by Dr. Mark Edwards
eptides are molecules formed by joining two to 50 amino acids. Larger amino acid sequences are called proteins. Peptides and proteins are present in every living cell and possess a variety of biochemical activities. They appear as enzymes, hormones, antibiotics, receptors, carriers and signal enhancers. Peptides may be harvested from a number of sources but algae are convenient because algae present simple cells.
Peptides and diabetes
A recent theory by a Harvard Medical School faculty team proposes that poorly presented peptides are more likely to cause diabetes and other autoimmune diseases, because they allow autoimmune T cells to escape deletion in the thymus. Once they begin circulating in the body, T cells are stimulated when they encounter high concentrations of the peptides that have been processed differently outside the thymus.
The connecting peptide, or C-peptide, is a short 31-amino-acid protein that connects insulin’s A-chain to its B-chain in the proinsulin molecule. A C-peptide test measures the level of the peptide in the blood, which provides a valuable metric for diabetes diagnostics. Insulin helps the body use and control the amount of glucose in the blood. The level of C-peptide blood test shows how much insulin the pancreas makes because C-peptide is found in amounts equal to insulin. The C-peptide does not affect the blood sugar level in the body.
Peptides are released into circulation at the onset of eating or shortly thereafter. Some act as satiety peptides. They provide feedback that tells the brain the stomach is full and to stop eating. Among these are the intestinal peptide, cholecystokinin (CCK), and the pancreatic peptides, glucagon and amylin. CCK was the first gut peptide shown to play a role in the control of eating. CCK peptides have been shown to create a feeling of fullness that inhibits food intake beyond individual meals and can do so over multiple days.
Peptides offer a therapeutic strategy to both mimic and enhance the body’s own satiety signals. The gut hormone peptide tyrosine (PYY), which is released postprandially from the gastrointestinal tract, has recently been shown to be a physiological regulator of food intake. In humans, a single 90-minute infusion of PYY markedly reduced subsequent 24-hour caloric intake in lean, normal-weight as well as obese subjects. Obese subjects have been found to have low levels of fasting and postprandial PYY, suggesting a role for this hormone in the pathogenesis of obesity.
Research at Indiana University offers hope for peptides that reduce obesity. Obese rodents were injected with a synthetic peptide that simultaneously mimicked two naturally occurring hormones. The synthetic molecule possessed key features of two natural peptide hormones, glucagon and glucagon-like peptide-1 (GLP-1), which are involved in regulating glucose metabolism and appetite control. When injected into obese mice, after one week the animals’ body weights had decreased by 25% and their body fat by 42%. Repeated treatment resulted in greater effect.
Biological differences between rodents and primates are a major hurdle for translation of anti-obesity and anti-diabetic strategies either discovered or developed in rodents to effective human therapeutics. Monkeys are closer relatives to humans and provide higher validity in medical research than rodents. Obese monkeys were given a peptide compound called adipotide. They lost 7 to 15% of their body weight and 14% off their waist. Adipotide resulted in rapid weight loss and improved insulin resistance in the obese monkeys.
UCLA researchers demonstrated that an algae-based dietary supplement called GABA might help inhibit development of insulin resistance and glucose intolerance. Both conditions are precursors to the development of Type 2 diabetes and metabolic syndrome. A naturally produced amino acid-like molecule, GABA was given orally to mice that were obese, insulin resistant and in the early stages of Type 2 diabetes. GABA suppressed the inflammatory immune responses that are involved in the development of this condition. GABA helped prevent disease progression and improved glucose tolerance and insulin sensitivity, even after onset of Type 2 diabetes in mice. Researchers also identified the regulatory immune cells that likely direct GABA’s activity in inhibiting inflammation. GABA taken as a supplement or related medications may provide new therapeutic agents for the treatment of obesity-related Type 2 diabetes and metabolic syndrome.
Immune system defense
Peptides activate the immune system, which increases growth and survival rates in meat and dairy animals. These tiny segments of protein increase the number, size and weight of eggs in fowl and increase hatch rate. Peptides counter bacterial and endotoxin anorexic effects, which improves health and vitality.
Antimicrobial peptides make up a part of the innate immunity of most organisms and are often involved in the immune system’s first line of defense when faced with an invader. Defensins peptides consist of 18-45 amino acids attached to small cysteine-rich cationic proteins. Defensins function as host defense peptides and are active against bacteria, fungi and many viruses. The immune system uses these antimicrobial peptides to assist in killing bacteria, by binding to the microbial cell membrane. Once embedded, they form pore-like membrane defects that allow cells to pump out unwanted toxic substances or allow entry of essential ions and nutrients. Protegrins are small peptides containing 16-18 amino acid residues. Protegrins are also highly microbicidal and also create membrane disruption, similar to other antibiotic peptides.
Algae-based bioactive peptides add significant value to food and animal feed. Natural algae peptides can reduce the total cost of growing animals by improving nutrient uptake, which reduces total food intake and animal waste. Peptides can add sensory appeal to foods, including color, aroma, mouth appeal and taste. Peptides can reduce animal stress, enhance digestibility and improve growth and development. Algae bioactive peptides offer a rich new set of medical products for people and animals.