Increased expression levels of PIEZO1 in visceral adipose tissue in obesity and type 2 diabetes are triggered by mechanical forces and are associated with inflammation

Abstract

Background: PIEZO1 has emerged as a mechanoreceptor linked with adipogenesis, adipose tissue (AT) inflammation and insulin resistance. We aimed to determine the impact of obesity and obesity-associated type 2 diabetes (T2D) as well as mechanical compression forces on the expression of PIEZO1 in visceral AT (VAT) and its relation with inflammation.

Methods: Blood and VAT samples were obtained from 100 volunteers. Static compression studies in VAT explants were performed to study the PIEZO1 response. The effect of bariatric surgery on the expression of Piezo1 was assessed in a rat model of diet-induced obesity.

Results: Obesity and obesity-associated T2D increased (P < 0.01) gene expression levels of PIEZO1 in VAT mainly due to adipocytes. SWELL1 and key markers of inflammation (NLRP3, NLRP6, IL1B, IL18 and IL8) were also upregulated in VAT in obesity and T2D being significantly associated (P < 0.01) with PIEZO1 levels. We further showed that the static compression of VAT explants promoted an upregulation of PIEZO1 (P < 0.01) and SWELL1 (P < 0.01) expression levels together with a strong increase in the expression and release of key inflammatory mediators. The treatment of THP-1-derived macrophages with the secretome of adipocytes from patients with obesity upregulated (P < 0.001) PIEZO1 levels. Rats undergoing bariatric surgery exhibited decreased (P < 0.01) expression levels of Piezo1 in the epididymal AT.

Conclusions: Static compression triggered an upregulation of PIEZO1 in VAT explants together with a strong inflammation. In addition, the increased expression of PIEZO1 in VAT in obesity and obesity-associated T2D, primarily attributable to adipocytes, is closely associated with SWELL1 and inflammatory markers.

Keywords: Inflammation; Mechanotransduction; Obesity; PIEZO1; Type 2 diabetes; VAT.

Fig. 1

Gene expression levels of PIEZO1 in visceral adipose tissue (VAT). A Bar graphs show the mRNA levels of PIEZO1 in VAT samples from volunteers with normal weight (NW) and people with obesity and normoglycemia (OB-NG) and with obesity-associated type 2 diabetes (OB-T2D). B Gene expression levels of PIEZO1 in adipocytes and stroma-vascular fraction cells (SVFC) obtained from patients with obesity. C Representative immunohistochemistry and (D) quantification (n = 6) for PIEZO1 in VAT from volunteers with NW, with OB-NG and with OB-T2D (magnification 100×, scale bar 50 µm). Differences between groups were analyzed by one-way ANOVA followed by Tukey’s tests as well as by unpaired two-tailed Student’s t test. ^***P < 0.001

Fig. 2

Impact of obesity and obesity-associated T2D on VAT expression levels of the key inflammation-related factors and their association with PIEZO1. Bar graphs show the gene expression levels of (A) LRCC8A/SWELL1, (B) NLRP3, (C) NLRP6, (D) IL1B, (E) IL18, (F) IL8, (G) SIRT1 and (H) CAV1 in VAT samples from volunteers with normal weight (NW) and people with obesity and normoglycemia (OB-NG) and with obesity-associated type 2 diabetes (OB-T2D). I Heatmap of the associations between gene expression levels of PIEZO1 and inflammation-related factors in VAT. Differences between groups were analyzed by one-way ANOVA followed by Tukey’s tests. ^*P < 0.05, ^**P < 0.01 and ^***P < 0.001. BMI, body mass index, BF body fat, LRCC8A/SWELL1 leucine rich repeat containing 8 VRAC subunit A, CAV1 caveolin-1, NLRP nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin, IL interleukin, SIRT1 sirtuin 1

Fig. 3

Gene expression levels of Piezo1 (A), Cav1 (C), Nlrp3 (E), Nlrp6 (G), Il1b (I) and Col11a1 (K) in the epididymal adipose tissue (EWAT) from rats fed a normal diet (ND) or a high-fat diet (HFD) and (B, D, F, H, J, L) after being submitted to sham surgery, single anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S), sleeve gastrectomy (SG) and pair-fed (PF). Differences between groups were analyzed by unpaired two-tailed Student’s t test as well as by one-way ANOVA followed by Tukey’s tests. ^*P < 0.05, ^**P < 0.01 and ^***P < 0.001. Cav1, caveolin 1; Col1a1, collagen 1a1; Il1b, interleukin-1β; Nlrp, nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin

Fig. 4

Effect of static mechanical compression on VAT explants. Gene expression levels of (A) PIEZO1, (B) SWELL1, (C) key inflammatory mediators and (H) extracellular matrix-related factors after 2 and 4 kPa of mechanical compression for 24 h. Secreted concentrations of the crucial inflammatory markers (D) IL-1α, (E) IL-1β, (F) IL-6 and (G) IL-8 in the culture media of human VAT explants after static compression for 24 h. Values are the mean ± SEM. Differences between groups were analyzed by one-way ANOVA followed by Tukey’s tests. ^*P < 0.05 and ^**P < 0.01. COL collagen; ELN elastin, IL interleukin, LOX lysyl oxidase, LRCC8A/SWELL1 leucine rich repeat containing 8 VRAC subunit A, MMP matrix metalloproteinase, NLRP nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin, SPP1 osteopontin, TLR4 toll-like receptor 4, TNF tumour necreosis factor-α

Fig. 5

Gene expression levels of PIEZO1 in human visceral adipocytes treated with different concentrations of (A) lipopolysaccharide (LPS), (B) interferon-γ (INF-γ, (C) transforming growth factor-β (TGF-β) and (D) insulin during 24 h. Values are the mean ± SEM. Differences between groups were analyzed by one-way ANOVA followed by Tukey’s tests. ^*P < 0.05, ^**P < 0.01 and ^***P < 0.001

Fig. 6

Effect of adipocyte-conditioned media (ACM) in THP-1-derived macrophages. Bar graphs show the effect of ACM (20 and 40%) from subjects with obesity incubated for 24 h on the transcript levels of PIEZO1. Differences between groups were analyzed by one-way ANOVA followed by Tukey’s tests. ^***P < 0.001

Fig. 7

Static compression triggered an upregulation of PIEZO1 and SWELL1 expression levels in visceral adipose tissue (VAT) explants together with a strong increase in the expression and release of key inflammatory mediators (IL1A, IL1B, IL6, IL8, NLRP3, SPP1, TNF) and the downregulation of extracellular matrix factors (COL1A1, COL6A3, ELN). Obesity and obesity-associated T2D increased gene expression levels of PIEZO1 in VAT mainly due to adipocytes. SWELL1 and key markers of inflammation were also upregulated in VAT in obesity and T2D being significantly associated with PIEZO1 levels. The treatment of THP-1-derived macrophages with the secretome of adipocytes from patients with obesity upregulated PIEZO1 levels. COL collagen, ELN elastin, IL interleukin, NLRP nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin, SPP1 osteopontin, SWELL1 leucine rich repeat containing 8 VRAC subunit A, TNF tumour necrosis factor-α