Persistent effects of pre-differentiation manganese exposure on adipogenesis and metabolic function in differentiated...

Obesity is a multifactorial metabolic disorder influenced by genetic, lifestyle, and environmental factors. Increasing evidence suggests that early-life environmental exposures can induce persistent alterations in adipose tissue, contributing to long-term metabolic dysfunction. Manganese (Mn) is an essential trace element involved in mitochondrial function, redox homeostasis, and energy metabolism; however, both Mn deficiency and overexposure have been associated with adverse metabolic outcomes. Despite epidemiological studies linking Mn exposure to obesity-related disorders, the cellular mechanisms underlying Mn-mediated metabolic disruption remain poorly understood. Here, we investigated whether transient Mn exposure during the early adipogenesis induces persistent molecular and metabolic alterations in mature adipocytes. Using the 3T3-L1 cell line, pre-adipocytes were exposed to increasing Mn concentrations (0, 5, 10, 50, 100, or 500 μM) during the first 48h of differentiation (confluence phase). Mn was subsequently removed, and cells were either maintained as non-differentiated controls or differentiated using a defined 3T3-L1 protocol designed to generate adipocytes with white morphology and beige-like features. Upon maturation, adipogenic markers, lipid accumulation, β-adrenergic-induced lipolysis, glucose transporter gene expression, and antioxidant defense-related protein and gene expression were assessed. Early Mn exposure elicited persistent concentration-dependent alterations in adipogenic programming, characterized by reduced lipid accumulation and sustained suppression of the adipogenic regulators PPARγ and C/EBPα. Fully differentiated adipocytes also exhibited persistently impaired expression of glucose transporter genes and reduced hormone-sensitive lipase activation, leading to diminished lipid mobilization under β-adrenergic stimulation. Combined, these findings demonstrate that transient Mn exposure during the initial stages of adipocyte differentiation is sufficient to cause long-term alteration of adipogenic programming and provides evidence for a mechanism of persistent metabolic disruption. Importantly, lower Mn concentrations were associated with selected persistent alterations in adipocyte maturation, whereas the strongest effects observed at 500 μM Mn likely included cellular stress or toxicity-associated responses.