Johan Louw

South African Medical Research Council | MRC · Biomedical Research and Innovation Platform

Wastewater-based epidemiology (WBE) has been an important tool for the detection of COVID-19 outbreaks. The retrospective analysis of COVID-19 data is vital to understand the spread and impact of the virus as well as to inform future planning and response efforts. In this study, we evaluated the SARS-CoV-2 RNA levels in wastewater from 21 wastewate...

Monitoring of SARS-CoV-2 RNA in wastewater has revealed the role of mobility in the transmission of coronavirus disease (COVID-19), and the surveillance of airport wastewater in cities across the world has demonstrated how travel entry points can give an indication of trends in transmission. This study undertook wastewater surveillance at the Cape...

Wastewater surveillance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has shown to be an important approach to determine early outbreaks of infections. Wastewater-based epidemiology (WBE) is regarded as a complementary tool for monitoring SARS-CoV-2 trends in communities. In this study, the changes in the SARS-CoV-2 RNA levels in...

Rooibos ( Aspalathus linearis ), an indigenous South African plant and its major flavonoid, aspalathin, exhibited positive effects on glycemia and dyslipidemia in animal studies. Limited evidence exists on the effects of rooibos extract taken in combination with oral hypoglycemic and lipid-lowering medications. This study investigated the combined...

Background The focus on traditional and complementary medicine for supplementation and treatment of diseases is high. Aspalathus linearis commonly known as Rooibos showed several beneficial effects, this led to the standardized production of a pharmaceutical grade green rooibos extract (Afriplex TM GRT) with enhanced polyphenolic content. The aim o...

This study was one of the first to detect Omicron sublineages BA.4 and BA.5 in wastewater from South Africa. Spearman rank correlation analysis confirmed a strong positive correlation exists between SARS-CoV-2 viral RNA in wastewater samples and clinical cases (r = 0.7749, p < 0.0001). SARS-CoV-2 viral load detected in wastewater, resulting from th...

This study uses wastewater-based epidemiology (WBE) to rapidly and, through targeted surveillance, track the geographical distribution of SARS-CoV-2 variants of concern (Alpha, Beta and Delta) within 24 wastewater treatment plants (WWTPs) in the Western Cape of South Africa. Information obtained was used to identify the circulating variant of conce...

The current severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnostic capacity is limited in defined communities, posing a challenge in tracking and tracing new infections. Monitoring student residences, which are considered infection hotspots, with targeted wastewater surveillance is crucial. This study evaluated the efficacy of SARS...

Noncommunicable diseases, such as type 2 diabetes (T2D), place a burden on healthcare systems worldwide. The rising prevalence of obesity, a major risk factor for T2D, is mainly attributed to the adoption of Westernized diets and lifestyle, which cause metabolic dysfunction and insulin resistance. Moreover, diet may also induce changes in the micro...

This study uses wastewater-based epidemiology (WBE) to rapidly and, through targeted surveillance, track the geographical distribution of SARS-CoV-2 variants of concern (Alpha, Beta and Delta) within 24 wastewater treatment plants (WWTPs) in the Western Cape of South Africa. Information obtained was used to identify the circulating variant of conce...

Recent scientific trends have revealed that the collection and analysis of data on the occurrence and fate of SARS-CoV-2 in wastewater may serve as an early warning system for COVID-19. In South Africa, the first COVID-19 epicenter emerged in the Western Cape Province. The City of Cape Town, located in the Western Cape Province, has approximately 4...

Metformin is considered a safe anti-hyperglycemic drug for patients with type 2 diabetes (T2D); however, information on its impact on heart failure–related outcomes remains inconclusive. The current systematic review explored evidence from randomized clinical trials (RCTs) reporting on the impact of metformin in modulating heart failure–related mar...

Non-communicable diseases contribute significantly to the disease burden within South Africa. In the most unequal of societies in the world, poverty and socio-economic disparity are amongst the greatest obstacles facing South Africans, impacting heavily on health care. Adverse socio-environmental factors, especially those experienced during early l...

Oral therapeutics used to treat type 2 diabetes and cardiovascular disease often fail to prevent the progression of disease and their comorbidities. Rooibos (Aspalathus linearis), an endemic South African plant used as an herbal tea, has demonstrated positive effects on glycemia and hypercholesterolemia. However, the treatment efficacy of rooibos e...

Recent studies have shown that the detection of SARS-CoV-2 genetic material in wastewater may provide the basis for a surveillance system to track the environmental dissemination of this virus in communities. An effective wastewater-based epidemiology (WBE) system may prove critical in South Africa (SA), where health systems infrastructure, testing...

The advent and evolution of next generation sequencing has considerably impacted genomic research. Until recently, South African researchers were unable to access affordable platforms capable of human whole genome sequencing locally and DNA samples had to be exported. Here we report the whole genome sequences of the first six human DNA samples sequ...

Impaired adipose tissue function and insulin resistance remain instrumental in promoting hepatic lipid accumulation in conditions of metabolic syndrome. In fact, enhanced lipid accumulation together with oxidative stress and an abnormal inflammatory response underpin the development and severity of non-alcoholic fatty liver disease (NAFLD). There a...

Evidence on the beneficial effects of resveratrol supplementation on cardiovascular disease-related profiles in patients with type 2 diabetes (T2D) is conflicting, while its impact on renal function and blood pressure measurements remains to be established in these patients. The current meta-analysis included randomized controlled trials (RCTs) rep...

Background and aims There is a general interest in understanding how the consumption of tea impacts cardiovascular function in individuals at risk of developing cardiovascular disease (CVD). The current review focuses on evidence from randomized controlled trials (RCTs) reporting on associations between tea consumption and endothelial function, in...

Dimethyl sulfoxide (DMSO) is one of the most commonly used pharmaceutical drugs in life sciences. Besides its use as a valuable cryoprotective agent, DMSO is considered by many as a universal solvent that can efficiently dissolve both polar and nonpolar compounds. For this reason, many studies have been performed exploring various compounds and ext...

Metformin is a widely used glucose-lowering drug, although its impact on adipose tissue function remains elusive. Adipose tissue-derived molecules regulate diverse physiological mechanisms, including energy metabolism, insulin sensitization, and inflammatory response. Alternatively, it has remained relevant to understand the therapeutic regulation...

Background Metabolic risk varies according to body mass index (BMI), body fat distribution and ethnicity. In recent years, epigenetics, which reflect gene-environment interactions have attracted considerable interest as mechanisms that may mediate differences in metabolic risk. The aim of this study was to investigate DNA methylation differences in...

Background Disruption of the hypothalamic–pituitary–adrenal (HPA) axis, a neuroendocrine system associated with the stress response, has been hypothesized to contribute to obesity development. This may be mediated through epigenetic modulation of HPA axis-regulatory genes in response to metabolic stressors. The aim of this study was to investigate...

Type 2 diabetes (T2D) is characterized by metabolic derangements that cause a shift in substrate preference, inducing cardiac interstitial fibrosis. Interstitial fibrosis plays a key role in aggravating left ventricular diastolic dysfunction (LVDD), which has previously been associated with the asymptomatic onset of heart failure. The latter is res...

Rooibos extracts, including its derived polyphenolic compounds, are increasingly explored for their ameliorative effects against diabetes-associated complications. An extract of ‘fermented’ (oxidized) rooibos (FRE) can protect cardiomyocytes from diabetic rats against oxidative stress-induced damage, however, its mechanism of action remains unknown...

Impaired mitochondrial function concomitant to enhanced oxidative stress-induced damage are well established mechanisms involved in hyperlipidemia-induced cardiotoxicity. Currently, limited information is available on the direct effect of myocardial lipid overload on endogenous coenzyme Q9/10 (CoQ9/10) levels in association with mitochondrial respi...

The advent and evolution of next generation sequencing has considerably impacted genomic research. Until recently, South African researchers were unable to access affordable platforms capable of human whole genome sequencing locally and DNA samples had to be exported. Here we report the whole genome sequences of the first six human DNA samples sequ...

Background/Aim: Gestational diabetes mellitus (GDM) is associated with short- and long-term complication in both mothers and offspring. Molecular mechanisms are attracting increased interest for their potential as biomarkers for GDM that could lead to improved detection of GDM with positive effects on health outcomes. The aim of this study was to e...

Rooibos (Aspalathus linearis ) has various health benefits. Two case studies have associated chronic Rooibos consumption with conventional prescription medications, including atorvastatin (ATV), with hepatotoxicity. Statins act by inhibiting hydroxymethylglutaryl‐coenzyme A reductase, a rate‐limiting enzyme in cholesterol synthesis. Although rare,...

Evidence from randomized controlled trials (RCTs) suggests that coenzyme Q10 (CoQ10) can regulate adipokine levels to impact inflammation and oxidative stress in conditions of metabolic syndrome. Here, prominent electronic databases such as MEDLINE, Cochrane Library, and EMBASE were searched for eligible RCTs reporting on any correlation between ad...

Isoorientin is a natural C-glucosyl flavone that is generating a lot of interest due to its multiple pharmacological activities. Increasingly experimental data have shown that the robust antioxidant and anti-inflammatory properties of isoorientin remain important in ameliorating a number of metabolic complications. In fact, plants rich in isoorient...

Recent evidence shows that rooibos compounds, aspalathin and phenylpyruvic acid-2-O-β-D-glucoside (PPAG), can independently protect cardiomyocytes from hyperglycemia-related reactive oxygen species (ROS). While aspalathin shows more potency by enhancing intracellular antioxidant defenses, PPAG acts more as an anti-apoptotic agent. Thus, to further...

The current study explored the effect of isoorientin on the metabolic activity and lipid accumulation in fully differentiated 3T3-L1 adipocytes. To achieve this, the 3T3-L1 pre-adipocytes were differentiated for eight days and treated with various concentrations of isoorientin (0.1-100 µM) for four hours. Subsequently, the metabolic activity, lipid...

The increasing prevalence of non-communicable diseases, namely cancer, Alzheimer’s (AD) and cardiovascular diseases (CVDs), worldwide continues to be a major health burden. Research attempts have been made to understand the pathophysiology and develop effective therapeutic agents for these diseases using conventional in vitro and ex vivo models. Du...

Stimulation of fat browning using natural bioactive products is regarded as one of the promising approaches to treat obesity and insulin resistance. Here, we investigated the physiological effects of isoorientin on glucose uptake and lipid accumulation in insulin resistant 3T3-L1 adipocytes. To achieve this, 3T3-L1 adipocytes were exposed to 0.75 m...

Aims: Coenzyme Q10 (CoQ10) is well known for its beneficial effects in cardiovascular disease (CVD); however, reported evidence has not been precisely synthesized to better inform on its impact in protecting against cardiovascular-related complications in diabetic patients. Materials and methodology: The current meta-analysis included randomized...

Food-derived bioactive compounds such as resveratrol are increasingly explored for their protective effects against metabolic complications. Evidence supports the strong antioxidant properties and therapeutic effects of resveratrol in managing diabetes and its associated complications. However, evidence informing on the comparative or combination e...

The increased use of herbal supplements as complementary or alternative medicines has become a clinical conundrum due to the potential for herb-drug interactions. This is exacerbated by an increased supply of new herbal supplements in the market claiming various health advantages. These herbal supplements are available as over-the-counter self-medi...

Objective: To evaluate T-helper cytokine responses in a short-term high fat diet (HFD) induced impaired glucose metabolism. To further evaluate the modulation of T-helper 1 (Th1) and T-helper 2 (Th2) cytokines using short-term low-dose aspirin in combination with metformin. Design: Two experiments were carried out in this study in order to evalu...

Chronic hyperglycaemia is a major risk factor for diabetes-induced cardiovascular dysfunction. In a hyperglycaemic state, excess production of reactive oxygen species (ROS), coupled with decreased levels of glutathione, contribute to increased lipid peroxidation and subsequent myocardial apoptosis. N-acetylcysteine (NAC) is a thiol-containing antio...

Increasing evidence implicate altered DNA methylation in the pathophysiology of gestational diabetes mellitus (GDM). This exploratory study probed the association between GDM and peripheral blood DNA methylation patterns in South African women. Genome-wide DNA methylation profiling was conducted in women with (n = 12) or without (n = 12) GDM using...

The T-helper (Th1/Th2) paradigm is widely studied for its role in modulating an adaptive immune response, especially in relation to the onset of various autoimmune diseases. In fact, emerging evidence clearly shows an inverse relationship between Th1/Th2 cytokines and the development of type 2 diabetes (T2D) complications, which is accelerated by a...

The diabetic heart has been linked with reduced endogenous levels of coenzyme Q9/10 (CoQ), an important antioxidant and component of the electron transport chain. Although CoQ has displayed cardioprotective potential in experimental models of diabetes, the impact of N-acetyl cysteine (NAC) on mitochondrial energetics and endogenous levels of CoQ re...

The diabetic heart has been linked with reduced endogenous levels of coenzyme Q9/10 (CoQ), an important antioxidant and component of the electron transport chain. Although CoQ has displayed cardioprotective potential in experimental models of diabetes, the impact of N-acetyl cysteine (NAC) on mitochondrial energetics and endogenous levels of CoQ re...

An aspalathin-rich green rooibos extract (Afriplex GRT™) has demonstrated anti-diabetic and hypolipidemic properties, while also moderately inhibiting CYP3A4 activity, suggesting a potential for herb–drug interaction. The present study, therefore, evaluated the effects of orally administered GRT on the pharmacokinetics of atorvastatin and metformin...

Obesity is a significant contributor to increased morbidity and premature mortality due to increasing the risk of many chronic metabolic diseases such as type 2 diabetes, cardiovascular disease and certain types of cancer. Lifestyle modifications such as energy restriction and increased physical activity are highly effective first-line treatment st...

Obesity rates continue to rise in an unprecedented manner in what could be the most rapid population‐scale shift in human phenotype ever to occur. Increased consumption of unhealthy, calorie‐dense foods, coupled with sedentary lifestyles, is the main factor contributing to a positive energy balance and the development of obesity. Leptin and insulin...

Maternal obesogenic environment plays a role in programming the susceptibility of the fetus to postnatal non‐alcoholic fatty liver diseases (NAFLD), a risk factor for cardiovascular diseases (CVD). NAFLD is a multisystem disease that is characterized by hepatic fat accumulation due in part, to dysregulated energy metabolism network through epigenet...

Excessive adiposity in an obese state is known to drive the onset of metabolic dysregulations, mostly involving chronic immune activation and oxidative stress. Prolonged inflammation and oxidative stress have been linked to impaired adipose tissue function and the development of the metabolic syndrome. Currently available therapies offer minimal pr...

Background: The prevalence of obesity and metabolic diseases continues to rise globally. The increased consumption of unhealthy energy-rich diets that are high in fat and sugars results in oxidative stress and inflammation leading to hypothalamic dysfunction, which has been linked with these diseases. Conversely, diets rich in polyphenols, which a...

Aspalathin is a rooibos flavonoid with established blood glucose lowering properties, however, its efficacy to moderate complications associated with hepatic insulin resistance is unknown. To study such effects, C3A liver cells exposed to palmitate were used as a model of hepatic insulin resistance. These hepatocytes displayed impaired substrate me...

Type 2 diabetic patients possess a two to four fold-increased risk for Cardiovascular Diseases (CVD). Hyperglycemia, oxidative stress associated with endothelial dysfunction and dyslipidemia are regarded as pro-atherogenic mechanisms of CVD. In this study, high-fat diet-induced diabetic and non-diabetic vervet monkeys were treated with 90 mg/kg of...

Raw experimental data. (XLSX)

Original Western blot picture of glucose transporter (GLUT) 2, experiment 1(A), experiment 2(B), experiment 3 (C) and representative cropped blot (D). C3A liver cells were cultured in EMEM supplemented with 8 mM glucose with or without 0.75 mM palmitate for 16 h, and then treated with aspalathin 10 μM for 3 h. Insulin (1 μM) was added during the la...

Original Western blot picture of phosphor-AMP-activated protein kinase (pAMPK) and total-AMP-activated protein kinase (tAMPK), experiment 1 (A, B), experiment 2 (C, D), experiment 3 (E, F) and cropped blot (G). C3A liver cells were cultured in EMEM supplemented with 8 mM glucose with or without 0.75 mM palmitate (Pal) for 16 h, thereafter treated w...

Original Western blot picture of phosphor-protein kinase B (pAKT) and total-protein kinase B (tAKT), experiment 1 (A, B), experiment 2 (C, D), experiment 3 (E, F) and cropped blot (G). C3A liver cells were cultured in EMEM supplemented with 8 mM glucose with or without 0.75 mM palmitate (Pal) for 16 h, thereafter treated with aspalathin 10 μM for 3...

Original Western blot picture for phosphor-phosphoinositide 3-kinase (pPI3K) and total-phosphoinositide 3-kinase (tPI3K), experiment 1 (A, B), experiment 2 (C, D), experiment 3 (E, F) and cropped blot (G). C3A liver cells were cultured in EMEM supplemented with 8 mM glucose with or without 0.75 mM palmitate (Pal) for 16 h, thereafter treated with a...

Original Western blot picture of carnitine palmitoyltransferase 1 (CPT1), experiment 1(A), experiment 2(B), experiment 3 (C) and cropped blot (D). C3A liver cells were cultured in EMEM supplemented with 8 mM glucose with or without 0.75 mM palmitate (Pal) for 16 h, and then treated with aspalathin 10 μM for 3 h. Insulin (1 μM) was added during the...

List of antibodies and relevant dilutions used in the current study. (DOCX)

Blood pressure (BP) is a complex trait that is regulated by multiple physiological pathways and include but is not limited to extracellular fluid volume homeostasis, cardiac contractility, and vascular tone through renal, neural, or endocrine systems. Uncontrolled hypertension (HTN) has been associated with an increased mortality risk. Therefore, u...

Background Insulin resistance is a hallmark of type 2 diabetes mellitus (T2DM) and the underlying cause of various metabolic changes observed in type 2 diabetic patients. This study investigated the molecular basis of the anti-hyperglycemic activity of the lanosteryl triterpene (RA-3), from Protorhus longifolia stem bark, in hyperlipidemic and stre...

We previously demonstrated that an aspalathin-enriched green rooibos extract (GRE) reversed palmitate-induced insulin resistance in C2C12 skeletal muscle and 3T3-L1 fat cells by modulating key effectors of insulin signalling such as phosphatidylinositol-4,5-bisphosphate 3-kinase/protein kinase B (PI3K/AKT) and AMP-activated protein kinase (AMPK). H...

[This corrects the article DOI: 10.3389/fendo.2018.00744.].

Metabolic complications in an obese state can be aggravated by an abnormal inflammatory response and enhanced production of reactive oxygen species. Pro-inflammatory response is known to be associated with the formation of toxic reactive oxygen species and subsequent generation of oxidative stress. Indeed, adipocytes from obese individuals display...

Type 2 diabetes (T2D) is a leading cause of death and disability worldwide. It is a chronic metabolic disorder that develops due to an interplay of genetic, lifestyle, and environmental factors. The biological onset of the disease occurs long before clinical symptoms develop, thus the search for early diagnostic and prognostic biomarkers, which cou...

Aspalathin (ASP) is a C-dihydrochalcone abundantly found in Aspalathus linearis. While we have provide evidence that ASP can protect H9c2 cardiomyoblasts against doxorubicin (Dox)-induced apoptosis through regulation of autophagy, the complete mechanism involved in the cardioprotective effect of this dihydrochalcone remains to be explored. Here we...

Background/Objective: Recently, several studies have reported that DNA methylation changes in tissue are reflected in blood, sparking interest in the potential use of global DNA methylation as a biomarker for Gestational diabetes mellitus (GDM). This study investigated whether global DNA methylation is associated with GDM in South African women. Me...