Leptin receptor deficiency impedes metabolic surgery related-weight loss through inhibition of energy expenditure in db/db mice.

BACKGROUND: Roux-en-Y gastric bypass (RYGB) surgery is an effective metabolic surgery against diabetes and obesity. Clinical evidence indicates that patients with severe obesity have a poor curative effect in losing weight if they suffer from leptin or its receptor deficiency, but the underlying mechanism remains elusive. Here, we investigated the effect of leptin receptor deficiency on metabolic dysfunction in db/db mice treated by RYGB surgery. METHODS: The db/db mice and their heterozygote control db/m mice were subjected to RYGB or sham surgery. Body weight, blood glucose, food intake and glucose tolerance were evaluated. Micro-PET/CT and histological analysis were performed to examine the glucose uptake of tissues and the fat changes in mice. The key factors in glucose and fatty acid metabolism were detected by western blot analysis. RESULTS: Compared with the sham group, the db/db mice in the RYGB group showed more significant weight regain after surgical recovery and improvement in hyperinsulinemia and glucose tolerance. However, the total body fat and multiple organ lipid deposition of RYGB-treated db/db mice was increased. The underlying mechanism studies suggested that the activation of AMPK regulated GLUT4 to increase glucose uptake, but AMPK could not promote fatty acid oxidation through the JAK2/STAT3 pathway under leptin receptor deficiency in db/db mice. CONCLUSION: We conclude that leptin receptor deficiency impedes the AMPK activation-mediated fat catabolism but does not affect AMPK-related glucose utilization after metabolic surgery in db/db mice. This result helps select surgical indications for patients with obesity and diabetes.

Assessment of sublingual microcirculation for the screening of diabetic nephropathy.

OBJECTIVE: To investigate the potential of employing sublingual microcirculation as an early noninvasive screening technique for diabetic nephropathy (DN). RESEARCH DESIGN AND METHODS: We recruited 89 patients with type 2 diabetes mellitus (T2DM) and 41 healthy subjects in this cross-sectional observational study. All participants underwent fluorescein fundus angiography, vibration perception testing, 10 g (Semmes-Weinstein) monofilament examination, nerve conduction velocity, and 24-h urine microalbumin determination. HbA1c, fasting plasma glucose, blood lipid, and estimated glomerular filtration rate(eGFR) were measured. Sublingual microcirculatory images were captured using side-stream dark-field (SDF) microcirculation microscopy, and total and perfused vascular density (TVD and PVD) were calculated. RESULTS: The sublingual microcirculatory parameters denoting microvascular density and perfusion were negatively correlated with both fasting plasma glucose (TVD, r = - 0.316, P < 0.001; PVD, r = - 0.350, P < 0.001; PPV, r = - 0.279, P = 0.001) and HbA1c (TVD, r = - 0.367, P < 0.001; PVD, r = - 0.423, P < 0.001; PPV, r = - 0.399, P < 0.001). Diabetes patients already had a reduction in sublingual microcirculation compared with healthy control, and more severe reductions in TVD (7.07 ± 1.64 vs. 9.67 ± 1.94 mm/mm2, P < 0.001) and PVD (5.88 ± 1.82 vs. 8.64 ± 2.46 mm/mm2, P < 0.001) were found in those diabetes patients developed microvascular complications. Sublingual microcirculation impairment was accompanied with higher urinary albumin creatinine ratio (UACR). Receiver operating characteristic (ROC) analysis showed that TVD (area under the curve, AUC = 0.890 [0.836 0.944], P < 0.001) and PVD (AUC = 0.883 [0.826, 0.940], P < 0.001) could be indicators for DN screening. We derived a combined predictor index (CPI) considering both TVD and PVD for screening DN, and both the AUC (0.892, [0.838 0.945], P < 0.001) and cutoff point of 11.30 mm/mm2 showed great improvement (sensitivity: 95.5%, specificity: 67.4%). CONCLUSIONS: Diabetes patients experienced impaired sublingual microcirculation, which was closely correlated with UACR. Sublingual microcirculation monitoring could be used for the noninvasive early detection of DN.

Thiazide-like diuretics attenuate agonist-induced vasoconstriction by calcium desensitization linked to Rho kinase.

Lowering blood pressure using thiazide-like diuretics, including chlorthalidone and hydrochlorothiazide, has been proven to be effective in clinical studies. However, the mechanisms by which thiazide-like diuretics lower blood pressure are still poorly understood. To evaluate whether thiazide-like diuretics cause calcium desensitization in smooth muscle cells, we measured their effects on agonist-induced increase of blood pressure in Wistar rats in vivo and on agonist-induced vasoconstriction of aortic rings, DNA synthesis, and protein synthesis, RhoA, Rho kinase, and intracellular calcium in vascular smooth muscle cells in vitro. Thiazide-like diuretics significantly attenuated angiotensin II-induced or norepinephrine-induced increase of systolic blood pressure in rats. Thiazide-like diuretics inhibited agonist-induced vasoconstriction of aortic rings in a concentration-dependent manner in the presence and absence of endothelium. The inhibitory effects of thiazide-like diuretics were similar to that of the specific Rho kinase inhibitor Y27632. RT-PCR and immunoblotting showed that RhoA and Rho kinase were significantly reduced in vascular smooth muscle cells after administration of thiazide-like diuretics. In contrast, thiazide-like diuretics did not affect protein tyrosine phosphatase-2 (SHP-2) expression. Agonist-induced changes of intracellular calcium were not affected by thiazide-like diuretics. The study indicates that thiazide-like diuretics inhibit agonist-induced vasoconstriction by calcium desensitization in smooth muscle cells linked to the Rho-Rho kinase pathway.