The diurnal rhythm of energy expenditure differs between obese and glucose-intolerant rats and streptozotocin-induced diabetic rats

Otsuka Long Evans Tokushima Fatty (OLETF) rats were developed as a model of noninsulin-dependent diabetes mellitus (NIDDM) with mild obesity. Changes in carcass composition and in the daily profile of energy expenditure were examined before and after manifestation of diabetes (8 and 24 wk, respectiv ely), and compared with the normal control Long Evans Tokushima (LETO) rats and streptozotocin (STZ)-induced diabetic LETO rats. OLETF rats had greate r body weights than LETO rats and significantly greater absolute and relati ve fat weights. A diurnal rhythm of energy expenditure associated with two peaks was observed in LETO rats, but the two peaks were not apparent in OLE TF rats at 24 wk of age. A diurnal rhythm associated with one peak was obse rved in STZ-induced diabetic LETO rats. Energy derived from fat constituted this peak; the pattern of the daily energy expenditure was significantly d ifferent from that of either nontreated LETO or OLETF rats at 24 wk of age. NIDDM in OLETF rats at 24 wk of age has only a small role in modification of the diurnal rhythm of energy expenditure, whereas STZ-induced diabetes s ignificantly affected the rhythm.