Mitochondrial Dysfunction and Adipogenic Reduction by Prohibitin Silencing in 3T3-L1 Cells

Abstract

Increase in mitochondrial biogenesis has been shown to accompany brown and white adipose cell differentiation. Prohibitins (PHBs), comprised of two evolutionarily conserved proteins, prohibitin-1 (PHB1) and prohibitin-2 (PHB2), are present in a high molecular-weight complex in the inner membrane of mitochondria. However, little is known about the effect of mitochondrial PHBs in adipogenesis. In the present study, we demonstrate that the levels of both PHB1 and PHB2 are significantly increased during adipogenesis of 3T3-L1 preadipocytes, especially in mitochondria. Knockdown of PHB1 or PHB2 by oligonucleotide siRNA significantly reduced the expression of adipogenic markers, the accumulation of lipids and the phosphorylation of extracellular signal-regulated kinases. In addition, fragmentation of mitochondrial reticulum, loss of mitochondrial cristae, reduction of mitochondrial content, impairment of mitochondrial complex I activity and excessive production of ROS were observed upon PHB-silencing in 3T3-L1 cells. Our results suggest that PHBs are critical mediators in promoting 3T3-L1 adipocyte differentiation and may be the potential targets for obesity therapies.

Prohibitin Overexpression in Adipocytes Induces Mitochondrial Biogenesis, Leads to Obesity Development, and Affects Glucose Homeostasis in a Sex-Specific Manner

“…The obese phenotype of Mito-Ob mice affirms the emerging notion that PHB and adipocyte mitochondria play a role in the regulation of adipose tissue homeostasis and metabolic regulation (1)(2)(3)(4)(8)(9)(10). However, the metabolic consequences of obesity in Mito-Ob mice are sex specific, suggesting that intrinsic differences exist in the way adipose tissues are regulated and/or respond to obesity development in male and female mice despite a similar underlying cause.…”

“…In addition, it is expressed in immune cells, such as macrophages (16). However, a similar effect of PHB manipulation in adipocytes in vitro and in vivo (4,(8)(9)(10) suggests that the phenotype we have observed is most likely due to the role of PHB in adipocytes. PHB translocates from mitochondria to the nucleus in response to estrogen (17).…”

“…Phb knockdown in Caenorhabditis elegans results in a significant reduction in intestinal fat content (8). Moreover, PHB overexpression in preadipocytes facilitates adipogenesis, whereas PHB silencing attenuates adipogenesis and mitochondrial function (4,9,10). Collectively, this evidence points to a role of PHB in adipose tissue biology; however, the precise mechanism involved remains to be determined.…”

Mitochondrial Actions for Fat Browning and Energy Expenditure in White Adipose Tissue

“…In clonal 3T3-L1 cells PHBs silencing reduced mtDNA copy number, impaired mitochondrial function and resulted in mitochondrial fragmentation. This, in turn, led to elevated ROS generation and adipogenic reduction combined with reduced expression of adipogenic markers (C/EBPb, PPARγ and aP2) and less lipid accumulation [60]. These findings were corroborated in the studies with human ASC treated with micro RNAs (miR-27a,b) targeting and silencing PHBs, which resulted in reduced PPARγlevels and less adipogenesis [56].…”

“…In fact, the levels of both PHB1 and PHB2 are significantly increased during adipogenesis of 3T3-L1 preadipocytes, especially in mitochondria [60]. PHBs inhibition was shown to impair adipogenesis and mitochondrial function both in 3T3-L1 cells and in human adipose-derived stem cells (ASC) [56,60].…”