PS-B08-7: L-CARNITINE AMELIORATES DIABETIC KIDNEY DISEASE BY ALLEVIATING MITOCHONDRIAL ABNORMALITY IN SDT-FATTY RATS

Abstract

Background and Aims: Abnormal fatty acid metabolism is associated with the progression of diabetic kidney disease (DKD). Carnitine plays a central role in β;-oxidation and energy production by transporting long-chain fatty acids from the cytoplasm to the mitochondria. Recently, we found that significant ectopic fat was accumulated in the kidney tissue in DKD patients compared with those in minimal change kidney disease patients. Juvenile visceral steatosis (jvs) mice, described as an animal model for systemic carnitine deficiency, introduce a marked ectopic fat accumulation in the kidney. These findings suggest that abnormal carnitine dynamics in DKD cause ectopic fat accumulation due to abnormality of the fatty acid metabolism. However, the association between abnormalities of carnitine metabolism and the progression of DKD is unknown. Method: Spontaneously Diabetic Torii (SDT) fatty rat, an obese type 2 diabetic model was used. Unilateral nephrectomy was performed and 0.3% salt water was administered at 6 weeks of age, and created a renal dysfunction model in SDT fatty rat (DKD model). Age-matched male Sprague-Dawley (SD) rat was used as a control. Experiment 1: We compared 3 groups; SD rats (n = 8), SDT fatty rats (n = 8), DKD rats (n = 8). Experiment 2: We compared 3 groups; SD rats with sham operation (n = 8), DKD rats (n = 7), DKD rats treated with L-carnitine administration (0.75% L-carnitine diet) for 10 weeks (n = 6). All rats were sacrificed at 17 weeks old. Carnitine was measured by the enzyme cycling method. Acylcarnitine was analyzed by the tandem-mass spectrometry. Results: Plasma and renal free carnitine levels and short/middle-long chain acylcarnitine ratio were significantly decreased in DKD rats compared with those in SD and SDT fatty rats. The renal expression levels of organic cation / carnitine transporter 2 (OCTN2), carnitine palmitoyl transferase 1a (CPT1a), CPT2 and carnitine acetyltransferase (CrAT) were significantly decreased in DKD rats compared with those in SD and SDT fatty rats. Similarly, peroxisome proliferator-activated receptor γ co-activator 1α (PGC1α) activity was decreased in DKD rats. L-carnitine administration significantly improved renal function, urinary albumin excretion, interstitial fibrosis and renal ectopic fat accumulation in DKD model rats. L-carnitine administration ameliorated the decrease of renal OCTN2, CPT1a, CPT2 and CrAT protein expression, and significantly improved PGC1α activity in DKD model rats. Furthermore, L-carnitine administration mitigated lipid peroxidation and mitochondrial dysfunction in DKD rats. Conclusion: L-carnitine administration might be a promising therapeutic strategy for improving renal function by alleviating mitochondrial dysfunction in DKD rat model.