Chronic hyperglycaemia in diabetes leads to the overproduction of free radicals and evidence is increasing that these contribute to the development of diabetic nephropathy. Among the spices, turmeric (Curcuma longa) is used as a flavouring and colouring agent in the indian diet every day and is known to possess anti-oxidant properties. The present study was designed to examine the effect of curcumin, a yellow pigment of turmeric, on renal function and oxidative stress in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced by a single intraperitoneal injection of STZ (65 mg/kg) in rats. Four weeks after STZ injection, rats were divided into four groups, namely control rats, diabetic rats and diabetic rats treated with curcumin (15 and 30 mg/kg, p.o.) for 2 weeks. Renal function was assessed by creatinine, blood urea nitrogen, creatinine and urea clearance and urine albumin excretion. Oxidative stress was measured by renal malonaldehyde, reduced glutathione and the anti-oxidant enzymes superoxide dismutase and catalase. Streptozotocin-injected rats showed significant increases in blood glucose, polyuria and a decrease in bodyweight compared with age-matched control rats. After 6 weeks, diabetic rats also exhibited renal dysfunction, as evidenced by reduced creatinine and urea clearance and proteinuria, along with a marked increase in oxidative stress, as determined by lipid peroxidation and activities of key anti-oxidant enzymes. Chronic treatment with curcumin significantly attenuated both renal dysfunction and oxidative stress in diabetic rats. These results provide confirmatory evidence of oxidative stress in diabetic nephropathy and point towards the possible anti-oxidative mechanism being responsible for the nephroprotective action of curcumin.

The chemopreventive action of carotenoids on proteinuria and lymphadenopathy were examined in autoimmune-prone MRL-lpr/lpr (MRL/l) mice. They were fed a synthetic full-fed diet (16-18 kcal/mouse/day) with supplementation of beta-carotene or astaxanthin (0.19 mumoles/mouse, 3 times a week), and the development of lymphadenopathy and proteinuria were examined. MRL/l mice fed a full-fed diet without the supplementation of carotenoids or those fed a calorie-restricted (CR) diet (10-11 kcal/mouse/day, 60% calorie intake of full-fed mice) were employed as controls. CR dramatically delayed the development of proteinuria and lymphadenopathy, as reported previously. Carotenoids also significantly delayed the onset of these symptoms in MRL/l mice fed a full-fed diet. Carotenoids were half as effective as CR and astaxanthin, a carotenoid without provitamin A activity, which appeared to exert more significant preventive actions than beta-carotene in delaying the development of these symptoms. Similar chemopreventive actions of carotenoids were also demonstrated in MRL/l mice fed a regular diet (Lab Chow). CR has been shown to augment IL-2 production and to decrease serum prolactin levels in this strain, which may be related to its dramatic preventive action of autoimmunity. However, carotenoids did not affect IL-2 production nor prolactin levels in full-fed MRL/l mice. The chemopreventive actions of carotenoids observed in autoimmune-prone MRL/l mice may be attributed to yet unknown mechanisms, apart from their provitamin A activity or oxygen-quenching activity.

Objective:Previous studies have reported that a vegetarian diet may lower blood pressure (BP), but the effect of diet on BP in asymptomatic participants with proteinuria is unknown. We examined the association of diet and BP in individuals with or without proteinuria.

Materials and Methods:This cross-sectional study analyzed data from participants who were more than 40 years old and received physical checkups at Taipei Tzu Chi Hospital from September 5, 2005, to December 31, 2016. Diets were assessed at baseline by a self-reported questionnaire and categorized as vegan, lacto-ovo vegetarian, or omnivore. There were 2818 (7.7%) vegans, 5616 (15.3%) lacto-ovo vegetarians, and 28,183 (77.0%) omnivores. The effect of different parameters on BP was determined using a multivariate multiple linear regression model with no intercept, with control for important characteristics and lifestyle confounders.

Results:The vegan group had a lower mean systolic BP (-3.87 mmHg,<0.001) and diastolic BP (-2.48 mmHg,<0.001) than the omnivore group. Participants with proteinuria had a higher systolic BP (4.26 mmHg,<0.001) and diastolic BP (2.15 mmHg,<0.001) than those without proteinuria. Interaction analysis indicated that vegan participants with proteinuria had a lower systolic BP (-2.73 mmHg,= 0.046) and diastolic BP (-2.54 mmHg,= 0.013) than other participants with proteinuria. However, individuals in the lacto-ovo group with proteinuria had a BP similar to other participants with proteinuria.

Conclusions:A vegan diet was associated with lower BP in asymptomatic participants with proteinuria. This diet could be a nonpharmacologic method to reduce BP.