Increased gastrin and calcitonin secretion after oral calcium or peptones administration in patients with hypercalciuria: a clue to an alteration in calcium-sensing receptor activity.

The calcium-sensing receptor (CaSR) has been detected in human antral gastrin-secreting cells, where, upon calcium and/or amino acid allosteric activation, it stimulates gastrin secretion. Patients with absorptive hypercalciuria (AH) display an enhanced gastric acid output; therefore, we evaluated the secretion of gastrin in subjects with AH (30 subjects vs. 30 healthy female controls, all postmenopausal) after oral calcium administration (1 g calcium gluconate) and, on a separate occasion, after peptone loading test (protein hydrolyzed, 10 g). Gastrin and monomeric calcitonin responses were higher in AH after both oral calcium administration (P < 0.01) and peptone loading (P < 0.01). Because the activation of CaSR by oral calcium and peptones directly induces gastrin release, the higher gastrin responses to these stimuli suggest an increased sensitivity of gastrin-secreting cells CaSR in patients with AH. A similar alteration in thyroid C cells might explain the enhanced calcitonin responses to both calcium and peptones. If the same alterations should in addition be present in the distal tubule (where CaSR is expressed as well), then a possible explanation for amino acid-induced hypercalciuria in AH would have been identified.

An inter- and intra-laboratory comparison of breath ¹³CO2analysis.

BACKGROUND: ¹³C breath test analysis requires accurate ¹³CO2measurements. AIM: To perform a multicentre study to evaluate the repeatability and reproducibility of breath ¹³CO2analysis. METHODS: Two series of 25 paired randomly coded tubes (each consisting of 23 ¹³CO2-enriched breath samples and two samples of standard reference pure CO2with certified δ ¹³C(PDB)) were sent to participating centres for ¹³CO2measurement. Each series of tubes was analysed 10 days apart. The repeatability and reproducibility of ¹³C measurements was assessed by Mandel's k and h statistics. RESULTS: Twenty-two centres participated in the study: 18 showed good inter- and intra-laboratory variability, whilst four showed abnormally high inter- or intra-laboratory variability. Breath test results were also significantly affected by the accuracy of the ¹³C analytical procedures. CONCLUSIONS: A low accuracy of ¹³C measurements may significantly affect the results of breath tests, leading to inappropriate clinical decisions. Standardization of ¹³C analysis is required to guarantee optimal ¹³C measurements and accurate ¹³C breath test results.

Effect of antioxidants on mitochondrial function in HIV-1-related lipoatrophy: a pilot study.

We investigated the effect of antioxidant supplementation on mitochondrial function, fat distribution, and lipid and glucose metabolism in HIV-1-infected patients with antiretroviral therapy (ART)-related lipoatrophy. 61 ART-treated HIV-1-infected patients with lipoatrophy were randomized to receive either n-acetyl-L-carnitine (n = 21), lipoic acid + n-acetylcisteine (LA/NAC) (n = 20), or no supplementation (n = 20) for 48 weeks. At baseline and at the end of treatment, mitochondrial function was studied by (13)C-methionine breath test and by mitochondrial (mt)-DNA quantification on circulating T-cells and subcutaneous adipose tissue. Body composition was assessed by dual-energy X-ray absorpiometry (DEXA). (13)CO(2)-exhalation increased between baseline and week 48 in both supplementation arms as evidenced by a higher delta over baseline excretion at 45 min (from mean ± SEM of 7.8 ± 1.08 to 9.9 ± 0.6, p = 0.04 in the n-acetyl-carnitine arm, and from 7.4 ± 0.8 to 11.5 ± 1.6, p = 0.01 in LA/NAC arm). Cumulative (13)CO2 excretion increased from median (interquartile range; IQR) of 3.25 (2.55-4.2) to 4.51 (4.12-5.2) in the carnitine arm; from 3.79 (2.67-4.37) to 4.83 (4.25-5.56) in the LA/NAC arm; p = 0.004, 0.02, respectively. mtDNA content increased in CD4+ T-cells from patients who received n-acetyl-carnitine (+30 copies/cell; p = 0.03), without significant difference by the overall comparison of the study groups. Fat body mass and lipid profile did not change significantly in any of the arms. Our study showed that antioxidant supplementation may have a protective role on mitochondrial function, with limited effects on the reversal of clinical lipodystrophic abnormalities in HIV-1-infected patients.

Biliary reflux and non-acid reflux are two distinct phenomena: a comparison between 24-hour multichannel intraesophageal impedance and bilirubin monitoring.

OBJECTIVE: Duodenogastroesophageal reflux (DGER) can greatly increase microscopic and macroscopic esophageal mucosal damage caused by acid. The aim of this study was simultaneously to assess the chemical composition of DGER by detecting bilirubin in the refluxate by means of Bilitec and describe its pH and physical properties by impedance monitoring, in order to prove that non-acid reflux and biliary reflux are two distinct phenomena. MATERIAL AND METHODS: Twenty patients with gastroesophageal reflux disease (GERD) with symptoms refractory to conventional proton-pump inhibitor (PPI) therapy or with atypical GERD symptoms were included in the study. All patients underwent upper gastrointestinal endoscopy and simultaneous Bilitec and intraeosophageal impedance (IIM) and pH monitoring. In the majority of patients (16/20), the tests were performed while assuming a standard PPI dose. RESULTS: Pathological bilirubin exposure, as defined by intraesophageal bilirubin absorbance above 0.14 for more than 3.9% of the time, was present in 9 cases, 6 of them with normal values of non-acid reflux, as detected by IIM. A pathological non-acid reflux, as defined by an IIM showing a percentage time with non-acid reflux greater than 1.4%, was observed in 5 patients, 2 of whom had no pathological biliary reflux, as detected by Bilitec. No correlation was found between the two indices, as expressed by an r-value of -0.12 (p>0.05). CONCLUSIONS: Our study confirms that biliary reflux and non-acid reflux as detected by Bilitec and by IIM, respectively, are two distinct phenomena that require different techniques in order to be assessed in humans.

[13C]Methionine breath test: a novel method to detect antiretroviral drug-related mitochondrial toxicity.

OBJECTIVES: A major side effect of antiretroviral drugs is nucleoside reverse transcriptase inhibitor (NRTI)-related mitochondrial toxicity, the in vivo diagnosis of which is difficult and not yet standardized. We used the [(13)C]methionine breath test to investigate hepatic mitochondrial oxidation in HIV-1-infected patients receiving antiretroviral therapy. PATIENTS AND METHODS: The [(13)C]methionine breath test was performed in healthy subjects (n=10), HIV-infected patients on antiretroviral therapy with (n=6) and without (n=15) hyperlactataemia and naive HIV-infected patients (n=11). After oral administration of [(13)C]methionine (2 mg/kg body weight), hepatic methionine metabolism was measured by breath (13)CO(2) enrichment, expressed as delta over baseline (DOB) every 15 min for 120 min by mass spectrometry. RESULTS: The four study groups showed a significant difference in (13)CO(2) exhalation (P=0.001). HIV-infected patients on antiretroviral therapy with normal serum lactate had reduced exhalation of (13)CO(2) compared with healthy subjects (DOB mean peak: 8.82+/-0.62 versus 11+/-0.9, P<0.05). HIV patients with hyperlactataemia had even lower values when compared with patients with normal lactataemia (DOB mean peak: 4.98+/-0.68 versus 8.82+/-0.62, P<0.05). CONCLUSIONS: The [(13)C]methionine breath test possibly showed mitochondrial impairment in antiretroviral-treated HIV-positive patients, particularly with hyperlactataemia. This non-invasive test can be used to monitor drug-related mitochondrial toxicity in vivo and to discover early and asymptomatic damage of the respiratory chain.