1. Diabetes Mellitus An Inborn Error of Metabolism ?
HKSPEM Clinical Meeting
8 May 2008
Diabetes Mellitus An Inborn Error of Metabolism ?
Dr Grace Poon
Department of Paediatrics and Adolescent Medicine
Queen Mary Hospital

2. PKH Male / 14 years
Para 1 FT LSCS for fetal distress in Canossa Hospital
Mother with GDM since 7 mths of gestation – on diet control
IUGR – induction of labour
Born SGA with birth weight of 2.4 kg
PGM and MGF both have NIDDM
Hospitalized for RSV bronchiolitis at 2.5 months
Developed DKA whilst in hospital – pH 7.05, BE -23, blood glucose 26.2 mmol/L, gross glucosuria and ketonuria

3. Complicated by acute pulmonary oedema and mild cerebral oedema
Diagnosed to have neonatal diabetes mellitus
Started on insulin therapy (Aug 94)
USG pancreas normal (Sep 94)
Could stop insulin after 5 months (Jan 95 at CA 8 months)
HbA1c 7.6% (Oct 94)  5.7% (Jan 95)

4. OGTT (May 95 – CA 1 year) 30min 60min 90min 120min 150min
30min
60min
90min
120min
150min
Insulin (mIU/L)
2.3
9.9
5.8
3.3
<1
C-peptide
(fasting ng/ml)
1.4
2.2
1.7
1.9
2.1
Glucose (mmol/L)
4.6
9.4 9
8.6
6.1
* Samples haemolysed: insulin and c-peptide could be spuriously low

5. Islet cell Ab negative (Sep 00)
Serial OGTT between 1996 to 2001 showed normal glucose response
HbA1c 5-6.1% (Mar 96 – Nov 02)
Onset of puberty since July 2005
Mar 1996
Jun 1996
Feb 1999
Feb 2000
Jan 2001
Sep 2001
Nov 2002
Mar 2005
HbA1c 5%
5.6% 6%
6.1%
5.9%
5.8%
6.5%

6. OGTT (Oct 05 – CA 11y 5m)
30min
120min
Insulin (mIU/L)
2.8
7.5 21
Glucose (mmol/L)
5.3
10.6
10.1
Impression: Impaired glucose tolerance HbA1c 6.7%

7. Defaulted FU until June 06 OGTT (Jun 06 – CA 12y 1m)
30min
120min
Insulin (mIU/L)
5.8 21
Glucose (mmol/L)
7.6
13.9
12.1
Impression: Diabetic response HbA1c 7.2%
Islet cell Ab negative

8. Glucagon stimulation test (Aug 06)
Glucose
(mmol/L)
Insulin (mIU/L)
C-peptide ( nmol/L)
T-5
8.5
4.2
0.41 T0
8.4
2.2
0.43 T5
9.4 30
1.15
T10
9.8
4.1
0.73
T15
10.9
4.6
0.5
Haemolysed samples

9. Daonil increased to 5mg daily since April 2008
Started on daily dose of Daonil (glibenclamide) 2.5mg since Aug 2006 (CA 12y 3m)
HbA1c
Daonil increased to 5mg daily since April 2008
Started on Daonil 
Jun 2006
Aug 2006
Jan 2007
Jun 2007
Aug 2007
Feb 2008
HbA1c
7.2%
7.8%
6.5%
6.2%
7.4%

10. Neonatal diabetes and abnormal development of the pancreas

11. Neonatal diabetes mellitus (NDM)
First described by Kitselle in 1852
Classically defined as diabetes mellitus occurring in the first 6 weeks of life in term infants
Some suggests a cut off for early onset DM at 6 months
Single gene disorders rather than classical autoimmune type 1 diabetes
Incidence: 1 in 300, ,000 live births
Transient (TNDM) vs Permanent (PNDM)
based on the grounds of resolution or persistence beyond the first year of life

12. Transient neonatal diabetes mellitus (TNDM)

13. TNDM TNDM contributes 50-60% of cases of neonatal DM
Develop diabetes in the first few weeks of life but go into remission in a few months
The pancreatic dysfunction may be maintained throughout life, with possible relapse to a permanent diabetes state usually initiated at times of metabolic stress such as puberty or pregnancy or as adults

14. Regular follow-up of TNDM is recommended and parents should be informed of the risk of recurrence
Remission of TNDM is temporary and more than 60% of cases relapse at a median age of 11 years
Fasting blood sugar and insulin, HbA1c and insulin sensitivity and insulin response of IVGTT are normal during the remission phase

15. Permanent neonatal diabetes mellitus (PNDM)

16. PNDM
Insulin secretory failure occurs in the late fetal or early postnatal period
Does not go into remission

17. Metz C et al. J Pediatr 2002;141:483-489
Comparison of several features in TNDM and PNDM cases in the French cohort (n=50)
TNDM (n=29)
PNDM (n=21)
p value
Gestational age (weeks)
38.2 ± 2.2
39.2 ± 1.6
p = 0.15
Birth weight (g)
1987 ± 510
2497 ± 690
p < 0.006
Birth length (cm)
44.3 ± 3.4
47.5 ± 2.4
Head circumference (cm)
31.5 ± 1.8
33 ± 1.9
p < 0.02
IUGR
(n=20/27) 74%
(n=7/19) 36%
p < 0.03
Median age at diagnosis (days) (range)
6 (1-81)
27 (1-127)
p < 0.01
Initial insulin dose (unit/kg/day)
0.6 ± 0.25
1.4 ± 1.2
Metz C et al. J Pediatr 2002;141:

18. TNDM vs PNDM Comparing with infants with PNDM, patients with TNDM:
More likely to have IUGR
Less likely to develop ketoacidosis
Younger at diagnosis of diabetes
Have lower initial insulin requirements
Considerable overlap occurs between the 2 groups and TNDM cannot be distinguished from PNDM on the basis of clinical features

19. Aetiology of transient neonatal diabetes mellitus (TNDM)

20. Transient neonatal DM Chromosome 6 anomalies Paternal duplications
Paternal isodisomy
Methylation defect
Potassium channel activating mutations
ABCC8 (SUR1) and rarely KCNJ11 (Kir6.2) mutations
Unidentified genetic defects

21. Chromosome 6 anomalies (OMIM 601410)

23. Chromosome 6 anomalies: a disease linked to imprinting
Uniparental isodisomy (UDP6)
2 haplo-identical copies of chromosome 6 inherited from the father with no contribution from the mother
Unbalanced duplication of paternal chromosome 6q24
Loss of the normal methylation from maternal 6q24

24. Two imprinted genes in 6q24
ZAC (Zinc finger protein associated with Apoptosis and cell Cycle arrest)
HYMAI (hydatidiform, mole-associated and imprinted transcript)

25. ZAC
A zinc finger protein which potently induces apoptosis and cell cycle arrest and prevents tumour formation
A key regulator of peroxisome proliferator-activated receptor gamma (PPAR)
Activation of PPAR is sufficient to inhibit -cell proliferation, and PPAR overexpression significantly compromises glucose-stimulated insulin secretion
Overexpression of ZAC, either due to extra copies of paternal origin or loss of the silencing effect of methylation on the maternal allele is the likely cause of 6qTNDM

26. HYMAI Uncertain if HYMAI plays a role in TNDM
It has no open reading frame and its function is not clear

27. Chromosome 6q anomalies
Usually present in the first week of life with profound diabetes requiring insulin therapy
Significant IUGR (mean BW 1980 gm at term)
Go into remission at a median age of 12 weeks
Likely to relapse at times of metabolic stress such as during puberty or intercurrent illness
Although the relapse is characterized by loss of classical insulin response to hyperglycaemia, there is evidence that insulin is still available, as there is excellent insulin response on glucagon stimulation, suggesting that the G-coupled protein receptor response remains intact through  cAMP (might be an area of therapeutic intervention in future)

28. Chromosome 6q anomalies
Some children have macroglossia and anterior abdominal wall defects, as described in Beckwith-Wiedemann syndrome
Not only do these children lose the maternal methylation at 6q, they also have hypomethylation at other imprinted loci, such as the Beckwith-Wiedemann locus, resulting in significant phenotypic variation
(Mackay et al. Hum Genet 2006;120: )

29. Chromosome 6 anomalies and the potassium channel activating mutations cause the vast majority of cases of TNDM

30. K+(ATP) channels in glucose metabolism

31. The islet KATP channel
A critical regulator of -cell insulin secretion
In the normal response to increased glucose exposure and its metabolism within -cell, ATP levels increase with a concomitant decrease in magnesium-adenosine diphosphate (Mg-ADP) levels, allowing closure of the KATP channel and membrane depolarization, which allows calcium influx into the cell and leads to insulin secretion

32. The islet KATP channel
A hetero-octamer made up of 2 types of subunits: 4 regulatory sulphonylurea receptors (SURs) embracing 4 pore-forming inwardly rectifying potassium channels (Kir)
A 1:1 SUR1:Kir6.2 stoichiometry is both necessary and sufficient for assembly of active KATP channels
SUR, a member of ABC transporter family, originates from 2 separate genes and therefore occurs in several spliced isoforms
SUR1 is found in the pancreatic - cell and neurons
SUR2A occurs in heart cells whilst SUR2B in smooth muscle

33. The islet KATP channel
Kir6.2 subunits form the channel pore in the majority of tissues, such as pancreatic -cell, brain, heart and skeletal muscle
Whilst Kir6.1 can be found in smooth vascular muscle and astrocytes
These different channel forms have different pore properties and adenine nucleotide sensitivities
The KCNJ11 (potassium inwardly-rectifying channel, subfamily J, member 11) and ABCC8 (ATP-binding cassette, subfamily C, member 8) genes, encoding the Kir6.2 and SUR1 respectively are located at 11p15

34. The channelopathies

35. Potassium channel activating mutations
Mutations in KCNJ11 and ABCC8 genes, encoding the Kir6.2 and SUR1 subunits of the pancreatic KATP channel involved in regulation of insulin secretion, account for 1/3 to 1/2 of the PNDM cases but also for TNDM cases
Molecular analysis of chromosome 6 anomalies and the KCNJ11 and ABCC8 genes provides a tool for distinguishing transient from permanent neonatal diabetes mellitus in the neonatal period

36. KCNJ11 mutations

37. KCNJ11 mutations
Mutations in KCNJ11 that encode the Kir6.2 subunit of the KATP channel are the most common cause of PNDM and account for 30% of all cases
The KATP channel is variably unresponsive to  ATP, making the membrane hyperpolarized and preventing influx of calcium and efflux of insulin

38. KCNJ11 mutations
Median age of presentation ~ 3-4 weeks of age as opposed to babies with 6q anomalies who tend to present in the first week of life
Born SGA but not as small as those with 6q anomalies (mean BW 2497g vs 1980g)
All display low insulin levels despite dramatic hyperglycaemia
30% with ketoacidosis
20% have associated neurological disease with developmental delay

39. KCNJ11 mutations
Epilepsy or muscle weakness is sometimes present, indicating that the same potassium channels play a role in the functioning of CNS
Children at the most severe end of this spectrum can be profoundly affected - ‘DEND’ (developmental delay, epilepsy and neonatal diabetes)
An intermediate form (i-DEND) associated with milder developmental delay and no epilepsy
The mutation causing isolated diabetes produce less change in ATP sensitivity than those associated with diabetes plus neurological disease (Q52R, V59G)

40. KCNJ11 mutations
Sulphonylureas close KATP channels by an ATP-independent mechanism
Some patients with diabetes due to Kir6.2 mutations have been successfully transferred to oral sulphonylurea therapy at doses ranging from mg/kg/day of glyburide
Pearson et al. demonstrated that 44 of 49 patients (90%) aged 3 months to 36 years could be successfully transferred to oral therapy with a highly significant and sustained improvement in HbA1c (8.1% to 6.4%)
Patients with neurological features are less likely to be successful in managing their DM using sulphonylureas
NEJM 2006;355:

41. ABCC8 mutations

42. ABCC8 mutations
The basal Mg-nucleotide-dependent stimulatory action of sulphonylurea receptor-1 (SUR1) encoded by ABCC8 is increased, which effectively prevents closure of the KATP channel
Recently Babenko et al. demonstrated that activating mutations in the ABCC8 gene encoding the SUR1 subunit of the channel can also cause permanent neonatal DM that is responsive to sulphonylurea therapy
NEJM 2006;355:

43. K+(ATP) channels and neonatal diabetes

44. Aetiology of permanent neonatal diabetes mellitus (PNDM)

45. Permanent neonatal DM (1)
Heterozygous activating mutation in KCNJ11 gene and in ABCC8 gene (Kir6.2 and SUR1 subunits of the pancreatic KATP channel)
Insulin (INS) gene mutation
Severe pancreatic hypoplasia associated with insulin promoter factor-1 (IPF-1) mutation and with cerebellar hypoplasia due to pancreatic transcription factor 1A (PTF1A) mutation
Homozygous glucokinase gene mutation: insensitivity to glucose

46. Permanent neonatal DM (2)
IPEX syndrome and FOXP3 mutation: diffuse autoimmunity
Associated with epiphyseal dysplasia: Wolcott-Rallison syndrome and EIF2AK3 gene mutation
Mitochondrial disease
Possibly associated with enterovirus infection
Associated with hypothyroidism, glaucoma and GLIS3 mutation

47. Insulin gene mutations

48. Insulin (INS) gene mutations
Stoy et al. reported 10 missense mutations in INS gene in 21 patients (20 with neonatal DM and 1 with type 2 diabetes) from 16 families in which NDM seems to segregate as a dominant trait and ABCC8 and KCNJ11 mutations were not found
Not associated with -cell autoantibodies
INS mutations accounts for 15-20% of cases of PNDM – similar to ABCC8 mutations (19%) but less than KCNJ11 mutations (30%)
Stoy J et al. PNAS 2007;104:

49. Insulin (INS) gene mutations
These patients are older at diagnosis, presenting at a median age of 9 weeks, with 15/16 being diagnosed in the first 6 months, 3 diagnosed between 6 months and 1 year, and the father of a proband at 30 years with type 2 DM
Usually presenting with DKA or marked hyperglycaemia and was treated with insulin from diagnosis
These patients with permanent diabetes without extrapancreatic features except for a low birth weight
Stoy J et al. PNAS 2007;104:

50. Pancreatic agenesis/hypoplasia and the insulin promoter factor-1 (IPF-1) gene

51. IPF-1 mutation and PNDM
First described in 1997 by Stoffers et al. in a child with PNDM and pancreatic exocrine insufficiency due to pancreatic agenesis (Nat Genet 1997;15: )
The proband was homozygous for a mutation (Pro63fsdelC) in IPF-1, the gene involved in the master control of exocrine and endocrine pancreatic development, being responsible for the coordinated development of the pancreas in-utero and also for the continued functional integrity of pancreatic  islet cells

52. IPF-1 mutation and PNDM
Within the extended family were 8 individuals in 6 generations with early-onset diabetes akin to type 2 diabetes
These were identified as heterozygotes for the same mutation with the mutant truncated isoform of IPF-1 acting as a dominant negative inhibitor of wild type IPF-1 activity; the resultant illness was reassigned as Maturity- Onset Diabetes of the Young (MODY) 4
Additional studies have also identified that less severe IPF-1 mutations can cause autosomal dominant late- onset forms of type 2 diabetes

53. IPF-1 mutation and PNDM
Only one further case report of pancreatic agenesis has been ascribed to an IPF-1 mutation and this was a compound heterozygous mutation of the gene
Since there is complete absence of pancreatic tissue and exocrine function is also compromised, these patients will require the use of pancreatic enzyme supplementation

54. Pancreatic agenesis/hypoplasia and the pancreatic transcription factor 1A (PTF1A) gene

55. PNDM with cerebellar hypoplasia
3 members of a consanguineous Pakistani family with neonatal diabetes and cerebellar hypoplasia were described in 1999
Suggestive of an autosomal recessive inheritance pattern
The infants all died within a few months of birth from a combination of metabolic dysfunction, respiratory compromise and sepsis
A further child of North European descent was later identified with an identical phenotype and complete pancreatic agenesis

56. PNDM with cerebellar hypoplasia
This syndrome was found to be linked to mutations in the transcription factor PTF1A, a major gene involved in pancreatic development and also expressed in the cerebellum
These patients have pancreatic hypoplasia associated with microcephaly linked to cerebellar hypoplasia
About 19 cases of pancreatic agenesis/hypoplasia have been published, but most cases remain unexplained at the molecular level

57. Glucokinase gene mutations

58. Glucokinase (GCK) mutations
MODY 2 is caused by mutations in the glucokinase gene and usually leads to mild hyperglycaemia in affected individuals
Glucokinase is a key regulator of glucose metabolism in islet cells controlling the levels of insulin secretion
Homozygous GCK mutations have been described but are uncommon causes of PNDM
This diagnosis should be considered in families with a history of glucose intolerance, MODY in first degree relatives and especially if consanguinity is suspected

59. IPEX (OMIM )

60. IPEX (Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked syndrome)
The only one of the currently identified neonatal diabetes syndromes in which autoimmunity plays a central role
Mutations in 2 genes have been identified: FOXP3 and CD25 (interleukin-2 receptor alpha)
Both genes are important for the normal function of regulatory T cells that play a central role in regulating adaptive immune responses to maintain tolerance to host tissues
In IPEX, this self-tolerance is lost and the result is a devastating autoimmune response

61. IPEX (Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked syndrome)
Type 1 diabetes auto-antibodies (GAD, IAA, ICA) are frequently described, as are those directed against the thyroid gland and various other organs
Enteropathy (100%), failure to thrive (>90%) and early- onset (often neonatal) diabetets (>90%) occur in almost all cases
Other features frequently described include exfoliative dermatitis, haemolytic anaemia, thrombocytopenia, Addison’s disease and autoimmune hypothyroidism

62. IPEX (Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked syndrome)
There are several treatment options for IPEX:
Supportive therapy
Immunosuppressive agents such as tacrolimus, steroid and cyclosporine have shown varying degrees of efficacy, but toxicity to other organs such as the kidney has been problematic
BMT
Prognosis remains guarded for children with this condition

63. Wolcott-Rallison syndrome (OMIM 226980)

64. Wolcott-Rallison syndrome
An autosomal recessive disorder characterized by infancy-onset diabetes (often within the neonatal period) associated with a spondylo-epiphyseal dysplasia
A constellation of other features includes hepatomegaly, mental retardation, renal failure and early death
Mutation of the gene encoding eukaryotic translation initiation factor 2-alpha kinase 3 (EIF2AK3) on chromosome 2p12 has been shown to cause this syndrome

65. Wolcott-Rallison syndrome
EIF2AK3 is highly expressed in islet cells, liver, kidneys and developing bone
It has a role in protein translation and regulates the synthesis of unfolded proteins in the endoplasmic reticulum which could account for the multiple system involvement reported in this condition

66. Mitochondrial diabetes

67. Mitochondrial diabetes
Neonatal diabetes may also exist in the context of a mitochondrial disorder
Usually associated with other organ dysfunction, which may be recognized after the diagnosis of neonatal DM
Commonly associated with sensorineural deafness
Characterized by progressive non-autoimmune -cell failure

68. Mitochondrial diabetes
Maternal transmission of mutated mitochondrial DNA can result in maternally inherited diabetes
Several mutations have been implicated but the strongest evidence relates to a point substitution at nucleotide position 3243 (A to G) in the mitochondrial tRNA [leucine (UUR)] gene

69. Other very rare forms of NDM

70. Heterozygous Hepatocyte Nuclear Factor (HNF) -1 mutation
Heterozygous mutations of the transcription factor HNF- 1 (HNF1 homeobox B) gene have been associated with a form of MODY5, which is characterized by dominantly inherited diabetes mellitus with renal cysts
This has been described in one child with PNDM and some small renal cysts whilst the other sibling only had transient hyperglycaemia but with more profound renal dysplasia

71. GLI-similar protein 3 (GLIS3) mutations
In 2006, Senee et al. described a frameshift mutation or deletions in the transcription factor GLIS3 in 3 consanguineous families with a history of neonatal diabetes, congenital hypothyroidism and facial dysmorphology (large, flat, square-shaped face with a thin and bird-shaped curved nose)
Additional features in some but not all patients included congenital glaucoma, liver fibrosis and cystic kidneys

72. Possible association with enterovirus infection
A single case report has suggested that maternal enterovirus (echovirus 6) infection in pregnancy (end of first trimester) can lead to autoimmune, neonatal-onset diabetes with the presence of anti-insulin and glutamic acid decarboxylase antibodies at or very soon after birth
Ruling out IPEX, the pancreas in this female child was very hypoplastic and the authors suggested a role for maternally transmitted enterovirus either by direct influence on pancreatic organogenesis or through aggressive -cell-targeted autoimmune attack
Diabetologia 2000;43:

73. Main types of neonatal diabetes, their genetic basis, co-morbidities, treatment, outcome and relative frequencies as potential diagnoses

74. Treatment options in neonatal diabetes mellitus

75. Insulin therapy and high caloric intake are the basis of treatment
All neonates presenting acutely with diabetes should be started on insulin therapy
In the case of 6q anomalies, diabetes will be transient but insulin is required until remission to prevent dehydration and allow normal growth
In permanent neonatal diabetes due to conditions other than KCNJ11 and possibly ABCC8 mutations, insulin is also required long-term
Some patients with mutations in KCNJ11 and ABCC8 may be transferred from insulin therapy to sulphonylureas

76. Genetic counselling
The risk of recurrence is different depending on whether it is the transient or permanent form of neonatal diabetes and the different molecular mechanisms identified

77. Chromosome 6 anomalies
Cases of UPD6 are sporadic with low recurrence risk to siblings and offspring
In familial cases of unbalanced duplication of 6q24, affected male will have 50% risk of passing it to an offspring; the risk of passing a duplication of 6q24 from the mother to her offspring is low
Imprinting anomaly: logic says that the mother should pass it on but so far no familial case is known and the risk of transmission is unknown. The cause of imprinting relaxation is not identified and the identified children with this anomaly are too young to procreate
The sibling and offspring risks for sporadic cases of methylation defect are not known

78. PNDM and Mendelian inheritance should be counselled accordingly
Recurrence risk is 25% in the autosomal recessive disorders ( EIF2AK, GLIS3, IPF-1 and PTF1A genes)
IPEX is an x-linked disorder
Mutations in genes encoding the potassium channel subunits are transmitted in the heterozygous state in a dominant way

79. Conclusions

80. Conclusions
Effective treatment of neonatal diabetes requires thorough understanding of the underlying disease processes
Successful studies illuminating these processes have not only improved our knowledge of pancreatic development and physiology, but also have revolutionized the treatment options for some patients
The progress made in our scientific and clinical understanding of these extremely rare diseases is a perfect example of how studying seemingly rare illnesses can improve our overall knowledge of much more common conditions

81. Thank you