As our pets eat their food, it passes from the stomach and into the small intestine. Whilst some of the digestive processes have already started, most of the chemical digestion that occurs in the small intestine relies on the activities of the pancreas, liver, and gallbladder. Let’s take a closer look at the function of the pancreas and its role in our pet’s digestion.
What is the Pancreas?
The pancreas is a gland found in the digestive system of our pet. It is made up of a head, a body and a pointy tail-like end. It is in the upper abdomen behind the stomach and carries out two main roles in the body:
The pancreas produces:
- Enzymes that break down foods in the intestine
- Hormones that regulate blood sugar levels
The pancreas is made up of small clusters of glandular epithelial cells. About 99% of these clusters constitute the exocrine portion of the organ.
These cells secrete a mixture of fluid and digestive enzymes known as pancreatic juice. Pancreatic juice consists mostly of water, but it also contains some salts, sodium bicarbonate and several enzymes. The sodium bicarbonate gives the pancreatic juice a slight alkalinity that buffers the stomach acid in the chyme that has just arrived in the small intestine. It also stops the action of pepsin and creates the correct pH for the action of the digestive enzymes to function.
The digestive juices that are made in the pancreas flow into the small intestine through a tube known as the pancreatic duct. In most bodies, this duct is joined by a similar duct coming from the gallbladder (the bile duct) before it reaches the small intestine. There is a circular muscle (sphincter) at the shared opening of the two ducts. This muscle controls the release of the digestive juices into the small intestine.
The digestive juices usually only start working once they enter the small intestine. But if the pancreas is inflamed (pancreatitis), they already become active in the pancreas. This can start causing a range of issues.
Digestive Enzymes
Enzymes are biological molecules (typically proteins) that significantly speed up the rate of virtually all of the chemical reactions that take place within cells.
When discussing the pancreas, there are three main types of enzymes:
- Lipases to break down fats
- Proteases to break down proteins
- Amylases to break down starch
The remaining 1% of the clusters called pancreatic islets (islets of Langerhans) form the endocrine portion of the pancreas. These cells secrete the hormones glucagon, insulin and more.
These hormones usually help to regulate blood glucose levels, stopping them from getting too high or too low.
Glucose Regulation
Glucose is a 6-carbon structure with the chemical formula C6H12O6. It is a source of energy for every organism in the world and is essential to fuel both aerobic and anaerobic cellular respiration.
Glucose often enters the body in isometric forms such as galactose and fructose (monosaccharides), lactose and sucrose (disaccharides), or starch (polysaccharide).
The body stores excess glucose as glycogen, which becomes liberated in times of fasting. Glucose is also derivable from products of fat and protein break-down through the process of gluconeogenesis.
Once glucose is in the body, it travels through the blood and to energy-requiring tissues. There, glucose is broken down in a series of biochemical reactions releasing energy in the form of ATP. The ATP derived from these processes is used to fuel virtually every energy-requiring process in the body.
As glucose is so important to life, it stands to reason that regulation of it is incredibly tight. And as we have noted, there are a number of hormones involved in this process.
Hormones involved in Glucose Regulation
Hormones Involved:
Insulin is a peptide hormone. Insulin plays an important role to keep plasma glucose value within a relatively narrow range throughout the day.
Insulin’s main actions are:
(1) In the liver, insulin promotes glycolysis and storage of glucose as glycogen (glycogenesis), as well as conversion of glucose to triglycerides
(2) In muscle, insulin promotes the uptake of glucose and its storage as glycogen
(3) in adipose tissue, insulin promotes uptake of glucose and its conversion to triglycerides for storage
Insulin lowers glucose levels.
Glucagon:
Glucagon acts exclusively on the liver to antagonise insulin effects on hepatocytes. It enhances glycogenolysis and gluconeogenesis. It also promotes oxidation of fat, which can lead to the formation of ketone bodies.
Glucagon increases glucose levels.
Levels of both insulin and glucagon vary depending on nutrient intake.
The Fed State:
The fed state occurs after a meal and is also known as the absorptive state. It is characterised by a high insulin to glucagon ratio.
Anabolic metabolism dominates in the fed state largely to replenish fuel stores, this is achieved by glycogen synthesis, fatty acid synthesis and protein and amino acid metabolism.
The Fasting State:
The fasting state occurs between meals and ensures a maintenance of blood glucose level. This state is characterised by a low insulin to glucagon ratio. This low insulin to glucagon ratio overall promotes catabolism in comparison to the fed state. In this state the major pathways include gluconeogenesis, glycogenolysis, protein catabolism, lipolysis, and ketone body metabolism
Endocrine cells secrete these respective hormones in response to external signals, such as nutrient intake or stress, via humoral, neural or hormonal signalling pathways.
The Brain-Islet Axis
The pancreas is highly innervated with both parasympathetic and sympathetic nerve fibres from the autonomic nervous system. At the same time, insulin receptors are widely distributed within the brain. In rat studies, lesions in various brain regions were shown to affect pancreatic hormone secretion.
Norepinephrine also inhibits insulin secretion, which is an important aspect of the fight-or-flight response.
Insulin release is stimulated by the cephalic phase, which is the period of anticipating a meal, to prepare the body to adequately respond to incoming nutrients.
The Liver-Islet Axis
The liver has a key role in glucose homeostasis by storing (glycogenesis) or releasing (glycogenolysis/gluconeogenesis) glucose.
The Gut-Islet Axis
The gut releases various hormones upon nutrient ingestion that bind to their respective receptors on pancreatic β-cells to potentiate insulin secretion. Incretins are a group of metabolic hormones that stimulate a decrease in blood glucose levels. They are released after eating and augment the secretion of insulin released from pancreatic beta cells of the islets of Langerhans by a blood glucose-dependent mechanism
Adipokines and Myokines – Islet Axis
Adipokines and myokines secreted from the adipose and muscle tissue, respectively, modulate insulin release.
Findings Here
When the Pancreas Goes Wrong
Exocrine Pancreatic Insufficiency
Exocrine pancreatic insufficiency (EPI) refers to reducing pancreatic enzyme activity (mainly pancreatic lipase) in the intestinal lumen below the threshold required for digestive functions. These changes could be due to inadequate pancreatic stimulation of pancreatic secretion, insufficient secretion of pancreatic digestive enzymes by the pancreatic cells, or outflow obstruction of the pancreatic duct, and inadequate mixing of the pancreatic enzymes with food.
Pets with EPI may present with clinical manifestations such as steatorrhea, flatulence, weight loss, and abdominal pain. EPI usually results in impaired of quality of life, increased risk of complications due to malnutrition and changes in bone density.
One of the main causes of EPI is pancreatitis.
Chronic pancreatitis is a condition affecting the pancreas where recurrent inflammation results. There are multiple theories for the pathogenesis of chronic pancreatitis, including toxic metabolic theory, oxidative stress theory, obstructive theory, and more.
Oxidative Stress Theory
Oxidative stress plays an important role in the pathogenesis of pancreatitis. Injury to the Pancreatic cells causes a complex cascade of events that includes increased production of reactive oxygen species (ROS) resulting in the oxidation of lipids and proteins and disruption of the pancreatic membrane.
Does My Dog Need Antioxidants?
Obstructive Theory
Obstruction is localized in the bile duct and pancreatic duct; what this means is that things aren’t flowing as they should. Obstruction can be anatomical, but it can also be associated with pre-existing health issues.
Biliary sludge is commonly seen in patients with recurrent acute pancreatitis. Gallbladder sludge is a collection of cholesterol, calcium, bilirubin, and other compounds that build up in the gallbladder. It is sometimes called biliary sludge because it occurs when bile stays in the gallbladder for too long.
What Can Go Wrong with My Dog’s Gallbladder?
There is also a theory linking chronic pancreatitis and pancreatic cancer to the exposure of environmental chemicals (xenobiotics). It is thought that islet cells play a role in detoxification processes and in autopsy studies, those with diminished pancreatic function possessed fewer enzymes to detoxify xenobiotics. Researchers concluded the expression of individual enzymes, and their distribution pancreatic cells may determine individual susceptibility to pancreatic disease. The take home here is to limit exposure to xenobiotics as much as possible.
Findings Here
Is Your Toxic Home Affecting Your Pet?
Does My Pet Need to Detox?
If you would like to learn more about pancreatitis, then check out our full guide below.
Pancreatitis: Natural Guide for Pets
If you have any concerns about your pet’s pancreatic function, check out our services to see if we can help.
Thanks for reading,
MPN Team
