Orie Yoshinari

Anti-diabetic effects of pumpkin and its components, trigonelline and nicotinic acid, on Goto-Kakizaki rats

The effects of a pumpkin paste concentrate and its components on oral glucose tolerance and serum lipid levels were determined in non-obese type 2 diabetic Goto-Kakizaki (GK) rats. In the oral glucose tolerance test, the pumpkin paste concentrate-fed group maintained a lower glucose level than the control group between 15 and 60 min. The compounds considered to be effective in improving glucose tolerance and contained in the methanol extract of the pumpkin in relatively abundant amounts were isolated and identified as trigonelline (TRG) and nicotinic acid (NA). Feeding a diet containing TRG and NA respectively improved and tended to improve glucose tolerance. The insulin level increased after 15 min in the TRG-fed GK rats and then gradually decreased over the next 120 min. In contrast, a gradual increase was seen in the insulin level over 120 min in the control GK rats not fed with TRG, suggesting that TRG could improve the insulin resistance. The serum and liver triglyceride (TG) levels in the TRG- and NA-fed GK rats were lower than those in the control GK rats. Lower activity of liver fatty acid synthase (FAS), and higher activity of liver carnitine palmitoyl transferase (CPT) and glucokinase (GLK) in the TRG- and NA-fed GK rats than in the control GK rats were observed. This suggests that the regulation of these enzyme activities by TRG and NA was closely related to the suppression of both TG accumulation and the progression of diabetes.

Trigonelline ameliorates oxidative stress in type 2 diabetic Goto-Kakizaki rats.

Previously, we showed that trigonelline (TRG) exerts antidiabetic effects in type 2 diabetic Goto-Kakizaki (GK) rats and also lowers blood and liver thiobarbituric acid reactive substances and urinary 8-hydroxydeoxyguanosine when compared with those levels in GK control rats without TRG. These results suggested that TRG also mitigates oxidative stress, which accelerates diabetes. In this study, the mechanisms of TRG prevention of oxidative stress were determined by measuring erythrocyte and liver antioxidant enzyme activities, and expressions of genes associated with reactive oxygen species production, and carbohydrate and lipid metabolisms by DNA microarray. Erythrocyte and liver glutathione peroxidase, and liver catalase activities in the GK rats fed with TRG were significantly lower than those of the GK control rats. TRG downregulated the gene expressions involved with NADPH oxidase and mitochondrial electron transfer system when compared with those of the GK control group. These results suggested that mitigation of diabetes by TRG is mediated by its ameliorating effects on oxidative stress.

Anti-diabetic effect of pyroglutamic acid in type 2 diabetic Goto-Kakizaki rats and KK-A y mice

With the rapidly increasing prevalence of type 2 diabetes mellitus (T2DM), specific dietary components with anti-diabetic efficacy could be one strategy with therapeutic potential. In the present study, the anti-diabetic effects of an amino acid, pyroglutamic acid (PA), found in vegetables and fruits were investigated in T2DM models using Goto-Kakizaki (GK) rats and KK-Ay mice by measuring glucose tolerance and other markers of diabetes. Moreover, the effect of PA on gene expression in GK rats was measured by DNA microarray analysis. Oral glucose tolerance and serum insulin levels were reduced by PA in both animal models. Serum and liver total cholesterol levels were also improved by PA. Expression of genes involved with gluconeogenesis and those involved with its related transcription factor were down-regulated by feeding PA. In KK-Ay mice, the glucokinase:glucose-6-phosphatase (G6Pase) activity ratio increased. From these results, it is suggested that dietary PA beneficially modifies glucose and lipid metabolism in diabetic animals, and can potentially contribute to the mitigation of T2DM.

Water-soluble undenatured type II collagen ameliorates collagen-induced arthritis in mice.

Earlier studies have reported the efficacy of type II collagen (C II) in treating rheumatoid arthritis (RA). However, a few studies have investigated the ability of the antigenic collagen to induce oral tolerance, which is defined as active nonresponse to an orally administered antigen. We hypothesized that water-soluble undenatured C II had a similar effect as C II in RA. The present study was designed to examine the oral administration of a novel, water-soluble, undenatured C II (commercially known as NEXT-II) on collagen-induced arthritis (CIA) in mice. In addition, the underlying mechanism of NEXT-II was also identified. After a booster dose (collagen-Freunds complete adjuvant), mice were assigned to control CIA group, or NEXT-II treatment group, to which saline and NEXT-II were administered, respectively. The arthritis index in the NEXT-II group was significantly lower compared with the CIA group. Serum IL-6 levels in the NEXT-II group were significantly lower compared with the CIA group, while serum IL-2 level was higher. Furthermore, oral administration of NEXT-II enhanced the proportion of CD4+CD25+T (Treg) cells, and gene expressions of stimulated dendritic cells induced markers for regulatory T cells such as forkhead box p3 (Foxp3), transforming growth factor (TGF)-β1, and CD25. These results demonstrated that orally administered water-soluble undenatured C II (NEXT-II) is highly efficacious in the suppression of CIA by inducing CD4+CD25+ Treg cells.

An Overview of a Novel, Water-Soluble Undenatured Type II Collagen (NEXT-II)

Background: Osteoarthritis, the most common form of arthritis, is a crippling, chronic debilitating bone disease that commonly affects humans, dogs, and horses. Inflammation and inflammatory responses are key factors for causing swelling, redness, pain, and loss of movement in arthritic animals and humans. Methods and Results: We developed a novel, water-soluble, undenatured type II collagen (NEXT-II) for osteoarthritis. NEXT-II demonstrated broad-spectrum safety and nonmutagenicity. NEXT-II exhibited significant efficacy in ameliorating pain and inflammation in collagen-induced arthritis in mice. NEXT-II enhanced the proportion of CD4+CD25+T cells, and gene expressions of stimulated dendritic cells induced markers for regulatory T cell such as forkhead box p3, transforming growth factor-β1, and CD25. Furthermore, NEXT-II was assessed in moderately arthritic dogs receiving either placebo or 10 mg NEXT-II over a period of 150 days. NEXT-II exhibited a significant reduction in overall pain, pain after limb manipulation, and pain after physical exertion compared to the control dogs. Physical health and serum chemistry (alanine aminotransferase, blood urea nitrogen, and creatine kinase) were not altered when these arthritic dogs were treated over a period of 150 days. Conclusions: These results demonstrate the broad-spectrum safety and efficacy of NEXT-II in ameliorating the symptoms of arthritis. Key Teaching Points: •A novel, water-soluble, undenatured type II collagen (NEXT-II) was developed for osteoarthritis. •The safety studies including acute oral and dermal toxicity, primary dermal and primary eye irritation, Ames’ bacterial reverse mutation assay, mouse lymphoma assay, and 150-day long-term safety studies were conducted. •NEXT-II exhibited significant efficacy in ameliorating pain and inflammation in collagen-induced arthritis in mice. •NEXT-II exhibited a significant reduction in overall pain in moderately arthritic dogs without changing physical parameters.

Antidiabetic Effects of Trigonelline: Comparison with Nicotinic Acid

The worldwide increase of diabetes mellitus is a serious problem because it induces many complex diseases. Although many foods are effective in preventing diabetes, the antidiabetic effect of trigonelline, which is naturally abundant in coffee, has not been examined in detail. In this essay, the antidiabetic effects of trigonelline on nonobese and obese models of type 2 diabetes mellitus are introduced. Furthermore, the effect of nicotinic acid, which is similar in its structure to trigonelline and partly produced from trigonelline, is determined and discussed.Abstract The worldwide increase of diabetes mellitus is a serious problem because it induces many complex diseases. Although many foods are effective in preventing diabetes, the antidiabetic effect of trigonelline, which is naturally abundant in coffee, has not been examined in detail. In this essay, the antidiabetic effects of trigonelline on nonobese and obese models of type 2 diabetes mellitus are introduced. Furthermore, the effect of nicotinic acid, which is similar in its structure to trigonelline and partly produced from trigonelline, is determined and discussed.