Dietary composition of carbohydrates contributes to the development of experimental type 2 diabetes

Sex-specific effects of a high fat diet on aortic inflammation and dysfunction

Obesity and vascular dysfunction are independent and sexually dimorphic risk factors for cardiovascular disease. A high fat diet (HFD) is often used to model obesity in mice, but the sex-specific effects of this diet on aortic inflammation and function are unclear. Therefore, we characterized the aortic immune cell profile and function in 6-week-old male and female C57BL/6 mice fed a normal chow diet (NCD) or HFD for 10 weeks. Metabolic parameters were measured weekly and fortnightly. At end point, aortic immune cell populations and endothelial function were characterized using flow cytometry and wire myography. HFD-male mice had higher bodyweight, blood cholesterol, fasting blood glucose and plasma insulin levels than NCD mice (P < 0.05). HFD did not alter systolic blood pressure (SBP), glycated hemoglobin or blood triglycerides in either sex. HFD-females had delayed increases in bodyweight with a transient increase in fasting blood glucose at week 8 (P < 0.05). Flow cytometry revealed fewer proinflammatory aortic monocytes in females fed a HFD compared to NCD. HFD did not affect aortic leukocyte populations in males. Conversely, HFD impaired endothelium-dependent vasorelaxation, but only in males. Overall, this highlights biological sex as a key factor determining vascular disease severity in HFD-fed mice.

An older diabetes-induced mice model for studying skin wound healing

Advances in wound treatment depend on the availability of animal models that reflect key aspects of human wound healing physiology. To this date, the accepted mouse models do not reflect defects in the healing process for chronic wounds that are associated with type two diabetic skin ulcers. The long term, systemic physiologic stress that occurs in middle aged or older Type 2 diabetes patients is difficult to simulate in preclinical animal model. We have strived to incorporate the essential elements of this stress in a manageable mouse model: long term metabolic stress from obesity to include the effects of middle age and thereafter onset of diabetes. At six-weeks age, male C57BL/6 mice were separated into groups fed a chow and High-Fat Diet for 0.5, 3, and 6 months. Treatment groups included long term, obesity stressed mice with induction of diabetes by streptozotocin at 5 months, and further physiologic evaluation at 8 months old. We show that this model results in a severe metabolic phenotype with insulin resistance and glucose intolerance associated with obesity and, more importantly, skin changes. The phenotype of this older age mouse model included a transcriptional signature of gene expression in skin that overlapped that observed with elderly patients who develop diabetic foot ulcers. We believe this unique old age phenotype contrasts with current mice models with induced diabetes.

Dietary potato intake and risks of type 2 diabetes and gestational diabetes mellitus

BACKGROUND & AIMS

Evidence regarding associations between potato consumption and type 2 diabetes (T2D) and gestational diabetes mellitus (GDM) risks is accumulating. This study aims to synthesize the evidence by conducting a meta-analysis of available studies.

METHODS

PubMed, Web of Science, EMBASE and Cochrane Library were searched (up to August 2020) to retrieve all eligible studies on the associations of interest. The risk estimates with 95% confidence intervals (CIs) were summarized using random- or fixed-effects model based on heterogeneity. Meta-analyses were performed for East and West regions separately. Dose-response relationship was assessed using data from all intake categories in each study.

RESULTS

A total of 19 studies (13 for T2D; 6 for GDM) were identified, including 21,357 T2D cases among 323,475 participants and 1516 GDM cases among 29,288 pregnancies. Meta-analysis detected a significantly positive association with T2D risk for total potato (RR: 1.19 [1.06, 1.34]), baked/boiled/mashed potato (RR: 1.08 [1.00, 1.16]), and French fries/fried potato (RR: 1.33 [1.03, 1.70]) intakes among Western populations. Dose-response meta-analysis demonstrated a significantly increased T2D risk by 10% (95% CI: 1.07, 1.14; P for trend<0.001), 2% (95% CI: 1.00, 1.04; P for trend = 0.02) and 34% (95% CI: 1.24, 1.46; P for trend<0.001) for each 80 g/day (serving) increment in total potato, unfried potato, and fried potato intakes, respectively. As for GDM, summarized estimates also suggested a higher though non-significant GDM risk for total potato (RR: 1.19 [0.89, 1.58]), and French fries/fried potato (RR: 1.03 [0.97, 1.09]) intakes in Western countries. In the dose-response meta-analysis, a significantly increased GDM risk was revealed for each daily serving (80 g) intakes of total potato (RR: 1.22; 95% CI: 1.06, 1.42; P for trend = 0.007) and unfried potato (RR: 1.26; 95% CI: 1.07, 1.48; P for trend = 0.006).

CONCLUSIONS

This study suggests that higher potato intake is associated with higher T2D risk among Western populations. The positive relationship presents a significant dose-response manner. Wisely controlled potato consumption may confer potential glucometabolic benefits.

Dysregulation of key cytokines may contribute to increased susceptibility of diabetic mice to Mycobacterium bovis BCG infection

Diabetes is one of the major co-morbidities contributing to the high global burden of tuberculosis (TB). The increased susceptibility of individuals with type 2 diabetes (T2D) to TB is multifactorial and may influence the efficacy of vaccines. This study was undertaken to determine the early immune responses that occur following infection with Mycobacterium bovis Bacille Calmette-Guérin (BCG) in a diet-induced murine model of T2D. The phagocytic capabilities of alveolar (AM) and resident peritoneal macrophages (RPM) were assessed using ex vivo assays. Compared to macrophages from non-diabetic mice, macrophages from diabetic animals showed decreased BCG uptake and killing and inflammatory cytokine production (TNF-α, MCP-1, IL-6, IL-1β). In vivo susceptibility to BCG was determined following intravenous infection and diabetic mice showed a trend towards increased mortality, higher bacterial burden in the lung, liver and spleen and increased inflammatory lesions compared to controls. Differences between tissue cytokines were observed as early as one day post-infection and by days 14 and 35, lung and liver TNF-α and IFN-γ levels were decreased in diabetic mice compared to controls. These results suggest that early dysregulated immune responses may influence the susceptibility of T2D mice to BCG infection.

Anti-mycobacterial function of macrophages is impaired in a diet induced model of type 2 diabetes

Type 2 diabetes (T2D) is one of the major risk factors for tuberculosis (TB). In this study, a diet induced murine model of T2D (DIMT2D) was developed and characterized in the context of metabolic, biochemical and histopathological features following diet intervention. Mycobacterial susceptibility was investigated using Mycobacterium fortuitum as a surrogate. Phagocytic capability of alveolar macrophages and resident peritoneal macrophages were determined by in vitro assays using mycolic acid coated beads and M. fortuitum. Results demonstrated that bacillary loads were significantly higher in liver, spleen, and lungs of diabetic mice compared to controls. Higher inflammatory lesions and impaired cytokine kinetics (TNF-α, MCP-1, IL-12, IFN-γ) were also observed in diabetic mice. Macrophages isolated from diabetic mice had lower uptake of mycolic acid coated beads, reduced bacterial internalization and killing and altered cytokine responses (TNF-α, IL-6, MCP-1). This model will be useful to further investigate different facets of host-pathogen interactions in TB-T2D.

Development of a diet-induced murine model of diabetes featuring cardinal metabolic and pathophysiological abnormalities of type 2 diabetes

The persistent rise in global incidence of type 2 diabetes (T2D) continues to have significant public health and economic implications. The availability of relevant animal models of T2D is critical to elucidating the complexity of the pathogenic mechanisms underlying this disease and the implications this has on susceptibility to T2D complications. Whilst many high-fat diet-induced rodent models of obesity and diabetes exist, growing appreciation of the contribution of high glycaemic index diets on the development of hyperglycaemia and insulin resistance highlight the requirement for animal models that more closely represent global dietary patterns reflective of modern society. To that end, we sought to develop and validate a murine model of T2D based on consumption of an energy-dense diet containing moderate levels of fat and a high glycaemic index to better reflect the aetiopathogenesis of T2D. Male C57BL/6 mice were fed an energy-dense (ED) diet and the development of pathological features used in the clinical diagnosis of T2D was assessed over a 30-week period. Compared with control mice, 87% of mice fed an ED diet developed pathognomonic signs of T2D including glucose intolerance, hyperglycaemia, glycosylated haemoglobin (HbA1c) and glycosuria within 30 weeks. Furthermore, dyslipidaemia, chronic inflammation, alterations in circulating leucocytes and renal impairment were also evident in ED diet-fed mice compared with mice receiving standard rodent chow. Longitudinal profiling of metabolic and biochemical parameters provide support of an aetiologically and clinically relevant model of T2D that will serve as a valuable tool for mechanistic and therapeutic studies investigating the pathogenic complications of T2D.

The Impact of Prior Flavivirus Infections on the Development of Type 2 Diabetes Among the Indigenous Australians

It is estimated that 5% of Australians over the age of 18 have diabetes, with the number of new cases increasing every year. Type 2 diabetes (T2D) also represents a significant disease burden in the Australian indigenous population, where prevalence is three times greater than that of non-indigenous Australians. Prevalence of T2D has been found to be higher in rural and remote indigenous Australian populations compared with urban indigenous Australian populations. Several studies have also found that body mass index and waist circumference are not appropriate for the prediction of T2D risk in indigenous Australians. Regional and remote areas of Australia are endemic for a variety of mosquito-borne flaviviruses. Studies that have investigated seroprevalence of flaviviruses in remote aboriginal communities have found high proportions of seroconversion. The family Flaviviridae comprises several genera of viruses with non-segmented single-stranded positive sense RNA genomes, and includes the flaviviruses and hepaciviruses. Hepatitis C virus (HCV) has been shown to be associated with insulin resistance and subsequent development of T2D. Flaviviruses and HCV possess conserved proteins and subgenomic RNA structures that may play similar roles in the development of insulin resistance. Although dietary and lifestyle factors are associated with increased risk of developing T2D, the impact of infectious diseases such as arboviruses has not been assessed. Flaviviruses circulating in indigenous Australian communities may play a significant role in inducing glucose intolerance and exacerbating T2D.

Murine models provide insight to the development of non-alcoholic fatty liver disease

Associated with the obesity epidemic, non-alcoholic fatty liver disease (NAFLD) has become the leading liver disease in North America. Approximately 30 % of patients with NAFLD may develop non-alcoholic steatohepatitis (NASH) that can lead to cirrhosis and hepatocellular carcinoma (HCC). Frequently animal models are used to help identify underlying factors contributing to NAFLD including insulin resistance, dysregulated lipid metabolism and mitochondrial stress. However, studying the inflammatory, progressive nature of NASH in the context of obesity has proven to be a challenge in mice. Although the development of effective treatment strategies for NAFLD and NASH is gaining momentum, the field is hindered by a lack of a concise animal model that reflects the development of liver disease during obesity and the metabolic syndrome. Therefore, selecting an animal model to study NAFLD or NASH must be done carefully to ensure the optimal application. The most widely used animal models have been reviewed highlighting their advantages and disadvantages to studying NAFLD and NASH specifically in the context of obesity.

Fruit intake decreases risk of incident type 2 diabetes: an updated meta-analysis

Association between fruit intake and risk of type 2 diabetes is inconsistent. In this study, we performed a meta-analysis of all prospective cohort studies to clarify the association between fruit intake and risk of type 2 diabetes. Relevant studies were identified by searches of the PubMed and Embase databases up to November 2013. The summary relative risks of association were obtained using a fixed- or random-effects model. A total of nine prospective studies (403,259 participants, including 27,940 with incident type 2 diabetes) from seven publications were included in the meta-analysis of fruit intake and risk of type 2 diabetes. We found that individuals in the highest category of fruit intake had a reduced risk of type 2 diabetes (relative risk 0.92, 95 % confidence interval 0.86-0.97, p = 0.003) compared to those in the lowest category, with moderate evidence of between-study heterogeneity (I (2) = 37.6 %, p = 0.12). There was an evident non-linear association of fruit intake with type 2 diabetes (P for nonlinearity <0.001). A non-linear threshold of 200 g/day of fruit intake was identified and the risk of type 2 diabetes reduced by about 13 % at this cut-off. Our findings are consistent with diet recommendations to consume about 200 g/day of fruits to prevent type 2 diabetes.

Dietary models of insulin resistance

Insulin resistance is a significant factor in the development of type 2 diabetes mellitus, however the connection between the Western diet and the development of insulin resistance has not been fully explained. Dietary macronutrient composition has been examined in a number of articles, and diets enriched in saturated fatty acids, and possibly in fructose, appear to be most consistently associated with the development of insulin resistance. However, mechanistic insights into the metabolic effects of such diets are lacking, and merit further study.

New technologies aiding dietary programmes for weight control: the oral glucose spray

To determine whether the administration of small amounts of glucose through an oral spray device (GSD) facilitates weight loss in overweight/obese subjects involved in a lifestyle modification programme. We randomly assigned 56 overweight/obese subjects to either the treatment group (n = 32) or the control group (n = 24). All subjects in both groups followed a structured dietary programme of 6,280.2 kJ (1,500 kcal)/day and exercised minimum 150 min a week and were followed-up for a period of 60 days. Subjects assigned to the treatment group were asked to spray, during early symptoms of neuroglycopenia, 10 puffs by GSD. GSD is a device that delivers to the buccal mucosa 50 mg of glucose per puff. A mean weight loss of 3.5 ± 3.0 kg in GSD-treated group compared to 1.7 ± 2.1 kg in control group (p = 0.01) was observed. Significant differences regarding reduction of BMI (-1.3 ± 1.0 vs. -0.7 ± 0.8 kg/m2; p = 0.01) and waist circumference (-3.5 ± 3.2 vs. -0.9 ± 3.5 cm; p = 0.02) were also detected. A short-term use of GSD, in association with dietary restriction and exercise, is helpful in improving weight loss and in reducing waist circumference in overweight/obese subjects.