Low-grade inflammation is an independent risk factor of heart disease, stroke, diabetes and mortality. Research findings suggest that atherosclerosis, which involves the formation of fatty deposits (plaques) and activity of free radicals and infectious agents in the arteries, can be likened to arthritis of the bones and joints because they are both inflammatory disorders. Inflammation precedes the detection of insulin resistance and therefore may be a good predictor of diabetes.
Further, it has been demonstrated that obese mice (ob/ob and db/db) have a disrupted mucosal barrier function and increased systemic inflammation (Brun et al., Am J Physiol Gastrointest Liver Physiol 292:G518-G525, 2007. 5 Oct. 2006). These observations were further extended to C57BL6/J mice maintained on high-fat-diet (Cani et al., DIABETES, VOL. 57, JUNE 2008, p 1470-1481) and nonobese diabetic mouse (Hadjiyanni et al., 2009). Cani and colleagues, gut.bmj.com, 2009) reported that in ob/ob mice, altering the gut microbiota reduced intestinal permeability and inflammation via a GLP-2 driven pathway. Further, the increased permeability observed in obese and diabetic patients is now is likely to have a more vital role in the disease progression than previously anticipated. Increased intestinal permeability leads to increased bacterial lipopolysaccharide (LPS) transport across the intestinal lumen. This increased LPS activates immune cells such as macrophages circulating and organ residing in the body causing low grade chronic inflammation involved in the pathogenesis of many diseases. This phenomenon is called metabolic endotoxemia (ME) and can be viewed as a novel concept in chronic disease pathology.
Targeting ME and associated diseases is within the scope of this invention. Diseases including type II diabetes mellitus, atherosclerosis, Parkinson's disease and cancer metastasis arise in the context of chronic low-grade inflammation, of which the source has not clearly been defined. Interestingly, several recent studies have demonstrated significant correlations between disease development and plasma endotoxin levels (Chang 2011, J Med Sci 2011; 31(5):191-209).
The hypothesized mechanism whereby a dual GLP2-GLP1 agonist will work in a obesity diabetes setting is depicted in FIG. 1. The GLP2 component reduces inflammation and metabolic endotoxemia whereas the GLP1 component provided glucose control and weight loss through classical GLP1 dependent mechanisms.
Human GLP-2 is a 33-amino-acid peptide derived from specific posttranslational processing of proglucagon in the enteroendocrine L cells of the intestine and in specific regions of the brainstem. It is co-secreted together with glucagon-like peptide 1 (GLP-1), oxyntomodulin, and glicentin, in response to nutrient ingestion.
GLP-2 induces significant growth of the small intestinal mucosal epithelium via the stimulation of stem cell proliferation in the crypts and inhibition of apoptosis in the villi (Drucker et al., Proc Natl Acad Sci USA 93:7911-7916 (1996)). GLP-2 also has growth effects on the colon. Furthermore, GLP-2 inhibits gastric emptying and gastric acid secretion (Wojdemann et al., J Clin Endocrinol Metab. 84:2513-2517 (1999)), enhances intestinal barrier function (Benjamin et al., Gut 47:112-9 (2000)), stimulates intestinal hexose transport via the upregulation of glucose transporters (Cheeseman, Am J Physiol. R1985-71 (1997)), and increases intestinal blood flow (Guan et al., Gastroenterology 125:136147 (2003)).
GLP-2 binds to a single G protein-coupled receptor belonging to the class II glucagon secretin family. The GLP-2 receptor is expressed in the small intestine, colon and stomach, which also are sites that are known to be responsive to GLP-2 (Yusta et al., Gastroenterology 119:744-755 (2000)). However, the target cell type for GLP-2 receptor stimulation in the gastrointestinal tract remains unclear, and the downstream intracellular mediators coupled to the GLP-2 receptor are poorly understood.
The demonstrated specific and beneficial effects of GLP-2 in the small intestine have raised much interest as to the use of GLP-2 in the treatment of intestinal disease or injury (Sinclair and Drucker, Physiology 2005: 357-65). Furthermore GLP-2 has been shown to prevent or reduce mucosal epithelial damage in a wide number of preclinical models of gut injury, including chemotherapy-induced enteritis, ischemic-reperfusion injury, dextran sulfate-induced colitis and genetic models of inflammatory bowel disease (Sinclair and Drucker Physiology 2005: 357-65).
Additionally, the expression of the GLP-2R mRNA in the stomach, (Yusta et al., 2000) together with the observation that GLP-2 reduces gastric motility and gastric acid secretion (Meier et al., GASTROENTEROLOGY 2006; 130:44-54) provides ample evidence that the stomach is either directly or indirectly responsive to GLP-2. Nonetheless, the use of GLP-2 or analogues of GLP-2 in conditions characterised by damage to the gastric lining has not yet been explored.
GLP-2 is secreted as a 33 amino acid peptide with the following sequence His-Ala-Asp-Gly-Ser-Phe-Ser-Asp-Glu-Met-Asn-Thr-Ile-Leu-Asp-Asn-Leu-Ala-Ala-Arg-Asp-Phe-Ile-Asn-Trp-Leu-Ile-Gln-Thr-Lys-Ile-Thr-Asp (SEQ ID NO: 1) It is rapidly cleaved by the enzyme DPP IV at the alanine (Ala) at position 2 relative to the N-terminus to form an inactive human GLP-2 peptide (3-33). This rapid enzymatic degradation of GLP-2(1-33), in addition to renal clearance, results in a half life of about 7 minutes (Tavares et al., Am. J. Physiol. Endocrinol. Metab. 278:E134-E139 (2000)).
Representative GLP-2 analogues are described, e.g., in U.S. Pat. Nos. 5,789,379; 5,994,500; 6,184,201; 8,184,208; International Publication Nos. WO 97/39031; WO 01/41779; WO 02/066511 and DaCambra et al. (Biochemistry 2000, 39, 8888-8894). All references cited herein are expressly incorporated by reference in their entirety.