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The kidney is the principal organ mediating klotho effects.

ABSTRACT: Klotho was discovered as an antiaging gene, and ?-Klotho (Klotho) is expressed in multiple tissues with a broad set of biologic functions. Membrane-bound Klotho binds fibroblast growth factor 23 (FGF23), but a soluble form of Klotho is also produced by alternative splicing or cleavage of the extracellular domain of the membrane-bound protein. The relative organ-specific contributions to the levels and effects of circulating Klotho remain unknown. We explored these issues by generating a novel mouse strain with Klotho deleted throughout the nephron (Six2-KL(-/-)). Klotho shedding from Six2-KL(-/-) kidney explants was undetectable and the serum Klotho level was reduced by approximately 80% in Six2-KL(-/-) mice compared with wild-type littermates. Six2-KL(-/-) mice exhibited severe growth retardation, kyphosis, and premature death, closely resembling the phenotype of systemic Klotho knockout mice. Notable biochemical changes included hyperphosphatemia, hypercalcemia, hyperaldosteronism, and elevated levels of 1,25-dihydroxyvitamin D and Fgf23, consistent with disrupted renal Fgf23 signaling. Kidney histology demonstrated interstitial fibrosis and nephrocalcinosis in addition to absent dimorphic tubules. A direct comparative analysis between Six2-KL(-/-) and systemic Klotho knockout mice supports extensive, yet indistinguishable, extrarenal organ manifestations. Thus, our data reveal the kidney as the principal contributor of circulating Klotho and Klotho-induced antiaging traits.

SUBMITTER: Lindberg K

PROVIDER: S-EPMC4178446 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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The kidney is the principal organ mediating klotho effects.

Lindberg Karolina K Amin Risul R Moe Orson W OW Hu Ming-Chang MC Erben Reinhold G RG Östman Wernerson Annika A Lanske Beate B Olauson Hannes H Larsson Tobias E TE

Journal of the American Society of Nephrology : JASN 20140522 10

Klotho was discovered as an antiaging gene, and α-Klotho (Klotho) is expressed in multiple tissues with a broad set of biologic functions. Membrane-bound Klotho binds fibroblast growth factor 23 (FGF23), but a soluble form of Klotho is also produced by alternative splicing or cleavage of the extracellular domain of the membrane-bound protein. The relative organ-specific contributions to the levels and effects of circulating Klotho remain unknown. We explored these issues by generating a novel mo ...[more]

PMID: 24854271

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Project description:α-Klotho is a known anti-aging protein that exerts diverse physiological effects, including phosphate homeostasis. Klotho expression occurs predominantly in the kidney and is significantly decreased in patients with chronic kidney disease. However, changes in serum klotho levels and impacts of klotho on outcomes among kidney transplant (KTx) recipients and kidney donors remain unclear. A literature search was conducted using MEDLINE, EMBASE, and Cochrane Database from inception through October 2019 to identify studies evaluating serum klotho levels and impacts of klotho on outcomes among KTx recipients and kidney donors. Study results were pooled and analyzed utilizing a random-effects model. Ten cohort studies with a total of 431 KTx recipients and 5 cohort studies with a total of 108 living kidney donors and were identified. After KTx, recipients had a significant increase in serum klotho levels (at 4 to 13 months post-KTx) with a mean difference (MD) of 243.11 pg/mL (three studies; 95% CI 67.41 to 418.81 pg/mL). Although KTx recipients had a lower serum klotho level with a MD of = -234.50 pg/mL (five studies; 95% CI -444.84 to -24.16 pg/mL) compared to healthy unmatched volunteers, one study demonstrated comparable klotho levels between KTx recipients and eGFR-matched controls. Among kidney donors, there was a significant decrease in serum klotho levels post-nephrectomy (day 3 to day 5) with a mean difference (MD) of -232.24 pg/mL (three studies; 95% CI -299.41 to -165.07 pg/mL). At one year following kidney donation, serum klotho levels remained lower than baseline before nephrectomy with a MD of = -110.80 pg/mL (two studies; 95% CI 166.35 to 55.24 pg/mL). Compared to healthy volunteers, living kidney donors had lower serum klotho levels with a MD of = -92.41 pg/mL (two studies; 95% CI -180.53 to -4.29 pg/mL). There is a significant reduction in serum klotho levels after living kidney donation and an increase in serum klotho levels after KTx. Future prospective studies are needed to assess the impact of changes in klotho on clinical outcomes in KTx recipients and living kidney donors.

Project description:Cellular senescence is an irreversible cell growth arrest and is associated with aging and age-related diseases. High plasma phosphate (Pi) and deficiency of Klotho contribute to aging and kidney fibrosis, a pathological feature in the aging kidney and chronic kidney disease. This study examined the interactive role of Pi and Klotho in kidney senescence and fibrosis. Homozygous Klotho hypomorphic mice had high plasma Pi, undetectable Klotho in plasma and kidney, high senescence with massive collagen accumulation in kidney tubules, and fibrin deposits in peritubular capillaries. To examine the Pi effect on kidney senescence, a high (2%) Pi diet was given to wild-type mice. One week of high dietary Pi mildly increased plasma Pi, and upregulated kidney p16/p21 expression, but did not significantly decrease Klotho. Two weeks of high Pi intake led to increase in plasminogen activator inhibitor (PAI)-1, and decrease in kidney Klotho, but still without detectable increase in kidney fibrosis. More prolonged dietary Pi for 12 weeks exacerbated kidney senescence and fibrosis; more so in heterozygous Klotho hypomorphic mice compared to wild-type mice, and in mice with chronic kidney disease (CKD) on high Pi diet compared to CKD mice fed a normal Pi diet. In cultured kidney tubular cells, high Pi directly induced cellular senescence, injury and epithelial-mesenchymal transition, and enhanced H2O2-induced cellular senescence and injury, which were abrogated by Klotho. Fucoidan, a bioactive molecule with multiple biologic functions including senescence inhibition, blunted Pi-induced cellular senescence, oxidation, injury, epithelial-mesenchymal transition, and senescence-associated secretary phenotype. In conclusion, high Pi activates senescence through distinct but interconnected mechanisms: upregulating p16/p21 (early), and elevating plasminogen activator inhibitor-1 and downregulating Klotho (late). Klotho may be a promising agent to attenuate senescence and ameliorate age-associated, and Pi-induced kidney degeneration such as kidney fibrosis.

Project description:BackgroundSoluble Klotho has multiple systemic salutary effects. In animals, both acute and chronic kidney disease models display systemic Klotho deficiency. As such, there is considerable interest in investigating soluble Klotho as a biomarker in patients with different types and severity of kidney diseases. Unfortunately, there remains uncertainty regarding the best method to measure soluble Klotho in human serum samples.MethodsUsing human serum samples obtained from several clinical cohorts with a wide range of kidney function, we measured soluble Klotho using a commercial enzyme-linked immunosorbent assay (ELISA) as well as with an immunoprecipitation-immunoblot (IP-IB) assay utilizing a synthetic antibody with high affinity and specificity for Klotho. Recovery of spiking with a known amount of exogenous Klotho was tested. A subset of samples was analyzed with and without the addition of a protease inhibitor cocktail at the time of collection or after the first freeze-thaw cycle to determine if these maneuvers influenced performance.ResultsThe IP-IB assay was superior to the ELISA at recovery of exogenous Klotho (81-115% versus 60-81%) across the spectrum of kidney function. Klotho measurements by IP-IB were highly correlated with estimated glomerular filtration rate (eGFR) (R = 0.80, P < 0.001) in comparison with the commercial ELISA, which exhibited minimal correlation with eGFR (R = 0.18, P = 0.12). Use of a protease inhibitor cocktail neither improved nor impaired performance of the IP-IB assay; however, subsequent freeze-thaw cycle resulted in a significant reduction in Klotho recovery and dissipated the correlation between Klotho levels and eGFR. With the ELISA, the use of protease inhibitor cocktail resulted in an increase in intrasubject variability.ConclusionsThe IP-IB assay is preferable to the commercial ELISA to measure soluble Klotho concentrations in never-thawed serum samples of humans with varying severity of kidney disease. However, due to the labor-intensive nature of the IP-IB assay, further research is needed to secure an assay suitable for high-throughput work.

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The kidney is the principal organ mediating klotho effects.

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The kidney is the principal organ mediating klotho effects.

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