Intestinal deletion of leptin signaling alters activity of nutrient transporters and delayed the onset of obesity in mice.

The importance of B-isoform of leptin receptor (LEPR-B) signaling in the hypothalamus, pancreas, or liver has been well characterized, but in the intestine, a unique site of entry for dietary nutrition into the body, it has been relatively ignored. To address this question, we characterized a mouse model deficient for LEPR-B specifically in intestinal epithelial cells (IECs). (IEC)LEPR-B-knockout (KO) and wild-type (WT) mice were generated by Cre-Lox strategy and fed a normal or high-fat diet (HFD). The analyses of the animals involved histology and immunohistochemistry of intestinal mucosa, indirect calorimetric measurements, whole-body composition, and expression and activities of nutrient transporters. (IEC)LEPR-B-KO mice exhibited a 2-fold increase in length of jejunal villi and have normal growth on a normal diet but were less susceptible (P<0.01) to HFD-induced obesity. No differences occurred in energy intake and expenditure between (IEC)LEPR-B-WT and -KO mice, but (IEC)LEPR-B-KO mice fed an HFD showed increased excreted fats (P<0.05). Activities of the Na(+)/glucose cotransporter SGLT-1 and GLUT2 were unaffected in LEPR-B-KO jejunum, while GLUT5-mediated fructose transport and PepT1-mediated peptide transport were substantially reduced (P<0.01). These data demonstrate that intestinal LEPR-B signaling is important for the onset of diet-induced obesity. They suggest that intestinal LEPR-B could be a potential per os target for prevention against obesity.

The transcription factor HNF-4α: a key factor of the intestinal uptake of fatty acids in mouse.

With an excessive postprandial accumulation of intestine-derived, triglyceride-rich lipoproteins being a risk factor of cardiovascular diseases, it is essential to characterize the mechanisms controlling the intestinal absorption of dietary lipids. Our aim was to investigate the role of the transcription factor hepatocyte nuclear factor (HNF)-4α in this process. We used transgenic mice with a specific and inducible intestinal knockout of Hnf-4α gene. One hour after a lipid bolus, in the presence of the lipase inhibitor tyloxapol, lower amounts of triglycerides were found in both plasma and intestinal epithelium of the intestine-specific Hnf-4α knockout (Hnf-4α(intΔ)) mice compared with the Hnf-4α(loxP/loxP) control mice. These discrepancies were due to a net decrease of the intestinal uptake of fatty acid in Hnf-4α(intΔ) mice compared with Hnf-4α(loxP/loxP) mice, as assessed by the amount of radioactivity that was recovered in intestine and plasma after gavage with labeled triolein or oleic acid, or in intestinal epithelial cells isolated from jejunum after a supply of labeled oleic acid-containing micelles. This decreased fatty acid uptake was associated with significant lower levels of the fatty acid transport protein-4 mRNA and protein along the intestinal tract and with a lower acyl-CoA synthetase activity in Hnf-4α(intΔ) mice compared with the control mice. We conclude that the transcription factor HNF-4α is a key factor of the intestinal absorption of dietary lipids, which controls this process as early as in the initial step of fatty acid uptake by enterocytes.

Evaluation of global left ventricular systolic function using three-dimensional echocardiography speckle-tracking strain parameters.

BACKGROUND: The aim of this study was to evaluate the capacity and reproducibility of three-dimensional echocardiographic (3DE) strain parameters in the assessment of global left ventricular (LV) systolic function. METHODS: A total of 128 subjects with differing LV ejection fractions were investigated using two-dimensional echocardiographic (2DE) and 3DE strains. Three-dimensional echocardiographic strain allows obtaining longitudinal, circumferential, radial, and area strains. First, values of global longitudinal strain (GLS) by 2DE and 3DE speckle-tracking analyses were compared. Thereafter, 3DE strain parameters were correlated with LV ejection fraction and indexed output. Last, the variability of 3DE versus 2DE strain measurements as well as recorded time of analysis were assessed. RESULTS: After excluding 21 patients for insufficient image quality, four for arrhythmia, two for severe valvular disease, and one for severe dyspnea, the final population consisted of 100 patients. Comparison between 2DE and 3DE GLS revealed high correspondence (r = 0.91, y = 1.04x - 0.71) and mean error measurement of -1.3% (95% confidence interval, -5.7 to 3.2). Among strain parameters, global area strain exhibited the highest correlation with LV ejection fraction (y = -1.65 + 10.4, r = -0.92, P < .001). Intraobserver measurement variability proved acceptable: 8% for GLS (vs 6% on 2DE analysis), 7% for circumferential strain (vs 15% on 2DE analysis), 7% for radial strain (vs 33% on 2DE analysis), and 5% for global area strain. The mean error between two measurements was lower with 3DE than 2DE analysis for circumferential and radial strains but similar for GLS. The mean time of analysis was of 117 ± 16 sec for 3DE analysis, which was 25% less than for 2DE analysis (P < .001). CONCLUSIONS: Of all strain parameters, new 3DE area strain correlated best with common LV systolic function parameters and is thus the most promising approach, while all 3DE strain markers exhibited good reproducibility.

Robustness of a new three-dimensional echocardiographic algorithm for left ventricular volume and ejection fraction quantification: experts vs. novices.

AIMS: We evaluated the ability of a new simplified algorithm for three-dimensional echocardiography (3DE) left ventricular (LV) measurements with minimal operator interaction to be reproducible and robust, independently of the experience. METHODS AND RESULTS: A total of 163 subjects were investigated using two-dimensional echocardiography (2DE) and 3DE. The 3D data sets were blindly analysed offline by novice investigators and experts. A subgroup of 30 patients was assessed using cardiac magnetic resonance imaging (CMRI) to compare end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF) obtained by 2DE, 3DE, and CMRI. Intra-observer and inter-observer variabilities of 2DE and 3DE measurements were evaluated according to level of experience. Mean time analysis of 3DE data was 23.2 ± 6.3s for the novice and 26.1 ± 4.1 s for the expert (P = ns). Correlations (r) and mean error measurements (MEM) between 3DE analysis by experts and novices were 0.91 and -3.5 mL for EDV, 0.97 and 4.3 mL for ESV, and 0.91 and -2.6% for EF, respectively. Correlations between 3DE and CMRI were good with low variability and greater agreement when compared with those between 2DE and CMRI. For the novice, MEM was -21.3 mL for EDV, -15.0 mL for ESV, and 2.3% for EF. MEM and 95% confidence intervals were wider for 2DE vs. CMRI than for 3DE vs. CMRI in relation to both expert and novice. CONCLUSION: This new semi-automated algorithm of LV endocardial border detection based on 3DE data appears suitable for clinical use by either expert or novice investigators with greater reproducibility and time of analysis than 2DE.

Tube feeding improves intestinal absorption in short bowel syndrome patients.

BACKGROUND & AIMS: Tube feeding, recommended for patients with short bowel syndrome in only the postoperative period, has not been compared with oral feeding for absorption. We studied whether tube feeding increased absorption in patients with short bowel syndrome following the postoperative period. METHODS: A randomized crossover study compared absorption between isocaloric tube feeding and oral feeding in 15 short bowel syndrome patients more than 3 months after short bowel constitution. An oral feeding period combined with enriched (1000 kcal * day(-1)) tube feeding was also tested. We measured the net intestinal absorption rates of proteins, lipids, and total calories using elemental nitrogen, Van de Kamer, and bomb calorimetry methods, respectively. RESULTS: Tube feeding increased the mean (+/-SD) percent absorption (P < .001) of proteins (72% +/- 13% vs 57% +/- 18%), lipids (69% +/- 25% vs 41% +/- 27%), and energy (82% +/- 12% vs 65% +/- 16%) compared with oral feeding. In the group given the combined feedings (n = 9), the total enteral intake and net percent absorption increased (P < .001) for proteins (67% +/- 10%), lipids (59% +/- 19%), and total energy (75% +/- 8%) compared with oral feeding. Absorption (kcal * day(-1)) was greater (P < .001) with tube (2225 +/- 457) and combined feedings (2323 +/- 491) than with oral feeding (1638 +/- 458). CONCLUSIONS: In patients with short bowel syndrome, continuous tube feeding (exclusively or in conjunction with oral feeding) following the postoperative period significantly increased net absorption of lipids, proteins, and energy compared with oral feeding.

Cryptosporidiosis induces a transient upregulation of the oligopeptides transporter (PepT1) activity in neonatal rats.

Cryptosporidium parvum is a parasitic protozoa increasingly appreciated as a cause of intestinal malabsorptive syndrome leading to malnutrition and/or growth failure. Because a major mechanism for apical peptide absorption by small intestine is via the proton-coupled transporter PepT1, we investigated the expression and functionality of this transporter in our model of acute cryptosporidiosis. Four-day-old Sprague-Dawley rats were inoculated by gavage with 5 x 10(5) oocysts of C. parvum and killed at Day 12 (peak of the infection) or Day 21 (spontaneous clearance of the parasite). PepT1 expression and functionality were quantified in the distal small intestine, preferential site of C. parvum implantation, and in the proximal small intestine, free of parasite, using Western blot and Ussing chambers, respectively. No difference in total PepT1 protein expression or in glycyl-sarcosine fluxes was observed in C. parvum-infected rats compared with controls either on Day 12 or on Day 21, both in the proximal and in the distal small intestine. However, a significant decrease of apical membrane protein expression of PepT1 was observed in C. parvum-infected enterocytes compared with controls. This maintained dipeptide transport observed despite villous atrophy and decreased expression of the protein at the brush-border membrane strongly suggest a transient upregulation of PepT1 activity, probably related to gamma-interferon regulation.

Cryptosporidium infection impairs growth and muscular protein synthesis in suckling rats.

This study aimed to explore the metabolic consequences of cryptosporidiosis in an acute experimental model both at the peak of infection and after parasite clearance. Four-day-old suckling rats were infected with 10(6) oocysts of Cryptosporidium parvum. At the peak of infection (day 8 PI), C. parvum resulted in a dramatic reduction both in nutrient intake (-50%) and body weight (16.3+/-5.2 vs 27.3+/-1.0 g, P<0.01) with a decrease in both lean body mass and adipose tissue. Muscular fractional and absolute synthesis rate were reduced (-15 and -55%, respectively). After parasite clearance (day 17 PI), body weight remained reduced in formerly infected animals (37.8+/-8.0 vs 47.8+/-4.2 g, P<0.01) whereas nutrient intake normalized and fractional synthesis rate slightly increased (+22%) compared to controls. Overall, our results show that the impact and consequences of cryptosporidiosis are far greater than generally appreciated, leading to major malnutrition in suckling rats.

The regionalization of PepT1, NBAT and EAAC1 transporters in the small intestine of rats are unchanged from birth to adulthood.

The ontogenetic development of PepT1, NBAT and EAAC1 along the vertical and horizontal axes of the rat small intestine was evaluated using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry. The proximodistal profiles of mRNA levels showed that PepT1 was evenly distributed, whereas NBAT had greater expression in the proximal part, and EAAC1 in the distal part. These regionalizations were the same from postnatal days 4 to 50. PepT1 and NBAT proteins were detected in the microvilli of enterocytes along the length of the villi. NBAT was also found in the cytoplasm. Surprisingly, EAAC1 was located exclusively in the microvilli of enterocytes in the crypt and the bases of the villi. These protein expression patterns were similar in all parts of the small intestine (proximal, median and distal), at all ages. We conclude that the expression of PepT1, NBAT or EAAC1 are differently regulated according to both the horizontal and vertical axes.