Adeno-associated virus-9 reverses delayed gastric emptying of solids in diabetic mice.

BACKGROUND: Gastroparesis is defined by delayed gastric emptying (GE) without obstruction. Studies suggest targeting heme oxygenase-1 (HO1) may ameliorate diabetic gastroparesis. Upregulation of HO1 expression via interleukin-10 (IL-10) in the gastric muscularis propria is associated with reversal of delayed GE in diabetic NOD mice. IL-10 activates the M2 cytoprotective phenotype of macrophages and induces expression of HO1 protein. Here, we assess delivery of HO1 by recombinant adeno-associated viruses (AAVs) in diabetic mice with delayed GE. METHODS: C57BL6 diabetic delayed GE mice were injected with 1 × 1012 vg scAAV9-cre, scAAV9-GFP, or scAAV9-HO1 particles. Changes to GE were assessed weekly utilizing our [13 C]-octanoic acid breath test. Stomach tissue was collected to assess the effect of scAAV9 treatment on Kit, NOS1, and HO1 expression. KEY RESULTS: Delayed GE returned to normal within 2 weeks of treatment in 7/12 mice receiving scAAV9-cre and in 4/5 mice that received the scAAV9-GFP, whereas mice that received scAAV9-HO1 did not respond in the same manner and had GE that took significantly longer to return to normal (6/7 mice at 4-6 weeks). Kit, NOS1, and HO1 protein expression in scAAV9-GFP-treated mice with normal GE were not significantly different compared with diabetic mice with delayed GE. CONCLUSIONS AND INFERENCES: Injection of scAAV9 into diabetic C57BL6 mice produced a biological response that resulted in acceleration of GE independently of the cargo delivered by the AAV9 vector. Further research is needed to determine whether use of AAV mediated gene transduction in the gastric muscularis propria is beneficial and warranted.

Roux-en-Y gastric bypass with a long versus a short biliopancreatic limb improves weight loss and glycemic control in obese mice.

BACKGROUND: Roux-en-Y gastric bypass (RYGB) results in long-term weight loss and reduced obesity related co-morbidities. However, little is known about how the lengths of the biliopancreatic limb (BPL), the alimentary limb (AL), and the common limb (CL) affect weight loss and glucose metabolism. OBJECTIVES: Our aim was to establish a RYGB obese mouse model with defined proportions of the AL and BPL and a constant CL to assess the effects on weight loss,glucose metabolism, and obesity-related co-morbidities. SETTING: In vivo mouse study. METHODS: Six-week-old male C57BL/6J mice fed with a high-fat diet (HFD) underwent bariatric surgery with defined BPL lengths: a very long, long, and short BPL (35%, 25%, and 15% of total bowel length), or sham surgery. The length of the AL was adjusted to achieve the same CL length. Mice were analyzed for weight loss, glycemic control, and obesity-related co-morbidities. RESULTS: Mice undergoing RYGB surgery with a very long BPL had excessive weight loss and mortality and were therefore not further analyzed. Mice with a long BPL showed a significantly increased total weight loss when compared with mice with a short BPL. In addition, a long BPL improved glucose tolerance, particularly early after surgery. A long BPL was also associated with lower triglyceride levels. Resolution of hepatic steatosis and adipose tissue inflammation was, however, not statistically significant. Of note, bariatric surgery dramatically changed gut microbiota, regardless of limb length. CONCLUSION: In obese mice, a long BPL results in enhanced weight loss and improved glucose tolerance. These findings could potentially be translated to humans by tailoring the BPL length according to body weight, obesity-related co-morbidities, and total bowel length of an individual patient.

Targeting colonic macrophages improves glycemic control in high-fat diet-induced obesity.

The obesity epidemic continues to worsen worldwide. However, the mechanisms initiating glucose dysregulation in obesity remain poorly understood. We assessed the role that colonic macrophage subpopulations play in glucose homeostasis in mice fed a high-fat diet (HFD). Concurrent with glucose intolerance, pro-inflammatory/monocyte-derived colonic macrophages increased in mice fed a HFD. A link between macrophage numbers and glycemia was established by pharmacological dose-dependent ablation of macrophages. In particular, colon-specific macrophage depletion by intrarectal clodronate liposomes improved glucose tolerance, insulin sensitivity, and insulin secretion capacity. Colonic macrophage activation upon HFD was characterized by an interferon response and a change in mitochondrial metabolism, which converged in mTOR as a common regulator. Colon-specific mTOR inhibition reduced pro-inflammatory macrophages and ameliorated insulin secretion capacity, similar to colon-specific macrophage depletion, but did not affect insulin sensitivity. Thus, pharmacological targeting of colonic macrophages could become a potential therapy in obesity to improve glycemic control.

Imatinib reduces non-alcoholic fatty liver disease in obese mice by targeting inflammatory and lipogenic pathways in macrophages and liver.

Macrophages have been recognized as key players in non-alcoholic fatty liver disease (NAFLD). Our aim was to assess whether pharmacological attenuation of macrophages can be achieved by imatinib, an anti-leukemia drug with known anti-inflammatory and anti-diabetic properties, and how this impacts on NAFLD. We analyzed the pro- and anti-inflammatory gene expression of murine macrophages and human monocytes in vitro in the presence or absence of imatinib. In a time-resolved study, we characterized metabolic disease manifestations such as hepatic steatosis, systemic and adipose tissue inflammation as well as lipid and glucose metabolism in obese mice at one and three months of imatinib treatment. Our results showed that imatinib lowered pro-inflammatory markers in murine macrophages and human monocytes in vitro. In obese mice, imatinib reduced TNFα-gene expression in peritoneal and liver macrophages and systemic lipid levels at one month. This was followed by decreased hepatic steatosis, systemic and adipose tissue inflammation and increased insulin sensitivity after three months. As the transcription factor sterol regulatory element-binding protein (SREBP) links lipid metabolism to the innate immune response, we assessed the gene expression of SREBPs and their target genes, which was indeed downregulated in the liver and partially in peritoneal macrophages. In conclusion, targeting both inflammatory and lipogenic pathways in macrophages and liver as shown by imatinib could represent an attractive novel therapeutic strategy for patients with NAFLD.