Gastrointestinal genetic reprogramming of vitamin A metabolic pathways in response of Roux-en-Y gastric bypass

Roux-en-Y gastric bypass (RYGB) is one of the most performed bariatric surgical techniques. However, RYGB commonly results, as side effects, in nutritional deficiencies. This study aimed to examine changes in the expression of vitamin A pathway encoding genes in the gastrointestinal tract (GI) and to evaluate the potential mechanisms associated with hypovitaminosis A after RYGB. Intestinal biopsies were obtained through double-balloon endoscopy in 20 women with obesity (age 46.9±6.2 years; body mass index [BMI] 46.5±5.3 kg/m2 [mean±SD]) before and three months after RYGB (BMI, 38.2±4.2 kg/m2). Intestinal mucosal gene microarray analyses were performed in samples using a Human GeneChip 1.0 ST array (Affymetrix). Vitamin A intake was assessed from 7-day food records and serum retinol levels were evaluated by electrochemiluminescence immunoassay. Our results showed the following genes with significant downregulation (p≤0.05): LIPF (-0.60), NPC1L1 (-0.71), BCO1 (-0.45), and RBP4 (-0.13) in the duodenum; CD36 (-0.33), and ISX (-0.43) in the jejunum and BCO1 (-0.29) in the ileum. No significant changes in vitamin A intake were found (784±694 retinol equivalents [RE] pre-operative vs. 809±753 RE post-operative [mean±SD]). Although patients were routinely supplemented with 3500 international units IU/day (equivalent to 1050 μg RE/day) of oral retinol palmitate, serum concentrations were lower in the post-operative when compared to pre-operative period (0.35±0.14 μg/L vs. 0.52±0.33 μg/L, respectively - P=0.07), both within the normal range. After RYGB, the simultaneous change in expression of GI genes, may impair carotenoid metabolism in the enterocytes, formation of nascent chylomicrons and transport of retinol, resulting in lower availability of vitamin A.

Roux-en-Y gastric bypass affects the expression of genes related to the intestinal folate metabolism pathway in obese women

OBJECTIVES

Roux-en-Y gastric bypass (RYGB) promotes sustained weight loss, and the resulting new gastrointestinal anatomy can contribute to nutritional depletions. Folate deficiency is one of the most frequently observed nutritional deficiencies after RYGB. The aim of this study was to assess whether RYGB affects the expression of genes related to the intestinal folate metabolism pathway as an additional molecular mechanism contributing to its postoperative deficiency.

METHODS

Biopsies from the duodenum, jejunum, and ileum of 20 obese women were collected before and 3 mo after RYGB. The expression of genes involved in intestinal folate metabolism was assessed by microarray and reverse transcriptase polymerase chain reaction (RT-qPCR). Folate intake (7-d food record) and plasma levels (electrochemiluminescence) also were measured.

RESULTS

Compared with the preoperative phase, transcriptomic alterations were observed in all intestinal segments studied after RYBG, mainly marked by decreased expression of genes encoding folate transporters/receptors and increased expression of genes involved in folate biosynthesis (P < 0.05). Reduced folate intake and plasma folate levels were also observed simultaneously (P < 0.05). Plasma folate concentrations correlated inversely with intestinal FOLR2 and SHMT2 genes (P < 0.001).

CONCLUSION

The present findings suggested that impaired expression of genes related to intestinal folate metabolism may contribute to the early systemic deficiency after RYGB and highlight a potential transcriptomic reprogramming of the intestine in response to RYGB to compensate for folate depletion induced by this surgical technique.

Fiber Bragg gratings with various chirp profiles made in etched tapers

We have studied, both theoretically and experimentally, fiber Bragg gratings with a number of different chirp profiles. These chirp profiles can easily be achieved by a recently demonstrated technique involving a taper of desired profile etched into the cladding of a fiber. The performances of gratings with linear, quadratic, periodically modulated, and step-chirp profiles are analyzed numerically. The versatility of the technique was demonstrated when linearly and quadratically chirped gratings were made as examples of continuous chirp, and gratings with step chirps were made as examples of discontinuously chirped structures.

Complex grating structures with uniform phase masks based on the moving fiber-scanning beam technique

We present experimental results of complex grating structures fabricated with uniform phase masks by the moving fiber-scanning beam approach. Pure apodized gratings with side-mode-suppression levels in excess of 40 dB, self-apodized linearly chirped gratings, and phase shifted gratings with narrow-band transmission peaks have all been realized.