Body weight control by a high-carbohydrate/low-fat diet slows the progression of diabetic kidney damage in an obese, hypertensive, type 2 diabetic rat model

High-Carbohydrate Diet Consumption Poses a More Severe Liver Cholesterol Deposition than a High-Fat and High-Calorie Diet in Mice

In the past few decades, many researchers believed that a high-fat and high-calorie diet is the most critical factor leading to metabolic diseases. However, increasing evidence shows a high-carbohydrate and low-fat diet may also be a significant risk factor. It needs a comprehensive evaluation to prove which viewpoint is more persuasive. We systematically compared the effects of high-fat and high-calorie diets and high-carbohydrate and low-fat ones on glycolipid metabolism in mice to evaluate and compare the effects of different dietary patterns on metabolic changes in mice. Sixty 8-week-old male C57BL/6 mice were divided into four groups after acclimatization and 15% (F-15), 25% (F-25), 35% (F-35), and 45% (F-45) of their dietary energy was derived from fat for 24 weeks. The body weight, body-fat percentage, fasting blood glucose, lipid content in the serum, and triglyceride content in the livers of mice showed a significantly positive correlation with dietary oil supplementation. Interestingly, the total cholesterol content in the livers of mice in the F-15 group was significantly higher than that in other groups (p < 0.05). Compared with the F-45 group, the mRNA expression of sterol synthesis and absorption-related genes (e.g., Asgr1, mTorc1, Ucp20, Srebp2, Hmgcr, and Ldlr), liver fibrosis-related genes (e.g., Col4a1 and Adamts1) and inflammation-related genes (e.g., Il-1β and Il-6) were significantly higher in the F-15 group. Compared with the F-45 group, the relative abundance of unclassified_f_Lachnospiraceae and Akkermansia was decreased in the F-15 group. While unclassified_f_Lachnospiraceae and Akkermansia are potentially beneficial bacteria, they have the ability to produce short-chain fatty acids and modulate cholesterol metabolism. In addition, the relative abundance of unclassified_f_Lachnospiraceae and Akkermansia was significantly positively correlated with fatty acid transporters expression and negatively correlated with that of cholesteryl acyltransferase 1 and cholesterol synthesis-related genes. In conclusion, our study delineated how a high-fat and high-calorie diet (fat supplied higher than or equal to 35%) induced obesity and hepatic lipid deposition in mice. Although the high-carbohydrate and low-fat diet did not cause weight gain in mice, it induced cholesterol deposition in the liver. The mechanism is mainly through the induction of endogenous synthesis of cholesterol in mice liver through the ASGR1-mTORC1-USP20-HMGCR signaling pathway. The appropriate oil and carbon water ratio (dietary energy supply from fat of 25%) showed the best gluco-lipid metabolic homeostasis in mice.

Unilateral nephrectomized SHR/NDmcr-cp rat shows a progressive decline of glomerular filtration with tubular interstitial lesions

In patients with diabetic kidney disease (DKD), the estimated glomerular filtration rate (eGFR) or creatinine clearance rate (Ccr) is always used as an index of decline in renal function. However, there are few animal models of DKD that could be used to evaluate renal function based on GFR or Ccr. For this reason, it is desirable to develop animal models to assess renal function, which could also be used for the evaluation of novel therapeutic agents for DKD. Therefore, we aimed to develop such animal model of DKD by using spontaneously hypertensive rat (SHR)/NDmcr-cp (cp/cp) rats with the characteristics of obese type 2 diabetes and metabolic syndrome. As a result, we have found that unilateral nephrectomy (UNx) caused a chronic Ccr decline, development of glomerular sclerosis, tubular lesions, and tubulointerstitial fibrosis, accompanied by renal anemia. Moreover, losartan-mixed diet suppressed the Ccr decline in UNx-performed SHR/NDmcr-cp rats (UNx-SHR/cp rats), with improvement in renal anemia and histopathological changes. These results suggest that UNx-SHR/cp rats could be used as a DKD model for evaluating the efficacy of therapeutic agents based on suppression of renal function decline.

Development of Wheat Bran Oil Concentrates Rich in Bioactives with Antioxidant and Hypolipidemic Properties

Wheat bran, an abundant byproduct of the milling industry, comprises fat-soluble bioactives and fibers. In the present study, two concentrates were prepared from wheat bran oil (WBO) using silicic acid coupled with acetone (WBA) and hexane (WBH). WBA extract had enhanced color and viscosity and was enriched with fat-soluble bioactives (sterols, oryzanol-like compounds, tocopherols, and carotenoids) as evidenced from NMR and other techniques. In in vitro studies, WBA exhibited significant free radical scavenging activity, limited DNA and LDL oxidation, and inhibiting HMG-CoA reductase and lipase activity better than WBH and WBO. Further, an in vivo study with WBA 2 or 3.5% containing high fat diet ameliorated malonaldehyde (MDA) level, lipid profile, and antioxidant enzyme (SOD, catalase, GPx, and GR) activities in liver. A possible reason for this effect is downregulation of HMG-CoA reductase expression with WBA. Thus, WBA has significant potential as an ingredient in health food formulations.

Relationship between Glycemic Load and Blood Lipid Level in Hospitalized Adult Chinese

BACKGROUND

Metabolic diseases in China have been on the rise in recent decades, partially due to reduced cereal consumption and excessive intake of low glycemic index (GI) foods such as meat and oil. Although the relationship between dietary glycemic load (GL) and various metabolic diseases has been extensively studied worldwide, it is unclear whether dietary GL is related to blood lipid levels and dyslipidemia risk in Chinese. The aim of the present study was to investigate the relationship between dietary GL and blood lipid levels and dyslipidemia risk in hospitalized Chinese adults.

METHODS

Dietary GL in 2258 hospitalized Chinese adults was calculated based upon GI, carbohydrate content and daily intake of individual foods. In addition, fasting total cholesterol (TC), triglycerides (TG), HDL cholesterol (HDL-C) and LDL cholesterol (LDL-C) data were collected. Multiple regression and logistic regression analysis were used to determine the relationship between dietary GL and plasma lipid levels or dyslipidemia risk.

RESULTS

Dietary GL remained inversely associated with blood total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) (P<0.01). With increasing dietary GL, risks of hypercholesterolemia and high blood LDL-C were significantly reduced (P<0.01). In the meantime dietary GL remained negatively associated with blood triglyceride (TG) and high-density lipoprotein cholesterol (HDL-C) (P<0.01), but showed no significant influence on risk of hypertriglyceridemia and low blood HDL-C (P>0.05).

CONCLUSION

High GL diet, as represented by traditional Chinese dietary pattern, may contribute to reduced risk of dyslipidemia in Chinese adults.

Renal changes in the early stages of diet-induced obesity in ovariectomized rats

The relationship between obesity and renal lesions, especially in low estrogen levels, has been less documented. The aim of this study was to assess the renal changes in diet-induced obesity in ovariectomized rats. Wistar rats were ovariectomized or sham-operated and divided into four groups: sham-operated rats fed a standard diet (SSD); ovariectomized rats fed a standard diet (OSD); sham-operated rats fed a high-fat diet (SHFD); ovariectomized rats fed a high-fat diet (OHFD). Body weight and blood pressure were measured weekly. The rats were killed 24 weeks after initiation of standard or high-fat diet treatment, the kidneys were removed for immunohistochemical and histological studies. Blood and urine samples were collected to quantify sodium, potassium and creatinine. OHFD rats presented increases in visceral adipose tissue, serum insulin levels, blood pressure and proteinuria, and a decrease in fractional excretion of sodium as well. Histological and morphometric studies showed focal alterations in the renal cortex. Expression of macrophages, lymphocytes, nuclear factor-kappa B (NF-kappaB), Proliferating Cell Nuclear Antigen (PCNA), angiotensin II (ANG II) and vimentin was greater in OHFD rats than in control rats. Thus, these results demonstrate that the high-fat diet in ovariectomized rats promoted renal function and structure changes, renal interstitial infiltration of mononuclear cells and increased expression of ANG II and NF-kappaB.

The comparative effects of perindopril and catechin on mesangial matrix and podocytes in the streptozotocin induced diabetic rats

BACKGROUND

Hyperglycemia and advanced glucose end substance (AGE) are responsible for excessive reactive oxygen species (ROS) production, which causes oxidative stress in diabetes mellitus. Oxidative stress and high blood pressure may cause injury and glomerulosclerosis in the kidney. End-stage kidney failure induced by glomerulosclerosis leads to microalbuminuria (Ma) in diabetic nephropathy. We investigated the effects of an angiotensin converting enzyme inhibitor (ACEI), perindopril, and an antioxidant, catechin, on podocytes and the glomerular mesangial matrix in experimental diabetic nephropathy using ultrastructural visualization and immunohistochemical staining.

METHODS

We compared 5 groups of male adult Wistar albino rats: a control group, an untreated diabetic group, and diabetic groups treated with perindopril, catechin, or catechin+perindopril.

RESULTS

Blood glucose values in all diabetic groups were significantly higher than in the control group (p < 0.001). The body weight in all diabetic groups was significantly lower than in the control group (p < 0.001, p < 0.05). The kidney weight in the catechin+perindopril-treated diabetic group was significantly lower than in the untreated diabetic group (p < 0.001). In all treated diabetic groups, Ma levels decreased significantly (p < 0.001). Mesangial matrix and podocyte damage increased in the untreated diabetic group, but the group treated with catechin+perindopril showed less damage. TGF-beta 1 immunostaining was significantly lower in the catechin-treated and perindopril-treated groups than in the untreated diabetic group (p < 0.001). Catechin was more effective than ACEI in preventing podocyte structure. Podocytes appeared to be the first cells affected in diabetes mellitus. When exposed to hyperglycemia, podocytes caused the mesangial matrix to expand.

CONCLUSIONS

Catechin and perindopril were more effective in preventing renal corpuscle damage when administered together.

Aldosterone antagonists in monotherapy are protective against streptozotocin-induced diabetic nephropathy in rats

Angiotensin converting enzyme inhibitors (ACEi) and angiotensin II receptor blockers (ARB) are the standard clinical therapy of diabetic nephropathy (DN), while aldosterone antagonists are only used as adjuncts. Previously in experimental DN we showed that Na/K ATPase (NKA) is mislocated and angiotensin II leads to superimposed renal progression. Here we investigated the monotherapeutic effect of aldosterone blockers on the progression of DN and renal NKA alteration in comparison to ACEi and ARBs. Streptozotocin-diabetic rats developing DN were treated with aldosterone antagonists; ACEi and ARB. Renal function, morphology, protein level and tubular localization of NKA were analyzed. To evaluate the effect of high glucose per se; HK-2 proximal tubular cells were cultured in normal or high concentration of glucose and treated with the same agents. Aldosterone antagonists were the most effective in ameliorating functional and structural kidney damage and they normalized diabetes induced bradycardia and weight loss. Aldosterone blockers also prevented hyperglycemia and diabetes induced increase in NKA protein level and enzyme mislocation. A monotherapy with aldosterone antagonists might be as, or more effective than ACEi or ARBs in the prevention of STZ-induced DN. Furthermore the alteration of the NKA could represent a novel pathophysiological feature of DN and might serve as an additional target of aldosterone blockers.

Irbesartan prevents metabolic syndrome in rats via activation of peroxisome proliferator-activated receptor γ

Irbesartan, an angiotensin-receptor blocker, is a known agonist of peroxisome proliferator-activated receptor (PPAR) γ. In this study, thirteen-week-old spontaneously hypertensive (SHR)/NDmcr-cp rats, representing a genetic model of metabolic syndrome, were treated daily with placebo, irbesartan (30 mg/kg), valsartan (10 mg/kg), or pioglitazone (10 mg/kg) for 4 weeks. Significant reductions in systolic blood pressure were seen in the irbesartan- and valsartan-treated groups, but not in the pioglitazone-treated group. Compared with the placebo group, plasma insulin, homeostasis model assessment of insulin resistance index, and plasma triglyceride levels were significantly lower while plasma adiponectin levels were significantly higher in the pioglitazone- and irbesartan-treated groups, but not in the valsartan-treated group. Significant increases in the gene expression of adiponectin and GLUT4 within adipose tissue were also observed in the pioglitazone- and irbesartan-treated groups, but not in the valsartan-treated group. These findings suggest that through PPARγ stimulation along with angiotensin II inhibition, irbesartan may be an optimal treatment option in the prevention of metabolic syndrome as well as hypertension.