Obesity is necessary but not sufficient for the development of diabetes mellitus.
To investigate whether inheritance or obesity plays a more important role in the development of non-insulin-dependent diabetes mellitus (NIDDM), female Otsuka-Long-Evans-Tokushima Fatty (OLETF) rats, which possess the diabetogenic gene, ODB-1, and Long-Evans-Tokushima-Otsuka (LETO) rats, which have no ODB-1, were compared. Neither strain becomes obese and diabetic when bred ordinarily. Female OLETF rats and male and female LETO rats were assigned to two groups of 20 rats each. Obesity was induced in one group by feeding a high-energy "cafeteria" diet (group D), and the other group was given standard chow (group C). Twenty male OLETF rats were used as NIDDM positive controls. At 25 weeks of age, the mean body weight of group D male LETO and female OLETF rats increased at a rate similar to that of male OLETF rats; female LETO rats did not show increased body weight. The incidence of diabetes mellitus in obese female OLETF rats in group D and positive control male OLETF rats was the same (80%). Only 30% of obese male LETO rats in group D developed diabetes mellitus. The insulin response to intravenous glucose in group D female OLETF rats was the highest for all groups but not sufficient to decrease blood glucose levels. In female OLETF rats, glucose infusion rate (GIR) during a euglycemic-hyperinsulinemic clamp test in group D was decreased to 50% of the group C value and tissue glucose uptake as determined by 3H-glucose infusion was significantly decreased in muscle. In male LETO rats, group D GIR was mildly decreased (80% of group C value) compared with the GIR of female OLETF rats. For obese group D female OLETF rats, abdominal fat increased more with obesity than in their male LETO counterparts. GIR was inversely correlated with the weight of abdominal fat when the data of all groups of animals were combined. The expression of GLUT4 mRNA and its protein level in adipose and muscle tissues and tumor necrosis factor alpha (TNF-alpha) protein in adipose tissue were not significantly different between group D and group C of both strains. In conclusion, the incidence of diabetes in female OLETF rats that possess the diabetogenic gene was significantly greater than in the LETO strains that do not possess the gene, in the presence of excess adiposity.
Ishida
K
K
Department of Laboratory Medicine, School of Medicine, The University of Tokushima, Japan.
Mizuno
A
A
Murakami
T
T
Shima
K
K
D000005:Abdomen; D000273:Adipose Tissue / Q000378:metabolism / Q000473:pathology; D000284:Administration, Oral; D000818:Animals; D001835:Body Weight; D003921:Diabetes Mellitus, Experimental / Q000209:etiology*; D005260:Female; D005947:Glucose / Q000378:metabolism; D015309:Glucose Clamp Technique; D005951:Glucose Tolerance Test / Q000379:methods; D051275:Glucose Transporter Type 4; D007275:Injections, Intravenous; D007328:Insulin / Q000494:pharmacology; D008099:Liver / Q000378:metabolism; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism; D009124:Muscle Proteins; D009132:Muscles / Q000378:metabolism; D009765:Obesity / Q000150:complications* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; C495694:Slc2a4 protein, rat; D005947:Glucose