Assessment of current status and geospatial analysis of compliance to bacteriological parameters: Tools to ensure access to safe water in Sri Lanka.

Compliance of drinking-water to bacteriological parameters serves as a surrogate measure of the risk of water-borne diseases. Understanding the risk of water-borne diseases could help promote healthy behaviors such as household water treatment and safe water storage practices and advocacy to increase access to centrally-managed piped water. The objective of this research was to assess the current status of compliance and to geospatially analyze the probability of compliance to bacteriological parameters in the Western Province of Sri Lanka. A drinking-water quality survey was conducted among 4508 households representing four water-source types: National Water Supply and Drainage Board (NWSDB), dug wells, Community Water Supply (CWS), and tube wells, and other sources. Besides, a detailed assessment of selected NWSDB and CWS supplies was done. Water samples were tested for the total coliform count, thermotolerant coliform count, and free residual chlorine levels against the Sri Lanka Standards. Indicator kriging was performed using the geospatial analyst tool of ArcGIS version 10.6 for different water source types to interpolate the probability of compliance for both total coliform count and thermotolerant coliform count. The bacteriological compliance decreased from NWSDB to tube wells and other sources to CWS to dug wells. The interpolation maps confirm the relatively higher compliance of NWSDB for bacteriological parameters compared to other sources. Areas with a high probability of compliance for both parameters show considerable overlap with urban areas with a supply of centrally managed water from the NWSDB. It is recommended to expand the coverage of NWSDB water, strengthen the drinking-water quality surveillance system and water safety plans, and promote household water treatment and safe storage practices in the Western Province of Sri Lanka.

Predictive modelling for COVID-19 outbreak control: lessons from the navy cluster in Sri Lanka.

In response to an outbreak of coronavirus disease 2019 (COVID-19) within a cluster of Navy personnel in Sri Lanka commencing from 22nd April 2020, an aggressive outbreak management program was launched by the Epidemiology Unit of the Ministry of Health. To predict the possible number of cases within the susceptible population under four social distancing scenarios, the COVID-19 Hospital Impact Model for Epidemics (CHIME) was used. With increasing social distancing, the epidemiological curve flattened, and its peak shifted to the right. The observed or actually reported number of cases was above the projected number of cases at the onset; however, subsequently, it fell below all predicted trends. Predictive modelling is a useful tool for the control of outbreaks such as COVID-19 in a closed community.

Islet amyloid inhibitors improve glucose homeostasis in a transgenic mouse model of type 2 diabetes.

Increasing evidence points to the cytotoxicity of islet amyloid polypeptide (IAPP) aggregates as a major contributor to the loss of ß-cell mass in type 2 diabetes. Prevention of IAPP formation represents a potential treatment to increase ß-cell survival and function. The IAPP inhibitory peptide, D-ANFLVH, has been previously shown to prevent islet amyloid accumulation in cultured human islets. To assess its activity in vivo, D-ANFLVH was administered by intraperitoneal injection into a human IAPP transgenic mouse model, which replicates type 2 diabetes islet amyloid pathology. The peptide was a potent inhibitor of islet amyloid deposition, resulting in reduced islet cell apoptosis and preservation of ß-cell area leading to improved glucose tolerance. These findings provide support for a key role of islet amyloid in ß-cell survival and validate the application of anti-amyloid compounds as therapeutic strategies to maintain normal insulin secretion in patients with type 2 diabetes.

Effects of high-fat diet feeding on Znt8-null mice: differences between ß-cell and global knockout of Znt8.

Genomewide association studies have linked a polymorphism in the zinc transporter 8 (Znt8) gene to higher risk of developing type 2 diabetes. Znt8 is highly expressed in pancreatic ß-cells where it is involved in the regulation of zinc transport into granules. However, Znt8 is also expressed in other tissues including α-cells, where its function is as yet unknown. Previous work demonstrated that mice lacking Znt8 globally were more susceptible to diet-induced obesity (Lemaire et al., Proc Natl Acad Sci USA 106: 14872-14877, 2009; Nicolson et al., Diabetes 58: 2070-2083, 2009). Therefore, the main goal of this study was to examine the physiological impact of ß-cell-specific Znt8 deficiency in mice during high-fat high-calorie (HFHC) diet feeding. For these studies, we used ß-cell-specific Znt8 knockout (Ins2Cre:Znt8loxP/loxP) and whole body Znt8 knockout (Cre-:Znt8(-/-)) mice placed on a HFHC diet for 16 wk. Ins2Cre:Znt8loxP/loxP mice on HFHC diet had similar body weights throughout the study but displayed impaired insulin biosynthesis and secretion and were glucose intolerant compared with littermate control Ins2Cre mice. In contrast, Cre-:Znt8(-/-) mice became remarkably obese, hyperglycemic, hyperinsulinemic, insulin resistant, and glucose intolerant compared with littermate control Cre- mice. These data show that ß-cell Znt8 alone does not considerably aggravate weight gain and glucose intolerance during metabolic stress imposed by an HFHC diet. However, global loss of Znt8 is involved in exacerbating diet-induced obesity and resulting insulin resistance, and this may be due to the loss of Znt8 activity in a tissue other than the ß-cell. Thus, our data suggest that Znt8 contributes to the risk of developing type 2 diabetes through ß-cell- and non-ß-cell-specific effects.

Regulation of glucagon secretion by zinc: lessons from the ß cell-specific Znt8 knockout mouse model.

In type-2 diabetes, hyperglucagonaemia aggravates elevated blood glucose levels. Relative to our knowledge of the ß-cell and insulin secretion, there remains a limited understanding of glucagon secretion in α-cells. Regulation of glucagon may be dependent on a combination of factors, which include direct glucose sensing by the α-cell, innervations from the autonomic nervous system and potential 'paracrine' actions by hormones and factors that are released by adjacent endocrine cells within the islets. The list of potential 'paracrine' regulators within the islet includes insulin, somatostatin, γ-aminobutyric acid, glutamate and zinc. Zinc crystallises with insulin in ß-cells and is co-secreted with insulin. In the scientific literature, the effect of exogeneous zinc on glucagon secretion has been debated. Here, we confirm that an increase in exogeneous zinc does inhibit glucagon secretion. To determine if there are physiological effects of zinc on glucagon secretion we used a ß-cell-specific ZnT8 knockout (Znt8BKO) mouse model. Znt8BKO mice, despite showing lower granular zinc content in ß-cells, showed no changes in fasted plasma glucagon levels and glucose regulated glucagon secretion. These findings suggest that zinc secreted from ß-cell does not regulate glucagon secretion.

Beta cell-specific Znt8 deletion in mice causes marked defects in insulin processing, crystallisation and secretion.

AIMS/HYPOTHESIS: Zinc is highly concentrated in pancreatic beta cells, is critical for normal insulin storage and may regulate glucagon secretion from alpha cells. Zinc transport family member 8 (ZnT8) is a zinc efflux transporter that is highly abundant in beta cells. Polymorphisms of ZnT8 (also known as SLC30A8) gene in man are associated with increased risk of type 2 diabetes. While global Znt8 knockout (Znt8KO) mice have been characterised, ZnT8 is also present in other islet cell types and extra-pancreatic tissues. Therefore, it is important to find ways of understanding the role of ZnT8 in beta and alpha cells without the difficulties caused by the confounding effects of ZnT8 in these other tissues. METHODS: We generated mice with beta cell-specific (Znt8BKO) and alpha cell-specific (Znt8AKO) knockout of Znt8, and performed in vivo and in vitro characterisation of the phenotypes to determine the functional and anatomical impact of ZnT8 in these cells. Thus we assessed zinc accumulation, insulin granule morphology, insulin biosynthesis and secretion, and glucose homeostasis. RESULTS: Znt8BKO mice are glucose-intolerant, have reduced beta cell zinc accumulation and atypical insulin granules. They also display reduced first-phase glucose-stimulated insulin secretion, reduced insulin processing enzyme transcripts and increased proinsulin levels. In contrast, Znt8AKO mice show no evident abnormalities in plasma glucagon and glucose homeostasis. CONCLUSIONS/INTERPRETATION: This is the first report of specific beta and alpha cell deletion of Znt8. Our data indicate that while, under the conditions studied, ZnT8 is absolutely essential for proper beta cell function, it is largely dispensable for alpha cell function.

Zinc, a regulator of islet function and glucose homeostasis.

It is well known that zinc is required in pancreatic beta-cells in the process of insulin biosynthesis and the maturation of insulin secretory granules. In fact, the zinc level in pancreatic islets is amongst the highest in the body and reduction in its levels in the pancreas has been associated with diabetes. High concentrations of zinc can also be toxic because of enhanced oxidative damage. The link between zinc, diabetes and islet dysfunction has recently been reiterated by genomewide association studies that identified an islet cell membrane zinc transporter, SLC30A8 (ZnT8), as one of the risk loci for type 2 diabetes. Here we explore the importance of both zinc and ZnT8 to islet biology and whole body glucose homeostasis.

Indinavir uncovers different contributions of GLUT4 and GLUT1 towards glucose uptake in muscle and fat cells and tissues.

AIMS/HYPOTHESIS: Insulin-dependent glucose influx in skeletal muscle and adipocytes is believed to rely largely on GLUT4, but this has not been confirmed directly. We assessed the relative functional contribution of GLUT4 in experimental models of skeletal muscle and adipocytes using the HIV-1 protease inhibitor indinavir. METHODS: Indinavir (up to 100 micro mol/l) was added to the glucose transport solution after insulin stimulation of wild-type L6 muscle cells, L6 cells over-expressing either GLUT4myc or GLUT1myc, 3T3-L1 adipocytes, isolated mouse brown or white adipocytes, and isolated mouse muscle preparations. RESULTS: 100 micro mol/l indinavir inhibited 80% of both basal and insulin-stimulated 2-deoxyglucose uptake in L6GLUT4myc myotubes and myoblasts, but only 25% in L6GLUT1myc cells. Cell-surface density of glucose transporters was not affected. In isolated soleus and extensor digitorum longus muscles, primary white and brown adipocytes, insulin-stimulated glucose uptake was inhibited 70 to 80% by indinavir. The effect of indinavir on glucose uptake was variable in 3T3-L1 adipocytes, averaging 45% and 67% inhibition of basal and maximally insulin-stimulated glucose uptake, respectively. In this cell, fractional inhibition of glucose uptake by indinavir correlated positively with the fold-stimulation of glucose uptake by insulin, and was higher with sub-maximal insulin concentrations. The latter finding coincided with an increase only in GLUT4, but not GLUT1, in plasma membrane lawns. CONCLUSION/INTERPRETATION: Indinavir is a useful tool to assess different functional contributions of GLUT4 to glucose uptake in common models of skeletal muscle and adipocytes.