Congenitally impaired hormone sensitivity of the adipose tissue of spontaneously diabetic mice, KK. Validity of thrifty genotype in KK mice

Hypoglycemic effect of hot-water extract of adzuki (Vigna angularis) in spontaneously diabetic KK-A(y) mice

OBJECTIVE

Recently, we reported that 40% ethanol fraction of hot-water extracts of adzuki (Vigna angularis; EtEx.40) suppressed the postprandial blood glucose level and serum insulin level in normal mice and streptozotocin-induced type 1 diabetic rats. The present study examined the hypoglycemic effect of EtEx.40 on blood glucose, insulin concentrations, organ weight, serum composition, and hepatic lipid content in spontaneously diabetic KK-A(y)/Ta Jcl mice, a model for type 2 diabetes.

METHODS

To investigate the prevention of type 2 diabetes by EtEx.40 ingestion, 4-wk-old non-diabetic KK-A(y) mice were fed an AIN-76 diet containing 5000 mg of EtEx.40/kg of body weight per day (EtEx.40) or an AIN-76 diet without EtEx.40 for 8 wk. Furthermore, to investigate the improvement of type 2 diabetes, 7-wk-old diabetic KK-A(y) mice were fed EtEx.40 for 4 wk.

RESULTS

Compared with the control group, EtEx.40 supplementation had a significant effect in lowering blood glucose levels, water intake, serum insulin levels, urinary glucose, urinary microalbumin/creatinine ratio, liver triacylglycerol, and total cholesterol levels. Similar results were observed in 7-wk-old diabetic KK-A(y) mice fed EtEx.40 for 4 wk. These effects were also found after short-term administration of EtEx40. Overall, EtEx.40 improved several diabetic symptoms in KK-A(y) mice.

CONCLUSION

EtEx.40 obtained from hot-water adzuki extracts showed preventive and ameliorative effects on the progression of diabetes in genetically diabetic KK-A(y) mice. In the present study, we conclude that the preventive and ameliorative effects by EtEx.40 were due to the modulation of blood glucose levels and the protective effect against oxidative damage in diabetes mellitus.

Anti-obesity and anti-diabetic effects of carteolol in non-insulin-dependent diabetic mice

1. When carteolol, a beta-adrenergic blocker, was administered to KK-Ay/Ta Jc1 mice that are obese and develop spontaneously non-insulin dependent diabetes, their increase in bodyweight was arrested from the age of 16 weeks. Since their intake of food and water was not influenced by carteolol treatment, compared with the control KK-Ay/Ta Jc1 mice, abolition of the weight gain might be attributed to increased energy metabolism. 2. Non-fasting serum glucose levels in carteolol-treated mice at the age of 17 weeks were within normal range (118 +/- 4 vs 186 +/- 12 mg/dL). An intraperitoneal glucose-tolerance test revealed that the carteolol treatment markedly restored glucose metabolism; fasting plasma glucose (88 +/- 6 mg/dL) was within normal range, and immunoreactive insulin (IRI; 5.8 +/- 0.8 vs 33.3 +/- 10.5 ng/mL) and plasma glucose levels at 60 min post glucose (361 +/- 44 vs 541 +/- 32 mg/dL) were significantly lower in carteolol-treated mice than those in the control group at the age of 20 weeks. 3. From these findings, carteolol is considered to have little effect on the growth of mice but to correct the obesity that develops after age 16 weeks, when their growth terminates. In addition, the normalization of blood glucose and marked decrease in IRI levels suggests that carteolol improves glucose tolerance by increasing the insulin sensitivity. 4. Since brown adipose tissue (BAT) is closely associated with thermogenesis and energy consumption, we tested whether carteolol may affect BAT.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone marrow transplantation as a strategy for treatment of non-insulin-dependent diabetes mellitus in KK-Ay mice

The effects of allogeneic bone marrow transplantation (BMT) on non-insulin-dependent diabetes mellitus (NIDDM) were examined using KK-Ay mice. KK-Ay mice reconstituted with KK-Ay bone marrow cells showed glycosuria, hyperinsulinemia, and hyperlipidemia. However, KK-Ay mice (H-2b) that had been lethally irradiated (9.0 Gy) and then reconstituted with T cell-depleted bone marrow cells from normal BALB/c mice (H-2d) showed negative urine sugar with decreases in serum insulin and lipid levels 4 mo after BMT. Morphological recovery of islets and glomeruli was also noted after allogeneic BMT. These findings suggest that BMT can be used to treat not only a certain type of NIDDM but also its complications such as hyperlipidemia and diabetic nephropathy.

Insulin receptor and postbinding defects in KK mouse adipocytes and improvement by ciglitazone

Alterations of the insulin receptor and of glucose metabolism were examined in adipocytes from genetically diabetic KK mice. Compared with those from control C57BL/6 mice, adipocytes from KK mice showed weaker insulin binding and were less sensitive and less responsive to insulin with respect to 3-O-methylglucose uptake and [1-14C]glucose oxidation. However, insulin had no difference in effect between the two groups of mice with respect to [6-14C]glucose oxidation, glyceride-glycerol synthesis, or fatty acid synthesis from [1-14C]- and [6-14C]glucose. [1-14C]Glucose oxidation of KK cells was also insensitive to insulin mimics such as vitamin K5 and H2O2. When adipose tissues were precultured with insulin or insulin mimics for 24 h, adipocytes from C57BL/6 mice showed decreased insulin binding, but KK cells did not. When administered orally to KK mice for 2 weeks, ciglitazone made adipocytes more sensitive to insulin, more responsive to insulin with respect to glucose uptake and oxidation, and more capable of binding insulin. Impairment of the downregulation at the insulin receptor caused by exposure to insulin or insulin mimics was normalized by ciglitazone treatment in KK cells. In conclusion, KK cells are insulin-resistant due to defects of the insulin receptor and postbinding system in the glucose uptake and pentose pathways. In addition, regulation of the insulin receptor seems to be closely related to the postbinding system.

Electrophoretic patterns of serum albumins collected from different blood vessels

Rabbit sera collected from different blood vessels, e.g. vena renales, vena mesenterica, vena portae, vena hepatica and aorta, were electrophoresed in an urea-containing polyacrylamide gel. The albumin fraction was separated into 5-6 sub-bands. The profile of these sub-bands (electrophoretic pattern) of the sample from one blood vessel differed from that of another blood vessel. Especially, the electrophoretic pattern of serum collected from the renal vein 2h after deprivation of food differed from that of other blood vessels. Free fatty acid concentrations of each sample were also measured, and differences in these levels were observed in sera collected from different blood vessels. However, the fatty acid concentrations in serum from the renal vein were not low enough to permit detection of any abnormality in electrophoretic pattern in the albumin. This suggests the possibility of decreased concentration of lysolecithin in the renal vein which binds to albumin and changes the electrophoretic mobility of albumin, as do the free fatty acids.

Laboratory animals exhibiting obesity and diabetes syndromes

Spontaneous hyperglycemia, hyperinsulinemia and obesity are common features for at least one period of the lifetime in some strains of mice. Both genetic and environmental factors are involved in the pathogenesis of the diabetes-like syndrome, making these strains excellent models for studies in both obesity and diabetes-like states. The metabolic peculiarities can be due to a dominant gene, as for the yellow obese, or a single recessive gene, as in the obese and the diabetes mouse; or they can be of polygenic origin, as for the KK and the NZO mouse. However, the severity of the metabolic disorder is due to the interaction of the mutant genes iwth modifiers in the bat genes themselves. Studies on the pathophysiology and biochemistry of these animals have revealed interstrain differences, different patterns of development of the metabolic disorder, and different degrees of severity of the diabetes-like syndrome. Although the primary causes of the syndrome remain unclear in some strains, an involvement of hypothalamic feeding centers has been implicated.