A new genetically obese-hyperglycemic rat (Wistar fatty).

The fa-gene was transferred from the Zucker rat (13 M strain) to the Wistar Kyoto (WKY) rat. The survey, performed at the 10th generation of backcrossing, showed that Wistar fatty rats (fa/fa), a congenic strain of WKY, developed obesity and obesity-related features, such as hyperinsulinemia and hyperlipemia, in the same manner as Zucker fatty rats. Males, but not females, showed hyperglycemia, glucosuria, and polyuria as early as 8 wk of age. Tolerance and insulin response to oral glucose were decreased with advancing age in males. The diabetic changes appeared to be caused by an interaction between predisposition to develop diabetes in the WKY rat and fa-induced obesity. This is because WKY rats were found to be less sensitive to insulin than Zucker rats by both the glucose tolerance test and the steady-state blood glucose method which estimates overall insulin sensitivity.

Reduction of insulin resistance in obese and/or diabetic animals by 5-[4-(1-methylcyclohexylmethoxy)benzyl]-thiazolidine-2,4-dione (ADD-3878, U-63,287, ciglitazone), a new antidiabetic agent.

Effects of 5-[4-(1-methylcyclohexylmethoxy)benzyl]-thiazolidine-2,4-dione (ADD-3878, U-63,287, Ciglitazone) on glucose and lipid metabolism were examined in various animal models. ADD-3878, administered as a dietary admixture (30-186 mg/kg/day) to obese-diabetic yellow KK (KK-Ay) mice, markedly suppressed the diabetic syndromes (hyperglycemia, hypertriglyceridemia, and hyperinsulinemia), accompanied by the reduction of insulin resistance as manifested by improvement of overall insulin sensitivity in either the insulin tolerance test or the steady-state blood glucose test. Chronic administration of ADD-3878 for as long as 12 wk to young yellow KK mice, which were in the early stage of diabetes and obesity, depressed age-dependent rises in blood glucose, plasma triglyceride, and insulin without exerting any effect on obesity. When orally administered to obese Zucker-fatty rats, ADD-3878 decreased plasma insulin and triglyceride in a dose-dependent manner (5-100 mg/kg/day). The treated rats showed increased tolerance and decreased insulin secretion in response to oral glucose. The glycemic response to insulin and the steady-state plasma glucose were also normalized in the treated rats. Chronic administration of ADD-3878 to young fatty rats for as long as 12 wk decreased the dose-dependent rises in blood glucose, plasma triglyceride, and insulin without exerting any effect on body weight. ADD-3878 had no effect on glucose and lipid metabolism of young Sprague-Dawley rats and mild streptozotocin-diabetic rats. However, in old Sprague-Dawley rats that were moderately insulin resistant and hyperlipidemic compared with young ones, ADD-3878 decreased plasma triglyceride and insulin and improved insulin sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin-like activities and insulin-potentiating actions of a modified insulin B21-26 fragment: beta-Ala-Arg-Gly-Phe-Phe-Tyr-NH2.

A modified sequence of insulin B21-26, beta-Ala-Arg-Gly-Phe-Phe-Tyr-NH2 (DP-432), was synthesized and tested for its biological activities. The hexapeptide, ip injected to mice, stimulated [U-14C]-glucose incorporation into diaphragm glycogen and adipose tissue total lipid. Neither plasma glucose nor FFA (free fatty acid) was reduced by the injection. However, when injected with epinephrine, the peptide prevented a rise of plasma FFA but not that of plasma glucose due to epinephrine. In vitro, the peptide stimulated glucose oxidation and inhibited epinephrine- or isoproterenol-stimulated lipolysis of mouse adipose tissue. Furthermore, when added along with insulin to incubation media, the peptide exaggerated the effects of insulin on both glucose oxidation and isoproterenol-stimulated lipolysis. The hexapeptide thus seems to have an insulin-potentiating action as well as insulin like activities on peripheral tissue.

Emeriamine, an antidiabetic beta-aminobetaine derived from a novel fungal metabolite.

Emeriamine [(R)-3-amino-4-trimethylaminobutyric acid], derived from a novel fungal metabolite "emericedin" [(R)-3-acetylamino-4-trimethylaminobutyric acid], was proved to be a strong and specific inhibitor of carnitine-dependent oxidation of long chain fatty acid (IC50; 3.2 X 10(-6)M) and its main inhibition site was shown to be carnitine palmitoyltransferase I located on the outer-surface of the mitochondrial inner membrane. Emeriamine also showed hypoglycemic and antiketogenic activities in a dose-dependent manner (1 - 10 mg/kg) when administered orally to fasted normal and diabetic animals.

Feeding in response to insulin and 2-deoxy-D-glucose in Zucker rats on dietary self-selection.

Adult male fatty and lean rats of Zucker strain were given access ad libitum to either a single nutritionally complete diet, or a self-selection regime with separate sources of three macronutrients, protein (casein), fat (hydrogenated coconut oil), and carbohydrate (sucrose). Animals on the single diet were fed on a powdered stock diet, and then switched to the self-selection regime. Energy intake on the self-selection regime was the same as that for the single diet condition in both fatty and lean rats. Fatty rats consumed 45% more energy than did their lean littermates. Further, fatty rats selected 47.0% of their total calories as protein, 30.1% as fat, and 22.9% as carbohydrate. The respective percentages for lean rats were 56.1, 13.0 and 30.9. In lean rats, the injection of insulin (10 U/kg) or 2-deoxy-D-glucose (500 mg/kg, 2DG) failed to increase energy intake, but increased carbohydrate intake 2 times by attenuating protein intake. Also in fatty rats, insulin did not increase energy intake, but it did increase carbohydrate by 50% by attenuating fat intake. 2DG decreased energy intake by attenuating carbohydrate and fat intakes in fatty rats. Fatty rats were slightly less hypoglycemic to insulin, but more hyperglycemic to 2DG than lean rats. These different self-selection patterns of fatty rats seemed to be associated with their endocrine, metabolic, and behavioral abnormalities.

Selective inhibition by neuraminidase of insulin action on hexose metabolism of mouse adipocytes.

Mouse adipocytes treated with neuraminidase showed a decreased response of glucose oxidation to insulin although insulin binding to the cells was normal. The decreased response was associated with the release of sialic acids from the cells by enzyme digestion. The hormone action on 2-deoxyglucose uptake was also decreased. However, the hormone action on glyceride-glycerol synthesis or lipogenesis from glucose was unaltered when enzyme-treated cells were incubated with higher glucose concentration (greater than or equal to 5 mM). However, at lower glucose concentrations (< 5 mM), in which glucose transport was a rate-limiting step, the hormone action was markedly decreased. When fructose was used as a substrate, the enzyme-treated cells showed an impaired response to insulin in fructose oxidation but not in glyceride-glycerol synthesis and lipogenesis from fructose. These results suggest that the postreceptor systems of insulin action on glyceride-glycerol synthesis and lipogenesis from hexose are different from those of the hormone action on hexose transport and oxidation. Furthermore, alteration in insulin-sensitive metabolic profiles may be caused, in part, by changes in glycoproteins and/or glycoplipids on the cell surface.

Determination of overall insulin sensitivity in diabetic mice, KK.

A convenient methods for determining the overall insulin sensitivity of small animals was established based on the steady state plasma glucose (SSPG) concentration methods of Shen, Reaven and Farguhar (1970). Subcutaneous injection into C57BL/6 mice of saline containing epinephrine, propranolol, glucose and (3H-3)glucose with or without insulin gave steady state levels of blood glucose (SSBG), plasma insulin (SSPI) and specific activity of blood glucose (SSBG), plasma insulin (SSPI) and specific activity of blood glucose after 45 minutes. Glucose turnover (GTN) and hepatic glucose output (HGO) were computed using specific activity of blood glucose and the influx rate of injected glucose. The method was applied to diabetic and insulin resistant mice, KK. There was no difference in GTN and HGO between KK and C57BL/6 mice regardless of whether insulin was injected or not. SSPI of both strains increased in the same injected or not, SSPI of both strains increased in the same injected or not. SSPI of both strains increased in the same fashion in response to increasing doses of the hormone. SSBG of both strains fell in response to increasing SSPI level, but the response of SSBG was less prominent in KK mice. Consequently, the insulin dose-response curve of SSBG apparently shifted rightwards in KK mice.

Inhibitory effect of idebenone (CV-2619), a novel compound, on vascular lesions in hypertensive rats.

The effects of a novel compound, 6-(10-hydroxydecyl)-2,3-dimethoxy-5-methyl-1,4-benzoquinone (idebenone, CV-2619), on cerebral and renal vascular changes were examined in stroke-prone spontaneously hypertensive rats (SHRSP) and in rats with experimentally induced hypertension. CV-2619 (35 mg/kg/day, p.o.) significantly inhibited the onset of cerebrovascular lesions (stroke) and the elevation of blood pressure in SHRSP with mild hypertension. A higher dose (2 X 50 mg/kg/day, p.o.) clearly delayed the onset of both stroke and proteinuria without any effect on the blood pressure in SHRSP with severe hypertension. In DOCA-salt hypertensive rats, CV-2619 (2 X 5 or 2 X 25 mg/kg/day, p.o.) dose-dependently inhibited decreases in body weight and water balance and the development of cerebral and renal vascular changes. These results suggest that CV-2619 inhibits the development of stroke and renal vascular lesions in hypertensive rats.

Genetic predisposition to stroke in spontaneously hypertensive rats.

Hypertension and stroke in spontaneously hypertensive rats (SHR) were investigated genetically using stroke-prone SHR (A3), stroke-resistant SHR (C) and their hybrids, hybrid of A3 and C (F1), offspring of F1 X F1 (F2), and those of backcrossing of F1 to the respective parental strains, BC(F1 X A3) and BC(F1 X C). The average blood pressure measured without anesthesia increased in the following order during the experimental period: C less than BC (F1 X C) less than F1 approximately F2 less than BC(F1 X A3) less than A3. The F2 represented a wider spread of variation than the F1, with some of the pressure extending into the range of both parental strains. When the drinking water was replaced with a 1% salt solution, the blood pressure increased and the onset of stroke markedly accelerated in all groups of SHR. Under the hypertensive conditions, the incidence of stroke was associated with A3-gene concentration rather than with the level of blood pressure. Similar but less dramatic effects of salt were observed in another series of hybrid groups derived from A3 and normal Wistar-Kyoto rats. These findings suggest that the genetic factors are of great importance in the development of stroke as well as hypertension in the SHR.

Prolonged fasting in mice: a more sensitive approach to genetic diabetes.

Effects of two different periods of fasting were studied on glucose tolerance and insulin response to glucose in genetically diabetic KK and nondiabetic C57BL/6J mice. Blood sugar levels of the KK mice did not differ markedly from those of the C57BL/6J mice at the fed state or after 8 h fasting. They were, however, significantly higher in the KK mice when fasted for 18 h. The serum IRI levels, which were at least twice as high in the KK mice, decreased more markedly after 18 h fasting. The KK mice showed impaired glucose tolerance after 8 h fasting, which became more pronounced after 18 h fasting. The insulin response to glucose in the KK mice was not altered after an 8-hour fast; it was, however, diminished greatly after an 18-hour fast. These data suggest that prolonged fasting is necessary to detect the diabetic traits in the KK mice. The C57BL/6J mice showed neither impaired glucose tolerance nor diminished insulin response to glucose at both periods of fasting. Studies with the F1 hybrids (KK male X C57BL/6J female), which carry half of the diabetic genes, suggest that the mode of inheritance of diabetes in the KK mice might be polygenic.

Metabolic studies on the development of ethanol-induced fatty liver in KK-Ay mice.

Mechanisms involved in the development of the alcoholic fatty liver in KK-Ay mice were investigated. Incorporation studies using [14C]acetate and [3H]palmitate indicated that the half-life of hepatic triglycerides was doubled in the ethanol-ingesting mice, and utilization of the exogenous fat was significantly increases as compared with that of the control. No persistent alteration was recognized in hepatic oxidation of palmitate, as estimated by in vitro experiments using liver slices obtained from control and ethanol-drinking mice. Enzymic studies indicated that the activities of acetyl COA carboxylase, ATP citrate lyase, malic enzyme, and 6-phosphogluconate dehydrogenase were increased with ethanol drinking. The increment in hepatic triglycerides accumulated during ethanol ingestion was largely accounted for by palmitoleic, oleic, and linoleic acids. These findings demonstrated an augmentation in hepatic lipogenesis as well as an increased utilization of exogenous fats. Ethanol drinking did not cause any appreciable change in plasma triglyceride level and metabolism of adipose tissue. In summary of the present studies, accelerated lipogenesis and increased utilization of the dietary fats may be possible causal factors in the alcoholic fatty liver of KK-Ay mice.