Adiponectin does not bind to gelatin: a new and easy way to purify high-molecular-weight adiponectin from human plasma

Isolation and purification of high molecular weight adiponectin from human plasma fraction

Adiponectin, a crucial protein hormone originating from adipose tissue, regulates key metabolic processes, including lipid metabolism, mitochondrial activity, and insulin sensitivity. These pleiotropic roles of adiponectin, along with its inverse correlation with metabolic disorders such as obesity, type II diabetes, and atherosclerosis, establish this protein as a potential therapeutic target. However, due to this complexity, challenges have arisen in its production with a natural conformation in bacterial or mammalian expression systems, hindering clinical translation. Furthermore, while inducers for adiponectin secretion or chemical agonists targeting adiponectin receptors have shown promise in laboratory settings, clinical studies with these agents have not yet been conducted. This study proposes a method for isolating and purifying natural high molecular weight (HMW) adiponectin from discarded plasma fractions during the conventional pharmaceutical protein manufacturing process. The process involved Cohn-Oncley fractionation, initial chromatography using reduced cellufine formyl, and subsequent purification via DEAE Sepharose chromatography. Characterization involved gel electrophoresis and biological assays on a hepatocyte cell-line. The purification process effectively captured adiponectin from the I + III paste, demonstrating that this fraction contained a significant portion of total plasma adiponectin. The two-step chromatography led to highly purified HMW adiponectin, confirmed by native-PAGE showing a 780 kDa multimeric complex. Biological assessments demonstrated normal downstream signaling, with HMW adiponectin inducing AMPK phosphorylation. This study demonstrates the feasibility of obtaining purified HMW adiponectin by repurposing plasma fractionation processes. It offers a promising avenue for the HMW adiponectin production, tapping into HMW adiponectin's therapeutic potential against metabolic disorders while optimizing plasma resource utilization in healthcare.

Suppression of Lipopolysaccharide-Induced IL-1β Gene Expression by High-Molecular-Weight Adiponectin in RAW264.7 Macrophages

Adiponectin is an abundant adipocytokine secreted by adipocytes. It exists in the plasma in its trimeric, hexameric, high-molecular-weight (HMW), and globular (a proteolytic product) isoforms. Adiponectin's anti-inflammatory effects on macrophages remain controversial. We have previously reported a simple and effective method for purifying native HMW adiponectin from human plasma. Here, we investigated whether native HMW adiponectin from human plasma has anti-inflammatory effects on macrophages. Pretreatment with human native HMW adiponectin inhibited lipopolysaccharide (LPS)-induced interleukin-1β (IL-1β) gene expression, but not tumor necrosis factor (TNF)-α expression. However, simultaneous treatment with HMW adiponectin and LPS did not inhibit IL-1β expression. Further, HMW adiponectin pretreatment decreases glycogen synthase kinase-3β (GSK-3β) inactivation by abrogating LPS-induced Akt (Ser473) phosphorylation, which subsequently suppresses LPS-induced CCAAT/enhancer binding protein β (C/EBPβ) protein translation and nuclear translocation. However, HMW adiponectin pretreatment did not affect LPS-induced nuclear factor-kappaB (NF-κB) activation. These results suggest that HMW adiponectin mediates potent anti-inflammatory activities in macrophages by inhibiting its Akt-C/EBPβ signaling pathway, thereby suppressing IL-1β gene expression.

Potentiated macrophage activation by acid sensing under low adiponectin levels

Adiponectin can protect against inflammation; one of the mechanisms involves direct, inhibition of macrophages (MΦ). We postulated that adiponectin anti-sense transgenic (AsTg) mice raised in our laboratory are prone to inflammation because of systemic low adiponectin levels. The writhing response to acetic acid was utilized as an in vivo inflammatory model, and using Ca(2)(+), response to the acid was exploited in vitro to evaluate the function of resident peritoneal MΦ. The in vivo response to the acid was increased and the Ca(2)(+) response of MΦ was enhanced in AsTg mice, compared with those in wild type (WT) mice. In parallel with these enhanced responses, MΦ from AsTg mice augmented TNF-α and IL-6 mRNA expression. We further analyzed the enhancement in activity of MΦ from AsTg mice by acid sensing using specific inhibitors, amiloride for acid-sensing ion channels (ASICs) and KB-R7943 for Na(+)/Ca(2)(+) exchangers (NCXs). Our results indicated that in AsTg mice, the Ca(2)(+) response to the acid was facilitated in MΦ by a low threshold of ASIC1 and NCX1 molecules and the activity of these channel was possibly regulated by adiponectin.

Effect of adiponectin on cardiac allograft vasculopathy

BACKGROUND

The role of adiponectin (APN), an adipose tissue-specific secretory protein, on chronic rejection after cardiac transplantation in APN-sense transgenic mice (APN-SE) was evaluated.

METHODS AND RESULTS

Heterotopic cardiac transplantation in major histocompatibility complex class II-mismatched mice was performed. B6.C-H-2(bm12)KhEg (Bm12) hearts were transplanted into APN-SE, and allografts were harvested at 8 weeks after transplantation. Quantitative polymerase chain reaction (PCR) and immunohistochemical staining showed that the expression of both AdipoR1 and AdipoR2 was induced in APN-SE recipients. Neointimal hyperplasia was significantly decreased in allografts transplanted into APN-SE (luminal occlusion, 8.9 ± 2.2%) compared to those transplanted into controls (49.4 ± 10.5%; P=0.011). APN-SE showed significantly reduced mRNA levels of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-2, IL-6, and monocyte chemoattractant protein-1 (MCP-1) by quantitative PCR. Western blot analysis revealed that the protein levels of IFN-γ and MCP-1 were reduced in APN-SE recipients. Proliferation of smooth muscle cells stimulated with activated T cells was suppressed by APN addition, and this effect was canceled by treatment with an adenosine monophosphate-activated protein kinase (AMPK) inhibitor.

CONCLUSIONS

APN plays a critical role in the attenuation of chronic rejection by suppressing inflammatory cytokine and chemokine expression and enhancing APN receptor expression. APN plays a beneficial role in reducing the progression of cardiac allograft vasculopathy through the AMPK pathway.