Association of low numbers of CD206-positive cells with loss of ICC in the gastric body of patients with diabetic gastroparesis

Intravenous immunoglobulin in drug and device refractory patients with the symptoms of gastroparesis-an open-label study

BACKGROUND

Gastroparesis is a complex clinical entity; many aspects of which remain unknown. Although most patients have idiopathic, diabetic, or postsurgical gastroparesis, many are thought to have measurable neuromuscular abnormalities. Immunotherapy has recently been utilized to treat suspected autoimmune gastrointestinal dysmotility.

METHODS

Fourteen patients with symptoms of gastroparesis (Gp) who were refractory to drug/device were selected from 443 Gp patients from 2013 to 2015 who were treated at the University of Louisville motility center. All patients underwent a structural and psychiatric evaluation along with detailed psychological and behavioral examination to rule out eating disorders. We performed detailed neuromuscular evaluation and all 14 patients received at least 12 weeks of intravenous immunoglobulin (400 mg/kg infusion weekly). Response was defined subjectively (symptomatic improvement) using standardized IDIOM score system.

KEY RESULTS

All 14 patients had serological evidence and/or tissue evidence of immunological abnormality. Post-IVIG therapy, there was a significant improvement in symptoms scores for nausea, vomiting, early satiety, and abdominal pain.

CONCLUSIONS AND INFERENCES

Although limited by the absence of placebo group, the data illustrate the role of autoimmunity and neuromuscular evaluation in patients with gastroparesis and support the utility of a diagnostic trial of immunotherapy in an effort to improve therapeutic outcomes for such patients.

A Critical Review of the Current Clinical Landscape of Gastroparesis

Gastroparesis has emerged as a common gastrointestinal disorder over the past few decades. It has been questioned whether this increase in prevalence reflects a true epidemic or rather the mislabeling of a variety of entities of similar symptomatology accompanied by a delay in the emptying of a meal from the stomach on a radionuclide gastric emptying study. Several factors contribute to this diagnostic morass, including a failure to recognize other conditions with similar symptoms, the relative convenience and accessibility of gastric emptying tests, the pervasive presence of some delay in gastric emptying in a variety of functional gastrointestinal disorders, and the confounding effects of certain therapies (opioids in particular) on gastric emptying rates. As a consequence, the label gastroparesis is affixed to patients whose symptoms have little to do with the rate at which food leaves the stomach and initiates a misdirected course of treatment that includes prokinetics, gastric electrical stimulation, and surgery. This strategy has already led to several well-documented therapeutic failures. When evaluating patients with upper gastrointestinal symptoms, the many facets of gastric and duodenal physiology that could contribute to symptoms should be considered, and a rush to attribute them to delayed gastric emptying should be resisted, as the subset of patients with accurately diagnosed gastroparesis is small. This opinion piece critically reviews the clinical landscape of gastroparesis as well as attempts to outline what should and should not be defined as clinically important gastroparesis.

Muscularis macrophages: Key players in intestinal homeostasis and disease

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Muscularis macrophages densily colonize the outermost layer of the gastrointestinal tract.

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Muscularis macrophages communicate with enteric neurons in a bidirectional matter.

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Muscularis macrophages are tissue-protective but can contribute to disease.

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Current challenges are to decipher therapeutic potentials of muscularis macrophages.

Macrophages residing in the muscularis externa of the gastrointestinal tract are highly specialized cells that are essential for tissue homeostasis during steady-state conditions as well as during disease. They are characterized by their unique protective functional phenotype that is undoubtedly a consequence of the reciprocal interaction with their environment, including the enteric nervous system. This muscularis macrophage-neuron interaction dictates intestinal motility and promotes tissue-protection during injury and infection, but can also contribute to tissue damage in gastrointestinal disorders such as post-operative ileus and gastroparesis. Although the importance of muscularis macrophages is clearly recognized, different aspects of these cells remain largely unexplored such their origin, longevity and instructive signals that determine their function and phenotype. In this review, we will discuss the phenotype, functions and origin of muscularis macrophages during steady-state and disease conditions. We will highlight the bidirectional crosstalk with neurons and potential therapeutic strategies that target and manipulate muscularis macrophages to restore their protective signature as a treatment for disease.

Repeat polymorphisms in the Homo sapiens heme oxygenase-1 gene in diabetic and idiopathic gastroparesis

BACKGROUND

Idiopathic and diabetic gastroparesis in Homo sapiens cause significant morbidity. Etiology or risk factors have not been clearly identified. Failure to sustain elevated heme oxygenase-1 (HO1) expression is associated with delayed gastric emptying in diabetic mice and polymorphisms in the HO1 gene (HMOX1, NCBI Gene ID:3162) are associated with worse outcomes in other diseases.

AIM

Our hypothesis was that longer polyGT alleles are more common in the HMOX1 genes of individuals with gastroparesis than in controls without upper gastrointestinal motility disorders.

METHODS

Repeat length was determined in genomic DNA. Controls with diabetes (84 type 1, 84 type 2) and without diabetes (n = 170) were compared to diabetic gastroparetics (99 type 1, 72 type 2) and idiopathic gastroparetics (n = 234). Correlations of repeat lengths with clinical symptom sub-scores on the gastroparesis cardinal symptom index (GCSI) were done. Statistical analyses of short (<29), medium and long (>32) repeat alleles and differences in allele length were used to test for associations with gastroparesis.

RESULTS

The distribution of allele lengths was different between groups (P = 0.016). Allele lengths were longest in type 2 diabetics with gastroparesis (29.18±0.35, mean ± SEM) and longer in gastroparetics compared to non-diabetic controls (28.50±0.14 vs 27.64±0.20 GT repeats/allele, P = 0.0008). Type 2 diabetic controls had longer alleles than non-diabetic controls. In all gastroparetic groups, allele lengths were longer in African Americans compared to other racial groups, differences in the proportion of African Americans in the groups accounted for the differences between gastroparetics and controls. Diabetic gastroparetics with 1 or 2 long alleles had worse GCSI nausea sub-scores (3.30±0.23) as compared to those with 0 long alleles (2.66±0.12), P = 0.022.

CONCLUSIONS

Longer poly-GT repeats in the HMOX1 gene are more common in African Americans with gastroparesis. Nausea symptoms are worse in subjects with longer alleles.

Diabetes and the Stomach

OPINION STATEMENT

Longstanding diabetes mellitus (both type 1 and type 2) can impair gastric motor function and cause significant upper gastrointestinal symptoms which significantly degrade quality of life, cause nutritional deficits, and degrade healthcare resource use. The most commonly considered gut complication of diabetes, diabetic gastroparesis, is a syndrome of delayed gastric emptying in the absence of mechanical obstruction which leads to symptoms of nausea, vomiting, postprandial fullness, early satiation, bloating, and upper abdominal pain. Gastroparesis also can lead to loss of glycemic control. A diagnosis of gastroparesis is made by documenting delayed gastric emptying and excluding mechanical obstruction. Gastric emptying scintigraphy is the most commonly utilized test for the diagnosis of gastroparesis but novel tests of gastric function have recently been introduced including the gastric emptying breath test and wireless motility capsule. Management most often is aimed at controlling symptoms, which includes dietary modification, optimization of glycemic control, and medication therapy with prokinetics, antiemetics, and neuromodulatory agents. Endoscopic and/or surgical therapies may be considered for refractory cases of gastroparesis. Recent research has provided new insights into the pathophysiology of this disease and is characterizing potential benefits of novel therapeutic agents which show promise in the treatment of this condition. This article will review the pathophysiology, new insights into disease mechanism, and treatment options for diabetic gastroparesis.

Intratumoral and peritumoral expression of CD68 and CD206 in hepatocellular carcinoma and their prognostic value

The aims of the present study were to determine whether the changes in density and location of CD68-positive and CD206-positive macrophages contribute to progression of hepatocellular carcinoma (HCC) and to evaluate prognostic values of these cells in post-surgical patients. A retrospective study involving 268 HCC patients was conducted. CD68-positive and CD206-positive macrophage infiltration in HCC tissues and adjacent tissues was examined by immunohistochemistry (IHC) and the relationship between the clinicopathological features and prognosis was analyzed. Receiver operating characteristics (ROC) curve was used to calculate diagnostic accuracy. There was an increase in CD68-positive and CD206-positive macrophage infiltration in adjacent tumor tissues compared with tumor tissues. ROC curve identified their optimal diagnostic cut-off values. The survival analysis showed that increased CD68 expression in adjacent tissues conferred superior overall survival (OS) and disease-free survival (DFS), while increase of CD206 in tumor yielded inferior OS and DFS. Cox regression analysis suggested both CD68-positive macrophages in adjacent area and intratumor CD206-positive macrophages as independent prognostic biomarkers for post-surgical HCC patients. Finally, a combination of CD68/CD206 and HBV-positive further improved prognostic stratification, especially in DFS. These results provide the first evidence for region- and subset-dependent involvement of CD68 and CD206 cells in HCC progression. A combination of CD68/CD206 density and HBV-positivity improves further predictive value for post-operative recurrence of HCC. Quantification of CD68/CD206 macrophages and their distribution can be exploited for better postsurgical management of HCC patients. These findings provide a basis for developing novel treatment strategies aimed at re-educating macrophages in tumor microenvironment.

Diabetic and idiopathic gastroparesis is associated with loss of CD206-positive macrophages in the gastric antrum

BACKGROUND

Animal studies have increasingly highlighted the role of macrophages in the development of delayed gastric emptying. However, their role in the pathophysiology of human gastroparesis is unclear. Our aim was to determine changes in macrophages and other cell types in the gastric antrum muscularis propria of patients with diabetic and idiopathic gastroparesis.

METHODS

Full thickness gastric antrum biopsies were obtained from patients enrolled in the Gastroparesis Clinical Research Consortium (11 diabetic, 6 idiopathic) and 5 controls. Immunolabeling and quantitative assessment was done for interstitial cells of Cajal (ICC) (Kit), enteric nerves protein gene product 9.5, neuronal nitric oxide synthase, vasoactive intestinal peptide, substance P, tyrosine hydroxylase), overall immune cells (CD45) and anti-inflammatory macrophages (CD206). Gastric emptying was assessed using nuclear medicine scintigraphy and symptom severity using the Gastroparesis Cardinal Symptom Index.

RESULTS

Both diabetic and idiopathic gastroparesis patients showed loss of ICC as compared to controls (Mean [standard error of mean]/hpf: diabetic, 2.28 [0.16]; idiopathic, 2.53 [0.47]; controls, 6.05 [0.62]; P=.004). Overall immune cell population (CD45) was unchanged but there was a loss of anti-inflammatory macrophages (CD206) in circular muscle (diabetic, 3.87 [0.32]; idiopathic, 4.16 [0.52]; controls, 6.59 [1.09]; P=.04) and myenteric plexus (diabetic, 3.83 [0.27]; idiopathic, 3.59 [0.68]; controls, 7.46 [0.51]; P=.004). There was correlation between the number of ICC and CD206-positive cells (r=.55, P=.008). Enteric nerves (PGP9.5) were unchanged: diabetic, 33.64 (3.45); idiopathic, 41.26 (6.40); controls, 46.80 (6.04).

CONCLUSION

Loss of antral CD206-positive anti-inflammatory macrophages is a key feature in human gastroparesis and it is associates with ICC loss.

Tumor necrosis factor alpha derived from classically activated "M1" macrophages reduces interstitial cell of Cajal numbers

BACKGROUND

Delayed gastric emptying in diabetic mice and humans is associated with changes in macrophage phenotype and loss of interstitial cells of Cajal (ICC) in the gastric muscle layers. In diabetic mice, classically activated M1 macrophages are associated with delayed gastric emptying, whereas alternatively activated M2 macrophages are associated with normal gastric emptying. This study aimed to determine if secreted factors from M1 macrophages could injure mouse ICC in primary culture.

METHODS

Cultures of gastric ICC were treated with conditioned medium (CM) from activated bone marrow-derived macrophages (BMDMs) and the effect of CM was quantified by counting ICC per high-powered field.

KEY RESULTS

Bone marrow-derived macrophages were activated to a M1 or M2 phenotype confirmed by qRT-PCR. Conditioned medium from M1 macrophages reduced ICC numbers by 41.1%, whereas M2-CM had no effect as compared to unconditioned, control media. Immunoblot analysis of 40 chemokines/cytokines found 12 that were significantly increased in M1-CM, including tumor necrosis factor alpha (TNF-α). ELISA detected 0.697±0.03 ng mL^-1 TNF-α in M1-CM. Recombinant mouse TNF-α reduced Kit expression and ICC numbers in a concentration-dependent manner (EC50 = 0.817 ng mL^-1 ). Blocking M1-CM TNF-α with a neutralizing antibody preserved ICC numbers. The caspase inhibitor Z-VAD.fmk partly preserved ICC numbers (cells/field; 6.63±1.04, 9.82±1.80 w/Z-VAD.fmk, n=6, P<.05).

CONCLUSIONS & INFERENCES

This work demonstrates that TNF-α secreted from M1 macrophages can result in Kit loss and directly injure ICC in vitro partly through caspase-dependent apoptosis and may play an important role in ICC depletion in diabetic gastroparesis.

Resident macrophages in the healthy and inflamed intestinal muscularis externa

Macrophages reside in a dense cellular network in the intestinal muscularis externa, and there is emerging evidence that the functionality of these cells determines the local microenvironment. Inflammatory responses during intestinal diseases change the homeostatic functionality of these cells causing inflammation and intestinal dysmotility. Such disturbances are not only induced by a change in the cellular composition in the intestinal muscularis but also by an altered crosstalk with the peripheral and central nervous system. In this review, we summarize the role of muscularis macrophages in the intestine in homeostasis and inflammation. We compare the functionality, the phenotype, and the origin of muscularis macrophages to their neighboring counterparts within the different layers of the intestine. We outline the cellular crosstalk with the enteric and the peripheral nervous system and summarize the current therapeutic approaches to modulate the functionality of these phagocytes.

Disorders of gastrointestinal hypomotility

Ingestion and digestion of food as well as expulsion of residual material from our gastrointestinal tract requires normal propulsive, i.e. motor, function. Hypomotility refers to inherited or acquired changes that come with decreased contractile forces or slower transit. It not only often causes symptoms but also may compromise nutritional status or lead to other complications. While severe forms, such as pseudo-obstruction or ileus, may have a tremendous functional impact, the less severe forms of hypomotility may well be more relevant, as they contribute to common disorders, such as functional dyspepsia, gastroparesis, chronic constipation, and irritable bowel syndrome (IBS). Clinical testing can identify changes in contractile activity, defined by lower amplitudes or abnormal patterns, and the related effects on transit. However, such biomarkers show a limited correlation with overall symptom severity as experienced by patients. Similarly, targeting hypomotility with pharmacological interventions often alters gut motor function but does not consistently improve symptoms. Novel diagnostic approaches may change this apparent paradox and enable us to obtain more comprehensive information by integrating data on electrical activity, mechanical forces, patterns, wall stiffness, and motions with information of the flow of luminal contents. New drugs with more selective effects or more specific delivery may improve benefits and limit adverse effects. Lastly, the complex regulation of gastrointestinal motility involves the brain-gut axis as a reciprocal pathway for afferent and efferent signaling. Considering the role of visceral input in emotion and the effects of emotion on visceral activity, understanding and managing hypomotility disorders requires an integrative approach based on the mind-body continuum or biopsychosocial model of diseases.

Genetics of enteric neuropathies

Abnormal development or disturbed functioning of the enteric nervous system (ENS), the intrinsic innervation of the gastrointestinal tract, is associated with the development of neuropathic gastrointestinal motility disorders. Here, we review the underlying molecular basis of these disorders and hypothesize that many of them have a common defective biological mechanism. Genetic burden and environmental components affecting this common mechanism are ultimately responsible for disease severity and symptom heterogeneity. We believe that they act together as the fulcrum in a seesaw balanced with harmful and protective factors, and are responsible for a continuum of symptoms ranging from neuronal hyperplasia to absence of neurons.

Emerging strategies for the treatment of gastroparesis

Gastroparesis is a syndrome of delayed gastric emptying in the absence of mechanical obstruction. Symptoms can be debilitating, affect nutritional states, and significantly impact patients' quality of life. The management of these patients can prove quite difficult to many providers. This article will review the current management recommendations of gastroparesis, discuss investigational medications and interventions, and summarize future directions of therapies targeting the underlying disease process. Current therapies are subdivided into those improving gastric motility and those directly targeting symptoms. Non-pharmacologic interventions, including gastric stimulator implantation and intra-pyloric botulinum toxic injection are reviewed. A discussion of expert opinion in the field, a look into the future of gastroparesis management, and a key point summary conclude the article.

Interleukin 10 Restores Gastric Emptying, Electrical Activity, and Interstitial Cells of Cajal Networks in Diabetic Mice

BACKGROUND & AIMS

Gastroparesis is a complication of diabetes characterized by delayed emptying of stomach contents and accompanied by early satiety, nausea, vomiting, and pain. No safe and reliable treatments are available. Interleukin 10 (IL10) activates the M2 cytoprotective phenotype of macrophages and induces expression of heme oxygenase 1 (HO1) protein. We investigated whether IL10 administration could improve gastric emptying and reverse the associated cellular and electrical abnormalities in diabetic mice.

METHODS

Nonobese diabetic mice with delayed gastric emptying were given either IL10 (0.1-1 μg, twice/day) or vehicle (controls). Stomach tissues were isolated, and sharp microelectrode recordings were made of the electrical activity in the gastric muscle layers. Changes to interstitial cells of Cajal (ICC), reduced nicotinamide adenine dinucleotide phosphate diaphorase, and levels and distribution of HO1 protein were determined by histochemical and imaging analyses of the same tissues.

RESULTS

Gastric emptying remained delayed in vehicle-treated diabetic mice but returned to normal in mice given IL10 (n = 10 mice; P < .05). In mice given IL10, normalization of gastric emptying was associated with a membrane potential difference between the proximal and distal stomach, and lower irregularity and higher frequency of slow-wave activity, particularly in the distal stomach. Levels of HO1 protein were higher in stomach tissues from mice given IL10, and ICC networks were more organized, better connected, and more evenly distributed compared with controls.

CONCLUSIONS

IL10 increases gastric emptying in diabetic mice and has therapeutic potential for patients with diabetic gastroparesis. This response is associated with up-regulation of HO1 and repair of connectivity of ICC networks.

Intrinsic Gastrointestinal Macrophages: Their Phenotype and Role in Gastrointestinal Motility

There is an increasing awareness of the role of macrophages in the regulation and maintenance of gastrointestinal function in health and disease. This work has proceeded in the context of an increased understanding of the complex phenotypic variation in macrophages throughout the body and has revealed previously un-identified roles for macrophages in diseases like gastroparesis, post-operative ileus and inflammatory bowel disease. Opportunities for exploiting the phenotypic modulation of tissue resident macrophages have been identified as possible therapies for some of these diseases. In addition, macrophages are an established component of the innate immune system that can respond to variations and changes in the intestinal microbiome and potentially mediate part of the impact of the microbiota on intestinal health. We reviewed the latest work on novel concepts in defining macrophage phenotype, discuss possible mechanisms of action for tissue-resident macrophages in the gut, address the significance of microbiome effects on macrophage phenotype and review the known and possible roles of macrophages in motility disorders of the gastrointestinal tract.

Novel insights into the effects of diabetes on gastric motility

Recent data from the Diabetes Control and Complications Trial/Epidemiology of Diabetic Interventions and Complications cohort indicate that the disease burden of gastroparesis in diabetes remains high, consistent with the outcome of cross-sectional studies in type 1 and 2 diabetes. An improved understanding of the pathogenesis of diabetic gastroparesis at the cellular level has emerged in the last decade, particularly as a result of initiatives such as the National Institute of Health funded Gastroparesis Clinical Research Consortium in the US. Management of diabetic gastroparesis involves dietary and psychological support, attention to glycaemic control, and the use of prokinetic agents. Given that the relationship between upper gastrointestinal symptoms and the rate of gastric emptying is weak, therapies targeted specifically at symptoms, such as nausea or pain, are important. The relationship between gastric emptying and postprandial glycaemia is complex and inter-dependent. Short-acting glucagon-like peptide-1 agonists, that slow gastric emptying, can be used to reduce postprandial glycaemic excursions and, in combination with basal insulin, result in substantial reductions in glycated haemoglobin in type 2 patients.

Gastroparesis

PURPOSE OF REVIEW

This review summarizes recent progress in the epidemiology, pathophysiology, and treatment of gastroparesis.

RECENT FINDINGS

The relationship between delayed gastric emptying and symptom pattern in gastroparesis and, related to it, its separation from functional dyspepsia remains an area of controversy and uncertainty. Pathophysiological studies have focused on the role of pyloric resistance and duodenal motility in generation of symptoms. In diabetic patients, glycemic control did not determine short-term changes in gastric emptying rate in type 2 diabetes, but poor glycemic control was a major risk factor for long-term development of gastroparesis in type 1 diabetes. At the cellular level, diabetic gastroparesis is characterized by loss of interstitial cells of Cajal (ICCs), and this is inversely correlated to the number of CD206+ macrophages, which are thought to have a protective effect on ICCs. Treatment trials have focused on dietary factors and a nasal spray formulation of metoclopramide. A meta-analysis of prokinetic studies found no association between symptom improvement and enhancement of gastric emptying in gastroparesis. Two controlled studies showed no benefit of tricyclic antidepressants (nortriptyline, amitriptyline) in idiopathic gastroparesis and functional dyspepsia with delayed emptying.

SUMMARY

The relationship between delay in gastric emptying, symptom pattern, and response to prokinetic therapy in gastroparesis is poor. In diabetes, gastroparesis is characterized by loss of ICCs, and this is inversely correlated to the number of CD206+ macrophages. Dietary interventions may help to alleviate symptoms. Tricyclic antidepressants do not provide symptomatic benefit to patients with idiopathic gastroparesis.

Diabetic Csf1op/op mice lacking macrophages are protected against the development of delayed gastric emptying

BACKGROUND & AIMS

Diabetic gastroparesis is associated with changes in interstitial cells of Cajal (ICC), neurons and smooth muscle cells in both animal models and humans. Macrophages appear to be critical to the development of cellular damage that leads to delayed gastric emptying but the mechanisms involved are not well understood. Csf1^op/op (Op/Op) mice lack biologically active Csf1, resulting in the absence of Csf1-dependent tissue macrophages. The aim of this study was to use Csf1^op/op mice to determine the role of macrophages in the development of delayed gastric emptying.

METHODS

Animals were injected with streptozotocin to make them diabetic. Gastric emptying was determined weekly. Immunohistochemistry was used to identify macrophages and ICC networks in the gastric muscular layers. Oxidative stress was measured by serum malondialdehyde (MDA) levels. Quantitative, reverse transcription PCR was used to measure levels of mRNA.

RESULTS

Csf1^op/op mice had normal ICC. With onset of diabetes both Csf1^op/op and wild type Csf1^+/+ mice developed increased levels of oxidative stress (75.8 ± 9.1 and 41.2±13.6 nmol/mL MDA respectively). Wild type Csf1^+/+ mice developed delayed gastric emptying after onset of diabetes (4/13) whereas no diabetic Csf1^op/op mouse developed delayed gastric emptying (0/15, P=0.035). ICC were disrupted in diabetic wild type Csf1^+/+ mice with delayed gastric emptying but remained normal in diabetic Csf1^op/op mice.

CONCLUSIONS

Cellular injury and development of delayed gastric emptying in diabetes requires the presence of muscle layer macrophages. Targeting macrophages may be an effective therapeutic option to prevent cellular damage and development of delayed gastric emptying in diabetes.

Role of estrogen in diabetic gastroparesis

Gastroparesis is a highly prevalent chronic disorder of the stomach, which is characterized by delayed gastric emptying and accompanied by a series of upper gastrointestinal symptoms. Diabetic gastroparesis (DGP) is one of the severe complications of diabetes, seriously affecting the patient's quality of life. At present, the pathogenesis of DGP is still unclear. The majority of DGP patients are women, and women's symptoms change with the fluctuation of the level of estrogen. Therefore, we speculate that estrogen may play an vital role in the stomach motility. Gastric emptying is an objective index for the diagnosis of gastroparesis. This article reviews the role of estrogen in DGP and the possible mechanisms.

Histologic changes in diabetic gastroparesis

The cellular abnormalities that lead to diabetic gastroparesis are increasingly being understood. Several key cell types are affected by diabetes, leading to gastroparesis. These changes include abnormalities in the extrinsic innervation to the stomach, loss of key neurotransmitters at the level of the enteric nervous system, smooth muscle abnormalities, loss of interstitial cells of Cajal, and changes in the macrophage population resident in the muscle wall. This article reviews the current understanding with a focus on data from human studies when available.

Macrophages in diabetic gastroparesis--the missing link?

BACKGROUND

Diabetic gastroparesis results in significant morbidity for patients and major economic burden for society. Treatment options for diabetic gastroparesis are currently directed at symptom control rather than the underlying disease and are limited. The pathophysiology of diabetic gastroparesis includes damage to intrinsic and extrinsic neurons, smooth muscle, and interstitial cells of Cajal (ICC). Oxidative damage in diabetes appears to be one of the primary insults involved in the pathogenesis of several complications of diabetes, including gastroparesis. Recent studies have highlighted the potential role of macrophages as key cellular elements in the pathogenesis of diabetic gastroparesis. Macrophages are important for both homeostasis and defense against a variety of pathogens. Heme oxygenase 1 (HO1), an enzyme expressed in a subset of macrophages has emerged as a major protective mechanism against oxidative stress. Activation of macrophages with high levels of HO1 expression protects against development of delayed gastric emptying in animal models of diabetes, while activation of macrophages that do not express HO1 are linked to neuromuscular cell injury. Targeting macrophages and HO1 may therefore be a therapeutic option in diabetic gastroparesis.

PURPOSE

This report briefly reviews the pathophysiology of diabetic gastroparesis with a focus on oxidative damage and how activation and polarization of different subtypes of macrophages in the muscularis propria determines development of delay in gastric emptying or protects against its development.