Metabolic effects of L-citrulline in type 2 diabetes

Lactobacillus murinus alleviates insulin resistance via promoting L-citrulline synthesis

AIMS

The role of Lactobacillus murinus as a potential probiotic is being explored. Our objectives were to explore the effects of Lactobacillus murinus on insulin resistance and the underlying mechanism.

METHODS

Insulin resistance animal models were applied to study the effect of L. murinus and the underlying mechanism by six weeks of treatment. Metformin was administered in vitro to analyze the growth and metabolites of L. murinus. Serum metabolites were further analyzed after L. murinus administration. The effect of L-citrulline and the underlying mechanism in alleviating insulin resistance were evaluated.

RESULTS

L. murinus not only reduced body weight gain and postprandial blood glucose (PBG) but improved impaired glucose tolerance (IGT) and insulin resistance. Moreover, L. murinus inhibited the secretion of pro-inflammatory factors (IL-1β, IL-6 and TNF-α) while promoted the secretion of anti-inflammatory factor (IL-10). Further, L. murinus promoted the expression of carnitine palmitoyl transferase 1 (CPT1) while inhibited phosphoenolpyruvate carboxykinase (PCK) and glucose-6-phosphatase (G6Pase). A total of 147 metabolites of L. murinus were identified, in which the content of L-citrulline increased to 7.94 times after metformin regulation. Further, the serum concentration of L-citrulline significantly increased after L. murinus administration. Similarly, L-citrulline reduced body weight gain and PBG, improved IGT and insulin resistance. Additionally, L-citrulline improved inflammation, promoted CPT1 while inhibited PCK and G6Pase.

CONCLUSIONS

L. murinus mediated by L-citrulline alleviated insulin resistance via promoting fatty acid oxidation and inhibiting gluconeogenesis, suggesting that supplementation of L. murinus could be a potential therapeutic approach for type 2 diabetes related to insulin resistance.

Ursodeoxycholic acid grafted chitosan oligosaccharide self-assembled micelles with enhanced oral absorption and antidiabetic effect of oleanolic acid

Oleanolic acid (OA) is a food-derived bioactive component with antidiabetic activity, but its water solubility and oral bioavailability are notably restricted. In this study, to overcome these limitations, ursodeoxycholic acid-modified chitosan oligosaccharide (UCOS) was synthesized to encapsulate OA in self-assembled nanomicelles (UCOS-OA). The encapsulation efficiency and drug loading of UCOS-OA were 86 % and 11 %, respectively. UCOS-OA exhibited enhanced gastrointestinal stability and prolonged intestinal retention time when compared with free OA, resulting in a 10.6-fold increase in oral bioavailability. The enhanced antidiabetic activity of UCOS-OA was confirmed in the type 2 diabetes mellitus mice model, as it significantly improved glycolipid metabolism disorders and mitigated liver injury. Furthermore, UCOS-OA ameliorated the dysbiosis of gut microbiota and fecal metabolites. In conclusion, UCOS serves as an effective polymeric carrier for encapsulating OA, thereby improving its bioavailability and antidiabetic activity. This work provides valuable insights for the advancement of oral delivery systems for bioactive compounds.

Anti-obesity and anti-diabetic effects of L-citrulline are sex-dependent

AIMS

Anti-diabetic and anti-obesity effects of L-citrulline (Cit) have been reported in male rats. This study determined sex differences in response to Cit in Wistar rats.

MAIN METHODS

Type 2 diabetes (T2D) was induced using a high-fat diet followed by low-dose of streptozotocin (30 mg/kg) injection. Male and female Wistar rats were divided into 4 groups (n = 6/group): Control, control+Cit, T2D, and T2D + Cit. Cit (4 g/L in drinking water) was administered for 8 weeks. Obesity indices were recorded, serum fasting glucose and lipid profile were measured, and glucose and pyruvate tolerance tests were performed during the Cit intervention. White (WAT) and brown (BAT) adipose tissues were weighted, and the adiposity index was calculated at the end of the study.

KEY FINDINGS

Cit was more effective in decreasing fasting glucose (18 % vs. 11 %, P = 0.0100), triglyceride (20 % vs. 14 %, P = 0.0173), and total cholesterol (16 % vs. 11 %, P = 0.0200) as well as decreasing gluconeogenesis and improving glucose tolerance, in females compared to male rats with T2D. Following Cit administration, decreases in WAT weight (16 % vs. 14 % for gonadal, 21 % vs. 16 % for inguinal, and 18 % vs. 13 % for retroperitoneal weight, all P < 0.0001) and increases in BAT weight (58 % vs. 19 %, for interscapular and 10 % vs. 7 % for axillary, all P < 0.0001) were higher in females than male rats with T2D. The decrease in adiposity index was also higher (11 % vs. 9 %, P = 0.0007) in females.

SIGNIFICANCE

The anti-obesity and anti-diabetic effects of Cit in rats are sex-dependent, with Cit being more effective in female than male rats.

Watermelon consumption decreases risk factors of cardiovascular diseases: A systematic review and meta-analysis of randomized controlled trials

This meta-analysis was conducted to examine the effects of watermelon supplementation on cardiovascular diseases (CVDs) risk factors in randomized controlled trials (RCTs). The comprehensive search was done in Cochrane Library databases, ISI Web of Science, PubMed, and Scopus up to March 2022. A random-effect model was used for computing weighted mean differences (WMD). Standard methods were applied to examine publication bias, sensitivity analysis, and heterogeneity. Of the 8962 identified studies, 9 RCTs were included in the final analysis. Watermelon consumption significantly decreased systolic blood pressure (SBP), total cholesterol (TC) and low-density lipoprotein (LDL). In addition, watermelon consumption led to a significant increase in fasting blood sugar (FBS). However, there was not any significant difference in other outcomes of interest including diastolic blood pressure (DBP), heart rate (HR), BMI, body fat, and serum levels of arginine, insulin, and CRP after watermelon supplementation. The current findings provide promising evidence of the antihypertensive effect of watermelon. However, due to the lack of evidence in human research, the result regarding the remaining outcomes needs to be used with caution. Furter RCTs with longer follow-ups and larger sample sizes should be done to confirm the current findings.