Intermittent fasting benefits on alpha- and beta-cell arrangement in diet-induced obese mice pancreatic islet.

AIMS: There is a pancreatic islet adaptation in obese subjects, resulting in insulin resistance and diabetes type 2. We studied the effect of intermittent fasting (IntF) on the islet structure of diet-induced obese (DIO) mice. METHODS: Three-month-old male mice fed a control diet (C, 10% Kcal fat) or a high-fat diet (HF, 50% Kcal fat) for two months (n = 20 each group). Then, half of each group did IntF (alternating 24 h fed/24 h fast), continuing in their diets four more weeks: C, C-IntF, HF, HF-IntF. Islets were prepared to microscopy or isolated for molecular analysis. RESULTS: HF group (vs. C group) showed hyperglycemia, hyperinsulinemia, hyperleptinemia, hypoadiponectinemia, glucose intolerance, insulin resistance, and islet hypertrophy with a consequent higher both the alpha-cell and beta-cell masses. In the HF group (vs. C), there was low PDX1 (pancreatic and duodenal homeobox 1), and IntF did not alter PDX1. There was a low p-AKT/AKT ratio (protein kinase B), and IntF enhanced it. Also, tumor suppressor p53 was increased, and IntF decreased it. IL (interleukin) -6 was higher in the HF group (vs. C), and HF-IntF (vs. C-IntF). Any significant change in NFkB was seen among groups. CONCLUSIONS: IntF improves pancreatic islet structure in DIO mice, even with continued HF diet intake, primarily considering on the alpha- and beta-cell masses regulation, then improving insulin signaling and decreasing cell apoptosis. Future research should explore whether the shortening of the IntF extend could maintain the benefits observed in the long term.

Deficiência de vitamina D e menopausa: efeitos no fígado e no tecido adiposo periovariano de camundongos / Deficiency of vitamin d and menopause: effects on liver and periovarian adipose tissue of mice

No presente estudo, avaliamos o impacto da deficiência de vitamina D em camundongos fêmeas ovariectomizadas. A hipótese do nosso estudo é que a deficiência de vitamina D aumenta a inflamação no tecido adiposo e promove acúmulo de gordura hepática em modelo de menopausa. Camundongos C57BL/6 fêmeas, com três meses de idade, foram ovariectomizados ou não, e divididos em grupos controle (C, alimentado com dieta padrão), ovariectomizados (Ovx, alimentado com dieta padrão), controle sem vitamina D (C (D-), alimentado com dieta padrão sem vitamina D) e ovariectomizados sem vitamina D (Ovx (D-), alimentados com dieta padrão sem vitamina D) por doze semanas. Como resultados, no grupo Ovx (D-), houve resistência à insulina e intolerância à glicose, além do aumento da massa corporal. No fígado, houve aumento da esteatose hepática, com consequente aumento da lipogênese e inflamação, fatores que foram comprovados pelo aumento na expressão de genes e proteínas responsáveis pelo metabolismo lipídico. Além disso, houve redução da beta-oxidação de ácidos graxos. No tecido adiposo periovariano, a ovariectomia aumentou a área média dos adipócitos e a expressão proteica e gênica de citocinas pró-inflamatórias. Associado aos achados supracitados, houve aumento do metabolismo local da vitamina D, como forma de compensar a deficiência dessa vitamina. Em conclusão, os achados experimentais atuais são robustos e demonstram que a ovariectomia e a restrição dietética de vitamina D em camundongos têm efeitos adversos aditivos que levam a um aumento da massa corporal, da esteatose hepática e resistência à insulina. Esses achados estão ligados ao aumento dos marcadores de lipogênese e diminuição da beta-oxidação, predispondo ao acúmulo de gordura no fígado, assim como o aumento da inflamação no tecido adiposo periovariano.

In the present study, we have evaluated the impact of vitamin D deficiency in ovariectomized female mice. The hypothesis of our study is that vitamin D deficiency increases the inflammation in adipose tissue and promotes accumulation of hepatic fat in the menopause model. Female C57BL / 6 mice, three months old, were ovariectomized or not, and divided into control (C, fed control diet), ovariectomized (Ovx fed control diet), control without vitamin D (D-), fed control diet without vitamin D) and ovariectomized without vitamin D (Ovx (D-), fed control diet without vitamin D) for twelve weeks. As a result, in Ovx (D-) group there was insulin resistance and glucose intolerance, as well as an increase in body mass. In the liver, there was an increase in hepatic steatosis, with consequent increase in lipogenesis and inflammation due to the increase in the expression of genes and proteins of lipid metabolism. In addition, there was a reduction of beta-oxidation and reduction of fatty acid oxidation. In periovarian adipose tissue, ovariectomy increased the mean area of adipocytes and protein and gene expression of pro-inflammatory cytokines. Associated with the findings, there was increase in the local vitamin D metabolism, to compensate the deficiency of this vitamin. In conclusion, that current experimental findings are robust showing that ovariectomy and vitamin D dietary restriction in mice have additive adverse effects that lead to increased body mass, hepatic steatosis and insulin resistance. These findings are linked to increase of lipogenesis markers and decreased of beta-oxidation, predisposing to accumulation of fat in the liver, as well as increased inflammation in periovarian adipose tissue.

Vitamin D Deficiency Increases Lipogenesis and Reduces Beta-Oxidation in the Liver of Diet-Induced Obese Mice.

The study was conducted to understand better the mechanisms involved in liver changes when there is a combination of diet-induced obesity (DIO) and vitamin D deficiency (VDD). After 8 wk of feeding a control diet (C group) or a high-fat diet (HF), both with vitamin D, and counterpart groups without vitamin D (VitD- groups), we found in plasma: higher alanine aminotransferase, and aspartate aminotransferase in the VitD- groups, and more elevated total cholesterol in the HF group. Compared to their counterparts, HF and HF/VitD- showed hyperinsulinemia and higher hepatic triglycerides and steatosis. The protein expressions of markers linked with the vitamin D action were altered by VDD (vitamin D receptor VDR, 25-hydroxyvitamin D-24-hydroxylase CYP24A1, CYP27B1, and CYP2R1). The hepatic lipogenesis and fatty acid synthesis were enhanced by VDD (peroxisome proliferator-activated receptor PPARγ, sterol regulatory element-binding proteins SREBP1c, carbohydrate-responsive element-binding protein ChREBP, and fatty acid synthase FAS), but markers of beta-oxidation were reduced (PPARα and phosphoenolpyruvate carboxykinase PEPCK). In conclusion, the study provides convincing new evidence that there is an additive and adverse effect on the liver caused by the combination of VDD and DIO. The essence of these changes in the liver is in an increased lipogenesis and a reduced beta-oxidation, which predisposes to the accumulation of fat in the liver, accompanied by IR. The worsening of the pathogenesis of NAFLD may tilt to more severe stages of liver disease.

Ovariectomy modify local renin-angiotensin-aldosterone system gene expressions in the heart of ApoE (-/-) mice.

AIMS: The evaluation of the local Renin-Angiotensin-Aldosterone system (RAAS) gene expressions in the heart of ovariectomized (OVX) apolipoprotein E deficient mice (ApoE). METHODS: Four-months old C57BL/6 female mice (wild-type, wt, n=20), and ApoE female mice (n=20), were submitted to OVX or a surgical procedure without ovary removal (SHAM) and formed four groups (n=10/group): SHAM/wt, SHAM/ApoE, OVX/wt, and OVX/ApoE. KEY FINDINGS: OVX led to greater body mass, plasma triglycerides (TG) and total cholesterol, and resulted in insulin resistance and altered RAAS gene expressions in the heart tissue. The gene expression of angiotensin-converting enzyme (ACE)-2 was lower in OVX/wt than in SHAM/wt (P=0.0004), Mas receptor (MASr) was lower in OVX/wt compared to SHAM/wt (P<0.0001). Also, angiotensin II receptor type 1 (AT1r) was higher in OVX/wt than in SHAM/wt (P=0.0229), and AT2r was lower in OVX/wt than in SHAM/wt (P=0.0121). OVX and ApoE deficiency showed interaction potentializing the insulin resistance, increasing TG levels and altering ACE and MASr gene expressions. ACE gene expression was higher in OVX/ApoE than in OVX/wt (P<0.0001), and MASr gene expression was lower in OVX/ApoE than in OVX/wt (P<0.0001). SIGNIFICANCE: The impact of OVX on local RAAS cascade in the heart of ApoE deficient animals, besides the metabolic changes culminating with insulin resistance, involves an upregulation of renin, ACE, and AT1r gene expressions. The findings may contribute to clarify the mechanisms of development of postmenopausal hypertension and the link between RAAS and apolipoprotein E.

Adverse effects of vitamin D deficiency on the Pi3k/Akt pathway and pancreatic islet morphology in diet-induced obese mice.

SCOPE: To investigate the impact of vitamin D deficiency on insulin resistance and abnormal glucose homeostasis in obesity. METHODS AND RESULTS: Sixty male C57BL/6 mice (3 months old) were fed a control diet (C-10% energy as fat) or a high-fat diet (HF-50% energy as fat), with or without vitamin D, for 8 weeks. There was no difference in body mass between the HF and HF/VitD- groups. Vitamin D deficiency (VitD) in the diet-induced obese mice increased hyperinsulinemia (p = 0.04), hyperleptinemia (p = 0.0002), insulin resistance (HOMA-IR, p = 0.04), and islet changes, including alpha and beta cell disarray. In the insulin signaling pathway, insulin receptor substrate 2 expression was upregulated in the C/VitD- group (p = 0.001) and downregulated in the HF/VitD- group (p = 0.009). Interestingly, forkhead box protein O1 expression was higher in the HF/VitD- group than in the HF group (p = 0.03), and pancreatic and duodenal homeobox 1 expression was lower in the HF/VitD-group than in the HF group (p = 0.025), indicating that the HF diet and vitamin D deficiency influenced the downregulation of the expression of these proteins (two-way ANOVA, p < 0.0001). CONCLUSION: Vitamin D deficiency exacerbated the adverse structural and physiological remodeling of pancreatic islets due to obesity, contributing to abnormal glucose homeostasis.