1. Monogenic Hypertension
Thitisak Kitthaweesin MD.

2. Monogenic Hypertension
HT is a major public-health problem
Molecular pathogenesis in most patients remains poorly understand
Genetic factors …known to play a role in determining inter-individual variation in BP.

3. Monogenic Hypertension
There are mutations and polymorphisms that altering BP in human
All the gene are involve directly or indirectly in control of Na reabsorption
Mutations have been found in monogenic hypertension diseases that cause disorders of BP regulation

4. Renin Aldosterone Dietary Na Na transport Kidneys Urinary Na
Angiotensinogen
ACTH
Adducin
Renin
GRA
Blood volume
Blood pressure
Aldosterone
Dietary Na
Adrenal hyperplasia
Na transport
Deoxycorticosterone
Kidneys
MN receptor
Progesterone
sensitivity
ENaC
(Liddle’s)
Cortisol
Urinary Na
Gordon’s
syndrome
Cortisone
AME

5. Renin Aldosterone Dietary Na Na transport Kidneys Urinary Na
Angiotensinogen
ACTH
Adducin
Renin
GRA
Blood volume
Blood pressure
Aldosterone
Dietary Na
Adrenal hyperplasia
Na transport
Deoxycorticosterone
Kidneys
MN receptor
Progesterone
sensitivity
ENaC
(Liddle’s)
Cortisol
Urinary Na
Gordon’s
syndrome
Cortisone
AME

6. Glucocorticoid-remediable aldosteronism (GRA)
AD monogenic HT
Results from a chimeric gene product that place 18-hydroxylase (Aldosterone synthase) under control of ACTH promoter
ACTH-regulated 18-hydroxylase activity is aberrantly expressed in Zona fasciculata and acts upon control to form 18-hydroxy cortisol and 18-oxocortisol

7. Aldosterone
Adrenal hormones are synthesized in different areas of adrenal cortex
ZG…Aldosterone
ZF…Glucocorticoid (cortisol)
ZR…Androgen,estrogen
ZG…well adapted for aldosterone production
low conc of 17-alpha hydroxylase
final step in conversion of corticosterone to aldosterone

8. Aldosterone Aldosterone synthase
>95% homology with 11-hydroxylase
convert deoxycortisol to cortisol in ZF
addition of hydroxyl group at C-18
oxidation to an aldehyde
Two distinct genes products perform terminal step in biosynthesis
11 beta-hydroxylase (CYP11B1)…glucocorticoid
18-hydroxylase or Aldosterone synthase (CYP11B2)…mineralocorticoid

9. Linkage analysis localized the gene to chromosome 8
Chimeric gene consisting of the promoter-regulatory region of CYP11B1 and structural portion of CYP11B2 is localized between CYP11B2 and CYP11B1
Protein product…perform all reaction required for aldosterone production >>>ACTH-dependent hyperaldosteronism
Ectopic expression of chimeric protein express CYP17…formation of 18-hydroxy and 18-oxocortisol (biochemical hallmarks)
Chimeric gene resulted from miotic mismatch and unequal crossing-over…located 5’ to intron 4 of CYP11B gene

10. GRA Aldo Aldosterone Cortisol Cortisol Aldo 18-OH Cortisol
Normal
GRA
Aldo
Aldosterone
A II
A II ZG ZG ZF ZF
ACTH
Cortisol
ACTH
Cortisol
Aldo
18-OH Cortisol
18-OXO Cortisol

11. GRA Clinical…volume expansion Salt-sensitive HT
Tend to have hypokalemic metabolic alkalosis
Low renin-High aldostertone
18-OH and 18-oxocortisol in plasma and urine
Replacement of prednisolone ameliorate HT & disappearance of abnormal stetroids

12. GRA and Pregnancy GRA not appeared to more prone to pre-eclampsia
GRA…chronic HT, increased risk of exacerbation of HT during pregnancy
Cesarean section rate > general and other obstetrics…2 folds
Wycoff JA et al. Hypertension, 2000

13. Apparent Mineralocorticoid Excess (AME)
AR form of monogenic HT
Results from inactivation of 11-beta-hydroxysteroid dehydrogenase type2 (11B-HSD2)
Causing reduced metabolism of cortisol to cortisone…local cortisol excess and MN response
Metabolic clearance of cortisol is prolonged in AME
Excess urinary excretion of the reduced metabolites of cortisol… increased Tetrahydrocortisol:tetrahydrocortisone Ratio

15. Fredrick V. Osorio and Stuart L. Linus

16. AME
Resembles the syndrome observed in persons integrity large amounts of licorice
Volume expansion
Salt-sensitive HT
Hypokalemic metabolic alkalosis
Low renin-Low aldosterone
HT respond to thiazide or spironolactone but no aldosterone and abnormal steroid products in urine

17. AME Palermo et al. ( NEJM, 1998 )
Resolution of AME syndrome after KT in 38 year old woman
Abnormal ratio of reduced metabolite of cortisol/cortisonr in urine was not corrected
Ratio of urinary free cortisol to cortisone was corrected and correlated with the resolution of the syndrome

18. Liddle’s syndrome AD form of monogenic HT Volume expansion
Salt-sensitive HT
Hypokalemic metabolic alkalosis
Low renin-Low aldosterone
Not respond to spironolactone
But triamterene can reduce BP

19. Liddle’s Syndrome
A 16 yr-old girl referred with a provisional diagnosis of primary aldosteronism
BP was consistently elevated at 180/120
Serum K was 2.6 mEq/l and serum HCO3- 30 mEq/l
The pt’s younger brother had BP 200/110,serun K 2.4 mEq/l and serum HCO3- 29 mEq/l

20. Liddle’s Syndrome Workup
Initial observation
Low rate of aldosterone secretion
No response to SV-9055,an inhibitor of aldosterone secretion
No response to spironolactone, a mineralocorticoid receptor antagonist
Triamterene a direct inhibitor of CCD Na+ and K+ transport , normalizes BP and serum K+
Renal transplantation normalize BP and serum K+ (Botero-Velez et al,NEJM 1994)

21. ENaC MUTATIONS IN LIDDLE’S
5 kindreds with c-terminal deletions of amino acid in Beta-ENaC (Shimkets et al,cell,1994)
1 kindred with c-terminal of 76 amino acid in Gamma-ENaC
2 kindreds with missense mutation of Gamma-ENaC ( Hansson et al, Nature,1995)
HYPERGENE data (Persu et al.Hypertension,1998)
Sequence analysis of Beta ENaC subunit in 532 HT proband (101 low renin HT)
Missense mutation in 7 unrelated individual,3 probands of African
Mutation …T594M -6%, G442V -34.8%

22. PY domain mutation,NEDD4 can’t bind,internalize and destroy
NEDD4 protein binds to PY domain >>> internalized and destroy
PY domain mutation,NEDD4 can’t bind,internalize and destroy

23. Regulation of ENaC
Daniela Rotin CO-NH,2000

24. Fredrick V. Osorio and Stuart L. Linus

25. Gordon’s syndrome
One or more gene responible for Type II pseudohypoaldosteronism
Linkage analysis to chromosome 1q31-q42, 17p11-q21, 12p?

26. Type II pseudohypoaldosteronism in adults with HT( Gordon’s syndrome )
HyperK , intact renal Na conservation
Normal renal function, HT, low PRA, low to normal PA
Normal antinatriuretic response to MN
But absent kaliuretic response
Distinguished from hyporenin/hypoaldosteronism by
Normal renal function
Absent Hx of DM, uniform presence of HT
Absence of salt wasting when dietary NaCl restrict
Lack of kaliuretic response to MN

27. Type II pseudohypoaldosteronism in adults with HT( Gordon’s syndrome )
Schambelan et al….primary defect may be related to “enhanced Cl reabsorption in early distal tubule”…limit Na delivery to more distal tubule,decreased lumen negativity,impaired K secretion due to voltage-shunt effect
Increased NaCl reabsorption expand ECF volume…HT and suppress RAAS
Hyper K contributes to inhibition of renin secretion
PA..normal or suppressed depending upon balance between inhibitory effect of volume expansion and stimulatory effect of hyper K

28. Type II pseudohypoaldosteronism in adults with HT( Gordon’s syndrome )
Rx with thiazides or loop diuretics …enhance renal H,K excretion…correct met acidosis, hyper K, HT, return PA&PRA to normal

29. Pseudohypoaldosteronism
Type II pseudohypoaldosteronism in adults with HT( Gordon’s syndrome )
NaCl reabsorption
ECF expansion Na
Cl shunt
Hyporenin/hypoaldo K H
hyperK
acidosis
Transtubular PD
K/H secretion

30. Mineralocorticoid Receptor Defect
Geller et al. ( Science, 2000 )
New mendelian form of HT caused by an activating mutation in MR
Screened MR coding regions in 75 individuals referred for evaluating monogenic HT
One patient…15 year boy with severe HT(210/120 mmHg), normokalemia, suppressed aldosterone level…Heterozygous for missense mutation altering Serine at codon 810 (S810) to Leucine (L810) …MRL810

31. Progesterone activates MRL810
MR is a ligand-activated transcription factor
Structures…
Long N terminal domain binds to transcription factors
Central DNA-binding domain
C terminal ligand-binding domain (LBD)
L810 mutation in LBD altered receptor-ligand specificity

32. Progesterone activates MRL810
No difference between receptor in response to MR agonosts ( aldosterone, cortisol)
But MRL810 proned to have significant activity in the absence of ligand
Antagonists of wild-type MR (progesterone)…potent agonists of MRL810
Spironolactone… activated MRL810 …...contraindicated in MRL810

33. Pregnancy in MRL810 2 affected women and 5 pregnants
Severe maternal HT, hypokalemia, hyperkaliuria
Termination of pregnancy or early delivery
No other signs of pre-eclampsia
Support of in-vitro finding that progesterone agonized MRL810

34. Progesterone-induced Activation of MRL810
Require a novel helix3/helix5 interaction
S810 on helix 5 was near alanine 773 (A773) on helix 3 but distance is too great for stabilizing effect
When L810 is substituted, longer non-polar leucine side chain come into close contact with A773

35. Progesterone-induced Activation of MRL810
How does this interaction allow progesterone-mediated activation of MR?
Progesterone distinguished from MR agonists by absence of C-21 hydroxyl group
C-21 hydroxyl group form hydrogen bond with carbonyl group of asparagine 770 (N770) on helix 3…necessary for aldosterone-induced activation of MR
In MRL810 …novel interaction of A773 with L810 replace this function

36. Helix3/helix5 interaction in progesterone mediated activation of MRL810
Geller DS et al. Science,2000

37. Autosomal-dominant HT with brachydactyly
First described bt Bilginturan et al. In 1973
Dramatic increase in BP with age and die of stoke before age 50
Map the gene to 12p
PRA and aldosterone are normal
Not salt-sensitive
Normal RAAS and catecholamine response

38. Autosomal-dominant HT with brachydactyly
Evidence of Neurovascular contact (NVC)
Left sided posterior cerebellar artery or ventricular artery loop or bilateral
May result in hyperactive dysfunction of underlying structures
HT ...may related to increased sympathetic activity

39. Thank You