Knochenfett: Pathophysiologische Wechselwirkungen mit dem Metabolischen Syndrom

Zusammenfassung

Knochenfett stellt ein bisher kaum untersuchtes Fettdepot dar. Diese Population von Fettzellen tritt in den Markhöhlen der meisten Röhrenknochen auf und akkumuliert mit zunehmendem Alter und wird aus diesem Grund seit einiger Zeit mit wichtigen Fehlfunktionen des Knochens im Alter in Zusammenhang gebracht. Aufgrund ihrer besonderen Mikroanatomie innerhalb des Knochens stellt diese Zellpopulation eine spezialisierte Form von Adipozyten dar, die sich zwar morphologisch kaum von den normalen Zellen des restlichen Körperfettes unterscheidet, sich aber in seiner physiologischen Funktion deutlich von ihnen absetzt. Bisherige Studien lassen im gesunden Zustand eine potenzielle regulatorische Rolle vermuten, in der die Fettzellen durch molekulare Interaktionen mit anderen Zelltypen des Knochens, beispielsweise Osteoblasten und hämatopoetischen Zellen, Anteil an der gesunden Knochenhomöostase haben. Unter pathologischen Konditionen, also mit zunehmendem Alter und bei metabolischen Erkrankungen wie Adipositas und Diabetes, verändern sich die molekularen Charakteristika des Knochenfettes zunehmend. Zudem beeinflussen metabolische Konditionen die Bildung von Knochenfett aus mesenchymalen Stammzellen, mitunter zulasten der Entstehung des normalen Knochengewebes, und könnten auf diesem Wege zum Abbau der Knochensubstanz und zur Entwicklung von Osteoporose und erhöhtem Faktur-Risiko beitragen. Zusätzlich beeinflusst Knochenfett den systemischen Energiestoffwechsel und kann durch die Sekretion von Adipokinen in einer Reihe von physiologischen Prozessen eingreifen.

Abstract

Bone marrow adipose tissue is a previously unrecognized depot of fat. Throughout life, this population of adipocytes accumulates in the marrow cavities of long bones and has therefore recently been linked to important aging-related bone disorders. Due to their particular micro-anatomical localization inside the bone, marrow-resident adipocytes represent a specialized type of fat cell that is morphologically almost indistinguishable from regular adipocytes of the other fat depots in the body but is clearly distinct regarding their physiological function. Previous studies have suggested a potential regulatory role in healthy individuals where fat cells influence physiological functions through molecular interactions with other cell types of the bone, such as osteoblasts and hematopoietic cells. Under pathological conditions, including aging and metabolic diseases such as obesity and diabetes, the molecular characteristics of bone marrow fat are increasingly detrimental and may trigger pathophysiological processes in the bone. Metabolic conditions may also influence the formation of bone fat from mesenchymal stem cells, sometimes at the expense of normal bone tissue formation. Metabolic diseases may thus contribute to bone tissue degeneration and the development of osteoporosis and increased fracture risk profiles. Conversely, bone fat affects systemic energy expenditure and regulates a variety of physiological processes through the secretion of adipokines.

Schlüsselwörter

Knochenfett - Osteogenese - Knochenheilung - Adipositas - Metabolisches Syndrom

Key words

Bone marrow adipose tissue - osteogenesis - bone healing - obesity - metabolic syndrome

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