👤 Ellen D McPhail

Amyloidosis derived from apolipoprotein C-II (AApoCII) is a recently discovered, rare form of amyloidosis. Data on clinical presentations and natural history are very limited. This study defines the clinicopathologic, proteomic, and outcome characteristics of renal AApoCII. Case series. Twenty-five renal AApoCII cases were identified from the Mayo Clinic Tissue Proteomics Laboratory archives from January 2008 through January 2024. All patients were White, 19 were≥65 years old at diagnosis, and 18 were female. Seven had a family history of chronic kidney disease (CKD). Patients presented with proteinuria (median 3.3g/day) and reduced kidney function (n=16; median creatinine, 1.6mg/dL). No patients had clinical evidence of other organ involvement by amyloidosis or features of monogenic hypertriglyceridemia. Histologically, amyloid deposits were often weakly positive for Congo red and involved glomeruli in all cases (with a nodular pattern in 22), whereas extraglomerular involvement was less common and generally mild. Proteomic analysis revealed abundant spectra for Apo C-II and for all 3 amyloid signature proteins (apolipoprotein E, apolipoprotein A-IV, and serum amyloid P) in all cases and detected an Apo C-II variant in 14 (K19T [p.Lys41Thr] in 12 and E47V [p.Glu69Val] in 2). Among 22 patients with follow-up information available, there were 12 end-stage kidney disease (ESKD) events and 2 deaths without ESKD during an average follow-up period of 75.5±12.5 (SE) months. Retrospective design, small sample size, APOC2 gene sequencing performed in a smaller subset. AApoCII mostly affects the kidney and manifests in the elderly with proteinuria and CKD. A minority of these patients had a family history of kidney disease. Kidney failure occurred in about half, whereas overall survival was more favorable. Amyloidosis derived from apolipoprotein C-II (AApoCII) is very rare, and data on clinicopathologic and outcome characteristics are scant. This study of 25 patients with AApoCII diagnosed by mass spectrometry at the Mayo Clinic Tissue Proteomics Laboratory revealed that most patients were elderly White females who presented with proteinuria and reduced kidney function, without involvement of other organs. A family history of kidney disease was often lacking. Pathologically, most cases exhibited nodular glomerular involvement. Proteomic analysis revealed abundant protein spectra for Apo C-II and amyloid signature proteins, and identified an Apo C-II variant in over half of cases (most commonly the p.Lys41Thr variant). The cumulative incidence of kidney failure was over 50% at 5 years follow-up. Only 4 deaths occurred over an average follow-up period of 76 months. Show less

Sporadic cases of apolipoprotein A-IV medullary amyloidosis have been reported. Here we describe five families found to have autosomal dominant medullary amyloidosis due to two different pathogenic APOA4 variants. A large family with autosomal dominant chronic kidney disease (CKD) and bland urinary sediment underwent whole genome sequencing with identification of a chr11:116692578 G>C (hg19) variant encoding the missense mutation p.L66V of the ApoA4 protein. We identified two other distantly related families from our registry with the same variant and two other distantly related families with a chr11:116693454 C>T (hg19) variant encoding the missense mutation p.D33N. Both mutations are unique to affected families, evolutionarily conserved and predicted to expand the amyloidogenic hotspot in the ApoA4 structure. Clinically affected individuals suffered from CKD with a bland urinary sediment and a mean age for kidney failure of 64.5 years. Genotyping identified 48 genetically affected individuals; 44 individuals had an estimated glomerular filtration rate (eGFR) under 60 ml/min/1.73 m Show less

Membranous nephropathy (MN) results from accumulation of antigen-antibody immune complexes along the subepithelial region of the glomerular basement membranes. Over the last years, 13 target antigens have been discovered and include PLA2R, THSD7A, EXT1 and EXT2, NELL1, SEMA3B, NCAM1, CNTN1, HTRA1, FAT1, PCDH7, NTNG1, PCSK6 and NDNF, accounting for 80-90% of MN antigens. MN associated with many of these antigens have distinctive clinicopathologic findings. It is important to accurately identify the antigen in MN. Immunohistochemical (IHC) and/or immunofluorescence (IF) methods are currently used to detect PLA2R, THSD7A, NELL1, SEMA3B and EXT1/EXT2. However, for the remaining antigens, IHC/IF methods do not exist and are not practical for detection. Here, we developed laser microdissection-based mass spectrometry methodology (LMD/MS) as a one-stop clinical test for the detection of MN antigens using paraffin-embedded kidney biopsy tissue. The LMD/MS test was validated in two steps. LMD/MS was used to detect the antigen in 75 cases of MN with known antigens and correctly identified the antigen in all these cases. Next, LMD/MS was used to identify the antigen in 61 MN cases where the antigen was unknown and identified one of the known antigens in 40 of 61 cases including many of the less common antigens. This lower-than-expected detection rate is explained by intentional enrichment of the cohort with PLA2R-negative MN. Overall, PLA2R was identified in 16.4%, one of the other antigens detected in 49.1%, and in the remaining 34.5% of cases, none of the above antigens was detected. Thus, LMD/MS is an extremely useful and reliable method for the detection of known MN antigens and possibly indicating an unknown MN antigen for eventual discovery. Show less

Dysfunctional metabolism lies at the centre of the pathogenesis for Non-Alcoholic Fatty Liver Disease (NAFLD) and involves mitochondrial dysfunction, lipid dysmetabolism and oxidative stress. This study, for the first time, explores real-time energy changes in peripheral blood and corresponding metabolite changes, to investigate whether mitochondria-related immunometabolic biomarkers can predict progression in NAFLD. Thirty subjects divided into 3 groups were assessed: NAFLD with biopsy-proven mild fibrosis (n = 10), severe fibrosis (n = 10) and healthy controls (HC, n = 10). Mitochondrial functional analysis was performed in a Seahorse XFp analyzer in live peripheral blood mononuclear cells (PBMCs). Global metabolomics quantified a broad range of human plasma metabolites. Mitochondrial carbamoyl phosphate synthase 1(CPS-1), Ornithine transcarbamoylase (OTC), Fibroblast growth factor-21 (FGF-21) and a range of cytokines in plasma were measured by ELISA. NAFLD patients with severe fibrosis demonstrated reduced maximal respiration (106 ± 25 versus 242 ± 62, p < 0.05) and reserve capacity (56 ± 16 versus 184 ± 42, p = 0.006) compared to mild/moderate fibrosis. Comparing mild/moderate vs severe liver fibrosis in patients with NAFLD, 14 out of 493 quantified metabolites were significantly changed (p < 0.05). Most of the amino acids modulated were the urea cycle (UC) components which included citrulline/ornithine ratio, arginine and glutamate. Plasma levels of CPS-1 and FGF-21 were significantly higher mild versus severe fibrosis in NAFLD patients. This novel panel generated an area under the ROC of 0.95, sensitivity of 100% and specificity 80% and p = 0.0007 (F1-F2 versus F3-F4). Progression in NAFLD is associated with mitochondrial dysfunction and changes in metabolites associated with the urea cycle. We demonstrate a unique panel of mitochondrial-based, signatures which differentiate between stages of NAFLD. Mitochondrial dysfunction in peripheral cells along with alterations in metabolites of urea cycle act as a sensor of hepatocyte mitochondrial damage. These changes can be measured in blood and together represent a unique panel of biomarkers for progression of fibrosis in NAFLD. Show less

In vivo mechanisms of amyloid clearance and cardiac tissue damage in cardiac amyloidosis are not well understood. We aimed to define and quantify the amyloid plaque proteome in cardiac transthyretin amyloidosis (ATTR) and light chain amyloidosis (AL) and identify associations with patient characteristics and outcomes. A proteomics approach was used to identify all proteins in cardiac amyloid plaques, and to compare both normal and diseased controls. All proteins identified within amyloid plaques were defined as the expanded proteome; only proteins that were enriched in comparison to normal and disease controls were defined as the amyloid-specific proteome. Proteomic data from 292 patients with ATTR and 139 patients with AL cardiac amyloidosis were included; 160 and 161 unique proteins were identified in the expanded proteomes, respectively. In the amyloid-specific proteomes, we identified 28 proteins in ATTR, 19 in AL amyloidosis, with 13 proteins overlapping between ATTR and AL. ATTR was characterized by a higher abundance of complement and contractile proteins and AL by a higher abundance of keratins. We found that the proteome of kappa AL had higher levels of clusterin, a protective chaperone, and lower levels of light chains than lambda despite higher levels of circulating light chains. Hierarchical clustering identified a group of patients with worse survival in ATTR, characterized by high levels of PIK3C3, a protein with a central role in autophagy. Cardiac AL and ATTR have both common and distinct pathogenetic mechanisms of tissue damage. Our findings suggest that autophagy represents a pathway that may be impaired in ATTR and should be further studied. Show less