Impaired Glucose Tolerance is Associated with Enhanced Platelet-Monocyte Aggregation in Short-Term High-Fat Diet-Fed Mice

High-dose oral contraceptives induce hyperinsulinemia without altering immune activation in diet-induced obesity which persists even following a dietary low-fat diet intervention

Combined oral contraceptives (COCs) are known to cause weight gain and alter metabolic and immunological pathways. However, modifications in arterial or venous thrombotic risk profiles of women of reproductive ages on COC remain unclear. The study aimed at assessing the impact of COC on immune activation in diet-induced obesity. We further established whether the dietary intervention of switching from a high-fat diet (HFD) to a low-fat diet (LFD) attenuates immunological responses. Twenty (n=20) five-week-old female Sprague Dawley rats were randomly divided into two diet groups of HFD (n=15) and LFD (n=5) and were monitored for eight weeks. After eight weeks, animals in the HFD group switched diets to LFD and were randomly assigned to receive high-dose COC (HCOC) or low-dose COC (LCOC) for six weeks. Animals on HFD significantly gained weight and had a higher lee index when compared to the LFD group (p < 0.05). Moreover, the triglyceride-glucose index, insulin, and other metabolic parameters also increased in the HFD group compared to the LFD group (p < 0.001). Consistently, the levels of interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-α), were elevated in the HFD group when compared to the LFD group (p < 0.05). Upon switching from a high-fat to a low-fat diet, insulin levels persistently increased in animals receiving HCOC treatment compared to the LFD and HFD/LFD groups (p < 0.05). Thus, in a rat model of HFD-feeding, short-term HCOC treatment induces long-term metabolic dysregulation, which persists despite dietary intervention. However, further studies are recommended to confirm these findings.

Potential regulatory role of PGC-1α within the skeletal muscle during metabolic adaptations in response to high-fat diet feeding in animal models

High-fat diet (HFD) feeding in rodents has become an essential tool to critically analyze and study the pathological effects of obesity, including mitochondrial dysfunction and insulin resistance. Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) regulates cellular energy metabolism to influence insulin sensitivity, beyond its active role in stimulating mitochondrial biogenesis to facilitate skeletal muscle adaptations in response to HFD feeding. Here, some of the major electronic databases like PubMed, Embase, and Web of Science were accessed to update and critically discuss information on the potential role of PGC-1α during metabolic adaptations within the skeletal muscle in response to HFD feeding in rodents. In fact, available evidence suggests that partial exposure to HFD feeding (potentially during the early stages of disease development) is associated with impaired metabolic adaptations within the skeletal muscle, including mitochondrial dysfunction and reduced insulin sensitivity. In terms of implicated molecular mechanisms, these negative effects are partially associated with reduced activity of PGC-1α, together with the phosphorylation of protein kinase B and altered expression of genes involving nuclear respiratory factor 1 and mitochondrial transcription factor A within the skeletal muscle. Notably, metabolic abnormalities observed with chronic exposure to HFD (likely during the late stages of disease development) may potentially occur independently of PGC-1α regulation within the muscle of rodents. Summarized evidence suggests the causal relationship between PGC-1α regulation and effective modulations of mitochondrial biogenesis and metabolic flexibility during the different stages of disease development. It further indicates that prominent interventions like caloric restriction and physical exercise may affect PGC-1α regulation during effective modulation of metabolic processes.

Subclinical cardiovascular outcomes of acute exposure to fine particulate matter and its constituents: A glutathione S-transferase polymorphism-based longitudinal study

To explore the acute subclinical cardiovascular effects of fine particulate matter (PM_2.5) and its constituents, a longitudinal study with 61 healthy young volunteers was conducted in Xinxiang, China. Linear mixed-effect models were used to analyze the association of PM_2.5 and its constituents with cardiovascular outcomes, respectively, including blood pressure (BP), heart rate (HR), serum levels of high-sensitivity C-reactive protein (hs-CRP), 8-hydroxy-2'-deoxyguanosine (8-OHdG), tissue-type plasminogen activator (t-PA), and platelet-monocyte aggregation (PMA). Additionally, the modifying effects of glutathione S-transferase mu 1 (GSTM1) and glutathione S-transferase theta 1 (GSTT1) polymorphisms were examined. A 10 μg/m³ increase in PM_2.5 was associated with -1.04 (95 % CI: -1.86 to -0.22) mmHg and -0.90 (95 % CI: -1.69 to -0.11) mmHg decreases in diastolic BP (DBP) and mean arterial BP (MABP) along with 1.83 % (95 % CI: 0.59-3.08 %), 5.93 % (95 % CI: 0.70-11.16 %) increases in 8-OHdG and hs-CRP, respectively. Ni content was positively associated with the 8-OHdG levels whereas several other metals presented negative association with 8-OHdG and HR. Intriguingly, GSTT1+/GSTTM1+ subjects showed higher susceptibility to PM_2.5-induced alterations of DBP and PMA, and GSTT1-/GSTM1+ subjects showed higher alteration on t-PA. Taken together, our findings indicated that short-term PM_2.5 exposure induced oxidative stress, systemic inflammation, autonomic alterations, and fibrinolysis in healthy young subjects. Among multiple examined metal components Ni appeared to positively associated with systematic oxidative stress. In addition, GST-sufficient subjects might be more prone to PM_2.5-induced autonomic alterations.

Amoxicillin modulates gut microbiota to improve short-term high-fat diet induced pathophysiology in mice

BACKGROUND

A high-fat diet (HFD) induced perturbation of gut microbiota is a major contributory factor to promote the pathophysiology of HFD-associated metabolic syndrome. The HFD could also increase the susceptibility to the microbial infections warranting the use of antibiotics which are independently capable of impacting both gut microbiota and metabolic syndrome. Further, the usage of antibiotics in individuals consuming HFD can impact mitochondrial function that can be associated with an elevated risk of chronic conditions like inflammatory bowel disease (IBD). Despite this high propensity  to infections in individuals on HFD, the link between duration of HFD and antibiotic treatment, and its impact on diversity of the gut microbiome and features of metabolic syndrome is not well established. In this study, we have addressed these knowledge gaps by examining how the gut microbiota profile changes in HFD-fed mice receiving antibiotic intervention in the form of amoxicillin. We also determine whether antibiotic treatment in HFD-fed mice may adversely impact the ability of immune cells to clear microbial infections.

METHODS AND RESULTS

We have subjected mice to HFD and chow diet (CD) for 3 weeks, and a subset of these mice on both diets received antibiotic intervention in the form of amoxicillin in the 3rd week. Body weight and food intake were recorded for 3 weeks. After 21 days, all animals were weighted and sacrificed. Subsequently, these animals were evaluated for basic haemato-biochemical and histopathological attributes. We used 16S rRNA sequencing followed by bioinformatics analysis to determine changes in gut microbiota in these mice. We observed that a HFD, even for a short-duration, could successfully induce the partial pathophysiology typical of a metabolic syndrome, and substantially modulated the gut microbiota in mice. The short course of amoxicillin treatment to HFD-fed mice resulted in beneficial effects by significantly reducing fasting blood glucose and skewing the number of thrombocytes towards a normal range. Remarkably, we observed a significant remodelling of gut microbiota in amoxicillin-treated HFD-fed mice. Importantly, some gut microbes associated with improved insulin sensitivity and recovery from metabolic syndrome only appeared in amoxicillin-treated HFD-fed mice reinforcing the beneficial effects of antibiotic treatment in the HFD-associated metabolic syndrome. Moreover, we also observed the presence of gut-microbiota unique to amoxicillin-treated HFD-fed mice that are also known to improve the pathophysiology associated with metabolic syndrome. However, both CD-fed as well as HFD-fed mice receiving antibiotics showed an increase in intestinal pathogens as is typically observed for antibiotic treatment. Importantly though, infection studies with S. aureus and A. baumannii, revealed that macrophages isolated from amoxicillin-treated HFD-fed mice are comparable to those isolated from mice receiving only HFD or CD in terms of susceptibility, and progression of microbial infection.  This finding  clearly indicated that amoxicillin treatment does not introduce any additional deficits in the ability of macrophages to combat microbial infections.

CONCLUSIONS

Our results showed that amoxicillin treatment in HFD-fed mice exert a beneficial influence on the pathophysiological attributes of metabolic syndrome which correlates with a significant remodelling of gut microbiota. A novel observation was the increase in microbes known to improve insulin sensitivity following amoxicillin treatment during short-term intake of HFD. Even though there is a minor increase in gut-resistant intestinal pathogens in amoxicillin-treated groups, there is no adverse impact on macrophages with respect to their susceptibility and ability to control infections. Taken together, this study provides a proof of principle for the exploration of amoxicillin treatment as a potential therapy in the people affected with metabolic syndrome.

Activated monocytes as a therapeutic target to attenuate vascular inflammation and lower cardiovascular disease-risk in patients with type 2 diabetes: A systematic review of preclinical and clinical studies

Low grade inflammation is associated with the progression of atherosclerosis. Patients with type 2 diabetes (T2D) have altered cholesterol levels, which are targeted by free radicals to promote lipid peroxidation. Elevated levels of monocyte-associated cytokines such as interleukin (IL)-6, monocyte chemoattractant protein 1 (MCP-1), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and tumor necrosis factor-alpha (TNF-α), subsequently drive endothelial tissue injury. In fact, the levels of circulating platelet-monocyte aggregates in patients with T2D is a robust marker for atherosclerosis and a cardiovascular disease (CVD)-risk factor. To identify eligible studies, we searched the major online databases using PubMed and Google Scholar. The cumulative evidence synthesized in the current review suggests that, traditional therapies which include thiazolidinediones, statins and some calcium channel blockers can be useful in the primary prevention of atherosclerosis by inhibiting the formation of monocyte-derived microparticles, and pro-inflammatory cytokines such as IL-6, TNF-α, MCP-1, and NF-κB in patients with T2D. Future studies are needed to ascertain whether the combination of dietary interventions and glucose or lipid lowering agents can provide an enhanced cardioprotection in patients with T2D.

Circulating

Impaired Glc tolerance and hyperinsulinemia are a hallmark of type 2 diabetes (T2D) and are associated with an altered innate and adaptive immune response. In this study, we used a high-fat diet (HFD)-induced model of pre-diabetes to explore the pathological implications of altered innate lymphoid cell (ILC) profiles in a state of impaired Glc tolerance. Sixteen male C57BL/6 mice were randomized to receive two experimental diets (n = 8 per group), low-fat (LFD), and HFD for 8-13 wk. We evaluated the levels of circulating innate lymphoid cells and their respective cytokines following HFD-feeding. The HFD group had impaired Glc tolerance, elevated insulin levels, and increased total cholesterol levels. Notably, the levels of circulating ILC1s were elevated following 13 wk of HFD-feeding. Moreover, the levels of TNF-α were decreased, but there were no changes in IFN-γ levels. Lastly, the levels of circulating ILC2s and ILC3s were comparable between the HFD and LFD group. The findings demonstrated that short-term HFD-feeding increases postprandial blood Glc, total cholesterol and insulin levels. However, the metabolic changes did not alter ILC2 and ILC3 levels and their respective cytokine profiles.

Differential expression of glycoprotein IV on monocyte subsets following high-fat diet feeding and the impact of short-term low-dose aspirin treatment

OBJECTIVE

To assess the levels of glycoprotein GPIV (CD36) expression on peripheral blood monocyte subsets, in a mouse model of glucose intolerance. Moreover, to determine the effect of; low-dose aspirin (LDA) alone, LDA combined with metformin, or clopidogrel alone, on the expression of CD36 on subsets of circulating monocytes.

METHOD

The study consisted of two experimental phases. In experiment one, the mice (n = 14) were randomised to receive a low-fat diet (LFD) or a high-fat diet (HFD) for eight weeks. Whereas the secondary phase of the experiment, comprised of twenty-four HFD-fed mice treated with LDA alone (3 mg/kg), or in combination with metformin (150 mg/kg), or clopidogrel alone (10 mg/kg) for six weeks. The surface expression of CD36 on monocytes was measured using flow cytometry.

RESULT

The levels of CD36 expression on monocytes were upregulated in the HFD-fed compared to LFD-fed group (p < 0.05). In addition, HFD group showed; no significant changes in body weight (p = 0.3848), however, blood glucose (p = 0.0002) and insulin (p = 0.0360) levels were markedly increased following HFD-feeding. Interestingly, all treatments reduced the expression of CD36 on monocytes, decreased fasting blood glucose levels (p = 0.0024) and increased circulating monocyte levels (p = 0.0217) when compared to the untreated HFD group. Moreover, treatment with LDA alone increased basophils levels (p = 0.0272), while when combined with metformin showed an improved effect in enhancing eosinophil levels (p = 0.0302).

CONCLUSION

HFD-feeding increased the expression of CD36 on monocyte subsets. LDA as a monotherapy or combined with metformin was as effective as clopidogrel monotherapy, in downregulating the expression of CD36 on monocyte subsets. These treatments may be of relevance in preventing cardiovascular complications associated with impaired glucose tolerance.

The prophylactic effects of vitamin K supplementation on coagulopathies associated with type 2 diabetes mellitus: A protocol for a systematic review and meta-analysis

BACKGROUND

The impact of vitamin K in ameliorating diabetes-associated complications, especially those linked with platelet activation and coagulation remains unclear. The current study aims to systematically explore and discuss the available evidence on the impact of vitamin K on the diabetes-cardiovascular disease (CVD)-associated complications.

METHODS

A systematic review of studies published on the MEDLINE (PubMed), EMBASE, and Google Scholar electronic database will be conducted. The review will include studies published from inception until May 25, 2020, reporting on the effect of vitamin K on CVD-related markers, especially coagulation factors and platelet activation in type 2 diabetes mellitus. Before the full-text screening, all studies will be screened by title, abstract, and keywords. The Downs and Black checklist will be used to assess the quality of the studies. Additionally, the Cochrane collaboration tool will also be used to evaluate the risk of bias across the included studies. Kappa Cohen's calculator will be used to assess the level of agreement between the authors.

DISCUSSIONS

This systematic review will not require ethical approval, and the results will be distributed through conference and peer-reviewed publications. Our results will assist current and future research scientists on the potential use of vitamin K as a protective therapy against CVD-related complications.

SYSTEMATIC REVIEW REGISTRATION

This protocol is registered on the International Prospective Register of Systematic Reviews (PROSPERO) registration number: CRD42020151667.