Publications

BACKGROUND

We recently reported on the enhanced expression of two isoforms of matrix metalloproteinase-2 (MMP-2) in human renal transplantation delayed graft function. These consist of the conventional secreted, full length MMP-2 isoform (FL-MMP-2) and a novel intracellular N-Terminal Truncated isoform (NTT-MMP-2) generated by oxidative stress-mediated activation of an alternate promoter in the MMP-2 first intron. Here we evaluated the effect of hyperglycemia and diabetes mellitus on the in vitro and in vivo expression of the two MMP-2 isoforms.

METHODS

We quantified the abundance of the FL-MMP-2 and NTT-MMP-2 transcripts by qPCR in HK2 cells cultured in high glucose or 4-hydroxy-2-hexenal (HHE) and tested the effects of the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC). The streptozotocin (STZ) murine model of Type I diabetes mellitus and renal biopsies of human diabetic nephropathy were used in this study.

RESULTS

Both isoforms of MMP-2 in HK2 cells were upregulated by culture in high glucose or with HHE. PDTC treatment did not suppress high glucose-mediated FL-MMP-2 expression but potently inhibited NTT-MMP-2 expression. With STZ-treated mice, renal cortical expression of both isoforms was increased (FL-MMP-2, 1.8-fold; NTT-MMP-2, greater than 7-fold). Isoform-specific immunohistochemical staining revealed low, but detectable levels of the FL-MMP-2 isoform in controls, while NTT-MMP-2 was not detected. While there was a modest increase in tubular epithelial cell staining for FL-MMP-2 in STZ-treated mice, NTT-MMP-2 was intensely expressed in a basolateral pattern. FL-MMP-2 and NTT-MMP-2 isoform expression as quantified by qPCR were both significantly elevated in renal biopsies of human diabetic nephropathy (12-fold and 3-fold, respectively).

CONCLUSIONS

The expression of both isoforms of MMP-2 was enhanced in an experimental model of diabetic nephropathy and in human diabetic nephropathy. Selective MMP-2 isoform inhibition could offer a novel approach for the treatment of diabetic renal disease.

Hepatic steatosis (HS) is common in individuals with hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infections, but the independent contributions of HCV and HIV to HS are unclear. Magnetic resonance imaging and spectroscopy were used to measure visceral adipose tissue (VAT) and liver fat fraction (LFF) (total lipids/[total lipids + water]) in 356 adults: 57 with HCV monoinfection, 70 with HIV/HCV coinfection, 122 with HIV monoinfection, and 107 with neither infection. Participants who were infected with HCV genotype 3 were excluded because of the genotype's reported steatogenic effects. For prevalence estimates, HS was defined as LFF ≥ 0.05. We estimated the association of HIV and HCV status with LFF using multivariable linear regression, adjusting for demographics, lifestyle, and metabolic factors including the homeostasis model assessment estimate of insulin resistance (HOMA-IR) and liver fibrosis defined using the aspartate aminotransferase-to-platelet ratio index (APRI). The prevalence of HS was highest in the uninfected (33%) and HIV-monoinfected (28%), followed by the HCV-monoinfected (19%) and HIV/HCV-coinfected (11%) (P = 0.003 across groups). Compared with uninfected participants-and after adjusting for demographics, lifestyle, and metabolic factors-HIV monoinfection, HCV monoinfection, and HIV/HCV coinfection were associated with 19% (95% confidence interval [CI], -39% to 6%), 38% (95% CI, -55% to -12%), and 42% (95% CI, -59% to -18%) lower LFF, respectively. HCV monoinfection and HIV/HCV coinfection remained strongly associated with lower LFF after further adjusting for APRI, and results were unchanged after excluding subjects with suspected cirrhosis. Among the entire cohort, Hispanic ethnicity, male sex, VAT, and HOMA-IR were independently associated with greater LFF.

CONCLUSION

Contrary to expectations, HIV/HCV-coinfected and HCV-monoinfected adults had significantly less liver fat than uninfected adults, even after adjusting for demographics, lifestyle, metabolic factors, and hepatic fibrosis. Our findings suggest that non-genotype 3 HCV infection may be protective against HS. The mechanisms by which this occurs and the impact of HCV treatment on HS requires further investigation. (Hepatology 2017;65:853-863).