Abstract
BackgroundWhite adipose tissue (WAT) is essential for energy storage as well as being an active endocrine organ. The secretion of adipokines by adipocytes can affect whole body metabolism, appetite, and contribute to overall health. WAT is comprised of lipid-laden mature adipocytes, as well as immune cells, endothelial cells, pre-adipocytes, and adipose-derived stem cells. In addition, the presence of extracellular matrix (ECM) proteins in WAT can actively influence adipocyte differentiation, growth, and function. Type I collagen is an abundant fibrous ECM protein in WAT that is secreted by developing adipocytes. However, the extent and overall effect of Type I collagen on adipokine secretion in mature adipocytes when added exogenously has not been established.MethodsWe characterized the effects of Type I collagen overlays prepared using two different buffers on adipocyte physiology and function when added at different times during differentiation. In addition, we compared the effect of collagen overlays when adipocytes were cultured on two different tissue culture plastics that have different adherent capabilities. Triglyceride accumulation was analyzed to measure adipocyte physiology, and leptin and adiponectin secretion was determined to analyze effects on adipokine secretion.ResultsWe found that collagen overlays, particularly when added during the early differentiation stage, impaired adipokine secretion from mature adipocytes. Collagen prepared using PBS had a greater suppression of leptin than adiponectin while collagen prepared using HANKS buffer suppressed the secretion of both adipokines. The use of CellBind plates further suppressed leptin secretion. Triglyceride accumulation was not substantially impacted with any of the collagen overlays.DiscussionAdipokine secretion can be selectively altered by collagen overlays. Thus, it is feasible to selectively manipulate the secretion of adipokines by adipocytes in vitro by altering the composition or timing of collagen overlays. The use of this technique could be applied to studies of adipokine function and secretion in vitro as well as having potential therapeutic implications to specifically alter adipocyte functionality in vivo.
Highlights
White adipocytes serve a crucial function in storing free fatty acids in the form of triglycerides (TG) for energy use (Berry et al, 2013) and to prevent toxic deposition of free fatty acids in ectopic sites (Bays, Mandarino & Defronzo, 2004)
Increased expression of C/EBP-α and PPAR-γ promote the expression of key proteins essential for lipid and carbohydrate storage proteins, such as glucose transporter 4 (Glut4) and perilipin (Plin1), allowing the formation of large lipid droplets that store TG and cholesteryl esters, which are a primary phenotype of terminally differentiated mature adipocytes (Berry et al, 2013)
Adiponectin enhances insulin sensitivity and induces the expansion of White adipose tissue (WAT), which prevents the toxic deposition of free fatty acids in other organs (Yamauchi et al, 2001; Yamauchi et al, 2002; Berg et al, 2001; Xu et al, 2003), whereas leptin acts through the sympathetic nervous system to induce lypolysis of WAT (Zeng et al, 2015)
Summary
White adipocytes serve a crucial function in storing free fatty acids in the form of triglycerides (TG) for energy use (Berry et al, 2013) and to prevent toxic deposition of free fatty acids in ectopic sites (Bays, Mandarino & Defronzo, 2004). Key adipokines include adiponectin, which is inversely associated with obesity and increased with fasting, and leptin, which is elevated in obese individuals and decreased with fasting (Stern, Rutkowski & Scherer, 2016) Both adiponectin and leptin are secreted from terminally differentiated adipocytes, and they act on WAT as well as distal tissues. Adiponectin enhances insulin sensitivity and induces the expansion of WAT, which prevents the toxic deposition of free fatty acids in other organs (Yamauchi et al, 2001; Yamauchi et al, 2002; Berg et al, 2001; Xu et al, 2003), whereas leptin acts through the sympathetic nervous system to induce lypolysis of WAT (Zeng et al, 2015). We characterized the effects of Type I collagen overlays prepared using two different buffers on adipocyte physiology and function when added at different times during differentiation. The use of this technique could be applied to studies of adipokine function and secretion in vitro as well as having potential therapeutic implications to alter adipocyte functionality in vivo
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