Research Introduction

Transcription

1 Research Introduction

2 Altered metabolism in polycystic kidney disease Telomerase activity in polycystic kidney disease cells

3 Autosomal dominant polycystic kidney disease ADPKD is the most common inherited kidney disease. Incidence 1 in 500 to 1 in 1000 worldwide. 600,000 patients in US Third most common single cause of ESRD world wide and accounts for 5-10% of ESRD in US ADPKD is caused by mutations of either PKD1 gene (around 85% of cases) on chromosome 16 or the PKD2 gene (around 15% of cases) on chromosome 4 There is evidence for a two hit mechanisms( germ line and somatic inactivation of two PKD alleles) explaining the focal development of renal and hepatic cysts

4 Polycystin 1 (PKD1) and Polycystin 2 (PKD2) extracellular Cell Membrane Intracellular

5 Polycystins localize to cilia and are activated by mechanosensation Normal PKD1 or PKD2 Mutant PC1 PC2 tubular lumen x x x PC1 PC2

6 Pathways up-regulated or down regulated in polycystic kidney disease

7 Altered Metabolism and Cancer

8 Altered Metabolism and Cancer Resting cell Proliferating cells

9 Metabolism in proliferating cancer cells Proteins Lipids Macro molecules Nucleotides Glucose Glutamine ATP

10 Altered metabolism and Cancer

11 Glutamine metabolism and Cancer

12 Altered metabolism and Cancer Do ADPKD cells behave like cancer cells?

13 Many of the signaling pathways activated in cancer cells are also active in ADPKD cells

14 Cells used for studies 1. NHK cells. Primary normal human kidney distal tubular epithelial cells isolated from nephrectomies. 2. ADPKD cells. Primary human ADPKD cells that are mutant for PKD1. PKD +/- ADPKD cells PKD -/- Isolate cyst lining epithelial cells

15 Upregulation of PKM2 isoform in PKD cells glutaminase APKD NHK APKD NHK PKM1 PKM2 actin

16 Glutaminase 1 is upregulated in ADPKD cells by camp Forskolin/cAMP Forskolin/cAMP APKD NHK APKD NHK APKD NHK anti-glutaminase KGA anti-glutaminase GAC glutaminase 1 KGA glutaminase 1 GAC

17 Inhibition of glutaminase 1 blocks cyst formation by PDK -/- cells in cell culture

18 Inhibition of glutaminase 1 lowers ATP levels in ADPKD but not NHK cells

19 Alpha Ketoglutarate- most abundant metabolite in the urine of rat model of PKD Nephrology 2012

20 Assess whether cyst formation in PKD -/- mice (knockout) is inhibited in by gls1 inhibitor BPTES Pkhd1-Cre; PKD fl/- BPTES postnatal day Sacrifice day 24 Vehicle control postnatal day 10-24

21 Treatment with BPTES slows cyst growth in PKD1 knockout model

22 Amino acids and glutaminolysis regulate mtorc1 Leucine GLS GDH Glutamine Glutamate Ketoglutarate PS6K PS6 Cell proliferation mtorc1 Cell 2012

23 Glutaminolysis regulates mtorc1 Cell 2012

24 Sirolimus and kidney growth in Autosomal Dominant Polycystic Kidney Disease 18 month randomized control trial 100 patients b/w the age group 18-40yrs- sirolimus (target dose 2 mg daily) or standard care Sirolimus level b/w 4 and 10 microgram/litre Estimated CrCl 70 ml/min Serial MRI to measure the volume of polycystic kidney disease At randomization- median kidney volume was 907cm3 (sirolimus) and 1003 (control group) Primary outcome- kidney volume at 18 months Secondary outcomes GFR and urine albumin excretion Results: Median increase in sirolimus group was 99 cm3( interquartile range ) Control group 97 cm3( interquartile range ) at 18 months GFR did not differ between two groups Urinary albumin excretion rate was higher in sirolimus group NEJM aug 2010

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26 NEJM august 2010 Everolimus in Patients with Autosomal Dominant Polycystic Kidney Disease 2 year, double blind trial 433 patients with ADPKD were assigned to receive either placebo or everolimus (2.5 mg bid) Estimated GFR of 30-89ml/min/1.73 m2 Primary outcome was change in kidney volume at 12 and 24 months as measured on MRI Secondary outcome was renal function (GFR, serum creatinine, proteinuria, incidence of newly developed ESRD) at 24 months Results: Total kidney volume increased between baseline and 1 year by 102 ml and 230 ml by 2 years in everolimus group Vs 157 ml by 1 year and 301 ml by 2 years in placebo group Mean decrement in estimated GFR after 24 months was 8.9 ml/min/1.73 m2 Vs 7.7 ml/min /1.73m2 in placebo group

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28 Rapamycin may not inhibit mtor in ADPKD kidneys Canaud et. al (2010) AJT

29 Do polycystic kidney disease cells have up regulated telomerase activity?

30 TELOMERE and TELOMERASE

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32 TELOMERES Telomeres are DNA-protein structures that protect the chromosome ends from degradation and fusion Telomere DNA sequence comprises of tandem repeats of the six nucleotide unit sequence TTAGGG. These sequences extend for thousands of bases at chromosome ends, averaging 10 kb in a newborn human s cord blood. Telomere DNA is bound by a specialized group of protective proteins collectively called shelterin

33 TELOMERASE Telomerase was first identified in ciliated protozoan tetrahymena Telomerase is a specialized DNA polymerase that synthesizes new telomere sequences onto chromosome ends. Telomerase is composed of the core telomerase protein TERT, which contains the telomerase reverse transcriptase domain and and an essential RNA component called TERC which provides the template for telomeric sequence synthesis Telomerase activity is regulated during development and has a very low level, almost undetectable in somatic cells. Telomerase is found in found in fetal tissue, germ cells Telomerase activity has been found to be up-regulated in most cancer cells thus allowing cancer cells to escape cellular senescence and becoming immortal.

34 Science 1994

35 N H K P K D 293 T cells Telomere length

36 Thank You!