Insulin negatively regulates dedifferentiation of mouse adipocytes in vitro

Abstract

Insulin plays an important role during adipogenic differentiation of animal preadipocytes and the maintenance of mature phenotypes. However, its role and mechanism in dedifferentiation of adipocyte remains unclear. This study investigated the effects of insulin on dedifferentiation of mice adipocytes, and the potential mechanisms. The preadipocytes were isolated from the subcutaneous white adipose tissue of wild type (WT), TNFα gene mutant (TNFα-/-), leptin gene spontaneous point mutant (db/db) and TNFα-/-/db/db mice and were then induced for differentiation. Interestingly, dedifferentiation of these adipocytes occurred once removing exogenous insulin from the adipogenic medium. As characteristics of dedifferentiation of the adipocytes, downregulation of adipogenic markers, upregulation of stemness markers and loss of intracellular lipids were observed from the four genotypes. Notably, dedifferentiation was occurring earlier if the insulin signal was blocked. These dedifferentiated cells regained the potentials of the stem cell-like characteristics. There is no significant difference in the characteristics of the dedifferentiation between the adipocytes. Overall, the study provided evidence that insulin plays a negative regulatory role in the dedifferentiation of adipocytes. We also confirmed that both dedifferentiation of mouse adipocytes, and effect of the insulin on this process were independent of the cell genotypes, while it is a widespread phenomenon in the adipocytes.

Dysfunction of insulin-AKT-UCP1 signalling inhibits transdifferentiation of human and mouse white preadipocytes into brown-like adipocytes

“…Total cellular RNA was isolated from cells at various time points in each group as previously described [ 16 ]. The primers used in this study are shown in Supplementary Table S1.…”

“…Deletion of adipocyte AKT causes severe WAT atrophy, and was accompanied by insulin resistance and other metabolic syndrome phenotypes [ 15 ]. Our previous study showed that insulin signalling negatively regulates humans and mice WACs dedifferentiation through the PI3K-AKT-mTORC1 signalling pathway [ 16 , 17 ].…”

Potential key factors involved in regulating adipocyte dedifferentiation

“…But the pAKT level in de‐differentiation was lower than that in differentiation. Further, blocking the insulin signal decreased the pAKT level (Zang et al, 2020). This suggests that insulin/AKT signaling does play a vital role in preventing adipocyte de‐differentiation (Figure 3).…”

“…Considering the key role of insulin in adipocyte differentiation, researchers speculate that it may also regulate de‐differentiation (El‐Chaâr et al, 2004; Zang et al, 2020). In mature adipocytes, insulin deficiency leads to decreasing lipid droplets and the emergence of fibroblast‐like cells resembling undifferentiated adipocytes.…”

“…At the molecular level, the morphological changes of mature adipocytes are accompanied by decreased expression of adipogenic genes, such as PPARγ2, C/EBPα, SREBP‐1 , and Adipoq . Similarly, blocking the insulin signal with OSI‐906 prompted de‐differentiation of fully differentiated adipocytes (Zang et al, 2020). Together, these results suggest that insulin does have an inverse role in regulating adipocyte de‐differentiation (Figure 3).…”