Osteoblast-like MC3T3-E1 Cells Prefer Glycolysis for ATP Production but Adipocyte-like 3T3-L1 Cells Prefer Oxidative Phosphorylation

Abstract

Mesenchymal stromal cells (MSCs) are early progenitors that can differentiate into osteoblasts, chondrocytes, and adipocytes. We hypothesized that osteoblasts and adipocytes utilize distinct bioenergetic pathways during MSC differentiation. To test this hypothesis, we compared the bioenergetic profiles of preosteoblast MC3T3-E1 cells and calvarial osteoblasts with preadipocyte 3T3L1 cells, before and after differentiation. Differentiated MC3T3-E1 osteoblasts met adenosine triphosphate (ATP) demand mainly by glycolysis with minimal reserve glycolytic capacity, whereas nondifferentiated cells generated ATP through oxidative phosphorylation. A marked Crabtree effect (acute suppression of respiration by addition of glucose, observed in both MC3T3-E1 and calvarial osteoblasts) and smaller mitochondrial membrane potential in the differentiated osteoblasts, particularly those incubated at high glucose concentrations, indicated a suppression of oxidative phosphorylation compared with nondifferentiated osteoblasts. In contrast, both nondifferentiated and differentiated 3T3-L1 adipocytes met ATP demand primarily by oxidative phosphorylation despite a large unused reserve glycolytic capacity. In sum, we show that nondifferentiated precursor cells prefer to use oxidative phosphorylation to generate ATP; when they differentiate to osteoblasts, they gain a strong preference for glycolytic ATP generation, but when they differentiate to adipocytes, they retain the strong preference for oxidative phosphorylation. Unique metabolic programming in mesenchymal progenitor cells may influence cell fate and ultimately determine the degree of bone formation and/or the development of marrow adiposity. © 2018 American Society for Bone and Mineral Research.

Exercise Degrades Bone in Caloric Restriction, Despite Suppression of Marrow Adipose Tissue (MAT)

“…CD36 upregulation in muscle can occur in the setting of increased dietary fat availability, driven by AMP-activated protein kinase (AMPK) activation. (84) It is unclear whether osteocytes, marrow adipocytes, and their progenitors rely on fatty acids or glucose in the calorierestricted state and exercised states. (83) in vitro experiments exhibited a preference for glucose as an energy source in cultured osteoblasts.…”

“…(83) in vitro experiments exhibited a preference for glucose as an energy source in cultured osteoblasts. (84) It is unclear whether osteocytes, marrow adipocytes, and their progenitors rely on fatty acids or glucose in the calorierestricted state and exercised states. Recent human metabolomic data obtained after 10 days of starvation points to a shift from carbohydrate to fatty acid metabolism.…”

Defining osteoblast and adipocyte lineages in the bone marrow

“…As such, a better understanding of the mechanisms influencing lipid storage in BMSC-derived cells and bone marrow adiposity can provide novel insights into preventing the decreased bone mass and increased fat deposition with age. Given the recently reported differences in the bioenergetic phenotypes of osteoblasts as compared to adipocytes (65), it will likely be critical to determine the relative importance of cellular energetic profile as compared to lineage commitment in the process of osteoblast versus adipocyte differentiation, particularly with aging.…”

Insulin Signaling in Bone Marrow Adipocytes

“…Hematopoietic progenitor cells exhibit differentiation dependent use of glycolysis or OxPhos [60,61]. Osteoblast lineage cells employ both oxidative and glycolytic metabolic pathways in undifferentiated state, but during osteoblast differentiation, glycolysis is the preferred energy source [62]. On the other hand, a pre-adipocytic embryonic murine cell line 3T3-L1 employs OxPhos during adipocyte differentiation [62].…”

“…Osteoblast lineage cells employ both oxidative and glycolytic metabolic pathways in undifferentiated state, but during osteoblast differentiation, glycolysis is the preferred energy source [62]. On the other hand, a pre-adipocytic embryonic murine cell line 3T3-L1 employs OxPhos during adipocyte differentiation [62]. Thus, commitment to either osteoblasts or adipocytes is associated with a characteristic bioenergetic profile that is maintained during differentiation.…”