Nck2, an unexpected regulator of adipogenesis

20 Years with SGBS cells - a versatile in vitro model of human adipocyte biology

20 years ago, we described a human cell strain derived from subcutaneous adipose tissue of an infant supposed to have Simpson-Golabi-Behmel Syndrome (SGBS), thus called “SGBS cells”. Since then, these cells have emerged as the most commonly used cell model for human adipogenesis and human adipocyte biology. Although these adipocyte derived stem cells have not been genetically manipulated for transformation or immortalization, SGBS cells retain their capacity to proliferate and to differentiate into adipocytes for more than 50 population doublings, providing an almost unlimited source of human adipocyte progenitor cells. Original data obtained with SGBS cells led to more than 200 peer reviewed publications comprising investigations on adipogenesis and browning, insulin sensitivity, inflammatory response, adipokine production, as well as co-culture models and cell-cell communication. In this article, we provide an update on the characterization of SGBS cells, present basic methods for their application and summarize results of a systematic literature search on original data obtained with this cell strain.

Exposure to 2,3,3',4,4',5-hexachlorobiphenyl promotes nonalcoholic fatty liver disease development in C57BL/6 mice

Previous in vitro studies have indicated that 2,3,3',4,4',5-hexachlorobiphenyl (PCB 156) may be a new contributor to metabolic disruption and may further cause the occurrence of nonalcoholic fatty liver disease (NAFLD). However, no study has clarified the specific contributions of PCB 156 to NAFLD progression by constructing an in vivo model. Herein, we evaluated the effects of PCB 156 treatment (55 mg/kg, i.p.) on the livers of C57BL/6 mice fed a control diet (CD) or a high-fat diet (HFD). The results showed that PCB 156 administration increased intra-abdominal fat mass, hepatic lipid levels and dyslipidemia in the CD-fed group and aggravated NAFLD in HFD-fed group. By using transcriptomics studies and biological methods, we found that the genes expression involved in lipid metabolism pathways, such as lipogenesis, lipid accumulation and lipid β-oxidation, was greatly altered in liver tissues exposed to PCB 156. In addition, the cytochrome P450 pathway, peroxisome proliferator-activated receptors (PPARs) and the glutathione metabolism pathway were significantly activated following exposure to PCB 156. Furthermore, PCB 156 exposure increased serum transaminase levels and lipid peroxidation, and the redox-related genes were significantly dysregulated in liver tissue. In conclusion, our data suggested that PCB 156 could promote NAFLD development by altering the expression of genes related to lipid metabolism and inducing oxidative stress.

Ca2+ entry via TRPC1 is essential for cellular differentiation and modulates secretion via the SNARE complex

Properties of adipocytes, including differentiation and adipokine secretion, are crucial factors in obesity-associated metabolic syndrome. Here, we provide evidence that Ca²⁺ influx in primary adipocytes, especially upon Ca²⁺ store depletion, plays an important role in adipocyte differentiation, functionality and subsequently metabolic regulation. The endogenous Ca²⁺ entry channel in both subcutaneous and visceral adipocytes was found to be dependent on TRPC1–STIM1, and blocking Ca²⁺ entry with SKF96365 or using TRPC1^−/− knockdown adipocytes inhibited adipocyte differentiation. Additionally, TRPC1^−/− mice have decreased organ weight, but increased adipose deposition and reduced serum adiponectin and leptin concentrations, without affecting total adipokine expression. Mechanistically, TRPC1-mediated Ca²⁺ entry regulated SNARE complex formation, and agonist-mediated secretion of adipokine-loaded vesicles was inhibited in TRPC1^−/− adipose. These results suggest an unequivocal role of TRPC1 in adipocyte differentiation and adiponectin secretion, and that loss of TRPC1 disturbs metabolic homeostasis.

This article has an associated First Person interview with the first author of the paper.

Summary: TRPC1 modulates Ca²⁺ entry, which is essential in adipocyte differentiation and adiponectin secretion, through facilitating SNARE complex formation, thereby maintaining metabolic homeostasis.

Nck1 Deficiency Impairs Adipogenesis by Activation of PDGFRα in Preadipocytes

Obesity results from an excessive expansion of white adipose tissue (WAT), which is still poorly understood from an etiologic-mechanistic perspective. Here, we report that Nck1, a Src homology domain-containing adaptor, is upregulated during WAT expansion and in vitro adipogenesis. In agreement, Nck1 mRNA correlates positively with peroxisome proliferator-activated receptor (PPAR) γ and adiponectin mRNAs in the WAT of obese humans, whereas Nck1-deficient mice display smaller WAT depots with reduced number of adipocyte precursors and accumulation of extracellular matrix. Furthermore, silencing Nck1 in 3T3-L1 preadipocytes increases the proliferation and expression of genes encoding collagen, whereas it decreases the expression of adipogenic markers and impairs adipogenesis. Silencing Nck1 in 3T3-L1 preadipocytes also promotes the expression of platelet-derived growth factor (PDGF)-A and platelet-derived growth factor receptor (PDGFR) α activation and signaling. Preventing PDGFRα activation using imatinib, or through PDGF-A or PDGFRα deficiency, inhibits collagen expression in Nck1-deficient preadipocytes. Finally, imatinib rescues differentiation of Nck1-deficient preadipocytes. Altogether, our findings reveal that Nck1 modulates WAT development through PDGFRα-dependent remodeling of preadipocytes.