This document summarizes information about diabetes, including its definition, classification, effects of insulin, and treatments. It begins with an overview of diabetes, defining it as a group of metabolic disorders involving hyperglycemia. It then discusses the two main types of diabetes - type 1 characterized by insulin deficiency and type 2 characterized by insulin resistance - and their causes. Subsequent sections provide details on insulin biosynthesis and secretion, its counter-regulation, effects in different tissues, and role in glucose homeostasis. The document concludes by outlining several classes of medications used to treat diabetes, including sulfonylureas, thiazolidinediones, and newer drugs that target incretin hormones.

1. Master Degree in Medical Biotechnologies
INTERNAL MEDECINE
DIABETES: THE BIOLOGICAL BASES OF
TREATMENT

2. DIABETES
DEFINITION: heterogeneous group of metabolic disorders that
share the phenotype of hyperglycemia
EPIDEMIOLOGY: diabetes prevalence is increasing worldwide,
it is similar in males and females and it is related with age:
• age < 20 years prevalence 0.19%
• age > 20 years prevalence 8.6%
• age > 65 years prevalence 20.1%
HEALTHCARE IMPACT: diabetes is the main cause of renal
failure, limbs amputation and blindness in adults (USA
epidemiologic data)

3. CLASSIFICATION
Type 1 Diabetes is characterized by insufficient insulin secretion
due to the loss of beta cells in Langherans Islets
• autoimmune (tipo IA)
• idiopathic (tipo IB)
Type 2 Diabetes is characterized by insulin resistence
• congenital (very uncommon)
• idiopathic (common, adult-onset, related with
obesity and metabolic syndrome).

7. INSULIN
• Insulin is syntetized by b cells into the Langerhans islets (endocrine
pancreas); from the polypeptidic precursor, consisting of a single chain of
86 aa, the preproinsulin, through a proteolytic process, we obtain the
proinsulin and from this, for detachment of an internal peptide of 31 aa,
called C-peptide, insulin is obtained. The active hormone is formed by two
amino acid chains of 21 and 30 aa, called A and B chain respectively,
joined together by disulfide bridges
• Insulin is a small protein (PM 6 kDa) that is stored in the cytoplasm of b
cells within secretory vescicles
• Insulin secretion is stimulated by: plasma glucose concentration, gastrin,
GP-1, VIP, aa, vagus nerve.
• Insulin secretion is Ca2+ dependent and it is strictly dependent also by ATP
intracellular concentration
• Insulin secretion shows a pulsatile profile with small peaks, that occur
every 10 minutes, and large peaks, lasting 2-3 hours, induced by meals.

8. COUNTER-REGULATION OF INSULIN
SECRETION
Insulin secretion is inhibited when plasma glucose concentration is lower than
70 mg/dL
In addition to direct control exerted by plasma glucose there are several
hormones that antagonize insulin:
• GLUCAGON (secreted by alpha cells in pancreas islet)
• CATECHOLAMINES
• CORTISOL

9. breakfast dinnerlunch sleep
PlasmaInsulin
Modified from:
1. Leahy JL. In: Leahy JL, Cefalu WT, eds. Insulin Therapy. New York, NY: Marcel Dekker, Inc.; 2002.
2. Bolli GB et al. Diabetologia. 1999;42:1151-1167.
Basal secretion
Post-prandial secretion
NORMAL INSULIN SECRETION PROFILE

10. INSULIN BIOSYNTESIS

11. INSULIN STRUCTURE
A-chain
B-chain

12. INSULIN EFFECTS
ANABOLIC EFFECT: Insulin determines internalization into
cells of glucose, FFA and aa, it activates enzymes involved in
glycogen synthesis, TG and proteins. Finally insulin inhibits
enzymes that degrade them
LIVER: Insulin increases glycogen, inhibits gluconeogenesis,
glycogenolysis, b-oxidation of fatty acids and ketogenesis
MUSCLE: Insulin increases the synthesis of insulin-
dependent glucose transporters (Glut-4) and induces its
translocation to the cell membrane, induces glycogen
synthesis, inhibits glycogenolysis.
ADIPOSE TISSUE: stimulates the storage of FFA in the form
of triglycerides, inhibits the hormone-sensitive lipase causing
block of hydrolysis of TG and fall of glycerol and FFA
plasma concentrations.

13. INSULIN EFFECTS

14. GLUCOSE HOMEOSTASIS

15. Date of download: 3/5/2015 Copyright © 2015 McGraw-Hill Education. All rights reserved.
Mechanisms of glucose-stimulated insulin secretion and abnormalities in diabetes. Glucose and other nutrients regulate insulin secretion by the
pancreatic beta cell. Glucose is transported by a glucose transporter (GLUT1 in humans, GLUT2 in rodents); subsequent glucose metabolism by
the beta cell alters ion channel activity, leading to insulin secretion. The SUR receptor is the binding site for some drugs that act as insulin
secretagogues. Mutations in the events or proteins underlined are a cause of maturity-onset diabetes of the young (MODY) or other forms of
diabetes. SUR, sulfonylurea receptor; ATP, adenosine triphosphate; ADP, adenosine diphosphate, cAMP, cyclic adenosine monophosphate. IAPP,
islet amyloid polypeptide or amylin.
Legend:
INSULIN SECRETION
From: Chapter 344. Diabetes Mellitus
Harrison's Principles of Internal Medicine, 18e, 2012

16. EFFETTI DELL’INSULINA NEL FEGATO

17. Date of download: 3/5/2015 Copyright © 2015 McGraw-Hill Education. All rights reserved.
Insulin signal transduction pathway in skeletal muscle. The insulin receptor has intrinsic tyrosine kinase activity and interacts with insulin
receptor substrates (IRS and Shc) proteins. A number of "docking" proteins bind to these cellular proteins and initiate the metabolic actions of
insulin [GrB-2, SOS, SHP-2, p110, and phosphatidylinositol-3&prime;-kinase (PI-3-kinase)]. Insulin increases glucose transport through PI-3-
kinase and the Cbl pathway, which promotes the translocation of intracellular vesicles containing GLUT4 glucose transporter to the plasma
membrane.
Legend:
INSULIN SIGNAL TRANSDUCTION
From: Chapter 344. Diabetes Mellitus
Harrison's Principles of Internal Medicine, 18e, 2012

18. INSULIN RESISTANCE
• is defined as the decreased ability of insulin to act effectively
on target tissues (especially muscle, liver, and fat)
• is a prominent feature of type 2 DM and results from a
combination of genetic susceptibility and obesity.
• Insulin resistance may remain silent for a long time, since
supranormal levels of circulating insulin will normalize the
plasma glucose.
• Insulin resistance impairs glucose utilization by insulin-
sensitive tissues and increases hepatic glucose output; both
effects contribute to the hyperglycemia

19. • Insulin resistance and abnormal insulin secretion are central to the
development of type 2 DM.
• Insulin resistance precedes an insulin secretory defect but diabetes
develops only when insulin secretion becomes inadequate.
• Type 2 DM is polygenic and multifactorial, since in addition to
genetic susceptibility, environmental factors modulate the
phenotype.
• The genes that predispose to type 2 DM are incompletely
identified, but recent genome-wide association studies have
identified a large number of genes involved; the most prominent is a
variant of the transcription factor 7–like 2 gene
• Genetic polymorphisms associated with type 2 diabetes have also
been found in the genes encoding the peroxisome proliferators–
activated receptor-γ, potassium channel, zinc transporter, IRS, and
calpain 10.
TYPE 2 DIABETES MELLITUS

20. SEVERE INSULIN RESISTANCE

21. OTHER MECHANISMS OF INSULIN
RESISTANCE

22. OBESITY AND INSULIN RESISTANCE
• Adipocytes secrete a number of biologic products
(nonesterified free fatty acids, retinol-binding protein 4, leptin,
TNF-α, resistin, and adiponectin)
• Adipokines modulate insulin sensitivity.
• The increased production of free fatty acids and some
adipokines may cause insulin resistance in skeletal muscle and
liver.
• Free fatty acids impair glucose utilization in skeletal muscle,
promote glucose production by the liver, and impair beta cell
function.
• In contrast, the production by adipocytes of adiponectin, an
insulin-sensitizing peptide, is reduced in obesity.and this may
contribute to hepatic insulin resistance.

23. • Adipocyte products and adipokines also produce an
inflammatory state and may explain why markers of
inflammation such as IL-6 and C-reactive protein are often
elevated in type 2 DM.
• In addition, inflammatory cells have been found infiltrating
adipose tissue. Inhibition of inflammatory signaling pathways
such as the nuclear factor κB (NF-κB) pathway appears to
reduce insulin resistance and improve hyper-glycemia in animal
models.
OBESITY AND INFLAMMATION

24. DEVELOPMENT OF DRUGS FOR
THE TREATMENT OF DIABETES
MELLITUS

25. 1. Drugs that sensitize the
body to insulin and/or
control hepatic glucose
production
2. Drugs that stimulate the
pancreas to make more
insulin
3. Drugs that slow the
absorption of starches
Thiazolidinediones
Biguanides
Sulfonylureas
Meglitinides
Alpha-glucosidase
inhibitors
MAJOR CLASSES OF
MEDICATIONS

26. NEW DRUGS
• INCRETINS

27. SULFONYLUREAS

28. THIAZOLIDINEDIONES
• PPAR-g nuclear receptor agonists (peroxisome proliferator-
activated receptor g)
 They increase the FFA storage in adipose tissue
reducing their circulating concentration
 induce expression on the cell membrane and
translocation of Glut-4
 reduce the adipocytes TNF-a release

29. In healthy subjects an
oral glucose load
stimulates an higher
insulin release (3-4
fold) with respect to iv
administration of the
same amount of
glucose. This “incretin
effect” is impaired in
patients with Type 2
diabetes.
INCRETIN EFFECT

30. GLP-1 and GIP are the two major incretin hormones found in
humans.
These incretins are released from the gut in response to ingestion
of food and collectively contribute to glucose control by:
 Stimulating glucose-dependent insulin release from
pancreatic beta cells (GLP-1 and GIP); insulin increases glucose
uptake in peripheral tissues (mainly muscle and fat) and
suppresses glucose production from the liver.
 Decreasing glucagon production from pancreatic alpha cells
(GLP-1) when glucose levels are elevated.
INCRETINS

31. GLP-1 (glucagon-like
peptide 1)
• Produced by L cells in
ileum and in colon
GIP (glucose-dependent
insulinotropic polypeptide)
• Produced by K cells in
duodenum and proximal
jejunum
INCRETINS
dipeptidyl peptidase-4 (DPP-4)
• Enzyme that rapidly inactivates endogenous
GLP-1 and GIP
• Its inhibition enhances and prolongs the actions
of both GLP-1 and GIP.

32. INCRETINS AND DPP-4

34. • Binds GLP-1 receptor
• More resistant than GLP-1 to the action of
DPP-4
• Originally isolated from Gila monster
saliva
I have never been called to attend a case of Gila monster
bite, and I don't want to be. I think a man who is fool
enough to get bitten by a Gila monster ought to die. The
creature is so sluggish and slow of movement that the
victim of its bite is compelled to help largely in order to get
bitten.
—Dr. Ward, Arizona Graphic, September 23, 1899
EXENATIDE

35. • Orally active DPP-4 inhibitor
• Prolungues and enhances the action
of endogenous GLP-1 and GIP.
SITAGLIPTIN

36. BRIEF INSULIN HISTORY
• Langerhans described pancreatic islets in the second half of the nineteenth
century
• after a few years it has been observed that dogs developed a syndrome
similar to DM after pancreatectomy
• in the early '900 has been observed that the administration of
hydroalcoholic extracts of pancreas was able to determine the reduction of
glycosuria in diabetic dogs
• in 1922 Banting and Best (Toronto) treated the first DM patient with
pancreatic islets extract
• Banting and Macleod, an expert in chemical extraction techniques, began to
develop a method that was used to obtain stable extracts of insulin and this
led them to win the Nobel Prize for Medicine in 1923

37. INSULIN TREATMENT
• after insulin discovery patients were treated with insulin preparations from porcine
or bovine pancreatic extracts for >70 years; these hormones were characterized by
immunogenicity because they present some differences in aa sequences with respect
to human insulin (1 and 3 aa respectively)
• with the advent of human insulin, beef and pork insulin are no longer produced
• Human insulin is produced by recombinant DNA technology
• In 1978 insulin became the first human protein to be manufactured through
biotechnology. A team of researchers from the City of Hope National Medical
Center and the biotechnology company Genentech managed to synthesize human
insulin in the laboratory using a process that could produce large amounts.
The team inserted the gene for human insulin into bacterial DNA, and used the
bacteria as miniature factories to make the A and B chains of the protein separately.
In a second step, a chemical process combined them. The result was human insulin,
without the problems animal insulin sometimes causes.
• Humulin, as the commercial product was called, revolutionized diabetes treatment
when it became widely available in the early 1980s. Today, almost all diabetic
people use recombinant human insulin instead of animal insulin.

38. Two approaches are used to modify the absorption and
pharmacokinetic profile of insulin.
• The first approach, which has been used for >70 years to alter
the absorption profile of native insulin, is based on formulations
that slow the absorption following subcutaneous injection.
• The other approach is to alter the amino acid sequence or protein
structure of human insulin so that it retains its ability to bind the
insulin receptor, but its behavior in solution or following injection
is either accelerated or prolonged in comparison to native or
regular insulin
INSULIN FORMULATION

39. INSULIN ABSORPTION: FROM
SUBCUTANEOUS TISSUE TO BLOODSTREAM

40. CHEMICAL MANIPULATION
• Slow insulin NPH (neutral protamine Hagedorn) o isophane
insulin suspension: zinc and protamine complexed insulin
suspension in phosphate buffer
• Because of this formulation, the insulin dissolves more gradually
when injected subcutaneously and thus its duration of action is
prolonged. NPH insulin is usually given either once a day (at
bedtime) or twice a day in combination with short-acting insulin.

41. GENETIC MANIPULATION
• Short-acting insulin analogs (lispro, aspart, glulisine) dissociates into
monomers almost instantaneously following injection. This property results in
the characteristic rapid absorption and shorter duration of action compared
with regular insulin. Two therapeutic advantages have emerged with these
analogs as compared with regular insulin: the prevalence of hypoglycemia is
reduced and glucose control is modestly but significantly improved.
• Slow-acting insulin analog (glargine or LANTUS) is a long-acting analog of
human insulin that is produced following two alterations of human insulin.
Two arginine residues are added to the C terminus of the B chain, and an
asparagine molecule in position 21 on the A chain is replaced with glycine.
Insulin glargine is a clear solution with a pH of 4.0, which stabilizes the
insulin hexamer. When injected into the neutral pH of the subcutaneous
space, aggregations occurs, resulting in prolonged, but predictable, absorption
from the injection site. In clinical studies glargine has a sustained peakless
absorption profile, and provides a better once-daily 24-hour insulin coverage
than NPH insulin.

42. Date of download: 3/6/2015 Copyright © 2015 McGraw-Hill Education. All rights reserved.
Insulin analogs. Modifications of native insulin can alter its pharmacokinetic profile. Reversing amino acids 28 and 29 in the B chain (lispro) or
substituting Asp for Pro28B (aspart) gives analogs with reduced tendencies for molecular self-association that are faster acting. Altering Asp3B
to Lys and Lys29B to Glu produces an insulin (glulisine) with a more rapid onset and a shorter duration of action. Substituting Gly for Asn21A
and lengthening the B chain by adding Arg31 and Arg32 produces a derivative (glargine) with reduced solubility at pH 7.4 that is, consequently,
absorbed more slowly and acts over a longer period of time. Deleting Thr30B and adding a myristoyl group to the ε-amino group of Lys29B
(detemir) enhances reversible binding to albumin, thereby slowing transport across vascular endothelium to tissues and providing prolonged
action.
Legend:
From: Chapter 43. Endocrine Pancreas and Pharmacotherapy of Diabetes Mellitus and Hypoglycemia
Goodman &amp; Gilman's The Pharmacological Basis of Therapeutics, 12e, 2011

43. INSULIN ANALOGUES

44. PHARMACOKINETIC

45. breakfast dinnerlunch sleep
PlasmaInsulin
Modified from:
1. Leahy JL. In: Leahy JL, Cefalu WT, eds. Insulin Therapy. New York, NY: Marcel Dekker, Inc.; 2002.
2. Bolli GB et al. Diabetologia. 1999;42:1151-1167.
Basal secretion
Post-prandial secretion
DO YOU REMEMBRE THE NORMAL INSULIN
SECRETION PROFILE?
Short-acting analog
Slow-acting analog

46. OTHER TREATMENT OPTIONS
• Continuous subcutaneous insulin infusion (CSII) pumps
• Pancreas islets transplantation
• Stem cells