Dietary and genetic evidence for enhancing glucose metabolism and reducing obesity by inhibiting klotho functions

Abstract

Klotho is a multifunctional protein involved in numerous biological functions, ranging from mineral ion metabolism to signaling activities. Recent studies have identified klotho as a target gene for peroxisome proliferator-activated receptor-γ (PPAR-γ), a master regulator of adipocyte differentiation, and an adipogenesis-promoting factor. In a similar line of observation, eliminating klotho function from mice resulted in the generation of lean mice with almost no detectable fat tissue. In contrast to the klotho-knockout mice (11.7±0.3 g at 9 wk), leptin-deficient (ob/ob) mice are severely obese (49.3±0.6 g at 9 wk), due to excessive fat accumulation. To study the in vivo role of klotho in obesity, we have generated and characterized ob/ob mice lacking klotho activity [ob/ob-klotho double-knockout (DKO) mice]. The ob/ob mice started to get bigger from 3 wk onward and gained almost 2 times more weight than their wild-type (WT) counterparts (WT vs. ob/ob: 34.8±1.3 vs. 65.5±1.2 g at 21 wk). The generated ob/ob-klotho DKO mice were not only viable throughout their adulthood but also showed markedly reduced fat tissue accumulation compared to their ob/ob littermates. The ob/ob-klotho DKO mice had significantly (P<0.01) less retroperitoneal, mesenteric, and epididymal fat accumulation, compared to their ob/ob counterparts. Similarly, the fatty liver that was consistently observed in the ob/ob mice was eliminated in the ob/ob-klotho DKO mice. Such structural improvement in the liver was also evident from markedly reduced fasting blood glucose levels in ob/ob-klotho DKO mice, compared to their ob/ob counterparts (ob/ob vs. ob/ob-klotho DKO: 266 ± 36 vs. 65±2 mg/dl). Finally, to study whether the absence of klotho can induce resistance to high-fat-diet-induced obesity, we provided a high-fat (60%) diet to klotho-knockout mice and compared them with normal-fat (20%) diet-fed klotho-knockout mice. No significant difference in body weight was detected in klotho-knockout mice fed either the normal-fat diet or high-fat diet, while WT mice fed the high-fat diet gradually gained body weight, compared to the normal-fat-diet-fed counterparts. The results of our dietary and genetic manipulation studies provide in vivo evidence for a role of klotho in obesity and offer a novel target to manipulate obesity and associated complications.

Klotho Coreceptors Inhibit Signaling by Paracrine Fibroblast Growth Factor 8 Subfamily Ligands

“…In such a case, the expression level of ␣Klotho would affect the signaling through FGFR-␤Klotho complex and vice versa. This might provide an explanation for the previously reported enhancement of putatively ␤Klotho-dependent metabolic effects when ␣Klotho is knocked out (44,47,69).…”

“…Potentiation of the hypoglycemic effect of insulin (47) and downregulation of circulating insulin levels (11) were used as readouts for FGF21-like metabolic activity. Mice were injected with insulin plus FGF21 29 -167 /FGF19 169 -216 , insulin plus FGF21, or insulin alone, and blood glucose concentrations were monitored for up to 1 h after the injection.…”

“…The ability of the FGF21 29 -167 / FGF19 169 -216 chimera to potentiate the hypoglycemic effect of insulin was used as a readout for FGF21-like metabolic activity (47). Eight-to 12-week-old mice of the C57BL/6 strain were fasted for 4 h and then bled from the cheek pouch for measuring fasting blood glucose levels.…”

Tumour-associated osteomalacia and hypoglycaemia in a patient with prostate cancer: is Klotho involved?

“…The recombinant FGF-21 protein retains its biological activity in Klb−/−mice, suggesting the existence of a β-Klotho-independent signalling pathway involving FGF-21 27. Genetically abolishing Klotho function in mice by knockout or knockdown of Kl resulted in the generation of lean mice with decreased white adipose tissue accumulation, including a reduced subcutaneous adipose tissue layer compared with that in wild-type mice 28. Intracellular lipid accumulation, particularly in skeletal muscle and liver, is usually associated with insulin resistance.…”

Vitamin D, phosphate, and vasculotoxicity

“…and klotho knockout mice also have high serum levels of calcium and 1,25(OH) 2 D 3 (Kuro-o et al 1997;Nakatani et al 2009;Ohnishi et al 2011a;Ohnishi et al 2011b;Ohnishi et al 2009a;Razzaque 2010, 2012;Sitara et al 2008). To determine the effect of high serum phosphate in vascular calcification, independent of high serum calcium and vitamin D levels, we generated FGF23 or klotho knockout mice with high serum calcium and 1,25(OH) 2 D 3 levels and relatively normal serum phosphate levels (Ohnishi et al 2009a;Ohnishi and Razzaque 2010;Sitara et al 2008).…”