Faculty Bibliography

Background: Cystinuria is a disease of impaired absorption of cystine and dibasic amino acids (DAA) from the intestine and renal tubule leading to formation of cystine kidney stones. However, the metabolic impact of reduced amino acid absorption and excessive loss in the urine is poorly understood. We measured endogenous, gut microbial, and xenobiotic metabolites, providing insight into consequences of the disease and its treatment.
Method(s): Urinary biochemicals were assayed using LC-MS in 293 urine specimens from patients with cystinuria or control urinary phenotypes. Multivariate statistical analyses were conducted to reveal statistically significant biochemical signatures of the disease and products of cysteine-binding thiol drugs (CBTDs). 16s rRNA gene sequencing was performed on fecal samples from 12 wildtype (WT) and 12 cystinuric (Slc3a1 knockout; KO) mice to evaluate their gut microbial composition.
Result(s): Cystinuric urine samples had elevated levels of cysteine-gamma-glutamyl cystine disulfide (glutathione precursor), indole-3-acetic acid (microbial tryptophan metabolism), and novel conjugated forms of putrescine (microbial DAA decomposition). Conversely, taurine (sulfur metabolism), indole-3-acetic acid-glucuronide, and novel urinary metabolite N-methyl pipecolic acid (lysine metabolism) were reduced in cystinuric urine. Where cysteine-bound CBTDs were observed, substantial amounts of "wasted" drug were also detected as CBTD homodimers, non-cysteine disulfides, and mixed drug disulfides. The differentiation of gut microbially-derived metabolites led us to evaluate the gut microbiome diversity and composition in a mouse model of cystinuria revealing clear beta diversity and taxa differentiation between WT and KO mice.
Conclusion(s): Cystinuria is associated with unique urinary metabolic profiles beyond hyperexcretion of cystine and DAA, indicating perturbed metabolic processes and potential gut microbial effects. Study of the gut microbiome of WT and KO mice provides the first evidence for them having distinct taxa, perhaps due to poorly absorbed DAA present in the intestinal lumen. Urinary profiles allow us to characterize the excretion profiles of CBTDs, providing insight which may be helpful to tailor treatment

Although a few reports in recent years have suggested that patients with antiphospholipid antibodies (aPL) are prone to developing primary anetoderma (PA), it is still unclear how often aPL are detected in unselected PA patients. We studied nine consecutive PA patients for the presence of autoimmune antibodies and disorders in general and the presence of aPL in particular. Six of the nine patients had clinical evidence of associated autoimmune disorders (Graves'disease and autoimmune haemolysis in one, systemic scleroderma in one, Hashimoto's thyroiditis in one, alopecia areata in one) and/or signs of hypercoagulability (recurrent fetal loss in two, recurrent stokes in one, recurrent deep vein thrombosis in one). In four ofthese six patients the onset of PA preceded these signs. Positive aPL was found in all: anticardiolipin (aCL) in six, anti-beta2-glycoprotein-I (a(beta)2GPI) in six and lupus anticoagulant (LAC) in four. The most frequent isotype was IgA. Among other autoantibodies found the most frequently was antinuclear antibodies. Four ofthe nine patients fulfilled the criteria for antiphospholipid syndrome (APS). It is concluded that PA is an important cutaneous sign for autoimmune disorders in general and the presence of aPL in particular. Hence, the work-up of these patients should include testing for LAC as well as for all different isotypes ofaCL and a(beta)2GPI. We recommend that PA be added to the list of the cutaneous manifestations of APS.

Interferons (IFNs) induce early-response genes by stimulating Janus family (Jak) tyrosine kinases, leading to tyrosine phosphorylation of Stat transcription factors. Previous studies implicated protein-tyrosine phosphatase (PTP) activity in the control of IFN-regulated Jak/Stat signaling, but the specific PTPs responsible remained unidentified. We have found that SH2 domain-containing PTP1 (SHPTP1; also called PTP1C, HCP, or SHP) reversibly associates with the IFN-alpha receptor complex upon IFN addition. Compared with macrophages from normal littermate controls, macrophages from motheaten mice, which lack SHPTP1, show dramatically increased Jak1 and Stat1 alpha tyrosine phosphorylation, whereas Tyk2 and Stat2 activation is largely unaffected. These findings correlate with selectively increased complex formation on a gamma response element, but not an IFN-stimulated response element, in motheaten macrophages. Our results establish that SHPTP1 selectively regulates distinct components of Jak/Stat signal transduction pathways in vivo.

Nine patients with subacute cutaneous lupus erythematosus (SCLE) are described, all of whom had systemic involvement of the disease although usually milder than in systemic lupus erythematosus. None of the patients had renal disease or died of SCLE.