The regulation of circadian rhythm by insulin signaling in Drosophila

LKRSDH-dependent histone modifications of insulin-like peptide sites contribute to age-related circadian rhythm changes

To understand aging impact on the circadian rhythm, we screened for factors influencing circadian changes during aging. Our findings reveal that LKRSDH mutation significantly reduces rhythmicity in aged flies. RNA-seq identifies a significant increase in insulin-like peptides (dilps) in LKRSDH mutants due to the combined effects of H3R17me2 and H3K27me3 on transcription. Genetic evidence suggests that LKRSDH regulates age-related circadian rhythm changes through art4 and dilps. ChIP-seq analyzes whole genome changes in H3R17me2 and H3K27me3 histone modifications in young and old flies with LKRSDH mutation and controls. The results reveal a correlation between H3R17me2 and H3K27me3, underscoring the role of LKRSDH in regulating gene expression and modification levels during aging. Overall, our study demonstrates that LKRSDH-dependent histone modifications at dilps sites contribute to age-related circadian rhythm changes. This data offers insights and a foundational reference for aging research by unveiling the relationship between LKRSDH and H3R17me2/H3K27me3 histone modifications in aging.

Circadian Disruption across Lifespan Impairs Glucose Homeostasis and Insulin Sensitivity in Adult Mice

Circadian rhythm disruption is associated with impaired glucose homeostasis and type 2 diabetes. For example, night shift work is associated with an increased risk of gestational diabetes. However, the effects of chronic circadian disruption since early life on adult metabolic health trajectory remain unknown. Here, using the "Short Day" (SD) mouse model, in which an 8 h/8 h light/dark (LD) cycle was used to disrupt mouse circadian rhythms across the lifespan, we investigated glucose homeostasis in adult mice. Adult SD mice were fully entrained into the 8 h/8 h LD cycle, and control mice were entrained into the 12 h/12 h LD cycle. Under a normal chow diet, female and male SD mice displayed a normal body weight trajectory. However, female but not male SD mice under a normal chow diet displayed glucose intolerance and insulin resistance, which are associated with impaired insulin signaling/AKT in the skeletal muscle and liver. Under high-fat diet (HFD) challenges, male but not female SD mice demonstrated increased body weight gain compared to controls. Both male and female SD mice developed glucose intolerance under HFD. Taken together, these results demonstrate that environmental disruption of circadian rhythms contributes to obesity in a sexually dimorphic manner but increases the risk of glucose intolerance and insulin resistance in both males and females.

Sleep and circadian rhythm disturbance in kidney stone disease: a narrative review

The circadian rhythm generated by circadian clock genes functions as an internal timing system. Since the circadian rhythm controls abundant physiological processes, the circadian rhythm evolved in organisms is salient for adaptation to environmental change. A disturbed circadian rhythm is a trigger for numerous pathological events. Recently, accumulated data have indicated that kidney stone disease (KSD) is related to circadian rhythm disturbance. However, the mechanism between them has not been fully elucidated. In this narrative review, we summarized existing evidence to illustrate the possible association between circadian rhythm disturbance and KSD based on the epidemiological studies and risk factors that are linked to circadian rhythm disturbance and discuss some chronotherapies for KSD. In summary, KSD is associated with systemic disorders. Metabolic syndrome, inflammatory bowel disease, and microbiome dysbiosis are the major risk factors supported by sufficient data to cause KSD in patients with circadian rhythm disturbance, while others including hypertension, vitamin D deficiency, parathyroid gland dysfunction, and renal tubular damage/dysfunction need further investigation. Then, some chronotherapies for KSD were confirmed to be effective, but the molecular mechanism is still unclear.

A phosphorylation-deficient mutant of Sik3, a homolog of Sleepy, alters circadian sleep regulation by PDF neurons in Drosophila

Sleep behavior has been observed from non-vertebrates to humans. Sleepy mutation in mice resulted in a notable increase in sleep and was identified as an exon-skipping mutation of the salt-inducible kinase 3 (Sik3) gene, conserved among animals. The skipped exon includes a serine residue that is phosphorylated by protein kinase A. Overexpression of a mutant gene with the conversion of this serine into alanine (Sik3-SA) increased sleep in both mice and the fruit fly Drosophila melanogaster. However, the mechanism by which Sik3-SA increases sleep remains unclear. Here, we found that Sik3-SA overexpression in all neurons increased sleep under both light-dark (LD) conditions and constant dark (DD) conditions in Drosophila. Additionally, overexpression of Sik3-SA only in PDF neurons, which are a cluster of clock neurons regulating the circadian rhythm, increased sleep during subjective daytime while decreasing the amplitude of circadian rhythm. Furthermore, suppressing Sik3-SA overexpression specifically in PDF neurons in flies overexpressing Sik3-SA in all neurons reversed the sleep increase during subjective daytime. These results indicate that Sik3-SA alters the circadian function of PDF neurons and leads to an increase in sleep during subjective daytime under constant dark conditions.

rdgB knockdown in neurons reduced nocturnal sleep in Drosophila melanogaster

Recent studies revealed behaviorally defined sleep is conserved across broad species from insect to human. For evolutional analysis, it is critical to determine how homologous genes regulate the homologous function among species. Drosophila melanogaster shares numerous sleep related genes with mammals including Sik3, salt-inducible kinase 3, whose mutation caused long sleep both in mouse and fruit fly. The Drosophila rdgB (retinal degeneration B) encodes a membrane-associated phosphatidylinositol transfer protein and its mutation caused light-induced degeneration of photoreceptor cells. rdgB mutation also impaired phototransduction and olfactory behavior, indicating rdgB is involved in the normal neural transmission. Mammalian rdgB homologue, Pitpnm2 (phosphatidylinositol transfer protein membrane-associated 2) was discovered as one of SNIPPs (sleep-need index phosphoproteins), suggesting its role in sleep. Here, we show that rdgB is involved in sleep regulation in Drosophila. Pan-neuronal and mushroom body (MB) specific rdgB knockdown decreased nocturnal sleep. MB neurons play a dominant role, since the rescue of rdgB expression only in MB neurons in pan-neuronal knockdown reversed the sleep reducing effect of rdgB knockdown. These results revealed the sleep-related function of rdgB in Drosophila which may be conserved across species.