Insulin and glucagon response of the diabetic Chinese hamster in the Asahikawa colony

Expanded Chinese hamster organ and cell line proteomics profiling reveals tissue-specific functionalities

Chinese hamster ovary (CHO) cells are the predominant production vehicle for biotherapeutics. Quantitative proteomics data were obtained from two CHO cell lines (CHO-S and CHO DG44) and compared with seven Chinese hamster (Cricetulus griseus) tissues (brain, heart, kidney, liver, lung, ovary and spleen) by tandem mass tag (TMT) labeling followed by mass spectrometry, providing a comprehensive hamster tissue and cell line proteomics atlas. Of the 8470 unique proteins identified, high similarity was observed between CHO-S and CHO DG44 and included increases in proteins involved in DNA replication, cell cycle, RNA processing, and chromosome processing. Alternatively, gene ontology and pathway analysis in tissues indicated increased protein intensities related to important tissue functionalities. Proteins enriched in the brain included those involved in acidic amino acid metabolism, Golgi apparatus, and ion and phospholipid transport. The lung showed enrichment in proteins involved in BCAA catabolism, ROS metabolism, vesicle trafficking, and lipid synthesis while the ovary exhibited enrichments in extracellular matrix and adhesion proteins. The heart proteome included vasoconstriction, complement activation, and lipoprotein metabolism enrichments. These detailed comparisons of CHO cell lines and hamster tissues will enhance understanding of the relationship between proteins and tissue function and pinpoint potential pathways of biotechnological relevance for future cell engineering.

Cell type-specific activation of metabolism reveals that beta-cell secretion suppresses glucagon release from alpha-cells in rat pancreatic islets

Abnormal glucagon secretion is often associated with diabetes mellitus. However, the mechanisms by which nutrients modulate glucagon secretion remain poorly understood. Paracrine modulation by beta- or delta-cells is among the postulated mechanisms. Herein we present further evidence of the paracrine mechanism. First, to activate cellular metabolism and thus hormone secretion in response to specific secretagogues, we engineered insulinoma INS-1E cells using an adenovirus-mediated expression system. Expression of the Na+-dependent dicarboxylate transporter (NaDC)-1 resulted in 2.5- to 4.6-fold (P < 0.01) increases in insulin secretion in response to various tricarboxylic acid cycle intermediates. Similarly, expression of glycerol kinase (GlyK) increased insulin secretion 3.8- or 4.2-fold (P < 0.01) in response to glycerol or dihydroxyacetone, respectively. This cell engineering method was then modified, using the Cre-loxP switching system, to activate beta-cells and non-beta-cells separately in rat islets. NaDC-1 expression only in non-beta-cells, among which alpha-cells are predominant, caused an increase (by 1.8-fold, P < 0.05) in glucagon secretion in response to malate or succinate. However, the increase in glucagon release was prevented when NaDC-1 was expressed in whole islets, i.e., both beta-cells and non-beta-cells. Similarly, an increase in glucagon release with glycerol was observed when GlyK was expressed only in non-beta-cells but not when it was expressed in whole islets. Furthermore, dicarboxylates suppressed basal glucagon secretion by 30% (P < 0.05) when NaDC-1 was expressed only in beta-cells. These data demonstrate that glucagon secretion from rat alpha-cells depends on beta-cell activation and provide insights into the coordinated mechanisms underlying hormone secretion from pancreatic islets.

Increased levels of advanced glycosylation end products in the kidney and liver from spontaneously diabetic Chinese hamsters determined by immunochemical assay

Increased levels of advanced glycosylation end products (AGEs) have been reported in tissues in association with diabetes mellitus. Thus, we measured tissue AGE levels and detected an accumulation of AGEs in the kidney and liver from spontaneously diabetic Chinese hamsters (CHAD) to determine the relationship between AGEs and diabetes mellitus. Diabetic CHAD aged 12 to 13 months were studied together with age-matched nondiabetic CHAD. We used an AGE-specific noncompetitive enzyme-linked immunosorbent assay (ELISA) with polyclonal anti-AGE-bovine serum albumin (BSA) antibody to measure tissue AGE levels. The samples extracted from the kidney and liver obtained from diabetic and nondiabetic CHAD reacted with anti-AGE-BSA antibody. When the absorbance of standard AGE-BSA (0.1 microg/mL) was expressed as 1 U, AGE levels in the kidney and liver from diabetic CHAD were significantly increased as compared with nondiabetic CHAD (kidney, 0.26 +/- 0.05 v 0.10 +/- 0.03 U/microg protein, P< .01; liver, 0.20 +/- 0.03 v 0.09 +/- 0.02 U/microg protein, P< .01). Positive AGE staining was observed in the renal cortex, especially in the tubules of diabetic CHAD, but little AGE staining was observed in the glomerulus by the immunohistochemical study. AGE staining was diffuse in the hepatocytes. These AGE levels were significantly correlated with fasting plasma glucose and glycated hemoglobin (P < .01, respectively). In conclusion, we have confirmed that AGE structures were expressed in the kidney and liver from CHAD, and these AGE levels were increased in diabetic CHAD. AGE staining was observed in the renal tubules and hepatocytes. Tissue AGE levels were positively correlated with glycemic control in CHAD.

Cadmium-metallothionein nephrotoxicity is increased in genetically diabetic as compared with normal Chinese hamsters

To investigate the extra susceptibility of diabetics to some nephrotoxic agents, adult normal and diabetic Chinese hamsters (6-7 animals in each group) were injected subcutaneously with different doses of cadmium-metallothionein (Cd-MT) equivalent to 0.0, 0.1 or 0.25 mg Cd/kg body weight and the first 24 hr urinary outputs were collected. Several days prior to exposure to the Cd-MT the diabetic hamsters were hyperglycaemic, and plasma insulin levels and body weights were elevated in some of the diabetics. The higher dose of Cd-MT caused significant spillage of N-acetyl-beta-glucosaminidase (U-NAG) activity and protein into the urine of both normal and diabetic animals. The higher dose of Cd-MT was more toxic to the diabetic kidneys because U-NAG levels were higher in the diabetics (2.5-fold higher than normal). U-Cd levels were proportional to the injected Cd-MT dose. U-Zn levels were not consistently affected by the injected Cd-MT although it had contained small amounts of Zn. Therefore, genetic diabetes in the Chinese hamster appears to increase susceptibility to acute cadmium-MT nephrotoxicity. The mechanisms underlying this need to be further investigated.

Natural history of B-cell dysfunction in spontaneously diabetic Chinese hamsters

To elucidate the pathogenesis of diabetes in spontaneously diabetic Chinese hamsters (CHAD strain), a longitudinal study from just after weaning to overt diabetic state was performed. Fasting and non-fasting plasma glucose, non-fasting plasma insulin and pancreatic hormone contents (insulin, glucagon and amylin) were measured, and light microscopic examination of pancreatic islets by immunohistochemical technique and pancreas perfusion study were performed. No insulitis was found in the islets of the CHAD strain. In animals aged 1 month, there was no significant difference in the percentage of B-cell area to islet area between the CHAD strain and the control. At this stage, hyperinsulinemia was observed despite normal plasma glucose levels both in fasting and non-fasting states. In the animals of the CHAD strain aged 2-4 months, insulin secretion from the pancreas, pancreatic insulin content and non-fasting plasma insulin level decreased in proportion to the decrease of B-cell mass. In animals aged about ten months, severe hyperglycemia and hypoinsulinemia were observed. We demonstrated the existence of amylin-like immunoreactivity in the B-cells of Chinese hamsters. However, no amyloid deposit was observed in the islets of the CHAD strain. After the onset of diabetes, amylin secretion from the pancreas and pancreatic amylin content in the CHAD strain were significantly lower than those in the control. We demonstrated the natural history of B-cell dysfunction in the CHAD strain. It could mean the process of B-cell exhaustion. The profile of the CHAD strain is similar to some types of human NIDDM. Therefore, the CHAD strain is a useful diabetic model in the study of NIDDM.

Polyol pathway in tissues of spontaneously diabetic Chinese hamsters (Cricetulus griseus) and the effect of an aldose reductase inhibitor, ONO-2235

1. Sorbitol and fructose levels were significantly elevated in the lens, the sciatic nerve, the retina and the kidney of diabetic Chinese hamsters and inositol level was significantly decreased in the lens and sciatic nerve of diabetics. 2. The activity of an aldose reductase in the kidney was not different between normal and diabetic Chinese hamsters. 3. An aldose reductase inhibitor (ONO-2235) had no effect in sorbitol, fructose and inositol contents of all these tissues from diabetic Chinese hamsters. 4. These results suggest that diabetic Chinese hamsters produce polyol accumulation in tissues but that there is a clear species-specific difference to inhibition of aldose reductase.

Decreased autophosphorylation and kinase activity of insulin receptors in diabetic Chinese hamsters

To clarify the role of the insulin receptor in diabetes, the hepatic insulin receptor was investigated in the spontaneously diabetic Chinese hamsters, which are the animal models for insulin-deficient diabetes. Insulin binding in the diabetic animals increased mainly due to an increase in the number of receptors. It was also observed that both the autophosphorylation and kinase activity of the hepatic insulin receptor were decreased in the diabetic animals compared to the control animals. These changes in the hepatic insulin receptor may be caused by the diabetes itself. As the phosphorylated protein of 95 kDa was immunoprecipitated by the anti-insulin receptor antibody (B-10, human) in both diabetics and controls, it was supposed that the 95 kDa protein would be the beta-subunit of insulin receptors, as in other animals. These animals seem to be useful for examining insulin receptors in diabetes.

Changes in the pancreatic A-, B- and D-cell populations during development of diabetes in spontaneously diabetic Chinese hamsters of the Asahikawa colony (CHAD)

We investigated the pathological changes in pancreatic islets during the development of diabetes in spontaneously diabetic Chinese hamsters of the Asahikawa colony (CHAD), using morphometric analysis and specific immunocytochemical methods. We also investigated the relationships between changes in islet cell composition and the hormonal changes in the plasma and pancreas. Plasma and pancreatic insulin levels were significantly lower in diabetic hamsters than in pre-diabetic hamsters. However, plasma insulin levels in the pre-diabetic hamsters were significantly higher than those in the hamsters from the non-diabetic control strain, although the pancreatic insulin content in the pre-diabetics was significantly lower than that in the non-diabetics. Since even a severely diabetic CHAD is alive for many months after the onset of the disease without injections of insulin, its clinical course seems to be close to that of type 2 human diabetes. In contrast, plasma and pancreatic glucagon levels were significantly higher in diabetic hamsters than in non-diabetics and pre-diabetics. There were significantly positive correlations between plasma and pancreatic insulin, and plasma and pancreatic glucagon levels in CHAD (P less than 0.01). On the other hand, no significant differences in the pancreatic somatostatin content were found among the non-diabetics, pre-diabetics, and severe diabetics. Significant correlations were found between plasma and pancreatic hormone levels (except for somatostatin) and the advance of diabetes in CHAD (P less than 0.01). Morphometric analysis by planimeter revealed that islets in the severe diabetics were 25% smaller than in the pre-diabetics. Significantly less B-cell area within the diabetic islets was found when compared with the non-diabetic and pre-diabetic islets. Significantly larger A- and D-cell areas within the diabetic islets were found compared with the non-diabetic and pre-diabetic islets. There was a significant correlation between the areas of the three types of cell within the islets and the severity of diabetes (P less than 0.01). It is suggested, therefore, that the pancreatic islet function in CHAD is closely associated with the morphologic changes in islet endocrine cells. The elevation of plasma and pancreatic glucagon levels and the marked increase of the A-cell area within the islets from severely diabetic CHAD may reveal an absolute increase of A-cell numbers.

Metabolic and morphological changes of the heart in Chinese hamsters (CHAD strain) with spontaneous long-term diabetes

We studied the effect of spontaneous long-term (9-10 months) diabetes on the heart of Chinese hamsters (CHAD strain) to elucidate the relationship between diabetes mellitus and cardiomyopathy. The diabetic hamsters, aged approximately 11 months, showed body weight loss, hyperglycemia (mean fasting plasma glucose 402 mg/dl), hypoinsulinemia, hyperlipidemia and ketonemia. The diabetic hamsters showed reduced activities of cytoplasmic glycolytic key enzymes; hexokinase, pyruvate kinase and phosphofructokinase, increases in cardiac glycogen and glucose-6-phosphate contents and a 40% decrease in cardiac ATP content, indicating decreased energy production. An accumulation of myocardial triglyceride and cholesterol was found in the diabetic hamsters. In addition, the cardiac norepinephrine content was increased in the diabetic hamsters, suggesting the presence of autonomic nervous disorder. Increased heart weight and thickening of the septum and both ventricular walls were found in the diabetic hamsters. Light-microscopic analysis revealed that 42.9% of the diabetic hamsters had myocardial degeneration without any vascular lesion of extramural large and intramural small vessels, whereas the non-diabetic controls had no myocardial or vascular lesions. These data suggest that the diabetic Chinese hamsters had cardiomyopathy, which is possibly caused by extravascular factors such as metabolic or autonomic nervous disorder although conclusive evidence is lacking.

Paradoxical glucagon response in perifused islets of the diabetic Chinese hamster

Dynamic insulin and glucagon response to glucose was examined in the perifusion system to investigate the relationship between pancreatic hormone content and the pattern of hormone secretion in diabetic Chinese hamsters of the Asahikawa colony (CHA). Isolated islets of normals and diabetics from the CHA were perifused. When the medium was changed to high glucose (500 mg/dl), a low insulin response and paradoxical glucagon response were seen in diabetics compared with normals. Positive correlations were found between pancreatic insulin and the amount of perifusate insulin, and glucagon content and glucagon release, respectively. It is suggested, accordingly, that pancreatic hormone content is related to the amount of hormone release in CHA. A negative correlation between the amount of perifusate insulin and glucagon release was found. It is suggested, therefore, that an impaired suppression of glucagon release in the diabetic CHA animals could be attributed at least to insulin deficiency. These findings agree with the histological discovery of decreased B-cells and increased A-cells in the diabetic islets. Both decreased B-cells and islet numbers could be the cause of the low insulin response to glucose. Increased numbers of A-cells with hyperfunction resulting from local insulin deficiency could be the cause of the paradoxical glucagon response.