Centrally circulating α-klotho inversely correlates with human obesity and modulates arcuate cell populations in mice.

Abstract

OBJECTIVE:

Our laboratory recently identified the centrally circulating α-klotho protein as a novel hypothalamic regulator of food intake and glucose metabolism in mice. The current study aimed to investigate novel molecular effectors of central α-klotho in the arcuate nucleus of the hypothalamus (ARC), while further deciphering its role regulating energy balance in both humans and mice.

METHODS:

Cerebrospinal fluid (CSF) was collected from 22 adults undergoing lower limb orthopedic surgeries, and correlations between body weight and α-klotho were determined using an α-klotho enzyme-linked immunosorbent assay (ELISA) kit. To investigate the effects of α-klotho on energy expenditure (EE), 2-day intracerebroventricular (ICV) treatment was performed in diet-induced obesity (DIO) mice housed in TSE Phenomaster indirect calorimetry metabolic cages. Immunohistochemical staining for cFOS and patch clamp electrophysiology were used to determine the effects of central α-klotho on proopiomelanocortin (POMC) and tyrosine hydroxylase (TH) neurons. Additional stainings were performed to determine novel roles for central α-klotho to regulate non-neuronal cell populations in the ARC. Lastly, ICV pretreatment with fibroblast growth factor receptor (FGFR) or PI3kinase inhibitors was performed to determine the intracellular signaling involved in α-klotho-mediated regulation of ARC nuclei.

RESULTS:

Obese/overweight human subjects had significantly lower CSF α-klotho concentrations compared to lean counterparts (1,044 ± 251 vs. 1616 ± 218 pmol/L, respectively). Additionally, 2 days of ICV α-klotho treatment increased EE in DIO mice. α-Klotho had no effects on TH neuron activity but elicited varied responses in POMC neurons, with 44% experiencing excitatory and 56% experiencing inhibitory effects. Inhibitor experiments identified an α-klotho→FGFR→PI3kinase signaling mechanism in the regulation of ARC POMC and NPY/AgRP neurons. Acute ICV α-klotho treatment also increased phosphorylated ERK in ARC astrocytes via FGFR signaling.

CONCLUSION:

Our human CSF data provide the first evidence that impaired central α-klotho function may be involved in the pathophysiology of obesity. Furthermore, results in mouse models identify ARC POMC neurons and astrocytes as novel molecular effectors of central α-klotho. Overall, the current study highlights prominent roles of α-klotho→FGFR→PI3kinase signaling in the homeostatic regulation of ARC neurons and whole-body energy balance.

• Authors: Taylor Landry, Peixin Li, Daniel Shookster, Zhiying Jiang, Hongli Li, Brenton Thomas Laing, Wyatt Bunner, Theodore Langton, Qingchun Tong, Hu Huang
• Journal: Molecular metabolism (Mol Metab) Vol. 44 Pg. 101136 (02 2021) ISSN: 2212-8778 [Electronic] Germany
• PMID: 33301986 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
• Copyright: Copyright © 2020 The Author(s). Published by Elsevier GmbH.. All rights reserved.

Chemical References

• Fibroblast Growth Factors
• Pro-Opiomelanocortin
• Glucuronidase
• Klotho Proteins

Topics

• Adolescent
• Adult
• Aged
• Aged, 80 and over
• Animals
• Arcuate Nucleus of Hypothalamus (metabolism)
• Body Weight
• China
• Energy Metabolism (physiology)
• Female
• Fibroblast Growth Factors (metabolism)
• Glucuronidase (metabolism)
• Humans
• Hypothalamus (metabolism)
• Klotho Proteins
• Male
• Mice
• Mice, Inbred C57BL
• Mice, Obese
• Middle Aged
• Neurons (metabolism)
• Obesity (metabolism)
• Pro-Opiomelanocortin (metabolism)
• Signal Transduction (physiology)
• Young Adult