Metabolic responses to exogenous ghrelin in obesity and early after Roux-en-Y gastric bypass in humans.

AIMS: Ghrelin is a gastric-derived hormone that stimulates growth hormone (GH) secretion and has a multi-faceted role in the regulation of energy homeostasis, including glucose metabolism. Circulating ghrelin concentrations are modulated in response to nutritional status, but responses to ghrelin in altered metabolic states are poorly understood. We investigated the metabolic effects of ghrelin in obesity and early after Roux-en-Y gastric bypass (RYGB). MATERIALS AND METHODS: We assessed central and peripheral metabolic responses to acyl ghrelin infusion (1 pmol kg-1 min-1 ) in healthy, lean subjects (n = 9) and non-diabetic, obese subjects (n = 9) before and 2 weeks after RYGB. Central responses were assessed by GH and pancreatic polypeptide (surrogate for vagal activity) secretion. Peripheral responses were assessed by hepatic and skeletal muscle insulin sensitivity during a hyperinsulinaemic-euglycaemic clamp. RESULTS: Ghrelin-stimulated GH secretion was attenuated in obese subjects, but was restored by RYGB to a response similar to that of lean subjects. The heightened pancreatic polypeptide response to ghrelin infusion in the obese was attenuated after RYGB. Hepatic glucose production and hepatic insulin sensitivity were not altered by ghrelin infusion in RYGB subjects. Skeletal muscle insulin sensitivity was impaired to a similar degree in lean, obese and post-RYGB individuals in response to ghrelin infusion. CONCLUSIONS: These data suggest that obesity is characterized by abnormal central, but not peripheral, responsiveness to ghrelin that can be restored early after RYGB before significant weight loss. Further work is necessary to fully elucidate the role of ghrelin in the metabolic changes that occur in obesity and following RYGB.

Retrospective Review of Multitarget Stool DNA as a Screening Test for Colorectal Cancer.

OBJECTIVES: To review the effectiveness of noninvasive multitarget stool DNA testing as a screening test for colorectal cancer. METHODS: We performed a retrospective review of patients referred to 2 high volume outpatient procedural centers for colonoscopy for positive Cologuard test. Positive findings for colorectal cancer based on pathologic findings and also advanced adenomas were recorded. Positive predictive value (PPV) was assessed. RESULTS: Of the 1585 patients evaluated and referred for colonoscopy from January 1, 2018 to November 1, 2019, for ICD-10 codes R19.5 (other fecal abnormalities) and K92.1 (melena), 84 were referred for a positive Cologuard test. Out of the 84, 6 were excluded based on family history of colon cancer in first degree relative or personal history of inflammatory bowel disease. Of the remaining 78 patients, 1 patient (1.3%) had colorectal cancer and 5 (6.4%) had advanced adenomas (>1 cm size, high grade dysplasia or villous). Postive predictive value for colorectal cancer was 1.3% and for precancerous lesions plus colorectal cancer was 7.7%. A total of 53 (68.0%) patients had either totally normal colonoscopy or hyperplastic polyps. Out of the 78 individuals in our study, 70 (89.7%) had normal findings, hyperplastic polyps, or non-advanced adenomas. CONCLUSIONS: Multitarget stool DNA testing carries an unacceptably low PPV to be utilized as a screening test for colorectal cancer. The study fails to detect both adenomas and colon cancer at a higher rate than screening colonoscopy in selected studies. The advantage of being noninvasive has been noted to increase colorectal cancer screening in otherwise non-compliant Medicare patients.