Beta-cell compensation and gestational diabetes

Gestational diabetes mellitus (GDM) is characterized by glucose intolerance in pregnant women without a previous diagnosis of diabetes. While the etiology of GDM remains elusive, the close association of GDM with increased maternal adiposity and advanced gestational age implicates insulin resistance as a culpable factor for the pathogenesis of GDM. Pregnancy is accompanied by the physiological induction of insulin resistance in the mother secondary to maternal weight gain. This effect serves to spare blood glucose for the fetus. To overcome insulin resistance, maternal β-cells are conditioned to release more insulin into the blood. Such an adaptive response, termed β-cell compensation, is essential for maintaining normal maternal metabolism. β-cell compensation culminates in the expansion of β-cell mass and augmentation of β-cell function, accounting for increased insulin synthesis and secretion. As a result, a vast majority of mothers are protected from developing GDM during pregnancy. In at-risk pregnant women, β-cells fail to compensate for maternal insulin resistance, contributing to insulin insufficiency and GDM. However, gestational β-cell compensation ensues in early pregnancy, prior to the establishment of insulin resistance in late pregnancy. How β-cells compensate for pregnancy and what causes β-cell failure in GDM are subjects of investigation. In this mini-review, we will provide clinical and preclinical evidence that β-cell compensation is pivotal for overriding maternal insulin resistance to protect against GDM. We will highlight key molecules whose functions are critical for integrating gestational hormones to β-cell compensation for pregnancy. We will provide mechanistic insights into β-cell decompensation in the etiology of GDM.

Allopurinol and valproic acid improve cardiac triglyceride and Na+-K+-ATPase activity independent of circulating aldosterone in female rats with glucose intolerance

Context: Studies have shown that cardiac triglyceride accumulation and impaired Na⁺-K⁺-ATPase activity are linked to diabetes- related cardiovascular disease, particularly in women.Objectives: We hypothesised that allopurinol (ALL) and valproic acid (VPA) treatment would improve cardiac triglyceride and Na⁺-K⁺-ATPase activity independent of circulating aldosterone in Combined Oral Contraceptive (COC)-induced dysglycemiaMaterials and methods: Rats received COC (1.0 μg ethinylestradiol and 5.0 μg levonorgestrel; po) with or without ALL (1 mg; po) and VPA (20 mg; po) for 6 weeks.Results: COC-treatment led to impaired glucose tolerance, accumulated abdominal fat, dyslipidemia, elevated plasma MDA, PAI-1 and aldosterone levels and also reduced plasma nitric oxide bioavailability and cardiac Na⁺-K⁺-ATPase activity. However, either ALL or VPA treatment ameliorated these alterations comparably independent of elevated aldosterone levelDiscussion and conclusion: Our results suggest that either ALL or VPA would improve cardiac TG and Na⁺-K⁺-ATPase activity comparably in COC-treated rats, regardless of circulating aldosterone level.

Myeloid FoxO1 depletion attenuates hepatic inflammation and prevents nonalcoholic steatohepatitis

Hepatic inflammation is culpable for the evolution of asymptomatic steatosis to nonalcoholic steatohepatitis (NASH). Hepatic inflammation results from abnormal macrophage activation. We found that FoxO1 links overnutrition to hepatic inflammation by regulating macrophage polarization and activation. FoxO1 was upregulated in hepatic macrophages, correlating with hepatic inflammation, steatosis and fibrosis in mice and patients with NASH. Myeloid cell-conditional FoxO1 knockout skewed macrophage polarization from pro-inflammatory M1 to anti-inflammatory M2 phenotypes, accompanied by the reduction of macrophage infiltration in liver. These effects mitigated overnutrition-induced hepatic inflammation and insulin resistance, contributing to improved hepatic metabolism and increased energy expenditure in myeloid cell FoxO1 knockout mice on HFD. When fed a NASH-inducing diet, myeloid cell FoxO1 knockout mice were protected from developing NASH, culminating in the reduction of hepatic inflammation, steatosis and fibrosis. Mechanistically, FoxO1 counteracts Stat6 to skew macrophage polarization from M2 toward M1 signatures to perpetuate hepatic inflammation in NASH. FoxO1 appears as a pivotal mediator of macrophage activation in response to overnutrition and a therapeutic target for ameliorating hepatic inflammation to stem the disease progression from benign steatosis to NASH.

Late gestational testosterone exposure causes glucose deregulation and elevated cardiac VCAM-1 and DPP-4 activity in rats

CONTEXT

Increased vascular cell adhesion molecule-1 (VCAM-1) has been reported to be a critical link between obesity and atherosclerotic cardiovascular diseases while dipeptidyl peptidase-4 (DPP-4) has been implicated in the development of disrupted glucose regulation and inflammation.

OBJECTIVE

This study aimed to investigate the effect of gestational testosterone exposure on glucose metabolism, atherogenic dyslipidemia, as well as circulating and cardiac VCAM-1, oxidative stress biomarkers and DPP-4 activity in pregnant rats.

METHODS

Pregnant Wistar rats received either vehicle or testosterone (0.5 mg/kg; sc) between gestational days 14 and 19.

RESULTS

Gestational testosterone exposure caused impaired glucose homeostasis that was accompanied with atherogenic dyslipidemia, elevated circulating and cardiac levels of VCAM-1, uric acid, malondialdehyde as well as increased DPP-4 activity. However, nitric oxide levels were decreased.

CONCLUSION

This study shows that gestational testosterone exposure causes glucose deregulation and atherogenic dyslipidemia that is accompanied by increased circulating and cardiac VCAM-1 and DPP-4 activity.

Hepatoprotective effects of Quassia amara stem bark against cadmium-induced toxicity in male Wistar rats

OBJECTIVES

The liver is one of the primary biorepositories of cadmium (Cd) and it has been implicated in the pathogenesis of hepatic diseases. Quassia amara stem bark has been reputed to have strong antimalarial, antimicrobial, antiulcerative and amoebicidal properties. This study aims to determine the effects of Q. amara on Cd-induced hepatotoxicity and lipid profile in male Wistar rats.

METHODS

The animals were divided into three groups of five animals each. Group 1 served as control while group 2 received Cd (5 mg/kg) for 4 weeks. Prior to Cd treatment, group 3 was treated with Q. amara extract (200 mg/kg) for 2 weeks and received the Q. amara and Cd simultaneously for 4 weeks.

RESULTS

Cadmium caused significant increase in serum total cholesterol and low-density lipoprotein (LDL) as well as increased hepatic malondialdehyde (MDA) when compared with the control group. On the other hand, Cd caused a decrease in serum high-density lipoprotein (HDL) and hepatic superoxide dismutase (SOD) when compared with control. However, treatment with Q. amara prevented Cd-induced changes in the lipid profile, augmented Cd-induced decline in SOD and also ameliorated the Cd-induced increase in MDA. Catalase level was however comparable across the groups.

CONCLUSIONS

Q. amara ameliorated the Cd-induced damage to liver by preventing dyslipidemia and oxidative damage in the hepatic tissue.

Acetate causes renoprotection like androgen and mineralocorticoid receptors blockade in testosterone-exposed pregnant rats

The kidney plays a critical role in human health and deviation from its normal function can lead to severe morbidity and mortality. Exposure to excess testosterone in women has been linked to several disorders, including kidney disorder and acting undoubtedly through androgen receptor (AR), whereas the involvement of mineralocorticoid receptor (MR) is unclear. Likewise, the renal effect of sodium acetate (SAc) during late gestational exposure to testosterone is not well known. We hypothesized that SAc or MR blockade would protect the kidney of testosterone-exposed pregnant rats against glutathione and adenosine depletion. Twenty-five pregnant Wistar rats were treated (sc) with olive oil, testosterone propionate (0.5 mg/kg) singly or in combination with SAc (200 mg/kg; p.o.), androgen receptor (AR) blocker, flutamide (Flu; 7.5 mg/kg; p.o.) or (MR) blocker, eplerenone (Eple; 0.5 mg/kg) between gestational days 14 and 19. Glutathione, adenosine and nitric oxide were decreased while uric acid (UA), xanthine oxidase (XO), malondialdehyde (MDA), lactate dehydrogenase activity and free fatty acids were increased in the kidneys of gestational rats exposed to testosterone. Also, plasma urea and creatinine were elevated. SAc and Eple reversed tested testosterone-induced effects in gestational rats. The exposure to testosterone impairs renal antioxidant defense via AR and MR during late gestation in pregnant rats. The study also provides evidence that sodium acetate protects the kidneys of gestational testosterone-exposed rats against defective antioxidant defense in like manner as MR or AR antagonist.

Treatment with acetate during late pregnancy protects dams against testosterone-induced renal dysfunction

Cardiometabolic diseases are complicated by renal damage. Gestational hyperandrogenism causes gestational metabolic dysfunction that is associated with fetal and maternal tissue derangements as well as post-partum maternal androgen excess. Acetate (Ace) conferred hepatoprotection in pregnant rats exposed to excess testosterone (Tes). The effect of excess androgenic exposure on maternal kidney during and after pregnancy is not clear. Therefore, this study investigated the effect of late gestational and post-gestational testosterone exposure on renal functions and plausible renoprotective role of gestational Ace treatment in dams. Thirty pregnant Wistar rats were grouped (n = 10/group) and treated (sc) with olive oil, testosterone propionate (0.5 mg/kg) with or without acetate (200 mg/kg sodium acetate; p.o) between gestational days 14 and 19. Data were obtained from half of the animals on gestational day 20. Data were also obtained from the other half (dams) after treatment of animals which received Tes with or without prior gestational acetate treatment with post-gestational Tes (sc; 0.5 mg/kg) for the last 6 days of an 8-week postpartum period. Biochemical and statistical analyses were performed with appropriate methods and SPSS statistical software respectively. Late gestational excess Tes led to low placental weight (p = 0.0001, F = 205.7), poor fetal outcomes, creatinine (p = 0.0001, F = 385.4), urea (p = 0.0001, F = 300.9) and renal uric acid (UA) (p = 0.0001, F = 123.2), gamma-glutamyl transferase (GGT) (p = 0.004, F = 26.9), malondialdehyde (p = 0.0001, F = 45.96), and lactate dehydrogenase (LDH) (p = 0.0002, F = 150.7). Postpartum Tes exposure also caused elevated plasma testosterone (p = 0001, F = 22.15), creatinine (p = 0.0002, F = 15.2), urea (p = 0.01, F = 13.8) and renal UA (p = 0.0001, 226.8), adenosine deaminase (p = 0001, F = 544.7), GGT (p = 0.0002, F = 401.4) and LDH (p = 0.01, F = 23.7). However, gestational acetate treatment ameliorated the renal effects of gestational and post-gestational Tes exposure. Taken together, gestational acetate would pre-programme dams against renal dysfunction caused by Tes exposure.

Ameliorative effect of low-dose spironolactone on obesity and insulin resistance is through replenishment of estrogen in ovariectomized rats

Women have a lower incidence of cardiovascular diseases (CVD) than men at a similar age but the reverse is the case after menopause, indicating a possible protective effect of estrogen on cardiometabolic function. Although various hormonal therapies have been formulated to combat the CVD risks in postmenopausal state, the beneficial effects have not been consistent. Obesity with insulin resistance (IR) is closely linked to CVD risks while ovariectomized rodents have been shown to mimic a state of obesity and IR. We therefore hypothesized that low-dose spironolactone would ameliorate obesity and IR in estrogen-deprived rats by replenishing estrogen and suppressing elevated glycogen synthase kinase-3 (GSK-3). Ten-week-old female Wistar rats were divided into 4 groups: sham-operated (SHM), spironolactone (SPL; 0.25 mg/kg), and ovariectomized (OVX) rats treated with or without spironolactone daily for 8 weeks. Results showed that estrogen deprivation through ovariectomy caused increased body mass gain and visceral adiposity that are accompanied by increased HOMA-IR, HOMA-β, 1-hour postload glucose, glucose intolerance, platelet/lymphocyte ratio, plasma insulin, atherogenic dyslipidemia, uric acid, GSK-3, corticosterone, and aldosterone and depressed 17β-estradiol. However, treatment of OVX rats with spironolactone ameliorated all these effects. Taken together, the results demonstrate that treatment with low-dose spironolactone improves obesity and IR, which appears to involve replenishment of estrogen and suppression of GSK-3 along with circulating mineralocorticoid and glucocorticoid. The findings imply a positive cardiometabolic effect of low-dose spironolactone usage in estrogen-deprived conditions.

Low-dose spironolactone ameliorates insulin resistance and suppresses elevated plasminogen activator inhibitor-1 during gestational testosterone exposure

CONTEXT

Elevated gestational circulating testosterone has been associated with pathological pregnancies that increase the risk of development of cardiometabolic disorder in later life.

OBJECTIVE

We hypothesised that gestational testosterone exposure, in late pregnancy, causes glucose deregulation and atherogenic dyslipidaemia that would be accompanied by high plasminogen activator inhibitor-1 (PAI-1). The study also hypothesise that low-dose spironolactone treatment would ameliorate these effects.

METHODS

Pregnant Wistar rats received vehicle, testosterone (0.5 mg/kg; sc), spironolactone (0.5 mg/kg, po) or testosterone and spironolactone daily between gestational days 15 and 19.

RESULTS

Gestational testosterone exposure led to increased HOMA-IR, circulating insulin, testosterone, 1-h post-load glucose, atherogenic dyslipidaemia, PLR, PAI-1 and MDA. However, all these effects, except that of circulating testosterone, were ameliorated by spironolactone.

CONCLUSIONS

These results demonstrate that low-dose spironolactone ameliorates glucose deregulation and atherogenic dyslipidaemia during elevated gestational testosterone exposure, at least in part, by suppressing elevated PAI-1.

Combined oral contraceptive and nitric oxide synthesis inhibition synergistically causes cardiac hypertrophy and exacerbates insulin resistance in female rats

Combined oral contraceptive (COC) use or inhibition of nitric oxide (NO) synthesis has been shown to cause hypertension and insulin resistance. However, the concomitant effects of COC and NO deficiency on the heart and glucose regulation are not well known. We therefore hypothesized that COC treatment during NO deficiency would lead to the development of cardiac hypertrophy that is associated with aggravated glucose deregulation, pro-inflammatory and pro-fibrotic biomarkers. Eight-week-old female Wistar rats were randomly allotted into control, NO deficient (N^G-nitro-l-arginine methyl ester: L-NAME; 20.0mg/kg b.w.), COC-treated (1.0μg ethinylestradiol+5.0μg levonorgestrel, p.o) and L-NAME+COC-treated groups. The animals were treated daily for 6 weeks. Systolic blood pressure was estimated by tail-cuff plethysmography, insulin resistance (IR) and β-cell function were estimated by homeostatic model of assessment (HOMA-IR and HOMA-β). Pro-inflammatory (C-reactive protein; CRP and uric acid) and pro-fibrotic (plasminogen activator inhibitor-1; PAI-1) biomarkers were estimated in the plasma. Cardiac histological examination was also done. Results show that COC or L-NAME treatments led to increased blood pressure, HOMA-IR, impaired β-cell function, PAI-1, CRP and uric acid, without significant effect on cardiac mass. L-NAME+COC-treated group had significantly higher blood pressure, HOMA-IR, impaired β-cell function, PAI-1, CRP and cardiac mass than COC- or L-NAME-treated groups. Histological examination validated that COC use during NO deficiency causes cardiac hypertrophy. The present study demonstrates that COC treatment and NO deficiency synergistically causes cardiac hypertrophy that is associated with aggravated glucose deregulation, atherogenic dyslipidemia, pro-inflammatory and pro-fibrotic markers.

Activation of cardiac renin-angiotensin system and plasminogen activator inhibitor-1 gene expressions in oral contraceptive-induced cardiometabolic disorder

CONTEXT

Clinical studies have shown that combined oral contraceptive (COC) use is associated with cardiometabolic disturbances. Elevated renin-angiotensin system (RAS) and plasminogen activator inhibitor-1 (PAI-1) have also been implicated in the development of cardiometabolic events.

OBJECTIVE

To determine the effect of COC treatment on cardiac RAS and PAI-1 gene expressions, and whether the effect is circulating aldosterone or corticosterone dependent.

METHODS

Female rats were treated (p.o.) with olive oil (vehicle) or COC (1.0 µg ethinylestradiol and 10.0 µg norgestrel) daily for six weeks.

RESULTS

COC treatment led to increases in blood pressure, HOMA-IR, Ace1 mRNA, Atr1 mRNA, Pai1 mRNA, cardiac PAI-1, plasma PAI-1, C-reactive protein, uric acid, insulin and corticosterone. COC treatment also led to dyslipidemia, decreased glucose tolerance and plasma 17β-estradiol.

CONCLUSION

These results demonstrates that hypertension and insulin resistance induced by COC is associated with increased cardiac RAS and PAI-1 gene expression, which is likely to be through corticosterone-dependent but not aldosterone-dependent mechanism.

Improvement of oral contraceptive-induced glucose dysregulation and dyslipidemia by valproic acid is independent of circulating corticosterone

CONTEXT

Cardiometabolic disorders are rapidly becoming major public health challenges. Valproic acid (VPA) is a widely prescribed anticonvulsant drug.

OBJECTIVE

We hypothesized that treatment with VPA would improve the regulation of glucose and atherogenic dyslipidemia through reduction in circulating corticosterone.

METHODS

Female Wistar rats recieved (p.o.) combined oral contraceptive (COC) containing 1.0 µg ethinylestradiol plus 5.0 µg levonorgestrel and valproic acid (VPA; 20 mg) for 8 weeks.

RESULTS

Treatment with COC led to elevated fasting blood glucose, insulin, corticosterone, triglycerides (TG), TG/HDL-cholesterol ratio, insulin resistance (IR) and impaired glucose tolerance. VPA significantly attenuated the alterations induced by COC treatment, but did not affect the corticosterone level. However, VPA treatment led to significant increases in plasma insulin, corticosterone, atherogenic lipids and impaired glucose tolerance in rats not treated with COC.

CONCLUSION

The findings in this study suggest that VPA mitigates against the development of COC-induced insulin resistance and dyslipidemia independent of elevated circulating corticosterone.

Acute high blood glucose level attenuates histamine-stimulated acid secretion in male Wistar rats

BACKGROUND

Studies have shown that the hyperglycemic state induced by intravenous glucagon or glucose infusion may lead to inhibition of gastric acid secretion through the inhibition of gastric vagus activity. Histamine is a well-known mammalian acid secretagogue and it stimulates acid secretion through H2 receptors. Therefore, the aim of this study was to determine what effect an acute hyperglycemic or hypoglycemic state would have on histamine-stimulated acid secretion.

METHODS

Male Wistar rats weighing between 200 and 250 g were divided into three groups that received an intravenous infusion of normal saline (control group), glucose (hyperglycemic group), or insulin (hypoglycemic group) followed by injection of histamine to stimulate acid secretion. The oesophageal and duodenal ends of the rats' stomach were cannulated with polythene tubing and the stomach was perfused at room temperature using a Langendoff perfusion apparatus. The effluent was collected in aliquots over 10 min per sample and its pH was measured.

RESULTS

There was a significant (p<0.05) decrease in acid secretion following histamine injection in the hyperglycemic rats, while histamine injection led to an increase (p<0.05) in acid secretion in the hypoglycemic rats.

CONCLUSIONS

These results show that hyperglycemic state would result in attenuated histamine-stimulated gastric acid secretion, while hypoglycemic state would lead to increased histamine-stimulated gastric acid secretion.

Effects of aqueous extract of Hibiscus sabdariffa on renal Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activities in Wistar rats

OBJECTIVE

To investigate the effects of oral administration of aqueous extract of Hibiscus sabdariffa on renal Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activities in rats.

METHODS

The 25 and 50 mg/(kg·d) of aqueous extracts of H. sabdariffa were respectively given to rats in the experimental groups for 28 d, and rats in the control group received an appropriate volume of distilled water as vehicle. Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activities in the kidney were assayed by spectrophotometric method.

RESULTS

Administrations of 25 and 50 mg/(kg·d) of aqueous extract of H. sabdariffa significantly decreased the Ca(2+)-Mg(2+)-ATPase activity in the kidney of rats (P<0.05). However, the renal Na(+)-K(+)-ATPase activity of the experimental rats was not affected by either dose of the extract. And the plasma Na(+), K(+) and Ca(2+) levels of the experimental rats had no significant changes. Administration of either dose of the extract did not result in any significant changes in body and kidney weights, the concentrations of plasma albumin and total protein, and alkaline phosphatase, aspartate aminotransferase and alanine aminotransferase activities. However, concentrations of creatinine and urea were significantly reduced by 50 mg/kg of the extract (P<0.05).

CONCLUSION

The present study indicates that oral administration of aqueous extract of H. sabdariffa may preserve the renal function despite a decreased renal Ca(2+)-Mg(2+)-ATPase activity.