insulin and the integrity of nerve fibre dr mv srishyla regional medical director novo nordisk india...
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Insulin and the integrity of nerve fibre
Dr MV Srishyla
Regional medical director
Novo Nordisk India
3rd DFSI conference,Jaipur, India12 Sep 2004
3rd annual conference, Diabetic Foot Society of India, Jaipur, India. 12 Sep 2004
•Nerve electrophysiology & morphology
•Animal studies
•Clinical studies
Nerve electrophysiology(1)
• Nerve conduction studies • NCV most sensitive index of severity of DSP• NAPA index of degree of fiber loss
• Relationship between DSP and risk factors• Pittsburgh epidemiology of diab complications study,
1989• DCCT, 1993• EURODIAB type 1 complications study, 1996• Seattle prospective diabetic foot study, 1997• Focus on identifying risk factors for presence of DSP
Nerve electrophysiology(2)
• Tkac I and Bril V. Diabetes Care Oct 1998• Studied the value of GHb, duration, age, sex and height
in predicting the electrophysiologic severity of DSP
• Used different models of severity
• GHb significantly related to severity
• GHb cut-off for highest predictive value
• GHb < 9% vs > 9% (poor control)
• Mean SNCV & SAMP 6.3% & 18% lower resp in poorly controlled
• Corresponds with that achieved in DCCT
Nerve morphology
• Perkins B, Greene D and Bril V. Diabetes Care Apr 2001• Studied the value of GHb, duration, age, sex and height
in predicting the morphologic severity of DSP
• Used different models of severity
• GHb significantly related to severity
• GHb cut-off for highest predictive value
• GHb < 9% vs > 9% (poor control)
• Mean FD 33% (3461 Vs 2334) lower in poorly controlled
•Nerve electrophysiology & morphology
•Animal studies
•Clinical studies
Study 1
•Brussee V, Cunningham FA and Zochodne DW, Diabetes July 2004“Direct insulin signaling of neurons reverses DN”
•Benefits of insulin independent of glycemia• Provides direct support for neurons and
peripheral axons
• Low doses – reverse conduction slowing (abnormal function) and axonal atrophy (abnormal structure)
Study 1: Neurons express insulin receptors
• Insulin had the capability of signaling sensory neurons
• FITC-labelled insulin (intrathecal) accessed and labeled individual lumbar dorsal root ganglion neurons.
L4-6 DRG Neurons
Saline inj
Insulin inj
Immunofluoroscence
Light
Non-diabetic rats
Study 1: Insulin improves conduction abnormalitiesS
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Higher dose of insulin completely reversed slowing of sensory nerve conduction
Study 1: Insulin prevents axonal atrophy
Myelinated sural sensory nerve sections
22.7
18.4
Insulin reversed distal sensory axonal atrophy
Control rat
Diabetic rat
Study 1: Effect of anti-insulin antibody
Non-diabetic rats
Sequestering endogenous insulin generates axonal abnormalities
Study 2
• Zochodne DW, Sun H and Eyer J, Brain Aug 2004
“Accelerated DN in axons without neurofilaments”
• Beneficial effects of insulin on axons when neurofilaments (critical latticework of axons) are damaged• Superimposed STZ-diabetes on transgenic mouse model
with deficient Nf-H protein
• Nf-replete and Nf-deficient diabetic and non-diabetic mice
Study 2: Neurofilament deficiency accelerates diabetic neuropathy - NCV
Diabetic mice lacking
neurofilaments, Nf-dia+,
show a decline in CV betn 4 and 8
weeks of diabetes
Study 2: Neurofilament deficiency accelerates diabetic neuropathy - Amplitude
Study 2: Effect of insulin – electrophysiology and morphology
Nf-Dia+ mice
Non-Neurofilament related actions – e.g new protein synthesis,
mitochondrial target etc
Study 3
• Huang et al, Diabetes, Aug 2003
“Insulin prevents depolarization of mitochondrial membrane in the presence of sustained hyperglycemia”
• Effect of insulin on mitochondrial membrane• Mitochondrial dysfunction
• depolarization / membrane potential measured as whole-cell fluorescent video imaging using rhodamine 123 (R123)
• CCCP ~ Carbonyl cyanide chlorophenylhydrazone
Study 3: Insulin prevents diabetes-induced
mitochondrial dysfunction
Study 3: Insulin action independent of blood glucose levels
Sensory neuron cultures were treated for 6 or 24 h with and without 1.0 nM insulin and mitochondrial polarization status calculated
Sensory neuron cultures were treated for 24 h with 10 or 50 mM glucose and with / without 1.0 nM insulin and mitochondrial polarization status calculated
Study 3: Insulin action independent of blood glucose levels
Summary animal studies
• Insulin signals neurons directly and has distal protective effects
• Insulin prevents axonal loss and atrophy through non-neurofilament related actions
• Insulin prevents depolarization of mitochondrial membrane in sensory neurons
•Nerve electrophysiology & morphology
•Animal studies
•Clinical studies
Studies of intensive insulin therapy
• DCCT, follow-up 6.5 years
• Oslo study, follow-up18 years
•Intensive therapy reduced •Confirmed clinical neuropathy by 64% •Abnormal nerve conduction by 44% •Abnormal autonomic function by 53%
•Nerve conduction velocities •Remained stable with intensive therapy•Decreased significantly with conventional
DCCT study
5%
13%
Ann Intern Med 1995;122:561-8
Oslo study
HbA1c Tertiles None or 1 nerve below ref for NCV
None or 1 nerve below ref for NAPA
<7.8% 92% 77%
7.9-8.4% 91% 73%
>8.4% 53% 53%
HbA1c strong predictor of nerve functionHbA1c<8.4% over 18 years assoc with near normal nerve function
Diabetes Care 2003;26:2400-4
Conclusion
Diabetic neuropathy - Mechanisms
Insulin restores balance between
Nerve degeneration and
regeneration
Diabetic neuropathy - Mechanisms
Insulin↓
Survival response mechanisms↓
PI3-kinase ↓
PKB/Akt↓
Expression/translocation of proapoptotic
factors e.g Bcl-2 proteins
Mixtard 50 study
NovoPen3 study
ICEON iSTART
Year 2000 2000 2002 2003
N 5009 2653 13070 13236
Age 53.3±13 50.3±13.1 53.67±15.6 53.17±9.93
Duration 10±6.9 9.3±6.1 7.87±5.51 7.15±5.18
BMI 24.6±4.9 24.97±4.15 24.83±4.01 24.83±4.35
FPG 192±63 173.9±54.4 203.16±48.8 190.08±41
PPPG 279±83 249.8±77.2 293.05±68.3 276.95±61
HbA1c 9.8±2.2 9.6±3.4 9.6±1.69 9.08±4.11
NN India Experience
Int J Diab Dev Countries 2001;21:133-7;Data on file, 2000; Novo Nordisk Diabetes Update, March 21-23, Colombo, Srilanka 2003: 80-92; iSTART meeting, Rome, 7 May 2004