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Wenhan Liu

Publications and source records attributed to Wenhan Liu.

6 recordsLinked to original sources
PubMed2025

Zinc status following different bariatric procedures: systematic review and meta-analysis.

INTRODUCTION: This study evaluated perioperative changes in serum zinc levels following different bariatric procedures and provided evidence-based recommendations for postoperative monitoring and supplementation. METHODS: PubMed, Embase, the Cochrane Library, Web of Science and CNKI were systematically searched from inception to July 2025. Eligible studies compared pre- and postoperative serum zinc levels in individuals with obesity undergoing bariatric surgery. Study quality was assessed using the Newcastle-Ottawa Scale (NOS), and the certainty of evidence was graded using the GRADE approach. Pooled analyses were conducted with StataSE 17.0. RESULTS: Twelve studies including 2,529 participants were analysed, with overall quality rated as high. Compared with baseline, pooled standardized mean differences (SMDs) in serum zinc at 3 months, 6 months, 1 year, and 2 years postoperatively were -0.12 (95% CI: -0.27 to 0.04, I2 = 57.9%, τ2 = 0.0265, p = 0.149), -0.36 (95% CI: -0.58 to -0.14, I2 = 82.2%, τ2 = 0.1043, p = 0.001), -0.35 (95% CI: -0.53 to -0.16, I2 = 81.9%, τ2 = 0.0769, p = 0.001), and -0.36 (95% CI: -0.95 to 0.24, I2 = 97.2%, τ2 = 0.3515, p = 0.240), respectively. Subgroup analysis showed no significant changes at 3 months across procedures. However, zinc levels significantly decreased at 6 and 12 months after Roux-en-Y gastric bypass (RYGB) and mini-gastric bypass (MGB), but not after sleeve gastrectomy (SG). At 2 years, no significant reduction was observed in any group. The certainty of evidence for zinc changes was rated as moderate. CONCLUSION: Serum zinc levels decline significantly during the first postoperative year, particularly after RYGB and MGB, while SG shows minimal impact. Routine zinc monitoring and individualized supplementation are recommended within the first year after surgery to prevent deficiency-related complications. REGISTRATION: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251138846.

Humans↗
PubMed2006

Method of x-ray anomalous diffraction for lipid structures.

The structures of the unit cells of lipid phases that exhibit long-range crystalline order but short-range liquid-like disorder are of biological interests. In particular, the recently discovered rhombohedral phase has a unit cell containing either the structure of a membrane fusion intermediate state or that of a peptide-induced transmembrane pore, depending on the lipid composition and participating peptides. Diffraction from such systems generally presents a difficult phase problem. The existing methods of phase determination all have their limitations. Therefore it is of general interest to develop a new phasing method. The method of multi-wavelength anomalous dispersion is routinely used in protein crystallography, but the same method is difficult for lipid systems for the practical reason that the commonly used lipid samples for diffraction do not have a well-defined thickness. Here we describe a practical approach to use the multi-wavelength anomalous dispersion method for lipid structures. The procedure is demonstrated with the lamellar phase of a brominated lipid. The method is general to all phases as long as anomalous diffraction is applicable.

Bromine↗
PubMed2006

Chain packing in the inverted hexagonal phase of phospholipids: a study by X-ray anomalous diffraction on bromine-labeled chains.

Although lipid phases are routinely studied by X-ray diffraction, construction of their unit cell structures from the diffraction data is difficult except for the lamellar phases. This is due to the well-known phase problem of X-ray diffraction. Here we successfully applied the multiwavelength anomalous dispersion (MAD) method to solve the phase problem for an inverted hexagonal phase of a phospholipid with brominated chains. Although the principle of the MAD method for all systems is the same, we found that for lipid structures it is necessary to use a procedure of analysis significantly different from that used for protein crystals. The inverted hexagonal phase has been used to study the chain packing in a hydrophobic interstice where three monolayers meet. Hydrophobic interstices are of great interest, because they occur in the intermediate states of membrane fusion. It is generally believed that chain packing in such a region is energy costly. Consequently, it has been speculated that the inverted lipid tube is likely to deviate from a circular shape, and the chain density distribution might be nonuniform. The bromine distribution obtained from the MAD analysis provides the information for the chain packing in the hexagonal unit cell. The intensity of the bromine distribution is undulated around the unit cell. The analysis shows that the lipid chains pack the hexagonal unit cell at constant volume per chain, with no detectable effect from a high-energy interstitial region.

Cholesterol↗
PubMed2005

Distorted hexagonal phase studied by neutron diffraction: lipid components demixed in a bent monolayer.

The recent discovery of a distorted hexagonal phase in 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine/1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPE/DOPC) mixtures raised the intriguing question as to whether lipid mixtures demix in a bent monolayer. We performed neutron diffraction on a mixture of headgroup deuterated DOPC-d(13) and nondeuterated DOPE to study the lipid distribution in the distorted hexagonal phase. The 1:1 lipid mixture in full hydration and 25 degrees C was in a homogeneous lamellar phase. Upon dehydration the mixture transformed to a rhombohedral phase, then to a distorted inverted hexagonal phase, and finally to a regular inverted hexagonal phase. In the distorted hexagonal phase, the diffraction pattern showed a two-dimensional monoclinic lattice with two reciprocal vectors of equal length (1.5 nm(-)(1)) forming an angle 53 degrees between them. Diffraction intensities measured while varying the D(2)O/H(2)O ratio in the humidity was used to solve the phase problem. The neutron scattering length density distribution of the distorted hexagonal phase was constructed. The constant density contours are approximately elliptical. The difference in the eccentricities of the contours between the water and lipid distributions indicates that the DOPE/DOPC ratio is not uniform around the elliptical lipid tube in the unit cell. DOPE is preferentially distributed at the vertex regions where the curvature is the highest. Thus for the first time it is shown that when a monolayer of a homogeneous lipid mixture is bent, the lipid components are partially demixed in reaching the free energy minimum.

Lipids↗
PubMed2004

Diffraction techniques for nonlamellar phases of phospholipids.

A neutron diffraction method applicable to nonlamellar phases of substrate-supported lipid membranes is described and validated. When prepared on a flat substrate, the resulting nonlamellar phases have layered symmetry which provides some advantages over powder diffraction for detailed structure determination. This approach recently led to the detection of a rhombohedral phase and a distorted hexagonal phase of lipids. Here the determination of intensity and phase information for such phases is demonstrated by application to the hexagonal phase of diphytanoyl phosphatidylcholine (DPhPC). The hexagonal symmetry is used to verify the data reduction procedure for the intensities of the diffraction peaks. Diffraction intensities measured while varying the D2O/H2O ratio in the relative humidity was used to solve the phase problem. The neutron scattering length density distribution of the hexagonal phase was constructed and analyzed to elucidate the packing of the lipid molecules. The structure of DPhPC in the hexagonal phase is of interest in connection with its stalk structure in the rhombohedral phase. We also found that the incorporation of tetradecane into the DPhPC hexagonal phase is limited, similar to the case for dioleoyl phosphatidylethanolamine.

Neutron Diffraction↗