Chronic circadian disruption on a high-fat diet impairs glucose tolerance

Oleanolic acid alleviates obesity-induced skeletal muscle atrophy via the PI3K/Akt signaling pathway

Oleanolic acid (OA) is a pentacyclic triterpene with reported protective effects against various diseases, including diabetes, hepatitis, and different cancers. However, the effects of OA on obesity-induced muscle atrophy remain largely unknown. This study investigated the effects of OA on skeletal muscle production and proliferation of C2C12 cells. We report that OA significantly increased skeletal muscle mass and improved glucose intolerance and insulin resistance. OA inhibited dexamethasone (Dex)-induced muscle atrophy in C2C12 myoblasts by regulating the PI3K/Akt signaling pathway. In addition, it also inhibited expression of MuRF1 and Atrogin1 genes in skeletal muscle of obese mice suffering from muscle atrophy, and increased the activation of PI3K and Akt, thereby promoting protein synthesis, and eventually alleviating muscle atrophy. Taken together, these findings suggest OA may have potential for the prevention and treatment of muscle atrophy.

Current perspective on circadian function of the kidney

Behavior and function of living systems are synchronized by the 24-h rotation of the Earth that guides physiology according to time of day. However, when behavior becomes misaligned from the light-dark cycle, such as in rotating shift work, jet lag, and even unusual eating patterns, adverse health consequences such as cardiovascular or cardiometabolic disease can arise. The discovery of cell-autonomous molecular clocks expanded interest in regulatory systems that control circadian physiology including within the kidney, where function varies along a 24-h cycle. Our understanding of the mechanisms for circadian control of physiology is in the early stages, and so the present review provides an overview of what is known and the many gaps in our current understanding. We include a particular focus on the impact of eating behaviors, especially meal timing. A better understanding of the mechanisms guiding circadian function of the kidney is expected to reveal new insights into causes and consequences of a wide range of disorders involving the kidney, including hypertension, obesity, and chronic kidney disease.

Eating during the biological night is associated with nausea

OBJECTIVES

This study assessed whether there was a time-of-day effect on nausea reports in participants during studies employing circadian protocols.

METHODS

Visual-analog-scales of nausea ratings were recorded from 34 participants (18-70years; 18 women) during forced desynchrony studies, where meals were scheduled at different circadian phases. Subjective nausea reports from a further 81 participants (18-35years; 36 women) were recorded during constant routine studies, where they ate identical isocaloric hourly snacks for 36-40 hours.

RESULTS

Feelings of nausea varied by circadian phase in the forced desynchrony studies, peaking during the biological night. Nausea during the constant routine was reported by 27% of participants, commencing 2.9 ± 5.2 hours after the midpoint of usual sleep timing, but was never reported to start in the evening (4-9 PM).

CONCLUSIONS

Nausea occurred more often during the biological night and early morning hours. This timing is relevant to overnight and early morning shift workers and suggests that a strategy to counteract that is to pay careful attention to meal timing.

Influence of circadian phase and extended wakefulness on glucose levels during forced desynchrony

OBJECTIVES

Circadian misalignment and sleep deprivation often occur in tandem, and both negatively impact glucose homeostasis and metabolic health. The present study employed a forced desynchrony protocol to examine the influence of extended wakefulness and circadian misalignment on hourly glucose levels.

METHODS

Nine healthy adults (4F/5M; 26 ± 4years) completed a 31-day in-laboratory protocol. After three 24 hour baseline days with 8 hours scheduled sleep opportunities, participants were scheduled to 14 consecutive 42.85 hour sleep-wake cycles, with 28.57 hours extended wakefulness and 14.28 hours sleep opportunities each cycle. Blood was sampled hourly across the forced desynchrony and over 600 plasma samples per participant were analyzed for glucose levels.

RESULTS

Both hours into the 42.85 hours forced desynchrony day and circadian phase modulated glucose levels (p < .0001). Glucose peaked after each meal during scheduled wakefulness and decreased during scheduled sleep/fasting. Glucose levels were, on average, lowest during the biological daytime and rose throughout the biological night, peaking in the biological morning. When analyzed separately for scheduled sleep vs. wakefulness, the peak timing of the circadian rhythm in glucose was later during sleep (p < .05). Glucose area under the curve levels increased rapidly from the beginning of the forced desynchrony protocol and were highest on the second forced desynchrony day (p < .01), returning towards forced desynchrony day 1 levels thereafter.

CONCLUSIONS

These findings have important implications for understanding factors contributing to altered glucose metabolism during sleep loss and circadian misalignment, and for potential physiological adaptation of metabolism in healthy adults, who are increasingly exposed to such conditions in our society.

Dietary Patterns and Circadian Syndrome among Adults Attending NHANES 2005-2016

The study aimed to assess the associations of dietary patterns and circadian syndrome (CircS). Data from National Health and Nutrition Examination Survey (NHANES) 2005-2016 were analyzed (n = 10,486). Factor analysis was used to construct dietary patterns based on two 24 h food recalls. CircS was defined based on components of the metabolic syndrome, with the addition of short sleep and depression symptoms. Multivariable logistic regression was used to analyze the associations. Two major dietary patterns were identified. The Western dietary pattern had high loadings of refined grains, solid fats, added sugars, and red and cured meats, while the prudent pattern was characterized by a high intake of vegetables, whole grains, oils, nuts, and seeds. The prevalence of CircS was 41.3%. Comparing extreme quartiles of intake, the odds ratios (OR) for having CircS were 1.96 (95%CI 1.53-2.53) and 0.71 (95%CI 0.58-0.86) for the Western pattern and prudent pattern, respectively. The association between the Western dietary pattern and CircS was stronger among men (OR = 2.05; 95%CI 1.48-2.85) and those with low income (OR = 1.94; 95%CI 1.27-2.96) and high education (OR = 3.38; 95%CI 1.90-6.04). The Western dietary pattern was associated with a higher likelihood of having CircS, while the prudent pattern was inversely associated with CircS.

Improvement in chrono-nutrition is associated with robust weight loss outcomes: An extension of the feasibility study

Previously we had demonstrated the development and feasibility of an integrated chrono-nutrition weight reduction program among non-shift workers with morning and evening chronotypes. In this current paper, we described the association between the changes in chrono-nutrition practice and weight loss outcomes upon completing the weight reduction program. A total of 91 overweight/obese non-shift workers participated in the 12-week integrated chrono-nutrition weight reduction program (Age: 39.6 ± 6.3 y; 74.7% women; BMI: 31.2 ± 4.5 kg/m²). All the assessments including anthropometry, dietary, sleep habits, physical activity, and process of change were measured during pre- and post-intervention. Participants who had lost ≥3% of their body weight were categorized as satisfactory weight loss outcome, and those who did not achieve 3% weight loss were categorized as unsatisfactory weight loss. The satisfactory weight loss had greater daily percent energy intake during earlier in the day from protein (Mean difference (MD): +3.2%, 95% CI: 1.6, 4.9, p < .001) and smaller intake from fat during later in the day (MD: -2.6%, 95% CI: -5.1, -0.1, p = .045), earlier last mealtime (MD: -49.5 min, 95% CI: -86.5, -12.6, p = .009) and midpoint of eating (MD: -27.3 min, 95% CI: -46.3, -8.2, p = .006), shorter eating window (-0.8 h, 95% CI: -1.4, -0.1, p = .031) and greater reduction in night eating syndrome score (MD: -2.4, 95% CI: -4.3, -0.5, p = .015) compared to unsatisfactory weight loss outcome. After accounting for potential confounders, the temporal pattern of energy, protein, and fat intake were associated with greater odds of achieving a satisfactory weight loss. The findings suggest a promising role of chrono-nutrition as one of the strategies in weight reduction intervention.

Desynchronizing the sleep---wake cycle from circadian timing to assess their separate contributions to physiology and behaviour and to estimate intrinsic circadian period

Circadian clocks drive cyclic variations in many aspects of physiology, but some daily variations are evoked by periodic changes in the environment or sleep-wake state and associated behaviors, such as changes in posture, light levels, fasting or eating, rest or activity and social interactions; thus, it is often important to quantify the relative contributions of these factors. Yet, circadian rhythms and these evoked effects cannot be separated under typical 24-h day conditions, because circadian phase and the length of time awake or asleep co-vary. Nathaniel Kleitman's forced desynchrony (FD) protocol was designed to assess endogenous circadian rhythmicity and to separate circadian from evoked components of daily rhythms in multiple parameters. Under FD protocol conditions, light intensity is kept low to minimize its impact on the circadian pacemaker, and participants have sleep-wake state and associated behaviors scheduled to an imposed non-24-h cycle. The period of this imposed cycle, Τ, is chosen so that the circadian pacemaker cannot entrain to it and therefore continues to oscillate at its intrinsic period (τ, ~24.15 h), ensuring circadian components are separated from evoked components of daily rhythms. Here we provide detailed instructions and troubleshooting techniques on how to design, implement and analyze the data from an FD protocol. We provide two procedures: one with general guidance for designing an FD study and another with more precise instructions for replicating one of our previous FD studies. We discuss estimating circadian parameters and quantifying the separate contributions of circadian rhythmicity and the sleep-wake cycle, including statistical analysis procedures and an R package for conducting the non-orthogonal spectral analysis method that enables an accurate estimation of period, amplitude and phase.

Chrono-communication and cardiometabolic health: The intrinsic relationship and therapeutic nutritional promises

Circadian rhythm, an innate 24-h biological clock, regulates several mammalian physiological activities anticipating daily environmental variations and optimizing available energetic resources. The circadian machinery is a complex neuronal and endocrinological network primarily organized into a central clock, suprachiasmatic nucleus (SCN), and peripheral clocks. Several small molecules generate daily circadian fluctuations ensuring inter-organ communication and coordination between external stimuli, i.e., light, food, and exercise, and body metabolism. As an orchestra, this complex network can be out of tone. Circadian disruption is often associated with obesity development and, above all, with diabetes and cardiovascular disease onset. Moreover, accumulating data highlight a bidirectional relationship between circadian misalignment and cardiometabolic disease severity. Food intake abnormalities, especially timing and composition of meal, are crucial cause of circadian disruption, but evidence from preclinical and clinical studies has shown that food could represent a unique therapeutic approach to promote circadian resynchronization. In this review, we briefly summarize the structure of circadian system and discuss the role playing by different molecules [from leptin to ghrelin, incretins, fibroblast growth factor 21 (FGF-21), growth differentiation factor 15 (GDF15)] to guarantee circadian homeostasis. Based on the recent data, we discuss the innovative nutritional interventions aimed at circadian re-synchronization and, consequently, improvement of cardiometabolic health.