Metabolomics analysis of islet regeneration in partial pancreatectomy mice reveals increased levels of long-chain fatty acids and activated cAMP signaling pathway.

Islet regeneration is a complex process involving multiple metabolic adaptions, but the specific characterization of the islet metabolome in relation to cell proliferation has not been established. This study aimed to investigate the metabolomic changes of regenerative islets from partial pancreatectomy (Ppx) mice and speculate underlying mechanisms. Islet samples were collected from C57/BL6 mice undergoing 70-80% Ppx or sham surgery, followed by analyses of glucose homeostasis, islet morphology, and untargeted metabolomics profiles using liquid chromatography-tandem mass spectrometry (LC-MS/MS). There is no difference in blood glucose and body weight between sham and Ppx mice. After surgery, the Ppx mice showed impaired glucose tolerance, increased Ki67 positive beta cells, and elevated beta-cell mass. LC-MS/MS analysis identified fourteen differentially changed metabolites in islets of Ppx mice, including long-chain fatty acids (e.g., docosahexaenoic acid) and amino acid derivatives (e.g., creatine). Pathway analysis based on the KEGG database revealed five significantly enriched signaling pathways including cAMP signaling pathway. Further immunostaining assay on pancreatic tissue sections showed the levels of p-CREB, a transcription factor downstream of cAMP, elevated in islets from Ppx mice. In conclusion, our results demonstrate that islet regeneration involves metabolic alterations in long-chain fatty acids and amino acid derivatives, as well as the activation of the cAMP signaling pathway.

Serum Spexin Level Is Negatively Associated With Peripheral Neuropathy and Sensory Pain in Type 2 Diabetes.

Background: Spexin is a novel peptide hormone and has shown antinociceptive effects in experimental mice. This study is aimed at evaluating the association of serum spexin level with diabetic peripheral neuropathy (DPN) and related pain in a Chinese population. Methods: We enrolled 167 type 2 diabetes mellitus (T2DM) including 56 patients without DPN (non-DPN), 67 painless DPN, and 44 painful DPN. Serum spexin was measured using ELISA. Logistic regression models were performed to analyze the independent effects of spexin on prevalence of DPN and painful DPN. In streptozotocin (STZ)-induced diabetic mice, mechanical pain threshold was measured using electronic von Frey aesthesiometer. Human peripheral blood mononuclear cells (PBMCs) were isolated and further stimulated with lipopolysaccharide without or with spexin. The gene expression was assayed by qPCR. Results: Compared with non-DPN, serum spexin level decreased in painless DPN and further decreased in painful DPN. The odds of DPN was associated with low spexin level in T2DM, which was similar by age, sex, BMI, and diabetes duration, but attenuated in smokers. The odds of having pain was associated with decreased spexin level in DPN, which was similar by age, sex, smoking status, and diabetes duration, but attenuated in normal weight. Furthermore, we observed that mechanical pain threshold increased in spexin-treated diabetic mice. We also found that lipopolysaccharide treatment increased the mRNA level of TNF-α, IL-6, and MCP-1 in human PBMCs, while spexin treatment prevented this increase. Conclusions: These results suggested that spexin might serve as a protective factor for diabetes against neuropathology and pain-related pathogenesis.

Causal effects of non-alcoholic fatty liver disease on osteoporosis: a Mendelian randomization study.

Background: Osteoporosis (OP) is a systemic skeletal disease characterized by compromised bone strength leading to an increased risk of fracture. There is an ongoing debate on whether non-alcoholic fatty liver disease (NAFLD) is an active contributor or an innocent bystander in the pathogenesis of OP. The aim of this study was to assess the causal association between NAFLD and OP. Methods: We performed two-sample Mendelian randomization (MR) analyses to investigate the causal association between genetically predicted NAFLD [i.e., imaging-based liver fat content (LFC), chronically elevated serum alanine aminotransferase (cALT) and biopsy-confirmed NAFLD] and risk of OP. The inverse variant weighted method was performed as main analysis to obtain the causal estimates. Results: Imaging-based LFC and biopsy-confirmed NAFLD demonstrated a suggestive causal association with OP ([odds ratio (OR): 1.003, 95% CI: 1.001-1.004, P < 0.001; OR: 1.001, 95% CI: 1.000-1.002, P = 0.031]). The association between cALT and OP showed a similar direction, but was not statistically significant (OR: 1.001, 95% CI: 1.000-1.002, P = 0.079). Repeated analyses after exclusion of genes associated with confounding factors showed consistent results. Sensitivity analysis indicated low heterogeneity, high reliability and low pleiotropy of the causal estimates. Conclusion: The two-sample MR analyses suggest a causal association between genetically predicted NAFLD and OP.

Circulating spexin levels are influenced by the glycemic status and correlated with pancreatic ß-cell function in Chinese subjects.

AIMS: Spexin plays a role in regulating glucose metabolism. This study investigated the spexin levels in different glycemic status and its association with insulin secretion in humans. METHODS: A total of 462 subjects were recruited in this study, including 52 healthy subjects, 106 first-degree relatives (FDRs) of type 2 diabetes mellitus (T2DM), 115 impaired glucose regulation (IGR), 80 newly diagnosed T2DM, and 106 established T2DM. Serum spexin was measured using ELISA. The homeostasis model assessment of insulin resistance (HOMA2-IR) and ß-cell function (HOMA2-ß), and Stumvoll index estimating first- and second-phase insulin secretion were calculated. RESULTS: Spexin levels were higher in FDRs [235.53 pg/ml (185.28, 293.95)] and IGR [239.79 pg/ml (191.52, 301.69)], comparable in newly diagnosed T2DM [224.68 pg/ml (187.37, 279.74)], and lower in established T2DM [100.11 pg/ml (78.50, 137.34)], compared with healthy subjects [200.23 pg/ml (160.32, 275.65)]. Spexin levels were negatively correlated with fasting plasma glucose (FPG) (r = - 0.355, P < 0.001), hemoglobin A1C (HbA1c) (r = - 0.379, P < 0.001), and HOMA2-IR (r = - 0.225, P < 0.001), and positively correlated with HOMA2-ß (r = 0.245, P < 0.001) after adjusting for age, sex, and BMI. Multivariate linear regression analysis showed that established T2DM and HOMA2-ß were independently associated with serum spexin levels. CONCLUSIONS: Serum spexin levels represented as a bell-shaped curve along the glycemic continuum and is closely related with insulin secretion in humans.

Combined therapy of GABA and sitagliptin prevents high-fat diet impairment of beta-cell function.

We recently demonstrated that combined therapy of GABA and sitagliptin promoted beta-cell proliferation, and decreased beta-cell apoptosis in a multiple low-dose streptozotocin (STZ)-induced beta-cell injury mouse model. In this study, we examined whether this combined therapy is effective in ameliorating the impairment of beta-cell function caused by high-fat diet (HFD) feeding in mice. Male C57BL/6J mice were fed normal chow diet, HFD, or HFD combined with GABA, sitagliptin, or both drugs. Oral drug daily administration was initiated one week before HFD and maintained for two weeks. After two weeks of intervention, we found that GABA or sitagliptin administration ameliorated the impairment of glucose tolerance induced by HFD. This was associated with improved insulin secretion in vivo. Notably, combined administration of GABA and sitagliptin significantly enhanced these effects as compared to each of the monotherapies. Combined GABA and sitagliptin was superior at increasing beta-cell mass, and associated Ki67+ and PDX-1+ beta-cell counts. In addition, we found that HFD-induced compensatory beta-cell proliferation was associated with increased activation of unfolded protein response (UPR), as indicated by BiP expression. This could be an important mechanism of compensatory beta-cell proliferation, and beta cells treated with GABA and sitagliptin showed greater UPR activation. Our results suggest that the combined use of these agents produces superior therapeutic outcomes.

Type IIB PKA is highly expressed in ß cells and controls cell proliferation via regulating Cyclin D1 expression.

ß cell number is maintained mainly by cell proliferation and cell apoptosis. Protein kinase A (PKA) pathway is an important intracellular signalling-mediating ß cell proliferation. However, the precise roles of PKA isoforms are not well-defined. We found that the RIIB subunit of PKA is expressed specifically by ß cells of mouse and human islets. Sixty percent pancreatectomy caused increased ß cell proliferation. Deletion of type IIB PKA by disruption of RIIB expression further promoted ß cell proliferation, leading to enhanced ß cell mass expansion. RIIB KO mice also showed increased insulin levels and improved glucose tolerance. Mechanistically, activation of type IIB PKA decreased Cyclin D1 levels and inhibition of RIIB expression increased Cyclin D1 levels. Consistently, activation of type IIB PKA inhibited cell cycle entry. These results suggest that type IIB PKA plays a pivotal role in ß cell proliferation via regulating Cyclin D1 expression.

[A hemifacial transplantation model in hares].

OBJECTIVE: To design an animal model to study the facial transplantation of allografts in rabbits. METHODS: Livid blue rabbits and New Zealand white rabbits was applied as experiment animal, to harvest hemifacial composite-tissue flap based in the common external carotid artery with the branch of the external mandibular artery and auricularis magna artery, then allotransplantation was performed with the livid blue rabbits as recipient while new Zealand rabbits as donor, the immunosuppressive agent comprised ciclosporin, azamun and prednisone. 25 couples of rabbits were divided three groups. Group A, 5 couples of rabbits, no administered immunosuppressive agent and the artery anastomosis with end-to-end. Group B, 10 couples of rabbits, administered immunosuppressive agent and the artery anastomosis with end-to-end. Group C, 10 couples of rabbits, administered immunosuppressive agent and the artery anastomosis with end-to-side. Postoperative, to observe the survive ratio of animal and composite-tissue flap, verified the practicability of model further. RESULTS: The blood supply of hemifacial composite-tissue flap is rich after allotransplantation. The survive ratio wasn't different with different procedure of the external carotid artery anastomosis. CONCLUSIONS: This is a successful model of composite face flap transplantation in the rabbits.