Management of the Bariatric Surgery Patient
Gastrointestinal Hormones
Gastrointestinal Hormones
TOP 10 TAKEAWAY MESSAGES:
Gastrointestinal (GI) Hormones
- Gastrointestinal hormones regulate caloric balance, hunger/ satiety food digestion, and nutrient utilization via central nervous system signaling, effects on GI motility, and GI enzyme release.
- Common GI hormone action in response to eating includes a decrease in hunger and facilitation of digestion (delayed gastric emptying, digestive enzyme release, and post-absorptive nutrient metabolism).
- The jejunum, the second longest segment of the small intestine, absorbs the greatest amount of simple sugars, fatty acids, proteins, minerals and vitamins.
- The ileum, the longest segment of the small intestine, absorbs bile salts, vitamin B12, some vitamins and some minerals.
- After food intake, most GI hormones decrease hunger/increase satiety.
- Among the few GI hormones that increase hunger between meals are ghrelin (“hunger hormone”) and neuropeptide Y (NPY). Positive caloric balance may not always be hunger-related.
- Illustrative GI hormones produced by the stomach include ghrelin and gastrin.
- Illustrative hormones produced by the pancreas include insulin, glucagon, pancreatic polypeptide (PP), amylin, and somatostatin.
- Illustrative GI hormones produced by the small intestine include cholecystokinin (CCK), secretin, motilin, and glucose-dependent insulinotropic peptide (GIP — also known as gastric inhibitory peptide).
- Illustrative GI hormones produced by the ileum and/or large intestine include fibroblast growth factor (FGF) 19, glucagon-like peptide-1, glucagon-like peptide-2, oxyntomodulin, and peptide YY (PYY).
Nutrient Absorption
GI Hormone Regulation of Caloric Balance, Food Digestion, and Nutrient Utilization
Illustrative Gastrointestinal Hormones and Function
Where Secreted | Gastrointestinal Hormone | Effect of Hormone on Eating Behavior | Effect of Eating on Hormone Secretion | Notes | Effect of Gastric By-pass and Sleeve Gastrectomy |
Stomach | Ghrelin (secreted by P/D1 cells) | ↑ Hunger | ↓ | ↑ With fasting ↑ Gastric emptying/ growth hormone (GH) | Ghrelin likely to decrease with sleeve gastrectomy (not so with gastric bypass) |
Gastrin (secreted by G cells in antrum) | ↓ Hunger | ↑ | ↑ Hydrochloride (HCI) acid and pepsinogen | ↓ Gastric bypass −/↑ Sleeve | |
Pancreas | Insulin (secreted by pancreatic beta cells) | ↓ Hunger | ↑ | ↑ Hunger with hypoglycemia ↑ Glucose transporter 4 in adipose tissue/muscle, glycogenesis, lipoprotein lipase activity, lipogenesis | ↓ Insulin resistance/ fasting insulin ↑ Insulin sensitivity/ insulin responsiveness |
Glucagon (secreted by pancreatic alpha cells) | ↓ Hunger | ↓ | ↑ Glycogen to glucose ↑ Postprandial glucagon in patients with type 2 diabetes mellitus (glucagon not suppressed) | Variable | |
PP [secreted by PP (F) cells] | ↓ Hunger | ↑ | ↓ Pancreatic exocrine secretion | Variable | |
Amylin (secreted by pancreatic beta cells) | ↓ Hunger | ↑ | ↓ Gastric emptying, glucagon | −/↓ | |
Somatostatin (secreted by D cells pylori antrum, duodenum, and pancreatic islets) | ↓ Hunger | ↑ | ↓ Growth hormone, gastrin, HCI, secretin, CCK, insulin, glucagon | −/↑ | |
Small Intestine (Mainly Duodenum and Jejunum) | CCK (secreted by I-cells) | ↓ Hunger | ↑ | ↑ Gall bladder contractility and bile, pancreatic enzymes ↓ Gastric emptying | ↑ Postprandial |
Secretin (secreted by S cells) | −− | ↑ | ↑ Pancreatic bicarbonate and bile ↓ Intestinal motility and gastric acid | Variable | |
GIP; Also known as Gastric Inhibitory Peptide – secreted by K cells | −− | ↑ | ↑ Insulin ↑ Glucagon postprandial | Variable | |
Motilin (secreted by M or Mo cells) | ↓ Hunger | ↓ (↑ with fasting) | ↑ Gastric motility, interdigestive migratory contractions (borborygmi) | ? | |
Ileum and/ or Large Intestine | FGF 19 [FGF 21 is produced by the liver] (secreted by ileal cells and regulated by farnesoid X receptors [FXR]) | ↓ Hunger | ↑ | ↓ Bile acids, glucose production ↑ Insulin sensitivity, glycogen synthesis | ↑ |
Glucagon like peptide-1 (secreted by ileum/colon L-cells) | ↓ Hunger | ↑ | ↑ Insulin ↓ Glucagon, gastric emptying | ↑ | |
Glucagon like peptide-2 (secreted by ileum/colon L-cells) | ↓ Hunger | ↑↑ | ↑ Glucose metabolism, intestinal mucosal growth, increases absorptive surface, epithelial brush-border nutrient transporters and digestive enzymes, intestinal blood flow, postprandial chylomicron secretion ↓ Gastrointestinal motility | ↑ | |
Oxyntomodulin (secreted by ileum/colon L-cells) | ↓ Hunger | ↑ | ↑ Glucagon-like peptide-1 (GLP-1) and glucagon receptor activity ↓ Gastric acid and gastric emptying | ↑ Gastric bypass − Sleeve gastrectomy | |
Peptide YY (secreted by ileum/colon L-cells) | ↓ Hunger | ↑ | ↓ Gall bladder and pancreatic secretions, gastric emptying | ↑ |
Bariatric Surgery
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Nutrient Considerations
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