Does superficial fat affect metabolite concentrations determined by MR spectroscopy with water referencing?

It has recently been reported in this journal that local fat depots produce a sizable frequency-dependent signal attenuation in magnetic resonance spectroscopy (MRS) of the brain. If of a general nature, this effect would question the use of internal reference signals for quantification of MRS and the quantitative use of MRS as a whole. Here, it was attempted to verify this effect and pinpoint the potential causes by acquiring data with various acquisition settings, including two field strengths, two MR scanners from different vendors, different water suppression sequences, RF coils, localization sequences, echo times, and lipid/metabolite phantoms. With all settings tested, the reported effect could not be reproduced, and it is concluded that water referencing and quantitative MRS per se remain valid tools under common acquisition conditions.

PCSK9 Plasma Concentrations Are Independent of GFR and Do Not Predict Cardiovascular Events in Patients with Decreased GFR.

BACKGROUND Impaired renal function causes dyslipidemia that contributes to elevated cardiovascular risk in patients with chronic kidney disease (CKD). The proprotein convertase subtilisin/kexin type 9 (PCSK9) is a regulator of the LDL receptor and plasma cholesterol concentrations. Its relationship to kidney function and cardiovascular events in patients with reduced glomerular filtration rate (GFR) has not been explored. METHODS Lipid parameters including PCSK9 were measured in two independent cohorts. CARE FOR HOMe (Cardiovascular and Renal Outcome in CKD 2-4 Patients-The Forth Homburg evaluation) enrolled 443 patients with reduced GFR (between 90 and 15 ml/min/1.73 m2) referred for nephrological care that were prospectively followed for the occurrence of a composite cardiovascular endpoint. As a replication cohort, PCSK9 was quantitated in 1450 patients with GFR between 90 and 15 ml/min/1.73 m2 enrolled in the Ludwigshafen Risk and Cardiovascular Health Study (LURIC) that were prospectively followed for cardiovascular deaths. RESULTS PCSK9 concentrations did not correlate with baseline GFR (CARE FOR HOMe: r = -0.034; p = 0.479; LURIC: r = -0.017; p = 0.512). 91 patients in CARE FOR HOMe and 335 patients in LURIC reached an endpoint during a median follow-up of 3.0 [1.8-4.1] years and 10.0 [7.3-10.6] years, respectively. Kaplan-Meier analyses showed that PCSK9 concentrations did not predict cardiovascular events in either cohort [CARE FOR HOMe (p = 0.622); LURIC (p = 0.729)]. Sensitivity analyses according to statin intake yielded similar results. CONCLUSION In two well characterized independent cohort studies, PCSK9 plasma levels did not correlate with kidney function. Furthermore, PCSK9 plasma concentrations were not associated with cardiovascular events in patients with reduced renal function.

Serum and fecal canine α1-proteinase inhibitor concentrations reflect the severity of intestinal crypt abscesses and/or lacteal dilation in dogs.

Gastrointestinal (GI) protein loss, due to lymphangiectasia or chronic inflammation, can be challenging to diagnose. This study evaluated the diagnostic accuracy of serum and fecal canine α1-proteinase inhibitor (cα1PI) concentrations to detect crypt abscesses and/or lacteal dilation in dogs. Serum and fecal cα1PI concentrations were measured in 120 dogs undergoing GI tissue biopsies, and were compared between dogs with and without crypt abscesses/lacteal dilation. Sensitivity and specificity were calculated for dichotomous outcomes. Serial serum cα1PI concentrations were also evaluated in 12 healthy corticosteroid-treated dogs. Serum cα1PI and albumin concentrations were significantly lower in dogs with crypt abscesses and/or lacteal dilation than in those without (both P <0.001), and more severe lesions were associated with lower serum cα1PI concentrations, higher 3 days-mean fecal cα1PI concentrations, and lower serum/fecal cα1PI ratios. Serum and fecal cα1PI, and their ratios, distinguished dogs with moderate or severe GI crypt abscesses/lacteal dilation from dogs with only mild or none such lesions with moderate sensitivity (56-92%) and specificity (67-81%). Serum cα1PI concentrations increased during corticosteroid administration. We conclude that serum and fecal α1PI concentrations reflect the severity of intestinal crypt abscesses/lacteal dilation in dogs. Due to its specificity for the GI tract, measurement of fecal cα1PI appears to be superior to serum cα1PI for diagnosing GI protein loss in dogs. In addition, the serum/fecal cα1PI ratio has an improved accuracy in hypoalbuminemic dogs, but serum cα1PI concentrations should be carefully interpreted in corticosteroid-treated dogs.