2026-03-14 | Inversed impaired osteogenic activity in children with severe obesity due to MC4R deficiency compared to LEP and LEPR deficiency.
Chronic obesity is associated with impaired bone health. However, few investigations have been conducted to assess bone physiology in early-onset obesity. In this study, we measured specific bone turnover and metabolic biomarkers in children with severe obesity with biallelic loss-of-function variants of the leptin (LEP), leptin receptor (LEPR), or melanocortin 4 receptor (MC4R) genes. Thirty-nine children aged 0.3-8.8 years with a BMI SDS ≥ 3, previously identified with pathogenic variants in LEP, LEPR, or MC4R, were recruited for the current study. Additionally, 13 age-matched children with severe obesity who tested negative for variants in known obesity-related genes were included, and another 13 unrelated age-matched children with normal body weight served as the control group. Serum osteocalcin, osteopontin, osteoprotegerin, and sclerostin levels were assessed using multi-analyte profiling. Serum leptin, insulin, and cortisol levels were determined using ELISA. Serum levels of osteocalcin and osteopontin, specific markers of bone formation, were significantly lower in children with LEP and LEPR biallelic variants than in the control group. In contrast, the values of these two biomarkers in children with MC4R deficiency were significantly higher than those in the other groups. No differences were observed in the bone resorption markers osteoprotegerin and sclerostin. Hyperleptinemia was more pronounced in children with LEPR deficiency. Serum insulin concentrations were elevated in individuals with MC4R deficiency, whereas serum cortisol levels were significantly higher in children with LEP deficiency than in all other groups. Our data demonstrate that osteogenic activity (but not resorption activity) is differentially affected in children with complete genetic disruption of the leptin-signaling pathway. Children with MC4R deficiency showed higher osteogenic markers, but children with LEP and LEPR deficiencies showed the opposite. Our results support the usefulness of bone turnover biomarkers for the assessment and management of bone health in different types of obesity.
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2025-11-18 | Obesity-induced leptin resistance is directly involved in skin fragility by decreasing type I collagen synthesis.
The relationship between obesity-induced leptin resistance and skin function remains unclear. In this study, we examined the effects of leptin signaling on collagen production in mouse skin. Mice were divided into three groups: control diet, high-fat diet, and switching diet (from the high-fat diet to the control diet). We measured the expression of leptin signaling-related genes and type I tropocollagen levels in the skin. In an additional experiment, leptin was administered to leptin-deficient ob/ob mice to examine the direct effect of leptin signaling on type I collagen synthesis in the skin. Type I tropocollagen levels and Ob-Rb gene expression were decreased in the high-fat diet group. These abnormalities were reversed by the switching diet. We also observed that type I tropocollagen levels were decreased in ob/ob mice, but this abnormality was reversed by leptin administration. It is likely that leptin will help to improve obesity-induced skin fragility.
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2025-10-04 | Leptin: 30 Years Later.
The discovery of leptin as an adipocyte-secreted hormone encoded by the ob gene whose absence produces severe obesity that is corrected by leptin repletion in both mice and humans was a transformative event in metabolic science. Leptin's discovery in 1994 accelerated the identification of central neuronal circuitry responsive to peripheral signals that regulate energy balance as well as metabolic, neuroendocrine, and other vital functions. Leptin's primary physiological role was initially viewed as preventing obesity by its levels rising, but subsequent research has emphasized the key role of falling levels to signal starvation. Resistance to leptin action, though partial, characterizes common forms of obesity. Despite much being learned about leptin signal transduction over 30 years, the precise molecular mechanisms for leptin resistance and common obesity remain unclear. Leptin therapy is effective in rare patients with congenital leptin deficiency and other low leptin conditions but not common obesity. Interestingly, reducing hyperleptinemia may prove useful in treating common obesity.
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