• A widespread pathological change is thickening of
capillary basement membrane, increase in vessel wall matrix and cellular
proliferation resulting in vascular complications like

• Lumen narrowing,

• Early atherosclerosis,

• Sclerosis of glomerular capillaries,

• Retinopathy,

• Neuropathy

• Peripheral vascular insufficiency.

• Enhanced glycosylation of tissue proteins due to persistent
exposure to high glucose concentrations and the accumulation of larger quantities
of sorbitol (a reduced product of glucose) in tissues are believed to be
causative in the pathological changes of diabetes.

Symptoms of
DM

• Frequent Urination

• Blurry Vision

• Tingling in Hand and Feet

• Sudden Weight Loss

• Always Hungry

• Always Thirsty

• Wounds take time to heal

Glycosuria

Types of
diabetes mellitus

Type 1
Diabetes

• Type 1 Insulin-dependent diabetes mellitus (IDDM)
/juvenile onset diabetes mellitus:

• There is β cell destruction in pancreatic islets; majority
of cases are autoimmune (type 1A) antibodies that destroy β cells are
detectable in blood.

• In all type 1 cases circulating insulin levels are low and
patients are more prone to ketosis.

• This type is less common and has a low degree of genetic
predisposition.

Type II
(NIDDM)

• Type II Noninsulin-dependent diabetes mellitus (NIDDM)/maturity
onset diabetes mellitus:

• Has a high degree of genetic predisposition; generally has
a late onset (past middle age). Over 90% cases of diabetes are type 2 DM.

• Cause: Reduced
sensitivity of peripheral tissues to insulin.

Type 2 Diabetes
causes

Insulin

• Insulin was discovered in 1921 by Banting and Best who
demonstrated the hypoglycaemic action of an extract of pancreas.

Insulin
structure

• Insulin is a two chain polypeptide having 51 amino acids
and MW about 6000. The A-chain has 21 while B-chain has 30 amino acids.

• There are minor differences between human, pork and beef
insulins: pork insulin is more homologous to human insulin than is beef
insulin.

• Insulin is synthesized in the β cells of pancreatic islets

Actions of
insulin

• Insulin facilitates glucose transport across cell
membrane; skeletal muscle and fat are highly sensitive.

• Insulin facilitates glycogen synthesis from glucose in
liver, muscle and fat by stimulating the enzyme glycogen synthase.

• Insulin inhibits gluconeogenesis (from pro- tein, FFA and
glycerol) in liver.

• Insulin inhibits lipolysis in adipose tissue and favours
triglyceride synthesis.

• In diabetes increased amount of fat is broken down due to
unchecked action of lipolytic hormones (glucagon) → increased FFA and glycerol
in blood → taken up by liver to produce acetyl-CoA.

• Normally acetyl-CoA is resynthesized to fatty acids and
triglycerides, but this process is reduced in diabetics and acetyl CoA is
diverted to produce ketone bodies (acetone, acetoacetate,β-hydroxy-butyrate).

• Insulin facilitates AA entry and their synthesis into
proteins, as well as inhibits protein breakdown in muscle and most other cells.

Insulin deficiency leads to protein breakdown → AAs are released
in blood → taken up by liver and converted to Glucose.

Actions of
insulin producing hypoglycaemia

Liver

Muscle

Adipose
tissue

▲Increases
glucose uptake and glycogen synthesis

▲Increases
glucose uptake and utilization

▲Increases
glucose uptake and storage as fat and glycogen

▲Inhibits
glycogenolysis and glucose output.

▲Inhibits
proteolysis and release of amino acids. into blood which form the substrate
for gluconeogenesis in liver

▲ Inhibits
lipolysis and release of FFA which form substrate for gluconeogenesis in
liver

▲Inhibits
gluconeogenesis from protein and FFA

Fate of
insulin

• Insulin is distributed only extracellularly.

• It is a peptide; gets degraded in the g.i.t. if given
orally.

• Injected insulin or that released from pancreas is
metabolized primarily in liver and to a smaller extent in kidney and muscles.

• The plasma t½ is 5–9 min.

Preparations
of insulin

• The older commercial preparations were produced from beef
and pork pancreas.

• They contained ~1%(10,000 ppm) of other proteins
(proinsulin, other polypeptides, pancreatic proteins, insulin derivatives,
etc.) which were potentially antigenic.

• They are no longer produced and have been totally replaced
by highly purified pork/beef insulins/recombinant human insulins/insulin
analogues.

Highly
purified insulin preparations

• In the 1970s improved purification techniques like gel
filtration and ion-exchange chromatography were applied to produce
‘monocomponent (MC)’ insulins which contain <10 ppm proinsulin.

• They are less antigenic.

Types of
insulin preparations

Regular (soluble)
insulin

• It is a buffered neutral pH solution of unmodified insulin
stabilized by a small amount of zinc.

• At the concentration of the injectable solution, the
insulin molecules self-aggregate to form hexamers around zinc ions.

• After s.c. injection, insulin monomers are released
gradually by dilution, so that absorption occurs slowly.

• Peak action is produced only after 2–3 hours and action
continues upto 6–8 hours.

Lente insulin
(Insulin-zinc suspension)

• Two types of insulin-zinc suspensions have been produced.

• The one with large particles is crystalline and
practically insoluble in water (ultralente). It is long-acting.

• The other has smaller particles and is amorphous
(semilente), is short- acting.

• Their 7:3 ratio mixture is called ‘Lente insulin’ and is
intermediate-acting.

Isophane (Neutral
Protamine Hagedorn or NPH) insulin

• Protamine is added in a quantity just sufficient to
complex all insulin molecules;

• Neither of the two is present in free form and pH is
neutral.

• On s.c. injection, the complex dissociates slowly to yield
an intermediate duration of action.

Insulin Preparations
available

• 1. Highly purified (monocomponent) pork regular insulin:
ACTRAPID MC, RAPIDICA 40U/ml inj.

• 2. Highly purified (MC) pork lente insulin: LENTARD,
MONOTARD MC, LENTINSULIN-HPI, ZINULIN 40 U/ml.

• 3. Highly purified (MC) pork isophane (NPH) insulin:
INSULATARD 40 U/ml inj.

Human
insulins

• In the 1980s, the human insulins (having the same amino
acid sequence as human insulin) were produced by recombinant DNA technology in
Escherichia coli—‘proinsulin recombinant bacterial’ (prb) and in
yeast—‘precursor yeast recombinant’ (pyr), or by ‘enzymatic modification of
porcine insulin’ (emp).

Human insulins available

• 1. HUMULIN R: Human regular insulin; 40 U/ml, 100 U/ml.

• 2. HUMULIN-L: Human lente insulin; 40 U/ml, 100 U/ml.

• 3. HUMULIN-N: Human isophane insulin 40 U/ml.

Availability
of insulin

• In the USA pork and beef insulins are no longer
manufactured, but they are still available in U.K., India and some European
countries.

• In Britain now > 90% diabetics who use insulin are
taking human insulins or insulin analogues.

• In India also human insulins and analogues are commonly
used, except for considerations of cost.

Reactions
to insulin

Hypoglycaemia

• can occur in any diabetic following inadvertent injection
of large dose, by missing a meal after injection or by performing vigorous
exercise.

• The symptoms can be divided into those due to counter-regulatory
sympathetic stimulation—sweating, palpitation, tremor;

• And those due to deprivation of the brain of its essential
nutrient glucose (neuroglucopenic symptoms)—dizziness, headache, behavioural
changes,fatigue.

• Treatment:
Glucose must be given orally or i.v. (for severe cases)—reverses the symptoms
rapidly.

Local reactions:

• Lipodystrophy of the subcutaneous fat around the injection
site may occur if the same site is injected repeatedly. This is rare with the
newer preparations.

Allergy:

• This is due to contaminating proteins, and is very rare
with human/highly purified insulins. Urticaria, angioedema and anaphylaxis are
the manifestations.

Uses of
insulin

• Diabetes mellitus

• Insulin is effective in all forms of diabetes mellitus and
is a must for type 1 cases, and gestational diabetes.

• Many type 2 cases can be controlled by diet, reduction in
body weight and appropriate exercise supplemented, if required, by oral
hypoglycaemics.

Insulin
requirment in Type 2 DM

• Insulin is needed by patients with type 2 DM patient when:

• Not controlled by diet and exercise or when these are not
practicable.

• Primary or secondary failure of oral hypoglycaemics or
when these drugs are not tolerated.

• Underweight patients.

• Temporarily to tide over infections, trauma, surgery,
pregnancy. In the perioperative period and during labour, monitored i.v.
insulin infusion is preferable.

• Any complication of diabetes, e.g. ketoacidosis,
nonketotic hyperosmolar coma, gangrene of extremities.

Dose of
insulin

• Most type 1 patients require 0.4–0.8 U/kg/day.

• In type 2 patients, insulin dose varies (0.2–1.6U/kg/day)
with the severity of diabetes and body weight:

• Obese patients require proportionately higher doses due to
relative insulin resistance.

Diabetic
ketoacidosis

• Generally occurs in insulin dependent diabetics. (Type 1
DM)

• Precipitating cause is infection; others are trauma,
stroke, pancreatitis, stressful conditions and inadequate doses of insulin.

Treatment of DKA

• Insulin

• Intravenous fluids

• KCl: When insulin therapy is instituted ketosis subsides
and K+ is driven back intracellularly— dangerous hypokalemia can occur.

• Sodium bicarbonate

• Antibiotics

Hyperosmolar
(nonketotic hypergly-caemic) coma

• occurs in type 2 DM.

• Uncontrolled glycosuria of DM produces diuresis resulting
in dehydration and haemoconcentration over several days → urine output is
finally reduced and glucose accumulates in blood rapidly to > 800 mg/dl,
plasma osmolarity is > 350 mOsm/ L → coma, and death can occur

Hyperosmolar coma management

• The general principles of treatment are the same as for
ketoacidotic coma, except that faster fluid replacement is to be instituted and
alkali is usually not required.

• These patients are prone to thrombosis (due to
hyperviscosity and sluggish circulation), prophylactic heparin therapy is
recommended.

Oral
hypoglycemic drugs

• These drugs lower blood glucose levels and are effective
orally.

• The chief drawback of insulin is—it must be given by injection.

Classification of Oral hypoglycemic
drugs

Enhance Insulin secretion

1. Sulfonylureas

• First generation: Tolbutamide

• Second generation: Glibenclamide, Glipizide,

2. Meglitinide
analogues

• Repaglinide, Nateglinide

3. Glucagon-like
peptide-1 (GLP-1) receptor agonists (Injectable drugs)

• Exenatide, Liraglutide

4. Dipeptidyl
peptidase-4 (DPP-4) inhibitors

• Sitagliptin, Vildagliptin.

Overcome Insulin resistance

1. Biguanide

• Metformin

2. Thiazolidinediones
(PPAR γ activator)

• Pioglitazone

Miscellaneous antidiabetic drugs

• α-Glucosidase inhibitors

• Acarbose, Miglitol, Voglibose

• Sodium-glucose cotransport-2 (SGLT-2) Inhibitor:
Dapagliflozin

Drugs which
enhance insulin secretion

Sulfonylureas
(K_ATPChannel blockers)

• Mechanism of action: Sulfonylureas provoke a brisk release
of insulin from pancreas.

Adverse effects of SU

• Hypoglycaemia

• Hypersensitivity

Meglitinide
analogues (K_ATP Channel blockers)

• MOA: release of
insulin from pancreas.

• Drugs:
Repaglinide, Nateglinide.

• They induce rapid onset short lasting insulin release.

• Administered before each major meal to control post
prandial hyperglycemia.

Glucagon-like
peptide-1 (GLP-1) receptor agonists

• GLP-1 is an important incretin released from the gut in
response to ingested glucose.

• It induces insulin release from pancreatic β cells,
inhibits glucagon release from α cells, slows gastric emptying and suppresses
appetite.

• Drugs available: Exenatide, Liraglutide(Victoza)

Dipeptidyl
peptidase-4 (DPP-4) inhibitors

• DPP-4 in rapid degradation of endogenous GLP-1, orally
active inhibitors of DPP-4 have been developed as indirectly acting insulin
secretagogues.

• Sitagliptin, Vildagliptin, Saxagliptin

Drugs which
overcome insulin resistance

Biguanide

• Phenformin higher risk of lactic acidosis banned in India
since 2003.

• Metformin:
Enhances insulin-mediated glucose uptake and disposal in skeletal muscle and
fat.

• Adverse effects:
Lactic acidosis, g.i. intolerance.

Thiazolidinedione
(PPAR
γ agonist)

Pioglitazone

• MOA: Glitazones
tend to reverse insulin resistance by enhancing GLUT4 expression and
translocation.

• Entry of glucose into muscle and fat is improved.

• (Rosiglitazone, is banned in India due to unacceptable
increase in risk of myocardial infarction, CHF, stroke and death.)

Miscellaneous

α Glucosidase inhibitors

• Acarbose: inhibits α-glucosidases, the final enzymes for
the digestion of carbohydrates in the brush border of small intestine mucosa.

• Flatulence, abdominal discomfort and loose stool are
produced in about 50% patients due to fermentation of unabsorbed carbohydrates.

Sodium-glucose
co-transport-2 (SGLT-2) Inhibitor

• Practically all the glucose filtered at the glomerulus is
reabsorbed in the proximal tubules.

• The major transporter which accomplishes this is SGLT-2,

• Inhibition of SGLT-2 induces glucosuria and lowers blood
glucose in type 2 DM, as well as causes weight loss.

Anti-Diabetic Drugs

Diabetes mellitus (DM) definition

Pathophysiology of DM

Symptoms of DM

Glycosuria

Types of diabetes mellitus

Type 1 Diabetes

Type II (NIDDM)

Type 2 Diabetes causes

Insulin

Insulin structure

Actions of insulin

Actions of insulin producing hypoglycaemia

Fate of insulin

Preparations of insulin

Highly purified insulin preparations

Types of insulin preparations

Regular (soluble) insulin

Lente insulin (Insulin-zinc suspension)

Isophane (Neutral Protamine Hagedorn or NPH) insulin

Insulin Preparations available

Human insulins

Human insulins available

Availability of insulin

Reactions to insulin

Hypoglycaemia

Local reactions:

Allergy:

Uses of insulin

Insulin requirment in Type 2 DM

Dose of insulin

Diabetic ketoacidosis