3. Serum C-peptide concentration-High in insulinoma.
4. Liver function tests.
5. Hormonal assay- Cortisol, Growth hormone etc.