A Nutritional Perspective of Ketogenic Diet in Cancer: A Narrative Review

The predominant use of glucose anaerobically by cancer cells (Warburg effect) may be the most important characteristic the majority of these cells have in common and, therefore, a potential metabolic pathway to be targeted during cancer treatment. Because this effect relates to fuel oxidation, dietary manipulation has been hypothesized as an important strategy during cancer treatment. As such, the concept of a ketogenic diet (KD) in cancer emerged as a metabolic therapy (ie, targeting cancer cell metabolism) rather than a dietary approach. The therapeutic mechanisms of action of this high-fat, moderate-to-low protein, and very-low-carbohydrate diet may potentially influence cancer treatment and prognosis. Considering the lack of a dietetics-focused narrative review on this topic, we compiled the evidence related to the use of this diet in humans with diverse cancer types and stages, also focusing on the nutrition and health perspective. The use of KD in cancer shows potentially promising, but inconsistent, results. The limited number of studies and differences in study design and characteristics contribute to overall poor quality evidence, limiting the ability to draw evidence-based conclusions. However, the potential positive influences a KD may have on cancer treatment justify the need for well-designed clinical trials to better elucidate the mechanisms by which this dietary approach affects nutritional status, cancer prognosis, and overall health. The role of registered dietitian nutritionists is demonstrated to be crucial in planning and implementing KD protocols in oncology research settings, while also ensuring patients’ adherence and optimal nutritional status.     

Nephropathy and Elevated BP in Mice with Podocyte-Specific NADPH Oxidase 5 Expression

NADPH oxidase (Nox) enzymes are a significant source of reactive oxygen species, which contribute to glomerular podocyte dysfunction. Although studies have implicated Nox1, -2, and -4 in several glomerulopathies, including diabetic nephropathy, little is known regarding the role of Nox5 in this context. We examined Nox5 expression and regulation in kidney biopsies from diabetic patients, cultured human podocytes, and a novel mouse model. Nox5 expression increased in human diabetic glomeruli compared with nondiabetic glomeruli. Stimulation with angiotensin II upregulated Nox5 expression in human podocyte cultures and increased reactive oxygen species generation. siRNA-mediated Nox5 knockdown inhibited angiotensin II–stimulated production of reactive oxygen species and altered podocyte cytoskeletal dynamics, resulting in an Rac-mediated motile phenotype. Because the Nox5 gene is absent in rodents, we generated transgenic mice expressing human Nox5 in a podocyte-specific manner (Nox5^pod+). Nox5^pod+ mice exhibited early onset albuminuria, podocyte foot process effacement, and elevated systolic BP. Subjecting Nox5^pod+ mice to streptozotocin-induced diabetes further exacerbated these changes. Our data show that renal Nox5 is upregulated in human diabetic nephropathy and may alter filtration barrier function and systolic BP through the production of reactive oxygen species. These findings provide the first evidence that podocyte Nox5 has an important role in impaired renal function and hypertension.Albuminuria is a clinical marker of kidney dysfunction that arises in most glomerulopathies and is associated with poor prognoses for ESRD, hypertension, and cardiovascular mortality. Changes to the podocyte (e.g., foot process effacement, hypertrophy, detachment, and loss) underlie the development and progression of albuminuria and thereby highlight the critical role for these cells in upholding the glomerular filtration barrier.^1,2 Therefore, identifying factors that induce podocyte injury and loss is essential to understanding the mechanisms of filtration barrier dysfunction.Of the many factors implicated in podocyte dysfunction, excessive production of reactive oxygen species (ROS; oxidative stress) may be particularly important.^3–6 Although sources of ROS are numerous, the NADPH oxidase (Nox) family of enzymes yields significant superoxide production in the kidney.^7–10 Nox-induced ROS production has been closely linked to various glomerular pathologies. In animal models of minimal change disease, membranous nephropathy, and FSGS, inhibition of Nox activity is associated with decreased podocyte effacement and amelioration of albuminuria.^11–14 In models of diabetic nephropathy, treatment with the Nox inhibitor apocynin, as well the antioxidant vitamin E, reduces oxidative stress, podocyte effacement and loss, and albuminuria.^6,15,16 Noxs are regulated by many factors, including the renin angiotensin aldosterone system.^5,9 Several studies have linked increased renin angiotensin aldosterone system activity to enhanced renal Nox activity and ROS generation.^5,17 Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers slow progression of proteinuria in models of diabetes, and these effects may be, in part, independent of their effects on systemic BP,^17–20 because direct activation of Nox enzymes through the angiotensin II (AngII)/AT1 receptor (AT1R) pathway leads to oxidative stress. In vitro studies in both human and rodent cell lines have also shown that Nox family member expression and activity are regulated by disease-associated factors, including AngII, ET-1, TGF-β, high glucose, mechanical stretch, and PDGF (factors that are upregulated in the diabetic milieu).^3,21–23The roles of Nox4, and to a lesser extent, Nox1 and -2, in the kidney have been examined, but nothing is known regarding the role of the most recently identified member of the Nox family, Nox5. The Nox5 gene is absent from the mouse and rat genomes, making the use of conventional animal models unfeasible. Unlike other Nox family members, Nox5 does not require membrane-bound or cytosolic components, such as p22phox or p47phox, for its activity, but is tightly regulated by changes in intracellular calcium levels.^24,25 Nox5 has a large amino terminal EF hand-containing domain that plays a critical role in its calcium-dependent activation along with several phosphorylation sites that alter the sensitivity of Nox5 to intracellular calcium.^26–29 Because AngII increases intracellular calcium concentrations, it seems to induce renal Nox5-dependent ROS generation, which was shown in human endothelial cells.²³ Here, we show that (1) Nox5 is upregulated in human diabetic glomeruli; (2) AngII stimulates ROS generation in human podocytes in a Nox5-dependent manner, a process associated with actin cytoskeletal reorganization and activation of Rac GTPase, which promotes podocyte motility in vitro; (3) mice that express human Nox5 in a podocyte-specific manner (Nox5β^pod+ mice) exhibit renal dysfunction, including albuminuria, podocyte effacement, glomerular basement membrane (GBM) thickening, interstitial fibrosis, and hypertension; and (4) Nox5^pod+ mice subjected to streptozotocin (STZ)-induced diabetes develop a more severe kidney phenotype than nontransgenic littermates. These novel data indicate the potential importance of podocyte Nox5 in human renal pathologies, such as diabetic nephropathy.     

Detection of nucleic acids via G-quadruplex-controlled l-cysteine oxidation and catalyzed hairpin assembly-assisted signal amplification

The development of simple, sensitive and cost-effective methods for specific nucleic acid detection has attracted tremendous attention due to its importance to the early diagnosis of genetic diseases and to biodefense applications. In this work, we demonstrated a fluorescent turn-off mode DNA assay based on l-cysteine-modulated synthesis of CdTe quantum dots (CdTe QDs), horseradish peroxidase-mimicking G-quadruplex–hemin–K⁺ complex controlled oxidation of l-cysteine to cystine, and catalyzed hairpin assembly (CHA)-assisted signal amplification. After the addition of target DNA, the CHA signal amplification reaction was triggered and numerous H1–H2 double-stranded DNA were formed, initiating the release of G-quadruplex sequences in H2 simultaneously. Thus, the degree of inhibition of the synthesis of CdTe QDs is proportional to the concentration of the G-quadruplex sequence in this method. In contrast, when the target DNA was absent, the CHA could not be triggered, and the fluorescence signal was high due to the remaining intact l-cysteine. Under optimal experimental conditions, the homogeneous fluorescence method achieved the detection of HIV DNA with a linear range from 0.1 pM to 1 nM and a detection limit of 0.12 pM. This novel biosensor exhibits excellent specificity in differentiating DNA sequences with a single-base and two-base mismatch. To the best of our knowledge, this a label-free and highly sensitive bioassay utilizing CHA-assisted signal amplification and G-quadruplex control of in situ synthesis of CdTe QDs strategy was not reported in previous. Thus, this proposed strategy is anticipated to find use in basic biochemical research and clinical diagnosis.

A novel homogeneous strategy for detection of DNA via biomimetic synthesis of luminescent QDs coupled with nucleic acid signal amplification.     

Long-term diabetic response to gastric bypass

Background

As obesity and type II diabetes continue to rise, bariatric surgery offers a solution, but few long-term studies are available. The purpose of this study was to evaluate the long-term outcomes of diabetic patients after gastric bypass.

Materials and methods

This was a retrospective cohort study of all diabetic patients undergoing gastric bypass at our institution, from 1998 to 2012. Patients were compared by postoperative diabetic response to treatment (i.e., response = off oral medication/insulin versus refractory = on oral medication/insulin) and followed at 1-, 3-, 5-, and 10-y intervals. Continuous data were analyzed using Student t-test or Wilcoxon rank-sum test. Multivariable, Cox proportional hazard regression model was performed to compute diabetic cure ratios and 95% confidence intervals.

Results

A total of 2454 bariatric surgeries were performed at our institution during the time period. A total of 707 diabetic patients were selected by Current Procedural Terminology codes for gastric bypass. Mean follow-up was 2.1 y. Incidence of diabetic response was 56% (1 y), 58% (3 y), 60% (5 y), and 44% (10 y). Postoperatively, responsive patients experienced greater percentage of total body weight loss (1 y [P < 0.0001], 3 y [P = 0.0087], and 5 y [P = 0.013]), and less hemoglobin A1c levels (1 y [P = 0.035] and 3 y [P = 0.040]) at follow-up than refractory patients. Multivariable analysis revealed a significant, independent inverse trend in incidence of diabetic cure as both age and body mass index decreased (P_trend = 0.0019 and <0.0001, respectively). In addition, degenerative joint disease was independently associated with responsive diabetes (cure ratio = 1.6 [95% confidence interval = 1.1–2.2]).

Conclusions

At follow-up, both groups in our study experienced substantial weight loss; however, a greater loss was observed among the response group. Further research is needed to evaluate methods for optimizing patient care preoperatively and improving patient follow-up.