DT-109
Diapin evaluated several 3 amino acid (AA) peptides administered with a glucose challenge, increased plasma insulin, glucagon-like 1 (GLP-1), and decreased blood glucose in both control and diabetic mice. The most active of the peptides screened was designated as Diapin, now known as DT-109 and has the sequence glycine-glycine-L-leucine. DT-109 is also active in a dose-dependent manner in oral glucose tolerance tests (https://pubmed.ncbi.nlm.nih.gov/24386218).
Non-alcoholic fatty liver disease (NAFLD) and Non-alcoholic steatohepatitis (NASH)
Studies in Mice
DT-109 glycemic control studies in mice also demonstrated lipid profiles were improved. Therefore, DT-109's affects on fatty liver disease was evaluated. A high-fat, fructose, and cholesterol diet was fed to mice for 12 weeks to pre-establish NASH. Mice continued on the NASH diet and were administered vehicle (water) or DT-109. DT-109 reversed pre-established NASH. In addition, DT-109 lowered circulating glucose, lipids, transaminases, and proinflammatory cytokines. Metagenomics, transcriptomics, and metabolomics, used to explore the underlying mechanism indicated DT-109 induced hepatic fatty acid oxidation (FAO) pathways, lowered lipotoxicity, and stimulated de novo glutathione synthesis. DT-109 also reduced the Non-alcoholic Fatty Liver Disease Activity Score (NAS) and fibrosis. Inflammatory infiltration and hepatic fibrosis were attenuated through suppression of NF-κB target genes and TGFβ/SMAD signaling. In the microbiome, Clostridium sensu stricto was markedly increased with NASH induction and decreased with DT-109 treatment. These data were published in Science Translational Medicine (https://pubmed.ncbi.nlm.nih.gov/33268508/) and Redox Biology (https://doi.org/10.1016/j.redox.2022.102313).
Studies in Non-human Primates
DT-109 was studied in non-human primates and was effective in reversing NASH.
Type 2 diabetes
In vitro studies
In vitro studies in immortalized pancreatic β cells, DT-109 increased insulin secretion into the culture medium. The response was observed in the presence or absence of glucose. Additional studies showed that DT-109 stimulates secretion of GLP-1 from an intestinal L cell line. Taken together, these results indicate DT-109 directly acts on pancreatic-derived cells to stimulate insulin secretion and on endocrine L-cells to secrete GLP-1. Direct effects on these cell lines suggest that DT-109 may act directly on the pancreas in vivo (https://pubmed.ncbi.nlm.nih.gov/24386218/).
A DT-109 chow diet-admixture administered to diabetic KKay mice for 4-weeks reduced blood glucose levels by 50% compared to untreated mice (Figure 4) (https://pubmed.ncbi.nlm.nih.gov/24386218/).
In acute oral glucose tolerance tests, DT-109 lowered blood glucose compared to vehicle treated controls (Figure 5).
Similar results were obtained in C57BL/6J mice fed either starch or glucose. The individual amino acids that comprise DT-109 had no significant effect on blood glucose in identical experiments at equivalent molar ratios.
DT-109 was also active when administered 30-60 min prior to glucose challenge. In C57BL/6J mice not challenged with glucose, DT-109 administration did not cause hypoglycemia, as the agent did not lower blood glucose over a 3 hr period.
Blood glucose was measured weekly in adult male Kkay diabetic mice (N=10/group) fed either a control (Group 1) or two separate dose levels of DT-109 containing chow diets (Groups 2 and 3). Blood glucose levels were significantly lower in the DT-109 treated groups compared to the control group.
DT-109 lowered blood glucose, in part, due to its ability to increase plasma insulin levels compared to the control group. With DT-109, the incretin protein GLP-1 (Figure 6A) and insulin (Figure 6B) increased more than twice the level observed in control treated animals 30 minutes after a glucose challenge.
Figure 5. Effect of DT-109 on blood glucose after oral load of glucose and DT-109 in KKAy diabetic mice.
Control Glucose 1.5mg/g
DT-109 1mg/g+Glucose 1.5mg/g
Figure 4. DT-109 decreases the blood glucose level of Kkay diabetes mouse in time- and dose-dependent manner.
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DT-109 Reverses Diet-Induced Non-Alcoholic Fatty Liver Disease Progression
C57BL/6J mice were fed a chow or a high-fat, fructose, and cholesterol (NASH-diet) diet for 12 weeks. Mice on the chow diet were then orally administered H20, while mice continued on the NASH-diet were administered either H20 or 0.5 mg/g/day DT-109 for an additional 12 weeks. Typical examples of whole liver (top row), Oil-red O staining for lipid droplets (middle row) and sirius red staining for collagen indicating fibrosis (lower row) in liver slices are shown for each condition.
glycine-glycine-L-leucine
Adult male Kkay diabetic mice were purchased from Jackson Lab. Control group was fed with regular chaw diet. Two Diapin groups were given different doses of Diapin mixed into the chow diet. Blood glucose was measured weekly. N=10/group. Blood glucose levels were significantly lower in the Diapin treated groups than in the control.
Adult male Kkay diabetic mice were purchased from Jackson Lab. In control group (red line, n=10), glucose was orally administered at dose of 1.5mg/g BW. In the DT-109 group (blue line, n=9), glucose and DT-109 were orally administered at doses of 1.5mg/g BW and 1mg/g BW, respectively. Blood glucose was measured at 0, 30, 60, 90 and 120 min after dosing. Blood glucose levels at 30, 60, 90 and 120 min in the Diapin group were significantly lower than those in the control group.
Figure 6. Effect of DT-109 on Plasma Glucacon-like Peptide-1 (GLP-1) and Insulin Levels in KKay Diabetic Mice 30 Minutes After an Oral Glucose Challenge
DT-109 1mg/g+Glucose 1.5mg/g
Control Glucose 1.5mg/g
Blood GLP-1 (pmol/L)
Control Glucose 1.5mg/g
DT-109 1mg/g+Glucose 1.5mg/g
Adult male KKay diabetic mice were purchased from Jackson Lab. Under fasting condition, in the control group (red bar, n=11), glucose was orally administered at dose of 1.5mg/g BW. In the DT-109 group (blue bar, n=11), DT-109 and glucose were orally administered at 1mg/g BW and 1.5mg/g BW, respectively. Blood samples were collected at 30 min after oral administration of glucose and DT-109. Plasma GLP-1 and insulin were measured.
To explore the structure-activity relationship of DT-109 on blood glucose, modifications were made to both the amino and carboxy termini of the peptide. Neither amidation of the carboxy terminus nor acetylation of the amino terminus had any significant effect on DT-109 activity either alone or in combination. The amino acid composition of DT-109 includes glycine and leucine. To determine if other amino acids could be substituted, the basic and polar histidine (GGH) was substituted for the neutral, non-polar leucine at the C terminus of DT-109. When administered with glucose, GGH had no effect on blood glucose compared to vehicle treated controls. This result suggests that there is a limitation to what amino acids can be substituted in the DT-109 molecule and retain activity.
DT-109 was characterized in three separate models (Figure 7). Treatment of diabetic KKay mice with DT-109 significantly increased plasma insulin levels (Figure 7A). Following oral administration of DT-109 in C57BL/6J mice demonstrated appearance of the drug in plasma peaking at 30 minutes at 27 nmol/dL (Figure 7B). INS-1 cells, a rat insulin secreting cell line, secrete insulin in a concentration-dependent manner in response to DT-109 (Figure 7C). These data were published by Zhang et al (https://journals.plos.org/plosone/article/authors?id=10.1371/journal.pone.0083509).
A. Plasma insulin levels in DT-109 treated diabetic mice. Fasted male KKay mice (n = 11/group) were orally administered either glucose (1.5mg/g) or DT-109 plus glucose (1.5mg/g). Blood samples were collected after 30 min for plasma insulin determination. B. DT-109 concentration in mouse plasma. Fasted male C57BL/6J mice (n=5/group) were orally administered DT-109 (1 mg/g bw) plus glucose (2 mg/g bw). Blood samples were periodically collected and DT-109 concentration was measured by an LC-MS/MS system. C. Effect of DT-109 on insulin secretion. INS-1 cells were treated with various concentration of DT-109 for 1 hour and supernatants were collected for insulin concentration. *P<0.05, compared with that in the absence of DT-109.
This reflects a low bioavailability of the peptide. This result, in combination with in vitro studies demonstrating a direct effect of on a pancreatic b cell line suggests that at least some of the effect of DT-109 is due to direct activity on pancreatic cells and intestinal L cells (https://journals.plos.org/plosone/article/authors?id=10.1371/journal.pone.0083509).
Arteriosclerosis/Coronary Artery Disease
DT-109 has been shown to prevent and treat atherosclerosis in an ApoE-/- mouse model fed a western diet (https://pubmed.ncbi.nlm.nih.gov/35447412/). Glycine deficiency has been documented in patients with significant coronary artery disease. Glycine deficiency exacerbates atherosclerosis in ApoE-/- mice. Either glycine or DT-109-treatment provides an athero-protective effect evidenced by reduced atherosclerosis in the whole aorta and aortic sinus concomitant with reduced superoxide formation. DT-109 activity was superior compared to that of glycine. In ApoE-/- mice with established atherosclerosis, DT-109 treatment significantly reduced atherosclerosis and superoxide, independent of lipid lowering effects. Mechanistic studies revealed that DT-109 induces glutathione formation in mononuclear cells (https://pubmed.ncbi.nlm.nih.gov/35447412/), (See Award+)