The Microbial Revolution in the World of Joint Replacement Surgery.

Background: The prevalence of revision surgery due to aseptic loosening and periprosthetic joint infection (PJI) following total hip and knee arthroplasty is growing. Strategies to prevent the need for revision surgery and its associated health-care costs and patient morbidity are needed. Therapies that modulate the gut microbiota to influence bone health and systemic inflammation are a novel area of research. Methods: A literature review of preclinical and clinical peer-reviewed articles relating to the role of the gut microbiota in bone health and PJI was performed. Results: There is evidence that the gut microbiota plays a role in maintaining bone mineral density, which can contribute to osseointegration, osteolysis, aseptic loosening, and periprosthetic fractures. Similarly, the gut microbiota influences gut permeability and the potential for bacterial translocation to the bloodstream, increasing susceptibility to PJI. Conclusions: Emerging evidence supports the role of the gut microbiota in the development of complications such as aseptic loosening and PJI after total hip or knee arthroplasty. There is a potential for microbial therapies such as probiotics or fecal microbial transplantation to moderate the risk of developing these complications. However, further investigation is required. Clinical Relevance: Modulation of the gut microbiota may influence patient outcomes following total joint arthroplasty.

The Cytoskeletal Transport Protein, Secretagogin, Is Essential for Diurnal Glucagon-like Peptide-1 Secretion in Mice.

The intestinal L-cell incretin, glucagon-like peptide-1 (GLP-1), exhibits a circadian pattern of secretion, thereby entraining diurnal insulin release. Secretagogin (Scgn), an actin-binding regulatory protein, is essential for the temporal peak of GLP-1 secretion in vitro. To interrogate the role of Scgn in diurnal GLP-1 secretion in vivo, peak and trough GLP-1 release were evaluated in knockout mice (Scgn-/-, Gcg-CreERT2/+; Scgnfl/fl and Vil-CreERT2/+; Scgnfl/fl), and RNA sequencing (RNA-Seq) was conducted in Scgn knockdown L-cells. All 3 knockout models demonstrated loss of the diurnal rhythm of GLP-1 secretion in response to oral glucose. Gcg-CreERT2/+; Scgnfl/fl mice also lost the normal pattern in glucagon secretion, while Scgn-/- and Vil-CreERT2/+; Scgnfl/fl animals demonstrated impaired diurnal secretion of the related incretin, glucose-dependent insulinotrophic polypeptide. RNA-Seq of mGLUTag L-cells showed decreased pathways regulating vesicle transport, transport and binding, and protein-protein interaction at synapse, as well as pathways related to proteasome-mediated degradation including chaperone-mediated protein complex assembly following Scgn knockdown. Scgn is therefore essential for diurnal L-cell GLP-1 secretion in vivo, likely mediated through effects on secretory granule dynamics.

Glucagon-Like Peptide-2 Stimulates S-Phase Entry of Intestinal Lgr5+ Stem Cells.

BACKGROUND & AIMS: Leucine-rich repeat-containing G-protein-coupled receptor-5 (Lgr5)+/olfactomedin-4 (Olfm4)+ intestinal stem cells (ISCs) in the crypt base are crucial for homeostatic maintenance of the epithelium. The gut hormone, glucagon-like peptide-21-33 (GLP-2), stimulates intestinal proliferation and growth; however, the actions of GLP-2 on the Lgr5+ ISCs remain unclear. The aim of this study was to determine whether and how GLP-2 regulates Lgr5+ ISC cell-cycle dynamics and numbers. METHODS: Lgr5-Enhanced green-fluorescent protein - internal ribosome entry site - Cre recombinase - estrogen receptor T2 (eGFP-IRES-creERT2) mice were acutely administered human Glycine2 (Gly2)-GLP-2, or the GLP-2-receptor antagonist, GLP-23-33. Intestinal epithelial insulin-like growth factor-1-receptor knockout and control mice were treated chronically with human Gly2 (hGly2)-GLP-2. Cell-cycle parameters were determined by 5-Ethynyl-2'-deoxyuridine (EdU), bromodeoxyuridine, antibody #Ki67, and phospho-histone 3 labeling and cell-cycle gene expression. RESULTS: Acute hGly2-GLP-2 treatment increased the proportion of eGFP+EdU+/OLFM4+EdU+ cells by 11% to 22% (P < .05), without affecting other cell-cycle markers. hGly2-GLP-2 treatment also increased the ratio of eGFP+ cells in early to late S-phase by 97% (P < .001), and increased the proportion of eGFP+ cells entering S-phase by 218% (P < .001). hGly2-GLP-2 treatment induced jejunal expression of genes involved in cell-cycle regulation (P < .05), and increased expression of Mcm3 in the Lgr5-expressing cells by 122% (P < .05). Conversely, GLP-23-33 reduced the proportion of eGFP+EdU+ cells by 27% (P < .05), as well as the expression of jejunal cell-cycle genes (P < .05). Finally, chronic hGly2-GLP-2 treatment increased the number of OLFM4+ cells/crypt (P < .05), in an intestinal epithelial insulin-like growth factor-1-receptor-dependent manner. CONCLUSIONS: These findings expand the actions of GLP-2 to encompass acute stimulation of Lgr5+ ISC S-phase entry through the GLP-2R, and chronic induction of Lgr5+ ISC expansion through downstream intestinal insulin-like growth factor-1 signaling.

Complementary and antagonistic effects of combined glucagon-like peptide-2 and glucagon-like peptide-1 receptor agonist administration on parameters relevant to short bowel syndrome.

BACKGROUND: Short bowel syndrome (SBS) is characterized by malabsorption requiring parenteral nutrition. The intestinotrophic glucagon-like peptide (GLP)-2 receptor agonist, h[Gly2]GLP2, is used to treat patients with SBS. Evidence suggests that GLP-1 receptor agonists such as exendin-4 (Ex4) may be beneficial in SBS given their ability to increase intestinal growth and delay gastric emptying (GE). METHODS: Intestinal growth, body weight (BW), food intake (FI), GE, gastrointestinal (GI) transit, intestinal permeability, and glucose tolerance were investigated in male and female C57/BL6 mice following vehicle, h[Gly2]GLP2, or Ex4 treatment, alone or in combination at "low," "medium," and "high" doses (0.1, 0.5, 1.0 and 0.01, 0.05, 0.1 µg/g, respectively). RESULTS: Only the h[Gly2]GLP2 low/Ex4 high-dose combination additively increased small intestinal (SI) weight compared with vehicle and both monoagonists (P < 0.01-0.001), via increased villus height (P < 0.01) and SI length (P < 0.05). This combination had no effects on BW; FI; and fat, liver, spleen, heart, and kidney weights but reduced GI transit (P < 0.001) versus low-dose h[Gly2]GLP2 monotreatment and abrogated the inhibitory effects of high-dose Ex4 on GE (P < 0.01) and of low-dose h[Gly2]GLP2 on intestinal permeability (P < 0.05). Ex4-induced improvements in glucose homeostasis were maintained upon combination with h[Gly2]GLP2 (P < 0.001). CONCLUSIONS: These findings suggest that combining specific doses of GLP-2- and GLP-1 receptor agonists additively improves SI growth and GI transit without detrimental effects on BW, FI, GE, and glucose homeostasis, and may be useful for the treatment of patients with SBS.

Trace Elements' Contamination of Pediatric Parenteral Nutrition Solutions in Canada: A Cause for Concern.

BACKGROUND: Trace elements' (TEs) contamination of parenteral nutrition (PN) solutions is an ongoing concern. The aims of this study were 1) to measure actual TE concentrations in PN admixtures compared with ordered concentrations and 2) compare TE intake with current recommendations. METHODS: PN admixtures from discarded bags were collected from patients receiving home PN and on inpatient wards. Samples were collected from 72 patients (39 inpatients, 33 receiving home PN). Age, percentage energy intake from PN, and PN orders were collected from patients' charts. PN samples were analyzed for TEs, including chromium (Cr) and manganese (Mn), and concentration measurements compared with ordered concentrations and current recommendations. RESULTS: Measured Cr and Mn concentrations were higher than ordered concentrations: 5.3 ± 1.7 vs 2.8 ± 1.5 µg/L; P < 0.0001 and 11.9 ± 5.9 vs 0.00 µg/L; P < 0.0001, respectively. Chromium contamination alone accounted for over 100% of current recommendations for patients 0-12 months and between 63% and 92% for children >1 year. Contamination of Mn provided all the measured Mn in PN admixtures, since Mn is excluded from PN orders at our institution. Between 70% and 120% of current Mn recommendations were met from contamination. CONCLUSIONS: Cr should be excluded from PN admixtures for children 0-12 months and only one-fourth the current recommendation should be added for pediatric patients >1 year. Manganese should also be excluded from PN admixture for pediatric patients but plasms monitoring 2-3 times per year is recommended for those on long-term PN.

Requirement for the intestinal epithelial insulin-like growth factor-1 receptor in the intestinal responses to glucagon-like peptide-2 and dietary fat.

The intestinal hormone, glucagon-like peptide-2 (GLP-2), enhances the enterocyte chylomicron production. However, GLP-2 is known to require the intestinal-epithelial insulin-like growth factor-1 receptor (IE-IGF-1R) for its other actions to increase intestinal growth and barrier function. The role of the IE-IGF-1R in enterocyte lipid handling was thus tested in the GLP-2 signaling pathway, as well as in response to a Western diet (WD). IE-IGF-1R knockout (KO) and control mice were treated for 11 days with h(GLY2 )GLP-2 or fed a WD for 18 weeks followed by a duodenal fat tolerance test with C14 -labeled triolein. Human Caco-2BBE cells were treated with an IGF-1R antagonist or signaling inhibitors to determine triglyceride-associated protein expression. The IE-IGF-1R was required for GLP-2-induced increases in CD36 and FATP-4 in chow-fed mice, and for expression in vitro; FATP-4 also required PI3K/Akt. Although WD-fed IE-IGF-1R KO mice demonstrated normal CD36 expression, the protein was incorrectly localized 2h post-duodenal fat administration. IE-IGF-1R KO also prevented the WD-induced increase in MTP and decrease in APOC3, increased jejunal mucosal C14 -fat accumulation, and elevated plasma triglyceride and C14 -fat levels. Collectively, these studies elucidate new roles for the IE-IGF-1R in enterocyte lipid handling, under basal conditions and in response to GLP-2 and WD-feeding.